... :■■_. ;..■■.. y aM cr r- fell- CORNELL UNIVERSITY. THE llostudl ^ momev Cib*a*B THE GIFT OF ROSWELL P. FLOWER FOR THE USE OF THE N. Y. STATE VETERINARY COLLEGE. 1897 Digitized by Microsoft® Digitized by Microsoft® This book was digitized by Microsoft Corporation in cooperation with Cornell University Libraries, 2007. You may use and print this copy in limited quantity for your personal purposes, but may not distribute or provide access to it (or modified or partial versions of it) for revenue-generating or other commercial purposes. Digitized by Microsoft® Digitized by Microsoft® Digitized by Microsoft® Digitized by Microsoft® Digitized by Microsoft® A TEXT-BOOK OF HISTOLOGY INCLUDING MICROSCOPIC TECHNIC BY A. A. gOHM, M. D., and M. VON DAVIDOFF, M. D. of the Anatomical Institute in Munich Edited, with Extensive Additions to both Text and Illustrations BY G. CARL HUBER, M.D. Junior Professor of Anatomy and Director of the Histological Laboratory University of Michigan Authorized Translation from the Second Revised German Edition BY HERBERT H. CUSHING, M.D. Demonstrator of Histology and Embryology, Jefferson Medical College, Philadelphia WITH 35t ILLUSTRATIONS PHILADELPHIA W- B. SAUNDERS & COMPANY LONDON: J6J, STRAND, W. C. 1900 Digitized byQWicrosoft® S5-/ ^^irte— Copyright, 1900, R (o ~) every time the milled head is moved 1 notch (toward the manipulator) the slide carrying the clamp holding the tissue is elevated 5 microns ; 2 notches would elevate the tissue 10 microns (tsVs" °f an i ncr J 4 notches, 20 microns (y^-j-j- of an inch), etc. It is not essential to have a lever attached to the instrument as above described, although this is very convenient ; if not present, the milled head is moved the desired number of notches with the hand. 46. In cutting paraffin sections with the sliding microtome the knife is placed at an angle of about 35 to 40 to the horizontal plate of the microtome. Sections are cut more easily with the knife in this posi- Digitized by Microsoft® 32 THE MICROSCOPIC PREPARATION. tion than when the knife is placed at right angles to the microtome, as is often recommended, and it does not seem that the tissues suffer materially from distortion when they are cut with the knife at an angle, as is some- times claimed. Before fastening the paraffin blocks into the clamp on the microtome, preparatory to cutting sections, the paraffin is trimmed with a sharp knife from the end of the paraffin block until the tissue is nearly exposed, care being taken, however, to leave a flat surface. The top of the paraffin block is then beveled off on three sides to within a very short distance of the tissue. The fourth side, that which faces the knife when the block is clamped in the microtome, should be trimmed only to within about yk of an inch of the tissue. This edge of paraffin is made use of, as will be seen in a moment, for preventing the sections from curling while they are being cut. The paraffin block is now ready to be clamped in the microtome. This is done in such a way that the paraffin block just escapes the knife when drawn over it. A number of rather thick sections (20 to 40 microns) are cut by moving the micrometer screw from right to left 4 to 8 notches every time the knife has been drawn over the paraffin block and has been brought back again, until it is noticed that the knife touches all parts of the top of the paraffin block, or until the tissue is fairly exposed. The succeeding sections may now be kept. It may per- haps be well to state that it is better not to try to cut very thin sections at the beginning ; sections 20 to 15 microns in thickness will answer very well. To begin with, then, the milled head of the micrometer screw is turned 4 notches from left to right, and the knife is drawn over the block with a steady, even pull, and without using undue pressure. Usually the sections will curl up as they are being severed from the paraffin block. This may very readily be prevented by holding the tip of a camel's-hair brush, which has been pointed by drawing it between the lips, against the edge of the section as soon as it begins to curl. A little practice will enable one to do this almost automatically. The sections are transferred to paper by means of the camel's-hair brush, which process is facilitated if the brush has been slightly moistened with saliva, as the section will then adhere lightly to the brush. 47. If the tissues are well imbedded and not too hard, and if the knife is sharp and properly adjusted, paraffin sections may be cut in such a way that each succeeding section adheres to the preceding one, so that actual ribbons of paraffin sections may be made. In order to do this, the knife should be at right angles to the microtome. The paraffin block should be trimmed in such a way that when clamped in the microtome ready for cutting sections, the surface of the paraffin block facing the knife should be exactly parallel to its edge, also to the opposite side of the block. In other words, 2 sides of the paraffin block should be parallel to each other and to the knife ; then if the paraffin is of the right consistency, which must be ascertained by trying, the sections as they are cut will ad- here to each other and form a ribbon. If the sections do not adhere to each other it is quite probable that the paraffin is a little too hard. This may often be remedied by holding an old knife or other metallic instru- ment which has been heated in a flame near the two parallel surfaces for a few moments. Care should be taken not to allow this instrument to touch the paraffin. This is a very convenient and rapid way of cutting par- affin sections. To facilitate the cutting of a paraffin possessing a rela- Digitized by Microsoft® THE MICROTOME AND SECTIONING. 33 tively low melting point in a room with a high temperature, the cooled knife of Stoss may be used. This is so made that a stream of ice-water may be passed through a tube running through the entire length of the back of the blade. 48. Celloidin Sections. — Before fastening the block of wood or vul- canized fiber to which the celloidin blocks have been fixed in the clamp on the microtome, the celloidin should be trimmed with a sharp knife from the top of the block until the tissue is nearly exposed, care being taken to leave a flat surface. The sides of the celloidin block are then trimmed down, if necessary, to within about -jL of an inch of the tissue. The block is now clamped in the microtome at such a level that it just escapes the knife when drawn over it. The knife is placed at an angle of about 45°, or at even a greater angle. During the process of cutting, the knife, as also the tissue, must be kept constantly moistened with 80% alcohol. This is perhaps most easily accomplished by taking up the 80% alcohol with a rather large camel's-hair brush and dipping this on the Fig- 4- — Sliding microtome of Jung. Medium-sized model No. IV. The instrument is shown from the left. On the right side is the plate placed at an acute angle, as a carrier for the sliding block to which the knife is fastened. Both are partly visible. The screws c serve to fix the knife (absent in the figure) in place. The rod (d) serves to turn the screws. On the left side of the microtome is fastened the diagonally placed side plate. On this, behind, rests (in the figure to the right) the microm- eter screw, and in front (in the figure to the left) the object carrier. celloidin block and on the knife. A number of rather thick sections are cut until the knife touches the entire surface of the block or until the tis- sue is well exposed. The sections may now be kept. The block is raised 20 to 15 microns, and the knife, which should be well moistened with 80% alcohol, is drawn over the block with a steady pull, not with a jerk. The sections are- transferred from the knife to distilled water. This is perhaps most conveniently done by placing the ball of one of the fingers of the left hand under the edge of the knife, in front of the sec- tion, and drawing the section down onto the finger with the camel's-hair brush. The finger is then dipped into the distilled water when the sec- 3 Digitized by Microsoft® 34 THE MICROSCOPIC PREPARATION. tion floats off. If the sections can not be stained within a few hours after they are cut, they are best transferred to a dish containing 80% alcohol, in which they may be left until it is desired to stain them. 4g. The other type of sliding microtome to be specially mentioned is that suggested by Professor Thoma and made by R. Jung, of Heidelberg. (Fig. 4. ) The immovable portions of this microtome consist of four plates, of which the lower rests as a horizontal base on a table. A second vertically placed plate rests along the middle of this base. The other two are fastened one on each side of the second plate in such a way that they are directed diagonally outward and upward, forming with the vertical plate acute angles whose apices are directed downward. One of these is attached horizontally to the vertical plate, the other obliquely, one end being attached lower than the other, thus forming an incline. Into the angles formed by the side and vertical plates fit solid metal bodies, which can be easily slid backward and forward on the smooth sur- faces arranged for this purpose. On these metal blocks the knife and the object are fastened, and they are therefore called the knife- and object-car- riers. The former runs on the horizontal, the latter on the inclined plane. The several holes bored in the upper surface of the knife-carrier are for the screw which fastens the knife in whatever position is most convenient. The knife is clamped down by the screw -head. The object -holder con- sists of an arrangement for the fixation of the object. This may be a simple clamp, into which the block of wood is fastened. It is, however, often necessary to move the object to be cut in different directions to obtain proper orientation, especially in the sectioning of embryos. In such cases an object-carrier provided with an arrangement for orientation is used. In the carrier is fastened a rectangular frame of metal which, by means of screws, may be turned on two axes at right angles to each other and thus fixed in any given position. In the middle of this revolv- ing frame of metal is an aperture into which a cylinder is fitted. In the case of paraffin preparations, this is filled with paraffin and the imbedded object attached to its upper end by heating. A special mechanism is pro- vided for the raising and lowering of the cylinder. The newer instru- ments are made on the same principle except that they have a screw at one side by means of which the whole apparatus may be raised or lowered, an arrangement that is especially adapted for long objects. Instead of containing a cylinder, the clamp may be made to fit a block of wood ; in this case the object is melted on to the upper surface of the block. In sectioning, the microtome is so placed before the operator that the plate upon which the knife-carrier moves is to the right. The object-car- rier should be at the end of the microtome nearest the worker. A for- ward motion of this carrier on its ascending path will cause the object to be raised. As the knife-carrier always moves in a horizontal direction, the blade will cut from the object a section the thickness of which will correspond to the distance which the object has been raised, and this is regulated by the distance that the object-carrier is moved forward. To measure this, the vertical plate of the microtome and the object-carrier are provided with a scale and nonius or vernier. To obtain a series of sections of exactly equal thickness, the arrangement by which the object-carrier is moved forward by hand is not sufficiently accurate. Very exact results are obtained with the help of a micrometer screw, which is attached behind the object-carrier and moves the object a certain distance at every turn. In the Thoma-Jung microtome a single Digitized by Microsoft® THE MICROTOME AND SECTIONING. 35 revolution of the screw raises the object 15//. A drum attached to the screw is marked off at its periphery into fifteen equal parts ; the turning of the screw one degree, therefore, raises the object 1 /1. By means of a cog arrangement it is possible to regulate automatically the raising of the object and consequently the thickness of the sections in the series. Before cutting, the paths upon which the knife- and object-carriers slide must be carefully cleaned and oiled ; so-called machine oil (four parts of bone oil to one part of petroleum) is the best for this purpose. Enough oil should be used, and care should be taken that the knife-car- rier moves easily from one end to the other of its pathway. The micro- tome knife should now be fastened into its holder, and the blade placed in such a position that it forms an acute angle with the upper edge of the vertical plate. The object is placed on the object-carrier, and fixed at the desired height, with the micrometer screw resting against the agate- plate of the object-carrier. The knife-carrier with its knife is now brought toward the operator, the slightest pressure being avoided, as otherwise the layer of oil disappears and the sections become irregular in thickness. The newest Jung microtomes have a rod pointing downward on the side of the knife-holder. The operator, resting a finger on the anterior surface of this rod, can pull the knife toward him, thus avoiding the possibility of any pressure on the apparatus. The knife having brought with it a section, it is often seen that the latter is not flat on the blade, but rolled. This condition may be avoided, as has been stated, by holding down the free edge of the section with a camel's-hair brush held in the left hand. There are also so-called section stretchers, which consist of rollers of different diameters. They are so attached above the blade of the knife that between them and the knife is a very narrow space through which the section must pass. These section stretchers are very difficult to put into position, and their action is uncer- tain, so that it is advisable to accustom one's self to the brush method, which affords good results after a little practice. After cutting the section the knife is pushed back to the opposite end of the instrument and again brought forward after turning the micrometer screw, thus producing a second section. After continued section-cutting the micrometer screw passes through its attachment to its full length and must then be screwed back and adjusted anew against the agate-plate. During this procedure the object-carrier should not be moved. R. Jung has re- cently produced a micrometer screw provided with a reversible arrange- ment by which the tedious process of turning backward is avoided. The knife may be fastened transversely to the long axis of the microtome, and if the paraffin and room temperature be favorable, ribbons can be cut. Celloidin sections may also be cut with this instrument. 50. The sliding microtomes may be provided with an arrangement for freezing tissues — a so-called freezing apparatus. This consists of a metal plate on which the tissue is laid ; an ether-atomizer plays upon its lower surface, cooling and finally freezing the object, which is then cut. A drop of fluid (physiologic saline solution, water, etc.) is placed upon the knife, in which the section thaws out and spreads. A better and more rapid method of freezing tissues consists in the use of compressed carbon dioxid, as recommended by Mixter. Cylinders containing about twenty pounds of the liquid gas may be obtained from Bausch & Lomb, who also make a small microtome designed for this purpose. In figure 5 is shown the lower third of a cylinder for compressed carbon dioxid Digitized by Microsoft® 36 THE MICROSCOPIC PREPARATION. firmly fastened to a thick board, and connected by means of a short piece of strong rubber tubing with the freezing box of the microtome. The handle of the escape valve is from 8 to 10 inches long, so that the quantity of escaping gas may be readily controlled. The pieces of tis- sue are placed on the freezing box of the microtome and the escape valve slowly opened until a small quantity of the gas escapes. Small pieces of tissue are frozen in about thirty seconds to a minute ; tissues taken from alcohol should be washed for a short time in running* water before freez- ing. A strong razor may be used for cutting sections ; or better, a well- sharpened blade of a carpenter's plane, as suggested by Mallory and Wright. Sections are transferred to distilled water or normal salt solu- tion, and if fixed may be stained at once. Sections of fresh tissue should be taken from the normal salt solution and transferred to a fixing fluid. 51. It is impossible to cut thin sections with a knife that is not sharp, or with one that is nicked. A few directions as to sharpening a micro- tome knife may therefore not be out of place. For this purpose a good Belgian hone is used, which should be moistened or lubricated with filtered kerosene oil as necessity demands. While sharpening the knife it is grasped with both hands — with one by the handle, with the other by the end. The hone is placed on a table with one end directed toward the person sharpening. If the knife is very dull, it is ground for some time on the concave side only (all microtome knives are practically plane on one side and concave on the other), with the knife at right angles to the stone. It is carried from one end of the stone to the other, edge foremost, giving it at the same time a diagonal movement, so that with each sweep the entire edge is touched (see Fig. 6). In drawing back the knife, the edge is slightly raised. The knife is ground on the concave side until a fine thread (feather edge) appears along the entire edge. It is then ground on both sides, care being taken to keep the knife at right angles to the stone, to keep it flat, and to use practically no pressure. It is a good plan to turn the knife on its back when the end of the stone is reached. On the return stroke, the knife is again held at right angles to the stone, the same diagonal sweep is used (see Fig. 6), so that the Digitized by Microsoft® THE MICROTOME AND SECTIONING. 37 whole edge of the knife is touched with each sweep. The grinding on both sides is continued until the thread above mentioned has disappeared. The knife should now be carefully cleaned and stropped, with the back of the knife drawn foremost. The strop should be flat and rest on a firm surface. Very good microtomes are manufactured by August Becker in Gottin* gen. Of these, Model A (after Spengel) is constructed on the same prin- ciple as the Thoma-Jung microtome. The knife-carrier rests on thick plates of glass in place of metal. The knife is moved by means of a crank. Model B (after Schiefferdecker, 86) is peculiar in that the specimen to be cut is raised by a micrometer screw in a vertical rather than a hori- zontal plane. The knife-carrier runs mechanically on horizontal glass plates. This microtome also possesses an automatic arrangement for the cutting of sections of equal thickness, so that when the micrometer screw is once regulated the knife-holder needs only to be moved back and forth Fig. 6— Diagram showing direction of the movements in honing, to make sections of a uniform thickness. With the help of both models (A and B), celloidin as well as paraffin objects can be cut. Instruments giving especially good results in the serial sectioning of paraffin objects are : (i) The Minot microtome, which can be obtained from Becker and from E. Zimmermann of Leipzig (Model D, Becker) . Here the knife is station- ary, with the edge of the blade upward, while the object is moved up and down by means of a crank, and at the same time pushed forward toward the blade. The thickness of the section is regulated automatically, and by merely turning the wheel a long series of sections may be made in a short time. (2) An ingenious and well-built instrument is the im- proved rocking microtome of R. Jung, in Heidelberg (Cambridge rocking microtome). The knife is stationary, with the edge upward. By means of a clever arrangement the object is advanced toward the knife. A lever causing a slight rotation of the axis upon which the object rests moves Digitized by Microsoft® 38 THE MICROSCOPIC PREPARATION. the object up and down. As a result, every section has not a plane sur- face, as is the case with other microtomes, but appears as a peripheral sec- tion of a cylinder the radius of which corresponds to the distance of the blade from the axis bearing the object-holder. (This drawback limits the use of the instrument. ) The mechanism has one advantage : excellent serial sections can be made, having a thickness of only i /,. (yid. Schieffer- decker, 92). Bausch & Lomb, of Rochester, N. Y., make excellent sliding microtomes. (Fig. 3. ) They have recently constructed for Minot an instrument in which the knife is fixed at both ends. The object-car- rier is elevated by a screw, and moves back and forth under the knife. D. THE FURTHER TREATMENT OF THE SECTION. J. FIXATION TO THE SLIDE AND REMOVAL OF PARAFFIN. Sections obtained by means of the microtome undergo further treat- ment either loose or, better, fixed to a slide or cover-glass, thus making further manipulation much easier. 52. The simplest, surest, and most convenient method of fixing par- affin sections to the slide is by means of the glycerin-albumen of P. Mayer (83.2). Egg-albumen is filtered and an equal volume of glycerin added. To prevent decomposition of the fluid a little camphor or sodium salicylate is placed in the mixture. A drop of this fluid is smeared on the slide or cover-slip as evenly and thinly as possible. A section or a series of sections arranged in their proper sequence is then placed upon the slide so prepared. Any folds in the section are smoothed out with a brush, and the section or the whole series gently pressed down upon the glass. When the desired number of sections are on the slide or cover-slip, they are warmed over a small spirit or gas flame until the paraffin is melted. At the same time the albumen coagulates. The sections are now fixed, and are loosened from the glass only when agents are used which dissolve albumen, as, for instance, strong acids, alkalies, and certain staining fluids. If it is desired that a given space, say the size of a cover-slip, be filled up with sections as far as possible, an outline of the cover-slip to be used may be drawn upon a piece of paper and placed under the slide in the required position. 53. A second and in many respects better method is the fixation of the section with distilled water (Gaule). The paraffin sections are spread in proper sequence on a thin layer of water placed on the slide. There should be sufficient water to float the sections. The slide is then dried in a warm oven kept at 30 to 35° C, or gently heated by holding it at some distance from a spirit or gas flame (the paraffin should not melt). By this treatment the sections are entirely flattened out. The superfluous water is either drained off by tilting or drawn off with blot- ting-paper, the sections are definitely arranged with a brush, and the whole is placed for several hours in a warm oven at 30° to 35 C. The sections thus dried are exposed, over a flame, to a temperature higher than the melting point of the paraffin, and from now on can be subjected to almost any after-treatment. The slide or cover-slip should be thor- oughly cleaned (preferably with alcohol and ether), as otherwise the water does not remain in a layer, but gathers in drops. The advantage of this method lies in the fact that the evaporated water can have no possible influence on the subsequent staining of the Digitized by Microsoft® THE FURTHER TREATMENT OF THE SECTION. 39 sections, while albumen, especially if it be in a thick layer, is sometimes stained, thus diminishing the transparency of the preparation. (For fix- ation with the stain vid. T. 79.) This method, although trustworthy for alcohol and sublimate prepara- tions, often fails with objects that have been treated with osmic acid, chrbmic acid and its mixtures, nitric acid, and picrosulphuric acid. In such cases advantage may be taken of the so-called Japanese method, which is a combination of the above fixation methods. A little Mayer's albumen is placed on the slide and so spread about that hardly a trace of the substance can be seen. The slide is then put in a warm oven heated to 70 C. This temperature soon coagulates the albumen, after which the sections are fixed to the slide by the water method (Rainke, 95). The procedure can be varied by adding to the distilled water one drop of glycerin-albumen or gum arabic to every 30 c.c. of water {vid. also Nussbaum) . When a large number of paraffin sections are to be fixed to cover-slips, the following method may be recommended : A small porcelain evapo- rating dish is nearly filled with distilled water and placed on a stand which elevates it 6 to 8 inches from the table. A number of sec- tions are placed on the water, which is then heated by means of a gas flame until the sections become perfectly flat, care being taken not to raise the temperature of the water sufficiently to melt the paraffin. Each section is then taken up on a cover-slip coated with a very thin layer of Mayer's albumen fixative. During this procedure the cover-slips are held by forceps, and the sections are guided by means of a small camel's-hair brush. When all the sections have thus been placed on cover-slips they are placed for four to six hours in a warm oven maintained at 30° to 35° C 54. Celloidin preparations can not be fixed to the slide with the same degree of certainty, although many sections may be treated at one time. The celloidin sections can be collected in their sequence on strips of paper by gently pressing such a strip, on the blade of a knife, onto the section floating in the alcohol. The sections adhere to the paper, and in this way the entire surface of the strip may be covered by series of sections. To prevent the drying of the sections, a number of such strips are laid in rows on a layer of blotting-paper moistened with 70% alcohol. A glass plate of corresponding size is painted with very fluid celloidin. After the layer of celloidin is dry, the strips of paper are laid, one by one, on the glass plate, with sections downward, and the fingers gently passed over the reverse side. This process is continued until the entire surface of the glass is covered. On carefully raising the strips it is seen that the sections will adhere to the layer of celloidin. (To prevent drying, sections must be kept moistened with 70% alcohol.) After first drying the sections with blotting-paper, a second layer of very thin celloidin is painted on the surface of the glass plate. When this layer is also dry, the plate with its adherent sections is placed in water. Here the double layer of celloidin containing the sections is separated from the glass, and is ready for further manipulation. Before mounting, the sheet of celloidin is cut with scissors into convenient portions. These methods of fixation are of especial importance in the prepa- ration of series of sections. By this .we mean an arrangement of the sec- tions in their natural sequence, thus making it possible to reconstruct the object from the sections. It is, however, advisable to fix all paraffin Digitized by Microsoft® 40 THE MICROSCOPIC PREPARATION. sections to a slide or cover-slip before subjecting them to further manip- ulation, even though the regular sequence be of no importance. 55. Removal of Paraffin. — Before paraffin sections, either fixed or loose, are subjected to further manipulation, the paraffin surrounding the tissues must be removed. This may be done by means of several agents having a solvent action on paraffin, such as xylol, toluol, oil of turpen- tine, etc. After the paraffin has been dissolved, the sections are trans- ferred to absolute alcohol and by this means prepared for further treatment with aqueous or weak alcoholic solutions. In the case of celloidin sections, if it be desirable to preserve the surrounding celloidin, care should be taken that the preparations should not come in contact with any agents dissolving celloidin. These latter are alcohols from 95 vf upward, ether, several ethereal oils, especially oil of cloves, but not the oils of origanum, cedar wood, lavender, etc. 2. STAINING. It is in most cases necessary to stain tissues to bring clearly to view the tissue elements and their relation to each other. The purpose of staining is therefore to differentiate the tissue elements. The differential staining is due to the fact that certain parts of the tissue take up more stain than others. Staining of sections may be looked upon as a microchemic color reaction, and has therefore a value beyond the mere coloring of sections so that they may be seen more clearly. Broadly speaking, stains used in microscopic work may be divided into basic stains, which show special affinity for the nuclei of cells and are therefore known as nuclear stains, and acid stains, which color more readily the protoplasm — protoplasmic stains. Certain stains, which we may know as selective stains (they maybe either basic or acid), color one tissue element more vividly than others, or to the exclusion of others. Since the various tissue elements show affinity for different stains, prepa- rations may be colored with more than one stain. Accordingly we have simple, double, triple, and multiple staining. Certain stains are also especially adapted for staining in bulk or mass — that is, staining a piece of tissue before it is sectioned. SECTION STAINING. Carmin. — 56. Aqueous Borax = carmin Solution 8 gm. of borax and 2 gm. of carmin are ground together and added to 150 c.c. of water. After twenty-four hours the fluid is poured off and filtered. The sections, previously freed from paraffin and treated with alcohol, are placed in this fluid for several hours (as long as twelve), and then washed out in a solution of 0.5 to if hydrochloric acid in 70% alcohol. They are then transferred to 70% alcohol. 57. Alcoholic Borax-carmin Solution. — 3 gm. of carmin and 4 gm. of borax are placed in 93 c.c. of water, after which 100 c.c. of 70% alcohol is added. The mixture is stirred, then allowed to settle, and later filtered. Sections are treated as in § 56. 58. Paracarmin is the carmin stain containing the most alcohol, and is therefore of great value. Carminic acid 1 gm. Aluminium chlorid 0.5 " Calcium chlorid . 4 " Alcohol, 70% 100 c.c. Digitized by Microsoft® STAINING. 41 Paracarmin stains quickly, is not liable to overstain, and is there- fore peculiarly adapted to the staining of large objects. Specimens are washed in 70% alcohol, with the addition of 0.5% aluminium chlorid or 2.5% glacial acetic acid in case of overstaining (P. Mayer, 92). 59. Czocor's Cochineal Solution. — 7 gm. of powdered cochineal and 7 gm. of roasted alum are kept suspended in 100 c.c. of water by stirring while the mixture is boiled down to half its volume. After cooling it is filtered and a little carbolic acid added. This fluid stains quite rapidly and does not overstain. Before the sections are placed in alcohol they should be washed with distilled water, as otherwise the alum is precipitated on the section by the alcohol. Partsch recommends the following solution of cochineal : Finely pow- dered cochineal is boiled for some time in a 5% aqueous solution of alum, and filtered on cooling, after which a trace of hydrochloric acid is added. It stains sections in two to five minutes. 60. Alum=carmin (Grenadier). — 100 c.c. of a 3% to 5% solution of ordinary alum, or preferably ammonia-alum, are mixed with o. 5 gm. to 1 gm. of carmin, boiled for one-fourth of an hour, and after cooling filtered and enough distilled water added to replace that lost by evaporation. This fluid stains quickly but does not overstain. Wash the sections in water. Hematoxylin. — 61. Bohmer's Hematoxylin: Hematoxylin crystals I gm. Absolute alcohol 10 c.c. Potassium alum 10 gm. Distilled water 200 c.c. Dissolve the hematoxylin crystals in the alcohol, and the alum in the distilled water. While constantly stirring, add the first solution to the second. The whole is then left for about fourteen days in an open jar or dish pro- tected from the dust, during which time the color changes from violet to blue. After filtering, the stain is ready for use. Sections, either loose or fixed to the slide or cover-slip, are placed in this solution, and after about half an hour are washed with water. If the nuclei are well stained the further treatment with alcohol may be commenced. Should the sections be over- stained, a condition showing itself in the staining of the cell-protoplasm as well as the nuclei, the sections are then washed in an acid alcohol wash (six to ten drops of hydrochloric acid to 100 c.c. of 70% alcohol) until the blue color has changed to a reddish-brown and very little stain comes from the section — usually about one to two minutes. They are then washed in tap -water, and passed into distilled water before placing in alcohol. 62. Delaf ield's Hematoxylin : Hematoxylin crystals 4 gm. Absolute alcohol 25 c.c. Ammonia alum, saturated aqueous solution 400 ' ' Alcohol, 95^ 100 " Glycerin 100 " Dissolve hematoxylin crystals in absolute alcohol and add to the alum solution, after which place in an open vessel for four days, filter, and add the 95 % alcohol and glycerin. After a few days it is again filtered. This fluid is either used pure or diluted with distilled water. Staining is the same as with Bohmer's hema- toxylin. Digitized by Microsoft® 42 THE MICROSCOPIC PREPARATION. 63. Friedlander's Glycerin-hematoxylin : Hematoxylin crystals .... 2 gm. Potassium alum . . 2 " Absolute alcohol 100 c.c. Distilled water 100 " Glycerin 100 " Dissolve the hematoxylin crystals in the absolute alcohol and the alum in the water ; mix the two solutions and add the glycerin. The mixture is filtered and exposed for several weeks to the air and light, until the odor of alcohol has disappeared, and then again filtered. It stains very quickly. Sections are afterward washed in water and are placed for a short time in acid alcohol if the nuclei are to be especially brought out. Ehrlich's Hematoxylin: Hematoxylin crystals 2 gm. Absolute alcohol 60 c.c. Glycerin 1 saturated with . . 60 " Distilled water J ammonia alum .... 60 " Glacial acetic acid 3 " The solution is to be exposed to light for a long time. It is ready for use when it acquires a deep-red color. Stain as above. 64. Hemalum (P. Mayer, 91). — 1 gm. of hematein is dissolved by heating in 50 c.c. of absolute alcohol. This is poured into a solu- tion of 50 gm. of alum in 1 liter of distilled water and the whole well stirred. A thymol crystal is added to prevent the growth of fungus. The advantages of hemalum are as follows : The stain may be used im- mediately after its preparation, it stains quickly, never overstains, especially when diluted with water, and penetrates deeply, making it useful for staining in bulk. After staining, sections or tissues are washed in distilled water. 65. Heidenhain's Iron Hematoxylin. — Good results, particu- larly in emphasizing certain structures of the cell (centrosome), are ob- tained by the use of M. Heidenhain's iron hematoxylin (92. 2). Tissues are fixed in saline sublimate solutions in twelve to twenty-four hours (yid. T. 19), after which they are washed for the same length of time in running water and then placed in the ascending alcohols. Very thin sec- tions (in case of amniota not over 4 /j.) are fixed to the slide with water and put into a 2 . 5 % aqueous solution of ammonium sulphate of iron for four to eight hours (not longer). After careful rinsing in water, the sections are brought into a solution of hematoxylin prepared as fol- lows : Hematoxylin crystals 1 gm., absolute alcohol 10 c.c, and dis- tilled water 90 c.c. This solution should remain in an open vessel for about four weeks, and, before using, should be diluted with an equal volume of distilled water. Staining takes place in twelve to twenty-four hours, after which the sections are rinsed in water and again placed in a like solution of ammonium sulphate of iron, until black clouds cease to be given off from the sections. They are rinsed in distilled water, passed through alcohol into xylol, and mounted in balsam. Should a protoplas- mic stain be desired, rubin in weak acid solution may be employed {yid. also M. Heidenhain, 96). Coal-tar or anilin stains. — Ehrlich classifies all anilin stains as salts having basic or acid properties. The basic anilin stains, such as safra- Digitized by Microsoft® STAINING. 43 nin, methylene-blue, methyl-green, gentian violet, methyl-violet, Bis- mark brown, thionin, and toluidin-blue are nuclear stains, while the acid anilin stains, such as eosin, erythrosin, benzopurpurin, acid fuchsin, lichtgrlin, aurantia, orange G, and nigrosin stain diffusely and are used as protoplasmic stains. 66. Safranin : Safranin , . i g m . Absolute alcohol 10 c.c. Anilin water 90 " Anilin water is prepared by shaking up 5 c.c. to 8 c.c. of anilin oil in 100 c.c. of distilled water and filtering through a wet filter. Dissolve the safranin in the anilin water and add the alcohol. Filter before using. Stain sections of tissues fixed in Flemming's or Hermann's solutions for twenty-four hours, and decolorize with a weak solution of hydrochloric acid in absolute alcohol (1 : 1000). After a varying period of time (usu- ally only a few minutes) all the tissue elements will be found to have become bleached, only the chromatin of the nucleus retaining the color. 67. Bismarck Brown — A very convenient color to handle is Bismarck brown. Of this, 1 gm. is boiled in 100 c.c. of water, filtered, and ji of its volume of absolute alcohol added. Bismarck brown stains quickly without overstaining, and is also a purely nuclear stain. Wash in absolute alcohol. 68. Methyl=green stains very quickly (minutes). 1 gm. is dis- solved in 100 c.c. of distilled water to which 25 c.c. of absolute alcohol is added. Rinse sections in water, then place for a few minutes in 70% alcohol, transfer to absolute alcohol for a minute, etc. 6g. Other so-called basic anilin stains can be used in a similar manner. Thionin or toluidin-blue in dilute aqueous solutions are espe- cially useful. Nuclei appear blue and mucus red. 70. Double Staining. — When certain stains are used in mixtures or in succession, all portions of the section are not stained alike, but certain elements take up one stain, others another. This elective affin- ity of tissues is taken advantage of 'in plural staining. If two stains are employed, one speaks of double staining. 71. Picrocarmin of Ranvier. — Two solutions are prepared, a satu- rated aqueous solution of picric acid and a solution of carmin in ammonia. The second is added to the first to the point of saturation. The whole is evaporated to one-fifth of its volume and filtered after cooling. The solution thus obtained is again evaporated until the picrocarmin remains in the form of a powder. A 1 °Jo solution of the latter in distilled water is the fluid used for staining. To stain with this solution, one or two drops are placed on the slide over the object and the whole put in a moist chamber for twenty-four hours. A cover-slip is then placed over the preparation, the picrocarmin drained off with a piece of blotting-paper, and a drop of formic-glycerin (1 : 100) brought under the cover-slip by irrigation. Proper differentia- tion takes place only after a few days, and the acid-glycerin may then be replaced by the pure glycerin. In objects fixed with osmic acid, the nuclei appear red, connective tissue pink, elastic fibers canary yellow, muscle tissue straw color, keratohyalin red, etc. 72. Weigert's Picrocarmin. — The preparation of Weigert's picro- carmin is somewhat simpler. 2 gm. of carmin are stirred in 4 c.c. Digitized by Microsoft® 44 THE MICROSCOPIC PREPARATION. of ammonia and allowed to remain standing in a well-corked bottle for twenty-four hours. This is mixed with 200 c.c. of a concentrated aqueous solution of picric acid to which a few drops of acetic acid are added after another twenty-four hours. The result is a slight precipitate that does not dissolve on stirring. Filter after twenty-four hours. Should the precipitate also pass through the filter, a little ammonia is added to dis- solve it. Both picrocarmin solutions dissolve off sections fixed to the slide with albumen. 73. P. Mayer's Picric=magnesia-carmin. 1. Magnesia-carmin ; Carmin I gm. Magnesia usta . . . o. I " Distilled water ... 20 c.c. 2. Picrate of magnesia ; Carbonate of magnesia 0.25 gm. Picric acid, 0.5$ in distilled water . . .200 c.c. Heat to boiling, cool and filter. One volume of the first solution is mixed with 9 volumes of the second. Another formula is magnesia-carmin solution 1 volume, magnesia- picrate solution 4 volumes, weak magnesia-carmin solution 5 volumes, magnesia water 100 c.c. The latter is made by allowing 0.1 gm. of magnesia usta to remain for one week in 100 c.c. of water, shaking from time to time. Sections are washed in either distilled or magnesia water. Staining takes place quickly ; the solution may be used for stain- ing in bulk. 74. Carmin-bleu de Lyon (of Rose). — Sections or pieces of tis- sue are first stained with carmin (alum- or borax-carmin) . Bleu de Lyon is dissolved in absolute alcohol and diluted with the latter until the solu- tion is of a light bluish color. In this the sections or pieces of tissue are after -stained for twenty-four hours (developing bone stains, for instance, blue). 75. Picric acid is often used as a secondary stain, either in aque- ous (saturated solution diluted 1 to 3 times in water) or in alco- holic solution (weak solutions in 70%, 80%, and absolute alcohol). Sections previously treated with carmin or hematoxylin are stained for two to five minutes, washed in water or alcohol, and transferred to abso- lute alcohol, etc. Sections stained in safranin can be exposed to the ac- tion of an alcoholic picric acid solution. A solution of picric acid in 70% alcohol may be used to wash sections stained in borax-carmin. This often gives a good double stain. Sections can also be first treated with picric acid and afterward stained with alum-carmin. 76. Hematoxylin=eosin. — Sections already stained in hematoxylin are placed for two to five minutes in a 1 % to 2 % aqueous solution of eosin or in a 1 % solution of eosin in 60% alcohol. They are then washed in water until no more stain comes away, after which they remain for only a short time in absolute alcohol. 77. Hcmatoxylin-safranin of Rabl (85). — Sections of prepara- tions fixed with chromic-formic acid or with a solution of platinum chlorid are stained for a short time with Delafield's hematoxylin (vid. T. 62), then counterstained for twelve to twenty-four hours with safranin and washed with absolute alcohol until no more color is given off. Digitized by Microsoft® STAINING IN BULK. 45 78. Ehrlich-Biondi Triple Stain — Of the many triple stains in use we mention only the most important, the rubin S — orange G — methyl- green mixture of Ehrlich and Biondi, employed according to the modifi- cation of M. Heidenhain (92. 2). The best results are obtained with objects fixed in saline sublimate solution. The three stains just mentioned are prepared in concentrated aqueous solutions (rubin S dissolves in the proportion of 1:5, orange G and methyl -green about 1:8). These con- centrated solutions are combined in the following volumes : rubin S 4, orange G 7, methyl -green 8. The stock solution thus obtained is diluted with 50 to 100 times its volume of distilled water before using. The sec- tions should be as thin as possible and fixed to the slide by the water method. They remain for twenty-four hours in the stain, and are then washed either in pure 90% alcohol or in such with the addition of a little acetic acid (1 to 2 drops to 50 c.c), until the rinsing fluid is no longer colored. Before staining it is occasionally of advantage to treat the sections with acetic acid (2 : 1000) for one to two hours. 79. P. Mayer (96) advises fixation of the sections to the slide with the staining solution instead of water. On heating the slide the sections stain very energetically, and results are obtained which would otherwise be difficult to produce. Before the sections are placed in xylol to remove the paraffin, they must be thoroughly dried. STAINING IN BULK. Instead of staining in sections, entire objects can be stained before cutting. This method is in general much slower, and demands, there- fore, special staining solutions, as, for instance : 80. Alcoholic borax-carmin solution (vid. T. 57). — Pieces y^ cm. in diameter remain in the stain at least twenty-four hours, are then decolorized for the same length of time in acid alcohol (0.5% to 1% hydrochloric acid in 70% alcohol), and after washing in 70% alcohol are transferred to 90% alcohol. Larger objects require a correspondingly longer time. 81. Paracarmin. — Treatment as in section staining, length of time according to size of object (vid. T. 58). 82. Alum-carmin of Grenacher (vid. T. 60). This never overstains. Time of staining according to size of object. Wash in water, then trans- fer to 70% and 90% alcohol. 83. Hemalum {vide T. 64), when diluted with water, is very useful for staining in bulk. After staining, objects should be washed with dis- tilled water. 84. Bohmer's hematoxylin (vid. T. 61) stains small pieces very sharply. Use the same as hemalum. 85. Hematoxylin staining according to R. Heidenhain's method is especially recommended for staining in bulk. Stain objects fixed in alcohol or picric acid twenty-four hours in a c-33% aqueous solution of hematoxylin ; transfer for an equal length of time to a 0.5% aqueous solution of potassium chromate, changing often until the color ceases to run. Wash with water and pass into strong alcohol. This stain also colors the protoplasm, and is so powerful that very thin sections are an absolute condition to the clearness of the prepa- ration. Digitized by Microsoft® 46 THE MICROSCOPIC PREPARATION. 86. If the objects have been fixed with picric acid and the latter has not been entirely washed out, staining in bulk by the above methods pro- duces very striking differentiation. 87. Pieces of tissue stained in bulk may be infiltrated, imbedded, and cut according to the ordinary methods. Under these circumstances, section staining is not necessary unless a still further differentiation be desired. 88. In general, then, the treatment of the object is somewhat as fol- lows : First, it is fixed in some one of the fixing fluids already described, then carefully washed, and in certain cases stained in bulk before infiltrat- ing with paraffin or celloidin ; or the staining may be postponed until the tissue has been cut. In the latter case, the sections are subjected to the stain either loose or fastened to the slide or cover-slip. 89. In all cases it is absolutely essential that the paraffin be entirely removed. After the sections have been stained and washed, they are transferred to absolute alcohol in case it be desired to mount them in some resinous medium. They may also be mounted in glycerin or acetate of potash, into which they may be passed directly from distilled water. 90. The method of staining tissues in sections or in bulk is shown in the following diagrams : In Bulk. 90 f alcohol Water Wash in water 70% alcohol Wash in acid alcohol \ jofo alcohol In Sections. Celloidin sections Paraffin sections in 90 f c alcohol I Remove paraffin \ Absolute alcohol { 90% alcohol Distilled water Distilled water Absolute alcohol Wash in Wash in acid water alcohol \ \ 70 % alco- 70% alco- hol hoi Absolute alcohol E. PREPARATION OF PERMANENT SPECIMENS. The resinous media used in the final mounting of preparations are Canada balsam and damar. gi. Commercial Canada balsam is usually dissolved in turpentine ; it should be slowly evaporated in casserole and then dissolved in xylol, toluol, or chloroform, etc. The proper concentration of the solution is found with a little experience. A thick solution penetrates the in- Digitized by Microsoft® PREPARATION OF PERMANENT SPECIMENS. 47 terstices of the section with difficulty, and usually contains air-bubbles which often hide the best areas of the preparation, and can only be re- moved with difficulty by heating over a flame. Thin solutions, on the other hand, have also their disadvantages ; they evaporate very quickly, and the empty space thus created between the cover-slip and slide must again be filled with Canada balsam. This is best done by dipping a glass rod into the solution and placing one drop at the edge of the cover -slip, whereupon the fluid spreads out between the cover -slip and slide as a result of capillary attraction. Canada balsam dries rather slowly, the rapidity of the process depending upon the temperature of the room. To dry quickly, the slides may be held for a few moments over a gas or alcohol flame, or they may be placed in a warm oven, where the prepara- tions become so dry in twenty-four hours that they can be examined with an oil-immersion lens. The oil used for this purpose should be wiped away from the cover-slip after examination. This can only be done, with- out moving the cover-slip, when the balsam is thoroughly dry and holds the cover -slip firmly in place. 92. Damar is dissolved preferably in equal parts of oil of turpentine and benzin. It has the advantage of not rendering the preparation as translucent as does Canada balsam. Otherwise it is used as the latter. g3. Since alcohol does not mix with Canada balsam and damar, an intermediate or clearing fluid is used in transferring objects from the former into the latter. Xylol, toluol, carbol-xylol (xylol, 3 parts ; car- bolic acid, 1 part), oil of bergamot, oil of cloves, and oil of origanum are ordinarily used. 94. The process is somewhat simpler where sections are fixed to the slide. Xylol is dropped onto the surface of the slide, or better, the whole preparation is placed for a few minutes in a vessel containing xylol until the diffusion currents have ceased (which may be seen with the naked eye). The slide is then taken out, tilted to allow the xylol to run off, wiped dry around the object with a cloth, and placed upon the table with the specimen upward. A drop of Canada balsam is now placed on the section (usually on its left side), and a clean cover -slip grasped with a small forceps. It is then gently lowered in such a way that the Canada balsam spreads out evenly and no air-bubbles are im- prisoned under the glass. When this is done the preparation is finished. g5. If one is dealing with loose sections, a spatula or section-lifter is very useful in transferring them from absolute alcohol into the clearing fluid— carbol-xylol or bergamot oil (xylol evaporates very rapidly) — and from this onto the slide. In doing this it is necessary that the sec- tion should lie well spread out on the section-lifter, wrinkles being re- moved with a needle or small camel 's-hair brush. In sliding the section off the spatula (with a needle or brush) a small quantity of the clearing fluid is also brought onto the slide. This must be removed as far as possible by tilting or with blotting-paper. The section can now be mounted in Canada balsam as before. For esthetic and practical reasons the student should see that during the spreading of the drop of Canada balsam the section remains under the middle of the cover-slip. Should it float to the edge, it is best to raise the cover -slip and lower it into place again. The cover-slip should never be slid over the specimen. g7. To mount in glycerin or acetate of potash (33% solution in dis- tilled water), the sections are transferred from water to the slide, covered Digitized by Microsoft® 48 THE MICROSCOPIC PREPARATION. with a drop of glycerin or acetate of potash, and the cover-slip applied. These methods are employed in mounting sections colored with a stain that would be injured by contact with alcohol, and where clearing is not especially necessary. g8. Farrant's Gum Glycerin. In place of pure glycerin the following mixture may be used : Glycerin . . . . . . 5° c - c - Water . . ... .... 50 " Gum-arabic (powder) 5° S m - Arsenious acid ... . . . . I " Dissolve tire arsenious acid in water. Place the gum-arabic in a glass mortar and mix it with the water ; then add the glycerin. Filter through a wet filter-paper or through fine muslin. gg. To preserve such preparations for any length of time the cover- glasses must be so fixed as to shut off the glycerin or acetate of potash from the air. For this purpose cements or varnishes are employed which are painted over the edges of the cover-slip. These masses adhere to the glass, harden, and fasten the cover-slip firmly to the slide, hermetically sealing the object. The best of these is probably Kronig's varnish, pre- pared as follows : 2 parts of wax are melted and 7 to 9 parts of colophonium stirred in, and the mass filtered hot. Before employing an oil-immersion lens it is advisable to paint the edge with an alcoholic solution of shellac. F. INTRODUCTION TO METHODS OF INJECTION. 100. A few remarks on the injection of the vascular system will not here be amiss, as it is only by this method that the relations of the blood- vessels to the neighboring tissue elements can be clearly brought out. The process consists in filling the vessels with a mass that can be injected in a fluid state but hardens readily, and is at the same time suitable for microscopic purposes and for sectioning methods. Of such substances there are a large number, and the technic of injection has been developed to such a degree that it has become a very important part of anatomic technic in general. Gelatin masses of different composition have come into general use for injecting the vascular system ; of these, we shall here mention a red and a blue mass. 101. Gelatin=carmin. — The first is a gelatin -carmin mass, and is prepared as follows: (1) 4 gm. of carmin are stirred into 8 c.c. of water and thoroughly ground. Into this a sufficient quantity of ammonia is poured to produce a dark cherry color and render the whole transpar- ent. (2) 50 gm. of finest quality gelatin is placed in distilled water for twelve hours until well soaked. It is then pressed out by hand and melted at a temperature of 70° C. in a porcelain evaporating dish. The two solutions are now slowly mixed, the whole being constantly stirred until a complete and homogeneous mixture is obtained. To this mass is added, drop by drop, a 25% acetic acid solution until the color begins to change to a brick red and the mass becomes slightly opaque. This should be very carefully done, as a single drop too much may spoil the whole. During this procedure the substance should be kept at 70 C. and constantly stirred. The change in color indicates that the reaction of the mass has become neutral or even slightly acid (an ammoniac solu- tion should not be used, since the stain diffuses through the wall of the Digitized by Microsoft® INTRODUCTION TO METHODS OF INJECTION. 49 vessel and colors the surrounding tissues) ; the whole is filtered through flannel while still warm. 102. The blue mass is prepared from an aqueous solution of Berlin blue. A saturated solution is made and poured (as above) into a solution of gelatin warmed to 70 C. until the desired intensity of color is ob* tained. 103. Injection masses already prepared are to be had in commerce. Besides those already mentioned, still others colored with China ink, etc. , are in general use. 104. Small animals are injected as a whole by passing the cannula of a syringe into the left ventricle or aorta. In the case of large animals, or where very delicate injections are to be made, the cannula is inserted into one of the vessels of the respective organs. The proper ligation of the remaining vessels should not be omitted. 105. Before injecting, the animals or organs are kept warm in water heated to about 38° C. in order to prevent the injection mass from hard- ening before passing into the smaller vessels. 106. Before injecting, it is always desirable to thoroughly bleed the animal, or press out as carefully as possible all the blood contained in the organ. 107. Organs injected with carmin are fixed in alcohol and should not be brought in contact with acids or alkalies. Such parts as are injected with Berlin blue are less sensitive in their after-treatment. Pieces or sec- tions that have become pale regain their blue color in oil of cloves. 108. If objects or sections injected with Berlin blue be treated with a solution of palladium chlorid, the bluish color changes to a dark brown which afterward remains unchanged (Kupffer). 109. In thin membranes and sections the vessel -walls can be rendered distinct by silver-impregnation, which brings out the outlines of their en- dothelial cells. This may be done either by injecting the vessel with a 1 °/o solution of silver nitrate, or, according to the process of Chrzon- szczewsky, with a 0.25% solution of silver nitrate in gelatin. This method is of advantage, since, after hardening, the capillaries of the in- jected tissue appear slightly distended. Organs thus treated can be sec- tioned, but the endothelial mosaic of the vessels does not appear definitely until the sections have been exposed to sunlight. no. By means of the above injection methods other lumina can be filled, as, for instance, those of the glands. As a rule, these are only par- tially filled, since they end blindly, and their walls are less resistant and may be damaged by the pressure produced by the injection. in. The injecting of lymph -channels, lymph -vessels, and lymph- spaces is usually done by puncture. A pointed cannula is thrust into the tissue and the syringe emptied by a slight but constant pressure. The injected fluid spreads by means of the channels offering the least resist- ance. For this purpose it is best to employ aqueous solutions of Berlin blue or silver nitrate, as the thicker gelatin solutions cause tearing of the tissues. 112. To bring out the blood capillaries and the lymphatic channels, Altman's process (79), in which the vessels are injected with olive oil, is useful. The objects are then treated with osmic acid, sectioned by means of a freezing microtome, and finally treated with eau de Javelle 4 Digitized by Microsoft® 50 THE MICROSCOPIC PREPARATION. (a concentrated solution of hypochlorite of potassium). By this process all the tissues are eaten away, the casts of the blood-vessels remaining as a dark framework (corrosion). The manipulation of these preparations is extremely difficult on account of the brittleness of the oil casts. For lymph -channels Altman {ibid. ) used the so-called oil -impregnation. Fresh pieces of tissues, thin lamellae of organs, cornea, etc., are placed for five to eight days in a mixture containing olive oil i part, absolute alcohol yi, part, sulphuric ether y 2 part (or castor oil 2, absolute alcohol 1, etc.). The pieces are then laid for several hours in water, where the externally adherent globules of oil are mechanically removed and those in the lymph -canalicular system are precipitated. The objects are now treated with osmic acid, cut by means of a freezing microtome, and corroded. In this case, the corrosive fluid (eau de Javelle) should be diluted two or three times. Digitized by Microsoft® GENERAL HISTOLOGY. I. THE CELL. During the latter part of the seventeenth century, Hooke, Mal- pighi, and Grew, making observations with the simple and imperfect microscopes of their day, saw in plants small compartment-like spaces, surrounded by a distinct wall and filled with air or a liquid ; to these the name cell was applied. These earlier observations were extended in various directions during the latter part of the seven- teenth and the eighteenth century. Little advance was made, however, until Robert Brown (183 1) directed attention to a small body found in the cell, previously mentioned by Fontana, and known as the nucleus. In the nucleus Valentin observed (1836) a small body known as the nucleolus. In 1838 Schleiden brought forward proof to show that plants were made up wholly of cells, and especially emphasized the importance of the nuclei of cells. In 1839 Schwann originated the theory that the animal body was built up of cells resembling those described for plants. Both Schleiden and Schwann defined a cell as a small vesicle, surrounded by a firm membrane inclosing a fluid in which floats a nucleus. This conception of the structure of the cell was destined, however, to undergo important modification. In 1846 v. Mohl recognized in the cell a semifluid, granular substance which he named protoplasm. Other investigators (Kolliker and Bischoff ) observed animal cells devoid of a distinct cell membrane. Max Schultze (1861) attacked vigorously the older conception of the structure of cells, proclaim- ing the identity of the protoplasm in all forms of life, both plant and animal, and the cell was defined as a nucleated mass of protoplasm endotved with the attributes of life. In this sense the term cell is now used. The simplest forms of animal life are organisms consisting of only one cell {protozoa). Even in the development of the higher animals, the first stage of development, the fertilized egg, is a single cell. This by repeated division gives rise to a mass of similar cells, which, owing to their likeness in shape and structure, are said to be undifferentiated. As development proceeds, the cells of this mass arrange themselves into three layers, the germ layers, the outer one of which is the ectoderm, the middle one the mesoderm, and the inner one the entoderm. In the further development, the cells of the germ layers change their form, assume new qualities, adapting 51 Digitized by Microsoft® 52 THE CELL. themselves to perform certain definite functions ; a division of labor ensues, — the cells become differentiated. Cells having similar shape and similar function are grouped to form tissues, and tissues are grouped to form orga.7is. We shall now consider the structure of the cell. Every cell consists of a cell-body and a nucleus. A. THE CELL-BODY. The body of the cell consists of a substance known as proto- plasm or cytoplasm. This is not a substance having uniform Vacuoles. Chromatin network. ,. Linin network. Nuclear fluid. Nuclear membrane. Cell-membrane. Exoplasm. - - Spongioplasm. Hyaloplasm. Nucleolus. Chromatin net-knot. - Centrosome. "~ Centrosphere. Foreign inclosures. Metaplasm. Fig. 7. — Diagram of a cell. physical and chemic qualities, but a mixture of various organic com- pounds concerning which knowledge is not as yet conclusive, but which in general are proteid bodies or albumins in the widest sense. In spite of the manifold differences in its composition, proto- plasm exhibits certain general fundamental properties which are always present wherever it is found. Ordinarily, protoplasm ex- hibits certain structural characteristics. In it are observed two con- stituents, — threads or plates, which are straight or winding, which branch, anastomose, or interlace, and which are generally arranged in a regular framework, network, or reticulum. These threads probably consist of small particles arranged in rows, called cell-microsomes (yid. van Beneden, 83 ; M. Heidenhain, 94 ; and others). This sub- Digitized by Microsoft® THE CELL- BODY. 53 stance is known as protoplasm in the stricter sense (Kupffer, 75) ; also as spongioplasm, or the fibrillar mass of Flemming (82). The other constituent of the cytoplasm is a more fluid substance lying between the threads in the meshes of the spongioplastic network, and is known as paraplasm (Kupffer), hyaloplasm, cytolymph, or the interfibrillar substance of Flemming. According to most investigators, the more important vital pro- cesses of the cell are to be identified with the spongioplasm, and are controlled by the nucleus, while the paraplasm assumes an inferior or passive role. Protoplasm displays phenomena of motion, shown on the one hand by contraction, and on the other by the formation of processes that take the form either of blunt projections or lobes, or of long, pointed, and even branched threads or processes known as pseudo- podia. The extension and withdrawal of the pseudopodia enable the cell to change its position. The point of such a process fastens to some object and the rest of the cell is drawn forward, thus giving the cell a creeping motion — wandering cells. Certain cells take up and surround foreign bodies by means of their pseudopodia. If these Cilia. Fig. 8. — Cylindric ciliated cells from the primitive kidney of Petromyzon planeri ; X 1200. bodies are suitable for nutrition, they are assimilated ; if not, they can, under certain circumstances, be deposited by the cell in cer- tain localities (Metschnikoff 's phagocytes). Similar thread-like processes which, however, can not be drawn into the cell, occur in some cells in the shape of cilia, which are in constant and energetic motion — ciliated cells. Certain cells possess only a single long pro- cess, by means of which unattached cells are capable of direct or rotating motion — -flagellate cells, spermatozoa. Inside of the cell-body the protoplasm also shows phenomena of motion, the streaming of the protoplasm. In plant cells there is often a noticeable regularity in the direction of the current. Men- tion should not be omitted of the so-called molecular or Brownian movement in the cells, which consists in a rapid whirling motion of particles or granules suspended in the protoplasm (Brown). Living protoplasm is irritable in the highest degree, and reacts very strongly to chemic and physical agents. It is very sensitive to changes in temperature. All the phenomena of life occur in greater intensity and more rapidly in a warm than in a cold temperature, Digitized by Microsoft® 54 THE CELL. this fact being very strikingly shown by the phenomena of motion in the cell, as also in its propagation. By subjecting protoplasm to different temperatures, its various movements can be slowed or quickened. It dies in too high or too low a temperature. Certain substances coming in contact with the cell from a given direc- tion have on it an attracting or repelling action. These phenomena are known as positive and negative chemotropism (chemotaxis) . The action of chemic agents on the different wandering cells of the body and on cer- tain free-swimming unicellular organisms naturally varies to a great degree. Among these phenomena must be included those produced by water (hydrotropism) and light (heliotropism). It is very probable that all these phenomena are of importance to the proper appreciation of some of the processes going on in the vertebrate body (as, for instance, in the origin of diseases caused by micro-organisms). Protoplasm may contain various structures. Of these, the vacuoles deserve special mention. They are more or less sharply defined cavities filled with fluid, and vaiy considerably in number and size. The fluids that they contain differ somewhat, but are always secreted by the protoplasm, and are, as a rule, finally emp- tied out of the cell. As a consequence, vacuoles are best studied where the function of the cell is a secretory one. Here they are often large, and sometimes fill up the whole cell, the contents of which are then emptied out {glandular cells). Contents of a solid nature, such as fat, pigment, glycogen, and crystals, are peculiar to certain cells. By these deposits the cell is more or less changed, the greatest variation in form taking place in the production of fat. The latter, as a rule, takes the shape of a globule, and greatly modifies the position of the normal con- stituents of the cell. Deposits of pigment alter the cells to a less degree. This substance occurs in the protoplasm either in solution or in the form of fine crystalline bodies. Glycogen is more gener- ally diffused, occurring very generally in embryonal cells and in the liver- and cartilage-cells of the adult. Occasionally we find larger crystals in animal cells, as, for instance, in the red blood-corpuscles of the teleosts. So-called margarin crystals sometimes occur in large numbers as stellate figures in dead fatty tissues kept at low temperatures. By employing certain methods the existence of granules can generally be demonstrated in protoplasm. Some authors even refer the vital qualities of protoplasm to these particular bodies (Alt- mann's bioblasts, 94). In some cases the outer layer of the cell-protoplasm shows dif- ferentiation, leading to the formation of a distinct cell-membrane (as in fat-cells, cartilage-cells, goblet-cells, etc.). F. E. Schulze has given it the name pellicula in cases where the entire cell is surrounded by a homogeneous layer, and cuticula or cuticle where only one side of the cell is supplied with the membrane (as in the intestinal epithe- Digitized by Microsoft® THE NUCLEUS. 55 lium). It is assumed that both spongioplasm and paraplasm are concerned in the formation of this membrane. In the protoplasm of many cells there is found a small body- known as the ceutrosome. This is usually situated near the nucleus of the cell, occasionally in the nucleus. Generally, it has the appear- ance of a minute granule, sometimes scarcely larger than a micro- some. It is often surrounded by a small area of a granular or finely reticular or radially striated cytoplasm, known as the attraction- sphere or centrospherc. B. THE NUCLEUS. The second constant element of the cell is the nucleus. As a rule, it is sharply defined, and in its simplest form consists of a round vesicle of a complicated structure composed of several sub- stances. The form of the nucleus corresponds in general to the shape of the cell ; in an elongated cell, it is correspondingly long, and flattened where the cell is plate-like in shape. The nucleus of a wandering cell that is in the act of passing through a narrow inter- cellular cleft adapts itself to the changes of form in the cell without being permanently altered in shape. In other words, the nucleus is soft, and can be easily distorted by any solid substances within or without the protoplasm, only to resume its original form when the pressure is removed. It possesses, then, a certain amount of elas- ticity. Movements of certain nuclei, entirely independent of the sur- rounding protoplasm, have often been observed. It is only rarely that the form of the nucleus differs materially from that of the cell. This, however, occurs in the nuclei of leucocytes, which are often irregular, and may even be ring-shaped. In certain arthrozoa, branching forms of nuclei occur, as also in the skin glands of turtles. The proportionate size of nucleus to cell-body varies greatly in different cells. Especially large nuclei are found in immature ova, in certain epithelial cells, etc. The contents of the nucleus consist of a framework or reticu- lum, in the meshes of which there is found a semifluid substance. In treating the nuclei with certain stains, the nuclear reticulum will be seen to consist of two constituents, a substance appearing in the form of variously shaped, minute granules, which stains deeply, and is, therefore, known as chromatin. This is imbedded in and deposited on a less stainable network, the linin. The meshes of this network are occupied by a transparent, semifluid substance, which does not stain easily, and is known as the achromatic portion of the nucleus. It is also known as paralinin, nuclear sap, karyolymph, or nucleoplasm. Chemically, chromatin belongs to those albuminous substances known as nucleins. In well-stained nuclei of considerable size the chromatin gran- ules are seen closely placed in a continuous row throughout the net- work of linin, which penetrates the nuclei in all directions. In Digitized by Microsoft® 56 THE CELL. every resting nucleus one or more small round bodies are found imbedded in the nucleoplasm. These are known as true nucleoli, and do not stain quite so deeply as the chromatin. The fact that certain reagents dissolve the chromatin, but not the true nucleoli, . proves that the substance of which the latter are composed is not identical with chromatin, — and is, therefore, known as paranuclein (F. Schwartz). In many cases we find in the linin, granules ' of a substance known as lanthanin, which displays a marked affinity for the so- called acid anilin stains, in contradistinction to chromatin, which stains principally with the basic anilin colors. These are known as oxychromatin granules in contradistinction to the basichromatin granules of the chromatin (M. Heidenhain, 94). The true nucleoli should not be confused with the slight swell- ings of the chromatin network found at the junction of the threads, and known as net-knots, or karyosomes. Surrounding the resting nucleus is usually a nuclear membrane resembling in many respects chromatin. As a rule, it does not form a continuous layer, but is perforated, having openings that contain nuclear fluid. We have, then, both substances, chromatin and nucleoplasm, as elements of the nuclear membrane. Besides this, the nuclear membrane receives an outer layer, differentiated from the protoplasm. Newer investigations have shown that even during a period of rest the relationship of the nucleus to the protoplasm of the cell is much more intimate than was heretofore believed (vid. B. Reinke, 94). A resting nucleus — i.e., one not in process of division — usually consists, therefore, of a sharply defined membrane, which has in its interior a chromatic (nuclein) and an achromatic (linin) network, a nuclear fluid (paralinin), and nucleoli (paranuclein). The chromatin of the nucleus is not always in the form of a net- work. In some cases — as, for instance, in the premature ova of certain animals (O. Hertwig, 93. II) and in spermatozoa — it is col- lected in compact bodies. In the ova it may often be mistaken for a true nucleolus (germinal spot). In this case, however, it consists of nuclein, and not of paranuclein. C NUCLEAR AND CELL-DIVISION. The founders of the cell theory believed in what may be known as a modification of the theory of spontaneous generation, stating that cells might originate from a structureless substance known as kyto- blastema or blastema, in which a nucleus was formed by precipita- tion. Henle (1841) drew attention to the fact that cells might mul- tiply by the separation of small portions of the cell-body, a process known as budding ; and Barry (1841) stated that during the multi- plication of cells the nuclei divided. The same year Remak Digitized by Microsoft® NUCLEAR AND CELL-DIVISION. 57 observed division of cells in the blood of embryos. Goodsir (1845) originated the theory that all cells were developed from preexisting cells. This was first clearly stated as a general law by Virchow (1855), and his saying, " Omnis cellula a cellula," is constantly being verified. Our more accurate knowledge of cell-division dates, how- ever, from more recent times (1873-80), when Schneider, Fol, Stras- burger, Flemming, and many others demonstrated that during the division of the cell the nucleus passed through a series of compli- cated changes which resulted in an exact division of the chromatin. The phenomena which usher in cell-division are especially noticeable in the nucleus, the elements of which are arranged and transformed in a typic manner. During the division of the nucleus the nuclear membrane is lost, and the relationship of the substances of the nucleus to the protoplasm of the cell is a very intimate one. As a consequence, during the middle phases of division there is no well-defined demarcation between the nucleus and the cell-body. As a rule, the mother cell and nucleus divide into two daughter cells, each having a nucleus, alike in every particular. It was early observed, however, that occasionally cells divided by a much sim- pler process, in which case the nucleus did not pass through such complicated changes. Accordingly, two distinct types of cell- division are recognized, which are distinguished as mitosis, karyoki- nesis, or indirect cell-division, and amitosis, or direct cell-division. Both lead to the formation of two nuclei, which are known as daughter nuclei as distinguished from the original mother nucleus. J. MITOSIS OR KARYOKTNESIS (INDIRECT CELL-DIVISION). The description of the process of mitotic cell-division is compli- cated by the fact that structural changes are observed which occur simultaneously in the nucleus, centrosome, and cytoplasm. This fact should be borne in mind, as, for the sake of clearness, a sepa- rate description of the changes involving each of these structures seems demanded. The process of mitotic cell-division may be divided into four periods or phases, which follow one another with- out clearly defined limits : The prophases, in which the nuclear membrane disappears, the chromatin is transformed into definite threads, and the centrosome and centrosphere undergo important changes. This is the prepar- atory stage. The metapliases, in which the division and the separation of the chromatin take place. The anaphases, in which the daughter nuclei are formed and the cell-protoplasm begins to divide. The telophases, in which the division of the cell is completed. To give a better understanding of this process, we have inserted a series of diagrammatic figures (9—19), giving the cells the shape of an ellipsoid. We can then distinguish a long axis, two polar Digitized by Microsoft® 58 THE CELL. - Cell-body. Centrosome. - Centrosphere. Fig. 9. Fig. 10. Chromosomes. - . Centrosome. Crown of chromo- some. Fig. 11. Fig. 12. Fig. 13. Fig. 14. Figs. 9-14. — Diagrammatic representation of the processes of mitotic cell- and nuclear division. Figs. 9-12, Prophases; Figs. 13, 14, metaphases. Fig. 9, Resting nucleus; Fig. 10, coarse skein or spirem ; Fig. II, fine skein or spirem; Fig. 12, segmentation of the spirem into single chromosomes; Fig. 13, longi- tudinal division of the chromosomes; Fig. 14, bipolar arrangement of the separated chromosomes. Digitized by Microsoft® NUCLEAR AND CELL-DIVISION. 59 Uniting filaments. Fig- IS- Fig. 16. - - Cell-plates. Chromo- somes. Fig. 17. Fig. IS. Nucleolus. Fig. 19. Figs. 15-19. — Diagrammatic representation of the processes of mitotic cell- and nuclear division. Figs. 15-18, Anaphases; Fig. 19, telophases. Fig. 15, wandering of the chromosomes toward the poles; Fig. 16, diaster; Figs. 17 and 18, formation of the dispirem; Fig. 19, two daughter cells with resting nuclei. To simplify the figures 12-17, we have sketched in only a few chromosomes. In Fig. 16 it is seen that the cell-body is also beginning to divide. Digitized by Microsoft® 6o THE CELL. Fig. 23. Fig. 24. Figs. 20-24. — Mitotic cell-division of fertilized whitefish eggs — Coregonus alius. Fig. 20, Cell with resting nucleus, centrosome, and centrosphere to the right of the nucleus ; Fig. 21, cell with two centrospheres, with polar rays at opposite poles of nucleus ; Fig. 22, spirem ; Fig. 23, monaster ; Fig. 24, metakinesis stage. regions corresponding to the ends of the axis, and an equatorial plane. The latter is horizontal to the axis, equally distant from both poles, and passes through the middle of the nucleus. The division of the cell takes place in this plane. A series of figures (20-27), showing the different phases of mitotic cell-division of the fertilized eggs of the whitefish {Coregonus albus), is given ; the changes involving the centrosome, centrosphere, and cytoplasm are clearly illustrated. Figure 28, showing a small portion of a sec- tion through the testis of the salamander, the object in which Flem- ming first observed this complicated series of changes, presents the appearance more generally seen during mitotic cell-division of the tissue cells of the higher vertebrates. (a) Prophases. — The changes occurring in the nucleus will be considered first. At the beginning of the process of mitosis, the chromatin network, consisting of chromatin granules, is transformed into a twisted skein of threads, beginning at the periphery of the Digitized by Microsoft® NUCLEAR AND CELL-DIVISION. 6l Fi g- 2 5- Fig. 26. Fig. 27. Figs. 25-27. — Mitotic cell-division of fertilized whitefish eggs — Corcgonus albus. Fig. 25; Metakinesis stage ; Fig. 26, diaster ; Fig. 27, late stage of dispirem, the cell-protoplasm almost divided. nucleus. This skein of threads is known as the spirem or mother skein, and may appear as a single thread, which breaks up into a definite number of segments, or the segments may appear as such when the skein is forming. At first the threads are coarse and often somewhat irregular, staining much more deeply than the linin network. The separate segments of chromatin are known as chromosomes (Waldeyer, 88). They appear, as a rule, in the form of rods varying in length and thickness, and staining very deeply, and often bent into characteristic U-shaped loops. The bent portion of each loop is called its crown. " Every species of plant or ani- mal has a fixed and characteristic number of chromosomes, which regularly recurs in the division of all its cells ; and in all forms arising by sexual reproduction the number is even " (Wilson, 96). In man the number of chromosomes is given as sixteen by Barde- leben (92) and Wilson (96), and as twenty-four by Flemming (98). During the formation of the spirem the nuclear membrane, as a rule, disappears. The nucleolus is also lost sight of, although the manner of its disappearance can not be definitely stated. The net- knots are no doubt taken up by the chromosomes. The chromo- Digitized by Microsoft® 62 THE CELL. somes are now free in the protoplasm ; gradually the crown of each chromosome approaches the center of the space occupied by the nucleus, and the chromosomes form a characteristic, radially arranged stellate figure, known as the monaster, in the equatorial plane of the cell. During the progress of the changes affecting the chromatin of the nucleus and resulting in the formation of the chromosomes, important phenomena are observed, connected partly with the achromatic substance of the nucleus, more especially with the centrosome, centrosphere, and cytoplasm of the cell. These phenomena result in the formation of a complicated structure known as the achromatic spindle or amphiaster. Its development is as fol- lows : The centrosome and centrosphere, as has been stated, usu- ally lie in the protoplasm to one side of the nucleus. If, at the be- ginning of the division, the centrosome be single, it divides, and the two centrosomes begin to separate, causing a division of the centro- sphere. Between the centrosomes are usually seen finely drawn-out connecting threads. The centrosomes, each of which is surrounded by a centrosphere, now move apart, and a structure known as the central spindle, and consisting of fine threads arranged in the form of a spindle, develops between them. At each end of the central spindle is found a centrosome surrounded by a centrosphere from which radiate into the cytoplasm fine fibers known as polar rays. During the formation of the achromatic spindle the nuclear mem- brane disappears and the chromosomes develop, as above described. Some fibers, which seem to have their origin from the centrosphere, grow into the spirem formed of chromosomes, which they appear to pull into the equatorial plane of the cell, which is also the equator of the central spindle. Thus, the nuclear figure above described as the monaster is formed. In other cases the centrosomes and centrospheres continue moving apart until opposite each other and separated by the nucleus (Figs. 21, 22). As the nuclear membrane disappears and the spirems and chromosomes are form- ing, the central spindle develops, its fibers running from centro- sphere to centrosphere. The polar rays also develop in the cyto- plasm at the same time. As the central spindle develops, the chromosomes arrange themselves or are arranged about its equator — monaster. (I?) Metaphases. — Usually, during the formation of the monaster, or immediately after its formation (sometimes in the spirem stage or even earlier), the most important process of cell -division takes place. Each chromosome divides longitudinally into two daughter chromosomes. The loops first divide at the crown, the cleft extend- ing up either limb until the free ends are reached. The smallest particle of chromatin divides, retaining the exact relative position in the twin chromosomes that it possessed in the mother chromo- some. The daughter chromosomes now wander over the central spindle, their crowns presenting, in opposite directions toward the poles of the cell. This process is known as mctakinesis. Two stel- Digitized by Microsoft® NUCLEAR AND CELL-DIVISION. 63 late figures are developed about the respective poles of the central spindle. The appearance presented is known as a diaster. Our knowledge of the part taken by the amphiaster or achromatic spindle in metakinesis is not above controversy. It would appear, however, that certain cytoplastic fibers, which arise from the cen- trosphere and hang over the central spindle and chromosomes, designated as mantle fibers, assist in drawing the daughter chromo- somes toward the poles of the central spindle. (&■&:■■■:■ ''%S£|| ; S , -f ml . '£& W ' Fig. 35. — Pigment cell from the skin of the head of a pike ; X 650. T. No. 122. its high refractive index, distorts the picture to a considerable extent, the mitotic figures are beautifully distinct. 124. Certain methods of treatment bring out in both cells and nuclei the presence of peculiar granules. The latter have been especially studied and described by v. Altmann (94, 2d ed. ). The methods that he applies are as follows : The specimens of organs of recently killed animals are fixed in a mixture consisting of equal volumes of a 5% aqueous solution of potassium bichromate and a 2% solution of osmic acid, remaining in the mixture for twenty-four hours. They are then washed for several hours in water and treated with ascending strengths of alcohol ; viz., 70, 90, and 100%. The specimens are now placed in a solution of 3 parts of xylol and 1 part of absolute alcohol, then in pure xylol, and finally in paraffin. The tissues imbedded in paraffin must not be cut thicker than 1 to 2 11. Altmann mounts according to the following method : A rather thick Digitized by Microsoft® 72 THE CELL. solution of caoutchouc in chloroform (the so-called traumaticin of the Pharmacopeia — i vol. guttapercha dissolved in 6 vols, chloroform) is diluted before use with 25 vols, of chloroform and the resulting mixture poured upon a slide. The latter is tilted, and after evaporation of the chloroform, heated over a gas flame. The paraffin sections are mounted upon the slides so prepared and then painted with a solution of guncotton in aceton and alcohol (2 gm. guncotton dissolved in 50 c.c. of aceton, 5 c.c. of which is diluted with 20 c.c. of absolute alcohol). After painting with this solution, the sections are firmly pressed upon the slide with tissue paper, and after drying are made to adhere more closely by slight warming. Fixation to the slide with water is equally good. The sections can now be treated with various staining solutions without becoming detached from the slides. The paraffin is gotten rid of by immersing in xylol, after which the specimens are placed in absolute alcohol. Fuchsin S. can be used as a stain (20 gm. fuchsin S. dissolved in 100 c.c. anilin water). A small quantity of this solution is placed upon the section, and the slide warmed over a flame until its lower surface becomes quite perceptibly warm and the staining solution begins to evaporate. The slide is then allowed to cool, washed with picric acid (concentrated alcoholic solution of picric acid diluted with 2 vols, of water), after which it is covered with a fresh quantity of picric acid, and again, but this time vigorously, heated (one-half to one minute). Occasionally the same results can be obtained by covering the section for five minutes with a cold solution of picric acid of the above strength. This last procedure has a decided influence upon the granula, and gives rise to a distinct differentiation between them and the remaining portions of the cell, the latter appearing grayish-yellow, while the granula themselves appear bright red. In some cases where the granula can not be sharply differentiated from the remaining structures, it may be necessary to repeat the staining process. Xylol-Canada balsam should not be used for mounting, as it has a bleaching effect upon the osmic acid in the specimen. Mount either in liquid paraffin (Altmann) or in undiluted Canada balsam, which is easily reduced to a fluid state, whenever needed, by heating. There is another method used by Altmann which deserves mention, but practical application of which must be improved upon in the future ; this consists in freezing the specimens and drying them for a few days in the frozen condition in a vacuum over sulphuric acid at a temperature of about — 30 C. According to Fischer, dilute solutions of pepton when treated with various reagents (especially with a potassium bichromate-osmium mix- ture) form precipitates and granules which are remarkable in that they react to stains exactly as do Altmann's granula. It is, therefore, doubt- ful whether Altmann's granules should be regarded as vital structures. 125. Altmann (92) has also devised a simpler negative method for demonstrating the granula. Fresh specimens are placed for twenty-four hours in a solution consisting of molybdate of ammonium 2.5 gm., chromic acid 0.35 gm., and water 100 c.c. ; then treated for several days with absolute alcohol, sectioned in paraffin, and colored with a nuclear stain such as hematoxylin or gentian. The intergranular network is colored, while the granula remain colorless. The amount of chromic acid used (0.25 to if ) varies according to the object treated ; if molyb- date of ammonium alone be used, the nuclei will appear homogeneous, Digitized by Microsoft® THE TISSUES. 73 while if an excess of chromic acid be employed, the nuclei will appear coarsely reticulated. This method leads to the formation of granula in the cells as well as in the nucleus. 126. By fixing and staining cells of widely different vegetable and animal types Butschli believes he has demonstrated the existence of proto- plasmic structures having the form of bubbles and termed by him micro- scopic foam-structures. Fixing is done either in picric acid solution or in weakly iodized alcohol. The specimens are then stained with iron-hema- toxylin — /'. e. , first treated with acetate of iron, rinsed in water, and trans- ferred to a 0.5% aqueous solution of hematoxylin (similar to the method of R. Heidenhain {yid. T. 85). Very thin sections are required (y 2 to 1 />.). Mounting is done, when the lighting is good, in media having low refractive indices, which emphasize the alveolar or foam -like structure of the protoplasm. Of various animal objects, Butschli especially recom- mends young ovarian eggs of teleosts, and blood-cells and intestinal epi- thelium of the frog, etc. It is still a matter of uncertainty whether or not the structures are actually present in living protoplasm. II. THE TISSUES. The first few generations of cells which result from the segmen- tation of the fertilized ovum have no pronounced characteristics. They are embryonic cells of rounded form, and are known as blas- tomercs. As they increase in number they become smaller and of polygonal shape, owing to the pressure to which they are subjected. From the mass of blastomeres, known as the morula mass, there are formed, under various processes described under the name of gastrulation, two layers of cells, the so-called primary germ layers, of which the outer is the ectoderm, the inner the entoderm. To the primary germ layers is added still a third layer, called the meso- derm ; it is derived from both the ectoderm and entoderm, but principally from the latter. From these three layers of cells, known as the primary blastodermic layers, are developed all the tissues, each layer developing into certain tissues that are distinct for this layer. In their further development and differentiation the cells of the blas- todermic layers undergo a change in shape and structure character- istic for each tissue, and there is developed an intercellular substance varying greatly in amount and character in the several tissues. In the tissues developed from the ectoderm and entoderm the cellular elements give character to the tissue, while the intercellular sub- stance is present in small quantity ; in the majority of the tissues developed from the mesoderm, the intercellular substance is abun- dant, while the cellular elements form a less conspicuous portion. The tissues derived from the ectoderm are : The epidermis of the skin, with the epidermal appendages and glands ; the epithelium lining the mouth, with the salivary glands and the enamel of the teeth ; the epithelium and glands of the nasal tract and the cavities opening into it ; the lens of the eye and retina, Digitized by Microsoft® 74 THE TISSUES. and the epithelium of the membranous labyrinth of the ear ; and finally, the entire nervous system, central and peripheral. From the entoderm : The epithelium lining the digestive tract, and all glands in con- nection with it, including the liver and pancreas ; the epithelium of the respiratory tract and its glands ; the epithelium of the bladder and urethra (in the male, only the prostatic portion, the remainder being of ectodermal origin). The cells of the mesoderm are early differentiated into three groups (Minot, 99) : (a) Mesotholium. — The mesothelial cells retain the character of epithelial cells. They form the lining of the pleural, pericardial, and peritoneal cavities, and give origin to the epithelium of the uro- genital organs (with the exception of the bladder and urethra), and striated and heart muscle tissue. (b) Mesenchyme, from which are derived all the fibrous connective tissues, cartilage, and bone, involuntary muscle tissue, the spleen, lymph-glands, and bone-marrow ; and cells of an epithelioid charac- ter, lining the blood and lymph-vessels and lymph-spaces, known as endothelial cells. (c) Mesameboid cells, comprising all red and white blood-cells. It would be extremely difficult to attempt a classification of tis- sues according to their histogenesis, as identical tissue elements owe their origin to different germinal layers. The classification adopted by us is based rather on the structure of the tissues in their adult stage. We distinguish : A. Epithelial tissues with their derivatives. B. Connective tissues ; adipose tissue ; supporting tissues (car- tilage, bone). C. Muscular tissue. D. Nervous tissue. E. Blood and lymph. A. EPITHELIAL TISSUES. Epithelial tissues are nonvascular, and composed almost wholly of epithelial cells, united into continuous membranes by a substance known as intercellular cement. They serve to protect exposed surfaces, and perform the functions of absorption, secretion, and excretion. The epithelia are developed from all of the three layers of the blastoderm. They secrete the cement-substance found between their contigu- ous surfaces. This takes the form of thin lamellae between the cells, gluing them firmly together. In certain regions the epithelial cells develop short lateral processes (prickles), which meet like structures Digitized by Microsoft® EPITHELIAL TISSUES. 75 from neighboring cells, thus forming intercellular bridges. Between these bridges are intercellular spaces filled with lymph-plasma for the nourishment of the cells. Epithelia do not, as a rule, possess processes of any length. However, it would appear that the base- ment membranes, situated beneath the epithelia, consist chiefly of processes from the basal portion of the cells. Some authors ascribe to them a connective-tissue origin, a theory which conflicts with the fact that such membranes are present in the embryo before connective tissue, as such, has been developed (jnembrana prima, Hensen, 76). The free surfaces of epithelia often support cuticular structures which are to be regarded as the products of the cells. The cutic- ular of neighboring cells fuse to form a cuticular membrane or mar- ginal zone which can be detached in pieces of considerable size (cuticula). In longitudinal sections the cuticula show, in many cases, a striation which would seem to indicate that they are com- posed of a large number of rod-like processes cemented together by a substance possessing a different refractive index. The cell-body is also striated for more than half its length, corresponding to the rods of the marginal zone. In the region of the nucleus at the basal por- tion the striation disappears, the cell here consisting of granular pro- toplasm of a more indifferent character. Since one surface of each epithelial layer lies free, and is conse- quently exposed to other conditions than the inner surface, certain differences are noticed between the two ends of each cell. The cells may develop cuticular structures as above stated. In other cases motile processes (cilia) are developed on their exposed surface, which move in a definite direction in the medium surrounding them, and by means of this motion sweep away foreign bodies. It is not strange that the free surface of the epithelia, exposed as it is to stimulation from without, should develop special structures for the reception of sensations (sense cells). On the other hand, the inner or basal surfaces of the cells usually retain a more indifferent character, and serve for the attachment of the cells and the conveyance of their nourishment. For this reason the nuclei of such cells are usually situated near the basal surface. From the above it is seen that the two ends of the epithelial cell undergo varying processes of differentiation, the outer being adapted more to the animal, the inner more to the vegetative functions. This differentiation has recently been known as the polarity of the cell. This polarity appears to be retained even when the cell loses its epithelial character and assumes other functions (Rabl, 90). With few exceptions, blood- and lymph-vessels do not penetrate into the epithelia, but the Tatter are richly supplied with nerves. The finer morphology of the epithelia will be described in the chap- ters on the different organs in Part II. Epithelia are classified according to the shape and relation of the epithelial cells. Digitized by Microsoft® 7 6 THE TISSUES. We give the following classification : 1. Simple epithelia (with or without cilia). (a) Squamous epithelium. (b) Cubic epithelium. c) Columnar epithelium. d) Pseudostratified columnar epithelium. 2. Stratified epithelia (with or without cilia). (a) Stratified squamous epithelium, with superficial flattened cells (without cilia). (b) Transitional epithelium. (c) Stratified columnar epithelium, with superficial columnar cells (with or without cilia). 3. Glandular epithelium. 4. Neuro-epithelium. J. SIMPLE EPITHELIUM. In simple epithelia the cells lie in a single continuous layer. Simple epithelia are very widely distributed. They line almost the entire alimentary tract, the smaller respiratory passages and air Fig. 36. — Isolated cells of squamous epithe- lium (surface cells of the stratified squamous epithelium lining the mouth) : a, a, Cells present- ing under surface ; i, cell with two nuclei. Fig. 37- — Surface view of squamous epithelium from skin of a frog ; X 4°°- Technic No. 124. sacs, the majority of the gland ducts, the oviducts and uterus, and the central canal of the spinal cord and ventricles of the brain. (a) Simple Squamous Epithelium. — In simple squamous epi- thelium the cells are flattened. Their contiguous surfaces appear regular, forming, when seen from above, a mosaic. The nuclei lie, as a rule, in the middle of the cell, and if the latter be very much flattened, the position of the nucleus is made prominent by a bulg- ing of the cell at this point. It occurs in the alveoli of the lung. (b) Simple Cubic Epithelium. — Epithelial cells of this type differ from the above only in that they are somewhat higher. They appear as short polygonal prisms. Their outlines arc, as a rule, not irregular, but form straight lines. Cubic epithelium occurs in the Digitized by Microsoft® EPITHELIAL TISSUES. 77 smaller and smallest bronchioles of the lungs, in certain portions of the uriniferous tubules and their collecting ducts, in the smaller ducts of salivary and mucous glands, liver, pancreas, etc. (c) Simple Columnar Epithelium. — In this type the cells take the form of prisms or pyramids of varying length. Cuticular structures are especially well developed. Columnar epithelium occurs in the entire intestinal tract from the cardiac end of the stomach to the anus, in certain portions of the kidney, etc. Goblet cell. Cuticular border. Fig. 38. — Simple columnar epithelium from the small intestine of man : a, Isolated cells ; d, surface view ; c, longitudinal section. Simple ciliated columnar epithelium is found in the oviduct and uterus, central canal of the spinal cord, and smaller bronchi. (d) Pseudostratified Columnar Epithelium. — This type is one in which all the cells rest on a basement membrane, but they are so placed that the nuclei come to lie in different planes. Thus, in a longitudinal section the nuclei are seen to be placed in several rows. The development of this type from the simpler forms occurs when the cells are too crowded to retain their normal breadth. As a result, they become pyramidal, alternate cells resting their bases or apices on the base- ment membrane. As the nucleus is usually situated at the broader portion of the cell, the result is that there are two rows of nu- clei simulating a stratified epithelium. Occa- sionally there are spindle-shaped cells wedged in between the pyra- midal cells, and as the broad portion of these cells is midway between the basement membrane and external surface, a third row of nuclei is seen midway between the other two. Such epithelia usually possess cilia (portions of the respiratory passages). '•/ 1 91 •111 \r /? /•/ •\pf#]|j* Fig. 39. — Diagram of pseudostratified col- umnar epithelium. 2. STRATIFIED EPITHELIUM. Should the increase of the cells forming the last type of simple epithelium proceed to such an extent that all the cells no longer rest on the basement membrane, an epithelium is formed having dis- Digitized by Microsoft® 73 THE TISSUES. Fig. 40. — Schematic diagram of stratified pave- ment epithelium. tinct layers of cells — a stratified epithelium. It is clear that all the cells of a stratified epithelium can not be equally well nourished by the blood-supply from the vessels in the highly vascular connective tissue beneath. The middle and outer layers of cells accord- ingly suffer. The deeper layers are much better nourished, and as a consequence their cells increase much more rapidly than those above ; they push outward, replacing the superficial cells as fast as they die or are thrown off! The proliferation of cells in a stratified epithelium occurs, therefore, chiefly in its basal layers. (a) Stratified Squamous Epithelium. — Stratified squamous epithelium with superficial flattened cells forms the epidermis with its continuations into the body, as, for instance, the walls of the oral cavity and the esophagus, the epithelium of the conjunctiva, the vagina, the external auditory canal, and the external sheath of the hair follicles. The cells of the basal layer are here mostly cubic-cylindric. Then follow, according to the situation of the epithelium, one or more layers of polyhedral cells, which become gradually flattened toward the surface, the outer- most layers consisting of thin plate-like cells. In stratified squamous epi- thelia, where the outer cells be- come horny (as in the skin), the stratification is still more special- ized. Here layers are inserted in which the horny or chitinous substance is gradually formed, although the cells do not be- come chitinous until the super- ficial layers are reached. Especially characteristic of stratified squamous epithelium is the arrangement of the connec- tive tissue on which this epithe- lium rests. There are cone-like projections, known as papilla, arising from the connective tissue beneath the epithelium, project- ing into the latter in such a way that on cross-section the junction of the two tissues appears as a wave-like line. These papilla; not onlyserve to fasten the epithelium more firmly to the connective tissue below, but influence very favorably the nourishment of the former by allowing a greater number of its basal cells to approximate the under- efe^M ?^t||f^JJ| Fig. 41. — Cross - section of stratified squamous epithelium from the esophagus of man. Digitized by Microsoft® EPITHELIAL TISSUES. 79 lying blood-capillaries. The pyramidal extensions of the epithelium between the papillae are designated interpapillary epithelial processes. In regions where the stratified squamous epithelium consists of many layers, the prickle cells, intercellular bridges, and the inter-- cellular spaces are especially well developed. These spaces facili- tate the passage of the lymph-plasma to the more superficial layers of cells. (b) Transitional Epithelium. — Transitional epithelium is a stratified epithelium occurring in the pelvis of the kidney, the ure- ters, bladder, and the posterior portion of the male urethra. It is composed of four to six layers of cells and rests on a connective tissue free from papillae. In sections the cells of the deeper layers appear to be of irregularly columnar, cubic or triangular shape. The Fig. 42. — Isolated transitional epithe- lial cells from the bladder of man : a, b, e, d, Large surface cells, c and d presenting the pitted undersurface ; e, variously shaped cells from the deeper layers. Fig. 43. — Cross-section of transitional epithelium from the bladder of a young child. cells forming the superficial layer are large, somewhat flattened cells, with convex free surfaces, often possessing two, sometimes three, nuclei. They cover a number of the cells of the layer just beneath them, their under surfaces being pitted to receive the upper ends of the deeper cells. In teased preparations the cells of the deeper layers appear very irregular, often showing ridges or variously shaped processes. (See Fig. 42.) (c) Stratified Columnar Epithelium. — In this type the super- ficial layer consists of columnar cells, the basal ends of which are usually somewhat pointed, or may branch. The deeper cells, which may be arranged in one or more layers, are of irregular, triangular, polyhedral, or spindle shape. It is found in the larger gland ducts, olfactory mucous membrane, palpebral conjunctiva, portions of the Digitized by Microsoft® 8o THE TISSUES. male urethra and the vas deferens, and in certain regions of the larynx. The ciliated variety of this epithelium differs from the foregoing in that the superficial columnar cells are provided with cilia. Strati- fied ciliated columnar epithelium is found in the respiratory portion Fig. 44. — Schematic dia- gram of stratified columnar epi- thelium. Fig. 45. — Ciliated cells from the bronchus of the dog, the left cell with two nuclei ; X 00 °- Technic No. 126. of the nose, larynx, trachea, and larger bronchi, in the Eustachian tube, epididymis, and a portion of the vas deferens. All epithelial cells are probably joined together by short pro- cesses forming intercellular bridges, the lymph supplying them with nourishment circulating in the intercellular spaces thus formed. Toward the surface, these intercellular spaces are roofed over, thus preventing the escape of the fluid. When seen from the surface, epithelia treated by certain methods (iron-hematoxylin) show the cells joined together by very minute, clearly defined and continuous Goblet cell. Fig. 46. — Cross-section of stratified ciliated columnar epithelium from the trachea of a rabbit. cement-lines. Bonnet has called them terminal ledges or bars (Schlussleisten). The function of this structure would seem to consist in its power to prevent the escape of lymph from the sur- face, and the penetration of micro-organisms (M. Heidenhain, 92 ; Bonnet, 95). Digitized by Microsoft® EPITHELIAL TISSUES. 