i\ -^^^« j^^"""" - JL. f H I SID LOGY ^^■^ '■w. 'J0\ »MiKlaaM<«>WM' "-Ibrary ^i™iMii]rriISi'IIff.',,.H3?""3' °' histolog olin,anx 3 1924 031 262 821 Cornell University Library The original of tiiis bool< is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924031262821 THE STUDENTS" Manual of Histology, FOR THE USE OF Students, Practitioners and Microscopists, Chas. H. StowelLj M. D., sistant Professot of Physiology and Histology, and the Instructor in the Physiological Laboratory of the University of Michigan. ILLUSTRATED BY ONE HUNDRED AND NINETY-TWO ENGRAVINGS. DETROIT: 1881. Entered according to the act of Congress, in the year i88r, by GEORGE S. DAVI^, In the Office of the Librarian of Congress, at Washington, D, C. PREFACE. HISTOLOGY has made such rapid advances within the past few years — not only regarding its place as a part of the science~of medicine, but also regarding the new facts discovered by working microscopists of both continents, — that a manual of this character, bringing the subject down to the present time, will, we trust, meet the wants, alike of the student, physician and microscopist. This manual is not intended to supercede either the large text- book of Strieker or the complete atlas of Klein or other similar works. While these works are necessary and invaluable to the teacher, yet it has been apparent to us for some years that they were altogether both too full and expensive to make them compan- ions of the student ; and now that our laboratories are so general that nearly every medical student studies the microscopic structures of the various tissues, even the admirable compend of Frey fails to supply the want, viz., necessary directions for preparing and preserving. We have endeavored, in this volume, to condense the descrip- tions as much as possible without injury to its completeness or accuracy. Of course there are many subjects concerning which our best students and writers materially differ, and as it would far exceed the limits of this work to engage in discussions, we have given in such cases, either those results most generally received or those to which most authority is attached, with, perhaps, the author's own particular views added. The ' laboratory work ' is, by no means, exhausted, nor is it even full. Those methods are given which are most familiar and which have proved the most satisfactory in our hands. '~^- So far as our knowledge goes these are the best methods known, yet others may be as good and it would not be surprising if some were found better. We have taken some care to discover who was the original owner of the drawings we have taken from other books. We have 3 PREFACE. found nearly everyone of them in several works and no credit given to anyone. When we were not positive, credit was given to to the author of the work in which the drawings were found. Credit should be given to Beale for figure 132. The re- maining drawings were all carefully and accurately made from specimens prepared by us, nearly all of which are now in our possession. We believe they can be fully relied upon as correct. The magnifying power used is given in each case, therefore when the size of any object is not given in the text it can be readily ascertained by dividing the size of the figure by the number of diameters it is magnified. The magnifying power was acertained by measuring the micrometer (Roger's) lines at ten inches from the eye-piece. The subject of the first chapter can be treated but briefly. To obtain anything like a complete knowledge of this subject it will be necessary to consult some of the following works: "Microscopical Technology," Dr. Carl Seller; "The Microscope and Microscopical Technology," Frey ; "How to use the Microscope," Beale. Our facilities for obtaining tumors have been ample, and their study has taken much of our time. .The illustrations given are from specimens of our own prepar- ing and they convey as accurate an idea as possible of the appear- ances of these growths as seen under the microscope. The concluding chapter on the principal starches is introduced because these grains are so frequently encountered in general work, and because the physician or microscopist is so often called upon to examine a specimen with reference to their presence. I am especially indebted to my former assistant. Dr. D. N.^De Tarr (now of the New York State Museum) for most valuable assist- ance both in the preparing and in the producing on paper of many of the specimens. For the neatness and tact displayed in the production of the book we all are alike grateful to the publisher. Chas. H. Stowbll. " physiological l abob atory, " Univbiisity of Michigan. March, 1881. CONTENTS. Preface, 3 CHAPTKR I. The Microscope, ii CHAPTER II. The Amoeba and the Cell, 29 CHAPTER III. Blood, 38 CHAPTER IV. Epithelium and Hair, 62 CHAPTER V. Connective-tissue Group, 73 CHAPTER VI. Teeth, go CHAPTER VII. Muscle, 98 CHAPTER VIII. Blood-vessels, 112 CHAPTER IX. The Respiratory Passages, 121 CHAPTER X. The Salivary Glands and the Pancreas, 130 5 INDEX. CHAPTER XI. The Pharynx, CEsophagus, Stomach and Intestine, 134 CHAPTER XII. The Liver, 144 CHAPTER XIII. The Kidney, 151 CHAPTER XIV. The Lymphatics, 162 CHAPTER XV. Nerve Fibres and their Modes of Termination, 173 CHAPTER XVI. The Spinal Cord, 186 CHAPTER XVII. The Brain, 196 CHAPTER, XVIII. Testicle and Ovar,y, 203 CHAPTER XIX. The Tongue, Skin, Lining of Nasal Cavity and the Ear, 214 CHAPTER XX. The Eye, 228 CHAPTER XXI. Tumors, 246 CHAPTER XXII. ' The Starches, 268 ILLUSTRATIONS. Fie. PAGE. 1. Compound Microscope 12 2. Eye-piece in Section 14 3. Objectives 15 4. Chromatic and Spherical Aberration 17 5. Eye-piece Micrometer 19 6. Camera Lucida 20 7. Turn-table 22 8. Microtome 23 9. Injecting Apparatus 27 10. Amoeba 30 11. Amoeba dividing 31 12. Human Ovum 32 13. Flattened, cylindrical and branched cells .- 33 14. Fully developed cell 83 15. Illustrating diminishing nuclei in cells 34 16. Pus in epithelial cells 35 17. An epithelial cell 36 18. Red blood-corpuscles of human embryo 41 ^9. Blood-cells from spleen pulp 42 20. Human blood 48 21. Blood corpuscles of man showing nuclei 51 22. Frog's blood 68 23. Relative sizes of corpuscles of different animals 56 24. Blood-crystals 57 25. Effect of reagents on blood 59 26. Pus 59 27. Ciliated epithelium and goblet cells 64 28. Epithelium from Intestine 65 39. Ciliated epithelium from uterus 67 30. Saliva 67 31. Pigmented epithelium 68 32. Epithelium from back of hand 68 33. Epithelium from the nail 69 34. Human hair 69 35. Cat's hair 70 36. Human hair sac 71 37. Transverse section of hair follicle 72 38. White fibrous and yellow elastic tissue 74 39. Connective-tissue cells 75 40. Adipose tissue 76 41. Pigmented connective-tissue cells 77 42. Hyaline cartilage 79 43. Thyroid cartilage 79 44. Transverse section of bone 81 45. Longitudinal section of bone 82 7 INDEX TO ILLUSTRATIONS. FIG. PAGE. 46. Lamellse of bone 83 47. Bone cells, highly magnified 84 48. Fl-esh bone cells 85 49. Sharpey's fibres 8r> 50. Cancellated bone Hfi 51. Longitudinal section of tooth, enamel 90 52. Transverse section of tooth 9 1 53. Cementum and dentine 9:^ 54. Membrane of dental tubes 98 55. Odontoblasts 04 56. Transverse section of inuscle 09 57. Sarcolemma of muscle 90 58. Striated muscle fibre 100 59. Mxiscle fibre, 101 60. Muscle fibre 10] 61. Muscle from Human heart 108 62. Muscle from diaphragm 104 63. Muscle cells - 104 64. Muscle cells lO.") 65. Termination of muscle in tendon 107 66. Trichinous muscle IOh 67. Fatty infiltration and degeneration of muscle 109 68. Capillary vessel from mesentery 112 69. Capiilaiy vessels , 113 70. Capillaries from muscle of a cat 114 71. Walls of an artery U5 72. Capillaries of the stomach of a cat 116 73. Capillaries of the villi of an infant I17 74. Capillaiies of human lung 117 75. Capillaries in the kidney ll,s 76. CapUlaries of mucous membrane of intestine 118 77. Capillaries of villi 119 78. Formation of bronelii and pulmonary cells 121 79. Lobule of human lung '. 123 80. One-half of frog's lung ^ . _ I34 81. Section of human lung 125 82. Section of lung of young child 126 83. Fragments of lung tissue 129 84. Salivary tubes 131 85. Submaxillary gland 132 86. Section of gastric mucous membrane I35 87. Horizontal section through fundus of stomach 135 88. Peptic glands 136 89. ' Fundus of a gland tube 137 90. Transverse section of the ileum of an infant 139 91. Vertical section of villus of small intestine X40 93. LieberkUhniau glands 141 93. Transverse section of an hepatic lobule I45 91 Hepatic and sublobular veins 146 indp:x to illustrations. FIG- PAGE. 95. Liver cells 147 96. Biliaiy capillaiy ; i48 97. ^ilia-iy capillary '. 149 98. Biliary capillary ] 4H 99. Diagram of the formation of the uro-genital oi'gan l.^l 100. Section of a kidney 152 101. Ilhistrating the pyramids of the kidney 153 102. Vertical section through the niedullarj- pyramids 154 103. Glomerulus of a rabbit 154 104. Capsule of a glomerulus 155 105. Malpighian bodies and tubes of the kidney ■.■■---. ISti 106. Section of an injc-cted kidney 15s 107. From kidney of the pig 159 108. Vascular an-angement of the kidney 160 109. Central tendon of the diaphragm 163 110. Lymphatic canal ItM 111. Section of lymphatic gland 165 112. Section of lymphatic gland 166 113. Section through Peyer's patch 167 114 Splenic artery with Malpighian bodies attached 168 115. Section of spleeit pulp 169 116. Section of spleen pulp 170 117. MeduUated nerve fibres 174 118. Varicose nerve fibres 175 119. Axis cylinder 1 76 ISO. Non-niedullated nerve fibres 177 121. Granglia cells 177 IJ^. Ganglion cell from hyla 179 123. Showing division of nerve fibres 180 124. Muscle fibres from guinea pig 181 125. Muscle fibres from frog 1S2 126. End bulb from conjunctiva of man 183 127. Pacinian corpuscle 184 128. Nei*v6 papillflB from stin 184 129. Sections of spinal cord of various animals 186 130. Diagrammatic section of cord 1S7 131. Sections of human cord 188 133. Section of the cord of a dog , 189 138. Nerve cells from cord of the ox 191 134. Nerve cells from human cord 192 185. Central canal of human cord 193 136. Section of human brain 197 137. Ganglia cells from brain 199 188. Vertical section of the testicle 20^ 139. Wall of a seminal tubule 206 140. Spermatozoa 207 141. Spermatozoa, highly magnified 209 142. Section of cat's ovary 210 143. Vertical section of an ovary 211 INDEX TO ILLUSTRATIONS. riG. PAGE. 144. GraaBan foUiole S12 145. Taste buds ^ 215 146. Cells from taste buds 216 147. Cells from olfactory region of frog 217 148. Epidermis 218 149. Prickle cells 218 160. Sudoriferous gland 219 IBl. Cochlea laid open 221 152. Membranous labyrinth 282 163. Otoliths 228 154. Diagram of auditory epithelium 223 156. Rods of Corti 224 156. Organ of Corti 225 157. TransTerse section of the eye 229 158. Section of the cornea of a rabbit 230 169. Corneal corpuscles 281 160. Surface of human iris 232 161. Connective substance of the retina 233 162. Nervous elements of the retina 234 163. Nervous elements of the retina.' 235 164. Rods of the retina '. 237 165. Fibrillated covering of the rods and cones 238 166. Macula lutea-and fovea centralis 240 167. Layer seen from without 241 168. Longitudinal view of fibres of lens 242 169. Section through margin of rabbit's lens 243 170. Fibroma 251 171. Lipoma 253 172. Myxoma 254 173. Lymphoma 265 174. PapiUoma 258 175. Adeno-Fibroma 259 176. Spindle cells 259 177. Myeloid cells 260 178. Melanotic cells 261 179. Large and small round cells 268 180. Stroma of scirrhus 263 181. Cells from scirrhus 264 182. Stroma of encephaloid 265 1&3. Colloid 266 184. Epithelioma 267 185. Potato starch 269 186. Wheat starch 871 187. Bean starch 272 168. Com starch 273 189. Rice starch 274 190. Oat starch 875 191. Buckwheat starch 276 192. Turmeric starch iWS CHAPTER I. The Microscope. THE word 'microscope' is a compound of two Greek words, fiikpoi, a small thing, and GkoTreoa, to view. Microscopes may be divided into two general classes, simple and compound. In a simple microscope we look at the object directly, while in a compound microscope we look at the magnified image of the object. Thils the difference is purely an optical one, for a simple microscope may be much more expensive and complex than a compound one, although as a rule the opposite is true. In the simple microscope the object is seen in its natural position, but in the compound microscope the image is re- versed, or inverted. This may be obviated by placing in the body of the microscope a set of lenses termed the erector. Very soon, however, the student becomes familiar with this in- version, and is not annoyed in the least by it. The compound microscope consists essentially of an ob- ject glass, or objective, which magnifies the object, an eye- piece which magnifies the image formed by the objective, a mirror to reflect the light and mechanical appliances. The Stand of a microscope includes all the framework to which are attached the eye-piece and the objective. Stands are sold separately by many makers, although one or more eye- pieces usually accompany them. The purchaser is thus left free to make his own selection of objectives. THE STUDENTS MANUAL OF HISTOLOGY, (Cut one-third of actual size.) I^Bausch and Lomb.] Fig. I. Compound Microscope. A, the base or foot; B, the body; C, the draw-tube; D, tha •rm; E, the collar; F, the coarse adjustment ; G, the fine adjustment; H, the stage; I, the ob- ject-carrier , K, the diaphragm, i, the mirror; a, the eye-piece ; 3, the objective. THE STUDENTS MANUAL OF HISTOLOGY. I3 A Stand usually consists of the ifollowing parts : The Base or Foot (Fig. i.) "A." Of all the forms the tri- pod meets the most general approval. The Body, "B," that part to which the objective is at- tached. The Draw-Tube, "C," which slides within the body. The Arm, "D," a support for the body. This is usually broken by a joint in order that the instrument may be inclined as seen in the figure. The Collar, " E," a tube surrounding the body. The Coarse Adjustment, "F," for coarsely focusing the instrument. The Fine Adjustment, "G," for more accurate work. This is one of the most desirable things about a stand and should be carefully examined by the purchaser. The Stage, "H," is that part upon which rests the object to be examined. An Object-Carrier, " I," is many times combined with the stage in order that the object may be more accurately and carefully moved about. Although not strictly necessary it is a great convenience. " Mechanical " stages are made for that purpose. The Diaphragm " K," is placed beneath the stage, pierced with different-sized openings, to regulate the amount of light. Several appliances are sometimes attached to the stand as aids to microscopical manipulation. It would be beyond the limits of this work to enter into their description or to mention the many accessories necessary to complete the outfit. The Mirror, " i," usually consists of two surfaces, a plane one which reflects the light feebly, and a concave one which concentrates the light upon the specimen. It is attached to a swinging bar beneath the stage in such a manner that light may be reflected from almost any quarter. On some stands it is so arranged that it can be thrown over the stage and the 14 THE STUDENTS MANUAL OF HISTOLOGY. light reflected on the top of an opaque specimen. This avoids the necessity of an extra condenser. The eye-piece, " 2 " consists of two glasses mounted in either hard rubber or brass. Midway between them is a diaphragm to cut off the outer rays of light. The eye-piece in most general use is known as the negative or Hughenian. In this eye-piece the convex side of the lenses is directed downward. The lens nearest the eye for this reason is called the eye-glass, and the one farthest from the eye, and nearest the field, is called the field-glass. X- C FIG. 2, Eye-piece in section, a, eye-glass ; b, diaphragm ; c, field-glass. The magnifying power of eye-pieces is designated by either numbers or letters. In this country letters are chiefly employed. The lowest power is known as " A" or No. i ; higher powers are known as " B " or No. 2, " C " or No. 3, and so on. The greater the magnifying power, the shorter will be the eye-piece. The short eye-piece, or the one with high power, is also known as the deep eye-piece ; the longer, or the one with less power, as the shallow eye-piece. One eye-piece, then, may be " A " or low, or shallow ; another may be " D " or high, or deep. As an eye-piece does not magnify the object itself but the image of the object produced by the.objective, it will be seen THE STUDENTS MANUAL OF HISTOLOGY. how any imperfection in the objective will be augmented. High eye-pieces should be used only with fine first-class objectives. The objective, "3," is usually composed of one or more systems of glasses. A system consists of two or more glasses. It is not made of a single glass because the powers of refraction and dispersion are not equally united in any single refracting medium. That is, in the same power of refraction one medium may give a much greater deviation to the colored rays than another. Crown and flint glass act with regard to each other in such a manner that if a crown glass lens be united with a flint glass lens, the refraction of the former is lessened by the dispersive action of the latter, while the color dispersion of the former is neutralized by the opposite action of the latter. Spherical aberration may be largely remedied by this same combination. The lenses are firmly cemented together by Canada balsam or Dammar. The glasses thus united constitute a system, and in Fig. " 3," three of these ^ FIG. 3. A, Achromatic objective of three systems; B, objective with high angle of aperture C, objective with low angle of aperture. The angle of aperture is the angle c a c. systems complete the objective. These systems are mounted in either brass or hard rubber, which at the upper end is provided with a screw of standard size. Such a sized screw is called a " Society Screw " and will fit in the body of any first-class stand. i6 THE students' manual of histology. An objective should possess the following good qualities : 1. Defining power. 2. Resolving power. 3. Freedom from spherical aberration. 4. Penetrating power. 5. Freedom from chromatic aberration. 6. Flatness of field. 7. Working distance. Defining power is without question the most important quality to be sought in a lens. Its presence makes the objec- tive of the utmost value, and its absence renders it simply- worthless. Defining power gives a clear, distinct and sharply cut out- line. Its absence is dendted by haziness, indistinctness and want of clearness. Resolving power enables closely approximated markings to be seen distinctly. While defining power shows the outline of a specimen well, resolving power enables the observer to de- tect the most intricate structure on its surface. Spherical aberration exists when the peripheral and cen- tral rays do not actually reunite in a point. Those rays passing near the periphery, being more strongly refracted, come to a focus sooner than those which pass through the central portion. Now if some parts of a lens bring the rays to a focus sooner than other parts, they must magnify more, thereby distorting the figure. This is found to be the case with all objectives having spherical aberration, causing what is known as "aberration of form." With penetrating power we look deep into the structure of the object. Chromatic aberration exists when a ray of light is not refracted as a whole, but is decomposed into rays of various colors, which are refracted in different degrees, forming a spec- trum. All objects examined now are seen fringed with colors THE STUDENTS MANUAL OF HISTOLOGY. 17 An objective is said to be " achromatic " when it is nearly, if not quite, free from this aberration. It is impossible to perfectly remedy these two aberrations, but by the use of the two kinds of glass mentioned above, they are nearly obviated. Objectives thus made are said to be " corrected." f\ -a* 3 FIG. A, chromatic aberration; a, c, rays ot white light; v, violet rays; r, red rays. B, spherical aberration. A Field includes all that is presented to the eye through the microscope. It is said to be flat when all parts of it are in focus at the same time. An objective with good defining power is very liable not to have a flat field, and a perfectly flat field is usually associated with poor defining power. Defining power should never be sacrificed for flatness of field, since with a good, fine adjustment the latter is easily remedied, while noth- ing can restore the former. Working distance is the distance between the front glass of the objective and the point in focus. Some manufacturers make objectives with a large working distance without materially affecting their defining or magnifying power. For many purposes such objectives are of great value. For a dis- cussion of the vexacious question of " angular aperture " we refer our readers to works on microscopical technology or to THE STUDENTS MANUAL OF HISTOLOGY. many articles in the various microscopical journals. The usual definition is this : Angle of aperture is the angle formed by two lines extending from the point in focus to the opposite sides of the aperture of the objective. While one school claims that a high angle has great resolving and poor penetrating powers, another school earnestly urges that both can be combined in the same objec- tive. Immersion objectives are those that require a drop of liquid between the end of the objective and the cover glass. Water is generally employed for this purpose, although glyce- rine, on account of its greater density, is sometimes used. By employing a liquid in this way the glass surfaces of the ob- jective and cover glass are, to a certain extent, extinguished and thus a considerable loss of light prevented ; at the same time the refraction of the rays of light at the upper surface of the.cover glass is very much diminished, so that many more rays of light pass into the microscope. The specimen is then better illuminated, and also better defined. Objectives are numbered according to their magnifying power. In this country the systsm is different from that abroad, where they are numbered i, 2, 3, 4, 5, etc. Here an objective is known as an inch, one-half inch, one-fourth, one- eighth, one-thirtieth, etc. These terms refer solely to the mag- nifying power. For instance, a one-fourth inch objective has the same magnifying power as a single lens whose focal distance is one-fourth of an inch. Each microscope should have with it a micrometer. Nothing can be more convenient or useful than a good eye-piece micrometer. Knowing 'the value of the spaces to which it is ruled, objects can be accurately and quickly measured. Of course, the value of these spaces will depend upon the objective used and the length of the tube of the micros- cope. By always using the draw tube fully extended the length of the tube will be fixed, and with the aid of a stage micrometer THE students' MANUAL OF HISTOLOGY. 19 ruled 100, 1000, 2000 lines to the inch, the value of the spaces of the eye-piece micrometer for the various objectives is reckoned once for all. This is done in the following manner : Bring in the field the lines of the stage micrometer ^-^ of an FIG. 5. Eye-Piece Micrometer. (Increased one-third.) inch apart ; place the eye-piece micrometer in its proper place in the eye-piece ; notice how many spaces of the eye-piece micro- meter cover one space on the stage micrometer. Using the X inch objective and the " C " eye-piece, we will assume that five spaces of the eye-piece micrometer cover one on the stage mi- crometer. Then one space on the eye-piece micrometer re- presents the -j^jVir oi an inch. Now remove the stage micro- meter and place in the field a specimen of blood, for instance, a white blood corpuscle is. seen just to fill two spaces in the micrometer. It is then the -5^^ of an inch in diameter. To determine the magnifying power of a microscope, it is inclined until the eye-piece is ten inches from the table. The lines of a stage micrometer are then accurately focused. By means of a "Camera Lucida" or "Neutral tint glass reflector" (Fig. 6), the magnified image is thrown upon a sheet of paper resting on the table and directly beneath the eye-piece. The lines are traced with a pencil while the eye is in the position noted in the figure, and their distance apart measured with a scale. This distance is divided by the distance between the lines on the stage micrometer, and the result will be the number of diameters the instrument magnifies — not the num- ber of times or areas, which would be the square of the diameters. Or the following method : Place a scale in front THE STUDENTS MANUAL OF HISTOLOGY. of and ten inches below the eye-piece. By looking in the instrument and keeping both eyes open, the lines of the stage micrometer can be seen resting on the scale, when their distance apart can be noted. Divide this distance by that between the lines on the micrometer, and the number of diameters will be given. Having no eye-piece micrometer, the size of any object is obtained in the following way : Assuming our microscope to FIG. 6. Carriera Lucida, or Neutral Tint Retlector. (Bausch and Lomb."^ magnify 500 diameters, the specimen to be measured is sub- stituted for the stage micrometer, and its image thrown down on the paper as were the lines of the micrometer, and its size measured with a scale. This measure is divided by the mag- nifying power of the instrument. Thus a red blood corpuscle appears on the paper }i of an 'inch in diameter. It has been magnified 500 diameters. Its true size then is -g^ of its apparent size, viz. raVrr °^ ^'^ '^ch. THE STUDENTS MANUAL OF HISTOLOGY. A microscope is said to be " in focus " when the specimen is seen to the best advantage. For the higher powers the fol- lowing rule should be observed : Incline the head until the eye is on a level with the stage. With the coarse adjustment place the objective very near the cover glass, within its focal length. Then, while looking in the microscope, focus up. If this rule be carefully observed, the breaking of cover glasses and the destruction of specimens will be materially diminished. For general microscopical work daylight is to be preferred. Not strong direct sunlight, which is only useful under special circumstances, but such an even, steady light as can be found by a window looking to the north. Nothing can take the place of this northern light, both when the sky is clear, and when, best of all, the sunlight is reflected from a white cloud. While gas-light and lamp-light are inferior to daylight and weakening to the eyes, direct sunlight is positively injurious. Transparent objects may be viewed by either direct or re- flected light. When the light passes directly through the specimen and microscope without having been reflected by the mirror, it is said to be direct. If the mirror be so placed that the reflected rays are in the optical axis of the microscope, the light is said to be central. If the mirror be turned to one side so that the rays pass through the object at an acute angle, oblique light is obtained. In the care of the microscope the following practical hints may not be out of place : When removing from, or placing on the stage a specimen, if the higher powers have been used, always raise the body of the instrument. It is rarely necessary to clean a good microscope. Use soft, chamois to clean, and camel's hair brushes to dust. Remove balsam, etc., from objectives by slightly moisten- ing the chamois in turpentine and carefully wiping it off. THE students' MANUAL OF HISTOLOGY. Avoid handling the instrument. Carry it by the arm. Always clean immersion objectives thoroughly, and imme- diately after using. When not in use, keep the instrument in its case or under a bell jar. However ; better let the instrument wear out rather than rust out. For practical work a good microscope need have but two eye-pieces of different powers, and a i in. and % in., or % in. and \ in. objectives. RG, 7. Turn-Table. iR. and J. Beck.) The beginner will need a pair of fine dissecting forceps, curved scissors, a knive or two, a few needles, a razor flat on one side and concave on the other for making sections, a few 'camel's hair brushes, chamois skin, glass slides and cover glasses. These, with the following list of twelve reagents, will complete the necessary outfit.' Other reagents and instruments will be added as their need becomes manifest. Many of them, however, the ingenuity of the worker, who is weaker in his pocket than in his head, will extemporize. Notably a " turn table " and "microtome." (Fig. 7 and 8.) THE student's manual of histology. 23 LIST OF REAGENTS. 1. Normal saline solution, 7. Canada balsam. J4 p. c. solution. 8. Carmine staining. 2. Glycerine. 9. Haematoxylin. ^■ Alcohol, 10. Oil of cloves. 4- Ether. 11. Dammar. ,s- Acetic acid. 12. White zinc cement. 6. Iodine solution. FIG. 8. Microtome. (R. and J. Beck.) For anything like a complete list of the various reagents, injecting and staining mixtures, and the methods of preparing them, the reader is referred to special works on those subjects. We append a few formulse in general use. BEALe's PRUSSIAN BLUE, FOR TRANSPARENT INJECTIONS. Common glycerine, i ounce. Spirits of wine, i ounce, 24 THE STUDENTS MANUAL OF HISTOLOGV. Ferrocyanide of potassium, 12 grains. Tincture perchloride iron, i drachm. Water, - 4 ounces. The ferrocyanide of potassium is to be dissolved in one ounce of the water and glycerine, and the tincture of iron (muriated tincture of iron) added to another ounce. These solutions should be mixed together very gradually and well shaken in a bottle. The iron being added to the solution of the ferrocyanide of potassium. When thoroughly mixed, the solutions should produce a dark blue mixture, in which no precipitate or fiocculi are observable. Next the spirit and the water are to be added very gradually, the mixture being con- stantly shaken in a large stoppered bottle. In cases, in which a very fine injection is to be made for examination with the highest powers, half the quantity of iron and ferrocyanide of potassium may be used. beale's acid carmine injecting fluid. Carmine, S grains. Glycerine, with 8 or 10 drops of acetic or hydrochloric acid, - - J^ ounce. Glycerine, i ounce. Alcohol 2 drachms. Ammonia, a few drops. Mix the carmine with a few drops of water and, when well incorporated, add about five drops of liquor ammoniee. To this dark-red solution about half an ounce of the glycerine is to be added, and the whole well shaken in a bottle. Next, very gradually pour in the acid glycerine, frequently shaking the bottle during admixture. Test the mixture with blue lit- mus paper, and if not of a very decidedly acid reaction, a few drops more of acid may be added to the remainder of the gly- cerine,, and mixed as before. Lastly, mix the alcohol and wa- ter very gradually, shaking the bottle thoroughly after adding each successive portion till the whole is mixed. THE students' MANUAL OF HISTOLOGY. 25 STAINING MIXTURES. BEALE's STAINING CARMINE, FOR STAIN- ING GERMINAL MATTER. Carmine, - lo grains. Strong liquor ammoniae, J^ drachm. Price's glycerine, - - - 2 ounces. Distilled water, - z ounces. Alcohol, - J4 ounce. The carmine in small fragments is to be placed in a test tube, and the ammonia added to it. By agitation and with the aid of the heat of a spirit lamp, the carmine is soon dis- solved. The ammoniacal solution is to be boiled for a few seconds, and then allowed to cool. After the lap.se of an hour, much of the excess of ammonia will have escaped. The gly- cerine and water may then be added and the whole passed through a filter or allowed to stand for some time and the per- fectly clear supernatant fluid poured off and kept for use. HEMATOXYLIN. Make a saturated solution of crystallized calcium chloride in 70 per cent, alcohol. Shake and let stand. Add alum to excess. Shake well, let stand, and then filter. Make a satu- rated solution of alum in 70 per cent, alcohol. Add this to the above filtrate in the proportion of 8 to i. To this mixture add drop by drop a saturated solution of hematoxylin in ab- solute alcohol until it has a somewhat dark purple color. Too deep staining can be removed by placing the section in dilute acetic acid. ANILINE BLUE-BLACK. Dissolve s grains of aniline blue-black in 100 c. c. of wa- ter. Dilute with water to any strength required. The following arc useful for MOUNTING MEDIA. Canada Balsam. Canada balsam to be used without heat. Prepared as follows : Heat some of the balsam over a sand bath until it is 26 THE students' MANUAL OF HISTOLOGY. hard when cold. Then dissolve it in a small quantity of ben- zole. To mount in Canada balsam the specimen is thoroughly saturated with alcohol. The excess of this removed with strips of cut blotting paper and oil of turpentine added. As soon as the section has become saturated or cleared the excess of oil is removed and the balsam added. Dammar. This is a great favorite with most histologists. It renders the tissues more transparent than balsam and is a convenient fluid to handle. It is prepared as follows : One half ounce each of dammar resin and gum mastic is dissolved in 3 ounces benzole and filtered. To mount a section in dam- mar, it is first left in alcohol, than transferred to absolute al- cohol until no water is in the section. The excess is removed by blotting paper and the oil of cloves added. Here it is al- lowed to remain until transparent. If it does not clear in a short time, in all probability the alcohol did not entirely re- move the water. Alcohol should be added again and allowed to remain longer on the specimen. Adding the oil a second time will doubtless clear up the section completely. Then re- move the excess of oil with blotting paper and add a drop or two of dammar and cover with thin glass. If glycerine or other fluid mounting medium be used, it will be necessary to make a cell in which can be placed the fluid and specimen. Cells are made with either of the follow- ing cements : Gold size, Brunswick black, White zinc. The border may be oval, square or circular, — if circular, a turn- table is employed in order that the circle may be true and sym- metrical. This soon hardens and forms a firm support for the cover glass, the edge of which should come just to the centre of the border. An extra layer of cement is now added, one- half of which reaches on the cover glass and the other half on the glass slide. For embedding mixtures the following are especially re- commended : THE student's manual OF HISTOLOGY. 27 Solid paraffin, 3 parts Cocoa butter, i part Hog's lard, 3 parts Solid paraffin, 2 parts Cocoa butter, i part Spernlafceti, i part soft. >• harder Solid paraffin, 3 parts ) Cocoa butter, 2 parts > hard. Spermaceti, i part ) Paraffin, 2 parts ) transp't and Vaseline, i part [ easy to cut. FIG. Injecting Apparatus. For further information on these subjects the reader is re- ferred to Beale on " How to Work with the Microscope," " The Microscope in Medicine," or to the admirable work of Frey's, "The Microscope and Microscopical Technology.'" 28 THE students' MANUAL OF HISTOLOGY. Figure 9 illustrates a cheap injecting apparatus, a repre- sents a pail partly filled with water, which can be raised or lowered, to regulate the pressure, by fastening one end of a cord to the handle of the pail and then passing the other end over a pulley fastened to the ceiling of the room ; ^ is a bottle with an air-tight fitting cork, pierced by two short glass tubes ; ^ is a bottle partly filled with the injecting mixture. Through the cork of this bottle are two glass tubes, one of which is short, while the other reaches very nearly to the bottom of the bottle , if is a brass nozzle with a stop-cock ; r, is rubber tub- ing, which unites the different parts as seen in the figure. A y-shaped glass tube can be inserted midway in the rubber tube between the two bottles, so that two bottles of the injecting mixture can be attached to the one large bottle, b, which is empty at first. A third glass tube can be placed in the cork of the bottle c, which can be united by rubber tubing to a U shaped glass tube partly filled with mercury, and thus the amount of pressure obtained. By raising the pail, the water descends the rubber tubing and compresses the air in the bottle b. The air is forced through the middle piece of rubber tubing and presses on the top of the injecting mixture in the bottle c, which is forced up the glass tube, along the rubber tube to the canula, and into the animal or organ to be injected. CHAPTER II. The Amoeba and the Cell. LOW down in the scale of animal life are found minute organ- isms of variable size inhabiting stagnant water, mud, and water in which animal matter has been infused and exposed to the direct rays of the sun. They have the appearance of a particle of the white of egg, clear and transparent, perhaps slightly granular, quite fluid in the centre and of firmer con- sistency towards the periphery. They are especially remarkable for their incessant and rapid changes of form, causing them to move about, but not in any particular direction. Their movements are efifected by a flow of their protoplasm, causing them to thrust out prolon- gations, known as pseudopodia. The dense exterior we know as the ectosarc, the more granular fluid interior, the entosarc. In some amoebae there appears a clear spot which dilates to a certain extent, then contracts rapidly and disappears, to reap- pear again with tolerable regularity. This is the contractile vesicle. It seems to serve two purposes, first, as a pump to force water into and out of the body, and second, as a means of procuring food, for when dilated to its full extent it will sometimes contract with such vigor as to break through the edtosarc and cause its contents to rush out into the liquid in which it lies. It then dilates, causing a strong suction force which drdws in a certain amount of water and with the water infusoria, entozoa and vegetal forms, the food of our amoeba. A nucleus and nucleolus are occasionally seen. 29 3° THE STUDENTS MANUAL OF HISTOLOGY. The first thing noticed in examining one of these little animals is, it is contractile. Its peculiar amoeboid movements, its flow of protoplasm, are identical in their fundamental na- ture with the movements occurring in a muscle during its con- traction. The second is, it is irritable and automatic. If a foreign body be brought in contact with an amoeba when it is at rest, movements result. These movements are not passive in their nature, proportionate to the force employed, but are the result of an explosion of the energy of its living matter. Rarely does one see the amoeba at rest. It is almost con- stantly changing its form, not from external stimuli, but from changes of its substance, the cause of which lies within tbe.body itself. The marked feat- ures of nervous tissue are its irritability and auto- matism. The third \s, it is secretory and excretory. Besides the method de- scribed above it will be noticed that our arnoeba has another way of procuring food, — by extending around it its pseudopodia until the particle is completely surround- ed by the living matter. Here the foreign body remains for a time. If it be suitable for food it soon becomes changed into material like the mass surrounding it, — into " amoeba stuff." Part of it may be changed and the remainder thrown off as excrementitious matter or the whole may be served in a ' similar manner. If all the particle be not assimilated then the amoeba simply moves away by its flow of protoplasm and leaves it behind. There must be chemical products present for the purpose of dissolving and effecting changes in this raw new material taken as food. These must be regarded FIG. to. Amceoa. nucleus ; , vacuole. b, foreign bodies ; THE STUDENTS MANUAL OF HISTOLOGY. 