COLUMBIA LIBRARIES OFFSITE HEALTH SCIENCES STANDARD HX00025321 i ■ HP "SHE] M SRfjjB rail Qr<) <56\ ^S Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/manualofhistologOOsatt A MANUAL HISTOLOGY EDITED AND PREPARED BY THOMAS E. SATTERTHWAITE, M.D. OF NEW YORK President of the New York Pathological Society, Pathologist to the St. Luke's and Presbyterian Hospitals, etc. IN ASSOCIATION WITH Drs. Thomas Dwight, J. Collins Warren, William F. Whitney, Clarence J. Blake, and C. H. Williams, of Boston; Dk. J. Henry C. Simes, of Philadel- phia ; Dr. Benjamin F. Westbrook, of Brooklyn ; and Drs. Edmund C. Wendt, Abraham Mayer, R. W. Amidon, A. R. Robinson, W. R. Birdsall, D. Bryson Delavan, C. L. Dana, and W. H. Porter, of New York City WITH ONE HUNDRED AND NINETY-EIOnT ILLUSTRATIONS NEW YORK WILLIAM WOOD & COMPANY 1881 COPYRIGHT BY WILLIAM WOOD & COMPANY 1881 Trow's Printing and Bookbinding Comtany 201-213 East iitk Street NEW YORK PREFACE. For some years past there lias been a general demand among the members of our profession for a manual of Histol- ogy, summarizing, in concise and plain language, our present knowledge in this fundamental branch of medicine. It is true many books have been written on the subject, but their great brevity, on the one hand, or an unnecessary diffuseness on the other, have prevented them from meeting with acceptance at the bauds of physicians and students. In the one class belong the little handbooks of Rutherford and Schaefer, which have done much to simplify and therefore popularize histology, but they were intended for beginners, and especially students doing class-work under the laboratory system now so much in vogue. But both physician and student need something of wider scope, and they have been compelled to turn to Klein & Smith, Strieker, or Frey, though no one of these excellent works is thoroughly adapted to their wants. Apart from the expense of the two former, they all are deficient in matters relating to human histology. The practical experience of a teacher made it evident also that the volume to fill such an obvious gap should take the form of a text-book. And the present time seemed opportune for its appearance, since we have latterly made much positive iv PREFACE. advance in histological studies, while histologists themselves are now more of one mind in microscopical mutters. That such a book should appear under American auspices seemed further to l"' eminently proper, as we have in various parts of the coun- try a goodly number of medical men who are either engaged in teaching histology or in studying some special branch of it. The advantages of utilizing their accumulated experiences was therefore apparent by the editor, and he gladly applied to them for assistance when it was found that one individual could not prepare the volume within a reasonable time or in a manner that would be satisfactory. It is hoped that the names of the collaborators furnish a sufficient guarantee that proper representatives of American histology have been selected. In some respects the object sought for has not been wholly attained, as, for example, in the effort to separate purely human histology from the comparative. But this is impossible at the present time, mainly because our knowl- ' edge is still too limited. It is a matter of regret, also, that the original illustrations have been so few in comparison with the total number, but the great expense attending their production would not warrant an}' one in attempting much in this direc- tion. Through the kind co-operation, however, of Messrs. Wil- liam Wood & Co., the editor has been able to utilize many excellent cuts that were in their possession. As a further means of relieving the tedium associated with a work that is so largely descriptive, the various authors have aimed to intersperse here and there throughout the text mat- ters of physiological or pathological import. Still, intelligent practitioners do not have to be reminded that rational thera- peutics has found a substantial support in the revelations of pathological anatomy, which, in turn, rests upon histology, PREFACE. V so that tlie relation between microscopic anatomy and the sci- entific practice of medicine is readily appreciated. Emanating as the volume does from American sources, the editor finds it a fitting place to give proper space to American contributions, and the reader may therefore find due notice of the physiological desquamation of blood-vessels, considerations on the nature of nerve-termini, matters relating to the intimate structure of the striped muscular fibre and nerves, with the results of studies on the structure and development of certain connective substances, and novelties in microscopic apparatus and methods. A sjDecial chapter is also given to the thick cutis vera, now for the first time described as a distinctive portion of the skin. In it will be found detailed the discovery of the fat-columns^ which are calculated to explain certain pathological changes that have been imperfectly understood. The first chapters of the book are devoted to the mechanism of the microscope, and to certain formal methods of work with which the beginner should be familiar. Of the illustrations, sixty-five were prepared for the volume, while forty have never, it is believed, appeared in book-form. The remainder are mostly from the manuals of Strieker and Frey. A limited number of bibliographical references have been in- serted where it was thought they were desirable in guiding the reader to the literature of the subject. For the prepara- tion of these tables and much valuable assistance, the editor here desires to express his thanks to Dr. E. C. Wendt, of this city. It was thought best to omit the subject of optical principles which figure so conspicuously in some of our histological manuals. Those who wish information on these matters are referred ta any of the standard text-books on physics, where VI I'll) '.FACE. the subjecl is treated at greater length than was permissible in the present instance. For a similar reason, and also because it would prove a needless expense, the price-lists of instrument-makers have been omitted. Full particulars relating to the various sorts of microscopes and their accessories can be obtained from any of i he leading opticians, who from time to time issue lists con- tinning ample illustrations of the most recent improvements in all that pertains to practical working of the instrument. In conclusion, the editor finds himself compelled to reiter- ate the well-worn statement, that circumstances over which he lias had no control have united to delay the press-work of the volume, and at the end have made its final revision rather hasty. A kind indulgence is therefore asked for any error that may, through oversight, have escaped his notice. T. E. S. TABLE OF CONTENTS. PART I. CHAPTER I. By THOMAS E. SATTERTHWAITE, M.D. Materials Requisite for Histological Work. — How to Use the Micro- scope.— Testing the Microscope. — Its Uses Page 1 Appliances for microscopic work, 1. Chemical reagents, 3. Illumina- tion, 4. Stage diaphragms, 5. The mirrors, 5. Direct and oblique light, 5. Arrangement of the object, 6. Kind of lens to use, 6. How to keep the instrument clean, 7. Magnifying power of a lens, 7. How to estimate the size of an object, 8. Testing a lens, 8. How to illuminate the object, 9. Testing the eye-piece, 10. Testing high lenses, 10. Measuring the angle of a lens, 10. CHAPTER II. By THOMAS E. SATTERTHWAITE, M.D. Methods for Preparing Microscopic Objects Page 12 General directions, 12. To prepare fresh objects for rapid examination, 13. Ordinary methods of preparing tissues, 13. Miiller's fluid, 14. Potas- sium bichromate solution, 14. Ammonia bichromate solution, 14. Alcohol and acetic acid mixtures, 14, 15. Molybdato of ammonia, 15. Solution of osmic and chromic acids, 15. Alcohol and acetic acid, and muriatic acid solution, 15. Method of hardening the brain, 15. How to embed speci- mens, 15. Embedding ia glycerine and tragacanth, 10. The hand section- cutter, 10. Freezing section-cutters, 17. Hailes' microtome, 19. The Vincent microtome, 21. Staining fluids, ammonia carmine, 21. Borax car- mine, 22. Double staining, 22. Haamatoxylon solutions, 23, 24. Solutions for multiple staining, 24, 25. Preparation of the cornea, 25. Triple stain- Ylll TABLE OF CONTENTS. ing, 20. Double, triple and quadruple staining, 20. Bismark brown, 2G. Solution of alum carmine, 27. Naphthaline yellow for bone, 27. Methyl green and induline, 27. Purpurine, 88. French archil, 28. Alizarine, 28. Metallic solutions, staining with osmic and oxalic acids, 28. Chloride of gold and lemon juice, 28. Nitrate of silver, 29. Chloride of gold, 29. Osmic acid, 29. Methyl green for waxy change, 29. Wickersheimer's liquid, 29. Methods of injecting the blood-vessels, 30. CHAPTER III. By THOMAS E. SATTERTIIWAITE, M.D. Tiie Blood Pag* 34 Red corpuscles, 34. Comparative measurements in men and animals, 30. Number of, 37. Corpuscles in an indifferent fluid, 38. Brownian and amoeboid movements, 39. Heating slide, 40. Action of dilute salt solution, 40. Action of distilled water— irrigation, 41. Action of carbonic acid gas, 42. Action of acids, 43. Action of alkalies, 44. Action of electricity, 44. Exhibition of the circulation, 45. Internal structure of red corpuscles, 40. Development, 47. White corpuscles, 48. Counting corpuscles, 48. Blood crystals, 53. Hemoglobin, 53. Hsemochromometer, 54. Bibliography, 54. CHAPTER IV. By THOMAS E. SATTERTHWAITE, M.D. Epithelium Page 5° Ordinary flattened or squamous epithelium, 57. Ciliated epithelium, 58. Effect of reagents, 59. Columnar or cylindrical epithelium, GO. Other va- rieties, 61. Structure of epithelial corpuscles, 01. Bibliography, 01. CHAPTER V. By THOMAS E. SATTERTHWAITE, M.D. The Connective Substance Group.— Mucous or Gelatinous Tissue.— Adenoid Tissue.— Neuroglia.— Fat Tissue.— Fibbous Tissue Prop- rb.— Corneal Tissue.— Intermuscular Tissue.— Tendon Tissue.— Elastic Tissue Page 02 Connective substances in general. 82. Mucous or gelatinous tissue. 63. Development of fibrous tissue, 64, 65. Fibrous tissue. 86. Adenoid tissue, 69. Neuroglia, 70. Tendon tissue, 72. Fat tissue, 7:5. Intermuscular tissue, 74. Corneal tissue, 75. Elastic tissue, 77. Pavement endothe- lium, 80. Bibliography, 81. TABLE OF CONTENTS. IX CHAPTER TL By THOMAS E. SATTERTHWAITE, M.D. The Connective- Substance Ghoup {Continued). — Cartilage Pngc 82 Hyaline cartilage, 82. Parenchymatous cartilage, 83. Division of the corpuscle, 84. Calcifications, 84. Methods of studying hyaline cartilage, 84. Yellow elastic cartilage, 85. Fibrous cartilage, 86. Structure of cor- puscle, 87. Bibliography, 88. CHAPTER VII. By THOMAS E. SATTERTHWAITE, M.D. The Connective-Substance Group (Continued). — Bone Page 89 Compact tissue, 89. Ossein, 89. Bone-corpuscles, 90. Haversian sys- tem, 90. Preparation of dry bone, 92. Preparations of decalcified bone, 92. Sharpey's fibres, 94. Cancellous tissue, 94. Marrow, 95. Periosteum, 95. Development of bone, 9G ; through cartilage, 97 ; from membrane, de- velopment and absorption, 99. Howship's lacunas, 100. Formation of cal- lus, 100. Bibliography, 101. CHAPTER Yin. By THOMAS E. SATTERTHWAITE, M.D. The Teetii Page 102 The enamel, 102. Dentine or ivory, 103. Dentinal globules, 104. Cement, 105. Pulp, 105. Development of teeth, 105. Primary enamel organ, 107. Development of enamel, 108. Bibliography, 108. CHAPTER IX. By THOMAS E. SATTERTHWAITE, M.D. General Histology of tite Nervous System Page 109 Nerve-fibres, 109. Myelinic fibres, 109. Staining in picro-carmine, 111. Staining with silver, 112. Staining with osmic acid, 113. Semi-desicca- tion, 113. Transverse sections of myelinic nerves, 114. Preparation by ammonia bichromate, 115. Modern conceptions of myelinic nerves, 116. Fibres of Rernak, preparations in osmic acid and picro-carmine, 118. Prep- arations of Remak's fibres in hsmatoxvlon, 118. Ganglionic bodies, 119. iglia "f the cranial and spinal nerves, 120. Gasserian ganglion, 120. Ganglionic bodies of the spinal cord, 120. Brain, 121. Sympathetic, 121. Meii cos, 122, Auerbach's plexus, 123. Termination of nerves, 128. Tactile corpuscles, 124. Pacinian bodies, 12-1. Nerve-terminations in muscle, 125; in epithelium, 12ii. Connective tissue of nerves, 126, Bibliography, 127 TABLE OF CONTENTS. PART II CHAPTER X. By THOMAS D WIGHT, M.D. MuscuiiAK Fibre Page 128 Involuntary muscular fibre, 128. Voluntary muscular fibre, 130. Physi- ological attributes, 134. Nuclei and muscle corpuscles, 130. Conclusions, 137. Peculiarities of voluntary muscles, 138. Termination of muscle in tendon, 139. Muscular fibre of the heart, 140. Bibliography, 140. CHAPTER XI. By EDMUND C. WENDT, M.D. The Blood -Vessels Page 14£ Capillary blood-vessels, 142. Vascular endothelium, 143. Capillaries proper, 144. Genesis, reproduction, and regeneration of capillaries, 150. Arteries, 151. Veins, 155. Peculiar vascular structures, 158. Blood-vas- cular glands, vascular plexuses, 158. Intercarotid gland, 1G0. Corpora cavernosa, 1G0. Vasa vasorum, lymphatics, and nerves, 161. Bibliography, 162. CHAPTER XII. By W. R. BIRDSALL, M.D. Tiie Lymphatic System Page 163 Modern views of, relative to connective tissue, 163. General histology, 164. Lymphatics of the mesentery, 165. Klein's studies on the omentum, 166. Perilymphangeal nodules, 167. Development of fat-tissue, 168. Lym- phatic radicles, 168. Artificial injection of lymphatics, 169. Endothelium and stomata, 169. False stomata, 170, 171. Intimate structure of lym- phatic vessels, 172. Variations in shape, 173. Topographical peculiarities, 174. Thoracic duct, 174. Subarachnoid and subdural spaces, 175. Lym- phatics of tendons, 175. Lymphatic glands, 175. Nerves of lymphatic nodes. 179. Injection of a lymphatic gland, 179. Method of studying, 179. Ranvier's method, 180. Other methods of injecting glands, 180. Bibli- ography, 182. TABLE OF CONTENTS. XI CHAPTER XIII. By A. MAYER, M.D. TnE Liter and Biliary Apparatus Page 183 Hepatic lobules, 183. Blood-vessels, 18G. Connective tissue, 188. Liver- cells, 189. Larger biie-ducts, 191. Glands of the ducts, 191. Capillary bile-ducts, 192. Do the bile-capillaries possess walls ? 196. Gall-bladder, 197. Lymph-vessels of the liver, 198. Nerves, 199. Bibliography, 199. CHAPTER XIY. By A. MAYER, M.D. The Kidney Page 201 General structure, 201. Renal tubules, 203. Their epithelium, 20G. The loops, 209. Their epithelium, 210. Intercalated portions, 211. Collecting tubules, 211. Their epithelium, 211. Blood-vessels of the kidney, 213. In- jecting the kidney, 214. Kidney stroma. 215. Nerves, lymphatics, capsule, calyx, 216. Natural injection by the sulphindigate of soda, 216. Bibliog- raphy, 222. CHAPTER XV. By J. HENRY C. SIMES, M.D. Male External and Internal Organs op Generation, wiTn their Glandular Appendages Page 223 Penis, 223. Urethra, 225. Cowper's glands, 227. Prostate, 227. Testi- cles, 229. Tunica vaginalis, 230. Hydatid of Morgagni, 231. Yas defe- rens, 232. Seminal vesicles, 235. Bibliography, 238. CHAPTER XVI. By J. HENRY C. SDIES, M.D. Female Extennal and Internal Organs op Generation, wrrn their Glandular Appendages.— Placenta Page 240 Labia majora, 240. Labia minora, 240. Clitoris, 240. Vestibule, 211. Glands of Bartholine, 241. Hymen, 241. Vagina, 241. Urethra, 242. 1 'torus, 243; Mucous membrane of, 243. Ovula Nabothi, 244. Fallopian tubes, 246. Ovary, 246. Graafian follicles, 248. Parovarium, 350. Pla- centa, 251. Bibliography, 251. Xll TABLE OF CONTENTS. CHAPTER XVII. By BENJAMIN F. WESTBROOK, M.D. The Bespebatoby Tbact Page 253 Larynx, 253. Ligaments of, 253. Cartilages, 254. Epiglottis, 255. Mucous membrane, 355. Trachea and primary bronchi; 257. Smaller bron- chi ami lungs, 2.*)!). Pleura, 205. Lymphatics of, 207. Pleural append- ages, 2G7. Bibliography, 867. CHAPTER XYIII. By A. R. ROBINSON, M.D. The Skin Page 209 General plan of arrangement, 209. Structure, 270. Different layers, 271. Epidermis, 271. Rete Malpighii, 271. Granular layer, 274. Stratum lucidum. 27-4. Corneous layer, 274. Subcutaneous connective-tissue layer, 27-1. Pacinian corpuscles, corium, 277. Blood-vessels, 279. Nerves, 279. Tactile corpuscles, 280. Sweat-glands, 282. Muscles, 287. The hair, 288. Nails, 293. Bibliography, 295. CHAPTER XIX. By R. W. AMIDON, M.D. The Central Nervous System Page 29G Spinal dura mater, 290. Spinal arachnoid, 297. Spinal pia mater, 297. General histology of the spinal cord, 298. Nerve-elements of the cord, 299. Special studies in different portions of the cord, 301. Medulla oblongata, 307. Olivary body, 310. Cerebellum, 317. Cerebral ganglia, 319. Cere- bral ventricles, 319. Cerebral cortex, 321. Structure of cortex, 323. Bib- liography, 325. CHAPTER XX. By C. H. WILLIAMS, M.D. Tiie Eye Page 328 Eyelids, 328. Eyelashes, 328. Tarsus, 329. Meibomian glands, 329. Conjunctiva, 330. Cornea, 331. Sclera, 337. Vitreous layer, 339. Ciliary body, 340. Retina, 343. Lens, 350. Lachrymal gland, 351. Bibliography, 352. CHAPTER XXI. By W. F. WHITNEY, M.D., and CLARENCE J. BLAKE, M.D. Tiie Ear Page 353 External ear, 353. Middle ear, 355. Eustachian tube, 355. Internal ear, 357. Membranous labyrinth, 358. Cochlea, 302. Bibliography, 307. TABLE OF CONTENTS. Xlll PART III. CHAPTER XXII. By D. BRYSON DELAVAN, M.D. The Nasal Fossae, Pharynx, and Tonsils Page 368 \~estibulum nasi, 368. Respiratory region, 368. Olfactory region, 370. Olfactory nerves, 372. Bowman's glands, 372. Pharynx, 373. Tonsils, 373. Bibliography, 375. ' CHAPTER XXIII. By D. BRYSON DELAVAN, M.D. The Mouth and Tongue Page 377 Tunica propria, 377. Blood-vessels, 379. Lymphatics, 379. The tongue, 380. Papillae, 380. Taste-goblets, 381. Bibliography, 384. CHAPTER XXIY. By EDMUND C. WENDT, M.D. The Alimentary Canal Page 386 Oesophagus, 386. Stomach, 388. Small intestine, 394. Large intestine, 400. Rectum, 401. Bibliography, 402. CHAPTER XXV. By C. L. DANA, M.D. The Sicken, Pancreas, Thymus, Thyroid, and Pineal Glands, and Pituitary Body Page 403 The spleen— coats, 403, 404. Malpighian corpuscles, 404. Pulp, 406. Blood-vessels, 407. Lymphatics, 409. Nerves, 409. Development, 409. Pancreas— excretory duct, 411. Blood-vessels, 411. Lymphatics, 411. Nerves, 411. Development, 411. Thymus gland, 412. Capsule, 412. Fol- licles, 412. Central canal, 414. Blood-vessels, lymphatics, development, 414. Thyroid body, 415. Blood-vessels, 416. Lymphatics, 416. Nerves, 416. Pineal gland, 417. Pituitary body, 417. Bibliography, 418. XIV TABLE OF CONTENTS. CHAPTER XXVI. By J. COLLINS WARREN, M.D. The Tnicic Cutis Vera page 439 Fat-columns, 421. Blood-vessels, 423. Lymphatics, 424. CHAPTER XXVII. By EDMUND C. WENDT, M.D. Urinary Excretory Passages.— Suprarenal Capsules page 428 Renal pelvis, 428. Ureters, 429. Bladder, 430. Suprarenal capsules, 431. Bibliography, 437. CHAPTER XXVIII. By W. H. PORTER, M.D., and E. C. WENDT, M.D. Mammary Gland Page 439 General considerations, 439. Nipple, 440. Galactophorous ducts, 441. Milk reservoirs, 441. Areola mamma), 4-12. Arteries, 442. Lymphatics, 443. Nerves, 443. Structure of expanded gland, 444. Of involuted gland, 446. Rauber's views, 450. Corpuscles of Donne, 450. Milk, 451. Devel- opment, 452. Plan of histological study, 455. Bibliography, 456. MANUAL OF HISTOLOGY HISTOLOGICAL METHODS. CHAPTER I. MATERIALS REQUISITE FOR HISTOLOGICAL WORK— HOW TO USE THE MICROSCOPE— TESTING THE MICROSCOPE— ITS USES. Very little apparatus and few reagents are essential for gen- eral histological work. Such as are really needed may be so arranged as to fit in a box or bag, that can be carried in the hand. First of all, the student should be provided with a Fig. 2. Fib. i. FlO. 3.— Curvocl Iris Scissors. '[xii V of small forceps, with either curved or straight points (Figs. 1, 2), according to individual fancy ; a pair of delicate curved iris scissors (Fig. '5) ; a few pipettes ; a glass rod or 2 MANUAL OF HISTOLOGY. two ; a spoon (Fig. 4) for lifting sections of tissues from the fluids in which they have been immersed; a pair of needles (Fig. 5) in handles for teasing or tearing tissues ; (the handles used for crochet needles, or the pin-slides sold by jewelers, may be fitted with ordinary milliner's needles, which are long, delicate, and flexible, and therefore well adapted for this -i.nmnm.mi «. I'.l^ Fig. 4. Fig. 5. — Microscopic Needle -holder. work) a sable or camel's hair brush for removing cellular elements, so as to bring particular parts into prominence ; bibu- lous paper ; a sharp knife (Fig. 6) for cutting thin sections ; ' 1 For this purpose the razors made by Le Coultre, in Geneva, have been highly recommended, but good knives may be obtained of almost any cutler ; indeed, most of the makers of surgical instruments furnish them ; they are usually fiat on one side and slightly concave on the other. MATERIALS REQUISITE FOR HISTOLOGICAL WORK. 3 five or six shallow porcelain dishes, ounce gallipots, with, flat bottoms, in which to soak the tissues when they have been cut ; glass slides for mounting specimens (the ordinary size is 3 x 1 inch) ; thin glass or mica covers (squares or circles) for cover- ing the specimens (three-quarters of an inch is a good diameter). Mica covers are much cheaper than glass, and are suitable for rapid work and when it is not desirable to make permanent preparations. Fig. 8. — Beer's Cataract Knife. In addition, a small Beefs cataract knife (Fig. 8) will be found useful for puncturing vessels and hollow organs to obtain samples of their fluid contents. All of these articles may easily be contained in the drawer of a box 10 x 12 inches in size ; ' the upper portion will hold the necessary reagents. These latter should comprise a small amount of a three- fourths per cent, aqueous solution of sodium chloride, about an equal amount of distilled water, dilute acetic acid, glycerine, and iodized se- rum;'' a fluid ounce of each will be all that is necessary, and for convenience of use they may be put in corked bottles pro- vided with capped pipettes passing through the corks. The vials and perforated corks may be obtained of almost any apothecary. The cap being of rubber, very small quantities of the fluid can be withdrawn from the bottle and pressed out as desired, either upon the slide or otherwise. Other reagents required are oil of cloves in a two-ounce stoppered bottle ; dammar varnish or Canada balsam, each in a capped bottle (Fig. 7), containing a glass rod ; a solution of logwood, and another of borax carmine,3 in ordinary glass stoppered two-ounce bottles, and a small vial of asphalt or some similar cement. It will be useful, in addition, to have a small bottle (4 oz.) of absolute alcohol, another (8 oz.) of com- mercial alcohol, some Muller's fluid3 (8 oz.), and a solution of the bichromate of potassium (gr. xv. — %].)• 1 T. II. .McAllister, optician, No. 40 Nassau Street, New York City, has made one for me which answers the purpose satisfactorily. Miller Iiros. , No. G!) Nassau Street and 12K> Broadway, New York City, also make and furnish cases for the same purpose. 4 Formula in the chapter on General Methods. 3 Ibid. 4 MANUAL OP" HISTOLOGY. No good histological work can be done without a note-book to record the results of observation. All such memoranda will be very useful for subsequent reference. A "heating slide, a gas chamber and a slide arranged for conducting electric cur- rents may also be desirable. They will be described in the chapter on I he Blood. The following substances that cannot be contained in a box, and arc necessary in some forms of microscopic work, may be mentioned: osmic acid (1 percent.), nitric acid (C. P.), distilled water, olive oil, caustic soda or potash, chloride of gold (\V per cent, sol.).' It is also very convenient to have at hand a short wooden rule which is divided into inches and tenths of an inch. The stage micrometer is also equally necessary. Other accessory materials will be described in their proper places. HOW TO USE THE MICROSCOPE.2 Illumination. — When the instrument is ready for use it should be placed upon a firm and rather low table, near a window, which does not receive the direct rays of the sun. If daylight is not to be obtained, a small kerosene hand-lamp will answer sufficiently well for illuminating purposes. The flame should be on a level with the reflecting mirror of the micro- scope, and quite near it. Sometimes a condenser is interposed, but this is rarely necessary, and, indeed, it may be said that it never comes into use in histological work. A thin sheet of blue glass may sometimes be found to assist the eye when artificial illumination is used, as the light is made white. Some microscope makers furnish with their instru- ments a set of blue glasses varying in color from very light to dark blue. They are rarely needed, as the eye soon becomes accustomed to continuous work for long sittings, even when strong light is employed. Those who work much with the microscope keep both eyes open, and use first one and then 1 Formula in the chapter on General Methods. 2 It is presumed that students engaging in histological work are more or less familiar with the mechanism of the microscope. For this reason the subject of optical principles and the description of the different parts of a microscope are omitted here. Those who may wish special information on these points are referred to Ap- pendix A. HOW TO USE THE MICROSCOPE. D the other. Some find it a great assistance to direct the un- engaged eye upon a dark object, such as a blackened card, which they fasten to the tube of the instrument near its top. As it is desirable that the lamp should only illuminate the reflector, a great many ingenious contrivances have been made to cut off the superfluous light. For this purpose some micros- copists interpose a piece of thin board, or a thick card, having a circular opening between the lamp and the reflector. Stage diaphragms. — When the pencil of light has been reflected from the mirror upon the opening in the stage, it is plain that a larger or smaller amount of light will pass, accord- ing to the size of the opening. The appliances that regulate this matter are called stage diaphragms — sometimes they are simply cylindrical tubes with capped upper extremities, each tube being provided with caps of varying aperture. The tubes are pushed into the stage from beneath. When polished they undoubtedly aid in converging the light upon the aperture. Other diaphragms are simply round holes in a circular revolving plate which is set into the stage. The diameters of the apertures vary from that of a pin's point to about three-fourths of an inch or even more. The revolving diaphragms have now come into general use, because they work simply and efficiently. Mr. Wale has de- vised one that is extremely ingenious. It has the advantage of a cylindrical diaphragm, in so far as it converges the pencil of light upon the diaphragmatic opening, while the size of the opening is regulated by the action of a single thumb-screw.1 It acts as the iris does in enlarging or diminishing the pupil, from which its name, the iris diaphragm. The mirrors. — Of these there should be two, one plane when a diffuse light is needed ; the other concave for a concentrated beam. The latter is frequently used, the former seldom. Direct and oblique light. — Thus far the descriptions have applied to direct light, and it is the only kind much used in histological work. In testing a lens, however, as with a diatom, it is often necessary to use oblique light in order to resolve a line or series of lines. In such cases the aperture in the stage should be made as large as possible, and the mirror, concave or plane, is to be carried well up nnder the stage, to the left or 1 See Appendix A. G MANUAL OF HISTOLOGY. right, so that the pencil of light may be thrown across the Object. By this means, little inequalities of the surface which would be invisible under direct light are clearly demonstrated. The poorer lenses, however, are those which necessitate oblique light. When reference is made to the definition of the lens, direct light is intended. Arrangement of the object. — When the object is to be ex- amined, it should be placed upon the glass slide, which is usu- ally one by three inches in superficial measurement, and as thin as is compatible with the usages to which it is put in ordinary microscopic work. The glass should be white in color, and free from any imperfections that can be detected by the eye. Usually a drop or two of water, a drop of glycerine, or a drop of water and glycerine in equal parts, is placed upon the slide. The object is then immersed in the liquid. It takes some little time for the fluid to permeate the specimen, so that it is ready for study. When pure glycerine is used fully ten minutes will generally elapse before the specimen is transparent. A covering glass is then cautiously let fall upon the liquid, care being taken that no bubble of air enters. The cover is then pressed down. In such cases, when the object is studied with high powers, the cover will often slowly rise and separate itself from the slide, so that the forceps or the finger may be neces- sary to press it back. This inconvenience is obviated by paint- ing a little Canada balsam or cement around the edge of the cover so as to hold it down. Tlie kind of a lens to be used. — For the first examination a low objective should be used, with a medium, not short, eye- piece. The tube should then be carried down until the object comes within the focus. Low powers should always be used at first, because they give a good idea of the object in its gen- eral features. Then the tube may be withdrawn, and a higher power sub- stituted, and so on, until the specimen has been studied in all its details. A convenient accessory is now made by most of the instrument makers; it is a "nose-piece" — a brass attach- ment which is screwed into the end of the tube, and carries two or more lenses.' 1 The double angular nose-piece made by Schrauer, 4G Nassau Street, costs $6, the triple, $20 ; all of the microscope makers are now prepared to furnish them. TESTING THE MICROSCOPE ITS USES. 7 The first named is usually fitted with a | and a -§■ inch lens ; in addition to these a TV immersion may be used for the triple nose-piece. How to keep the instrument clean. — After using the instru- ment it should always be wiped dry, as it is damp from the moisture of the breath and hands. The lenses should be re- turned to their cases, and, if necessary, the surfaces are to be rubbed off with a bit of soft chamois skin or fine linen. Water will remove almost all the dirt from the anterior lens, but occa- sionally it may be necessary to use alcohol. In such cases but very little is requisite, as it may penetrate behind the anterior lens and dissolve the Canada balsam that cements the different portions together. It is well for the student to familiarize himself at first with certain common objects that are apt to be met with in all forms of microscopic work, such as the little foreign substances that go to make up the dust of rooms ; these include minute bits of wood, cotton and linen fibres, particles of wool, hairs of various animals, feathers, etc. The imperfections in the glass should also be noted, and especially the curious red figures sometimes resembling butter- fly wings, caused by an accumulation in the flaws of the glass of a red substance — the red oxide of iron — used by manufac- turers in polishing glass. These red figures are often wonder- fully alike, and have given rise to singular errors among micro- scopical workers. TESTING THE MICROSCOPE— ITS USES. Magnifying power of a lens. — To determine the actual magnifying power of a lens in combination with the particular eye-piece that happens to be in use, the ordinary method is as follows : The glass stage micrometer, which is ruled off into tenths, hundredths, and thousandths of an inch, is placed upon the, stage and focussed. This having been done, the wooden rule, which we have already alluded to and which is divided into inches and tenths of an inch, is laid alongside of the micro- meter-slwli'. One eye, looking outside of the tube, reads off the number 8 MANUAL OF IIISTOLOGY. of divisions of the wooden rule corresponding to a single divi- sion of thr micrometer slide as seen with the other eye directed through the tube of the microscope. By this method of double vision, as it were, a comparison is instituted between the two rules, and the ratio that one bears to the other may be estimated. Suppose, for example, that-nJV* °f :,n mrh on the scale of tin- stage micrometer is equal to yV of an inch on the wooden rule. The ratio of tAtt to T3ff will represent the magnifying power of that particular combination. Reducing these fractions to a common denominator they stand to one another as 1 to 200. The object has therefore been magnified two hundred times. With a short eye-piece the power is greater and it increases in proportion as the tube is drawn out. It is customary how ever to assume a certain length of the draw- tube as the stand- ard : this is twenty-five centimetres or about eight inches. How to estimate the size of an object. — To estimate the size of an object is a much easier task. Place the stage micrometer upon the stage of the microscope and then slip the micrometer eye-piece into the draw-tube. The micrometer eye-piece is simply an ordinary ocular with a glass cover fitted into the diaphragm. The micrometer consists of a series of parallel lines ruled across it at regular distances apart. By focussing the lines on the stage micrometer one may readily count the actual fractions of an inch corresponding to a single division in the micrometer eye-piece. Thus, for example, if we find that a single division of the micrometer eye-piece corresponds to TDVo of an inch, and that a lymphoid corpuscle covers half a division, its diameter is necessarily ¥yVo of an inch. Testing a lens. — A lens should be free from certain defects, as we have already stated. First of all it should have no spherical aberration ; the objects seen upon the edge of the field should be sharply defined, and all objects having parallel sides should appear as such. In other words, they should not be distorted. Secondly, they should have no color or, at least, as little as possible. This defect, however, has never been entirely overcome; some glasses are over-corrected and then the pre- vailing color is blue ; others are under-corrected and then the prevailing color is red. TESTING THE MICROSCOPE — ITS USES. 9 It is a matter of some indifference which color prevails. These defects are best seen by observing a babble of air in a fluid specimen. The prevailing color is seen at the periphery of the bubble. Thirdly, all objects in the field should appear with equal distinctness, whether at the periphery or in the centre. If a fine powder, such as lycopodium be strewn over the field, the granules should be seen as distinctly at the edges as at the centre ; an ordinary thin section of any microscopic object will also exhibit this defect, if it exist. Fourthly, the glasses should have good penetration. This enables the observer to see the general aspect of bodies better, though it may not make him see objects quite as sharply ; the former depending upon a large angle of aperture, and the latter (definition) upon a small one. To be able to have at the same time both great resolving and great defining power is the highest desideratum, and it has been the merit of our American makers to increase the angle of aperture and still maintain a high denning power. For ordinary histological purposes, a lens that will show the oscillatory movement in the mucous or salivary corpuscles is sufficiently high for practical purposes. This is accomplished by the ordinary student's one-fifth of Grunow, for example. If, however, we are studying the delicate intercellular sub- stance of the brain and connective-tissue corpuscles, bacteria, etc., a somewhat higher power is needed. For such studies it is desirable to have an immersion lens, such as the No. 10 or 12 Hartnack or Prazmowski, or a -^ or ,ls of other good makers, such as Wale, Tolles, etc. In using these high powers it is necessary to place a single drop of water on the anterior lens and depress the tube until the drop touches the circle or cover. The drop of water utilizes light that would otherwise be lost, mag- nifies slightly, and corrects, so that the image is made brighter and more distinct. The new oil immersion of Zeiss is highly recommended by Woodward of Washington. In using such a lens, a drop of oil is substituted for water. We are hardly yet prepared to decide whether oil is preferable on the whole to water. How to illuminate the microscope. — In doing ordinary microscopic work it is best to use day-light, such as is reflected from a clear sky. It is not well to use direct sun-light, but to 10 MANUAL OF HISTOLOGY. receive illumination from a point opposite to the sun. North light is very excellent. If artificial light is to be used, an ordinary kerosene burner will answer sufficiently well, even better than gas. Some of the highesl Lenses require artificial light. Testing the eye-piece. — Eye-pieces are usually free from serious defects, but if we are desirous of testing one, the fol- lowing method may be followed : Select a combination of lens and eye-piece that gives a per- fectly flat field. Then remove the eye-piece and substitute the one that is to be tested. If now the image is no longer flat, the eye-piece has aberration of form and should be rejected. Testing high lenses. — In combinations that magnify about five hundred times, a good test is the pleurosigma angulatum, one of the diatoms. A lens that will demonstrate three sets of lines by direct light has a proper amount of defining power, and with the other qualifications already mentioned, is suit- able for the finer sorts of microscopical work. This task is easily accomplished by either the No. 10 immersion of Hart- nack or Prazmowski, the TV of Wale, and also by lenses of other good makers. To test the magnifying power of lenses even more accurately, Nobert's test plates may be used. They consist of bands of fine lines from nineteen to thirty in number. It has usually been thought that the eighth or ninth of their series is a good test ; the nineteenth band,' however, has been defined by a ten immersion Ilartnack, and probably by a goodly number of American lenses. (See Appendix.) Measuring the angle of a lens. — Take an instrument of which the pillar is hinged, and which also revolves on its ver- tical axis. Measure off on the table, in front of the instrument, a semi- circle with the pillar as a fixed point. Divide the semicircle into the proper number of degrees, viz., 180. Place opposite the instrument, and without the circle, a candle or lamp. Then interpose between the two a screen hav- ing an aperture to admit a small beam of light. Revolve the tube on its axis until the light can no longer be seen ; then 1 According to Carpenter, the nineteenth band contains 113,595.13580 spaces to the inch. TESTING THE MICEOSCOPE ITS USES. 11 count off the number of degrees which the instrument has passed over. Suppose, that, in a given case, the number be seventy ; then revolve the instrument in the opposite direction and count as before. The number of degrees will of course be the same. Add the two figures together, and the total number of de- grees (viz., 140) will represent the angle of aperture. CHAPTER II. METHODS FOE PREPARING MICROSCOPIC OBJECTS. General directions. — Microscopic work should be done at a rather low table, not more than thirty inches high, and resting squarely upon the floor, so that it cannot be jarred by move- ments in the room. In most laboratories small and short mi- croscopes are preferred ; they are now made by nearly every optician. The total height, when the stand is vertical, need not be more than eleven or twelve inches. For various reasons, which soon become apparent to those who do much histological work, it is seldom necessary to provide the stand with a hinge- joint, which allows the tube to be inclined toward the observer. A vertical and rigid stand is steadier, less expensive, and. ex- cept in very rare instances, all that is required in medical work. When the microscopist is about to commence his examina- tion, he should select the various materials that are likely to be needed, and place them near him on the table, so as to be within easy reach of his hand. Special tables for microscopic work may be provided with rows of drawers upon either side of the worker. In them should be kept all the microscopic accessories that he expects to use, such as glass slides and covers, wooden boxes for specimens, labels, a note-book for rough sketches and annotations, a bit of chamois skin for cleaning the lenses and other adjuvants which are found useful. By so doing, these materials are kept free from dust, and stand ready for use at any time. A small vessel holding clean water to wash the covers and slides, a receptacle of some kind for the waste, and a clean, fine, and soft towel should not be for- gotten, as they are always useful for every kind of microscopic work. The instrument is best kept under a bell-glass on the table. If, however, it has to be taken about from place to place, it METHODS FOR PREPARING MICROSCOPIC OBJECTS. 13 should be packed in its box, and the accessories may also be kept in a suitable chest, such as has been described, and which is made by a number of opticians. After the directions that have been given, it seems hardly necessary to add that everything pertaining to the work should be carefully cleansed after using, and put away in its proper- place, so as to be immediately available at any future time. The expenditure of a little time in these details is more than counterbalanced by the greater rapidity and effectiveness of subsequent work. How to prepare afresh microscopic object for rapid exam- ination.— When practicable, every specimen should be studied as early as possible after removal from the body, and this is important even if it is to be hardened and prepared for per- manent preservation. Take a clean slide, which, of course, should be reasonably thin ; place it before you upon a white ground (some micro - scopists have a square plate of marble set into the table); mois- ten the slide with a drop of some indifferent fluid, such as iodized serum or, perhaps, a three-fourths per cent, aqueous solution of common salt ; then place in the drop the fragment to be examined. Small particles are more easily studied than large ones. Usually the substance should be spread out a little with needles. In one or two minutes it is ready for examination. By this method striped muscular tissue may easily be detected ; and it also happens to be a good example because it is very frequently brought to microscopists for examination. In certain forms of dyspepsia, especially in women, it is common for ingested meat to pass through the alimentary tract with very little change. Prepared for the microscope in this simple way the peculiar markings of striped muscle may be observed at once, and even if the meat has been boiled. If, however, the material to be examined is opaque, we add to the drop of serum another of glycerine ; the latter alone re- fracts the light too much, and is therefore undesirable. When, however, it is combined with an equal amount of serum or the salt solution, the fluid lias a proper refractive power for most histological purposes. The microscopist should now let fall upon the drop a cover glass, and place the slide upon the stage of the microscope. Nothing is required to keep the cover in 14 MANUAL OF HISTOLOGY. place. Examine at first with a low power, and then with a higher one, until the specimen has been studied in all its details. THE ORDINARY METHODS OF PREPARING TISSUES. M'dllef s fluid.— -It is customary to use Muller's fluid to render tissues firm, so that they may be easily cut with the knife, and made thin enough for microscopic studies. The for- mula is (by weight) bichromate of potassium, 2 parts, sulphate of soda, 1 part, distilled water, 100 parts. This fluid, which is of a brown color and transparent, is admirably adapted for hardening and preserving permanently nearly all the tissues of the body ; though for the brain and cord it is unsatisfactory without the subsequent use of other reagents. It is, however, very cheap, and specimens may be preserved in it for years, and still retain the characteristics which make them suitable for microscopic study. Potassium bichromate solution. — Some microscopists prefer simply a solution of the bichromate of potassium (gr. xv. — 5 j.). It is well, in this case, to put the specimens into a fresh solution every day for several days. Subsequently they are to be hard- ened in alcohol. The strength of the latter should at first be eighty per cent., then ninety per cent., and finally may be ninety-five per cent. The alcoholic process requires a few ad- ditional days. Solutions containing chromic acid or the bi- chromates are objectionable if the specimen is to be used for coarse demonstration, because the yellow or brown color of the acids is difficult to remove. Prolonged soaking in distilled water will accomplish a great deal, but the final color is gener- ally a clay brown. Of course this objection does not apply to microscopic sections, and indeed it appears as if the chromic acid and chromate solutions prepare them particularly well for the process of staining in various colors. Ammonia bichromate solution. — Gerlach has recommended this reagent in one or two per cent, solutions for hardening the brain and cord. It is to be used as the preceding (Frey). Alcohol and acetic acid mixture (Lockhart Clarke). — Two objects were sought by their combination : one to coagulate albuminous matters by the alcohol, the other to render them transparent. The proportion was alcohol three parts and THE ORDINARY METHODS OF PREPARING TISSUES. 