81 3. GLANDULAR EPITHELIUM. (a) The Gland-cell. — Certain cells lying scattered among other epithelial cells produce substances that are extruded and utilized in the body economy. The protoplasm of such a cell elaborates in its interior a substance that takes the form of vacuoles or granules, which gradually distend the cell ; the substance thus produced is finally given off as the secretion. All these phases of the activity of a gland-cell are included under the term secretion. Isolated glandular cells are frequently met with in epithelia, and are known in general as unicellular glands. They occur especially in the intestinal and respiratory epithelium, where, owing to their shape, they are termed goblet cells. All the intestinal epithelial cells and many of the cells of respiratory epithelium, have the power of changing into goblet cells. These are distinguished from the neigh- boring cells by the fact that their free ends are clearer and more Cilia. Mucin. Nucleus. Basal process. Fig. 47. — Goblet cells from the bronchus of a dog. The middle cell still possesses its cilia ; that to the right has already emptied its mucous contents (collapsed goblet cell) ; X 600. Technic No. 128. vesicular, while their basal portions, containing the nuclei, are narrow and pointed. The clear substance elaborated by the protoplasm of the cell, but not yet extruded, is mucin. On closer examination it is seen that this substance fills the interspaces of a very fine proto- plasmic network continuous with the protoplasm surrounding the nucleus. Thus we have, during the phases of secretion, two distinct sub- stances in the cell-body : the one the original protoplasm of the cell — protoplasm (Kupffer) ; the other its product, in this case mucin — paraplasm (Kupffer). When the secretion is extruded the goblet cell collapses and then appears as a thin cord between the neighbor- ing cells. There is as yet some question as to whether a collapsed goblet cell dies after the expulsion of its. contents, or whether it may again become stored with mucin. Should it be destroyed, its place is soon occupied by the closing in of contiguous cells. 6 Digitized by Microsoft® 82 THE TISSUES. Multicellular glands originate by the metamorphosis of a num- ber of adjacent cells into glandular cells. This is usually accom- panied by a more or less marked dipping down of the epithelial layer into the underlying connective tissue. The simplest form of such an invagination is a cylindrical tube lined entirely by glandular cells. A further differentiation may take place in that all the in- vaginated cells do not assume a secretory function, those at the upper portion of the tube forming the lining membrane of an excre- tory duct. The originally uniform tube is thus differentiated into an excretory and a secretory portion. Multicellular glands may lie entirely within the epithelium, and are then known as intra-epithelial glands, in contrast to the extra-epithe- lial or ordinary type, the greater part of which lies imbedded in the under- — Lumen of gland. &'.;» GlandSr :; '®»-%i Reticulum. Nucleus of connec- tive-tis- sue cell. Blood- vessel. Fig. 60.- -Reticular connective tissue from lymph-gland of man ; X 2 ^°- preparation. Brush woven, as in fascias, the dura mater, and the firm, fibrous capsules of some of the organs. (a) In areolar connective tissue the bundles of white fibers, which vary greatly in size and which often divide and anastomose with portions of other branching bundles, intercross and interlace in all directions. If the bundles of fibers are numerous, the interlacement is more compact, thus forming a dense areolar connective tissue ; if less numerous, the network is more open, as in loose areolar connective tissue. Elastic fibers are always found in areolar connective tissue, though in varying quantity. They anastomose to form a network with large, irregular meshes, and run on or between the bundles of white fibers. The meshes between the bundles of fibers, and the minute spaces between the fibrils in these bundles, are occupied by a semifluid, homogeneous substance known as the ground-substance, or matrix. The fibrous elements of areolar connective tissue are, Digitized by Microsoft® 94 THE TISSUES. therefore, imbedded in this ground-substance, in which they develop. In dense areolar connective tissue the fibrous elements appear to have nearly displaced the ground-substance. In the ground-sub- stance are found irregular, branched spaces, — cell-spaces, — in which lie the cellular elements of this connective tissue. These spaces anastomose by means of their branches, thus forming part of a system of spaces and small chan- nels, known as the lymph canal- icular system. These spaces and channels permeate the ground- substance in all directions, and serve to convey lymph to the tissue elements. The cell-spaces and their anastomosing branches can be demonstrated by immers- ing areolar connective tissue (preferably from a young animal), spread out in a thin layer, in a solution of silver nitrate ( I % ) until the tissue becomes opaque. If then the" tissue is exposed to sunlight, the silver is reduced in the ground-substance, giving it a brown color, while the cell-spaces remain unstained. The ground- substance of areolar connective tissue contains mucin. The cellular elements of areolar connective tissue, which, as above stated, are imbedded in the cell-spaces, are either fixed con- Fig. 61. — Areolar connective tissue from the subcutaneous tissue of a rat. Elastic fibers not shown. "*,:.■>:-•■'■ § % * Fig. 62. — Cell - spaces in the ground- substance of areolar connective tissue (sub- cutaneous) of a young rat. Stained in silver nitrate. Fig. 63. — Three connective-tissue cells from the pia materof a dog. Stained in methylene-blue {intra vitani). nective-tissue cells or wandering or migratory cells. The former are again divided, according to their shape and structure, into true connective-tissue cells or corpuscles, granular cells, plasma cells, and pigment cells. The connective-tissue cells or corpuscles are flattened, variously shaped cells of irregular form, usually having many branches. The Digitized by Microsoft® THE CONNECTIVE TISSUES. 95 protoplasm is free from granules ; the nucleus, situated in the thicker portion of the cell-body and of oval shape, shows a nuclear net- work and one or several nucleoli. The cells assume the shape of £•$%» \»3 Fig. 64. — Two pigment cells found on the capsule of a sympathetic ganglion of a frog. the space that they occupy and nearly fill. The branches of neigh- boring cells often anastomose through the fine channels uniting the cell-spaces. Granular cells are thus named because in their protoplasm are found rather coarse granules of an albuminous nature which stain Bacterium in a vacuole. Fig. 65. — Leucocyte of a frog with pseudopodia. The cell has included a bacterium which is in process of digestion. (After Metschnikoff, from O. Hertwig, 93, II). readily in many anilin stains, notably eosin. They are of irregular form, and are generally found in the neighborhood of blood-vessels. The nucleus is relatively large and of round or oval form. Digitized by Microsoft® 96 THE TISSUES. Plasma cells, first described by Waldeyer, show large vacuoles in their protoplasm. Pigment cells are branched connective-tissue cells, in the proto- plasm of which are found brown or nearly black granules. In man they occur in the choroid and iris and in the dermis. In the lower animals they have, however, a much wider distribution, and in the frog and other amphibia they are very large and irregular. These cells have the power of withdrawing their processes and, to a limited degree, of changing their location (dermis). The wandering or migratory cells are described in this connec- tion not because they form one of the structural elements of areolar connective tissue, but because they are always associated with it. They are lymph- or white blood-cells, which have left the lymph- or blood-vessels and have migrated into the lymph canalicular system. They possess ameboid movement, and wander from place to place, Fibrils. Nucleus. Fig. 66. — Fibrous connective tissue (areolar) from the great omentum of the rabbit ; X 400. Technic No. 17. and are the phagocytes of Metschnikoff. They seem to be intrusted with the removal of substances either superfluous or detrimental to the body (as bacteria). These are either digested or rendered harm- less. The wandering cells even transport substances thus taken up to some other region of the body, where they are deposited. In the peritoneum and other serous membranes the network formed by the fibrous tissue lies in one plane, and does not branch and intercross in all directions, as where areolar tissue is found in larger quantity. (Fig. 66.) (U) Tendons, aponeuroses, and ligaments represent the densest variety of fibrous connective tissue, and are composed almost wholly of white fibrous tissue. This is found in the form of rela- tively large bundles of white fibrils, having a parallel or nearly parallel course. In tendons these bundles are known as primary tendon bundles or tendon fasciculi. The fibrils of white fibrous con- Digitized by Microsoft® THE CONNECTIVE TISSUES. 97 nective tissue forming the fasciculi are cemented together by an in- terfibrillar cement substance. Here and there the fasciculi branch at very acute angles and anastomose with other fasciculi. The fas- ciculi are grouped into larger or smaller bundles, the secondary tendon bundles, which are surrounded by a thin layer of areolar con- nective tissue, and in part covered by endothelial cells. Between the tendon fasciculi there is found a ground-substance, interfascicu- lar groimd-substance, identical with the ground-substance in areolar connective tissue. In this there are cell-spaces occupied by the tendon cells, morphologically similar to the branched cells of areolar connective tissue. The tendon cells are arranged in rows between the tendon fasciculi. They have an irregular, oblong body, containing a nearly round or oval nucleus. Two, three, br even more wing- Tendon cell. . Tendon fibers. r !''■ ' v /Tendon \ -x T * ->-J / \ " _< -^ --. ^ y' -^ v, /' " Tendon _^*-^ fasciculus. Fig. 67. — Longitudinal section of tendon ; Fig. 68. — Cross-section of secondary X270. tendon bundle from tail of a rat. like processes (lamella?) come from the cell-body and pass between the tendon fasciculi. In cross-section the tendon cells have a stellate shape. The secondary tendon bundles are grouped to form the tendon, and the whole is surrounded and held together by a layer of areolar connective tissue, called the peritendineum. From this, septa pass in between the secondary tendon bundles, forming the internal peri- tendineum. The blood- and lymph-vessels and the nerve-fibers reach the interior of the tendon through the external and internal peritendineum. The structure of an aponeurosis and a ligament is like that of a tendon. The structure of a fascia, the dura mater, and the more fully 7 Digitized by Microsoft® 9 8 THE TISSUES. developed gland capsules, differs from that of the formed connective tissues above described, in that the fasciculi are not so regularly arranged, but branch and anastomose and intercross in several planes. (c) Elastic Fibrous Tissue. — In certain connective tissues the elastic fibers predominate greatly over the fibers of white fibrous connective tissue. These are spoken of as elastic fibrous tissues and their structural peculiarities warrant the making of a special sub- group. The ligamentum nuchae of the ox consists almost exclu- sively of elastic fibers, many of which attain a size of about io/i. The elastic fibers branch and anastomose, retaining, however, a generally parallel course. They are separated by a small amount of areolar connective tissue, in which a connective-tissue cell is here and there found, and are grouped into bundles surrounded by thin layers of areolar connective tissue ; the whole ligament receives an Nucleus of con- nective-tissue cell. Fig. 69. — Tendon cells from the tail of a rat. Stained in methylene- blue {intra vitam). Fig. 70. — Cross-section of ligamentum nuchse of ox. investment of this tissue. In cross-sections of the ligamentum nuchas, the larger elastic fibers have an angular outline ; the smaller ones are more regularly round or oval. (Fig. 70.) In man the ligamenta subflava, between the lamina? of adjacent vertebra?, are elastic ligaments. In certain structures (arteries and veins), the elastic tissue is arranged in the form of membranes. It is generally stated that such membranes are composed of flat, ribbon-like fibers or bands of elastic tissue arranged in the form of a network, with larger or smaller openings; thus the term fenestrated membranes. Mall has reached the conclusion that such membranes are composed of three layers — an upper and a lower thin transparent layer in which no openings are found and which are identical with the sheaths of elastic fibers described by this observer, and a central layer, containing openings, and staining deeply in magenta. This substance is identical with the central substance of elastic fibers. Digitized by Microsoft® THE CONNECTIVE TISSUES. 99 4. ADIPOSE TISSUE. In certain well-defined regions of the body occur typical groups of fixed connective-tissue cells which always change into fat-cells (fat organs.Toldt). Connective -tissue cells in various other portions of the body may also change into fat-cells, but in this case the fat, as such, sometimes disappears, allowing the cells to resume their original con- nective-tissue type, only again to appear and a second time change the character of the tissue. The formation of fat is very gradual. Very fine fat globules are deposited in the cell ; these coalesce to form larger ones, until finally the cell is almost entirely filled with a large globule (vid. also H. Rabl, 96). As the fat globule grows larger and ^^ggae^- — Nucleus. larger, the protoplasm of the cell, to- J ft Protoplasm, gether with its nucleus, is crowded to fl H the periphery. The protoplasm then H K Fat drop, appears as a thin layer just within the ^B wt" CeI1 - membrane - clear cellular membrane. The nucleus ^^^^^^ becomes flattened by pressure, until Fig. 71.— Scheme of a fat-cell. in profile view it has the appearance of a long, flat body. In regions in which large masses of fat- cells are developed, they are seen to be gathered into rounded groups of various sizes (fat lobules) separated by strands of con- nective tissue. Numerous blood-vessels are imbedded in this con- nective tissue, penetrating into the lobules and there breaking up into a rich capillary network. Microscopically, fat is easily recognized by its peculiar glistening appearance (by direct light). It has a specific reaction to certain reagents. It becomes black on treatment with osmic acid, and is stained red by Sudan III. 5. CARTILAGE. The simplest type is hyaline cartilage, so named because of its homogeneous and transparent ground-substance. Cartilage cells, as such, are of various shapes, and have no typical appearance. They are usually scattered irregularly throughout the matrix, but are often arranged in groups of two, three, four, or even more cells. At the periphery of cartilage, either where it borders upon a cavity (articular cavity) or where it joins the perichondrium, the cells are arranged in several rows parallel to the surface of the tissue. Cartilage cells often contain glycogen, either in the form of drops or diffused throughout their protoplasm. The matrix of cartilage is the product of the cell. It is not present in the so-called precartilage (embryonal cartilage), in which the cells lie close together with their membranes touching. The ground-substance is gradually formed as follows : The membranes of the cells thicken, pressing the cells apart. Inside of the mem- branes the cells divide, and each resulting cell again forms a mem- Digitized by Microsoft® IOO THE TISSUES. brane. Membranes of the mother cells fuse to form the ground- substance or matrix. The newly created membranes of the daughter cells pass through the same process, and fuse not only with each Matrix. — r*$$ Cartilage cell. ™^ fc ~ '" %■■■ Fig. 72. — Hyaline cartilage (costal cartilage of the ox). Alcohol preparation; X 300. The cells are seen inclosed in their capsules. In the figure a are represented frequent but by no means characteristic radiate structures. other, but also with the matrix. The cartilage thus gradually as- sumes the appearance of its adult stage. The youngest cells also possess membranes which separate them from the ground-sub- stance. These are known as the capsules. The spaces occupied by the cells are called lacuna. ■Fig- 73- — From a section through the cranial cartilage of a squid (after M. Fiirbringer, from Bergh). From the description just given it would seem that cartilage grows only by intussusception, but as a matter of fact an apposi- tional growth, although in a lesser degree, also takes place. It Digitized by Microsoft® THE CONNECTIVE TISSUES. IOI occurs where the cartilage borders upon its connective-tissue sheath or perichondrium, a vascular, fibrous-tissue membrane composed of white and. elastic fibers, which covers the cartilage except where it forms a joint surface. The relations of the cartilage and peri- chondrium are extremely intimate. Fibers are seen passing from the perichondrium into the cartilaginous matrix, and the connective- tissue cells appear to change directly into cartilage-cells. m &M fj&i&lM .-.J I;. . 1 j -"'.'■ [(fy, 1/ ' {. if ) 'iM ' ii] : ^ 0f{^ '. '■ ' , ', , u.§ ffl , ^ ; -' £ nifi !i !? '« ! , ' 1 "' White fibrous connec- tive tissue. White fibrocartilage. sf p ?■ -/_, " 'f @ <^\^ m £ 1 » 9 .® '.- 81% SOc • : - ' ■•-',; &ft c^'/_L'Ti^Uered hyaline st^fl - / cartilage. Fig. 8l. — Longitudinal section through a long bone (phalanx) of a lizard embryo. The primary bone lamella originating from the periosteum is broken through by the peri- osteal bud. Connected with the bud is a periosteal blood-vessel containing red blood- corpuscles. structural changes have taken place at the center of ossifica- tion. Its commencement is marked by a growing into the cartilage of one or several buds or tufts of tissue derived principally from the osteogenetic layer of the periosteum. As the periosteal buds grow into the cartilage, some of the septa of matrix separating the altered cartilage-cells disappear, and the cells become free and probably degenerate. In this way the cartilage at the center of ossi- Digitized by Microsoft® THE CONNECTIVE TISSUES. IO9 fication becomes hollowed out, and there are formed irregular anas- tomosing spaces, primary marrow spaces, separated by partitions or trabeculse of calcified cartilage matrix. Into these primary mar- row spaces grow the periosteal buds, consisting of small blood- vessels, cells, and some few connective-tissue fibers, forming embry- onic marrow tissue. Some of the cells which have thus grown into ossification. mmmfmm Periosteal bone lamella. Primary marrow spaces. Fig. 82. — Longitudinal section of the proximal end of a long bone (sheep embryo) ; X 3°- the primary marrow spaces arrange themselves in layers on the trabecular of calcified matrix, which they envelop with a layer of osseous matrix formed by them. The cells thus engaged in the formation of osseous tissue are known as osteoblasts. Ossification proceeds from the center of ossification toward the Digitized by Microsoft® no THE TISSUES. extremities of the diaphysis (in a long bone), and is always preceded, as at the center of ossification, by the characteristic structural changes above described. Beginning at the center of ossification and proceeding toward either extremity of the diaphysis, the enlarged and vesicular cartilage-cells will be observed to be arranged in quite reg- ular columns, separated by septa or tra- becular of calcified cartilage matrix. The cells thus arranged in columns show the degenerative changes above described. They are shrunken and flattened, and their nuclei, when seen, stain less deeply than the nuclei of normal cartilage-cells. Beyond this zone of columns of altered cartilage-cells are found smaller or larger gi'oups of less changed cartilage-cells, and beyond this zone, hyaline cartilage. The arrangement of the cartilage- cells in the columns above mentioned is, according to Schiefferdecker, mainly due to two factors — the current of lymph plasma which flows from the center of ossification toward the two extremities of the cartilage fundament, and the mutual pressure exerted by the groups of carti- lage-cells in their growth and prolifera- tion. Ossification proceeds from the cen- ter of the diaphysis toward its two ex- tremities by a growth of osteoblasts and small vessels into the columns of carti- lage-cells. Here, also, these degenerate, leaving in their stead irregular, oblong, anastomosing spaces, separated by septa and trabecular of calcified cartilage ma- trix on which the osteoblasts arrange themselves in layers, and which they envelop in osseous tissue. In a longi- tudinal section of a long bone, preformed in cartilage, the various steps of endo- chondral bone-development may, there- fore, be observed by viewing the prepa- ration from either end to the center of the diaphysis, as may be seen in figures 82, 83. The former represents the appear- ance as seen under low magnification, the latter a small portion of such a section from the area of ossification, more highly magnified. Adjoining the primary marrow spaces is vesicular cartilage and columns and groups of cartilage-cells and finally hyaline car- tilage. Digitized by Microsoft® Fig. 83. — Longitudinal sec- tion through area of ossification from long bone of human em- bryo. THE CONNECTIVE TISSUES. I I I In the upper portion of figure 83 is observed a zone composed of groups of cartilage-cells, adjoining this a zone composed of columns of vesicular and shrunken cartilage-cells, the nuclei of which are indistinctly seen. These columns are separated by septa and trabeculae of calcified matrix. This zone is followed by one in which the cartilage-cells have disappeared, leaving spaces into which the osteoblasts and small blood-vessels have grown. In cer- tain parts of the figure, the osteoblasts are arranged in a layer on the trabecular of calcified cartilage, some of which are enveloped in a layer of osseous matrix, less deeply shaded than the darker car- tilage remnants. As the development of endochondral bone proceeds from the center of ossification toward the extremities of the diaphysis in the manner described, the primary marrow spaces at the center of ossi- fication are enlarged, a result of an absorption of many of the smaller osseous trabecular and the remnants of calcified cartilage matrix enclosed by them. In this process are concerned certain large and, for the most part, polynuclear cells, which are differentiated from the embryonic marrow. These are the osteoclasts (bone break- ers) of Kolliker (73). They are 43 ji to 91 fi long and 30// to 40// broad, and have the function of absorbing the bone. The spaces which they hollow out during the beginning of the process appear as small cavities or indentations, containing osteoclasts either single or in groups, and are known as Howship's lacuna. All bone absorption goes hand in hand with their appearance. At the same time, the osseous trabeculae not absorbed become thickened by a deposition of new layers of osseous tissue (by osteoblasts), during which process some of the osteoblasts are enclosed in the newly formed bone and are thus converted into bone-cells. In this way there is formed at the center of ossification a primary or embryonic spongy or cancellous bone, surrounding secondary marrow spaces or Haversian spaces, filled with embryonic marrow. This process of the formation of embryonic cancellous bone follows the primary ossification from the center of ossification toward the extremities of the diaphysis. It should be further stated, that long before the developing bone has attained its full size — indeed, before the end of embryonic life — the embryonic cancellous bone is also absorbed through the agency of osteoclasts. The Haversian spaces are thus converted into one large cavity, which forms a portion of the future marrow cavity of the shaft of the fully developed bone. The absorption of the embryonic cancellous bone begins at the center of ossification and extends toward the ends of the diaphysis. Some time after the beginning of the process of bone develop- ment at the center of ossification of the diaphysis, centers of ossification appear in the epiphyses, the manner of the develop- ment of bone being here the same as in the diaphysis. Several periosteal buds grow into each center of ossification, filling the irregular spaces formed by the breaking down of the degener- Digitized by Microsoft® I I 2 THE TISSUES. ated cartilage-cells. Osteoblasts are arranged in rows on the trabecular of cartilage thus formed, which they envelop in osseous tissue. As development proceeds, the primary osseous tissue is converted into embryonic cancellous bone as above described. In the development of the epiphyses, as in the development of the smaller irregular bones, the formation of bone proceeds from the center or centers of ossification in all directions, and not only in a direction parallel to the long axis of the bone as described for the diaphysis. The epiphyses grow, therefore, in thickness as well as in length, by endochondral bone-development. There remains between the osseous tissue developed in the dia- physis and that in the epiphyses, at each end of the diaphysis, a zone of hyaline cartilage in which ossification is for a long time delayed ; this is to permit the longitudinal growth of the bone. These layers of cartilage constitute the epiphyseal cartilages. Here the periosteum (perichondrium) is thickened and forms a raised ring around the cartilage. As it penetrates some distance into the substance of the cartilage, the latter is correspondingly indented. (Fig. 82.) The im- pression thus formed appears in a longitudinal section of the bone as an indentation, — the ossification groove (encoche d 'ossification, Ranvier, 89). That portion of the perichondrium filling the latter is called the ossification ridge. The relation of the elements of the perichondrium to the cartilage in the region of the groove just described is an extremely intimate one, both tissues, perichondrium and cartilage, merging into each other almost imperceptibly. It is a generally accepted theory that so long as the longitudinal growth of the bone' persists, new cartilage is constantly formed at these points by the perichondrium. In the further production of bone this newly developed cartilage passes through the preliminary changes necessary before the actual commencement of ossification — i. c, it goes through the stages of vesicular cartilage and the formation of columns of cartilage-cells, in place of which, later, the osteoblasts and primary marrow cavities develop. By the development of new cartilage elements from the encoche the longitudinal growth of the bone is made possible ; at the same time, those portions of the cartilage thus used up in the process of ossification are immediately replaced. (Fig. 84.) The following brief summary of the several stages of endochon- dral bone-development may be of service to the student : 1. The embryonic cartilage develops into hyaline cartilage, beginning at the centers of ossification. 2. The cartilage-cells enlarge and become vesicular. In the diaphysis of long bones such cells are arranged in quite regular columns, while in the epiphyses and irregular bones this arrange- ment is not so apparent. 3. Calcification of the matrix ensues ; the cartilage-cells disap- pear (degenerate) ; primary marrow spaces develop. 4. Ingrowth of periosteal buds. The osteoblasts are arranged Digitized by Microsoft® THE CONNECTIVE TISSUES. "3 in layers on the trabecular of calcified cartilage, which they envelop with osseous tissue. 5 . Osteoclasts cause the absorption of many of the smaller osseous trabeculae ; others become thickened by a deposition of new layers of osseous tissue. Osteoblasts are enclosed in bone- tissue and become bone-cells. In this way there is formed embry- onic cancellous bone, bounding Haversian spaces inclosing embry- onic marrow. 6. In the diaphysis, the greater portion of the embryonic can- cellous bone is also absorbed (by osteoclasts) ; the Haversian spaces unite to form a part of the marrow space of the shaft of the bone. 2. Intramembranous Bone. — This, the simpler type of ossifi- cation, occurs in bone developed from a connective- tissue founda- tion, and is exemplified in the formation of the bones of the Epiphyseal - bone. Ossificatioi ridge. Epiphysea cartilage _Blood- vessel. /> - . -4- Fig. 84. — Longitudinal section through epiphysis of arm bone of sheep embryo ; X I2> a, b, Primary marrow spaces and bone lamellae of the diaphysis. cranial vault and the greater number of the bones of the face, and also in bone developed from the periosteum (perichondrium) sur- rounding the cartilage fundaments of endochondral bone. All fibrous-tissue bone is developed in the same way. The intramembranous bone-development begins by an approxi- mation and more regular arrangement of the osteoblasts of the osteogenetic layer of the periosteum about small fibrous-tissue bundles. The osteoblasts then become engaged in the formation of the osseous tissue which envelops the fibrous-tissue bundles. In this way a spongy bone with large meshes is formed, consisting of irregular osseous trabecular, surrounding primary marrow spaces. These latter are filled by embryonic marrow and blood-vessels de- veloped from the tissue elements of the periosteum not engaged in the formation of bone. Digitized by Microsoft® 114 THE TISSUES. Intramembranous bone first appears in the form of a thin lamella of bone, which increases in size and thickness by the formation of trabecular about the edges and surfaces of that previously formed and in the manner above described. A layer of intramembranous bone thus surrounds the endochondral bone in bones preformed in hyaline cartilage. The two modes of ossification may, therefore, be observed in either a cross or a longitudinal section of a develop- ing bone preformed in hyaline cartilage. In such preparations the endochondral bone can be readily distinguished from the intra- > I - - 91 ) «U< :.<'., ®/»W j'laliM^^rJk, -Primary - ' e f ; f marrov . mm •mmmm H5'€ : < > i i >'©; ; ' I ,' ; 1 ..: "- :'-, ' Fig. 85. — Section through the lower jaw of an embryo sheep (decalcified with picric acid) ; X 3 00 - At a and immediately below are seen the fibers of a primitive marrow cavity lying close together and engaged in the formation of the ground- substance of the bone, while the cells of the marrow cavity, with their processes, arrange themselves on either side of the newly formed lamella and functionate as osteoblasts. membranous bone by reason of the fact that remnants of calcified cartilage matrix may be observed in the osseous trabeculae of the former. It will be remembered that these osseous trabeculae de- velop about the calcified cartilage matrix remaining after the dis- appearance of the cartilage -cells. In figure 86, which shows a cross-section of a bone from the leg of a human embryo, these facts are clearly shown. A study of this figure shows the endochondral bone, with the remnants of the cartilage matrix (shaded more Digitized by Microsoft® THE CONNECTIVE TISSUES. I I 5 deeply) inclosed in osseous tissue, making up the greater portion of the section and surrounded by the intramembranous bone. In figure 87, more highly magnified, the relations of endochon- dral to intramembranous bone and the details of their mode, of development are shown ; also the structure of the periosteum. As was stated in the previous section, soon after the formation of the endochondral bone, this is again absorbed ; the process of endochondral bone-formation and absorption extending from the center of ossification toward the ends of the diaphysis. Before the absorption of the endochondral bone, the intramembranous bone has attained an appreciable thickness and surrounds the marrow cavity formed on the absorption of the endochondral bone. Before, • .-• ■ ■''-'' '■'' ' '"' . V-- ."' ' ■ ■ ■ .■■■{: ■ I : Fig. 86.— Cross-section of developing bone from leg of human embryo, showing endo- chondral and intramembranous bone-development. however, the marrow cavity can attain its full dimensions, much of the intramembranous bone must also undergo absorption. While intramembranous bone is being developed from the periosteum and thus added to the outer surface of that already formed, osteoclasts are constantly engaged in its removal from the inner surface of the intramembranous bone. The marrow cavity is thus enlarged, the process continuing until the shaft attains its full size. The compact bone of the shaft is developed from the primary spongy intramembranous bone after the following manner : The primary marrow spaces are enlarged by an absorption, through the agency of osteoclasts, of many of the smaller trabecular of osse- Digitized by Microsoft® n6 THE TISSUES. ous tissue and by a partial absorption of the larger ones, the primary marrow spaces thus becoming secondary marrow spaces, or Haversian spaces. The osteoblasts now arrange themselves in layers Marrow - space. Blood-ves-_ sel. Osteoblasts. - Remnants of cartilage matrix. Bone-cells.- mm Osteoblasts., ^ e»- Fig. 87. — From a cross-section of a shaft (tibia of a sheep) ; X 55°- In the lower part of the figure is endochondral bone-formation (the black cords are the remains of the cartilaginous matrix) ; in the upper portion is bone developed from the periosteum. about the walls of the Haversian spaces and deposit lamella after lamella of bone matrix, concentrically arranged, until the large Haversian spaces have been reduced to Haversian canals. During Digitized by Microsoft® THE CONNECTIVE TISSUES. I I J this process many of the osteoblasts become inclosed in bone matrix, forming bone-cells and the blood-vessels of the Haversian spaces remain as the vessels found in the Haversian canals. The spongy intramembranous bone not absorbed at the commencement of the formation of the system of concentric lamella?, remains between the concentric systems as interstitial lamella?. The circum- ferential lamella? are those last formed by the periosteum. Calcifica- ation of the osseous matrix takes place after its formation by the osteoblasts. From what has been stated it may be seen that the shafts of the long bones and bones not preformed in cartilage develop by the process of intramembranous bone-formation, while the cancellous bone in the ends of the diaphysis and in the epiphyses is endochon- dral bone. Further, that long bones grow in length by endo- chondral bone-development, and in thickness by the formation of intramembranous bone. In the development of the smaller irreg- ular bones, both processes may be engaged ; the resulting bone can not, however, be so clearly defined. TECHNIC. 133. One of the methods for examining connective-tissue cells and fibers is that recommended by Ranvier (89) ; it is as follows : The skin of a recently killed dog or rabbit is carefully raised, and a 0.1% aqueous solution of nitrate of silver injected subcutaneously by means of a glass syringe. The result is an edematous swelling in which the connective- tissue cells and fibers (the latter somewhat stretched) come into imme- diate contact with the fixing fluid and are consequently preserved in their original condition. In about three-quarters of an hour the whole eleva- tion should be cut out (it will not now collapse) and small fragments placed upon a slide and carefully teased. Isolated connective-tissue cells with processes of different shapes, having the most varied relations to those from adjacent cells, are seen. The fibers themselves either consist of several fibrils, or, if thicker, are often surrounded by a spirally encir- cling fibril. By this method numerous elastic fibers and fat-cells are also brought out. If a drop of picrocarmin be added to such a teased prepa- ration and the whole allowed to remain for twelve hours in a moist chamber, and formic glycerin (a solution of 1 part formic acid in 100 parts glycerin) be then substituted for twenty-four hours, the following in- structive picture is obtained : All nuclei are colored red, the white fibrous connective-tissue fibers pink, the fibrils encircling the latter brownish - red, and the elastic fibers canary yellow. The peripheral protoplasm of the fat-cells is particularly well preserved, a condition hardly obtain- able by any other method. 134. Connective tissue with a parallel arrangement of its fibers is best studied in tendon, those in the tails of rats and mice being particularly well adapted to this purpose. If one of the distal vertebra? of the tail be loosened and pulled away from its neighbor, the attached tendons will become separated from the muscles at the root of the tail and appear as thin glistening threads. These are easily teased on a slide into fibers and Digitized by Microsoft® 1 1 8 THE TISSUES. fibrils. Such preparations are also useful in studying the action of reagents (see below). The substance resembling mucin which cements the fibrillae together is soluble in lime-water and baryta-water — a circumstance made use of and recommended by Rollet (72, II) as a method for the isolation of connective-tissue fibrils. In necrotic tissue the fibers show a degenera- tion into fibrils (Ranvier, 89). If connective tissue be heated in water or dilute acids to 120 C, and the fluid then filtered, a solution is obtained from which collagen can be precipitated by means of alcohol. This is insoluble in cold water, alcohol, and ether, but is soluble in hot water and when dissolved in the latter and cooled, becomes transformed into a gelatinous substance. Unlike mucin and chondrin this substance does not precipitate on the addition of acetic and mineral acids. Tannic acid and corrosive sublimate will cause pre- cipitation, as also in the case of chondrin, but not with mucin (vid. also Hoppe-Seyler). 135. Elastic tissue may be obtained by treating connective tissue with potassium hydrate solution, and if the alveoli of the lungs be treated for some time with this reagent, very small elastic fibers can be obtained. By this means the connective-tissue fibers are dissolved, but not the elastic fibers. Particularly coarse fibers are found in the ligamenta subflava. 136. According to Kiihne, connective and elastic tissues are differ- ently affected by trypsin digestion — /. e., alkaline glycerin-pancreas extract at 35 C. — white fibrous connective tissue being resolved into fibrils, while elastic tissue is entirely dissolved. 137. Elastic fibers remain unchanged in acetic acid, and even when boiled in a 20% solution they only become slightly brittle. They are, however, rapidly destroyed by concentrated hydrochloric acid, although in a 10% solution at ordinary temperature no change is seen. In a 50% solution the fiber is dissolved in seven days, and in a concentrated solu- tion in two days. The inner substance of the fiber is first attacked, then the membrane. To demonstrate this membrane, the fibers are boiled several times in concentrated hydrochloric acid and the whole then poured into cold water. Occasionally, a longitudinal striation of the membrane is seen, indicating a fibrillar structure. Concentrated solutions of potassium hydrate disintegrate the fibers in a few days ; weak solutions, more slowly. A 1 Sarcolemma. Sarcoplasm. .Cohnheim's area. - Sarcoplasm. -Fibrils. -Sarcolemma. f Fig. 93' — Transverse section through striated muscle-fibers of a rabbit. I and 3, from a muscle of the lower extremity ; 2, from a lingual muscle ; X 9°°- Technic No. 163. In 2, Cohnheim's fields are distinct ; in I, less clearly shown : in 3, the muscle-fibrils are more evenly distributed. in the regions of the uniting bridges, where the sarcoplasm is more abundant (see Fig. 92), giving these zones a clearer appearance. This gives the striated muscle- fibers their characteristic cross-striation. The sarcoplasm is found in greater abundance between the muscle-columns than between the fibrils in the columns. The sarcoplasm between the muscle- columns appears in the form of narrower or broader lines, parallel to the long axis of the muscle-fibers, giving the cross-striated muscle-fiber also a longitudinal striation. The sarcoplasm between the muscle-columns is seen to best advantage in cross-sections Digitized by Microsoft® MUSCULAR TISSUE. 127 of the muscle-fiber. Here it appears in the form of a network inclosing the muscle-columns. Thus, we have in a cross-section slightly darker areas, the cross-sections of the muscle-columns, known as Cohnheim's fields or areas, separated by the network of sarcoplasm. (Fig. 93.) In a striated muscle-fiber the darker and fainter bands (larger seg- ments of the fibrils) are doubly refracting, anisotropic, while the clearer bands (sarcoplasm) are singly refracting, isotropic. The relative group- ing of the two unequally refracting substances is, however, somewhat complicated, a condition which has given rise to much discussion as to the finer structure of the muscle-fiber. It should be remembered that the anisotropic and isotropic substances of the fiber are respectively placed in the same plane, so that the cross-striation of the entire fiber is fairly regular. The thickness of the bands varies considerably, often appearing as fine lines. In a definite segment the grouping is very regular, and the structure of such a segment is exactly repeated throughout the entire length of the fiber. A segment of this description contains in its center a broad disc of aniso- tropic substance — the transverse disc ( Q) (Fig. 94) ; this is di- vided through its middle by a less refractive (isotropic) narrow band, known as the median disc of Hensen (K). Above and below the transverse disc ( Q) is a disc of isotropic substance (_/); these in turn border upon the intermediate discs of Krause (Z). There are consequently in each segment or muscle-casket four discs — the transverse disc ( Q) divided into two parts by the median disc of Hensen (/z), with above and below the two isotropic discs (_/"), outside of which lie the intermediate discs of Krause (Z). One of the best objects for the study of transverse striation is the muscle of some of the arthropods (beetles). Here it will be noticed that the disc (J") is separated by an anisotropic disc through its center into three: (1) an isotropic disc (_/) ; (2) an anisotropic disc (jV), the "accessory disc" of Engelmann, Krause 's "transverse membrane"; and (3) still another disc of anisotropic substance (£), Merkel's "ter- minal disc. ' ' In other words, the number of discs in a segmental unit is increased to six: Q divided by h, twoy's, two JS's, and Z. It should be remarked here that all the doubly refracting substances appear as light, Fig. 94. — Diagrams of the transverse striation in the muscle of an arthropod ; to the right with the objective above, to the left with the objective below its normal focal dis- tance (after Rollett, 85): Q, Transverse disc ; h, median disc (Hensen); E, terminal disc (Merkel); N, accessory disc (Engelmann); J, isotropic substance. Digitized by Microsoft® 128 THE TISSUES. and the singly refracting as dark, bands when the objective is raised just a trifle above its focal distance. The contrary is the case on lowering the objective to a point just below its focal distance. (Fig. 94.) In figure 95 is shown a portion of a striated muscle-fiber of man very highly magnified. The larger and darker transverse disc (Q) formed by the larger segments of fibrils is divided by a light line (/z), Hensen's median disc ; the clearer band, largely sarcoplasm, is divided by a dark line, the intermediate disc of Krause ; this falls in the plane of the granules on the fine bridges uniting the larger segments of the fibrils. After a prolonged treatment with 98 ,-m g§3 WW Nucleus. Contractile substance. Nucleus. Fig. 100. Fig. 101. Longitudinal and cross-section of muscle-fibers from the human myocardium, hard- ened in alcohol ; X 640. The muscle-cells in the longitudinal section are not sharply defined from each other, and appear as polynuclear fibers blending with each other. Between them lie, here and there, connective-tissue nuclei. consequently to be regarded as in a perpetual stage of transition, the destruction and compensatory reproduction of its elements going on hand in hand. Its destruction is ushered in by a process which can be compared to a physiologic contraction. Nodes or thickened rings are formed, and at these points the muscle-substance separates into fragments with or without nuclei (sarcolytes), which are then absorbed, in most cases without phagocytic aid. This loss of sub- stance is replaced by new elements developed from the free sarco- plasm, which is characterized by rapid growth and increase in the number of its nuclei. The result is that new elements are formed which have been called myoblasts. The process by which myo- blasts are changed into the finished muscle-fibers is exemplified in the embryonal type of development of the tissue. Digitized by Microsoft® 132 THE TISSUES. CARDIAC MUSCLE-CELLS. The muscle-cells of the heart differ in structure- from the ordi- nary type of transversely striated muscle-fibers. The heart muscle- cells are short, irregularly oblong cells, often branched, possess no sarcolemma, and have one, occasionally two, centrally placed nuclei. In the smaller muscle-cells a cross-section often shows an arrange- ment of the fibrils radiating from the axis. The heart muscle-cells are cemented end to end to form anastomosing heart muscle-fibers ; these are arranged in bundles or in the form of a network. The muscle-cells of the so-called fibers of Purkinje lie immediately beneath the endocardium, and are remarkable in that their proto- plasm is only partially formed of transversely striated substance, and that only at their periphery. Such cells are found in great numbers in some animals (sheep), but rarely in man. Heart muscle has a rich blood supply, which will be considered more fully when the heart is discussed as an organ. For the nerve-endings in smooth and striated muscle-fibers see the chapter on Nervous Tissues. TECHNIC. 161. Fresh, striated muscle-fibers may be isolated by teasing them in an indifferent fluid (vid. T. 13). After a short time the sarcolemma may separate as a very fine membrane. If a freshly teased muscle be placed in a cold saturated solution of ammonium carbonate, the sar- colemma will become detached in places within five minutes (Solger, 89, III). 162. Striated muscle-fibers may be examined in an extended condi- tion by placing an extremity in such a position as to stretch certain groups of muscles. A subcutaneous injection of 0.25-0.5 c.c. of a 1% osmic acid solution is then made. The acid penetrates between the fibers and fixes them. Pieces of muscle are then cut out and washed in dis- tilled water. Teased fibers, even if not stained, will show the stria- tion plainly if mounted in glycerin. Muscles thrown into a state of tetanic contraction by electric stimulation may also be fixed in this state and later examined. 163. Cross-sections of muscles, extended and fixed in osmic acid, also show the relation of the fibrils to the sarcoplasm (Cohnheim's fields). A remarkable quantity of sarcoplasm in proportion to the number of fibrils is seen, for instance, in the muscles which move the dorsal fin of hippocampus ; among the mammalia a similar condition is found in the pectoral muscles of the bat (Rollett, 89). 164. In the muscles of all adult vertebrates (except the mammalia) the nuclei lie between the fibrils. In young mammalia they also have this position, but in the adult animals only the nuclei of red muscles are found between the fibrillfe ; in all other muscles the nuclei are under the sarcolemma. 165. The fibrillar structure of muscle-fibers can be seen by teasing old alcoholic preparations, or tissue treated with weak chromic acid (0.1%) or one of its salts. Digitized by Microsoft® THE NERVOUS TISSUES. I 33 166. In alcoholic preparations of mammalian muscle, the cross- striation is clearly seen, and is intensified by staining with hematoxylin. This stain colors everything anisotropic in the muscle, but does not affect the remaining structures. Similar results may be obtained with other stains, such as basic anilin dyes, but not with the same precision as with hematoxylin. 167. A certain species of beetle {Hydrophilus") is admirably adapted for the study of the finer details of striation. The beetle is first wiped dry and then immersed alive in 93% alcohol. On examining in dilute glycerin after from twenty-four to forty-eight hours, the substance of its muscles will show disintegration into Bowman's discs (vid. p. r28). The latter swell up in acids and are finally dissolved, as may be seen, by adding a drop of formic acid to a specimen prepared as above (Rollet, 85). 168. In order to study the relation of muscle to tendon, small mus- cles with their tendons are put into a 35% potassium hydrate solution for a quarter of an hour, after which the specimen is placed upon a slide and teased at the line of junction of the two tissues. This will separate the muscle-fibers from their respective tendon -fibrils (Weismann). 169. Similar results may be obtained by immersing a frog in water at a temperature of 55° C, in which the animal soon dies with muscles perfectly rigid. As soon as the water begins to cool (one-quarter hour) the frog is removed and a small piece of its muscle cut out and teased in water on a slide (Ranvier). 170. Cardiac muscle-cells are isolated by maceration for twenty-four hours in a 20% solution of fuming nitric acid (potassium hydrate with a specific gravity of r.3 will do the same in one-half or one hour). The margins of the cells may be brought more clearly into view by placing pieces of heart muscle for twenty -four hours inao.5^1 aqueous solution of silver nitrate and then cutting into sections. 171. Isolated fibers of Purkinje are obtained by immersing pieces of endocardium (0.5 mm. in size) in 33% alcohol and then teasing them on a slide. The sheep's heart is especially well adapted for this purpose. 172. Nonstriated muscle-fibers are isolated in the same way as heart muscle. In thin cross-sections (under 5 /*■ in thickness) of intestinal muscle, preferably of a cat, fixed in osmic acid, the intercellular bridges may be seen here and there between the fibers. D. THE NERVOUS TISSUES. The entire nervous system, peripheral as well as central, is com- posed of cells possessing one or many processes. These cells develop early in embryonic life from certain ectodermal cells (neuro- blasts) of the neural canal, which is formed by a dorsal invagination of the ectoderm. The neuroblasts soon develop processes, — many of them in loco, others only after wandering from the neural canal. The processes of the nerve-cells are of two kinds : (i) un- branched processes having a nearly uniform diameter throughout, Digitized by Microsoft® 134 THE TISSUES. with lateral offshoots known as collateral branches ; these, as we shall see, generally form the central part of a nerve-fiber, and are known as neuraxes (Deiters' processes, axis-cylinder processes, neurites, neuraxones or axones) ; and (2) processes which branch soon after leaving the cell-body and break up into many smaller branches ; these are the dendrites, or protoplasmic branches. In the spinal ganglia and the homologous cranial ganglia these morpho- logic differences in the processes are not observed, theneuraxis and the dendrites of each presenting essentially the same structure. To the entire nerve-cell, cell-body and processes the term neurone (Waldeyer, 91) has been applied ; neura (Rauber), or neu- rodendron (Kolliker, 93). The neuraxes of many neurones attain great length. Those of some of the neurones, the cell-bodies of which are situated in the lower part of the spinal cord, extend to the foot. In other regions neuraxes nearly as long are to be found, and in the majority of neu- rones the neuraxes terminate some distance from the cell-body. It is therefore manifestly impossible in the majority of cases to see a neu- rone in its entirety. Usually, only a portion of one can be studied in any one preparation. Consequently, the more detailed descrip- tion which follows will deal with the neurone in this fragmentary manner. The cell-bodies of the neurones, to which the term " nerve-cells " or "ganglion cells" is usually restricted, the den- drites and neuraxes, often forming parts of nerve-fibers, and their mode of terminating, will receive separate consideration. NERVE-CELLS, OR GANGLION CELLS j THE CELL-BODES OF NEURONES. The cell-bodies of nerve-cells are usually large. The bodies of the motor neurones of the human spinal cord measure 75 to 150 p, their nuclei 45 )i, and their nucleoli 1 5 fi. The smallest nerve-cells, the neurones of the granular layer of the cerebellum, are 4 to 9 /i in diameter. The protoplasm of nerve-cells shows a distinct fibrillar structure and the fibrils may be followed into the processes. (Fig. 102.) Their nuclei are also large, with very little chromatin, but as a rule are supplied with a large nucleolus. After treatment by certain special methods, the protoplasm of the ganglion cells shows granules or groups of granules which show special affinity to certain stains, consequently known as chromato- phile granules ; these are densely grouped around the nucleus, so that the cell-body shows an inner darker and an outer lighter por- tion. These chromatophile granules, also spoken of as tigroid granules or as the tigroid substance, as a rule are not arranged in concentric layers, but lie mostly in groups, giving to the protoplasm a mottled or reticular appearance. In the cells of the anterior horns (man, ox, rabbit) the granules join to form flakes, which are also more numerous in the region of the nucleus. In all cases the Digitized by Microsoft® THE NERVOUS TISSUES. 1 35 granules or flakes are continued into the dendrites of the cell. Here they change their shape into long pointed rods, with here and there nodules, which are probably the chief causes of the varicosities so often seen in dendrites (Golgi's method). The cell usually has a clear, nongranular peripheral border (not a membrane), and in the case of large cells there is a similar area around the nucleus, the inner border of which belongs to the nuclear membrane. H. Held has found that the chromatophile granules are brought out by treat- ment with alcohol and acid fixing fluids, but not in alkaline or neu- tral. They appear, according to the treatment, as fine or coarse granules. They can not be seen in fresh nerve-cells. He conse- quently regards them as artefacts — precipitations of the protoplasm due to reagents {vid. A. Fischer, T. 124). At its junction with the cell the neuraxis spreads out into a cone which is entirely free from granules, and apparently fitted into a' depression in the granular substance of the cell (implantation cone). The cellular substance between the chromatophile granules con- sists also of very fine, highly refractive granules, which appear to be arranged in a reticulum surrounding the chromatophile granules Nucleus. ^_^gg£v Nucleolus. **^^^ '~~^^^^\ Fibrillar structure. |£V^-- "" \£^$£^sjf^si|V Medullary sheath. Fig. 102. — Bipolar ganglion cell from the ganglion acusticum of a teleost (longi- tudinal section). The medullary sheath of the neuraxis and dendrite is continued over the ganglion cell ; X 800. Technic No. 175- (vid. Nissl, 94, and v. Lenhossek, 95), and the recent observations of Apathy and Bethe make it very probable that in the intergranular substance of the protoplasm of the nerve-cell there exist very fine fibrils which may be traced into the processes of the cell. It requires, however, further observation before more positive statements may be made concerning them. Besides the granules above mentioned, and which are revealed by special methods, there are found in the protoplasm of many of the larger nerve-cells pigment granules of a yellow or brown color which stain black with osmic acid. The dendrites are usually relatively thick at their origin, but gradually, as a result of repeated divisions, taper until their widely distributed arborescent endings appear as minute threads of widely different shapes. When treated by certain methods, they present uneven surfaces studded with varicosities and nodules, in contradis- tinction to the neuraxes, which are smooth and straight. Their ter- minal branches end either in points or in small terminal thickenings. The groups of terminal end-branches of a dendrite (also of a neur- axis) are known as telodendria (Rauber), or end-branches. The Digitized by Microsoft® 136 THE TISSUES. branches of the dendrites form a dense feltwork, which, together with the cell-bodies of the neurones and with other elements to be described later, constitute the gray substance (gray matter) of the brain and spinal cord. All neurones, with possibly a few exceptions, possess only a single neuraxis. Neurones without a neuraxis have never been found in vertebrates. The neuraxis usually arises from a cone- shaped extension of the cell-body free from chromatophile granules, the implantation cone, more rarely from the base of one of its dendrites, or from a dendrite at some distance from the cell-body. Its most important characteristics are its smooth and regular contour and its uniform diameter. At some distance from the cell- body, usually near its termination, now and then in its course, a neuraxis may divide into two equal parts. Golgi (94) called attention to the fact that the neu- raxes of certain neurones (Pur- kinje's cells in the cerebellum, pyramidal cells of the cerebral cortex, and certain cells of the spinal cord) give off lateral pro- cesses, the collateral branches. Nucleus. "~ Implanta- tion cone. Fig. 103. — Chromatophile granules of a ganglion cell from the Gasserian ganglion of a teleost : a, Nucleus ; b, implantation Fig. 104. — Nerve-cell from the ante- rior horn of the spinal cord of an ox, showing coarse chromatophile flakes. Two types of cell are recognized according to the disposition of their neuraxes : In the first the neuraxis is continued as a nerve- fiber ; in the second and rarer type it does not long preserve its independence, nor is it continued as a nerve-fiber, but soon breaks up into a complicated arborization, the neuropodia of Kolliker (93). The latter type of cell occurs in the cortex of the cerebrum and cerebellum and in the gray matter of the spinal cord. The cells of the two types can be simply described as having long (type I) or short, branched neuraxes (type II). The neuraxes of the cells of type I possess the collateral branches which end in small branching tufts. In its simplest form, a neurone consists of a cell-body and a neu- raxis with its telodendron. In more complicated types one or several Digitized by Microsoft® THE NERVOUS TISSUES. 137 dendrites may be present, as also collaterals from the neuraxis, and in rare cases even several neuraxes. According to the number of its processes, a ganglion cell is known as unipolar, bipolar, or multipolar. Dendrite. Neuraxis Neuraxis. Dendrite. Fig. 105. — Motor neurones from the anterior horn of the spinal cord of a new-born cat. Chrome-silver method. Although neurones present a great variety of morphologic dif- ferences, — large and variously shaped cell-bodies or small ones scarcely larger than the nucleus ; large and numerous dendrites or Telodendrion. Dendrite. Cell-body. — Neuraxis. Fig. 106. — A nerve-cell with branched dendrites (Purkinje's cell), from the cerebellar cortex of a rabbit ; chrome-silver method ; X I2 5- few and less conspicuous ones, — and although these various forms are widely distributed and intermingled in the different parts of the nervous system, yet in many regions there are found nerve-cells of fixed and characteristic morphologic appearance, which would Digitized by Microsoft® I38 THE TISSUES. enable a determination of their source. A few of the most charac- teristic types are here figured and may receive brief consideration. In the anterior horn of the spinal cord are found large multipolar neurones (motor neurones), with numerous dendrites, which termi- nate after repeated branching in the neighborhood of the cell-body, while the neuraxis with its collateral branches proceeds from the cell-body and becomes a part of a nerve- fiber. (Fig. 105.) In the cerebellum are found large neurones, discovered by Pur- kinje, and known as Purkinje's cells, with flask-shaped celi-body, from the lower portion of which arises a neuraxis with collateral branches, Branching of a dendrite. Neuraxis and collaterals. Fig. 107. — Pyramidal cell from the cerebral cortex of man ; chrdme-silver method : a, b, t; Branches of a dendrite. from the upper portion one or two very large and typic dendrites the smaller branches of which are beset with irregular granules. (Fig. 106.) In the cortex of the cerebrum occur large neurones, each with a cell-body the shape of a pyramid (pyramidal cell of the cerebral cortex), from the apex of which arises one large dendrite, and from angles at the base, or from the sides of the cell-body, several smaller dendrites. The neuraxis arises from the base directly or from one of the basal dendrites. (Fig. 107.) Digitized by Microsoft® THE NERVOUS TISSUES. 139 In figure 108 is shown a neurone with relatively small cell-body and short dendrites, from the granular layer of the human cere- bellum. The function of the dendrites has given rise to considerable dis- cussion. Golgi and his school regard them as the nutrient roots of the cell, a theory which is opposed by Ramon y Cajal (93, I ), van Gehuchten (93, I), and Retzius (92, II). According to the latter, all the processes of the nerve-cell are analogous structures ; they pass out from a sensitive element, and probably have a correspond- ingly uniform function. In the spinal ganglia and the homologous cranial ganglia, are grouped the cell-bodies of neurones (peripheral sensory neurones, peripheral centripetal neurones) which differ in many respects from those above described. In the peripheral sensory neurones the Neuraxis. ■ — Telodendrion. Fig. 108. — Nerve-cell with dendrites ending in claw-like telodendria ; from the granular layer of the human cerebellum ; chrome-silver method ; X IIQ - Nucleus. Fig. 109. — Ganglion cell with a pro- cess dividing at a (T-shaped process); from a spinal ganglion of the frog ; X 2 3°. Technic No. 178. neuraxes and dendrites have essentially the same structure, both forming part of a nerve-fiber. From a relatively large, nearly round, oval, or pear-shaped cell-body there arises a single process, which, at a variable distance from the cell-body, divides into two branches forming a right or obtuse angle with the single process (T-shaped or Y-shaped division of Ranvier, 78). Both of these branches form the central axis of a nerve-fiber ; one of the branches passing as a nerve-fiber to the spinal cord or brain, as the case may be ; the other forming a nerve-fiber which passes to the periphery. (Figs. 109 and no.) The ganglion cells of the spinal ganglia and homodynamic structures of the brain are therefore apparently unipolar cells, but, as Ranvier has shown, their processes are subject to a T-shaped or Y-shaped division. The branches going to the periphery are re- Digitized by Microsoft® 140 THE TISSUES. garded as dendrites, the others as neuraxes. As to the significance to be attached to the single process, the theory of v. Lenhossek Fig. no. — Ganglion cell from the Gasserian ganglion of a rabbit ; stained in methylene- blue {intra vitani). (94, I) that it represents an elongated portion of the cell, and that therefore the origin of the dendrite and that of the neuraxis are in this case close together, is very plausible. In the embryo these ganglion cells are at first bipolar, a process arising from each end of a spindle-shaped cell ; as de- velopment proceeds, the two pro- cesses approach each other and ultimately arise from a drawn-out portion of the cell - body, the single process. (Fig. m.) The sympathetic ganglia are composed mainly of the cell- bodies and dendrites (also some structures to be mentioned later) of neurones of the sympathetic nervous system. In nearly all vertebrates, and with but few ex- ceptions in any one ganglion, these neurones are multipolar and resemble morphologically the multipolar ganglion cells of the anterior horn of the spinal cord, though they are somewhat smaller. In the cell-body there may be ob- Digitized by Microsoft® Fig. in. — Three ganglion cells from a spinal ganglion of a rabbit embryo. The cells are still bipolar. Their processes come together in later stages, and finally form the T-shaped structure seen in the adult animal ; chrome - silver method ; Xi7<>. THE NERVOUS TISSUES. I4I served fine chromatophile granules and a large nucleus and nucleolus. From the cell-body there proceed a varying number of dendrites which branch and rebranch and terminate, as a rule, near the cell- body, forming plexuses in the ganglia. The neuraxis arises either directly from the cell-body from an implantation cone, or from one of. the dendrites at a variable distance from the cell-body. (Fig. 1 12.) In nearly all ganglia a few unipolar or bipolar cells are to be found. In the sympathetic nervous system of amphibia the sympathetic neurones are unipolar ; the single process present is the neuraxis. A most important result of the more recent investigations on the nervous system is the theory of the independence of the neurone. Each neurone develops from a single cell (neuroblast), and func- tionates as an independent cell under physiologic and pathologic conditions. Only very rarely has any direct connection between two neighboring neurones been demonstrated, so rarely that the Fig. 112. — Neurone from inferior cervical sympathetic ganglion of a rabbit ; methylene- blue stain. scattered observations at hand do not vitiate the above statement. Recent investigations have, however, shown that, while a neurone is a distinct anatomic unit, it is always found associated with other neurones. Nowhere in the body of a vertebrate does one find a neurone completely disconnected from other neurones. This asso- ciation of one neurone with one or several other neurones is always effected by a close contiguity existing between the telodendria (end-branches) of the neuraxis of one neurone with the cell-body or dendrites of one or several other neurones. The telodendron of the neuraxis of one neurone may form a feltwork inclosing the cell- body of one or several neurones, forming structures known as terminal baskets or end-baskets, or the end ramifications of the neuraxis of a neurone may come in very close proximity to the end-branches of the dendrites of one or several neurones. By this contiguity of the telodendria of the neuraxis of one neurone with Digitized by Microsoft® 142 THE TISSUES. the cell-bodies or the dendrites of other neurones, they are, without losing their identity, linked into chains, so that a physiologic conti- nuity exists between them. In such neurone chains the dendrites are regarded as cellulipetal, transmitting the stimulus to the cell ; the neuraxes as cellulifugal, transmitting the impulse imparted by the cell to the motor nerve-endings or central organs (Kolliker, 93). The entire nervous system may therefore be said to be made up of such neurone chains, the complexity of which varies greatly according to the number of neurones which enter into their construction. This subject will be considered more fully in a chapter on the nervous system. ... Fibrils of axial cord. Neurilemma. Segment of Lantermann. II) the whole very delicate In the nerve- THE NERVE-FIBERS. The neuraxes of the cells of type I, and the dendrites of the peripheral sensory neurones (spinal ganglia and homologous cranial ganglia), form the chief element in all the nerve-fibers. In the nerve-fibers they pos- sess a distinctly fibrillar structure. The fibrils composing them, the axis-fibrils, are imbedded in a semifluid substance, the neuroplasm (Kupffer, 83, being surrounded by a membrane, the axolemma. fibers, the axis-fibrils and the neuroplasm form axial cords which are surrounded by a special membrane or membranes, the presence or absence of which serves as a basis for a classification of nerve- fibers. Two kinds are distinguished, medullated and nonmedullated nerve - fibers. In medullated nerve-fibers, the axial cords (neuraxes of cells of type I, and dendrites of spinal ganglion cells) are sur- rounded by a highly refractive substance very similar to fat, which is blackened in osmic acid, the so-called medullary or myelin sheath. In a fresh condition this sheath is homogeneous, but soon changes and presents segments separated from each other by clear fissures. These seg- ments vary in size and are known as " Schmidt-Lantermann-Kuhnt's segments." On boiling in ether or alcohol the entire medullary sheath of a nerve-fiber does not dissolve, but a portion is left in the shape of a fine network which is not affected by exposure to the action of trypsin. From the latter circumstance it has been thought that this network consists of a substance very similar to horn, and is therefore known as neurokeratin (horn-sheath, Ewald and Kiihne). On burning isolated neurokeratin, an odor exactly like that of burn- Digitized by Microsoft® Fig. 113. — Longitudinal section through a nerve- fiber from the sciatic nerve of a fr°g ! X 830. Technic No. 175- THE NERVOUS TISSUES. 143 ing horn is given off. It is thought that the meshes of this neuro- keratin network contain the highly refractive substance similar to fat, composing the greater portion of the medullary sheath. The medullary sheath is interrupted at intervals of from 80 to 900 ju, the constrictions thus formed being known as the nodes of Ranvier. The smaller the fiber, the less the distance between the nodes. In a fiber with a diameter of 2/1 the internodal segments are usually about 90 /i in length. In peripheral nerves the medullary sheath is in its turn sur- rounded by a clear, structureless membrane, the neurilemma or sheath of Schwann. Nerve-fibers contain here and there relatively long, oval nuclei (neurilemma-nuclei) which are surrounded by a small quantity of protoplasm, and are situated in small excavations between the neurilemma and the medullary sheath. In the higher vertebrates a single nucleus is found midway between each two Fibrils of axial cord. Medullary sheath. ' — Fibrils. Fig. 1 14. — Transverse section through the sciatic nerve of a frog ; X 820. Technic No. 175 : At a and b is a diagonal fissure between two Lantermann' s segments; as a result, the medullary sheath here appears double. (Compare Fig. 113.) nodes ; in the lower vertebrates (fishes) several scattered nuclei (5-16) may be found in each internodal segment. At the nodes, where the medullary sheath is interrupted, the neurilemma is thickened and contracted down to the axial cord (contraction-ring). Just beneath the contraction-ring, Ranvier found that the axis- cylinder presents a slight, biconic swelling {renflement biconique). Thus the sheath of Schwann represents a continuous tube through- out the length of the fiber in contrast to the medullary sheath. In the nerve-fibers of the spinal cord and brain there is no neurilemma, although the medullary sheath is present. In the fresh nerve-fiber the axial cord fills the space (axial space) within the medullary sheath, and appears transparent. After treatment with many fixing fluids the neuroplasm coagulates and shrinks, no longer filling the entire axial space, but appears in the latter as a wavy cord composed of an apparently homogeneous Digitized by Microsoft® 144 THE TISSUES. mass, the fibrillse of which are no longer recognizable. Such pic- tures, which formerly were supposed to represent the normal condi- tion of the nerve-fibers, gave rise to the conception of an axis-cyl- inder (vid. Technic). That which is known as an axis -cylinder is therefore, in reality, the changed contents of the axial space. It may be stated, however, that the term axis-cylinder is still much used, since the methods commonly employed in the investigation of the nervous system do not preserve the axial cord in its integrity, but nearly always result in the for- mation of an axis-cylin- der. Consequently, al- though we shall make use of the term, its limit- ations are to be kept in mind. Medullated nerve fibers vary greatly in di- Ranvier's node. Fig. 115. — Medullated nerve- fibers from a rabbit, varying in thickness and showing internodal segments of different lengths. In the fiber at the left the neuri- lemma has become slightly separated from the under- lying structures in the region of the nucleus ; X x \°- Technic No. 173. ■ Nucleus. Fig. 116. — Remak's fibers (nonmedullated fibers) from the pneumogastric nerve of a rabbit ; X 360. Technic No. 1 79. ameter, but whether this points to a corresponding variation in function has not been fully decided. Fine fibers possess a diameter of 2-4 ji, those of medium size 4-9 /A and large fibers 9-20^ (Kolliker, 93). A division" of medullated fibers during their course through a nerve is relatively rare. The greater number of fibers pass unbranched from their central origin to the periphery, and only when in the neighborhood of their terminal arborization do they begin to divide. A point of division is always marked by a node of Ranvier. Digitized by Microsoft® THE NERVOUS TISSUES. I45 The segmental structure of nerve-fibers would seem to give the impression that they are formed by a number of cells fused end to end. After what has been said with regard to ganglion cells and their processes, this can be the case only so far as the nerve-sheaths are concerned. According to this theory, the formative cells of the latter gather in chains along the neu raxes or dendrites, forming a mantle around them, and in the adult nerve-fibers taking the shape of the segments or internodes just described (His, 87 ; Boveri, 85). The points at which the sheath-cells are joined would then corre- spond to the nodes of Ranvier. Other investigators have concluded that the whole nerve -fiber is developed from a terminal apposition of ectodermal cells. In this case not only the sheaths of the fibers but also the corresponding portions of the nerve processes are formed by them (Kupffer, 90). In both theories the neurilemma corresponds to the cell-membrane ; in the former the neurilemma nucleus corresponds to that of the sheath-forming cell, in the latter to that of the formative cell of the whole nerve segment. It should be noticed that, according to the second theory, a fiber segment is the product of a single cell, while according to the first it is evolved from at least two cells (ganglion cell (process) and sheath-forming cell). The former theory is now very generally accepted. The nonmedullated nerve-fibers, Remak's fibers, possess no medullary sheath ; the axial cord shows nuclei which can be re- garded as belonging to a thin neurilemma. The majority of the neuraxes of the neurones of the sympathetic nervous system are of this structure, although small medullated nerve-fibers (the neuraxes of sympathetic neurones) are found in certain regions. All nerve -fibers, medullated as well as nonmedullated, in the central and peripheral nervous system, lose the sheaths here de- scribed before terminating ; the axis-cylinders (axial cords) ending without special covering (naked axis-cylinders). These terminal branches are, in fixed and stained preparations, beset with small thickenings — varicosities — which vary greatly in size and shape. Nerve-fibers presenting such appearances are spoken of as varicosed fibers. The varicose enlargements may be regarded as small masses of neuroplasm ; the fine uniting threads, as representing the axial fibrils. In the peripheral nervous system the nerve -fibers are grouped to form nerve-trunks. The nerve-fibers, as has been stated and as will be seen from the diagram (Fig. 117) on the next page, are the neuraxes of neurones, the cell-bodies of which are situated in the spinal cord or brain and in the sympathetic ganglia, and the den- drites of peripheral sensory neurones, the cell-bodies of which are found in the spinal and homologous cranial ganglia. In the nerve-trunks the nerve-fibers are gathered into bundles termed funiculi. The nerve-fibers constituting such a bundle are separated by a small amount of fibro-elastic tissue, containing here and there connective-tissue cells, the endoneurium. This is continu- 10 Digitized by Microsoft® 146 THE TISSUES. ous with a dense, lamellated fibrous sheath surrounding each funicu- lus, the perineurium. Between the lamella? of this sheath are lymph- spaces, communicating with the lymph-clefts found between the Neuraxis of peripheral sensory neurone. Dendrite of per- ipheral sen- sory neurone. Spinal ganglion. Anterior horn of gray matter of spinal cord. Neuraxis of peripheral motor Sympathetic ganglion. Nerve-trunk. — Neuraxis of sympathetic neurone. Fig. 117. — Diagram to show the composition of a peripheral nerve-trunk. Epineurium. — - Axis-cylinder. \- --Neurilemma. §11 r iM m -Endoneurium. -Perineurium. Fig. 118. — Part of a cross-section through a peripheral nerve treated with alcohol. The small circles represent the cross-sections of medullated nerve-fibers ; the axis-cylin- ders show as points in their centers. The 'nerve is separated by connective tissue into large and small bundles — funiculi ; X 75- Digitized by Microsoft® MOTOR NERVE-ENDINGS. 1 47 nerve-fibers of the funiculi ; consequently, the lamella? are covered by a layer of endothelial cells. In the larger funiculi, septa of fibrous connective tissue pass from the perineurial sheath into the funiculi, dividing them into compartments varying in shape and size ; these are spoken of as compound funiculi. The funiculi of a nerve- trunk are bound together by an investing sheath of loose fibro-elastic tissue, continuous with the perineurial sheaths, which penetrates between the funiculi, and which contains fat-cells, blood-vessels, and lymph-vessels ; the latter being in communication with the lymph- spaces of the perineurial sheaths. When a nerve-trunk divides, the connective-tissue sheaths above mentioned are continued on to the branches, and this even to the smallest offshoots. Thus, single fibers even possess a connective- tissue sheath, — Henle's sheath, — which consists of a few connective- tissue fibers and of flattened cells. PERIPHERAL NERVE TERMINATIONS. According to the character of the peripheral organs in which the telodendria of nerve-fibers (neuraxes of type I cells and dendrites of spinal ganglion cells) occur, the nerve-fibers are known as motor and sensory nerve -fibers, the terminations as motor and sensory nerve-endings. Motor Nerve-endings (the Telodendria of Nerve-fibers Ending in Muscle Tissue). — The motor nerve-endings in striated, voluntary muscle tissue will first be considered. The motor nerve-endings in voluntary muscle tissues are the endings of neurones (peripheral motor neurones), the cell-bodies of which are situated in the ventral horns of the spinal cord and in the medulla. The neuraxes of these cells leave the cerebrospinal axis as medullated nerve-fibers (motor fibers) which, after branching, end in the muscle-fibers in the so-called motor endings. In figure 119 is represented, by way of diagram, a complete peripheral motor neurone. Each motor nerve - fiber branches repeatedly before terminating, although this branching does not often take place until near the termination of the nerve- fiber. Kolliker estimates that in the sternoradialis of the frog, each motor fiber innervates about twenty muscle-fibers ; but whether this number may be regarded as the average number of muscle-fibers receiving their motor nerve-supply from one motor neurone can not be stated with any degree of certainty at the present time. Each motor ending represents the termination of one of the ter- minal medullated branches of a motor nerve-fiber. The neuraxis of this fiber passes under the" sarcolemma and terminates in a teloden- dron (end-brush) in an accumulation of sarcoplasm, in which are found numerous muscle nuclei, forming a more or less distinct ele- vation on the side of the muscle-fiber, Doyere's elevation. The medullary sheath accompanies the nerve-fiber until it passes under the sarcolemma, when it stops abruptly. The neurilemma of the Digitized by Microsoft® 148 THE TISSUES. nerve-fiber becomes continuous with the sarcolemma of the muscle- fiber at the place where the neuraxis passes under the sarcolemma. Henle's sheath continues over the motor ending as a thin sheath, containing here and there flattened nuclei, the telolemma nuclei. With the majority of the reagents used to bring to view, the motor endings, notably chlorid of gold, the sarcoplasm, in which Dendrite. Neuraxis. Medullary sheath. Nucleus of neurilemma. Internodal segment. Motor ending. Collateral branch. Neurilemma. Node of Ranvier. Axis-cylinder of medullated nerve-fiber. Muscle-fibers. Fig. 119. — Diagram of peripheral motor neurone. the telodendron of the nerve-fiber is found, has a granular appear- ance, and is consequently differentiated from the remaining sarco- plasm of the muscle-fiber. To this the term granular sole plate has been applied, the nuclei contained therein being known as sole nuclei, the whole ending as the motor end-plate. If the above interpreta- Digitized by Microsoft® MOTOR NERVE-ENDINGS. 1 49 tion of the structure of the motor nerve-ending is correct, there would seem to be no reason why the sarcoplasm in which the telo- dendria occur should be considered other than the sarcoplasm of the muscle-fiber, the nuclei as muscle-nuclei ; the terms motor end- plate, granular sole plate, and sole nuclei would therefore seem un- necessary and misleading. In figures 121 to 125 are shown motor nerve-endings from several vertebrates as seen when stained with gold chlorid. The mass of sarcoplasm in which the neuraxes terminate as above described is about 40 to 60 /jl long, 40 //broad, and 6 to 16 (i thick ; these dimensions vary greatly, however ; they may be greater or less than the averages here given. In amphibia the motor nerve-endings are not so localized as in the majority of vertebrates, as above described, but are spread over a relatively greater surface of the muscle-fiber, and there is no distinct accumulation of the sarcoplasm, and the muscle-nuclei are Fig. 120. — Motor nerve-ending in voluntary muscle of rabbit, stained in methylene- blue (intra vitam) (Huber, DeWitt, "Jour. Comp. Neurol.," vol. vil) : A, Surface view ; B, longitudinal section through motor ending ; C, cross-section : a, a, a, neuraxes of nerve-fibers ; s, s, s, sarcolemma ; nl, nl, neurilemma ; d, Doyere' s elevation ; m n , muscle nuclei ; tn, telolemma nucleus. relatively less numerous. The telodendrion of the nerve-fiber is, however, under the sarcolemma, between it and the contractile sub- stance of the muscle-fiber. (Fig. 126.) The number of motor nerve-endings in a striated, voluntary muscle-fiber depends on its length, short fibers having, as a rule, one ending, longer fibers two, or even more. Heart muscle-cells and nonstriated muscle-cells receive their motor nerve-supply from neurones of the sympathetic nervous sys- tem. The cell-bodies of these neurones are situated in sympathetic ganglia ; the neuraxes, the majority of which form nonmedullated nerve-fibers, branch repeatedly, forming primary and secondary plexuses which surround the larger or smaller bundles of heart muscle-fibers or involuntary muscle-cells. From these plexuses, naked, varicosed axis-cylinders, or small bundles of such, penetrate between the muscle-cells, also forming plexuses. The fine fibers of this terminal plexus give off from place to place small, lateral Digitized by Microsoft® i5o THE TISSUES. Nerve. Fig. 122. f l-MJ:'!i' l ':j':. J .ul.': !! .- , il Nerve. So-called granular sole. End-brush. Sarco- lemma. Figs. 123 and 124. Fig. 125. Figs. 121-125. — Motor endings in striated voluntary muscles. Fig. 121, from Psendopus Pallasii ; X IDO - Fig 122, from Lacerta viridis : X I0 °* Figs. 123 and 124, from a guinea-pig; X 7°°- F'g- I2 5> f ,om a hedge-hog; X 1200. As a consequence of the treatment (T. 182, I) the arborescence is shrunken and inter- rupted in its continuity. In Figs. 121 and 122 the end-plate is considerably larger than in 123 and 124. In Fig. 121 it is in connection with two nerve-branches. Fig. 125 shows a section through an end-plate. The latter is bounded externally by a sharply de- fined line, which can be traced along the surface of the muscle-fiber. This is to be re- garded as the sarcolemma. Digitized by Microsoft® SENSORY NERVE-ENDINGS. 151 twigs, which end on the muscle-cells. In heart muscle these lateral twigs may end in one or two small granules, or in a small cluster of such granules (Fig. 1 27) ; in involuntary, nonstriated muscle the ending is very simple, the small lateral twigs terminating in one or two small granules. (Fig. 128.) Sensory Nerve-endings. — The sensory nerve-endings are, in their essentials, the peripheral telodendria of dendrites of peripheral sensory neurones. The cell-bodies of such neurones, as has been stated, are found in the spinal and homologous cranial ganglia. /-»./ Fig. 126. — Motor nerve-ending in striated voluntary muscle of a frog ; methylene- blue stain (intra vitam) (Huber, DeWitt) : A, Surface view ; B, cross-section ; s, s, sarcolemma ; «/, neurilemma. emfiitr >J i 'V \ ?< _&*rt muidecflL muscle Ceu nucleus 3 m UL — TZcreejioer ^,' ■■ — C-bSJ Seetiott. Fig. 127. — Motor nerve-ending on heart muscle-cells of cat ;~ methylene-blue stain (Huber, De Witt). !) Fig. 128. — Motor nerve-ending on involuntary nonstriated muscle-cell from intestine of cat ; methylene-blue stain (Huber, De Witt). Of the two branches arising from the single process possessed by each peripheral sensory neurone, the one going to the periphery is regarded as the dendrite and forms the axis-cylinder of a medullated nerve-fiber, such nerve-fibers constituting the sensory nerves of the peripheral nerve -trunks. A peripheral sensory neurone may there- fore be diagramed as in figure 129. The statement was made above that the essential portion of a sensory nerve-ending is a telo- dendrion (end-brush) or several telodendria of the dendrite of a peripheral sensory neurone. The character of a sensory nerve- Digitized by Microsoft® 152 THE TISSUES. ending depends, therefore, on the complexity of this end-brush and on its relation to the other tissue elements which take part in the formation of the sensoiy nerve-endings. Bearing this in mind, the following classification of such nerve-endings can be made : i. Free Sensory Nerve-endings. — In these the telodendrion is not Cell-body Neuraxis, ends in spinal cord or brain. T-shaped division of Ranvier. Dendrite, a sensory nerve- fiber in nerve-trunk. Diagram of a peripheral sensory neurone. inclosed in an investing capsule which forms a structural part of the ending. 2. Encapsulated Endings. — In which the telodendrion or several telodendria are surrounded by an investing capsule which separates them more or less completely from the surrounding tissue. i. Free sensory nerve-endings are found in all epithelial tis- sues and in fibrous connective tissue of certain regions. A sensory Digitized by Microsoft® SENSORY NERVE-ENDINGS. 153 nerve-fiber terminating in such an ending usually proceeds without branching to near its place of termination, where, while yet a medullated fiber, it branches and rebranches a number of times, Fig. 130. — Termination of sensory nerve-fibers in the mucosa and epithelium of the ure- thra of cat; methylene-blue preparation (Huber, " Jour. Comp. Neurol.," vol. x). always at the nodes of Ranvier, the resultant branches diverging at various angles. If the free sensory endings are in epithelial tissue, Digitized by Microsoft® 1 54 THE TISSUES. these larger medullated branches are situated in the connective- tissue mucosa under the epithelium. From these larger medullated branches, are given off smaller ones, also medullated, which may divide further, and which pass up toward the epithelium, and near its under surface divide into nonmedullated branches. Nonmedullated branches are also given off from the medullated ones as they approach the epithelium, leaving the parent fibers at the nodes of Ranvier. Many of the nonmedullated branches thus formed, after coursing a variable distance under the epithelium, enter it and break up into numerous very small branches, which, after repeated divi- sion, terminate between the epithelial cells in small nodules or discs of variable size and configuration. The small branches result- ing from a division of one of the larger nonmedullated branches constitute one of the terminal telodendria or end-branches of the dendrites of peripheral sensory neurones terminating in free sensory nerve-endings. In fibrous connective tissue the same general arrangement of the branches prevails. In figure 130 is shown the peripheral distribution of the dendrite of a peripheral sensory neurone terminating in a free sensory nerve-ending. 2. Encapsulated Sensory Nerve=endings. — These nerve -end- ings maybe divided into two quite distinct groups, — such as have a relatively thin fibrous-tissue capsule, containing mainly telodendria of the nerve or nerves terminating therein, and such as have a distinctly lamel- lated, fibrous tissue capsule, usually investing, besides the nerve-termi- nation, other tissue elements. To the former group belong three types of sensory nerve -endings, which, owing to their similarity of struc- ture, may be described together. Fig. 131. — End-bulb of Krause ^, ' , , , , ,, r T ? from conjunctiva of man ; methylene- These are the end-bulbs of Krause, blue stain (Dogiel, "Arch. f. mik. Meissner's tactile corpuscles, and Anat.," vol. xxxvn). the genital corpusc i es . They have all been investigated recently by Dogiel, and the account here given follows closely his description. End-bulbs of Krause. — Under this designation there are described a variety of endings which vary slightly in size and shape. They are found in the conjunctiva and edge of the cornea, in the lips and lining of the oral cavity, in the glans penis and clitoris, and prob- ably also in other parts of the dermis. In form they are round, oval, or pear-shaped. Their size varies from 0.02 to 0.03 mm. long and from 0.015 to 0.025 mm. broad for the smaller ones, and from 0.045 to °- 10 mm - l° n & ar >d from 0.02 to 0.08 mm. broad for the larger ones. They have a relatively thin capsule in which nuclei are quite numerous. One, two, or three medul- lated nerves go to each end-bulb. These may lose their medul- Digitized by Microsoft® SENSORY NERVE-ENDINGS. 155 lary sheath at the capsule or at a variable distance from it. The naked axis-cylinders, soon after entering the capsule, divide into two, three, or four branches, which form several circular or spiral turns in the same or in opposite directions. These fibers then divide into varicose branches, which undergo further division, the resulting branches interlacing to form a bundle of variously tangled fibers which may be loosely or tightly woven. Between the nerve-fibers and their branches, within the capsule, there is found a semifluid sub- stance, which is granular in fixed preparations. Mcissncrs Corpuscles. — These corpuscles are found in man in the subepidermal connective tissue of the hand and foot and outer surface of the forearm, in the nip- ple, border of the eyelids, lips, glans penis and clitoris. They are most numerous in the palmar sur- face of the distal phalanx of the fingers. They are oval in shape, sometimes somewhat irregular, and vary in size, being from 45 /i to 50 n broad and from 1 10 [i to 1 80 // long. They possess a thin connective -tissue capsule, in which are found round or oval nuclei, some of which have an oblique position to the axis of the corpus- cle. One medullated nerve ends in the smaller corpuscles, two or three or even more in the larger ones. After piercing the capsule, the medullated nerves lose their medullary sheaths, the naked axis-cylinders making a variable number of circular or spiral turns, some of which are parallel, others crossing at various angles. These larger branches are all beset with large, spindle-shaped, round, or pear-shaped varicosities. The larger branches, after making the windings mentioned, break up into many varicose branches, which interlace and form a most com- plex network. One usually finds one or several larger naked axis- cylinders, which pass up through the axis of the spiral of fibers thus formed ; these give off branches which contribute to the spiral formation. Genital Corpuscles. — These corpuscles are found in the deeper part of the mucosa of the glans penis and the prepuce of the male and the clitoris and neighboring structures of the female. Their shape varies ; they may be round, oval, egg- or pear- Fig. 132. — Meissner's tactile corpus- cle ; methylene-blue stain (Dogiel, " In- ternat. Monatsschr. f. Anat. u. Phys.," vol. IX). Digitized by Microsoft® i S 6 THE TISSUES. shaped, or even slightly tabulated. Their size varies from 0.04 to o. 10 mm. in breadth and from 0.06 to 0.40 mm. in length. They are surrounded by a relatively thick fibrous capsule, consisting of from three to eight quite distinct lamellae, between which irregu- lar flattened cells with round or oval nuclei are found. Within this capsule, there is found a core, which seems to consist of a semi- fluid substance, slightly granular in fixed preparations, the nature of which is not fully known. The number of sensory nerves going to each corpuscle varies from one to two for the smaller ones, and from eight to ten for the larger corpuscles. The medullated nerves, after entering the corpuscle, divide dichotomously, the resultant branches assuming a circular or spiral course, and interlacing in various ways, within the capsule. After a few turns, the medullated branches lose their medullary sheaths and undergo further di- vision, often dividing repeatedly. The nonmedullated nerves re- sulting from these divisions, the majority of which are varicose, form a most complicated net- work, the whole nerve network presenting a structure which re- sembles a tangle of fine threads. In the meshes of this network is found the semifluid substance of the core. Now and then some of the larger fibers of the network leave the corpuscle and terminate in neighboring corpuscles, or pass to the epi- thelium, where they end be- tween the cells. These three sensory nerve- endings — end-bulbs of Krause, Meissner's tactile corpuscles, genital corpuscles — are, as Dogiel has stated, very similar in structure. Each has a thin connective-tissue capsule, surrounding a core, consisting of a semifluid substance, concerning which our knowledge is as yet imperfect. One or sev- eral medullated nerves go to each corpuscle, which, after losing their medullary sheaths, divide and subdivide into numerous fine varicose branches, which are variously interwoven, forming a more or less dense plexus of interlacing and, according to Dogiel, anas- tomosing fibers. The chief differences are those of form and size, and of position with reference to the epithelium. Of the three forms of endings, the genital corpuscle is the largest, and occupies the deep- est position in the subepithelial connective tissue ; Meissner's cor- puscle is intermediate in size, and is found immediately under the epithelium ; while the end-bulbs of Krause are the smallest of these Fig- '33- — Genital corpuscle from the glans penis of man ; methylene-blue stain (Dogiel, "Arch. f. mik. Anat,," vol. xli). Digitized by Microsoft® SENSORY NERVE-ENDINGS. I 57 three forms of sensory endings and may be found in the papillae or in the deeper connective tissue. A somewhat smaller nerve-ending of long, oval, or cylindric form, known as the cylindric end-bulb of Krause, is found in various parts of the skin and oral mucous membrane, in striated muscle and in tendinous tissue. These corpuscles consist of a thin nucle- ated capsule, investing a semifluid core. The nerve-fiber, after losing its medullary sheath and fibrous sheath (the latter becomes continuous with the capsule), passes through the core, generally without branching, as a naked axis-cylinder, terminating at its end, usually in a small bulb. (Fig. 134.) The majority of the sensory nerve-endings with well-developed lamellated capsules are relatively large structures. We shall con- sider especially the Vater-Pacin- ian corpuscles, the neuromus- ----- ^ ■*-.__ cular end-organs, and the neuro- tendinous end-organs. Vater-Pacinian Corpuscles. — These corpuscles are of oval shape and vary much in size, the largest being about o. 10 of an inch long and 0.04 of an inch Fig . I34 ._ Cylindric end-bulb of broad. The greater portion of Krause from intermuscular fibrous tissue. the corpuscle is made up of a se P tum of cat ; ^thylene-blue «««in. series of concentric lamellae, vary- ing in number from twenty to sixty. These lamellae are made up of white fibrous tissue fibers, rather loosely woven, between which is found a small amount of lymph, containing usually a few leucocytes. The lamellae are covered on both surfaces by a layer of endothelial cells (Schwalbe). Between two consecutive lamellae there is found an interlamellar space, also containing lymph. The axis of the cor- puscle is occupied by a core, consisting of a semifluid, granular substance, in the periphery of which oval nuclei are said to be found. Usually one large medullated nerve-fiber goes to each cor- puscle. The fibrous tissue sheath of this nerve-fiber becomes con- tinuous with the outer lamellae of the capsule. The medullary sheath accompanies the axis-cylinder through the concentric lamel- lae until the core is reached, where it disappears. The naked axis- cylinder usually passes through the core to its distal end, where it divides into three, four, or five branches which terminate in large, irregular end-discs. The axis-cylinder may, however, divide soon after it enters the core into two or three or even four branches, these passing to the distal end of the core before terminating in the end-discs above mentioned. Both Retzius and Sala state that the naked axis-cylinders, after entering the core, give off numerous short side branches, terminating in small knobs, which remind these ob- servers of the fine side branches or thorns seen on the dendrites of Purkinje's cells and of the pyramidal cells of the cortex, when stained Digitized by Microsoft® 158 THE TISSUES. after the Golgi method. In company with the large nerve -fibers here mentioned, Sala has described other nerve-fibers, quite independent of them and much finer, which after entering the corpuscle divide repeatedly, the resulting fibers forming a plexus around the central fiber. A small arteriole enters the corpuscle with the nerve-fiber, dividing into capillary branches found between the lamellae of the capsule. The Vater- Pacinian corpuscles have a wide distribution. They are numerous in the deeper parts of the dermis of the hand and foot, and also near the joints, especially on the flexor side. They have been found in the periosteum of certain bones and in tendons and intermuscular septa, and even in muscles. They are further found in the epineurial sheaths of certain nerve-trunks and near F 'g- *35- — Pacinian corpuscles from mesorectum of kitten : A, Showing the fine branches on central nerve-fiber ; B, the network of fine nerve-fibers about the central fiber; methylene-blue preparation (Sala, "Anat. Anzeiger," vol xvi). large vessels. They are numerous in the peritoneum and mesentery, pleura and pericardium. In the mesentery of the cat, where these nerve-endings are large and numerous, they are readily seen with the unaided eye as small, pearly bodies. In the bill and tongue of water birds, especially of the duck, are found nerve-endings, known as the corpuscles of Herbst, which re- semble the Vater- Pacinian corpuscles ; they differ from the latter in having cubic cells in the core. (Fig. 136.) Neuromuscular Nerve End-organs. — These nerve end-organs consist of a small bundle of muscle-fibers, surrounded by aninvest- Digitized by Microsoft® SENSORY NERVE-ENDINGS. 159 ing capsule, within which one or several sensory nerves terminate. They are spindle-shaped structures varying in length from 0.75 to 4 mm., and in breadth, where widest, from 80 to 200 p. (Sherrington, 94). In them there is recognized a proximal polar region, an equatorial region, and a distal polar region. The muscle-fibers of this nerve-ending, known as the intrafusal fibers, which may vary in number from 3 or 4 to 20 or even more, are much smaller than the ordinary voluntary muscle-fibers and differ from them structur- ally, and result from a division of one or several muscle-fibers of the red variety. In the proximal polar region the intrafusal fibers present an appearance which is similar to that of voluntary muscle- fibers of the red variety ; in the equatorial region they possess rela- - Nucleus of lamellae. End-cell of core. Lamellae. frfL- Axis-cylinder in core. Cubic cells of core. Termination of medul- lary sheath. Axis-cylinder of nerve-fiber. Medullary sheath of nerve-fiber. Neurilemma and sheath of Henle. Fig. 136. — Corpuscle of Herbst from bill of duck ; X °°°- Technic No. 296. tively few muscle-fibrils and are rich in sarcoplasm and the muscle- nuclei are numerous ; the striation is here indistinct. In the distal polar region the intrafusal fibers are again more distinctly striated and, a short distance beyond the end-organ, become greatly reduced in size, and terminate as very small fibers, still showing, however, a cross-striation. In figure 137 is shown a single intrafusal muscle- fiber. Owing to the length of such a fiber it was necessary to rep- resent it in several segments. The intrafusal muscle-fibers are surrounded by a capsule con- sisting of from four to eight concentric layers of white fibrous tissue. At the proximal end this capsule is continuous with the connective Digitized by Microsoft® i6o THE TISSUES. tissue found between the muscle-fibers — endo- and perimysium. It attains its greatest diameter in the equatorial region of the nerve end-organ, and becomes narrower again at its distal end, where it may end in tendon or become continuous with the connective tissue :sL*#:»j»^if«r^wKTBr5fc; Fig. 137. — Intrafusal muscle-fiber from neuromuscular nerve end-organ of rabbit : A, From proximal polar region ; B, equatorial region ; C, distal polar region. of the muscle. Immediately surrounding the intrafusal fibers is found another connective -tissue sheath known as the axial sheath, and between this and the capsule there is found a lymph-space bridged over by trabecular of fibrous tissue, to which the name periaxial lymph-space has been given. (Fig. 138.) By degenerating the motor nerves going to a muscle, Sherrington g*-% ^"""'WSf 'SS^ a Fig. 138. — Cross-section of a neuromuscular nerve end-organ from interosseous (foot) muscle of man ; fixed in formalin and stained in hematoxylin and eosin. determined that the nerve-fibers ending in the neuromuscular nerve end-organs were sensory in character. The manner of termination in these end-organs of the nerve-fibers ending therein has been studied by Kerschner, Kolliker, Ruffini, Huber and DeWitt, and others. Digitized by Microsoft® SENSORY NERVE-ENDINGS. 161 One or several (three or four) large medullated nerves, surrounded by a sheath of Henle, terminate in each neuromuscular end- Fig. 139. — Neuromuscular nerve end-organ from the intrinsic plantar muscles of dog ; from teased preparation of tissue stained in methylene-blue. The figure shows the intrafusal muscle-fibers, the nerve-fibers and their terminations ; the capsule and the sheath of Henle are not shown (Huber and DeWitt, "Jour. Comp. Neurol.," vol. vn). organ. As these nerves enter the capsule, the sheath of Henle blends with the capsule. The medullated nerve-fibers now and 11 Digitized by Microsoft® ID2 THE TISSUES. then divide before reaching the nerve end-organs, and divide several times as they pass through the capsule, periaxial space, and axial sheath. Within the axial sheath, the medullary sheath is lost, and the naked axis-cylinders terminate in one or several ribbon - like branches which are wound circularly or spirally about the intrafusal fibers (annulospiral ending) or they may terminate in a number of larger branches which again divide, these ending in irregular, round, oval, or pear-shaped discs {flower-like endings), which are also on the intra- fusal fibers. These flower-like endings are usually at the ends of the annulo- spiral fibers. In the smaller end- organs only one area of nerve-termi- nation has been observed ; in the larger, two, three, or even four such areas may be found. Neuromuscular nerve end-organs are found in nearly all skeletal muscles (not in the extrinsic eye muscles nor in the intrinsic muscles of the tongue), but they are especially numerous in the small muscles of the hand and foot. They are found in amphibia, reptilia, birds, and mammalia, presenting the same general structure, although the ultimate termination of the nerve-fibers varies somewhat in the different classes of vertebrates. Neurotendinous Nerve End -organ (Golgi Tendon Spindle). — In 1880 Golgi drew attention to a new nerve end-organ found in tendon, describing quite fully its general structure and less fully the nerve termination found therein. These nerve end-organs are spindle-shaped structures, which in •man vary in length from 1.28 mm. to I.42 mm., and in breadth from 0.17 mm. to 0.25 mm. (Kolliker). Ciaccio mentions a neurotendinous nerve end- organ found in a woman, which was 2 or 3 mm. long. A capsule consisting of from 2 to 6 fibrous, tissue lamellae, and broadest at the equatorial part of the end-organ, surrounds a number of in- Fig. 140. — Neurotendinous nerve end-organ from rabbit ; teased preparation of tissue stained in methylene-blue (Huber and DeWitt, "Jour. Comp. Neurol.," vol. x). Digitized by Microsoft® SENSORY NERVE-ENDINGS. 