31 as secretions. Our amoeba is certainly excretory. In man, the digestive, urinary, and pulmonary tracts, and the epithelia represent this physiological property of the amoeba. The fourth is, it is metabolic. Constantly undergoing chemical change. Certain cells in the human body are specially reserved for carrying on chemical changes. Their material is derived from the blood and their products are finally returned to it. Such cells are the fat cells, liver cells, also the lymphatic and ductless glands, and in one sense, the blood. The fifth is, it is reproductive. After attaining a certain size or living a longer or shorter life, it may by division resolve itself into two parts, each of which is capable of living as a complete unit. The amoeba divides by becoming constricted in its centre, by its protoplasm flowing in opposite directions, or by a pseudopodium detach- ing itself from the body of the cell. Cer- tain cells are set apart in the human body for the accomplishment of this purpose. Such col- lections of cells are the ovary and the testis. Man, then, is but a federation of amcebi- form units. Certain of these units have been exclu- sively set apart for the manifestation of certain of the properties of protoplasmic matter. These groups have re- ceived the name of "tissues." With this grouping there has come a change in structure in order that the part might better perform its function. At one period in the history of these cells they were as simple as our amoeboid unit, in fact, for that matter, at an early period in the history of every life the whole being, the embryo, was but a mass of units as simple in their FIG. Amoeba dividing, 32 THE STUDENTS MANUAL OF HISTOLOGY. Structure as the amoeba. Some cells remain in this amoeboid condition in the body for a considerable time ; such cells are the mucous and pus corpuscles, and the white corpuscles of the blood. At abound, then, we pass from this low creature to the highest to find that the tissues of the latter are but collections of the former. So a tissue is chosen and with the aid of the knife and needles its parts are fQr a time successfully sep- arated. But at last a period arrives when even this will not answer, and we turn to the microscope to find our tissue infinitely compounded of thousands of the smallest eleftients. To discover and to examine these constitute the science of tissues, or histology. While the cell existed as an amoeba it acted in an inde- pendent manner, but now that it is in the service of a unity of cells it is a subordinate and must conform itself to its sur- roundings. Each cell in the body then is a living individual with an individual function. Some of these cells are very small, for we shall see that it is possible for five millions of them to be contained in a particle of the sub- stance of the body no larger than a cubic millimetre. While some are FIG. 12. Human ovum, a, vitellrne i ..i it membrane; b, vHeiius; c, germinal SO large they are nearly, if not quite, vesicle ; d, germinal spot ^-^-^^^ ^^ ^^^ Unaided eye. In Shape, also, there is the greatest variation. First, there is the spheroidal cell, from which the bodies of all the higher animal have proceeded, the ovum. As a result of com- pression and adaptation come other cells, from the slender cylindrical to the flat scaly. Still other cells appear with branched processes growing from their bodies in oppo- site directions. There exists, then, every variety of shape THE STUDENT S MANUAL OF HISTOLOGY. 3i and form in the fully developed cells, although we shall see further on that early in their history they were all alike, simple undifferentiated bioplasm. In a well developed epithelial cell from the surface of the tongue two parts are readily recog- nized. First, the nu- cleus, a round or oval body, occupying a small part of the cell near or in its centre, and, second, the part of the cell surround- ing this. In the alkaline so- lution of carmine (page 25) we possess an agent capable of coloring the different parts of a tissue or cell to different degrees. In a cell it is noticed that the inner- most part is invariably colored the most intensely. In the case of the epithelial cell the nucleus will be stained a deep red by the carmine, while the outer part remains unaf- fected. Now if any young or rapidly growing epithelial surface be examined, as the layer of epithelium over a papilla of the tongue, those cells nearest the blood-vessels will be seen to take the carmine staining completely. They are composed of nucleus matter alone ; from this matter must come all the future parts of the cell. No matter how high or complex the tissue, it must proceed from this first living germinal matter, the bioplasm of Beale. If the cells be examined a little further from our nutrient vessel a material will be seen sur- 13. A, flattened epithelial cells; B, cylindrical cells; C, branched connective tissue cell, x 400. FIG. 14. Fully developed cell. a, formed material; b, nucleus; c, nucleolus. 34 THE students' manual OF HISTOLOGY. rounding tlje nucleus, which does hoc take carmine staining. This was once living nucleus matter but now from coming in contact with air or fluids death occurs upon its surface and the nucleus or germinal matter becomes changed to lifeless formed material. Still farther away on the surface of the papilla the nucleus has nearly disappeared. It is now so far removed from its supply of pabulum that it has become gradually changed. Nutritious material then is deposited from the blood, first, in the centre of the living part of each cell, and while the inner part of each cell, the nucleus,- is being constantly replenished, its outer part is as con- stantly passing into lifeless formed material. All matter must be nucleus matter before it can become formed material. Only nucleus matter can be said to live. It lives, because it is capable of converting material unlike itself into material like itself. The nuclei of muscle convert common pa- bulum into muscle nuclei which is thence converted into muscle formed material. The nuclei of nerve cells are capable of taking some of the same ,M^v J- • • u pabulum and converting it into nerve FIG. 15. Illustrating diminish- ^ ^ ing nuclei in cells as they approach nuclei and theuce iuto uctve formcd the surface, a, cells near blood- vessels; b, cells remote from blood- material. Thus, man, a federation of vessels, these cells is capable of converting his food into materials like his own body, hair, nails, skin, etc., while the dog by eating of the same food will convert it into its own peculiar tissues. The youngest, most recently deposited matter of a tissue is found in its nuclei, the oldest in its formed material. There is a law in the body by which the amount of pabulum supplied to the nuclei by the blood, just equals the wear and waste of the cells. THE students' manual OF HISTOLOGY. 35 But if from any cause the part be irritated, be spurred to in- creased action, then an extra amount of blood flows to the part, an extra amount of pabulum is furnished to the germinal matter, causing it to increase rapidly. Now from two to five nuclei are seen in one cell. If the process goes on the ■changes become so rapid that the germinal matter does not change into formed material, and there now appear a multi- tude of round, globular bodies, in cells, and on the surface of cells, familiarly known as pus. Doubtless some of these cells are the migrated white corpuscles of the blood, but the mass of them represent living germinal matter undergoing rapid changes and possessed of a low vitality. This germinal matter may come from any irritated cell. It must be borne in mind that the supply, and change of pabu- lum to the' germinal matter, and from it to the formed material of the body, are constant and uninterrupted. From what has been said it must be evident that com- pared to human life, the life of any one FIG. 16. Pus in epithelial ^.gH Jg yg^y ghort. ■cells found in urine, x 250. -' When we consider the immense numbers removed daily from the surface of the body by the friction of clothing — laying aside the work of the sponge and towel — some idea can be gained how active must be the changes going on just be- neath the surface. Add to this the number rubbed off by ever}' act of moving the tongue, in speaking, drinking, and eating, and we commence to understand how most of the cells are destined to an early death. This great loss is replaced by the formation of new cells and by the division of those already formed, — the nucleus dividing first, then the whole cell becoming separated into two by constriction. In order to understand the most complex we study the most simple. That we may the better understand the highest, we watch the lowest, for they all receive new material and 36 THE students' manual OF HISTOLOGY. transform it into the constituents of their own bodies. They live, they grow, they reproduce their kind, they die. Our knowledge of the structure of cells and of their nuclei has been greatly increased by the labors of such men as Kleinenberg, Heitzman, Auerbach, Flemming, Klein and others. In No. 71, 1878, p. 315, and in No. 74, 1879, p. 125,. of the Quarterly Journal of Microscopical Science, are ar- ticles by E. Klein, giving personal observations on the structure of cells and nuclei. The first article opens with a resume of the work of several observers. From this we learn that Frommann described a network of fibrils in the nuclei of many kinds of cells as early as 1867. In 1873, Heitzmann asserted that the substance of various cells, amoebse, blood-corpuscles, cartilage cells, bone cells, epithelial cells, etc., contains a network of minute fibrils, into which pass fibrils radiating from the interior of the nuclei of those cells. To demonstrate this structure Klein places the tissue into a 5 per cent, so- lution of chromate of ammonia in a FIG 17 Epithelial cell closed vesscl. It is kept here for about r^tidtttwT''; '■ 24 hours. It is then washed in water (Klein) ^^j. ^^jQuj. half an hour, when it is placed in a dilute solution of picro-carmine, where it is left till it assumes a deep pinkish-yellow tint. Examined in glycerine the nuclei show a beautiful net- work of fibrils, " Intranuclear network." The nucleus is surrounded by a membrane which is in connection with the fibrils of the nucleus. The fibrils vary in the different nuclei. They may be fine, delicate and smooth, or coarse, of irregular outline and convoluted. Klein regards the " granules," or minute bright spots seen in nuclei, as representing the fibrils of the net- THE STUDENTS MANUAL OF HISTOLOGY. 37 Avork seen in optical transverse section or at the point of anastomosis. Some fibrils, however, are possessed of irre- gular thickenings. He believes the so-called " nucleoli " are accumulations or local thickenings of the fibres .of the in- tranuclear network. In many cells there exists a delicate fibrillar network in the cell substance — in the "formed material" of Beale. "Intracellular network." There is a direct, anatomical continuity of the fibrils of the intracellular network with those of the intranuclear network. In the meshes of this fibrillar network is a homogeneous "inter- fibrillar substance." CHAPTER III. Blood. BLOOD may be described as a tissue, the discs forming the essential element, the cells ; while the plasma represents the matrix in a liquid condition. If the matrix of bone could be liquefied so that the bone cells could freely move about, it could be well compared to blood as a tissue. Or if some re- agetit could be applied to completely solidify the plasma, we should have a tissue not very unlike cartilage. As early as 1661 Malpighi discovered little particles in the blood of the hedgehog, which he thought were little par- ticles of fat, but these were really the corpuscles of the blood. Only a few years later Leuwenhoek described quite minutely the corpuscles, which he had discovered in human blood, al- though the very best lenses at his disposal were made by him- self and did not magnify over 160 diameters. To him is given the honor of first discovering the corpuscles of the blood. It was not until a century later that another kind of corpuscles was discovered by Hewson, known as the white or colorless corpuscles, white globules, or the " leucocytes of Robin." Beside the liquid plasma, blood consists of, — First, red corpuscles. Second, white corpuscles. Third, accidental or temporary ingredients. 38 THE STUDENTS MANUAL OF HISTOLOGY. 39 The corpuscles and plasma bear the following relations to each other. BY VOLUME. BY WEIGHT. SPECIFIC GRAVITY. Plasma, 60 per ct. 55 per ct. 1030 ) Corpuscles, 40 per ct. 45 per ct. 1088 j '°^^ The blood is distributed through the body of man in the following proportions : One-fourth in the heart, lungs, large arteries and veins. " " " " liver. " " " " skeletal muscles. " " " " other organs. In the organs of the rabbit Ranke found the blood dis- tributed as follows : PER CENT. OF TOTAL BLOOD. In the spleen, - .23 " brain and spinal cord, 1.24 " kidneys, 1.63 " skin, 2.10 " intestines, 6.30 " bones, etc., 8.24 ' heart, lungs and great blood vessels, 22.76 " skeletal muscles, 29.22 " liver, 29.30 The total quantity of blood in the human body is esti- j»ated by different writers at from ^ to -^ of the body weight. In the rabbit, ^ of body weight. " " dog, ^ " " " " cat, ^ " " " '■ " frog, h " " 40 THE STUDENTS MANUAL OF HISTOLOGY. THE RED CORPUSCLE. As seen in a single layer under the microscope the red corpuscles are of a yellowish-green tint, and it is only when seen in masses, that they present a reddish color. These red corpuscles are found in the blood of all the vertebrates, even in the lowest form, the amphioxus. THEIR ORIGIN AND DEATH. They are present in the blood of the embryo when the foetus is little more than -^ inch in length. At this time they are much larger than those found in the adult, varying in size from -j^ to xsVir °^ ^^ '"^^^ '"^ transverse diameter. In shape they are circular, oval, or globular. Nearly all have a nucleus readily seen without the aid of reagents. What is the origin of these primary red corpuscles of the embryo ? Early in the history of the embryo the rudimentary heart consists of a mass of epithelial cells, and radiating from it are two or more tracts — generally one on each side — which, by their subdivision, form the vascular area. These cells are nucleated and vary in shape according to the pressure to which they have been subjected. In size they agree with the early red corpuscles described above. At a certain time some of these nucleated cells in the in- terior of the mass composing the rudimentary heart, become loosened from their fellows. The exact time of this occur- rence and its cause are not known. There are certain normal functions of the body performed in a regular way; the cause or causes of the regularity remaining in obscurity. , We only, know that these particular cells are separated from the' rest to serve a special purpose as; carriers of oxygen. The remaining cells become transformed into the tissue composing the walls of the vessel, which, by twisting upon it- self, finally becomes the heart. There is reason to believe that THE STUDENTS MANUAL OF HISTOLOGY. 41 throughout the vascular area, cells in the interior of the blood- tracts become loosened from their fellows, while the remaining ones are metamorphosed into the walls of the vessels. These loosened cells may be either slightly or quite deeply colored, It would seem . that the haemoglobin is deposited as small granules in different parts of the cells, to become evenly dis- seminated afterwards. At this time there are large, circular, oval, nucleated 'red blood-corpuscles, identical with those seen as late as the middle period of uterine life. They increase greatly by cell division, at least until the embryo reaches a certain age, after which their multiplication may be due to other causes. FIG. 18. Red blood-corpuscles of the human embryo, undergoing cell-division. ^ (From Kirke.) The development of the red corpuscles in -the adult is, and must be, different from their embryonic origin. The baSis upon which this assertion rests must be stated, for it might be said that the corpuscles in the adult are either the identical ones found in the embryo, or that they are formed from these by cell division. The first statement, cannot be true, for there is every reason to believe that the red blood-corpuscle is exceedingly short-lived, (see Foster's Physiology, 3d edition, p. 35.) The number of corpuscles in the blood varies greatly at different times, as is proved by counting them. . Again, ^fter hejiior- 42 THE STUDENTS MANUAL OF HISTOLOGY. rhage or disease, the normal amount may be regained in a very- short time. If the urinary and bile pigments are derived from the hemoglobin, the number of red corpuscles destroyed must be very great. The second assertion cannot be true, for the corpuscles very seldom, if ever, increase by cell division in the adult {Ibid., p. 36.) They must, therefore, have an origin entirely distinct from that of the embryonic cells. The following serves to strengthen an old theory and answer some objections to it. If we take the pulp of the spleen and examine it carefully, there may be. seen large circular cells, colored with haemo- globin. These cells are, perhaps, the protoplasmic cells of Kolliker. Some of them contain in their interior, the remains of from one to ten red cor- puscles. The reason why these very large cells are not found in the circu- lation, is probably because they are too large to enter the venous capillaries (see histology of the spleen.) Their large size is attained by appro- priating to themselves, through their amoeboid movements, the remains of one or more red corpuscles ; this oper- ation must take place in the spleen pulp outside of the vessels. Their size will prevent them from entering the first FIG. 19. Blood cells from venous Capillaries, until they have un- ^''^^"''"(Hariey & Brown.) dcrgouc Cell division. This division may be due to the same cause that keeps the amoeba about an average size, viz.: the attraction of its constituent particles for each other not being equal to the external pressure after they attain a certain growth. As a re- swM of cell division, spherical, nucleated, colored corpuscles THE students' manual OF HISTOLOGY. 45 would be produced, sufficiently reduced in size to enter the ciircalation ; and we have proof positive that they do enter as suggested above. Special precautions must be taken to de- monstrate the presence of these corpuscles in the circulating^ blood, ^nd Sc'hmidt believes them to be always present in nor- mal blbod, in' limited n-onabers. They are also seen in the medulla of bone. They have the "appearance of white blood- corpuscles, colored with the haemoglobin of the red. When lymph, taken from the thoracic duct or any other lymph vessel in the system, is examined immediately, it is found to be colorless, or nearly so ; but when allowed to clot, it assumes a decided pinkish tinge, which, by microscopical examination, is found to be caused by the presence of red blood-corpuscles. The red corpuscles appearing so constantly after the withdrawal of the lymph from the body, could hardly have an accidental origin. (Dalton's Physiology, 6th ed., p. 368.) Recklinghausen saw the white cells of frog's blood develop into red corpuscles, even when out of the body. (Arch, fur Mic. Anat., 1866, p. 137.) Were there not such a difference between them in structure and form, these facts would Jead to the conclusion that the white corpuscles give origin to the red. Kolliker, Neu-mann, -and Schmidt are of the opinion that the nucleus disappears from the white cells, while Huxley holds that the red corpuscles represent the bare nucleus of the former. Beale has taught us, that as the . cell grows in age its nucleus diminishes in size. His method of staining certainly supports his statements. (Beale, Mic. in Med., 4th ed., pp. 232 and 259.) If the hxmoglobin is not deposited in the white corpuscles until they have reached a certain age, they will be entirely without a nucleus. If, as clahned by Bottcher and verified at this laboratory (see Quar. Mic. Journal, October, 1878, p. 46), the red corpuscle has a nucleus, the haemoglobin must have been deposited prior to the time just given. 44 THE STUDENTS MANUAL OF HISTOLOGY. This time may be associated with the period when the white cell ceases its active amoeboid movements, becoming passive, a condition which would occur most naturally when it was old and its nucleus small. The appearance obtained from following the methods of Bottcher is said to be due to 'the' coagulating effect of the corrosive sublimate on the albunien- of the red corpuscle. If this be true, it seems strange that the coagulating agent does not serve all red corpuscles alike and give a nucleus to each one. This bleaching, hardening and staining method of Bottcher proves the existence of three classes of red cor- puscles. The red corpuscles (very few in number) having a nu- cleus and nucleolus, are recently derived from young white corpuscles. Those having a nucleus only, are either from older white corpuscles or are the older forms of the red ones possessing a nucleus and nucleolus ; while those consisting of a homogeneous mass are either directly grown from the older white 'corpuscles, or are the oldest forms of those composing the first or second class. The results of Beale's investigations lead to no other conclusion, and the recent researches on the structure of the nucleus by Aurbach, Hertwig, Priestley and Klein, do not, in the least, invalidate these statements. Although there may be a difference, in .-the structure of the red and white corpuscles, it is only such a difference as the growth of cells renders necessary. Some reason must be given for the change in shape from a spherical body to a biconcave disc. Haemoglobin possesses a great avidity for oxygen, it also retains this property when united with the white corpuscles, and under proper conditions, will combine with this gas even in excess. Will this excess of oxygen have any effect on the shape of the corpuscle ? THE students' MANUAL OF HISTOLOGY. 45 Using a carbonic acid gas apparatus, of the kind de- scribed in the Hand-Book for the Phys. Lab'y, by Burdon-San- derson, and examining the blood in a suitable chamber, the effects of the gas on the red corpuscles can be studied. It is not to be expected that the carbonic acid will unite with the red corpuscles, but the intention is to displace the excess of oxygen so far as possible, and thus reduce the red corpuscles nearer to the condition of the white. Experiments lead to the conclusion that one of the changes resulting from this displacement of the excess of oxygen, is to render the biconcave red corpuscles more globular. The alter- ation is not a complete one. The red corpuscle does not be- come as spherical as the white, but such a complete change might be confidently expected if all the excess of oxygen could be removed. The change in form, however, is sufficient to give rise to the belief that oxygen is the active agent in caus- ing the biconcave shape. In speaking of the difference in color between arterial and venous blood, Foster says (Foster's Physiology, 3d edition, s page 354, 1880) : "There may be other changes. * * * When a corpuscle swells, its refractive power is diminished. * * * Anything, therefore, which swells the corpuscles, tends to darken blood. * * * Carbonic acid has ap- parently some influence in swelling the corpuscles.'" And it might be added, it swells them because it displaces the excess of oxygen as described above. There is no such excess of oxygen in the white corpuscles, because they have no hsemo- globin to draw oxygen to them. Dissolve out the haemoglobin or remove the excess of oxygen from the red corpuscles, and they will not be unlike the white in shape. Hence, all that is necessary to change a white to a red corpuscle is to dissemi- nate haemoglobin through the substance of the latter ; this will attract an excess of oxygen, and a change in shape will result. 46 THE students' MANUAL OF HISTOLOGY. If the corpuscles have such a short existence, the question naturally arises : Where and how do they die ? The serum of fresh blood contains no dissolved haemo- globin, so that if any red corpuscles are destroyed in the cir- culation, either the number must be very small, or else the hemoglobin must be speedily transformed into some other body. Experiments made to show that the liver is a place of d ,struction for the red cells have given contradictory results. However, " a careful examination of the figures leads to the conclusion that the red globules are rather destroyed than formed in the liver." {Physiology, Kuss, 2d edition, page 124, 1875-) An account of the histology of the spleen will throw light upon the matter under consideration. (See histology of the spleen.) Following the divisions of the splenic artery, it it seen to ■divide again and again, until finally the branches diminish to the size of capillaries. These soon become indistinct. Cell •demarcations may still be recognized, but these also soon dis- appear, and there is now a minute blood current without definite walls. " As the failing branch of a drying brook wanders at last between the pepples of its bed, slender and scanty, so is it with these finest blood-currents." The blood enters the splenic artery and flows undisturbed through its branches to the very finest capillaries. The walls that separate it from the soft tissue now disappear, and it has to pass through a quantity of splenic tissue, with nothing to keep it from immediate contact with that tissue. Having no walls to confine it, it flows now this side and then the other side of the " pebbles " (lymphoid cells) of its bed. One portion of the red elements of the blood passes through this tissue into the primordial venous capillaries, and finally reaches the general circulation through the veins. THE STUDENTS MANUAL OF HISTOLOGY. 47 Another portion, however, meets a mechanical death by stick- ing fast to the splenic tissue. The study of blood teaches that for the colored elements movement is life and rest is death. (Frey's Comp. of Histology, 1876, p. 121.) The red corpuscles, being thus brought to rest, find their grave. But the younger corpuscles do not allow the older ones to remain quiet ; for, with an amoeboid motion, the white cells envelop the dead bodies of the red and greedily appro- priate them to their own use. In this way, the large white corpuscles mentioned above originate. If the spleen becomes enlarged, what will be the probable result ? The larger it becomes, the more tissue there will be through which the red elements must pass, the more fine blood-currents without walls, therefore the greater the destruc- tion of the red cprpuscles. On the other hand, the number of the white cells will be correspondingly increased ; for the spleen must be considered as a birth-place of the white cor- puscles. (Foster's Physiology, 3d ed., p. 38.) The equilibrium will thus be destroyed and there will fol- low a great destruction of the red and a great increase in the number of the white corpuscles ; the extent of which will de- pend upon the size of the spleen. Extirpation of the spleen does not always cause the result anticipated, and it is asserted that the number of white cor- puscles is not materially changed, neither does hypertrophy of the lymphatics always follow. In answer to this it may be said that extirpation of one kidney does not always lead to any material change in the amount of urine, neither does a microscopical examination of the remaining kidney, after a time, show any increase in size of either the tubuli or glom- eruli. (Flint's Physiology, Vol. III., 1876, p. 404.) The spleen is classed with the adenoid tissues. (Frey, Kiiss, &c.) Extirpate the spleen, and, as in the case of the kidney, the remaining adenoid tissues will carry on the work. 48 THE students' manual of histology. When the spleen is removed an abnormal condition is in- duced and it would be difficult to assert where the red cor- puscle meets its death. Therefore, the origin of the very first red corpuscle is from nucleated cells in the vascular area ; a little later in em- bryonic life, from cell division. Their origin in the adult is from the leucocytes ; the latter, becoming impregnated with haemoglobin, owing to the action of oxygen change to bicon- cave discs ; the nucleus of the white cells becoming gradually changed into the formed material of the red. Their death is owing to a mechanical cause in the spleen, and probably oc- curs, to some extent, in the liver also. THEIR SHAPE. In shape they are circular, flattened, biconcave discs with rounded borders. When seen on the side the centre appears either light or dark, depending on the focus. Acting as a biconcave lens, when the objective is slightly within the focus, the centre appears light, when without the focus, dark. This led the older observers co regard this centre as a nucleus. They were "optically deluded." (See Fig. 21.) Their shape is FIG. 20. A. Human blood In rouleaux, a, white corpuscles, x 400. B, Human red blood-corpuscles, a, seen on edge, b, white corpuscle, x 1000. readily altered by the aid of reagents and is spontaneou s y changed by their removal from the circulating fluid unless especial precautions be taken for their preservation. The red corpuscles of all the mammalia are of this shape with one ex- ception, the camelidas, in which they are oval. THE STUDENTS MANUAL OF HISTOLOGY. 49 THEIR NUMBER, VOLUME AND SUPERFICIES. They exist in great numbers. It has been estimated that in man there are five millions of them in a cubic millimetre of blood. Welcker estimates the mean volume of a red corpuscle to be .000,000,072,214 of a cubic-millimetre, and the super- ficies .000,128 of a square millimetre. Taking the number of corpuscles in a cu. mm. at five million, we should have in one cubic millimetre of blood 640 square millimetres of surface. In an ordinary man of 140 pounds weight, we will say there are 12 pounds of blood, a low estimate according to many authorities. If the amount of superficies of the red corpuscles be computed for the whole 12 pounds of blood, it will give us in round numbers 38,000 square feet. Although the circulation is complete in a less time, yet a quantity of blood, equal to the whole amount in the body, passes through the lungs in not far from forty-five seconds of time. In forty-five seconds the heart will beat about fifty times. Then one beat of the heart must send into the lungs 760 square feet of surface to be oxi- dized. In the normal condition then there is this amount of surface of red corpuscles in the lungs at any one time, exposed to atmospheric action. We are better prepared now to under- stand why blood is capable of absorbing 13 times as much oxygen as the same amount of water. The red corpuscles contain less water than the serum. In 100 parts of wet cor- puscles there are of water 56.5 parts, and of solids 43.5 parts. Haemoglobin constitutes over 90 per cent, of the dried organic matter of the human red corpuscles. THEIR STRUCTURE. The structure of these bodies is of great interest. They are so susceptible to the action of reagents, and are so liable to undergo various changes when removed from the circulating fluid that their study is most difficult. Two questions present themselves : Has the mammalian red corpuscle an investing membrane ? Has it a nucleus ? In reply to the first so THE STUDENTS MANUAL OF HISTOLOGY. we say : the eifect of mechanical agents, the fact that at no time is anything seen at all resembling a torn or empty mem- brane, and the effect of heat ; the study of these makes one believe that this body is without a membrane. Believing the red corpuscle of newt's blood to possess an envelope, and knowing that the mammalian corpuscle acts toward reagents like it, Rutherford, from analogy, infers the existence of a membrane in the latter. Hensen and others are of like opinion. The majority of histologists, however, fail to find satisfactory evidence of the existence of such a membrane. It appears that the outer part of the corpuscle is more dense than the inner. It conforms more nearly to our ideas of the •' formed " part of a cell. Has the red corpuscle a nucleus ? The great majority of histologists are ready to answer positively, No. But in the Arch, filr Mic. Anat., Bd. 4, Professor Bottcher gives the results of some researches on this subject, confirming him in the belief first advocated by Rollet. He uses a saturated solution of corrosive sublimate in 96 per cent, alcohol, and into fifty volumes of this solution, one of blood is to be rapidly diffused. By this means the coloring matter of the corpuscle is taken out — bleached — and thus the internal structure brought more clearly to view. This solution preserves the corpuscles as well. By agitating the mixture now and then the process is hastened, and in about twenty-four hours the corpuscles aref allowed to subside, the superincumbent fluid poured off and\ pure alcohol added in like amount. In another twenty-four hours this is poured off and, distilled water added. The corpuscles are now thoroughly washed, and are not acted upon by the water. Professor Bottcher employs eosin, haematoxylin, picric acid and carmine as staining agents, but prefers the first. He finds three classes of corpuscles : THE STUDENTS MANUAL OF HISTOLOGY. 5* First. Homogeneous and shiny throughout. Second. Added to this a granular mass in the center which stains readily. Third. Besides the cortical layer and protoplasm, in- closed in the latter is a marked nucleus and a nucleolus. Some blood was exam- B FIG. 21, The red blood corpuscles of man, treated by Bcettcher's method. A, homogeneous throughout. B, showing nucleus, C, showmg nucleus and nu- cleolus. (Selected from Bcettcher's article, Oct., '^77) Quarterly Journal of Mic'l Science.) ined from a man acci- dentally poisoned with an alcoholic solution of corro- sive sublimate with the result of finding nuclei in the corpuscles. As soon as the public announcement of Professor Bottcher's discovery came to our notice, his method was carefully followed at this laboratory, the blood from several mammalia be- ing examined. In nearly every case the first and second classes of corpuscles were found. It was quite rare to find those cells showing a nucleolus also. Only a few Were found in all our work that appeared to be changed by the action of the reagent used. This nucleus has been demonstrated to students in the laboratory and to different members of our faculty. Various methods have been successfully Used by different workers to show this nucleus. In the hands of others these same methods fail to produce the desired results. The real question at issue is this : Is the body found inside the mammalian red corpuscle, both with and without reagents, d nucleus ? We are told that there is a structure characteristic of nucleus matter, an intra-nuclear fibrillar network ; but one is unable many times to see this network in that part of the cell admitted by all to be the nucleus ; and as a fact all 52 THE STUDENTS MANUAL OF HISTOLOGY. nuclei do not seem to be possessed with it. Without any such distinctive structure as a guide how can we decide whether this is a nucleus or not ? No other way appears open to us but a course of reasoning such as is advanced on page 44 on the origin of this body. The question must be regarded as unsettled, for while our own believe makes us declare in favor of the presence of a nucleus we would remind the- student that such is not the generally accepted view, which is, that the red corpuscle is a homogeneous mass without membrane or nucleus. THEIR SIZE AND MEDICO-LEGAL VALUE. The size of these corpuscles varies not only in the same individual at different times, but also in the same drop of blood examined at any one time. The size usually given is from the -j^^- to -j-gVir ^^ ^'■^ inch. The following is a list of measurements of the red corpuscles of different animals as given by Gulliver : Dog, -rhr Horse, -^^ Cat, i^ Goat, -5^ Hog, -rh^ Sheep, ^^ Ox, j^ Red squirrel, ^roVir Brown rat, ■g-g'jy Black squirrel, ^-gVr Mouse, ^^ Gray squirrel, jJ^^ (For full table see Sydenham edition of Hewson's works, p, 237.) What is the value of these corpuscles in criminal cases ? That is, by a microscopical examination of a blood stain or clot, either fresh or otherwise, can we distinguish human blood from that of the inferior animals ? This must be con- sidered a very easy matter in some cases. Take, for instance, the red corpuscles of all the birds, reptiles, amphibia and fishes, here they are large oval bodies with a large round or oval nucleus. The only known exception .to this is in the case of the family of lampreys. In these fishes the corpuscles are circular, yet they have a nucleus very easily seen without the THE STUDENTS MANUAL OF HISTOLOGY. 