.■■;:■•■-■■■>..; ' ■ " • - ■■■■■I CORNELL UNIVERSITY THE Sflouier Hetertnatg lOtbranj FOUNDED BY ROSWELL P. FLOWER for the use of the N. Y. State Veterinary College 1897 = micros 3 1 ^rt CO '== ^ s? I\J —^ 3| J^ — (0 )~ : Q. oo 2 L = 3 : q w 8===8 *? r- CT =.§ Bl 00 ) o> ■2 = •*» Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://archive.org/details/cu31924001036882 THE MICEOSCOPE MICROSCOPICAL TECHNOLOGY A TEXT-BOOK FOR PHYSICIANS AND STUDENTS BY HEINEIOH FREY Professor of Medicine in the University of Zurich TRANSLATED AND EDITED BY GEORGE E. CUTTER, M.D. Surgeon New York Eye and Ear Infirmary ; Ophthalmic and Aural Surgeon to the St. Catherine and Williamsburgh Hospitals, Etc., Etc. Illustrated by Three Hundred and Eighty-eight Engravings on Wood NEW YORK WILLIAM WOOD & COMPANY 1880 OOPYBIOHT BY WILLIAM WOOD & COMPANY. 1880. Trow's Printing and Bookbinding Company, 201-213 Bast i2« Street. NHW YORK. CONTENTS. PAGE Translator's Preface v Introduction ix SECTION FIRST. Theory of the Microscope 1 SECTION SECOND. Apparatus for Measuring and Drawing 32 SECTION THIRD. The Binocular, the Stereoscopic, and the Polarizing Microscope.. 46 SECTION FOURTH. Testing the Microscope 53 SECTION FIFTH. Use of the Microscope — Microscopic Examination ... 83 SECTION SIXTH. The Preparation of Microscopic Objects 103 SECTION SEVENTH. Fluid Media and Chemical Reagents — Titkition 117 SECTION EIGHTH. Methods of Staining— Impregnation with Metals— The Drying and Freezing Processes 147 SECTION NINTH. Method of Injecting 172 IV CONTENTS. SECTION TENTH. PAGE The Mounting and Arrangement of Microscopic Objects 207 SECTION ELEVENTH. Blood, Lymph, Chyle, Mucus, and Pus 233 SECTION TWELFTH. Epithelium, Nails, Hair 256 SECTION THIRTEENTH. Connective Tissue and Cartilage 274 SECTION FOURTEENTH. Bones and Teeth 296 SECTION FIFTEENTH. Muscles and Nerves 316 SECTION SIXTEENTH. Vessels and Glands 381 SECTION SEVENTEENTH. Digestive Organs 422 SECTION EIGHTEENTH. Pancreas, Liver, and Spleen 459 SECTION NINETEENTH. Respiratory Organs 485 SECTION TWENTIETH. Urinary Organs 502 SECTION TWENTY-FIRST. Sexual Organs : 533 SECTION TWENTY-SECOND. Organs op Sense 554 Index 007 Price-Lists of Microscope-Makers 627 TRANSLATOR'S PREFACE. Any attempt on my part, by way of introduction or commendation of Professor Frey's work, must, I feel, be altogether misplaced and unnecessary. Although the treatise has been but a few years before the public, four large editions have already been issued, and a copy is always found on the table of those microscopists who are able to read it in the original. I have been induced to undertake the arduous labor of preparing a translation of the work by the hope that it might stimulate and facilitate the study of this important branch of science in this country. An apology may be thought necessary for the style of the translation, — in having followed the German so liter- ally. The nature of the subject, however, involving as it does such very minute descriptions, and the frecpient repe- tition of the same terms, added to the impossibility of doing justice in any other way to the author's condensed style, have necessitated a rigid adherence to the original text. The few additions which have been made are enclosed within brackets. George R. Cutter, M.D. New York, October, 1872. TRANSLATOR'S PREFACE TO THE SECOND EDITION. In preparing this edition, the work has been thor- oughly revised, a large amount of new matter and many new illustrations have been added ; a bolder-faced type has been used, and the size of the page increased. It is hoped that the very favorable reception ex- tended to the previous edition by the profession at large, and by the medical press, will also be granted to the present. George R. Cutter, M.B., No. 312 Second Avenue, New York. Jantjaey, 1880. INTRODUCTION. " To endeavor to discover new methods of investigation appears to me tp be one of the most important duties of every observer. To communicate these to his pupils must be the desire of every teacher of any branch of natural science." — (L. Beale : How to Work with the Microscope, p. 3. ) Within the last ten years the Microscope, that instrument which has conquered a new world of minuteness for natural science, has become widely known. Already a considerable number of these instruments are yearly issued from the large and celebrated establishments of Europe ; and not less noticeable is the number of those which are constructed and sold by less renowned opticians. The opinion is now admitted that the microscope is quite as indispensable for the scientific, as the stethoscope and pleximeter for the jM-'actical requirements of the physician. Through Schwann's classical work we have learned that the human body is formed, in all its parts, from cells and then- derivatives, and that the cell is the ultimate organized unity of animal life. As in the province of anatomy we cannot understand the structure of any portion of the body without this little microscopical foundation-stone, even so little do we succeed in comprehending the physiological action, if we disregard the isolated action of these ultimate organized unities. The united action of an organ is only the result of all the single actions of cells, of the " elementary organisms," as they were afterwards called. Thus, Histology has become an indispensable member in the series of anatomico-physiolo- gical sciences. Health and disease appear, in the ingenuous view of man, to be sepa- rated by a wide abyss ; an opinion which, in the domain of science, is drawn like a red thread through so many nosological systems of X INTRODUCTION. former clays. The recognition of the contrary is properly greeted as a great advance in physiological opinion. The processes which take place in the diseased body are actually, for us, but modifications of those which occur in the normal ; the same physiological laws obtain in the one case as in the other ; and those also which, in a material regard, occur in the diseased body, the metamorphosis, separation, and new formation of its elements, obey the same laws of cell-life which we recognize in the normal organism. The eminent significance of pathological histology requires no wider discussion, nor is it necessary further to recommend the instru- ment by means of which histology is chiefly created. Microscopy is, however, as some of our readers will have already expe- rienced in their first attempts, dehcate work. How many a student, how many a physician, impelled by the great value of such studies, has pro- cured a microscope only to perceive, to his great dissatisfaction, how httle he is qualified to use it. Here, as in all departments of human efficacy, a period of apprenticeship is necessary, — an arduous season of sowing before attempting to reap the plenteous harvest. The microscope is a delicate implement ; like other comphcated in- struments, its use must be learned. The faculty of seeing with it must likewise be acquired, which also requires some perseverance, if we would attain to the accurate vision which is here indispensable. The art to observe and investigate requires the employment and knowledge of many smaU, and therefore, at first, apparently unimportant accessories. The time is past when it was thought possible to fathom the finer textural relations of a piece of fresh tissue by picking, and, perhaps, the assistance of pressure and a httle acetic acid. Modern chemistry, to which medicine is extremely indebted, has also furnished the microsco- pist with a series of the most important accessories. Thus, now-a-days, knives and needles, the syringe, the scales, and many other artifices are employed in the investigation of the tissues of the body. We shall readily comprehend, from what has been said, that our so in- dustrious epoch in a microscopical regard, among many sound investiga- tions, also annually produces over-hasty performances which show how little then- authors have learned to overcome the most elementary difficul- ties. This remark, however, is not written to discourage ; it should, on the contrary, only indicate that the most complete familiarity with the instru- INTRODUCTION. xi nient and with the entire technique should be the indispensable prelimi- nary of every microscopical investigation. Though that school which offers the practical instruction of a teacher is always the best, it is not permitted to every one to walk hi this path to learning. Here written directions tind their place, and, provided they are judicious and practical, may afford a sufficient compensation, and make a microscopical observer out of the beginner. The literature of the microscope is already voluminous. Admirable and copious works exist in the German, Hollandish, and English lan- guages, such as those of Mold, Harting, and Carpenter. But in the Ger- man there is a great deficiency of concise works especially adapted to the practical wants of the physician, as we have only the obsolete work of Vo- gel. L. Beale has produced two able text-books for the English. May our little work serve as a guide for students and physicians till the time, at least, when a better pen shall produce a better substitute. That we premise the mechanism of the instrument and the use of its several parts is obviously necessary ; for a knowledge of the implements must always precede the labor which they are to perform. That we limit ourselves, in this section, to that which is most important and in- dispensable, and touch but lightly the difficult, and in all its parts by no means definitely settled, optical theory, requires no further justification. Another portion of our work treats of the various methods of investiga- tion at present in use. A third part, finally, completes the directions for investigating the various tissues and parts of the body in a normal and pathological condition. Possibly, in the department of pathology we niay have been too concise for a portion of our readers. The investiga- tion of sputum, pus, urinary sediment, and tumors usually occupies a much larger space in books on this subject. But, true to our maxim, that the most accurate knowledge of the normal relations should precede every investigation of their pathological condition, we endeavor, first of all, to make the former clear and then join the latter supplementarily. As every pathological new formation repeats, more or less, the type of the normal structure, so are the methods of investigating diseased tissues and portions of the body almost the same. With regard to the literature of the microscope, we would particularly mention the following works : — J. Vogel, Anleitnng zum Gebrauche des Mikroskops, Leipzig, 1841. Xll INTRODUCTION. — H. v. Mold, Mikrographie, Tubingen, 1846. — C. Robin, Du micro- scope et des injections, Paris, 1871. — P. Harting, Das Mikroskop, 2. deutsche Originalausgabe, besorgt von Theile, 3 Bde., Braunschweig, 1866.— W. Carpenter, The Microscope, 4th Edition, London, 1868.— L. Beale, How to Work with the Microscope, 4th Edition, London, 1867, and; The Microscope in its Apphcation to Practical Medicine, 4th Edition, London, 1877. — H. Schacht, Das Mikroskop, 3. Auflage, Berlin, 1862. — C. Niigeli und S. Schwendener, Das Mikroskop, Leipzig, 1867. — L. Dippel, Das Mikroskop und seine Anwendung, Braunschweig, Bd. 1, 1867, und Bd. 2, 1872. — L. Ranvier, Traite dhistologie technique, Paris, 1875. Section first. THEORY OF THE MICROSCOPE. That wonderful organ, the human eye, lias often been com- pared to the camera obscura, and the comparison is, indeed, an excellent one. As the collective lens projects an inverted diminished image at the background of the latter apparatus, which is received on the ground-glass plate, so the collective refracting media of the eye produce the same inverted dimin- ished image at its profundity, which is received on the retina. Probably all of our readers are aware that the dimensions which an object appears to the eye to possess, depend upon the size of the angle of vision ; an angle which one receives by combining, through straight lines, the corresponding terminal points of the object, and of the image received in the eye. A glance at fig. 1 will render this intelligible. The curved Fig. 1. Visual angle and apparent magnitude of the object. line at b a represents the image, projected upon the fundus oculi, of the arrow A B, placed before the organ of vision ; a is united by a line to A, & by a second one to B. Thus arises the visual angle A B = 6 o a. All bodies whose terminal points touch the lines A a and B 5, appear to the eye to be of the same size. A needle held close before the eye may, under 6 SECTION FIRST. these circumstances, have the same apparent dimensions as a long pole which stands in the distance. When the arrow is brought nearer to the eye, to A' B' for instance, it projects the image b* a*, causing the angle of vision A' o B' ; the arrow, however, appears to be larger. If the angle of vision falls be- low a certain size, the object ceases to be visible. A thick wire, for example, if considerably removed from our eye, is no longer perceived. If we bring the wire nearer and nearer, whereby the visual angle is also increased, it appears at first as a fine thread, then with increasing diameter. We therefore instinctively ex- amine small objects at a certain proximity. But a continued approach also finds its limit at last ; the wire, which was still distinctly seen, becomes indistinct, and finally, having been brought quite close to the eye, becomes entirely invisible. On what does this last condition depend ? It is known that the image of an object projected by a col- lective lens alters its position according as the object is removed from or brought nearer to the lens. In the first case the image approaches the lens, in the latter, it recedes farther behind it. 'Now, as the human eye acts in the same manner as a lens, and accurate vision only occurs when the rays of light, coming from any point of an object, are so refracted as to be again united at the retina, so, in reality, a distinct image can only be possible at a certain distance. But daily observation teaches us some- thing further ; we see remote and near objects, one after an- other, with equal accuracy. The eye must, therefore, possess a correcting apparatus, in order to adjust its refracting media for proximate and remote bodies ; it accommodates, as the physiologists say. This process of accommodation is, however, disregarding in- dividual variations, limited. The image of an object, brought more and more near to the eye, falls at last behind the retina. In our fig. 2, the> arrow placed at A would give a distinct imao-e, the rays of light diverging from a point p being united at a point r on the retina. Should the arrow, however, be brought so near as B to the organ of vision, this union can no longer take place at the retina. The rays of light proceeding from p* come together farther behind this membrane, at r*. Very small objects, therefore, when brought too near to the THEORY OF THE MICROSCOPE. human eye become invisible ; here, as we shall soon see, other accessories are necessary. The distance from the eye at which objects of medium size Fig. 2. Position of an object, and union of the rays which proceed from it in the eye. can be most sharply discerned, is called the mean distance of vision. This is usually considered to be from 8 to 10 inches, or 25 centimetres, for the normal eye. The closest proximity at which an object is still visible is called the near point. Near- sighted eyes permit of a few inches nearer approach, far-sighted ones find their limit sooner ; the first refract more, the latter less strongly. Such a small body may, however, readily be made visible by placing a convex lens between it and the eye. The reason is easily understood. The point placed at O, fig. 3, produces its image at r, and is therefore no longer perceptible to the eye. If we now place the lens L, whose focus is at F, between, the rays of light receive the direction indicat- ed by the dotted lines, are less divergent on reaching the eye, and are, consequently, united on the retina at R. Thus a dis- tinct image is formed. It will also be observed, that by the use of such a lens the image thus received is enlarged. Now whence does this arise ? Let us suppose that the object is placed at A B, fig. 4, and that a convex lens is brought between it and the eye. The cone of rays which proceeds from any point of the arrow, for example from A, projects its rays A 6, A C, A c on to the lens, and these, with the exception of the rays A C, are refracted by Fig. 3. Action of a convex lens when an object is brought near the eye. 4 SECTION FIRST. the lens in the direction b I and c % ; receiving a slight diver- gence, as if they proceeded from the more distant point A*, Fig. <1. An object magnified by a convex Iciik. they arrive at the eye and are united on the retina. The same is repeated for the cone of rays B, etc. ; thus an inverted image of the arrow is formed in the eye. The object appears to the organ of vision to be placed, not at A B, but at A* B*, and therefore enlarged. As a proof that the image caused by a convex lens is always apparently more remote than the object itself, look at a piece of paper through the lens, and attempt to touch the edge of it with the point of a needle. The needle will invariably be directed some distance beneath the paper. Such convex lenses are usually called loups, so long as their magnifying power does not exceed 15 or 20 diameters, and so long as during their use they can be guided by the human hand. When the magnifying power of such lenses is greater, so that a stand is necessary to support them during their use, the combination is called a simple micro- scope. The impossibility of making a sharp line of de- marcation between the two kinds of instruments is self- evident, as weak convex lenses are also fastened to a stand, and numerous so- called loup-supporters are also employed (tig. 5). There are many varieties of loups, but we must refer to more detailed works for their description. Their value and applica- Fig. 0. Nachot'H simple loup-Btand. THEORY OF THE MICROSCOPE. 5 tion in natural philosophy is also too well known to render it necessary for us to say more on the subject. A good loup, magnifying 10 or 15 times, is indispensable. The simple microscope of Plossl, of Vienna, is seen in fig. 6. A metal bar (a) supports, at half its height, a horizontal plate which is bored through its centre, the stage (&) of the micro- scope. This can be elevated or depressed by means of the rack (c). The movable mirror (/) placed beneath, serves to reflect the light on to the object to be examined, which is placed on Fig. 6. Plussl's simple microscope. Fig. 7. Nachet's simple microscope. the stage. If, instead of transmitted light, it be desired to ex- amine the object by reflected light, after the manner of our usual vision, the mirror is thrown out of action, or an opaque plate is placed on the stage. The horizontal arm (d), on the upper extremity of the stand, carries the magnifying glass, the lens (e). It can be removed from the opening in the arm and replaced by another. The simple microscope of Nachet, of Paris (fig. 7), likewise has a convenient form. The movement is made by a rack, which elevates or lowers the lens, in contradistinction to the stand of Plossl, in which the stage moves up and down. Two additional plates on the stage, bent downwards, serve as sup- ports for the hands during the manipulation. Both instru- ments have clamps on the stage, for the purpose of fixing the object. 6 SECTION FIRST. The simple microscope is now-a-days indispensable to the natural philosopher, as an instrument for dissecting. It is, however, no longer, or but little, employed for scientific inves- tigations. When a tube is placed over the magnifying-glass of the simple microscope, and the object is placed somewhat beyond the focus of the lens, an enlarged, inverted image of the same is projected within the tube. In fig. 8 we can readily perceive this relation. If we con- nect the lens L with a fun- nel, whose diameter ex- tends from e* to d*, we may receive the image on a ground-glass plate. When this aerial image is again enlarged by means of a convex lens, we have the compound dioptrical microscope. The differ- ence between these two in- struments consists in this, that in the simple micro- scope the object itself, in the compound, on the con- trary, the enlarged image of the object is seen. Our fig. 8 may represent the compound microscope in its simplest form. The united cone of rays c* a* 5* diverge from the eleva- tion e* d* to the upper lens, from whence, after their refrac- tion, they arrive, under a slight divergence, at the human eye. At the same time, however, we find that the cone of rays which proceed from the terminal points d and e of the arrow, are united at d* and e*, they do not arrive at the upper lens. We perceive, therefore, in our example, only the length b-c of the arrow. A smaller arrow, circumscribed in this dimension (see 4 c Fig. 8. The compound microscope in simplified form. THE0EY OF THE MICROSCOPE. 7 lower part of fig. 8), would, on the contrary, be distinctly seen. The dotted lines, which pass to c** and &**, the prolongation of the rays refracted by the upper lens, give, at the same time, the apparent size under which the arrow b c is seen. An explanation of the image c* a V: &* of the arrow is neces- sary, in one other regard ; it appears curved, while the arrow itself is straight. If we hold it as established that the point of union of a cone of rays falls farther behind the lens from a near object than it does from one lying more remote ; and if we re- member that b and d, c and e are situated farther from the op- tical middle point than a, then we can readily understand why the surface of the image is curved. The knowledge of magnifying-glasses and the art of grind- ing them already existed in antiquity and the early middle ages. The invention of the compound microscope occurred, on the contrary, at a considerably later epoch. There is no longer any doubt that an humble Hollandish spectacle-grinder, Zach- arias Janssen, of Middelburg, probably about the year 1590, produced the first instrument of this kind. Other authorities mention, without sufficient foundation, the Netherlander, Cor- nelius Drebbel, Galilei and another Italian, Fontana, as the discoverers. Harting, with his usual carefulness, investigated this question of the invention several years ago. The oldest compound microscopes were, however, very in- complete instruments, and were encumbered with great optical dehciences. These imperfections rendered themselves suffi- ciently perceptible with weaker powers, and attained, with somewhat stronger glasses, such a rapid increase as to render the whole combination nearly useless. In order to understand this, we must recall to our minds a few well-known optical principles. The term angle of aperture of a lens denotes the angle which is formed by the focus and the two r terminal points of v the diameter of the )-, lens. Thus, g f U is the angle of aper- ture of our fig. 9. Only so long as this angle remains small, do the peripheral and central rays actually reunite in a point, as we have thus v Fig. 9. Spherical aberration. 8 SECTION FIRST. far, for the sake of greater simplicity, assumed. When the angle of aperture is greater, only those rays of light (BB) which are nearly parallel to the axis (A) of the lens, and which pass through its central portions, are united at the focus F, while those rays (CO) which pass nearer the periphery of the lens are more strongly refracted and find their focus already in/. This property of refraction is called the spherical aberration. If we cause the rays which proceed from a small luminous body to pass through such a lens, we receive at F the image projected by the central rays. It is not sharp, however, but is surrounded by a halo or circle of diffusion, caused by the periph- eral rays, which have become divergent again. If we apply a dark disk with a circular opening, a so-called diaphragm or stop DD, the peripheral rays are intercepted, and we receive a distinct though faintly illuminated image at F; also at/', when we obstruct the central rays, and thus permit only the peripheral rays to pass through the lens. Such annular dia- phragms are extensively employed in practical optics, for the purpose of improving the images. We here mention another, for the theory of the microscope, important effect of this spherical aberration. When very small cones of rays arrive at a convex lens of considerable diameter, as is the case with the ocular O in tig. 8, those which pass through the periphery of the lens necessarily receive a stronger refraction than the more central ones. The peripheral points of the image must, accordingly, appear nearer each other than _ / ^=ppp X / \ /-I ! \ [ \ / \ : / ^/ "*-j — i — -j- Fig. 10. Quadratic net-work. Fig. 11. Image distortion. Fig. 18. Imago distortion. the internal portions. A wire net-work, tig. 10, presents an aerial image, such as is represented by fig. 11. If we observe the quadrangular net-work through such a loup we receive a diametrically opposite phantom, after the manner of our fig. 12. In both cases arises, therefore, a distortion of the image. THEORY OF THE MICROSCOPE. A second not less palpable inconvenience in the use of such lenses arises in consequence of their chromatic aberration. A ray of white light (fig. 13, B or C), in passing through a A ~~\ C . H ^-""^ Fig. 13. Chromatic aberration. convex lens would not be refracted as a whole, but would be decomposed into rays of various colors, which suffer deviation in varying degrees in the direction of the plane of refraction, and thus form a spectrum, at one extremity of which the strongest refracted, the violet («), and at the other, the least deviated, the red ray (r) appears. From what has just been said it follows, that with ordinary convex glass lenses we perceive the object indistinctly defined and surrounded with colored borders. Both faults increase rapidly with the increase of curvature of the lenses. The older microscopes, therefore, produced images which were faintly illuminated, insufficiently defined, and surrounded with colored borders. The image projected by an imperfect object lens was still further magnified by the likewise imper- fect ocular lens. Achromatic lenses have now taken the place of the old use- less glasses. By this name is indicated such with which the foci of the various colored rays of light are united, in other words, those which show the object free from colored borders. The powers of refraction and of dispersion are not united in equal proportions in any single refractive medium, as has been known for a long time. One medium gives, in the same power of refraction, a greater deviation to the colored rays than an- other. There are two different kinds of glass which act in this manner with regard to each other — crown-glass and flint-glass. The latter is partly composed of lead, and has a considerably greater power of dispersing the colored rays than the former. If we combine a bi-convex crown-glass lens with a plano- concave flint-glass lens (both are generally cemented together with Canada balsam) we obtain a combination in which the re- 10 SECTION FIRST. Fig. 14. Achromatic lens. fraction of the convex crown-glass lens is lessened, but not de- stroyed, by the dispersive action of the flint-glass lens. At the same time, however, the color dispersion (v r, iig. 14) of fclie crown-glass lens is /"W1 ^<> neutralized by the contrary action of the flint-glass lens, so that the violet and red rays are accu- rate^ united in P, at the central focus of the lens. The image here produced will either be colorless or have its natural color. Such a combination presents, at the same time, an expe- dient by which the spherical aberration may also be substan- tial^ improved. A double lens, with which the spherical as well as the chro- matic aberration is annulled, is usually called aplanatic. But in reality it is impossible to completely obviate either the spherical aberration (for reasons, to discuss which here would lead us too far) or the chromatic, for even when the violet and red marginal rays are made to unite, the ratio of the disper- sion of the various colored rays of the spectrum is never en- tirely equal. Should, therefore, even with a double lens, the violet and red ra} r s of light be united, the edges of the image would still exhibit traces of the ununited central rays of the spectrum. The edges appear greenish yellow. It is customary, therefore, in the construction of double lenses for the microscope, to give a slight preponderance to the flint-glass lens, so as to obtain a bluish tinge, which is more agreeable to the eye ; the double lens is then said to be over-corrected. A double lens is under- corrected when a reddish border is perceptible. As, in regard to color dispersion, one speaks of over- and under-correction, the same mode of expression is also used in speaking of the correction of spherical aberration. While the discovery of achromatism had alreadj^, in the middle of the previous century, led to the production of im- proved telescopes, the smallness of the object lens discouraged the microscope-makers from making the same experiment on the latter. According to Harting's statement, the Hollander, Hermann THEORY OP THE MICROSCOPE. 11 Van Beyl. produced the first achromatic microscope, in a very satisfactory manner, in the year 1807. Four years later, Fraunhofer, the renowned optician of Munich, supplied achro- matic instruments. In the year 1824 the two Chevaliers of Paris, under the direction of Selligue, combined for the first time several achromatic objective lenses into one system. The Italian Amici, of Modena, then acquired an immortal renown in the sphere of microscopical improvements. Other opticians followed him with worthy emulation, among which, for the end of the first half of the present century, we will particular- ize only PlossL of Vienna ; Schiek, of Berlin ; and Oberhau- ser, of Paris.' The instrument soon became as useful and com- plete as that of the eighteenth century was unserviceable and incomplete. The commencement of the great and brilliant era of modern microscopy is cotemporary with these improvements of the instrument. But the recent past has also presented many permanent and important improvements, as we shall hereafter see. Let us return, however, to the mechanism of our instru- ment. If we glance at fig. 8, we shall perceive that the image of the arrow produced by the achromatic lens is now free from colored borders and the spherical aberration essentially cor- rected, but the incurvation and distortion of the same, as well as the diminutiveness of the field of vision, that is, the plane surveyed by the eye-piece, remains as before. Among the accessories which are employed for further cor- rection is a very old one, namely, the introduction of another convex lens into the tube of the microscope. This, fig. 15, C, is placed between the objective L and the ocular O, so, how- ever, as to occupy a position beneath the point of union c* a* b* of the cones of rays refracted by the objective lens from the object. The advantage obtained by the introduction of such a con- vex lens or field-glass is manifested in various ways. Firstly, the rays proceeding from the points b and c of the arrow are refracted by the convex lens towards its axis, as may be seen in the figure. Without the field-glass the image would be pro- jected at c* a V: 6* too much extended to be surveyed from the ocular lens. An image is now projected at c** a** &**' which, though not so large, still comprises the entire arrow. Secondly, 12 SECTION FIRST. the clearness of the image is increased by the held-glass, as all the rays, which, without this lens, would have produced the image c* a* &*, are now united in the smaller space of the image c** a** b**. Thirdly, such a held-glass, in connection with the ocular, may serve to improve the correction of the spherical and chromatic aberration. Fourthly— and in this lies Fig. 15. The compound microscope with a field-glass. a great advantage — the field-glass obviates the distortion of the image and the unequal enlargement of the various portions of the field of vision connected with it. As we have already learned, the rays passing through the marginal portions of the lens are more strongly refracted than those passing through its central portions, in consequence of the spherical aberration, THEORY OF THE MICROSCOPE. 13 and the axial and peripheral points of the image approach each other proportionately (fig. 11). Now, as the ocular lens, for observing the aerial image c** a** &** exerts exactly the con- trary effect (fig. 12) by its considerable diameter, the entire correction may be obtained by the proper nse of an ocular and a field-glass (fig. 10). These various, and, for the most part, highly important ad- vantages secured by the addition of a field-glass render it appreciable that the latter is no longer omitted in any of the compound microscopes of the present time, and that it has be- come an integral element of all its combinations.* We have remarked above that, since the year 1824, the in- dividual achromatic double lenses are combined with each other into, so-called, systems. Various advantages are thereby obtained. It is very difficult to construct a double lens of crown and flint glass with a short focus, while several weaker ones combined give the same magnifying power as the simple objective, and are much easier to make. Then, as we have also seen, by the combination of a single crown and flint glass lens, whereby, also, a small angle of aperture must always be given to the lens, the spherical and chromatic aberration are essen- tially lessened, but not entirely obviated. By a«suit- able combination of several double lenses, where the aberrations of one lens are made to correct the op- posite ones of another, a considerable further cor- rection is obtained, and a much larger angle of aper- ture may be used ; in this manner the greatly im- JS^V^ proved lenses of our microscopes of the present day ture ' are produced. In these only two, or, at most, three double lenses are combined with each other (fig. 16). The earlier opticians generally designated the several double lenses by a series of numbers, 1, 2, 3-6, the weakest bearing the lowest number, and screwed them together into a system (for example, 1, 2, 3, and 4, 5, 6). In this way, with a moder- ate number of single lenses, a series of systems may be con- structed, it is true ; but two things which are of greater impor- * E. Abbe, of Jena, has recently attempted to modify the theory of the compound microscope. He divides the total effect of our instrument into a lower Ioup action and an upper telescopic action. For many purposes this plan is certainly convenient ; we doubt, however, that it will accomplish much. Pih. 16. An achromatio ob- 14 SECTION FIRST. tance, the accurate centering (that is, the falling together of the axes of the lenses in a single straight line) and the proper dis- tancing of the single lenses from each other, cannot be so ac- curately accomplished as where these are permanently com- bined with each other in systems. The preference has, there- fore, very properly been given to the latter arrangement, and, though the former is the least expensive, it should be entirely discarded. The permanent systems are variously designated by the opticians ; either by numerals increasing with the strength of the combination, or by a series of letters. The manner of expression of the English opticians is peculiar. They speak of I--, s-, tV> Hf °f an incu combinations of lenses, making the in- crease of the strength of their systems the same as that of a simple lens of i, i, T V, Jt mcn focus. The stronger modern lens systems are, at present, differ- ently arranged. The lower, nearly semiglobular crown glass lens (with the plane surface turned downwards) is combined generally with two, more rarely three strongly over-corrected crown-flint glass lenses. The combination of the lenses with each other is arranged so that the strongest, smallest lens (end or front lens) turns downwards, the weakest upwards (fig. 16). A somewhat greater focal distance is thus obtained, and such angles of aper- ture may be given to the lenses, that all the rays of a cone of light c a l> received by the lower lens may also pass through the entire combination of lenses. Only in this way has it been possible to give the above-mentioned high angle of aperture to the objectives, which must naturally increase the brightness of the image, and besides, as we shall see hereafter, considerably increase the intrinsic power of the combination also. The ordinary eye-piece of our microscopes (fig. 17, O), also called the Huyghenian or negative eye-piece, consists of a longer or shorter tube carrying at its upper end the plano-con- vex lens A, whose plane surface is turned towards the eye of the observer, while the plano-convex lens C, with its curved surface also turned downwards, is screwed into the lower end of the tube. The aerial image P* falls, as we have seen, be- tween the held and ocular glass. Every microscope is supplied with several such eye-pieces of various strengths, designated by numbers. The eye-pieces become shorter in proportion to the increase of their magnifying power. Another form is called THEORY OF THE MICROSCOPE. 15 the Ramsden. or positive eye-piece. It also consists of two plano-convex lenses ; but their curved surfaces are turned towards each other, and they lie nearer together. Here the image does not fall between the held and ocular glasses, a but lies at a short distance beneath the former. The latter eye-piece is, however, but little used. Kellner' s orthoscopic eye- piece is a modification of that of Huyghens, or the nega- tive ; its field-glass is bi-con- vex. It presents a very large field free from image distor- tion, without, however (and in this I must agree with Harting), appreciably in- creasing the optical power. Hartnack has recently constructed a new, strong eye-piece, the oculaire liolos- tere. It consists of a sin- gle conical- shaped piece of glass, after the manner of the Coddington lens, and mag- nifies about ten times. It has thus far, however, presented me no considerable advan- tages. In order to render the Huyghenian eye-piece as free as possible from spherical and chromatic aberration, it has been proposed to make it aplanatic and to combine it with an aplanatic objective system. Such aplanatic eye- pieces are to be found with many instruments. Their magnifying power is weak and the field of vision small. The compound microscope. 16 SECTION FIRST. The usual arrangement is different. It consists of the use of eye-pieces which are by no means entirely aplanatic, and the aberration present in the eye-piece is made to correct the oppo- site aberration of the lens system. Objectives of somewhat over-corrected chromatic, and also spherical aberration are combined with under-corrected eye-pieces. An objective which was rendered as aplanatic as possible would, on the contrary, if combined with one of the ordinary eye-pieces, produce an imperfect image. While therefore aplanatic lenses are neces- sary for the loup and the simple microscope, the art in the production of a compound dioptrical microscope rests directly in the removal of the aberrations of the objective by means of the contrary aberrations of the eye-piece. It is only thus that an image free from defects may be obtained, in a manner sim- ilar to that already mentioned of correcting one double lens of an aplanatic system by means of the other. In eye-pieces the distance of the field-glass from the ocular lens is of importance. If the former glass is made to approach the latter, the aerial image is greater ; if the latter glass be made to approach the former, it is smaller. The opticians, as a rule, fix both the glasses of an eye-piece in an unchangeable position ; they select the ones offering the most advantageous action. The length of the tube of the microscope, which in increasing also increases the magnifying power, is likewise of importance to the advantageous combined action of the ocular and objective systems. Less increase in the length of the microscope tube is permissible with a higher degree of over- correction of the lenses than with a weaker one. Still another element is associated with the optical relations enumerated, for a knowledge of which we have to thank Amid. At the present time it receives due attention, whereas for a long- time it was entirely ignored. We refer to the thickness of the scale of glass with which it is customary to cover the object for microscopical examination. The thickness of the glass cover exerts considerable influence on the sharpness of the ima<;-e, especially when strong lenses are used. An object which, un- covered, or with a very thin glass cover, presents a sharp image, becomes somewhat dim and foggy, and the appreciability of its details diminishes, if a thicker cover be used. Inversely, many lenses only manifest their highest capabilities when a covering- glass is used. THEORY OF THE MICROSCOPE. 17 Now, on what does this influence of the cover depend, and what are the means for its correction % Let P, fig. IS, be a thick glass plate, and a a point of light from which proceeds a cone of rays. The rays on entering the glass will be re- fracted in various degrees. The ex- ternal, most ob- liquely incident rays a f and a g will be the most strongly refracted and will assume the directions ./',/'* and g g*. the more internal rays a d and Fig. 18. Effect of the covering-glftsa. a e will be less influenced, and the more central rays a b and a e will be still less deflected from their course. On from the fflass the most external rays are refracted in the direction f*f** and g* g**, the more internal ones in the direction d* d** and e* e**, and those most internal in the direction 5* &** and c* c**. The luminous spot will appear to the eye as though it were seen nearer in the glass, and instead of one luminous point a series of points lying over each other will seem to be present ; as h for the rays b and c, i for d and e, k for f and g. If, instead of a point, we have an object, it will make an impression as if it consisted of a series of images lying over each other. We receive, therefore, the same effect as from spherical aberration, and in a degree which increases with the thickness of the glass covers. It will therefore be appreciable how imperfect such a course of the rays of light must render the image of an object with a lens which is arranged for uncovered objects ; for the same reason, an objective constructed by the optician for a covered test ob- ject will only develop its perfect action when a suitable cover is used. Weaker combinations manifest this influence of the glass covers only in a minor degree, however ; stronger ones, on the contrary, in a very appreciable manner. This influence of the cover may be counteracted by chang- ing the length of the microscope tube, and also by altering the distance between the ocular and field glasses. It is advisable, in a practical point of view, to use a system with its appropri- 18 SECTION FIK8T. ate covers only, and to Lave special thicknesses of glass for each system. Another method is now becoming more generally adopted. By changing the position of the individual lenses of a combina- tion this action of the glass cover may be obviated, and thus one and the same system may be employed either for uncovered objects or for such as have covers of various thicknesses. For this purpose the individual double lenses of a system are ar- ranged so that their relative positions may be changed by means of a fine screw ; thus the observer is enabled to make the neces- sary change at any moment. Such combinations are called objectives with correcting apparatus. They are naturally more expensive than ordinary objectives and require in their use a certain amount of practice and some outlay of time, but the arrangement is almost indispensable for very high powers. The rule is, that with increasing thickness of the cover the individual lenses of the system must be brought nearer to each other, while for very thin covers they must be moved farther apart. In fig. 19, the objective represented with a correcting ap- paratus has a small metallic slider, which, mov- ing up or down, indicates the various positions of the lenses. Fir,. 39. Art™- Having familiarized ourselves with the objec- rarrectinr'applra 11 - tive and the eye-piece, we are now in condition to examine more closely the construction of a mod- ern compound microscope. The optical portion is of the greatest importance ; the arrangement of the stand is, on the contrary, of much less con- sequence. Good lenses with suitable eye-pieces, placed on a very imperfect stand, would enable an observer to recognize subtile structural conditions which would be concealed from another, whose instrument combined an imperfect optical ap- paratus with a very superior mechanism. Nevertheless, dis- regarding the tediousness of the manipulation, poor, incomplete stands exert an immediately injurious effect on the optical per- formances of a microscope, by not permitting of the necessary modifications of the illumination. Every modern instrument requires several objectives ; name- ly, a weak, a medium, and a strong one ; the combinations of each should, preferably, be permanent. Large microscopes THEORY OP THE MICROSCOPE. 19 A B ?" JL have a more abundant supply of objectives, five or six, and even more, and among them the most powerful ones, in the production of which great proficiency has been developed of late, as we shall see further on. These very high powers are not required for ordina- ry investigations, and can, therefore, be more readily dispensed with than combi- nations of medium strength. A few eye-pieces, at least two, are necessary; a weak one, magnifying about three or four times, and a stronger one of double that strength. It might readily be be- lieved that a considerable number of eye-pieces with increasing, and, finally, with very high magnifying power, would be of advantage to our instrument. But this is erroneous. Let us remember that an enlarged image would be projected by the objective L, fig. 20, into the tube R, and would not be without defects, as it is im- possible to produce mathe- matically correct lenses. The image would be magnified by the eye-piece, and, nat- urally, its imperfections in the same proportion also. The eye-piece does not, therefore, like the objective, permit us to penetrate more deeply into the structure of the object ; it only enlarges the images of the latter. The use of somewhat stronger eye-pieces has the advantage, how- ever, of enabling us to recognize many things more readily, Fig. 20. 20 SECTION FIRST. because they are more enlarged. But in using still stronger eye-pieces, we soon arrive at a limit where the image is impaired. The most beautiful and elegant images are obtained witli very weak eye-pieces. Nevertheless, many of the more modern lenses bear considerably stronger eye-pieces than those of a former epoch, which must always be regarded as a proof of superior optical perfection. No further observations are necessary, therefore, to show that it is impossible to compensate for the poverty in lenses of a microscope by a profuse endowment of eye-pieces. It is also evident that the value of an enlargement, obtained with a stronger objective and a weaker eye-piece, stands higher than that of another, where a strorjg eye-piece is used with a weaker objective. Older German microscopes frequently have only weak objectives, but are, on the contrary, furnished with sev- eral eye-pieces of too great strength. This is to be regarded as a fault. At the commencement of the fifth decade of this century, for example, the instruments of Schiek compared very disadvantageously, in this regard, with those of Oberhauser. The tube of the microscope, as well as that of the eye-piece, has its inner surface blackened, and is either in one piece (fig. 20, R), and therefore incapable of extension, or it is composed of two pieces which glide over each other, after the manner of the telescope. That the latter is to be regarded as the better arrangement is proved by several previously mentioned optical principles. An immoderate elongation of the ocular tube is likewise attended with optical disadvantages. The objective (L) is to be fastened on to the lower end of the tube by means of a screw. The stage (T) is the metal plate perforated in its centre, already described in speaking of the simple microscope, for the reception of the object (P. E.) to be examined. The stage should not be too small, and especially not too narrow. Objective and object must be capable of being moved from or towards each other, as circumstances may require. All com- pound microscopes have arrangements for this purpose, that is, for focussing the object. Shoving the microscope tube with the hand through a metal sheath is a very primitive contriv- ance, and is only practicable with weak powers. Various expedients are employed for more accurate altera- THEORY OF THE MICROSCOPE, 21 tion of the focus. This may be accomplished, to a considerable extent, by means of a single mechanism, when the latter is carefully constructed. In fact, the older instruments fre- quently have no other. As a rule, the tube of the microscope is made to screw up and down on its support ; less frequently employed, and still less to be recommended, is a movable stage, the tube being immovable. With the more carefully constructed modern stands a double mechanism is provided, one of which serves for the coarse, and the other for the fine adjustment. Such a distri- bution of the work naturally deserves the preference. The coarser movements are made either by machinery, or, what answers just as well and is more practicable by reason of its greater simplicity, the tube of the microscope may be moved in a sheath which surrounds it, by the hand. The finely con- structed micrometer screw, which moves the microscope, is used for more accurate focussing ; the practised observer almost never removes his hand from it in making delicate in- vestigations and when using the higher powers. Ordinary incident light is rarely used for the illumination of the object, and then only when the lowest powers are em- ployed. When strong illumination is required, a convex lens (a, fig. 21) with a long focus is employed. It should be movable in various directions, and placed either on a stand d b c, or on a ring which is to be shoved over the tube of the microscope. Objects are most frequently illuminated by means of transmitted light, the light being re- ceived on a mirror (fig. 20, S) placed beneath the stage, and reflected through the opening to the object (P). The mirror must be fastened to the stand in such a manner as to permit of the greatest free- dom of movement. The arrangement of many of the smaller instruments, permitting the mirror to move around its horizontal axis only, is an impor- tant imperfection. Small microscopes have only a concave mirror, by which the incident rays (a a) are reflected in a convergent direction (b b) to the hole in the stage. Larger instruments have a mirror with one of its sur- faces concave and the other plane. The latter surface gives a Fig. 21. Illumi- nating lens. 22 SECTION FIRST. less intensive illumination than the former, and is, therefore, more frequently used with the weaker powers. Careful illumination is a very important accessory in micro- scopical examinations, and is not to be obtained with the above- mentioned contrivances alone. Other special apparatuses are consequently necessary. For many examinations, especially of delicate, finely bordered objects, the light reflected through the opening of the stage would give a much too dazzling illumi- nation. A portion of the rays must therefore be cut off. This is accomplished by diminishing the opening of the stage ; for this purpose the so-called screens or diaphragms are used. Two forms are employed ; the rotary and the cylindrical diaphragm. The rotary diaphragm (a, fig. 22) has a circular form and is fastened under " the stage by means of a button. A series of circu- lar openings diminish, with the exception of the largest, the aperture of the stage. The smallest holes are em- ployed with the highest powers. Cylindrical diaphragms are cylindrical tubes which have at their upper ends a circular disk with an opening of varying size (fig. 22, 6, c). They are inserted into the opening of the stage, either imme- diately or by means of a socket. To develop their complete action, some contrivance is necessary, by means of which they can be raised or lowered. Both arrangements accomplish their objects ; but the cylin- drical diaphragm deserves the preference, as it permits of finer gradations of illumination. On many of the older instruments we find both these kinds of diaphragm combined. For many purposes, instead of the ordinary illumination, generally called central light, it is necessary to reflect the light from beneath in a more or less oblique direction on to the ob- ject, called oblique illumination. For this purpose, the minor should have the utmost freedom of motion, because it is some- times necessary to give it a very lateral position. A further modification of the illumination is obtained by in- Fig. 22. Diap!ira. APPARATUS FOR MEASURING AND DRAWING. It is unnecessary to mention how important the measuring of objects seen under the microscope is for scientific work. In fact, various and, in part, ingenious methods were proposed in the infancy of microscopy for determining the size of objects. The reader will find more on this point in the excellent work of Harting. At the present time, we have measuring apparatus of rela- tively greater accuracy. Two forms of micrometers are to be particularly discriminated ; namely, first, the screw microme- ter, and, second, the glass micrometer. The screw micrometer is a somewhat complicated but, when the workmanship is good, very accurate, and, therefore, also very expensive implement. Its arrangement rests upon the following. If a cobweb thread is drawn across the eye-piece, it is self-evident that a microscopical object may be so guided through the field of vision, by means of a stage moved by screws, that its anterior border first cuts the thread, and then gradually passes bej^ond it, till at last only the posterior mar- gin of the object exactly touches the thread. Now, the screw micrometer is such a movable stage. It has a double plate, the upper one of which is movable, by means of a very fine micrometer screw, over the lower one, which is fastened to the stage of the microscope. A partial view of this arrangement is afforded by fig. 25, 1. The extent which it is necessaiy to turn the screw, in order to move the object, in the manner in- dicated, through the field, may be read from the index of the upper plate and the divisions on the drum of the screw. The unities of these screw micrometers vary. Those of Plossl give ri) l m of a Vienna inch, those of Schiek, Tir V T and -j-oJ-^ of a Parisian line. The ocular screw micrometer is an advantageous APPARATUS FOR MEASURING AND DRAWING. 33 modification of the screw micrometer, especially the improved form described several years ago by Mohl. Nowadays, however, the expensive screw micrometers are rarely used ; the much simpler and less expensive glass micro- meters are used in their stead. It is well known that the art of engraving fine divisions on a glass plate, by means of the diamond point, has made great strides, and in a later section we shall see the marvellous mani- festation of this skill in Nobert' s test plates. The line is now divided, with the greatest elegance, into 100, 500, and 1,000 parts. In some of these micrometers the lines are all of equal length ; those are better in which the greater divisions are indicated by longer lines, as is the case with our ordinary rules. A modification, which is convenient for many purposes, consists in the crossing at right angles of one series of lines by a second series, generally so that quadratic spaces resul t. JSTow, such micrometers are capable of the simplest appli- cation as object bearers. Let us assume that we have a divi- sion where the value of each space is T J n '", it is self-evident, that a microscopical object which occupies two of these spaces is Tj-lnj'", and another, which covers five, is 1 fo'" in size. However efficient these methods may seem, at the first glance, to be, they are nevertheless very inconvenient, and it is therefore no longer customary to use them. First, because the minuteness of many objects requires a very finely divided and therefore very expensive micrometer. Then, in cleaning them they become injured in a comparatively short time, and gradu- ally become seriously impaired. Further — and this is of much greater moment — the objects to be measured very often lie obliquely, and not parallel to the lines, however fortunately they may be placed on the micrometer. Finally, the case of- ten arises where it is necessary to estimate the value of a frac- tion of a space, whereb}^ the eye may be deceived. From the above mentioned it will be conceivable that the glass micrometer, in the form of an object bearer, has been dis- carded except for certain special purposes. These micrometers are now placed in the eye-piece, as ocu- lar micrometers, in the form of circular glass plates. They lie on its diaphragm, between the field glass and the ocular lens (fig. 20, B). 34 SECTION SECOND. Such, ocular micrometers (fig. 41) have naturally quite a dif- ferent action. When the glass plate lies on the stage, the divisions and the object are equally enlarged by the entire dioptrical apparatus of the instrument. In the latter case, that is, when placed in the eye-piece, the micrometer is enlarged by the weak ocular lens only, and appears to the eye simultaneously with the image of the object to be measured, which is enlarged by the objective and again somewhat diminished Eye-piece mi- b} r the field glass. This may be accomplished with glass micrometers which are coarser, and therefore more accurate, and also less expensive to con- struct. They do not wear out, and any object in any position on the slide may be instantaneously measured, so soon as the eye-piece containing the micrometer has been substituted for the ordinary one, and adjusted by turning it in the tube. But with more opaque objects an inconvenience arises in the diffi- culty of seeing the micrometer divisions over the object to be measured. No microscope should be without such a microm- eter, which may be obtained for a few (4-5) thalers. In con- sequence of the unequal visual distances of different observers, it is necessary to vary the adjustment of the ocular micrometer by means of a screw arrangement, so that it and the object may simultaneously appear alike distinct to any eye. It should not be forgotten, in using the eye-piece microme- ter, that its value is a relative one, depending on the strength of the objective used (therefore variable with immersion lenses), and the length of the microscope tube, which always determines the size of the image. It is most advantageous to have the lat- ter completely drawn out when measuring. We have a very simple procedure for determining the value of the micrometer in the eye-piece ; we avail ourselves of the aid of a glass micrometer on the stage. Assuming that it has a Paris line divided into 100 portions ; with the objective A, perhaps five spaces of the eye-piece micrometer will exactly cover one space on the stage micrometer ; the value of one of its spaces for the objective A is therefore xfa'". To obtain greater accuracy, various portions of the stage micrometer should always be used for the measurement, and the mean of 10-15 single measurements drawn. Always keep in the middle APPARATUS P0R MEASURING AND DRAWING. 35 of the field to avoid any distortion of the image that may be present. In this manner the value of the eye-piece micrometer for the various objectives of a microscope is reckoned and tab- ulated. Besides this most simple eye-piece micrometer, serving completely nearly all the purposes of measurement, various other modifications have been produced, but we cannot at present enter into their consideration. Those who are inter- ested in the subject may read the respective section in Har- ting's work. All statements as to the size of microscopical bodies natur- ally depend upon the unity of measure on which they are based. Microscopists, as a rule, use the measure in general use in their country ; those of England use the English inch, which is divided into decimal and duodecimal lines ; those of France use the Paris line or the millimetre. In Germany one of the two last mentioned unities of measure is generally used, though the Vienna and Rhine lines are also used. The Paris measure is most convenient, and the millimetre deserves the preference. It is very convenient to use the thousandth part of a millimetre as a unity, under the name of micromillimetre, mmm or p, as proposed by Harting. There is no actual ad- vantage in this ; it is merely convenient from its brevity. A millimetre is 0.4433 of a Paris line. 0.4724 of an English duodecimal line. 0.4587 of a Rhenish line. 0.4555 of a Vienna line. The Paris line is 2.2558 millimetres. " English " 2.1166 " Rhenish " 2.1802 " Vienna " 2.1952 " . For further comparison we give a small table for reducing Paris lines to millimetres and vice versa. Millimetre. Paris lines. Millimetre. Paris lines. 1. — 0.4433 0.4 = 0.1773 0.9 = 0.3990 0.3 = 0.1330 0.8 — 0.3546 0.2 = 0.0887 0.7 = 0.3103 0.1 = 0.0443 0.6 = 0.2060 0.01 = 0.0044 0.5 = 0.2216 0.001 = 0.0004 SECTION SECOND. ris lines. Millimetres. Paris lines. Millimetre. 1. = 2.2558 0.4 = 0.9023 0.9 = 2.0802 0.3 = 0.6707 0.8 = 1.804? 0.2 = 0.4512 0.7 = 1.5791 0.1 = 0.2256 0.6 1.3535 0.01 = 0.022G 0.5 1.1279 0.001 = 0.0023 Fig. 42. C. Schmidt's goniometer. a b c, graduated disk ; &, nonius at the border of the eye-piece p ; e, lens fur reading off. The goniometer is an apparatus used for measuring the angles of crystals. A simple and efficient arrangement (fig. 42), contrived by C. Schmidt for this purpose, consists of the following : —A circular plate, a b c, divided into thirds of a degree, is placed around the (fixed) microscope tube, at its upper end. To the outer edge of an eye-piece (p), provided with a crossed thread, a vernier (d) is fastened. The an- gle of the crystal to be measured is brought to the centre of the cross, and the threads are made to cover both sides of the angle in succession. The extent which it is necessary to turn the eye-piece in order to effect this is read off at the vernier, above which a plano-convex lens ( a nd the highest, No. 18, to fa", of the English. Still stronger systems have been recently constructed in England, according to our views, without benefit ; for with a No. 11 or 12 of Hartnack's establishment we have arrived toberably near the present limits of practical optics. It is, self-evidently, of great practical value to find objects which are as homogeneous as possible, and of such delicate and line texture that, in their resolution, the optical, or, more cor- rectly speaking, the penetrating power of a lens may be accu- rately estimated. They are called "test objects." Their study is of interest and importance. To the beginner, who is desirous of ascertaining the capacity of the instrument which, perhaps, he has but recently obtained, such test objects are to be recom- mended as discipline ; since their resolution is by no means easy, and with them the accurate adjustment of the focus, and the skilful application of the illumination, may be learned. Some of these test objects, the finer ones, are so difficult as to occupy the beginner for hours in vain, and may occasion much labor even for the practised. By careful practice one may arrive at a certain virtuosoship, and thus, in a few minutes, appease the novice, who possibly begins to despair of his instru- ment, by showing him an example of what it is capable of per- forming in skilful hands. Then the endeavor to discover finer and more difficult test objects, thus always holding a higher aim before the optician, has led to the great emulation existing at TESTING THE MICROSCOPE. 61 the present time in the construction of objectives. It is there- fore unjustifiable to regard the study of such tests with con- tempt, as is occasionally to be observed among notable micro- scopists.* In the course of time, such test objects have been frequently highly commended and, with the increasing perfection of prac- tical optics, again abandoned. Therefore, all those which were recommended before 1S40, all the various hairs and scales of butterflies and wingless insects, f may be regarded as conquered territory. To attempt to test a first-class modern microscope with these expedients of a former epoch, would be an insult to the optician from whose establishment the instrument has pro- ceeded. In the year 1846, H. von Mohl, one of the first judges of the microscope, called attention to the brighter scales of the anterior wing of the Papilio JaniraQ, a knowledge of which he had obtained through the Italian, Amici, the most renowned constructor of microscopes of that epoch. Together with the familiar longitudinal lines, fine, closely approximated (^Vo mm. apart), sharp, and not granular transverse lines appear, fig. 60. Mohl remarked, at that time, that with a magnifying power not exceed- ing 200, nothing was to be seen of these trans- verse lines, and that it was necessary to have an instrument with very strong and very good lenses to recognize the transverse markings, sharply and distinctly, with 220 to 300 fold linear enlargement. He cited only the micro- scopes of Amici, Plossl, and a single one of r ' ' ° Fig. 60. Scale of Oberhauser, as at that time standing the test Pa P ili0 Janira - thoroughly. I still remember very well how I, as a student, with a, for that time, very serviceable Schiek's microscope, — my com- panion for many years, — was obliged to vex and trouble myself to obtain only a passable view of these transverse markings. * M. Schiff has expressed the same sentiments with regard to the value of test objects. We cannot agree, however, with many of his views regarding the diatoma scales. f It is well known that the trichina disease has, in our day, led to the production of an innumerable quantity of cheap instruments, intended only for the microscopic examination of meat. The well-known scales of the Lepisma Saccharinum, a wing- less insect, are useful for testing them. We shall refer to this subject at the exami- nation of the muscles. 62 SECTION FOURTH. Nowadays an instrument would be called bad which, with a magnifying power of 200, left anything to be desired in re- solving a Janira scale. By means of a large Hartnack instru- ment, made in the year 1861, I see them (in a test object coming from Kellner) without any precautionary measures, even with 120-fold enlargement (objective No. 5, eye-piece No. 2). At the present time, the scales of the Papilio Janira deserve to be regarded as a means of testing objectives of medium strength only. The silicious envelopes of the Diatomacese have taken the place of the butterfly scales ; those with the finest and most closely placed markings are employed.* The fineness of the markings may be represented in a table collated by Harting from English sources. The Pinnularia nobilis has from 4 to 6 striations in the tJ-jj of a millm, " Pleurosigma formosum it 12 to 14 .i it it u " " attenuatuni it 15 to 16 " " il u " " angulatum '< 22 to 23 " .1 li " Grammatophora marina " 25 ti it it tl " Nitzschia sigmoidea " 30 to 31 ii it .1 n " Navicula rhornboides (arEnis, Amicii) " 30 it K 11 it " Surirella gemma (lon- gitudinal lines) tt tt 30 to 32 ii it it ft " Grammatophora subti- lissima it 32 to 34 u " " Frustulia Saxonica " " 34 to 35 it if Ei Of the numerous Diatomacese there are several which de- serve mention as being of particular importance ; namely, — the Pleurosigma angulatum and Nitzschia sigmoidea, already mentioned in the table ; then, the Navicula Amicii, Surirella Gemma, and the Grammatophora subtilissima, made known by the deceased Professor Bailey, of North America. The last two objects (we have these always in mind, as they are to be obtained from Bourgogne of Paris) are extremely difficult, * Abbe has endeavored to show the effect produced here by the curving or diffrac- tion phenomena of the light. According to his views, such test images are not conformable to reality, and some modern lenses of gigantic power, of jfo to -j-/ focus, are superfluous articles of luxury. I am much inclined to admit that he is right, although I would place the effectiveness of our best lenses somewhat higher than he has done. According to my experience, we arrive at the limits by using a combina- tion which magnifies with a weak eye-piece 1000-fold. TESTING THE MICROSCOPE. 63 and in resolving them the microscope withstands a hard trial. Reinicke (Beitrage zur neueren Mikroskopie, 3. Heft. Dres- den, 1863) has called attention to the Frustulia saxonica, mounted in Canada balsam, as a very subtile test object. Its transverse lines do not stand very close to each other, but are very delicate and dim cult to perceive. At the last London Industrial Exhibition the Navicula affinis, mounted in Canada balsam, was used as a test object. Their longitudinal striations are re- solved without difficulty, while, on the con- trary, their transverse lines are very sharp and fine, so that I must pronounce their solution (in Bourgogne's preparations) more difficult than the Surirella Gemma and Graminatophora. Bailey has also recommended the Hyaloidiscus subtilis.* The Pleurosigma angulatum, fig. 61, fur- nishes, with oblique light, an excellent means of testing the resolving power of good objec- Flo . M . nem-osigma tives of medium and greater power, but should an(?ulatum ' expose all its delicate markings with a good immersion lens with simple central illumination. With oblique light this test object is entirely too easy for immersion lenses. If the examination of the Pleurosigma angulatum is com- menced with a weak objective, it appears smooth and without marking's. Passing, together with the application of oblique illumination, to stronger lenses, a period arrives when systems of lines sparkle forth, which run, in part, diagonally over the scale, in part obliquely and crossing each other. Sometimes * J. D. Moller, of Wedel, Holstein, has recently produced a very excellent but expensive Diatom test- plate. Each one contains 20 Diatoms, arranged according to their value as test objects, as designated by Dr. Grunow, namely : 1 . Triceratimn Favus; 2. Pinnularia nobilis ; 3. Navicula Lyra var. ; 4. N. Lyra; 5. Pinnularia in- terrupta var. ; 0. Stauroneis Phcenicenteron ; 7. Grammatophora marina (more coarsely marked than Bourgogne's variety) ; 8. Pleurosigma Balticum ; 9. P. acu- minatum; 10. Nitzschia amphioxys; 11. Pleurosigma angulatum; 12. Grammato- phora Oceanica subtilissima (marina) ; 13. Surirella Gemma (transverse lines) ; 14. Nitzschia sigmoidea ; 15. Pleurosigma Easciola var. ; 10. Surirella Gemma (longitu- dinal lines) ; 17. Cymatopleura elliptica ; 18. Navicula crassinervis, Frustulia Sax- onica ; 19. Nitzschia curvula ; 20. Amphipleura pelluciUa. Kodig, of Hamburg, also issues a similar Diatom plate. 64 SECTION FOUKTII. the one, sometimes the others of these lines are most distinct, according as the oblique light passes through the scale. They come forth gradually and quite sharp, and in fortu- nate cases one may distinguish all three — the two oblique ones cutting each other at angles of nearly 60° (not 53) — at the same time with perfect distinctness, all lying, according to my view, in the same plane. It is still believed that we have here to do with perfectlj'' straight lines. By using an immersion lens with central illumination, they appear to surround a series of extremely small and very delicate hexagonal areolations in close approximation, fig. 62. These A iQt i0 1$ i$ i$t <£i i$ (mt/ \j!@ i© $ © : ® '6 1© '© '©, 1ft \ \ )W ® I® l@ © '© ® © l© © I! \ jm >© # # <% * ri i© m © ;©T J® '(gl i0 «© I© © I© I© I® @ iigj [^1/ Cr® i© # ® ;© © «® i@ ® f ,gi rx " # ^ (# Hi [0 .© ® #£1" //"a if i n :«s (© I© © i .@ rx \\ tziZ-A^i P P p »' p P P lsaaa -^AtAAXX® ®j® P i® rx \\\ Fig. G2. Areolations of the Plcuro- ^igma angulatum; from a photograph. Fig. 63. Areolations of the Pleurosigma angu- latum. appear, according as the focus is altered, either dark ami sur- rounded by bright margins, fig. 63, or bright, with dark mar- gins, fig. 62. So much may be stated with entire certainty. Now arises, however, the difficult and by no means definitely settled question :— Are the areolations concave and their mar- gins elevated, or, on the contrary, are the latter furrows be- tween projecting area?? Both propositions have been sus- tained by distinguished observers. I formerly regarded the depression as probable, and also that the focus was correctly adjusted when the areolations appear dark. M. Schultze has also expressed the same opinion, in accordance with certain rules (see below) established by Weleker. I afterwards adopted the contrary view. This does not appear to be the place to enter further into this subject. A good objective, magnifying about 80 or 100 times, should, with the proper oblique illumination, enable one to recognize the systems of lines sharply and distinctly on all the scales ; TESTING THE MICROSCOPE. 65 while weaker objectives, magnifying 40 or 50 times, should show something of the lines. When it is found impossible to obtain oblique illumination, this inconvenience may be reme- died by means of a condenser, with its central portion obscured. Oblique illumination and a stage capable of rotation are of great assistance. Hartnack's immersion lenses Nos. 9, 10, or 11 show the areee very distinctly and beautifully, with central illumination, and even with an unfavorable sky. Other opti- cians, Amici, Nachet, and some English and German artists, have also been able to resolve them with their strongest lenses in the manner last mentioned. Hartnack's newly constructed objective No. 9, not intended for immersion, accomplishes the same, as I have myself witnessed, likewise his latest No. 8 ; even an excellent No. 7, received several years ago, gives the same result, with similar central illumination and elevated con- cave mirror. The other test objects already mentioned, Nitzschia sigmoi- dea, Surirella Gemma, Grammatophora subtilissima, and Navi- cula rhomboides are much more difficult, and can only be re- solved by means of suitable oblique illumination and very ac- curate correction of the objective. The first is the easiest ; the last three, on the contrary, serve to test the best and most powerful modern immersion lenses. As was just mentioned, the Nitzschia sigmoidea is the easiest of these objects to resolve. With oblique illumi- nation, the lona; and narrow valve shows a series ^^^ of very tine and compact transverse lines. Bour- f^^^^^ gogne's preparations of the Nitzschia sigmoidea h ^jj £ are mounted dry. The Surirella Gemma, fig. 64, is a very delicate test object, and only to be mastered with much pains. Seen from its broad surf ace, the oval disk shows parallel ridges running as far as the cen- tral line. Between these appear very readily a I^^SllRj^y series of fine, but distinct, transverse lines. It is W^KSff these latter lines, cutting the transverse ones at \y^= -J right angles, which give the Surirella Gemma iS? its value as a test object of the first class. Undu- p ia . 64. smireiia, lating curved lines of extreme fineness should appear, which give to the whole an interwoven appearance like basket-work (fig. 65). With the aid of bis best lenses, ill 66 SECTION FOURTH. Hartnack even succeeded in resolving these undulating lines into a series of very narrow hexagonal areolations (fig. 66). Bourgogne's preparation is also mounted dry. The Grammatopliora subtilissima, mounted by Bourgogne ffl Fig. 65. Longitudinal lines on the sili- cious envelope of the Surirella Gemma. Fig. t!6. The same, resolved into areola tions. in Canada balsam, is equally difficult. I do not know whether it is identical with the species first used by the American mi- croscopist, Professor Bailey, of West Point, U. S. Besides, it seems that two kinds of valves of unequal difficulty have there been pronounced to be Grammatopliora subtilissima. Seen from its broad surface, the silicious envelope presents the appearance of an oblong square, with blunted corners (fig. 67, 1). It is divided into three regions by the two peculiarly curved longitudinal furrows. The two lateral regions (a) of every valve should exhibit very fine and compact transverse lines (2a), with the aid of good oblique illumination. The cen- tral portion does not show any markings. This is, however, only a portion of the markings we are at present able to recognize. Other sharper and more coarsely marked species of the genus Grammatopliora show these trans- verse lines, intermingled with a double series of oblique lines crossing each other at an angle of 60°, so that exactly the same markings result which we have previously described in the Pleurosigma angulatum. These oblique lines of the Grammato- pliora subtilissima also appear to be quite separated. Hart- nack informs me that he has succeeded in resolving them with one of his strongest objectives, and I believe that I have myself caught at least a glimpse of them, with an immersion lens No. 10. We. add, finally, a few remarks on the Navicula rhoin- boides, sporangial form" (Jig. 68). Its somewhat undulating, * The Navicula in question was used at the last London Industrial Exhibition, as N. affinis, and was given to me in the form of a preparation by Bourgogne, as N. Amicii. I have to thank Tb. Kulenstein for the definition given in the text. TESTING THE MICROSCOPE. 67 longitudinal lines (a) may be recognized with oblique light and a good immersion lens, without much trouble. They may be from 0.0002 to 0.0001S of a Paris line distant from each other. Fig. 07. 1, Grammatophora subtilissima. , transverse lines of the same. *Aim k r AJ Fig. 68. Nuvicula rhomboicles. dinal, fr, transverse lines. The elegant transverse lines (b) of the specimen in Canada balsam appear much more compact and extremely delicate. To recognize them, very oblique light and the most accurate correction of the immersion objective is necessary.* All organic test objects have, as a fault, the peculiarity that they are not exactly alike, but are, in the most fortunate cases, only very similar. It was, therefore, a fortunate idea of No- bert's to produce glass plates with bands of parallel lines, the distances between the lines constantly decreasing. The oldest of these plates, made about 1845, presented ten bands. In the first band, the distance between the lines was T - Vu'"j in the last t^Vu'"- At the present time, with the progress of practical optics, such plates would no longer afford a means of testing first-class microscopes. Nobert afterwards made plates with 30 bands ; but these marvelous productions of art cost 30 thalers. Quite recently he has issued a plate with 19 bands ; the lines in its last division are TIr ?nr5- of a line apart. Thus markings as fine as those of the Diafomacese have been made by art. Nevertheless, these wonderful plates of Nobert's also have the fault of not being identical, although, in the most recent ones, the differences are almost imperceptible. Diversity of opinion still prevails regarding the resolution of the last * The recognition of these transverse lines may be accomplished almost instantly by an expert, with a Hartnack No. 11 immersion objective. I have succeeded in doing this, though with some trouble, even with a No. 9 of this optician. Let me remark, incidentally, that the latter combination should also resolve the Surirella Gemma and Grammatophora subtilissima. 68 SECTION FOURTH. bands, and this is connected with the still unsettled question, as to where the limits of accurate vision with our modern mi- croscopes lies. We here introduce a table of the divisions of the last two test plates : — Plate with 30 hands. Plate with 19 bands. 1. Band 0.001000 of a Paris line. 5. " 0.000550 10. " 0.000275 15. " 0.000200 20. " 0.000167 25. " 0.000143 30. " 0.000125 1. Band nfa 2. ' ' — i -^- 1 5lTO 3. 2.000 4. 26 00 5. \i 00 6. u 1 3"5 0" 7. T"oo~u 8. 3~5 0~0 0. 5 UUO 10. 11. b 000 12. 1T60O 13. TTHJU 14. " -A Te oo 15. H 000 16. "8"5 00" 17. 5 0V0 18. ^5 0"o 19. ■ l __1 TITuOO The resolution of these lines with oblique light has been employed as a means of testing objectives. Harting was able, years ago, with a Hartnack's immersion lens No. 10, to recog- nize the lines in the 30th band of the older plates, and the res- olution of the 25th, 26th, and even the 27th band is not an un- usually great achievement. M. Schultze succeeded in resolving the 15th band of the more recent plate, and I afterwards re- solved the 17th band with objective No. 11. In the year 1869, an American, Woodward, whom we have to thank for excellent photographs of test objects, also mastered the 19th band of this wonderful test plate. Several years since, Schultze tested a series of the best mod- ern objectives with central illumination. The highest perform- ance consisted, at that time, in resolving the 9th band with an immersion lens No. 10 of Hartnack, and one of Merz's ^V". I have repeated this experiment. My immersion objective No. 11 resolved the 12th, less distinctly the 13th, No. 10 the 11th, and the combination No. 7 of most recent construction, the 7th of this test plate. ' TESTING THE MICROSCOPE. 69 We have, finally, to discuss the question as to what precepts and advice are to be given to those who desire to procure a microscope ; how should the instrument be constructed, and which optical establishment deserves, at present, to be most recommended. He who desires to possess a first-class instrument will gen- erally select one of the large microscopes with a horseshoe stand, rig. 69, as constructed by Oberhauser and imitated by other opticians. Its conveni- ence of manipulation, com- bined with a certain simplicity, render it a truly model stand. The large stage, its capability of being rotated (which, how- ever, requires very accurate workmanship, and is therefore expensive), the micrometer screw for the fine adjustment, and the mobility of the mirror, are extraordinary advantages. The illuminating apparatus might, it is true, be improved, still it suffices for most pur- poses. When the stands which the English opticians select for their larger instruments (see page 29, fig. 39) are compared with it, they appear to be un- pleasantly loaded with screws and unessential appurtenan- ces, which inconvenience one who daily works with the in- strument, as it is better to do with the human hand much which is there allotted to mechanical contrivances. For medical purposes the rotary stage may be readily dis- pensed with ; less readily the oblique illumination ; and this, which may be added with little expense, should, indeed, no longer be omitted from any instrument of medium class. Smaller horseshoe stands, similar in construction to the larger Fig. G9. Hartnack's large horseshoe microscope. 70 SECTION FOURTH. stand, but without the rotary stage, deserve, therefore, to be especially recommended. Still smaller stands should possess a plane and concave mirror, and at least a rotary diaphragm to regulate the illumination, or, which is better, several cylindrical diaphragms, as well as a stage an inch and a half wide. When there is no oblique illumination, a simple condenser, similar to the one represented in rig. 24, may be used as a substitute. When there is but a simple mirror, no rotary diaphragm, and the stage is very narrow, as is the case in Hartnack's older microscope a l'hospice, the stand is certainly deficient. Nevertheless, the mechanical portion of a microscope is a secondary consideration and of minor importance ; in the opti- cal apparatus is founded the actual value of the instrument. One or the other form of instrument will be selected, ac- cording as a greater or lesser price can be afforded. Beginners, especially, should not have recourse to the largest, most expen- sive microscopes, as their manipulation is more difficult, and considerable practice is required before very powerful first-class lenses can be used. The strangest notions not unfrequently prevail with regard to the optical portion. How often is the question still heard : How much does this instrument magnify 1 How often are mi- croscopes ordered from an optician, with a magnifying power of from 5-600 diameters. Nothing shows a greater misconcep- tion of the optical performance of our instrument, as it is only necessary to add a perhaps uselessly strong eye-piece, to change a serviceable magnifying power of 400 diameters into a com- pletely unserviceable one of 800, and, therefore, of no value to the instrument. The individual objectives with the various eye-pieces form, each for themselves, a particular microscope. For this reason, one should have at least a twofold combination of lenses, if possible, three, — a weak, a medium, and a strong one. A double combination of lenses may be obtained from one system, in the most economical manner, by removing its lowermost lens. Many of the most simply constructed instruments have only one such objective, with two eye-pieces. Good micro- scopes of this kind may be obtained for 20 thalers. It is better to have several objectives with inseparable lenses. We would here call to mind what we have previously said with regard to the great value of weaker powers. They should TESTING THE MICROSCOPE. 71 never be wanting. At least one objective of medium strength is also a valuable addition. Finally, a stronger objective, which, with a weak eye-piece, magnifies from 200 to 250 times, and, with a stronger one, affords a good and thoroughly ser- viceable magnifying power of 300 to 350, should not be wanting on any microscope. These, usually, completely suffice, especially if another eye- piece with a glass micrometer is added. Such instruments are to be purchased for 30, 40, and 50 thalers, according to the stand, and, when obtained from the best modern establishments, stand higher, as to their capabilities, than the large micro- scopes constructed thirty years ago at three or four times their price. Stronger objectives are very beldom required ; their addition naturally increases the cost considerably. For the commencement we would advise the omission of the very strongest objectives, especially those with apparatus for correction which are delicate to manipulate, as well as immersion lenses (fig. 70), and to select in their place a combination which works dry. With this, the magnifying power might be increased to 450 or 600, and n Jif ^^5^' rarely, even in extended scientific researches, ob J ecti¥C No - '■>• would a higher magnifying power be missed. Such instru- ments, of excellent quality, may be bought on the continent for about 70 or 80 thalers. Other more or less expensive accessories, such as drawing and polarizing apparatuses, are, as a rule, added to the larger instruments only. The value of a microscope being founded on its optical por- tion, on the excellence of its lenses, the question here arises as to the present productions of the various optical establishments. It is very difficult to render an impartial decision on this point. Disregarding a certain amount of odium in which one would be placed with the opticians not accorded the first rank, one should have just made a long journey, instituted for this purpose, through Germany, France, England, and North America, for in this department our industrial epoch exhibits a steady prog- ress, one maker being surpassed by another. The problem of the construction of weak, medium, and or- dinary stronger objectives has been solved in a perfectly satis- 72 SECTION FOURTH. factory manner by a considerable number of modern opticians, so that every year a large number of excellent microscopes, thoroughly adequate to all the requirements of the physician, are put in the market. It is true that certain objectives of one maker are superior to the same lenses of another maker ; but these differences do not appear to exert any great influence on their practical requirements, and are only to be discovered by the practised eye. The effort to obtain a large angle of aper- ture has stamped modern objectives with a peculiar character. We would give the practical advice, not to purchase an instru- ment of an unknown optician, or, at least, not without having it tested by an expert, and to have the greatest mistrust of all charlatanical recommendations, whether they come from the optician himself or from a writer glorifying him. The various optical establishments differ greatly in the con- struction of very powerful, or the most powerful combinations, as to the greatest excellence which may be accomplished in this department. Therefore, he wdio would procure a first-class in- strument should proceed with circumspection. Twenty-five years ago several large firms in England main- tained a higher rank in this department than the Continental opticians had obtained, if we disregard the Italian savant and distinguished microscope-maker, Amici (f 1S63). ]Sf o impartial person, who knows how to test a microscope, could deny this, if he were to compare hrst-class instruments originating in that epoch. Since that time the emulation of the Continental opti- cians has spurred the most skilful on to even higher produc- tions ; the difference lias become less and less, and has finally disappeared. Indeed, a few which have been jjroduced among us of late deserve, perhaps, to be placed higher. At the same time there is a very considerable difference in price between the larger kind of English instruments and those of Germany and France. For example, a single objective with a nominal focus of Vjr hich, made by Powell and Lealand, of London, costs somewhat more than f 6 pounds, while Ilartnack, of Paris, fur- nishes a combination equally strong, No. f a immersion, for 200, and a still stronger one, No. 11, for 250 francs. The strong- est objective, -gV inch, of the London firm mentioned is charged at 31 pounds 10 shillings in the price-list ; in that of the Pari- sian optician, at 500 francs. Large modern microscopes of the most renowned English TESTING- THE MICROSCOPE. 73 makers have not been accessible to me. I am, therefore, un- able to say how far the achievements of former years have been surpassed. Several years ago, Harting, one of the first and most profound judges of the microscope, passed the highest encomiums on the powerful and most powerful objectives of Andrew Ross, as well as of Powell and Lealand. Several years ago, the ^V inch objectives of the latter firm became quite nu- merous in England, and obtained great appreciation at the In- dustrial Exhibition in 1862. Another of -5V inch is announced in the new price-current. Beale has praised it very highly. I became acquainted with it in the year I860 ; so slightly, how- ever, that I am unable to express an opinion. Among the Continental opticians, Hartnack, of Paris, the successor to Oberhauser (Place Dauphine, No. 21), stands first, according to mj^ views. Not only that his immersion lenses have not as yet been equalled by any Continental microscope- maker, but the weaker objectives, which are so very important, have also been very much improved, and from the industry and carefulness of this highly accomplished artist, further improve- ments are to be expected. Thus, objective No. 5 has already an angle of aperture of about 80°. Hartnack' s Nos. 7 and 8, especially, are excellent, and, like all of his apparatuses, to be recommended for their slight expense. The former has within a few years been brought to an ever higher stage of consumma- tion, as well in penetrating as in defining power, as I know from numerous comparisons and tests, and with an angle of aperture of about 100°, forms a wonderful combination for his- tological investigations. No. 8 has 125-130°, No. 9 (dry), 155- 160° total aperture. The smallest microscope a Phospice, with objective No. 7 and a sufficiently broad stage, may be obtained for the low price of 65 francs ; though deficient with regard to the illumi- nating apparatus, it is nevertheless very serviceable for medical purposes. A somewhat larger instrument with a rotary diaphragm and a wide stage, with a weak objective and the No. 7 just mentioned, together with several eye-pieces, costs 115 francs, which is increased, when the objective No. 8 is added, to 165 francs. Disregarding the absence of oblique illumination, we should scarcely wish for anything further. It is very con- venient for travelling, on account of its small size. 74 SECTION FOUKTII. The small horseshoe microscope, No. viii. , is a very conve- nient stand, permitting of oblique illumination. With three objectives, 4, 7, and 8, together with the necessary eye-pieces, it costs 275 francs. During a series of years a considerable number of instruments of this kind have passed through my hands, and I know of no other modern microscope which I should be more inclined to recommend to physicians and stu- dents who are able to afford the moderate price. If, instead of a No. 8, an immersion lens No. 9 is taken, the price is in- creased to 390 francs. Besides this stand, Hartnack has recently introduced a still more simplified form, with a rotary diaphragm and a bronzed foot. With objectives 4 and 7, and two eye-pieces, it costs 140 francs. If the foot is replaced by a simple slab, the price is reduced to 120 francs. Hartnack makes his large microscope onlj' in the larger form, and with a rotary stage ; together with four ordinary objectives it usually receives a No. 9 immersion lens, costing, with this addition, 750 francs, at present the best Continental instrument. Nachet, of Paris (Nachet et ills, Rue St. Severin, No. 17), has also obtained a considerable reputation as a microscope constructor. Several large microscopes, constructed several years ago, resembling the English pattern, capable of being in- clined, and furnished with a condenser, were very good for that time. What progress Nachet has since made in the con- struction of the most powerful objectives, I have unfortunately not become sufficiently informed. I had recentty in my hands an immersion objective No. 7, a little weaker than Hartnack 1 s No. 10 ; it was very good. Several small microscopes which I formerly tested were, as well in their mechanical as in their optical portions, excellent and very cheap, costing only 200 francs. Nachet' s prices are as follows : — The large stand, fig. 40, fashioned after the English microscopes, and arranged for inclining, with very numerous accessories and seven objectives, costs 1,300 francs; the older large instrument 1,150, and more simply furnished 650 francs. Smaller instruments, with varions, in part very convenient stands, may be obtained from Nachet for 500, 380, 200, 150, 125, and 70 francs. Hartnack' s pupil, C. Verick, Rue de la Parcheminerie, No. 2, Paris, is a very skilful optician. Several instruments, which I have accurately tested, varied from 700 to 900 francs. They TESTING THE MICROSCOPE. 75 are of the first rank, are equal to the best of modern micro- scopes, and are superior to many which, in Germany, espe- cially, have been lately so loudly trumpeted. The older firm of Chevalier has recently taken a new start, through the son, Arthur Chevalier (Palais Royal, No. 158). A competent judge, von Heurck, has recently given prominence to Chevalier s optical productions. Unfortunately, I have not as yet seen anything from this establishment. Among the purely German opticians, if one may use the expression, I mention first Zeiss, of Jena. I am indebted to this optician for the opportunity of seeing his most recent len- ses. Zeiss has at present nine different efficient stands, worth from 18 to 150 marks. His twelve dry lenses are marked ac- cording to their strength with the letters A to F; some of them have two letters. The first costs 12 marks, the others vary from 27 to 66 marks ; No. F costs 84 marks. All these lenses are of excellent workmanship. No. F, a dry lens, with 150° aperture and the nominal focus of T y, is such a strong and ex- cellent combination that a higher power will rarely be necessary. A few years ago he reconstructed all these lense combina- tions on formula computed by Professor Abbe, of Jena. He also made three immersion systems with 180° aperture, which perform exceedingly well. The strongest of these systems with a perfected correcting apparatus corresponds to 2 y' of the English. It costs 270 marks. The former establishment of Gundlach, in Berlin, has passed into the hands of Seibert and Kraff t, and removed to Wetzlar. Seibert, an excellent optician, placed all his lenses in ray hands at Zurich, two years since. They were all very good, the stronger and strongest ones excellent. The most recent im- mersion systems, No. 7, ^", No. S, -fa", and No. 9, gV", which I recently received, are among the best I have ever seen. I would, therefore, at present, give the palm to Hartnack and Seibert. The prices of the distinguished technician are rela- lively low. In Munich, G. and S. Merz, into whose hands the renowned institute of Fraunhofer-Utzschneider has passed, produced ex- cellent instruments ten years since. Unfortunately, many of their lenses have, in consequence of an unfortunate selection of the kinds of glass, proved undurable, so that many complaints have arisen. 76 SECTION FOURTH. In Wetzlar, about 1840, C. Kellner supplied instruments which were excellent for that time. His immediate successors, Belthle and Rexroth, have in their price-currents microscopes from 35 to 120 thalers. Belthle showed me good instruments years ago. Since Belthle' s death, the business has passed into the hands of Leitz. His productions merit entire recognition. Another establishment in the same place is that of Engelbert & Hensoldt. Their instruments are likewise very good. Moller and Emmerich, of Giessen, have supplied micro- scopes for several years. F. W. Schiek (Halle' sche Strasse, No. 14) is the oldest firm in Berlin. Some of his productions, which I have recently seen, were equal to any made at the present time, being very good, at a moderate price. The stands and objectives resemble those of Hartnack in form and designation. In Gottingen, R. Winkel has recently produced instruments. One, which I saw several years ago, was very good. How far Merkel was justified in giving unfounded praise to this micro- scope, I am unable to decide. It is, unfortunately, impossible to get a sight of anything from that place. S. Plossl (alte Wieden, Theresianumgasse, No. 12) was the first maker in Vienna. The excellent instruments of Amici, of Italy, have obtained great renown. They were the best Continental microscopes from 1840 to 1850, the deceased Amici having at that time acquired the greatest merit in the construction of improved microscopes. I know nothing further of his instruments pro- duced more recently. The three most renowned London firms are : Powell & Lea- land (170 Euston road), Andrew Ross (7 Wigmore street, Ca- vendish square, W.), continued, since the death of the founder, by the son, Thomas Ross, and Smith, Beck & Beck (6 Coleman street). Among the remainder we will also mention Pillisclier (88 New Bond street), W. Highley (70 Dean street, Soho square, 10), and Baker (44 High Holborn). It is highly commendable that, for a series of years, the English have endeavored to pro- duce instruments which might be as cheap as possible and, at the same time, good. Thus, for example, a number of estab- lishments furnish very fine instruments even for £5, as Pillisclier, Smith, Beck & Beck. Among the microscope-makers of North America, the most TESTING- THE MICROSCOPE. 77 important are Spencer, Tolles, and W. Wales. Zentmayer has recently produced very good stands. The optical perform- ances do not surpass those of our best European instruments ; the prices, however, are enormous (H. Hagen). [The history of the microscope as an American instrument commences at a very recent date. I am informed by Mr. T. H. McAllister, optician of this city, that in the year 1840, when the United States Exploring Ex- pedition to the South Seas, under Commodore Wilkes, was fitting out, it was thought necessary to have a microscope. It was then discovered that none was to be had. The various makers of scientific and philosophical instruments were applied to, but none of them could furnish the expedition with the desired microscope. In this dilemma a private individual was applied to, and an instrument was finally obtained from Dr. Paul Goddard, of Philadelphia. It was a French microscope, which would now be considered very inferior, but was the best instrument then to be had in this country. Since that time the instrument has come into general use, and in certain departments of the manufacture of microscopes this country has become pre-eminent. Scarcely had the English microscope-makers published those inventions and discoveries which rendered achromatic microscopes really possible, and elevated the instrument from the position of a mere scientific plaything to that of an instrument calculated for the most accurate investigations, before Charles A. Spencer, of this State, succeeded in producing lenses which at once took a front rank among the art productions of the world. Spencer and his pupil Tolles, Wales, Grunow, Zentmayer, and perhaps a few others, have since that time kept up the reputation of the American lenses, and to-day there is no country in the world in which are produced finer object glasses than those of domes- tic make. Previous to Spencer 1 s time, some few microscopes and objec- tives had been constructed by amateurs, but their authors have never become celebrated in this department. Spencer was induced, Avhile still a hid, by the perusal of the article on optics in the "Edinburgh Encyclopaedia," to construct a compound microscope. His first lens was made when he was about twelve years of age ; this first attempt was followed by others, at intervals, during subsequent years. After making 7S SECTION FOURTH. several compound microscopes, and a reflecting one upon the original plan of Prof. Amici, lie constructed several Gregorian and Newtonian telescopes with specula of six and eight inches diameter, some of which were quite successful. It was not till the publication of the ' ' Penny Magazine ' ' and the "Library of Useful Knowledge," however, that he became aware of the improvements which had been made in Paris and London in the achromatic microscope. The results obtained by Goring and Pritchard in both the achromatic and reflecting microscopes excited his attention especially. The discovery by the former of the effects of angle of aperture was a powerful inducement for Spencer to perfect himself more thoroughly in this branch of optical science. About this time he also learned of the successful researches of Guinaud, Fraunhofer, and Fara- day in the manufacture of optical glass. By laborious and pro- tracted experiments, frequently working over the furnace for eighteen consecutive hours, he succeeded in improving the homogeneousness and other qualities of the glass considerably, which enabled him to make an evident advance upon his pre- vious efforts in constructing lenses. A few instruments were made for personal friends, but it was not till later, about 18-17, that Spencer became a professional microscope-maker. About this time he visited New York City, and was introduced by Dr. John Frey to the late Prof. C. R. Gilman. Dr. Gilman had a microscope, constructed by Cheva- lier, of Paris, which he showed to Spencer and induced him to make one like it. The result was, that Prof. G. sold his Cheva- lier instrument and replaced it with the one made by Spencer. This instrument was completed in November, 1847. In bring- ing it to New York, Mr. Spencer stopped at West Point, and showed his microscope to the late Prof. Bailey, then the ac- knowledged chief of microscopical observers of this country. It was with this instrument that Prof. Bailey resolved the Na- vicula Spencerii, noticed in the first edition of Quekett on the Microscope. This author, at page 440, in speaking of the N. Spencerii, says : " that an object glass, constructed by a young artist of the name of Spencer, living in the backwoods, had shown three sets of lines on it, when other glasses of equal power, made by the first English opticians, had entirely failed to deiine them." The information which Quekett' s treatise contained concern- TESTING THE MICROSCOPE. 79 ins the discoveries of Lister and the labors of Amici and Ross, was extremely useful to our ' ' Yankee backwoodsman. ' ' In the account given of Ross's discovery of the effect of thin glass covers upon the correction of an objective, the announcement was made that "on several occasionst he enormous angle of 135° had been obtained," and that, ''135° is the largest angular pen- cil that can be passed through a microscopic object glass." This statement, coming from a source so generally considered authoritative, arrested Spencer's attention and led to an imme- diate theoretical and practical examination of its validity. The supposed theoretical grounds of the assumption not having been found to sustain Mr. Ross's position, conclusive evidence of its incorrectness was speedily obtained by the construction of a ^ in. objective, having an angle of aperture of 146°. An increase of the angle of aperture of the higher powers had been made from time to time, until the maximum angle of 17S°, for the T V, was obtained in June, 1851; and subsequently the medium and lower powers were correspondingly improved. An investigation into the practicability of so far increasing the defining and resolving powers of the objectives of medium focal lengths was made, and results have been obtained which could not, clprio?'i, have been expected. The angle of aperture of the i has been increased to 175°, and its defining and resolv- ing powers are such that it bears oculars bringing its amplify- ing powers up to twelve hundred diameters, without any con- siderable deterioration in the sharpness of its images. With it the 19th band of Nobert's test plate has been resolved with or- dinary daylight illumination and with artificial light. The residual errors have been the subject of continued investigation since then, and they afford an ample field for the exercise of the highest mental powers and manual skill. We have now to speak of another Automath, Mr. J. Grunow, who came from Berlin to this country in 1849, and settled in New Haven, Conn. He was induced by Drs. Henry Van Ars- dale and C. R. Gilman to study optics and to commence the manufacture of microscopes. Grunow was his own teacher, and had been engaged in an entirely different business previous to his arrival in this country. He constructed his first micro- scope for Dr. Van Arsdale in 1852, and soon afterwards a second one for Prof. Gilman. About this time Grunow' s 80 i SECTION FOURTH. brother became associated with him and constructed the stands, which were models of good workmanship. It may be interesting in this connection to remark that Prof. Riddell of this country, the inventor of the binocular microscope, used for his experiments in this direction prisms made by Fitz, of New York. The first binocular microscope, however, was constructed for Prof. P., in 1853, by Grunow. A very valuable improvement, made by Grunow, consists in letting the rotary diaphragm into the upper surface of the (im- movable) stage in such a manner that it is just below the level of the same, and can be rotated without disturbing the slide on which the object is placed. In this way the full optical effect of the diaphragm is obtained exactly at the point where it is needed. Mr. P. B. Tulles became a pupil of Spencer in 1843. In ISoGhe commenced business for himself, and after several years removed to Boston, Mass. Mr. Tolles is the author of a number of valuable improve- ments in microscopical accessories ; among these his stereo- scopic binocular and solid eye-pieces, his method of adjusting for cover by making the front lens stationary and no back lash, as well as his method of making two fronts to an objective — one immersion, and one dry — deserve especial mention. The excellent quality of his objectives has earned him a world-wide reputation. Mr. J. Zentmaj-er, of Philadelphia, was introduced to the American microscopic public by Mr. T. II. McAllister. The first instrument which he made was for Dr. Paul Goddard, of that city, in the year 1S5S. This instrument is now in the pos- session of Dr. Squibb, the Chemist, of Brooklyn, N. Y., and is almost identical with the present "Grand American Stand." Zentmayer is the inventor of several valuable improvements in microscopical accessories, which will be mentioned in the price-list, at the end of this book. The elegant workmanship of his stands is unsurpassed by those of any other maker. Mr. Wm. Wales was a pupil of Smith and Beck, in Lon- don. He came to this country about 1862. After remaining here for a few months, he went back to England, but soon re- turned to Port Lee, N. J. Since this time his lenses have con- stantly improved in quality, and are considered by many com- TESTING THE MICK0SC0PE. 81 petent judges to be equal to, if they do not excel, those of any other maker in the world. Mr. L. Miller was formerly in the employ of Tolles, but commenced business for himself in 1868. Some of his lenses which I have seen were very good. In addition to the firms above mentioned, excellent instru- ments are also furnished by McAllister, Queen, Bausch and Lomb, and W. H. Bulloch. The microscopes made in this country are generally to sup- ply the home demand, and but few have been exported. Some have found their way to Europe, where they have been criti- cally examined by the French and English makers, and various important improvements, which originated with American makers, have been appropriated by them. For instance, in " Carpenter on the Microscope," London, 1868, will be found, on page 68, a description of a piece of microscopic apparatus, invented by Zentmayer in 1862, but which was copied by a Paris maker, to whom Dr. Carpenter gives the credit of being the inventor. In speaking of this instrument (Nachet's student's micro- scope), Dr. Carpenter says : — " The chief peculiarity of this in- strument, however, lies in the stage, which the author has no hesitation in pronouncing to be the most perfect of its kind that has yet been devised." The instrument from which Na- chet copied the circular stage was made by Zentmayer in 1864 for Dr. W. W. Keen, of Philadelphia, who showed it three dif- ferent times to M. Nachet, and had it packed by him, in the spring of 1865, for transportation. The American microscopes are characterized by extreme simplicity, combining all that is necessary for a good working instrument, and rejecting numerous complicated movements and much superfluity of workmanship which some foreign makers seem to consider essential. The form of stand which has found most favor in this coun- try is the one devised by Mr. Gt. Jackson, of London. It con- sists mainly of a stout bar which carries the body, stage, acces- sory box, and mirror ; securing steadiness, equal distribution of tremor, and facilitating the centring of the accessories and achromatic illumination. It will be found, on examination, that modifications of this principle have been applied in nearly all of our American microscopes. 6 82 SECTION FOURTH. As complete descriptions of the various instruments, objec- tives, and accessories will be found in the price-lists of the dif- ferent makers, at the end of this book, it is unnecessary to allude to them in this place. Microscopes of American manufacture, from their com- parative cheapness — to the cost of importation must be added the duty, which is 45 per cent, ad valorem — and the facility with which they can be obtained, offer inducements to stu- dents and others to procure their instruments at home, and thus save time to themselves, while they stimulate the manu- facturers to make increased efforts to attain even greater excel- lence.] Section fifty. USE OF THE MICROSCOPE.— MICROSCOPIC EXAMINATION. Practical directions for learning to work with the micro- scope may be given pretty rapidly and without difficulty, while it is painfully troublesome for the beginner to acquire this from written instructions. We shall therefore limit ourselves to rendering some of the chief points prominent, and must leave many other things for the microscopist to study out for himself. Suitable illumination is of great value for microscopic work. As most examinations are made with transmitted light, and the application of natural light is, in this case, to be preferred to any artificial illumination, the selection of a working room is not a matter of indifference. When possible, one should be selected which lies towards the northwest or northeast, and affords an outlook, so that a larger portion of the sky may be used for the reception of the rays of light. In the narrow streets of cities, only the upper stories of the houses can gen- erally be used. It is convenient to have windows on two sides of the room ; but those of the side opposite to the windows which are in use should be closed by a dark curtain or shutters. For ordinary investigations, one may without disadvantage place the instrument on a table standing near the window, and thus make the preparations and examine them on one and the same table. But when the best possible illumination is re- quired, such a position should not be selected for the micro- scope ; the instrument should be placed at a considerable dis- tance, from six to nine feet or more, from the window. A dark shade, which can be placed over the stage by means of a ring fastened to the microscope tube, will shut off all incident light 84 SECTION FIFTH. from the object, and essentially improve the image. Such shading of the stage should never be neglected when making observations with polarized light, or resolving very difficult test objects with oblique illumination. The condition of the sky is of importance for the illumina- tion. A clear blue sky gives a very fine, soft light which does not tire the eye, and is sufficiently bright for all but the very strongest objectives. A dull, white, uniform cloudiness is still more preferable. Bright white clouds, which lie near the sun, should not be selected, on account of their dazzling light. The rapid passing of white clouds over a blue sky, when the atmos- phere is strongly agitated, is very unpleasant and troublesome. When the sun shines through the window, a white curtain drawn over it or lowered from a roller is of service. To illuminate the field, the microscope is turned towards the window, and the mirror is rotated and moved with one hand, while the observer is looking through the instrument. When the best light has thus been found, the object to be examined is placed on the stage of the microscope and the further correc- tion of the field is commenced ; for example, lowering the cy- lindrical diaphragm or slightly altering the position of the mir- ror, the object being constantly kept in sight. When the mirror is freely movable, it is unnecessary to alter the position of the instrument ; but the limited movement of the mirror which many of the smallest microscopes permit, often requires a turning and moving of the microscope. The beginner generally thinks that he can accomplish most with a brightly illuminated field, and thus he works, dazzled by a sea of light, with weeping, rapidly tiring eyes. The ex- perienced observer is accustomed, as a rule, to diminish the in- tensity of the light considerably. Together with the protection of the organ of vision, it is only in this way that the finest de- tails of the microscopic image can be perceived. The skilful application of the illuminating apparatus and the use of the diaphragm should therefore at once be practised by the begin- ner as much as possible. When the instrument has a mirror with plane and concave surfaces, the former is used with the weaker objectives and a bright light, the latter with the stronger objectives and a light which is less intense. A very perceptible deficiency is always connected with instruments not having such an arrangement. This may be remedied in a measure, it USE OF THE MICROSCOPE. 85 is true, by turning the microscope, or by holding the hand in certain positions before it. Considerable practice is requisite with the obliqne illumina- tion (fig. 71). The aperture of the stage must be freed from diaphragms, or any other apparatus which may be under the stage, and the various positions of the mirror are to be tried Fig. 71. Oblique position of the mirror on the horseshoe stand. while the eye is looking into the microscope. Ai the same time, while the mirror is brought up close beneath the stage, the illumination is made as oblique as possible. Truly diabol- ical illumination is thus sometimes obtained, which, however, shows many fine details in an astonishing manner. When the microscope has a well-centred rotary stage, its rotation is of 86 SECTION FIFTH. great importance with this illumination. An observer who is familiar with his instrument and well versed in this department of microscopical technology, will be able to show many things, to the astonishment of the unpractised investigator, which the latter was unable to accomplish after hours of unsuccessful labor. The resolution of the systems of lines of the Pleuro- sigma angulatum into areolations, with strong objectives, and the exhibition of the markings of the Surirella gemma and Gi-rammatophora subtilissima by means of the strongest immer- sion lenses, may be designated as specimens of the art of ob- lique illumination. This is, however, only of minor value for our purposes. "No one should make any protracted microscopic investiga- tions by the aid of the artificial light of a lamp or gas flame if he can possibly avoid it, or would spare his eyes. In Northern Europe, during the winter, there are days when the natural light is entirely unserviceable, and, vexed by the miserable light, one finally has re- course to artificial illumination. When it is necessary to resort to artificial light, an ordinary mod'erateur, which should not be too high, an Argand or a petroleum lamp, with a globe of opalescent glass, is worthy of recommendation. A petroleum lamp (fig. 72), provided with a large condensing lens, recently constructed by Hartnack, is very convenient ; it should also have a shade. Properly constructed gas lamps may also be employed with advantage. A number of these, with very judicious ar- rangements, have been invented and recom- mended hy English microscopists. A proper moderation of the light is here urgently necessary. The illumination may be essentially improved by placing a co- balt-blue glass of greater or lesser intensity between the lamp flame and the object. It may be placed on the mirror or, better, on the stage. A black pasteboard screen with apertures of various sizes, which may be placed in front of the micro- scope parallel with the mirror, and on which the blue glass may be fastened with wax, forms a cheap accompaniment of HartnacVs micro- USE OF THE MICROSCOPE. 87 the large Oberhauser-Hartnack microscope, and deserves to be highly recommended for its important action. A rotary dia- phragm should be placed behind the screen. In place of the above, blue glasses of various sorts, which can be shoved into a metallic ring, may be inserted into the stage, as necessity may require. Such an arrangement may be readily applied to all of the larger stands. [A very ingenious arrangement of the illumination has been contrived by my friend, Dr. Edward Curtis, of this city. A small lamp, similar to the one represented in fig. 72, is placed in a cigar-box, which stands on one of its ends. On one side of the box is cut a small aperture, in which is placed a piece of blue glass, to soften the light as it passes to the micro- scope mirror. Another larger opening is made in the front of the box and is occupied by three different glasses. The one nearest the lamp is a square piece of ground glass ; the next one is also square and flat, but colored blue. Finally, a plano- convex glass lens of long focus is placed at such an inclination as to condense the rays of light, thus softened, on to the work- table for use in dissecting or arranging preparations.] Although direct sun and lamp light is to be entirely rejected for ordinary investigations, these most intense of all illumi- nating methods must, on the contrary, be selected for many investigations with polarized light. Opaque objects require illumination by incident light with seclusion from transmitted rays. Ordinary daylight is suffi- cient for very weak powers ; with stronger ones, more intense illumination is necessary. Sun-light may be used in certain cases. Numerous contriv- ances are in use for concentrating the light on the object. A plano-convex lens of large focus (fig. 21), which is placed be- fore the instrument, is generally sufficient ; this may also be accomplished with a glass prism. Lieberkiihn's illuminating apparatus also deserves mention as a good and very suitable contrivance, although it is rarely employed in medical investi- gations. The object to be examined will have to undergo a prelimi- nary preparation, if it be not already a permanent preparation. This process, which naturally varies considerably according to circumstances, generally rendering the examination possible with transmitted light, however, we shall soon treat more in 88 SECTION FIFTH. detail. Let the remark here suffice, that the preparation is to be made with care and the observance of the greatest cleanli- ness ; and then, on the other hand, we would say, not to do too much of a good thing, that is, not to select too large pieces for examination. Beginners fail in this very generally, and place under the microscope masses which, divided, would have furnished a dozen serviceable preparations. One rarely exam- ines with incident light alone, in which case the object can be placed uncovered and dry on the stage of the microscope. As a rule, it is necessary to moisten the preparation (with water, preserving fluids, glycerine, etc.; see below). With weak powers the object may still remain uncovered, and, in fact, many things are thus examined, although the preparation is generally placed in a watch-glass, a glass box, or a cell, instead of on a simple slide. If, however, one has recourse to higher powers, it will be necessary to cover the object with a plate of glass. This should be thin, and as clean as possible. All fluids must be prevented from running over its free surface, as the image becomes some- what dim and indistinct with ordinary objectives, although, as previously mentioned, with the new immersion systems a drop of water must be placed on the upper surface of the covering glass. In the application of the covering glass, all contact of its surfaces with the fingers is to be avoided ; held by its sides, it is to be laid over the object. Some caution is necessary with very delicate objects ; for example, a primitive mammalial ovum might be crushed by covering it awkwardly ; the ele- ments of the fresh retina might have their connection destroyed, etc. Simple contrivances serve for the protection of such prep- arations ; a piece of hair or bristle, or the fragment of a thin film of glass, may be placed between the slide and the covering glass. A large drop of the fluid medium may also be used, so that the covering glass swims over it. Inversely, a narrow strip of blotting-paper may be shoved under the covering glass, and thus gradually diminish the fluid medium. In this way the pressure of the covering glass may be increased at pleasure. The adjustment is made, while looking through the micro- scope, by sinking the tube. This is done either by simply shoving it down through its sheath with the hand, or, when there is a coarse screw, by moving it downwards with the lat- USE OF THE MICROSCOPE. 89 ter. In doing this, thrusting the lens against the preparation is to be avoided, because the latter may be spoiled and its covering glass broken, and in certain cases the lens may also be injured. It is well lor beginners to make this movement in the contrary direction, that is, elevating instead of depressing the tube, which is to be so adjusted that there is only a small space between the covering glass and the lens, and then moved upwards. Accurate adjustment requires some practice, and is not very easy with strong objectives. That the correct adjust- ment has been made, is shown when the contours of the object are sharpest and finest. Here the fine adjusting screw comes in play. The preparation is to be first examined with low powers and transmitted central light, gradually passing to higher powers ; very weak eye-pieces being constantly employed. In some cases the tube of the microscope may be shortened with advan- tage. [The changing of the objectives is facilitated by the employ- ment of a "nose-piece." This is an apparatus having two or more arms capable of revolving and carrying the objectives at their peripheral extremities. The mechanism is to be screwed on to the lower end of the microscope tube, the same as a sim- ple objective. The various objectives are brought into position successively by simply turning the arms. Further movement and accurate centring is controlled by means of a catch. The original "nose-piece," invented by Brooke, of London, re- volved on a horizontal plane, but by a more recent improve- ment the objectives which are not in use are elevated obliquely, and only become vertical at the moment they are adjusted to the axis of the microscope tube, so that they do not in any manner interfere with the manipulation of the stage. This ac- cessory is almost indispensable for those who work much with the microscope.] It is a general mistake of beginners, who under-estimate the value of low powers, to use high powers at the very commence- ment of the examination. As, however, only the weak objec- tives afford a somewhat extended field of vision, while with stronger lenses it is extremely small, it results that the employ- ment of weak combinations is of great importance for the si- multaneous survey of the whole, as well as to give the observer the first ideas as to the relation of its several parts. 90 SECTION FIFTH. One then gradually passes to the employment of stronger objectives ; at first, always with very weak eye-pieces. When working with cylindrical diaphragms it is necessary to vary them, exchanging those with large apertures for those with smaller ones, likewise occasionally exchanging the plane mir- ror for the concave, and in all cases adjusting as accurately as possible with the micrometer screw. When the observer has found it necessary to make use of his higher powers, he may proceed to employ somewhat strong- er eye-pieces ; but he should be sparing in their use. One is soon convinced that less is obtained with them, which results from their optical nature, than would be at first believed. The image is larger, whereby some points may at first appear more distinct. Au enlargement is soon arrived at, however, which does not show any more, but rather less, than the weaker of the previously employed eye-pieces, the brightness of the field and the sharpness of the image having considerably diminished. Very strong eye-pieces, which are added to the larger instru- ments as an optical supplement, are articles of luxury, and are scarcely of any use. Objectives which are well made as to their optical portions bear stronger eye-pieces than those which are less fortunate in their construction. Nevertheless, even in this case, one should be careful of forcing the magnifying power by means of the eye-piece. The latter, it is true, might be still more improved, and it is to be wished that capable opticians might turn their attention to this subject. The orthoscopic eye-pieces which, so far as I am aware, were first constructed and sold by the unfor- tunately so early deceased Kellner, of Wetzlar, give a very flat image, but have shown me nothing further, even in their stronger numbers. It follows from what has just been said, that he who can ob- tain about the same magnifying power in a double manner, that is, by means of a weak objective and a strong eye-piece, or by means of a strong objective and a weak eye-piece, should always have recourse to the latter. The effort of the older op- ticians to combine weaker objectives with relatively stronger eye-pieces cannot, therefore, — we repeat it, — be approved of, and is at present being more and more abandoned. The ojects of histological and medical investigations will seldom require the application of oblique illumination. If it be USE OP THE MICROSCOPE. 91 desired to learn the effects of the latter, the directions given above are to be followed. When reagents are to be used, it is customary, as a rule, to add a drop of them to the preparation by means of a pointed glass rod, either by removing and replacing the covering glass, or by placing the drop at its edge, so that it may how under the cover and unite at this point with the fluid in which the specimen is mounted. A gradual streaming in of the reagent may be obtained by means of a thread of lint which lies half under the glass cover, half free on the slide where it receives the drop. A better way is to place an evenly cut strip of blotting- paper close to one side of the covering glass, and then add the reagent at the other. In this manner the change of fluids takes place with rapidity, and one soon learns to control it at pleasure. For the protection of the instrument, it is necessary to ob- serve due caution with reagents, especially when using strong acids, alkalies, and all substances which attack the lead of the flint glass. Concentrated muriatic and nitric acids are to be avoided as much as possible, and care shonld be used with vol- atile acids and ammonia. Sulphuretted hydrogen should never be used. All of these reagents require the use of the largest possible covering glasses. If a lens should unfortunately be- come moistened with the reagent, it must be immediately dipped into distilled water. Chemical processes which develop vapors should in no case be undertaken in the microscopic work-room. The destructive effects of snch influences are best shown by the unfortunate condition in which the microscopes of chemical laboratories are usually found. The repeated packing and unpacking of the microscope is too troublesome for those who use it daily, and not at all bene- ficial to the mechanism of the stand. It is therefore preferable to place the instrument on a thick piece of cloth, on the work- table, and under a bell-glass or a glass case, which affords suf- ficient protection from dust. The eye-pieces, the objectives shut up in their case, and such other things as are daily used may be kept under a second smaller bell-glass. It is advisable to heat the room during the winter, to prevent dampness. The instrument should be re-examined every time that it is used, especially by the beginner, before being replaced under 92 SECTION FIFTH. the glass case. Stains are to be removed from the brass work with a linen rag ; dust which has settled on the mirror, eye- piece, etc., by means of a fine camel' s-hair brush. Although these procedures consume some time, they are still of great value for the protection of the instrument and the preservation of its original power of performance, especially if the objectives are also examined each time they are used. The objectives are best cleaned, after removing the dust with a camel' s-hair pencil, by means of a piece of fine linen rendered soft by frequent washing. Fine leather or elder pith may also be used. Some stains are to be removed with distilled water ; others, as glycerine for example, require a cloth freshly moist- ened with alcohol. A larger quantity of alcohol is to be avoided, as the fluid might possibly get into the setting of the lens and reach the Canada balsam which cements the crown and flint glasses together. This wetting of the lenses rarely happens to the more ex- pert. It is obvious, that where reagents are being used it is to be particularly avoided, and the greatest caution is therefore requisite. The objectives used should be as weak as possible with long foci, and, when much of this kind of work is to be done, the stage is to be covered with a glass plate, which latter may be fastened with clamps, when there are any on the stage. Broad slides for the specimens also afford some protec- tion. Notwithstanding every precaution, the optical portions of the instrument require cleaning, after a time, in consequence of a fatty coating which settles on the objective and eye-piece, and renders the image quite dim. Instruments which have been used for years almost always show this coating. One should not be too anxious about such a cleaning process, as by using a good brush and fine linen the glasses of the microscope do not suffer in the least. The microscopist's work-table should be large and massive, so that it may stand sufficient^ firm. A hard-wood board, at one or both sides of which small slabs of slate may be inserted for objects which require preparatory manipulation to rest upon, is most to be recommended as a table-top. A series of drawers is a valuable addition to the table. A number of smaller accessory apparatuses which are necessary to the microscopist may be kept in these, and are best pre- USE OF THE MICROSCOPE. 93 served in tliis way from dust and other contaminating in- fluences. In these are kept the slides, the various sorts of glass cov- ers, glass vessels, drawing arrangements, accessory apparatus for the microscope, the linen rags for cleaning, etc. A few bell-glasses and glass cases are necessary on the work- table to protect things which have been temporarily set aside from dust. Reagents are to be removed from the table after being used, and kept in another place. The question as to what corporeal and psychical qualities the microscopist should possess, is discussed with great pro- foundness in many works. We think that it may be here omitted. Acute mental organs, calmness, love of truth, and talent for combination are qualities which the physician and the naturalist should always possess. He who has not these, whose perceptive faculties are clouded and the impartiality of whose observations are constantly disturbed by a lively, ex- cited imagination, should keep away from the microscope as well as from the profession of medicine. For microscopical observation and work it is necessary to have visual organs capable of moderate endurance. Somewhat short-sighted, light eyes are generally the best adapted. He who is so fortunate as to possess two equally good eyes, should accustom himself to employ them alternately. Every micro- scopist who uses one eye for a long time continuously in look- ing into the microscope while the other eye, though remaining open, is unemployed, knows how much the acuteness of the one has increased, while the passive eye has acquired a certain irritability, so that when the latter is used in order to relieve the other, the field of vision appears much brighter and weari- ness soon makes its appearance. Where one eye is evidently weaker than the other, the microscopical work naturally falls to the latter. One should accustom one' s self from the begin- ning, while looking with one eye into the instrument, to keep the other open also. The attention is concentrated so predom- inantly in the active organ that the observer is no longer con- scious of the impressions made on that which is unemployed. For the protection of the visual powers, one should not work too continuously, avoiding the earlier morning hours, as well as the time immediately after dinner. Leave off as soon 94 SECTION FIFTH. as fatigue commences. For beginners especially, whose eyes often become rapidly tired from the unusual nature of the visual act, this is advisable, until later when long practice has accustomed them to more continuous labor. Whether to stand or sit while working, is to be determined by one' s previous habits. Bending the head down over verti- cal microscopes usually causes but little inconvenience. Eng- lish microscopists, however, as a rule lay great weight on the oblique or horizontal position of the tube and of the whole in- strument, to prevent the neck from becoming tired, or a how of blood to the head, so that not only their large, but also quite simple microscopes have such an arrangement. But, accord- ing to our Continental notions, the inconvenience of an oblique or vertical position of the stage is too great, when more than the examination of tests is concerned ; this arrangement has not, therefore, become very generally adopted. Very important for the protection of the eyes is the pre- viously mentioned judicious shading of the held, and the skil- ful application of the diaphragm (fig. 22, page 22). The gift of seeing and observing with the microscope is, like all human abilities, unequal, greater with one person, less with another ; but with a little perseverance it may be acquired to a sufficient degree by most persons. The peculiar nature of the microscopic images causes some difficulties for every commencing observer. The compound microscope shows us only that stratum of the object which lies directly in the focus, and everything else, which lies in other planes, either not at all or only indistinctly. At the same time, in the usual manner of examination, the whole specimen is transparent, illuminated from beneath and not from above, as in ordinary vision. Things which lie in other planes, higher or lower, only appear after altering the focus, and this condition is much more appreciable with strong objectives of a high angle of aperture than with weaker objectives of a lower angle of aperture. Hence it follows, that Ave are able to recognize immediately the outline of an object, and the relation of length and breadth, but not its thickness or its entire form. We are able to obtain these only by a combination of the various mi- croscopic images received by varying the focal adjustment. Here the beginner frequently meets with considerable difficul- ties, and errors may arise from improperly combining the images. USE OF THE MICROSCOPE. 95 In this kind of vision we are deprived of the aid which enables us, in ordinary vision, to judge rapidly of the shape of the object. The form of a microscopic object, regarded with inci- dent light, is, for this reason, generally more readily compre- hended. The appreciation of the form of a blood-cell is not difficult for those who are somewhat practised, but the contrary is the case in ascertaining the polyangular shape of many diatomacefe, or the form of a cavity in an organic part. The comparison of a number of sections made in horizontal, ver- tical, and oblique directions, a means resorted to by botanists especially, is here, when practicable, of great value. The estimation of the form is difficult in still another man- ner, namely, in consequence of the extraordinary diminutive- ness of an object. With a little practice it is not difficult to recognize the relations of relief in a microscopic object, for ex- ample, to distinguish a somewhat larger concave surface from a convex one, if only by means of a combination of various images. When such surfaces are extremely small, as is the case, for example, with the delicate areolations of the so fre- quently employed test object, the Pleurosigma angulatum, the discrimination is very difficult. Thus, as has been previously remarked, these last-mentioned areola? have been declared by some excellent observers to be convex, by others to be exca- vated, and the matter has not yet been definitely decided. Welcker has given us a good means for discriminating be- tween convex and concave bodies. The former act as convex lenses, the latter as concave. When we start with the tube in a medium position, a convex body will appear lighter by rais- ing the microscope tube, a concave by lowering the tube ; a globular structure and a hollow sphere, a ridge and a furrow, may thus be discriminated. It is much easier to recognize the shape of microscopic ob- jects by means of weaker objectives than by the employment of very strong combinations with large angles of aperture, so that herein also lies a weighty argument in favor of the former. Although the practised microscopist may accomplish his pur- pose with very strong objectives, still it is frequently desirable to have a well-constructed medium power, with the smaller angle of former days, added to one's instrument. The English opticians have sought relief in this direction by adding a dia- phragm to the lenses with large angles of aperture. 96 SECTION FIFTH. One soon learns to appreciate the foreign substances which contaminate the microscopic image, much of which may be avoided by neatness and carefulness in making the preparation. One should make one's self familiar, and as soon as possible, with the appearance of air bubbles, oil globules, starch gran- ules, fibres of linen and cotton, etc. It is also important to compare the image which an object presents by transmitted light with that which it affords by in- cident light. Among other things, the appearance of one and the same object in media of various refracting powers is also to be studied. The optical portion of microscopic work is much more diffi- cult to acquire than the manual, such as the cautious use of the adjusting screws and the mirror, and the steady and not jerking movement of the object through the field. In this place the important principle should be impressed, that movements which can be securely accomplished by the human hand are to be left to it, and are not to be executed by screws and other mechanical contrivances. Every experienced microscopist will regard the massive accessory apparatus of the large English microscopes as being somewhat superfluous and inconvenient. The inversion of the image by the compound microscope causes some difficulty for the beginner. One soon becomes accustomed to this, however, and finally to such a degree that it is no longer noticed, and one is only reminded of it when using an erector (where the inverted image is again inverted by means of a lens placed within the tube of the microscope, or by a prism on the eye-piece). As this inversion is attended with optical disadvantages, such instru- ments have not been extensively adopted, and are only convenient for microscopic dissections when furnished with weak lenses. Hartnack has recently obtained a very con- siderable improvement by means of his image-in- verting eye-piece (fig. 73). This has above the fis. ra. Hart- ocular lens, that is, above the lower ring-shaped iD U geyVpiicr invert " projection, a complicated prism, which produces a complete inversion of the image with a very bright though somewhat small field. It costs a little more than thirty francs. Finally, one word more is necessary concerning the phe- USE OF THE MICROSCOPE. 97 nomena of movement visible under the microscope. Not every- thing which is here seen in motion is, for that reason, to be pronounced vital. Currents sometimes occur in water, with which one should become familiar in order to guard against error in other cases. For instance, if alcohol is mixed with water, the small bodies suspended in it acquire a rapid motion, which continues until botli fluids are equalized, that is, have become thoroughly blended. Then very small particles of substances which are insoluble in water present an uninterrupted dancing motion, the cause of which is still unexplained, but is, at all events, a purely physical phenomenon. This movement is called the "Bruno- nian molecular motion." Finely powdered charcoal, small crystals, the granules of a coloring material exhibit the same peculiar dancing movement as the molecules of fat and melanine taken from the animal body. In certain cases we can observe the same motion in the fluid contents of cells as are taking place in the surrounding fluids. On the vertebral column of the frog, at the points of exit of the spinal nerves, lie small white collections of columnar- shaped crystals of the carbonate of lime. These, deposited in a drop of water, present one of the finest examples for the study of the molecular movement. Larger crystals, of about xirr to sir"', lie perfectly quiet, so long as there is no current in the fluid. Those of half this size are seldom found to have the dancing motion. The smaller the columns are, the more gen- erally the movement is to be met with, and the smallest, of xoW and smaller, on which we are no longer able to recognize the columnar form, are engaged in a continual, restless motion. The examination of the molecular movement is instructive for the beginner in still another regard. One readily forgets how much the excursions of a moving object are enlarged by the optical apparatus of the microscope. The dancing of a small molecule will appear slight to the eye with 200-fold en- largement, but very energetic, on the contrary, with an enlarge- ment of 1000-1500 diameters. This is repeated in the vital movements which are seen with the instrument. An animalcule which we examine with very strong lenses shoots quickly through the field, while with the 7 98 SECTION FIFTH. lowest powers it does not swim with any considerable degree of rapidity through the water. When the circulation in the web of the frog's foot or in the tail of its larva is examined with high powers, the blood-corpuscles hasten through the capillary passages, while in reality the current in the capillary vessels is quite slow. There is still another consideration which is not to be disre- garded in observing the phenomenon of microscopic motion. When a series of movements follow each other with great rapidity, we may readily recognize the total movement, but not the single motions ; these are separately appreciable to the eye only when the entire phenomenon is retarded. We shall be- come acquainted with an example of this, the ciliary movement, in a later section. Finally, we have to mention still another series of movement phenomena which has recently attracted the attention of investi- gators more and more, — we refer to the changes in shape of the living animal cell. Isolated examples of this marvellous change of shape, espe- cially in the bodies of the lower animals, were known long ago. At present it is known that the young animal cell, so long as the cell body still consists of the original substance, the so-called protoplasma, is endowed in the highest organisms also with a capacity for independent vital contraction. Numerous cells of the normal superstructure, likewise pathological new formations — so long as they possess the character of youthfulness — present the changes mentioned. Such cells have been seen to pass out (after the manner of the amcebfe) through. the walls of the capillaries (A. Waller, Cohnheim), to wander through the lining tissue, and to take up into their contractile cell-like bodies small particles, such as molecules of iudigo, anilin, cin- nabar, and carmine, the finest milk globules, and even extrava- sated colored blood-corpuscles ; so that the view here opens into a new world of minute actions, and it has already furnished extremely important information, to which we shall again refer. If in any microscopic investigations the most conservative preparation is requisite, it is just here. In order not to kill the cell prematurely, one must employ a truly indifferent fluid medium. Whoever proceeds to make such investigations with the old idea of possessing such indiffer- ent fluids in solutions of sugar and salt, albumen and water, or USE OF THE MICROSCOPE. 99 Fig. 74. Recklinghausen's moist chamber. humor vitreus, will soon become convinced of the contrary. In general only those fluids which surround the cell in the body can be called truly indifferent. In many cases the indication may be fulfilled with iodine-serum (see below), or a similar com- position. The greatest caution is necessary to prevent pressure and evaporation. The very thin covering glass is to be support- ed by placing beneath it the frag- ments of one of its predecessors, which are usually not very rare with the microscopist, or — what is for many cases still better — the covering glass is entirely omitted. Recklinghausen has invented a very efficient little apparatus for preventing the evaporation of the fluids. This, the "moist chamber," the reader will readily comprehend by glancing at fig. 74. The object is placed on the somewhat broad ground slide (d) in the usual manner. The glass ring (a), with its under surface likewise ground off, rests on the slide at some distance from the object. This ring may, in certain cases, be made higher. A tube (b) of thin rubber is fastened as firmly as possible about the ring. The upper end (c) of the tube is fastened round the neck or tube of the microscope with a small rubber band. In order to keep the space thus enclosed satu- rated with moisture, two strips of elder pith or bibulous paper, saturated with fluid, are to be placed at the inner surface of the glass ring, and the external surface of the lower border of the Fig. 75. A more simplified moist chamber. ring is to be surrounded with several little pads of moist blot- ting-paper. A moist chamber may be made in still another, more simpli- 100 SECTION FIFTH. fied manner (fig. 75). A glass ring (&), a few millimetres in height, is to be cemented on to an object slide (a). A few drops of water are to be cautiously placed at the inner edge of the former with a brush. The object is to be placed on a circular covering glass (c) and the latter then turned over and placed on the ring ; in this way all pressure is necessarily avoided. One may thus — with the aid of an immersion objective — fol- low the movement of these cells for hours, and even days. The last-mentioned simple apparatus may be readily convert- ed into a gas-chamber (fig. 76). The thick glass plate shows a ring ground out at the bottom of the chamber. Two glass tubes are cemented into the two half canals. One of these tubes (a), connected with the caoutchouc tube a" serves for the entrance of the gas, the other (a') for its exit. The covering glass may be more securely adapted to the glass ring with a cement. Although we can in this manner, at the ordinary temperature of the room, study the cell life of a cold-blooded vertebrate ani- mal, for example, in the connective tissue, cornea, blood, and lymph of a frog, we cannot, with the same success, study those from the body of a warm-blooded animal. The movement is too rapidly retarded by the surrounding coldness. A condition as to temperature resembling that of the living organism must be attained for the success of the observation. The older mi- croscopists helped themselves in this dilemma, so far as it was possible to do so, by using warmed slides. Beale afterwards constructed a warmable stage, but of rather crude form. Quite recently a celebrated investigator, M. Schultze, has rendered a great service by producing an apparatus of this kind which ful- fils the indications more completely. USE OP THE MICROSCOPE. 