15 acetic acid one part. It is said that by this method sections of the cord may be made transparent in a few hours (Frey). Alcohol and acetic acid mixture (Moleschott). — This "strong acetic acid mixture," of which the formula is strong acetic acid (1.070 sp. gr.), 1 vol.; alcohol (.S15 sp. gr.), 1 vol.; distilled water, 2 vols., causes the connective-tissue substances to be- come very transparent. Delicate textures do not tolerate it well (Frey). Molybdate of ammonia has been recommended by Krause for hardening specimens. It has met with some favor. Solution of osmic and chromic acids. — Flesch recommends a union of these acids for hardening and decalcifying bone. It is also useful for hardening other tissues. His formula is as follows : osmic acid, 10 parts ; chromic acid, 25 ; aq. destill., 100. Alcohol and acetic acid and muriatic acid solution. — Beale gives the following formula : water, 1 oz. ; glycerine, 1 oz. ; spirit, 2 oz. ; acetic acid, 2 drachms ; hydrochloric acid, £ drachm. This is said to harden well and be suited for epithe- lial structures (Frey). Method of hardening the brain. — Hamilton recommends the following method : pieces of brain and cord cut into sec- tions not more than an inch in length, or length and breadth, are immersed in a fluid containing three parts of Muller's fluid and one of methyl alcohol, and put away for some three weeks in a refrigerator. Then they are to be soaked in a solution of the bichromate of ammonia (1-400) for a week ; another week in a solution of 1-100 ; a third week in a solution of 1 to 50; and finally kept in chloral hydrate (12 gr. to the ounce). Be- fore cutting, they are to be washed twelve hours or more in water ; they then are to stand forty-eight hours in a syrup containing two parts of refined sugar to one of water. He then cut3 with Rutherford's microtome. Staining is done with osmic acid and carmine. For clarification he uses oil of cloves or turpentine. How to embed specimens. — When a piece of tissue is so small that it cannot be held in the hand, it is customary to embed it in some substance of about the same consistence. A combination of wax and oil answers the purpose very well; they should be mixed in about equal proportions in a porce- lain dish, and then heated together until the wax is thoroughly 16 MANUAL OF HISTOLOGY. melted. This having been done, a mould should be at hand to receive both the embedding mixture and the piece of tissue. Various moulds are in use. Some are made of tin-foil, and are shaped like a common earthenware garden-pot. A fine, long cambric needle should be passed through the tis- sue, and then (the mould being placed in position) the point of the needle is to be pushed through the bottom into the table beneath. Then the mixture of the liquid wax and oil, which has been heated to the point of melting and no more, should be poured slowly into the mould, so as to slightly cover the specimen. During the process of hardening, minute bubbles of air will be liberated from the tissue ; they will escape more rapidly, and the embedding material will harden more quickly and thor- oughly, if the microscopist blows gently and continuously on the surface of the liquid. Just at the moment when the mass is no longer liquid, the needle should be suddenly withdrawn. As soon as it is hard throughout, the tin-foil mould may be torn off by breaking the edge at any point with the finger. The foil tears like paper. When moulds are not at hand, an excellent substitute may be made with ordinary writing paper. Some confectioners make them of pressed paper. Embedding in glycerine and tragacanth. — Mr. John Ste- venson's plan is as follows: He takes two drachms of gtyce- rine and mixes them with one drachm and a half of powdered gum tragacanth. The tissue to be cut is then placed in a small pill-box, and the mixture poured in. The box is then laid away in a cool place from eight to twelve hours, when sections may be made with the knife. In case the specimen is to be preserved for a longer time, the bottom of the box may b(3 taken off, and the side slit up. The specimen will now be found embedded in a solid elastic cake, and may be slipped into alcohol until required. When it is to be kept in spirits less than twenty-eight hours, the mixture should be glycerine, 2 drachms ; powdered tragacanth, 1 drachm ; gum arabic, 15 grains. Tissues that have lain in spirit should be steeped in cold water a few hours before embedding. The hand section-cutter is used by some microscopists. It is simply a cylinder which is designed to receive the object and the material in which it is embedded. A plunger, which is driven up from beneath by the revolution of a screw, pushes THE ORDINARY METHODS OF PREPARING TISSUES. 17 up the specimen so that it may be sliced off by an ordinary knife. For some purposes it is very useful. Freezing section-cutters. — Of these there are many in use, and they have certain advantages. In conjunction with Dr. J. H. Hunt, of Brooklyn, I have devised a modification of the ordinary instrument.1 (Fig. 9.) Fin. 9. — Freezing section-cutter : B, metallic box : S. cylinder; a, well; c, c, frame for holding knife A, A ; G, indicator; D, milled head; F. F, plugs; E, F, tubes to fit in well; H, H, covers to metallic box ; K, binding screw attaching box to table. It consists of the brass cylinder, S, made of rather large size, and placed in the centre of a metallic box, B. The length of the cylinder, with driver, D, is about' five inches. The diameter of the well, a, measures If inch. Fitted round and about the cylinder is a plate of glass which from its smooth- ness permits the knife to sweep it easily. Tin; knife, A, A, is large, measuring 13 inches in length, in- cluding handle ; in breadth, If inch. It is fitted into a brass frame, e, c, 7£ inches in length and 3£ in breadth. Two strong brass springs, and two sliding clamps, hold it in place. The knife is slightly concave on both sides. The well is so large that it will hold an ordinary kidney after hardening, or at, least so much of it that a transverse sec- 1 Made by Miller Bros., 1313 Broadway, New York city. 2 18 MANUAL OF HISTOLOGY. tion may be made of the whole organ at one sweep of the knife. The knife and frame are modifications of those devised by Dr. E. Curtis of this city, and the section-cutter and box are not dif- ferent in any essential particulars from those in common use. They are larger, however, and the indicator, G, enables the observer to determine with accuracy the thickness of his sec- tions. Thus, in my own instrument thirty-one turns of the milled head drives the plug forward one inch. Each revolution consequently drives the specimen forward ^T inch. Now, the circumference of the milled head is marked off into thirty divisions. When the indicator marks that the plug has been driven forward one division, the distance traversed will be -^^ inch. It is easy, therefore, to determine the thickness of any sec- tion with considerable accuracy. When it is desirable to put the instrument in use, the plug that is to be used is well oiled, as also the thread of the driver, and the metallic box is filled with a mixture of ice and snow. It is necessary to be particular and oil the bearings thoroughly, else they will bind and the instrument will be clogged while the freezing process is going on. The usual plan is to soak the tissue (as Dr. Pritchard suggests) in a thick solution of gum, which cuts like cheese when frozen. The soaking should continue for a number of hours, say until the next day. When the tissue is ready, a thick solution of the gum should be poured into the well and the tissue held until it is fixed by the ice. Some non-conductor is to be placed over the well as soon as fixation has commenced, in order that ac- cess of heat may be prevented. If ice is used it should be ground up finely and then packed tightly about the well ; snow is better. The whole process takes only ten or fifteen minutes. The freezing section-cutter is of use when we are desirous of making a rapid examination of fresh tissues. It is obvious that they are seen under more natural circum- stances than when they have passed through the bichromate or chromic acid solutions, or alcohol, all of which cause more or less change in such delicate substances. It has been hoped that by the freezing method we should THE ORDINARY METHODS OF PREPARING TISSUES. 19 learn much that is new about the finer structures of the brain and the character of the corpuscular elements of the body, but as yet it has not reached our expectations. Ha lies' s microtome. — A very ingenious and excellent instru- ment (Fig. 10) has been devised by Dr. William Hailes, Pro- fessor of Histology and Pathological Anatomy at the Albany Medical College. Objections to it will be mainly on the ground of price. Dr. Hailes uses it as a simple instrument or as a freez- ing microtome, arranged either for ice and salt, ether-spray, rhigoline, etc. The employment of ice and salt (coarse) is preferred, be- cause it costs but little and freezes the mass solidly and quickly, and, if desired, 500 or 1,000 sections can be obtained in a few moments, depending, of course, upon the rapidity and skill of the operator. The time of freezing is about seven minutes, except in very warm weather, when it requires a few moments longer. The instrument does not work quite so satisfactorily in very warm weather, owing to the rapid melting at the surface of the preparation. It is absolutely necessary that the mass should be frozen solid, or the sections cannot be cut smoothly. An extra freezer may be employed, and while one specimen is being cut the other is being frozen ; by exchanging cylinders (they being interchangeable) no delay is necessary. The art of cutting is readily acquired. Two hundred or two hundred and fifty sections have been made in a minute, and of a uniform thickness of -^Vo- of an inch. It is not necessary to remove the sections from the knife each time, but twenty or thirty may be permitted to collect upon the blade. They lie curled or folded up upon the knife, and when placed in water, straighten themselves out perfectly in the course of a few hours. The knife employed is an ordinary long knife from an amputating case. Perfectly fresh tissues may be cut without any previous preparation, using ordinary mucilage (acacia) to freeze in, but most specimens require special preparation. If preserved in Mnller's fluid, alcohol, etc., they require bo be washed thoroughly for several hours, and then, according to the suggestion of Dr. David J. Hamilton, F.R.C.S., etc., of 20 MANUAL OF ITISTOLOOY. the University of Edinburgh, Scotland, the specimen is placed in a strong syrup (sugar, two ounces ; water, one ounce) for twenty- lour hours ; it is then removed to ordinary mucilage for forty- eight hours, and finally is cut in the freezing microtome. These sections may be kept indefinitely in a preservative Fig. 10. i n i-jj !S§ i slJSnDrf^l fi«. 11 ^Jf Fig. 10. — Poly-microtome (without freezing apparatus) : A, small well fitting on pyramidal bedplate ; B, pyramidal bed-plate containing different sizes; C, micrometer screw; D, ratchet-wheel attached to screw; E, lever actuating the micrometer screw bj means of a pawl engaging in teeth of ratchet-wheel ; F, arm carrying a dog, which prevents back motion of screw ; (J, regulator for limiting the throw of Lever, and consequently governing the micrometer screw ; H, lever-nnt tor i i x i i r_r regnlator; I, index, with pointer and graduated scale, from 1/9400 inch to 1/S00 inch ; IC. knife for cutting sections; L, knob to turn micrometer screw direct when pawls are detached ; M, table clamp ; T, table of microtome, with glass top in facilitate cutting. l'Ki. 1 1 . — ( Very much reduced in size). A, B, tube containing specimen which is surrounded by freez- t are in tin receiver C, D ; B, F, revolving hopper with wings, W, W, for stirring the ice ; G, out- let for melted ice. fluid recommended by Dr. Hamilton : destil., aa. 3 iv. ; acid, carbolic, gtt. iij. addition of alcohol, 3 ij., is advisable. B. Glycerin., aqua3 Boil and filter. The STAINING FLUIDS. 21 Tlie Vincent microtome. — This instrument, which was de- vised by Dr. Vincent, of New York city, is a flat piece of steel (Fig. 12) 12 inches long by 2 — 2| inches wide, with a bevelled cutting edge, 6 inches long. The handle is simply the rounded and smoothed extremity of the knife. It has been in use at the School of Histology connected with the Columbia Veterinary College, and has proved to be a very efficient knife. The mode of action is very simple. The object having been previously placed in any ordinary hand-cylinder and mounted Fig. 12. in wax, paraffine, or pith, the sections are made by a stroke of the knife, which is pushed straight forward. As will be readily seen, the larger the section the wider the knife must be. The blade is made of the best plate steel, and is easily kept in order. STAINING FLUIDS. Ammonia carmine. — This is one of the oldest and best known solutions. Take one part, by weight, of the best car- mine, which is known as " No. 40," dissolve it in 100 parts of distilled water, and add one part of aqua ammonite. The pre- vious dull color now gives place to a most brilliant and deep red. It is necessary, however, that the carmine be either neu- tral or very faintly alkaline, else the color will diffuse and the tissues will not be differentiated. Expose the fluid, therefore, for some weeks to the air, or evaporate over the water-bath until the odor of ammonia is no longer perceptible. The nuclei should be deeply and brightly stained, while the intercellular substance is in no way affected. If, however, diffusion has taken place, a great deal of it may be removed by soaking the section in a saturated alcoholic solution of ox- alic acid. When a brick-red color has in this way been ob- tained, the object has been accomplished. Crystals of oxalic acid are apt to be found in specimens that have been prepared 22 MANUAL OF HISTOLOGY. in this way. It is therefore desirable, after using the acid, to wash thoroughly in alcohol or water. Borax car mine (Arnold's formula). — The following method is given by Dr. M. N. Miller as the one in use by students in the histological laboratory of the New York University. It originated with Prof. J. W. S. Arnold. A saturated solution of borax is prepared in a wide-mouthed pint bottle. The borax should be in some excess. "No. 40" carmine is now added to the solution under constant agitation, until after a while it no longer dissolves, and an excess remains at the bottom of the vial, mingled with the crystals of borax. After twenty-four hours the supernatant fluid is decanted. To this clear portion f. fij. of alcohol are added, and f. 3 j. of caustic soda solution (U. S. P.). The staining solution is now ready. Or, the alco- hol may be omitted (Arnold), and the liquid evaporated to dry- ness ; the red amorphous mass is then powdered. Of this, 15 grains are placed in an ounce of water, to which f . 3 j. of alcohol is added.1 Sections, after staining, should be washed in alcohol to re- move the superfluous coloring fluid, and then transferred to a saturated solution of oxalic acid in alcohol to fix the color. The oxalic acid is then washed out in alcohol ; finally the sec- tions are cleared up in oil of cloves, and mounted in balsam or dammar. Double staining by borax carmine and indigo carmine. — Drs. W. T. Norris and E. O. Shakespeare, of Philadelphia, have recommended a method which is a modification of Mer- kel's. Two staining fluids are made, one red and the other blue. The red one contains carmine, gr. 7£ ; borax, 3 ss. ; dis- tilled water, 3J. The blue contains indigo carmine, 3ss.; bo- rax, 3 ss. ; and distilled water, 3 vij. After thorough trituration the ingredients are mixed and left in a vessel ; the supernatant fluid is then poured off. The sections, if previously hardened in bichromate, picric acid, or chromic acid, should be well washed ; they then are to be placed for a few minutes in a mixture (equal parts) of the red and blue fluids, then transferred, without washing, to a satura- ted solution of oxalic acid and allowed to remain in it rather less time than in the staining fluid. "When sufficiently bleached 1 [This preparation of borax carmine is the best that I have ever used. — T. E. S.] STAINING FLUIDS. 23 the sections should be washed in water until every trace of ox- alic acid is removed. Sections thus prepared may be mounted in balsam or dammar. Connective- tissue substances are blue, while the nuclei are red. The osseous lamellae of bone are blue, the cells in the lacunae red, while the marrow is apple- green. Picro-carmine (Miller's). — Add one part of a saturated so- lution of picric acid to two parts of the 15-graih borax carmine solution (Arnold's). The epithelium of the glands and the muscles are stained yellow, while the nuclei of the cells and the connective tissues acquire the carmine color. Sections should remain in the picro-carmine solution for about twenty-four hours. Next they are washed quickly in water, then in alcohol, after which they are transferred to the oil of cloves. (For Ran- vier's method of making picro-carmine, see the chapter upon the Histology of the Nervous System.) Hematoxylin solution (Boehmer's). — Dissolve 20 grains of hematoxylin in one-half an ounce of absolute alcohol ; then dissolve 2 grains of alum in an ounce of water. Some drops of the first solution are added to the second, which, after a short time, becomes a beautiful violet. It improves after keeping for a few days, and should always be filtered before using (Thin). Hematoxylin solution (Kleinenburg's). — First make a satu- rated solution of the chloride of lime in seventy per cent, alco- hol, and add alum to saturation. Then make a saturated solution of alum in seventy per cent, alcohol. Add the first to the second in the proportion of one to eight. To the mixture add a few drops of a saturated solution of hematoxylin in absolute alcohol (Thin). Hematoxylin solution (Miller's method). — Take a pint bot- tle, as in the former process, fill with water, and add about an ounce of common extract of logwood in coarse powder. Allow this to remain in a warm place for twenty -four hours, with occasional stirring. After the expiration of this time add pow- dered commercial alum until the liquid changes from the muddy brown color given by the logwood to a brilliant purple. The alum is to be added until no change is produced. An excess of the salt will do no harm. Add about f. 3 j. of alcohol, and aft'-i- decanting or filtering it is ready for use. One may omit the alcohol at this stage, and evaporate to dryness as in the borax-carmine process. The powder thus obtained is 24 MANUAL OF HISTOLOGY. added to water when required. Three grains to the ounce of water Avill give a fluid that will stain alcohol-hardened tissue in from ten to fifteen minutes. A solution containing ten grains to the ounce will stain very quickly. If it is desired to keep the solution, add f. § j. of alcohol for each ounce. Hema- toxylin stainings are soaked in water for a few minutes to wash out the alum, then transferred to alcohol, clarified in the clove oil, and finally mounted in balsam or dammar. Klein's formula for hematoxylin. — Mix in a mortar 5 grammes of the officinal extract of hematoxylin, with 15 grammes of alum, and pulverize carefully. To this add grad- ually 25 c.c. of distilled water, and filter. To the residue add 15 c.c. of distilled water and again mix in a mortar, and filter; to this filtrate add 2 grammes of alcohol. Now mix the two filtrates and keep in a glass-stoppered bottle. If the liquid should at any time become muddy, filter again. Care must be taken to prevent any acid from intermingling with the fluid. Acids cause the hematoxylin to turn red ; for this reason, sec- tions which have been hardened in chromic acid should be placed in a watch-glass and covered with distilled water, to which add a drop or two of a 30 per cent, solution of caustic potassa ; allow it to remain therein 10 to lo minutes. To use the hematoxylin fluid, add a few drops to an ounce of distilled water, so as to make a pale violet solution ; allow sections to remain in this solution for 12 to 24 hours. Or, a stronger so- lution may be employed which will stain specimens in 10 to 30 minutes, and still give good results. Mount in glycerine, ace- tate of potassa, balsam, or better, resinous turpentine. Eosine solution. — Eosine, first introduced by Fischer in 1875, is much used in staining fresh preparations. It is cus- tomary to have a strong solution of one to ten or twenty on hand. A few drops are then added to a watch-glassful of water or alcohol. Fresh tissues are both stained and hardened. It affects the body of the cells, together with the nuclei. It is apt to diffuse, unless special care is taken, and long soaking, say for twenty-four hours, is practised. Double- staining with eosine and, other aniline colors. — Schiefferdecker first stains in an alcoholic solution of eosine and then in a one per cent, watery solution of an aniline color (dahlia, methyl violet, or aniline green). Care must be taken not to extract the color when dehydrating the specimen in STAINING FLUIDS. ZO alcoliol according to the usual method ; very deep staining is therefore desirable. Green coloration of the nuclei. — To effect this, Tafani em- ploys a fluid containing three or four parts o£ a saturated watery solution of aniline blue to some six or seven parts of a saturated watery solution of picric acid. Eosine and licematoxylinfor staining bone. — Busch recom- mends eosine and hematoxylin for double-staining the zone of ossification in growing bone. The sections of decalcified bone are first immersed a few days in a one-half per cent, chromic acid solution, or in a one per cent, solution of the bichromate of potassium, and then, after washing with water, in a watery solution of eosine. In young bone, where ossification is pro- gressing, the cartilage matrix is blue, while the nuclei of the cartilage-cells adjoining the line of bone are red ; the contents of the medullary spaces are also bright red, while in the bone trabecles there is a combination of blue and red. Eosine for 'permanent specimens. — Renaut has employed eosine to differentiate all forms of protoplasm, whether bodies or their processes. He either employs a watery solution alone, or with the admixture of one-third its volume of alcohol. The coloration is obtained after immersion of the sections from one-half minute to one minute. They are then washed in distilled water, and may be preserved in a neutral solution of glycerine to which one per cent, of chloride of sodium has been added to prevent the glycerine dissolving the eosine. These preparations will then remain unchanged for months. In examining the fixed corpuscles of the subcutaneous tis- sue, the same author injects beneath the skin a solution of eosine and water (1-500), and then removes a portion of the in- filtrated tissue with the scissors. The fibrous fascicles are un- affected, while the elastic fibres take the color deeply. The fixed corpuscles appear as red granular plates, while their nuclei take a very intense color. This reagent, therefore, is well suited for the study of connective tissues. In special instances the silver method may be used first, and then the eosine. Preparation of the cornea. — Klein has adopted the follow- ing plan for exhibiting this most delicate tissue. He first burns the centre of the cornea of a kitten with caustic potash, and then, twenty-four hours later, brushes the surface with nitrate 20 MANUAL OF HISTOLOGY. of silver, and, lialf an hour afterward, immerses it in water acidulated with acetic acid ; after a day or two it is found to have a glutinous appearance. The lamellae arc then easily stripped oil", and in the middle portions, the corneal corpuscles assume a purplish-brown color while their nuclei are uncol- ored. The outlines of the lymphatic channels are also sharply defined. Pirro-liccmatoxyMn and eoslne {triple-staining). — Wendt has described a method of double-staining by picric acid and hematoxylin. Only the very thinnest sections, however, give satisfactory results. A strong solution of hematoxylin is first employed. In this the sections are allowed to remain about twelve hours. After washing them in water, they are placed in a saturated solution of picric acid and carefully watched. They may be removed from time to time, examined with a low power, and, when properly stained, put in alcohol and mount- ed in Canada balsam with as little delay as possible. To ob- tain triple-staining, eosine may be conveniently combined with this picro-lnematoxylin method. To insure good results some amount of practice is necessary. Double, triple, and quadruple staining. — Dr. Gibbes re- commends for double-staining, immersion first in picro-carmine and then in logwood, or which is better, immersion first in a spirituous solution of rosine or aniline violet, and then in an aqueous solution of aniline blue or iodine green. In obtaining more than two colore there is considerable difficulty. To ac- complish it he uses first the chloride of gold or picro-carmine and then the spirituous and aqueous solutions of the ani- lines. Staining loith Bismarlc broion. — Make a watery solution of gr. ij. — 3j*., heat and filter; soak in the solution about three minutes ; set the color with acetic acid (glacial) 4 per cent. for half a minute. After dehydrating with alcohol mount in dammar varnish. Weigert prepares the Bismark brown as follows : he makes a concentrated aqueous solution by boil- ing in water, filtering from time to time. He also uses a weak alcoholic solution, and combines with other colors. [To combine with eosine — put the sections in a strong aqueous solution of Bismark brown ; remove after about two minutes, set in weak acetic acid (four per cent.), then place in a weak alcoholic or aqueous solution of eosine, and then again in the acetic acid solution. — T. E. S.] STAINING FLUIDS. 27 Solution of alum-carmine. — Grenadier recommends this fluid : Take a one to live per cent, solution of ordinary alum, or ammonia alum ; boil witli one-half to one per cent, powdered carmine for twenty minutes. Filter, and add a little carbolic acid to preserve. Naphthaline yellow for hone. — In sections of the femur from a foetal pig, three and a half inches in length, the follow- ing method was found to yield very excellent results : After immersion for three days in Miiller's fluid, sections were made, and, after washing in water, immediately dipped in an alcoholic solution of naphthaline yellow (gr. iv. — § j.) ; after eight to ten minutes the sections were removed, and dipped in a watery solution of acetic acid of three per cent. ; then they were immersed for about ten minutes in the ordinary solution of ammonia-carmine, rendered neutral by exposure to the air. The sections were again dipped in the acetic acid solution in order to set the color, and then placed in alcohol of eighty per cent., and subsequently in absolute alcohol. The specimens thus stained showed a matrix of deep trans- parent chrome yellow. The young bone-cor£)Uscles and osteo- blasts, on the other hand,- together with the fibrous tissue, assumed a brilliant rose color, thus affording an excellent con- trast between forming and formed bone. Staining with methyl-green and induline. — Calberla has introduced two new substances into use, viz., methyl-green and induline. The one stains the nuclei of the cells of the sub- cutaneous tissue, the nuclei of vessels and nerve-sheaths rose color, while the cells of the corium and their nuclei are a violet red ; the other colors the cells of the Malpighian layer a greenish blue. Combinations of methyl green and eosine are also recommended. Eosine (one part) and methyl green (sixty parts) are to be dissolved in a thirty per cent, solution of warm alcohol. The epithelial nuclei take a violet blue, the nuclei of connective tissue a greenish blue, and the cell-body a red color. Singular differentiations are made ; thus, while the striated muscle is red, the nuclei are green. On the other hand, smooth muscular tissue is green, and the intercellular substance red. In the salivary glands the cells of the excretory ducts are 1)1 no, while the so-called secretory cells are red. In- duline dissolves in warm water and in dilute alcohol. Take a 28 MANUAL OF HISTOLOGY. concentrated watery solution, dilute it with six times its vol nine of water, then immerse the preparations from 5 to 20 minutes, wash them out and clarify in oil of cloves or glycerine. The peculiarity of this material is that it never affects the nucleus, but only the cell-body. More frequently, however, it is the intercellular substance that is colored blue. Purpurine. — Ranvier has recommended this dye, which is extracted from madder. Alum (one part) is dissolved in dis- tilled water (two hundred parts) ; the fluid is then heated to the boiling point in a porcelain dish. Then a small quantity of purpurine is dissolved in distilled water and added to it. Sufficient purpurine should be added to leave a residue, by which it is certain that the solution is saturated. While still hot it is to be filtered into alcohol of one-fourth the total volume. The fluid has an orange red color, and is more effi- cient when fresh. Sections should be immersed from 24 to 48 hours. French archil — Staining with extract. — Wedl uses this substance, which, after the loss of the ammonia, is dissolved in 20 c.c. absolute alcohol, 5 c.c. acetic acid of 1.070 sp. gr., and 40 c.c. of distilled water so as to make a saturated solu- tion. Protoplasm and matrix, but not nuclei, are colored a beautiful red. Alizarine. — This aniline color is recommended by Than- hoffer, but experience is limited with reference to it. It has a golden yellow color, and is easily fixed by the tissues. METALLIC SOLUTIONS. Staining with osmic and oxalic acids. — Broesicke adopts the following method : Little pieces of fresh or freshly dried preparations are left for an hour in a one per cent, solution of osmic acid ; then they are carefully washed and soaked in a cold saturated solu- tion of oxalic acid, and finally examined in water or gly- cerine. Elastic fibres are yellow, fat is black, while the walls of capillaries and many connective- tissue substances are red. Chloride of gold and lemon juice. — Ranvier is in the habit of demonstrating the corneal nerves by using lemon- METALLIC SOLUTIONS. 29 juice in which the tissue is left five minutes. Then it is soaked for 15 to 20 minutes in 3 c.c. of a one per cent, solution of the gold chloride, and finally 25 to 30 minutes in distilled water to which one or two drops of acetic acid has been added. After two or three days' exposure to the sun, the fibres become dis- tinct. Nitrate of silver in solution (gr. j. — iv. — 3 j.) is much used. The details of the method will be found in the Chapter on the Lymphatics. Chloride of gold has also been much used in studying the so-called lymph-canalicular system of the cornea. The method of employing it will be found in the section relating to the cornea. Osmic acid in solution is also very useful. Its effects are given in the chapter on the General Histology of the Nervous Sj'stem. JIdlujJ-green for showing waxy cliange. — Curschmann, of Hamburg, has recommended this reagent to effect the same object as the violet de Paris of Cornil. A solution of about five grains to the ounce is used. The specimens are bathed in the fluid a few minutes or hours. They take the color quickly. After staining they may be mounted in glycerine. The amy- loid material assumes a brilliant rose color. The surrounding tissue takes a dull green. Wicker slieimefs preserving liquid. — This material has been extensively used of late, and there are several formulas for it. Among the most recent modifications is that made by Tin:: firm of Poetz & Flohr, of Berlin. For immersing speci- mens the ingredients are : arsenious acid, 12 grains ; sodium chloride, 60 grains; potassium sulphate, 150 grains; potassium nitrate, 18 grains; potassium carbonate, 15 grains; water, lo litres ; glycerine, 4 litres ; wood naphtha, f litre. A modified fluid is used for injecting the blood-vessels. This is suitable for all fresh tissues, preserving them in their natural color and consistence. If the tissues are to be used subsequently for the micro- scope, it is said that they should be washed thoroughly in water, but it seems from recent experiments that the fluid un- fits 1 ln-iii for minute examination. It is also rather expensive, and has an extremely pungent and unpleasant odor. 30 MANUAL OF HISTOLOGY, METHODS OF INJECTING THE BLOOD-VESSELS.' Good injections are hard to make, requiring skill, patience, and practice. First of all, it is essential to have a perfectly transparent injecting material. This is usually made up with gelatine and colored by carmine or Prussian blue. When carmine/ is used it is customary to dissolve it in ammonia, ni- ter, and then add it to the solution of gelatine. In order to obtain a neutral or faintly acid liquid, acetic acid is added, drop by drop, until the alkalinity is overcome, but there must, at the same time, be no precipitation of carmine, which is best detected by the granules of carmine seen in the field of the microscope. If alkaline, the color diffuses and the result is a failure. It is difficult to lay down any rule in reference to the amount of acetic acid necessary ; the color of the liquid is the best and only satisfactory test. The ammoniacal odor, if very slight, cannot be detected, and therefore is useless as a test. A slight excess of acid, however, will do no harm. The preparation of the blue injecting fluid is less difficult. Usually Brucke"s soluble Berlin blue is used; it can be procured at most of the large drug stores, but if not obtaina- ble, may be made as follows (Klein) : " Take of potassic ferrocyanide 217 grammes, and dissolve in one litre of water (solution A). Take one litre of a ten per cent, solution of ferric chloride (solution B). Take four litres of a saturated solution of sulphate of soda (solution C). Add to A and B two litres of C. Then, with constant stirring, pour the ferric chloride mixture into a vessel, collect the precipitate upon a flannel strainer, returning any blue fluid which at first escapes through the pores of the flannel ; allow the solutions to drain off. Pour a little distilled water over the blue mass, returning the first washing if colored, and renew the water from day to day until it drips through permanently of a deep blue color. This is a sign that the salts are washed away, and all that is further necessary is to collect the pasty mass from the strainer and allow it to dry." Having obtained the soluble Berlin blue, it will be much 1 Prepared for the editor by Dr. W. H. Porter, Curator of the Presbyterian Hos- pital, New York city. METHODS OF INJECTING THE BLOOD-VESSELS. 31 simpler to inject both arteries and veins with the same solution. If a small animal is to be employed (as the rabbit, for instance) it will be found most convenient to inject through the aorta. If, however, an organ from the human body is to be injected, through the main vessels of that part. To commence with, the kidney is probably the best, as it is small and of firm consis- tence. For injecting with the red gelatine liquid the following rules will be found of service, and yield good results : Take 40 grammes of Cox's best English gelatine, place it in a jar, and add just water enough to cover it ; let it stand for several hours, when it will imbibe the water, being hygro- scopic ; it may then be dissolved over a water-bath. Take of the carmine 22 grammes and dissolve in 40 c.c. of aqua ammoniffi, then add 240 c.c. distilled water, and filter. The preparation of the carmine solution had better be com- menced the day before, as it takes about twenty-four hours to filter. The gelatine and carmine solutions are raised, separately, to the same temperature, when the gelatine solution is gradu- ally added to the carmine solution, under constant stirring. The injection fluid, which is now of a deep cherry-red color and alkaline reaction, is precipitated with acetic acid until the deep cherry color gives place to a bright red, and the ammoniacal odor is exchanged for that of acetic acid. At this point a little more acid may be added without doing harm. In case the liquid should be found too concentrated, a little more water may be added. For the blue mass the following method may be adopted : Take 66 grammes of gelatine, and prepare as in the former case. Add 4 grammes of soluble Berlin blue in substance and 360 c.c. of water. The blue will also be found slow in filtering. When both are heated to the same temperature add the gelatine to the blue solution, with constant stirring. When this has been done, a solution of the iron salts may be added to intensify the blue color, care being exercised not to add enough of the iron to coagulate the gelatine. This liquid also may be diluted if found so concentrated that it will not flow easily. The liquids having been prepared, the organ carefully removed from the body, thoroughly washed out and heated to a tem- perature of 98° P., everything is ready for injection. The fill- 33 MANUAL OF HISTOLOGY. ing of the vessels may be accomplished in one of two ways: either by forcing in the fluid with a Byringe or by the pressure of a column of water. The Byringe is the simplest, but requires practice and skill in manipulation. Having inserted the canula into the artery, the kidney may be entirely filled with either the red or blue injecting liquid. When the organ is seen to be swollen, tense, and well colored the vessels must be tied off, and the kidney placed in a freez- ing mixture until the gelatine has set. When this is accom- plished, the organ should be cut into small pieces, and placed first in a weak solution of alcohol (seventy per cent, or h and the strength of the alcohol gradually increased until the specimen is sufficiently hard for cutting. The object of using weak alcohol is to prevent too great shrinkage of the gelatine. If two colors are used, it is impossible to tell beforehand how much fluid will be necessary to fill the arterial and venous sys- tems, and not have the one encroach on the other. For an ordinary kidney, about 250 c.c. of the injecting liquid should be prepared to fill the arterial vessels, and nearly double to fill the veins. The following rules must be observed in inject- ing : keep the gelatine solutions and the organ as nearly as possible at the same temperature. Immerse the organ in warm water during the process. Avoid the entrance of air into the canula when connecting the syringe. Inject slowly, and give the fluid time to work its way into the minute capillary rami- fications. The above rules can be applied to any organ, with such modifications as will suggest themselves to the operator. BIBLIOGRAPHY. Klein. Handbook of the Physiological Laboratory. Edited by Sanderson. Vol. I. 1873. Bcsch. Arch. f. Mikroskop. Anat. XIV. 1877. Norms and Shakespeare. American Journal of the Medical Sciences, Oct., 1877. RexauT. Archives de physiol. 2me S-.rie, T. IV. 1877. Sciiaefer. Histology and the Microscope. Philadelphia, 1877. Thin. Practical Histology. London, 1877. Wkndt. Ueber die Hardersche Druse, etc. Strassburg, 1877. Ranvier. Traite technique d' histologic. Paris, 1877-8. Buoesicke, J. Med. Centralblatt. 46. 1878. BIBLIOGRAPHY. 33 Calberla. Morpholog. Jahrb. III. H. & S.'s Jahrb. I. 1878. Hamilton. Journal of Anatomy and Physiology. Vol. XII. 1878. Millek. New York Medical Record, Feb. 2, 1878, p. 97. Ranvier. Journ. de micrographie. H. & S.'s Jahrb. 1878. Scuiefferdecker. Arch. 1'. mikrosk. Anat. XIV. 1878. Tafani. Journal de micrographie. 1878. Wedl. Virchow's Archiv, 74. 1878. Weigert. Arch. f. mikrosk. Anat. XV., p. 259. 1878. Flesch. Archiv f . mikrosk. Anat. XVI., p. 300. 1879. Grenacher. Arch. f. mikrosk. Anat. XVI., p. 463. 1879. Klein and E. Noble Smith. Atlas of Histology. 1879-80. Curschmann. Archiv f. Path. Anat. LXXIX., III. 1880. Frey. The Microscope and Microscopical Technology. New York, 1880. Gibbes. Lancet, March 20, 1880. Hailes. An Improved Microtome. New York Medical Record, July 24, 1880. Thaniioffer, L. v. Das Mikroskop u. seine Anwendung. Stuttgart, 1880. Vincent. New York Medical Record, June 12, 1880. Wickersiieimer. Arch. f. Pharm. New Remedies, May, 1880. Gibbes. Practical Histology and Pathology. Philadehphia, 1881. Seiler. Compendium of Microscopical Technology. Philadelphia, 1881. Stowell. The Student's Manual of Histology. Detroit, 1881. Harris and Power. Manual for the Physiological Laboratory. New York, 1881. 3 CHAPTER III. THE BLOOD. Ix man and most vertebrates the blood consists of a clear iiuid, the liquor sanguinis or plasma, in which a large num- ber of corpuscles are very evenly distributed. Of these there are two prominent varieties, differing much in character — the red and the colorless or -white. The former are greatly in ex- cess, and give to the liquid its characteristic -red appearance. In relative proportion the two vary greatly within certain limits. Usually there is but one of the white to 600 or 1,200 of the red ; but these numerical relations are disturbed by vari- ous diseases, and the white may equal the red, or even, in rare cases, exceed them. In fresh liquid blood the corpuscles are the only solid mat- ters visible under the microscope ; nor is there any difference in this respect witli coagulated blood, when the quantity is large. If, however, a little should be allowed to dry, fibrin may be deposited nnder the form of delicate filaments, which are superimposed on one another without definite order. In one hundred volumes of blood there are said to be thirty- six volumes of corpuscles and sixty-four of plasma. This ratio, however, is altered somewhat by different conditions, such as the age and health of the individual. The red corpuscles in man and other mammals, with very few exceptions, are bi-concave bodies, circular in outline. In birds, amphibia, and almost all fishes they are also bi-concave or hollowed out at the centre, but have an elliptical contour. In the human species nuclei or central bodies appear at a very early period of life, but subsequently are invisible, unless arti- ficial means are used to display them. In birds, amphibia, and fishes a rounded prominence is also seen at the centre, which is particularly well marked when the corpuscle happens to be THE BLOOD. 35 turned so that its edge meets the eye. This prominence cor- responds to the ordinary nucleus of other elementary bodies or cells. In this position the peculiar shape of the corpuscles, with their constricted centres and rounded extremities, has suggested a comparison between them and the little cakes known as lady's-fingers. (See Fig. 13.) It is obvious also that this varying thickness of the disk will have some effect upon the microscopic image, for the whole superficies cannot be in focus at one time, even when the cor- Fig. 13.— Bed corpuscles of the frog. (Rollett.) Fig. 14.— Human red blood-corpuscles : a, globules showing the double contour ; b. globules turned on edge ; c, the same in rouleaux like coin. (Rollett.) puscle is turned flatwise to the eye. There will be some differ- ence between the level of the thickest and thinnest portions. As a result, when one is dark the other is bright, when one is well defined the other is blurred. This statement serves for an explanation of the double contour that is sometimes observed in human blood (see Fig. 14), though it has also been offered in support of the theory that the semi-solid and elastic matter of which the disk is mainly composed has an external envelope or limiting membrane of different density. It is to be remem- bered, however, that the property of double refraction which explains the double contour, belongs to all transparent bodies that have rounded edges, such as drops of water or oil, in which cases there is plainly no enveloping or peripheral wall. When Hie- lens and eye-piece are suitably combined, as in the best microscopes, the double marking is of ten difficult or im- ible todiscover. On tie- other hand a poor optical com- bination will generally exhibit it to an unpleasant degree, and 36 MANUAL OF HISTOLOGY. especially if greal amplification is aimed at. Lenses of very high power are also apt in any case to exhibit the same ap- pearances. Measurements of (he red corpuscles in man and ani- mals.— The average diameter of the human red globule is -till a matter of discussion. The faulty measurements of the older writers have led to some misconception on these points, and the matter lias required new study. Welcker, who has long been an authority on the Continent, gave .00774 mm. as the average breadth in the human male, with a minimum of .0045 mm., the latter from personal observation. A maximum of .010 mm. has been given by Max Schultze, while Frey places the average thickness at .0018 mm. Later investigations by Hayem show that a diameter of .012 mm. or even .014 mm. may be reached, while he has known it to fall as low as .0022 mm. Elsberg gives the mean diameter of the red blood-corpuscle at .0075 mm., agreeing very nearly with Welcker. He has observed a maximum of .01016 mm., and a minimum of .00422 mm. Measurements of single corpuscles have no value in deter- mining the particular animal from which the blood has been obtained, and this is an object of prime importance in medico- legal cases. It is common, therefore, to make a hundred or more single measurements, and then take the average of them. And yet this figure may vary considerably in different individ- uals, or even in the same one. In the blood of the puppy, for instance (the size of the dog's corpuscle being very nearly that of man's), a recent observer found that the average diame- ter of fifty corpuscles varied only two-millionth of an inch from a like average of fifty taken from his own blood. In another instance, taking forty from a puppy, he found that the average differed only seven-millionth of an inch from a similar average of his own (Woodward). Opposite is given a table of blood-corpuscle measurements by Welcker and others. By referring to it, the cat's and rabbit's corjrascles will be found to have an average diameter which is not far distant from man's and dog's, while the minimum and maximum diameters of each show conclusively that a large number of their corpuscles would be likely to equal man's, and there- fore make it impossible to distinguish one from the other. To obviate this source of error a very large number of corpuscles THE BLOOD. 37 would have to be measured separately, as we have already- seen, and then an average taken of them, all, before even a guarded opinion could be given as to the source of the blood. Still other difficulties, however, are apt to beset the microscop- ist. The blood is usually dried and in small quantity. The disks are then shrunken. If we endeavor to restore them to their original shape, as by soaking in blood-serum, we are never sure of having accomplished the object, or that we have not overdone it. This statement will be better understood by experiments that will be detailed at another point in this chapter. Where blood-corpuscles are elliptical, as in birds, there is much less opportunity for error. Measurements of red Blood-corpuscles. Maximum diameter. Minimum diameter. Average diameter. Dog Cat Rabbit Sheep Goat (old) " (eight days old) Moschus javanicus Elephant Pigeon (old) " (fledgling) Chicken Duck Vespertilion Triton crista tus Salamantlra Cryptobranchus Japonicus Lepidosiren annectens mm. .0082 .0074 .0080 .0050 .0046 .0066 .0030 .0106 .0160 .0140 .0132 .0140 .0066 .0327 .0415 .0579 .0440 mm. .0065 .0058 .0062 .0038 .0036 .0039 .0022 .0084 .0132 .0116 .0104 .0118 .0054 .0259 .0302 .0460 .0360 mm. .0073 .0065 .0069 .0050 .0041 .0054 .0025 .0094 .0147 .0126 .0121 .0129 .0061 .0293 .0378 .0512 .0410 Average length. Average breadth. mm. .058 .075 mm. .034 .047 77^ number qfthe red < /lobules. —It has commonty been held that the blood of :in adult man contains 5,000,000 red corpus- cles in each cubic millimetre. In amende conditions this num- ber may be reduced below 3,000,000, while in fair physical 38 MANUAL OF HISTOLOGY. health it has reached 6,000,000 and over. Under ordinary cir- cumstances 4,500,000 is thought to argue a fair bodily condi- tion (Iv ;■ Quite recently Hayem lias given an instance where the number was reduced to 800,000. This extraordinary state he has called aglobulie intense; the name aglobulie extreme was given to a condition observed on another occasion where he counted only 450,000 corpuscles. The blood-globules in ossible to obtain aqueous humor, an excellent substitute may be found in the fresh fluid from a hydrocele or ovarian cyst, or we may use serum to which iodine has been added, which is then called iodized serum. To six ounces of the fluid twenty grains of finely powdered iodine are added. After prolonged agitation the iodine will be dissolved, and the mixture thus prepared maybe kept for a numb'? of months. Suspended in this liquid the blood is studied to advantage with a lens of moderate power, such as an ordinary THE BLOOD. 