163 trafusal tendon fasciculi. The capsule is continuous at the prox- imal and distal ends of the end-organ with the internal periten- dineum of the tendon in which it is found. The number of the intrafusal tendon fasciculi varies from eight to fifteen or even more. They are smaller than the ordinary tendon fasciculi, from which they originate by division, and structurally resemble embryonic tendon, in that they stain more deeply and present many more nuclei than fully developed tendon. The intrafusal tendon fasciculi are surrounded by an axial sheath of fibrous tissue, between which and the capsule there is found a periaxial lymph-space. r _ ...... ,J^PH^ I Fig. 141. — Cross-section of neurotendinous nerve end-organ of rabbit ; from tissue stained in methylene-blue : m, Muscle-fibers ; t, tendon ; c, capsule of neurotendinous end-organ ; m n, medullated nerve-fiber (Huber and DeWitt, " Jour, of Comp. Neurol.," vol. X). The termination of the nerve-fibers ending in these end-organs has been studied by Golgi, Cattaneo, Kerschner, Kolliker, Pansini, Ciaccio, Huber and DeWitt. One, two, or three large medullated nerve-fibers, surrounded by a sheath of Henle, end in each end- organ ; as they pass through the capsule, the sheath of Henle blends with the capsule. The medullated nerve-fibers before enter- ing the capsule usually branch several times, branching further within the capsule and axial sheath. Before the resultant branches terminate on the intrafusal tendon fasciculi, the medullary sheath is Digitized by Microsoft® 164 THE TISSUES. lost, the naked axis-cylinder further dividing into two, three, or four branches, each of which runs along on the intrafusal fasciculi, giving off numerous short, irregular side branches, which partly enclasp the tendon fasciculi and end in irregular end-discs. Some of the ter- minal branches pass between the smaller fibrous tissue bundles of the fasciculi, ending between them. In these end-organs, the larger nerve-branches are found near the center of the bundle of intrafusal tendon fasciculi, the terminal branches and the end-discs nearer their periphery. The neuroten- dinous nerve end-organs are widely distributed, being found in all tendons although not equally numerous in all. Like the neuromus- cular nerve end-organs, they are especially numerous in the small tendons of the hand and foot. Sensory nerve end-organs, which resemble in structure the neurotendinous end-organs here described, though somewhat smaller than these, have been found in the tendons of the extrinsic eye-muscles. In this brief account of the mode of ending of the telodendria of the dendrites of peripheral sensory neurones (sensory nerve-fibers) it has not been possible to discuss any but the more typical varie- ties of sensory nerve-endings. Other nerve -endings will be consid- ered in connection .with the several organs to be treated later. For a fuller discussion of this subject, the reader is referred to special works and monographs. TECHNIC. 173. Fresh medullated nerve-fibers, when teased in an indifferent fluid \vid. T. 13), show the peculiar luster of the medullary sheath, and also the nodes of Ranvier, the neurilemma with its nuclei, and the seg- ments of Lantermann. At the cut ends of the fibers, the typical coagula- tion of their medullary portions is seen in the form of drops of myelin. All these structures can also be seen after using 1 f osmic acid. A nerve (not too thick) is placed in a 1% aqueous osmic acid solution, then washed for a few hours in distilled water, and finally carried over into absolute alcohol. After dehydration, small pieces are cleared with oil of cloves and the fibers teased apart upon a 'slide. The medullary sheath is stained black and hides the axial space, the nodes are clear, the neu- rilemma is sometimes seen as a light membrane, and the nuclei of the fibers are of a lenticular shape, and stained brown. 174. The nodes of Ranvier may also be demonstrated by means of silver nitrate solution. Fresh nerve-fibers are either teased in distilled water to which a trace of 1 % silver nitrate solution has been added (the nodes of Ranvier appear after a short time as small crosses), or whole nerves are placed for twenty-four hours in a 0.5% aqueous solution of silver nitrate, washed for a short time with water, hardened in alcohol, after which they are imbedded in paraffin and cut longitudinally. Exposure to light will soon bring out the ' ' crosses of Ranvier ' ' at the nodes. The appearance of these crosses is due to the fact that the silver nitrate solution first penetrates at the nodes of Ranvier, and then passes by capillary attraction along the axial cord for some distance. After the reduction of the silver, the cruciform figures appear colored Digitized by Microsoft® THE NERVOUS TISSUES. I6 5 black. Occasionally, a peculiar transverse striation is seen in the longi- tudinal portions of the crosses. These are known as Frommann's lines. Their origin and significance have not as yet been satisfactorily ex- plained. 175. To demonstrate the fibrils of the axial cord a piece of a small nerve is stretched on a match or toothpick and fixed for four hours in a 0.5% osmic acid solution, after which it is washed in water for the same length of time and immersed in 90 c / alcohol for twenty-four hours. The preparation is now stained for another twenty-four hours in a saturated aqueous solution of fuchsin S and then placed for three days in abso- lute alcohol. Finally, the nerve is passed as rapidly as possible through toluol, toluol-paraffin, and then im- bedded in paraffin. The proper orientation of the specimen is of the greatest importance, as is also the cutting of thin sections. In a lon- gitudinal section red fibrils of almost uniform thickness and evenly dis- tributed throughout the axial space are seen lying in the colorless neuro- Medullary sheath. Axis-cylin- der. Fig. 142. — Ranvier's crosses from sci- atic nerve of rabbit ; X I2 °- Technic No. 174. Frommann's lines can be seen in a few fibers. Fig. 143. — Medullated nerve-fiber from sciatic nerve of frog. In two places the medullary sheath has been pulled away by teasing, showing the " naked axis-cylin- der" ; X 212 - Technic No. 176. plasm, and parallel to the long axis of the nerve-fiber. In cross-section the axial fibrils appear as evenly distributed dots. Attention must be called to the fact that the fibrils are not equally well stained in all cases (Kupffer, 83, II ; compare also Jacobi and Joseph). 176. When the fiber is less carefully treated, the fibrils fuse with the neuroplasm to form the ' ' axis-cylinder ' ' of authors. As the appearance of the latter is due to a shrinkage of the contents of the axial space, it is easy to understand that one reagent may have a greater effect in this re- spect than another. The thinnest axis-cylinders are produced by chromic acid and its salts, while thicker ones are seen in nerve-fibers fixed in alcohol. These variations are best seen in cross-sections, in which the Digitized by Microsoft® 1 66 THE TISSUES. Dendrite. axis-cylinders sometimes appear as round dots and again as stellate figures. The latter are due to pressure on the shrinking axial cord by the unevenly coagulated medullary sheath. As the medullary sheath in such preparations crumbles away in many places, large areas of the axis-cylinder may often be isolated by teasing (Fig. 143). 177. If freshly teased fibers be treated with glacial acetic acid, the axis-cylinders swell up and issue from the ends of the fibers in irregular masses showing fine longitudinal striation (Kolliker, 93). The structures of the axial space dissolve in 1 °J C hydrochloric acid, as well as in a io°fc solution of sodium chlorid (Halliburton). 178. For the isolation of ganglion cells, 33% alcohol, 0.1 to 0.5% chromic acid, or 1 a / solution of potassium bichromate may be used. Small pieces of the spinal cord and brain containing ganglion cells are treated with a small quantity of one of the above solutions for one or two weeks. After this interval the prepara- tions may be teased and the isolated ganglion cells stained on a slide and mounted in glycerin. They may even be fixed in situ by injecting a 1 r / ( , solution of osmic acid or 33% al- cohol into the areas of the brain or spinal cord containing ganglion cells. The region thus treated is then cut out and teased. In preparations fixed in alcohol and stained with thionin, or in those treated with corrosive sublimate and subsequently stained with hematoxylin, chro- matophile bodies are seen in the ganglion cells. 179,. The nonmedullated or " Remak's fibers" are obtained by teasing a sympathetic nerve, or, better, a piece of the vagus previously treated with osmic acid. Between the blackened medullated fibers of the pneumogastric are seen numerous unstained fibers of Remak. The fibers of the olfactory nerves are stained brown by osmic acid. 180. Short muscles (ocular muscles or intercostal muscles) are em- ployed in demonstrating the motor nerve -endings in muscles, the fresh specimen being treated with 1 f acetic acid. 181. Furthermore, the gold methods for the demonstration of the nerve-fibers in the cornea, first discovered by Cohnheim (67, II) and still used to-day, may be employed : Small pieces of muscle are placed in a 1 , as seen from the edge. Fig. 146. — So-called "rouleau" formation of human erythrocytes ; X 1500. Fig. 147. — Hemin, or Teichmann's crystals, from blood stains on a cloth. Fig. 148. — " Crenated" human red blood- cells ; X 1500. Fig. 149. — Red blood-corpuscles sub- jected to the action of water ; X l$oo : a, Spheric blood-cell ; b, "blood shadow." change in the form of the cells, which assume a crenated or stellate shape. The red blood-cells of blood mounted in normal salt become crenated in a short time for the same reason. Red blood- cells are variously affected by different fluids. In water they become spheric and lose their hemoglobin by solution. Their remains then appear as clear, spheric, indistinct blood shadows, which may, how- ever, be again rendered distinct by staining with iodin. Dilute acetic acid has a similar but more rapid action, with this peculiarity, that before becoming paler the blood-cells momentarily assume a darker hue. Bile, even when taken from the animal furnishing the blood, exerts a peculiar influence upon the red blood-cells ; they first become distended, and then suddenly appear to explode into Digitized by Microsoft® BLOOD AND LYMPH. 171 small fragments. Dilute solutions of tannic acid cause the hemo- globin to leave the blood-cells, and coagulate in the form of a small globule at the edge of the blood-cell. In alkalies of moderate strength the red blood-cells break down in a few moments. Besides the disc-shaped red blood-cells, every well-made prep- aration shows a few small, spheric, nonnucleated cells containing hemoglobin. These, however, have received as yet but little attention. M. Bethe makes the statement that human blood and the blood of mammalia contain corpuscles of different sizes, bearing a definite numerical relationship to each other. " If they be classified according to their size, and the percentage of each class be calculated, the result will show a nearly constant proportional graphic curve varying but slightly, according © 9 Fig. 150. — Red blood-corpuscles from various vertebrate animals ; X 1000 (Welker's model) : a, From proteus (Olm) ; b, from frog ; i\ from lizard ; d, from sparrow ; c ', from camel ; fandg, from man ; h, from myoxus glis ; z", from goat ; /&, from musk-deer. to the animal species." According to M. Bethe, dry preparations of human and animal blood may be distinguished from each other, with the exception of the blood of the guinea-pig which presents a curve identical with that of human blood. The red blood-cells of mammalia, excepting those of the llama and camel species, are in shape and structure similar to those of man. The red blood-cells of the llama and camel have the shape of an ellipsoid, flattened at its short axis, but also nonnucleated. We have already made mention of the fact that the embryonal erythrocytes are nucleated ; the question now arises as to how, in the course of their development, they lose their nuclei. Three pos- sibilities confront us : First, either the embryonal blood-cells are destroyed and gradually replaced by previously existing nonnucle- Digitized by Microsoft® 172 BLOOD AND BLOOD-FORMING ORGANS. ated elements ; or, second, the nonnucleated red cells are formed from the nucleated by an absorption of the nucleus (or what appears to be such to the eye of the observer, Arnold, 96) ; or, finally, the nucleus is extruded from the original nucleated cell. According to recent investigations (Howell) the third possibility represents the change as it actually takes place. In all vertebrate animals except mammalia, the red blood- corpuscles are nucleated. They are elliptic discs with a biconvex center corresponding to the position of the nucleus. The blood- cells of the amphibia (frog) are well adapted for study on account of their size. They are long and, as a rule, contain an elongated nucleus with a coarse, dense chromatin framework, which gives them an almost homogeneous appearance. The cell-body may be divided, as in mammalia, into stroma and hemoglobin. When sub- jected to certain reagents, the contour of the cells appears double and sharply defined. This condition is, however, no proof of the existence of a membrane ; yet, as modern observers have demon- strated, a membrane may be totally or partly isolated (Lavdow- sky). The blood-cells of birds, reptiles and fishes are similarly constructed. The diameter of the erythrocytes varies greatly in different ver- tebrate animals, but is constant in each species. We append a table of their number in a cubic millimeter and size in man and certain animals as compiled by Rollett (71, II) and M. Bethe : Species. Man . . . Monkey . . Hare Guinea-pig . . . Dog Cat Horse .... Musk-deer . . Spanish goat Domestic chaffinch Dove Chicken Duck . Tortoise Lizard . Snake . Frog . Toad Triton . (Homo) . . . (Cercopith. ruber) (Lepus citniculus) (Cavia cob.) . . . (Canis fain.) . . . (Felts dom.) (Equuscab.) . . . (Moschus jav.) , , (Capra his.) ( Fringilla dom. ) . (Columba) . . . (G alius dom.) . . (Anas bosch.) . . ( Testudo graced) (Lacerta agil.) . . (Coluber natr.) . . (Rana temp. ) . . (Bufo vulg.) . . . (Triton crist.) . . Size. 7.2-7. 7 V 7.16 7.48 7.2 6.2 5-58 2-5 4.25 Length, Breadth, L. B. L. B. L. B. L. B. L. B. ■ L. B. L. B. L. B. L. B. No. IN Cubic Milli- meter. 5,000,000 • 6,355,000 . 6,410,000 • S,859,SOO 6,650,000 9,900,000 ■ 7,403,500 . 19,000,000 II. 9 6.8 H-7 6-5 12. 1 7.2 12.9 8.0 21.2 12.45 15-75 9-i 22.0 13.0 22.3 15-7 21.8 15-9 29-3 19-5 2,010 000 629,000 1,292,000 829,400 393,200 389,000 103,000 Digitized by Microsoft® BLOOD AND LYMPH. 173 Species. Salamander (Salamandra mac.) [Proteus angu.) Sturgeon [Aapenser Si.) . . Carp [Cyprinus Gobid) . Size. Length , Breadth, L. B. L. B. I.. B. 37-8 23.8 58 35 13-4 10.4 17.7 10. 1 No. IN Cubic Milli- meter. . . 80,000 • ■ 35,OO0 3. WHITE BLOOD-CORPUSCLES. The white blood-cells contain no hemoglobin and are nucleated elements which, under certain conditions, possess ameboid move- ment. Their size varies from 5 //to 10 p., and they are less numer- ous than the red blood-corpuscles, one white blood-cell to from three hundred to five hundred red cells being a normal proportion. In Fig. 151. — From the normal blood of man; X 1200 (from dry preparation of H. F. Miiller) : a, Red blood-cell ; b, lymphocyte ; c .and d, mononuclear leucocytes ; e, transitional leucocyte ; _/"and£", leucocytes with polymorphous nuclei. the normal blood the white blood- cells vary in shape, and the fol- lowing varieties are distinguished: (1) Small and large lympho- cytes ; (2) mononuclear leucocytes ; (3) transitional leucocytes ; (4) leucocytes, either polymorphonuclear or polynuclear. The lymphocytes form about 20 fo of the white blood-cells. They vary in size from 5 p. to 7. 5 p and possess a relatively large nucleus, which stains rather deeply, surrounded by a narrow zone of protoplasm. The leucocytes vary in size from 7 p to 10//. The mononuclear leucocytes, constituting about 2^ to 4^ of the white blood-cells, have a nearly round or oval nucleus, which usually does not stain very deeply, and which is relatively smaller than that of the lymph- ocytes. The transitional leucocytes, forming also about 2% to Digitized by Microsoft® 174 BLOOD AND BLOOD-FORMING ORGANS. 4% of the white blood-cells, are developed from the mononuclear variety and represent transitional stages in the development of mononuclear leucocytes to those with polymorphous nuclei. The nucleus in the transitional form is similar in size and structure to that of the mononuclear variety, but of a more or less pronounced horse- shoe-shape. The leucocytes with polymorphous nuclei, developed from the transitional forms, are very numerous in the blood, form- ing about 70% of the entire number of white blood-cells. They are also the cells which show the most active ameboid movement when examined on the warm stage. They possess variously lobu- lated nuclei, the several nuclear masses often being united by del- icate threads of nuclear substance. A leucocyte with a poly- morphous nucleus becomes a polynuclear cell in case the bridges of nuclear substance uniting the several lobules of the nucleus break through. In the protoplasm of the transitional leucocytes, the polymorphonuclear, and the polynuclear forms are found fine and coarse granules. Our knowledge of these granules has, however, y 6 Fig. 152. — Ehrlich's leucocytic granules; X 1800 (from preparations of H. F. Miiller) : a, Acidophile or eosinophile granules, relatively large and regularly distributed ; £, neutrophile granules ; fi, amphophile granules, few in number and irregularly dis- tributed ; } , mast cells with granules of various sizes ; 6, basophile granules, (a, S, and c'. From the normal blood ; y, from human leukemic blood ; /3, from the blood of guinea-pig.) been greatly extended since Ehrlich has shown that the granules of leucocytes show specific reactions toward certain anilin stains, or combinations of such stains. He divides the granules of the leuco- cytes into five classes which he terms respectively a-, /3-, Trabecula. Fig. 154. — Section through a mesenteric lymph-gland of cat, with injected blood-vessels ; X 50 : a, Medullary substance ; b, cortical substance with cortical nodules. lary substance and the capsule at the hilum. The sinus is therefore intimately connected not only with the capsule, but also with the trabecular. At the hilum the loose lymphoid tissue represents a terminal sinus (Toldt). The inner wall of the capsule and the trabecular with their pro- cesses are covered by flattened endothelial cells which are continu- ous with those of the afferent and efferent lymph-vessels. The lymph flows into the gland through the afferent vessels, and passes along into the interior through the spaces offering the least resist- ance (sinuses). The latter represent those peripheral portions of the nodules and of the medullary cords in which the lymphoid tissue is present in loose arrangement. The lymph consequently envelops not only the lymph-nodules of the cortical substance, but also the medullary cords, and finally streams into the terminal sinus and Digitized by Microsoft® i8o BLOOD AND BLOOD-FORMING ORGANS. then into the efferent channels. As a result the lymph takes with it the newly formed cells of the lymph-nodules and the medullary cords, and passes out much richer in cellular elements than on its entrance. A large number of arterial blood-vessels enter the lymph-gland through the hilum and penetrate into the interior of the organ through the trabeculae. After passing through the sinuses they break up into capillaries in the medullary cords or in the lymph- nodules of the cortical substance. The sinuses, then, contain no <»0 *^i® e% Germ center. Mitosis. Lymph-sinus. Fi g- IS5-— From a human lymph-gland; X 2 4°- At " are seen the concentrically arranged cells of the lymph-nodules. (Fixation with Flemming's fluid.) capillaries. The arterial capillaries pass over into the venous capil- laries, and the veins resulting from the union of the latter pass to ■ the periphery of the organ side by side with the arteries. C THE SPLEEN. The spleen is a blood-forming organ, in which white blood-cells and, in embryonic life and under certain conditions in adult life also, red blood-cells are formed — the former in the adenoid tissue (Mal- pighian corpuscles) and spleen pulp, the latter only in the spleen pulp. The spleen is covered by peritoneum, and possesses a capsule Digitized by Microsoft® THE SPLEEN. Itfl consisting of connective tissue, elastic fibers, and nonstriated muscle- cells. This capsule sends numerous processes or trabeculae into the interior of the organ, which branch and form a framework in which the vessels, especially the veins, are imbedded. This con- nective-tissue framework breaks up to form the reticular tissue which constitutes the ground substance of the spleen. On examining a section of the spleen with the low-power mag- nifying glass, sections of the trabeculae, and round or oval masses of cells, having a diameter of about 0.5 mm., and in structure and ■ '■.■-.•■,-* .r-.v.i ; ?--:■■■: . .- -'.'■■ ■' ■■.'■-. .-.-■*■. '' ■ '-,v aijvi ■>-.T/*'- 'H-^->:. ■'Sr^W "^•■u, * '\ - Vi't£,y - Blood-vessel. -■ - ■ WW..* Jj;B| lip Trabecula.-^'— v; f U'liii4_Trabecula. ■■■■•■' -Spleen pulp. p^r-- - Malpighian cor- puscle with germ center. , : # Fig. 156. — Part of a section through the human spleen; X 75- (Sublimate fixation.). At a is an oblong Malpighian body with a blood-vessel. appearance similar to the lymph-nodules (Malpighian corpuscles), are clearly defined ; between and around these structures is a tissue rich in cells, blood-vessels and blood-corpuscles, known as the spleen pulp. The organ has a very typical blood supply. Its arteries enter at the hilum, or indented surface, and its veins pass out at the same place. On the penetration of the vessels through the capsule, the latter forms sheaths around them (trabeculae), but as soon as the arteries and veins separate, the trabecular envelop the veins alone. Digitized by Microsoft® 1 82 BLOOD AND BLOOD-FORMING ORGANS. The arteries break up into smaller branches, which in turn divide into a large number of tuft-like groups of arterioles. Soon after their separation from the veins, the adventitia (outer fibrous tissue coat) of the arteries begins to assume a lymphoid character. This lymphoid tissue increases here and there to form true lymphoid nodules, pos- sessing all the characteristics already mentioned — reticular tissue, germ centers, etc. These are the Malpighian bodies, or corpuscles ; they are not very plentifully represented in man. The Malpighian bodies with their germ centers are formative centers for the lympho- cytes. The newly formed cells pass into the pulp and mix with its elements, which are then bathed by the blood emptying from the arterial capillaries into the channels of the pulp. The lymphoid sheaths and nodules derive their blood supply from arteries which arise from the lateral branches of the splenic vessels, and which divide into capillaries inside of the lymph sheaths or nodules, and only assume a venous character outside of the lymphoid substance. These vessels constitute the nutritive vascular system of the spleen. The small arterial branches above- mentioned break up into very fine arterioles which gradually lose their lymphoid sheath, so that branches with a diameter of 0.02 mm. no longer possess a lymphoid sheath, but again assume an adventitia of the usual type. The smallest arterioles now pass over into capillaries which are for a time accompanied by the adventitia (capillary sheath), while the terminal branches have the usual structure of the capillary wall and are gradually lost in the meshes of the pulp. (See below.) On the other hand, the beginnings of the venous capillaries may be dis- tinctly seen in the pulp spaces. Groups of these capillaries com- bine to form larger vessels, which, however, still retain a capillary structure, and these again form small veins which unite to form the larger veins. Mall, whose recent contributions on the structure of the spleen have greatly extended our knowledge of the microscopic anatomy of this organ, states that the trabecular and vascular systems together outline masses of spleen pulp about 1 mm. in diameter, which he has named spleen lobules. Each lobule is bounded by three main in- terlobular trabecular, each of which sends three intralobular trabe- cular into the lobule which communicate with each other in such a manner as to divide the lobule into about ten smaller compartments. An artery enters at one end of the lobule and, passing up through its center, gives off a branch to the spleen pulp found in each of the ten compartments formed by the intralobular trabecular. The spleen pulp in these compartments is arranged in the form of anastomosing columns, or cords, to which Mall has given the name of pulp cords. The branches of the main intralobular artery, going to each compartment, divide repeatedly ; the terminal branches course in the spleen-pulp cords, and in their path give off numerous small side branches which end in small expansions known as the ampulla of Thoma. " The first two-thirds of the ampulla are lined Digitized by Microsoft® THE SPLEEN. 183 with spindle-shaped cells lying on a delicate framework of reticulum. Through the last third, at the junction with the vein, no cell bound- aries can be demonstrated. In fact, it appears as if this portion of the ampulla were cut up by fibrils of the reticulum passing across it " (Mall). The veins of the lobule begin in a system of venous spaces surrounding the pulp cords. These are in communication with intralobular veins, often associated with intralobular trabecular, and the latter empty into the interlobular veins found in some of the interlobular trabeculae. Mall further states that " the ampullae and venous plexus have very porous walls, which permit fluids to pass through with great ease and granules only with difficulty. In life the plasma constantly flows through the intercellular spaces of the pulp cords, while the blood-corpuscles keep within fixed channels." The accompanying diagram (Fig. 157), slightly, though immate- Capsule. Intralobular trabecula. Artery to one of the ten compartments. Intralobular artery. ' ; — Interlobular trabecula Intralobular trabecula. - Malpighian corpuscle. Fig. 157. — Diagram of lobule of the spleen (Mall, " Johns Hopkins Hospital Bulletin," Sept., Oct., 1898). Intralobular venous spaces. — Intralobular vein. Ampulla of Thoma. -* Spleen pulp cord. — Interlobular vein. — Intralobular vein. rially, modified from one given by Mall, shows clearly the trabecular and vascular systems of a spleen lobule. In larger spleens there may be some two hundred thousand of these lobules. In a dog weighing 10 kg. there are on an average some eighty thousand (Mall). The splenic pulp consists of a very delicate reticulum, in the meshes of which are found (1) fully developed red blood-cells ; (2) now and then nucleated red blood-cells ; (3) in many animals giant cells ; (4) cells containing red blood-corpuscles and the remains of such, with or without pigment ; (5) the different varieties of white blood-cells, especially a relatively large proportion of mononuclear leucocytes. Pigment granules, either extra- or intracellular, also occur in the splenic pulp. The pigment probably originates from disintegrating erythrocytes. Besides these are found, especially in Digitized by Microsoft® 1 84 BLOOD AND BLOOD-FORMING ORGANS. teased preparations, long, spindle-shaped and flat cells, which are probably derivatives of the connective-tissue cells of the pulp and of the endothelium and muscular fibers of the vessels. ^M Fig. 158. — Cells containing pigment, blood-corpuscles, and hemic masses from the spleen of dog; / 1800 (from cover-glass of H. F. Miiller). F'g- '59- — From the human spleen ; X 8° (chrome-silver method) : a, Larger fibers of a Malpighian body ; b, reticular fibrils (Gitterfasern). In embryonic life and under certain conditions in postembryonic life (after severe hemorrhage and in certain diseases) red blood-cells are developed in the spleen pulp. The nucleated red blood-cells Digitized by Microsoft® THE BONE-MARROW. 1 85 from which they develop may lose their nuclei in the spleen pulp or only after entering the circulation (compare Bone-marrow). By means of certain methods, especially the chrome-silver method (Oppel, 91), a very delicate reticular network — i. e., that surrounding the capillary walls — may be brought to view in the spleen. The fibers composing it have been called by Kupffer retic- ular fibers. The spleen receives medullated and nonmedullated nerve-fibers ; the latter are much more numerous. The medullated nerve- fibers are no doubt the dendrites of sensory neurones. Their mode of ending has, however, not been determined. It is probable that they will be found to terminate in the fibrous-tissue coat of the vessels, and in the trabecular and capsule. The nonmedullated nerve-fibers, no doubt the neuraxes of sympathetic neurones, are very numerous ; they enter the spleen with the artery and mainly follow its branches. By means of the chrome-silver method, Retzius (92) has shown that in the rabbit and mouse these nerve- fibers follow the vessels, forming plexuses which surround them, the terminal branches of these plexuses terminating in free endings in the muscular coat of the arteries. Here and there a nerve-fiber could be traced into the spleen pulp. The mode of ending of such fibers could, however, not be determined. The nonstriated muscle- cells of the trabecular and capsule no doubt also receive their inner- vation from the nonmedullated nerves (neuraxes of sympathetic neurones). D. THE BONE-MARROW. The ingrowing periosteal bud which ushers in the process of endochondral ossification constitutes the first trace of an embryonal bone-marrow (compare p. 108). It consists mainly of elements from the periosteum which penetrate with the vascular bud and later form the entire adult bone-marrow. The red bone-marrow is formed first. This is present in embryos and young animals, and is devel- oped from the above elements during the process of ossification. As Neumann (82) has shown, the red bone-marrow of the human embryo is first formed in the bones of the extremities and gradually replaced in a proximal direction, so that in the adult it is found only in the proximal epiphyses, in the flat bones and in the bodies of the vertebrae. In the remaining bones and parts of bones the red bone-marrow is replaced by the yellow bone-marrow (fat- marrow). As a result of hunger and certain pathologic conditions the yel- low bone-marrow changes into a gelatinous substance, which, how- ever, may again assume its original character. The red bone-marrow, surrounded by a delicate fibrous-tissue membrane, the endosteum, is a tissue consisting of various cellu- lar elements imbedded in a matrix of reticular tissue, similar to the Digitized by Microsoft® 1 86 BLOOD AND BLOOD-FORMING ORGANS. adenoid reticulum. Aside from these cellular elements, the marrow contains numerous vessels (see below), fixed connective-tissue cells, etc. The typical cellular elements of red bone-marrow are : i. The Marrow-cells, or Myelocytes. — These are cells, slightly larger than the leucocytes, possessing a relatively large nucleus of round or oval shape, rarely lobular, containing a relatively small amount of chromatin. In the protoplasm of these cells are found (in man) neutrophile granules and now and again small vacuoles. They are said to contain various pigment granules. These cells are not found in normal blood, but are found in circulating blood in certain forms of leukemia, where they may be distinguished from the mononuclear leucocytes partly by their structure, more particu- Fig. 160. — Cover-glass preparation from the bone-marrow of dog; X I2 °° (from preparation of H. F. Miiller) : a, Mast-cell ; b, lymphocyte ; c, eosinophile cell ; d, red blood-cell ; e, erythroblast in process of division ; f, f, normoblast ; g, erythroblast. Myelocyte not shown in this figure. larly by the presence of neutrophile granules not found in the mononuclear leucocytes. 2. Nucleated Red Blood-cells containing Hemoglobin. — Two varieties of these cells are recognized structurally, with interme- diary stages, as one variety is developed from the other. The erythroblasts, being genetically the earlier cells, possess relatively large nuclei with distinct chromatin network, surrounded by a protoplasm tinged with hemoglobin, and are often found in a stage of mitosis. The other variety of nucleated red blood-cells, the normoblasts, are developed from the erythroblasts. They contain globular nuclei, staining deeply, in which no chromatin network is recognizable, and surrounded by a layer of protoplasm containing hemoglobin. The normoblasts are changed into the nonnucleated Digitized by Microsoft® THE BONE-MARROW. 187 red blood-discs by the extrusion of the nucleus. This process occurs normally in the red bone-marrow, or in the venous spaces of the bone-marrow (see below). In certain pathologic conditions, nucleated red blood-cells are found in the circulation. • 3. Cells with Eosinophil Granules. — In the red bone-marrow are found numerous eosinophile (acidophile) cells, some with round or oval nuclei (mononuclear eosinophile cells), others with horse- shoe-shaped nuclei (transitional eosinophile cells), and still others with polymorphous nuclei. The latter, which are the most numer- ous, are no doubt the mature cells, and are identical with those elements of the blood having the same structure. d _ e -f - g Fig. 161. — From a section through human red bone-marrow; X °8°- Technic No. 216 : a, f, Normoblasts ; b, reticulum ; c, mitosis in giant cell ; d, giant cell ; e, h, myelocytes ; g, mitosis ; i, space containing fat-cells. 4. The various forms of leucocytes and the lymphocytes found in blood and lymph. 5. The giant cells (myeloplaxes), which are situated in the center of the marrow, and contain simple or polymorphous nuclei, or lie adjacent to the bone in the form of osteoclasts, which are, as a rule, polynuclear (compare p. ill). The physiologic significance of the giant cells is still obscure. They probably originate from single leucocytes by an increase in size of the latter, and not, as many assume, from a fusing of several leucocytes. The giant cells are endowed with ameboid movement, and often act as phagocytes (the latter quality is denied them by M. Heidenhain, 94). Digitized by Microsoft® ISO BLOOD AND BLOOD-FORMING ORGANS. M. Heidenhain (94) has made a particular study of the giant cells. According to him the nuclei of these cells take the form of per- forated hollow spheres whose thick walls contain ' ' endoplasm. ' ' The latter is continuous with the remaining protoplasm of the cell, the " exo- plasm " through the "perforating canals" of the nuclear wall. The exoplasm is arranged in three concentric layers, separated from each other by membranes, the external membrane of the outer zone being the membrane of the cell. The outer layer or marginal zone is of a transient nature, but is always renewed by the cell. Thus, the cell-membrane is replaced by the secondary membrane situated between the second and third zone. According to the same author the functions of the giant cells appear to consist in " the selection and elaboration of certain albu- minoid substances of the lymph and blood currents, which are later returned to the circulation." The number of centrosomes occurring in the mononuclear giant cells of the bone-marrow is very large, and in some cases, as in a pluripolar mitosis, may even exceed one hundred in number. The distribution of the blood-vessels in the bone-marrow is as follows : On entering the bone the nutrient arteries divide into a large number of small branches, which then break up into small arterial capillaries. The latter pass over into relatively large venous capillaries, whose walls either finally disappear entirely or are broken through in many places so that the venous blood pours into the spaces of the red bone-marrow where the current is very slow. The blood passes out by means of smaller veins formed by the conflu- ence of the capillaries which collect the blood from the marrow. It is worth mentioning that the venous vessels, while inside of the bone-marrow, possess no valves ; but, on the other hand, they have an unusually large number of valves immediately after leaving the bone. Yellow bone-marrow is derived from red bone-marrow by a change of the marrow-cells into fat-cells. The gelatinous marrow, on the contrary, is characterized by the small quantity of fat which it contains. Neither the yellow nor the gelatinous bone-marrow is a blood-forming organ (compare Neumann, 90; Bizzozero, 91 ; H. F. Miiller, 91 ; van der Stricht, 92). E. THE THYMUS GLAND. The thymus gland is usually considered as belonging to the lymphoid organs, although in its earliest development it resembles an epithelial, glandular structure. In the epithelial stage, this gland develops from the entoderm of the second and third gill clefts. Mesodermic cells grow into this epithelial structure, proliferate and then differentiate into a tissue resembling adenoid tissue. It retains this structure until about the end of the second year after birth, when it slowly begins to retrograde into a mass of fibrous tissue, adipose tissue, and cellular debris, which structure it presents in adult life. Digitized by Microsoft® THE THYMUS GLAND. 189 larger lobes By means of connective-tissue septa, the thymus is divided into d these again into smaller lobes, until finally a number of very small, almost spheric structures are formed — the lobules of the gland. These consist of a reticular connective tissue much more delicate at the periphery than at the center of the '■"■ ;^?i l -^Sfe» d Fig. 162. — A small lobule from the thymus of child, with well-developed cortex, presenting a structure similar to that of the cortex of a lymph-gland ; X 60 : a, Hilus ; b, medullary substance ; c, cortical substance ; d, trabecula. lobule. In the meshes of the reticular tissue are cellular elements, in structure similar to the lymphocytes, which are more numerous at the periphery of the lobule than at its center, so that we may here speak of the lobule as divided into a cortical and a medullary portion. The latter is usually entirely surrounded by the cor- tical substance, but may pene- trate to the periphery of the lobule, allowing the blood-ves- sels to enter and leave at this point. In the cortical sub- stance occur changes which result in the formation of structures closely resembling the cortical nodules of lymph- glands. Until recently, little was known of the significance of this organ. A careful study re- vealed a similarity between cer- tain cellular elements of the thymus and the constituents of the blood-forming organs, — a similarity still more striking from the presence of nucleated red blood-cells in the thymus. Logically, then, the embryonal thymus is to be regarded as one of the blood-forming organs (Schaffer, 93, I). The meshes of the capillary network are much wider in the medullary than in the cortical substance of the Fig. 163. — Hassal' s corpuscle and a small portion of medullary substance, showing reticulum and cells, from thymus of a child ten days old. Digitized by Microsoft® I9O THE CIRCULATORY SYSTEM. lobules, but small arteries also penetrate directly into the cortex. The lymphatics, concerning the origin of which nothing certain is known, pass out side by side with the arteries. It is probable that the peripheral looser portion of the cortex represents a lymph-sinus. During embryonic life from the fourth month on and for some time after birth, there are found in the thymus peculiar epithelial bodies, known as the corpuscles of Hassal. They are spheric struc- tures, about 0. 1 mm. in diameter, whose periphery shows a con- centric arrangement of the epithelial cells. In their central portions are found a few nuclear and cellular fragments. These bodies occur only in the thymus gland. They are remnants of the primary epithelial, glandular structure of the thymus, and are formed by an ingrowth of mesoderm which breaks down the epithelium into small irregular masses, mechanically compressed by the proliferating mesoderm. II. THE CIRCULATORY SYSTEM. The walls of the blood-vessels vary in structure in the different divisions of the vascular system. All the vessels, including the heart, possess an inner endothelial lining. In addition to this, the larger vessels are provided with other layers, which consist, on the one hand, of connective and elastic tissue and, on the other, of non- striated muscle-fibers. The vessels are also richly supplied with nerves, that form plexuses in which ganglion cells are sometimes found, and in the larger vessels the outer layer is honeycombed by nutrient blood-vessels, called vasa vasorum. In the heart, the mus- cular tissue is especially well developed. According to the structure of the vessels, we distinguish, in both arteries and veins, large, medium-sized, small, and precapillary vessels, and finally, the capil- laries themselves. The latter connect the arterial and venous pre- capillary vessels. In the lymphatic system we must further dis- tinguish between the larger lymph-vessels, the sinuses, and the capillaries. A. THE VASCULAR SYSTEM. J. THE HEART. In the heart there are recognized three main coats — the endo- cardium, the myocardium, and the pericardium or epicardium. The endocardium consists of plate-like endothelial cells, with very irregular outlines. Beneath this endothelial layer is a thin membrane composed of unstriped muscle-cells, together with a small number of connective-tissue and elastic fibers. Below this is a somewhat thicker and looser layer of elastic tissue connected ex- ternally with the myocardium. Between the two layers are found, here and there, traces of a layer of Purkinje' s fibers (compare p. Digitized by Microsoft® THE VASCULAR SYSTEM. I9I 132). Purkinje's fibers are found in the heart of many mammalia, although absent in the heart of the human adult. The auriculove utricular valves of the heart represent, in general, a duplication of the endocardium. The layer of smooth muscle- fibers found in the latter is better developed on the auricular sur- face, while the elastic tissue is more prominent on the ventricular surface. At the points of insertion of the chordae tendinese the con- nective-tissue layer is strongly developed and assumes a tendon-like consistency. The semilunar valves of the aorta and pulmonary artery have a similar structure. In the nodules of these valves the elastic fibers are especially dense in their arrangement. The myocardium is made up of the heart muscle-cells already described (vid. p 132). Between the heart muscle-fibers and bundles of such fibers are thin layers of fibrous connective tissue containing a network of capillaries. The myocardium of the auricles may be divided into two layers, of which the outer is common to both auricles ; the heart muscle-fibers of this layer have a nearly circular arrangement. Three layers of muscle-fibers are met with in a longitudinal section through the ventricular wall, the outer and inner being chiefly longitudinal in direction, although not exactly parallel. In the left ventricle the outer layer is very strongly devel- oped. The musculature of the auricles is almost completely sepa- rated from that of the ventricles by means of the anmdus fibrosus atrioventricularis , which consists in the adult of connective tissue containing numerous delicate and densely interwoven elastic fibers. The pericardium consists of a visceral layer, the epicardium, ad- hering closely to the myocardium, and a parietal layer (pericardium), loosely surrounding the heart and continuous at the upper portion of the heart with the visceral layer. Between the two layers is the pericardial cavity, containing a small quantity of a serous fluid — the pericardial fluid. In the visceral layer (the epicardium) we find a connective-tissue stroma covered by flattened endothelial cells. A similar structure occurs also in the parietal layer, although here the connective -tissue stroma is considerably reinforced. De- posits of fat, in most cases in the neighborhood of the blood-vessels, are sometimes seen between the myocardium and the visceral layer of the pericardium. According to Seipp, the distribution of the elastic tissue in the heart is as follows : The endocardium of the ventricles contains far more elastic tissue than that of the auricles, especially in the left ventricle, where even fenestrated membranes may be present. In the myocardium of the ventricles there are no elastic fibers aside from those which are found in the adventitia of the contained blood- vessels. In the myocardium of the auricles, on the contrary, such fibers are very numerous and are continuous with the elastic elements in the walls of the great veins. The epicardium also pre- sents elastic fibers in the auricles continuous with those of the great veins emptying into the heart, and in the ventricles continuous with Digitized by Microsoft® I92 THE CIRCULATORY SYSTEM. those in the adventitia of the conus arteriosus. In those portions of the heart-wall containing no muscular tissue the elastic elements of the epicardium are continuous with those of the endocardium. In the new-born the cardiac valves possess no elastic fibers, although they are present in the adult. They are developed on that side of each valve, which, on closing, is the more stretched — for instance, on the auricular side of the auriculoventricular valves. The heart has a rich blood supply. The capillaries of the myo- cardium are very numerous, and so closely placed around the muscle bundles that each muscular fiber comes in contact with one or more capillaries. In the endocardium the vessels are confined to the connective tissue. The auriculoventricular valves con- tain blood-vessels, in contradistinction to the semilunar valves, which are non -vascular, while the chorda; tendineae are at best very poorly supplied with capillaries. The coronary arteries, which terminate in the capillaries above mentioned, are terminal arteries in the sense that " the resistance in the anastomosing branches is greater than the blood pressure in the arteries leading to those branches (Pratt, 98). This observer has further shown that the vessels of Thebesius (small veins which open on the endocardial surfaces of the ventricles and auricles and communicate directly with all the chambers of the heart) "open from the ventricles and auricles into a system of fine branches that communicate with the coronary arteries and veins by means of capillaries, and with the veins, but not with the arteries, by passages of somewhat larger size''; so that, although the blood supply through the coronary arteries for a given area of the myocardium is cut off, the heart muscle of this area may receive blood through the vessels of Thebesius. Lymphatic netzvorks have been shown to exist in the endocar- dium, and their presence in the pericardium is not difficult to demon- strate. Little is known with regard to the lymph-channels of the myocardium. The nerve supply of the heart includes numerous medullated nerve-fibers, the dendrites of sensory neurones, and numerous non- medullated fibers, the neuraxes of sympathetic neurones. Smirnow (95) described sensory nerve-endings in the endocardium of amphibia and mammalia, which he suggests may be the terminations of the depressor nerve. Dogiel (98) has corroborated and extended these observations, and has described complicated sensory telodendria situated both in the endo- and pericardium. The latter states that, after forming plexuses and undergoing repeated division, the medul- lated sensory nerves lose their medullary sheaths, the neuraxes further dividing in numerous varicose fibers, variously interwoven and terminating in telodendria, which yary greatly in shape and configuration. These telodendria are surrounded by a granular substance containing branched cells, probably connective-tissue cells, the interlacing branches of which form a framework for the Digitized by Microsoft® THE VASCULAR SYSTEM. 1 93 telodendria. Similar sensoiy nerve-endings occur in the adventitia of the arteries and veins of the pericardium (Dogiel, 98) ; and Schemetkin has shown that sensory nerve-endings occur in the adven- titia and intima, especially in the latter, of the arch of the aorta and pulmonary arteries. In the heart, under the pericardium on the posterior wall of the auricles and in the sulcus coronarius, are found numerous sympathetic neurones whose cell-bodies are grouped to form sympathetic ganglia. The neuraxes of these sympathetic neurones — varicose, nonmedullated nerve-fibers — form intricate plexuses situated under the pericardium and, penetrating the myo- cardium, surround the bundles of heart muscle-fibers. From the varicose nerve-fibers constituting these plexuses, fine branches are given off, which terminate on the heart muscle-cells in a manner previously described (see p. 149 and Fig. 127). The cell-bodies of the sympathetic neurones, the neuraxes of which thus terminate on the heart muscle-fibers, are surrounded by end-baskets, the telodendria of small medullated nerve-fibers which reach the heart through the vagi. The slowed and otherwise altered action of the heart-muscle, produced on stimulating directly or indirectly the vagus nerves is therefore due not to a direct action of these nerve- fibers on the heart muscle-cells, but to an altered functional activity produced by vagus stimuli in at least some of the sympathetic neu- rones situated in the heart, the neuraxes of which convey the im- pulse to the heart muscle. The heart receives further nerve supply through sympathetic neurones, the cell-bodies of which are situated in the inferior cervical and stellate ganglia, the neuraxes of which enter the heart as the augmentor or accelerator nerves of the heart. The mode of ending of these nerve-fibers has not as yet been fully determined. It may be suggested as quite probable that they ter- minate on the dendrites of sympathetic neurones, the cell-bodies of which are not inclosed by end-baskets of nerves reaching the heart through the vagi, as above described. It is also possible that they end directly on the heart muscle-cells. The cell-bodies of the sympathetic neurones, the neuraxes of which form the augmentor nerves, are surrounded by the telodendria of small medullated fibers, forming end-baskets, which leave the spinal cord through the anterior roots of the upper dorsal nerves. Besides the nerves here described, nonmedullated nerves (whether the neuraxes of sympa- thetic neurones, the cell-bodies of which are situated inside or out- side of the heart has not been fully determined), form plexuses in the walls of the coronary vessels, terminating, it would seem, on the muscle-cells of the media (vasomotor nerves).' 2. THE BLOOD-VESSELS. A cross-section of a blood-vessel shows several coats. The inner consists of flattened endothelial cells, and is common to all vessels. The second varies greatly in thickness, contains most of Digitized by Microsoft® 194 THE CIRCULATORY SYSTEM. the contractile elements of the arterial wall, and is known as the media, or tunica media. Its elastic fibers have in general a circular arrangement and are fused at the inner and outer surfaces to form fenestrated membranes, the lamina elastica interna and externa. Outside of the media lies the adventitia or tunica externa, consist- ing in the arteries almost entirely of connective tissue and in the veins principally of contractile elements, smooth muscle-fibers. Between the internal elastic membrane and the endothelial layer is a fibrous stratum which varies in structure in the different vessels of larger caliber. This is the subendothelial layer, or the inner fibrous layer, and forms, together with the endothelium, the intima Intima. Elastica in- terna. Endothelium of the intima. > Media. Fenestrated elastic mem- brane. Elastica ex- terna. Inner layer of adventitia. Outer layer of adventitia. Yasa vasorum. ';- Fig. 164. — Cross-section of the human carotid artery ; X I S°' or tunica intima. Bonnet (96), as a result of his own investigations, suggests a somewhat different classification of the layers composing the arterial wall. According to him, the endothelium alone con- stitutes the intima. The elastic membranes, both internal and external, together with the tissue lying between them, and that between the internal elastic membrane and the intima, constitute the media. The tissue layers outside the external elastic membrane form the tunica externa (adventitia). (a) Arteries. — In the great arterial trunks, such as the pulmo- nalis, carotis, iliaca, etc., the tunica media possesses a very typical structure. It is divided by means of elastic fibers and membranes Digitized by Microsoft® THE VASCULAR SYSTEM 195 (fenestrated membranes) into a large number of concentric layers containing but few muscle-fibers. Here also the tunica media is separated from the intima by an elastic limiting membrane, the fenestrated membrane of Henle, or the lamina elastica interna. In the aorta this membrane as such is not recognizable. The intima presents three distinct layers — the inner composed of flattened endo- thelial cells, and the other two consisting chiefly of elastic tissue (fibrous layers). Of these latter the inner is the richer in cellular Endothelium of the intima. ■Intima. Media. Adventitia with nonstriated mus- cle-fibers in cross- section. Fig. 165.— Section through human artery, one of the smaller of the medium-sized ; X 640. elements and has a longitudinal arrangement of its fibers, while the outer is the looser in structure, possesses few cellular elements, and shows a circular arrangement of its fibers. The adventitia is also made up of fibro-elastic tissue, but in this case with a still looser structure and a longitudinal arrangement of its elastic fibers. In the outer portion of the adventitia the white fibrous tissue is more abundant. The adventitia is rich in blood-vessels. The medium-sized arteries differ in structure from the larger in that the elastic elements of the intima and media are replaced to a considerable extent by nonstri- ated muscular fibers. To this type belong the majority of the arterial vessels, ranging in caliber from the brachial, crural, and radial arteries to the supraorbital artery. In these the intima shows, besides its endothelium, only a single connec- tive-tissue layer with numerous longitudinal fibers, the subendo- thelial layer, which is thin and is limited externally by the fenes- trated membrane of Henle (lamina elastica interna). The media no longer gives the impression of being laminated, but consists of circularly arranged muscle-fibers separated from each other by elastic fibers and membranes and a small amount of fibrous connective tissue in such a way that the muscle-cells form more or less clearly defined groups. Here also Digitized by Microsoft® Fig. 166. — Precapillary vessels from mesentery of cat : a, Precapillary artery ; b, precapillary vein possessing no muscu- lar tissue. 196 THE CIRCULATORY SYSTEM. the media is limited externally by the external elastic membrane. The adventitia, which becomes looser externally, is not so well de- veloped as in the larger vessels, but presents in general the same structure. In certain arteries (renal, splenic, dorsalis penis) it shows in its inner layers scattered longitudinal muscle-cells, which, how- ever, may also occur in other arteries at their points of division. With regard to the elastic tissues, the arteries of the brain differ to some extent from those of the remainder of the body. The elastica interna is much more prominent, the elastic fibers in the ^'Intima. V Elastica interna. lii^^'-^S^^ik /'Media. > <.,»"»»_ Fenestrated elastic ■ membrane. Inner layer of the adventitia with ■• longitudinally ar- ranged muscle- cells. Connective tissue of the adventitia. Nerve. Fig. 167. — Cross-section of human internal jugular vein. At the left of the nerve are two large blood-vessels with a smaller one between them (vasa vasorum) ; X I S°- circular muscular layer are fewer, and the longitudinal strands are almost entirely lacking (H. Triepel). The walls of the smaller arteries consist mainly of the circular muscular layer of the media. The intima is reduced to the endo- thelium, which rests directly on the elastic internal limiting mem- brane. Outside of the external limiting membrane is the adventitia, which now consists of a small quantity of connective tissue. The vasa vasorum have disappeared. To this type belong the supra- orbital, central artery of the retina, etc. In the so-called precapillary vessels the intima consists only Digitized by Microsoft® THE VASCULAR SYSTEM. 197 of the endothelial layer. The internal elastic membrane is very delicate. The media no longer forms a continuous layer, but is made up of a few circularly disposed muscular fibers. The adven- titia is composed of a small quantity of connective tissue, and con- tains no vasa vasorum. (b) Veins. — In the foregoing account of the structure of the arteries we have described the structure of their walls according to the caliber of the vessels. Such a differentiation in the case of the veins would be impossible, since sometimes veins of the same cali- ber present decided differences in structure in various parts of the body. For the sake of convenience, we will commence with the de- scription of a vein of medium size. Its intima consists of three layers : (1) Of an inner layer of endothelium ; (2) of an underly- ing layer of muscle-cells, interrupted here and there by connective tissue ; and (3) of a fibrous connective-tissue layer containing fewer elastic but more white fibrous connective -tissue fibers than is the case in the arteries. Externally, the intima is limited by an in- ternal elastic layer. The . . media is in general less highly developed than that of a corresponding artery, and contains muscle-cells which have a circular ar- rangement which in some veins form a continuous layer, although they some- times occur as isolated fi- bers. The adventitia shows an inner longitudinal muscular layer, which may be quite promi- nent and even form the bulk of the muscular tissue in the wall of the vein. Otherwise the adventitia of the veins belonging to this class corresponds in general to that of the arteries of the same size ; but here also we have, as in the intima, a preponderance of white fibrous connective -tissue elements. In the crural, brachial, and subcutaneous veins, the muscula- ture of the media is prominent ; while in the jugular, subclavian, and innominate veins, and in those of the dura and pia mater, the muscular tissue of the media is entirely wanting, and, as a conse- quence, the adventitia with its musculature, if present, is joined directly to the intima. In the smaller veins the vascular wall is reduced to an endothe- lial lining, an internal elastic membrane, a media consisting of interrupted circular bands of smooth muscle-fibers (which may be absent), and an adventitia containing a few muscle -fibers. The precapillary veins, which possess in general thinner walls than the corresponding arteries, present a greatly reduced intima and ad- ventitia, while the media has completely disappeared. Media. Adventitia with nonstriated muscle-cells in cross-sec- tion. Fig. 168. — Section of small vein (human) ; X640. Digitized by Microsoft® 198 THE CIRCULATORY SYSTEM. The valves of the veins are reduplications of the intima and vary slightly in structure at their two surfaces. The inner surface next to the blood current is covered by elongated endothelial cells, while the outer surface possesses an endothelial lining composed of much shorter cellular elements. The greater part of the valvular structure consists of white fibrous connective-tissue and elastic fibers. Flattened and circularly arranged muscle-cells are met with at the inner surface of many of the larger valves. The elastic fibers are more numerous beneath the endothelium on the inner surface of the valves (Ranvier, 89). (c) The Capillaries. — The capillaries consist solely of a layer of endothelial cells, accompanied here and there by a very delicate struc- tureless membrane, and rarely by stellate connective-tissue cells. The connective tissue in the immediate neighborhood of the capillaries is modified to such an extent that its elements, especially those of a cellular nature, seem to be arranged in a direction parallel with the Fig. 169. -Endothelial cells of capillary (a) and precapillary (It) from the mesentery of rabbit ; stained in silver nitrate. long axis of the capillaries. When examined in suitable prepara- tions, the endothelium of the capillaries is seen to form a continuous layer, the cells of which are, as a rule, greatly flattened and present very irregular outlines. It is a well-known fact that a migration of the leucocytes occurs from the capillaries and smaller vessels (compare p. 175). In this connection arises the question as to whether or not the cells pass through certain preformed openings in the endothelium of these vessels, the so-called stomata, or through the stigmata and intercel- lular cement uniting the endothelial cells. The latter seems more probable, as stomata do not occur normally in the capillary wall. This subject will be further touched upon in the description of the lymphatic system. The capillaries connect the arterial and venous precapillary ves- sels, and in general accommodate themselves to the shape of the elements of tissues or organs in which they are situated. In the Digitized by Microsoft® THE VASCULAR SYSTEM. I 99 muscles and nerves, etc., they form a network with oblong meshes, while in structures having a considerable surface, such as the pul- monary alveoli, the meshes are more inclined to be round or oval ; such small evaginations of tissue as the papillae of the skin contain capillaries arranged in the shape of loops. In certain organs — as, for instance, in the lobules of the liver — the capillaries form a distinct network with small meshes. (d) Anastomoses, Retia mirabilia, and Sinuses. — In the course of certain vessels, abrupt changes are seen to occur — as, for instance, when a small vessel suddenly breaks up into a network of capillary or precapillary vessels, which, after continuing as such for a short distance, again unite to form a larger blood-channel, the latter then dividing as usual into true capillaries. Such struc- tures are known as retia mirabilia, and occur in man in the kid- Sensory nerve-ending. Plexus of vasomotor nerves. Fig. 170. — Small artery from the oral submucosa of cat, stained in methylene- blue, and showing a small portion of a sensory nerve-ending and the plexus of vasomotor nerves. ney, intestine, etc. Again, instead of breaking up into capillaries, a vessel may empty into a large cavity lined by endothelial cells (blood sinus). The latter is usually surrounded by loose con- nective tissue and is capable of great distention when filled with blood from an afferent vessel, or when the lumen of the efferent vessel is contracted by pressure or otherwise. The cavernous or erectile tissue of certain organs is due to the presence of such sinuses (penis, nasal mucous membrane, etc.). If vessels of larger caliber possess numerous direct communications, a vascular plexus is the result ; but if such communications occur at only a few points, we speak of anastomoses. Especially important are the direct communications between arteries and veins without the mediation of capillaries. Certain structural conditions of the tis- sue appear to favor such anomalies, which occur in certain exposed Digitized by Microsoft® 200 THE CIRCULATORY SYSTEM. areas of the skin (ear, tip of nose, toes) and in the meninges, kid- ney, etc. The blood-vessels, and more particularly the arteries, possess a rich nerve supply, comprising both nonmedullated and medullated nerves. The nonmedullated nerves, the neuraxes of sympathetic neurones, the cell-bodies of which are situated as a very general rule in some distant ganglion, form plexuses in the adventitia of the vessel-walls ; from this, single nerve-fibers, or small bundles of such, are given off, which enter the media and, after repeated division, end on the involuntary muscle-cells in a manner previously de- scribed. (Seep. 149 and Fig. 128.) Through the agency of these nerves, the caliber of the vessel is controlled. They are known as vasomotor nerves. Quite recently Dogiel, Schemetkin, and Huber have shown that many vessels possess also sensory nerve-endings. The medullated nerve-fibers terminating in such endings, branch repeatedly before losing their medullary sheaths. These nerve-fibers with their branches accompany the vessels in the fibrous tissue immediately surrounding the adventitia. The nonmedullated ter- minal branches end in telodendria, consisting of small fibrils, beset with large varicosities and usually terminating in relatively large nodules. The branches and telodendria of a single medullated nerve-fiber (sensory nerve) terminating in a vessel are often spread over a relatively large area, some of the branches of such a nerve often accompanying an arterial branch, to terminate thereon. In the large vessels, the telodendria of the sensory nerves are found not only in the adventitia, but also in the intima, as has been shown, by Schemetkin. (See p. 193.) B. THE LYMPHATIC SYSTEM. J. LYMPH-VESSELS. The larger lymph-vessels — the thoracic duct, the lymphatic trunks, and the lymph-vessels — have relatively thin walls, and their structure corresponds in general to that of the veins. They possess numerous valves, and are subject to great variation in cali- ber according to the amount of their contents. When empty, they collapse and the smaller ones are not easily distinguished from the surrounding connective tissue. Timofeew and Dogiel. (97) ha ,_ e shown that the lymph-vessels are supplied with nerves, which in their arrangement are similar to those found in the arteries and veins, though not so numerous. The latter, who has given the fuller description, states that the nerves supplying the lymph- vessels are varicose, nonmedullated fibers which form plexuses sur- rounding these structures. The terminal branches would appear to end on the nonstriated muscle cells found in the wall of the lymph-vessel. Digitized by Microsoft® THE LYMPHATIC SYSTEM. 201 2. LYMPH CAPILLARIES, LYMPH-SPACES, AND SEROUS CAVITIES. The walls of the lymph capillaries consist of very delicate, flat- tened endothelial cells, which are, however, somewhat larger and more irregular in outline than those of the vascular capillaries. The two may also be further differentiated by the fact that the diameter of the lymph capillaries varies greatly within very short distances. From a morphologic standpoint, the relations of the lymph capil- laries to the vascular capillaries and adjacent tissues are among the most difficult to solve. The distribution of the lymph-vessels and capillaries can be studied only in injected preparations, and it is easily seen that structures of such elasticity and delicacy are pecu- liarly liable to injury by bursting under this method of treatment. The resulting extravasations of the injection-mass then spread out in the direction of least resistance and still further obscure the picture, rendering it difficult to determine what spaces are preformed and what are the result of the injection. So much is, however, cer- tain : that the more carefully and skilfully the injection is made, the greater are the areas obtained, showing the injection of true lymph capillaries. In some regions very dense networks of lymph capillaries sur- rounding the smaller blood-vessels have been demonstrated. Larger cleft-like spaces, lined with endothelium and communicating with the lymphatic system, are also found surrounding the vessels, peri- vascular spaces. These are present in man in the Haversian canals of bone tissue, around the vessels of the central nervous system, etc., and are separated from the actual vessel-wall by flattened endo- thelial cells. As in the case of the so-called perilymphatic spaces, the walls of the perivascular spaces are joined here and there by connective-tissue trabecular covered by endothelium. Such struc- tures exist in the perilymphatic spaces of the ear, the subdural spaces of the pia, the subarachnoidal space, the lymph-sinuses, etc. The perivascular spaces are better developed in the lower animals (amphibia, reptilia, etc.) than in mammalia. The cell-spaces, with their anastomosing processes, found in con- nective tissue and previously described as the lymph-canalicular system, possess no endothelial lining and communicate directly or indirectly with the lymph capillaries. To the lymphatic system belong also the body-cavities, the pleural, pericardial, and peritoneal cavities. The walls of these consist of a connective-tissue stroma rich in lymph-spaces, lymph capillaries and lymph-vessels, and are lined by a layer of mesothelial cells. In them are found the stig- mata and stomata mentioned in a former section. (See p. 85.) The synovial spaces belong also to the lymphatic system ; they are lined by a layer of endothelial cells. Mention has been made of the migration of leucocytes and, under certain conditions, of red blood-cells through the walls of blood capillaries, and in the case of the former through the walls of Digitized by Microsoft® 202 THE CIRCULATORY SYSTEM. lymph capillaries and lymph-vessels and spaces. This diapedesis of leucocytes probably takes place by a wandering of these cells through the stigmata and intercellular cement uniting the endo- thelial cells lining these spaces, and through the stomata in regions where these occur. According to later investigations, it would seem that leucocytes may bore through endothelial cells, and thus migrate from the vessel or space in which they are found previous to such migration. Kolossow (93), as a result of his investigations, advances still another theory. He believes that he has demonstrated that the cells lining the body-cavities are joined to each other by protoplasmic processes, and that their inner surfaces are covered by a cuticular membrane. These structures are especially well seen in the serous membranes of certain reptiles. Between the cells and between the protoplasmic processes connecting them are spaces which may be compared to the intercellular spaces found in the epidermis. It is thought by him that on stretching the serous membranes, the spaces between the lining cells become larger, and the cuticular portions of the cells become separated from each other, and in this way the stomata and stigmata are thought to be tem- porarily formed, and through these the migration of the leucocytes is believed to occur. This process is also supposed to occur in the smaller vessels and in the vascular and lymphatic capillaries. How- ever, this whole question needs further investigation. C THE CAROTID GLAND (GLANDULA CAROTICA, GLOMUS CAROTICUM). At the point where the common carotid divides, there lies in man a small oval structure about the size of a grain of wheat, known as the carotid gland or the glomus caroticum. It is imbedded in connective tissue, surrounded by many nerve-fibers, and on account of its great vascularity has a decidedly red color. The connective- tissue envelope of the gland penetrates into the interior in the form of septa, which divide its substance into small lobules, and these in turn into smaller round masses, the cell-balls. A small branch from the internal or external carotid enters the gland, where it branches, sending off twigs to the lobules, and these in turn still smaller divisions to the cell-balls. The latter vessels break up into capillaries, which merge at the periphery of each cell-ball to form a small vein, from which the larger trunks that pass from the lobules are derived. Each lobule is thus surrounded by a venous plexus from which the larger veins originate that leave the organ at sev- eral points. The cell-balls are composed of cellular cords, or trabecular, the elements of which are extremely sensitive to the action of reagents. The cells are round or irregularly polygonal and separated from each other by a scanty reticular connective tissue. The capillaries already mentioned come in direct contact Digitized by Microsoft® THE CAROTID GLAND. 203 with the cells of the cell-balls. The organ contains a relatively large number of nerve-fibers, and a few ganglion cells. As the individual grows older, the organ undergoes changes which finally make it unrecognizable. The former belief that the carotid gland was developed as an evagination of one of the visceral pouches has been replaced by a newer theory which gives it an origin solely from the vessel-wall (vid. Schaper). The structure of the coccygeal gland is in general like that of the carotid gland here described. Septum. Trabecula of cells in cross- section. Distended blood capil- laries. Efferent vein. Fig. 171. — Section of a cell-ball from the glomus caroticum of man ; X IDO - (Injected specimen, after Schaper. ) TECHNIC (BLOOD AND BLOOD-FORMING ORGANS). 184. Red blood-corpuscles may be examined in the blood fluid without special preparation. The tip of the finger is punctured and a small drop of blood pressed out, placed upon a slide, and immediately covered with a cover-glass and examined. In such preparations the red blood- cells soon become crenated. The evaporation causing the crenation may be prevented by surrounding the cover-glass with oil (olive oil). A fluid having but a slight effect upon the red blood-cells is Hayem's solution, which, however, is not adapted to the examination of leucocytes. It consists of sodium chlorid 1 gm., sulphate of soda 5 gm., corrosive subli- mate 0.5 gm., and water 200 gm. The fresh blood is brought directly into this solution, the amount of which should be at least one hundred times the volume of the blood to be examined. The fixed blood-cells sink to the bottom, and after twenty-four hours the fluid is carefully poured off and replaced by water. The blood-corpuscles are then removed with a pipet and examined in dilute glycerin. They may be stained with eosin and hematoxylin. Digitized by Microsoft® 204 THE CIRCULATORY SYSTEM. 185. Fresh red blood-corpuscles may also be fixed in osmic acid and other special fixing agents. This is done by dropping a small quantity of blood into the fixing fluid ; the blood-cells immediately sink and allow the osmic acid to be decanted ; they are then washed with water, drawn up with a pipet, and examined in dilute glycerin. 186. A method almost universally used consists in preserving the blood-corpuscles in dry preparations. A drop of fresh blood is placed between two thoroughly cleaned cover-glasses, which are then quickly drawn apart, leaving on the surface of each a thin film of blood which dries in a few moments at ordinary room temperature. The specimens are further dried for several hours at a temperature of 120 C. After they have been subjected to this process, they may be stained, etc. 187. The same results may be obtained by treating specimens dried in the air with a solution of equal parts of alcohol and ether for from one to twenty-four hours, after which they are again dried in the air, and are then ready for further treatment. 188. A cover-glass preparation of fresh blood may also be treated for a quarter of an hour with a concentrated solution of corrosive sublimate in saline solution, then washed with water, stained, dehydrated with alcohol and mounted in Canada balsam. A concentrated aqueous solution of picric acid may also be used, but in this case the specimen should remain in it for from twelve to twenty-four hours. 189. The elements of the blood may also be examined in sections. Small vessels are ligated at both ends, removed, fixed with osmic acid, corrosive sublimate, or picric acid, and imbedded in paraffin. igo. After fixation by any of the above methods the blood-cells may be stained. Eosin brings out very well the hemoglobin in the blood- cells' coloring it a brilliant red ; the stain should be used in very dilute aqueous or alcoholic solutions (1% or less), or in combination with alum (eosin 1 gm., alum 1 gm., and absolute alcohol 200 c.c, E. Fischer). Eosin may also be used as a counterstain subsequent to a nuclear stain — for instance, hematoxylin. The preparation is stained for about ten min- utes, then washed in water or placed in alcohol until the blood-cells alone remain colored ; the cover -glass preparation should then be thoroughly dried between filter-paper and mounted in Canada balsam. Besides eosin, other acid stains — as orange G, indulin, and nigrosin — have the property of coloring blood-cells containing hemoglobin. 191. Blood platelets are best fixed with osmic acid, and may be seen without staining. They may also be stained and preserved in a sodium chlorid solution to which methyl-violet is added in a proportion of 1 : 20000 (Bizzozero, 82). Afanassiew adds 0.6% of dry peptone to the solution (this fluid must be sterilized before using). 192. The leucocytes of the circulating blood and those found in certain organs possess granulations which were first studied by Ehrlich and his pupils, and which may be demonstrated by certain methods. The names given to these granulations are based upon Ehrlich's classifica- tion of the anilin stains, which differs from that of the chemist. This author distinguishes acid, basic, and neutral stains. By the acid stains he understands those combinations in which the acid is the active staining principle, as in the case of the picrate of ammonia. Among these are congo, eosin, orange G, indulin, and nigrosin. The basic stains are Digitized by Microsoft® TECHNIC (BLOOD AND BLOOD-FORMING ORGANS). 205 those which, like the acetate of rosanilin, consist of a color base and an indifferent acid. To these belong fuchsin, Bismarck brown, safranin, gentian, dahlia, methyl -violet, methylene-blue, and toluidin. Finally, the neutral anilins may be considered as those stains which, like the pic- rate of rosanilin, are formed by the union of a color base with a color acid. The granula may be demonstrated in dry preparations as well as in those fixed with alcohol, corrosive sublimate, glacial acetic acid, and sometimes even Flemming's solution. Five kinds of granules are distin- guished, and designated by the Greek letters from alpha to epsilon. 193. The a-granules (acidophile, eosinophile) occur in leucocytes of the normal blood, in the lymph, and in the tissues, and are differen- tiated from the others by their peculiar staining reaction to all acid stains. They are first treated for some hours with a saturated solution of an acid stain (preferably eosin) in glycerin, washed with water, subsequently col- ored with a nuclear stain (as hematoxylin or methylene-blue), and then dried and mounted in Canada balsam. Sections may be treated in the same way, with the exception that after being washed with water, they are first dehydrated with absolute alcohol before mounting in balsam. ig4. Another method by which both nuclei and granules are stained consists in the use of Ehrlich's hematoxylin solution {vid. T. 63, page 42), to which 0.5% eosin is added. Before using, the solution should be permitted to stand exposed to the light for three weeks. This mixture stains in a few hours, after which the preparation is washed with water, treated with alcohol, and then mounted in Canada balsam. The a-granules appear red, the nuclei blue. 195. The /J-granules (amphophile, indulinophile) stain as well in acid as in basic anilins. They do not occur in man, but may be observed in the blood of guinea-pigs, fowl, rabbits, etc. They are demonstrated as follows : Equal parts of saturated glycerin solutions of eosin, naph- thylamin-yellow, and indulin are mixed, and the dried preparations treated with this combination for a few hours, then washed with water, dried between filter-paper, and mounted in Canada balsam. The amphophile granules are stained black, the eosinophile granules red, the nuclei black, and the hemoglobin yellow. ig6. The ^--granules, or those of the mast=cells, are found in normal tissues and also in small quantities in normal blood, and are found in larger numbers in leukemic blood. They may be shown by two methods : ( 1 ) A mixture is made consisting of concentrated solution of dahlia in glacial acetic acid 12.5 c.c, absolute alcohol 50 c.c, distilled water 100 c.c. (Ehrlich). The treatment is the same as for the amphophile gran- ules ; (2) Westphal's alum-carmin-dahlia solution {vid. Ehrlich). This mixture is used in staining dry preparations as well as sections of objects fixed for at least on"e week in alcohol. Alum 1 gm. is dissolved in dis- tilled water 100 c.c, and carmin 1 gm. added. The whole is then boiled for one-quarter hour, cooled, filtered, and 0.5 c.c. of carbolic acid added (Grenacher's alum-carmin, vid. T. 60). This solution is now mixed with 100 c.c. of a saturated solution of dahlia in absolute alcohol, glycerin 50 c.c, and glacial acetic acid 10 c.c, the whole stirred and allowed to stand for a time. The specimen is stained for twenty-four hours, decolorized in absolute alcohol for the same length of time, and finally mounted in Canada balsam. The ^-granules are colored a dark blue and the nuclei red. A simpler method of demonstrating the Digitized by Microsoft® 206 THE CIRCULATORY SYSTEM. ^-granules consists in overstaining dry and fixed cover-glass preparations with a saturated aqueous solution of methylene-blue, decolorizing for some time in absolute alcohol, drying between filter-papers, and mounting in Canada balsam. 197. The ^-granules (basophile) occur in mononuclear leucocytes of the human blood. Their staining may be accomplished in a few min- utes by treating fixed cover-glass preparations with a concentrated aqueous solution of methylene-blue, after which they are washed with water, dried between filter-papers, and mounted in Canada balsam. 198. The e- or neutrophile granules which are found normally in the polynuclear leucocytes of man (as also in pus-cells), in some of the transitional cells, and in the myelocytes, are stained by Ehrlich as follows : 5 vols, of a saturated aqueous solution of acid fuchsin are mixed with 1 vol. of a concentrated aqueous solution of methylene-blue. To this 5 vols, of water are added, and the whole allowed to stand for a few days, after which the solution is filtered. This mixture stains in five minutes, and the specimen is then washed with water, etc. The neutrophile granules are colored green, the eosinophile granules red and the hemoglobin yellow. igg. Neutrophile and eosinophile granules may also be stained in Ehrlich' s neutrophile mixture : Orange G, saturated aqueous solution, . 130 to 135 c.c. Acid fuchsin, " " " . . 80 to 120 " Methyl-green, " " " . . 125 " Distilled water, 300 " Absolute alcohol, 200 " Glycerin, 100 " Mix the above quantities of orange G, acid fuchsin, water, and alco- hol in a bottle and add slowly, while shaking the bottle, the methyl-green and finally the glycerin. The cover-glass preparations should be fixed in the ether and alcohol solution for about one hour, or fixed with dry heat at a temperature of no° C. for from fifteen to thirty minutes. Float the preparation on a small quantity of the stain for about fifteen minutes, wash in water, dry and mount in balsam. The red blood-cells are stained a reddish -brown color (brick-color), all nuclei a light blue-green, the eosinophile granules a fuchsin-red, and the neutrophile granules a violet- red. Griibler, of Leipzig, has prepared a dry powder, known as the Ehrlich-Biondi-Heidenhain three-color mixture, which is prepared for use by making a 0.4% solution in distilled water, to 100 c.c. of which are added 7 c.c. of a 0.5% aqueous solution of acid fuchsin. 200. The hemoglobin shows itself in the form of crystals. In certain teleosts the crystals are formed in the blood-corpuscles around the nuclei and often within a short time after death. In old alcoholic specimens, hemoglobin crystals (blood crystals) are found in the vessels and were first discovered here by Reichert in the blood of the guinea-pig. They have been found in large quantities in the splenic blood of a sturgeon which had been preserved for forty years in alcohol. The hemoglobin crystals belong to the rhombic series of crystallographic classification. The simplest method of demonstrating hemoglobin crystals is probably the following : The blood is first defibrinated by whipping or agitating with mercury, after which process sulphuric ether is added, drop by drop, until the mixture has been made laky ; this change may be detected Digitized by Microsoft® TECHNIC (BLOOD AND BLOOD-FORMING ORGANS). 207 macroscopically by the sudden change from an opaque to a dark, trans- parent, cherry-red color. No red blood-cells should now be seen under the microscope. The preparation is placed on ice for from twelve to twenty-four hours after which a drop of the blood is placed on a slide. In half an hour it will be seen that the margin of the drop has begun to dry. A cover-slip is now applied and, after a few minutes, numerous crystals are seen to form at the margin of the drop, a process which may be followed under the microscope. Large hemoglobin crystals are ob- tained by Gscheidtlen as follows : Defibrinated blood is placed in a glass tube, which is then hermetically sealed. The blood is now sub- jected to a temperature of about 40 C. for two or three days ; if then the glass be broken and the blood poured into a flat dish, large hemoglobin crystals are immediately formed. 201. Crystals also appear if a drop of laky blood be placed in a thick solution of Canada balsam in chloroform and covered with a cover-slip. 202. Hemin crystals (Teichmann's ^r-s, crystals ; hemin is hematin-chlorid) in the shape of rhombic plates are very easily obtained from the blood. A drop of the latter is placed on a slide and care- fully mixed with a small drop of normal salt solution. This is then carefully warmed until the fluid evaporates and leaves a reddish - brown residue, after which a cover-glass is applied and glacial acetic acid added until the space between slide and cover -glass is filled. The prep- aration is now heated until the acetic acid boils. As soon as the latter evap- orates, Canada balsam may be brought under the cover-glass, thus producing a permanent specimen. AVhen fluids or stains suspected of containing blood are to be examined, the hemin crystals be- come of the utmost importance, as their demonstration is then a positive indication of the presence of blood. Fluids are evap- orated and treated with glacial acetic acid as above directed. Suspected blood stains on cloth are treated as follows : Small pieces are cut from the cloth in the region of the stain, soaked in normal salt solution, and the resulting fluid treated as above. If the stain is on wood or other solid object, the stain is scraped off and dissolved in normal salt and then tested for hemin crystals. Hemin crystals are almost or entirely insoluble in water, alcohol, ether, ammonia, glacial acetic acid, dilute sulphuric acid, and nitric acid. They are, however, soluble in potassium hydrate. 203. A third form of crystals occasionally found in the blood and frequently in the corpora lutea and, under pathologic conditions, also in apoplectic areas, are the hematoidin crystals first discovered by Yirchow. Masses of these crystals have an orange color. Microscopically, they appear as red rhombic plates. As they are soluble in neither alcohol nor chloroform, they are easily preserved in Canada balsam. Their Digitized by Microsoft® Fig. 172. — Fibrin from laryngeal vessel of child ; X about 300. 208 THE CIRCULATORY SYSTEM. artificial production has as yet never been accomplished. Hematoidin contains no iron. 204. The fibrin thrown down when the blood coagulates may be demonstrated upon the slide in the form of very fine particles and fila- ments. A drop of blood is brought upon the slide and kept for a time in a moist chamber or on the table until it begins to clot ; after which a cover-slip is applied and the preparation washed with water by continued irrigation. In this manner most of the red blood-corpuscles are removed. Lugol solution may now be added, which stains brown the filaments of the fibrin network adherent to the slide. In order to see the fibrin net- work in sections, it is better to use specimens previously fixed in alcohol ; the sections are stained for ten minutes in a concentrated solution of gen- tian-violet in anilin water (Weigert), rinsed in normal salt solution, treated for about ten minutes with iodo-iodid of potassium solution, and then spread upon a slide and dried with filter-paper. They are now placed in a solution consisting of 2 parts of anilin oil and 1 part of xylol until they become perfectly transparent. This solution is then replaced by pure xylol and finally by Canada balsam. The fibrin network is stained a deep violet. 205. There are different methods and a variety of material at our dis- posal for the demonstration of the blood current through the vessels. The best object for this purpose is probably the frog. The procedure is as follows : The animal is immobilized by poisoning with curare. y 2 gm. of a 1 °Jo aqueous solution injected into the dorsal lymph-sac will immobilize the frog in a short time. The exact dose can not, however, be given, as the commercial curare is not a uniform chemical compound ; the dose must therefore be ascertained by experiment. As is well known, curare affects exclusively the nerve end-organs of striated voluntary muscle, but does not affect either the heart muscle or unstriated muscular tissue ; hence the utility of curare for this purpose. In order to see the blood current, it is only necessary to stretch the transparent web between the frog's toes and fasten it with insect needles to a cork plate having a suitable open- ing. If the cork plate be large enough to accommodate the whole frog, it may be placed in such a position that its opening lies over that in the stage of the microscope. The web thus spread out may be examined with a medium magnification. The tongue of the frog is also used for the same purpose. As the latter is attached to the anterior angle of the lower jaw, it may be conveniently drawn out, suitably stretched, and then placed over the hole in the cork plate. A very good view of the circula- tion may be obtained by examining the mesentery of a frog. The migra- tion of the leucocytes through the vessel-walls can also be studied in such preparations. An incision o. 5 cm. in length is made in the right axillary line through the skin of a frog (best in the male), care being taken not to injure any vessels (which can be seen through the skin in frogs possessing little pigment) . The abdominal muscles are then incised and a pair of forceps introduced to grasp one of the presenting intestinal loops. The latter is then attached to the cork plate with needles, and the mesentery carefully stretched over the opening. On examining the specimen it is best to moisten it with normal salt solution and to cover the area to be examined with a fragment of a cover-glass. The lung may also be exam- ined, but here the incision must be farther forward. 206. To obtain a general idea of the structure of lymphatic glands, Digitized by Microsoft® TECHNIC (BLOOD AND BLOOD-FORMING ORGANS). 200. sections are made of small glands fixed in alcohol or corrosive sublimate. They are then stained with hematoxylin and eosin. In such preparations the cortical and medullary substances can be studied ; the trabecule and blood take the eosin stain. 207. The flattened endothelial cells covering the trabecule are brought to view by injecting a o. 1 c / c solution of silver nitrate into a fresh lymph- atic gland. After half an hour the gland is fixed with alcohol and car- ried through in the regular way ; the sections should be quite thick (not under 20 /jl). After the sections have been mounted in Canada balsam and exposed to light for a short time, the endothelial mosaic will be seen wherever the silver nitrate has penetrated. 208. Fixing with Flemming's solution and staining with safranin is the best method for studying the germ centers of the lymph-follicles. Other fluids which bring out the mitoses may also be employed. 209. Reticular tissue is best demonstrated by sectioning a fresh gland with a freezing microtome, removing a section to a test-tube one-quarter filled with water, and agitating it. The lymphocytes are thus shaken out of the meshes of the reticulum, leaving the latter free for examination. 210. The same results can be obtained by placing a section prepared in the above-named manner upon a slide, wetting it with water, and carefully going over it with a camel's-hair brush. The lymphocytes ad- here to the brush. Both methods (His, 61) may be applied to hardened sections which have lain in water for a day or so. In this case, how- ever, the removal of the lymphocytes is not so easy as in fresh sections. 211. In thick sections the reticulum is hidden by the lymphocytes. If, on the other hand, very thin sections (not over 3 11) be made, especially of objects fixed in Flemming's solution, the adenoid reticulum stands out clearly without any further manipulation. 212. The reticular structure may also be demonstrated by an artificial digestion of the sections with trypsin. The sections are then agitated in water, spread on a slide, dried, then moistened with a picric acid solu- tion (1 gm. in 15 c.c. of alcohol and 30 c.c. of water), again dried, cov- ered with a few drops of fuchsin S solution (fuchsin S 1 gm., alcohol 33 c.c, water 66 c.c), and left to stand for half an hour. The fuchsin solution is then carefully removed, the section washed again for a short time in the same picric acid solution, then treated with absolute alcohol, xylol, and finally mounted in Canada balsam. The reticular tissue of both lymphatic glands and spleen are stained a beautiful red (F. P. Mall). 213. The treatment of splenic tissue is practically the same as that of the lymphatic glands. 214. In all these organs (lymph-glands, spleen, and bone-marrow) a certain amount of fluid may be obtained by scraping the surface of the fresh tissue. This may then be examined in the same manner as blood and lymph (see Technic of same). Sections of lymph-glands and spleen previously fixed in alcohol, mercuric chlorid, or even in Flemming's solution may be examined by the granula methods of Ehrlich. 215. By using the chrome-silver method a peculiar network of retic- ular fibers may be seen in the spleen. (Gitterfasern ; Oppel, 91.) 216. The examination of the bone-marrow belongs also to this chap- ter. The marrow of the diaphysis is taken out by splitting the bone 14 Digitized by Microsoft® 2IO THE DIGESTIVE ORGANS. longitudinally with a chisel. With a little practice, it is easy to obtain small pieces of the marrow, which are then fixed by the customary methods and cut into sections. In the epiphysis the examination is confined either to the pressing out of a small quantity of fluid with a vice, or to the decalcification of small masses of spongy bone, containing red bone-marrow. In the first case, methods applicable to blood examina- tion are employed ; in the second, section methods (see also the petrifi- cation method, T. 158) are used. The methods given for the prepara- tion of lymph-glands and spleen are also applicable in many cases. 217. Enderlen has demonstrated reticular fibers (Gitterfasern) in the bone-marrow by means of the chrome-silver method. TECHNIC (CIRCULATORY SYSTEM). 218. To obtain a topographical view of the layers composing the heart and vessels, sections are made of tissues that have been fixed in Miiller's fluid, chromic acid, etc. If the specimens are to be studied in detail, small pieces must be used, and are best fixed in chromic-osmic mixtures or corrosive sublimate. Celloidin imbedding is recommended for general topographic work. The further treatment is elective. 219. The endothelium of the intima may be brought to view by silver nitrate impregnation methods, by injecting silver solutions into the vascu- lar system, etc. (jvid. T. 109). The endothelial elements of the smallest vessels and capillaries are then clearly defined by lines of silver. Larger vessels must be cut open, the intima separated, and pieces of its lamellae examined. 220. With regard to the isolation of the muscle-cells of the myocar- dium and of the walls of the vessels, see T. 170 to 172. 221. Elastic elements, plates and networks are best observed in the tunica media of the vessels, very small pieces of which are treated for some hours with 33% potassium hydrate. 222. The appropriate stains for sectionwork are those which bring out the elastic elements and the smooth muscle-cells. For the former, orcein is used (vid. T. 138). 223. For demonstrating the distribution of the capillaries, the reader is referred to the injection methods {vid. T. 100 et seq.) The lymph- capillaries are injected by puncture (T. in) ; compare also the methods of Altmann (T. 112). III. THE DIGESTIVE ORGANS. The intestinal canal with the glands derived therefrom originates from the inner layer of the blastoderm, the entoderm. The latter, however, does not extend to the external openings of the body, as the ectoderm forms depressions at these points which grow inward toward the still imperforate fore and hind gut to communicate finally with its lumen. This applies as well to the formation of the primitive oral cavity, which is separated only secondarily into oral and nasal cavities, as to the anus. The anterior boundary Digitized by Microsoft® THE ORAL CAVITY. 2 I I between the ectodermal and entodermal portions of the digestive tube consists of a plane passing through the opening of the pos- terior nares and continued downward along the palatopharyngeal arch. Everything lying anterior to this is of ectodermal origin, therefore the entire oral and nasal cavities with their derivatives. The lining of these cavities consists, however, of a true mucous membrane, closely resembling in its structure that of the intestinal tract. A. THE ORAL CAVITY. The epithelium of the oral mucous membrane is of the stratified squamous type, differing from the epithelium of the epidermis in that the stratum granulosum does not appear here as an inde- pendent layer. The stratum lucidum is also wanting, and the cornification of the layer analogous to the stratum corneum of the skin is not complete (compare Skin). In the mucous membrane the cells of even the most superficial layers contain nuclei, which, although partly atrophied, still show chromatin, and as a conse- quence are easily demonstrated. Beneath the epithelium lies a tissue of mesodermic origin, also belonging to the mucous membrane and known as the mucosa or stratum proprium (lamina propria, tunica propria), in which nu- merous glands are situated. The mucosa consists of a fibrillar connective tissue with few elastic fibers, and of adenoid tissue containing numerous lymphoid cells ; essentially, therefore, a diffusely distributed adenoid tissue with occasional lymph-follicles imbedded in its substance. The mucosa presents numerous papillae, which are either simple or compound (branched) eleva- tions of the mucosa, varying in length and density, according to their location and extending for variable distances into the over- lying epithelium. As in the papillary layer of the corium (see Skin), so also here the superficial layer of the stratum proprium contains very fine elastic and connective-tissue elements which con- tribute to the structure of the papillae. All these papillae contain capillaries and arterioles which are derived from an arterial network in the mucosa. The lymphatics are similarly arranged. At the red margin of the lips the papillae are unusually high and are covered at their summits by a very thin epithelial layer (Fig. 173). Besides the sebaceous glands which lie at the angles of the mouth, and whose ducts open at the surface, there are here no other glandular structures. In the mucosa of the mucous membrane of the lips and cheeks the papillae are low and broad ; here also open the ducts of compound lobular, alveolar glands, the glandulcz labiates and buccales whose structure is similar to that of the large salivary glands (see these). The gums possess very long and attenuated papillae, covered by a very thin layer of epithelium, therefore bleeding at the slightest injury. That part of the gum Digitizeaby Microsoft® 212 THE DIGESTIVE ORGANS. covering the tooth has no papillae. The gums contain no glands. The papillae of the hard palate are arranged obliquely, with their points directed toward the opening of the mouth. The papillae of the soft palate are very low and may even be absent. They are somewhat higher on the anterior surface of the uvula. On the posterior surface of the latter occur ciliated epithelia distributed in islands between the areas of stratified squamous epithelium. In the soft palate and uvula are found small mucous glands. Under the mucous membrane there is a layer consisting princi- Transitional zone with irregular papilla;. n_ Hairfol- C->7 licks. Epider- mis. Duct of gland. Epithe - 1 i u m of mu- cous mem- brane. Gland. Fig- '73- — Section through the lower lip of man ; Y 18. pally of connective tissue and elastic fibers, the submucosa (stratum submucosum, tela submucosa). In the mucous membrane of the mouth the transition of the tissue of the mucosa into that of the submucosa is very gradual. The submucosa of the hard palate is closely connected with the periosteum and contains, especially at its posterior portion, numerous glands. In other regions of the mouth (lip) the glands extend also into the submucosa. The mucosa and epithelium lining the mouth cavity are richly supplied with nerves which terminate either in special sensory Digitized by Microsoft® THE ORAL CAVITY. 