101 Schultze' s apparatus* is represented by our fig. 77. A brass plate A, which is notched (c) posteriorly, so as to fit on to the sup- port of the microscope, is to be fastened on to the microscope stage with clamps. It is perforated at a for the illumination, and at its front part, in the middle, the thermometer (d) is placed slantingly ; at the corners are the two arms b. Two small spirit lamps under the latter supply the heat. The lower extremity of the thermometer is enclosed in the brass case Bra, which has Fig. 77. Schnltze's warmable stage. two somewhat thicker wooden ledges at its sides. The ther- mometer winds round the aperture in the stage, passes uncovered and horizontally, for a short distance, on its under surface, and then bends to pass through the opening b to arrive at the face of the graduated metal plate. It has been ascertained by experi- ment that the actual temperature of the object is indicated by the thermometer. It is scarcely necessary to remark, that it is most advantageous to use immersion lenses and the moist chamber with the hot stage. Unfortunately, this apparatus has an unpleasant defect, as Engelmann has shown. The temperature of the object is occa- sionally reduced very considerably by the metallic setting of the lens and the microscope tube, so that, in this case, the focal distance of the objective exerts a marked influence. The inser- * It may be obtainde of the mechanician Giessler, in Bonn, for 27 marks. 102 SECTION FIFTH. tion of a bad conductor of heat between the lens and the micro- scope tube has been proposed. An ivory tube, 30 mm. in height, applied in this manner, lessens this defect very materially. Quite recently Strieker and Sanderson, Panum and E. A. Schaefer have invented complicated apparatus serving the same purpose. Various arrangements have been contrived for the purpose of conducting electrical currents through an object under the microscope. We introduce, as an example, the simple one of Harting (fig. 78). Fig 78. Harting's electrical apparatus. Two somewhat narrow strips of tin-foil A B are fastened with starch paste on to a glass slide a bed; a portion of the tin-foil projects beyond the ends of the slide, so as to connect with the conducting wires of the galvanic apparatus. The central portion of the slide remains free. The two glass plates d e f g and h i 7c I are to be cemented over these strips of tin-foil with marine glue or a mixture of pitch and rosin, for the stage clamps to rest on. The two polar wires p and p (for which platinum is the best material) are not fastened ; they receive the curve shown in the figure at C. The part m r s rests on the tin-foil, the other curved portion m t v (to which may be given any curve desired) dips its point into the examining fluid, which in our drawing is surrounded by a cell D. Harting' s apparatus may be readily modified. Section 5u*tl). THE PREPARATION OF MICROSCOPIC OBJECTS. With the exception of the finished preparations of a collec- tion, in most cases the objects to be examined require prepara- tion, which, as Ave have already remarked, should be as careful and cleanly as possible. It is only when the blood, mucus, pathological fluids, etc., are examined, that the mere spreading out of a drop of the same is sufficient. The object slides, which are simply strips of glass, serve for the reception of the object to be examined. Several dozen of them should be kept on hand in a clean condition, protected from dust in an accurately closing box. Good slides should be made of pure glass, preferably without an}^ color, and the edges should be ground, for the protection of the instrument. Too great thickness of the glass renders the use of the stronger objec- tives and the cylindrical diaphragms, which then become neces- sary, inconvenient. Therefore, the thickness of the slides should not exceed i-i'". The most convenient form is that of a long square (3 inches by 1 inch), but when the stage is narrow they should be of a corresponding width. Square slides are less suitable. One should also accustom one' s self to place the object to be examined in the centre of the slide. It is rarely examined in the dry condition, but, as a rule, with the addition of some fluid ; as, water, glycerine, etc. This is to be added at the com- mencement of the preparation. One soon learns to judge of the quantity which is necessary. The object to be examined, if it is large, and especially if it is thick, — as for example, when one desires to examine a small embryo or an injected specimen of considerable size, — is to be placed with some fluid in a watch-glass under the microscope. Small quadratic glass boxes, about an inch or an inch and a half 104 SECTION SIXTH. in size and two or three lines in depth, are more convenient for this purpose (fig. 79). Small glass boxes with covers, as represented in our fig. 80, of nearly natural size, are still better. They may be purchased quite cheap of E. Seybold's suc- cessors, in Cologne. Glass cells, as made by the Eng- lish (see further on, at the prepara- tion of microscopic objects), may also be employed with advantage. Thick slides with an excavation in the centre are less suitable. The preparation is seldom ex- amined uncovered ; such a method of examination is confined almost entirely to the cases last mentioned. The covering glasses or covering scales, which have been so frequently alluded to, serve for a covering. Pieces of pretty thick glass were formerly used with low powers ; at Fig. 70. Glass box. Fig. SO. Glass box with its cover. present these have gone out of use, since thin and even very thin glass may be obtained from England at slight cost. As we have seen in an earlier section, the thickness of the covering glass exerts considerable influence on the opti- cal performance of the stronger objectives. It is well, there- fore, to have these glasses arranged in a series of various thick- nesses, which are kept in separately designated boxes. It is necessary to have them from £-$-'", to those of T \ r - T V'" m thickness, according to the objectives with which they are to be used. Even the pressure of this thin glass is occasionally too great for very delicate objects, if one desires to avoid crushing or splitting them. In such cases it is necessary to insert a harder substance between the slide and the cover, a pre- cautionary measure which has already been alluded to on a pre- ceding page. Thicker covers may be cut from thin plate glass. THE PREPARATION OP MICROSCOPIC OBJECTS. 105 A few special instruments are requisite for making prepara- tions. But one should not think that they are indispensable. In practised hands the same and even more may be accom- plished, in a shorter time, with simple tools than with compli- cated ones. A number of microscopic knives, small forceps, and scissors have been invented, it is true, but they are gener- ally used by their inventors only, and are, as a rule, quite worthless trash. First of all, one should have several tine forceps terminating in thin points for seizing objects. Such should be selected as have light springs, and not the stiff ones which many anato- mists are accustomed to use. The points should be either quite smooth or only slightly grooved. A hooked point is un- suitable. Many objects, especially those of a delicate nature, are more conveniently moved with a camel's hair-brush. The scissors are most frequently used for dissecting. A fine pair of so-called eye scissors is indispensable. A small pair with curved blades is very convenient for many purposes ; here and there, a pair of fine elbow scissors also renders good service. A few small knives, though useful, are of relatively inferior value. Several very fine scalpels with narrow-pointed blades, when possible, of somewhat strongly hardened steel, are more serviceable. The ordinary anatomical scalpels are much too clumsy, and, as a rule, are made from too soft steel to be use- ful for the microscopist. When a still finer cutting instrument is necessary, the ordi- nary cataract needle is to be used. It is also extremely useful for moving small objects. The tearing of microscopic objects is frequently necessary in histological investigations. This may be accomplished with very finely pointed steel needles, of medium length, let into wooden handles. When this picking process is necessary it should, in consequence of the minuteness of the elements of the human bod}', always be performed with accuracy ; devo- ting the few minutes required, as one will be rewarded for the little pains, by a good preparation. Beginners very frequent- ly fail in this. They stop picking too soon on a preparation which was too large at the commencement. Not unfrequently, in such cases, the work is so fine that one must have recourse to magnifying glasses, to the loup or 106 SECTION SIXTH. the simple microscope. A very great inconvenience is con- nected with the latter when nsed with stronger lenses ; the shortness of the focus soon renders needle-work impossible. Zeiss deserves credit, therefore, for having produced the use- ful microscope represented in fig. 81. It has, on a short tube, an objective consisting of three lenses, and has a concave lens as an eye-piece. It permits the use of needles, even with 150- 200 fold enlargement. The image inverting eye-piece of our fig. 73, p. 96, permits a similar use of a compound microscope. Fig. SI. Zeiss' new directing microscope. [A very economical and efficient substitute for the simple microscope has been devised by Dr. Curtis. It consists simply of a binocular ophthalmoscope, the mirror of which is replaced by a biconvex lens of one or two inches focus. The whole rests over a small aperture in a little wooden box, the front and part of the sides of which are removed for convenience of manipulation with the preparation which is placed on a sup- port in the box. As will be readily appreciated, this gives an THE PREPARATION OF MICROSCOPIC OBJECTS. 107 upright, stereoscopic image, and a considerable magnifying power.] It is often found necessary to make very thin sections from fresh, and especially from artificially hardened tissues. Knives with double blades running parallel, and close to each other, have been used for this purpose. The double knife invented by Professor Valentin has become the best known. It is not Fig. 82. Double knives. 1, that of Valentin ; 2, the improved English instrument. easy to produce a good instrument, such as is represented by our fig. 82, at 1, and when not well made it is entirely unser- viceable. This instrument has received a judicious improve- ment in the hands of English cutlers. We see such an im- proved form of the double knife represented in the same cut, at fig. 2. Even with this improved instrument, unfortunately, not much can be accomplished, as I know from experience. It is much more desirable to make thin sections, with the free hand, by means of a good razor. Any one who has such an one at his command, and has acquired the necessary dex- terity, will discard the double knife. Good English razors, of light construction, with small blades, are the most suitable. For many purposes, it is well to have them ground flat ; but it is preferable to have the blade ground hollow for very thin and fine sections. To preserve it in a proper condition, it is neces- sary that it should be well sharpened, and the strap should be frequently used. The blade, as well as the preparation to be cut, must be well moistened, for when they are dry a good sec- tion can never be made. The fine section is best removed from the wet blade by means of a brush ; it is then to be carefully and cautiously spread out on the slide. For making very large sections with sufficient delicacy, however, the razor is unser- viceable, in consequence of the thickness of the back of its 108 SECTION SIXTH. blade. In such cases, according to Thiersch, another instru- ment may be advantageously employed ; it consists of a knii'e- blade of the thickness of paper (about 1 cm. in breadth by 20 cm. in length), which is to be stretched in a watchmaker' s or- dinary saw-bow. [The best razors which I have seen for anatomical work are those made by Le Coultre, in Switzerland. The blades are as thin as paper, and are made of good material. The price varies according to the width and number of the blades. Those with one wide blade cost 81.75, gold ; with two wide blades, $2.50.] The so-called microtomes are used for making sections of uniform thickness, or a whole series of sections. Many of these instruments have been invented, and some of them are quite expensive. I have found Sckiefferdecker's, a modification of the instru- ment invented by J. Smith, very good (fig. 83). It permits of a the use of any razor, either dry or moist. The razor is moved with the free hand, and the preparation is held firmly and moved forward by means of a micrometer screw. The microtome consists of two brass rings, with the greater portions soldered, and placed one above the other. A space is left between them above. They are here provided with deckers microtome, " x about half the actual screw courses, and receive a short tube which also has screw courses. This has above a broad brass flange, the outer margin (6) of which is divided into 100 parts, and is bent downwards at an obtuse angle for the protection of the knife. A complete turn of the screw elevates the preparation 1 mm. ; a turn of one division is 0.01 mm. An indicator (e) is attached for reading oif . The preparation is inserted into a larger piece of firmer ani- mal tissue, such as hardened liver or spinal cord, or into elder pith, or imbedded in any other manner and then fixed in the half tube (a) which is adjusted by the horizontal screws (d). [A very efficient "section cutter" has been contrived by Dr. Edward Curtis, of this city, to whom I am indebted for the accompanying wood-cut. The following description of the apparatus, and the manner of using it, is condensed from an article presented by Dr. C. at THE PREPARATION OP MICROSCOPIC OBJECTS. 109 the annual meeting of the American Ophthalmologic^ Society, held at Newport, July, 1871. The apparatus is shown in tig. 83 s . "It consists of the part A (fig. I.), for holding the object to be cut, modelled after a form of section cutter in common use ; and of the cutting part B, after my own device, composed of a long straight knife held FIS.I F1GII FIG III FIG IV Fig. 83*. Curtis 1 " section cutter. " in a frame. The holder, A, consists of a heavy brass plate, faced with glass, six inches long by three and three-quarters wide, from the centre of which is sunk a hollow cylindrical barrel, one inch and three-quarters in depth, and one inch and one-quarter in diameter, inside measurement. Through the bottom piece of this barrel (which unscrews for convenience) works a screw shaft, furnished with a large milled head. The threads of the screw are fifty to the inch, and the circumference of the milled head is marked, off into eighths, so that, if desired, the thickness of the sections cut can be measured. Attached to the under surface of the face plate, near one end, is a screw clamp for fastening the apparatus to the edge of a table, so as to leave both hands of the operator at liberty to work the cutter. "The principle of this ' holder,' as it might be called, is very simple. The object to be cut is first embedded in a cast of wax and oil, or paraffine, made to exactly fit the bore of the barrel ; this mass is then pressed into the barrel, pushed upward by turning the milled head of the screw-shaft until it projects slightly above the level of the face-plate, when the projecting 110 SECTION SIXTH. part is cut off by a sweep of the knife. Another turn, or a fraction of a turn, of the milled head is then made, and again the projecting portion is cut off, this time as a smooth, even sec- tion of microscopic thinness. For a cutter I had a straight knife made, with a blade eight inches long, one and a quarter inch wide, and three-twentieths of an inch thick at the back, and with the sides concave like a razor. This I at first used by itself, sweeping it over the surface of the holder in cutting the sections, but I found that, from the length and thinness of the blade, it was apt to bend under pressure, and so fail to cut an even section, and also that the edge soon got dull from friction upon the face-plate. To obviate these difficulties. I conceived the idea of having the knife fixed in a frame which should answer the double purpose of holding the blade stiff, and carry- ing it with the edge raised slightly above the level of the sur- face of the holder, so that the under surface of the arms of the frame should be the bearing surface upon the holder, and the edge of the knife be allowed to touch nothing but the tissue to be ciit. The design of the frame will be seen at once from the figure ; it is made of brass, and the knife is pushed into place from behind, under a couple of springs, which hold the blade down, and, when pressed home, the knife is kept from slipping back by a little fastening, which is pushed against the back of the blade and then fixed by a turn of a quick screw. Besides the advantages of the frame in holding the knife stiff, and keep- ing its edges from scraping over the surface of the holder, its weight and broad tread make it sweep much more steady and true than that of a light knife used by itself." This apparatus is so efficient that Dr. (J. has often cut with it sections of an entire human eye, thin enough for microscopical examination. In preparing the tissue and cutting the sections, however, there are one or two points which it is necessary to observe in order to get the best results. The tissues are to be hardened in the usual manner, with bichromate of potash and alcohol. When the consistence is suitable for cutting, the piece is to be transferred to oil of cloves, where it is allowed to stay until thoroughly impregnated with the oil ; this takes from half an hour to several hours, according to the size and solidity of the specimen. The piece is now to be embedded for cutting. "In order to get a mould for the paraffme which shall yield THE PREPARATION OF MICROSCOPIC OBJECTS. Ill a cast of the right size to go into the barrel of the section-cut- ter, a solid brass plug (rig. IV. of the woodcut), one inch high, and made to exactly fit the bore of the barrel, forms part of the apparatus. In one end of it an oval excavation is countersunk, to let the cast of paraffine take a firm hold of its surface, and to keep the same from turning round under the pressure of the knife. A strip of letter-paper, about two inches and a half wide, is now wrapped tightly around this plug, the plug being in the middle of the strip, so that the paper projects at both ends. The part projecting beyond the fiat end of the plug is folded down over it, and the opposite projecting cylinder of paper then forms a cup, with the excavated face of the plug for a bottom, of the exact calibre of the barrel of the section- cutter. Into this the melted paraffine is to be poured. A cap- sule containing paraffine, or wax and oil, in considerable excess of the amount required for the embedding, is held over a lamp till the mass is just melted, when it is taken off and the piece of tissue dropped into it and stirred about for a few minutes to rinse off the excess of oil of cloves. Then some of the melted material is poured into the paper mould, the piece of tissue immediately transferred to the same, arranged in proper posi- tion, and the whole set aside to cool. When perfectly cold and hard, the paper is unwrapped, care being taken not to loosen the paraffine cast from the brass plug, and cast and plug toge- ther are then pushed into the barrel and holder, and each sec- tion is cut by a sidelong sweep of the cutter. It is usual in cutting sections to flood the surface of the tissue and the blade of the knife with alcohol, so that the section, in cutting, floats freely over the blade. 1 ' In this apparatus, however, from the great length of the knife, and from the fact that its edge is raised off the surface of the holder, this procedure is impracticable ; but I find that I get even more perfect sections by the plan of cutting dry — that is, without flushing the surface of the tissue with any fluid. It will be seen in the figure that the knife is set at a slight angle in the frame ; and this obliquity seems to give the section a tendency to curl away from the knife-blade in the cutting, so that in this dry process there is not only no more, but there is actually less danger than by the wet method of the section clinging to the blade, and so getting torn. But here the pre- liminary impregnation of the tissue with oil of cloves is essen- 112 SECTION SIXTH. tial ; for, were it in alcohol, the microscopically thin section would instantly become ruinously dry as soon as cut. The oil of cloves, however, from its very slight volatility, keeps the tissue of the section moist until it can be transferred to a fluid. But it will not do so long, and hence the moment a section is cut it should be promptly seized and dropped into fluid ; and if, from imperfect impregnation before embedding, the surface of the cut tissue looks dry, it should be moistened only by a touch of a camel's hair brush dipped in oil of cloves. If the sections are not to be stained, they are dropped into turpentine as soon as cut ; this dissolves the adhering wax or paraffine very promptly if slightly warmed, and the sections are then ready for examination or mounting. If they are to be stained, they are put into alcohol instead of turpentine. This in a few minutes dissolves out the oil of cloves, and the sections are then put at once into the carmine staining fluid. "The woodcut represents two accessory pieces of apparatus that have not been alluded to. Fig. III. represents a secondary barrel with a half-inch bore, which can be screwed into the bottom-piece of the main barrel to diminish its size when an3 r small pieces of tissue are to be imbedded. It has a plug made to lit it similar to the large plug of the main barrel. Fig. II. is a simple and ingenioirs contrivance, devised by Mr. Wale, the maker of the instrument, for holding hard substances which will bear squeezing, and which, therefore, it is not necessary or desirable to imbed, such as cartilage, horn, wood, etc. It con- sists simply of a brass plug, made to fit the barrel of the sec- tion-cutter, hollow, but with the bore slightly conical, and with a screw-thread cut. on its face. A few wedge-shaped pieces of soft wood of different sizes, roughly whittled out, complete the apparatus. Supposing a stick of wood is to be operated on, it is grasped between two of the wedges of the right size, being allowed to project somewhat above their tops, the whole pressed firmly into the conical bore of the plug, and with a turn or two the soft wood of the wedges is tightly grasped by the screw- thread of the plug, and the object to be cut, tightly jammed between the wedges, is immovably fixed. Sections can be cut from the projecting portion in the usual way. It may be re- marked, in passing, that the cutter for anatomical tissues must not be used for hard substances. For these a strong, heavy knife or chisel of less brittle temper is to be employed. THE PREPARATION OF MICROSCOPIC OBJECTS. 113 "In conclusion, it may not be amiss to state that the sec- tion-cutter and accessories can be obtained (to order) of Messrs. Hawkins & Wale, physical instrument makers, Stevens' Insti- tute of Technology, Hoboken, New Jersey. Price $30, or, without the knife-frame, $20. The knife is a simple affair and can be made by any first-class manufacturing cutler from the dimensions given above, Mine was made by Mr. A. Eickhoff, 381 Broome Street, New York, price $3." In most mechanical microtomes the knife or cutting instru- ment is carried through the tissue like a chisel, that is to say, the cutting edge is pressed through the tissue. Dr. Seiler, of Philadelphia, has devised a section-cutter which combines the advantages of hand cutting and the me- chanical microtome. It consists of two rigid, parallel arms of metal, which at one end revolve on pivots attached either to the microtome itself, or to the table to which the microtome is to be clamped. ^ On the other end of these arms are fastened revolv- ing clamps which hold the knife, the edge of which, when in position, rests upon the glass plate of the microtome. The handle of the knife is removed, so as to prevent a slipping and a hinderance to the motion of the knife, but can be easily at- tached by means of a screw, for the purpose of stropping. When in position, and ready for cutting, the knife is pressed upon the glass plate, and a slight side motion is given to it by the hands, which causes it to pass through the tissue and cut a thin, even section without any difficulty. In order to cut well and evenly, the knife must be carried through the substance to be cut, es- pecially if it is soft, in a slanting direction, so that each point of the edge describes a curve which is equal to a part of a circle. This is exactly what takes place with this apparatus when the knife is used, the radius of the curve being the length of the arms from the centre of the clamps to the centre of the pivots.] Let us now pass to these embedding methods. They serve to enclose very small objects which can no longer be held, like coarser substances, in the fingers of the left hand while making the sections. Small objects may be advantageously placed in a thick solution of gum-arabic, or embedded in a mixture of wax and oil (Strieker), in parafiine, or in a mixture of glycerine and gelatine (Klebs). We give several recipes which may be readily modified as may be necessary. 1. Embedding in gum. A paper cone or box is to be filled 114 SECTION SIXTH. with a very concentrated solution of gum-arabic ; in this mass is placed the object, from which the water has been drawn out by means of alcohol. The whole is then to be placed in alcohol for two or three days, and is then in a condition proper for cut- ting. The sections are to be washed out with water. 2. Embedding in a mixture of wax and oil. Equal parts of each are to be warmed in a porcelain dish till they become fluid, and the mixture is then poured into a paper box. The preparation is to be deprived of its water with alcohol, and rendered transparent by means of an ethereal oil ; it is then placed in the mixture, and is ready for cutting as soon as the latter has become cold. The sections are to be washed out in oil of turpentine. 3. Embedding in paraffine. A cavity, made in a piece of paraffine, is partially filled with melted paraffine. In the latter is placed the object, which has been hardened in chromic acid and alcohol. Paraffine is again poured in, and the whole may afterwards be placed in alcohol. In many cases it is sufficient to drop a little melted paraffine on to a slip of gutta-percha, place the object on it, and cover the latter by dropping on a little more paraffine (His). Embedding in a mixture of five parts paraffine, two of spermaceti, and one of lard, has recently been recommended (Rutherford, Pritchard). 4. Embedding in a mixture of glycerine and gelatine. Alcohol or chromic acid preparations may be placed in a mix- ture composed of about one volume of a very concentrated so- lution of isinglass and half a volume of pure glycerine. The whole, when cooled, is to be replaced in chromic acid or alco- hol, where the preparation and the gelatine become sufficiently hard. 5. Embedding in transparent soap. Flemming dissolves it in one-third to one-half its volume of alcohol. The alcohol pre- parations are enclosed in the warmed mass and set aside for a day or two so that the latter may dry. The embedding medium is completely transparent (a great advantage), and the object can now be cut with a dry blade. The soap may be dissolved with distilled water, and the pre- paration mounted in glycerine. THE PREPARATION OE MICROSCOPIC OBJECTS. 115 6. Embedding in Albumen and Tallow. Bunge invented the following mixture : Take fresh white of egg, after removing the chalazse, 24 ccm., which is to be combined with 2$ ccm. of a ten per cent, solution of soda by shaking them together in a wide test tube. Then melt 9 ccm. of tallow in a similar glass, and add the other solution. The preparation is placed in a paper box and the mixture poured in. It hardens in a few minutes and is placed in absolute alcohol (Bresgen). [A very efficient embedding mixture con- sists of one part of mutton tallow and two parts of paraffine. ] For very hard substances, such as bones and teeth, the knife is no longer serviceable for making thin sections. In such cases a small saw with a watch-spring blade is to be used, and the section is to be ground down on a whetstone. This can be best and most rapidly accomplished with a rotary stone. The ordinary camel' s-hair pencil is an indispensable imple- ment for the histologist. In addition to its usefulness for re- moving dust from the lenses of the microscope, it is also very extensively used in preparing specimens. It is the best thing to use for removing foreign bodies and fragments of tissue from the surface of preparations, and for spreading out thin and delicate sections on the slide. When it is necessary to remove from an object the cellular elements, which often occur in such great profusion as to conceal the entire arrangement of its su- perstructure, this may be much better accomplished by the pencilling method, originated by His, than with the stream Fig. 84. Pencilling microscopic objects. from a wash-bottle. The specimen is to be thoroughly moist- ened and covered with fluid (generally glycerine and water), and then brushed with a camel's hair pencil of medium size, the perpendicular strokes rapidly following each other (fig. 84). 116 SECTION SIXTH. The fluid gradually thickens and the tissue becomes transpar- ent. After a few minutes the preparation is to be turned over, and the process repeated on its other surface. In this manner, and occasionally removing the old fluid and replacing 1i t with new, the isolated frame-work gradually makes its appearance. It is also very serviceable to pencil an object while it is floating in a larger quantity of fluid — for example, in one of the above-mentioned glass boxes. A considerable amount of patience is necessary to make good preparations in this way, and still more to obtain the proper consistence of the object to be prepared. When it is not sufficiently hardened, it becomes filled with rents, even when the brush is care- fully used. Such tissues generally become quite ser- viceable after hardening for a day or two longer. It is much worse when an over-hardened tissue is to be prepared in this manner. In sxich cases one can obtain only an imperfect preparation or none at all ; it is no longer possible to remove the cells. As a rule, the thing is then to be entirety abandoned, for a subse- quent softening rarely leads to success. Billroth has also given some particular directions on the pencilling method. Thc'pipSic. Tne brushing may also be replaced by a carefully practised shaking out of the preparation. A strip of bibulous paper may be used for removing super- fluous fluids from the slides. It is more convenient to use a small pipette (fig. 85), an instrument which can hardly be dis- pensed with in making permanent specimens. Scrtion 0CDcntf). FLUID MEDIA AND CHEMICAL REAGENTS. TITKITION. Animal tissues are comparatively seldom examined in a simple dry condition, but, as a rule, a fluid is added. This fluid may act indifferently, although this is more rarely the case than is generally imagined ; it may act chemically on the ob- ject ; it may withdraw fluid from it, or allow fluid to pass into it, so that shrinking or swelling results ; finally, it may produce changes in the refractive conditions of the tissue. Let us first investigate the latter. The greater the contrast between the refractive power of the object and that of the sur- rounding medium, the sharper will the former appear. Thus many delicate structures may be most distinctly recognized when dry and surrounded by atmospheric air, while the addi- tion of water, by changing the refraction of the light, perhaps entirely prevents the details from appearing, or renders them very indistinct. Many textural relations of animal tissues are exceedingly difficult to recognize, in consequence of the slight difference between their refractive power and that of the sur- rounding water. We must, therefore, coincide with Harting. who says, the discovery of a fluid medium of less refractive power than water would afford very valuable assistance in many investigations. Other methods of rendering many things darker and more distinct, such as tinging the tissues, the appli- cation of reagents which coagulate and therefore darken them, are discussed further on. Certain reagents, acetic acid for ex- ample, act very advantageously by rendering a constituent part, as for instance the nucleus of a cell, darker, while the re- fractive power of the surrounding substance is diminished. The action of acetic acid on connective tissue affords us an in- structive example of how little one is justified in assuming, from a single method of investigation, that there is nothing in 118 SECTION SEVENTH. the field because there is nothing to be seen there. By causing the finest fibres into which the intercellular substance of con- nective tissue is split up to swell, their refractive power and that of the surrounding fluid is rendered similar, so that one might think that the fibrillse had been dissolved by the reagent, were it not for other methods which cause the reappearance of the fibres which had been rendered invisible by the acid. On the other side, the necessity often makes itself felt of rendering objects which are too dark, and therefore no longer recognizable, as transparent as possible by means of a fluid which refracts the light strongly. Hence strong solutions of sugar, gum, or albumen may be used, when it is necessary to clear up tissues which are saturated with water. In modern times we have learned to recognize in glycerine an invaluable accessory of this nature ; creasote also deserves recommenda- tion. Tissues which are free from water are more permanently cleared up by means of turpentine oil, Canada balsam, or anis oil. While the index of refraction of water is 1.336, glacial acetic acid has that of 1.38, pure glycerine 1.475, equal parts of glycerine and water 1.40, oil of turpentine 1.476, Canada balsam 1.532-1.549, and that of anis oil is even 1.811. How much the appearance of a microscopic object is deter- mined by the refractive power of the fluid medium is self-evi- dent. A small glass rod lying in water can be readily recog- nized with exactness, in consequence of the difference of the exponents of refraction. When it is placed in Canada balsam, whereby they become nearly similar, the glass rod ceases to glisten and can only with great attention be distinguished from a flat band. If anis oil be selected as a medium, an image is received as though there was a cavity in the oil (Welcker.) The necessity for the discovery of an actually indifferent fluid medium, that is, one which does not change the tissue, cannot be impressed with sufficient force on the hearts of micro- scopists. We have fallen into the beaten track of ascribing, with generous credulity, to water such a role, but which, in fact, it does not play. It is conceded that a small fraction, at the most, of the animal tissues make an exception, and the energetic action of water on the colored blood corpuscles and the elements of the retina cannot be denied. That the number of tissues affected by water is much greater, and that very few can re- main indifferent to it, is very clear to a few persons, but is by FLUID MEDIA AND CHEMICAL REAGENTS. 119 no means generally known. While so many have recently oc- cupied, themselves with the enclosmotic processes of physical physiology, in the particular domain of microscopy, no investi- gation of this process has yet been commenced. Theory requires that each constituent of the body should be examined in a fluid medium which resembles, in respect to quality and quantity, the fluid which saturates the living tis- sue. Naturally, this requirement cannot be completely ful- filled in practice ; our aim should be to approach it as nearly as possible. Saliva, vitreous humor, amniotic liquor, serum, and diluted albumen are generally recommended as suitable media for the investigation of delicate changeable tissues, and in certain cases, they accomplish their object in a satisfactory manner. But do not expect them to suffice for every case. Not unfre- quently one and the same tissue of different species of animals reacts differently with the same fluid medium, as may be seen with the blood corpuscles. An important and readily proved observation is the fact that the addition of the slightest quantity of carbolic acid to such animal fluids prevents decomposition. This is more ser- viceable than the previously recommended camphor. A physical examination made by Graham presents us with a key to the nature of these indifferent fluids. In an exceedingly interesting work (Annalen der CJiemie und Pharmazie, Bd. 121, S. 1), this scholar some time ago called attention to the fact, that two groups of substances, which he has designated by the names of Crystalloids and Colloids, are to be distinguished according to their }30wer of diffusion. The former, belonging to the crystalline bodies, dif- fuse rapidly and remind one in this regard of more volatile substances ; the latter, characterized by their inability to as- sume the crystalline condition, show a very slight diffusibility. Among the organic bodies may be numbered, for example, gum, starch, dextrine, mucus, albumen, and gluten. "When a column of water is placed over a solution which contains both these varieties of substances, chloride of sodium and albumen, for instance, the salt will penetrate to the upper- most stratum of the fluid, while the albumen, in consequence of its slight diffusibility, will not pass anything like so far up- wards, so that the upper strata remain free from it. Gelati- 120 SECTION SEVENTH. nous matters from the colloid series, such as mucus, for in- stance, permit a very easy passage to readily diffusible mat- ters, but resist very energetically that of less diffusible ones, and do not let other colloid matters pass through. By means of suitable membranes of this kind, crystallized matters may be separated from colloid substances, and the latter may be thoroughly purified in this waj r . According to Graham's ob- servations, readily diffusible substances, such as chloride of so- dium, even spread themselves through a stiff jelly with almost the same facility as in pure water. It is self-evident that these investigations are of great signi- ficance in connection with the processes of diffusion in the tis- sues composed of colloid substances. The above-mentioned indifferent fluids now appear to us in a new light. They always contain colloid and crystalloid sub- stances. Vitreous humor contains 987 parts of water to about 4.6 parts of colloid matter, 7.8 of crystalloid substance (that is, chloride of sodium). In amniotic liquor about the same proportions are met with. In 1000 parts occur about 3.8 of colloid substance (albumen), 5.8 of salts, together with 3.4 of urea. In serum we have about 8.5 per cent, of colloid and 1 of crystalloid substances. After what has been said it is nnnecessary to remark that fluids which contain only crystalloid or only colloid matters can make no claim to the character of truly indifferent media, although they may not perceptibly alter the contours and forms of the tissue elements for a long time. Accordingly, it has very properly been suggested that the microscopist should always have such indifferent fluids in rea- diness, the more so as solutions of albumen or liquor amnii may readily be preserved from decomposition for months by placing a piece of camphor in them (M. Schultze). A solution of albumen, of known quantitative composition, purified by means of Graham's dialyser, and to which a certain quantity of chloride of sodium is to be added, may be preserved with the aid of a piece of camphor, and will be very serviceable if diluted with water each time that it is used. It is useless, however, for the preservation of large pieces of tissue. It is obvious that the addition of colloid substances to solu- tions of the salts ordinarily used by microscopists also deserves a trial. FLUID MEDIA AND CHEMICAL REAGENTS. 121 Scliultze lias more recently recommended, in the warmest manner, an albuminous fluid tempered with iodine — and in fact, according to my own experience it is exceedingly serviceable. " Jod-serum," as he calls it, consists of the amniotic fluid of the embryo of the ruminantia, to which a concentrated tincture of iodine or a strong solution of iodine in hydriodic acid is added. About six drops are to be added to the ounce while shaking the mixture. The color of the solution is at first wine yellow, but after a few hours it becomes paler ; this paleness afterwards increases, and the subsequent addition of a few drops of the iodine solution becomes necessary. Our mixture forms an excellent fluid for the examination of delicate fresh tissues, and is also a very good and very preservative macerat- ing medium, acting in this way even for hours or days. We must here give a piece of advice which is of great importance in the numerous macerations of this kind which are necessary, namely, to have the piece which is to be placed in them very small, and the quantity of the fluid as large as possible. An artificial mixture, composed of 1 ounce of the white of an egg, 9 ounces of water, 2 scruples of chloride of sodium, with the corresponding quantity of tincture of iodine, appears to form a substitute. In the use of water, in which case distilled water should be employed, the swelling of the delicate tissues is, possibly, very considerable ; not unfrequently they may even be more perma- nently altered ; so that it is advisable for any one who would protect himself from deception to try other fluid media also, in order to decide what has remained unaltered in his micro- scopic image, and what has been acted upon by the water. Glycerine has already been mentioned several times in these pages. Together with its property of rendering tissues trans- parent, which is of inestimable value for such as have been hardened and rendered opaque by reagents, it forms a preser- vative, though not indifferent medium for many tissues, and even for the prolonged preservation of larger pieces. Its power of rendering tissues transparent may be restrained by the addi- tion of water. A mixture recommended by Schweigger Seidel, composed of 1 part of pure glycerine to 9 parts of distilled water, is useful for the examination of numerous objects. Many delicate structures shrink in glycerine, it is true, but after longer action they again become filled out and clear. A 122 SECTION SEVENTH. number of really chemical reagents — for example, acetic acid, formic acid, iodine, tannin, and chromate of potash — may be advantageously combined with it, and it also forms an ingre- dient of cold injection masses (see below). Finally, it presents the best tiuid for mounting moist tissues. Nowadays chemical reagents are very frequently employed in microscopic investigations, and the number of these which are necessary for various histological and medical purposes is by no means small. They are the same as are generally used for zoochemical investigations. They are chiefly employed in microscopical investigations when we wish to ascertain the nature of amorphous and crys- talline deposits, the disposition of elementary granules, or the constitution of tissue elements. The ordinary solutions, natu- rally from a reliable source, are used for these processes. Their application, however, requires great foresight with re- gard to the microscope, if one would protect it from injury. We therefore repeat certain precepts which have already been given. The lenses should never be wetted with the fluids. Only the weaker objectives, with long foci, are to be used, and the covering glasses should be as large and broad as possible. In order to prevent the fluids from running on to the stage, the slides should not be too narrow. I generally cover the stage completely with a glass plate of the same size with ground edges, a precautionary measure worthy of recommen- dation to those who have the protection of their instruments at heart. When the stage consists of a plate of ground black glass, as is the case with some of the older microscopes, it is very convenient for chemical examinations. The reagent is either simply added to the microscopic pre- paration by means of a pointed glass rod, the covering glass being previously removed, or the fluid is allowed to flow under the edge of the cover to the object ; it may also be allowed to enter gradually, in order to observe the successive changes which occur during its action. A thread of lint, one end of which is placed under the cover, may be used as a conductor, or two very narrow strips of bibulous paper may be placed at opposite borders of the cover, one of which serves to remove the old fluid while the new is being introduced by the other, whereby, however, the entrance of the reagent is more rapid and its effects are more enereretic. FLUID MEDIA AND CHEMICAL REAGENTS. 123 More important than this momentary use of chemical re- agents is the continuous application of the same for a longer period as hardening, preservative, or macerating fluids. Ani- mal tissues are frequently allowed to remain in the solutions for hours or even days consecutively. This method has been frequently used in modern times, and to it is due most of the knowledge that has been obtained in latter years concerning the tissues, etc., of the human body. Its perfection should, therefore, be of great interest to every investigator. Its appli- cation, however, requires an exact procedure. Above all things, one should avoid all such old delusions as when putting a tis- sue in acetic or sulphuric acid, or in solutions of potash or soda, to disregard the strength of the solutions, or the relative volume of the tissue to that of the fluid. Hence it is the duty of every one who employs any of these chemical methods, or recommends a new one, to describe his process accurately. A watch-glass, or a small shallow glass box may be used when the process is to continue but a few moments. For more continued action, small bottles with wide mouths and ground glass stop- pers are to be used, or, still better, small gradu- ated cylinder glasses (fig. 86). The vessels should always be labelled, to avoid confusion, to remem- ber the date, etc. We will now proceed to the consideration of the reagents which are at present most frequently used. 1. Among the strong mineral acids, sulphuric, muriatic, and nitric acids, in a concentrated form, act destructively on most histogenetic substances. Nevertheless, they afford an impor- tant means of isolating certain tissues, inasmuch as they dis- solve their connecting or cementing substance, and also, in part, the connective tissue which occurs in them. In a more diluted condition they form useful hardening solutions for various tissues, while with a still higher degree of dilution we obtain the action of weak acids on various tissue elements, causing them to become transparent, to dissolve, or to swell up. In this way these acids may constitute very important macerating mediums. Sulphuric Acid.— The purified concentrated English sul- Fig. Sfi. Gradua- ted cylinder glass. 124 SECTION SEVENTH. phuric acid, non-fuming, with a specific gravity of 1.85-1.83, is to be used. The concentrated acid is but rarely used. Still it is an ex- cellent auxiliary in the investigation of the horny structures (the cornified epithelium, the nails, the hair), for isolating the cells of these tissues. It also forms alone, or combined with iodine, a good reagent for cholesterin ; the latter combination is also useful for cellulose or amyloid substances. Sugar and sulphuric acid redden many organic substances, such as albu- minous and amyloid bodies, oleic acid, etc. Strongly diluted sulphuric acid hardens albuminous tissues, acting similarly to chromic acid (see this). It has the advan- tage over the latter of rendering gelatinous and connective tis- sues transparent, and, at the same time, so consolidated that thin sections of them may be made. Moreover, less depends on the accurate concentration of sulphuric acid than on that of chromic acid.* When connective tissue is treated for twenty-four hours with highly diluted sulphuric acid, 0.1 grm. to 1000 grammes of water, and warmed to a temperature of from 35° to 40° C, it is resolved into gelatine ; so that in this way other elements are spared as much as possible, and may be isolated from connec- tive tissue. Kuhne has employed this method with good suc- cess for muscular fibres. Sulphurous Acid. — It has been recommended by Klebs to add a small quantity of sulphurous acid to a solution of cane- sugar of 5 per cent, (one drop of a pretty concentrated solution of the former to one ccm. of the latter fluid) for loosening epi- thelium, and for rendering connective tissue transparent with- out causing infiltration. Nitric Acid. — The pure concentrated nitric acid of the chemical laboratories of 1.5 specific weight may be used, or acids containing more water, with a specific weight of 1.4 to 1.2 (the latter is the officinal nitric acid). The former (1.5), mixed with chlorate of potash, destroys * M. Schultze, who has presented us with these statements, employs an acid of 1.839 specific weight, of which about 18 drops make 1 gramme and 22 a scruple. He recommends, as a mean, 3 to 4 drops to 1 ounce of water (with extremes of 1 to 10), and praises its effects for hardening the supporting substances of the central organs of the nervous system, of the retina, and also the reticulated tissues of the lymph glands and kindred organs. FLUID MEDIA AND CHEMIOAi REAGENTS. 125 connective tissue in a short time, and is therefore a good medi- um for isolating muscular fibres (Kiihne). This may also be accomplished, though more slowly, with weaker acids. This reagent, recommended by Schultze, is frequently used by bota- nists ; it deserves further trial for animal tissues. Caution in its application is always advisable. The property of nitric acid of coloring albuminous matters yellow is, in general, rarely made use of in microscopical inves- tigations. Strong nitric acid serves to isolate connective-tissue cor- puscles, bone corpuscles and their processes, as also the denti- nal canals. Nitric acid of 20 per cent, was recommended many years ago by Reichert and Paulsen as a medium for the isolation and recognition of the elements of the smooth muscles. Diluted nitric acid (5 to 10 per cent.) is also used for the extraction of the so-called bone earths (a mixture of lime and magnesia salts) from calcified cartilages and bones ; although hydrochloric acid and, still better, chromic, lactic, picric, or pyroacetic acids may be employed for this purpose. In a condition of extreme dilution (0.1 per cent.), nitric acid has recently been tried by Kolliker for rendering muscles transparent. It does not present any special advantages. Muriatic Acid. — Pure muriatic acid, thoroughly saturated with chlorine, of 1.19 specific weight, is not at all, or only rarely, used undiluted for histological investigations. Strong muriatic acid is frequently used for dissolving the intercellular substance of connective-tissue organs, and for isolating the connective tissue corpuscles and their radiating tubular sys- tems, as in the cornea, the teeth, and bones. This action gen- erally requires some time, occasionally a number of days, By this means the intercellular substance of the muscles (Aeby) and of the urinary tubes (Henle) has been dissolved. An acid which has been diluted with water till it ceases to smoke, is frequently used for this purpose. The time required is gen- erally 12-14 hours ; weaker acids act more slowly. The object is then to be washed out and macerated, for a day at least, in distilled water. When this process succeeds, the whole may be rapidly and beautifully isolated by the careful use of the needles. An important modification of the above-mentioned process consists in boiling pieces of the kidney for 6-8 hours 126 SECTION SEVENTH. in alcohol of 90 per cent., to which i to £ per cent, by volume of purified muriatic acid of the greatest possible strength has been added. The operation is to be conducted on the water- bath, in an alembic provided with a cooling apparatus (Ludwig and Zawarykin). This process is also useful for other glands. Tomsa has recommended boiling for one or two days, and sub- sequent washing in water for isolating the cutaneous nerves. Size injections with Prussian blue retain their color and the consistence of the vessels with both methods. Muriatic acid, of the same dilution as the nitric acid, may be used for ex- tracting the bone earths. In a high degree of dilution (0.1 per cent.) it forms a medium for macerating connective tissue and rendering it transparent, the cells and elastic tissue of which then appear very beautifully. Our acid also dissolves the fleshy substance of muscular fibres, and may thus be ad- vantageously employed in the examination of muscular tis- sues. Phosphoric Acid. — Strelzoff recommends this for removing the lime from embryonic bones, especially at an advanced stage. Boric Acid. — This has thus far been used but slightly, as for example, by Bruecke, in the examination of blood-cells. He uses a solution which contains 2 per cent, of the pure melted salt. According to Kollmann this is an energetic re- agent. Chromic Acid. — Since Hannover, in the year 1840, recom- mended chromic acid to microscopists as a medium for harden- ing animal tissues, its reputation has been constantly increas- ing, especially since the inaccurate method of estimating the strength of its solutions from their color has been abandoned for that by means of the scales. It is extremely useful for hardening the brain and medulla oblongata, as well as the peripheral nervous apparatus. Not unfrequently it is more serviceable than alcohol, which exerts too great a change on these tissues, while the latter is either equal or preferable to the former for other organs, such as most glandular structures, the intestinal canal, etc. Well-crystallized chromic acid, as free as possible from sul- phuric acid, should always be used. It should be kept in a well-closed vessel, in a dry place, and the portion to be used should be dried over sulphuric acid previous to its employment. FLUID MEDIA AND CHEMICAL REAGENTS. 127 To economize time, a considerable quantity of a strong solution may be kept on hand, which may be rapidly diluted to any de- gree desired by means of a graduated measure. I dissolve 2 grammes in 98 grammes (or cubic centimetres) of distilled water, so that a 2 per cent, solution stands ready. For hardening purposes a chromic acid solution of from 0.5 to 1, or, at most 2 per cent, is necessary. In no case should a higher degree of concentration be used, and generally the weaker ones work better. Very fresh tissues usually require weaker, older pieces somewhat stronger solutions. Very fine results may be obtained, especially when the pieces are not very volu- minous, by commencing with a weak solution (about 0.2 per cent.), and then, after a few days, changing the fluid for one of stronger concentration (0.5 to 1 per cent.), in which the object is to remain for days and weeks, until it has obtained the de- sired consistence. Then — in consequence of the readiness with which fungi are formed in chromic acid solutions — the hardened preparation should be kept in diluted alcohol. When a voluminous organ is to be hardened it is advisable, before placing it in the chromic acid, to drive the same solution through the blood-vessels. However, with all chromic acid operations, very much de- pends on the proper degree of concentration, and this is not always hit upon even by the most experienced ; this is all the more so, as the contamination with sulphuric acid is quite vari- able. Very voluminous organs may present a hardened peri- phery, while the interior is decomposed. Portions which are over-hardened have their tissue elements very much shrunken, and are often found to be so hard and brittle that it is no longer possible to make thin sections from them. An improve- ment may sometimes be obtained by laying the piece of organ in glycerine for several days. It is preferable to add some of this to the chromic acid at the very beginning. So much for these concentrated hardening solutions of chro- mic acid. This reagent has, however, when highly diluted, still another and more important property, namely, of preserv- ing the finest textural relations while exerting a somewhat ma- cerative action on them. So that in this way very delicate or- ganizations, especially in nervous tissues, may be made visible which remained completely hidden in the examination of the fresh tissue. For this very reason it has exerted a very endur- 128 SECTION SEVENTH. ing influence in the histology of the higher nerves of sense, to which fact the works of M. Schultze especially testify. It has since been used with success for the investigation of the central organ of the nervous system, the ganglia, and also for glandu- lar structures. In general, according to present experience, only a concen- tration of from -J- to J of a grain to the ounce of water, that is, a solution of from 0.025 to 0.05 per cent., is applicable for this purpose, and in fortunate cases the desired effect is accom- plished in from one to three days. Others (Deiters, J. Arnold, Kuhne) have even descended to solutions of from 0.02 to 0.01 per cent, and less — and even to these an effect cannot be de- nied. The volume of the fluid and that of the portion of tissue placed in it are here of greater importance than for simple hardening. Generally, when the latter is small and the fluid plentiful, the action is naturally more energetic and rapid, so that in this case the limits may easily be exceeded. It is proper, therefore, not to select too small a piece, and not to add too large a quantity of fluid. When the object is too small, the same effect takes place as with stronger solutions ; they re- ceive a lively yellow color and become opaque ; when of the proper proportions they become paler and semi-transparent. We have already mentioned above the interesting and, in their consequences for practical microscopy, very important observations of Graham on the colloid and crystalloid sub- stances. Schultze (who was the first among German histolo- gists to comprehend the full significance of Graham's observa- tions) has properly called attention to the fact that the action of chromic acid is not alone concerned in this case, but to this is also added, when the piece is large and the quantity of fluid moderate, the preponderating effect of the colloid substances of the tissue ; such as blood, mucus, and albumen. Hence a fluid results which consists conjointly of crystalloid and colloid sub- stances ; while a small piece of tissue placed in a larger quan- tity of chromic acid solution is subjected, almost entirely, to the action of this crystalloid substance alone. At present microscopic technology is only in its youth, not to say childhood. In a riper period such combinations will certainly play an important role. Schultze informed us that he made investigations relative to this subject, and that a FLUID MEDIA AND CHEMICAL REAGENTS. 129 watery solution of gum-arabic appeared to be suitable as a col- loid substance. Similar, but much weaker and more slowly commencing ef- fects are also produced by bichromate of potash, which will be spoken of further below. Finally, still another very advantageous use has been made of chromic acid ; namely, for extracting the earthy salts from so-called ossified cartilage, and also from bones. It is especi- ally commendable for foetal tissues. Generally it is necessary to have a higher degree of concentration (about 2 per cent., Thiersch), and, during an exposure of several weeks, the fluid should be frequently changed. It is well to add a little glyce- rine. The effect may be increased by a little hydrochloric acid, without injury to delicate textures. The decalcified specimen, after being washed, is to be placed in absolute or strong alco- hol for further hardening. Lactic Acid, has been recommended by Strelzoff for remov- ing the lime from embryonic bones — and rightly so. Oxalic Acid. — Oxalic acid was formerly but little or not at all used by histologists. Some time since M. Schultze insti- tuted a series of experiments with it which assign it a not un- important rank among the microscopist's reagents. A cold saturated solution of oxalic acid (one part of pure ciystallinp hydrated acid requires for its solution 15 parts of water) causes connective tissue structures to swell and become transparent, while the tissue elements which are formed of albuminous sub- stances retain their sharp contours, become somewhat hardened and permit of convenient isolation. Extremely delicate ele- ments of the body, such as the rods of the retina and the olfac- tory cells, are preserved in it excellently. The length of time is of relatively slight importance, so that the examination may be commenced after a few hours or several days. According to Schultze's experience, an alcoholic solution of oxalic acid acts more strongly than the watery, and appears to present certain advantages for many purposes. Finally, oxalic acid is used in carmine tingeing in the same manner as acetic acid, although more circumscribed in its ap- plication, of which mention will be made later. Acetic Acid.— The hydrated acetic acid, thoroughly pure acetic acid, acidum aceticum glaciale, should always be used when an accurate estimation is necessary (since the so popular 9 130 SECTION SEVENTH. specification of the specific weight affords no definite conclusion as to the amount of water present), and combined drop by drop, or in greater quantity, with water. Acetic acid, which is so rapid in its action, is one of the old- est and most frequently enqfioyed reagents in animal histology. Its property of rendering nuclei within the cells visible, or of causing them to appear isolated after the destruction of the envelope and cell body ; and further, of giving to connective tissue a crystalline transqarency, and disclosing its admixture in the cells, elastic fibres, vessels, nerves, etc., has especially led to its general employment. Only at a later period were quantitatively defined solutions of acetic acid, as well as combinations of the same with other fluids, especially alcohol, employed for more prolonged action on animal tissues. Even a few drops of the acid to the ounce of water is sufficient to induce considerable transparency of the connective tissue in a few days. In this way, for example, the intestinal ganglia lying in the submucosa ; furthermore, the marvellous ganglionic plexuses, discovered years ago by Auer- bach, between the muscular layers ; also muscle cells in the mucous membranes, on vessels, etc., are made to appear dis- tinctly. For the recognition of smooth muscles, Moleschott used a 1 or 1} per cent, solution of acetic acid for a few min- utes. One part by measure of strong acid, of 1.070 specific weight, is to be mixed with 99 of water, that is, H to 98^. More recently, Kolliker has used very dilute acetic acid for rendering the muscles of the frog transparent, in order to dis- cern the nerve terminations, and the reagent accomplishes this exceedingly well. He recommends the addition of S, 12, or 16 drops of the acidum aceticum concentratum of the Bavarian pharmacopoeia, of 1.045 specific weight, to 100 cubic centimetres of water. I have substituted 1 to 2 drops of hydrated acetic acid to 50 cubic centimetres of water. Acetic acid of from 0.3 to 0.2 per cent, has been employed by others for many purposes. Auerbach recently studied the action of varied degrees of concentration on animal cells. Solutions of 1-0.08 per cent, (in the mean from 0.2-0.1) are very suitable for obtaining a nearly correct image ; as is also a mixture of 7 per cent, cane sugar and 0.06 per cent, acetic acid. Acetic acid, diluted to an extreme degree, is also to be recom- mended for softening thin sections from parts which have been FLUID MEDIA AND CHEMICAL KEAGENTS. 131 dried in the air ; also for washing out specimens after they have been tinged in carmine, in order to fix the red in the nucleus. This will be again alluded to further below. Maceration in acetic acid presents a certain difficulty in the recognition of delicate structural relations, in so far as that the part should be examined at the right time. Before this period, the swelling and transparency are still too little developed ; later, however, the changes induced in the tissue by the acid have become too considerable. Beale has recommended the combination of acetic acid with gtycerine. Vinegar. — The employment of ordinary cooking vinegar offers no kind of advantage. In it connective tissue becomes transparent like glass, after 6, 8, or 12 hours. If the tissue be- comes too soft to permit of sections being made, this may often be remedied by placing it, supplementarily, in a solution of chromic acid. It will frequently be found useful to boil in vinegar animal tissues which are to be dried. Pyroligneous Acid. — Pyroligneous acid (none but the puri- fied, or acidum pyrolignosum rectificatum, should ever be em- ployed) has frequently been used for rendering connective tissue structures transparent, and especially with a certain pre- dilection for pathological tissues. It exerts a similar, though not entirely the same effect as diluted acetic acid, inasmuch as it possesses, together with the macerating action, a hardening effect (from admixture of products of the dry distillation of the wood). Diluted pyroligneous acid should always be used for macerating, if it be desired to avoid marked textural changes of the elements which then become visible through the connective tissue. Pyroligneous acid, diluted according to circumstances with an equal, double, or quadruple volume of water, is a good accessory for many structural conditions ; for example, in the recognition of the corneal cells and their contents, the course of the nerves in the sub-mucous connective tissue, etc., and es- pecially structures which are embedded in connective tissue, such as glandular elements, vessels, pathological new forma- tions, etc. The desired effects generally take place after one or more days, often enough again disappearing, as a result of continued maceration. Consequently, without regarding the smell or its injurious effects on the blades of the knives, there is an inconvenience in the employment of our reagent. Besides, 132 SECTION SEVENTH. pyroligneous acid preparations do not usually keep well when put up in glycerine. We have, therefore, discontinued the use of this fluid for many investigations. Still, it is useful for extracting the bone earths from calcified cartilage and from normal and pathological bone-tissues. Formic Acid has been proposed in the place of acetic acid (Ranvier). Tartaric Acid has recently been recommended simply for the reduction of gold preparations. Osmic xic/c? (hyperosmic acid). — Within a few years this has come into frequent use through M. Schultze and others ; it is readily reduced by several tissues and substances. It shares this property with several similarly applicable salts of the nobler metals, which will also be mentioned hereafter. Picric Acid. — Recommended in part as a means of tingeing, by Schvvarz, in part for hardening tissues. According to Ran- vier' s experience, a concentrated solution produces an excellent consistence, even in 24 hours. Neither shrinking nor coagula- tion of albumen occurs, and lime salts are extracted at the same time. I can only coincide in these statements. A further use is made of this acid in the preparation of Ranvier' s picro-car- mine. Iodine. — A solution of iodine, about 1 part iodine (it is well to combine with it 3 parts of iodide of potassium) to 500 of water, may be used for tingeing animal cells. Nevertheless, we have better and newer methods of tingeing. A solution of iodine serves the microscopist for the recognition of amylum, and, in combination with sulphuric acid, of amyloid and cellu- lose. For this purpose a watery solution, which should not be too strong, is allowed to act energetically, and then a drop of concentrated sulphuric acid is added. Iodine vapor is recommended by Rollett for the examina- tion of connective tissue structures, such as the cornea. A so- lution is prepared by shaking metallic iodine with water, the iodine is allowed to settle, and a small quantity of the slightly colored solution is placed in a moist chamber containing the object to be examined. Waldeyer states, however, that this reagent produces alterations. It has already been remarked above (page 121) that iodine forms a constituent of an important mixture, the so-called "jod-serum," recently invented by Schultze. FLUID MEDIA AND CHEMICAL REAGENTS. 138 2. Among the alkalies, solutions of potash, soda, and am- monia are frequently used. They are of quite inestimable value for the investigation of animal tissues ; this is especially true of the first two substances. There is one disadvantage, however, connected with the use of alkalies, namely, that ob- jects which have been macerated in them can hardly be pre- served permanently. Caustic Potash (hydrate of potassa). — The melted form, the kali causticum in baculis, is used. As this attracts water and carbonic acid from the air with great eagerness, it and its solu- tions must be kept in well- stoppered bottles. The kali causticum in baculis of commerce contains, in addition to carbonic acid, a variable and not inconsiderable quantity of water, which constitutes an inconvenience in its application. The strong solution of potasli softens the substance of many elements, and induces in them a condition which is very favor- able to the imbibition of water, which afterwards penetrates very rapidly, so that the cells swell up, burst, etc. Manifold use has been made, in the investigation of tissues, of the resolving and destructive properties of potash solutions. The manner in which potash solutions act varies entirely ac- cording to their strength ; a subject to which Donders first drew attention many years ago. A saturated, or at least very strong solution softens many elements, without dissolving or attacking them very strongly. Although diluted solutions produce this effect more or less rapidly, they also frequently dissolve the intermediate connecting- substance, the tissue cement, and thus become an extremely important, in many cases invaluable accessory. Credit is due to Moleschott for having more recently recommended 30 to 35 per cent, solutions of potash as excellent reagents. To make a 32.5 per cent, so- lution of potash he uses 32.5 parts by weight of kali causticum in baculis, which is to be dissolved in 67.5 parts by weight of distilled water. An exposure of \ to \ an hour or more is an extremely useful means of isolating muscular and nerve ele- ments, glandular passages, and even ordinary ciliated and ol- factory cells. Schultze, who, together with other histologists, has likewise made use of potash solutions, employed for the last -mentioned delicate cell formations solutions of the strength of 28, 30, 32, 35, and 40 per cent. For other purposes, weaker 134 SECTION SEVENTH. solutions of 5 to 10 per cent, are necessary, as will be indicated in speaking of the individual tissues. Naturally, in the his- tological examination, the same solutions should be employed as a fluid medium, and the use of water avoided, as otherwise the rapidly dissolving effect of diluted solutions would take place. Caustic Soda (hydrate of soda). — The white melted mass is used for making the solution. Although solutions of soda have been used experimentally, they present no superiority, when concentrated, to those of potash. Weaker solutions are generally necessary, about two-thirds of the potash quantity (corresponding to the atomic weight) being used. Liquor Ammonia. — The action of ammonia on animal tis- sues is similar to that of potash and soda. Ammonia is useful for neutralizing acids which have been applied to a tissue ; also as a means of dissolving carmine. Lime-water. — Rollett has recently made us familiar with lime-water, which was previously but little noticed, as an im- portant accessory for the investigation of connective-tissue structures, and especially tendons. After remaining in it for six or eight days, a piece of connective tissue may be readily divided into its fibrilla? by the use of the needle. It is there- fore one of the animal cement substances which is here dis- solved. Baryta-water. — The same result may be obtained with con- nective tissue by means of the much more energetically acting baryta-water, in from four to six hours, as is afforded by lime- water after several days' action. At the same time, the swell- ing is rather greater, and the transparency somewhat more considerable. In both cases, before the application, the tissue is to be washed with distilled water, or still better, with dis- tilled water to which a minimum of acetic acid (just enough to neutralize it) has been added. 3. Salts. Chloride of Sodium. — Formerly, weak solutions of common salt were commonly regarded as indifferent media. According to Graham's observations, a colloid substance (albumen or gum- arabic) should always be added. A ten per cent, solution has frequently been used of late (Schweigger-Seidel and others). It has also been frequently used as a macerating medium, even for long-continued action. FLUID MEDIA AND CHEMICAL REAGENTS. 135 According to Auerbach's experience, solutions of from 0.5 to 1.5 per cent, are tolerably neutral to fresh animal nuclei. Other degrees of concentration produce entirely different effects ; those of from 3 to 14 per cent, distend, so that the nucleus is trans- formed into a completely homogeneous body. Concentrated solutions of 35 per cent, have a hardening action. Solutions of chloride of sodium containing hydrochloric acid are recom- mended by Yon Ebner for decalcifying bone tissue. A special application of the chloride of sodium is also made in the impregnation of tissues with nitrate of silver, which will be alluded to hereafter. It is likewise an ingredient of various preservative fluids. Chloride of Calcium. — Chloride of calcium in solutions of medium strength (one part of dry chloride of calcium to two or three parts of water) has been recommended as a fluid me- dium for microscojnc preparations, in consequence of its well- known property of attracting water. It has also been recom- mended for rendering sections of the spinal cord, etc., trans- parent, for which purpose it is not very serviceable. It has a peculiar effect on muscles. Acetate of Potash, in a nearly concentrated watery solu- tion, has recently been recommended by M. Schultze as an ex- cellent preserving medium. Chlorate of Potash. — This is onlj T used in combination with nitric acid (see this), as Schultze' s reagent. Extremely vary- ing degrees of concentration of this mixture have been made use of in animal histology, and the desired effect has naturally been obtained in very unequal spaces of time. Hypochlorate of Soda. — Eau de Javelle, which is used for bleaching, has recently been recommended by A. Budge and Arndt for the examination of nervous structures. It destroys the connective tissue. Cyanide of Potash. — This has been used quite recently to clear up gold preparations which have been too deeply stained, or those which have subsequently become too dark. A watery solution of 5 per cent, is less suitable ; a mixture obtained by adding 5 ccm. of a ten per cent, solution of cyanide of potash in water to 35 ccm. of glycerine is better. The pre- paration may remain in the latter for hours and even days. The former solution acts too energetically and rapidly (L. Gerlach). 136 SECTION SEVENTH. Nitrate of Soda. — A ten per cent, solution acts similarly to a chloride of sodium solution ; but it permits of subsequent staining witli silver (Lott). Phosphate of Soda. — Solutions of phosphate of soda of 5 to 10 per cent, have been considerably used by microscopists. According to my experience thus far, they do not present any advantages. Bichromate of Potash (Red Chromate of Potash). — The purest possible crystallized material should be used. The ac- tion of this salt, which may be very suitably combined with glycerine, is similar to that of chromic acid, but weaker, and not so rapid in its appearance. For hardening many tissues it is extremely serviceable ; and perhaps it is better than the free adulterated acid ; it also exerts a much less coagulating effect on albumen. Besides this, the solutions of this salt have the advantage of not readily developing mould, which is a great fault of chromic acid solutions. It has also been recommended to commence the hardening process with our salt, and then to continue it with the free acid (Deiters). Where one part of chromic acid would be sufficient, it is re- quisite to have several parts of chromate of potash. Thus, where a given effect might be obtained with a fluid containing from -J- to \ of a grain of free chromic acid, to accomplish the same without the acid, the fluid would require from 1 to 4 grains of the salt. However, for delicate investigations, much less depends on the accurate concentration of the solutions of chromate of potash than of the chromic acid. A mixture of the salt in question with sulphate of soda has been recommended by II. Midler for hardening the retina. The tissue should be exposed to its action for at least two weeks. Bichromate of potash, 2 — 2i grammes. Sulphate of soda, 1 grammes. Distilled water, 100 grammes. This mixture, the " Midler's eye-fluid, 1 ' is also very useful for preserving many other tissues, such as mucous membranes, glands, and even ciliated cells. It preserves delicate embryos exquisitely, and may naturally be modified according to ne- cessity. A combination of Midler's fluid with an equal quantity of s FLUID MEDIA AND CHEMICAL REAGENTS. 137 saliva forms an excellent macerating medium, to be continued for several days. Czerney, and subsequently Langerlians have very rightly recommended this mixture. It renders excellent service, for example with the epithelium of the conjunctiva and the aural cavity. MonocTir ornate of Potash. — Recently made known by Robin. Stronger facts are necessary. Bichromate of Ammonia. — This has been recommended in the place of the bichromate of potash in solutions of 1 or 2 per cent., for hardening the central organs of the nervous system by Gerlach, and of the latter strength for sudoriparous glands by Reynold. Monochr ornate of Ammonia. — More recently used in a 5 per cent, solution for the examination of the kidney (Heidenhain) and in a 1 per cent, for ganglia (Arndt). Molybdate of Ammonia. — This was recently recommended by Krause as an indifferent medium for tingeing. Chloride of Iron. — This iron salt was formerly used by Fuhrer and Billroth for hardening the spleen, which becomes sufficiently hardened in from 1 to 2 hours in a solution of the color of Madeira or Malaga wine. Chloride of iron is at present supplanted by superior hardening media. Chloride of Mercury. — The chemical effects of the sublimate are well known. Macerating for several da)^s in a solution of this salt may be advantageously used for hardening and isolating the axis cylinders. Although this reagent has found but little application, still it forms an element of several very serviceable preservative fluids. Nitrate of Silver. — This has recently come into use for a pe- culiar tingeing process of the tissues, especially through His and Recklinghausen (see below). Chloride of Gold. — This was advantageously emploj^edfor a similar purpose by Cohnheim, Kolliker, Eberth, Gerlach, and many others. Chloride of Gold and Calamine. —This has been employed by Gerlach. Chloride of Gold and Soda is used by Waldeyer. Chloride of Palladium was first used by F. E. Schulze. Chloride of Platinum. — As Merkel informs us, this salt hardens tissues and gives them, at the same time, a diffuse yel- low tinge, especially those of flattened organs. Equal portions 138 SECTION SEVENTH. of solutions of chromic acid and chloride of platinum (each 1 : 400) are recommended for the connective-tissue frame-work of the retina. 4. Alcohol. — Alcohol, the most common of the preservative fluids for animal tissues, is of inestimable value for histological investigations. The use of alcohol has come more into the foreground chiefly within a few years, since we have learned to recognize in glycerine an incomparable means of rendering transparent animal tissues which have been hardened and hence become cloudy. It is only for certain purposes that chromic acid deserves the preference. Either small pieces of the en- tirely fresh organ are placed in a relatively considerable quan- tity of alcohol free from water, or several sorts of alcohol are employed. Weak alcohol is used for the first few days ; this is then replaced by stronger, and perhaps, later, a still stronger one is employed. I know of no better reagent for hardening glandular organs, the digestive canal, or injected preparations, and for rendering them tit for sections and brushing. Lat- terly, entire series of investigations have thus been made almost exclusively with alcoholic preparations. The circumstance that the specimens do not spoil in well-closed vessels constitutes an advantage over chromic acid, which so readily develops the formation of fungi. The latter is, on the contrary, preferable to alcohol for the recognition of many of the finest structural conditions, for the central organs of the nervous system, and for the organs of sense. Alcohol is also frequently applicable in other ways. First of all, for microscopic objects which are to be deprived of their water with the utmost possible sparing of the texture, for the purpose of being afterwards mounted in Canada balsam or similar resinous masses. In such cases the thin sections are to be placed for one or two days in absolute alcohol. From this they go into oil of turpentine. We learned above that stronger solutions of chromic acid harden, and weaker ones macerate. The same is repeated by this fluid. A very watery alcohol is an excellent protective macerating medium. Ranvier uses one part alcohol of 36° Car- tier (this contains 84. 4G per cent, by weight of absolute alcohol) and two parts of distilled water, and allows it to act for twenty- four hours. He recommends this mixture highly, a recommen- dation in which I concur most completely. FLUID MEDIA AND CHEMICAL REAGENTS. 139 Furthermore, alcohol forms an ingredient of Beale's cold injecting fluid, which will also be alluded to further on. Finally, alcohol is also an ingredient of several recently re- commended mixtures, the description of which follows : — L. Clarke and Beale's Mixtures. These serve to make delicate parts hard and at the same time clear. The fundamental idea consists in employing two sorts of substances, one of which hardens the albuminous elements of the tissues, while the other renders them transparent. Beale, who has occupied himself considerably with the action of these solutions, remarks that they must be varied according to ne- cessity, also that by the addition of glycerine to the mixture its refractive power may be increased according to circumstances. He recommends in general alcohol, glycerine, acetic acid, hydro- chloric acid, potash, and soda. The last two acids as well as alcohol coagulate albuminous matters ; acetic acid, potash, and soda render them transparent ; alcohol dissolves fat. When several of these materials are combined in a solution, the above mentioned effects are obtained. (a.) Alcohol and Acetic Acid. — L. Clarke used in his inves- tigations a mixture of acetic acid and alcohol, which, as I have also convinced myself, renders sections of the spinal cord mar- vellously clear, even in a few hours, and permits many things to be better recognized than by other methods customary for this purpose. Lenhossek also appears to have made use of this process in his investigations on the spinal cord. Clarke's recipe, naturally to be modified according to ne- cessity, is to combine three parts, of alcohol with one part of acetic acid. (b.) Moles choW s mixture of Acetic Acid and Alcohol. — Moleschott recommends the following modification of Clarke's method : — Strong acetic acid (1.070 sp. wt.) 1 volume. Alcohol (0.815 sp. wt.) 1 " Distilled water 2 " He calls this his strong acetic acid mixture. This fluid is very serviceable for hardening many organs, causes the connective- 140 SECTION SEVENTH. tissue portions to become transparent, and renders those formed .of albuminous matters distinctly prominent. Delicate textures do not, as a rule, tolerate it so well. Another weaker acetic acid mixture was afterwards recommended, consisting of Acetic acid (same as above) 1 volume. Alcohol 25 Distilled water 50 " (c.) Alcohol, Acetic Acid, and Nitric Acid. — Beale recom- mends the addition of a little nitric acid to the mixture of alco- hol and acetic acid for the examination of epithelial structures. This is also to be varied as necessity may require. A recipe given by the author runs as follows : — Water 1 ounce. Glycerine 1 " Spirit 2 " Acetic acid 2 drachms. Hydrochloric acid \ drachm. Alcohol and Soda. — Beale obtained excellent results, in many investigations, from the use of a fluid composed of alco- hol and a solution of caustic soda, in the proportion of from eight to ten drops to each ounce of alcohol. Many tissues are, at the same time, rendered very hard and transparent in such a mixture, and it is particularly adapted, according to his ex- perience, for investigations upon the character of calcareous matter deposited in tissues in various morbid processes, also in tracing the stages of ossification in the early embryo. It ren- ders all the soft tissues perfectly transparent, but exerts no action on the earthy matter of bone. The most minute ossific points can therefore be very readily discovered. A foetus, for example, prepared by being soaked for a few days in this fluid, and preserved in weak spirit, forms a very beautiful pre- paration. This fluid will also be found very useful in investi- gations upon soft granular organs. Beale found it of special service when working at the anatomy of the liver. Methyl Alcohol. — In England, where the high spirit duty imposes an obstacle to the employment of the ordinary (ethyl) FLUID MEDIA AND CHEMICAL REAGENTS. 141 alcohol, methyl alcohol (pyro-acetic spirit) is frequently used as a substitute ; this is however unnecessary on the Continent. Methyl alcohol has found special application as an addition to Beale's cold injection fluid (see below), and also in mounting microscopic specimens in Canada balsam. Sections which have been deprived of their water by means of absolute alcohol are placed for a short time in strong methyl alcohol, then taken out of this and, just as they are commenc- ing to dry, thrown into oil of turpentine. The latter penetrates sections which have been in methyl alcohol, as I have learned by experience, somewhat more readily than those which are brought from the absolute alcohol directly into this oil. Never- theless, methyl alcohol may be readily dispensed with for this purpose. Chloroform. — Thus far it has been very little used for his- tological investigations, but forms the best medium for dissolv- ing and thinning the Canada balsam, which is so important for practical microscopy. Cfdoral Hydrate. — Diluted with water this has quite recent- ly been used in the examination of the central nervous system and the retina (Butzke). JEtTier. — This serves to dissolve fat in microscopic work. It also dissolves Canada balsam. Collodium. — So far, this has only been used for recogniz- ing the axis cylinder of nerve fibres. According to the state- ments of Pfiuger and my own observations, it acts instantane- ously. Oil of Turpentine. — This comes next to chloroform as a medium for thinning Canada balsam. It also forms the most important medium for rendering transparent dried sections, or those which have been deprived of their water by absolute alcohol. We will return to this subject more in detail further below. Creosote. — Creosote forms an element of preservative mount- ing fluids (Harting). It has recently been recommended by Stieda, after the ex- ample of Kutschin, as a very rapidly acting medium for ren- dering microscopic sections transparent. The property which creosote has of rapidly making preparations which still contain water transparent, is of great importance. By this means, ob- jects which have lain in ordinary spirits, and even chromic acid, 142 SECTION SEVENTH. can be used after a few minutes. But when a preparation is to be arranged for mounting in Canada balsam, good oil of turpentine deserves the preference, decidedly, according to our experience. Oil of Gloves. — This was first made known by Rindfleisch, as a medium for rendering tissues transparent, in the place of ■ the oil of turpentine ; it lias also been warmly recommended by others. It renders tissues which contain water transparent in the same manner as creosote, but more slowly. A series of other ethereal oils, such as cinnamon, anise, bergamot, and rosmarine oils, act similarly to it, while others, like oil of tur- pentine, render only objects which have been deprived of their water transjoarent ; as orange, juniper, mentha crispa, citron, and cajeput oils (Stieda). Benzine. — This has been proposed for dissolving and thin- ning Canada balsam in the place of chloroform and oil of tur- pentine (Bastian). Toldt recently recommended pure benzine as an excellent medium for making fat tissue transparent, after the previous momentary action of alcohol. Carbolic Acid. — For the purpose of resisting the decompo- sition of bodies, it has recently been recommended to add car- bolic acid to wet mountings. It will probably have a future in histology. Thymol acts very much better. It is to be tried in watery solutions of 1 : 200-1000. In what has been mentioned above, we have been obliged to adhere to the methods which are still generally used by micro- scopists for determining the proportions of their reagents. Titrition is a far more certain and a much more convenient method for ascertaining the strength of a solution, and for pro- ducing them of definite proportions. In order to estimate the acid and alkaline contents of such fluids the following is necessary : — The apparatus (tig. 87), which is quite indispensable for the investigation, consists of : — (a) two Mohr's burettes (1) of about 60 ccm. capacity divided into -} of a ccm. : (I>) a pipette (2) which will allow from 10 to 15 ccm. to run out, and is divided into T V of a ccm., and finally (c) a cylindrical measure (3) of 100 or several hundred ccm. capacity. The divisions of the latter are from 5-5, or 10-10 ccm., and must retain the desig- nated quantity of fluid, and not allow it to How out ; while the FLUID MEDIA AND CHEMICAL REAGENTS. 143 As to the burette, it part with the reagent ■** burette and pipette are so divided as only to designate the number of ccm. which they allow to flow or drop out. (Such burettes, pipettes, and cylindrical measures may now be pur- chased everywhere). The use of the pipette is self-evident, is filled to the zero division at its upper (the test acid or the test alkali), and, by making slight pressure J on the clamp, the fluid is allow- ed to flow out either in a stream or by single drops, as may be necessary. The normal acid and normal alkali solutions are used for the construction of the test fluids, so far as determining the ordi- nary reagents (acids and alka- lies) is concerned. Under these are understood solutions which contain an equivalent weight of the active substance of the re- agent, expressed in grammes, dissolved in 1000 ccm. (1 litre) of fluid. The Normal Oxalic Acid Solution. — In its formation 6.4 grammes of pure crystallized, uneffloresced oxalic acid is to be dissolved in water, and this solution diluted sufficiently to make 100 ccm. of fluid. (The volume is always to be meas- ured at the same temperature at which the solution is to be used, therefore at 14 to 16 R.) This normal oxalic acid solution is, ployed, that is, in the preparation of other normal acid and normal alkali solutions. For this reason the greatest accu- racy and care should be employed in the preparation of this first and most important solution. One ccm. of this oxalic acid solution contains, as we are Fig. 87. Apparatus for titrition. 1, a Molar's burette, with, the clamp at a, which is opened by- pressing on the two metallic buttons at &, allow- ing the fluid to escape from the tube c ; 2, a pi- pette ; 3, a cylindrical measure. however, only indirectly em- 144 SECTION SEVENTH. already aware, 0.064 grin, of oxalic acid. For its saturation the corresponding equivalent of bases is necessary, therefore of — a. Soda 0.031 grm. NaO. b. Potash 0.0472 " KO. c. Ammonia 0.017 " NH 3 . d. Lime 0.028 " CaO. e. Baryta 0.0765 " BaO. 2. Normal Potash Solution. — From a freshly prepared so- lution of potash, free from carbonic acid, take, with a pipette, 5 ccm., color it to a weak blue with a few drops of tincture of lacmus, and, while stirring, allow the normal oxalic acid solu- tion to flow into it from the burette till the color begins to turn red. Given, we bad used 8 ccm. of normal acid solution; we then add to each 5 ccm. of our potash solution, 3 ccm. of water. In this case we have a normal potash solution ; 1 ccm. of the same is just sufficient to saturate 1 ccm. of the oxalic acid solu- tion ; it therefore contains the above-mentioned quantity of potash, or 0.0472 grm. It is clear that with the aid of this potash solution the quan- tity of acid present in any fluid may be determined at pleasure. By the neutralization of 1 ccm. of our normal potash solution is indicated the presence of — a. Sulphuric acid = 0.04 grm. S0 3 . b. Nitric " = 0.054 " NO . c. Muriatic " = 0.0365 " HOI. d. Acetic " = 0.06 " C 4 H 4 4 . We limit ourselves in this citation to the investigation of the most important acids. 3. As actually pure oxalic acid belongs to the more expen- sive reagents, it is unnecessary to use just this acid in the esti- mation of alkalies. Sulphuric acid is generally used. Nothing is easier than the preparation of the normal sulphuric acid so- lution. Sulphuric acid, diluted at pleasure, is allowed to flow from a burette into 5 ccm. of normal potash solution, to which several drops of tincture of litmus has been added, till it be- comes red. The acid and alkali solutions are then to be di- luted corresponding to what was mentioned above concerning potash, until an equal number of ccm. of each exactly neutral- FLUID MEDIA AND CHEMICAL REAGENTS. 145 ize each other. Accordingly, 1 ccm. of this normal suphuric acid contains 0.04 grm. of S0 3 , and for its neutralization exactly the same quantities of the bases are necessary as were previous- ly given for oxalic acid. Finally, we add two other test fluids, namely : — 1. The nor- mal silver solution for the quantitative estimation of common salt. One ccm. of the T V normal solution contains 0.0108 Ag\, or 0.0170 AgON0 5 . It corresponds to 0.00585 Nad. 2. The normal chloride of sodium solution, used for the quantitative estimation of nitrate of silver. One ccm. of the T \ normal so- lution contains 0.00585 NaCl, and corresponds to 0.0170 AgON0 5 . In both cases a precipitate of chloride of silver takes place, which collects in lumps by strong shaking ; the operation is completed when a drop of the test fluid no longer induces precipitation. To make the recognition more certain in the first of the two processes, several drops of simple chro- mate of potash solution may be added to the common salt solu- tion, in which case the complete precipitation of the chloride of silver will be indicated by the red color of the chromate of silver which is formed. A few examples may serve to make the method of employ- ment clear. 1. We have 10 ccm. of a solution of soda, which required 22.2 ccm. of normal sulphuric acid for its neutralization. Now 1 ccm. of the normal sulphuric acid corresponds to 0.031 grm. NaO. By multiplication with 22.2 the quantity of soda con- tained in 10 ccm. of the titrated fluid will be found to be 0.6S82, consequently 6.8S2 per cent, (disregarding the specific weight). 2. A solution of ammonia requires for 10 ccm. 12.6 ccm. normal sulphuric acid. One ccm. normal sulphuric acid cor- responds to 0.017 HK,. The quantity of ammonia is, therefore, 2.142 per cent. 3. 5 ccm. of acetic acid solution requires 41.7 ccm. of the normal potash solution, 10 would therefore require double this quantity, or 83.4. But the cubic centimetre of normal potash solution corresponds to 0.06 of acetic acid, and hence the pro- portion of acetic acid is 50.04 per cent. 4. 10 ccm. of a solution of common salt requires, for ex- ample, 12 ccm. of the T V normal silver solution. Now as 1 ccm. of the T V normal silver solution corresponds to 0.00585 NaCl, the common salt solution contains 0.702 per cent, of NaCl. 10 146 SECTION SEVENTH. 5. 10 com. of a solution of nitrate of silver requires 15.5 ccm. of the T V normal chloride of sodium solution. But 1 ccm. of the T V common salt solution corresponds to 0.017 AgONO„ and the silver solution contains 2.635 per cent, of AgON0 6 . 6. Supposing we desire to construct a 40 per cent, solution of acetic acid from the diluted acetic acid mentioned in No. 3. We learn from the proportion 40 : 100=50.04 : x , that we have to dilute 100 ccm. of the acetic acid solution, which has been estimated by titrition, to 125.1 ccm. 7. Let us suppose the case, that we wish to prepare a soda solution of 20 per cent., and that a solution which we have ti- trated showed a proportion of 37.5 per cent, of NaO. We find by calculation that 100 ccm. of the latter solution is to be di- luted to 187.5 ccm. 8. We wish to make a 1 per cent, solution of nitrate of sil- ver. For this purpose we use the 2.635 per cent, solution of nitrate of silver of No. 5. It requires diluting with water to 263.5 ccm. 0ation <£igl)tl). METHODS OF STAINING— IMPREGNATION WITH METALS— THE DRYING AND FREEZING PROCESSES. I. Methods oe Staining. Delicate animal tissues frequently gain an extraordinary dis- tinctness when impregnated with indifferent coloring materials, and complicated structures are frequently essentially cleared up in the same way. The non-reception of the color by other tissue elements is also of great value for assisting our discrimi- nation in certain cases. These staining processes, therefore, form a very important accessory for histological investigations, and science is greatly indebted to Professor Gerlach, the in- ventor of carmine tingeing. The subsequently discovered haematoxyline tingeing is of equal value and, in part, even superior. All other coloring materials are of a second or third rank, as I have learned from the experience of many years. 1. GerlaoKs Method of Tingeing with Carmine. Gerlach first gave us this process in a small work (" Mikro- skopische Studien aus dem Gebiete der menschlichen Morpho- logie." Erlangen), which appeared in the year 1858. In his carmine injections he had already noticed the eagerness with which the nuclear structures of the blood-vessels absorbed the carminate of ammonia, and how differently they behaved in this respect to the cells and intercellular substance. The cells also absorb coloring matter, but much more slowly and with greater difficulty, and always in lesser quantity than the nuclear form- ations. Intercellular substances act nearly indifferently. Gerlach' s first experiments were made on the brain and spinal cord. Fine sections of organs previously hardened in 148 SECTION EIGHTH. chromate of potash were placed in a moderately concentrated solution of the carminate of ammonia and left in it for 10 or 15 minutes. He then soaked them for several hours in water, which was frequently renewed, then treated them with acetic acid and placed them in absolute alcohol to remove the water. The carmine solution tinges even when it is still more diluted. Gerlach observed this at the very first, having one night left a section of a convolution of the cerebellum lying in some water slightly contaminated with carmine. In this case things showed themselves which were not to be recognized by the first method of staining. Thereupon Gerlach employed 2 or 3 drops of a concentrated solution of ammonia carmine to the ounce of water, leaving his sections in it from 2 to 4 days. This is the purport of the first statement of the inventor. Since that time carmine tingeing has come into the most frequent use. Several years ago one observer went so far as to assume the presence in the central organs of several kinds of nerve cells, to which he assigned different functions according to their capacit}^ for absorbing carmine.* The directions for its use have been more or less fortunate. From what my own experience has taught, two evils are to be especially avoided in carmine staining ; one is an excessive tingeing, ultimately inducing a very deep and diffuse red, which does not permit of further recognition of the preparation ; the other is an infiltration of the elements of the tissue in con- sequence of the action of the ammonia. Solutions as free as possible from ammonia should therefore be used. For this purpose take several grains of carmine, com- bine it with an ounce of distilled water and a few drops of am- monia. The fluid, in which a portion of the carmine has become dissolved, is to be filtered. Another portion of the carmine, which remains on the filter, may be kept for future use. When the filtrate has any appreciable smell of ammonia, the latter should be allowed to escape bj^ leaving it in an open vessel under a bell-glass for a half or a whole day. If, after a time, granules of carmine are deposited, a drop of liquor am- monia serves to redissolve them. However, all solutions of * As carmine acid on boiling with dilute sulphuric acid is divided as a glycoside into pure sugar and carmine red. Hollett has recently used the latter substance in a watery solution as a tingeing medium. METHODS OP STAINING. 149 carmine are very decomposable and their coloring power, un- fortunately, very unequal — an inconvenience which cannot be entirely obviated. The fluid thus obtained is, when used for tingeing, to be added, drop by drop, to water, in order to obtain at pleasure a lighter or more intensive red. For very delicate objects a combination of the coloring water with an equal quantity of glycerine is advantageous. I recommend for this purpose three to six grains of carmine dissolved in exactly the necessary quantity of ammonia and mixed with one ounce of distilled water. To the Altered fluid, one ounce of good glycerine and two or three drachms of strong alcohol are to be added. The solution is to be used either as it is or with a further addition of glycerine. For many purposes, as for example, the double tingeing with hsematoxyline and carmine, to be described below, a con- centrated solution of the latter coloring material, containing as little ammonia as possible, is to be recommended. The length of time which it is necessary for a portion of tis- sue to remain in the fluid is determined by the intensity of the color of the latter. Strong solutions tinge sufficiently in a few minutes, weaker ones require several hours. The preparations may be left without disadvantage for twenty-four hours in very weak solutions. The addition of 0.5 — 1 per cent, of common salt has recent- ly been advised for limiting the swelling of the preparation (Leptschinsky). The stained pieces, when taken out, are first washed with pure water. They are then exposed for several minutes to a solution of acetic acid. I employ, as a rule, an ounce of dis- tilled water with two or three drops of glacial acid ; although a much stronger acid may be used for a much longer time without harm. The process may be readily modified where it is desirable to avoid the further infiltration of the tissue with water. The stained object may be deprived of its water with absolute alcohol, and then exposed to the glacial acid from one to twenty-four hours (Thiersch), or an acidulated alcohol may be directly applied. This may also be accomplished, as Beale correctly remarks, with glycerine containing glacial acetic acid (five drops to the ounce). Only with tissues of very unequal capacity for swelling, a saturated watery solution of oxalic acid 150 SECTION EIGHTH. deserves the preference to acetic acid (Thiersch). Nevertheless, it finally extracts the red from the nucleus, and the color is less intensive. Fresh tissues, or those hardened in alcohol, color best ; not so good, and somewhat more slowly, those which have been hardened in chromic acid or chromate of potash. Good carmine preparations show the nuclei intensively red- dened, likewise the axis cylinder of the nerve fibres. The col- oring of the protoplasma is usually less lively ; the connective tissue interstitial substance appears colorless, etc. One soon learns to properly estimate the intensity of the color of the tissue. In general, the preparations destined for wet mounting (in weakly acidulated glycerine) are to be less deeply tinged than those for resinous mounting. The latter (best mounted cold in Canada balsam dissolved in chloroform) often furnish charming preparations for review. Injected specimens are very susceptible of tingeing with many colors, such as chrome yellow and sulphate of baryta. The best kinds of soluble Prussian blue are also useful for staining ; although a somewhat more strongly acidulated wash- ing-water is necessary to retain the lively blue. It is more ap- propriate for objects injected with carmine to stain them blue or violet ; nevertheless very handsome appearances may also be obtained with a very light red carmine. The employment of ordinary red ink, of which use lias here and there been made, is to be little recommended. 2. Thiersch's Carmine Fluid. Professor Thiersch employs several methods of staining. a: Red Fluid. Carmine 1 part. Caustic ammonia 1 " Distilled water 3 parts. This solution is to be filtered. A second solution is to be prepared of — Oxalic acid 1 part. Distilled water 22 parts. One part of the carmine solution is to be mixed with 8 parts of the oxalic acid solution, and 12 parts of absolute alcohol are to be added, and filtered. METHODS OF STAINING. 151 If the filtrate is orange-colored instead of dark-red, more ammonia is added to compensate for the preponderance of ox- alic acid, and the orange becomes red. The orange color may also be used for staining. If crystals of oxalate of ammonia are afterwards formed in the solution, which may take place from the addition of liquor ammonia or alcohol, it must be fil- tered a second time. According to Thiersch's experience, this solution stains tis- sues very uniformly in the short space of from 1 to 3 minutes, without causing them to swell and without loosening shreds of epithelium. After the staining, the coloring material adhering to the surface of the preparation is to be washed off with alco- hol of about 80 per cent. When the color has become too dark or diffuse, the preparation is to be washed out with an alcoholic solution of oxalic acid. b. Lilac Carmine Fluid. Borax 4 parts. Distilled water 56 " Dissolve and add, of carmine 1 part. The red solution is to be mixed with twice its volume of ab- solute alcohol, and filtered. Carmine and borax remain on the filter ; this precipitate, dissolved in water, may be again used. Thiersch found that this solution colored more slowly than the simple red one, and that it was especially attracted by car- tilage and by bones which have been decalcified by chromic acid. Alcoholic solutions of oxalic and boracic acids serve for washing. Preparations may be very beautifully stained by tingeing them in the lilac solution and then placing them for an instant in the red fluid. 3. BeaVs Carmine Fluid. This meritorious investigator has recommended the follow- ing mixture : Carmine 10 grains. Strong liquor ammonia i drachm. Good glycerine 2 ounces. Distilled water 2 " Alcohol \ ounce. 152 SECTION EIGHTH. The pulverized carmine is to be placed in a test tube and the ammonia added to it. By agitation, and with the aid of heat, the carmine is soon dissolved. The ammoniacal solution is to be boiled for a few seconds and then allowed to cool. After the lapse of an hour, much of the excess of ammonia will have escaped. The glycerine, water, and alcohol may then be added, and the whole passed through a filter or allowed to stand for some time, and the perfectly clear supernatant fluid poured off and kept for use. Various tissues require very unequal time for staining. Heidenhain's process (first used for the mucous membrane of the stomach) is a modification of Beal's method. The solu- tion is to be prepared without the alcohol, and the superfluous ammonia almost entirely removed by warming on the water- bath, or the addition of acetic acid. (The proportion of ammo- nia is proper when, after 24 hours, all the carmine of a solution remaining in a small open dish has become deposited in gran- ules.) The specimen is to be placed in a watch-glass with this nearly free from ammonia solution. This watch-glass, and another containing water and a trace of ammonia, are to be placed in a flat glass vessel which can be accurately closed and left for 24 hours. Afterwards washed in glycerine, and then placed in pure glycerine, the preparations are to be exposed in the same manner to the vapor of a small quantity of acetic acid. Such a protective method of staining certainly presents manifold advantages. Modifications of the same may also be readily made. 4. Acid Carmine Fluid. Schweigger-Seidel recommends the following method for tingeing objects previously treated with acids: — An ordinary ammoniacal solution of carmine is to be mixed with acetic acid in excess and filtered. The red solution thus obtained stains diffusely ; but after the addition of glycerine, tempered with a little muriatic acid ( 1 : 200), to the microscopic preparation, the cell body is seen to gradually lose its color, and the car- mine is only retained by the nucleus. For mounting in gly- cerine, the preparation is to be washed with water containing acetic acid. I have dissolved carmine in acetic acid, then filtered and METHODS OF STAINING. 153 subsequently diluted with water at pleasure. A fluid is thus obtained which tinges sufficiently in from a few hours to a half or a whole day. This tingeing method is highly recommend- able for injection preparations made with Prussian blue.* 5. Picro-Carmine Tingeing. Ranvier, a meritorious investigator, is the discoverer of this method of tingeing. I accomplished nothing with the picro- carmine prepared according to his earlier recipe. We now have the following method : The ammoniacal solution of carmine is added to saturation to a saturated watery solution of picric acid. The original volume is evaporated one-fifth. The cooled solution deposits a slight sediment of carmine. After filtration, the filtered solution is evaporated to dryness, whereby a reddish ochre yellow powder is obtained. This is used to make a one per cent, solution with distilled water, which requires, when kept, an occasional filtration. This is serviceable. The recipe communicated by C. Baber, according to the experience of Malassez, is still more accurate : Carmine 1 grm. Liquor ammonia 4 ccm. Water 200 grms. Mix, and add picric acid 5 " Shake and decant, so that the undissolved excess of picric acid remains behind. The fluid, after having stood for several days, with occasional shaking, is exposed to the air in a saucer for several weeks until dried. The red powder is dissolved in water in the proportion of two parts to one hundred, and after several days Altered through a double thickness of filter paper. The fluid should now be yellowish red, with no smell of am- monia. A drop on white filter paper, when dried, makes a yel- low-red bordered spot. A few drops of carbolic acid prevents decomposition of the fluid. Washing in distilled water draws the picric acid out of the preparation ; glycerine, on the contrary, does not. * Pure carmine red (see note p. 148), dissolved in water acidulated with acetic acid, also forms a serviceable tingeing medium, according to Rollett. 154 SECTION EIGHTH. For mounting, Baber recommends a mixture of ten drops of glycerine with an equal quantity of water, to which one drop of the picro-carmine solution has been added. The tingeing is rapid, and occurs in various shades in the several tissues. 6. Staining with Anilin Red {Fuchsin). The idea of employing the anilin colors, so much used at present, for tingeing animal tissues was very natural. A se- ries of experiments which I had undertaken for this purpose showed the pre-eminent usefulness of this coloring material. Fuchsin (crystallized) 1 centigramme. Absolute alcohol 20-25 drops. Distilled water 15 cubic centimetres. A beautiful moderately intense red color results. It colors many of the animal tissues almost instantly, and without alter- ing them. It is especially adapted for the study of epithelium, hyaloid membranes, the lens and corpus vitreum. Diluted with a little water, this solution tinges the vibrating cilia of the ciliated epithelium of the frog, without causing the motion to cease. The colored blood cells also become stained, although slowly. The same solution of fuchsin is also useful for color- ing the ganglion cells and the cellular elements of lymphatic glands ; but it appears to me to be not so well adapted for car- tilage and bones. The nerve tubes, after an immersion of sev- eral hours, become slightly red, and their axis cylinders be- come sensibly darker. The above examples show that the solution produces effects which are superior in many respects to those obtained with carmine. The promptitude and uniformity of the coloration are qualities which render the fuchsin solution especially valu- able as a staining medium for instantaneous demonstrations, and for coloring pale delicate cells, which thus become more distinct without suffering alteration. It is very unfortunate that alcohol soon extracts the color, so that it is impossible to preserve the preparations in Canada balsam." 7 * * The nitrate of rosanilin (Magenta red) in watery solution has been recom- mended by Roberta and Abbey ; tannic acid in an alcoholic solution by Jackson. METHODS OF STAINING. 155 7. Purpurine Tingeing. Kanvier recommends this coloring matter, which is prepared from madder. A small quantity of purpurine, to which a little water has been added, is poured into a boiling watery solution of alumen (1 : 200). The purpurine is dissolved in a few min- utes, though the quantity must be such that some purpurine remains undissolved. The hot fluid is to be filtered into a ves- sel which contains a quarter of the volume of alcohol of 36° ac- cording to Cartier's scale. A fluorescical fluid is obtained, which is of a beautiful orange red by transmitted light. It may be preserved for about a month in a vessel with a glass stopper, but so soon as deposits commence in it it should be rejected. 24-48 hours are requisite for its action. The advantages of this method consist, according to the in- vestigator mentioned, in the fact that it produces an excellent tingeing of the nucleus, while the cell protoplasma remains nearly colorless. It also leaves the nervous elements colorless, while the connective tissue frame-work is tinged. I acknowledge that this coloring matter has remained be- hind my expectations. 8. Eosine Tingeing. This newly discovered body (the potash salt of the tetrabro- mofluoresceine) has recently been made known as a tingeing medium by E. Fischer. It may be used dissolved in water (1:10-20); or the coloring matter may be precipitated from this solution by the addition of an acid, and subsequently redissolving it in alcohol, preferably in absolute alcohol in the proportion of 1 : 20-30. According to my experience, the eosine tingeing is infinitely behind carmine and hsematoxyline tingeing. 9. Tingeing with Aniline-iodine Violet. This body, obtained from iodine methyl and aniline (of doubtful iodine contents) forms, as Jurgens found, an excel- lent accessory for the recognition of the amyloid substance. It is used in solution in water, 1 : 100 and more, and allowed to act for a short time. It assumes a lively red color, while the 150 SECTION EIGHTH. remaining tissue takes on a dull violet tone. Fresh tissues are used, as well as such as have been hardened in chromic acid or Mueller's fluid. Alcoholic preparations, washed out in water, are also very suitable. 10. Blue Colors for Staining. It is desirable in many cases to make use of a blue fluid, es- pecially for staining specimens injected with carmine. Other preparations also appear very beautiful when stained with this fluid, so that for many purposes I am inclined to give it the preference to carmine. Several of these methods are now prac- tised, as with the sulph-indigate of potash (so-called indigo car- mine), with anilin blue, and soluble parme, hsematoxyline, and chinoline blue. a. Blue Sta ining with Indigo Carmine. The following solution has been recommended by Professor Thiersch : Oxalic acid 1 part. Distilled water 22 — 30 parts. Indigo carmine, as much as the solution will take up. The soda salt also affords an excellent blue fluid. If the blue color is in excess it may be removed with a solution of ox- alic acid in alcohol. This blue fluid (which may also be diluted at pleasure with alcohol), when concentrated, tinges very rapidly and uniformly. According to the observation of its inventor, it is very suitable for coloring the axis cylinders and nerve cells of the brain and spinal cord, previously hardened in chromic acid. Canada balsam preparations, which I obtained from Thiersch many years since, have preserved their blue color unchanged to the present time. b. Anilin Blue Fluid. Ordinary anilin blue* is insoluble in water. By treating it with sulphuric acid, the soluble blue may be obtained. This * It may also be used in alcoholic solution for coloring objects which have been hardened in absolute alcohol. Glycerine serves for mounting. METHODS OF STAINING. 157 may be simply dissolved in water until it assumes a deep cobalt color, or the following solution may be prepared : Soluble anilin blue 2 centigrammes. Distilled water 25 cubic centimetres. Alcohol 20 — 25 drops. This iiuid stains tissues preserved in alcohol of a lively blue, and in a few minutes, but those preserved in chromic acid are not colored so rapidly. This color may be preserved in water, alcohol, and glycerine, and is not altered by the addition of acids. The lymphatic glands, spleen, walls of the intestines, and more particularly sections of the brain and spinal cord, as- sume, under its influence, a fine appearance. I have made very extended use of it for years and can recommend it thoroughly, although it furnishes only perishable preparations. This method of staining has recently been improved by Heidenhain and Rollett. The former employs the neutral re- acting aqueous solution in still higher dilution, so that, when poured into a watch-glass, it shows on a light ground a forget- me-not blue color. The sections (from alcoholic preparations) remain for a day in 4 ccm. of this fluid in a moist place, and are then to be immediately mounted in glycerine- 1 and cemented. The color and coloring power of the solution are considerably increased by the addition of a little acetic acid, or even its vapor ; the vapor of ammonia, on the contrary, deprives it of its color entireby. Rollett dissolves 1 grm. of the coloring matter in 400 ccm. water. The objects, when very dark blue, are placed in distilled water, and here, with occasional shaking, lose the excess of the coloring medium. c. Soluble Panne Fluid. This substance, which is obtained by treating diphenylate of rosanilin with sulphuric acid, when dissolved in water in about the proportion of 1 : 1000, gives a gorgeous blue, running into violet, and colors the various tissues in a few minutes. They are then to be washed in water, and either examined in glycerine, or, after being deprived of their water by absolute alcohol, are to be mounted in Canada balsam. The latter ob- jects are, unfortunately, of a somewhat perishable nature. 158 SECTION EIGHTH. d. Tingeing with Qhinolin Blue (Cyanine.) Dissolved in alcohol of 36° (Carfcier) and cautiously diluted with water, this has been recommended by Ranvier for fresh tissues as well as for those which have been hardened in alco- hol or picric acid. Fat assumes the deepest blue color. 11. Violet Tingeing with Hcematoxylin. Boehmer has brought to our knowledge, in hsematoxylin, an extremely valuable coloring medium of variable permanence. The presence of an acid or of an alkali in small quantities caiises, however, a subsequent fading or discoloration. After numerous trials I recommend dissolving about 1 grm. of the coloring material in 30 grms. of absolute alcohol. Then pre- pare an alum solution which contains 0.5 — 1 grm. of the salt in 30 ccm. of distilled water. The alcoholic solution of hsema- toxylin is to be added to this, drop by drop, till a deep violet blue color is obtained. The fluid must then stand for several days exposed to the air and then be filtered. Subsequent fil- tration s from time to time are unavoidable. A beautiful violet blue tingeing is obtained after 5, 10, 20 or 30 minutes. I have also operated with stronger solutions, and made solutions of hsematoxylin which colored excellently in from a half to a whole minute. Nevertheless — do not forget it — the tingeing power of such a solution may have changed considerably after a few days. A new trial must then be made. Distilled water is used to wash out the preparation. I be- lieve, from previous experience, that the subsequent action of a weak alum solution renders the tingeing more permanent. If the color is too deep, by laying the preparation from 4-12 hours in an alum solution, a brighter and very pretty though bluer color may be obtained. Rindfleisch recommends another process. A concentrated watery solution of the coloring matter, and a similar solution of alum are prepared. To use them add to a small quantity of the former as much of the latter as to cause the brown red color to become violet red. When this is diluted with about five times as much water, a blue violet tingeing fiuid is obtained, in which the preparations become stained in from one to three minutes. METHODS OP STAINING. 159 For rapid staining, as in demonstrations in lectures, I pre- fer hematoxylin to carmine decidedly ; also, in accordance with Waldeyer, Eberth, and others, for tingeing preparations which have been stained with nitrate of silver (see below). As has been said above, chromic acid preparations, when tinged in this manner, do not permit of permanent mounting, though objects which have been hardened in alcohol keep well. Alco- holic preparations, previously injected with carmine, when properly treated with our coloring matter make beautiful ob- jects, which permit of permanent mounting in resinous sub- stances. A watery solution of logwood, with a little alum, also produces a similar tingeing which is less sensitive to acids. 12. Blue Tingeing with Molybdate of Ammonia. Krause has recommended this salt in a neutral solution of 5 per cent, as an indifferent medium for giving a marine blue color to various tissues, as those of the nervous aj>paratus, lymphatic glands, and ciliated epithelial cells. The staining is completed in 24 hours, at an ordinary temperature and under the action of light. The preparations become brown, and assume a consistence suitable for making sections by supple- mentary exposure to the action of tannic acid (1 : 1.5) or pyro- gallic acid (20 per cent.). 13. Double Staining with Carmine and Picric Acid. To the methods of staining previously known, a new one has been added, by E. Schwarz, for double tingeing. He com- bines staining with carmine with that by picric acid. That author places the tissues in a mixture consisting of 1 part creosote, 10 parts acetic acid, and 20 parts water. The preparations are to be immersed in this mixture, while it is boiling, for about a minute, and are then to be dried (for two or three days). Thin sections are to be made and immersed for an hour in water slightly acidulated with acetic acid, and than washed out in distilled water. Next they are to be put in an extremely dilute watery solution of ammoniacal carmine, and, after being again washed in water, are exposed for two hours to a solution of picric acid (0.066 grm. to 400 ccm. water). 160 SECTION EIGHTH. The sections are then placed on a slide, the superfluous acid is allowed to flow away, and a mixture of 4 parts of creosote to 1 part of turpentine, which has become resinous from age, is dropped on to it. In about half an hour the specimen, which has become transparent, is to be mounted in Canada balsam. If it is undesirable to use the creosote mixture, the sections are to be removed from the watery picric acid solution to an alcoholic mixture of corresponding strength, in order to deprive them of their water. A peculiar effect is thus obtained. Epithelial and glandu- lar cells, muscles, and the walls of vessels show a yellowish color with reddened nuclei, while the connective tissue is not colored by the picric acid, and only presents the carmine color. These preparations are very handsome, and the method pro- mises to be of importance, especially for the demonstration of muscular elements. 14. Tingeing with Carmine and Indigo-carmine. According to Merkel's directions, add to the solution of in- digo-carmine mentioned at p. 156 an ammoniacal solution of car- mine until a violet color is obtained. Precipitated carmine reqidres the addition of ammonia. This fluid, which keeps for some time, colors the nerve medulla of brain preparations blue, the blood-corpuscles green, everything else red. Ossifica- tion preparations, previously decalcified in Mueller's fluid and hydrochloric acid, become blue in the bone substance, in all the remaining parts red. The preparation is afterwards mounted in Canada balsam. 15. Tingeing with Indigo-carmine and, Picric Acid. Jullien mixes both fluids. A double tingeing, which be- comes pale in glycerine, is thus obtained. The connective tis- sue is blue, and the epithelium yellow. 16. Tingeing with Hematoxylin and Carmine. Strelzoff, a Russian physician, is the inventor of this pro- cess, which, for developing, previously decalcified bones, pro- duces exquisite objects, though according to numerous trials METHODS OF STAINING. 161 of my own, it is hardly applicable to other organs. The sec- tions are stained with a hematoxylin solution, and then after washing out in distilled water, are placed in a solution of car- mine as free as possible from ammonia. After washing out a second time they may be again exposed to the action of a weaker solution of alum. The remains of cartilage appear blue, the bone substance red. These preparations cannot, however, be mounted in resinous substances, and can only be kept temporarily in glycerine. Hsematoxylin, unfortunately, does not become permanently attached to tissues previously exposed to acids, and, sooner or later disappears in both kinds of preserving fluids.* 17. Double tingeing with Solution of Logwood and Picric Arid, Kutschin recommends that developing bones which have been lying in Mueller s fluid (p. 136) should be washed out and exposed to the action of a watery solution of the first mentioned coloring matter in alum, and then place them in a saturated so- lution of the picric acid in alcohol. The cartilage remains and the cell nuclei become blue, the protoplasma of the medullary cells and the bone lamelhe assume the } T ellow color of the pic- ric acid. Such images are not always pretty, as I can certify. Thus far, I have made no further investigations by this method. IS. QerlacKs Complicated Tingeing. The meritorious investigator \ises for transverse sections of dried vessels a weak solution of logwood containing a minimal quantity of alum, for one day. Then follows, for several min- utes, the action of a "pure" acetic acid, and then, for an equal period, that of a " tolerabl)^ dilute" picric acid. After washing out, there is a triple coloration of the muscular, elas- tic, and connective- tissue elements. Such objects permit of mounting in gljT.erine or Canada balsam. * One may also proceed inversely, staining the objects first in a solution of car- mine free from ammonia, and then exposing- it to the action of hematoxylin or a so- lution of logwood (Rollett). I also succeeded in obtaining beautiful double tingeing of embryonic bones (but only such) with aniline blue, or panne soluble and car- mine. 11 162 SECTION EIGHTH. II. Metallic Impregnations. Within a few years histological investigation has gained important accessories in several readily reducible combinations of the noble metals. Aqueous solutions of nitrate of silver, osmic acid, chloride of gold and of palladium, have thus far come into use. Their effects are essentially different, so that we shall have to discuss each solution by itself. a. Nitrate of Silver. Lapis infernalis, in solution or in substance, has been used for a number of years for obtaining precipitates of silver in the cornea. This method was first extensively used by Reckling- hausen (" Die Lymphgefasse," Berlin, 1862) on animal tissues. His then endeavored to ascertain the nature and conditions of the precipitates. Touching the lining cornea with the surgeon's crayon of nitrate of silver has, however, yielded far better results. The thicker corneas of larger animals can only, in this manner, be effectively mastered (Eberth). We shall return to this at the eye. The most extended use, good and bad, has been made in histological work of the nitrate of silver solution mentioned. Only fresh (or but slightly altered) tissues, which are still saturated with the albuminous organic fluids, are suitable for impregnation with silver. As the action of nitrate of silver is, for the most part, confined to the surface, they should be chiefly thin, membranous structures. Artificial surfaces, made by the knife, generally produce only very unsatisfactory results. It is preferable to employ only very weak solutions, those of 0.5, 0.25, and 0.2 per cent., or still weaker, according to cir- cumstances. Frequently the immersion lasts for only the frac- tion of a minute, till the fragment of tissue is seen to assume a whitish color. It is then to be washed in water and exposed to the light until a brownish color is noticed. The examina- tion may be made in acidulated water or glycerine. Tingeing, especially with hematoxylin, may also be advantageously combined with this process. To increase its durability, Legros recommends the immersion METALLIC IMPREGNATIONS. 163 of the colored object in a solution of hyposulphite of soda for an instant ; it is then to be washed in distilled water. Silver preparations which have become too dark may be brightened up again by a prolonged action of this salt. Although the silver method produces excellent specimens in many cases, there are a number of defects connected with it besides those which have been mentioned. One of these is that the nuclear structures very soon become indistinct, and later disappear entirely. Then, with every precaution, the desired result is not always obtained, and the appearances which the strongly acting nitrate of silver produces are frequently very dissimilar, and are often so heterogeneous that the observer remains completely confused by them. The greatest foresight in the interpretation of such artificial productions is therefore necessary — and this, unfortunately, has been frequently neg- lected. The silver treatment gives decidedly the best results with epithelium, especially with unstratified pavement cells, and the membranes and tubes covered by them. Here we have pro- duced a mosaic, consisting of sometimes finer, sometimes broader, dark lines of demarcation, which enables us to recog- nize the contours of the cells most distinctly. This results either from blackening of the cement substance, or from the formation of the dark precipitate of silver in the narrow fur- rows between the cells. Such appearances are in no wise liable to misinterpretation so soon as the nuclei can be recognized or the scales isolated. We shall afterwards see to what beautiful discoveries in the structure of the finest blood and lymph pas- sages this method has led. Kecently injections have been made into the living frog of solutions as low as 1 : 2000, and even 8000. However, even in this case, instead of the bright field sur- rounded by dark lines, we sometimes have a diffuse, brownish darkening of the scales, without the black lines of demarca- tion. The outlines of smooth muscle cells are also made visible in a beautiful manner by this reagent. How far it may serve for demonstrating the finer structural relations of nerve tissue, future investigations will have to decide. Opinions have thus far agreed quite as little with regard to the importance of the nitrate of silver solution for connective 164 SECTION EIGHTH. tissue and relative structures ; on the contrary, the views of observers are very widely separated on this point. According to Recklinghausen's statements, a diffuse colora- tion of the basis substance takes place, from which the cavities and cells glimmer forth in the form of bright spaces. Exactly the reverse may also take place, a dark, granular precipitate of silver being formed in them, while the interstitial substance remains bright. It has been recommended to use a solution of common salt to obtain the latter appearance (His). We are inclined not to advise the silver method for connec- ive tissue. Thiersch, an unsurpassed technist, has shown that thin sec- tions of alcoholic preparations may also be suitably treated with this silver salt. Such objects are placed for about five minutes in an alco- holic solution of nitrate of silver (1 : 5000), and at the same time shaken. They are then placed for several seconds in an alco- holic solution of common salt, continuing the shaking. Sub- sequently, exposed more or less to the light, these objects be- come slightly stained, but sufficiently so to show the various tissue elements satisfactorily. Carmine injections, treated in this way, mounted in resinous substances, afford excellent, ex- tremely durable specimens, as I have learned from experience. h. Other Silver Salts. Alferow recommends the picric, acetic, citric, and lactic ox- ide of silver in solutions of 1 : 800, to which are added 10-12 drops of a similar free acid. The same old method is used ; the contours are clearer, and the pernicious effects are less than with the nitrate of silver. c. Osmic Acid (Hyperosmic Acid). "The treatment of animal tissues with solutions of osmic acid (OsO,), introduced by M. Schultze,* permits of a very manifold application. Organic substances reduce the acids from their solutions, and hence a combination of the former with a lower grade of oxidation, or perhaps with metallic os- * I am indebted for this notice to the discoverer of this reagent. Let it there- fore remain here unchanged as a memento of the highly meritorious deceased ! METALLIC IMPREGNATIONS. 165 mium results, wliicli combination, sooner or later, and indepen- dent of light, assumes a dark bluish black color, and resists decomposition. The reduction does not follow in the tissue as a granular precipitate ; on the contrary, the elementary struc- tures, if fresh when immersed in it, retain the same transparency and texture which they have in life, and are only altered so far as color is concerned. These changes of color take place in different tissues with very different degrees of rapidity, and on this is based an important advantage of the method. Evidently this condition is due to a difference in the reducing power, or to the relation of the organic substances to the reduced lower grade of oxidation. Through this peculiarity, osmic acid may render structural relations visible, which could in no other way be so summarily demonstrated. This is the case with the ter- minal tracheal cells in the luminous organ of the Lampyris. All kinds of fat cells and fat drops, and the medullary matter of central and peripheral nerves become rapidly colored black ; more slowly, the substance of the ganglion cells and of the axis cylinders, the muscular fibres, and all highly albuminous ele- ments, such as cells rich in protoplasma, red blood-corpuscles, and the fibres of the lens. The intercellular substance of con- nective tissues which afford gelatine and mucus, cellulose, amy- lum, the watery intercellular fluid of many vegetable cells, which only contain traces of dissolved organic substances, color most slowly of all (M. Schultze and Rudneff j. The chief value of the method depends on the property of osmic acid of pre- serving the most delicate, perishable tissues, which are most sensitive to reagents, in a condition apparently the same as in life ; as for example, embryonic tissues, the cells of connective tissue, the central organs and peripheral portions of the nervous system, the retina, etc. In this respect osmic acid excels all previously known reagents, as, properly applied, it prevents all granular coagulation, and does not allow even the structural changes which result from spontaneous post-mortem coagula- tion to take place. It is preferable to make use of pretty strong, that is, from one to two per cent., watery solutions. It is best to allow the tissues to remain in this solution but a short time, from a quarter of an hour to twenty-four hours. If al- lowed to act for several hours or days, the piece becomes quite hard and of a very dark color. As the solution does not pene- trate very deeply, very small pieces should be selected for im- 166 SECTION EIGHTH. mersion. Weaker, T '„- per cent, solutions, which do not harden the tissues so much, may also be advantageously used. The exhalations from osmic acid are injurious to the respiratory organs and the conjunctiva, and are therefore to be carefully avoided." Osmic acid has become generally naturalized in a few years as an excellent accessory. It belongs to the most important acquisitions of microscopic technique. It is necessary, in con- sequence of its volatility, to use small bottles with ground glass stoppers, in which the pieces of tissue are to remain. A subsequent instructive tingeing may occasionally be obtained with carmine, and also with hematoxylin. It should not be forgotten, however, that our reagent is not infallible. Many modern investigators have also gone too far in this direction in their blind reliance. d. Osmiamide. Owsjannikow recommends Fremy's osmiamide (1 : 1000), that is, the amide combination of osmious acid Os0 3 , which is OsO„H 2 N, as a substitute for the disagreeable volatile acid. e. Chloride of Gold. The action of the chloride of gold, which Cohnheim intro- duced into histology, is much slower and less energetic than that of a solution of nitrate of silver, so that a prolonged im- mersion of the (freshest possible) tissue is necessary, whereby the quantity of the fluid appears to make comparatively little difference. A 0.5 per cent, solution of the gold salt is to be used ; it is preferable to temper it with a minimal quantity of acetic acid. Leave the specimen in the solution from 15 or 20 minutes to an hour or more, till the former assumes a distinct straw color, which here, in contradistinction to nitrate of silver, penetrates deeply. After washing the preparation in ordinary or distilled water, place it for 24 to 48 hours or more in acidu- lated water, leaving the vessel exposed to the light. If the reduction has taken place, the color varies ; in the best cases it is a beautiful intense red, sometimes violet blue or a deep gray. They afterwards grow darker, assuming even a black tone of color. METALLIC IMPREGNATION'S. 167 According to Cohnlieim's experience, the chloride of gold does not act on cornified cells and those having no protoplasma, like simple flattened epithelium and the scales of epidermis (nor on their so-called cementing substance) ; furthermore, it does not act on the interstitial substance of connective tissue and cartilage. Finally, it exerts no effect on the cell nucleus ; still this is well preserved, the action of the gold impregnation being in general much milder and much less alterative than that of the silver impregnation. Others (Waldeyer, Loewe), say the nucleus swells. On the contrary, the chloride of gold is energetically and with relative rapidity reduced by the pro- toplasma of the cell, such as that of the lymphoid and glandu- lar cells and the cellular elements of the connective tissue and cartilage ; further, by the capillary vessels and the muscles. The chloride of gold reduces most energetically— and herein the chief value of this new method appears to lie — the elements of the nervous system, the ganglia, the medullary sheaths of the nerves, which assume a dark, almost blue red color, and the axis cylinder, which assumes a brighter, more lively red color. According to what has just been mentioned, the impregna- tion with gold promised to be of the greatest importance for the finer anatomy of the nervous system, the originator of the method having also succeeded in making a beautiful discovery in the corneal nerves. Unfortunate^, the method soon proved to be almost capriciously uncertain, in many cases leaving one entirely in the lurch, while other observers again obtained favorable results. Many have made use of solutions as weak as 0.005 per cent. Immersion in a solution of sulphate of oxide of iron is said to induce rapid reduction (Nathusius). The reduction occurs still more rapidly, however, according to Henocque, when the gilded object is taken out of the water and placed in a bottle with a ground glass stopper, and which is filled with a concentrated solution of tartaric acid, and ex- posed to the action of nearly boiling water. Complete reduction takes place in 20, 15 or less minutes. Boettcher recommends, as an improvement of a process given by Bastian, placing the cornea for 15-20 minutes in a 0.2 per cent, solution of chloride of gold, and then in a little bottle, with a tightly closing glass stopper, which contains formic acid 1 part, amylalcohol 1, and water 100 parts. The reduction is said to be completed in twenty-four hours. 168 SECTION EIGHTH. Chloride of gold objects, after being carefully washed out, permit of staining with hematoxylin (Eberth). Those which are immoderately dark may be bleached by means of a cyanide of potash solution, mentioned at p. 135. Nerves which have not yet become visible may be rendered distinct by adding to the washing water of the gold preparation, for a quarter to half an hour, one or two drops of a photographic bringing-out fluid which contains pyrogallic acid (Hoyer). Gold preparations are, unfortunately, incapable of perma- nent mounting. f. Chloride of Gold and Potassium, and g. Chloride of Gold and Sodium. The first salt was used by Gerlach in very weak solutions for sections of the spinal cord which had been hardened in the bichromate of ammonia ; subsequently for the examination of the nerve terminations in transversely striated muscle, as well as by L. Gerlach for the nerves of the heart. For the cornea, Hoyer prefers this salt to the chloride of gold, as a cleaner preparation. Arnold has made use of this salt, also highly diluted, for the fresh sympathetic nerve of the frog. Further below we shall return in greater detail to this method. Chlo- ride of gold and sodium has thus far been used only for the examination of the cornea (Waldeyer). h. Protochloride of Palladium (Chloride of Palladium). A few years ago, F. E. Schulze made us acquainted with the action of this salt. In order to dissolve the dry salt in distilled water, it is necessary to add a slight quantity of mu- riatic acid. He employs a solution of 0.1 per cent. (1 : 800 — 1 : 1500). From a half to a whole ounce of this fluid (of a wine- yellow appearance) hardens a piece of tissue of the size of a bean, in the course of two or three da}s, to a consistence proper for cutting, and at the same time colors it. According to the experience of the discoverers, chloride of palladium is especially adapted for the recognition of striated and smooth muscles, which thereby become brownish and straw-colored. Cells rich in protoplasma (epidermis and glands) likewise assume a yellow color. Cornified, fat, and connective tissues do not THE DRYING METHOD. 169 become colored. Furthermore, the medullary matter of the nerves assumes a black color, by direct action. Schulze also praises this reagent for the retina and crystalline lenses ; like the chloride of gold, it causes the nuclear formations to appear sharply, and by subsequently tingeing the connective tissue with carmine, very instructive preparations are afforded. It is an unpleasant circumstance that with many tissues, as the brain and epidermis, the action remains quite superficial. The preparations are to be carefully washed and mounted in glycerine. i. Prussian Blue. Leber recommends a peculiar method of impregnation, more especially, however, for the cornea of the frog. The fresh or- gan is to be immersed for several minutes in a 0.5-1 per cent, solution of a protoxide salt of iron. It is then to be taken out for the removal of its epithelium, after which it is to be re- placed in the fluid for a short time, so that the total action amounts to about five minutes. After washing the cornea with water, it is to be seized with the forceps and moved to and fro for a few moments in a 1 per cent, solution of ferrocyanide of potassium till the preparation assumes an intense and uniform blue color. Finally, after again washing the specimen in water, it shows a colored basis substance, while the corneal cells and canals have remained transparent. The color pene- trates very deeply, and subsequent tingeing with iodine, car- mine, and fuchsine readily succeeds. This method promises to be useful. III. The Drying Method. We also add to the methods above mentioned, that of drying animal tissues. The object of this process is to give the parts such a degree of hardness and firmness, by depriving them of their water, that the thinnest sections may be obtained by the aid of a sharp knife, which again swell up by the addition of water, and thus resume their natural appearance. We have already, in a previous section, become acquainted with a series of chemical reagents, such as chromic acid, chromate of potash, and alcohol, which are used for the same purpose. The drying process is decidedly better adapted for many tissues and parts of the body, as it does not render them 170 SECTION EIGHTH. opaque. Especially compact structures, organs rich in con- nective tissue, as the skin, the tendons, and the walls of vessels, also the lungs (even injected preparations of the same), mus- cles, epidermis, crystalline lens, and the umbilical cord, may be treated in this manner with the greatest advantage. The dry- ing process is less suitable for glands, lymphatic glands, and delicate mucous membranes. It is unserviceable for the brain, spinal cord, the nerves, and their terminal expansions in the higher organs of sense, in consequence of their extreme soft- ness and instability. The management of the parts is very simple. They may be dried on a board or a piece of cork, to which in certain cases a convex surface may be given. To avoid wrinkling, many textures may be advantageously stretched out and fastened to the board or cork with pins. The temperature should not be too low, as decomposition might take place ; but considerable elevation of temperature is to be avoided on account of the co- agulation of the albumen. A temperature of 30 or 40° C. is most suitable. The siin of a warm day may also be very well employed for this purpose. If it be desired to avoid warmth, the sulphuric acid or the chloride of calcium apparatus of the chemical laboratories may be used. The pieces selected for drying should not be too large, and the diying should not be overdone, as they may become so brittle as to prevent one from obtaining fine sections, in conse- quence of the cracks and flaws which occur. Now and then it will be found most suitable to have a piece not entirely dried, having the consistency of wax. Naturally the blade of the knife should be dry. If the preparation is on cork, this may be used as a support in cutting, hard wood being injurious to the knife. The thin sections which are made are to be softened in pure water, or in water to which a little acetic acid has been added. If they are to be stained, they may be placed directly into the ammoniacal solution of carmine. It is less convenient to soften the sections on the slide than in a watch-glass or a glass box. This process requires a few minutes' time, in order to allow the air vesicles to escape from the spaces of the tissue. Dried pieces kept in a box, with the addition of a piece of camphor, constitute excellent material for many histological demonstrations. THE FREEZING METHOD. 