39 i inch. The contents of the disk will appear homogeneous, which is a term that merely indicates an apparent absence of structure. The nucleus and nucleolus should also be invisible. The shape of the corpuscles is oval, and they are flattened and have rounded edges, with hollowed centres, in which a promi- nence is usually seen (Fig. 13). The protoplasm is the sub- stance of which the disk is made ; it has a light yellow color, and is dull or pellucid in appearance, much like semi-solid jelly. Brownian and amoeboid movements. — Using the same method of preparation the white corpuscles or leucocytes are seen to good advantage. They are much smaller than the red disks (in the frog— the reverse of human blood), and there is wide range in size, one histologist (Klein) having described as many as thirty varieties. In the interior, little dark spots are sometimes seen in constant vibration. By a skilled observer they are readily detected, even with a good \ inch glass. When such specks are numerous the bodies are said to be granular. In the newt's blood this phenomenon is usually best seen. The word granule has been applied in these cases from the notion once prevalent that the little dots were molecules sus- pended in a menstruum of some sort that filled the corpuscle. This subject is now eliciting much study, but the movement, whatever its significance may be, is called the Broionian move- ment. Klein, who states that the newt's leucocyte is traversed by an intracellular network, believes that the movement just described is due to the motion of the " disintegrated network" under the stimulus of imbibed water. Under this explanation the oscillatory movement in the corpuscles of the human saliva would indicate death rather than life. When fluid has been withdrawn by evaporation the phenomenon ceases. According to other histologists this vibratile motion is an indication of vital action. The remarkable change in form which these corpuscles un- dergo is a more positive indication of vital power in the leuco- cyte. When the little body is placed under conditions which imitate those of its natural state it commences to put forth processes and then withdraw them, carrying on these move- ments slowly, but with a certain degree of regularity. While this is being accomplished the corpuscle is observed to move abont from place to place. 40 MANUAL OF HISTOLOGY. Fig. 15. — Leucocytes: a, putting out pro- cesses; b, having withdrawn them. (Rollett.) In Fig. 15 the leucocytes are seen. Those marked with the letter a are engaged in amoeboid motion. The one marked b i? in a state of contraction. This phenomenon is called amoe- boid movement, because it resem- bles that of the amoeba — the lit- tle microscopic organism found in stagnant water. In order i<» permit these changes to continue for some length of time, it is well to paint a little oil or glycerine around the edge of the circle. Evaporation is thus prevented. If the icarm slide be used the changes will follow with greater rapidity. Both Brownian and amoeboid movements are usually confined to a limited number of the corpuscles, and the former often to only a small portion of the interior. The slide ' for heating consists of an ordinary glass slide (Fig. 16) upon which is riveted a thin copper plate (b) perfor- ated in the centre, so as to allow space for the drop of blood which is to be examined. From the copper plate extends an arm (c) over which is slipped a spiral copper wire (e), which is heated by the flame of an alcohol lamp. By this means the glass plate is kept warm and with it the drop of blood. In order to secure a proper amount of heat and no more, it is customary to put a little bit of cocoa butter upon the corner of the slide. The butter melts at the tem- perature of the body, and after this point has been reached the lamp should be carried along the wire away from the slide until the precise distance is found at which this particular degree of heat will be maintained. Action of a dilute salt solution. — It is often difficult, and, Fig. lfi. — Slide for heating : a, slide; 6, copper plate ; c, arm over which the spiral wire (d) is slipped 1 Made by T. H. McAllister, 49 Nassau Street, New York City. THE BLOOD. 41 indeed, impossible, to obtain aqueous humor or even an animal fluid such as has been described, and microscopists have accord- ingly made use of a substitute that can be prepared at any time and kept indefinitely. This is a solution of common salt in distilled water (1 — 400). Add a drop of fresh frog's blood to a drop of the salt solution, mix them well, and it will be seen that the delicate protoplasm of the red blood-corpuscle, most susceptible of change, is not altered in appearance, though the body itself will change in form from the elliptical to the spher- ical. This salt solution has been found, in practice, an excellent substitute for blood-serum, and is very generally used in ex- amining fresh specimens, where it is important to avoid any material change in the corpuscle. Action of distilled water — Irrigation. — The effect of water is also noteworthy, as it is a very important consideration in both histological and pathological work, especially the latter. Take a drop of frog's blood, add to it an equal quantity of distilled water and apply a cover. The nucleus or central body will now be readily seen, surrounded by a yellow border ; the body of the corpuscle or peripheral part will at the same time gradually become paler and larger. Now add distilled water slowly, drop by drop, in the following way : Take a long strip of tissue or filter paper about half the length of the slide and in breadth equal to one-half the diameter of the cover. Apply the water with an ordinary minim dropper, close to the edge of the cover, on the side opposite to the paper strip. This latter will now take up the excess of water and cause a stream to puss through the specimen. This process is called irrigation. Push the paper a short distance under the edge of the cover, and the solid particles in the fluid will be carried to the edge of the paper, where they will remain at rest and may be ob- served at one's leisure. This plan is often useful in other sorts of microscopic work, as in looking for renal casts, urinary crystals, etc. It may save much valuable time. I first learned it from my friend, Dr. Edward Curtis, of this city. Continued addition of water will cause the corjDiiscles to swell and after a time burst, or, at any rate, become so expand- ed that they can scarcely be seen. When water is applied slowly to human blood, the corpuscles soon begin to lose their 42 MANUAL OF HISTOLOGY. disk-like form and assume a spheroidal, perhaps spherical con- tour. The coloring matter then escapes, in most instances, and they become quite transparent (see Fig. 17). Such corpuscles are often seen in human urine where they appear as colorless rings. In frog's or newt's blood the body of the disk first imbibes the Fig. 17. — Human red blood-globules : a, with haemoglobin ; 6, without it. (Rol- litt.) Fig. 18. — Red corpuscles of the frog that have imbibed water. (Rollett.) water ; later, the nucleus, which then has a sharply defined outline. Sometimes the material of which the body is largely composed (haemoglobin) is gathered about the nucleus, sending off radiating prolongations to the periphery, while the imbibed fluid is stored in the intervening spaces (see Fig. 18). Action of carbonic acid gas. — This experiment requires a special apparatus. First of all it is essential to have a moist chamber (Fig. 19). Take a small, flat bit of wood about \\ inch wide, 3 inches long, and f inch thick ; make a square opening in the centre, sufficiently large to admit an ordinary £ inch cover-glass ; this is to be pressed to the bottom and firmly fixed, thus making a shallow well with a glass bottom. Into this cham- ber are admitted, through side holes, glass tubes (one on each side), so that air or gases can be carried into the chamber. When in use, the chamber is kept moist by a drop of water, which is put in on«» corner of the well, while the specimen of blood to be ex- amined is dropped upon a large glass cover, and the latter in- verted over the mouth of the well. In determining the effect of carbonic acid gas upon animal life, we have merely to con- nect the gas-chamber just described with a jar in which carbonic THE BLOOD. 48 acid gas is generated. Fig. 19 illustrates a gas or moist cham- ber of the same general character, and devised by Dr. J. H. Hnnt, of Brooklyn. Take a large gallon flask, fill it partly full of pulverized marble-dust, attach it by means of a rubber tube through a perforated stopper to a Wolff's bottle, which latter must be connected with the moist chamber. Now gener- ate the carbonic acid gas in the flask by pouring muriatic acid upon the marble-dust. When the gas is being evolved it will be known by the ebullition of the water in the Wolff's bottle. Now place the moist chamber upon the stage of the micro- scope. Take a drop of newt's blood, dilute it with serum or an indifferent fluid, and mount it upon a glass cover, which invert over the well, first seeing that the edge of the cover is oiled, so that it will remain in place. Now connect the tube of the moist chamber with the tube of the gas-generator, and the carbonic acid gas will enter and pass through the chamber. The rapidity with which the current moves may be regulated by a spring- clip. As soon as the gas enters, the central body or nucleus becomes distinctly visible, and is surrounded by a yellow halo ; when, however, the gas is withdrawn and atmospheric air is admitted, the nucleus and colored zone disappear. This double experiment may be repeated a number of times. Finally a point will be reached where all action will cease. This cen- tral body, under such circumstances, has been called the zooid, and the corpuscles proper the oikoid (Bruecke). Action of acids upon the blood. — Acetic acid is commonly used in observing the changes that are produced by an acid solution. Take the ordinary dilute watery solution of acetic acid (1 per cent.) so much used in laboratories, add a drop of it to an equal amount of frog's blood. The red globules instantly exhibit nuclei. The colorless globules also cease their motion, if any has existed, and they become granular and shrivelled. The term granular is used merely in a relative sense and has no Bpecial reference to granules whether present or not, but merely to an appearance that has already been explained. These phenomena are more marked if the solution is con- centrated. The red bodies, also, in such case, are apt to crack and split up. A good way of determining the proper strength for the ordinary acetic acid solution is to pour a little into an ordinary watch-glass, and then add chemically pure acetic 44 MANUAL OF HISTOLOGY. acid drop by drop until the solution is faintly acid to the taste. Action of alkalies upon the blood. — Take a drop of the newt's blood and mount it in a drop of serum or of salt solu- tion. Then, affixing a strip of bibulous paper in the way that has been described, add drop by drop a weak solution of aqua ammonia?. A similar strip of paper, somewhat larger in size, upon the other side, will cause a current and carry the corpus- cles to the side of the field where the paper strip is Largest, and there the corpuscles may be observed at rest, and the altera- tions effected by the alkali duly noted. It will be seen that after a little time the corpuscles, both red and colorless, will swell up and finally, after a time, provided the alkali be in sufficient amount, disappear or become so expanded as to be invisible. Sometimes they will burst, leaving the field evenly stained with a homogeneous glutinous-looking substance. Action of elect ric it i/. — It seems to make little difference, so far as the microscope is concerned, whether the continuous or interrupted current is employed, as in either case the phe- nomena observed are the same in quality. Take bits of tin- foil and attach them to an ordinary glass slide, in such a way that they are just 4- inch distant from one another. The pieces of foil should be triangular in shape and have their pointed extremities turned to one another. The specimen should be a drop of newt's blood diluted with an equal amount of serum, both perfectly fresh. They should be intimately mixed with a glass rod. Depositing a drop of this solution upon a cover-glass, it should be inverted and placed upon the slide in such a wa}^ that it occupies an intermediate position between the bits of tin-foil. The ordinary stage clips of the microscope are then to be used in holding the slide firmly in position and to press upon the tin-foil. The only remaining task is the attaching of conducting wires from the electrical instrument, one to each clip. The bits of tin-foil are easily fastened to the slide ; they have merely to be hammered out flat, when they will adhere by simple pressure. Sometimes it may be desirable to approxi- mate the poles. In such cases it is necessary to use two fine bits of platinum wire. They should be flattened, and shaped like the letter S. Rest them upon the bits of tin-foil, opposite to one another and at the required distance apart. The cover- THE BLOOD. 45 glass should press on them. Some little mechanical dexterity is required to get them in position, and they are apt, after using, to become so charged that their action upon the corpuscles commences before they are connected with the battery. The phenomena at the negative pole are those of an acid ; at the positive, those of an alkali. At a distance from the line of the current, secondary changes occur of a less regular character. Halting has devised an apparatus which is somewhat more elaborate, but in principle the same. Other changes in the red corpuscles. — If a drop of blood be taken from the tinge]", by pricking with a needle (the triangu- lar or glovers is the best), it will be seen after a time that the exterior of the corpus- cle is indented or crenated, as this change is called. It is well shown in Fig. 20. Examination of the circulation in the web of a frog's foot. — Take a medium-sized frog and curarize him by injecting beneath FlG 20._Hnman^: the skin, with an ordinary hypodermic syr- red corpuscles created. (r0i- inge, two drops of a weak solution of curara (1 — 2,000 in water) or a few minims of a 50 per cent, solution of chloral hydrate (Schaefer). After a variable time the ani- mal will be completely paralyzed, but the circulation will go on as before. There are many difficulties in the use of curara, depending on the variable strength of the drug, the idiosyncrasies of the animal, and other causes that we do not appear to understand. A solution which will produce a proper amount of paralysis in a frog on one day will rapidly kill another frog the next day. To ensure any reliability of action, it is well to have a specimen of which the strength has been properly tested. Then, if time enough is at one's disposal, a weak solution, such as the above, may be injected every hour until the symptoms of the drug are apparent. If the subsequent recovery of the animal is not of vital importance, the amount may be increased, for the circu- lation will often be well shown, even if the animal does not eventually survive. B£y friend, Dr. W. H. Welch, who is in charge of the Histological Labora- tory at the Bellevue Medical College, employs a watery solution of curara. He keeps on hand a i per cent, solution of the drug ( 1 gramme to 200 c.c. of distilled waterj, and then dilutes it as occasion may warrant to £ percent., or even -fa r>er cent. (1 — 500 or 1 — 1,000). Of this diluted solution he injects four or five drops into the dorsal lymph-sac of the frog. A still more dilute solu- tion be i often in the habit of using, so that the frog does not come under the influence of the drug for an hour or an hour and a half. After twenty-four to 46 MANUAL OF HISTOLOGY. forty-eight hours the animals entirely recover, but if a stronger solution is used, he finds the results are frequently fatal, though the animals may survive long enough to iterant a ready demonstration of the circulation, emigration of leucocytes, etc. Now envelop his body in a damp cloth and extend him upon a cork plate about a quarter inch thick and large enough to support the entire bod}'. Make a small opening in the cork, and over it place the web of the frog's foot, fastening the latter by ordinary pins. The circulation may in this way be studied at one's leisure. The red and white blood-corpuscles are seen in the arteries, veins, and capillaries. While the red bodies pass rapidly through the central portions of the vessels, the white creep slowly along the walls, altering their shape as they meet with any obstruction. Where, however, a small artery divides, it will sometimes be seen that the corpuscles, especially the red, are caught at the bifurcation; part 1 (ending to go down one branch, and part down the other ; taking, in fact, the shape of a saddle-bag. Such a phenomenon exhibits the elastic and distensile properties of the corpuscle. Apply an irritant, such as a weak solution of nitrate of silver, and after prolonged and careful watching, the gradual exit of both white and red cor- puscles may be seen. This procedure requires extreme pa- tience and a co-operation of peculiarly fortunate conditions, which are not likely to favor the beginner in microscopy. Internal structure of the red corpuscles. — As yet the inti- mate structure of blood-corpuscles is a matter little understood, though an abundance of theories are rife about it. Klein main- tains that these corpuscles, in common with others in the body, are traversed by an intracellular network. In the red cor- puscles of the newt, especially, he says there is a network of fibrils, with an interfibrillar hj^aline ground substance, both together forming the so-called stroma. The nucleus contains a network of fibrils in connection with the network of the cor- puscle proper ; the haemoglobin, a colored fluid, is contained in the substance of the meshes of the network of the corpuscle proper. Drs. Cutter, of Boston, and Heitzmann, of this cit}^ also state that there is an intracellular network. The former regards it as due to the mycelium of a parasitic growth. Dr. Elsberg, of this city, also states that he finds a reticu- lar appearance after using a solution of the bichromate of THE BLOOD. 47 potash (30 per cent, to 50 per cent, of a saturated solution in water). Real granules are often present in the corpuscles, as may be proved by adding water in large quantity. They will then become greatly distended, and bursting, the granules will be scattered throughout the field. If finely ground vermilion is sprinkled in the liquid, some of the white corpuscles will take up the granules, perhaps with- out losing their amoeboid character ; finally, they may eject them after a longer or shorter sojourn. According to Boettcher, the human red blood-corpuscle has a nucleus. He exhibits it in the following way : Taking a saturated solution of corrosive subli- mate in alcohol (96°), he diffuses about fifty volumes with one of blood. The corpuscles are deprived of their hpematin, but at the same time are preserved. The mixture is frequently agitated, but in about twenty-four hours it is allowed to subside, when the superincumbent fluid is poured off and alcohol added. By further agitation for another twenty-four hours the corpuscles are thoroughly washed, and then settle at the bottom of the vessel. Prof. Boettcher claims in this way to have found three classes of red globules. The first are homo- geneous and shiny throughout ; the second are clear externally, but granular within ; the third variety exhibit a nucleus and nucleolus. Development of tlie blood-corpuscles. — In early foetal life all the corpuscles are colorless (Klein). According to Balfour and Foster, both colored and colorless corpuscles, at least in the chick, are developed from solid sprouts of protoplasm, de- rived from the middle germinal layer. There seems good rea- son, however, to believe that the leucocytes are formed in part, at least, from the lymphatic glands, and Klein thinks that they are thrown off from the "germinating buds" of serous membranes. Later, the red ones make their appearance, and for a time are nucleated. The investigations of Neumann and Bizzozero, showing that the red corpuscles in the medulla of bones are also nucleated, favors the theory that bone-marrow is one of the theatres for such corpuscular metamorphosis. According to Hayem the production of red corpuscles in the blood is accomplished through the agency of Jmmatoblasts, i.e., minute red corpuscles. In convalescence from acute fe- vers, or after a considerable loss of blood, these smaller bodies may be observed in the blood for a variable time, even some weeks. 48 M AN UAL OF HISTOLOGY. According to Recklinghausen, the colorless corpuscles may l"' generated from the red corpuscles, but it is probable thai they may be formed in the tis- sues at many points, and the connect Lve substances through their intimate asso- ciation with the lyinjihatics are capable of manufacturing them in almost any quantity. Neither of the two varieties of corpuscles, the red or the white, have a cell-wall or outer investing membrane that can be demonstrated, though it is not unlikely that the outer layer of protoplasm has greater density than tho more internal portions. White or colorless blood-corpuscles. — The white blood-cor- puscle is much larger, on an average, in the human species, than the red. It is rounded in form, and is estimated as varying between .0077 and .0120 mm. The average is .0091 nun. (Frey). In contour they are apt to be more or less rough, and exhibit processes. In some of these corpuscles the nucleus is distinct, though when quite fresh a nucleus is rarely seen. If the eye of the observer can watch the corpuscle when it is upon a heated stage and under suitable conditions, its division may be seen. The number contained in the system is variable, as we shall see, depending upon a great number of conditions. The personal observations of the author do not incline him to regard the network which has attracted so much attention of late years as satisfactorily shown to exist in living corpus- cles, although there is no question but that it has been seen in corpuscles after exposure to chemical reagents. According to Dr. Richard Norris, there is, in mammals, a third corpuscular element which is usually invisible and of the same size as the red ones. Some doubt is thrown upon his alleged discovery, by the fact that the method he employs is likely to produce artificial appearances, and therefore leads to the supposition that the alleged bodies were merely red corpuscles decolorized. Mode of counting the blood-corpuscles. — Thanks to the instruments of Malassez, Hayem and Nachet, and Gowers, we are in a position to count the red blood-corpuscles with a fair degree of accuracy. The methods are somewhat different, but are not difficult to understand. Schaefer describes his plans as follows : In order to separate the corpuscles and prevent coagulation, the blood used is first diluted to a definite extent — say a hundred times — with a 10 per cent, solution of sulphate of soda. The mixing can be per- formed in a measuring-glass if the blood is in sufficient quan- THE BLOOD. 49 fcity, but if only a small drop is obtainable, such, for example, as is got by pricking the finger, a mixer is better. This con- sists of a capillary tube terminating in a bulb, the capacity of the bulb between the marks 1 and 101 being exactly 100 times that of the tube from its point to the mark 1. A small glass ball is inclosed in the bulb, and serves, by its movements, to facilitate the mixing. The capillary tube is allowed to fill with blood as far as the mark 1 ; sulphate of soda solution is then sucked up as far as the mark 101. As it passes in, it of course pushes the blood before it into the bulb, and the two are there thoroughly mixed by gentle agitation. The next thing is to count the corpuscles in a known quan- tity of the mixture. The most convenient plan is that of Hayem and Nachet. A slide is used, having a glass ring \ mm. in depth, cemented on to its upper surface. A drop of the mixture, but not enough to fill the cell so formed, is j)laced in the middle of the ring, and a perfectly flat cover-glass is so laid on that the drop touches and adheres to it without reaching the sides of the cell. The slide is placed on the microscope, and as soon as the corpuscles have settled down to the bottom of the drop, the number in a definite area is counted. If the area chosen is \ mm. square, this will give the number which were contained in \ mm. cube of the mixture, and multiplying this by the number of times the blood was diluted, the result will be the number of corpuscles in \ mm. cube of blood. Schaefer thinks that it is more convenient to have the quad- ratic markings upon the micrometer glass of the eye-piece than upon the slide, which is a practical point. The quadratic markings are shown in Fig. 22. To measure any square, it is only necessary to take the stage micrometer, ruled in milli- metres and decimals, and adjusting the draw tube, make the side of one square correspond exactly to an interval of \ mm. on the. stage micrometer. It will then be convenient to mark the tube at this point, and then, in all subsequent work, if the tube be kept at this line and a slide is used of the thickness of the micrometer and the same lens and eye -piece, the side of a square will always be \ mm. This method is the one in general use. Another less frequently employed is that of Malassez, which is also described by Schaefer as follows : A little of the mixture of blood and sulphate of soda is transferred to a very fine flat- 4 50 MANUAL OF IHSTOLOGY. tened capillary tube, the capacity of a given length of which has been ascertained previously and marked on the slide to which the tube is fixed. Thus, in his capillary tube a length of 400 mi- cromillimetres represents the t^V-f Part °f a cubic millimetre of the mixture. The counting is performed with the aid of a squared ocular micrometer, the microscope tube having been previously so adjusted by the aid of a stage micrometer that the side of the square shall have the value of one of the lengths (400 /i ' for example) marked on the slide. The result of the Fig. 21. — Hayem and Nachet's apparatus for blood-counting. counting gives the number of corpuscles in a known quantity (tbV.^ c.mm.) of the mixture, and the number in a whole cubic millimetre can therefore be readily determined. Dr. Keyes uses a modification of the method of Hayem and Nachet, making a dilution of 1 to 250, in order to render the counting more easy. In Fig. 21 the pipette, A, is filled up to the mark, 5 D ; it is then emptied into the glass vessel, F. The pulp of the finger of the patient whose blood is to be tested should be pierced with a triangular needle (glover's). Quick 1 A micromillimetre (jj.) = lt>l00 mm. THE BLOOD. 51 but firm pressure down the finger will at once force out a drop from the punctured spot. The blood must be drawn imme- diately into the capillary pipette lest it coagulate. When the pipette is full to the mark 2, its point should be rapidly wiped clean of any blood adhering to the outside, and the contents at once blown into the artificial serum in the cup, F. A little suction back and forth clears the tube of any blood-corpuscles which may have adhered to the glass within. Both tubes should be carefully washed before being put away. The mixture is now to be thoroughly agitated with the glass rod, and before it has time to settle, a drop is placed in the middle of the cell on the slide, D, care being taken that the drop is not large enough to touch any part of the circumference of the cell. The covering glass, E, should at once be placed upon the cell. Should the drop be too large, so that when the thin cover is adjusted it spreads out too much, the glass should be cleansed and the attempt made anew. Finally, a small drop of water or saliva is applied to the edge of the covering glass, under which it circulates around the top of the cell, serving to hold the cover in place and pre- vent evaporation. The slide is then put in position and when the corpuscles have all settled to the bottom of the fluid, the counting should begin. The following detailed plan is then given by Dr. Keyes : "It is better to count each of the sixteen squares and write down its number separately, so that in counting the square beneath it, should there beany doubt about counting a given corpuscle lying upon the line, a glance at the number recorded for the square above may remove all doubt. Many corpuscles will be found lying upon the outside lines bounding the large square. I have adopted the rule of rejecting all those lying upon the upper and right-hand outside lines (of the large Bquare) and counting all those lying on the lower and left- hand outside lines. After having thus obtained the nunJber of red corpuscles Fig. 22. — Blood corpuscles as seen with the squared ocular micrometer. (Keyes.) 52 MANUAL OF HISTOLOGY. sit tinted within the large square, it becomes easy, by a simple equation, to find the number in a cubic millimetre. A single count, however, exposes to sources of error, and in order to approach more nearly to exactness, I have uniformly counted the number contained in the large square in live different por- tions of the field (sometimes ten), and have taken a mean of the whole number of counts as the standard. The computation is as follows : The glass cell on the slide is ' mm. deep. The eye-piece micrometer marks off £ mm. square, therefore the count of red corpuscles (or white, as the case may be) must indicate the number contained (in the dilu- tion used) in \ mm. cube. But \ mm. cube is jfa of a c.mni., therefore the number counted must be multiplied by 125 ; and the blood was diluted by adding 250 parts of fluid to 1 of blood (2 c.mm. to500c.mm.), therefore the product above obtained must be again multiplied by 251 to get the number of corpus- cles in a c.mm. of pure blood. Instead of multiplying twice, a single multiplication by the product of 125 x 251, 31,375, will give the same result." This method should, theoretically, be absolutely accurate, but there are vari- ous errors which will unavoidably creep in. First of all, the tubes should be verified as to accuracy. This has been done for me at the Winchester Observa- tory, of Yale College, by Leonard Waldo, Esq., the astronomer in charge. My larger glass tube is slightly different in shape from the one here represented, and is marked so that the line at ^ indicates a capacity of 500 cubic millimetres (0.5005 grammes of distilled water at 26.4° C). The cubical contents of the reservoir from the point to the line i = 0.2425 + 0.008 = 2505 grammes = 250 c.mm., approximately. Accordingly, the marks i and | indicate i and i a cubic centimetre, within a limit of error so small as to be practically insensi- ble. The smaller glass tube, which is capillary, is marked 2, 2i, 4, and 5. The level 5 indicates a capacity of 5 c.mm. The capacity between the pointed extremity and 2 is 2 c.mm., less ^t-tt c.mm. ; the space between 2 and 2-£ con- tains .55 c.mm. ; the space between 2^- and 4 contains 1.45 c.mm. ; the space between 4 and 5 contains exactly 1 c.mm. (Waldo). The determination of these capacities was made by using distilled water, and comparing the weight, when filled to the various levels, with the same tube after careful drying. These estimates are given to show one of the errors which may be met with, and that an instrument, before using, should be verified by some one who has special means for determining capacities of this kind. My eye-piece mi- crometer was made for me by Rogers, of Cambridge, and the entire field was subdivided into squares, so that every portion of it may be counted without moving the slide. My method has been practically the same as that of Dr. Kjyes, except that I prefer diluting with one thousand parts of the diluent, THE H^EMOCHROMOMETER. 53 and use iodized serum in place of urine. The ordinary i per cent, solution of common salt in water will also answer sufficiently well. Recent investigations, such as those conducted by Drs. Cut- ter and Bradford, of Boston, have established that there is great variation in the number of globules of an individual, de- pending on various causes, such as the locality from which the blood is drawn, the loss of fluids, as by diarrhoea, sweating, increased urinary secretion, etc., and even the period of the day, week, or 3'ear. These general conclusions have also been sustained by Hayem, of Paris, in researches which are still being prosecuted. When one further considers that we have no definite stand- ard of comparison ; that the instrument is apt to be imperfect ; that there is a liability of errors to the amount of 10 per cent.; that skill and practice are required in manipulation, it is by no means difficult to see that the hsematometer is not calculated at present to introduce much scientific precision into medicine, unless the most extraordinary precautions are taken in every case, and these all duly noted. Blood crystals. — The pigment of the blood occurs usually in an amorphous form, and is called haematine. The brownish red needles found in extravasated blood are known as haema- toidine. Hcemoglobin also occurs in most mammalian blood, and is deposited under the form of rhombic plates. It is estimated that about 125 grammes are present in the blood of a healthy adult. THE HiEMOCIIROMOMETER. According to Mantegazza and others, richness in haemoglo- bin indicates a corresponding richness in red corpuscles, and any special depth of color in the blood may be regarded as im- plying a certain given number of red corpuscles to the cubic millimetre. While this ratio appears to hold true in health, it fails in disease Thus, a condition which we recognize as anae- mia may be almost wholly due to a loss of haemoglobin in the corpuscle, or an actual loss of red corpuscles, together with a diminished amount of haemoglobin in those that remain. In the cachexia of cancer tin- number of the oorpnscles may be sustained, but their haemoglobin diminished. In diabetes mel- 54 MANUAL OF HISTOLOGY. litus, on the other hand, there may be an excess of red cor- puscles, while there is a diminution of their haemoglobin. In anaemia, from hemorrhage, there is an actual loss both of cor- puscles and of haemoglobin in those that remain. To facilitate the estimation of haemoglobin, an Instrument has been devised by Malassez and Wrick (Paris), called the hcemochromometer,' which is easily manipulated, and bids fair to establish some facts of practical utility (see Archiocs de l>h !is., 1877, p. 1). It consists of a hand-screen, to which a movable jirismatic trough, containing a colored fluid, is attached, and a modified Potain pipette. By means of this apparatus the richness of the blood in haemoglobin, and the maximum quantity of oxy- gen which it can absorb, may be determined. To use the ap- paratus the pipette is first filled up to a certain point with the blood to be examined, and then diluted with 100 parts of water. The reservoir of the pipette is then filled with the diluted blood. The screen has two holes ; behind one of these the prismatic trough is made to slide up and down, the color of the fluid contained in it of course varying in intensity, according to the extent of the upward and downward motion. Behind the other oj>ening the reservoir of the pipette is secured by means of a little elastic ring. The screen is now held against the light (preferably white light ; sunlight is to be especially avoided), and the trough moved until the color of the blood mixture is matched by its own color. Then the figure on the scale attached to one side of the trough is read off, and this indicates, by reference to the table annexed to the apparatus, the points to be determined. If the blood to be examined be deeply colored, the aqueous blood-mixture is made in the pro- portion of \ to 100 ; if it be but slightly colored, in the propor- tion of 2 to 100. BIBLIOGRAPHY. Welcker. Pragervierteljahreschr. XLIV., p. 60. 1854. Zeitschr. f. rat. Med. 3, XX., p. 280. Sciidltze, Max. Archiv f. mikrosk. Anat. I., p. 35. 1865. lioi.LETT. Strieker's Manual of Histology. New York, 1872. Woodward. Am. Jour, of the Med. Sci., Jan., 1875. N. Y. Med. Rec, Jan. 31, 1880. 1 To be obtained of J. F. Reynders & Co., New York city. BIBLIOGRAPHY. 55 Kelsch. Arch, de Phys. Vol. II. 1875. Keyes. Am. Jour, of the Med. Sci., Jan., 1876. Heitzmann. New York Med. Jour.. April, 1877. Mantegazza. Berl. Klin. Woch., April 1, 1878. Ranvier. Traite technique d'histologie. Paris, 1877 et seq. Hayem. Archives de Phys. 2 Ser., T. VI., p. 201 et seq. 1879. Bizzozero, G., and Salvioli, G. Centralb. f. d. Med. Wiss. 16, p. 273. 1879. Pouchet. Gaz. Med. de Paris. 14, 16. 1879. Cutler, E. G., and Bradford, E. H. Journal of Phys. Vol. I. 1878—1879. Boettcuer. Archiv f. mikrosk. Anat. Bd. XIV. p. 73. 1877. Klein and E. Noble Smith. Atlas of Histology. 1879. Elsberg. Annals of the N. Y. Academy of Sciences. Vol. I. , Nos. 9 and 10. 1879. (A very extensive bibliography.) Satterthwaite, T. E. Arch, of Comp. Med. N. Y. II. 1880. Baxter and Willcock. Lancet, March 6, 13, 20, 1880. CHAPTER IV. EPITHELIUM. The skin, mucous surfaces of the body and various pas- sages in connection with them, are evenly coated with bodies of peculiar shape, which are united together to form a cover- ing of one or more layers. In some places, as upon the external portions of the epider- mis, the corpuscles are more or less flattened. Elsewhere, as in the ducts of secreting glands and in the trachea and fallopian tubes, they are cylindrical, and the free extremities are often surmounted by cilia — fine, hair-like processes, which have a vibratile movement that propels solid matters, such as sputa and ova, in some special direction. In other parts, again, as in the collecting tubes of the kidney, near the apices of the pyra- mids, a cuboidal variety is found. Intermediate or transitional forms are also frequently met with in all parts of the body. A characteristic of epithelium which is especially note- worthy is that the same species is not found uniformly in the same position. Sometimes this mutation of type is governed by the physical laws that regulate the growth and development of the subject, or it may be a consequence of disease. An ex- ample of the former peculiarity is to be noted in the larynx, where the ciliated corpuscles of infancy part with their cilia from advancing age, or indeed may become flattened. As an example of pathological change it is not uncommon to find villosities covered with the most beautifully marked cylindrical epithelium, springing from the ordinary mucous membrane, just where the superficial corpuscles happen to be somewhat flattened in their normal state. The use to which the part is put has also an important influ- ence in governing the shape and other attributes of the corpus- cles. Where they are exposed to the drjdng action of the air, to harsh usage, and continued friction, as upon the hands and EPITHELIUM. 57 feet, they become flattened, dry, and horny ; in the interior of the body, on the other hand, where such conditions do not exist, they are succulent and pliable. Ordinary flattened or squamous epithelium. — This is best obtained by scraping the back of one's tongue with a blunt instrument. The scrapings should then be mounted in equal parts of the common salt solution (-J- per cent.) and glycerine. The epithelial bodies may in this way be readily studied. They are separate or grouped together in collections of two or more. In diameter they vary between T^U1I and -g^ inch. The sur- faces are all bevelled, and at the same time are uneven or ridged ; consequently they overlap one another to a certain degree, and the inequalities of one corpuscle fit into those of another. The most superficial epithelium is the thinnest, and, conversely, the deepest is apt to be the most nearly spheroidal. Intermixed in the mucus will be seen the so-called mucous or salivary corpuscles. They are not very numerous, but are de- tected by the "molecular" or Brownian movement of their in- terior: In size they closely resemble the white corpuscles of the blood, but, as a rule, exhibit no amoeboid motion ; the white glob- ules, on the other hand, rarely have any Brownian movement. The surfaces of the epithelia are often so covered with bac- teria that they are only recognized with some difficulty. These little bodies are wonderfully uniform in size, and are disposed in the most regular manner. Looking straight down upon them they appear to be minute spheres with a diameter aver- aging between stoot an(l ttwts inch. Closer inspection and examination of the corpuscles at their free edges shows that the bacteria are in reality rod-shaped, and that they adhere to the corpuscles by their extremities, standing in such cases vertical to the surface. A high power, such as the immersion TV, develops this point quite clearly. Incidentally the mucin of the mucus may be seen to advan- tage in the scrapings of the mouth or tongue. To a drop or two add another drop of commercial alcohol and a drop of the or- dinary ha'matoxylin solution. The alcohol will coagulate the mucin, which then takes the form of filaments and branching networks ; the Logwood will make them distinctly visible Epithelium from the skin may be studied in one of two methods. Take a fresh specimen from the palmar surface of the hand or plantar of the foot, freeze it in a section cutter, 58 MANUAL OF HISTOLOGY. take off a thin slice with a knife, immerse for a few seconds in a dilute solution of acetic acid (■£ per cent.), and then mount in glycerine and water ; or a similar portion of the skin may be steeped in a weak, sherry-colored, watery solution of the bichro- mate of potassium (gr. ij. — iij. — f. 1 j.) for several days and then hardened in alcohol, first of 80 per cent., then of 90 per cent., finally of 95 per cent, strength ; this latter process taking several days, and ending when the specimen is thoroughly hard. Sec- tions may then be made in the usual way. By the use of acetic acid the nuclei will readily be seen in the lower strata of the epi- dermis, while the outermost layers have none, or, at least, none that can be demonstrated by the usual histological methods. Three different strata can now be recognized : 1, the stra- tum co?'neum, or corneous layer, in which the corpuscles are flattened, and appear to have no nuclei ; 2, the rete mucosum, or malpighian layer, immediately underlying the former, and composed of cuboidal elements, armed with spines or prickles, as they are often called ; lastly, 3, there is the pigmented layer, which overlies the papillae. The bodies of the latter corpuscles are infiltrated with particles of melanine, which is the cause of the dark color in the skin of the negro and swarthy races. Maceration of the epidermis in liquor potassae is an excellent method for exhibiting the individual elements ; after a few min- utes they will swell up and detach themselves from one another. It was thought, until quite recently, that these prickle cells interdigitate with one another, but Eanvier has claimed that they are continuous with those of adjacent corpuscles (see chapter on the Skin). This point is difficult to set- tle, as it requires a special method and lenses of high power. Eanvier injected a one-fourth per cent, solution of osmic acid into the lower layers of the epider- mis, using a hypodermic syringe, and driving the fluid right and left. There is a form of flattened and pigmented epithelium that may be seen by examining the external surface of the choroid, the ciliary processes, and the posterior surface of the iris. In the choroid these bodies look like a mosaic of polyhedral cells. Such specimens may be permanently preserved by simply dry- ing them, and then mounting in dammar or Canada balsam. Ciliated epithelium. — The movement of living cilia is readily seen. All that is necessary is to take the common frog (Rana temporaria), draw out his tongue, and then observing the teat- like projections at the posterior part, snip one off. EPITHELIUM. 59 This little piece is then to be mounted in a one-fourth per cent, salt solution, or serum, and examined. Along the free edge of the mucous membrane the cilia will be seen engaged in active vibratile motion. The appearance presented by a broad expanse of moving cilia has been aptly described as resembling a field of grain which is being swept by the wind, though the motion is often much more rapid than this comparison would imply. It will be seen that various substances, such as blood globules, are propelled in a definite direction. When the frog's mouth is open, all solid particles that are lodged upon the mucous membrane are carried quietly but inevitably toward the gullet, and down toward the stomach. The power of the ciliary movement may be estimated, in a measure, by placing some light but adhering body upon the anterior portion of the roof of the mouth, and then inverting the animal. The sub- stance immediately begins to ascend against gravity, and soon is wedged in the gullet. The same force, though acting in an opposite direction, expels mucus, pus, and indeed all solid matters, from the cavities of the human lungs ; it also propels the ova through the Fallopian tubes into the uterus. In ex- cessive catarrh from mucous membranes the epithelial bodies may themselves be expelled, so that they are not infrequently found with their cilia attached, as in the nasal discharges. After death cilia are hard to recognize ; they contract down to little knobs on the surface of the cells, and can only be demonstrated when the eye looks directly down upon them. Osmic acid is useful to preserve them in their natural condition. Take a fresh specimen and immerse it for twenty-four hours in a one-fourth percent, osmic acid solution, and for another twenty-four hours in dilute alcohol ; then tease and mount in glycerine and water. It will be observed that each cilium is a slim, straight rod, which is apparently structureless ; they rest upon a band, which, with a high power, may be seen to have vertical striations. Effect of reagents. — By making use of the moist chamber (Fig. 19, p. 42), and placing a drop of chloroform in the cor- ner of the cell, it will be seen that the action of the cilia rap- idly stops, while, if the chloroform be removed, it will again resume its activity. If carbonic acid gas is admitted, the action of the cilia will at first be accelerated, but subsequently retarded, and eventu- ally stopped (Kuehne). GO MANUAL OF HISTOLOGY. After shutting off the carbonic acid gas and admitting oxy- gen, the action will again commence. When the ordinary motion has ceased, the gradual application of heat will cans • it to return ; but if the temperature be raised continuously, a point will soon be reached where the excessive heat will cause the motion again to stop. Columnar or cylindrical epithelium. — This is the epithe- lium par excellence of the digestive tract, clothing the mucous membrane from the cardiac orifice of the stomach to the anus. It is also found at the orifices of the ducts of the large excretory glands, such as the liver and pancreas, in the milk-passages of the nipple, and in some parts of the generative system. These cells are tall and narrow, standing vertical to the surface of the mucous membrane. Sometimes they are broadest at their free extremity, at other times about the middle, so that when viewed from above they appear to be separated from one another. The nuclei are rounded, and are either placed about the middle of the cell or near the attached border. They admit of consider- able variation, however, as to size and shape, some of those in immediate contact being broad at one extremity, and some broad at the others ; the free edge also may be uneven. Scrape the surface of a frog's tongue or a rabbit's intestine after washing ; the cells will be seen to advantage. Place some of the scrapings in a drop of glycerine and water to which another drop of dilute acetic acid (I per cent.) has been added, and mount. In this way the nuclei will be brought clearly into view. The cells closely resemble in their shape the columnar variety, except that they have no cilia. Among them will almost always be found chalice or goblet cells. They lie among the columnar corpuscles, and are usually shorter, but broader, expanding in the centre, and terminating at their attached extremities in a single or double process. The sur- face is cupped. They contain one or more nuclei ; whether they are a distinctive cell or not is as yet uncertain. Some suppose them to be the ordinary columnar cell undergoing mucoid degeneration ; others that they are not epithelial at all. Frey regards them as artificial productions.1 1 The most rational explanation is that furnished by F. B. Schultze. The intra- fibrillar substance is, according to this observer, converted into hygroscopic mucin, which swells up. This constitutes a change in the cell which, from being columnar, becomes goblet-shaped. The wall finally ruptures, and the mucin is poured out. EPITHELIUM. 