213 nerve-endings or in free sensory nerve-endings, or on the blood- vessels. In the papillae of the mucosa are found corpuscles of Krause. (See p. 154.) The nerves terminating in free sensory endings are the dendrites of sensory neurones (medullated sensory nerves), which, while yet medullated, branch and form plexuses with large meshes, situated in the submucosa and deeper portion of the mucosa. The medullated branches of the nerve-fibers constitut- ing these plexuses proceed toward the epithelium, dividing further in their course. Immediately under the epithelium the medullated branches lose their medullary sheaths, divide further, and form the subepithelial plexuses. The nonmedullated branches enter the epithelium, where they form telodendria (end-brushes), the terminal branches of which surround the epithelial cells, between which they end either in very fine granules or in small groups of such, or, again, in variously shaped end-discs. (See Fig. 130.) The blood- vessels are richly supplied with vasomotor nerves, the neuraxes of sympathetic neurones, which terminate on the muscle-cells of the vessels. In the adventitia are also found free sensory nerve- endings. (See Fig. 170.) J. THE TEETH. Structure of the Adult Tooth. — The adult tooth is made up of three substances — the enamel, the dentin, and the cementum. The latter covers that part of the tooth within the alveolar process of the jaw and also the root of the tooth. The enamel caps that part of the tooth projecting into the oral cavity, the crown of the tooth. The neck of the tooth is the region where the cementum and enamel come in contact. The greater part of the tooth consists of dentin, which is present in the crown as well as in the root. All the substances of the tooth just mentioned become very hard from the deposition of lime -salts. Every tooth contains a cavity sur- rounded by dentin, the pulp cavity, or dental cavity. This is filled with a soft tissue, the pulp, consisting of white fibrous tissue, ves- sels, and nerves. That part of the pulp cavity lying in the axis of the fang is called the root-canal ; by an opening in the latter (fora- men apicis dentis) the pulp is connected with the periosteal con- nective tissue of the dental alveolus. The enamel is a very hard substance, the hardest in the body, and may be compared to quartz. In uninjured teeth the enamel is covered by an exceedingly thin, structureless enamel membrane (cuticula dentis). The enamel contains very little organic substance (from 3 fo to 5 fo), in consequence of which it is soluble in acids with scarcely any residue. The elements composing it are prismatic columns, the enamel prisms, which occupy the whole thickness of the enamel from the superficial membrane to the dentin. These are thicker at the surface of the tooth than at the dentin, and in trans- verse section show a hexagonal or polygonal shape. They are Digitized by Microsoft® 214 THE DIGESTIVE ORGANS. course through Pulp cavity. joined to each other by a cement-substance which is somewhat more resistant than the substance of the prisms themselves. In the adult they are entirely homogeneous, but in embryos and even in the new-born they show a (fibrillar) longitudinal striation. In their the thickness of the enamel they change their direction by a series of symmetrical curves, and cross each other in groups in a typical manner. There are also seen in the enamel the parallel lines known as the lines of Retzius (see Fig. 174), which are to be regarded as traces of the strata caused by the peri- odic deposition of lime- salts ; they are very vari- able, as their structure depends on the nutritive condition during the depo- sition of the lime - salts (Berten). The dentin is, next to the enamel, the hardest tissue of the tooth. After its decalcification a sub- stance is left which yields gelatin. The dentin is permeated by a system of canals having usually a transverse direction, the so-called dentinal tubules, which are from 1.3 /x to 4.5 {J. in diameter. These originate in the pulp cav- ity, and during their course become slightly curved, like the letter S- At their outer third they branch and become constantly smaller. As a rule, they extend as far as the en- amel, although a few now and then even cross the boundary of the enamel. They never reach the cement, but leave here a free zone in which the ground-substance of the dentin alone is present. The dentinal tubules possess sheaths, the sheaths of Neumann, which may be isolated, analogous to the sheaths of the canaliculi of bone, and which contain throughout their entire length filiform prolonga- Dentin. Cementun Fig. 174. — Scheme of a longitudinal section through a human tooth. In the enamel are seen the "lines of Retzius." Digitized by Microsoft® THE I'EETH. 215 tions of certain pulp-cells (odontoblasts), the dentinal fibers. Ac- cording to v. Ebner, the ground-substance of the dentin consists of bundles of connective-tissue fibrils, which in the root run parallel to the long axis of the tooth, and in the crown have a direction at right angles to that of the dentinal tubules. The S-shaped curves of the latter give rise to the lines of Schrager in the dentin, which are visible with an ordinary magnifying glass. Peculiar, irregularly branched spaces are often seen in the dentin. These are the inter- globular spaces, and represent areas in which calcification has not taken place. The cementum is closely adherent to the dentin, and consists of Enamel. ._ Branching of the dentinal tubules. Dentinal tubules. Interglobular ^| space. Fig. 175. — A portion of a ground tooth from man, showing enamel and dentin ; X 1 7°- Technic No. 225. bone tissue, the parallel lamellae of which contain, as a rule, no Haversian canals. There occur, however, cement lamellae, which in places lose their bone-cells. A peculiarity of the cementum is the presence of a large number of Sharpey's fibers, which are especially abundant in those areas containing no bone-corpuscles. These fibers are usually found in an uncalcified condition. The tooth-pulp is a tissue resembling embryonic connective tis- sue, consisting of connective -tissue fibrils, branched connective- tissue cells, and a semifluid, interfibrillar ground-substance. It is characteristic of this tissue that the fibrils never join to form con- nective-tissue fibers. At the surface of the pulp is a continuous Digitized by Microsoft® 2l6 THE DIGESTIVE ORGANS. layer of cells, the odontoblasts. These are columnar cells with basal nuclei and two or three processes extending into the can- aliculi of the dentin, forming here the dentinal fibers already de- scribed. As a rule, the odontoblasts also send a single fiber into the pulp. These may intertwine and give rise to a network within its substance. The tooth is joined to the periosteum of the alveolus by a re- duplication of the latter over its root, the dental periosteum or peridental membrane. This consists of bundles of connective tissue (elastic fibers are here absent) directly continuous with Sharpey's fibers in the cementum. At the neck of the tooth the peridental membrane disappears in the submucosa of the gum ; in D d -- b Fig. 176. — A, Longitudinal section through a human molar from the center of the enamel layer, decalcified with dilute hydrochloric acid ; B, tangential, C, radiate, and X), transverse section through the dentin of a human tooth, showing the fibrillar struc- ture of the ground-substance (taken from v. Ebner, 91) : n and b, Two layers in which the direction of the enamel prisms changes ; in c is seen a dentinal fiber with its sheath ; e, groups of fibrils ; d t dentinal tubules. the former are found here and there peculiar masses of epithelial cells representing the remains of the enamel organs. The tooth-piilp has a rich blood supply. A small artery enters the pulp cavity through the apical foramen, which, as it passes up through the pulp, gives off numerous smaller branches which end in a capillary network situated under the layer of odontoblasts. Numerous medullated nerve -fibers (dendrites of sensory neurones) enter the pulp cavity through the apical foramen. Some of these lose their medullary sheaths soon after entering, or just before entering, the pulp, and divide into long, fine, varicose fibers which interlace to form a loose plexus under the odontoblasts. Other Digitized by Microsoft® THE TEETH. 217 Cementum medullated fibers, grouped into small bundles, ascend in the pulp for variable distances ; the nerve-fibers of the bundles then sepa- rate and as single fibers approach the superficial portion of the pulp, and, after losing their medullary sheaths, divide into fine varicose fibers forming under the odontoblasts a plexus continuous with the plexus above mentioned. From the varicose nerve-fibers of this plexus small terminal branches are given off which termi- nate between the odontoblasts, or pass through the layer of odontoblasts, to end between these and the dentine (Retzius, 94 ; Huber, 98). Medullated nerve-fibers also terminate in free end- ings in the peridental membrane. Development of the Teeth. — In the second month of fetal life the first traces of the teeth are seen in the development of a groove along the inner edge of the fetal jaw, the dentinal or en- amel groove. From the floor of the latter an epithelial ridge is formed constituting the anlage of the enamel organs and known as the dentinal ridge, or enamel ledge. At those points at which the milk-teeth later appear, the enamel ledge develops solid protuberances corre- sponding in number to the temporary teeth. These are known as the dentinal bulbs or enamel germs. In their first stage of development the enamel germs are knob- like, but later their bases spread, and they become flattened and finally cup- shaped by the pushing up into them of connective - tissue projections, the den- tinal papillce. At the same time they gradually sink deeper into the underlying tissue, but still remain con- nected, by means of a thin cord, with the epithelium of the enamel ledge, which now lies on the inner side of the .enamel germs. The enamel germs now differentiate into enamel organs. In this stage they consist of an outer layer of columnar epithelial cells, which are to be regarded as a direct continuation of the basal cells from the epithelium of the oral mucous membrane, or still better, of the enamel ledge ; the epithelium in the interior of the organ is derived from the stratum Malpighii of the oral epithe- lium. The cells of this layer, however, undergo a change in shape and structure, in that an increased quantity of lymph-plasma or intercellular substance collects in the interspinous spaces between the cells, pushing the cells apart, and allowing their processes to Fig. 177. — Cross-section of human tooth, showing cement and dentin; X 212 - Technic No. 225 (viit. also Technic 152). At a are seen small interglobular spaces (Tomes' granular layer) . Digitized by Microsoft® 2l8 THE DIGESTIVE ORGANS. develop until the cells finally assume a stellate shape. In this way the enamel pulp is gradually formed. The next stage is character- ized by a vertical growth of the dentinal papillae, which soon be- come surrounded on all sides by the cap-like enamel organs. The cylindric cells (enamel cells) of the enamel organs lying next to the papillae become lengthened, and after passing through further changes, finally develop into the enamel prisms of the teeth. At the periphery of the dentinal papillae, there is differentiated a layer of columnar cells, the odontoblasts, which have a connective-tissue origin, and later form the dentin. During these processes a connective -tissue mantle, the dental sac, rich in cellular and fibrous elements, is formed around each tooth anlage. The earliest appearance of the enamel is in the form of a cuticu- lar membrane, developed from the ends of the enamel cells resting on the dentinal papilla, this cuticular membrane appearing in the form of a thin layer covering the top of the dentinal papilla. Some time later, short striated processes — Tomes' processes — appear on the Odontoblasts. Odontoblasts. Terminal nerve- fiber. Terminal nerve- fiber. Fig. 178. — Nerve termination in the pulp of a rabbit's molar, stained in methylene- blue (intra vitam) : a, Odontoblasts seen in side view ; b, a number of odontoblasts seen in end view, showing a terminal branch of a nerve-fiber situated between the odonto- blasts and the dentin (Huber, "Dental Cosmos," October, 1898). lower end of each of the enamel cells (the end toward the dentinal papilla). These are imbedded in a cement-substance, forming a continuous layer. The Tomes' processes are regarded as the be- ginnings of the enamel prisms. Calcification begins in the middle of these processes ; they thicken at the expense of the cement- substance surrounding them, which later also calcifies. The enamel as a whole thickens by the elongation of the Tomes' processes of the enamel cells and by their subsequent calcification. The process ends finally in the death and partial absorption of the enamel cells and the remaining elements of the enamel organs ; these structures persist for a short time after the eruption of the tooth as a cuticular sheath. The dentin is developed by the odontoblasts by a process analogous to that observed in the formation of bone by the osteo- blasts. These epithelioid cells secrete at their outer surfaces a Digitized by Microsoft® &■ CuiM - p Fig. 179. "%?•*:■ Fig. 1S0. 4~~~-^- E# V/:; ;■.%-$# :1W' : . ; Fig. 181. Fig. 182. Figs. 179-182. — Four stages in the development of a tooth in a sheep embryo (from the lower jaw) : Fig. 179, Anlage of the enamel germ connected with the oral epithelium by the enamel ledge; Fig. 180, first trace of the dentinal papilla; Fig. 181, advanced stage with larger papilla and differentiating enamel pulp ; Fig. 182, budding from the enamel ledge of the anlage of the enamel germ, which later goes to form the enamel of a permanent tooth ; at the periphery of the papilla the odontoblasts are beginning to differentiate. Figs. 179, 180, and 181, X IIQ ; F 'g- l82 » X 4°- a, a, a, a, Epithelium of the oral cavity ; b, b, b, b, its basal layer ; c, c, c, the superficial cells of the enamel organ; d,d,d,d, enamel pulp; p,p,p, dentinal papilla; s, s, enamel-forming elements (enamel cells) ; 0, odontoblasts ; S, enamel germ of the permanent tooth ; v, part of the enamel ledge of a temporary tooth ; u, surrounding connective tissue. 219 Digitized by Microsoft® 220 THE DIGESTIVE ORGANS. Enamel pulp. - Enamel cells. 1 homogeneous substance which fuses to form a continuous layer, the membrana prmformativa. The further development of the dentin is as follows : Its ground-substance is deposited at the cost of the lateral portions of the odontoblasts (under the membrana praeforma- tiva), the axial portion of the cells remaining intact as the dentinal fibers ; the basal portions of the cells containing the nuclei persist, later constituting the odontoblasts of the adult pulp. By the fusion of the segments of the ground-substance formed by each cell, it becomes a homogeneous mass, but soon displays connective-tissue fibrils which gradually undergo a process of calcification. The mem- brana pra^formativa has no fibers and calcifies much later. It lies im- mediately beneath the enamel or the cementum, and in the normal tooth always contains small in- terglobular spaces. In the adult tooth this mem- brane in its entirety is known as Tomes' gran- ular layer. The cementum is merely a periosteal growth of bone originat- ing in the tissue of the dental sac and adhering to the dentin. Although at first the enamel or- gan almost entirely sur- rounds the dentinal pa- pilla, later a portion of that part of it in the re- gion of the fang is ab- sorbed in order to allow the cementum to reach the surface of the dentin. Remains of this regressive portion persist as the epithelial nests of the dental root (compare p. 216). The contents of the dentinal papillae change into the tissue of the dental pulp. As early as the third month outgrowths appear on the inner side of the enamel ledge next to the partly developed milk-teeth, which represent the anlagen of the enamel organs of the permanent teeth. Their further development is similar to that of the milk teeth. The enamel organs of the molars are also developed from an enamel ledge which is practically a backward continuation of the embryonic enamel ledge. With their crowns presenting, the temporary teeth -Odontoblasts. Fig. 183. — A portion of a cross-section through a developing tooth (later stage than in Fig. 182) ; X 720 : The dentin is formed, but has become homo- geneous from calcification. Bleu de Lyon differen- tiates it into zones (a and b). At c is seen the in- timate relationship of the odontoblasts to the tissue of the dental pulp. Digitized by Microsoft® THE ORAL CAVITY. 221 at last break through the epithelium of the gums. When the de- velopment of the permanent teeth is so far advanced that they are ready to perforate, regressive processes begin at the roots of -the milk-teeth, which are due, as in like conditions of the bone, to the action of certain cells, which are here known as " odontoclasts." The crowns of the milk-teeth are then thrown off, one by one, by the growing permanent teeth . For further information as to the teeth and their development, see the articles by Ebner (91), whose studies we have to a great ex- tent followed on this subject. , 2. THE TONGUE. The Lingual Mucous Membrane and its Papillae. — The mucous membrane of the tongue differs in general very little from *S Fig. 184. — Fungiform papilla from human tongue. that lining the rest of the oral cavity. It must, however, be borne in mind that in the greater part of the tongue the submucosa is poorly developed, and as a consequence the mucous membrane on the upper surface and base of. the tongue is scarcely movable. Other peculiarities of the lingual mucous membrane are the absence of glands in the mucosa on the upper surface of the tongue, — although glands are found in the musculature of the tongue, their ducts passing through the mucosa, — the presence of epithelial papillae, and of lymph -follicles at the base of the tongue. The upper surface of the tongue is roughened by the presence of epithelial projections, the lingual papilla. The latter are almost entirely epithelial structures, and should not be confused with those papillae which are composed exclusively of connective tissue. There Digitized by Microsoft® 222 THE DIGESTIVE ORGANS. are several classes of lingual papillae — the filiform, the fungiform, and the circumvallate papillae. The most numerous are the thread- like or filiform papilla (from 0.7 to 3 mm. long). These are scat- tered over the entire upper surface of the tongue, and consist of conic projections of the epithelium and of the mucosa. The con- nective-tissue portions of these papillae are very thin and long. The basal layers of the epithelium can not be distinguished from the same layers covering the surrounding mucosa, but the more super- I Papilla filiformis. -Connective-tissue papilla. m r X^iy-^jll ^.L)-_ Mucosa. < ' «' -Basal epithelial layer. Fig. 185. — From a cross-section of the human tongue, showing short, thread-like papillae (filiform) ; X J 4°- ficial layers are differentiated, in that their cells are arranged parallel to the long axes of the papillae and overlap each other like tiles (Fig. 185). Their free ends are often continued into several spine- like processes. Less numerous than the filiform are the fungiform papilla (from 0.7 to 1.8 mm. in height) scattered here and there between the former. They are nearly hemispheric in shape, and are joined to the surface of the tongue by a slightly constricted base. At times they are even partly sunk into the mucous membrane. The mucosa is raised under the epithelium to form connective-tissue papilla? (Fig. 184). On the free surface of the fungiform papillae Digitized by Microsoft® THE ORAL CAVITY. 223 are sometimes found taste-buds, or taste-goblets, which lie im- bedded in the epithelium and extend through its entire thickness. The circumvallate papillce occupy a definite region on the upper surface of the tongue, and are arranged in two rows, forming almost a right angle, with the apex directed backward and situated just in front of the foramen caecum (Morgagni). These papillae are few in number, about eight to fifteen in all. In shape they are similar to those of the fungiform type, but are much larger (about 1 or 2 mm. in diameter), and sunk so deeply into the mucous membrane that the latter forms a wall around their sides. Here also the mucosa passes up into the papillae and forms con- nective-tissue papillae of its own at the upper surface, while at the sides it merely adheres to the smooth inner surface of the epithelial layer. Taste -buds are found in the epithelium at the sides of the papillae, and also in that of the ridges surrounding the papillae. At the sides of the human tongue and near its base are the so-called fimbria HngicoB. These are irregular folds of mucous membrane, -*n & ~"»k W3® Fig. 186. — Longitudinal section of foliate papilla of rabbit, showing taste-buds. the sides of which also contain taste -buds. In the rabbit they are more regular in structure and consist of parallel folds of mucous membrane thickly dotted with taste-buds, and are termed the foliate papilla. In place of the circumvallate papillae, the guinea-pig pos- sesses structures similar to the foliate papillae of the rabbit. Into the depressions in which the circumvallate papillae lie and into those between the folds of the fimbriae linguae open the ducts of numerous serous glands, the glands of Ebner (see below). The Taste-buds. — The gustatory organs in the form of taste- buds are found on the surface of the tongue, principally on the lateral surfaces of the circumvallate papillae and the fimbriae linguae (foliate papillae). They are also occasionally met with in the epithelium of the fungiform papillae and the soft palate, and on the posterior surface of the epiglottis. They always lie imbedded in the epithelium and extend through its entire thickness ; they are ovoid in form, with base downward and the smaller pole at the Digitized by Microsoft® 224 THE DIGESTIVE ORGANS. surface. The whole structure is surrounded by the epithelium of the mucous membrane of the regions in which they occur, except at the attenuated outer end of the taste-bud, where, by means of a small opening, the taste-pore, it communicates with the oral cav- ity. Most of the cells constituting the taste-buds are elongated, spindle-shaped structures, extending from one end of the organ to the other, with spaces between them. There are four varieties of these cells : (i) The outer sustentacular or tegmental cells, lying at the periphery of the organ with a nucleus in their center, and having a short, cone-shaped cuticular projection ; (2) the inner sustentacular or rod-shaped cells, which are more slender structures with basally situated nuclei and without a cuticular projection ; between the latter are (3) elongated, spindle-shaped, neuro-epithe- Epithelium. Taste-buds. Groove sur- rounding \ \ papilla. Fig. 187. — Longitudinal section of a human circumvallate papilla ; X 2 °- lial cells, with the nucleus of each in the thickest portion of the cell, and with slender, stiff processes projecting into the taste-pore ; . (4) a few broad basal cells, communicating with each other as well as with the sustentacular cells by numerous processes. We have, therefore, in the cells of the first, second, and probably fourth varieties, elements which belong exclusively to the sustentacular apparatus of the organ (Hermann, 85, 88). Von Ebner found in the taste-buds of the circumvallate papillae of man, monkey, and cat, as well as of the papillse foliata; of the rabbit, an open space situated between the taste-pore and the tip of the taste-bud (Fig. 188). These spaces vary according to the species, and are bounded above by the summits of the tegmental cells and laterally and below by the more centrally situated sus- Digitized by Microsoft® THE ORAL CAVITY. 225 Process of Epithe- lium. tentacular cells. The cavities are often 10 p. in depth, and are filled with a fluid apparently in communication with the fluid .of the depression into which the circumvallate papillae are sunk. The processes of the neuro-epithelial cells project into the cavity from its floor and lateral walls, but do not extend as far as the taste- pore. The circumvallate papillae are differentiated from the adjacent surface of the tongue by the development of a solid encircling epithelial ridge. Nu- merous taste-buds ap- pear on the surface quite early in the his- tory of the embryo. These, however, dis- appear completely when the permanent taste buds develop from the basal cells of the epithelial ridge. Similar phenomena occur in the fungiform papillae (Hermann, 88). The neural epith- elia of the taste-gob- lets were formerly re- garded as directly connected with the nerve-fibers by means of long processes, but the latest researches have shown that dendrites of sensory neurones (sensory nerves) enter the taste-buds and end free in telodendria. The latter sur- round the neuro-epithelial and, to some extent, the sustentacular cells, their relations depending upon contact. The Lymph-follicles of the Tongue (Folliculi linguales) and the Tonsils.- — At the root of the tongue, and especially at its sides, are numerous elevations due to the increased quantity of lymphoid tissue found in the mucosa of these regions, the lingual tonsils, or lingual follicles. In the center of each follicle is a cavity communicating with the exterior and caused by an invagination of the epithelium. The lymphoid tissue contains a number of more or less distinctly defined lymph-nodules, some even showing germ centers (vid. p. 178). The whole structure is surrounded by a connective -tissue capsule. The epithelial walls of the follicular cavities often show extensive degenerative changes, which are accompanied by increased migration of leucocytes into the oral cavity. These leucocytes change (according to Stohr, 84) into the so-called mucous or salivary corpuscles of the saliva. The pharyn- geal tonsils may be regarded as clusters of small lymph-follicles, Tegmental f cell. Neuro-epithe- lial cell. Sustentacular cell. Terminal branches of nerves. Fig. 188. — Schematic representation of a taste-goblet (partly after Hermann, 88). 15 Digitized by Microsoft® 226 THE DIGESTIVE ORGANS. similar to those found in the tongue. They are covered by a stratified pavement epithelium, resting on a mucosa possessing papilla? folded to form pits or crypts of irregular shape. The adenoid tissue of the tonsil is found in the form of diffuse ade- noid tissue and a varying number of more or less clearly defined follicles of adenoid tissue often showing germ centers of Flemming. Epithelium.— Lymph-follicle Epithelial l±„^. i l:^_ crypt. ^£ ' %' : Connective-tis- S. sue capsule. -_. \ a/ ■y ■ 'y Fig. 189. — Section through tonsil of dog ; X 20 : At a and at the opposite side the epithelium is composed of a very thin layer of cells. Fig, 190. — The area designated by a in the previous illustration, shown by a higher magnification ; X about 150 : a, Leucocytes in the epithelium ; b, one of the spaces in the epithelium filled with leucocytes and more or less changed epithelial cells ; c, blood-vessel ; cl, normal epithelium ; e, basal cell of the same. The epithelium lining the crypts or cavities of the tonsils shows, as in the lingual follicles, extensive degenerative changes, resulting mainly in the formation of variously shaped, communicating spaces filled with lymphocytes and leucocytes. (See Fig. 190.) Besides the nerves terminating in the taste-buds, the tongue is Digitized by Microsoft® THE ORAL CAVITY. 227 richly supplied with sensory nerves which terminate in free sen- sory endings, which may be traced into the epithelium, and which are especially numerous in the fungiform and circumvallate papillae ; or in smaller or larger end-bulbs of Krause found in the mucosa of the fungiform papillae. The motor nerves of the tongue terminate in motor-endings. Intermediate duct. GLANDS OF THE ORAL CAVITY. The glands of the oral cavity comprise numerous lobular, tubulo-acinous glands situated in the mucosa and submucosa of the lips, cheeks, and tongue, and three pairs of lobar, tubulo - acinous glands — the parotid, submaxil- lary, and sublingual glands. These are classified according to their secretions into those secreting principally mucus (human sublin- gual and many of the smaller oral glands), and known as mucous glands ; those secreting a fluid al- buminoid substance containing no mucus, the serous glands (parotid glands and the small glands near the circumvallate. papillae) ; and those having a mixed secretion, mucous and serous glands (human submaxillary). The ducts of all these glands open into the cavity of the mouth. The ducts of the smaller oral glands are, as a rule, short and pass up through the mucosa and the epithelium to open on the free surface. The principal excretory ducts of the salivary glands are Steno's ducts (Stenson's ducts), passing from the parotid glands to the mouth ; Wharton's ducts, the ducts of the submaxillary glands, and Bartholin's ducts for the sublingual glands. The salivary glands consist of numerous lobules and small lobes of glandular tissue, surrounded by a thin fibrous-tissue capsule which sends septa and trabeculae between the lobules and lobes. The duct of each gland on reaching the gland divides into smaller ducts, which penetrate the gland between the lobes, the interlobar ducts ; these in turn divide into ducts of the next order, which pass between the lobules, the interlobular ducts. The interlobular ducts pass over into short cylindric tubes which enter the lobules, and are known as intralobular ducts. These are followed by very short, narrow tubules, the intermediate ducts or tubules, Digitized by Microsoft® Fig. 191. — Scheme of a salivary gland. 22 8 THE DIGESTIVE ORGANS. which finally terminate in the alveoli or acini, irregular and some- what tortuous tubular structures with a lumen and possessing an epithelium characteristic of the particular variety of the gland (see below). The epithelium lining the different portions of the large excretory ducts varies somewhat. For a short distance from their oral end they are lined by a stratified columnar epithelium con- sisting of two layers of cells (Wharton's ducts are now and then lined for a short distance by a stratified pavement epithelium continuous with that lining the mouth). Beyond this stratified columnar epithelium, which extends for a variable distance, the large excretory ducts, the interlobar and interlobular ducts are lined by a pseudostratified columnar epithelium, possessing two rows of nuclei (Steiner). Outside of the epithelial lining there is found a firm fibro-elastic covering, forming the wall of the ducts. The intralobular ducts are lined by a single layer of columnar cells, the basal half of each cell showing a distinct striation. The interme- diate portions of the ducts are lined by a low, cubic, or flattened epithelium. Between the membrana propria and the secreting epithelium of the tube, and more especially in the acini, are branched cells which anastomose with each other, the so-called basket cells. Their processes penetrate between the glandular cells and form a sup- porting structure for them. The homogeneous membrana propria surrounding the entire glandular tube is in close relationship to these cells. We shall now consider more in detail the structure of the alveoli or acini of the salivary glands. SALIVARY GLANDS. The Parotid Gland (Serous Gland). — The epithelial cells lining the acini of this gland are short, irregularly columnar or cubic cells, their structure changing according to their physiologic condi- tion. When at rest the secreting cells are only slightly granulated and contain a large quantity of clear secretion (paraplasm), while the nuclei are irregular and indented. As soon as the protoplasm of the cells commences the formation of secretion, the cells become smaller, more granular and opaque, and their nuclei assume a spheric shape ; when, however, the cells throw off a portion of the granular material, an immediate increase in their protoplasm is noticed. After a long period of secretion the cells become still smaller and their contents still more turbid. They now contain very little protoplasm. These phenomena can only be regarded as due to the fact that the granular paraplasm is formed at the expense of the protoplasm of the cell during the period of rest. The Sublingual Gland (Mucous Gland). — In the acini of mucous glands there are found two varieties of cells : (i) True mucous cells, which, when filled with secretion, are large and Digitized by Microsoft® SALIVARY GLANDS. 229 clear, with their nuclei always at the periphery. During the ex- pulsion of the secretion the mucous cells decrease in size and become cloudy, while the nuclei leave the periphery and increase in size. (2) Cells rich in protoplasm, situated in close apposition to the membrana propria. These cells resemble in structure serous cells, and are found either singly or in groups of crescentic shape. They are known as the crescents of Gianuzzi or the demilunes of Heidenliain. The margins of the individual cells composing the crescents are often so faintly outlined that the whole structure has the appearance of a large polynuclear giant cell. Intralobu- lar duct. Connective tissue be- tween lobules. a*- Blood-ves- Fig. 192. — Section through salivary gland of rabbit, with injected blood-vessels ; X 7°- The demilunar cells have been variously interpreted by different observers. They have been regarded as permanent cells with a special secretion, as transitional structures, and again as cells des- tined to replace the degenerated mucous cells. Stohr (87) be- lieves that the cells of the acini are never destroyed in the process of mucous secretion, and that the crescents of Gianuzzi are there- fore merely a complex of cells containing no secretion, which have been crowded to the wall by the adjacent enlarged and distended cells. Solger (96), on the other hand, does not regard the demi- lunes as transitional structures whose function is to replace the Digitized by Microsoft® 230 THE DIGESTIVE ORGANS. destroyed cells, but considers them to be permanent secreting cells — an opinion which he bases on the results of special methods of investigation. According to him, then, the mucous salivary glands are mixed glands, in that the demilunes consist of cells of a serous type, while the remaining elements are mucous in character. The destruction of mucous cells during secretion is not admitted by him Gland cell _ of acinus. Intralobu- lar duct. Intermedi- ate duct. ''■■if A:^..^]^ Fig. 193. — Section from parotid gland of man. (compare also R. Krause). This latter view seems more in accord with recent observations. The Submaxillary Gland (Mixed Gland). — With regard to the mixed glands it is sufficient to say that there is a simultaneous secretion of serous and mucous fluids, and that these two sub-, stances are produced in separate but adjacent acini, of which the Intermediate UmzLj^ _j_^ _^ ffl , f ;" . - /,^ v , duct. JSP^Li i 'i-SCf iif M%& Crescents of Gianuzzi. Fig. 194. — From section of human sublingual gland. one type possesses a structure identical with that found in the parotid and the other with that in the sublingual. By means of various methods the existence of a network of tubules surrounding the glandular cells may be demonstrated both in the serous and mucous glands. The same arrangement may be Digitized by Microsoft® SALIVARY GLANDS. 231 Fig. 195. — A number of alveoli from the submaxillary gland of dog, stained in chrome- silver, showing some of the fine intercellular tubules. observed in the case of the cells forming the demilunes. The course of these tubules may be followed to their junction with the lumen of the secreting portion of the gland tubule, and the whole structure would seem to indicate that the entire surface of the cells is concerned in the act of secretion (Erik Miiller, 95 ; Stohr, 96, II). As to the part that the intermediate tubules and the intralobular tubes play in the process of secretion, Merkel's (83) theory is of interest. He believes that the former yield a part of the water in the saliva, while the salts are ' furnished by the rod - shaped epithelium of the intralobular tubes. These views of Merkel have been questioned, as it has been shown by chemic analysis that the relative quantity of water and salts in the secretion of the salivary glands is not at all proportionate to the number of the intermediate tubules and intralobular tubes. For exam- ple, Werther finds that although a great many intermediate tu- bules are present in the par- otid gland of the rabbit and none at all in the submaxillary gland of the dog, nevertheless the secretions of these glands contain equal quantities of water. Furthermore, the secretions of the parotid of the rabbit and of the sublingual of the dog show equal quantities of salts, in spite of the fact that in the former there are large numbers of intralobular tubes with rod-shaped epithelium and in the latter none at all. THE SMALL GLANDS OF THE MOUTH. Besides the larger glands, there are in the oral cavity numerous small lobular, tubulo-acinous and simple branched tubulo-acinous glands. They are mostly of the mixed type, and are called, accord- ing to their location, glandulse labiales, palatinse and linguales. Serous glands, known as v. Ebner's glands, occur in the tongue, their ducts opening into the depressions of the circumvallate and foliate papillae. The absence of intralobular tubes and well-defined intermediate tubules is characteristic of all the smaller glands of the oral cavity. As a consequence the secreting tubules are composed almost entirely of those parts corresponding to the acini of the larger glands. It appears that the smaller mucous glands, except those of the lips (J. Nadler), do not, as a rule, contain typical demilunes. The salivary glands and smaller glands of the mouth have a Digitized by Microsoft® 232 THE DIGESTIVE ORGANS. rich blood supply. In the salivary glands the arteries follow the ducts through their repeated branching, ultimately ending in capil- laries which form a network inclosing the acini and the terminal portions of the system of ducts. The lymphatics begin in clefts in the connective tissue surround- ing and separating the acini. Larger lymph-vessels are found in the connective tissue separating the lobules and lobes of the gland. The nerve supply of the salivary glands, may, owing to the im- portance of these structures, receive somewhat fuller consideration. Their nerve supply is from several sources. That of the sublin- gual and submaxillary glands will be considered first. Sensory nerve-fibers (no doubt the dendrites of sensory neurones, the cell- bodies of which are situated in the geniculate ganglion) terminate in free sensory endings in the large excretory ducts and their branches. These medullated fibers accompany the ducts in the form of small bundles. From place to place one or several fibers leave these bundles and, after dividing a number of times, lose their medullary sheaths. After further division the nonmedullated branches form plexuses under the epithelial lining of the ducts. From the fibers of these plexuses terminal fibrils are given off, which enter the epithelium, to end, often near the free surface, on the epithelial cells (Arnstein, 95; Huber, 96). The secretory cells of the acini receive their innervation from sympathetic neurones. The cell-bodies of those supplying the sublingual glands are grouped in a number of small, sympathetic ganglia situated in a small triangle formed by the lingual nerve, the chorda tympani and Wharton's duct, the chorda- lingual triangle. These ganglia may be known as the sublingual ganglia (Langley). The cell-bodies of the sympathetic neurones supplying the secretory cells of the submaxillary glands are grouped in small ganglia situated on Wharton's duct just before it enters the gland, in the hilum of the gland, and on the interlobar and inter- lobular ducts ; they may be spoken of collectively as the submax- illary ganglia. In the glands under discussion, the neuraxes of the sympathetic neurones are grouped to form small bundles, which divide repeatedly, the resulting divisions joining to form plexuses situated in the outer portion of the walls of the ducts, and as such may be followed along the ducts, the bundles of nerve-fibers be- coming smaller and the division of the bundles of fibers and the individual fibers occurring oftener as the smaller divisions of the system of ducts are reached. On reaching the acini, the terminal branches of the nerve-fibers form a plexus outside of the basement membrane, epilamellar plexus ; from this branches are given off which penetrate the basement membrane, some forming zhypolam- ellar plexus, others ending on the gland-cells in small granules or clusters of granules (Arnstein). Throughout their entire course the neuraxes of the sympathetic neurones are varicose, nonmedullated nerve-fibers. The nerve-fibers of the chorda tympani end in ter- minal end-baskets, inclosing the cell-bodies of the sympathetic Digitized by Microsoft® THE PHARYNX AND ESOPHAGUS. 233 neurones found in the sublingual and submaxillary ganglia, and not in the glands, as generally stated by writers. The increase of secre- tion from the submaxillary and sublingual glands on direct or indi- rect stimulation of the chorda tympani is due, therefore, not to a direct stimulation of the gland-cells by the fibers of this nerve, but to a stimulation of the sympathetic neurones of the sublingual and submaxillary ganglia, the neuraxes of which convey the impulse to the gland-cells. These glands have a further nerve supply from the superior cervical ganglia of the cervical sympathetic. The neuraxes of sympathetic neurones, the cell-bodies of which are situated in the superior cervical ganglia, accompany the blood-vessels to the sub- lingual and submaxillary glands ; their mode of termination is, however, not as yet determined. The cell-bodies of the sympathetic neurones here in question are surrounded by end-baskets of nerves which leave the spinal cord through the second, third, and fourth dorsal spinal roots. The blood-vessels of the salivary glands are also richly supplied with vasomotor nerves, the neuraxes of sympa- thetic neurones, which terminate on the muscle-cells of their walls. The nerve supply of the parotid glands is, in the main, like that of the other salivary glands here described, although it has not been worked out with the same detail. The cell-bodies of the sympathetic neurones, the neuraxes of which innervate the gland-cells, are, it would appear, situated in the otic ganglia. The nerve-ending in the smaller glands of the mouth is similar to that given for the salivary glands, as has been shown by Retzius and other observers. It is very probable that the cell-bodies of the sympathetic neu- rones, the neuraxes of which innervate the glands of the tongue, are situated in the small sympathetic ganglia found on the lingual branches of the glossopharyngeal and lingual nerves. B. THE PHARYNX AND ESOPHAGUS. The mucous membrane of the pharynx and esophagus is similar in structure to that of the oral cavity. The epithelium is of the stratified squamous variety, and also contains prickle cells and keratohyalin. (See Skin.) A stratified ciliated epithelium is present only in the fornix in the region of the posterior nares. The area covered by this type of epithelium is more extensive in the fetus and newrborn, and extends over the whole nasopharyngeal vault. In the human embryo the superficial epithelial cells of the esophagus possess cilia up to the thirty- second week (Neumann, 76). The papillae of the mucosa are loosely arranged and are in the form of slender cones. The mucosa of the pharynx contains diffuse adenoid tissue rich in cells which in some places forms accessory tonsils (z'id. p. 225). There are but few mucous glands in the submucous tissue of the esoph- agus, but when present they contain well-marked demilunes. In Digitized by Microsoft® 234 THE DIGESTIVE ORGANS. man the ducts of these glands do not reach the surface between the connective-tissue papillae, as in the external skin, but pass up through them into the epithelium and thus to the surface. A layer consisting of nonstriated muscle-fibers, the muscularis mucosa, the majority of the cells of which show a longitudinal arrangement, is found between the mucosa and submucosa in the esophagus, but not in the pharynx. The external muscular coat of the pharynx is made up of transversely striated muscle-fibers, arranged in a complicated man- ner. This tissue extends downward to about the middle of the !^s; lESSsKS'".''^ Epithelium. Muscularis mucosae. Submucosa. Circular layer of muscle. .,, $i| V-- Longitudinal Vw,vv k - muscle layer. Outer connec- tive - tissue coat. Fig. 196. — Section of esophagus of dog; X '8. esophagus, in which it consists of an outer longitudinal and an inner circular layer. In the lower half of the esophagus nonstriated muscle-fibers alone are present. There is no sharply defined line of demarcation between the two types of muscular tissue, as the fibers of the unstriped variety penetrate for some distance upward into the substance of the striated muscle, giving the tissue here a mixed character. Digitized by Microsoft® THE STOMACH AND INTESTINE. 235 C THE STOMACH AND INTESTINE. J. GENERAL STRUCTURE OF THE INTESTINAL MUCOUS MEMBRANE. The mucous membrane of the stomach and intestine, unlike that of the esophagus and oral cavity, possesses an epithelium of the simple columnar variety with elongated cells (about 22 /u in Alveolus -fx of gland. <£j Mucosa. Basal epi- thelial cells. Gland- cells. _ Branched papilla of mu- cosa. Fig. 197. — Part of section of human esophagus, showing duct of mucous gland ; X I2 °- height). In the intestine the epithelium shows a well-marked striated cuticular border, striated protoplasm in the outer ends of the cells, extending to the immediate vicinity of the nuclei, which are situated in the basal portions of the cells. The basal portion of each cell consists of nonstriated protoplasm, ending in a longer or shorter process which extends to the basement membrane, or possibly Digitized by Microsoft® 236 THE DIGESTIVE ORGANS. even penetrates it. The epithelial cells have the power of produc- ing mucus, a phenomenon which, in the normal condition, rarely embraces whole areas of epithelium ; these cells (goblet cells) are usually surrounded by others which are unchanged (for details about goblet cells see General Histology, p. 81). Throughout the entire intestinal tract the epithelium forms simple, branched, and compound tubular and alveolar glands. These are depressions lying in the mucosa, and only in the duodenum extend beyond it into the sub- mucosa. The mucosa consists of adenoid tissue, containing relatively few cells. It fills the interstices between the glands, and often forms a thin but continuous layer (granular layer of P. Mall) below the glands. It is therefore obvious that the development of the mucosa is inversely proportionate to the number and the density of arrangement of the glands ; when the latter are present in large numbers, as, for instance, in the stomach, the mucosa is reduced to a minimum. In the small intestine it forms not only the perma- nent folds, but also certain finger-like elevations known as villi, which are covered with epithelium and project into the lumen of the intes- tine, thus increasing to a considerable extent the surface area of the mucous membrane. In the mucosa are found small nodules of adenoid tissue. These are spoken of as lenticular glands when occurring in the stomach, as solitary glands when found in the upper portion of the small intestine and in the large intestine. In the lower portion of the small intestine they are grouped to form the agminated glands, or Peyer's patches, which, when large, extend into the submucosa. Beneath the stratum proprium is a layer consisting of two or three strata of unstriped muscle- fibers, the muscularis mucosa. As a rule, it is composed of an inner circular and an outer longitudinal layer. This arrangement is interrupted only where the larger glands and follicles penetrate into the sub- mucosa. The epithelium with the glands, the mucosa with its lymph-nodules, and the muscularis mucosae form together the mucous membrane, or tunica mucosa. Below the mucous membrane is the connective-tissue submucosa. This is characterized by its loose structure, and consequently affords considerable mobility to the mucous membrane. In the small intes- tine it forms a large number of permanent transverse folds known as valvules conniventes (Kerkring). In the submucosa of the duodenum occur the secreting portions of Brunner's glands (gland- ule duodenales), and in the small intestine the larger lymph-nodes and Peyer's patches. External to the submucosa is the muscular coat, which generally consists of two layers of unstriped muscle-tissue. The inner layer is composed of circular fibers (stratum circulare) ; the outer layer, of longitudinal fibers (stratum longitudinale). In the colon the longi- tudinal layer forms definite bands, the tcznice coli. In some regions the circular fibers are also considerably reinforced, particularly in Digitized by Microsoft® THE STOMACH AND INTESTINE. 237 the plica sigmoidece which lie between the taeniae coli. At these points the longitudinal layer also is thickened. In the rectum the circular fibers form the internal sphincter ani muscle. In the stomach a third layer is added to the two already mentioned, with fibers running obliquely. It lies internal to the circular fibers, but does not form a continuous layer. According to Legge, elastic fibers are present throughout the entire digestive tract of all adult mammalia and vary only in minor details in the different species. In regions in which the tunica mus- cularis is prominent the elastic fibers attain a considerable size. There is also a difference in their development in carnivora and herbivora. In general, they form a dense network, present not only in the serous layer, but also in the submucosa and beneath the epithelium. These fibers preserve the elasticity of the intestinal walls and resist any hyperextension of the glands and follicles. The intestine is covered externally by the peritoneum, forming the serous coat, which consists of an inner, very thin connective- tissue layer (subserosa) and an outer layer of mesothelial cells. Epithelial cell. 2. THE STOMACH. The general structure of the gastric mucous membrane is essen- tially the same as that of the intestinal canal. It presents, however, depressions known as gastric crypts, due to an infolding of the epithelium into which the gastric glands open. In the fundus the crypts attain a depth of from one-fifth to one-sixth the thick- ness of the mucous membrane. In the pylorus they are deeper, many of them here extending through half the mucous mem- brane and some even reaching the muscularis mucosae. The epithelium of the crypts and that of the folds between them is composed of long, slender cells, with basally situated nu- clei. That portion of the cell- body near its free margin contains very little protoplasm, but is, on ' the other hand, rich in paraplasm ; the region of the cell containing the nucleus possesses more protoplasm. This part of the cell extends downward in a curved process of diminishing size, which assumes a position parallel to the corresponding parts of the neigh- boring cells, and finally penetrates the basement membrane. Into a single gastric crypt of the human fundus empty from three to seven gastric glands. Each gland consists of a simple tube, from Digitized by Microsoft® Fig. 198. — Epithelium of human stom- ach, covering the fold of mucosa between two gastric crypts ; X 7°°' Technic No. 241. 238 THE DIGESTIVE ORGANS. 0.4 to 2.2 mm. in length, whose inner segment, opening into the crypt, is quite narrow, and is known as the neck of the gland. The main portion of the gland is called its body, and the region at the distal blind end the fundus. In the gastric glands, more especially in the cardia and fundus of the stomach, two varieties of gland-cells are found. The cells of the one variety lie against the walls of the gland — that is, they rest on its basement mem- brane — and are particularly numerous in the neck and body of the gland, but not so numerous in its fundus. These are known as the parietal, oxyntic or delo- morphous cells (R. Heiden- hain, 69 ; Rollet, 70). Their bodies often extend more or less beyond the even line Bodies of gas- tric glands. • Gastric crypts and necks of glands. f Fundus. Fig. 199. — From vertical section through fundus of human stomach ; X °° : a an( ^ ^> Inter- lacing fibers of the muscularis mucosas ; from a and b muscular fibers enter the mucosa. The fibers of the layer b penetrate those of layer a. Fig. 200. — A number of gastric glands from the fundus of the stom- ach of young dog, stained after the chrome-silver method, showing the system of fine canals surrounding the parietal cells and communica- ting with the lumen of the glands. of the remaining cells, thus forming, together with the membrana propria, a protuberance (particularly noticeable in the pig, where almost the entire cell may be enveloped by the basement membrane, giving it an appearance of being entirely extraglandular). Toward the lumen of the gland the contour of these cells is modified by pressure on the part of the adjacent cells belonging to the other variety, and they are indented according to the number of the latter. Digitized by Microsoft® THE STOMACH AND INTESTINE. 239 Occasionally, a process is seen extending from a parietal cell to the lumen of the gland. The parietal cells are larger than the cells of the other variety and richer in protoplasm ; they are of an irregular oval or triangular shape and possess, as a rule, a single nucleus. According to Erik Miiller and Golgi (93), there exists in the peripheral protoplasm of each parietal cell a system of canals in the form of a network communicating with the lumen of the gland and varying in structure according to the physiologic condition of the cell — wide-meshed in a state of hunger and fine-meshed during Epithelium of esophagus. - Mucous cardiac gland. :< 3|gi£jf=r — Junction of ":^23^a esophagus • 3P=5s?s>^,_ and stomach. 3«*-^ ~~ Epithelium of stomach. 5 Gastric crypt. ' ' JirtjJ. ' Fig. 201. — From a section through the junction of the human esophagus and cardia ; X 50. digestion. A peripheral zone differing from the rest of the cell- body may occasionally be demonstrated in the parietal cells (mouse) by using the method of von Altmann (vid. T. 125). The second variety of glandular cells is represented by the central, chief, peptic, or adelomorphous cells. These are short, irregular, columnar structures whose narrower portions point toward the lumen of the gland. They are situated either directly between the lumen and the basement membrane of the gland, or their Digitized by Microsoft® 240 THE DIGESTIVE ORGANS. Epithelium of fold be- tween gas- tric crypts. Gastric ■ crypt. basilar surfaces border on a delomorphous cell. They are found throughout the tubule of the gland and occupy the spaces between the delomorphous cells. Their protoplasm is dark and the nuclei are, as a rule, somewhat smaller than those of the parietal cells. In both varieties of cells mitoses are rarely present in man. In the delomorphous cells pluripolar mitoses are sometimes seen. At the cardia the stratified squamous epithelium of the esopha- gus terminates abruptly, the basilar layer of this epithelium being continued as the simple columnar epithelium of the stomach. (Fig. 20 1.) In that region of the gastric mucous membrane bor- dering upon the cardia are mu- cous glands ( cardiac mucous glands) similar in appearance to those of the esophagus. The crypts of this region are not supplied with true gastric glands, the latter first making their ap- pearance at some distance from the cardia and increasing in length toward the fundus. The structure of the pyloric region of the stomach differs in some respects from that of the cardiac end and fundus. There is, however, no sharply defined boundary between fundus and pylorus, but a transitional zone in which changes gradually take place. Toward the pylorus the gastric crypts gradually become deeper and the parietal cells de- crease in number. Here also the glands begin to branch. In the pylorus itself the crypts fre- quently extend half-way through the thickness of the mucous membrane, often even penetrat- ing to the muscularis mucosae, in which case the corresponding tubules become tortuous and arch over the muscularis mucosae. The most important feature is that in the great majority of the tubules only a single variety of cell is present in the pyloric gland. (Only here and there are found parietal cells in the pyloric glands of the human stomach.) These cells may be compared with the chief cells of the glands in the fundus. They are columnar, but of much more uniform structure — a condition probably due to the general absence of delomorphous cells. In the immediate vicinity of the gastroduodenal valve the pyloric glands become shorter, Digitized by Microsoft® Pyloric gland. Muscularis mucosae. Fig. 202. - through human Technic No. 241 -From vertical section pylorus ; X about 60. THE STOMACH AND INTESTINE. 24I — Mucosa. and other glands, which extend into the submucosa, and which are identical in structure with the glands of Brunner in the duod- enum, make their appearance. In this portion of the pylorus are also a few scattered villi, which from their structure may be con- sidered as belonging to the duodenum (yid. Fig. 208). In the normal condition the mucosa of the stomach seldom con- tains solitary lymph-nodules (lenticular glands) in the fundus region, but frequently in the pyloric region ; well-defined lymph-nodules are constantly present in the immediate vicinity of the pylorus. The muscularis mucosae is usually composed of three layers, the fibers of the individual layers forming distinct interlacing bun- dles. Individual muscle-fibers very frequently branch off from the inner layer, assume a vertical position and disappear among the glands. Similar arrangements are also seen in the muscularis mucosae of the stomach (Fig. 199). Only the inner and middle layers of the muscular coat of the stomach enter into the formation of the sphinc- ter pylori (Fig. 208). The fibers of the outer layer, however, pene- trate through the sphinc- ter pylori and may even be traced into the sub- mucosa. When these alone contract, the mus- cular bundles of the sphincter act somewhat as pulleys, and a mod- erate dilatation of the lumen of the pylorus is the result ( dilatator pylori, Rudinger, 97 ). (For further particulars about the stomach, compare Oppel, 96.) The changes which the epithelium and the secretory cells of the stomach undergo during secretion are of special importance. These relations have been carefully studied in animals by R. Heidenhain (83). As far as our present knowledge goes, it would seem that the same processes also occur in man. In a state of hunger the chief cells of the fundus are large and clear, the parietal cells small ; in certain cases the parietal cells abandon their mural position and, like the chief cells, border upon the lumen of the gland. During the first kw hours of digestion the chief cells remain large, but become somewhat turbid, while the parietal cells increase in size. In the dog from the sixth to the ninth hour of digestion, the chief cells diminish in size and become cloudy, while the parietal cells re- main large and even increase in size. From the fifteenth hour on, the process becomes reversed ; the chief cells enlarge and become clear, 203. — From section through human pylorus ; X 600. Technic No. 241. 16 Digitized by Microsoft® 242 THE DIGESTIVE ORGANS. and the parietal cells diminish in size. In a condition of hunger the cells of the pylorus are clear, of medium size, and do not begin to enlarge until six hours after feeding. From the fifteenth hour on, the cells become smaller and more turbid, while the nuclei return Chief cell. Lumen. Parietal cell. Mucosa. M J'\ ~-^ T ■ o ■ ;: Fig. 204. — Section through fundus of human stomach in a condition of hunger ; X 5 00, Technic No. 242. XmmSBBmfr Chief cell. Fig. 205. — Section through fundus of human stomach during digestion; XS 00 - Technic No. 242. to the center of the cells. Since chemic examination has shown that the amount of pepsin found in the gastric mucous membrane increases with the enlargement of the chief and pyloric cells, and decreases with their diminution in size, there can be hardly any Digitized by Microsoft® THE STOMACH AND INTESTINE. 243 doubt that this ferment is elaborated by these cells. The pro- cess consists either in a direct change of the cellular protoplasm into the ferment, or in a preliminary stage before its final trans- formation into the finished ferment. It is assumed that the parietal cells secrete the acid of the gastric juice, although, in spite of all efforts, it has not yet been definitely proved that these cells possess an acid reaction. The vascular and lymph-vessels of the stomach, and also its nerve supply, will be considered in a general discussion of these structures pertaining to the entire intestinal canal. 3. THE SMALL INTESTINE. The mucous membrane of the small intestine is characterized by the presence of villi. These are more or less elongated elevations of the mucous membrane projecting into the lumen of the intestine. They greatly increase the surface of this portion of the intestine and are actively concerned in the absorption of its contents. The mu- cous membrane also forms permanent folds in both the duodenum and the remainder of the small intestine, the valvular conniventes (Kerkring). Upon these the villi rest, and, indeed, it is probable that the very existence of the plicae is due to the blending of the basilar ends of the villi. The latter are leaf-shaped in the duod- enum, columnar in the jejunum, and club-shaped in the ileum. The epithelium of the intestinal mucous membrane covers the villi in a continuous layer, and penetrates into the mucosa to form the glands. Its structure is essentially the same in all regions of the small intestine, the cells being of the high columnar variety with free surfaces covered by wide, striated cuticular borders. The basilar portions of these cuticular borders are nearly always homo- geneous, and upon vertical section give the appearance of a fine line. The cuticular borders of adjacent cells blend with each other, form- ing a continuous membrane, large areas of which may be detached from the villi (cuticula). The body of the cell consists of a gran- ular, reticular, or striated protoplasm, containing, especially at the beginning of mucous secretion, clear vacuoles of different sizes — mucus. If the cuticular margin be intact, a confluence of the vacu- oles may form a large drop of mucus. The nuclei lie usually in the basilar third of the cells, and only where they show mitoses, as for instance in the tubular intestinal glands, do they pass to the free ends of the cells. The basal ends of the epithelial cells in the small intestine are also seen to be pointed, and the probability is that they rest upon the basement membrane. The question has, however, not been fully settled. The epithelial cells undergo a special metamorphosis, after which, by an increased production of mucus, they change into gob- let cells. From recent investigations it would seem that any epithelial cell, whether it be situated upon the upper surface of a Digitized by Microsoft® 244 THE DIGESTIVE ORGANS. villus or deep down in one of the tubules of the intestinal glands, is capable of transformation into a goblet cell. The number of goblet cells is subject to great variation ; they are found singly in small numbers, or are very numerous, according to the stage of digestion and quantity of food in the intestine. The manner in which an ordinary epithelial cell changes into a goblet cell is very easily explained if the mechanical action on the cell caused by an accumu- lation of secretion be taken into consideration. As the secretion increases in quantity the upper portion of the cell becomes distended, and the remains of the protoplasm, together with the nucleus, are pushed toward the nar- row base of the cell ; the cuticular zone is stretched, bulges into the lumen of the intes- tine, and is finally perfor- ated, and perhaps even thrown off. In this way the cell loses its mucous secretion, collapses, and then appears as a thin, almost rod - like struc- ture, with a long nu- cleus. It is the gener- ally accepted theory that such an empty goblet cell may again assume the shape of an ordinary epithelial cell and repeat the process just de- scribed. Leucocytes are some- times found within the epithelial cells, but more usually between them, and according to Stohr (84, 89, 94), when seen in these positions, are in the act of migrating' into the lumen of the intestine. That some of these cells actually pass into the lumen is probably true ; but as yet no leucocytes have ever been observed in the cuticula itself, and neither is the number of cells found in the lumen of the intestine proportionate to the leuco- cytes present in the epithelium. Since many are seen in the epithe- lium undergoing karyokinetic division, it is more probable that a part of them actually wander into the epithelium for the purpose of Digitized by Microsoft® Mucosa. Muscularis mucosas. Fig. 206. — Section through mucous membrane of human small intestine ; X 88. Technic No. 243 : At a is a collapsed chyle-vessel in the axis of the villus. THE STOMACH AND INTESTINE. 24s division (chemotaxis ?), only to return to the mucosa after the com- pletion of the process (compare p. 54). Into the spaces between the villi open numerous tubular glands. These are seldom branched, and are known as Lieberkuhn' s glands, or crypts. Their length varies from 320 fi to 450 [i. They are regularly arranged in a continuous row, and often have an ampulla- like widening of their lumina extending almost to the muscularis mucosae, but never quite reaching it. They are uniformly distrib- uted not only throughout the small intestine, but also throughout the large intestine and rectum. Their cells are somewhat lower than those of the villi, and pos- sess a very narrow cuticular zone. The cells are, how- ever, conical, — a condition probably due to the curva- ture of the glandular wall, — the base of each cone lying toward the basement membrane, the apex toward the lumen of the gland — a condition opposite to that found in the villi. Numer- ous goblet cells are also present. They vary only slightlyin shape during mu- cous secretion, and never, as in the villi, assume the form of goblets with distinct pedicles. Mitoses are al- ways seen in the intestinal glands, especially in cells which do not contain mu- cin. They are readily dis- tinguished, since the nuclei in process of division, as we have seen, lie outside of the row formed by the re- maining nuclei. The plane of division in these cells lies horizontal to the long axis of the gland, so that an increase in the number of cells results in an increase in the area of the glandular walls. Mitoses are very rarely observed in the epithelium covering the villi. If, therefore, any cells be destroyed on the surface of the villi, it must be assumed that the loss is replaced by new elements pushed up from the glands below (Bizzozero, 89, 92, I). The entire duodenum, as well as that part of the pylorus in the immediate vicinity of the pyloric valve, is characterized by the presence of glands of a second type. In the duodenum these are Digitized by Microsoft® Fig. 207. — Longitudinal section through sum- mit of villus from human small intestine ; X 9°° (Flemming's solution) : At a is the tissue of the villus axis ; b, 'epithelial cells ; c, goblet cell ; d, cuticular zone. 246 THE DIGESTIVE ORGANS. seen intermingled with the glands of Lieberkuhn, and in the pylorus with the pyloric glands. These glands, Brunner's glands, have a diameter of from o. 5 to 1 mm., and are compound, branched tubu- lar glands, with tubules provided with alveoli, especially along their lower portions. The bodies of the glands are situated principally in the submucosa, although a part may be in the mucosa. In the stomach they open into the gastric crypts, in the intestine either in- dependently between the villi, or into the glands of Lieberkuhn. Here the glandular cells are in general similar to those of the pyloric glands, although, as a rule, somewhat smaller than the latter. Just as the duodenal glands extend into the stomach, so also the pyloric glands of the latter are found in the upper portion of the duodenum. Besides short villi, there are also present in the duodenum depres- sions of the mucous membrane analogous to the gastric crypts. The glands of Lieberkuhn begin at a certain distance from the pylorus ; at first they are short, and do not attain their customary length until a point is reached at which the gastric glands extending into the duodenum finally disappear (vid. Fig. 208). It is therefore obvious that a transition zone exists between pylorus and duodenum, and that a distinct boundary line can not be drawn between the two, at least so far as the mucous membrane is concerned. The duodenal glands, as their name would indicate, are present only in the duod- enum. Between the jejunum and ileum there is no distinct boundary, not even when microscopically examined. The differences are mostly of a quantitative nature ; in the jejunum the valvulae conniventes are more numerous than in the ileum, and the villi more slender and closer together. The glands of Lieberkuhn also appear to be more numerous in the jejunum. The mucosa of the small intestine consists of reticular adenoid tissue containing lymph-cells. It supports the glands and extends into the villi whose axes it forms. The mucosa is separated from the glands, from the epithelium of the villi, as well as from that of the remaining surface of the intestine by a peculiar basement membrane. The latter somewhat complicates a proper histologic analysis, and as a consequence opinions regarding its structure and significance vary considerably. By some it has been described as a homo- geneous, hyaline, and exceedingly fine membrane containing nuclei, by others as a lamella consisting entirely of endothelial cells. At all events, there are certainly nuclei in the basement membrane. Beneath the basement membrane is a marginal layer of a more fibrillar character. This is closely associated with the mucosa, and may be regarded as a differentiation of the latter. Toward the muscularis mucosae the mucosa is terminated by a reticulated elastic membrane (F. P. Mall, in the dog), containing openings for the entrance of vessels, nerves, and muscle-fibers. The muscularis mucosa consists of two layers of unstriped muscular fibers arranged in- a manner similar to that in the external muscular tunic — i. e., having an inner circular and an outer longi- Digitized by Microsoft® THE STOMACH AND INTESTINE. 247 tudinal layer. The fibers are frequently gathered into bundles, which appear to be separated from each other by connective tissue. From both layers, but more especially from the inner, muscle-fibers are given off at right angles, which enter the tunica propria and pass between the glands of Lieberkuhn, and even into the villi. In the latter these muscle-fibers are arranged in bundles, and lie «if-; ':4!g 4^M -Submucosa. Longitudinal muscular layer. Sphincter -''.' ,0% pylori. i-;, : i /'/' I i'i iM;% ■ v ,<. •-■-'■ it.,™ 11 ' ' W Muscularis --Pyloric glands. Brunner's glands. ->;£o " Lymph- Villus. nodule. S& — a ] ''''; , 'dS^^^*Wz^!a'~~~ Muscularis mucosae. Submucosa. ' Villus. Brunner's glands. IP* \Blood-vessel. '"••Glands of Lieberkuhn. Fig. 208. — Section through the junction of the human pylorus and duodenum ; X about 15 : At a the pyloric glands extend into the duodenum. near their axes around the lacteal vessels. The contraction of these fibers causes a contraction of the entire villus. Lymph-nodules are distributed throughout the mucosa of the small intestine, occurring either singly, as solitary follicles, or aggregated, as Peyer's patches. At the points where they occur, Digitized by Microsoft® 248 THE DIGESTIVE ORGANS. the villi are absent and a lateral displacement of the glands of Lieberkuhn is observed. The lymph-nodule is usually pyriform in shape. The thinner portion protrudes somewhat in the direction of the lumen of the intestine, while the thicker portion extends outward to the muscularis mucosae, the latter being frequently in- dented or even perforated if the lymph-nodules be markedly devel- oped. Their structure is similar to that of the lymph-follicles (see under these), and consists of reticular adenoid tissue, supporting lymph-cells. It should be remembered that every .nodule may possess a germ center. Peyer's patches are collections of these lymph-follicles. The surface of the nodule presenting toward the lumen of the intestine is covered with a continuous layer of intestinal epithelium. In man the summit of that portion of the Leucocyte in epithe- lium. Epithelium. Crypt. Intermedi- ary zone. Submucosa. Fig. 209. — Section of solitary lymph-nodule from vermiform appendix of guinea- pig, showing crypt ; X about 400 (Flemming's fluid). nodule projecting into the lumen of the intestine presents but a slight depression of the intestinal epithelium, while in some animals (guinea - pigs), and especially in the nodules composing Peyer's patches, there is a deeper depression, even leading to the formation of a so-called "crypt" or "lacuna" (vid. Fig. 209). At the summit, the intestinal epithelium where it comes in contact with the lymph-nodule, is peculiarly altered. In most cases there is an absence of a basement membrane, the epithelium resting directly upon the lymphoid tissue. No clearly defined boundary between the two is distinguishable (intermediate zone of v. David- off ) ; they are therefore in the closest relationship to each other. The basal surfaces of the epithelial cells are fibrillar, the fibrils seeming to penetrate into the adenoid reticulum of the follicles. Digitized by Microsoft® THE STOMACH AND INTESTINE. 249 4. THE LARGE INTESTINE, RECTUM, AND ANUS. The small intestine ends at the ileocecal valve. At some dis- tance from the margin of the valve the villi of the ileum become broad and low. In the immediate vicinity of the valve their basilar portions become confluent, forming- a honeycomb structure which supports a few villi. At the base of the honeycomb open the glands of Lieberkuhn. On the cecal side of the valve the villi become fewer in number and finally disappear, while the folds which give the honeycomb appearance persist for a considerable distance. In Intestinal epithelium. Mucosa. Muscularis mucosae. Fig. 210. — From colon of man, showing glands of Lieberkuhn ; X 2 °°- the adult cecum the villi are absent. The mucosa and glands pre- sent a structure similar to that of the remainder of the large intes- tine. In the mucosa of the vermiform appendix is found a relatively large number of solitary lymph-follicles, occasionally forming a continuous layer. The marked development of the lymph-follicles encroaches upon the glands of Lieberkuhn, so that many are obliterated ; they are penetrated by the adenoid tissue, the epithe- lial cells of the glands mingling with the lymph-cells. What finally Digitized by Microsoft® 250 THE DIGESTIVE ORGANS. becomes of the secretory cells has not been definitely ascertained (Riidinger, 91). In the colon the villi are wanting, while the glands of the mucosa are densely placed and distributed with regularity. The glands of Lieberkiihn in the colon are somewhat longer, and as a rule contain many more goblet cells than those in the small intestine. Only the neck and fundus of the glands show cells de- void of mucus. Transitional stages between the latter and the goblet cells have been observed in man (Schaffer, 91). Solitary lymph-follicles are found throughout the colon. They are situated in the mucosa, onfy the larger ones extending into the submucosa. The glands of Lieberkiihn are displaced in the regions of the lymph- follicles. Epithe- Gland. -- Submu- cosa. Fig. 211. — A solitary lymph-follicle from the human colon : At a is seen a pronounced concentric arrangement of the lymph-cells. The tcenice and plica semilunares cease at the sigmoid flexure, and are replaced in the rectum by the plica transversales recti. Permanent longitudinal folds, the so-called columnm rectalcs Mor- gagni, are present only in the lower portion of the rectum. Here the intestinal glands are longest but disappear simultaneously with the rectal columns. At the anus the mucous membrane of the rectum forms a narrow ring devoid of glands, covered by stratified pavement epithelium, and terminating in the skin in an irregular line. The transition from the mucous membrane to the skin is gradual, yet reminding one of the appearance presented at the junction of the esophagus with the cardiac end of the stomach. External to the anus, and at a distance of about one centimeter from it, are numerous highly developed sweat-glands, the circum- anal glands, which are almost as large as the axillary glands. Digitized by Microsoft® THE STOMACH AND INTESTINE. 251 5. BLOOD, LYMPH, AND NERVE SUPPLY OF THE INTESTINE. In general, the following holds true with regard to the blood- vessels of the intestinal tract (further details will be discussed in dealing with the vessels of the various regions of the intestine) : The arteries enter along the line of the mesenteric attachment and penetrate the longitudinal muscular layer. Between the two mus- cular layers branches are given off which form an intermuscular plexus, from which, in turn, smaller branches pass out to supply the muscles themselves. The arterial trunks penetrate the circu- lar muscular layer and form an extensive network of larger vessels in the deeper layer of the submucosa. This is known as Heller' s plexus (F. P. Mall). From this, radiating branches are Region of the bodies of the gastric glands. Fig. 212.- -Section through fundus of cat's stomach, injected ; X °°. -■Muscularis mucosae. The blood-vessels are given off which supply the muscularis mucosae, forming under the latter a close network of finer vessels. This plexus, together with that of Heller, gives rise to vessels which penetrate the mus- cularis mucosae and break up into capillaries in the mucous mem- brane. The veins of the mucous membrane form beneath the muscularis mucosae a plexus with small meshes, giving off many radiating branches ; these in turn unite to form an extensive net- work of coarser vessels. Veins extend from the latter and unite to form larger trunks, which then lie side by side with the arteries. According to Mall, delicate retia mirabilia occur here and there in the venous network in the submucosa of the intestine of the dog. In the esophagus the arteries end in a capillary network situated Digitized by Microsoft® 252 THE DIGESTIVE ORGANS. in the mucosa and extending into the connective-tissue papillae of the mucosa. The vessels of the stomach are arranged in plexuses in the muscular coat, submucosa, and beneath the muscularis mucosae, as previously described. From the plexus beneath the muscularis mu- cosae, small branches are given off which pass through this layer and in the mucosa form a capillary network, consisting of relatively small capillaries, which surround the gastric glands, this plexus being par- ticularly well developed in the region around the body and neck of the glands, where the parietal cells are most numerous. The capil- laries of this network are continuous with capillaries of a much larger size, forming a network surrounding the gastric crypts and situated immediately under the epithelium lining the mucosa of the stomach. The blood is collected from this capillary plexus by small veins which pass nearly perpendicularly through the mucosa, forming a plexus above the muscularis mucosas, from which small veins pass through the muscularis mucosae to the venous plexus in the sub- mucosa. The blood-vessels of the mucosa of the small intestine may be divided into (1) the arteries of the villi and (2) the arteries of the intestinal glands. The former arise principally from the deep arterial network in the submucosa, then penetrate the muscularis mucosae and give off branches at acute angles which continue without further branching into the summits of the villi. Within the villi themselves the arteries lie in the axes. The broader villi may contain two arteries. The circular muscle-fibers of the arteries gradually disappear inside of the villi (dog), and at the summit of the latter the vessels break up into a large number of capillaries. These form a dense network extending beneath the basement mem- brane and into its marginal layer. These networks give rise to venous capillaries which unite to form small vessels and finally end in two or more larger veins inside of the villi. These latter are con- nected with the venous network in the mucosa. The glandular arteries, derived principally from the superficial network of the submucosa, also pass through the muscularis mucosae and break up internally into capillary nets which encircle the intestinal glands ; these give rise to small veins which empty into the venous plexus of the mucosa. The veins of the plexus in the mucosa unite to form larger branches, which connect with the plexus in the submucosa (compare Fig. 213). In the dog these trunks inside of the muscularis mucosae are encircled by bundles of muscle-fibers (sphincters, F. P. Mall). The capillaries of the solitary lymph-nodules do not always penetrate into the centers of the latter, but often leave a central nonvascular area. The blood-vessels of the mucosa of the large intestine are, in their distribution, similar to the glandular vessels of the small intes- tine and stomach. The lymph-vessels begin in the mucosa near the epithelium, pass Digitized by Microsoft® THE STOMACH AND INTESTINE. 253 down between the glands, and are arranged in the form of a net- work just above the muscularis mucosae, but with coarser meshes than that formed by the blood-vessels. Here the valves begin to make their appearance. The lymph-vessels pass through the mus- cularis mucosas and in the outer portion of the submucosa form a plexus with open meshes, from which are derived the efferent ves- sels which penetrate the muscular coat and thus gain access to the mesentery. In their course through the muscular coat they com- municate with the branches of a plexus of lymph-vessels situated between the two muscular layers, and also with lymph-vessels found in the serous coat. Central chyle- vessel of vil- lus. / 1~ Chyle-vessel. Mucosa. Muscularis mucosas. £ — Submucosa. Plexus of lymph -ves- sels. Circular mus- cular layer. Plexus of lymph-ves- sels. Long. muse. layerwiththe serous coat. Fig. 213. — Schematic transverse section of the human small intestine (after F. P. Mall). The lymphatics of the small intestine begin in the axes of the villi. When filled, these lymph-vessels are conspicuous, irregularly cylindric capillary tubules, lined by endothelial cells, and. known as the axial canals, the chyle-vessels, or the lacteals of the villi. They are hardly discernible when collapsed. If the villus be broad, it may contain two chyle-vessels, which then join at the apex of the villus, and may also be connected with each other by a few anasto- moses. At the base of the villus the chyle-vessel enters a lymphatic capillary network, the structure of which is due to the confluence Digitized by Microsoft® 254 THE DIGESTIVE ORGANS. of similar canals. Numerous lymph-vessels from this network penetrate the mucous membrane in a vertical direction, uniting at the bases of the intestinal glands to form a second plexus — sub- glandular plexus of the mucosa. A few of the lymph-vessels pene- trating the mucous membrane directly perforate the muscularis mucosae to join the lymphatic network of the submucosa. The subglandular plexus also communicates with the submucous lymphatic plexus by means of small radiating branches (vid. Fig. 213). The solitary lymph-nodules themselves contain no lymphatic vessels, but are encircled at their periphery by a network of lymph capillaries. The same is true of the nodules in Peyer's patches. It is an interesting fact that in the rabbit lymph-sinuses exist around Peyer's patches, giving to the latter a still greater similarity to the nodules of lymph-glands. The solitary nodules of the same Fig. 214. — A portion of the plexus of Auerbach from stomach of cat, stained with methylene-blue [intra vitam), as seen under low magnification. animal are not surrounded by the sinuses just mentioned (Stohr, 94)- The structures of the alimentary canal receive their innervation mainly from sympathetic neurones, the cell-bodies of which are grouped to form small ganglia, located at the nodal points of two plexuses, one of which is situated between the two layers of the muscular coat, the other in the submucosa. These two plexuses are found in the entire digestive tract, although not equally well developed in its different regions. The outer plexus, the more prominent of the two, situated between the two layers of the muscu- lar coat, is known as the plextis mycntcricns, or the plexus of Auer- bach. It consists of innumerable small sympathetic ganglia, united by small bundles of nonmedullated fibers, containing here and there a much smaller number of medullated nerve-fibers. The cell-bodies of the sympathetic neurones of this plexus are grouped to form the Digitized by Microsoft® THE STOMACH AND INTESTINE. 255 sympathetic ganglia. The dendrites, the number of which varies for the different cells, divide and redivide in the ganglia, some ex- tending into the nerve bundles uniting the ganglia. The neuraxes of the sympathetic neurones of the ganglia form nonmedullated nerve-fibers, which leave the ganglia by one of the several roots possessed by each ganglion, and, after repeated division and forming intricate plexuses in the circular and longitudinal layers of the mus- cular coat, terminate on the involuntary muscle-cells of these layers. The plexus in the submucosa, known as the. plexus of Meissner, is similarly constructed, although it contains fewer and much smaller ganglia and the meshes of the plexus are much finer. It commu- nicates by numerous anastomoses with the plexus of Auerbach. The neuraxes of the sympathetic neurones of this plexus have not been traced, with any degree of certainty, to their terminations. Numerous nonmedullated nerves enter the muscularis mucosje and, according to Berkley (93, I), form in the dog terminal bulbs and nodules which perhaps rep- resent the endings of motor (sympathetic) nerves in this ' layer. Nerve-fibers have also been traced into the mucosa, and in the vicinity of the glands and in the villi are found numerous exceedingly fine nerve-fibers which inter- lace, but in the greater por- tion of the intestinal tract the endings of these fibers have not been fully worked out. That they end on the gland- cells seems very probable from observations made by Kytmanow (96), who was able, by means of the methylene-blue method, to stain plexuses of fine nerve-fibrils surrounding the gastric glands of the cat, some of these fibrils being traced through the basement membrane of the glands and to and between the gland-cells, where they ter- minated in clusters of small nodules on both the chief and parietal cells. The plexus of Meissner is not so well developed in the esophagus as in the remaining portions of the digestive tract. That the cell-bodies of many of the sympathetic neurones of Auerbach's and Meissner's plexuses are capable of being stimulated by cerebrospinal nerves seems certain from observations made by Dogiel (95), who has shown that many small medullated nerve- fibers which enter the digestive tract through the mesentery (small and large intestines) terminate after repeated division in terminal end-baskets which surround the cell-bodies of many of the sympa- thetic neurones of these plexuses. Similar nerve-fibers ending in Fig. 215. — From thin section of esophagus of cat, showing the epithelium and a portion of the mucosa and the terminal nerve-fibrils in the epithelium (from preparation of Dr. DeWitt). Digitized by Microsoft® 256 THE DIGESTIVE ORGANS. baskets have also been observed in the ganglia of the plexuses of the stomach and esophagus. Large medullated nerve-fibers, the dendrites of sensory neurones, have also been traced to the alimen- tary canal. In the esophagus these pass to the mucosa, where, after repeated division, they lose their medullary sheaths, the non- medullated terminal branches forming a subepithelial plexus from which terminal, varicose branches, further dividing, enter the strati- fied epithelium and may be traced to near the surface of the epithe- lium. Large medullated nerve -fibers may be traced through the ganglia of Auerbach's and Meissner's plexuses in the stomach and intestinal canal and through the nerve bundles uniting these ganglia (Dogiel, 99), but the termination of these fibers has not been deter- mined. 6. THE SECRETION OF THE INTESTINE AND THE ABSORPTION OF FAT. The cells of Brunner's glands are similar in many respects to those of the pyloric glands. During digestion they show analogous changes — i. e., the secretory cells are large and clear during a state of hunger, and become smaller and opaque during the process of secretion. Another and still greater similarity between Brunner's glands and the pyloric glands is established by the fact that the cells of the former, especially during hunger, have been shown to be rich in pepsin. It is well known that the goblet cells of the intestinal glands are very numerous during starvation, and that they nearly disappear after continued functional activity ; furthermore, they en- tirely disappear in certain portions of the rabbit's intestine after pilocarpin-poisoning. It would therefore appear that the principal physiologic function of the glands of Lieberkuhn is to secrete mucus, although the possibility of the production of another secretion, especially in the small intestine, must not be excluded (compare R. Heidenhain, 83). Until recently it was believed that the fat contained in the food was emulsified in the intestine, and furthermore that the bile acted upon the cuticular margins of the epithelial cells in the villi in such a manner that an assimilation of the emulsified fat by the cells of the villi (not by the goblet cells) was made possible. It has been re- peatedly observed that the epithelial cells contained fat granules during absorption. Hence a mechanism was sought for which would account for an assimilation of globules of emulsified fat on the part of the cells. It seemed most probable that protoplasmic threads (pseudopodia) were thrown out from each cell through its cuticular zone, which, after taking up the fat, withdrew with it again . into the cell. But when it was shown that, after feeding with fatty acids or soaps, globules of fat still appeared in the epithelial cells as before, and that the chyle also contained fat, the hypothesis was Digitized by Microsoft® THE LIVER. 257 suggested that the fat is split up by the pancreatic juice into glycerin and fatty acids, and that the fatty acids are then dissolved by the bile and the alkalies of the intestinal juice, only again to combine with the glycerin to form fat within the epithelial cells. It remains for the histologist to ascertain the exact mechanism in the cell which changes the fatty acids into fat. Altmann (94) claims that certain granules of the cells (elementary organisms) offer a solution to this problem. The manner in which the fat globules gain access to the central vessels of the villi is a question which has not as yet been settled. D. THE LIVER. In the adult the liver is a lobular, tubular gland with anastomos- ing tubules. When viewed with the unaided eye or under low magnification the liver is seen to be composed of a large number Intralobular vein. Branch of hepatic artery. Interlobular connective tissue. Fig. 216. — Section through liver of pig, showing chains of liver-cells ; X 7°- of nearly spheric divisions of equal size ; this is particularly notice- able in some animals, especially in the pig. These divisions are the liver lobules and have a diameter of from 0.7 to 2.2 mm. They are separated from each other by a varying amount of interlobular con- nective tissue, which is a continuation of the capsule of Glisson, a fibro-elastic layer surrounding the entire liver and covered for the greater portion by a layer of mesothelium. In the interlobular septa are found the larger blood-vessels, bile passages, nerves and lymph-vessels. On examining a thick section of the liver with a low power, a radiate structure of the lobule is noticeable, and an open space is seen in its center, which according to the direction of the section, is either completely surrounded by liver tissue or con- nected with the periphery of the lobule by a canal. This open 17 Digitized by Microsoft® 258 THE DIGESTIVE ORGANS. space represents the central or intralobular vein of the lobule which belongs to the system of the inferior vena cava. From the center of the lobule toward its periphery extend numerous radiating strands of cells, which branch freely and anastomose with each other, and are known as the trabecule, or cords of hepatic cells. Be- tween the latter are small, clear spaces occupied partly by blood capillaries and partly by the intralobular connective tissue. The above description is in some respects not a true statement of the appear- ance presented by the human liver, as in the latter one or more lobules may blend with each other, thus rendering the individual lobules less distinct. The hepatic cords consist of rows of hepatic cells. The cells Portal inter- - lobular branch, cut longitudi- nally. The same, cut transversely. Anastomos- es between vessels of several lobules. Fig. 217.. -Section through injected liver of rahbit. The boundaries of the lobules are indistinct ; X about 35. are usually polyhedral in form, with surfaces so approximated that a cylindric capillary space, known as the bile capillary remains be- tween them. The angles of the cells also show grooves which join those of the neighboring cells to form canals in which lie the blood capillaries*. A closer examination of the hepatic cells reveals the fact that they possess no distinct membrane, and, in a resting state, usually contain a single nucleus, although some possess two. It is an interesting fact that nearly all the hepatic cells of some animals — as, for instance, the rabbit — contain two nuclei. The cell-bodies of the hepatic cells, which average from 18// to 26// in diameter, show a differentiation into protoplasm and paraplasm. This is especially manifest in a state of hunger. In this condition Digitized by Microsoft® THE LIVER. 259 it is seen that the network of protoplasm around the nucleus is un- usually dense, and becomes looser in arrangement as it extends toward the periphery of the cell-body. The paraplasm is slightly granular, and contains glycogen and bile drops during the func- tional activity of the cell (secretion vacuoles). The vacuoles in the paraplasm play an important part in the secretion of the cell, and are Intralobular vein. Fig. 218. — Human bile capillaries. The capillaries of one lobule are seen to anas- tomose with those of the adjoining lobule (below, in the figure) ; X Ito (chrome-silver method). Vacuole of secretion. Tubule of same. Bile capillary. -Vs^ Fig. 219. — Human bile capillaries as seen in section ; X4^° (chrome-silver method). due to the confluence of minute drops of bile into a large globule. As soon as the vacuole has attained a certain size it tends to empty its contents into the bile capillary through a small tubule connect- ing the vacuole with the bile capillary (Kupffer, 73, 89). The bile capillaries are, as we have remarked, nothing but tubu- lar, capillary spaces between the hepatic cells, with no distinct indi- Digitized by Microsoft® 26o THE DIGESTIVE ORGANS. vidual walls. They may be compared to the lumen of a tubular gland, although in the human liver their walls consist of only two rows of hepatic cells. In the lower vertebrates the walls of the bile capillaries appear in transverse section to consist of several cells (in the frog generally three, in the viper as many as five). The bile capillaries naturally follow the course of the hepatic cords — i. e., in man extending radially. They form networks, the meshes of which correspond to the size of the hepatic cells. At the periphery of the lobule the hepatic cells pass directly over into the epithelial cells of the smaller interlobular bile-ducts. The epithelium of the latter is of the cubical variety, its cells being considerably smaller than the hepatic cells. At the point where the hepatic cells become J$,^d>, -^ Bile capillaries, continuous with the walls of the smaller passages we find a few cells of gradually decreasing size which represent a transition stage from the cells of the bile capil- Fig. 220. — Schematic diagram of he- patic cord in transverse section. At the left the bile capillary is formed by four cells, at the right by two ; the latter type occurs in the human adult. Fig. 221. — From the human liver, showing the beginning of the bile-ducts ; X 9° (chrome-silver). laries (hepatic cells) to those of the interlobular bile passages. The vascular system of the liver is peculiar in that, besides the usual arterial and venous vessels common to all organs, there is found another large afferent vein — the portal vein. It arises from a confluence of the superior and inferior mesenteric, the splenic, coronary veins from the stomach, and cystic veins. It divides into two branches, the right supplying the right lobe of the liver, the left the remaining lobes. These branches again divide into numerous smaller branches, the smallest of which finally reach the individual lobules. While still within the inter- lobular tissue, the branches of the portal vein receive the venous • blood from the hepatic arterial system. These smaller divisions constitute the internal radicals of the portal vein, since they are within the liver itself. Along its whole course through the inter- lobular connective tissue the portal vein and its branches are accom- panied by divisions of the hepatic artery and bile passages. In a transverse section of the liver the arrangement of these structures in the interlobular tissue is such that the cross-sections of the vessels Digitized by Microsoft® THE LIVER. 26l belonging to the hepatic vein are seen to be at some distance from the closely approximated branches of the portal vein and bile pas- sages. Branches of the portal vein encircle the liver lobules at different points, and while they remain within the interlobular con- nective tissue, are known as interlobular veins. From these, small offshoots are given off to the lobules which, on entering, divide into capillaries and form a closely reticulated network between the hepatic cords. The meshes of this network are about as large as an hepatic cell, each cell coming in repeated contact with the blood capillaries. All of these capillaries pass toward the central or intralobular vein of the lobule, which during its efferent passage through the lobule continues to receive capillaries from the portal Blood capillaries. Intralobular vein. Cord of hepatic cells. Interlobular vessel. Fig. 222. — Injected blood-vessels in liver lobule of rabbit ; X Ioa system. The intralobular veins unite to form the sublobular veins, situated in the interlobular connective tissue, and these unite to form the larger hepatic veins which empty into the inferior vena cava. The relations of the various blood-vessels within the lobule are in themselves somewhat difficult of comprehension, but the whole be- comes still more complicated when the reciprocal relations of the vessels and bile capillaries are taken into consideration. In order to understand the structure of the liver lobule, with its hepatic cords, vessels, and bile capillaries, the following points should be borne in mind : The course of the bile capillaries is along the sur- faces, and that of the blood-vessels along the angles of the hepatic cells ; every cell comes in contact with a bile capillary and a blood Digitized by Microsoft® 262 THE DIGESTIVE ORGANS. capillary. The latter, however, do not come in contact with the former, but in man are separated by at least half the breadth of a hepatic cell. In animals in which the bile capillaries are bounded by more than two cells, the blood-vessels extend along the outer sides of the hepatic cells ; here the bile and blood capillaries are separated from each other by the breadth of a whole cell. The connective tissue within the hepatic lobules presents points of interest which, however, are not demonstrable in organs treated by ordinary methods. But when the liver tissue is treated by a certain special method {vid. T. 258), an astounding number of fibers are seen extending in regular arrangement from the periphery toward the central vein. These fibers are extremely delicate, of nearly equal size, and intermingle in such a manner as to form an envel- oping network about the blood capillaries (Gitterfasern ; Kupffer ; Intralobular vein. Boundary of - lobule. Fig. 223. — Reticulum (Gitterfasern) of dog's liver; X I2 ° (gold-chlorid method). Oppel, 91 ; vid. Fig. 223). A few coarser fibers (radiate fibers, Kupffer, 73) seem to enter in a less degree into the formation of the sheath around the blood capillaries ; they also extend from the periphery toward the center of the lobule and form a coarse reticu- lum, the meshes of which are drawn out radially. The radiate fibers are less prominent in man, but are numerous and well devel- oped in animals (rat, dog). With what exuberance the intralobular connective tissue may develop, is seen in the accompanying sketch of a sturgeon's liver, which is taken from one of Kupffer's prepara- tions. Certain peculiar cells — the so-called stellate cells of Kupffer (76) — occur exclusively in the lobule, and are seen only after a special method of treatment. They are uniformly distributed, of differ- ent shapes, elongated, and end in two or three pointed projec- Digitized by Microsoft® THE LIVER. 263 tions. They are smaller than the hepatic cells, and contain one or two nuclei. In a recent communication Kupffer (99) states that the stellate cells belong to the endothelium of the intralobular capillaries of the portal vein. In such cells blood-corpuscles and fragments of such were often found. The endothelium of these capillaries possesses, therefore, a phagocytic function, taking up particles of foreign mat- ter, blood-corpuscles, etc. The efferent ducts of the liver, the bile-ducts, are lined by col- umnar epithelium, varying in height in direct proportion to the cal- iber of the passage. The smallest ducts possess a low, the medium sized a cubical, and the larger a columnar epithelium. The smaller bile-ducts have no clearly defined external walls other than the membrana propria ; the larger ones, on the other hand, possess a Connective-tissue fibers. Fig. 224. — Connective tissue from liver of sturgeon. At a is an open space from which the hepatic cells were mechanically removed during treatment. -connective-tissue sheath which may even present two layers in the larger passages. Unstriped muscular fibers occur in the large ducts, but do not form a continuous layer until the gall-bladder is reached, where two layers are found. The epithelium of the gall-bladder is of the columnar variety, with nuclei in the lower thirds of the cells ; a cuticular zone is either absent or very poorly developed. The mucous membrane of the gall-bladder is raised into folds having a peculiar reticular arrangement. The gall-bladder contains a few mucous glands •; these are, however, more numerous in the hepatic, cystic, and common bile-ducts. Besides the network of lymph-vessels accompanying the portal vein and hepatic artery, there are also lymphatic networks about the branches of the hepatic vein (v. Wittich). The lymph-ves- sels penetrate the liver lobules and pass between the hepatic cells Digitized by Microsoft® 264 THE DIGESTIVE ORGANS. and the blood capillaries to form perivascular capillary lymph- spaces. Berkley (94) has described several divisions of the intrinsic nerves of the liver, all connected and morphologically alike. These nerves are no doubt the neuraxes of sympathetic neurones, the cell-bodies of which are located in ganglia outside of this organ. No medul- lated fibers were found by him, although it seems probable that the nerve-fibrils terminating between the cells of the bile-ducts (see be- low) are terminal branches of sensory nerve-fibers. The nerves of the liver accompany the portal vessels, the hepatic arteries, and the bile-ducts. The first division of the nerves, embracing the larger number of the intrinsic hepatic nerves, accompany the branches of the portal vessels, form plexuses about them, and end in inter- lobular and intralobular ramifications, the latter showing here and there knob-like terminations on the liver-cells, and, in their course, give off here and there branches which end on the portal vessels. Intralobular vein — Interlobular con- nective tissue. "Stellate cells. Fig. 225. — Part of a section through liver lobule from dog, showing stellate cells ; X 168 [yid. T. 257). The nerve-fibers following the hepatic arteries are in every respect like the vascular nerves in other glands. Some of the terminal branches seem, however, to end on hepatic cells. The nerve-fibers following the bile-ducts may be traced to the smaller and medium-sized ducts, forming a network about them, and ending here and there in small twigs on the outer surface of the cells, and occasionally, it would seem, between the epithelial cells lining the ducts. The suggestion seems warranted that these terminal fibrils are the end- ings of sensory nerves. Some of the nerve-fibers following the bile-ducts may be traced into the hepatic lobules. The intralobu- lar plexus is formed, therefore, by the terminal branches of the non- medullated nerve-fibers accompanying the portal 'and hepatic ves- sels and the bile-ducts. In the wall of the gall-bladder are found numerous small sympathetic ganglia formed by the grouping of the cell-bodies of sympathetic neurones (Dogiel). The neuraxes of these Digitized by Microsoft® THE PANCREAS. 265 innervate the nonstriated muscle of this structure. Large, rriedul- lated nerve-fibers may be traced through these ganglia which appear to end in free sensory endings in and under the epithelium lining the gall-bladder (Huber). In the human embryo the liver originates from the intestine during the second month as a double ventral diverticulum. Later solid trabecular' masses are developed which then unite and become hollow. At this stage the whole gland is uniform in structure, as a division into lobules does not take place until later. The bile capillaries are surrounded by more than two rows of cells. In this stage the embryonal liver suggests a condition which is permanent during the life of certain animals. Only later when the vena? ad- vehentes, which later represent the branches of the portal vein, penetrate the liver, is there a secondary division into lobules (about the fourth month), by which process the primitive type gradually changes to that characteristic of the adult. Nucleus and outer zone. E. THE PANCREAS. Like the liver, the pancreas is an accessory intestinal gland, and originates as a diverticulum of the intestine. It remains in perma- nent communication with the intestine by means of its duct — the pancreatic or Wirsungian duct. The pancreas is composed of numerous microscopic lobules, surrounded by connective tissue which penetrates into the lob- ules and between the alveoli and is accompanied by vessels and nerves. The secretory portion of the organ may be regarded as a branched tubulo-acinal gland with terminal alveoli, the latter forming the principal por- tion of the gland. The epi- thelial walls of the alveoli con- sist of a number of secretoiy cells, whose appearance varies according to the functional state of the organ. The basilar portions of the cells present a homo- geneous protoplasm, while those parts of the cells bordering upon the lumen are granular. The relation of these zones to each other depends upon the physiologic condition of the gland ; during starvation the internal or granular zone is wide and promi- nent ; after moderate secretion the cells become as a whole some- what smaller, the granules decrease in number, and the outer or protoplasmic zone increases in size. After prolonged secretion there is an entire absence of the granules, and the whole cell appar- ently consists of homogeneous protoplasm. It is therefore probable Fig. 226. — Transverse section through alveolus of frog's pancreas. Technic No. 125- Digitized by Microsoft® 266 THE DIGESTIVE ORGANS. that during a state of rest peculiar granules (zymogen granules) are formed at the expense of the protoplasm, and that these granules represent a preliminary stage of the finished secretion. During the functional activity of the gland the granules gradually disappear, while the fluid secretion simultaneously makes its appearance in the lumen, although the granules have as yet never been observed in the lumen itself. After secretion the cell grows again until it reaches its original size, only again to begin the formation of zymo- gen granules. Whether the cells of the gland are destroyed or not during secretion is still a matter of uncertainty. An intermediate tubule similar to those of the salivary glands connects with each alveolus, and then passes over into a short in- tralobular duct. This is lined, as in the salivary glands, with columnar epithelial cells, which are not, however (at least in man), striated at their basal ends. The intralobular ducts merge Centro-acinal cell. Fig. 227. — From section through human pancreas ; X about 200 (sublimate). into excretory ducts, which finally empty into the pancreatic duct. The epithelium of the excretory ducts is simple columnar in type. Goblet cells are seen only in the pancreatic duct. In the secreting alveoli small protoplasmic, polygonal, and even stellate cells are often seen, the so-called centro-acinal cells, or cells of Langerhans. The significance of these structures is not fully understood. Langerhans himself supposed that they belonged to the walls of the excretory ducts. This interpretation seems war- ranted by the fact that it has been found that the secreting cells of the alveoli are directly joined to the low cells of the intermediate tubules. When the alveoli lie closely packed together, the ad- joining intermediate tubules fuse and are reduced to one or, at most, a few cells. As a result a condition is seen within the alveolar complexus, especially when the excretory ducts are in a collapsed state, closely resembling the structures seen by Langer- Digitized by Microsoft® THE PANCREAS. 