171 IV. The Freezing Method. This process, which has been made use of more recently, also affords good results, and in a mnch more conservative manner than that of drying. The preparation is allowed to freeze at a temperature of 6, 8, 10, or 15° C, according to ne- cessity, until it assumes a consistency which will permit fine sections to be made with a cooled razor. The object is more convenient to handle if it is allowed to freeze on a strip of cork ; it is also judicious to make use of an artificial freezing mixture. Nerves and muscles have been treated in this manner with good results (Chrzonszczewsk}^ Cohnheim). Glands, such as salivary glands, livers, kidneys, spleens, the lungs, the skin, and the bodies of embryos also afford excellent appearances (Kolliker) ; likewise ganglia (Arnold). Indifferent media, such as iodine serum, are to be used in examining the sections. The freezing method is, however, by no means neutral. Numerous rents and clefts are formed at the same time, which may readily pass unnoticed on subsequent thawing. Corrobo- ration by other methods is, therefore, quite necessary (Key and Retzius). t? Section Nintl). METHOD OF INJECTING. Of the greatest value for histological studies is the artificial filling of the vascular systems of the part to be examined with colored masses ; a procedure which, unfortunately, is still too much neglected by many, inasmuch as, without having obtained the necessary practice, it may here and there appear as though such a procedure were somewhat superfluous — a luxurious ad- junct. And yet this important accessory should never be neg- lected in any investigation which is at all accurate of normal or pathological textural relations ; for much in the construction of an organ at once assumes the greatest clearness and intelli- gibility after its capillary system has been filled, and the de- sired disclosures with regard to the vascular abundance or pov- erty of a part are at once obtained. The art of injecting can only be learned, and its execution is by no means easy. Much, indeed the greater part, depends on apparently unimportant expedients, on little artifices, as well as on a skill only to be obtained by practice. Nevertheless, with the necessary perse- verance, and by not being discouraged by the almost unexcep- tionably unsuccessful first attempts, one soon attains the de- sired skill, especiallj' if one renounces the idea of obtaining perfectly beautiful injections at the beginning. Success is gradually more and more readily obtained, and the satisfaction derived from the little work of art which is finally produced, has already been for many the incentive to further investiga- tions. In the following pages we shall attempt to bring before the reader the most important of the technicalities of injecting, and to render especially prominent that which we have learned from our own experience in regard to this subject. At the same time we are quite willing to admit that others might have re- METHOD OF INJECTING. 173 placed many things that are here noticed with much that would perhaps have been better. Although all such directions are not capable of thoroughly supplying that which may be ob- tained much more rapidly from the practical instruction of an experienced teacher, they will, nevertheless, present serviceable hints to many autodidacts. It will not be without interest, however, to previously give a cursory glance at the history of the origin of this art. The art of injecting, filling the canal systems of the body with colored or other readily recognizable masses, is, in its first crude commencement, relatively an old one. Hyrtl, in his im- portant " Handbuch der praktischen Zergliederungskunst," Wien, 1860, has given us an accurate and interesting history of this process. As early as the seventeenth century, wax and also mercury were used for this purpose. Gelatine was first employed for injections in the beginning of the eighteenth cen- tury. Among the older anatomists, the Hollander, Ruysch (1638- 1731), through his methods of injecting, obtained great renown — undeservedly, as we are at present, after accurate historical investigations, obliged to say, like so many of the celebrities of older and newer times. Tallow (tempered, in part, with-wax), colored with cinnabar, formed the mass used by him. N. Lieberkiihn (1711-1746), on the contrary, accomplished consid- erable for his time, as early as the first half of the eighteenth century. Even at the present time his preparations deserve to be called excellent, as we are assured by Hyrtl, the most com- petent investigator in this department. He made use of a mix- ture of wax, colophony, and turpentine, and, as a coloring medium, cinnabar. At a more recent period, Sommering, D6T linger, and Berres accomplished considerable in this depart- ment. Among those more recently engaged in this direction, the name of Hyrtl shines above all others. Others may be honorably associated with him, as, for example, Quekett, Ger- lach, Thiersch, Beale, etc. Naturally, the method of injecting interests us here only in so far as it is adapted for microscopico-histological studies, so that we shall pass over with entire silence the technicology of coarser injections. Among the numerous methods, two kinds may be distin- guished : 174 SECTION NINTH. 1. Mixtures which are fluid when warmed, and again become solid when cooled. 2. Mixtures which flow when cold. Among the materials of the flrst kind, resinous and gelati- nous substances have, as was above remarked, come into use. Hyrtl, who, among the living, has had the greatest experience in this department, informs us that the former renders excel- lent service in the injection of glandular organs and all capil- lary vessels of larger diameter ; but, on the contrary, in other parts of the body — for example, in filling the subserous blood- vessels or those of the mucous membranes of the air-passages, the oesophagus, the stomach, the perichondrium, the medulla of bones and of the testicle — they are unserviceable. It is alto- gether an error to believe that a certain injection mixture is equally useful for all organs. The Vienna anatomist prepares a resinous mixture in the fol- lowing manner : He evaporates the purest copal or mastic var- nish to the consistence of syrup, and then mixes with it about one-eighth as much cinnabar, which is to be carefully rubbed with the varnish on a grinding-slab. A very slight addition of virgin wax is also made, to give the mixture more consistence. Some time ago I made use of such a mixture, by Avay of experiment, and saw how, with a little practice, very handsome objects might be obtained, if the preparations were not required for finer histological studies, but rather for use with weaker magnifying powers. Those who desire to investigate the finer structure of the organ to be injected should, therefore, have recourse to gela- tine. The low degree of temperature at which a gelatine injec- tion is possible, although not sufficient for the resinous injec- tion, is an advantage which cannot be too highly prized. Very properly, therefore, histologists have preferred the use of gela- tinous mixtures for their injections, Summering and Dollinger having even in olden times accomplished excellent results with the same. The subsequent drying which ensues with the ordi- nary older methods of preservation is accompanied by a certain shrinking of the tubes which have been filled, an evil which is induced by the loss of water ; so that such objects frequently do not exhibit the full, firm appearance presented by the resi- nous preparations. Nevertheless, the much greater readiness with which the watery solution of gelatine passes through the METHOD OF INJECTING. 175 vessels whose walls are moistened with water is an advantage which can be obtained with no other mixture which solidifies, especially for organs with narrow capillaries. Moreover, this shrinking may be considerabty limited by careful mounting. Disregarding the coloring materials at present, in order to prepare such a solution of gelatine and afterwards make use of it, several precautionary measures are necessary. Isinglass, as a relatively pure gelatine, has been frequently used. It is in no wise necessary, and its high price and the slowness with which it hardens in cooling are to be designated as disadvantages. More recently I have frequently used the thin, transparent gelatine tablets which are met with in com- merce as "Gelatine de Paris," and which constitute, it is true, a mixture which is also not to be numbered among the cheapest. The latter may be formed, however, from the better sorts of or- dinary Cologne gelatine. For dissolving gelatine the process most to be recommended is the following : The gelatine is to be broken to pieces and then soaked in distilled or rain water for several hours. The water is to be poured off and renewed, the gelatine is then to be dissolved in a water bath, never immediately over the fire, and the solution filtered through flannel into a porcelain dish. The coloring material, the necessary directions for which follow further below, is to be added to the solution while it is still warm. The consistence which is to be given to the gelatine mixture should be dependent on the individual circumstances. A thin gelatine fluid is sufficient, if a pulverized granular coloring matter is added in the form of a thick pulp. If the coloring material is directly precipitated in the injection fluid by pouring together solutions of two kinds of substances, a saturated gelatine fluid should be employed. With a little practice one soon learns to hit upon the proper proportions.* In using such an injection fluid it is to be warmed in the same manner, for which purpose the same dish may be used several times in rapid succession. Such a fluid cannot be kept for a long time, however (even in a camphorated atmosphere), without moulding, or even without losing its former homoge- neous constitution, which is so important ; so that one is often * The addition of glycerine is often useful. 176 SECTION NINTH. put to the unpleasant, time-consuming necessity of preparing the gelatine fluid anew.* For the further treatment of specimens injected with gela- tine, see the end of this section. Quite a variety of coloring materials may be advantageous!} 7 added to the gelatine fluid ; they will be mentioned further below. The use of injection mixtures which solidify on cooling al- ways consumes time, as was remarked, and requires a variety of arrangements. The discovery of a material which is fluid when cold, and which may be used at any time, must therefore appear to be of great value. A number of such mixtures have been invented and recommended in the course of time. We will first mention a process practised by Bowman, the English histologist, which, although it may be momentarily employed, is less serviceable for producing a good injection than for coloring the blood-vessels of an organ and rendering them visible for microscopic examination. This method consists in forcing two solutions of salts after each other through the same vascular system, in which a lively colored precipitate is thus produced. Bowman used for this purpose the acetate of lead and the chromate of potash. A few experiments which I once made with this method gave a satisfactory view of the course of the vessels. But such a preparation is by no means beautiful. For his cold injections, as he informs us in his "Zergliede- rungskunst," Hyrtl also employs the previously mentioned re- sinous mixture, to which he gives the consistence of an ordinarj 7 " coarse injection fluid b} T the addition of a little wax and red lead. He rubs a portion of the same in a dish, with the addi- tion of ether, to the consistence of syrup. He then adds the coloring material, in about the proportion of 1:8, and again rubs the whole with ether until the mixture becomes completely fluid. Hyrtl commends the facility and convenience of manip- ulation of this method. In consequence of the evaporation of the ether, the injected organ is ready for examination in a quarter of an hour. I have of late made the most extended use of a mixture re- commended by Beale ("The Microscope in its Application to Practical Medicine.''' London, 1858, p. G7), which is composed of glycerine, water, and alcohol, for tilling the smaller vascular ,: More recent recipes of Thiersch and others follow below (p. 185). METHOD OP INJECTING. 177 systems. This mixture excels all others with which I am ac- quainted for its facility of penetration, besides which it affects the tissues less than any of the mixtures in use. As the mix- ture does not become decomposed or altered in any way, it may be preserved for any desirable length of time. It is par excel- lence the histologist's injecting fluid, and when the preparations are mounted moist they present a most exquisite appearance. It has also afforded me very passable results when mounted dry by means of Canada balsam prepared in a special manner. Still the gelatine fluids are preferable for the latter preparations, and, in consequence of their consistence, they are indispensable for injecting the larger organs. Having discussed the injecting fluids which are at present generall} r made use of, let us now pass to the consideration of the coloring materials which may be employed with the same. These coloring substances may be divided into granular, per- mitting of examination only with incident light, and transpar- ent, suitable for ordinary histological investigations. Those of the first series are very numerous and were alone employed for the older injections. The number of the latter is, on the con- trary, much smaller, consisting at the present time of only a few coloring materials. If resinous mixtures are used, it is most convenient to em- ploy the finest oil colors for artists, which are to be purchased in thin leaden tubes — a j^rocedure made use of by Hyrtl. Among these "colors in tubes," the Vienna naturalist recom- mends for red, Chinese vermilion ; for } T ello\v, orange chrome yellow ; for green, emerald green and verdigris ; for white, Nottingham white and Cremnitz white ; for blue, a mixture which he prepares from the last white color and Prussian blue. These colors are expensive, it is true, but are of a fineness such as no one can prepare for one's self. They are therefore to be designated as of the first rank for opaque injections. If gelatine is used as the solidifying substance, it is custom- ary to employ red, yellow, or white fluids. a. Red Mixture (Cinnabar). Cinnabar is most commonly employed for this purpose. Commencing with a small quantity of a fine quality, it is to be rubbed up as carefully as possible in a mortar, with the grad- 12 178 SECTION NINTH. ual addition of water, and the process continued in this man- ner. A little carmine may be rubbed up with it, to heighten the color. The coloring matter is then to be gradually added to the warm gelatine solution, which is, at the same time, to be carefully stirred. It is a common fault of beginners that they use too little cinnabar, and hence they obtain an injection fluid with which separated scattered granules of coloring matter afterwards appear in the vessels. A good cinnabar injection should, on the contrary, yield a coherent coralline red color. In consequence of its considerable weight, cinnabar has the un- pleasant peculiarity of collecting at the bottom of the gelatine solution, so that it is necessary to stir the mass before its use. None of the other opaque coloring materials should be used in the form of the commercial preparations, unless they can be given to a professional color-rubber for pirlverization, as it is otherwise impossible to reduce the granules to the necessary fineness. It is much preferable to procure them by careful precipitation from diluted solutions. b. Yellow Color (Chrome yellow). 1 regard this as the best and most readily manageable of all the opaque coloring materials. In order to obtain a good chrome yellow, 30 parts by weight of sugar of lead may be dissolved in 2 ounces of water, and likewise, in the same quan- tity of water, 15 parts of red chromate of potash. By care- fully mixing these fluids, preferably in a high glass cylinder, a very finely granulated chromate of lead is produced, which is gradually deposited at the bottom of the vessel. This is to be washed with distilled water and then added, in the form of a thick slime, to the gelatine solution. Harting (in his work on the Microscope, Vol. II., p. 123) gives the following recipe (which I have also found to be ser- viceable) : — 4 ounces If drachm of acetate of lead, or sugar of lead, is to be dissolved in a quantity of water sufficient to make the whole volume 16 ounces. 2 ounces 1 drachm 28 grains of bichromate of potash are to be dissolved in a quantity of water sufficient to make the whole volume 32 ounces. In preparing the injecting fluid, take one part by measure of the solution of sugar of lead, 2 METHOD OP INJECTING. 179 parts by measure of the solution of chromate of potash, and likewise 2 parts bj 7 volume of a saturated solution of gelatine. The chrome-yellow is to be first precipitated in a special ves- sel, and afterwards added to the gelatine. The precipitated chrome-yellow should not be allowed to stand too long, as it assumes a coarse granular form, in consequence of the con- glomeration of the colored molecules. c. White Color. Carbonate of Lead. Zinc White. Sulphate of Baryta. A serviceable white fluid can only be obtained with diffi- culty, as in most of them the granules are usually too coarse. Harting, who instituted a series of experiments on this sub- ject, gives the following recipe for producing a useful carbon- ate of lead : — 4 ounces \\ drachm of the acetate of lead are to be dissolved in water, so that the whole corresponds to a volume of 16 ounces. 3 ounces If drachm of carbonate of soda are to be dissolved in water, and the whole likewise made up to 16 ounces. For the injection fluid, take one part by measure of the first solution, the same quantity of the second, and combine them with two parts of gelatine solution. Harting remarks concerning this fluid, that it passes through the vessels better than white lead combined with gelatine. I formerly obtained tolerable injections with finely-pulver- ized zinc white. I have not used this coloring material, how- ever, for years. As a very fine white, although the color does not assume such complete uniformity, I recommend the sulphate of baryta. I made the most extended use of this material years ago, and am inclined to prefer it to the chrome-yellow, when it is necessary to have a finely-granulated and therefore readily penetrating fluid, though the preparations are less beautiful. I employ the following process :— The salt in question is to be precipitated from about 4 to 6 ounces of a cold saturated solution of chloride of barium, in a glass cylinder, by the care- ful addition of sulphuric acid. After standing for some time, nearly the whole of the fluid, which has again become clear, is to be poured off, and the remainder, with the sulphate of ba- 180 SECTION NINTH. ryta, which is deposited at the bottom of the vessel, is to be added, in the form of a thick slime, to about an equal volume of a concentrated solution of gelatine. d. Chloride of Silver. Teichmann, in his excellent work, mentions a new, very effi- cient, although expensive injecting mixture of chloride of sil- ver. He commends the same as rendering excellent service in certain cases, and says that its molecules possess a very con- siderable fineness, occasionally similar to those of chyle. It is an unpleasant circumstance that the mixture becomes black from the action of the light and sulphuretted hydrogen. But, like sulphate of baryta, the combination is so fixed that decom- position does not take place with the employment of reagents, and the specimens inay be preserved in chromic acid, etc. Three parts of nitrate of silver in solution are to be com- bined with the solution of gelatine, and then one part of com- mon salt is to be added. Considerably superior to these granular substances are the transparent coloring materials, that is, those whose particles are so fine that even with high magnifying powers the injected vessels still show a homogeneous color. Such injections are particularly to be recommended for histological investigations, as it is by their use onlj r that it is possible to recognize the re- maining structural conditions, while a complete injection with opaque mixtures conceals, more or less, the finer structure of the organ. They will be substituted for the granular coloring- materials by any one who has used them a few times when well prepared. The reproach which has here and there been made concerning these colors that they transude, refers only to those which are badly made, but is not applicable to good transparent materials. Unfortunately, the number of these is, as yet, but very small. Until recently, besides the soluble Prussian blue, there was only a red coloring material, carmine, known. Professor Thiersch, who has earned so much credit hj his methods of injecting, has recently enriched us with a solu- ble yellow and green, and was so friendly as to communicate to me their composition. We shall first speak of such of these coloring materials as are adapted for gelatine injections. METHOD OE INJECTING. 181 A number of different mixtures are at present known un- der the name of transparent Prussian blue. Of these, the second receipt deserves but little recommendation, as the blue color gradually fades, especially when the preparation is pre- served in glycerine. The first coloring material is, on the con- trary, excellent, and the last is also very much extolled. Nevertheless, I know of no Prussian blue which lasts longer than ten years in injection preparations. In this regard the excellent coloring matter stands infinitely behind carmine. I have lost hundreds of the most splendid injection preparations in this manner to my greatest sorrow. 1. Thiersch's Prussian Blue with Oxalic Acid. The best receipt with which I have become acquainted runs as follows : — Prepare a cold saturated solution of the sulphate of the protoxide of iron (A), a similar one of ferrocyanide of potas- sium, that is, prussiate of potash (B), and thirdly, a saturated solution of oxalic acid (C). Finally, a warm concentrated solu- tion (2 : 1) of fine gelatine is necessary. About half an ounce of the gelatine solution is to be mixed in a porcelain dish with 6 ccm. of the solution A. In a second larger dish, one ounce of the gelatine solution is to be combined with 12 ccm. of the solution B, to which 12 ccm. of the oxalic acid solution C is afterwards added. When the mixtures in both dishes have cooled to about 25 or 32° C, the contents of the first dish are to be added drop- wise, and with constant stirring, to the mixture in the latter. After complete precipitation, the deep blue mixture which is formed is to be heated to 70 or 100° C. for a time and constantly stirred ; finally, it is to be filtered through flannel. The injecting fluid thus obtained keeps excellently in Can- ada balsam. The depth of its color may be readily modified to any desired degree by adding a larger quantity of the gela- tine solution. 2. Prussian Blue dissolved in Oxalic Acid. A pure Prussian blue, preferably one that has been obtained by precipitation, is to be dissolved with the necessary quantity of oxalic acid. The color is certainly very intense, so that a 182 SECTION NINTH. moderate quantity is sufficient to give a lively blue color to a dish of gelatine solution. This mixture, like all transparent coloring matters, in consequence of the infinite fineness of its granules, readily passes through the fine capillaries. Harting recommends the following method (in which the quantity of oxalic acid appears too great) : — Take 1 part of Prussian blue, 1 part oxalic acid, 12 parts water, and 12 parts concentrated solution of gelatine. First, rub the oxalic acid in a mortar, and then add the Prussian blue. Thereupon the water is to be gradually added while con- stantly rubbing, and finally this blue fluid is to be added to the gelatine. 3. Prussian Blue from Sulphate of Peroxide of Iron and, Ferrocyanide of Iron. This color, which was first employed by Schroder van der Kolk and afterwards recommended by Harting, is a good one, although it requires somewhat more time for its preparation. Its granules are extremely fine, and hence it flows very readily. Nevertheless, the older preparations of my collection have latety become considerably faded, so that I rather prefer Thiersch's blue. I have used the blue made exactly according to Harting' s receipt, so that I can only recommend that. 3|- ounces of sulphate of iron is to be dissolved in from 20 to 25 ounces of water and slightly warmed. Then, b}- the addi- tion of 4| drachms of sulphuric acid, of 1.85 sp. wt.. and the necessary quantity of nitric acid, the iron is changed to an oxy-salt. A sufficient quantity of water is then added to make the whole volume of fluid 40 ounces. 3 ounces Gf drachms of ferrocyanide of potassium (yellow prussiate of potash) is to be dissolved in water, and the whole volume of fluid increased to 80 ounces. 1 part by measure of the solution of oxide of iron, 2 parts by measure of the solution of yellow prussiate of potash, and likewise 2 parts of the gelatine solution are to be employed. In order to prevent the gelatine from collecting in lumps and becoming ropy, I recommend the following method. The solution of ferrocyanide of potassium should be warmed and combined with the heated solution of gelatine. The solution METHOD OP INJECTING. 183 of sulphate of protoxide of iron is then to be added by drops, and while constantly stirring the mixture, which is finally to be filtered through flannel. "■a* 4. Soluble Prussian Blue. This is obtained by adding to a solution of ferrocyanide of potassium in excess, a solution of perchloride of iron, or of another oxy-salt. The precipitate is to be collected on a filter, and after the fluid has Altered away, again washed with dis- tilled water till (after the removal of the salts which were in the solution) a blue color begins to appear in the filtrate. The blue mass which is thus obtained becomes so finely divided in water, that the impression of a solution arises. Several years ago Briicke recommended the following re- ceipt for preparing such a soluble Prussian blue : — Ferrocyanide of potassium 217 grammes, dissolved in 1 litre of distilled water. Perchloride of iron 10 grammes, in 1 litre of distilled water. Sulphate of soda, a cold saturated solution. One volume of each of the two first solutions is to be mixed with one volume of the soda solution. The iron and soda solu- tion is then to be gradually mixed with the ferrocyanide and soda solution with constant stirring. Sections of organs injected in this manner often appear col- orless, but subsequently assume the blue color in oil of turpen- tine. They fade subsequently, however. 5. GerlacK s Carmine Fluid. A good carmine mixture remains unexcelled as a transpar- ent red. This substance requires careful preparation, it is true, and when not properly prepared it is completely useless, as it transudes in all directions. "Well prepared, it is of the first rank and of the greatest durability. Professor Gerlach, the inventor of the method of injecting with carmine, has had the kindness to communicate to me the composition of the fluids used by him, and to permit me to make them public. Dissolve 5 grammes of the finest possible carmine in 4 grammes of water and J grm. of liquor ammonia. The mix- 184 SECTION NINTH. ture should be allowed to stand for several days in a vessel not closed air-tight, and then mixed with a solution containing 6 grammes of fine white French gelatine to S grm. of water. A few drops of acetic acid are then to be added, and the mixture injected at a temperature of 40^5° C. I have made the most extended use of carmine fluids for a long time, and recommend, after many trials, the following method : — Have ready a solution of ammonia and one of acetic acid, of which the number of drops necessary to neutralize each other has been previously determined. Take 30-40 grains of the finest carmine, a determined num- ber of drops of the solution of ammonia (the quantity may be greater or smaller as may be desired), and about half an ounce of distilled water ; all of these are to be put in a mortar, and the carmine dissolved by rubbing. The solution is then to be filtered, which requires several hours, and a considerable loss of ammonia ensues in consequence of evaporation. The ammoniacal solution of carmine is to be mixed with a filtered, moderately -heated concentrated solution of fine gela- tine while stirring. The whole is then to be slightly heated on the water-bath, and the number of drops of the acetic acid so- lution necessary to neutralize the original solution of ammonia is to be slowly added, still constantly stirring the mixture. By this procedure a precipitation of the carmine in an acid solution of gelatine is obtained. If it be intended to inject organs of strongly alkaline reaction (for instance, those of human bodies which have been dead for some time), the acid- ity of the fluid ma}^ be increased by the further addition of several drops of acetic acid. The proportion of gelatine is to be increased or diminished according as a deeper or brighter red is desired. This simple procedure never fails, if the carmine used be of a good sort (which is of great importance), and an increase of temperature bej^ond about 45° C. be avoided during the injec- tion. A more rapid process is to thoroughly dissolve carmine in ammonia, add the coloring matter to the hot gelatine, precipi- tate with acetic acid, and filter the whole through flannel. The latter process suffices completely for the expert. For the preservation of such a fluid — and, we might add, of METHOD OF INJECTING. 185 other injection fluids containing gelatine— add a small quantity of carbolic acid dissolved in distilled water. Thiersch proceeds otherwise. He adds sulphate of quinine to the water used for dissolving the gelatine, in the propor- tion of 0.25 grms. to 30 grms. of dry gelatine, and, in addition, boils pieces of camphor with it. 6. Thiersch's Transparent Yellow. This beautiful yellow, which requires some care, however, to prepare it well, is to be obtained in the following manner : — Prepare a watery solution of chromate of potash, in the proportion of 1 : 11 (A), and a second solution, equally strong, of the nitrate of lead (B). Combine one part of the solution A with four parts of a concentrated solution of gelatine (about 20 com. to 80) in a dish. In a second dish, two parts of the solution of lead (B) is to be mixed with four parts of gelatine (about 40 ccm. to 80). The contents of both dishes are then to be slowly and care- fully mixed with each other at a temperature of about 25-32° C, and with constant stirring. This mixture is to be heated to about 70 or 100° C. , on the water-bath, for a considerable time (half an hour or more), and finally filtered through flan- nel. When a dish of this yellow mixture has stood for some time, it is generally necessary to heat it for a considerable time and filter it again, in order to render it serviceable. I have used a double quantity of the solutions A and B for many purposes with advantage. 7. Hoyefs Transparent Yellow. Hoyer recommends the following mixture as a yellow of the finest division, which also appears transparent in the smaller vessels and has a lively color : — Equal parts of a solution of gelatine, a concentrated solu- tion of bichromate of potash, and the same of sugar of lead (the neutral acetate of lead), are to be combined with each other in such a manner that the solution of gelatine and that of the bi- chromate of potash are united, and then heated nearly to the 186 SECTION NINTH. boiling point. To this is carefully added the sugar of lead so- lution, which should also be previously warmed. This mass, according to my experience, stands after Thiersch's yellow. 8. Robin' s Yellow Mass. He recommends a saturated solution of the sulphate of cad- miumoxyd, 40 ccm. with 50 ccm. glycerine ; then a concen- trated solution of the sulphate of soda, 30 ccm. with 50 ccm. glycerine. Both fluids are carefully united by stirring and added to gelatine in the proportion of 1 : 3. The color is beau- tiful to the naked eye, but is unfortunately coarse-grained and bad. 9. Tliiersclv 's Transparent Green. Equal parts of the blue gelatine solution as used by Thiersch, and the yellow one mentioned under 6, when carefully mixed, heated for some time, and then filtered, make a good and hand- 10. Bob in's Green. Take 80 ccm. of a concentrated solution of arsenite of pot- ash with 50 parts of glycerine. A second fluid consists of 40 ccm. of a saturated solution of copper oxyd, combined with 50 ccm. of glycerine. Combine them and add to one part of the green substance three parts of gelatine. Many transparent coloring materials are capable of a more advantageous application, however, than being combined with gelatine. They are combined with a peculiar mixture which flows when cold, and in this manner are obtained the best injec- tion fluids yet known for histological investigations. As we have made frequent use of them, the compositions used follow. 1. Beale' s Ordinary Blue. Dissolve 15 grains of ferrocyanide of potassium with 1 ounce of distilled water in a flask. Dilute from \ a drachm to 2 scruples of the English muriated tincture of iron with another ounce of water. It is well to have this tincture of sesquichlo- METHOD OP INJECTING. 187 ride of iron accurately prepared according to the British phar- macopoeia, by a good apothecary, in sufficient quantity to last for some time. The latter fluid is added by drops to the former, at the same time shaking it smartly. A mixture is then pre- pared of water 2 ounces, glycerine 1 ounce, ordinary (ethyl) al- cohol 1 ounce, and methyl alcohol 1\ drachm.* This mixture is to be carefully added to the blue colored fluid, the flask be- ing smartly shaken during the process, and the charming blue injection fluid is ready for use. 2. Beetle 1 s -Finest Blue. Beale has recently ("How to work with the Microscope." Third edition, p. 200) given a modified formula for the prepa- ration of a cold flowing blue injection fluid, which, when well prepared, surpasses all others that I know of in fineness, so that after standing quietly for weeks the appearance of a solu- tion remains unchanged, and there is not the least sediment formed. I prepare it, somewhat modified, in the following manner : — Combine 10 drops of the muriated tincture of iron mentioned with half an ounce of good glycerine in a flask ; in another flask 3 grains of ferrocyanide of potassium dissolved in a little water, to which is to be added another half ounce of glycerine. Both solutions are then to be very carefully mixed together, shaking them smartly, and finally half an ounce of water with 3 drops of strong muriatic acid is to be added. 3. Richardson' s Blue. B. Wills Richardson {Quart. Journ. of Micr. Science, Vol. 8, p. 271) recommends another composition. 10 grains of pure sulphate of iron is to be dissolved in 1 ounce of distilled water, and 32 grains of ferridcyanide of po- tassium in another ounce of water. As with Beale' s blue, these two solutions are then gradually mixed together in a bottle, the iron solution being added to that of the ferridcyan- ide, and mixture insured by frequent agitation. This makes a * The methyl alcohol in this and the third formula is a superfluous addition, and in consequence to be omitted. 188 SECTION NINTH. beautiful greenish blue, in which there is as little appearance of granules to be recognized with the naked eye as in Beale's mixture. Then the mixture mentioned under No. 1, consisting of water, glycerine, and the two alcohols, is to be carefully added and considerably shaken. 4. Mutter's Blue. W. Miiller prepares in a simple way a cold flowing blue mixture by the precipitation of soluble Prussian blue from a concentrated solution by means of 90 per cent, alcohol. The coloring matter is thus precipitated in a state of most extreme fineness, and a completely neutral fluid is obtained. 5. Beetle's Carmine. Mix 5 grains of carmine with a few drops of water, and when well incorporated add from five to six drops of liquor ammonia. To this solution about half an ounce of glycerine is to be added, and the whole well shaken. Another half-ounce of glycerine, containing eight or ten drops of concentrated ace- tic or hydrochloric acid, is to be slowly and gradually added to the carmine solution, frequently shaking during the mixture. The carmine thus becomes very finely granular, and the whole assumes a bright arterial red color. For its dilution a mixture is used consisting of half an ounce of glycerine, 2 drachms of ordinary alcohol, and 6 drachms of water. 6. White Fluids. As I have not, as yet, been able to find a third transparent coloring material for cold flowing injections, I have used an opaque mass, the sulphate of baryta. The mass is, as was re- marked, very finely granular, and is capable of being combined with a blue, if it be desired to inject the arteries and veins sep- arately. I employ the following process : — The salt is reprecipitated from a cold saturated solution of 4 ounces of chloride of barium by adding, drop-wise, sulphuric acid. After standing for some time (12 to 24 hours) in a tall cylindrical glass vessel, it is deposited at the bottom. About half the fluid, which has again become clear, is now to be METHOD OP INJECTING. 189 poured off, and the remainder, well shaken up, is to be com- bined with a mixture of one ounce each of alcohol and glyce- rine. These masses* — we repeat it — are distinguished by their great permeability, so that we prefer them to all gelatinous sub- stances for the injection of lymph passages and glandular canals. They also have the extraordinary advantage of being capable of preservation for months without alteration, so that they are instantly at hand. They are kept in small bottles with well-fitted glass stoppers. The requisite quantity for an injection is poured into a porcelain dish, and it is then ready for use.f 7. Solution of Nitrate of Silver. Within a few years a solution of nitrate of silver has been used for injections, in order to render the cells of vessels visi- ble. The animal is bled to death, a solution of nitrate of sil- ver (0.25, 0.5-1 per cent.) is then injected, which is to be fol- lowed after a few minutes by a stream of water ; or, a mixture of gelatine and a solution of nitrate of silver is used, in order to gain a more permanent distention. Sections of the organ are made and exposed to the light, and then hardened in *W. Miiller, in Ms excellent monograph on the spleen, also mentions a cold flowing, brownish red mass, which is obtained by precipitation from a solution of the chromate of copper with ferrocyanide of potassium. Chrornate of copper is obtained by digesting equivalent portions of sulphate of copper with chromate of potash, and washing out the brown precipitate. The latter readily dissolves in chromic acid in excess, and may be precipitated from the diluted solution, by means of ferrocyanide of potassium, in the form of an extremely fine brownish-red sedi- ment of ferrocyanide of copper. It may be at once injected, without further addi- tion than the solution of bichromate of potash which has been formed, and thus, at the same time, serve as a medium for hardening the tissue. f I have recently employed with advantage soluble Prussian blue simply dissolved in water for the injection of the ducts of glands, urinary canals, and biliary plexuses, also for lymphatic canals. 10 grains of sulphate of iron dissolved in 1 ounce of water, 32 grains of red prussiate of potash in another ounce of water, and both care- fully combined (see above), make a good fluid. If the canals to be filled are very fine, double the quantity of each salt is to be added to each ounce of water. Gly- cerine may be added if desirable. The red mixture recommended by Kollmann is serviceable. 1 gramme of carmine is to be dissolved in a little water with 15-20 drops of concentrated ammonia, and diluted with 20 ccm. glycerine. An additional 20 ccm. of glycerine is to be tempered with 1 8-20 drops of strong muriatic acid and carefully added to the carmine solution, at the same time shaking the latter strongly. It may be subsequently diluted by the addition of about 40 ccm. of water. 190 SECTION NINTH. alcohol. By this simple method the entire vascular arrange- ment may also be recognized with the same distinctness as by the ordinary injections with colored masses. After having become acquainted with the fluids used for in- jecting, and the manner of preparing them, we now pass to the consideration of the apparatus and the act itself of injecting. All who have frequently practised this operation will agree with us that a very simple apparatus is all that is required. Before discussing the method of injecting which is most important and most frequently used, namely, that by means of the syringe, it is necessary to mention several other modern processes which, according to our own experience and that of others, may be practised with facility and success, and will, without doubt, lead to the extension of our knowledge in many directions — we mean the self-injection of the living ani- mal and the injection by means of constant pressure. The idea was sufficiently obvious of permitting the escape of a definite quantity of blood from the body of the living animal by opening a vein, and replacing what was lost by an innocuous colored fluid, so that the contractions of the heart would fill certain vascular districts with it in a much less injurious manner than can be accomplished by the human hand. Chrzonszczewsky made us acquainted with these methods some time since. They consist in the introduction of the wa- tery solution of the carminate of ammonia. 10 ccm. of blood may be removed from the jugular of a medium-sized rabbit, and replaced by the same quantity of a solution of carmine, by means of the syringe to be mentioned below, without injury to the blood with which it becomes mixed. An adult animal bears 15 ccm., a dog of medium size, 25. Even during the injection, the reddening may be recog- nized on certain portions of the surface. If the larger vessels are then rapidly ligated, first the vein and then the artery, a physiological injection of the blood passages is obtained. The kidneys, spleen, etc., may be advantageously treated in this manner. At the same time, this carmine injection may be accomplished not only from the vascular system, but also from the stomach, rectum, and abdominal cavity, and in amphibia from the lymph cavities. The inventor recommends the solution of 2 drachms of car- METHOD OP INJECTING. 191 mine in 1 drachm of liquor ammonia, the same to be diluted with one ounce of water. Naturally, this solution is to be fil- tered before using. The organ is to be placed in acidulated alcohol to cause the granular fixation of the carmine. Such injections obtain a high value in still another manner Not only this carmine solution, but also a cold concentrated solution of sulph-indilate of soda is rapidly excreted by the kidneys, and the latter substance also into the biliary passages after large quantities have been injected. If the ureter be ligated immediately after injecting the rabbit, and the animal killed after three-quarters of an hour to one hour, the entire system of urinary canals will be found filled with carmine. In injecting the biliary passages with the blue fluid, it is un- necessary to apply the ligature. In both cases, however, it is necessary to wash the blood-vessels subsequently, and to re- place the original coloring-matter which remains in them with another. The organs injected with blue are next placed in a concentrated solution of chloride of calcium, and then in abso- lute alcohol, where the coloring matter becomes fixed in fine granules. Heidenhain has recently given more accurate directions for the use of indigo-carmine in the study of the kidneys. The ordinary commercial indigo-sulphate of soda is an im- pure product, a variable mixture of various substances, gener- ally three in number : a, the indigo blue-sulphate ; b, the in- digo blue-hyposulphate ; and c, the phcenizine-sulphate of soda. The chemically pure soda (or potash) combinations act in an entirely different manner for our purpose. The former salt is readily soluble in water, nearly insoluble in absolute alcohol, but more readily soluble in alcohol con- taining water. It is completely precipitated from its solutions by concentrated solutions of salt. The second salt, on the contrary, is soluble in water as well as in absolute alcohol, and is not precipitated by neutral salts. The third combination, the phoenizine sulphate salt, is of much more difficult solution in water than a, is precipitated by a slight addition of salt, and is readily dissolved in alcohol. For the following purpose, Heidenhain found only the combinations a and c useful, and the salt b was quite unsuit- able and pernicious. A rabbit of medium size requires about 25-50 ccm., a me- 192 SECTION NINTH. dium sized dog 50-75 ccm. of a cold saturated solution of the indigo blue sulphate of soda. Since we have gone so far, we will also give the remainder of Heidenhain's method. When the animals have ]3assed blue urine for a time, they are to be killed by bleeding and the kidneys examined in part immedi- ately, fresh in thin sections, in part after fixation of the coloring matter and subsequent hardening in absolute alcohol. For the former purpose it is best to inject the renal vessels instantane- ously with absolute alcohol. Heidenhain also discovered an excellent method for the self- injection of the biliary passages of the frog. A piece of indigo carmine, about the size of a pea, is placed in the lymph sac of the thigh, the wound of the skin is then closed as firmly as possible with a string. The biliary passages of the animal are found to be splendidly injected after twenty-four hours. We have recently, through Thoma and Arnold, become ac- quainted with a remarkable and astonishing action of indigo carmine. Brought in a proper manner, through a vein, into the blood passages of a living frog, it stains the homogeneous sub- stance which cements the epithelial cells, the so-called " cement substance/' We shall return to this subsequently. Injecting by means of constant pressure also has great ad- vantages for many purposes. First, Ave may learn by this means to estimate the pressure which is necessary to fill certain portions of the blood and Ij'mph passages, or of the glandular canals ; then, besides a very high pressure we can also use a very low one, and finally it permits of making the injection with extreme slowness, which the human hand refuses to do, in consequence of fatigue. Beautiful results have been obtained by this method for the tymphatic passages and also for the glandular canals (kidney and liver). A simple way of making such injections is by means of a graduated glass tube (fig. 88 b), which should not be too small, held by a support (a). To the lower end of this is firmly secured an india-rubber tube (c), the lower extremity of which terminates in a metallic tube which can be closed by means of a cock (fig. 88 d, 89) ; this tube should fit into the aperture of the canules of the ordinary injecting apparatus. The canule should be tied into the vessel of the organ to be injected, in the manner hereafter indicated, and placed in a convenient METHOD OF INJECTING. 193 position near the glass tube, which is secured in a perpendicu- lar position, having been previously rilled to a certain height and the stop-cock turned off. The end of the tube is to be cau- tiously but securely inserted into the aperture of the canule and the cock opened. The original pressure may be maintained Fig. 88. Simple injecting apparatus, with, a glass tube. Fig. 90. Injecting apparatus, with a column of mercury. or increased, as necessity may require, by pouring in more fluid. Such an arrangement may be left to itself for a number of hours or even days. If it be desired to use the pressure of a column of mercury, the readily constructed apparatus, represented in less than half size by fig. 90, is to be recommended. A glass bottle (a) is to be closed by an accurately fitting cork (preferably of gutta-percha) perforated by two holes. Through these holes pass two glass 13 194 SECTION NINTH. tubes perpendicularly ; one of them (e), which is graduated, and slightly funnel-shaped at the top, extends nearly to the bottom of the bottle. A second one (,/'), which is bent on itself, terminates just beneath the cork. The continuation of the ex- ternal portion of the latter tube is formed by a caoutchouc tube (g) firmly secured to it, at the termination of which the above- mentioned metallic tube with a stop-cock (Ji) is inserted and receives the canule (/). At the upper funnel-shaped opening () ; the funnel is prolonged by means of a caout- chouc tube (to), into the lower end of which is secured a finely pointed glass tube (;/). It is used for pouring in the mercury, and has on the caoutchouc tube a clamp (o), or preferably a screw-clamp. In preparing the apparatus for use, the lower part of the glass vessel is filled with mercury (d), the cock of the delivery- tube is then opened and the vessel filled to the upper edge with the injecting fluid. The cork with the two tubes is now to be firmly pressed into position, the funnel-shaped opening of the perpendicular tube being at the same time securely closed by the pressure of the thumb, care being also taken that the lower end of the tube dips beneath the mirrored surface of the mer- cury. If mercury be now poured into the funnel-shaped open- ing, the knee-shaped tube will become filled with the injection fluid, which soon issues without air-bubbles from the aperture of the metallic tube. The stop-cock is then to be closed and the end of the metallic tube carefully but firmly inserted into the mouth of the canule. The stop-cock should then be opened a second time, when the colored fluid will flow into the organ, and the column of mercury in the vertical glass tube will rapidly sink. This may be raised, by a subsequent addition of the metal, to an elevation of 20, 30, or 40 mm. (in many or- gans to double this or more), as may be desired. The flowing of the mercury may easily be so regulated, by means of the clamp, that the amount of pressure is constantly maintained.* If the column finally ceases to sink, the injection may be dis- * When it is necessary to employ a very slight pressure of known degree, it is advantageous to bend the tube which is connected with the funnel four times at right angles, so that it runs downwards and again upwards, outside the bottle and beneath the prolongation of the level of the mercury, somewhat in the form of a manometer (Mac-Gillavry). METHOD OE INJECTING. 195 continued or the pressure cautiously increased, according to circumstances. The apparatus described serves its purpose in practical hands, as I know from experience. But it is defective. The quicksilver comes in immediate contact with the injection mass, and must be subsequently purified. Then — and the defect is appreciable with a very low pressure — unpleasant momen- taneous increase of the pres- sure occurs from the pour- ing in of the quicksilver. An arrangement after the manner represented in fig. 91, where the inclosed compressed air performs the expulsion of the injec- tion mass, appears more suitable. The bottle A re- ceives the injection mass, which flows out through the rubber tube i and the canule Tc. This bottle is connected with the bottle B, which is partially filled with quicksilver and re- ceives the tube e, by means of two knee-shaped glass tubes, the latter being join- ed through a rubber tube. The latter bottle may have at its bottom an exit cock. This arrangement is not ne- cessary, though it is very convenient. It is unnecessary to re- mark that cold fluids are here in place. It is preferable to use a watery solution of Prussian blue or the Richardson mix- ture. The apparatus just described may also be readily used for injecting with gelatine (Ludwig). The bottle is to be placed in a tin chest of considerable size, which rests on feet and contains a table for the support of the organ which is to be injected. This chest is to be filled with warm water and Fiq. 91. Apparatus for injection with mercury and compressed air (after Toldt). A, injection bottle ; B, air chamber ; 6, c, glass tubes with connecting rubber tube ; a, glass tube for the column of mercury ; ff, and h, appara- tus for securing the tubes ; z, rubber tube ; fc, canule fast- ened in. 196 SECTION NINTH. the temperature maintained by means of an alcohol or gas flame. A well-adapted arrangement for this purpose, designed by Harting, will be at once made intelligible to the reader by our fig. 92. We are indebted to Professor Hering, of Vienna, for an excellent apparatus for such injections. By it the pressure on the fluid may be accurately measured and uniformly main- Fig. 92. Harting's injection chest, a, chest ; c, false bottom for the injection bottle ; /, thermometer ; 6. compartment for the reception of the preparation ; d, perforated plate, the position of which may be altered by means of the chains e. tained. The arrangement is by no means simple, so that we must refer to a description given of it by Toldt. We now pass to the consideration of the method most exten- sively used, that of the syringe. The small German-silver injection syringes (fig. 93, 1), which may be bought of Charriere or Luer, in Paris, for a few tha- lers, with a half-dozen or a dozen different canules (2, 3), are sufficient for all purposes, and will render equally good service for a number of years if used with some care. It is only neces- sary to carefully smear the piston from time to time with tal- low, in order to preserve the smooth, easy movement which is METHOD OF INJECTING. 197 so extremely necessary. It is also necessary to clean the syringe after being nsed for resinous injections with turpentine, and after gelatine with hot or cold water; it is then hung up by the ring of the piston-rod to permit the water to drain away. If, after a long interval of time, the caoutchouc of the piston no longer fits closely, the syringe is to be unscrewed and the piston placed for a half or a whole day in cold, or several minutes in hot water. It has then become sufficiently swollen again, and, when rubbed with tal- low, the piston performs its duty anew. Resinous masses always have the inconvenience of requiring a time-consuming cleansing of the syr- inge. The canules should also be cleaned with water after having been used, and should be stood upon a warm plate to dry. Nothing fur- ther is necessary to keep the larg- er tubes open. A thin silver wire should always be introduced into the finer and finest ones after clean- ing them, as, without this precau- tionary measure, the narrow passage is found to be closed, that is, rusted, and frequently it causes all subse- quent experiments to remain Avith- out results. Those who inject much require several of these syringes. It is also very convenient to have a large syr- inge, of about double the capacity of the small instruments, for filling extended systems of vessels, as the repeated removal for filling the syringe is always an unpleas- ant procedure ; and it is just in removing and in replacing the syringe that the beginner so readily meets with a misfortune. The canules themselves do not require any ring-shaped pro- jection, but rather a notched edge, for convenience in holding them. For frequent work it is necessary to have at least a dozen on hand ; it is still better to have even a greater stock of the Via. 93.— Syringe for Injections. 1. a, the tube, with the projecting edges 6, and c, (for convenience in holding), and the cap/, which is to be screwed on; d, piston-rod with the ring e ; g. the aper- ture (mouth-piece) of the syringe, with a silk thread wound round it. 2 and 3. Canules of the finest variety. 198 SECTION NINTH. most varying calibre, from about two mm. aperture to that of capillary fineness. I use those of German silver for large ves- sels ; the finest are of sheet-iron, and therefore unfortunately of a perishable nature. The remaining contrivances consist of strong, well-waxed silk thread of several sorts, several curved and straight needles, a pair of fine scissors, small ordinary and curved for- ceps, also several slide forceps (or other clamping apparatus, fig. 94) for possible emergencies. These, together with cold water, are sufficient for cold mas- ses. For gelatine injections it is also necessary to ' have a kettle with hot water and a double water-bath. The latter are ordinary deep copper basins, which are filled with warm water and kept at an elevated temperature by means of a spirit-lamp burning fig. 04. under them. They serve to receive the dishes of gelatine. Gelatine masses should never be warmed directly over a fire ! Together with plates or porcelain dishes, it is also convenient to have an oblong lead chest for the recep- tion of the organ or the body of the animal to be injected warm. The chest should have divergent walls and a drain- tube near the bottom, with a stop-cock. Objects for injecting are generally selected from parts as fresh as possible — that is, from animals which have just been killed. I have frequently used small animals while they were still warm, directly after death, which is preferably induced by bleeding. In this way I have obtained the best results, except where muscular parts were concerned ; in which case, espe- cially when injecting warm masses, the rigor mortis, which fre- quently occurs suddenly, renders the injection impossible. Very soft parts may be previously immersed for a day in alcohol, in order to render them harder. By means of this procedure I have frequently succeeded in injecting the spleen after having been unsuccessful with fresh organs, notwith- standing every precaution. In injecting the blood-vessels of bodies not so fresh, the coagulation of the blood is a great dis- advantage, which often ruins the whole process. It has been frequently recommended in such cases to precede the injection mass with a stream of water, and in certain cases this proced- ure is serviceable. But generally we soon meet with numerous extravasations, and we are compelled to discontinue at an METHOD OF INJECTING. 199 early period, long before a complete injection has been accom- plished. The blood-vessels of pathological new formations are gen- erally difficult to inject. The walls of the vessels are readily ruptured in consequence of their extreme delicacy. It is also frequently necessary to ligate numerous lateral branches. Cold transparent masses should only be used here, if anywhere. But with skill and perseverance much may be accomplished. Un- fortunately, this department has been altogether too much neglected by pathological anatomists, with the exception of Thiersch. In order to inject the lymphatic vessels, for which purpose all bodies are not equally suitable, I have frequently placed the dead body in water for a series of hours, so that these vessels might in this way become more thoroiighly distended. One may also frequently have the pleasure of seeing the lymphatic vessels become well filled, after having forced a stream of water through the arteries of the oigan for some time. Another method is likewise useful. I kill the animal by a blow on the head or by strangulation, then open the thorax, avoiding the blood-vessels, and ligate the ductus thoracicus high up. The body then remains undisturbed for 2-6 hours. The lymphatic vessels are now sought out, and are, for the most part, found to be filled and distended in a very satisfactory manner. The ex- periment may be made of ligating the efferent canals or the veins of the larger glands in the living animal, and thus causing the lymphatic vessels to become firm and distended. The freshest possible material should be selected for injec- tions of the glandular canals. The canule may be inserted di- rectly, or the passage may be made to appear more distended by previously forcing water through the artery, at the same time compressing the veins slightly, also first endeavoring to cause the secretion to flow out. In this case great caution is always necessary. In searching for a blood-vessel, an artery, or a vein, avoid all unnecessary cutting, as small branches may thus be readily in- jured, which afterwards makes it necessary to stop the rent with ligatures or the application of sliding forceps, and thus cause an unpleasant interruption to the progress of the work. In opening the vessel, which is best done under water, avoid making the slit too large, and above all do not make a transverse 200 SECTION NINTH. cut on a small artery, as in the introduction of the canule the vessel might readily be torn in two. By opening the vessel un- der water the entrance of air, which is always to be carefully avoided in injecting, is, for the most part, prevented. But there is still some air in the canule which is to be introduced. In or- der to remove this, the tube should be filled with water and the posterior opening closed with a cork before the introduction of the canule, a little precautionary measure which, like so many others, apparently unimportant, renders very great service in injecting. The mouthpiece of the syringe should also be passed beneath the surface of the water, and then introduced into the opening of the canule. The canule having been successfully introduced into the ves- sel, it next becomes necessary to secure it by means of a care- fully waxed silk thread. The necessary skill is soon acquired, the thread being either seized with the forceps and passed be- neath the vessel or brought round it threaded in a needle. Large vessels should be tied as firmly as possible ; with smaller ones more circumspection is required, and with very fine ones, especially embryonic branches, the greatest care is necessary. If the canule has a ring-shaped groove, which should always be the case with large ones, the ligature is to be placed at that part. If there is no groove, the greatest attention is to be paid to the application of the ligature, to prevent the tube from slip- ping out. In such cases the practised hand of an assistant, who places a finger over the opening of the canule without pressing the tube deeper into the vessel, renders an important service. The same process is to be followed in tying the canules into the ducts of glands. Lymphatic vessels require greater at- tention. That it is necessary to inject in the direction in which the valves open is self-evident ; although, in a few cases, the re- sistance which they present may also be successfully overcome. Still it is only rarely and for special purposes that this proce- dure can be made use of ; as, for instance, I succeeded in this way, several years ago, in injecting the lymphatic glands from the vas efferens. It frequently happens, however, that a well-distended lym- phatic vessel, which appears very inviting for injection, can nevertheless not be taken advantage of, especially when the vessel is very fine. The colorless fluid escapes on opening the vessel, and frequently the whole vessel becomes almost unrec- METHOD OF INJECTING. 201 ognizable. One is sometimes tormented for a long time in en- deavoring to introduce the canule within the collapsed walls ; attempt after attempt may fail, until after a time, in successful cases, the desired object is attained. Coolness and patience are to be recommended to those who desire to accomplish anything in this direction. When the fine lymphatic vessels in the interior of an organ are to be injected, Hyrtl and Teichmann's puncturing method is the process chiefly employed. Hyrtl sometimes makes a puncture from the cavity of a blood-vessel into the surrounding tissue in order to open some of the lymphatic vessels which may be present, and thus, in fortunate cases, inject the lymphatic canals from and with the blood-vessel. Another way is to make a small opening directly into the tissue, in order to inject imme- diately from this into any of the lymphatic vessels which may have been opened, and from these into larger systems. This may be accomplished in two ways. With larger can- ules, a needle may be passed through the tube ; after having inserted the canule into a small opening in the tissue, the needle may be pressed forward and the tube made to follow till the desired point is reached, when the needle is to be withdrawn. Where the walls were very thin, I have had better success by another method. A small puncture is to be made with a fine cataract-needle or the point of a fine scissors which lias been dipped into the injection fluid. The tube is now to be passed into the small opening, recognizable by the little point of color, and very slowly and carefully pushed forward with an easy rotating movement. When one has the requisite practice and patience for this process, lymphatics may be injected even where the method of preceding the canule with the pricking instrument would fail. Nevertheless, it always remains a diffi- cult piece of work — as, for instance, in the small intestines of the Guinea-pig — to guide the tube along in the submucous tis- sue, as the slightest awkwardness in the movement causes a perforation of the mucous membrane. Many attempts will fail, till at length, by a lucky hit, the injection succeeds. All who desire to accomplish anything in this direction should first practise on organs which are easy to inject, of which, fortunately, there are many. Try, for instance, the vermiform process of the rabbit, in which th» injection is very easy ; then the small intestine of the sheep, the testicle of the calf, and the 202 SECTION NINTH. Peyer' s glands of the last-named animal, and proceed gradu- ally to more difficult organs. In many cases it is unnecessary to tie the canule, as compression may often be better made with the fingers of line sliding forceps. If a ligature be used, a very fine needle should be employed, and the loop should be tightened with the greatest precaution, as very frequently the point of the canule is finally thrust through the walls of the vessel. Punctures which are too large permit the escape of the injection iiuid. Teichmann, who has obtained great ex- perience in this direction, very properly remarks that a punc- ture made at random is not sufficient, but that it is to be made in a direction where fine lymphatic vessels are supposed to be. If the extravasation which forms at the commencement re- mains small, the injection frequently succeeds. If it is large at the very beginning, and increases rapidly, stop, for the proce- dure has failed. If a rapidly-increasing extravasation subse- quently takes place, it is likewise necessary to discontinue at once. Very cautious management of the syringe is for the most part necessary, especially at the commencement of the injection. But we have wandered from our subject. When the tube has been firmly secured in position, the syringe is to be thor- oughly filled from beneath the surface of the injection fluid; and while the canule, which is now opened, is seized and some- what raised by the index and middle fingers of the left hand, the mouthpiece of the syringe is to be inserted as deeply as possible. The syringe is to be held by the middle phalanges of the index and middle fingers of the right hand, and the thumb is placed in the ring of the instrument. It is important that the forearm should, at the same time, rest quietly and conveniently on the table. In this manner, therefore, the injection of the mass com- mences : two fingers of the left hand holding the canule, three of the right the syringe, the piston being pressed forwards as slowly as possible and with the utmost steadiness. Every awkward, spasmodic impulse is to be avoided, especially to- wards the end of an injection. If the work succeeds, the col- ored mass is seen to move forward in the vascular system, and it is noticed how in some places the capillary systems become filled, how these latter places constantly become more numer- ous, and at the same time increase at the periphery until they METHOD OF INJECTING. 203 flow together. During this, the finger feels a gradually increas- ing pressure, and one soon learns to accommodate the motion of the piston to it. If two or three additional syringefuls of the mass be necessary, the syringe is to be removed, preferably before it is entirely emptied, and the opening of the can- ule closed with the thumb of the left hand. The syringe is to be refilled either by the operator, with his right hand, or by an assistant. If one possesses several syringes furnished with similar mouthpieces, it is well, when injecting large organs with cold masses, to have several of them lying tilled near him at the very commencement, so as to instantly exchange the emp- tied syringe for one that is filled. When the injection is completed, whereby it is often well to ligate the opposite vessel in order to prevent an escape of the fluid, the canule is to be closed by means of a stopper of cork, or better of metal, fitted into its opening, or by means of the above-mentioned (p. 192) short tube with a stop-cock. The in- jected vessel is now tied further below, and the other ligature which holds the canule is finally removed, so that the tube may be taken out. Although the above-mentioned manipulations are soon learned with a little aptness, it is difficult to properly estimate the moment when the injection must be discontinued. Here the beginner very readily errs, and even the most practised now and then has his unlucky day. Too little may be done ; the injection is then insufficient, only small places are filled, or fine capillary systems even not at all. Inversely, an injec- tion pushed too far leads to extravasations, and finally to an unserviceable preparation. If it be noticed that numerous though at first small extravasations form, desist, or they will be seen to increase in a frightful measure. That a considerable escape of the injection fluid requires an instant cessation in order to rescue what is possible, is self-evident. If Beale's cold mixture be employed, towards the end of the injection the colorless fluid is seen to be pressed through the walls of the urinary canals and the envelope of the organ, appearing on the surface as a fatty, glistening moisture. Then is the time to leave off ; it would be too soon in most cases before this exudation takes place. The double injection is naturally much more difficult than the single ; firstly, on account of the entire procedure, and 204 SECTION NINTH. then wliile too much should not be sent through one system, that of the vein, tor instance, in order that the possibility may remain for the one injection to meet that from the second sys- tem in the capillaries. For injecting arteries and veins, such masses should always be used, if possible, which give a pleas- ant blending of colors when they meet ; for example, Prussian blue and carmine, Prussian blue and white, while yellow and green appear less handsome to the eye. Masses which flow when warm and harden when cooled generally deserve the preference for these cases, and with gelatine masses I usually allow some time to elapse between the first and second in- jection, so that the former may at least acquire some firm- ness. For most cases, the vein may be first injected and then tied in the usual way. Afterwards, if there be considerable resistance, the artery with its ramifications are to be injected. For many organs, as for instance the eye, or the spleen, it is well to drive the injection mixture intended for the venous system through the artery first, and then, through the same vessel, the second mass which is to serve for the arterial sys- tem. Not unfrequently the injection may be essentially regu- lated by keeping open or closing the terminal vein. If, together with the blood-vessels, it be also intended to inject the lymphatics, or, in a glandular organ, its system of canals, the blood-vessel may either be injected first and then the latter, or inversely. If the lymphatics are to be injected by the puncturing method, avoid injuring the injected blood- vessels as far as possible. For all injections of the glandular passages and the lym- phatics, transparent cold mixtures deserve the preference, as was already remarked, on account of their ready permeability, as well as in consequence of the less degree of injury which their employment exerts on the tissues. Although the directions given are in no wise to be regarded as complete, and require special modifications for special or- gans, which are only to be obtained by experiment, they will, nevertheless, considerably facilitate the labors of the begin- ner. A successful injection having been made, the further ques- tion now arises : what is to be done with the specimen in order to prepare it for examination ? As was above remarked, warm injections require, beyond METHOD OF INJECTING. 205 all things, the necessary time for the mass to harden. Resi- nous substances require a longer time than gelatine. With Beale's cold mixture, the objects may be used at once ; with Hyrtl's ether injection, the injected organ may be used after a quarter of an hour. When a specimen has been injected with a gelatine mass, it should without delay, or at most only sufficient to wash off its surface, be placed in ice-water (in winter, snow), and left till the mass has become hardened. This may be readily recognized when the contents of the larger vessels no longer yield when felt with the points of the fingers. The injected organ is placed, for farther hardening and preservation, in weak, and then in stronger alcohol. It is well to let it lie quietly in this for several days before proceeding further. It is better to place very sensitive objects, directly after the in- jection, in alcohol which has been previously placed in ice, or which has been cooled b}^ putting pieces of ice in it (Thiersch). A few drops of acetic acid are to be added to the alcohol for injections with Prussian blue. Naturally, even here, numerous modihcations are necessary in certain cases. Thus smaller organs may be left in the alco- hol without cutting them, as also groups of organs and the entire bodies of the smaller mammalia, which may be prepared after a few days. It is preferable to open an intestinal canal, which has been injected with gelatine, after the injection fluid has hardened. This should be done in water, and the canal washed out carefully. Portions of intestine with the lym- phatics injected I cut open, and run a stream of water through the canal to wash out its contents, and then place the prepara- tion for a day or more in alcohol. Large organs after being- immersed in alcohol, for example, the kidney of one of our ruminata, should be cut open on the following day at furthest, lest the cortex should harden while the internal portion decom- poses. Immersion in chromic acid solutions is also applicable to such purposes, Prussian blue being well preserved in them ; but it is rare that alcohol can be altogether dispensed with. I also place organs injected with Beale's mixture, almost without exception, in alcohol, in order to obtain the necessary harden- ing of the tissue. After a few days, when the preparation has acquired the necessary firmness, it may be examined by the ordinary meth- 206 SECTION NINTH. ods already given. Thin horizontal and vertical sections, for example, are to be freed from particles of coloring matter which have escaped by washing, or, still better, by means of a camel' s-hair pencil. They are then to be reviewed with the microscope, and, if it be desired to preserve them permanently, they are to receive such further treatment as may be neces- sary. The old method of mounting dry is to be recommended when the preparation is to be used as an opaque object. It is still better to mount it carefully in Canada balsam, which will be treated of in the following section. Glycerine is being more and more employed for mounting histological preparations, and, as may be readily conceived, it reproduces the natural relations, although connected with the very great disadvantage of being much less durable. For the preservation of injected organs for a considerable length of time, alcohol, weak or strong, according to circum- stances, is used. Section ftentl), THE MOUNTING AND ARRANGEMENT OF MICROSCOPIC OBJECTS. The reader will have perceived from the preceding sections that it is by no means one of the simplest and easiest things to obtain useful microscopic specimens, even if, at the same time, we also disregard the rareness of many, as, for instance, those of embryonic and pathological occurrences. The desire to pre- serve for the longest possible time such objects as are only obtained with trouble or the concurrence of fortunate circum- stances is also sufficiently obvious ; and, in fact, the effort to obtain such preparations is as old as microscopy itself. The value of such collections is quite as great for the study of this branch of natural science as for that of others. Commencing with crude attempts in the preservation of hard structures, dried preparations of injections, etc., the in- dustry of the investigators has gradually brought better and better methods to light, so that this now constitutes an impor- tant section of microscopic technology. At the same time, although much has been accomplished in this department, still more remains to be attained and explored ; most of those branches relating to preserving being at the present day still in an incipient condition. Many portions of the body may be sufficiently well pre- served in ordinary alcohol for the purpose of having at hand material from which, in case of necessity, a serviceable prep- aration may be made with rapidity and little trouble. Hard- ened glands, intestines, the central portions of the nervous sys- tem, tumors, injections with gelatine and cold masses, such as have been described in the previous section, and embryos, may be preserved in the most convenient manner in well-closing glass bottles, and constitute, especially for a teacher, invalu- able material for instruction. 208 SECTION TENTH. But, in most cases, the matter is not so simple when a defi- nite microscopic preparation is to be preserved. For this pur- pose certain methods are necessary. Hard structures of many kinds, especially those of a trans- parent nature, scales of diatomes, thin sections of bone and teeth, and crystals, may be permanently preserved in a very simple way if they are placed on a slide and covered with a thin covering glass, and the latter fastened to the former. Various substances may be used for this purpose ; as, thick gum-arabic (a solution of gum with powdered starch is good), wax, resinous substances of thick consistence, and Canada bal- sam. For the protection of the fragile covering glass, the whole may afterwards be covered with colored paper, through which an aperture has been made with a punch. It is well for those who work much with such objects to have lithographed covers prepared, the posterior surfaces of which are gummed for the sake of economizing time. On one surface of the slide the paper should project beyond its edges in such a manner that thej^ may be covered hy it, while the other surface of the glass plate requires a smaller covering. One soon acquires the little dexterity necessary to apply these covers. The gummed sur- face should only be slightly moistened, so that when pressed on to the slide the gum will not exude and flow over the visible portion of the preparation. Very many such preparations, which are in circulation and to be purchased, may be recom- mended as models ; as, for instance, those of Bourgogne, in Paris; Moller, in Wedel (Holstein) ; and Eodig, in Hamburg. But, as we have already remarked, only a small number of objects, which are transparent per se, permit of this most sim- ple method of treatment. The greater portion of those which are to be preserved dry require, in order to render them trans- parent, to l)e mounted in a substance which refracts the light strongly, in a gradually hardening resinous material. For this purpose there is none more important or more generally used than the Canada balsam, and, indeed, it suffices for all cases. Other resinous substances, such as copal lack, damar varnish, and mastic are really superfluous, and are, at most, only to be used here and there b}^ way of experiment. Several sorts of Canada balsam occur in commerce. To be good it should be of thick consistence, nearly colorless, and thoroughly transparent. It is to be kept in wide-mouthed ves- THE MOUNTING, ETC. 209 sels closed with glass stoppers, in order to limit as much as possible its tendency to harden in the air. If, in consequence of the prolonged action of the air, it has become much hardened it may be thinned, after being moderately warmed, with oil of turpentine, or, which is less preferable, with a little chloro- form. The preparation to be mounted must be thoroughly dry. Hence, in many cases a preparatory drying process will be ne- cessary. For this purpose the preparation maybe placed over a water-bath, or over sulphuric acid or chloride of calcium. Many preparations may be advantageously placed in oil of tur- pentine, in which they are to be left for at least a few minutes. If the specimen to be mounted contains air, a longer immersion in turpentine, occasionally in that which is warmed, will be ne- cessary. The preparation should be mounted in the following man- ner. The dry, cleanly-washed slide is to be moderately warmed over the spirit-lamp, but never to an extreme degree. A drop of the balsam is then to be taken from the bottle by means of a pointed glass rod and placed on the slide. It will then spread out into a layer which, in fortunate cases, will be quite homo- geneous aud contain no air-bubbles. But if any of the latter remain in the stratum of balsam (if the slide be too warm they are developed by the boiling of the balsam), they are made to burst by touching them with the point of a heated needle, or are brought to the edge of the layer of balsam with the point of a cold needle. The object to be mounted is now placed in position, and a second drop of balsam is placed over it by means of the glass rod. The two layers of balsam will soon Mow together if the procedure be rapid or the slide be again slightly warmed. The clean and moderately warmed covering glass is now to be seized with the forceps and placed in an in- clined position, with the side opposite the forceps lowest, over the layer of balsam, and then allowed to gradually assume a horizontal position till it completely covers the object. If there be any air-bubbles still remaining, they may be driven to the margin of the covering glass by careful pressure on its other edge, provided the mounted object be of a nature- which permits of the necessary pressure. The preparation is now to be reviewed with the aid of a low power. If several air-bubbles are still to be discovered, it is preferable to place 14 210 SECTION TENTH. the slide on a warm body (in winter it is best to place it on the cover of an earthenware stove) covered with a bell-glass, and left for several hours, whereby, at the same time, the balsam hardens more rapidly, and on this account it is an advantageous procedure, even where there are no air-bubbles. If too much Canada balsam has been used, a quantity of it usually spreads beyond the edge of the covering glass, or even on to its surface. In such cases it is necessary to wait till the balsam hardens, after which it may be scratched off with a knife-blade, and the surface of the glass cleaned with a rag freshly moistened with oil of turpentine or benzine. The hardening of the balsam at the interior of the prepara- tion proceeds very slowly, so that it still remains fluid for days, and even weeks, while the edges have become hard. By an awkward manipulation the covering glass may be displaced and the preparation ruined. Subsequent warming is here of service. Hard structures may be thus treated for several days. Soft animal parts require a more conservative treatment. An immoderate, too long continued heating gives the resinous mounting material an unpleasant yellow. Occasional^ a Canada balsam is met with which is at first of a somewhat more fluid consistence. In this case the mount- ing may be done on a cold slide, which always economizes a certain amount of time. Such preparations should always be placed for a time on a slightly warmed support, so as to dry more rapidly. Although it is quite necessary to accomplish the expulsion of the air-bubbles from most specimens mounted in Canada balsam, there are other objects in which the air con- tained in the finest canals is of importance for the recognition of certain structural peculiarities, and the air must therefore be retained. If, for example, we place a section of bone directly, or after having been in turpentine, into Canada balsam which is very fluid, the canaliculi and the cavities of the bone become filled with this medium, which gradually penetrates in all direc- tions and forces out the air. But the processes of the bone corpuscles and the canaliculi appear distinct only when they contain air, and it is only in this way that the bone presents a characteristically elegant appearance. Such preparations must be mounted warm with the thickest possible Canada balsam. For this purpose the balsam may be THE MOUNTING, ETC. 211 placed in an open vessel in a warm place, and covered with a bell-glass nntil it becomes quite hard and firm. It is unneces- sary to remark that previous immersion of the object in oil of turpentine is here to be avoided, and that in mounting it is ne- cessary to expose the Canada balsam, slide, and cover to a con- siderably elevated temperature. Frequently — especially with histological work — when it is desired to mount a very thin and delicate specimen, as the object is warmed, it will be seen, to one's great vexation, to shrink, become curved, and finally break. Here a solution of Canada balsam in ether, or, still better, in chloroform, filtered through ordinary filtering paper, is in place ; it may be diluted according to circumstances. By means of a brush or a glass rod it is placed cold on the slide, the object is placed in this, then more fluid is added, and finally the covering glass is laid on. As the dissolving medium evaporates, the air generally enters on one side between the plates of glass. In such cases the preparation is to be held in a slanting position, and a few drops more of the solution added until the process of mounting is finally completed. The whole procedure, which may also be employed for more substantial objects, is very convenient and cleanly. A solution of Canada balsam in benzine has also been recently recommended (Bastian). Walmsley dissolves thick- ened Canada balsam in pure benzine to the consistence of cream. But how should one proceed when one of the soft watery tissues, such as the greater portion of our body presents, is to be placed in Canada balsam \ How are injected preparations to be treated ? That this can only be accomplished by intermediate pro- cesses is self-evident. That is, the water must be expelled by a fluid which mixes with it ; this is to be replaced by another, etc., until at last the Canada balsam may be used for the final saturation. Suppose we have a thin section of the spinal cord, kidney, or spleen, which has been tinged with carmine or some other coloring material, or the section of an intestine, brain, or lymphatic gland, with the blood-vessels and lymphatics in- jected, and we desire to mount the same as a dry preparation, but at the same time to avoid the shrinking occasioned by sim- 212 SECTION TENTH. pie drying, which would change the preparation, in fortunate cases, to a caricature, or, in less fortunate ones, to hiero- glyphics. The object is to be placed for a day in very strong, or better, in absolute alcohol ; from this it is transferred to strong methylated alcohol for half an hour, although this in- termediate step may also be dispensed with. By this means the water has been removed and the alcohol has taken its place. The preparation is now to be removed from the alcohol, pref- erably by means of a filter, and just as it begins to dry it is placed in oil of turpentine. The previously mentioned small, flat glass boxes are very suitable for this purpose. Sometimes the process of becoming transparent can be very conveniently followed under the microscope. Then, by placing a thick plate of glass which just covers the preparation over it, it will be pressed against the flat bottom of the vessel, and all curv- FlG. '.)5. Frey's compression apparatus. ing of the object will be prevented, and the shrinking will be limited to a considerable degree, even though the specimen re- mains in the oil of turpentine for several days. After several hours, all the alcohol is expelled by the turpentine, and the object is ready for mounting in the chloroform solution of Can- ada balsam. If it be desired to use a still stronger pressure on tougher structures (and this may also be necessary, subsequently, for preparations mounted in resinous substances), it is advisable to employ the simple apparatus of fig. 95 with its lead tubes, under which is placed either the glass box or the Canada bal- sam preparation with its covering glass. Excellent preparations may thus be obtained when one has once mastered this method. All injected specimens (those with nitrate of silver also) should be mounted dry in this way only. THE MOUNTING, ETC. 213 In the same manner many histological details, even cylindrical epithelium and other delicate cells, may be preserved so as to be visible, and if carefully tinged with carmine or blue, they may be rendered still more distinct. All the transparent colors which were mentioned as suitable for combination with gelatine are well preserved in this way. At the same time we would also add, as a precautionary rule, to add a drop of glacial acetic acid to the alcohol used for drawing the water out of preparations injected with Prussian blue. We would here add still another little precautionary meas- ure. It is best to allow very thin and delicate sections to be- come sufficiently dry on the filter, then to cut out the portion of paper on which the object rests and immerse it in oil of tur- pentine. By a slight movement the preparation may then be floated off from the paper. We have placed this procedure, with all its minutiae, before the reader, because of its great importance. Here, as everywhere, the greatest cleanliness, the use of filtered fluids, etc., is necessary. The employment of other resinous bodies in the plaoe of Canada balsam has been suggested and, in fact, a number have been recommended, such as damar, copal, mastic, etc. Several years ago I made extended experiments with them, and now recommend : Damar Resin in Turpentine. The preparation is very simple. The powdered material is placed in a bottle and pure oil of turpentine poured on it ; the bottle is to be lightly corked and exposed for 24-48 hours to a moderate heat. Then filter and evaporate the excess of tur- pentine by letting it stand for some time in an open vessel un- der a bell glass. This mass is more colorless than Canada balsam. The con- tours of the objects remain more distinct. The drying of the preparation is much slower, however, than with the former resinous mounting. Mastic in C7doroform. The powder is dissolved in a similar manner in the fluid and filtered. The contours of the preparation are tolerably sharp, 214 SECTION TENTH. better than in objects mounted in Canada balsam. The mass is somewhat yellow, and permits of only moderate warming in the artificial drying of the preparations. The intermediate stage of the oil of turpentine and its shrinking effect may be avoided by means of solutions of resi- nous matters in absolute alcohol which permit of mounting- cold without any clouding of the objects, but they do not per- mit of a highly increased temperature for rapid drying. Goloplionmm. Thiersch has quite recently made use of colophony for mount- ing such preparations. He prepares it in the following man- ner : — It is best for the microscopist to prepare the colophony himself, and a solution of it in absolute alcohol of syrupy con- sistence should be used. The advantage which this material presents is, that the preparation may be placed in it directly from the absolute alcohol, without becoming cloudy and with- out prejudice to the durability of the specimen. Venetian tur- pentine is to be dissolved in an equal volume of sulphuric ether, and the solution filtered through paper. The ether and oil of turpentine are then to be expelled by the heat of a mod- erate fire, till the residuum shows a shell-like fracture when cold. I have worked considerably with this mass, which, when well prepared, has the color of Canada balsam. The contours are sharper and prettier than with any resinous material with which I am acquainted. The drying is, unfortunately, ex- tremely slow. Nevertheless, I can recommend this substance in the highest degree. I have had specimens for four years, which are still well preserved. Sandarac. Powdered and treated with absolute alcohol, and digested for a day at a moderate temperature, this resin yields a filtrate which is but slightly yellow. When concentrated we have an excellent, very rapidly solidifying material for mounting. The contours of the objects become very indistinct, however, after a series of months. Many tingeing materials, such as hsema- THE MOUNTING, ETC. 215 toxylin commence, to fade. After this unpleasant experience of latter years, I no longer recommend the sandarac resin. But the natural condition of the tissues is completely repre- sented only when mounted in a moist condition. This method permits of the most accurate recognition of delicate textural relations, pale cells and fibres, etc., and should not be omitted with any tissue in the production of histological collections, as, even in cases where good dry preparations can be obtained, it affords an instructive comparison. Among all the preservative fluids for animal soft parts there is none which stands higher, at the present time, than glycerine. Its strong refractive power, its property of combining with water and of attracting the same from the atmosphere, render it an invaluable medium for mounting animal tissues containing water. It may be truly said, that what Canada balsam is to dry tissues, glycerine is to moist ones. The ordinary impure glycerine may be used in the prepara- tion of a temporary specimen, for brushing, etc., but not, how- ever, for permanent preparations. Here the purified glycerine, containing no lead and as little water as possible, is always to be used. Undiluted, it renders the preparation very transparent; occasional^, after a time, too much so. For many objects it must, therefore, be diluted with distilled or camphor water in about equal proportions, more or less, according to circum- stances. It is very useful, indeed almost indispensable, to wash the preparations which are to be permanently mounted for several days in pure glycerine, or a mixture of glycerine and water, in a small vessel, whereby the degree of transpar- ency which they will assume may be ascertained at the same time. The preparation is then to be mounted in the ordinary man- ner by means of one of the cements hereafter mentioned. The superfluous glycerine, which spreads beyond the covering glass, may be removed with a fine pipette and dried with a cloth moistened in alcohol. The nature of glycerine is such as to render it unnecessary to be in haste in the application of the cement, so that a number of specimens may be allowed to ac- cumulate before it is laid on to the borders. For many purposes I have found it well to add two drops of strong muriatic acid to the ounce of glycerine. Objects injected with carmine or Prussian blue always require this addition, 216 SECTION TENTH. otherwise the color will fade and disappear after a time. Ace- tic acid accomplishes the same purpose, and possibly better. Ranvier has recently proposed the combination with formic acid (1 : 100). As glycerine is a constituent of many mixtures, so also may many other materials be added to it, and thus produce more complicated mounting fluids. Thus, for example, gelatine, gum-arabic, etc., may be combined with the glycerine. Deane recommends a mixture of glycerine 4 ounces, distilled water 2 ounces, and gelatine 1 ounce. The latter is to be first dissolved in the water and the glycerine then added. I have had no experience with tannin and glycerine. Beale also recommends one of these combinations of glyce- rine with gelatine. A certain quantity of pure gelatine is al- lowed to soak in water until it swells up and becomes soft. It is then placed in a glass vessel and melted by the heat of boil- ing water (that is, on a water-bath). To this fluid an equal quantity of strong glycerine is added and filtered through flan- nel. The mixture may be kept for any length of time, and only requires to be slightly warmed before being used. Klebs employs 2 parts of a concentrated solution of isinglass and 1 part of pure glycerine slightly warmed. Bastian recommends a mixture of 15 parts of glycerine and 1 part of carbolic acid for mounting tissues not tinged. Farrants employs a still more complicated mixture, consist- ing of equal parts of gum-arabic, glycerine, and a saturated so- lution of arsenious acid. The mixture is to be used in the same way as the Canada balsam. Although gtycerine is the most important preservative fluid now known, answering all the requirements for many animal tissues, nevertheless one should not believe that everything can be preserved in it with success. Delicate, fresh watery tissues, for example, blood-corpuscles or ganglion cells, soon lose a portion of their water and become distorted. The strong re- fractive power of glycerine is, therefore, a disadvantage for transparent tissues, however excellent it may appear to be for those which are hardened. Besides glycerine, a whole series of preservative fluids have been tried and recommended, of which one is sometimes here, another sometimes there to be used with success. It is always well in mounting objects not to place im- plicit trust in such recommendations, but rather to make a THE MOUNTING, ETO. 217 series of experiments with various preservative fluids, of which only the best are to be retained after a subsequent examination. The deceased M. Schultze recommended, as a medium for mounting, a substance used by botanists, a nearly saturated solution of the acetate of potash in water, especially for osmic acid preparations which do not bear glycerine. Without re- moving the covering glass, a drop of this strong solution of potash is added to the microscopic preparation as it lies in water or an indifferent solution. A day later, the water having been in the mean time removed by evaporation, the cement is to be applied; although one may wait still longer. This method has been used for several years. Goadby's solution, the conserving liquor of the English, has obtained a certain renown. It consists of : — Bay salt 4 ounces. Alum 2 ounces. Corrosive sublimate 4 grains. Boiling water 4 pints. This composition, which brought the discoverer a consider- able sum, does not prove suitable for mounting transparent preparations, as they gradually become opaque and are finally rendered unserviceable. On the contrary, I have seen opaque preparations of injections mounted in this fluid, which were made in England, and which left nothing to be desired. Val- entine afterwards remarked that the tissues of sea animalcula are very well preserved in this fluid. The beautiful prepara- tions of vitreous-like medusa?, salpida?, etc., in the naturalist's collections also harmonize with this observation. Pacini has recommended certain preservative fluids, as modifications of this mixture, which contain sublimate, com- mon salt or acetic acid, but no alum, including glycerine, how- ever, as a useful addition, and intended for preserving various tissues. They are incomparably more serviceable and deserve accurate consideration. They are represented by the following two formulae : — Corrosive sublimate 1 part. Pure chloride of sodium 2 parts. Glycerine (25° Beaume) 13 parts. Distilled water 113 parts. 218 SECTION TENTH. This mixture is allowed to stand for at least two months. After that time it is prepared for use by mixing one part of it with three parts of distilled water and filtering it through fil- tering-paper. Blood-corpuscles are preserved in it exceedingly well, as my own observations have proved. According to Pacini, it is equally well adapted for nerves and ganglia, the retina, cancer cells, and especially delicate proteinous tissues. A second mixture consists of : — Corrosive sublimate 1 part. Acetic acid 2 parts. Glycerine (25° Baume) 43 parts. Distilled water 215 parts. This mixture is prepared for use in the same manner as the preceding. It is said to destroy the colored blood-corpnscles, but preserves the lymph-corpuscles of the blood intact. Further modifications of these mixtures, as they are em- ployed in the Pathological Institute of Berlin, are represented, according to Cornil, by the following : — l. Corrosive sublimate. ... - 1 Chloride of sodium 2 Water 100 3. Sublimate 1 Chloride of sodium 2 Water 300 5. Sublimate 1 Acetic acid 1 Water :;00 7. Sublimate 1 Acetic acid 5 Water 300 2. Sublimate 1 Chloride of sodium 2 Water 200 4. Sublimate 1 Water 300 6. Sublimate 1 Acetic acid 3 Water 300 8. Sublimate 1 Phosphoric acid 1 Water 30 No. 1 is used for preserving the vascular tissues of the warm-blooded animals. No. 2 for those of cold-blooded crea- tures. No. 3 for pus-corpuscles and related structures. No. 4 THE MOUNTING, ETC. 219 for blood-globules. No. 5 is intended for epithelial cells, con- nective tissues, and pus-cells, when the nuclei are to appear at the same time. No. 6 is applied to the preservation of connec- tive-tissue structures, the muscles and nerves. No. 7 serves for glands, and No. 8, finally, for cartilaginous tissues. Very dilute solutions of corrosive sublimate are in fact very useful as preservative fluids, but the degree of concentration shoidd be determined every time they are used, for which rea- son it is judicious to mount several examples of a preparation in solutions of different strengths. Harting recommends solu- tions of 1 part of corrosive sublimate to 200-500 of distilled water. He remarks that it is only in such solutions that he is able to preserve the blood-corpuscles. Those of man and the mammalia require ^-J^ of the sirblimate, those of birds -j^, those of frogs 4-^. Some of these solutions which I have tested ap- pear to be useful. His recommendation of these solutions for the brain, spinal cord, and retina appears less justifiable, but, on the contrary, they are useful for cartilage, muscle, and crys- talline lens. All solutions of corrosive sublimate readily cause the preparations to become dark and less transparent. Chromic Acid and Chromate of Potash. — Dilute solutions of chromic acid and of the bichromate of potash, combined according to circumstances with glycerine, may be advanta- geously employed as preservative fluids. A mixture of equal parts of glycerine and Midler's preservative fluid (p. 136) ap- pears to be very useful. The latter, undiluted, also occasion- ally forms a very serviceable medium for mounting very deli- cate textures. A solution of chloride of calcium is a fluid popular with the botanists for mounting. It appears to be less serviceable for animal specimens. Harting praises the saturated solution of the pure salt, or one diluted with the 4-8 fold volume of water. Preparations of teeth and bones and sections of hairs are said to keep well in it. I acknowledge that thus far my experiments, not very numerous, it is true, with the solution of chloride of calcium have afforded me only very moderate results. Harting recommends solutions of the carbonate of ' potash in 200-500 parts of water as the best medium for mounting nerve fibres. I have had no experience with this solution. Accord- ing to the same authority, arsenate of potash in solution 220 SECTION TENTH. with 160 parts of water also exerts the same effect on nerve fibres. Watery Solution of Creosote. — According to Harting's ex- perience, a solution obtained by the distillation of creosote with water, or the saturated and filtered solution of creosote in a mixture of 1 part alcohol of 32° and 20 parts of water is a good preservative medium for many tissues, such as muscle, connective tissue, tendon, decalcified bones and teeth, and likewise the crystalline lens. Arsenlous Acid. — This is to be boiled with water in excess, and, after cooling, filtered and diluted with three times its vol- ume of water. It is used for the same purposes as the solution of creosote, and is also suitable for the preservation of fat cells (Harting). Methyl alcohol, considerably diluted with water, in the proportion of one to ten, has been recommended by Quekett. If, after several days, the fluid becomes cloudy, it should be filtered. Like the acetic acid solution, it causes most prepara- tions to assume a granulated condition after a time. Methyl alcohol and creosote are also elements of a compli- cated fluid mentioned by Beale. Creosote 3 drachms. Wood naphtha 6 ounces. Distilled water 64 Chalk, as much as may be necessary. It is prepared in the following manner : — Mix first the naphtha and creosote, then add as much prepared chalk as may be sufficient to form a thick, smooth paste ; afterwards add, very gradually, a small quantity of the water, which must be well mixed with the other ingredients in a mortar. Add two or three small lumps of camphor and allow the mix- ture to stand in a lightly covered vessel for a fortnight or three weeks, with occasional stirring. The almost clear superna- tant fluid may then be poured off and filtered if necessary. It should be kept in well-corked or stoppered bottles. This mix- ture forms a modification of Thwaite's fluid for preserving desmidise. Topping' [ s Fluids. — He recommends the employment of one part of absolute alcohol to five parts of water ; and where the preservation of delicate colors is necessary, he dissolves one THE MOUNTING, ETC. 221 part of acetate of alumina in four parts of distilled water. The latter mixture, diluted with an equal volume of glycerine, has preserved carmine injections for me very well over three years. Deane's Flat id. — He praises a mixture of six ounces of pure glycerine, nine ounces of honey, a little alcohol, and a few drops of creosote, for the preservation of animal and vege- table structures. The mixture is to be filtered while warm. Plain slides and covering glasses may be used for mounting very thin objects. A larger or smaller drop, as may be neces- sary, of the preserving fluid may be placed immediately on to the former by means of a brush or a glass rod, and the speci- men, seized with delicate forceps or a cataract needle, is placed in this, care being taken that it is covered by the fluid. The covering glass, the under surface of which has been breathed on, is then placed over the specimen in the manner indicated for mounting in Canada balsam. One should avoid employing too large a quantity of the preservative fluid, as it is then lia- ble to escape at the sides, or to flow over the edges of the cov- ering glass. In such cases the excess should be removed by means of a very finely pointed pipette, or by the application of narrow strips of bibulous paper. In both cases the edges are also to be dried with a linen rag, care being at the same time taken not to displace the cover. Sometimes air-bubbles remain and can only be removed by slight pressure. It is well to cut a piece of fine writing-paper about an inch long in such a man- ner as that it will form a long, narrow triangle, measuring about 2'" at its base. The point of this is now to be passed between the slide and covering glass ; frequently the air-bub- ble can be conveniently shoved out with it. Although with Canada balsam as soon as the covering glass is successfully placed in position the whole process is essen- tially terminated, a further enclosure of the edges not being in reality necessary, although even here the specimen receives greater protection and a more attractive appearance by means of a finishing touch ; it is otherwise with objects mounted moist ; they must be cemented ; — a procedure which will re- ceive more especial mention further below. If, however— and this will generally be the case— a some- what thicker object is to be mounted, or if it be feared that the cement as it hardens will subsequently press the covering glass 222 SECTION TENTH. too much, against the preparation and thus injure it, a firm substance should be interposed between the two glasses. Sil- ver wires or narrow strips of paper are to be recommended as simple contrivances ; various thicknesses of them may be pre- pared and placed under two opposite borders of the covering glass, or a narrow paper frame may be substituted. But then the insinuation of an air-bubble is quite possible, and the first layer of cement should not consist of a substance which is very fluid or which hardens very slowly, as it would then either penetrate into the preserving fluid immediately, or the exter- nal coating would afterward in contracting press in the inter- nal layers. This procedure, in its further development, leads to the construction of a framework which is sometimes shallow, sometimes deep, and which is fastened to the slide. The flat case thus obtained is called a cell. Very manifold directions have been given concerning the construction of such cells. The more simple ones will be pre- ferred unless greater cheapness renders another procedure de- sirable. Cells may be made of gutta-percha, caoutchouc, and glass. The latter are the best, but also the most expensive. Gutta-percha Cells. — Gutta-percha occurs in commerce in sheets of varying thickness. A good sheet should be even, Fig. 96. G-utta-peroha oe homogeneous, and flexible. If crooked or cracked, it may be made to assume the former condition by dipping it in boiling water. With a ruler and knife quadratic or oblong square pieces may be cut out in the same way as from pasteboard ; they should, however, be narrower than the slide. In these a round, oval, or oblate square aperture is to be cut with a punch and hammer, to contain the preparation and the con- serving medium (fig. 90). THE MOUNTING, ETC. 223 Caoutchouc Cells. — These are also made from the commer- cial sheets, which may be placed one over the other and readily made to stick together by heating them, when it is necessary to construct cells with high walls. Glass Cells. — These deserve the preference, but if bought ready made from the glass-cutter they are rather more expen- sive. Glass rings of different diameters and varying depths are used, but they have the inconvenience of requiring circular covering glasses. Quadratic or oblong square plates, resem- bling those of gutta-percha, and provided with circular open- nings, are useful. Those of half a line in depth and with a round aperture of about four lines in diameter will be found to suffice for most histological purposes. Excellent glass cells, made in England, have lately been brought to my knowledge through Thiersch. They are made of glass slides several lines in thickness, perforated by a circular aperture of considerable size, with covering glasses cemented to both surfaces. The perfectly injected eyes of white rabbits, divided in halves and thus mounted with their natural curva- ture in Canada balsam, constitute one of the handsomest prep- arations which Thiersch has produced. Any one to whom economy of time is of less importance, can himself prepare glass cells in still another way (fig. 97). He Fig. 97. Glass cell with cover. should have strips a line or so in breadth, cut from plate-glass (or, if able to use the diamond, he may cut them himself) ; these should be of two sorts, one of 6-7"' in length, another form only 3-4'" in length. With these the walls of the cell are to be constructed. Beale, who, as is customary with Englishmen, explains the matter accurately, gives several additional practical directions. A thin glass cover may be used for the construction of very shallow cells. The thin glass may be cemented while warm 224 SECTION TENTH. to a glass ring, or over a hole in a plate of glass, by means of the marine glue which is soon to be described. A hole is then to be forced through it with the point of a three-cornered file, and this is to be enlarged to the margin ; the cracks do not extend across that part of the glass which is cemented. The perforated glass may be readily removed when again heated. A blunt-cornered, square cell may be made by bending a sin- gle strip of glass in the blow-pipe flame and melting the ends together. Beale recommends flint-glass for this purpose. In practised hands, this is certainly a very good way of making deep and large cells. All these cells must be cemented to the slide. But gutta- percha may be warmed in hot water, and its under surface then carefully dried and secured to the heated slide. This method has not proved to be durable. Marine glue may be used, after the manner of the English, for cementing the glass cells. This substance is prepared by dissolving, separately, equal parts of shellac and india-rubber in naphtha, and afterwards mixing the solutions thoroughly, with the application of heat. It may be rendered thinner by the addition of more naphtha. Marine glue is also readily dissolved by ether or a solution of potash. According to Quekett, the variety known in commerce as G. K. 4 is best adapted for microscopic purposes. The following process is necessary for cementing with marine glue : The slide is to be warmed on a heated plate of metal (the English use a table of sheet-iron supported by four feet, with a spirit-lamp burning under it). A narrow strip of the cement is then melted on the heated slide and made to extend over all the places on which the walls of the cell are to rest. Firm pressure is then to be made over the cell, and the whole placed aside to cool. The excess of glue may afterwards be removed with the blade of a knife. A weak solution of potash may be used for cleaning the cell. According to Harting, the following mixture serves for ce- menting the india-rubber cell : One part of very finely divided gutta-percha is to be mixed with fifteen parts of oil of turpen- tine, and dissolved at a gentle heat with constant stirring. It is then to be filtered through cloth, and one part of shellac added to the filtrate ; this is also to be dissolved at a moderate temperature and with constant stirring. The heating is to be THE MOUNTING, ETC. 225 continued until a drop of the mixture, when allowed to fall on a cool surface, becomes tolerably hard. In this condition, the cement is ready for use. When afterwards used, a little oil of turpentine is to be added. In order to fasten a caoutchouc cell, it is first to be held under the centre of the slide ; and exactly over it, on the upper surface of the slide, a thin layer of the warm cement is to be laid on with a brush. The cell is now to be pressed into posi- tion on the upper surface of the heated slide, which is then turned over and allowed to lie on a flat surface till the cement has cooled. Harting's gutta-percha cement may also be used in the same manner for fastening glass cells, and for building them out of four strips of glass. The latter may also be accomplished with still another ce- ment. 1 part of india-rubber is to be dissolved in 64 parts of chlo- roform, and then 16 parts of dried powdered mastic added. A thin layer of the cold mixture is to be placed on the slide with a brush ; the cell is then to be warmed and pressed into position. This cementing of the cell may also be accomplished in a ver} r simple manner by means of a concentrated solution of shellac in alcohol. Whichever method is employed, it is well to fasten the cell as carefully as possible, in order that no leak or entrance of air into the cell may afterwards occur. A glass cell should always have a roughened surface for the cement. The surfaces may readily be roughened by rubbing on a flat stone with emery powder. Cells of tin-foil have also been recommended, but I have had no personal experience with them. Cells may also be made with certain cements ; these are entirely sufficient for many thin objects. Bourgogne's asphalt cement may be used for this purpose ; I prefer it to the white cement made by Ziegler, in Frankfort-on-the-Main (Friedberger Gasse, 23), formerly recommended but now found to be liable to crack. An oblong square, a quadrate, or a circle may be made with it on a slide, and left to harden. The cell having been filled with the preservative fluid, and the object immersed in it, and care having been taken that 15 18. Placing the covering-glass in position. 226 SECTION TENTH. there are no air-bubbles present, the covering glass is breathed on and placed in position in the usual manner (fig. 98). The latter should always be somewhat smaller than the cell, so as not to completely cover its outer margin. The superfluous fluid is to be removed with caution, however, as otherwise air-bubbles may again enter. Now commences the cementing of the covering glass. This must be done at once, unless the preserva- tive fluids be glycerine or a solution of chloride of calcium, in which case the process may be delayed. Four-cornered covering glasses regularly cause greater trouble in cementing than the circular ones. The latter may now be obtained, at a moderate price, from England, in Germany through glazier Vogel, in Giessen, and in Hamburg through the microscopical institute of Rodig. By the aid of the turn-table* represented in fig. 100, the cementing is a small matter. The round brass plate of the simple apparatus has a bow, which exerts pressure from a spring, and which may be elevated by the counter-pressure of the ringer. Concentric circles engraved in the brass, according to the size of the covering glasses, show the place where the brush, which is held perpendicularly, is to draw the ring either on the slide or, when the covering glass is in position, over both. For this purpose the turn-table must be made to rotate slowly by the motion of the finger on the small notched disk beneath the table. Dip the smallest possi- ble brush in the cement, and press it at first very lightly on the glass, and afterwards turning the table more slowly, more firmly, but always perpendicularly. One soon learns to form even rings. The cement should, however, be of a more fluid consistence than that which is used for four-cornered covering glasses. In order to prevent a cemented preparation from curving, it is advisable to use the simple, cheap compression apparatus already mentioned at p. 212, fig. 95. * This, as well as the compression apparatus, fig. 95, rnay be obtained from Th. Ernst, the optician, in Zurich. THE MOUNTING, ETC. 227 A considerable number of cements have come into use, and preparations may be mounted with several of them with equal perfection and security. At present a solution of asphalt (Brunswick black) is most frequently used. Various sorts occur in commerce ; it consists of a solution of asphalt in linseed oil and turpentine. Good Brunswick black should have a transparent, homo- geneous black appearance. As in the application of other ce- ments, a camel's -hair brush is used, the stroke passing along the edge of the cover, whereby the latter as well as the slide re- ceives a stripe of cement (fig. 99). With a little practice, one soon learns to judge of the proper quantity to use, and to draw a handsome border. If, in the course of time, the Brunswick ,.„„.,, ,. , ,, , ' Fig. 99. Making a border with Brunswick black. black becomes too thick, it may be diluted with turpentine. Besides being dirty to handle, it also has the disadvantage of having a tendency to become cracked and fissured, and, after weeks and months, in conse- quence of its further contraction, to press the fluid out from the cell. It has therefore been recommended to strengthen the margins about every six months with a new layer of cement. This cement may also be considerably improved by the addi- tion of a small quantity of a solution of caoutchouc in benzine. In consequence of its great tendency to the above-mentioned defects, I have, of late, either entirely ceased to use the ordi- nary Brunswick black, or only use it for the first coating, es- pecially when strips of paper are placed between the slide and cover, and then, after several days, an external layer of cement is to be placed over this. I have recently become acquainted with the Brunswick black used by Bourgogne, of Paris, and can only speak of it in the highest terms. Unfortunately, its composition is unknown to me. It dries with comparative rapidity, and a single coating is quite sufficient. [A very good and durable substitute for Brunswick black may be found in the "Liquid Stove Polish," prepared in Eng- land and sold in this country.] 228 SECTION" TENTH. A fluid mixture, coming from England under the name of gold-size, is excellent for cementing preparations of thin objects mounted in glycerine, and is also to be recommended as being clean to handle. It is a complicated mixture. Beale gives the following directions for its composition : — 25 parts of linseed oil are to be boiled with one part of red lead, and a third part as much umber, for three hours. The clear fluid is to be poured off and mixed with equal parts of white lead and yellow ochre, which have been previously well pounded. This is to be added in small successive portions, and well mixed ; the whole is then again to be well boiled, and the clear fluid poured off and kept in a bottle for use. It is applied with a brush ; a second layer may be added after half a day. It is better to leave specimens thus prepared for a considerable time before making the final application of cement. The turn-table and round covering glasses permit of a much more simple procedure. A cement ring is made on the slide Fig. 100. English turn-table, with Frey's improvement. with Bourgogne's mass, with the margin of the ring of cement extending beyond that of the covering glass. This makes a flat cell. The object is placed in this with a carefully measured drop of fluid. A minimal covering of cement goes over the ring, the covering glass is placed in position and pressed on the sticky substance. One or more layers of cement are subse- quently added to the borders. Dry mounted preparations are also treated in this manner occasionally. At the commencement period of microscopical technique various cements were used for the moist mounting of animal preparations. In the earlier editions of this book I recom- mended Ziegler's white cement ; now, after many years' ex- perience, I must acknowledge very wrongly. All such speci- mens of my collection of preparations have, without exception, THE MOUNTING, ETC. 229 been ruined by rents and cracks in this cement (often, it is true, only after a long period). Schacbt recommended the so-called mask lac, which dries very rapidly, as a cement for wet preparations, and also as a coating for specimens mounted in Canada balsam or copal. The variety of lac used by him is designated as No. 3, at Bese- ler s lac manufactory in Berlin (Schutzen Strasse, No. 66). I made considerable use of this lac several years ago, and do not hesitate to recommend it as being the next best to Bourgogne's cement. When concentrated it forms an excellent enclosure for four-cornered covering glasses ; when diluted with absolute alcohol it is also serviceable for round covers, with the use of the turn-table. It is of a deeper, purer black than Bourgogne's cement, which has a more brownish black appearance. We also mention a cement which is to be used in the man- ner already indicated as a final coating for Canada balsam prep- arations. We are indebted for a knowledge of this to a friendly communication from Thiersch. When the specimens have been mounted for several days, weeks, or even months in pure Canada balsam, or a solution of the same in chloroform, they are surrounded with a border * of Canada balsam dissolved in chloroform, in the manner indi- cated above (fig. 99 and 100) for asphalt. Later — but never before the second or third day, still better after weeks or months — a final coating is to be applied. This consists of a colored and thick varnish of shellac. It is found ready pre- pared with alcohol at the wholesale druggists. It is to be carefully evaporated to the consistence of thin mucilage and colored with a filtered, concentrated solution of anilin blue or gamboge in absolute alcohol. Finally, about a scruple of cas- tor oil is to be added to each ounce of the mixture, and after some further evaporation it is to be preserved in a well-closed vessel. If, after a time, it should become too concentrated, this may be remedied by the addition of a few drops of abso- lute alcohol. This varnish is to be applied with a brush to the borders of the Canada balsam. It becomes hard in a few hours, and then * With alcoholic resinous solutions I also frequently use a preliminary enclosure of Canada balsam in chloroform, and then, after several days, use the above-men- tioned Bourgogne's black cement. 230 SECTION TENTH. forms an elegant and hermetic covering for objects mounted in resinous substances. The aniline blue has entirely faded, however, after a few- years. Finally, the form and size of the slides are not unimportant for the elegant appearance of a collection of preparations. Similarity of form, so far as it is possible, is desirable for greater convenience of keeping or of occasional transporta- tion. The art of grinding the edges of the slides may soon be learned by employing a very thick plate of glass and a fine sort of emery powder, which is to be made into a paste with water. The slide should not be too small, so that sufficient space may be left at the ends of the preparation to affix two labels, one of which is to contain the general designation, while on the other especial remarks, the number of the collection, etc., may be placed. In certain cases there should also be room left for the indicator.* Such slides will frequently afford room for larger objects, and thus render it unnecessary to select a differ- ent form for special objects ; as, for example, when an exten- sive section of bone or a voluminous injected preparation is to be mounted. I prefer a glass slide like those of the English collections, three British inches long by one inch wide (72 mm. by 24 mm.), above all others (fig. 101). The preparations of Bourgogne of Paris also have this convenient and handsome form. Slides of a larger size are unnecessary and appear too unwieldy. But * Various indicators or object-finders have been proposed for enabling one to find any particular place in a preparation. Fine divisions, like those of a rule, may be photographed on narrow strips of paper, and one of these strips pasted at one of the broad, and one at one of the narrow margins of the cover ; for example, at the right and the lower side of fig. 101. A rectangular plate of metal, or, better still, a small square, consisting of two narrow strips of brass meeting each other under an angle of 90°, is used for ascertaining the particular portion of the object ; this is to be noted on the preparation, and may be again readily found with the little plate or the square. The best — because the most simple — arrangement has been indicated by Hoffmann. Two crosses are to be scratched at either side of the aperture of the object stage of the microscope, the one standing ( + ), the other reclining ( x ). If, now, the portion of the preparation to be marked is situated in the centre of the field, both crosses are to be drawn with ink on the slide exactly over those of the stage. It is only necessary to place these marks over each other again in order to at once find the object. THE MOUNTING, ETC. 231 those of a smaller size should also never be employed. A pat- tern, proposed in Giessen, 48 mm. in length by 28 mm. in width, is inelegant, and much less convenient than the English. If it be desired to place microscopic preparations in layers, for the sake of greater economy of room, either in keeping or in transporting them, the employment of protection-ledges (Schutzleisten) is to be recommended. These are narrow strips Fig. 101. English object slide. of glass which are to be cemented across the slide at either side of the object. They should naturally be higher than the cover and the cell. Although this arrangement is, of itself, quite practical, it nevertheless diminishes the room necessary for the labels to an unpleasant extent. For preserving and arranging specimens, boxes of wood or pasteboard, with grooved wooden racks at the sides, which hold the slides securely, are occasionally used. As, with these, the slides stand vertically and the preparations may in consequence readily sink, when mounted in resinous sub- stances which have not thoroughly hardened, or when other fluid media have been used, the upright position of such boxes deserves the preference. On the other hand, trays of wood or pasteboard with very low borders, or plain drawers, may be used ; they may either be arranged to slide out, like a chest of drawers, or they may simply rest on each other and be removed from the chest by means of loops. Slides of the most vary- ing sizes may be conveniently placed in them at the same time, and the sinking of the preparation is also avoided. This arrangement, however, is not serviceable for transporta- tion. Here, as with all collections (increasing in degree with its growth), regularity and occasional revision are imperatively necessary. As every assiduous microscopist of the present time pos- 232 SECTION TENTH. sesses his own collection of preparations, so likewise do the various microscopical associations of Germany. For example, those of Frankfort-on-the-Main and of Griessen, as also the Microscopical Society of London. Among the private collections we enumerate the celebrated one (preparations of injections) of Hyrtl, in Vienna ; that of Kolliker, in Wtirzburg ; Gerlach, in Eiiangen ; those of Thiersch and Leuckart, in Leipzig ; Welcker, in Halle ; and Schultze, in Bonn. In Holland is the collection of Harting ; in London are those of Carpenter, L. Beale, L. Clarke, and others, likewise that of the College of Surgeons ; in Manches- ter, that of Williamson. Among the Swiss collections may be mentioned those of His, in Basel ; in Zurich, those of Goll and myself. Preparations may be purchased of Hyrtl and CI. A. Lenoir, in Vienna ; J. D. Moller, in Wedel, Holstein ; C. Rodig, in Hamburg ; Schaffer and Budenberg, in Magdeburg ; Bour- gogne (9 Rue de Rennes), Paris ; of Smith and Beck, also of Topping (4 New Winchester Street, Pentonville), and of Pil- lischer (88 New Bond Street), London. Injections and other preparations of the author are to be obtained from the Magde- burg establishment already mentioned, from Lenoir, in Vienna, a,nd from the optician Th. Ernst, in Zurich. Section QHoKntl). BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. The investigation of these cell-containing fluids belongs to the more easy and simple labors of the microscopist, inasmuch as a drop of the same, having been placed on the slide by means of a glass rod, and spread out into a thin layer by the covering glass, suffices for the first examination. But care is to be used in the selection of actually indifferent media, espe- cially in the examination of living cells. 1. Among the animal fluids mentioned, the blood is the most delicate substance, so that circumspection is necessary for the recognition of its normal condition. In order to examine human blood, it is only necessary to prick the point of the finger and allow a drop to exude, which is then received on the slide. For more continued and pro- longed investigations a quantity of blood is to be obtained by means of venesection, and beaten to separate the fibrin. The blood of the smaller animals is to be obtained by opening one of the larger vessels of the heart ; the blood may be received in a test tube. If allowed (^'"W^ to remain in this, or in a cylindrical vessel, ^-^ ^^ the cells gradually sink and the serum which Q IJ remains above them becomes colorless. This c-u (&\- a fluid is the best medium for use in the inves- \r TT ,, , Fig. 102. Human blood- tisation ceUs - a < a < Been from " * above ; 6, half ; c, c, en- In consequence of the extraordinarily large tu-eiy from the siae ; a, a *- J ~ lymph corpuscle. number in which the colored cells (fig. 102, a, l>, c) occur in the blood, it should be spread out in a very thin layer, so as to bring these elements distinctly into view. Slight compression made on the covering glass with the point of the needle will facilitate the examination considerably. In human blood (fig. 102), when these cells have their broad sur- 234 SECTION ELEVENTH. face turned towards the observer, they present the well-known form of circular disks {a, a), but when standing on their sides they appear biscuit-shaped (c, c). Dilution of the blood requires some little attention. The serum of the blood, if disposable, is best for this purpose. Solutions of salt, sugar, or crystalloid matter may also be used with advantage for a momentary examination, provided they are of the proper degree of concentration. The Pacinian fluid (sublimate, salt, and glycerine with water), which has already been mentioned (p. 217), is very suitable if it happens to be at hand, and I know of no other fluid which is capable of preserving our cells in so excellent a manner for years. The iodine serum is also very useful, and likewise, according to Rollett, a mixture resembling Midler's eye fluid. The latter consists of one part of a cold saturated solution of the bichro- mate of potash, 5 parts of a similar solution of the sulphate of soda, and 10 parts of water. Such dilutions will also be necessary when it is desired to cause the colored blood-cells to roll, in order to recognize their form. The pressure of the point of a needle on the edge of the covering glass will then induce the desired current in the fluid. Upon carefully focussing, the hu- man colored blood-cells will appear to present a yellowish circumference and a colorless centre. If the tube of the microscope be depressed a little, the central portion becomes somewhat darker. The colorless cells of the blood 103. Contractile colls from human ■ - , i -1 i , • i -\ originate in the lymphatic glands, the spleen, and the marrow of bones. Dilution with an indifferent fluid is also necessary for their recognition, and, in consequence of the small number of these elements, they require some little search (figs. 102, d, 103). Even in human blood taken directly from the vein, one may, with a 4-600 fold enlargement, and without any further precautionary measures, observe the remarkable changes of form of the living colorless cells, which may slowly pass through the series of alterations which we have sketched (fig. 103). But if the warm stage (p. 101) and a temperature of 38- BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 235 40° C. be used, and iodine serum added, the play of move- ments mentioned becomes extraordinarily lively. A portion of the colorless cells now creep about between the colored blood- corpuscles and present, with constantly changing form, the strangest variety of shapes. Granules of carmine, molecules of cinnabar and indigo, which have been added to the fluid, are now readily taken up into the cell-body (Schultze). An ex- tremely fine granulated anilin blue, which has been precipi- tated from the alcoholic solution by means of water, is very ex- cellent. — If this apparatus is wanting, one may readily per- ceive the same condition in the lymph corpuscles of frog's blood, with the aid of the moist chamber. Very beautiful ap- pearances may be obtained with the latter animal, if a drop of its fresh blood be allowed to coagulate on the under surface of the covering glass, in a moist chamber (after the manner of our fig. 73). One soon notices, after a zone of serum has formed at the borders of the coagulum, that, in consequence of their lively wandering from the clot, many of these amoe- boid cells have penetrated the ring of fluid, and that the surface of the coagulum is also thickly covered by them (Rollett). We will here mention still another method which has re- cently led to scientific results of the highest interest (Colm- heim). A small quantity (at most, a few ccm.) of one of the above- mentioned finely granulated coloring materials, suspended in water, is to be injected, for several days after each other, into one of the large lymph spaces which lie under the skin of the frog. A Pravaz syringe, such as is used in practical medicine, may be used for the injection. On examining a drop of the blood, a considerable number of the colorless cells will now be seen to be stuffed ("gefiittert"). We shall afterwards return to this matter. Some preparation is necessary in order to count the num- bers of both kinds of cells. The test blood must naturally be spread out into the thinnest layer, and the space to be sur- veyed divided. An eye-piece micrometer with a small number of quadratic fields fulfils this object. In consequence of the sparseness of lymph-cells in normal human blood (0.5 to 2-3 per thousand), and likewise in mammalia, it is necessary to count a large number of blood-corpuscles in order to obtain 236 SECTION ELEVENTH. even a tolerably accurate result. One should not stop under 10,000-15,000* The fluid of the blood, the so-called plasma, appears, as a rule, entirely clear like water, and free from all elementary forms, and therefore is not an object of microscopic examina- tion. As a result of an exuberant reception of fat in the blood, the unsaponified fat of the chyle (see below, at this fluid) may appear in it in the condition of the finest division, in the form of dust-like molecules. It was formerly hoped that the microscopist might discover changes in the form of the blood-cells in disease, and in this way be able to promote pathological physiology as well as diagnosis. These beautiful dreams have not, in general, been fulfilled. However various its composition may be, the blood presents the same microscopic appearance. It is also to a cer- tain degree the case, that even with regard to the normal life of the blood a considerable obscurity still prevails, — that we have but an extremely incomplete conception of the new for- mation and disappearance of the cells. However, although nothing of importance is to be perceived in the endosmatic changes in form of the colored blood-cells, which have been here and there described in processes of dis- ease, and just as little in the shreds of the loosened epithelium of the vessels, the microscope has nevertheless afforded us an interesting glimpse of two pathological processes of our fluid ; we mean the so-called leucsemia and melansemia. The former, coinciding with an increase in volume of the spleen and often, at the same time, of the lymphatic glands, although but seldom caused by enlargement of the latter organs alone, leads to a constant increase in the number of col- orless cells in the blood, so that finally the alteration of the blood no longer remains concealed from the naked eye. A drop of such blood (obtained by pricking the point of the fin- ger with a needle) shows, together with the colored, a consid- erable number of colorless blood-corpuscles. This may pro- * Malassez has recently given very accurate directions for counting the blood-cor- puscles, but which cannot be understood, however, without figures showing the ap- paratus to be used. The author found the number of colored blood-cells in a cubic millimetre to vary from 18,000,000 to 3,000,000 for mammals, from 4,000,000 to 1,000,- 000 for birds, from 2,000,000 to 700,000 for osseous fish, from 230,000 to 140,000 for cartilaginous fish. BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 237 ceed to such an extent that to three colored blood-corpuscles there will be oue or even two colorless ones, and in certain cases the number of the latter variety of cells will be greater than that of those containing hsematin. Transition forms of both kinds of cells may also be met with (Klebs, Eberth). In malignant forms of intermittent fever the enlarged spleen has been seen to have a blackish appearance. The microscope shows, as a cause of this change of color, granulated lymphoid cells, often of considerable extent, and which contain within them granules of the black pigment. Passing out through the splenic vein, they become mixed with the blood and are seen in this fluid when it is subjected to microscopic examination. In consequence of their size they produce obstructions in certain capillary districts, especially in the brain and liver. Embryonic blood is to be examined in the same manner. The Avarmable stage is to be used when it is desired to follow the very rapid progress of the division of the nucleated colored cells. The instability of these cells is, moreover, very great, so that one may often be misled by artificial products. Recklinghausen communicated a singular discovery to us a few years ago. After a series of days one may see the lym- phoid cells become transformed into red blood-corpuscles, in blood taken from the frog, if one understands rjreserving its vitality. For this purpose the blood is to be received in a glazed por- celain dish, which is to be placed in a large glass vessel, the air in which is to be daily renewed, and kept constantly moist. After twenty-four hours the coagulation gives place to a pro- cess of liquefaction ; a few days later, island-like collections of contractile lymphoid cells have become formed ; after 11-21 days one may recognize the first of the new-formed blood-cor- puscles. Frog' s blood may be preserved in this way for thirty- five days without decomposition taking place. By means of an electrical discharge the colored blood-cor- puscles are rendered corrugated, at first with coarse, then with fine indentations.* These processes afterwards disappear, and the blood-corpuscle becomes transformed into a smooth bor- dered globule, which finally undergoes discoloration (Rollett). * The thorn-apple form appears to occur by no means rarely in the blood of patients with fever. 238 SECTION ELEVENTH. The living blood-cells of man and the mammalia undergo a very singular alteration (fig. 104) when exposed to a tempera- ture of 52° C. on the hot stage, represented in fig. 75. A num- ber of deep indentations rapidly take place, which very soon become constrictions, causing the formation of globules on the surface of the cell. These are either separated at once or con- tinue for a time to be connected, by means of a long, slender pedicle, to the remainder of the cell body (a). The strangest appearances are thus caused, such as bead-like rods, globules with projections like handles, etc. When these fragments be- Fig. 104. Human blood-cells I to 52° C. Fig. 105. a. Human blood-cells under the action of water ; &, in evaporating blood ; c, in a dried condition ; d, in coagulated blood ; e, rouleaux-like arrangement. come separated, they commence the most lively molecular move- ment (Beale, M. Schultze). The treatment of the blood-corpuscles with chemical reagents is indispensable for the accurate investigation of their structure, and is a very good exercise for the beginner, especially if the large nucleated cells of the naked amphibia are used in the place of the small non-nucleated corpuscles of human and mammalial blood. Distilled water is used to cause them to swell (fig. 105, a). The bright central portion disappears at once and a uniformly yellowish structure is seen which rapidly loses its color, and which, in rolling, permits its globular form to be recognized. In this way the granulated nucleus may be rendered distinct in the blood-cells of fish, amphibia, and birds. Many watery solutions in a condition of extreme dilution exert a similar ef- BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 239 feet. For comparison, it is useful to treat, in a similar manner, the large nucleated blood-cells of the first three classes of ver- tebrates. In order to obtain them in a shrivelled condition (iig. 105, b). it is only necessary to leave a drop of blood uncovered on a slide for a few minutes, in which case the familiar corru- gated and indented forms make their appearance. A very small drop of blood, taken from the living body by pricking with a fine needle, not unfrequently presents this indented ap- pearance of the cells on the glass slide at once. We can obtain a similar effect by means of numerous concentrated solutions, such as those of salt, sugar, and gum. If, on the contrary, we rapidly dry the blood-corpuscles on a glass slide, we have the appearance represented by fig. 105, c, a form in which the blood-corpuscles may be very well pre- served as a permanent preparation. Other reagents dissolve its substance, and in this way de- stroy the cell. Diluted acids produce this effect, likewise weak solutions of the alkalies. Although concentrated sohitions of the latter cause the blood-corpuscles to swell, they do not de- stroy them, even after acting on them for hours. A saturated solution of potash is, as Donders found, an excellent medium for rendering the cells of dried blood again visible. Many materials have a coagulating effect on the cell sub- stance of the blood-corpuscles. Among these are to be enu- merated alcohol, concentrated chromic acid, sublimate, and other metallic salts. In defibrinated, but also very generally in a drop of freshly removed blood, one may observe the familiar joining together of the colored cells with their broad surfaces, the so-called rouleau formation (fig. 105, e). This arrangement is missed only in the more distended and globular cells of the blood in the splenic and hepatic veins. In order to ascertain the appearance of coagulated blood, one may either allow a drop of blood to coagulate on the slide, or the finest possible section may be taken from a clot. The cells will then be seen to be embedded in a homogeneous layer of fibrin which has the appearance of folds or filaments (fig. 105, d). Indifferent fluids are necessary in the examination of blood extravasations, for the proper estimation of the condition of the cells. 240 SECTION ELEVENTH. The origin of fresh clots of blood, treated in the same man- ner, may be ascertained by microscopic analysis. One will be able, for example, to distinguish, by their form and size, the cells of the blood of birds from those of human blood, etc., and in this way to detect impostors. It is difficult, and in many cases impossible, to render a decision in old masses of dried blood. The character of a spot which is suspected to be blood may, on the contrary, be determined in the most certain man- ner by means of Teichmann's hsemine test, a subject to which we shall again refer. The accessories mentioned under lymph and chyle are to be used when the further investigation of the colorless blood-cells is necessary. It is only under certain circumstances that the colored blood-cells can be tinged with carmine, but this may be readily accomplished with anilin red ; still, nothing is to be gained thereby. The above-mentioned process of rapid drying may be very advantageously employed for preserving blood-cells perma- nently as preparations for a collection. I have in my possession preparations of the blood of different animals which are more than twenty years old, and which leave nothing to be desired. The first-mentioned Pacinian fluid is adapted for mounting the cells of human blood moist ; Pacini's second mixture (see p. 218) serves for the colorless cells of the blood. Solutions of sublimate, as formerly mentioned (p. 218), have also been recommended. Harting employs for the blood-cells of man and the mammalia, 1 part of bichloride of mercury to 200 of water, for those of birds 1 to 300, for those of the frog 1 to 400. Remak employed, for embryonic blood-cells, very weak solutions of the bichromate of potash, of chromic acid (0.03 per cent.), and of sublimate (0.03 per cent.). We should make ourselves responsible for a considerable deficiency were we to omit mentioning the various crystalliza- tions which are to be obtained from the colored blood-corpus- cles. This subject has in our day been zealously and persist- ently investigated ; but, regarded from a scientific point, this matter leaves, even yet, much to be desired. From the blood of man and the various vertebrated animals, including birds, one may obtain the coloring substance of the cells in a crystalline condition ; the so-called blood-crystals be- BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 241 ing formed. This substance has been called haemoglobin or hsemato-crystalline. Many investigations have been instituted concerning these remarkable structures by Funke, Lehmann, Kunde, Teichmann, Rollett, Bojanowski, and others ; Reichert having previously discovered in them a crystallized, colorless, albuminous body. According to the general acceptation, the blood-crystals present various forms, such as prisms, tetrahedes, hexagonal tables and rhomboids. The prismatic form is regarded as the most common, and ap- pears in man and most of the mammalia (fig. 106 a, c), to- gether with which, rhomboid- al tables (6) may also be met with. Tetrahedal (but not regular) crystals are formed by the haemoglobin of the guinea-pig (d) and, as is gen- erally alleged, of the mouse ; rhomboidal crystals are met with in the hamster (e), hex- agonal tables (/) in the squir- rel (and mouse ?).* With regard to the man- ner of producing blood-crys- tals, we limit ourselves to the following examples : — They are to be prepared for microscopic examination according to Funke' s direc- tions. A drop of blood is to be placed on the glass slide, where it is left in contact with the air for several minutes. A drop of water is then to be added, and the whole breathed on a few times. A covering glass is now placed over it, and evaporation allowed to take place slowly, whereby the crystallization is promoted by the action of the light. Fig. 106. Blood-crystals of man and several of the mammalia, a, blood-crystals from human venous blood ; £, from the splenic vein ; c, crystals from the blood of the heart of the cat ; d, from the jugular vein of the guinea-pig ; e t from the hamster ; and /, from the jugular of the squirrel. * In reality, nearly all blood-crystals belong to the rhomboidal system, only those of the squirrel to the hexagonal. 