61 Other varieties of epithelium will be taken up in connection with the different organs. As already stated, many transi- tional varieties occur, even in direct association with the typi- cal forms we have described. Structure of epithelial corpuscles. — According to the views of Heitzmann, Klein, and others, the substance of the cor- puscle is pervaded by a network, the minute fibres of which may be seen under a lens of high power. The nucleus or cen- tral body is also similarly provided. Within the meshes of this network there is a hyaline substance, the abundance or paucity of which determines the size of the meshes. The "granules," which have often been described, are, ac- cording to this view, the nodal points of the meshwork. It is also stated that the epithelial cells sometimes have a tine limiting membrane (Klein) ; but even in such instances it is merely a condensation of the outer part of the corpuscle. Within the nucleus there are also, according to the same ob- servers, fibres, within the meshes of which are not infrequently real granules (nucleoli). The epithelial corpuscles are at- tached together, either by an interlacement of their processes, as in the liver, or by a peculiar cement substance, as in pave- ment epithelium, or by a continuity of their processes, as in the rete mucosum. Recent histological studies have narrowed the field formerly occupied by the epithelial bodies, and, in accordance with these views, the flattened corpuscles which cover serous mem- branes, such as the pleura and peritoneum, will be arranged under the connective-tissue series, rather than under the epi- thelial. The reasons for this change will be given in a subse- quent chapter. BIBLIOGRAPHY. BOHULTZK, M. Die Stachel- und Riffzellen. Virchow's Arch., Vol. XXX., 1864, p. 860. BOHULTZE, F. E. Epithel. u. Drusenzellen. Arch. f. mikrosk. Anat. 1867. Ranvieb. Traito technique d' histologic Paris, 1875. DEL •, i fi;i.D. Studies in Pathological Anat. New York, 1878 et seq. KLEIN and B. Noble SMITH. Atlas of Histology. 1879-80. Heitzmann. New York Medical Record. July 81, 1880, p 188. FRET. The Microscope and Microscopical Technology. New York, 1880. CHAPTER V. THE CONNECTIVE SUBSTANCE GROUP. MUCOUS OR GELATINOUS TISSUE ; ADENOID TISSUE ; NEUROG- LIA ; FAT TISSUE ; FIBROUS TISSUE PROPER ; CORNEAL TIS- SUE ; INTERMUSCULAR TISSUE ; TENDON TISSUE ; ELASTIC TISSUE. The term connective substance was first proposed by Reich- ert in 1845, and is now applied to a class of animal tissues whose offices are very important in the economy. Prominent among them is bone, which forms the solid framework of the body, gives it strength, and supplies points of attachment for muscles and tendons ; another group comprises the ligaments, which assist in holding the bony parts, and also some organs, in their proper relations ; others again, of a more delicate nature, fur- nish support or protection for epithelial bodies, blood-vessels, and nerves. Just at the present time the histology of connec- tive substances has an important bearing on many points that relate to inflammation, degeneration, and the development of certain new growths, and it is therefore desirable to have a clear conception of them. This object is best effected by studying each variety separately, not only in its normal condition, but under the changes it exhibits when acted on by the factors that are concerned in the processes of disease. It is a property of these substances that they supplant one another at different times or under peculiar circumstances. As an example, the hyaline cartilage of young life may change into true bone in old age, while, on the other hand, there is always a tendency for fully formed tissue, if inflamed, to re- vert toward the embryonic type. The connective substances ma}r be subdivided as follows : 1, mucous or gelatinous tissue ; 2, adenoid tissue ; 3, neurog- THE CONNECTIVE SUBSTANCE GKOUP. 63 lia ; 4, fat tissue ; 5, fibrous tissue proper ; 6, corneal tissue ; 7, intermuscular tissue ; 8, tendon tissue ; 9, elastic tissue ; 10, bone ; 11, cartilage ; 12, enamel ; and 13, dentine. The word connective tissue was first proposed by Johannes Mueller, and is sometimes used as synonymous with connective sub- stance, but erroneously. The former is merely a variety of the latter, and is usually intended to indicate one or other of the flexible connective substances that form the interstitial material of the body, and in that sense we shall use it for convenience sake, but without implying any special histological character. In precise histological descriptions it is always best to use the special name of the variety intended, such as mucous tis- sue, adenoid tissue, and the like, where the structure happens to be known. It is also well to state here that the term "cellular" tissue, found in many of our anatomies, is apt to mislead the student. The word "cellular" has no reference to cells, i.e., corpuscles, but to the large cavities or spaces that exist in all loose connec- Fig 23.— Gelatinous or mucous tissue. Human umbilical cord. tive tissues, of which the subcutaneous is an example. These spaces are easily seen by the naked eye, when inflated with air. Mucous or gelatinous tissue.— This is the most simple form that is met with. It is seen to great advantage in the embryonic umbilical cord, which also contains several other varieties of connective tissue. The following method has been found best suited to demon- strate it. Take a small piece of cord at about the third month and immerse it ;i few weeks in Mueller's fluid ; make a thin sec- tion through the very soft gelatinous part, then soak it a few minutes in distilled water, to which subsequently a few drops 64 MANUAL OF HISTOLOGY. of acetic acid are to be added so that the solution shall not con- tain more than 1 per cent, of acid, and then mount in glyce- rine. It will then be seen that the softest portion contains numbers of irregularly-shaped, thin plates, some provided with an oval, flattened nucleus, others having none that are appa- rent (Fig. 23). Some of these flattened bodies anastomose by these processes with those of other plates, others are quite free. The substance lying between the cells, the intercellular sub- stance, is quite homogeneous, or slightly granular, in the softest portions, and has at first no defined fibrillation. In the neigh- borhood of the former tissue, lines of fibrillation occur, while at the same time these flattened bodies become smaller, although they are still flattened (Fig. 24, b). Mucous or gelatinous tissue, Fig. 24.— Connective tissue in an advancing stage of development. From the umbilical cord. as it is seen in the umbilical cord of an embryo, is properly an embiyonic or developmental form of connective tissue which is never found in normal adult life. All the phases of develop- ment may here be seen, from the most primitive, comprised in Wharton's jelly, to the firm, fibrous fascicles that encircle the vessels. Properly speaking, the true mucous tissue is, as its name implies, a viscid material, and, indeed, is much like half-set glue, in which the corpuscles are scattered with little or even no cohesion. The intercellular substance differs from albumen in not con- taining sulphur ; from chondrin and gelatin, in not being pre- cipitated by boiling, tannin, or the bichloride of mercury. THE CONNECTIVE SUBSTANCE GEOUP. 65 At an early stage there are no marks of fibrillations in the intercellular substance, but later fibrils are seen in the vicinity of the corpuscles, and are some of the early signs that organi- zation of the tissue is commencing. The corpuscles at the same time become smaller, and about the central body or nucleus we see a delicate expansion (Fig. 24 a), which is the envelope of the connective -tissue corpuscle — a film of great tenuity. Klein believes that in these corpuscles there are two portions, a granular or firmer part continuous with the processes, and a delicate expansion that is hardly visible. It is certain that the connective-tissue corpuscle is frequently in connection with one or more of its fellows by a mutual anastomosis of processes. The fibrillation appears to be at first limited to certain areas about the cellular elements, so that the long, flattened and pointed lamellaB of fibrous tis- sues on which the corpuscles are attached look like large cor- puscles with correspondingly large nuclei. Using a camel' s- hair brush and pencilling off the specimen under examination, after soaking in a 10 per cent, watery solution of common salt, the apparent nuclei with their delicate envelopes are partiallj^ (Fig. 24 b) or wholly removed. We then see small strips of more or less fibrillated tissue, having no central body that can be recognized, even with the use of strong staining solutions. These and similar observations tend to establish a conviction that the fibrillated portion arises from the soft, gelatinous ma- terial by a process of fibrillation inaugurated by the presence and under the formative action of the connective-tissue cor- puscle. It is not impossible that the fibrin of the blood, which, though fluid in the blood-current, is often known to be de- posited in delicate filaments, may contribute largely, if not wholly, to the formation of the fibrilla3. As the tissue becomes firmer, the little plates with their anastomosing branches form a loose network which separates the fibrils into distinctive bundles or fascicles, and encircles them more or less completely. There is another view which is offered as an explanation of the process by which connective tissue becomes organized. It is this. The change is derived wholly from the corpuscles. Some of them split up into fibrils, constituting the fibrous part of the tissue; the others remain, and are developed into connective:- tissue corpuscles. This view has the support of excellent hisi.ologists. 5 66 MANUAL OF HISTOLOGY. The white corpuscles of the blood are pre-eminent]}'- suited for building tissue. When blood is organized, which occurs not infrequently, the white corpuscles at once assume an im- portant role, while the red are soon melted down into a homo- geneous mass, that is usually absorbed. This change is ob- served under various pathological conditions. Fibrous tissue. — This substance, which is also known as fibril lated connective tissue, is the fully developed material that has just been described. It occurs either in parallel Fig. 25. — Reticular form of connective tissue. From the human umbilical cord. bundles or fascicles, in interlacing lamellae, or as a fenestrated material containing larger or smaller openings. A special va- riety, the reticular, is seen to great advantage in the umbilical cord of an infant at birth (Fig. 25). If a cut be carried through the spongy portions of the cord, it will be seen that the tissue is composed of bright, shining, branching bundles, d, superimposed upon which are a num- ber of oval, flattened plates, a, at intervals ; about them is THE CONNECTIVE SUBSTANCE GROUP. 67 a delicate envelope, b, which appears to be highly elastic, so that it will stretch or relax, according as the networks are compressed or dilated. By teasing with needles or immersion for a few days in a 10 per cent, watery solution of common salt, these corpuscles can often be separated from the bundles, and then they will be seen to form a connected system. When entirely isolated from one another, they often appear spindle- shaped. That this is not their character may be shown by passing a current of fluid through the specimen — a method already described under the name of irrigation. It is accom- plished in this way : having affixed small strips of filter-paper to the edges of the cover on either side, and moistened one side with fluid, the excess will be absorbed by the other slip, caus- ing a current by which the corpuscles may be made to roll over. We then learn that they are disks of an irregularly flattened form, having longer or shorter processes (c, c, Fig. 25) — variations in form which seem to depend, in a great measure, upon the tension to which they are exposed, and the position they occupy in the tissue. This explanation will serve to show why all measurements of such corpuscles are merely approximative, and have but little value. They are shrunken by immersion in alcohol, swollen by the imbibition of water, are drawn out into long, flattened spindles when the tissue is put on the stretch, or become rounded, per- haps nearly spherical, during relaxation. They may assume almost any form as the result of pressure. The nucleus may be regarded as more of an exception to this rule ; at any rate it seems that in fresh specimens, when the substance has been swollen by immersion in water, it is always oval and flattened. The bundles upon which these bodies lie are somewhat cylindrical in form, branched, and composed of separate fila- ments, that can be separated by Mueller's fluid, or a 10 per cent, watery solution of common salt. Two other forms of corpuscles may also be noticed : (1) the kind observed by Waldeyer, and called plasma cells, and thought by him to be corpuscles peculiarly prone to take up fat to make i'at tissue, bodies four or five times the size of a lymphoid corpuscle, and rounded in form, containing a cen- tral body ; and (2) the ordinary lymphoid corpuscles, seen at times in all tissues. 08 MANUAL OF HISTOLOGY. The form of fibrous tissue that occurs in parallel lamellae is well shown in the mesentery of the frog, and in serous mem- branes generally. No great difficulty will be met with in pre- paring this tissue, for it is only necessary to remove it from the frog in the fresh state, acidulate it in a weak (1 per cent.) watery solution of acetic acid, and mount it in glycerine. It will be seen that these so-called spindle-cells are really flattened plates, when viewed flat-wise, and generally irregu- larly quadrilateral, though the form varies somewhat in each instance. It is not improbable that some which appear spindle-shaped, and lie in the interfascicular sjiaces, have a double office, one of which is to guard the nutrition of the tissue, and the other to form a partial lining of a lymphatic channel. The researches Fia. 26. — Connective tissue in the mpsentery of the frog. of Klein tend to establish this double relation, for they show that these corpuscles lie in the walls of the lymphatic radicles, which are themselves in direct communication with the perito- neal cavity by breaks in the endothelial connective-tissue cor- puscle coating and in actual apposition with the endothelial elements of the serous membranes. During the last few years there has been a tendency to regard the serous membranes, especially such as have large openings and slight reticula, as having no connective-tissue corpuscles, other than the endothelial, which form THE CONNECTIVE SUBSTANCE GROUP. Gi) a covei'ing over them. In the larger trabecles, however, there are connec- tive-tissue corpuscles, in addition to those just mentioned ; they are well seen in profile, interposed between the bundles (Fig. 26). Adenoid tissue (Fig. 27). — Adenoid tissue is the name given to the delicate substance that forms the framework of the lym phatic glands. It consists of fibres in networks which form an <2> Pig. 27. — Adenoid tissue from a human lymphatic gland. intricate texture, that is filled with the rounded bodies com- monly known as lymphoid cells. It is exceedingly difficult to analyze these tissues, because it is not easy to demonstrate any- thing that conveys to the eye our idea of a cell, i. e., excepting, of course, the lymphoid corpuscle. The best mode of proced- ure is the following : Take a lymphatic gland — such as the in- guinal in the early stage of inflammation : harden at first, in Mueller's fluid, and then in alcohol, and make sections through it. On viewing such a specimen under the microscope it will exhibit a delicate meshwork, packed with lymphoid corpuscles (Fig. 27, a). Now, if we take such a section and agitate it in a test-tube with water for a considerable length of time, and then place it upon a glass slide, pencilling it with a camel's-hair 70 MANUAL OF HISTOLOGY. brash, most of the lymphoid cells will be removed, and the delicate network, c, will be very thoroughly exposed. It will be seen that, at certain parts of this meshwork, there are flattened bodies, b, of small size, lying upon the larger cords of the meshes. It has been held by Klein and other his- tologists that the reticulum is made of branching corpuscles ; but this statement must be modified. In some instances the appearance of netted corpuscles is well seen in those portions of the glands that are regarded as the lymph passages, where the adenoid tissue forms the framework of the part. The net- work seems to be comprised of delicate, silk-like cords, enclos- ing vast numbers of lymphoid corpuscles, and exhibiting, at the nodal points of the meshes, flattened corpuscles. These delicate fibres, however, are often replaced by heavy trabecles, c, such as are seen in the figure, and after continual inflamma- tions the diameter of these latter may be found greater than that of the spaces. In these latter instances it is often difficult to find any cor- puscular elements that may not be separated from the fibres ; and, indeed, large areas of these fibrous networks may, by dil- igent pencilling with a camel' s-hair brush, be swept clean of corpuscles. But neither this rough method, nor agitation in a test-tube, will always succeed in separating all the corpuscles from the fibres, even after an immersion in common salt solu- tion for many weeks. The sum of the whole matter is, that adenoid tissue does not generally consist of a network oi' branching corpuscles, as has been claimed, but rather of a net- work of fibrous cords, on which the corpuscles are superim- posed ; they may anastomose, but this point seems difficult to demonstrate in most cases. Possibly higher powers than those now in use, or some new method may solve the question. Where the fibrous networks have attained some thickness, there is no doubt that we find the ordinary flattened connective-tissue plates lying on the bundles and surrounded by a delicate envelope. Neuroglia (Fig. 28). — But a short time since it was not known positively whether the delicate, supporting substance of the nervous system, especially of the brain, was granular or fibrous. Even after Virchow insisted that this substance was like the other tissues, known as connective, doubt was thrown upon the matter, for the defining power of most objectives then THE CONNECTIVE SUBSTANCE GROUP. 71 used was insufficient to make out such delicate objects. At the present time the actual existence of a network is hardly called in question, for it may be demonstrated with really good glasses, such as some of the immersion lenses (No. 10) of Hart- nack's system, and, indeed, by other lenses made both at home and abroad. As to the question of the corpuscular elements there is more doubt, and it can hardly be said that their exact form and shape have been definitely agreed upon by histolo- gists. We find, it is true, that where there is a considerable deposit of connective mate- rial along the central canal of the spinal cord, we have the ordinary fibres and corpuscles already described, and so, too, near the surface of the con- volutions. When, however, we examine the supporting substances of the white and gray masses there is less cer- tainty. The actual condition may be tolerably well seen by adopting the following plan. Place any portion of the brain or cord a few days in a weak solution of bichro- mate of potash (5 per cent.) or Mueller's fluid, then immerse it in alcohol until hard ; make thin sections and stain for twenty-four hours with the follow- ing solution of hematoxylin : haernatoxylini, gr. lij. ; aluminis, 1 j. ; aquae, 1 viij. ; mix and strain. Wash in distilled water and mount in glycerine, tease with needles and examine with a high power; there will then be little difficulty in seeing that the delicate supporting substance of both gray and white matter consists of fibres. They may even be distinctly isolated, for the coloring matter darkens them somewhat and they become hardened at the same time so as to be somewhat stiff and unyielding. It will be seen that many fibrils are disposed in parallel rows which perhaps can hardly be called bundles, but rather thin laminae; other similar fibrils cross them at various angles, giving to the whole, with a moderately high power, the appearance of a very delicate Fig. 28. — Human brain showing neuroglia. 72 MANUAL OF HISTOLOGY. mesh work, a. It does not appear as if the fibrillse anastomose with one another, though this point cannot now be definitely settled. It must be stated that some of these fibrils are possi- bly nerve-elements, and yet this is doubtful, because they do not even seem to be connected with the nerve-fibres ' that are distinctly shown by this method of pre]:>aration. Granular appearances are always noted in the brain, which is to be expected when cross-sections are made of the delicate librillaB. Three kinds of corpuscles are met with in the brain and medulla. The first are the variously shaped ganglionic corpuscles or cells, Fig. 28, b, b, b ; secondly, the ordinary lymphoid cells, c, c, which are generally seen to have a pale envelope about them ; lastly, smaller corpuscles, d, d, of irre- gular shapes, and many of them undoubtedly flattened and appearing to have branching processes. They may be found in considerable numbers, and can be isolated so that there is no doubt that they exist. The fibrilla3 of the neuroglia do not differ substantially in size from the fibrillse of fibrous tissues elsewhere. Tendon-tissue (Fig. 29). — Tendon-tissue may be well studied in the gastrocnemius of the frog. It is prepared like the preceding. If, how- ever, it is desirable to show the nuclei in adult tissue, it is well to use nitrate of silver. Cut a thin section of a fresh tendon and ex- pose it for a few minutes in a £ per cent, solution of nitrate of silver, until the section is turbid or milky, then place in the sunlight, and in a few min- utes the turbid color will give place to dark brown or black, owing to the deposit of silver, and the tissue may then be mounted in glycerine and examined. This method will show the corpuscular bodies to advantage. V& Fig. 29.— Tendon-tissue from the frog. 1 To avoid confusion they are not represented in the drawing. THE CONNECTIVE SUBSTANCE GROUP. 73 In some cases better results are obtained by the use of chloride of gold. The method is as follows : Freeze a small portion of a tendon, then make the thinnest possible section, acidulate it slightly and immerse in a | per cent, solution of chloride of gold until a strong yellow color has been obtained, then soak in a i per cent, solution of dilute acetic acid and expose to the sunlight until a purple or reddish color has been obtained. This will take a variable time, and is not always successful, for reasons which are not easy to understand. At considerable distances from one another there will be seen small dark bodies, which are the corpuscles already de- scribed. It is difficult to determine whether or not these cor- puscles are connected together. To isolate them, take a small piece of young tendon- tissue, immerse three or four days in a 10 per cent, solution of common salt, and then tease. In this way the cells may be liberated, and they will prove to be irre- gularly flattened plates. Sometimes they lie at the intersection of several bundles and then have separate expansions for each bundle ; the plates then lie at various angles with one another, and if one be seen edgewise it looks as if the corpuscle proper were traversed by a line. Silver or gold, the latter especially, is generally necessary to- show the corpuscles in old tendons. The same method shows the fibrillated tissue to advantage. The large tendon bundles are often covered with endothelium (connective-tissue corpuscles), which are continuous and form a complete invest- ment. For the smaller bundles the tendon-corpuscles do not by any means form a connected sheath. In very young tendons they are quite near to one another, though even at this time they only form a partial investment for the bundles ; but as tie- tendon grows older the corpuscles become smaller, with- draw from one another, and sometimes almost disappear. Tendon bundles, like other forms of connective tissue, are often encased in a transparent, delicate membrane, not unlike the sarcolemmaof striped muscular tissue. It is well shown by immersing the tendon in a dilute solution of acetic acid. Fat tissue.— The ordinary iibrillated connective tissue often becomes (lie deposit for oil, which fills the corpuscles, making them swell out enormously. This is fat tissue. An excellent 74 MANUAL OF HISTOLOGY. way of showing it consists in making a seel ion through fat tis- sue thai lias been hardened in alcohol or Mueller's fluid, or bol h. The phenomena will, in this way, be well shown. After im- mersion in an acid solution, it will be Been that the fatty acids crystallize in the centre of the sac. The nature of the evidence that fat corpuscles are really the altered corpuscles of the fibrous tissues is as follows: They occupy the same position, being in rows, between the bundles, just as the other corpuscles that we have mentioned ; a few oil drops at iirst appear, then others, until finally they coalesce into a single large drop, which fills the corpuscle ; if fat tissue be pressed, and the oil escapes, the walls of the fat-corpuscles collapse, and then the flattened nuclei may be observed on the side of the cell-body. Waldeyer believes that there is a peculiar corpuscle, three to five times the size of the lymphoid, and roundish, which is especially prone to take up fat, and be converted into a fat- corpuscle. This body, known as the plasma cell, is the second element that forms the fat-cell. The change is said to occur only occa- sionally, and under favorable conditions of alimentation (Klein). The same author states that there is also a' third way in which fat is formed : In many parts of serous membranes, espe- cially in connection with the large vessels, there appear "no- dules or cords, which are made up of multiplying connective- tissue cells." The cells increase, the matrix is converted into a network, lymph-corpuscles appear, the tissue is supplied with arteries, veins, and capillaries, and resembles lymphatic tissue. Sometimes these structures persist as they are ; in other cases they are converted into fat-tissue. Ranvier recommends the following plan of demonstrating fat-tissue : He injects beneath the skin a weak solution of os- mic acid (1-1000). The connective-tissue corpuscles may be seen to be more or less filled with oil-globules. The property of taking up oil is not peculiar to these cor- puscles already described, but belongs, physiologically, to the liver, to adult cartilage, the glandular elements of the female breast during lactation, and the glandular epithelium of the sebaceous glands. Intermuscular tissite. — It has been claimed by some that THE CONNECTIVE SUBSTANCE GROUP. 75 there is a form of spin die-cell in the intermuscular tissue of the frog's thigh. This, however, is apparent rather than real. We find broad plates, in which are oval, flattened bodies, placed at certain distances apart (Fig. 31). These, seen in profile, appear spindle-shaped. There is something peculiar about such bodies, for they seem to bear a close relationship to the elastic networks, a, so that, in some cases, it appears as if the flat- tened central bodies were directly connected with the elastic fibres, as stated by Boll. In many instances these elastic fibres lie upon the plates, b, which themselves rest in a homogeneous, intermediate, and apparently structureless substance. This tissue is therefore similar, in some respects, to mucous tissue. Corneal tissue. — The cornea consists of thin, fibrous bands, each one partly anastomosing with its adjacent neighbor. Between them are well-marked corpuscles lying in clefts — the corneal spaces. The term cornea] corpuscles, however, is even now applied to the spaces by some of the best-known writers, and it seems evident that there is doubt as to whether real corpuscles exist or not. Recently the subject has been restudied by Waldeyer, and the author has been able to verify his conclusions in a great measure, both as to the character of the corpuscles and the spaces in which they lie. In general, these bodies appear, as stated by Waldeyer, to be flat, having a considerable amount of protoplasmic material about their nuclei (Fig. 30), though in the direction of the per- iphery they gradually taper off into thin expansions, which are nearly homogeneous, and extending from them are distinct processes which in part unite with those of other corpuscles, not materially differing in this respect from tendon-tissue and the other varieties. In them is the same flattened, oval body, whirl i. when seen on the side, is rod-shaped, b, and is sur- rounded by an irregular envelope that assumes almost any shape Thus the corpuscles are not always flat, though they are usually so. Their shape depends upon many different causes, such as the method of preparing the tissue, the amount of laceration to which it is subjected, etc. The best method of examining the cornea consists in preparing it by the gold me- thod, already described. 76 MANUAL OF HISTOLOGY. After the tissue has been properly stained, which is known when it has taken a mauve or violet tint, as already stated, tin; specimen should be allowed to stand in the sun. Thin lamel- lae are then torn off with the forceps and mounted in dammar varnish or Canada balsam. After the specimen has been made thoroughly transparent by soaking in oil of cloves, it will then be seen that there are bodies within certain well-defined areas — the corneal spaces, - ~j ■ — ^ * *i Fig. 30. — Corneal tissue. From the rabbit. as they have been called by Recklinghausen and others. These bodies are disposed at quite regular intervals throughout the cornea, and are generally flat with rounded contours, though often they have processes extending from them in various direc- tions. In the accompanying drawing the spaces may be dis- tinctly seen, as well as the variously shaped corneal corpuscles. One, c, is crowded into the prolongation of a corneal space, while another, b, is connected by its processes with a neighbor- ing corpuscle. One corneal space, a, is entirely empty. These differing conditions are in a measure due, probabl}r, to the THE CONNECTIVE SUBSTANCE CROUP. 77 laceration of the tissue in preparing it, some of the bodies having been torn out and others forced to the side of the cor- neal space. There seems to be a very general agreement that the intercellular substance may be separated into indepen- dent fibrils ; but I have seen no decisive proof bearing on this point. Elastic tissue. — This differs from the other forms micro- scopically and chemically, though it is often combined with them in the body. It is also convenient to class it by itself for other reasons, chief of which are, that its corpuscular ele- ments have not yet been definitely shown in adult tissue. Yirchow, some years ago, stated that this tissue, as well as other connective substances, was comj)osed of networks, the substance of the fibres containing certain markings, and he in- ferred that these latter might be the corpuscles of the tissue. Elastic fibres were, however, according to him and others, noth- ing but the ordinary fibrous tissue condensed. Each fibre was hollow and capable of conveying the nutritive juices. Henle, in his earlier writings, regarded the elastic fibres as emanating from the nuclei, of which, in fact, he stated they were prolongations. Subsequently, he seems to have believed that the fibres originated in the basis substance. Reichert could not trace the connection between the nuclei and the elastic fibres, and, when the latter had formed, the former had disappeared. Boll, however, distinctly stated that the elastic fibres, each one constituting an "elastic cord," arise from the plate-like cells. Ranvier examined tendon- tissue, as mentioned before, but he was only able to find the elastic fibres after boiling the tis- sue from eight to ten hours. It is proper, however, to add here, that elastic fibres are very uncommon in tendon-tissue, at least they have not often been observed. The fibres of the elastic substance are pretty readily re- cognized by the fact that they are not colored by carmine or haematoxylin, and do not swell with acetic acid ; they branch dichotomously, these branches forming, witli similar branches of other elastic fibres, networks. Elastic tissue prevails in the ligamentum nuchae of the ox, in the serous membranes generally, and in the subcutaneous connective tissue of the skin, as well as in the delicate inter- 78 MANUAL OF IIISTOLOGY. muscular substance already described. It will generally be round that where this material occurs in bundles it is not be- cause there are no meslies, but rather because they are com- pressed laterally, so as not to be apparent unless most carefully teased apart. When such fibres are broken off, their extremi- ties curl up ; further, the fibres are unaffected by being boiled in solutions of strong acids and alkalies, such as 35 per cent. Pig. 31.— Elastic tissue networks. From the frog. solutions of caustic potash, or nitric acid (standard prepara- tions commonly used in laboratories), unless the action is pro- longed for a considerable time. These networks are beautifully shown by taking the mesentery of the frog when slightly con- tracted after immersion in acetic acid. The fibrillated connec- tive tissue will then swell up and become invisible, while the elastic fibres are unaffected. The ligamentum nuchse also affords an excellent oppor- tunity for studying this tissue by itself. To render the work more easy, the specimen may be allowed to soak a few days in a 10 per cent, watery solution of common salt, so that it may be the more easily teased. In the subcutaneous connective tissue of the skin the elastic fibres are well shown by hfema- toxylin preparations. Being unaffected by this staining solu- tion they appear as bright, silk-like cords, which lie in close apposition with the wavy bundles, and the branches arch over the bundles, to anastomose with corresponding branches of ether bundles, so that in this way meshes are formed. Some writers have spoken of little knobs at the nodal points of the meshes, but these appearances have been illusory. Recklinghausen seems to have believed with Virchow, that the elastic fibres contain peculiar nuclei of their own, which in THE CONNECTIVE SUBSTANCE GROUP. 79 adult tissue become extremely small, and are represented by the dark markings seen in them. Thin, of London, has claimed that they originate in branching corpuscles, which by their coalescence form the network, and the remains of the nucleus may be shown by hematoxylin. These markings may, it is true, be seen in the ligamentum nuchse of the ox, but it is doubtful whether they are nuclei or mere clefts in the tissue. Examination by the author, with such high powers as Gund- lach's No. 15 immersion, and Wale's TV, have failed to clear up the matter. Good examples of human elastic tissue are found in the sloughs of ulcers and in the sputa of phthisical patients. In some portions of the body these networks are stouter, as in the bronchi and trachea ; here they almost form a layer by themselves ; some of the fibres are even said to have a sheath. There is a variety that has been called, by Henle, perforated membrane. It is found in arteries and veins. The fibres are broad and the meshes very small. There are also "continuous elastic membranes." They are made up of fibrils, react chemi- cally like elastic tissue, and have no meshes. Such is Bow- man's elastic membrane in the human cornea, which is very distinct in man, also Descemet's membrane — the posterior elastic membrane of the cornea. In various parts of the body, beneath the epithelium, there are other elastic membranes which will be noticed in their proper places. The elastic membrane, made of endothelium, and forming the basement membrane of gland-ducts, must not be confounded with those first described. The growth and development of connective tissue varies ac- cording to the particular type. It is probable, however, that all the corpuscles are first round, but soon become flattened and have a delicate envelope (Fig. 32, b). About this is a further lightly attached investment, which, uniting with those of other similar bodies, is the commence- ment of the intercellular substance. At first the plate-like bodies lie in niches, as it were, in the intercellular substances, and if oii<' is bi-usli^d out it leaves a socket behind it (Fig. 32, c). They are often arranged in rows, as in the drawing, which was taken from a fibroma of the scalp. As the intercellular sub- stance increases the corpuscles become smaller, while imme- 80 MANUAL OF HISTOLOGY. diately under them thin laminse are formed, probably from the effused fibrine — the commencement of fibrillation. As the corpuscles become smaller their envelope shrinks, and they recede from one another. Yet, in many cases, they may retain connection with one another by means of their pro- cesses. In advanced life these cor- puscles are generally more or less flattened, but their form is also con- siderably modified by the age of the tissues and various mechanical alter- ations to which they are subjected, according to the particular locality in which they occur or the province they have to fill. By referring to Fig. 32 it will be seen that the delicate protoplasm, b, has processes which come clearly in- to view where the corpuscles are iso- lated. Pavement endothelium {epithelv- um). — From the views that have been advanced it is plain that we are pre- pared to abandon the old idea that the mesentery, peritoneum, the pleura, endocardium, serous cavities, and ten- dinous sheaths are lined with epithe- lium. It is becoming more and more evident from studies in the lymphatics that they are lined with connective-tissue corpuscles, which, on the one hand, are in actual continuity with the interfascicular connective-tissue cor- puscles, and, on the other, with the pavement corpuscles of the serous cavities. It is but a step farther and in the same direction to trace the endothelium of the endocardium out through the arteries and veins into the capillaries and recog- nize the connective-tissue corpuscle as the one cellular element of all these tissues. The special methods by which these parts are studied may.be found described in the chapters more es- pecially devoted to these topics. Nitrate of silver and chloride of gold are still prominent among the reagents that demon- strate them most distinctly. Ehrlich has recentl}'- described peculiar connective-tissue Fig. 32. — Development of fibrous tis- sue. Fibroma of the scalp. BIBLIOGRAPHY. 81 corpuscles, which he previously supposed to be identical with Waldeyer's plasma cells, but which he is now inclined to re- gard as a distinctive group of bodies. They are characterized by a special power of intense coloration in specimens treated with certain of the aniline dyes. Red and violet colors appear to be best suited to reveal the presence of these bodies, called by Ehrlich granular cells. Acetic acid produces a diffuse staining of the nucleus in these aniline stained cells. At the same time the conspicuous granules lose their color. The same author also states that the granular cells commonly found in such great abundance in inflammatory processes are not modi- fied leucocytes, but are derived from the fixed connective- tissue corpuscles. According to Ravogli, the connective-tissue corpuscles of the corium and subcutaneous tissue are branching cells, whose processes unite to form anastomoses. With advancing age these cells undergo structural alterations, and their processes begin to form reticula of elastic tissue. Simultaneously with this metamorphosis the cell-bodies are said to become flattened, elongated, and united in longitudinal rows. At length the cells as well as their processes are transformed into ordinary elastic tissue. BIBLIOGRAPHY. Satterthwaite, T. B. On the Structure and Development of Connective Sub- stances (Prize Essay). New York Med. Jour., July, 1876, and Monthly Micro- scop. Jour., October and November, 1876. Flemming. Arch. f. Anat., etc. 1879. 401—454. Stricker. Allg. Wien. med. Ztg. 1879. XXIV., 547. Kollmann. Centralbl. f. d. med. Wiss. 1878. XVI., 881. Ehrlich. Verhandl. d. Berliner phys GeselL Jan. 17, 1879; Arch. f. Anat. u. Phys Phys. Abtheil. pp. 166—169. 1879. Ravogli. Wien. med. Jahrb. Heft 1, p. 49. 1879. Also the more recent text-books of r£lein and Ranvier. 6 CHAPTER VI. THE CONNECTIVE SUBSTANCE GEOUP— Continued. CARTILAGE. Cartilage is divided into three prominent varieties : 1, hyaline; 2, fibrous ; and 3, elastic or yellow. There is, in addition, a form called ossifying, which will be described in connection with the development of bone. Hyaline cartilage is the tissue from which the bones of the skeleton are first made ; it is also found in the articular and costal cartilages, and in the cartilages of the larynx, trachea, and bronchi ; possibly also in some of the nasal cartilages, and in portions of the sternum. All of these tissues consist of a solid material or matrix^ in which are capsules which contain the true cartilage corpuscles. The character of the intercellular substance determines the particular variety. Thus, l^aline cartilage appears, under the microscope, to be structureless and homogeneous. Fibrous cartilage, on the other hand, has distinct lines of fibrillation extending through it. Elastic cartilage is permeated by net- works of elastic fibrils. Hyaline cartilage, though so-called because of its apparent absence of structure, is now known to be less often structure- less than has been supposed, for the researches of Tillmanns have revealed distinct marks of fibrillation in some adult artic- ular and costal cartilages. Soaking the tissue in a 10 per cent, solution of common salt will dissolve out the cement sub- stance and isolate fibrils, though the tissue has previously ap- peared homogeneous. Staining with the picro-carminate of ammonia (Ranvier's formula) will also demonstrate the fibrils. Each capsule is probably invested by a delicate membrane, which is thicker in some instances than in others. Extending THE CONNECTIVE SUBSTANCE GROUP. 83 from this cavity are minute canals, which communicate with those of other capsules in many instances, and thus, in all probability, establish a system of serous channels which convey the plasmatic fluid, i.e., the lymph. Many years ago H. Mueller gave a description of minute passages radiating out from the cartilage capsules. Since this time the matter has been studied by numbers of observers, but opinions have been divided as to their existence. More recently A. Budge has detailed a method by which he claims that a complete lymphatic system can be demonstrated in hyaline cartilage. Em- ploying a solution of Berlin blue, he injected the cartilage of an epiphysis from which the articular lamella had been cut off. Having thus opened and exposed the substance of the cartilage, he found it permeated with minute blue net- works that were in communication with the cartilage capsules. A connection with the lymphatics of the bone was also shown. Nykamp, who prosecuted his investigations about the same time (1876-77), verified the work of Budge, though his methods were different. He experi- mented on rabbits, injecting one gramme of indigo carmine (in substance) into the abdominal cavity. Blue granules appeared in certain spaces, which had shown themselves to be hollow passages by a previous soaking in the neu- tral chromate of ammonia. The cartilage commonly known as hyaline was also, by tins means, shown to be fibrillated. Round about every cartilage capsule there is usually an area of hyaline material. When very thin sections of cartilage are made, these areas sometimes become visible ; soaking in acids is said also to bring them into prominence (Klein). The amount of intercellular substance in comparison with the capsules varies ; as a rule, there is less of this substance near the periphery of the cartilage. When the amount is so very small that the tissue is almost cellular, it is called par- enchymatous cartilage ; this condition is observed in all carti- lages, at an early stage of development, and in some portions of the adult forms. The cartilage corpuscles are rounded bodies, sometimes oval and sometimes pyriforin. In the nor- mal condition they fill up the capsule, but after the application of reagents that shrivel, such as alcohol, they are withdrawn from the walls of the capsules, being only attached at a few points (perhaps where their processes extend out through the canaliculi). The cell-corpuscles and nuclei are said, by some recent ob- servers, to exhibit networks in their interior (Schleicher and Flemming). They frequently contain, in addition, moving bodies, which are often oil-globules of minute size. 84 MANUAL OF HISTOLOGY. The cartilage capsules do not usually appear to have any connection with one another when examined in an indifferent fluid, though in the episternal cartilage of the frog, immedi- ately beneath the perichondrium, a connection may occasion- ally be seen. Division of the cartilage corpuscle. — One of the prominent features seen in cartilage is the division of the cartilage cor- puscle. First we notice the splitting of the nucleus ; then of the corpuscle itself. When such a division has taken place the corpuscles are called daughter -cells (Fig. 33). As a next step each daughter-cell may divide and again subdivide, and Fig. 33. — Fresh cartilage from the triton. (Rollett.) thus we have developed in one capsule four or eight cor- puscles. Sometimes it will be observed in the same specimen that with each division of a corpuscle, hyaline matter from without the capsule pushes in, and so from the original capsule two are now formed. Calcification of hyaline cartilage. — Hyaline cartilage in old age is infiltrated by a deposit of the salts of lime, which, when seen under the microscope, have a granular appearance. The deposit occurs first round about the cartilage capsule (Ranvier). Nerves and blood-vessels are not supplied to hyaline car- tilage proper, though blood-vessels which belong to adjacent tissues sometimes dip into it or pass through it. Methods of studying hyaline cartilage. — An excellent and simple plan is to snip off the tip of the episternal cartilage THE CONNECTIVE SUBSTANCE GROUP. 