267 hans. Peculiar cells, wedged in here and there between the secre- tory cells, but resting on the membrana propria, have also been observed. They undoubtedly are sustentacular cells of the gland (cuneate cells, Podwyssotzki, 82). The membrana propria of the alveoli is probably homogenous. Immediately adjoining it is another delicate but firm membrane, consisting of fibrils whose structure in many respects resembles that of the reticular fibers (Gitterfasern) in the liver and spleen, but which are here in relation to the alveoli (Podwyssotzki, 82). In warm- and cold-blooded animals, groups of cells differing in arrangement, size, and structure from the secretoiy cells, are found among the gland tubules and alveoli of the pancreas ; these are known as the intertubular cell-masses , or areas of Langerhans. They Outer zone of — - a secretory & cell. H Connective ,-^L tissue. Larger gland - duct. Intermediate tubule. Inner granular zone of secre- tory cells. Fig. 228. — From section through human pancreas; X45° (sublimate). consist of slightly granular cells, smaller than- the secretory cells of the alveoli, arranged in the form of anastomosing trabeculae, with irregular spaces, varying in size, separating the trabecular. Dogiel (93) has shown that in a well-preserved human pancreas treated by the chrome-silver method, in which the gland ducts even to their finest intra-alveolar branches were well stained, no ducts were found in the areas of Langerhans. Such areas are, in the human pancreas, usually separated from the surrounding gland tissue by a small amount of connective tissue. They possess a blood supply, consisting of relatively large capillaries found in the spaces formed by the trabeculae of cells above mentioned. The areas of Langer- hans have been variously interpreted. They have been looked upon as small areas of gland tissue in process of degeneration, or Digitized by Microsoft® 268 THE DIGESTIVE ORGANS. again as areas of embryonic gland tissue. From their structure and distinct blood -supply, and the fact that no ducts have been traced into these areas, it seems probable that they are small masses of cells forming a secretion which passes into the blood-vessels — in- ternal secretion. The blood-vessels enter the gland with the pancreatic duct, divide into smaller branches in the lobules, and finally break up into Centro-acinal cell. Secretory cell. — Intermediate duct. Fig. 229. — Scheme showing relation of three adjoining alveoli to excretory duct, illustrating origin of centro-acinal cells. Blood capillary. Alveolus of gland. Area of Langer- hans. Fig. 230. — From section of human pancreas, showing gland alveoli surrounding an area of Langerhans. capillaries which encircle the secreting alveoli. The meshes of the capillary network are not all of the same size. In some regions they are so wide that quite large areas of the alveoli are without blood-vessels. The nerves of the pancreas have been investigated by Cajal and Sala (91) and Erik Muller (92), who find in this gland large num- bers of nonmedullated nerve-fibers, some coming from sympathetic Digitized by Microsoft® TECHNIC. 269 ganglion cells situated in the pancreas and others entering from without. The nonmedullated nerve-fibers form plexuses surround- ing the excretory ducts and end in periacinal networks. Fibrils from the network about the alveoli were traced to the secretory cells. A portion of the nonmedullated nerves in the pancreas form perivascular plexuses. The development of the pancreas is peculiar in that the larger portion, together with the duct of Santorini, originates from the dorsal intestinal wall, and a smaller portion from the ductus chole- dochus. The latter part, with its accessory pancreatic duct, fuses with the former, after which there is a gradual retrogression of the duct of Santorini, so that finally the entire secretion of the pancreas almost invariably flows into the pancreatic or Wirsungian duct. TECHNIC. 224. The oral mucous membrane may be fixed with corrosive sublimate or alcohol, stained in bulk, and examined in cross-section. If special structures, such as glands, nerves, or the distribution of mitoses, are to be examined, special methods must be adopted. 225. In order to obtain a general view of the structure of the teeth, the latter must be macerated and ground as in the case of bone (T. 152). 226. The relations of the hard and soft parts in undecalcified teeth are best studied by the use of Koch's petrifaction method (irid. T. 158). 227. The teeth may also be examined in section, and when decalci- fied are treated as bone (vid. T. 157). Hydrochloric acid, dilute chromic acid, and picric acid dissolve the enamel prisms, their cement-substance being the first to disappear (von Ebner, 91). 228. The enamel of young teeth stains brown in a solution of chromic acid or its salts, and blackens in osmic acid. In the enamel cells, globules are seen, which are stained in osmic acid. If longitudinal sections of the enamel be corroded with hydrochloric acid, the cruciform arrangement of the enamel prisms is plainly seen. 229. The fibrils of the dentin may be demonstrated by decalcifying a tooth in the fluid recommended by von Ebner (T. 157), the teeth of young individuals being well adapted for this purpose. Occasionally carious teeth also show the fibrils plainly. Corrosion with hydrochloric acid produces the same result. 230. The cementum, especially that part lacking in cells, contains a large number of Sharpey's fibers. 231. The development of the teeth is studied in the embryo; the jaw-bone is fixed, decalcified, and cut in serial sections. The most con- venient material is a sheep embryo, which can almost always be had from the slaughter-house. 232. To study the taste-buds of the tongue and the relations which their constituent cells bear to each other, fixation in Flemming's fluid is recommended. The orientation of the taste-buds must be very care- fully done, after which exactly longitudinal or transverse serial sections are made (not thicker than 5 fi) and stained with safranin-gentian-violet (vid. T. 120). Digitized by Microsoft® 270 THE DIGESTIVE ORGANS. 233. The nerves in the taste-buds are brought out either by Golgi's method, the methylene-blue method, or by the use of gold chlorid. If the last be used the procedure is as follows : A papilla foliata of a rabbit is removed with a sharp razor and placed for ten minutes in lemon juice, then in gold chlorid for from three-quarters of an hour to one hour, after which the specimen is placed in water weakly acidulated with acetic acid (5 drops to 100 c.c. of water) and exposed to the light. As soon as reduction has taken place the specimen is treated with alcohol and cut in vertical sections. These may be treated for a short time with formic acid (in which they swell slightly), washed with water, and mounted in glycerin. 234. In certain objects, such as the nictitating membrane of the frog, certain lobules of the rabbit's pancreas (the latter being so thin as to be especially well adapted for microscopic examination), etc., the glandular structure may be examined in normal salt solution. 235. Microscopically, the glands present varying pictures according to the phase of secretion in which they are fixed. Specimens in the different stages may be obtained either by feeding and then killing the animal after a definite period, or by irritating certain nerves, or finally by the use of certain poisons especially adapted to this purpose, such as atropin and pilocarpin. In the rabbit, for instance, 1 c.c. of a 5% solution of pilocarpin hydrochlorate or 1 c.c. of a 0.5% solution of atropin sulphate is used for each kilogram of the animal's weight. In atropin-intoxication secretion is suppressed, while in pilocarpin-poisoning it is increased. By this method cells are obtained either full of secretion or containing no secretion at all. 236. Sections should be made from carefully selected material which has been fixed either in Flemming's solution or corrosive subli- mate, although fixation with strong alcohol also gives instructive pictures. 237. In preparations fixed with Flemming's solution the crescents of Gianuzzi stain somewhat more deeply than the remaining cells of the alveoli, and in objects that have been treated with alcohol or corrosive sublimate and then stained with hematoxylin the crescents take on a very deep color. The intermediate tubules of the salivary glands also assume a deeper stain with hematoxylin and carmin. The intralobular tubes are particularly well defined by certain stains, as for instance when Congo red is used after staining with hematoxylin ; other acid anilin stains may also be used (compare T. 242). The intralobular tubes of most salivary glands (not, however, of the parotid of the rabbit nor of the sublingual of the dog) are stained a dark -brown color (calcareous reaction) by agitat- ing small, fresh pieces of tissue in order to facilitate the entrance of air, and then treating them with a dilute aqueous solution of pyrogallic acid. The stain persists for some time in specimens preserved in alcohol. Sec- tions made by free hand from tissues treated by this method give excel- lent results (Merkel, 83). 238. Mucin is soluble in dilute alkalies, as for instance lime-water, and may be precipitated from these solutions by the addition of acetic acid, although the precipitate does not redissolve in an excess of acetic acid ; mucin is also precipitated by alcohol, but not by heat. Mucin- ogen does not stain with hematoxylin, as does mucin. By this latter test a gland in a state of functional activity may be differentiated from one at rest (R. Heidenhain, 83). After treatment with alcohol, safranin Digitized by Microsoft® TECHNIC. 27 1 stains mucin orange-yellow. For the demonstration of mucin, more es- pecially in alcoholic preparations, H. Hoyer (90) has recommended thionin or its substitute, toluidin-blue. Indeed, the basic anilin dyes in general seem to have a particular affinity for mucin. 239. P. Mayer (96) recommends the following two solutions for the staining of mucin : (1) Mucicarmin — Carmin 1 gm., aluminium chlorid 0.5 gm., and distilled water 2 c.c. are stirred together and heated over a small flame till the mixture becomes quite dark. As soon as the mixture has attained the consistency of thick syrup, 50% alcohol is added and the whole transferred to a bottle in which it is shaken after the addition of more alcohol. Finally, still more 50% alcohol is added until the whole amounts to 100 c.c. Before using, this stock solution is diluted tenfold with tap-water rich in lime-salts. (2) Muchematein : (a) Aqueous solution — 0.2 gm. of hematein is ground in a mortar con- taining a few drops of glycerin; to this are added 0.1 gm. aluminium chlorid, 40 c.c. glycerin, and 60 c.c. distilled water. (<5) Alcoholic solution— 0.2 gm. hematein, 0.1 gm. aluminium chlorid, 100 c.c. 70% alcohol, and 1 or 2 drops of nitric acid. Both of these solutions are used for staining mucin in sections and thin membranes. By the use of these methods the mucous acini of mixed glands are shown with ease and pre- cision. Under favorable conditions the whole secretory and excretory system of the gland may be brought out by Golgi's method (see this). 240. In order to obtain a general structural view of the esophagus a small animal may be selected, in which case small pieces of tissue are fixed and imbedded in paraffin. If a large animal is used, the tissue is imbedded in celloidin. 241. The mucous membrane of the stomach should be fixed while still fresh and warm, the best fixative for this purpose being corrosive sub- limate. Mixtures of osmic acid are also serviceable, but fixing with cor- rosive sublimate increases the staining power of the tissue. In order to preserve the stomach and intestine in a dilated condition, they should be filled with the fixing fluid and after ligation placed whole in the fixing agent. 242. In gastric mucous membrane that has been fixed either with cor- rosive sublimate or alcohol, the parietal cells are easily differentiated from the chief cells by staining. The most reliable and convenient method is as follows : Sections fastened to the slide by the water-albumin fixative method are stained with hematoxylin and then placed in a dilute aqueous solution of Congo red until they assume a red color (minutes); they are then washed with dilute alcohol until the parietal cells appear red and the chief cells bluish (Stintzing). Almost all acid anilin dyes have an affinity for the parietal cells ; hence the red stains may be com- bined with hematoxylin and the blue ones with carmin. The chief cells then take the color of the carmin or hematoxylin, and the parietal cells that of the anilins. 243. An accurate fixation of that portion of the small intestine pos- sessing villi is attended with great difficulty, since the axial tissue of the villi shows a tendency to retract from the epithelial layer surrounding it (the latter becoming fixed first) ; and as a consequence spaces are formed at the summits of the villi which undoubtedly represent artefacts. A good method is to cut pieces from tissue while still warm and fix in osmic acid. If portions of the intestine be filled with alcohol or corrosive sub- limate and thus dilated, both the glands and villi are shortened. The Digitized by Microsoft® 272 THE DIGESTIVE ORGANS. methods above mentioned for staining mucin may be used to stain the goblet cells. The villi may also be examined in a fresh condition in one of the indifferent fluids (vid. T. 13). For this purpose the intestine of the mouse is especially well adapted. 244. The absorption of fat is best studied in preparations fixed in osmic acid, and especially in those treated by Altmann's method {vid. T. 124). 245. The technic for the solitary lymph-follicles and Peyer's patches is the same as that for lymph-glands. For this purpose the cecum of a rabbit or guinea-pig is the best material. 246. The nerves of the intestinal mucous membrane are best demon- strated by means of the methylene-blue method or Golgi's method (vid. Technic), and the coarser filaments of Auerbach's and Meissner's plexuses may also be stained by the gold method (Lowit's procedure, T. 182). Good results are also obtained by staining with hematoxylin such speci- mens as have been previously fixed and distended with alcohol. The plexuses then appear somewhat darker than the remaining tissue of the isolated mucous membrane or muscular layer. 247. The arrangement of the liver lobules is best seen in the pig's liver. In the human liver and in most domestic animals the lobules are not sharply defined, two or three adjacent lobules merging into each other. In the liver of the fetus, of the new-born, and of children, the lobules are seen indistinctly or not at all, although the perivascular spaces of the blood-vessels are better seen than in the adult. 248. The liver-cells are best examined by treating small pieces of tissue with 1 °J osmic acid or osmic mixtures ; in the latter case subse- quent treatment with pyroligneous acid is necessary (T. 18). Good results can also be obtained by fixing with corrosive sublimate and stain- ing with hematoxylin (after M. Heidenhain, T. 65). 249. In order to see the glycogen in the liver-cells Ranvier (89) proceeds as follows : A dog is fed on boiled potatoes for two days, after which sections of its liver are cut with a freezing microtome and examined in iodized serum (T. 13). In a short time the glycogen is stained a wine-red. If the preparation be now exposed to osmic acid vapor, the stain will remain fixed for from twenty-four to forty-eight hours. Glyco- gen is insoluble in alcohol and ether, and stains a port wine-red in iodin solutions ; the color disappears when the specimen is warmed, but returns again on cooling. 250. The distribution of the hepatic blood-vessels is usually demon- strated by injection of the portal vein, as the injection of the hepatic artery does not,' as a rule, give such satisfactory results. 251. The injection method is also employed for the demonstration of the bile capillaries. Chrzonszczewsky recommends the following so-called physiologic autoinjection : A saturated aqueous solution of indigo-carmin is injected into the external jugular vein three times in the course of one and one-half hours (dog 50 c.c. each time, cat 30 c.c, full-grown rabbit 20 c.c). The animal is then killed and small pieces of its liver fixed in absolute alcohol or in potassium chlorid ; in the latter case a saturated solution of the salt may be injected into the blood-ves- sels. A subsequent injection of the blood-vessels with carmin -gelatin may also be employed and the whole liver then hardened in alcohol. By Digitized by Microsoft® TECHNIC. 273 this method the bile capillaries finally become filled with the indigo-car - min by a gradual elimination of the substance from the blood- and lymph- vessels and passage through the cells into the biliary system, while the blood-vessels themselves are distended by the carmin-gelatin. In the frog, the demonstration of the biliary passages is more easily accomplished by injecting 2 c.c. of the indigo-carmin solution into the large lymph- sac arid killing it after a few hours. The liver is then fixed in the manner described above and is then ready for further treatment. 252. The bile passages may also be injected directly through the hepatic duct or the ductus choledochus. For this purpose it is best to use a concentrated aqueous solution of Berlin blue (Berlin blue that is soluble in water) . The results obtained by this method are not, however, always satisfactory, and even in the best of cases only the peripheral por- tions of the liver lobules are successfully injected. 253. The bile capillaries may be impregnated with chrome-silver. Fresh pieces of liver tissue are placed for two or three days in a potas- sium bichromate -osmic acid solution (4 vols, of a 3% bichromate of potassium solution and 1 vol. of 1 % osmic acid) and then transferred to a 0.75% aqueous solution of silver nitrate. After rinsing in distilled water the specimens are cut with a razor, the sections again washed with distilled water, placed for a short time in absolute alcohol, cleared in xylol, and finally preserved in hard Canada balsam. Both celloidin and paraffin imbedding are admissible, but either process must be hurried, as the preparation always suffers under such treatment. In the finished specimen, the bile capillaries appear black by direct light. 254. Another method which brings to view more extensive areas of the bile capillaries is as follows : A piece of liver tissue from a freshly killed animal is fixed in rapidly ascending strengths of potassium bichromate solution (from 2% to 5%). After three weeks the specimen is placed in a 0.75% silver nitrate solution, when after a few days (very marked after eight days) the bile capillaries, if examined in sections, will appear black by direct light (Oppel, 90). 255. Sometimes the bile capillaries are brought out in preparations treated by the method of R. Heidenhain (T. 85), although only small areas are colored and these not constantly. The application of other stains, as for instance the method of M. Heidenhain (T. 65) following the gold chlorid treatment, often results in the staining of small areas of bile capillaries. 256. In all the methods used for the demonstration of the bile capil- laries, whether physiologic autoinjection, direct injection, or impregna- tion, the secretion vacuoles of the liver-cells are clearly brought to view. 257. By treating pieces of liver tissue according to the method of Kupffer (76) the connective tissue of the liver, especially the reticular structure (Gitterfasern), is shown. Fresh liver tissue is cut with the double knife and the thinnest sections placed for a short time in a 0.6% sodium chlorid solution or in a 0.05% solution of chromic acid. From this they are transferred to a very dilute solution of gold chlorid (Gerlach) (gold chlorid 1 gm., hydrochloric acid 1 c.c, water 10 liters), and kept for one to several days in the dark until they assume a reddish or violet color. If the staining has been satisfactory (which is by no means always the case), the reticular fibers, and occasionally also the stellate cells, are 18 Digitized by Microsoft® 274 THE DIGESTIVE ORGANS. seen. Instead of the double knife the freezing microtome may be used and the method continued as stated (Rothe). 258. The reticular fibers are seen under more favorable conditions by using the following method, recommended by Oppel (91) : Fresh pieces of tissue fixed in alcohol are placed for twenty-four hours in a o. 5 °/ aque- ous solution of yellow chromate of potassium (larger pieces in stronger solutions up to 5%), then washed with a very dilute solution of nitrate of silver (a few drops of a 0.75% solution to 30 c.c. distilled water), and transferred to a 0.75% solution of silver nitrate. In twenty-four hours the intralobular network surrounding the blood capillaries will have be- come stained. The best areas lie at the periphery of the specimen, and extend about 1 mm. into the parenchyma. Free-hand sections are made, or the specimens are quickly imbedded in celloidin or paraffin, to be cut afterward by means of the microtome. The same results are obtained by placing small fresh pieces of the tissue for two or three days in a 0.5% chromic acid solution and then one or two days in a 0.5% solution of silver nitrate. The further treatment is as in the preceding method. 259. The method of Mall ( vid. T. 212) is also employed in the examination of the hepatic connective tissue. 260. The following method is recommended by Berkley for demon- strating the nerves of the liver : Small pieces of liver tissue from 0.5 to 1 mm. in breadth are placed in a half-saturated aqueous solution of picric acid for from fifteen to thirty minutes, and then in 100 c.c. of potassium bi- chromate solution that has been saturated in the sunlight and to which 16 c.c. of 2^1 osmic acid has been added. The specimens now remain in this fluid for forty-eight hours in a dark place, and at a temperature of 2 5 C. After this the tissue is treated with a 0.25% to 0.75% aqueous solution of silver nitrate for five or six days, washed (quick imbedding may be employed), cut, cleared in oil of bergamot, and mounted in xylol -Canada balsam. 261 . The cellular elements of the pancreas may be examined without further manipulation in very thirf lobules from the rabbit (Kiihne and Lea). 262. There are various methods of differentiating the inner and outer zones of the cells. In sections of the tissue fixed in alcohol, car- min stains the outer zone of the cells more intensely than the inner (R. Heidenhain, 83). For the staining of the inner zone, fixation in Flem- ming's fluid is to be recommended, then staining with safranin, and finally washing in an alcoholic solution of picric acid. The granules of the inner zone (zymogen granules) appear red. These also stain red with the Biondi-Ehrlich mixture (T. 78). The simplest and most precise method of demonstrating the zymogen granules is that of Altmann (T. 124). The secretory and excretory ducts of the pancreas are shown, as in the case of the salivary glands, by the chrome-silver method (compare T. 253). Digitized by Microsoft® THE LARYNX. 275 IV. ORGANS OF RESPIRATION. A. THE LARYNX. The greater portion of the laryngeal mucous membrane is cov- ered by a stratified columnar ciliated epithelium containing goblet cells, and resting on a thick basement membrane. The epithelium covering the free margin of the epiglottis, the true vocal cords, and ffig^j. »i\\v Glands in fals vocal cord. Stratified pavement epithelium of true \ vocal cord. \ Stratified ciliated col- uinnai epithelium. F'g- 231. — Vertical section through the mucous membrane of the human larynx ; XS- Digitized by Microsoft® 276 ORGANS OF RESPIRATION. part of the arytenoid cartilage as far as the cavity between these cartilages, is of the stratified squamous variety, and is provided with connective-tissue papilla?. The mucosa contains many elastic fibers, and is rather firmly connected with the structures underneath it, but is somewhat more loosely connected in the regions supplied with squamous epithelium. In it are found branched tubulo-acinal glands, which may be single or arranged in groups. These are found at the free posterior portion of the epiglottis, in the region of the latter's point of attachment — i. c, in the so-called cushion of the epiglottis. Larger collections of glands are found in the false vocal cords, and on the cartilages of Wrisberg (cuneiform cartilages), which appear almost imbedded in the glandular tissue. In the remaining parts of the larynx glands are found only at isolated points. The true vocal cords have no glands. The cartilages of the larynx are of the hyaline variety, with the exception of the epiglottis, the cartilages of Santorini (the latter are derivatives of the epiglottis, Goppert), the cuneiform cartilages, the processus vocalis, and a small portion of the thyroid at the points of attachment of the vocal cords, which consist of elastic car- tilage. The vascular supply of the larynx is arranged in three super- imposed networks of blood-vessels. The 1 capillaries are very fine, and lie directly beneath the epithelium. The lymphatic network is arranged in two layers, the superficial being very fine and di- rectly beneath the network of blood capillaries. The nerves of the laryngeal mucous membrane will be de- scribed in connection with those found in the trachea. B. THE TRACHEA. The trachea is lined by a stratified ciliated columnar epithelium containing goblet cells and resting on a well-developed basement membrane. The mucosa is rich in elastic tissue. In the super- ficial portion of the mucosa the elastic fibers form dense strands, which usually take a longitudinal direction. The deeper layer of the mucosa is more loosely constructed, and passes over into the perichondrium of the semilunar cartilages of the trachea without any sharp line of demarcation. Numerous leucocytes are scattered throughout the mucosa, and are also frequently found in the epi- thelium. Connecting the free ends of the semilunar cartilages, which are of the hyaline variety, are found bundles of nonstriated muscle tissue, the direction of which is nearly transverse. The trachea contains numerous branched tubulo-acinal glands of the mucous variety containing here and there crescents of Gianuzzi. The glands are especially numerous where the tracheal wall is devoid of cartilage. The larynx and trachea receive their nerve supply from sensory Digitized by Microsoft® THE BRONCHI, THEIR BRANCHES, AND THE BRONCHIOLES. 277 nerve-fibers and sympathetic neurones. These have been described by Ploschko (97) working in Arnstein's laboratory. According to this observer, the sensory fibers divide in the mucosa, forming sub- epithelial plexuses from which fibrils are given off which enter the epithelium of the larynx and trachea and, after further division, end on the epithelial cells in small nodules, or small clusters of nodules. In the trachea of the dog, such fibrils were traced to the ciliary border of the columnar ciliated cells before terminating. Numerous sympathetic ganglia are found in the larynx and trachea. In the latter they are especially numerous in the posterior wall. The neuraxes of the sympathetic neurones forming these ganglia were traced to the nonstriated muscular tissue of the trachea. The cell- bodies of these sympathetic neurones are surrounded by end-baskets of small medullated fibers terminating in the ganglia. Medullated Fig. 232. — From longitudinal section of human trachea, stained in orcein. nerve -fibers, ending in the musculature of the trachea in peculiar end-brushes, were also described by Ploschko. C THE BRONCHI, THEIR BRANCHES, AND THE BRONCHIOLES. The primary bronchi and their branches show the same general structure as the trachea. The epithelium of the bronchi of medium size (up to 0.5 mm. in diameter) consists of a ciliated epithelium having three strata of nuclei. Kolliker (81) distinguishes a deep layer of basilar cells, a middle layer of replacing cells, and a super- ficial zone consisting of ciliate and goblet cells. The number of the last varies greatly. Glands are found only in bronchial twigs that are not less than 1 mm. in diameter ; as in the trachea, they are branched tubulo-acinous glands of the mucous variety. Digitized by Microsoft® 278 ORGANS OF RESPIRATION. In these structures the mucosa contains a large number of elastic fibers, the greater part of which have a longitudinal direction. Furthermore, numerous lymph-cells are found, and here and there a lymph-nodule. The muscularis presents, as a rule, circular fibers, which do not, however, form a continuous layer. The cartilaginous framework here no longer consists of symmetrically arranged rings, but of irregular platelets, which are absent in bronchial twigs less than 0.85 mm. in diameter. The smaller bronchi subdivide into still finer tubules of less than 0.5 mm. in diameter (bronchioles), which contain neither car- stratified cili- ated columnar epithelium. — Elastic fibers, cut trans- versely. i£ — Gland. a: - -% » — Cartilage. :•/• •'■'■: .- Connective tissue. Fig. 233. — Transverse section through human bronchus ; X 2 7* tilage nor glands. The stratum proprium, as well as the external connective-tissue sheath, becomes very thin ; and the epithelium now consists of but one layer, but is still ciliated. Digitized by Microsoft® RESPIRATORY BRONCHIOLES AND INFUNDIBULA. 279 D. THE RESPIRATORY BRONCHIOLES, ALVEOLAR DUCTS, AND INFUNDIBULA. The bronchioles are continued as the respiratory bronchioles. Ay hf f /' N? ^ - -■ Artery. Bronchiole. Respiratory ^ bronchiole. l ffM$?M : duct. «>k- ¥-%ji^&-i- JpSfsL. -' ?&Al 7 O-L -Vft , * ' t - -,-■1 >-H Hx ITVtxa * v ^-:> ;V v. -"ft/ 1 * Fig. 235. Figs. 234 and 235. — Two sections of cat's lung : Fig. 234, X S 2 I Fig. 235, X 35- The epithelium of the latter is ciliated in patches, but ultimately be- comes nonciliated, and assumes the character of the respiratory epi- Digitized by Microsoft® 28o ORGANS OF RESPIRATION. thelium. (See below.) The fine tubular segments of the respiratory passages, lined by an epithelium which marks the transition from the mixed to the respiratory epithelium, are known as the alveolar ducts. The muscle-fibers may be traced as far as these segments, where they are lost. Both in the walls of the respiratory bron- chioles and along the alveolar ducts there occur diverticula called alveoli. Each alveolar duct is continuous with a so-called infundibulum. Section of al- veolus of lung. Fig. 2 36. — Internal surface of a human respiratory bronchiole, treated with silver nitrate ; X 2 34 (after Kolliker). The general shape of the latter is conical, the base of the cone be-, ing turned away from the duct. Numerous diverticula are present in the walls of the infundibula, known as the air-sacs or alveoli of the lung. The epithelium of the infundibulum (1 1 ji to 1 5 [i in diam- eter) and of its alveoli (the so-called respiratory epithelium) con- sists of two varieties of cells (F. E. Schulze) — smaller nucleated elements and larger nonnucleated platelets (the latter derived very probably from the former). The arrangement of the epithelial cells Digitized by Microsoft® RESPIRATORY BRONCHIOLES AND INFUNDIBULA. 281 is generally such that the nonnucleated platelets rest directly upon the blood capillaries, while nucleated cells lie between them. The basement membrane beneath the epithelium of the respiratory pas- sages gradually becomes thinner as it approaches the infundibula, and in the latter is scarcely to be seen. In amphibia the epithelium of the alveoli consists of cells, of which the portion containing the nucleus forms a broad cylindric base ; from the free end of each cell a lateral process extends over the adjoining capillary to meet a similar process from the neighboring cell. When viewed from above, the basal portion of the cell appears dark and granular, while the processes are clear and transparent. These cells, together with their prolongations, are about 50 /j. in diameter. The surface view greatly re- sembles that of the human respiratory epithelium (Duval, Oppel, 89]. Nonnucleated epi- thelial cell. . Nucleated epithelial cell. Fig. 237. — Inner surface of human alveolus treated with silver nitrate, showing respira- tory epithelium ; X 2 4° (after Kolliker). The walls of the infundibulum and its alveoli are encircled by very delicate elastic fibers. The lung tissue is arranged in small lobules, which form defi- nite units in its anatomy and pathology (Councilmann, 1900). These lobules have a diameter of from 1 to 3 cm. in the adult, and from 0.5 to 1.5 cm. in the child from two to eight years old. They are of pyramidal shape, the apex of the lobule being formed by a small bronchus. They are separated from one another by a small amount of interlobular fibrous tissue. The small bronchus entering the apex of each lobule divides within the lobule several times, each bronchiole becoming a respiratory bronchiole, alveolar duct, and infundibulum, with alveoli or air-sacs associated with them. The visceral and the parietal layers of the pleura consist of a layer of fibro-elastic tissue covered by a layer of mesothelium. The blood-vessels of the lung have been described by Miller Digitized by Microsoft® 282 ORGANS OF RESPIRATION. (93) working under Mall's direction. His account is closely fol- lowed in the following description : The pulmonary artery follows closely the bronchi through their entire length. An arterial branch enters each lobule of the lung at its apex in close proximity to the bronchus. After entering the lobule the artery divides quite ab- ruptly, a branch going to each infundibulum ; from these branches the small arterioles arise which supply the alveoli of the lung. " On reaching the air-sac the artery breaks up into small radicals which pass to the central side of the sac in the sulci between the air-cells, and are finally lost in the rich system of capillaries to which they give rise. This network surrounds the whole air-sac and communicates freely with that of the surrounding sacs." This capillary network is exceedingly fine and is sunken into the epi- thelium of the air-sacs so that between the epithelium and the capil- lary there is only the extremely delicate basement membrane. The infundibula, the alveolar ducts and their alveoli, and the alveoli of the respiratory bron- chioles are supplied with similar capillary networks. The veins collecting the blood from the lobules lie at the periphery of the lobules in the interlobular con- nective tissue, and are as far dis- tant from the intralobular arteries as possible. These veins unite to form the larger pulmonary veins. The bronchi, both large and small, as well as the bronchioles, derive their blood supply from the bronchial arteries, which also partly supply the lung itself. Capillaries derived from these ar- teries surround the bronchial system, their caliber varying according to the structure they supply — finer and more closely arranged in the mucous membrane, and coarser in the connective-tissue walls. In the neighborhood of the terminal bronchial tubes the capillary nets anastomose freely with those of the respiratory capillary system. From the capillaries of the bronchial arteries, veins are formed which empty either into the bronchial veins or into the branches of the pulmonary veins. The lymphatics of the lung originate between the alveoli. They form two sets of vessels (Councilmann, 1900) — the one found in the interlobular connective tissue, which communicates with lymph- vessels in the pleura, forming a rich plexus, terminating in several lymphatic vessels, provided with valves, which end in the lymph- glands at the root of the lung, and " a central set which accompa- Digitized by Microsoft® QOllfO Fig. 238. — Scheme of the respiratory epithelium in amphibia : The upper figure gives a surface view : b, Basilar portion ; a, the thin process. The lower figure is a sec- tion : (?, Respiratory epithelial cell ; 6, blood- vessel ; c, connective tissue around the al- veoli. RESPIRATORY BRONCHIOLES AND INFUNDIBULA. 283 nies the pulmonary artery and passes directly into the bronchial glands at the hilum of the lung." Accompanying the bronchi and bronchial arteries are found numerous nerve-fibers, of the nonmedullated and medullated varie- ties, arranged in bundles of varying size, in the course of which are ^A^/ k £ Fig. 239. — From section of human lung stained in orcein, showing the elastic fibers sur- rounding the alveoli. S & Vwsfc, Fig. 240. — Section through injected lung of rabbit. Blood capillaries seen in surface view. Alveolus in cross- section. found sympathetic ganglia. Berkley (94), who has studied the dis- tribution of the nerves of the lung with the chrome-silver method, finds that in the external fibrous layer of the bronchi is found a plexus of very fine and of coarser fibers, from which branches are Digitized by Microsoft® 284 ORGANS OF RESPIRATION. given off which end in the muscle tissue of the bronchi, and others which pass through this layer to form, after further division, a sub- epithelial plexus from which fibrils may be traced into the connec- tive-tissue folds in the larger bronchi and between the bases of the epithelial cells in the smaller bronchi and bronchioles. Some few fibrils were traced between alveoli situated near bronchi, " termi- nating, apparently, immediately beneath the pavement epithelium in an elongated or rounded minute bulb ; " these may, however, repre- sent endings on nonstriated muscle tissue. The bronchial arteries have an exceedingly rich nerve supply. E. THE THYROID GLAND. The thyroid gland is developed from three sources : Its middle portion, the isthmus of the gland, originates as a diverticulum of -. Lumen of follicle. -. Connective tissue. Epithelium of follicle. Fig. 241. — From section through thyroid gland of child. the pharyngeal epithelium, from what is later the foramen caecum of the tongue ; both lateral portions, the right and left lobes, are formed from a complicated metamorphosis of the epithelium of the fourth visceral pouch. These various parts unite in man into one, so that in the adult the structure of the organ is continuous. The thyroid gland consists of numerous noncommunicating acini or follicles of various sizes lined by a nearly cubic epithelium ; the lobules are separated from each other by a highly vascularized connective tissue, continuous with the firm connective-tissue sheath surrounding the whole gland. The follicles are either round, polyhedral, or tubular, and are occasionally branched (Streiff ). At an early stage the acini are found to contain a substance known as " colloid " material {ind. Technic). Langendorff has shown (vid. Technic) that two varieties of cells exist in the acini of the thyroid body — the chief cells and colloid Digitized by Microsoft® THE THYROID GLAND. 285 cells. Those of the first variety apparently change into colloid cells, while the latter secrete the colloid substance. During the formation of this material the colloid cells become lower, and their entire contents, including the nuclei, change into the colloid mass. Hiirthle distinguished two processes of colloid secretion ; in the one the cells remain intact, in the other they are destroyed. He claims that the colloid cells of Langendorff participate in the former pro- cess, while in the latter they are first modified (flattened) and then changed into the colloid substance. The colloid material may enter the lymph-channels, either directly by a rupture of the acini, or indirectly by a percolation of the substance into the intercellular clefts, whence it is carried into the larger lymphatics. Anderson (91) and Berkley (94) have studied the distribution of the nerve-fibers of the thyroid gland with the chrome-silver method ; the account given by the latter is the more complete and will be followed here. The nonmedullated nerves entering the gland form plexuses about the larger arteries, which are less dense around the smaller arterial branches. Some of these nerve-fibers are vascular nerves and end on the vessels ; others form perifollicular meshes surrounding the follicles of the gland. From the network of nerve- fibers about the follicles, Berkley was able to trace fine nerve fila- ments which seemed to terminate in end-knobs on or between the epithelial cells lining the follicles. Even in the best stained prepa- rations, however, not nearly all the follicular cells possess such a ., nerve termination. In methylene-blue preparations of the thyroid gland (Dr. De Witt) some few medullated fibers were found in the nerve plexus surrounding the vessels. In a number of preparations these were traced to telodendria situated in the adventitia of the vessels, showing that at least a portion of these medullated nerves are sensory nerves ending in the walls of the vessels. PARATHYROID GLANDS. Small glandular structures found on the posterior surfaces of the lateral lobes of the thyroid were discovered by Sandstrom in 1880. They are surrounded by a thin connective-tissue capsule and divided into small imperfectly developed lobules by a few thin fibrous-tissue septa or trabeculse, which support the larger vessels. The epithelial portions of these structures consist of relatively large cells and capil- lary spaces. According to Schaper (95), who has recently subjected these structures to a careful investigation, the epithelial cells have a diameter which varies from 10 fi to 12 fi, possessing nuclei 4 ft in diameter. These cells are of polygonal shape and have a thin cell-membrane, a slightly granular protoplasm, and a nucleus pre- senting a delicate chromatic network. The cells are arranged either in larger or smaller clusters or, in some instances, in anastomosing trabeculse or columns, consisting either of a single row or of several rows of cells. Between the clusters or columns of cells are found rela- Digitized by Microsoft® 286 ORGANS OF RESPIRATION. tively large capillaries, the endothelial lining of which rests directly on the epithelial cells. Connective -tissue fibrils do not, as a rule, follow the capillaries between the cell-masses. The structure of the parathyroid resembles in many respects that of certain embryonic stages of the thyroid, and it has been suggested that these bodies represent small masses of thyroid gland tissue, retaining their em- bryonic structure. Schaper has observed parathyroid tissue, the cells of which were here and there arranged in the form of small follicles, some of which contained colloid substance. Such obser- vations lend credence to the view regarding the parathyroid as an embryonic structure. Whether "in this stage they form a special secretion has not been fully determined. (See Schaper, 95.) ,r^ I WL ■6- '-?■,. Fig. 242. — From parathyroid of man. TECHNIC. 263. For the demonstration of the larynx and trachea, young and healthy subjects should be selected. Pieces of the mucous membrane or the whole organ should be immersed in a fresh condition. Sections through the entire organ present only a general structural view; but if a close examination of accurately fixed mucous membrane be desired, the latter should be removed with a razor before sectioning and treated separately. 264. Chromic-osmic acid mixtures are recommended as fixing agents, and safranin as a stain. Besides the nuclear differentiation, the goblet cells stain brown, and the elastic network of the stratum proprium and the submucosa a reddish-brown. For examining the epithelium, isolation methods are employed, such as the Yi alcohol of Ranvier (T. 128). 265. The examination of the respiratory epithelium is attended with peculiar difficulty ; it is, perhaps, best accomplished by injecting a 0.5% solution of silver nitrate into the bronchus until the lumen is completely filled, and then placing the whole in a 0.5% solution of the same salt. After a few hours, wash with distilled water and transfer to Digitized by Microsoft® THE URINARY ORGANS. 287 70% alcohol. Thick sections are now cut and portions of the respiratory passages examined ; the silver lines represent the margins of the epithe- lial cells. Such sections should not be fastened to the slide with albumen, as the latter soon darkens and blurs the picture. These specimens may also be stained. 266. For the elastic fibers, especially those of the alveoli, fixation in Miiller's fluid (T. 27) or in alcohol and staining with orcein is a good method. Fresh pieces of lung tissue treated with potassium hydrate show numerous isolated elastic fibers. 267. Pulmonary tissue may be treated by Golgi's method, which brings out a reticular connective-tissue structure in the vessels and alveoli {iiid. T. 252, Oppel). 268. The pulmonary vessels may be injected with comparative ease. 269. The thyroid gland is best fixed in Flemming's solution ; it is then stained with M. Heidenhain's hematoxylin solution or, better still, with the Ehrlich-Biondi mixture which differentiates the chief from the colloid, cells ; the former do not stain at all, while the latter appear red with a green nucleus (Langendorff ). The colloid substance of the thy- roid gland does not cloud in alcohol or chromic acid, nor does it coagu- late in acetic acid, but swells in the latter; 33% potassium hydrate hardly causes the colloid material to swell at all, though in weaker solu- tions it dissolves after a long time. V. THE GENITO-URINARY ORGANS. A. THE URINARY ORGANS. J. THE KIDNEY. The kidney is a branched tubular lobular gland, which in man consists of from ten to fifteen nearly equal divisions of pyramidal shape known as the renal lobes. The apex of each pyramid (the Malpighian pyramid) projects into the pelvis of the kidney. The kidney is surrounded by a thin but firm cap- sule consisting of fib- rous Connective tissue " — aJ^ — Artery. containing a few elas- tic fibers and, in its Vein, deeper portion, a thin layer of nonstriated muscle-cells Fig ' 2 43-— Kidney of new-born infant, showing a _ distinct separation into reniculi ; natural size. At a is The Secreting por- seen the consolidation of two adjacent reniculi. tion is composed of a large number of tubules twisted and bent in a definite and typical manner, the uriniferous tubules. In each one of these tubules we distinguish the following segments : (i) Bowman's capsule, or the ampulla, surrounding a spheric plexus of capillaries, the glomerulus, which, with the capsule of Bowman, forms a Malpighian corpuscle ; Digitized by Microsoft® 288 THE GENITOURINARY ORGANS. (2) a proximal convoluted portion ; (3) a U-shaped portion, con- sisting of straight descending and ascending limbs and the loop of Henle ; (4) a distal convoluted portion or intercalated portion ; and (5) an arched collecting portion ; from the confluence of a num- ber of these are formed the larger straight collecting tubules, which, in turn, finally unite to form the papillary ducts or tubules of Bellini, which pass through the renal papillae and empty into the renal pelvis. Besides the uriniferous tubules the kidney con- tains a complicated vascular system, a small amount of connective tissue, etc. B C Fig. 244. — Isolated uriniferous tubules : A and B, from mouse j C, from turtle. In all three figures a represents the Malpighian corpuscle ; b, the proximal convoluted tubule; c, the descending limb of Henle' s loop; d, Henle' s loop; e, the straight col- lecting tubule ; /, the arched collecting tubule. In a longitudinal median section the kidney is seen to be com- posed of two substances, — the one, the medidlary substance, pos- sessing relatively few blood capillaries and containing straight collecting tubules and the loops of Henle ; the other, the cortical substance, richer in blood-vessels, and containing principally the Malpighian corpuscles and the proximal and distal convoluted tu- bules. In each renal lobe we find these two substances distributed as follows : The Malpighian pyramid consists entirely of medullary substance, which sends out a large number of processes, the medul- Digitized by Microsoft® THE URINARY ORGANS. 289 lary rays, or pyramids of Ferrein, toward the surface of the kidney. The latter do not, however, quite reach the surface, but terminate at a certain distance below it ; they are formed by collecting tubules which extend beyond the medullary substance. The entire remain- ing portion of the kidney is composed of cortical substance ; be- tween the medullary rays it forms the cortical processes, and at the periphery of the kidney, where the medullary rays are absent, the cortical labyrinth. Those portions of the cortical substance sep- arating the Malpighian pyramids are known as the columns of Bertini, or septa renis. Column of Ber tini. - Papilla. Lobule of adi- pose tissue. Blood-vessel. - Fig. 245. — Median longitudinal section of adult human kidney ; nine- tenths natural size. In the peripheral portion the limits between its renal lobes are no longer recogniz- able. The various segments of the uriniferous tubule are characterized by their shape and size and by their epithelial lining. The Malpighian corpuscle has a diameter of from 1 20 // to 220 [1. The capsule surrounding the glomerulus consists of two layers, which are to be distinguished from each other when its relation to the glomerulus is taken into consideration. The capsule forms a double-walled membrane around the glomerulus ; a condition which is easily understood by imagining an invagination of the 19 Digitized by Microsoft® 290 THE GENITOURINARY ORGANS. glomerulus into the hollow capsule. Between the inner wall cov- ering the surface of the glomerulus (glomerular epithelium) and the outer wall (Bowman's capsule) there remains a cleft-like space which communicates with the lumen of the corresponding urinifer- ous tubule. In the adult the glomerular epithelium is very flat, with nuclei projecting slightly into the open space of the Malpig- hian corpuscle. The epithelium of the outer wall is somewhat higher, but still of the squamous type. The capsule of Bowman communicates with the proximal convoluted tubule by means of a short and narrow neck. Its epithelium passes over gradually into Fig. 246. — From section of cortical substance of human kidney ; X 2 4° : a > Epi- thelium of Bowman's capsule; b and d, membrana propria; c, glomerular epithelium; e, blood-vessels ; f, lobe of the glomerulus ; g, commencement of uriniferous tubule ; h, epithelium of the neck ; 7', epithelium of proximal convoluted tubule. the cubical epithelium of the neck, which, in turn, merges into that of the proximal convoluted tubule. The proximal convoluted portion, from 40 fi to 70 fi in diameter, is lined by short columnar epithelial cells, the protoplasm of which is striated and may be separated by means of certain reagents into fibers (R. Heidenhain, 83). In man the nuclei are situated in the upper portions of the cells, while the basal portions show the stria- tion more distinctly. The cells, especially in their indifferent, non- striated regions, are so intimately connected that the cell limits are not always distinguishable. In well -fixed preparations the inner portions of the cells often show a narrow striated border, Digitized by Microsoft® THE URINARY ORGANS. 291 often giving the appearance of short cilia. In the guinea-pig the basal regions of the lateral surfaces of the cells constituting the epithelium of the proximal convoluted portion present numerous projections which interlock and give to a surface view an irregular fringe-like outline. In cross-section the cells appear to be striated from their bases upward to the middle of the nucleus. Here, how- ever, the striation is without doubt due to the outlines of the irreg- ular ridges. (Fig. 248.) These structural relations have lately been confirmed in the case of the guinea-pig, and also found to hold true for man (Landauer). This striation is much coarser than that 1 Nuclei of en- d o t h e 1 ial cells of blood capillaries. . Lumen of uriniferous tubule. - Striated border. Fig. 247. — Section of proximal convoluted tubules from man ; X 5^0. found by Heidenhain, but both are, under certain circumstances, seen together. The descending limb of Henle's loop, from gp. to 1 5 p. in diameter, is narrow and possesses flattened epithelial cells, the centers of which, containing the nuclei, project into the lumen of the tubule. These central projections of the cells are not directly opposite those of the cells on the opposite wall, but alternate with the latter, thus giving to the lumen a zigzag outline corresponding to the length of the cell. The thick portion of the loop, for the most part repre- sented by the ascending limb.from 23// to 28// in diameter, possesses a columnar epithelium similar to that of the proximal convoluted Digitized by Microsoft® 292 THE GENITOURINARY ORGANS. portion. Here, however, the basal striation of the cells is not so distinct, the lumen is somewhat larger than that of the descending limb, and by treatment with certain reagents the epithelium may Nucleus • Nucleus. Fig. 248. — Epithelium from proximal convoluted tubule of guinea-pig, with surface and lateral views (chrome-silver method) ; X 59° : "> a < The irregular interlacing pro- jections. IV \'l ' 1 I <» 750* Fig. 249. — From cortical portion of longitudinal section of kidney of young child. often be separated as a whole from the underlying basement mem- brane. The distal convoluted or intercalated portion, from 39^ to 45^ in Digitized by Microsoft® THE URINARY ORGANS. 293 diameter, is only slightly curved (2 to 4 convolutions). Its epi- thelium is relatively high, though not so high as that lining the proximal convoluted portion and not so distinctly striated. The cells are provided with large nuclei and their basal portions are joined by interlacing projections. The next important segment is the short arched collecting portion, which has nearly cubical epithelial cells and a lumen somewhat wider than that of the intercalated tubule. The smaller straight collecting tubules have a low columnar epithelium with cells of somewhat ir- regular shape, the basal portions of which are provided with short, irregular, intertwining processes, which serve to hold the cells in b — Fig. 250. — Section of medulla of human kidney ; X about 300 : a, a, a, Ascending limb of Henle's loop ; b, b, b, blood-vessels ; c, c, c, descending limb of Henle's loop. place. The diameter of the collecting tubules measures from 45 p. to 7$ ft. In the larger collecting tubules the epithelium is more regular and becomes higher as the tube widens. These tubules gradually unite within the Malpighian pyramid and the regions adjacent to the columns of Bertini to form about 20 papillary ducts from 200 /z to 300^ in diameter. The latter have a high columnar epithelium, and empty into the pelvis of the kidney at the apex of the papilla, forming the foramina papillaria. Besides the epithelium, the uriniferous tubules possess an ap- Digitized by Microsoft® 294 THE GENITOURINARY ORGANS. parently structureless membrana propria, that of the collecting tubules being very thin. According to Riihle (97), the membrana propria of the uriniferous tubules consists of fine circular and longi- tudinal fibers which are at no point connected with the cells, and which represent nothing more than a thickened and more regularly distributed layer of the interstitial reticular tissue. The basement membrane of the vascular loops in the glomeruli also appears to have a fibrous structure and presents numerous fine openings. Between the Malpighian pyramids are found the columns of Bertin, presenting a structure similar to that of the cortex of the kidney, and extending to the hilum of the kidney. Between the uriniferous tubules and surrounding the blood- vessels of the kidney there is found normally a small amount of connective tissue. Between the convoluted portions of the tubules this is present only in small quantity, a somewhat greater amount Papillary duct I Blood-vessel. Fig. 251. — From longitudinal section through papilla of injected kidney ; X 4° : thelium of collecting tubule under greater magnification. Epi- being found in the. neighborhood of the Malpighian corpuscles, in the boundary zone between the cortex and medulla and between the larger collecting tubules in the apices of the Malpighian pyra- mids. From what has been said concerning the uriniferous tubule it must be evident that its course is a very tortuous one. Beginning with the Malpighian corpuscles, situated in the cortex between the medullary rays, the tubule winds from the cortex to the medulla and back again into the cortex, where it ends in a collecting tubule, which passes to the medulla to terminate at the apex of a Malpig- hian pyramid. The different portions of the tubules have the following positions in the kidney : In the cortex between the medul- lary rays are found the Malpighian corpuscles, the neck, the proxi- mal and distal convoluted portions of the uriniferous tubule, and the Digitized by Microsoft® THE URINARY ORGANS. 2 9 S arched collecting tubules. The medullary rays are formed by the cortical portions of the straight collecting tubules and a portion of the ascending limbs of Henle's loops. The medulla is made up mainly of straight collecting tubules of various sizes and of the de- scending limbs and loops of Henle's loops, the latter being often found in the boundary zone between the cortex and medulla. (See Fig. 250.) The blood-vessels of the kidney have a characteristic distribu- tion, and are in the closest relationship to the uriniferous tubules. "Boundary line between two Malpighian pyramids. *r.~~ Uriniferous 0v;' ; tubules. .>""• O ■ /yn (g-g ■CD, '°^vg5 y fi£ °o^ ^*>^K ^ fed * s .. ' .-?^. <5 ■A.-^_^. Fig. 252. — Section through junction of two lobules of kidney, showing their coalescence ; from new-born infant. The renal artery divides in the neighborhood of the hilum into two branches, — a dorsal and a ventral, — which again divide, the result- ing trunks giving off lateral branches to the renal pelvis, supplying its mucous membrane and then breaking up into capillaries which extend as far as the " area cribrosa." The venous capillaries of this region empty into veins which accompany the arteries. Besides these, other arteries originate from the principal branches, or from their immediate offshoots, and pass backward to supply the walls of the renal pelvis, the renal capsule, and the ureter. The main Digitized by Microsoft® 296 THE GENITOURINARY ORGANS. trunks themselves penetrate at the hilum, and divide in the columns of Bertini to form arterial arches (arteriae arciformes) which extend between the cortical and medullary substances. Numerous vessels, the intralobular arteries, originate from the arterias arciformes and penetrate into the cortical pyramids between the medullary rays. Here they give off numerous twigs, each of which ends in the glomerulus of a Malpighian corpuscle. These short lateral twigs are the vasa afferentia. Each glomerulus is formed by the breaking down of its afferent vessel, which, on entering the Malpighian cor- puscle, divides into a number of branches, each in turn subdividing into a capillary net. From each of these nets the blood passes into a somewhat larger vessel constituting one of the branches of the efferent vessel which carries the blood away from the glomerulus. Since the afferent and efferent vessels lie in close proximity, the capillary nets connecting them are necessarily bent in the form of loops. The groups of capillaries in a glomerulus are separated from each other by a larger amount of connective tissue than separates the capillaries themselves, so that the glomerulus may be divided into lobules. In shape the glomerulus is spheric, and is covered by a thin layer of connective tissue over which lies the inner mem- brane of the capsule, the glomerular epithelium. On its exit from the glomerulus the vas efferens separates into a new system of capillaries, which gradually becomes venous in character. Thus, the capillaries which form the glomerulus, together with the vas efferens, are arterial, and may be included in the category of the so-called arterial retia mirabilia. Those capillaries formed by the vas efferens after its exit from the Malpighian corpuscle lie both in the medullary rays and in the cortical pyramids. The meshes of the capillary net- works distributed throughout the medullary rays are considerably longer than those of the networks supplying the cortical pyramids and labyrinth, the latter being quadrate in shape. The glomeruli nearest the renal papillae give off longer vasa efferentia which extend into the papillary region of the Malpighian pyramids (arteriolae rectae spurise) and form there capillaries which ramify throughout the papillae with oblong meshes. Arterial retia mirabilia also occur in the course of the vasa afferentia between the intralobular arteries and the glomeruli, but nearer the latter. Each is formed by the breaking down of the small afferent vessels into from two to four smaller branches, which then reunite to pass on as a single vessel. In structure these retia differ greatly from the glomeruli in that here the resulting twigs are not capillaries and have nothing to do with the secretion of urine (Golubew). From the vasa afferentia arterial twigs are occasionally given off, which break down into capillaries within the cortical substance. Other arteries originate from the lower portion of the intralob- ular arteries or from the arciform arteries themselves and enter the medullary substance, where they form capillaries. These Digitized by Microsoft® THE URINARY ORGANS. 297 vessels constitute the so-called " arteriolar rectae verse." Their capillary system is in direct communication with the capillaries of the vasa afferentia and "vasa recta spuria." The intralobular arteries are not entirely exhausted in supplying the vasa afferentia which pass to the glomeruli. A few extend to the surface of the kidney and penetrate into the renal capsule, where they termin- ate in capillaries which communicate with those of the recur- rent, suprarenal, and phrenic arteries, etc. Smaller branches Arched collecting- tubule. Straight collect- ing tubule. Distal convoluted tubule. Artery of capsule. Malpighian cor- puscle. Proximal convo- /' luted tubule. Loop of Henle. -zi^ Collecting tubule. Arteria arcuata. \. Capillary net- work. Vas afferens. Large collecting- tubule. Papillary duct. --Glomerulus. Vena arcuata. Fig. 253. — Diagrammatic scheme of uriniferous tubules and blood-vessels of kidney. Drawn in part from the descriptions of Golubew. from these latter vessels may penetrate the cortex and form glomeruli of their own in the renal parenchyma (arteriae capsulares glomeruliferae). These relations, first described by Golubew, are of importance not only in the establishment of a collateral circula- tion, but also as a partial functional substitute in case of injury to the renal arteries. The same author also confirms the statements of Hoyer {jf) and Geberg, that between the arteries and veins of the kidney, in the cortical substance, in the columns of Bertin, and Digitized by Microsoft® 298 THE GENITOURINARY ORGANS. at the bases of the Malpighian pyramids, etc., direct anastomoses exist by means of precapillary twigs. From the capillaries the venous blood is gathered into small veins which pass out from the region of the medullary rays and cortical pyramids and unite to form the "intralobular veins." These have an arrangement similar to that of the corresponding arteries. The venous blood of the labyrinthian capillaries also flows into the intralobular veins, and as a result a peculiar arrangement of these vessels is seen at the surface of the kidney where the capillaries pass radially toward the terminal branches of the intralobular veins and form the stellate figures known as the vence stellatce. This sys- tem is also connected with those venous capillaries of the capsule which do not empty into the veins ac- companying the arteries of the capsule. The capillary system of the Malpighian pyramids unites to form veins, the "venulae rectse," which empty into the venous arches (venas arciformes) which lie parallel with and adjacent to the corresponding arteries. The larger veins are found side by side with the arteries and pass out at the hilum of the organ. The lymph-vessels of the kidneys need to be investigated further. Lymph clefts have been observed in the cortex between the convoluted tubules ; these have been traced into larger vessels found in the capsule. The kidneys receive their innerva- tion through nonmedullated and medul- lated nerve-fibers. The former accom- pany the arteries and may be traced along these to the Malpighian corpus- cles. From the plexuses surrounding the vessels small branches are given off, which end on the muscle-cells of the media. According to Berkley, small nerve-fibrils may be traced to the uriniferous tubules, which pierce the membrana propria and end on the epithelial cells. Dogiel has shown that medullated (sensory) nerve-fibers terminate in the adventitia of the arteries of the capsule. The most important investigations into the secretory processes of the uriniferous tubules are those of R. Heidenhain (83) who used indigo-carmin in his researches. If a saturated aqueous solution of indigo-carmin be injected into the blood-vessels of a rabbit, the elimination of the substance will be found to take place through the kidneys as well as by means of the other excretions. Microscopic examination of such a kidney reveals the fact that the proximal convoluted tubules and ascending limbs of the loops of Fig. 254. — A, Direct anasto- mosis between an artery and vein in a column of Bertin of child ; B, bipolar rete mirabile inserted in the course of an arterial twig. Dog' s kidney (after Golube w) . Digitized by Microsoft® THE URINARY ORGANS. 299 Henle are alone concerned in the elimination of the substance, while apparently water alone is filtered through the remaining seg- ments of the uriniferous tubules. Among others, Disse has recently taken up the subject of cellular secretion in the uriniferous tubules. According to him, we may distinguish in the convoluted tubules (1) those with a wide lumen, having low cells apparently with no cell limits and no distinct basilar zone, but with peculiar structures which may be likened to cuticulse, so called, or a striated border (Tornier) (Fig. 247) ; (2) tubules with a narrow lumen and wedge-shaped epithelial cells, with indistinct cell limits and diffusely granular protoplasm ; (3) tubules with an extremely narrow lumen and high epithelial cells with differentiated protoplasm, the basal portion of which is dark and striated, the upper clear and contain- ing the nucleus. These results are not, however, confirmed by the painstaking researches of Sauer. This author finds that the secre- tory portions of the uriniferous tubules (convoluted portions of the tubules and part of the loops of Henle) always have the same un- changed epithelium, but that, during secretion, the lumina of the tubules are subject to great variation ; in tubules with scarcely recognizable lumina the epithelial elements are high and narrow ; in those with wide lumina, low and broad. In the former the stria- tion of Heidenhain is naturally fine ; in the latter, somewhat coarser. The peculiar terminations of Tornier are found by Sauer during all phases of secretion. According to this view, then, neither the striation of Heidenhain nor the terminations of Tornier are tem- porary appearances due to a particular phase of secretion, but represent permanent structural peculiarities of the cells in certain definite portions of the uriniferous tubules. The volumetric changes in the uriniferous tubules also probably influence the form and number of the indentations in the epithelial cells described on page 291. The permanent kidney is developed as early as the fifth week of embryonic life. The renal anlagen, from which the epithelium of the ureter, renal pelvis, and uriniferous tubules is formed, originate from the median portion of the posterior wall of the Wolffian duct. These buds grow with their blind ends extending anteriorly, and are soon surrounded by cellular areas, the blastema of the kidneys. After the renal bud has become differentiated into a narrow tube (the ureter) and a wider central cavity (the renal pelvis) hollow epithelial buds are developed from the latter. These extend radi- ally toward the surface of the renal anlagen, where they undergo a T-shaped division. These latter are the first traces of the papillary ducts and collecting tubules. The cup-shaped capsules are formed by the invagination of the ends of the tubules by the glomeruli which originate separately and in this way become connected with the uriniferous tubules. The remaining portions of the adult urin- iferous tubules are gradually formed from the tubes connecting the glomeruli with the collecting tubules. Digitized by Microsoft® 300 THE GENITOURINARY ORGANS. 2. THE PELVIS OF THE KIDNEY, URETER, AND BLADDER. The renal pelvis, ureter, and urinary bladder are lined by strati- fied transitional epithelium. Its basal cells are nearly cubical ; these support from two to five rows of cells of varying shape. They may be spindle-shaped, irregularly polygonal, conical, or sharply angular, and provided with processes. Their variation in form is probably due to mutual pressure. The superficial cells are large Superficial epi- thelial cells. Epithelium. Mucosa. %5& •"?fe Inner longitud- inal muscular layer. Middle circular muscular layer. Outer muscular layer. Fig- 255. — Section of lower part of human ureter ; X I 4°- and cylindric, a condition characteristic of the ureter and bladder. Their free ends and lateral surfaces are smooth, but their bases pre- sent indentations and projections due to the irregular outlines of the underlying cells. The superficial cells often possess two or more nuclei. The mucosa often contains diffuse lymphoid tissue, which is more highly developed in the region of the renal pelvis. A few Digitized by Microsoft® THE SUPRARENAL GLANDS. 3OI mucous glands are also met with in the pelvis and in the upper por- tion of the ureter. The ureter possesses two layers of nonstriated muscle-fibers — the inner longitudinal, the outer circular. From the middle of the ureter downward a third external muscular layer is found with nearly longitudinal fibers. The urinary bladder has no glands, and its musculature appar- ently consists of a feltwork of nonstriated muscle bundles, a condi- tion particularly well seen in sections of the dilated organ. But even here three indistinct muscle layers may be distinguished, the outer and inner layers being longitudinal and the middle circular. A remarkable peculiarity of these structures is the extreme elasticity of their epithelium, the cells flattening or retaining their natural shape according to the amount of fluid in the cavities which they line (compare London, Kann). The nerve supply of the bladder has been studied by Retzius, Huber, and Grunstein in the frog and a number of the smaller mammalia. Numerous sympathetic ganglia are observed, situated outside of the muscular coat, at the base and sides of the bladder. The neuraxes of the sympathetic neurones of these ganglia are grouped into smaller or larger bundles which interlace and form plexuses surrounding the bundles of nonstriated muscle-cells. From these plexuses nerve-fibers are given off, which penetrate the muscle bundles and end on the muscle-cells. The cell-bodies of the sym- pathetic neurones are surrounded by the telodendria of small medullated fibers, which terminate in the ganglia. Passing through the ganglia large medullated fibers (sensory nerves) may be ob- served which pass through the muscular coat, branch repeatedly in the mucosa, and lose their medullary sheaths on approaching the epithelium in which they end in numerous telodendria, the small branches of which terminate between the epithelial cells. The ureters are surrounded by a nerve plexus containing non- medullated and medullated nerve-fibers. The former end on cells of the muscular layers ; the latter pass through the muscular layer, and on reaching the mucosa branch a number of times before losing their medullary sheaths. The nonmedullated terminal branches form telodendria, the terminal fibers of which have been traced between the cells of the lining epithelium (Huber). B. THE SUPRARENAL GLANDS. The suprarenal gland is surrounded by a fibrous-tissue capsule containing nonstriated muscle-cells, blood- and lymph-vessels, nerves, and sympathetic ganglia. The glandular structure is divided into a cortical and a medullary portion. In the former are distin- guished three layers, according to the arrangement, shape, and structure of its cells — an outer glomerular zone, a middle broad fas- cicular zone, and an inner reticular zone. According to Flint, who Digitized by Microsoft® 302 THE GENITO-URINARY ORGANS. worked in Mall's laboratory, and whose account will here be fol- lowed, the framework of the gland is made up of reticulum. In the glomerular zone this reticulum is arranged in the form of septa, derived from the capsule, which divide this zone into more or less regular spaces of oval or oblong shape. In the fascicular zone the reticulum is arranged in processes and fibrils running at right angles to the capsule. In the reticular zone the fibrils form a dense network, while in the medulla the reticular fibrils are arranged in processes and septa which outline numerous spaces. Capsule. »J ?U: Zona glomerulosa. Zona fasciculata. :.\ftl PC Zona reticularis. Fig. 256. — Section of suprarenal cortex of dog ; X I2a The gland-cells of the glomerular zone are arranged in coiled col- umns of cells found in the compartments formed by the septa of reticulum above mentioned. The cells composing these columns are irregularly columnar, with granular protoplasm and deeply stain- ing nuclei. In the fascicular zone the cells are arranged in regular columns, consisting usually of two rows of cells, and situated be- tween the reticular processes, which run at right angles to the cap- Digitized by Microsoft® THE SUPRARENAL GLANDS. 303 sule. The cells of this zone are polyhedral in shape, with gran- ular protoplasm often containing fat droplets and with nuclei containing little chromatin. Similar cells are found in the reticular zone, but here they are found in small groups situated in the meshes of the reticulum. The cells of the medullary substance are less granular and smaller in size than those of the cortex, and are grouped in irregular, round, or oval masses bounded by the septa of reticulum. These cells stain a deep brown with chromic acid and its Fig. 257. — Arrangement of the intrinsic blood-vessels in the cortex and medulla of the dog's adrenal (Fig. 17, Plate V, of Flint's article in "Contributions to the Science of Medicine," dedicated to Professor Welch, 1900). salts, and the color can not be washed out with water — a peculiarity which shows itself even during the development of these elements, and which is possessed by few other types of cells. Numerous ganglion cells, isolated and in groups, and many nerve-fibers occur in this portion of the organ. The blood-vessels of the suprarenal glands are of special interest, since it has been shown that the secretion of the glands passes directly or indirectly into the vessels. The following statements Digitized by Microsoft® 3O4 THE GENITOURINARY ORGANS. we take from Flint : The blood-vessels, derived from various sources, form in the dog a poorly developed plexus, situated in the capsule. From this plexus three sets of vessels are derived, which are distributed respectively in the capsule, the cortex, and the medulla of the gland. The vessels of the capsule divide into capillaries, which empty into a venous plexus situated in the deeper portion of the capsule. The cortical arteries divide into capillaries which form networks, the meshes of which correspond to the arrangement of the cells in the different parts of the cortex, encircling the coiled columns of cells in the glomerular zone, while in the fascicular zone the capillaries are parallel with occa- sional anastomoses. These capillaries form a fine-meshed plexus in the reticular zone and unite in the peripheral portion of the medulla to form small anastomosing veins, from which the larger veins are derived. The latter do not anastomose, and are therefore terminal veins. The arteries of the medulla pass through the cortex without giving off any branches until the medulla is reached, where they break up into a capillary network surrounding the cell masses situated here. The blood from this plexus may be col- lected into veins of the medulla which empty into the terminal vein or some of its larger branches, or may flow directly into branches of the venous tree. The endothelial walls of the capil- laries rest directly on the specific gland cells, with the intervention here and there of a few reticular fibrils. According to Pfaundler, the walls of the blood-vessels of the entire suprarenal body consist solely of the tunica intima. The nerves of the suprarenal glands have been studied recently by Fusari and Dogiel (94) ; the description given by the latter will here be followed. Numerous nerve-fibers, both nonmedullated and medullated, arranged in the form of a plexus containing sym- pathetic ganglia, are found in the capsule. From this plexus numerous small bundles and varicose fibers enter the cortex, where they form plexuses surrounding the columns of cells or groups of cells found in the three zones of the cortex and about the vessels and capillaries of the cortex. The nerve-fibers of these plexuses are on the outside of the columns and cell groups and do not give off branches which pass between the cells. The nerve supply of the medullary substance is very rich, and is derived mainly from large nerve bundles which pass from the plexus in the capsule to the medulla, where they divide and form dense plexuses which surround the groups of gland-cells and veins ; from these plexuses fine varicose fibers pass between the gland-cells, forming intercel- lular plexuses. In the medulla there are found in many animals large numbers of sympathetic cells, some isolated, others grouped to form small ganglia. Pericellular networks surround the cell- bodies of certain of these sympathetic cells. (For further informa- tion concerning the suprarenal glands consult Gottschau, Weldon, Hans Rabl, C. K. Hoffmann (92), Pfaundler, Flint, and Dogiel.) Digitized by Microsoft® TECHNIC. 305 TECHNIC. 270. The arrangement of the cortical and medullary portions of the kidney is best seen in sections of the kidney of small mammalia, cut in the proper direction, and, if possible, embracing the whole organ. If, on the other hand, the finer epithelial structures are to be examined, small pieces are first fixed in osmic acid mixtures or in corrosive sublimate. 271. Impregnation with silver nitrate (method of Golgi or Cox) reveals some points as to the relation of the cells of the uriniferous tubules to each other. 272. In order to isolate the tubules, thin strips of kidney tissue are treated for from fifteen to twenty hours with pure hydrochloric acid having a specific gravity of 1.T2 (for this purpose kidney tissue is used taken from an animal killed twenty-four hours previously). It is then washed, teased, and examined in glycerin (Schweiger-Seidel). Fuming nitric acid (40% ), applied for a few hours to small pieces of tissue, occa- sionally isolates the uriniferous tubules very extensively. The further treatment is then the same as after hydrochloric acid. A 35% potassium hydrate solution may also be employed. The isolated pieces are, however, not easily preserved permanently. 273. The epithelium of the uriniferous tubules may be isolated either in yi alcohol (vid. T. 128) or, according to R. Heidenhain (83), in a 5% aqueous solution of neutral ammonium chromate. The latter method shows clearly the striation of the epithelium. 274. The autophysiologic injection with indigo-carmin (Chrzon- szczewsky vid. T. 245), applied as in the case of the liver, fills the urin- iferous tubules, which may then be further examined in sections. 275. The blood-vessels are examined in injected specimens (injection of the kidney is easily accomplished). In larger animals the injection is made into the renal artery, while in smaller ones the whole posterior half of the body is injected through the abdominal aorta. 276. The ureter and bladder are cut open, fixed, and then sectioned. In this way the organs are shown in a collapsed condition, in which the arrangement of the epithelium is totally different from that found in the distended organs. In order to observe them in the latter condition the fix- ing agent is injected into the ureter or bladder, when, after proper liga- tion, they are placed in the same fixing agent. 277. The usual fixing fluids are employed in the demonstration of the suprarenal capsule ; but mixtures containing chromic acid, whether Flem- ming's fluid, chromic acid, or its salts, are of special importance in the examination of the organ, since the medullary substance of the suprarenal capsule stains a specific brown when treated by these mixtures (a con- dition only reduplicated in certain cells of the hypophysis). This brown staining also occurs when the cortical and medullary portions are entirely separated, as is the case in certain animals and during the development of the suprarenal capsule. The fat found in the cells of the suprarenal cortex is not identical with that of the rest of the body, as it may be dis- solved by chloroform and oil of bergamot out of tissue fixed with osmic acid (Hans Rabl). Digitized by Microsoft® 306 THE GENITOURINARY ORGANS. C THE FEMALE GENITAL ORGANS. J. THE OVUM. The product of the ovaries is the matured " ovum," or egg, hav- ing a diameter of from 0.22 to 0.32 mm. It forms a single cell with a thick membrane, from 7 p. to 1 1 /i in thickness, known as the zona pellucida. The ovum consists of a cell-body known as the yolk or vitellus, and a nucleus, from 30 p. to 40^ in diameter, termed the germinal vesicle. The vitellus consists of two sub- stances — a protoplasmic network, with a somewhat denser arrange- ment at the periphery of the cell and in the neighborhood of the germinal vesicle, and of small, highly refractive, and mostly oval bodies imbedded between the meshes of the protoplasm — the yolk globules. These latter, as a rule, are merely browned on being treated with osmic acid, although occasionally a true fatty reaction may be obtained. The germinal vesicle is surrounded by a distinct membrane having a double contour. In its interior we find a scanty lining framework containing very little chromatin, and one or two relatively large false nucleoli, or germinal spots, from y/i to 10/i in diameter, due to a nodal thickening of the chromatin. In the latter a further very distinct differentiation is sometimes seen in the shape of a small body (vacuole ?) of doubtful origin, which has been called Schron's granule. The germinal vesicle and spot were formerly known as " Purkinje's vesicle" and "Wagner's spot," respectively, from their discoverers. 2. THE OVARY. The ovaries are almost entirely covered by peritoneum. The mesothelial cells of the latter, however, undergo here a differentia- tion, to form the germinal epithelium. At the hilum the peritoneal covering is absent, and it is here that the connective-tissue elements of the ovarian ligament penetrate into the organ to form its con- nective-tissue framework, the so-called stroma of the ovary. At an early period in the development of the ovaries, the germinal epithe- lium begins a process of invagination into the stroma of the ovaiy, so that at the periphery of the organ a zone is soon formed which consists of both connective tissue and epithelial (mesothelial) ele- ments. This zone is called the cortex, or parenchymatous zone. That portion of the organ in the neighborhood of the hilum (aside from the rudimentary structure known as the epoophoron) consists of connective tissue containing numerous elastic fibers and unstriped muscle-cells, and is known as the medullary substance, or vascular zone. This connective tissue penetrates here and there into the cor- tex, separates the epithelial elements of the latter from each other, and is in direct continuation with a stratum immediately beneath the germinal epithelium, called the tunica albuginea. This latter layer of connective tissue is very distinct in the adult ovary, although its Digitized by Microsoft® THE FEMALE GENITAL ORGANS. 307 structure and thickness vary to a considerable extent. In young ovaries it is irregular, but shows in its highest development three layers distinguishable from each other by the different direction of the fibers. In the medullary substance the connective -tissue fibers are long, in the cortex short, and in the zone containing the follicles (see below) are mingled with numerous connective -tissue cells. Nonstriated muscle-fibers occur exclusively in the medulla. Here they are gathered in bundles which accompany the blood-vessels, and may even form sheaths around the latter. They are especially prominent in mammalia. The germinal epithelium is distinguished from that of the re- maining peritoneum by the greater height of its cells, which are Young follicle with ovum. Primordial ova Ovum with fol Hcular epithe^ lium. Fig. 258. — Section from ovary of adult dog. At the right the stellate figure repre- sents a collapsed follicle with its contents. Below and at the right are seen the tubules of the parovarium (copied from Waldeyer). cubical or even cylindric in shape. At an early period in the devel- opment of the ovaries this epithelium pushes into the underlying embryonic connective tissue in solid projections, to form the primary egg tubes of Pfluger, the cells of which very soon begin to show differentiation. Some retain their original characteristics and shape, while others increase in size, become rounded, and develop into the young ova. Those retaining their indifferent type become the fol- licular cells surrounding the egg. This differentiation into ova and follicular elements may even occur in the germinal epithelium itself, in which case the larger round cells are known as the primitive or primordial ova. In the further development of the ovarian cortex Digitized by Microsoft® 3o8 THE GENITOURINARY ORGANS. the primitive egg tubes are penetrated throughout by connective tissue, so that each egg tube is separated into a number of irregular divisions. In this way a number of distinct epithelial nests are formed, which lose their continuity with the germinal epithelium and finally lie imbedded in the connective tissue. According to the shape and other characteristics of these epithelial nests, we may distinguish several different groups: (i) The primitive egg tubes Germinal epi- — thelium. . Tunica albu- ginea. - Follicular ^ epithelium. ~~ Ovum. Granular layer of largre Graafian follicle. Fig- 2 59- — From ovary of young girl ; X !9°- of Pfliiger; (2) the typical primitive follicles — i.e., those which contain only a single egg-cell (present in the twenty-eighth week of fetal life) ; (3) the atypic follicles — i. c, those containing from two to three egg-cells ; (4) the so-called nests of follicles, in which a large number of follicles possess only a single connective-tissue en- velope ; (5) follicles of the last-named type which may assume the form of an elongated tube, and which are then known as the con- Digitized by Microsoft® THE FEMALE GENITAL ORGANS. 3O9 stricted tubes of Pfliiger. The fourth, fifth, and possibly the third types are further divided by connective-tissue septa, until they finally form distinct and typical follicles (Schottlander, 91, 93). In the adult ovary true egg tubes are no longer developed. Isolated invaginations of the germinal epithelium sometimes occur, but apparently lead merely to the formation of epithelial cysts (Schottlander). The theories as to when the formation of new epithelial nests or follicles ceases are, however, very conflicting, some authors believing that cessation takes place at birth, others that it continues into childhood and even into middle age. The typical primitive follicle consists of a relatively large egg- cell surrounded by a single layer of smaller cubical or cylindric follicular cells. The growth of the follicle takes place by means of mitotic division in the follicular cells and increase in size of the ovum. The egg-cell is soon surrounded by several layers of cells, and gradually assumes an eccentric position in the cell complex. At a certain distance from the ovum and nearly in the center of the follicle one or more cavities form in the follicular epithelium. These become confluent, and the resulting space is filled by a fluid derived, on the one hand, from a process of secretion and, on the other hand, from the destruction of some of the follicular cells. The cavity is called the antrum of the follicle, and such a follicle has received the name of Graafian follicle. Its diameter varies from 0.5 to 6 mm. The follicle in- creases in size through cell-proliferation, the cavity increasing and gradually inclosing the egg together with the follicular cells imme- diately surrounding it, although the latter always remain connected with the wall of the vesicle at some point. The egg now lies imbedded in a cell-mass, the discus proligerus, which is composed of follicular epithelium, and projects into the follicular cavity. The follicular epithelium forming the wall of the cavity is known as the stratum granulosum, the cavity as the antrum, and the fluid which it contains as the liquor folliculi. Those follicular cells which immediately surround and rest upon the ovum are some- what higher than the rest and constitute the egg epithelium, or corona radiata. During the growth of the follicle the connective tissue surround- ing it becomes differentiated into a special envelope, called the theca folliculi. In it two layers may be distinguished — the outer, the tunica externa, consisting of fibrous connective tissue, is continu- ous with the inner, or tunica interna, rich in blood-vessels and cellular elements. The follicle gradually extends to the surface of the ovary, at which point it finally bursts (see below), allowing the ovum to escape into the body cavity and thus into the oviduct. During the growth and development of the ovarian follicles the ova undergo certain changes of size and structure which may receive further consideration. These have been described for the human ovary by Nagel (96), whose account will here be followed. The Digitized by Microsoft® Fig. 263. Figs. 260, 261, 262, and 263. — From sections of cat's ovary, showing ova and follicles in different stages of development ; X 22 S : "1 "> "> n > Germinal spots ; i, b, b, b, germinal vesicles ; c , c, c, c, ova ; - Mucosa. Fig. 268. — From uterus of young woman; X 34- (From a preparation by Dr. J. Amann.) entering the mucosa, where they form capillary networks surround- ing the glands and a dense capillary network situated under the uterine epithelium. The veins form a venous plexus in the deeper portion of the mucosa, especially well developed in the cervix and os uteri. From this plexus the blood passes to a second well- developed venous plexus situated in the stratum vasculosum of the muscular layer, whence the blood passes to the plexus of uterine and ovarian veins. The lymphatics begin in numerous clefts in the uterine mucosa ; Digitized by Microsoft® 320 THE GENITOURINARY ORGANS. from here the lymph passes by way of lymph-vessels to the mus- cular coat, between the bundles of which are found numerous lymph-vessels especially in the middle or vascular layer. These lymph-vessels terminate in larger vessels found in the subserous connective tissue. The uterus and Fallopian tubes receive numerous medullated and nonmedullated nerves. The latter terminate in the muscular layers. Medullated fibers have been traced into the mucosa, where they form plexuses under the epithelium, from which branches have been traced between the epithelial cells and between the gland-cells. In the course of the nerves ganglion cells of the sympathetic type have been observed. Fig. 269. — From section of human vagina. In the vagina we distinguish also three coats — the mucous membrane, the muscular layer, and the outer fibrous covering. The epithelium of the mucous membrane is of the stratified squamous type, and possesses, as usual, a basal layer of cylindric cells. The mucosa of the vagina consists of numerous connective- tissue fibers mingled with a number of exceptionally coarse elastic fibers. Papillae containing blood-vessels are present everywhere ex- cept in the depressions between the columns rugarum. It is generally stated that the vagina has no glands, but according to the observa- tions of von Preuschen and C. Ruge, a few isolated glands occur in Digitized by Microsoft® THE FEMALE GENITAL ORGANS. 321 the vagina. They are relatively simple in structure, form irregular tubes, and are lined by ciliated columnar epithelium. The excre- tory ducts are lined by stratified squamous epithelium. Diffuse adenoid tissue is met with in the mucosa, which sometimes assumes the form of lymphatic nodules. The muscular coat, which in the lower region is quite prominent, may be separated indistinctly into an outer longitudinal and an in- ner circular layer ; the latter is, as a rule, poorly developed, and may be entirely absent. The muscular coat is especially well developed anteriorly in the neighborhood of the bladder. ■ ■ ■--■ $m \&$\Wm Fig. 270 — From section of human labia minora. The outer fibrous layer consists of dense connective tissue loosely connected with the adjacent structures. At its lower end the vagina is partially closed by the hymen which must be regarded as a rudiment of the membrane which in the embryo separates the lower segment of the united Miillerian ducts from the ectoderm of the sinus urogenitalis. Accordingly, the epithelium on the inner surface of the hymen partakes of the character of the vaginal epithelium ; that on the outer surface re- sembling the skin in structure (G. Klein). Digitized by Microsoft® 322 THE GENITOURINARY ORGANS. The epithelium of the vestibulum gradually assumes the char- acteristics of the epidermis ; its outer cells lose their nuclei and sebaceous glands occur here and there in the neighborhood of the urethral orifice and on the labia minora. Hair begins to appear on the outer surface of the labia majora. The clitoris is covered by a thin epithelial layer, resembling the epidermis. This rests on a fibrous-tissue mucosa having numerous papillae, some of which contain capillaries, others special nerve- endings. In the clitoris of the adult no glands are found. The greater portion of the clitoris consists of cavernous tissue, homol- ogous to the corpora cavernosa of the penis ; the corpus spongi- osum is not present in the clitoris. The glands of Bartholin the homologues of the glands of Cowper in the male, are mucous glands situated in the, lateral walls of the vestibule of the vagina. The terminal portions of their ducts are lined by stratified squamous epithelium. Free sensory nerve-endings, with or without terminal enlarge- ments, have been demonstrated in the epithelium of the vagina (Gawronski). The sensory nerve-fibers form plexuses in the mucosa, and lose their medullary sheaths as they approach the epithelium. Sympathetic ganglia are met with along the course of these nerves, and nonmedullated nerves terminate in the involuntary muscular tissue of the vaginal wall. In the connective-tissue papillae and in the deeper portions of the mucosa of the glans clitoridis are found, besides the ordinary type of tactile corpuscles and the spherical end-bulbs of Krause, the so- called genital corpuscles (see p. 155). Numerous Pacinian cor- puscles have been observed in close proximity to the nerve-fibers of the clitoris and the labia minora. In varying regions of the medullary substance of the ovary, but more usually in the neighborhood of the hilum, there occur irregular epithelial cords or tubules provided with columnar epithe- lium, ciliated or nonciliated, which constitute the paroophoron. These are the remains of the mesonephros, and are continuations of that rudimentary organ — the epoophoron — of similar structure which lies within the broad ligament. The separate tubules of the epoophoron communicate with the duct of Gartner (Wolffian duct), which in the human being is short, ends blindly, and never, as in certain animals, opens into the lower portion of the vagina. These derivatives of the primitive kidney consist of blindly ending tubules of varying length lined by a ciliated epithelium, the cells of which are often found in process of degeneration. The hydatids of Morgagni are duplications of the peritoneum. Digitized by Microsoft® THE MALE GENITAL ORGANS. 323 D. THE MALE GENITAL ORGANS. J. THE SPERMATOZOON. The semen, or sperma, is a fluid that, as a whole, consists of the secretion of several sets of glands in which the sexual cells, the spermatosomes, or spermatozoa, which are formed in the testes, are suspended. We shall first consider the structure of the typical adult sperma- tosome, taking up consecutively its component parts. Three prin- cipal parts may be distinguished — the head, the middle piece, and the tail or flagellnm. The round or oval body of the head termi- nates in a lanceolate extremity. The former consists of chromatin, and is most intimately associated with the phenomenon of fertiliza- tion. The middle piece, which is attached to the posterior end of the head, is composed of a protoplasmic envelop which surrounds a portion of the so-called axial thread. The latter is enlarged ante- riorly just behind the head to form the terminal nodule, which fits into a depression in the head. From the middle piece on, the axial thread Fig. 271. — Diagram showing the general characteristics of the spermatozoa of various vertebrates : a, Lance ; b, segments of the accessory thread ; c, accessory thread ; d, body of the head ; e, terminal nodule ; f, middle piece ; g, marginal thread ; h, axial thread ; i, undulating membrane ; k, fibrils of the axial thread ; /, fibrils of the marginal thread ; ;/;, end piece of Retzius ; », rudder-membrane. is continued into the tail of the spermatozoon, and is here sur- rounded by a transparent substance — the sheath of the axial thread. The envelop is lacking at the posterior extremity of the tail, where the axial thread extends for a short distance as a naked filament called the end-piece of Retzius. From the middle piece a still finer thread is given off, the marginal thread, which extends at a certain distance from the axial thread as far as the end-piece of Retzius. In its course it crosses and recrosses the axial thread at various points, and may even wind around it in a spiral manner. In all in- stances it is connected with the sheath of the axial thread by a delicate membrane — the undulating membrane . Another and still more delicate filament — the accessory thread — runs parallel with the axial thread along the surface of its sheath and terminates at a cer- tain distance from the end-piece of Retzius. Near the extremity of the flagellum and immediately in front of the end-piece is another and shorter membrane, — the rudder membrane , — which is continu- ous with the undulating membrane. Maceration reveals a fibrillar Digitized by Microsoft® 3 2 4 THE GENITOURINARY ORGANS. structure of both the axial and marginal threads (Ballowitz), while the accessory thread is separated into a number of short segments. In mammalia, and especially in man, the spermatozoa seem to be more simply con- structed. Here the head is pyriform, and somewhat flattened, with a slight ridge along the depression at either side of its anterior thinner portion (Fig. 272). In some mammalia (mouse), the head is provided with a so- called cap, which corresponds to the lance previously mentioned. The middle piece is relatively long and shows a distinct cross- striation, which may be attributed to its spiral structure. Here also the middle piece is tra- versed by the axial thread, which ends at the head in a terminal nodule, and may be sep- arated as in other mammalia into a number of fibrils. Some years ago Gibbes described an undulating membrane in the human sper- matozoon, an observation which was confirmed by W. Krause (81). The head of the human spermatosome is from 3 /i to 5 /u long, and from 2 fj. to 3 n in breadth ; the middle piece is 6 fj. long and 1 ji in breadth ; the tail is from 40 {J. to 60 fi long, and the end-piece 6 fi long. The spermatozoa are actively motile, a phe- nomenon due to the flagella, which give them a spiral, boring motion. They are character- ized by great longevity and are very resistant to the action of low temperatures (i>id. Pier- sol, 83). In some species of bat the sper- matozoa penetrate into the oviduct of the female in the fall, but do not contribute to im- pregnation until the spring, when the ova mature. (For the structure of the spermatosomes see Jensen, Ballowitz.) Fig. 272. — Human spermatozoa. The two at the left after Retzius (81) ; the one at the extreme left is seen in profile ; the other in surface view ; the one at the right is drawn as described by Jensen : a, Head ; b, terminal nod- ule ; c, middle piece ; , ciliated epithelium; l, glandular structure ; d, connective tissue. Fig. 278. — Cross-section of vas epididymidis of human testis. found an inner circular and an outer, though thin, longitudinal layer of nonstriated muscular tissue. An aberrant canaliculus also communicates with the vas epi- didymidis, and is here known as the vas aberrans Halleri. Num- Digitized by Microsoft® THE MALE GENITAL ORGANS. 329 bers of convoluted and blindly ending canaliculi are frequently found imbedded in the connective tissue around the epididymis. These constitute the paradidymis, or organ of Giraldes. The blood-vessels of the testis spread out in the corpus High- mori and in the tunica vasculosa of the connective-tissue septa and of the tunica albuginea, their capillaries encircling the seminal tu- bules in well-marked networks. The lymphatic vessels begin in clefts in the tunica albuginea and in the connective tissue between the convoluted tubules. They con- verge toward the corpus Highmori and pass thence to the spermatic cord. Retzius (93) and Tim- ofeew (94) have described plexuses of nonmedul- lated, varicose nerve-fibers surrounding the blood- vessels of the testis. From such plexuses single fibers, or small bundles of such, could be traced to the seminiferous tubules, about which they also form plexuses. Such fibers have not been traced into the epithelium lining the tubules. In the epididymis Timofeew found numerous sympa- thetic ganglia, the cell- bodies of the sympathetic neurones of which were surrounded by pericellular plexuses. In the wall of the vas epididymidis and the vasa efferentia were observed numerous varicose nerve-fibers, arranged in the form of a plexus, many of which seemed to terminate on the nonstriated muscle cells found in these tubes. Some of the nerve -fibers were traced into the mucosa, but not into its epithelial lining. Fig. 279. — Section of dog's testis with in- jected blood-vessels (low power) : a, Seminifer- ous tubule; 6, connective-tissue septum; c, blood- vessel. 3. THE EXCRETORY DUCTS. The vas deferens possesses a relatively thick muscular wall, con- sisting of three layers, of which the middle is circular and the other two longitudinal. The subepithelial mucosa is abundantly supplied with elastic fibers and presents longitudinal folds. The lining epi- thelium is in part simple ciliated columnar and in part stratified ciliated columnar, with two rows of nuclei. The cilia are, however, often absent, beginning with the lower portion of the vas epidi- Digitized by Microsoft® 330 THE GENITO-URINARY ORGANS. dymidis. According to Steiner, the epithelium of the vas deferens varies. It may be provided with cilia in the lower segments, or it may even be similar to that found in the bladder and ureters. The inner muscular layer is wanting in the ampulla of the vas deferens ; here the epithelium is mostly simple columnar and pig- mented. Besides the folds, there are also evaginations and tubules which sometimes form anastomoses — structures which may be re- garded as glands. The seminal vesicles are also lined, at least when in a distended condition, by simple, nonciliated columnar epithelium containing yellow pigment. In a collapsed condition the epithelium is pseudo- stratified, with two or even three layers of nuclei. The arrange- ment of the epithelial cells in a single layer would therefore seem to be the result of distention. The mucous membrane shows Epithelium. Inner longi- tudinal muscular layer. Middle cir- cular mus- cular layer. Fig. 280. — Cross-section of vas deferens near the epididymis (human).. numerous folds, which, in the guinea-pig for instance, present a delicate axial connective-tissue stroma. Besides scanty subepithe- lial connective tissue, the seminal vesicles are provided with an inner circular and an outer longitudinal layer of muscle-fibers. Sperma- tozoa are, as a rule, not met with in the seminal vesicles. The epithelium of the ejaculatory ducts is composed of a single layer of cells ; the inner circular muscle-layer is very poorly devel- oped. In the prostatic portion of the ejaculatory ducts the longi- tudinal muscle-layer mingles with the musculature of the prostate and loses its individuality. The ejaculatory ducts empty either directly into the urethra at the colliculus seminalis, or indirectly into the prostatic portion of the urethra through the vesicula prostatica. The prostate is a compound branched alveolar gland. Its capsule Digitized by Microsoft® THE MALE GENITAL ORGANS. 