16 242 SECTION ELEVENTH. Bojanowski recommends the following procedure : Blood, as it escapes from the vein, or still better, such as is taken from the vessels of a dead animal, is to be kept in a vessel for 2-4 days in a cool place, whereby the coagulum begins to dis- solve into a thick, fluid, dark red to blackish mass. A drop of this fluid is to be placed on the slide, covered, and exposed to the light for a few hours. The crystals may then be seen. If the blood which is to be used for this purpose is too thick, the drop may be very suitably diluted with distilled water. Rollett, who has also produced a very valuable work on blood-crystals, makes use of a blood, the cells of which have been destroyed by freezing and remelting. The formation of crystals also readily takes place in electrified blood, and in that of the guinea-pig (which of all kinds of blood crystallizes the most readily) this is often so rapid as to appear "as though the crystals had been struck out with the spark." Blood from which the gases have been pumped out is also well adapted for obtaining haemato - crystal- line. Chloroform with the access of air also causes the formation of our crystals (Bottcher). Lehmann has taught us how f$lfB W " "tf f\~~ SiAl to produce crystals of the hydro- II §^\^jl|l%A N ^afiH^'\ chlorate of haematin (figs. 105, " - '' '''"'-' ; ' '■--^ -■*•"-'*: 106). They are to be obtained by Fig. 107. Crystals of hydro-chlorate of has- treating f l'esll blood Or large matin. & o spots of blood which are two days old with alcohol containing oxalic acid and ether (1 part alcohol, 4 parts ether, and T V of a part of oxalic acid). Preserved in well-closed bottles, the crystals are gradually precipitated from the fluid ; the process is hastened by the addition of chloride of calcium which has become liquefied by exposure to the air. Where the separation takes place more rapidly the crystals are more of the acicular form, as represented at the lower part of fig. 107 ; if more slowly, either the hexagonal tables of fig. 107 or the crystals which are represented in fig. 108. They appear to have a long and narrow laminated shape and twisted one or two times on BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 243 their long axis. They are very thin, of a brownish and brown- ish-green translucency, as represented at the upper half of fig. 108. If allowed to remain for some time in the mixture of alcohol and ether in which they were precipitated, we have pro- duced, as another modification, the crystals given in the lower half (to the right) of the figure, quadratic and also rhomboidal black tables which, by more ac- curate examination, prove to be fiat rhomboidal octahedrons. Teichmann has produced crys- tals of the same modification of hsematin and called them hse- min. The coloring matter of the Fig. 108. Crystalline forms of the hydro- chlorate of haimatin. blood, in its different conditions, is to be dissolved by means of hot concentrated acetic acid, so as to become separated in crys- talline form as it cools. A con- dition of the precipitation is the presence of alkaline chlorates. The hsemin crystals obtained present the appearances repre- sented in fig. 109, as rhomboidal tables of a blackish-brown, sometimes blacker, more rarely light-brown color. By proper treatment the crystals with which we are at present occupied may be obtained from blood which is either fresh or decomposed by putridity, from that which is dried, and even from the oldest blood-stains. Hsemin is there- fore of great importance in a forensic point of view, and forms the best means of recognizing the origin from blood of a suspected stain. If it be desired to produce a some- what larger number of crystals, a quan- tity of blood is to be boiled for about a minute or two in the 10-20 fold volume of glacial acetic acid and filtered. As the fluid cools it becomes somewhat cloudy, and a blackish sediment is deposited, consisting of crystals of hsemin. Pig. 109. Cryrtals of. hsemin. 244 SECTION ELEVENTH. For the momentary demonstration the following process is to be employed : — A drop of blood is to be rapidly dried on the slide, over the spirit lamp, and then scraped to a powder with the point of a knife. About 10-20 drops of anhydrous acetic acid is to be added and allowed to boil a few times ; the slide is then to be set aside for a few moments. A drop of blood, diluted with 15-20 drops of glacial acetic acid and placed in a watch-glass on the stove, also forms the crystals in question, as the fluid evaporates. They are likewise deposited when blood is mixed with an excess of concentrated acetic acid. Af- ter a few days a film, consisting of these crystals, is formed on the surface ; after the removal of this a second is formed, and so on. In order to obtain the hsemin crystals from an old blood- stain, the stained substance is isolated and placed in a test- tube, glacial acetic acid is then poured over it and boiled for a few minutes ; it is then filtered into a watch-glass. This fluid, to which more acid is to be added, is then exposed to evapora- tion in a warm place. I am indebted to the kindness of Dr. A. Schmidt, of Frankfort, for a preparation of hsemin which was obtained from a pocket-handkerchief saturated with blood at Sand's execu- tion. Hsemin crystals, in consequence of their durability, may be very readily preserved as microscopic preparations. They may be mounted dry or in gly- cerine. In old blood extravasations, for ex- ample, those of the brain, in hemor- rhagic infarctions of the spleen, in ob- FlG. 110. Crystals of hfematoidin. -, . . -. . . . n , , (Ordinary form.) iiterated veins, in tlie corpus luteum crystals of hsematoidin, discovered by Virchow, are formed (fig. 110) ; they differ from the biliru- bin which occurs in the bile. They generally occur in small rhomboidal prisms of a lively orange or ruby-red color, with dark carmine-red borders and edges. Together with these, amorphous precipitates of hsematoidin, in granular and globu- lar masses, will be frequently met with. Staedeler succeeded, by treating the ovaries of the cow with chloroform, or with sulphuret of carbon, in obtaining uncom- BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 245 monly large crystals (fig. Ill) of our coloring material, some of them measuring even 0.2'". These make their first appearance under the microscope as acute-angled, three-sided tables, with one convex side (a), although this convex side may also be re- placed by two direct lines, so that deltoid tables (6) result. Two such tables usually become united like twins, their con- vex sides coming in contact with or overlapping each other, and melting together (5, c). In this manner are formed the rhomboidal tables, usually designated as heematoidin (fig. 110). As a rule, there are at first indentations in the place of the ob- tuse angle of the rhombus, which gradually become filled out (d, d). Not unfrequently two other crystals also become united with the first two individual crystals, so that four-rayed Fig. 111. Very large crystals of hfematoid- in obtained from the ovarium of the cow by treating with chloroform. Fig. 112. The blood-current in the web of the frog, a, the vessel with the colored blood-corpuscles in the axial portion, and the colorless cells in that portion of the current near the walls ; &, the epithelial cells of the tissue. stars now appear (e). By the filling out of their re-entering angles four-sided tables (f, g) are formed, which, by increas- ing their thickness, finally assume the appearance presented by dice when seen somewhat from the side (Staedeler). Preparations of hsematoidin may be readily and well pre- served dry or lying in glycerine. We have reserved the most interesting portion of this sec- tion for the end ; the movement of the blood in the living ani- mal body is still to be discussed. In order to see the blood flowing through the vessels of the living animal (fig. 112), it is necessary to select transparent localities. The web of the hindfoot of the frog, the transpar- 246 SECTION ELEVENTH. ent tail of the larvse of the frog and salamander, the embryos of fish and small recently-hatched fish are exceedingly well adapted for the first observations. If the larvae of frogs are used, the anterior portion of the body is to be enveloped with a strip of moistened blotting- paper, and the tail, after being moistened with water, is to be covered with a thin covering glass. If the frog itself is to be used, a strip of wood or cork containing a glass window, 5 or 6 lines in size, which goes over the hole in the stage, is to be em- ployed. The frog is to be wrapped in a moistened rag, or en- closed in a small linen bag, and secured to the wooden strip. The web is to be expanded by means of pins (but without too great tension), and, after being moistened with water, a thin covering glass is to be placed over it ; it is best to have the lat- ter three-cornered or rhomboidal in shape. Instead of the sim- ple strip of wood, a small table may be very suitably arranged for supporting the frog. Frog-holders have been invented for this purpose ; they are quite superfluous. If one has the re- markable muscle-poison, woorara, at one's disposal, it is only necessary to inject a minimal quantity of the same under the skin to render our animal, after a few hours, immovable for a considerable time — one or two days — so that the simplest Fig. 113. Object-slide fur the larvse of frogs and salamanders. arrangement is then all that is necessary. An object slide of considerable size, on which is cemented a small, thick, right- angled plate of glass with a cork ring surrounding it, for fast- ening the toes to, is then sufficient. For tadpoles, the ante- rior portion of the body may be simply enveloped in a strip of blotting-paper, and the tail, with the addition of water, covered with a thin glass. Object slides with long, four-sided excava- tions, as proposed by F. E. Schulze, and represented in section by our fig. 113, are very well adapted for the examination of the larva? of naked amphibia? and young fish. The head goes under the edge a, and the tail of the animal lies on the inclined surface b. The whole is to be covered with a thin glass. The apparatus may be very readily constructed by cementing four pieces of glass on to a slide. BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 247 In examining the circulation, only very weak lenses should be employed at first, in order to obtain a more considerable view of the relations of the currents. Then proceed to the use of higher powers, with which the details, especially in the capillary vessels, are to be investigated. It is unnecessary to remark that the apparent rapidity of the current is in this way very much increased. In reality, this is by no means considerable in the capillary districts. A corpuscle of frog's blood passes through the fifth or fourth part of a line in a second. The colored, in contradistinction to the colorless elements of the blood of the adult animal, are without any vital contrac- tibility, as may be best learned by just these observations of the circulation of the frog ; it is only possible to recognize here certain passive changes of the so flexible and elastic cells. A discovery recently made concerning an anomalous condi- tion of the blood-cells of the mammalia is of interest. So long as they remain in the circulation, they but rarely appear in the above-mentioned form of the passive condition, but rather pre- sent the greatest variety of shapes, so that that which in the frog formed an exception has here become the rule. Even this only concerns a passive condition, for as soon as they become quiet they again resume the familiar cup shape (Rollett). The mesentery of the frog is to be recommended for study- ing the condition of the circulation during the process of in- flammation (Cohnheim). Take a sufficiently large plate of glass, cement to this a small glass disk nearly a line in thick- ness and of about 12 mm. diameter, and around the latter a narrow (about 1 mm. broad) cork ring. An opening is to be made through the abdominal walls on the left side of a frog which has been paralyzed with woorara, the mesentery is to be drawn out, and the loop of intestine fastened with a few fine needles to the cork ring. The simple irritation of the air produces the inflammation, and if the mesentery be pro- tected from drying the process may be studied for many hours. Small mammalia, maintained in a condition of narcosis by means of ether or chloral, may also be used for such investiga- tions, although with the assistance of manifold complicated apparatuses (Strieker and Sanderson). 248 SECTION ELEVENTH. But let us return to the mesentery (fig. 114) of our frog ! Dilatation of the vessels (at least of the capillaries) gradually takes place, sluggishness of the current follows, and numerous lymphoid cells collect at the colorless peripheral portion of the veins. The lymphoid cells (a, 6) begin to migrate through the uninjured walls of the latter (B) and of the capillaries (A); col- ored corpuscles also pass through the capillaries into the neigh- boring tissues. After a half or a whole day, when the surface of the mesentery is covered by a dull grayish layer of pus-cells, these remarkable phenomena have commenced in full force. The pus-cells have therefore come from the blood-vessels (Cohn- heim). If a finely granular coloring material has been previ- Fig. 114. Blood-vessels of the irritated mesentery of the frog, with emigration of the lymphoid cells (after S hours). A, a larger capillary shows at a emigrating, and at b emigrated cells. .B, a vein ; at a the lymphoid cells closely crowded against the walls, and pressing through, at b external to the vessel ; c, colored blood-corpuscles. ously injected into one of the lymph sacs of the animal, a part of these cells will contain coloring matter. If, on the contrary, the circulation be arrested by ligating the crural vein, the blood-corpuscles will be seen to be pressed closely together in the vessels of the web of our animal. Here, also, there is a passive escape of colored blood-cells. It is al- most impossible, on the contrary, for the lymphoid corpuscles to manifest their vital contracting power, in consequence of the compression exerted by the overloaded condition of the vessel. Here their active emigration generally fails, or is but very slight. BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 249 A similar emigration of the lymphoid cells also takes place in normal life. The movable cells, which wander through the spaces in the connective tissue, are to be reckoned among these. Cohnheim's beautiful observations, which confirm the older views of A. Waller, possess an extraordinary range and have rapidly called forth an entire literature. Opinions are still un- defined with regard to this subject. Do all these migratory cells and pus-corpuscles originate in the blood, and, having mi- grated, are they incapable of further increase by division ? May not pus-cells proceed from the cellular elements of the connec- tive tissue ? Finally, are these emigrants capable of being transformed into other tissue elements ? The latter is not to be doubted ; and very many observers have affirmed the division of the lymphoid cells, as well as their origin from the cells of the connective tissue. We shall again refer to some of these points. 2 and 3. The examination of lymph or chyle is also very easy ; only some little preparation is necessary for obtaining the material. In order to obtain lymph, a mammal is to be killed by a blow on the head, and, after carefully opening the thorax, a ligature is to be applied to the ductus thoracicus. The lymphatic vessels will be found to be swollen even after a quarter of an hour, and the distention is increased by waiting for a longer time. If the animal has been killed several hours after a plentiful meal containing fat, the lacteals become filled with a milk-white fluid and stand out in the most beautiful manner. With small herbivorous animals, for instance, rab- bits, an elastic catheter may be introduced into the oesophagus, and a considerable quantity of milk injected through this into the stomach. After ail interval of several hours the lacteals will be found magnificently filled. The lymphatic or lacteal vessels are then to be ligated in pieces about one inch in length, a ligature being applied at each end, and the vessel carefully separated from the connective tissue. The separated vessels are to be cleaned by washing in water and again dried, after which they are to be opened over a watch-glass or a slide. If the lymph-corpuscles are desired for rapid demonstration only, the necessary material may be obtained by pricking any lymphatic gland. In lymph and chyle we find, by 2-400 fold enlargement, the 250 SECTION ELEVENTH. characteristic cells (fig. 115), the same with which we have al- ready become familiar in the blood as colorless blood-corpus- cles. When examined in their natural fluid, these structures do not, as a rule, show anything further than a granulated globule of varying size (fig. 115 1-4). If this examination is made with the necessary precautionary measures, the same change of form of the cell may here be found, as an evidence of a vital contractibility, which we have mentioned above (p. 234) concerning the colorless elements of the blood. In order to demonstrate further the y^y w ^7 manner of its organization (nucleus and (*») f5Y ff») (GT\ cell-body), water or extremely diluted V ,2— a ^-^ acetic acid may be used. (Stronger no. lie. Lymph-ceiis. acids s00n dissolve the envelope of the cell and its contents.) These changes are represented in the figure from 5 to 13. The ammoniacal solution of carmine, fuchsine, and aniline blue may be used for staining. Innumerable fat molecules, in the condition of the finest division, occur in the milk-white chyle, as the cause of its color. These atoms require a strong (4-000 fold) enlargement. For their preservation, the mixture mentioned at p. 218 (No. 3), consisting of sublimate (1), salt (2), and water (300), is to be recommended ; Pacini's second fluid may also be em- ployed. 4. Mucus does not require any preparation. It may be either scraped with the blade of a knife from the surface of the mucous membrane, or it may be obtained from the nose or re- spiratory organs, etc. A moderate quantity is to be placed on the slide. Uncommonly tough masses of mucus are to be di- vided with the scissors. The microscopic examination (with a 2-400 fold enlarge- ment) shows us a somewhat irregular constitution. We meet with an extremely variable quantity of the same colorless gran- ulated cells which have just been referred to as colorless blood- corpuscles, and also as elements of the lymph and chyle, the "lymphoid cells." The name of mucous corpuscles has been given them ; only in the cavity of the mouth these structures are called salivary corpuscles. In the latter place, coinciding with the thinner and more watery fluid, granular movements BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 251 are observed in the interior of the cells. Conformably to this, a cessation of these movements may be produced by the addi- tion of concentrated solutions ; they may also be incited in all other lymphoid cells by removing them to a very watery neigh- borhood (C. Richardson). Together with these, is also associ- ated an extremely variable quantity of the desquamated cells of the existing epithelial formation, and likewise the separated cells of the various mucous glands. In consequence of its viscid nature, there are very generally air-bubbles imprisoned within the mucus. Furthermore, there are also very many extraneous admixtures to be seen ; as the remains of food, for example, fibres of meat, grains of starch, particles of dust, threads of fungus, and many others. The recognition of the latter ingre- dients requires a certain amount of practice. I have tried a number of conserving fluids for preserving mucus, but thus far without any notable results. 5. The same granulated cell formation — we know it already — occurs finally as an element of a pathological fluid, the pus ; it re- ceives the name of pus-cell, or pus- corpuscle. A fluid may be recognized as pus, not by its constitution, but rather by the number of its cells. Pus-cells are the extravasated colorless blood - corpuscles which have collected at the point of irrita- tion. The formation of these struc- tures in the interior of epithelial cells (fig. 116), where, by the destruction of the mother cell, the contained cell was set free, was also formerly assumed (Remak, Buhl, Rindtleisch). These observations are certainly correct. If the thin, watery secretion of the mucous membrane in the first days of a catarrh be examined, one may perceive, according to the va- riety of the epithelium, together with free pus-corpuscles, ordi- nary desquamated epithelial cells, and others with contents such as are represented in the figure mentioned. But the ex- planation must be very different. These structures which lie before us are those vagabonds of the body, the wandering cells, which have penetrated from the tissue of the mucous mem- brane into the epithelial cells. Pig. 116. Pus-cells of man and mam- malia lying in the interior of epithelial cells. 252 SECTION ELEVENTH. We shall afterwards speak of a possible and probable for- mation of pus-cells from the connective-tissue cells. Naturally a collection of the pus-cells never takes place on the surface of a mucous membrane. They may afterwards be found scattered through the tissue of the interior of an organ (for instance, in the inflamed cornea) also ; they may then collect in great num- bers beneath the epithelium, Anally force off the epithelial cov- ering, and thus cause an erosion and an ulcer, or, when in in- ternal parts, they may cause the formation of an abscess in consequence of the melting down of the neighboring tissues. Pus-corpuscles are naturally to be examined in the same manner as the elements of lymph and chyle. The vital changes of form of pus-cells have become known to us within a few years. If after about two daj r s, as the re- sult of the application of an irri- tant to the cornea of a frog, its humor aqueus becomes cloudy, the latter will show a number of energetically contracting proteus- like cells (fig. 117). Thin, thread- like processes may give the pus- corpuscle a radiated appearance (a), which may afterwards change to an irregular indentated form (b). Not unfrequently the pro- cesses become further ramified, and, by the meeting and blending of neighboring branches (c), retic- ular processes result (c, d). Long, extended forms sometimes show themselves temporarily (e, /). A reception of neighboring small molecules, such as carmine, within the interior of the cell may also be observed (/;). The pus-cells of man and the mammalia also possess a sim- ilar vital changeability of form. A similar alteration of shape may be recognized when these cells are in the spaces of a more compact tissue ; as for instance in the cornea. Here, it is true, the cells generally appear stretched out and rendered narrow, being constrained by the limited space. Such a locality also presents the best opportunity to follow the above-mentioned progression, or wandering of these con- Fig. 117. Contractile pus-cells from the hu- mor aqueus of the frog, a-k, vital changes of the cell ; b. a pus corpuscle with granules of carmine in its interior ; I, the dean cell. BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 253 tractile structures through, the passages alluded to. This is not unfrequently quite energetic. However, it is not even neces- sary to have an inflamed organ, for the same lymphoid cell, with the same variation and the same progression, also occurs in the normal cornea. The most conservative treatment, the avoidance of positive fluid media, of pressure, and of evaporation are absolutely necessary, if one desires to witness the remarkable phenomena mentioned. The intermingling of other cells, such as epithelium and blood-corpuscles, is recognized without trouble. Many transformations take place in pus, which we cannot at present discirss further. We will only mention one of these, the acid fermentation of pus. It precedes the alkaline de- composition, and brings with it anatomical and chemical altera- tions. When the reaction is some- what acid, the nuclei of the pus- cells become visible. The neutral fats are decomposed, and free fatty acids make their appear- ance in a crystalline form. Such are shown in our fig. 118, partly in the shape of needles, and partly in pointed, lamellated masses ; together with these are the rhomboidal plates of choles- terin. A mixture consisting of 1 part sublimate, 1 part salt, and 300 water, is used for preserving them. Another preservative fluid has been recommended for causing the nuclei to ap- pear : — 1 part sublimate, 1 part acetic acid, and 300 water (p. 218). We should make ourselves responsible for a deficiency, if we avoid mentioning in this little book certain microscopic parasites of the smallest dimensions, and which have recently attracted a constantly increasing attention. This is the most suitable place for their discussion. We refer to the bacteria, vibriones, and kindred structures. Minimal structures with a filamentous, sometimes homo- Fig. 118. Acid pus from an old abscess of the upper part of the thigh. 254 SECTION ELEVENTH. geneous, sometimes moniliform body of varying length, and which are met with in unspeakable numbers in decaying sub- stances hi the living as well as in the dead organism, have long been known. They were at first assumed to be animals, aud with apparent justice, as some of them presented a very lively change of place. At present most investigators, and all bot- anists, who have busied themselves with these smallest of the small, regard the bacteria and their connections as vegetable organisms belonging to the very lowest rank in the group of Sehizomyeeta. By many, and probably rightly, a finely granular substance imbedded in a homogeneous gelatinous-like matrix has been drawn into the circle of development of the bacteria. It has been called zoogloea (Colin), micrococcus (Hallier). microsporon (Klebs). Other observers went still further. They included a structure consisting of long, very fine filaments, the so-called leptothrix. which we shall again meet with as occurring in the human mouth. Contradictions have, nevertheless, not been wanting. All these assertions are dubious, however, in con- sequence of the extraordinary diminutiveness of these little parasites. According to our present knowledge, these bacteria are the producers or. at least, the bearers of putrefaction. They arrive in the living organism, or in portions which have died, less by means of the air than by water and by contact wirh already polluted bodies. Their increase is then quite incredible. The decomposing properties of these smallest structures prove to be very considerable. The firmest tissues succumb to them at last. The bacteria are not mentioned here on this account, how- ever. They are also the producers or, at least, the bearers of contagion in some, perhaps in many affections, the so-called infective diseases. A French physician, Pavaine, many years ago found such bacteria, in innumerable quantities, motionless in the blood of animals with disease of the spleen. Such blood, inoculated into other mammals, produced the same diseased process ; gangrene of the spleen again resulted. In other diseases also, such as gangrene of the lung, in diphtheria, a dangerous affection of the human oral and pharyngeal cavities, bacteria are found in the sputa and the BLOOD, LYMPH, CHYLE, MUCUS, AND PUS. 255 exudated matters, and the disease may be inoculated. A simi- lar phenomenon also occurs in pyemic and septicemic affec- tions, also in variola (Rindfleisch, Waldeyer, von Reckling- hausen, Klebs, Eidam and Loevinson, Eberth), perhaps, also, in Asiatic cholera (Klob). It is not to be accepted that the same variety of bacteria can exert such dissimilar effects ; they are rather to be consid- ered as an indifferent transporting medium of the contagious matter, conducted through the lymph and blood, and deposited in remote localities. The highest powers of our modern immersion systems, in addition to the most rigid precautionary measures, are neces- sary in the investigation of this very obscure department. Lostorfer's so-called syphilis corpuscles have nothing to do with bacteria. These small molecules, which occur after a few days in the blood of patients thus diseased, and also in smaller numbers in the blood of other people, are granular precipitates of an albuminous body. Section todftl). ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. The various so-called corneous tissues of tlie human body- require similar methods of examination, in consequence of the resemblance in their chemical constitution, and may therefore be very appropriately discussed together. 1. Under the name of epithelium are understood the cover- ings of crowded cells which are presented by the various sur- faces of the body, partly as simple layers, partly as stratified layers. According to the form of the cells, the pavement or flattened epithelium, consisting of flattened elements, is dis- tinguished from the cylindrical, in which the cells are long and narrow. Furthermore, we have as modifications the cili- ated epithelium, in which the surface of the cell is covered with very fine cilise which vibrate during life, and the pigment- ed epithelium, containing within the cell granules of black pigment, the so-called melanine. According to their genesis, all the cell layers of the upper- most and lowest germinal layers are regarded as true epithe- lium. The cellular coverings of the cavi- ties of the middle germinal layer are called endothelium; they are always unstratified. Layers are in general found only in flattened epithelium. The cylindrical forms a single layer, which, it is true, is also the case with many other cover- FlG. 119. Flattened epithelium . p , .. ,, * , « of the mucous membrane of the mgs ot pavement-shaped cells, tnat IS, mouth of man. ' all endothelium. The adjacent wood-cuts may serve to represent the various forms of epithelium. Fig. 119 presents the flattened epithe- lium of the cavity of the mouth ; fig. 120, the cylindrical ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 25? variety from the intestinal canal, while fig. 121 shows the cili- ated, and fig. 122 the pigmented form. It is scarcely necessary to remark, that only stratified epithelium is visible to the naked human eye, while such cellu- lar coverings, when they consist of but few layers or only a sin- Fig. 1*20. Cylindrical epithe- lium of the large intestine of the rabbit. Fig. 121. Various forms of the ciliated cells of mamma- lia. Fig. 123. Pigmented pavement epithelium (so-called polyhedral pigment cells) of the sheep. gle one, are only rendered apparent by the aid of the micro- scope. Thus, the densest epithelial covering, that of the ex- ternal skin, was known in olden times, while, for instance, a knowledge of the simple cell coverings of the surfaces of serous membranes and of the vessels is an acquisition of a more recent period. In order, therefore, to obtain the first view of the epithelial cells of a surface, it is sufficient to separate the cells from their natural connections with the clean blade of a scalpel, and to transfer them with a little fluid to the slide. One will then meet in part with isolated structures, in part with whole shreds of connected cells. That which is here artificially accomplished is in many cases performed by nature. The pressure and friction which many surfaces of the body undergo, disconnects the epithelium from its basis. In this manner are separated the cells of the epi- dermis, and those of the various mucous membranes. Old cells fall off spontaneously, as it is said. The mucous cover- ings of the various mucous membranes exhibit in varying abundance the desquamated epithelium of the membrane in question, as, by way of example, we find in the mucus of the mouth, the oldest and largest cells of the flattened epithelium ; in that of the nose and air-passages, the ciliated cells ; in that of the intestinal canal, the cylindrical epithelium. However, much of the epithelium of the body appears to be of a more enduring nature ; it is less rapidly renewed, and we 17 258 SECTION TWELFTH. do not notice that spontaneous desquamation. As examples, we have the flattened cells which cover the posterior surface of the cornea, the pigmented pavement epithelium of the eye. etc. Moreover, the cells of which these coverings are composed prove to be very delicate when acted upon by reagents, and do not resist decomposition for any length of time. The cells of all unstratified epithelium are seen to be com- posed of soft and readily alterable albuminous matters. Hence the greatest freshness of the tissue is necessary for their ex- amination. It would be a piece of folly to look for them in a cadaver which is several days old. In this case they would be either entirely destroyed, or onbv fragments of them would be found. Simple pavement epithelium or endothelium, a-s it occurs on the posterior surface of the cornea, on the serous membranes, and the inner surfaces of the vessels, is to be obtained by scraping and examined with strong (400-fold) magnifying power. The isolated cells are frequently so pale that, even with eonsid- -erable shading of the field, it is desirable to have them tinged. Solutions of carmine, haunatoxyline. aniline blue or aniline red may be used for this purpose. We would especially recommend the latter as coloring instantly, and not exerting any alterative effect. Very dilute acetic acid may be used to render the nuclei more distinct, although there is rarely any occasion for its use. It is somewhat difficult to obtain a simultaneous view of these simple tesselated cells and their basement membrane. Thin vertical sections of the previously dried tissue will rarely lead to the desired results, as the cells, as a rule, become sepa- rated by the reapplication of moisture. A characteristic view may be more readily obtained from parts which have been hard- ened in chromic acid or alcohol. In the vascular system the free border of a valve is a favorable locality for the recognition of its epithelial covering. A view of the epithelium of the serous membranes may be obtained by carefully separating a shred of the membrane from its bed and forming a fold of its free surface. If the posterior surface of the cornea be energeti- cally scraped, inverted pieces of the membrane of Descemet with its epithelial covering may sometimes be seen in the preparation. Recklinghausen's method of impregnation with silver (see p. 162) is also an excellent means of demonstrating the contours ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 259 of pale epithelial cells. The boundary -lines become extremely distinct, even after a slight action of the silver solution, as the precipitation takes place in the intercellular or cement sub- stance first, and the cell cavities remain free. If it be desired, the nuclei may be afterwards stained with carmine. The epithe- lium appears with such distinctness in the small blood and lymphatic vessels, that the course of these vessels may be rec- ognized the same as in an injected preparation. Even in the cavernous passages or the sinuses of the lymphatic system, an epithelial covering may in this way be made visible through- out (fig. 123, a, h). We shall afterwards learn what re- markable information the silver treat- ment has recently furnished concerning the structure of the capillaries. We must return to the cement sub- stance of the epithelial and endothelial cells. The beautiful works of Arnold and Thoma have shown that the injection of Prussian blue in the blood-passages of the dead frog colors this cement border blue. This is also to be recognized when sulphate of sodium is carefully injected into the blood-vessels of the living frog in small doses, at slowly repeated intervals, and the tongue, the object to be examined, is drawn out, and a current of a 1.5 per cent, solution of salt made to flow over it, and a dilatation of the blood-vessels occurs. Alternated in- jections of suitable solutions of cyanide of iron and potash and chloride of iron also produce a similar effect. A solution of good China ink with common salt is still better. As this color- ation of the epithelial cement borders has been noticed in the most various portions of the body of the frog, and also in the mammalial animal, it appears probable that the former is con- cerned in the nutrition of our cell tissue. For further details, especially the apparatus used, we must refer to the original. Indifferent fluids are to be recommended rather than water as media for the examination of this endo- and epithelium. I have not, as yet, been able to preserve these structures very well when mounted moist, but silver preparations keep very well, especially in Canada balsam. Cylindrical epithelium from the surface of lymphatic canals after impregnation with sil- ver. «, elongated ; &, broader mo- saic. solution of indigo 260 SECTION TWELFTH. Tlie pigmented pavement epithelium (the polyhedral pig- ment cells of a former time), which occurs in the eye, and covers the choroid with a simple, the ciliary processes and the pos- terior surface of the iris with a stratified layer, is to be ex- amined in the same manner. Shreds of the same may be readily removed with a scalpel or a brush, and, when carefully spread out with the brush, they present the beautiful mosaic (fig. 122) to view. Such shreds, when folded, present a side view of the cells. Chromic acid preparations and dried eyes may also be used for demonstrating the epithelial formations of which we are at present speaking. If one desire to observe the molecular movement of the black pigment granules, it is only necessary to make pressure with the covering glass in order to liberate the cell contents, which then begin their movements in the water. In this case it is advantageous to use the strongest objectives, so as to magnify the movements of the granules as much as pos- sible. The highest modern magnifying powers appear to indicate a crystalline constitution of these molecules. They may be successfully mounted in glycerine, Midlers fluid, and Canada bal- sam. The methods of investigating cylindri- cal and ciliated epithelium are also the same. Scraping with the blade of a knife fur- nishes ample views of these cells, isolated and hanging together in shreds (fig. 124). Cylindrical epithelium may be most ad- vantageously examined several hours after death, as they are then more readily separated from their parent tissues. Not unfrequently, groups of cells have their free surfaces turned towards us, and thus present, seen in bird's-eye perspective, the familiar, elegant mosaic (5). In investigating the epithelium of the mucous membranes, it is well to postpone the examination till a few hours after the death of the animal, or to place the organs of an animal which has just been killed, for example the trachea or the small in- testine of a mammal, in a refrigerator, and keep them there, in their mucus, for several days. The cells may then be easily Via. 124. Cylindrical epithe- lium from the small intestine of the rabbit, a. Side-view of the cells, with the thickened and somewhat elevated yearn, which is permeated by porous canals; b. view of the cells from above, whereby the apertures of the porous canals appear as small points. ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 261 isolated. Iodine serum, or some other neutral fluid, is useful for the closer investigation. The dried mucous membrane may be used in order to obtain a view of the cylindrical epithelium with its attachments. Wet preparations, that is, such as have been hardened by means of chromic acid, bichromate of potash, and alcohol, are much more suitable. If the part was sufficiently fresh when im- mersed, the epithelial covering will be beautifully seen on thin sections, made with a sharp razor. The appearances are ren- dered much more distinct by tingeing with carmine or hsema- toxyline. Indifferent fluids, tingeing, and the application of dilute acetic acid, are generally employed for the further investigation of this structure. An animal killed during the digestion of fat may be used for demonstrating the passage of molecules of chyle through the cylindrical epithelial cells of the small intestine (with this point the previous section. Chyle, is to be compared) The thickened seam which occurs on the free surface of the cylindrical cells of the small intes- tines, etc., has more re- cently been subjected to an accurate investigation, and found to be permeated by line vertical lines (com- pare tig. 125, also 124). Most investigators of the present time accept these lines for the optical expression of fine passages which pass through the seam, so-called porous canals, an opinion which is also entertained by the writer of these lines. Strong magnify- ing powers, especially immersion systems, are requisite for the recognition of the subtile textural relations. The animal may be used immediately after being killed, but it is better to expose the intestine to the air for several hours, which will facilitate the separation of the cells. Intestinal mucus, blood serum, weak solutions of chromic acid, solutions of salt (2 per cent.), and of phosphate of soda (5 per cent.), may be used as media. The Fig. 125. The same cells. At a, the seam is lifted up by the action of water and slight pressure ; at &, appearance in the natural condition ; at c, a portion of the thickened border destroyed; at d, e. /, it has become resolved into isolated rods or prismatic pieces by the prolonged action of water. 262 SECTION TWELFTH. ' addition of water lias a destructive effect on the seam. The individual pieces separate from eacli other in the direction of the vertical lines ; not unfrequently, the appearance is present- ed as if the cell had a border of cilia (d, e,f), which was also the opinion of the first observers (Gruby and Delafond). A similar effect is produced by maceration for about six hours in phos- phate of soda (5 per cent.), or the so-called strong acetic acid mixture of Moleschott (Coloman Balogh). All that was said concerning the cylindrical cells also holds good for the examination of ciliated epithelium ; only, one should commence as soon as possible after death, and make use of indifferent media, as water usually attacks the fine cilia and soon causes them to fall off. On the contrary, a strong solution of potash, from 28 to 40 per cent., preserves them very well, as Schultze ascertained. Tingeing with aniline red is very useful ; it may be rapidly done, and — in the frog at least — does not cause the ciliary movements to cease. Mounting in strongly diluted glycerine is to be recommend- ed for preserving cylindrical epithelium, especially that which has been hardened by means of alcohol, f have not as yet succeeded in keeping the ciliated cells, with the preservation of their cilia, for any length of time. Before proceeding to the lamellar epithelium, we will allude to the most remarkable vital phenomenon of the tissue, the vi- bratory or ciliary motion. Since the vibratory phenomenon outlasts the death of the creature and the separation of the cell from its natural con- nections for a very unequal length of time, in the individual animal groups, it is of the greatest importance to make a suita- ble selection. Mammalia and birds, in which the movements of the cilia very rapidly cease, are therefore to be avoided in the first examinations. The naked amphibia, salamanders and frogs, are best adapted ; the larger size of their cilia also con- stitutes a second and not unimportant advantage. Many of the invertebrates, such as the river muscles of the genera unio and anodonta, as well as the genus cyclas, which have on their gills a covering of ciliated cells with splendid long hairs, are exceedingly well qualified for this purpose. By using very powerful lenses one may also obtain a view of an important textural condition in the vibratory cells of the intestine of the ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 263 river muscle. The cilia are the continuations of fine proto- plasma filaments of the cell-body (Eberth, Marchi). The fluid media are of great importance in the study of the vibratory movements. It is asserted in general that everything which does not affect the cell substance chemically allows the ciliary movement to continue ; everything, on the contrary, which alters its molecular condition terminates the movements once for all. The indifferent natural fluids should therefore be preferred to all others. Blood serum in the first line, also liquor amnii, vitreous fluid, milk, and even urine form excellent fluid media. Iodine serum appears to be very serviceable ; bile exerts an unfavorable effect. The addition of pure water increases the activity of the vibrations for a short time, to cause them to cease all the sooner. An alkaline reaction of the fluid media is to be denoted as favorable, acid as unfavorable. Oxygen has an exciting, carbonic acid a paralyzing effect (Kiihne). A moderate increase of temperature increases the activity ; a higher temperature, which destroys the life of the protoplasma, exerts the same effect on the allied ciliary movement (Roth). In order to commence the first observations, a piece is to be cut from a membrane covered with ciliated cells (for example, the mucous membrane of the gums, or the pericardium of the frog), serum is to be added, and the membrane folded in such a manner that its cellular surface forms the free border of the fold. In order to avoid pressure, which might dislodge the slippery mucous membrane or force the folds apart, the frag- ment of a somewhat thick covering glass is to be laid in the fluid and the preparation covered ; or the specimen may be made to adhere to the under surface of the covering glass and placed in the moist chamber (fig. 75). Blood-cells which float in the fluid form a valuable addition (they may be replaced by particles of coal, granules of indigo, and carmine). If the examination be made with a low power, a movement, a vibration, as the phenomenon has been appropriately named, is recognized at the margin of the fold. The corpuscles will now be seen driven forward in a rapid current, which is always in a definite direction ; and if the fold shows hills and valleys, one may see some of the corpuscles driven forward and then suddenly thrown back again. The older observers were led to think of electrical attraction and repulsion. When the phe- 264 SECTION TWELFTH. nomenon begins to be paralyzed and the magnifying power is somewhat increased, the movement becomes more distinct and appreciable. The regular and simultaneous vibration of the cilia now appears like an undulating border, like the flaring of a candle, or the rippling of a clear rivulet in the sunlight. If we follow the vibratory movement for a still longer time, and at the same time increase the magnifying power, a moment arrives in which the individual cilia may be distinctly seen to vibrate, biit only one direction of the excursion can be recog- nized at first. Already the blood-corpuscles are driven past more slowly, and we are able to perceive how a cell is driven down into a valley and then, by means of the microscopic whirlpool, it undergoes the above-mentioned repulsion. If the examination be still further prolonged, the number of the in- dividual vibrations becomes less and less ; we can now see both of the excursions of the cilia, and a moment soon arrives when small bodies suspended in the water — in our example, the blood-cells — present only irregular fluctuating movements in front of the ciliated margin. Finally, the cessation, the expira- tion of the movements appear. Over a certain space all the cilia are stiff and motionless. There may still be a vibratory movement in the neighborhood for a short time ; finally, this ceases also. It was a beautiful discovery of Virchow's, that the ciliary movement which has but just ceased may be again called to life for a short time. Veiy dilute solutions of potash and soda are necessary for this purpose. If the isolated piece of mucous membrane is not too large, one may watch it as it is slowly driven from its positioii by the united labor of its innumerable cilia. The ciliary movement may also be examined in still another manner — and this is to be especially recommended for more accurate investigations with powerful lenses. The epithelium is to be separated in shreds by scraping somewhat energetically the surface of the exposed mucous membrane. Here one may at first recognize a few groups of cells engaged in the most ac- tive rotatory movements, also isolated disconnected cells with vibrating cilia, etc. With regard to the number of vibrations which take place in a given space of time, the cilia move so rapidly at first that an estimation having any degree of accuracy is not to be ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 265 thought of. It has been assumed that there were a few hun- dred vibrations to the minute, but this is an uncertain valua- tion, and is really much too low. Afterwards it becomes more and more easy to count them. The manner in which the cilia vibrate is by no means always the same. Purkinje and Valentin, who investigated the ciliary movements in the most thorough manner a number of years ago, distinguish four varieties of movements : the hook-like, the funnel-shaped, the oscillating, and the undulatory. The first variety is regarded as being by far the most frequent. According to Engelmann's beautiful investigations, on the contrary, the ciliated cell, when thoroughly unimpaired, only exhibits the undulatory motion. All other forms of vibration are caused by the cilia having become stiff and motionless in certain places. The examination of the ciliary movement in mammalia and birds requires the rapid preparation of the tissue immediately after the death of the animal, the addition of its blood, iodine serum, and the hot stage. Sometimes, in spite of all haste, one is too late, in other cases the vibration continues to be lively for several minutes. A few cases are known, in which, long after death, in the bodies of mammalia which have -become quite cold, the liveliest ciliary movements were still perceptible to the astonished eye. I have mj'self observed such a case, years ago. Human ciliated cells with well-preserved cilia can only be observed in a cadaver which is quite fresh ; those with moving cilia may be obtained under certain circumstances from the liv- ing. If one bores with a feather (the beard of which has been cut short) in the upper part of the nose, ciliated cells which are still living may sometimes be found in the mucus which is thus rubbed off. They may be more readily obtained by ex- amining the thin watery secretion from the nasal or respiratory mucous membranes at the commencement of a severe acute catarrh. In such cases, together with regular shaped ciliary cells, abnormal examples will also be found in great numbers, some which are swollen, others which present a more globular form, and within which may be recognized a granular body, a pus-cell (fig. 116,/, p. 251). (Eindfleisch.) All of the varieties of simple epithelium which have thus far been mentioned consist of relatively alterable soft cells. 266 SECTION TWELFTH. It is different with the stratified flattened epithelium, as met with on many mucous membranes, and most strongly de- veloped as a covering to the external integument. In these cases it is only the deeper layers of younger cells which still retain a similar soft and readily alterable con- stitution. As it appears, these are to a great extent joined together in a very peculiar manner (Schultze). The surfaces of these membraneless structures (fig. 126, a, b) are everywhere covered with points, prickles, and ridges which insinuate themselves between i ,0:^ ^2^1 P^ Fig. 126. So-called stach- el or riff cells, a, from the deeper layers of human epi- dermis ; &, cell from a pa- pillary tumor of the hu- man tongue (observed by Schultze). those of the neighboring cells "like the bris- tles of two brushes when pressed together," so that the name stachel and riff cells is quite appropriate. The older layers of this variety of epithe- lium show, on the contrary, cells with smooth- er surfaces, which, in becoming flattened and spread out, are also chemically altered. They consist of a much more resistant modification of albumen; they are cornihed, as it is said. The methods of examination are therefore to be modified. It is self-evident that the various layers, even to the young- est, may be brought to view by scraping, and at the same time one of the ordinary methods of tingeing may be advantageously employed, especially for the young- est cells. By the use of reagents, and especially of a weak acid, we may recognize a considerable power of resistance in the older scale-like epithelial cells, while those which are younger are soon attacked and only their nuclei remain. In order to isolate the cells, it is well to macerate for a day or two in iodine serum, in a 10 per cent, solution of common salt, in Czerney's mixture of Midler's fluid and saliva (p. 137), or, as Langerhans recommended, in concentrated nitric acid. The most manifold and in part strongest cell forms are then met with (fig. 127) in a quite unexpected manner. Fig. 127. Corneal epithelium of the calf (maceration preparation), from Muller's Uuid mixed with saliva. ENDOTHELIUM AND EPITHELIUM, NAILS, HAIE. 267 Drying and hardening in alcohol are employed for obtain- ing transverse sections through a whole stratum of epithelium. The first method is in general to be preferred for the external integument, the last for the mucous membranes. Weak tinge- ing with carmine and subsequent washing in water acidulated with acetic acid yields excellent preparations. The cell nuclei may be recognized even in the most superficial layers of the epithelium of mucous membranes, while the quite colorless non-nucleated scales of the cornified epidermis appear in the most beautiful manner above the deeper layers which are stained. Impregnation with silver may also be used here with good results. There is no medium which renders such good service in the examination of the stratified flattened epithelium as alkalies, especially potash and soda. By the use of these reagents the cells may be made to assume a sometimes lower, sometimes higher degree of distention ; they may be isolated, their nuclei destroyed while their membranes are preserved ; and finally, they may be entirely dissolved. The use of alkaline solutions is, therefore, of the greatest value in the enumeration of the superimposed layers, as, on the other hand, they reveal the structural conditions of the epithelial cells better than any other method. A strong solution of potash or soda forms a combination with the substance of the flattened epithelium in question which causes the cell to swell and which eagerly mixes with water, and thus induces an increasing intumescence till the cell is finally dissolved. Concentrated solutions therefore exert a different effect from those which are more diluted, and the quantity of potash especially which a fluid medium contains is of the greatest importance. Moleschott, who has examined this subject more accurately, has instituted a series of experiments on this point. He made use of the dried tissue. A strong solution of potash of 35 per cent, induces only a moderate distention ; the cells form a very elegant mosaic and their nuclei are preserved. The intercellular or cement sub- stance which unites the cells is gradually dissolved, the cells become isolated and float about in the fluid. The nuclei are preserved even with solutions of 30 per cent., but they are rapidly attacked by those which are weaker, below 20 per cent. 268 SECTION" TWELFTH. In order to cause a considerable distention of the cells, to the form of elliptical vesicles, the tissue is to be placed in a solu- tion of potash of 30-10 per cent, for the space of about four hours. If water be added to these swollen cells, they become dis- tended into vesicles which are as transparent as glass, and soon dissolve. Before this, however, the reduction of an albuminous matter (their corneous substance) may be in- duced in the epithelial cells of the prepara- tion, by over-saturating the fluid with acetic acid. Prom what has been said, the corre- sponding illustrations of our fig. 128, which represent the pavement epithelium of the cav- ity of the mouth (1), as well as that of the ex- ternal integument (2) under such treatment, must be intelligible. The cells are gradu- FlG. 128. 1. Epithelial cells : at a. an unaltered flat cell from the cavity uf the mouth ; at b-f, the same variety of cells after treat- ment with caustic soda, some still with nuclei (&, c, fl), some already without nuclei (e, /) ; at g, after the action of soda with the ad- dition of acetic acid. 2. Epidermoid cells: a. unaltered ; &, at the commencement of the soda action ; at c, the more prolonged ally diSSOlVeCl ill Vd'y action of the reagent ; d, with the addition of acetic acid. . weak sol utions, from 10-5 per cent., of potash, but weaker solutions, under 5 per cent., exert less effect on this tissue. Solutions of soda may also be employed with advantage, but they must be more dilute. A solution of chloride of gold (0.005 per cent.) and its reduc- tion by means of sulphate of iron (p. 167), has recently been recommended by Nathusius for the cornified tissues. Such preparations may afterwards be exposed to the alkalies with advantage. For the examination of the stratified flattened epithelium, fine vertical sections of the tissue which has been thoroughly hardened in alcohol or chromic acid are to be especially rec- ommended. Tingeing with carmine should also not be neg- lected. ENDOTHELIUM AND EPITHELIUM, NAILS, HAIK. 269 The cornified cells may be readily mounted in preservative fluids. Glycerine is to be used with stained sections. They often make right handsome preparations when deprived of their water and mounted in Canada balsam. 2. The tissue of the nails. In consequence of their consist- ence, the nails permit of sections being made in the various directions without further preparation, but their elements are combined in such a manner that one can see nothing but a ho- mogeneous tissue which, in consequence of its brittleness, is permeated by numerous rents and flaws. Reagents which soften and dissolve the intercellular substance are, therefore, indispensable. Sulphuric acid and alkaline solutions have been used. The former, even concentrated, act but slowly when cold, although after a few days epithelial disks may be dis- tinctly recognized. By boiling they make their appearance very rapidly, even in half a minute. The nuclei do not become sufficiently visible by this method. Solutions of potash and soda act very much better, as was indicated by Kolliker many years ago. One may often obtain very handsome specimens of isolated and distended cells, in which the nuclear formations not unfrequently stand out very beauti- fully, even without using solutions of known strength. A solution of potash of about 25-27 per cent, ap- pears to be suitable. Weak solu- tions destroy the nuclei. A momentary boiling in a dilute solution of soda (about 10 per cent.) also frequently affords very charac- teristic views. The structure of the nails may be demonstrated in this way almost instantaneously. Fig. 129 shows us the cells of the nails isolated in the latter manner. As is well known, numerous epithelial new formations occur. Cysts and encysted tumors are, for the most part, lined with pavement cells. Hypertrophied growths of the skin, indura- tions, verruca and hornlike excrescences present an arrange- ment which is similar to the strata of the cornified epidermis and which require analogous methods of examination, such as Fig. 129. Tissue of the human nail, in part after the action of the solution of .soda. a, cells of the most superficial layers in profile ; &, a cell seen from above ; c, half profile ; d, a number of cells which are ren- dered polyhedral by the pressure of their neighbors ; «, a cell, the nucleus of which is beginning to disappear ; /. cells of the deepest layer (stratum mucosum Malpig- hii) ; at £/, one of these cells with double nucleus. 270 SECTION TWELFTH. drying, vertical sections, solutions of potash, etc. The pearl- like tumors (among which are to be reckoned Hassal' s concen- tric bodies of the thymus) and the epithelial cancers or can- croids also have an epithelial character, the first in the form of benign, the latter in the form of malign neoplasms. The pre- paratory methods are to be adapted to their varying consistence. The fresh tissue may be examined in part as fine sections and picked preparations, in part after the use of hardening agents. Tingeing and the alkalies are also to be employed. Nails un- dergo but slight changes. 3. Hair and its tissue. We shall as- sume that the complicated structure of the human hair has already been learned from the text-books on histology. In order to examine the hair with its sac and the most inferior portion of its bulb, a hair of strong calibre is to be pre- pared from the skin, or a piece of the skin of the head which has either been dried in the air or hardened by means of alcohol, may also be used with advan- tage. But in making vertical sections, it is necessary to keep as close as possible to the directions in which the hair passes through the skin. Transverse sections through the hair and all its coverings (fig. 130) may be obtained in a similar manner. Moleschott recommends the im- mersion in his strong acetic acid mixture for a few months. A hair which has been slowly drawn out from the head may be used for the first examination. The root will often be found covered with the white substance of the so-called root-sheath, with the exception of its lowermost portion, which has remained with the terminal part of the bulb in the follicle. White hairs are most suitable ; blond are better than dark. Water or glycerine may be used as a medium. Weak powers will then permit of the recog- nition of the essential structural conditions. Fig. 130. Transverse section through a human hair and its follicle, a, hair ; 6, epidermis of the same ; c, inner, and d. outer layer of the inner root sheath ; e, outer root sheath ; /, its periph- eral layer of elongated cells ; ff, structureless membrane of the hair sac ; 7i, its middle, and i, ex- ternal layer. ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 271 No farther preparation with the exception of strong lenses, and at most the use of acetic acid, is necessary for examining the finer structure of the outer root-sheath (figs. 130, e, 131, c). The inner root-sheath (fig. 130, c, d) may be obtained either from sections, made parallel with the surface of the skin of hairy parts of the body, or from hairs which have been drawn out after stripping off the outer sheath and removing it from the shaft of the hair. It may also be seen on short transverse sections, made through the bulb of the moistened hair while lying on the slide, and then picked with needles. Although the first few attempts may fail, a little attention and the use of strong lenses will lead to the recognition of the two differently shaped layers of cells (figs. 130, c, d, 131, a, b) of the inner sheath. The structure of the shaft and bulb of the hair, as well as the epidermoid covering, may even now be recognized to a certain Fig. 131. Cells of the root-sheaths ; inner root-sheath with Henle's (a) and Huxley's (b) layer; c, cells of the external sheath. Fig. 132. a, cells of the hair- bulb ; b, from the commencement of the shaft ; c, cortical mass treat- ed with sulphuric acid, and at d, separated into plates ; e, /, cells of the cuticle of the hair. extent. Reagents, the application of which we will now con- sider, are necessary for the further penetration into their struc- ture. Let us commence with the last-mentioned covering of epi- dermoid cells (figs. 130, I), 132, e,f). The action of concentrated sulphuric acid for a few minutes, the importance of which was indicated many years ago by H. Meyer, is an excellent means of separating the cells. The same result may be accomplished with alkalies, though much more slowly. Moleschott praises a 272 SECTION TWELFTH. potash solution of 4.6 per cent. When this has acted for about forty hours (in the cooler temperature of winter) the cells begin to separate from the shaft of the hair. After three or four days the cells are everywhere isolated in the most beautiful manner. Solutions of soda may also be used. The use of concentrated sulphuric acid at a moderate tem- perature is the best means of demonstrating the cortical layer of the shaft of the hair, and for isolating the peculiar plate-like cells. After several minutes it will be found that the cuticle is commencing to separate, and that the surface of the shaft has become rough and felt-like. After a short interval, espe- cially when the hair is made to roll with a little pressure, the spindle-shaped cells begin to peel off. The inner layers (b d) afterwards become separated, until, finally, the medullary sub- stance is exposed. These plates may also be split off in groups by mechanical means. For this purpose, a dry hair is to be placed on the slide and scraped in the direction from the point towards the root. The scrapings are to be moistened and placed under the microscope (c). Alkalies were long since recommended for rendering visible the shrunken air-vesicles of the medulla (Kolliker). For the medullary cells of the hairs of the beard, and especially blond hairs, Moleschott praises the maceration, for one or two days, in a 3 per cent, solution of soda. Placing the hair for several days in a 2 per cent, solution of potash, or a longer immersion in one of 4.6 per cent, produces good specimens. The following process is most to be recommended for ob- taining transverse sections through the hair-shaft : A bundle of hairs is to be imbedded in one of the mixtures mentioned at page 114. Then (and even here a microtome is useful) a sharp razor is used, and the sections are subsequently freed from the embedding mixture. To obtain transverse sections of the deep- er portions of the hair, from the part situated beneath the skin, such as is represented in our fig. 130, a preliminaiy hardening with absolute alcohol is necessary, and the section should be tinged with hsematoxyline. With some practice, the most charming specimens may thus be obtained. No other tingeing material renders equal service. The emplo_yment of very dilute acetic acid is very iiseful for examining the cells of the outer root-sheath. Stronger ENDOTHELIUM AND EPITHELIUM, NAILS, HAIR. 273 solutions of potash are used for the cells of the inner root- sheath. We shall afterwards consider a few of the pathological con- ditions. The first rudiments of foetal hairs are obtained from sections of skin hardened in chromic acid or alcohol. Tingeing with carmine is very useful. The later stages of development are studied in a similar manner. Hair preparations are to be mounted dry in Canada balsam or in glycerine, according to circumstances. 18 Section &t)irtcmtf). CONNECTIVE TISSUE AND CARTILAGE. Modern histology designates at present with the name of connective substance a series of tissues which are nearly re- lated, although proving different enough in their terminal forms, and which are all, directly or indirectly, interchange- able. They also take their origin from very similar textures, and thus present substantial evidence of being members in a natural series of relationship. Gelatinous tissue, reticular and ordinary connective tissue, fat, cartilage, bone, and dentine are to be enumerated here. These members also resemble each other in still another physiological regard. They are tissues of low rank, which do not take part in the higher vital processes, but, on the con- trary, they form throughout the whole body, in all its parts, a widely expanded framework (although of varying quantity), in the spaces of which are embedded other tissues, such as muscles, nerves, vessels, glandu- lar cells, etc. Virchow deserves the credit of having, by a series of investigations, shown the im- portance of connective tissue in pathological new formations. 1. As gelatinous tissue, we Flo. 133. Tissue of the vitreous body of a hu- JJ» x« • 1 ni_ j. man embryo at the fourth month. distinguish SOlt transparent masses, consisting of round or star-shaped cells (figs. 133, 134), which have between them a con- siderable quantity of an ordinary homogeneous, slimy intercel- lular substance. Nearly all of them belong to the total period of life, and concern either transitory organs or are only devel- opment stages of the ordinary connective tissue. A single one of these, of a peculiar watery form with stunted cells, persists : CONNECTIVE TISSUE AND CARTILAGE. 275 the vitreous body of the eye (fig. 133). The extreme softness of all these tissues renders it very difficult to obtain tolerable preparations. At the most, the pale and delicate cells may be studied with a strongly shaded field with- out further treatment. Hardening media are therefore necessary, and among these chromic acid and bichromate of potash take the first rank. As a rule, a chromic acid solution of 0.5-2 per cent, hardens the tissue to such an extent that sections may be made from it with a sharp razor. With one of the organs which belongs here, the umbil- ical cord, the drying method may be very suitably employed. Neumann has given a peculiar but very appropriate process for the vitreous humor. It is to be saturated for 1-2 days with the albumen of an egg, and then hardened by a momentary immer- sion in hot water, after which it is to be placed in alcohol. In this way the organ is not only rendered more consistent, but also darker. In consequence of the delicacy and pale- ness of the cells of gelatinous tissue, tinge- ing is very much in place. Excellent prepa- rations of the vitreous fluid are obtained with aniline blue. Preparations of the gelatinous tissues may be preserved, after tingeing, in glycerine. 2. With the name of reticular connective tissue we desig- nate a reticulated framework made up of star-shaped cells, which no longer harbors in its sometimes wider, sometimes ex- tremely narrow meshes the mucous fluid of the gelatinous tissue ; on the contrary, its contents are different. They con- sist either of lymph-corpuscles — in which case the tissue has re- cently been called ' ' adenoid " or " cytogenetic ' ' (His, Kolliker) — or of drops of fat (hibernating glands), or of nervous elements (spinal cord, brain and retina). Here, as in the whole connective substance group, we cannot speak of a sharply demarcated tissue. The reticulated often passes over into ordinary con- nective tissue, and probably also into gelatinous tissue. Fig. 134. Cells of the ena- mel organ of a four months' embryo ; at o, smaller, at 6, larger and more developed star-shaped cells. 276 SECTION THIRTEENTH. If any tissue of the body is qualified for showing the great value of the more modern methods of investigation, it is just this reticular connective tissue (fig. 135) which for many years has been frequently examined and formerly caused numerous controversies. All the forms in which our tissue occurs in the lymphatic glands, lymphoid follicles of the thymus, spleen, in- testinal mucous membrane, etc., are too soft to permit of an examination being made without previous preparation. It is, therefore, indispensable to employ hardening media for several days beforehand. Among these, chromic acid, bichromate of Fio. 135. Reticulated connective tissue from a Peyer's follicle of an old rabbit, o, the capillary ves- sels ; &, the reticulated connective tissue framework ; c, lymph corpuscles. potash, and alcohol take the first rank. When these glandular organs or the intestinal mucous membrane have attained the proper degree of hardening, the finest possible sections are to be made from them with the sharp and moistened blade of a razor. These sections are to be carefully brushed, in the man- ner indicated by His, with a soft camel' s-hair brush. Tingeing with carmine and hsematoxyline, and subsequent washing in slightly acidulated water, serve for demonstrating the nuclei at the nodular points of the network. They will then be readily seen, especially in young subjects. However, all of the innu- CONNECTIVE TISSUE AND CARTILAGE. 277 merable nodular points do not have a nucleus, as not only the simple processes of the cells, but also the ramifications of these processes become united with each other, so that the cell radii present, together with the nucleated centres, a number of non- nucleated nodular points. Tingeing with carmine will also prevent one from mistaking the stained nucleus for the trans- verse section of a vertically ascending colorless reticulated fibre. In older animals — and our drawing is taken from such a one — ■ the nuclei may, indeed, be entirely wanting in a few places, and frequently only such as are stunted and shrivelled can be rec- ognized. In conditions of irritation, however, they soon re- sume their former distended appearance. A larger or smaller residue of the lymph-corpuscles (c) will be perceived in the meshes of the tissue, according as the brushing is continued for a longer or shorter period. In many cases it is not easy to hit upon the proper degree of hardening, and on it, in reality, everything depends. If the preparation is over-hardened, it does not permit of the sufficient removal of the lymph-cells ; if not hardened to a sufficient degree, the whole frequently falls to pieces after a few strokes with the brush. For the intestinal mucous membrane and most of the lymphoid organs I prefer alcohol to chromic acid. The pieces, which should not be too large, are to be placed in a consider- able quantity of fluid for the first two days. This should consist of alcohol of about 36°, which is to be diluted with an equal part of water. The fiuid is then to be replaced by the same alcohol, but without the former addition of water ; generally, after from four or five days to a week the tissue is in a proper condition for brushing. Well-hardened pieces may in this way be preserved in weak alcohol for months and years. Very strong alcohol is to be entirely avoided. If it be desired to use chromic acid, commence with a solu- tion of about 2-5 per thousand, and proceed gradually, chang- ing the fluid to one of 1 per cent. Chromate of potash is to be used in a corresponding quantity (concerning which p. 136 is to be compared). The reticular connective tissue of the lymphatic glands, Peyer's follicles, and the Malpighian bodies of the spleen, may be recognized with comparative facility. The thymus and the 278 SECTION THIRTEENTH. tissue of the pulp of the spleen give more trouble. Its recog- nition is difficult in the hibernating glands, which I have investigated with Hirzel, and to a still higher degree in the nervous organs, especially in the gray substance of the spinal cord and the brain, likewise the retina of the eye. More dilute solutions of chromic acid than those above mentioned (£-J- gr. to 1 ounce) are to be used, and allowed to act for several days. Very strong objectives should also be used. We shall return to this subject in speaking of the organs in question. Tinged preparations, mounted in dilute glycerine, afford the best specimens for a collection. 3. The examination of fat tissue is sim- ple and causes no trouble, whether a sim- ple form of the same (fig. 136) is concerned, or a pathological new formation, for exam- ple a lipoma. The determination of the origin and retrogression is more difficult. ^'M'^jfT,^* A small piece of the tissue (a) is to be completely filled with fat, lying F V / toother in groups b, free gio- picked in the thiid media and then reviewed bules of fat ; c, empty envelopes, -t with a low power. The large, sometimes smoother, sometimes rougher cells will be recognized pressed closely together, often with a polyhedral flattening. At the same time, a number of free globules of fat (b) will be met with in consequence of the laceration of the cells which has occurred. The optical properties of both are quite similar. We perceive a pellucid, sometimes slightly yellowish tinged substance, having sharp, dark contours with transmitted light, but with incident light a silver-like lustre and a whitish or yel- lowish periphery. While the fat-cells are of a definite size, that of the free drops of fat varies exceedingly. The latter flow together under pressure, but the cells do not. Osmic acid deserves recommendation for the recognition of small masses of fat, whether free or contained in cells. It stains them black, as we have already learned (p. 165). In order to demonstrate the cell membrane, it is necessary either to rupture the cell, in which case the former remains behind as a collapsed sac (c) after the fat has flowed out, or the fat is to be removed by chemical means with alcohol, ether, or benzine, which last was recently recommended by Toldt for CONNECTIVE TISSUE AND CARTILAGE. 279 Fig. 137. Human fat-cells containing crystals, a, a few needles ; 6, larger cluster ; c, the cells themselves having these clusters within them ; d, an ordi- nary fat-cell free from crystals. this purpose. The nucleus may be demonstrated by tingeing it with carmine in the ordinary way. The treatment with picric acid and carmine, and the subse- quent addition of formate of glycer- ine, affords very handsome specimens (Flemming). Not ^infrequently, a deposition oc- curs within the fat- cells of crystalline needle-shaped masses (fig. 137, c), the same as we have already met with in acid pus. A prolonged immersion in glycerine almost invariably produces such a crystallization within the cell cavity. In order to study the blood-vessels of fat tissue, injections are to be made with transparent masses, carmine, or Prussian blue, and in making the microscopic examination pure glycerine is to be used as a medium, which last, in consequence of its strong refracting power, is very well adapted for fat-cells in general. Glycerine (pure or mixed with formic or carbolic acid, p. 216) is to be used for mounting, or, if the fat tissue is injected, Canada balsam or alcoholic resinous solutions may be advan- tageously employed. 4. Ordinary connective tissue is very widely diffused, and consists, in its developed form, of a fibrous substance which is divisible into bundles and fibrillse, and in which long or stel- late cells, the frequently mentioned connective-tissue corpiiscles, are met with, as are also the various phases of elastic tissue. The whole lies embedded in an extremely variable quantity of homogeneous basis substance. If living connective tissue be selected from a suitable place, for instance, in the frog, the thin transparent membrane (to which Kuhne called attention) between the crural muscles (fig. 138), and examined with the addition of lymph, one may recog- nize in the pellucid basis-substance the fibrillse (/) and bundles of the connective-tissue fibres (g), and also a network of very fine elastic fibres {h). The connective-tissue corpuscles then appear as flat, membraneless cells, consisting of a nucleus and fine granular protoplasma. Several varieties of these cells may 280 SECTION THIRTEENTH. be noticed (a and b, c, d and e), and one may at the same time convince one's self that the first two varieties of the connective- tissne corpuscles (a, b, c) have a sluggish, but unmistakable vital contractility, so that the cell a gradually changes to such forms as are repre- sented in our figure at b. However, as we now know, the shape is even yet not completely described. An uncommonly pale marginal portion, which very readily escapes no- tice, as well as accessor plates resting laterally at various angles on the flat cell, and which are recog- nized with still greater dif- ficulty, give this thing, Fig. 138. A piece of living connective tissue from the ripper part of the thigh of a frog (the cells are represented somewhat more pressed together than they usually lie), a, contracted cell ; b, radiated, expanded connective-tissue cor- puscles, one of them without a visible nucleus : c, one with a vesicular nucleus; d and e, immovable cells;/, fibrillai : £/, simple bundle of connective tissue ; A, plexus of elastic fibres. even in the higher ani- mals, the shape of an ir- regular paddle-wheel (fig. 139, a). Such connective- tissue cells have lately been met with very widely diffused (Waldeyer, Kanvier, and others). In addition to this cell form, the connective tissue contains, sometimes more rarely, sometimes more frequently, another (fig. Fig. 130. Cells of the human connective tissue. a, flat and shovel-shaped elements ; o, coarse granule cells. Flo. 140. So-called plasma cells &, collected around a vessel a. From the testicle of the rat. 139, &), which probably has a more embryonic character. It is more plump, the granules are coarser ; it has not the lamellar and veil-like system of processes. The latter elements, which CONNECTIVE TISSUE AND CARTILAGE. 281 have been called ' ' plasma, or perivascular cells ' ' ( Waldeyer), generally lie in the vicinity of the blood-vessels. Together with these, the remarkable amceboid migratory cells, the emigrated lymph-corpuscles, which we mentioned at p. 248, are met with. Accordingly, the fixed have been dis- tinguished from the migratory cells of the connective tissue. Certain places are also found in the warm-blooded animals which permit of the examination of living cells ; as, for example, the thin connective tissue which covers many of the muscles of the smaller mammals (Rollett). As the proportion of the cells, fibrillse, and elastic elements varies considerably, the form of the tissue is necessarily modi- fied in accordance with these several admixtures. The diver- sity which the twisting and in- terweaving of its bundles pre- sent is not less considerable. If a piece of dead connective tissue be prepared in a fluid medium with the aid of sharp needles, it may be very readily separated into the above-men- tioned strings or bundles (fig. 141). The bundles themselves show a striation running paral- lel with their long axes, and may be separated, in accordance with the latter, into finer strings, and, finally, into extremely thin, homogeneous, more or less undulating fibres or threads, the so-called primitive fibrillse. While in former times the anatomists adopted a fibrillated condition of the connective tissue as a simple expression of this very easily made observation, Reichert, in the middle of the fifth decade of this century, pronounced these fibres to be arti- ficial products, and the longitudinal striations to be the optical expression of the folding and wrinkling of a thoroughly homo- geneous membrane. Controversies were waged for a long time concerning the latter acceptation. It was only at a later period, when the method of isolation by chemical means had been discovered, that the pre-existence of these fibrillee (which the reader already Fig. 141. Connective-tissue bundles (at the left, several isolated fibriliai) wich very abundant ho- mogeneous interstitial substance. 282 SECTION THIRTEENTH. recognizes from fig. 138), could be proved in the most indubi- table manner. If the connective tissue be treated alternately with reagents which cause it to swell and to shrink, the finest fibres appear in the most beautiful manner (Henle). Further observations were then made by Roilett. If a portion of human tendon be immersed for a week or more in lime-water, and then a bundle of it placed on the slide, one may readily succeed, by inserting the preparing needles into the middle of the same, in drawing it out into longitudinal fibres of greater or lesser calibre, which cross each other at acute angles. All attempts at spreading out the tissue as a homogeneous membrane in accordance with Reiehert's views are unsuccessful, and cause it to split up into fibrillge. Baryta- water produces the same effect, but in a much shorter time — from 4 to 6 hours. For the microscopical investigation it is necessary to remove the hydrate of lime or baryta, either by washing for a long time in water, or by the addition of so much acetic acid as just suffices to neutralize the lime or baryta. The lime or baryta water dissolves an albuminoid body, which is evidently the ce- ment substance of the fibrillfe. Hypermanganate of potash (Roilett) and a 10 per cent, solu- tion of common salt (Schweigger-Seidel), also cause this disso- lution of the inter-fibrillary intermediate substance. Although one series of connective-tissue textures behave similarly in this regard, others present a deviation. The co- rium may serve as an example. This is separated by the same treatment into stronger, apparently entirely homogeneous fibres^ which can only be split up into the longitudinally arranged fi- brillpe after a long-continued maceration (from 10 to 12 days) in lime- water. According to Roilett' s observations, the fasciculi of the scle- rotica, the aponeuroses, the fibrous capsular ligaments, the dura mater, and the interosseous ligaments, are formed after the type of the tendons. The examination of connective tissue by polarized light also speaks for the presence of the fibrillse. They are positively double refracting, and the optical axis lies in the longitudinal direction of the fibrillae. None of the reagents which maintain the fibrous appearance of the connective tissue alter the optical nature of the same to any considerable extent. On the con- CONNECTIVE TISSUE AND CARTILAGE. 283 trary, methods of treatment which render the connective tissue apparently homogeneous, also change the double refraction very much (W. Muller). The same arrangement as in the external skin is found in the conjunctiva, the subcutaneous cellular tissue, the submu- cous tissue of the intestinal canal, and the tunica adventitia of the vessels. The interweaving of the connective-tissue bundles, and the entire arrangement of a connective-tissue part, may be recog- nized in dried preparations by making coarse sections from them and simply softening these in water. Tingeing with car- mine may also be suitably employed. A finely punctated substance may be discovered in the transverse sections of the fasciculi, which many microscopists have declared to be the transverse sections of the connective- tissue fibrillse, as, for example, in the tendons. In order to demonstrate the cellular and elastic elements which occur between the fibriUse, reagents have been used for many 3 r ears which cause the fibrillse to swell, and at the same time lower their refractive power to such an extent that it be- comes equal to that of the water which is added. Thus is caused an apparent dissolution of the fibrillse, and the remain- ing elements of the connective tissue are rendered prominent, although the cells have undergone extensive modifications and disfigurations. This manner of action has been longest known in connection with acetic acid, but other organic acids may also be employed. Pyro-acetic acid has been frequently used for this purpose, sometimes undiluted, sometimes diluted with an equal volume of water. Mineral acids, such as nitric and muriatic acids, in a condition of extreme dilution, exert a similar effect. It is only necessary to neutralize the acid with ammonia to cause the fibrillse to reappear. The connective- tissue fibres also undergo the same swelling in alkalies as in these acids. As was the case with epithelium, the supplementary addition of water produces a rapid dissolu- tion of the fibres. In still another, much more conservative manner, namely, by employing a fluid medium of strong refractive power, the embedded structures may be recognized in the unswollen con- nective tissue. Glycerine is of the highest value in this regard. 284 SECTION THIRTEENTH. The swelling of the connective tissue from the above-men- tioned action of acids may give rise to peculiar appearances. In many portions of the body the connective-tissue bundles are invested like a sheath by a condensed substance. Now this expands to a much slighter degree, and consequently it is not unfrequently torn across and then more and more pressed together by the contained mass, which protrudes with a certain force, until finally, in consequence of the strong compression, it has assumed the form of a ring. This ring is very similar in appearance to that of an elastic fibre running in a circular direction, for which it has also frequently been mistaken. This phenomenon has been considerably discussed in former and more recent periods, and even Flem- ming, the latest and very capable observer, has not, in my opinion, been very fortunate in this direction. But enough about the fibrilhe. Let us inquire into the methods of examining the cells. A thin strip of interstitial connective tissue may be cut from the living body, and, after being moist- ened with lymph and enclosed in the moist cham- ber, examined. The appearances presented are in- structive ; but the wrinkling of such a lamella is a fatal circumstance, as every observer has experi- enced. We are therefore indebted to Ranvier, a French histologist, for the discovery of a new method. Artificial oadema is to be produced by injecting the tissue. Iodine serum, or a weak so- lution of the chromate of potash, for instance, may be injected into the subcutaneous or intermuscular connective tissue of a frog. A beautiful preparation may be obtained by rapidly placing a fine section of this gelatinous infiltrated mass on the slide under the covering glass. A weak solution of nitrate of silver (0.1 per cent.) is in a still higher degree qualified as an injecting fluid, as by this means the pale borders of the connec- tive-tissue cells are covered with a granular precipitate and thus rendered more distinct. Masses which become hardened, such as solutions of gelatine, are much preferable. Flemming, imitating Eanvier's process, made use of the glycerine-gelatine mentioned at page 216. That is : gelatine I, distilled water ■§, Fig. 143. A con- nective-tissue bun- dle from the base of the human brain, treated with acetic acid. CONNECTIVE TISSUE AND CAKTILAGE. 285 glycerine £. The mixture is heated to about 40° C, and about one-tenth of its volume of a 5 per cent, solution of nitrate of silver added. The parts are to be frozen by packing in ice. Sections are to be exposed to the light for about half an hour, and then tinged with picro-carmine. After about one hour the preparation is to be washed several times, and finally treated with water containing 3-4 per cent, of acetic acid. Formerly, the cellular elements were isolated by dissolving the intercellular substance. This readily succeeds, as the lat- ter becomes changed into gelatine. As is well known, connective tissue may be converted into gela- tine by treating it for a variable length of time with boiling water. This action is, however, altogether too energetic for histo- logical purposes. The softer connective tissue, at least, may be dissolved by other means in a much more conservative manner. After softening it for about a day in very slightly acidulated water, it may be dissolved in 24 hours by moderately warming Fig. 143. Spindle cell from the tendon of a hog's embryo eight inches long, a, cell with protoplasma ; b, connective-tis- sue fibrillar. Fig. 144. Soft connective tissue from the vicinity of the tendo Achillis of a human embryo of 2 months, a, spindle cells ; b, a very elongated one ; c, intercellular substance with fibrillar. the water to 35-40° C. At the muscular tissue we shall again have to speak of this procedure, which deserves a more ex- tended application. It would lead us too far to describe these artificially changed connective- tissue cells in this place. For the rest we refer to the two adjoining figures, 143 and 144, which were drawn from alcoholic preparations. 286 SECTION THIRTEENTH. Fig. 145. Various forms of human clastic fibres, #, unbranchetl ; /> and c, ramified. Coliuheim has very properly recommended the impregnation of connective tissue with gold. The great majority of the so-called elastic fibres (fig. 145) are undoubtedly of a sol- id nature, and all attempts to stain them with carmine fail. The great power of resistance which they pre- sent renders their exami- nation comparatively easy and simple. Parts which are very rich in elastic tissue re- quire a somewhat more careful preparation, fn this way the great exten- sibility of the finest fibres (a) will be noticed ; at the same time it will be seen that these fibres may as- sume the strangest con- volutions in the swollen connective tissue. Thicker elastic fila- ments prove to be much less extensible, and frequently present themselves as fragments (c). The fasciculi of a tendon of the external skin or of the sub- cutaneous cellular tissue may be employed for the first exami- nation of connective tissue. Do not spare the trouble of un- ravelling a very small piece in water or an indifferent fluid. For demonstrating the connective- tissue corpuscles, it is cus- tomary to use reagents which cause the tissue to swell, especi- ally acetic acid. Tingeing with carmine and hsematoxyline is also useful. Kanvier has also made us acquainted with a use- ful method of examining tendinous tissues. The extremely thin fibres from the tails of small mammalia, such as young rats, mice, and moles are used. If the last caudal vertebrae be torn from their attachments, a considerable length of the tendons remains connected with the separated parts. Their ends are to be fastened to the slide with sealing- wax, carmine is then to be employed, together with the usual supplementary treatment with acetic acid. The preparation may also be first left for a day in a one per cent, solution of CONNECTIVE TISSUE AND CARTILAGE. 287 osmic acid and then washed out and left for 24 to 48 hours in picro-carmine. It is subsequently submitted to various meth- ods of treatment, such as picking, longitudinal and transverse section. In consequence of the small size of the object, it is well to embed it, in gum arabic, for instance. The preparations, after treatment with acetic acid, are to be mounted in glycerine, either pure or containing formic or car- bolic acid. Elastic fibres become distinct after treatment with acids and alkalies, as well as after the action of solutions of fuchsin (von Ebner). An opportunity of studying them is presented in the sub- cutaneous cellular tissue, the corium, and the ligamentum nuchse of the mammalia. A more suitable object for learning the great diversity in the manner of appearance of elastic tissue can scarcely be found than the wall of a large artery from one of the larger mammalia, the various layers of which are to be separated with forceps and scalpel. Embryonic connective tissue (and many of the pathological new formations of our tissue, at a similar stage of organization and consistence, are to be enumerated here) is to be examined partly fresh in indifferent fluids, partly after the production of an cedema, and finally, although not so good, in preparations hardened by chromic acid or chromate of potash. In order to decide what is here present as elastic tissue (fig. 146), the use of alkalies, preferably boiling for a short time in a 10-15 per cent, solu- tion of potash, should not be neglected, as the connective-tissue corpuscles (A, a) are in this way made to disappear, but not the elastic fibres (B, c). Both elements react alike with acetic acid. At the commencement of this section we alluded to the im- portance, which is indeed very great, of connective tissue in pathological formative processes. We are prevented by the narrow limits of our little book from making more than a few Fig. 146. From the liga- mentum nucha? of a hog's embryo, S inches long. A, Bide view ; a, spindle cells in a fibrous basis substance b (alcohol preparation) ; B the elastic fibres brought out by- boiling in a solution of potash. 288 SECTION THIKTEENTH. remarks on this subject, which is now being so completely rev- olutionized. Although, until within a few years, it was generally con- sidered that pathological growths consisting of lymphoid cells were formed by the division of the normal connective- tissue cells, the emigration of the former elements from the blood passages has become prominent, in consequence of the Weller- Cohnheim theory. It is certain that this plays an important though not exclusive role, as, according to Strieker's experi- ence, a complete absence of participation cannot be ascribed to the neighboring connective-tissue corpuscles. At all events, in such difficult matters, one should avoid springing with incon- siderate haste from one extreme to the other, and thus entirely ignoring the physiological origin of the lymphoid cell. Such collections of cells may again disappear, the mass melting down and becoming "pus," in the old sense of the word. They may also become organized, that is, form new con- nective tissue accompanied by the growth of vessels in them, whereby the migratory cells are transformed into connective- tissue corpuscles and an interstitial substance which is split up into bands and fibres. Parts which have been divided are reunited in this manner, and then one speaks of cicatricial tis- sue. Loss of substance, occasioned by suppuration or ulcera- tive destruction, undergoes essentially the same restorative process. Luxurious growths of this unripe tissue, which is overloaded with lymphoid cells, constitute the so-called granu- lations. Hypertrophic connective-tissue formations are frequently found as a result of a continued distention of a part with blood, the so-called congestive and inflammatory processes, but likewise without any cause, spontaneous, as it is said. Thick- ening of the various integuments, the corium, the fibrous and serous membranes, etc., are to be enumerated here ; likewise interstitial growths between muscles, nerves, glands, etc. In these cases the microscopic examination shows an increase in the number of the cells and of the intercellular substance. The various tumors consist either entirely of connective tis- sue, or, together with other elements, have at least a connec- tive-tissue framework. The forms in which they appear differ extremely. In many we meet with an entirely undeveloped structure, resembling granulation tissue or that of lymphatic CONNECTIVE TISSUE AND CARTILAGE. 289 glands, as, for instance, in syphilitic tumors and in tubercle. Others, the polymorphous group of the sarcomata, constitute a transition to a more highly organized variety of our tissue. The latter belong, for the most part, to the fibroid or cellular tissue tumors. The lipomata are formed of connective tissue with collections of fat-cells, a pathological fat- tissue. New formations of gelatinous tissue also occur under various cir- cumstances and constitute the myxomata. The carcinomata or cancerous tumors, those enigmatical and most dangerous new formations of the body, are embedded, at least in the normal connective- tissue textures, and show, in conformity therewith, a framework consisting of a connective- tissue intercellular substance. In the sometimes larger, some- times smaller spaces of this framework lie embedded cells which may, in certain cases, resemble those of pavement epi- thelium, but generally, however, they present a character which does not thoroughly correspond to that of any of the normal cells, although they may have taken their origin from glandular or epithelial cells. These "cancer cells" are capa- ble of an unlimited, exuberant multiplication. It is customary to distinguish between certain forms of carcinoma. A tumor is generally called scirrhus (Faserkrebs) when there are only small collections of cells embedded in a firmly interwoven con- nective-tissue framework, so that the tumor possesses through- out the character of hardness and firmness. Inversely, one speaks of medullary carcinoma where large aggregations of cells occur in spaces of considerable size, the whole having a softer consistence, and the groups of cells forming masses of a butter-and-cream-like nature. If the cells have the appear- ance (but not the group-like arrangement) of pavement epithe- lial cells, we have one form of epithelial cancer, while the others have cylindrical cells, in both cases certainly descend- ants from the epithelial and glandular cells. If the substance of the framework presents a strongly marked fungous (alveo- lar) structure, and in the numerous spaces lie cells which are undergoing the colloid transformation, we have the alveolar or colloid cancer of the pathological anatomists. It is well known that sharp boundaries between these various forms of carcino- ma do not exist, that they frequently pass into each other, and that in one and the same tumor, some localities may be more of one character, and others more of another. 19 290 SECTION THIRTEENTH. Finally, let us inquire into the method of examining these abnormal connective- tissue structures. They are substantially the same as those which we have mentioned for the normal tissues. Sometimes one procedure, sometimes another will be necessary, according to the exceedingly variable consistence. In a fresh condition, and by the employment of truly indiffer- ent media, we may obtain satisfactory views of the cells and their transformations by picking, by scraping the cut surfaces, etc. Hardening methods (chromic acid, chromate of potash, and alcohol) are generally resorted to in order to ascertain the further arrangement. It is very well to place small pieces of such tumors, and if possible while still warm, in a considerable quantity of absolute alcohol. One may then proceed, even after a few hours, to the preparation of thin sections (Wal- deyer). Even here, tingeing with carmine and especially hsema- toxyline, shows many things very handsomely ; brushing leads to the isolation of the framework substances. Fine sections also constitute the most important means of ascertaining the re- lations of the so important region of demarcation between the normal and diseased connective tissue. It will be necessary to mount most preparations of connec- tive tissue in huid, if they are to be kept as permanent speci- mens. The first of Pacini's fluids (p. 217), also a solution of sublimate (1), salt (2), and water (100) may be employed. An- other mixture, consisting of sublimate (1), acetic acid (3). and water (300) is also well adapted for preserving, although the action of the acid makes itself felt. Gtycerine media will be resorted to, as a rule. If an untinged preparation is to be mounted, the glycerine is to be diluted with a larger quantity of water, so that the former may not become too transparent. Stained specimens permit of the use of a more concentrated glycerine. The latter preparations, for example a cornea, the section of a tendon or of a scirrhus, deprived of their water by means of absolute alcohol, not unfrequently present a very fine appearance when mounted in Canada balsam. 5. The examination of the cartilage tissue is very simple, as it has a degree of consistence which permits of thin sections being made without any further preparation. Cartilage which has been hardened in alcohol, chromic and picric acids also affords very characteristic and good specimens. Notwithstanding its consistence, cartilage is a tissue which CONNECTIVE TISSUE AND CARTILAGE. 291 requires foresight in the employment of fluid media, if one de- sires to have a view of the unaltered texture. Even ordinary water has a strongly alterative action on the cartilage cells, especially those of young animals. There are three varieties of cartilage to be distinguished : the hyaline, with a homogeneous inter- stitial substance (fig. 147) ; the fibrous or reticular, with a basis substance which is split up into bands (fig. 148) ; and fi- nally, the connective-tissue cartilage (tig. 149), in which a few cartilage cells are found between the bundles of connec- tive tissue. For the first examination a fcetal car- tilage may be used, the fine sections from which, in consequence of their trans- parency, require a certain shading of the field. A bone which is commencing to ossify may be used for studying the forma- tion of the daughter-cells. These cell formations may be met with, of an elegant appearance, close to the calcitied tissue. The articular cartilages of adults form very suitable objects, Fig. 14T. Hyaline cartilage. Fig. 148. Reticular cartilage from the human concha auris. a, cells ; 6, homogeneous zone ; c, elastic reticulum. Fig. 149. Connective-tissue cartilage. and the costal cartilages of older men (fig. 150) are especially useful for investigating the textural changes which occur in cartilage which is undergoing senile degeneration. Together with ordinary semi-transparent places (a) in the section, others will be discovered which appear more opaque with transmitted 292 SECTION THIRTEENTH. light, and with incident light they have a peculiar asbestos-like lustre. The transformation of the interstitial substance into a system of delicate fibres (c) running in a parallel and straight direction may also be seen ; one may also meet with large, often colossal moth- er-cells (d, e), with whole generations of daughter-cells, to which Donders call- ed attention many years ago. Such a costal cartilage af- fords an excellent opportunity for studying the vari- ous stages of thick- ening of the cap- sules of the carti- lage cells (/'). Frequent endeav- ors have been made of late to demon- strate a network of plasmatic canals (juice canalicules) permeating the car- tilaginous matrix. For this puipose use has been made of os- mic acid (Bubnoff, Hertwig), a ten per cent, solution of chromic acid, nitrate of silver (Heitzmann) — and, according to our opinion, only arte- facts have been described. Indigo-carmine, placed in the body of a living frog, permeates the cartilaginous matrix after a number of days (4 to 7) and subsequently undergoes granular precipitation in and around the cell body (L. Gerlach). Calcified cartilage tissue requires various methods of treat- ment, according to the quantity of calcareous molecules em- bedded in it. If the latter be but scanty, an ordinary watery medium suffices. If the calcification be more extensive, glycer- ine or Beale's mixture of alcohol and soda is to be used, in Fig. 150. Costal cartilage of an old man. a, homogeneous ; b, split up into bands ; c, fibrous interstitial substance ; <2, e, large mother- cells ; /, a mother-cell with considerably thickened capsule. CONNECTIVE TISSUE AND CARTILAGE. 293 consequence of its stronger refractive power. A stage of calci- fication soon arrives, however, in which even these reagents are no longer capable of rendering the opaque, dark preparations transparent. Various methods are here advisable. A one or two per cent, solution of chromic acid with a few drops of muriatic acid may be used (H. Mueller). Pyroligneous, lactic (p. 129), and picric acids (p. 132) are more serviceable. After the solution of the lime molecules, the preparation is rendered very intelligible by the addition of glycerine. We shall soon see, when speaking of the process of ossification, how important these methods are for the recognition of extremely difficult relations. The epiglottis or the cartilage of the ear is to be selected for the first examination of reticulated cartilage. In consequence of the opacity of the basis substance, the section cannot be made too thin. At the borders of such a preparation one not unfrequently meets with a few of the cartilage cells projecting more or less above the interstitial substance. In order to study the genesis of our tissue, select the auri- cular cartilage of mammalial embryos, which should be imbed- ded for the purpose of making thin sections (0. Ilertwig). Among reagents, the action of a one per cent, solution of osmic acid for an hour or two has been recommended. It colors the elastic elements dark. It is also tinged by a very dilute solution of the soluble aniline blue. Object tinged with carmine, and then, after washing out in acidulated water, treated with this preparation of aniline, show the cellular elements red, and the elastic blue in a colorless matrix (Ewald). The examination of connective-tissue cartilage requires the same methods as connective-tissue. The intervertebral ligaments are to be selected for demon- strating the varieties of cartilage in a small space near each other. The polarizing microscope teaches us that cartilage likewise belongs to the double refracting tissues. We are not as yet sufficiently enlightened with regard to the direction of the op- tical axis. Recently, by means of energetic reagents, the apparently homogeneous substance of hyaline cartilage has been com- pletely reduced to a system of thick rings or area? surrounding the individual cells or groups of cells ; and in this manner the 294 SECTION THIRTEENTH. origin of these basis substances from the cellular elements has been proved beyond all doubt (Heidenhain, Broder). In order to obtain this important appearance (fig. 151), the cartilage may be digested in water, at a temperature of from 35 to 50° C. ; it may be exposed to the action of diluted sulphuric acid (1 : 25), or the fa- miliar mixture of nitric acid and chlorate of potash may be used. We would especially recommend the latter, particularly the com- bination of 80 ccm. of nitric acid of 1.16 sp. wt. with an equal quantit} 7 of distilled water, fig. i5i. Thyroidcar- and the addition, at an ordinary temperature, Hlage of the swine. The „ „. . , , „ , basis substance is divid- of sumcieiit cliiorate of potash to saturate. ed into cell-districts by . „ „ , , , . , , . means of chlorate of pot- Alter a few days the desired reduction will ash and nitric acid. -, -, ,-i .-n •, be obtained, and the appearances will be ren- dered very beautiful by tingeing with aniline-red or carmine. According to Landois' experience, these areas are even rendered distinct by tingeing with fuchsine sections of cartilage which have been deprived of their water by means of alcohol. How- ever, even without any artificial interference, the central por- tion of the cartilage of the ensiform process of the rabbit usu- ally presents the same appearance of the basis substance (Remak). It affords excellent view 7 s, the best and most in- structive with which I am acquainted. There are various means for dissolving the interstitial sub- stance of cartilage. This is effected by immersion for several hours in a concentrated solution of potash. The same object may be accomplished by immersion for four hours in sulphuric acid containing an atom of hydrate water, and the subsequent addition of water. The means most commonly used, however, is a long-continued boiling in water. While the cartilages of small embryos undergo this solution after several hours even at a moderate temperature, the older tissues require, with the ac- cess of air, to be boiled for 12, IS, sometimes 24 to 48 hours. If the cartilage which is being treated in this manner be ex- amined at each stage of its decomposition, one may recognize the obstinacy with which the cartilage cells themselves resist the boiling temperature, and that in none of their parts do they contain any gelatine-producing substance. Even when the en- tire basis substance is dissolved one may meet with numerous cells tioatimr in the fluid. CONNECTIVE TISSUE AND CARTILAGE. 295 The capsules of the cartilage cells also resist the effects of the boiling water more energetically than the interstitial sub- stance, so that the chondrogenous matter of the latter is in no wise to be regarded as being the same as that of the capsules. The substance of reticular cartilage shows the extraordinary insolubility of the so-called elastic tissue. Pathological cartilage tissue is not a rare occurrence. It appears as an inflammatory new formation in chronic arthritis and in the formation of callus ; but, as a rule, such cartilagi- nous tissue makes its appearance in the form of tumors, the so- called enchondromata. The textural conditions of such carti- laginous tumors present different appearances, the same as in the normal tissue. Thus the basis substance may appear homogeneous (and this is predominantly the case), in places it may form an elastic framework, or, finally, it may have a con- nective-tissue character ; not unfrequently one may meet with all three of these varieties of cartilage in the various parts of one and the same enchondroma. It would be superfluous to enter further into the considera- tion of the methods of examination ; they are the same as for the normal tissue. Various fluids have been recommended for preserving pre- parations of cartilage. Even distilled or camphor water renders good service. Glycerine, strongly diluted with water (2 parts water. 1 part glycerine), also acts advantageously, at least in many cases. Harting sometimes employs creosote water (p. 220), sometimes a solution of sublimate (1 part to 2-500 water). I have also used the latter fluid with success. Furthermore, the sublimate in combination with phosphoric acid (sublimate 1, phosphoric acid 1, and water 30) has also been recommended (p. 218). According to my present experience I would here prefer the Farranfs fluid. Cartilage strongly tinged with car- mine or hjematoxyline, and deprived of its water by means of absolute alcohol may be mounted in Canada balsam with ad- vantage. Section jFottrtctntt). BONES AND TEETH. We consider these two members of the connective- sub- stance group in a special chapter because they require peculiar methods of investigation, in consequence of their hardness and density. There are two kinds of preparatory treatment of the bones and teeth, according as one desires to preserve these parts with their inorganic elements or deprived of the same. Let us first speak of the latter. The removal of the bone earths is best effected by the meth- ods already mentioned in connection with calcified cartilage tissue (p. 293). The older process, the use of dilute muriatic and nitric acids, appears less suitable. Whether the one or the other process is adopted, changing the fluid and a certain patience are necessary. Always make use of very small pieces of tissue. The methods mentioned produce decalcification while the organic substratum becomes swollen. The immersed object will be seen to become gradually paler and more flexible, and finally to resemble cartilage in appear- ance and consistence. The action of the acid is now to be dis- continued, and the bones or teeth carefully washed out with water. The parts which have thus been decalcified, or — to use a badly-selected expression — the bone and tooth cartilages, then permit of the same methods of examination as cartilage tissue proper. These methods are most to be recommended for all investigations where it is necessary to obtain a large series of views with economy of time and labor. Dried speci- mens may be decalcified in this manner as well as those which are fresh, taken directly from the body. Bones in the latter condition, treated with chromic acid, show at the same time BONES AND TEETH. 297 ^ the substance which fills their canals and cavities, the me- dulla. Decalcified in the same manner, the texture of the dentine and also of the cement may be well recognized, but not that of the enamel, in consequence of the considerable amount of min- eral elements which it contains. Naturally, more energetic measures are necessary if it be desired to isolate the walls of the canaliculi and lacunae together with the cell remnants, that is, the bone corpuscles of the bone and the dentinal tubes of the dentine. Virchow showed how to liberate the bone corpuscles in this way, years ago. A thin piece is to be removed from a fresh bone and either simply macerated in muri- atic acid or boiled, in a decalcified condi- tion, in distilled water, or (which is pref- erable) in a solution of soda. A period then arrives in which the tissue assumes a pulp-like softness. Preparations which are now examined (fig. 152) show us, es- pecially if a slight pressure be made on the covering glass, the bone corpuscles to- gether with their processes and nuclei protruding from the dis- solved basis substance. Occasionally, some of these may be entirely isolated in this way (a, c, d). That they may have undergone considerable changes in consequence of this ener- getic treatment is sufficiently obvious. Forster has made us acquainted with another method of iso- lation by means of strong nitric acid. Thin pieces of the dried bone or tooth are to be placed in concentrated or but slightly diluted nitric acid, to which a little glycerine is added. The desired effect is obtained after a series of hours, sometimes not till the following day. Even bones in which all the soft parts are destroyed yield a similar appearance with the same treat- ment (Neumann). A maceration in strong muriatic acid, likewise a protracted boiling of the piece of decalcified bone in a Papin's digester, also causes the destruction of the interstitial substance and the isolation of the bone-corpuscles with their systems of pro- cesses. Thin scales of bone fall to pieces after the action of Fig. 152. Remains of the bone- corpuscles with, their boundary layer, from the decalcified sh:ift of the femur, after boiling in a solution of soda, abc, corpuscles containing nuclei (at 6, an adhe- rent residue of the basis sub- stance) ; d, a bone-corpuscle with, a crumbled nucleus. 208 SECTION FOURTEENTH. diluted solutions of potash or soda for half a day or several hours. A more accurate examination of our bone-corpuscle now shows that its form may be likened to that of a plum pit. To demonstrate the bone-cells proper (fig. 153), however, very thin scales of fresh bone, and especially such as are carefully tinged with carmine or hsematoxyline, are necessary. These (b), surrounded by the already mention- ed elastic boundary of the basis substance («), represent the bone-corpuscles of the foregoing woodcut. The impregnation with gold has also been recommended for the recognition of the bone- cells. The thin bones of the cranium of the water salamander, after an immersion of from one hour to an hour and a half in a 1 per cent, solution, and a subsequent reduction in acidulated water, yield good specimens in from one day to a day and a half. The adherent soft parts may be scraped from the bone Fig. 153. Bone-cells from the fresh ethmoid bone of the mouse, tinged with carmine, a, limiting layer ; &, cell. while it is in the gold solution. Even fragments of large bones permit of this treatment (Joseph). The walls of the dentinal tubes of dentine may also be iso- lated by similar methods. In fragments of fresh teeth one may see these tubes occupied by a system of soft fibres (fig. 154, c), which latter rep- resent the processes of the dentinal cells of the tooth-pulp, or the so-called odonto- blasts (b) (Tomes). An entirely different procedure is ne- cessary for the examination of the calcare- ous tissue of the bones and teeth. Thin plates must be sawed from the bone and ground on a stone till they have become as thin as paper, and have acquired the transparency necessary for their examination. The whole procedure requires time, is troublesome, and therefore, as a rule, it is shunned by microscopists. However, with a little perseverance, one may obtain excellent and uninjured prepara- tions. The desired object may be accomplished in various ways, and there are numerous methods extant for producing sections Fig. 154. Two dentinal cells, b, which pass with their proces- ses through a portion of the dentinal canals at a, and pro- trude from the fragment of den- tine at c ; after Beale. BONES AND TEETH. 299 of bones and teeth. We will here communicate to the reader a procedure which leads to the production of very beautiful specimens, and the outlines of which were given a few years ago by Reinicke. A fine saw, the blade of which is made from a watch-spring and is held by screws, is employed for sawing out the plates of bones or teeth. The bone or tooth is to be firmly secured in a vice. Brittle objects which are liable to splinter are to be pre- viously wrapped in paper. After sawing out the plate, it is to be ground on a small ro- tary grindstone, the handle of which is to be turned by the left hand while the plate is pressed by the fingers of the right hand on one of the flat surfaces of the stone. The stone is to be kept moistened by means of a trough placed under it containing water. If this tolerably inexpensive apparatus is not at hand, the first excess may also be removed with a file. In order to obtain a smooth surface, the thin preparation is now to be placed on a fine flat whetstone, such as is used for sharpening razors ; in this way, held by the fingers, it may be further ground on both surfaces. This may also be accom- plished between two such whetstones, and indeed more rapidly. Small objects are to be previously cemented on to a glass plate with Canada balsam ; ether serves best for loosening the bone and for removing the remains of the balsam. The bone may also be very conveniently cemented with red sealing-wax, and the adequate thinness of the section may finally be recognized by the liveliness with which the red shines through it. The sealing-wax is to be dissolved with strong alcohol. The prepa- ration is then to be cleaned in water, either with a earner s-hair brush or a soft tooth-brush, and dried. If the grain of the whetstone is sufficiently fine, nothing further is necessary. If one desires to obtain a better polish, one may employ a glass plate or a piece of soft leather which is nailed to a fiat strip of wood, and which is smeared with tripoli or some other polishing powder. A beautiful polish may also be produced in a short time with fine emery paper. A preparation obtained in this way — for example, a transverse section (fig. 155} — presents a charming appearance. The various general or fundamental lamellse (a, d, b) may be recognized passing throughout the entire bone, and the transverse sections of the Haversian canals, with their special lamellae (c) surrounding them, as well as the 300 SECTION FOURTEENTH. innumerable so conspicuous lacunae with their canaliculi (e), may also be seen. To obtain these appearances, however, the latter system of canals must be dry and rilled with air. A section which is sufficiently §TlfL"'^^^: :£r5|§ thin presents this appearance with- out any addition, and in this con- dition it may enter the collection as a permanent preparation. Very handsome preparations are obtain- ed by melting the sections into a resinous substance. Ordinary fresh Canada balsam is not adapted for this purpose, as, in consequence of the slowness with which it hardens, the air escapes more or less com- pletely from the section. In order to obtain a good medium for mount- ing, proceed in the following man- ner : — A quantity of fresh Canada balsam is to be poured into a watch- glass, and placed, with a bell-glass over it, on a warm stove for several days, until the Canada balsam has become quite hard and solid. With this, and by strongly heating the glass slide, the sections of bones and teeth may be mounted without dis- placing the air, especially if the preparations are exposed to the cold immediately afterward. There is still another, much more convenient and better process. The lamella of bone may be sur- rounded with a warm solution of filtered gelatine. When this has cooled and dried, any resinous mounting material suffices. If, on the contrary, it be desired to bring the lacuna? and canaliculi filled with fluid into view, in the form of cavities, oil of turpentine is to be used in the examination ; and for mounting permanently, fresh fluid Canada balsam. Tingeing with carmine and luematoxy line may precede as a useful acces- sory (fig. 156). Fig. 155. Transverse section of a human metacarpal bone. cells. a, muscular fibres ; 6, rows of fat- cells. Fig. 184. Fatty degenerated humau muscular fibres, a, slighter ; b, increas- ed ; c, highest degree. ened the greatest interest among physicians and laymen ; we refer to the occurrence of trichinae in the transversely striated muscular tissue. The trichina spiralis, these small forms of nematodes, are, as is well known, eaten with the flesh of the hog, and, after a few days, they arrive at a condition of sexual ripeness in the human intestinal canal, so that we now meet with examples of some- what larger females (measuring more than V") and smaller males (intestinal trichinae). About a week after the transplanta- tion they produce a multitude of very small living young ones, which, after perforating the walls of the intestines, And their way into the muscles. Here they force themselves through the sarcolemma into the fibres of this tissue, in which they increase considerably in size, so that they ma}" obtain a longitudinal di- mension of from J- to %'" (muscular trichinae). All the transversely striated muscles, with the exception of MUSCLES AND NERVES. 333 the heart, serve as a location for these small parasites, whose number may not unfrequently become extraordinarily large, in consequence of repeated immigrations. Nevertheless, the muscles of the jaw and neck and the diaphragm are distin- guished as favorite localities. The tendinous extremity of the muscles — obviously because there is here a mechanical impedi- ment to further emigration — usually shows the greatest abun- dance of the dangerous guests. The little worm devours a portion of the fleshy mass beneath the sarcolemma of the muscular fibre, where it gradually rolls itself up in a spiral manner. Around this a capsule (fig. 185) is gradually formed, which requires months for its completion. While this is taking place, we see the muscular corpuscles of the neighborhood increasing luxuriously and forming a more compact internal investing layer, to which the thickening sarcolemma is also associ- ated as an external layer. The form aud size of the capsules vary, we meet with r „ ,.-. incapsuiated w- oval (more rarely cask-shaped), spindle, and jES^^iS <" r lemon-shaped forms, generally with consid- erably thickened extremities. The length is usually 0.2, 0.3, 0.5'". The calcification of the capsule, which commences in the internal portions, begins late (scarcely before the expiration of a year). This process, with its further development, renders the whole thing visible to the unaided eye as a white point, which was not the case with its earlier phases. The trichinae were first discovered many years ago, in just this latter con- dition, in which the parasite may preserve its extremely tenacious life for many years in the calcified capsule. The examination of muscles infected with trichinae is very easy. Thin sections made in the direction of the fibres, with or without picking apart, will show the presence of the worms when examined in the ordinary fluid media, with the addition of acetic acid or alkalies. A magnifying power of about 40 diameters suffices for the first examination ; for more accurate investigation one of 150 or 200 should be used.* In invalids, * This object may be accomplished with ordinary and therefore cheaper micro- scopes, with which the several enlargements mentioned in the text may be obtained. 334 SECTION FIFTEENTH. where trichuriasis is suspected, fragments of muscle may be removed, from the body with a small harpoon-shaped instru- ment. For the microscopical examination of the flesh of the hog, a number of very thin, as large as possible, sections should be taken from the muscles of various parts of the body, but especially from the chief localities of the parasites. Only injected muscles, or those intended for polarized light, are to be mounted in Canada balsam for preservation. Suitable tinged preparations imbedded in Thiersch's colophonium afford excellent views. Objects which are destined to show the finest textural relations must, naturally, be mounted in glycerine diluted with water. The elements of the nervous system are marked by exceed- ingly variable qualities, so that in their investigation numerous precautionary measures become necessary. We distinguish, as is taught by every hand-book, white and gray substance. The former consists exclusively of one of the two elements of tubes or fibres, called nerve- tubes, nerve-fibres, primitive fibres of the nervous system. In the gray substance we meet with the second element, together with a sometimes slighter, sometimes greater quantity of the nerve-fibres. This second element, the ganglion-body, ganglion-cell, or nerve-cell, is generally a large cellular structure with a vesicular-shaped nucleus. The other constituents consist of connective substance in various stages of development, and blood-vessels. In order to see the nerve-tubes, which consist of an albumi- nous central fibre, the so-called axis cylinder ; of a peculiar substance surrounding this, the nerve-medulla or the medullary sheath ; and of a very fine envelope surrounding the whole and holding it together, the primitive sheath or the sheath of Schwann, in as unaltered a condition as possible, we cannot proceed too rapidly, and must, at the same time, avoid almost all preparatory manipulation. For this reason, there are but few parts of the bodies of vertebrated animals which afford suitable objects. The cornea of a small mammalial animal just With this optical apparatus, the weaker power should show distinctly the larger scales of the lepisma saccharinum (p. 61), while the stronger combination should afford a satisfactory image of the smaller forms of the scales of this insect, with their longitudinal and oblique lines. Some of the modern "trichina microscopes" fulfil these requirements in a satisfactory manner, but a quantity of the most miser- able trash has also been put in circulation. MUSCLES AND NERVES. 335 killed, for example, that of a rabbit or of a mouse, may be ex- amined on the warm stage without the addition of any fluid medium. The cornea should be incised at its margin. A very fine form of nerve-fibres will here be met with. The frog affords better preparations ; its transparent eyelid shows larger tubes, isolated or lying together in bundles. The tails of their larvae permit the observation to be made on the living creature. Quite fresh, unaltered nerve-fibres should present the ap- pearance of entirely homogeneous, opaline, cylindrical fibres, in which there is no trace of any further composition to be recognized. The addition of iodine serum is here to be recom- mended. If we take a nerve from the body of an animal recently killed and pick it in water with needles, notwithstanding the greatest rapidity of manipulation, it is no longer possible to obtain the natural con- dition ; on the contrary, its appearance is more or less changed ; there is an alteration of the medullary sheath which it has been agreed to call a coagulation. Our fig. 186 may represent the com- mencement of this coagulation. In the beginning it gives the nerve-fibre a darker contour. Soon, however, we see a thin peripheral layer coagulated and separated by a second, more internal and finer line from the central portion of the medulla, which is not, as yet, drawn within the sphere of these changes. But to present these "double contours" the nerve- tubes must have a certain thickness (a, b). If the transverse diameter falls below a certain size, the tubes then and afterwards appear with only simple contours (c, d, e), but at the same time they readily assume a peculiar appearance, — they become "vari- cose," as it is called. Further changes render the coagulated peripheral layer broader, and frequently show an irregularity of the inner con- tours. The process may here become stationary ; the coagu- lated portion protects the internal, still uncoagulated medulla to a certain extent. But generally this is also drawn into the Human nerve-A- broad ; 6, medium ', d, e, fine. 336 SECTION FIFTEENTH. sphere of the changes ; the previously homogeneous appear- ance is lost ; a few lumpy formations make their appearance in it and increase in number and size ; not unfrequently the whole becomes a granular, crumbling mass. But all nerve-tubes do not behave in exactly the same way ; we may meet with them lying close beside each other, showing various phases of coagu- lation. We have not yet perceived anything of the axis-cylinder and the delicate envelope. The so-called nerve-medulla is a mixture of peculiar sub- stances of cerebrine and lecithine, with a very changeable body belonging to the albuminous group. We shall therefore un- derstand why reagents, such as strong alcohol, concentrated chromic acid, a solution of corrosive sublimate, and many others which have a coagulating effect on albumen, should also produce the more advanced phases of coagulation almost instantaneously. For the same reason it is unnecessary to state that such a coagulated nerve-medulla, by the addition of alkaline solutions, such as those of potash or soda, again assumes a more fluid and homogeneous condition, and exudes from the cut ends of the nerve-tubes in the shajje of double-contoured, fat-like drops and filaments. If strong pressure be made with the covering glass on the nerve-tubes, treated in this manner with alkalies, the medulla may be forced out of many of them, and in this way the empty, homogeneous, extremely delicate primitive sheath may be seen. If careful search be made among the nerve-iibres, which have been isolated by picking a nerve-trunk apart, a few will be met wi th in which their contents have been somewhat displaced, in consequence of the pulling and the pressure of the prepar- ing needle ; and the sheath, which is generally collapsed, may also be recognized for a short distance. It was frequently denied, at a former epoch, that the axis- cylinder was an integral constituent of the nerve-tubes, and this was quite proper, for, with the accessories then employed, it could only be brought to view in an isolated condition. At the present day it is a small matter to demonstrate these fibres in all nerve-tubes ; and we have the choice between several methods. For the demonstration of the same, Schulze's reagent, the MUSCLES AND NERVES. 337 mixture of chlorate of potash and nitric acid, may be employed (Budge and Uechtritz). Chloroform renders good service (Wal- deyer), and collodion is very excellent (Phiiger). A fresh nerve is to be picked apart on the slide, without any addition of fluid. A large drop of collodion is then to be added, the cover- ing glass placed over it, and the examination made immediately. The nerve- tubes rapidly become more and more pale, and, instead of the dark medulla, only a few granules are to be seen enveloped by the distinct primitive sheath. This becomes contracted, and thus fre- quently shows a series of extremely char- acteristic invaginations. The axis-cylin- der appears in each tube as a pale fibre. During the contraction of the nerve-fibre it frequently appears to be too long ; and not unfrequently, under the eye of the ob- server, it shoves itself through the axis to- wards the periphery, and protrudes as a fibre from the cut extremity (fig. 187, b). This interesting appearance may be followed in this manner for a short time, but it soon undergoes further changes, and often becomes entirely unserviceable in a quarter of an hour. I afterwards found in aniline red of the above-mentioned (p. 154) strength a new accessory for the demonstration of the axis - cylinder in fresh medullated tubes. Frog's nerves, picked apart and placed in the solution, show in from 4 to 12 hours the beautifully reddened axis-cylinders glistening through the fatty enveloping mass. Still other methods permit of the recognition of the axis- cylinder in a beautiful manner. Thus, after a longer treatment with strong alcohol or ether, it may be rendered visible in the tubes deprived in this way of their fat. A solution of subli- mate and Moleschott's acetic acid mixture also afford good specimens. Chromic acid preparations (or those obtained by means of chromate of potash) present very beautiful appear- ances. Long, hardened filaments frequently project from the cut extremities (e). Fig. 187. Various nerve-fibres. a, after treatment with absolute alcohol ; b, with collodion ; c, fibre of the lamprey ; d. of the olfactory nerve of the calf ; e and /, nerve-fibres from the human brain. 338 SECTION FIFTEENTH. Impregnation with various metals has also been used re- cently for demonstrating the axis-cylinder. Nitrate of silver (fig. 188, e) either gives it a uniform dark color, or causes it to as- sume a peculiar transversely striated appearance, reminding one of muscular fibre (Frommann, Grandry). The chloride of gold, recommended by Cohn- heim (if successfully employed), shows the axis-cylinder shining bright-red through the dark-red medullaiy substance ; it after- wards appears blackened. Osmic acid, on the contrary, very soon blackens the nerve- medulla, while the axis-cylinder remains colorless or only slightly browned (M. Schultze), so that we possess in our re- agent an excellent accessory for deciding the presence or absence of the medullary sheath of the peripheral ramifications of the nerves (b, c, (I). We have another interesting condition to mention here. Years ago we were fam- iliar with constrictions in freely exposed nerve-fibres, after the manner of our fig. 188, a. We all considered them, at that time, to be accidental phenomena, products of the preparing needle. Ranvier recently learned their regular occurrence, and showed in the most certain manner that, between every two of these con- strictions, the " constriction rings " {Selinur- ringen, as we have happily translated the word into German), a cell nucleus always occurs. The investing and isolating medullary sheath of the nerve-fibre is regularly wanting at the constriction ring ; the axis-cylinder is here naked and freely exposed to the inter- change of material. Treatment with osmic acid with subse- quent hsematoxyline tingeing (b, c, d) is best for the demonstra- tion. We have finally to mention the recognition of the axis-cyl- inder in transverse sections of previously hardened nerve- trunks ; this is also of particular interest in still another regard. If a human or mammalia! nerve be immersed for a short time, Fig. 188. Nerve-fibres of the frog. t(, after treatment with picro-carmine ; b, c, rf, with osmic acid ; e, with ni- trate of silver. MUSCLES AND NERVES. 339 ..■/jj i • : ■ * li'33 ■ M if m 1 first in chromic-acid solution of 0.2, then in one of 0.5 per cent., it will attain such a consistence as to permit the finest trans- verse sections to be made with a sharp razor. These, tinged with carmine, are to be deprived of their water by means of absolute alcohol, and, after soaking in turpentine, mounted in Canada balsam. Then, the medulla having become transpar- ent, the axis-cylinder may be recognized as a small reddened circle, surrounded by transparent medulla, which forms a sin- gle or multiple circle around the axis cylinder (a condition to which attention was called several years ago by Lister and Turner, and which it has not as yet been possi- ble to explain), and finally the whole is found Hi to be surrounded by the simple contour of the transversely divided primitive sheath. Formerly, the axis-cylinder was generally regarded as a homogeneous structure, although there has never been any want of manifold testimony to its more complicated formation. Newer, more conservative methods, show that it is with great probability composed of the finest fibres, the axis fibrillje of Waldeyer or the primitive fibrillse of M. Schultze (fig. 189). The white substance of the brain and spinal cord serves best for their recognition in niedul- lated nerve-fibres. The fresh object may be examined in blood-serum with very strong magnifying powers, but it is preferable to macerate for a day or more in iodine -serum. Osmic acid (f-4 per cent.) renders excellent service. After a short action the axis-cylinder becomes sufficiently hardened without any granular opacities, and shows the longitudinal markings very distinctly, especially when freed from the medullary sheath (Schultze). Medullated tubes are not shown by all the nerve-trunks in man and the mammalia, however. The fibres of the olfactory nerve (fig. 187, cl) all appear pale and nucleated, and by proper treatment may be resolved into a bundle of the finest primitive fibrillse. In the ramifications of the sympathetic nervous sys- tem of man and the higher vertebrata, there also occurs, inter- mingled with medullated nerve-tubes, a system of pale, nucleated 1 I l 1 i I Fig. 1S9. Fibrillated arrangement of the axis- cylinder, after Schultze. a, a thick axis-cylinder from the spinal cord of the ox ; 6. nerve-fibre from the brain of the torpedo. 340 SECTION FIFTEENTH. fibres, which bear the name of Remak's fibres, after their dis- coverer, Remak (fig. 190, b). Considerable controversy has arisen as to their nature, whether nervous or of connective tis- sue ; but at the present time there is no further doubt as to their nervous constitution. Indeed, in the earlier embryonic periods, all nerve-tubes appear pale, non-medullated and nu- cleated. Finally, in the lower vertebrata, all the nerve-tubes may remain through life at this stage of development, as, for instance, in the lamprey, of which such a nerve is represented by our fig. 187, c. For the examination of these pale, nucleated fibres, the fresh tissue may be employed, with picking and perhaps the Fig. 190. Sympathetic nerve-branch. Two medul- latedj nerve-tubes (a), sur- rounded by numerous fibres of Remak (6). Pig. 191. Ranglion-cells of the mammalia. A, cells with connective-tissue envelopes, from which spring Remak's fibres d, a ; a, a cell without a nucleus; o, two single nu- cleated ones ; and c, one with two nuclei ; B, a ganglion body without an envelope. addition of a weak acid. A longer immersion in very dilute acetic acid (about 20-fiO ccm. water, with a few drops of hy- drated acetic acid) is preferable. A maceration in weak solu- tions of chromic acid and of chromate of potash, of the degrees of concentration given by Schultze (comp. above, p. 12S), also produces very beautiful specimens. Osmic acid is more suitable. Chloride of palladium has also been recommended by Bidder. I recommend tingeing with luematoxyline or picro-carmine for demonstrating the nu- clei. The examination of the nerve-fibres in polarized light shows the interesting fact of a double refracting positive sheath, and MUSCLES AND NERVES. 341 a likewise double refracting but negative medulla. The long axis of the primitive fibres and the optical axis coincide. Val- entin, to whom we are indebted for this interesting result, re- marks that we may thus, with the aid of the polarizing appa- ratus, distinguish the me- dullated from the non- medullated nerve- tubes. We have now to speak of the examination of the second elementary form of the nervous system, the ganglion- cells (figs. 191, 1 Q9^ Fig. 192. A multipolar ganglion-cell from the gray sub- "/ ' stance of the human brain. These appear as cells of considerable size, although subject to great variation in this regard, with large, round, vesicular nuclei and a rather thick, very finely granular, sometimes colorless, sometimes pigmented cell-body, which usually hardens into a thin rind at its periph- ery. Accessory envelopes are found covering these ganglion bodies in the peripheral ganglia, and are either (as is generally the case in the lower vertebrates) a homogeneous membrane or a thicker, nucleated, connective- tissue substance, which shows numerous nuclei imbedded in it, and not unfrequently runs out into thread-shaped processes presenting the appearance of Eemak's fibres. An epithelium-like lining on the inner surface of these envelopes is of interest. Nitrate of silver, or the method of impregnating with gold indicated by Gferlach (p. 168), may be employed for demonstrating the latter. The first incomplete view of the ganglion bodies maybe ob- tained either by selecting a small ganglion, for example, a spinal ganglion of a frog or a mouse, and carefully picking it apart with sharp-pointed needles, with the addition of an in- different fluid medium, or a thin section from a larger fresh ganglion may be subjected to the same treatment. Naturally, by this procedure, numerous divisions of the connection take place, and the absence of a sufficient insight into the arrangement of the whole is felt. To obtain these, places should be selected in small creatures where microscopic ganglionic swellings occur on fine nerve-branches, which may be viewed in their totality without preparatory manipulation. ft 342 SECTION FIFTEENTH. For this purpose the frog stands in the first line. The small 1 imbedded ganglia, frequently consisting of only a few cells, which may be recognized on the cardiac nerves in the septum of the ventricles, or on the branches of the sympathetic system, afford admirable specimens. Schwalbe praises the spinal gan- glia of the lizard. A very dilute acetic acid may here be used with advantage. Strongly diluted phosphoric acid has also- been recommended for this purpose. The relation of the nerve-fibres to the ganglion bodies is of great importance. As is known, the opinions of investigators have undergone great changes in this regard of late years, and even at the present time we are far from meeting with coin- ciding or even similar views. Although it was at first considered that there was but a simple juxtaposition of both elementary forms in a ganglion (Valentin), connections of the ganglion-cells with the nerve- tubes were afterwards frequently observed (Wagner, Eobin, Bidder, and others), and the doctrine of bipolar, multipolar, unipolar, and apolar ganglion-cells founded. This is not the place to test the correctness of these various opinions, and we must refer on this point to the text-books on histology. The several animal groups are of very unequal service for ascertaining the origins of such fibres by means of picking. The scanty admixture of a soft, loose connective tissue with the nervous elements of a ganglion facilitates the acquisition of this knowledge very much. A more plentiful admixture of a firmer, interweaved connective-tissue formation either ren- ders the isolation difficult to a high degree, or makes it entirely impossible. The cartilaginous fishes (rays), therefore, form extremely favorable objects in the former regard, and many- osseous fishes are, at least, serviceable. The bodies of the naked amphibiae are less suitable, and the ganglia of man, the mammalia, and birds are scarcely to be mastered with the preparing needles. Suitable ganglia, for example, those of the trigeminus, vagus, and the spinal nerves of the pike and the burbot (Gadus lota) may be picked apart either fresh or, which may not be called unserviceable, a few hours, 10-15, after death. A pre- paratory maceration for a day in dilute chromic acid (0.1-0.5 per cent.) may also be employed. We also recommend the trial of a method indicated by J. Arnold, which affords good MUSCLES AND NERVES. 343 results, at least with the frog. The ganglion is to be placed for four or five minutes in acetic acid of 0.3-0.2 per cent., and then for twelve to forty-eight hours in a 0.02-0.01 per cent solution of chromic acid. The preparatory treatment with a very dilute solution of chloride of gold (0.005 per cent.) has also been used (Bidder). Notwithstanding every precaution, numerous fractures and lacerations are unavoidable. Hardening in chromic acid or in chromate of potash may also be used with the higher ver- tebrates. In such cases one should begin with weak solutions of the acid, of 0.2-0.5 per cent., change them frequently, and gradually increase the concen- tration. The chromate of potash is employed in corresponding quantity (comp. p. 136). The ganglia thus hardened permit of very thin sections being made with a sharp razor, which are to be examined in glycerine diluted with water. One will thus be able to recognize appearances, for instance, in a sympathetic ganglion of a mammalial animal, which come near to our fig. 193, which is indeed drawn somewhat diagrammatically. Multipolar cells (d, d) are, as it seems, of very frequent occurrence in the sympathetic ganglia of the mammalia, in contradistinction to those of the lower verte- brata, in which bipolar and unipolar constitute the rule. The ganglion-cells of the sympathetic of the rabbit and the guinea- pig appear to have two nuclei. More recently we have become acquainted with other suita- ble methods. These sections of chromic-acid preparations may be placed for 12-24 hours in a solution of osmic acid (1 per cent.), in which the nerves become blackened. The solution of the chloride of palladium (1 : 500) is still better, however, because it hardens and colors at the same time. Even after 24 hours (if the fluid has been changed in the meantime) the ganglion may show a blackish-gray color and be ready for Fig. 193. A sympathetic ganglia of a mam- malial animal. The medullated nerve-tubes of the three trunks, a, b, c. pass through a profuse, nucleated fibrous tissue ( Remak's) ; d, multipolar ganglion-cells; at d*, one with a dividing nerve fibre ; e, unipolar. /, apolar cells. 344 SECTION FIFTEENTH. preparation. If the cut surface is still yellow, a further action till a following day is then sufficient. Very instructive ap- pearances result, as the connective tissue is pale, the ganglion- cells yellow-brown, and the nerve- fibres blackish (Schwalbe). These hardened ganglia may be examined in still another way. The sections are to be stained, then de- prived of their water by means of absolute alcohol, and oil of turpen- tine added. If the brain of a small mammal, a rabbit, or a guinea-pig, be thoroughly injected from the arch of the aorta with carmine gelatine, the Gasserian ganglion, after deli- cate staining with carmine, affords excellent specimens of this kind. Within a short time another in- teresting structural condition has been observed in the ganglion-cells of the sympathetic of the frog (fig. 194). From the cell (a) — and from the central portion of its body — arises a straight fibre (c, e) (axis cyl- inder), in which a nuclear forma- tion is not unfrequently remarked. These are surrounded by one or sev- eral spiral fibres, which likewise pre- (d). They originate from the surface of the cell Fig. 194. Ganglion-cell from the sym- pathetic of the hyla or green-tree frog (after Beale). a. cell-body ; &, sheath ; c, straight nerve-fibre ; and d, spiral fibre ; continuation of the former, e, and of the latter, /. sent nuclei body. This was the condition which Beale found in glycerine prep- arations tinged with carmine. Arnold, an able investigator, who made use of the method * mentioned at p. 342, states that * In a second article the author communicates new and more complicated meth- ods for the investigation of these ganglion -cells. To isolate the spiral fibres in the greatest possible length, immerse them in 5 ccm. of nitric acid of from 0.01 to 0.02 per cent. Even after Ave to ten minutes the structure of the ganglion-cell becomes clear. After an immersion of from twelve to twenty-four hours, however, these fibres may be followed very far into the nerve-trunk, and be seen to become true nerve-fibres. Chloride of gold also colors both varieties of fibres, the straight as well as the spiral. Immerse the tissue in 4-5 ccm. of a 0.02-0.05 per cent, mixture MUSCLES AND NERVES. 