53 use of reagents, hence are readily distinguished. If, then, the question arises, " Is this human blood ? " and upon examina- tion corpuscles are found of oval shape, the answer, No, can positively be given. If, however, the corpuscles are found circular in shape, and no visible nucleus without reagents. A S ®© *-^ ' FIG. 23. A. a, red corpuscles viewed within the focus; b, the same without the focus. X 750. B, Frog's blood, x 400. then an entirely different problem is involved, for with one exception (cameleidce) the corpuscles of the blood of all the mammalia are of this shape. Here the question must be decided by measurement. First of all there must be fixed, if possible, a Standard size for the human red corpuscle, for the size of the corpuscles of many of the inferior animals is so nearly like that of man that our figures in each case must give a fixed average size. Has the red corpuscle of man a fixed size ? Most assuredly No, for it will be a difficult matter even to get an average size. In examining a drop of blood with high powers, one very frequently finds a few minute colored corpuscles below the j^jVo °^ ^^ inch. No ac(5t)unt will be taken of these in arriving at the size of the red cor- puscle, they are easily excluded, and are few in number. The following are the average measurements of the red corpuscles of man : Gulliver, -jtVir °f ^^ inch. Flint, TpsVtr Dalton, 3^jT to y^^ir " Richardson, ^^^ " 54 THE STUDENTS MANUAL GF HISTOLOGY. Woodward, s^^^ of an inch. Frey, ^^ to ^^^ " Welcker, ^^zW Our own observations give -j-sW ^^ ^^^ mean. Thus it cannot be said that there is any settled average size, each investigator having an average of his own. While some are found as small as the -g-jVr o^ ^^ inch, others are as large as the tjtjVb- of an inch. Schmidt says, however, that over 90 per cent, of the corpuscles found in a single specimen are of the same dimensions. This much can be said, that after measuring a large number of corpuscles, if their average diameter is either -s-jVir o"^ TsVir o^ ^" inch, or any fractional part between these two (yjVir ^"'^ tsW) ^^^ blood may be that of man. While a number of the lower animals have blood corpuscles within these limits, (monkeys, ba- boons, etc., beaver, guinea-pig, porcupine, etc.), yet only the blood from certain of the inferior animals will be liable to enter a medico-legal contest. Can dog's blood be told from huinan ? Mr. Woodward must have settled this point conclusively. " The average of all the measurements of human blood I have made, is rather larger than the average of all the measurements of dog's blood. But it is also true that it is not rare to find speci- mens of dog's blood in which the corpuscles range so large that their average size is larger than that of many samples of human blood." The mean average of corpuscles in 22 drops of human blood (1766 corpuscles) ranged from .000,- 309 to .000,343 of an English inch. Nearly the same num- ber of corpuscles of dog's blood gave .000,296 to .000,340 of an inch. (Monthly Mic'l Jour., 1876, p. 132.) Can the blood of the cat, hog, horse, sheep and ox be told from human ? Although the corpuscles of the blood of the dog and of man are so nearly identical that even in freshly prepared THE STUDENTS MANUAL OF HISTOLOGY. 55 specimens they cannot be distinguished positively from each Other ; yet the corpuscles of the blood of the animals just mentioned, — cat, hog, etc., — are so much smaller than human blood-corpuscles that a positive distinction is possible, not only in freshly prepared specimens, but also when they are found in stains, clots, etc. If, then, the question is asked, — Is this the blood of man as distinguished from the blood of all other animals ? We shall be forced to reply, it is impossible to tell. If, however, the question is to decide between the blood of man and one of the inferior animals many times a most positive answer can be given. Between the blood of man and his most constant companion, the dog, there seems to be no difference, while it is possible to tell the difference between the blood of man and the blood of the sheep, hog horse and ox. To examine the stain, some of the dried blood is scraped from the surface to which it is attached, and the dried clot placed on a slide, over this is placed a thin glass cover, and a drop of the .75 per cent, salt solution being placed at its edge' runs under the cover and' moistens the specimen. The specimen is then examined with the highest power at com- mand. If particles of clot are so deeply colored that the corpuscles are indistinct, their coloring matter may be washed out by a current of the salt solution. This current is easily established by placing' a piece of blotting paper just oppo- site where the solution is applied. If now the corpuscles are too pale they can be colored. Those corpuscles most perfect in shape should be chosen, a large number of them accurately measured and their average diameter ascertained. BLOOD CRYSTALS. Blood crystals may readily be obtained from the rat as follows : a drop of blood is mixed with twice its volume of water and then allowed to evaporate slowly. Prismatic crystals 56 THE STUDENTS MANUAL OF HISTOLOGY. of hemoglobin will be seen. The blood of the guinea-pig crystal- lizes very easily giving the beautiful tetrahedral crystals seen in fig. 24. In the squirrel the" crystals are hexagonal tables. The blood of most of the mammalia including man, yields generally pris- matic or rhomboidal crystals. To obtain hsemin crystals, a drop of blood is placed in a watch crystal and about 20 times its bulk ofglacial acetic acid add- ed. The mixture is then warmed and as it evapor- ates the desired crystals will be formed ; or to a drop of dried human blood add a few crystals of common salt, cover with a thin film of glass and place a drop of glacial acetic acid to its edge and allow it to run under and come- in contact with the blood. The specimen is then carefully warmed and soon the reddish- brown haemin crystals ap- pear. FIG. 33. Showing relative size of red blood-cor- puscles of different animals. I, man. 2, whale. 3, ele- phant. 4, mouse. 5, horse. 6, musk deer. 7, humming bird. 8, pheasant. 9, pigeon. 10, snal Transverse section of bone (man,) a, Haversian canals, b, lacunae, c, canaliculi, x 50, and impregnated with insoluble inorganic salts. By the action of dilute acids the carbonic acid is eliminated from its combi- 82 THE STUDENTS MANUAL OF HISTOLOGY. nation with the lime which is rendered soluble, while the bone becomes soft without changing its form. The soft matrix rep- resents the "ossein," which is composed of minute fibrils arranged parallel to, or interlacing each other. The bone corpuscles are lacunae with long branches, canaliculi, by means of which they may anastomose with neigh- • boring lacunae. Each lacuna contains a nucleated cell of pro- toplasm, the bone cell proper. For histological study bone may be divided into two classes, compact and spongy. In compact bone we recog- nize ; I, Haversian canals. II, bone lamellae. Ill, bone cells. I. The Haversian canals are for the purpose of conveying blood-vessels and lymphatics. They vary in size, but average about the -5^ of an inch in diameter. They may be round or oval in shape. Where the bone is most compact near the outer surface they are very small, but towards the central cavity they acquire a large size. In a longitudinal section these canals may be seen to "form elongated meshes, communi- cating with each other by branches given off at acute angles or more generally by means of short oblique branch- es. . They open either upon the external compact substance of the bone or into the central FIG. 45. ing bloodvessels. i, -'I'll Longitudinal section of bone show- (Haversian canals.) x 25. THE STUDENTS MANUAL OF HISTOLOGY. 83 medullary spaces. They are lined with a delicate mem- brane. Around these Haversian canals are seen in transverse sections, layers of rings termed lamellae. II. These are arranged as follows : i. Concentrically. As many as fifteen lamellae are occasionally counted around one canal, but the number varies exceedingly, the smaller FIG. 46. Transverse section of bone, showing lamellae, x 50. canals having fewer than the larger ones. 2. Interstitial lamellae. These are more or less curved and run in various directions. 3. The circumferential lamellae are disposed parallel to and in contact with the periosteum externally and limiting internally the large medullary canals. 84 THE STUDENTS MANUAL OF HISTOLOGV. III. The bone corpuscles are found between the lam- ellae and are arched to correspond with their curve. They are quite numerous. Welcker gives on the average 740 to the square millimetre, and Harting 910. They appear as dark, black figures with a central body, lacuna, and branched FIG. 47. Two bone corpuscles. It will be noticed that many of these canaliculi are not connected with the lacunae. They belong to other lacunee not shown in the drawing, x 600 fibres given off on either side, canaliculi ; these communicate with others from other cells and thus the lacunae are con- nected together. The majority of the canaliculi are given THE STUDENTS MANUAL OF HISTOLOGY. 85 off at right angles to the lamellae but some pass off in all directions. In thin longitudinal sections this is well seen as is also their inter-comm.unications. The canaliculi open in the Haversian canals, on the surface of the bone, and in the large central medullary cavity. In living bone the lacunae are completely filled with protoplasmic cellular matter, — ■ containing a nucleus and sometimes a nucleolus, — which sends prolongations into the canaliculi. Between the lamellae of compact bone are fibrous bundles im- pregnated with lime salts and known as the " perforating fibres of Sharpey." They are connected with the periosteum from which they have their origin, and they are present in all bone developed in connection with the periosteum. This leads us to a consideration of the .membrane sur- rounding bone, the periosteum. This is composed of two layers. The external layer _ iff consists of a dense, firm, fibrous tissue. In some parts it covers the bone with but a single layer of con- nective tissue bundles, while in others two or three layers are recognized. A few blood-vessels supply this layer. The internal layer has, in addition to the connective FIG. 48. Bone cells from fresh young bone of human tibia, filled with nucleated germinal matter, x 600. FIG. 49. The Sharpey's fibres, b, of a periosteal lamella of the human tibia, a, c, lacunae, (from Frey.) 86 THE STUDENTS MANUAL OF HISTOLOGY. tissue bundles, a large number of nucleated cells of various sizes. In young growing bone, sharp points project into this layer, which are often covered with a layer of nucleated cells, " osteoblasts." In the central cavity of long bones and filling them com- pletely is a peculiar yellow or red substance called marrow. Both these varieties have a large supply of blood-vessels. Placed under the microscope the yellow marrow in seen to consist largely of fat cells, connective-tissue cells and nucleated cells similar in appearance to lymph corpuscles; these are the marrow cells. The red marrow as found in the meshes of spOngy bone contains fewer fat cells and more marrow cells. Here are found large, colored, nucleated corpuscles. These are probably the intermediate forms between lymph cells and colored blood corpuscles. Here also are the large, many nucleated, giant cells of Robin. F!G. 50. Canceltated bone, from head of human femur, xas. THE students' MANUAL OF HISTOLOGY. 87 METHODS OF EXAMINING. For a typical specimen of compact tissue a longitudinal and transverse section of one of the long bones of the body should be prepared, as for instance, sections from the humeras or femur. The bone selected should be entirely free from grease and of a pure white color. With a fine saw a thin section is cut and transferred to a hone or fine grindstone-. In this laboratory oil stones are used, each stone measuring six inches long, two wide and one thick. The surfaces of these hones are freed from grease or dirt by washing them in warm soda water. The section of bone is placed between the fiat surfaces of two of these hones. They are kept con- stantly wet with water. The lower hone rests on a table, while the operator moves the upper hone over it rapidly, and pressing hard upon it at the same time. The more force used the sooner will the work be over. These active measures are continued until the bone is as thin as a sheet of writing paper. Now the force is very slight, just the weight of the hone, and the motion is slower and slower. The section is ground in this way until it is extremely thin, as easily bent as thin paper, perfectly transparent, so much so that when wet and placed over the finger, it can scarce- ly be seen, so thin that under the % inch only one layer of cells can be made out. This whole process need not occu- py over twenty or thirty minutes. The section is now trans- ferred' to a glass slide and thoroughly washed in distilled water by aid of a camel's hair brush. It is then removed to a clean, dry slide and allowed to dry. If in drying it tends to curl, another slide had better be placed over it. The Canada balsam used should be hard when cold, — so hard that it can be chipped off in flakes with a knife. Ordi- nary balsam can be made in this condition by exposure to the air for a long time, or better still, by the application of heat for a short time, until the volatile matters are driven off. 88 THE students' manual of histology. A drop of this balsam, melted, is placed on a warm glass slide, also a drop in the centre of a cover glass. The slide and cover are kept warm over a flame until the balsam has evenly diffused itself. If any air bubbles appear they may be removed by touching them with a hot needle or by skim- ming them off by drawing the needle horizontally over the surface of the drop. The slide is now removed to the table and in a moment or two the cover also. When the balsam on the slide is slightly cool, but before it is cold, the bone is placed upon it. The cover is now inverted over it, and pressed against the slide. In a few moments the balsam is very hard, when the excess can be chipped off with a knife and cleaned by rubbing with a cloth moistened in turpentine. If the balsam be too hot when the bone_ is placed upon it, it will run into the lacunae and canaliculi, and the specimen will not show to advantage ; if too cold the cover glass can not be pressed down tightly. In this latter case the specimen can be gently warmed and the cover pressed down. The specimen is immediately exposed to the cold, to harden the balsam as soon as possible. If successfully treated nothing can exceed the beauty of these sections. The lacunae and canaliculi are filled with air and surrounded by the balsam. They now appear in- tensely black and show to the best advantage possible. For $ number of years we have followed this method and invariably have success. Over a thousand of these specimens are mount- ed by students in this laboratory each college year, and a poor specimen would be hard to find, notwithstanding stude'nts are recommended by some authors not to mount this tissue as it is so tedious to prepare and shows so poorly when pre- pared. After a little experience the whole preparing aticj mounting need not exceed thirty minutes. For longitudinaf sections more care is necessary to keep the balsam frppji entering the cavities. It is advisable, therefore, at first nqt to grind these sections quite as thin as the transverse. THE students' MANUAL OF HISTOLOGY. 89 To macerate bone a .5 per cent, solution of chromic acid, to which has been added a few drops of hydrochloric acid, is employed. The bone should be cut in small pieces and the amount of the solution used should be very large. In a few days sections can be made in any direction with a razor. A saturated solution of picric acid, as recommended by Ranvier, is very useful. The pieces of bone should be small and crys- tals of the acid should be added from time to time. Fresh bones stained exhibit the bone cells, or the bone may be de- calcified by chromic acid. Small pieces are immersed in a large quantity of the solution which should be very weak at first, I to 500, and gradually changed every day or two for stronger ones, until in a week it may reach i to 200. The bone has been long enough in the mixture when a needle can be passed through its middle. Thin sections can be made with a razor ; after thoroughly washing in water to remove all traces of the acid, they are stained with haematoxy- lin and mounted in dilute glycerine. Decalcified bone is used to demonstrate Sharpey's fibres. One of the blades of a pair of forceps is inserted into the outer surface of the bone and a thin strip torn off. Examining several of these strips one will find on some the tapering fibres " looking like nails driven through a board." The fiat bones of the skull are the best to use for this purpose. CHAPTER VI. Teeth. A TOOTH may be said to be an enlarged papilla of the mouth which has undergone such histological and chemical changes that it has acquired a remarkable degree of hardness. In the fully developed tooth there are three parts: i, the crown, the free part projecting above the gums. 2, the neck. FIG. 51. A. Longitudinal section of a tooth, a, enamel, b, dentine, c, cementum. d, pu1|> cavity. B, enamel rods, isolated by acids, longitudinal view. C, transverse view of rods. D, the rods or prisms seen in situ. B. C. and DX400. 3, the fang, the part projecting 90 surrounded by the gum. THE STUDENT S MANUAL OF HISTOLOGY. 91 into the alveolus of the jaw. In the centre of the tooth is a canal with an opening at the apex of the root, terminating above after entering the crown. It may be simple or multiple, d'epending on the number of fangs to the tooth. The great mass oTthe tooth is composed of a substance much harder than bone teiTned dentine ; covering the crown of the tooth is the enamel, while surrounding the fang is a bony substance, cementum. THE CENTRAL OR PULP CAVITY. The central or pulp cavity is completely filled with a soft substance known as the dental pulp. This consists of connective tissue, nucleated cells, blood-vessels and nerves. The nucleated cells are distributed through the mass of the pulp but mostly cover it as a distinct cell membrane. They are oblong in shape and measure from yzW ^'^ "rJr °^ ^"^ ''^^^ in length and -g^^ in breadth. This membrane, the mem- brana eboris, will cling to the walls of the pulp cavity when the pulp is removed. The cells composing it were named by FIG. 52, A, Transverse section of fang of a bicuspid tooth, x 5, a, cementum. b, dentine, c, puip cavities B, transverse, and c, oblique sections of dentine. X400. Waldeyer the odontoblasts. Each cell sends one process or more into the tubules of the dentine, while other processes unite with those from neighboring cells in the membrane, and in the interior of the mass. Thus all the deep and superficial cells are connected with each other and indirectly with the 92 THE STUDENTS MANUAL OF HISTOLOGV. processes in the dental tubes. The vessels form a capillary net-work. The nerves end in fine non-medullated fibres which are distributed at the surface of the pulp between the superficial cells. Boll observed in the teeth of rodents, macerated one hour in a -j^ per cent, solution of chromic acid with the membrana eboris preserved in connection with the pulp, a large numb.er of extremely fine fibres that passed outwards and, in teased preparations, accompanied the dentinal processes as fine hairs. By their length and direction they appeared to enter the dental tubes, and although no traces of them have been satis- factorily demonstrated, it is altogether probable that Boll's be- lief is the correct one. b FIG. 53. Section through cementum and periphery of dentine, a, bone cells in cementum. b, Interglobular spaces, c, fine dentinal tubes at surface of the dentine, x 400. It is a well known physiological fact that nerves are more sensitive at their terminal points than along their course. Dentists find upon operating on ihe teeth that on reaching an4 cutting the periphery of the dentine great pain is experienced by the patient, but as soon as the cutting is deeper the pain is materially lessened. This is exactly what would follow if the nerve fibres terminated at the ends of the dental tubes, at the •THE STUDENTS MANUAL OF HISIOLOGY. 93 periphery of the dentme. If single nerve fibrils do not thus extend into these tubuli, then ii would appear they must be connected in such a way with the odontoblasts that the pro- cesses of the latter are capable of transmitting the properties of the former. We are most favorably inclined to accept the views of Boll. THE DENTINE. The dentine presents a yellowish-white fibrous appearance and is one of the hardest constituents of the body. It has a firm matrix arid extremely fine canaliculi, the so-called, den- tinal tubes. At the larger ends their average diameter is about 4 g i ft j) of an inch and they are separated from each other by two or three times their width of matrix substance. They commence by circular openings on the walls of the pulp cavity and extend radially outwards, making spiral turns, like a cork- screw, on their way, this twisted appearance is easily seen in decalcified specimens. While extending outwardly to the enamel or cement they give off numerous branches by which they and their contents anastomose freely. At the surface of the dentine these are ex- tremely fine and many of them terminate in larger or smaller cavities at this point known as the inter- globular spaces of Czermak. The tubes are lined with a sheath, the dentinal sheath, which is readily seen in softened specimens. In these sheaths lie the dentinal fibres of Tomes. They are the greatly elongated processes of the odontoblasts with perhaps nerve elements. They are solid and homo- geneous, and easily stained with carmine. In old teeth these fibres evidently do not extend to the finest terminal points of the tubes, although in the young they certainly do. FIG. 54. Showing membrane lining dentinal tubules. (Boll). 94 THE STUDENTS MANUAL OF HISTOLOGY. In that part of the dentine which is just beneath the cementum and sometimes in that just beneath the enamel, there is a large number of spaces, interglobular spaces, the granular layer of Purkinje. Many of the dentinal tubes end in these spaces. They have a ragged outline and many short pointed processes. They denote an arrest in the develop- ment of the tissue at that point. Dental tubes pass through them uninterrupted (Tomes). Besides the tubes there is a substance with- in them which takes carmine stain- FiG. 55. Odontoblasts, a, portion ing only with difficulty. In a ■of dentine, b, two odontoblasts which <=> j ,pass with their processes through a por- transvcrse scction of dentine rings tion of the dentinal canals and protrude . from them at c. (Beaie). are Seen conccntnc with the cavity of the pulp. These rings may be due either to curves of the dental tubes, each tube curving at the same distance from the surface or to rows of interglobular spaces. CEMENTUM. Cementum is absent from the crown of the teeth of man. (See cuticle of the enamel.) It commences just over the ■enamel at the neck of the tooth and forms a thick coating over the fangs. At the end of the root it is often found thickened by an exostosis. It is composed of a matrix identical with bone, and of lacunae and canaliculi. The latter are much longer and more numerous than in true bone. They communi- cate directly with some of the dental tubes and also with each other. Some lacunse are seen with sharply defined contours and with short processes. They are the "encapsuled lacunae " first described by Gerber. In this way a single lacuna or sev- eral of them, maybe enclosed. Here in the cementum, as in bone, are the penetrating fibres of Sharpey, representing calci- THE STUDENTS MANUAL OF HISTOLOGY. 95 fied bundles of connective tissue. Where the cementum com- mences at the neck of the tooth no lacunse are found and it appears structureless. THE ENAMEL. Upon the outer surface of the dentine of the crown of the tooth is the enamel, the hardest substance of the body. It is com- posed of closely crowded polyhedral prisms, the enamel prisms, enamel columns, enamel rods. They are about ^^^f, of an inch in diameter and mostly pursue a direction from the dentine toward the surface. They are in close contact with each other, and so far as can be demonstrated there is no intervening sub- stance to unite them together, although the action of certain reagents in isolating the rods leads one to suspect here, as else- where, a "cement substance." Nearly all the fibres run the whole length of the enamel but some are seen in the outer portions which do not penetrate far into the interior. Transverse lines or striations are seen on isolated fibres as well as continuous over adjacent ones. Hertz believes that these lines represent an " intermittent calcification " of the fibre. Tomes and Waldeyer think that they are due to varicosities in the individual fibre. It is a very remarkable appearance and difficult to account for. If hydrochloric acid be added to the fibres after they have been isolated, they will break up into small cubic fragments of about equal size, corre- sponding to the striations on their surface. With the exception of these striae, the enamel rods appear perfectly homogenous, yet it is observed that acids act upon the central part of the fibre, before they do on the periphery. This is readily under- stood when the formation of the enamel is understood. The hardening salts are deposited first in the periphery of the cells and gradually reach the centre, so that in immature fibres may be seen a central canal. Soon this difference is obliterated as calcification progresses ; but when the acids act upon them this 96 THE students' manual of histology. action is reversed, the more recently deposited calcified sub- stance is sooner affected. There are coarser striations, consisting of a series of con- centric lines crossing the enamel fibres. They are of a brown- ish color and are known as the "brown striae of Retzius." It is possible that they mark the different stages of the growth of this structure. While one end of the fibre is implanted in de- pressions in the dentinal surface, the other terminates as a free end to form part of a beautiful hexagonal mosaic. THE cuticle. Covering the surface of the enamel is an exceedingly tough membrane, the cuticle of the enamel, Nasmyth's membrane. In thickness it is not more than -j^jVo to ytoWo "^ ^"^ i^^h. In young teeth this is easily detached after slight action of hydro- chloric acid, but it is doubtful if it exists in the teeth of the adult. Although very tough and unaffected by acids, yet it is not so hard as the enamel and is on this account generally worn away. Silver staining shows it to be composed of cells of an epithelial type. On its under side are the indentations for the reception of the free ends of the enamel fibres. Tomes regards this cuticle as a thin covering of young and incomplete cementum. METHODS OF EXAMINING. Sections of unsoftened teeth can be made in any desired di- rection, ground and mounted precisely as recommended for bone, giving the very best results. The methods for softening teeth are the same as those for softening bone. A 10 per cent, solution of hydrochloric acid is generally useful. If this solution be strengthened the dentinal substance will be destroyed and the sheaths lining the tubes will remain for a considerable length of time. Only young developing teeth in a fresh condition should be subjected to the action of acids for the purpose of isolating the enamel rods. Their transverse lines may be seen by adding muriatic acid. THE STUDENTS MANUAL OF HISTOLOGY. 97 The dental pulp is studied by using a reagent that softens the parts around it, at the same time that it hardens the pulp itself. Such a reagent is picric acid. The fresh tooth is broken open by the blow of a hammer and placed at once in a saturated solution of the picric acid. More crystals of the acid are added from time to time and the tooth is frequently stirred in the mixture in order that fresh parts of the solution may come in contact with it. As soon as the tooth is soft enough to allow a needle to pass through it, it is transferred to alcohol. The alcohol is changed daily until it fails to be colored by the acid. Thin verticle sections are cut with a razor, stained n haematoxylin, and mounted in glycerine. CHAPTER VII. Muscle. 11 yrUSCLE may be divided into two general classes: 1. Striated, i. Non-striated, 2. Striped, 2. Smooth, 3. Fibres of animal life, 3. Fibres of organic life, 4. Voluntary, 4. Involuntary, 5. Responds rapidly. 5. Responds slowly. Thus there are five different terms applied to each of the classes. Some of them are based upon histological and others upon physiological distinctions. There is one muscular organ in the body that cannot be classed with either of these divisions. It not only possesses properties belonging to both, but has in addition characteris- tics not found in other muscles. The heart deserves a place by itself and will be treated apart from striated muscle, although its intimate structure is so nearly identical with it. In study- ing striated muscle the unaided eye at once discovers a thin membrane surrounding the whole muscle and sending pro- longations into the body, giving the familiar appearance of a fine or coarse grained muscle. If a muscle be cut transversely this membrane will show to good advantage. The external in- vesting membrane consists of a. more or less dense connective tissue known as the perimysium, while the portion running through the muscle, dividing it into compartments, is called the endomysium. Each of these compartments is a fasciculus, and a fasciculus is* a bundle of small fibres, the cut ends of 98 THE STUDENTS MANUAL OF HISTOLOGY. 99 FIG. 56. Transverse section of a small muscle of a frog, a, perimysium, b, endomysium, c, cut end?of muscle fibres, showing as dots, x 1 5. which are seen in the figure as small dots. These fibres may- extend through the whole length of the shorter muscles, but usually in the skeletal muscles they are only from i^ to 2 inches in length, although this varies greatly in the same musgle and in different muscles. The diameter of the fibres is also of varying size from the thickness of a single contractile disc, to the ^^ of an. inch in man, and to a very much larger size in some of the lower ani- mals. Their diameter will average not far from the -j-^^ of an inch. This diameter is said to be much less in the female, but prac- tical experience will not warrant the assertion. These fibres end rather abruptly, the sarco- lemma extending over the end of each fibre and becoming lost in the inter - fibrillar connective tissue. The sarcolemma is a transparent, homogeneous, very thin and highly tenacious mem- brane closely investing each muscle fibre. It is invisible in fresh muscle, but is easily de- monstrated by the aid of re- agents. Figure 57 shows this membrane extending from one end of the broken fibre to the other. To obtain this view a small piece of frog's muscle was teased and while looking through a dissecting microscope, pressure was made with a needle over one of the FIG. 57. Sarcolemma of muscie /frog!s). A. a, ends of a broken fibre, b, sarcolemma^ X 35. B, Showing sarcolemma, more hig^ily magnified. fibres. The muscle THE students' MANUAL OF HISTOLOGY. substance was broken and then contracted either way, leaving the sarcolemma intact. By staining with carmine the mem- brane was sufficiently colored to enable us to procure good micro-photographs of the specimen. Just beneath the sarco- lemma are the numerous nuclei of the muscle fibre. They are situ- ated between the muscle substance and the sarcolemma, and do not form a part of the latter, neither is the sarcolemma developed from these nuclei, but from others, no trace of which can be seen in the adult muscle. According to Klein each nucleus contains an intra- nuclear fibrillar net-work. They are much more numerous in young, growing muscle. Rollett describes the nuclei found in muscles of the amphibia, fishes FIG. 58. Striated muscle fibre of the ^ , . j . . ... frog The nuclei stained with hannatoxy- and birdS aS CXlSting Wlthm the lin, X 200. , , ... muscle substance, a condition similar to that found in the heart of man. These nuclei are easily demonstrated by adding dilute acetic acid to a fresh specimen, or by employing one of the several staining fluids. They are often seen surrounded with a border of finely granular substance. A muscle fibre is di- vided iiito two substances by broad dim bands and bright nar- row ones. 'The former is the contractile part of the fibre and is composed of contractile discs, while the narrow bright bands correspond to the interstitial discs. During contraction the first become more transparent, thinner in their longitudinal di- rection and correspondingly thicker transversely. The second become more opaque. At figure 59 a, is seen a contractile disc, while b. represents the interstitial disc. Thus in living muscle THE STUDENTS MANUAL OF HISTOLOGY. it is seen there are no longitudinal striae. By studying one of these contractile discs more carefully it becomes differentiated into thin oblong rods, each rod the length of the disc. Each of these rods represents a single sarcous element, which is the anatomical element of the con- tractile dfec. These sarcous elements are arranged so close to one another during the life of the muscle, that they appear as one, and the disc was said to be homoge- neous. However, by the use of reagents, or many times spon- taneously, during and after life they become separated- -BfRen a fluid substance is pressed out which appears to be identical with the myosin discovered by Kiihne. Now if alcohol be used ;-ct / FIG. 59. Muscle fibre, a, contractile disc, b, interstitial disc, c, sarcous elennents. d, iransverse membrane of Krause. n, nuclei, s, sarcolemma, (Klein.) for hardening the muscle, the sarcous elements will be arranged endwise, and as a result of these elements being placed end to end, we have the appear- ance of long slender fibrils, the primi- tive fibrillae. If, however, in/ the place of the alcohol, hydrochloric acid be used, then the sarcous elemenljs appear arranged sideways and wef have the transverse discs. A muscle fjbre then is either a bundle of primitive fibrils or of transverse discs which ever Way we look separating inToT'tranwers" d' { B, longitudinal fibnis. Prepared .Upon It. I from separate specimens, x 30a. Very intimately connected with the sarcolemma of a fibre, THE STUDENTS MANUAL OF HISTOLOGY. are membranous septa which stretch across the muscle at regu- lar intervals. These septa are the transverse membranes of Krause. They divide the fibre into a number of equal sized compartments, "known as muscle compartments." This mem- brane of Krause passes directly across the fibre midway be- tween two contractile discs, dividing the intervening inter- stitial disc into two equal parts. Each of these parts is known as a lateral disc, each disc belonging to different muscular compartments. A small granule is found in some muscles di- rectly at the end of each sarcous element. This arrangement is so constant in some muscles, that it has been given a name, the "granular layer of Flogel." A transverse section of these sarcous elements presents a fine granular appearance, leading one to believe that they are composed of most minute fibrils. It is certain that they are not optical units, but consist of minute doubly refractive elements, the "discliaclasts of Briicke." A muscle then is a collection of fasciculi. A fasciculus is a collection of fibres. A fibre is a collection of muscle compartments. {Transverse membranes of Krause. Sarcous elements. Myosin, and sometimes the granular layers of Flogel. This kind of muscle is found in all the skeletal muscles of the body, in the muscles of the oral cavity, pharynx, larynx, oesophagus, lower part of the rectum, diaphragm, middle and outer ear, sphincter vesicae, part of muscles of the prostate, and modified in the heart. Although a few of the striated muscle fibres of the body divide, yet such is not the rule. Aside from these few muscles the heart presents distinctive characters particulars in which it differs histologically from the ordinary striated muscles described above. First, the fibres have no sarcolemma; second, they are smaller; third, they divide; fourth, they anastomose; fifth, they are divided into nucleated cells; sixth, the nucleus is within the muscle substance of each cell. THE students' MANUAL OF HISTOLOGY. 103 Figure 61 represents some of these peculiarities. The fibres are much smaller in some parts of the heart than in others. In examining a transverse section some fibres will be found very small indeed. These small fibres are the ends of one of the divided fibres, and when it is remembered that they frequently divide and ter- minate in a pointed end, this great irregularity in size can be readily accounted for. At quite regular distances the fibres are crossed with a faint l^ne, and midway between two of these lines is a nucleus which is situated within the substance in the centre of the cell. Many times these cells are so arrang- ed that on a thin section, it ap- FIG. 61. Muscle from the heart of man, pg^^S that the end of One Cell prepared from fresh specimen, cut with froezmg r microtome and stained, x 150. Jg placed jUSt OppOSite the centre of another near it, so that the ends of the cells look not unlike a series of steps. Meyer tells us that the more a muscle works the deeper is its color, but according to Ranvier there may be well defined structural differences between the pale and the deeply colored muscles. If the diaphragm be examined a great number of large nuclei or " muscle cells " will be found. They may be in suf- ficient numbers to form a nearly complete layer around the fibre. All fibres do not seem to be affected alike in this respect. The work of the diaphragm must necessitate a great amount of waste and repair, hence the large number of bioplasts. The second class, involuntary, unstriped muscle, is widely 104 THE students' MANUAL OF HISTOLOGY. diffused throughout the body. (See Strieker, pp. 150, 151.) This tissue is aggregated into larger or smaller bundles and is composed of elongated spindle-shaped cells held together by a 'C *•- Jf , FIG. 62. Muscle from diaphragm with large number of bioplasfs. (Klein.) transparent semi-fluid substance identical with that which unites epithelial and endothelial cells. The cell is composed FIG. 63. Muscle cells. A, transverse sections through bundles of smooth fibres. B, cells from small artery of guinea-pig. C, cell from intestine of man. D, celt containing far globules (uterus). E, cells from artery (man), x 400, of a longitudinally striated substance in the centre of which is a nucleus not infrequently multiple, and usually in the middle THE students' MANUAL OF HISTOLOGY. 