85 from the frog ; strip it of perichondrium and mount in serum. The shoulder-girdle of the triton (newt) may also be employed. It will then be seen that there are numbers of granular cor- puscles, with nuclei scattered irregularly throughout an ap- parently homogeneous, i.e., structureless matrix. If now a little water be added to the preparation, it will be seen that the corpuscles are made to shrivel, and in so doing they expose the wall of the cavity or capsule in which they lie. The cor- puscles do not appear to have any uniform size or shape : some- times they are single ; again they are double (daughter-cells) ; occasionally they are united with the corpuscles in adjacent capsules. The nucleus is apt to be round and full ; the corpus- cles are apt to be filled with dark spherical bodies which are usually fatty molecules, as may be shown by employing a di- lute solution of osmic acid (1 per cent.). Using the silver method it will be seen that there exists, in the apparently homogeneous matrix, numbers of corpuscles whose nature is not fully under- stood. Incidentally it may be mentioned that the silver method often exhibits curious markings in all tissues. Sometimes these appearances are due to the silver itself, and some caution is therefore necessary in deducing conclusions from the method. The gold method ' shows that there are concentric rings about the capsules, but it is highly probable that this phenomenon is artificial. Ranvier recommends, as a staining fluid, purpurine, the formula of which is as follows : Take one gramme of powdered alum and add to it two hundred grammes of distilled water, which boil in a porcelain dish. To this solution add some pow- dered purpurine diluted with water. If the boiling be now con- tinued, a portion of the purpurine will dissolve. Filter while warm, and receive the colored fluid in a flask which contains 60 c.c. of alcohol. This liquid has a rose-orange color. The nuclei of the corpuscles will be colored red and have a double contour ; the cell-body will be bright red. Hyaline cartilage may be well exhibited in the respiratory tract of young children, as in the cricoid cartilage of an infant two or three years old. Yellow elastic or reticular cartilage is a very distinctive form. It consists of the hyaline variety permeated with elas- tic networks. Examples of it may be obtained from the human 1 See chapter on General Methods. 86 MANUAL OF HISTOLOGY. epiglottis, laryngeal cartilages, and the pinna of the ear (Fig. 34). The presence of elastic fibres is proved by their resistance to boiling in acids and alkalies, and their failure to color with carmine. Sections may be made with the knife and prepared in almost any of the ways already mentioned. The appearances already described are not seen in the early development of elastic tissue, but are easily identified in adult Fig. 34. — Section of the boiled and dried auricle of the human ear : a, retiform cartilage ; t>, connec- tive tissue. (Rollett.) life. Even then the elastic fibrils may only be found in the in- terior of the cartilage, while at the periphery the matrix is hyaline. Elastic cartilage is coated over with a delicate mem- brane— the perichondrium. Fibrous cartilage. — This variety is also known as fibril- lated or fibro-cartilage. The matrix has probably no elastic fibrils, but is interspersed with connective-tissue bundles. It is found in the cartilages which make the lips of the joints, the inter-articular cartilages, the cartilaginous deposits in tendons, the cartilage of the symphysis pubis and of glenoid fossae, and possibly in the intervertebral ligaments and sesamoid carti- lages. There is often more or less hyaline material about them. In many instances the line of distinction between cartilage and fibrous tissue is difficult to make out. "Where, however, dis- tinct corpuscles can be demonstrated, the tissue may properly be regarded as cartilage. These bodies are similar to those seen in hyaline and reticular cartilage. Division of the cartilage-corpuscle. — A problem that has THE CONNECTIVE SUBSTANCE GROUP. 87 attracted the study of various histologists for a number of years, since Leidy, in 1849, first directed attention to it, is the mode in which cartilage-corpuscles divide. Various theories have been afloat, each with its special supporters. Dr. W. S. Bigelow, of this country, in 1878 reviewed the subject carefully, pursuing his investigations on the- hyaline cartilage of the triton, tree-toad, frog, various fishes, the guinea- pig, foetal pig, and the human embryo in health and disease. His inquiries were especially concerned with reference to the statement of Buetschli, that in the divisions of the corpuscles, the splitting of the nucleus and cell-body are simultaneous. As the result of Dr. Bigelow' s work, he concludes that the old theory is still tenable, viz., that at first there is a division of the nucleus, and that subsequently a septum is found in the cell-body. After division takes place the matrix of the carti- lage penetrates between the corpuscles, and thus two cavities are formed. This view has received confirmation from very extended and elaborate researches by Schleicher, to which Flemming has also expressed a provisional assent. Structure of the cartilage-corpuscle. — According to Schlei- cher the nuclei are provided with peculiar filaments and gran- ules which undergo amoeboid movements when they are in the act of dividing. In the cell-body of young cartilage-corpuscles he has seen no network, such as has been described by some later writers (Heitzmann, Klein, etc.), though in the adult tissue peculiar linear markings are evident. He thinks that the nu- cleus is not permeated by a network, but is homogeneous. Eeticulated appearances are apt, he thinks, to be the result of using reagents that alter the natural quality of the tissues. According to Flemming, the nucleus of the cartilage-corpus- cles contains a network which gives the appearances described as " coarsely granular." In the drawings of this author the cell-bodies nowhere exhibit a network, but, on the contrary, linear markings, which have often a concentric direction. In many, the internal structure is represented as homogeneous. The conflict of opinion now apparent in this matter, and the marked differences in the micro- scopic drawings of the same object, make it apparent that these topics are still to be regarded as subjudice. Structure of the intercellular substance. — According to Spina there is an intra- cellular substance in cartilage which is directly continuous with the intercel- lular substance, which itself exhibits an extremely delicate network. This MANUAL OF HISTOLOGY. condition, which he regards as an early form of cartilage, undergoes changes, in so far that the intercellular network is enlarged and narrowed so as to give the appearance of fascicles or bundles of parallel fibre.-. The meshes are filled with a finely granular substance which is thought to be partly formed at the expense o: Eba method employed in demonstrating these ap- pearances consisted in taking the articular extremities of frog's bones, im- mersing th&m three to four days in alcohol, then cutting thin sections, and finally, examining them in alcohol. BIBLIOGRAPHY. TlLLMAJrys. ArchiTf-miirosk-Aiiat. X. Bd. X. p. 401. 1874 Bui>ge. A. Archiv f. mikrosk. Anat Bd. XIV.. S. 65. 1837. :?. Aro'iiv f. r^krc=k. Arat. Bd. XIV.. S. 492. 1877 MAMM. Sradien am Knochen u. Knorpel. Wien. med. Jahrb. 1872. V. and H's Bericht Bigelow, W. 5. Arch, i mikrosk. Anat. XVI., i. t87S Schleicher. Ibid. F:.ZMMryo. Ibid. KUBDI nd E. Haras Smith's Atlas of Histology. 1879—1880. BAWtm. Tra::^ technique dTiistologie. 1877. Buetschll Zeitsohr. f. wiss. Zool. 29. p. 200. I ,. de k. Akad. der Wka Li LXXX.. LXXXI. 1879, 1880. CHAPTER VII THE CONNECTIVE SUBSTANCE GROTT.— Continued. BOXE. Theee are two principal varieties of bone known to anato- mists, the compact and the cancellous or spongy. The former is found in the shafts of all the long bones of the body and along the outer surface of all the short and flat bones. The latter occurs in the articular extremities of all long bones and in the interior of all short and flat bones. Compact tissue consists of an unyielding, almost inelastic, massive framework, which is traversed by networks of blood- vessels and lymphatics, and perhaps by nerves. The dense organic substance forming the groundwork of all bone — — is in reality nothing but a form of connective substance almost precisely resembling ordinary fibrous tissue, but which is evenly infiltrated with minute molecules of the carbonates and phosphates of lime and some other inorganic salts. These insoluble matters are so thoroughly intermixed with the fibrous tissue that they give it great solidity, though at the same time they restrict its flexibility, and therefore increase its suscepti- bility to fracture. Like other forms of the connective-tissue series, it contains corpuscles that are disposed in a regular way between lamel- lae, which here correspond to the fascicles of fibrous tissue. The province of these corpuscles is doubtless the same as that of other connective-tissue corpuscles, viz., to preside over the nu- trition of the tissue in which they are found. After decalcification by strong acids, such as the nitric or muriatic, if the residue be boiled it will yield gelatin or chon- drin. These corpuscles that have just been described are not al- 90 MANUAL OF HISTOLOGY. ways easily recognized, and, in fact, have often been ignored by writers of anatomical text-books. They were not detected for a long time, because the capsules in which they are em- bedded received all the attention, and were even called bone- corpuscles. But when it was discovered by Virchow that these bodies had nuclei, and that they could be separated, to- gether with their processes, from the bone, it was supposed that the nutrition of the tissue was maintained through them, acting in the capacity of hollow tubes. This view Virchow at one time supported. Subsequently it was discovered that in- jection fluids could be forced into the canaliculi and round about the corpuscles, so that three facts became assured : (1) the existence of capsules in the bony substance with radiating and anastomosing passages, the lacunae and canaliculi ; (2) the presence of nucleated and branched corpuscles in the lacunae ; and of spaces (3) about the nucleated corpuscles and their processes, suitable for the movement of fluids designed for the nutrition of the part. The structure of bone then became clear, and its similarity with other connective substances well established. These bony canaliculi extend to the wall of the Haversian canal, the great channel conveying the blood-vessels and larger lymphatics. Thus a lymph-canalicular system permeates the bone in close connection with the blood-vessels, bathing every bone-cor- puscle. When a cross-section is made of any long bone, it will be observed that most of the lamellae have a concentric arrange- ment about each Haversian canal (Fig. 35, b). But it will also be seen that there are other groups of lamellae whose arrange- ment is slightly different. For example, at the periphery of the bone their direction is parallel with the surface. Such lamellae may be represented at a. They are known as the intermediate or circumferential (Tomes and De Morgan). Another group, only partly encircling each canal, is known as the peripheric or interstitial, c. The first mentioned, imme- diately about the canal, are the concentric, b. Schaefer believes with Sliarpey that each lamella consists of fibres crossing each other diagonally, and separated on either side by a homogeneous layer. According to Von Ebner, the peculiar cross striations belong only to Canada balsam preparations that are old. These markings are due to the peculiar refractive power of the balsam which fills the canaliculi. THE CONNECTIVE SUBSTANCE GROUP. 91 The arrangement just described is found in all compact bone where there is any considerable thickness, but when, as in flat bones, the cortex is very thin, the lamellae often pursue a straight and parallel course. Some of these lamellae or plates exhibit transverse striations ; others are homogeneous. In Fig. 35 may be seen the lacunae lying between the lamellae. They appear as dark spaces disposed at quite regular intervals and, having their long axes parallel with the course of the lamellae. Laterally each corpuscle gives off numbers of pro- cesses, many of which branch, while all, or near- ly all, anastomose with corresponding branch- lets of other corpuscles- A branchlet is also given off from the end of each corpuscle, and forms a connection with the adjacent bodies lying in the same inter- lamellar space and in the same plane. The Haversian canals form a broad-meshed network through- out the bone, establishing a communication between the central marrow cavity and the external surface of the bone (Fig. 36). The arrangement of parts comprised by each Haversian canal, with its investing lamellae, and interposed lacunae and their anastomosing canaliculi constitutes an Haversian system. Though found mainly in the compact tissue, they may also be seen in the large trabeculae of the spongy substance. As seen in Fig. 36, the Haversian canals form a network of which the longitudinal tubes are the larger and longer. Besides convey- ing blood-vessels and lymphatics they have a certain amount of connective tissue which varies according to the locality, and establishes a more or less complete connection between the con- nective tissue of the marrow cavity and of the periosteum. In young bone this is well seen ; in adult bone the direct continuity fan with difficulty be traced, as the vessels are apt to till the tubes pretty completely. Fig. 35. — Transverse section of human femur, deprived of inorganic material by hydrochloric acid. (Rollett.) 92 MANUAL OF HISTOLOGY. Preparation of dry bone. — In order to study the char- acteristics which have just been described, any human long bone may be taken. It should be stripped of its soft parts, bleached, and well dried. Thin sections are then to be made both in a longitudinal and transverse direction, with a watch- spring saw. Next, cleanse them well in water to which a little bicar- bonate of soda has been added ; then place on a whetstone and grind down by rubbing backward and forward with the finger until they are suffi- ciently thin ; or the sections may be placed between two plates of ground glass and rubbed down. Finally, when so thin that type may be read through them, mount either dry or in Canada balsam or dam- mar varnish. All the char- acteristics already described may then be seen. Preparation of decalci- fied bone. — Another method consists in first removing the earthy salts. If it is desira- ble to accomplish the work rapidly, cut the bone to be prepared into the smallest available pieces and immerse from four to five days in a 10 per cent, watery solution of Fio. 36. -Longitudinal section of human ulna, show- hydl'Ocllloi'ic add. ing the Haversian canals forming meshes. (Rollett. ) m, n , . „ . , . Ihe completion of this process may be determined by testing the bone with a fine cam- bric needle. So long as it meets with resistance, the presence of the bone-earths is certain ; on the other hand, if it enter easily, the process of decalcification is over, and the piece ready for cutting. Now wash thoroughly in water, so as to remove the acid, place in 80 per cent, alcohol, gradually increasing the strength to 95 per cent. The specimen is then ready for use and may THE CONNECTIVE SUBSTANCE GROUP. 93 be treated precisely as any other tissue of the body. If more time is at the disposal of the student, chromic acid may be used in a J per cent, solution. This process is rather slow, re- quiring several months. It may be materially hastened by the use of nitric acid (2 per cent.). It has been found that after immersion in chromic acid for a few days, the soft parts are rendered insensible to the action of other strong acids, such as nitric and hydrochloric, when used in the dilute form. These chromic acid preparations are exceedingly beautiful objects Fig. 37.— Bone lacunae with their processes. (Rollett.) when seen with low powers. The matrix is of a deep grass green. If a thin section is stained with borax-carmine (Arnold's formula) the bone-corpuscles and connective tissue are stained red, and the contrast of color brings out the finer elements very distinctly. Picro-carmine may also be used, and then the muscular tis- sue, if any chance to adhere to the bone, is stained yellow ; or eosine and haimatoxylin may be used instead of borax car- mine, and thus very excellent examples of triple staining pro- cured. Sometimes a saturated solution of picric acid is em- ployed to decalcify, but the excess of acid, after taking out the bone-earths should be thoroughly removed by soaking in 94 MANUAL OF HISTOLOGY. water before immersion in any staining fluid. In preparing a specimen for cutting with the knife it may conveniently be held in the hand, or, if the microtome is used, the bone may be embedded in the ordinary mixture of wax and oil, pith, or liver, according to methods already described. Rutherford re- commends glycerine jelly for thjs purpose. Any of these plans of preparing decalcified bone will reveal the presence of the bone-corpuscles within the lacuna). These will be found to correspond quite closely in size and shape with the cavities. They may also be shown to have a direct continuity with the connective-tissue corpuscles of the perios- teum. In growing bone this is more evident. A nucleus can also sometimes be seen in the bone-corpuscle. In Fig. 36 the lacunae, with their canaliculi, are well shown. Sharpens perforating fibres. — Attached to the outer sur- face of compact tissue, and penetrating the bone at right an- gles, are certain fibres which have been named after Sharpey, their discoverer. Take a flat bone of the skull that has been decalcified, seize pieces with the forceps, tear them out from the surface, and examine in water. In some of the fragments the bundles of fibres will be seen ; in others the lamellse, perforated for the fibres. If a portion of tendon adhere to the bone, and a sec- tion be made through the two at their line of apparent junc- tion, it will be seen that the tendon-fibres are continuous in the bone with Sharpey' s fibres. A ver}' prevalent view is that they constitute the remains of the periosteal processes, which we shall see are largely con- cerned with the ultimate development of bone. Cancellous tissue. — All of the elements of bone, that go to make up a Haversian s}rstem, are found in the cancellous tissue, so that, in this respect, it does not differ from the com- pact. The chief peculiarity lies in the marrow cavities, or channels, as they might appropriately be called, and they indi- cate either, on the one hand, that the bone is passing through a developmental stage ; or that it is being rarefied by a process of retrograde metamorphosis ; or, finally, that it has reached a stadium of repose in either of the first-named changes. These points will be further particularized when the growth and de- velopment of bone is explained, but the reader is now prepared THE CONNECTIVE SUBSTANCE GROUP. 95 for the rather remarkable proposition that compact bone is formed ont of spongy, and spongy out of compact. These marrow channels are a series of branching and anasto- mosing tubes, rich in corpuscular elements and vessels. In young bone the latter are known as red marrow. When a longitudinal section has been made through a tubular bone, it will be seen that the channels are enclosed in an osseous net- work, whose meshes differ much in shape. In the articular extremities they are long and narrow ; at other points, more nearly quadrilateral. There is a second variety of marrow, known as yelloio, which is found in the central cavity of the long bones. The yellow color is due to the presence of fat, though it also contains peculiar, small, colorless corpuscles, not unlike the leucocytes of the blood, and known as marrow-cells, together with the ordinary branched and nucleated connective-tissue corpuscles, also large multi-nucleated bodies that are usually granular and sometimes striated, and blood-vessels. The large corpuscles are the myeloplaxes of Robin (giant-cells). The red marrow also contains marrow-cells, though but few fat-cells. It is remarkable for being the seat of the peculiar nucleated blood-corpuscles that have been described by Xen- mann and Bizzozero. They are transitional between the white and the red in size, and have a uniform yellowish green color (Klein). The authors above referred to found the nucleated corpuscles in the red marrow of the ribs and bodies of the vertebrae ; they resembled blood-corpus- cles that are found in the human embryo, and were regarded as evidence that the bones have bloodmaking properties. Later researches (Orth and Litten) have seemed to corroborate these views, and to have shown that in certain morbid states of the blood, as in carcinoma, phthisis, and syphilis, an effort of this kind is made for the relief of the constitutional infection. Experiments upon dogs have also added further testimony and have shown that after extreme artificial anfemia there is a new formation of blood-globules, in which the nucleated bodies play an active part, together with other elements, such as the giant-corptudes of Hayem, etc. These views, however, have met with opposi- tion, and Rutherford (" Pract. Histology," p. 88) maintains that the nucleated corpuscle is an indication of corpuscular disintegration rather than of new- formation. The periosteum is a layer of dense fibrous tissue closely covering the bone, and connected with it by a thinner layer of 96 MANUAL OF HISTOLOGY. looser texture. The external portion may be composed of sin- gle, double, or treble laminae of varying thickness. The inner or osteogenetlc portion is of great interest and importance, as it contains the osteoblasts, which are active agents in the formation of a great part of all bones, as we shall presently see. Development of bone. — Views as to the method by which bone is formed have undergone great changes within the past few years, and it may be stated that most modern observers have given in their adhesion to the theory that bone is not developed by a calcification of cartilage, but by a long and complicated series of changes inaugurated by the corpuscles of the marrow cavities, on the one hand, and those of the periosteum, on the other. These conclusions have been the result of very extended researches conducted by a variety of methods and upon many kinds of animals. As the mode of growth in man and horned cattle is identical, a good method of procedure is as follows. Take the hoof of a yearling bullock, and, removing the bones, macerate them a few days in a 10 per cent, watery solution of l^drochloric acid and then in chromic acid (gr. ij. — 33.). In a few days they will be decalcified sufficiently to allow of a thin section being shaved off from the surface so as to include parts where ossifi- cation has already commenced. The sections may then be stained in a neutral solution of carmine and mounted. The gradual stages between the advancing bone and the liquefying cartilage can now be studied. Following the changes from the surface of the articulation toward the centre of the bone, there is seen at first, beneath the fibrous layer, a stratum of hyaline cartilage. The corpuscles are long, flattened^ and lie parallel with the surface. Passing to a greater depth they become larger, and increase in number by gradual progression. As these capsules enlarge and their contents multiply, they begin to be arranged about the wall of the cavity, while the matrix gradually wastes away. A little farther and there is a deposit of calcific material in the intercapsular sub- stance. Another step internally and the cartilage capsules have in part coalesced, and now they are beginning to be filled by the marrow tissue pushing up from the central parts of the bone. When the connective tissues and vessels that constitute this arborescent growth have entered the capsules, the corpus- THE CONNECTIVE SUBSTANCE GROUP. 97 cles that line them are called osteoblasts. Whether or not they are identical with the cartilage-corpuscles, or belong to the budding marrow-processes, seems to be a matter of doubt. Klein intimates that the cartilage-corpuscles disintegrate. Ran- vier has seen no proof of it. It is probable that some of the cartilage-corpuscles persist, certainly to a limited extent, and preside over the remains of the calcified cartilage. The bulk of the new bone is made up, however, of new material which is deposited under the form of concentric lamellae about the marrow cavities, most likely by a proliferation of the osteoblasts. These changes may all be observed to advantage in the specimen just mentioned, and the successive gradations of the process can be conveniently magnified, so as to be easily seen, by making sections obliquely to the surface of the bone. With a low power the specimens will have uncommon beauty, as the corpuscles take the carmine well, while the interstitial tissue is of a bright, transparent grass-green. In a vertical section of a long bone, while the process is essentially the same, there are some modifications in the suc- cessive steps. Thus the spongy bone of the epiphysis en- croaches on the cartilage, causing it to be absorbed in the man- ner already described, but the intermediary cartilage, lying between the epiphysis and diaphysis, is seen to have its cor- puscles arranged in long lines parallel with the axis of the bone {"step-ladders"). The bone meshes of the encroaching bone are also shaped in correspondence with the cartilage cap- sules, that is, they are long and narrow. Formation of bone through the medium of cartilage. — The successive changes in this species of bone development have been best described by Klein. According to him the hyaline cartilage that is destined to prepare the way for bone is covered with perichondrium, consisting like the periosteum of two layers. This membrane does not at first contain mature fibrous tissue, but merely the rudiments of it, under the form of spin- dle-shaped corpuscles ; its internal layer, however, is early pro- vided with spherical corpuscles, the future osteoblasts, and is rich in vessels. Subsequently this osteogenetic envelope puts out processes (periosteal processes, Virchow) that penetrate into the carti- lage-capsules, which, melting as the external growth makes its 7 OS MANUAL OF HISTOLOGY. way inward, develop communications between the capsules, so that in this way a cartilaginous network is formed that is filled with the arborescent tissue. This change in the cartilage, which is characterized by absorption and rarefaction, is called cliondro -porosis. At a more advanced stage the cartilage around the oldest channels has become transparent in places, while the walls are irregular, because portions of calcified trabecule project into them. These irregular spaces are called primary marrow cavities. Now upon the walls may be seen, not the cartilage- corpuscles, but the osteoblasts, which are proceeding to develop concentric layers of osseous tissue. When this process has been completed, the osseous tissue will be found to have replaced the calcified cartilage, and true bone has been formed. But this action may be no sooner completed than absorption will again commence, and at first in the last or most internal layer of the Haversian system. This process is essential for the development of the central marrow cavity. After an Haversian system has been removed, the matrix will also disappear. Now, while this cavity is filling up with marrow a gradual development of bone is taking place from the periosteum, which slowly encroaches upon the bone whose formation we have just described. This last stage results in the formation of adult bone. When it has been completed all the first formed bone has been absorbed before it. This periosteal or metaplastic bone is at first spongy, as is all new bone ; in the fulfilment of its task it next appears to form compact bone, and then part of this latter is rarefied, as, for example, along the wall of the central cavity. Thus, as we have already seen, compact bone is formed from spongy, and spongy from compact. The peri- pheric or interstitial lamellae are either the remains of calcified and unabsorbed trabecule, or perhaps the walls of other Haver- sian systems forming sides of the bony network. Formation of bone from membrane. — This second method of bone-formation is seen in the bones of the skull and face. The steps are precisely similar to those already described. The inner layer of the periosteum, which is lined with osteoblasts, produces both matrix and bone corpuscles by a process of bud- ding. The change first begins at the joints of ossification. THE CONNECTIVE SUBSTANCE GROUP. 99 At first the bone is spongy, bnt later absorption takes place — osteoporosis. Around some of the marrow-tubes concentric lamellae are formed, and in this way a Haversian system de- velops. The unabsorbed portions of the trabeculse are thought to constitute the lamellae known as the intermediary. Com- pact tissue is thus formed from spongy. This theory, which has been placed in its present acceptable light by Klein, is very simple and appears to accord with observation, and explains all the phenomena. Yet those who have believed in the direct transmutation of cartilage into bone are still in the field. Kolliker maintains that both views are correct. According to this last named author the differences between primary or primordial and the tegumentary or secondary bones are, from a morphological point Of view, sharp and complete. The former are ossifications of the carti- laginous skeleton. The tegumentary are never cartilaginous at first ; the primordial bones, on the other hand are, without exception, formed from cartilage. The method and manner in which bony tissue is formed is the same in both bones. The pri- mordial skeleton in the lower vertebrates ossifies only in part from the peri- chondrium, in part perichondrally, and, in part, endochondrally. According to Kassowitz, in the tuberosities and spines of the bones the periosteal processes of the periosteum, which develop the bone, are primarily cartilaginous, the fibrillated tissue being converted into hyaline cartilage, which is at first calcified and then undergoes direct conversion into bone. According to the experiments of Strawinsky a transplanted periosteum will develop either bone or cartilage, when the conditions are favorable. The con- ditions of nutrition determine which it shall be. When the supply is best, cartilage i3 formed ; when poorest, bone. The earliest evidences of ossification were seen by this observer between the fourth and fifth days. The formation of vessels preceded that of bone. Absorption commenced between the second week and the second month. The new formation of periosteum is partly derived from the border of the wound and partly from the Haversian canals, which contain a small amount of connec- tive tissue. Development of bone and absorption. — It has been seen that these two processes go on hand in hand. As soon as the periosteum has commenced to deposit new layers of bone on the surface of the primary spongy bone, absorption takes place along the marrow canal. First of all, as we have already said, the innermost of the concentric lamella) yield. In this way the Haversian canals are widened and become Haversian spaces, as they were at first; then the interstitial lamella), and finally 100 MANUAL OF HISTOLOGY. the spaces disappear, and in place of them there is a single dilated central cavity. Howship's lacunas are the pits or lacuna? seen in bone beneath the periosteum. They usually contain a multinuclear corpuscle (giant-cell), which is in some way related to absorp- tion, and, therefore, has received the name osteoclast (KOlli- ker). It has been surmised (Klein) that they are the agents by which an acid is formed that dissolves the lime-salts. AVhether they are developed out of the osteoblasts or not is a matter of uncertainty. All the steps, both in development and absorption of bone, have been carefully studied and placed upon a most satisfac- tory foundation (Lieberkiihn and Bermann). The absorption of bone has also been actually proved by measurements of the bones in children (Schwalbe). By comparing the bones of the third and fourth years of life, it was found that the marrow cavity had enlarged in the latter, while the compact bone had diminished in thickness. The change commenced at the sixth month. This physiological process is closely allied to the pathological one exhibited in rachitis ; in the latter the de- velopment of bone from the periosteum has the character of foetal bone, but the formation of the lamellae is slow and incomplete. It has been claimed that the growth of bone takes place by an expansion of the intercellular substance (Strelzoff), but this is denied (Kolliker, Wegener, Schwalbe, and others). The ossein appears to increase somewhat, but it is at the ex- pense of the bone- corpuscles, which are thereby diminished in size. Formation of callus. — The method is the same as in the de- velopment from periosteum. A corpuscular blastema is devel- oped from the periosteum and intermuscular tissue. This presses in between the fibres and bundles of the loose con- nective tissue, pressing them asunder, assuming considerable volume. This new tissue is hyaline cartilage. In from three to six weeks it ossifies, being in part directly transformed into bone, in part mediately, i.e., through the agency of medullary spaces and osteoblasts. Where the extremities of the bone are widely separated there is a formation of bone in the medullary spaces of the broken ends of the bones. The pre-existing bone- corpuscles have no part in the new-formation. This compact THE CONNECTIVE SUBSTANCE GROUP. 101 bone thus formed will be absorbed in a few months, in its internal portions, by rarefying ostitis, so that the marrow cavi- ties of the broken diaphysis will be in communication. BIBLIOGRAPHY. The student is referred, for further particulars, to Klein's Atlas of Histology, Ran- vier's Traite technique d'histologie, Strieker's Manual of Histology, and also to the following recent writers : Schaefer. Pract. Histology. 1872. Liebebkuhn and Bermann. Ueber Resorption der Knochensubstanz. 1877. Aufrecht. Ueber Riesenzellen in Elfenbeinstiften. Med. Centralblatt, No. 28. Jahresb. d. Fortschritte der Anat. und Phys. 1878. Arnold, J. Virchow's Archiv. Bd. 71, p. 17. 1877. VON Ebner. Sitzungsbericht der Wiener Akad. III. Abtheil. Bd. 75. Hofmann und Schwalbe's Jahresb. 1878. Kassowitz. Med. Centralblatt, No. 5. Hofmann und Schwalbe's Jahresb. 1878. Schwalbe. Sitzungsb. der med. naturwiss. Gesellschaf t zu Jena. 1877. H. und S.'s Jahresb. 1878. Strawinsky. Ueber Knochenresorption. H. und S.'s Jahresbericht, p. 109, 1878. Litten, M., and Orth, J. Berliner klin. Woch. No. 51, p. 743. 1877. KoLLiKER. Entwickelungsgeschichte. V. und S.'s Jahresb. 1878. CHAPTER VIII. THE TEETH. From the standpoint of descriptive anatomy, every tooth is composed of three parts : (1) the crown, that portion which stands above the level of the mucous membrane of the gum ; (2) the neck, a constricted part at the level of the gum ; and (3) the root, which terminates in one or more fangs, and is firmly embedded in the alveolar process of the jaw. Each fang also is pierced from below by a canal, which extends up into the crown, and is filled by a soft material rich in nerves and ves- sels, called the pulp, which has the special province of sup- plying nutriment to the dense tissue about it. From a histological point of view, every tooth may be di- vided into : 1, enamel ; 2, dentine, or ivory ; 3, cement, or true bone. The enamel forms the covering for the crown, the cement for the root ; but they meet at the neck, and there the cement slightly overlaps. The ivory or dentine lies intermediate be- tween the outer coatings and the pulp. The enamel. — This substance, which is the hardest met with in the body, consists of a series of long polyhedral columns grouped in bundles and disposed mostly at right angles to the surface of the dentine which lies beneath it. Each column or pillar is a hexagonal prism, having a diameter varying between Tofiro and -g^go inch. When viewed in cross-section these col- umns look like a tesselated pavement. They are not, however, closely applied to one another, but have interspaces which are said to be filled with a homogeneous substance or fluid. All of the groups of columns do not stand vertical to the dentine ; some are parallel to it, and thus are interwoven with the vertical ones. This crossing of the fibres produces an alternation of light and dark bands (Fig. 38, 1). But there are other systems of markings. In the same figure are wavy THE TEETH. 103 lines running parallel to the surface. These are the " brown, parallel stripes of Metzius." They pursue a somewhat curved course. No unity of opinion exists about their significance, one (Hertz) attributing them to deposits of pigment, another (Von Bibra) to the pres- ence of the oxide of iron. Still other striae are ob- served, and are thought to represent the zigzag or spiral course of the enamel prisms. It is observed that when the prisms are isolated, which can be accomplished by immersion in a dilute hy- drochloric acid solution, they have a somewhat spiral form, and have bulging sides and cross markings, the signifi- cance of which will be alluded to at another place. Near the line of the dentine there are spaces between theprisms which are continuous with the cavities in the dentine. These are called the in- t( rf /lobular spaces of CzermaJc. They also oc- cur at irregular intervals in the dentine. In young subjects there is a delicate mem- brane covering the sur- face of the enamel. It is composed of laminated epithelial scales, and corresponds to the corneous layer of the skin, of which, indeed, if represents the vestiges. The dentine or Ivory (Fig. 38, 2) consists of a dense and hard matrix impregnated with the salts of lime. It contains Fig. 38.— Premolar tooth of the cat, in situ. Vertical section, magnified 15 diameters. 1, enamel with decussating and parallel stria; ; 2, dentine with Schreger's lines ; Ii, ce- ment ; 4, periosteum of the alveolus ; 5, inferior maxillary bone. (Waldeyer.) 104 MANUAL OF HISTOLOGY. numerous passages having, like the enamel prisms, a direction at right angles to the surface of the bone. These passages, the dentinal canals, are united with one another laterally by minute oblique branches, and form undoubtedly open channels of communication between the pulp cavity and the spaces be- tween the enamel prisms in the crown and the bone lacunae of the cement in the fang. Each canal is lined with a particularly delicate and resistant membrane, the den- tinal sheath of Neumann. Upon the internal surface of the dentine, or the external surface of the pulp- tissue, is the layer of odontoblasts (Schwann). These cor- puscles, according to Waldeyer, have long branching processes ex- tending in three directions, inward into the pulp-cavity, outward through the dentinal channels, forming the dentinal fibres of Tomes, and laterally so as to form connection with adjacent corpus- cles. On the outer surface of the dentine the canals connect with the interglobular spaces of Czer- mak, and they in turn are con- tinuous with interstices between the enamel prisms. The dentinal tubules never appear to be in di- rect communication with the enam- el spaces, but only mediately, as has been described. These cavi- ties are filled with protoplasmic material. Those immediately adjoining the cement are small in size, and form what is known as the granular layer of Tomes or PurJcinje. Dentinal globules (Fig. 39, 2) is the name given to certain spheroidal masses that are regarded (Waldeyer) as calcified remains of the corpuscles in the spaces. The contours of these masses correspond in outline with those of the interglobular spaces. Fig. 39. — Canine tooth of man, present- ing a portion of the transverse section of the root : 1. cement with large lacunas and parallel striae ; 2, interglobular substance ; 8, dentinal tubules. Magnified 300 diame- ters. (Waldeyer.) THE TEETH. 105 Beneath the cement the intercommunication of interglobu- lar spaces and bone-lacunse is well shown. The interglobular substance is apt to be present in layers ; the lines which are then called the incremental lines of Salter, are supposed to show that there has been growth by successive stages. The lines of Schreger (Fig. 38, 2) are also waving parallel lines ; they are thought to be due to the curvature of a series of adjacent fibres. In some instances vascular channels have been found in the dentine, which has acquired the name osteo or vaso- dentine. In pathological conditions masses have also been found containing bone-lacunse. They have been called odonto- mata by Virchow. The cement is true bone-tissue, containing lacunae and canaliculi, and in them the bone-corpuscles with their pro- cesses. The matrix is also subdivided into lamellae. The peri- osteum of the gum dipping down into the bony socket from the surface of the gum forms a coating over the cement. Oc- casionally Haversian canals and blood-vessels are seen where the cement is thick (Salter). Sharpey' s fibres may also be seen, according to Waldeyer. The pulp is a substance that belongs to the connective- tissue series. Adjoining the dentine are two layers of corpus- cles. The nearest are long cylindrical bodies whose oval nuclei are distant from the dentine. Wedged in between them, and forming a layer intermediate between them and the pulp, are peculiar branched corpuscles of a spindle or pyramidal shape. According to Klein, these latter send processes into the den- tinal tubules, while, according to Waldeyer and Boll the odon- toblasts send the fibres, and are also connected to one another by lateral processes. The pulp tissue is very rich in non- medullated nerves ; their prolongations penetrate between the odontoblasts, but it is a matter of question whether they enter the dentinal canals. Capillaries are abundant and form close networks in the pulp. The lymphatics are said to accompany the blood-vessels and to be surrounded by endothelial sheaths. Development of the teeth. — Waldeyer, whose views on the teeth are the most complete and satisfactory extant, makes the following succinct statement : "The anatomical model of a tooth of a vertebrate animal is a large papilla of the mouth or of the pharyngeal mucous 106 MANUAL OF HISTOLOGY. membrane, which in consequence of chemical and histological conversion of its constituents has acquired a remarkable degree of hardness, and according to whether the connective-tissue substance of the papilla participates in the hardening or not, two large groups of teeth are distinguished — dentinal teeth and horny teeth. The horny teeth are by far the most simple in Fig. 40. — Vertical section of the inferior maxilla of a hu- man fcetus,measuring 11 ctras. from the vertex to the coccyx. Magnified 25 diameter?. 1, dental groove; 2, remains of the enamel germ ; 3, enamel organ presenting externally epitheli- um, as also where it forms the enamel germ of the papillae of the dental sacculus ; 4, secondary enamel germ : rudiment of the permanent tooth ; 5, dental germ : 6, lower jaw ; 7, Meckel's cartilage. (Waldeyer.) Fig. 41. — 1, various forms of odontoblasts, with the three kinds of processes ; 2. three enamel cells, with a few cells (if the stra- tum intermedium attached : 3, an enamel cell, with a small portion of enamel ; 4, fragments of ena- mel fibres from young and soft enamel ; 5, old enamel fibres with transverse stria? and rounded ex- tremities. (Waldeyer.) their structure. They appear as more or less developed papil- lae covered with a thick horny investment. They are never continuous with portions of the skeleton, but constitute the transition to other horny formations, as hairs, stings, etc." "In the dentinal teeth the connective-tissue matrix of the papillae plays a most important part in the hardening process, which here proceeds in a manner precisely similar to the ossi- fying process, except that no true bone is formed, but only an allied substance, of much harder consistence, and differing more or less in histological structure, termed dentine. The epi- thelium of the tooth papilla? either atrophies to a rudimentary THE TEETH. 107 horny investment — the cutlcula (membrane of the enamel) — or it becomes elongated in a remarkable manner into long, petri- fied prisms, which collectively invest the dentine and are known as the enamel." Preparations for the development of the teeth take place at a time when the epithelium of the mucous membrane of the mouth is found growing downward, like a solid peg, with a rounded extremity. This has been called the primary enamel organ. As a next step, the material which is to give form to the tooth pushes upward as a papillary growth, and meeting the epithelial peg, pushes in or invaginates its rounded extremity. This is the tooth papilla, and as it pushes upward the pri- mary enamel organ becomes the secondary enamel organ, or the enamel cap. We have now two tissues which are embedded in the soft embryonic substance, that happens at this early period to be gelatinous. That portion of it immediately surrounding the papilla and cap is called the tooth-sac. The papilla, which becomes highly vas- cular, is covered, on its outer surface, by the odontoblasts, a layer of columnar epi- thelial corpuscles, which elongating, are transformed directly into the dentinal sub- stance at their outer extremity. According to Kolliker and others, they excrete the dentine. The former view seems to have the most weight of argument in its favor, but it seems less likely that the odon- toblasts both make the matrix and send fibres into the tubulae. The view of Klein already given seems to be preferable, and in conformity with what we know of other connective substances. The separation of the tooth-sac from the mucous membrane is effected by the gelatinous tissue, which, gradually closing in the neck of the sac, finally cuts it off. The epithelium of the enamel cap is abundant and of various kinds ; into it push a number of papillary processes downward from the gelatinous tissue. Later the enamel cap is changed into three membranes. Fig. 42. — Longitudinal sec- tion of a milk tooth from the foetal sheep, carried through the margin of the dentine pulp and adjoining portion of the enamel organ. Magni- fied 2(10 diameters. 1, dental sacculus ; 2, external epithe- lium and stratum interme- dium here united to the in- ternal epithelium or enamel cells ; 3, after the disappear- ance of the enamel pulp ; 4, young layer of enamel de- tached from the enamel cells ; 5, dentine ; 6, odontoblasts ; 7, part of the dentine pulp. (Waldeyer.) 