345 both varieties of fibres arise from the nucleolus of the ganglion- cell. I could not convince myself of this, and am inclined to regard Beale's spiral fibre as elastic. Nevertheless, by this the possibility is not to be denied that, in the bipolar ganglion- cells, where both nerve- fibres arise close to each ^ \ % other, the one may sur- round the other with con- volutions. Remarkable ganglionic apparatuses of microscop- ical fineness have recently been discovered in the walls of the abdominal viscera. To these belong the gan- glia in the submucous con- nective-tissue of the diges- tive apparatus (fig. 195), discovered by Meissner, and then investigated by Reniak, Manz, Kollmann, Billroth, and others. Like- wise the plexus rr^entericus, pointed out by Auerbach, a highly developed ganglionic net-work between the two muscu- lar layers of the intestinal canal. The examination of these submucous nerve-ganglia has for the most part been made with the aid of maceration in pyro- acetic acid. But many observers (Billroth, for example) have committed the fault of allowing this reagent to act in much too energetic a manner, and were therefore able to describe arte- factions only. Portions not too large, taken from the fresh body, are to be placed in purified pyroligneous acid diluted Fig. 195. A ganpdion from the submucous tissue of the intestinal canal of a child ten clays old (pyroacetic acid preparation), a, ganglion ; b, its radiating nerve branch- es ; c, injected capillary net-work. of 1 per cent, acetic acid and chloride of gold and potassa. When the first traces of a violet color make their appearance (after about three to four hours), the main trunk of the sympathetic is to be placed in 10 ccm. of acetic acid of the above- mentioned strength. The color has become intense in from four to five days, and the connective tissue remains light and loose. A microscopic preparation, to which acidulated glycerine has been added, is now to be placed on a white surface, and exposed to the action of day- or sun-light for the further reduction of the gold. After four to five days the straight nerve-fibre has become bright red ; the thickest of the spiral fibres also present the same appearance, while the finer ones only gain an in- tense color on the eighth or tenth day. 346 SECTION FIFTEENTH. with one or several times its volume of water. After one, two, or three days the examination should be attempted on vertical sections, or the isolated submucous tissue (likewise surface sec- tions of the latter made with the scissors), in order to recognize the horizontal ramifications. A certain attention is always necessary in this case, because exactly the proper degree of maceration must be employed in the investigation, and an excessive action of the pyroacetic acid soon follows. The py- roacetic acid may also be replaced with very dilute acetic acid. One may also succeed, for example, in the new- born child, in demon- strating this ganglion- ic plexus (tig. 196, 1) in the fresh intestinal canal, with the cells (a) and the pale nerve- fibres (b, e). Fine ver- tical sections may be employed, or (which has proved to be more suitable) a portion of the intestine may be well stretched, and the muscular layer and the mucous membrane carefully dissected from both sides, so that the submucous connective tissue remains isolated. Even without any further addition, one may, with some pains, discover a few ganglia, but as soon as the connective tissue has been rendered transparent, by means of very dilute acetic acid, the whole arrangement may be readily seen. Simple chromic acid preparations also fre- quently afford good specimens, at least in vertical sections. The ganglionic plexus mentioned has been, in an almost in- comprehensible manner, asserted to be a capillary net- work. All doubt may be removed by injecting a portion of intestine with Prussian blue or sulphate of baiyta, and immersing it in pyroacetic acid (fig. 195, c). The plexus myentericus (fig. 197) of the larger mammalia and of man is only to be recognized with difficulty and pains, in consequence of the thickness of the muscular coat. Macera- Fio. l'.)f». 1. A large ganglion from the Bmall intestine of a child 10 days old. a, the ganglion, with the ganglion cells ; o, c. efferent nerve-branches, with pale nucleated fibres in a fresh con- dition. 2. Such a nerve-trunk from a boy 5 years old, with three pale primitive fibres, treated with pyroacetic acid. MUSCLES AND NERVES. 347 tions in dilute pyroacetic acid or acetic acid, also appear to constitute the best accessories. The demonstration succeeds very readily, on the contrary, with smaller animals, such as rabbits, but especially with guinea-pigs, rats, and mice. A portion of the small intestine, still better of the colon of a guinea-pig, immersed in purified pyroacetic acid diluted with several times its volume of water (20 to 15 per cent.), will after 24 hours (or even sooner) have acquired such a swollen and Fig. 197. Plexus myentericus, from the small intestine of the Guinea-pig. a, nervous plexus ; &, gan- glia ; c, lymphatics. macerated condition as that the mucous membrane may be readily removed. If the thin muscular and serous layers be now immersed in watery glycerine, and placed under the microscope with a low magnifying power, a surface view of the whole elegant nervous apparatus (a, b) may be at once ob- tained. We have since become familiar with better methods. L. Gerlach has recently investigated this nerve-plexus more accurately. Those animals are best adapted in which the slightly developed longitudinal muscular stratum can be read- ily drawn with the serosa away from the transverse layer, as, for example, guinea-pigs, rabbits, doves. The plexus myenter- icus then remains adherent to this longitudinal layer. This result may be accomplished even in fresh objects, but better with such as have remained for 12-24 hours in dilute solutions 348 SECTION FIFTEENTH. of bichromate of potash or in a 10 per cent, solution of com- mon salt. In other creatures, such as the sheep, hog, man, this mechanical separation succeeds imperfectly, even after the object has remained in these solutions for days. The prepara- tions are to be colored in acid carmine, and finally placed in acidulated glycerine. In order to isolate the ganglion-cells of our plexus, let a 10 per cent, solution of common salt act on this stratum for 8-10 days, changing the fluid daily. Objects which have been treated with osmic acid may also be macerated in glycerine. The best views are furnished by the guinea-pig. In addition to the coarse plexus, the plexus myentericus presents a finer network of nervous cords. To demonstrate the latter, place the detached muscular membrane for three or four days in solutions of bichromate of potash of about 1 : 300, and remove them to a chloride of gold solution of 1 : 10000. They remain in the latter till the margins of the preparation have a weak violet color. This should occur in 6-8 hours. The object is then to be washed out, deprived of its water and mounted in a resinous medium. The structure of the central organs of the nervous system, the spinal cord and brain, is so complicated and obscure, and at the same time the subject of such frequent controversy, that it would lead us far beyond the limits of this book if we were to enter at all into the details of these textural condi- tions. We therefore limit ourselves chiefly to the description of the methods of investigation generally employed at pre- sent. These may be divided into two series : first, such as are in- tended for isolating the elementary structures ; and then the others, which are to harden the central organs to such a degree as that thin sections may be conveniently made from them, and thus an appreciation of the entire arrangement obtained. It is hardly necessary to remark that a thorough promotion of our knowledge requires the combination of both these methods of investigation. The older investigators frequently attempted to examine the ganglion-cells and nerve-fibres in picked preparations of portions of brains and spinal cords, which were as fresh as pos- sible, as well as of those which were not so fresh. The delicate nervous structures are too intimately united by the connective- MUSCLES AND NERVES. 349 tissue framework, however, for one to hope to find more than their fragments. And, in fact, we have more recently discov- ered much better and more productive methods. The highly diluted solutions of chromic acid, and of the bichromate of potash, recommended by Schultze, as well as the process re- cently practised by Ranvier, the preliminary injection of a 0.33 per cent, solution of osmic acid into the fresh gray sub- stance of the brain, constitute accessories of the first rank, as they exert a partly macerating, parti y hardening effect on the various elements of these organs, without producing any deeper textural changes. The reader would deceive himself, however, if he were to regard the successful application of the solutions as a relatively easy affair. Even after following certain directions, selecting only fresh, preferably still warm organs, and especially those of the larger mammalia, such as the ox and calf ; furthermore, not to place too large pieces in a relatively small quantity of fluid ; there are, nevertheless, many difficulties still remaining. Next arises the problem of hitting upon the proper degree of concentration of these fluids, and this, lying within pretty nar- row limits, requires careful experiment, as further differences present themselves according to the warmth, nature, and age of the animal. Solutions which, to the ounce of water, contain more than 0.1-0.125 gr. of the chromic acid, or more than 2 grains of its potash salt, are absolutely objectionable. Even much higher degrees of dilution are frequently employed with advantage. Let us listen to Deiters, the most competent of the modern investigators in this department of technology. He recom- mends the immersion at first in a solution of chromate of pot- ash, which contains 0.5 gr. to the ounce, till the second day, whereby the desired result is not unfrequently obtained. If the latter has not yet taken place, or if it be desired to preserve the preparation for a few days longer, this solution may be doubled in strength for an additional day, and then increased to 2 grains for another twenty -four hours. Not unfrequently weaker than half-grain solutions are to be preferred. Thus, one may commence with 0.125 and 0.25 gr. and then terminate with 0.5 gr. ; or solutions of chromic acid may be first em- ployed, and then its salt, whereby greater looseness of the pre- paration is obtained. The strength in which the chromic acid 350 SECTION FIFTEENTH. is employed is from 0.033, 0.05 to 0.1 gr. to the ounce. Two days are to be allowed to pass without changing the fluid ; on the third day it is to be renewed. Now, occasionally even sooner, a very good degree of maceration for many parts is ob- tained. For the combination of both these methods it is rec- ommended, after using the chromic acid for two days, to place the piece in a 0.5 gr. solution of chromate of potash, then on the following day in one of 1 gr., afterwards perhaps increasing the strength to 2 grs. After this, to obtain a considerably ma- cerated condition of the framework substance, such objects may be advantageously exposed to the action of extremely dilute solutions of the alkalies. A drop of a 28 per cent, solu- tion of caustic potash may be added to the ounce of water ; after having been exposed to this for an hour, the preparation is to be removed and washed (in dilute chromic acid, for in- stance), then replaced in the solution of chromate of potash, which should contain at first 0.5, the following day 1, after- wards perhaps 2 grs. to the ounce. The simpler of these methods, or a combination of them (it is better to employ several of them simultaneously), will, to- gether with many failures, also afford suitable objects for ex- amination, although they only continue to be serviceable for a few days. It is best to remove a small portion of the tissue with the point of a knife, and pick it apart as carefully as pos- sible. With such accessories Deiters succeeded in making a re- markable discovery concerning the multipolar ganglion-cells of the central organs. They (fig. 198) have two kinds of pro- cesses. The greater proportion of the latter are only continua- tions of the same protoplasma-like substance which is presented by the body of the ganglion-cell. These processes, the "pro- toplasma processes''' of Deiters, divide into manifold ramifica- tions, until at last they disappear as the finest terminal branches in the supporting substance. At the first glance an exceedingly long process (a) may be distinguished from the protoplasma processes, which arises either from the cell-body itself or from one of the broadest of the former processes ; it never presents any ramifications, and is afterwards covered by a medullary sheath. Deiters has called it the "axis-cylinder process." Finally, one may also recognize, passing off at right angles from the protoplasma processes of our multipolar ganglion-cells, MUSCLES AND NERVES. 351 extremely fine filaments (5, 5), which the above-mentioned in- vestigator believes to be a second system of extremely fine axis-cylinders. Still another method has recently been recommended by Gerlach, an investigator who has accomplished much for micro- scopical technology, for isolating these ganglia and a very fine nervous net-work (that is, their proto- plasma processes) connected with them (of which, according to his views, the gray substance of the spi- nal cord consists). Thin longitudinal sections are to be made with a razor, preferably through the region of the an- terior horns of the quite fresh and still warm spinal cord of a mammalial animal. These are to be placed for 2-3 days in very weak solutions of the bichromate of am- monia (0.01-0.02 per cent.). They are then to be placed in a like- wise extremely dilute ammoniacal solution of carmine, which produces the neces- sary tinge in about a day. Those portions which are thinnest and best tinged are then to be carefully picked apart. Still another complication of the structure of these ganglion- cells of the central organs has been observed. According to Schultze's investigations, both varieties of the processes of the Fig. 198. Multipolar ganglion-cell from the anterior horn of the spinal cord (of the ox), with the axis-Cylinder process (a), and the branched protopiasma processes, from which at b the finest fila- ments arise (after Dciters). 352 SECTION FIFTEENTH. central ganglion-cells (fig. 199) present a fibrillated structure ; this is most distinct in the axis-cylinder (a), however, while in the protoplasma processes (b) there is a greater quantity of agranular intervening substance. The " primitive fibrillsQ " (p. 339) may be followed into the body of the ganglion - cell, where they are seen to have a complicated course. This arrangement, first noticed by Remak, may be observed without dif- ficulty in fresh speci- mens simply moistened with serum, or in osmic acid preparations. Frommann asserts that he has ascertained by treatment with ni- trate of silver, that these fibrilla? originate in the nucleoli and are sur- rounded like a sheath by tubes which proceed from the nuclei. Arnold also informs us of sim- ilar results. He used serum or chromic acid (0.01 per cent.) and elim- inate of potash (0.02-0.05 per cent.) as fluid media. These points will have to be decided by future investigations. It was supposed, many years ago, that the nerve-fibres origin- ated in the nucleolus and nucleus of the ganglion-cell (Harless, Axinann, Lieberkuhn, Gh Wagner), The art of giving the substance of the brain and spinal cord a consistence suitable for making sections has been possessed for many years. Alcohol, the solutions of chromic acid and of the bichromate Fig. 199. Ganglion-cell from the anterior horn of the spinal cord of the ox, after Schnltze. a, axis-cylinder ; ft, cell-pro- cesses. MUSCLES AND NERVES. 353 of potash, and ammonia are used for hardening. Whether the one or the other of these fluids is used, only pieces of the brain and spinal cord which are quite fresh and carefully removed from the recently killed animal and deprived of their envelopes, should ever be immersed in them. The pieces should not be too large. If their volume be too large, the exterior may acquire a good consistence, but the central portions will, on the contrary, remain soft or even become decomposed. I would recommend, as a useful method, to allow such pieces to float in a tall glass cylinder, suspended by means of a silk thread to a hook in the glass stopper. Betz subsequently confirmed this. Among the reagents mentioned, alcohol takes the lowest place. Preference has therefore, for many years, been given to solutions of chromic acid and the chromate of potash. Here we must also censure the custom of estimating the strength of these solutions only by their color. Now and then the proper degree of concentration may be obtained in this way ; but in many cases one will be deceived and fail in obtaining the de- sired result, which might have been accomplished with less trouble by making an accurate solution. Now, what degree of concentration should be given to such solutions ? Here it must be remembered that the fluids used by former observers were generally much too strong, so that a considerable shrinking of the tissues took place, and not unfre- quently the whole became entirely too brittle to permit of a section being made. A chromic acid solution of 1 per cent, is certainly too strong for commencing the hardening. I have obtained good results with mammalial animals as well as with cold-blooded vertebrates, such as fishes and frogs, when I com- menced the hardening with solutions of 0.2 per cent.; then changed the chromic acid after a few days, replaced it by a stronger solution, and thus finally arriving at those of 1 per cent. Bichromate of potash is to be used in the corresponding strength of 2-6 per cent. (comp. p. 136). Heifers employed the following method for hardening the brain and spinal cord : He first im- merses the preparation for one or two weeks in a solution of the chromate of potash (15 grains to the ounce of water). Then (when a uniform saturation has taken place and the hardening has commenced) the preparation is placed either immediately or after washing out the potash salt, in a solution of chromic 23 354 SECTION FIFTEENTH. acid which contains 2 grains to the ounce and may be increased to 3 grains. Gerlach recommends the use of a 1-2 per cent, solution of the bichromate of ammonia for at least fifteen or twenty days, occa- sionally for five weeks. It is impossible to state anything definite with regard to the time which is generally required for the hardening. Chromic acid salts act more slowly, the free acids more rapidly. I have often found that the spinal cord of small animals has become sufficiently firm in a week in these solutions of the free acid. As a rule, a space of three to four weeks, not unfrequently still longer — six weeks or more, is necessary. There is great varia- tion, however, in this regard. Reissner is therefore correct in asserting that the central parts, especially the spinal cord of the various kinds of animals, also show differences in regard to the time which is requisite to harden them. It is generally stated, it is true, that the hardening takes place more rapidly with small animals than with those which are larger. This is, how- ever, by no means universally the case, as, according to his ex- perience, the spinal cord of the calf becomes hard in weaker solutions than does that of the rabbit, the mouse, or the rat. To ascertain the proper degree of consistence, nothing further is necessary than to make a trial section with the razor from time to time. The hardening should have progressed in exactly such a manner as that with the moistened blade, a very thin layer may be removed conveniently and without crumbling. If the tissue crumbles it is already overhardened ; if the consis- tence is insufficient, only thick sections are possible. In the latter case a further immersion is necessary ; in the former, the procedure is a failure. If one has been so successful as to have obtained the proper consistence, the hardened object is to be placed, after having been washed, in weak watery alcohol. It may be preserved in this for a long time without undergoing any changes, to serve for future investigations. With some practice and a good razor one soon learns to make marvellously thin sections. In doing this, the object is to be held with the points of the first three fingers of the left hand, and care is to be taken to keep the preparation and the blade sufficiently moistened with alcohol. It is impossible to hold very small objects, such as the spinal cord of a mouse, for MUSCLES AND NERVES. 355 instance, with, the points of the lingers. They may be placed in a larger animal booty, the spinal cord of a larger animal for instance, or in a piece of elder pith ; or an embedding method (p. 113) may be employed. Sections may be cut with the free hand, or an ordinary microtome (p. 108) may be used. Sections made in all directions are naturally necessary, in order to construe from the various preparations the structure of such central parts as the spinal cord, for example. Trans- verse sections are first made, then longitudinal ones, of which vertical and horizontal longitudinal as well as oblique (that is, such as are made, for instance, from the right posterior cornua towards the left anterior cornua) sections are of importance. Those which are made oblique to the long axis of the cord ap- pear to be of less importance. For most examinations it is advantageous to tinge the sec- tions thus obtained. Staining with carmine is nowadays gen- erally employed in these cases, and, according to our experi- ence, it is of the first rank for such things. Here, as with all delicate tissues, I employ a solution of carmine obtained with a minimum of ammonia, which is to be considerably diluted with water, and then an equal volume of glycerine added. The sections are to be washed out in very di- lute alcohol, to free them from any chromic acid which may be present, and then placed in the solution to acquire the desired redness, for which two, four, eight to twelve hours is necessary, according to the concentration of the coloring medium. The object is next to be placed for a short time in clean water to wash out the superfluous carmine, then in water very slightly acidulated with a few drops of acetic acid, or in dilute alcohol thus acidulated. The diffuse redness disappears, and the remaining carmine is then fixed to the cells, nuclei, and axis- cylinders. If individual differences occur with regard to the capability of imbibition of the tissue elements of the brain and spinal cord, the epithelium, ganglion bodies, axis-cylin- ders, and the nuclei of the connective-tissue framework are to be designated as those parts which become especially impreg- nated with the coloring matter. Hfematoxyline also furnishes very excellent specimens ; unfortunately, like all objects which have been treated preliminarily with acids, they perish rapidly. Aniline blue deserves to be recommended (p. 156). Preparations thus treated may be examined in a moist con- 356 SECTION FIFTEENTH. dition. Glycerine may then be used to increase their trans- parency. The preparation may be rendered more permanently trans- parent, however, by immersing it, after it has been carefully and cautiously deprived of its water, in oil of turpentine or Canada balsam. This method is the most popular at present, and also affords the most beautiful and most durable prepara- tions for a collection. We refer for it to page 212 of our book.* We would here earnestly recommend the alcoholic resinous solutions (p. 213). Metallic impregnations were then tried. I would not advise osmic acid, having accomplished nothing with it. Beautiful but, unfortunately, perishable preparations are occasionally obtained with chloride of gold. Several years ago Gerlach praised the treatment with chlo- ride of gold and potash as an excellent means of rendering the course of the nerve-fibres in the spinal cord visible. Fine transverse sections are made from the spinal cord after it has been hardened by immersion for 3-6 weeks in a solution of the bichromate of ammonia. The sections are to be placed for 10 or 12 hours in a 0.01 per cent, solution of the gold salt to which a little acetic or muriatic acid has been added. Then (when the white substance has gained a pale lilac color, and the gray presents but a slight tinge), the section is to be washed with a to-and-fro movement, continued for several minutes in very dilute li3 r drochloric acid (1 : 2-3000). Gerlach now places * We here add several other methods : — 1. Years ago Lockhart Clarke, who was afterwards imitated by Lenhossek, made use of the following process : The fresh spinal cord is to be hardened in alcohol ; the first day it is to be placed in such as is diluted with an equal volume of water, then left in pure alcohol until thin sections are possible, a condition which is generally obtained, in the cooler portion of the year, in from 5-G days. The sections are then to be immersed for 1-2 hours in the mixture mentioned at page 139, consisting of 1 part acetic acid and 3 parts alcohol. In this, not only the nerves and fibrous ele- ments are rendered more sharply prominent, but the gray substance is also rendered quite transparent. 2. J. Dean, to whom we are indebted for a very superior work on the central or- gan, hardens in alcohol or chromic acid, and colors the washed sections moderately in glycerine-carmine, in which they remain from 4-8 hours, according to the intensity of color desired. Alcohol, oil of turpentine, and Canada balsam are then employed. According to Dean, thick copal varnish is often preferable to the balsam for the rec- ognition of flue details. Dean also praises Clarke's method highly, and, we will add, very appropriately, if the mixture is allowed to act on tinged preparations. MUSCLES AND NERVES. 357 it for about 10 minutes in a mixture of 1 part muriatic acid and 1000 parts alcohol of 60 per cent., and afterwards, finally, for a few minutes in absolute alcohol. Oil of cloves serves to render the section transparent, and it is then mounted in Canada bal- sam, which terminates this somewhat complicated process. To render the ganglion-cells visible, it is necessary, before immers- ing the preparation in the gold salt, to employ one of the other methods of metallic impregnation for several hours, such as that with chloride of palladium (p. 168), or, which the author prefers, to make use of a very dilute solution of a metallic salt which has not been previously employed in histology, the nitrate of uranium. Henle and Merkel stain alcohol preparations with molyb- danate of ammonia* (p. 137) ; chromic acid objects first with chloride of palladium and then with a stronger carmine solu- tion, which here acts very rapidly, coloring the medulla yellow and the axis cylinder red. Betz, finally, recommends the following method (in which iodine is used for the first time) : The preparation is first placed for days in a 70-80 per cent, alcohol, which is colored light brown by the addition of iodine. As the tissue becomes impregnated with the latter material, the subsequent addition of drops of a strong alcoholic solution of iodine is necessary. The arachnoid and pia mater are to be removed during the first few days. After this merely preliminary hardening, place the object in a 30 per cent, solution of bichromate of potash, taking such precautions as may be necessary to prevent the preparation from rising and swimming on the surface. It is allowed to stand in a cool jjlace, and the several portions of the spinal cord harden in unequal periods. After washing out in water place them in a 0.5-1 per cent, solution of this salt, where they may remain for months. The sections (of spinal cord or cerebellum) are deprived of their water for a few days, tinged with carmine, again deprived of their water in alcohol which is gradually strengthened, and * The authors use the following process : 1 vol. of a concentrated solution of the molybdanate of ammonia is diluted with 1-2 vols, of distilled water. Then add the point of a knife-full of iron-filings and so much officinal muriatic acid as suffices to produce a dark blue, almost black color (a brown color is useless). After ten minutes, filter. 12-15 hours are necessary for staining. 358 SECTION FIFTEENTH. finally in absolute alcohol, then rendered transparent in resin- ous turpentine, and, finally, mounted in a solution of gum dammar in turpentine. We must refer to the original for further details. Schiefferdecker places the spinal cord for about a month continuously in Mueller's fluid, then places the preparation in water for a da}-, and again hardens it in alcohol. The sections are placed either in a solution of chloride of palladium (l : 10- 000) or one of chloride of gold (1-5 : 10000). The durability of these preparations is, unfortunately, limited. With industry and perseverance, and by the aid of the methods of preparation which have been given, one may suc- ceed in recognizing the more important textural relations of the spinal cord (those of the brain with greater difficulty),* whereby, as was remarked, the examinations should commence with transverse sections. At the same time one will also recognize the great difficulty of accurately describing the tex- tures of the central organs — a difficulty which is founded in part on the nature of the object ; in part, also, on the methods of investigation, which still remain insufficient. Many observ- ers have certainly exaggerated the results of their investiga- tions very much, frequently drawing very false conclusions from fragmentary isolated appearances. Other investigators have, however, become infected with an excessive skepticism. Attempts have even been made to disprove the reticulated commissural communication of the large multipolar ganglionic bodies in the anterior cornua of the spinal cord, as also the continuation of some of their processes into nerve-fibres of the anterior motor root. In our opinion these textural conditions may be observed with entire certainty, although only with difficulty and on very rare occasions. To obtain injected preparations of the brain and spinal cord, one should proceed in the following manner. One of the * Betz uses a somewhat modified method for the cerebrum divided through the corpus callosum. It is first placed in tincture of iodine highly diluted with water to a light brown color. After standing in a cool place for 24-48 hours, remove the pia mater as carefully as possible, add to the old fluid about half its quantity of alcohol containing iodine, and reimmcrse the brain for 24-72 hours. To complete the hard- ening, place it for 10-14 days in 70 per cent, tincture of iodine, and, finally, in a 4 per cent, solution of chromate of potash. Well-hardeued brains permit of making very large and very thin sections with the aid of special microtomic apparatus (Betz, Oudden, Schiefferdecker). MUSCLES AND NERVES. 359 smaller mammalia, a rat, a Guinea-pig, a rabbit, or a cat may- be selected, and the cannla inserted into the commencement of the aorta, after this vessel has been ligated below the carotids and the snbclavians. The injection readily succeeds on the fresh body (with some loss of injecting fluid, it is true) with cautious management of the syringe. But to judge of the cor- rect moment for terminating the procedure is somewhat diffi- cult. If a white rat or an Albino rabbit has been used, the complete injection of the ej-eball affords a criterion. To inject the upper half of the spinal cord, the aorta is to be ligated as it passes through the diaphragm, and the procedure completed as above mentioned. Deep-red carmine-gelatine constitutes the best injection fluid. Alcohol is used for hardening, and hfematoxyline for staining the sections. Prussian blue is to be preferred, if it be desired to accomplish the former with chromic acid, and an acetic acid solution of carmine for subse- quent tingeing. Key and Retzius have recently investigated the serous and lymphatic spaces of the brain and spinal cord. They injected colored fluids, by a constant and low pressure, beneath the dura mater or the arachnoid. Further information may be obtained from the hand-books on histology. A further difficulty in the investigation of the central organ of the nervous system is found in distinguishing the connec- tive-tissue framework (neuroglia) from the nervous elements. Although the tacit presumption, that everything which is present in the brain and spinal cord must also be of a nervous nature, was accepted for many years, the extensive occurrence of a connective-tissue substance, in which the nervous tissue elements are imbedded, was afterwards rightly maintained by Bidder and his followers, although with some exaggeration. There is repeated in the brain and spinal cord, therefore, one of those undeveloped, reticular connective substances, such as have been frequently observed of late in the human body — one of those reticulations and frameworks with cell-bodies in some of the nodal points. In the white substance this is of a more compact structure, and appears in transverse sections as a net-work with isolated nuclei and round apertures for the reception of the nerves (fig. 200). The reticular connective tissue in the cortical layer of the 360 SECTION FIFTEENTH. Fig. 200. The con nective • tissue frame work from the poster! or column of the hu man spinal cord. white substance passes uninterruptedly into the pia mater, where it is more richly developed and the reticulations become very much liner. The reticular framework of the gray substance of the spinal cord likewise appears to be extraordinarily del- icate, and frequently the meshes are extremely T^mH^IO^ ^ ne ' This also appears extremely developed and with distinctly radiated connective-tissue cells in the interior of the so-called central thread of ependyma. Such a supporting substance certainly oc- curs in the brain also, although not so well known (fig. 201). In the gray substance of the cortex, the net-work, which has nuclei in its nodal point, as- sumes an infinite fineness and delicacy of its fibres and meshes, so that its existence has frequently been totally denied. Methods of maceration, such as were recommended by Deiters (p. 349), serve for the recognition of these framework substances, which are also extremely important for the pathol- ogists. The action of nitrate of silver on segments of the fresh tissue, with a subsequent addition of glycerine, has also been used with success (Frommann) : likewise osmic acid. For the examination of the gray substance of the brain, Ranvier recommends the following process : Inject a solution of osmic acid (1: 300) into the tissue, pick this apart after an hour or two in distilled water and stain with picro-car- mine. The connective-tissue elements and the ganglion-cells show with equal perfection. Grerlach recommends the two methods of treat- ment with chloride of gold and potash and car- mine, mentioned above (p. 356), for distinguish- ing the neuroglia of the gray substance from the very fine net-work of nerve-fibres which also occurs there. Only the nervous elements, but not those of the connective tissue, become colored. For the diagnosis of nervous and con- nective-tissue cells in them, a suitable reagent is still wanting. Tumor-like new formations of the framework substance mentioned occur in the central organs and in the retina. They have been called glioma (Virchow). Fig. 201. Porous tissue of the eray substance of the hu- man cerebellum ; ob- tained with extreme- ly dilute chromic acid. MUSCLES AND NERVES. 361 Fig. 202. Amyloid cor- puscles from the human brain. A deposit of peculiar structures, frequently discussed of late, the so-called amyloid bodies, corpuscula amylacea (fig. 202), takes place in this framework substance after death, as a result of decomposition, and even during life in abnormal conditions. These, varying in size, occur as globular, ovoid, or double-loaf-shaped structures, in which a distinctly stratified appearance may frequently be recognized under the micro- scope. In these cases they remind one very much of amylon granules, for which they have also been mistaken. Their reaction may be that of amylon, taking a blue color with a solution of iodine. Others, on the contrary, assume a violet hue from the action of iodine and sulphuric acid (see p. 132), and put one in mind of cellulose. The best and finest results, a beautiful blue and red tingeing, are presented by the aniline iodine violet recently recommended by Jiirgens (p. 155), per- mitting of a distinction from a starch granule. In addition, let it be re- marked that similarly reacting masses may also make their appearance in many other parts of the body, and an amyloid degeneration has con- sequently been recently as- sumed. As we are at present re- ferring to chemical matters, let us also at the same time mention the so-called myeline. It appears under the micro- scope in the form of double contoured drops and lump- like masses, and is also not limited to the nervous sys- tem. Our fig. 203, in its lower half, may afford us a representation of this optical peculiarity of that substance. The upper portion of the drawing is occupied by crystals of cholesterine, a pecu- liar substance, widely spread throughout the animal body Pig. 203. Crystals of cholesterine and deposits of myeline. 362 SECTION FIFTEENTH. (which has also been more recently discovered by Beneke and Kolbe in plants). This cholesterine forms an element of the nerve-substance ; it also occurs in the blood, though in small quantity, more abundantly in the bile (and especially in the biliary calculi) ; likewise in most of the other animal fluids, with the exception of the urine. Finally, it occurs in patho- logical fluids and tumors, and has the signification of a product of decomposition. It occurs in very delicate, thin, rhomboidal tables (with acute angles of 79° 30', also of 87° 30', and of only 57° 20'), and is thus for the most part readily recognizable. It likewise shows certain characteristic reactions. If a mixture of 5 parts of sulphuric acid (of 1.85 sp. wt.) and 1 part of water be added to the crystals of our substance under the microscope, a pecu- liar change of colors takes place. The borders of the tablets become carmine red, then, with a commencing dissolution into drops, violet. If iodine and sulphuric acid be applied, pure cholesterine assumes a blue ; impure, a violet, reddish, or vari- egated color. The whole affords a beautiful microscopical image, but is, as a rule, without any practical value, as the shape of the crystals is for the most part entirely sufficient for the recognition of cholesterine. We have, finally, to mention the methods of investigation which are used at present for the recognition of the termina- tions of the nerves. These vary exceedingly, according to the constitution of the part to be investigated, as, together with the examination of the freshest possible and the altered elements, there is also an innumerable quantity of methods employed which vary with the parts of the body. Let us commence with the manner of termination of the motor nerves, especially those in the transversely striated mus- cles. The tissue taken from an animal which has just been killed is to be first employed, as, immediately before the rigor mortis takes place, the muscular filaments present a considerable de- gree of transparency, which soon gives place to a more cloudy condition. In such investigations the object is to be examined either without any fluid medium, and covered with a thin glass scale only (which may, at the most, be very carefully pressed upon, to give a smooth surface), or with the addition of indif- MUSCLES AND NERVES. 363 ferent fluids. Only certain, especially thin membranous mus- cles, are adapted for such investigations. The orbital muscles of small mammalial animals, and among these the retractor bulbi (of the cat), also the psoas muscle of these animals, fur- thermore the flat muscles which pass from the hy- oid bone to the lower jaw of the frog, and the cuta- neous thoracic muscle of this ani- mal, the very short muscles in the tail of the lizard, etc., may be advanta- geously employed. One may also, without trouble, succeed in obtain- ing appearances like our fig. 204, with suitable pre- parations, from the frog. The di- vision of the dark- bordered primi- tive fibres into me- dullated branches, and their contin- ued splitting up intO finer dark Fig. 2(M. Kadiatlon of the nerves In the voluntary muscles of the tog. 1 « , A nerve-fibre, a, without a neurilemma, with repeated subdivisions into OneS, may be IOl- several smaller branches, b, b : c, a nerve-fibre with a neurilemma of , -. .. the simplest kind, without division. lowed, until at last fine terminal branches appear to end in the muscular fila- ments. It was believed for many years, in fact, that we had thus penetrated to the ultimate terminal branches. A series of investigations lately undertaken shows that these earlier views are at all events untenable, and that the nerve-dis- tribution takes place beyond these alleged terminal branches. 304 SECTION FIFTEENTH. The results of the observations instituted by Kuhne, Margo, Kolliker, Rouget, Krause, Engelmann, and others do not, how- ever, agree. Still, after unprejudiced examination, it can no longer be doubted that the nerve perforates the sarcolemma (whereby its neurilemma becomes continuous with the latter), and terminates beneath it in a nucleated, fine, granular, lamel- lated substance. The latter, however, pass at their borders and inner surfaces uninterruptedly into the sarcous substance of the muscular filaments (Rouget, Engelmann). Our fig. 204 shows the terminal structures in question, which have been suitably designated by the name of "terminal plates," from the psoas of the guinea-pig, at the left in profile, at the right as seen from above. In mammalia, in which they are well developed, the terminal plates have a magnitude varying in the mean between 0.0177 and 0.0267'". The number of their nuclei fluctuates be- tween 4, 6, 10, and 20. The terminal plates be- come more and more sim- plified in the lower verte- brates. As has been shown by more recent t i o n s ( K u h n e, mann), however, these ter- minal plates do not repre- sent the entire arrange- ment. Suitable profile views show that the axis-cylinder becomes divided and spread out into a tree-shaped figure in the external portion of the terminal plate. Beneath it, "like a sole," lies the granular nucleated mass. Most of the accessories which have thus far been employed are intended to render the whole muscle, or at least a part of it, as transparent as possible, so that the distribution of the nerve-fibres may be better followed than in the unaltered tis- mvestiga- Engel- Fig. 205. Two muscular filaments from the psoas of tte Guinea-pip. a, &, the primitive fibres and their continua- tion into the two terminal plates e, f ; C, neurilemma con- tinuous with the sarcolemma #, g ; /i, muscular nuclei. MUSCLES AND NERVES. 365 sue ; and secondly, to isolate the transversely striated mus- cular filaments with as little injury as possible, and subject them to examination freed from their interstitial connective tissue. The alkalies are unserviceable for the former purpose, but various acids, highly diluted, are, on the contrary, very good. Kolliker recommends the dilution of 8, 12-16 drops of aci- dum acet. concent, of the Bavarian Pharmacopoeia, of 1.045 sp. wt., with water to 100 ccm. and to immerse in it the cutaneous thoracic muscle of the frog for 1^-2 hours, after which time it is said to become transparent like glass. I have accomplished the same result with 1-2 drops of hydrated acetic acid to 50 ccm. of water. Highly diluted acetic acid also proves very serviceable for the muscles of other animals (Engelmann). I would also give this acid the first rank for such purposes. Mus- cles which have thus been rendered transparent may be pre- served for some time in 1-2 per cent, acetic acid. Muriatic acid of 0.1 per cent, is likewise a suitable reagent. It produces a similar condition of the muscle in from eight to twelve hours at the ordinary temperature of the room. The action for twenty-four hours of nitric acid, of the same concentration as the hydrochloric acid, is also serviceable. The still living muscular fibres, fortunately isolated by me- chanical means, often give the most, characteristic appear- ances. We have received from Kukne a good method for the fur- ther isolation of the muscular filaments (naturally, with as little injury as possible). He was able, by means of the mixture of nitric acid and chlorate of potash, mentioned above at the muscular tissue, p. 323, to isolate the muscular filaments with the adherent nerve- fibres very handsomely ; but it was impossible to ascertain the further distribution of the latter. On the contrary, the treat- ment, which we have also mentioned, with extremely dilute sul- phuric acid, and the subsequent digestion in water, constitutes a very suitable process. Krause recommends, furthermore, the immersion of the muscles for several days in a 33 per cent, solution of acetic acid, and then the isolation of the filaments by careful picking from the swollen connective tissue. He also obtained good preparations by placing them in a 2 per cent, solution of the 366 SECTION FIFTEENTH. cliromate of potash, with the subsequent action of 25 per cent, acetic acid. He furthermore praises solutions of sublimate of 0.3-0.5 per cent., and the subsequent treatment with the same acid ; and finally, sulphuric acid of 0.1 per cent. The so readily decomposable structures of warm-blooded animals are less to be recommended than those of the scaly am- phibia? for seeing the arborescent distribution of the nerve- fibres in the terminal plates. A lizard or a ring-snake, killed twenty-four hours previously by destroying the central nervous system, presents with the addition of a 0.5 per cent, solution of chloride of sodium, very character- istic appearances (Engelmann). Others recommend solutions as high as one per cent, of this salt. The most recent observer of these relations, who has rendered great ser- vice to microscopic technology, Pro- fessor Gerlach, has come to quite dif- ferent results. According to his views (which are not entirely shared by us) there exists in the transversely striated filament a fine terminal nervous net- work, which finally coales- ces with the sarcous substance. This author tested most accurately the silver treatment for- merly recommended by Cohnheim, as well as the gold method, and has given very careful directions for its rather useless employment. We omit these here, and refer to the original. We will mention only the gold method, which has already been recommended, and which afforded him by far the best results. Use a solution of chloride of gold (1 : 10000 parts of water) and frog's muscles, preferably 6-9 hours after death, at a period where possibly the acid condition of rigor mortis be- gins to terminate. The frog may advantageously be rendered tetanic by a blow on its head, and the leg, the gastrocne- mius of which is to be used, cut off. The muscles of mam- mals should be used earlier, though it is very difficult to hit the right period. The frog's muscle is, according to Q-erlach's directions, to Fig. 20fi. Muscular filament (a), of the lizard ; fr, nerve-fibre : c, its branches with the peculiar terminal figure d. MUSCLES AND NERVES. 367 be picked apart into bundles, placed in the gold solution, and kept in a dark place for 10-12 hours. It is then to be washed out in weakly acidulated water and proceeded with further in the familiar manner. Mount in glycerine with gum or a minimum of muriatic acid. A reddish tinge shows a successful, a yellowish one an unsuccessful impregnation. If the prepa- ration is immoderately dark, some improvement may be ef- fected by a solution of cyanide of potash in water (1 : 200). I have repeated all this, unfortunately with slight results, as I must confess. The most recent investigator in this domain, A. Ewald (he has justly announced his opposition to Gerlacli's views), has recommended the isolation of the muscular fibres of the gas- trocnemius of the frog in a drop of 0.5 per cent, solution of com- mon salt, and, after washing out in distilled water, placing the preparation from J-J a minute in a 0.1 per cent, solution of nitrate of silver. For the examination, use a mixture of water 100, glycerine 100, formic acid 1. To impregnate with gold, isolate the fibres in a solution of chloride of palladium (of the color of Rhine wine) and then place them either 12-18 hours in G-erlach's gold solution or for a minute in a 0.2 per cent, solu- tion of chloride of gold and potash. This immersion, as well as the subsequent deprivation of water (for about twelve hours) is best in the dark. Ewald recommends as a fluid medium a mixture of glycerine 40, water 20, and a drop of a muriatic acid which contains 25 per cent, of chloride of hydrogen. The silver preparation of the muscle may be rendered more durable by a subsequent short impregnation with gold. It is much more difficult to follow the terminal forms of the nerve-fibres in the smooth muscles than in the transversely striated tissue, and our knowledge is therefore very uncertain on this point. The broad ligaments of the uterus of the rabbit (Frankenhauser), likewise the urinary bladder and the small arteries of the frog (Klebs, Arnold), are at present considered the most suitable objects for examination. Highly diluted ace- tic and chromic acids are to be tried here. Klebs recommends a 5 per cent, solution of cane-sugar to which sulphurous acid is added, and the subsequent immersion in phosphate of soda. Frankenhauser advises highly diluted chromic acid, 3V~tV P er cent., and also acetic acid of 20 per cent. Finally, we are in- debted to Arnold for very accurate directions. The object is 368 SECTION FIFTEENTH. to be placed for two to four minutes in 4 ccm. of acetic acid of 0.5-1 per cent., and then for half an hour in the same quantity of chromic acid of 0.01 per cent. This investigator found the gold method, and likewise the treatment of transverse sections of frozen muscles with chloride of gold and chromic-acid solu- tions, advantageous. Impreg- nation with gold by Henocque's modification (p. 167) is the best method. According to the investiga- tions of Frankenhauser and Ar- nold, however, the termination is very peculiar. These nerves form manifold net-works. A sec- ondary plexus of this kind lies close to the muscular layer (fig. 207). It consists of fine, pale, nucleated filaments. Still finer fibres spring from it to form a new net-work with small meshes, the extremely fine terminal fib- rillse of which are said to end in the nucleoli of the contractile fibre-cells. This condition may be represented to the reader by the above figure. The correct- ness of this statement has of late, however, again become very questionable. Engelmann, in a re-examination, was unable to see any trace of this manner of termination — and we have been equalty unfortunate. Klein also saw, a few years since, only a very narrow terminal net-work. To examine the still imperfectly determined nerve termina- tion of the muscles of the heart, take the thin, transparent septum auriculorum of the naked amphibke, especially the land salamander. Highly diluted acetic acid may be used alone or combined with chromic acid. The recognition of this will be very uncertain in other portions of the heart of verte- brate animals. Impregnation with gold may be used, prefer- ably a 0.01 per cent, solution of chloride of gold and potash, allowing it to act for 24-48 hours ; or the action for two days of a 20 per cent, nitric acid. Instead of this, the fresh, tissue may be picked apart in nearly neutral fluids, such as a solution Fig. 207. Alleged nerve-termination in the muscular coat of a small artery of the frog, after Arnold. MUSCLES AND NEKVES. 369 of common salt (0.5) or osmic acid (0.1 per cent). The dog and guinea-pig are to be recommended among the mammalia. These directions, coming from Langerhans, have recently been rendered more complete in a beautiful study by the younger G-erlach. The latter recommends to cut the heart from a frog and wait till a mechanical irritation no longer produces con- traction. The septal parietes of the atria are then rapidly re- moved and placed in a mixture, consisting of chloride of gold and potash 1, muriatic acid 6, and water 12000. It remains in this solution, protected from the light, for 14-16 hours. It is then washed for several minutes in water containing muriatic acid (1 : 1000), and placed in a mixture consisting of muriatic acid 1, water 100, and glycerine 400. Here the reduction by the action of light takes place in two or three days. Some in- crease of transparency may be obtained with a cyanide of pot- ash and glycerine mixture (p. 135). Immersion for about a day in weak picric acid, with the subsequent use of picro-carmine, is also useful. For isolating, Gerlach recommends maceration in Schultze's reagent. The nerves of the cornea of the eye, which have been for- merly and recently frequently examined, present interesting objects to the microscopist. Soon after entering the cornea at its periphery, they lose their medullary sheath, become pale, and form a plexus which permeates the corneal tissue, of very fine fibrillge with nucleat- ed enlargements at their nodal points. Nerve-fibres pass from this net-work in two directions : those which proceed in the one direction terminate in the corneal tissue itself ; while the others, after perforating the anterior homogeneous limiting layer (Hoyer), find their terminus in the epithelium (Cohnheim). The cornea, removed from an animal immediately after death, is naturally to be employed for examination. One may here, for example, with the cornea of a frog, proceed in the following manner (Kuhne) : The point of a knife-blade is to be inserted near the sclerotic border, and the aqueous humor drawn out with a pipette ; the cornea is to be rapidly separated with a pair of fine sharp scissors and placed on a slide, with the small quantity of aqueous humor from the pipette. The whole is then placed in the previously (p. 99) described moist chamber, to remain for hours under the microscope, and at the same time to gradually reveal not only the course of the nerves, but 24 370 SECTION FIFTEENTH. also many other remarkable tilings in the most conservative manner. The procedure mentioned may also be used, with slight modifications, for other animals. The corneas of the smaller animals, the mouse, the rat, and the squirrel, are generally to be recommended. They are to be removed in connection with a narrow zone of the sclerotic, and it will generally be necessary to make several incisions in the direction of the radii. If one desires to employ reagents, the highly diluted acetic acid recommended by Kolliker for the nerves of the muscles (p. 365) is advisable (Muller and Saemisch). Even after 10-15 minutes the epithelium may be removed with the forceps ; while at least several hours' action of the reagent is necessary for the examination of the nerves. The action of very dilute chromic acid (0.1-0.01 per cent.), to which 0.25 per cent, of chloride of sodium maybe added, is also advantageous, at least with the frog (Kuhne). No certain results have yet been obtained concerning the termination of the corneal nerves in the true corneal tissue. It has been assumed that there was a connection between the ter- minal fibrillse and the cell processes of the radiated corneal corpuscles (Kuh- ne). We have been inform- ed there is a termination in the nucleolus of the latter elements (Lipmarn, Lav- dowsky) ; while others deny all connection with the corneal cells, as, for in- stance, B. Rollett, Klein. To recognize the pene- tration of the (extremely line) nerve-fibres into the epithelium of the conjunc- tiva, and thus to verify Cohnheim's beautiful discovery, one should resort to chloride of gold (p. 100), chloride of gold and potash (Hoyer), as well as chloride of gold and soda (Waldeyer), and use the eyes of guinea-pigs and rabbits (fig. 208). The frog's cornea shows its Fig. 208. The cornea of the rabbit in verdcaJ transversa section, after treatment with chloride of gold. a t the older ; 0, the young epithelial cells of the anterior surface ; c, corneal tissue; d, a nerve-branch; e, finest primitive^ fibres ; /, their distribution and termination in the epithe- lium. MUSCLES AND NERVES. 371 epithelial nerve-distribution even without any reagents, by simply remaining in the moist chamber (Engelmann). In consequence of the capriciousness of the gold method, there is here no dearth of processes. We communicate a few of recent origin. Klein uses a modification of Henocque's process (p. 167.) It is said to present infallible results for these epithelial nerves. The fresh organ of the rabbit is placed, with its external surface upwards, forf-1 hour in a 0.5 per cent, solution of chloride of gold, then, secluded from the light for 6-10 hours, in distilled water, which washes it out. The original straw yel- low color has now changed to a gray. Now place it in a small bottle which contains 5-10 ccm. of a nearly saturated solution of tartaric acid. The bottle is then to be placed in a nearly equal quantity of water heated to 40-50° C. A lively violet red- dish color is then rapidly obtained, which, on the cooling of the water, passes into an impure but deep brown-red color. A re- newed washing for several hours in distilled water then follows. Hoyer, in an excellent article, gives us the following direc- tions : Use a 0.5 per cent, solution of either chloride of gold, or better, chloride of gold and potash. A cornea well impregnated with gold should, however, still be moderately transparent and evenly tinged throughout gold yellow. If it remains whitish or cloudy in its interior, only an incomplete result is to be ex- pected. With smaller animals, rabbits and guinea-pigs, re- maining in the solution, ^-1 hour generally suffices ; larger ani- mals require a longer time or a stronger solution of gold. A complete and good impregnation caunot be obtained with the cornea of the ox. This process succeeded with fresh human eyes, when the solution of chloride of gold and potash of the above-mentioned strength, to which a little acetic acid was added, was allowed to act for 2-5 hours, although the latter re- agent cannot otherwise be pronounced advantageous. Hoyer recommends for the epithelial nerve- distribution the following : When a cornea which is well impregnated with gold has, after remaining for 16-24 hours in 30-60 ccm. of distilled water, begun to assume a weak, grayish-blue color, one or two drops of a photographic reproducing fluid, which contains py- rogallic acid, may be added to the water and the latter allowed to act for i-i hour. The result is still better than by Klein's method. 372 SECTION FIFTEENTH. We thus become acquainted in the most certain manner with the penetration and termination of the iinest nerve-fibres in an epithelial layer. Many additional observations of a relative nature have been made in modern times. Thus, Hensen informs us that in the tail of the frog's larva he saw the terminal branches of the cutaneous nerves termi- nate in the form of infinitely fine filaments in the nucleoli of the epidermoid cells. Lipmann recently asserted the same with regard to the pavement epithelium of the posterior surface of the frog's cornea. He employed the chloride of gold. These obser- vations (which would prove a parallel case with the contractile fibre-cells) still await confirmation. Langerhans — again with the help of the gold method — found that in the human cutis branches of pale nerve-fibres penetrate between the cells of the rete Malpighii ; here they probably enter small radiated cells, the ascending processes of which are said to terminate with slight enlargements beneath the stratum corneum. In the investigation of the true terminal plexuses of the finer non-medullated nerve-fibres, which have been repeatedly examined of late, special use has been made of the gold method. To obtain the first view of the numerous nerves of the dental pulp, one of the large incisor teeth of the rabbit is to be crushed and the examination made in iodine-serum. The finest terminal fibril] se (which probably penetrate a portion of the dental tubes) are difficult to examine. Chloride of gold and osmic acid are of no service (Boll). Solutions of chromic acid are the most useful. Disregarding the higher nerves of sense at present, we here treat only of the so-called terminal knobs, the tactile and the Pacinian bodies, remarkable terminal structures which have been discovered and more closely investigated within the last few years. The terminal knobs, for a knowledge of which we are in- debted to Krause, are represented by the drawings, fig. 209 and 210. In mammalial animals, as it is known, they are of an oval form (1, a), while in man they are more globular in shape (2, a). They belong especially to certain mucous membranes, although they may also occur in the external integument. The ocular conjunctiva is to be selected for their examina- tion, and it is preferable to use the fresh, warm eye of an ani- MUSCLES AND NERVES. 373 mal, sucli as the calf or hog, that has just been slaughtered. Portions of the conjunctiva are to be carefully freed from the connective tissue which lies be- neath it, and examined without any fluid media. With a little persever- ance, the structures in question may be recognized in the connective tissue by their bright appearance. An ex- amination of this kind always pre- sents difficulties, however. Krause has made us acquainted with a good accessory, which is to be especially employed with organs which are no longer fresh, and may therefore be used with those of man. This consists in an immersion in or- dinary vinegar, continuing for several days or a week. The tissue is ren- dered transparent, and the arrange- ment of the nerves ma}^ be observed in an elegant manner. Single nerve- Fio. 209. Terminal knobs. 1, from the conjunctiva of the calf, a, knob; c, the medullated nerve-fibre, dividing at * ; 6, its pale terminal portion. 2, from man. fibres are found to enter the terminal knobs which are now become cloudy and have dark contours. The pale ter- minal fibres can no longer be perceived by this method, however. Longworth, the last investigator of the terminal bulbs, calls attention to the high value of osmic acid. A fresh eyeball, with as much conjunctiva as possible, is necessary. Sutures are placed in the border of the latter and sewed back in places to the posterior half of the eyeball. These prevent the conjunctiva from shrink- ing. The eye is then either placed in 0.33 per cent, osmic acid, or held by a thread, exposed to the vapor of such a solution. In both cases 12-14 hours' action is necessary. The epithelium may now be removed, either with a brush or by scraping with the point of the finger, and carefully removed portions of the mucous membrane examined with the addition of dilute acetic Fig. 210. A smaller human termi- nal bulb, a, nerve ; 6, sheath ; c, por- tions of the nerve without recogniz- able termination ; d, cells of the inte- rior ; e nerve termination in a cell. 374 SECTION FIFTEENTH. acid (1-2 per cent.). Tingeing with weak solutions of carmine and hsematoxyline may also follow. By the aid of this process (and it is more serviceable than impregnation with gold) Longworth found the interior of the human terminal bulbs (rig. 210) composed of cells, and the nerves terminating in the latter (e). Merkel recently made the interesting discovery of the tactile cells. In the tongue of the bird — the duck and goose are most suit- able — one meets, with transparent cells of considerable size with a large round nucleus. A nerve-fibre terminates in this, with a pale axis-fibre. These simple rounded tactile cells may rest on each other with their broad surfaces, and thus are formed the complicated tactile-cell formations of our fig. 211, Pig. 211. Complicated tactile cells. a t from the cere of the duck's bill ; b and c, of the soft lingual papilla? of the same creature. Fig. 212. Two nervous papilla? from the volar surface of the index finger, with the tactile bodies and their nerves. a, b, c. Here, also, the axis-cylinder terminates in the proto- plasma of the several cells. Such tactile cells are also found in mammalial animals and in man, not unfrequently crowded into the lowermost strata of the pavement epithelium. For their recognition, use the tongue as well as the cere of the bill of the water-fowl mentioned, and place small pieces for a day or two in a 0.5-1 per cent, solution of osmic acid. Wash them oiit in water for an equal length of time, and then transfer them to strong alcohol, in which, after 14-21 days, MUSCLES AND NERVES. 375 they acquire the best color and consistence. In mammals our structures occur in the most sensitive portions of the skin, as on the snout (the pig's snout, for example), the lips, ears, the sacs of the tactile hairs, etc. The true tactile corpuscles of man (fig. 212), discovered long since, probably share a near relationship with these tactile-cell groups of Merkel. They occur in the corium of certain localities (the volar surface of the fingers and toes, the palm of the hand, and the sole of the foot, etc.) ; they lie embedded in a portion of the so- called tactile papilla?, but form tolerably difficult objects for investigation, especially in regard to the nerve termination. Various methods of examination have been employed in the investigation of the tactile bodies. The freshest possible human integument, when stretched, permits of quite thin vertical sections being made with a sharp knife. These, in consequence of their fibrillated structure, re- quire additional measures to render them transparent. There are two media especially which are used for this purpose : a sometimes more concentrated, sometimes more dilute solution of soda, and the diluted acetic acid. The former affords quite handsome, but also very perishable specimens. Thin sections placed in a watch-glass swell considerably after a time, and then permit the epidermoidal layer to be removed. Any frag- ments of the rete Malpighii which may remain are to be re- moved by brushing. The examination is to be made with a strongly shaded field, and also, according to circumstances, with the employment of a drop of acetic acid. Other investi- gators have given the dilute acetic acid entire preference over the solution of soda, and in fact, it cannot be denied that many details of the tactile bodies, and especially of the course of the nerve to and in the same, may be more conveniently brought to view by means of this reagent. Such sections, tinged with carmine, present handsome appearances. Fresh integument, such as that of the point of the finger, may likewise, when carefully dried, present serviceable views in vertical sections, the more so if tingeingwith carmine is also employed. Suitable portions of the integument with their natural injection, or injected with Prussian blue and treated in this manner, are adapted for distinguishing the two kinds of sensitive papillse of the skin from each other. Chromic acid 376 SECTION FIFTEENTH. and even alcohol preparations occasionally show very hand- some tactile bodies. Transverse sections of the papillary bodies of the skin, hardened in alcohol or chromic acid, tinged with carmine, can- not be dispensed with. Gerlach, years ago, made as acquainted with another method. A piece of integument removed from the volar sur- face of the ringer is to be placed for a moment in hot, and then in nearly boiling water. The epidermis is then to be taken off, and any portions of the same which may remain are to be removed with a brush. The piece of skin is then to be hardened for several days in a solution of the chromate of potash. Transverse sections are now to be made from the papillae with a razor, and placed in water under the micro- scope. Strong acetic acid serves to render them transparent. The transverse sections of the nerve-fibres may be recognized within the tactile bodies. Injected skin is to be used in order to avoid confounding them with transversely divided capillary vessels. All these methods of investigation of a former period are unserviceable, however, when the termination of the nerves is concerned. Here the freezing method, in combination with the impregnation with metals, such as chloride of gold, osmic acid, and chloride of palladium, promises the most. Among these, however, we, with Langerhans and Merkel, give the preference to the osmic acid (0.5-1 per cent.), chloride of gold here renders much less service. The nerve termination remains dark, not less so the signification of the transversely oblong corpuscle of our fig. 212. They have been declared to be terminal pieces of the nerve-fibres, connective-tissue nuclei, and also optical expressions of the surfaces of separation and contact of the tactile cells which are stratified over each other ; we are therefore not yet able to state anything with certainty in this connection. There is still remaining to consider the remarkable Pacinian or Vaterian body (fig. 213), the most complicated form of these terminal bodies of the nerves of sensation. It is preferable to select for their investigation the mesen- tery of the cat, in which they at once become evident to the eye, and are isolated by slight preparation. By the applica- tion of indifferent fluids they present excellent specimens, in MUSCLES AND NERVES. 377 Fig. 213. Pa entery of a cat. which the structure, the concentric capsules (5), the entering nerve («■), with the pale terminal filament (c), may be readily recognized. Here, also, the latter distinctly shows a combina- tion of primitive, or axis-fibrillte, as was ascertained by Gran- dry and confirmed by Schultze, Michelson, and Ciaccio. Previous injection with cold-nowing trans- parent masses is a good accessory ; diluted acetic acid and tingeing may also be employed. Dilute chromic acid, or corre- sponding solutions of chromate of potash, may likewise be employed for their preservation and examina- tion. I find the acetic-acid-alcohol mixture less suitable. The best ac- cessory is osmic acid (0.5-1 per cent.). I have not yet succeeded very well in preserving the prepara- tions in acetate of potash. Sharp needles and the simple microscope serve for the detachment of the cap- sules. Impregnation with silver also shows on these the fam- iliar mosaic. Is the axis canal or the inner bulb of our structure actually homogeneous, as it has the appearance of being, or is it formed of cells, like a human terminal bulb (fig. 210) i A. Budge has followed Key and Retzius in assuming this to be the case. After the Pacinian corpuscle has remained for a day or two in chromate of ammonia, a drop of eau de Javelle (p. 135) is to be added ; when the contours have become distinct it is to be tinged with a 0.2 per cent, solution of chloride of palladium. The Pacinian capsules of man are to be obtained without much trouble, by preparing the cutaneous nerves of the palm of the hand and the sole of the foot. The methods of investi- gation are the same as for those of the cat. The textural conditions of the nervous system in the foetus, and the history of the origin of their elements, are, as yet, by no means known with desirable certainty. The embryos of our domestic mammalia or of the hen, which have been im- ian body from the mes- a, Nerve-fibre ; b, the capsules ; c, the pale-contoured terminal filament of the nerve-tube. 378 SECTION FIFTEENTH. inersed, as fresh as possible, in dilute solutions of chromic acid, or of the bichromate of potash and slowly hardened, are to be employed. Transverse sections of hardened embryos afford very fine review preparations for the spinal cord, the spinal ganglia, etc. The objects tinged with carmine are to be mounted in Canada balsam. Many characteristic views of the peripheral nerves of the foetal period may be readily obtained in the fresh larva? of the frog and salamander. Together with the nitrate of silver and the chloride of gold treatment (Eberth), a very excellent pro- cedure, given by Hensen, may also be employed. The larvae are to be dipped for 20-50 seconds in a chromic acid solution of from 3-4 per cent., and are then thrown, still living, into spring-water. Then, or after half an hour, the epithelium may be removed from their tails by brushing. Eberth recommends for the same purpose to place the frog's larvae for a half or a whole hour in a weak solution of nitrate of silver (1 gr. to 5 ounces). In consequence of the extreme delicacy and alterability of these tissues, however, the most conservative methods are always the best. Somewhat more strongly hardened embryos afford good preparations relating to the structural conditions of the devel- oping spinal cord and brain. The changes in form of the for- mer, and also of the spinal ganglia, with a progressing develop- ment, may be readily perceived. Here, also, chromic acid and bichromate of potash deserve decided preference over alcohol. Transverse sections, with the aid of carmine tingeing, suffice for the first examinations. Concerning the tunics of the central organ, it is better to examine the arachnoid and pia mater fresh, employing the re- agents which are customary for connective-tissue parts. The numerous capillaries, and the small arterial and venous branches which are associated with them, cause the latter membrane to appear very well adapted for the study of the vessels. In suitable specimens (as well as in mechanically iso- lated vessels of the nerve-substance) one may readily recognize that the formation of tubercles commences in the adventitia. It was thought that the rudimentary cells, which are found here (the so-called vascular nuclei), increased by proliferation. At the present time, a wandering of the lymphoid cells of the MUSCLES AND NERVES. 379 blood into the surrounding layer has become more probable. If suppuration takes place in the pia mater, in consequence of inflammatory irritation, the emigration of the lymph-cells from the blood-current may be most distinctly recognized (Rind- fleisch). The dura mater may be examined fresh, dried, or hardened by means of chromic acid,— methods which are also employed with the neurilemma of the larger nerves. The plexus choroidei scarcely requires special directions ; its injection with tliat of the brain readily succeeds. Here Midler's mixture (p. 130) affords good preparations. The calcareous concretions of the same, the so-called brain-sand (which, as is known, also occurs in the human pineal gland), are to be studied with the employ- ment of acids and media for rendering them transparent, espe- cially glycerine. The pituitary gland, for which the calf is to be especially recommended (Peremeschko), is to be hardened in chromic acid, Midler's fluid, or alcohol. Thin sections, brushed and tinged with carmine, readily yield the essential appearances. We have already noticed above the great difficulties which the investigation of the normal textural conditions of the cen- tral organs of the nervous system still present. Hence, we shall comprehend that their numerous pathological alterations are still very inadequately known, and have only been assailed, histologically, with slight results. It is usually accepted that the nervous elements indeed undergo numerous secondary pro- cesses of degeneration, such especially as the fatty, and also amyloid and colloid transformations, but that the true new for- mations proceed from the connective-tissue framework and from the vessels. The correctness of the former doctrine has more recently, however, become doubtful, and the lymphoid migra- tory cells exert at present a deep and disagreeable influence on the latter. The finer textural conditions of the framework substance are also uncommonly difficult to follow, as the very methods of hardening which are customary for the normal structure frequently render very little service in the domain of pathology, so that often one is able to examine only fresh ob- jects. For connective-tissue formations one should try very weak chromic acid, according to Schultze (p. 127), likewise Muller's fluid, diluted with about an equal volume of water, also Ranvier's injection of osmium (p. 360). Finally, immersion 380 SECTION FIFTEENTH. in osmic acid, as well as the skilful employment of tingeing methods, will afford much additional assistance. Good review preparations are not unfrequently afforded by a method practised by Billroth, — placing small pieces of brain and spinal cord in powdered carbonate of potash or chloride of calcium for 24 hours. By this means the objects usually gain a degree of consistence which permits of fine sections being made ; these are to be examined in water (or with the addition of glycerine). To investigate the fatty degeneration of the nerve-fibres, as well as the textural changes which occur in the peripheral por- tion of a divided nerve, the animal which has been subjected to the above operation is to be examined, after the proper in- terval of time, either quite fresh or with the employment of the solutions of free chromic acid and of bichromate of potash, which have been recommended for the spinal cord and brain. The finest results are obtained by treatment with osmic acid (Eichhorst), which is to be combined with tingeing with carmine or hsematoxyline. This is one of the few structural changes of the nervous apparatus which present but slight difficulties to the practised observer. Section Sixtccntl). VESSELS AND GLANDS. The methods of investigating the vessels differ somewhat according as the contained mass consists of blood or of lymph ; furthermore, they vary considerably in proportion to the size of the vessels. One variety of accessories is therefore necessary in the examination of the capillaries and small vessels ; others are required for the investigation of the larger and largest trunks. The finest canals of the blood-pas- sages are, as is known, the capillaries (fig. 214, 1 a, 2), which are very thin, nucleated, branched membranous tubes. The narrowest capillaries (1 a), which, however, do not occur in all parts of the human body, are only sufficiently wide to allow of the passage of the blood-cells singly, one after the other. A similar condition recurs in the several groups of vertebrated ani- mals, modified, naturally, by the size of the blood-corpuscles. Frogs and naked amphibife have therefore capil- laries of much more considerable diam- eter than are met with in the human body, and the capillaries of these crea- tures are consequently better adapted for many investigations than our own. Until recently the purport of the almost universally accepted history of the development of the capillary vessels was that they originated in the blending of the formative cells which, coming together in a single row, opened into each other, so that Pio. 214. 1. Capillary with thin nuclei, a and b. 2. double contoured walls, y. Small artery with the en- dothelial layer a, and the middle layer b. walls and the Capillary with 382 SECTION SIXTEENTH. tlie cell-cavities became united into a capillary tube, the mem- branes of the cells were transformed into the wall of the vessel, and the persisting nuclei into the nuclear formations of the latter. It has been ascertained by the concurrent investigations of several observers (Hoyer, Auerbach, Eberth, and Aeby) that the walls of the capillary vessels are not in reality structure- less, but rather that they are formed by the melting together of very thin and fiat nucleated cells (the cavity of the capillary is therefore an intercellular passage). The boundary lines of these cells are only to be rendered visible by means of impreg- nation with silver, and were previously entirely overlooked. This important discovery may be readily verified (figs. 215, 216 and 217). A frog, a mouse, or a guinea-pig is to be allowed Fig. 215. Capillary net-work from + he lung of the fro£T, treated with a solution. of nitrate of silver. 6, vascular cells ; a, their nuclei. Fig. 216. Capillary vessel from the mesentcrium of the Guinea-pig, after the action of a solution of nitrate of sil- ver, a, vascular cells ; b, their nuclei. Fig. 217. A capillary from the mesentery of the frog, injected with a solution of silver. The stomata appear at a, «, and &, between the vascular cells. to bleed to death, and then a 0.25 per cent, solution of silver is to be injected into the vessels. The simple immersion of organs, such as the retina or pia mater of mammalial animals or of man, which are deprived of their blood, also leads to the desired result. The object is to be washed in spring water and examined in acidulated glycerine. More recently increased attention has been paid to a some- VESSELS AND GLANDS. 383 what more complicated arrangement of the capillaries which occurs in the lymphoid organs, the lymphatic glands, the Peye- rian and solitary follicles, the tonsils, Malpighian bodies of the spleen, the thymus gland, and also in other glands. It consists in the spreading out of the reticular connective tissue of these organs, in the form of a membrane, around the primary walls of the capil- laries, and thus forming a second acces- sory layer, a so-called adventitia capil- laris. This may be represented by fig. 218, 6. Furthermore, microscopic vas- cular trunks may be surrounded with a larger intervening space, by a connec- tive-tissue sheath (a) whereby the cavity which is thus formed (lymph- sheath) serves for the current of the lymph (c). There are by no means many organs which are adapted for the primary ex- amination of the capillary vessels of man and the mammalia. The most suitable, and therefore, also, the most generally recommended, appear to be the brain, the pia mater of the same, the retina of the adult body, and the lymphoid organs. To obtain characteristic views from the former parts a small blood-vessel which is barely visible in the gray substance is to be seized and an attempt made to remove it by traction. It is then to be placed in water and freed from any adherent brain- matter by means of the wash-bottle, or, still better, by brush- ing. In this way will be perceived a trunk with abundant ramifications and numerous capillaries as terminal branches, and not only these finest forms of vessels may be studied, but also a series of transformations into more complicated vessels. The pia mater when picked also affords excellent objects, es- pecially if portions be selected which pass over a furrow be- tween the convolutions of the brain. The capillaries of the retina are to be treated in the same manner as those of the brain-substance. The organs belonging to the lymphatic system require some- what greater preparations for the investigation of their capilla- ries. Either none at all or only extremely unsatisfactory views Fig. 21S. Capillary vessels and small trunks of the mammalia?, a, capillary vessel frum the brain ; b, from a lymphatic gland ; c, a some- what larger trunk with a lymphatic sheath from the small intestine ; and d, transverse secth in of a small artery of a lymphatic gland. 384 SECTION SIXTEENTH. are to be obtained from the fresh parts. For this reason, pre- paratory hardening methods (chromic acid, alcohol, etc.) are to be first employed. Thin sections from the tissue which has become more resistant must then be freed from the innumera- ble lymph-corpuscles which till the connective-tissue net-work before the desired delicate capillaries can be brought to view. Any ordinary preparation serves for the recognition of the nuclei. These are rendered sharper by dilute acetic acid, like- wise by carmine tingeing, which, together with staining with haematoxyline and aniline blue, deserves recommendation. Chloride of gold also affords serviceable specimens. We must return once more to the capillary vessels. Years ago, dark points, as well as smaller and larger circu- lar black markings, were seen at the angles of contact of these flat endothelial cells, after treatment with silver (Auerbach). It was evident that there was here a cement substance which might permit of the escape of the blood-cells. Arnold called the smallest of these formations "Stigmata," and regarded them as a normal occurrence, while he considered the larger ones (fig. 217, b) to be caused by vascular distention, and gave them the name of "Stomata." We agree with this com- pletely. In organs with fibrous structure, even where there is a con- siderable vascularity, we may, as a rule, search in vain for capillaries except we employ especial accessories for rendering them prominent. The empty capillaries disappear most com- pletely in the fibrillary tissues. The familiar action of acetic acid may here be made use of, or, which is to be preferred, the preparation may be first colored with carmine and then subse- quently exposed to the action of the acid. After what has just been mentioned it is unnecessary to dis- cuss further the great value of transparent injection with Prus- sian blue or carmine for rendering the capillary and larger vessels of an organ visible ; the silver solution (p. 189) may also be used with advantage. 40-60 grms. of gelatine solution may also be combined with 20-50 centigrms. of nitrate of silver, the latter being first dissolved in a little water. This method, originated by Chrzonszczewsky, I have not found to possess any essential superiority to a simple solution of silver. The slight trouble of injecting should, in fact, never be shunned in sticIi investigations, as the structural relations of all organs VESSELS AND GLANDS. 385 are usually rendered much more comprehensible as soon as the distended capillaries have afforded a landmark for the eye. Where it is possible to retain the blood in a vascular dis- trict, such natural injections may replace the artificial ones, but the preparations should not be moistened with water. If a frog or a salamander be at hand, the capillaries of cer- tain parts of the bod}^ may be examined with advantage for comparison with the human textural condition. From the first animal (^preferably killed by means of ether or chloroform) the lower eyelid or one of the flat, transparent muscles which we have mentioned above (p. 363), is to be taken. The membrana hyaloidea also affords magnificent views. The larger blood-vessels which follow these no longer show the original simplicity of structure possessed by the capillaries. First appears the original capillary membrane (fig. 214, 3) meta- morphosed with cells and longi- tudinally arranged nuclei (a) ; then a second layer with trans- versely arranged smooth muscu- lar elements scattered through it, the nuclei of which are seen at b. This is the earliest ap- pearance of a tunica media seu rnuscularis, to which in vessels of a somewhat larger calibre is gradually associated the tunica cellulosa, the external connec- tive-tissue layer. In other ves- sels the epithelial tube is seen to be surrounded by an elastic in- ner membrane ; this is the first appearance of the tunica serosa. We meet with other trunks (and these have for the most part the character of venous tubes) which present the most internal cellular layer, the elastic inner membrane, and the adventitia ; but, on the contrary, no trace of any muscular middle layer can be recognized in them. A complete contrast is presented by the arterial trunks (fig. 219), the muscular middle layers of which are very strongly 25 Fig. 219. A small arterial trunk without an epi- thelial covering, b. the homogeneous elastic inter- nal layer ; c, the middle -layer, consisting of trans- versely arranged fibre-cells ; d, the external con- nective-tissue covering. 386 SECTION SIXTEENTH. developed, and its contractile fibre-cells are found packed closely together. The methods for investigating these vessels are the same as for the capillaries. Even the localities, such as the substance of the brain, the pia mater, and the lymphoid organs frequently remain the same. Together with these the mesenteric arteries may also be used with advantage. Advantageous use may be made of tingeing methods, especially of carmine tingeing with the subsequent action of acetic acid, and also of dilute acids and alkalies. Transparent injections are very useful here, especially for estimating the extremely variable thickness of the walls of small venous and arterial branches. The endothelium in somewhat larger trunks is to be ex- amined in part in fresh, unaltered specimens, or by means of carmine tingeing and silver impregnation (see page 259). Tingeing with carmine, the application of potash solutions of 30-35 per cent., and of 20 per cent., nitric acid are to be re- commended for the recognition of the muscular layer. The action of nitrate of silver may also be employed for rendering visible the contours of the individual contractile fibre-cells. The usefulness of still another method here makes itself felt, which is of unsupersedable importance in the examination of larger and the largest vessels — we refer to the preparation of thin sections through their walls. Drying was formerly em- ployed for this purpose. At the present time the embedding method of objects previously hardened in alcohol or chromic acid (p. 113) has taken its place. These preparations afford handsome sections of such vessels (fig. 218, d). Beale distends such arterial and venous trunks as much as possible by the energetic injection of uncolored gelatine, and then makes fine sections through the hardened mass. He recommends this method very properly, especially for the demonstration of the contractile fibre-cells. We re- commend for this purpose especialty the Malpighian bodies of the spleen, the follicles of the lymphatic glands and of the kidney, whereby the slight trouble of a careful brushing should not be avoided. Vessels whose walls can no longer be seen in their totality with tlie microscope require the preparation of thin, partly longitudinal, partly transverse sections. The fresh vessel may, without further treatment, be dried or embedded, and then ex- VESSELS AND GLANDS. 387 amined with the application of acids and alkalies, or it may be previously boiled in vinegar or dilute acetic acid. The action of 20 per cent, nitric acid, likewise Schulze's treatment with chloride of palladium, and the subsequent tingeing with car- mine, and hsematoxyline tingeing deserve to be recommended. As additional modern methods we also mention : 1. The Schultze reagent (p. 124). Fresh vessels are to be treated with chlorate of potash and a nitric acid of only 20 per cent. After 10-14 days the elastic elements are destroyed, the muscular preserved (von Ebner). 2. The double tingeing of Schwarz with carmine and picric acid (p. 159). 3. Gerlach's complicated tingeing (p. 161). 4. Hsematoxyline tingeing. The muscles and their nuclei become intensely colored, the connective tissue slightly, the elastic fibres not at all (Bresgen). 5. Treatment with chloride of palladium of 0. 1 per cent, to tinge the muscular elements yellow. 6. Von Ebner' s method. Aniline red (p. 154) stains the elastic elements of the walls of the vessels. If we tinge first with solution of hsematoxyline and then with fuchsine, interesting but, unfortunately, perishable appearances are presented, as I can testify from my own experience. The various strata of elastic membranes, connective tissue, and muscular layers are by these various methods rendered most distinctly visible. The best views are obtained of the development of the muscular layers in arteries and veins of medium size, and of the retrogression of this tissue in the largest vessels. It will frequently be found that the epithelium is no longer preserved. A second, and indeed older procedure, consists in opening a vessel while it is in a moist condition, and then with the scalpel and forceps separating, under water, the individual layers suc- cessively from within outwards, or from without inwards, to study them with the application of suitable media. By scrap- ing the fresh specimen with the blade of a scalpel, larger or smaller shreds of the epithelial covering may be readily brought to view. The free border of the valve of a vessel not i;nfre- quently presents a fine view of this covering, and, at the same time, a good means of measuring the slight thickness of the same. For the recognition of the vascular nerves, a net-work of very 388 SECTION SIXTEENTH. line pale filaments, which occupies the tunica media and the contiguous portions of the external layer, select the mesentery of a frog, treat it with dilute acetic acid, and remove the en- dothelium by brushing (His) ; or try the gold method. The arrangement of the various capillary districts according to the magnitude and manner of distribution of the vessels, as well as the size of the tissue-spaces surrounded by the meshes of the net-work, has occupied the attention of anatomists and physiologists for a long time. Even the charming appearances which successful preparations of this kind unfold under the microscope must exert an attractive influence. Then it is only by the vascularity of an organ that a conclusion can be made as to the quantity of matter which it assimilates, either in its own interest or for the service of other organs (glands). The relative arrangement of the capillaries is of great importance in the mechanism of the circulation.. As the technology of injection has already been mentioned in detail in a previous section (p. 172), we may simply refer to the same. For the study of the capillaries, as has been already remarked, one should only examine objects injected with trans- parent masses in a moist condition (either quite fresh or after a short immersion in alcohol, and then with a subsequent addi- tion of glycerine), as opaque masses conceal too much, and all &vy preparations present a distorted appearance. The simple injecting fluids (the cold flowing Prussian blue of Beale or of Richardson, see p. 187) will suffice for most of the investigations of the capillary net-works. If one desires to employ a double injection, Beale's carmine mixture (p. 188) may be added. Gel- atine must be added to the coloring matter for larger portions of the body. It would lead us beyond the limits of this little work were we to mention here more fully the various appearances of the capillary net-work according to the size of the vessels and meshes, as well as the form of their arrangement. A few re- marks may therefore be sufficient, and the text-books on his- tology recommended for further instruction. Many parts of the body, as is known, remain entirely with- out vessels ; others are but slightly vascular, and are only per- meated at considerable distances by capillary vessels ; while in the extremely vascular organs the capillaries are closely ap- proximated to each other, and the meshes are smaller. VESSELS AND GLANDS. 389 The anatomists have distinguished two fundamental forms of capillary net-works, according to the shape of the parenchy- matous spaces surrounded by them ; namely, 1, the straight, and 2, the circular net- work. Both forms arrange themselves according to the shape of the tissue elements. Circular parts formed of cells or gland vesicles have a similar shaped, that is, circular net-work of vessels ; while those with a decided fibrous disposition, or parts formed of glandular passages and tubes running in a parallel direction, present the straight capillary net-work. Fig. 220 shows the straight capillary net-work of the trans- Fig. 220. Vessels of the voluntary, transversely striated muscle, a, ar- terial ; 6, venous branch ; c, the straight capillary net-work. Fig. 221. Vessels from a vertical section of the mucous membrane of the stomach ; the fine arterial branch divides into a straight capillary net-work, which forms cir- cular meshes at the surface of the mucous membrane, and passes over into the thick venous trunk. versely striated muscle ; fig. 221 the same of the mucous mem- brane of the stomach surrounding the gastric glands. The latter assumes the form of a circular net-work at the surface of the mucous membrane, where the gland-ducts terminate with round apertures. We have already, in a previous section (p. 278), learned that the lobules of fat-tissue consist of groups of large globular 390 SECTION SIXTEENTH. cells. The capillary net-work, fig. 222, is in accordance there- with. A likewise more circular, but large-meshed and pecu- liarly formed net- work of capillaries is seen in the inner layer Fig. 222. Vessels of tie fat-cells. A. Arterial (a) and venous (6) branches, with the capillaries be- tween them. B, the capillaries around three cells. Pig. 223. Vessels of the human retina. rial, c, venous branch ; b, the capillaries. of the retina (fig. 223). Where small papillary projections appear (external integument and many mucous membranes), we meet with simple capillary loops (fig. 224) ; where these are larger, with a looped net-work, as in the intestinal villi. The arrangement of the capillary net-works of the human organism Fig. 224. Capillary loops of the papillae of the skin (in othci's appear the tactile bodies). is frequently of such a peculiar nature that the practised observer can readily recognize, with the greatest certainty, from what part of the body the preparation is obtained. The first appearance of the vessel in the embryo, as well as VESSELS AND GLANDS. 391 the subsequent formation and transformation of the foetal vessels, constitute, as is known, a very difficult and therefore still, to a great extent, deiicient section of histology. Very young embryos of birds, mammalia, and fishes are to be recommended for the investigation of the origin of vessels. Among these, the embryos of the hen have been employed for many years and stand in the first line, in consequence of the facility with which suitable material may be obtained. The formation of the first capillary reticulation may be observed in the area vasculosa from the end of the first and on the second day of incubation. For this purpose, the germinal membrane is to be cut out beneath the surface of lukewarm water to which a little chloride of sodium and albumen has been added. It is then to be examined either quite fresh with the application of an indifferent fluid, or of a strongly diluted solution of chromic acid ; or, which is to be considered as m ore advantageous for many purposes, after having been hardened in chromic acid or bichromate of potash, it is to be investi- gated with the aid of glycerine and tingeing methods. Sections through the area vasculosa, treated in the latter manner, also present instructive appearances (Kolliker), so that one may readily recognize the endothelial cell formation of the walls of these earliest vascular canals. Foster and Bal- four, in a beautiful little book, recommend the examination of the living germinal membrane with the aid of the warm stage, the action for a minute of a 0.5 per cent, solution of chlo- ride of gold, the use for half an hour of a 0.5 per cent, osmic acid, and the immersion for a day in the 1 per cent, solution of bichromate of potash which we have already mentioned. In order to follow the further peripheral formations of ves- sels one may use the embryos of the hen at a more advanced stage, for example, their allantois ; or the embryos of mamma- lia may be employed. In the latter, the urinary sac, the mem- brana capsulo-pupillaris and hyaloidea of the eye also afford admirable preparations. i A very convenient object for examination is presented dur- ing the early part of the summer by the tail of the frog's larva. As the living animal may be examined either on the Schulze' s object-bearer (p. 246), or by means of a strip of moist blotting- paper wrapped round its body without injury, and again placed in the reservoir, it is possible to follow from day to day, in one 392 SECTION SIXTEENTH. and the same specimen, the alterations in the vascular forma- tions which take place in accurately designated places. Fur- ther assistance is afforded by brushing off the epithelium, as performed by Hensen (p. 378). According to the beautiful investigations of Arnold we may at present formulate the structure of the new vessels somewhat as follows : A protoplasma, capable of further independent develop- ment, is produced by the vascular cells forming the Avails of the already existing capil- laries. Fig. 225, p, p, and fig. 226, a, a. From the shooting out of the proto- plasma are formed sprouts (tig. 225, 1, p) and filaments (fig. 225,2, 3, p,p, and fig. 225, a, a), which, by the run- ning together of opposite protoplasma bodies, are transformed into cords (fig. 225, 2, j>). On the melting down of the axis portion of these cords we have proto- plasma tubes. By the fur- ther metamorphosis of the walls there occurs (in a manner very difficult to understand) the appear- ance of nuclei. The hitter are at first small and indis- tinct, subsequently they are larger and appear more distinct. Up to a certain stage of development no blood-vessel shows a dis- tinct silver mosaic. Cell-like elements with a body consisting of protoplasma are then formed by a sort of segmentation of the parietal substance. From these, finally, arise the mature vascular cells, the nucleated, homogeneous lamella of our figs. 215, 216, and 217. Pathological changes of the blood-vessels, as is known, are Fig. 225. Development of new capillaries, from the tail of the tadpole, p, p, protoplasm sprouts and cords. VESSELS AND GLANDS. 393 met with often enough. In so far as they consist of a meta- morphosis of the structure, they affect the larger trunks, espe- cially of the arteries, much more frequently than the finest ar- FlG. 226. From the vitreous body of a fcetal calf. Two vessels with an adventitia, united by a proto- ptasma cord. At a, the insertion of the same into the primary vascular membrane. terial and venous terminal branches, or the capillaries lying between them. In the arterial walls of older persons there are generally found — increasing in frequency with the advance in life — changes of the inner vascular membrane in the form of smaller or larger whiter or yellower spots and plates projecting some- what above the surface. These are found, by microscopical analysis, to consist of collections of fat-molecules. There may afterwards be a softening and breaking down of these fatty de- generated places. In the atheromatous processes, also, we again meet with the same fatty deposits, but in the deeper strata of the interna con- tiguous to the muscular coats, after a proliferating thickening of the inner coats of the vessels has taken place as a result of an irritation. Here, also, a softening of the fatty infiltrated place occurs, and the melting process advances at the expense of the remaining layers of the inner coat of the vessel. When a regular atheromatous pulp (which may force its way into the blood-passage) has been formed, its elements are shown by microscopical analysis to consist of fat-molecules, isolated or united in globular conglomerations, crystals of cholesterine, and fragments of tissue. These thickened places in the intima 394 SECTION SIXTEENTH. may, however, undergo still another degeneration, a hardening, which may also be combined with the former ; they may be- come calcified, and form hard plates or tablets in the walls of the vessel. By such atheromatous changes in the arterial walls are caused, at least to a great extent, arterial aneurisms which in part permit of the recognition of all three of the groups of layers, although thickened and metamorphosed in part after the destruction of the intima, or also of the muscular coat, con- sist either of both coats or of the connective- tissue coat alone, which latter then presents transformations, thickenings of its tissue, etc. — matters which we cannot consider further at present. The question arises — How are such abnormities of the arte- rial walls to be examined ? In general, by means of the same methods with which we have already become acquainted in the examination of the nor- mal structure. By pulling off the individual layers from the fresh specimen, then on horizontal and vertical sections of the walls after hardening in alcohol or chromic acid, or finally by the aid of the embedding and drying methods. The coats, boiled in vinegar and then dried, also afford handsome sections whereby the fat-molecules of the atheromatous mass make their appearance in an elegant manner. Atheromatous pulp is, like pus, etc., to be spread out with water. The method of examination also remains the same for the pathological metamorphoses of the structure of the veins. As with the arteries, we here omit the dilatations of the veins, and the occlusions from thrombi and emboli (that is, clots which have originated in a remote locality, and, carried forward by the blood, have finally become wedged into a vessel). Only those layers of the walls which contain vessels, especially the adventitia and the middle layer, are at first concerned in the inflammatory processes of the veins. At the same time there is tumefaction, the formation of so-called exudation masses, and an accumulation of pus-corpuscles. The inner coat, which is not immediately concerned in the inflammatory process, is also at last, as a result of these structural changes, drawn into the sphere of the process. It appears cloudy, thickened, rough, and may become separated in shreds. Such rough inner surfaces of venous as well as arterial ves- VESSELS AND GLANDS. 395 sels frequently receive aggregations of coagulated fibrine from tlie blood. Consequently we see such deposits on the intima of inflamed veins, as well as on softening atheromatous patches and in the dilated sacks of aneurismal arteries. Pathological changes of small vessels, microscopic arteries and veins, escape the notice of the physician much more readi- ly, as will be appreciated, and also cause much slighter effects during life. In amyloid degeneration of the smaller arteries the middle coat is seen to be the seat of the deposit, and not the intima (as Rindfleisch asserts). Jurgen's reagent (p. 155) is the most serviceable for the recognition of these deposits. The fibre- cells of the muscular coat lose their structure and become transformed into amyloid flakes ; and in calcifications, also, the deposit of bone-earth takes place in this contractile element. The small arteries of the brain-substance occasionally un- dergo an interesting metamorphosis. In vessels of extreme minuteness, up to those of 0.5'" in diameter, a tearing of the inner and middle coats takes place ; extravasated blood be- comes infiltrated under and into the adventitia, and arches this forward, in various ways, into vesicles and knobs. If, at last, the external connective-tissue layer also becomes torn through, apoplectic effusions occur. Should it hold, however, a strik- ing microscopic appearance is unfolded in the gradual meta- morphosis and breaking down of the extravasated blood-cor- puscles ; so-called granule cells, aggregations of brown and yellow pigment, and their final dissolution may be observed. Fine microscopic veins and their branches, which are pass- ing over into capillaries, occasionally show similar varicosities of their lumen. Although with the above-mentioned arteries the bulging is caused by the laceration of the coats and the ex- travasation of the blood, here all three of the coats are unin- jured. Calcareous and fatty degenerations, and likewise deposits of pigment, have been noticed in the capillaries as well as in the smallest arterial and venous branches which are associated with them. Furthermore, emboli of the same, as well as thick- enings of their walls, belong to the more interesting occur- rences. Calcifications have thus far been noticed chiefly in the ca- pillaries of the brain ; they occur very rarely. Much more fre- 396 SECTION SIXTEENTH. quently, especially in the brain of older persons, fatty degen- erations, groups of aggregations of small fat-molecules around the nuclei, or in the place of the same, are noticed. This struc- tural metamorphosis is occasionally diffused, in the most ex- tended manner, throughout a whole brain. Deposits of black pigment molecules have been observed in the capillaries of the spleen, liver, and also of the brain, in melamemia. Peculiar emboli of the finest arteries and veins from masses of fluid fat have also been noticed more recently in so-called pyaemia (E. Wagner). We have already mentioned above the normal occurrence of the adventitia of capillaries. Something of the kind is also met with under abnormal circumstances. The capillaries of a part in a condition of inflammatory irritation gradually receive an aggregation of spindle-shaped cells, precisely similar to those which occur in the normal development. Very fine appear- ances of this kind may be obtained from the inflamed cornea. An aggregation of this undeveloped connective-tissue forma- tion of the gelatinous tissue may also appear as an adventitia around capillaries (Billroth). In all textural changes of the capillaries, like those of the larger and largest trunks, the greatest attention is to be paid to the nuclear formation of the so-called vascular cells, as it is just these epithelioid cells which rapidly assume a condition of luxurious proliferation, and thus give rise to numerous new formations (Thiersch, Waldeyer, Bubnoff, Kanvier). The structural changes which have thus far been mentioned of the smaller and smallest vessels coincide exactly with those of the normal body in so far as the methods necessary for their examination are concerned. A matter which has caused numerous controversies is the manner in which the origin of vessels takes place under patho- logical conditions. Such productions of new blood-vessels, as is known, are not rare occurrences, and appear in hypertrophied organs, in neoplasms, in so-called pseudo-membranes, and granulations. Quite massive new formations of blood-vessels may be recog- nized in the so-called vascular tumors. Numerous sack- and knob-shaped expansions of the dilated capillaries are met with in the capillary talengiectasias, especially such as occur in the skin. The methods for examining the tissues of the skin must VESSELS AND GLANDS. 397 here be employed. Preparations boiled in vinegar and then dried afford characteristic views. When snch newly-formed vessels are examined they show either — and this is generally the case — the character of the capillaries or those of the arteries and veins, while the blood which circulates through them presents nothing especial. Their diameters are either those of the normal condition, or they are increased frequently in the most remarkable manner. At the same time partial dilatations of the walls frequently occur. Knob-shaped pouches are also met with, especially in vascular tumors, which require more accurate investigations. At a former period, swayed by the theory of spontaneous cell-formation and the exudation doctrine of that time, it was frequently asserted that these pathological vessels (like the blood contained in them) originated independently of those of the neighboring nor- mal tissue, and only subsequently became united with the ad- jacent vessels. At the present day we may say that this theory was false, and it has also never failed to be frequently at- tacked. No new for- mation of vessels de- viating from that of the foetal body occurs in the domain of path- ology. In both cases the new vessels arise by growth from the existing ones, or at the commencement by the development of an intermediate lacunar current. The former process is the same as that with which we have become familiar in the formation of embryonic vessels. The same protoplasms formations, offshoots, filaments, cords, and tubes are met with following each other. The tail of the frog's larva, as it commences to be reproduced (Arnold), permits of highly interesting investigations, with which figs. 227 and Fig. 227. Development of the capillaries in the regenerating tail of the tadpole, a, b, c, d, sprouts and protoplasma cords. 398 SECTION SIXTEENTH. 228 (the same vascular division twenty-four hours later) are to be compared. According to more accurate investigations which have been made, the formation of vessels in a tumor, like a so-called pseu- do - membrane, ap- pears to take place but slowly and grad- ually, and thus to form a striking con- trast to the rapidity with which, for in- stance, an aggrega- tion of pus-cells may take place. Either the fresh tissue or that hard- ened in alcohol, chromic acid, etc., is to be employed for examination. The escape of the blood-corpuscles from the newly-formed vessels, which readily occurs in such preparations, is a very unfortunate circumstance, and is responsible to a considerable extent for the scanty results which so many investigators have obtained in this direction. If the injection with transparent masses, which is frequently difficult, it is true, succeeds, the whole naturally gains extraordinarily in clearness. Thus Thiersch made the in- teresting observation in the healing of wounds of the tongue, that at the commencement a system of lacuna-like passages is formed in the granulation-tissue which lead from the loosened arterial walls to similarly constituted veins. Conditions which the healthy spleen (see below) shows during life. The largest proportion of these "plasmatic" canals afterwards disappear, but a poi'tion of them become widened and form blood-convey- ing vessels, and the cells of their walls are produced by the ad- jacent tissues. The lymphatics, as is known, show in their large trunks a structure reminding us of that of the veins, and also coincide with them in the abundance of their valves. The latter also Fig. 228. The same vascular district 24 hours later, a and d have become pervious ; b and c are still solid in their middle por- tions. VESSELS AND GLANDS. 399 continue in the fine branches, and give them a very character- istic knotty appearance. So long as such a constitution can be recognized, the walls of these tubes, although at last simplified to a structureless membrane, are formed of a special tissue which differs from the neighboring tissues. The same methods are employed for the examination of the walls of these vessels as for the arteries and veins. Large trunks may be dissected out, slit up, and examined by pulling off the individual layers, or, after drying, longitudinal and transverse sections may be made. It is best to inject small trunks with pure gelatine by tying in a line canule ; after cool- ing, thin transverse sections may be made. The finer lymphat- ics appear at first to form cavities and pas- sages surrounded only by connective tissue. By the application of the dilute solution of nitrate of silver (preferably in the form of an injection), it has been ascertained, however, that these also have a wall consisting of the characteristic vascular cells (fig. 229, a). While the latter, in the capillaries of the blood-passages, however, usually presents a certain independence in opposition to thead- r \ L Fig. 229. A lymphatic ea- lacent tissues, the walls of the lymph-canals n»i from the large intestine ^ x of the Guinea-pig. a, vas- ai'e intimately blended with the neighboring <=mar ceii; », intercalary u o o plate. connective tissue. In investigating the arrangement of the finer lymphatics of an organ, the injection of cold, flowing, transparent masses of Prussian blue and carmine (see pp. 1S7-S) is to be employed, together with the subsequent hardening in alcohol. In doing this the canule is either to be tied in or the method by punc- ture is to be used. The injection is sometimes easily accom- plished in some parts of the body, occasionally only with the greatest difficulty. The natural injection, which, for the blood-vessels, may af- ford to the unpractised a substitute for the artificial injection, is, from the nature of the enclosed fluid, of very limited impor- tance for the lymphatics. The lymph proper disappears as a colorless fluid in the tissue of the organ, and the small vessels only glimmer forth from the tissue where a pathological color- ing matter, of the bile or of the blood, for example, is retained and mixed with the lymph. The chyle, on the contrary, forms, 400 SECTION SIXTEENTH. as is known, a milk-white fluid, in consequence of the larger amount of fat which it contains, and hence its vessels are seen distended in a beautiful manner. Mammalial animals, especi- ally young suckling examples, killed during the digestion of fat (3-5 hours after its reception) afford, therefore, excellent objects for the study of the chyle ducts and vessels, a subject to which we shall return at the investigation of the organs of digestion. We cannot yet leave our lymphatic canals. We have still to discuss an important question of structure. The connective tissue, as has long been known, is manifoldly permeated by a system of fine clefts and passages, which con- tains a fluid. To this has been given the name of the juice clefts (Waldeyer) or juice canals (Recklinghausen). It is seen instantaneously and very beautifully in the cornea of the eye. Now, in the normal condition, does this system of the so- called juice clefts have a connection with the previously de- scribed lymph canals, perhaps also with the blood passages ? This has certainly been frequently asserted ; according to our opinion, however, not with complete justice. If these lymphatic passages be injected with caution and without immoderate consumption of time (Hyrtl, Teichmann, His, Frey, Langer), nothing passes over into these juice clefts. The " stigmata" close here just as completely as in the blood- vessels (fig. 217). As a result of an immoderate (or also of a too long-con- tinued weaker) pressure — probably this scarcely ever happens in healtlry life — however, the " stigmata " mentioned distend into "stomata;" and now a direct communication is established between both varieties of passages. Such an one exists, on the contrary, in the normal condition between the cavities of serous sacs and their lymphatics. The finer blood-vessels also behave exactly similar to these lymph-canals. As a result of continued distention of the vascular tube the stigmata become dilated and permeable ; the injection mass now passes into these juice canals (von Wini- warter, Arnold). Passing to the methods, we find the frog the most service- able animal for experiment. The first of the two observers mentioned drew a loop of in- testine out through an incision in the abdomen, excited in- VESSELS AND GLANDS. 401 flammation in it by means of cantharidine, then returned it, and closed the wound with a suture. The next day the blood passages of the cadaver were injected with thin blue gelatine, using the constant pressure. A similar injection also succeeds, however, by the heart's action of the living animal. The cold flowing mass is injected into the vena cava through a fine glass tube. Arnold, one of our most excellent histologists, has made this experiment to a much greater extent and with great acuteness. As Cohnheim had already shown, the web membrane of the frog may be used for this purpose, enclosing either the entire hind-leg or the exposed vena cruralis in a ligature. The tongue may also be used, placing a thread, with the aid of a line needle, around the venous trunks — either the V. mediana or the V. laterales. Then wait two or three days, when the artificial in- jection of the blood passages can be perceived in the animal after it is killed. If, however, it be desired to demonstrate the transition from the lymph passages to these juice clefts, according to Arnold, a broad ligature is to be placed around the thigh of a frog and tighten it moderately. The swollen limb is to be injected by the puncturing method on the third day, after killing the ani- mal by bleeding. The canule is to be first introduced into the lymph reservoir surrounding the foot joint, and from here into one of the smaller lymphatic spaces which are situated between the toes. The passages of the web membrane now become in- jected and we likewise perceive the passage of the mass into these juice clefts. If it be desired to follow relative (or also other) observations in the living creature under the microscope, it is advisable, in order to prevent drying, to keep a constant minimal current of fluid, such as a dilute solution of common salt, passing in a suitable manner over transparent parts. Thoma has recently given us excellent directions for this " irrigation process." Un- fortunately, in consequence of the narrow limits of our little book, we cannot enter further into the discussion of this subject, or the very convenient apparatus of this able investigator. Pathological new formations of lymphatics, especially in tu- mors, are of frequent occurrence, although this subject, in con- sequence of the difficulty of its investigation, still represents almost a terra incognita. Krause has communicated a few ob- 26 402 SECTION SIXTEENTH. servations concerning them. He succeeded, in scirrhus and medullary sarcoma, in injecting trunks lying in the connective- tissue bands of the framework, and likewise large vessels in myoma of the labia. J. Neuman successfully injected the pathologically changed skin. May these experiments very soon be further extended ! The structure of the lymphatic glands has recently become considerably more comprehensible from the labor of a number of observers (Billroth, Frey, His, Recklinghausen). The extreme softness and the opacity of the fresh organ, caused by the presence of millions of lymph-corpuscles, leads to the employment of hardening methods and brushing. These methods are the customary ones. Immersion in alco- hol, at first in such as is ordinarily used for preparations, which has been diluted with about half its volume of water, leads, as a rule, in from 5-8 days, to the desired object, especially if the precaution is observed to change the fluid frequently. The alcohol finally added should no longer become cloudy. If a sufficient consistence is not obtained in this manner, stronger alcohol, and finally that which is almost free from water, may be used, and thus, not unfrequently in the middle or towards the end of the second week, preparations will be obtained which are suitable for sections and for brushing. Over-hardening is, however, to be most carefully avoided if the framework sub- stance is to be examined, while strongly indurated alcoholic preparations afford the best specimens for the investigation of the blood- and lymph -vessels of these organs. For many pur- poses chromic acid and bichromate of potash deserve the pre- ference to alcohol. Commence with weak solutions and pro- ceed very gradually to stronger ones. The shrivelling which is usually connected with alcoholic preparations may thus be frequently avoided to a considerable degree. Solutions of the bichromate of potash, of a corresponding concentration, are also very serviceable. All lymphatic glands once hardened by any of these ways may be preserved for a long time in a serviceable condition, and may be used for occasional observations. Small, fresh lymphatic glands from healthy bodies do not, as a rule, present any difficulties in hardening. It is otherwise with those which are very voluminous, or no longer fresh, as well as with those which are affected by many varieties of degeneration. Thus, for example, typhus mesenterial glands VESSELS AND GLANDS. 403 require much care, as a rule, and the object is not always accomplished. The previous injection of the hardening fluid through the blood or lymphatic vessels of the organ to be immersed is a useful accessory with such organs as are difficult to manipulate. Attempts may be made in vain to harden these very glands by immersing them for 8-14 days in alcohol of in- creasing strength, and finally in that which is almost absolute, success only being obtained afterwards by placing them in chromic acid solutions. Toldt has recommended another procedure which permits of the preparation of the thinnest sections, and thus renders the trouble of brushing unnecessary to a great extent. The fresh glands are to be placed for 3-4 days in very "dilute, wine-yellow ' ' chromic acid. When the hardening has reached the interior it is to be placed for the same length of time in glycerine di- luted with an equal part of distilled water. It would appear almost superfluous to give fur- ther directions for the ex- amination of the frame- work of the alveoli or follicles (fig. 230, d) and . , . . m1 Fig. 230. Section through one of the smaller lymphatic lympliatlC VeSSelS (e). Hie glands, with the current of the lymph— half diagrammatic -. -. n . figure, a, the capsule ; b, septa between the alveoli or fflandS Of younger am- follioles ot the cortex (a) ; c, system of septa of the medul- ° . lary substance as far as the hilus of the organ : e. lymph- mals, Or SUCh as are in a tnbea of the medulla;/, afferent lymphatic currents, which ' f surround the follicles and flow through the spaces of the Swollen Condition are tO medulla : g, union of the latter into an afferent vessel (h) ' at the hilus of the organ. be employed for the first recognition of the cellular character of the reticular tissue. Among the tingeing methods, that with carmine accomplishes most in these cases. The reagents mentioned at the smooth muscles are employed for the recognition of the fibres of this tissue at and in the septa, especially the treatment with chlo- ride of palladium and the double staining with picric acid and carmine (p. 159). The blood-vessels may be injected either from the small ar- terial branches which enter the gland when the organ is suffi- ciently voluminous, or, in smaller glands, by the neighboring- large trunks ; thus, for example, the pancreas Asellii of the 404 SECTION SIXTEENTH. smaller mammalia may be injected from the mesenteric arteries and the portal vein. Here the double injection readily succeeds. A few years ago I gave more accurate directions for the in- jection of the lymphatics (/', g, h) by the afferent and efferent lymphatic vessels of the glands. In these cases, as a rule, finding the lymphatics usually causes greater difficulty than the subsequent manipulations. Transparent and — as I will add, relying on recent experi- ence — cold-flowing injection masses should always be used. But not all lymphatic glands are adapted for injecting. As with all injections of lymphatics, fat subjects and bodies already commencing to decompose are to be avoided. (Edema- tous portions of the body are usually best qualified. A pre- paratory immersion in water for several hours may also prove advantageous. If a niammalial animal be employed, the following proce- dure presents the greatest advantages. The animal is to be killed by a blow on the head, or by strangulation. The duc- tus thoracicus is to be immediately ligated high up, and the bodjr allowed to lie for 2-6 hours. After this interval the lym- phatics are, for the most part, lirnily distended, and readily permit of the injection being made in the direction in which their valves open. In injecting the vasa efferentia, on the con- trary, it is difficult to overcome the resistance of the valves, and it only succeeds in isolated cases. The various degrees of distention are here of great impor- tance for the intelligibility of the whole current. At the com- mencement, therefore, only injections which have been early discontinued should be used, proceeding gradually to the em- ployment of those which have been more prolonged. The in- jection of a second or even third lymphatic gland by the vasa efferentia of a previously injected gland affords very fine specimens. It has already been remarked, at page 201, that Hyrtl and Teichmann have facilitated this procedure considerably by means of the puncturing method ; and in fact this process ac- complishes a great deal for the lymphatic glands. Fine tubes, cautiously introduced beneath the capsules of larger and smaller glands, as a rule, readily iill the investing spaces of the follicles, and from these the passages of the medullary sub- stance. This method is indeed inestimable for the examination VESSELS AND GLANDS. 405 of the passages of pathologically metamorphosed lymphatic glands. It may be practised with the syringe or with the con- stant pressure. A skilful hand will rarely have recourse to the latter, however. True glands, belonging in the narrower sense of the word to the lymphatic system, will be met with only in extremely rare cases naturally injected with decomposed hsematine, in a con- dition serviceable for the microscopical analysis. On the con- trary, animals fed with fat, or the bodies of persons who have died in the act of digesting fat, present a very important and instructive natural injection of the chyle-glands. Take one of the smaller mammalia, — for example, a rabbit or a small dog, — and introduce a considerable quantity of milk through an (Esophageal catheter into its stomach. The animal is to be killed after from 4-7 hours, and, as a rule, the most exquisite injection of the entire chylous system will be found. The recognition, by a finer analysis, of the chyle-fat in the interior of a somewhat more voluminous lymphatic gland is, however, a precarious matter. Fresh sections may be treated with a solution of albumen, as recommended by Brucke. At- tempts should be made to render preparations which have been hardened in dilute chromic acid or weak alcohol transparent by means of soda solution. I have never seen any great effects from drying such glands either with or without a previous im- mersion in boiling water. Extremely small chyle-glands, especially those consisting of a single follicle, such, for instance, as are found in the ab- dominal cavity of the rabbit, when examined fresh without further addition, and in the condition of fat assimilation, afford, on the contrary, handsome appearances. The self-injection of the lymphatic glands lias also been em- ployed. Toldt employs for this purpose a very finely granula- ted aniline blue, precipitated from an alcoholic solution by the addition of water. It may be injected under the skin of the living animal, and being conveyed by the afferent lymphatic vessel, the injection of the neighboring gland may be ex- pected. Or, the lymphatic glands lying in the vicinity of the liver of the dog may be selected. As, according to Hering's experience, the hepatic lymph of narcotized creatures is rich in red blood-corpuscles which have escaped from the blood-vessels, one may accomplish the ob- 406 SECTION SIXTEENTH. ject by injecting this aniline mass for 7-8 hours in repeated doses of 12 grammes about every 10-15 minutes, in the vena cruralis of an animal narcotized with opium. As is known, the human lymphatic glands are subject to numerous structural changes. A part of the latter are to be regarded as senile metamorphoses ; others are of a more patho- logical nature. Among the former (which may also occur at a relatively early period of life), we must especially adhere to three ; namely, the formation of fat-cells, the pigmentation of the lymphatic glands, and the metamorphosis of the framework substance into ordinary connective tissue with the gradual destruction of the entire organ. The fat-cells take their origin from the connective-tissue corpuscles of the framework of the lymphatic gland, and, as a rule, affect the cortical substance of the gland. It is only in rare cases that they are noticed in the lymph-tubes of the medullary substance. The glandular structure of the lymph- atic gland disappears more and more in proportion as groups of fat-cells take the place of single cells. The pigmentation of the lymphatic glands, as is known, affects the bronchial glands chiefly, and is, after certain periods of life, an almost regvdar occurrence, although of extremely varying degrees. If this process be followed from its very commencement it will be seen that, at least in most cases, the exciting cause is an inflammatory irritation of neighboring parts of the lungs. The consecutive tumefactions of the lymphatic glands, which are so frequent and with which prac- tical physicians are familiar, are accompanied by very extra- ordinary enlargements of their finest blood-vessels, so that, for example, almost all the capillaries are found to be dilated to four and even six times their ordinary diameter. In conse- quence of these expansions, an exudation of the coloring mat- ter of the blood takes place in the bronchial glands (and under certain circumstances in the lymphatic glands of other parts of the body also), so that the gland, saturated with a brownish fluid, assumes a ' ' splenoid ' ' appearance. At the same time lacerations of individual vessels and extravasations are also met with here and there. The molecules of black pigment arise by intermediate stages from the gradual transformation of the coloring matter of the blood. VESSELS AND GLANDS. 407 Most of the cases of pigmented bronchial glands originate, however, from an entirely different source. It is inspired coal- dust which, having penetrated the pulmonary parenchyma, is brought through the lymphatics to the bronchial glands, and is here slowly deposited in the course of years. We shall have to mention this ' ' anthracosis ' ' again at the respiratory organs. In this manner, then, varying extremely in degree, pigmen- tations of the bronchial glands take place. Those of slight de- gree give the organ a sprinkled and spotted black appearance, but in higher degrees cause the black appearance to extend over greater distances, and even throughout the entire thick- ness of the organ. While lower phases of this melanosis prove to be relatively indifferent for the organ affected, stronger pigmentations lead to the connective- tissue metamorphosis and atrophy of the lymphatic gland. Such connective-tissue metamorphoses show bundles of stri- ated and fibrillary tissue, at first isolated and then developed in the most extensive manner at the expense of the reticular framework. The characteristic structure of the organ disap- pears more and more, and finally, together with the loss of all the lymphatic passages, the whole gland becomes degenerated into a connective- tissue mass. These processes are observed with pigmentations, but also without them. The external lymphatic glands appear to be more subject to this process than those which are situated deeper in the body. The ordinary methods suffice for the examination of the most prominent structural conditions. The previous injection of the blood-vessels with cold-flowing mixtures should, when possible, be at least attempted. The true pathological metamorphoses of the lymphatic glands affect in part the framework, in part the lymph-corpus- cles, and in part both elements together. The structural changes of our organ in abdominal typhus are not very easy to follow. In the first, so-called catarrhal period of this disease, a tumefaction of the organ is met with, which consists chiefly of one of the above-mentioned extensive dilatations of the finest blood-vessels. The investing spaces of the lymphatic-gland follicles are enlarged, and in these are found a number of large multinuclear cells (which may also be found, although in smaller quantity, in other irritated condi- 408 SECTION SIXTEENTH. tions). The participation of the framework-substance appears, on the contrary, to be remarkably slight. At later periods these cells break down under fatty degeneration, and produce collections of very unequal extent, of a finely granular sub- stance, the medullary typhous matter. Not unfrequently these form local softenings, into the sphere of which are drawn the adjacent tissues, the framework with the blood-vessels. In favorable cases the finely granular substance is again removed by the efferent lymph-current. A similar process, only much more sluggish in its progress, is met with in tuberculous and scrofulous lymphatic glands. Here, together with the breaking down of the framework substance, the same degeneration also appears — a fine, molecu- lar, fatty, waterless matter with interposed, shrunken lymph- corpuscles. These " cheesy metamorphosed" masses may have various destinies allotted to them ; they may be reabsorbed, become indurated and calcified, or soften and give rise to the formation of a fistulous passage. A series of investigations which I was enabled to institute in leucaemia of our organ show that there is here essentially only an increase of volume. The structure usually remains normal. In other jiathological conditions the participation of the framework substance is more extensive. Thus, in secondary inflammatoiy conditions of our organ, the meshes of the net- work are seen to gradually become narrower, the trabecular in- crease in size, and distinct nuclei are again formed in the nodal points. In the more voluminous organs, where the expansions of the capillaries already mentioned may be recognized, there maybe a gradual obliteration of the textural differences of the septa of the medullary and cortical substance. The lymphatic passages disappear, and the organ has become incapable of per- forming its functions. The later appearances of such lymphatic glands vary considerably, however. An interesting structural condition is sometimes presented in such cases, by the enormous thickenings of the capillary walls which are caused by the ag- gregation of spindle-cells. Allied structural conditions are presented by the hypertro- phies of the lymphatic glands. Here the capsule, the septa, and, at last, the medullary substance also, become transformed into a reticular tissue, which is uniform throughout the entire VESSELS AND GLANDS. 409 organ, and encloses numerous lymph-cells. This transforma- tion of the capsule enables one to appreciate how the adjacent connective substance may be drawn into the sphere of the same metamorphosis, and a fusing together of the neighboring lym- phatic glands take place. The reticular framework is either like the normal, or the meshes are seen to be narrower. In other cases the fibres become much more strongly developed, so that a coarse-banded framework, like that of a carcinoma, may be formed. In the latter processes the large nucleated cancer-cells are met with in the meshes, varying in form and arrangement. Formerly, the inflexible trabecular framework, which per- meates the lymphatic channels (investing spaces), appeared to constitute the chief starting-point of the metamorphosis in question, as the cancer-cells arise in its nodal points, and its trabeculse become the stroma of the carcinoma. At the present day, an original immigration of the first cancer-cells through the vas afi'erens into the investing spaces has become more probable. The glandular tissue becomes slowly and gradually atrophied. A newer and more successful method of investigating these diseased lymphatic glands consists in their injection, and in the study of their lymphatic channels by the aid of the puncturing method. In such an organ, so long as there is a simple tume- faction, whereby those enormous distentions of the capillary blood-vessels are frequently met with, the lymphatic passages are all permeable. If the metamorphosis of the gland progres- ses further, as in typhus, and a breaking down of tin.' lymph- corpuscles into the fine granular t- typhus substance 1 ' occurs, such places become stopped up ; the channels of hypertrophied lymphatic glands likewise become impermeable to a great ex- tent. These are a few of the results which the author of this work has, thus far, obtained by suitable injections. Many dark points still exist with regard to the origin of the lymphatic glands and lymphatic vessels of the foetal body. Many years ago we became acquainted, through Kolliker, with interesting lymphatic vessels in the tail of the frog's larva. These run near the capillary blood-vessels, and appear as deli- cate, twig-like, ramified canals, without the reticular intercom- munications of those vessels, and are characterized by the numerous small pouches into which their delicate walls are ex- 410 SECTION SIXTEENTH. panded. They contain a colorless fluid, almost free from cells, and it is certain that they are without an epithelial lining. Aggregations of neighboring spindle-cells are frequently met with on the membrane of the vessel. We now turn to the methods of investigating glandular tis- sue. Three elements participate in the formation of a gland, or — when its volume is greater and the structure more compli- cated — of its subdivisions. A transparent, apparently struc- tureless membrane (membrana propria), constitutes the frame- work, and thus determines the form of the organ or part of the organ ; strata of cellular elements (gland-cells) cover the inner surface of the latter and play an important role in the forma- tion of secretions. Finally, the external surface of the struc- tureless membrane is covered by a reticulation of capillary ves- sels, from the contents of which the matters for secretion are taken in the form of watery solutions. Our fig. 231, which presents the lower halves of long, simple, tubu- lar glands from the gastric mucous membrane, may afford us a repre- sentation of this condition. The fine contours of the sinuous, blind-sack- like tubes present the optical ex- pression of the membrana propria ; nucleated fine granular cells form the contents, and a capillary net- work, sjiread out in the tubu- lar form, surrounds the individual organ with elegant incurva- tions. None of the glandular organs of the human body are without capillaries and gland-cells. This is not the case, however, with the membrana propria. It may be absent, and, indeed, under manifold conditions. In the first place, we see that the fine membrane which is present in the earliest period of life is blended with neighboring parts, as in the liver. Or, the same lias been absent from the commencement, and a firmly woven, connective-tissue limiting-wall encloses the aggregation of cells at all periods of life. Finally, we have learned through more recent researches that a wicker-work of flattened, multi-radi- ated connective-tissue cells becomes visible in this membrana Fig. 231. Gastric glands of the dog, with cells and capillary vessels. VESSELS AND GLANDS. 411 Fig. 232. Plexus of star- shaped connective- tissue cells from the membrana propria, isolated by maceration. From the subuiaxill ary gland of the aog, after Boll. propria (fig. 232). This condition has been especially noticed in racemose glands (salivary, lachrymal, and lacteal glands), but also in the tubular glands of the mucous membrane of the stomach. Macerating methods and sec- tions through hardened preparations are employed in these cases. An entire muster- roll of methods has been recommended: vinegar ; the 33 per cent, solution of pot- ash ; the maceration for several days in iodine-serum, and then, subsequently for 2i hours, in a chromic acid solution of -^ per cent, (or, chromate of potash ^ per cent.) ; the immersion in osmic acid of \ per cent. ; and the hardening by means of alco- hol or the bichromate of potash, with subsequent carmine tingeing. However, the numerous glands of the human body are of such manifold natures, according to their size, their complexity, and their entire structure, that the example made use of above can in no Avise suffice for their comprehension. Together with the simple tubular glands which we have already become familiar with in the gastric glands of the stomach, other more complicated ones occur in which the lower cajcal ex- tremity, with or without dividing, forms a number of coil - shaped convolu- tions. These organs have been provided with the ap- propriate name of convo- luted glands. The most extended and familiar ex- ample of them is presented by the sudoriparous glands of the skin (fig. 233, a, b). The net-work of vessels which encircles the coil becomes a sort of wicker-work with rounded meshes (e). The kidney and the testicle, two large, voluminous organs of the body, present much longer cylindrical Fig. 23.3. A human sudoriparous pland, a, the coil, sur- rounded by the commencement of venous vessels; b, the excretory duct ; c, the basket-like capillary plexus sur- rounding the coil, and the arterial trunk. 412 SECTIOK SIXTEENTH. tubes with divisions and reticular intercommunications. Fig. 234 represents these glandular tubes of the kidney, the so-called urinil'erous tubes (1, 2). Another form of glands, the racemose, is very widely dif- fused. Roundish or elongated sacks (gland-vesicles), which are smaller or larger, longer or shorter, have their outlets associated together in groups. Such groups of sacks (gland-lobules) are again united by short ducts and by elongations of the mem- brana propria, and thus, sometimes in a slightly, sometimes Fig. 234. Uriniferous tubes from the human kidney, 1, Side view : a, b, canals filled with cells ; c, one partially tree from cells ; 2, transverse section of the same ; 3, gland-cells. Fig. 235. Human Brunner's glands. more considerably (fig. 235), and sometimes extremely compli- cated manner, the racemose gland is formed. The changes which are here to be observed, and the manner in which the efferent canal-work gradually advances to a more compound texture — these, as well as many other particulars, must be learned by reference to the text-books on histology. Notwithstanding many subordinate variations, there is one and the same fundamental design present in all, and easy to be observed from the mucous follicles, which are to be called almost microscopical, to the most voluminous examples, such as the salivary glands and the pancreas. The glands-cells (which we have still to mention more espe- cially) present numerous variations according to the nature of the actual secretion ; the capillary net-work surrounding them, on the contrary, always exhibits circular meshes (tig. 236). VESSELS AND GLANDS. 413 There is still a third form of glandular organs ; such, namely, in which the membrana propria constitutes a round- ish vesicle, closed on all sides, with cells in its in- terior, and surrounded externally with a net- work of capillaries; the entire organ being com- posed of a large or larger proportion of such vesi- cles embedded in a con- nective - tissue ground- work. The ovary (fig. 237) represents the latter ar- rangement. Its gland- vesicles, called Graafian follicles (c, d), contain, together with small roundish gland-cells, a large globular cell, the ovum. The latter, Iry the rupture of the (rather complicated) wall, having arrived at the end of its existence, undergoes Fig. 236. Vascular net-work of the rabbit's pancreas. ), others («), which were characterized o, Becner-ceiiu ; », cylindrical epithe- by varying contents, a difference of form, and above all by the absence of a cell-membrane at the upper free extremity, were discovered long ago at more or less regular distances from each other, and varying in number. The structures in question resemble sometimes a pear, sometimes a wide-bellied drinking glass. F. E. Schulze met with them throughout the entire intestinal canal, and in its tubular glands 438 SECTION" SEVENTEENTH. in the vertebrate animals, in the passages of the lungs, and in creatures living in water (fishes and amphibia), on the skin. He has given them the name of ' ' Becherzellen ' ' (cup-shaped cells), and declares them to be mucous-secreting structures. A recently killed animal is to be used for their investiga- tion, and the examination made either immediately, with the addition of indifferent media, such as iodine-serum, or after immersion for several days in Midler's fluid. Nitrate of silver has also been employed. Our lymphoid cells penetrate into the interior of the cylin- drical epithelial cells, as probably do also in the rabbit the still so enigmatical Psorosperms (Klebs, Frey, and others), and not only into the cylindrical cells of the small intestines, but also into those of Lieberkuhn' s glands as well as those of the biliary passages. The resorption of the chyle-fat by the cylindrical cells of the intestinal villi may be observed in fresh and hardened speci- mens. The handsomest appearances may be obtained in the smaller mammalia by the previously mentioned injection of milk. Seldom, and only by a rare chance, can the body of a human being who has suddenly died during the digestion of fat be obtained. The examination must naturally be made as soon as possible, as the decomposition which takes place so rapidly in the digestive canal obliterates the delicate textural relations. Older cadavers are entirely useless, as the fine chyle molecules in the intestinal villi usually flow together into large drops, and nothing remains of the cylindrical epi- thelium. The contents of the Lieberkuhn' s glands also show beauti- fully and distinctly in quite fresh intestines, by the addition of indifferent fluids ; likewise in alcohol and chromic acid pre- parations. Their cylindrical gland-cells (between which, as Schulze saw, cup-shaped cells occur) are also quite perishable, so that one often meets with only the finely granular, nucleated contents of the tubular glands as an artefact. Hardening methods are to be employed for all the remaining structural conditions. The drying process was formerly em- ployed, in consequence of the poverty of the technique of that period. There is one investigation, the study of the Brunner's glands (fig. 264), and their peculiar cells (fig. 265), for which we would still recommend this procedure, modified by previously DIGESTIVE ORGANS. 439 Fig. 264. Human Brunner's gland. boiling the tissue in vinegar. In fact, handsome preparations may thus be obtained, and the marvellously elegant ramifi- cations of the efferent passages may often be followed in the interior of the body of the racemose gland, especially in thin vertical sections. Schwalbe recently rec- ommended pyroligne- ous acid for a simi- lar purpose. Never- theless, at the present day the same purpose is also fulfilled by hardening with chro- mic acid, chromate of potash, and especially with absolute alcohol, methods which, togeth- er with that of freezing, constitute the most im- portant accessories for the remaining structures of the intesti- nal canal. With them, one may even recognize the oblong, complicated form of the acini and the cylindrical form of the cells of the Brunner's glands (Schlemmer). The latter are quite different from the elements of the Lie- berkuhn's tubes, but quite similar to those of the gastric mu- cous glands (Schwalbe). The circumstance is interesting that the cells of the quies- cent and active Brunner's glands (like those of the submaxil- lary gland and gastric tubes) also differ from each other (Heidenhain). Tingeing and brushing may be added ac- cording to necessity for the further study of the intestines. The tissue of the mucous membrane (fig. 266) is differently constituted from that of the stomach. In the latter organ we meet with ordinary fibrous connective tissue. A looser reticulated substance, with nuclei in individual nodal points, has here taken its place. Lymphoid cells (a) lie embedded in the meshes, and are especi- ally numerous in the small intestine. We have here, therefore, Pie. 265. Isolated cells of the Brunner's gland of the hog. 440 SECTION SEVENTEENTH. Fig. 266. From the email intestine of the rabbit, a, tissue of the mucous membrane ; b. lymph-canal ; c, spaces for the Lieberkiihnian glands; d, transverse section of the Lieber- kiihnian glands filled with cells. a variety of the reticular lymph-cell producing connective sub- stance, which is similar to the framework substance of the lymphatic glands (comp. p. 275). The tissue of the intestinal mucous membrane, however, bears a character of irregularity and mutability which we do not meet with in the lymphatic glands, at least under normal conditions. This tissue becomes condensed in- to a more homogeneous membra- nous layer around the glandular tubes at the surface of the intes- tinal villi, and also forms the limit- ing layer of the lymphatic canals which pass through the mucous membrane. In places, especially toward the surfaces of the larger blood-vessels and lymphatics, the tissue of the mucous mem- brane may assume a different appearance, and may even permit of the recognition of the wavy fibrous bundles of the ordinary connective tissue. On the other side, however, as will soon be shown, the tissue in question passes continuously over into the regular reticulated framework of the solitary and Peyerian follicles. In conform^ with this is a textural condition which is in- teresting for the nature of connective tissue in general. Within a certain space we perceive, at slight distances from each other, the one variety of connective tissue becoming metamorphosed into the other, occurrences which, as is known, pathological his- tology has so frequently shown to take place temporarily after each other. The conditions which have just been mentioned are related first of all to the small intestine of man, the mammalia, and birds. The tissue of the mucous membrane of the large intes- tine appears to be modified more in accordance with the fibrous connective tissue, and is usually poorer in lymph-cells. Brushing the reticular tissue of these mucous membranes may be accomplished with tolerable facility, and in young creatures the recognition of the nuclear formations is not difficult. In those which are older the number of the nuclei is indeed diminished. DIGESTIVE ORGANS. 