105 of the long axis of the cell, or in the thickest part of it, which may bring the nucleus nearer one end than the other. The nucleus is usually oblong and is composed of a fine net-work of fibrils which anastomose (Klein) at the poles of the nucleus with the bundle of fibrils composing the central part of the cell, the true contractile substance. FIG. 64. Non-stnated muscle cells, (after Klein.) Each cell is surrounded by a fine sheath, which shows a transverse linear marking, especially if the cell be examined in a contracted state. The ends of the cell are drawn out into fine points, and in the arteries and veins the extremities are frequently branched. The longest and thickest cells are found in the walls of the intestine, the shortest in the arteries, the Io6 THE students' MANUAL OF HISTOLOGY. thinnest in the tubes of the sweat glands (Klein.) Fat gran- ules are frequently imbedded in the cells. This is well seen if some of the cells be examined from the uterus a few weeks after delivery. While some will be filled with fat, others will be nearly destroyed by the degenerative process. Granules are nearly always present at the two ends of the nucleus. METHODS OF EXAMINING. To examine microscopically the general appearance of striated muscle, a small fasciculus may be taken from the body of any of the vertebrates, and by a slight amount of teasing in some normal fluid, good views are obtained. How- ever, it is better to remove from the under side of the lower jaw of the frog one of the thin fiat muscles so suitable for study. The frog should first be decapitated or pithed and the muscle removed carefully without teasing or straining. The tissue should be placed on the glass slide at once and moisten- ed with blood-serum or normal sahne solution. Very satis- factory views of the transverse striations and in sopie cases of the longitudinal striations will be obtained in this way. If the individual fibres are desired, they are easily separated from each other by the aid of needles. The nuclei can be recognized after the addition of dilute acetic acid. The sarcolemma so closely surrounds the muscular elements that it is not visible by the ordinary methods of examination. Yet many times in teasing the muscle, some of the fibres have been pressed upon and broken, and the contractile substance has contracted at either end, leaving the clear transparent sarcolemma as seen in figure 57. If water be added to a fresh specimen it will soon pass through the delicate sarcolemma, causing it to separate from the tissue, so that there is a transparent border at the edge of the fibre. Many times, too, the sarcolemma will bulge out at the end of a fibre in the form of a little pouch. To study farther, some of the tissue may be placed for a few days in a .2 per cent, solution of hydrochloric acid, then thesarcous THE STUDENTS MANUAL OF HISTOLOGY. 107 elements will appear arranged sidewise into transverse discs, each disc equatiitig in length a single sarcous element, and in width the same as the muscte iibre. At the same time place a specimen in a .5 per cent, solution of -chromic acid. If some of the tissue be placed in Miiller's fluid for a couple of weeks or longer, but slight teasing will cause the muscle fibrils to fall apart. Alcohol and chromic acid will cause the sarcous elements to become arranged longitudinally, giv- ing the appearance of longitudinal fibrils, each fibril being just the width of a single sarcous element, and as long as the muscle fibre itself. To demonstrate the relation of muscle to tendon, a small shred of muscle with its tendonous attach- ments must be placed from 20 to 30 minutes in a 35 p. c. solution of pot- ash, when the appearance seen at figure 65 will frequently be observed. It will be noticed that the sarco- lemma is still intact, but that the fibres of the tendon have become separated from the muscle fibre. There has been no teasing or injuring of the tissues, and one is forced to believe that the two were cemented together, and that the potash solution dissolved this cement. It seems safe to assert that muscle is united to tendon by a cement, which is dissolved by a 35 p. c. solution of potash in from 15 to 30 minutes. The examination of muscle for trichinae is very simple. Small shreds of the muscle should be teased with needles in some normal fluid media, and examined at once with a low power; one giving 50 diameters will be suf- ficient at first, although for a more careful examination one of 250 or 300 diameters should be employed. Thin sections can FIG. 65. Tffrminalion of muscle in tendon, ffom tail of young mause. a, muscle fibre, b, sarcolemma. c. ten- don, X 50. io8 THE students' manual of histology. be made with a razor through the trichinous muscle hardened in alcohol, using the proper care that the sections be made in the direction of the fibres. The worms are seen coiled up as FIG. 66. Trichinous muscle. A, from psoas muscle of hog, B, encysted trichina from arm of man. B, x 35. in figure '66. They may be found in any of the transversely striated muscles with the exception of the heart. They are most frequently found, however, in the diaphragm and muscles of the jaw and neck. They are in greatest abundance at the tendonous extremities of the muscles, for they are here pre- vented from moving farther. In the hog, fragments of muscle should be examined especially from the ham and tenderloin. They are usually found arranged spirally just beneath the sar- colemma. This spiral arrangement gives them their specific name, trichina spiralis. They were discovered in January, i860, by Professor Zenker of Dresden. In 1864 Professor Dalton counted the number of trichinae in a piece of muscle ■^ inch square and -^ inch thick, and found 12. This would THE students' MANUAL OF HISTOLOGY. 109 give abbut 85,000 to the cubic inch. In another specimen of the sanle size he found 29 trichinae, giving again in round numbers 208,000 to the cubic inch. The trichinae in half a pound of infested meat would be sufficient in a few days to develop the extraordinary number of 30,000,000. When it is remembered that each of these worms must puncture the mucous membrane in its way to the muscles, it is readily un- derstood why they should occasion such notable disturbance. As found in .muscles they are usually surrounded by a cyst containing granules or calcareous matter. In size they aver- age about ^ inch in length and -g^ inch in thickness. They retain their vitality in the encysted state for a great length of time. Muscle sometimes becomes streaked with fat when it can be ejfamined either fresh or after being treated with Mailer's FIG. 67, A, latty infiltration of heart (man). X7S. B, fatty degeneration of muscte from arm of boy, amputated on account of paralysis of three years standing. fluid or chromic acid. When the fat is confined to the con- nective tissue between the muscle fibres as in obesity, nothing serious can result from it, unless in some particular organs THE STUDENTS MANUAL OF HISTOLOGY. ■when it may cause a dilatation and weakening from pressure. A specimen of fatty infiltration is seen at figure 67. When the fat molecules are arranged in rows correspond- ing to the longitudinal striae, they usually increase in number until all the contractile substance disappears and the muscle fibre becomes transformed into a row of fat cells, the fatty de- generation causing a complete wasting of the muscle. Non- striated muscle cells undergoing this fatty metamorphosis are found in the uterus a few weeks after delivery, when in order for this organ to become reduced to its previous size many of the cells become thus broken down and carried out of the body. Striated muscle is best preserved in dilute glycerine, equal parts of glycerine and water, — which has been slightly acidulated by acetic acid. The glycerine will have the effect of causing the transverse striae to show exceedingly well, aside from being a most excellent preservative fluid. Muscle may be preserved in Canada balsam also, and always should be so mounted if the specimen is to be examined by polarized light. For the purpose of studying the spindle cells of involuntary muscle, a piece of the organ containing it, as the bladder of the frog, is placed in a very weak solution of bichromate of potash (i to 800) for 'orty-eight hours. At the end of this time slight teasing with needles will be sufficient to separate some of the cells from the large piece. Dilute nitric acid, 20 or 25 p. c. solution, does not fail to give good results. The specimen is allowed to remain in the acid 30 to 36 hours, when, by teasing in water each cell can be brought clearly into view. Before teasing, the tissue may be stained to advantage with haematoxylin. By removing the epithelial cells from the linner surface of the bladder of the frog, by washing and brushing with a camel's hair brush, and by staining with picrocarmine or hseniatoxylin, most beautiful specimens can be obtained. A specimen mounted in glycer- ine and treated as just described, is in the author's posses- THE STUDENTS MANUAL OF HISTOLOGY. 1 1 1 sion, showing the nuclei of the cells, the stained blood-vessels, and the blood-corpuscles with stained nuclei in the vessels. Nitrate of silver affords the best exhibition of the arrange- ments of the cells. About .5 per cent, solution is allowed to come in contact with the tissue for two or three minutes only. This is washed off with distilled water and the speci- men is placed in dilute alcohol and exposed to the direct rays of the sun. In a few minutes it can be mounted in glycerine, when the outline of each cell will be distinctly seen. A one or two p. c. solution of acetic acid will show quite distinctly the individual cells, only a few minutes im- mersion being required. Weak solutions of chromate of am- monia are recommended by Klein. CHAPTER VIII. Blood- Vessels. THE blood is conducted from the heart by highly elastic arteries with a circular muscular element, which relatively increases in thickness as the arteries diminish in size. It is returned to the heart by the less elastic veins which have a variable muscular element. Between the two systems of ves- sels are the capillaries of exceedingly small but variable size. THE CAPILLARIES. The finest capillaries in the body are barely sufficient to al- low the passage of the blood- corpuscles, one after the other, often so small as to compress them and change their form. They may be said to vary from WsiF to ^JjTT of an inch in diameter. In the nervous tis- sue and retina they are found the smallest, in mucous mem- branes they are of medium size, while in the bones and glands they are the largest. They do not diminish or increase in size as do the arteries and the veins, 112 FIG, 68. Capillary from mesenterium. Treated with nitrate of silver and stained with hsematoxylin. a, cell plates, u, nu- clei, s, stomata. x 409. THE students' MANUAL OF HISTOLOGY. "3 for they form a plexus of vessels of nearly uniform diameter inosculating in every direction. Their average length is about -^ of an inch. Although their diameter is so small and their length so short, yet the number is so large that their capacity is immense. It has been stated that the entire capacity of the capillary system is a number of hundred (400 to 800) times as great as that of the whole ar- terial system. These estimates, however, partake of the curious and are mere suppositions. Without the aid of reagents the structure of the capillaries appears very simple. A few nuclei with, nucleoli are seen scattered along the walls of an elastic hyaline membrane. Ni- trate of silver dispels this illu- sion and resolves this homo- geneous membrane into a single layer of nucleated cell-plates, united together by a " cement substance ," which is stained a deep black by the solution. If the capillaries become distended in any way, this ce- ment is liable to give way and minute openings appear, which after a time may become enlarged into stomata. These open- ings may be present in the capillaries when they are not dis- tended, but as a rule in this condition of the walls of the ca- pillaries these "stomata" are not true openings, being covered with the cement substance. Through these stomata the white corpuscles migrate and the red find an exit, being forced out passively. Purves, proved that the white corpuscles migrated through these openings, by staining capillaries through which emigration had been going FIG. 69. Capillary vessels and fine ' branches of the mammalia, a, capillary ves- sel fiom the brain, b, from a lymphatic gland, c, a somewhat larger branch with a lymph-sheath from. the small intestine, and d, a transverse section of a small artery of a lymphatic gland. (Frey.) 114 THE STUDENTS MANUAL OF HISTOLOGY. on. In some of the larger capillaries there is an outer sheatto of connective-tissue cells surrounding this single layer oi epithelial cell-plates. This layer forms a reticulum, in the meshes of which are lymphoid elements. THE ARTERIES. Passing now to the larger vessels a gradual increase in diameter is observed, and transversely arranged nuclei are seen. This is the very commencement of the muscular layer, and marks it as a commencing ar- tery in contradistinction to a capillary. If a me- dium sized artery be ex- amined as directed below, four layers will be recog- nized. The most internal endothelial layer consists of a layer of flattened nucleated endothelial cells, rendered visible by nitrate of silver staining. By endothelium is un- derstood a layer of flat cells which covers any membrane not a mucous membrane or one lining the cavity or canal of a secreting gland. They Fig. 70. Capilianes of injected muscle of cat. X ,00. y^^y j^ ^^^j^ shapcand outline, are held together by a " cement substance " and are demonstrated by the aid of a .25 to .5 p. c. solution of nitrate of silver. THE STUDENTS MANUAL OF HISTOLOGY. IIS External to this layer is a longitudinally striated mem- brane, the hyaline elastic coat. The net-work of elastic fibres is arranged parallel to the long axis of the vessel. The third coat from within, the intima, is termed the middle layer of un- striped muscle. The cells are arranged for the most part transversely. It is the most conspicuous of all the coats in all the arteries and is very distinct in the larger ones. The muscle cells first formed only a single layer, but they gradually increased until now they con- stitute an individual coat. In most of the arteries there is a fine granular connective tissue and a few elastic fibres between the muscle cells. Some of these cells are arranged ob- liquely, or even longitudinally. In some arteries there are no muscle cells whatever. The fourth, or most external coat, the adventitia, is composed of connective tissue with longitudinally arranged cells. Between this and the intima, in the larger arteries, there is an elastic membrane, the external elastic coat. It is composed of a net- work of fine elastic fibres. The adventitia is relatively very thick in small arteries, being as thick as the muscular layer. In large arteries it is not nearly as thick, and at the commence- FIG. 7 I . . ransverse section of the wal Is of an artery, a, lining, endothelial layer, b, elastic layer, c. muscular layer. _d, con- nective.tissue layer, x lOO. (Quain.) roent of the aorta, it is a very thin plate. THE VEINS. Commencing at the capillary there is observed, first, be- ade tHe endotheUal layer, not a layer of muscle cells as in the ii6 THE STUDENTS' MANUAL OF HISTOLOGY. artery, but a layer of a fine longitudinal net-work of fibres. The cells of the endothelial layer are shorter and broader, and are not as fusiform in shape as the corresponding layer in arteries. The adventitia is about the same as that in the ar- teries. In a large number of the veins, muscular tissue is found in this external coat. The whole walls are thinner than ^^l^^z^^-'"^ FIG. 72. Blood-vessels of the stomach of a cat. ■) in arteries of corresponding luminas, and the yellow elastic tis- sue that gives to the large arteries their thicli walls is so scanty in the veins that when they are cut across they collapse and their cavity is obliterated. The valves of the veins are folds of the intima and part of the muscular medium, although some veins are entirely without this ' muscular medium. Arn- stein and Steida claim that the trunks of the venae pulmonales have striped muscle in their walls. Steida says there is an in- ner circular ^nd outer longitudinal coat continued from the THE STUDENTS MANUAL OF HISTOLOGY. 1 17 FIG. 73. Two villi from ileum of infant, x 100. Fig. 74. Btood-vessels of human lung, i^ larger vessels, b, capillary net-work, x 400^ ii8 THE students' manual OF HISTOLOGY. FIG. 75, Looped- capillaries in kidney, a, afferent vessel, b, efferent vessel, c, glo- merulus. X 75. muscular walls of the left auricle. The arteries some- times terminate in veins with- out the intervening capillaries, as in the tip of the nose, fingers and toes, and matrix of nails (Smith.) In the cavernous tis- sues of the genital organs there are large wide sinuous spaces, the walls of which are com- posed of elastic 'and unstriped muscular tissue. The arteries convey blood to these spaces and the veins carry it back. '^IG, 76. Stood- vesse s beneath mucous membrane of intestine of infant. THE students' manual OF HISTOLOGY. II9 The walls of the blood-vessels are supplied with quite a rich plexus of capillary blood-vessels which penetrate the external layers, but never the internal. They are called the " vasa-vasorum " and are in nowise connected with the vessels on which they are distributed. They arise from some vessel at a considerable distance from their point of distribu- tion and supply the walls with nutritive materials. Nerves are freely distributed. METHODS OF EXAMINING. The walls of capillaries can be studied best by isolating some of the vessels of the pia mater. A small piece of brain substance is clipped from the exterior of a con- volution with the pia mater attached. The section is removed to a slide with the pia mater on the glass. By aid of a camel's hair brush the cerebral matter is washed away and a drop of a .5 per cent, silver solution added. In two or three minutes this is removed and distilled water added. The specimen is exposed to the Hght until it is colored brown, when it is placed in glycerine and mounted. The capillaries in the /mesentery of the frog, or tail of the tadpole, can be de- monstrated in this ~way. The silver maps out the cells with unerring accu- racy, and encloses a FIG. 77. View obtained by changing focus of figure 76, showingnUCleuS Itl eaCll OnC. viNi of intestine, etc. x 35. j^ j^e VCSSCls frOm . 120 THE STUDENTS MANUAL OF HISTOLOGY, the pia mater, one frequently sees the termination of a capillary and commencement of an artery, by the appearance here and thereof a muscle cell coiled round the vessel. With a freezing microtome transverse sections of the different arteries and veins can be made from the fresh specimens. The silver method is recommended for the study of the endothelial layers of all vessels. For the intima, a section of the vessel is placed in a i per cent, solution of potassic bichromate for several days, then it can be pulled off with forceps, stained, examined, and mounted in glycerine. Chromic acid preparations are valuable here. For the further study of this layer consult the chapter on mus- cular tissue. CHAPTER IX. The Respiratory Passages. THE lungs first appear as an elevation on the anterior sur- face of the canal which becomes the oesophagus into which the elevation soon opens, forming a hoUow sac. At its lower extremity a bifurcation appears, dividing the tube into two FIG. 78, Formation of the bronchial ramifications and of the pulmonary cells. A, B, development of the lungs, after Rathke, C, D, histological development of the lungs after J. Muller. (Lcnget) branches. These branches divide again and again until the whole of the bronchial system is complete. Then the pulmo- nary vesicles are developed and last of all the trachea. THE LARYNX. The general surface of the larynx is covered with a layer THE STUDENTS MANUAL OF HISTOLOGY. of Stratified epithelial cells, largely of the ciliated variety. Be- neath this is a layer of mucous membrane containing a net- work of capillaries, f Between these two layers can occasionally be demonstrated a layer of connective-tissue cells. The nerves terminate in the mucosa in the form of terminal bulbs. The epiglottis is composed of a basis of reticular or elastic car- tilage and deep layers of epithelial cells cover its anterior sur- face, while the posterior surface has a much less covering of the same kind. THE TRACHEA, The trachea is a fibrous tube, composed of fifteen or twenty hyaline cartilaginous half-rings embedded in its anteri- or walls, together with all the layers present in the larynx. On its internal surface is a continuation of the ciliated cells of the larynx. Just beneath this layer is a thick basement membrane. External to this is the mucosa, and still more external a layer of loose connective tissue containing glands. A layer of striated muscle fibres stretches between the anterior surface of the ends of the incomplete cartilaginous rings. Between every two of these rings are strong bands of elastic and connec- tive tissue. tHE BRONCHL The bronchi have essentially the same structure as found in the trachea. Lining their tubes until they are reduced to jijj- of an inch in diameter are ciliated epithelial cells. As the passages become finer and finer by their division, the cartil- aginous half-rings disappear, and simple lamellae appear in their place. Smooth muscular fibres continue as rings round the bronchial tubes to near their points of termination. The walls grow thinner and more delicate in structure ; and when the tube is reduced to -^ of an inch in diameter, pavement epi- thelium takes the place of the ciliated. This continues until THE STUDENTS MANUAL OF HISTOLOGY. 123. thelial cells. the branch is reduced so that it measures but -^ of an inch, when it has only a basement layer of elastic fibrous tissue, lined with a thin mucous membrane covered with pavement epi- It is now known as the "ultimate bronchial tube.'" It terminates in a pyramidal sac called the " pulmonary lobule,"^ which when moderately extend- ed is about ^ of an inch in diameter. It represents the lung of the frog in miniature. THE LUNGS. First of all then we must study the simple structure of the amphibian lung. The ani- mal is killed by breaking up- the brain substance (pithing). The abdominal walls are opened in the median line with a pair of straight scissors^ , ^ , , ^ , ... , The under blade is then pushed FIG. 79. Lobule of human lung, a, ultimate * bronchial tube ; b, interior of lobule, c, pulmo- yp under the Stemum, CarC be- nary vesicles, x 15. ^ .,,..,. ing exercised that it is kept m close apposition to the inner surface lest it wound the heart. The sternum is cut through in the median line, and just be- neath it lies the heart in its pericardial sac, uninjured and still beating. The mouth is opened, when a little papilla at its back part appears. This is the slit glottis of the frog, formed by folds of the mucous membrane of the mouth, in each fold of which is a cartilage of similar form, the arytenoid cartilages. Between these folds and in this slit place thfe end of a small blow-pipe, or what answers every purpose, a small glass pipette. If! now air be forced through this tube the lungs will expand to their full capacity and rise out of and above the walls of the 124 THE students' MANUAL OF HISTOLOGY- FIG. 80. One-half frog s lung ; show- ing interior division into air cells. Natural size. opened thorax. An assistant now passes a thread tightly around the base of each lung and by aid of a pair of scissors both lungs are removed, inflated and uninjured. If placed near a warm stove, or in the sunlight, they soon dry and retain their expanded form for an indefi- nite time. When dry they can be opened and their internal arrange- ment examined even with the unaided eye. Each lung is a transparent oval sac, pointed at its posterior ex- tremity and covered with a layer of pleuro-peritoneal membrane. (The internal surface is not smooth as in the salamander's, and the newt's, but is divided into a num- ber of smaller cavities formed by folds of the walls of the pulmonary sac. These folds divide the cavity into a number of " air cells," increasing the extent of surface and thus giving more room for the distribution of the branches of the pulmonary artery. Of such a structure is each pulmonary lobule, of the human lung. Each pulmonary lobule is divided into compartments by irregular partitions, on the walls of which the blood-vessels ramify. These compartments are known as the "pulrpppary vesicles;" they correspond to the "air cells" of the frog's lung. Their average diameter is about -j^ of an inch. It has been estimated that in the lungs of man there are. eighteen hundred millions of them, exposing a surface of fourteen hundred square feet. The walls of the vesicles are composed of a thin connective tissue surrounded by elastic fibres. Unstriped muscle is absent from the greater part of the alveolar wall, ex- isting in small amount sometimes toward its base. The vesicles are lined with polyhedral cells, between which are THE STUDENTS MANUAL OF HISTOLOGY. 1 25 larger or smaller openings which lead into the lymph canalic- ular system (Klein). In the lungs is a rich, close net-work of FIG. 81. a, walls of alveolar duct, b, walls of alvebli. c, large flat nucleated cells lining alveoli. (Modified from Klein & Smith.) capillaries. The meshes are usually small, but vary according to the degree of distention of the vesicle. They are formed from the repeated divisions of the pulmonary artery and com- pletely encircle each individual vesicle ; giving rise in this con- nection to an uncommonly close net-work of tubes, which are but slightly embedded in the alveolar walls. The greater part of the walls of the blood-vessels extend into the central cavity,. so that if the lung be but partly inflated, they will hang in loops in the lumen of the alveolus. METHODS OF EXAMINING. In order to study the lung tissue, portions of fresh lung may be teased or picked. Acetic acid or alkalies added, and examined at once. This shows readily the elastic fibres. The frog's lung may be inflated and dried as described above, and 126 THE students' MANUAL OF HISTOLOGY. thin sections made in every direction. The sections can be moistened, stained, and treated with the acetic acid when quite FIG. 82. Transverse section through the pulmonary substance of a child of nine months a, number of pulmonary cells, b, surrounded by the elastic fibrous net-work, which bound them in a trabecula-like manner, and, with the thin structureless membrane, forming their walls (a) ; d, portions of the capillary net-work with their vessels curved in a tendril-like manner, projecting into the cavities of the pulmonary cells, c, remains of the epithelium. (Frey.) satisfactory examinations can be made. If possible however, the blood-vessels and the air passages should be fully injected. It is in this way only that one gets anything like an intelli- gent view. In the smaller animals the venas cavse are tied, and the nozzle of the syringe secured in the right ventricle. The left ventricle is opened to allow the escape of the blood as it is forced out by the injecting material. At the same time the in- jecting mixture is flowing in the vessels the lungs are partially expanded by means of a blow-pipe in the trachea or bronchus. In a few moments the opening in the left ventricle is closed to prevent the escape of any of the injecting mixture. The color of the lungs will decide when they are sufficiently inject- THE STUDENTS MANUAL Or HISTOLOGY. 1 27 ed. Prussian blue has afforded all that could be desired in our hands. Then very small pieces of the injected lung are placed in melted cocoa-butter and allowed to remain there for two or three hours, when they are removed and the butter allowed to harden. Thin sections can be made with a razor in every direction, with or without the aid of the microtome. Instead of inflating the lungs with air,melted cocoa-butter may be used. Oil of cloves dissolves out the butter in a short time, when alcohol can be added to get rid of the oil. The specimens can be stained now with carmine or logwood, cleared in oil, and mounted in dammar. These organs may be hardened by in- jecting in the trachea, or one of the bronchi, a weak solution of chromic acid, -J- per cent. Enough should be injected to distend the lungs slightly, when the trachea or bronchus should be tied and the whole lung placed at once into some of the same solution. The lungs must be cut in small pieces in a few days and placed in a fresh solution, either of the same strength or slightly in- creased. In a week or ten days the pieces are transferred to dilute alcohol and in a few hours to spirits of full strength. Sections can be made now, stained, cleared and mounted. The lungs of embryos should be studied especially. Simple hardening in alcohol, staining and clearing, will be sufficient to enable one to recognize the structure of the whole organ. Pigmented lungs or portions of lung are not uncommon. A fine, black, granular pigment is observed in the walls of the alveoli. This may be caused by small effusions from the pul- monary capillaries ; yet it is almost invariably of extraneous origin, being composed of minute particles of carbon inhaled in the smoke and soot. The lungs of those employed in coal mines are made sometimes quite black by their inhaling par- ticles of carbon in a finely divided state. Some of these par- ticles may enter the lymphatics and be carried to the lymph glands of the bronchi, or to more distant structures. Animals 128 THE students' MANUAL OF HISTOLOGY. confined in a sooty room suffer this same pigmentation of their lungs. If it is desired to examine lung tissue after it has under- gone some of the progressive inflammations, small pieces should be hardened in chromic acid or Miiller's fluid and sec- tions carefully made at the proper time. In suspected cases of phthisis where it is very desirable to know the progress made by the disease, great aid may be procured maqy times by an examination of the sputa of the patient. It is now a recognized fact that phthisis has been diagnosed and is diagnosed in this way, weeks, months before other signs are manifest. As expected ingredients in the sputa, one finds remains of food, starch granules, epithehum, air bubbles, mucous cells, pus cells, blood corpuscles, large granular cells, and perhaps, pig- ment cells. If now besides these there are found fragments of lung tissue, as yellow elastic fibres, it shows that there must be a disintegration of the pulmonary tissue, a condition which must denote serious trouble. If these fibres are not found it does not by any means prove that serious trouble may not exist, but their presence is very significant. Some special directions should be given to the patient whose sputa we are about to collect. First, the mouth should be carefully and thoroughly rinsed and teeth brushed after each meal. Second, the vessel in which the sputa are collected should be scrupulously clean. Third, if the patient is in the habit of using tobacco, it should be denied during the collection of the sputa, as the fibres of the leaf might mislead and cause a wrong diagnosis. If the amount of sputa is small, then all raised during the twenty- four hours should be saved. If large, that first raised in the morning should be preferred. Any little grayish masses should be chosen and placed at once under the microscope. Acetic acid will clear up the mucous, etc., and render more distinct the yellow fibres if they THE STUDENTS MANUAL OF HISTOLOGY. 129 are present. If this examination reveals nothing, the following method should be adopted : Make a solution of sodic hydrate, 20 grains to the ounce FIG. 83. Fragments of lung tissue (yellow elastic fibres). Sputa Uom case of phthisis. Mucus, pus, epithelium, granular matter, etc., were in great abundance, x 215. of water. Mix the sputa with an equal bulk of this solution and boil. Then add to this mixture 4 or 5 times its bulk of cold water. If possible, pour into a conical-shaped glass and set aside. Soon the yellow fibres, if present, will fall to the bottom ; from here they can be drawn up with a pipette and examined. Several glass slides should be examined at a single sitting, and the examination should be repeated every few days until the presence or absence of these fibres is satisfactorily demonstrated. CHAPTER X. The Salivary Glands and the Pancreas. THE salivary glands all resemble each other in general structure, although minor differences exist. The differ- ence in the secretions of the different glands depends upon a slight difference in their anatomical structure. In all the glands the gland tissue is divided by connective- tissue septa into lobes and lobules. The connective-tissue frame-work surrounds the ducts and gives support to the blood-vessels, nerves, etc. The largest (microscopical) ducts are lined with a single layer of columnar epithelial cells. In their walls are non- striated muscle cells. In the smaller ducts there is a relative- ly small lumen lined with columnar epithelial cells which are composed of closely arranged, thick, longitudinal rods (K61- liker.) These rods anastomose laterally to make the intra- cellular net-work of Klein. The small ducts branch into still smaller ones which ultimately terminate in the alveoli of the gland substance. Just before the duct terminates it becomes narrower, sometimes branched, its lumen smaller, and its epithelial cells become a single layer of flattened cells. The terminal alveolus is a rounded sac, convoluted and wavy in appearance. These extend in every direction. They average about the j^ of an inch in diameter. These follicles 130 THE students' MANUAL OF. HISTOLOGY.' 131 or alveoli represent the rounded sac-like terminations of the salivary tubes. Between these are blood-vessels, capillaries, nerves, lymphatics, and connective tissue. In the parotid gland — the only true salivary gland — and in most of the lobules of the submaxillary, the lumen of the alveoli is small ant' lined with a single layer of glandular epi- thelial cells, which are columnar in shape but very short. During secretion the lumen is smaller and the lining cells are broader. In a few of the lobules of the submaxillary and in FtG. 84. Two salivary tubes from the lobule of a muciparous gland, entering Ihe main duct, a, duct of th^ lobule, b, salivary tube, c, follicles, on one side, as they appear in situ. d, follicles separated from each other, showing the windings and offshoots of the salivary tube. (Kolliker.) nearly, if not all of those of the sublingual the alveoli are larger and lined with two kinds of cells, i. The mucous cells are like the goblet cells already described. These con- tain a transparent substance called mucigen (Heidenhain), which during the secretion of the gland is transformed into mucin. 2. The crescents of Gianuzzi. These are composed of nucleated, polyhedral, granular cells, smaller than the mucous cells and situated in the periphery of the follicle. They are arranged very close together after the fashion of a crescent. They represent young mucous cells. After exhaustion of a gland, after the mucous cells have given off their mucin, they disappear, and now only a granular substance remains in the body of the cell. The alveoli are surrounded by a fine capil- lary net-work of blood-vessels and lymphatics. 132 THE STUDENTS MANUAL OF HISTOLOGY. A net-work of fine nerves intra-lobular connective tissue. IS seen in connection with the In this net-work are numerous ganglia composed gener- ally of unipolar ganglion cells. The fine nerve branches terminate in the epithelial cells lining the salivary tubes, each cell representing the terminal organ of each nerve fibre. METHODS OF EXAMINING. Small pieces of the gland are placed in a saturated solution of pic ric acid for 48 hours. Sections can then be made with a freezing micro- tome. Heidenhain employs absolute alcohol and stains with carmine. Small pieces can be macerated in, at first, a weak solution of chromic acid -^ grain to the ounce of water, and gradually increased to Yz grain to the ounce. The ducts are best injected with the Prussian blue. Osmic acid affords a useful reagent, especially for the study of the epithelial cells. A .5 per cent, solution should be employed, and small pieces of the tissue allowed to remain in it for 48 hours. If this reagent is used for hardening, a weaker solution (.25 per cent.) should be used, and the tissue allowed to remain in it for 2 or 3 days, when sections can be made >yith: the freezing microtome. THE PANCREAS. The pancreas was formerly known as the " abdominal FIG. 85, The submaxillary gland of the dog. a, mucous cells, b, protoplasma cells, c, crescent, d, transverse section of an excretory duct, with the peculiar cylindrical epithelium. (After Heidenhain.) THE STUDKNTS MANUAL'OF HlSTOI,OGY. 1 33 salivary gland." It is divided into lobes and lobules and in its intimate structure resembles the salivary glands. The tis- sue is some softer than that belonging to these glands ; this is simply because the lobes are not so compactly arranged. The cells in the alveoli resemble those of the parotid. CHAPTER XL The Pharynx. CEsophagus. Stomach and Intestine. THE PHARYNX. THE walls of the pharynx are composed of transversely- striated muscles with fibrous connective tissue. They are lined by a mucous membrane which is covered with a layer of epithelial cells, columnar and ciliated in the upper third, but squamous and destitute of cilia below. The mucous mem- brane is rich in mucous glands which, in the upper part, collect in groups with a common excretory duct. THE CESOPHAGUS. At about the commencement of the oesophagus (cricoid cartilage) the striated muscle walls of the pharynx are re- placed by the smooth muscle tissue until very soon there are two muscular layers, an external longitudinal, and an internal circular. This arrangement of muscle extends throughout the remainder of the alimentary canal. Beneath the internal cir- cular layer is a coat of submucous areolar tissue, in which are the glands opening on the surface of the mucous membrane. The mucous membrane is quite thick and is arranged in longi- tudinal folds when the oesophagus is not distended. It pro- jects into the epithelial layer as small cylindrical papillae, in the centre of which may be a lymphatic, terminating in a loop or in a single blind vessel. A thick layer of flattened epi- thelium covers the membrane and extends to the cardiac 134 THE STUDENTS MANUAL OF HISTOLOGY. 135 /wv^V^ orifice of the stomach. Between the mucous and submucous coats is a longitudinal layer of smooth muscle fibres, which forms a continuous coat at the lower part of this tube. This is the muscularis mucosa. THE STOMACH. The stomach is surrounded by a serous coat derived from the peritoneum, beneath which is a smooth muscular layer, continued directly from the ceso- phagus and arranged the same as described for that tube. Still deep- er than this is another layer of mus- cular tissue arranged in an oblique manner. Between the muscular and mucous coats is a quantity of areolar tissue in which are found FIG. 86 Vertical section of the hu- , hInnH - vpsspk fat rplU ftr man gastric mucous membrane ; a, sur- tne DIOOU - VCbijeib, Idl CCllS, CIC. facepapiite. b, glands. iF.ey.) ^j^^ mucous membrane is at once very complex and very inter- esting. It is loosely attached to the muscular coat and is easily movable over it ; so that when the stomach is empty it is thrown into numerous folds, or rugae, which have a general longitudinal di- rectionjand are most marked along • the great curvature. 'J'hey ■ are entirely obliterated when the organ is distended; Lining the mucous membrane over the whole surface of the transversely" FIG. 87. of stomach of dog. Horizontal section through fundua 'sg. The peptic glands are cut , cells lining lumen cf gland, b.' , . , ^ , parietal ce'lls, (after Klein and Smith.) x Stomach is a layer of columnar 400. 