108 MANUAL OF HISTOLOGY. The middle membrane is a peculiar cellular network, formed by the transformation of the middle epithelium layer into a network of cells, below which there is a deposit of a hyaline material. The inner membrane is formed of cylindrical epithe- lial bodies, which are called enamel-cells ; outside of them are one or more layers of polygonal cells ; they form the stratum intermedium of Hannover. The outer membrane is composed of several layers. Finally, the middle membrane disappearing, the outer and inner membranes are brought into close apposition. Development of the enamel. — This is formed by the enamel- cells {inner epithelium, Kolliker), presumably in the same way as the dentine by the odontoblasts. There is a direct con- version of the outer extremities of the enamel-bodies into en- amel. Kolliker, Hertz, and Kollmann, however, regard the enamel as an excretion from the enamel-cells. The former view appears the more natural, especially as the enamel-prisms are continuous with the enamel-cells, having the same form and shape. The successive stages of growth, it is believed, give rise to the transverse markings. Whether or not, in the interstitial substance of the enamel, there are corpuscular elements (Boedecker), is a matter that will require further investigation. The outer membrane even- tually gives rise to the cuticle covering the enamel. The development of the cement takes place precisely as bone is produced, viz., from the periosteum, or, which is the same in this instance, from the fibrous tissue of the tooth-sac, the periodontium. BIBLIOGRAPHY. The following1 systematic works and journal articles may be consulted : Retzius. Muller's Archives. 1837. Kasmyth. Med.-Chir. Trans. Vol. 22. 1839. Kolliker. Man. of Human Histology. 1853. Wenzel. Arch. d. Heilkunde. 1868. Henle. Anatomie. 1871. Stricker. Manual of Histology. Am. Ed. 1872. Tome3. Manual of Dental Anatomy, Human and Comparative. Lond., 1876. Owen. Comparative Anat. and Phys. of Vertebrates. 1866. Boedecker. Dental Cosmos. XXL, 409— 416. Phil., 1879. Heitzmann. Microscopic Anat. of Human Teeth. Med. Rec, N. Y., 1879. XV., 187. Klein. Atlas of Histology. 1879—80. CHAPTER IX. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. We may gain a clear conception of the nervous system in its general outlines by remembering that it consists essentially of a series of delicate cords which, on the one hand, proceed from the nucleated bodies of the gray matter, conveying voli- tional impulses to the periphery of the organism ; or, on the other hand, of sensitive peripheral extremities that take up the impression of external objects and carry them back to the cen- tral gray substance. In either case both the conducting cords and the central corpuscles of the gray matter possess no distinctive differences, such as may be appreciated by the microscope, while, on the other hand, the peripheral termini appear under many different forms, the peculiarity of ending being dependent in part upon the type of tissue in which they are found, partly upon the office they have to perform, and partly upon other causes that are unknown to us. The nerve-centres are located in the brain, spinal cord, and in the ganglia of the cerebro-spinal and sym- pathetic system. The methods of nerve-terminations that have been described may be briefly enumerated here. They are by (1) peculiar terminal bodies, (2) loops, (3) networks, (4) end bulbs, (5) proto- plasmic bodies (cells), (6) free or pointed extremities. Nerve-fibres. — Of these there are three kinds that have distinctive differences : 1. The myelinic or medullated fibres. 2. Fibres of JRemak. 3. Ultimate fibrils. Intermediate forms, such as have been described by various writers, under the names of protoplasmic processes, primitive fasciculi or naked axis- cylinders, varicose cylinders, etc., will be noticed in other con- nections. Myelinic fibres.— These are also known as the medullated. 110 MANUAL OF HISTOLOGY. To the naked eye they appear white and glistening, and are the main constituents of the peripheric nerves, though they occur in less number in the sympathetic and also in the brain and cord. Each fibre is made up of three distinct parts : (a) a central cylindrical cord, the axis-cylinder, about which is a (b) coating of soft homogeneous fatty material, called myeline (medulla, white substance of Schwann), forming for the axis- cylinder a sort of tubular sheath, while exterior to both is a delicate membrane or envelope (c), the sheath of Schwann or primitive sheath.1 These fibres run a parallel unbranching course, except near their termini or origin, and are surrounded by a connective-tissue coating of varying thickness. Their diameter varies also according to their situation and the degree of their tension or relaxation. In the nerve-trunks the average diameter lies between ^ and -j-^j- millimetre. In the brain they are described as having sometimes a diameter of -^.millimetre, but it is difficult to determine the presence of a medulla in such email fibres. To study the properties of a myelinic nerve, we may take a portion of the sciatic from a frog that has just been killed. Having removed it with care and placed it in a drop of water on a slide, we should separate the fibres carefully with needles, taking care not to tear them. Then adjusting a covering glass, it will be seen that from the broken end of the nerve a soft substance is exuding (Fig. 43, b) ; in a few minutes it is pushed off in the form of drops of irregular shapes (Fig. 43, c). This material is the myeline or medulla. It will be seen to re- fract the light strongly, and show concentric markings. It will also be seen that each fibre has a double contour and is divided at tolerably regular intervals by transverse divisions, which are now known as Ranmef s nodes. (See Fig. 47.) Midway be- tween each node we may perhaps see an oval body surrounded by a broad expansion of protoplasm. In a few fibres we may even see that a fine thread-like process is projecting from the broken ends of the nerve-fibre — the axis-cylinder (Fig. 43, d)~ while the whole fibre is enclosed by a delicate tightly investing membrane, the sheath of Schwann. Possibly we may also see the 1 A most unfortunate source of confusion among histologists has arisen from the use of the word neurilemma, which by some is spoken of as synonymous with Schwann's sheath (Frey), and by others as the connective tissue which binds the nerve-fibres together (Klein, Rutherford). We shall avoid the term altogether. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. Ill oblique or arrow markings (incisures of Schmidt) (Fig. 43, f), which seem first to have been accurately described by Schmidt, of New Orleans, later by Lantermann, of Cleveland, Shaw, and others. The same appearances can be also obtained by the use of iodized serum. The double contour is not visible in all the myelinic nerves, but is most marked where they show varicose swellings, a con- dition that is due to a preponder- ance of myeline at the enlarged point. From this fact and anoth- er, that the drops of myeline when separated from the fibre show the same double contour, it is argued that the double marking in the fibre is due to a refracting (double) of the myeline, and has nothing to do with the membranous sheath. These varicosities just mentioned are not to be confounded with the bulgings of the ultimate fibrils, or with the "necklace" appearances seen in the course of the fibres of Remak, both of which latter may probably be regarded as artificial productions, either from stretching in the act of teasing or from the imbibition of water. In the brain of the calf they are frequently seen, and they are said to be found in the intracranial part of the olfactory, optic, and acoustic nerves. The fibres in which this change occurs are usually quite small. Staining in pier o-car mine. — This reagent has been recommended by Ranvier factorily prepared by Rutherford's process.1 tions not to injure the nerve in removing it, mount in the solu- 1 He takes 100 c.c. of a saturated solution of picric acid. Next he prepares an ammoniacal solution of carmine by dissolving one gramme in a few c. c. of water, with the aid of an excess of ammonia and heat. He then boils the picric acid solu- tion on a sand-bath, and when boiling adds the carmine solution. The mixture is Fig. 43. — a, Myelinic fibre in a state of " coagulation ; " 6, myeline exuding from the broken end of the fibre ; c, drops of mye- line .separated from the nerve-fibre ; d, axis cylinder ; e, nucleus of Henle's sheath ; /, arrow markings. It is satis- Taking precau- 112 MANUAL OF HISTOLOGY. tion. The nuclei will then be stained a brick-red, while the sheath of Schwann, and, in fact, the whole nerve, will be stained yellow. It is said that, if the axis-cylinder projects, it will be stained a bright red, though twenty-four hours may be required to effect the staining. In my hands picro-carmine has not proved so successful a coloring agent as some others. Staining icith the nitrate of silver. — The sciatic or any peripheral nerve may be employed. Expose it without re- moval in a frog that has just been killed. Then dry up all fluid from about it, and pour on a solution of the nitrate (1 to 1,000). In this way the nerve-fibres will be made rigid. They are then to be removed with a pair of delicate scissors, and placed in a flat vessel containing a little more of the solution. After a few minutes the nerve will look turbid, and then it should be cut out and washed in distilled water, and exposed to the sunlight. In a variable time (ten to fifteen minutes) the turbid appearance will give way to a brown coloration. Exam- ining a single funicu- lus or bundle in gly- cerine, it will be seen that it has an endothe- lial coating of one or more layers (Fig. 44). If another funiculus be separated with fine needles,1 the same care being taken to spread the fibres apart and not tease, and so lacerate them, it will be seen that each fibre con- tains a series of Latin crosses at certain pretty regular intervals. The transverse bar of the cross corresponds to the "annular constriction" seen in Ranvier's node, while the axis-cylinder forms the longitudi- nal bar. Close observation with high powers will show that this latter is marked by transverse lines of a dark brown or Fig. 44.— Funiculus or Nerve Bundle covered with Endothe- lium (Epithelium). From the sciatic of the frog. — Hartnack, object. 4, oc. 2. then evaporated to dryness, the residue dissolved in 100 c.c. of water, and filtered. If the solution is not clear, he adds more ammonia, evaporates, and then dissolves as before. 1 Milliners' are the best. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 113 black {Frommanri 's lines). It appears probable, as Ranvier explains, that, owing to the break in the myeline, at the "an- nular constriction," the particles of silver gain an entrance to the axis-cylinder at this the only unprotected spot. If the action of the salt is long con- tinued, the axis-cylinder is col- ored for a somewhat longer distance. The transverse bar seems to be formed of two conical segments set base to base. The position of this bi- conical segment usually cor- responds in position with the "annular constriction," but .. , n ,-. , ,1 Fig. 45. — a, Kanvier's disk ; &, Frommann's lines; it WOllld appeal* that they may c, nucleus of interannular segment. be separated, for, when the tissue of the nerve has been put upon the stretch, the biconical segment may be drawn away from the annular constriction. (See Fig. 45.) Kow, as Schwann's sheath is understood to end at the an- nular constriction, where it is cemented to the next adjoining segment just as epithelial cells are joined together, the biconi- cal disk may belong to the axis-cylinder exclusively, and merely constitute a dividing line between its segments. Ac- cording to Engelmann, the axis-cylinder is divided up into portions corresponding with the interannular segments. According to Rawitz, Schwann's sheath does not end at the nodes, but is continuous with the sheath of the adjacent interannular segment. Staining of the nerve in osmic acid — semi-desiccation. — Osmic acid is one of the most valuable reagents for histological work, and the method now to be described (a modification of Ranvier' s') succeeds well. Take the frog's sciatic, or any other peripheral nerve, carefully remove a portion with the surround- ing tissue, keep the whole extended with pins, upon a flat bit of cork, and then dip it into a vessel containing a 1 per cent, watery solution of osmic acid.2 The vessel is then to be exposed to the light. The whole nerve will be more or less thoroughly 1 Lemons sur l'Histologie du Syatome Nerveux, Paris, 1878. 1 The solution should, of course, have beea kept in a dark bottle away from the light. 114 MANUAL OF HISTOLOGY. L. stained in a few hours. The external portions, however, will be stained in a few minutes, and they may be removed by care- ful separation with fine needles. To mount, take a glass slide and slip it under the nerve-fibres, while the needle is employed to carry them up on to a dry part of the slide where they can be placed side by side. Then remove the excess of water with bibulous paper, and let the fibres get so dry that they adhere to the slide. Place about them a ring of tis- sue-paper, so that when the cover is adjusted it will not press upon the fibres. Fix the cover at different points with paraffine, then put a drop of glycerine upon one side, and a drop of water upon the other. The union of water and glycerine should be allowed to go on for twent37-four hours in a damp place. The con- strictions and arrow-markings are usually well seen. The nuclei also are occasionally to be found in a niche of the myeline. These bodies, however, are better seen in specimens that have been a short time (fifteen or twenty minutes) in osmic acid, and then in picro-carmine a few hours. It still is a question among histologists whether the arrow-markings are artificial or not ; each of the sections lying between the markings is called the cylindro-conical segment {Hohlcy Under, Kuhnt). (See Fig. 43.) Transverse sections of myelinic nerves. — Certain points are best seen by making trans- verse sections. Prepare the sciatic of a frog or any of the human peripheral nerves by im- mersing a few days in a sherry-colored solution of bichromate of potash, or in Mueller's fluid,1 and then in 90 per cent, of alcohol, until the tis- sue is hard enough to cut. Then it is to be mounted in the microtome with wax and oil of about its own consistence. Sections are to be made with the razor; or it may be mounted in elder-pith in the following way : bore out from the centre of the pith-cylinder a cylindri- 1 The well-known eye-fluid, of which the composition is : Bichromate of potash, 2 to 2% grammes; sulphate of soda, 1 gramme; distilled water, 100 grammes. Fig. 46. — Human myelinic nerve : a, In- terannular segment ; b, Ranviers node ; c. nu- cleus of the interannu- lar segment sunonud- ed by granular proto- plasm ; d. Henle's sheath with nucleus. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 115 cal hole a little larger than the trunk of the nerve, then im- merse the whole in water, and the pith will begin to swell. As soon as it has firmly embraced the nerve, sections may be made with the knife. Ammonia-carmine will stain the axis- cylinder well, but the outline of the cut will appear irregular rather than round. This appearance is doubtless artificial. In my hands, borax-carmine ' has proved much better than the ammonia-carmine, as it diffuses very little, and much of the excess may be removed by dilute acetic acid (about i percent.), in which the specimen should remain, from a few seconds to a minute or two, until it has become bright to the eye. The fur- ther steps in the process of making a permanent preparation are the same as those for other specimens; i.e., it may be mounted in glycerine and water, or clarified by clove-oil and mounted in dammar varnish or Canada balsam. Preparation by the bichromate of ammonia. — Ranvier em- ploys of this a 2 per cent, solution, allowing the specimen to remain, with frequent changes of the fluid, from two or three months to a year. The sections are to be stained in ammonia-carmine or picro-carmine, and mounted in glycerine. It will then be seen that immediately about the axis-cylinder is a sheath. This is called by Ranvier the sheath of Mauth- ner, from the author who described it. (See Fig. 46, b.) Specimens prepared J^'$^^A£^Z in the ordinary way, by long immer- j-mn*-i **-««-* sion in Mueller's fluid alone, or sub- sequently in the chromic acid solution (gr. ij. — 1 j.) and stained with ammonia-carmine, occasionally show the same thing. Sometimes histologists find that embedding in gum succeeds best in securing these transverse sections of nerves. The diffi- culty of the task is one of considerable moment. The method is as follows : Take a fresh nerve, harden it in osmic acid (1 per cent., if it is desirable to expedite the process, or TV per cent, if it is not necessary to conclude the examination the same day). Then, when the nerve is thoroughly blackened all through, ■The powder is prepared by Eiraer & Amend, of this city (205 to 211 Third Avenue), according to Arnold's formula. The strength required i? gr. xv. — §j. distilled water. 116 MANUAL OF HISTOLOGY. it is to be immersed in water for a few hours ; then in 90 per cent, alcohol, and then in a weak solution of gum-arabic, which fills the interstices between the bundles, and finally in strong alcohol (95 per cent.), which hardens the gum sufficiently. The sections, cut as thin as possible, should be placed on a slide to remove the excess of alcohol, which may be done with filter-paper. A drop of water is then to be added ; about the cover put a few drops of carbolized water ; remove to a damp place. At the end of twenty-four hours the gum will have dissolved, and then the glycerine may be allowed to enter slowly without displacing the elements (Ranvier). In examining such cross-sections, the medullated nerves will present various diameters, and the contour of the myelinic sheath will vary in width and outline according as* the cut comes through the broadest part of the arrow-marking, or through the thin overlapping parts. (See Fig. 43.) If the cut chances to pass close to the annular constriction, no myeline will of course be seen. For these reasons, the cross-sections of such nerves, when stained with osmic acid, are very different. Modern conceptions of myelinic nerves. — The specimens that have been studied according to the methods given will not have shown any termination of the nerves, or any division, either into trunks of any considerable size or into the fibrils of which they are said to be composed. They do, however, as we have already said, divide both near their origin and near their termination. It is presumed that each fibril of which the axis- cylinder is composed passes directly through from its point of origin of the nerve-centres, to its final point of distribution, without branching. It is difficult, however, with the instru- ments in ordinary use, to see any distinct marks of fibrillation in cross-sections of the axis-cylinder, and it is in them that we should expect to see them best. The ideas of Ranvier are well worthy of consideration, as he has given more form and solid- ity to our conception of the intimate structure of a myelinic nerve-fibre than any previous writer. According to him, each section of nerve between the annular constrictions represents an ultimate morphological element. It is, in fact, a tubular cell, whose proper external portion (the membrane of the cell, according to common phraseology) is the sheath of Schwann, while the myeline or medulla fills the interior, just as in adi- pose tissue a globule of oil fills out and distends an ordinary GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 11 7 connective- tissue corpuscle. Each of these bodies, which he calls an interannular segment, begins and ends at the constric- tion. It contains a single ovoid flattened nucleus, which fills a niche in the myeline, and is surrounded by a broad, thin ex- pansion of protoplasm (the body of the corpuscle). The axis- cylinder has nothing to do with this body that we have de- scribed, except that it pierces it. Instead of stopping short at each constriction, it goes on indefinitely. As we have already seen, the annular constriction and the biconical disk are not always at the same point, which argues strongly for Kanvier's views. The myelinic sheath probably protects the delicate fibre from external injury, but whether it also insulates it, is problematical. In the foetus all nerves are devoid of myeline. Fibres of Remcik. — These are called by some the amyelinic or non-medullated fibres, by others the pale, gray, or gelati- nous fibres. The term Remak's fibres has come into use re- cently as the distinctive name for certain nerve-fibres abound- ing in the sympathetic, as distinguished from others which also contain no myeline, and are found in the cranial portions of the optic, auditory, and olfactory nerves. Each fibre is marked with oval nuclei at pretty short intervals, and has an indistinct longitudinal striation, probably the evidence of fibrils such as are believed to exist in the axis-cylinder. The nuclei are imbedded in a homogeneous sheath. There being no breaks in the continuity of the fibre, there can be no sheath of Schwann in the sense that has been described. In diameter each fibre va- ries between -^ and Th> millimetre. In 1838 Remak first called attention to them, but his views were received with disfavor. More recently, Max Schultze, Frey, Leydig, and Henle have joined in representing them as long, cylindrical, continuous, slightly striated, and dotted with nuclei. The fibres of Remak are found in great abundance in all the nerves of the organic system, but they also exist in all the mixed nerves, varying with the kind of nerve and the animal. They are not found in special nerves. The pneumogastric of the cat is well adapted for the study of them, as the myelinic fibres are present in considerable quantity, and make the mechanical separation of the bundle easy. Associated with them, fibres are often seen, that are shown in Fig. 48, c. They are delicate, run a wavy course, and sometimes exhibit curious varicosities (a), (necklace appearance). The nuclei are placed at about the 118 MANUAL OF HISTOLOGY. same distances apart as in the other form of fibre already men- tioned. Preparation in osmic acid and picro-carmine. — Remove the pneumogastric in the following way, from a cat that has just been killed : Having exposed the nerve, slip under it in situ a long narrow strip of cork, to which, pin down the nerve with some adjacent tissue, all of which may be removed at once and placed in a solution of osmic acid (1 — 1,000) for twenty-four hours ; the nerve may then be separated from its attachments and placed in the picro-carmine solution for still another twenty -four hours. The excess of the col- oring agent may be removed by dipping for a few seconds in acetic-acid solution (| per cent.), and then the nerve may be placed in alcohol, afterwards in water, and fin- ally mounted in glycerine. It will be seen that the nerve- fibres are stained a reddish yellow, while the nuclei are brick-red. The picric-acid yellow is apt, however, to diffuse. Careful separation of the fibres may show that they branch, as shown in Fig. 48, A, B ; and yet this char- acteristic, which Ranvier in- sists upon, is by no means easy to see in most of the fibres, in fact it requires much care- ful work before it is apparent. The myelinic nerves will be dis- tinguished by their greater average size, their dusky, granular medulla, broken at points, and by the axis-cylinder, which, if it does not project, may be seen winding spirally along be- neath its medullary coat. In them, too, as a rule, each in- terannular segment contains but one nucleus. Preparation of ItemaJc' s fibres in hematoxylin. — One of _r Fio. 48. — Fibres of Remak. A, Pneumogastric of the cat — hematoxylin specimen : a, nerve nu- clei ; 6, appearances of branching ; c, connective- tissue sheath. B, Same. Picro-carmine specimen. The branching in this case is more evident. C, Same — hoematoxylin specimen. The necklace ap- pearance is fthown at a. GENERAL HISTOLOGY- OF THE NERVOUS SYSTEM. 119 the most rapid and successful methods is by the use of hsema- toxjlin. The pneumogastric nerve of a cat is removed and immediately placed in the hematoxylin solution ; then, after thorough staining, which may only take a few minutes, in dilute acetic acid ($ per cent.), and finally mounted in gly- cerine. In this way the nuclei will be stained a beautiful pur- ple, while the fibres will be unaffected. The number of nuclei and absence of medulla will serve to distinguish the fibres of Remak from the medullated. It is* difficult by any method of preparation to see that there are any precise limits to the lon- gitudinal lines in the fibres, i.e., that the striation is due to little, short, narrow rods, lying side by side (Ranvier). The nitrate of silver demonstrates no transverse markings and no constrictions or crosses. There is but little likelihood in these specimens to mistake the fibres for connective-tissue bundles. In the first place, the nuclei, and what cell-bodies happen to be about them, of the one, are small, flattened, ovoid bodies occurring at pretty regular intervals, while the connective-tis- sue corpuscles are usually larger, longer, and, though they may appear oat-shaped, when the side is turned to the observer, are broad plates with irregular edges when seen flatwise. In the second place, the fibres run their course in long, narrow bundles, as no connective tissue does. Ganglionic bodies. — Of these there are three kinds : 1. Those that are connected with the spinal and some cerebral nerves. 2. Those found in the gray substance of the brain and spinal cord. 3. Those in the ganglia of the sympathetic sys- tem. These bodies are of such large size that they may often be seen with the naked eye. In the human species the}r are usually in close connection with the origin of the nerves, though they also may be interspersed at points through the course of the fibres or may be present near their points of distribution {ganglia of AuerbacJi). Their immediate connection with the nerve-fibre is made in the following ways : 1. A large process, which does not at first appear to branch, passes off, and is continuous with the axis-cylinder. 2. Fine branches are given off from one or more corpuscles, and, uniting, contrive to form a nerve-fibre (either a fibre of Remak or a myelinic fibre). 3. These branches after combination may pass through a gangli- onic corpuscle, which then is called bipolar (Gerlach, Wal- deyer). In the sympathetic system we have the unbranched 120 MANUAL OF HISTOLOGY. process and the superficial or spiral fibre, which corresponds to the branched fibre of the ganglionic bodies of the brain and spinal nerves. Ganglia of the cranial and spinal nerves. — These organs, which appear to the naked eye as nodular enlargements of the nerves with which they are connected, consist of groups of peculiar large corpuscles which are interspersed among the nerve-fibres. In shape they are usually large and ovoid, or pear-shaped. About and between them are bands of connective tissue studded with nuclei, forming for each separate body a kind of capsule ; the vascular supply to them is liberal. The contents of these bodies are soft, elastic, and beset with gran- ules. They have a large, globular, or ovoid nucleus or nucleo- lus, and may appear to have no process, or to be unipolar or bipolar, as in the lower animals.1 Examination of the Gasserian ganglion in the frog. — Take a frog that has just been killed, or, better still, one that has been some time in Mueller' s fluid ; trace the fifth nerve into the skull. On it will be seen, just within the bone, a yel- low enlargement. This is to be removed with forceps and teased with needles. The ganglionic bodies usually appear to have no processes (apolar), but they probably have one or more, and the apparent absence of them is because they have been torn off in teasing. Examination of the ganglia of the spinal cord. — Take the cord of a bullock, and prepare it while fresh, or after it has been a greater or less time in Mueller' s fluid, or a weak so- lution of the bichromate of potash (gr. xv. — 3 j.). Having cut it into transverse segments, the gray substance may be easily seen. Snip out with fine curved scissors small pieces from the anterior horns in the lumbar regions where the corpuscles are very numerous ; if the specimen be fresh, immerse in osmic acid (1—1,000) for twenty-four hours. Then, by careful brush- ing in water with the camel' s-hair brush, or by teasing, or agi- tation in a test-tube with a little distilled water, some of the ganglionic corpuscles will be successfully removed. They will be seen to vary much in size, and be multipolar, i.e., they will exhibit a very large number of branches (De iter's protoplasmic 1 According to Key and Retzius, they are probably all unipolar. Stud, in der Anat. d. Nerven-Syst., 2 Hiilfte, V. and H.'s Jahresb., 1878. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 121 processes) which divide and subdivide, and, it is said, form a network which unites with a similar one proceeding from the ganglionic bodies of the posterior roots. There is, in addition, a single straight process (naked axis- cylinder), which, proceeding outward, soon receives a medul- lary sheath. The nucleus is very large and circular, and usu- ally displays a nucleolus. The contents of the body of the corpuscles are more or less granular, and a mass of pigment in " granules is usually seen piled up in some one portion. The corpuscles thus separated may be preserved in glycerine and water, or, after staining in borax-carmine, in dammar varnish or Canada balsam. In the posterior horns the corpuscles are similar in character, but smaller. Gerlach claims that the ganglionic bodies of the anterior horns are connected together through networks formed of the branching processes given off from each. Carriere, working under Prof. Kollman, of Mu- nich, has examined the spinal cord of the calf in the fresh con- dition, and has satisfied himself that the ganglionic corpuscles are connected together by their fine processes, being thus in agreement with Stilling, Wagner, Eemak, and many others. — Arcli.f. miJcroskop. Anat., xiv., 2, 1877. Ganglionic bodies in the human brain. — Thin sections made through the cortex of the human brain show that there are conical ganglionic corpuscles of medium size, whose base is directed toward the white substance, and apex toward the superficies. From either end processes are given off, from the broad end several, and from the apex a single one ; both subse- quently branch. In the upper strata the corpuscles are small- est. Disseminated throughout this substance are two other forms of corpuscles, one star-shaped (spider-cells),1 and the other the lymphoid corpuscles that belong to all tissues of the body. Possibly the spider-cells, which have a variable number of processes, are the cells of the neuroglia. Brush-cells'1 have also been described. Perhaps they should also be regarded as a variety of the spider-cells. Ganglionic bodies of the sympathetic system.— They occur either singly or in groups, interspersed among the nerve-fibres, or in lines, or form enlargements in the nerve-plexuses, as 1 Described by Jastrowitz. 2 Arch. f. mikroBk. Aaat., 1874, LXI., p. 93. 123 MANUAL OF HISTOLOGY. in the digestive tract. Preparations of the cnpliac ganglion ot the frog may be made according to the methods that have al- ready be»-n described. The aorta and bulbus arteriosus of the frog are recommended by Klein, and the gold method is the to show them. It was in these corpuscles of the green tree-frog that Beale noticed a spiral fibre. It was a delicate one, wind- ing round the axis-cylinder, finally going off in an opp direction. He also thought, from an examination of the gan- glia in the mammalia, that the same fibre existed in them. Sub- sequently Julius Arnold corroborated his views, and even de- scribed a network of fibres which was connected with the nucleolus, and extended through the corpuscle, at its final exit forming the spinal fibre. Recent observers, however, have failed to confirm Arnold's opinion, and even the existence of a spiral fibre is held to be in doubt.1 These corpuscles, which are either globular or oblong, may appear to be apolar. unipolar, bipolar (when two processes are given off in the opposite direc- tions), or multipolar (when two are given off in the same direc- tion, or several are given off in various directk Jfeisstier's plexus. — This network, named after its dis- coverer, is situated in the submucous tissue, and consists of nerve-bundles of medium size, which have nodular enl; - ments studded with nuclei at certain points. An excellent way of securing them is the following : Take a piece of cat's intestine, three or four inches in length ; cleanse thoroughly by passing through it a stream of water ; then ligate one ex- tremity. Fill an ordinary two-ounce syringe with a solution of the chloride of gold (£°). Slip the nozzle into the other end of the intestine, and, tying it in, inject with such force as to dis- tend the gut to its utmost extent without bursting. Then pass another ligature round the gut beyond the nozzle, and draw it tight. Remove the syringe, and place the specimen in an open vessel containing the same solution, but allowing fully one- half of it to be uncovered by the liquid. After twenty-four hours the part thus exposed will have taken a mauve or violet color. Then remove from the liquid, and open with scissors, let it partly dry, and, seizing the mucous membrane with the forceps, tear it off in pieces. The submucous tissue will then 1 Key and Retzius did not find the Bpiral fibre in the human species, but in the frog occasionally. Op. cit. Many other excellent observers agree with them. GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 123 be exposed, and small bits are to be torn ont in a similar way. They may be mounted in glycerine or dammar varnish. The nerve-trunks can be readily seen ; they will contain, on an average, from two to three fibres perhaps, and form a large- meshed plexus. The ganglionic enlargement may be found where three or four bundles meet, or in the course of a single bundle. The diameter of the enlargement is three to five times the size of the bundle. AueroaclC s plexus, called after its discoverer, is seen by taking the same specimen, and tearing out thin laminse from the muscle, at the junction of their longitudinal and trans- verse coats. The ganglionic bodies are nodular, and contain numerous nuclei. It is said that they may be isolated by immersion of the muscular tissue eight to ten days in a 10 per cent, solution of common salt. Guinea-pigs furnish the best specimens.1 There are both coarse and fine networks. Termination of nerves. — There are various methods which have been described, and these are : 1, by undivided or free endings (tendons, conjunctiva) ; 2, by end bulbs (cornea) ; 3, by terminal loops ; 4, in corpuscles (seminal canals — Letzerich) ; 5, by networks (peritoneum) ; or, finally, 6, in a special appa- ratus (Pacinian or Meissner's corpuscles). When nerves termi- nate by networks, the meshes may be formed from the medul- lated fibres, or those of Remak, and may consist of one or more fine fibrils. They have been found in the skin, and are to be seen in the submucous tissue of the intestines, in the cornea, and elsewhere. Termination by bulbs has been closely investi- gated by Krause. The bulbs are described as having a diam- eter of ^V millimetre, and ovoid-shaped in man, with a thin capsule of connective tissue. One or more fibres appear to enter the bulb, and, penetrating some distance, end in a knob. They have been found in the conjunctiva, in the mucous mem- brane of the floor of the mouth, lips, soft palate, and tongue, and in the glans penis and clitoris. In the cavity of the mouth they are placed in the papilla?. The bodies Krause has ob- served in the clitoris are somewhat peculiar ; they are variously shaped, and have a mulberry-like surface. These corpuscles, about which there has been so much dis- cussion, and which some excellent observers ( Waldeyer, Arnold) 1 Frey : Das Mikroskop. , Leipzig, 1877. 124 MANUAL OF HISTOLOGY. had failed to see, were investigated a few years ago by Long- worth, of Cincinnati, and their existence established as a matter of no doubt. He took the human eye, freshly removed with the conjunctiva, and made the examination immediately. At- taching the conjunctiva with threads, so that it preserved its natural tension, he immersed it in a $ per cent, solution of os- mic acid, or exposed it to the vapor of the same solution. After twelve to twenty-four hours the membrane was deeply stained, and the epithelium could usually be removed with a brush or the finger-nail. Next, a thin piece of cornea was removed and examined in water, or in 1 to 2 per cent, acetic- acid solution. It was then mounted in glycerine. This method was preferred to the gold chloride. In some conjunctivae they wrere found almost entirely absent ; in others, or in certain por- tions, quite numerous. The entire interior was seen to be filled with nucleated corpuscles. Waldeyer, in commenting on the work of Dr. Longworth, agreed to it full}r, and retracted his former opinions. He places these bodies intermediate between the tactile and Pacinian bodies. The tactile corpuscles of the skin (called also Meissner's or Wagner's corpuscles) are to be seen in the papillae, and especially well in the tips of the fingers, and in the internal genitals. They have a length of about -fa millimetre. Speci- mens hardened and preserved in the ordinary way show them well. They are oblong, rounded, and marked by transverse wavy lines. A nerve-fibre may be seen running into their centre. The Pacinian bodies, discovered by Vater, in 1741, but first carefully described by Pacini, of Pisa, are oval or pear-shaped bodies, attached to the nerves like berries to a stem. They are found in the subcutaneous tissues of the finger (Kolliker), in the labia majora, prostate, corpora cavernosa, and in many other places. They are seen to the best advantage, however, in the mesentery of the cat, where they are so large as to be easily visible to the naked eye. Cut out a small piece of the mesentery, place it in a weak solution of osmic acid (1 — 100), and after a few minutes, when it has become brown, detach the capsule carefully with needles. Mounting at once in glycerine, the whole interior of the Paci- nian will be superbty shown, constituting one of the most beau- tiful specimens in histology. The medullated nerve may be GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 125 seen winding in at one end (Fig. 49), covered with a dense coat- ing of connective tissue, and accompanied by a small arter\\ After penetrating a variable distance, it leaves its medulla and is continuous with a straight fibrillated band that is called the core. It terminates in one or more granular expansions, appar- ently. In two cases, how- ever, I saw the nerve passing through the body, giving off its medulla on entering it, and assuming it again on leaving. This has been observed by Klein, Pappenheim, and oth- ers. Round about the core, forming a series of pretty reg- ularly oval markings, are con- centric tunics. Toward the periphery they are at a pret- ty even distance apart. Be- tween them, applied closely to the tunics,1 are small ovoid nuclei. The spaces between the lamellse are probably filled with a clear fluid. In my experience these bodies are not successfully pre- served in glycerine, even after hardening in osmic acid. The chloride of gold may answer better. Nerve - terminations in muscle are quite easily seen. It is only necessary to take a bit of muscle from the thigh of a frog just dead, and immerse it in dilute acetic acid, and then in glycerine. When the tissue is thoroughly transpa- rent, as it will be in a few minutes (ten or fifteen), there will be little difficulty in finding a medullated nerve, and then in tracing it into a muscle-fibre. Reaching the sarcolemma, it 1 According to Schaefer, the nuclei belong to epithelioid corpuscles which cover the tunic on both sides. Practical Histology, p. 134; Quarterly Microscop. Journ., lbT.j. Fio. 49. — Pacinian body from the cat's mesentery. 126 MANUAL OF IIISTOLOGY. penetrates it at a prominence (Doyere's eminence). From this point it divides into fibrils, which form delicate networks, and one, or possibly two filaments will be seen to enter an irregular body placed in the centre of the fibre. This body is highly nucleated, and may without much difficulty be distinguished from the muscle nucleus, which lies either on the bundle or in it. This body is called the motor ial plate. It is not certain, however, that the ultimate fibrils actually end there, for in some instances one is in connection with one side, and one with the other. Varicosities are described in the primitive fibrils when osmic acid or chloride of gold is used. Gschleiden, of Breslau, one of the most recent writers on this subject, has traced (in the leech) the ultimate fibrils to the cement substance between the contractile muscle-corpuscles (unstriped muscular tissue). He never saw them end in plates or in networks. Ganglion-cells are closely attached to the fibres near their termination, and they may be unipolar, bi- polar, or even multipolar, the former being the most numer- ous. Termination of nerves in epithelial bodies has been de- scribed by a good many observers. The demonstration of such endings, however, is extremely difficult. The ultimate fibrils are liable to be confounded with elastic tissue, possibly with connective-tissue fibres. To be quite sure of their character they should be traced into connection with nerve-trunks, on the one hand, or ganglionic bodies on the other. Connective tissue of nerves. — -In our description we have adhered to the idea that the sheath of Schwann is the one that immediately incloses the medulla, without any intervening substance. Ranvier has called the first sheath, exterior to Schwann's, "the sheath of Henle." (Fig. 43, e.) The term perineurium is often applied to the sheaths of the funiculus or bundle. The connective tissue separating the funiculi in a large trunk has been called the endoneurium, while epineurium is the great sheath of the whole trunk. Each bundle or funiculus, the smallest element that we see in making a gross dissection of a nerve, is covered with one or more layers of endothelium, forming a special sheath. These funiculi do not run parallel without anastomosing, but two, joining, form a third, which again divides. There is much practical difficulty in the way of giving pre- BIBLIOGRAPHY. 127 cise limits to these sheaths, from the fact that they are apt to be continuous with one another, while one or more may be absent, according to the size or quality of the nerve. BIBLIOGRAPHY. Cohnheim. Virchow's Archiv. Vol. XXX VIII. , p. 343. 1867. Cleveland. Ueber d. feineren Bau d. Markhalt. Nervenfasern. Arch. f. mikrosk. Anat., 1870. Vol. XIII., p. 1. Schultze, Max. Strieker's Histology, p. 117. 1872. Schmidt. On the Construction of the Dark or Double-bordered Nerve-fibre. Month. Micros. Journ., May 1, 1874. Longworth. Arch. f. mikrosk. Anat. Vol. II. 1875. Schaefer. Practical Histology. Quart. Micr. Journ., p. 134. 1875. Kratjse. Arch. f. mikrosk. Anat. Vol. XII. 1876. Shaw. Some Peculiarities in the Myelinic Peripheral Nerves, etc. Jour, of Nerv. and Ment. Dis., Jan., 1876. Gschleiden. Arch. f. mikrosk. Anat. Vol. XIV. 1877. Rantier. Lecons sur l'histoire du systeme nerveux. 1878. Key and Retzius. Stud, in d. Anat. d. Nerv. -Syst. V. & H.'s Jahresb. 1878. His, W. Arch. f. Anat. u. Phys., p. 455. 1879. Rawitz, B. Arch. f. Anat. u. Phys. 1879. Rumpp. Zur Histol. d. Nervenfaser, etc. Unt. d. Phys. Inst. d. Univ. Heidelberg. Vol. II. Schultze, H. Axencylinder u. Garjglienzelle. Arch. f. Anat. u. Phys. 1879. KChne, W. Zur Histol. d. motor. Nervenendig. Unt. d. phys. Inst. d. Univ. Heidel- berg. Vol. II. Hesse, Fr. Zur Kennt. d. peripher. Markhalt. Nervenfaser. Arch. f. Anat. u. Phys. 1879. Kuhne, W., and Steiner, J. Beobacht. ueber Markhaltige u. Marklose Nerven- fasern. Unt. d. Phys. Inst. d. Univ. Heidelberg. Vol. III. His, W. Ueber d. Anfiinge d. peripher. Nerven- System. Arch. f. Anat. u. Phys., p. 455. 1879. Waldeyer. Ueber die Eadig. d. sensiblen Nerven. Arch. f. mikros. Anat. Vol. XVII., pp. 367-382. 1880. Ranvier. Lecons d' anat. gen. App. nerveux term. , etc. Paris, 1880. PART II. CHAPTER X. MUSCULAK FIBRE. Br THOMAS D WIGHT, M.D., Instructor in Topographical Anatomy and in Histology at Harvard University. The physiological attribute of muscular tissue is contrac- tility. This may or may not be under the control of the will. The structure of voluntary muscular fibre is very different from that of the involuntary. This distinction, however, is not absolute. The muscular fibre of the heart presents a structure intermediate between the two typical forms. Striped fibres are found in some places, as, for instance, in the upper part of the oesophagus, over which most people have little or no control. There is also an un- doubted difference in the manner of contraction among volun- tary muscles. Whether this is associated with a difference of structure is an interesting but very uncertain question that will be alluded to later. INVOLUNTARY MUSCULAR FIBRE. Unstriped muscular fibre is shown with great advantage in the bladder of the frog. It should be stained with gold chlo- ride, logwood, or carmine.1 After the specimen has lain two 1 If one's object is to study the muscular tissue only, gold has no advantages over the other agents, and should not be used, because it is less certain. The writer has obtained remarkably beautiful stainings of the bladder by using carmine, following Beale's method. IN VOLUNTAS Y MUSCULAR FIBRE. 129 or three days in glycerine, the lining epithelium is easily brushed off. The bladder of the frog is peculiarly favorable, because it affords an opportunity of studying the fibres, both Fig. 50. Fio. 51. Fig. 52. Fio. 50.— Muscular fibres treated with serum. Fio. 51. — Muscular fibres from the muscular tissue of the intestine, isolated by means of nitric acid. Fio. 52. — Muscular fibres from a pleuritic membrane. J. Arnold. separately and in bundles, in its walls and in the coats of the minute arterioles which nourish it. The plain fibre is composed simply of one or more elongated 9 130 MANUAL OF HISTOLOGY. cells. (Fig. 50.) The nucleus is at about the middle. The cell swells out around the nucleus, and quickly contracts again be- yond it. A small cell, such as is found in the wall of a small blood-vessel, is consequently spindle-shaped, but we find many in the frog's bladder that run out into fine threads of indefinite length. Sometimes one end of a cell divides into two fibres. (See Figs. 51 and 52.) The nucleus sometimes appears to be homogeneous, though it usually contains one or more granules, sometimes considered to be nucleoli. When using a high power the writer has some- times found that the nucleus contained many granules, so ar- ranged as to suggest very strongly a transverse striation. A row of granules at each end of the nucleus is sometimes found. Muscular fibres in the walls of small, transparent blood-vessels are very instructive objects, because by changing the focus we can observe them as they curve round the vessel, both in longi- tudinal and in transverse section. At those places where a transverse section of one end of the cell is in focus we see what appears to be a granule merely. If another part near the nu- cleus is brought into focus, it shows as a small circle, while if the nucleus happens to be cut transversely, it gives the effect >of a dark spot inside a circle. VOLUNTARY MUSCULAR FIBRE. No tissue is more easily recognized than striped muscular fibre, yet none is more difficult to understand.1 The fibres are cylinders or irregular prisms of varying length. Their diameter in the human body varies, according to Frey, from .0113 to .0563 mm. Each fibre is tightly inclosed in a struc- tureless elastic membrane, called the sarcolemma. This sheath is not very easily demonstrated ; but if fresh muscle be roughly picked to pieces in water, shreds of it may be seen at the torn ends of fibres, and sometimes it can be made out where the muscular substance has been injured in the course of a fibre. 