331 consists of dense layers of nonstriated muscle-fibers, connective tissue, and yellow elastic fibers. Processes and lamellae composed of all these elements extend into the interior of the gland, converg- ing toward the base of the colliculus seminalis. Between the larger trabecule are situated numerous glands, consisting of large, Fig. 281. — Cross-section of wall of seminal vesicle, showing the folds of the mucosa (human). irregular alveoli, separated by fibromuscular septa and trabeculse. The alveoli are lined by simple columnar epithelium, the inner portion of the cells often showing acidophile granules. Now and then the alveoli present a pseudostratified epithelium, with two rows of nuclei (Rudinger, 83). A basement membrane, although Digitized by Microsoft® 332 THE GENITOURINARY ORGANS. present, is difficult to demonstrate. The numerous excretory ducts, lined by simple columnar epithelium, become confluent and form from 15 to 30 collecting ducts which empty, as a rule, either at the colliculus seminalis or into the sulcus prostaticus. Near their terminations the larger ducts are lined by transitional epithelium similar to that lining the prostatic portion of the urethra. In the alveoli of the glands, peculiar concentrically laminated concrements are found, known as prostatic bodies or concretions (corpora amylacea). They are more numerous in old men, but are found in the prostates of young men and also of young boys. The secretion of the prostate (succus prostaticus) is not mucous in character, but resembles a serous secretion and has an acid reac- tion. The vesicula prostatica (sinus pocularis) is lined by stratified epithelium, consisting of two layers of cells and provided with a dis- tinct cuticular margin upon which rest cilia. In its urethral region occur short alveolar glands. The glands of Cowper are branched tubular alveolar glands, the alveoli being lined by mucous cells. Crescents of Gianuzzi are, however, seldom seen. The smaller excretory ducts, lined by cubical epithelium, unite to form two ducts, one on each side of the urethra ; these are 1 y 2 inches long, and are lined by stratified epi- thelium consisting of two or three layers of cells. The blood-vessels of the prostate ramify in the fibromuscular trabecular and form capillary networks surrounding the alveoli. The veins collecting the blood pass to the periphery of the gland, where they form a plexus in the capsule. The lymphatics begin in clefts in the trabecular and follow the veins. The terminal branches of the vessels supplying Cowper's glands are, in their arrangement, like those of other mucous glands. Numerous sympathetic ganglia are found in the prostate under the capsule and in the larger trabecular near the capsule. The neuraxes of the sympathetic cells of these ganglia may be traced to the vessels and into the trabecular ; their mode of ending has, however, not been determined. Small medullated nerve-fibers terminate in these ganglia in pericellular baskets. Timofeew has described peculiar encapsulated sensory nerve-endings, found in the prostatic and membranous portions of the urethra of certain mam- malia. They consist of the terminal branches of two kinds of nerves, inclosed within nucleated laminated capsules : one large medul- lated nerve -fiber, after losing its medullary sheath, breaks up into a small number of ribbon-shaped branches with serrated edges, which may pass more or less directly to the end of the nerve-ending or may be bent upon themselves ; and very much smaller medullated nerve-fibers which, after losing their medullary sheaths, divide into a large number of varicose fibers which form a dense network en- circling the ribbon-shaped fibers previously mentioned. • The penis consists of three cylindric masses of erectile tissue — the two corpora cavernosa, forming the greater part of the penis Digitized by Microsoft® THE MALE GENITAL ORGANS. 333 and lying side by side, and the corpus spongiosum, surrounding the urethra and lying below and between the corpora cavernosa. The two latter are surrounded by a dense connective-tissue sheath, the tunica albuginea. These erectile bodies are surrounded by a thin layer of skin, containing no adipose tissue and no hair-follicles. The corpus spongiosum is enlarged anteriorly to form the glans penis. The principal substance of the erectile bodies is the so-called erectile tissue : septa and trabecular, consisting of connective tissue, elastic fibers, and smooth muscle-cells inclosing a sys- tem of communicating spaces. These latter may be regarded as venous sinuses, the walls of which, lined by endothelial cells, are in apposition to the erectile tissue. Under certain conditions the venous sinuses are distended with blood, but normally they are in a collapsed state and form fissures which simulate the clefts found in ordinary connective tissue. In other words, there is here such an arrangement of the blood-vessels within the erectile tissue that the circulation may be carried on with or without the aid of the cavernous spaces. The arteries of the corpora cavernosa possess an especially well-developed musculature. They ramify through- out the trabecular and septa of the erectile tissue and break up within the septa into a coarsely meshed plexus of capillaries. A few of these arteries empty directly into the cavernous spaces. On the other hand, the arteries give off a rich and narrow-meshed capillary network immediately beneath the tunica albuginea. This is in com- munication with a deeper and denser venous network, which, in turn, gradually empties into the venous sinuses. Aside from these there are anastomoses between the arterial and venous capillaries, which later communicate with the venous network just mentioned. The blood current, regulated as it thus is, may pass either through the capillaries alone, or may divide and flow through both these and the venous sinuses. These conditions explain both the erec- tile and quiescent state of the penis. The relations are somewhat different in the corpus spongiosum urethra? and in the glans penis. The epithelium of the urethra varies in the several regions. The prostatic portion possesses an epithelium similar to that of the bladder. In the membranous portion, the epithelium may be simi- lar to that found in the prostatic portion, but more often pre- sents the appearance of a pseudostratified epithelium with two or three layers of nuclei. The cavernous region is lined by pseudo- stratified epithelium, except in the fossa navicularis, where a stratified squamous epithelium is found. Between the fibro-elastic mucosa and the epithelium there is a basement membrane. There occur in the urethra, beginning with the membranous portion, ir- regularly scattered epithelial sacculations of different shapes. Some of these show alveolar branching, and are then known as the glands of Littre. The submucosa of the cavernous portion of the urethra, which Digitized by Microsoft® 334 • THE GENITO-URINARY ORGANS. contains nonstriated muscle-tissue arranged circularly, is richly sup- plied with veins, and contains pronounced plexuses communicating with cavernous sinuses, which correspond in general to those of the corpora cavernosa penis. In the glans penis the cavernous spaces are small and of more regular shape than in the corpora cavernosa. The glans is covered by a layer of stratified squamous epithelium, often possessing a thin stratum corneum (see Skin). Near the corona of the glans penis there are now and then found small sebaceous glands (see Hair), known as glands of Tyson. The prepuce is a duplication of the skin, the inner surface present- ing the appearance of a mucous membrane. The nerves terminating in the glans penis have recently been studied by Dogiel, who made use of the methylene-blue method in his investigation. He finds Meissner's corpuscles in the connective- tissue papillae under the epithelium, Krause's spheric end-bulbs somewhat deeper in the connective tissue, and the genital corpuscles situated still deeper (see Sensory Nerve-endings). In the epithelium are found free sensory nerve-endings. Pacinian corpuscles have also been found in this region. 4. SPERMATOGENESIS. In order that the student may obtain an understanding of the com- plicated process of spermatogenesis we shall give a description of it as it occurs in salamandra maculosa, which of all vertebrate animals presents the phenomena in their simplest and best known form. The student should understand, however, that many of the details here described have not been observed in the testes of mammalia ; and, since the spermatozoa of many of the mammalia are of simpler structure than those of the salamander, the development of the spermatozoa of the former is consequently simpler. It should also be noticed that the general structure of the testes of the salamander differs in some respects from that of the testes of mammalia, as given in the preceding pages. At first the seminiferous tubules consist of solid cellular cords, and it is only during active production of spermatozoa that a central lumen is formed, in which the spermatosomes then lie. The cells which compose these solid cords may be early differentiated into two classes — those of the one class being directly concerned in the pro- duction of the spermatosomes ; those of the other appearing to have a more passive role. The cells of the first class — the spermatogo- nia, or primitive seminal cells — undergo a process of division accom- panied by an increase in size. In this way they soon commence to press upon the cells of the second class — the follicular or sustentaai- lar cells. The result is that the nuclei of the latter are forced more or less toward the wall of the seminal tubule, while their proto- plasm is so indented by the adjacent spermatogonia that the cells Digitized by Microsoft® SPERMATOGENESIS. 335 assume a flattened cylindric shape presenting indentations and processes on all sides. In this stage the spermatogonia have a radiate arrangement and entirely surround the elongated susten- tacular cells. At present three periods are distinguished in the development of the male sexual cells (spermatosomes) from the spermatogonia. The first period embraces a repeated mitotic divi- sion of the spermatogonia — the period of proliferation. In the sec- ond, the spermatogonia, which have naturally become smaller from repeated division, begin to increase in size — the period of growth. The third is characterized by a modified double mitotic division without intervening period of rest, and results in the matured sper- matozoa — the period of maturation, figure 283. During the third period, a very important and significant process takes place — the Primordial sexual cell. < Zone of proliferation. Spermatogonia.,, / \ / \ / (The generations are much larger.) /Zone of growth. Spermatocyte I order.- Spermatocytes II order. "• • 5 Zone of maturation. Spermatids ■» • • • ' Fig. 283. — Schematic diagram of spermatogenesis as it occurs in ascaris (after Boveri). ("Ergebn. d. Anat. u. Entw.," Bd. I.) reduction in the number of chromosomes, so that in the spermatids, the chromosomes are reduced to half the number present in a somatic cell of the same animal. The manner in which this reduc- tion in the number of chromosomes takes place will be described as it occurs in salamandra maculosa. After the cells composing the last generation of spermato- gonia have attained a certain size (period of growth), they under- go karyokinetic division. First, the usual skein or spirem is formed, but instead of dividing into twenty-four chromosomes, as in the somatic cell, the filament of the skein segments into only twelve loops. The cell thus provided with twelve chromosomes now enters upon the period of maturation, and is known as a spermatocyte of the first order, or a " mother cell " (O. Hert- Digitized by Microsoft® 336 THE GENITOURINARY ORGANS. wig, 90). The division of these cells is heterotypic (vtd. p. 64) ; the chromosomes split longitudinally and in such a way that the division begins at the crown of the loops, extending gradually toward their free ends. In this case the daughter chromosomes remain for some time in contact, so that the metakinetic figure resembles a barrel in shape. Finally, the daughter chromosomes separate and wander toward the poles. As soon as the daughter stars (diaster) are developed, the number of chromosomes is again doubled by a process of longitudinal division. The spermatocyte of the first order thus divides into two spermatocytes of the second order, or daughter cells (O. Hertwig, 90). The nuclei of the daughter cells now contain twenty-four chromosomes, as is the case in the somatic cell, and, without undergoing longitudinal split- ting, the daughter chromosomes are distributed to the two nuclei of the spermatids. In other words, the latter contain only twelve chromosomes. The spermatozoa are formed from the spermatids by a rearrangement of the constituent elements of these cells. It may thus be said that even in the stage of the segmenting skein in the mother cells, the spermatocytes of the first degree contain twice as many chromosomes as a somatic cell, a condition which is first clearly seen in the stage of the diaster (here only an apparent duplication in the diaster stage). As a result, there is, first, a de- crease in the double number of chromosomes found in the sperma- tocytes of the second degree to the normal number ; second, a decrease in the number of chromosomes in the spermatocytes of the third degree (spermatids) to one-half the number present in a somatic cell, a condition probably due to the fact that here there is no stage of rest nor longitudinal splitting of the chromosomes. This is the general process in heterotypic division. Besides the heterotypic form, there occurs in the division of the spermatocytes another (homeotypic) form of karyokinetic cell-division. This dif- fers from the heterotypic in the shortness of the chromosomes, the absence of the barrel phase, the late disappearance of the aster, and the absence of duplication in the chromosomes of the diaster. According to Meves (96), the spermatocytes of the first degree undergo heterotypic, those of the second degree, homeotypic division. The spermatids develop into the spermatozoa, beginning imme- diately after the close of the second division of maturation. This process has been fully described for salamandra maculosa by Her- mann, Flemming, Benda, and others, but need not engage our attention at this point beyond the statement that the chromatin of the nuclei of the spermatids develops into the heads of the sperma- tozoa, while the remaining structures are developed from the proto- plasm. " The mature spermatozoon of the salamander represents a completely metamorphosed cell ; in the course of its develop- ment no portion of the original cell is cast off" (Meves, 97). Spermatogenesis in mammalia may be compared to the foregoing Digitized by Microsoft® SPERMATOGENESIS. 337 process, with the exception that here the different stages are seen side by side in the seminiferous tubule and without any apparent sequence, making the successive stages more difficult to demon- strate. The various generations of cells form columns, and are arranged in such a manner that the younger are found near the lumen and the older close to the wall of the tubule. (Figs. 284 and Fig. 284. — Schematic diagram of section through convoluted seminiferous tubule of mammal, showing the development of the spermatosomes. The number of chromo- somes is not shown in the various generations of the spermatogenic cells. The pro- gressive development of the spermatogenic elements is illustrated in the eight sectors of the circle : «, Young sustentacular cell ; b, spermatogonium ; c, spermatocyte ; d, spermatid. In I, 2, 3, and 4 the spermatids rest on the enlarged sustentacular cell in the center of the sector ; on both sides of the sustentacular cells are the spermatogenic or mother cells in mitosis. In the sectors 5> 6, 7, and 8 spermatozoa are seen in ad- vanced stages resting on the sustentacular cells, with new generations of spermatids on each side. [From Rauber (after Brown) with changes (after Hermann) . ] 285.) These columns are separated from each other by high sus- tentacular cells, or Sertoli's cells or columns. The metamorphosis of the cells into spermatids and spermatosomes is accomplished by the changing of the cells bordering upon the lumen and then of those in the deeper layers, etc., into spermatids and then into spermatosomes. During this process the spermatids arrange 22 Digitized by Microsoft® 338 THE GENITOURINARY ORGANS. themselves around the ends of Sertoli's columns, a phenomenon which was formerly regarded as representing a copulation of the two elements, although it was clearly understood that no real fusion or interchange of chromatin occurred, but that the close relations of the two were for the purpose of furnishing nourishment to the developing spermatosomes. The whole forms a spermato- blast of von Ebner. Since the spermatids lining the lumen are changed into spermatozoa, and the process is repeated in the cells of the deeper layers as they come to the surface, the result is that the entire column is finally used up. The compensatory elements are supplied by the proliferation of the adjacent spermatogonia. The resulting products again divide, and thus build up an entirely new generation of spermatogenic cells. Hand in hand with these progressive phenomena occurs an extensive destruction of the cells taking part in spermatogenesis. This is shown by the presence of so-called karyolytic figures in the cells, which later suffer complete demolition. These developmental changes are represented in the preced- Fig. 285. — Section of convoluted tubule from rat's testicle (after von Ebner, 88). The pyramidal structures are the sustentacular cells, together with spermatids and spermatosomes. Between these are spermatogenic cells, some of which are in process of mitotic division. Below, on the basement membrane and concealing the spermato- gonia, are black points representing fat-globules, a characteristic of the rat's testicle. Fixation with Flemming's fluid. ing schematic figure (Fig. 284), and may in part be observed in figure 285. In mammalia it has been possible to trace the development of the spermatids into the spermatosomes. These phenomena have been studied and described by numerous writers, and although many conflicting views have been expressed, the essential steps of this process seem quite clearly established. The account here given is based in part on the recent observations of v. Lenhossek and the observations of Benda. Before considering the method of development of the spermatosomes from the spermatids, a few words concerning the structure of the latter may be useful. The sharply outlined spermatid possesses a slightly granular protoplasm and a round or slightly oval nucleus with a delicate chromatic network. In the protoplasm there is found a sharply defined globule, known as the sphere or sphere substance, which lies near the nucleus and Digitized by Microsoft® SPERMATOGENESIS. 339 presents throughout a nearly homogeneous structure. This sub- stance is first noticed in the spermatocytes, disappears during the cell-divisions resulting in the spermatids, and reappears in the latter. In the protoplasm of the spermatid, lying near the nucleus, there is further found a small globular body, the chromatoid accessory nucleus of Benda, smaller than the sphere and staining very deeply in Heidenhain's hematoxylin. A true centrosome may also be found in the spermatid. The nucleus of the spermatid develops into the head of the spermatosome, during which change the originally spheric nucleus becomes somewhat flattened and at the same time assumes a denser structure and moves toward that portion of the spermatid pointing away from the lumen of the seminiferous tubule. Accompanying these changes in the nucleus, marked changes are observed in the shape and structure of the sphere, which marks the position of the future anterior end of the head of the spermatosome, and applies itself to the nucleus on the side pointing away from the lumen of the tubule. In this position it differentiates into an outer clear homogeneous zone and a central portion which stains more deeply and to which v. Lenhossek has given the name akrosome. From these structures are developed the head-cap and the lance of the spermatosomes, which differ in shape and relative size in the sper- matosomes of the different vertebrates. Recent investigation seems to establish quite clearly that the axial thread of the tail is devel- oped from the centrosome (from the larger, if two are present), which is situated at some distance from the nucleus. Soon after the begin- ning of the development of the axial thread the centrosome wanders to the posterior part of the future head of the spermatosome (the pole of the nucleus opposite the head-cap) and becomes firmly attached to the nuclear membrane in this position (observations made on the rat by v. Lenhossek, and on the salamander by Meves). The middle piece and the undulating membrane, it would appear, are differentiated from the protoplasm, although the question of the mode of their development is still open to discussion. The chro- matoid body assumes a position near the axial thread at its junc- tion with the cell membrane ; its fate has not, however, been fully determined. According to Hermann (97), the end-piece in the selachia is derived from the centrosome, the ring-shaped body from the invagi- nated half of the intermediate body of the spermatid formed during the last spermatocytic division, and the axial thread from filaments of the proximal half of the central spindle. The lance, according to him, represents a modified portion of the nuclear membrane of the spermatid. For further particulars regarding spermatogenesis see the in- vestigations of v. la Valette St. George, 67-87; v. Brunn, 84; Biondi, Benda, Meves, and v. Lenhossek. Digitized by Microsoft® 340 THE GENITOURINARY ORGANS. TECHNIC. 278. The ovaries of the smaller animals are better adapted to study than those of the human being, since the former are more easily fixed. 279. The germinal epithelium and its relations to the egg-tubes of Pfliiger are best studied in the ovaries of young or newly born animals — cats, for instance, being especially well adapted to this purpose. 280. Normal human ovaries are usually not easily obtainable. Human ovaries very often show pathologic changes, and in middle life frequently contain but few follicles. 281. Fresh ova may be easily procured from the ovaries of sheep, pig, or cow in the slaughter-houses. On their surfaces are prominent trans- parent areas — the larger follicles. If a needle be inserted into one of these follicles and the liquor folliculi be caught upon a slide, the ovum may as a rule be found, together with its corona radiata. That part of the preparation containing the ovum should be covered with a cover-glass under the edges of which strips of cardboard are laid. If no such strips are employed, the zona pellucida of the ovum is likely to burst in the field of vision, giving rise to a funnel-shaped tear. These tears have often been pictured and described as preformed canals (micropyles). 282. The best fixing fluid for ovarian tissue is Flemming's or Her- mann's {yid. T. 17, 18), either of which may be used for small ovaries or pieces of large ovaries ; safranin is then used for staining. Good results are also obtained with corrosive sublimate (staining with hematoxylin according to M. Heidenhain), and also with picric acid (staining with borax-carmin). 283. The treatment of the Fallopian tubes is the same as that of the intestine ; in order to obtain cross-sections of a tube it is advisable to dis- sect away the peritoneum near its line of attachment and then distend the tube before fixing. It is instructive to dilate the tube by filling it with the fixing agent, thus causing many of the folds to disappear. 284. No special technic is necessary in fixing the uterus and vagina. The epithelium is, however, best isolated with one -third alcohol (yid. T. 128). 285. Seminal fluid to which normal salt solution has been added may be examined in a fresh condition. The effect upon the spermatozoa of a very dilute solution of potassium hydrate ( 1 °]o or weaker) or of a very dilute acid (acetic acid) is worth noticing. The spermatozoa of sala- mandra maculosa show the different structural parts very clearly (lance, undulating membrane, marginal thread, etc.). In macerated prepara- tions (very dilute chromic acid), or in those left for some time in a moist chamber, the fibrillar structure of the marginal and axial threads may be seen quite distinctly. The spermatozoa may also be examined in the form of dry preparations (treatment as for blood), stained, for instance, with safranin. Osmic acid, its mixtures, and osmic vapors are useful as fixing agents, certain structures being better brought out so than by employing the dry methods. 286. In examining the testicle (spermatogenesis) it is advisable to begin with the testis of the salamander, which does not show such com- plicated structures as do the testes of mammalia. Here also either Flem- ming's or Hermann's fluid maybe used as a fixing agent, the latter being Digitized by Microsoft® THE SKIN. 341 followed by treatment with crude pyroligneous acid {vid. T. 18). For the salamander Hermann recommends a mixture composed of ijd plati- num chlorid 15 c.c, 2 ^7-w •■■(*■> ■>■■■■ •<& '* ■■- - rv - I- r ' 0_ u>,, , rn W% S :f Fig. 289. — Cross-section of human epidermis ; the deeper layers of the stratum Malpighii are not represented ; X 75°- The smallest papillae are found in the mammae and scrotum — from 30 fi to 50 /j. long. The surface of the pars papillaris is covered by an extremely delicate membrane — the basement membrane. Accord- ing to most authors, the basal cells of the epidermis are simply cemented to this structure. Others believe that the epithelial cells are provided with short basilar processes which penetrate into the basement membrane and meet here with similar structures from the connective-tissue cells of the corium. This would give the base- ment membrane a fibrillar structure (Schuberg). The subcutaneous layer contains numerous more or less verti- cal strands of connective tissue, containing numerous large elastic- tissue fibers and joining the stratum reticulare of the corium to the Digitized by Microsoft® 346 THE SKIN AND ITS APPENDAGES. superficial fascia of the body or underlying structure, whatever that may be. These strands are the retinaculcz cutis, and inclose in their meshes masses of fatty tissue which form the panniculus adiposus. The latter varies greatly in thickness in different parts of the body. The vertically arranged cords of connective tissue are accompanied by blood-vessels, nerves, and the excretory ducts of glands. Smooth muscle-fibers are also present in the skin, and around the hair follicles are grouped into bundles. Nearly continuous layers of smooth muscle tissue are found in the subcutaneous layer of the scrotum (forming here the tunica dartos), in the perineum, in the areola? of the mammae, etc. In the face and neck striated muscle-fibers also extend outward into the corium. Even in the white race certain regions of the epidermis always contain pigment — as, for instance, the areolae and mammillae of the Stratum corneum. Fig. 290. — Cross-section of negro's skin, showing the intimate relationship of the pigment cells of the corium to the basilar cells of the epidermis. The latter are more deeply pigmented at their outer ends. The pigment granules may be traced into the outermost layers of the stratum corneum ; X S 2 S- mammary glands, the scrotum, labia majora, around the anus, etc. In these regions the epithelial cells and the connective-tissue cells of the pars papillaris corii contain a variable number of small pigment granules. The latter occur chiefly in the basal cells of the epider- mis and diminish perceptibly in the cells of the overlying layers, so that in those of the stratum corneum few, if any, are left. In negroes and other colored races the deep pigmentation is due to a similar distribution of the pigment granules in the entire epidermis ; but even here the pigmentation decreases toward the surface, although the uppermost cells of the stratum corneum always con- tain some pigment. The nuclei of the cells are always free from the coloring-matter. The question as to the origin of the pigment is as yet unsolved. This much is known : that in those regions where pigment is present certain branched and deeply pigmented connec- Digitized by Microsoft® THE SKIN. 347 tive-tissue cells are found immediately beneath the epidermis, sending out processes which may be traced outward between the cells of the stratum Malpighii (Aeby). This fact has led some authors to believe that the connective tissue is in reality the source of the pig- ment, and that by some unknown process the latter is taken up and conveyed to the cells of the epidermis. This theory would preclude a direct production of pigment granules in the epidermal cells. But although it can not be denied that the pigment may be derived from the connective tissue, it is hardly logical to assume a priori that epithelial cells are not capable of pigment production, since, in other regions of the body, pigment formation may be observed in cells of undoubted epithelial origin, as, for instance, in ganglion cells and in the pigment epithelium of the retina. An interesting proof that the processes of pigmented connective-tissue cells actually penetrate the epidermis is afforded by the case reported by Karg, of transplanta- tion of a piece of skin from a white man to a negro. After some time the piece of white skin became pigmented. Reinkehas demon- strated that the pigment in certain cells is in combination with certain definite bodies. The latter have been given the botanical name of tropJioplasts. If the pigment be removed, colorless tropho- plasts are left. They may be tinged with certain stains. In the epidermis of the white race trophoplasts are also constantly present, although they are only slightly or not at all pigmented (Barlow). The following may be said concerning the vascular system of the skin : The arteries which supply the skin with nutriment penetrate the corium and form a characteristic network in its lowest stratum. They also anastomose freely in the fascia and the subcutaneous layer. From this plexus branches pass outward to form a second or subpapillary plexus. From the latter, branches are again given off which, without further anastomoses, pass along beneath the rows of papillae and supply each separate papilla with capillary twigs. These in turn pass over into venous capillaries which unite and also form several plexuses, corresponding m general to those of the arterial system. The uppermost venous plexus lies beneath the papillae, each venule corresponding to a single row of papillae and anastomosing with its neighbors. The second plexus is found immediately beneath the first, the third in the lower portion of the corium, and the fourth at the junction of the cutis and subcutis. Near the middle of the subcutis the arteries show a circular muscu- lature, but the veins are already thus provided in the network between the cutis and subcutis, where they also seem to possess valves. As already stated, the subcutaneous fat is divided into lobes by transverse and longitudinal bundles of connective tissue ; a second system of bundles midway between the cutis and fascia separates the panniculus adiposus into an upper and a lower layer. The former is supplied by direct arterial branches ; the latter, by branches passing backward from the cutaneous network. Those regions which are subjected to great external pressure are supplied by Digitized by Microsoft® 348 THE SKIN AND ITS APPENDAGES. a greater number of afferent vessels the caliber of which is increased. In regions where the skin is very mobile the arteries are greatly convoluted. All these vascular peculiarities are present in the new- born (Spalteholz). The lymph-vessels of the true skin are also distributed in two layers — a deep and wide-meshed plexus in the subcutis, and a superficial narrow-meshed plexus immediately beneath the papillae. Into the latter empty the lymph-vessels coming from the papillae. After treating the skin by certain methods, a fine precipitate may be noticed here and there in the papillary region of the corium, a proof that lymph clefts are present. These are regarded as the beginnings of the cutaneous lymphatic system. They may also be Stratum corneum. - - Nerve-fiber. Fig. 291. — Nerves of epidermis and papillze from ball of cat's foot ; X 75- traced into the epithelium, where they are in direct communication with the interspinal spaces between the epithelial cells (Unna). Cells are also met with in the interspinal spaces of the epidermis ; these are migratory cells, or cells of Langerhans. The skin owes its great sensitiveness to the numerous nerves and special nerve-endings present, not only in the epithelium, but also in the corium and subcutis. In certain regions of the skin the nerves have been traced into the epithelium. In the finger-tip, for instance, numerous nerves are seen in the epidermis, where they branch and end in telodendria with or without small terminal swell- ings. There is no direct communication between the terminal Digitized by Microsoft® THE SKIN. 349 nerve filaments and the epithelial cells. (Fig. 291.) In certain peculiarly sensitive regions, as the end of the pig's snout, the nerve- fibers end in distinct saucer-like discs (tactile menisci) which, as a rule, clasp the lower ends of the basal Malpighian cells. The special sensory nerve-endings are situated in the corium and subcutis. Of these, we may mention ,the tactile corpuscles Meissner, the end-bulbs of Krause, the Pacinian corpuscles, Ruf- fini's nerve -endings, and the Golgi-Mazzoni corpuscles. All these special sensory nerve-endings with the exception of the two last mentioned have been discussed in a former chapter (p. 1 54). Meiss- ner's tactile corpuscles are situated in the tactile papillae of the true skin. They are especially numerous in the hand and foot. In the distal phalanx of the index-finger every fourth papilla is a tactile papilla, containing one or sometimes two corpuscles of Nerve-fiber. trz-)-— Nerve-fiber. 8& -/ — — Capsule. Nerve-fiber. Nerve-fiber. Fig. 292. — Meissner' s corpuscle from man ; Fig. 293. — Meissner' s corpuscle from man ; X 750. Technic No. 295. X 75°- Technic No. 295. Meissner. They are, however, not nearly so numerous in other parts of the hand or in the foot. These corpuscles are further found on the dorsal surface of the hand and volar surface of the forearm, in the nipple and external genitals, in the eyelids (border), and in the lips. In figures 292 and 293 are shown two Meissner's corpuscles, giving the , appearance presented by these end-organs when not stained with special reference to nerve terminations. For the latter see figure 132. The Krause's end-bulbs, both spheric and cylindric, are, as a rule, situated a short distance below the papillary layer, although they are frequently found in the papillae. They occur in man in the conjunctiva, lips, and external genitals, and in the mucous mem- branes previously mentioned (p. 154). See page 154 and figure 131 for their structure. Digitized by Microsoft® 35° THE SKIN AND ITS APPENDAGES. In the palm of the hand and sole of the foot, the subcutaneous connective tissue contains numerous Pacinian corpuscles. They occur also along the nerve-fibers of the joints and in the periosteum of the extremities. (See Fig. 135.) Very recently Ruffini demonstrated in the human corium the existence of peculiar nerve end-organs, which consist of a connec- tive-tissue framework supporting a rich arborization of telodendria. They occur side by side with the Pacinian corpuscles and in appar- ently equal numbers. These nerve terminations resemble in many respects the neurotendinous spindles (see Fig. 140), although they present certain structural differences. Instead of intrafusal tendon fasciculi, the Ruffini end-organ is composed of white fibrous and elastic tissue. In this end-organ the medullated nerves make long and tortuous turns before becoming nonmedullated, and the terminations of these nerve-fibers oc- cupy the whole of the cross-section. The Golgi-Mazzoni corpuscle re- sembles in structure the Pacinian corpuscle, although it possesses fewer lamellae and a relatively larger core, and the nerve - fibers terminating therein are more extensively branched than in the Pacinian corpuscle. Ruf- fini has found these nerve-endings in the subcutaneous tissue of the finger- tips. The blood - vessels of the skin are richly supplied with vasomotor nerves, which terminate in the non- striated muscle of the vessel walls. These vasomotor nerve - fibers are neuraxes of sympathetic neurones. In aquatic birds, and more es- pecially in ducks, the waxy skin of the beak and the cornified portion of the tongue contain the so- called corpuscles of Herbst, which resemble the Pacinian corpuscles in general structure, but have cubical cells in the core. In the same tissues are also found the corpuscles of Grandry, 60 /u long and 40 p. broad. They consist of a thin connective-tissue capsule, con- taining two or three large cells. The nerve-fiber retains its medul- lary sheath for some distance within the capsule. The axis-cylinder ends in discs situated between the cells inclosed by the capsule. Terminal disc of — nerve-fibers. Epithelial cell. Connective-tissue capsule. Nerve-fiber. Fig 294. — Grandry' s corpuscles from bill of duck ; X S°°- Technic No. 296. B. THE HAIR. The hair and nails are regarded as special differentiations of the skin. Hair is found distributed over almost the entire extent of the skin, varying, however, in quantity and arrangement in different Digitized by Microsoft® THE HAIR. 351 regions. None whatever is present in the palm of the hand and sole of the foot. In the third fetal month small papillary elevations of the skin are seen to develop in those areas in which the hairy growth later appears. Under each of these elevations there occurs a proliferation of the cells of the Malpighian layer downward into the corium. Although the elevations soon disappear, the epithelial ingrowth continues and finally forms the hair germ. This is soon surrounded by a connective-tissue sheath from the corium, in which two layers may be distinguished. At the lower end of the hair germ the corium is pushed upward, forming a papilla which pene- trates into the thickened bulb of the germ. This is called the hair papilla. In the mean time the hair germ itself is undergoing marked differentiation. An axial portion, forming later the hair and inner root-sheath, and a peripheral, constituting later the outer root- sheath, are developed. From the latter are derived also the first traces of the sebaceous glands, which in the adult state are in close relationship to the hair and empty their secretion into the space between the hair and its sheath. As soon as the various layers of the hair are complete it grows outward, breaking through the over- lying layers of the epidermis. The visible portion of the hair is called the hair shaft, and that portion below the skin is the hair root. The lower portion of the hair resting upon the papilla is known as the hair bulb, and the sheaths encircling the root and bulb are called the root- sheaths, the entire structure constituting the hair follicle. The adult hair is covered by a thin cuticle, consisting of over- lying plate-like cells, 1.1 fi thick, most of which possess no nuclei. Beneath the cuticle is the cortical layer, composed of several strata of long, flattened cells from 4. 5 p. to 11 ft broad and provided with nuclei. These are also known as the cortical fibers of the hair. Upon treatment with ammonia the fibers separate into delicate fibrils, the hair fibrils (Waldeyer, 82). Scattered between and within the cells of the cortical layer are varying quantities of pigment granules. The axial region of the hair is occupied by the medullary substance, from 1 6 ft to 20 ft in diameter. This may be lacking ; but if present, consists of from 2 to 4 strata of polygonal, nucleated and pigmented cells. The hair shaft often contains air vesicles. The inner root-sheath consists of three concentric layers — first, of an outer single layer of clear nonnucleated cells, the so-called layer of Henle ; second, of a thicker middle layer, made up of two strata of nucleated cells containing eleidin, the layer of Huxley ; and, third, of an inner cuticle, bordering upon the hair. The outer root-sheath is made up of elements from the stratum germinativum. Here we have to do with prickle cells, surrounded by an outer layer of columnar elements. The connective-tissue portion of the hair follicle is composed of an outer, looser layer of longitudinal fibrous bundles ; of an inner, compacter layer of circu- Digitized by Microsoft® 352 THE SKIN AND ITS APPENDAGES. lar fibers ; and of an innermost well-developed basement mem- brane — the glassy membrane. At a certain distance above the root bulb all the layers of the Stratum Malpighii of outer root-sheath. Inner — Huxley's layer.^ root- sheath. i^^M^mri"^ Hairpapilla - Blood-vessel. Glassy layer of hair bulb. Connective tis- sue of the cutis. Fig. 295. — Longitudinal section of human hair and its follicle ; X about 300. epithelial portion of the hair follicle are well developed and distinct from each other. This condition changes toward the hair papilla Digitized by Microsoft® THE HAIR. 353 as. well as toward the hair" shaft. Below, in the region of the thick- ened hair bulb, the root-sheaths begin to lessen in thickness, their layers becoming more and more indistinct toward the base of the hair papilla. Finally, all differentiation is lost in the region where they encircle the neck of the papilla. Toward the shaft of the hair, the root-sheath also undergoes changes. In the region into which the sebaceous glands empty, the inner root-sheath disappears, while the outer becomes continuous with the stratum germinativum of the epidermis ; the outer layers of the latter — the stratum granu- losum, stratum lucidum, and stratum corneum — push downward between the outer root-sheath and the hair to the openings of the sebaceous glands. Regarding the growth of the hair, two theories are prevalent. Glassy layer. Fig. 296. — Cross-section of human hair with its follicle ; X about 300. The one theory assumes that the elements destined to form the epithelial root-sheaths are derived from the epidermis by a constant process of invagination. The component parts of the hair would thus be continuous with the layers of the root-sheaths, and conse- quently with those of the epidermis. Thus the basal cells of the external root-sheath would extend over the papilla, and be continu- ous with the cells of the medulla of the hair (these relations are especially well defined in the rabbit), and the stratum spinosum (middle layer of stratum Malpighii) of the outer root-sheath would be continuous with the cortical substance of the hair. According to this theory also, the layer of Henle would correspond to the stratum lucidum of the epidermis, and at the base of the hair Digitized by Microsoft® 354 THE SKIN AND ITS APPENDAGES. would become its cuticle, while the layer of Huxley would form the cuticle of the inner root-sheath (Mertsching). The other theory assumes that the hair is derived from a matrix, consisting of proliferating cells situated on the surface of the papilla. From these germinal cells would be derived the medullary and cortical substance of the hair, its cuticle, and the inner root-sheath (Unna). The shedding of hair is common to all mammalia, a phenomenon occurring periodically in the majority of species. In man the pro- cess is continuous. Microscopic examination shows that the hair destined to be shed becomes loosened from its papilla by a cornifi- cation of the cells of its bulb. At the same time the cortical por- tion of the hair bulb breaks up into a brush-like mass. Such hairs are called bulb hairs, in contradistinction to papillary hairs. In the region of the former papilla there arises, by a proliferation of the external root-sheath, a bud which grows downward, from which a new hair with its sheaths and con- nective-tissue papilla is developed. The result is that the developing new hair gradually pushes the old hair outward until the latter fin T ally drops out. The exact details of this process have given rise to considerable discussion (vid. Gotte and Stieda, 87). Adjacent to the hair follicles are bundles of smooth muscle- fibers, known as the arrectores pi- lorum. They originate from the papillary layer of the corium and extend to the lower part of the connective -tissue sheath of the hair follicles. In their course they not infrequently encircle the sebace- ous glands of the follicle. Since the hair follicles have a direction oblique to the skin surface, forming with it an acute and an obtuse angle, and since the muscle is situated within the obtuse angle, its function may easily be conceived as being that of an erector of the hair. The hair papillae are veiy vascular. The nerve-fibers of the hair follicles have recently been studied by a number of investigators, with both the Golgi and the methylene- blue methods. It has been shown that the hair follicles receive their nerve supply from the nerve-fibers which terminate in the immediate skin area. Each follicle receives, as a rule, only one nerve-fiber, which reaches the follicle a short distance below the mouth of the sebaceous gland. The nerve-fiber, on reaching the Digitized by Microsoft® Inner root- sheath. Outer root- sheath. Glassy layer. Fig. 297. — Longitudinal section through hair and hair follicle of cat ; X 160. Technic No. 291. THE NAILS. 355 follicle, loses its medullary sheath and divides into two branches, which surround it in the form of a ring. From this complete or partial ring of nerve -fibers numerous varicose fibers proceed upward parallel to the axis of the follicle for a distance about equal to the cross-diameter of the follicle, to terminate, it would seem, largely outside of the glassy layer (Retzius). In certain mammalia the nerve-fibers end in tactile discs, found in the external root-sheaths of the so-called tactile hairs. The muscles of the hairs receive their innervation through the neuraxes of sympathetic neurones, which reach the periphery from the chain ganglia through the gray rami communicantes. These nerves are known as pilomotor nerves, and when stimulated, excite contraction of the erector muscles of the hairs, causing these to assume an upright position and producing the appearance termed goose skin, or cutis anserina. Langley and Sherrington have made interesting and important observations on the course and distribution of the pilomotor nerves. C THE NAILS. The nails are a peculiar modification of the epidermis. The external arched portion is called the body of the nail ; that area upon Nail wall."- Nail. Stratum Malpighii. Stratum cor-r neum of the \ nail groove. ( Fig. 298. — Longitudinal section through human nail and its nail groove (sulcus) ; X 34- which the latter rests, the nail bed, or matrix ; and the two folds of epidermis which overlap the nail, the nail walls. The groove which exists between the nail wall and nail bed is known as the sulcus of the matrix, and the proximal imbedded portion of the nail as the nail root, since all growth of the nail takes place in this region. The nail bed consists of the corium, which is here made up of a dense felt-work of coarse connective -tissue fibers. Immediately beneath the nail the corium is raised into a number of more or less symmetric longitudinal ridges, which again become con- tinuous with the connective-tissue papilla? of the skin at the line where the nail projects beyond its bed. The depressions between the ridges are occupied by epidermal cells, which also form a thin covering over the ridges themselves. Digitized by Microsoft® 356 THE SKIN AND ITS APPENDAGES. These cells correspond here to the basilar layer of the stratum Mal- pighii. The stratum granulosum is not uniformly present, although occurring as isolated areas in the region of the nail root and lunula, the white area of demilunar shape at the proximal portion of the nail. Unna has demonstrated that the pale color of the lunula and root of the nail is due to the presence of keratohyalin. Formerly, this peculiarity was attributed to a difference in the distribution of the vessels in the various portions of the nail bed. The body of the nail, with the exception of the lunula, is transparent — a con- dition which may be explained by the fact that the elements of- the nail correspond to those of the stratum lucidum. As a consequence, the vessels of the matrix shine through, except at the lunula, where the keratohyalin granules render the nail opaque. The nail itself consists of elements homologous to those of the stratum lucidum. They are flat, transparent cells, closely approxi- mated, and all contain nuclei. The cells overlie each other like tiles, and are so arranged that each succeeding lower layer projects Stratum Mal"-3k> -\ <*?- — -~— rar^_ ^ Nail wall.-;" V. «SH7?V>?rS£j * &■ Fig. 299. — Transverse section through human nail and its sulcus ; X 34- a little further distalward than the preceding. At the period when the nails are formed, about the fourth month of fetal life, sulci are already present. The first trace of the nail is seen as a marked thickening of the stratum lucidum in the region which later be- comes the body of the nail ; in this stage the structure is still cov- ered by the remaining layers of the stratum corneum, constituting the eponychium. The embryonal nail then spreads in all directions until it finally reaches the sulcus. Henceforward the growth is uniform. The eleidin normally present in the stratum lucidum of the skin also occurs in the nail, and is derived, as we have already seen, from the keratohyalin. It may readily be conceived that later, when growth is confined to the root of the nail, keratohyalin is also present. As soon as the nail begins to grow forward, in the ninth month, the greater part of the eponychium is thrown off; but during the entire extrauterine life, a portion of the eponychium is retained at the nail wall, and as hyponychium on the anterior and under surface of the nail. Digitized by Microsoft® THE GLANDS OF THE SKIN. 357 Gland-cell. Fig. 300. — Cross - section of tubule of coiled portion of sweat-gland from human axilla. Fixation with sublimate ; X 600. D. THE GLANDS OF THE SKIN. The glands in the skin are of two kinds — sweat-glands and sebaceous glands. A modification of the latter is seen in the mam- mary glands. 1. The Sweat-glands. — The sweat-glands, or sudoriparous glands, are distributed throughout the entire skin, but are especially numerous in certain re- gions — as, for instance, the axilla, palm of the hand, and sole of the foot. They lie imbedded either in the adipose tis- sue of the true skin, or still deeper in the subcu- taneous connective tissue (axilla). To this group of glands belong also the ceriuninous glands of the ear, the glands of Moll in the eyelid, and the cir- cumanal glands. The sweat-glands are simple tubular in type, and their secreting portion is coiled ; hence the name coil-glands. The coil is, as a rule, 0.3 or 0.4 mm. in di- ameter, but in the axilla reaches from 3 to 7 mm. The excretory duct (the su- doriferous duct) is nearly straight during its course up- ward through the corium, and always enters the epider- mis between two papilla? of the corium. From here on, its course is spiral, and it should be borne in mind that in its passage through the epidermis it has no other wall than the epidermal cells of the various layers through which it passes, although these cells are arranged con- centrically around the lumen of the duct. The lining of the secretory or coiled portion of the sweat- gland consists of cubical cells with finely granular protoplasm and round or oval nuclei possessing one or two nucleoli. In the excre- Digitized by Microsoft® Fig. 301. — Tangential section through coiled portion of sweat-gland from human axilla. Sublimate fixation ; X 7 00 - 358 THE SKIN AND ITS APPENDAGES. tory segments, the cells are arranged in two layers. The membrana propria is very delicate, and in both regions of the gland apparently structureless. External to the basement membrane is a fine con- nective-tissue sheath. A marked peculiarity of the secretory por- tion of the gland consists in a longitudinal layer of smooth muscle- fibers between the membrana propria and the glandular epithelium. The presence of this structure can be accounted for only by assuming that it is an epithelial derivative. The changes in the gland cells during secretion have not been sufficiently studied, but this much is certain, that the secretory phe- nomena are not similar to those in the sebaceous glands (see below). To the glandular secretion must be added also the serum-like fluid oozing from the canalicular lymph-spaces in the stratum Mal- pighii into the epidermal portion of the excretory duct (Unna). The development of the sweat-glands begins in the fifth month of fetal life. At first solid cords grow from the stratum germi- nativum of the epidermis into the corium. Later, in the seventh month, these become hollow. Capillary networks surround the secreting portions of the sweat-glands. The nerves of the sweat-glands have been studied with the aid of the methylene-blue method by Ostroumow, working under Arnstein's direction. These glands receive their innervation through the neuraxes of sympathetic neurones, the terminal branches of which form an intricate network just outside of the basement membrane, known as the epilamellar plexus. From this plexus fine, varicose nerve-fibers pass through the basement membrane, and, after coursing a shorter or longer distance with or without further division, end on the gland-cells, often in clusters of small terminal granules united by delicate threads. 2. The Sebaceous Glands. — The distribution of the sebaceous glands in the skin is closely connected with that of the hair follicles into which they pour their contents. Exceptions to this rule occur in only a few regions of the body, as, for instance, in the glans penis and foreskin (Tyson's glands), in the labia minora, angle of the mouth, glandular tarsales, and the Meibomian glands of the eyelids, etc. As a rule the sebaceous gland empties by a wide excretory duct into the upper third of the hair follicle. The walls of the duct also produce secretion, and can therefore hardly be differentiated from the rest of the gland. At its base the duct widens and is pro- vided with a number of simple or branched alveoli. The sebaceous glands are therefore of the type of compound alveolar glands, vary- ing in length from 0.2 mm. to 5 mm. They are surrounded by connective-tissue sheaths, which at the same time cover the hair follicles. Inside of the sheath is the membrana propria, which is a continuation of the glassy membrane of the follicle. The two or three basal strata of glandular cells must be regarded as a direct continuation of the elements of the external root-sheath. In the Digitized by Microsoft® THE GLANDS OF THE SKIN. 359 more centrally placed strata the cells are distinctly changed in char- acter ; their contents consist of fat globules, varying in size and distributed throughout the protoplasm, giving this a reticular appearance, while the nuclei suffer compression from the accumu- lation of the fat globules and gradually become smaller and more angular. Finally, the cells change directly into secretion, which is then poured into the hair follicle as sebum. It is thus seen that in the secretion of sebum the cells are consumed and must be re- placed. This renewal takes place by the constant proliferation of the basilar cells, which push the remains of the secreting cells upward and finally take their places. The final disintegration of the cells occurs either within the gland itself or between the hair follicle and the hair. The secretion contains fatty globules of varying size, which occur either free or attached to cellular detritus. Fig. 302. — Section of alveoli from sebaceous gland of human scalp. 3. The Mammary Glands. — The mammary glands are also included among the cutaneous glandular structures. They are developed early, but not until the fifth month is it possible to dis- tinguish a solid central portion, with radially arranged tubules terminating in dilatations. The structures are all derived from the basal layers of the epidermis. From birth to the age of puberty the organs are in a state of constant growth, and are early sur- rounded by a connective -tissue sheath. The alveoli, which have been developed in the. mean time, are still solid and relatively small. Up to the twelfth year the glands remain identical in structure in boys and girls. In the female the mammary glands continue to develop from the age of puberty ; in the male, on the other hand, they undergo a retrograde metamorphosis, ending, finally, in the atrophy of all except the excretory ducts. The mammary glands Digitized by Microsoft® 360 THE SKIN AND ITS APPENDAGES. do not attain their full stage of development in women until the last months of pregnancy, and are functionally active at parturition. The human mammary gland when fully developed has the fol- lowing structure : It consists of about twenty lobes, separated from each other by connective-tissue septa. These . lobes are again divided into a larger number of lobules, and these in turn are com- posed of numerous alveoli, which, as in the case of the lung, pre- sent lateral sacculations. The alveoli are provided with small excretory passages, which unite and finally form the larger ducts. Shortly before terminating at the surface of the mammilla, each Alveolus. Aft Connective- w- tissue 1 stroma. n^if .Mrs W\ m ':>, M.:. QTWBrai ^ Duct and alveoli. Adipose tissue. Fig. 303. — From section of mammary gland of nullipara. (From Nagel's "Die weiblichen Geschlechtsorgane," in " Handbuchs der Anatomie des Menschen," 1896.) mammary duct widens into a vesicle, the sinus lactiferus. The number of excretory ducts corresponds to that of the larger lobes. The ducts are lined by simple cubical epithelium, except near the termination in the nipple, where they are lined by stratified pave- ment epithelium, and surrounded by a fibrous tissue sheath. The epithelium of the alveoli differs according to the state of functional activity. In a state of rest it consists of a single layer of glandular cells of nearly cubical shape which stain deeply, the internal surfaces projecting into the lumen. At the beginning Digitized by Microsoft® THE GLANDS OF THE SKIN. 36 1 of secretion the cells increase in length and fat globules make their appearance in their distal ends. At the same time a corresponding increase in size occurs throughout the entire alveolus. Finally, the free ends of the cells, which contain the most fat globules, are con- stricted off, after which the fat globules are freed in the lumen. The secretory portion of the alveolus is then composed of low epithelial cells, in which the process begins anew. The process of milk secre- tion therefore consists in throwing off the inner halves of the cells containing the fat globules, and in regeneration of the cells from the nucleated remains of the glandular epithelium. Whether a karyokinetic division of the nuclei occurs in this process is not known, and how often the process of regeneration may be repeated in a single cell is not capable of demonstration. It is certain, how- ever, that entire cells are destroyed, to be replaced later by new elements. The membrana propria of the alveoli appears homo- geneous. Between it and the glandular cells are so-called basket cells, similar to those in the salivary glands. Benda regards the basket cells as nonstriated muscle elements, having a longitudinal direction, making the structure of the alveoli of the mammary gland similar in this respect to that of the secreting portion of the sweat-glands. The skin of the mammilla is pigmented, and the papillae of its corium are very narrow and long. In the corium are also found large numbers of smooth muscle-fibers, which form circular bun- dles around the excretory ducts. In the areolae of the mammae are the so-called glands of Montgomery, which very probably repre- sent accessory mammary glands. These are especially noticeable during lactation. The mammary glands possess many lymphatics. These are especially numerous in the connective-tissue stroma between the lobules and alveoli. The vessels form capillary networks surround- ing the alveoli. The lymph-vessels collect to form two or three larger vessels, which empty into the axillary glands. The mam- mary gland receives its nerve supply from the sympathetic and cerebrospinal nervous systems through the fourth, fifth, and sixth intercostal nerves. The terminations of the nerves in the mammary gland have been studied by means of the methylene -blue method by Dmitrewsky, working in the Arnstein laboratory, who finds that the terminal branches form epilamellar plexuses outside of the base- ment membrane of the alveoli, from which fine nerve branches pass through the basement membrane and end on the gland cells in clusters of terminal granules united by fine filaments. The nipple has a rich sensory nerve supply. In the connective-tissue papillae are found tactile corpuscles of Meissner. The milk consists of fat globules of varying size, which, how- ever, do not coalesce — an attribute due to the presence of albu- minous haptogenic membranes surrounding the globules. Shortly before, and for some days after, parturition the milk contains true Digitized by Microsoft® 362 THE SKIN AND ITS APPENDAGES. nucleated cells in which are fat globules ; these are known as the colostrum corpuscles. They probably represent cast-off glandular cells in a state of fatty degeneration. Some authors regard them as leucocytes which have migrated into the lumen of the gland and there undergone fatty degeneration. This milk is known as colostrum. TECHNIC. 287. Good general views of the skin can be obtained only from sections. Any fixation method may be employed, although alcohol is preferable on account of the better subsequent staining. For detail work Flemming's solution, corrosive sublimate, or osmic acid is the best. Sectioning of the skin is attended with many difficulties, and large pieces can be cut only in celloidin. Small and medium-sized pieces may be cut in paraffin ; but even in this case the skin must be rapidly imbedded in the paraffin — i. e. , it must not remain too long in either alcohol or toluol — and the paraffin must have only the consistency necessary to cut well (about 50 C. melting- point) . In order to obtain good paraffin sections of the skin the follow- ing procedure is recommended : Pieces fixed in Flemming's solution or osmic acid are kept in 96% alcohol, then placed for not more than twenty- four hours in absolute alcohol and imbedded in paraffin by means of the chloroform method. In the chloroform, chloroform -paraffin, and pure of paraffin they remain for one hour each. The paraffin used should consist two parts paraffin of 42 C, and one part paraffin of 50° C. melting-point. The thermostat must be kept at 50° C. (R. Barlow). The sections should not be mounted by the water-albumen method. 288. In sections of epidermis which have been freshly fixed with osmic acid, the stratum corneum may be clearly differentiated into three layers (probably because of the defective penetration of the reagent) — into a blackened superficial, a middle transparent, and a still lower black layer (vid. Fig. 304). 289. In tissue fixed in alcohol or corrosive sublimate the stratum lucidum stains yellow with picrocarmin, but is very weakly colored by basic anilin stains. In unstained preparations the stratum lucidum is glass-like and transparent. Eleidin is diffusely scattered throughout both the stratum lucidum and stratum corneum. Like keratohyalin, it stains with osmic acid and also with picrocarmin, but not with hematoxylin. Nigrosin stains eleidin, but not keratohyalin. 2go. Keratohyalin is insoluble in boiling water and is not attacked by weak organic acids. It dissolves, however, in boiling acetic acid, but is not changed by the action of pepsin or trypsin. The keratohyalin granules of the stratum granulosum swell in from 1 P ar t °f the tortuous duct of a sweat-gland in the epidermis ; b, duct of same sweat-gland in the corium. water, and alcohol. Small pieces taken from such specimens are readily teased and show both isolated and small groups of attached prickle cells. 2g2. The distribution of the pigment in the skin is best studied in unstained sections. With a nearly closed diaphragm and under medium magnification the pigment granules appear darker on raising the tube and lighter upon lowering it. 293. In sections of skin treated with Flemming's fluid, the structure of the cutis also may be studied. The medullary sheaths of the nerve- fibers and the fat appear black. In preparations stained with safranin the Digitized by Microsoft® 364 THE SKIN AND ITS APPENDAGES. elastic fibers are colored red and are very distinct (Stohr and O. Schultze). For the orcein method according to Unna, see T. 138. 294. Hair may be examined in water without further manipulation. The cuticle is then seen to consist of polygonal areas, the border-lines of which correspond to the limits of the flattened cells. By slightly lower- ing the objective the cortical substance comes into view with its indistinct striation and occasional pigmentation. The medullary substance, if pres- ent, may also be seen with its vesicles containing air. Both the cortical and cuticular cells may be isolated, the process consisting in treating the hairs for several days with 33 °Jo potassium hydrate solution at room tem- perature, or in heating the whole for a few minutes. Concentrated or weak sulphuric acid produces the same result. On warming a hair in sul- phuric acid until it begins to curl and then examining it in water, we find that the cortical and medullary layers as well as the cuticle are separated into their elements. Treatment of the skin with Miiller's fluid, alco- hol, or sublimate is recommended for the examination of hair and hair follicles. The orientation of the specimen should be very precise, in order to obtain exact longitudinal or cross-sections of the hair. There is hardly a structure of the body which is more suitable for staining with the numerous coal-tar colors than the hair and its follicle (Merkel). 295. The corpuscles of Meissner may be best obtained from the end of the finger. After boiling a piece of fresh skin from the finger-tip for about a quarter of an hour, the epidermis may be easily removed ; the papillas are now seen on the free surface of the cutis. A portion of the latter is cut away with a razor and examined in a 3 % solution of acetic acid. The corpuscles are readily distinguished. Their relations to the nerves should be studied in specimens fixed with osmic acid or gold chlorid. The terminations of the nerves in these end-organs are best seen in preparations stained after the intra vitam methylene-blue method. 296. The corpuscles of Herbst and Grandry are found in the waxy skin covering the bill, and in the palate of the duck (especially numerous in the tongue of the woodpecker). For the study of the nervous ele- ments the following method is useful : Pieces of the waxy skin are removed with a razor and placed for twenty minutes in 50% formic acid. After washing the specimens for a short time in distilled water they are transferred to a small quantity of 1 % gold chlorid solution (twenty min- utes), then again rinsed in distilled water, and placed for from twenty- four to thirty-six hours in the dark in a large quantity (}i liter) of Pichard's solution (amyl alcohol 1 part, formic acid 1 part, water 100 parts) . After again washing in water the specimens are transferred to alcohols of gradually increasing strengths and finally imbedded in celloidin or celloidin-paraffin. 297. The Pacinian corpuscles occur in the mesentery of the cat and may be examined in physiologic saline solution. 298. The nerves of the epidermis are demonstrated by the gold- chlorid method (see p. 166). But even here the chrome-silver method and the intra vitam methylene-blue method yield extremely good results, and may be used with great advantage in the study of the nerves in the cutis. 2gg. The so-called tactile menisci are very numerous in the snout of the pig and the mole. Bonnet recommends for these structures fixation in °-33% chromic acid solution {vid. T. 26), overstaining with hematoxylin, and differentiation in an alcoholic solution of potassium ferricyanid. Digitized by Microsoft® THE SPINAL CORD. 365 VII. THE CENTRAL NERVOUS SYSTEM. In a study of the minute anatomy of the central nervous system consideration should be given to the arrangement of the nerve-cells and nerve-fibers in the various regions, and to the mutual relations which the elements of the nervous system bear to one another. In a text-book of this scope, however, we shall be unable to enter into the consideration of these subjects in detail, but must content our- selves with a very general discussion of the structure of certain regions of the central nervous system and an account of a few typical examples illustrating the mutual relationship of the nerve-elements to one another. We shall, therefore, give a general description of the structure of the spinal cord, cerebellum, cerebrum, olfactory lobes, and ganglia. In this description we have drawn freely from the results of the researches of Golgi (94), Ramon y Cajal (93, 1), von Lenhossek (95), Kolliker (93), and van Gehuchten (96). A. THE SPINAL CORD. The spinal cord extends from the upper border of the atlas to about the lower border of the first lumbar vertebra. It has the form of a cylindric column, which at its lower end becomes quite abruptly smaller, to form the conns medullaris, and terminates in an attenu- ated portion — the filum tcrminale. It presents two fusiform enlarge- ments, known as the cervical and lumbar enlargements respectively. The spinal cord is partly divided into two symmetric halves by an anterior median fissure and by a septum of connective tissue, extend- ing into the substance of the cord from the pia mater (one of the fibrous tissue membranes surrounding the cord), and known as the posterior median septum. Structurally considered, the spinal cord consists of white matter (mainly medullated nerve-fibers) and gray matter (mainly nerve-cells and medullated nerve-fibers). The white and the gray matter present essentially the same general features at all levels of the spinal cord, although the relative proportion of the two substances yaries somewhat at different levels. The different portions of the cord present also certain structural peculiarities. The distribution of the gray and the white substances of the spinal cord is best seen in transverse sections. The varying shape of the spinal cord in the several regions and the changing relations of the gray to the white substance are shown in the illustrations of cross-sections of the adult human spinal cord (see p. 366). The gray substance is arranged in the form of two crescents, one in each half of the cord, united by a median portion extending from one half of the cord to the other, the whole presenting some- what the form of an H- The horizontal part contains the commis- Digitized by Microsoft® 3 66 THE CENTRAL NERVOUS SYSTEM. Fig. 305. — Four cross-sections of the human spinal cord ; X 7 : A, Cervical region in the plane of the sixth spinal nerve-root ; B, lumbar region ; C, thoracic region ; D, sacral region (compare with Fig. 306). (From preparations of H. Schmaus.) Digitized by Microsoft® THE SPINAL CORD. 367 sures and the central canal of the spinal cord, while the vertical limbs or crescents extend to the ventral and dorsal nerve-roots, forming the anterior and posterior horns. The former are, as a rule, the larger, and at their sides (laterally) the so-called lateral horns may be seen, varying in size in different regions. In each anterior horn are three main groups of ganglion cells : the ventro- lateral, made up of root or motor nerve-cells ; the ventromesial, composed of commissural cells ; and the lateral (in the lateral horn), containing column cells. At the median side of the base of each posterior horn we find a group of cells and fibers known as the column of Clark, most clearly defined in the dorsal region, while in the posterior horn itself is the gelatinous substance of Rolando. Aside from these, numerous cells and fibers are scat- tered throughout the entire gray substance. The motor nerve-cells lie in the ventrolateral portion of the ante- rior horn, their neuraxes extending into the anterior nerve-root. Their dendrites are distributed in a lateral, dorsal, and mesial direc- tion, the two former groups ending in the anterior and lateral col- umns, the mesial in the region of the anterior commissure. Some of the mesial dendrites extend beyond the median line and form a sort of commissure with the corresponding processes of the other side. The commissural cells lie principally in the mesial group of the anterior horn, but occur here and there in other portions of the gray substance. Their neuraxes form the anterior gray commis- sure with the corresponding processes from the other side. After entering the white substance of the other side, these neuraxes undergo a T-shaped division, one branch passing upward and the other downward. The column cells are small multipolar elements, represented by the cells of the lateral horns, although they are also found throughout the entire gray mass. Their neuraxes pass directly into the anterior, lateral, and posterior horns. The cells of the column of Clark, or nucleus dorsalis, are of two kinds — those in which the neuraxes pass to the anterior commis- sure (commissural cells) and those in which the neuraxes pass into the direct cerebellar tract of the same side. The plurifunicular cells are cells the neuraxes of which divide two or three times in the gray substance, the branches then passing to different columns of the white matter on the same or opposite side of the cord. In the latter case the branches must necessarily extend through the commissure. The cells of the substantia gclatinosa (Rolando) are cells with short, freely branching neuraxes, which end after a short course in the gray mass (Golgi's cells). The posterior horn con- tains marginal cells, spindle-shaped cells, and stellate cells. The first are situated superficially near the extremity of the posterior horn, their neuraxes extending for some distance through the gela- tinous substance of Rolando and then into the lateral column. The spindle-shaped cells are the smallest in the spinal cord and possess a rich arborization of dendrites extending to the nerve-root of the pos- Digitized by Microsoft® 3 68 THE CENTRAL NERVOUS SYSTEM. terior horn. Their neuraxes, which originate either from the cell- body or from a dendrite, pass over into the posterior column. The stellate cells are supplied with dendrites, which either branch in the substance of Rolando or extend into the column of Burdach. The gray matter contains, further, numerous medullated nerve- fibers, in part the neuraxes of the nerve-cells previously mentioned, and in part collateral and terminal branches of the nerve-fibers of the white matter with their telodendria ; also supporting cells, known as neuroglial' cells (to be discussed later), and blood-vessels. The white matter of the spinal cord consists of medullated fibers, which are devoid of a neurilemma, of neurogliar tissue, and of fibrous connective tissue. In each half of the cord the white substance, which surrounds the gray, is separated by the gray matter and its nerve -roots into horn Posterior cell. Crossed pyram- idal column. Golgi cell of posterior horn. Direct cerebel- lar column. Column cells. Golgi'scommis- sural cells. Gowers' column. Motor cells. Collaterals of crossed pyramidal column. Collaterals ending in the gray matter. Direct pyramidal column. Fig. 306. — Schematic diagram of the spinal cord in cross-section after von Lenhos- sek, showing in the left half the cells of the gray matter, in the right half the collateral branches ending in the gray matter. three main divisions or columns: The first division, lying between the anterior median fissure and the anterior horn, is the anterior column ; the second, lying between the anterior and posterior horns, is the lateral column (since the anterior and lateral columns belong genetically to each other, the term anterolat- eral column is often used) ; and the third, lying between the poste- rior nerve-root and the posterior median septum, is the posterior column. By means of certain methods it has been possible to separate the white substance into still smaller divisions, the most important of which may here be described. In each anterior column is found a narrow median zone extend- ing along the entire length of the anterior median fissure and con- Digitized by Microsoft® THE SPINAL CORD. 369 Digitized by Microsoft® 370 THE CENTRAL NERVOUS SYSTEM. taining nerve-fibers which come from the pyramids of the medulla. The majority of the pyramidal fibers cross from one side of the cord to the other in the lower portion of the medulla, at the crossing of the pyramids, and form a large bundle of nerve-fibers found in each lateral column, which will receive attention later. Some of the pyramidal fibers descend into the cord on the same side, to cross to the opposite side at different levels in the cord. These latter fibers constitute the narrow median zone, on each side of the anterior median fissure previously mentioned, forming the anterior or direct pyramidal tract, or the column of Tiirck. Between the direct pyramidal tract and the anterior horn lies the anterior ground bundle. In the lateral columns are found a number of secondary col- umns, which may now be mentioned. In front of and by the side of the posterior horn in each lateral column lies a large group of nerve-fibers, forming a bundle which varies somewhat in size and shape in the several regions of the spinal cord, but which has in general an irregularly oval outline. These nerve-fibers are the pyramidal fibers, previously mentioned, which in the lower part of the medulla cross from one side to the other, and for this reason are known as the crossed pyramidal fibers, forming the crossed pyramidal columns. External to these columns and to the poste- rior horns, and extending from the posterior horns half-way around the periphery of the lateral columns, lie the direct cerebellar col- umns, consisting of the neuraxes of the cells of the columns of Clark, which have an ascending course. Lying just external to and between the anterior and posterior horns is a somewhat irregular zone, the mixed lateral column, containing several short bundles of fibers, the anterior of which are probably motor ; the posterior, sensory. In the ventrolateral portions of the lateral columns, between the mixed lateral and the direct cerebellar columns and extending as far backward as the crossed pyramidal columns, lie two not well-defined columns, known as the ascending anterolat- eral or Gowers's columns and the descending anterolateral col- umns ; the former are nearer the outer portion of the cord. In the posterior column we distinguish a median and a lateral column. The former lies along the posterior median septum, and may even be distinguished externally by an indentation ; its upper portion tapers into the fasciculus gracilis. This is the column of Goll, and it contains ascending or centripetal fibers. The lateral tract lies between the column of Goll and the posterior horn, and is known as the column of Burdach, posterior ground-bundle, or posterolateral column. It contains principally the shorter tracts, or bundles of longitudinal fibers connecting the adjacent parts of the spinal cord with one another. Many of the nerve-fibers of the posterior column are the neu- raxes of spinal ganglion cells which enter the spinal cord through the posterior roots. The cell-bodies of the spinal ganglion or sen- Digitized by Microsoft® THE SPINAL CORD. 37 1 sory neurones are situated in the spinal ganglia found on the pos- terior roots of the spinal nerves. In the embryo they are distinctly bipolar, but during further development their two processes approach each other, and then fuse for a certain distance, forming finally single processes which branch like the letter T. In reality, then, there are two processes which are fused for a certain distance from the cell-body of each neurone. The peripherally directed process is regarded as the dendrite of the cell, and the proximal as the neuraxis passing to the spinal cord. The neuraxes enter the spinal cord through the posterior roots and pass to the posterior columns, where they divide, Y-shaped, into ascending and much shorter descending branches, from each of which numerous collateral branches are given off. From the preceding account of the white matter of the spinal cord, it may be seen that it consists of longitudinally directed neu- raxes arranged in so-called short and long tracts or columns. The neuraxes constituting the former, after a short course through the gray matter, emerge from it, and after giving off various collaterals, again penetrate into the gray matter, where their telodendria enter into contact with the ganglion cells. The long columns consist of the neuraxes of neurones the cell-bodies of which are situated in the cerebrum or cerebellum, and of neurones the cell-bodies of which are in the spinal cord or spinal ganglia and the neuraxes of which terminate in the medulla or cerebellum. The nerve-fibers of the various columns give off numerous collaterals which enter the gray matter to end in telodendria. The collaterals of the posterior col- umns end : (i) between the cells of the gelatinous substance Of the posterior horns ; (2) in the columns of Clark ; (3) in the anterior horns, these constituting the principal portion of the so-called reflex bundles ; (4) in the posterior horn of the opposite side. The col- laterals of the lateral columns pass horizontally toward the central canal, some ending in the anterior horn, others closely arranged near the columns of Clark, and some arching around the central canal, forming with the corresponding fibers of the other side the anterior bundles of the posterior commissure. The collaterals of the anterior columns form well-marked plexuses in the anterior horns of the same and opposite sides. We have still to describe the two commissures. The anterior consists of: first, neuraxes from the commissural cells ; second, dendrites from the lateral group of the anterior horn cells ; and, third, the collaterals of the anterolateral column, which end in the gray substance of the other side of the cord. The posterior com- missure is probably composed of the collaterals from all the remain- ing columns. The posterior bundle of this commissure comes from the posterior column ; the middle, from the posterior portion of the lateral column ; and the anterior, or least developed, from the anterior portion of the lateral column, possibly also from the anterior column. Digitized by Microsoft® 3^2 THE CENTRAL NERVOUS SYSTEM. In the gray commissure, nearer its anterior border, is situated the central canal of the spinal cord, continuous above with the ventricular cavity of the medulla and terminating caudally in the filum terminale. This canal is not patent in the majority of adults, being occluded from place to place. The canal is lined by a layer of columnar cells, developed from columnar cells, known as spongio- blasts, lining the relatively larger canal of the embryonic spinal cord. In young individuals these cells are ciliated and their basal portions terminate in long, slender processes. B. THE CEREBELLAR CORTEX. In the cerebellar cortex we distinguish three general layers — the outer molecular, the middle granular (rust-colored layer), and the inner medullary tract. Blood-vessel Dendrite. SW^^^^^« N fib , ^■>j*-*>^-r-3^-:^=.--r^s4&^_"' - -^■:"»a~-^^ : -^2S^i- Nerve-fiber layer. Fig. 308. — Section through the human cerebellar cortex vertical to the surface of the con- volution. Treatment with Miiller' s fluid ; X IJ 5' The molecular layer contains three varieties of nerve-cells, those of Purkinje, which border upon the granular layer, the stel- Digitized by Microsoft® Digitized by Microsoft® 374 THE CENTRAL NERVOUS SYSTEM. late cells, and the small cortical cells. The cells of Purkinje pos- sess a large flask-shaped body (about 60 fi in diameter), from which one or more well-developed dendrites pass toward the periphery. The latter branch freely and the main arborization has in each case the general shape of a pair of deer's antlers. These dendrites extend nearly to the periphery of the cerebellar cortex. In a section horizontal to the surface of the organ the dendrites of the Purkinje's cells are seen to lie in a plane very nearly vertical to the surface of the convolutions, so that a longitudinal section through the latter would show a profile view of the cells. In other words, they have an appearance much like that of a vine trained upon a trellis. The neuraxes of the cells of Purkinje arise from their basal Dendrite. Cell-body. — Neuraxis. — Claw-like telo- dendron of dendrite. Fig. 310. — Cell of Purkinje from the human cerebel- lar cortex. Chrome-silver method ; X I2 °- Fig. 311. — Granular cell from the granular layer of the hu- man cerebellar cortex. Chrome- silver method ; X IO °' (inner) ends and extend through the granular layer into the medul- lary substance. During their course they give off a few collaterals, which pass backward to the molecular layer and end in telodendria near the bodies of the cells of Purkinje. The stellate cells lie in various planes of the molecular layer. Their peculiar interest lies in the character of their neuraxes. The latter are situated in the same plane as the dendrites of the cells of Purkinje, run parallel to the surface of the convolution, and possess two types of collaterals. Those of the first are short and branched ; those of the second branch at a level with the cells of Purkinje, and form, together with their telodendria, basket-like nets around the bodies of these cells. The small cortical cells of the molecular layer are found Digitized by Microsoft® THE CEREBRAL CORTEX. 375 in all parts of this layer, but are more numerous in its peripheral portion. They are multipolar cells with neuraxes which are not readily stained and concerning the fate of which little is known. The granular layer contains two varieties of ganglion ele- ments, the so-called granular cells (small ganglion cells) and the large stellate cells. The dendrites of the granular cells are short, few in number (from three to six), branch but slightly, and end in short, claw-like telodendria. Their neuraxes ascend vertically to the surface and reach the molecular layer. At various points some of them are seen to undergo a T-shaped division, the two branches then running parallel to the surface of the cerebellum in a plane vertical to that of the dendrites of the cells of Purkinje. Large numbers of these T-shaped neuraxes produce the striation of the molecular layer of the cerebellum. It is very probable that during their course these parallel fibers come in contact with the dendrites of the cells of Purkinje. The large stellate cells are fewer in number and lie close to the molecular layer, some of them even within this layer. Their dendrites branch in all directions, but extend principally into the molecular layer. Their short neuraxes give off numerous collaterals which end in telodendria among the granular cells. The medullary substance is composed of the centrifugal neu- raxes of the cells of Purkinje and of two types of centripetal neu- raxes, the mossy and the climbing fibers. The position of their corresponding nerve-cells is not definitely known. The mossy fibers branch in the granular layer into numerous twigs, and are not uniform in diameter, but are provided at different points with typical nodular swellings. These fibers do not extend beyond the granular layer. The climbing fibers pass horizontally through the granular layer, giving off in their course numbers of collaterals, which extend to the cells of Purkinje, up the dendrites of which they seem to climb. In the medullary portion of the cerebellum are found a number of groups of ganglion cells known as central gray nuclei. The nerve-cells of these nuclei are multipolar, with numerous, oft- branching dendrites and a single neuraxis. G THE CEREBRAL CORTEX. The cell-bodies of the neurones of the cerebrum are grouped in a thin layer of gray matter, varying in thickness from 2 to 4 mm., — which, as a continuous sheet, completely covers the white matter of the hemispheres, — and in larger and smaller masses of gray mat- ter, known as basal nuclei. In our account of the histologic struc- ture of the cerebral hemispheres we shall confine ourselves in the main to a consideration of the cerebral cortex, the thin layer of gray matter investing the white matter. Digitized by Microsoft® 376 THE CENTRAL NERVOUS SYSTEM. From without inward the following layers may be differentiated in the cerebral cortex : (i) a molecular layer ; (2) a layer of small pyramidal cells ; (3) a layer of large pyramidal cells ; (4) a layer of polymorphous cells ; and (5) medullary substance or underlying nerve-fibers. Aside from neurogliar tissue, we find in the molecular layer a large number of nerve-fibers, which cross one another in all direc- tions, but, as a whole, have a direction parallel with the surface of the brain. Within this layer there are found : (1) the tuft-like telo- dendria of the chief dendritic processes of the pyramidal cells ; (2) the terminations of the ascending neuraxes, arising mostly from the polymorphous cells ; and (3) autochthonous fibers — i. e., those which arise from the cells of the molecular layer and terminate in this layer. The cells of the molecular layer may be classed in three general types — polygonal cells, spindle-shaped cells, and triangular or stellate cells. The polygonal cells have from four to six den- drites, which branch out into the molecular layer and may even penetrate into the underlying layer of small pyramidal cells. Their neuraxes originate either from the bodies of the cells or from one of their dendrites, and take a horizontal or an oblique direction, giving off in their course a large number of branching collaterals, which terminate in knob-like thickenings. The spindle=shaped cells give off from their long pointed ends dendrites which extend for some distance parallel with the surface of the brain. These branch, their offshoots leaving them at nearly right angles, the majority passing upward, assuming as they go the characteristics of neuraxes having collaterals. The arborization is entirely within the molecular layer. The triangular or stellate cells are similar to those just described, but possess not two, but three, dendrites. The triangular and spindle-shaped cells, with their numerous den- dritic processes resembling neuraxes, are characteristic of the cere- bral cortex. The elements which are peculiar to the second and third layers of the cerebral cortex are the small (about 10 p in diameter) and large pyramidal cells (from 20 p to 30 p in diameter). They are composed of a triangular body, the base of the triangle being down- ward and parallel to the surface of the brain, of a chief, principal, or primordial dendrite ascending toward the brain-surface, of several basilar dendrites arising from the basal surface of the cell-body, and of a neuraxis which passes toward the medullary substance and which has its origin either from the base of the cell or from one of the basilar dendrites. The ascending or chief dendrite gives off a number of lateral offshoots which branch freely and end in terminal filaments. The main stem of the dendrite extends upward to the molecular layer, in which its final branches spread out in the form of a tuft. The neuraxis, during its course to the white substance, gives off in the gray substance from six to twelve collaterals, which divide two or three times before terminating. Digitized by Microsoft® THE CEREBRAL CORTEX. 377 Aside from the fact that the layer of polymorphous cells con- tains a few large pyramidal cells, it consists principally of (i) mul- tipolar cells with short neuraxes (Golgi's cells) and (2) of cells with only slightly branched dendrites and with neuraxes passing toward the surface of the brain (Martinotti's cells). Both these types of cells are, however, not found exclusively in the layer of polymorphous cells, but may be met with here and there in the layers of the small and large pyramidal cells. The dendrites of the cells of Golgi are ■ Molecular layer. Layer of small pyr- amidal cells. ■ Layer of large pyr- atmdal Secondary cells - dendrite. Layer of polymor- phous cells. Medullary substance. Basal den^ drite. Neuraxis with col- laterals. Fig. 312. — Schematic diagram of the cerebral cortex, after Golgi and Ramdn y Cajal. Fig. 313. — Large pyramidal cell from the human cerebral cortex. Chrome-silver method ; X I 5°- projected in all directions, those in the neighborhood of the medul- lary substance even penetrating into this layer. The neuraxes break up into numerous collaterals, the telodendria of which lie ad- jacent to the neighboring ganglion cells. The cells of Martinotti, which, as we have seen, occur also in the second and third layers, are either triangular or spindle-shaped. The neuraxis of each cell originates either from the cell-body or from one of its dendrites, and Digitized by Microsoft® 378 THE CENTRAL NERVOUS SYSTEM. gag>-- d ascends (giving off collaterals) to the molecular layer, in which it finally divides into two or three main branches ending in telo- dendria. Occasionally it divides in a similar manner in the layer of small pyramidal cells. In the medullary substance the following four classes of fibers are recognized : (i) The projection fibers (centrifugal) — i. e., those which indirectly connect the elements of the cerebral cortex with the periphery of the body ; their course may or may not be interrupted during their passage through the basal nuclei ; (2) the commissural fibers, which, according to -;- "".-".-'""- """"'S--- "-.--t-V,.-;- - the original definition, pass ;>./.;-:'(_. ' ~i\ , V: ; """'■*£';.-■ through the corpus callo- -— a sum and anterior commis- sure, thus joining corre- sponding parts of the two hemispheres ; (3) the asso= ciation fibers, which con- nect different parts of the gray substance of the same hemispheres ; and (4) the centripetal or terminal fibers — i. e., the terminal arborizations of those neu- raxes, the cells of which lie in some other region of the same or opposite hemi- sphere, or even in some more distant portion of the nervous system. The pro- jection fibers originate from the pyramidal cells, some of them perhaps from the polymorphous cells. The commissural fibers are also derived from the pyramidal cells, and lie somewhat deeper in the white sub- stance than the association fibers. With the exception of those which join the cunei and those which lie in the anterior commissure, all the commissural fibers are situated in the corpus callosum. They give off during their passage through the hemispheres large num- bers of collaterals, which penetrate at various points into the gray substance and end there in terminal filaments. In this respect their arborization is contrary to the old definition of these fibers, and the latter must be completed by the statement that, besides joining symmetric points of the two hemispheres, they also, by means of m mm n Fig. 314. — Schematic diagram of the cerebral cortex : a, Molecular layer with superficial (tan- gential) fibers ; 6, striation of Bechtereff-Kaes ; c, layer of small pyramidal cells ; d, stripe of Bail- larger; e, radial bundles of the medullary sub- stance ; /, layer of polymorphous cells. Digitized by Microsoft® THE OLFACTORY BULB. 379 their collaterals, may connect other areas of the gray substance with the peripheral regions supplied by their end-tufts (Ramon y Cajal, 93). The association fibers have their origin also in the pyramidal cells. In the medullary substance their neuraxes divide T-shaped, and after a longer or shorter course penetrate into the gray substance of the same hemisphere, where they end as ter- minal fibers. A few collaterals are, however, previously given off, which also terminate in the same manner in the gray substance. The association fibers form the bulk of the medullary rays. On examining a vertical section through one of the cerebral convolutions a number of successive striations may be seen. These are more or less distinct, according to the region, and consist of strands of medullated nerve-fibers between the layers of cells, and parallel with the surface of the convolution. The most superficial form a layer of tangential fibers. Between the molecular layer and the layer of small pyramidal cells is the striation of Bechtereff and Kaes, and in the region of the large pyramidal cells the striation of Baillarger (Gennari) corresponding to the striation of Vicq d'Azyr in the cuneus. In figure 314 the medullary substance is seen below, with rays, composed of parallel bundles of fibers, passing upward into the gray substance ; in reality these fibers penetrate much higher than is shown in the illustration. D. THE OLFACTORY BULB. The olfactory bulb is composed of five layers, which are espe- cially well marked on its ventral side : first, the layer of peripheral nerve-fibers ; second, the layer of olfactory glomeruli ; third, the stratum gelatinosum, or molecular layer ; fourth, the layer of pyr- amidal cells (mitral cells) ; and, fifth, the granular layer with the deeper nerve-fibers. The layer of peripheral fibers is composed of the nerve- bundles of the olfactory nerve which cross one another in various directions and form a nerve-plexus. The glomerular layer con- tains peculiar, regularly arranged, round or oval, and sharply defined structures, which were first accurately studied by Golgi. They are known as glomeruli (from 100 p. to 300 p in diameter), and are in reality complexes of intertwining telodendria. As we shall see, the epithelial cells of the olfactory region of the nose must be regarded as peripheral ganglion cells and their centripetal (basal) processes as neuraxes. The telodendria of these neuraxes, together with those of the dendrites from the mitral or other cells, come in contact with each other within the olfactory glomeruli. The molec- ular layer consists of small, spindle-shaped ganglion cells. Their neuraxes enter the fifth layer and their short dendrites end in ter- minal ramifications in the glomeruli. The mitral cells give off neuraxes from their dorsal surfaces which also enter the granular Digitized by Microsoft® 3 8o THE CENTRAL NERVOUS SYSTEM. layer, but the majority of their dendrites break up into terminal ramifications in the olfactory glomeruli, as just described. The granular layer (absent in the illustration) is made up of nerve-cells and nerve-fibers ; but, aside from these, we find also large numbers of peculiar cells with a long peripherally and several short centrally directed dendrites. No neuraxes can be demonstrated in these cells (granular cells). This layer also contains the stellate ganglion cells. The latter are not numerous, but lie scattered, and each pos- sesses several short dendrites and a peripherally directed neuraxis which ends in the molecular layer in a rich arborization. The deep nerve-fibers are grouped into bundles which inclose between them the granular and stellate cells just mentioned. These nerve-fibers Layer of olfactory^ glomeruli. Peripheral nerve- fibers. Fig- 3iS- — The olfactory bulb, after Golgi and Ram6n y Cajal. not shown. The granular layer is are derived partly from the neuraxes of the pyramidal or mitral cells and partly from the cells of the molecular layer, while some of them are centripetal fibers from the periphery, which end between the granules of the fifth layer. E. EPIPHYSIS AND HYPOPHYSIS. In mammalia the epiphysis, or pineal gland, consists of a fibrous capsule derived from the pia mater, from which numerous fibrous tissue septa and processes pass into the gland, uniting to form quite regular round or oval compartments in which closed follicles or alveoli, whose walls consist of epithelial cells, are found. Digitized by Microsoft® EPIPHYSIS AND HYPOPHYSIS. 38 1 The epithelial cells forming the walls of the follicles are of cubic or short columnar shape, and may be arranged in a single layer or may be pseudostratified or stratified. Follicles completely filled with cellular elements are found. Other follicles contain peculiar con- cretions, known as brain-sand or acervulus, of irregular round or oval or mulberry shape. Medullated nerve -fibers have been traced into the epiphysis, but their mode of termination is not known. The hypophysis, or pituitary body, consists of two lobes. The posterior or infundibular lobe is developed from the floor of the first primary brain-vesicle, and remains attached to the floor of the third ventricle by a stalk, known as the infundibulum ; the anterior or glandular lobe develops from a bud derived from the primary oral ectoderm, known as Rathke's pouch. The distal end of this pouch comes in contact with the anterior surface of the lower portion of the infundibulum, and becomes loosely attached to it. As the bones at the base of the skull develop, the attenuated oral end of Rathke's pouch atrophies, the distal end becoming finally completely severed from the buccal cavity. In the infundibular lobe of the hypophysis of the dog, Berkley (94) described three portions presenting different microscopic struc- ture. His account will here be followed : (i) An outer stratum consisting of three or four layers of cells resembling ependymal cells, which are separated into groups by thin strands of fibrous tissue entering from the fibrous covering of this lobe. (2) A zone consisting of glandular epithelial cells which in certain places are arranged in the form of alveoli, often containing a colloid substance. This zone merges into the central portion, (3), containing variously shaped cells and connective-tissue partitions with blood-vessels. In this portion neurogliar cells (see these) and nerve-cells were stained by .the chrome-silver method. The glandular or anterior lobe resembles slightly in structure the parathyroid. This lobe is surrounded by a fibrous tissue capsule and within it are found variously shaped alveoli or follicles, or, again, columns or trabeculae of cells separated by a very vascular connective tissue. In the alveoli or columns of cells are found two varieties of glandular cells, which may be differentiated more by their staining reaction than by their size and structure, although they present slight structural differences. One variety of cells pos- sesses a protoplasm which shows affinity for acid stains ; these are known as chromophilic cells. They are of nearly round or oval shape, with nuclei centrally placed, and have a protoplasm present- ing coarse granules. The other variety of cells, known as chief cells, are more numerous than the chromophilic. They are of cubic or short columnar shape, with nuclei placed in the basal portions of the cells and with protoplasm showing a fine granulation and with an affinity for basic stains. Now and then alveoli containing a colloid substance, similar to that found in the alveoli of the thy- roid gland, may be observed. The blood-vessels of the glandular Digitized by Microsoft® 3 82 THE CENTRAL NERVOUS SYSTEM. portion are relatively large, the majority of them having only an endothelial lining. In the glandular portion of the hypophysis of the dog, Berkley (94) found small varicose nerve-fibers belonging to the sympathetic system. From the larger bundles, which follow the blood-vessels, are given off single fibers or small bundles of such, which end on the glandular elements in numerous small nodules. F. GANGLIA. In the course of peripheral nerves are found numerous larger and smaller groups of nerve-cells, known as ganglia. The neurones of these ganglia are in intimate relation with the neurones of the cen- Fig. 316. — Longitudinal section of spinal ganglion of cat. tral nervous system, and may, therefore, be discussed with the lat- ter. According to the structure and function of their neurones, the ganglia are divided into two groups — (1) spinal or sensory ganglia and (2) sympathetic ganglia. The spinal ganglia are situated on the posterior roots of the spinal nerves. Certain cranial ganglia — namely, the Gasserian, geniculate, and auditory ganglia, the jugular and petrosal gan- glia of the glossopharyngeal nerves, and the root and trunk ganglia of the vagi — are classed with the spinal ganglia, since they present the same structure. The spinal and sensory cranial ganglia are surrounded by firm connective- tissue capsules, continuous with the perineural sheaths of the incoming and outgoing nerve-roots. From Digitized by Microsoft® GANGLIA. 