136 THE STUDENTS MANUAL OF HISTOLOGV. cells -g^ to Y^TT ^^ ^" ''^'-^ high, and j^iVrr to -g-jV? °^ ^^ '"*^'* broad. Among these cylindrical cells are a few that are gob- let-shaped; especially is this true during digestion when many of these cells are seen. The epithelium extends into the ducts of the glands which are placed perpendicularly to the surface. Beneath the layer of epithelium is a basement membrane of flat nucleated endothelial cells. In the mucous membrane are > found connective-tissue cells, endothelial cells, lymph cells and the glands and their tubes. If the surface of this membrane be examined with the aid of a common lens small depressions are seen about ithe Y^ of an inch across. On these alveoli are the small round openings of the ducts of the tubular glands. Two kinds of glands are imbedded in the mucous membrane; those in the pyloric portion — pyloric glands, and those in the other portions, — peptic glands. The peptic glands consist of three or four gland tubes, ' closed at their deep extremity, which empty into one common FIG. 88. Peptic gland from cardiac portion duCt. A gland is divided intO of human stomach. 1, Excretory tube, lead'ng . to the surface, a, Tubular follicles, containing three parts, itS duCt, neck and spheroidal cells. [Kollikor.) rr., , , , body. The duct extends from -J^ to -J- the whole length of the tube; the neck from -J- to -J- of the same distance. Both the duct and neck are lined with the same cells that cover the free surface of the mucous membrane, with this difference, that in the neck the cells are shorter and THE STUDENTS MANUAL OF HISTOLOGY. I37 the nuclei smaller. Outside of these cells, but inside the walls of the tube, are other nucleated cells of a granular appearance. They do not form a Continuous layer, being found only here and there. For a long time they were described as " peptic cells," but Heidenhain showed their position in the tube, and gave them the name of "parietal cells." The body of the gland is lined with a layer of cells directly continuous with those of the neck^ only here the cells are more columnar. They have a spherical or oval nucleus which takes staining very readily. But few parietal cells are seen in the body of the gland, and they decrease very rapidly towards the fundus (Rollet.) During digestion the cells in the body of the glands become thicker, more opaque and granular, giving the whole gland a broader appearance (Heidenhain.) As these glands approach the pyloric portion of the stomach, the ducts become longer and the remaining portions shorter. It has been noticed in some animals that when the peptic O---^^^ 1^^^^^,^ and pyloric glands meet, they not only intermix, but also that the peptic glands become trans- formed into the pyloric. , . ^ _, . , , , „ The pyloric glands have a FIG. 89. Fundus ot a gland tube. The chief '^■' ° cells a, have a distinct reticulum, b, the nu- mUCh longer duCt, with a very cleated parietal cells, c, lumen of tube. (.After Klein.] x 450. short neck. ■ The body is com- posed of two or more tubes. The lumen of the gland is many times larger than in the other glands. No parietal cells are found in these glands. By some they are regarded as simple peptic glands, while this is denied by others; they are certainly not mucous glands as was formerly supposed. These glands continue to the pyloric orifice, and then pass through into the duodenum as Brunner's glands, which are 138 THE students' MANUAL OF HISTOLOGY. identical with them in structure. A layer of muscle fibres separates the mucous from the submucous tissue (musculrisa mucosse.) The fine terminal arterial branches enter the mucous mem- brane and form a plexus upon the walls of the gland; branches of this plexus surround the mouths of the glands and borders of the -alveoli; (see figure 72.) The lymphatics arise in the mucous membrane by a net-work of vessels, situated" between the tubules. They are not as superficial as the blood-vessels, and they commence as loops, or in dilated extremities. Be- neath the mucous membrane they empty into a fine plexus, then pierce the muscularis mucosae to form another coarser plexus in the submucous coat; the branches then penetrate the muscular layers and follow the direction of the blood-vessels until they reach some of the lymphatic glands found on the surface of the stomach. Fine nerve gangliated plexuses are seen between the mus- cular layers and in the submucous coat. THE INTESTINE. The walls of the intestine, both small and large,- 'are the same as those of the oesophagus and stomach, viz.: .1, an epi- thelial layer resting on 2, a mucous membrane beneath which is 3, the muscularis mucosae which in turn is surrounded by 4, a submucous tissue, and external to this are 5, the circular, and 6, the longitudinal layers of muscle cells. A serous covering, from the peritoneum, surrounds the whole. THE SMALL INTESTINE. The mucous membrane of the small intestine is thrown into a number of folds which cannot be obliterated by the dis- tention of the canal. These are the valvulae conniventes. They extend one-half or two-thirds of the distance around the canal, are about ^4 of an inch wide and are placed in clos^ THE students' manual OF HISTOLOGY. 139 succession. Small processes ai the mucous membrane cover these folds completely, and fill the spaces between them. These, prolongations are the villi; they are from -^^ to ^ of an inch- long, and are most numerous in the duo- denum and jejunum.' Krause estimates the whole number in the intestine to be at least four millions. Colum- nar epithelial cells cover the villi and the mucous fnembrane of the small intestine throughout its entire length. At the base of each villus is a small arterial branch which runs in the centre toward the surface. It soon gives off a number of branches to make a most beautiful capillary net- work which terminates in a vein, and this in turn penetrates the mucous coat to pass into the submucous layer (see figure 73.) The small tymphatic,-or lacteal, occupies.thexentre of the vil- lus, usually as a single tube, sometimes double, with walls of a single layer of endothelial cells or plates. It usually com- mences as a blind tube, with perhaps a dilated extremity and surrounding it are a few muscle cells arranged in a longitudinal man-ner. These cells are prolongations from the muscularis- mucosee and when stimulated they cause a decided retraction of the villus. The matrix of each villus is composed of a delicate retic^ ulum in which are seen a few nucleated fat cells. This retic- ulum forms the interstitial substance of the basement mem- brane, between the covering of epithelial cells and the mucous FIG. go. Transverse section of the ileum of an infant, injected. a, blood-vessejs filled with the injecting ma- terial. I3, muscle walls, c, villi, 140 THE students' MANUAL OF HISTOLOGY. membrane; from this, prolongations extend between "the epithelial cells on the surfaces of the villi; it forms the inter- stitial substance between the endothelial plates composing the wall of the lymph capillaries, and also of the blood capillaries. k FIG. 91. Vertical section of a villus of the small inlestine of a cat; hardened tn chromic^ acid, a,* streaked basal border of epithelium, b, cylindrical epithelium, c, goblet cells, d. central lymph vessel, e, smooth muscular fibres whieh lie nearest to the lymph vessels, f, ade- . noid stroma of the villus in which lymph corpuscles lie. (Klein.; A very interesting question presents itself here as to , the man- ner in which chyle prasses- from the interior "of the intestine into the lacteals and blood-vessels. It is quite generally taught that the minute chyle globules pass directly into the body of the cells covering the villi, and thence pass into the capillaries or lymph ducts. Thus Kolliker and others have described and illustrated these particles of oil as passing through the cells. The researches of Dr. Watney, under the direction of E. Klein, have thrown much needed light upon this subject. According to these authorities the epithelial cells are engaged here in secreting mucus and not in absorption. Absorption THE STUDENTS MANUAL OF HISTOLOGY. 141 takes place through the interstitial substance of this delicate reticulum. The chyle globules then pursue the foUowing^ course: They enter the interstitial substance between the epithelial cells and pass into the directly continuous basement membrane; from here they pass into the matrix reticulum of the villus, and finally into the interstitial substance between the endothelial plates into the blood or lymph channels. Thus it is seen that there is a continuous lymph-canalicu- lar system from the free border of the villus to the central vessels. This affords a very satisfactory explanation of the absorption from this canal, for, owing to the centripetal direc- tion of the flow in the lymphatic vessels, there must be a strong tendency for matter out- side the vessels to pass into their interior. At the base of the villi are the crypts of Lieber- kuhn. These are minute tubes placed perpendi- cularly to the surface, and consist of tubes lined with columnar epithelium. They are from ^ to ^ of an inch in length and •jpi-j- of an inch broad. In the submucous tissue of the duodenum are the glands of Brunner, identical with the pyloric glands. Between the longitudinal and circular layers of muscle is a plexus of band-like nerve branches, among which are groups of glanglion cells, called the " plexus mesentericus of Auerbach." Branches pass from this plexus into the sub- mucous tissue to give rise to the "plexus of Meissner." Here are unipolar, bipolar, and multipolar ganglion cells. FIG. 92. Lieberklihnian glands (a) of the cat, with the intestinal villi (b) situated over them. (K()tliker.) 342 THE students' MANUAL OF HISTOLOGY. Branches are distributed from both these plexuses in every -direction. THE LARGE INTESTINE. The walls of the large intestine resemble in all respects those of the small. The mucous membrane, however, is. destitute of villi, but more freely supplied with the crypts of Lieberkiihn. Here these glands are placed more closely together, are longer and more numerous. METHODS OF EXAMINING. There are many methods employed to demonstrate the structure of these organs. Only stomachs from recently killed animals should be chosen, for if only a short time has elapsed since the death of the animal, the softer struct- ures of the inner coats will be affected. A piece of stomach an inch square, or several such pieces are placed in Muller's fluid, to be transferred in a week or ten days to alcohol. Vertical sections show all the coats to good advantage. Small pieces can be hardened in al- cohol alone, and stained with carmine. Sections should be made perpendicular to the free surface of the mucous mem- brane, in order to obtain good views of the glands. For this purpose, small pieces from different parts of the mucous membrane are placed immediately in absolute alcohol. When hardened, vertical sections are made as thin as possible, and stained in carmine or hgematoxylin. The sections are well preserved in glycerine or dammar. Horizontal sections show the different parts of the glands cut across. They are to be stained and mounted as the others. Small pieces of the mucous membrane are placed in a X per cent, solution of osmic acid for 24 hours and sections made with the freez- ing microtome. This process demonstrates the cells in the glands in a very satisfactory manner. THE STUDENTS MANUAL OF HISTOLOGY. 143 To Study the blood-vessels of the organ, the entire animal, if small, should be injected. Beautiful preparations are made from the stomach of a cat or rabbit, injected with Prussian blue or carmine. Pieces of the small intestine are treated like those of the stomach, only in the injected specimens sections should be made with the aid of a freezing microtome in order that the villi may not be injured. Such specimens should be stained but slightly. To examine the lacteals, the animal should be given a meal composed largely of fatty matters, and then killed in 3 or 4 hours. Small pieces of the mucous membrane are placed in a I per cent, solution of osmic acid and allowed to remain therein nearly 48 hours. This stains all the fatty particles black, and thus shows the outlines of the lacteal in the centre of the villus. Chromic acid, chromate of potash, teasing, penciling, and tingeing should not be forgotten CHAPTER XII. The Liver. THP liver is very edfly to show itself, for it has attained comparatively an enormous size by the end of the first month of uterine life. Buds or projections appear on either side of the intestine to form the two principal lobes of the liver. It soon occupies nearly the whole of the abdominal cavity and in proportion to the body weight, bears the fol- lowing relation according to Berlach: At the end of the first month as i to 3. At full term as r to 18. In the adult as 1 to 36. It is very soft in structure during the first months, but as its development progresses its tissue becomes more firm. The liver is very peculiar in its structure, and is unlike any of the other glands of the body. By the unaided eye one is just able to discern on the natural external surface of the human liver an innumerable number of pentagonal or hexagonal islets, known as the hepatic lobules. They are about -^ of an inch in diameter and their number corresponds with the number of central veins. In the liver of the pig these lobules are easily dis- tinguished by the naked eye, for a considerable amount of connective tissue completely separates them from one another. In the human liver this connective tissue is not nearly so well developed, and in many parts of the organ the surface of one lobule is in direct contact with the adjacent ones. Each lobule is composed essentially of two substances : 144 THE STUDENT S MANUAL OF HISTOLOGY. 145 the liver cells and the capillaries. The capillaries present an uncommonly complicated net-work. Commencing with the portal vein, it is seen to enter the transverse fissure together FIG. 93. Transverse section of a single hepatic lobule. (Sappey.l 1, intralobular vein, cut across. 2, 2, 2, 2, afferent branches of the intralobular vein. 3, 3, 3, 3, 3, 3, 3, 3, branches of the portal vein, with its capillary branches, forming the lobular plexus, extend- ing to the intralobular vein. with the hepatic artery, hepatic duct, nerves and lymphatics, surrounded and bound together by a fibrous connective tissue, the capsule of Glisson. From the portal vein are given off small branches which pass between adjacent lobules. As these terminal branches extend only between the lobules and never enter within them, they are called the intermediate veins, interlobular veins. From these veins branches are de- rived, which rapidly divide into a close capillary net:Work, and approach the centre of the lobule in a radial manner. The net-work is formed by horizontal or transverse branches con- necting the principal capillaries as they pass from the periph- ery to the centre of the lobule. This forms a "lobular plexus" of capillaries, with each vessel about the Tj-jVir o^ ^^ ''^'^h ■ in 146 THE students' manual OF HISTOLOGY. diameter. As they near the centre of the lobule, they unite' together to form veins of considerable size, which empty into a single centrar vessel placied in the long axis of the lobule. This vessel, from its central .position, is called the intralobular vein. It is from the xs'^nr. to the -^^ of an inch in diameter and empties into a larger vessel just at the base of the lobule, from its position, named the sublobular vein. These veins collect the blood from all parts of the liver, and convey it to larger vessels, which become larger still, until the three hepatic veins are formed. At the termination, then, of the portal vein, are the interlobular branches, and the intralobular vessels mark the commencement of the hepatic veins, the lobular plexus being the intermediate system of capillaries. The hepatic veins have very ihin walls, mich thinner than the por- tal, and they are not surrounded by any Gl^sson's capsule, but are quite firmly united to the hepatic tissue. The hepatic artery enters FIG. 94. a, smaiT hepatic vein, b, sub- the shcath at the transvcrse tabular veins, c, lobules. (Kiernan.) j. , . ,. , . fissure, and immediately gives off branches to the walls of the portal vein, and a very rich plexus to the walls of the hepatic duct, so that when this artery is thoroughly injected it almost covers, with its capillaries, the walls of the duct. It supplies also, the- capsule of Glisson, the branches known. as capsular branches. Branches of this artery are interlobular, and accompany the branches of the portal vein. According to Beale, these branches lead into special veins, which accompany the arteries in couples, and join the interlobular branches of the portal. According to some observers, the capillaries and veins from the hepatic artery join the capillaries of the lobules by an THE students' MANUAL OF HISTOLOGY. 147 anastomosis of the blood-capillaries of the bile ducts with the capillaries of the lobules. All the space not occupied by the capillary net-work is filled with the glandular cells of the organ. These are circular when seen single, but angular, pentagonal, or hexagonal when viewed in thin sections of the liver. They are about the Yihrv °^ ^^ ^'^^^ '" diameter, and are provided with a well marked nucleus. Here again is the inter- cellular and intranuclear fibrillar net-work of JKlein and others. Some FIG. 95. Liver cells, a, contain- of the ccUs have two Huclei, and ngfat. X400. . ^ r 1 1 1. 1 mmute fat globules, one or more to to each cell are very generally seen. The fatty embedments are present in the liver cells of adults whose diet is rich, and they occur also in the young infant, and in the fattened lower animals. The liver cells may become in this way crowded with fat, which soon dissappears when the manner of living is changed. Small particles of pigmentary matter are sometimes abundant in the cells, giving them a peculiar brownish appear- ance. Each cell is in direct contact by some of its surface with a blood-vessel. It is with the greatest difficulty that the bile capil- laries can be investigated. A fine system of bile ducts is recognized running with the interlobular branches of the por- tal vein. Into these fine branches empties a delicate net-work of the.fiijest .biliary capillaries, their diameter varying from the -j-jfjnj to the xTfr)r o^ ^^ '^^^^h- These capillaCries run between the liver cells, and thus enclose polygonal sprees of the shape and diameter of a single cell. In this way every liver cell, from the periphery to the centre of the lobule, is in contact, by one part or another of its surface, with these fine biliary pass- 148 THE students' MANUAL OF HISTOLOGY. ages. These capillaries always pursue a course with reference to their keeping, as far as possible, from the blood capillaries, for there always remains part of a cell between the bile capil- FIG, 96. Biliary cipillary of the rabbit's liver. 1. A part of the lobule; aiVena hepatica, b, branch of the portal vein, c, biliary ducts, d, capilliaries. 2. The biliary capillaries (_b) tn their relation to the capillary blood-vessels (a). 3. The relation of the biliary capillaries . to the hepatic cells, a, capillaries, b, hepatic cells, c, biliary ducts, d, capillary blood- vessels (after Frey.) lary and blood capillary. These biliary canals pass between the boundary surfaces of two neighboring cells, and hot simply .^long their bord,ers; in this. way th^ surface of a cell may be divided into two equal or unequal parts. Whenever a bile duct is found along the border of a cell, it will be noticed that no blood capillary comes in contact with that part of the cell in any way. It is impossible, then, to find a fine bile passage and a blood capillary without intervening cell substance, and more than this, if a few cells exist in the liver not touched by blood- vessels, they are sure to come in contact with a fine gall duct. Authorities are about equally divided on the question of the bile capillaries having a membrana propria. Some hold that the liver cells themselves form the walls of the ducts, while others describe and illustrate these finest ducts as possessing a THE students' MANUAL OF HISTOLOGY. 149 very tenacious, but delicate membrane. The latter view, we believe, is the correct one. FIG. 97. From investigations of H. R. Stiles on -the Texas cattle disease, a, bile capillaries, b, liver cells, c, mennbrana propria of tlie bile capillary. METHODS OF EXAMINING. The usual methods are followed in studying this organ, viz.: Injecting, hardening and staining. To examine the unin- jected liver, small pieces are placed at once in Miiller's fluid and al- lowed to remain there for two weeks, at least. A large amount 6i the fluid should be used. The Science' (Hayes) 1879, July, by w. G. pieces are then placcd in dilute al- bile capillary, .... , , • cohol for a day or two, and then in alcohol of full strength for two or three days longer. Sections can be made now without trouble, and stained with haematoxy- lin. Sections should be made in at least two directions: FIG. 98. From Quarterly Jour, MetJ. ■ , July, by Vy. G. b, bile capillary, ISO THE STUDENTS MANUAL OF HISTOLOGY. First, parallel to the surface, in order to cut the intralobular veins across, and show the arrangement of the lobular plexus of capillaries and their relation to the liver cells. Second, ver- tical to this surface, showing the intralobular veins along their length, and their terminations in the sublobular vein. These vessels are seen to much better advahtage in injected speci- mens. The liver of the rabbit or cat is especially suitable for injection. The animal should be killed by bleeding. A branch of the artery, or portal or hepatic vein, or branch of a duct may be injected, or several of these may be injected at the same time with different colored mixtures. As in the case of many of the vessels of the different organs, so here especi- ally will it be wise to make a slit through the walls of the vessel in a longitudinal direction, and insert the pipe into this rather than into the opening of the cut end of a vessel. In this way a pipe can be inserted into a vessel scarcely larger than the pipe itself. To inject the portal vein thoroughly, first a solution of salt should be injected in order to wash out the blood. To inject the biliary passages, the pipe of the injecting apparatus . is secured in the common bile duct, and slight pressure employed. The Prussian blue .mixture is satisfac- tory here, and as soon as a few of the lobules are seen colored by the blue, the duct should be tied, and that part of the organ placed in Miiller's fluid, afterwards in spirits, and finally stained slightly with hasmatoxylin, cleared in oil of cloves, and mounted in dammar. CHAPTER XIII. Kidney. THE first trace of a urinary apparatus is found at an early period of embryonic life, and consists of two organs known as t'he Wolfifian bodies; these are fully developed by the end of the first month and hardly to be detected after the second. At this early period the alimen- tary canal is a blind tube from which is given off a diverticulum. From this canal three diverticula arise. From the anterior one will be de- veloped the female generative organs — uterus, fallopian tubes, and the analogous organs in the male — prostatic vesicle and appendage to epididymis. From the posterior one will be developed the kidneys of the adult. Between these two will arise the Wolffian bodies. When fully developed, they will correspond in structure to the true kidney ; the tubules however will be about four times as large. The physiology of these bodies is not un- derstood, but it • is altogether probable that they aijswer the same purpose in the embryo that the kidneys do in the adult, viz. : They throw off from the body some principle that would be injurious to it if retained. 15-1 FIG. 99. Diagrann of the forma- tion of the uro-genital organs, i. a, intestinal canal with protuberance b. 2. The protuberance is very much developed, a, allantois. b, the urachus. c, ^he bladder, d, the genito-urinary sinus, with three protuberances. 1. duct of MUller. 2. Wolffian body. 3, the kidney. (alter Kubs.) 152 THE students' MANUAL OF HISTOLOGY. At this early history in the life of the embryo, the Wolffian bodies, liver, and intestine fill the abdominal cavity, and they are the only organs of any size present. After the first month these bodies commence to diminish in size while the organs be- hind them as rapidly increase in size. The result of this is, that at the end of the second month the order has been re- versed, and now the true kidneys rise from behind the tem- porary or false ones, and by their rapid grow;th leave the atrophied Wolffian bodies at their lower parts. FIG, too. Vertical section of the kidney. fSappey.) 1,1,1,2,5, 3, 3, 4, 4, 4, 4, pyramids of Malpighi. 5, 5, 5, 5, 5, 5, apices of the pyramids surrounded by the caiices. 6, 6, cqlumns of Bertin. 7, pelvis of the kidney. 8, upper extremity of the ureter. The kidney of the adult is likened to a bean in shape; the concavity of the bean representing the hilum of the kidney. THE students' manual OF HISTOLOGY. 153 organ. At this place the ureter receives the urine, and the blood-ves- sels find their entrance and exit. A vertical section through this organ, from its convex to its concave borders reveals from twelve to twenty eminences projecting into the pelvis ; these are the papillae. On each papilla there are from twelve to twenty openings which rep- resent the terminations of that number of collecting tubes. The unaided eye readily discerns a difference in structure between the part of the organ lying towards its concavity and the part towards its convexity. The part toward the papillae has a fibrous parallel arrangement, while the other part is darker, homogeneous, or granular in appearance. The former is the medullary and the latter the cprtical substance of this The medullary substance can be divided into pyramids; each pyramid having a papilla for its apex and an imaginary line between the medullary and cortical portions for its base. If one of the twelve or twenty tubes forming each papilla be examined, it will be seen to divide into two or more branches, each of these branches dividing again until they are reduced in size to about the -j^ of an inch. This process of division is generally com- J-mucou3 tissue. I, lymphoid tissue of the latter. (After Frey.) x 32. lymphatics. In the soft spleen substance are seen cylindrical masses of adenoid tissue, averaging about the -^ of an inch in diameter, and surrounding the arterial branches. These are the malpighian corpuscles or the lymphatic follicles of the spleen. In some cases these follicles are situated on the side of the arterial wall, or the vessel may pass directly through their centre, or what is most generally the case, the blood-vessels are situated excentrically, surrounded by a greater amount of i68 THE STUDENTS MANUAL OF HISTOLOGY. adenoid tissue on one side than on the other. Branches ex- tend into the corpuscle from the blood-vessel. Now the ex- ternal connective-tissue coat of the. small arteries becomes transformed into lymphoid tissue, so that these Malpighian corpuscles represent localized expansions of this external coat. The meshes are filled with lymphoid cells, and capillaries are freely supplied. FIG. 1 t4. Small artery, to which Mjip.gn corpuscles are attached, x 10. (Kolli| ' umns ; k, anterior, I, posterior, nenre-roots. 1 88 THE STUDENTS MANUAL OF HISTOLOGY. The posterior fissure is not so distinct as 'the anterior, but extends nearly to the centre, this also receives a fold of the pia mater. The two surfaces of this reflected fold often become united so that the fissure is obliterated. FRAME-WORK OF THE CORD. Prolongations of the pia mater not only enter the fissures but also minute septa between sec- tions of the white substance. They carry blood-vessels with them. A semifluid, homogeneous substance^ fills all the interstices between the nerve substance proper of the cord. This is the neuroglia matrix of Klein. There are also minute fibrils, forming I g a net- work, quite similar to elastic tis- sue, neuroglia fibrils. These fibrils pursue a longitudinal direction in the white substance, but every direction in the gray. There are present also branched, nucleated, connective-tissue cells. The "neuroglia" of the cord is -composed of all three, matrix, fib- rils, and cells. The greater the one of these parts, so much the greater the others. The amount of neuroglia varies in the different parts of the cord. , WHITE SUBSTANCE. A thin transverse section of the cord reveals two substances, a central or gray substance, resembling in shape a FIG. 1,1. Transverse section of capital H, and 3. peripheral or white heighte''"''/,' upper cervic'ai°'°B! substancc. The white substance r7ir°Sg:men,.E,S;of cach half . of the cord may be F coccygeal, (partly from Quain). ^jj^idgj i^to three columns. The antc- THE STUDENTS MANUAL OF HISTOLOGY. 189 rior (ventral) column includes all that part of the cord which is bounded internally by the anterior median fissure, exter- nally by the anterior cornu and the nerves emerging from it to give rise to the anterior spinal nerves, and posteriorly by the . gray substance. It is continuous with the anterior pyramids of the medulla. The lateral column is bounded ife"f^^ :^:*(7m riG. 132. Transverse sectioli of one-half of the spinal cord of a dog. x 15. internally by the gray matter, and anteriorly and posteriorly by the anterior and posterior cornua. It is continuous with the lateral column of the medulla, and is much the largest of the three columns. 190 THE STUDENTS MANUAL OF HISTOLOGY. The posterior (dorsal) column is bounded internally by the posterior median fissure and externally by the posterior cornu. This is directly continuous with the restiform body of the medulla. Besides the neuroglia and its nutritive system of vessels, nerve fibres are seen running mostly in a longitudinal direc- tion. In a transverse section of the cord the white sub- stance appears composed entirely of these minute cylinders cut across. The axes of these fibres take the staining readily, and each one is seen surrounded by a transparent zone which represents the myeline. Just external to this is the frame-work of the cord, for there is no positive evidence of a sheath of Schwann. Not all of these fibres, how- ever, pursue a horizontal direction, for in a transverse section, just at the base of the anterior median fissure, a band of nerve fibres is seen passing horizontally from the gray matter of one side to the white of the other ; this is the anterior white commissure. This commissure makes a direct connection between the white matter of one side and the gray matter of the oppo- site side. Still other fibres are seen passing from the gray matter of the anterior cornua into the white matter of the later- al tracts, also similar fibres from the posterior cornua pursuing the same oblique direction. Horizontal fibres pass from the posterior nerve roots into the gray matter of the poste- rior cornua, and some of their fibres having their origin in the anterior cornua pass obliquely through the white sub- Stance to form the anterior nerve roots. THE GRAY SUBSTANCE is represented by the Latin capital H, and presents two anterior and two posterior cornua. The anterior cornua are thicker, blunter, with a serrated appearance at the mar- THE students' MANUAL OF HISTOLOGY. 191 gin, and they do not extend to the surface of the cord. Here are found the largest nerve cells in the body. In a well stained specimen of the spinal cord of the dog in the author's possession these large cells are visible to the naked eye. They are arranged in three groups, inner, anterior, and lateral, named in the order of the size of their cells. The cells are large, with branched and FIG. I33. Nerve cells from anterior horn of the spinal cord of the ox. Obtained from fresh specimen by staining with hsematoxylin, x 150. unbranched procesess, having a nucleus and nucleolus sur- rounded by a membrane with an intranuclear net-work (Klein). The unbranched processes are known as "axia^cylinder" pro- longations. While there is usually one, there may be two of these in one cell. They ultimately receive a medullary substance and sheath to form a nerve fibre. Cells are known as apolar, unipolar, bipolar and multipolar, accord- ing to the number of processes or poles proceeding from 192 THE students' MANUAL OF HISTOLOGY.' them. Small nerve cells are found here which exist in greater numbers in the posterior cornua. FIG. 134. Nerve cell from anterior horn of the hunnan cord, a, axis cylinder process. (Gerlach). X 150. The posterior cornua are narrower and longer, extend- ing nearer to the surface than the anterior. Near their termination is an enlargement, named from its appearance, substantia gelatinosa. At the base of the posterior cornua, internally, a little back of the central canal is a mass of cells, restricted nearly to the dorsal region, known as Clarke's column. A little anterior to the middle of the commissure that connects the two parts of . the cord is seen the central canal which varies in diamet^ throughout the whole length of the cord. In carefully , prepared specimens THE STUDENTS MANUAL OF HISTOLOGY. 193 it is visible to the naked eye. It is in communication above with the fourth ventricle and extends below to the ter. mination of the cord. It is lined with cili- ated, columnar, epithelial cells which have a long, slender filament extending into the connective-tissue, which surrounds the canal just outside the cells. The space between the filaments of these cells and the connective-tissue is filled with a fine granular substance, which Gerlach FIG. 135. Wall of the belicvcs to bc " connectivc-tissue, devoid central canal of the sprnal cord, a, connective tissue, of elastic fibre nct-work." A few nuclei b, fine granular substance. c, ciliated cell in way of devei- are scen hcrc, from which probably will opment. d, ciliated epithe- .,,.,,, ^ Mum. (Gerlach.) bc developed new epithelial cells. In early life this canal is filled with a fluid, — the cerebro-spinal fluid — but in the adult the canal is more or less com- pressed by the proliferation of the cells, and not capable of holding so much fluid. Anterior to the central canal, between it and the anterior white commissure, is a band of gray matter, the anterior gray commissure. Posterior to the central catial, between it and the base of the posterior median fissure is a similar band of gray matter, the poste- rior gray commissure. Beside the cells in the gray matter, there is a minute net-work of fibrils known as " Gerlach's nerve net-work." This net-work is composed of minute primitive nerve fibrils, some of which have been seen to anastomose with the ulti- mate branches or divisions of nerve fibres from the poste- rior nerve root. All the branched processes of the nerve cells anastomose with Gerlach's nerve net-work. Nerve cells in the anterior cornua are attached to this net-work, while at the same time they are attached, through their axis- cylinder prolongations to meduUated nerve fibres. Although 194 THE STUDENTS MANUAL OF HISTOLOGY. the nerve cells in the posterior cornua anastomose with Gerlach's net-work, there is no direct union with nerve fibres. Some of the nerve fibres originating in the anterior cornua pass to the lateral tracts and proceed direct to the brain as longitudinal fibres, not attached to any ganglion cells. (Klein). Numerous fibres pass horizontally through the anterior portion of the posterior horns. (Gerlach. Brauch). Bundles of fibres run longitudinally through about the middle of the posterior horns (Smith). In the dorsal region are bundles of fine fibres from Clarke's columns of ganghon cells running in three direc- tions, I, backward, 2, crossing each other, and 3, passing in an outward direction (Gerlach). The spinal cord is well supplied with blood-vessels. METHODS OF EXAMINING. Many methods are given for preparing the cord for study. The following method is in constant use at this laboratory : The cord is removed carefully from its bed and cut at once, with a razor wet with alcohol, into pieces about y^ of an inch in length. These are immediately placed in a large amount of MuUer's 'fluid. In a few days they are taken out and stripped of their membranes. This is not done at first from fear of injuring the soft tissue. They are replaced in the fluid where they can remain for an indefinite length of time without injury, or in a few days more may be placed in alcohol where they remain for three or four days, when they are transferred to abso- lute alcohol, until the requisite hardness is obtained. This is discovered by repeated trials although it will not vary far from twenty-four to thirty-six hours. If over-hardened the sections crumble ; if not hardened sufficiently the tissue springs, and .only thick sections can be obtained. The piece is usually embedded, and then either held in the THE students' manual OF HISTOLOGY. I95 hand or placed in the microtome, the tissue and razor being flooded with afcohol. The thin section is now slightly washed by allowing a few drops of water to flow over it. Haematoxylin, carmine and aniline blue are valuable color- ing agents. When carmine is used, it is better to dilute Seal's carmine one-half with water and to allow the sec- tions to remain in it from two to twelve hours. For class work, it is used full strength, and the specimens remain in it from fifteen to thirty minutes. Distilled water is now flowed over the section until the excess of carmine is removed, when a few drops of a one per cent, solution of acetic acid are added. This is removed and alcohol sub- stituted, which is replaced by absolute alcohol in about fifteen minutes. In about five minutes this is removed and the oil of cloves added. In a short time the speci- mens have cleared, when they are preserved in dammar. This gives great contrast between the two substances of the cord, stains the cells, their nucl i and nucleoli and the axis-cylinders in a most beautiful manner. Fresh speci- mens may be placed in the freezing microtome, the sections stained, and satisfactorily examined immediately. There are many valuable methods of treating the cord for exami- nation; these are given in full in our works on microscopic- al technology. CHAPTER XVII. The Brain. THE neuroglia of the brain is quite similar to that of the spinal cord. There are a few differences, e. g. in the white matter are seen small round cells between bundles of fibres, which are collected in masses in certain parts of the brain, as in the olfactory lobes. Boll describes connec- tive-tissue cells in the gray matter surrounding the blood- vessels. Duke Charles, of Bavaria, says that there are color- less blood-corpuscles around these vessels both in disease and in health. The membrane lining the ventricles of the brain is a continuation of that lining the central canal of the spinal cord and is covered with a similar layer of ciliated cells. It is an accumulation of neuroglia, and is known as the ependyma. WHITE MATTER. In the white substance of the brain the nerve fibres are meduUated as in the spinal cord, but are without any sheath of Schwann. Some of these fibres are extremely minute, while others are of medium size. These fibres con- nect the different parts of the brain substance as follows : 1. Those uniting the gray matter of the hemispheres with the large cerebral ganglia. 