441 The Lieberkuhnian glands of the small intestine (fig. 267) and the tubular glands of the large intestine (fig. 268), which are quite identical with the former, repeat in their arrangement Fig. 2(17. Lieberkuhnian glands of the cat, with de- composed contents. Fir. 268. Tubular glandsofthe large intestine of the rabbit after treatment with caustic soda. Flo. 2«). Apertures of the glands of the large intestine (representing at the same time the transverse sections of deeper-lying portions of the glands) from the rabbit. and frequency the conditions of the stomach. They are to be examined with the same accessories. On thin horizontal sec- tions of freshly immersed parts one may become convinced of the epithelium -like arrangement of the cells, and see how these, conically sloped towards each other, turn their bases outwards and their narrow terminal surfaces towards the axis of the tube (figs. 266, 269). A special membrana propria to demarcate them from the surrounding tis- sue of the mucous membrane, that is, an independent and firm boundary layer of the adjacent loose connective tissue, cannot be denied. The muscular tunic of the mucous membrane is brought to view by means of the same accessories as were used for that of the stomach. Peculiar phenomena are pre- sented by the intestinal villi which are met with in the shape of variously-formed projec- tions, pressed closely together in large numbers over the whole surface of the small intestine (Fig. 270, b). Fiq. 270. Small intestine of the cat. in vertical section, a, the Lieberkuhnian glands ; b, the in- testinal villi. 442 SECTION SEVENTEENTH. Their tissue (fig. 271) bears the same character as that of the remainder of the mucous membrane, and is, as was remarked, membranously thickened at the outer surface, as well as towards the chyle vessel (d) which passes through its axis. In birds I succeeded, years ago, in bringing to view a distinctly reticular external surface (as on the surface of a lymphatic gland-follicle) with the greatest certainty. Eberth also found the same in the goose, and was able to recog- nize a similar condition of the surface of the villi in the mammalia and in man. The in- testinal villi of the rat are best adapted for this purpose. Hardening for a month in Midlers eye-fluid has been recommended by that investigator. Longitudinally arranged smooth muscular cells (c) also occur embed- ded in the tissue of the villi, and give these organs their vital contractility, which has been known for a long time, and which is so important for the onward movement of the chyle. Horizontal sections of the villi may be made from well-hardened intestines by means of a very sharp razor with tolerable facility ; I find it difficult, on the contrary, to obtain a good vertical section, even from the voluminous villi of larger mammalia, whether the dried or the hardened intestine, or an embedding process be employed. The submucous tissue is to be investigated with the cus- tomary methods. The accessories which have been already mentioned (p. 345) serve for the examination of the ganglionic plexuses which occur here (figs. 195, 196). Their arrangement is to be studied partly on vertical sec- tions, partly on surface views of the submucous tunic from which the muscular and mucous membranes have been separated. The muscular tunic is to be examined according to the direc- tions previously given for that tissue (p. 317). The remarkable ganglionic plexus, discovered by Auerbach between the circular and longitudinal muscular-layers of the intestine, has also been noticed at the nervous system (p. 347). Injections of the blood-vessels of the intestinal canal suc- ceed with such relative facility (in the smaller creatures, by t ' d f A Fig. 271. An intestinal vil- lus, a, the cylindrical epi- thelium with its thickened eeam; b, capillary net-work ; c, smooth muscular tissue ; d, central chyle-vessel. DIGESTIVE ORGANS. 443 the coeliac and mesenteric arteries as well as by the portal vein ; in larger ones, by the arterial and venous branches, after the ligation of those which supply the neighboring districts), and afford such a permanent landmark, that they should never be neglected. A capillary net- work encircles the tubular glands with an abundant, extended, reticular formation in the same manner as in the stomach, so that there, where the surface of the mucous membrane remains smooth, the arrangement is quite the same. Our fig. 272, which presents the capillary Fig. 272. Semi-diagrammatic figure of the vascular arrangement in the gastric-mucous membrane (repre- senting at the same time that of the colon). Fig. 27-j. The vascular net-work of an intestinal villus of the hare, with the arterial trunk, 6, the capillary net-work, c, and the venous branches, a. net-work of the gastric mucous membrane in vertical section, may also be regarded as a figurative representation of the blood-vessels in the deeper portions of the colon. There, however, where projections, papilla?, and villi occur — and this is the case for the entire small intestine, as also, occasionally, for portions of the large intestine — we meet with corresponding modifications of the vascular arrangement. In the intestinal villi especially, the latter become very character- istic and elegant. There is here a so-called looped net-work, that is, two or more larger trunks pass over into each other in a loop-like manner at the summit of the villus, and are united in their course by an intermediate, more circular meshed net- work. In larger villi, as our fig. 273 shows, the arrangement 444 SECTION SEVENTEENTH. may become considerably complicated ; in small specimens, those of the mouse, for instance, it remains much more simple. The capillary net-work abrays lies in the peripheral portion of the villus, so that the central portion is occupied by the lac- teal vessel which is soon to be described. The blood readily remains in this vascular district, so that those who shun the trouble of an artificial injection may obtain quite handsome views of the capillaries of the villi from the body of an animal which has been killed several hours previ- ously by strangulation. The villus-like projections which may make their appear- ance in the large intestine, such, for instance, as occur in re- markable perfection in the upper portion of the rabbit' s colon, have a similar arrangement of the blood-vessels, but differ com- pletely from the glandless villi of the intestines, by being, like the smoothly spread mucous membrane of the colon, permeated by glandular tubes in close apposi- tion. Finally, as regards the lymphat- ics of the intestinal canal, or the so- called lacteals of these parts, much may be recognized, even without in- jections, in bodies in which the di- gestion of fat has commenced, and, in fact, in former times, many ob- servers have obtained valuable in- formation in this way. The accumu- lation of chyle may be observed with Fig. 274. Intestinal villus of a kid, killed P ~ilif ,-,-. +1. • j* f"U„ iv> f ~cfi v»nl during digestion, with the lacteal vessel in ld.GU.lty 111 tile aXlS OI tUe mteblin.ll theaxlB ' villi (fig. 274), and with somewhat greater difficulty the vessels filled with fat of the mucous mem- brane and submucous layers (p. 400). A suitable medium for rendering such preparations transparent is still wanting, and it is also impossible to keep them in a moist condition for a long time. My attempts, at least, have been entirely frustrated. The artificial injection by means of the puncturing method was, therefore, a great improvement, and has, within a few years, increased our knowledge of the lymphatics of the intes- tinal canal considerably. I believe that I have simplified and facilitated the procedure essentially by the employment of the cold-flowing transparent mixtures. DIGESTIVE OKGANS. 445 These injections succeed with, greater or lesser facility, and occasionally only with difficulty, according to the frequency and extent of the lymphatic passages and lymphatics with valves which lie in the submucous tissue. The small intestine of the sheep forms a very favorable object, as the submucous layer is occupied, or rather constituted, by a surprisingly large number of very extensive lacteals. The rabbit must also be designated as an animal adapted for these investigations, but the thinness of the intestinal parietes renders the introduction of the fine canules somewhat difficult. The procedure succeeds with less facility, in consequence of the narrowness and greater sparsity of the lymphatics, in the calf and the hog, the dog and the cat ; still less in man, although, with some persever- ance, one may also succeed with infantile as well as (quite fresh) adult bodies. With such intestines as are difficult to manage, one may commence with the Peyerian follicles, which are generally easier to inject, and thus from them fill the neighboring portions of the small intestines with their villi. In the sheep and rab- bit, on the contrary, where the canule is well introduced, a practised hand almost always succeeds in forcing the mass over more considerable surfaces. Filling the lymphatics of an entire intestine of the sheep, by means of a series of individual injec- tions, of which Teichmann speaks, is, in fact, no great proof of skill. It would lead us too far, were we here to describe more mi- nutely the relative arrangements of the horizontal lymphatic plexuses in the submucous tissue, the vessels which pass from them into the muscular-tunic, as well as the canals which pass up between the tubular glands and frequently reunite in a plexiform manner (fig. 275, d). In the intestinal villi, which vary considerably in form and size, being long and thin, and also quite broad and low, there are lacteals of varying diameter with coecal extremities ; in the first case they are single (a), in the latter, double (b) or manifold (c). They may then pass into each other at the extremity of the villus in an arched manner (c), or still maintain the independent coecal termination (6). Transverse branches occur more frequently in the deeper por- tions of these more complicated lymphatics. The injection of the lymphatics in the large intestines, that is, in their mucous membrane, is much more difficult to accom- 446 SECTION SEVENTEENTH. plish. Their occurrence is considerably less frequent, and the entire arrangement is quite variable in the different animals. Horizontal reticulations, passing through the mucous mem- Fia. 275. Vertical Faction through the human ileum, a, intestinal villi with single; &, with double; c, with triplicate lacteals ; t/, lacteals of the mucous membrane. brane with short knotty vertical passages, and level ramifica- tions passing along the base of the mucous membrane with longer canals, ascending at right angles, etc., also occur. These lymphatics, which have essentially increased our knowl- edge of the processes of absorption in the intestinal canal, are at present recognized in the ruminantia, the rodentia, and the carnivora. In man (where they are certainly not wanting), the experimental proof of their presence has not, as yet, been ad- duced. Have these lymphatics of the intestine a special vascular wall, or are they merely cavities bounded by connective tis- sue ? Recent investigations leave no further doubt that beneath the serous coverings, and in the muscular layers of the intes- tinal canal, true ' ' vessels ' ' contain the chyle. Their knotty appearance, caused by the valves, speaks in favor of this, and the walls are also recognizable after the connective tissue has been rendered transparent by means of acetic acid, pyrolig- neous acid, etc. In part, perhaps in most of the mammalia, this texture is still maintained in the lymphatics of the sub- mucous tissue, while in others there is even here a formation of passages with lacunae, that is, vessels without an independ- ent vascular wall. Throughout the mucous membrane proper, on the contrary, it is certain that only the latter are present. They are all, nevertheless, lined with the peculiar vascular DIGESTIVE OEGANS. 447 cells (see p. 399). These lymphatics are therefore bounded by a very thin but entirely connected epithelium, and this invest- ment is so accurate as to serve the same purpose, at least for the normal condition, as any vascular membrane. Not a granule of the injection mass passes into the adjacent tissue without a rupture, notwithstanding the "stigmata" (p. 384) which occur between many of the vascular cells. We have frequently injected the small intestines with the finest mix- tures under a high degree of pressure, so that the ducts of the intestinal villi, being considerably distended, compressed the spongy tissue of the latter powerfully, but even then not a molecule of the injection mass passed into the tissue. That, on the contrary, an individual immigration into the lymphatics of the relatively gigantic lymph-corpuscles, such as are pro- duced in such abundance by the reticular tissue of the mucous membrane, may occasionally take place is evident. Neverthe- less, according to our views, these cells of the intestinal mucous membrane are, under normal conditions, without a future ; they arise and disappear in the meshes of the reticular tissue. On the other hand the possibility cannot be denied, that in morbid processes a more plentiful transmigration into the lymphatic current may take place through the dilated stigmata, the stomata of Arnold. Lymphatic follicles are to be found, although varying in quantity, in the intestinal canals of all of the higher verte- brates and of man. They occur partly isolated or in very small groups, and are then called solitary follicles ; they are also, in part, united into larger collections and form the plaques of the Peyerian glands. The latter structures are most plentiful in the lower por- tions of the small intestine, but may also — and this is a regu- lar occurrence in many luammalia — be met with in the large intestines. Generally the isolated follicles also show similar conditions. The structures with which we are occupied, especially the Peyerian glands which are the most thoroughly understood, are embedded in the mucous membrane and the submucous tissue. Thus we see in the vertical section of the small Peyer's patch of a rabbit (fig. 276) the bases of these follicles (&, c) with a globular form in the submucous layer. Other follicles are much higher and more slender, frequently 448 SECTION SEVENTEENTH. assuming an appearance resembling the sole of a shoe, and are accompanied by an increased thickness of the mucous membrane and submucous tissue. At an earlier period, which was poor in methods of investigation, the study of these organs was diffi- cult, so that notwithstand- ing the interest awakened »y these Fig. 27f>. Vertical section through a fresh Feyer's patch of the ileum from the rabbit. ", intestinal villi ; 6, c, follicles. the participation of structures in dis- eases, especially those of a typhoid nature, our knowl- edge of them could not be made to progress properly. At the present time the hardening methods, especially the immersion in alcohol or chromic acid (drying is not so good) are conducive to the purpose. With these must naturally be associated the, in general, not easy (complete) injection of the blood-vessels, Fig. 277. Vertical section through a human Payer's patch, with its lymphatics injected, a, Intestinal villi with their lacteals; h, Liebcrkuhnian glands; c, muscular layer of the mucous membrane ; t/, apex of the follicle ; e, middle zone of the follicle ; /, basis portion of the follicle ; a, continuation of the lacteals of the intestinal villi into the mucous membrane proper; //, rctioular expansion of the lymphatics in the middle /.one ; i, their course at the base of the follicle ; A-, continuation into the lymphatics of the submu- cous tissue ; /, follicular tissue in the latter. and the sometimes easier, sometimes more difficult, injection of the lymphatics. The Peyerian follicle (fig. 277) consists, as was remarked, of a sometimes more globular, sometimes more oblong basis por- DIGESTIVE ORGANS. U9 tion (/) extending freely into the submucous tissue. In many- creatures there is a system of connective-tissue partition walls between the basis portions. Secondly, we find the follicle (corresponding to the entire form) projecting freely into the in- testinal canal, with a sometimes higher, sometimes flatter apex (d). These, covered with cylindrical epithelium, are surround- ed by more or less prominent elevations of the mucous mem- brane, which are generally furnished with villi (a, a). Between the apex and base a middle zone (e) remains. In it the demarcation of the two follicular portions is wanting. In vertical and horizontal sections it is seen, on the contrary, how in this middle strata all the follicles of one plaque pass into those of another, and then how this zone is continued Fig. 278. The tissue of the Peyerian follicle of an adult rabbit, exposed by brushing, n, capillary ves- sels; &, reticular framework ; c, lymph corpuscles. uninterruptedly into the adjacent tissue of the mucous mem- brane (I). This is the metamorphosis of the reticular connec- tive tissue of the mucous membrane into the reticular frame- work of the lymphatic gland follicle, of which we have already spoken on a previous page. Here also the net-work of the follicle (fig. 278, 6) is essen- tially the same as occurs in the large Ivmphatic glands ; in 29 450 SECTION SEVENTEENTH. Fr&. 279. Vertical section through an injected Peyerian capsule of the rabbit, with the capillary net-work of the same, a, the larcrur lateral vessel*, b, and those of the intestinal villi, c. young bodies it is a cellular reticulation, in older ones it con- sists more of trabecule with shrunken nuclei in individual nodal points. Towards the periphery of the basis portion the tissue assumes a more finely reticulated character (as also oc- curs towards the investing spaces of the follicles of the lym- phatic glands) ; in the central portions, on the contrary, the meshes are not unfrequently larger. The blood-vessels of the Peyerian glands have recently been frequently described, so that it must appear superfluous to al- lude to them more thor- oughly again. Only the remark, together with several examples, may here find place, that a non-vascular central portion of the fol- licle does not, as a normal occurrence, exist. Incomplete in- jections, it is true, give, frequently enough, the false image of capillary loops in the internal portions of the follicle. Our figures 279 and 280 represent this arrangement of the vessels in a small Peyerian patch of the rabbit, from a very complete injection mounted dry. We have also, in addition, accurately re-examined the arrangement in moist specimens from a series of consecutive sections. Good injections of the lymphatics teach the following : — The lymphatic vessels (fig. 277, a, a) which return from the in- testinal villi (the so-called lacteals) form a reticulum (g) around the tubular glands (b) which occur in the villous elevations, and this is continuous with a net-work of reticular^ enclosed vessels (7i) which surrounds the middle zone of each follicle. The latter then open either into a simple investing cavity which surrounds the basis portion like a shell (rabbit, sheep, calf), exactly similar to that of the alveolus, or this is replaced by a net-work of separated passages and lacuna? encircling the basis of the follicle in a similar manner, so that this portion of the Peyerian follicle (k, i) appeal's like a toj^-ball around which a thread is wound (as in man, the dog, and the cat). From the latter system of vessels (or from the simple investing DIGESTIVE OKGANS. 451 space) finally arise the efferent lymphatics of the submucous layer (yfc). The reader will comprehend that follicles of the latter vari- ety are more difficult to inject than those of the first form with the simple shell-like in- vesting spaces. The vermiform pro- cess, as well as the small and scanty cpecum of many carnivora consists, in a remarkable manner, of only a closely crowded collection of follicles. The processus vermifor- mis of man and of the rabbit represents, infact, aPeyerian plaque which, largely extended, forms an entire portion of in- testine. Teichmann suc- ceeded in injecting them in man ; the injection of the vermiform process of the rabbit is a mere child's play, and the entire organ deserves to be most urgently recommended to any one who desires to study the Peyerian follicles. Numerous pathological metamorphoses of the intestines be- come objects of microscopic investigation. The same methods which we have mentioned in the investigation of the normal structures are generally employed. It should be made a rule to obtain the freshest possible objects, as the decomposition which soon commences changes the soft tissues in such a man- ner as to render them unintelligible. The pathological new formations in the intestinal canal are, in general, the same as in the stomach. Thus we meet with similar pigmentations, connective- tissue productions, lipomata, etc. Carcinomatous tumors occur in the large intestines, especially in the rectum. Tubercles, on the contrary, are met with chiefly in the ileum, less frequently in the jejunum and colon. It is the lymphoid, the solitary, as well as the agminated (Peyerian) follicles of Fig. 2S0. Transverse section through the equatorial plane of three Peyerian capsules of the same animal, <£, the capillary net-work ; b. the larger annular-shaped vessels. o 452 SECTION SEVENTEENTH. these parts whicli, like other lymphatic glands, are especially affected by this process. More accurate histological investiga- tions of this metamorphosis with the aid of m odern accessories would be in place. Tumefactions of the follicles show them- selves conjointly with capillary distentions and cell prolifera- tions. Later, the destruction of numerous lymph-cells takes place and the finely granular so-called tubercle mass is formed. This softens and occasions the formation of ulcers. Usually, the lymphatic glands of the mesentery also take part in this process. The structural conditions of the follicles in abdominal typhus are very similar in an anatomical point of view. In the first or catarrhal period, the capillaries of the Peyerian follicles are frequently widened to a considerable degree. Large multinu- clear lymph-corpuscles are met with here, exactly in the same manner as in the typhoid metamorphosis of the lymphatic glands (p. 407). By means of several injections made at an earlier period, I was able to obtain the conviction, at least, that in this stage the lymphatics of the Peyerian glands are still thoroughly permeable. Later, with the destruction of the cells, the former appear to become stopped up and imperme- able. It does not seem to be in place here to speak further of the associated processes of absorption, of the softening of the contents of the follicles, and of the formation of intestinal ulcers and sloughs. The latter masses consist of fine granular matter, nuclei, cells, cell remains, etc. The associated process of cicatrization takes place naturally, by a new formation of connective tissue. Accurate conclusions are not easily ob- tained in these cases, as I know from my own experience, so that a careful investigation of the cases at hand is very desir- able. Finally, with regard to the methods of preserving microscop- ical preparations of the digestive canal. The vertical and hori- zontal sections may be preserved moist, with or without pre- vious staining, either in watery or more concentrated glycerine. If they have been carefully washed before being placed in the latter fluid, they keep well, as a rule, as do also preparations of their vessels and lymphatics injected with transparent masses (carmine, Prussian blue). According to previous expe- rience, the nervous and ganglionic plexuses of the intestinal canal may be best preserved by freeing them from the residue DIGESTIVE ORGANS. 453 of their acid by washing in distilled water some time before mounting. The method of depriving tinged preparations of their water by means of absolute alcohol, and the subsequent mounting in Canada balsam dissolved in chloroform, must be designated as very serviceable for many of these purposes. Beautiful and durable review preparations for low powers may be obtained in this way. If it be desired to mount thicker masses, as, for instance, a portion of intestinal mucous mem- brane with the villi erect, glass cells are to be employed. A skilful manipulator will be able to make a handsome prepara- tion with one, even with Canada balsam. There remains for us to consider, finally, the intestinal con- tents, and the faecal masses which are formed from the latter. Although these are not often objects of medical examination, and though disgust deters many observers from the investiga- tion of the latter substances, nevertheless, in consequence of the multiplicity of their elements, they are both very instruc- tive, and not always easy objects of microscopic examination. The alimentary pulp which has been altered by the saliva and the gastric juice, and has left the stomach, has, as you know, received the name of the chyme. In its further progress there become mixed with it the secretions of the liver, of the pan- creas, and of the various follicles of the mucous membranes, as well as exfoliated epithelium, gland-cells, and the mucous corpuscles of the intestinal canal ; while other matters, such as fat, albuminous bodies, and salts are removed by absorption into the lacteal system. The chyme natu- rally presents very considerable differences according to the na- ture of the food ; in the carnivora it is different from that of the herbivora. We omit here the substances which are dissolved in the chyme. Its elements consist of molecules and drops of fat, altered muscu- lar fibres, portions of connective tissue (in carnivorous animals fragments of cartilage and bone), starch-granules, various vege- table tissues, etc. Fig. 281, which represents the contents of 454 SECTION SEVENTEENTH. the small intestine of a rabbit, may give us a conception of the constitution of the chyme af ter a vegetable diet. In the speci- men we meet with starch-granules in various stages of dissolu- tion, in part already changed into empty hollow vesicles, epi- dermoidal tissue, prosenchyma cells, spiral fibres, etc. By the onward movement through the large intestine, the mass undergoes further changes. The digestive properties of the so-called intestinal juices make themselves felt ; the lym- phatics absorb the fluid portions, and, by the transformation of the biliary pigment, as well as by putrefactive decomposi- tion, the masses assume the color and smell of faeces. Numerous elementary particles of the food, such as fila- ments of muscular substance, fat-tissue, bundles of connective tissue, elastic fibres, etc., are still to be met with. The mus- cular fibres are frequently separated into disks, and have a greenish tinge from the biliary pigment. Numerous remains of vegetable alimentary matters, starch granules, spiral vessels, epidermoidal tissue, substances which we have already men- tioned in speaking of the contents of the small intestines, show themselves in the human excrements. Remarkable faecal dis- charges which cause great solicitude to hypochondriacs, and may also astonish the physician, ma}' frequently be readily demonstrated by the microscopical examination to be merely remains of food. The human faeces are always very rich in fragments and filaments of the Leptothrix. With the name of meconium has been designated the dark, pitch-like stools of the new-born child. They contain decom- posed bile, separated and decaying epithelium and cells of the intestinal canal, as well as small hairs from the integument which have been swallowed with the amniotic fluid. The me- conium is rich in fats, and the ethereal extract forms a deposit of numerous crystals of cholesterine. Numerous alterations in consistence, color, and constituents are presented by the ftecal masses in disease. The most re- markable stools are found in dysentery, abdominal typhus, and cholera. The alimentary constituents here diminish more and more, as does also, as a rule, the decomposed bile ; the intestinal secretions and the separated cells, on the contrary, increase. Albuminous masses, coagulated fibrine, and blood may be associated with them. DIGESTIVE ORGANS. 455 Dysenteric stools contain desquamated cylindrical cells, mucous and pus corpuscles, cell nuclei, gland-cells, fibrinous coagula, blood-cells, and clots of blood. The peculiar evacuations which occur in abdominal typhus, at the height of the disease, show, together with epithelium, gland-cells, pus corpuscles, and a fine granular substance with nuclei, which has been regarded as the cast-off ulcerative prod- ucts of the Peyerian and solitary glands. Not unfrequently, blood-corpuscles also occur in these evacuations. We mention, finally, the cholera stools. The rice-water-like dejections in this disease contain very large numbers of mu- cous corpuscles, but, on the contrary, only very little cylin- drical epithelium. Crystalline deposits of the ammonio-phosphate of magnesia Fig. 2S2. Crystals of the ammonio- phosphate of magnesia. Fig. 2S3. Crystals of taurin. a, completed six-sided prisms * b, indefinite sheath-like masses from an impure solution. (fig. 282) are found in the alkaline faeces of healthy as well as of diseased persons. They present a rhomboidal form, and most frequently appear as three-sided prisms with the two cor- ners corresponding to one side blunted, in the so-called coffin- lid form. In consequence of the general diffusion of the phosphatic salts of magnesia in the solid and fluid portions of the organ- ism, the double combination we are at present considering forms one of the most frequent occurrences as a result of the development of ammonia. Seldom, on the contrary, do we find in the intestinal canal (but even in the stomach, however) crystalline deposits of taurin, a conjugate compound of one of the two biliary acids (fig. 283). Further chemical procedures are necessary, as a 456 SECTION SEVENTEENTH. rule, for the recognition of this body, as well as of ckoles- terine. We cannot leave the microscopical analysis of the faeces without first mentioning certain of its animal parasites. A large infusory animalcule, covered on all sides with cilia, the Paramaecium coli of Malmsten, has hitherto had no practi- cal significance. It has been observed a few times in the large intestines of human cadavers, as well as in the stools. The same is also true of the Cercomonas intestinalis, a small crea- ture provided with a whip-like cilia, discovered by Lambl. It has been met with in the hyaline intestinal excretions of chil- dren, in intestinal catarrhs, as well as in typhoid and choleraic diseases (Davaine). Quite fresh intestinal evacuations, or such as have not yet become cold, should be used for their investi- gation (Ekecrantz). The microscopical recognition of the ova of the most familiar human helminths is, on the contrary, of much greater practical importance (Davaine, Lambl, Leuckart, and others). Leaving out of consideration the trichina, tlie embryos of which creep out in the maternal body and then perforate the intestinal walls, the ova of the remaining nematodes do not become de- veloped in the human body, but are expelled and appear in the stools ; likewise, although merely casually, those of the tape- worms which have been set free by the rupture of a proglottis. It is easy to recognize the ova of the parasites dwelling in the lower portion of the intestine, especially of the Oxyuris vermi- cularis, numbers of which are presented by every microscopical preparation taken from the external surface of a portion of faeces (Vix). It is more difficult, on the contrary, to discover the ova of the nematodes which live higher up in the intestinal canal, such as the Ascaris, as they do not occur in the mucus which envelopes the solid faecal masses, but rather in the in- terior of the latter. The more solid masses of the faeces are to be spread out with water for the examination, or the coating of slime is to be se- lected (with Oxyurs). The mucous coating scraped from the intestinal walls with a spatula also presents an abundance of this helminth (Vix). We give a short resume of the characteristics of the ova of these helminths (fig. 284), after a drawing kindly furnished us by Leuckart. DIGESTIVE ORGANS. 457 Tiicoceplialus dispar(2). Ova double contoured, oval, trun- cated at botli poles, shell and vitellus of a brownish color. Length, 0.0239-0.0257'" ; breadth, 0.0111'". Ascaris lumbricoides (1). Ova roundish or oval, measuring Fig. 2S4. Ova of the most familiar helminths of man, from a drawing communicated by Prof. Lenckart (all magnified 370 diameters). 1. Ascaris lumbricoides. 2. Tricocephalus dispar. 3. Oxyuris vermicu- laris. 4. Distoma hepaticum. 5. D. lanceolatum. 6. Taenia niediucanellata. 7. T. solium. 8. Bothrio- cephalus latus. 0.0363-0.0386", next to the largest of all. The shell of the ovum has a double contour and is still covered by the transpar- ent, indentated areole of an albuminous enveloping substance. Oxyuris vermicularis (3). Ova mostly transparent, double contoured, oval shell (frequently having an asymetrical curva- ture). Length, 0.0231-0.0248'" ; width, 0.0102-0.0115'". Distoma hepaticum (4). Eggs oval, very large, yellowish. Length, 0.0572-0.0616'" ; breadth, 0.0332-0.0399'". The ante- rior pole with the operculum more flattened. Egg-shell double, contents a cell aggregation and vitelline spheres. Distoma lanceolatum (5). The brown double-shelled oval eggs are much smaller, 0.0177-0.0199'" long, 0.0133'" broad, are evacuated at a later period than the previous variety, and contain an oval embryo, measuring 0.0115-0.0133'", with clusters of granules in the posterior parts of its body. Bothriocephalus latus (8). Eggs oval, averaging 0.0310'" 458 SECTION SEVENTEENTH. in length and 0.0199'" in the middle transverse diameter ; they are enveloped by a simple, hard, brown shell, whose anterior pole constitutes a distinctly interrupted, hood-shaped oper- culum. Taenia solium. The ova, which develop within the so-called proglottides, present variations in accordance with their age. The oviim (7), which contains an embryo sometimes, shows an oval enveloping layer of albumen and a globular, thick, mani- foldly contoured, brownish inner shell 0.0133'" in diameter, the surfaces of which are covered with closely arranged ciliae. This contains the spherical embryo, which measures 0.008'", and is provided with six booklets. Sometimes the outer layer of substance (which formed the original vitelline layer) is wanting. Undeveloped ova are smaller, globular, at first with- out the inner envelope, and enclose a vitelline sphere and a special aggregation of embryonic cells. Taenia mediocanellata. Ova (6) quite similar, but markedly oval and almost regularly provided with the original vitelline membrane. The size and other characteristics of the egg-shell the same as in the previous animal. Together with these, the presence in the faeces of the familiar hooks of the Taenia and their younger forms, as well as, in the trichina disease, the sexually mature examples of these worms, is applicable for the diagnosis of a helminthic disease. 0cction <£igl)teentt). THE PANCREAS, LIVER, AND SPLEEN. We have still remaining the two large glandular organs con- nected with the intestinal canal, the pancreas and the liver. The spleen- is also to be discussed here. We can dispatch the pancreas — concerning which Langer- hans and Heidenhain have recently instituted excellent studies — with rapidity. The water salamander or, among mammalial animals, the gland of the rabbit, spread out flat, are adapted for the first examination of our organ. If, after the manner of Heidenhain, the dog be used, take the thicker portions of the gland for hard- ening in absolute alcohol, and remove the mesenterial cover- ing, as the latter shrinks very much in the reagent mentioned and presses the gland-cells together. The human pancreas appears less convenient. Even in this manner one may recognize the peculiar dispo- sition of the gland-cells, which appear hyaline peripherically, and granular towards the centre. Heidenhain recommends, as an additional accessory, osmic acid of 0.15-0.2 per cent., and then (as the best reagent) neutral chromate of ammonia in 5 per cent, solution. The last-mentioned reagent is excellently adapted for the isolation of Langerhans' spindle-cells of the efferent system of canals, as well as the numerous trunks of pale nerve-fibres of the pancreas. In order to isolate the peculiar gland cells, use a 5 per cent, solution of hydrate of chloral, which is to be renewed. As water exerts an uncommon distending effect on the granules of the pancreatic gland-cells, it cannot be supposed that the latter are of a fatty nature. A warmth of 50° C. ex- cites coagulation. Injections of the blood-vessels succeed readily ; those of the 460 SECTION EIGHTEENTH. gland-ducts (tig. 285) are to be attempted with cold flowing mixtures, with Briicke's soluble Prussian blue, for example. The syringe may suffice for this purpose, when carefully di- rected. The constant pressure renders better service for injecting the finest capillary passages (c) which run between the gland-cells. The liver, on the con- trary, requires a more ac- curate discussion, in con- sequence of its numerous peculiarities. The inves- tigation of this, the most voluminous of all the glands of the body, is in fact difficult, so that some of its structural conditions still remain matters of controversy. Each of the previous- ly mentioned glandular organs shows the observ- er at once, together with the parenchyma cells, an investing membrana propria (which, it is true, may be replaced by the adjacent connective-tissue layer). While now the cells of the liver are to be recognized with the greatest facility, the ques- tion as to the existence of the membrana pro- pria causes the microscopist great embarrass- ment. The most simple procedure suffices to dem- onstrate the hepatic cells (fig. 286). If the fresh organ be cut into, and a knife-blade scraped over the cut surface, the brownish mass, diluted with some fluid, presents numerous examples, either single, in series, or in reticulated fragments. The adjacent figure shows the characteristic form, the finely granular cell-contents, very generally intermingled with isolated fat-molecules and the nucleus, two of which not un- Fig. 2S5. Glandular canals oT the rabbit's pancreas, after Saviotti. a, Larger excretory duct ; &, that uf an acinus ; c, finest capillary ducts. Fia. 2SG. Human he- patic cells. a, with single ; b, with double nuclei. THE PANCREAS. LIVER, AND SPLEEN. 401 frequently lie in one cell-body (according to our present views, a proof of the cell-division). A special cell-membrane cannot, however, be demonstrated on the cells of the liver ; its place is occupied much more by a somewhat hardened cortical layer. The so-called hepatic lobules have been distinguished for a long time. These islets of the substance of the tissue are some- times brownish red internally with a brownish periphery, some- times the colors are reversed. In most mammalia they become blended with each other at their peripheries, but are, neverthe- less, here and there more distinctly demarcated. The microscope shows as a cause for such a sharp division of the hepatic lobules a strongly developed connective-tissue boundary layer. The liver of the cat, the sheep, and more especially that of the pig, is of this variety. Many things which are only to be recognized with difficulty in the organ of other animals and of man, appear more distinctly in the last-men- tioned animal. The pig's liver has, therefore, very properly been recommended by modern histologists as an extremely suitable object for examination. With the aid of a sharp scalpel a fine transverse section may be obtained from such a lob- ule of the quite fresh organ, just beneath the surface, for instance. Valentine's double- knife (p. 107) has been recom- mended by others for this purpose. It is much better, as we shall have to mention hereafter, to make use of liv- ers hardened in alcohol or chromic acid for the prepara- tion of such specimens. We also recommend the freezing method. Such a transverse section (fig. 287) shows the columns of the liver-cells or the cell-network arranged in a general radiated manner, and, at the same time, these columns of cells united together in a reticular manner by short transverse rows. In human and mammalian livers the cells of such a net-work usually lie in single rows, and are only double in places at the nodal points ; nevertheless, many varia- FlG. 287. Transverse section of a human hepatic lobule. 462 SECTION EIGHTEENTH. tions occur. A system of similar spaces appears in such prep- arations, for the most part with great distinctness. If for the purpose of further investigations the blood-vessels be filled with transparent substances (either as a single injection by the vena hepatia or the portal vein, or with two masses by the two veins simultaneously), the radially arranged capillary net-work appears with surprising beauty, and one is at the same time convinced that the origin of the above-mentioned spaces, which were shown by the transverse section of the hepatic lobule, is due to the capillaries of the vascular net- work, and likewise that the rounded central space (fig. 287) is the transverse section of -'-■"-', a branch of the hepatic vein (vena intralobularis of Kiernan). Fig. 288 may repre- sent to the reader the finer arrangement of the blood - vessels. Several lobules appear to be sup. plied by each branch of the portal vein with finer ramifications, running in a lateral direction, which are confined to the inter- vening spaces between the lobules (venpe interlobulares), and in the centre are noticed the branches of the hepatic nervous sys- tem. A few branches of the hepatic artery also enter the capil- lary net-work at its peripheral portion, so that the injection may be practised by the latter vessel with the same success as by the portal veins. Even in the fresh condition, the previously injected liver shows the capillary net-work occupied by the columns of the hepatic cells, so that two kinds of net-work, that of the blood- vessels and that of the cellular trabecular, are actually thrust into each other. In well-hardened organs, however, where the razor affords very fine sections, these investigations may be made in a much finer manner. Simple alcohol may be employed, and likewise Clarke's mixture of alcohol and acetic acid (p. 139). Beale especially recommends the use of alcohol to which a Pig. 2SS. The injected liver of the rabbit with the branches of the portal and hepatic veins. THE PANCREAS, LIVER, AND SPLEEN. 463 few drops of a solution of soda has been added (p. 140). Such preparations, freed from adherent matters by washing, and tinged with carmine or (which is likewise to be highly recom- mended) hseniatoxyline, afford exactly the appearance as if the cells were embedded quite free in the spaces of the capillary net- work. This view was, in fact, maintained for a long time, although the contrary opinion might also have been defended with the same propriety, namely : that a cellular net-work, enclosed in a homogeneous membrane, was permeated by the reticulated lacunar system of capillary blood-currents. The modern accessories have led us a considerable step further in this matter. Fine sections from a liver hardened to the consistence suit- able for brushing (I generally employ alcohol for this purpose, at first with considerable water, then with less) permit of the re- moval of the liver-cells, although only over more limited spaces (fig. 2S9). In this way there is left a fine and extremely delicate net-work (a) formed of a homoge- neous membrane which separates the blood-current from the cell columns. If carmine tingeing be resorted to, the columns of hepatic cells which were not removed by the brushing will appear very beautifully ; then, however, one will also recognize in this hyaline membrane of the reticular framework, together with the capillary nuclei, a few small and more rounded nuclei which are, in adult crea- tures, for the most part shrunken. If the liver of a new-born child, of a human embryo of the later months, or of a mammalial animal of a corresponding period of life, be used, the fine hyaline membrane alluded to appears in places with great distinctness as a double membrane, one of the layers of which corresponds to the capillary walls, while the other limits the cellular net-work. According to this, there is no longer any doubt that a thin, often indeed extremely fine layer of homogeneous connective- tissue supporting substance (in continuity with the connective Fig. 289. Framework substance from the liver of the rabbit. , the rounded cella of the inner surface lined with epithelium (c). 498 SECTION NINETEENTH. (c) which are shorter and more flattened against each other, and within the same a homogeneous viscous iiuid. The cavity is surrounded by a close capillary net-work which is easily injected from the artery, fn the connective tissue of a group of cavities run line canals, originating in the numerous superficial lympha- tic vessels with valves, forming sometimes closed, sometimes irregular circular-shaped, sometimes only arched columns. Still finer lymphatic canals not unfrequently pass between a few cavities. Their injection may also be readily accomplished by means of the customary puncturing method in the new-born and the child, in the dog and the rabbit. Hardening in chromic acid or alcohol serves for the prepara- tory treatment. Thin sections show many things more beauti- fully after tingeing than in an uncolored condition. The frame- work is easy to isolate by brushing. The thyroid gland of the calf, macerated in pyroligneous acid, is to be recommended for the recognition of the nerves (Pere- meschko). Osmic acid has not afforded us here any results worthy of mention. In the place of the viscous fluid mass there occurs (and it is indeed frequently noticed even in the bodies of new-born chil- dren), together with dilatations of the gland- ular cavities, another homogeneous, more solid contained matter, the colloid, a modi- fio. wo. ooiMa motamor- tied albuminous substance (fig. 309). It is phosis. a. Grland vesicle of the™ ... , , . t> ,i 1 1 rabbit; b, commencing coiioid formed by the metamorphosis of the cell- inetainurphosis of the calf. ni • -i -i ■ t t t contents of the epithelium, whereby tlie cells are destroyed. We have already mentioned the colloid degeneration, which, though not constituting a very frequent occurrence, appears in the similarly formed hypophysis cerebri, also attacks the cells of carcinomatous neoplasms, and may give rise to colloid carcinoma (p. 289). In the slighter degrees, the dilatation of the cavities, and the compression of the interstitial connective tissue coincident therewith is moderate, so that al- though narrowed, and here and there atrophied, the lymphatic passages may be rendered apparent by injection. The capillary net-work retains the old permeability, and the epithelial cells still appear preserved. Higher degrees of this colloid metamorphosis show, together RESPIRATORY ORGANS. 499 with an increase of volume, that the whole organ is permeated by transparent, sometimes smaller, sometimes larger colloid lumps. The epithelium of the distended cavities has disap- peared, and the compression of the connective tissue has be- come such that, though the blood still passes, an impermeability for the lymph has taken place. All attempts at injection re- main unsuccessful, and, from the nature of the colloid matter, a resorption through the capillary walls is no longer to be thought of. Thus arises the goitre, that disease which is still so obscure in its etiological relations. With further accumulations of the colloid masses the connec- tive-tissue interstices disappear, and as the excavations unite, these masses become joined together. In this way larger and larger spaces become filled with such masses, and the connec- tive-tissue stroma lying between them appears as if macerated. An entire lobe may finally present a single collection of colloid. Sections of the injected organ, deprived of their water by means of absolute alcohol, may be mounted in Canada balsam ; the remaining preparations are to be mounted moist in dilute glycerine. Not less obscure in its function and in its structure, the thymus appears, at the present time, to be not entirely compre- hensible. It also undergoes, although later, a transformation, that is, a metamorphosis into fat-tissue. The elements which constitute the lobes of our organ have been described by authors as granules or acini. They remind one in their texture of a lymphatic follicle, and show the same connective-tissue reticular framework, with nuclei at the nodal points and permeated with capillaries ; likewise the same filling up of all the intervening spaces by an innumerable quantity of lymphatic cells. Nevertheless, a more thorough investigation also reveals many deviations. In fine, transverse sections of hardened organs, the thymus follicle contains in its centre a cav- ity filled with a cloudy fluid, the further explanation of which is obtained by side views. In such, cul-de-sac-like ducts appear to come from the follicle, and these canals from each lobe be- come conjoined below. Herein lies, according to my view, the rudiment of the further diverticulated, foetal thymus-gland tube, and not a lymphatic canal-work, as His, in a beautiful work, has declared the same to be. Firstly, notwithstanding numer- ous attempts, it has not been possible for us to accomplish a 500 SECTION NINETEENTH. lymph injection of the organ and of these passages ; then — and npon this point greater weight may be laid — the more recent investigations have demonstrated entirely different arrange- ments of the lymphatic channels in the lymphoid follicles. A delicate vascular net-work (but also not entirely corresponding to the ordinary arrangement of that of the lymphatic follicles) permeates the follicles of the thymus. In the calf (fig. 310) the peripheral portion of the latter is surrounded in a circular manner by arte- rial (a) and venous (b) branches, and the capillary net-work (c) resembles that of a Peyerian follicle, but naturally bends with all its tubes around the central canal(fZ) in a loop-like man- ner (His). In the human thymus, on the contrary, the arteiial branches run in the interior of the lob- ules and follicles. The ven- ous ring of the latter re- mains, however, the same as in the calf. Some time after birth (pretty early in well-nourished calves, probably much later in man) commences an extensive transfor- mation of the stellate cells of the thymus stroma into globular fat-cells, and of the neighboring reticular-fibres into a more homogeneous matter which envelops the latter. The microscopic examination shows interesting transformations of the capillary net-work and a gradual disappearance, frequently united with fatty degeneration, of the lymph-cells of such metamorphosed localities. A quite similar process may also, as I have shown, attack the follicles of the lymphatic glands. Peculiar structures of the contents of the thymus are pre- sented by the so-called concentric corpuscles. Their stratified investment consists, according to Paulitzky, of pavement- shaped epithelial cells (comp. p. 270). The methods for examining the thymus gland are various. For hardening, use at first very watery, later somewhat stronger solutions (chromic acid from 0.1-0.2, then from 0.5 percent., Fig. 310. Portion of the calf's thymus, after His. The rings of the arterial branches (a) and venous branches (b) with the capillary net-work (c) and the cavities of the acini (d). KESPIEATOKY ORGANS. 501 chromate of potash in corresponding strength, strongly diluted alcohol). Only in this way can the reticular framework be brushed out over larger distances. Increased hardening leads to the recognition of the passages described, and of the walls of the blood-vessels. Kolliker recommends boiling in ordinary water to render the canal-work of the thymus visible. Subsequently hardened in alcohol, such organs are said to permit of good sections being made ; that observer also recommends the boiling of this organ in vinegar. The blood-vessels are not very easy to inject, as it is always necessary to ligate a number of them, or to compress them with the sliding forceps. An opaque mass, chrome-yellow, for ex- ample, is very handsome for review preparations (which may be mounted dry) ; for histological purposes select carmine and Prussian blue. Watery glycerine serves for their preservation. It has already been remarked above that, thus far, attempts at injection have not shown any lymphatics in the interior. May another be more fortunate, and thus elucidate in this structural relation that organ which, as the at present last of its species, must awake the interest of histologists. Section Croenttett). URINARY ORGANS. The investigation of the urinary apparatus, and especially of the secretion produced by it, lays claim in a high degree to the interest of the medical world ; indeed, the signification of the urine at the sick-bed has been valued for thousands of years, and often also overestimated in the most ridiculous manner. The kidney, as is known, constitutes the most important organ of the urinary apparatus. An external brown-red mass, the cortical substance, en- velops in the mammalia and man an internal, paler mass, the medullary substance, which presents even to the naked eye a radiated fibrous appearance. The latter, in most mammalial animals, enters the pelvis of the kidney with a single ridge- shaped point ; but is, on the contrary, in man (and also the pig) separated into a number of larger conical-shaped divisions which turn their points towards the hilus. These are the so- called Malpighian or medullary pyramids. The cortical tissue extends down between the lateral surfaces of the same like a septum (columnse Bertini). A connective-tissue supporting substance permeates both substances, and consequently the whole organ. The essential conditions of the finer structure of the kidney also seemed for a long time to be firmly settled. The radiated fibrous medullary substance was regarded by the anatomists and physiologists as consisting of the urinifer- ous canalicules which opened free at the pyramidal points, and which, from here, with n^^merous acute-angled divisions and diminutions in size induced thereby, passed towards the corti- cal substance. In passing over into the latter, they were said to lose their previous rectilinear direction, to assume an extremely URINARY ORGANS. 503 complicated tortuous course, and finally, enlarged in a spheri- cal manner, to terminate as capsules of tlie Malpighian vas- cular coils (fig. 311). Especially after Bowman, in the year 1842, had discovered the manner of termination (or origin) of the urinif erous canali- cules just mentioned, the struc- ture of the mammalian kidney was regarded as assured and near to a conclusion. The merit is due to Henle of having brought a new element of agitation into this subject. He discovered, a number of years ago, in the medullary sub- stance of the organ, together with the long-known open uri- niferous canals, a system of finer, loop - shaped passages (which turn their convexities towards the points of the papil- lae). He also succeeded, in sev- eral mammalial animals, in in- jecting, from the ureter, the straight canals of the medullary substance, as well as their rec- tilinear continuations through the cortex to close beneath the renal capsules. As, however, all attempts to inject, from these passages, the loop-shaped canalicules of the medulla as well as the convoluted ones of the cortical substance failed, this savant took — as we now know, erroneously — the loop-shaped passages for a system of closed canals not connected with the former, and maintained that each of the two sides of the loop terminated, finally, in a convoluted tube ending in a Bowman' s capsule in the cortical layer. Henle came, hereby in conflict with several older reports of injections, which told of successful injections of the entire canal-work as far as the capsule of the glomerulus, in mam- malial animals and in man (Gerlach, Isaacs). Neither could Fig. 311. From the cortical substance of the hu- man kidney, a, Arterial trunk giving off the affer- ent vessels b, of the glomerulus c*, d ; c, efferent vessels of the latter ; d, the capsule of Bowman, with its continuation into the convoluted uriniferous ca- nalicnle of the cortex (e). 504 SECTION TWENTIETH. the (occasionally easy) injection of the entire canal-work of the kidney from the ureter, which may be accomplished in the lower vertebrates, be made to coincide with this (Hyrtl, Frey). In consequence of a large series of new investigations (among which we would designate the work of Ludwig and Zawarykin, as well as that of Schweigger- Seidel as the most important), Henle's statements have been modified and our knowledge of the mammalial kidney not inconsiderably en- larged, although even now there are still many points in the structure of the kidney remaining to be investigated. The primary fundamental view of the structure of the kid- ney may be obtained with any mammalial animal ; the most conveniently and summarily, it is true, in the organs of very small creatures (guinea-pig, marmots, moles, quite especially, however, the bat and the mouse). A fine longitudinal section from the med- ullary substance of the fresh organ shows the open, uriniferous canalicules, covered by a transparent, low, cylindrical epithelium, and a distinct lumen. Their ramifications may be represented by fig. 312 (a preparation which, however, was obtained by another method). These may be readily distinguished from the blood-vessels, if the latter have been previously injected with cold-flowing Prus- sian blue. A cautious picking apart with the preparing needle will also isolate a few of these uriniferous canalicules, and lead to the recognition of the acute-angled divisions. With a sharp razor one may also succeed in obtaining sufficiently thin, transverse sec- tions of the cortical substance to show the meandering con- volutions of their uriniferous canalicules, the darker, more granular, thick epithelium of the latter, the Bowman's cap- sules, and (if a moderately large amount of blood has remained) the reddish-yellow Malpighian vascular coils. The latter ap- pear most beautifully and sharply with all artificial injections. Even here a diligent picking enables the observer to recog- nize isolated continuations at least of the uriniferous canals into the widened capsules (fig. 311, e, d), although this communication Fig. 312. The ramifica- tions of a uriniferous canal from the medullary sub- stance of the new-born cat (muriatic acid preparation). a-e, divisions of the first to the fifth order. (Original sketch by Schweigger-Sei- del.) URINARY ORGANS. 505 can only be recognized with difficulty in this way. The most favorable for the recognition of the latter are the kidneys of the lower vertebrates, such, for example, as the frog, the triton, and salamander (although their structure is not the same) ; among the mammalial animals I would most recommend the organs of the mole. The gland-cells become transparent by the addi- tion of alkalies, and their structural condition is not unfre- quently rendered more distinct. The earlier knowledge of the kidney was obtained in this way, and, towards the close of the first half of this century, our information concerning the same remained stationary at about this stage. The more recent times have made us acquainted with sev- eral other very important methods of investigation. Let us mention first the section through the artificially hardened organ. Most (and especially almost all pathologico-histologi- cal) examinations are at present made in this manner. Here also the freezing method proves to be extraordinarily conserva- tive. Recourse may, furthermore, be had to chromic acid, its potash-salt, or — which is best — to absolute alcohol. We ob- tain in this manner, without trouble, very fine and instructive longitudinal views and — what is of the greatest importance for many textural conditions — good representations from trans- verse sections of the kidneys. We would also recommend here the previous injection of the ves- sels, in small kidneys, with cold flowing, in more voluminous or- gans, with solidifying, transparent masses. The slight trouble will be richly repaid in the subsequent ex- amination. Staining methods are of the highest value for the recog- Fig. .313. Transverse section through a renal pyramid of the new-born child, a, collective tubes with cylindrical epithelium ; &, descend- ing aide of the looped canal with flat cells; c, returning side of the loop with granular cells ; d, transverse sections of vessels ; e, connective- tissue framework substance. nition of the renal tissue in the . healthy and pathologically altered condition. In the medullary substance we again recognize, in vertical sections, the relations of the fresh preparation ; in transverse sections (fig. 313), on the contrary, the lumina of the uriniferous canals, the straight ones with their cylindrical epithelium (a) as well as the loop-shaped ones with, 506 SECTION TWENTIETH. for the most part, quite flat cells (b), reminding one of vascu- lar epithelium, and also the connective-tissue stroma of the medullary substance (e). Fine longitudinal sections of the cortical substance (fig. 314) show, on the contrary, how this, the stratum of the con- voluted uriniferous canals (B), is perme- ated at rapidly fol- lowing intervals by thin bundles of uri- niferous tubes, hav- ing a straight course (A) which diminish in size as they pass outwards, and only become lost in con- volutions (d) just be- neath the surface of the kidney. These groups of straight passages, whose cali- bre is also variable (a, b), penetrate the layer of the convolut- ed canals in the same manner, we might say, that a board is perforated by numer- ous pegs driven close- ly together into it. These bundles of straight canals which Fig. 314. Vertical section through the renal cortex of the new- born child (semi-diagrammatic). -1-1, medullary rays ; B, cortical Bubstance proper; a, collective tube of the medullary ray ; b, finer uriniferous canalicules of the latter ; c, convoluted canalicules of the cortical substance ; d. their peripheral stratum : e, arterial branch ; f, glomeruli ; g, continuation of a uriniferous canal into the Bow- man's capsule ; li, the renal tunic with its lymph-spaces, i. were previously seen, and which are continuations of the famil- iar straight passages of the medullary substance, have been called pyramidal processes (Henle) or medullary rays (Lud- wig). We shall soon return to the consideration of their sig- nification. The tissue of the convoluted uriniferous canals lying between them may be considered, although indeed only factitiously, as consisting of individual pyramidal pieces which have their bases turned towards the renal capsules. These are the cortical pyramids of Henle. URINARY ORGANS. 507 Fig. 315. Surface section through the cortical substance of the kidney of the new-born child (semi-diagrammatic), a. Transverse section through the uriniferouscanalieitlesof the medullary ray; b, convoluted canals of the cortical sub- stance proper ; c, glomeruli and capsules of Bowman. Transverse sections of the cortex (fig. 315) show both varie- ties of the uriniferous canals ; those of the medullary rays cut transversely (a), those of the ordinary cortical substance (b), in all possible forms. The connective-tissue stroma may also be readily recognized at the same time. If the study of the epithelium be renounced, I would here recommend still another method which became b - ^ a, ^JU' known to me through Billroth. If a portion of kidney be treated for a very short time with boil- ing vinegar it will, after having been dried, or hardened by means of chromic acid or alcohol, afford very handsome views of the glandular passages in the medulla and cortex. The chemical method of isolation has more recently assumed the greatest importance in the investigation of the kidney. The fresh tissue (or also that which has been hardened in alco- hol), treated with strong muriatic acid (p. 125), suffers, after a series of hours, an almost complete destruction of the connec- tive-tissue interstitial substance, while the blood-vessels, and especially the uriniferous canals, remain completely intact ; and not unfrequently even their epithelium is almost entirely preserved. These canals may then be isolated by very slightly shaking or a gentle manipulation with the needles, or, already floating in the fluid, they may be fished out with a curved glass rod. The whole has, it is true, become very frail and readity destructible ; nevertheless, we may frequently succeed in tinge- ing them slightly with carmine, and mounting them very hand- somely in watery glycerine. The muriatic acid may be used in various ways for this pur- pose. The ordinary commercial muriatic acid has frequently been diluted with water until it ceased to fume, and the object im- mersed in it from twelve to twenty-four hours. Schweigger- Seidel employed the officinal, pure muriatic acid of the Prus- 508 SECTION TWENTIETH. sian pharmacopoeia (of 1120 sp. wt.), and allowed the pieces taken from an animal killed about a day previously to macerate in it from fifteen to twenty hours. Stronger acid acts rapidly, but attacks the gland-cells energetically ; that which is weaker requires more time. The pieces must afterwards be carefully washed with distilled water, and a subsequent maceration of the same for one or more days in water will, for the most part, essentially further the isolation. Boiling with this acid or with alcohol containing muriatic acid, has also been recom- mended. If the chemical isolation has been successfully accomplished (which is not always the case, however), such objects (fig. 312, figs. 316-319) afford the circumspect observer extremely im- portant information. It is naturally impossible, even with the most conservative manipulation, to isolate a uriniferous canal throughout its entire course ; it is here, therefore, only a question of obtaining the longest possible fragments and of their combination. The expert will obtain these in lengths of from 1-2'", at least here and there. In consequence of the enormous length of the canal- work in question in the kidneys of the larger creatures, a suc- cessful result becomes much more difficult in them than in the organs of the smallest mammalia. The kidneys of the mole, the bat, the marmot, the mouse, rat, and guinea-pig deserve to be chiefly recommended. As Prussian blue is preserved in the acid macerating fluid, the blood-vessels are to be previously in- jected, a precautionary measure which is extremely important for the study of the medullary loops. If the examination be commenced with the medullary sub- stance from the apex of its pyramids, one may recognize how the open canals, with their characteristic epithelial covering, form a number of rapidly following forked divisions (fig. 312, a-e, 316, a, b), and then, the branches having become narrower, assume a straight course and pass unchanged for long distances through the medullary substance (fig. 316, c) until they arrive at the ex- ternal portion of the medulla, which is characterized by tuft- shaped blood-vessels (boundary layer of Henle). Between them appear, throughout all the layers of the pyramids, the much narrower loop-shaped canaliculi (d), which are lined with flat, transparent cells. Their returning sides, that is, the ones which again tend towards the cortex, may show them- URINARY ORGANS. 509 enlarged and filled with darker granular gland- selves to be cells. The open canals in leaving the boundary layer pass, for the most part single, more rarely by twos, into each medullary ray, through which they continue towards the surface of the kidney (fig. 314, A). The appropriate name of collective tubes has been given them (a). The above-indicated differences in the epithelium here become less distinct. The remaining considerably narrower canals of the medullary ray con- sist of the descending (that is, turned towards the hilus) and the returning sides of the loop-shaped canals (b). The collective tube, having arrived near- er the surface of the kidney, gives off more numerous branches (figs. 318, c, 319, c), and terminates above in arched ramifications (figs. 318, d, 319, d), which, especially in the smaller animals, may present a zigzag appearance ("intercal- M§ a ry portions" or " con- necting canals"). From them, but also deeper from the stem of the collective tube, rapidly narrowing canals of vari- ous forms arise, the de- scending sides of the loops (e), whose en- trance here from the medullary substance has been shown in other macerated preparations. Having thus become acquainted with the one side as an offshoot or a terminal branch of the open uriniferous canals, k Wi T Fig. %Yt. Looped ca- nalicule from a renal pyramid of the new- born child, a, 6, The two sides; c. another canah- eule ; d, capillary vessel. Fig. 316. Vertical section through the medullary pyramids of the pig's kidney { so mi- diagrammatic), a, the trunk of a uriniferous canal opening at the apex of the pyramid : 6 and c, its system of branches; a, the loop-shaped uriniferous canals ; e, vascular loops, and/, divisions of the vasa recta. 510 SECTION TWENTIETH. the question still arises, what becomes of the other, the re- turning side (figs. 318, and 319, g, g). This, accompanied by the canalicules of the medullary ray, bends deeper or higher from the group in a lateral direction Fig. .'318. "Vertical section from the kidney of the guinea-pig (muriatic acid preparation). a, Trunk of a collective tube ; o, its branches ; c, further division ; d, convoluted canal (in- tercalary portion); e, descending side of a loop-shaped uriniferous canal; /, loop; f/ 7 returning side ; and /i, continuation into con- voluted canals of the cortical substance. Fig. 319. Vertical section from the kidney of the mole (muriatic acid preparation), c, Term- inal branch of the collective tube; d, convolut- ed portion of canal ; e, descending side of the looped canal ; /, loop ; g, h, returning side and continuation into the convoluted canalicules i ; ft, neck-piece of the latter; /, Bowman's capsule; m, glomerulus. (figs. 318, 7t, 319, Ji\ assumes another convoluted course, gains at the same time an increased diameter and a darker granular epithelium, and becomes an ordinary convoluted uriniferous canal of the cortical substance proper, and, finally, with nu- merous windings and curves, terminates as the Bowman's cap- sule of the glomerulus (fig. 319, >t, I). We must here pass over in silence many peculiarities of a subordinate nature. We will only mention two conditions here, namely, that of UEINAKY ORGANS. 511 Pie. 320. granamatic). tlie epithelial lining of the Bowman's capsule (fig. 320), and the nature of these more cloudy epithelial cells. The inner surface of the Bowman's capsule has a layer of pavement-cells (g) of considerable size, which may be easily rendered visible by means of nitrate of silver (either by simple immersion or by injecting from the artery). More difficult of recogni- tion, and in a singular manner not permitting of the impregnation with silver, is a layer of smaller and higher cells, which cover the sur- face of the glomerulus {/). They are to be seen in the frozen organ, according to Chrzonszczewsky, and, according to Heidenhain, also in kidneys which have been treated with simple chromate of ammonia (5 per cent.) and picked apart. An- other good method consists, accord- ing to the last-mentioned investiga- tor, in injecting the renal veins with absolute alcohol and then coloring the sections with carmine solution. First use the embryonic organ, and subsequently that of a mammalial animal. Heidenhain has acquired great merit in furthering our knowledge of these more cloudy epithelial cells. Besides oc- curring in the convoluted uriniferous canals, they may also be found in the ascending side as well as in the so-called interca- lary portion. This superior investigator here found an unsuspectedly complicated structure. The cell, his "rod-cell," showed the portion of its body which is turned outwards transformed into rods. In order to confirm this entirely correct statement, one may use, in the first place, the entirely fresh organ of the hedge- hog, rat, and dog (that of the ruminantia and rodentia is not so good), and the highest magnifying powers. Positive fluid media are to be carefully avoided, for these rod-cells prove to be very delicate, and subject in the highest degree to disten- tion. Glcmerulus of the rabbit (dia- a, Vas afferens ; 6, vas effer- ens ; c, glomerulus : d, under portion of the capsule (without epithelium) ; e, neck ; /, epithelium of the glomerulus ; and g, that of the inner surface of the capsule after treatment with silver. 512 SECTION TWENTIETH. If it be desired to explore the remarkable cell structure in hardened objects, harden fresh pieces in absolute alcohol (but not for too long a period), and subsequently use glycerine or a muriatic acid of 0.1 per cent. Both purposes are accom- plished at once, however, by absolute alcohol strongly acidu- lated with pure acetic acid. Tingeing accomplishes nothing here. Or, the fragments of the fresh kidney may first be placed for twenty-four hours in the above-mentioned ammonia salt, and subsequently, when carefully washed, in absolute alcohol. Finally, the organ may also be injected by the blood-vessels with a saturated solution of chloride of calcium, and then pieces placed in absolute alcohol. In order to make isolation preparations with the needles, it is advisable to employ the action for several hours of our sim- ple chromate of ammonia. Not less important for the investigation of the structure of the kidneys is the injection of their glandular canals from the ureter. Cold-flowing mixtures are to be used for this purpose. The addition of alcohol is not suitable for such investigations, although also not an absolute hindrance, as has been here and there asserted. It is most suitable to select a watery Prussian blue or carmine, to which glycerine or gum-arabic may be added (see p. 139). The varying pressure of the injecting syringe is less suitable than the constant pressure of a column of fluid or quicksilver (comp. p. 103), which may be gradually increased. Such in- jections then require many hours, and, notwithstanding every precaution, not unfrequently remain without the desired re- sult. While the simply-constructed kidneys of a frog or of a coluber natrix may be injected with facility, the attempts mis- carry in small mammalial animals from speedy extravasations into the venous system. Only embryonic kidneys, in conse- quence of the slightly developed medullary substance, occa- sionally afford the cautious experimenter a successful result. As a rule, the organs of the dog, the sheep, the calf, and the pig are to be used, and in as fresh a condition as possible. The pig's kidney may be injected under the pressure of a quick- silver column of 50-100 millimetres and more. One succeeds with comparative facility, after filling the open canals of the medulla (fig. 316), in forcing the injection mass to the end of the medullary rays and their systems of URINARY ORGANS. 513 branches. The descending sides of the looped canals, which • are turned towards the hilus, may also be filled with relative facility, and are characterized by tneir smaller diameter. The colored fluid passes with greater difficulty through the loop itself, and into the returning side. The most rarely — and it is appreciable from the nature of the contents and the convo- lutions — does one succeed in forcing the injection mass through the convoluted canali- cules of the cortex into the capsules of Bowman. Numer- ous successful results have, how- ever, been more recently ob- tained, and thus the inferences presented by maceration con- firmed (Ludwig - Zawarykin, Kollmann, Chrzonszczewsky, Hertz, Frey, and others.) Our diagram, fig. 321, may represent to the reader the re- sults of the injection, of which only the chief points have been described. To recapitulate, let us again follow the course which the se- cretion must take from the glomerulus. Surrounded by the capsule of Bowman (g), it passes over into the convolut- ed uriniferous canalicule (/), which, after its convolutions, assumes a straight course to- wards the apex of the papilla. Changing the epithelium, it passes more or less downwards, through the papilla (e), bends around in a loop-like manner, and again returns with the other side to the cortex (d). This side, later or earlier, alters its character, becomes broader and more convoluted (c), and enters, sooner or later, in connection with other similarly constituted passages, into the collective tube (&), which, uniting with others 33 Fig. 321. Diagrammatic representation of the course of the uriniferous canal in the perpendicu- lar section (very much shortened). B. cortex; M. medulla ; *, margin ; a, efferent canal-work with the system of branches h\ c, transition- canal (or intercalary portion) in the ascending or returning portion ; e, descending ; /, convoluted uriniferous canal of the cortex ; g, capsule with glomerulus. 514 SECTION TWENTIETH. at an acute angle (a), finally pours out the urine at the apex of the papilla. The new method, the self-injection of the living animal, with which Chrzonszczewsky has made us acquainted, has al- ready been mentioned in a previous section of this book (p. 190). Although the appearances thus obtained are variable and not always comprehensible, repetitions of the experiment with injections of a solution of carmine into the jugular of the rabbit have nevertheless afforded me good results. And the injection of indigo-sulphate of soda has succeeded still better. We cannot 3 r et, however, leave this subject, this injection of the indigo-sulphate of soda. We have still to mention a more recent, excellent study of Heidenhain's, the technical portion of which we have already mentioned in part at p. 191 of our book. The highly important physiological fact was ascertained that it is not the glomerulus of our organ, but rather the convoluted system of canals which secretes this blue coloring matter. I had already seen this a few times before, with von Ewetzky, in the rabbit. Heidenhain subsequently communicated some additional technical directions. These relate to the further treatment of the kidneys when their canals have thus been filled. The organ is to be directly injected by the blood-vessels with abso- lute alcohol, then separate the capsule, and place small pieces, 2-3 mm. thick, in the fluid just mentioned. Quite fresh kid- neys may also be examined at once in glycerine saturated with chloride of calcium. They afford the same result. We have still to mention the connective-tissue stroma, as well as the blood and lymph passages of our organ. The course of the vessels in the kidney has been so fre- quently described (in an especially excellent manner by Hyrtl), that we may here limit ourselves to the most necessary state- ments. The branches formed by the division of the renal artery and vein pass through the medullary substance between the several Malpighian pyramids. At the basis of the latter, bow- like arrangements of both varieties of vessels are noticed. From the arterial arches arise then, in the form of branches, the coil-supporting arteries of the cortical substance, which keep in the axial part of a portion of cortex (cortical pyramid) bounded by two medullary rays, and towards the periphery URINARY ORGANS. 515 kidney. Glomerulus of the pig'e give off the afferent vessels of the glomerulus (fig. 314, e, f ; fig. 323, I). This, the vas afferens, undergoes, in man, further acute-an- gled divisions within the coil-shaped convolutions (fig. 311, h, and fig. 322), and forms, after the con- volutions, by the reunion of the latter branches, the efferent vessel, the vas efferens (fig. 311, c, 323, d). The lat- ter then disappear in a capillary net- work with elongated meshes which encircles the straight uriniferous ca- nals (fig. 323, e). From the periphery of the latter are first formed those capillary tubes (/) which encompass with rounded meshes the convoluted uriniferous canalicules (*) of the cortical substance proper. The most superficial stratum of the cortical substance, which is free from vascular coils, receives its capillaries substantially from the efferent vessels of the superficial glomeruli ; much more sparsely (and certainly not in all mammalial animals) from several of the terminal branches of the glomerular arte- ries, which pass directly and im- mediately forward to this periph- eral layer. Venous roots appear close be- neath the capsule in the form of star-shaped figures ; other venous roots arise deeper in the connective tissue. Generally coalescing into larger trunks, both varieties of venous branches empty at the boundary of the cortex and med- ulla into the arched vessels. Fig. 323. From the kidney of the pig (semi-diagrammatic), a, arterial branch; b, afferent vessel of the glomerulus, c ; d, vas efferens ; e, breaking up of the same into the straight capillary plexus of the medullary ra y ! /, rounded plexus of the convoluted canals, i ; ff t commencement of the venous branch. The long, rectilinear vascular tufts, which appear between the uriniferous canicules in the med- ullary substance (its boundary layer), then extend downward and either pass over into each other in a loop-like manner, or form a delicate net-work around the apertures of the uriniferous canals at the apex of the pyramid, and are called vasa recta (fig. 316, e, /). Be- 510 SECTION TWENTIETH. tween these there also appears a capillary net-work of finer tubes. A great diversity of opinion prevails concerning the origin of these vasa recta. According to our observation, they have essentially, if not also exclusively, a venous character, as they are formed from continuations from the capillary net-work of the medullary rays. The vasa effer- entia of deeply situated glomeruli are joined to them as arterial supplies. Quite unimportant, finally, are the arterial branches (arteriole rectse), which, even before the giving off of the glomeruli, FIG. 324. From the boundary layer of the human kidney, a, Arterial trunk ; &, one branch, and e another which furnishes the vasa afferentia of two glomeruli at c and * w Fig. SS4. Fermentation — mould and vibrionic formations in the urine. similarly colored sediment is deposited at the bottom of the vessel. This consists of the familiar crystals of the ammo- nio-phosphate of magnesia (fig. 332). The precipitates of the urate of ammonia also show themselves. This consists of strongly contoured, often quite dark globules, which are fre- quently covered with fine points, and thus remind one of TJEINAKY ORGANS. 529 morning stars, or they may also have club-like, corrugated processes on them, and thereby assume an appearance similar to bone-cells. Fine needle-shaped masses may also be met with. Fig. 333 represents these conditions, together with crys- tals of the oxalate of lime and the ammonio-phosphate of mag- nesia. The fermentative fungus also disappears from the acid urine, and in its place appear the elements of mould and nu- merous confervoid growths. Numerous fine granular masses, vibrionse, likewise make their appearance. Our fig. 334 may, in its middle portion, represent such mould formations, while to the left and below vibrionas are delineated. The upper por- tion is occupied by the fungus of the cryptococcus cerevisise from yeast, the right lower corner by the fermentative fungus of diabetic urine. Alkaline fermentation of the urine may take place, in an abnormal manner, very soon after its evacuation. In conse- quence of the fermentative action of the mucus and pus of the bladder, urine which has been retained there is decomposed into carbonate of ammonia, and may thus be evacuated in an alkaline condition. The needle-shaped groups of urate of am- monia represented in the upper part of tig. 333 came from such urine in a case of paralysis of the bladder. Spontaneous deposits of other matters are rare phenomena. In a few cases only have crystals of cys- tine — those readily recognizable, delicate six-sided tables, such as are represented by fig. 335 — been found in human urine. The remarkable and rapid de- struction of the liver-cells, which has received the name of yellow atrophy of the liver, has been mentioned on earlier pages of this book (p. 471), and it was remarked that this degeneration produced large quantities of leucine and tyrosine. These, ex- creted by the kidneys, appear in the urine of such patients. Brownish spherical druses of tyrosine have been noticed in the urinary sediment deposited. A drop evaporated on the microscopic glass slide shows yellowish tyrosine druses em- 34 Fig-. 335. Crystals of cystine. 530 SECTION TWENTIETH. bedded between membraniform and globular deposits of leu- cine (Frerichs). Among the remaining precipitates of urinary constituents which are only to be obtained as a result of further chemical procedures, let us here mention only the crystalline forms of combinations of urea with nitric and oxalic acids (fig. 336). Fig. 3-36. Crystals of the combinations of urea with nitric and oxalic acids. urea. a, a, nitrate, 6, 6, oxalate of Their production, as also the occurrence of other matters, such as sarcocine, xanthine, etc., we must leave to the text-books on physiological chemistry. The anatomical methods of examining the various sediments of the urine are of a very simple nature. After standing for some time, the clear fluid is poured from the vessel and the re- mainder is placed in a watch-glass, glass box, or glass beaker, from which a drop is to be removed by means of a glass rod or a pipette and placed on the microscopic glass slide. It is con- venient to have a small burette with a caoutchouc tube and clamp, after the manner of the larger one used for titrition (fig. 87, 1, p. 143), with a fine glass tube for the exit. The burette is to be filled with the sediment, or the still clear urine which is to form a sediment, and the drops are allowed to flow on to the slide by opening the clamp. With regard to the preservation of urinary sediments in the form of objects for a collection, it may be stated that those which consist of tissue elements are not capable of being kept permanently. Crystalline sediments, on the contrary, are to be allowed to dry on a glass slide and then mounted with Canada balsam, or some other resinous body. URINARY ORGANS. 531 A few words may be devoted, at the close of this section, to the supra-renal glands. These organs, which are remark- ably developed in the earlier foetal period, occur in a less vigorous condition in the adult, and are then frequently very fatty, almost fatty degenerated. They show, as is known, a firmer, reddish-yellow cortex (fig. 337) which, in human beings, Fig. 337. Cortex of the numan supra- renal gland in vertical section, o, small- er, 6, larger gland-cylinders ; c, capsule. Fig. 338. Cortex of the human supra- renal gland, more strongly magnified, a. gland -cylinder ; 6, interstitial connective tissue. also permits of the recognition of a narrow, darker, and, after death, not unfrequently liquefying inner zone, and a softer, grayish-red medullary substance. The former (fig. 338) con- sists of the same connective-tissue stroma (b) which we have already described for the hypophysis cerebri and thyroid gland, and which is prolonged inwards from the capsule in radiated lamellae. Numerous cavities are found in it ; they grow smaller and smaller in an outward direction (fig. 337, a) ; in the middle they are oblong and cylindrical (b). Their con- tents are a varying number of granular cells. In the medul- lary substance there is a much finer connective-tissue stroma which contains transversely oval cavities filled with variable cells, but which contain but little fat. The latter, but not the cellu- lar elements of the cortex, become brown in a remarkable man- ner, as Henle found, from the action of bichromate of potash. 532 SECTION TWENTIETH. In certain mammalial animals the medullary substance is very rich in nervous plexuses containing ganglion-cells, and, indeed, a connection of our organ with the embryonic sympathetic can scarcely be denied. The number of the blood-vessels is also quite considerable. Delicate fine capillaries, formed from the numerous smaller arterial branches from the capsule, en- circle the cavities of the cortex and pass over into a highly developed venous net-work. The vessels of this net-work are, however, increased in diameter ; they pass through the con- nective tissue of the medulla and lead into the large single or double veins which lie in the interior of the organ. The lym- phatics require more accurate investigation ; the puncturing method has thus far yielded me no results, while the blood- vessels, for example, those of the calf, may be readily injected by the artery as well as by the vein. Very handsome injec- tions may be obtained with the guinea-pig, as well as the rat, from the aorta and lower vena cava. The supra-renal bodies of the new-born and very young animals, and also those of embryos, from the later periods of embryonic life, are to be selected for examination. Some things may be recognized, even in sections from fresh organs, with the aid of acids and alkalies. Far better views are afforded by supra-renal glands which have been hard- ened in chromic acid, Midler's fluid, or absolute alcohol, with the assistance of brushing and tingeing. The nerves may be studied on the fresh organ with the addition of alkalies or osmic acid, or on preparations which have been immersed in dilute acetic or pyroligneous acid, as well as in weak chro- mic acid. Sections deprived of their water by means of abso- lute alcohol are to be mounted in Canada balsam or similar resinous matters, or, when moist, in glycerine. Section tocnts-Jtat SEXUAL ORGANS. Among the female generative organs the uterus and the lac- teal glands are the most important. The ovary (fig. 339) shows, as is known, the rounded, closed Fig. 339. The ovary. «, the stroma : &, smaller Graa- fian follicles ; c, a larger one ; d, afresh corpus luteum, with the proliferated cell-layer of the inner surface*; e, an old corpus luteum ; o", veins with their ramifica- tions, /, in the organ. Fig. 340. Mature ovum of the rabbit. a. zona pellucida ; b, yolk ; c, germ ve- sicle ; rf, germinal spot. glandular capsule (b, c) which contains the primitive ovum embedded in a firm connective- tissue framework or stroma. These ova are set free by the rupture of this capsule, or the Graafian follicle ; this takes place in the human female at periods of four weeks, corresponding to those of menstruation ; in the mammalia it occurs at the period of heat. The follicle itself cicatrizes by a connective-tissue formation, and disap- pears. By this metamorphosis it produces the so-called cor- pus luteum (d, e). Other ova probably undergo dissolution in the unopened gland capsule (Slavjansky). If one desires to obtain a primary view of the ovum (figs. 340 534 SECTION TWENTY-FIRST. and 341, a), this most beautiful cell-formation of the body, the ovarium of a mammalial animal just killed is to be used. The larger Graafian follicles (fig. 341) may be readily cut out from the stroma with a curved scissors and opened on the microscopic glass-slide. The ovum may be perceived as a Fig. 341 . Mature follicle. d, connective-tisane wall ; t a, ovum : epithelial stratum covering the same, b, and lining the cavity, c ; outer surface of the follicle. small white point in the exuding, slightly cloudy contents, by a sharp eye, even without any further accessories ; while a less perfect organ of vision requires a loupe, or the very weak magnifying power of a microscope, for its discovery. The adherent, frequently thick covering of follicular epithelium (fig. 341, b) is to be removed by means of a cataract needle ; a very thin and light covering glass is to be used, with the inter- position of a piece of human hair. The cell capsule, zona pellucida (fig. 340, a), the contents of the yolk (5) and the nucleolus, the so-called germinal spot (d), may be readily seen ; the recognition of the fine contours of the germinal vesi- cle of the nucleus (c) will, on the contrary, cause some diffi- culty. A 3^400-fold enlargement is to be employed for this purpose. A cautious pressure made on the covering glass with the point of a needle, while the observer looks through the instrument, will then cause the rupture of the thick envelope of the ovum SEXUAL ORGANS. 535 and permit of the recognition of the nature of the exuding yolk substance, as well as the germinal vesicle with the germinal spot. With human females, the freshest possible ovaries of youth- ful individuals are to be selected, preferably those who have died suddenly. Persons who have been lying sick for a long time, and those of a more advanced age, frequently cease to show the ova with any distinctness. If the trouble of separating the Graafian follicles from their attachments, especially the very diminutive ones of our smaller mammalial animals, be feared, the ovulum may also be ob- tained by scraping the cut surface of the ovary. An indifferent fluid medium will here be necessary. Young, smallest possible follicles, carefully separated from the stroma, may be reviewed in their totality with low magni- fying powers ; in this way they will show the ovulum, the epithelium, and the parietes of the glandular capsule. The examination of the fresh ovaries may also suffice to es- tablish the main points concerning the nature of the framework substance, as well as the cell changes which take place in the corpus luteum. If, on the contrary, a more accurate analysis of the ovary is to be made, the fresh organ must be hardened. If the freez- ing method be omitted, the ordinary fluids are to be employed, among these I would give the first place to absolute alcohol and chromate of potash. The blood-vessels should also, when pos- sible, be previously injected. Tingeing with hsematoxyline or carmine, and in the latter case combined generally with wash- ing in acetic acid water, constitutes an additional excellent ac- cessory. The connective-tissue framework forms towards the centre a nucleus of the organ, and is extremely rich in blood- and lymph- vessels ; externally it is a non-vascular framework, in the smaller and larger spaces of which are contained the ova. The youngest of the latter appear in extraordinary numbers in its peripheral portion (fig. 342, c, d), the "zone of the primordial follicles." Here lie the most unripe ova, beautiful cells with- out envelopes, surrounded by a mantle of small, epithelium- like elements (fig. 343, 1). The developing ovulum (2) soon shows the latter cells as a double layer, and on it itself a cap- sule, the zona pellucida (2, a) is perceived. A cavity (fig. 342, d) 536 SECTION TWENTY-FIRST. is afterwards formed by the separation of the follicular epithe- lium, and finally we receive the appearance of the ripe follicle, Fig. 342. Ovary of the rabbit, a, epithelium (serosa) ; &, cortical or external fibrous layer; c, youngest follicles ; rf, a somewhat more developed older one. represented in fig. 341. The latter occur only in limited num- bers in the ovarium. They have a connective-tissue wall. An inner stratum (d) shows an extraordinarily rich net-work of cap- illaries, while larger vessels are contained in a more peripheral layer (e). If we add the layer b of our fig. 342 as a connective-tissue boundary layer to the organ, and remark, finally, that a stratum of cylindrical cells, the ovarian or germinal epithelium (a), covers the surface, then we have presented in a few sen- tences an outline of the structure of the ovary. Fine transverse sections of the hardened ovary show these relations without difficulty. If the plane of the section be favorable, the ovulum may also be perceived in large fol- licles, embedded in the epithelial layers of the latter (very frequently lying to the inner side). Occasionally, with strongly hardened ovaries, such fine sections of the smaller folli- cles may be obtained with a sharp knife, that the ovulum may likewise be seen in the section ; sometimes only the zona, after the loss of the yolk and nucleus. Fig. 343. Youngest folli- cles from the ovary of the rabbit. At 1 the ovulum a is still without a zonapellu- cida ; at 2 this commences to surround the ovum a. SEXUAL ORGANS. 537 We have more recently received very important informa- tion, through Pfliiger, concerning the formation of the Graafian follicles, which established the truth of the older but no longer- regarded observations of Valentine and Billroth, and afforded an interesting parallel between the testicle and the ovary. Other observers afterwards coincided, and Waldeyer has pro- duced a beautiful monograph. Ac- cording to this, the ovary consists originally of ordinary oblong, oc- casionally, however, also of quite irregularly formed cell aggrega- tions, the follicular chains or ovular strands (fig. 344). In these primor- dial follicular rudiments are formed the ova ; the follicles become sepa- rated from them by constriction, but may still remain connected with each other in rows, and may conti- nue to increase in size (Pfluger's "follicular chains"). The whole formation, although possibly it may also repeat itself in after-life, is, however, very transitory, and was consequently overlooked for so long a time. Young kittens in the first weeks of their life are to be recom- mended here ; as fluids, weaker so- lutions of chromate of potash, or the Midler's eye-fluid. A stratum of free ovum cells, which is said to have been observed close under the surface of the ovary (Schron, Grohe), does not exist, as the small cells of the so-called formatio granulosa surround- ing these ovula were destroyed by the action of the reagents (alcohol and strong chromic acid). Now whence came the ovular strands and the ovules which they contain ? The peculiar ovarian epithelium (fig. 345, a), which we have previously mentioned, sends conical proliferations (5) into the peripheral stratum of the organ. Some of the cells of the cone become ova, and by separation from the epithelial matrix the ovular strand is formed. Fig. 344. Follicular chains from the ovary of the calf. 1. With ova forming. 2. At a, showing the constriction into a Graafian vesicle. 538 SECTION TWENTY-FIEST. The Graafian follicle constantly approaches the surface of the organ in proportion as it approaches its maturity, so that, finally, entirely matured, it is only covered by a thin fibrous layer of the albuginea. It is well known that as a result of increased congestion of Fig. 345. From the ovfiry of a young slut, after Waldeyer. «, germinal epithelium; &, ovarial tube; e, the same in oblique and transverse sections ; c, a racemose group of young follicles. the walls of the follicle, the collection of fluid in a Graafian vesicle becomes greater and greater, and that thus a rupture of the latter may take place, naturally at the point of the slightest resistance, that is, at the surface of the ovary. This bursting of the follicular walls, which frees the ovulum and renders its further development possible, is also promoted by still another phenomenon, a cell-proliferation at the base and on the lateral walls of the follicle. A recently ruptured follicle of the human female occasion- ally presents us a lump of coagulated blood (coming from the lacerated parietal vessels), but always, however, the layer of plicated substance which has a yellowish appearance from the fat it contains. Our fig. 339 at d* shows this proliferating stratum, which probably consists of derivatives from the cap- sular epithelium, but principally, however, of the cells of the inner parietal layer, and which also, at this time, contains nu- merous emigrated lymphoid cells (Waldeyer). While a portion of these cells are destroyed by fatty degeneration, an active formative process is maintained in others, in consequence of which a vascular young connective tissue is formed, which di- minishes the interior space more and more, and not only com- pletely fills the cavity of the follicle, but also causes a consid- SEXUAL ORGANS. 539 erable hypertrophy. The presence, at this time, of a rich, deli- cate, vascular net-work in the corpus luteum is proved by injec- tion. We recommend for this readily practicable experiment the ovarium of the sow, in which the oviducts and uterus also afford very handsome objects. The progressive metamorphosis has herewith reached its height. The young connective-tissue contained substance shrivels more and more (probably with a simultaneous atro- phy of the vessels), the tissue becomes firmer, more like a cica- trix. Such remains of the corpus luteum may still be seen for a longer period. The whole process, however, proceeds much more rapidly , "^ in a corpus luteum caused by an ordi- j&. ■ * ■** „ „ nary menstruation than in one where «||p" 13 ^ ^* ^ ^ the escaped ovum has been impregnat- tU m Pj *&a ^ ed. It has been asserted, in accordance m* ^U ' herewith, that there are two forms of W° ^-?' /\/\ ^^ the corpora lutea. feCiC?^T^v^ -P" In the portion of the blood -clot which °' " (T^V^^ remains behind, the crystallization of W the htematoidine (fig. 346), which we rio . a46 . CrystaleofhiEmatoiaine . have already mentioned, takes place. Among the pathological occurrences, the formation of cysts are, as the practical physician knows, of extraordinary fre- quency in the human ovaries. A portion of these — and, in- deed, the greater — certainly correspond to hydropically dis- tended Graafian vesicles. Others of these formations origi- nate, on the contrary, from a proliferation of the stroma of the ovarium. The walls are formed of connective-tissue substance, and the mucilaginous contents of colloid degenerated con- fluent cells. Innumerable quantities of such structures, with very slight dimensions, may be found in an ovary. A number of larger ones may be met with, or one grown to a gigantic size may be found. The most remarkable form of ovarian cyst is that, however, where a part of the parietes has assumed the structure of the corium, with papillae, hair follicles, sebaceous and sudoriparous glands, and where hairs, occasionally united into long bundles, are met with (dermoid cysts). Even teeth, pieces of bone, and hyaline cartilage may be found in such cysts. The remaining contents are formed by a pap-like mass, consisting of desquamated epithelium, fat molecules, and crys- 540 SECTION TWENTY-FIRST. tals of cholesterine. (Similar capsules, with such strange con- tents, have also been found in other organs ; for instance, in the lungs.) An explanation of the remarkable production is, at the present time, impossible. The contents are to be examined in the fresh condition, bones and teeth after the manner of the normal structures, and the walls on objects hardened by means of alcohol. Preparations of the ovaries, tinged and deprived of their water by means of alcohol, may be very suitably mounted in Canada balsam ; otherwise, dilute glycerine is to be se- lected. Concerning the efferent passages, the oviducts, it may be said that their mucous membranes, muscular and serous lay- ers, are to be examined in the same manner as those of other large glandular canals. The ciliated epithelium requires quite fresh objects ; a previous hardening is most suitable for the re- mainder. Injected organs are to be selected for the investiga- tion of the folds of mucous membrane which are frequently quite complicated. The womb or uterus also possesses an epithelial layer formed of ciliated cells, and a tubular-shaped mucous mem- brane containing glands. These tubular follicles, lined with cylindrical cells, are to be observed in fresh female mammalial animals, partly immediately, partly after hardening, by means of vertical and horizontal sections. In the human female the uterine follicles appear particularly fine during menstruation or in the first months of pregnancy. The increase in volume of the womb during pregnancy is ex- hibited principally by its muscular portion, which consists of contractile fibre-cells. We first see an increased growth of these elements, in part into structures of gigantic length. Even on this account the massiveness of the muscular portion must be considerably increased. Besides this, a new forma- tion of such muscular cells also takes place (although in its details not yet explained), especially in the first half of preg- nancy. The mucous membrane also increases considerably, becomes loosened in its connection with the muscular layer, and forms the decidua of the ovum. After the birth the contractile fibre-cells return to a shorter length ; a part of them are, however, without doubt, destroyed by fatty degeneration. Numerous depositions of small fat SEXUAL ORGANS. 541 molecules in the fibre-cells are, besides, a quite extended phe- nomenon. The remains of the mucous membrane are then removed in childbed by the lochial secretion. The manner in which the new mucous membrane of the uterus is formed requires more accurate investigation. The energetic proliferating vegetation, the active change of its elements which the uterus presents under abnormal condi- tions, asserts itself in the sphere of pathology, and thus pro- duces the so frequent new formations, among which the so- called fibroid, hard fibrous tumors, are the most widely dif- fused. These consist sometimes exclusively of fibrillated con- nective tissue permeated by blood-vessels, sometimes of the above, mingled with contractile fibre-cells, occasionally, how- ever, also, almost entirely of smooth muscular tissue. They supplant the normal tissue in proportion to their growth. If connected with the wall of the organ by means of a pedicle, they are called uterine polypi. Their examination is to be made in accordance with the directions which have been given for the developed connective tissue. Cancerous tumors of the womb are also of frequent occur- rence. They frequently appear in the form of epithelial can- cer. We may pass over the methods of investigating the uterus, the vagina, and the external genitals. The accessories are in part the same as those which we have already mentioned above for mucous membranes and smooth muscles, in part those of the skin, which are to be discussed in the following section. Let it here be mentioned, however, that it has been recom- mended for the uterine muscular tissue to boil the uterus for a few minutes, and to join with this an immersion in carbonate of potash. Furthermore, the maceration in pyroligneous acid, and the employment of alcohol, with subsequent drying, after which thin sections are to be exposed to the action of the 20 per cent, nitric acid. Cabinet preparations of the tissue of the womb, and of the textures of the external genitals are to be prepared by the me- thods now employed for the mucous membrane, the skin, and the muscular tissue. The mucous secretion of the female genitals originates first and principally from the cervix uteri, the mucous membrane 542 SECTION TWENTY-FIRST. of which contains numerous fossae or mucous follicles; and then from the glandless vaginal mucous membrane. The for- mer has an alkaline reaction, appears hyaline, tough, and te- nacious, and contains numerous mucous corpuscles together with scanty pavement epithelial cells. In contact with the acid vaginal mucus it becomes cloudy. The latter, an almost limpid fluid substance, is very scanty in young maiden bodies, except during the menstrual periods ; in blennorrhoeas of the genital mucous membrane, as well as with women far advanced in pregnancy, it increases in quantity, and the vaginal mucus becomes cloudy, milk or pus-like. The elements of the vagi- nal secretion, which are shown by the microscope to increase in quantity in proportion to the increase of consistence and opacity, are again mucous corpuscles and pavement epithe- lium. In the vagina] mucus of non-pregnant persons, but espe- cially, however, in the pregnant, there occurs, together with several vegetable parasites, as for example, oidium albicans (p. 429), an interesting animal parasite, the Trichomonas vagi- nalis, discovered by Donne. This is an infusorium which is provided with a ilagellum and vibratile ciliee ; it moves actively in pure mucus, but very sluggishly, on the contrary, in that diluted with water. This infusorium appears to be entirely absent from the normal secretion of the vagina of unimpreg- nated females (Kolliker and Scanzoni). A speculum is to be employed in order to obtain the secre- tion in question. The vaginal mucus may be obtained by scraping with a spatula. It is difficult to obtain the mucus from the cervix unmixed with vaginal secretion. The addition of water is naturally to be avoided in the microscopical exami- nation of the Trichomonas. The menstrual blood from the ruptured capillaries of the uterine mucous membrane has usually (perhaps from the ad- mixture of secretions from the mucous membrane) lost its co- agulability. It shows, together with the blood-cells, numer- ous granulated structures, mucous corpuscles, also separated ciliated cells which have lost their vibratory cilise. Shreds or connected masses of the uterine mucous membrane may be caused by more considerable separations, so that a formal decidua spuria has been spoken of. The lochial secretion consists at first almost entirely of blood SEXTJAL ORGANS. 543 which comes from the torn vessels of the contracting uterus. In the first days after the birth, when a brown-red mucous fluid, with a few flakes and shreds, usually come away, the microscope shows as elements, together with sometimes unal- tered, sometimes swollen or indented blood-corpuscles, pave- ment-shaped cells, granulated structures (mucous and pus cor- puscles), effete cells as well as their ruins, fat-molecules, and likewise, here and there, cholesterine tables. In the latter periods, where the blood-corpuscles decrease more and more in numbers, and finally disappear altogether, the number of the granulated cells usually increases in an inverse ratio. Towards the end the lochial secretion gradually assumes the Fig. 347. 1. Rudiment of the lacteal gland in the foetus, a, &, epidermis ; c, cell aggregation ; d, fibrous layer. 2. From a seven-months 1 foetus, a, central sub- stance ; &, larger, c, smaller outgrowths. Fig. 348. The milk-gland of another embryo, a, the central club-like mass, with smaller internal, &, and larger external, c, outgrowthB. character of a mucus rich in cells. The examination presents no kind of difficulty. For its reception, flat oval plates may be used (Werthheimer). The lacteal glands are formed in the fourth and fifth month of human embryonic life, after the manner of other cutaneous glands, by solid papillary projections of the foetal epidermoidal cells, covered by a fibrous layer of the corium (fig. 347, 1, d). Several weeks later (fig. 347, 2, and 348) such a club-like pa- pilla (a) has, by division of its cells, sent down new papillfe (b, c), from which the chief excretory passages are afterwards formed, which, by further proliferations of this kind, produce the first rudiments of the gland-body. Even at the hour of birth, however, a rudimentary formation of gland vesicles has 544 SECTION TWENTY-FIRST. not taken place, and, while the ducts become hollow, their out- growths remain at the stage of solid cell-aggregations. The larger gland divisions keep to the periphery, the smaller ones to the inner portions of the whole organ. The lacteal glands preserve this undeveloped, more foetal character, even during the period of childhood, in the male as well as in the female sex. While it is true that even here the lacteal gland of the female has advanced more rapidly than that of the male, it is only at the entrance of puberty that a further development of the former becomes energetic. Numerous gland-vesicles are the result. Nevertheless, the organ still remains far behind its complete development, for which the first pregnancy is neces- sary. After the delivery it generally receives that organization. Atrophy is first introduced by the period of involution ; fat- tissue takes the place of the gland-body. The lacteal gland of the male, on the contrary, remains at the lower stage throughout the whole life. The developed gland of the sexually mature female contains, in a condition of rest, an epithelial lining of ordinary rounded, polygonal gland-cells. In the gland-vesicles of the cow, the same finest reticular canal-work which we mentioned formerly (p. 460) at the pan- creas and other racemose glands has been injected (Grianuzzi and Falaschi). The mammary gland, as is known, presents manifold patho- logical new formations. In many of them the development takes place from the proper gland-bodies. Thus, for example, at the period of involution small cysts, filled with a mucila- ginous fluid, are of frequent occurrence. They arise from a metamorphosis of the gland-lobules, the distended vesicles of which become united with each other. New formations of gland-substance, under pathological conditions, have also been ascribed to the organs under consideration, and have been described as "adenoid" tumors. Soft, but especially hard cancers, cysto-sarcoma and simple sarcomatous tumors also occur. Concerning the point of origin, the same uncertainty prevails here as elsewhere. The examination of the lacteal glands (normal as well as diseased) is, for the most part, to be made (in the usual man- ner) on hardened organs, by means of fine sections. A prepar- SEXUAL OEGANS. 545 atory immersion in very dilute acetic acid, in diluted pyro- ligneous acid, or a brief boiling, is useful. For the first rudi- mentary appearances, human embryos at about the fifth month are to be selected ; for the later appearances, the bodies of children. The material necessary for the recognition of the completely developed gland can only be obtained from a female who has borne children. The active organ may be ob- tained from the bodies of the lying-in. Injections of the larger glandular passages from the lacteal sinuses succeed with toler- able facility ; the constant pressure is to be employed for the injection of the finest passages. The milk of the human female and of the mammalia is formed by the liberation of the fat produced in the cells of the lacteal glands, which thus becomes suspended in the glandular fluid rich in albumen and sugar. The secretion under consideration presents a near relation- ship, in this regard, with the less fluid substance secreted by the sebaceous follicles of the external integu- ment, and, in fact, we are in a position to vin- q" ° dicate, by the aid of facts in embryology, the o q°° same manner of origin of both varieties of glands. o ° Ordinary milk shows, in a clear fluid, an in- &\ numerable quantity of globular fat-drops, the ^a*. ig| &r so-called milk globules (349, a). These, which vgP * may be examined even with medium powers, PlG . 349 . E i eme n. never flow together after the manner of free ord : iiS'™ S miik 1 - 1 giob- fat, but rather possess a delicate investment of tostr'a^'co^uscies. 00 " coagulated casein. It is only when this is dis- solved bj' means of acetic acid or alkalies, that the union of the free drops of fat is noticed under the microscope. If the secretion of the milk takes place less energetically, as is the case with the so-called colostrum, and the secretion which occurs during the latter period of pregnancy, as well as in the first days after the delivery, this rapid destruction of the gland-cells is absent, and we still meet with them in part (over- loaded with fat to a high degree, it is true) as constituents of the evacuated fluid. We also meet with fragments of these cells and membraneless conglomerations of fat. These are the so-called colostrum corpuscles of the authors (fig. 349, b) ; they do not appear to be wholly without vital contractility (Strieker, Schwarz). A few remain for a long time in the milk of women. 35 546 SECTION TWENTY-FIRST. A larger number of such structures in the milk, months after the delivery, must, on the contrary, be denoted as abnormal. Abnormal constituents of the milk are of secondary impor- tance. Blood-cells, and also lymphoid corpuscles, may be met with in it ; their recognition is not difficult. Remarkable colorations may occur in milk which has stood for some time ; thus blue and yellow colors have been observed. In such cases the microscope has shown vibrionic, and also pro- tococcus formations. A drop of milk spread out in a thin layer will, without any further manipulation, present its elements to view in the same manner as other cell-containing fluids, as, for instance, the blood. Strong magnifying powers are unnecessary ; permanent preservation will hardly be undertaken. Among the parts of the male generative organs we will first speak of the testicles, taking it for granted that the coarser structural conditions are al- ready known. Numerous, but not complete connective- tissue septa, arising from the fibrous tunic (the tunica albuginea) converge to unite, in the upper part of the testicle, in a firmly wo- ven, connective tissue, wedge-shaped mass, the so-called corpus Highmori. The gland substance, consisting of reticularly united and convoluted canals, the so-called seminal ca- naliculi, is thereby divided into conical, lobu- lar convolutions. The appearance of such a seminal canali- cule may be represented by the adjoining fig. 350. It is filled with cellular elements (5), which have yet to be more particularly dis- cussed. Its walls, which are quite thick in man, consist of several strata of cell-lamellse imbedded one over the other and united in a membraniform manner. The innermost lay- ers of these strata close completely, while the more external ones have a reticular arrangement. A soft, loose connective tissue is met with between the seminal canaliculi. In smaller mammalial animals, for example the rabbit and the rat, which latter was recommended by von Fig. 350. Human semi- nal canaliculi, with the gland-cells b, and the con- nective-tissue tunic a. SEXUAL ORGANS. 547 Ebner, this is very scanty and soft, so that these canals may regularly fall apart. The organ of such creatures, hardened in Midler's fluid and alcohol, requires, therefore, a preliminary imbedding (p. 113) when line sections are to be obtained. In other animals, for example, the calf (Prey), the cat, and the boar (Mihalkovics), the latter procedure niay be dispensed with. We would rec- ommend hsematoxyline as the best coloring material. For the isolation of the seminiferous canals, employ the maceration in muriatic acid (p. 125). Mihalkovics recommends for the human testicle, the immersion in f hydrochloric acid and •J water, allowing the action to continue for a day or two at a temperature of about 30° C. and subsequent removal to dis- tilled water, till the preparation comes apart. The remainder is completed with the prepar- ing needles. We have already (p. 280) mentioned the coarsely granulated, so-called plasma-cells of the connective tissue (fig. 351) which be- sides occurring in other organs is also pro- fusely developed in the testicles of many mammals as an investing substance, around the finer blood-vessels. We recommend the rat and the cat for their study, and hsematoxyline as a color- ing medium. The preliminary puncturing method and the in- jection of weak (0.25 per cent.) solutions of osmic acid, with subsequent hardening in absolute alcohol, affords excellent views of these cells, as well as of the genesis of the seminal filaments which is to be discussed hereafter. The seminal canals then coalesce and finally form a single vessel, a tolerably large canal, which, with innumerable convo- lutions, forms the so-called body and tail of the epididymis ; it afterwards straightens and becomes the vas deferens. The epididymis shows, in addition, a ciliated lining of its convo- luted seminiferous canals (Becker), in places with gigantic cells and vibratile cilise. The blood-vessels, which are very easy to inject, pass from without and from the corpus Highmori into the organ, per- meate the septula, and finally encircle the seminiferous canals with a wide-meshed (but not particularly abundant) net-work of capillaries. Fig. 351. So-called plasma- cells, b, surrounding a blood- vessel, a, of the rat's testicle. 548 SECTION TWENTY-FIRST. The first accurate information concerning the lymphatics was furnished by Ludwig and Tomsa. In fact, nothing is easier than the injection of the organ by means of a puncture. A surprising picture of numerous vessels (Ludwig and Tomsa) unfolds itself here, and, as it appears, in exactly the same manner in all mammalial animals. A very extensive net- work of lymphatics, with valves, lies under the serous cover- ing, permeates with its branches the albuginea, and spreads itself out beneath the same to a likewise verj r compact net-work of passages enclosed by connective tissue. Some of these pas- sages pass at once between d the seminal canals ; the greater portion, however, first pass through the fam- iliar septula, and finally likewise enter the loose connective tissue lying be- tween the glandular pas- sages (fig. 352, a, b). The spaces of this connective tissue, in so far as they are Flo. 352. From the testicle of the call, a, seminiferous . . . o canals seen in more oblique, », in more transverse sec- not OCCUpied by Semimfer- tions ; c, blood-vessels ; d, lymphatics. -J; tit ous canals and blood-ves- sels (c), are filled with lymphatic fluid (d). We meet with this in a remarkable manner, in small mammalial animals especi- ally, the seminal canals of which, having but very little inter- stitial connective-tissue, are regularly bathed in lymph. Mihal- kovics recommends for the closer study of the lymphatics the injection of a 0.25 per cent, solution of osmic acid. For the re- cognition of the endothelial cells of our lymphatics, either the injection of a solution of nitrate of silver or the immersion of the sections in such a solution of 0.25-0.125 per cent, may be employed (Tommasi). To obtain the entire arrangement of the seminal canals, they are to be injected with transparent cold-flowing masses or with gelatine. Grerlach gives us the following directions for the injection of these passages with gelatine : The testicle is to be placed in a weak solution of potash for 4-6 hours, to dissolve out the cells and the entire contents as much as possible. An attempt is then to be made to remove the mass by cautious pressure, SEXUAL ORGANS. 549 after wliich the organ is to be washed off in water. The air contained in the glandular canals is to be drawn out as thoroughly as possible, and the injection fluid (colored with carmine or chromate of lead) is to be forced in very slowly. During this procedure the organ should be kept in warm water. The vas deferens must be studied hardened in fluids. A mammalial animal just killed is to be used for the ciliated epithelium of the epididymis. The mostfrequent pathological new formations of the testicle are soft tumors, appearing in the form of medullary carcinoma and sarcoma. In the so-called cysto- sarcoma we meet with larger or smaller vesicles partly filled with water, partly with colloid substance, which proceed from transformations of the seminal canals. Concerning the deeper, efferent, and copulating organs of the male generative apparatus, it may be remarked that the ductus ejaculatorii and seminal vesicles have the same struc- ture as the vas deferens, and are to be examined in a similar manner. In the latter is found, together with spermatic fila- ments, a transparent albuminous substance, which undergoes a gelatinous coagulation, to afterwards resume a fluid condi- tion. It is the same substance which the evacuated sperm contains. The prostate, a racemose glandular aggregation, is very rich in smooth muscular tissue. The latter elements may be exam- ined in the fresh organ with the reagents usually employed for this tissue, such as the potash solution or a 20 per cent, nitric acid. For the investigation of its further structure, the organ is to be hardened, either with alcohol, or first with Midler's fluid, and then tinge with hsematoxyline or picro- cannine. One may then recognize the absence of a membrana propria, and the development of a double layer of the gland- cells (Langerhans). The prostatic secretion contains an unaltered albuminous body, which is tinged violet-blue by the excellent Jiirgen's reagent (p. 155). The prostatic stones, concentric structures, occasionally of considerable size, are tinged by this aniline- iodine-violet, sometimes blue or blue-violet, sometimes in the centre red and at the periphery blue, whereby all transitions of color may be wanting. The same condition prevails in the 550 SECTION TWENTY-FIRST. familiar corpuscula amylaceo. We believe with Jurgens that the red color belongs to the developed amyloid stage, and the blue-violet to the albuminous primary stage. The glands of Cowper are to be examined in the same way as other racemose glands. Osmic acid, Mul- ler's fluid and the customary tingeing methods are also employed. The tissue of the caver- nous organs consists of elas- tic and connective - tissue fibres, intermixed with smooth muscles. The latter are to be studied in a fresh condition, the remainder, on alcoholic preparations, where we would recommend the previous injection with uncolored gelatine. These also afford opportunity, es- pecially in transverse sec- tions, for studying the male urethra. To follow the vas- cular arrangement of the cor- pora cavernosa (fig. 353), in- jections are to be made with transparent blue or red gelatine fluid, and the preparation somewhat strongly hardened. The lymphatics of the glans penis are to be injected by the punctur- ing method (Belajeff). We have finally to consider the semen (sperm). A drop of evacuated human seminal fluid spread out in a thin layer, without any further addition, on the microscopic slide, shows, with a magnifying power of about 400 diameters, a number of peculiar structures, the so-called spermatic filaments, spermatic animalculse (spermatozoa, zoosperms). These (fig. 354) permit of the recognition of an anterior broader flattened portion, the head (a) ; and a more posterior long filament, with a relatively thick commencing portion, the so-called middle-piece (b) ; and a terminal filament (c) of extreme fineness. Fig. 353. From the peripheral portion of the corpus cavernosum penis, by a low magnifying power. 1. o, so-called superficial, and b, deeper cortical network. 2. Insertion of arterial branches ((t) in the passages of the deeper cortical network (copied after Langer.) SEXUAL ORGANS. 551 The remarkable movements which these structures present in evacuated living semen have at all times awakened the aston- ishment and interest of the observer ; and, in fact, a wonderful appearance is presented on looking down into this confused mass and observing the spermatic filaments dart- ing wildly about. A closer investigation of this busy multitude shows that the individual sper- matic element makes undulating and whip-like movements of the filament, and is thereby pushed from the place. | An independent change of position, directed to- wards a definite object, for which earlier observers mistook the phenomenon (and in harmony there- with declared the spermatic elements to be animal beings), is, however, in no wise the case. If the via. 354. s P er- ° n ' ' mntozoa of the phenomenon be followed throughout a longer pe- sheep, after ± ° ° 1 Schweigger-SeideL riod, it will be seen how, after the manner of the ft he . ad < b < j^ & - 7 ' die-piece ; c, tail. nearly related ciliary motions, the movements gradually become extinct ; how the energy of the filament- ary movements decreases more and more, and thereby the change of place ceases ; how weaker and weaker contortions of the filaments are then to be noticed in the spermatozoa, which can no longer move from the place, until finally the whole becomes quiet. We would, in addition, repeat here a re- mark which we have already made ; namely, as each excursion appears very much exaggerated by the strong objective (p. 97), the irregular advance of the spermatozoa should not be over- estimated. It is in reality but very slow.. More indifferent fluids, blood- serum, lymph, white of egg, iodine-serum, solutions of sugar (1060-1030 sp. wt.), urea (10-5 per cent.), neutral salts of the alkalies (chloride of sodium, one per cent.), and earths may be employed as media. Pure water increases the energy of the movement of mammalial sperma- tozoa, at most for a very short time, to lead to a rapid cessation, whereby the filamentous extremity bends itself into the form of a loop. Everything, on the contrary, which acts chemically, generally arrests the movement once for all. Spermatozoa which have become quiet from too watery media may fre- quently be temporarily restored to life by means of a concen- trated solution (of sugar, chloride of sodium or albumen), and inversely. As on the motus vibratorius, so also on the move- 552 SECTION TWENTY-FIRST. Fig. 3j5. Portion of a transversely divided seminiferous canal of the rat (osmic acid preparation), a, parietes with cell nuclei; o, parietal cells with spermatoblasts c, the latter with small, narrow nucleus-like corpuscles ; (I, in- ner cell layer. ments of the spermatozoa a peculiarly stimulating effect is exerted by dilute solutions of the alkalies and caustic potash of 1-5 per cent. (Kolliker). The alka- line fluids of the body therefore also maintain the vitality of the spermatic filaments for a long time. In a similar manner a suitable solution of sugar with 0.1-0.05 per cent, of caustic potash also acts excellently. Moreover, accord- ing to Mantegazza, human spermatozoa preserve their vitality and capability of motion within the broad thermometric limits of from — 15 to + 47 degrees of the centigrade thermometer. In order to examine the cellular con- tents of the seminiferous canals, use transverse sections through the suitably hardened organ. The same process is also advisable for the investigation of the still controversial genesis of the spermatozoa. Von Ebner has properly recommended the rat in con- sequence of the size and peculiar struc- ture of the head of its seminal filament. We recognize that the outer cell layer of the seminiferous canal presents a pris- matic radial form, and that the develop- ment of these remarkable structures takes place from this, while the inner cellular elements remain without a future. From the former arise quite peculiar structures (fig. 355, b). When developed, they re- semble somewhat a thick, ill-shaped can- delabrum. These "spermatoblasts, 1 ' as they have been christened by von Ebner, each produce a nucleus (c) in their nodu- lar offshoot. It becomes the head of the seminal filament (fig. 356, 1, b), while the protaplasma of the cellular thing which is turned inwards, that is towards the axis- canal, grows out into a filament (c). Each of the Ebner's sper matoblasts («), accordingly, produces several spermatic fila Fig. .35G. Spermatozoa of tho rat, undergoing: development. 1. Spermatoblast, n, with the head, 6, and filament, c. 2. Nearly mature spermatozoon with adherent re- mains of the protoplasma. SEXUAL ORGANS. 553 merits, which are at last set free (2), and lie in the seminiferous canal with their tails directed upwards and downwards. Thus we view the matter, at the present time, in accordance with Neu- mann, von Ebner, and Mihalcovics. The relatively resistant substance of which the spermatic filaments consist readily permits of their being preserved dry as cabinet preparations, and also of being softened with water from dried seminal stains, and thus recognized with the micro- scope. From the great importance which the recognition of the latter is for the medical jurist (and it may still be accom- plished after years), the simple procedure may here find its place. The suspicious portions are to be cut from the body or bed linen, and having been reduced to small pieces, placed in a watch-glass or glass box, with the addition of a small quantity of water. After a time, a quarter or half hour, during which the pieces of linen have been several times stirred about in the water with a glass rod, this fluid is to be examined, and then the fluid pressed drop by drop from the fragments on to the microscopic slide. Any spermatozoa which may be present will thus be discovered with certainty, and there is scarcely any possibility of mistaking them. 0ection ^tomtg-sccortft. ORGANS OF SENSE. 1. The human skin consists of the epidermis, the corium, and the subcutaneous cellular tissue ; the latter being rich in fat. Numerous nerves, blood-vessels, and lymphatics per- meate it ; innumerable glands lie imbedded in it ; the hairs and nails, finally, constitute special organs. All these have already been individu- ally mentioned in previous sections, so that we can only present a short recapitula- tion of the whole. The structure of the skin may be represented by fig. 357, a vertical section of the same from the point of the finger. The cornified epider- mis appears at a with its numerous layers of flattened cells ; the (punctated) layer beneath it (b) represents the so-called Malpighian rete mucosum. The papillae of the cutis appear at c, and beneath them commences the sirperficial extension of the corium, which is sometimes thinner, sometimes thicker, and passes into the subcutaneous cellular tissue without any sharp line of demarcation. Among the con- stituents of the latter we perceive the coil-shaped bodies of the so-called sudoriparous glands, g, the ascending ducts of which Fig. 357. Human skin in transverse section, a, su- perficial layers of the epidermis; 6, MalpighiaH rete mucosum. Beneath the latter is the corium, forming the papillae above at c, and terminating below in the subcutaneous connective tissue, in which, at h, aggre- gations of fat-cells appear ; tf, sudoriparous glands, "With their excretory ducts e and/,' i e-ii-i i i ■ tents of the sebaceous follicles, the skm is, according to Kolliker, to be previously softened ; then, with the epidermis, the hairs, with their root-sheaths and the cell masses of the sebaceous follicles, are often rendered very finely prominent, though, even here, hardening in absolute alcohol accomplishes more than all these old methods. The blood-vessels of the skin are to be examined on fine vertical and horizontal sections of transparently injected or- gans. In the papillse, at the point of the finger, an extensive natural injection is frequently met with, so that the transverse section of the dried skin, by the addition of a 30 to 40 per cent, solution of potash, affords very handsome views of the vascular loops. The puncturing method serves for injecting the lymphatic passages, which are likewise only enclosed by connective tissue (Teichmann). It is advisable to loosen the epidermis in water to which acetic acid and alcohol have been added, as directed by J. Neumann. In a very excellent work, that author used carmine with glycerine or carbonate of lead, rubbed up with OEGAWS OF SENSE. 557 the fluid mentioned, for injecting the lymphatics. It is well- as we can recommend from our own experience— to stretch the piece of skin to be injected over the index ringer of the left hand in making the punctures. The latter should penetrate sometimes less, sometimes more deeply in various places. We find a deeper, wider net-work, and a more superficial one with narrower passages. From the latter pass up to the papillae of the skin partly cul-de-sac axis canals, partly loops. The subcutaneous connective tissue, the lobules of the fat cells, the follicles of the hairs and the sudoriparous glands, also have their lymphatics. Finally, Neumann has the merit of having successfully attacked the lymphatics of the pathologically metamorphosed skin, following certain preliminary statements of Teichmann and Biesiadecky. For the study of the muscular tissue of the skin, the tinge- ing with carmine and subsequent treatment with acetic acid, the already frequently mentioned double tingeing of Schwarz, and the application of the chloride of palladium (I. Neumann) and also hsematoxyline, are to be recommended. Concerning the cutaneous nerves, we would first refer to what was mentioned at page 375 about the MerkePs tactile cells and also the tactile bodies. For the study of these elements in other localities, the same methods, the treatment of thin sections from the fresh or dried skin, with acetic acid and alkalies, and furthermore with Muller's fluid or the so much praised chloride of gold, and likewise osmic acid, are to be taken into consideration. The Pacinian corpuscles, which, together with terminal knobs, also occur on the external genitals of both sexes (Krause, Schweigger-Seidel), are to be examined by the meth- ods customary for these structures. Peculiar organs nearly related to the terminal knobs were met with by Krause on the sensible nerves of the penis and clitoris. These, the "genital nerve-corpuscles," are embedded in the corium and mucous membrane proper (not in the papil- lae), and differ from the ordinary terminal knobs by their more considerable dimensions and more irregular forms. For their examination, the discoverer recommends : firstly, quite fresh, when possible still warm, preparations without any media ; then injections, and an immersion in 3 per cent, acetic acid. 558 SECTION TWENTY-SECOND. More recently in other portions of the integument, fine, non-medullated nerve-fibres are said to have been seen to ter- minate with button-shaped swellings between the cells of the Malpighian rete mucosum (Langerhans). The treatment of the freshest possible thin sections with chloride of gold has been recommended for their recognition. The embryos of man and the mammalial animals, hardened in chromic acid, are used for the foetal skin. On small foetuses the latter generally separates very readily, and is to be exam- ined on surface sections with glycerine, whereby a conservative tingeing with hsematoxyline or carmine renders good service. With older embryos fine vertical sections are to be made with a razor. It is relatively easy, on such, to see the first rudi- ments of the sudoriparous glands and hairs, and also on the latter the sebaceous follicles, and to follow their further de- velopment. The pathological changes of a part so complicated in its structure as the human integument are of a very manifold nature. A few, such as are connected with the epidermis, have been already mentioned (pp. 269, 270). Inflammatory conditions show sometimes an implication of the whole skin, sometimes of only the superficial portions. Extensive emigrations of colorless blood-corpuscles occur there (Volkmann and Steud- ener). Desquamations of entire layers of epidermis (scarla- tina), local separations of the horny layer from the Malpi- ghian stratum, by collections of a fluid containing pus-cells, occur as a result of this vascular congestion. The numerous diseases of the skin affect sometimes the epithelial, sometimes the connective-tissue portion, sometimes both at once. Elephantiasis shows a more extended and enormous hyper- trophy of the corium and of the subcutaneous cellular tissue. Local proliferations of the tactile papillae of the skin are pre- sented by the warts and condylomata, whereby dilatations and enlargements of the capillaries are met with. The vascular nsevi and telangiectasia in general form more extended super- ficial occurrences of the latter kind. Follicular tumors and cysts, of frequent occurrence in the skin, proceed undoubtedly in many cases from dilatations and degenerations of the hair- sacs and their sebaceous follicles. These frequently present the so-called atheromata ; that is the follicle, lined with a pave- ORGANS OF SENSE. 559 ment epithelium, contains a grit-like pulpaceous mass, in which the microscope enables us to recognize exfoliated epithe- lial cells, fat-molecules, and crystals of cholesterine. The maggot-pimples or comedones present slighter meta- morphoses of the sebaceous follicles and hair-sacs, produced by accumulated secretions. If this accumulation is confined to the sebaceous follicles (to be explained by impeded evacuation), hordeolum or milium is produced. The degeneration of the hair-sacs is accompanied by that of the respective sebaceous follicles. The number of vegetable and animal parasites found in and on the human skin is a considerable one. Many of these con- stitute quite indifferent phenomena ; others cause appreciable effects, and become causes of diseases, the appreciation of which dates from the discovery of these structures by means of the microscope, and which appear in part on and in the hairs, in part on the horny layer of the epidermis, partly also in the nails (though the nail fungi require further investigation). Among the epiphytes or vegetable parasites we will next mention the Tricophyton tonsurans of Malmsten. It leads to the destruction of the hairs of the head in the form of rounded patches (herpes tonsurans). One rinds only spores of about 0.0022", or also rows of the same. These first develop in the root of the hair, then in the shaft, which it splits extensively, so that in consequence the hair breaks off at about a line be- yond its exit ; the root and shaft of the hair are likewise de- stroyed. The systematic position of the Tricophyton tonsurans is still a matter of controversy. Another vegetable parasite of the hairs of the human head, the Microsporon Audouini of Gruby, which causes the porrigo decalvans, behaves in a similar manner. It consists of rounded and oval spores (of 0.0004-0.0022'") and a net-work of curved' undulating filaments. These develop externally on the shaft of the hair, and occur in such numbers around the portion of hair which projects from the skin, that it becomes destroyed, and remnants $ to 1 line long stand out from the skin. The case is said to have been one of herpes tonsurans, however. Another fungus of the same name, the Microsporon menta- grophytes of Robin, grows by preference in the follicles of the beard hairs, and causes an inflammation and the formation of pus around the hair-follicle— the so-called mentagra. The 560 SECTION TWENTY-SECOND. microscope shows us between the hair-sac and shaft larger spores and filaments than in the previous variety. The last two varieties are uninvestigated botanically. Finally, in the Microsporon furfur of Robin groups of double-contoured spores of 0.002'" longitudinally arranged cells and branched filaments of 0.0004-0.0002'" in diameter may be recognized. The basis for the development of this epiphyte is, however, different ; namely, the horny layer of the epidermis, where it causes yellowish spots and a f urf uraceous exfoliation (pityriasis versi- color). The favus-fungus, Achorion Schoenleinii of Remak, occurs principally on the hairy portions of the skin of the head, and is the cause of the scall, porrigo favosa — an eruption occurring mostly during childhood. It becomes developed first in the hair-sac, where it surrounds the hair and grows into it ; then, and indeed principally, on the epidermis. There may be dis- tinguished, according to Robin, the 0.0013"' broad inarticulate filaments of the mycelium, the somewhat broader unbranched, but articulated receptacula, in the interior of which series of round and oval spores, 0.0013-0.0026'" in size, develop. The natxire of this parasite is still doubtful ; possibly it is a mould-fungus. The favus-scab shows under the microscope a fine granular mass, which surrounds the fungus-substance proper. Externally this consists principally of the mycelium, more internally of the receptacula, and quite internally of the spores. The examination of all these epiphytes requires in general strong, 4-600-fold, magnifying powers. For the study of the hair fungi, the stumps are to be pulled out with forceps and rendered transparent by means of pure glycerine or oil of turpentine. With the fungi growing on the epidermoidal • scales, the addition of alkalies, the dilute solutions of potash and soda are to be employed. Among the animal parasites, epizoa, of the human skin, two may here be mentioned, both mites of lower organization : the hair-sac mite, Demodex folliculorum, Owen ; and the itch- mite, Sarcoptes hominis. Both live in the skin and produce quite different effects. While the first animal constitutes a quite indifferent parasite, the Sarcoptes scabii causes the fam- iliar complication of symptoms known under the name of the itch (scabies). ORGANS OF SENSE. 561 The Demodex folliculorum (fig. 359) shows a sometimes more, sometimes less elongated body without bristles or hairs. On the fore part of the body in the young creature there are three, on the mature animal four pairs of stump- like legs. The length of this small parasite is from $-i'". It lives generally in scanty numbers in the excretory ducts of the sebaceous follicles and hair- sacs, that is, the space between the hair-shaft and the root-sheath, and deposits its eggs in its dwell- ing-place. It occurs in the sebaceous follicles of the face, and with especial frequency in those of the nose. If the respective glands of the latter locality are strongly developed, the smegma may be squeezed from the opening by pressure, the (JSt^BwMdS mass spread out in water, and the mites examined. £olllculorum - With dead bodies vertical sections of the skin are to be pre- pared. Not to be confounded with the hair-sac mite is the larger itch-mite. This, which is represented very much enlarged in our fig. 360, has a rather broad, oblong body, from -J— i'" in length, covered with hairs and bristles. The first two pairs of legs are placed very far in front ; they are short, and with a stalked sucker. After a considerable interval follow the last two pairs of stump-like legs, which terminate in long bristles. The ovum, which is not unfrequently found in the body of the female animal, is (as also in the Demodex) of considerable size, and the young animal is likewise six-footed. The itch-mite most frequently infests the human skin be- tween the fingers and on their inner surfaces ; they may, how- ever, occur on all parts of the body. It penetrates beneath the epidermis, and forms beneath the same a serpentine passage, which appears brown from the fgeces of the animal. The animal is met with as a small white point at one end of this passage. To obtain the mite for microscopic examination (which does not require a strong magnifying power), the passage is to be slit up with a cataract-needle, and the white point lifted out on the point of the needle. For a more accurate study, the portion of skin which contains the acarus is to be made into a fold, and this epidermis and upper portion of cutis removed with a curved scissors. Spread out on the microscopic slide, 36 5G2 SECTION TWENTY-SECOND. the preparation is to be allowed to dry gradually, and then rendered transparent by means of oil of turpentine or Canada balsam. A longer immersion of the moist piece of skin in Fig. 3b'0. The itch-mite, Sarcoptes hominis, from a photograph. concentrated glycerine also affords the necessary degree of transparency. 2. The organ of taste has already been discussed in describ- ing the organs of digestion (p. 424) ; so that we may refer to the same, and here treat only of the manner of termination of the nerves of sense. Investigations which were earlier instituted on the human and mammalial tongues, on their papillae fungiformes and cir- cumvallatse, in regard to the distribution of the nerves, yielded an unsatisfactory result, and showed only the nerve-trunks with divisions and plexiform communications, terminating finally in pale, non-medullated fibres. Terminal knobs were described here years ago by Krause. In the circumvallated OEGANS OF SENSE. 563 Fig. 361. From the lateral gustatory organ of the rabbit. The gustatory ledges in vertical section, after Engelmann. papillse of man and the mammalia, Loven and Schwalbe recent- ly discovered peculiar terminal apparatuses, denoted by the name of the "gustatory buds." They occur especially in the lateral walls of these papil- lse, but not unfrequently also at the inner surfaces of the surrounding ledges of mucous membrane. Our fig. 361, a transverse section through the lateral gustatory organ at the root of the tongue of the rabbit, discov- ered by Engelmann and Wyss, may afford us a primary repre- sentation of this terminal apparatus of the gustatory nerves embedded in the epithelium. We may obtain a more accurate appreciation from fig. 362. The parietes of the gustatory bud (1) consist of flattened, lancet-sha]3ed cells (2 a), which stand perpendicularly by the side of each other, comparable to the staves of a barrel or the sepal leaves of a flower- bud. These are the "cover-cells." The pointed portion of our organ perforates the epithelial covering. Small roundish spaces occur here. They are formed in part by several epidermis cells, in part only by twos, or finally even by a single one. In the interior of the organ appears a second cell-formation, the "gusta- tory cell" (2 b). A spindle-shaped body, as we see, extends above into a rod, and is prolonged below to a thin branched filament. It penetrates in- to the tissue of the mucous membrane. At the summit of the rod, finally, a short fine cilium shows itself. A plexus of medullated and non- medullated nerve-fibres has been met with beneath the gusta- tory bud. The communication of these with the lower fila- mentous termination of the gustatory cells still remains to be proved. Fig. 362. 1. Gustatory bud of the rabbit. 