383 these capsules connective -tissue septa and trabeculae pass into the interior of the ganglia, giving support to the nerve-elements. The cell-bodies (ganglion cells) of the neurones constituting these ganglia are arranged in layers under the capsule and in rows and groups or clusters between the nerve-fibers in the interior of the ganglia. More recent investigations have shown that several types of neurones are to be found in the spinal and cranial sensory gan- glia ; of these, we may mention the following: (1) Large and small unipolar cells with T- or Y-shaped division of the process. These neurones, which constitute the greater number of all the neurones of the ganglia under discussion, consist of a round or oval cell-body, from which arises by means of an implantation cone Fig. 317. — Ganglion cell from the Gasserian ganglion of a rabbit ; stained in methylene- blue {intra vitam), a single process, which, soon after it leaves the cell, becomes in- vested with a medullary sheath and usually makes a variable num- ber of spiral turns near the cell-body. According to Dogiel, this process divides into two branches, usually at the second or third node of Ranvier, sometimes not until the seventh node is reached. Of these two branches, the peripheral is the larger, and enters a peripheral nerve-trunk as a medullated sensory nerve-fiber, termi- nating in one of the peripheral sensory nerve-endings previously described. The central process, the smaller of the two, becomes a medullated nerve-fiber, which enters the spinal cord or medulla in a manner described in a former section. The cell-body of each of these neurones is surrounded by a nucleated capsule, continuous with Digitized by Microsoft® 3«4 THE CENTRAL NERVOUS SYSTEM. the neurilemma of the single process. (2) Type II spinal ganglion cell of Dogiel. Dogiel has recently described a second type of spinal ganglion cell which differs materially from the type just described. The cell-bodies of these neurones resemble closely those of the typ- ical spinal ganglion neurones. Their single medullated processes divide, however, soon after leaving the cells into branches which divide further and which do not pass beyond the bounds of the gan- glia but terminate, after losing their medullary sheaths, in compli- cated pericapsular and pericellular end-plexuses surrounding the capsules and cell-bodies of the typical spinal ganglion cells. (3) Mul- tipolar ganglion cells ; in nearly all spinal and cranial ganglia there are found a few multipolar nerve-cells, which in shape and struc- ture resemble the nerve-cells of the sympathetic system. Fig. 318. — Diagram showing the relations of the neurones of a spinal ganglion ; p. r., posterior root; a. r., anterior root ; p. s., posterior branch and a. i., anterior branch of spinal nerve ; w. r., white ramus communicans ; a, large, and b, small spinal ganglion cells with T-shaped division of process ; c, type II spinal ganglion cells (Dogiel) j s, multipolar cell ; d, nerve-fiber from sympathetic ganglion terminating in pericellular plexuses (slightly modified from diagram given by Dogiel). Entering the spinal ganglia from the periphery are found a rel- atively small number of small, medullated or nonmedullated nerve- fibers, probably derived from sympathetic ganglia. These nerve- fibers, medullated and nonmedullated, the former losing their medullary sheaths within the ganglia, approach a spinal ganglion cell, and after making a few spiral turns about its process, termi- nate in pericapsular and pericellular end-plexuses. Dogiel believes that the cell-bodies and capsules thus surrounded by the terminal branches of the sympathetic fibers terminating in the spinal ganglia belong to the spinal ganglion cells of the second type first described by him. In figure 318 is represented by way of diagram the structure of a spinal ganglion. In the medium-sized cells (from 30 fi to 45 fi in diameter) of the Digitized by Microsoft® GANGLIA. 385 spinal ganglia of the frog, von Lenhossek (95) found centrosomes surrounded by a clear substance (centrospheres). The entire struc- ture lay in a depression of the nucleus and contained more than twelve extremely minute granules (centrosomes), which showed a staining reaction different from that of the numerous concentrically laminated granules present in the protoplasm. This observation is interesting in that it proves that centrosome and sphere occur also in the protoplasm of cells which have not for a long time under- gone division and in which there is no prospect of future division. Sympathetic Ganglia. — The ganglia of the sympathetic ner- vous system comprise those of the two great ganglionated cords, found on each side of the vertebral column and extending from its cephalic to its caudal end, with which may be grouped certain cranial ganglia having the same structure, — namely, the sphenopalatine, otic, ciliary, sublingual, and submaxillary ganglia ; also three un- Fig. 319. — Neurone from inferior cervical sympathetic ganglion of a rabbit ; methylene- blue stain. paired aggregations of ganglia, found in front of the spinal column, of which the cardiac is in the thorax, the semilunar in the abdomen, and the hypogastric in the pelvis ; and further, large numbers of smaller ganglia, the greater number of which are of microscopic size and are found in the walls of the intestinal canal and bladder, in the respiratory passages, in the heart, and in or near the majority of the glands of the body. The sympathetic ganglia are inclosed in fibrous tissue capsules continuous with the perineural sheaths of their nerve-roots. The thickness of the capsule bears relation to the size of the ganglion, being thicker in the larger and thinner in the smaller ones. From these capsules thin connective-tissue septa or processes pass into the interior of the ganglia, supporting the nerve elements. The sympathetic neurones, the cell-bodies and dendritic processes of which are grouped to form the sympathetic ganglia, are variously 25 Digitized by Microsoft® 386 THE CENTRAL NERVOUS SYSTEM. shaped unipolar, bipolar, and multipolar cells, the cell-bodies of which are surrounded by nucleated capsules, continuous with the neurilemma of their neuraxes. In the sympathetic ganglia of mam- malia and birds the great majority of sympathetic neurones are multipolar, although in nearly all ganglia a small number of bipolar and unipolar cells are to be found, usually near the poles of the ganglia. The dendrites of the sympathetic neurones in any one ganglion branch repeatedly. Of these branches, some extend to the per- iphery of the ganglion, where they interlace to form a peripheral subcapsular plexus, while others interlace to form plexuses between the cell-bodies of the neurones in the interior of the ganglion — pericellular plexuses. These pericellular plexuses are external to the capsules surrounding the cell -bodies of the sympathetic neurones. Fig- 320. — From section of semilunar ganglion of cat ; stained in methylene-blue, intra vitam (Huber, Journal of Morphology, 1899). The neuraxes of the sympathetic neurones, the majority of which are nonmedullated, the remainder surrounded by delicate medullary sheaths, arise from the cell-bodies either from implanta- tion cones or from dendrites at variable distances from the cell- bodies, leave the ganglion by way of one of its nerve-roots, and terminate in heart muscle tissue, nonstriated muscle, and glandular tissue, and to some extent in other ganglia, both sympathetic and spinal. Terminating in all sympathetic ganglia are found certain small medullated nerve-fibers, varying in size from about 1.5 fx to 3 f±. The researches of Gaskell, Langley, and Sherrington have shown that these small medullated nerve-fibers leave the spinal cord through the anterior roots of the spinal nerves from the first dorsal to the third or fourth lumbar and reach the sympathetic Digitized by Microsoft® GANGLIA. 387 ganglia through the white rami communicantes. Similar small medullated nerve-fibers are found in certain cranial nerves. These small medullated nerve-fibers, which may be spoken of as white rami fibers, after a longer or shorter course, in which they may pass through one or several ganglia without making special con- nection with the neurones contained therein, terminate in some sympathetic ganglion in a very characteristic manner. After enter- ing the sympathetic ganglion in which they terminate, they branch repeatedly while yet medullated. The resulting branches then lose their medullary sheaths and divide into numerous small, varicose nerve -fibers, which interlace to form intracapsular plexuses, which surround the cell-bodies of the sympathetic neurones. In the sympathetic ganglia of mammalia such intracapsular pericellular Fig. 321. — From section of stellate ganglion of dog, stained in methylene-blue and alum carmin : a, white ramus fiber (Huber, Journal of Morphology, 1899). plexuses may be very simple, consisting of only a few varicose nerve-fibers, or very complicated, consisting of many such fibers. In the sympathetic ganglia of reptilia, in which are found very large sympathetic neurones, the white rami fibers are wound spirally about the cell-bodies of such neurones before terminating in com- plicated pericellular plexuses. In the frog and other amphibia the sympathetic neurones are unipolar nerve-cells. The white rami fibers terminating in the sympathetic ganglia of amphibia are wound spirally about the single processes of these unipolar cells while yet medullated fibers, but they lose their medullary sheaths before ter- minating in the intracapsular pericellular plexuses. From what has been said concerning the white rami fibers and their relation to the sympathetic neurones, it is evident that the sympathetic neu- Digitized by Microsoft® 388 THE CENTRAL NERVOUS SYSTEM. rones, the cell-bodies and dendrites of which are grouped to form the sympathetic ganglia, form terminal links in nerve or neurone chains ; the second link of these chains is formed by neurones the cell-bodies of which are situated in the spinal cord or medulla, the Fig. 322. — From section of sympathetic ganglion of turtle, showing white rami fibers wound spirally about a large process of a unipolar cell, and ending in pericellular plexus (Huber, Journal of Morphology, 1 899). neuraxes leaving the cerebrospinal axis through the white rami as small medullated nerve-fibers, which terminate in pericellular plex- uses inclosing the cell-bodies of the sympathetic neurones. Large medullated nerve-fibers, the dendrites of spinal ganglion neurones, reach the sympathetic ganglia through the white rami. Fig. 323. — From section of sympathetic ganglion of frog, showing spiral fiber (white ramus fiber) and pericellular plexus (Huber, Journal of Morphology, 1899). They make, however, no connection with the sympathetic neurones, but pass through the ganglia to reach the viscera, where they ter- minate in special sensory nerve-endings or in free sensory nerve- endings. Digitized by Microsoft® RELATIONSHIP OF NEURONES. 389 G. GENERAL SURVEY OF THE RELATIONS OF THE NEURONES TO ONE ANOTHER IN THE CENTRAL NERVOUS SYSTEM. The following figures illustrate the modern theories with re- gard to the relationship of the neurones in a sensorimotor reflex cycle. The pathway along which the impulse from the stimulated area of the body is transmitted to the motor nerve end-organ tra- verses two neurones (primary neurones) which are in contact by means of their telodendria situated within the gray matter of the spinal cord. The cell-body of the sensory neurone lies within the spinal ganglion ; that of the motor neurone, in the anterior horn of the spinal cord. The dendrite of the sensory neurone commences mN Fig. 324. — Schematic diagram of a sensorimotor reflex arc according to the modern neurone theory ; transverse section of spinal cord : mN, Motor neurone ; sN, sensory neurone ; C 1 , nerve-cell of the motor neurone ; C 2 , nerve-cell of the sensory neurone ; d, dendrite ; n, neuraxis of both neurones ; t, telodendria ; M, muscle-fiber ; h, skin with peripheral telodendrion of sensory neurone. as a telodendrion in the skin and transmits a cellulipetal impulse, while its cellulifugal neuraxis and telodendrion (the latter in the gray matter of the cord) transfer the impulse to the cellulipetal telodendrion of the motor neurone. The cellulifugal neuraxis of the latter finally ends as a telodendrion in the muscle. (Figs. 324 and 325.) In the case of longer tracts the conditions are somewhat more complicated, as, for instance, in tracing the impulse along the sen- sory fibers to the cortex of the brain, and from there along the motor fibers to the responding muscle. In such cases secondary neurones are called into play by means of their telodendria, which are necessarily in contact with the primary neurones just described. Digitized by Microsoft® 39° THE CENTRAL NERVOUS SYSTEM. When we take into consideration the simplest possible case, that of the motor segment of such a neurone-chain, we find, for instance (Fig. 326), that the neuraxis of a pyramidal cell in the brain cortex (psychic cell) enters the white substance and traverses it as a nerve- fiber through the peduncle and the pyramid into the crossed pyramidal tract of the opposite side. Here its telodendria come in contact with those of the motor neurone of the anterior horn. In the foregoing instance the motor nerve tract is composed of two neurones — of a motor neurone of the first order, extending from the cortex of the brain to the anterior cornua of the spinal cord, and of a motor neurone of the second order, the elements of which extend from the anterior cornua to the telodendria in the muscle. c» v- F'g- 3 2 S- — Schematic diagram of a sensorimotor reflex cycle ; sagittal section of the spinal cord: C 1 , Motor cells of the anterior cornua; n, «, neuraxes ; sN, sensory neurone ; C 2 , spinal ganglion cell ; C, collaterals of the sensory neuraxes ; d, dendrite of sensory neurone ; the broken lines at the cells on the left indicate their dendrites. The sensory tract may likewise be composed of neurones of the first and second orders. The cellulifugal neuraxis arising from a cell of the spinal ganglion passes to the posterior column of the cord, gives off collaterals to the latter, and then passes upward by means of its ascending branch through the posterior column to the medulla. Although here the relationship is not so clearly defined as in the motor tract, it may nevertheless be assumed that the cellu- lifugal (but centripetally conducting) neuraxis at some point or other terminates in telodendria (sensory neurone of the first order), which enter into contact with the corresponding structures of a cell of the spinal cord or medulla oblongata. These cells would then Digitized by Microsoft® RELATIONSHIP OF NEURONES. 391 constitute the sensory neurones of the second order. Exactly how their cellulifugal neuraxes end has not as yet been fully determined, but it is very probable that in this case the telodendria are repre- sented by the coarse end-fibers which penetrate into the brain cor- tex, and here seem to come in contact with the dendrites of the pyr- amidal cells. srt 1 -sW Fig. 326. — Schematic diagram of the reflex tracts between a peripheral organ and the brain cortex: H, Cerebral cortex; mJV 1 , motor neurone of the first, sJV z , sensory neurone of the second, degree ; C 1 , motor cell of the spinal cord ; C 2 , sensory cell of a spinal ganglion; C 3 , pyramidal cell of the brain cortex (pyschic cell) ; C 4 , nerve-cell of a sensory neurone of the second degree ; n,n,n,n, neuraxes ; d, d, dendrites ; c, c, c, c, collaterals; t, t, telodendria; sN 1 , sensory neurone first degree; mN*, motor neurone second degree. Digitized by Microsoft® 392 THE CENTRAL NERVOUS SYSTEM. H. THE NEUROGLIA. We may now consider the neuroglia, a tissue distributed throughout the central nervous system and looked upon as a sup- porting tissue. Its relation to the other tissues has long been a matter of controversy, but modern observers have shown conclu- sively that the neuroglia is of ectodermic origin, at least so far as its cellular elements are concerned. At an early stage of embryonic development there are seen in the spinal cord, and also in the brain, elements radially disposed around the neural canal, which upon closer observation appear to be processes emanating from the epithelial cells lining the neural canal. These processes may undergo repeated dichotomous divi- sion, ending finally in a swelling near the periphery of the cord. These cells are known as epen- dymal cells, and are differenti- ated from ectodermal cells, called spongioblasts. In later stages the radial arrangement is still preserved, but the cell-bodies no longer all border upon the cen- tral canal, many being found at varying distances from the latter. At this stage in the development of the spinal cord, the elements retaining their original charac- teristics are situated only in the region of the ventral and dorsal fissures of the spinal cord, and during further development in- crease in number. These observations would seem to indicate that at least a portion of the neurogliar cells, which develop from the ependymal cells previously mentioned, originate from the epithelium of the central canal, and that from here they are gradually pushed toward the periphery of the cord. This assumption is still further strength- ened by the fact that later the epithelial cells of the central canal still continue to divide. Later observations (Schaper, 97) show, how- ever, that neurogliar cells develop also from certain undifferentiated germinal cells of the neural canal, of ectodermal origin, which wander from their position near the neural canal toward the per- iphery of the medullary tube, where they develop into neurogliar cells. In the adult the epithelium of the central canal and that of the brain cavities (the ependyma) is of the pseudostratified variety with Fig. 327. — Neurogliar cells : a, From spinal cord of embryo cat ; b, from brain of adult cat ; stained in chrome-silver. Digitized by Microsoft® THE MEMBRANES OF THE CENTRAL NERVOUS SYSTEM. 393 two or three strata of nuclei. The basilar processes of the cells are very long, may be branched, and, as a rule, describe a tortuous course. The shape and structure of the neuroglial- cells (spider-cells) vary somewhat in different parts of the central nervous system. From the bodies of these cells numerous delicate processes are sent out, which in the one variety of cell — that occurring principally in the white matter — do not branch. Similar cells, with shorter but occa- sionally dividing processes, are situated for the most part in the gray matter. Other neuroglial' cells may be distinguished from the varieties just described by the smaller number of their processes and by their correspondingly larger bodies. A large proportion of the fine fibers found in the gray and the white matter are processes of the neurogliar cells. Whether the spinal cord contains other similar cellular and fibrillar elements of mesodermic origin is an unsettled question. There seems to be no doubt, however, that connective tissue (other than that composing the pial processes) always accompanies the numerous blood-vessels penetrating into the spinal cord. The majority of investigators have described the various fibers and fibrils brought to view by certain methods as processes of the neurogliar cells. Weigert (95) and Mallory have demonstrated, by means of special methods, the existence of neuroglia-fibers in the adult human brain which are nowhere connected with cellular ele- ments, although they frequently group themselves around a cell as an axis, and thus simulate with the latter the "spider-cells" of some authors. The neurogliar elements of the embryo and fetus have as yet never been demonstrated by Weigert's method, but have, as a rule, been studied by means of Golgi's method. Reinke (97) has very recently found in the white matter of the adult human spinal cord neurogliar cells with processes and neuroglia-fibers having no connection with cells. I. THE MEMBRANES OF THE CENTRAL NERVOUS SYSTEM. The membranes of the central nervous system (meninges) are three in number : the outer, or dura mater : the middle, or arach- noid ; and the inner, or pia mater. Around the brain the dura mater is very intimately connected with the periosteum and presents a smooth inner surface. It con- sists of an inner and an outer layer, the two being separated from each other only in certain regions. At such points either the inner layer is pushed inward to form a duplicature, as in the falx cerebri and falx cerebelli, tentorium, and diaphragma sellae, or the outer layer is pushed outward to form small, blindly ending sacs. The venous and lymphatic sinuses lie between the two layers. The outer Digitized by Microsoft® 394 THE CENTRAL NERVOUS SYSTEM. layer of the dura is continued some distance along the cerebrospinal nerves. The dura mater of the spinal cord does not form the periosteum for the bones forming the vertebral canal ; these possess their own periosteum. The spinal dura mater is covered on its outer surface by a layer of endothelial cells and is separated from the wall of the vertebral canal by the epidural space, containing a venous plexus imbedded in loose areolar connective tissue and adipose tissue. The dura consists chiefly of connective-tissue bundles having a longitudinal direction along the spinal cord. Within the cranium, however, the bundles of the inner and outer layers cross each other ; those of the outer having a lateral direction anteriorly and a mesial posteriorly ; those of the inner, a mesial direction anteriorly and a lateral posteriorly. In the falx cerebri, tentorium, etc., the fibers are arranged radially, extending from their origin toward their borders. The shape and size of the connective-tissue cells vary greatly, and their processes form a network around the bundles of connective tissue. Few elastic fibers are present, and, according to K. Schultz, these are entirely absent in the new-born ; they are somewhat more numerous in the dura of the spinal cord. The dura is very rich in blood-capillaries, and the presence of lymphatic channels in com- munication with the subdural space may be demonstrated by means of puncture-injections. The inner surface of the dura mater is cov- ered by a layer of endothelial cells. The dura mater is quite richly supplied with nerves, especially in certain regions. These are of two varieties : ( i) Vasomotor fibers, which form plexuses in the adventitial coat of the arteries, and would seem to terminate in the muscular coat of the arteries ; (2) medullated nerve-fibers, which either accompany the blood-vessels in the form of larger or smaller bundles or have a course inde- pendent of the vessels. After repeated division these medullated nerve-fibers lose their medullary sheaths and terminate between the connective-tissue bundles in fine varicose fibrils, which may often be traced for long distances (Huber, 99). The arachnoid is separated from the dura by a space which is regarded as belonging to the lymphatic system — the subdural space. The outer boundary of the arachnoid consists, as does the inner lin- ing of the dura, of a layer of flattened endothelial cells. The arach- noid is made up of a feltwork of loosely arranged connective-tissue trabecular, which also penetrate into the lymph-space between it and the pia — the subarachnoid space. For a short distance from their points of origin the cerebrospinal nerves are accompanied by arachnoid tissue. In the brain the arachnoid covers the convolu- tions and penetrates with its processes into the sulci. These pro- cesses are especially well developed in the so-called cisterns ; in the cisterna cerebellomedullaris, fossae Sylvii, etc. In the spinal cord the subarachnoid space is separated by the ligamenta den- ticulata into two large communicating spaces — a dorsal and a ven- Digitized by Microsoft® THE MEMBRANES OF THE CENTRAL NERVOUS SYSTEM. 395 tral. The dorsal space is further divided by the septum posticum, best developed in the cervical region. At certain points, usually along the superior longitudinal sinus, the outer surface of the arachnoid is raised into villi, which are covered by the inner layer of the dura, and form with the latter the Pacchionian bodies or granulations. These villi are connected with the arachnoid by pedicles so delicate that they often seem to be suspended free in the venous current of the sinus. The subarachnoid space contains numerous blood-vessels, some of which are free and others attached to the arachnoid. Their adventitia is covered by endothelium ; hence the subarachnoid space would seem to assume here the character of a perivascular space. The trabeculae and membranes composing the arachnoid tissue show a great similarity to those of the mesentery, and es- pecially to those of the omentum. The whole constitutes a typical are- olar connective, tissue, interrupted at numerous points and covered by a continuous layer of en- dothelial cells. Large numbers of spiral fibers are found here twining around single or groups of connective-tissue fi- bers. The pia mater cov- ers the entire surface of the brain and spinal cord, dipping down into every fissure and crevice. In the spinal cord it con- sists of an outer and an inner lamella, the former being com- posed of bundles of connective tissue containing elastic fibers. As a rule, the course of the fibers is longitudinal. Externally this layer is covered by a layer of endothelium. The blood- vessels lie between the outer and inner layers of the pia. The inner layer (pia intima) is made up of much finer elements, and is covered on both sides by endothelium. It is this layer which accompanies the blood-vessels penetrating into the spinal cord, surrounding their adventitia and forming with the latter the limits of their perivascular spaces. These are in communication with the Digitized by Microsoft® White matter. Fig. 328. — Section through the cerebral cortex of a rabbit. The blood-vessels are injected ; X 4°- 396 THE CENTRAL NERVOUS SYSTEM. interpial spaces, and, by means of the adventitia of the blood-vessels, with the subarachnoid space. Aside from those just described, numerous fine, nonvascular, connective-tissue septa penetrate from the pia mater into the substance of the spinal cord. Wherever the pia mater penetrates the spinal cord, the latter is hollowed out, forming the so-called pial funnels. The pia does not everywhere lie in direct contact with the sur- face of the spinal cord ; for between the cord and the pia there is generally found a neuroglial' covering, formed by the expanded ends of the radial processes from the neuroglial' cells (glia covering or subpia). The posterior longitudinal septum of the spinal cord consists (in the thoracic region) exclusively of neuroglial' elements, but in the cervical and lumbar regions the pia also enters into its peripheral formation. In the brain, however, the conditions are somewhat different. Here the external layer of the pia disappears, leaving only a single layer analogous to the pia intima of the spinal cord. The pia mater enters into the formation of the choroid plexus. This structure consists of numerous freely anastomosing blood- vessels, which form villus-like processes, the surfaces of which are covered by squamous or cubic epithelial cells. This epithelium is regarded as a continuation of the ventricular epithelium, and is cili- ated, at least in embryonic life and in the lower classes of verte- brates. From an embryologic point of view the whole structure represents the brain-wall reduced to a single layer of epithelium (internal epithelial investment) pushed forward into the ventricle by the vessels and pia mater. Since the dura and arachnoid accompany the cerebrospinal nerves for some distance, it is obvious that the lymph-vessels of the nasal mucous membrane (see these) may also be injected from the subarachnoid space (compare also Key and Retzius). The pia mater, like the dura mater, receives two varieties of nerve-fibers : (1) Vasomotor fibers, which form plexuses in the ad- ventitial coat of the arteries and terminate in the muscular layer of the arteries. These may be traced to the small precapillary branches of the vessels. (2) Larger and smaller bundles of rela- tively large, medullated nerve-fibers, which accompany the larger pial vessels, forming loose plexuses in or on the adventitial coat of the vessels. After repeated divisions these medullated nerves lose their medullary sheaths and terminate, in the adventitia of the ves- sels, in long, varicose fibrils or in groups of such fibrils (Huber, 99)- Digitized by Microsoft® BLOOD-VESSELS OF THE CENTRAL NERVOUS SYSTEM. 397 J. BLOOD-VESSELS OF THE CENTRAL NERVOUS SYSTEM. The blood-vessels of the central nervous system present certain peculiarities, which deserve special consideration. In the spinal cord the arteries, surrounded by pial tissue (con- nective-tissue septa), extend as far as the gray matter, but give off numerous lateral branches during their course through the white matter. The capillaries form a much closer meshwork in the gray matter than in the white. The perivascular spaces throughout the central nervous system are separated from the substance of the brain and spinal cord by an endothelial membrane, the internal endothelial layer of the pia intima (Key and Retzius), and are easily injected from the pia. In the cerebral cortex the capillaries are particularly numerous, and are closely meshed wherever groups of ganglion cells occur. In the medullary substance they are somewhat less closely arranged, their meshes being oblong. In the cerebellum the arrangement is analogous. Of all the layers composing the cerebellum the granular is the most vascu- lar ; within it the capillaries are also densely arranged, and form a close network. TECHNIC. 300. The organs of the central nervous system are best fixed in Miil- ler's fluid {vid. T. 27), washed with water, cut in celloidin, and stained with carmin. Such preparations are suitable for general topographic work. 301. Special structures — as, for instance, the medullary sheaths of the nerve-fibers, the ganglion cells, the relations of the different neurones and dendrites to one another, etc. — require different treatment. 302. The medullary sheath may be demonstrated as follows (Wei- gert): Pieces of tissue (spinal cord, for instance), fixed as usual in Miil- ler's or Erlicki's fluid {yid. T. 27 and 29), are transferred without wash- ing to alcohol, imbedded in celloidin, and cut. Before staining the sections it is necessary to subject them to the mordant action of a neutral copper acetate solution (a saturated solution of the salt diluted with an equal volume of water) . The sections may be subjected to the mordant action of this solution, but the following procedure is more conveni- ent : The specimens, imbedded in celloidin and fastened to a cork or a block of wood, are placed for one or two days in the copper solution just described. At the expiration of this time the pieces of tissue will have become dark, and the surrounding celloidin light green. They are then placed in 80% alcohol, in which they may be preserved for any length of time. The sections are then stained in the following solution : 1 gm. of hematoxylin is dissolved in 10 c.c. absolute alcohol, and 90 c.c. of distilled water are then added (the fluid must remain exposed to the air for a few days) ; the addition of an alkali — as, for instance, a cold satu- rated solution of lithium bicarbonate (1 c.c. to 100 c.c. of hematoxylin solution) — brings out the staining power of the solution at once. In Digitized by Microsoft® 39§ THE CENTRAL NERVOUS SYSTEM. this stain the sections are placed (at room-temperature) for a day, and then in a thermostat (40° C. ) for a few hours. The sections, now quite dark, are washed in distilled water and then placed in the so-called dif- ferentiating fluid. The latter consists of borax 2 gm., ferrocyanid of potassium 2.5 gm., and distilled water 100 gm. In this fluid the color of the sections is differentiated by virtue of the circumstance that the medullary sheath retains the dark stain, while the remaining structures, such as the ganglion cells, etc., are bleached to a pale yellow. The time required for this differentiation varies, but it is usually complete at the end of a few minutes. The sections are then washed in distilled water, dehy- drated in alcohol, cleared in carbol-xylol (carbolic acid 1 part, xylol 3 parts) and mounted in balsam. 303. Weigert's new method is more complicated, but fruitful of cor- respondingly better results. The preliminary treatment remains the same. After the tissues have been imbedded in celloidin and this hardened in 80% alcohol, they are transferred to a mixture composed of equal parts of a cold saturated aqueous solution of neutral copper acetate and 10% aqueous solution of sodium and potassium tartrate, and the whole is placed in the thermostat. Larger pieces — as, for instance, the pons Varolii of man — may remain in the solution longer than twenty-four hours, after which time, however, the mixture must be changed ; but in no case should the specimens be permitted to remain longer than forty-eight hours in this solution. The temperature in the thermostat should not be high, otherwise the specimens will become brittle. The objects are now placed in a simple aqueous solution of neutral copper acetate, either saturated or half diluted with water, and again put in the oven. They are then rinsed in distilled water and placed in 80 % alcohol ; after remaining in this for one hour, they are in a condition to cut, but may be preserved still longer if desired. Cut and stain in the customary manner. The staining solution is prepared as follows : ( of its volume of absolute alcohol. The sections are placed in a watch-crystal containing some of the latter mixture until they turn black (a few minutes). As soon as the silver salt is completely 26 Digitized by Microsoft® 402 THE CENTRAL NERVOUS SYSTEM. reduced, the sections are placed for from ten to fifteen minutes in 70% alcohol, then for five minutes in a 20% solution of sodium hyposulphite and, finally, washed for some time in distilled water, after which they may be stained, and even treated with acid alcohol and potassium hydrate. The following simple method for permanently mounting Golgi prepar- ations under a cover-glass has been recommended by Huber. After impregnation with chrome-silver the tissues are hastily dehy- drated, imbedded in celloidin, and cut in sections varying from 2 5 /,. to 100 /x in thickness. The sections are then dehydrated and placed for from ten to fifteen minutes in creosote, from which they are carried into xylol, where they remain another ten minutes. The sections are then removed to the slide. The xylol is then removed by pressing sev- eral layers of filter-paper over the section. On removing the filter-paper the sections are quickly covered by a large drop of xylol balsam and the slide is carefully heated over a flame for from three to five minutes. Be- fore the balsam cools the preparation is covered with a large cover-glass, warmed by passing several times through the flame. 310. Kopsch (96) places specimens in a solution composed of 10 c.c. of formalin (40% formaldehyd) and 40 c.c. of a 3.5% solution of potas- sium bichromate. For objects 2 c.c. in size 50 c.c. of the fluid are em- ployed ; but if the specimens be large, the mixture must be changed in twelve hours. At the end of twenty-four hours this fluid is replaced by a fresh 3.5% potassium bichromate solution, and the specimens are then transferred to a 0.75% solution of silver nitrate (after two days, if the tissue be the liver or stomach ; and after from three to six days, if retina or central nervous system). After this treatment the objects are car- ried over into 40% alcohol and, finally, into absolute alcohol, imbedded as rapidly as possible, and cut. The sections are mounted in balsam without a cover-glass. 311. Ehrlich's methylene -blue method consists in an intra vitam staining of ganglion cells, nerve-fibers, and nerve-endings. The method is much more applicable to the staining of peripheral ganglia (spinal and sympathetic ganglia), peripheral nerves, and nerve-endings than to stain- ing the elements of the central nervous system, although the latter may also be stained by means of this method. Two methods for bringing the stain in contact with the nerve-tissues are now in use : (1) injecting the methylene -blue solution into the living tissues through the blood-vessels ; (2) adding a few drops of the stain to small pieces of perfectly fresh tissues removed from the body. The solu- tion used for injecting the tissues is prepared as follows : 1 gm. of methyl- ene-blue 1 is mixed in a small flask with 100 c.c. of normal salt solution and heated over a flame until the solution becomes hot. It is then allowed to cool ; when filtered, it is ready for use. A cannula is tied into the main artery of the part in which it is desired to stain the nerve elements, and sufficient of the foregoing methylene-blue solution injected to give the part a decidedly blue color. After the injection the part to be studied remains undisturbed for about one-half hour, after which time small, or at least thin, pieces of the tissue to be studied are removed to a slide moistened in normal salt solution, and exposed to the air. The tissues remain on the slide until the nerve-cells, nerve-fibers, or nerve- 1 Methylenblau, rectificiert nach Ehrlich, Griibler, Leipzig. Digitized by Microsoft® TECHNIC. 403 endings seem satisfactorily stained. After placing the tissues on the slide, they are examined under the microscope (without covering with a cover- glass) every two or three minutes, until such examination shows blue color in the neuraxes of the nerve-fibers and their terminations, or in the nerve-cells, if there be any in the tissues examined. Care should be taken not to miss the time when the staining has reached its full develop- ment, as the blue color usually fades again and only inferior preparations are obtained. Tissues thus stained may be fixed by one of two methods (or modifi- cations of these methods), the selection of the method depending some- what on the results desired. If it is desired to gain preparations giving the general course of nerves, the formation of nerve-plexuses, the relations of afferent and efferent nerves to the nerve-cells in ganglia, or the gen- eral arrangement of the terminal branches of nerve-fibers in nerve end- organs, the tissues are placed in a saturated aqueous solution of ammo- nium picrate (Dogiel) in which the blue color of the tissues is in a short time changed to a purplish color. In this solution the tissues remain for from twelve to twenty-four hours, and are then transferred to a mixture consisting of equal parts of a saturated aqueous solution of ammonium picrate and glycerin, in which they remain another twenty-four hours ; they may, however, without detriment remain in the mixture several days. The tissues are then mounted in this ammonium picrate-glycerin mixture. If, on the other hand, it is desired to section tissues stained intra vitam in methylene-blue, the following method, slightly modified from that given by Bethe, is suggested. The following fixative is prepared : Ammonium molybdate, 1 gm. ; distilled water, 10 c.c; hydrochloric acid, 1 drop. The solution is prepared by grinding the ammonium molybdate to a fine powder, removing it to a flask, and adding the required quantity of water. The flask is now heated until the ammonium molybdate is entirely dissolved, when the hydrochloric acid is added. Before using this fixative it is necessary to cool it to 2°-5° C. It is, there- fore, well to prepare it before the injection is made, and surround it with an ice mixture. In this fixative the tissues remain for from twelve to twenty-four hours. After the first six to eight hours it is not necessary to keep the fixative below ordinary room-temperature. After fixation the tissues are washed for an hour in distilled water. They are then hard- ened and dehydrated in absolute alcohol. It is advisable to hasten this step as much as possible, though not at the risk of imperfect dehydration. The tissues are then transferred to xylol and imbedded in paraffin, sec- tioned, fixed to the slide or cover-glass with albumin fixative, and may be double stained in alum-carmin or alum -cochineal. After staining in either of these stains, the sections are thoroughly dehydrated and cleared in oil of bergamot. The oil is washed off with xylol and the sections are mounted in Canada balsam. 312. In staining nerve-fibers with methylene-blue by local application of the stain to the tissues, the tissues to be studied are removed from an animal which has just been killed, divided in small pieces, and placed on a slide moistened with normal salt solution. A few drops of a -w-^fo to -j-V% solution of methylene-blue in normal salt solution are added from time to time. — sufficient to keep the tissues moistened by the solution, but not enough to cover them. The preparations are examined from time to Digitized by Microsoft® 404 THE CENTRAL NERVOUS SYSTEM. time, under the microscope, to see whether the nerve elements are stained. The length of time required for staining by this method varies. Some- times the nerve elements are stained in half an hour ; again, it may re- quire two and one-half hours ; on an average, about one hour. As soon as the tissues seem well stained they are fixed as previously directed. Dogiel has found that sympathetic ganglia and sensory nerve-fibers of the heart removed from the human body several hours after death may be stained by means of the foregoing method. In order to obviate the necessity for the low temperature of the pre- vious method, Bethe (96) has recommended the following procedure : According to the method of Smirnow and Dogiel, he first employs as a preliminary fixing agent a concentrated aqueous solution of ammonium picrate. In this he places the tissue, previously treated with mefhylene- blue, for from ten to fifteen minutes. Without further washing the larger objects are immersed in a mixture composed of ammonium molybdate (or sodium phosphomolybdate) 1 gm., distilled water 20 c.c, and pure hydrochloric acid 1 drop. The following mixtures may also be employed for the same purpose : ammonium molybdate (or sodium phosphomo- lybdate) 1 gm., distilled water 10 c.c, 2 Blood-vessel. Fig. 346.— Transverse section through an osseous and membranous semicircular canal of an adult human being; X 5° (after a preparation by Dr. Scheibe): a, Connective- tissue strand representing a remnant of the embryonic gelatinous connective tissue. Such strands serve to connect the membranous canal with the osseous wall. macula cribrosa, through which the nerves penetrate to the macula of the utriculus. The utriculus and sacculus fill only a part of the inner cavity of the osseous vestibule. Between the osseous and membranous portions remains a space traversed by anastomosing connective-tissue trabeculae, and lined by endothelium, which also forms an investing membrane around the trabeculae. These trabe- culae pass on the one side into the periosteum lining the vestibule, Digitized by Microsoft® 442 THE ORGAN OF HEARING. and on the other, into the wall of the utriculus and sacculus. The. cavity which they thus traverse represents a perilymphatic space. (Compare Fig. 346, which shows analogous relations in the semi- circular canals.) The wall of the utriculus, especially its inner portion, consists of dense fibrous connective tissue, most highly developed in the region of the macula acustica. In the immediate vicinity of the macula utriculi the epithelium of the utriculus is high columnar in type ; in the remaining portion it consists of a single layer of low columnar cells, with a distinct basement membrane ; the epithelium of the macula itself is also high, and is composed of two kinds of elements — of sustentacula!" elements and of the so-called auditory hair-cells. The sustentacula cells are tall epithelial cells resting on the basement membrane by means of their single or cleft basal plates. Each possesses an oval nucleus lying at or beneath the center of the cell. The hair-cells are peculiar cylindric elements with somewhat thickened and rounded bases. One end extends to the surface of the epithelium, while the other, which contains the nucleus, extends only to the center of the epithelial layer. The free end is provided with a cuticular zone supporting a number of long, stiff hairs, which often coalesce to form single threads. On the surface of the epithelium, which must be regarded as a neuro-epithelium, are crystals of calcium carbonate, known as oto- liths, each of which incloses a minute central vacuole (Schwalbe). The otoliths are inclosed in a homogeneous substance, the otolithic membrane , which coagulates in a network of filaments when sub- jected to the action of fixing agents. The nerve-fibers going to the macula penetrate the wall, and, under the epithelium, undergo dichotomous division, and, after fur- ther division, form, in the region of the basilar ends of the auditory cells, a plexus consisting of fine ramifications, and embracing the lower ends of the auditory cells. A few fibers extend still further upward, where their telodendria enter into intimate relations with the acoustic cells (v. Lenhossek, 94, 1). The structure of the sacculus is in every respect like that of the utriculus, and a further description of it is therefore unnecessary. 2. THE SEMICIRCULAR CANALS. The membranous semicircular canals are attached at their con- vex surfaces to the periosteum of the bony canals, which they only partly fill, the remaining cavity being occupied by an eccentrically situated perilymphatic space traversed by connective-tissue trabecule. The walls of the perilymphatic spaces of the semicircular canals, like those surrounding the utriculus and the sacculus, are lined by endothelium, which covers, on the one hand, the periosteal surface of the bony semicircular canals, and, on the other hand, the outer wall of the membranous canals, together with the connective-tissue Digitized by Microsoft® THE INTERNAL EAR. 443 trabeculse. The connective-tissue walls of the membranous canals are structurally similar to those of the utriculus and sacculus. Hensen compares their structure to that of the substantia propria of the cornea. In the adult, the inner layer of the wall of the canals supports here and there papillary elevations, which, however, disappear along its attachment to the bony semicircular canal (Rudinger, 72, 88). The epithelium lining the membranous semicircular canals is simple squamous in character and very evenly distributed over the entire inner surface, including the papilla? previously mentioned. On the concave side of each semicircu- lar canal the epithelial cells are some- what narrower and higher. This inner and higher epithelium (raphe), extending along the concave side into the ampulla?, marks the region at which the semicir- cular canals were constricted off from the pocket-like anlagen. The epithe- lium of the ampullae (Fig. 347), with the exception of that in the region of the raphe, is of the squamous type. At the cristae of the ampullae, however, there is found a neuro-epithelium similar to that of the maculae. The cells adjoining both ends of the cristse are high columnar, and to these the squamous epithelium is joined. The columnar cells just men- tioned form the so-called semilunar fold. Otoliths are also present upon the neu- ro-epithelium of the cristas. Here the structure corresponding to the otolithic membrane of the utriculus and sacculus is called the cupula. In preserved spec- imens it presents the appearance of a coagulum, showing a faint striation ; in the fresh condition, it has never been recognized as a distinct struc ture, at least in the lower classes of vertebrates. Fig. 347. — Part of a verti- cal section through the anterior ampulla, showing the membran- ous wall, a portion of the "crista acustica," and the "planum semilunatum" (after Retzius) : a, Semilunar fold ; b, crista acus- tica ; c, nerve-fibers ; d, blood- vessels. 3. THE COCHLEA. The cochlea consists of an osseous portion, the bony cochlea, a membranous portion, the cochlear duct, and two perilymphatic canals. The bony cochlea consists of a central bony axis of conical shape, the modiolus, around which is wound a spiral bony canal, having in man a little over two and one-half turns, the modiolus forming the inner wall of this canal. The summit of the cochlea, which has the shape of a blunt cone, is formed by the blind end of this bony canal, and is known as the cupola. The modiolus further Digitized by Microsoft® 444 THE ORGAN OF HEARING. gives support to a spiral plate of bone, the lamina spiralis ossea, which extends from the lower part of the modiolus, and, forming two and one-half spiral turns, reaches its top, where it ends in a hook-like process, the hamulus. This bony spiral lamina partly divides the bony cochlear canal into two parts, the division being completed by a fibrous tissue membrane, the lamina spiralis mem- branacea, which extends from the free edge of the osseous spiral lamina to a thickened periosteal ridge, the ligamentum spirale, lining the outer wall of the bony cochlear canal. The canal above the lamina spiralis (bony and membranous) is known as the scala vestibuli, that below as the scala tympani. Both are perilymphatic canals, and communicate in the region of the last half-turn of the cochlea, by means of a narrow canal, the helicotrema, partly sur- rounded by the termination of the bony spiral lamina, the hamulus. The scala vestibuli is in free communication with the perilymphatic space of the vestibule ; while the scala tympani communicates with perivascular spaces surrounding the veins of the cochlear aqueduct, which latter empty into the jugular veins. The scala tympani ter- minates at the secondary tympanic membrane, closing the fenestra rotunda. The cochlear duct, which, as will be remembered, communicates with the sacculus by means of the canalis reuniens, is a long tube closed at both ends, the one end representing the vestibular sac, or ccecum vestibulare, and the other the cupolar extremity, or ccecum cupolare, also known as the lagena. The cochlear duct forms about two and three-fourths spiral turns, its length being about 3.5 mm. Its diameter gradually increases from its lower to its upper or distal extremity. The cochlear duct lies above the lamina spiralis, and, in a section of the cochlea parallel to the long axis of the modiolus, it is of nearly triangular shape, with the somewhat rounded apex of the triangle attached to the osseous lamina spiralis. In the cochlear duct we may distinguish the following parts : (1) the outer wall, which is intimately connected with the periosteum of the bony cochlear canal ; (2) the tympanal wall, resting on the membranous basilar membrane, with its highly differentiated neuro-epithelium, the spiral organ of Corti ; and (3) the vestibular wall, bordering on the scala vestibuli, the intervening structures forming a veiy delicate membrane — the vestibular or Reissner's membrane. From the account given thus far, it may be seen that within the bony cochlear canal there are found three membranous canals, running parallel with one another and with the osseous lamina spi- ralis about which they are grouped. Two of these membranous canals, the scala vestibuli and the scala tympani, are perilymphatic spaces, and are consequently lined by endothelial cells ; between them is found the cochlear duct, from its position known also as the scala media, lined by epithelial cells. These three membranous canals retain their relative position in their spiral course about the modiolus, and, in a section through the cochlea parallel to the bony Digitized by Microsoft® THE INTERNAL EAR. 445 axis of the modiolus, would be met with at each turn, and at each turn present essentially the same relative position and structure. Figure 348 is sketched from such a section, and shows the appear- ance presented by a section through one of the turns of the bony cochlear canal as well as a section of the contained osseous lamina spiralis, the scalae, and the cochlear duct. We may now proceed with a fuller consideration of the structures mentioned. Fig. 348. — Section through one of the turns of the osseous and membranous coch- lear ducts of the cochlea of a guinea-pig ; X 9° : A Scala vestibuli ; m, labium vestibu- lare of the limbus ; n, sulcus spiralis internus ; o, nerve-fibers lying in the lamina spi- ralis ; p, ganglion cells ; q, blood-vessels ; a, bone ; b, Reissner's membrane ; Dc, ductus cochlearis ; d, Corti's membrane ; f, prominentia spiralis ; g, organ of Corti ; h, liga- mentum spirale ; i, crista basilaris ; k, scala tympani. The lamina spiralis ossea consists of two bony plates which in- close between them the ramifications of the cochlear nerve. The vestibular surface of the osseous lamina spiralis is covered by peri- osteum, which is continuous with a peculiar tissue, known as limbus spiralis. The latter begins at the point of attachment of Reissner's membrane, extends peripherally (externally), and ends in two sharp ridges, of which the shorter, the labium vestibulare, projects Digitized by Microsoft® 446 THE ORGAN OF HEARING. into the inner space of the cochlear duct and continues into the tectorial membrane ; while the other and longer, the labium tym- panicum, becomes attached to the wall of the scala tympani and continues into the basilar membrane. Between the two ridges is a sulcus, the sulcus spiralis interims. (Fig. 348.) The limbus spiralis is a connective-tissue formation in the region of the cochlear duct connected with the periosteum of the osseous spiral lamina and extending from the point of attachment of Reissner's membrane to the labium tympanicum. The tissue of the limbus spiralis is dense and richly cellular, and simulates in its structure the sub- stantia propria of the cornea. A casual view would seem. to disclose a high columnar epithelium, but upon closer observation, it is seen that the cellular elements are interspersed with fibers which extend to the surface. Some investigators regard this tissue as fibrocar- tilage ; others, again, as a tissue sui generis, consisting of epithelial cells mingled with connective-tissue fibers. If the labium vestibulare of the limbus spiralis be examined from the vestibular surface, a number of irregular tubercles are seen at its inner portion (near Reissner's membrane), while at its outer portion long, radially dis- posed ridges may be observed, the so-called auditory teeth of Huschke. The connective-tissue wall of the sulcus spiralis internus consists of a nonnucleated fibrillar tissue which is continued into the labium tympanicum. The latter is perforated by nerves, thus giving rise at this point to the foramina nervosa. Between the point of attachment of Reissner's membrane and the labium vestibulare, the superficial epithelium of the limbus spiralis is flat, and lines the auditory teeth and the depressions between them in a continuous layer. The epithelium of the sulcus spiralis internus is somewhat higher. The ligamentum spirale forms the thickened periosteum of the outer wall of the osseous cochlear canal. It presents two inwardly projecting ridges, the crista basilaris, to which the membranous lamina spiralis is attached, and the prominentia spiralis, which con- tains one or several blood-vessels ; between the two ridges lies the sulcus spiralis externus. The portion of the ligamentum spirale forming the periosteum of the bony cochlear canal consists of a fibrous tissue containing many nuclei, but changes internally into a looser connective tissue. The connective tissue lying external to the outer wall of the cochlear duct is very dense and rich in cellular elements and blood-vessels, but in the crista basilaris it changes to a hyaline, noncellular tissue, continuous with the lamina basilaris. That portion of the spiral ligament lying between the prominentia spiralis and the attachment of Reissner's membrane is known as the stria vascularis. The epithelium covering this area (a portion of the epithelium lining the cochlear duct) consists of cubic, darkly granulated cells, which show no distinct demarcation from the underlying connective tissue, and consequently appear to have blood-capillaries extending into the epithelium itself. Digitized by Microsoft® THE INTERNAL EAR. 447 The membranous lamina spiralis, or the basilar membrane, extends from the tympanic lip of the osseous spiral lamina to the crista basilaris of the ligamentum spirale. As already stated, the tissue composing the labium tympani- cum of the limbus extends into the basilar membrane. In this membrane the surface toward the cochlear duct is known as the cochlear surface, that toward the scala tympani as the tympanic surface. Two layers are differentiated in the basilar membrane, the lamina basilaris propria and the tympanic investing layer. The lamina propria consists, in turn, of (i) radially arranged basilar fibers, or acoustic strings ; (2) two thin strata of a homogeneous substance, one above and the other below the layer of basilar fibers, the upper of which is the thicker and nucleated ; and (3) a fine cuti- cula, of epithelial origin, lying on the cochlear side. The tympanic investing layer is highly developed in youth, but later becomes thinner, and may then be differentiated into a connective-tissue layer, regarded as a periosteal continuation of the tympanic por- tion of the osseous lamina spiralis, . and an endothelial cell layer belonging to the lining of the perilymphatic space or the scala tympani. In the vicinity of the labium tympanicum is a blood- vessel situated within the tympanic investing layer of the basilar membrane — the vas spirale. Reissner's membrane consists of an exceedingly thin connective- tissue lamella, lined on the side of the cochlear duct by a layer of flattened epithelial cells and on the vestibular side by a layer of endothelial cells. The epithelium lining the cochlear duct is occa- sionally raised into small villus-like projections. The Organ of Corti. — In the region of the labium tympan- icum of the limbus spiralis and in the greater portion of the adjoining basilar membrane, the epithelium of the cochlear duct is peculiarly modified, forming here a neuro-epithelium, which receives the terminal ramifications of the cochlear nerve and is known as the spiral organ of Corti. Passing from the labium tympanicum to the ligamentum spirale, the following three regions may be recognized in the organ of Corti : An inner region, composed of the inner sustentacular cells and the inner auditory cells ; a middle region, consisting of the arches of Corti ; and an outer region, in which are found the outer auditory cells and the outer sustentacular cells or Deiters's cells. Two cuticular membranes are in close relationship to the organ of Corti : namely, the lamina reticularis and the membrana tectoria, or membrane of Corti. In figure 349, a sketch of the organ of Corti and adjacent structures, it may be observed that the epithelium lining the sulcus spiralis internus (at the right of the figure) is of the pavement variety, and that the epithelium becomes gradually thicker until the organ of Corti is reached, where it becomes suddenly elevated in the form of a wall. In this, two varieties of cells are distinguished Digitized by Microsoft® 448 THE ORGAN OF HEARING. — sustentacular cells and inner auditory cells. The sustentacular cells, which follow the flattened cells, become gradually higher from within outward and occupy three or four rows. Next come the inner auditory cells, cylindric elements, somewhat rounded and thickened at their nucleated basilar ends. The latter do not extend to the basilar membrane but end at about the level of the center of the inner pillars. At the free end of each cell is an elliptic cuti- cular zone, somewhat broader than the end-surface of the corre- sponding cell. In man about twenty rigid filaments, known as auditory hairs, are found resting on each elliptic cuticular zone. These are either arranged in a straight row or they describe a slight curve. The middle division of the organ of Corti, the arches of Corti, consists of long slender structures, known as pillar cells, or, briefly, pillars, resting firmly upon the basilar membrane and forming an arch at the vestibular side of the latter. They surround, by the jS j f J Fig. 349. — Organ of Corti: At x the tectorial membrane is raised; c, outer sus- tentacular cells ; d, outer auditory cells ; /, outer pillar cells ; g, tectorial membrane ; A, inner sustentacular cells ; i,p, epithelium of the sulcus spiralis internus ; k, labium ves- tibulare ; e, tympanic investing layer ; m, outer auditory cells ; n, n, nerve-fibers which extend through the tunnel of Corti ; o, inner pillar cell ; q, nerve-fibers ; b, b, basilar mem- brane ; a, epithelium of the sulcus spiralis externus ; r, cells of Hensen ; s, inner audi- tory cell ; /, ligamentum spirale (after Retzius). union of their free ends, a space which, as seen in figure 349, appears triangular in section. This is the tunnel of Corti. According to their position, we distinguish inner and outer pillars, the inner being more numerous than the outer. Including the entire extent of the lamina spiralis membranacea, we find that there are about 6000 of the inner and 4500 of the outer pillar cells. Each pillar cell originates from an epithelial cell, and is found to be composed of a protoplasmic portion containing the nucleus, which may be regarded as a remnant of the primitive cell, and of a cuticular formation derived from the primitive cell, forming the elongated body of the pillar cell — the pillar. The free adjoining ends are called the heads of the pillars. The head of the inner pillar is provided with a flattened process, the head-plate, which extends outward and forms an obtuse angle with the axis of the Digitized by Microsoft® THE INTERNAL EAR. 449 pillar. Under this plate, and at the outer side of the head of the inner pillar, is a depression into which fits the head of the outer pillar. The latter also extends outward in the shape of a phalan- geal plate, with a thinner process, the phalangeal process, at its end. The phalangeal plate and process lie under the head-plate of the inner pillar, the process extending a little beyond this, forming an acute angle with the head of the outer pillar. At the inner side of the head of the outer pillar is a convex articular surface, with which, as a rule, two, and occasionally even three, articular sur- faces of the inner pillars come in contact. The outer and inner pillars appear to possess an indistinct longitudinal striation, and their basilar plates are continuous with the extremely fine cuticula covering the basilar membrane. The inner margins of the basilar plates belonging to the inner pillars border on the foramina ner- vosa ; while the outer margins of the basilar plates belonging to the outer pillars come in contact with the basal end of the inner- most row of the cells of Deiters in the outer region of Corti's organ. The protoplasmic portions of the pillar cells, constituting what are known as basal cells, lie against the basilar plates of the corresponding pillars, — i. e., on the basilar membrane, — and partly cover the bodies of the pillars, especially the surfaces toward the tunnel. In order to comprehend the relative position of the inner audi- tory cells to the inner pillars, it may be stated that one auditory cell rests upon every two inner pillars. The outer region of Corti's organ is joined directly to the outer pillar cells, and consists of four rows of auditory cells alternating with an equal number of sustentacular cells or Deiters's cells. Following these structures and in contact with them are the outer- most sustentacular cells, known as Hensen's cells. The outer auditory cells have a structure similar to that of the inner auditory cells, but possess a more slender body. They do not extend as far as the basilar membrane, but end at a distance from the latter equal to about double their own length. The cutic- ular zone of each outer auditory cell likewise assumes the form of an ellipse, with its long axis pointing radially. The surface of this zone also is provided with about twenty stiff auditory hairs, arranged in the form of a decidedly convex arch, the convexity of which points outward. At a short distance from the cuticular zone of each outer auditory cell is a peculiar round body, found only in these cells, the significance of which is unknown. Deiters's cells rest on the basilar membrane, and in shape resem- ble a flask with a narrow neck, known as the phalangeal process, the latter lying between the auditory cells. The nuclei of Deiters's cells lie in the upper parts of the thickened basal portions of these cells. With each Deiters's cell there is associated a cuticular structure, which extends along the surface of each cell in the form of a thin 29 Digitized by Microsoft® 450 THE ORGAN OF HEARING. fiber, the sustentacular fiber, and which is found partly within and partly without the cell. The sustentacular fiber begins near the center of the thicker basal portion of the cell-body and extends first into the cell itself, then passes to the surface, and, entering the phalangeal process, passes to the top of the cell and expands as a plate, to which the name phalangeal plate has been given. The latter is broader than the phalangeal process, and since, as we shall see, the phalangeal plates are joined to one another, as well as to the elliptically shaped cuticular zones of the outer auditory cells, there remains a space between the cells of Deiters and the auditory cells, as also between the outer pillars and the innermost of the outer auditory cells, known as Nuel's space. To the basal regions of the inner row of the cells of Deiters is joined the basal plate of the outer pillars of the arches of Corti. Next to the outer row of Deiters's cells are the cells of Hensen, arranged in about eight radially disposed rows. They form an eminence which is high internally, but gradually decreases in height externally. The somewhat narrowed bases of Hensen's cells prob- ably extend, without exception, to the basilar membrane. The free surfaces of these cells are likewise covered by a thin cuticular mem- brane. In man the cells of Hensen usually contain yellow pigment ; in the guinea-pig, as a rule, fat ; and in the rabbit, generally rudi- ments of sustentacular fibers. Externally the cells of Hensen gradu- ally change into elements of a more cuboid type — the cells of Claudius, of which there are about ten rows, radially disposed. The surfaces of the latter also possess a cuticular margin ; the nucleus is at the center of each cell and pigment is also present. Darker elements with more basally situated nuclei sometimes occur be- tween these cells, giving rise to the appearance of a double-layered epithelium (Bottcher's cells). Thus far we have considered in detail the cells comprising the organ of Corti, and described their relative positions and sequence from within outward. In order to give a clearer understanding of the mutual relations of these cells, from within outward and in the direction of the spiral turning of the cochlea, we shall now consider the appearance presented in a surface view of the organ of Corti. From within outward a surface view of the organ of Corti pre- sents the following characteristics : The somewhat broadened hex- agonal outlines of the inner sustentacular cells adjoin the epithelial elements of the sulcus spiralis internus and terminate externally in a spiral undulating line (if seen for only a short distance, this line appears straight). On this line border the contours of the cuticular zones belonging to the inner auditory cells. The outer margins of the cuticular zones come in contact with the head-plates of the inner pillars, the cuticular zone of one inner auditory cell coming in contact with at least two head-plates. The externally directed pro- cesses of the head-plates belonging to the inner pillars come in contact with one another and end in a spiral line which for a short Digitized by Microsoft® THE INTERNAL EAR. 451 distance is apparently straight. The head-plates of the inner pillars cover the head-plates of the outer pillars (which also come in con- tact with each other), also their phalangeal plates, but not their phalangeal processes, which thus pro- ject beyond the line formed by the outer borders of the head-plates of the inner pillars. It should be men- tioned that about three head-plates belonging to the inner pillar cells are in apposition to every two head-plates and their phalangeal processes of the outer pillar cells. The succeeding four rows, from within outward, are made up of alternately placed cutic- ular zones of the outer hair cells and the phalangeal plates of the Deiters's cells, alternating like the squares of a chess-board. This regular arrange- ment is lost in the outer row of Deiters's cells. The cells of Hensen adjoin this row, and when viewed .from the surface, present the appearance of irregular polygons. This arrangement is, however, sel- dom found to be as typical as that just described ; although the relations of the cells to one another always correspond in general to the forego- ing scheme. In the cupolar and vestibular sacs the neuro-epithelium changes into an epithelium of an indifferent type. The lamina reticularis is formed by the cementing together of the pha- langeal processes of the outer pillars and the phalangeal plates of Deiters's cells, and is continued externally by a cuticular membrane which covers the cells of Hensen and, as a much thin- ner cuticular membrane, extends over the cells of Claudius. In this mem- brane there are found three or four rows of small apertures, into which the outer hair cells project. The membrana tectoria Cortii is attached to the limbus spiralis, but becomes free at the margin of the labium vestibulare and thick- ens considerably, again becoming thinner toward its free end. Fig. 350. — Surface of the organ of Corti, with the surrounding struc- tures, from the basal turn of the cochlea of a new-born child ; the original drawing reduced one-half (after Retzius, 84): a > Epithelium of the sulcus spiralis externus ; b, Hensen' s cells ; c , terminal frame ; Miinchen. Bonnet, R., 78, Studien iiber die Innervation der Haarbalge der Hausthiere, in Morph. Jahrb., Bd. IV, S. 329-398, T. 17-19. — 95 1 Ueber " Schlussleisten " der Epithelien, in D. med. Wochenschr., 1895. — 96, Ueber den Bau der Arterienwand, in D. med. Wochenschr., Nr. 1. Born, G. , 94, Die Struktur des Keimblaschens im Ovarialei von Triton taniatus, in Arch. mikr. Anat., Bd. XL1II, S. 1-79, T. 1-4. Boveri, Th. , 85, Beitrage zur Kenntniss der Nervenfasern, in Abh. Akad. Miinchen, Bd. XV, S. 421-495, 2 T. — 87, I, Ueber die Befruchtung der Eier von Ascaris megalocephala, in Sitz.-Ber. Ges. Morph. Phys., Miinchen, Bd. Ill, S. 71-80. — 87, 2-88, Zellenstudien, in Jena. Zeit. Naturw., Bd. xxi, S. 423 515, T. 25-28, und Bd. XXII, S. 685-882, T. 19-23. — 88, Die Vorgange der Befruchtung und Zelltheilung in ihrer Beziehung zur Ver- erbungsfrage, in Verb. Anthropol. Ges., Miinchen, 30. November, S. 13 (Separa- tum), T. 13, 14. — 96, Ueber das Verhalten der Centrosomen bei der Befruchtung des Seeigel-Eies nebst allgemeinen Bemerkungen iiber Centrosomen und Verwandtes, in Verb. Physik. Med. Ges., Wiirzburg, N. F., Bd. xxix, S. 1-75, 1 Fig. Brauer, August, 93, Zur Kenntniss der Spermatogenese von Ascaris megalocephata, in Arch. mikr. Anat., Bd. xlii, S. 153-213, T. 12, 13. Brown, Robert, 29, Mikroskopische Beobachtungen, u.s.w., aus dem Englischen ubersetzt von Beilschmied, Niimberg. Brunn, A. v., 84, Beitrage zur Kenntniss der Samenkorper und ihrer Entwickelung bei Saugethieren und Vogeln, in Arch. mikr. Anat., Bd. xxiii, S. 108-132, T. 7 A. — 92, Beitrage zur mikroskopischen Anatomie dermenschlichen Nasenhohle, in Arch, mikr. Anat., Bd. xxxix, S. 632-651, T. 29, 30. Budge, A., 77, Die Saftbahnen im hyalinen Knorpel, in Arch. mikr. Anat., Bd. xiv, S. 65-73, ['. JB. — 79, Weitere Mittheilungen iiber die Saftbahnen im hyalinen Knorpel, in ibid., Bd. xvi, S. 1-15, T. 1. Biihler, A., 94, Beitrage zur Kenntniss der Eibildung beim Kaninchen und der Mark- strange des Eierstockes beim Fuchs und Menschen, in Zeit. Wiss. Z., Bd. lviii, S. 3H-339. T. 18, 19. Biingner, Otto v., 91, Ueber die Degenerations- und Regenerationsvorgange am Nerven nach Verletzungen, in Beitr. path. Anat., Ziegler, Bd. x, S. 321-393, T. 16, 17. Biitschli, O. , 92, Untersuchungen iiber mikroskopische Schaume und das Protoplasma, Versuche und Beobachtungen zur Losung der Frage nach den physikalischen Be- Digitized by Microsoft® 464 REFERENCES TO LITERATURE. dingungen der Lebenserscheinungen, 234 Sn., 23 Fig., 6 T., Separat-Atlas von 19 Mikrophotographieen, Leipzig. Carriere, J., 82, Kurze Mittheilungen zur Kenntniss der Herbst'schen und Grandry- schen Korperchen in dem Schnabel der Ente, in Arch. mikr. Anat., Bd. XXI, S. 146-164, T. 6. Ciaccio, 90, Sur les plaques nerveuses finales dans les tendons des vertebres, Archives Ital. de Biologie, Tome xiv, p. 31. Clark, J. 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Abbe's apparatus, 19 Absorption of fat by intestine, 256 Accessory disc of Engelmann, 127 thread of spermatosome, 323 Acervulus, 381 Acetate of potash, mounting in, 47 Acetic acid, action of, on connective tissue, 118 sublimate solution as fixing fluid, 24 Achromatic portion of nucleus, 55 spindle, 62 Acid stains, 40 Acidophile cells, 187. See also Cells, eosinopliile. granules, technic of, 205 Adipose tissue, 99 Agminated lymph-nodules, 177 Akrosorne, 339 Alcohol as fixing solution, 22 Altmann's method of demonstrating gran- ules in cells, 72 of mounting, 71 process of injection, 149 Alum-carmin as stain, 41 Alveolar ducts, 279 glands, S4 Alveoli, S4 of glands, 84 of lungs, 280 Amitosis, 57. 64 Amphiaster, 62 Amphibia, epithelium of alveoli of, 2SJ. Amphophile granules, technic, 205 Ampulla of Thoma, 1S2 Anaphases, 57, 63 Anastomoses of vessels, 199 Anilin stains, 42 Annulospiral nerve-ending, 162 Annulus fibrosus, 436 atrioventricularis, 191 Anterior elastic membrane of cornea, 410 endothelium of iris, 416 epithelium of crystalline lens, 428 ground bundle, 370 lymph-channels of eye, 429 Anterolateral columns, ascending, 370 descending, 370 Antrum of Graafian follicle, 309 Anus, 24Q Apathy' s method for demonstration of fibril- lar elements of nervous system, 404 4 43° Chemotaxis, 54 Chemotropism, 54 Chief cells of acini of thyroid body, 284 of hypophysis, 381 of stomach, 239 Chondrin, 103 Choroid, 407, 412 arteries of, 416 layers of, 412 plexus, 396 Choroidal fissure, 408 Chromatin, 55 Chromatolysis, 68 technic of, 68 Chromatophile granules of ganglion cell, 134 Chromic acid as fixing solution, 24 for cells, 69 Chromophilic cells of hypophysis, 381 Chromosomes, 61 daughter, 62 Chrzonszczewsky's physiologic auto-injec- tion, 272 Chyle-vessels, 253 Cilia, 75 movement of, 87 of eyelids, 430 Ciliary body, 407, 412, 414 nerve supply of, 417 glands, 414 of Moll, 430 muscle, 414 processes, 414 Ciliated cell, 53 Circulatory system, 190 technic of, 210 Circulus arteriosus iridis major, 416 minor, 416 Circumanal glands, 250, 357 Circumvallate papillae, 223, 225 Clarke's column, 367 Claudius' cells, 450 Clitoris, 322 Cloquet's canal, 429 Coal-tar stains, 42 Cochlea, 443 bony, 443 perilymph of, 454 spiral ganglion of, 452 Cochlear duct, 443, 444 Cohnheim's fields, 127 method for demonstrating nerve-fibers, 166 Coil-glands of skin, 357 Collective lens, 19 Colloid cells of acini of thyroid body, 284 material, 284 Colostrum, 362 corpuscles, 362 Columnse rectales Morgagni, 250 Columns of Bertini, 289 of Burdach, 370 of Clarke, 367 of Goll, 370 of Tiirck, 370 Commissures, 371 Compound microscope, 17 Concretions, prostatic, 332 Condensers, 19 Cone-fibers of retina, 419 Cone-visual cells, 419 Coni vasculosi Halleri, 326 Conjunctiva, 430 scleral, 409 Connective tissue, 89. See also Tissue, connective. Connective-tissue cells, fixed, 94 Conus medullaris, 365 Convoluted tubules, 325, 327 Corium, 341, 344. See also Dermis. Cornea, 407, 410 nerves of, 412 technic of, 434 Corneal corpuscles, 41 1 spaces, 411 technic of, 434 Corona radiata, 309 Corpora amylacea, 332 Corpus albicans, 315 Highmori, 325 luteum, 313 Corpuscles, connective-tissue, 94 blood-, red, 169 white, 173 bone, 104 isolation of, 123 colostrum, 362 corneal, 411 genital, 155 Golgi-Mazzoni, 350 Hassall's, 189, 190 Malpighian, 180, 182, 287, 289 Meissner's, 155 technic of, 364 of Grandry, 350 technic of, 364 of Herbst, 158, 350 technic of, 364 Pacinian, 157 technic of, 364 Corrosive sublimate as fixing fluid for car- tilage, 120 as fixing solution, 23 for fixing cells, 69 Cortical cells, small, of cerebellar cortex, 374 Digitized by Microsoft® INDEX. 487 Cortical layer of hair, 35 1 nodules of lymph-glands, 179 substance of kidney, 288 Corti's arches, 448 organ, 447 cells of, 447 characteristics of, 450 tunnel, 448 Cover-slip, 20 Cowper's glands, 332 Cox' s method for demonstration of ganglia cells, 401 Crescents of Gianuzzi, 229 Crista basilaris, 446 Cristae, 440, 441 Crossed pyramidal columns, 370 Crosses of Ranvier, 164, 165 Crystalline lens, 428 Cupola, 443 Currents of diffusion, 27 Cuticle, 341. See also Epidermis. of hair, 351 Cuticula, 54, 75 dentis, 213 Cuticular membrane, 75 ridge, 436 structures, 75 Cutis, 341 Cytoplasm, 52 Cytolymph, 53 Czocor's cochineal solution, 41 Damar as mounting medium, 47 Daughter chromosomes, 62 stars, 336 Decalcification, 122 v. Ebner's method, 122 Decalcifying fluids, 122 hydrochloric acid, 122 nitric acid solution, 122 Deiters's cells, 449 processes, 134 Delafield's hematoxylin, 41 Delomorphous cells, 238 Demilunes of Heidenhain, 229 Dendrites, 134, 135 of sensory neurones, 216 Dendritic fibrous structures of Gruber, 437 Dental sac, 218 Dentin, .214, 218 Dentinal bulbs, 217 fibers, 215, 216, 218 papillae, 217 tubules, 214 Dermis, 341 lymph-vessels of, 348 Descemet's membrane, 411 Descending anterolateral columns, 370 Deutoplastic granules, 31 1 Diapedesis, 175, 201 Diaster, 63, 336 Diffuse cells of retina, 425 spongioblasts, 424 Diffusion, current of, 27 Digestive organs, 210 Digestive organs, technic of, 269 Dilator muscle of pupil, 416 Direct cell-division, 57, 64 cerebellar columns, 370 pyramidal tract, 370 Discus proligerus, 309 Dispirem, 63 Double knife, 21 staining, 43 of cells, 69 Doyere's elevation, 147 Ductus endolymphaticus, 440, 454 Dura mater, 393 Ear, 435 external, 435 internal, 439 middle, 437 technic of, 455 vestibule of, 439 Ectoderm, 51, 73 tissues derived from, 73 Egg tubes, primary, of Pfliiger, 307 Ehrlich-Biondi triple stain, 45 Ehrlich's hematoxylin, 42 leucocytic granules, 174 methylene-blue method for ganglion cells and nerve-fibers, 402 neutrophile mixture, 206 Ejaculatory ducts, 330 Elastic fibers, 91 fibrous tissue, 98 membrane, anterior, of cornea, 410 posterior, of cornea, 411 Eleidin, 343 Embryonal cartilage, 99 Enamel, 213 germs, 217 prisms, 213 Encoche d' ossification, 112 End-brush, 147, 151 End-bulb of Krause, 154 cylindric, 157 Endocardium, 190 Endolymph of membranous labyrinth, 453 Endomysium, 129 Endoneurium, 145 Endoplasm, 188 End-organs, nerve, neuromuscular, 158. See also Nerve end-organs, neuro- muscular. neurotendinous, 162 Endosteum, 185 Endothelial and mesothelial cells, relations of, 87 cells, 74, 86 demonstration of, 88 Endothelium, 85 anterior, of iris, 416 End-piece of Retzius, 323 Engelmann's accessory disc, 127 Entoderm, 51, 73 tissues derived from, 74 Eosinophile cell, 187. See also Cell, eosin- ophile. Digitized by Microsoft® 488 INDEX. Eosinophile granules, 1 74. See also Gran- ules, eosinophile. Ependymal cells, 392 Epicardium, 191 Epidermis, 341 compensation for desquamation of, 344 layers of, 341 nerves of, technic of, 364 pigment in, 346 technic of, 362 Epidural space, 394 Epilamellar plexus, 232, 358 Epimysium, 129 Epiphysis, 380 Epithelial cells, isolated, examination of, 87 tissue, 74 technic of, 87 Epithelium, anterior, of crystalline lens, 428 ciliated, islands of, in cervical canal, 318 columnar, pseudostratified, 77 simple, 77 examination of, 87 germinal, of ovary, 307 glandular, 81 neuro-, 85 of urethra, 333 posterior, of iris, 416 respiratory, 280 simple, 76 cubic, 76 squamous, 76 stratified, 77 columnar, 79 squamous, 78 technic of, 87 transitional, 79 Eponychium, 356 Epoophoron, 322 Erlicki's fluid, 25 Erythroblasts, 186 Erythrocytes, 169 Esophagus, 233 technic for, 271 Eustachian tube, 438, 439 Excretory duct of testis, 329 ducts, membrane of, 82 Exoplasm, 188 External auditoiy canal, 435, 436 limiting membrane of retina, 420, 422 Eye, 407 anterior lymph-channels of, 429 development of, 407 fetal blood-vessels of, 429 general structure of, 407 pigment layer of, 418 protective organs of, 430 technic for, 433 tunics of, 407 Eyeball, 407 interchange of fluids in, 429 Eyelids, 430 conjunctival portion of, 430 cuticular portion of, 430 middle layer of, 432 "third," 432. Fallopian tubes, 316 nerve-supply of, 320 technic for, 340 Farrant's gum glycerin, 48 Fasciculus gracilis, 370 Fat, absorption of, by intestine, 256 lobules, 99 Fat-cell, scheme of, 99 Fat-marrow, 185,188 Female genital organs, 306 pronucleus, 67 Fenestra cochlea, 438 rotunda, 438 Fenestrated membranes, 98 Ferrein' s pyramids, 289 Fertilization, diagram of, 66 process of, 65 Fetal blood-vessels of eye, 429 Fiber, cone-, of retina, 419 dentinal, 215 elastic, 91 intrafusal, of neuromuscular nerve end- organs, 159 Kupffer's reticular, 185 lens, 428 Muller's, of retina, 422 muscle-, striped, 124 nerve-, 142. See also Nerve-fiber. Purkinje's, 190 muscle-cells of, 132 Remak's, 145 rod-, of retina, 419 Sharpey's, 106 sustentacular, of Deiters's cells, 450 tunnel-, 452 white, of connective tissue, 90 Fiber-baskets of retina, 423 Fibrae circulares, 415 Fibrillar mass of Flemming, 53 Fibrils of axial cord, demonstration of, 165 Fibrin, 176, 207 demonstration of, 208 Fibrocartilage, white, 102 Fibro-elastic cartilage, 102 Filiform papillas, 222 Filum terminale, 365 Fimbria linguae, 223 Fixation to slide, of sections, 38 Fixing methods, 22 solutions, 22 acetic sublimate, 24 alcohol, 22 chromic acid, 24 corrosive sublimate, 23 for cartilage, 120 Erlicki's, 25 Flemming' s, 22 Fol's, 23 formalin, 25 formol, 25 Hayem's, 203 Hermann's, 23 Muller's, 24 nitric acid, 24 osmic acid, 22 for cartilage, 120 Digitized by Microsoft® INDEX. 489 Fixing solutions, picric acid, 23 picric-nitric acid, 23 picric-osmic-acetic acid, 24 picric-sublimate-osmic acid, 24 picrosulphuric acid, 23 Rabl's, 24 Zenker's, 25 Flagellate cell, 53 Flagellum of spermatosome, 323 Flemming's fibrillar mass, 53 interfibrillar substance, 53 solution, 22 for fixing cells, 69 Flower-like nerve ending, 162 Fluids in eyeball, interchange of, 429 Foam-structures, 73 Foliate papillae, 223 Follicles, simple, of adenoid tissue, 177 Follicular cells, 334 Folliculi linguales, 225 Fol's solution, 23 Fovea centralis, 421 Fontana's spaces, 415 Foramen apicis dentis, 213 Foramina nervosa, 446 papillaria, 293 Formalin as fixing solution, 25 Formol as fixing solution, 25 Fragmentation, direct, 65 Free-hand sectioning, 21 Freezing apparatus for sliding microtome, Friedlander' s glycerin-hematoxylin, 42 Front lens, 19 Fundus of fovea centralis, 421 Fungiform papillae, 222 Funiculi of nerve-trunk, 145 compound, 147 Ganglia, 382 spinal, 382 sympathetic, 385 Ganglion cell, 134 bipolar, 135, 137 chromatophile granules of, 134 demonstration of, 166 layer of retina, 420, 425 multipolar, 137 of Dogiel, in spinal ganglia, 384 sympathetic, 140 technic of, 399 unipolar, 137 spiral, of cochlea, 452 Gartner' s duct, 322 Gastric crypts, 237 glands, 237 body of, 238 fundus of, 238 neck of, 238 Gastrulation, 73 Gelatin-carmin as injection fluid, 48 Gelatinous substance of Rolando, 367 Genital corpuscles, 155 organs, female, 306 Genital organs, male, 323 Genito-urinary organs, 287 Germ centers of lymphoid tissue, 175, 178 layers, 51 Germinal cells, 85 epithelium of ovary, 307 spot, 56 vesicle, 65 Germs, enamel, 217 Giant-cells, 64, 187 Gianuzzi's crescents, 229 Giraldes, organ of, 329 Gland-cell, 81 Glands, alveolar, 84 Brunner's, 236, 246 capsule of, 84 carotid, 202 ceruminous, 357, 436 ciliary, 414 Moll's, 430 circumanal, 250, 357 classification of, 82 coil-, of skin, 357 gastric, 237. See also Gastric glands. lacrimal, 432 lenticular, 241 Lieberkiihn' s, 245 lymph-, 177, 178. See also Lymph- glands. mammary, 359. See also Mammary glands. mixed, 230 mucous, 228 multicellular, 82 of Bartholin, 322 of Bowman, 457 of Cowper, 332 of Littre, 333 of Moll, 357 of Montgomery, 361 of mouth, small, 231 of oral cavity, 227 of skin, 357. See also Skin, glands of. of Tyson, 334 parotid, 228 pineal, 350 saccular, 84 salivary, 228. See also Salivary glands. sebaceous, 358 serous, 228 structure of, 82 sublingual, 228 submaxillary, 230 sudoriparous, 357 suprarenal, 301. See also Suprarenal glands. sweat-, 357 thymus, 188 thyroid, 284 tubular, 82 branched, 83 compound, 83 reticulated, 83 Glandula carotica, 202 Digitized by Microsoft® 49° INDEX. Glandulse buccales, 211 duodenales, 236 labiates, 211 Glandular cells, 54, 239. See also Cell, glandular. epithelium, 81 Glassy layer of choroid, 412, 414 membrane, 352 Glia covering of pia mater, 396 Glisson's capsule, 257 Glomeruli arteriosi cochleae, 453 Glomerulus, 287 Glomus caroticum, 202 Glossary of literature, 460 Glycerin, Farrant' s gum, 48 mounting in, 47 Glycerin-albumen for fixing paraffin sec- tions to slide, 38 Goblet cells, 81 Gold chlorid as stain for capsules of car- tilage, 1 20 Golgi-Mazzoni corpuscle, 350 Golgi's cell of cerebral cortex, 377 methods for demonstration of ganglion cells, 399 mixed, 401 rapid, 401 slow, 400 preparations, methods of mounting, 402 tendon spindle, 162 Goll's column, 370 Gowers's columns, 370 Graafian follicle, 309 antrum of, 309 bursting of, 313 Grandry's corpuscles, 350 technic for, 364 Granular cells, 95 of cerebellar cortex, 375 layer, Tomes', 220 sole plate, 148 Granules, acidophile, technic for, 205 amphophile, technic for, 205 basophile, 174 technic for, 206 demonstration of, in cells, 71 deutoplastic, 311 eosinophile, 174 cells with, 187 technic for, 205 interstitial, of Kolliker, 129 leucocytic, Ehrlich's, 174 mast-cell, technic for, 205 neutrophile, 174 technic for, 206 yolk, 311 Gray matter, 136 substance of spinal cord, 365 Ground bundle, anterior, 370 plexus of cornea, 412 Ground-substance, interfascicular, 97 of areolar connective tissue, 93 of cartilage,, 99 Gruber's dendritic fibrous structures, 437 Gustatory organs, 223 Hair, 350 auditory, 448 bulb, 351, 354 cells of utriculus, 442 cortical layer of, 35 1 cuticle of, 351 follicle, 351 nerve-fibers of, 354 germ, 351 glassy membrane of, 352 growth of, 353 medullary substance of, 35 1 olfactory, 457 papilla, 351 root, 351 root-sheaths of, 351 inner, 351 outer, 351 shaft, 351 shedding of, 354 technic for, 364 Hamulus, 444 Hassall's corpuscles, 189, 190 Haversian canals, 103 spaces, ill Hayem's solution, 203 Hearing, organ of, 435 technic for, 455 Heart, 168, 190 coats of, 190 elastic tissue of, distribution in, 191 muscle-cell, 149 nerve supply of, 192 Heidenhain's demilunes, 229 iron-lack hematoxylin, 42 Helicotrema, 444 Heliotropism, 54 Heller's plexus, 251 Hemalum as stain, 42 Hematin, 169 Hematoidin, demonstration of, 207 Hematoxylin as stain, 41. See also Stains. Delafield' s, for demonstrating canalicular system in cartilage, 1 20 Hematoxylin-eosin as stain, 44 Hematoxylin-safranin of Rabl as stain, 44 Hemin, 169 isolation of, 207 Hemoglobin, 169 demonstration of, 206 Hemokonia, 176 Henle's layer, 351 loop, 288, 291 ascending limb of, 288, 291 descending limb of, 288, 291 sheath, 147 Hensen's cells, 449, 450 median disc, 127 Hepatic cells, cords of, 258 cords, 258 Herbst's corpuscles, 158, 350 technic for, 364 Hermann's solution, 23 Heterotypic form of mitosis, 64 Highmore, body of, 325 Hilum of lymph-gland, 178 Digitized by Microsoft® INDEX. 49 I Histology, general, 51 special, 168 Homeotypic mitosis, 64 Honing microtome knife, 36 Horn-sheath of nerve fibers, 142 Howship' s lacunae, ill Huber's method for mounting Golgi's pre- parations, 402 Huschke's auditory teeth, 446 Huxley' s layer, 351 Hyaline cartilage, 99 Hyaloid arteries, posterior, 429 canal, 429 membrane, 427 Hyaloplasm, 53 Hydatids of Morgagni, 322 Hydrochloric acid as decalcifying fluid, 122 Hydrotropism, 54 Hymen, 321 Hypolamellar plexus, 232 Hypophysis, 381 Imbedding, 25 celloidin, 28. See also Celloidin imbed- ding. celloidin-paraffin, 29 paraffin, 26. See also Paraffin imbed- ding. tissues, box for, 26 Immersion lens, 19 Implantation cone, 135 Indifferent fluids, 21 Kronecker's, 21 physiologic saline solution, 21 Ranvier's iodin and potassium iodid, 21 Ripart and Petit' s, 21 Schultze's iodized serum, 21 Indirect cell-division, 57 Inferior nasal artery of retina, 427 vein, 427 papillary artery, 426 vein, 426 Infiltration, 25 celloidin, 28. See also Celloidin infil- tration. celloidin-paraffin, 29 paraffin, 26. See also Paraffin infiltra- tion. Infundibula, 279 Injection fluids, 48 Berlin blue, 49 gelatin-carmin, 48 methods of, introduction to, 48 of lymph-channels, 49 of lymph-spaces, 49 of lymph-vessels, 49 Inner molecular layer of retina, 420, 423 nuclear layer of retina, 420, 423 Intercellular bridges, 75, 342 demonstration of, 88 spaces, 75 substance, 73 Interfascicular ground-substance, 97 Interfibrillar substance of Flemming, 53 Interglobular spaces, 215 Interlobular duct of pancreas, 266 Intermediate disc of Krause, 127 tubule of pancreas, 266 Internal auditory artery, 452 limiting membrane, 422 Interpapillary epithelial processes, 79 Interstitial granules of Kolliker, 129 Intertubular cell-masses of pancreas, 267 Intestine, 235 absorption of fat by, 256 blood supply, 251 large, 249 lymph supply of, 25 1 mucous membrane of, structure of, 235 nerve supply of, 251 1 secretion of, 256 small, 243 axial canals of, 253 crypt of, 248 lacuna of, 248 technic for, 271 Intracapsular plexuses, 387 Intralobular arteries of kidney, 296 vein, 258, 261, 298 Iodo-iodid of potassium stain to demon- strate glycogen in cartilage, 121 Iris, 407, 412, 415 diaphragm, 18 layers of, 415, 416 nerve supply of, 417 Islands of ciliated epithelium in cervical canal, 318 Isolating fluids, 87 Japanese method for fixing paraffin sec- tions to slide, 39 Jung's sliding microtome, 33, 34 Karyokinesis, 57 Karyokinetic cell-division, heterotypic, 336 homeotypic, 336 Karyolymph, 55 Karyolysis, 68 technic of, 68 Keratohyalin, 342 technic for, 362 Kidney, 287 arched collecting portion of tubules, 288, 293 blood-vessels of, 295 cortical substance of, 288 distal convoluted portion of tubules, 288, 292 intercalated portion of tubules, 288, 292 medullary substance of, 288 pelvis of, 300 proximal convoluted portion of tubules, 288, 290 straight collecting tubules of, 288 Knife, double, 21 Kolliker' s interstitial granules, 1 29 muscle columns, 126 Digitized by Microsoft® 492 INDEX. Kopsch's technic for ganglion cells, 402 Krause's end-bulb, 154 cylindric, 157 intermediate disc, 127 transverse membrane, 127 Kronecker's fluid, 21 Kronig's varnish, 48 Kupffer's method of treating liver tissue, 273 reticular fibers, 185 Kytoblastema, 56 Labium tympanicum, 446 vestibulare, 445 Labyrinth, bony, 439 development of, 454 membranous, 439, 440 osseous, 439 Lacrimal apparatus, 432 gland, 432 sac, 433 Lacteals of villi, 253 Lacuna of small intestine, 248 Lacuna;, Howship's, III of bone, 103, 104 of cartilage, 100 Lagena, 444 Lamellae, 97 marrow, 104 of bone, 104 periosteal, 104 Lamina basilaris propria, 447 choriocapillaris, 413 cribrosa, 409, 425 elastica interna, 195 fusca, 409 propria of oral cavity, 211 reticularis, 447, 451 spiralis membranacea, 444, 447 ossea, 444, 445 suprachoroidea, 412 vasculosa Halleri, 413 Langerhans, areas of, 267 cells of, 266 Lanthanin, 56 Large intestine, 249 Larynx, 275 Lateral column, 367 mixed, 370 Layer of Henle, 351 of Huxley, 351 Leucocytes, 173, 187 polynuclear, amitotic division of, 64 Lens, 407 apochromatic, 19 capsule, 428 collective, 19 crystalline, 428 fibers, 428 front, 19 immersion, 19 ocular, 19 suspensory ligament of, 428 technic of, 434 Lenticular glands, 241 291. See also Leydig's cells, 431 Lieberkuhn' s crypts, 245 glands, 245 Ligaments, 96 Ligamentum pectinatum iridis, 415 spirale, 444, 446 Limbus spiralis, 445 Limiting membrane, external, 420, 422 internal, 422 Lingual mucous membrane, 221 papillae of, 221 papillae, 221 Linin, 55 Liquor folliculi, 309 Literature, glossary of, 460 Littre's glands, 333 Liver, 257 development of, 265 lobules, 257 lymph-vessels of, 263 nerves of, 264 technic of, 274 technic of, 272 Kupffer' s method, 273 vascular system of, 260 Lobes, renal, 287 Lobules, fat, 99 liver, 257 spleen, 182 Loop of Henle, HenWs loop. Lowit's method of demonstrating nerve- fibers, 167 Lung, blood-vessels of, 281 lymphatics of, 282 tissue, 281 Lunula, 356 Lutein cells, 314 Lymph, 168 canalicular system, 94 capillaries, 201 Lymphatic glands, capsule of, 178 technic for, 208 system, 200 Lymph-channels, anterior, of eye, 429 injection of, 49 Lymph-follicles of tongue, 225 of tonsils, 225 solitary, 177 Lymph-glands, 177, 178 Lymph-nodules, 177 agminated, 177 Lymphocytes, 173, 175, 187 Lymphoid tissue, 177 Lymph-sinus, 179 Lymph-spaces, 201 injection of, 49 periaxial, of neuromuscular end-organ, 160 perichoroidal, 413 Lymph-vessels, 168, 200 injection of, 49 Macerating fluids, 87 Macula acustica sacculi, 441 utriculi, 441 Digitized by Microsoft® INDEX. 493 Macula lutea, 421 region of, 421 Magenta red as stain for connective tissue, 119 Male genital organs, 323 pronucleus, 67 Malpighian bodies, 180, 182 corpuscles, 180, 182, 287, 289 layer, technic of, 363 Mammary glands, 359 human, structure of, 360 lymphatics of, 361 milk of, 361 Mantle fibers, 63 Marginal thread of spermatosome, 323 zone, 75 Marrow, bone-, 185. See also Bone-mar- row. cell, 186 fat-, 185, 188 spaces, primary, 109 secondary, in Martinotti's cells of cerebral cortex, 377 Mast-cell granules, technic of, 205 Matrix of areolar connective tissue, 93 of cartilage, 99 of nail, 355 sulcus of, 355 Mayer' s picric-magnesia-carmin, 44 Median disc of Hensen, 127 Mediastinum testis, 325 Medullary cords, 179 cortex, projection fibers of, 378 rays, 288 sheath, 142 technic, 397-399 substance, association fibers of, 378 centripetal fibers of, 378 commissural fibers of, 378 of cerebellar cortex, 375 climbing fibers of, 375 mossy fibers of, 375 of cerebral cortex, 378 of hair, 35 1 of kidney, 288 of ovary, 306 terminal fibers of, 378 Medullated nerve-fibers, 144 Meissner's corpuscles, 155 technic of, 364 plexus, 255 Membrana capsulopupillaris, 429 prseformativa, 220 prima of epithelium, 75 propria, 84 pupillaris, 429 tectoria Cortii, 447, 451 Membranous labyrinth, 439, 440 Meninges of central nervous system, 393 Merkel's terminal disc, 127 Mesameboid cells, 74 Mesenchyme, 74 Mesoderm, 51, 73 cells of, 74 Mesothelial and endothelial cells, relations of, 87 Mesothelium, 74, 85 Metakinesis, 62 Metaphases, 57, 62 Methylene-blue for staining of nerve-fibers, 403 Methyl-green, 43 Metschnikoff's phagocytes, 53 Microscope and its accessories, 17 coarse adjustment of, 18 compound, 17 description of, 17 fine adjustment of, 18 parts of, 17 simple, 17 Microscopic preparation, 20 technic, introduction to, 17 Microtome, 30 knife, honing of, 36 sharpening of, 36 laboratory, 31 rocking, 31 sliding, 31 cutting celloidin sections with, 33 paraffin sections with, 31 freezing apparatus for, 35 of J un g, 33. 34 varieties of, 37 Migratory cells, 94, 96, 1 75 Milk, 361 Mitosis, 57 demonstration of, 69 heterotypic form of, 64 homeotypic, 64 Mitotic cell-division, diagrammatic, 58 of fertilized whitefish eggs, 60 Mixed gland, 230 lateral column, 370 Modiolus, 443 Molecular movement of cells, 53 Moll's ciliary glands, 430 glands, ciliary, 357 Monaster, 62 Mononuclear eosinophile cells, 187 Monostratified cells of retina, 425 Montgomery's glands, 361 Morgagni's hydatids, 322 Morula mass, 73 Mother skein, 61 Motor endings in striated voluntary mus- cle, 150 end-plate, 148 nerve-endings, 147 neurones, 138 peripheral, diagram of, 148 Mounting, 21, 46 Altmann' s method of, 7 1 Mouth, small glands of, 231 Muchematein, 271 Mucicarmin, 271 Mucosa of oral cavity, 211 Mucous glands, 228 membrane of intestine, 236 Miiller's fibers, 415 of retina, 422 fluid, 24 Multicellular glands, 82 Digitized by Microsoft® 494 INDEX. Muscle-casket, 127 Muscle-cell, 123 cardiac, 132 heart, 149 nonstriated, 124, 149 of fibers of Purkinje, 132 smooth, 124 striped, 123 unstriped, 123 Muscle-columns of Kolliker, 126 Muscle-fasciculi, 129 Muscle-fibers, striped, 124 Muscular tissue, 123 technic of, 132 Muscularis mucosae of intestine, 236 of pharynx, 234 of small intestine, 246 Myelin sheath, 142 Myelocytes, 186 Myeloplaxes, 187 Myoblasts, 131 Myocardium, 191 Nail, 355 bed, 355 sulcus of, 355 body of, 355 lunula of, 356 matrix, 355 sulcus of, 355 root, 355 walls, 355 Nasal artery, inferior, of retina, 427 superior, of retina, 427 cavity, 456 technic of, 457 duct, 433 vein, inferior, of retina, 427 superior, of retina, 427 Nerve, auditory, 452 end-organs, neuromuscular, 158 axial sheath of, 159 distal polar region of, 159 equatorial region of, 159 intrafusal fibers of, 159 proximal polar region of, 159 neurotendinous, 162 end-organs of Golgi-Mazzoni, 350 of Grandry, 350 of Herbst, 159 of Krause, 154 of Meissner, 155 of Ruffini, 350 optic, 425. See also Optic nerve. pilomotor, 355 Nerve-cell, 134. See also Ganglion cell. Nerve-ending, annulospiral, 162 flower-like, 162 motor, 147 sensory, 151 encapsulated, 152, 154 free, 152 Nerve-fiber layer of retina, 425 Nerve-fibers, 142 Nerve-fibers ending in muscle tissue, telo- dendria of, 147 medullated, 144 nonmedullated, 145 staining of, with methylene-blue, 403 Nerve-trunk, peripheral, diagram to show composition of, 146 Nervous system, central, 365 blood-vessels of, 397 membranes of, 393 technic of, 397 tissue, 133 technic of, 164 tunic of eye, 407, 418 Neura, 134 Neuraxones, 134 Neurilemma, 143 nuclei, 143 Neurites, 134 Neuroblasts, 133 Neurodendron, 134 Neuro-epithelial cells, 85 Neuro-epithelium, 85 Neuroglia, 392 staining of, 406 Neurogliar cells, 393 Neurokeratin, 142 Neuromuscular nerve end organs, 158. See also Nerve end-organs, neuromuscular. Neurone, 134 cell-bodies of, 134. See also Ganglion cell. centripetal, peripheral, 139 motor, 138 peripheral, diagram of, 148 relationship of, 389 sensory, peripheral, 139 diagram of, 152 Neuroplasm, 142 Neuropodia, 136 Neurotendinous nerve end-organs, 162 Neutrophile granules, 174 technic of, 206 mixture, Ehrlich's, 206 Nitric acid, aqueous solution of, as decal- cifying fluid, 122 as fixing solution, 24 Nodes of Ranvier, 143 demonstration of, 164 Nodules, 177 cortical, 179 lymph-, 177. See also Lymph-nodules. secondary, I75> 178 terminal, of spermatosome, 323 Nonmedullated fibers, demonstration of, 166 nerve-fibers, 145 Nonstriated muscle-cell, 124, 149 Normoblasts, 186 Nuclear division, 56 membrane, 56 sap, 55 stains, 40 Nucleated red blood-cells containing hemo- globin, 186 Nucleolus, 5 1 true, 56 Nucleoplasm, 55 Digitized by Microsoft® INDEX. 495 Nucleus, 51, SS dorsalis, 367 segmentation, 65 Nuel's space, 450 Objective system, 19 Ocular lens, 19 Odontoblasts, 215, 216, 218 Oil of bergamot as clearing fluid, 47 of cloves as clearing fluid, 47 of origanum as clearing fluid, 47 Olfactory bulb, 379 glomerular layer, 379 granular layer, 380 layer of mitral cells, 379 of peripheral fibers, 379 of pyramidal cells, 379 molecular layer of, 379 stratum gelatinosum, 379 cell, 456 hairs, 457 region of nasal cavity, 456 Oocytes, 312 Oppel method for demonstrating reticular liver fibers, 274 Optic cup, 408 nerve, 407, 425 blood-vessels of, 426 papilla, 420 region of, 420 stalks, 408 vesicles, primary, 407 secondary, 408 Ora serrata, 422 Oral cavity, 211 glands of, 227 technic of, 269 Orbiculus ciliaris, 414 Orcein as stain for connective tissue, 118 Organ of Corti, 447. See also Corti's organ. Organs, blood-forming, 168 Osmic acid as fixing solution, 22 for cartilage, 1 20 Osseous labyrinth, 439 Ossification, 107 centers of, 107 groove, 112 ridge, 112 Osteoblasts, 109 Osteoclasts, III Otolithic membrane, 442 Otoliths, 442 Outer fiber layer of retina, 420 molecular layer of retina, 420, 423 Ova, 65 primitive, 307 Ovary, 306 blood-vessels of, 316 cortex of, 306 germinal epithelium of, 307 medullary substance of, 306 stroma of, 306 technic of, 340 Ovula Nabothi, 318 Ovum/ 306 Ovum, changes in, during development, 31 1 ripe, 312 technic of, 340 Oxychromatin granules, 56 Oxyntic cells, 238 Pacchionian bodies, 395 Pacinian corpuscles, technic of, 364 Pal's method for demonstration of medul- lary sheath, 398 Pancreas, 265 blood supply of, 268 interlobular duct of, 266 intermediate tubule of, 266 intertubular cell-masses of, 267 nerve supply of, 268 technic of, 274 Pancreatic duct, 265 Panniculus adiposus, 346 Papilla spiral is-cochlese, 441 Papillae, 78 circumvallate, 223, 225 dentinal, 217 filiform, 222 foliate, 223 fungiform, 222 hair, 351 lingual, 221 optic, 426 region of, 420 tactile, 345 vascular, 345 Papillary artery, inferior, 426 superior, 426 vein, inferior, 426 superior, 426 Paracarmin as stain, 40 Paradidymis, 329 Paraffin imbedding, 26 diagram for, 28 infiltration, 26 diagram for, 28 removal of, 40 sections, cutting of, with sliding micro- tome, 31 distilled water for fixing of, to slide, 3 8 fixing of large number to cover-slips, 39 glycerin-albumin for fixing of, to slide, 38 Japanese method of fixing to slide, 39 Paralinin, 55 Paranuclein, 56 Paraplasm, 53, 81 Parathyroid glands, 285 Parenchymatous tissues, sectioning of, 21 Parietal cells, 238 Paroophoron, 322 Parotid gland, 228 Pars ciliaris retina, 414, 422 iridica retinee, 422 papillaris, 344 reticularis, 344 Partsch's cochineal solution, 41 Digitized by Microsoft® 496 INDEX. Pellicula, 54 Pelvis of kidney, 300 renal, 299, 300 Penis, 332 erectile tissue of, 333 nerve supply of, 334. Perforating fibers of cornea, 41 1 Periaxial lymph-space, 160 Pericardium, 191 Pericellular plexuses, 386 Perichondrium, 101 Perichoroidal lymph-spaces, 413 Perilymph of cochlea, 454 Perilymphatic spaces, 201 Perimysium, 129 Perineurium, 146 Periosteum, 203 Peripheral centripetal neurones, 139 motor neurone, diagram of, 148 nerve terminations, 147 sensory neurones, 139 diagram of, 152 Peritendineum, 97 Perivascular spaces, 201 Petit and Ripart's solution, 21 Petit's canal, 428 Pfliiger's primary egg tubes, 307 Phagocytes, 1 75 Metschnikoff ' s, 53 Phalangeal plate, 449, 450 process, 449 Pharynx, 233 Physiologic excavation of retina, 420 Pia intima, 395 mater, 395 Pial funnels, 396 Picric acid as fixing solution, 23 for cell, 69 as stain, 44 Picric-magnesia-carmin as stain, Mayer's, 44 Picric-nitric acid as fixing solution, 23 Picric-osmic-acetic acid solution as fixing fluid, 24 Picric-sublimate-osmic acid solution as fix- ing fluid, 24 Picrocarmin as stain for connective tissue in cartilage, 120 for elastic fibers in cartilage, 120 of Ranvier, 43 of Weigert, 43 Picrosulphuric acid as fixing solution, 23 Pigment, 90 cell, 71, 95, 96 in epidermis, 346 layer of eye, 418 membrane, 408 of eye, 407 origin of, 316 Pillar cells, 448 heads of, 448 Pilomotor nerves, 355 Pineal gland, 380 Pituitary body, 381 Plasma cells, 96 Plexus, choroid, 396 Plexus, epilamellar, 232 ground, of cornea, 412 hypolamellar, 232 intracapsular, 387 myentericus, 254 of Auerbach, 254 of Heller, 251 of Meissner, 255 pericellular, 386 subepithelial, of cornea, 412 superficial, of cornea, 412 Plicae palmatte, 318 semilunares, 250 sigmoideEe, 237 transversales recti, 250 Plural staining, 43 Polar body, 65 field, 64 rays, 62 Polarity of cell, 75 Polygonal cells of cerebral cortex, 376 Polykaryocyte, 175 Polymorphous cells of cerebral cortex, 377 Polynuclear cells, 64 leucocytes, 64 Polystratified cells of retina, 425 Portal vein, 260 Posterior elastic mpmbrane of cornea, 41 1 epithelium of iris, 416 hyaloid arteries, 429 Potassium bichromate-osmic acid solution, 400 Precapillary arteries, 196 veins, 197 Precartilage, 99 Primary blastodermic layers, 73 germ layers, 73 marrow spaces, 109 optic vesicles, 407 tendon bundles, 96 Primitive ova, 307 seminal cells, 334 Primordial ova, 307 Prominentia spiralis, 446 Promontory ridge, 439 Pronucleus, female, 67 male, 67 Prophases, 57, 60 Prostate, 330 blood-vessels of, 332 nerve supply of, 332 secretion of, 332 Prostatic bodies, 332 concretions, 332 Protoplasm, 51, 81 Protoplasmic currents, 68 stains, 40 Protozoa, 51 Pseudopodia, 53 Pulp cords of spleen, 182 Pupil, dilator muscle of, 416 sphincter muscle of, 416 Purkinje's cells, 138 of cerebellar cortex, 374 fibers, 190 muscle-cells of, 132 Digitized by Microsoft® INDEX. 