2. Those uniting identical parts of the two hemispheres e. g. corpus callosum. 196 THE students' MANUAL OF HISTOLOGY. 197 3. Those joining dif- ferent parts of the same hemsiphere. 4. Bundles of fibres connecting the hemis- pheres with the cere- bellum. We owe our present knowledge largely to Meynert, the highest authoritiy on these subjects. He regards those fibres that unite the gray matter of the cerebrum with the large cerebral ganglia as the projection sys- tem of the first order. Those fibres which pass between the cere- bral ganglia and the gray matter around the ventricles, he considers the p r o- jection system ' of the second order. These are motor fibres passing through the crus cerebri and the pons into the white substance of the cord. The nerve fibres com- posing the roots of the 5 FIG. 1 36. Transverse section from a sulcus of the 3d frontal convolution of man. x too. (Charged from Meynert). The medullary substance is not given in the drawing. , The gray substance of the medulla. 198 THE students' MANUAL OF HISTOLOGY. cerebral nerves he regards as the projection system of the third order. GRAY MATTER. Meynert classifies the gray matter under the following four divisions : I. The cortex of the cerebral hemispheres. ' Corpora striata. .. The large cerebral ganglia ^^^^^^^ Corpora quadrigemina, ' Rhomboidal fossa. Aqueductus sylvii. Tuber cinereum. Gray matter lining ventricles. Infundibula. 4., The cortex and central gray matter of the cerebellum. Here in the gray matter is a fibrillar net-work correspond- ing to Gerlach's nerve net-work in the spinal cord. Multi- polar ganglion cells are met yfith everywhere, varying in size and generally possessed of one unbranched process, the axis cylinder, which becomes a meduUated nerve fibre. In the cortex of the cerebral hpmispheres are the follow- ing five layers of Meynert : 1. Neuroglia and nerve net-work with small multipolar ganglion cells. 2. Small, pyramidal, closely crowded ganglion cells. 3. Numerous large ganglion cells, not crowded. These cells have (a), a branched process directed towards the surface, (b) branched lateral processes, (c) an axis-cylinder process in the centre of the basis processes. ; 4, Small irregular ganglion cells with few branched pro- cesses. . He regards the first three layers as containing the motor cells and the last layer as connected with sensory nerves. , ' 5. Branched, spindle-shaped ganglion cells parallel to THE STUDENTS MANUAL OF HISTOLOGY. 199 the surface. All of these cells have a nucleus and gener- ally a nucleolus. Meynert gives the following deviations from this rule ■ 1. In' the gray matter of the posterior portion of the occipital lobe about the sulci hippocampi there are eight layers. The prominent feature here is "small multipolar cells "the granular formation of Meynert.'" 2. In the cortex of the hippocampus major the small cells of the fourth layer are wanting. The second and thir'd layers are the chief elements. FiG. 137. Ganglia cells from cerebral convolutions, a 400. 3. In the walls of the fossa sylvii the fifth layer is most prominent. 4. In the bulbus olfactorius there is a central cavity lined with ciliated cells. The upper part is composed of white matter, the lower of gray matter. This gray matter consists of the following four layers from below upwards. A, THE STUDENT S MANUAL OF HISTOLOGY. non-medullated nerve fibres which pass into the olfactory nerve. B, a layer of glomeruli; each glomerulus consisting of a convolu- tion of an olfactory nerve fibre with many nucleated Deiter's cells. C, multipolar ganglion cells, spindle or pyramidal shaped. D, a net-work of fibrils with groups of nuclei. In all these ganglia the cells are multipolar; spindle- shaped in the optic thalami and containing pigment in the corpora striata. CELLS OF THE GRAY MATTER. The ganglion cells of the gray matter are multipolar, and by their axis-cylinder processes give origin to the cerebral nerves. They are collected together in groups, each group giving origin to some particular nerve. The group of cells or " nucleus " of the optic nerve is a collection of multipolar cells of many sizes. The "nucleus" of the motory root of the fifth is situated in the anterior portion of the fossa rhomboidalis. They are large multipolar cells containing pigment. The cells are smaller in the sensory nucleus. In the " nucleus " of the facial, in the outer part of the superficial olivary body and on the floor of fourth ventricle, are very large multipolar cells. The "nucleus" of the acoustic nerve is in the fossa rhomboidalis near the sur- face. In the lateral anterior part of this fossa is the "nucleus" of the abduceus. Situated in this fossa also are the " nuclei " of the glosso-pharyngeal and vagus. The cells are spindle- shaped. The cortex of the cerebellum shows five layers. 1. A matrix of fibrillar nerve net- work and fine branced processes passing to the surface from the deeper layer of cells 2. Large, spindle-shaped ganglion cells, Purkinje's cells. These cells have two processes. A branched process extending into the above layer and an unbranched or axis- cyUnder process passing deeper. 3. A nuclear layer. This is between the second layer and the white substance. It is composed of minute fibrils with a great number of spherical nuclei. The corpora dentati THE STUDENTS MANUAL OF HISTOLOGY. and olivary bodies are composed of a fine nerve net-work and slender multipolar ganglion cells. The brain is rich in blood- vessels. METHODS OF EXAMINING. Two methods are quite useful for examining fresh brain. Each of these methods has us advantages. The first method will be found in full in the September number of the Monthly Microscopical Journal, vol. XVI, page 105, by Bevan Lewis. His method is briefly this : There are three stages of the process. 1. The preparatory stage, which consists in making as thin vertical sections as possible of the gray mat- ter. The specimen is held in one hand between the thumb and fingers and with a sharp razor in the other, by a sweeping cut tolerably thin sections can be obtained. The upper surface of the knife should be deeply concave and kept flooded with alcohol. These sections are floated on a slide and a few drops of Miiller's fluid placed over them. This is allowed to cover them completely and to make a pool around them for some seconds. The cover glass is then applied and by aid of a pencil or strongly mounted needle, steady gentle pressure is made on the centre of the cover until the nervous matter becomes a thin transparent film. The superfluous fluid is removed by rinsing in water and the slide is then transferred to alcohol. In about thirty or forty seconds the slide is re- moved from the dish of alcohol and while one edge of the cover-glass is steadied by the fingers, the blade of a penknife is gradually inserted beneath the opposite edge. The thin film will be left floating on the glass-slide or adhering to the cover-glass. The specimen is washed to free it from spirit by inclining the slide and allowing dirops of water from a large camel's hair brush to flow over it. 2. The staining stage. A drop of a i per cent, solution of aniline black is placed on the film and as soon as the re- THE STUDENTS MANUAL OF HISTOLOGY. quisite color has been acquired, the slide is transferred to a vessel containing water and gently lowered in it. By gently moving the water above it with a brush the superfluous dye floats away. Other staining agents, notably carmine, may be used. 3. The mounting stage. All fluid is drained pff the specimen and it is placed under a bell jar with sulphuric acid. When perfectly dry add oil of cloves. This is removed when it has rendered the film transparent and dammar added and then the cover glass. The Sankey method. Another excellent method was de- scribed in the April Tramber of the Quarterly Microscopical Journal of 1876. Sections are cut as by the above method, only they may be as thick as the one-tenth of an inch. They are stained in a 7 p. c. solution of aniline blue-black. In three hours the staining is removed and water added until it washes away the excess of the staining. The specimens are floated on a clean slide, allowed to drain, and then exposed to the air in a dry place for twenty-four or forty-eight hours. At the end of this time the section will be firmly dried to the glass. It is now in a condition to have its upper surface planed off with a razor or other suitable instrunpent, taking care not to scrape the specimen away at any place. Dammar is added (oil of cloves not necessary) and the cover-glass applied per- manently if an examination of the specimen is satisfactory. The nerve-cells usually show to good advantage by this method. The brain may be hardened by processes recommended for the spinal cord. A 2 or 3 p. c. solution of bichromate of ammonia is a useful hardening agent. Small portions placed in Miiller's fluid and then in alcohol are suitable for study. CHAPTER XVIII, Testicle and Ovary. THE TESTICLE. THE testes are small glandular bodies from one and one- half to two inches in length, one inch in breadth and one and one-fourth inches in their antero-posterior diameter. The testes appear very early in foetal life as two ovoid bodies situated at the inner borders of the Wolffian bodies. Two ducts are seen at their outer borders ; the inner one, the duct of the Wolffian body, becomes the vas deferens of the male and disappears in the female ; the outer one, the duct of Miiller, becomes the fallopian tube in the female and disap- pears in the male. , The coverings of the testicle are described fully in the general works on anatomy. The minute structure of the gland substance only will occupy our attention. When viewed with the naked eye the substance is of a reddish-yellow color, and is divided into a number of pyram- idal lobes, the bases of which are directed toward the sur- face of the organ. Their number has been variously estimated at from 250 to 400. They vary in size according to the num- ber of convoluted tubes they contain, for each lobe has from one to five or even more tubes — tubuli seminiferi — thrown into coils which are loosely held together, so that by careful dis- 203 304 THE students' MANUAL OF HISTOLOGY. Timito Viip"'^ tiom^*'}"'^ section under water they can be disentangled to a considerable extent. It is estimated that 840 of these tubes are in each testicle and that each tube is on an average 30 inches in length and from ^^^ to y^ of an inch in diameter. Each tube commences by several blind extremities or by anastomosing loops. Their walls consist of several layers of epithelial cells. The tubes from the different lobes sometimes anastomose with each other. Sometimes the several tubes of each lobe, together with tubes from the adjoining lobes unite to- gether to form one canal. In this way about twenty canals are formed in each organ. At first these canals are quite tortuous but as they pass toward the poster- ior surface of the testes they become nearly straight — vasa recta — when they pass through the mediastinum forming a close net-work of tubes — ^the rete testis. The mediastinum is formed by a prolongation of the fibrous covering of the testis (tunica albuginea) into the posterior border of the gland and from this septum proceed the septa of fibrous tissue that divide the gland into its numerous lobes. Having traversed the substance of this fibrous septum the tubes leave the organ by from 12 to 20 canals known as the vasa efferentia. These tubes are about the -^ of an inch in diameter and have walls FIG. 138. Vertical section of, the testicle to show the arrangements of the ducts, (Gray.) THE STUDENTS MANUAL OF HISTOLOGY. 20S of fibrous tissue and muscle cells. At first these vessels are quite straight but as soon as they increase in size they become exceedingly convoluted. The epididymis is the long narrow body lying along the outer edge of the posterior border of the testis. It consists of an upper, enlarged extremity, the globus major, which is united to the testis by the vasa efferentia ; also a lower ex- tremity, the tail or globus minor, and also a central portion or body. After leaving the testicle the vasa efferentia form small cone-shaped masses — coni vasculosi — which together consti- tute the globus major of the epididymis. These soon unite in one convoluted tube to form the body and globus minor of the epididymis. When this tube is unravelled it measures not far from twenty feet in length ; at its commencement it is about Tjiy of an inch in diameter ; it is reduced to -^ of an inch before reaching the globus minor, however it soon increases in size again. It is lined with ciliated columnar cells and its walls, thin at first, are thick and well provided with muscle cells toward its lower end. The motion of the cilia is in an outward direction (Becker.) After leaving the globus minor the duct turns upon itself to form the vas deferens. This tube is about two feet in length and on an average \ of an inch in diameter. It is very hard and cordy to the feel and it extends from the globus minor along the inner surface of the epididymis, behind the spermatic cord to the internal abdominal ring. From here it passes into the pelvis, down the side to the base of the blad- der, where it unites with the duct of the seminal vesicle of the corresponding side to form one of the ejaculatory ducts. The vas deferens is lined with columnar epithelial cells, without cilia. The seminal-vesicles — vesiculce seminales — are composed of convoluted tubes, which, when unravelled, are three or four feet in length, and lined with short prismatic epithelial cells. 2o6 THE STUDENTS MANUAL OF HISTOLOGY. The vas aberrans of Haller is a small elongated mass, composed of a single convoluted tube, which is given off from the lower part of the epididymis as a diverticulum of the canal forming that body. When unravelled the tube varies from two to fourteen inches in length. It represents the remains of one of the tubes of one of the Wolffian bodies which still remains attached to the excretory duct. In the commencing portion of the vas deferens is the organ of Girardfes. It is known also by the name of parepididymis ; it is made up en- tirely of canals. The seminal tubes in the adult testis are lined with several layers of epithelial cells, called the seminal cells. Those cells situated next to the walls of the tube are known as the outer cells and those situated near the lumen are the inner seminal cells. FIG. r39. A portion of the wall of a seminal tubule of the testicle of the dog. a, seminal cells, b, spermatoblasts, c, earliest stage in the formation of the spermato- zoa, d, spermatozoa more fully developed. (Klein and- S(;nith.) x 450. Klein notices two kinds of cells in the outer layer : i, those having an oval- transparent nucleus limited by a mem-* brane and provided with one, two Or three nucleoli ; 2, those THE STUDENTS MANUAL OF HISTOLOGY. 207 with a spherical nucleus, the cells smaller than the former, and the nucleus, not limited by a membrane. The inner seminal cells contain in their matrix a convo- lution of rods, twisted in various directions and anastomosing with one another. The nuclei of the cells nearest the lumen of the tube very frequently undergo division, the cells them- selves dividing afterwards. Not unfrequently multinuclear cells are seen with from six to ten nuclei. Each nucleus is spherical in shape and is not limited by a membrane. FIG. 140. Spermatozoa, a, of the blaps mortisago. b, of the house-mouse, the bat. d, of the sheep, e, of the Raja batis. f, of man. c, of As these cells become developed into the spermatozoa, they have been named by Sertoli, the spermatoblasts. Study- ing one of these cells with a spherical nucleus, it is noticed, first, that the nucleus becomes limited by a membrane and is placed near the edge of the cell. The nucleus looses its retic- ulated appearance and its substance becomes collected in one part so that a clear space, a clear tube, is left. The nu- cleus becomes gradually more disc -shaped, and the cell sub- stance is drawn*out into a club-shaped granular body which is 2o8 THE students' MANUAL OF HISTOLOGY. separated from the nucleus by the clear space mentioned above (Klein.) By other gradual changes the epithelial cell finally becomes a fully developed spermatozoon, which has a well defined oval head, behind which is the middle-piece of Schweigger-Seidel, attached to which is the tail ending in a very fine pointed extremity. The nucleus of the inner epithelial cell has become the head of the spermatozoon, the granular body has become the tail, and an outgrowth of the nucleus has become the middle- piece. From the researches of H. Gibbes, [Quarterly Journal of Microscopical Science, Oct., 1879] we learn that each sper- matozoon of many of the vertebrates consists of [i] a long, pointed head, [2] an elliptical structure joining the head, [3] a filiform body, [4] a fine filament much longer than the body and connected to it by [5] a homogeneous membrane. When living this filament is in constant motion and has a con- tinuous waving from side to side. He is " confident that the substance of which the head is composed shows a different chemical reaction to the rest of the organism." The waving filament was seen in the spermatozoa of the following mam- mals: The horse, dog, bull, cat, rabbit, guinea-pig, and man. He draws the following conclusions : 1. That the head of the spermatozoon is enclosed in a sheath which is a continuation of the membrane which sur- rounds the filament and connects it to the body. 2. That the substance of the head is quite distinct in its structure from the other parts and that it is readily acted upon by alkalies ; these reagents having no effect on the other parts except the membranous sheath. 3. That the motive power lies in a great measure in the filament and the membrane attaching it to the body. THE STUDENTS MANUAL OF HISTOLOGY. 209 THE OVARY. The tissues of the hilum consist of connective-tissue, blood-vessels, muscle cells, etc. Covering the free surface of the ovary is a layer of short, columnar, nucleated epithelial cells, the "germinal layer" of Waldeyer. In the cortical por- tion of the ovary there is a layer of tissue free from ova , this has been named by Henle the tunica albuginea. Spindle- shaped cells are met with as well as branched cells. Besides these cells there are groups of nucleated, polyhedral cells ; Balfour regards these cells as the remains of the epithelial cells of the Wolffian bodies, as do also His, Waldeyer and others. The Graafian follicles are of many sizes and shapes. The smaller ones are situated near the surface, just beneath the albuginea ; while the larger ones are in the deep seated portions of the organ. The small follicles are so closely and densely arranged just un- der the albuginea that they constitute a distinct layer, the "cortical layer" of Schronn. FIG. 141, Two fully developed spermatozoa. a, ofthehorse. b, of the triton cristatut. Around the larsfer folHclcs the (H. Gibbes.) ° THE STUDENTS MANUAL OF HISTOLOGV. spindle-shaped cells are arranged concentrically, forming an investment to the follicle, the "tunica fibrosa" of Henle. Each follicle is surrounded by a membrana propria, in which are seen a few nuclei. Just beneath this layer is one of epithelial cells, the membrana granulosa, and within these cells is the ovum. The membrana granulosa varie from a single layer of flat cells in the smaller follicles to columnar shaped cells of one, two or more layers in the larger ones. a— I FIG. 142. Portion of.a section of a cat's ovary, a, layer of small ovigerms. b, » follicle farther advanced. The ovum is covered with the cells of the discus proligwus. X 35. The ovum of the fully developed follicle lies in a mass of cells which project from the membrana granulosa like a mound. This projection is called the discus proligerus. In the smaller follicles the ovum is surrounded by a mass of cells which are everywhere in close contact with the membrana propria, but soon a fluid appears between some of the cdls, causing little cavities which increase in number and size until these several inter-cellular cavities become confluent and the ovum at last becomes separated from the membrana propria^, except where it remains connected by the intervening discus THE STUDENTS MANUAL OF HISTOLOGY. proligerus. This fluid is called the liquor folliculi. In this fluid are seen occasionally a few small, more or less vacuolated cells. They once belonged to the follicular epithelium, but are now undergoing retrogressive changes [Klein] and will soon disappear. FIG. 143. Vertical section through the ovary of a half-grown cat Si germinaf epi- thelium of the surface, b, albuginea. c, Graafian follicles, x 350. (Klein & Smith.) The ovum is the nucleated cell embedded in the discus proligerus. Its nucleus is known as the " germinal vesicle " and its nucleolus or nucleoli as the " germinal spot or spots." The protoplasm immediately surrounding the nucleus is more transparent than that at the periphery of the ovum. Surrounding the ovum is a clear, transparent ring, the zona- pellucida, which, according to Waldeyer and others, often shows in the mature ovum a vertical striation caused by the continuation as fine threads of the epithelial cells surrounding this zone. • " Many follicles arrive at the stage of ripeness before putoerty is reached and are subject to a process of degenera- THE STUDENTS MANUAL OF HISTOLOGY. tion. But this process involves also follicles of earlier stages and even the smallest follicles." [Klein and Smith, Atlas of Histology, p. 290, 1880.] METHODS OF EXAMINING. The testis. The familiar process of hardening in Muller's fluid and transferring to alcohol is a very satisfactory one for this organ. The tubes can be teased apart \w these prepara- tions to good advantage, al- though for this purpose the method of Sappey is in some respects superior, small por- tions of the organs are placed for one or two days in a mix- ture of hydrochloric acid, one part, and water two parts. By the aid of a fine syringe the organ may be injected at several points with a i per cent, solution of osmic acid. The specimen is then placed in al- cohol, when after a few days it is sufficiently hardened to ad- mit of thin sections being made FIG. 144. Graafian follicle, a, spindle-cells . . .. . rT-ii ■ of stroma, b, membrana propria et granulosa, m VariOUS direCtlOnS. 1 hlS c, zona pellucida. d, ovum with its germinal _ • 1. ■ .^i 1 j j vesicle and germinal spot, x 350. (Klein and prOCCSS IS highly rCCOmmended ^'"'*^ by Mihalkovics. The Ovary. Beautiful sections of the ovary of the cat are in the author's possession, made from specimens hardened in Muller's fluid and alcohol, stained with carmine, cleared in oil of cloves and mounted in dammar. From the fresh ovary of the dog or rabbit, ova may be obtained as follows : While the ovary is held firmly in the THE student's MANUAL OF HISTOLOGY. 213 hand, the most prominent Graafian folHcle is pricked and its contents received on a glass slide in a drop of normal fluid. If present the ovum is easily recognized when it should be examined, uncovered and with a low power. Afterwards a higher power may be substituted, covering the specimen, but inserting beneath the cover a piece of paper to avoid pressure. CHAPTER XIX. The Tongue, Skin, Lining of the Nasal Cavity and the Kar. THE mucous membrane lining the mouth is covered with a thick layer of stratified epithelial cells ; and among these cells are a few that are connected together by fine fila- ments, although they are separated from each other by the or- dinary cement-substance. When the parts are inflamed, the intercellular substance is increased and the connecting fila- ments show to much better advantage. These are the " prickle-cells " of M. Schultze. In the mucous membrane are numerous large mucous glands. The duct of each gland is a single layer of endothelial cells and it is a direct contin- uation of the basement membrane, which here, as in other parts of the alimentary canal, is between the layer of epithelial cells and the mucosa. Lining the duct is a layer of nucleated columnar cells. Upon reaching the submucous tissue the duct divides into a number of branches. These branches are con- voluted, and they have one or more short lateral branches. The body of the gland is lined with cells identical with those lining the mucous salivary glands. When the gland is inac- tive these cells are transparent and are filled with mucigen which is changed into mucin during secretion. The tongue is essentially a muscular organ, covered with mucous membrane. On its dorsal surface are three kinds of 214 THE STUDENTS MANUAL OF HISTOLOGY. 215 papillae; the circumvallace, fungiform, and filiform. The first are seen with the unaided eye at the base of the tongue, ar- ranged in the form of a V. The second are distributed over the surface of the tongue and are visible also to the unaided eye. The third are the most numerous as well as the smallest. They are not especially concerned in the sense of taste. In the circumvallate and in many of the fungiform papillae there are peculiar bud or flask shaped organs — the organs of taste — the gustatory buds — the taste buds of Schwalbe. They are about -yf^ of an inch high in man, and they exist in large num- FIG. 145. Taste buds, a, epithelial surface, (Klein and Smith.) X450. bers. They are covered externally with one, usually two or more, layers of long, tapering, flat cells, which are in close contact with each other. They surround the opening of the organ above and " stand like the staves of a barrel." These peripheral cells surround the central or taste cells. The central cells are slender, nucleated and spindle- shaped. The nucleus causes an enlargement of the cell at that point. The cells terminate above in a rod shaped ex- tremity at the opening of the organ; below they terminate in a slender often bifurcated extremity which, it is supposed, passes as a nerve axis or axis fibrilla into the gustatory nerve. Fine nerve fibrils are certainly connected with these taste cells. (Englemann, Homgschmied.) Situated near the taste buds are serous glands, embedded in the mucous membrane. The bodies of these glands are 2l6 THE students' manual of histology. like the parotid in structure. There are no mucous cells found in them. In all probability they secrete a watery sub- stance which is poured over the parts containing the taste buds and thus they assist in the distribu- tion of the substance to ' be tasted. The nerves of the pa- pillae contain end bulbs (Krause), and the tactile corpuscles of Meissner can be demonstrated, (Geber). FIG. 146. Cells from taste buds, a, cover cells.. MUCOUS b, cellsfrom central part. 1 , the fine extremity which projects at the orifrce of the bud 2, the deep ex- tremity whtch becomes continuous with fine nerve fibrils. (After Englemann and Klein.) MEMBRANE OF THE NOSE. Only a portion of this membrane (Schneiderian) is of especial interest in this connec- tion. The portion which contains the terminations of the olfactory nerve is distributed over the upper portion of the septum, and the upper and middle turbinated bones. Non- ciliated epithelial cells cover this highly vascular membrane m these regions, although the ciliated variety abounds in the other parts. Glands are scattered freely through the membrane. The yellowish appearance of this membrane is due to the presence of yellowish granules in the long columnar cells covering its surface. These cells send long processes down- wards, which usually give off numerous branches which anas- tomose with other branches (Martin) from neighboring cells, to make a continuous net-work just beneath this layer. Be- tween these cells are nucleated, spindle-shaped ones — the ol- factory cells of Schultze. One end of these cells terminates in a fine process on a level with the surface of the columnar cells THE students' MANUAL OF HISTOLOGY. 217 between which they lie; the other end terminates below in a fine filament which may be di- rectly connected with a fine axis fibrilla from one of the non-meduUated fibres of the olfactory nerve. THE SKIN. The importance of this com- plex structure of the body is very evident when we consider the variety of its functions and the extent of its surface. It forms a protective covering for the body; it is an organ of tac- tile sensibility, it preserves the external forms of the muscles; it is an organ of excretion, and it aids in maintaining the nor- mal temperature of the body. FIG. 147. I, Cells of the regio olfactoria of Ihcfrog. a, an epithelial cell, terminating be- In the CaSC Of an average SlZe low tn a ramified process, b, olfactory cells ... , . with the descending filament, d, the peripheral man itS SUrlaCC IS CqUal tO SIX- rod, c, and the long vibratile ciliae. e. 2, cells, r ^ j r trom the same region of man. The references teen Square ICCt, and Ot an the same, "nly short projections, e, occur (as . , , artefacts) on the rods. 3, fibres o the olfactory average SlZC WOman, tWClVC nerve from the dog. At a, dividing into fibrillffl, r . own as the stratum bacillosum and it represents the terminal cells of the optic nerve. It is composed of two elements, rods and cones. With one exception, to be described later, the rods are more numer- ous than the cones, the letter becoming less and less numerous as the periphery is approached. The rods are long cylinders, in length equal to the thickness of this layer and in diameter about the Yrkw^ ^^ ^" ^^^^- They are composed of two regu- lar parts, an outer and an inner segment. The outer segment THE STUDENTS MANUAL OF HISTOLOGY. 237 refracts the light more strongly than the inner, which is paler and more granular. The former will not take staining, the latter stains readily with carmine, iodine, etc. The outer seg- ment breaks up into a number of superposed transversed discs only g^^j^j^ of an inch thick. On this segment can be seen a longitudinal striation, due to fine longitudinal grooves or de- pressions. This segment pene- trates into the pigmentary layer with a rounded point. Ritter says he has seen a primitive nerve iibrilla in the axis of the rods. At the outer border of the inner seg- ment, and forming a part of it, is a plano-convex body, the " lenti- form body," the "rod-ellipsoid" of Krause. The inner segment terminates below in a long, point- ed filament, a primitive nerve fibril. The cones are about one-half the length of the rods and are similar to them in structure. The outer segment is known as the "cone-rod," and it possesses in common with the rods a tendency to break up into transverse discs, although this tendency is not so gi^eat as in the rods. The inner segment or cone-body is like the rods, longitudinal- ly striated. In the cone-body a structure is found identical with the rod-ellipsoid of Krause. These appearances in both rods and cones are due prob- ably to this fact : the upper part only of the inner segment is longitudinally striated, for the lower part is homogenous. FIG. 164, Rods of the retina. From the monkey. A, rods, after maceration in iodized serum, the outer segment (b) truncated, the inner segment (a) coagu- lated, granular, and somewhat swollen, c, filament of the rods, d, nucleus. B, rods from the frog. 1 , fresh , magnified 500 diameters, a, inner segment, b, outer segment, c, lentiform body, d, nucleus. 2, treated with dilute acetic acid and broken up into plates. (Schultze.) 238 THE STUDENTS MANUAL OF HISTOLOGY. In the case of the rods the fibrillated part of the inner segment occupies about the outer one-third, while in the cones it occupies as much as the outer two-thirds. The outer parts are strongly refractile, which fact does not appear to depend in the least on the degree of fibrillation of the segments, for sometimes the outer part of the inner segment of the cones appears entirely free from fibrils, yet it is easily distinguished by its great refracting power. The third layer consists of granules or nuclei in connection with the deli- cate prolongations of the rods and cones. The granules of the rods are swellings on the prolongations, one to each fibre. They are situated some distance from the bases of the rods, near the molecular layer. Each enlargement has a nucleus and is characterized, according to Henle, by a cross-striped appearance. The rod fibril prolonged from this granule is interrupted by numerous varicosities and finally terminates in. a larger varicosity just before entering the molecular layer. The granules of the cones are not crossed by any bands. Each granule has a nucleus and nucleolus and the whole cone fibre is mych larger than that of the ihr'fodll^d ■'cones'"', ,Todf'^! Tods. The fibre terminates below in rmL°'T?id-.iCen;:d','iir an expanded extremity from which ThTtibHL'prliec'biyond .tin': procecd numerous prolongations into ner member. The oute ds wanting. (Schultze.) ner member. The outer member ^^iq molCCUlar layCf, THE STUDENTS MANUAL OF HISTOLOGY. 239 In the molecular layer little is to be recognized but a granular appearance, minute fibrillae and a few nuclei. The inner nuclear layer consists mainly of nucleus bodies, like those of the outer nuclear layer, only larger. In the layer of nerve cells are fo.md large multipolar cells resembling those found in the brain. * They measure from the ■j-jijj-j- to the Tj-^-j- part of an inch in diameter. Each cell has an unbranched process, axis cylinder, which passes inwards among the fibres of the inner layer, with one of which it doubt- less becomes continuous. The branched processes extend into the outer layer and are soon lost in its substance. As a rule they exist in a single layer, but near the yellow spot they are from five to ten layers deep. The eighth layer is composed of the most minute nerve fibrils varying from sbloo ^° sriiTTr P^"^' of an inch in diameter. The delicate structures of the retina are held in place by a system of connective-tissue fibres, the " supporting fibres of Miiller." These fibres commence just beneath the inner retinal layer, where by connected bases they form a boundary line, — the membrana limitans interna. The fibres then pass through the several layers, as illustrated in the figure, until they reach the bases of the rods and cones, where they form a boundary line also, — the membrana limitans ex- terna. From here branches pass between the rods and cones and invest their bases. MACULA LUTEA. The macula lutea is an oval spot about ^ of an inch in its horizontal diameter. Its yellow color is due to the presence of a peculiar yellow pigment, whifeh is not deposited in grains. It is a diffuse hyaline coloring matter, soluble in water or alco- hol. The macula lutea presents the following histological peculiarities : I. The layer of nerve fibres is wanting. 240 THE STUDENTS MANUAL OF HISTOLOGY. 2. The layer of ganglionic nerve cells is increased from a single layer to six or eight layers'; when they reach the fovea centralis they are entirely absent. 3. Several of the remaining layers diminish in thickness as they approach the yellow spot and disappear at the fovea c»«^ centralis. 4. As a result of these changes only two layers remain at the central depression, the outer nuclear layer and the layer of rods and cones. Even these exhibit peculiarities. 5. The fibres with which the nuclei of the third layer are connected, are arranged in an oblique direction, reducing the layer much in thickness. At the borders of the macula lutea the cones are separated from each other by a single layer of rods, while in the fovea cen- tralis the rods are altogether absent. Here the cones are longer and more slender than elsewhere. FIG. 166. Diagrammatic section of human retina through the macula lut^a and fovea cen- tralis. I, internal surface of the retina, in contact with the vitreous body. 2, ganglionic layer of nerve cells. 3, intermediate layers of the retina, disappearing at the centre of the .macula lutea. 4, layer of nuclei, showing the oblique course of the fibres iii this region. 5, layer of rods and cones, consisting at its central portion exclusively oftattenuated and elongated cories. 6, external surface of the retina, in contact with the choroid. In the middle of the diagram Is the depression of the fovea centralis. (Schultze.) THE STUDENTS MANUAL OF HISTOLOGY. 241 VITREOUS HUMOR. The vitreous- humor occupies about four-fifths of the eye- ball and is of a soft gelatinous consistence. A concavity exists in its forepart for the reception of the lens and its capsule. When treated with certain reagents it has the appearance of being composed of distinct membranes, arranged concentric- ally, and between these membranes there is a fluid substance. A radial striation has been observed in the human vitreous body. Very nearly in the antero-posterior axis of the eye is a canal, lined with a distinct membrane and filled with a fluid ; it extends from the optic nerve to the posterior capsule of the lens. This is the " canal of Stilling." In the vitreous body are corpuscles resembling white blood-cor- puscles. The hyaloid membrane is an exceed- ingly delicate membrane, measuring about •j-jiffP of an inch in thickness. It is in con- tact with the retina externally and with the vitreous body internally. When near the FIG. 167. The rod layer . -^ j- -j ■ . . seen from vvUhout a, cones. Ciliary proccsses It oividcs mto two parts. b, cone rods, c, ordinary _,, i ■„ i- t i. rods. 1, from the macula lu- The posterior portion lines the concavity Mme.'''3'!VrSmThe*cen°tre*of in the forepart of the vitreous body. The ,h. retina. (Haimhoiu.) interior dividcs into two parts, i. The anterior of these parts is known as the zone of Zinn ; it ter- minates in the anterior capsule of the lens, and it is thrown into folds or plaits that correspond with the folds of the ciliary processes into which they fit closely. 