1 Any attempt at an account of the many views that have been ami are held, would make this article far too long. A few only will he mentioned, and these inci- dentally It is hoped that this defect, if it be one, will be compensated for by the fulness of the bibliography. VOLUNTARY MUSCULAR FIBRE. 131 The existence of a sarcolemma being admitted, it is clear that it must be highly elastic so as to accommodate itself to the changes both of length and breadth which the fibre undergoes. The phenomena of contraction show, moreover, that it must be attached at definite points to the muscular substance. Fresh muscular fibre of a vertebrate animal, when teased out and examined under a moderately high power, presents a series of alternate black and white cross stripes, which are held to be characteristic of voluntary muscle. (Fig. 53.) This appearance is beautifully distinct in some fibres, and very vague in others. It may vary greatly in different parts of the same fibre ; the stripes may run perfectly straight across the fibre ; they may present a uni- form curve, or they may be interrupted at intervals, some parts of the line being in advance of others. (See Fig. 53. ) As a fibre taken from an animal im- mediately after death naturally draws it- self together (without, however, necessarily presenting the phenomena of physiologi- cal contraction), it is desirable to ascertain whether this modifies the appearances. To do this, fibres from a recently killed animal should be ex- amined in a state of extension. A cut should be made in the body of a muscle, a few fibres teased out and stretched on the slide under the covering glass before their attached ends are divided. It will be seen that the light stripe is more affected by the stretching than the dark one, though both are broader than in the non-extended fibre ; but the most important effect is the appearance, often seen with high powers, of a very narrow, in- terrupted black line in the middle of the light band. Beside this cross striation, the fibres of vertebrates show more or less plainly minute longitudinal lines. It is to be no- ticed that when the cross stripes are very distinct the longitu- dinal ones are very faint, or even invisible, and that when the latter are well marked the former are the reverse of it. Some reagents tend to divide a fibre into disks, others into fibrillar. Among the former are solutions of acetic acid in water (1 in Fig. 53. — Striped muscular fibre : a, black stripe ; b, in- termediate stripe ; c, white stripe ; n, nucleus. After Ranvier. 132 MANUAL OF HISTOLOGY. 100 — 200), hydrochloric acid (1 in HO — 200), and among the latter a solution of chromic acid (1 in 200). It is very probable that the amount of longitudinal striation varies in different muscles, being related, perhaps, to physiological properties^ or possibly the result of mechanical causes. It is certain that both kinds of striation may be found in great perfection in fibres treated with almost any reagent that does not destroy them. Some- times muscle is seen to be split into fibrilke, each of which shows the transverse stripe, though the shreds are so line that each disk is represented by a dot merely.1 This may be de- tected very well in the muscle of the lobster after it has been picked to pieces in glycerine. Returning to the transverse stripes in vertebrates, the stria) are very near together in the frog, and thus this useful animal is not specially desirable. The muscle of the rabbit is much better, and human muscle is, perhaps, better still. The muscle of the human embryo in the last months of pregnancy is par- ticularly good. A very high power will often show the narrow black line in the midst of the white band. Sometimes one edge of each black stripe will be very sharply marked against the glaring white, while the other side will present a less marked contrast. If the stage of the microscope admits of rotation,8 in- structive effects can also be obtained. As the field turns round, the brightness at the sharp border of the black stripe gradually decreases, to return on the other side. Again, this change may not occur. Sometimes, when the upper edge of the fibre is pre- cisely in focus, the black and white stripes may be made to ap- parently exchange places, if the lens is slightly depressed. This is probably to be accounted for as follows : First, we may for the present assume that the black and white bands are caused by disks of different nature. Take a series of such disks and imagine them somewhat inclined to one side, like a roll of coins on their edges leaning against a support. A vertical line, representing the line of vision, that passes through a black disk at the upper border of the roll will strike a light one at a deeper level. A peculiar effect may be obtained by removing the diaphragm and employing very oblique light. The black 1 The fact that muscle removed from the body can be reduced to fibrillar does not prove that these are pre-existing elements. 2 It is to be regretted that this movement is not more common. VOLUNTARY MUSCULAR FIBRE. 133 band then is often replaced by two narrow black lines with a light space between them. This is more frequently observed when the rays strike the fibre longitudinally. The fibres of invertebrates, though on the same plan as those of higher animals, are better fitted for study, because the elements are farther apart, and because the phenomena of con- traction may, in some cases, at least, be observed under the microscope. The muscles from the thorax and legs of large flies are very good. Merkel recommends that they be examined in fresh al- bumen from the egg, in which they will continue to contract. The fibre is crossed by narrow black stripes which, be it re- membered once for all, correspond to the black stripes of ver- tebrate muscle. On each side of these stripes there is a bright, glittering border, which gradually shades off into a dull band, midway between the two stripes. The substance between the black stripes is all of one nature, the difference between its middle and end portions being an optical effect. The dull band corre- sponds to the fine line which high powers reveal in vertebrate muscle. Its greater breadth is due to the greater distance of the black stripes. Fibres from the legs and wings of the large water-beetles (Hydro- philus and Dytiscus) are admirable objects. Schafer's valuable obser- vations were made on those of the legs. He found the black stripe to consist of a double row of highly refracting granules, which were the ends of dumb-bells embedded in the contractile substance. These struc- tures are arranged side by side, the * adjacent ends of the dumb-bells forming the stripe, while the handles constitute the slight longitudinal striations. (See Fig. 54.) The bright borders are due to the refraction of light from the spherical heads of the dumb-bells. It is clear that they must cause a greater amount of rays to pass through the sub- stance directly beside them than go through the substance midway between them, which latter appears dark in conse- Fig. 54. — Muscle of large water-beetle (Dytiscus) : «, chill band ; b, bright space around ; c, the highly refractive ends of the dumb-bells ; , nu- r . i" . clei of the tunica adventitia; endotnelia. My reasons for so doing are &, muscle nucleus ; c, elastic " ip internal tunic ; d, membrane as follows : In the blood-vessels ot young formed of fusiform ceiis. animals and newly born infants I have fre- quently noticed thick, dark, and granular bodies immediately below the endothelial lining. These subendothelial cell-plates were smaller and more polyhedral than ordinary endothelia, and invariably contained one or even two nuclei. They ap- peared to resemble germinating endothelial cells, such as Klein has described as occurring in serous membranes. They did not, however, occur in single layers, as Klein has seen them, 154 MANUAL OF HISTOLOGY. but in strata. They were observed in particular vessels of young animals. It seems likely that these cells disappear or shrivel with the growth of the individual, but their sudden reap- pearance in pathological processes leads the author to believe that at least some of them persist through life. Talma ( Vir- chow's Arch., Vol. LXXVIL, pp. 242-269) observed similar elements, but thinks they are derived from the ordinary en- dothelia, instead of vice versa. He is also convinced that the latter are merely modified leucocytes ; but this view has been shown to be erroneous by Virchow (Archiv f. path. Anat., Vol. LXXVIL, pp. 380-383). Endothelial desquamation is probably, as already stated, a physiological process of constant Fig. 68. — Transverse section through small artery and vein : A, artery ; a, intima with bulging en- dothelial cells, the vessel being drawn in a state of contraction ; b, internal elastic coat, wavy for same reason ; c, media ; d, adventitia. B, vein, same denominations. occurrence, and in some respects analogous to the epithelial shedding from the surface of the skin and mucous membranes. The media musculosa, or middle coat, consists of superim- posed layers of smooth muscle-elements disposed in groups. Most of them lie transversely to the course of the vessel. The intervals between neighboring groups are occupied by connec- tive tissue and elastic fibres, arranged in networks. This inter- stitial substance becomes augmented with the increasing calibre of the artery. In the largest trunks it all but replaces the muscle-cells. Here, however, the elastic fibres also reach their maximum development, encroaching upon the connective-tissue elements until the latter become quite inconspicuous. Besides its principal transverse layer, the media also contains fusiform muscle-cells, placed in an oblique or longitudinal direction. THE BLOOD-VESSELS. 155 They are scattered irregularly throughout the middle coat. Sometimes the intima and the adventitia also contain sparsely distributed muscle-cells. The arterial muscular coat is dis- tinctly separated from the intima by the interposition of the internal elastic coat. Externally a sharp boundary is formed either by the adventitia or by the external elastic coat. The latter appears as a separate membrane in arteries of small and medium size. There are, however, exceptions to this rule. The external elastic coat consists of a close network of delicate jm^tj'f [ ,!V";.", / * Fig. 69. — Longitudinal section of pulmonary artery. Mounted in glycerine and acetic acid after de- siccation of the artery, a. Internal portion of intima ; 6, external portion of intima ; c, internal elastic coat ; d, media, showing cross sections of muscle fibres and elastic tissue ; e, adventitia. elastic fibrils, anastomosing with similar adventitial reticula. The adventitia is composed of interlacing bundles of connec- tive tissue, commingled with elastic lamellae of varying thick- ness. The veins. — From their origin in the capillaries to the point where they enter the trunk proper, the veins preserve through- out a uniform type of structure. But no sooner have they penetrated into the visceral cavities of the body than we find them undergoing considerable alterations, which may either increase or diminish the complexity of their structure (Ran- vier). The veins are far more numerous than the arteries. They are also, as a rule, wider and more dilatable, and have thinner coats. It is owing to the latter peculiarity that the 156 MANUAL OF HISTOLOGY. color of the blood is seen through their semitranslucent walls. Finally, they branch more frequently than the arteries. Three main coats or tunics enter into the composition of most veins. These resemble the corre- sponding arterial struc- tures, and have likewise received the names of in - tima, for the internal endo- thelial lining ; media, for the middle muscular ; and adventilia, for the external connective-tissue coat. Veins, however, differ from arteries in the feebler development of their mus- cular coat, in the compara- tive paucity of elastic ele- ments, a greater laxity of their intima, and the presence in some of valves. We may distinguish veins of smaller calibre, or venules, from the vessels of medium and large size. The venules, like the arterioles, in certain respects resemble the capillaries. As Fig. 70. — Portion of innominate vein of dog, after in- jection of a solution of silver nitrate. The endothelial cells and their nuclei are visible. The media shines through this layer. Fig. 71.— Arteriole and venule from child's mesentery, treatment by acetic acid and glycerine : A, ar- tery ; a. nucleus of muscle-cell of media ; b, same in transverse section (optical). B, vein ; c, nucleus of connective tissue constituting media, which in these minute veins contains no muscle-cells; «/, nucleated connective tissue. it may become important to differentiate the minuter forms of vessels, we will here briefly indicate the main points of dis- tinction between full-sized capillaries, small veins, and arte- THE BLOOD-VESSELS. 157 rioles. In the latter, the endothelial cells are more nearly fusiform, longer, and somewhat narrower than in the venules. In the capillaries, their form and dimensions hold an interme- diate position between the arterial and venous types. The middle coat is entirely wanting in capillaries, and is much less conspicuous in the small veins than in the arterioles. In fact, under ordinary circumstances, the muscle-coat forms by far the most characteristic distinguishing feature between these ves- sels. Venules quite frequently have only a few sparsely scat- tered muscle-cells, in place of the continuous muscular layer which exists in minute arteries. The former also are either altoge- ther deficient in the in- ternal elastic coat, or the presence of this struc- ture is barely indicat- ed by delicate elastic fibres ; these latter usu- ally have a longitudinal direction. On the other hand, arteries of corre- sponding calibre are mostly furnished with a distinct elastic inner coat. Finally, with re- gard to the adventitia, we find it more highly developed proportionally in venous than in arterial vessels, whereas capillaries commonly have only a few faint fibres to denote the presence, in them also, of this coat. The internal elastic coat of the larger and largest veins is very feebly developed in comparison with that of the arteries. Distinct fenestrated membranes are scarcely ever encountered. Veins are likewise possessed of an internal fibrous layer, but here again we observe that comparatively feeble development of a coat which in the arteries is quite conspicuous. Among the many special characteristics of the various reins in different regions, we will only mention the following : the jugular veins show well-marked elastic reticula, the meshes of which contain sparse muscular elements. In the femoral, Fig. 72.— Longitudinal section of popliteal vein : a, intima; b, media ; c, adventitia. 158 MANUAL OF HISTOLOGY. brachial, and subcutaneous branches there is a media of con- siderable dimensions. The inferior vena cava has, in addition to a transverse layer of muscle-cells, a longitudinal one of greater thickness, and, besides these, contains muscle-cells, which are scattered through its elastic coat. The veins of the meninges of the encephalon and cord, the retina, the bones, and the muscles, and the jugular, the subclavian, the innomi- nate, and the thoracic portion of the vena cava are all entirely devoid of a true muscular coat. The veins of the gravid ute- rus have only longitudinal muscle-elements. In addition to an outer longitudinal layer, the vena cava, the azygos, the renal, the hepatic, the internal spermatic, and the axillary veins pos- sess an inner circular layer. The iliac, the femoral, the popli- teal, and several other veins contain a middle coat of transverse muscle-cells, between internal and external longitudinal layers. The valves of the veins consist of longitudinal bundles of connective tissue commingled with scanty elastic fibrils, and containing nucleated cells. The inner endothelial layer appears to be a direct continuation of the intima of the vein. That portion of the subendothelial tissue which does not face the blood-current is less developed than the part turned toward it ; the elastic fibres of the latter are also barely visible. The at- tached valvular border frequently presents transversely dis- posed muscle-elements. Eberth has denied their occurrence, but they have been repeatedly observed by Ranvier and other competent histologists. Peculiar vascular structures. — The following structures are remarkable for the conspicuous and characteristic development of their blood-vessels the vascular membranes, tunicas vascu- losaz, such as the pia mater of the brain and spinal cord, and the choroid coat of the eye. In these we find that the excessive vascularity is intended to nourish, not the membranes them- selves, but the organs which they invest. Blood-vascular glands, vascular plexuses. — In man, two bodies of peculiar structure represent this group. They are the coccygeal gland of Luschka, and a rudimentary organ called the intercarotid gland. Both consist essentially of con- voluted blood-vessels and nerves, imbedded in a nucleated con- nective-tissue stroma. The coccygeal gland is a small, rounded, pinkish body, of rather firm consistence, and is connected by a pedicle with the middle sacral artery. This pedicle contains THE BLOOD-VESSELS. 159 blood-vessels and nerves. The arteries entering the gland-like body become convoluted, and show numerous tubular, fusi- form, or ampullar dilatations. Sometimes they have terminal sacculi, closely resembling minute aneurisms, and giving the organ its glandular appearance. Indeed, Luschka has called them gland-tubules and vesicles. After death they are com- Fio. 73. — Section of a naturally injected coccygeal gland : a, vessels ; 6, collection of cells. Eberth. monly found to be empty, but by proper management a good natural injection with blood may be readily obtained. Both capillaries and veins also present lateral varicosities, studding them in groat number. All these vessels have the usual endo- thelial lining. External to this there appear aggregations of rounded or polygonal cells. They are furnished with nuclei, and receive an investment corresponding to the vascular ad- 160 MANUAL OF HISTOLOGY. ventitia, but containing comparatively more nuclei than that structure. The inter carotid gland differs from the coccygeal in its larger size, and because it contains accumulations of ganglionic nerve-cells. These are derived from the carotid plexus. Here the vascular sacculi also more nearly resemble dilated capilla- ries, whereas in the other body they approach the arterial type. In all other respects the structure of these vascular plexuses is identical. Some authors regard the spleen and the supra- renal capsule as belonging to this group of blood-vascular glands. The author sees no necessity for so considering them, and the subject may therefore be dis- missed without fur- ther comment. Corpora caverno- sa.— They consist in great part of dilated blood-vessels, chief- ly of the venous type. These inter- communicate very freely, and when filled with blood cause the organ to assume the peculiar condition known as erection. The penis and the clitoris are supplied with caver- nous bodies. The urethra of the female and the vestibule also contain them. Interlacing bundles of muscle-fibres, together with similar bands of connective tissue, form a framework for the support of the vascular structures mentioned. The latter present the ordinary endothelial lining. Several years ago Dr.H. J. Bigelow succeeded in demon- strating the existence of cavernous tissue in the nasal fossa?. In a letter to the author, Dr. Bigelow states that his point was " the demonstration of an abundant and true cavernous structure and erectile tissue on and about the turbinated bones, occupying the place of what had been previously supposed to be only venous sinuses, the loops of Kohlrausch. The new re- sult obtained was due to a different mode of preparation. Kohl- Fio. 74.— A, cellular vascular sheath, from the coccygeal plexus : a, connective tissue with scattered cells pnfl nuclei ; ft, round and polyeonal cells lying immediately upon the capillary wall, c ; B, a capillary from the coccygeal plexus, with a vascular sheath very rich in cells. References as in A. Eberth. BIBLIOGRAPHY. 161 rausch injected from the jugular vein ; I [Dr. Bigelow] inflated the tissue locally, as if it were in the penis." Vasa vasorum, lymphatics, and nerves. — Nutrient ves- sels are found in the walls of all the larger arteries and veins, where they occupy the adventitia. Sometimes they are seen to dip down into the outermost portions of the media. Lym- phatics occur as clefts or spaces between the various tissues of all arterial and venous trunks. Some vessels are ensheathed by a lymphatic membrane, which is sometimes furnished with a lining endothelium. Such structures are called perivascular, or, better, circumvascular spaces. They may be found in connection with the omental and the mesenteric vessels, also the splenic and the hepatic arteries, as well as certain menin- geal vessels of the brain and cord. Nerve-fibres are seen to pass to many of the blood-vessels. They enter the adventitia, and at its internal boundary sud- denly appear to divide into numerous filaments, the ultimate distribution of which has not hitherto been satisfactorily ascer- tained. They seem to terminate in the muscle-cells of the media. Beale considers the presence of ganglion-cells in the vascular nerves as of constant occurrence. The author cannot admit the truth of this general statement, having discovered such cells in only exceptional instances. There is no discerni- ble difference of structure between the vaso-constrictor and the vaso-dilator nerve-fibres. BIBLIOGRAPHY. la addition to the well-known standard treatises by Bichat, Kolliker, Henle, Sappey, Krause, Frey, Leydig, Teichmann, Strieker, Klein, Ranvier, Donders, Vier- ordt, Luschka, Pouchet et Tourneux, the following may be consulted : Ludwig. De arteriarum tunicis. Lipsiae. 1739. Rauschel. De arteriarum et venarum structura. Vratisl. , 183b". ROBOT. Sur la structure des arteres. Compt. rend. 1847. Scnui.TZE. De art. struct. Gryph., 1850. Remak. Hist. Bemerk. ueber d. Blutgefiisswande. Mailer's Arch. , p. 96. 1850. BCOOVD. Syst. capillaire sanguin. These. Paris, 1853. Rkmak. Entwickelung d. Wirbelthiere. Berlin, 1855. Remak. Klappend. Venen. Deut. Klinik. 1856. Hack el. Muller's Aroh. 1857. Luschka. Virch. Arch. XVIII.. p. 106. 1860. 11 162 MANUAL OF HISTOLOGY. Hoyer. Arch. f. Anat., p. 244. 1865. Klebs. Virch. Arch. Vol. XXXII. , p. 172. 1865. Aeby. Med. Cent. Zeit. No. XIV. 1865. Chrzonszczewsky. Virch. Arch. Vol. XXXV. 1865. Eberth. Virch. Arch. Vol. XLIII., p. 136, and Centralblatt, p. 19G. 1865. AUERBAcn. Virch. Arch. Vol. XXXIII. 1865. Med. Cent. Zeit. No. X. Gimbert. Structure et texture des arteres. These. Paris, 1865. Journ. de l'anat. et de la phys. Robin, p. 536. 1865. Fasce, Luigi. Istologia della arterie. Palermo, 1865. Langhans. Virchow's Arch. Vol. XXXVI., p. 197. 1866. His. Die Haute und Hohlen d. Korper's. Basel, 1866. Legros. Journal de l'anat. et de la phys. No. III., p. 275. 1868. Tolubew. Beitr. z. Kennt. d. Baues u. d. Ent. d. Capill. Arch. mikr. Anat., p. 49. 1869. Zeegler. Exp. Unt. ueber d. Herk. d. Tuberkelelemente. Wiirzburg, 1875. Ziegler. Unt. ueber pathol. Bind. u. Gefassneubildg. Wiirzburg, 1876. Kolliker. Entwickelungsgeschichte. Leipzig, 1876. Disse. Arch. f. mikros. Anat. Vol. XVI., p. 1. 1879. Illtmann. Arch. f. mikros. Anat. Vol. XVI., p. 111. 1879. CHAPTER XII. THE LYMPHATIC SYSTEM. By Db. W. R. BIBDSALL, New York City. Histological research lias brought to light within recent years no more important or interesting facts than those con- nected with the lymphatic system ; interesting, in exhibiting entirely new features in tissues which had previously been carefully studied ; and important in their physiological, and, particularly, in their pathological relations. Assisted by experimental pathology, it is still in this direc- tion that we are to look for advancement in pathological his- tology, for there can be no doubt that heretofore too little attention has been paid to the lymphatic system, both in its histological details and in its topographical anatomy. Present condition of the mews on the structure of the lym- phatic system — Relations to the connective tissues. — Unfor- tunately we have still a great variety of contradictory observa- tions, and various interpretations of the same observations. Through this maze of uncertainties it is not easy to lead the student to a settled opinion, nor can all the phases of this many- sided subject be presented. It shall be our aim, however, to draw the outlines. If the student wishes to follow out the controversies, he will be aided by the references which are appended to this chapter. It may be said that we have, to a great extent, returned to the views of the older anatomists and physiologists, and be- lieve that the whole connective- tissue formation is a network of channels ; that its interstices are, directly or indirectly, con- nected with the lymphatic capillaries and larger vessels ; that, in short, the lymphatic system is pre-eminently a connective- tissue circulatory system, irregularly distributed, it is true, but 1G4 MANUAL OF HISTOLOGY. found in one form or another wherever this tissue exists, and constituting in the serous membranes a great absorbent sys- tem, with its special connections, the lacteals, the lymphatic nodes or glands, and the fat-tracts. The important patho- logical processes, both acute and chronic, connected with these membranes are due principally to the fact that they are parts of this great lymphatic sj'stem. Of course we must not lose sight of the connections of the latter with the complimentary blood-vascular system ; the ten- dency has been too much in the opposite direction, however, and this more extensive, though less visible, system has been too often neglected in favor of its more prominent companion, in the consideration of processes of nutrition and of patho- logical changes. General histology of the lymphatic system — Previous ideas. — In describing the lymphatic system, only its general histology will be considered, the details of its special distribu- tion and arrangement being classed with the description of the different organs with which it is associated. Since the serous membranes have come to be regarded as important parts of the lymphatic system, being, in fact, great membranous expansions of that system, they are naturally and easily considered in con- nection with each other. It is not intended to treat of them here in their special details, but merely to make a general his- tological study of them as a class. It is convenient to begin with them in taking up the study of the origin of the lymphatic system. With Virchow originated the theory that the starting-point of the lymphatics is from hollow anastomosing cells, the con- nective-tissue cells, whose prolongations communicate to form continuous tubes. He termed them plasma cells. Kolliker supported this doctrine, and a similar view was held by Ley- dig. Henle held a different opinion, whilst Bnicke and Ludwig reverted to the ancient theory of Bichat, that the interstitial spaces of the connective tissue are the true sources of the lym- phatics. Recklinghausen, introducing nitrate of silver as a reagent, showed that the lymphatic vessels are lined, and the serous membranes covered, with flat cells, forming an endo- thelial layer. He observed the passage of milk and fine gran- ules, through openings in the central tendon of the diaphragm, from the peritoneal to the pleural surface. He believed also THE LYMPHATIC SYSTEM. 1G5 that he had discovered a system of canaliculi in connective tis- sue, which he termed sap or juice canaliculi (saftkanalchen). His views, as modified somewhat later, are, that the connective tissue is traversed by serous canaliculi or plasmatic channels which are directly continuous with the lymphatic vessels. "Not mere fissures in the connective tissue, but interstices of the fibrous fasciculi and lamellae of connective tissue, cemented to one another by a tenacious, homogeneous, firm material, in which the serous canaliculi are buried." Tfie lymphatics of the mesentery. — A portion of the mesen- tery between the trabecules, taken fresh from a cat and stained with nitrate of silver, exhibits on both surfaces an endothelial layer, the cells of which possess an irregular outline, marked by the deposit of silver, either in a supposed intercellular sub- stance or in crevices between the cells. Sometimes this outline is polvgonal, sometimes sinuous, crenated, or even sharply den- tated. It may be an even, fine line, or it may possess irregu- larities as if beaded. At the union of these lines, that is, where two or more cells terminate, a round, irregularly triangular, or spindle-shaped spot may be often observed, which is stained like the intercellular line, or in a lighter or darker shade. There are other spots of larger size, presenting the appearance of openings ; we shall refer to them again. The surface of the cells may be clear, or granular, sometimes it is qnite dark, vann- ing with the degree of staining and the condition of the tissue ; a nucleus can usually be seen at a slightly deeper level. This is plainly visible in unstained or slightly stained specimens, or where special reagents have been used to make the nuclei promi- nent, as hematoxylin or picro-carminate of ammonia. The granular appearance spoken of is sometimes confined to a series of cells which surround a stoma, or the black spots mentioned, while the neighboring cells maybe clear; 'in other cases, sev- eral corpuscles in the form of an irregular tract may present this appearance. Klein has observed cells which are club-shaped, undergoing a budding pro- cess, i.e., giving off little bodies resembling lymphoid corpuscles. He has given the term germinating endothelium to these cells. Other histologists have made similar observations. Underneath and around the nuclei a delicate, intricate, re- ticulum of elastic fibres may be seen plainly in unstained speci- 166 MANUAL OF HISTOLOGY. mens, and by careful focussing in silver preparations. Accord- ing to Ranvier, they are connected near their point of union by a very thin, elastic, fenestrated membrane. Below the layer of elastic fibres is the connective tissue which forms the basis of the membrane. It consists of fasciculi, which are straight, or wavy, according to the degree of tension of the membrane, or its fasciculi are held together by the elastic fibres, which penetrate from the reticulum on each side. They usually pre- sent a decidedly convoluted appearance in ordinary specimens, and in consequence of the contiguous fasciculi not possessing corresponding convolutions, clear interspaces are seen. Some- times the fibres are very irregular in their arrangement. Ran- vier claims that an interfascicular membrane can be demon- strated here also. Ordinary flat, branching connective-tissue cells are distributed through this tissue ; they lie upon and between the fasciculi ; they are particularly numerous under the endothelial layer. Lymphatic and blood-capillaries trav- erse the interspaces and run upon the fasciculi. In the mesen- tery and pleura they form a wide-meshed plexus ; in the peri- cardium a close plexus. To see the features of the deeper portions to advantage, we must remove the superficial endothelial layer before staining with silver. Klein's method of studying the omentum. — Klein has de- scribed a very careful process for doing this, and as he claims it must be followed in detail to obtain the results at which he has arrived, we reproduce it : "To prepare the omentum, a rab- bit is killed by bleeding ; the stomach is exposed ; after having pushed the intestine to the right side, the free surface of the omentum is pencilled several times from the large curvature toward the diaphragm, with a fine camel's-hair pencil moistened with fluid of the abdominal cavity. After that, a \ or \ per cent, solution of nitrate of silver is allowed to flow over the omentum from a large capillary-tube until the membrane has become slightly milky (one or two minutes are generally suffi- cient) ; after that, the stomach, together with the omentum, spleen, pancreas, and a portion of the duodenum is cut out and transferred to a large capsule with distilled water ; after some time the water is renewed and the omentum is separated under water, together with the spleen and pancreas, from the stomach, with scissors, and is transferred to common water. Those part? THE LYMPHATIC SYSTEM. 167 of the omentum which are seen to contain small patches are cut out and mounted A failure is more frequent than a success. Either the surface has not been pencilled enough, and then the endothelium of both surfaces is colored, and consequently, hardly anything is to be seen of the cellular elements of the ground-substance ; or the surface has been pencilled too hard, and then the arrangement of the ground- substance is altered, its bundles appear considerably stretched and distinctly fibrillar." When these patches referred to, found in the mesentery, and particularly in the omentum, are examined, they are ob- served, according to Klein, to consist of systems of somewhat flattened, finely granular, nucleated, branched corpuscles con- nected together ; the spaces which appear clear between them forming the lacunae and canaliculi, corresponding to Reckling- hausen's lymph canalicular system. The nuclei of these cells are sharply defined, oval, and possess one or two nucleoli. Lymphoid corpuscles are found in these spaces, and also slightly larger corpuscles, which are supposed to be derived, in part, at least, from the branched cells by a process of bud- ding. Klein calls these patches lympTiangeal patches or nod- ules, and lympTiangeal tracts. He divides them into two classes. The pertly mpTiangeal nodules or tracts which lie closely connected with, but principally outside of, the lymphatic ves- sels, are accumulations of more or less flat, branched cells, which, by their growth and proximity to one another, make the canaliculi shorter or close them entirely. The second class de- velop within the lymphatic vessels, and are termed endolym- phangeal nodules or tracts. They consist of those which perfectly resemble adenoid or reticular tissue, and those which are formed of a reticulum of branched cells, their spaces being filled with liquid or a few lymphoid corpuscles. The last form may have a rich blood-capillary plexus, and the branched cells may possess buds, pedunculated and non-pedunculated, sup- posed to represent different stages in the formation of a lym- phoid corpuscle. These tracts and nodules are found most frequently in the neighborhood of the blood-vessels and trabe- cular In young animals they are much less numerous and more Isolated than in adults, where they have become fused into extensive tracts inconsequence of the growth and division 1C8 MANUAL OF niSTOLOOY. of the branched cells. Ranvier has described similar struc- tures under the name "tadies Zaiteuses." Development of fat-tissue. — Their relation to the develop- ment of fat-cells is of extreme interest. If we accept the views of Klein and Flemming, the branched cells are converted into fat-cells, and the former observer has pointed out that, by fol- lowing up a perilymphangeal tract into a vascularized fat-tract, we may find all stages of conversion into fat-tissue. The fat- tracts are found in the same location as the perilymphangeal tracts, that is, along the larger blood-vessels, and the greater the number of the former the less there are of the latter. The conversion of branched cells into fat-cells varies in different animals, and in different membranes of the same animal, and under different conditions of nutrition. The formation of lym- phoid corpuscles, supposed to go on from the branched cells, must cease, necessarily, when they become converted into fat- cells, and it is found that they are, in fact, present in less num- bers when the latter process is going on. Let us consider the relations of these branched cells to the lymphatics. The larger blood-vessels are usualty accompanied by a lymphatic on each side, which gives off branches at irregular intervals, finally breaking up into a capillary plexus, which ma}^ ensheath the accompanying blood-vessels, or even enclose a blood-capillary plexus. When the latter exists in a perilymphangeal nodule, the lymphatic capillary may apparently communicate directly with the lacunre and canaliculi, the endothelial cells compos- ing the capillary being continuous with those which invest the spaces, and covering externally, it may be, the blood-capillary as well (Klein, Del afield). Course and termination of the lymphatic radicles. — In tracing the lymphatic capillaries we find that they run in every direction, branching irregularly, and vary in calibre and num- ber in different parts. It is very difficult to trace one of them to a positive termination. The interstices of the connective- tissue fasciculi in brushed silver preparations sometimes pre- sent an irregular shape, as if they were enclosed by irregular cells. This appears to me to be often due to the convolutions of the fasciculi, made more irregular, perhaps, by a cement substance, or an interfascicular substance, either fluid or semi- fluid, which lias been coagulated by the processes following death, and by the action of our reagents. The irregular action THE LYMPHATIC SYSTEM. 169 of silver, which produces so many doubtful pictures, may aid in producing this appearance. The extreme mobility necessary in some forms of connective tissue demands extreme flexibility as a quality of its elements, thus facilitating great variation in structural arrangement under different conditions. Artificial injection of the lymphatics. — If we inject this tissue, by puncture with a hypodermic syringe, we can fill the lymphatic vessels and also the interstices, so that they are continu- ous ; but the question whether this is a natur- al or an artificial trans- ition is one about which histologists still differ. Theoretically, we may consider that such com- munications exist to some extent, at least when greatly increased vascular tension takes place. But, at the same time, many, or even most of the in- terstices may be closed spaces. It is not a matter of great consequence, physiologically speak- ing, since not only fluids but lymphoid corpuscles can penetrate partitions which fail to resist so slight an injecting force as is sufficient to unite these spaces and the lymphatic capillaries.1 The fact that injections can be made without forming a com- munication (Frey) does not prove that the latter does not exist ; it may be due to an imperfect injection. As we shall see later, the wandering propensities of the lymphoid cor- puscles would almost exclude the possibility of the connective- tissue interstices remaining closed spaces everywhere. Endothelium and stomata. — We have already referred to Fig. 75.— From mesentery of cat: silver-stained right por- tion denuded of endothelium, showing, A. branched cells, with B, intervening spaces ; left portion, endothelial layer preserved ; C, pseudo-stoinata ; D, nuclei ; E, elastic fibres. 1 Thoma and Arnold have shown that injections into the veins, in a living animal, of insoluble coloring matters (not distending the vessels, however), pass between the endothelial cells and find their way into the clefts and channels of the deeper tissues. The possibility of absorption taking place through the intercellular substance which, after all, may only be a semifluid material filling a space which varies in size under uiff'.-rent conditions, throws light on many of the difficult problems of absorption, secretion, and excretion, and numerous pathological processes. 170 MANUAL OF HISTOLOGY. Recklinghausen's observation, that communication exists be- tween the abdominal and pleural cavities by means of small openings in the central tendon of the diaphragm. By injecting some insoluble coloring matter, held by iluid in suspension, into the abdominal cavity, he obtained a fine injection of the lymphatics of the central tendon, and was able to detect the substance on its pleural surface. The experiment may be re- versed by injecting the pleural cavity. He was able to see the actual passage of milk-globules into these openings by remov- ing a portion of the fresh tendon upon a cork ring, its pleural surface upward, placing a drop of milk upon it, and observing with the microscope the nearly round openings, large enough to admit at once two or three of the milk-globules which ran toward these openings in little eddies, and disappeared below. He stained this membrane with nitrate of silver, and found that the openings corresponded to perforations between the endothelial cells leading perpendicularly or obliquely to the lymphatics. Schweigger-Seidel and Doigiel observed similar openings leading from the abdominal cavity, through the retro- peritoneal membrane, into the cysternce lymphatics magna, of the frog. Dj^bkowsky showed that colored fluids placed in the pleural cavity were absorbed by the lymphatics of the inter- costal pleura. Schweigger-Seidel, Doigiel, and Ludwig con- firmed the observations of Recklinghausen in connection with the central tendon of the diaphragm, and it is now generally admitted that such openings exist, not alwaj^s freely open, however, but sometimes with a valve-like cleft. It must not be understood that the small bead-like spots and the dark spots between the cells are true stomata. It is not definitely known, in fact, what they realty represent. Oedmannson first described them, not only on the serous membranes, but also on the endothelial layer of the chj^le-vessels. They are very numerous directly over the lymph-vessels of the central tendon on its peritoneal surface (Dybkowsky). Ranmer's mews on false stomata. — Ranvier has an in- geneous theory explaining the formation of these objects, which have been termed false stomata, also of the true sto- mata and the fenestra of the omentum. He considers that the lymphoid corpuscles, which are always to be found in serous cavities, penetrate the membrane, making a depression or per- foration, sometimes remaining, sometimes escaping again. In THE LYMPHATIC SYSTEM. 171 the majority of cases the black spots are formed by the albu- minous serum which these openings retain by capillary attrac- tion, having been coagulated and stained by the nitrate of silver, producing a ping. In other cases, a globular cell re- sembling a lymphoid corpuscle occupies the stoma, surrounded by a black margin due to the action of the silver. Other cells have a greater resemblance to small endothelial cells than to lymphoid corpuscles. The irregularity of their distribution in different membranes, in different animals, and at different ages, seems to favor the idea of such an accidental manner of formation. Klein on true and false stomata. — Klein divides the sto- mata vera, or true stomata, into two classes : a, those which form the mouth of a vertical lymphatic channel leading to a superficial vessel (they have a special endothelial lining) ; and b, those formed by discontinuity between the endothelium of the surface leading into a simple lymphatic sinus near the sur- face, and lined only on the lower surface with endothelium. Pseu- do-stomata, or false stomata, may be produced, according to this observer, by the prolongations of the sub- endothelial branched cells bn -i .,• . Fig. 76.— Frond of fern (Osmunda Clayto- eCOmillg tree by projection OUt- niana), under-surface showing stomata. ward between the endothelial cells. In pathological conditions he has seen an extensive cell-proliferation going on from one of these projecting pseudo- stomata. Ranvier accounts for the origin of the fenestra of the omentum in a similar manner, as for the stomata. It is of interest to know that the openings do not exist before birth, bnt increase in size and number as age advances. Klein, on the other hand, considers that the. openings in the omentum are produced by a process of vacuolation. The arrangement of the connective-tissue fasciculi around these openings is not that of complete rings, but is such that each opening is bordered by several fibres which take part in the formation of other openings in consequence of the irregularity in their arrangement. The endothelial cells may form a com- 172 MANUAL OF HISTOLOGY. plete tube in some of the narrow trabecule, in which a sin- gle cell may complete the circumference. Klein states that when these openings take place, the connective-tissue cells pre- viously situated between the connective-tissue bundles, come to lie on the lateral surface which is now free. This, he thinks, establishes the fact that the latter may be converted into true endothelial cells. Delafield, in considering the ques- tion of the re-formation of the endothelium on serous mem- branes, after hydrothorax, remarks that it would seem to be reproduced from the old endothelium, or from migrating white Fig. 77.— From silver-stained omentum of cat: A, fenestra; B, intercellular 1 ines of upprr Barfaoe; C, nuclei of same ; D, intercellular lines of lower surface ; E, nuclei of same ; F, nuclei in wall of opening ; corresponding cell-forms, part of upper and part of lower surface. blood-cells, or from sub-endothelial connective-tissue cell-. although he has not seen sufficient proof to establish any of these theories. The nerves of the peritoneum have been studied by Cyon. They enter the mesentery with the blood-vessels as fasciculi of medulla ted nerve-fibres, and, dividing laterally, lose their med- ullary sheath and form a plexus, the fibres of which show projecting nuclei at various points. The walls of the arteries receive a rich supply of these fibres. A lymph-space, surround- ing the fibres, can sometimes be demonstrated. Intimate structure of lymphatic vessels.— A lymphatic ves- sel may be considered as a serous membrane with only one free surface, rolled in the form of a tube, its endothelial layer form- ing the intima, resting upon an elastic reticulum, and an ad- ventitia or external envelope of connective-tissue fasciculi, as in the serous membranes. In the finest capillaries only the en- dothelial layer is independent, although they lie surrounded THE LYMPHATIC SYSTEM. 