497 Purkinje's vesicle, 306 Purpurin, alkaline, as stain for calcium carbonate in bone, 122 Pyramidal cells, large, of cerebral cortex, 376 of cerebral cortex, 138 small, of cerebral cortex, 376 columns, crossed, 370 tract, direct, 370 Pyramids of Ferrein, 289 Quintuple hydroquinon developer, 401 Rabl's hematoxylin-safranin stain, 44 solution, 24 Rami cochleares, 452 vestibulares, 452 Ram6n y Cajal' s technic for retina, 435 Ranvier's crosses, 164, 165 iodin and potassium iodid solution, 21 method for demonstrating spaces in bone, 121 for examination of connective tissue, 117 nodes, 143 .demonstration of, 164 picrocarmin, 43 Real image, 19 Recessus camera; posterioris, 427 cochlear, 454 Rectum, 249 Red blood-cells, nucleated, containing hemoglobin, 186 blood-corpuscles, 169 bone-marrow, 185 Reissner' s membrane, 444, 447 Relationship of neurones, 389 Remak' s fibers, 145 demonstration of, 166 Renal lobes, 287 pelvis, 299, 300 Renflement biconique, 143 Respiration, organs of, 275 technic of, 286 Respiratory bronchioles, 279 epithelium, 280 region of nasal cavity, 456 accessory cavities of, 456 Rete testis, 325, 327 Retia mirabilia, 199 Retina, 407, 408, 418 blood-vessels of, 426 layers of, 418-420, 423 macula lutea of, 421 Miiller's fibers of, 422 optic papilla of, 420 ora serrata of, 422 pars ciliaris retinas, 422 iridica retinae, 422 relation of elements of, to one another, 423 technic of, 434 Retinacula; cutis, 346 Retzius, end-piece of, 323 32 Digitized by Ribbon sectioning, 32 Ripart and Petit's solution, 21 Ripe ova, 312 Rocking microtome, 31 Rod-fibers of retina, 419 Rod- visual cells, 418 Rolando's gelatinous substance, 367 Root-sheaths of hair, 351. See also Hair, root-sheaths of. Rose's carmin-bleu de Lyon, 44 Rouleaux, 169, 170 Rudder membrane of spermatosome, 323 Saccular glands, 84 Sacculus, 440, 441, 454 Saccus endolymphaticus, 440, 454 Safranin as stain, 43 Salivary glands, 228 blood-supply of, 232 lymphatics of, 232 nerve supply of, 232 scheme of, 227 Sarcolemma, 125 Sarcolytes, 131 Sarcous elements, 126, 128 Scala media, 444 tympani, 444 vestibuli, 444 Schlemm' s canal, 409 Schmidt - Lantermann-Kuhnt's segments, 142 Schultze's iodized serum, 21 Schwann's sheath, 143 Sclera, 407, 409 blood-vessels of, 410 technic of, 434 Scleral conjunctiva, 409 sulcus, inner, 410 Sebaceous glands, 358 Secondary marrow spaces, III nodule, 175, 178 optic vesicle, 408 tendon bundles, 97 Secretion of intestine, 256 process of, 84 vacuoles, 259 Section staining, 40 stretchers, 35 Sectioning, 21, 30 double knife for, 21 free-hand, 21 of parenchymatous tissues, 21 ribbon, 32 Segmentation cell, 64 nucleus, 65 Selective stains, 40 Semen, 323 technic of, 340 Semicircular canals, 442 anterior superior vertical, 440 external, 440 horizontal, 440 posterior inferior vertical, 440 Semilunar fold, 443 valves, 191 Microsoft® 498 INDEX. Seminal cells, primitive, 334 vesicles, 330 Sense cells, 75 Sense-organs, special, general considera- tions of, 458 Sensory nerve-endings, 151 encapsulated, 152, 154 free, 152 neurones, peripheral, diagram of, 152 Septa renis, 289 Septum posticum, 395 Serous cavities, 201 gland, 228 Sertoli's cells, 326 Sexual cells, matured, 65 Sharpening microtome knife, 36 Sharpey, fibers of, 106 Sheath of Schwann, 143 Sihler's method of demonstrating nerve- endings, 167 Silver-impregnation of thin membranes, 49 Simple epithelium, 76. See also Epithe- lium, simple. microscopes, 17 Sinus, 199 blood, 199 lactiferus, 360 pocularis, 332 Skin, 341 and appendages, 341 technic of, 362 blood-vessels of, 350 glands of, 357 nerve-endings in, 348 nerves of, 348 pigment of, technic of, 363 structure of, technic of, 363 technic of, 362 true, 341 vascular system of, 347 Slides, 20 Sliding microtome, 31. See also Micro- tome, sliding. Small intestine, 243. See also Intestine, small. ' Smell, organ of, 456 technic of, 457 Sole nuclei, 148 plate, granular, 148 Solitary lymph-follicles, 177 Somatic cell, 65 Soudan III as stain for fat, 1 20 Special histology, 168 sense-organs, general considerations of, 458 Specimens, drawing of, 20 examination of, 19 permanent, preparation of, 46 Sperma, 323 Spermatids, 66, 336 development of, into spermatosomes, 336 Spermatoblast, 338 Spermatocytes, 66 of first order, 335 Spermatogenesis, 334 Spermatogones, 66 Spermatogonia, 334 Spermatosome, 323 accessory thread of, 323 axial thread of, 323 sheath of, 323 development of, from spermatids, 336 flagellum of, 323 head of, 323 marginal thread of, 323 middle piece of, 323 rudder membrane of, 323 tail of, 323 terminal nodule of, 323 undulating membrane of; 323 Spermatozoa, 53, 65, 66 Spermatozoon, 323. See also Spermato- some. Sphincter muscle of pupil, 416 Spider-cells, 393 Spinal cord, 365 anterior median fissure of, 365 gray substance of, 365 horns of, 367 posterior median septum of, 365 structure of, 365 white substance of, 365 ganglia, 382 ganglion cell of Dogiel, 384 Spindle cells of cerebral cortex, 376 Spiral ganglion of cochlea, 452 Spirem, 61 Spleen, 180 lobules, 182 Splenic pulp, 183 Spongioblasts, 392 diffuse, 424 stratum of, 424 Spongioplasm, 53 Staining, 40 double, 43 in bulk, 45 diagram showing method, 46 in section, diagram showing method, 46 neurofibrils and Golgi-nets, Bethe's method for, 405 of cells, 69 of nervous tissue, 402 of neuroglia, 406 plural, 43 purpose of, 40 section, 40 Stains, 40 acid, 40 alkaline purpurin, for calcium carbonate in bone, 122 alum-carmin, 41 anilin, 42 basic, 40 Bismarck brown, 43 borax-carmin, alcoholic, 40 aqueous, 40 carmin, 40 carmin-bleu de Lyon, of Rose, 44 coal-tar, 42 Czocor's cochineal solution, 41 Ehrlich-Biondi triple, 45 Digitized by Microsoft® INDEX. 499 Stains for adipose tissue, 119 gold chlorid, for capsules of cartilage, 120 hemalum, 42 hematoxylin, 41 Bohmer's, 41 Delafield's, 41 for demonstrating canalicular sys- tem in cartilage, 1 20 Ehrlich's, 42 for lime-salts in bone, 122 Friedlander' s glycerin-, 42 Heidenhain's iron, 42 hematoxylin-eosin, 44 hematoxylin-safranin of Rabl, 44 iodo-iodid of potassium, to demonstrate glycogen in cartilage, 121 magenta red, for connective tissue, 119 methyl-green, 43 nuclear, 40 orcein, for connective tissue, 118 paracarmin, 40 Partsch's cochineal solution, 41 picric acid, 44 picric-acid-fuchsin, Van Gieson's, 399 picric-magnesia-carmin, Mayer's, 44 picrocarmin, for connective tissue in car- tilage, 120 for elastic fibers in cartilage, 120 Ranvier's, 43 Weigert's, 43 protoplasmic, 40 safranin, 43 selective, 40 Soudan III, for fat, 1 20 Stellate cells, 262 large, of cerebellar cortex, 375 of cerebellar cortex, 374 of cerebral cortex, 376 Stellulae vasculosae, 414 Stomach, 235, 237 technic of, 271 Stomata, 85 Straight tubules of testis, 325 Stratified epithelium, 77 Stratum circulare, 437 corneum, 343 gelatinosum, 379 germinativum, 341 granulosum, 309, 341 lucidum, 343 technic of, 362 Malpighii, 341 technic of, 363 proprium of oral cavity, 21 1 radiatum, 437 spinosum, 342 spongioblasts, 424 submucosum of oral cavity, 212 Stria vascularis, 446 Striation of Baillarger, 379 of Bechtereff and Kaes, 379 Striped muscle-cell, 123 muscle -fibers, 124 Stroma of red blood-cells, 169, 1 70 of iris, 416 Stroma of ovary, 306 Subarachnoid space, 394 Subdural space, 394 Subepithelial plexus of cornea, 412 Sublingual gland, 228 Submaxillary gland, 230 Submucosa of intestine, 236 of oral cavity, 212 Subpia, 396 Substantia gelatinosa, 367 propria of cornea, 410 Succus prostaticus, 332 Sudoriferous duct, 357 Sudoriparous glands, 357 Sulcus of matrix of nail, 355 scleral, inner, 410 spiralis internus, 446 Superficial plexus of cornea, 412 Superior nasal artery of retina, 427 vein, 427 papillary artery, 426 vein, 426 Suprarenal glands, 301 blood-vessels of, 303 nervesof, 304 technic for, 305 Suspensory ligament of lens, 428 Sustentacular cells, 85, 224, 334 fiber of Deiters' cells, 450 Sweat-glands, 357 nerves of, 358 Sympathetic ganglia, 140, 385 Tactile papillje, 345 Taenia coli, 236 of large intestine, 250 Tapetum cellulosum, 413 fibrosum, 413 Taste-buds, 223 Taste-pore, 224 Teasing, 20 Technic, microscopic, introduction to, 17 Teeth, 213 adult, structure of, 213 auditory, 446 development of, 217 pulp of, 215 Tegmental cells, 224 Teichmann's crystals, 169 isolation of, 207 Tela submucosa, 212 Telodendria, 135 of nerve-fibers ending in muscle tissue, 147 Telodendrion, 147, 151 Telolemma nuclei, 148 Telophases, 57, 64 Temperature, effects of, on tissues, 27 Tendons, 96 bundles, primary, 96 secondary, 97 fasciculi, 96 spindle, Golgi, 162 Tenon's capsule, 409 Terminal disc of Merkel, 127 Digitized by Microsoft® 500 INDEX. Terminal ledges, 80 nodule of spermatosome, 323 Testes, 324 blood-vessels of, 329 lymphatics of, 329 nerve- supply of, 329 technic of, 340 Theca folliculi, 309 Thoma' s ampullae, 182 Thymus gland, 188 Thyroid gland, 284 Tigroid granules, 134 Tissue, 73 adipose, 99 stains for, 119 connective, 89 areolar, 93 cellular elements of, 94 ground-substance of, 93 matrix of, 93 fibrous, 93 mucous, 92 Ranvier's method for examination of, 117 reticular, 92 technic of, 117 effects of temperature on, 27 epithelial, 74 erectile, of penis, 333 fibrous, elastic, 98 frozen with carbon dioxid, cutting of, 35, 3° lymphoid, 177 muscular, 123 technic of, 132 nervous, 133 technic of, 164 Toluol as clearing fluid, 47 Tomes' granular layer, 220 processes, 218 Tongue, 221 lymph-follicles of, 225 Tonsils, lymph-follicles of, 225 Tooth-pulp, 215 Trabeculse of liver, 258 Trachea, 276 Transitional eosinophile cells, 187 Transverse disc, 127 membrane of Krause, 127 Triangular cells of cerebral cortex, 376 Trophoplasts, 347 Trypsin digestion for differentiating con- nective and elastic tissues, 118 Tubular glands, 82. See also Glands, tubular. Tubule, dentinal, 214 intermediate, of pancreas, 266 straight collecting, of kidney, 288 uriniferous, 287, 293 schematic diagram of, 297 Tubuli recti of testis, 325 Tunica albuginea, 84, 324 dartos, 346 externa of eye, 407 fibrosa oculi, 407, 409 interna of eye, 407, 418 Tunica media of eye, 407, 412 mucosa of intestine, 236 propria of oral cavity, 211 sclerotica, 407, 409. See also Sclera. vaginalis, 324 vasculosa, 324 of eye, 407, 412 Tunnel of Corti, 448 Tunnel-fibers, 452 Tiirck's column, 370 Tympanic investing layer of basilar mem- brane, 447 membrane, 436 layers of, 436 Tympanum, 437 Tyson' s glands, 334 Undulating membrane of spermatosome, 323 Unstriped muscle-cell, 123 Ureter, 299, 300 Urethra, epithelium of, 333 submucosa of cavernous portion of, 333 Urinary organs, 287 technic for, 305 Uriniferous tubules, 287, 293 schematic diagram of, 297 Uterus, 317 blood supply of, 319 layers of, 318 lymphatics of, 319 nerve supply of, 320 technic of, 340 Utriculosaccular duct, 440 Utriculus, 440, 441, 454 wall of, 442 Vacuoles, 54 secretion, 259 Vagina, 320 sensory nerve-endings in, 322 technic of, 340 vestibule of, 322 Valvulse conniventes, 236 Van Gieson's picric-acid-fuchsin stain, 399 Vas aberrans Halleri, 328 deferens, 329 epididymidis, 326, 328 spirale, 447 Vasa afferentia, 178, 296 efferentia, 178, 325, 327 recta spuria, 297 Vascular canals, 103 papillse, 345 system, 190 tunic of eye, 407, 41 2 Vater-Pacinian corpuscles, 157 Veins, 197 central, 258 intralobular, 258, 261, 298 portal, 260 precapillary, 197 smaller, 197 valves of, 198 Digitized by Microsoft® INDEX. 50I Venje arciformes, 298 stellate, 298 vorticosae, 413 Ventrolateral column, 367 Ventromesial column, 367 Venulse rectse, 298 Vesicula prostatica, 332 Vestibular membrane, 444, 447 Vestibule of ear, 439 of nasal cavity, 456 of vagina, 322 Villi of mucous membrane of small in- testine, 243 of small intestine, lacteals of, 253 Virchow's bone corpuscles, 104 isolation of, 1 23 Virtual image, 19 Visual cells, 418 Vitreous body, 407, 427 membrane, 412, 414 Volkmann's canals, 106 von Ebner's process of decalcification, 122 von Koch's technic for bone, 123 Wagner's spot, 306 Wandering cells, 53, 94, 96 Water, distilled, for fixing paraffin sections to slide, 38 Weigert's methods for demonstration of medullary sheath, 397, 398 picrocarmin, 43 Wharton's jelly, 92 White blood-corpuscles, 173 fibers, 90 fibrocartilage, 102 rami communicantes, 387 fibers, 387 substance of spinal cord, 365 Wirsungian duct, 265 Wolffian duct, 322 Xylol as clearing fluid, 47 as intermediate fluid, 26 Yellow bone-marrow, 185, 188 Yolk granules, 311 Zenker's fluid, 25 Zinn's arterial circle, 426 zonule, 428 Zona pellucida, 31 1 Zonula ciliaris, 407, 428 Zonule of Zinn, 428 Digitized by Microsoft® Digitized by Microsoft® Digitized by Microsoft® Digitized by Microsoft® Catalogue the Medical Publications of : W. 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"We can commend it most heartily, not only to all students of physioiogy, but to every physi- cian and pathologist, as a valuable and comprehensive work of reference, written by men who are of eminent authority in their own special subjects." — London Lancet. " To the practitioner of medicine and to the advanced student this volume constitutes, we believe, the best exposition of the present status of the science of physiology in the English language." — American Journal of the Medical Sciences. An American Text-Book of Surgery. Third Edition. By 1 1 Eminent Professors of Surgery. Edited by William W. Keen, M.D., LL.D., F.R.C.S. (Hon.); and J. William White, M.D., Ph.D. Handsome octavo volume of 1230 pages, with 496 wood-cuts in the text and 37 colored and halftone plates. Thoroughly revised and enlarged, with a section devoted to " The Use of the Rontgen Rays in Surgery." Cloth, $7.00 net ; Sheep or Half Morocco, $8.00 net. Over 35,000 Copies Sold. " Personally, I should not mind it being called THE Text-Book (instead of A Text-Book), for I know of no single volume which contains so readable and complete an account of the science and art of Surgery as this does." — Edmund Owen, F.R.C.S., Member of the Board of Examiners of the Royal College of Surgeons, England. " It this text-book is a fair reflex of the present position of American surgery, we must admit it is of a very high order of merit, and that English surgeons will have to look very carefully to their laurels if they are to preserve a position in the van of surgical practice." — London Lancet. "The work is without doubt the best single- volume surgery extant and will remain the lead- ing text-book as long as it is kept up to its present high standard." — The Clinical Review, Chicago. Illustrated Catalogue of S^Mm'WBrliS^ ooks" free on application. MEDICAL PUBLICATIONS THE NEW STANDARD THE NEW STANDARD The American Illustrated Medical Dictionary. For Practitioners and Students. A Complete Dictionary of the Terms used in Medicine, Surgery, Dentistry, Pharmacy, Chemistry, and the kindred branches, including much collateral information of an encyclo- pedic character, together with new and elaborate tables of Arteries, Muscles, Nerves, Veins, etc.; of Bacilli, Bacteria, Micrococci, Strepto- cocci ; Eponymic Tables of Diseases, Operations, Signs and Symptoms, Stains, Tests, Methods of Treatment, etc., etc. By W. A. Newman Dorland, A.M., M.D., Editor of the "American Pocket Medical Dictionary." Handsome large octavo, nearly 800 pages, bound in full flexible leather. Price, $4.50 net ; with thumb index, $5.00 net. Gives a Maximum Amount of Matter in a Minimum Space and at the Lowest Possible Cost. This is an entirely new and unique work, intended to meet the need of practition- ers and students for a complete up-to-date dictionary of moderate price. It contains more than twice the material in the ordinary students' dictionary, and yet, by the use of a clear, condensed type and thin paper of the finest quality, it forms an extremely handy volume only 1^ inches in thickness. It is a beautiful specimen of the book- maker's art. It is bound in full flexible leather, and is- just the kind of a book that a man will want to keep on his desk for constant reference. The book makes a special feature of the newer words, and defines hundreds of important terms not to be found in any other dictionary. It is especially full in the matter of tables, containing more than a hundred of great practical value. An important feature of the book is its hand- some illustrations and colored plates drawn especially for the work, including new colored plates of Arteries, Muscles, Nerves, Veins, Bacteria, Blood, etc., etc. — twenty- four in all. The book will appeal to both practitioners and students, since, besides a complete vocabulary, it gives to the more important subjects extended consideration of an encyclopedic character. This new work has been aptly termed by a competent critic "The New Standard." The American Pocket Medical Dictionary. Edited by W. A. Newman Dorland, M.D., Assistant Obstetrician to the Hospital of the University of Pennsylvania ; Fellow of the Amer- ican Academy of Medicine. Containing the pronunciation and defini- tion of the principal words used in medicine and kindred sciences, with 64 extensive tables. Handsomely bound in flexible leather, with gold edges. Price $1.00 net ; with thumb index, #1.25 net. THIRD EDITION, REVISED. This is the ideal pocket lexicon. It is complete, defining all the terms of modern medicine, and forming an unusually complete vocabulary. It gives the pronunciation of all the terms. It makes a special feature of the newer words neglected by other dictionaries. It contains a wealth of anatomical tables of special value to students. It forms a handy volume, indispensable to every medical man. "This dictionary is, beyond all doubt, the best one among pocket dictionaries. " — .5V. Louis Medical and Surgical Journal. " This is a handy pocket dictionary, which is so full and complete that it puts to shame some of the more pretentious volumes. 'Irr-fournaJ of th^American^Medical Association. v Digitized! ay Microsoft® OF W. B. SAUNDERS &> CO. The American Year-Book of Medicine and Sur- gery. A Yearly Digest of Scientific Progress and Authoritative Opinion in all branches of Medicine and Surgery, drawn from journals, mono- graphs, and text-books of the leading American and Foreign authors and investigators. Arranged with critical editorial comments, by eminent American specialists, under the editorial charge of George M. Gould, M.D. Year-Book of 1900 in two volumes — Vol. I., including General Medicine ; Vol. II., General Surgery. Per volume : Cloth, $3.00 net; Half Morocco, $3.75 net. Sold by Subscription. " It is difficult to know which to admire most — the research and industry of the distinguished band of experts whom Dr. Gould has enlisted in the service of the Year-Book, or the wealth and abundance of the contributions to every department of science that have been deemed worthy of analysis. ... It is much more than a mere compilation of abstracts, for, as each section is entrusted to experienced and able contributors, the reader has the advantage of certain critical com- mentaries and expositions . . . proceeding from writers fully qualified to perform these tasks. . . . It is emphatically a book which should find a place in every medical library." — London Lancet. Abbott on Transmissible Diseases. The Hygiene of Transmissible Diseases : their Causation, Modes of Dissemination, and Methods of Prevention. By A. C. Abbott, M.D., Professor of Hygiene and Bacteriology, University of Pennsylvania. Octavo, 3 1 1 pages, with numerous illustrations. Cloth, $2.00 net. It is not the purpose of this work to present the subject of Hygiene- in the compre- hensive sense ordinarily implied by the word, but rather to deal directly with but a section, certainly not the least important, of the subject — viz., that embracing a knowl- edge of the preventable specific diseases. Incidentally there are discussed those numerous and varied factors that have not only a direct bearing upon the incidence and suppression of such diseases, but are of general sanitary importance as well. " The work is admirable in conception and no less so in execution. It is a practical work, simply and lucidly written, and it should prove a most helpful aid in that department of medicine which is becoming daily of increasing importance and application — namely, prophylaxis." — Phila- delphia Medical Journal. Anders* Practice Of Medicine. Fourth Revised Edition. A Text-Book of the Practice of Medicine. By James M. Anders, M.D., Ph.D., LL.D., Professor of the Practice of Medicine and of Clinical Medicine, Medico-Chirurgical College, Philadelphia. In one handsome octavo volume of 1292 pages, fully illustrated. Cloth, $5.50 net; Sheep or Half Morocco, $6.50 net. FOUR. EDITIONS IN THREE YEARS. The third edition of this work was so quickly exhausted as to render it unnecessary to make extensive alterations in the present issue. Numerous changes in the text, however, have been made in all parts, and considerable new matter has been added, with a view to enhancing the general usefulness of the work. A number of subjects have been written anew, among which some of the more important are Sprue, Ileo- colitis in Children, and Acute Cholecystitis. The modern methods of diagnosis, as well as the most recent advances in therapeutics, have been introduced. " It is an excellent book, — concise, comprehensive, thorough, and up to date. It is a credit to you ; but, more than that, it is a credit to the profession of Philadelphia — to us." — James C. Wilson, Professor of the Practice of Medicine and Clinical Medicine, Jefferson Medical College, Phila. "The book is a good one, and for the average general practitioner will be of distinct service for its detail of treatment. " — s ^(fa\$fr$}ty\$$%i8ft$ s P itai - MEDICAL PUBLICATIONS AshtOtl's Obstetrics. Fourth Edition, Revised. [See Saunders' Que stion-Comp ends, page 37.J Baldy — American Text-Book of Gynecology. [See American-Text-Book of Gynecology, page 4.] Ball's Bacteriology. Fourth Edition, Revised. [See Saunders' Question-Compe?ids, page 37.J Bangs and Hardaway — American Text-Book of Genito-Urinary and Skin Diseases. [See under American Text-Books on page 4.] Bastin's Botany. Laboratory Exercises in Botany. By Edson S. Bastin, M.A., late Professor of Materia Medica and Botany, Philadelphia College of Pharmacy. Octavo, 536 pages, with 87 plates. Cloth, $2.00 net. " It is unquestionably the best text-book on the subject that has yet appeared. The work is eminently a practical one. We regard the issuance of this book as an important event in the his- tory of pharmaceutical teaching in this country, and predict for it an unqualified success." — Alumni Report to the Philadelphia College of Pharmacy. Beck on Fractures. Fractures. By Carl Beck, M.D., Surgeon to St. Mark's Hospital and the New York German Poliklinik, etc. With an appendix on the Practical Use of the Rontgen Rays. 335 pages, 170 illustrations. Cloth, $3.50 net. Just Issued. In this book the author devotes particular attention to the value of Rontgen rays in the diagnosis of different varieties of fractures. Publications on this subject hitherto have not claimed to be more than tentative sketches. This book represents an effort to embody in a systematic treatise the important essentials of this subject, based on the extensive experience of the author in X-ray work. This comparatively new field Dr. Beck has made practically his own, and the large number of skiagraphs contained in the book have been pronounced by competent critics the finest specimens of such work in existence. " This work is important as being the first attempt to bring before the profession in a sys- tematic way the study of fractures by means of the Rbntgen rays. The use of the Rontgen rays with its technique is fully explained, and the practical points are brought out with a thoroughness which merits high praise." — Medical Record. Beck's Surgical Asepsis. A Manual of Surgical Asepsis. By Carl Beck, M.D., Surgeon to St. Mark's Hospital and the New York German Poliklinik, etc. .306 pages ; 65 text-illustrations and 12 full-page plates. Cloth, $1.25 net. Boisliniere's Obstetric Accidents, Emergencies, and Operations. Obstetric Accidents, Emergencies, and Operations. By L. Ch. Bois- liniere, M.D., late Emeritus Professor of Obstetrics, St. Louis Medi- cal College. 381 pages, handsomely illustrated. Cloth, $2.00 net. Digitized by Microsoft® OF W. B. SAUNDERS cV- CO. Bohm, Davidoff and Huber's Histology. A Text-Book of Human Histology. Including Microscopic Technic. By Dr. A. A. Bohm and Dr. M. von Davidoff, of Munich, and G. Carl Huber, M.D., Junior Professor of Anatomy and Director of Histological Laboratory, University of Michigan. Handsome octavo of 503 pages, with 351 beautiful original illustrations. Cloth, $3.50 net. Just Issued. The work of Drs. Bohm and Davidoff is well known in the German edition, and has been considered one of the most practically useful books on the subject of human histology. This American edition, though based upon the second revised German •edition, has been in great part rewritten and very much enlarged by Dr. Huber, who has also added over 100 original illustrations. The book contains particularly full and explicit instructions in the matter of technic, and it will undoubtedly prove of the utmost value to students and practical workers in the histological laboratory. BrOCkway's Medical PhysiCS. Second Edition, Revised. [See Saunders' Question- Compends, page 37.] Butler's Materia Medica, Therapeutics, and Pharmacology. Third Edition. Revised. A Text-Book of Materia Medica, Therapeutics, and Pharmacology. By George F. Butler, Ph.G., M.D., Professor of Materia Medica and of Clinical Medicine in tne College of Physicians and Surgeons, Chicago. Octavo, 874 pages, illustrated. Cloth, $4.00 net ; Sheep or Half Morocco, #5.00 net. A clear, concise, and practical text-book, adapted for permanent reference no less than for the requirements of the class-room. The recent important additions made to our knowledge of the physiological action of drugs are fully discussed in the present edition. The book has been thoroughly revised and many additions have been made. "Taken as a whole, the book may fairly be considered as one of the most satisfactory of any single -volume works on materia medica in the market."— Journal of American Medical Association. Cerna on the Newer Remedies. Second Edition. Revised. Notes on the Newer Remedies, their Therapeutic Applications and Modes of Administration. By David Cerna, M.D., Ph.D., Demon- strator of Physiology in the Medical Department of the University of Texas. Rewritten and greatly enlarged. Post-octavo, 253 pages. Cloth, $1.00 net. Chapin on Insanity. A Compendium of Insanity. By John B. Chapin, M.D., LL.D., Physician-in-Chief, Pennsylvania Hospital for the Insane; Honorary Member of the Medico-Psychological Society of Great Britain, of the Society of Mental Medicine of Belgium, etc. i2mo, 234 pages, illus- trated. cloth - # J - 2 5 net. " The practical parts of Dr Chapin' s book are what constitute its distinctive merit. We desire especially to call attention to the fact that on the subject of therapeutics of insanity the work is exceedingly valuable. It is not a made book, but a genuine condensed thesis, which has all the value of ripe opinion and all the charm of a vigorous and natural style." '—Philadelphia Medical J»» rnal - Digitized by Microsoft® 10 MEDICAL PUBLICATIONS Chapman's Medical Jurisprudence and Tox- icology. Second Edition, Revised. Medical Jurisprudence and Toxicology. By Henry C. Chapman, M.D., Professor of Institutes of Medicine and Medical Jurisprudence in the Jefferson Medical College of Philadelphia. 254 pages, with 55 illustrations and 3 full-page plates in colors. Cloth, $1.50 net. "The best book of its class for the undergraduate that we know of." — New York Medical Times. Church and Peterson's Nervous and Mental Diseases. Second Edition. Nervous and Mental Diseases. By Archibald Church, M.D., Pro- fessor of Nervous and Mental Diseases, and Head of the Neuro- logical Department, Northwestern University Medical School, Chicago; and Frederick Peterson, M.D., Clinical Professor of Medical Diseases, Woman's Medical College, New York ; Chief of Clinic, Nervous Department, College of Physicians and Surgeons, New York. Handsome octavo volume of 843 pages, profusely illustrated. Cloth, $5.00 net ; Sheep or Half Morocco, $6.00 net- This book is intended to furnish students and practitioners with a practical work- ing knowledge of nervous and mental diseases. Written by men of wide experience and authority, it presents the many recent additions to the subject. The book is not filled with an extended dissertation on anatomy and pathology, but, treating these points in connection with special conditions, it lays particular stress on methods of examination, diagnosis, and treatment. In this respect the work is unusually complete and valuable, laying down the definite courses of procedure which the authors have found most generally satisfactory. " The work is what it aims to be — an epitome of what is to-day known of nervous diseases, prepared for the student and practitioner in the light of the authors' experience. From article to article there is full consideration, and from page to page almost uniform excellence. . . We believe that no work having at the same time the merit of sound subject-matter presents the difficult subject of insanity in such a reasonable and readable way." — Chicago Medical Recorder. "The volume remains a compact, thorough, and modern presentation of the most recent conceptions of nervous and mental diseases. To be clear, brief, and thorough, and at the same time authoritative, are merits which ensure popularity. The medical student and practitioner will find in this volume a ready and reliable resource." — New York Medical Journal. Clarkson's Histology. A Text-Book of Histology, Descriptive and Practical. By Arthur Clarkson, M.B., CM. Edin., formerly Demonstrator of Physiology in the Owen's College, Manchester ; late Demonstrator of Physiology in Yorkshire College, Leeds. Large octavo, 554 pages; 22 engrav- ings in the text and 174 beautifully colored original illustrations. Cloth, strongly bound, $4.00 net. " The work must be considered a valuable addition to the list of available text-books, and is to be highly recommended." — New York Medical Journal. " This is one of the best works for students we have ever noticed. We predict that the book will attain a well-deserved popularity among our students." — Chicago Medical Recorder. Cohen and Eshner's Diagnosis. Second Edition. Revised. [See Sa^^g^ofy-^mj^s, page 37 .] OF W. B. SAUNDERS &> CO. 11 Corwin's Physical Diagnosis. Third Edition, Revised. Essentials of Physical Diagnosis of the Thorax. By Arthur M. Corwin, A.M., M.D., Instructor in Physical Diagnosis in Rush Medical College, Chicago; 219 pages, illustrated. Cloth, $1.25 net. "It is excellent. The student who shall use it as his guide to the careful study of physical exploration upon normal and abnormal subjects can scarcely fail to acquire a good working knowl- edge of the subject." — Philadelphia Polyclinic. " A most excellent little work. It brightens the memory of the differential diagnostic signs, and it arranges orderly and in sequence the various objective phenomena to logical solution of a careful diagnosis." — Journal of Nervous and Mental Diseases. Cragin's Gynecology. Fourth Edition, Revised. [See Saunders' Question-Compends, page 37.] Crookshank's Bacteriology. Fourth Edition, Revised. A Text-Book of Bacteriology. By Edgar M. Crookshank, M.B., Professor of Comparative Pathology and Bacteriology, King's College, London. Octavo volume of 700 pages, with 273 engravings and 22 original colored plates. Cloth, $6.50 net; Half Morocco, $7.50 net. " To the student who wishes to obtain a good risume' of what has been done in bacteriology, or who wishes an accurate account of the various methods of research, the book may be recom- mended with confidence that he will find there what he requires." — London Lancet. DaCosta's Surgery. Third Edition. Revised. Modern Surgery, General and Operative. By John Chalmers Da Costa, M.D., Professor of Practice of Surgery and Clinical Surgery, Jefferson Medical College, Philadelphia ; Surgeon to the Philadelphia Hospital, etc. Handsome octavo volume of n 17 pages, profusely illustrated. Cloth, $5.00 net ; Sheep or Half Morocco, $6.00 net. Enlarged by Over 200 Pages with More Than 100 New Illustrations. The remarkable success attending DaCosta's "Manual of Surgery," and the general favor with which it has been received, have led the author in this revision to produce a complete treatise on modern surgery along the same lines that made the former editions so successful. The book has been entirely rewritten and enlarged by over 200 pages. More than 100 new illustrations have been added. The old editions have long been a favorite not only with students and teachers, but also with practising physicians and surgeons, and it is believed that the present work will find an even wider field of usefulness. " The author has presented concisely and accurately the principles of modern surgery. The book is a valuable one, which can be recommended to students, and is of great value to the general practitioner." — American Journal of the Medical Sciences. " We know of no small work on surgery in the English language which so well fulfils the requirements of the modern student." — Medico- Chirurgical Journal, Bristol, England. Davis's Obstetric Nursing. Obstetric and Gynecologic Nursing. By Edward P. Davis, A.M., M.D., Professor of Obstetrics in the Jefferson Medical College and Philadelphia Polyclinic ; Obstetrician and Gynecologist to the Phila- delphia Hospital. i2mo volume of 350 pages, fully illustrated. Ready Shortly. Digitized by Microsoft® J ^ 12 MEDICAL PUBLICATIONS De Schweinitz on Diseases of the Eye. Third Edition, Revised. Diseases of the Eye. A Handbook of Ophthalmic Practice. By G. E. de Schweinitz, M.D., Professor of Ophthalmology in the Jefferson Medical College, Philadelphia, etc. Handsome royal octavo volume of 696 pages, with 256 fine illustrations and 2 chromo-lithographic plates. Cloth, $4.00 net ; Sheep or Half Morocco, $5.00 net. The third edition of this book, destined, it is hoped, to meet the favorable recep- tion accorded to its predecessors, has been revised thoroughly and much new matter introduced. Particular attention has been given to the important relations which micro-organisms bear to many ocular disorders. Several new paragraphs appear, among which are considerations of new forms of Conjunctivitis and Corneal Affection, Rbntgeji Rays for Detecting Foreign Bodies in the Vitreous, Eucain, and Holocain. Certain articles, as well as a portion of the chapter on Operations, have been largely rewritten. New illustrations have been added. " It is hardly too much to say that for the student and practitioner beginning the study of Oph- thalmology, it is the best single volume at present published." — Medical News. " A clearly written, comprehensive manual. One which we can commend to students as a reliable text-book, written with an evident knowledge of the wants of those entering upon the study of this special branch of medical science." — British Medical Journal. " A work that will meet the requirements not only of the specialist, but of the general practi-' tioner in a rare degree. I am satisfied that unusual success awaits it." — William Pepper, M.D., Professor of the Theory and Practice of Medicine and Clinical Medicine, University of Penn- sylvania. De Schweinitz and Randall — American Text- Book o_f Diseases of the Eye, Ear, Nose, and Throat. [See American Text-Book of Diseases of the Eye, Ear, Nose, and Throat, page 3. J Dorland's Dictionaries. [See American Illustrated Medical Dictionary and American Pocket Medical Dictionary on page 6.] Dorland's Obstetrics. A Manual of Obstetrics. By W. A. Newman Dorland, M.D., Assis- tant Demonstrator of Obstetrics, University of Pennsylvania; Instruc- tor in Gynecology in the Philadelphia Polyclinic. 760 pages ; 163 illustrations in the text and 6 full-page plates. Cloth, $2.50 net. " By far the best book on this subject that has ever come to our notice."— American Medical Review. " It has rarely been our duty to review a book which has given us more pleasure in its perusal and more satisfaction in its criticism. It is a veritable encyclopedia of knowledge, a gold mine of practical, concise thoughts." — American Medico-Surgical Bulletin. Durck and Hektoen— Atlas of Pathologic His- tology. [See Saunders 1 Medical Hand- Atlases, page ^.1 Digitized by Microsoft® '^ s •" J OF W. B. SAUNDERS & CO. 13 Eichhorst's Practice of Medicine. A Text-Book of the Practice of Medicine. By Dr. Herman Eichhorst, Professor of Special Pathology and Therapeutics and Director of the Medical Clinic, University of Zurich. Translated and edited by Augustus A. Eshner, M.D., Professor of Clinical Medicine in the Philadelphia Polyclinic. In Press. Friedrich and Curtis on the Nose, Throat, and Ear. Rhinology, Laryngology, and Otology and Their Significance in Gen- eral Medicine. By Dr. E. P. Friedrich, of Leipzig. Edited by H. Holbrook Curtis, M.D., Consulting Surgeon to the New York Nose and Throat Hospital. Octavo, 348 pages. Cloth, $2.50 net. Just Issued. In this work the author's object has been to point out the interdependence between disease of the entire organism and diseases of the nose, pharynx, larynx, and ear, and to incorporate the new discoveries of these specialties into the scheme of general medicine. He has endeavored to point out the means of an active co-operation •between general medicine and the above-named specialties, and thus to bring to the attention of the general practitioner special symptoms and methods which should be of the greatest importance to him in the recognition and treatment of his cases. Frothingham's Guide for the Bacteriologist. Laboratory Guide for the Bacteriologist. By Langdon Frothingham, M.D.V., Assistant in Bacteriology and Veterinary Science, Sheffield Scientific School, Yale University. Illustrated. Cloth, 75 cts. net. Garrigues' Diseases of Women. Third Edition, Revised. Diseases of Women. By Henry J. Garrigues, A.M., M.D., Gynecol- ogist to St. Mark's Hospital and to the German Dispensary, New York City. Octavo, 756 pages, with 367 engravings and colored plates. Cloth, $4.50 net ; Sheep or Half Morocco, $5.50 net. The entire work has been carefully and thoroughly revised ; what seemed antiquated or of minor importance in a text-book has been left out ; a large amount of new material has been incorporated, bringing the work absolutely up to date, and many new illustrations have been added. " We think it one of the few really good books on gynecology for the general practitioner." — New York Medical Journal. "Taken as a whole, the work is one of the most complete which we have seen printed in English." — Bulletin of Johns Hopkins Hospital. " The work can be earnestly recommended as a faithful exponent of American gynecology, conceived in a spirit of moderation and conservatism." — Medical Record. " It reflects the large experience of the author, both as a clinician and a teacher, and compre- hends much not ordinarily found in text-books on gynecology. The book is one of the most com- plete treatises on gynecology that we have, dealing broadly with all phases of the subject." — Ameri- can Journal of the Medical Sciences. " One of the best text-books for students and practitioners which has been published in the English language ; it is condensed, clear, and comprehensive. The profound learning and great clinical experience of the distinguished author find expression in this book in a most attractive and instructive form. Young practitioners to whom experienced consultants may not be available, will find in this book invaluable counsel and help." — Thad. A. Reamy, M.D., LL.D., Professor of Clinical Gynecology, Medical College of Ohio. Digitized by Microsoft® 14 MEDICAL PUBLICATIONS GleaSOIl's Diseases of the Ear. Second Edition, Revised. [See Saunders' Question- Compends, page 37.] Golebiewski and Bailey— Atlas of Diseases Caused by Accidents. [See Saunders' Medical Hand- Atlases, page 3 5. J Gould and Pyle's Curiosities of Medicine. Anomalies and Curiosities of Medicine. By George M. Gould, M.D., and Walter L. Pyle, M.D. An encyclopedic collection of rare and extraordinary cases and of the most striking instances of abnormality in all branches of Medicine and Surgery, derived from an exhaustive research of medical literature from its origin to the present day, abstracted, classified, annotated, and indexed. Handsome imperial octavo volume of 968 pages, with 295 engravings in the text and 12 full-page plates. POPULAR EDITION: Cloth, $3.00 net : Half Morocco. $4.00 net. In view of the great success of this magnificent work, the publisher has decided to issue a " Popular Edition " at a price so low that it may be procured by every student and practitioner of medicine. Notwithstanding the great reduction in price, there will be no depreciation in the excellence of typography, paper, and binding that character- ized the earlier editions. " The authors have rendered a great service to writers and teachers, and many will have their labors greatly lightened by a reference to this storehouse of information." — Journal of the Amer- ican Medical Association. "The book is a monument of untiring energy, keen discrimination, and erudition. . . . We heartily recommend it to the profession." — Lancet, London. " Drs. Gould and Pyle have evolved in this volume a monumental work of industry and patience and skill, and have contributed a priceless addition to the medical literature of the world." University Medical Magazine. Grafstrom's Mechano-Therapy. A Text-Book of Mechano-Therapy (Massage and Medical Gym- nastics). By Axel V. Grafstrom, B.Sc, M.D., late Lieutenant in - the Royal Swedish Army ; late House Physician City Hospital, Black- well's Island, New York. i2rrio, 1 39 pages, illustrated. Cloth, $ 1 .00 net. Griffith On the Baby. Second Edition, Revised. The Care of the Baby. By J. P. Crozer Griffith, M.D., Clinical Professor of Diseases of Children, University of Pennsylvania ; Phy- sician to the Children's Hospital, Philadelphia, etc. i2mo, 404 pages, with 67 illustrations in the text and 5 plates. Cloth, $1.50 net. " The best book for the use of the young mother with which we are acquainted. . . . There are very few general practitioners who could not read the book through with advantage." — Archives of Pediatrics. " The whole book is characterized by rare good sense, and is evidently written by a master hand. It can be read with benefit not only by mothers, but by medical students and by practi- tioners who have not had large opportunities for observing children." — American Journal of Obstetrics. Digitized by Microsoft® OF W. B. SAUNDERS eV CO. 15 Griffith's Weight Chart. Infant's Weight Chart. Designed by J. P. Crozer Griffith, M.D., Clinical Professor of Diseases of Children in the University of Penn- sylvania, etc. 25 charts in each pad. Per pad, 50 cts. net. Griinwald and Grayson — Atlas of Diseases of ■the Larynx. [See Saunders' Medical Hand- Atlases, page 34.J Haab and De Schweinitz — Atlas o_f External Diseases of the Eye. [See Saunders' Medical Hand- Atlases, page 34. J Hart's Diet in Sickness and in Health. Diet in Sickness and in Health. By Mrs. Ernest Hart, formerly Student of the Faculty of Medicine of Paris and of the London School of Medicine for Women ; with an Introduction by Sir Henry Thompson, F.R.C.S., M.D., London. 220 pages. Cloth, #1.50 net. Haynes* Anatomy. A Manual of Anatomy. By Irving S. Haynes, M.D., Adjunct Pro- fessor of Anatomy and Demonstrator of Anatomy, Medical Depart- ment of the New York University, etc. 680 pages, illustrated with 42 diagrams in the text and 1 34 full-page half-tone illustrations from original photographs of the author's dissections. Cloth, $2.50 net. "This book is the work of a practical instructor — one who knows by experience the require- ments of the average student, and is able to meet these requirements in a very satisfactory way. The book is one that can be commended." — Medical Record, New York. Heisler's Embryology. A Text-Book of Embryology. By John C. Heisler, M.D., Professor of Anatomy in the Medico-Chirurgical College, Philadelphia. Octavo volume of 405 pages, handsomely illustrated. Cloth, $2.50 net. The facts of embryology having acquired in recent years such great interest in connection with the teaching and with the proper comprehension of human anatomy, it is of first importance to the student of medicine that a concise and yet sufficiently full text-book upon the subject be available. It was with the aim of presenting such a book that this volume was written ; the author, in his experience as a teacher of anatomy, having been impressed with the fact that students were seriously handi- capped in their study of the subject of embryology by the lack of a text-book full enough to be intelligible, and yet without that detail which characterizes the larger treatises, and which so often serves only to confuse and discourage the beginner. "The book is written to fill a want which has distinctly existed and which it definitely meets ; commendation greater than this it is not possible to give to anything." — Medical News, New York. "We can heartily recommend the book and believe it will be of great value."— New York Medical Journal. Hektoen and Riesman — American Text-Book of Pathology. [See American Text-Book of Pathology, page 5.] Digitized by Microsoft® 16 MEDICAL PUBLICATIONS Hirst's Obstetrics. Second Edition. A Text-Book of Obstetrics. By Barton Cooke Hirst, M.D., Pro- fessor of Obstetrics in the University of Pennsylvania. Handsome octavo volume of 848 pages, with 618 illustrations and 7 colored plates. Cloth, $5.00 net ; Sheep or Half Morocco, #6.00 net. This work is intended as an ideal text-book for the student no less than an advanced treatise for the obstetrician and for general practitioners. It represents the very latest teaching in the practice of obstetrics by a man of extended experience and recognized authority, which fact, combined with the brilliant presentation of the sub- ject, renders it one of the most notable books on obstetrics. " It is a fresh, live contribution to the subject, written in a broad and catholic spirit, and gains by contrast to the various systems so much in vogue at the present day. Dr. Hirst has the experi- ence, the facility of pen, and the knack of teaching; he knows how to separate the chaff from the wheat ; the consequence is an admirable text-book of obstetrics — modern, scientific, convincing." — The Medical News, New York. "The illustrations are numerous and are works of art, many of them appearing for the first time. The arrangement of the subject-matter, the foot-notes, and index are beyond criticism. As a true model of what n modern text-book on obstetrics should be, we feel justified in affirming that Dr. Hirst's book is without a rival." — New York Medical Record. "The number of excellent text-books on obstetrics is so great that any new book, to merit and secure the attention of the profession, must possess a high grade of excellence. Such merit is possessed by Dr. Hirst's book. The work is pre-eminently a practical one, and will be valuable whether in the hands of a tyro in obstetrics or in those of a veteran practitioner who wishes to ascertain the latest and best in this line of work." — Philadelphia Medical Journal. Hofmann and Peterson — Atlas of Legal Medicine. [See Saunders' Medical Hand- Atlases, page 34.] Howell— American Text-Book of Physiology. [See American Text-Book of Physiology, page 5.] Hyde and Montgomery on Syphilis and the Venereal Diseases. Syphilis and the Venereal Diseases. By James Nevins Hyde, M.D., Professor of Skin and Venereal Diseases, and Frank H. Montgomery, M.D., Associate Professor of Skin, Genito-Urinary, and Venereal Diseases in Rush Medical College, Chicago, 111. Octavo, 594 pages, profusely illustrated. Cloth, $4.00 net. Second Edition, Revised and Greatly Enlarged. In the present edition every page has received careful revision ; many subjects, notably that on Gonorrhea, have been rewritten and much new material has been added throughout the book. With a view to better illustration of the subjects con- sidered, a number of new cuts have been introduced and a series of handsome colored lithographic plates. This revision has enhanced the practical value of the work and enormously increased its field of usefulness. " There are few books which approach it in clearness, and for thorough adaptation to students' needs it is without a peer in the language."— Journal of Cutaneous and Genito-Urinary Diseases. " We can commend this manual to the student as a help to him in his study of venereal dis- eases." — Liverpool Medico- Chirurgical Journal. "The best student's manual which has appeared on the subject." — St. Louis Medical and Surgical Journal. Digitized by Microsoft® OF W. B. SAUNDERS 6- CO. 17 The International Text-Book of Surgery. In Two Volumes. By American and British Authors. Edited by J. Collins Warren, M.D., LL.D., F.R.C.S. (Hon.), Professor of Surgery, Harvard Medi- cal School, Boston ; and A. Pearce Gould, M.S., F.R.C.S., Lecturer on Practical Surgery and Teacher of Operative Surgery, Middlesex Hospital Medical School, London, Eng. Vol. I. General Surgery. — Handsome octavo, 947 pages, with 458 beautiful illustrations and 9 lithographic plates. Vol. II. Special or Regional Surgery. — Handsome octavo, 1072 pages, with 471 beautiful illustrations and 8 lithographic plates. Sold by Subscription. Prices per volume : Cloth, $5.00 net ; Sheep or Half Morocco, $6.00 net. In presenting a new work on surgery to the medical profession the publisher feels that he need offer no apology for making an addition to the list of excellent works already in existence. Modern surgery is still in the transition stage of its development. The art and science of surgery are advancing rapidly, and the number of workers is now so great and so widely spread through the whole of the' civilized world that there is certainly room for another work of reference which shall be untrammeled by many of the traditions of the past, and shall at the same time present with due discrimi- nation the results of modern progress. There is a real need among practitioners and advanced students for a work on surgery encyclopedic in scope, yet so condensed in style and arrangement that the matter usually diffused through four or five volumes shall be given in one-half the space and at a correspondingly moderate cost. The aim of the editors has been to produce a reliable text-book of surgery embodying a clear but succinct statement of our present knowledge of surgical path- ology, symptomatology, and diagnosis, and such a detailed account of treatment as to form a reliable guide to modern practice. While not aiming at the merely novel, they have carefully omitted antiquated methods and they believe that the reader will find in these pages only what is practically useful to-day. The ever-widening field of surgery has been developed largely by special work, and this method of progress has made it practically impossible for one man to write authoritatively on the vast range of subjects embraced in a modern text-book of surgery. In order, therefore, to accomplish their object, the editors have sought the aid of men of wide experience and established reputation in the various depart- ments of surgery. They have been able, by means of careful scrutiny and editing of the manuscripts, to secure uniformity of standard and teaching. One of the most timely features of the work is the extended consideration given to Military, Naval, and Tropical Surgery. The treatment of these topics is based on the latest experiences of Military and Naval warfare, including that gained during the Spanish- American war and the present wars in the Philippines and in South Africa, and bringing the subject absolutely down to date. " It is the most valuable work on the subject that has appeared in some years. The clinician and the pathologist have joined hands in its production, and the result must be a satisfaction to the editors as it is a gratification to the conscientious reader." — Annals of Surgery . "This is a work which comes to us on its own intrinsic merits. Of the latter it has very many. The arrangement of subjects is excellent, and their treatment by the different authors is equally so. What is especially to be recommended is the painstaking endeavor of each writer to make his subject clear and to the point. To this end particularly is the technique of operations lucidly described in all necessary detail. And withal the work is up to date in a very remarkable degree, many of the latest operations in the different regional parts of the body being given in full details. There is not a chapter in the work from which the reader may not learn something new." — Medical Record, New York. Digitized by Microsoft® 18 MEDICAL PUBLICATIONS Jackson's Diseases of the Eye. A Manual of Diseases of the Eye. By Edward Jackson, A.M., M.D., Emeritus Professor of Diseases of the Eye in the Philadelphia Polyclinic and College for Graduates in Medicine. i2mo volume of 535 pages, with 178 beautiful illustrations, mostly from drawings by the author. Cloth, $2.50 net. Recently Issued. This book is intended to meet the needs of the general practitioner of medicine and the beginner in ophthalmology. More attention is given to the conditions that must be met and dealt with early in ophthalmic practice than to the rarer diseases and more difficult operations that may come later. It is designed to furnish efficient aid in the actual work of dealing with disease, and therefore gives the place of first importance to the recognition and management of the conditions present in actual clinical work. " It is truly an admirable work. . . . Written in a clear, concise manner, it bears evidence of the author's comprehensive grasp of the subject. The term ' multum in parvo ' is an appropri- ate one to apply to this work. It will prove of value to all who are interested in this branch of medicine." — Medical Record, New York. Jackson and Gleason's Diseases of the Eye, Nose, and Throat. Second Edition, Revised. [See Saunders' Question- Compends, page 37. J Jakob and Eshner — Atlas of Internal Medicine and Clinical Diagnosis. [See Saunders' Medical Hand-Atlases, page 34.J Jakob and Fisher— Atlas and Epitome of the Nervous System. [See Saunders' Medical Hand- Atlases, page 35.] Heating's Life Insurance. How to Examine for Life Insurance. By John M. Keating, M.D., Fellow of the College of Physicians of Philadelphia ; Vice-President of the American Paediatric Society ; Ex- President of the Association of Life Insurance Medical Directors. Royal octavo, 2 1 1 pages. With a plate prepared by Dr. McClellan from special dissections, and numerous other illustrations. Cloth, $2.00 net. Keen on the Surgery of Typhoid Fever. The Surgical Complications and Sequels of Typhoid Fever. By Wm W. Keen, M.D., LL.D., F.R.C.S. (Hon.), Professor of the Principles of Surgery and of Clinical Surgery, Jefferson Medical College, Phila- delphia ; Corresponding Member of the Societe de Chirurgie, Paris ; Honorary Member of the Societe Beige de Chirurgie, etc. Octavo volume of 386 pages, illustrated. Cloth, #3.00 net "This is probably the first and only work in the English language that gives the reader a clear view of what typhoid fever really is, and what it does and can do to the human organism. This book should be in the possession of every medical man in America." — American Medico- surgical Bulletin. Digitized by Microsoft® OF W. B. SAUNDERS & CO. 19 Keen's Operation Blank. Second Edition, Revised Form. An Operation Blank, with Lists of Instruments, etc., Required in Various Operations. Prepared by W. W. Keen, M.D., LL.D., F.R.C.S. ( Hon.), Professor of the Principles of Surgery and of Clini- cal Surgery in Jefferson Medical College, Philadelphia. Price per pad, blanks for fifty operations, 50 cts. net. Keen and White — An American Text-Book of Surgery. [See American Text-Book of Surgery, page 5.] Kyle on the Nose and Throat. Second Edition. Diseases of the Nose and Throat. By D. Braden Kyle, M.D., Clini- cal Professor of Laryngology and Rhinology, Jefferson Medical College, Philadelphia ; Consulting Laryngologist, Rhinologist, and Otologist, St. Agnes' Hospital. Octavo, 646 pages ; over 1 50 illustrations and 6 lithographic plates. Cloth, #4.00 net; Half Morocco, $5.00 net. This book presents the subject of Diseases of the Nose and Throat in as concise a manner as is consistent with clearness, keeping in mind the needs of the student and general practitioner as well as those of the specialist. The illustrations are particularly fine, being chiefly original. With the practical purpose of the book in mind, extended consideration has been given to details of treatment, each disease being considered in full, and definite courses being laid down to meet special conditions and symptoms. " It is a thorough, full, and systematic treatise, so classified and arranged as greatly to facili- tate the teaching of laryngology and rhinology, and must prove most convenient and satisfactory both for students and practitioners. " — International Medical Magazine. " A valuable guide for both the student and practitioner in all that pertains to diseases of the nose and throat. It is a practical book, and will be a valuable addition to the library of the gen- eral practitioner." — Chicago Medical Recorder. Laine's Temperature Chart. Temperature Chart. Prepared by D. T. Laine, M.D. Size 8x 13^ inches. A conveniently arranged Chart for recording Temperature, with columns for daily amounts of Urinary and Fecal Excretions, Food, Remarks, etc. On the back of each chart is given in full the method of Brand in the treatment of Typhoid Fever. Price, per pad of 25 charts, 50 cts. net. Leroy's Histology. The Essentials of Histology. By Louis Leroy, M.D., Professor of Histology and Pathology, Vanderbilt University, Nashville, Tennessee. l2mo. 225 pages, with 71 original illustrations. Cloth, gi.oo net. A New Volume in Saunders' Question-Compend Series. The object of this book is to collect within a limited space and in a convenient form the essential facts in histology. At the same time the author has endeavored not to sacrifice clearness and intelligibility to the necessities of condensation. While specially designed for students, the work will be useful to practitioners who desire to acquire in a short time sufficient histology to enable them understandingly to read pathology. The illustrations^j^h^vf Jujp/^ft^^^l and particularly fine. 20 MEDICAL PUBLICATIONS Levy and Klemperer's Clinical Bacteriology. The Elements of Clinical Bacteriology. By Dr. Ernst Levy, Pro- fessor in the University of Strassburg, and Felix Klemperer, Privat- docent in the University of Strassburg. Translated and edited by Augustus A. Eshner, M.D., Professor of Clinical Medicine in the Philadelphia Polyclinic. Octavo, 440 pages, fully illustrated. Cloth, $2.50 net. This book represents an attempt to group the results of bacteriological investiga- tion from a clinical point of view. Bacteriology has become more and more an indis- pensable aid to medical art. It has enlarged our comprehension of the nature of infectious diseases, and it has established their prophylaxis, diagnosis, and treatment upon a broader basis. The work aims to show how useful to the physician in his double capacity of counselor of the well and coadjutor of the sick are bacteriological thought and action. "The book is one with which every practitioner who desires to keep in touch with the advances of his profession should be familiar. " — New York Medical Journal. Lockwood's Practice o_f Medicine. A Manual of the Practice of Medicine. By George Roe Lockwood, M.D., Professor of Practice in the Woman's Medical College of the New York Infirmary, etc. 935 pages, with 75 illustrations in the text and 22 full-page plates. Cloth, $2.50 net. "Gives in a most concise manner the points essential to treatment usually enumerated in the most elaborate works." — Massachusetts Medical Journal. Long's Syllabus of Gynecology. A Syllabus of Gynecology, arranged in Conformity with " An Amer- ican Text-Book of Gynecology." By J. W. Long, M.D., Professor of Diseases of Women and Children, Medical College of Virginia, etc. Cloth, interleaved, $1.00 net. Macdonald's Surgical Diagnosis and Treatment. Surgical Diagnosis and Treatment. By. J. W. Macdonald, M.D. Edin., F.R.C.S., Edin., Professor of the Practice of Surgery and of Clinical Surgery in Hamline University ; Visiting Surgeon to St. Barnabas' Hospital, Minneapolis, etc. Handsome octavo, 800 pages,. fully illustrated. Cloth, $5.00 net ; Sheep or Half Morocco, $6.00 net. This work aims in a comprehensive manner to furnish a guide in matters of surgi- cal diagnosis. It sets forth in a systematic way the necessities of examinations and the proper methods of making them. The various portions of the body are then taken up in order and the diseases and injuries thereof succinctly considered and the treatment briefly indicated. Practically all the modern and approved operations are described with thoroughness and clearness. The work concludes with a chapter on the use of the Rbntgen rays in surgery. "A thorough and complete work on surgical diagnosis and treatment, free from padding, full of valuable material, and in accord with the surgical teaching of the day." — The Medical News New York. "The work is brimful of just the kind of practical information that is useful alike to students- and practitioners. It is a pleasure to commend the book because of its intrinsic value to the medi- cal practitioner." — Cincinnati Lqticet-£linic.. ... *.^ v Digiuzea by Microsoft® OF W. B. SAUNDERS &> CO. 21 Mallory and Wright's Pathological Technique. Pathological Technique. A Practical Manual for Laboratory Work in Pathology, Bacteriology, and Morbid Anatomy, with chapters on Post-Mortem Technique and the Performance of Autopsies. By Frank B. Mallory, A.M., M.D., Assistant Professor of Pathology, Harvard University- Medical School, Boston; and James H. Wright, A.M., M.D., Instructor in Pathology, Harvard University Medical School, Boston. Octavo, 396 pages, handsomely illustrated. Cloth, $2.50 net. This book is designed especially for practical use in pathological laboratories, both as a guide to beginners and as a source of reference for the advanced. The book will also meet the wants of practitioners who have opportunity to do general path- ological work. Besides the methods of post-mortem examinations and of bacterio- logical and histological investigations connected with autopsies, the special methods employed in clinical bacteriology and pathology have been fully discussed. " I have been looking forward to the publication of this book, and I am glad to say that I find it to be a most useful laboratory and post-mortem guide, full of practical information and well up to date." — William H. Welch, Professor of Pathology, Johns Hopkins University. " One of the most complete works on the subject, and one which should be in the library of every physician who hopes to keep pace with the great advances made in pathology." — Journal of the American Medical Association. Martin's Minor Surgery, Bandaging, and Ven- ereal Diseases. Second Edition, Revised. [See Saunders' Question-Compends, page 37.] Martin's Surgery. Seventh Edition. Revised. [See Saunders' Question-Compends, page 37.] McFarland's Pathogenic Bacteria. Text-Book upon the Pathogenic Bacteria. By Joseph McFarland, M.D., Professor of Pathology and Bacteriology in the Medico- Chirurgical College of Philadelphia, etc. Octavo volume of 621 pages, finely illustrated. Cloth, $3.25 net. Third Edition, Increased in Size by Over 100 Pages. Since the work first appeared, extensive progress has been made in the subjects of which it treats, making it necessary to materially increase the size of the book. The matter upon Infection and Immunity has been entirely rewritten ; other new chapters appear here and there, and much of the substance of the book has been altered or recast. The principal changes will be found where the advances have been most rapid —that is, under Tuberculosis, Diphtheria, Tetanus, Plague, etc. Much new matter has been added to the Technic of Bacteriology. " It is excellently adapted for the medical students and practitioners for whom it is avowedly written. . . . The descriptions given are accurate and readable, and the book should prove useful to those for whom it is written." — London Lancet. "The author has succeeded admirably in presenting the essential details of bacteriological technics, together with a judiciously chosen summary of our present knowledge of pathogenic bac- teria. . '. . The work, we think, should have a wide circulation among English-speaking students of medicine." — New York Medical Journal. " It may be looked upon as an exceedingly comprehensive and well thought-out manual from which to study the morphology a ^ff ; 1 fg^f^ h ^g^°gg)^ acteria -" — BriHsh Medical Journal. 22 MEDICAL PUBLICATIONS Meigs on Feeding in Infancy. Feeding in Early Infancy. By Arthur V. Meigs, M.D. Bound in limp cloth, flush edges, 25 cts. net. Moore's Orthopedic Surgery. A Manual of Orthopedic Surgery. By James E. Moore, M.D., Pro- fessor of Orthopedics and Adjunct Professor of Clinical Surgery, Uni- versity of Minnesota, College of Medicine and Surgery. Octavo volume of 356 pages, handsomely illustrated. Cloth, $2.50 net. A practical book based upon the author's experience, in which special stress is laid upon early diagnosis and treatment such as can be carried out by the general practitioner. The teachings of the author are in accordance with his belief that true conservatism is to bq found in the middle course between the surgeon who operates too frequently and the orthopedist who seldom operates. " A most attractive work. The illustrations and the care with which the book is adapted to the wants of the general practitioner and the student are worthy of great praise." — Chicago Medi- cal Recorder. "A very demonstrative work, every illustration of which conveys a lesson. The work is a most excellent and commendable one, which we can certainly endorse with pleasure." — St. Louis Medical and Surgical Journal. Morris's Materia Medica and Therapeutics. Fifth Edition, Revised. [See Saunders' Question- Compends, page 37. 1 Morris, Wolff, and Powell's Practice of Medi- cine. Third Edition, Revised. [See Saunders' Question- Compends, page 37.J Morten's Nurses' Dictionary. Nurses' Dictionary of Medical Terms and Nursing Treatment. Con- taining Definitions of the Principal Medical and Nursing Terms and Abbreviations ; of the Instruments, Drugs, Diseases, Accidents, Treat- ments, Operations, Foods, Appliances, etc., encountered in the ward or in the sick-room. By Honnor Morten, author of " How to Become a Nurse," etc. i6mo, 140 pages. Cloth, $1.00 net. Mracek and Bangs— Atlas of Syphilis and the Venereal Diseases. [See Saunders' Medical Hand-Atlases, page 34.J Mracek and Stelwagon— Atlas of Diseases of the Skin. [See Saunders' Medical Hand-Atlases, page 34.J Nancrede's Anatomy. Sixth Edition. Thoroughly Revised. [See Saunders' Question- Compends, paee 3 7 1 Digitized by Microsoft® b J/ J OF W. B. SAUNDERS & CO. 23 Nancrede's Anatomy and Dissection. Fourth Edition. Essentials of Anatomy and Manual of Practical Dissection. By Charles B. Nancrede, M.D., LL.D., Professor of Surgery and of Clinical Surgery, University of Michigan, Ann Arbor. Post-octavo, 500 pages, with full-page lithographic plates in colors and nearly 200 illustrations. Extra Cloth (or Oilcloth for dissection-room), $2.00 net. Nancrede's Principles of Surgery. Lectures on the Principles of Surgery. By Chas. B. Nancrede, M.D., LL.D., Professor of Surgery and of Clinical Surgery, University of Michigan, Ann Arbor. Octavo, 398 pages, illustrated. Cloth, $2. 50 net. The present book is based on the lectures delivered by Dr. Nancrede to his under- graduate classes, and is intended as a text-book for students and a practical help for teachers. By the careful elimination of unnecessary details of pathology, bacteriology, etc., which are amply provided for in other courses of study, space is gained for a more extended consideration of the Principles of Surgery in themselves, and of the application of these principles to methods of practice. " The author is deserving of the highest praise for the manner in which the subject has been presented. The work is written in a scientific spirit, and presents each subject in the light of the most recent scientific investigations. . . . Should be of inestimable value not only to the student of to-day but to the graduate of past years." — American Journal of the Medical Sciences. " The subject is treated on the most recent lines of scientific research ; the facts. are impressively presented and the practical side is always well in touch with the theory." — Annals of Surgery. Norris— American Text-Book of Obstetrics. [See American Text-Book of Obstetrics, page 4.] Norris's Syllabus of Obstetrics. Third Edition, Revised. Syllabus of Obstetrical Lectures in the Medical Department of the University of Pennsylvania. By Richard C. Norris, A.M., M.D., Instructor in Obstetrics and Lecturer on Clinical and Operative Obstetrics, University of Pennsylvania. Crown octavo, 222 pages. Cloth, interleaved for notes, $2.00 net. Ogden on the Urine. Just issued. Clinical Examination of the Urine and Urinary Diagnosis. A Clinical Guide for the Use of Practitioners and Students of Medicine and Surgery. By J. Bergen Ogden, M.D., Instructor in Chemistry, Harvard Medical School ; Assistant in Clinical Pathology, Boston City Plospital. Handsome octavo, 416 pages, with 54 illustrations and a number of colored plates. Cloth, $3.00 net. The design of this work is to present in as concise a manner as possible the chem- istry of the urine and its relation to physiologic processes ; the most approved work- ing methods, both qualitative and quantitative ; the diagnosis of diseases and disturb- ances of the kidneys and urinary passages. In addition to chemic and microscopic methods, which have been described in detail, special attention has been paid to diag- nosis, including our present knowledge of the character of the urine, the diagnosis and differentiation of diseases of the kidneys and urinary passages ; an enumeration of the prominent clinical symptoms of each disease ; and, finally, the peculiarities of the urine in certain general diseases of the body. Digitized by Microsoft® 24 MEDICAL PUBLICATIONS Penrose's Diseases of Women. Third Edition, Revised. A Text-Book of Diseases of Women. By Charles B. Penrose, M.D., Ph.D., formerly Professor of Gynecology in the University of Penn- sylvania ; Surgeon to the Gynecean Hospital, Philadelphia. Octavo volume of 531 pages, handsomely illustrated. Cloth, $3.75 net. In this work, which has been written for both the student of gynecology and the general practitioner, the author presents the best teaching of modern gynecology untrammeled by antiquated theories or methods of treatment. In most instances but one plan of treatment is recommended, to avoid confusing the student or the phy- sician who consults the book for practical guidance. "I shall value very highly the copy of Penrose's 'Diseases of Women' received. I have already recommended it to my class as THE BEST book." — Howard A. Kelly, Professor of Gynecology and Obstetrics, Johns Hopkins University, Baltimore, Md. " Although we have already called attention to its peculiar value as a practical hook for the student, we feel that the new edition should not be dismissed without further commendation. . . . We can only reaffirm our belief that Dr. Penrose has rendered a distinct service to his generation by giving us what approaches very closely to the ideal text-book. We predict that its superiority will be recognized by teachers as well as students. ' ' — American Journal of the Medical Sciences. Powell's Diseases erf Children, second Edition. [See Saunders' Question-Compends, page 3 7. J Pryor — Pelvic Inflammations. The Treatment of Pelvic Inflammations through the Vagina. By W. R. Pryor, M.D., Professor of Gynecology in New York Polyclinic. i2mo, 248 pages, handsomely illustrated. Cloth, $2.00 net. " This subject, which has recently been so thoroughly canvassed in high gynecological circles, is made available in this volume to the general practitioner and student. Nothing is too minute for mention and nothing is taken for granted ; consequently the book is of the utmost value. The illus- trations and the technique are beyond criticism." — Chicago Medical Recorder. Pye's Bandaging. Elementary Bandaging and Surgical Dressing. With Directions con- cerning the Immediate Treatment of Cases of Emergency. For the use of Dressers and Nurses. By Walter Pye, F.R.C.S., late Surgeon to St. Mary's Hospital, London. Small i2mo, with over 80 illustra- tions. Cloth, flexible covers, 75 cts. net. Pyle's Personal Hygiene, just issued. A Manual of Personal Hygiene. Proper Living upon a Physiologic Basis. Edited by Walter L. Pyle, M.D., Assistant Surgeon to the Wills Eye Hospital, Philadelphia. Octavo volume of 344 pages, fully illustrated. Cloth, $1.50 net. The object of this manual is to set forth plainly the best means of developing and maintaining physical and mental vigor. It represents a thorough exposition of living upon a physiologic basis. There are chapters upon the hygiene of the digestive appa- ratus, the skin and its appendages, the vocal and respiratory apparatus, eye, ear, brain, and nervous system, and a chapter upon exercise. The book is the conjoint work of several well-known American physicians and medical teachers, each writing upon a subject to which he has given special study, thus assuring for the book an originality and authority not possessed hv any similar treatise. „ n OF W. B. SAUNDERS S* CO. 25 Raymond's Physiology. A Manual of Physiology. By Joseph H. Raymond, A.M., M.D., Professor of Physiology and Hygiene and Lecturer on Gynecology in the Long Island College Hospital ; Director of Physiology in the Hoagland Laboratory, etc. 382 pages, with 102 illustrations in the text and 4 full-page colored plates. Cloth, $1.25 net. "Extremely well gotten up, and the illustrations have been selected with care. The text is fully abreast with modern physiology." — British Medical Journal. Salinger and Kalteyer's Modern Medicine. Modern Medicine. By Julius L. Salinger, M.D., Demonstrator of Clinical Medicine, Jefferson Medical College, and F. J. Kalteyer, M.D., Assistant Demonstrator of Clinical Medicine, Jefferson Medical College. Handsome octavo, 801 pages, illustrated. Cloth, $4.00 net. Just Issued. This is a work for students and practitioners, in which internal medicine is con- sidered in relation to etiology, symptomatology, pathology, diagnosis, and treatment, especial prominence being given to practical methods in the examination of blood, sputum, gastric secretions, and urine, and to methods of physical diagnosis. In the present era the practice of medicine includes the study of a number of these special- ties, so that it has frequently been necessary for the student to procure separate books upon these topics. For this reason it has appeared advisable for the authors to include in the volume, as far as possible, the essentials of these branches as applied to Clinical Medicine. The matter represents the very latest approved knowledge in the various departments, the newest works in English, French, and German having been consulted throughout the preparation of the book. Saundby's Renal and Urinary Diseases. Lectures on Renal and Urinary Diseases. By Robert Saundby, M.D. Edin., Fellow of the Royal College of Physicians, London, and of the Royal Medico-Chirurgical Society ; Professor of Medicine in Mason College, Birmingham, etc. Octavo volume of 434 pages, with numer- ous illustrations and 4 colored plates. Cloth, $2.50 net. Saunders* Pocket Medical Formulary, sixth Edition, Revised. By William M. Powell, M.D., Author of " Essentials of Diseases of Children " ; Member of Philadelphia Pathological Society. Con- taining 1844 formulae from the best-known authorities. With an Appendix containing Posological Table, Formulae and Doses for Hypodermic Medication, Poisons and their Antidotes, Diameters of the Female Pelvis and Fetal Head, Obstetrical Table, Diet List for Various Diseases, Materials and Drugs used in Antiseptic Surgery, Treatment of Asphyxia from Drowning, Surgical Remembrancer, Tables of Incompatibles, Eruptive Fevers, etc., etc. Handsomely bound in flexible morocco, with side index, wallet, and flap. $2.00 net. New Edition, Enlarged by Over 200 New Formulae. " This little book, that can be conveniently carried in the pocket, contains an immense amount of material It is very useful, and, as the name of the author of each prescription is given, is unu- sually reliable."-^*/ ^fe^. Microsoft@ 26 MEDICAL PUBLICATIONS Sayre's Pharmacy. Second Edition, Revised. [See Saunders' Question-Compends, page 37.] Schaeffer and Edgar— Atlas of Obstetrical Diag- nosis and Treatment. [See Saunders' Medical Hand-Atlases, page 35.] Schaeffer and Norris— Atlas of Obstetrics. [See Saunders' Medical Hand-Atlases, page 3 5. J Scudder's Fractures. Second Edition, Revised. The Treatment of Fractures. By Chas. L. Scudder, M.D., Assistant in Clinical and Operative Surgery, Harvard Medical School. Octavo, 433 P a g es > w i tn nearly 600 original illustrations. Polished Buckram, $4.50 net ; Half Morocco, $5.50 net. First Edition (2500 Copies) Exhausted in Five Months. This book is intended to serve as a guide to the practitioner and student in the treatment of fractures of bones, being a practical statement of the generally recognized methods of dealing with fractures. The attention of the student" is diverted from theories to the actual conditions that exist iii fractured bones, and he is encouraged to determine for himself how to meet the conditions found in each individual case. Methods of treatment are described in minute detail, and the reader is not only told, but is shown, how to apply apparatus, for, .as far as possible, all the details are illus- trated. This elaborate and complete series of illustrations constitutes a feature of the book. There are nearly 600 of them, all from new and original drawings and repro- duced in the highest style of art. "It is in the highest degree practical. Too much credit cannot be given to the author for the care which he has taken to describe the methods of examination and treatment so exactly as to enable the practitioner to understand them without difficulty. The illustrations are abundant and the text clear ; the methods given are elaborately illustrated and explained. This makes the work particularly valuable to the general practitioner." — University Medical Magazine. " This admirably illustrated and carefully written work furnishes one of the best guides with which we are familiar in the management of the accidents that fall within the range of this difficult branch of surgery." — Chicago Medical Recorder. "The work produces a favorable impression by the general manner in which the subject is treated. Its descriptions are concise and clear and the treatment sound. The physical examination of the injured part is well described, and . . the method of making these examinations is illustrated by a liberal use of cuts."— American Journal of the Medical Sciences. " The present work covers the ground admirably. . . . The text is excellent and the illustrations are accurate. . . . This treatise expresses the idea of a clear-thinking worker in a most interesting field of surgery." — New York Medical Journal. Senn's Genito-Urinary Tuberculosis. Tuberculosis of the Genito-Urinary Organs, Male and Female. By Nicholas Senn, M.D., Ph.D., LL.D., Professor of the Practice of Surgery and of Clinical Surgery, Rush Medical College, Chicago. Handsome octavo volume of 320 pages, illustrated. Cloth, $3.00 net. "An important book upon an important subject, and written by a man of mature judgment and wide experience. The author has given us an instructive book upon one of the most important subjects of the day." — Clinical Reporter. "A work which adds another to the many obligations the profession owes the talented author." Chicago Medical Recorder. Digitized by Microsoft® OF W. B. SAUNDERS &■> CO. 27 Senn's Practical Surgery. Practical Surgery. By Nicholas Senn, M.D., Ph.D., LL.D., Pro- fessor of the Practice of Surgery and of Clinical Surgery, Rush Medi- cal College, Chicago. Handsome octavo volume of 800 pages, profusely illustrated. In Press. This book deals with practical subjects, and is intended for the general practi- tioner, special attention being paid to emergency surgery. Shock, hemorrhage, and wound treatment are fully considered, and a complete account is given of gunshot wounds and their treatment. All emergency operations that come under the care of the general practitioner are described in detail and fully illustrated. The experimental work of the author has been utilized whenever it was deemed necessary to serve as a basis for new methods of practice. The section on Military Surgery is based on the author's experience as chief of the operating staff with the army in the field during the Spanish-American War, and on his observations during the Greco-Turkish War. Intestinal Surgery is given a prominent place, and the consid- eration of this subject is the result of the clinical experience of the author as surgeon and teacher of surgery for a quarter of a century. Senn's Syllabus o_f Surgery. A Syllabus of Lectures on the Practice of Surgery, arranged in con- formity with " An American Text-Book of Surgery." By Nicholas Senn, M.D., Ph.D., LL.D., Professor of the Practice of Surgery and of Clinical Surgery in Rush Medical College, Chicago. Cloth, $1.50 net " The author has evidently spared no pains in making his Syllabus thoroughly comprehensive, and has added new matter and alluded to the most recent authors and operations. Full references are also given to all requisite detail s of surgical anatomy and pathology. ' ' — British Medical Journal. Senn's Tumors. Second Edition, Revised. Pathology and Surgical Treatment of Tumors. By N. Senn, M.D., Ph.D., LL.D., Professor of Surgery and of Clinical Surgery, Rush Medical College ; Professor of Surgery, Chicago Polyclinic ; Attend- ing Surgeon to Presbyterian Hospital ; Surgeon-in-Chief, St. Joseph's Hospital, Chicago. Second Edition, Thoroughly Revised. Octavo vol- ume of 718 pages, with 478 illustrations, including 12 full-page plates in colors. Prices : Cloth, $5.00 net ; Sheep or Half Morocco, $6.00 net. In the present edition the text has been carefully revised and many additions have been made. A new section has been added on Sarcoma of the Decidua. Many of the old illustrations have been eliminated, and are replaced by others intended to explain more satisfactorily the subjects they represent. Most of the new illustrations are original. "The most exhaustive of any recent book in English on this subject. It is well illustrated, and will doubtless remain as the principal monograph on the subject in our language for some years. The book is handsomely illustrated and printed, and the author has given a notable and lasting contribution to surgery ." —Journal of the American Medical Association. "Altogether it is a broad book, full of interesting facts, eminently sound in its pathology, and founded on an exceptionally large experience of a conscientious and painstaking observer." — Medical Record, New York. Shaw's Nervous Diseases and Insanity. Third Edition, Revised. [See Saundprs' Question- Comp ends, page 37.J L Digitized by Microsoft® 28 MEDICAL PUBLICATIONS Starr — American Text-Book of Diseases of Children. [See American Text-Book of Diseases of Children, page 3.] Starr's Diets for Infants and Children. Diets for Infants and Children in Health and in Disease. By Louis Starr, M.D., Editor of "An American Text-Book of the Diseases of Children." 230 blanks (pocket-book size), perforated and neatly- bound in flexible morocco. $1-25 net. Stelwagon's Diseases of the Skin. Fourth Edition, Revised. [See Saunders' Question-Compends, page 3 7. J Stengel's Pathology. Third Edition, Thoroughly Revised. A Text-Book of Pathology. By Alfred Stengel, M.D., Professor of Clinical Medicine in the University of Pennsylvania ; Visiting Physician to the Pennsylvania Hospital ; Physician to the Philadelphia Hospital, etc. Handsome octavo, 873 pages, nearly 400 illustrations, many in colors. Cloth, $5.00 net ; Sheep or Half Morocco, $6.00 net. In this work the practical application of pathological facts 1o clinical medicine is considered more fully than is customary in works on pathology. While the subject of pathology is treated in the broadest way consistent with the size of the book, an effort has been made to present the subject from the point of view of the clinician. The general relations of bacteriology to pathology are discussed at considerable length, as the importance of these branches deserves. The pathology of individual organs and tissues is treated systematically and quite fully under subheadings that clearly indicate the subject-matter to be found on each page. The present edition has been thor- oughly revised with the intention of bringing the subject-matter up to date and ampli- fying the sections on Pathologic Physiology. The favorable reception of previous editions has convinced the author that his purpose of supplying a moderate-sized book on clinical pathology has found favor with the profession. " I consider the work abreast of modern pathology, and useful to both students and practi- tioners. It presents in a concise and well-considered form the essential facts of general and special pathological anatomy, with more than usual emphasis upon pathological physiology." — William H. Welch, Professor of Pathology, Johns Hopkins University, Baltimore, Md. " This volume is intended to present the subject of pathology in as practical a form as possible, and especially from the point of view of the clinical pathologist. These objects have been faithfully carried out and a valuable text-book is the result. Taking the book as a whole we can most favor- ably recommend it to our readers as a thoroughly practical work on clinical pathology." — The Lon- don Lancet. "The outcome of the effort is a source of satisfaction and congratulation. The work is in every way to be cordially commended." — Philadelphia Medical Journal. Stengel and White on the Blood. The Blood in its Clinical and Pathological Relations. By Alfred Stengel, M.D., Professor of Clinical Medicine, University of Penn- sylvania ; and C. Y. White, Jr., M.D., Instructor in Clinical Medi- cine, University of l^^ d ^ jcrosom In Press. OF W. B. SA UNDERS & CO. 29 Stevens' Materia Medica and Therapeutics, second Edition, Revised. A Manual of Materia Medica and Therapeutics. By A. A. Stevens, A.M., M.D., Lecturer on Physical Diagnosis in the University of Pennsylvania ; Professor of Pathology in the Woman's Medical Col- lege of Pennsylvania ; Physician to St. Agnes' Hospital. Post-octavo, 445 pages. Flexible Leather, $2.00 net. ' ' The author has faithfully presented modern therapeutics in a comprehensive work, and, while intended particularly for the use of students, it will be found a reliable guide and sufficiently comprehensive for the physician in practice.' ' — University Medical Magazine. Stevens* Practice of Medicine. Fifth Edition, Revised. A Manual of the Practice of Medicine. By A. A. Stevens, A.M., M.D., Lecturer on Physical Diagnosis in the University of Pennsyl- vania ; Professor of Pathology in the Woman's Medical College of Pennsylvania. Specially intended for students preparing for gradua- tion and hospital examinations. Post-octavo, 5 19 pages; illustrated. Flexible Leather, $2.00 net. "The frequency with which new editions of this manual are demanded bespeaks its popularity. It is an excellent condensation of the essentials of medical practice for the student, and may be found also an excellent reminder for the busy physician." — Buffalo Medical Journal. Stewart and Lawrance's Medical Electricity. [See Saunders' Question- Compends, page 37.] Stewart's Physiology. Fourth Edition, Revised. A Manual of Physiology, with Practical Exercises. For Students and Practitioners. By G. N. Stewart, M.A., M.D., D.Sc, lately Examiner in Physiology, University of Aberdeen, and of the New Museums, Cambridge University ; Professor of Physiology in the Western Reserve University, Cleveland, Ohio. Octavo volume of 894 pages ; 336 illustrations and 5 colored plates. Cloth, $3.75 net. In the present edition the book has been revised and in parts rewritten. A con- siderable amount of new matter has been added, especially to the chapter on The Central Nervous System. The additions in the other parts of the volume have been balanced, for the most part, by the omission of some passages and the abridgment of others, so that its bulk is only slightly increased. " It will make its way by sheer force of merit, and amply deserves to do so. It is one of the very best English text-books on the subject." — London Lancet. "Of the many text-books of physiology published, we do not know of one that so nearly comes up to the ideal as does Professor Stewart's volume." — British Medical Journal. Stoney's Materia Medica for Nurses. Materia Medica for Nurses. By Emily A. M. Stoney, Graduate of the Training-School for Nurses, Lawrence, Mass.; late Superintendent of the Training-School for Nurses, Carney Hospital, South Boston, Mass. Handsome octavo volume of 306 pages. Cloth, $ 1.50 net. "So far as we can see, it contains about everything that a nurse ought to know in regard to drugs. As a reference -book for nurses, it will, without question, be very useful." —Journal of the American Medical Association. Digitized by Microsoft® 30 MEDICAL PUBLICATIONS Stoney's Nursing. Second Edition, Revised. Practical Points in Nursing. For Nurses in Private Practice. By Emily A. M. Stoney, Graduate of the Training-School for Nurses, Lawrence, Mass.; late Superintendent of the Training-School for Nurses, Carney Hospital, South Boston, Mass. 456 pages, illustrated with 73 engravings in the text and 8 colored and half-tone plates. Cloth, #1.75 net. In this volume the author explains, in popular language and in the shortest pos- sible form, the entire range of private nursing as distinguished from hospital nursing, and the nurse is instructed how best to meet the various emergencies of medical and surgical cases when distant from aid or when thrown on her own resources. An especially valuable feature of the work will be found in the directions to the nurse how to improvise everything ordinarily needed in the sick-room. The Appendix contains much information in compact form that will be found of great value to the nurse, including Rules for Feeding the Sick ; Recipes for Invalid Foods and Beverages ; Tables of Weights and Measures ; List of Abbreviations ; Dose-List ; and a complete Glossary of Medical Terms and Nursing Treatment. " There are few books intended for non-professional readers which can be so cordially endorsed by a medical journal as can this one." — Therapeutic Gazette. " This is a well-written, eminently practical volume, which covers the entire range of private nursing as distinguished from hospital nursing, and instructs the nurse how best to meet the various emergencies which may arise, and how to prepare everything ordinarily needed in the illness of her patient." — American Journal of Obstetrics and Diseases of Women and Children. Stoney's Surgical Technic for Nurses. Bacteriology and Surgical Technic for Nurses. By Emily A. M. Stoney, late Superintendent of the Training-School for Nurses, Carney Hospital, South Boston, Mass. 1 2mo volume, fully illustrated. Cloth, $1.25 net. Just Issued. This work is intended as a modern text-book of Surgical Nursing both in hospital and private practice. The first part of the book is devoted to Bacteriology and Anti- septics ; the second part to Surgical Technic, Signs of Death, and Autopsies. The matter in the book is presented in an attractive and practical form, and it will doubt- less prove of distinct value to all nurses who are called upon to attend surgical cases. Thomas's Diet Lists. Second Edition, Revised. Diet Lists and Sick-Room Dietary. By Jerome B. Thomas, M.D., Visiting Physician to the Home for Friendless Women and Children and to the Newsboys' Home; Assistant Visiting Physician to the Kings County Hospital. Cloth, $1.25 net. Send for sample sheet. " This book will save the practitioner a great deal of work, and be distinctly to his advantage."— Journal of the American Medical Association. "The collection of diet-lists and the accompanying sick-room dietary is a convenience that will be appreciated by every physician." — New York Medical Journal. Thornton's Dose-Book and Prescription-Writing. Dose-Book and Manual of Prescription-Writing. By E. Q. Thorn- ton, M.D., Demonstrator of Therapeutics, Jefferson Medical College, Philadelphia. 334 pages, illustrated. Cloth, #1.25 net. " Full of practical suggestions ; will take its place in the front rank of works of this sort "— Medical Record, New York. Digitized by Microsoft® OF W. B. SAUNDERS & CO. 31 Van Valzah and Nisbet's Diseases of the Stomach. Diseases of the Stomach. By William W. Van Valzah, M.D., Pro- fessor of General Medicine and Diseases of the Digestive System and the Blood, New York Polyclinic ; and J. Douglas Nisbet, M.D., Adjunct Professor of General Medicine and Diseases of the Digestive System and the Blood, New York Polyclinic Octavo volume of 674 pages, illustrated. Cloth, $3.50 net. An eminently practical book, intended as a guide to the student, an aid to the physician, and a contribution to scientific medicine. It aims to give a complete description of the modern methods of diagnosis and treatment of diseases of the stomach, and to reconstruct the pathology of the stomach in keeping with the revelations of scientific research. The book is clear, practical, and complete, and contains the results of the authors' investigations and their extensive experience as specialists. Particular attention is given to the important subject of dietetic treatment. The diet-lists are very complete, and are so arranged that selections can readily be made to suit individual cases. "This is the most satisfactory work on the subject in the English language." — Chicago Medi- cal Recorder. " The article on diet and general medication is one of the most valuable in the book, and should be read by every practising physician." — New York Medical Journal. " Its chief claim lies in its clearness and general adaptability to the practical needs of the gen- eral practitioner or student. In these relations it is probably the best of the recent special works on diseases of the stomach." — Chicago Clinical Review. Vecki's Sexual Impotence. The Pathology and Treatment of Sexual Impotence. By Victor G. Vecki, M.D. From the second German edition, revised and enlarged. Demi-octavo, 291 pages. Cloth, $2.00 net. Vierordt's Medical Diagnosis. Fourth Edition, Revised. Medical Diagnosis. By Dr. Oswald Vierordt, Professor of Medi- cine at the University of Heidelberg. Translated, with additions, from the fifth enlarged German edition, with the author's permission, by Francis H. Stuart, A.M., M.D. Handsome royal octavo volume of 603 pages ; 194 fine wood-cuts in text, many of them in colors. Cloth, $4.00 net; Sheep or Half Morocco, $5.00 net. In this work, as in no other hitherto published, are given full and accurate expla- nations of the phenomena observed at the bedside. It is distinctly a clinical work by a master teacher, characterized by thoroughness, fullness, and accuracy. It is a mine of information upon the points that are so often passed over without explanation. Es- pecial attention has been given to the germ-theory as a factor in the origin of disease. In the present edition of this highly successful work many alterations have been made, especially in the sections on Gastric Digestion and the Nervous System. It will be found that all the qualities which served to make the earlier editions so acceptable have been developed with the evolution of the work to its present form. " Rarely is a book published with which a reviewer can find so little fault as with the volume before us. Each particular item in the consideration of an organ or apparatus, which is necessary to determine a diagnosis of any disease of that organ, is mentioned ; nothing seems forgotten. The chapters on diseases of the circulatory and digestive apparatus and nervous system are especially full and valuable. The reviewer would repeat that the book is one of the best — probably the best- which has fallen into his hands."; 32 MEDICAL PUBLICATIONS Watson's Handbook _for Nurses. A Handbook for Nurses. By J. K. Watson, M.D. Edin. American Edition, under supervision of A. A. Stevens, A.M., M.D., Lecturer on Physical Diagnosis, University of Pennsylvania. i2mo, 413 pages, 73 illustrations. Cloth, $1.50 net. This work aims to supply in one volume that information which so many nurses at the present time are trying to extract from various medical works, and to present that information in a suitable form. Nurses must necessarily acquire a certain amount of medical knowledge, and the author of this book has aimed judiciously to cater to this need with the object of directing the nurses' pursuit of medical information in proper and legitimate channels. " The intelligent nurse will find this a most convenient manual, and there are many things in it that the physician might find of use. In recommending text-books to nurses it could be put in the first rank." — Journal of the American Medical Association. Warren's Surgical Pathology. Second Edition. Surgical Pathology and Therapeutics. By John Collins Warren, M.D., LL.D., F.R.C.S. (Hon.), Professor of Surgery, Harvard Medical School. Handsome octavo, 873 pages; 136 relief and lithographic illustrations, 33 in colors. With an Appendix on Scientific Aids to Surgical Diagnosis and a series of articles on Regional Bacteriology. Cloth, $5.00 net; Sheep or Half Morocco, $6.00 net. In the second edition of this book all the important changes have been embodied in a new Appendix. In this new chapter the author has aimed to present in as practical a manner as possible the resources of surgical pathology. In addition to an enumera- tion of the scientific aids to surgical diagnosis, there is presented a series of sections on regional bacteriology, in which are given a description of the flora of the affected part, and the general principles of treating the affections they produce, based upon the views of the best authorities. " It is the handsomest specimen of book-making . . . that has ever been issued from the American medical press." — American Journal of the Medical Sciences, Philadelphia. " A most striking and very excellent feature of this book is its illustrations. Without excep- tion, from the point of accuracy and artistic merit, they are the best ever seen in a work of this kind. Many of those representing microscopic pictures are so perfect in their coloring and detail as almost to give the beholder the impression that he is looking down the barrel of a microscope at a well-mounted section." — Annals of Surgery. Wilson — American Text-Book of Applied Thera- peutics. [See American Text-Book of Applied Therapeutics, page 3. J Wolff on Examination o_f Urine. [See Saunders' Question- Compends, page 37.I Wolff's Medical Chemistry. Fifth Edition, Revised. [See Saunders' Question-Compends, page 3 7. J Zuckerkandl and DaCosta — Atlas of Operative Surgery. TSee Saunders' Medical Hand-Atlases, page 34. 1 L Digitized by Microsoft® '* s ^ J Saunders' Medical Hand-Atlases. The series of books included under this title surpass any similar volumes ever published for scientific accuracy, picto- rial beauty, compactness, and cheapness. f, t « Each volume contains from Colored 50 to 100 colored plates, Plates. besides numerous illustra- tions in the text. The col- ored plates have been executed by the most skillful German lithographers, in some cases more than twenty impressions being required to obtain the desired result. Each plate is accompanied by a full and appropriate description, and each book contains a condensed but adequate out- line of the subject to which it is devoted. One of the most valu- Substitute aD ' e features of these *«._ r^1i-»j—~1 atlases is that they for Clinical offer a ready an £ Observation, satisfactory substi- tute for clinical ob- servation. Such observation, of course, is available only to the residents in large medical centers ; and even then the req- uisite variety is seen only after long years of routine hospital work. To those unable to attend important clinics these books will be absolutely indispensable, as presenting in a complete and convenient form the most accurate reproductions of clinical work, interpreted by the most competent of clinical teachers. In planning this series of Moderate books arrangements were Price. made with representative publishers in the chief medical centers of the world for the pub- lication of translations of the atlases into nine different languages, the lithographic plates for all being made in Germany, where work of this kind has been brought to the greatest perfection. The enormous' expense of making the plates being shared by the various publishers, the cost to each one was reduced to practically one- tenth. Thus by reason of their universal translation and reproduction, affording international distribution, the publishers have been enabled to secure for these atlases the best artistic and professional talent, to produce them in the most elegant style, and yet to offer them at a price heretofore unapproached in cheapness. Four More During the past year, Saunders' Medical Languages. Hand-Atlases have been translated and published in four more languages — Dutch, Japanese, Roumanian, and Bohemian — so that now this remarkable series can be had in thirteen different languages, or practically every language of the civilized world. The various languages in which the volumes have appeared include Eng- lish, German, French, Italian, Russian, Spanish, Japanese, Dutch, Danish, Swed- ish, Roumanian, Bohemian, and Hunga- rian. Two years ago Mr. Fifty Saunders contracted tl „ j with the original pub- 1 iiuusana lisher for IOOO0O cop i e s Copies. of the twenty-six vol- umes that are to com- pose this series of books. Of these twen- ty-six volumes only_ ten have appeared, and yet 50,000 copies have already been imported. The volumes in this series are selling with remarkable rapidity, and there is every indication that over 100,000 copies will be sold of these ten volumes alone. Basing the sales of future numbers on those already issued, the prospects are that the original contract will be exceeded three times over, and that the sale of the complete series will reach at least 300,000 copies. On account of the marked favor with which these books have been received by the medical profession, and the enormous sales that they seem destined to reach, the publisher has been enabled to prepare and furnish special additional colored plates, making the series even handsomer and more complete than was originally intended. As an indication Adopted by the of the great prac- U. S. Army. t ' ca ^ va ' ue of the Atlases and of the immense favor with which they have been received, it should be noted that the Medi- cal Department of the U. S. Army has adopted the " Atlas of Operative Surgery " as its standard, and has ordered the book in large quantities for distribution to the various regiments and army posts. For list of volumes see next two pages. SPFCIAI ^ s '' ' s '""possible to realize the beauty of these Atlases without an opportunity to 2 _ examine them, we make the following offer : Any one of these books will be sent OFFER.. to physicians, postpaid, upon request. If you want the book, you have merely to remit the price ; if not, return the book by mail. Descriptive circular, containing sample plates, sent free on application to the publisher. Digitized by Microsoft® Saunders' Medical Hand-Atlases. VOLUMES NOW READY. Atlas and Epitome of Internal Medicine and Clinical Diag- nosis. By Dr. Chr. Jakob, of Erlangen. Edited by Augustus A. Eshner, M.D., Professor of Clinical Medicine, Philadelphia Polyclinic. 68 colored plates, 64 text-illustrations, 259 pages of text. Cloth, $3.00 net. "The charm of the book is its clearness, conciseness, and the accuracy and beauty of its illus- trations. It deals with facts. It vividly illustrates those facts. It is a scientific work put together for ready reference." — Brooklyn Medical Journal. Atlas of Legal Medicine. By Dr. E. R. von Hofmann, of Vienna. Edited by Frederick Peterson, M.D., Chief of Clinic, Nervous Dept, College of Physicians and Surgeons, New York. With 120 colored figures on 56 plates and 193 beautiful half-tone illustrations. Cloth, $3.50 net. "Hofmann's ' Atlas of Legal Medicine' is a unique work. This immense field finds in this book a pictorial presentation that far excels anything with which we are familiar in any other work. ' ' — Philadelphia Medical Journal. Atlas and Epitome of Diseases of the Larynx. By Dr. L. GrOnwald, of Munich. Edited by Charles P. Grayson, M.D., Physi- cian-in-Charge, Throat and Nose Department, Hospital of the University of Pennsylvania. With 107 colored figures on 44 plates, 25 text-illustra- tions, and 103 pages of text. Cloth, $2.50 net. •' Aided as it is by magnificently executed illustrations in color, it cannot fail of being of the greatest advantage to students, general practitioners, and expert laryngologists." — St. Louis Medi- cal and Surgical Journal. Atlas and Epitome of Operative Surgery. By Dr. O. Zucker- kandl, of Vienna. Edited by J. Chalmers DaCosta, M.D., Professor of Practice of Surgery and Clinical Surgery, Jefferson Medical College, Phila- delphia. With 24 colored plates, 217 text-illustrations, and 395 pages of text. Cloth, #3.00 net. " We know of no other work that combines such a wealth of beautiful illustrations with clearness and conciseness of language, that is so entirely abreast of the latest achievements, and so useful both for the beginner and for one who wishes to increase his knowledge of operative surgery." — Munchener medicinhche Wochenschrift. Atlas and Epitome of Syphilis and the Venereal Diseases. By Prof. Dr. Franz Mracek, of Vienna. Edited by L. Bolton Bangs, M.D., Professor of Genito-Urinary Surgery, University and Bellevue Hos- pital Medical College, New York. With 71 colored plates, 16 black-and- white illustrations, and 122 pages of text. Cloth, $3.50 net. "A glance through the book is almost like actual attendance upon a famous clinic." — Journal of the American Medical Association. " Atlas and Epitome of External Diseases of the Eye. By Dr. O. Haab, of Zurich. Edited by G. E. de Schweinitz, M.D., Professor of Ophthalmology, Jefferson Medical College, Philadelphia. With 76 colored illustrations on 40 plates and 228 pages of text. Cloth, $3.00 net. " It is always difficult to represent pathological appearances in colored plates, but this work seems to have overcome these difficulties, and the plates, with one or two exceptions, are absolutely satisfactory." — Boston Medical and Surgical Journal. Atlas and Epitome of Skin Diseases. By Prof. Dr. Franz Mracek, of Vienna. Edited by Henry W. Stelwagon, M.D., Clinical Professor of Dermatology, Jefferson Medical College, Philadelphia. With 63 colored plates, 39 half-tone illustrations, and 200 pages of text. Cloth, $3.50 net. "The importance of personal inspection of cases in the study of cutaneous diseases is readily appreciated, and next to the living subjects are pictures which will 'show the appearance of the disease under consideration. Altogether the work will be found of very great value to the general practitioner. ' ' —Journal of the ^fiffigfflffWUjffiggfi Saunders' Medical Hand-Atlases. VOLUMES JUST ISSUED. Atlas and Epitome of Special Pathological Histology. By Dr. H. Durck, of Munich. Edited by Ludvig Hektoen, M.D., Professor of Pathology, Rush Medical College, Chicago. In Two Parts. Part I. Just Ready, including the Circulatory, Respiratory, and Gastro-intestinal Tract, with 120 colored figures on 62 plates and 158 pages of text. Part II. Ready Shortly. Price of Part I., $3.00 net. Atlas and Epitome of Diseases Caused by Accidents. By Dr. Ed. Golebiewski, of Berlin. Translated and edited with additions by Pearce Bailey, M. 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