2. a, cover-cells ; 2 b, rod-cells; 2 c, a rod-cell with a fine terminal fila- ment. 564 SECTION TWENTY-SECOND. The circumstance is interesting that an analogous gustatory- organ also occurs in man, according to Krause and Ajtai. It is a structure with folds, resting on its lateral border, with gustatory buds, the papillse 1'oliacea. It had already been seen in old times. Even earlier they succeeded in recognizing, with some prob- ability, the termination and the terminal structures in the frog's tongue (Shultze, Key). Fungiform papillse stand separated over the tongue of the frog. The lateral portions of these projections and the edges of the surfaces are covered by ordinary cylindrical epithelium. The plateau of the papillse shows, on the contrary, surrounded by ciliated cylinders, another covering of non-ciliated cells which, on suitable chromic acid preparations, after brushing off the ordinary epithelium, may sometimes be brought to view sitting like a crown on the gustatory papillse. Between these non-ciliated cells lie other structures, spindle-shaped cell-bodies, which pass upward into a fine rod, terminating at the surface of the epithelial crown. Downwards, on the contrary, it runs out into a very fine filament, which, with certain reagents, appears varicose, and which must be regarded as the terminal branch of an axis cylinder which has been split up in a tuft- like manner. The nerve-fibres, therefore, split up into fine fibrillse, pass over into these rod-bearing gustatory cells. These statements of Schultze and Key have, however, been more re- cently modified by Engelmann. He denies this connection of the nerve-fibres with the "gustatory cells," and describes a third (hitherto confounded with the gustatory cells) structure,, the ' ' forked cell, ' ' with a small ellipsoid body, which is pro- longed above and below into forked processes. The central processes of the forked cells, with great probability, pass over, under further division, into the axis-cylinders of the nerve- fibres. Possibly, however, both varieties of cells are of a nervous nature. Engelmann has recently collected the methods of investiga- tion. For the primary examination, the dried mammalial tongue (appropriately that of the rabbit) may be employed. The sec- tions are to be softened in dilute acetic acid and glycerine. The organ may also be hardened for a day in osmic acid (0.5- 1.5 per cent.). The freezing method also affords good results. ORGANS OF SENSE. 565 For the study of the finer structure, the maceration in iodine-serum and the immersion for several days in chromic acid (1-2 per cent.) to which an equal volume of glycerine may be added, are to be recommended. Such preparations must then be subjected to a very careful picking under the simple microscope. According to Engelmann's experience, extremely fine-pointed glass rods are superior to the finest steel needles. Wyss gives the preference among all methods to an immersion for about three weeks in Miiller's fluid. Dried tongues, or those which have been frozen in a suit- able manner, serve for following the nerves. Sections obtained by the freezing method may be subsequently treated with chloride of gold (0.1-0.5 per cent.) or osmic acid (0.25-2 per cent.). The nerve expansions under the gustatory nerve be- came distinct for Schwalbe after a maceration for several days in chromic acid (0.02 per cent.) or bichromate of potash (0.5-1 per cent.). Wyss made use of the gold method. 3. Further advanced, especially by the admirable investiga- tion of M. Schultze, is, on the contrary, our knowledge of the organ of smell, that is, of the manner of termination of the olfactory nerve. Before we consider the remarkable structural conditions of this locality, however, let us mention the other portions of the organ of sense. No portion of either of the chief cavities, except the upper- most parts, participates immediately in the perception of smell, and does not contain any fibres of the specific nerves, but only those from the trigeminus, the terminations of which are at present still unknown. Disregarding the entrance to the nose, a ciliated epithelium is found as a covering to the proper nasal fossse and the ac- cessory sinuses. The mucous membrane, thinner in the ac- cessory sinuses, is, in its submucous connective tissue, firmly united with the bones, so that it constitutes at the same time a periosteum. In the proper nasal fossae it becomes thicker, and very rich in blood-vessels and racemose mucous glands. The particular manner in which these parts, as well as the cartilage and bones of the parietal system, are to be investigat- ed, does not require further discussion. In catarrhal conditions of the nasal mucous membrane we see at first an extensive exfoliation of the ciliated cells, which are met with in the mucus coming under examination partly 566 SECTION TWENTY-SECOND. still ciliated (and even in motion), partly without cilise. To- gether with the regularly shaped cylindrical cells, others of a more irregular and more rounded form are met with. Large cellular structures, which have arisen from the metamorphosis of the normal epithelial formation, contain, at this commencing period of the nasal catarrh, in addition to their nucleus, granu- lated lymphoid cells (mucous or pus-corpuscles) which have penetrated from without. Nearly all these elements soon dis- appear, with the exception of the last-mentioned structures, which are met with in enormous quantities in the thick yellow- ish secretion of the later periods. Phenomena which we have previously alluded to under similar irritated conditions of the respiratory organs (pp. 491-2) and of the urinary bladder (p. 523) also repeat vmgJ themselves here. ^-""■■JrilllilJIIiil iliJIllHtaEbh- As was said, the greater portion of the olfactory re- gion does not par- ticipate immedi- ately in the per- ception of smell, as the termination of the specific nerve of sense is met with only in a limited portion. Such places, called re- Fig. 363. The regio olfactoria of the fox in vertical section, cylindrical epithelium of the same. <7, Stratum of the nuclei ; olfactory cells; c, of the pigment. A, The adjacent ordinary ciliated /-£_, Oj^m np „ 11T \ n epithelium, e, The boundary between them. C, Ordinary racemose \Ug. ODOJ, OOCtll III mucous glands. D, Bowman's glands, with the duct d. E, Branch of the olfactory nerve. /, Ascending branch with further divisions. "ft,?! 'the giones olfactorise all vertebrate ani- mals, but present numerous differences. While the walls of the remaining por- tion of the olfactory cavity are covered with ordinary ciliated cells (A), there appears, as a covering for the regio olfactoria, a likewise unstratified, but non-ciliated cylindrical epithelium of a peculiar kind (B), mingled with cells terminating in rod-like processes, similar to those we have just become acquainted with in the frog' s tongue. The signification of nervous terminal cells cannot be denied to these structures, although the continual transition of the lower varicose terminal fibre into the fibrillse ORGANS OP SENSE. 567 of the olfactory nerve, cannot yet be demonstrated with cer- tainty (either by Schultze or others, as for instance C. K. Hoff- mann). The extraordinary delicacy and decomposability of the tissue-elements under consideration (which can only be managed by macerating and preserving fluid of a definite composition), render it appreciable that during a long period the microscopists either did not re- cognize the complicated structure at all, or interpreted it erroneously. In the mammalia and in man the regio olfactoria distinguishes itself from the remaining nasal mucous membrane by a peculiar color, by a yellow or yellow-brown tinge. This proceeds from fine pigment mole- cules, which are embedded partly in the bodies of the non-ciliated cylin- drical epithelial cells, j3artly in the cells of an especial gland-formation occurring here. Yertical sections of the part which has been hardened in strong chromic acid serve for the pri- mary survey. These nucleated cylin- drical cells (fig. 364, 1 a, 2 a) may be recognized from suitable side views. They send filamentous processes in a downward direction, which pass in- to communication with each other by means of branches, and, having ar- rived at the margin of the mucous membrane, they undergo a further more profuse division, so that they, at least in places, pass overin- to a reticulum which is very delicate and difficult to understand, and which often spreads into a kind of homogeneous lamella (similar to the membrana limitans of the retina). Between these cylindrical cells are noticed in considerable numbers the so- called olfactory cells (fig. 364, 1 5, and 2 6), structures which are analogous to the gustatory cells. At very different eleva- tions between the epithelial cells lies a spindle-shaped nucleated cell-body (1, 2, 5), which extends upwards into a fine rod (c), and downwards into an extremely fine varicose filament (d). Fig. 364. 1. Cells of the regio olfactoria of the frog, a, An epithelial cell, termi- nating below in a ramified process ; &, ol- factory cells with the descending filament, d, the peripheral rod c, and the long vi- bratile ciliie e. 2. Cells from the same re- gion of man. The references the same, only short projections, e, occur (as arte- facts) on the rods. 3. Fibres of the ol- factory nerve from the dog ; at a, divid- ing into fine fibrillar 568 SECTION TWENTY-SECOND. The end of the rod which has reached the surface appears to terminate quite naked in all mammalial animals ; small and quite short styliform projections (2 e), which may be noticed on it, are the contents which have swollen out from the effects of reagents. This appendix is also absent in fishes which smell in water. In birds and amphibia, which smell in the air, on the contrary, quite large in part, extremely long cilia}, sometimes slightly, sometimes not at all movable, occasionally single, oc- casionally in numbers, appear on the free extremity of the rod, so that the surface of the regio olfactoria is surmounted by a regular hair-forest. It is thus shown in our fig. 364, 1 e, from the frog. However, we may not conceal the fact that the latest observer, Exner, denies this sharp demarcation between the two varieties of cells completely. Seen from the surface, one may recognize how the pig- mented cylindrical cells are surrounded in a circular manner by these rods ; while by the side view the rods are to be per- ceived between the cylinders, as well as stratified in a deeper position, the spindle-shaped cell-bodies of the structures with which we are at present occupied. Very fresh cadavers are necessary to obtain the same struc- tures, cylinder- and olfactory-cells, in man. Particularly wor- thy of recommendation for this purpose are the bodies of new- born children. In the adult, where the numerous nasal ca- tarrhs have preceded, the sharp difference in color between the regio olfactoria and the remaining portion of the nasal mucous membrane is, for the most part, wanting, and the textural pe- culiarities are likewise, as a rule, not so accurately demarcated as in the mammalial animal. Otherwise, entire conformity prevails. Peculiar glands (fig. 363, D), intermediate in form between simple cylinders and racemose glands, and called "Bowman's glands" by Kdlliker, in honor of their discoverer, are situated in the middle portion of the regio olfactoria, and permeate this remarkable cell-stratum with their narrowed excretory ducts. Their bodies, lying in the connective tissue, have no membrana propria, and consist of those yellow or yellow-brown pigmented gland-cells of which mention has just been made. The adja- cent mucous membrane, on the contrary, shows ordinary race- mose mucous glands (C). Although an ordinary ciliated epithelium is found in places in the human regio olfactoria, yet ORGANS OP SENSE. these true racemose gland-formations follow immediately. Of interest is the circumstance that the Bowman's glands occur in all the higher vertebrate animals, but are absent in fishes which smell in the water. The olfactory nerve (fig. 363, E) presents only non-medul- lated elements in its branches. These appear at first as pale nucleated fibres, quite similar to those which we meet with in many sympathetic nerves, as, for instance, in those of the spleen. By suitable treatment, however, one succeeds in separating the olfac- tory nerve-fibre into extremely fine fibrillse en- closed in homogeneous sheaths ; it is therefore a primitive bundle. The finer branches of the olfactory nerve (fig. 363, f, g) ascend between the glands of the regio olfactoria, and thus arrive at the margin of the epithelium. Here they divide into the finest filaments or primitive fibrillse. These, quite similar to the processes of the olfactory cells, and appearing varicose under the same conditions as those, permeate the fine latticed reticulum formed by the spreading of the pro- cesses of the cylinder-cells, to finally, as we must admit and have already remarked, be- come united with the processes of the olfactory cells (fig. 365). Such a union is, however, totally denied by Exner. According to him, the branches of the olfac- tory nerves terminate towards the surface of the connective tissue of the mucous membrane in a nucleated net-work. The epithelial and olfactory cells shoot outwards from this net- work. This net-work with both varieties of cells constitute, therefore, the terminal appa- ratus of the olfactory nerve. In his excellent monograph, Schultze has given us a long series of directions for the demonstration and investigation of these extremely subtile textural relations, and thereby made an extremely important contribution to microscopic technology. To obtain a primary view of the cells of the regio olfactoria l—f Fig. 3fi5. Probable ter- mination of the olfactory nerve in the pike (after Schultze). «, Olfactory cells ; b, rods : c, lower varicose filament, e, ax- is-fibrillffi in the sheath /; d, ppreading out of these; at wanting connection with the same nbrillze, c. 570 SECTION TWENTY-SECOND. from the body of a mammalial animal just killed, thin sections obtained with the scissors may be placed under the microscope, with the addition of the most indifferent possible fluid media. In these the olfactory cell-rods will be discovered between the non-ciliated epithelial cylinders as hyaline rods. However, even with the employment of vitreous fluid, one will soon see hyaline drops, which proceed from the decomposing olfactory cell-rods, coming out over the margin of the epithelial surface, a decomposition which takes place with even greater rapidity from the addition of water. Schultze found the addition of a not too watery glycerine useful. Fine vertical sections of or- gans, hardened in stronger chromic acid, or dried and softened in acidulated water, also fulfil this purpose. To isolate the epithelial structures (and this separation is more difficult to accomplish in warm-blooded vertebrates than in cold-blooded ones), the employment of conservative and macerating fluids is necessary. This effect is rapidly and thoroughly obtained by the use of the 30-40 per cent, solution of potash, or one of soda of 20-25 per cent. If quite fresh pieces of the ethmoid bone, with the adherent mucous mem- brane, be immersed in this and, after the lapse of a half or a whole hour, the epithelium be scraped off, the separation may be accomplished on the microscopic slide. With weaker solutions one must wait two or three hours. The well-pre- served cylinder-cells and rods, a portion of them still in con- nection with the splindle-shaped olfactory cells, may then be readily recognized, and in amphibia and birds, even the olfac- tory ciliae ; on the contrary, there is usually nothing preserved of the descending line filamentous processes of the latter. To obtain a surface view, the epithelial covering, macerated in a solution of potash or treated with glycerine, is to be used. Better, though much more slowly, commencing (from two to three days) effects may be obtained by maceration in a very dilute solution of chromic acid (whereby the immersed portion should not be too small, nor the quantity of fluid too great) 0.05-0.03 per cent, solutions are to be recommended for the quite fresh mammalial animal. For the human olfactory or- gan, when it can be obtained, about twelve hours after death, Schultze employed the action of a chromic acid solution of 0.05 per cent, for from one to three days. Cold-blooded verte- brate animals require somewhat stronger solutions than the OEGANS OF SENSE. 571 mammalia ; birds somewhat weaker ones (to 0.01 per cent.). (The division of the bundles of the olfactory nerves into primi- tive fibrillse may also be accomplished in this way.) The extraordinary advantage which such solutions present for the study of the regio olfactoria, consists in rendering visi- ble varicose swellings on the very fine lower filamentous pro- cesses of the olfactory cells, as well as the finest terminal fibril- lse of the nerves of sense (a superiority which also belongs to the reagent for analogous textural conditions of the remaining higher nerves of sense). As has already been frequently men- tioned, the bichromate of potash may be employed instead of chromic acid ; its action takes place slowly. Schultze em- ployed solutions of 0.1-0.5 per cent., and obtained the desired preparations after 1-6 days. The Midler's fluid, which is, as I found, very suitable for the examination of the cochlea when diluted with water, I also recommended years ago in several degrees of dilution. Ac- cording to Hoffmann's experience, diluted with an equal part of water, and sometimes acting only one or two days (frog), sometimes for nearly two weeks (mammalia), it in fact consti- tutes the best of all macerating media. Schultze has discovered and recommended still other simi- lar acting fluids. The concentrated watery solution of oxalic acid preserves (p. 129) the olfactory cells, their rods and varicose filaments (but not the cylinder-cells) quite exquisitely ; and one has the great advantage of not being too dependent upon the time, so that the examination may be made even after a few hours, and also after days. The connective tissue swells in it and becomes more transparent, while albuminous tissues retain their sharp contours and become somewhat harder. Sulphuric acid in a condition of high dilution, in medium of 0.6 per cent. (0.2-1 per cent, and more), also preserves the olfactory cells very well, and still more diluted it renders the filaments varicose. The connective tissue, however, does not swell in it as in the previous acid, but is rendered much more beautiful and sharp. Here also too small pieces should not be taken, and the preparation is to be tried even after a few hours. The immersed pieces keep for days and weeks if they are not ruined by the formation of mould. This acid is less praised by Hoffmann. .'572 SECTION TWENTY-SECOND. Exner praises as the best reagent the immersion for a quar- ter or half hour in a 0.5-2 per cent, osmic acid. The object has then to macerate in water for hours, days, and even weeks. A few drops of acetic acid may be added to the water. Epi- thelium is to be exposed to this treatment for a longer period than nervous elements. Finally, Babuchin has here employed impregnation with gold. To obtain degrees of hardening which are suitable for the preparation of thin sections, and which should present the arrangement of the mucous membrane, the glands of Bowman and the course of the nerves, one may employ, together with the Miiller' s fluid, higher degrees of concentration of chromic acid and chromate of potash, and subsequently examine with glycerine, acetic acid, etc. Moleschott' s so-called strong acetic- acid mixture (p. 139) has also been especially recommended by Balogh. Strongly hardened objects, as well as the preparations of the remaining portions of the nasal mucous mem- brane, one should attempt to mount in glyce- rine. The olfactory cells and the ovlindrical epi- thelium lying between them may be still more suitably preserved in Miiller' s fluid diluted with an equal quantity of water. 4. The organ of vision, from its greater com- plication, requires a more detailed discussion. The eyelids, with the cutis accompanying them, their connective-tissue so-called tarsal car- tilage, and the embedded Meibomian glands (fig. 7 % 366), which in their form remind one of those of ^9D Bowman in the olfactory organ, as well as the Fro. 366. a human conjunctiva of their posterior surface and of the eyeball, together with the epithelial covering which clothes it, require but brief discussion. Their tissues are to be examined in general in accordance with previous direc- tions. It is advisable, as Waldeyer states, to take the freshest possible eyelid, stretch it moderately on a cork plate, place it in absolute alcohol, or first in Midler's fluid, and then, after washing, harden it in the former fluid. Hardening in a 0.5 per cent, solution of chloride of gold is also to be recommend- ORGANS OE SENSE. 573 ed. Hfematoxyline or carmine is to be used for tingeing sec- tions. It may be well to subject the latter tinged preparations to the energetic action of acetic acid, as it renders the embedded glands, hair follicles, etc., more distinct. To isolate the epithelium, use a 10 per cent, solution of common salt, and also Czerny's mixture of Miiller's fluid and saliva (pp. 136-7). The lachrymal glands are to be examined in the same man- ner as other racemose glands (pp. 412, 417). The conjunctiva of the eye (frequently a lymphoid infil- trated connective tissue) contains throughout the entire line of transition numerous racemose mucous glands, while in the conjunctiva of the eyeball (the portion surrounding the cornea) of the ruminantia, coil- shaped glands, quite similar to those of the skin, have been discovered (Manz). Maceration in dilute acetic acid or pyroligneous acid will make them readily visible. For the recog- nition of the peculiar nerve termina- tions in the Krause's knobs (fig. 367), the fresh, still warm eye of one of our slaughter-house animals may be used. The conjunctiva is to be removed with rapidity, but with the utmost caution, and searched with low powers and without the addition of any medium. The necessary details concerning the reagents have already been mentioned at pp. 373-4. According to Ciaccio and Longworth, the gold method may also be used with advantage. We have also previously mentioned (p. 370 and fig. 208) the remarkable termination of very fine nerve fibrillse in the epi- thelium of the corneal conjunctiva, as well as the methods usually employed at present. The blood-vessels of the conjunctiva present nothing re- markable. The lymphatics of the human conjunctiva form a highly developed net-work of passages of considerable size over the sclerotic, which also occupies the peripheral portion Fio Terminal knobs . the calf ; 2, from man. 574 SECTION TWENTY-SECOND. Flo. 368. Trachoma, gland of the ox, with injected lymphatics, in vertical section. a t submucous lym- phatic vessel ; c, its distribution to the passages of the follicle b. of the cornea for about one millimetre in breadth, and consist- ing here of finer canals with bow-like terminations (Teich- mann). Among mammalial animals I have succeeded in inject- ing such canals in the calf. Interesting phenomena of the conjunctiva are presented by the trachoma glands, as they have been called ; lymphoid folli- cles very similar to those of the intestinal canal, and quite variable in number and arrangement. The injection in the ox (fig. 368) shows that knotty lymphatics (a) of consider- able size run towards their lower surface, and, after the loss of their vascular walls, form a highly developed net- work of lymphatic canals around them, from which finer reticular canals encircle the follicle and spread themselves out in a delicate manner (c) in the lymphoid stratum, unit- ing the follicles (5). Their most superficial portions, that is, those turned towards the epithe- lial layer, run more horizontally, and send off fine terminal canals which present quite superficial csecal terminations. The whole is enclosed in connective tissue, and the entire ar- rangement is related in the most intimate manner to that of a Peyerian plaque ; only the blood-vessels of the follicles are here less abundant and less regular. Our structures are en- tirely wanting, however, in new-born animals (Blumberg, Schmid). The eyes of younger oxen or older calves, and cold-fiowing mixtures are to be used for injections, which should be made in the so-called Bruch's aggregation of the trachoma glands of the lower eyelid. The other aggregation may, however, also be very readily injected ; and furthermore, the injection of the blood-vessels by the smaller arteries also succeeds without great difficulty, while with smaller mammalial animals the entire head must be injected from the aorta with colored gelatine. The procedure is difficult in man and many other mammalial animals. The preparations are to be hardened in alcohol for examination. ORGANS OF SENSE. 575 With regard to the eyeball itself, it may be said that its examination is one of the most remunerative labors of the microsoopist ; but at the same time, however, in one of its ele- ments (the retina) combined with the greatest difficulties. One should always use the quite fresh, still warm eyes of the larger slaughtering animals, especially those of the ox, calf, and sheep, as well as indifferent fluid media, such as the vitreous and aqueous humors which are always at hand. If the eyes have been removed with a little care, the artery may be readily found lying near the optic nerve and employed for injecting (the injection of the human eye is more difficult in consequence of the smallness of the artery). Such injections, when they are to be followed by histological investigations, are always to be made with cold-flowing mixtures, the Prussian blue or carmine. The injection of an eye of one of the larger animals, after the numerous divided vessels have once been ligated, usually suc- ceeds in from two to three minutes. Even after a quarter of an hour one may commence with the dissection and examina- tion. The system of the uvea, especially, shows many things in a much more instructive manner than in the injected organ, and the unpigmented tapetum of such eyes affords a further advantage for many investigations. Where especial reference is to be made to injected preparations, inject with carmine gel- atine. The eyes of the smaller mammalial animals are to be in- jected from the aorta simultaneously with and under the same precautions as the brain (pp. 358-9). White rabbits afford excellent objects. The eyeballs of this animal, divided in halves and mounted in glass cells with Canada balsam, which have been put in circulation by Thiersch, may be recommended as true models of the modern injection technique. If it be desired to accomplish a double injection, Prussian blue is to be first thrown into the artery, and a second injection of carmine gela- tine is then to be made by the same vessel. Leber has recently instituted excellent studies of this kind, with cold-flowing masses and the use of the constant pressure. We have recently obtained, through Schwalbe, excellent investigations of the lymphatics of the eyeball. This author used in part cold-flowing, colored masses, in part gelatine solutions, as well as solutions of nitrate of silver. He recom- mends the puncturing method, with very fine canules, the points of which are ground under an angle of 40° to the long axis. 576 SECTION TWENTY-SECOND. To inject the posterior lymphatics, puncture the sclera be- tween the corneal margin and the equator of the eyeball, avoiding, however, the vicinity of the vense vorticosse. For the anterior lymphatics, puncture partly in the anterior chamber, partly in the canal of Petit. For further particulars we must refer to the original. The investigation of such fresh eyes requires in part trans- verse sections, as of the cornea and sclerotic ; but generally, however, a dissection of the membranous structures. These may be first reviewed unpicked with vitreous fluid, or the ad- dition of reagents, and hereby folds which are artificially made are for the most part very instructive, or they are to be divided with fine needles. Much may be recognized in such a manner concerning the texture of the eyeball, and even of the retina. In this way all the former (and in part adequate) knowledge of the same was obtained ; and even with the employment of other more modern methods, the criterion of the fresh condition can never be dispensed with. Certain elements of the eyeball, on the contrary, are in part so transparent, in part so delicate and soft, that hardening (and darkening) methods of treatment be- come indispensable. And it is frequently only in this way that thin sections succeed either with the free hand or with the aid of the microtome. Many structural conditions, the termi- nation of this and that structure, the relations of continuity of the one with the other, etc., can only be ascertained with ade- quate certainty from such preparations. Those two methods which we have already had to mention in connection with so many organs, the drying and the hardening by means of re- agents, are also employed here. For the former purpose the eyeball is to be divided at the equator, and the vitreous body (generally also the lens) removed. Both segments should be spread over the surface of cork, cut into semispheres. This drying method is, however, of subordinate importance, and has, therefore, of late been more and more abandoned. For hardening, use either absolute alcohol or — what is far more customary — chromic acid (0.5-0.2 per cent.) and chromate of potash. The bulb may be either divided, only cut open, or even left entirely unopened (in which case a stronger solution of the hardening medium is to be selected). The Midler's eye- fluid (p. 136) is very excellently adapted for hardening the un- opened, immersed eyeball. It is necessary, it is true, to wait ORGANS OF SENSE. 577 two or three weeks for the adequate effect ; but the eye may also be allowed to lie in it for months and even years without any harm, and with this accessory very handsome specimens of most parts of the bulb may be obtained. The mixture has therefore, with propriety, come more and more into use among ophthalmologists. If a weaker action is aimed at, it is to be diluted with water ; to ob- ; d tain stronger hardening, a little chromic acid is to be added. Injected eyes may also be hardened in this man- ner, though the color suffers somewhat. If it be desired to avoid this, employ cold- flowing baryta masses (p. 188). Let us next examine the methods for investigating the capsular system, the cor- nea and sclerotic. The structure of the cor- nea (fig. 369), with both its epithelial layers, the strati- fied of the anterior (d), and the simple cell - covering of the posterior surface (e), with the two hyaline boundary layers of the so-called lamina elastica anterior (b), and the membrane of Descemet (c) appearing under them, as well as the ordinary corneal substance (a) and their cel- lular elements, have been so frequently treated of and dis- cussed of late that it would be superfluous to enter further into the textural relations in question. The best descriptions of the cornea are those of His, Kuhne, Engelmann, Schweigger-Seidel, Rollett and Waldeyer. We have received a number of methods of examination in the course of time. 37 Fig. 309. The cornea of the new-born in vertical section (but considerably shortened), a, Corneal tis- sue ; b, anterior, c, posterior hyaline layer ; d, stratified pavement epithelium ; e, simple epithelial layer. 578 SECTION TWENTY-SECOND. For the recognition of the effete corneal corpuscles and their contents, use very weak acetic acid, or extremely dilute chro- niic-acid solutions of 0.01 per cent. Here, however, as with all the following methods, artificial (and often very considerable) alterations are not to be avoided, as the interstitial substance swells and the cells usually shrink. Drying is also useful for certain purposes. Very thin sec- tions, either only softened in weakly acidulated water, or first tinged in carmine and then washed out with diluted acetic acid, afford good review specimens. For many purposes of investigation, however, the quite fresh transparent cornea is indispensable. The structure is taken from the animal immediately after death, and a cut is made in it from the side. Humor aqueus may serve for moistening, and the moist chambers (p. 99) for its preservation. Frequent use has more recently been made of the most un- injured possible cornea of the frog (Kuhne, Recklinghausen, Engelmann). The cornea is to be examined with its posterior surface turned upwards, preferably without any covering glass and with an immersion system. At first one sees next to nothing in the hyaline transparent tissue ; at most, striations of the same and traces of the corneal nerves. After a more close examination one finds small isolat- ed, dull glistening structures of a sometimes rounded, some- times elongated, occasionally crooked form. The observer con- vinces himself that these bodies stretch out delicate processes and draw others in ; in short, constantly change their form and location. These are the already mentioned (p. 252) wandering cells of Recklinghausen. If we wait half an hour longer, the corneal corpuscles begin to stand out from the tissue in the form of extremely pale, polygonal appearing dull spots. If about another half hour be allowed to pass, our corneal corpuscles become more distinct ; the dull spots are connected with each other by radiated pro- cesses ; the reticulum of cells is visible. Nuclei are not yet to be discerned in the latter. Kuhne asserts that he has con- vinced himself of a vital contractility in these stellate cells. Engelmann saw no trace of this in his re-examination. The change of form and location of the wandering cells is, on the other hand, to be observed now as before (and with proper treatment for a long time yet). ORGANS OF SENSE. 579 We will here mention still another interesting and impor- tant observation concerning the latter cell-formation. We have already (p. 98) alluded to the reception of small granules into the interior of such amoeboid structures. If a small incision be made at the sclerotic border of the cornea of a living frog, and granules of cinnabar or carmine be rubbed into it, the cor- nea, isolated after twelve hours or more, will show a number of these cells with the colored molecules in their interior, occa- sionally considerably removed from the wound, wandering through the tissue. His, a meritorious investigator of our membrane, recom- mends first the acetic acid with iodine staining, to cause the corneal cells to appear through the transparent interstitial sub- stance. According to him, however, the immersion in purified pyro- ligneous acid, diluted with an equal volume of water, or even more, constitutes a main accessory. The cells, with more cloudy contents, then appear through the somewhat swollen, more transparent interstitial substance. The hardening prop- erty which, as is known, is also associated with the distending power of the pyroligneous acid, is also of great worth here for rendering fine transverse sections feasible. These may be ver- tical, exactly similar to those from the dried object, and then (which is not possible with the latter material) the very much more instructive horizontal sections. Entire corneas may also be preserved for years in pyroligneous acid. Another mixture, mentioned by Remak, consisting of dilute pyroligneous acid, watery alcohol, and a weak solution of sul- phate of copper, causes less swelling, but otherwise yields quite similar appearances. Chromic acid presents no advantage over pyroligneous acid. Hypermanganate of potash (Rollett) or a 10 per cent, solu- tion of common salt (Schweigger-Seidel) may be used for the demonstration of the corneal fibrillae. Other reagents, such as concentrated chromic acid, Miiller's fluid, saturated solutions of sugar, dilute alcohol of 50 per cent., and MerkePs chromic acid and chloride of platinum mix- ture (pp. 137-8), exert a shrinking effect on the interstitial sub- stance, and have been recommended for demonstrating a fibril- lary structure of the corneal tissue. Rollett praises, furthermore, exposing the cornea, mois- 580 SECTION TWENTY-SECOND. tened with humor aqueus, to the action of iodine vapor. Use a somewhat high moist chamber, after the manner represented by fig. 75, p. 99. The cornea adheres to the under surface of the covering glass, the bottom of the chamber is covered with a watery solution of iodine (metallic iodine shaken in water). Waldeyer has subsequently, however, and very properly, de- clared this method to be too positive in its action. Frequent use has also been made of the silver method in the examination of the cornea and a reticulum of star-shaped fig- ures, which appear sometimes bright out of a darker basis sub- stance, sometimes dark with bright- er surroundings, pronounced to be the net-work of corneal cells. We have re- cently received a whole series of di- rections in refer- ence to this sub- ject, for the re- sumption of the study of the process of inflammation has late- ly led a number of investigators to our organ. We present a few of these. One of our most distinguished histologists , Waldeyer, rec- ommends placing tl\e entire, completely fresh eyeball (with small animals the whole head, after removing the lids) in the silver solution. The epithelium should previously be removed from the anterior surface, however. This is best accomplished by the action of the warm vapor of water, continued till a slight cloudiness occurs, and thereupon the careful use of a brush moistened with humor aqueus (Recklinghausen). Use weak solutions of silver, from 0.5-1 per cent. The period of action may extend from a half to a whole hour, for example, with the frog (Eberth). Washing the silver preparation and then tingeing it with hsematoxyline often affords the most charming preparations. Von Thanhoffer places the whole globe, without the pre- vious removal of the epithelium, in a 1-2 and 3 per cent, solu- tion of nitrate of silver. The reagent should act in the dark Fig. 370. The human cornea impregnated with silver, with the trans- parent so-called corne;il corpuscles (cleft system) ; to the left below, four metamorphosed parenchyma cells. ORGANS OP SENSE. 581 for 5-15 minutes. The mammalia! eye is to be removed from such solutions after 5-8 minutes, and the epithelium scraped off. It is then to be returned to the silver solution for 5-10 minutes ; still treating the object in the dark. The chloride of gold and its potash and soda salts are more protective, and, therefore, present more reliable results. The cellular elements and the nerves are either alone or predomi- nantly colored, and the latter preserve every detail (Cohnheim), even should the nuclei of the corneal cells become distended (Waldeyer). The reagent is, therefore, here of the first rank. Its hardening property enables us, besides, to prepare sections perpendicular and parallel to the surface. Unfortunately, from the capriciousness of the gold method, some trials have succeeded, while others have not, and thus a number of meth- ods have been introduced. The latter, naturally praised by their inventor, are usually more or less censured by the imita- tor. We have already, in an earlier section of our little book (p. 167), mentioned the process which the inventor of the gold method, Cohnheim, has used, as well as the methods of He- nocque, Bastian, and Bottcher. The latter, intended primarily for the cells, gave us unsatisfactory distentions. Hoyer recommends the method mentioned at p. 371 for the corneal nerves. Finally, we would again call attention (also for the corneal nerves) to a method of Kleins (p. 371), which is claimed to be infallible. Corneas, impregnated with gold, likewise permit of subse- quent tingeing with hsematoxyline. A combination of the silver and gold methods has been used for the cornea. For this purpose Rollett exposes the cornea of the frog to a 0.5 per cent, solution of nitrate of silver, then to a solution of chloride of gold of the same strength, after which it is placed for a longer period in slightly acidulated water. Then, after the reduction has taken place under the action of light, the corneal cells appear granular and yellowish in the dark ma- trix. Von Thanhoffer uses, for the study of the nerves and cells of the frog, osmic acid of 1 per cent., in which the whole eye- ball is immersed for 5-10 seconds with the cornea turned 582 SECTION TWENTY-SECOND. downwards. It is then placed in a silver solution of the same strength for 5-10 minutes, protected from the light. If the cor- nea has acquired a grayish brown color, it is placed in a solu- tion of common salt or pure water, and exposed to the sun- light until after a few minutes a dark coffee-brown color ap- pears. Glycerine is used for the examination. To inject the canal-work of the corneal tissue, take larger mammalial animals, and use the puncturing method. Waldeyer recommends a turpentine solution of alcannine and the deep brown ethereal extract of anacardium nut. Concerning the two hyaline limiting layers of the cornea, it may be stated that the membrane of Descemet may be readily isolated by scraping with the firm pressure of a scalpel. An incomplete separation of the membrana elastica anterior from the deeper corneal tissue may be accomplished by maceration in muriatic acid. Dried sections mounted in Canada balsam are to be em- ployed for recognizing the double refraction of the interstitial substance. The organ of smaller embryos affords handsome prepara- tions for the cells and interstitial substance. His recommends the foetuses of the cow and hog of about 5 ctm. The blood-vessels occupy only the peripheral portion of the organ in the adult, as we learn from artificial and natural in- jections. The magnificent transparency of the so accessible cornea renders it more than any other structure appropriate for artifi- cial inflammatory irritations, and the study of the tissue- metamorphoses which take place thereby. It is therefore frequently employed for such investigations, and the facts obtained interpreted in accordance with the prevailing patho- logical views. While years ago the profound work of His appeared to lend an important support to Virchow's theory concerning the participation of the connective-tissue corpuscles in the inflammatory process, at the present time the case is entirely reversed, and the cornea has become a favorite object of study for demonstrating the correctness of the Waller- Cohnheim theory of the immigration of lymphoid cells. The doubters have also resorted to this field. To produce inflammation of the cornea, keratitis, our struc- ture may be irritated in several different ways, as by the in- ORGANS OF SENSE. 683 sertion of threads and silver wires, the application of tincture of cantharides, chloride of zinc, or, still better, a pencil of nitrate of silver (Eberth). The latter should be pointed and further polished with pumice-stone. It is well to tinge such corneas with hsematoxyline or to subject them to a subsequent im- pregnation with gold. Here also the coloring matter mentioned may finally be allowed to act for a time (Eberth). Muller's fluid and hsematoxyline are also recommended. The desired inflammation is obtained in rabbits after twenty-four hours, in summer frogs after two to three days, but only after double this time in hibernating frogs. If cinnabar, carmine, or, still better, aniline blue suspended in water has been injected with a Pravaz' syringe into one of the lymph spaces of such a frog, no serious disturbance of the health of the animal is caused. The stuffed lymphoid cells now penetrate as pus-corpuscles from the periphery into the cornea, to adhere to the place of irritation. It is only a few of these cells, however, which bear the colored granules in their bodies as a mark of their origin. A considerably larger number of these can only be obtained when this coloring matter has been injected for several consecutive days into the various lymphatic spaces. However, even in a cauterized cornea, if it is only obtained living, lymphoid cells accumulate in such quantities around the point of irritation, that the migratory cells present in it at the moment of separation do not suffice to supply the demand (Hoffmann and Recklinghausen). An origin of these cellular elements from the stellate corneal corpuscles cannot, according to this, be denied, however earnestly it may and will be op- posed. The net-work of blood-vessels which may cover the anterior surface of the cornea, as a result of inflammation, requires, after the beautiful statements made by Thiersch concerning the vascularization of wounds (p. 398), a renewed investigation. Portions which have been removed are regenerated by newly formed corneal tissue. The yellowish margin which the cornea shows in the so-called arcus senilis, consists of a deposition of fat in the corneal cells, and also in their interstitial substance ; it is therefore one of those commencing fatty degenerations, such as likewise make their appearance at a more advanced age in other parts of the body. 584 SECTION TWENTY-SECOND. Corneal preparations may be tinged, and, after extraction of their water by means of absolute alcohol, mounted in Canada balsam. A moist mounting in watery glycerine is, as a rule, employed. The tissue of the sclerotica, as is known, is continuous with that of the cornea, but consists, after the manner of the fibrous membranes, of a fibrillated intercellular substance, which is changed by boiling into ordinary gelatine, and not, like the cornea, into chondrin. The flattened bundles of these fibrillar cross each other nearly at right angles. Fine elastic elements and a reticulum of connective-tissue corpuscles stand out from the hyaline interstitial substance after the application of acetic acid. The fresh tissue teased out into fine pieces, and objects hard- ened or dried in the same manner as the cornea, serve for the examination. If the iris and choroid have been retained on them, the immediate transition of these tissues into that of the sclerotic may be finely observed ; likewise the transverse section of the canal of Schlemm, the origin of the musculus ciliaris and the prolongation of the membrane of Descemet into the so-called ligamentum iridis pectinatnm. The system of the uvea consists of the choroid and iris, membranes which contain muscular fibres and are rich in pigment and vessels. They are cov- ered on their inner surfaces by a pigmented epi- thelium (fig. 371), the so-called polyhedral pig- ment-cells of an earlier epoch. For the demon- stration of these cells (which are, however, with fig. 37i. Profile much greater propriety to be included with the human rottaS'epithe" retina), the fresh eye may be used, or one which llum ' has been divided and hardened either by means of chromic acid, chromate of potash, or Midler's fluid. Small portions of the black covering of the exposed inner surface may be removed with the scalpel or the cataract-needle. They are then to be spread out with needles or the brush, and cov- ered with a right thin covering glass. Strongly hardened eyes permit of transverse sections of the entire uvea, and hence pro- file views of the epithelial covering. Our cells send downwards, that is, towards the centre of the eyeball, either pigmented filaments or, occasionally, also, a kind of membranous tube (Schultze, Marano). These prolon- ORGANS OE SENSE. 585 Fio. 372. Stellate pipment- cells (pigmented connective- tissue corpuscles), from the mainmalial eye. gations ensheath the so-called rods of the retina, remarkable structures wliicli we shall soon have to discuss. Interesting views are presented by an Albino eye, that of a white rabbit, or the unpigmented covering on the so-called tapetum of one of our ruminantia. Viewed from the surface, a mosaic of polyhedral cells will be perceived, and, in the lat- ter locality, appearances will be at the same time obtained which show that on the peripheral portion of the tapetum cells, with a scanty deposi- tion of melanine, form the transition into ordinary pigment-cells. The choroid proper consists, as is known, of a soft connective tissue, show- ing stellate cells united in a reticular man- ner, and which is permeated by an extraor- dinary quantity of blood-vessels. These cells characterize themselves by a great dis- position to develop pigment molecules in their bodies and to thus become stellate pigment-cells (fig. 372). We distinguish several layers of the choroid. An external looser stratum of soft connective tissue, rich in pigmented cells (lamina fusca, supra-choroidea), serves for the connection with the inner surface of the sclerotic. Its structure may be readily recognized in fresh, picked preparations ; likewise its rela- tions with the neighboring tissues in sections through the sclerotic and uvea of an eye strongly hardened in chromic acid. Beneath the lamina fusca follows a middle layer of this connective-tissue substance, present- ing the larger arterial and venous ramifications. The fresh tissue, or an eye which has been in- jected with a transparent mixture, serves for the recognition of this slightly pigmented layer. Finally, as a third layer appears, a more homo- geneous unpigmented stratum, the so-called chorio-capillaris, which contains a remarkably rich, very narrow-meshed reticulum of delicate capillary vessels (fig. 373). Here also recourse may be had either to an injected organ (calf, sheep, cat), or a portion of choroid may be taken from a chromic-acid preparation and Fio. 3T3. Capillary arrangement from the chorio-capillaris of the cat. 586 SECTION TWENTY-SECOND. freed as well as possible from the external layers and, by cau- tious brushing in glycerine, from the pigmented pavement epi- thelium which covers the inner surface. A sufficient quantity of blood-corpuscles will generally be found retained in the capillary net-work. The fine hyaline, more independent boundary layer of the chorio-capillaris, towards the pavement epithelium, has been designated as the elastic layer of the choroid. For its primary recognition a fold of the fresh choroid may be used ; acids and alkalies serve as media. A longer action of a. 10 per cent, solution of common salt causes this to appear fibrillated. These lamellae undergo interesting senile metamorphoses, thickenings, spherical and druse-like concretions, frequently with deposits of lime-molecules, which may dislodge the pig- ment epithelium and compress the retina (Muller). Other hyaline membranes of the eye also increase in thickness with age. The injection preparations mentioned, deprived of their water with alcohol, may be beautifully mounted in cold Canada balsam (diluted with chloroform) ; the others are to be mounted moist. For the primary recognition of the ciliary muscle, sections from a dried eye may be used. Here the rows of fibres run- ning in a meridional direction may be perceived, and on good sections also the circularly arranged ones which Muller dis- covered. For further investigations, use the reagents custom- ary for the connective tissue and the contractile fibre-cells, the 30-40 per cent, potash solution, the chloride of palladium with a subsequent carmine tingeing, the double staining of Schwarz, etc. According to Flemming, the contractile fibre- cells may still be isolated, after hardening in chloride of pal- ladium, by means of the potash solution mentioned. A long, 12 to 24 hours' action of the latter is then necessary. The examination of the ciliary body is to be made on fine sections from an eye which has been injected with transparent gelatine fluids, and hardened in chromic acid or alcohol. The delicate rich reticulum of vessels may in this way be most accurately followed. Here, as with the iris, the eye of the white rabbit injected with carmine deserves the preference. For the primary recognition of the structure of the iris, avoid dark-eyed creatures, as the stellate pigment-cells which ORGANS OP SENSE. 587 occur in their tissue increase the difficulty of the examination very much. The eye of a new-born or of a bright-eyed child deserves to be recommended here. The methods consist, after the removal of any pigmented epithelial layer which may be present (and which may be previously macerated in acetic or oxalic acid) by means of the brush, firstly in tearing, then in the examination of whole pieces with the use of acetic acid for connective tissue, and of the dilute soda solution for the nerves. For the smooth muscular tissue use the reagents now generally employed for that tissue, and which have just been mentioned. One may thus convince one's self of the existence of a dilatator pupillpe, concerning which numerous controversies have lately arisen, and which is, nevertheless, not so very difficult to recognize. The whole or half of the iris of a small white rabbit may be used for the study of the coarser arrange- ment of the muscles when treated with acetic acid, and also with the addition of soda for following the nerves of the iris with lower magnifying powers. Such objects, tinged with hsematoxyline or carmine, in the latter case washed out in weak acetic acid, become very handsome, as do also transparent injections of the blood-vessels. There is nothing especial to be re- marked concerning the methods of pres- ervation. Concerning the refracting organs, the lens and the vitreous body, the tissue of the latter has already been mentioned in one of the preceding sections of our book (p. 275) ; the crystalline lens, on the contrary, although in reality an epithelial structure, has not yet been discussed. The fresh eye of any somewhat large mammalial animal may be employed for the examination of the lens-capsule (fig. 374, a) and of the extremely delicate pavement epithelium (&) which occurs on the posterior surface of the anterior segment of the capsule. The capsule, isolated with the lens, is to be liberated by an incision and placed in fragments under the microscope, with the addition of vitreous Fig. o74. Diagrammatic represen- tation of the human crystalline lens, a, the capsule ; c, the lens-nbres with widened ends (d), becoming inserted at the anterior layer of the epithelium (&), and also inserted posteriorly into the capsule (e) ; /, the so-called nu- clear zone. 588 SECTION TWENTY-SECOND. fluid. Weak powers, with a strongly shaded field, show the borders and folds of the hyaline membrane at once. Stronger objectives show the thoroughly homogeneous structure of the hyaline membrane, and with repeated considerable shading, the pavement-shaped epithelium may be recognized. The addition of aniline red is here very convenient, as the tingeing follows very rapidly and without any alteration of the tissue. Other tingeing methods also accomplish the object. For the capsular epithelium, one may resort to chromic acid, the bichromate of potash, nitrate of silver, and chloride of gold. On a fresh section of a lens, however, even with the use of these two accessories, one would be able to recognize the lens-fibres (fig. 375) only very incompletely. Various accessories are to be rec- ommended here, as the maceration in highly diluted sulphuric acid (4-5 drops of the acid of 1.838 sp. wt. to one ounce of water), which isolates the lens-fibres (v. Becker) ; in mu- riatic acid of 0.1-1 per cent. (Morig- gia) ; further, the preparatory hard- ening in chromic acid, bichromate of potash, or Midler's fluid (Zernoff). The object may likewise be obtained with alcohol, though not so well ; and also by peeling off thin scale- like portions from a dried lens. The organ being of itself quite transpar- ent, with many chromic-acid prepa- rations, the use of media which tend to increase the transparency, such as glycerine, is to be avoided. Such objects may occasionally be very suit- Others, which are more opaque, can be again rendered transparent by means of glycerine or acetic acid. An immersion, lasting for 15 minutes, in a nitrate of silver solution of 0.125-0.1 per cent, has also been praised (Robinsky), likewise dilute solutions of osmic acid (Arnold). The lens-tubes and the nuclei of the equatorial zone readily Fig. 375. Lens-fibres of the human em- bryo of eight months, r/. Fibres with a nucleus ; 6, one which still presents the cellular character ; c, the flattened form of the side view ; d, fibres with two and three nuclei. ably tinged with aniline. ORGANS OP SENSE. 589 Pig. 376. Transverse section of the lens-fi- bres from the dried organ. appear (fig. 374,/). To recognize the relations of origin of these fibres to the epithelium of the capsule, one may use a strongly hardened lens which is within its capsule, and the equatorial as well as meridional sections from that region. Equatorial sections may be obtained from the adequately hardened crystalline lens, and may thus permit of the recogni- tion of the delicate mosaic of the lens-tubes cut at right angles. A lens which has become considerably dried in the air, if em- ployed at the proper moment, has not unfre- quently acquired such a degree of consistence as to permit of convenient cutting without splintering. From it very handsome trans- verse sections may be obtained (tig. 376). A similar appearance may be obtained from ground sections of a strongly hardened lens. The previous saturation with a mixture of gum mucilage and a little glycerine is also to be tried in drying. Opacities of the lens-capsule, in part, with depositions of elementary granules, likewise embedments of fat-molecules in the epithelial cells and lens-fibres, of granules between the latter, de- posits of lime, etc., are not unfre- quent occurrences. The methods of examination are the same. Human and mammalial embryos, hardened in absolute alcohol or chro- mic acid, serve for ascertaining the primary origin and the foetal structu- ral conditions of the lens (fig. 377) and the vitreous body. In embryos of the sheep of 6-7'", everything is still cel- lular ; in human foetuses of about 8-9 weeks, the lens also seems to be consti- tuted of only delicate spindle-shaped cells (Kolliker). The condition of a pig's foetus of two inches is shown in our figure. Foetuses of this animal of 3£" have already a fibrous nucleus (Schwann). Preservation is to be attempted with strongly watered gly- cerine. The membrana hyaloidea is readily recognized in the hard- ened and also in the fresh organ. Fig. 377. a-c. Lens-cells of & two- inch fcetus of the pig. a, Original cells ; i, oval elongated ; c, grown longer in the transition into lens-tubes ; rf, epitheli- um of the lens, from an eight months' human embryo ; e, cells of the so-called humor Morgagnii. 590 SECTION TWENTY-SECOND. In such conditions, after brushing off the epithelium, the fibres of the zonula Zinuii may be perceived with some difficul- ty, but they appear far more beautifully and sharper in the suitably hardened eye. If we now proceed to the nervous portion of the eyeball, the retina, there lies before us in the so difficult to compre- hend, extremely complicated structure of the most delicate and changeable membrane, one of the most troublesome, but likewise, also most attractive objects of microscopic investiga- tion. An infinite amount of work has already been done in older and more recent times in the investigation of the so wonderful retina ; and, though the knowledge concerning this membrane has made very great progress by the aid of the mod- ern accessories, there remains to the present hour unsolved many textural questions of physiological importance. To obtain the primary review preparations recourse will nowadays be generally had to an artificially hardened eye. An opened eyeball may be immersed in chromic acid of 0.5-0.2 per cent, (if unopened the concentration may be increased), or the corresponding quantity of the bichromate of potash. At present we can recommend nothing more highly for the un- opened bulb than Muller' s fluid. It preserves the cones and rods very beautifully, which, with the other solutions, does not succeed or only very incompletely ; the examination may be made after 2-3 weeks (but also much later). Alcohol, which was formerly regarded as inappropriate, has more recently been highly recommended (Henle, Ritter) ; likewise, for the con- nective-tissue part at least, the mixture (mentioned at p. 137-8) of chloride of platinum and chromic acid (Merkel). Thin vertical sections, from the fundus of the bulb may also be readily made with a sharp knife with such retinas. Such a vertical section, examined in the hardening fluid with the addition of a little glycerine (according to circumstances it may very suitably be previously tinged with glycerine-carmine), and cautiously covered with a very thin covering glass, shows at once the numerous layers of the retina which were conquered for science with such difficulty, and of which the adjacent sketch (fig. 378) may recall the necessary conception to mind. The various localities of the retina, if treated in the same man- ner, will present their primary structural peculiarities. Assisted by the advanced knowledge of the connective sub- OEG-ANS OF SENSE. 591 stances, one may at present recognize in any retina a consider- ably developed connective-tissue framework substance, the perception of which is, however, considerably impeded by the extraordinary fineness of the elements. The best investigation of this framework substance was made by M. Schultze. This is permeated by the nervous elements, among which are to be enu- merated the layer of optic nerve-fibres (fig. 378, 7) and Of the ganglion-cells of the inner portion (6) ; then the cones (and rods) of the outer layer (1), and likewise a part of the elements of the granular layers (2, 4) ; as also, finally, a system of radially arranged finest nerve-fibres, which have only re- cently been distinguished from the connective-tissue supporting fibres. The verification on the fresh eye will be necessary even for what has thus far been described. The eye is to be opened under iodine-serum in a dish, and a portion of the retina re- moved. A fold having been carefully made, and a piece of thin glass placed near it, to protect it from the pressure of the covering glass, the various lay- ers may be more or less distinctly recognized. Fine vertical sections are, nevertheless, more suitable. Do not believe that immense skill is necessary for their preparation. The piece of retina carefully separated from a fresh ox-eye, is to be placed on the microscopic glass slide, or on a cork plate, and a little vitreous fluid or iodine- serum added. The attempt is then to be made with a sharp moistened blade, such as that of a cataract-knife, or the convex one of a small scalpel, by careful pressure and a rocking motion, to obtain as fine as possible sections. Many of these attempts will fail, but a few objects will possess sufficient thinness to permit of a successful examination, if treated with the same precautions as a fold. For further studies such sections (in which it is true one is Fig. 378. Vertical transverse sec- tion of the human retina (made about half an inch from the point of entrance of the optic nerve). 1, Layer of rode and cones ; 2, external granular layer ; 3, inter-granular layer; 4, internal granular layer ; 5, fine .granular layer ; 6, layer of ganglion-cells ; 7. expan- sion of the optic nerve-fibres ; S, radial fibres; 9, their insertion into the in- ner limiting membrane, the membrana limitans interna, 10. 592 SECTION TWENTY-SECOND. not protected from a displacement of the elements, and which therefore require a comparison with other methods) may be further picked. It is also suitable to employ with them a weak chromic acid, or the dilute Midler's fluid. A portion of the above-mentioned connective-tissue frame- work of the retina may be recognized even by the aid of the previous methods ; though even a half-way sufficient view is never obtained. As Schultze has shown, other methods are necessary for this purpose, the same as have already been men- tioned at the organs of smell. Among these are to be enumerated chromic acid in a con- dition of extreme dilution (p. 128), the very watery sulphuric acid (p. 124), and the concentrated oxalic acid solution (p. 129). To obtain a primary view of the connective-tissue framework structure of the retina, that investigator says that the eye of a fish is to be used, as the arrangement is easier to understand here than in the mammalial animal. The bulb of a river perch which has just been killed is to be divided through the equator and placed for three days in the familiar highly diluted chromic acid solution, which contains t,£,| grain of the acid (or i-2 grs. of bichromate of potash) to the ounce of water. The exami- nation is then to be made, cautiously picking, and using the high magnifying powers of a Hartnack's immersion system. While the connective-tissue framework substance is thus ren- dered recognizable by the chromic-acid solution, the latter has likewise the already mentioned excellent property of causing varicosities on the finer nerve-fibres, and of rendering it possi- ble to distinguish the two systems of fibres in the retina as in the regio olfactoria. The concentrated watery solution of oxalic acid is also an excellent medium for this examination and discrimination, as it renders the connective-tissue framework paler and hardens the nervous elements somewhat, and thus renders them more distinct. One is not confined to a definite time by this means, as the examination may be made after a few hours, or even after several days. Sulphuric acid of 0.6 per cent, preserves the nervous elements very well, but also at the same time those of the connective- tissue framework. The scientist mentioned afterwards found in osmic acid an ORGANS OF SENSE. 593 important accessory for the investigation of the textural condi- tions under consideration. We shall return to the same. By such methods the connective-tissue framework substance has presented the following arrangement (fig. 379, A). The entire retina is per- meated by it, with the ex- ception of the bacillar layer. A system of radial or Miil- lerian supporting fibres (e) forms, with its innumerable fine processes, a delicate net- work which in two places, namely, in the intergranu- lar layer (d) as well as the fine granular layer (g), as- sumes an extraordinary fineness and compactness, and here becomes changed to a regular spongy tissue, related to that of the gray substance of the brain. Inwards, these supporting fibres, uniting together and spreading out in a peculiar manner, form a hyaline con- nective-tissue boundary lay- er, the membrana limitans interna (J) which, after treat- ment with a 0.25-0.5 per cent, solution of nitrate of silver, presents an irregu- lar, black bordered mosaic (Schwalbe). Externally, over the so-called external granular layer, a second, similar boundary layer, but finer and perforated in a sieve-like manner, may be terna (a). If the finer textural conditions 38 Fig. 379. Diagrammatic representation of the retina of man and the vertebrata, aftur M. Schultze. A, connective- tissue framework of the retina, a, membrana limitans ex- terna ; e, radial or Mullerian supporting fibres, with their nuclei e' '; /, limitans interna ; d, framework substance of the intergranular, and g, of the fine granular layer. B, ner- vous elements of the retina ; &, rods with outer and inner portions, as well as the rod-granule (6'); c, cone with the rod and granule (c'J ; d, expansion and apparent termi- nation of the cone-fibres in the intergranular layer, with the transition into finest fibrillar ; /, granules of the inner - granular layer ; r/, confused mass of finest fibrillar in the fine granular layer ; h, ganglion-cells ; h\ their axis-cylin- der processes ; /, layer of nerve-fibres. seen. This is the limitans ex- of the nervous elements of 594 SECTION TWENTY-SECOND. the retina, as well as finally the connection of the same, are to be investigated, the methods which have until recently been employed in this difficult domain have already been mentioned in the preceding. Maceration may be accomplished with the various acids mentioned for the connective-tissue framework, among which the highly diluted solutions of chromic acid have been most employed. Corresponding solutions of the bichromate of potash, as well as Miiller' s fluid diluted with water, are also to be recommended as suitable. A careful picking naturally follows. For hardening, to subsequently obtain very fine sections, the stronger solutions of chromic acid and its potash salt, as well as, above all, the Midler's fluid, are employed. A very conservative tingeing with carmine will render many things more distinct, although its value proves to be less here than for many other organs. We scarcely need to remark that for such infinitely delicate textural conditions the strongest objectives must be used. The rods and cones usually keep well in weak solutions of chromic acid and chromate of potash ; the extremely dilute solutions mentioned by Schultze are unserviceable. The Miil- ler' s eye-fluid preserves them well. Schultze found the rods excellently preserved in the concentrated oxalic acid ; the above-mentioned sulphuric acid of 0.6 percent, is also useful for the rods. The recognition of the latter with the external and internal portions is relatively easy in the quite fresh eye, with the addition of humor aqueus and vitreous or iodine-se- rum, whereby we meet at the same time with a quantity of fragments and in part strangely disfigured specimens. A por- tion of fresh retina, with the external surface turned upwards and placed under the microscope without a covering glass, forms the best object for the recognition from above of the mosaic of the rods and cones. The external and internal portions of the rods, the former (fig. 379, B, b, figs. 380, and 381) of stronger refractive power, the latter delicately contoured and becoming reddened in the carmine solution (Braun), are to be discovered with tolerable facility ; likewise the very fine and perishable filament which arises from the pointed end of the inner member. Schultze succeeded years ago, with his familiar highly diluted chromic ORGANS OF SENSE. 595 acid solutions, in demonstrating varicosities on these, and thereby their nervous nature in contradistinction to the con- nective-tissue supporting fibres. The impossibility of following these finest rod-fibres through the entire thickness of the retina was known even at that time, as their course is maintained in a radial direction over limited portions only. Fig. 3S0. Structure of the rods (Schultze). 1. Those of the guinea-pig in a fresh condi- tion, with inner and outer portions to the left, in connection with a transversely striated granule. 2. Those of the Macacus cynomol- gue, macerated in iodine-serum, with Hitter's filament. Fig. 381. Structure of the rods (Schultze). 1, from the chicken ; 2, from the frog (in a fresh condition) ; 3, from the salamander (likewise fresh) ; 4, from the pike (also fresh) ; 5, the division into plates of a rod from the frog treated with acetic acid ; «, lenticular body. The recognition of the cones (fig. 379, B, c, fig. 382, fig. 383, 2) as well as their rod-shaped terminal portions (cone-rods) also succeeds with the older methods, although the extraordinary changeability of the cone-rod renders the perception of its true structure very difficult. The external granular layer, occurring under the limitans externa, shows with tolerable facility the varicose rod-fibres, as well as the small spindle-shaped and transversely striated cells (rod-granule) embedded in it, with a nucleus and nucle- olus. One likewise perceives, joined to the inner extremity of the cone, the analogous (but not as in the rod-granule, fig. 380, 1, transversely striated) structure, the cone-granule. Years ago H. Muller correctly recognized differences in these rod and cone-granules. A difference could be recognized between the broader fibres passing from the cones and the finer varicose rod-fibrillge, and they seemed to terminate in a strange manner with conical, widened, terminal portions at the margin of the 596 SECTION TWENTY-SECOND. intergranular layer (Muller, Henle), so that, for a time, even Schultze had doubts of their nervous nature. Against this, however, the macula lutea, formed entirely of more slender Fig. 382. ConeR. «, from man, with a decom- posed external portion and fibrillary appearing in- ner portion ; b, from the Macacus cynomolgus, after maceration in dilute nitric acid, with the lenticular body (Schultze). Fig. 383. Fibrillated covering of the rods and cones, after Schultze. 1. Rods, 2, cones of man ; a, outer ; o, inner portion ; c, rod- filament ; d, limitans externa. 3. Rods of the sheep. The fibrillar project beyond the inner portion ; the outer portion is wanting. cones, with their obliquely arranged cone-fibres, formed an im- portant objection. The inner granular layer (fig. 379, 7?,,/) likewise shows without difficulty a small cell with a nucleus and nucleolus, analogous to that which appeared to us as the rod-granule in the external granular layer of the retina. From both poles of a number of these so-called granules arise very fine radial fila- ments, in which, however, no connection with the varicose fibres of the rods can be recognized. Years ago Muller and Schultze succeeded in distinguishing the oval nuclei of the framework of supporting fibres (A, e) from these granules. By the aid of the older methods one may recognize with ORGANS OF SENSE. 597 relative facility, especially in large mammalial animals, the layer of the multipolar ganglion-cells (B, h) and its varying thickness in the various portions of the retina, ^either does the flattened extension of the (as a rule non-medullated) retinal fibres (i) in the inner layer of nervous elements present any great difficulties, either as surface views or their vertical sec- tions. An exquisite object is afforded by the retina of the rabbit and the hare, where our nerve-tubes, streaming in by way of exception, as two rows of medullated fibres, may be everywhere readily noticed. We have here mentioned, with the most concise brevity, the chief results of earlier investigations. The great differences which the retina presents in the various groups of vertebrate animals also become more and more apparent (Miiller). The gigantic rods of the frog, the peculiar twin-cones of the osseous fishes, the often delicately colored fat-globules at the base of the cone-rods in birds and squamigerous reptiles, must capti- vate the interest of the observer. We can at present say that rods and cones are widely diffused among the vertebrate animals, but are by no means everywhere present. Most mam- malial animals (ape, ox, horse, dog, etc.) have them similar to those of man. The eye of the bat, the hedgehog, the mole, the mouse, and the guinea-pig has, however, only rods and no cones. The latter structures are quite scanty and undeveloped in the retina of the rabbit and the cat. Birds have an excess of cones (only in owls these elements recede entirely and colored fat-globules are wanting). Only cones, and no rods, appear in the retinas of lizards and serpents. Rays and sharks, in contradistinction to the osseous fishes, are entirely without cones (Schultze). We cannot here enter further into the im- portant physiological consequences of these remarkable con- ditions. It suffices for us to have made mention of them for practical purposes, for the selection of materials for investi- gation. As was mentioned, a further excellent accessory for the ex- amination of the retina has become known through M. Schultze in osmic acid (p. 165), and this reagent has been employed in superior investigations with the greatest success.* * Chloride of gold and chloride of gold and potassium deserve a more accurate trial for the retina. 598 SECTION TWENTY-SECOND. For its application a 2 or 1 per cent, solution should be kept on hand, so that it may be diluted at pleasure in a meas- uring glass. One may go down to 0.1 per cent., or even lower. Stronger solutions of 1-0.25 per cent, cause rapid hardening (without inducing coagulations), so that after an immersion of even half an hour portions of the retina may be divided, in the direction of their radial fibres, into lamellse, and the nervous elements may be recognized, while the connective-tissue sup- porting apparatus is rendered but slightly prominent. Such preparations may be left for a day in the solution, and, washed out in water (which also serves as a medium for osmium pre- parations), they may be preserved for days for further examina- tion likewise in alcohol and acetate of potash. The blackening, which appears very rapidly, is more regu- lar at the commencement. Later, the nerve-fibres frequently become colored, the fine granular and intergranular layers more intensely than the other portions. The outer portion of the rod appears, as a rule, darker and sharply contrasted from the inner portion, quite especially and very remarkably so in the frog and in fishes. Weaker degrees of concentration of the osmic acid of 0.2 per cent, and less, no longer cause hardening alone, but also exert, at the same time, a macerating effect. The preparation is now less brittle and permits of picking with needles. It is gen- erally sufficient to allow the action to continue for a half or a whole day. The nerve-fibres may assume varicosities in these watery solutions. The connective-tissue framework becomes hardened later than the nervous elements. To thoroughly preserve the rods and cones, take a vitally warm eye, remove the posterior segment of the sclerotic to be- yond. the equator, and immerse in a solution which contains about two per cent, of the dry acid. The desired effect is ob- tained in a few hours. The fluid media and preservative fluids have already been mentioned. Schultze arrived at important results for the external por- tion of the retina. The rod-fibres arrive, as far as the inter- granular layer (fig. 379, B), to here ; with slight intumescences, withdraw from observation. The broader cone-fibres are quite similar to an axis-cylinder, permit of the recognition of delicate longitudinal striations (perhaps as an indication of a further OKGANS OF SENSE. 599 composition), and form at the same locality the already men- tioned conical expansion (d). From the base of the latter arises a new system of extremely fine fibrillse, which, with nu- merous divarications, assume another, and, indeed, horizontal course. Varicosities speak for the nervous nature of the latter fihrilla?. The connection of the nervous elements in the inner layers of the retina still remains quite obscure. Whether the radial fibres of the inner granular layer (/'), which are united to a granule, are connected with the confused mass of finest fibril- he which arise from the resolution of the cone-fibres, we are not yet able to say. The similar mass of fibres, perhaps arising from the radial fibres of the inner granular laj'er, also passes through the fine granular layer (c/), to finally pass over into the fine or so-called protoplasma processes of the ganglion-cells (h) (comp. p. 351, fig. 198). Should this conjecture of 8011111126' s prove to be true (whereby a parallel with the texture of the gray sub- stance of the central organ results), and should the system of processes of a cone-fibre hereby enter into different gan- glion-cells, complication of the nervous channels would indeed result which could not be mastered by our present acces- sories. Probably an inwardly directed broad process of the gan- glion-cells of the retina corresponds to the so-called axis-cylin- der process of the central cell, and simply assumes the form of a primitive fibre of the nervous layer (7i). It would lead us far beyond the narrow limits of this book, and the requirements of our circle of readers, were we to here make more complete mention of the most recent acquisitions in this domain. Thus a problematical axis-filament has been ascribed to the rods (fig. 380, 2) which is certainly wanting in the outer portion (Schultze). At the inner portion of the rod, where it joins the outer portion, a singular lenticular body of semispherical or piano-parabolic form has been met with (fig. 381, a). Something of the kind also appears to occur in the cones (fig. 382, i). For the (certainly transitory) preservation of these structures the solution of the bichromate of potash may be tried. Of interest is furthermore a disk-like structure of the rods (fig. 381, 5), which was incompletely seen many years ago, 600 SECTION TWENTY-SECOND. but which has been recently more accurately recognized and studied. On the fresh rod it is seldom that anything of it can be seen, only examinations with oblique light and a rotary stage show us a trace of the same, if one of the strongest im- mersion systems can be tised. It becomes distinct only when distending reagents are resorted to, as, for example, dilute serum to which a little acetic acid may be added, dilute nitric acid, etc. Osmic acid (1-2 per cent.) also affords good prepa- rations and, with careful picking in water, presents transverse sections of these plates. The same foliaceous disintegration also occurs on the outer portions of the cone-rods (figs. 382, 383, 2, a). Finally, M. Schultze (we have thus far quoted from his works) found an infinitely delicate longitudinal fibrillary struc- ture covering the rods and cones externally throughout their entire length (fig. 383). One may think of the primitive fibril- lse of the axis-cylinders and ascribe the latter signification to the rod- and cone-fibres. Still the connective-tissue nature of this external striation is undoubted. It belongs to a very deli- cate envelope which is connected with the limitans externa. More recently the indefatigable investigator, now deceased, discovered in the interior of the inner members of the cones and rods a very fine filamentous apparatus. The latter is possibly of a nervous nature, and corresponds to the primitive fibrillse of the axis-cylinder formerly looked for on the outer sur- face. For this purpose, also, osmic acid constitutes the best ac- cessory. The macula lutea and fovea centralis require no new methods. Their structure must be ascertained from the text-books on histology. The usual hardening treatment with chromic acid and chro- mate of potash (and alcohol) also serves to show the relation of the blood-vessels to the retinal layers, and their advancement to near the intergranular layer ; while the delicate vascular net-work in its extension (fig. 384) (for the demonstration of which we recommend the injection of the eye of the ox and the sheep) requires surface views. With regard to the pathological changes of the retina, we are at present acquainted with hypertrophies of the connective- tissue parts, with a corresponding degeneration of the nervous ORGANS OF SENSE. 601 elements, proliferations of the granular layers, amyloid bodies, fatty degeneration of the nervous (but also of the connective- tissue) parts, embolia of the retinal vessels, likewise pigmenta- tions coming partly from the extravasated blood, partly caused by the proliferated choroidal epithelium which has penetrated the retina, and which latter hereby frequently lies near the retinal blood-vessels, etc. Tumors of the retina are, as a rule, either sarcomata or glioma (p. 360), and only very rarely carcinomata. Preparations from more hardened retinas (after the use of Muller's fluid) may be readily preserved in glycer- ine in the form of review specimens ; for many views we would recommend tinge- ing them with carmine. The finest textural relations of the several layers and their ele- ments could not, on the con- trary, from the condition of the microscopical technique, be preserved for a long time. Attempts to mount them in their macerating fluids rapidly came to an end, as a rule, in the destruction of the preparation. M. Schultze subsequently gladdened us with the important information that osmium preparations may be preserved for years in a solution of the acetate of potash (p. 217). This succeeds occasionally. Foetal eyes may be studied on very small embryos immersed fresh in chromic acid. With older foetuses the eye is to be taken out and further treated in accordance with the directions given for the adult. The eyes of new-born kittens are to be recommended for injecting the magnificent vascular net-work of the membrana capsulo-pupillaris. 5. With regard to the organs of hearing, the external parts of the same, such as the auricle and the external auditory canal, require no special directions. The ceruminous glands, with their coil-shaped bodies and Fig. 3S4. Vessels of the human retina, a, arterial ; c, venous branches ; b, the capillary net-work. 602 SECTION TWENTY-SECOND. short excretory ducts, are to be examined in the same manner as the related sudoriparous glands. The membrana tympani is to be studied either in the fresh condition, with the aid of the knife and needles, and with the use of acetic acid as well as the alkaline solutions, or the pre- viously dried organ is employed for fine sections, whereby we would also urgently recommend the usual tingeing methods. Total views are obtained with resinous mounting media. The epithelium and the lymphatics are rendered distinct by nitrate of silver ; for the demonstration of the nerves use chlo- ride of gold (Kessel). The walls of the cavity of the tympanum and Eustachian tube, with the covering of ciliated cells, the ossicula auditus, with their porous bone substance and their transversely striated muscles, are to be examined by the methods customary for the tissues in question. The investigation of the labyrinth is far more difficult. Even the opening by means of saw and chisel must be accom- plished with caution ; and from the delicacy of many structural conditions, only quite fresh, just previously killed animals are to be used. For the primary examination the labyrinths of larger mammalial animals, such as the calf and ox, are to be selected. If a certain practice in such procedures has once been acquired, the exposure also succeeds later with smaller creatures — the dog, the cat, and the rabbit. The great alter- ability of the elements also renders it necessary, as with the retina, to use fluid media which are as indifferent as possible ; among these we would recommend blood- and iodine-serum, vitreous fluid, and dilute albumen. Dilute solutions of chromic acid may also be suitably applied to the fresh tissue. The decalcification of the bones with chromic acid, in order to make transverse sections, seems to be of the greatest impor- tance for the first views. For further studies we would also advise hardening and especially the immersion in solutions of chromic acid, bichromate of potash, and Midler's fluid. The latter fluid, diluted with an equal volume of water, may be very highly recommended. The aggregations of ear-stones or otoliths (as the polariz- ing microscope teaches, columns crystallized in the arragonite form) may be perceived in the sacculi of the vestibule as white spots, surrounded by an especial thin membrane. They are ORGANS OF SENSE. 603 generally small and, according to many statements, possess an organic basis. Their appearance may be represented by fig. 385. With regard to the distribution of the acoustic nerve on both sacculi of the vestibule, and on the membranous ampullae of the semicircular canals, the coars- er arrangement is not difficult to recognize. The nerve-fibres enter duplicatures of the walls, which are, especially in the ampullae, dis- tinctly recognized as prominences projecting into their cavity. This projection, called the septum ner- veum, contains the termination. An earlier epoch, without having any presentiment of the difficulties of such investigations, would here convince itself of the presence of terminal loops. That conditions also occur here which are quite similar to Fiq. 885. Otoliths. those we have mentioned in connection with other organs of sense; that there are auditory cells as well as olfactory and gustatory cells, was first demonstrated by Reich and M. Schultze ; the former by the investigation of the lamprey, the latter by that of the ray and shark. Our fig. 386 may bring such conditions of the plagiostomy before the reader, and show the characteristic cells, c, with their rod-shaped projection, d, and their lower fine terminal filament, e. The latter is undoubtedly the ter- minal nerve-fibrilla, although even here a continuous connection could be rec- ognized by M. Schultze with as little certainty as in the olfactory organ. Strange Ions; hairs also occur on the peculiar epithelium of this locality. Here also chromic acid, with those dilute solutions which we have had to mention so frequently for the higher organs of sense, plays at the present time the role of the most important accessory. Osmic acid and chloride of gold will be tried by some subsequent observer. Fig. 3b(i. From the' crista acustica of the ampullar of Raja clavata. a, cylin- der cells; &, basal cells; c, fibre cells, "with the upper rod-shaped processes d, and lower fine fibrillary ones e ; f, nerve -fibres', becoming at g pale rami- fying axis-cylinders. 604 SECTION TWENTY-SECOND. According to the few observations which have at present been published, similar textural conditions appear to occur in the vestibulum of the mammalial animal (ox). Although all of our knowledge of these subtile arrangements is still in em- bryo, a penetration of the nerve fibrillse into a peculiar ejjithe- lium and the existence of specific cells is nevertheless quite certain. Infinitely more difficult, and leading into a true chaos of the most intricate structural conditions, is the termination of the nervus cochlearis in the Reissnerian cochlear canal, or the so-called scala media. Since Corti undertook the first success- ful excursion into this domain full of wonders, our knowledge has been enriched by each of the subsequent investigations by the discovery of new fragments. Within a period not long elapsed, Deiters especially has rendered the greatest service in connection with the structure of the cochlea ; and Kolliker, by the discovery and closer investigation of the almost forgotten Reissnerian cochlear canal, has established a new accejDtation of the scala media. Among the numerous successors, we men- tion only the names of Hensen, Botcher, Waldeyer, and Gott- stein. It would lead us far beyond the limits of this work were we to mention here the structural conditions which have thus far been investigated, especially the structure of the so-called Cortian organs (fig. 387). Notwithstanding all previous efforts, the knowledge of the nerve terminations is not as far advanced as in the other organs of sense. Probably, however, the ter- minal nervous structures of the nervus cochlearis (f) are pres- ent in certain ciliated cells (i andp, q, r). The exposure of the parts in question may be accomplished and learned on the quite fresh auditory apparatus of one of our larger cattle (the ox). After some practice this may also be gradually achieved with smaller creatures. Fragments which are obtained in this manner from the scala media are to be examined by means of indifferent media or strongly diluted chromic acid. The latter, or chromate of potash, also serves for the immersion and hardening of the opened cochlea. For many cellular conditions of the Cortian organs, high degrees of dilution, similar to those introduced into histology by Schultze, are to be tried ; and certainly also osmic acid, chlo- ride of gold, and chloride of gold and potassium. To obtain OEGANS OF SENSE. 605 transverse sections of the entire Reissnerian cochlear canal, the organ, previously hardened by means of chromic acid or Mid- ler's fluid, is to be cautiously decalcified by adding a few drops Fig. 387. The Corti's organ of the dog in perpendicular section ; a, b, homogeneous stratum of the mem- brana basilaris : u, vesicular stratum ; u, tympanic stratum with nuclei and protoplasma : «, labium tym- panicum of thecrysta spiralis ; a 1 , continuation of the tympanic periosteum of the lamina spiralis ossea ; c, thickened commencing portion of the membrana basilaris, together with the place of section ; h, of the nerve d, and r, blood-vessels ; /, the nerve ; ff, epithelium of the sulcus spiralis externus ; /, inner hair-cell with the basal process, £, surrounded by nuclei and protoplasma (of the " granule stratum "), into which the nerves radiate ; ?i, base or foot of the inner pillar of the Corti's organ ; 7/j, its " head piece," connected with the same part of the outer pillar, the lower part of which is wanting, while the next following pillar, o. presents the middle part of the base ; p. q, r, the three outer hair-cells ; z, a so-called supporting cell of Hensen ; I, lamina reticularis ; w, nerve-fibre terminating at the first of the outer hair-cells. of muriatic acid to these fluids and frequently changing the entire mixture. The lamina spiralis of the larger animals may be isolated and exposed to such a procedure. The nerve dis- tribution in the zona ossea may likewise be brought to view in this manner. Several years ago Hensen, to obtain the mem- brane of Corti in its position, made use of a three months' immersion in Midler's fluid, and injected tolerably concen- trated gelatine through a puncture in the tympanum secunda- rium, which then transuded into the cochlear canal. The ex- ternal wall of the cochlea was afterwards broken open, and the scala media with the gelatine cast isolated. Hensen also found carmine imbibition appropriate here. Waldeyer, one of the most excellent investigators in this difficult domain, recommends, besides the review of fresh ob- jects in humor aqueus, the osmic acid, to which he ascribes the same importance as for the retina of the eye. Degrees of con- centration of 0.1-1 per cent, are to be used ; the former for picking, the latter for hardening. A solution of chloride of sodium of 0.25-0.5 per cent, rendered him excellent service for 606 SECTION TWENTY-SECOND. the former preparations. Chromic acid of 0.05 per cent, chlo- ride of gold, according to Cohnheim' s directions, and a 1 per cent, solution of nitrate of silver, are likewise useful for many purposes. To obtain good section preparations, remove as much bone as possible from large cochlea, and make two or three small openings into the capsule. Smaller organs, on the contrary, are to be left intact. The cochleae are then to be placed for a day in a liberal quantity of a solution of chloride of palladium (0.001 per cent.), or in one of osmic acid of 0.2 per cent, if the organs are small ; while more voluminous ones require an increased concentration of 0.5-1 per cent. Such objects are then to be exposed to the action of absolute alcohol for twenty- four hours, and at once placed in the decalcifjdng fluid. Waldeyer found chloride of palladium (0.001 per cent.) with t l part muriatic acid, or chromic acid of 0.25-1 per cent, most serviceable for the latter purpose. After the decalcification, the preparations are to be washed out with absolute alcohol ; it may then (for the subsequent preparation of sections) be embedded in a piece of fresh spinal cord or fresh liver, and the whole then replaced in the absolute alcohol. During the hardening the enveloping piece of organ shrinks so firmly around the cochlea that the latter remains immovable and permits the desired sections to be made. Before this embedding the cavity of the cochlea may be filled with gelatine glycerine (1 : 1), or (not so good) with a mixture of wax and oil. This filling, however, is not absolutely necessary. The primary views of the cochlear canal may be obtained without great difficulty from embryos, treated in a similar manner, by means of suitable transverse sections through the petrous bone. For cabinet preparations the same remarks apply which we have made (p. 601) concerning the retina. Preparations of the Cortian organ, however, I have preserved for years entirely unaltered in watery glycerine. Hensen recommends the watery solution of arsenious acid for mounting. Acetate of potash should also be tried. INDEX. INDEX. Abbe's theory of the microscope, 13, note ; on curva- ture phenomena of the light, and microscopic de- ceptive images, 62,note Abdominal typhus, changes of the lymphatic glands in, 407 ; of their lymphatics, 407 ; of the Peyerian follicles, 452 ; of faecal masses in, 455 ; changes of the spleen in, 483 Aberration, chromatic, of tfte lenses, 9; chromatic, of the microscope, 55 ; spherical, of the lenses, 8 ; spherical, of the microscope, 54 Abscess, 252 Accessory apparatus for microscopic drawing, 3S Accommodative power of the eye, 2 Acetate of potash, 135, 217 Acetic acid and alcohol mixture, 139 Acetic acid, concentrated, 130 ; Moleschott's diluted, 130 ; Kolliker's very dilute, 130 ; Prey's, 130 ; swelling action on certain tissue elements, 131 ; for washing objects tinged with carmine, 149; with glycerine, 149, 216 Acetic acid, glacial, index of refraction of , 118 Acetic acid hydrate, 129 Achorion Schoenleinii, 560 Achromatic double lenses, 9 ; lens, 9 Adenoid tissue, see Reticular Connective Substance ; sarcoma of the mammary glands, 544 Adjustment of focus, apparatus for, 20, 21 Aeby employs concentrated muriatic acid for isolat- ing muscles, 125, 324 ; finds the capillaries to con- sist of cells, 382 Aerial image of the compound microscope, 8 ; of the improved, 13 Air-bubbles, removal of, from Canada balsam, 209 ; occurrence of, in saliva, 429 ; in lung preparations, 486 ; in sputum, 494 Alcannine solution, 582 Alkalies, 133; their action on the epidermis, 267; on the tissue of the nails, 269 ; dilute, their action on the ciliary motion, 264 ; on the movement of the spermatozoa, 552 Alcohol, action of, 138 ; a constituent of other mix- tures, 139 Alcohol mixtures, 139 ; with acetic acid (Clarke's), 139 ; Moleschott's acetic acid mixture, strong, 139 ; weak, 140 ; with, acetic and nitric acid, 140 ; with soda, 140 Alum with corrosive sublimate and chloride of sodi- um, 217-8 Alveolar cancer, 289 Alveolar epithelium of the lungs, 489 Alveoli of the lungs, 488 Amici shows the influence of the covering glass, 16 ; microscope of, 72 ; microscopical improvements of, 11 ; on the muscular filaments of the house-fly, 328-9 ; his prisms, 51 Ammonia, bichromate of, 137 ; for the central or- gan of the nervous system, by Gerlach, 351 ; sim- ple chromate of, 137 ; for the gland-cells of the kidney, by Heidenhain, 511 39 Ammonia liquor, 134 * Ammonia, molybdate of, 137 ; fur the central organ I of the nervous system, by Henle and Merkel, 357 ; for salivary glands, by Krause, 426 : Ammonio-phosphate of magnesia crystals in the j faeces, 455 ; in the urine, 528 I Amyloid bodies. 361 ; degeneration, see various or- gans ; reactions, 124, 132, 155, 474 | Amylon, see Starch 1 Anacardium nuts, 582 j Analyzer, 49 ; over the ocular, 49 ; in the ocular, by I Hartnack, 49 ] Andrejevic on biliary capillaries, 465 I Aneurisms, 394 | Angle of vision determines the apparent size of an object, 1 , Anilin blue as a tingeing medium, 156 ; for gastric glands, 433 Anilin-iodine-violet, 155 1 Anilin red as a tingeing medium, 154 ; for the recog- I nition of the axis cylinder, 337 Anis oil, index of refraction of, 118 Anthracosis of the lungs, 491 ; of the lymphatic glands, 407 Aperture, angle of, of the lenses, 7 ; of objectives, 14, importance and size of, 57; available portion | of, 59 ; of Hartnack's systems, 60 ; other excellent ' modern objectives, 60 Aplanatic double lens, 10; eye-piece, 15; objec- ! tives, 14 ' Apolar ganglion cells, see Nervous System Apophysis cerebri, 379 Apparatus for drawing, 37, 38 Apparatus for injecting by constant pressure, 192- 4; with a column of fluid, 192; with mercury, i 193-4 Apparatus for measuring, 32 ; angles (goniometer), ; 36 Apparatus for micro-photography, Gerlach's, 41 ; Moitessier's, 42 | Appreciation of microscopic images, 94 ; of their | conditions of relief, 95 ! Arcus senilis, 583 Argand lamp 86 | Arnold's studies on smooth muscles, 317; their nerves, ! 367 ; the new formation of vessels, 392 ; Arnold i and Thoma on the bluing of the cement ledges of | the epithelium, 259 Arrangement and use of the Gerlach's photographic apparatus, 41 ; of Moitessier's, 42 Arsenious acid in watery solution, 220 ; with glyce- : rine, by Farrants, 216 ' Arteries, see Vessels Arteriolar recta_ j (kidneys), 516 ■ Ascaris lumbriooides (ova in faeces), 457 I Asphalt cement, 227 ; Bourgogne's, 227 : making a I border with, 227 I Atheroma of the skin, 558 1 Atheromatous processes, 393 610 INDEX. Atrophy, see the organs; acute yellow of the liver, 471 Auditory apparatus, 601 ; ceruminous glands, 601 ; membrana tympani, cavity of the tympanum, 602 ; otoliths, 602 ; eacculi of the vestibula of Ashes, 603 ; vestibulum of mammalial animals, 604 ; cochlea, 6U4 ; difficulty of the examination, 604 ; cochlear canal, 604 ; Hensen and Waldeyer's methods, 604 Auditory cells, 604 Auditory ossicles, 602 Anerbach's studies of the cell nucleus, 130 ; plexus myentericus, 346 ; finds the capillaries to consist of cells, 382 Axis cylinder of the nerve-fibres, 336 Axis fibrillar of the axis cylinders of the nerve-fibres, 339, 600 B. Bacteria, 253 ; their nature, 254 ; fine granular basis (zooglia of Conn, micrococcus of Hallier, microspo- ron of Klebs), 254; bearer of putrefaction, 254; occurrence in diseases, 254 Bailey recommends Hyaloidiscus subtilis as a test object, 63 ; Grammatophora subtilissima, 66 Baryta, sulphate of, as an injection mass, 179, 18S ; directions for preparing, 179 Baryta water, 134 Bastian recommends carbolic acid and glycerine as a preservative fluid, 216 Beale, works on the microscope, xi., xii. ; treatise on micro-photography, 40 ; B. and Clarke's alcohol mixtures, 139 ; mixture of alcohol, acetic acid, and nitric acid, 140 ; alcohol and soda, 140 ; for calci- fied cartilage, 292 ; on carmine tingeing, 151 ; cold (lowing injection mixtures, 186-7; with Prus- sian blue, 1S7 ; with carmine, 188 ; mounting fluid, 216 ; directions for preparing glass cells, 223 ; on ganglion cells, 344; directions for hardening livers, 462 Becherzellen, 438 Bell glass, for covering the microscope, 91 ; for cov- ering specimens, 98 Benecke on micro-photography, 40 Benzine, 142 Berre's injections, 173 Bichromate of potash, 136 ; (see Chromate of Pot- ash) Bidder on the connective-tissue framework sub- stance of the central organs of the nervous sys- tem, 359 Bile, 468; coloring matter of, red, bilirubin, 469 ; relation to, and difference from hasmatoidin, 469 Biliary passages, finest, 464 ; capillaries, injection of, by Budge, Anduejevic, MacG-illavry, Frey, He- ring and Eberth, 465 ; procedure and selection of objects, 465 ; filled by pathological concretions, s 469 ; sediments, 469 Bilifulvin, 469 Biliptuein, 469 Bilirubin of Staedeler, 469 Billroth recommends chloride of iron, 137 ; describes the reticulum of the spleen pulp, 480; shows the connection of the muscular filaments of the tongue with connective-tissue corpuscles, 424 ; on the ex- amination of the kidneys, 507 ; on the typhoid spleen, 483 Binocular microscopes, 46 ; of Nachet, 47 ; stereo- scopic, 47 ; arrangement of Wenham, Riddell, Ross, and Crouch, 47-8 Binocular stereoscopic eye-piece of Hartnack, 48 ; of Tolles, 80 Bipolar ganglion cells, see Nervous System Bizzozero, on the formation of colored blood corpus- cles from the lymphoid cells of the bone marrow, 311 Bladder, urinary, 622 ; epithelium of, 522 ; changes in catarrh, 523 Blood, 233; to obtain, 338; colored cells of, 233; colorless cells of, 234 ; their vital changes of form, 234 ; locomotion and reception of granules, 235 ; I enumeration of both kinds of cells, 235 : pathologi- i cal changes, 236 ; leucaemia and melanamiia, I 236 ; embryonic blood, 237 ; formation from lym- j phoid cells of the frog, according to Recklingh.au- j sen, 237; change of the colored blood corpuscles I by heat, 238 ; reagents, 238 ; cabinet prepara- tions, 240 ; blood crystals, 241 ; htemoglobine, I 241 ; haDmin and hrematoidine, 241 ; examina- tion of the circulation, 245 : Schulze's slide for frog and salamander larvae, 246; behavior of the blood-cells of the living mammalial animal, accord- ing to Rollett, 247; Oohnheim's directions, 247; Strieker and Sanderson's, 247 ; emigration, ac- cording to Waller and Cohnheim, 249 ; blood in vomit, 436 ; in sputum, 494 ; in urine, 523 Blood cells, see Blood Blood corpuscles, see Blood Blood crystals, see Blood Blood lymph glands (spleen), 479 Blood-vessels, 3S1 ; capillaries, 381 ; composed of cells, 382 ; adventitia, 383 ; objects and methods for examination, 383 ; value of artificial injections, 3S3 ; natural injection, 384 ; ^ stigmata " and " stomata, 11 384 : larger vessels, arteries, and veins, 385 ; their examination, 386 ; drying and embed- ding, 386 ; pulling off the several layers. 387 : new tingeing methods, 387 ; capillary net-work, 3S8 ; treatment of the injected capillary district. 38S ; j straight and circular network, 389 ; loops, 390 ; I first appearance in the embryo, 390 ; method of in- vestigation, 391 ; examination of the tail of the j frog's larva, according to Arnold, 392 ; further ' transformation of the foetal vessels, 392 ; patholo- I gical conditions of the blood-vessels, 393; athero- ! matous processes, 393 ; aneurisms, 394 ; changes in the veins, 394 ; changes in smaller vessels, 395; smaller arteries of the cerebral substance, 395; calcareous, fatty, and pigment degenerations, 395- | 6 ; melana?mia, 396 ; emboli, 396 ; pathological new formation of vessels, 396 ; signification of the j vascular cells in pathological transformations, ac- cording to Thiersch, Waldcyer, and Bubnoff, 396; Arnold's studies, 397; methods of examination, 398; observations of Thiersch in healing wounds, 398 Blood-vessels, injection of. 172, 190; of pathological objects, 199 ; with the syringe, 196 ; with constant pressure, 192; scl [-injection of the living animal, 190 Blood-vomiting, 436 Boiling animal tissues (the smooth muscles), 317 ; in vinegar, 131 Bone cartilage, see Bones Bone corpuscles, see Bones Bones, 296 ; preparatory treatment, 296 ; decalcifica- tion, 296 ; isolation of the cells with strong acids, 297 ; recognition of the cells by tingeing with car- mine, hamiatoxylme and gold impregnation, 298; Sharpey's fibres, 303 ; preparation of sections, 299 ; texture of bone, 299; lamella?, 299; bone-spaces and cells, 29S-I ; medullary canals, 299 ; mounting the sections, 300; injection of the blood-vessels, 301 ; injection of the bone-spaces and cariuliculi ac- cording to Gerlach, 301 ; behavior in polarized light. 301; fibrous nature of the basis substance according to von Ebner. 302 ; origin of bone, 305; endochondral bone, 305 ; absorption of the carti- lage, 305 ; ossification points, 305; cartilage me- dulla, 306 ; fate of the cartilage medulla cells, 307 ; Gegenbaur's osteoblasts, 308 ; new formation of bone substance, 309 ; osteogenous and osteoid tis- sue, 310 ; absorption of the bone substance, 310 ; growth of bones, 310 ; development from a connec- tive tissue basis, 311 ; periosteal bone, 310 ; exami- nation of bone medulla, 311 ; origin of blood-cells according to Neumann and Bizzozero, 311 ; bones in rachitis, 311 ; method of examining fectal bones, 310 ; new formation of bone substance under abnor- mal conditions, 312; callus, 313 ; regeneration of lout portions, 313 ; hyperostosis, 313 ; exostosis, 313; sclerosis, 314; osteo-sarcoma, 314; origin of bone substance in connective tissue parts, 314 ; absorp- tion processes, 314 ; Haversian spaces, 314 ; How- INDEX. 611 ship's lacuna 3 !. 314 ; Kolliker's osteoclasts, 314 ; os- teoporosis, 314 ; osteomalacia, 314 ; caries, 315 ; process of decalcification, 315 ; method of examin- ing decalcified bones, 315 Bone tissue, see Bones Bothriocephalus latus, ova in faeces, 457 Bourgogne's microscopic preparations, 232 ; Bruns- wick black, 227 Bowman's directions for making chrome yellow, 176 ; theory of the muscles, 328 ; work on the kid- ney, 503 ; capsule of the glomerulus of the kidney. 503 ; glands of the regio olfactoria in the higher animals, 568 Brain, 348 ; membranes of, 378 : sand, 379 Bright's disease of the kidneys, 520 Bronchi, 485 Bronchial glands, see Lymph Glands Brooke's revolving nose-piece, 80 Briicke defines the optical condition of the muscular filament, 381 ; hiR soluble Prussian blue, 183 Brunner's gland, 239 Brnnonian molecular motion. 97; in cells, 97; of small crystals. 97 ; their rapidity, 97 ; in salivary corpuscles, 429 Brushing method of His, 115 Brushing out raicroscupic preparations, 115 Budge (and Uechtritz) recommend chlorate of pot- ash and nitric acid for the axis cylinder, 337 ; on the finest biliary passages, 405 Burette, 142 ; for examining urinary sediments, 530 Calcification, see Cartilage Callus, 313 Camera lucida of Chevalier and Oberhauser, 38 ; ob- scura, eye compared to a, 1 Canada balsam, its index of refraction, 118 ; for mounting cabinet preparations, 208 ; varieties, 208 , col d-fi owing, 210 ; dissolved in chloroform and ether, 141, 211 ; removal of the excess from the slide, 210 ; removal of the air bubbles, 210 ; artificially hardened for mounting bones, 211 Cancerous tumors. 289 Cancroid, see Epithelial Cancer Caoutchouc, 225 ; cement, 225 ; cells, 223 Capillaries, see Blood-vessels ; their composition of cells according to Hoyer, Auerbach, Eberth, and Aeby, 381 Carbolic acid, 142 ; with glycerine according to Bas- tian, 216 Carbonate of lead, 179 Carcinoma, 289 Caries, 315 Carmine, 147; solution in ammonia, 148, 183, 188; injection mass of Gerlach, 183-4 ; of Beale, 151 ; of Kollmann. 189, note ; with glycerine, 149 ; for self- injection, 190 Carmine tingeing, invented by Gerlach, 147; wash- ing in acetic acid, 149 ; Beale's, 151 ; Heidenhain's, 152 ; Thiersch's with oxalic acid, 150 ; with borax, 151 ; acid carmine fluid, 152 Carpenters work on the microscope, xi, xii Cartilage, 290 ; various forms, 291 ; hyaline, fibrous, or reticular and connective-tissue cartilage, 291 ; method of examining the hyaline cartilage, 291 ; costal cartilage, 291 ; large primary and secon- dary cells, 292 ; decalcified cartilage, 292 ; exami- nation of reticular cartilage, 293 ; behavior of car- tilage in polarized light, 293 ; cartilage capsules, 295 ; destruction of the intermediate substance by chemical means, 294 ; pathological cartilage tissue, 295; methods of preservntion, 295 Cartilage cells, nee Cartilage Cartilage medulla cells, see Bones Cartilage, ossification of, 291 Cataract needle, 105 Catarrh of the bladder, 523 Cavernous body of the male generative organ, 550 Cell, recognized by Schwann as the elementary form of the body, ix. ; change of form of the lining. 98, 100, 247, 249, 252 ; method of examining with the moist chamber and the warm stage, 99-101 ; I locomotion of, 98 ; of pus-cells through the spaces ! of the cornea, 252 ; Cells for microscopic preparations, 222-3 i Cements, 227 ; asphalt, 227 ; Bourgogne's, 227 ; gold ; size, 228 ; masklac, 229 I Cementum, see Teeth j Central light for illumination, 222 ; for examining I test objects (Nobert's plates), 68 | Central organ of the nervous Bystem, see Nervous | System j Central rays, refraction of, 8 1 Cercomonas intestinalis of Lambl, 456 Ceruminous glands of the ear, 601 i Chamber, moist, of Recklinghausen, 99; combined I with the warm stage, 100 ; ordinary moist cham- I ber, 99 ; gas, of Strieker, 100 : Charriere's injection-syringe, 196 1 Chevalier and Selligue produce achromatic objec- tives, 11; construct camera lucida, ^88 ; micro- scopes, 25, 77 , Chinulin blue (cvanin), 158 I Chloral hydrate, 141 | Chlorate of potash, 135 I Chloride of calcium, 135 ; constituent of preservative I fluids, 219 1 Chloride of palladium, recommended by Schulze, 137. ! 168 Chloride of platinum, used by Merkel, 137 Chloride of silver, Teichmann's, ISO Chloride of sodium, 134 ; in impregnations with sil- ver, 135, 164; with alum and sublimate, 217; a constituent of preservative fluids, 217-19; in ten per cent, solution for smooth muscles, 319 ; for the cornea, 579 Chloride of sodium crystals from the urine, 527 Chloroform, 141 ; for recognizing the axis-cylinder, 337 Cholepyrrhin, 4(i9 Cholera vomit, 436 ; stools, 454 Chotesterine, properties of and occurrence of in nerve-tissue. 361 ; in meconium, 454 ; in the bile, 469 Chorio-capillaris, 485 Choroid, 584 Chromate of ammonia, 137 Chromate of potash, 136; action, 136; constituent of Mailer's fluid, 136 Chromatic aberration, 9 Chrome yellow precipitated in the blood-vessels by Bowman, 176 ; Harting's method of preparation, 178; Hoyer's transparent, 185; Thiersch's, 185 Chromic acid. 126 ; recommended by Hanover, 126 ; its action, 126; degree of concentration, 127 ; very dilute solutions, according to Schultze, 128 Chrzonszczewsky's self- injection of living animals, 190 ; of the liver, 466 ; of the kidney, 514 Chyle, 249; obtaining, 249; cells, 250; chyle-dust, 250 ; preservation, 250 Chyle-fat in cylinder epithelium, 438 Chyle-passages, 444 Chyle-vessels, see Lymphatics j Cicatricial tissue, 288 Ciliary body, 586 ; muscle, 586 I Ciliary epithelium, see Epithelium ! Ciliary movement, 262 ; Cinnabar, as an injection mass, 177 ! Circulation, investigation of, 245 ; in amphibia, 246; ' in mammalia, 247; in inflammation, 247; in im- | peded circulation, 248 1 Cirrhosis of the liver, 476 Clarke's (and Beale's) alcohol mixture, 139; method of examining the central organ of the nervous sys- tem, 356 Cleaning the glasses of the microscope, 92 Clove oil, recommended by Rindfleisch, 142 Coagulation of the blood, 239 ; of the nerve medulla, 335 Cochlea, 604 Cochlear canal, 604 ; nerve, 604 Cohnheim employs chloride of gold, 137, 166 ; con- firms Waller's observations on the passage of lym- phoid-cells through the uninjured walls of vessels, 612 INDEX. 249 ; immigration of the latter cells in the inflamed cornea, 5S3 ; studies of blood-stasis, 248 ; exam- ines sections of frozen striated muscles, 322 ; C. and Hoyer discover the penetration of corneal nerves into the epithelium, 370 Cold-flowing injection masses, 186 Collective lens of the compound microscope, 11 ; its action, 11 Collective lens, renders small bodies visible, 5 ; shows them enlarged, 5 : for opaque objects, 21 ; inserted into the stage, 23: on the photographic microscope, 23 ; on the polarizer, -19 Collective tubes of the urinlferous canals of the kid- ney, soy Collodium, 141 Colloid (alveolar) cancer, 289 Colloid degeneration, 289 ; of the glands, 420 ; of the thyroid, 497 Colloid substances of Graham, 119 Colophony dissolved in absolute alcohol as a substi- tute for Canada balsam, 214 Colors, covering, 38 ; transparent, 38; granular for injections, 177; transparent, 177; colors in tubes for injections, recommended by Hyrtl, 177 Colostrum corpuscles, 545 Columnar Bertini, 502 Comedones, 559 Compression apparatus of Frcy, 212 Concentric bodies of the thymus, 270, 500 Condensers, 23 ; their action, 23 ; achromatic of the English, 23 ; of Dnjardin, 23 ; of Hartnack, 23 Cones of the retina, 595-7 Connective substance, 274; reticular, 275; method of demonstration, 276; hardening, 270; varying condition in certain parts, 277; preservation of preparations, 277; myxomatu, 289 Connective tissue, 274, 279; ordinary, 279; living, according to Kiihne, 279 ; different cell forms, 280 ; fixed and migratory cells, 280-1 ; elastic elements, 281 ; demonstration of the intermediate substance, 282 ; pre-existence of the fibrillar, 282 ; demonstra- tion of the same by chemical means, by Hollett, 282; double refracting, 282; in polarized light, 282; demonstration of the connective-tissue cor- puscles, 280 ; methods of Kanvier and Flemming, 2S4 ; elastic sheaths around bundles, 283 ; trans- formation of the interstitial substance into gelatine, 285; impregnation with gold, 286; elastic fibres, 286; objects for examination, 286 ; embryonic con- nective tissue, 287 ; pathological connective tissue and its signification, 287; Waller and Cohnheim's investigations, 288 ; hypertrophic connective tis- sue, 288; cicatricial tissue. 288; basis of benign and malignant tumors, 2y8-9 ; methods of examin- ing the pathological forms, 290 ; cabinet prepara- tions, 290 Construction of the modern microscope, 18 Constriction rings of the nerve-fibres (Ranvier's), 338 Convoluted glands, see Glands ; of the skin, see Sudoriparous Glands ; of the conjunctiva, 573 ; of the organ of audition, 601 Copal lac, 213 Copper, chromate of, 189, note ; sulphate, 189, note Corium, see Skin Cornea (organ of vision), 577; corneal nerves, 369; by Hoyer and Cohnheim, 370 ; by Engelmann, 871 ; statements of Saemisch and Miiller, 370 Corneal corpuscles, 578 ; their pathological changes, 583 Corneal nerves, see Cornea Corneous layer of Remak, 414 Corml communicates the composition of preserva- tive fluids, SIS Corpus Highmori, 546 Corpus luteum, 539 Correction of the aberration of a lens, 13, 14 ; appar- atus for objectives, 18, 58 Corrosion method for tho lungs, 487 Corti's organ, 604 Cortical pyramids of the kidney, 506 Costal cartilages, see Cartilage Covering glass, thickness and optical effect of, 16-7 ; correction for thickness, 17, 104 ; supporting for very delicate objects, 104 Cowper's glands, 550 Crabs, river, for the demonstration of the sarcous elements of muscles, recommended by Eackel, 329 Creosote, 141 ; and methyl-alcohol, 220 ; recommend- ed by Stieda for rendering tissues transparent, 141 ; used by Schwarz, 159 Crouch's stereoscopic microscope, 48 Crown-glass, refraction and color dispersion of, 9- 10 ; lenses, 9 Cryptococcus cerevisire in the digestive apparatus, 437 ; in the urine, 529 Crystalline lens, see Lens of the Eye Crystalloid substances of Graham, 119 Curtis, Dr. E., improvement of illumination, 87 ; improved section-cutter, 108-113 ; substitute for simple microscope, 106 Curvature of the microscopic image, 7, 8 Cutaneous nerves, 372, 375, 376 Cutaneous warts, 558; dry, 269 Cutter, G. R., on American microscopes, 77-82 Cyanin, 158 Cylinder cells of the regie olfactoria, 567 Cylinder diaphragms, 22 ; their application, 22 Cylinder epithelium, see Epithelium Cylinder glasses for reagents. 123 Cystic tumors of the skin, 558 Cystine in the liver, 473 ; in the urine, 529 Cysts, formation of, in the kidney, 521 ; in the ovary, 539 ; in the mammary glands, 544 ; in the skin, 558 Cytogenic tissue, see Connective Substance (reticu- lar) Cytogenous tissue, 275 Damar varnish, 213 Daughter (secondary) cells of cartilage, see Carti- lage Dcane's mounting fluid, 216; preservative fluid, 221 Dean, J., method for examining the central organs, 356 Decalcifying method for cartilage, bone and dental tissues, 293, 296, 297 Decidua of the ovum, 540 ; spuria of menstruation, 542 Defects of the older compound microscopes, 7 Defining powers of a microscope. 56 Deiters on the cochlea, 604 ; directions for examin- ing central organs of nervous system, 35-3 Delomorphous cells, 431 Demodex folliculorum, 560 Dentine, 29S ; cells and their processes, 298 Dermoid cysts of the ovary, 539 Descemet's (Demounts) membrane of the cornea, 577 Deyl, H. Van, made the first achromatic micro- scope,ll Dialyser of Graham, 120 Diaphragms, 22; their effect on a lens, S, of the compound microscope, 22; their use protects the eyes, 84 Diatomacea? as test objects, 61 ; various sorts and their resolution, 61-67 Diatom test-plate of MiHler and Rodig, 63, note Digestive apparatus, 422; material for examination, 422; lips with their glands, 422; mucous mem- brane of the oral and pharyngeal cavities, 422; papillae, 42-3 ; glands, 423 ; nerves, 42-3 ; tongue, 424 ; divisions of its muscular filaments, and methods of examination, 424 ; blood-vessels and lymphatics, 424 ; tonsils and lingual follicles, 425 ; salivary corpuscles, originating in part in the ton- sils, 425; salivary glands, 426 ; methods of Pfluger Heiilenhain, Krause, and Ranvier, 426-27 ; sub- maxillary gland in a quiet and in an irritated con- dition. 427 ; oral cavitv. 428 ; Leptothrix buccalis, 428; Oidium albicans,"429 ; saliva, 429; itsconsti- INDEX. 613 ' tuents. 429 ; salivary corpuscle?, 429 ; granular movements within them, 429; cesophagus, 430 ; stomach, 430 ; methods of examining. 430 ; gas- tric glands, 430 ; double cell forms, 431 ; active and inactive condition, 432 ; covering of the gas- tric surfaces, 432 ; gastric mucous glands, 432 ; tissue of the mucous membrane, 433 ; lenticular glands, 483; muscles and nerves of the mucous membrane, 433; Lovcn discovers the lymphatics of the mucous membrane, 434 ; pathological changes. 434: mammillated condition, 434; hy- pertrophy of the muscular tissue, 435 ; vomited matters, 435 ; constituents, 435 ; acid matters in pyrosis. 430 ; green substances. 4o6 ; rice-water- like matters in cholera, 436 ; bloody matters, 436 ; cryptococcus cerevisiae, 437 ; sarcena ventriculi, 437; Oidium albicans, 437; intestinal canal, 437; cylindrical epithelium, 437 ; Becher cells, 438 ; probable penetration of mucous and pus corpus- cles into these cells, 438 ; immigration of psoro- sperms, 43S : chyle-fat passing the cylinder cells, 438 : method of examining the intestine, 438 ; Brunner's glands, 438-9 ; nature of the mucous membrane, 439 ; process of examination, 440 ; Lieberkuhn's glands, 441 ; muscular tunic of the mucous membrane, 441 ; intestinal villi, 441 ; method of examining, 442 ; muscular tissue of the intestine and submucous tissue. 442; injection of the blood-vessels, 442; natural injection, 444; chyle-vessels, 444 ; their natural and artificial in* jection, 444 ; injection of the lymphatics of the small intestine, 445 ; lymphatic vessels and pas- sages, 446 ; lymphatic follicles, solitary and Peye- rian glands, 447 ; structure and methods of ex- amination, 44S ; parts of the Peyerian follicle, 449 ; blood-vessels, 450 ; lymphatics, 450 ; Peyerian follicles in the vermiform process, 451 ; changes of the intestinal mucous membrane, 451 ; of the Peyerian follicles in disease, 451 ; in abdominal typhus, 452; methods of preservation, 452 ; con- tents of the intestine, 453; chyme, 453; con- tents of the large intestine, 454 ; faeces, 454 ; meccraium, 454 ; faecal matters in disease, 454 ; dysenteric stools, 455 ; cholera stools, 454 ; mat- ters passed in abdominal typhus, 455 ; crystals of the ammonia-phosphate of magnesia, and their significance in fasces, 455 ; crystals of taurine, 455 ; animal parasites, 450 ; Paramecium coli. 456 ; Cercomonas intestinalis, 450; ova of helminths, 456 ; trichina spiralis, 456 : methods of examining the helminthian ova, 456 ; ova of Tricocephalus dispar, 457; Ascaris lumbricoides, 457: Oxjiiris vermicularis, 457; Distomahepaticum, 457, Lan- ceolatum, 457 ; Bothriocephalus latus, 457 ; Taenia solium, 458 ; mediocanellata, 458 ; booklets of the taenia, 45S Dippers work on the microscope, xii Distoma. ova of in fasces (D. hepaticumandlanceola- tum), 457 Dollinger's injections, 173 Bonders explains the action of potash solutions, 133; recommends costal cartilage, 292 Donne publishes an atlas of daguerreotypes, 40 ; dis- covers the Trichomonas vaginalis, 542 Double injection, see Injection. Double knife of Valentin, 107 ; improved form of the English, 107 Double lens, see Lens. Double refraction, weak, its recognition, 50 Double tingeing with carmine and picric acid, 159 ; with carmine and indigo-carmine, 160 : with in- digo-carmine and picric acid, 160 ; with hajma- toxyline and carmine, 100 ; with hasmatoxyline and picric acid, 161 ; Geriach's complicated, 101 Drawing microscopic objects, 36 ; its value, 36 ; directions for, 37 ; apparatus for, 38 Drebbel, Cornelius, as a discoverer of the compound microscope, 7 Drying method, 169 Ductus ejaculatorii, 549 Dujardin, see Illuminating Apparatus Dumb-bells of uric acid, 527 Dysenteric stools, 455 E. Eberth finds the capdlaries composed of cells, 382; investigation of the biliary capillaries, 465 Ebner, von, fibrous nature of bone substance, 302 Ebstein on gastric mucous glands, 433 Elastic fibres in sputum, 496 Elastic tissue, .see Connective Tissue Electric apparatus of Harting, 102 Elementary organisms (cells), ix Elephantiasis, 558 Embedding methods, 113 ; in gum, wax and oil, paraffiae, glycerine and gelatine, transparent soap, albumen and tallow, 113-115 Emboli of the finest vessels, 395 ; from fluid fat, 390 ; from pigment flakes, 395 Emigration of lymphoid ceils from the blood-vessels, 249 ; of the red blood-corpuscles, 248 Enamel organ, see Gelatinous Tissue Enamel, see Teeth Enchondromata, 295 Endostcum, see Bone Endothelium, see Epithelium Engelmann on the termination of the nerves of the voluntary muscles, 364 ; on the termination of the gustatory nerve of the rabbit, 563 Eosin tingeing, 155 Epidermis (see Epithelium), 256, 266 Epididymis, 547 ; its ciliated cells, 547 Epiphytes. 559; their examination, 559 Epithelial cancer, 270, 2S9 Epithelium (and endothelium), 256; pavement cylin- der, ciliated and pigment, 256 ; endothelium, 256 ; method «>f demonstration, 257; simple pavement (endothelium J, 258 ; silver impregnation, 258 ; bluing of the cement ledges, according to Arnold and Thimia, 259; examination of pigment-cells, 260 ; molecular movement of the pigment granules, 260; cylinder epithelium, 260; porous canals on cylinder-cells, 261: methods of preserving, 262; ciliary movement, 262 ; choice of suitable mate- rial, 262 ; fluid media. 263 ; microscopic image of the ciliary motion, 263 : movement reproduced by dilute alkalies, according to Virchow, 264 ; forms of the movement, according to Purkinje and Val- entine, 205; statements of Engelmann, 265; diffi- culty of the examination in warm-blooded verte- brates and man, 265 ; obtaining ciliated cells in acute catarrh of the nose and respiratory passages, 265 ; stratified pavement-epithelium and epider- mis, 266 ; stachel and riff-cell6 of the deeper layers, 266 : method of examination. 266 ; action of potash solutions, 267 ; chloride of gold, 268 ; method of preservation, 269 ; epithelial new formations of a pathological nature, 269 ; indurations and warts, 269 ; pearl-like tumors and concentric bod- ies of the thymus, 270 ; epithelial cancer (can- croid), 270 ; epithelial cells of the organs of sense — see these Epizoa. 560 ; their examination, 561 Ether dissolves fat and Canada balsam, 141 Eustachian tube, 602 Examination with the microscope. 8-3 ; with magni- fying powers of increasing strength, 94 Exostosis, 313 Exudation-cylinders of the uriniferous canals in Bright's disease, 520 ; in the urine, 523 Exudations, asserted organization of, 288 Eye-ball, ■see Organ of Vision, 572 Eye-lids, 572 Eye-piece micrometer, 32 ; its action, 34 ; valuation of its divisions, 34 : dependence of the same on the objectives, 34; with screw, 32; improved by Mohl, 33 Eye-pieces of the oldest compound microscopes, 6 ; of the improved instruments, 11 ; designation ac- cording to their strength, 14 ; shortening with the increase in strength, 14; ordinary (negative) of Huygens, 14 ; positive of Ramsden, 15 ; orthoscope of Kellner, 15 ; holosteric, 15 ; aplanatic, 15 ; under corrected, 16; position of the lenses in an eye- piece, 16 ; use of weak eye-pieces, 89, 90 ; limits of the use of strong eye-pieces, 90 ; uselessness 614 INDEX. of very strong ones, 90; image-inverting ocu- lar of I-Iartnack. % : spectroscopic of Hartnack, Zeiss, anil Herz, 51, 52 Eye, see Organ of Vision, 572 ; hypermetropic, 3 ; myopic, 3; as a camera obscura, 1 ; protecting the, in microscopic work, 84, 98 F. Farrant's mounting fluid, 210 Fat cells, see Fat Tissue Fat emboli in the capillaries, 396 Fat tissue, 278 ; demonstration, 278; crystallization of contents of cell, 270 ; blood-vessels, 279 ; mount- ing, 279 ; new formation as lipoma, 278 Fatty acids, crystals of in pus, 253 ; in fat cells, 279 Fatty degeneration, see the several organs Fatty liver, 470 Favus crusts, 560 ; fungus, 500 Fermentation of pus, 253 ; of urine, acid, 526 ; alka- line, 529 Fermentative fungus in the stomach, 437; in acid urine, 526 ; in alkaline, 529 Ferrocyanide of copper, 189, note Fibre-cells, contractile, see Muscles Fibrin, 239 ; coagulation of, 239 ; cylinder, see Exu- dation-cylinder Fibroid, consisting of connective tissue, 289 ; of the uterus, 541 Field, flattening of, by the collective lens, 12 Field of vision, rendering the same plain, and correc- tion of the image by the collective lens, 12 Finder (indicator), 230, note Flakes, containing blood-corpuscles, of the spleen, 481 Flattening the field by the collective lens, 12 Flemming's transparent soap, 114 ; on connective- tissue cells, 284 Flint glass, refraction and color dispersion of, 9 ; lenses, 10, 49 Fluid media for microscopic preparations, 117 ; in- different, 118; more active ones, 121; their opti- cal effects, 121 ; action on certain elementary forms, 117; importance of truly indifferent ones, 117; requirements of such, 118; crystalloid mat- ters, 119; colloid substances, 119; combination of both, 120; iodine serum, 121 Follicular chains of the ovary, of Pfluger, 537 Follicular tumors of the skin, 458 Fontana, asserted inventor of the microscope, 7 Food, remains of, in the saliva, 429; in vomited matters, 435; in the small intestines, 453; in the freces, 454 Forceps, 105 Forked cells of the lingual papilla?, according to Engelmann, 564 Formic acid in combination with glycerine, recom- mended by Ranvier as a mounting fluid. 216 Forster isolates bone corpuscles with strong mineral acids, 297 Fovea centralis of the retina, 000 Freezing method for obtaining fine sections, 171 Frerichs on liver diseases, 409 Frey, testing lenses, 68 ; recommends anilin red for tingeing, 154; and for the axis-cylinder, 337; on purpurin, 155 ; on eosin, 155 ; anilin blue, 157 ; panne soluble, 157; haamatoxyline solution, 158; cold-flowing injection masses, 186, 189; carmine for injections, 184 ; sulphate of baryta, 179, 1SS ; recipe for chloride of silver, 180 ; for a watery Prussian blue for injecting glandular canals, 189, note; improved turntable, 212 ; very dilute acetic acid for muscular nerves, 130, 365; on biliary capillaries, 405 ; on lymphatics of the thyroid gland, 497 ; on absence of lymphatics in the thy- mus, 501 ; on lymphatics of the trachoma glands, 574 ; on injections of the uriniferous canals, 513 Frustulia Saxonica as a test object, 03 Fuchsin, see Anilin Red Fuhrer recommended chloride of iron for hardening spleen, 137 Fungus, filamentous, of the mouth (Leptothrix buc- calia), 428 G. Galilei, asserted inventor of the microscope, 7 Ganglion cells, see Nervous System ; layer of the retina, 596 Gas chamber of Strieker, 100 Gastric carcinoma (false), 435 Gastric glands, 430 Gastric mucous glands, 432 Gastric mucus, 432 Gegenbaur's osteoblasts, 303 Gelatine as an injection mass, 174 ; varieties, 175 Gelatine with glycerine, 175 Gelatinous tissue, 274 ; varieties, 274 : vitreous body, 275; enamel organ, 275; methods of examination and preservation, 275 ; new formations, myxoma, 289 Generation, female organs of, 533 ; structure of the ovary, its stroma and follicles, 533 ; the ovum, 533; its constituents and the methods for its in- vestigation, 534; the germ, 535; development of the follicle, 536 ; Pfluger's observations, 537 ; rup- ture of the follicle, 538 ; formation of the corpus luteum, 538 ; its ultimate fate, 539 ; crystals of ha;matoidine in it, 539; pathological conditions of the ovary, 539 ; ovarial cysts, 539 ; with the structure of the skin, 539 ; oviducts, 540 ; uterus, 540 ; mucous membrane and glands, 540 ; muscu- lar portion, 540 ; pathological conditions of the uterus, 541 ; fibroid tumors, polypi and carcino- mata, 641 ; vagina and external genitals, 541 ; secretion of the cervix uteri, 541 ; vaginal mucus, 542; trichomonas vaginalis. 542 ; menstrual blood, 642 ; lochial secretion, 543 ; lacteal glands, 543 ; development, 543 ; of the male and female, 544 ; pathological conditions, 544; cysts and adenoid tumors, 544; methods of examining the organ, 544 ; milk, 545 ; milk-globules, 545 ; colostrum corpuscles, 545 ; methods of examining the milk, 546 Generation, male organs of, 546 ; testicles, 546 : semi- niferous canals, corpus Highmori, 540 ; epididymis, 547; blood-vessels, 547; lymphatics, 548; patholo- gical new formation of the testicle, 549 ; methods of injection and examination, 548 ; ductus ejaculatorii, 549 ; prostate, 549 ; its concretions. 549; Cowper's glands, 550 ; cavernous organs, 550 ; seminal fila- ments, 550 ; movements, action under reagent?, 551 ; development, 552 ; preserving the filaments, 553 ; recognition of the same in seminal stains, 553 Gerlach, photographing apparatus of, 41 ; increase of magnifying power by means of photography, 45; inventor of carmine tingeing, 147 ; studies on nerve terminations in transversely striated muscles, 366; application of chloride of gold and potash, 357 ; complicated tingeing, 161 ; carmine injection, 183 ; injections of bones. 301 ; method of examin- ing the tactile bodies, 370 ; of injecting the semi- nal canals, 548 Germinal spot and vesicle, see Ovum Gianuzzi on the submaxillary gland, 427 Gillavry, Mac, on biliary capillaries. 405 Gingival papilUe, 423 Gland capillaries, see Glands Glands. 410 ; structure, membrana propria, cells and vessels, 410 ; tubular glands, 411 ; coil-shaped, 411 ; racemose, 412 ; their vascular net-work, 412 ; closed gland capsules, 413; capsules of the ovary, 413; blood vascular glands, 414; thyroid gland, 414; lymphatic glands, 414; gland-cells, 414; their ori- gin in the corneous and intestinal gland layers, 414 ; arrangement, 416 ; in mucous and serous glands, 416; perishable nature, 410 ; formation of the secretion, 416 ; physiological destruction of the cells in many secretory processes, 416 ; method of examination, 417; injections, 4i9; finest gland canalioules or gland capillaries, 419 ; examination of foetal glands, 420; pathological changes, 420; INDEX. 615 participation of the frame-work, 420 ; of the cells, 420 ; new formation of gland tissue, 421 Gland tissue, see Glands Glass boxes, 104 ; quadratic, 103; larger, for cover- ing the specimen, 93 Glass cells, 223 Glass micrometer, 33 ; its divisions, 33 ; as an object slide (objective micrometer), 33 : in the eye-piece, 33-34 Glass prisms, 38, 4G-47 Glass rod, its appearance in various fluid media, US Glioma of the brain, 360 ; of the retina, 601 Glycerine as a medium for rendering tissues trans- parent, 118: index of refraction, 118; for wet mounting, 215 ; with water and muriatic acid, 215 ; with acetic acid, 210 ; with formic acid, 216 ; with carbolic acid, 216 : with gelatine, 114, 216, 284; with tannin, 216; gum-arabic and arsenious acid, 216 ; carmine, 149, 151 Goadby's fluid, 217 Goitre. 499 Gold, chloride of, 137, 166; and potash, 137, 168; and soda, 137, 16S Gold size, 228 Goniometer of C. Schmidt, 36 Goodsir, J., discovers Sarcina ventriculi, 437 Graafian follicle of the ovary, 533 Graham on colloid and crystalloid substances, 119 Grammatophora subtillissima, 62, 66 Grandly, composition of the axis cylinder of the Pacinian corpuscle, 377 Granulations, 288; in Bright's disease, 521 Granule cells, 495 Granule layer of the retina, 596 Growths, horny, of the skin, 269 Grunow, J., sketch of, 79 Gum with glycerine, 216; for embedding, 113; as an addition to chromic acid, 129 Gustatory cells, see Gustatory Organ Gustatory organ, 562 ; nerve distribution, 562 ; dis- covery of the nerve distribution in the gustatory buds, 583 ; in the papillao of the frog's tongue, by Schultze, Key, Engelmann and Wyss, 563; gusta- tory cells, 563 ; forked cells of Engelmann, 564 Gustatory papillae of the frog's tongue, 504 Gutta-percha cement, 224; cells, 222 H. flackel recommends crabs for the demonstration of the sarcous elements of striated muscles, 329 Heematine crystals, 243 Haemato -crystalline, 241-242 Hasmatoidine crystals, 244; in ruptured Graafian follicles, 539 Hematoxyline, 158 ; with carmine, 160 Hematoxylin e solution, 158 HEemoglobine crystals, 241 Hagen on American microscopes, 77 Hair, 270 ; method of examining, 270 ; hair sac, 271; shaft and bulb, 271 ; root -sheath, 271; epi- dermic covering of the hair, 272; transverse sec- tion through the hair, 272 ; cells of the external root-sheath. 271 ; fcetal hairs, 273 ; mounting methods, 273 ; in dermoid cysts of the ovary, 539 ; their origin, 539 ; diseases, see Skin ; fungi, 559 ; hair sac mite, 560 Hannover recommends chromic acid, 126 Hardening by chromic acid, 126; directions for, 127: chromate of pota.sh, 135; picric acid, 132; alcohol, 138; freezing, 171 Harting, his work on the microscope, xi., xii. ; in- vestigates the question of the invention of the compound microscope, 7 ; explains the action of the immersion system, 59 ; electric apparatus, 102 ; recommends weak solutions of sublimate for pre- serving, 219; chloride of calcium, carbonate of potash and aqueous solution of creosote. 219, 220 ; on the refractive power of fluid media, 117 ; direc- tions for making chrome-yellow and carbonate of lead, 179 ; Prussian blue in oxalic acid, 182 ; from sulphate of iron and ferro-cyanide of potash, 182 ; j tin case for injecting, 196; gutta-percha cement, 224 ; india-rubber cement, 225 Hartnack, his holosteric eye-piece, 15 ; stereoscopic, 48 ; image inverting, 96; spectral apparatus, 51 ; flint-glass lens over the polarizer, 49; improves the analyzer, 49; his lenses and their angles of aperture, 60 ; immersion systemg, 60 ; their angles of aperture tested by Harting, 59 ; action with tesr, objects, 65-68 ; resolve the lines of the suri- rella gemma into hexagonal area?, 66; large horse- shoe stand, 27-28, 69, 85 ; the smaller stand, 30, 70 ; other instruments, 71 ; his lamp, 86 Hassal's concentric bodies of the thymus, 270, 500 I Haversian canals and spaces, see Bones | Heart, branched muscular fibres of, 322; position of i the nuclei in the Earcous substance, 322 ; nerves of I the heart, 368 Heidenhain, his method of tingeing with carmine, 152; with aniline blue, 157 ; on cartilage capsules, 294 ; on salivary glands, 427 ; on gastric glands, 430-431 ; on the pancreas, 459; on the structure of the kidney, 511. 534 Helminthian ova In the feces, 456 Henle recommends ' strong muriatic acid for the urinifcrous canals of the kidney. 125 ; investigates the course of the urinifcrous canals, 503 Henocque's method of impregnation with gold, 167 Henson on the structure of the muscular filament, 330 ; examination of the nerve termination in the tail of the frog's larva, 372 ; method with the coch- lear canal, 605 Bering's apparatus for injecting by constant pres- sure, 196 ; examination of the biliary capillaries, 465 Herpes tonsurans. 559 His, brushing method, 115 ; silver impregnation, 137, 164; adenoid tissue, 275; work on the cornea, 577 ; on the thymus, 499 Histology of the normal and abnormal body, and its significance, xi Hoffmann's indicator, 230, note Holosteric eye-piece, 15 Hornlayer of Remak. 414 Howship's lacuna} of the bones, 314 Hoyer, Ms yellow transparent coloring matter, 185; discovers the structure of the capillaries, 382 ; and Cohnheim discovered the penetration of corneal nerves into the epithelium, 370-371 Huyghen's negative eye-piece, 14 Hyaloidiscus subtilis, recommended by Bailey as a. test object, 63 Hyperosmic acid, see Osmic Acid Hypertrophies, -see The several organs Hypophysis cerebri, 379 Hypoxanthine (sarcine) in the liver, 472; in the urine, 530 Hyrtl, history of injections, 173; resinous masses and their use, 174 ; gelatine masses, 174 ; cold- flowing masses dissolved in ether, 176 ; recom- mends colors in tubes for injections, 177 ; punc- turing method, 201 ; examines the kidneys, 502, 514 Illuminating apparatus of Dujardin, 23 ; of Lieber- kuhn, 87 Illuminating lens for opaque objects, 21 Illumination by incident light, 21, 87 ; by trans- mitted, 21, 83 ; by artificial, 86 ; by central, 22; by oblique, 22; employment of central illumination, 84; with cylindrical and rotary diaphragms, 22 ; with a condenser, 23 ; of the field depends on the condition of the sky, 84; method of improving, used by Dr. Curtis, S7 Image, aerial, of the compound microscope, 6 ; of the improved. 13 Image diatortion, S Image inverting microscope, 06 ; eye-piece, 96 Image of the compound microscope, 6, 7 ; clearness of the same increased by the field glass, 11-13; curved, of the simple compound microscope, 7 ; 616 INDEX. enlarged, 7 : inversion of the same by the micro- scope, 6, 94 Images, microscopical, peculiarities of, 94 ; their re- lations of height and depth, 94; judging of the form from these, 94 ; value of weak objectives thereby, 95 ; increased difficulty of their apprecia- tion from extreme diminutiveness of the bodies, 95: appreciation of their relations of relief, 95; "Welcker's directions for this purpose, 95 Immersion lenses, 58 ; of Hartnack, 58 ; of Towell and Leland, 60 ; their action explained and tested by Harting, 59 Increase of the magnifying power by photographic means, 45 Indicator (object-finder), 230 ; Hoffmann's arrange- ment, 230. note Indigo carmine, 15'i Indurations, 269 Infarction, hemorrhagic, of the spleen, 483 ; uric acid, of the kidney, 521 Inflammatory globules, 495 Infundibula of the lungs, 4S7 Injection clamps (serres fines), 19S Injection masses for glandular canals, 189, note Injection material for the blood-vessels, 198; organs which are fresh, and those which are older and have been in alcohol, 198 ; for lymphatics, 199 ; for glandular canals, 199 Injection methods, 173; with hardening, 174; and cold-flowing masses, 174; resinous masses, 174; their preparation according to Hyrtl, 174; gelati- nous masses, 174 ; their superiority, 174 ; their preparation, 175; treatment of preparations in- jected with gelatine, 176; cold-flowing mixtures containing glycerine, alcohol, and water, 176 ; their superiority, 177 Injection mixtures, cold-flowing, with Beale's Prus- sian blue, 186 ; with Richardson's blue, 187; with Muller's blue, 188; with Beale's carmine, 188 ; with sulphate of baryta, according to Frey, 183 Injection of the brain and spinal cord, 358 Injection of the several organs, see these Injection procedure with blood-vessels, 198 ; with lymphatics, 199; with lymphatics by the punctur- ing method of Hyrtl and Teichmann, 201 ; with thin-walled parts. 201 ; with glandular passages, 199; filling the syringe during the injection, 200 ; forcing in the mass, 202 ; ligation of the vessel, 200 ; closing the canule, 200 ; completion of the injection, 203 ; double injection of the blood-ves- sels, 203 ; injection of the blood-vessels and lym- phatics, 204 ; after-treatment of the injected ves- sels, 205 ; hardening the preparations, 205 ; mount- ing methods, dry and wet, 206 Injections double, see Injection Methods Injection, spontaneous, of the living animal, accord- ing to Chrzonszczewsky, 190 ; with carmine and indigo carmine, 191 ; of the lymphatic glands with aniline blue, according to Toldt, 405 Injection syringes, 196; their canulcs, 196; their management, 197 ; tying in the; canule, 200 ; fill- ing the syringe, 202; management of the piston, 202 ; closing the canule, 203 Injections, their importance for histological work, 172; the art in its infancy, 173 ; in its present con- dition, 113 ; colors for, 177-188 ; the granular pro- duced by precipitations in the vessels, 178 ; colors in tubes, 177 ; red, cinnabar, 177 ; yellow, chrome yellow, 17S ; white, lead and zinc white, sulphate of baryta, 179 ; chloride of silver, 180 ; transparent, 180 ; Thiersch's Prussian blue, 181 ; Prussian blue in oxalic acid, 181 ; Prussian blue from sulphate of iron and cyanide of iron and potash, 182,; soluble PrusHinn blue, 183 ; O-erlach's carmine mass, 183 ; Frey's method, 184; Thiersch's transparent yellow, 185 ; Hoyer's, 185 ; Robin's yellow, ISO ; Thiersch's transparent green, 186 ; Beale's ordinary blue for cold-flowing masses, 186 ; Beale's best blue, 187 ; Richardson's blue, 187; MuUer's, 1S8 ; Beale's car- mine, 188 : Frey's baryta mass, 188 ; Hyrtl's colors with resinous masses, 174 Injection with constant pressure, 192; with the glass tube and column of fluid, 192; with mercu- rial pressure, 193 ; with compressed air, 195 ; Harting's injection chest, 196 ; Hering's appara- tus, 196 Intercalary piece in the cortex of the kidney, 509 Intergranular layer of the retina, 593 Intestinal contents, 453 ; ganglia, 345 ; glands, 441 ; villi, 441 Intestinal gland-layer, 414 Intestines, 437 (see Digestive Apparatus) Inversion of the microscopic image, 6 Iodine, 132; with sulphuric acid, its action on amy- lon, amyloid, cellulose and cholesterine, 124 ; va- por, according to Rollett, 132 lodine-scmm of Schultze, 121 Iris, 584, 586 Iron, chloride of, 137, 183. 186, 187 ; sulphate of, for making Prussian blue, 182 ; tincture of chloride of, 186, 187 Itch, the, 560 ; mite, 561 J. Janssen, inventor of the compound microscope, 7 Javelle water (hypochlorate of soda), 135 Juice canals of Recklinghausen, 400 Juice clefts of "Waklcycr, 400 Jurgen's reagent for amyloid, 155 Kellner's microscope, 70 ; orthoscopic eye-piece, 15 Key confirms the connection of the muscular fila- ments of ihe tongue with connective tissue cor- puscles, 424 ; with Schultze discovers the termina- tion of the gustatory nerves, 564 Kidney (urinary apparatus), 502 Kidneys, Bright's disease of the, 520 Klein's method of gold impregnation, 371, 581; method of examining the spleen, 478 Knives, 105 Kbllikcr describes the osteoclasts, 314 ; recommends very dilute acetic acid for muscular nerves, 130, 305; ver}' dilute muriatic acid, 365; very dilute nitric acid, 365; on cytogenous tissue, 275; re- commends boiling the thymus, 501 ; follows the lymphatics in the tail of the frog's larva, 409 ; ex- amines with Scanzoni the mucus of the female genital organs, 542 Kollniann's carmino mass, 1S9, note Krause, W., examination of the nerve terminations in muscles, 304 ; recommends dilute acetic acid for muscular nerves, 365 ; discovers the terminal knobs, 372 ; recommends dilute acetic acid for the latter, 373 ; uses molybdenate of ammonia for the salivary glands, 426 Kuhnc recommends very dilute sulphuric acid for muscular nerves, 365; nitric aeid and chlorate of potash for isolating muscular fibres, 323 ; investi- gation of the cornea, 369, 57S Kutschin recommends creosote, 141 ; his double tingeing, 161 L. Labels, placing them on the object slides, 231 Lambl's cercomonas intcstinalis, 456 Lamina clastiea anterior of the cornea, 577 ; of the choroid, 586; spiralis of the cochlea, 605 Landoisuscs fuchsinc for cartilage, 29-1 Lardaccous liver, 474 Larynx, 485 Lead, carbonate of, 179 Leber's impregnation with Prussian blue, 169 Lcgros uses hyposulphite of soda for objects im- pregnated with silver, 162 Lchuiunn on crystuls of muriate of hamiatine, 242 INDEX. 617 Lena combination, inserted in the stage, 23 Lens (double) achromatic, of crown and flint glass, 9 ; applied to the microscope by Van Deyl and Fraunhofer, 11 ; aplanatio, 10 ; over and under corrected, 10 Lens of the eye, 587 ; its capsule, 587 ; fibres, 588 ; changes in disease, 589; development, 589 Lenticular glands, 433 Leptothrix buecalis, 438 ; in faeces, 454 Leucaemia, 236 Leucine from the liver, 472 ; in urine, 529 Lieberkutm's injections, 173 ; arrangement for illu- mination, 87 ; glands, 441 Light, central and oblique, 22, 85 ; polarized, 48 Lime, carbonate of, its crystals suitable objects for the study of the molecular motion, 97 ; in the organ of hearing, 602 ; oxalate of, in urine, 527 ; in the exudation cylinders of Bright's disease, 524 ; infarctions of the kidney, 522 ; lime-water used by Rollett for connective tissue, 134 Line, Paris, reduced to millimetres, etc., 35 Lingual follicles, 425 Lipoma. 27S Lips and their sebaceous follicles, 422 Liquid stove-polish, a substitute for Brunswick black, 227 Lister and Turner on the inner circle of the trans- verse section of the nerve tube, 330 Liver, 460 ; cells, 460 ; lobules, 461 ; methods of de- monstration, 461 ; transverse section of a lobule, 461; blood-vessels and injections, 462; capillary net-works and their cells, 462 ; membrana propria, 464; finest biliary passages, 464 ; their injection, 464 ; lymphatics, 467 ; nerves, 468 ; Pfluger's latest process, 468; bile, 46S; its normal constitution, 468 ; sediments, 469 ; cholesterin, 469 ; bilirubin, 469; pathological changes of the liver, 469; hy- pertrophy, 469 ; brown molecules of the hepatic cells, 470 ; deposits of fat in the hepatic cells, 470 ; method of examining fatty liver, 470 ; fatty de- generation, 471 ; destruction of the liver in acute yellow atrophy, 471 ; chemical constituents of the diseased liver, 472 ; tyrosine, 472 ; leucine, 472 ; hypo xanthine (sarcine), 472 ; xanthine, 473 ; cys- tine, 473 ; emboli of the hepatic vessels by pig- ment flakes in inelanamiia, 474 ; amyloid degenera- tion (waxy or lardaceous liver), 474 ; examination of the amyloid substance, 474 ; tubercles, 475 ; cirrhosis, 476 ; carcinoma, 476 Lochial secretion, 542 Loupe, 4 ; stand, 4 Lovin'a discovery of lymphatics in the gastric mu- cous membrane, 434 ; the gustatory buds of the tongue, 563 Ludwig and Tomsa on the lymphatics of the testicle, 548 ; L. and Zawarykin on the kidneys, 504 Luer's injection syringes, 196 Lungs (respiratory apparatus), 485 ; vesicles of, 487 ; epithelium, 486 ; fibres of in sputum, 496 ; capil- lary loops, 4S9 Lymph, 249 ; how to obtain it, 249 ; cells (corpus- cles), 250 ; mounting, 250 Lymph corpuscles in lymphoid organs, 402 ; in the mucous membrane of the intestines, 439 ; in the spleen, 480 ; in the thymus, 499 Lymphatic glands, 402 ; methods of examination, 402 ; Toldt's method, 403 ; framework, 403 ; in- jections, 404 ; puncturing method, 404 ; natural injection, 405 ; treatment of chyle glands filled with fat, 405 ; pathological and other changes, 406 ; fat-cell tissue, 406 ; pigmentations, 406 ; melanosis, 406 ; anthracosis, 407 ; bronchial glands, 407 ; connective- tissue metamorphosis, 407 ; anatomical conditions in abdominal typhus, 407 ; in tubercu- losis and scrofula, 408; inflammatory conditions and hypertrophies, 408; value of injections in these cases, 409 ; development in the foetus, 409 Lymphatics, 398 ; structure and examination of the larger and smaller trunks and lacunae, 399 ; silver impregnation, 399 ; injection, 399 ; lacteals, 400 ; new formation of lymphatics in neoplasms, ac- cording to Krause and Neumann, 401 Lymphoid cells, 234 Maceration in acids, of connective tissue, 283 ; of bones and teeth, 296 ; of the muscles, 318 ; of the kidneys, 507 Macula lutea of the retina, 600 Magnifying glasses known even in the middle ages, 7 Malmsten's Paramecium coli, 456 Malpighian vascular coil of the kidney, 504 ; cor- puscles of the spleen, 479 ; pyramids of the kid- ney, 502; rete mucosum of the skin, 554 Mammilla ted condition of the gastric mucous mem- brane, 434 Margo examines the nerve termination in the mus- cles, 364 Marine glue, 224 Masklack, black, 229 Mastic in chloroform, 213 McAllister ou American microscopes, 77 Measure, units of, for microscopic determinations of size, 35 Measures, microscopic, 33-36 Measuring apparatus, microscopic, 32-35 Measuring cylinder, 142 Meconium, 454 Medullary rays of the kidney, 506 Meibomian glands, 572 Meissner discovers the ganglionic plexus in the sub- mucous tissue of the digestive canal, 345 Melanasmia, 236 ; condition of the liver and spleen in, 4S4 ; condition of the cerebral vessels in, 396; emboli of the hepatic vessels, 474 ; of the kidneys, 519 Melanine, 256, 585 Melanosis (and anthracosis) of the bronchial glands, 406-407 ; of the lungs, 490, 491 Membrana limitans interna of the retina, 593 ; ex- terna, 593 Membrana propria, see Glands Membrana tympani, 602 Menstrual blood, 542 Mentagra, 559 Mercury, chloride of, 137, 219; with alum and chlo- ride of sodium, 217 Mercury, column of, for injecting, 193-194 Merz microscopes, 25, 77 Metallic impregnations, 162 ; nitrate of silver, 162; other silver salts, 164 ; osmic acid, 164 ; osmiamide, 166; chloride of gold, 166; chloride of gold, potash, and soda, 168; chloride of palladium, 168; Prus- sian blue, 169 Methyl alcohol, 140 ; as a constituent of cold-flowing injection mixtures, 187; of preservative fluids, 220 Meyer, H., recommends sulphuric acid for separating the epidermoid covering of the hair, 271 Mica scales, 51 Micrococcus of Hallier, 254 Micrometer eye-piece, 32-34 Micrometers, 32-33 Micrometer screw, 21 Micromillimctre, 35 Microscope, compound, selection of, 69; arrangement of, 11 ; simplest form of , 6, 7; improved form 11, 18; tube, 20 ; objectives, 13,14, 18 ; eye-pieces, 14, 15, 16, 18 ; mirror, 21 ; diaphragms, 22 ; condensers, 23 ; use of the instrument, 83 ; illumination, 83 ; posi- tion hi the room, 83 ; cutting off incident light by a dark screen, 83 ; illumination dependent on the condition of the sky, 84 ; oblique and artificial illumination, 85-86 ; lamps, 86 ; illumination with incident light, 87 ; adjustment. 