2. The posterior of these parts is very thin and is attached to the posterior capsule of the lens. These two parts by their division enclose a tri- angular space, called the " canal of Petit." After death this canal is found filled with a serous fluid. THE LENS. The lens is a transparent bi-convex body placed directly 242 THE STUDENTS MANUAL OF HrSTOLOGY. behind the pupil. It is completely surrounded by a thin mem- brane, the capsule of the lens, — which is lined with a layer of delicate cells. The lens is about one-third of an inch in its transverse, and one-fifth of an inch in its antero-posterior diameters. Its posterior surface is more convex than its anterior. When viewed with a low power the lens presents a star with from nine to sixteen radiations. In the foetus there are but three radiations upon either surface. The rays of the stars of one side are situated between the rays of the other side; The outer portions of a fresh lens are much softer than the inner portions and they are easily detached from them ; the hard centre is known as the nucleus of the lens. The lens is com- posed of a great number of six sided prisms arranged closely together with but little intervening cement-substance. These fibres are about the -^^-^^ of of an inch broad and their edges are many times quite regularly dentated. They pass in a curved direction from the centre and from the rays of the star to the periphery where they turn and pass over to the other side to its star. The fibres of the super- longrtudinai view of the fibres of ficial layers have an oval nu- showing the serrated edges. „1„„„ 1 section of the fibres of the clcus and somctimes a nu- (Koiiiicer.) cleolus, proving that all the fibres of the lens must be regarded as elongated cells. In the more internal parts of the lens the nuclei are absent and the fibres are harder. The ' capsule of the lens is a very thin, transparent membrane, about -^^fj-rr of an inch thick at FIG. 168. A, the tens from the ox, (Quain, ) B, transverse lens from the human eye. THE STUDENTS MANUAL OF HISTOLOGY. 243 its centre and so elastic that when ruptured it will frequently contract with sujfificient force to expel the lens body. It is lined anteriorly with a layer of nucleated polygonal cells aver- aging T-jVir o^ ^^ '"^^ ^^ diameter. No such cells line the posterior part. METHODS OF EXAMINING. To understand the relations of the different parts to each other, sections of the whole eye should be made by the aid of the freezing microtome. The cornea may be studied in many different ways. The different layers should be examined first. For this pur- pose the cornea is removed from the eye of an ox and placed at once in Miiller's fluid where it is allowed to re- main for two weeks, when it is trans- ferred to alcohol. In two or three days sections can be made vertical to the surface, stained in hsematoxylin, cleared in oil of cloves and mounted in dam- mar. To see the branching and anasto- mosing connective-tissue corpuscles the cornea is placed in a .J- per cent, chloride of gold solution until the tissue is of a pale, yellow color ; after washing it is transferred into water slightly acidulated with acetic acid. Upon exposure to light the specimen turns to a violet color when it is examined with a high power. If the epithelial cells render the ^'°' oM^he ?a°bbits" *ns"!how- Specimen indistinct they are removed margin tng the transition of the epithelium into the lens fibres. (Babuchin.) by brushing or scraping. After the 244 THE STUDENT S MANUAL OF HISTOLOGY. gold Staining the corneal corpuscles may be isolated. For this purpose a 25 per cent, solution of sodic hydrate is used ; this destroys the intermediate substance before it does the cor- puscles. The cornea, deprived of its epithelium is placed in this solution for 30 or 40 minutes, when the alkali is replaced by water, to which has been added a few drops of acetic acid. If portions of this membrane be examined in glycerine the cor- puscles will be displayed beautifully ; the delicate nerve fibrils and the anastomosing branches of the cells will be clearly brought out. Nitrate of silver staining can be employed and the tissue treated as usual in such cases. To examine the retina an unopened eyeball is placed in Miiller's fluid for two weeks and then transferred to alcohol for a few days. Sections of the retina made vertical to the surface can be examined in glycerine or first stained slightly with carmine. Sections should be examined from different parts of the retina when the local changes will be made ap- parent. Sections should be made from a retina hardened in osmic acid. For this purpose small pieces are removed as carefully as possible and placed in a 2 per cent, solution of this acid. Here they should remain for six or eight hours, when they should be washed thoroughly in water, stained with hsematoxy- lin, embedded, sections cut and examined. To macerate the retina and thus .procure its elements in an isolated condition several reagents are employed. Notably the 2 per cent, osmic acid solution. After remaining in this solution for six or eight hours a piece of the retina is trans- ferred to a glass slide and by the aid of needles carefully teased in dilute glycerine ; or the a,cid may be reduced one- half and the tissue allowed to remain in it 24 hours. The retina is suitable for teasing just after removal from Miiller's fluid. THE STUDENTS MANUAL OF HISTOLOGY. 245 The retina in the fresh condition should be examined. As soon as removed from the eye a piece of it is teased with needles in a drop of the aqueous humor, covered, and examined with a high power. The lens is hardened in Muller's fluid and alcohol for ob- taining sections. To isolate the fibres it is boiled for ten minutes in a i per cent, solution of sulphuric acid and then teased in glycerine. If too transparent slight tingeing with aniline blue will be suitable. Many times very instructive sections are obtained from a lens that has been exposed to the air on a glass slide for a day or two. It has acquired such a degree of consistence that sections can be cut conveniently in the direction to show the delicate hexagonal cut ends of the lens fibres. Other parts of the eye should be hardened in Muller's fluid and alcohol for examination ; sections made and stained as with the simpler tissues. To study the vascular arrangement, the eye of an ox is carefully removed from its bony socket and injected from the artery with the Prussian blue. For general purposes of study the human eye is preferred if it can be obtained perfectly healthy and in a fresh condition. If not, the eyes of the pig, albino rabbit and ox will be found very suitable. CHAPTER XXI. Tumors. HYPERTROPHY may be defined to be an increased nu- tritive activity of a part. It may be either simple or numerical. By simple hypertrophy is understood an enlarge- ment of a part by the increase in size of its anatomical ele- ments. In numerical hypertrophy the enlargement takes place through an increase in the number of cells. These are gener- ally associated. Hypertrophy is most frequently met with in the muscular system where it is often conservative in nature, as when the walls of the bladder are increased in thickness to give addition- al power to overcome some obstruction at its base, e. g. en- larged prostate, etc, or when the walls of the intestine become thickened above a point of obstruction, or when the gastroe- nemei become largely developed in the ballet dancer to over- come the extra strain put upon them. This increased activity may give rise to entirely new elements — ^to new formations. The inflammatory new formations are very unstable and when their cause, usually some irritation, is removed, they will have a strong tendency to return to a healthy standard or condition. The non-inflammatory have great independence, grow by an inhei'ent activity of their own, and are constantly tending to become removed farther and farther from a healthy condition. Their general tendency is to increase in size, although after a 246 THE STUDENTS MANUAL OF HISTOLOGY. 247 time they may remain permanent. To this class belong the new formations, known as tumors. A tumor is many times pathological simply because its specific elements occur in a place where they do not normally belong. Virchow calls a tu- mor composed of but one tissue "histioid," when composed of several tissues "organoid." When in addition to the latter there are organ-like tissues "systematoid." If a new formation occurs in a tissue agreeing with it in structure it is said to be "homologous." If unlike it, it is "heterologous." All of the pathological elements found in a new formation, including the cells, nuclei, matrix, vessels, etc., are prototypes of those found in the normal tissues, only undergoing change and destruction more readily. The cells of these growths are reproduced most frequent- ly by cell division, the nucleus dividing first, followed by a division of the formed part of the cell. This has been ob- served to occur in a very few seconds. Sometimes the nucleus alone will divide, these nuclei thus formed dividing again and again, until one cell may possess in this way, from four to twenty or more nuclei. These cells are known as the "giant," "mother," or "mye- loid" cells. They are found normally in the medullary sub- stance of bone. Pathological cells then come from pre-existing cells, and when newly formed are usually small and round, having a nu- cleus and also nucleolus, or composed of nucleus matter alone, simple undifferentiated protoplasmic cells. At this stage it would be impossible to tell the future of the growth. Like the small cells of the embryo, they are entirely undifferentiated. These cells may be the round cells of a sarcoma or the cells of connective tissue. As soon as a tumor is completely developed it is liable soon- er or later to undergo some of the forms of degeneration. If it 248 THE students' manual OF HISTOLOGY; has been of short duration, attained a considerable size, and if it is composed largely of cells, then it will undergo these changes all the more rapidly. If it has been of slow growth and its elements are developed into tissue, then it Will not be liable to degenerate. Fatty degeneration is most commonly met with. This is probably due to the fact that in the rapid formation of new tissue there is not a proportionately new formation of blood-vessels, and as a result of the insufficient circulation and want of nutritive material, the fatty metamorphosis occurs. Tumors may also undergo pigmentary degeneration, usu- ally from a deposit of melanin. This is a black, or nearly black, substance found physiologically in the skin and eye. It is seen either as free granules in the tumor or deposited in the cells. It does not appear to be at all susceptible to reagents, and its origin is probably the same as that of hsematoidin. In caseation the fluids are absorbed and the elements are dried up, changed into a yellowish cheesy material, which process may continue until the whole mass may become surrounded by a capsule of fibrous tissue. In calcification, small calcareous particles are infiltrated through the mass. Sometimes soften- ing liquefies the whole mass into a thin liquid, which under the microscope is seen to consist of broken down material, granu- lar matter, fat, etc. Colloid and mucoid degenerations also occur when the al- buminous ingredients are tfartsfbrmed into substances chemi- cally resembling mucin and an allied colloid material. A tumor is malignant when it has a tendency to recur in the same or some distant place after its removal. It is innocent when this tendency is not present. The term "malignancy" then, is purely a clinical one and does not refer to any property of the growth to destroy life. The heterologous character of a growth is an evidence of its malig- nancy. In the examination of tumors the fresh cut surface should THE STUDENTS MANUAL OF HISTOLOGV. 249 be scraped and this examined for cells, their shtipe, number, size, nuclei, the size and number of nuclei in each cell, all should be carefully noted. Then the tumor should be cut in small pieces not over one-half an inch square and placed at once in dilute alcohol, to be replaced in a few days by common methylic alcohol, and if the tissue still remains too soft for cutting thin sections, stronger alcohol may be added for a day or two. Miiller's fluid may be employed, but at this laboratory the best results have been obtained by the use of alcohol alone. In two weeks the tissue will be of sufficient consistence to allow thin sections to be made with the aid of a razor. By holding the piece of tissue firmly between the thumb and fingers of the left hand, the razor held in the right hand can be drawn from heel to point over the tissue cutting the section sufficiently thin for examination. Or by using one of the embedding mixtures already given the piece may be embedded in the microtome and sections cut as has been described. The arrangement of the fibres and cells should be noticed together with any alveolar stroma that may be present. Carmine and haematoxylin are useful staining agents. If it is desired to secure the specimen permanently it should be cleared in the oil of cloves and mounted in dammar. It is very difficult to make a satisfactory classification of the new formations. The classification given in T. Henry Green's " Pathology and Morbid Anatomy" is as free from ob- jections as any with which we are acquainted. It is here given with slight changes : CLASSIFICATION OF TUMORS. I. Type of the fully developed connective tissues. Type of fibrous tissue, . - - Fibroma. Type of adipose tissue, - - - Lipoma. 25° THE STUDENTS MANUAL OF HISTOLOGY. Type of cartilage tissue, - Enchondroma. Type of bone tissue, - - Osteoma. Type of mucous tissue, - - - Myxoma. Type of lymphatics, - - - Lymphoma. II. Type of higher tissues. Type of muscle, ... Myoma. Type of nerve, - - - . .. Neuroma. Type of blood-vessels, - Angioma. Type of papillae, - -. Papilloma. Type of secreting glands, - Adenoma. III. Type of embryonic tissue. — The sarcomata. Spindle-celled sarcoma. Round-celled sarcoma. Myeloid sarcoma. IV. The carcinomata. Scirrhus. Encephaloid. Colloid. Epithelioma. FULLY DEVELOPED CONNECTIVE TISSUE. Of the two kinds of corpuscles found in connective tissue, the movable or wandering kind is the most important in this connection. In size, contractility, ability to wander, etc., they seem identical with the white blood corpuscles and pus cor- puscles. In all probability they have their origin in the blood. It is not known whether they can pass into the regular connec- tive-tissue corpuscle or not. Neither is it known in what channel they move. TYPE OF FIBROUS TISSUE. Fibroma, fibroid or connective-tissue tumor. This tumor consists of quite distinct fibres that are without any arrange: ment, and separated only with difficulty. If the section be made across a blood-vessel the fibres will be seen running a cir- THE"ST«4aENTs' MANUAL OF HISTOLOGY. 251 cular manner around it, as seen at the 4eft upper corner of figure 170. Only a few cells will be found, and these are most abundant in the neighborhood of blood-vessels. They are usually of the spindle-shaped or stellate variety. Nuclei that take the staining readily are seen distributed over the field. As a rule there are but few blood- vessels, but it sometimes occurs that the walls of the vessels have become firmly united with the structure of the tumor, hence if the growth be cut into or injured severely the mouths of the vessels will not be able to contract and Fis. 170. Fibroma. profuse hemorrhage results. In size the fibromata vary from a very small circumfer- ence to an immense growth. Their form is also varying. The fresh cut surface is usually dry, only in the rapidly growing younger growths when a serous or mucous fluid exudes. Arising from the skin they are usually softer and less dense than those found in other parts, and in this situation are usu- ally single. They are generally limited by a capsule and have a slow growth, occurring in middle and advanced life. They increase in size by a central growth, by a multiplication of their own elements, and do not invade the surrounding healthy structure. * They are then innocent growths and cause disturbance to the organ or. tissue in which they are situated and to the whole organism only from their size. The fibromata are not liable to undergo degeneration. Fatty degeneration, calcifica- tion, mucoid softenings and hemorrhages are met with usually affecting only a part of the growth. Growing beneath the ■gkin these tumors are sometimes soft, without a capsule arid 252 THE STUDENTS MANUAL OF HISTOLOGY. multiple. They are known here as wens. Nasal polypi are a variety. So is a tumor often described as a neuroma, which under the microscope is seen not to consist of true ' nerve tissue, but is fibrous. These growths usually commence from the connective-tissue surrounding the nerve, the neurilemma, and by increasing in size, either press upon the nerve proper or grow around it and thus as they increase in size they com- press the nerve. They are generally small, round, hard tumors that are painful in the extreme. Uterine fibroids are rarely composed of fibrous tissue. They will be described under muscular tumors. The fibromata are frequently com- bined with other forms. TYPE OF ADIPOSE TISSUE. In structure a lipoma resembles ordinary adipose tissue, consisting of large cells that are fully distended with fat. The nuclei of the cells are not visible unless the fat be dissolved from the cells, or unless a cell is found containing but very little fat. They vary in size, frequently attaining a most enor- mous growth. The fresh cut surface shows fatty tissue. It occurs most frequently in parts where fat normally exists, rarely in other parts, is usually sharply circumscribed, encap- suled, grbws slowly and with a central growth. It has no ten- dency to return after removal. It rarely undergoes any of the deg;en- ^rations and when occurring only small parts are affected. Figure 171 shows a thin section of this tumor with the inter- cellular connective-tissue. ; ..'..■-,.-. io 1-'.: I ■. .'I TYPE OF CARTILAGE. Enchondroma, chondroma. This tu- mor is rarely found composed of cartilagin- FiG. 171. Lipoma. ous tissuc alonc but usually combined THE STUDENTS MANUAL OF HISTOLOGY. 253 with connective tissue. It may be either hyaline, reticular or fibrous cartilage, or all three combined. The number and size are very variable. Some are spindle-shaped, some stel- late and movable. Usually, however, they resemble the cells of normal cartilage. The enchondromata vary in size, are usually single, occasionally multiple. They occur in the early part of life, even in the new born. By far the greater number affect the bones and most frequently the medulla. Thus the articulating surfaces are rarely affected. They may arise from cartilage itself, their likeness to normal cartilage is then more exact. In some of the softer forms there is a tendency to return after removal, affecting even the lymphatics, and in the young causing cachexia. The malignant properties of the enchondromata, when present, are probably due to the fact that sarcomatous elements are associated with them. How- ever healing almost invariably occurs after complete extirpa- tion, and in the case of a pure enchondroma malignancy may be said to be entirely absent. Of the many degenera- tions to which this tumor is subject calcification is the most common. Ossification sometimes affects the periphery of the growth so that it is surrounded by a thin bony wall. Spiculae of bone are frequently found through the growth. A speci- men in the author's possession shows about one-third of the growth truely ossified, the remainder resembling normal carti- lage. The line between the two being sharp and distinct. For an illustration of this kind of growth see cartilage. TYPE OF BONY STRUCTURE. Osseous tumor, Osteoma. In the case of this tumor the bony appearance is the natural result of development, whereas in many other cases — tumors having undergone osseous de- generation — it is accidental. It has an independent growth and is not to be confounded with the products of inflammatioa aS4 THE students' manual OF HISTOLOGY. of bone, as the callus after fractures, etc. Most of the osteo- mata arise from connective-tissue. They may have their origin from cartilage bone, or the periosteum of bone. Those having their origin apart from bone, heterologous, are known as osteophytes. They are found near diseased joints, near the seat of inflammatory processes and in many other situations. They are found not uncommonly in the lungs and brain. They are to be carefully distinguished from growths that have become partly ossified, for in the latter case they might be more or less malignant, while a true osteoma is perfectly inno- cent. The homologous exostoses are found most frecfliently on the external and internal surfaces of the skull, in the orbit, on the upper and lower jaw, etc. They are troublesome only "when some neighboring part is affected by pressure. The appearance under the microscope is not unlike that of the true bone, at least the lacunae and canaliculi, are present, although not arranged in any order. TYPE OF MUCOUS TISSUE. Myxoma, mucous tumor, tumor mucosus, gelatiniform or colloid sarcoma. A myxoma con- sists of a mucous basis substance in which are spindle-shaped or stellate cells which anastomose with each other. Some of these cells are shown in figure 172. A few are round or oval or spherical. This is very generally the case in the younger growths. If young and rapidly growing the number of these cells will be largely in- creased proportionately. A nucleus is seen in each of the cells* Sometimes two nuclei are present. The refracting power of the mucus is so great that some care is necessary in order to see the outlines of the cells. Staining will be of advantage FIG. 172. Myxoma. THE STUDENTS MANUAL OF HISTOLOGY. 255 here. The cells are easily obtained by simply scraping the cut surface and adding a little saline solution to the scrapings. They are closely related to cells found in the sarcomata, and by many are so classed. The same kind of tissue exists in two places in the body physiologically, in the vitreous humor of the eye and in the umbilical cord. The myxoraata usually occur as single tumors, and are generally round, uniform and small. The fresh cut surface may show septa of connective tissue, giving the growth a soft but quite firm consistence, or the connective tissue may be nearly, if not entirely absent. There will then escape a viscid mass of mucilagenous consistence to such a degree that the whole tumor will become flattened and formless. Their most favorite seat is in the adipose tissues and they are here gener- ally encapsuled. Their growth is usually slow although they are many times of extraordinary size. The walls of the blood- vessels are very thin and liable to rupture. Hence the fre- quency with which sanguineous cysts are met with. The cells themselves may become destroyed by either fatty or mucoid degeneration. As a rule the myxomata are i n noce nt growths. Sometimes, however, they exhibit malignant properties. This probably is due to the fact that many times these growths are combined with others, especially the sarcomata. Figure 172 represents some of the cells of a myxoma removed from the FIG, 173. Lymphoma. Vagina. The growth was about the size of a walnut. TYPE OF LYMPHATIC TISSUE. Lymphoma, Lymphadenoma. Figure 173 represents a section of a lymphoma of the arm. It is not very unlike a 256 THE students' MANUAL OF HISTOLOGY. lymphatic gland in structure, consisting of a basis of distinct fibres which branch and cross each other like a net-work, and of cells identical with the white blood corpuscles. These cells fill up the space in the basis, but in the figure they have been nearly all removed by brushing the section with a camel's hair brush moistened in water. The firmness of the tumor will de- pend upon the comparative amount of basis fibres and nu- cleated cells. If the growth is young and increasing rapidly in size then the cells will be the more prominent part of the growth. Later the number will diminish and the reticulum become thicker and firmer. These tumors not infrequently ac- quire a large growth even infiltrating the surrounding tissiues. They are homologous primarily and become heterologous only from the new tissue extending into surrounding parts, or from their growing in a place where the lymphatics are very small and few in number. The lymphomata are innocent growths and are not liable to undergo degenerative changes. In the disease known as "Hodgkin's disease'' the new growths in various parts of the body are like the one described. The enlargement of the spleen in leukaemia is of the same nature. TYPE OF MUSCULAR TISSUE. Myoma. A tumor composed of striated muscle is one of the rarest of the new formations. A myoma composed of smooth or non-striated muscle is most frequently met with in the uterus, where it is generally known as a "uterine fibroid," and when projecting into the cavity of the uterus or extending by a pedicle out of the neck is called a "uterine polypus." The muscle cells form one but not the only element. Connec- tive tissue may exist in great abundance. This is especially the case in the older growths. In the new growths it is not uncommon to find almost exclusively the characteristic non- striated muscle cells. There are few blood-vessels distributed THE STUDENTS MANUAL OF HISTOLOGY". 257 through the connective tissue. These are homologous growths, of slow growth, usually single, but often multiple. They are liable to undergo softening, or more freqently to be- come calcified. They are perfectly innocent, exhibiting no tendency to return after removal. TYPE OF NERVOUS TISSUE. Neuroma. These consist of true nerve fibres and are not the growths so commonly met with growing from the sheath of nerves or within the sheath. They are composed of ordinary medullated nerve fibres associated with connective tissue. They are found on the ends of divided nerves, growing after amputations. They are usually very small nodules, innocent, and are remarkable largely for the great pain they cause. TYKE OF BLOOD-VESSELS. Angioma. These tumors are composed of blood-vessels held together by connective tissue. The diagnosis is readily made without the aid of the microscope. TYPE OF PAPILLA. Papilloma, papillary or villous tumor. This tumor con- sists of a body of connective tissue with a covering of epitheli- al cells, resembling the papillae of the skin. They are rarely without blood-vessels which end either in a capillary net-work work or in single loop. Cells may be seen scattered through the connective-tissue basis. The epithelial covering is gener- ally like that from which the part arises. The papillomata may occur on any surface of the body, but more generally where papillae and villi normally exist. They occur singly or many papillae may be affected giving the growth a cauliflower appearance. The papillomata exhibit no tendency to return after removal, yet in many ways they may become serious troubles. They are liable to undergo ulceration, followed by 258 THE STUDENTS MANUAL OF HISTOLOGY. hemorrhage, especially when situated in the bladder and in- testine. Warts of the skin, common warts and horny growths are varieties of this class, so also are the condylomata and venerial warts. Figure 174 rep- resents a growth of this character. This will not be mistaken for epithelioma, for in the case of a papilloma, the epithelial cells are in their normal relations to the part, they are homologous, while in an epithelioma the cells are heterologous. TYPE OF GLAND TISSUE. Adenoma, glandular tumor. In structure an adenoma is like that tissue in which it is found, or from which it originated, for it may after a time become com- FiG. 174. Papilloma. pletcly Separated from the old gland. Its function will not be like the normal gland how- ever. Indeed it can be said to have no function whatever. The adenomata are very difficult tumors to diagnose, being very liable to undergo the degenerations, especially the forma- tion of cysts and the changing into calcareous forms. They are frequently, perhaps most frequently, found in the female mammae. They are very commonly associated with other forms as adeno-sarcoma, adeno-myxoma, etc. In the mammary gland an adenoma is most frequently associated with a fibroma, giving rise to the familiar adeno-fibroma. Here the aceni of the gland are separated from each other by a large growth of fibrous tissue between them, or a bundle of aceni may be separated from another bundle by an hyper- trophy of the intervening connective tissue. This may de- THE STUDENTS MANUAL OF HISTOLOGY. 259 velop to such an extent that the secreting tubes of the gland will be nearly obliterated. Figure 175 represents the aceni of the gland widely separated from each other. The growth of these tumors is usually slow. While they are primarily innocent they may assume malignant proper- ties. TYPE OF EMBRYONIC TISSUES, THE SARCOMATA. Fibro-cellular, fibro- plastic, fibro-nucleated, recurrent fib- roid, myeloid. The sarcomata are divided into varieties ac- fcording to the majority of their cells. The spindle-celled sar- coma is composed almost en- tirely of long fusiform, com- paratively thick-bodied, n u - cleated cells. The processes from either end of the cell are usually long and not infrequently branched. Each cell is possessed with one nucleus frequently with two nuclei. This variety is the most common of this large class of new formations. Figure 176 represents some of these cells taken from the leg of a man. The leg had been diseased nearly two years. A majority of the cells were large, the nucleus multiple in many cells, and a number of free nUclei or small round cells were in the field also. The disease had affected the tibia to its very centre, so that FIG. 175. gland. Adeno-fibroma, from mammaiy FIG, 176. Spindle- cells, from sarcoma of leg. 26o THE STUDENTS MANUAL OF HISTOLOGY. deep in the growth were found the myeloid cells, seen at figure 177. The spindle-shaped cells vary much in size, both in the same growth and also in different growths. Some growths will be composed almost entirely of cells averaging [-jijj-ji^ of, an inch length, while FIG 177. libra. Myeloid cells, from sarcoma of TTiTO others of much larger cells, of twice the size, with larger nu- clei, and some growths combine the two. The cells are many times arranged close together, so that there is scarcely any space between them, givirig but a small quantity of intercellular substance, which in turn may be either fluid, or granular, or firm and fibrillated. Large cells, large nuclei, and the presence in a cell of more than one nucleus, are evidenceSiOf a high degree of malignancy. The cells are not infrequently arranged parallel to each other, running in bundles all through the growth, giving it very much the appearance of a fibroma. This tumor arises as do all the sarcomata, from pre-existing connective tissue, and in- creases, either by multiplication of its own elements (central growth), or by continually invading the healthy tissue aro/.nd it (peripheral growth), which is highly characteristic of all this class. The sarcomata are usually quite vascular, the walls of the blood-vessels being composed of embryonic tissue, ren- der them exceedingly liable to rupture, causing the formation of sanguineous cysts, severe hemorrhage, etc. They are also very liable to undergo fatty degeneration. Although this va- riety may become encapsuled, it possesses unmistakable malig- nant properties. The growth is usually rapid. Figure 178 represents the cells from a melanotic sarcoma of the eye. This tumor extended into the vitreous humor from the choroid, was globular in shape and a trifle over one- THE STUDENTS MANUAL OF HISTOLOGY. 261 FIG. 178. Melanotic cells, from sar- coma of choroid. half an inch in diameter. These cells are mostly spindle- shaped and nucleated, but they now contain a large amount of dark colored pigment melanin, rendering the nuclei obscure, and many times invisible. The large majority of these growths is found primarily in the eye, where this pigment normally exists. They may arise from the superficial integument. S o m e - times this pigment will be de- posited only in a slight degree, giving the growth a brownish ap- pearance. Then too, only a few of the cells may be thus affected. Again the pigment may be in such excess that the tumor will be a black color. These tumors are very liable to have their elements conveyed to distant parts by the blood-veesels in which case their melanotic character will accompany them. In this way secondary growths are found in the liver, kidneys, lungs, etc. The laboratory is in possession of a liver three- fourths of which has become transformed into little melanotic growths, varying in size from a pea to masses two inches in diameter. This variety of the sarcomata is perhaps the most malignant of all, exceeding in this particular many of the cancers. An osteoid sarcoma is usually a spindle-celled sarcoma that has either become truly ossified, or more or less hardened by calcareous deposits. It is important to recognize the sar- comatous element, inasmuch as the innocence or malignancy of the growth will depend upon it. Some acid, as dilute hy- drochloric, may be used to dissolve out the calcareous matters when it can be examined for the characteristic cells, which, if found, will decide its malignancy. Figure 179 shows the large and small round cells of a sar- coma, growing in the- orbit after enucleation. This tumor re- 262 THE students' manual OF HISTOLOGY. curred after removal, causing the death of the patient. A sar- coma composed of round cells is usually of much softer con- sistence than one composed of spindle cells. Such a sarcoma © ^©%" is composed of true embryonic connec- '~1\?^''^ ^ ^^^^ tissue, with a fine granular inter- * ® »!^^^ ■" "3 cellular substance. The smallest cells -®r\%^*'®C* t3-^Q carmine staining evenly, evidently ^^^■i^ consisting of nothing but free nucleus _,„ , J I, J matter. The larger cells have a FIG. 179. Large and small round o cells from sarcoma of orbit. nucleus while the largest have frequent- ly two nuclei, with nucleoli. The cut surface yields a juice rich in cells. This variety increases with a rapid growth by invading the healthy surrounding structures, involving the lymphatics and internal organs. It is full of blood-vessels easily ruptured. It is not to be mistaken for encephaloid cancer, which it resembles by physical characters. Here the cells are of a nearly uniform size and character, and there is an entire absence of an alveolar stroma. When an alveolar stroma is present careful attention must be given to notice whether the cells are grouped together in these alveolar spaces or exist singly and alone. If the latter then it is termed an alveolar sarcoma, if the former, it belongs to one of the cancers. It is often very difficult to distinguish be- tween the two. Figure 177 illustrates the large many nu- cleated cells of the myeloid sarcoma. This variety is usually found growing in connection with bone, especially from the medullary cavity. The nuclei vary in number from two or five to ten or fifty. These large cells are generally separated from each other by a number of cells of the spindle-shaped variety, among which are seen a few round or oval ones. It is quite frequently encapsuled, most frequent in early life, and is the least malignant of all the sarcomata. Thus it will be seen that all the sarcomata possess malig- nant properties, in this respect ranking next the cancers. THE students' manual OF'HISTOLOG y. 263 They disseminate by means of the blood-vessels, and thus rarely infect the lymphatics, a clinical distinction between these growths and the cancers, marked and distinct. For this reason they are reproduced with greater rapidity than the cancers. The lung being the most favorite seat for the secon- dary growths. No one variety of the sarcomata is necessarily malignant, while again the same variety may recur in the same place many times. THE CARCINOMATA. A cancer is a growth consisting of a fibrous, alveolar stroma, the meshes of . which are filled with cells of an epi- thelial type. While the cells have no " specific " character, yet they are recognized by their large size, irregular shape, the prominence, number and size of their nuclei and nucleoli. These cells exhibit every possible shape, as seen in figure 181. They are full of granular matter and from their great liability to undergo fatty degeneration they usually contain some fat globules. In the juice of the cancers will be found numerous free nuclei, especially in the younger and softer growths. Cells not very unlike these are found in the normal tissues or in those tissues when slightly inflamed. The day of the " specific cancer cell " is nearly over, in fact there is no such thing at the present time, the very best pathologists hold strictly that " every pathological growth has its physiological proto- type." If cells are found in a FIG. 180. stroma of Scirrhus. growth of the character de- scribed above and illustrated at figure 181, then that growth must be looked upon with suspicion, but before pronouncing it a cancer two other things must be carefully noted ; first, the 264 THE students' manual OF HISTOLOGY. Stroma, and second, the arrangement of the cells within the alveoli. The stroma, or solid portion of the cancer generally consists of a frame-work of connective tissue as seen at figure 180, so arranged that round or oval alveoli are formed freely communicating with one another, in which are grouped to- gether the cells described above. The amount of stroma varies exceedingly. Sometimes it is so great as to form the largest part of the tumor. The alveolar spaces are then very small, and the growth will be hard to the touch, and the cut surface will yield but little juice. Again it may be very scanty as in the rapid growing and young cancers. Every possible degree as to quantity exists. Cancers have been found in all tissues save cartilage. The female mamm3e, uterus, lower lip, stom- ach, liver, oesophagus and lymphatic glands are all favorite places for the development of the cancers. They may occur alone or in great number, and appear as tumors or as infil- trations. They are very rarely separated from the healthy tissues surrounding them by a capsule, but on the contrary show a close connection with them. The blood-vessels are arranged very different from those found in the sarcomata. In the latter it will be remembered the vessels ramify all through the growth, and their walls be- ing composed of embryonic connective tissue, they easily rup- ture and then the elements are easily and rapidly disseminated. While in the former — the cancers — the blood-vessels course within the stroma and very rarely indeed do they communicate with the alveoli. Thus, it is very rare, if ever, that the cancers are disseminated by means of the blood-currents. However a FIG. 181. Cells from Scitrhus. study of the lymphatics shows them to be numerous, accompanying the blood-vessels and com- municating freely with the alveoli spaces. The elements thus THE students' manual OF HISTOLOGY. 