88 ; caution in the use of reagents, 91 ; cleaning the glasses, 92 ; test- ing, 53 ; the magnifying power, 53 ; the spherical and chromatic aberration, 545 ; the flatness of the field, 55; defining power. 56; penetrating power, 57; value of the optical portion, 70; of the me- chanical portion, 70 Microscope, invention of the compound, by Janssen, 7 ; claimed by Drebbel, Fontana, and Galilei, 7 Microscope, its importance for the physician, ix. ; lit- erature of, xii 618 IHDISX. Microscope lamps, 86 Microscope makers, price lists of, see Appendix Microscope, oldest compound, its invention, 17; its incompleteness, 17 Microscope, simple, 5 ; its arrangement (stand, stage, mirror, etc.), 5; of importance only for making preparations, 0; instruments of Hossel and Nachet, 5 ; Dr. Curtis 1 substitute for, 106 Microscopes, American, 77-82 Microscopes, compound binocular, 47 ; of Nachet, 47 • multocular, 47 ; photographic, 41 ; polarizing, 49 ; stereoscopic, 47 ; of Crouch, 48 ; Riddell, 47 ; Wenham's arrangement, 47; of Nachet, 48; Hart- nack's arrangement, 4t> Microscopes, improvements of, by van Deyl, Fraun- hofer. Selllgue, Chevalier, Amici, 11 Microscopes of various makers, 71-77 ; American, 77-82 Microscopic vision, x, 84, 94 Microscopist, qualifications of the, 93 Microspoi-on of Klebs, 254 ; Audouini, 559 ; nienta- grophytes, 559 ; furfur, 500 Microtomes, 108 ; Schiefferdecker's, 108 ; Curtis, 108; Seller's, 113 Miliary tubercle of the cerebral vessels, 378 ; of the spleen, 483 ; of the lungs, 492 Milium, 559 Milk, 545 ; globules, 545 ; glands, 543 ; new forma- tions of, 544 Miller, L., notice of, 81 Millimetre reduced to Paris lines, etc., 35 Mineral acids, 123 Mirror of the simple microscope, 5 ; of the compound microscope, with a plane surface, 21, S4 ; with a concave surface, 21, 84 Mixture of Muller, 136 ; of G-oadby, 217 ; of Pacini, 217; of others, 216-221; cold- (lowing for injec- tions, 174-180, 186 ; hardening, 174 Moderation of the light, 84, 94 ; moderation of the lamp-light by bine glasses, 86 Moderator lamp, 86 Mohl, work on the microscope, xi., xii. ; recom- mends the condenser for the polarizing micro- scope, 50 ; an improved screw micrometer for the eye-piece, 33 ; the scales of the Papilla Janira as a test object, 61 Moitessier on micro-photography, 40 ; his photo- graphic apparatus, 42, 43 Molecular movement of small bodies, see Brunonitm Movement Moleschott recommends a strong and a weak mix- ture of acetic acid and alcohol, 139-140 ; potash solutions, 133 ; investigates the action of potash so- lutions on epithelium, 267 ; on smooth muscles, 318 Molier's preparations, 232 ; diatomic test-plate, 63, note Mulybdate of ammonia, 137 Mother (primary) cells in cartilage, 292 Mould formation in urine, 529 Mounting media, 20G ; resinous. 20S-214 ; fluid, 215 ; simple, 215 ; complicated, 216-221 Movement phenomena, vital, 97 ; amoeboid of the cells, 98 ; of small bodies, 97 ; molecular, 97 Mucous corpuscles (lymphoid cells), 250 ; origin, etc., 250 ; their preservation, 251 ; of the oral cavity (salivary corpuscles), 425 ; in vomited matters, 430 ; in the small intestine, 439 ; in the evacua- tions of pyrosis and cholera, 436, 455 ; in sputum, 495; in fpeces, 453; in urine, 523; in the vaginal mucus, 542; iu the nasal mucus, 566 Mucous glands of the mouth and pharynx, 422 ; of the small intestines, see Brunner's Glands ; sub- maxillary as a mucous gland, 427 Mucous membrane of the digestive organs, 423, 430, 439 ; of the respiratory organs, 485 ; of the blad- der, 522 ; of the nose, 565 Mucus, 250 Mnguet (thrush), 429 Muller, H., reenmmends chromic acid with muriatic acid for decalcifying, 293; on the retina, 597; M. and Sumisch examine the corneal nerves, 370 MiiUer, W., his Prussian blue, 188 ; brown injection fluid, 189, note ; studies on the spleen, 482 Miiller'a fluid, 136 Multipolar ganglion-cells, see Nervous System Muriatic acid, concentrated, 125 ; strong, 125 ; di- lute, 126 ; use of the strong acid for the urinifer- ous canals, according to Henle and others, 125; in extreme degrees of dilution, 120 Muscles, 316; smooth and striated, 316; form and physiological condition, 310 : method, of examin- ing the smooth, 316; contractile fibre-cells, 317; their isolation, 317; with nitric and muriatic acids, 318 ; dilute acetic acid and acetic acid mix- ture, 318 ; potash solutions, 318 ; solutions of common Bait, 319 ; degeneration and new forma- tion, 319; striated, 319; methods of examination, 319 ; recognition of the sarcous substance, 326 ; of the nucleus, 320 ; of the sarcolemrna, 321 ; rela- tions, 321 ; transverse sections of the muscular filaments, 321; their isolation, 322-324; chemical accessories, chlorate of potash with nitric acid, according to Kuhne and von Wittich, 323; very dilule sulphuric acid, 823; by heating in hermeti- cally sealed glass tubes, according to Rollett, 324 ; by concentrated muriatic acid, according to Aeby, 324 ; by potash solutions, 324 ; relation to the ten- dons, 324 ; method of demonstration, by Weismaun, with potash solutions, 324 ; pointed muscular fila- ments, 325 ; capillary vessels, 326; nerve termina- tions, see Nervous System; explanation of the longitudinal and transverse markings, 327 ; fibrilla theory, 327 ; Bowman's theory, 32S ; sarcous ele- ments, 328 ; studies with reagents, 329 ; sarcous elements of the fly, according to Amici and Prey, 328 ; new investigations of Krause and Hensen, 330 ; double and single refracting strata, accord- ing to Briicke, 331 ; origin of the striated muscle, 331 ; fatty degeneration, 331 ; pathological changes, 332 ; trichina, 332 ; their capsules, 333 ; examina- tion of trichinized muscles, 333 ; typhus metamor- phosis, according to Zenker, 332 ; mounting pre- parations, 334 Muscular fibres in vomited matters, 435 ; in fasces, 454 Myeline, 361 Myxoma, 289 N. Nachet's microscopes, 25, 81, 74 Naavi, vascular, 558 Nail fungus, 559 Nails, 269; human nails without reagents, 269; with alkalies and sulphuric acid, 269 Nasal catarrh, 565 Nasal mucous membrane, 565 Nathusius reduces gold preparations with sulphate of iron, 167, 268 Navicula affinis, 63, note ; Amicii, 62. 66, note ; rhom- boides (sporangia! form), 66 Near point, 3 Negative (Huyghenian) eye-piece, 14 Negative, photographic, 45 Nerve cells, see Nervous System Nerve corpuscles of the genitals, 557 Nerve fibres, see Nervous System Nervous system, 334 ; elements of. 334 ; nerve-fibres, 334 ; ganglionic or nerve cells, 334 ; constituents of the nerve-fibres : axis cylinder, medulla, primitive sheath, 334 ; suitable localities for examination, 334 ; homogeneous nerve-fibres, 335 ; coagulation of the medulla, 335 ; its nature, 335 ; action of reagents, 336; axis cylinder, 336 ; chemical accessoriesforits demonstration, 337-338 ; nitric acid and chlorate of potash, according to Budge andTJechtntz, 337 ; col- lodium, according to Piiuger, 337 ; chloroform, ac- cording to Waldeyer, 337 ; aniline red, 337 ; metal- lic impregnations, 338 ; Ranvier's constriction rings, 338 ; transverse sections of hardened nerves, 338 ; concentric circles according to Lister and Tur- ner, 339 ; composition of the axis cylinder of the finest filaments, axis or primitive fibrillar, 339; non- mednllat.ed fibres of the olfactory nerve. 339 ; Re- nmk's fibres, 340; embryonic nerve-fibres, 310; INDEX. 619 method of examining the nnn-medullated tubes, 340 ; by polarized light, according to Valentin, J841 ; ganglion- cells, 341 ; appearance, 341 ; processes, 341; apolar cells, 342; methods, 342; origin of the fibres, 342; suitable objects, 342; methods of demonstration, 343 ; ganglion-cells, according to Beale and Arnold, 344 ; ganglionic reticular : intes- tinal ganglia m the submucous tissue of the diges- tive organ, discovered by Meissner. 345 ; methods of demonstration, 345 ; pyroligneous acid, 345 ; Au- erbach's plexus myentericus, 346; methods, 346- 348; central organs of the nervous system, brain and spinal cord, 34S ; examination of, in a fresh condition, 34S ; nerve-fibres, 349 ; multipolar gan- glion-cells, 350 ; maceration methods, 349 ; accord- ing to Deiters, 341); multipolar g..nglion-cells ac- cording to this investigator, 350 ; axis cylinder pro- cess and protoplasma processes, 350 ; complicated structure of tbe ganglion-cell, according to Reinak and Schultze, 351 ; Gerlach and Prohmann's meth- od of procedure, 351-352 ; hardening methods, 353 ; with alcohol, 353 ; chromic acid and chromate of potash, 353 ; more accurate directions for chro- mic acid, 353 ; chromate of ammonia, 354 ; prepara ■ tion of sections, 354 ; their treatment for moist pre- parations, 355 ; for dry, 356 ; Clarke's method, 356 ; Deane's, 356 ; later statements, 357 ; difficulty of the investigation of the brain and spinal cord, 35S ; statements of Schieffer decker, 35S ; direc- tions for injecting the blood-vessels in the central organs, 858; connective-tissue framework ("neuro- glia), 359; Bidder's investigations, 350; occur- rence in the white substance of the spinal cord and brain, 350 : amyloid corpuscles, 361 ; myelinc, 361 ; cholesterinc, 361 ; nerve terminations, 362 ; of mo- tor nerves in striated muscles, 362; suitable objects. 362—363 ; new investigations of Kiihne, Margo, K61- liker, Bouget, Krause, Engelmann. 364; methods, 364 ; very dilute acetic acid, according to Kolliker, Engelraann, and Prey, 365 ; diluted, according to Krause, 365 ; dilute muriatic acid, 365 ; isolation of the muscular filaments with the nerves, 365; in the smooth muscles, 367 ; in the heart, 368 ; in the cornea, 369; termination in ttie epithelium, 370 ; methods, 371 ; Muller and Sof-niisch's direc- tions, 370 ; Hover's, 371 ; cutaneous nerves of the frog's larva, 372 ; tooth-pulp. 372 ; terminal bulbs of Krause. 372 ; methods, 373 ; tactile cells, 374 ; tactile bodies, 375 ; methods, 375 ; Gerlach's, 376 ; Pacinian or Vatcrian corpuscles. 376 : methods, 377 ; development of the nerve-fibres, 377 ; mem- branes, 37S ; pineal gland and brain sand, 379; pathological conditions, 379 ; methods, 379 Nervus acusticus, 603 ; cochlearis, 604 ; olfactorius, 569 ; opticus, 591 Neumann's treatment of the vitreous body, 275 ; of bones and teeth, 207 ; on carious teeth, 303 ; on the formation of colored blood corpuscles from the lymphoid cells of the bone medulla, 311 New formation of connective tissue, 288-289 ; varie- ties of, see the several organs and tissues Nicol's prisms. 49 Nitric acid, concentrated, 124 ; with chlorate of pot- ash, 124, 135 ; of 20 per cent., according to lteich- ert and Paulsen, 125, 318 ; dilute, 125 ; very dilute, according to Kolliker, 125 Nitzehia sigmoidca as a test object, 62, 65 Nobert's test-plate, 67 ; as a test-object, 67, 68 ; used by Schultze, 68 Normal solutions (titrition), 143-146 O. Oberhauser, his older microscopes, 11 ; camera lucida, 38 ; horse-shoe microscope, 27, 28 Object-finder, 230 ; Hoffman's arrangement, 230, note Object glass micrometer, 34 Object slides, form of the, 230 Objectives, achromatic, made by Chevalier and Sel- ligue, 11 ; their action, 11 ; aplanatic, 16 ; desig- nation of, 14 ; with movable and immovable lenses, 14 ; with connecting apparatus, 18, D8 ; with apparatus for correction and immersion, 58 ; angles of aperture, 14, 59 ; weak, in combination With strong eye-pieces, 1!) ; strong, with weak eye-pieces, 20 ; value of weak objectives in con- tradistinction to strong ones, 89, 95 ; for the recognition of the relations of relief of micro- scopic objects, 95; over-corrected, 16 Objectives of the oldest compound microscope, 9 ; of the modern, 11 Odontoblasts, 29S Oidium albicans (thrush) in the oral cavity, 429; in the stomach, 437 Oils, ethereal, 142 Olfactory cells. 567; rods, naked or with cilia, 568; connection with the axis cylinders of the olfactory nerve, 569, 571 ; Schultze" s directions for their investigation, 569 Olfactory organs, 565; structure of the ordinary mucous membrane, 565 ; catarrhal processes in this, find the formation thereby of mucous and pus corpuscles, 565 ; regio olfactoria, 51)6 ; its structure, 566 ; the epithelial covering, 566 ; ol- factory cells, 567 ; their connection with axis cylinders of the olfactory nerve, 569, 571 ; Bow- man's and mucous glands, 568; methods of ex- amination, 570, 571 Olfactory nerve, pale fibres of, 569 Ollier's experiments with the periosteum, 313 Oral cavity, 422 ; condition of, 428 Orthoscopic eye-piece, 15, 90 Osmiamide, 166 Osmic acid (hyperosmie acid), 132, 164; acetate of potash for mounting, 217 ; its use in investigations of the retina, and Schultze's directions for this purpose, 592, 597 OssiCUla auditus, 602 Ossification of cartilage, 292 Ossification point of bones, 305 Ossification, process of, set Bones Ossification, sen Bones Osteoblasts, 308 Osteoclasts of Kolliker, 314 Osteogenesis, 305 Osteogenous tissue, 310, 314 Osteoid tissue, 310 Osteomalacia, 314 Osteophytes, 314 Osteoporosis, 314 Osteosarcoma, 314 Otoliths, 602 Ovary (sexual organ), 533 ; cj'sts of, 539 Over-corrected objectives in combination with under-corrected eye-pieces, 16 Oviducts, 540 Ovum, 534; zona pellueida, yolk, germinal vesicle, and germinal spot. 534 Owsjannikow employs osmiamide, 166 Oxalate of lime, see Lime, Oxalate of Oxalic acid in watery solution, 129 ; in alcohol, 129 ; constituent of Thiersch's tingeing fluids, 150, 156; dissolving medium for Prussian blue, 181; its action on the regio olfactoria, 571 ; on the retina, 592 Oxyuris vermicularis, ova of, in fasces, 457 Pacinian bodies, 376 Pacini's preserving fluids, 217, 218 Paddle-wheel cells of the connective -tissue of Wal- deyer, 280 Palladium, see Chloride of Palladium Pancreas, 459; methods, 459; gland-cells, 459; blood-passages, 460 Paper strips, 222 Papilio janira, scales of, as a test-object, 61; their resolution with Hartnack's and other microscopes, 61,62 Papilla foliata of the tongue, 564 Parafflne, 114 620 INDEX. Parasites, animal, in the fseees, 456; in vaginal mucus, 542 ; ova of, in the fasces, 456 ; of the skin, 560 Parasites, vegetable, in the oral cavity, 428 ; in the stomach, 437; in the faeces, 454; in the urine, 525, 528; of the skin, 559, 500 Parme, soluble, 157 Paulsen, see Reichcrt Pavement epithelium, see Epithelium Pearl tumors, 270 Pencils for dramnp, 37 ; how to point them, 37 Penetrating power of the microscope, 57 ; nature of, and testing the, 57 Pepsine granules, 431, 432 Peptic gastric glands, 431 ; cells (covering or delo- morphous cells), 431 Pericardium, 493 Periosteum, see Bones Peripheral rays, refraction of, by a lens, S Peritoneum, 493 Peyerian glands (see Digestive Apparatus), 447 Pflugcr recommends collodium for the axis cylinders, 141, 337 ; his investigation of the salivary glands, 426; of the hepatic nerves, 40S ; of the ovary, 537 Pharyngeal mucous membrane, 423 Photogenic lamp, 43 Photographic microscopes, 41-42 ; their arrangement, according to Gerlach, 41 ; according to Moitessier, 42; manipulation, 43, 44 Photography, microscopic, 40 ; observations on, by Gerlach, Beale, and Moitessier, 40 ; its application, 44 ; used by Gerlach for increasing the enlarge- ment, 45 Picking preparations, 105 Picric acid, recommended by Schwarz for tingeing, 132 ; by Itanvier for hardening tissues, 132 Picro-carmine of Ranvier, 153 Pigment-cells, polyhedral, see Epithelium ; stellate, 585 Pigmentation, abnormal, see The Several Organs Pigmented epithelium (polyhedrie pigment-cells), see Epithelium of the uvea, 5S4 Pipette, 116; for titrition, 142 Pityriasis versicolor, 56G Plaques, Peyerian, 451 Plasma-cells of the connective tissue, by Waldever, 281 Pleura, 493 Pleurosigma angulatum as a test-object, 03 ; its res- olution by Hartnaek's microscope, 65 Plexus myentericus of Auerbach, 346 Plossl's microscopes, the older, 11 ; modem instru- ments, 76 Polarizer. 49; its position, 49 Polarizing microscope, 49 Polishing sections of bones and teeth, 299 Porrigo decalvans, 559 ; favosa, 660 Positive eye-piece oE Ramsdeu, 15 Potash, 133; chlorate of, in combination with nitric acid, 135; acetate of 135, 217; caustic, 133; car- bonate, 219 ; potash solutions, weak and strong, 133, 134; Moleschott's solutions, 133; Schultze's, 133 ; and iron, cyanide of, 182 Powell and Lealand, their immersion objectives tested by Harting, 60 ; their microscopes, 76 Preparation instruments for microscopical investiga- tions, 105 ; their simplicity, 105 Preparation of microscopical objects, 103; avoiding too large pieces, 88, 105 Preparations, cementing of. 221; fastening the cells with marine glue, 224; process, 224 ; with gutta- percha cement, 224; with india-rubber, dissolved in chloroform, 225 ; cement frames, 225 ; laying on the covering glass, 226 ; the rotary table, 226 ; cementing with asphalt lac, 227 ; Bourgogne's do., 227 ; gold size, 228 ; Ziegler's white cement, 228 ; black mask lac, 229; cementing Canada balsam preparations with shellac varnish, 329 Preparations for a cabinet, how to make them, 207 ; preserving in weak alcohol, 2(17 : dry preparations, 208; dry, in Canada balsam, 208; with heating, 209; withouL heating, 210; with Canada balsam, dissolved in ether or chloroform, 211 ; depriving the tissues of their water, 212 ; immersion in tur- pentine, 213 ; from turpentine into Canada bal- sam, 212 ; other mounting media : gum dammar in turpentine, 213 ; mastic in chloroform, 213 ; colo- phony, 214 ; sandarac in alcohol, 214 ; moist pre- parations, 215; with glycerine, 215 ; glycerine and water, 215; acidulated glycerine, 215; glyce- rine and gelatine, 210 ; and tannin, 216 ; and for- mic acid, 216 ; and carbolic acid, 216 ; with gum, glycerine, and arsenious acid, 216 ; acetate of pot- ash, 217; Goadby's fluid, 217; Pacini's fluids, 217 ; mixtures of the Berlin Pathological Institute, 218 : corrosive sublimate, 219 ; chrumic acid and chromate of potash, 219 ; chloride of calcium, 219 ; creosote. 220 ; arsenious acid, 220 ; methyl alcohol, 220 ; and creosote, 220 ; Topping's fluid, 220 ; Deane's fluid, 221 Preparations, microscopic, S7, 103 ; directions for making; covering and moistening them, 104; mounting by simply laying on the covering glass, 104 ; strips of paper or silver wire between slide and cover, 222 ; with a cell, 222 ; of gutta-percha, india-rubber, or glass, 222, 223; tin-foil, 225; ce- ment. 225 ; rotary table, 226 ; size and form of the slides,(23U ; indicator, 230, note ; slides with ledges, rf rf 231 ; labels, 231 ; cases for preparations, 231 ; com- mercial preparations, 232 ; collections, 232 Preparing microscope, new, of Zeiss, 106; Curtis 1 substitute for, 106 Preserving fluids, 215 ; of glycerine, 215 ; with mu- riatic, acetic, or formic acid, 215, 216 ; tannin in glycerine, 216 ; glycerine and gelatine. 216 ; glyce- rine and gum arabic, 216 ; glycerine and carbolic acid, 216 ; with acetate of potash, according to Schultze, 217 ; Goadby's fluid, 217 ; Pacini's, 217 ; of the Berlin Pathological Institute, 218 ; with cor- rosive sublimate, 219 ; with chromic acid and chro- mate ot potash, 219 ; chloride of calcium, 219 ; car- bouate of potash, 219 ; arsenious acid, 220 ; creosote; 220 ; methyl alcohol, 220 ; Topping's fluid, 220 ; Dcane's fluid, 221 Pressure cock, 143, 104 Price lists of microscope makers, see Appendix Prices, differences of, of Continental and English microscopes, 72 Primary cells in cartilage, 292 Primitive fibrillte of the axis cylinders in the nerve- fibres, 339 Prisms for drawing, 38 ; in the binocular and mul- tocular microscopes, 46-48 Processus vcrmiformK 451 ; facility of injecting the lymphatics of, in the rabbit, 201, 451 Procuring a microscope, 69 Prostate, 549 Prostatic calculus, 549 Protoplasma, 98; its changps, 9S ; processes of the central gang lion- eel Is, 350, 351; those of the reti- na, 399 Prussian blue, 1S1-1S3 : as a medium for impregna- tions, recommended by Leber, 169 : soluble, 183 Psorosperms of the rabbit. 438 Pulp of the spleen, see Spleen Pulp of the teeth, see Teeth Tunch, 222 Purkinje, with Valentine, investigates the ciliary movement, 265 Purpnrine tingeing, 155 Pus, 251 ; cells or corpuscles, 251 ; emigration from the blood-vessels, 248, 251 ; assumed formation in their epithelial cells and connective- tissue cor- puscles, 252 ; amoeboid transformations of the cells, 252; their migrations, 252; method of ex- amining, 253; acid and alkaline fermentation, 253 ; method of preserving, 253 ; corpuscles in small intestines, 455; in sputum, 494; in urine, 523 ; in vesical catarrh, 523 ; in vaginal mucus, 552 ; in nasal catarrh, 566 ; occurrence in corneal spaces, 583 Tyramidal processes of the kidney, 602 Pyrogallic acid, 159 Pyroligncous acid, its use in histology, 131 Pyrosis, vomiting in, 436 INDEX. 621 Q. Quokotf s injections, 173 ; recommends dilute me- thyl alcohol as a preserving fluid, 220 ; designation of the proper variety of marine glue for cement- ing, 22-1 Rachitis, Sll Itadial fibres of the retina, 593 Ramsdeu's eye-piece, 15 Hanvicr, his work, xi., xii. ; recommends picric acid, 132; picro-carmine, 153; glycerine with, formic acid, 216 ; studies of connective-tissue cells, 280 ; method for examining the tendons, 286 ; conBtriction rings of the nerve-fibres, 338 Razors, 107 ; English, 107 ; Swiss, 108 ; form of the blade, 107 ; grinding and sharpening, 107 Reagents, chemical, 122; their use, 1^2; method of application to the microscopic preparations, 122 ; their more prolonged action, 123; accurate deter- mination of their strength, 123 Recklinghausen, Von, recommends nitrate of silver, 137, 102 ; his moist chamber, 09 ; investigates the amoeboid cell movements, 98, 252; discovers the formation of red blood-corpuscles from the lym- phoid cells in the frog, 237 Reduction table of the millimetre and the Paris line, 35, 36 Reichert's connective-tissue theury, 2S1 ; R. and Paulsen's use of nitric acid for the study of the smooth muscles, 125, 318 Reinicke recommends frustulia Saxonica as a test- object, 63 Reissncr on the cochlear canal, 60-1 Refraction, index of, of anis oil, acetic acid, glyce- rine, Canada balsam, oil of turpentine and water, 118 Refractive power of the fluid medium and of tlio object, 118 ; of the fluid media changes the micro- scopic image, 118 Regio olfactoria, 506 Relief, relations of, of microscopic imnges — see Mi- croscopic Images Remak discovers the pale fibres of the sympathetic nerve, 340 ; demonstrates the corneous and intes- tinal gland layer, 414; investigates the develop- ment of the liver, 464 Resolving power of the microscope, 57 ; its relations to the angle of aperture, 57 Respiratory apparatus, 485 ; larynx, trachea, and bronchi, 485; lungs, 485 ; mcthodsof examination, 486 ; drying, 4S6 ; hardening, 480 ; infundibula, and alveoli, 4S7 ; method of demonstration, 487 ; corrosion method, 487; closer examination of the pulmonary vesicles or alveoli, 487 ; pulmonary epithelium, 489; injection of the blood-vessels, 489; lymphatics, 400; nerves, 490; foetal lungs, 490 ; changes in disease, 490 ; pigmentations and their signification, 490; anthracosis, 491; pus- corpuscles, 491 ; inflammation, 401 ; tuberculosis, 492; origin of Che tubercular elements, 492 ; soft- ening, 493 ; caverns and the nature of their walls, 493 ; pleura (pericardium and peritonaeum), 403 ; sputum, 493; constituents of the latter, 494; mu- cus and pus corpuscles, 495; granule-cells (in- flammatory globules), 495 ; pigment-cells, 495 ; blood, 406; elastic fibres, 490; crystals of ammo- nio-phosphate of magnesia, 497 ; method of exam- ination, 496 Retina (visual apparatus), 590 Richardson, his blue injection mass, 187; on lym- phoid cells, 251 Riddell's binocular stereoscopic microscope, 47, 80 Riff cells of Schultze, 266 Rindfleisch uses oil of cloves, 142 ; directions for the treatment of the lungs, 486 Ripmann uses strong muriatic acid for the division of the tongue muscles, 424 Robin's leptothrix buccalis, 428 Rodig's diatome test-plate, 63, note ; his preparations, 232 Rod-cells of the kidney, according to Hcidenhain, 511 Rods of the retina, 594 Rollett recommends lime and baryta water for con- nective tissue, 134 ; on blood-crystals, 242 ; dis- solves the connective tissue of muscles in hermeti- cally sealed tubes by slight wanning, 324 ; demon- stration of the connective-tissue nbrilbe, and their double arrangement, 282 ; on gastric glands, 431 ; on the cornea, 577 Root-sheath, see Hairs Ross, A., increases the angle of aperture of objec- tives, 57 ; his microscopes, 76 ; his binocular ste- reoscopic microscope, 47 Rotary disk, 22 Rouget on the termination of the nerves in the vol- untary muscles, 364 Rubber, its use in microscopic drawing, 37 Ruysch's injections, 173 S, Sago spleen, 484 Saliva, 429 Salivary corpuscles, 429 ; of the tonsils, 425 ; move- ments of their granules, 429 Salivary glands, 426 Saemisch, with Miiller, examines the corneal nerves 370 Sandarac resin in alcoholic solution, 214 Sareina ventriculi in the contents of the stomach, 437 ; in the urine, 525 Sarcine or hypoxanthine in the liver, 472 ; in the urine, 530 Sareolemma. see Muscles Sarcoma, 2S9 ; adenoid, of the lacteal glands, 544 Sarcoptes hominis, 560 ; method of examining, 501 Sarcous elements, see Muscles Saws for fine sections of hard tissues, 115 Scabies, 500 Seala media of the cochlea, 6i>4 Scales of the papilio janira, 61 Scall (porrigo favosa), 560 Scanzoni, with Kollikcr, examines the mucus of the female genitals, 542 Schacht recommends black mask lac, 220 Schick's older microscopes, 11 ; later instruments. 76 SchielTerdecker, his microtome, 108 ; on the spinal cord, 358 Schlemm's canal, 5S4 Schmidt, C, goniometer, 36 Selidnn on the sarcous elements of muscles, 329 Schron's investigations of the ovary, 537 Sehulze, F. E., employs chloride of palladium, 137, 16S ; examines the Becher cells of the epithelium, 437, 438 Schulze's reagent, 125, 135 Schultze recommends iodine-serum as an indifferent fluid, 121 ; his warm stage, 101 ; compares objec- tives by central illumination with Nobcrt's latest test-plate, 68 ; recommends very dilute solutions of chromic acid, 128 ; of bichromate of potash, 136; of sulphuric acid, 124, note ; oxalic acid, 129 ; potash solutions, 133; osmic acid, 132, 164; solu- tion of acetate of potash for mounting, 217; on stachel and riff-cells, 266; on primitive fibril] a? in the axis cylinder, 330; on the complex structure of the gang] ion- cell, 351 ; examines, with Key, tho termination of the gustatory nerve in the frog's tongue, 504 ; investigations of the olfactory rnucoua membrane, 567 ; follows the olfactory nerve to its termination, 509 ; on the retina. 501-001 ; on the terminations of the auditory nerve, 603 Schwalbe on gustatory buds, 563 ; on the lymphatics of the eye, 575 Schwan teaches that the cell is the elementary struc- ture of tho animal body, ix Schwarz invents double tingeing with picric acid and carmine, 159 Schweigger-Scidel recommends glycerine and water, 622 INDEX. 121 ; acid carmine mixture, 159 ; on the kidneys, 604 Sciopticon, 44, note Scissors, 105 Sclerotic, 5S4 Screw for moving the microscope, 21 ; fine (micro- meter screw), 21 Screw micrometer, 32 ; divisions of that of Schiek and Plossl, 32 ; in the eye-piece, 32 Sebaceous glands of the skin, 555, 55G ; development in the foetus, 55S ; their cells, 416, 417 ; formation of these glands in cysts of the ovaries, 539 Sections through hard objects, method of making, 115, 299 ; through very small objects, 113 Seibert's microscopes, 25, 31, 77 Seiler, C, his section-cutter, 113 Selenite plates, 51 Self -injection of the living animal, 190 Selligue, see Chevalier Semen, 550 Seminal canaliculi, 545 ; filaments, ' 550 ; stains, their investigation, 553 ; vesicles, 549 Sense, organs of, 554 Serous glands, 416, 423 Serres fines, 198 Shading microscopic drawings, 37 Sharpey's fibres of bones, 303 Shellac varnish, with anilin blue or gamboge, for cementing Canada balsam preparations, accord- ing to Thiersch, 229 Silver, acetate of, 164 Silver, citrate of, 164 Silver impregnation, 162 ; Recklinghausen's method, 162; duration of the action, 162; with the subse- quent action of common salt, 164 ; His'' method, 164 ; Legros 1 , 162 ; Thiersch's, 164 ; with other salts of silver, 164 Silver, lactate of, 164 Silver mosaic in the blood-vessels and lymphatics, 163, 382, 399 Silver, nitrate of, 137, 162 Silver, picratc of, 164 Silver wire for supporting the covering glass, 222 Size, apparent, of an object determined by tho an- gle of vision, 1 Skin, 554 ; its structure, 554 ; epidermis, 554 ; Mal- pighinn rete mucosum, 554 ; corium, 554 ; sudori- parous glands. 555 ; sebaceous follicles, 556 ; blood- vessels, 556; lymphatics, 556; cutaneous nerves, 557; foetal skin, 558 ; cabinet objects, 562; path- ological changes of tho skin, 658 ; inflammatory conditions, 558 ; hyper trophies, 558; elephantia- sis, 558 ; warts and condylomata, 558 ; vascular nasvi, and teleangiectasia, 558 ; cysts, 553 ; athe- romata, 558 ; comedones, 559; milium, 559 ; vege- table parasites, 559 ; trioophyton tonsurans, 559 ; microsporon Audouini, 559; microsporon nicnta- grophytes and furfur, 559, 560 ; aehorion Schiin- leinii, 560; animal parasites, 560 ; demodex folli- culorum, 560 ; sarcoptes hominis, 560 Slides, 103 ; various forms, 103, 230 ; with protec- tion ledges, 231 Sliding arrangement on objectives with correcting apparatus, 18 .Smith and Beck's microscopes, 31, 76 Soda solutions, 134; phosphate of, 136; nitrate of, 136 ; hypochlorate of (eau de Javelle), 135 Soemmering^ injections, 173 Softening dried sections, 130, 170 Solitary glands, 447 Spectral apparatus of Merz, 51 ; of Hartnack and Prazmowsky, 51, 52 Spencer, Charles A., notice of, 77 Spherical aberration of lenses, 8 Spinal cord (see Nervous System), 348 Spleen, 476; difficulty of the examination, 476; the fresh organ, 477 : hardening methods, with alco- hol, chromic acid, and chromate of potash, 477- 478; sections, 478 ; hardening pathological organs, 478 ; mounting, 479 ; results of investigations, 479; Malpighian corpuscles, 479; pulp and its canals, 480 ; blood-passages, 481 ; flakes contain- ing blood-corpuscles, 481 ; lymphatics, 482 ; Tomsa's statements, 482 ; trabecule, 482 ; nerves. 482 ; changes in disease, 482 ; in leucaemia, 483 in abdominal typhus, 483 ; miliary tubercle, 483 hemorrhagic infarction, 483 ; hypertrophy, 483 . pigmentation, 484 ; amyloid degeneration, 484 ; its two varieties, 484 ; mounting diseased spleens, 484 Sputum, 493-497 Stachel (and riff) cells of Schultze, 266 Stage of the simple microscope, 5 ; of the compound, 20 ; rotary of the horseshoe stand, 29 Stage, warm, of Schnltze, 101 ; its defects according to Engelmann, 101 Starch granules in the saliva, 429 ; in vomited mat- ters, 435 ; in the small intestine, 453 ; in thefteces, 454 Starch, react!, ns of, 132, 435 Steel needles, 105 Stein on micro-photography, 44 Stereoscopic microscope, 47 Stieda recommends creosote for rendering prepara- tions transparent, 141 Stigmata of the vessels, 384 Stomach, 430 Stomata of the vessels, 384 StrclzofTs double tingeing, 160 Sublingual gland, see Salivary Glands Submaxillary gland, see Salivary Glands Sudoriparous glands, 411, 555; development, 558 ; in cysts of the ovary, 539 Sulphate of baryta, 179 Sulphate of iron, 181 Sulphuric acid, concentrated, 123 ; with iodine, 132 ; dilute, 124 ; very dilute, according to Kuhne, 124 ; action on the tissue of the hair, 271 ; on the nails, 269 ; on the crystalline lens, 588 Supra-renal glands, 530 ; structure of, 530 ; nerves, blood-vessels and lymphatics, 532; methods of in- vestigation, 532 Surirella gemma, as a test-object, 62, 65; its trans- verse lines resolved into areolations by Hartnack, 66 Sympathetic nerve-fibres, 339; ganglia, 342-348 Syphilis corpuscles of Lostorfer, 255 Tactile bodies, 372 Tactile cells of Merkel, 374-375 Ttenia hooklets in the fasces, 45S Txnia mediocanellata, ova of, in faeces, 458 ; solium, ova of, in fasces, 458 Tannic acid, 159 Taurine in the feces, 455 Teeth, 296; decalcifying, 290-297 ; decalcified en- amel, 303 ; chemical isolation of the dentinal tubes, 298 ; sections, and the method of preparing them, 298-299 ; mounting, 300 ; carious teeth, 303 ; enamel, 303; sections, 304 ; isolation of the prisms, 304 ; tooth-pulp, 304 ; development of the teeth, 304 ; methods, 305 ; formation of teeth in the em- bryo, 305 ; in cysts of the ovaries, 539 Teichmann recommends chloride of silver for injec- tions, ISO ; employs the puncturing method for in- jecting the lymphatics, 201; shows how to make crystals of hsemine, 243; on blood-crystals, 241 Telangiectasia, 558 Tendons, Kanvier's method of examining, 2S6 ; rela- tion to the muscle. 324-325 Terminal knobs, 372, 573 ; plates of the voluntary muscles, 364 Termination of the nerves, see Nerves. Test acid, 143 Test alkali, 143 Test-objects, 60 : their value, 60 ; enumeration of the most important ones, 61-68 Test-plate of Nobert. 33 ; as a test object, 67-68 Testicle (see Sexual Organs), 545 Testing the microscope, 53 ; its magnifying power, 53 ; the correction of spherical and chromatid aberration, 54-55; the plane field of vision, 55; the latest immersion systems, by Hartiug, 59 INDEX. 623 Theory of the microscope, 1 Thiersch's injections, 173 ; various injection masses: red, 1S5 ; blue, 181; yellow and green, 185-186 J tingeing methods, 150; with carmine and oxalic acid, 150; and borax, 151 ; with indigo-carmine, 156 ; method of impregnating alcohol prepara- tions with silver, 164; mounting for Canada bal- sam preparations, 229 Thrush (oidium albicans) in the oral cavity, 429; in the stomach, 437 Thymus gland, 499 ; its structure, 499 ; canal sys- tem, 499 ; vascular arrangement, 319 ; concentric bodies, 169, 320 ; methods of examining, 500 ; lymphatics of, cannot be injected, 500 Thyroid gland, 497 ; relationship with other organs, 497 ; blood- and lymph-passages, 498 ; structure, 497-498 ; method of investigation, 498 ; colloid de- generation and goitre, 498-499 Tin chest for injections, 195 Tin-foil cells, 225 Tingeing, 147 Tingeing methods, 147; with red coloring matters, 147; blue, 156; with carmine, invented by G-er- lach, 147 ; directions for carmine tingeing, 148 ; for injected tissues, 150; with glycerine-carmine, according to Frey, 149; with Thiersch's carmine, 150 ; lilac, according to Thiersch, 151 ; according to Beale, 151 : Heidcnhain's modification, 152 ; Echweigger-Seidel's acid carmine tingeing, 152; with picro-carmine, according to Itanvier and Flemming, 153 ; with aniline red, according to Frey, 154 ; purpurine tingeing, 155 ; cosine tinge- ing, 155 ; with aniline-iodine violet, 155 ; with blue coloring matters, 156 ; with indigo-carmine, 156 : with aniline blue, according to Frey, 157 ; Heidcnhain's and Hollett's modification, 157 ; with Parme soluble, 157 ; with chinoline blue (cyan- ine), 15S ; with violet, hoe matoxy line, 158 ; bluish, with the molybdate of ammonia, according to Krausc, 159 ; double tingeing with picric acid and carmine, by Schwarz, 159 ; with carmine and in- digo-carmine, 160 ; with indigo-carmine and pic- ric acid, 160 ; with hajmatoxyline and carmine, by Strelzoff, with luematoxylineand picric acid, 1G1 ; Gerlach's complicated tingeing, 161 Tissue cement of the epithelium, 259 ; of the mus- cles, 325 Titrition apparatus, 142 ; method, 143 ; examples, 145-146 Toldt's recommendation of benzine, 278 ; self-injec- tion of the lymphatic glands, 405 Tolles, B. B., notice of, 80 Tomsa, see Ludwig ; T. on the spleen, 4S2 Tongue (see Digestive Apparatus), 424 ; muscular tissue, 424 ; division of the muscular filaments, 424 ; connection with connective-tissue corpus- cles, 424 ; nerves, 424, 562 ; their terminations examined by Schultze and Key, 5(i4 ; modiried by Engelmann, 564; follicular glands, 425 Tonsils, 425 Toppings rluid, 220 Trachoma glands of the conjunctiva, 574 ; their lymphatic-, 574 : method of injection, 574 Transparent, reagents for rendering tissues, 118 Transparent soap, as an embedding medium, ac- cording to Flemming, 114 Trichina spiralis in muscles, 332; examination of the trichinized muscles, 333 ; trichina in the fasces, 456; microscopes for examining, 333, note Tricoccphalus dispar, ova of, in the fasces, 456 Trichomonas vaginalis, 542 Trichophyton tonsurans, 559 Tube of the microscope, 20 Tubercle, 289 Tubular glands, .see Glands Turn-table, Prey's improved, 226 Turpentine, od of, its property of rendering tissues transparent, 141; index of refraction, 118; me- dium for dissolving Canada balsam, 141 ; removal of the preparation from alcohol to oil of turpentine, and from this to Canada balsam, 212 Tympanic cavity, 602 Tyrosine in the liver, 472 ; in the urine, 529 0. Ulcers, 252 Urate of ammonia, 525, 52S ; of soda, 525 Urea, nitrate and oxalate of, 530 Ureter, 522 Urethra, 522 Uric acid, 526 ; infarctions, 521 ; salts, 52H Urinary fermentation, acid, 526; alkaline, 529 Urinary organs, 502; importance for the physician, 502 ; kidneys with medulla and cortex, 502 ; earlier views, 503 ; Horde's newer observations, 503 ; later investigations, 504; method of examining, 504; hardening, 505 ; longitudinal and transverse sec- tions, 505-506; chemical isolation, 597; injection of the uriniferous canals. 512 ; Heidenhain's more recent investigations, discovery of the rod-cells, 511 ; self-injection, 514 ; diagram of the course of the canalicules, 513; arrangement of the vessels, 514; vasa recta, 515 ; double injection, 517 ; selec- tion of material, 517 ; framework substance, 517 ; lymphatics, 517; pathological changes, 518; im- portance of the gland-cells and framework, 518; hypertrophy, tubercle, fatty, pigment, and amy- loid degeneration, 518, 519 ; Bright's disease, 520 ; precipitates in the uriniferous canals, 521 ; uric acid and lime infarctions, 521, 522; calices and pel- vis of the kidney, ureters, and bladder, 522 ; epi- thelium of the bladder, 522 ; urine, see this Urinary sediments, 525; method of examination, 530 Urine, 523; fresh, normal, 523; constituents, 523; abnormal constituents in disease : epithelium, mu- cous, and pus-cells, blood corpuscles, 523 ; fibrin or exudation cylinders, 52-3 ; sarcina ventriculi. 525 ; sediments of crystalline and amorphous substances, 525; urate of soda, 525 ; acid fermentation. 526 ; uric acid of various crystalline forms, 52fi ; oxalate of lime, 527; fermentative fungi, 529; anunonio- phospbate of magnesia, 528; urate of ammonia, 528 ; formation of mould and vibriona; in alkaline urine, 529 ; crystals of cystine, 529 ; leucine and tyrosine, 529 ; urea combined with nitric and oxa- lic acid, 530 ; sarcine and xanthine, guanine, 530 ; method of examining the precipitates, 530 Uriniferous canalicules, 502 ; loop shaped of the kid- ney, according to Henle and others, 503-507 Uterine cancer, 541 Uterine fibroids, 541 Uterine glands, 540 Uterine polypi, 541 Uterus (see Sexual Apparatus), 540 Uvea, 584 Vagina, 541 Vaginal mucus, 542 Valentine, his double knife. 107 ; the older form and the English improvement, 107 ; his and Purkinje'a examination of the ciliary movement, 265 ; exam- ines the behavior of muscles in polarized light, 331 ; the nerves, 341 Vas deferens, 547 Vascular new formations, 396 Vatcrian bodies, 376 Veins, see Blood-vessels Vestibule of the fish, sacculi of the, 603 Vessels, see Blood- and Lymph-vessels ; for titrition, see Titrition Method Vibriona?. sea Bacteria ; formation of, in alkaline urine, 529 Vinegar. 131 ; boiling the kidney in, recommended by Billroth, 507 Vision, angle of, determines the apparent size of an object. 1 Vision, distance of, medium, 3 Vision, field of, levelling the same, and correction of the image by the collective lens, 12 Visual apparatus. 572; rye-lids, 572; Meibomian and lachrymal glands, 572. 573 ; conjunctiva, 573; coil-shaped glands, terminal knobs, 573 ; blood- 624 IXDEX. vessels, lymphatics and trachoma glands, 573-574 ; eye-ball, 575 ; method of injecting and examining, 575-576 , cornea, 577 ; methods of examining, 577- 578 ; pathological changes, 682 ; development and immigration of pus corpuscles, 583 ; sclerotic, 584 ; uvea, 584 ; pigment epithelium, 584 ; choroid with its layers, 585-586 : chorio-capillaris, 585 ; senile metamorphoses uf the elastic lamellae, 58(1 ; iris, 5S6 ; vitreous body, 587 ; lens, 587 ; its meta- morphoses, 589 ; its development, 589 ; membrana hyaloidea. 589; zonula Zinnii, 590; retina, 590; its structure, 591 ; various layers, 591 ; connec- tive-tissue framework, 592 ; method of investiga- tion, 592; rods and cones. 594; intergranular layer, 593 ; membrana limitans, 593 ; granular layer, 596 ; layer of ganglion cells, 597 ; nerve fibres, 597 ; conjectured arrangement of the ele- ments, 597 ; latest discoveries concerning the rods and cones, 599 ; vessels. 600 ; pathological condi- tions, 600 ; foetal eyes, 601 Virchow's discovery of hrematoidine, 244 ; direc- tions for isolating bone ceils, 297 ; for reproducing the ciliary movements, 264 "Vitreous body of the eye, 275, 587 Vix gives directions for the examination of helmin- thian ova in the human faeces, 456 Vomited substances (comp. Digestive Apparatus), 435 W. Wagner, E., on the liver, 46$ ; on fat embolia of the capillaries, 396 Waldeyer's paddle-wheel cells and plasma cells of the connective tissue, 280 : studies on carcinoma, 289, 290 ; axis fibnlhe of the nerves, 339 ; investigation of the cochlear canals, 605, 606 Wales, Wm., notice of, 80 Warming the gelatine masses for injections, 175, 195, 198 Warts, 558 ; dry, 269 Watch-glasses, 103 Water -bath for gelatine injections, 19S Water-colors for microscopic drawings, 37 Water, its use, 118 : index of refraction, 118 ; is not an indifferent fluid, 118, 120 Water, removal of, from the tissues by means of alcohol, 138, 141, 212 Wax as an injection mass, 173-176 Waxy liver, 474 Weismann shows how to ascertain tne relation of the muscular fibres to the tendon by means of potash solutions, 324 Welcker's method of distinguishing between ele- vated and depressed surfaces, 95 ; shows how microscopic images are changed by the refractive power of the fluid media, 118 Wenham's arrangement of the binocular stereoscopic microscope, 47 Whetstone, rotary, 115 Wittich's method of isolating striated muscles, 323 Work-room of the mleroscopist, 83 Work-table of the microscopist, 92 X. Xanthine in the liver, 473 ; in the urine, 530 Y. Tolk, see Ovum Zawarykin and Ludwig on the kidney, 504 Zeiss 1 microscopes, 25, 75 ; new dissecting micro- scope, 106 Zenker describes the changes of the muscles in typhus, 332 Zentmayer, J., notice of, 80 Ziegler's cement, 225, 22S Zinc white, as an injection mass, 179 Zona pellucida, see Ovum Zonula Zinnii, 590 Zooglcea (Cohn), 254 Zoosperms, see Seminal Filaments. PRICE-LISTS. PRICE-LISTS OF MICROSCOPE FIRMS. No. 1. — Price-IAsi of the Achromatic Microscopes of Dr. E. Hartnack, jVo. 39 Waisen /Strasse, Potsdam (1879). Price in Francs and Marks. Remaeks. — All microscopes are contained in a mahogany case, furnished with a lock and key. The microscopes 1, 2A, 3, and3A, are furnished with lens systems of older construction ; the remainder have new lens systems, with large angles of aperture. The polarizing apparatus may be used most advantageously on microscopes Nos. 7, 7A, and 8. Prom the following tables other systems and eye-pieces, which are required in the place of the custom- ary ones, as, indeed, any desired outfit, may be readily reckoned. A. Prices of tlie Microscopes. No. I. — Small microscope (d'hospice), with a lens system No. 7, and an eye-piece No. 3 ; magnify- ing power, 300 ; with a dozen slides and thin covers, brass forceps, scalpel, and preparing needles 75 fr. = 60 marks. No. IIA. — Microscope with firm stage, micrometer screw over the stem ; mirror freely movable for oblique illumination ; with the lens systems 4, 7, and the eye-pieces 2 and 3 ; magnifying power from 50, 65, 220, and 300, and an illuminating lens for opaque bodies. . 135 fr. = 108 marks. The same instrument, with the addition of objective No. 8 and eve-piece No. 4 ; magnifying power, 50-600 1S5 fr. ~ 148 marks. No. III. — Microscope, with the upper portion of the stand similar to the previous one ; with horse- shoe foot ; freely movable mirror for oblique illumination ; optical apparatus the same, 155 fr. = 124 marks. To obtain a magnifying power up to 600 205 fr. = 1 64 marks. No. IIIA. — Microscope similar to the previous one, but with a joint on the stem for obtaining an oblique position ; optical apparatus the same 170 fr. =: 136 marks. To obtain a magnifying power up to 600 220 fr. = 176 marks. No. VI. — Dissecting microscope, with long focal distance and inversion of the image ; magnifying power (withuut changing the lenses or eye-pieces) from 10-100, rotary stage, with glass plate 250 fr. = 200 marks. No. VII.— New, large microscope, the mechanical and optical construction of which differ essen- tially from the older large stand. It consists of 5 lenses, systems 2, 4. 5, 7, and the immcT- sion and correction system 9, and 5 eye-pieces (one of which has a micrometer) ; magnifying power from 25-1,300 (each succeeding enlargement twice as great as the previous one). Coarse movement by an adjusting screw, the fine one by a micrometer screw. Large illumi- nating lens for opaque objects ; all the necessary accessory apparatus 750 fr. = 600 marks. The same instrument, with a joint for inclining 800 fr. = 640 marks. No. VILA — Microscope similar to the previous one, but smaller, and with a lower stage; optical arrangement the same 650 f r. — 520 marks. The same instrument, with a joint for inclining 680 fr. = 544 marks. No. VIII. — New small stand, the arrangement of which, with the exception of the rotation of the stage and the coarse movement by means of a rack, presents the sfime advantages as No. 7, with the objectives Nos. 4, 7, 8, and eye-pieces 2, 3, and 4 ; magnifying power, 50-650, 275 fr. = 220 marks. The same instrument, with the systems 4, 7, and 9, the latter with immersion and correction ; 3 eye-pieces, one of which is provided with a micrometer, magnifying 50-1,000, 300 fr. — 312 marks. The same, with a joint for inclining 405 fr. - 324 marks. 628 PRICE-LISTS OF MICROSCOPE FIRMS. B. Prices of the Individual Liens Systems, and of the other Accessory Apparatuses, LENS SYSTEMS OP OLDER CONSTRUCTION. MAGNIFYING POWER WITH THE EYE-PIECES. System. Eye-piece No. 1. No. 2. No. 3. No. 4. No. 5. No. 6. Price. No. 1 12 20 30 40 75 110 150 250 330 15 30 40 50 1U0 150 220 300 430 25 40 50 65 150 220 300 400 620 'ioo 200 300 450 600 850 2 20 " 20 " 20 " 30 " 1 35 " [ 35 " 1 4 o " ! 60 " 16 " 3 16 " 4 16 " 5 24 " 6 28 " 7 28 " 8 800 1000 32 •' 9 48 " NEW LENS SYSTEMS, WITH LARGE ANGLES OP APERTURE. Equivalent Eye-piece System. focus in No. 2. No. 3. No. 4. No. 5. No. 6. Price. inches. No. 1 2 15 20 25 20 francs, 16 marks. 2 1 25 30 45 20 16 ' 3 X 50 60 80 i20 30 » 24 ' 4 H 60 70 90 140 30 " 24 ( 5 a 100 125 160 240 35 28 6 X 150 ISO 240 350 40 " 32 7 1-6 200 240 300 450 600 760 40 32 1 8 1-9 250 300 400 600 800 1000 50 40 4 9 1-11 350 400 550 860 1100 1400 75 " 60 " NEW SYSTEMS WITH IMMERSION AND CORRECTION. Equivalent System. focus in inches. No. 1. No. 2. No. 3. No. 4. No. 5. No. 6. Price. No. 9.... 1-12 410 4S0 630 950 1300 1500 150 francs. 120 markB. 10.... 1-16 520 600 750 1100 1500 1800 200 " 160 " 11.... 1-18 600 690 S50 1250 1750 2500 250 " 200 " 12.... 1-21 710 820 1010 1490 2060 2800 300 " 240 " 13.... 1-25 820 950 1170 1730 2370 3100 350 " 2S0 " 14.... 1-30 930 1080 1340 2000 2080 3360 400 " 320 " 15.... 1-33 1040 1200 1500 2200 3000 3600 450 " 360 " 16.... 1-40 1200 1400 1750 2570 3500 4200 500 " 400 " 17.... 1-45 1400 1600 2000 2940 4000 4800 500 " 400 " 18.... 1-60 1560 1800 2250 3300 4500 5400 500 " 400 " Plain eye-piece, Nos. 1, 2, 3, 4, and 5 10 fr. = S marks. Holosteric eye-piece 15 fr. = 12 " Spitzen eye-piece 25 fr. = 20 " Micrometer eye-piece 25 fr. = 20 " Binocular stereoscopic eye-piece, which shows the objects erect ISO fr. = 144 " Movable stage 60 fr. = 48 " New compressorium 30 fr. = 24 " Stage micrometer, mounted in brass, the millimetre divided into 100 equal parts 20 fr. = lfi " New movable micrometer (gives accurately 0.0001 millimetre) 50 fr. =40 " Improved patent polarizing eye-piece, a prism with a large field, and a graduated circle, 60 fr. = 4S '* PRICE-LISTS OF MICROSCOPE FIRMS. 629 Goniometer 60 fir. = 48 marks. Universal goniometer 150 fr. = 120 " Spectral apparatus for microscopical studies, with prisms iu rectilinear arrangement, tubes for the fluids for comparison of the absorptions 120 fr. = 96 marks. Dujardin's illuminating apparatus (improved construction) 50 fr. = 40 " Camera lucida of Oberhiiuser ; also serving for the conversion of the vertical into the horizontal microscope 50 fr. = 40 marks. Camera lucida of Milne-Edwards und Doyt-re 35 fr, — 28 marks. Brucke's loup (improved construction) 20 fr — 16 marks. Stand for this loup '.30 fr. = 24 marks. Lamp for microscopic examinations, with a large lens for obtaining parallel rays ; to use with gas or petroleum 35 fr. = 28 marks. Loup for ophthalmologists 10 fr. =8 marks. Loups 5-15 fr — 4-12 marks. Object slides, first quality, per dozen 2 f r. 50 cts. = 2 marks. " " second " " 1 fr. 25 cts. = 1 mark. Covering glasses, per dozen 1 fr. 25 cts, = 1 mark. " " per hundred 6 f r. 25 cts. = 5 marks. No. 2. — Nachet & Son, 17 Hue Saint Severin, Paris (1879). Prices in Francs. 1. Microscope, large model, improved, complete and binocular, suspended on the axis in such a manner that it may be inclined and remain fixed in any position between the horizontal and vertical. Coarse adjustment by rack-work; two movements for tine adjustment, one acting on the column supporting the body, the other very delicate and belonging especially to the tube carrying the objectives, and so disposed as to establish a constant elasticity for the pro- tection of the objectives in case of contact with the preparation. The stage is rotable, and is furnished with a double plate, and so arranged that the objects may be moved without touching them. The stage is furnished with a glass plate to resist the destructive effects of reagents. Illumination by a double mirror movable in all directions. A sliding arrangement, placed between the mirror and the stage, permits of the removal of the diaphragms and of focussing the condensers with the greatest precision. Micrometric apparatus for introducing the micrometer into the eye-pieces without deranging them, and for accurately adjusting it to the focus of the eye, and for placing it in all parts of the field of vision. Eight objec- tives with correcting apparatus, from No. to No. 7, magnifying from 30-1,400 diameters ; four eye-pieces, binocular apparatus, goniometer, camera lucida, polarizing apparatus with selenite plates, condenser, eye-piece, and stage micrometers. Condensing lens on a stand. Accessories for preparing. Strong mahogany case with brass corners, lined with velvet; objectives ; in a separate case 1,400 fr. 2. Microscope, large model, mounted like No. 1. Rotary stage with a black glass plate for use with acids. Rack-work for coarse adjustment, slider for diaphragms and condenser, double mir- ror, 3 eye-pieces, 6 objectives, Nos. 0, 1, 2, 3, 5, 7, for immersion and correction, magnifying from 30-1,400 diameters. Camera lucida, eye-piece, and stage micrometers, condensing lens, accessories for dissections, etc. Mahogany case, brass corners, etc 680 fr. 3. Vertical, large model, rotary stage, coarse and fine adjustment, arrangement for introducing the diaphragms and condenser without deranging the object; eye-piece and stage micrometer; 5 objectives, Nos. 1, 2, 3, 5, 7, immersion and correction, magnifying from 30-1, 40U diameters. 3 eye-pieces, camera lucida, condensing lens, accessories for dissecting, etc. Mahogauy ca.se, etc 550 f r. 4. "Microscope d disposition particuliiire" to reduce the height as much as possible, model of Prof. H. de Lacaze-Duthiers — same objectives as in the model No. 3 C50 fr. 5. Microscope, medium model for inclining. Coarse and fine adjustment, rotary stage and glass plate, double mirror, apparatus for adjusting diaphragms beneath the object, etc. ; 5 objec- tives. No. 1, 2, 3, 5, 7, immersion and correction, magnifying, with three eye-pieces, from 30- 1,400 diameters ; condensing lens, accessories, eye-piece, micrometer, etc. Mahogany case. .500 fr. 6. Vertical, medium model, similar to No. 3; rotary stage, black glass plate, 5 objectives. Nos. 1, 2, 3, 5, 7 ; immersion and correction, 3 eye-pieces, eye-piece micrometer, condensing lens, accessories 450 f r. 7. New model for inclining. Immovable stage, black glass plate, coarse and fine adjustment, dia- phragm arrangement as in medium models ; condensing lens, 3 eye-pieces, 4 objectives, Nos. 1, 3, 5, 7; immersion and correction, magnifying from 25-1,400 diameters; condensing lens, accessories 430 fr. 8. Same microscope with 3 objectives, Nos. 1, 3, 5 ; magnifying 30-700 diameters 280 fr. 9. Small model for inclining; mirror freely movable, movable diaphragm, coarse and tine adjust- ment, draw tube, 2 objectives, Nos. 1, 3; 2 eye-pieces, magnifying from 30-700 diameters; condensing lens, accessories 150 fr. 10. Small model, vertical. Mirror freely movable ; 2 objectives, Nos. 1, 3 ; 2 eye-pieces, condensing lens, accessories. Mahogany case *■*» f r. 630 PRICE-LISTS OP MICROSCOPE FIRMS. 11. More simple microscope. Cast-iron base, 1 eye-piece, 1 objective, No. 3 ; maximum 380 diam- eters, accessories. Mahogany case 80 fr, 12. Large model, binocular microscope. Constructed in such a manner as that the prismatic appa- ratus gives at pleasure stereoscopic or pseudoseopic images. The eye-pieces may be approxi- mated or separated according to the distance between the eyes of the observer; coarse and fine adjustment, may be inclined horizontally, 3 objectives, Nos. 0, 1, 3 ; movable stage, con- densing lens. Mahogany case. . . 500 fr. 13. Small model, binocular, for inclining ; coarse and fine adjuetm' nt, 8 objectives, Nos. 0, 1, 3 ; 2 eye-pieces, condensing lens 350 fr. 14. Binocular apparatus, applicable to all microscopes, with arrangement for adjusting to distance between the eyes ; 2 eye-pieces, no objectives 150 fr. 15. Binocular, stereoscopic and pseudoscopie apparatus, applicable to all microscopes 175 fr. 16. Microscope for two persons, lo observe simultaneously the same object. Objectives, Nos. 0, 1, 3 ; condensing lens, accessories, etc. ; ease 300 fr, 17. Double body tu apply to ordinary instruments 2 eye-pieces, no objectives SO fr. 18. Microscope for three persons to observe simultaneously ; coarse and fine adjustment; each ob- server may adjust the focus separately ; 3 objectives, Nos. 0, 1, 3 ; case 400 fr. 19. New large model, inverted, with a silvered mirror at the crossing of the rays. In this micro- scope the distance between the objective and the eye-piece may be increased to 90 cuntimetres or a metre without inconvenience. This combination requires a very delicate construction of the mounting. The strongest objectives may be used in this form of instrument, the loss of light produced by the silvered mirror (Foucault's method) being insignificant. Achromatic condenser, mirrors, 2 eye-pieces, no objectives 800 fr. 20. Inverted microscope for chemical studies. The objectives being placed under the object, there is no liability of clear vision being impaired by the accumulation of vapors. The stage is gilded ; 4 objectives, Nos. 0, 1, 3, 5 ; 1 movable eye-piece, accessories, alcohol lamp on an ar- ticulated support, excavated slips of glass, thin covers. Mahogany case 350 fr. 21. New inverted microscope for the study of anatomical elements in gases at a steady temperature, with numerous accessories ; 3 objectives, Nos. 1, 3, 5 : 2 eye-pieces ; case 500 fr. 22. Pocket microscope. The instrument is 90 millimetres long by 50 millimetres broad, can be used with high powers ; objectives Nos. 1, 3, 5 are usually added ; one eye-piece, slides and covers, all in a compact leather case 200 f r. 23. New portable microscope, larger than the preceding one, enclosed in a case, 14 centimetres long by 8 broad ; movable mirror ; all objectives mav be used ; with 3 objectives, Nos. 1,3, 5. and 1 eye-piece ISO f r. 24. Dissecting microscope, model of Dr. Cosson. This instrument has on one side an arm for carrying the doublets for dissections, and on the other a column with a horizontal support for the body of the microscope. It may be used either as a simple or compound microscope at pleasure. Coarse adjustment for the doublets, fine for the compound microscope. Two ob- jectives, Nos. 1 and 3 ; eye-piece, 3 doublets, of varying powers ; condensing lens ; case. . . . 140 fr. 25. Stage of this microscope alone, as a simple microscope with 3 doublets, and base, with articula- tions for supporting the doublets ; accessories ; case 50 fr, 26. Dissecting microscope for laboratories, model of Prof. C. H. Robin. May be used with glass dishes or plates of cork on which opaque objects are fixed. It gives erect images and magni- fies from 8-70 diameters 120 fr. A stage with a mirror may be added for di ssccting very small objects 20 fr. 27. Hand microscope for demonstrations. The instrument may be placed on a stand till the object is permanently adjusted, and then passed among the audience. All kinds of illumination may be used ; coarse and fine movement; without objective 80 fr. 28. Microscope on a support, for aquaria, without objective 120 fr. 29. Photographic microscope, with accessories and a series of objectives 300 fr. 30. Dark chamber, etc. 80 fr. Moitessicr's photographic frames 45 fr. OBJECTIVES. MOUNTED IMMOVABLE. No. 15 fr. 1 20 fr. 2 25 fr. 3 30 fr. No. 4. 5. B. 7. ..-5fr. . 40 f r. .50 fr. .80 fr. OBJECTIVES WITH CORRECTION. No. 3 5(1 fr. 4 60 fr. 5 15 fr. No. 6 100 fr. 7 125 fr. PRICE-LISTS OF MICROSCOPE EIRMS. 681 IMMERSION OBJECTIVES. MOUNTED IMMOVABLE. 70 fr. | No. 7 IMMERSION OBJECTIVES WITH CORRECTION APPARATUS. No. 6 120 fr. 7 15Ufr. S -300 fr. II 250 fr. .10 SOOfr. 11 350 fr. 13 400fr. LINEAR MAGNIFYING POWER OBTAINED BY THE COMBINATION OF THE OBJECTIVES WITH THE EYE-PIECES. ORDINARY OBJECTIVES. (1 Eye-pieces -{2 tS Corresponding focus in inches Angle of aperture — degrees . . . » 1 so 80 40 100 60 140 2 1 10 15 EttMEBSION AND COBEECTION OBJECTIVES. \l Eye-pieces -iZ u::::::;;:::::: Corresponding focus in inches. Angles of aperture — degrees. . 460 580 600 900 000 1400 1200 1750 1-10 1-14 140 160 775 1100 1600 2000 1-15 175 9 10 11 900 1150 1320 13C0 1560 1S00 2000 2200 26S0 2600 2750 3150 1-20 1-30 1-40 175 175 175 1700 2400 3261) 4500 1-50 175 31. Simple microscope for dissections, with doublets, rack-wort for coarse adjustment, two wings at the sides of the stage for the support ot the hands in fine dissections, with two doublets and case 60 fr. 32. Binocular microscope for dissections, magnifying 10-150 diameters 150 fr. 33. Section-cutter 60 fr. 34. ' L simplified 35 fr. 35. Microtome for holding the objects to make sections by hand with glass plate, model of Dr. Hayem IS fr. 36. Compressor 30 fr. 37. Eye-pieces, each 10 fr. 38. Eye-piece micrometer 15 fr. No. 3. — C. Yerick (Pupil o/'Hartnack), Jttuede la Parcheminerie, No. 2 7 Paris (1877). Price in Francs. No. 1. Large microscope, with complete stand ; movable binocular arrangement to fit on any other instrument. Coarse movement by a rack, finer by a micrometer screw. Kotary stage covered with black glass. The mirror is movable vertically, horizontally, forwards and backwards, to permit of oblique illumination in all directions. The vertical movement is very important to increase or diminish the intensity of the light, without changing the distance of the diaphragm; perpendicular diaphragm carrier with vertical movement; joint with arrange- ment for securing in any position : revolver arrangement for changine the lenses of newest construction, 6 objectives, Nos. 0, 2, 3, 6, 8 (dry system) and No. 10 (with immersion and cor- 632 PKICE-LISTS OF MICROSCOPE FIKMS. rection) ; 3 eye-pieces, Nos. 1, g, 3 (No. 2 with micrometer and screw for changing position). These optical combinations furnish magnifying powers from 18-1,200. Large illuminating lens on a stand. Accessory apparatus, slides and covers ; mahogany box with handle 980 fr. No. 2. Large microscope, but of simpler construction. Coarse and fine adjustment as in No. 1. The upper portion of the tube can be drawn out to obtain the proper position for the objec- tive and eye-piece. Rotary stage, covered with black glass ; movable mirror as in No. 1 ; movable diaphragm carrier. Arrangement for oblique position as in No. 1, Five objectives, Noe. 0, 2, 6, 7 (dry system), and 10 (with immersion and correction) ; 3 eye-pieces, Nos. 1, 2, 3 (No. 2 with micrometer and screw for changing position). Magnifying power from 18-1,200. Illuminating lens as in No. 1 ; the same accessories and same box 750 fr. No. 3. Medium microscope. The same double adjusting arrangement, tube to draw out, rotary stage with black glass plate ; oblique illumination as in the larger stands ; the diaphragm movable vertically ; oblique position with checking arrangement; objectives Nos. 0, 2, 6, 8 (dry system) ; 3 eye-pieces, Nos. 1, 2, 3 (No. 2 with micrometer). Illuminating lens, acces- sory apparatus, box as above 550 fr. The same stand without the rack 500 fr. No. 4. Smallest instrument; rotary stage covered with black glass; coarse adjustment through the neck, fine by micrometer screw, with oblique illumination and inclining position. Objec- tives Nos. 0, 2, 0, 7 ; eye-pieces Nos. 1, 2, 3 (No. 2 with micrometer) ; illuminating lens, etc. .390 fr. The same instrument, with screw for changing position and the same optical constituents. 440 fr. No. 5. Stand with non-rotary black glass stage ; double motion, oblique illumination, objectives Nos. 2, 6, 7 ; eye-pieces 1 and 3. Magnifying power from 60-780 ; inclining position, smaller illuminating lens, etc 260 fr. Same instrument, with screw for changing position 310 fr. No. 6. Instrument with two columns for laboratories 165 fr. No. 7. Horse-shoe student's stand without inclining ; double motion; oblique illumination; objec- tive No. 2 ; eye-piece No. 1 ; magnifying power from 60-100 95 fr. With objective 6 105 fr. No. 8. Travelling and pocket microscope without optical apparatus. Price of tlie Objectives, with their Magnifying Power. (The magnifying power obtained with the tube elongated or shortened is here separated.) Objective. No. 00 . 0. 1. 2 3 4 6 7 7 (new). 8 Eye-piece 1 12 10 18 25 30 35 60 100 80 ISO 130 210 no 290 250 400 310 '500 30 60 80 110 170 220 Bill) 50 1UII 150 2111 31 III •toil 550 420 720 40 '.III 120 170 250 330 480 75 140 220 290 430 570 781.1 570 880 45 100 130 200 2011 650 550 S5 170 250 350 620 660 800 600 1050 20 francs. 20 " 25 " 25 » 35 " 35 '• 35 " 40 " 75 " 60 " Equivalent focus in English inches. 2X 2 1 H 1-6 1-9 1-9 1-11 NEW OBJECTIVES, WITH IMMERSION AND CORRECTION. Objective. Eye-piece 1 2 3 4 Price. Equivalent focus in English inches. No. 8 200 440 310 580 330 600 380 700 450 800 350 620 400 670 450 760 500 S80 550 950 500 880 550 950 620 1120 690 1200 750 1300 610 950 670 1200 800 1300 900 1600 1070 1690 90 francs. 120 " 150 " 200 " 250 " 1 11 " 9 " 10 1 16 " 11 " 12 1 21 PRICE-LISTS OP MICROSCOPE FIRMS. 633 Ranvier's microtome for animal objects 12 fr. Rivet's microtome for vegetable objects SO fr. Kunekel's loup stand 40 fr. Alalassez's apparatus for counting blood-cells, with quadratic, eye- piece micrometer 60 fr. Image inverting binocular arrangement 180 fr. Eye-piece 10 fr. Holosteric eye-piece IS fr. Micrometer eye-piece 20 fr. Photographic arrangement 50 fr. Stage micrometer in 100 15 fr. " 500 20 fr. " 1000 30 fr. Improved rotary stage GO fr. New compressorium 35 fr. Polarizing apparatus 45 fr. " M with a polarizing eye-piece having a graduated circle GO fr. Horizontal movable micrometer 50 f r. Improved Dujardin illuminating apparatus 45 fr. Goniometer -50 f r. Camera lucida of Oberhiiuser 50 fr. Milne-Edwards and Doyerc '-5 fr. Mathiasen 20 fr. Loups 8-25 fr. No. 4.— Carl Zeiss, Jena (1877). Prices in Mark*. Objectives and Eye-pieces, No. System. Angle of Aperture. Equivalent focus. Magnifying Power at 155 millimetres. Length of Tube for 250 millimetres. Visual distance with Eye-piece. Price in Marks. 1 2 3 4 5 1 2 3 4 5 6 7 8 9 10 11 12 1 o w- GQ P a aa A AA B BB C CC D DD E E 20° 20° 1 33° \ 40° | 00° f 48° 1 90° f 72° 1 100° f 105° 105° 30, 45, 60 mm. 32 mm. 10 mm., %" Eng. 10 mm., 2 5" 6 4 mm., X" 4.2 mm., 1-6" 2.8 mm., 1-0" 1.8 mm., 1-14" 5 to 18 45 70 110 ISO 240 380 20 25 60 95 140 220 330 500 "40 85 125 200 300 450 720 "50 110 160 260 400 600 950 "70 150 220 350 550 840 1400 12 27 (24 (30 130 its 136 148 142 154 06 84 13 .14 IB c r no. l O m si it " 2 180° 180° 180° 3.0 mm., 1-8" 1 220 1.7 mm., 1-15" 400 1.0 mm., 1-25" 680 300 530 900 420 700 1300 600 1020 1700 790 1500 2800 90 144 277 634 PRICE-LISTS OP MICROSCOPE FIRMS. No. 5. — Seibert & Krafft, successors to E. Gondlach, Wetzlar (1876). Prices in Marks. Objectives. Objective. No. 00 I II Ill IV V.a V. b VI. a.... VI. 6.... VII. a... VII. b... VIII. ... IX X Focus of the Equivalent Lenses. Eng. in. 2 1-2 13-4 1 15 13 1-1 1-8 1-8 1-12 1 12 1-lti 1-16 1-2-1 1-32 1-50 Mm. 63.5 41.4 25.5 12.7 y.7 6.4 3.2 3.2 2.1 2.1 1.6 1.6 1.1 0.8 0.5 Angle of Aperture. Degrees. 10 15 20 38 50 Wl 130 150 105 105 175 175 175 175 175 Without correction screw With " " Without " " With " " Immersion without correction lt with 24 21 18 IS 18 27 36 48 60 75 60 75 120 180 300 Magnifying Power. Objective No. 00. 0. I. II. 45 III. IV. V. VI. VII. VIII. IX. X. With Eye-piece No. 10 18 30 66 100 200 305 460 650 950 1450 I.... 16 26 45 70 100 150 305 460 690 1000 1430 2200 II.... 24 40 68 100 150 220 450 609 1000 1360 2170 3300 III... 32 54 90 140 200 300 610 930 1375 2000 2880 4400 Eye-piece No. 0. I., II., Ill 7J» marks. Eye-piece No. III., with arrangement for micrometer, and micrometer 12 marks. Microphotographic objective, 1 in 36 marks. " % in 30 marks. " " V B in 45 marks. No. 6. — G. & S. Merz (formerly Utzschneider & Fraunhofer), Munich (1872). Price in Thalers. Objectives. Focus of the Equivalent Lenses. Angle of Aperture. Trice. 1", 1-2", 1-3" 20°-40° 10 Thalers. 1-6", 1-9" . . 100° 120° 16 1-12" 140° 20 1-15" | 1-18" f 1-21" 1 Ordinary and immersion systems — 140°-150° ■! 24 44 60 PRICE-LISTS OF MICROSCOPE FIRMS. 635 No. 7. — Powell & Lealand, 170 Euston Road, London (1879). Price in £. s. d. Compound Microscopes. £ s. d. 1. Large compound microscope, on an improved construction, with 1 inch of motion to the stage in rectangular directions by screw and pinion : slide holder and spring clip ; also wheel and pinion which rotates the whole concentric with the optical tube, combined with very thin stage for the oblique illumination of objects, either by the mirror or achromatic prism, with graduated silver circle, which can be used as a goniometer: coarse and fine adjustments to the body, with graduated sliding tube ; substage, with rotary, rectangular, and vertical motions, for the adaptation of the achromatic condenser, paraboloid, etc. ; graduated stage plates and clamp, to act as finder ; large plane and concave mirrors, with double arm, and 2 eye-pieces Wenham's binocular arrangement for low powers, with 3 eye-pieces Powell & Lealand's patent ditto, which allows the highest powers to be used with it No. 4 and 5 eye-pieces Improved condenser, with revolving diaphragm and central stops, by which arrangement the relative sizes of the apertures and stops can be varied at pleasure, — achromatic combina- tion, with 170 degrees of aperture One pair of Kelner's orthoscopic eye-pieces Two animalcule cages Stage forceps YTollaston's camera lucida Silver side reflector Erector for dissecting with compound body Polarizing apparatus, with series of revolving selenitcs Indicator to eye-piece Annular condenser Compressorium Frog plate Rectangular achromatic prism for oblique illumination, to fit into stand of buirs-eye condenser . Lister's dark wells, with fittings Large bull's-eye condenser on stand Small ditto, with joints to fit into microscope stand Diaphragm, with Kainey's light modifier Screw micrometer .... Spotted lens Brooke's double arm, angular form (first made by P. & L. ) Stage micrometer Pliers 1-50 inch object glass 1-25 li ''■ " 1-16 X 1 tl " " \% 2 ■ '■ •' 3 » •' 1; 4 M 4i " Lieberkuhn's 2 inch 14/-, \% inch 12/-, 1 inch 10/-, % inch, 7/-, U inch 6/- Immersion arrangement to the % inch and 1-16 inch Spanish mahogany case 4 12 £200 15 2. Large compound microscope, on an improved construction, with J^-inch of motion to the stage in rectangular directions by screw and pinion ; sliding and revolving slide bolder and spring clip, coarse and fine adjustments to the body, with graduated sliding tube ; sub- stage, with rotary, rectangular, and vertical motions, for the adaptation of the achromatic condenser, paraboloid, etc. ; plane and concave mirrors, with double arm, by which means a very oblique light can be thrown upon the object ; and 2 eye-pieces 26 3. Compound microscope, on an improved construction, with %-inch of motion to the stage in rectangular directions by screw and pinion ; sliding and revolving slide holder and spring 38 8 10 8 3 2 8 8 3 8 14 10 1 1 1 1 1 5 5 1 10 1 10 8 1 15 13 1 3 19 10 4 10 10 1 10 6 4 SI 10 u 21 16 16 9 9 5 5 6 3 3 3 2 15 2 15 1 10 2 9 4 4 630 PRICK-LISTS OF MICROSCOPE FIRMS. £ e, d. clip, coarse and fine adjustments to the body, with graduated sliding tube ; substage, with rectangular and vertical motions, fur the adaptation of the achromatic condenser, paraboloid, etc. ; plane and concave mirrors, and 2 eye-pieces . 18 10 4. Portable compound microscope stand, having %-incii motion to stage in rectangular direc- tions by screw and pinion ; sliding and revolving slide holder and spring clip, coarse and fine adjustments to the body; substage, with rectangular and vertical motions, for the adaptation of the achromatic condenser, etc. ; plane and concave mirrors, with, double arm, by which means a very oblique light can be thrown upon the object ; and 2 eye-pieces. 18 5. Compound microscope staiid, with %-inch of motion to the stage by means of a lever; coarse and fine adjustments to body, plane and concave mirrors, and 2 eye-pieces 11 Ditto, the stand, pillar, and limb in bronze 9 6. Compound microscope, with 1 inch and J£ inch achromatic object glasses, with apertures of 28 and 95 degrees respectively, 2 eye-pieces, plane and concave mirrors, revolving diaphragm 13 Student's microscope^ with "WenhanTs binocular arrangement, with % inch motion to stage by screw and pinion ; coarse and fine adjustments to body 14 Dissecting stand, with rack and pinion movements ; compound body, made to receive the object glasses and eye-glasses of the above microscopes, and elongating arm '?, 10 fj Spanish mahogany case for No. 1 microscope, with box for apparatus 4 12 Spanish mahogany case for No. 2 or No. 3 microscopes, with box for apparatus, and drawers for objects 5 o Honduras ditto, with box for apparatus 8 10 Spanish mahogany case for portable microscope 1 16 Case for No. 5 or 6, with packing for apparatus 1 15 Honduras case for dissecting stand 1 5 Q Achromatic Object OlasNes for microscopes. Object Glasses. 4 i 3 2 in 1 % % % 4-ld u H X 1-5 % K % 1-12 1-16 1-25 1-50 Magnifying Power with the various Angular Aperture. Eye-pieces. Price. Lieber- No. 1 2 3 4 5 f, 8. degrees 12 18 ! 25 50 75 1 10 12 10 24 32 64 06 9 15 14 25 37 50 100 150 2 15 14 20 37 50 : 74 150 220 3 12 30 50 74 1 100 200 300 3 3 10 32 75 111 ; 150 300 450 3 10 10 70 100 148 | 200 400 600 5 7 40 J . 4 4 80 125 187 1 250 500 750 5 5 7 05 200 296 1 400 800 1200 5 fi 6 130 17 7 140 On a new formula .... 'I 100 250 | 370 | 600 1000 1500 6 6 140 On a new formula .... q 100 7 140 400 502 800 1600 2400 8 s 145 600 888 1200 2400 3600 12 19 175 800 1184 1600 3200 4800 16 16 100 1250 1850 2500 5000 7500 21 150 2500 3700 6000 10000 15000 31 10 Qt tO Jjf, >„', 1-] 2, or 1-lfc No. 8. — Ross & Co., 164 JVew Bond Street, London (1879). No. 1. Improved Monocular Microscope Stand, Ross model, with coarse and fine adjustments for focusing, mie eye-piece, graduated concentric rotating stage, having one inch of rec- tangular motion, rack and screw movements, clamping lever for fixing the instrument at any angle, graduated sub-stage for holding and adjusting illuminating and polarizing ap- paratus, diaphragm plate, plane, and concave mirrors No. 1A. Monocular Microscope Stand, with one eye-piece, coarse and fine adjustment for fo- cusing, graduated concentric rotating stage, having one inch of rectangular motion rack and screw movements, clamping lover for fixing instrument at any angle, graduated sub- stage for holding and adjusting illuminating und polarizing apparatus, diaphragm plate plane and concave mirrors ... ' No. 2A. Monocular Microscope Stand, with one eye-piece, coarse and fine adjustment for fo- cusing, mechanical stage with rotating movement, having »., -inch of rectangular motion £ s. d. 33 35 PRICE-LISTS OF MICROSCOPE FIRMS. 637 £ s, d. mechanical sub-stage for holding and adjusting: illuminating and polarizing apparatus, clamping lever for fixing the instrument at any angle, plane and concave mirrors with jointed arm 25 No. 3A. Monocular Microscope Stand, with one eye-piece, coarse and fine adjustments for focusing, mechanical stage with rotating movement, mechanical sub-stage for holding and adjusting illuminating and polarizing apparatus, clumping lever, plane and concave mirrors with jointed arm 20 No. 2. Monocular Microscope Stand, with one eye-piece, coarse and fine adjustments for focus- ing, mechanical stage with rotating movement, having J^-ineh of rectangular motion, mechanical sub-stage for holding and adjusting illuminating and polarizing apparatus, plane and concave mirrors with jointed arm 23 No, 3. Monocular Microscope Stand, with one eye-piece, coarse and flue adjustments for fo- cusing, mechanical stage with rotating movement, having %-mch of rectangular mo- tion, mechanical sub-stage for holding and adjusting illuminating and polarizing appa- ratus, plane and concave mirrors with jointed arm 18 No. 1A. Binocular Microscope Stand, with two ^eye-pieces, coarse and fine adjustments for focusing, graduated concentric rotating stage, having one inch of rectangular motion, rack and screw movements, clamping lever, graduated sub-stage for holding and adjust- ing illuminating and polarizing apparatus, diaphragm plate, plane and concave mirrors, and Wenham's binocular arrangement 42 U No. 2. Binocular Microscope Stand, with two eye-pieces, rack and pinion adjustment for focus- ing, sliding and rotating stage, plane and concave mirrors with jointed arm, and Wen- ham's Binocular arrangement 17 No. 3. Binocular Microscope Stand, with two eye-pieces, coarse and fine adjustments for focus- ing, mechanical stage with rotating movement, having X-inch of rectangular motion, mechanical sub-stage for holding and adjusting illuminating and polarizing apparatus, plane and concave mirrors with jointed arm, and "Wenham's binocular arrangement 25 Ross' New Patent Object Glasses. Devised by Me. WENHAM. The undoubted superiority of our Patent Objectives (as confirmed by leading microscopists) has de- termined us to abandon the old construction from the X-inch upwards. In the new combination a great increase of brilliancy and definition is obtained by dispensing with six surfaces formerly used. Aperture about Magnifying Powers with Eye-pieces, about Price. A. B. O. D. E. P. £ s. d. 1-2 inch 1-2 ■ 3-10 " 45° 80° 60° 90° 85° 120° 130° 140° 150° 100° 100 100 165 165 250 250 340 500 750 1200 160 160 265 265 400 400 540 800 1200 2000 250 250 410 410 620 620 850 1200 1800 3100 400 400 660 660 1000 1000 1300 2000 3000 5000 500 500 820 820 1250 1250 1700 2500 3700 6200 800 800 1300 1300 2000 2000 2700 4000 6000 10000 4 4 5 5 4 10 8-10 '■ 5 10 1-5 " 5 5 1-5 '• 6 6 1-7 " 7 7 1-10 '■ 1-15 " 9 9 12 12 1-25 " ... 21 The higher powers, from the l-5th upwards, can be used cither dry or immersed, merely by approxi- mating the lenses with the adjusting collar to the mark " Wet, 1 ' thus avoiding the cost of extra fronts and loss of time in changing them. Ross' Low Power Objectives. Object Glass. *4 *3 3 *1¥ n l Aperture Magnifying Powe r with Eyepieces. about A. B. C. 1). 9° 12 18 25 40 10° 15 20 35 50 12° 15 20 35 50 12° 25 40 00 100 15° 25 40 60 100 15° 35 60 95 150 20° 35 60 05 150 15° 50 80 125 200 25° 50 80 125 200 35° 80 130 200 300 : Price. £ s. d. 1 11 3 3 2 2 3 3 3 3 6 o 3 10 3 10 The Objectives marked thus,* being triplets, are best suited for use with eye-pieces of low power. Their angular aperture is not so great, nor their defining power equal to the more perfectly corrected combinations. 638 PRICE-LISTS OF MICROSCOPE FIRMS. No. 9.— C. Baker, 244 and 245 High Holborn, London (1879). £ 8. d. No. 1. Highly finished large compound microscope stand, with all the latest improvements, having double supports to prevent vibration, vertical rack adjustment for the approximate focus, and fine screw-motion for the more delicate optical adjustment. A mechanical stage, with one-inch motion in opposite directions; a sliding and rotating object holder; a supplementary stage, with vertical rack and centering adjustment for applying the dia- phragm ; polariscope, achromatic condenser, spot lens, etc., etc., with plane and concave mirrors, and two eye-pieces 21 No, 1A. A large microscope stand, with mechanical stage, quick and slow motion, double mir- ror, two eye-pieces, etc, etc., as above, but without the supplementary stage. 14 10 No. IB. A smaller ditto, and in every respect as No. 1A 11 10 No. IB. A ditto, without mechanical stage 7 15 No. 3. A superior finished binocular microscope stand, with a pair of eye-pieces, double mirror, circular rotating stage, and quick and slow motions 6 Ditto, ditto, with racks to eye-pieces, as shown above 7 No. 4. A similar stand, but of larger and more massive construction, to which a sub-stage and all accessories can be adapted No. No. . 5. Tlte Student's Microscope, a well-finished instrument, with quick and slow motions, cir- cular rotating stage, a combination of three achromatic object glasses, live box, stage, and dissecting forceps 4 10 . 6. Tlie Educational Microscope. — This exceedingly cheap achromatic microscope, which is so strongly recommended by most of tho Professors at the various Colleges, Schools, and institutions for public and private education, has quick and slow motion, sliding stage, live box, stage forceps, dissecting forceps, with three achromatic object glasses in combi- nation, all packed in a neat mahogany case T?ie Medical Microscope. — A superior finished microscope on the Continental model, having sliding body, micrometer. screw fine adjustment, joint to incline at any angle, and im- proved adjusting mirror, with two eye-pieces, in mahogany case 3 3 One-quarter-inch English object glass 1 10 One-inch " " 1 5 Condenser for opaque objects 9 Divided glass disk to aid in drawing and measuring objects 4 The Seaside Microscope. — This convenient and extremely portable microscope is adapted for travelling', or use at the seaside, as it packs, with object glasses and apparatus, within the space of 9 inches by 5 inches. It has rack adjustment, draw tube with one eye-piece, double mirror, and circular revolving glass stage 2 15 Ditto, ditto, with fine adjustment 3 5 Mahogany case for ditto 15 A superior finished dissecting microscope, with rack adjustment, three object glasses, etc., in neat case 2 3 3 C* Baker's Achromatic Object Classes. Angular Aperture. Four-inch 8 degrees. Three-inch 10 " Two-inch 12 Ditto 15 •' One and a half inch 20 " One inch 15 " Ditto 23 Ditto 30 Two-thirds inch 35 Half inch, with adjustment 60 " Ditto, without 40 Four-tenths, with adjustment 70 '■ Ditto, ditto, 05 Quarter-inch, with adjustment 75 " Ditto, ditto, 05 Ditto, without adjustment 75 •' One-eighth, ditto, with adjustment 115 ll Ditto, ditto, 125 1 5 1 16 1 10 1 17 6 1 17 6 1 10 1 17 6 2 a 5 8 2 10 3 5 3 10 3 5 3 15 2 10 5 5 (', (i PRICE-LISTS OF MICROSCOPE FIRMS. 639 Apparatus for Achromatic microscopes. £ s. d. Polariscope, with extra large pair of prisms, fitted and attached complete 1 12 6 Ditto, with analyzer expressly mounted for the binocular microscope 1 15 Ditto, with revolving analyzer 1 17 6 Folariscopes for student's or educational microscope 1 5 Dr. Beale's neutral tint glass reflector for drawing 6 Brooke's double ncse piece, for carrying two object glasses to facilitate the change of focus. ... 110 Ditto for students' microscopes 12 6 C. Baker's triple ditto, for three object glasses 1 10 Extra eye- pieces from 6s. to 12 6 Kelner's orthoscopic achromatic eye-piece, giving very large field 1 Revolving selenite stage, with complete set of selenites 2 Erecting glasses for dissecting, applied to draw tubes 10 Ditto prisms for dissecting, applied to any monocular microscope 1 Camera lucida for drawing the magnified image 15s. to 1 5 Stage forceps from 3s. 6d. to 7 6 Dissecting forceps Is. to 1 9 Micrometer for stage 4 6 Ditto for eye-piece, mounted in brass S Ditto, ditto, unmounted 6 Maltwood's finder - 5 6 Animalcule cages from 2s. 6d. to 10 Frog plate from 5s. to G 6 Glass troughs for viewing circulation of plants from Hollow glass slides Comprcssoriums - from Glass stage plates Daylight reflector, fitted to object glasses 15 Ditto, with universal movements adapted to instrument 1 1 No. 10. — Chas. Collins, 157 Great Portland Street, London (1879). Collin^ 9 Student's Microscope 7 7 1 Eye-piece. Flat and concave mirrors. Draw tube. Wheel of diaphragms. Rack adjustment. Axes for inclining to any angle. Fine " , 1-in and hi-m. objectives. Top sliding stage. i Tweezers and glass plate. Packed in Polished Cabinet. Mechanical stage, extra 2 2 3 (i g 6 II 1 Collins' Harley Binocular Microscope 15 15 With mechanical stage. Condenser. Rack to draw tubes. Diaphragm. One pair of eye-pieces. Flat and concave 1-in, objective, B. Series, if-in. " " Mahogany case. Collins' Histological Student's Microscope The microscope with coarse adjustment. One eye-piece. | &-in. objective. Fine adjustment. Concave mirror. 1-in. objective. Mahogany ease. . n 640 PRICE-LISTS OF MICROSCOPE FIRMS. Collins' Best Harley Binocular microscope, Jackson Plan. Pair of A eye-pieces. B C 4-in. objective, A Series. 2-In. " " 1-in. /n-in. " " X-in. (L :t Webster's achromatic condenser, with Collins' graduating diaphragm. Live box. Compressor. Zoophyte trough. Stage forceps. Side parabolic illuminator. Large stand condenser. Large polariscope. Camera for drawing objects. Micrometer for stage. Frog plate. Double nose-piece. Mahogany cabinet. £ 8. d. 60 A Series.— Best Achromatic Object Glasses. These Object Glasses are guaranteed of the Highest Standard, both for Penetrating and Defining Power. Objective. Angle of Aperture, about Price. £ t. a. Linear Magnifying Power, with each Eye-piece. A. B. C. D. 9° 12° 15° 26° 85° 90° 90° 100° 100° 140° 15 1 15 1 15 1 16 2 3 10 3 10 4 4 10 5 10 12 15 25 50 80 100 146 200 250 500 18 20 40 80 130 160 255 340 400 870 25 35 60 125 200 250 460 690 620 1500 40 2-in 50 100 1-in 200 2-3-in 300 1-2-in 4-10-in 400 560 1-4-in 720 1-5-in 1000 1-8-in 1850 JB Series.— Achromatic Object Glasses. Objective. Angle of Aperture, about Price. £ s. d. Linear Magnifying Power, with each Bye-piece. A. B. C. D. 3- in 10° 13° 22° 40° 45° 95° 80° 95° 80° 100° 1 2 6 12 6 12 15 2 5 2 10 1 17 6 2 10 1 17 6 3 3 15 22 50 100 100 200 200 250 250 500 20 40 80 160 160 340 340 400 400 870 35 60 125 250 250 590 590 620 620 1500 50 2-in 100 1-in. 200 1-2-in 400 1-4-in 1-4-in 400 720 720 1-5-in 1000 1-8-in 1000 1850 The objectives of both series are cut to the standard screw of the Royal Microscopical Society. No. 11. — R. & J. Beck, London, and 1016 Chestnut Street, Philadelphia (1879). First Class microscope Stands. New large best binocular microscope stand, with concentric rotating stage and iris diaphragm, ro- tating and centering sub-stage, most complete movements to the body, stage, and double mirror, two pairs of : eye-pieces, pliers, forceps, etc., mounted on two pillars $250 00 New large best monocular microscope stand, with concentric rotating stage and iris diaphragm, rotating and centering sub-stage, most complete movements to the body, stage, and double mirror, two eye-pieces, pliers, forceps, etc., mounted on two pillars 200 00 New smaller binocular microscope stand, on tho same principle, and with the same actions as No. 36, two pairs of eye-pieces, pliers, forceps, etc., but with single pillar 150 00 Now smaller monocular microscope stand, on tho same principle, and with the same actionB as No. 37, two eye-pieces, pliers, forceps, etc., but with single pillar 115 00 PRICE-LISTS OF MICROSCOPE FIRMS. 641 First Class Objectives. No. Focal Length Linear Magnifying Power nearly, with Eye-pieces. No. 1. No. 2. No. 3. No. 4. No. 5. Angle of Aperture, about. Price. 4 inches 3 " 2 " IX " J 'I ! 1 \ \ \ 3 1 ! 3 \ \ \ 3 1 1 1 10 IX 18 o 20 4 30 5 70 8 120 14 146 18 200 84 225 18 225 18 400 50 500 60 900 80 900 80 1800 160 16 3 20 4 38 6 56 7 130 14 810 84 855 32 340 42 400 35 4U0 35 680 S5 870 100 1570 150 1570 150 3140 360 26 5 40 G 70 8 100 12 220 85 370 34 460 48 500 63 700 60 700 60 1180 140 1500 180 2750 300 2750 300 5500 600 32 6 48 7 85 12 180 15 370 37 460 46 560 60 780 85 860 SO 860 80 1440 ISO 1850 190 3450 350 3450 350 6900 700 53 8 74 10 130 15 190 32 410 48 710 70 890 80 1130 180 1450 130 1450 130 2340 380 3800 370 4950 900 4950 900 9900 1800 Degree. 1 * \ " I S3 \ 32 \ 55 [■ 90 } - > 85 r 100 y i2o [■ 160 r 140 j- 170 f 140 70 Ditto if drawn out, add for $15 00 71 Ditto if drawn out, add for 27 50 78 Ditto if drawn out, add for 27 60 73 Ditto if drawn out, add for 27 50 74 \% inch Draw-tube closed Ditto if drawn out, add for 25 00 75 4-10 " Ditto if drawn out, add for 40 00 76 4-10 " X " 1-5 " 1-5 " Ditto if drawn out, add for 60 00 77 Ditto if drawn out, add for 40 00 78 Ditto if drawn out, add for 40 00 79 Ditto if drawn out, add for 50 00 80 M " Ditto if drawn out, add for 65 00 81 1-10 " immer Ditto if drawn out, add for each inch 50 00 82 1-20 " 1-20 " immer 1-40 " Ditto if drawn out, add for 120 00 83 Ditto if drawn out, add for 110 01 84 Ditto if drawn out, add for each inch 150 00 Apparatus. Sorby's spectroscope eye-piece, for the microscope, in mahogany case. (See " Popular Science Ke- view," No. 18) $45 00 Sorby's dichroiscope 8 25 Sorby's standard spectrum-scale 8 25 Orthoscopic eye-pieces, giving a very large field, each 8 25 Eye-pieces for the improved large microscope, each 6 50 Eye-pieces for the improved smaller microscope, each 00 Erecting-glass 8 00 Draw-tube for first class microscopes 4 00 Achromatic condenser, with revolving diaphragm, with stops, aperture from 25° to 100°, complete adjustments, applicable to the first class stands only 40 00 Achromatic condenser, without diaphragm, aperture from 20° to 60°, complete adjustments 20 00 Bight angle prism, for reflecting the light more perfectly than the Hat mirror, for the first class stands only 20 00 Amici's prism, for oblique light, for the first class stands only 16 50 Amici's prism, on separate stand ™ *" Nachet's prism, for oblique light ° 25 Wenham's parabolic reflector, for the first class stands 13 50 Wenham's parabolic reflector, for the second class stands 13 50 41 642 PEICE-LISTS OF MICROSCOPE FIRMS. Spot lens, mounted in brass fitting $4 25 Equilateral prism on stand, for oblique illumination 8 00 Adapter on stand, for use of object glass as condenser 4 50 Brown's iris diaphragm 16 60 Polarizing apparatus, with 1 film of selenite 20 00 Polarizing apparatus, with extra large polarizing prism. 32 50 Darker's series of selenites, adapted for the first class stands only 30 00 Selenite film, of two colors 2 00 Selenite stage, red and green, or blue and orange, each 3 00 Barker's selenite stage, giving 13 tints 10 50 Black glass, for polarizing light 4 00 Bundle of glass, for polarizing light 8 00 Two double-image prisms and selenite film, with fittings to eye-piece, and brass plate with holes. ... 10 50 Single double-image prisms, in fitting 7 25 Crystals to show rings around the optic axis, each from 4 U0 Tourmalines, each from 7 00 Beck's patent illuminator, in a brass box, for viewing objects as opaque under high powers 4 00 White cloud illuminator 4 00 Parabolic illuminator, fitted to the \% inch and % inch object glasses 8 25 Parabolic illuminator with fittings adjusting it to any object glass 10 00 Parabolic illuminator, same as No. 128, with the addition of Sorby's reflector 10 00 Large bull's-eye condensing lens, on stand 8 00 Large bull's-eye condensing lens, on stand, with lamp attached 10 00 Smaller condensing lens, with fitting to limb of the first class stands 7 25 Smaller condensing lens, on stand 5 00 Side silver reflector, with fittings to limb of the first class stands 8 25 Side silver reflector, on stand 8 25 Rainey's light moderator, on stand 8 25 Three dark wells and holder 5 00 Opaque di^k revolver, one tray of disks in case 13 50 Opaque disk revolver, with three trays of disks, forceps, capsule of gold size, in mahogany case, complete 23 50 Opaque disk revolver and forceps 8 00 Boxes containing 24 disks 4 00 Trays containing 24 disks 4 00 Three-pronged forceps, in German silver, with screw adjustment 6 50 Three-pronged forceps 5 50 Stage forceps 3 00 Stage mineral holder 8 25 Eye-piece micrometer, with Jackson's adjusting screw 8 00 Stage micrometer, mounted in brass 4 00 Stage micrometer, mounted in card 2 00 Maltwood's finder in case 3 00 Indicator to each eye-piece 2 00 Leeson's goniometer 20 00 Wollaston's camera lucida, with lens to magnify pencil point 8 00 Neutral tint glass camera lucida 3 00 Steel disk camera lucida 6 00 Brook's double nose-piece, in aluminium, curved 23 50 Brook's double nose-piece, curved 11 75 Quadruple nose-piece 27 50 Quadruple nose-piece in aluminium 4C 00 Lever compressorium 7 50 Parallel compressor 8 00 Beversible compressor 8 00 "Wenham's compressorium, for use with Wenham's parabola 3 00 Screw live box 5 50 Large live box - 3 25 Smaller live box.... 2 75 Large glass trough, with wedge and spring complete 3 25 Smaller glass trough, with wedge and spring complete 2 75 GlaBs slip, with ledge 40 PRICE-LISTS OF MICROSCOPE FIRMS. 643 Growing cell, for preserving objects alive in water for many days $4 00 Set of six live traps and trough, in case, complete 11 75 Live trap 3 00 Frog plate, with bag, etc., complete 4 00 Glass slip, with hollow and ledge 50 Glass slip, with hollow and ledge and lip. 1 75 Glass tubes, set of three 25 Key for tightening joints of first-class instruments 1 75 Opal glass, for moderating the light, 3x1 inch 40 Blue glass for moderating the light, 3x1 inch 40 Astral oil lamp, flat wick and shade, with arrangement for varying height of flame above the table 6 00 Case for lamp No. ISO, and one chimney 4 00 Gas lamp, Argand burner, shade, and six feet of flexible tubing, with arrangement for varying height of flame above the table 12 00 Fiddian's microscope illuminator, in case 15 00 Popular Series of Object Glasses. Linear Magnifying Power nearly. Degrees Lieber- Focal of Angle of Price. No. kiihn's for Object Price. Length. With Bye-pieces. Aperture. Glasses. Draw tubes. No. 1. No. 2. No. 8. 3 inch. Closed. 12 20 40 8 $13 00 2 Closed. 24 40 70 10 12 00 m " Closed. 2!) 48 00 15 15 00 237 IX inch. $3 75 1 Closed. 55 9(1 100 22 15 00 288 1 3 00 X " Closed. 120 200 360 40 17 50 239 X " 3 00 a " Closed. 210 350 000 75 20 00 % '■ Closed. 420 700 1000 85 30 00 Closed. 800 1200 2000 100 50 00 The Economic Microscope and Apparatus. The Monocular Economic Microscope, with sliding coarse adjustment, 1-inch and J£-ineft object glasses, one eye-piece, concave mirror, condensing lens, glass plate with ledge, brass pliers and diaphragm, in mahogany case 35 00 The Monocular Economic Microscope, with rack and pinion coarse adjustment, with 1-inch and X-inch object glasses, two eye-pieces, concave and plane mirrors, side condensing lens, dia- phragm, stage forceps, pliers, glass slip, with ledge, in mahogany case 50 00 The Binocular Economic Microscope, with movable glass stage, concave and plane mirrors hung on jointed arm to swing above the stage, lever adjustment for different -widths of eyes, two pairs of eye-pieces, the same objectives and accessories, in mahogany case 80 00 Eye-pieces for the former, Nos. 1, 2, or 3, each 4 00 Eye-pieces for the second, Nos. 1 , 2, or 3, each 5 00 Side condensing lens 1 75 Stage forceps 2 00 Fliers 35 Additional Apparatus. Lieberkiihn to 1-inch object glass. Dark well Achromatic condenser and fitting Wenham's parabolic reflector for dark field illumination Flat mirror (in which case a double one is substituted for the concave single one, which has to be returned) Polarizing apparatus, complete with prisms, film of selenite, and adapter WollastonV camera lucida for drawing an object Glass micrometer, ruled into one-hundredths and one-thousandths of an inch Small live box Glass trough, complete with wedge and spring All the above "Additional Apparatus," if ordered at once Movable glass stage for the Economic Monocular Microscope 3 00 1 75 8 CO S 00 2 75 12 00 6 00 2 00 2 00 37 50 7 50 644 PRICE-LISTS OF MICROSCOPE FIRMS. Price L.ist of tlie Economic Object Glasses. Focal Length. Linear Magnifying Power, nearly. Degrees of Angle of Aperture. Price. With Bye-pieces. 2 inches. 1 inch. % inch. 3£ inch. % inch. -h in^- Draw tube. 1 Closed. | Open, j Closed. 1 Open, j Closed. j Open. j Closed. j Open. 1 Closed. ( Open. I Closed, j Open. No. 1. IB 26 48 68 76 110 150 216 290 410 660 925 No. 2. 20 34 68 93 100 145 200 290 390 560 900 1260 No. 3. 34 1 67 f 105/ 155 f 170 1 240 f 340 1 480 f 660 1 900 f 1500 1 2100 f 9° 16° 36° 70° 65° 100° $6 00 7 00 9 00 10 00 17 50 35 00 The New Binocular National Microscope, with 1-inch and % -inch object glasses, having the respec- tive apertures of 19 and 75 degrees, and magnifying from about 47 to 450 diameters ; 2 pairs of eye-pieces, stage forceps, condensing lens on stand, a glass plate, with ledge for the ex- amination of objects in fluid, and a pair of pliers; the whole packed in an elegant French polished mahogany case, with good brass handle and lock, and a drawer for the accessories, §100 00 The New Monocular National Microscope, with two eye-pieces, and the same object glasses and fittings as the above. In mahogany case 75 00 The New Binocular National Microscope, with 1-inch object-glass, 1 pair of eye-pieces, Nos. 1 or 2, as desired, stage forceps, condensing lens, on stand, glass plate and pliers. In mahogany case 85 00 The New Monocular National Micmscops, with 1 eye-piece, Nos. 1 or 2, as desired, and the same object glasses and fittings as with the above. In mahogany case 60 00 The New Binocular National Microscope Stand, with one pair of eye-piecee, concave and plane mirrors, diaphragm, stage forceps, glass plate, pliers, etc 65 00 The New Monocular National Microscope Stand, with one eye-piece, concave and plane mirrors, diaphragm, stage forceps, glass plate, pliers, etc 40 00 Mahogany Cabinet for the New National Microscopes 10 00 " " " " " " with side-case and fittings for all accessories. . 15 00 Tlie National Series of Objectives. Focal Length. Linear Magnifying Power, ne arly. Degrees of Angle of Aperture. Price. "With Eye-pieces. Draw-tubes. Closed. Closed. Closed. Closed. Closed. Closed. Closed. Closed. No. 1. 12 23 47 65 100 200 365 730 No. 2. 20 43 78 110 170 340 620 1240 No. 2. 32 70 116 170 260 520 955 1930 7° 10° 19° 25° S8° 75° 95° 110° £6 00 6 00 2 " 1 " 8 00 % " . % " Y, " 1-16 " 30 00 Every description of mounting apparatus and materials, fully illustrated and described in their full catalogue, mailed to any address. PRICE-LISTS OF MICROSCOPE FIRMS. 645 No. 12. — J. Zentmayer, 147 South Fourth Street, Philadelphia, Pa. (1879). Zeutmayer's American Centennial Stand* {Patented 187a) American centennial binocular, with 5 eye-pieces ; diatom stage, draw-tube, bulPs-eye condenser, 3, 4 and 5-inch objectives, 12° angular aperture, iy : inch, 22° ; 8-10 inch, 32° ; 4-10 inch, 80°, ad- justable for thin covers ; 1-5 inch, 85°; 1-5 inch, 120°, adjustable ; polarizer, complete ; Darker's selenites, Bicknell's achromatic condenser, achromatic condenser, with centering adjustment and achromatic combination of % and 1-5 inch ; double nose-piece (angular), eye-piece micro- meter, stage micrometer, camera lucida. parabola, erector, stage forceps, blue and ground- glass shade, 1 animalcule cage (large), 1 animalcule cage (small), WenhanTs compressorium, achromatic oblique prisoi, right-angle prism, instead of mirror ; parabolic silver side reflector, with Sorby's reflector ; 1 pair of orthoscopic eye-pieces, indicators to 2 eye-pieces, mineral holder, mechanical finger, Maltwood finder, amplifier, dark wells, Lieberkiihn's to \% and 8-10 objectives, and polished mahogany case, with side case $765 00 American centennial stand, with 3 eye-pieces, and same accessories as above 715 00 American centennial stand, with 5 eye-pieces ; diatom stage, bull's-eye, \% inch objective, 22° ; 8-10 inch, 32° ; 1-5 inch, 120° (adjustable) ; polarizer, complete ; 2 selenites, Bicknell's aohro- matic condenser, indicator to A eye-piece, camera lucida, stage micrometer, animalcule cage, Wenham's compressorium, and polished mahogany case, with side case 490 00 American centennial stand, with 3 eye-pieces ; same accessories as above 440 00 American centennial stand, binocular, with 5 eye-pieces 300 00 American centennial stand, monocular, with 3 eye-pieces 250 00 Concentric adjustable diatom stage 20 00 Best mahogany case, with fine handle, and side case for accessories 30 00 Zentinayer's United States Array Hospital Stand. (Patented 1876.) United States army hospital stand, binocular, with 4 eye-pieces ; 8-10-inch objective, 32° angular aperture ; 1-5 inch 90° angular aperture ; camera lucida, stage micrometer, and mahogany case 173 00 United States army hospital stand, monocular, with 2 eye-pieces, and same accessories as above. . .133 00 The above is the manner in which the stand was fitted out for the United States Government Hos- pitals ; it may, however, be fitted out, if so desired, with any of the object glasses or accessories from the lists. United States army hospital stand, binocular, with 4 eye-pieces and mahogany case 130 00 United States army hospital stand, monocular, with 2 eye-pieces and mahogany case 90 00 Zentmayer s American Histological Stand. {Patented 1S76). American histological stand, with 1 eye-piece (A or B) ; 8-10 inch objective, 24° aperture ; 1-5 inch objective, 75° aperture (which easily resolves p. angulatum), and neat walnut case, with lock and handle 50 00 American histological stand, with same accessories as above, but with addition of rack and pinion, instead of sliding tube for coarse adjustment 58 00 American histological stand, same as above, but with binocular attachment, and 1 pair of eye- pieces so 00 American histological stand, with sliding tube coarse adjustment, 1 eye-piece, and walnut case.... 32 00 American histological stand, with rack and pinion coarse adjustment, 1 eye-piece, and walnut case . 40 00 American histological stand, binocular, with 1 pair of eye-pieces, and walnut case 02 00 Accessories for Histological Stand. Extra eye-pieces 5 00 Polarizer, complete, with 1 selenite 15 00 Selenites 100 Neutral tint camera ' 3 00 Stage micrometer, 100-1000 1 00 Eye-piece micrometer (disk) 2 00 646 PRICE-LISTS OF MICROSCOPE FIRMS. Hemispherical spot lens $4 00 Adapter for using objective as achromatic condenser 1 00 Stage forceps 1 75 Animalcule cage 2 00 Double nose-piece 6 00 Glass sliding stage, with spring and ivory-pointed screw, complete 4 00 Rotating stage-plate, with clips 2 00 Woodward's prism, unmounted 1 50 Woodward's prisms, mounted 4 00 Zentmayer's Clinical Stand. Clinical stand, with 2 eye-pieces ; 8-10 inch objective, 20° angle of aperture ; 1-5 inch objective, 75° angle of aperture (non-adjustable). Securely packed in a neat walnut case 50 00 Large Dissecting microscope. Complete 50 00 Botanical Dissecting microscope. Comploto 14 00 Achromatic Object Glasses, Zentmayer's Objectives, 3, 4, and 5 inch combined 15 00 1)4 inch, angle of aperture 23 degrees 15 00 S-10 " " 32 " 18 00 % < l »' 32 " 18 00 4-10 " li 80 lt adjustable 30 00 1-5 " " 120 " " 35 00 8-10 •■ " 26 " 10 00 110 il " 00 " 22 00 1-5 « lt 00 » 18 00 1-10 « " 140 " immersion 20 00 Accessories* Achromatio condenser, with centering adjustment and achromatic combination of % and 1-5 inch.. 38 00 Achromatic condenser (Bicknell's), with blue and ground glass 20 00 Achromatic oblique prism 14 00 Amplifier 8 00 Animaculc cage (large size) 3 50 Animacule cage (small size) 3 00 Ad j datable sub-stage adapter 15 00 Adapter for using an objective as achromatic condenser 1 00 Adapter for using an objective us achromatic condenser, with centering adjustment 7 50 Blue glass cap 1 50 Blue and ground glass shade (changeable) , 4 00 Bull's-eye condenser, for centennial stand 10 00 Bull's-eye condenser, for army stand 5 00 Camera lucida 6 00 Barker's selenites 30 00 Dark wells and holders (set oE three) . . 5 00 Double nose-piece (straight) 9 00 Doable nose-piece (angular") 13 00 Draw-tube (graduated) 4 00 Erector fi 00 Eye-pieces for centenn ial stand, each 6 00 Eye-pieces for United States army stand, each 00 Eye-pieces, Kellner orthoscopic, each 8 25 Frog-plate, complete 4 00 Q lass slips, with ledge, each 30 Indicators to eye-piece.", each 2 00 Jackson eye-piece micrometer 00 PRICE-LISTS OF MICROSCOPE EIRMS. 647 Lieberkuhn to 3 inch, 2 inch, and X% inch objectives, each $6 00 Lieberkuhn to S-10 inch and % inch objectives, each 4 50 Lieberkiibn to 4-10 inch and ^ inch objectives, each 4 00 Mechanical finger ( Zent mayer's) 25 00 Maltwood finder 3 00 Polarizing apparatus for Centennial stand 32 00 Polarizing apparatus for army stand 22 00 Parabola (Wenham's) 13 50 Parabolic silver side reflector 8 00 Parabolic silver side reflector, with Sorby's reflector 15 00 Right angle prism, for reflecting the light more perfectly than the plane mirror 20 00 Selenites, each ... 1 50 Separate monocular body, complete with gradual draw-tube and fine adjustment 30 00 Stage forceps 3 25 Stage micrometer— 100 and 1,000 to the inch 1 00 Stage micrometer— 100, 1,000, and 2,000 to the inch 1 50 Stage micrometer — millimetre and 1-10 and 1-100 of millimetre 1 50 Stage mineral holder . . 00 WenhanTs compressor — 3 50 "White cloud illuminator 4 00 Woodward's prism, unmounted, $1-5X1 ; mounted 8 00 Zoophyte trough 3 50 Astral oil lamp, fitted to mahogany board for centennial stand, with silvered mica shade 14 00 Astral oil lamp, flat wick and plain shade 6 00 Astral oil lamp and silvered mica shade S 00 Silvered mica shades 2 00 No. 13.— G. S. Woolman, 116 Fulton Street, New York (1879). 1. Histological and dissecting microscope combined, with good \ inch objective 25 00 2. Compound microscope, with hinge, sliding tube, and micrometer adjustment, 1 eye-piece, 1 inch and H inch objectives 35 00 3. Same, with 2 eye-pieces and rack and micrometer adjustment 50 00 4. Same as No. 3, binocular 80 00 5. Compound microscope, concentric stage rack and micrometer adjustment, 2 eye-pieces, 1 inch and X inch objectives 75 (JO 6. Same as No. 5, binocular 100 00 7. "Woodward prisms for oblique illumination 1 ^ 8. Polariscope, with selenite and adaptors 1° °" 9. Section cutters 4 50 10. " with clamp screw 6 ^ 11. Seilee's section-cutting machine -*~ 5 " 12. Agent for New York of Charles A. Spencer & Sons' object glasses and K. & J. Beck's micro- scopes. 13. National self-centering turn-table. . . 14. Glass slips, ground edges, per gross . 6 00 3 75 No. 14.— Price List of J. Gkunow's Objectives for Physicians and Students, 70 West Thirty-ninth Street, New York (1879). 3 inch, angle of aperture, 12 degrees IX " " " 15 " 120 ° „ ,. ., .< 25 u 15 00 2 ., ,. ,, ~- : .c 18 00 u " " - ioo •■ ."::::::.'."..'.'.".'.■.".'.■"' a v° 1-6 " " " 140 ' ; (adjustable for cover) 2o m 1-8 " « " 150 ■' " " 300 ° 1-12 " <■ « 105 » «' " 35U0 N.B.— The 1-6, 1-8, and 1-12 inch are either dry or immersion objectives, at the option of the purchaser. , . „ . . 10 00 Angular double nose-piece .. . , i. 18 00 u triple 648 PRICE-LISTS OP MICIiOSCOPE PIKMS. Straight double nose-piece $8 00 12 00 6 00 " triple Frog plate Improved Strieker's warm stage 12 00 Orthoscopic or Kellner eye-piece 00 Section cutter 12 00 No. 15.— W. Wales, Fort Lee, N. J. (1879). First Quality Objectives. 4 inch, angle of aperture, 9 degrees 15 00 3 " " " 12" 1700 IX " •' - 23 " 1700 1 'i « ■- 25 " 18 00 % " " " 30 " 18 00 4.10" " " 75 " 30 00 410" '• - 95 " 35 00 4-1(1" " " 115 " 40 00 1-5 " " " 100 " (adjustable) 30 00 1-5 " '■ ■■ 135 " " 35 00 1-5 " " " 170 " " 40 00 1-10 " " " 170 " " immersion) 45 00 1-15" " " 170 " " " 65 00 1-25" " " 160 " " " 100 00 Wales' ex. pat. back for photographing 15 00 " front " 15 00 Best Students". 1)4 inch, angle of aperture, 23 degrees 15 00 % " " " 30 " 15 00 1-5 " " " 100 " 20 00 1-10" " " 135 " (immersion) 25 00 Economic. l>i inch, angle of aperture, 15 degrees 6 00 % " " " 20 " 6 00 1-5 " " " 80 " 12 00 1-10" " " 120 " (immersion) 20 00 No. 16. — Miller Brothers, 1213 Broadway and 69 Nassau Street, JVew York (1879). No. 1, Binocular Microscope, is of first-class quality in every respect. The stand is firm and free from tremor under observation, even while the adjustment of apparatus may be going on. The binocular mechanism is very superior, realizing both the stereoscopic and perspective views of the object with remarkable ease and perfection. In addition to a rectangular motion of one inch in each direction and rotation by hand, the whole stage rotates concentrically and independently by means of a rack and pinion on a circular plate, graduated so as to form a goniometer or position micrometer. The secondary or sub-stage has adjusting screws for cen- tering all the supplementary apparatus which it receives, and affords facilities for the manipu- lation and use in the most convenient and efficient manner, possessing also the means of rota- tion by rack and pinion, with graduated divisions at the circumference. The fine adjustment is of the most delicate and perfect construction, the index reading off differences iu the focal position nf the objective to the five-thousandth part of an inch, perceptible to the observer's eye. Price of this microscope, including 4 eye-pieces 320 00 If with single body, 2 eye-pieces 260 00 No. 2. This instrument is constructed on the same general plan as No. 1, but is rather smaller. The stage has the usual rectangular motion and one of rotation, without rack and pinion. In workmanship, finish, accurate fitting, and optical qualities it is the same as No. 1. The sub-stage has a rotating cylinder, with adjustments for centering the apparatus which it receives, and provides for their use and application with freedom. The flat and concave mirror is fitted on a double arm to facilitate the oblique reflection of light. The price, binocular, with 4 eye-pieces, is 280 00 If single body, with 2 eye-pieces 200 00 PRICE-LISTS OF MICROSCOPE FIRMS. 649 Stand, 12 inches In height, and draw tube ; heavy base and arm of green japanned cast-iron ; body and ail other parts of well-finished brass ; the body can be inclined to any angle. Coarse adjustment by spiral motion, fine adjustment by a new construction, which is efficient with high powers. Plane and concave mirrors adjustable for oblique light ; revolving diaphragm inlaid even with the stage ; the stage is of glass, with perfectly smooth motions in all direc- tions. One eye-piece, 3 objectives, 1)4, %, and % inch of focus, of our own make. This in- strument having been designed under advice of our most eminent physicians, professors, and amateurs in microscopes, is cheerfully recommended by them, especially for medical purposes. The whole, packed in an upright black walnut wood case, with drawer, price $50 00 Miller Brothers' First-Class Objectives. 4 inch, angular aperture, 9 degrees 12 00 3 " " " 12 " ..'.'.'.'..'.'.'.'.'." 16 00 2 " " " 15 " 18 00 V4 " " " 20 " 20 00 1 " " " 25 " 20 00 % " " " 32 *' 22 00 X " " " 60 " 25 00 X* " " " 75 " 36 00 X " " " 90 " 30 00 H* " " " 130 " 40 00 1-5*" " '« 130 " 50 00 1-8*" '■ " 145 " 60 00 1-18*" '• " 175 " (immersion; 100 00 1-30*" " " 170 " " 130 00 1-40*" " " 170 " " 150 00 All marked (*) have adjustment for covering glass. Student's Objectives. 3 inch ' 10 00 2 " 10 00 IX - 10 00 1 " 10 00 % '■ woo X " 10 00 X " 15 00 Miller's Achromatic Triplets. (Mounted in G-old and Silver.) Gold mountings, 1, %, X, X inch 15 00 Silver " " " " 10 00 Sorby's pocket spectroscope 15 00 Sorby's micro-spectroscope, fitted to any stand, complete 40 00 Extra eye-pieces, A, B, 0, and D each, 6 00 Erecting eye-piece for dissecting 9 00 Improved micrometer eye-piece 10 00 Eelner's orthoscopic eye-piece, C or D, double size field . 9 00 Achromatic condenser, with revolving diaphragm and complete adjustments 35 00 "Webster's achromatic condenser $15 00 to 20 00 Bull's-eye condenser, on stand $2.00, 4.50, to 10 00 Amici's prism, for oblique illumination, mounted on a separate stand 20 00 Nachet's prism, " " 9 00 Rectangular prism, reflection of parallel rays 18 00 Wenham's parabolic reflector $9.50 ; best, 14 00 Silver slide reflector, for opaque objects 9 00 Silver parabolic stage reflector 9 50 Brook's arm, for two objectives $6 00 to 8 00 " forthree " 20 00 Stage micrometer, ruled 100 and 1,000 *. 2 25 " " ruled 100, 1,000, 2.000, 3,000, and 4,000 " " (2 millimetres), ruled in 100 each, with figures 2 50 Maltwood's object finder, in case 3 00 650 PRICE-LISTS OE MICROSCOPE FIRMS. Stage tweezers on jointed arm , $3 50 Zoophyte trough, complete with wedge and spring 2 50 Live boxes for insects §'2,50 to 3 00 Frog and fish plate, complete in glass or metal 2.50 to 4 50 Glass fish boxes 3 50 Glass stage plates, various 50c. and 1 25 Holman's life slide 1 50 " current slide _ 1 50 " syphon slides complete 4 50 Miller's prism, for oblique illumination, mounted in German silver $25. 00 and 35 00 Head's prism 12 00 Plain achromatic condenser, with. ,Y-inch objective, central and annular stops 20 00 Read's hemispherical or kettle-drum condenser 13 50 Camera lucida, Wollaston's $B 00 to 10 00 §8.00 and 10 00 " " neutral tint glass 3 00 Polarizing apparatus $20.00 and 25 CO Selenites, selected colors, $1.00 each ; brass-mounted 2 25 Set of Darker's three selenites, revolving, brass-mounted, showing 13 colors and complementary tints IS 00 Lister's set dark wells 5 00 Dark field condenser, with adjustment $4.00 to 5 00 Miller's stage light modifier, set of three colors. , 3 50 Skeleton stage for very oblique illumination 4 00 Turn-table for making cement cells and finishing slides, complete 4 00 Miller's machine for cutting wood, medical, and other sections $5.00, 7.00, 12.00, 15 00 Diamond for cutting glass slips $4.00 to 10 00 '' thin glass and for writing 4 00 Machine for cutting circlers in thin glass with diamond, complete 13 00 Flatted crown glass slips, 3 by 1 inch dozen, 15c, gross, 1 50 " with ground edges dozen, 30c, gross, 3 50 " " " extra thin dozen, 75c., gross, 7 00 Plate glass slips, excavated cells dozen, 3 00 Round glass ring cells dozen, 1 00 " " fixed on slips each, 25 Bone ring cells, assorted sizes dozen, 50 Thin glass covers, cut round dozen, 25, 30, 40, 50c. ; ounce, 3 50 " " cut in squares " " " ounce, 3 00 " " cut round and square, very thin $6.00 to 12 00 Thin glass in sheets 1 50 Superfine white name labels, oval, in packets 25c. to 50 Colored backB and gilt fronts, with holes punched, per 1000 1 50 f ' holes not punched, per 100 50 Gilt front, " " " 75 Round punches for this purpose each 50c. to 1 00 No. 17. — Bausch & Lome OpticaWo. Rochester, JV. Yi, and 37 Maiden Lane, New York (1879). No, 500. Library Microscope. — This microscope has a finely finished and japanned foot, arm with joint to incline, a nickel-plated body or tube, carrying the optical parts of the instrument and adjustable by rack and pinion, with draw-tube to increase magnifying power; a concave mirror, swinging so as to give oblique illumination when desired, and capable of being brought above the stage for illumination of opaque objects. The screw at the lower end of the tube is so arranged as to permit the attachment of achromatic triplets, so that if desired a much higher magnifying power than the above can be obtained. The stage is made of hard rubber, which is not injured by water or ordinary fluids, and is provided with spring clamps for holding object-slides. The camera lucida which accompanies this microscope, although exceedingly simple, is a valuable addition to the same, and greatly adds to its useful- ness ; it is very easily managed and a little practice will enable anybody to make by the aid of it drawings of tho magnified image of microscopic objects. The microscope has one eye- piece and a divisible twn-lens objective, giving, in combination with the draw-tube, magnif ymg power of from 50 to 125 diameters. It is accompanied by a glass slide with cell for fluids, a plain glass slide and one object. A neat black walnut case encluses the instrument and accessories. Price 10 00 PRICE-LISTS OF MICROSCOPE FIRMS. 651 The same, with two achromatic doublets $12 00 No. 510. Family Microscope. — The base and pillars of this microscope are of cast-iron, neatly japanned. They support the axis which carries the arm m such a way that the instrument may be inclined to any angle. Back and pinion for adjustment of focus, made with such exactness as to leave no perceptible jar, and neither lost or lateral motion while adjusting. In order to give greater sensitiveness to the adjustment, the milled heads of the pinion have been made of large dimensions, in consequence of which the lower and medium powers can be adjusted and used with great ease. The tube is supplied with standard society screw. The mirror, which is concave, is so arranged that it can, it desired, be swung above the stage for the illumination of opaque objects. A revolving diaphragm is fixed beneath the stage. This stand is accompanied by one eye-piece, B (No. 830), mounted in either hard rubber or brass, and one objective, % inch (No. 620), which divides so as to permit the separate use of the posterior combination, thus giving the power of an excellent X% inch. Range of magni- fying power, from 50 to 100 diameters. In upright walnut case, with handle, lock and key, drawer for accessories, and receptacle for objectives and eye-pieces 20 00 No. 520. Educational Microscope.— ~ This instrument has a japanned cast-iron base, inlaid with soft rubber pads on the under surface, on which the weight of the instrument rests, thereby neu- tralizing any tremor or vibration communicated from surrounding objects, and preventing the instrument from slipping or sliding. Solid brass pillars, supporting axis for the arm which carries the body tube. Rack and pinion for coarse adjustment. Fine adjustment as above described. Revolving diaphragm below the stage, concave mirror, which may be arranged for either central or oblique light. One eye-piece, B (No. 830). Two objectives, 2 inch {No. 005), and 4-10 inch (No. 625). Range of magnifying power, 30 to 135 diameters. In upright valnut case, with handle, lock and key, drawer for accessories and receptacles for objectives and eye-pieces 30 00 No. 525. Research Microscope, — This microscope is constructed after an entirely new pattern. It has a neatly japanned iron arm and base, the latter inlaid with soft rubber pads, and of such construction and weight as to counterbalance the instrument at any inclination of its body. Finely finished brass pillars supporting the axis, which permits the body to incline at any angle. The tube has nickeled inner draw-tube, giving a range of 3 inches. Coarse adjust- ment by rack and pinion; fine adjustment by micrometer and screw, acting on our patent fine adjustment. This new style of fine adjustment is a peculiar feature of all our higher- priced microscopes. It consists of two parallel blades of thin spring steel, placed one above the other, each fastened with one end to the arm, with the other to the body, and acted upon by a fine micrometer screw, attached to a lever protruding from the body, by means of which the latter may be raised or depressed, with extraordinary delicacy of adjustment. It has no lost motion, and having no friction is not liable to deterioration. The stage is made of brass, and is made as thin as is consistent with firmness and freedom from tremor. Removable spring clips on stage. The mirror-bar is hung on a point placed above the stage and be- tween this and the arm. It swings to any obliquity and any angle above the stage for the illumination of opaque objects. Plain and concave mirror adjustable along the mirror-bar. One eye-piece, B (No. 830). Objectives 1 inch (No. 610), and % inch (No. (135). Camera lucida. Range of magnifying power from 54 to 250 diameters. In neat black walnut case, with handle, lock and key, drawer for accessories and receptacles for objectives and eye-pieces 45 00 Same with standard size sub-stage and revolving diaphragm, adjustable along the mirror-bar, inde- pendent of the mirror and entirely removable, extra 3 00 In place of the brass stage we affix our glass stage with slide carrier, as described in No. 550, extra. . 5 00 No. 530. Students Microscope . — The stand of this microscope is constructed -with a japanned cast- iron foot, nicely finished, inlaid with soft rubber pads. Brass pillars which support the axis in such a way as to allow the body to be inclined to any angle, the instrument remaining well balanced, in all positions of the body. Brass arm, coarse adjustment by sliding tube, the latter nickel-plated ; fine adjustment by fine micrometer screw, acting upon our patent movement described with Microscope No. 525. The stage is supplied with spring clips, and with an adjiistable shoulder to vary the position of the object-slide on the stage, and to keep it parallel to the latter. Plain and concave mirrors, arranged so that their distance from the object may be varied, and adjustable for oblique light ; revolving diaphragm under the stage. Two eye-pieces, A (No. 825), and C (No. 835), the latter arranged with a slot to receive eye-piece micrometer. Eye-pieces furnished mounted either in hard rubber or brass, at purchaser's option. Two objectives, viz., % inch (No. 615), and 1-5 inch (No 640). Camera lucida and eye-piece micrometer. Range of magnifying powers from 50 to 375 diameters. In upright walnut case, with handle, lock and key, with drawer for accessories, and receptacles for eye-pieces and objectives 50 00 No. 535. Student's Microscope. — The same stand as No. 530. with rack and pinion for coarse adjustment. Fine adjustment the same as No. 530. Rub-stage for accessories into which a revolving diaphragm is fitted, the latter being removable. Plain and concave mirrors, arranged so as to allow the most oblique light for high powers. and also a variation in their distance from the object. Accompanying accessories the same as with No. 530. Magnifying power also the same. In upright, walnut case, with handle, lock and key, drawer for accessories and receptacles for eye-pieces and objectives 60 00 652 PRICE-LISTS OF MICROSCOPE FIRMS. No. 540. Student's Microscope. — The general construction of this microscope is the same as of No. 535, with the exception of the stage, which consists of a solid glass plate resting on two brass pieces joined to the arm. This glass plate is provided with a movable metallic slide-holder, which serves as a substi- tute for a so-called mechanical stage. It is of very light weight and rests on the surface of the immovable glass stage on only four small points protruding from the plate, while the prolongations of the latter, bent downward and backward, and acting as springs, press against the under side of the glass plate with just sufficient force to keep it in its place when the body is inclined. This pressure can be varied at the option of the manipulator ; spring clips are provided to hold the object-slide. This construction of the object-slide carrier, in combination with the smoothness of the surfaces of the glass stage, reduces the friction to a minimum, and renders the movement of the former very delicate, smooth and firm. Two small knobs on the slide carrier facilitate the movement. The slide carrier can be detached from the stage if so desired. The sub-stage consists of a brass ring, joined to the brass pieces supporting the glass stage, and is of the standard size. Revolving diaphragm fitted to sub-stage. Accompanying accessories the same as with No. 530. Magnifying power also the same. In upright walnut case, with handle, lock and key, drawer for accessories and receptacles for objectives and eye- pieces $70 00 No. 550. — Physicians Microscope. — The stand of this microscope is firm and well balanced, finely finished, and of superior workmanship throughout. It is a microscope best adapted for the use of physicians and students of histology, and is extensively used at present by professional men, and in many of our most prominent institu- tions of learning. Heavy japanned cast-iron foot, of neat design and finish, inlaid on the under surface with three soft rubber pads. Strong solid brass pillar and arm, both connected by a well-fitting joint, which allows the body to incline to any angle. Pillar and arm so marked as to indicate the correct inclination of the body for the use of the camera lucida. Draw-tube, having a range of 2)4 inches, and supplied with a stop when drawn to standard length. It is nickel-plated, and has a firm but perfectly smooth movement. Coarse adjustment by rack and pinion, free from either lateral or lost motion. Fine adjustment by sensitive micrometer screw, acting upon our patent movement as described with No. 535. Large stage, free from tremor, and sup- plied with sub-stage to receive diaphragm, polarizer, etc. The diaphragm receives three extra caps, having apertures of }4, \% and 2y, millimetres, and so fitted that they are in the cor- rect centre of the held, and just below the plane of the stage. If desired, a simple revolving diaphragm will be fitted into the sub-stage, in place of the above. Large plane and concave mirrors, and mirror-bar arranged with a double joint, so that they can be brought to any obliquity, and can be swung above the stage for the illumination of opaque objects. Eye-pieces, A (No. 825) and G (No. 835), the latter arranged with slot for micrometer, mounted either in hard rubber or brass, at the option of the purchaser. Objectives, % inch (No. 615), and 1-5 inch (No. 640). Camera lucida, eye-piece micrometer. Magnifying powers, with tube at full length, 50 to 375 diameters. In upright walnut case, with handle, lock and key, drawer for accessories, and receptacles for objectives and eye-pieces 60 00 No. 555. Physiciaii's Microscope. — The stand of this instrument is of the same general construction as that of No. 550, with the exception of the stage, which consists of a solid glass plate, as described with No. 540, with this difference, that the sub-stage is fitted into the glass plate by a society screw ; this arrangement prevents any light from below being thrown upon the objects, except through the central opening of the diaphragm. Diaphragm as described with No. 550, or with ordinary revolving diaphragm. Accessories the same as with No. 550. Range of magnifying power also the same. In upright walnut case, with handle, lock and key, drawer for accessories, and receptacles for objectives and eye-pieces 65 00 No. 560. Large Student' 'sMlcroscope.— -This microscope is designed for the use of higher powers in the more delicate microscopical investigations. It has a heavy cast-iron foot, neatly japanned, inlaid at the under side with soft rubber pads. Solid brass pillars supporting axis, the latter and the pillars so marked as to indicate the proper inclination of the tube for using camera lueida. Brass arm, carrying body tube and supporting glass stage, the same as described with microscope No. 540. Coarse adjustment by rack and pinion, fine adjustment by sensitive micrometer screw, act- ing on our patent motion as described with No. 525. Plane and concave mirrors, with sub-stage of standard size, revolving diaphragm fitted into and separable from latter, all attached to the swinging mirror-bar, the axis of which is placed on the level of the object, so that diaphragm and mirror swing concentrically around the same. Mirrors movable on the mirror-bar to and from the object, and can also be en- tirely detached. The distance between the sub-stage and the object can be varied by revers- ing the former. The sub-stage can also be detached when greater obliquity of light is desired. Three eye-pieces A (No. 825), B (No. 830), and C (No. 835), mounted either in hard rubber or brass, and the C eye-piece arranged with slot for micrometer. Three objectives, 2 inch (No. 605), % inch (No. 615), and 1-6 inch immersion (No. 680). Range of magnifying power, from 22 to 450 diameters. In upright walnut case, with handle, lock and key, drawer for accessories, and receptacles for objectives and eye-pieces JJO qq No. 570. Professional Microscope.— -This instrument is provided with a heavy brass foot, highly finished, inlaid with three soft rubber pads at the under surface. Two solid brass pillars support the axis for inclination of the body. Two strong screws with milled heads, placed at PKICE-LISTS OF MICROSCOPE FIRMS. 653 the ends of the axis, serve to tighten or loosen the connections by means of which the arm can be made to move with more or less ease. Course adjustment by rack and pinion, moving a long prismatic slide accurately fitted, at- tached to the body, and arranged for compensation of wear, Fine adjustment by micrometer screw, with milled head, silvered and graduated, acting upon our patent movement described with No. 525. Glass stage with slide holder similar to that described with Microscope No. 5-40, but is of larger dimensions, circular in form, and fitted to receive the hemispherical immersion con- denser. In this stage we gain thinness, while still maintaining its stability. The slide carrier moves in any direction, and also revolves. Sub-stage and mirrors (plane and concave) are fastened to the swinging mirror bar, the axis of which is fixed in the plane of the object, thereby permitting the accessories and mirror to swing concentrically around the object:. The mirror may be brought to any obliquity and swung above the stage for the illumination of opaque objects. The mirror, as well as the sub-stage, can be moved on the mirror bar to and from the object, and both can be removed altogether, in an improved manner. The sub-stage ring receives the revolving diaphragm, condenser, etc., and auxiliary ring with internal society screw, which accompanies the instrument, and to which objectives and other auxiliaries may be fitted. Three periscopic eye-pieces, B (No. 855), C (No. 800), and D (No. 865), the latter arranged with slot for micrometer. Four objectives, 2-inch (No. 605), %-inch (No. 615), 1-5- inch (No. 640), and > e '-inch immer- sion, adjustable for cover correction (No. 695). Hemispherical immersion condenser (No. 975). Range of magnifying power, from 30 to SOU diameters. In upright walnut case, with handle, lock and key, drawer for accessories, and receptacle for objectives and eye-pieces $200 00 Objectives. STUDENT'S SERIES. Focus. Angular Aperture. Adjustment. Price. No. 600 4 inch. 2 1 3-4 1-2 4-10 " 3-10 " 1-4 " 1-5 1-8 6° 12° 20° 27° 40° 55° 75° 100° 110° 120° Non-adjustable. *6 00 6 00 " 605 " 610 "615 6 00 8 00 " 620 9 00 " 625 "630 . 11 00 "635 14 00 " 640 15 00 " 645 18 00 The low-power objectives of this series are remarkable for their excellent definition. The %-inch which accompanies our stands when so enumerated in the price-list, has obtained a celebrity for its extreme flatness of field and excellent definition ; the 3-10 resolves PI. Angulatum by a slight obliquity of light ; the X resolves the same by central illumination ; the 1-5 the same into dots by central light and the finer lines of the Surrirella Gemma (dry) with ease. PROFESSIONAL SERIES. Focus. Angular Aperture. Adjustment. Price. No. 650. .. 4 inch. 2 " :T 3-4 " 1-2 " 1-4 " 1-6 " Im. 1-6 " " 1-8 " " 1-8 " " 1-12 " " 1-16 " " 10° 15° 36° 35° 60° 110° 165° 165° 170° 170° 175° 175° Non-adjustable. Adjustable. Non-adjustable. Adjustable. $13 00 " 655 " 660 . 13 00 15 00 "670 14 00 15 00 " 675 16 00 " 680 20 00 "685 23 00 " 690 23 00 " 695 25 00 "700 30 00 " 705 35 00 The lower powers of this series are all two-system, and are remarkable for their perfect correction and beautiful definition. They will compare favorably with any made of corresponding powers. The % easily resolves PL Angulatum by central light ; the 1-6 has extremely large working distance, which is also the case with the higher powers. Those from 1-8 upward will resolve all objects on Holler's dry plate. 654 PRICE-LISTS OF MICROSCOPE FIRMS. FIRST-CLASS SERIES. No. 710. " 715. " 720. " 725. " 730 " 735. " 740. " 745. " 750. " 755. Focus. I 4 i 2 1 1-2 4-10 1-6 1-8 1-10 1-12 1-16 Angular Aperture. 12° 20° 42° 85° 110° 180° 180° 180° 180° 180° Adjustment. Price. Non -adjustable. $15 00 it " 18 00 it " 22 00 U it 25 00 II 11 28 00 Adjustable. 35 00 " 42 00 11 46 00 " 50 00 " 75 00 The lower powers have highest resolving power. The X'irich resolves PL Angulatum ; the 4-10 the same with central light ; the 1-6 and higher powers have au immersion angle of 130°, and will resolve the most difficult tests. The adjustable objectives are in new and beautiful form of mounting, have inner. "motion giving rec- tilinear movement to posterior systems, and are arranged with graduated and silvered collar. With New Compensating Adjustment for Cover Correction. {Patented Jan. 1, 1878.) STUDENT'S SEEIES. Focus. Angular Aperture. Price. No. 760 3-10 inch. 1-4 " 1-5 " 1-6 " 1-8 " 75° 105° 112° 115° 120° $17 00 IS 00 "765 " 770 20 00 " 775... 22 00 "780 24 00 These objectives are of the same optical standard as those mentioned in preceding Student's Series, but give higher results on account of the perfect adjustment. The ,^-inch of this series resolves Cyma- topleuro elliptica (dry mount), or No. 17 on MOller's plate, and the others give proportionately good per- formance. They all have large working distance. PROFESSIONAL SERIES. No. 785 " 790 " 795 Focus. 1-5 inch. 1-6 " 1-8 " Angular Aperture. 120° 170° 170° $25 00 2S 00 33 00 The performance of these is unsurpassed for dry- working objectives. They are mounted in the same elegant form of mounting as described in First-class Series. Focus. Angular Aperture. Price. No. 800 4-10 inch. 116° $35 00 Hiiysrnian Eye-pieces. No. 825A. or 1%-inch, mounted in hard rubber or brass $3 00 No. 830B. or i " " " " " 3 00 No. 8350, or % " " " " " 3 00 No. S40T). orX " " " " " 3 00 No. 845B and D combined in one 4 50 PRICE-LISTS OF MICROSCOPE FIRMS. 655 Periscopic Eye-pieces. No. S50A, mounted in hard rubber or brass $11 00 No. 855B, " " " u 10 00 No. S60C, 9 50 No. 8G5D, " ■' " " DUO Higher powers 9 00 Eye-pieces C and D arranged with slot to receive micrometer, and supplied with ring to exclude light, eye-lens being adjustable for focus, 75 cents extra. No. S70. Aplanatic triplet, 17-32 inch diameter, 1 inch focus, in tortoise-shell mounting 10 00 No, 875. Same in brass mounting, nickel-plated 10 50 No. SS0. Aplanatic triplet, 1-1-32 inch diameter, % inch focus, in tortoise-shell mounting 9 00 No. SS5. Same in brass mounting, nickel-plated 9 50 No. S90. Aplanatic triplet, 11-32 inch diameter, y t inch focus, in tortoise-shell mounting 8 00 No. 895. Same in brass mounting, nickel -plated 8 50 No. S9S, Achromatic magnifier, two doublets, giving powers of 7, 10, and 18 diameters, in tortoise- shell mounting 9 00 No. 900. Double convex condensing lens, \% inch diameter, on stand 1 25 No. 905. Bull's-eye condenser, \% in. diameter, on stand 2 50 No. 910. " " 1 7 8 in. " " 4 50 No. 915. " " %% in. " *' 7 50 No. 920. " " 3 in. '■ " 10 00 No. 925. " " 3 in. M with joint 12 00 No. 930. Mirror stand, for supporting mirror to illuminate opaque objects 1 00 No. 940. Polariscope, mounted in brass and arranged with adapter to fit into the tube above the objective, with opening on each side to allow the inner prism to be turned 11 50 No. 945. Paraboloid, for dark ground illumination 8 00 No. 950. Camera lucida, prism for any eye-pieces 5 50 No. 955. Camera lucida, neutral tint , 1 50 No. 960. Spot lens, with society screw 2 50 No. 975. Hemispherical immersion condenser. This condenser is mounted in brass, and made to fit either in stage or stationary sub-stage. It con- sists of a truncated cone of crown glass, with a convex base, the centre of convexity of which coincides with the point where the optical axis of the microscope crosses the place of the object, and where all the light which passes through the condenser concentrates. No matter in what position the mirror may be placed, the light always enters the convex side of the condenser without refraction, and is therefore free from aberration. The best results are attained when the plane surface of the condenser is connected with the under surface of the object slide by water or glycerine 10 00 No. 980. Achromatic condenser, mounted in brass, and fitted for sub-stage, with revolving dia- phragm having central stops 25 00 No. 985. Paraboloid for dark ground illumination, with adjustable stop, mounted in brass and fitted for sub-stage 10 00 No. 990. Paraboloid plain, mounted in brass and fitted for sub-stage 8 50 No. 995. Spot lens, mounted and adapted to fit sub-stage 4 00 No. 1000, Polariscope, with extra large prisms, and selenite plate ; the analyzer is connected with goniometer and separate eye-piece 40 00 No. 1005. Polariscope mounted in hard rubber, with separate and revolving eye-piece , 15 00 No. 1010. Camera lucida with prism, with lens to magnify pencil-point to fit "any instrument 8 00 No. 1015. Eye-piece micrometer, divided in 1-10 or 1-20 mm 1 00 No. 1020. "Woodward prism for gaining great obliquity of light 2 00 No. 1025. Double nose-piece (bent) 00 The obstacle to the more extensive use of this exceedingly useful accessory has been the fact that, no matter how well centered the nose-piece may be, objectives not specially fitted to it will be out of the line of the optical axis, and that each must separately be brought in focus when used, thereby causing incon- venience and delay. We therefore arrange, when a double nose-piece is desired, the powers of the objec- tives accompanying our microscopes in pairs, in such a way that each pair is correctly centered, and cor- responds in focus without necessitating further adjustment. No. 18.— T. H. McAllister, 49 Nassau Street, New York (1879). Professional Microscope Stand. Price, with 2 eye-pieces 69 00 Walnut case, with lock and handle 4 50 The Professional microscope is 15 inches high when inclined at angle for convenient obser- vation ; the base and body of brass, finely finished, with extension draw-tube. The quick focal adjustment is by chronometer chain, much more uniform and exact than the ordinary rack movement ; the fine adjustment is bya delicate micrometer screw moving the entire optical system vertically ; glass stage plate, movable in every direction ; concave and plain. 656 PRICE-LISTS OF MICROSCOPE FIRMS. mirrors, etc. ; removable collar beneath the stage for carrying polarizer, parabola, and other accessories. The mounting for objectives is made with the " Society Screw," so thai the objectives of all first-class makers can be used with the instrument. Physician' 1 s Microscope Stand. Price, with 2 eye-pieces i&oO 00 Walnut case, with lock and handle 3 50 The Physician's microscope is a first-class instrument, especially adapted for the use of medical men. It is very compact in form, but capable of receiving all the accessories usually desired. The main tube of the body is about six inches long, thus enabling an observer to use the microscope with case in a vertical position, so often necessary when fluid objects are on the stage ; the total height from the table to the eye-piece 1 1 inches, yet can be increased to the usual height of the large stands by the extension of the draw-tube. The focal adjustments are the same as in the professional microscope ; movable glass stage after the construction originated by Zentmayer; concave and plane mirrors; removable collar beneath the stage for carrying polarizer, parabola, and other accessories ; society 6crew mounting for objectives. StetdenCs Microscope Stand. Price, with 1 eye-piece 30 00 Walnut case, with lock "and handle . 3 50 The Student's microscope is a neat, serviceable instrument, adapted for a good tl working " microscope. It stands 12 inches high when conveniently inclined ; the base is of iron, bronzed, of neat design ; the body of brass, well finished, with extension draw-tube; the quick focal adjustment is by a chronometer chain movement, as in the Professional and the Physician's Microscope stands, and the fine adjustment is by a micrometer adjustment attached to the stage ; concave and plane mirrors ; removable collar beneath Che stage for carrying polarizer, parabola, etc ; society screw mounting for the objectives. * # * Tlie Students microscope is offered, with, good achromatic French objectives^ 1 inch and Ibth inch, giving every grade of magnifying power from 50 to 450 diameters, complete in walnut case, with lock and handle 43 00 Microscopic Accessories. Bull's-eye condensing lens, on brass stand, for the " Professional " microscope 8 00 " " lt " for the " Physician's " or the " Student's 11 microscope.. 5 00 Polarizing apparatus for the " Professional " microscope 20 00 " " " "Physician's" " 15 00 " " " "Student's" " 12 00 Animalcule cage, best 3 50 " " second quality 2 00 Zoophyte trough 2 50 T. H. McAllisters reflector for drawing ; more practical than the camera lucida, and can be attached to any microscope 2 00 Stage micrometer, 1-100, 1-1000 1 25 Eye-piece micrometer 4 U0 Maltwood finder 3 00 Erector 7 00 Amplifier 1 50 Stage forceps 2 50 German study lamp, nickel-plated, latest improved 6 00 Holman life slide 1 50 " current slide 1 50 " Byphon slide 4 00 Mounting Materials. Glass object slides, 3x1 inches per dozen, IS to 60c. " " " per gross, $1.50 to 6 00 Thin glass covers, various sizes, circles and squares per dozen, ISc. to 35c. ; per ounce, §1.50 to 3 00 Section cutters $4.00 to 20 00 Turn-tables 3.00 to 7 00 Canada balsam per bottle, 50 Damar cement 50 White zinc cement » 50 Glycerine jelly 50 Gold size 25 Brunswick black 25 Carmine, ammonia, borax 25 Carmine or indigo 25 Aniline— magenta, blue, or violet 25 PKICE-LISTS OF MICROSCOPE FIRMS. 657 Eosin 25 Hematoxylin 25 Glass-capped bottle for balsam, etc 50 Dropping and dipping tube 10 Labels, square, for 3x1 inch slides per 100 25 " oval , « 10 Cabinets, white wood, for 35 objects , 15 M polished mahogany, 36 objects, flat , $3 00 72 " " '..'..'.'. 500 " " " 144 " '- 8 00 11 " " 13 drawers, 600 objects 28 00 " '• 20 » 1,200 « '.'" 40 00 Mounted specimens for the microscope, from $1.50 per dozen upwards. No. 19. — Charles A. Spenuer & Sons, Geneva, JV. Y. (1872). Stitdenfs Microscope, No. 1, height, 15 inches ; weight, 6 pounds. The arm, pillar, and base are of japanned iron ; arm attached by cradle joint, and taking any position from vertical to horizontal ; coarse adjustment by sliding tube in velveted clip, and the fine by milled head upon the stage ; by a curved arm the double mirror (plane and concave) has a lateral movement for oblique light, or may be swung above the stage for side illumination of opaque objects. It is furnished with B eye-piece, 1 inch objective of 20 degrees angle of aperture, with a very flat and well defined field, giving a power of 85 diameters ; a % inch of 60 degrees angle of aper- ture, adjustable by front lens, giving a power of 325 diameters. In neat cabinet GO 00 Stand No. 2, like No. 1, with addition of rack and pinion for coarse adjustment, and micrometer screw and lever, fine adjustment to nose-piece ; camera lucida and animalcule cage ; same objectives, eye-piece, and cabinet 100 00 Stand No. 3. Stand of finished bronze and brass ; complete as in No. 2 ; A and B eye-pieces ; 2 inch objective of 12 degrees angle of aperture ; 1 inch objective of 20 degrees angle of aper- ture ; K inch of 60 degrees ; camera lucida, cabinet 125 00 Standard Microscope, No. 1. — Stand 17 inches high, weight, 11 pounds. This mounting of the sim- plest and cheapest form; has the arm, pillar, and base of finished japanned iron; the arm attached by cradle joint, and taking any position from vertical to horizontal ; the coarse adjustment by rack and pinion, or by new friction pinion ; the mirror (plane and concave) adjustable for oblique light or for side illumination of opaque objects ; packed in cabinet 75 00 Other forms and sizes of stands made to order. First-class Objectives.— targe Angles of Aperture. Focal Length. Angle of Aperture. Price. Focal Length. Angle of Aperture. Price. $35 30 30 30 40 40 45 50 X inch a " % '■ 160° 170° to 175°, new form. 175°, new form. 175°, 175°, 175°, 175°, $65 a 751 ,3 27° 37° 30° 40° to 45° 80° 90° IX inch 80 Z 1-12 inch 1-15 or 1-10 inch. 1-20 inch 1-50 " 100 1 B 1 " X " 120 fg 150 £ 4-10 inch 200 J 5' 1-4 or 1-5 140° p First-class Objectives.— Medium and Smaller Angles of Aperture. Focal Length. Angle of Aperture. Price. Focal Length. Angle of Aperture. Price. 2 inch 1 " 12° 20° 55° to 60° 40° non-ad- juBtment. 818 20 35 20 1-4 or 1-5 inch . . 1-5 or 1-6 inch . . 1-13 inch 80° 60°, adjust, by fr. lens. 180° 140° $35 25 X " 40 70 Objectives are made with the L. M. Society's screw, or our standard bayonet catch, as may be desired. 658 PRICE-LISTS OF MICROSCOPE FIRMS. No. 20. — B,. B. Tolles (Charles Stodder, Agent), Devonshire /Street, Boston, Mass. (1879). Student's Microscope. Fifteen inches high, weight, six pounds. The base, uprights, and curved arm are of iron, hand- Bomely japanned ; on a trunnion joint, made on a new p]an to wear well, by which the instru- ment can be placed in any position, from vertical to horizontal, with a stop to prevent move- ment in either direction beyond these points. It is furnished with a 1 inch eye-piece, 2 second quality objectives, of about 1 inch and % inch power, giving about 80 and 35(1 diame- ters ; a plain stage, with spring clips for holding the object slides; revolving diaphragm, concave mirror, with movement to give oblique light ; for illumination of opaque objects the mirror is removed to an upright stand ; coarse adjustment for focus is effected by sliding the compound body, which is held in its place by a spring ; fine adjustment by a movable plate and screw on the stage, which is efficient with high powers. Price, in an upright black wal- nut case $50 00 Stand and case alone 28 00 VABIATIONS AND ADDITIONS. Extra eye-pieces, 2 inches, \% inch, and % inch, each 4 00 Superior camera lucida 5 00 Sub-stage for accessory apparatus 5 00 Sliding stage, giving vertical and horizontal motions by the hand, and adapted for the use of Malt- wood's finder 15 00 Fine adjustment by lever and micrometer screw 20 00 Rack and pinion for coarse adjustment 12 00 Draw tube 4 00 Plain mirror 3 00 Thin glass stage to rotate on the optical axis 10 00 The stand all brass 10 00 15. Large Microscope. This instrument is intended to meet the wants of the highest scientific investigation; to attain everything that the microscopibt can accomplish, without sparing the cost, and to permit the use of all the modern assessory apparatus. It is constructed on the curved arm (Jackson) model. The instrument is 18 inches high and weighs about 14 pounds. It is of simple con- struction, with fewer screws and pieces than any other first-class microscope. The curved arm is supported on a steel trunnion, between two strong brass pillars, made for durability, and not liable to get out of order, and provided with a method of compensation fur wear. Has rack and pinion for coarse, and micrometer screw for fine adjustment of focus; gradu- ated draw tube ; sub-stage with rack and pinion, and centering screws for accessory appara- tus ; plane and concave mirrors on double-jointed firm ; Tolles's thin stage, admitting light of great obliquity, with rectangular movements by screw and rack and pinion, and rotation on the optical axis of about 326 degrees— all that is essentially necessary. Price. 225 00 A modification of this size, with the stage carried by friction rollers, and entire rotation on the optical axis, can be made at an advanced price. A. Largest Microscope. This instrument is one of the largest yet produced anywhere. It is similar in all respects of style and construction to the B instrument, but larger and heavier, weighing 20 pounds. The stage is six inches in diameter, and makes a complete revolution on the optical axis. The whole instrument rotates on a stout plate graduated to degrees. Price of stand 300 00 Can be furnished with radial arm, which describes a curve, of which the focal point is the centre, to carry accessory apparatus at any angle, for 50 00 A graduated arc registers the obliquity of the incident light. The Professor's Microscope. This is an instrument similar to the clinical. It is intended to pass around a class of students. Is provided with a means of clamping the object slide to the stage, so that the particular object the lecturer is explaining cannot be moved out of the field, while each observer can adjust the focus to his own eye. Price, without objectives 25 00 This instrument, and the "Pocket," are used without a stand by holding it in the hand and looking at the light. The Pocket Microscope. For clinical and field, or seaside use ; is a simple tube inches long, with ^ inch objective and B eye-piece ; fine and coarse adjustment for focus ; a stage with spring clips to hold the object, PRICE-LISTS OP MICROSCOPE FIRMS. 659 which can be removed when not in use, and the objective covered with a brass cap, making the most compact and efficient portable instrument in use. Price $25 UO With a draw tube for increasing the power . Microscope Objectives. FIRST QUALITY OP LARGE ANGULAR APERTURE. These are made for the highest requirements of the microscopist and histologic, as tracing nerve- fibre, cell-formation, resolution of Nobert's lines, etc., etc. X inch, angle of aperture, 0C° to 80° -10 UO 4-10 inch, " " 90° to 120° 45 00 4-10 " " " 135 c tol45° 05 00 This objective may be used as an achromatic condenser, with special advantage. 3£ or 1-5 inch, angle of aperture 120° to 130° 15 00 % or 1-5 up to 150° 55 00 Jforl-5 " " " up to 180° TO 00 1-6 inch. §5 advance on H inch. 180° 70 00 1-8 " angle of aperture to 160° 70 00 1-8 " '• " to 180° 80 00 1-10 " $5 advance on price of 1-8 inch. 180° 85 00 1-19 " angle of aperture under 140° 80 00 1-12 " " " up to 100° !)0 00 1-12 " " " up to 1S0° 110 00 1-15 " " " up to 160° 110 00 1-15 " " " np to 180° 120 00 120 " " " up to 180° 150 00 1-25 " " " up to 180° 175 09 1-50 " " '■ by special contract. 1-75 " All objectives of 180° may be duplex front, or three systems. FIRST QUALITY OBJECTIVES. Having less angular aperture, more penetration, with first-class adjustment for cover. 1-2 inch, angle of aperture 00° or less 35 00 4-10 inch, " " 85° or less 10 00 1-4 and 1-5 inch, angle of aperture 100° to 120° 40 00 1-6 inch, angle of aperture 100° to 120° 45 00 1-8 " '• " 100°tol80° 15 00 1-10 " " " 100°tolC5° 50 00 1-12 " " '' 120° 55 00 1-15 •' " " 120° 00 00 1-20 " " " 140° 80 00 All of 1-5 inch, or higher powers, will be made either dry or immersion, at the s:ime price, to work both ways with the same lens. With an extra "front" lens $10 to 2-5ths extra. All the foregoing have Tolles's adjustment for covering glass, which does not move the front lerrs, and has no back lash. FIRST QUALITY OBJECTIVES. Without adjustment for cover. 4 inch, adjustable to 3 inch 35 00 2inch 20 00 2 inch, higher angle of aperture 1% and 1 inch in one 23 00 25 00 10 00 23 00 30 00 1 " 30° X " new formula, specially flat field 30 00 }$ " 25° to 40° s3 °° % " specially constructed for viewing opaque objects 23 00 Ji' " 40° to 70°, adjusting by front lens, specially constructed for viewing opaque objects 23 00 660 PEICE-LISTS OF MICROSCOPE FIRMS. SECOND QUALITY OBJECTIVES. Without adjustment for cover. 1-8 inch, immersion, 120° $25 00 1-10 '■ '■ 120° 30 00 1-6 " 90" to 100° 18 00 1-4 or 1-5 inch, 70° to 90°, will resolve well PI. angulation 15 00 H inch, 40° to 50°. Has a long working distance for opaque objects 12 00 Xinch 12 00 2 and 124 inch 8 00 1 inch 6 00 All objectives are made with the ' l Society " screw, so as to fit all recent EDglish or American stands, unless ordered otherwise. No. 21.— W. H. Bulloch, 126 Clark Street, Chicago, 111. (1879). Al. Congress patent, May 27, 1879, with all the latest improvements. Binocular mechanical stage, concentric; adjustable to the optic axis ; swinging sub-stage and mirror ; broad gauge screw for wide angle ; low powers ; safety nose-piece, with Society screw ; rack and pinion coarse motion; lever slow motion, moving the whole body; adjustable sub-stage, revolving wiMi rack and pinion (the stage, sub-stage, mirror, base, and side of body tube are graduated). Iris, and G-illet diaphragm, 5 eye-pieces 300 00 Professional stand, patent 1879; 16 inches high when arranged for use; swinging sub-stage and mirror; can be used over the stage ; rack and pinion coarse motion; lever fine adjustment, moving the whole body ; London Society screw, also the broad gauge screw ; sliding glass stage; has complete revolution, and is adjustable ; single pillar and tripod base; Gillet diaphragm, 2 eye-pieces, and case ^0 00 Biological stand, patent 1870 ; 12^ inches high when arranged for use ; stage %% inches from table when in a horizontal position ; tube 5 inches long, but with draw to 1) inches ; rack and pinion coarse motion; lever fine motion, moving the whole body; single pillar and tripod base; stand all brass ; plain stage, with spring clips. Diaphragm, sub-stage, and mirror each swing over the stage. Stand, 1 eyepiece, and case 40 00 , ■ . ■... ,,.■...■: , v ■...>, :■';■':•:■•■■■:■■■ -:■:■{:-■■■[■>■■■■■'',■■ "■;■■■- ■ ■. ■."';■■ ■■■ ■•■','■ • ■ •■■-■ V\-V , ;; :, ;,::r\-.>:-; -::■ ■■■■ . ; ■■>■ >■. ....... ............ .