265 enter the lymphatics readily and are carried to the nearest glands where they are caught in its meshes and are carried further on, not however until the gland itself has become suf- ficiently affected to furnish other elements. In the cancers, then, dissemination is slow and accomphshed through the lymphatics. All cancers are very liable to undergo fatty me- tamorphosis, especially the young and rapidly growing vari- eties. Scirrhus or chronic cancer, as its name implies, is of slow growth and of a firm and hard structure. In this variety the al- veoli are small and comparatively poor in cells. Instead of the organs affected being increased in size they are many times actually reduced, often depressed in the centre and firmly at- FIG. 1 82. stroma of encephaloid. tached to the skin. A microscopical examination of the centre of this growth may reveal nothing but cicatricial tissue. The cells have suffered degeneration, while the stroma has atro- phied and contracted. At the periphery will be found a zone ' of cells, and free nuclei infiltrating the neighboring tissues. Between the two will be seen the characteristic alveolar stroma as at figure i8o, together with the cells as at figure i8i. Its most frequent seat is in the female mammae and in the 266 THE students' manual OF HISTOLOGY. Stomach. The secondary growths arising from it are generally encephaloid. Encephaloid or acute cancer differs from the above mostly in its rapid growth and small amount of stroma. It is usually very soft and by scraping the fresh cut surface an abundance of juice is given off, rich in cells, free nuclei, granular matter, etc. Figure 182 illustrates the stroma smaller, and the alve- olar spaces correspondingly larger than found in scirrhus. Il is not of so frequent occurrence as scirrhus, arising as a secondary growth of the latter. By colloid is understood a degeneration of the above varieties. A section of colloid shows a small amount of stroma FIG, iB^ Colloid. and nearly entire absence of cells. The alveolar spaces are quite well marked, being generally round, varying in size, and filled with the soft, colorless, glistening colloid material, in which are a few cells. Many times the cells themselves appear filled with this same material. Epithelioma or cancroid varies much according to its situation. Arising from the cutaneous or mucous surface the cells will be found to correspond with the cells taken from those surfaces. Like those found on these surfaces they are usually irregular in shape, containing generally one nucleus. THE students' MANUAL OF HISTOLOGY. 267 sometimes two nuclei. Their arrangement is most peculiar and characteristic. They appear to arrange themselves in groups and thus they form the " concentric globes " or " epi- thelial nests." These nests are frequently so large as to be visible with the naked eye, especially when they are of a yel- lowish color from becoming hard and dry. The epithelium is here heterologous in its nature, extending from the surface into the subjacent connective-tissue, giving the great charac- teristic of this variety. The point of junction of the cutaneous and mucous surfaces is its favorite seat. Here on the lower lip it is usually seen to commence as a small ulcer, caused by some external irritation, which grows quite rapidly, becoming firm and indurated, with an ulcerating surface. Under pres- sure the cut surface may yield little worm-like curdy masses, such as can be forced from the sebaceous glands of the skin. By many authors this is con- sidered very characteristic. While all the cancers are highly. malignant, some pos- FiG. 184. Epithelioma. scss this property to a much greater degree than others. The vascular and rapidly grow- ing encephaloid reproduces itself in the neighboring lymphat- ics the most rapidly, while the chronic scirrhus is nearly its equal, colloid is the least so of the three. Epithelioma is by far the least malignant of all the cancers, in this respect rank- ing below some of the sarcomata. Its thorough removal is not likely to be followed by a return of the growth. It may extend, however, and infect muscle, bone, and lymphatics. It rarely reproduces itself in internal organs, but when it does so the secondary growths correspond to the primary one. CHAPTER XXII. Starch. STARCH is the most generally diffused, excepting pro- toplasm, of all vegetable substances within the cell-wall. When found in the older structures, roots, stems, seeds, etc., it is found nearly pure; when found in freshly-growing tissue it is in union with chlorophyll. Starch grains contain carbon, oxygen, hydrogen, and some mineral matter. They are in- soluble in water, alcohol, ether, and oil; are destroyed by potassa, and colored blue or violet by iodine — the color de- pending on the density of the granule and the strength of the iodine. The starch grains of different families and different species of the same family differ so much in size and general appearance as to be easily identified. The largest starch grains known are those of tous-les-mpis, which are frequently ^^ of an inch in length, while the smallest are those of rice, which are occasionally TniV"? ^^ ^" '"'-'^ ^"^ diameter. Potato Starch. — Botanists have taken the potato-starch grain as the typical form with which they compare others. So we should have a good knowledge of this grain. ' If the com- mercial starch is not accessible, the grains can easily be obtain- ed by cutting a fresh potato with a clean knife, and then float- ing on a glass slide, with a drop of water, the white substance which adheres to the side of the knife. Or, shave off a very thin slice of the potato, and place it in a watch-crystal in a 268 THE STUDENTS MANUAL OF HISTOLOGY. 269 little water; the fine sediment settling to the bottom will be the starch.' There are two leading theories regarding their growth. Some claim that the surface of the grain is formed first, and that it grows by layers being deposited on the inner surface of the case, which gradually expands until it reaches its normal size. The other and the more generally accepted opinion is, that the nucleus is formed first, and the grain grows by means of deposits of starchy matter around this nucleus, and each successive layer contains less moisture than the preceding layer; this explains the appearance of rings or laminas seen so plainly FIG. 1 85. Potato Starch, x 375. in the potato and many other starches. A new theory has been advanced in Sachs' Botany (page 59), which is too long, however, for an explanation in this connection. In specimens which have been subjected to even a slight degree of dry heat, there appears a black line or star-shaped mark over the nucleus. The heat evaporates the moisture from the grain, and there must be a shrinkage on the surface to correspond with the evaporation. This is the greatest over the nucleus where is the greatest moisture. The grains are round, ovate, irregularly oval, or egg-shaped, nearly transparent; nucleus 270 THE STUDENTS MANUAL OF HISTOLOGY. eccentric (not in the centre), and in the smaller end of the grain, and surrounded by numerous distinct rings or laminae. The grains are very irregular in size; the smallest are just perceptible, and the largest are frequently ^^ of an inch in length. A very decided cross is seen when viewed with polarized light, the arms of the cross radiating from the nucleus, not from the centre of the grain. This is the cheap- est and the most common starch; there being from ^800,000 to $1,200,000 worth thrown on the market annually. Probably the greatest part is used for adulterations. Arrow-root Starch closely resembles potato-starch. The grains are much more uniform in size than those of the potato, and are about -g-J^ of an inch in length. The nucleus is gen- erally in the larger end of the grain, while in the potato-starch, as before mentioned, it is in the smaller end; while the rings are finer and more numerous. Thirty or forty rings can fre- quently be counted in one grain, while potato-starch some- times has only three or four. Arrow-root starch takes a dis- tinct cross with polarized light. It is very frequently adul- terated with potato starch. Wheat Starch. — Pure wheat starch can be obtained by cut- ting through a kernel of wheat, and scraping with the point of a knife a little from the central part of the kernel on a glass slide. There are two distinct kinds of grains found here; small spherical or angular grains floating frequently in a mass, many times more numerous than the large grains, and about -J-J5L-5 of an inch in diameter. The others are large, lenticular grains, which, when viewed on the face, appear like a spherical grain. When viewed on the edge, they have the appearance of a double-convex lens. This lens shape can easily be proved by touching the cover glass gently with a pencil-point, and •watching the grains roll over in the field. This should always be done when testing for adulterations with starch grains. There is seldom any nucleus, but when it is present it is cen- THE student's MANUAL OF HISTOLOGY. 27 I tral, and still more seldom are there any rings. When viewed with polarized light, only a faint cross is seen if any.* When subjected to dry heat, the grains are changed very much in afi- pearance; being warped considerably from their normal shape. They are larger, more brittle, and more transparent. Yet gen- erally they can be identified when subjected to either dry or moist heat, if the moist heat be not raised to the boiling point. The large grains of wheat starch in their normal state are very uniform in size for the same variety, but the starch-grains of the different varieties differ considerably in size. The average FIG. 186. Wheat starch. X375, diameter of the grain in the eight varieties examined is ^^ of an inch.f Barley and rye are closely related to wheat. All of *The statement is made by some botanists that wlleat starch gives a cross under polarized light, but I have never been able to detect any closer approach to one than a nearly uniform shadovr floating over the grain. tThese measurements have been made with considerable care. In each case zo grains, as nearly typical as possible, were selected, and acciu-ately measured; the average was then taken, with the following results: The largest grains of Treadwell wheat measured z-86i of an inch in diameter; Deihl, 1-816; Wicks, 1-881; Egyptian, 1-994; Russian, 1-1174; Clawson, i-i2,'>6; SchafEer, i-iooo; Vienna flour, i-86i. There is also con- siderable difference in the size of the sma'l grains. Schaffer small grains measure 1-4700 of an inch in diameter; Treadwell, 1-6102; Vienna flour, 1-5166; Russian, 1-4000; Egyp- tian, 1-6000. 272 THE STUDENTS MANUAL OF HISTOLOGV. these are used extensively for adulterations. Barley Starch is composed of large and small grains. The large grains are smaller than those of wheat; being about y^ig-j5- of an inch in diameter. There is less difference between the long and the short diameters than in wheat starch, so that when the grains are rolled over they present less of a lens- shape, being rounder. Rings and a star-shaped nucleus are quite frequently apparent. The small grains are more angular, frequently having a nucleus, and average -^^-^ of an inch in diameter. No cross is seen when viewed with polarized light. FIG. 187. Bean Starch. X375. Rye Starch grains are larger than those of wheat, very seldom do they show any rings, and when present they are eccentric; occasionally a star-shaped and central nucleus is present. The large grains average t^ of an inch, the small grains ^^^^ of an inch in diameter. A distinct cross is seen in rye starch with the polarized light. After examining these starches in their natural condition, they should be subjected to both dry and moist heat, and examined, as their appearance is THE STUDENTS MANUAL OF HISTOLOGY. 273 much changed by heating. As adulterants, they are frequent- ly so treated. Bean Starch. — We have here a very different appearance from any other starch, excepting that of the pea. The grains are regularly oval and quite uniform in size. A dark line with ragged edges generally extends the whole length of the grain; cross-marks being frequently seen. Faint rings are seen near the edge of the grain. The grains average about •j^ of an inch in length and -j-^ of an inch in breadth. Dry heat renders the grains more brittle, and destroys the nucleus, Corn starch. X375, but not the rings. Moist heat expands, distorts, renders more transparent, and destroys both rings and nucleus. Pea Starch is the nearest like that of bean starch. The grains are smaller and more slender, being generally less than y^- of an inch in length. Corn Starch. — We come now to a starch grain bounded by plane faces and angles instead of curves. The grains are angular, have no rings, and present a round or star-shaped cen- tral nucleus. The average grain is ysVtt "^ ^"^ ''^'^'^ '"^ diameter. The shape is only slightly changed by dry heat, but is entirely 274 THE STUDENTS MANUAL OF HISTOLOGY. destroyed by moist heat. The grains found in the central or outer part of the kernel of corn are more angular than those found in the inner part. This variety is frequently substituted for wheat flour, under the name of " amylum." Rice Starch. — The starch grains of rice resemble very closely those of corn. They are much smaller, however; being only jA^ Oof an inch in diameter. The grains are angular; being bounded by plane sides only, are without rings, and have a central nucleus which is either a dot, a line, or star-shaped. The grains are aggregated together in angular or very ir- FIG. 189. Rice Starch, x 375. regular-shaped masses. Rice is used much more extensively in England as an adulterant than in America, and commercial rice flour is frequently adulterated with corn starchj Oat Starch is the nearest like that of rice, and it is quite difficult to distinguish between them. Oat starch is both com- pound and simple. The compound grains or masses are oval, spherical, or egg-shaped; the surface of the masses being smooth, while those of rice are irregular. The divisions into grainlets show very distinctly. The simple grainlets are larger than those of rice; being ^^^^ of an inch in diameter, and THE STUDENTS MANUAL OF HISTOLOGY. 275 bounded by one or two curved faces. They are without nuclei and without rings. A faint cross is seen with polarized light. Buckwheat Starch is made up of both compound and simple grains. The compound grains or masses are cylindrical or prismatic. When cylindrical, the curving surface is perfectly smooth, but the ends are irregular, as though they had been broken. These masses are very numerous and char- acteristic, and somewhat resemble the cell-contents of black FIG. 190. Oat Starch, x 375. pepper; being coarser, however than the latter. Black pepper is largely adulterated with buckwheat. For this reason buck- wheat should be compared with some of ihe grains from the central part of black pepper, which can be easily obtained by scraping it out with the point of a pen-knife. The grainlets of buckwheat starch are like those of rice, in having a, central nucleus and no rings, and are like those of oat, in having one or more curved faces. In size, they are about ^^^ of an inch in diameter. A correct knowledge of these starches, so closely 276 THE STUDENTS MANUAL OF HISTOLOGY. related to rice, can be obtained only by faithfully comparing- each under the microscope with starch from the latter source. Sago Starch is obtained from the parenchyma or pith of several different varieties of palms. Sago appears in market in a variety of forms; as pearl sago, white sago, sago flour, sago meal, etc. When examined with the microscope, the starch grains of sago appear quite large compared with those of the other starches. They are oval, ovate, or elliptical in shape; much broken, generally one extremity is rounded, and the other extremity, or the sides near it, appear to be clipped, FIG. 19 which is due to the pressure of the adjoining starch grains. The nucleus is eccentric, as indicated by a dark cross or slit which frequently extends the length of the grain ; the surface is irregular or tuberculated, and marked by a few distinct rings, fewer than are seen in the potato-starch grain. The grains exhibit a faint cross when viewed with polarized light. The starch grains composing commercial sago are so changed by the process to which they are subjected before being ready for market, that there is little resemblance between them and the fresh grains. The starch grains found THE students' manual of HISTOLOGY. 277 in the pearl sago are the most changed by heating. Sago is not used so much in this country tor an adulterant as in Europe. Commercial sago is frequently adulterated with po- tato starch, sometimes with rice. Sometimes there is an entire substitution of potato starch for the sago. Any adulteration used for sago can readily be detected by the microscope, by noticing the above described characteristics. Tapioca Starch is prepared from manioc or cassava, or, according to Linnaeus, from the root of Janipha Manihot. In the preparation of tapioca for market, the substance is sub- jected to a temperature of loo degrees C, which changes the appearance of the starch grains very much from what they are in their fresh state, yet they are not entirely destroyed. The heat partially dissolves the outer case of the starch grains, which renders tapioca slightly soluble in water. The grains are quite uniform in size (about Tj-jVir of an inch in diameter); they are round or cup-shaped, with flattenings here and there, due to the pressure of neighboring grains. The starch grains of tapioca are generally found floating in the field singly, but in the growing root they are found compounded of two, three, or four grains each. A distinct and large circular nucleus is seen in fresh specimens. In dried specimens the nucleus is marked by a distinct star or cross. Tapioca is adulterated with rice, sago, and potato starch. Potato flour is frequently prepared like pearl tapioca, and sold as such. Tapioca is used quite extensively in England as an adulterant, but not so much • in America. These starches, sago and tapioca, are so much changed in the different commercial varieties, /. e., pearl, white, meal, etc., that to become well acquainted with them one should examine each variety carefully. An illustration or drawing of these in their fresh state would hardly be of value in identifying the starch grains as we find them in market as an adulterant. Turmeric Starch is from the rhizome of Curcuma longa, 378 THE students' manual of histology. and is imported principally from Southern Asia. The paren- chyma is packed full of starch in angular or roundish masses. Turmeric is used extensively as a coloring material, to give deeper color to the spices which have been adulterated with some of the flours. When a ground spice, as, for example, mustard, contains turmeric, even if not in large quan- tities, its presence can be detected by exposing the mustard to the light, when it will fade to a dingy yellow. Its presence can also be detected by treating the suspected substance with potassa, and if turmeric be present the substance will turn a FIG. 192. Turmeric Starch, x 375. deep yellow or brick-red color. The starch grains are quite uniform in size, and in shape are elliptical, oval, or like flat- tened discs, sometimes even truncated. The nucleus is at one extremity, and has the appearance of being entirely out- side of the grain proper. Rings quite distinct, numerous and uniform in density, pass around the grains like zones, and pre- sent a beautiful appearance in a fresh grain. Commercial turmeric has been heated so much in preparation for market that frequently the rings cannot be seen, and even the normal THE students' manual OF HISTOLOGY. 279 shape of the grain is lost. In the fresh state they show a de- cided cross or black bands with the polarized light; but this is seldom seen in commercial turmeric. The coloring material is a deep, reddish yellow, and is contained in special cells of the parenchyma. The starch grains are white. The action of iodine and potassa is the same here as with all starches, but sulphuric and sulphochromic acids are of perhaps more value in this case, for they turn the coloring matter to a peculiar rose-pink. In the examination of mustard, this test is valuable. Of the twenty specimens of mustard examined, during the past two years, every one contained turmeric. It is used to color many other spices. The turmeric of commerce is itself adulterated frequently with corn starch, etc. Ginger Starch grains are irregularly spherical, oval, or disc-shaped, closely resembhng those of turmeric, belonging to the same family, Zingiberaceae. The nucleus is at the extrem- ity, as if it were hardly a part of the grain, the rings are numerous and uniform. A cross is seen with polarized light. Much of the ginger of the market has been scalded, which causes the starch grains to lose their normal shape. It is diffi- cult then to see the rings, and the cross, which was seen with the polarized light, is destroyed. In examining the starch from the root, as found in the stores, the starch grains at the centre will be found to be more perfect than those taken from near the surface of the root.* •The following references may be of value to those wishing to carry the study of the starches farther; Hassall's "Adulterations in Food and Medicine;" Sachs' '*Botany," page 56 ; Souberian, "Dictionnaire des Falsifications ;" Wiesner, "RohBtoffe des Plan- zenreiches," pp. 239-289 ; Planchon, ^'Determination des Drogues Simples," Vol, II,, chap. XIII; NSgeli, "Die StSrkekomer," Zurich, 1858, 4°, Fluckiger und Hanbury's "Pharmacographia." INDEX. - PAGE. Abducens nerve, nucleus of 200 Acid, carbonic 67 Acoustic nerVe, nucleus of 200 Adenoid tissues 47 Adenoma 258 Adeno-myxoma 258 Adeno-sarcoma 258 Adipose tissue 76 Adipose tissue, tumor of 252 Alkaline fluids 67 Amceba 29, 36 properties of 30, 31 size of. 42 Amylum 274 A ngle of aperture 17 definition of 18 Angioma 257 Anuine, blue-black 25 red 66 Aqueductus sylvii ig8 Arnold, ground plexus of 181 intermediary plexus of 181 Arteries 114 coats of 114 commencement of 114 termination in veins of 118 Artery, hepatic ■ 145, 146 Auerbach, plexus mesentericus of 141 Balsam, how to remove 21 Blood 38 action of reagents upon 58 white corpuscles of 61 color of 45 composition of , 38 corpuscles and plasma cf 39 crystals of 55 distribution of 39 dog's and human , 54 in criminal cases 52 methods of examining 56 number of corpuscles in 49 origin of white corpuscles of 61 Tea corpuscles of 40, 165, 168 classes of 51 color of 40 composition of 49 effect of carbonic acid on. . 45 graveof 47 medico-legal value of . . . . 52 nucleus of. 43, 50 number of 41 origin and death of 40,41 shape of 48 size of 52 structure of 49 superficies of 49 where found 40 : 283 Blood- Illative number of white dnpuscles in 60 toteJ quantity of 39 volume of 49 white corpuscle of 35, 58, 59, 196 Blood-corpuscles, structure of 36 when discovered 38 Blood-stains, how examined 55 Blood-vessels — 112 methods of examining — 119 nerves of 8« tumor of 857 walls of 119 Bone. articulating surfaces of 78 canaliculi of ..... . 82 cells of 36,81,84 compact 82 Haversian canals of 82 lacunae of 82 lamellse of 83 lymph capillaries of 170 marrow of 85 matrix of 8i methods of examining 87 ossein of 82 Eeriosteum of 85 harpey's fibres of 85, 94 tumor of 253 Bowman, membrane of 228 Brain ig6 blood-vessels of 196 cerebellum of 200 connection of different parts of . . . 196 corpora dentati 200 ependyma 196 gray matter of 198 layers of 198 methods of examining 201 Meynert's layers of ig8 nerve fibres of 196 neuroglia of 196 olivary bodies of 200 projection system of 197 white matter of 196 Bronchi 122 termination of 123 Brownian movement 68 Bulbus olfactorius 199 Comers hair brushes 21 Camera lucida 18 Canada balsam 25 without heat 25 Cancer 263 blood-vessels of 264 cells of 263 colloid 266 INDEX. PAGE. Cancer, encephaloid 261 epithelioma 266 lymphatics of 264 scirrhus 265 stroma of 264 where found 264 Canal, alimentary 151 Cancroid 266 Capillaries, m lymph 169 of bone 112 of glands 112 of mucous membranes 112 of nervous tissue 112 of retina 112 size of 112 stomata of 113 structure of 113 Carcinomata, the 263 Carmine, injecting fluid 24 staining fluid 25, 33 Cartilage 36, 78 cells of 78 cricoid 134 deposit of lime in 79 fibrous 78 hyaline 78, 79 lacunae of 78, 79 lymph channels of 79 methods of examining 80 of vertebrae 79 reticular 78, 79 rin^ of 79 tumor of 252 varieties of 78 yellow-elastic 79 where obtained 80 Cavity, oral 102 Cells 29, 32 adipose tissue 76 air 124 blood 36. 168 bone 36, Sx, 84 cancer 263 can ilag-e 36, jH ciliated 63, 66 columnar 62 connective tissue 73^ 76 cornea .'-J 231 Deiter's 200 Deitcr's hair 224 different forms of 32^ 33 division of 35 epithelial ^3. 36 fixed 73, 74 ganglion 141 giant 247 goblet 65, 131 growth of ._ 34 increased nuclei in .' 35 large and i*mall round 262 liver 145, 147 loss of 35 lymphoid i£8 melanotic 26r migratory 73 2 PAGE. Cells, mobile 73 mother 267 mucous 131 muscle 103, 10^, 105 multipolar ganglion , — ig8 myeloid 247, 260 nerve 191 nucleus of 34 of cornea 231 of gray matter 20c of myxoma 254 of nails 68 of retina 239 of seminal tubes 206 of taste buds 216 of tubes of kidney 151 olfactory 216 parietal 137 pathological 247 pavement 62 peptic 137 pigment '. . .77, 78 plasma . > 74 prickle 214, 218 Jh'urkin je'5 200 Sertoli 207 spleen pulp ' 42 spindle '. ^ 259 squamous 67 stratified 68 structure of 36 Cement-substance 63, 73 Cerebral ganglia 198 Cerebellum 198 cortex of 200 layers of 200 i Chamois skin 2r Chondrin 78 Chon-iroma 252 C'.iromatic aberration 16 Chyle 140, 141 Cilia 63 Clarke's column 192 Colloid cancer 266 Color, change of, in animals 77 Condylomata 258 Conjunctiva, follicles of 166 Connective-! issue.. 73 tumor of 250 Corium 70 Cornea, lymph capillaries of 170 Corpora, albicantia 198 dentaii 200 quadrigemina 198 striata 198 Corpuscles, of blood 40 salivary 68 Corti, organ of 224 Czermak, interglobular spaces of 93 Dammar 26 Defining pow^er 17 Deg'enerations 247 Deiter's cells 200 Deiter's hair cells 224 Demour, membrane of 229 PAGE. Dental pulp 97 Diaphragm 102, 103, loS muscle cells of 103 work of 103 Doyerc's mount 180 Duct, hepatic 145 Duodenum 137, 139 E^I" Z20 canals of 220 endolymph of 220 labyrinth of . .' 220 lobe of 79 methods of examining 226 middle and outer 102 modiolus 221 nerves of 223 organ of corti 224 otoliths 222 vestibule of 220 Electrical currents 67 Embedding mixtures 26, 27 Embryonic tissues, tumors of 259 Encephaloid cancer 266 Enchondroma 252 Epididymis 205 appendage to 151 EpitheWal cells 36 Epithelioma 266 Epithelium 66 buccal 67 cement-substance of 63 ciliated 63, 66 methods of examining 64 pigmented 68 squamous 67 stratified 68 structure of 62 where found 66, 67 Examining, methods of adipose tissue 77 blood 56 blood-vessels 119 bone 87 brain 201 cartilage 80 ciliated epithelium 64 ear 226 eye 24 i for sputa fibres 129 intestine 142 kidney 160' liver 149 , lung 135 lymphatics 171 muscle 106 nerve fibres 175 ovary 212 salivary glands 132 skin J . . . 226 spinal cord 194 stomach 142 teeth 96 testis 212 tongue 224 tumors 248 Examining, white fibrous tissue 7^ yellow elastic tissue 76 Eye, 228 canal of Petit 241 canal of Schlemm 230 capsule of lens of 242 cells of cornea of 231 choroid 68, 232 ciliary muscle 233 ciliary processes 68 cornea of 228 hyaloid membrane of 241 iris 68, 233 layers of retina of 236 lens of 241 ligamentum iridis pectinatum of 229 macula lutea 239 membrana fusca 228 methods of examining 243 peculiarities of, at macula lutea 240 pupil of 234 retina 112, 235 sclerotic of 228 vitreous humor of 241 zone of Zinn 233 Eye-piece, of microscope 14 deep 14 negative 14 shallow 14 structure 14 Facial nerve 200 Fascia, inier-muscular 75 lymph capillaries of 170 Fat, in muscle 109 Fibres, nerve 173 ganglionic nerve 177 sputa 128 termination of nerve 173 Fibro-cellular tumor 259 Fibro nuclear tumor 259 Fibro-plastic tumor 259 Fibroma 250- Field, flat 17 Fifth nerve, nucleus of 200 Focussing, rule for 21 Fos-;a, Sylvii igg Frog, lung of 123 C^-nglia, cerebro-spinal 178 sympathetic 178 Gelatine 73 Gcrlach's nerve net-work 193 Gianuzzi, cells of 131 composii ion of 131 crescents of 131 Girardes, organ of 206 Glands, abdominal salivary 133 Brunner's 137 during secretion 131 lymphatic 164 mucous 134, 214 parotid 131 peptic 136 Peyer*s 161 pyloric 136 28q INDEX. PAGE, Glands, salivary 130 sebaceous 219 serous 215 submaxillary 131 sudoriferous 219' thymus 166 Gland-tissue, tumor of 25S Glisson, capsule of 147 Glomeruli 155 CrlossQ-pharyngeal nerve, nucleus of... 200 Gluten 73 Glycerine 26 Graafian follicles 209 Granules, fat 106 pigment 157,168 Gray matter, lining ventricles ig8 Green, classification of tumors by 249 H aematoxylin 25 Hair — 62,69 different layers of 69, 70, 71 gray 69 growth of 71 properties of 69 sacs of 71, 72 size of 69 sudden blanching of 69 to obtain sections of 72 Haller, vas aberrans of 206 Heat 67 Heart, peculiarities in structure of 98, 102, 108 rudimentary 40 Henle, loops of 156 Hippocampus major iq9 Hodgkin, disease of 256 Hypertrophy 246 I nfundifula. . , 198 Injecting apparatus 28 Injecting mixtures 23, 24 Intestine 134 ,138, 152 examination of 143 glands of 142 large 142 mucous membrane of.. 138, 142, 162 small 138 villi of 62,139 blood-vessels of 139 lymphatics of 139 number of 139 valvulae conniventes of 138 walls of 138 Illumination 21 central light 21 day light 21 direct light 21 gas light 21 north light 21 oblique li^ht 21 reflected light 21 sun light 21 J ejunum 139 ICebs, muscular fibrils of 181 2 PAGE. Kidney ^5^ arteriolae rectae of '59 arterial system of 158 Bowman's capsule of ^55 capsule of glomeruli of ^55 cells of, tubes of ^57 centro-tubular membrane of 157 cortical portion of ^54 cortical pyramid of i54. first trace of 151 glomeruli of i5S intercalary portion 156 loops of Hf nle of i55 lymphatics of t6o Malpighian, bodies of 155, 159 medullary portion of 154 medullary rays of 154 medullary substance of 153 methods of examining 160 nerves of 160 papillae of 153 physiology of 157 shape of 152 straight uriniferous tubes of — 154 urtiniferous canals of 155 venous system of 159 Wolffian bodies of 151 Klein, neuroglia matrix of 188 Krause, bulbs of 182 rod ellipsoid of 237 terminal plate of 180 Kuehne, end plate of : 180 Lacunae 78, 79 Langerhaus, layer of 218 Larynx 121 Lewis', method of preparing brain by. . .201 LieberkiJhn, crypis of 141, 142 Lipoma 252 Liver 144, 152 arteries of 145 bile capillaries of C47 capilUries of 145 cells of 145, 147 ducts of 145 early appearance of 144 examination of 149 injection of 150 lobules of J 44 of pig .v-V '44 relative weight of 144 size of lobules of 144 veins of 145 inter lobular 145 intra lobular 146 walls of bile capillaries of 148 Lung 123 air vesicles of. 124 caoillaries of 125 first appearance of 12 1 how inflated 1 23 injection of 126 in phthisis 128 lobules of 124 lymph capillaries of 170 methods of examining 125 ' 86 INDEX. PAGE. Lung, of frog i23 how prepared 123 pigmented 127 Lymph 43 Lymph-capillaries i6g Lym^ph-channels 79 Lymphatic glands 164 blood-vessels of 165 corpuscles of 165 cortex of 164 course of lymph in. . . 165 follicles of 164 matrix of 165 medulla of 164 sheath of 164 Ltymphatics 162 methods of examining 171 puncturing method 162 stomata of 162 how demonstrated •. 163 structure of 162 vessels of 162 Lymphatic-tissue, tumor of 255 Lymphoid organs 166 Lymphoma 255 nFiacula lutea 239 Magnifying power, how determined ig Mafigfnancy 248 Malpighian, bodies 155 corpuscles 167 Meissner, plexus of 141 tactile corpuscles of 184 Melanin 248 Membrane, centro-tubular 157 Membranes, lymph capillaries of 170 Meynert, layers of rg8 Micrometers 18 Microscope 1 1 accessories to 22 care of 21 compound 1 1.- erector to n eye-piece of 14 names of parts of 13 objective of 14, 15 simple XI stands 11 when in focus 21 Mounting media 25, 26 Mucigen 131 Mucin 65, i3r Mucous-tissue, tumor of 254 Muscle g8 cells of 103, 104, 105 color of 103 compartments of 102 contractile discs of 100 discliaclasts of 102 endomysium of g8 fasciculus of g8 fatty degeneratirn of 109 " iaflltration of log fibres of 98, gg granular layer 102 PAGtt. Muscle, how divided 98 interstitial discs of 100 involuntary and unstriped 103 Krause's membrane of 102 lateral disc s of 102 longitudinal striae of 101 lymph capillaries of 170 myosin of loi nuclei of 100 of alimentary canal 134 perimysium of 98 primitive fibrillae of lor relation to tendon of 107 rods of loi sarcolemma of gg, 108 skeletal 102 striated, where found 102 termination of nerve fibres in 180 transverse discs of loi trichinse in 107 Muscle cells, degeneration of no Muscularis mucosae 135 Muscular-tissue, tumor of 256 Myeloid cells 259 Myoma 256 Mvosin lot Myxoma 256 Nails 68 Nasmythj membrane of 96 Neutral tint reflector 18 Neuroma 257 Net-work, intracellular 37 intranuclear 36 Nerve-fibres 173 axis cylinder of 174 axis fibrillae of 175 constriction rings of 175 different parts of 173 division of 179 ganglionic 177 how divided 173 lymph capillaries of 170 medulla of 174 meduUated 173 methods of examining 175 modes of termination of 179 non-medullated 176 of the brain 196 olfactory 177 Remak's 177 size of 173 termination of, in conjunctiva.. . 182 in cornea 185 in ear 223 in nose 217 in salivary glands 132 in skin 184 in striated muscle 180 in teeth 92 in tendon 182 in tongue 216 in unstriated muscle. 180 Nerve-tissue^ tumor of 257 New formations 246 287 INDEX. PAGE. New formations, cells of 247 Nose, ending of nerve fibres in 217 mucous membrane of 216 olfactory cells of 216 Nuchas, lig;amentum 76 Nucleus of nerves ^ 200 Odontoblasts 91 Obesity 109 CEsophagus 102, 134 mucous membrane of 134 muscle fibres of 134^ 135 Objectives 17 achromatic 17 corrected 17 good qualities, of 15 how numbered 18 immersion iS, 22 structure of 15 systems of 15 Olivary bodies 200 Optic nerve, nucleus of 200 Optic thalami 200 Organs, lymphoid 166 Ossein 82 Osseous tumor 253 Osteoblasts 86 Osteoma 253 Ovary 209 cortical layer of 209 coverings of 209 germinal layer of 209 germinal spot 211 germfnal vesicle : 211 Graafian follicles 204 liquor folhculi 211 membrana granulosa 210 metliods of examining 212 ovum z JO tissues of 209 tunica albuginea 209 tunica fibrosa 210 Ovum 210 Pacinian bodies 183, 219 Pancreas 130, 132 Papillae, tumor of 257 Papillomp. 257 Parepididymis 206 Penetrating power 16 Perichondrium 78 Petit, canal of 241 Peyer's glands ^ - - ■ 166 Pharynx 102, 134 lining of 134 mucous membrane of 134 walls of 134 Pigment, cells 77 excretion of 158 granules ■ 68, 77 Pigments, bile, urinary 42 Process, vermiform 167 Projection system, of the first order 197 ■' second order. 197 '' third " 198 PAGE. Prostate, muscles of 103 Prussian blue 23 Pulmonary lobule 123, 124 Puncturing, method of injecting by 167 Purkinje, granular layer of 94 cells of 200 Pus...; 35* 59 Reagents 23 Rectum 102 Recurrent fibroids 259 Remak's fibres 177 Ranvier, constricton rings of 175 Respiratory passages 121 bronchi of 121 lirynx of 121 lungs of 123 trachea of 122 Retzius, brown striae of 96 Rhomboidal fossa 198 S aliva 67 Salivary glands .130 alveoli of 130 ducts of 130 lobes of 130 varieties of 130 Sankey, method of preparing brain by. 202 Sarcoma, spindle- celled 259 alveolar 262 large and small round celled. 262 melanotic 260 myeloid 260 osteoid 261 Sarcomata, the 259 Schlemm, canal of 230 Schronn, cortical layer of 209 Schwalbe, ta ste buds of 215 Schultze, olfactory cell of 216 prickle cells of 214 Schwann, sheath of 173 Schweigger-Seidel, middle piece of 208 Scirrhus cancer 265 Seminal vesicles 205 Sertoli, cells of 207 Sharpey, fibres of 85 Silver staining 65 Size of an object 20 Skin - 217 epidermis of . '. 217 glands of 219 layers of 217 lymph-capillaries of 170 methods of examining 226 papillae of 218 Spinal cord 186 blood-vessels of 194 cells of ,191 193 central canal of 192 Clarke's column of 192 commissures of 190 cornua of 191, 192 course of fibres of 194 enlai^ements of 187 fissu.es of 187 288 INDEX. PAGE. Spinal cord , frame-work of i8d Gerlach's nerve net- work of 193 gray substance of 190 length of 186 ligamentum denticulatum.. 186 membranes of 186 methods of examining 194. neuroglia of 188 subarachnoidean tissue of.. 186 white substance of 188 Spermatoblasts 207, 208 Spermatozoa 207 Spherical abberration 16 Spleen 166 blood-vessels of 169 cells of 168 coats of 167 extirpation of 47, 48 follicles of 167 Malpighiaa corpuscles of 167 Sputa, in suspected phthisis 128 Stand, of microscope 12 different parte of 13 Starch 368 arrow root • 270 barley 272 bean 273 buckwheat , 275 corn 273 ginger 279 oat 274 pea 273 potato 268 rice 274 rye 272 sago 276 tapioca 277 turmeric 277 wheat 270 Staining— mixtures 25, 66 Stilling, canal of 241 Stomach 134 blood-vessels of 138 coats of 13s glands of 136 lymphatics of 138 methods of examining 142 mucous membrane of 135, 167 nerves of 138 peptic glands of 136 peptic glands of, during digest'n 137 pyloric glands of 137 Substance, interfibrillar 37 Xaste-buds 215 Teeth 9° brown striee of enamel of 96 cementum of 94 cuticle of g6 dental pulp of 97 dentinal sheath of 93 dentine of 93 enamel of 95 interglobular spaces of 93 methods of examiaing 96 Teeth, nerves of 92 parts of 90 pulp cavity of 91 Tendon 73, 75 lymph capillaries of 170 termination of nerve fibres in 182 Testicle 203 coverings of 203 development of 203 divisions of 203 epididymis 205 mediastinum of 204 organ of Girardes 206 rete testis of 204 seminal tubes of 206 seminal vesicles 205 spermatozoa 207 tubes of 203 tunica albuginea 204 vasa recta of 204 vas aberrans of , 206 vas deferens of 205 vasa efferentia of 204 Tissue, adipose 76 connective 73 nervous 112 sub-cutaneous 73, 75 white fibrous 73, 75 yellow elastic 75 Tongue 214 methods of examining 204 nerves of papillae of 216 papillae. of 215 serous glands of 215 taste-buds of 215 Tonsils 167 Trachea 122 Trichinae 107 size, shape of 109 vitcUity of 109 when discovered 108 where found 107 Tuber cinereum 198 Tubes, fallopian 151 Tumors 246 cells of 247 classification of 249 degenerations of 247 examination of 248 when malignant 248 Urine, solid constituent of 158 water of 157 Uterine fibroids 256 Uterine polypus 256 Uterus 106, 151 Vagus nerve, nucleus of 200 Valentin, membrane of 171 Vasa- vasorum 1 19 Veins 115 hepatic 146 interlobular 145 intralobular 146 ^portal 145 Vermiform process 167 289 INDEX. PAGE. Vesicae, sphincter 102 Vesical, prostatic 151 Villous tumor 257 inf ^Ideyer, germinal layer of 2oq Warts 258 White fibrous tissue 73 effects of reagents on 73 Wolffian bodies 15^ disappearance of 152 PAGE. Wolffian bodies, purpose of 15J size of. . .i 152 structure of 151 Working distance 17 Yellow elastic tissue 75 structure of 76 ■where found 76 Xinn, zone of 233 George S. Davis, Medical Publisher. THE STUDENTS' MANUAL OF HISTOLOGY. BY CHARLES H. STOWELL, M. D., Professor of Physiology and Histology, and Instructor in the Physiological Laboratory,, University of Michigan. The design of Professor Stowell has been to furnish a much needed text book for the student of histology and as a complete guide for the practitioner and mi- croscopist. Its text is lavishly illustrated with 193 wood engravings. Cloth, price $8.00. Homoeopathy— What Is It? BY PROF. A. B. PALMER, M. D., Of the University of Michigan. 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