173 by elastic fibres and connective-tissue fasciculi. In the larger trunks, smooth muscular elements form a middle layer. The endothelial cells of the lymphatics have a more sinuous outline than the spindle-shaped cells of the blood-capillaries ; they are often irregularly dentated like the cranial sutures. The calibre of the lymphatics is also much more irregular than that of blood-vessels. As they increase in size, the tissues external to the endothelium assume more and more the character of ves- Fig. 78. — Central tendon of the rabbit, treated with solution of nitrate of silver, the most superficial Herons layer immediately adjoining the pericardium being shown : n, lymphatic capillaries ; ft, their ori- gin : c, serous canals with communications; ri. serous canals equal in width to the origin of the lympha- tic vessels; e, blood-vessel with epithelial cells. Magnified 300 diameters. Recklinghausen. sels with independent walls ; they finally resemble the veins in the largest trunks, except that they possess more muscular tissue than the latter. The diameter of the lymphatic capillaries is very variable ; they are generally larger than the blood-capillaries, ranging from 0.013—0.045 mm. (Frey). Branches of 0.2256— .2609 mm. may possess three layers (Kolliker). The vessels are richly supplied with valves, which are formed from the intima. Variations in shape. — Here let us consider an important characteristic of the lymphatic system, viz., its irregularity. 174 MANUAL OF HISTOLOGY. In this respect it contrasts very decidedly with the blood-vas- cnlar system. In the calibre of its vessels in different regions, in different parts of the same organ, and even in different parts of the same vessel, it is extremely irregular. A vessel of small calibre may suddenly expand into a saccular shape, which may have its diverticula or branches, or may form a chain of lacunae. It is true that these dilatations are formed just in front and behind the valves quite regularly, but they are also found everywhere, being, in fact, a characteristic of these ves- sels. Topographical peculiarities. — Nor is a uniform direction to be observed in the distribution of these vessels, for while they usually accompany arteries, lying outside the accompanying veins, they frequently take strange courses. A lymphatic may suddenly leave its companions to strike across a comparatively non- vascular held of tissue to share its fortunes with another set of blood-vessels. Respecting the capillary lymphatics, their place seems to be the middle ground between the blood- capillaries, just where we would expect to find this drainage system.1 They lie deeper in the skin and mucous membrane than the blood-vessels (Recklinghausen). The dispute con- cerning the question as to whether the smaller lymphatics have a distinct wall or are simple spaces, probably has been largely due to the variation in the structure of the lymphatics in the same tissue or organ in different animals, or in the same animal at different ages. The thoracic duct, which represents the other extreme in the structure of lymphatic passages, has an endothelial layer supported by a reticulum of elastic fibres, which mingles with the next layer, consisting of smooth muscular elements run- ning in every direction, the transverse elements predominating. The adventitia of connective-tissue fasciculi and elastic fibres completes its coats. The muscular layer in man is highly de- veloped compared with quadrupeds (Ranvier). 1 On the external ear of a rat whose blood-vessels are injected with colored gela- tine, and whose lymphatic vessels are rendered visible by silver, the larger centrifu- gal lymph-vessels are seen, even with low powers, to be surrounded by a network of blood-capillaries. The same has been demonstrated in tbe mesentery, the dia- phragm, and the posterior extremities. — Ueber ein die Lymphgefasse um-spinnendes Netz von Rlutcapillaren, von Alex. Dogiel. Arch. f. mikroskop.- Anat Bd. 17. 3. Heft, S. 3,15-340. THE LYMPHATIC SYSTEM. 175 Tlie subarachnoid and subdural lymph-spaces and their prolongations. — Axel Key and Retzius have shown that be- sides the great subarachnoid and subdural lymph-spaces of the brain and spinal cord, connecting with them are spaces en- closing the nerve-fibres of the cord, and, what is still more remarkable, extending outward on the peripheral nerves. The nerves of special sense, the olfactory, the optic, and the audi- tory, form no exception to this rule. Even the ganglia of the sympathetic system and their fibres have similar spaces, which are in connection with the cord. Nor is this the end of the intricate labyrinth. Each nerve-fibre has a space immediately outside of the sheath of Schwann, between the latter and the so-called fibrillary sheath, through which it communicates with the perineural sheath-space, and through the latter with the lymph-spaces of the central nervous system. That they are true lymphatic spaces is shown by the fact that they are lined by a layer of endothelial cells. Obersteiner demonstrated by injections that the nerve-cells also possess pericellular spaces connected with those of the corresponding fibres, a fact which I can corroborate. Key and Retzius say that this whole lym- phatic system is nowhere in direct communication with the ordinary lymphatic system, and that they have never seen the latter injected through the former, except when extravasation occurred. Bogras was the first (1825) to inject the nerves. He used quicksilver, and succeeded in injecting the peripheral nerves up to the ganglia, and made injections from the dura down to the ganglia. He failed with the olfactory, optic, and acoustic. Cruveilhier, and later, Robin, confirmed the fact that such injections are possible. Robin, in 1858, and after- ward, His, in 1863, demonstrated the perivascular lymph- spaces of the central nervous system. Lymphatics of tendons. — Axel Key and Retzius, and also Hertzog, have shown that the tendons possess spaces which may be injected. From the spaces formed by the endotenium and the peritenium, which communicate, connections exist with the deep and superficial lymphatics of the tendon. The development of the lymphatics is by a process of bud- ding and vacuolation similar to that which takes place in the blood-vessels. Lymphaiic glands.— -We now pass to the consideration of the lymphatic bodies called glands, ganglia, or nodes. Their 17G MANUAL OF HISTOLOGY. distribution does not concern us here; it is sufficient to say- that they are very variable in size and number in different regions, being supplied to nearly all the lymphatic trunks, with which they are connected by the so-called afferent and efferent branches. The former usually consist of several small branches ; the latter generally enter as single large trunks. The shape of the lymph-nodes may be spherical, oval, ob- long, or reniform. In the latter, which is by far the most fre- quent form, the afferent vessels penetrate the capsule on the convex surface, while the efferent branch escapes at the nil us. In the other forms it is difficult to determine which are the afferent and which the efferent vessels. A lymph-node con- sists essentially of spheroidal and cylindrical masses of reticular tissue, containing lymphoid corpuscles, richly supplied by a blood-capillary system, and sustained in place by a framework of connective tissue, with elastic and sometimes muscular ele- ments, forming a network around the masses for the circula- tion of lymph, and expanding externally to form a capsule. The gland is usually divided by histologists into a cortical and a medullary portion, the former being simply that part in which the lymphoid masses assume a spheroidal form (the follicles), this being the more peripheral portion of the node, or the part farthest from the hilus, when that exists. The medullary sub- division represents the remaining portion, and its lymphoid material is in the form of cylindrical or cord-like prolongations from the follicles. The capsule is composed of connective tis- sue, the fibres of which run in different directions in its exter- nal layers, possessing elastic fibres, fiat cells, and a slight amount of fat-tissue. The lymphatics of the capsule are found mostly in its outer layers. The inner layers present a more stratified appearance on account of the regularity of their bundles and the interposed connective-tissue cells. An elastic network and smooth muscular elements are found here, and also in the septa, and are developed in some animals to a high degree. It is from the inner layers of the capsule that the septa are given off to form the framework of the node. These consist primarily of trabecule, which, passing between the fol- licles, converge toward the medullary portion, where they inter- lace with the lymphoid cords of the latter, and may again unite at the hilus {stroma of His). They have a structure similar to that found in the portion of the capsule from which they have THE LYMPHATIC SYSTEM. 177 their origin. These septa are not complete partitions, but consti- tute an open framework, which, in consequence of its radiating arrangement, produces wider spaces in the cortical than in the medullary portion. To this the follicles correspond by being broadest at their peripheral portions. It must not be under- stood that the lymphoid masses, either follicular or cylindri- cal, are closely embraced by the septa ; they are separated from the latter, and from the sheath as well, by spaces, the " invest- ing spaces of the follicular portion" (Frey), or sinuses of the Fig. V.). — Section of the medullary substance of a lymphatic gland from the ox : a, follicular cord ; 6, trabecule; c, path pursued by the lymph ; d, blood-vessels. Magnified 30U diameters. Kecklinghausen. cortical substance (Ranvier), and the lymph-passages (Frey) or cavernous plexus (Ranvier) of the medullary portion. These spaces are maintained by a network of line fibres (tenter-fibres of Frey) derived from the septa, being given off at nearly right angles to the latter. The bundles of fibres composing them divide and reunite, forming meshes, and extend to the follicles and cords. In reality, they do not end here, but are continued to form the reticular tissue of these bodies by dividing into a still finer network, which differs in the different portions only 178 MANUAL OF HISTOLOGY. hy slight variations in the size of the meshes and the fineness of the fibres, the meshes being longer and narrower in the peri- pheral portions of the follicles and in the cords than in the central part of the former. This sort of tissue has received different names : cytogenous tissue (Kolliker), adenoid tissue (His), reticular tissue (Frey, Ranvier). It is, as the latter name implies, a network, the fibres of which run in every direction, being applied to one another in the same manner as the fibres of the omentum already described. The nuclei, which are more oval and larger than the lymphoid corpuscles, appear at the junction of fibres, simply rest upon them, and can be re- moved by brushing. They are endothelial cells, and in silver- stained preparations an endothelial layer can be seen to cover the septa, the reticulum of the lymph-passages, and the folli- cles in the same manner that the fine bundles of the omentum are covered ; that is, the spaces between the bundles are no- where covered, but each bundle is wrapped by these cells. This can only be seen after the lymphoid corpuscles that occupy the meshes have been removed by brushing. The endothelial layer is continuous with that of the afferent and efferent \yva- phatic vessels, which communicate with the lymph-spaces of the node, as shown by injections. According to Klein, the clinical nature of reticular tissue does not correspond to connective tissue proper or to elastic tissue. Filling the meshes of the follicular and cjdindrical portions of the lymphoid masses are the lymplwid corpuscles, two or more in each mesh. Lymphoid corpuscles are also found in the investing or lymph-spaces, but they are easily brushed out, while a much longer brushing is required to de- tach them from the other portions. The corpuscles are some- what larger than the colorless blood-corpuscles, though vari- able in size. They possess a single prominent nucleus, which is readily stained by most coloring matters. The amount of protoplasm they possess is small. When examined in a moist chamber at a temperature of 36° to 37° C, some of them ex- hibit amoeboid movements, the small ones having the least protoplasm around their nuclei being most active (Ranvier). Klein states that corpuscles are to be found which are larger than the others, having more protoplasm, and often two nuclei. He considers them in a more advanced stage of development than the others. THE LYMPHATIC SYSTEM. 179 The arteries and veins of the lymphatic nodes have their chief entrance at the hilus, with the efferent lymphatic vessels. The main trunks divide to pass into the septa. Still finer divisions pass into the reticular tissue, forming a rich capillary network in the follicles and cylinders, most marked at the sur- face of these bodies. In the cylinders a single axial arterial branch, surrounded by a peripheral capillary system, may fur- nish the supply. Another source of blood-supply may be from the capsule ; small branches, both arterial and venous, which ramify in its layers, send finer branches inward, encircling the follicles and traversing the septa and reticulum of the lymph- spaces. The capillaries possess, besides their proper wall, a sheath derived from the reticulum. Nerves of the lymphatic nodes. — Little is known on this point. Nerve-fibres enter with the blood-vessels in some of the larger glands of man (Kolliker), and non-medullated nerve- fibres have been seen in the lymphatic nodes of the ox. Con- cerning the lymphatics, they exist, as we have seen, in the outer layers of the capsule, and do not differ from those in other regions, forming a network in the capsule. They are continuous externally with the afferent lymphatics, and inter- nally with the lymph-spaces already described. The numerous lymphoid organs are all constructed upon a plan similar to that of the nodes, in that they all represent modifications in the arrangement of reticular tissue and its vascular supply. Injection of a lymphatic gland. — We may obtain an injec- tion of the lymph-passages in the node by puncturing the capsule with an ordinary hypodermic syringe (a method for which we are indebted to Hyrtl), and injecting a mixture of Prussian blue and gelatine (soluble blue, 25, solid gelatine, 1). It is best to inject one of a series of connected nodes, in place, exposing them by dissection in a freshly killed animal. One gland is then injected from the other through the afferent and efferent vessels (Ranvier). They are excised and hardened in Muller's fluid or alcohol ; sections are then made with a micro- tome, after which they may be washed in water, stained for a few minutes in picro-carminate of ammonia (1 per cent.), again washed, and then mounted in glycerine or Canada balsam. Method of studying the gland substance. — For the purpose of demonstrating the reticulum of the lymph-spaces and the 180 MANUAL OF HISTOLOGY. lymphoid masses, the node must be hardened in alcohol, bi- chromate of potassa, or (Ranvier's method) placed for twenty - lour hours in a concentrated solution of picric acid ; sections are then to be made, after which they are gently brushed and agitated in water with a camel' s-hair brush to disengage the lymphoid corpuscles (we are indebted to His for the method of brushing). After staining, preferably with hematoxylin, which exhibits, in a beautiful manner, the lymphoid corpuscles and the darker nuclei of the endothelial layer, they may be mounted in the usual manner. Ranmef s plan. — The plan particularly recommended by Ranvier is as follows : the node remains for twenty-four hours in a mixture of alcohol (36° Carder), one part, water, two parts ; then for twenty-four hours in a syrupy solution of gum- arabic, and is afterward hardened in alcohol sufficiently for section cutting in a microtome. Floating them in a shallow, flat dish, in water two or three centimetres deep, the gum is dissolved, and the brush used in a very delicate manner ; the sections may then be stained and mounted, as described above. The degree of hardness, and the force and duration of the brush- ing process, will determine the result, which practice only will make perfect. The lymphoid corpuscles in the lymph-passages, that is to say, in the parts which fill with the blue injection fluid, as previously described, are first removed, and additional brushing, when the proper degree of hardening has been at- tained, will enable one to remove these bodies from the folli- cles and cords, and also to remove the endothelial cells which rest upon the fibres of the reticulum and septa. Other methods of injecting glands. — A node removed imme- diately after death and injected by puncture with a 1 per cent, solution of hyperosmic acid, then placed in water for one or two hours, and afterward hardened in alcohol, cut in sections, colored by picrocarminate of ammonia, and mounted, gives good results. The best method for showing the endothelial layer is by interstitial injection (puncture) with a solution of nitrate of silver, 1—300 ; harden afterward by freezing, and make sec- tions. Before closing this chapter, let us take a retrospective view of our subject. In doing so, it is almost impossible to avoid associating the connective-tissue cell with other forms which THE LYMPHATIC SYSTEM. 181 seem to be its antecedents, modifications, or derivatives, viz., the extensive system of branched corpuscles in the matrix of the serous membranes, whose growth and proliferation form large tracts when they possess a sufficient blood-supply, and between which the lymph circulates, affording a channel of escape for the dischaiged bits of protoplasm, their offspring ; the throwing off of similar bits of protoplasm by the surface endothelium of the serous membranes ; the probable transfor- mation of the branched cells into fat-cells, and the conversion of a branched connective-tissue cell into an endothelial cell, when it reaches a free surface. Again, the fact that similar endothelial cells line the blood and lymph channels, and also cover the reti- culum of the lymphatic nodes and follicles, and that in the latter forms, when we have also a rich capillary blood-supply — that is, a supply of oxygen — the accumulation and probable, elaboration, if not proliferation, of lymphoid corpuscles goes on in a more extensive manner than in the lymphangeal tracts ; taken together, all point to the idea that they are different forms of protoplasm which have been converted, or are con- vertible, one into the other under proper conditions of tempera- ture, food-supply, and excitability, the definite limitations of which are but imperfectly known. In the germinating tracts, superficial and deep, of the serous membranes, in the lymphatic nodes and follicles of the ali- mentary canal, and also in the lymphoid organs (spleen, ton- sils, etc.), we have active forms, reproduction by budding, and division. The formation of the lymphoid corpuscles, which may be considered as so many amoebae sporting in a nutritious fluid, and engorging themselves with that which is brought to them by the agency of the absorbents and lymph-channels, under conditions favorable to great activity, free to penetrate most of the tissues, and, perhaps, become fixed forms. These processes of activity, when confined to the limits of the organs mentioned, are conducive to life and growth, but occurring in the allied forms that have become fixed, as the corneal branched cells, the connective-tissue cells, or the endothelial cells, to any considerable extent, inaugurate the processes of disease and death. Thus these comparatively indefinite and undifferen- tiated forms of protoplasm may be said to be keys to life and death. 182 MANUAL OF HISTOLOGY. BIBLIOGRAPHY. Authors referred to in the text : Bicuat. Anat. gen. Second edition. 1812. Ibid. Traite des membranes. 1816. Remak. Miiller's Archiv. 1850. Brlcke. Ueber die Chylusgefiisse, etc. Sitzb. der Wiener Akad. 1853. Leydig. Lehrbuch d. Histologic, etc. 1857. ViRCHOW. Cellular Pathology. 1860. Oedmannson. Virchow\s Archiv. Bd 26. 1863. Chrzonszczewsky. Virchow's Archiv. Bd. 31. 1864. His. Archiv f. mikrosk. Anat. Bd. I. 1865. Schweigger-Seidel and Doigiel. Arbeit, a. d. phys. Lab. z. Leipzig. 1866. Kolliker. Handbuch der Gewebelehre. 1867. Cyon. Arbeit, a. d. Phys. Anstalt. in Leipsig. 1868. Robin. Diet. Ency. Sc. Med. 1870. Recklinghausen. The Lymphatic System. Strieker's Histology. 1872. Klein. The Lymphatic System. 1873. Dybkowsky. Arbeit, a. d. Phys. Anstalt. in Leipsig. Arnold, J. Archiv f. path. Anat. Bd. 58, p. 203. 1873. Thin. Proc. Royal Soc. Vol. 22. 1874. Thoma. Centralbl. f. d. med. Wiss. 1875. Archiv f. path. Anat. Bd. 64. 1875. Key, Axel, and Retzius. Archiv f. mikrosk. Anat. Bd. IX. 1875. (Abstract of large work on the nervous system. ) Hertzog. Zeitschr. f. Anat. und Entwick. 1875. Ranvier. Traite technique d'histologie. 1877 et seq. Delapield. Path. Studies. New York, 1878—80. Frey. The Microscope, etc. New York, 1880. Among the more recent authors that have written on this subject are : Hoggan. Proc. Royal Soc. 1876—77. (Two articles. ) Lewis. Proc. Roy. Society. 1877. Robin and Oadiat. Journ. de l'anat. et de la phys. 1876. No. 6. Budge. Arch. f. mikrosk. Anat. Bd. X. 1876. Riedel. Archiv f. mikrosk. Anat. Bd. XL 1877. Wittich. Mittheil. a. d. k. phys. Lab. 1878. Mierzyewski. Jour, de l'anat. et de la phys. Paris, 1879. Renaut. Comptes rendus Acad, des Sci. Paris, 1879. Weber-Liel. Arch. f. path. Anat. Bd. LXXVII. 1879. Fischer. Arch. f. mikr. Anat. XVII. 1879-80. Sitna. Wien. med. Presse. XXL 1879. CHAPTER XIII. THE LIVER AND BILIARY APPARATUS. By DR. ABRAHAM MAYER, Curator of the Manhattan Eye and Ear Hospital, New York City. The liver is enclosed in a connective-tissue capsule, the peritoneum, which also gives off secondary folds, or duplica- tures, called ligaments, by which the organ is held in proper connection with the adjacent parts. The thickness of the cap- sule is about 0.03 mm., and its free surface is covered with the flattened corpuscles that belong to serous membranes gener- ally. This connective-tissue covering is furthermore composed of thin laminae, which contain a large number of elastic fibres. At the transverse fissure, where it is continued into the inte- rior of the organ, the same character is maintained. Here it encircles vessels, ducts, and nerves, forming the so-called Glisson's capsule, which, indeed, with its minute ramifications, traverses the whole interior of the gland. The liver contains, in addition to the glandular substance, blood-vessels, lympha- tics, nerves, and gland-ducts, the whole held together by the framework of connective tissue just mentioned, which in the human species is but imperfectly developed. The hepatic lobules. — The glandular parenchyma consists of the so-called hepatic lobules, which in the human liver are not completely separated from one another, for the reason just named. In some of the lower animals, however, this sepa- ration is more perfect. In the hog's liver, for example, the septa are so well developed that the lobules are plainly recog- nizable by the naked eye. To isolate the human lobules is a matter of some difficulty ; but it can be accomplished by macerating the organ in water from twelve to twenty-four hours. These lobules are also known as the hepatic acini, or in- 184 MANUAL OF HISTOLOGY. suIcb of the liver. Their form is irregularly polyhedral, and they usually measure about 4x1 mm. At their bases they are attached to short twigs of the hepatic vein, which have a thickness of from 0.03 — 0.06 mm., and traverse the lobules in the axes of their long diameters. As the hepatic vein ascends through the lobule, it gives off innumerable capillary branches, almost at right angles to its course. The latter pursue their way to the periphery of the lobule, and hence have a radial direction. These capillaries further subdivide within the lob- ules, and are united to each other by transverse branches, forming a network with small meshes. At the periphery the capillaries join the rami- fications of the portal vein. The latter divides within the liver into nu- merous branches, which again subdivide at the surfaces of the lobules. Their ultimate ramifica- tions form the boundary lines between adjoining hepatic lobules, and it is for this reason that they have been called interlobular veins.1 For a similar reason the branches of the hepatic vein, which traverse the centres of the lobules, have been called intralobular ' or central veins * (Fig. 80). The interlobular veins are contained within interlobular or intermediate (Hering) canals ; these are easily demonstrable in the hog's liver. In this animal the adjoining edges of three or four hepatic lobules combine to form a canal which con- tains the interlobular vessels. The latter are surrounded by connective tissue, which is continuous with that of the septa between the lobules. In the human liver there is a similar arrangement, but in it the septa of connective tissue do not completely separate the lobules, and, excepting at the inter- FlG. 80. — Injected liver of rabbit, showing branches to portal vein, capillaries, and the hepatic veins in the centres of two lobules. Frey. ■Kieman: Philosoph. Trans., 1833. 5 Venas Centrales, Krugenberg, Miiller's Archiv, 1843. THE LIVER AND BILIARY APPARATUS. 185 lobular canals, the parenchyma of contiguous lobules appears to coalesce. Nevertheless, the substance of the human liver can be di- vided into distinct lobules, and the terminal branches of the portal veins may be regarded as their natural boundaries (Figs. 80 and 87). Starting with the portal veins, therefore, the course of the blood is as follows : portal veins, interlobular veins, cap- illaries, intralobular veins, hepatic veins, and inferior vena cava. Sublobular veins, according to Kiernan, are such branches of the hepatic vein as are placed under the bases of several lobules, and collect the blood from their central veins. The liver may be injected either through the portal or he- patic veins, or through both. Good specimens may be ob- tained by injecting the fresh liver of a dog or rabbit with carmine - gelatine through the portal vein, then inject- ing fluid Berlin blue into the hepatic vein, and afterward hardening the organ in alco- hol. The central vein and adjacent capillaries will thus be filled with a blue mass, while the interlobular and portal veins, with the per- ipheral capillaries, will con- tain the transparent red mass. The color of the cut sur- face of the liver in its natu- ral condition is of a uniform reddish brown tint, and its lobular structure is not readily made out. Usually, however, we find two shades or gradations in color ; one, corresponding to the central veins of the lobules, is of a dark red ; the other, corre- sponding to the periphery of the lobules, is a lighter and yel- lowish red. Occasionally these conditions are found to be reversed, and the difference of color is due to the fact that after death the central and other hepatic veins are filled with blood, while the portal and its branches are empty ; and also because Fig. 81. — Transverse section of a human lobule, showing opening for central vein. Ecker. 186 MANUAL OF HISTOLOGY. the deposit of bile-pigment takes place at the centres of the lobules about the intralobular veins ; whereas a i'atty infiltra- tion, such as may occur in normal livers, takes place at the periphery. Not uncommonly the yellowish red color at the boundary of the lobules exists under the form of delicate markings, which are nothing more than the emrjty interlobular branches of the portal vein. Kiernan occasionally observed in young subjects that the portal vein was distended with blood, while the hepatic vein was empty. In such cases the periphery of the lobules was of a darker color than their centres. The Mood-vessels of the liver. — These have been partly de- scribed above. The hepatic artery, and duct, and portal vein enter the liver at the transverse fissure, enclosed within Glis- son's capsule, and continuously subdivide as they push their way through the parenchyma. The subdivisions of the portal vein never anastomose, but are distributed around the surfaces of the lobules, forming their boundaries. At the periphery they break up into capillaries which enter the lobules. These are about 0.02 mm. in diameter, and form a network, the meshes of which are scarcely wider than capillaries. Within the lobule the capillaries unite to form the central vein, and these then empty into branches of the hepatic vein. The subdivi- sions of the hepatic vein are also devoid of anastomoses, but after traversing the posterior portion of the liver in canals (which they embrace closely), unite to form the hepatic vein. A peculiarity of this latter vein is the fact that its larger branches give off successively small lateral twigs, which enter the bases of the neighboring lobules, so that after dividing such a branch lengthwise it would seem to be pierced by small circular openings, which are the orifices of the lateral branches. Not unfrequently a central (hepatic) vein will divide into two branches within a lobule, in which case the latter seems to possess two apices, which become joined together as we ap- proach its base. The connection between the portal and hepatic veins takes place only through their capillaries. The hepatic artery is comparatively small. It enters the liver together with the duct and portal vein, and at once breaks up into branches, which, anastomosing with each other, form a large-meshed network. The arterial branches are distributed to the vessels mentioned, which they enclose, and also to the THE LIVER AND BILIAKY APPARATUS. 187 connective tissue which surrounds the latter. The hepatic arte- ry also gives off nutrient branches which supply its own walls, and small twigs, which, piercing the substance of the liver be- tween the lobules, supply the branches of the hepatic vein. The ultimate branches of the artery are contained within the interlobular canals, and break up into capillaries at the peri- phery of the lobules, which they traverse for a short distance to form a distinct network. There is no communication between the intralobular capillaries of the hepatic artery and those of the portal vein. The former seem destined to supply the ad- jacent vessels, and probably the small amount of intralobular connective tissue to be spoken of hereafter. It has been thought by some (Chronszewski, Rindfleisch, and others) that the capillaries of the hepatic artery end midway between the interlobular and cen- tral veins, within the lobule. Beale and Kiernan have noticed that an arterial branch here and there enters a lobule ; while Theile, Davis, and others describe a capillary network about the periphery of the lobules. Finally, branches of 0.05 to 0.1 mm. in diameter are dis- tributed to the capsule of the liver, where they break up into capillaries, radiating in all directions and anastomosing with each other to form a large-meshed network, which communi- cates with the capillaries of the phrenic, mammary, and supra- renal arteries. This plexus empties into small twigs, the so- called inner roots of the portal vein. The capillaries of the liver may be injected either through the hepatic or portal vein, or both, as before stated. For in- jecting the hepatic artery the author prefers his cold solution of carmine-glycerine.1 The gland to be injected must be as fresh as possible. If, for example, a dog be selected for this purpose, the abdomen should be opened and the animal allowed to bleed to death by section of the vena cava. Now introduce into the hepatic artery the canula of a syringe filled with the carmine-glycerine, secure it in place and inject. Harden the organ in alcohol, cut sections, and mount in balsam. The liver will not be uniformly injected, and only those portions can be utilized in which the injected mass seems to be widely diffused. If, in addition to the artery, the hepatic vein be injected with a blue colored mass, beautiful results may be obtained. Sections in which the lobules are cut transversely show the 1 See chapter on the Kidney. 188 MANUAL OF HISTOLOGY. central veins occupying the position of the axes of the lobules and the capillaries, pursuing a radial course and anastomosing with each other by transverse communications. Since the capillaries successively divide from the centre toward the periphery, it follows that they are much less numer- ous at the former than at the latter point. A section through the long axis of an acinus will show that the central vein is divided lengthwise, and that the capillaries are given off from it almost at right angles to its course. Nearer the summit of the lobule, however, the central vein is seen to break up into diverging capillaries. If the section has been made to one side of the central vein, but yet parallel with its axis, many capillaries will be cut across, more or less transversely, and will then appear as small, circular, or oval rings. The connective tissue of the liver. — Glisson's capsule is formed of longitudinal bundles of connective tissue which are loosely interwoven. It serves to bind together the hepatic 7$&& 'w2 artery, portal vein, and hepatic duct, and also fills out the small spaces left between the ramifications of these vessels (Fig. 82). Sections from a liver hardened in chromic acid or alcohol, and immersed in a di- lute solution of caustic potassa, or simply pencilled, show the connective tissue well. About the hepatic vein it is thin and dense, and firmly united to the glandular structure, so that when cut transversely these vessels appear to gape. In the camel the connective tissue is greatly developed,1 even more so than in the hog. The interlobular septa are very dense and fibrillated ; in the interior of the lobule the connective tissue has a lamellar structure. According to Ewald and Kuehne, minute bundles of fibrous tissue extend beyond this interlobular connective tissue, and piercing the lobules eventually surround the central veins. Fig. 82. — Connective tissue of a child's liver, after hardening in alcohol and pencilling : a, a, capillary vessels con raining a few blood-globuleR ; 6, 6, connective-tissue fibrils ; c, c, liver-cells not removed by pencilling. 1 Turner, Wm., Journal of Anat. and Phys., Vol. XI., p. 2. THE LIVER AND BILIARY APPARATUS. 189 Tlie liver-cells. — The liver-cells are found lying within the meshes of the capillary network of the lobules. If we bear in mind the shape of the intralobular capillary reticulum, the arrangement of the hepatic cells will be readily understood. The meshes of the capillary network have about the same diameter as the capillaries themselves. Hence it follows that the cells which occupy these meshes must also have the appear- ance of a reticulum. But inasmuch as the vascular meshes contain two or three liver-cells, it is evident that two neighbor- ing capillaries must be separated from each other by at least one liver-cell. Hence, in sections where the capillaries are cut transversely, their circular openings will be surrounded by a ring of liver-cells, or a circle of capillaries will enclose a mass of glandular substance. In sections which cut the central vein transversely the radiating capillaries will enclose radiat- ing rows of liver-cells. (See Fig. 81.) These are either joined to one another by the intervention of other liver-cells, or they are separated from one another by transverse capillary branches. On the other hand, in sections where the central vein is cut lengthwise, the (nearly) parallel intralobular capillaries will ap- pear separated from one another by correspond- ing rows of liver-cells. The glandular substance of the liver would then be composed of small, solid columns or rows of cells united to each other by other cells, thus forming one connected mass, and containing within its meshes the cap- illary network. In the fresh state the liver-cells appear as spherical or egg-shaped bodies, usu- ally presenting facets. They are somewhat flat- tened by being pressed against one another (Fig. 83). Corpuscles possessing processes are some- ,. fio. 83. -Human ' * x ox- hver-cells: a, with sin- timeS found. gle nucleus; b, with double nucleus. Frey. The hepatic cells are about 0.013—0.02 mm. in diameter, and possess one or two nuclei,1 which are gener- ally spherical, although they occasionally appear to be flat- tened ; the diameter is 0.006—0.007 mm. The liver-cells do not possess any membrana propria, but a hardened boundary layer seems to exist in its place. It is probable also that the 1 Occasionally three or five nuclei, especially in young subjects (Beale). 190 MANUAL OF HISTOLOGY. cells are bound together by a colloid substance, although this is a point which has not yet been definitely settled. Sections of a dog's liver, immersed for a short time in dilute osmic acid, will occasionally exhibit a brown or black tracing between adjoining cells. Pres- sure on the cover glass will part them and leave the darkened material free in the field of vision. I have satisfied myself that this tracing is not of a nerve, biliary duct, or connective-tissue fibril ; it is either a portion of the boundary layer of a liver-cell, or, as I suppose, a colloid substance between two cells. This appearance, however, is not constant. The protoplasm is of a dark brownish or greenish color. It is viscid, and contains numerous granules of small size, in ad- dition to smaller or larger fat-droplets.1 In livers hardened by chromic acid or alcohol, the shrinkage of the cells causes them to appear polyhedral, and they also seem much darker than in the fresh state. If the portal or hepatic vein has been injected, the cells will show distinct indentations produced by the dis- tended capillaries. When liver-cells are treated with diluted acetic acid, their protoplasm becomes pale, while their nuclei are rendered more conspicuous. In a dilute solution of caustic potassa the cells swell up, become rounded, and are finally dissolved. With water they also swell up, become paler and more rounded, and at length disintegrate. In the fresh state, by the addition of an indifferent fluid (£ per cent, solution of chloride of sodium, or iodized serum), the liver-cells are said to show protoplasmic movements. The granular substance of the liver-cells has been shown (by Schiff, in frogs, and by Nasse, in certain mam- malia) to consist of an animal amylum, which is converted into sugar through the agency of a peculiar ferment. The fat-droplets may be either small in number and size or quite numerous and large. Not infrequently they coalesce to form larger fat-globules. In the so-called fatty infiltration they are very large, and compose the greater part of the cells. The nuclei are granular, and where two or more of them occupy the same cell, they may apparently be united to each other. 1 According to Kupffer and Klein the substance of the cells is composed of a honeycombed network, i.e., an intracellular reticulum. Klein says the nucleus is lim- ited by a thin membrane, and includes an intranuclear network, containing occa- sionally one or two nucleoli. The intranuclear network is in continuity with the intracellular one, and the network of contiguous cells are in connection with one another (Klein and Smith : Atlas of Histology). THE LIVER AND BILIARY APPARATUS. 191 Division of a nucleus, as described by Kolliker, I have never been able to confirm. When two nuclei are placed in contact, there may be an appear- ance of division, but the actual process is not easy to see. Thin liver sections may be stained either in carmine fluid or hsematoxylon, and preserved in glycerine or balsam. The larger bile-ducts. — If, for the sake of convenience, we imagine that the hepatic duct enters the liver to be distributed to its substance, we may describe it as giving off two primary branches at the transverse fissure, one passing to the right lobe, the other to the left. As these branches continue their course, following the subdivisions of the hepatic artery and portal vein, they also undergo successive divisions, and at length enter the interlobular canals. In this position their diameter varies between 0.02 and 0.03 mm. The primary branches do not, however, pass unchanged into the liver tissue. They ramify even before entering the gland, but such vessels are distributed only to the under surface (Henle). Other biliary ducts, given off in the trans- verse fissure, form a network on the upper surface, as may' be demonstrated by injecting the hepatic duct with carmine-gly- cerine. The branches of these networks then enter the liver- tissue and ramify throughout it, following the subdivisions of the hepatic artery and portal vein. As the divisions of the hepatic duct diminish in size, the thickness of their walls undergoes proportionate diminution. The trunk of the hepatic duct comprises an internal layer measuring 0.15 mm. in thickness, and an external layer of 0.2 — 0.3 mm. Both of these coats are composed, according to Henle, of interlacing connective-tissue bundles, in which elas- tic fibres are freely intermixed. These ducts have an internal lining of cylindrical epithelium, which is 0.05 mm. in height. Even where the branches measure only 0.2 mm. in diameter they have cylindrical epithelium surrounded by a single layer of connective tissue longitudinally disposed, in which there are also muscle-corpuscles, distinguished by their long, rod- shaped nuclei (Ileidenhain). The most minute biliary pas- sages consist of a structureless membrana propria, which is lined with flattened cylindrical epithelia. Glands of the ducts. — In the trunk of the hepatic duct and . its subdivisions, down to those branches of which the diameter is not less than 0.5 mm., the mucous membrane is provided 192 MANUAL OF HISTOLOGY. with numerous irregular excavations, measuring 0.15 — 0.3 mm. in their long diameter. In this trunk there occur also a great number of pores or orifices, which, on examination, prove to be the mouths of the passages leading from simple and com- pound gland like bodies, the so-called glands of the bile-ducts. The simple glands consist merely of single vesicles, or alveoli, with afferent passages, all of which are imbedded in the mu- cous membrane ; or of two or more vesicles with a single pas- sage. The compound glands are formed by the union of two or more simple ones, which have a common passage. Thejr are quite large, and their expanded portions lie on the outer sur- face of the hepatic duct. When filled by injection with gela- tine they are visible to the naked eye. The passages pierce the walls of the duct at an acute angle, pursuing a course within its walls, nearly parallel to the duct itself ; the opening into the mucous membrane is therefore quite a distance from the gland-vesicles. According to Henle, these compound glands are not found in the larger branches of the hejmtic duct, but they occur frequently in the network of bile-ducts situated in the transverse fissure. Allusion has already been made to them. The vesicles measure 0.04 mm. in diameter, and, like the excavations in the larger branches of the duct, are lined with a cylindrical epithelium, in no way differing from that of the duct itself; the afferent passages also possess the same kind of epithelium. Structures allied to these excavations and glands occur in small number in the bile-ducts ' which are found in the liga- mentum triangulare and on the diaphragm, where they appear as villous prominences on the duct-walls. According to Theile, Weber, and others, these bile-ducts represent the last vestiges of an atrophied liver substance, the existence of which dates back to infancy, or perhaps to fetal life. The excavations in the larger branches are either simple diverticula of the internal walls, or the openings of lateral bile- ducts ; the punctate pores are the orifices of the outlet pas- sages of duct-glands. Capillary bile-ducts. — When the larger bile-ducts, by con- Vasa aberrantia of E. H. Weber. THE LIVER AND BILIARY APPARATUS. 193 tinuous subdivision, have at length reached the interlobular canals, in conjunction with the branches of the portal vein and hepatic artery, they send capillary branches within the sub- stance of the lobule, and thus form an intralobular network. These capillary ducts are of extreme delicacy, measuring only from 0.001 to 0.0012 mm. In order to demonstrate them fully the}^ should be filled by natural injection. The substance to be employed for this pur- pose is a solution of pure indigo-carmine. The animal serving for injection (rabbit or dog) should be secured in the manner described in the chapter on the Kidney, where all the neces- sary manipulations are fully detailed. The best results are obtained by injecting a cold, saturated solution of indigo- carmine into the external jugular vein, directing the stream toward the periphery (brain) ; 5 or 10 ctgms. are to be injected at intervals of thirty to forty minutes, and the injection con- tinued until from 25 to 50 ctgms. have been used, the amount varying according to the size of the animal. It takes a longer time for the elimination of indigo-carmine through the capillary bile-ducts than for the same process by way of the renal tubules, and a larger amount of solution will therefore have to be em- ployed. As soon as large quantities of the indigo solution have been injected into the jugular vein, the animal becomes uncon- scious and there is a decrease of temperature ; hence, it should be covered over with layers of cotton-batting. After a variable time (three to twelve hours) the animal is killed in the follow- ing manner : The abdomen is opened and the canula of a large syringe filled with absolute alcohol secured in the lumen of the portal vein ; the inferior vena cava is then cut across above the entrance of the hepatic vein, and the piston of the syringe pushed home. The liver, which before was of a uniform blue color, now presents a marbled appearance, not unlike that of malachite. Or, the portal vein may be injected with the writer's carmine- glycerin*', the vena cava having been divided as above. In either case the liver is to be removed at once and placed in a vessel containing absolute alcohol, and while immersed in that lb i id cut into small fragments. Sections may then be made in a few hours. The arrangement of the bile-capillaries differs in different animals, hi the rabbit, for instance, they lie between the ad- 194 MANUAL OF HISTOLOGY. joining surfaces of two contiguous cells, and rarely in the canals formed by the edges of three or more cells (Hering '). So that while the blood-capillaries occupy the canals previously described, the bile-capillaries form an independent network be- tween the boundary surfaces of the liver-cells (Figs. 84 and 85). In cross sections they may be seen, appearing as small, circular Fig. 84. Fig. S5. Figs. 84 and 85. — Injected liver of rabbit. The narrow, reticulated bile-capillaries are shaded with 'longitudinal, the broader blood-capillaries with transverse lines. Within the boundary line or septum of two contiguous cells the cross-section of a bile-capillary is seen as a dark spot or point. The liver cellt contain one or two nuclei. In Fig. 84, the bile-capillaries are slightly distended by the artificial injec- tion ; in Fig. 85, markedly so. Hering. openings between the cells, while in longitudinal sections they present a linear arrangement (Figs. 85 and 86). In the dog this arrangement is the same, only here the bile-capillaries occur more frequently in the canals formed by the edges of the lower cells. According to Hering, both in rabbits' and dogs' Livers the blood-capillaries are separated from the bile -capillaries by the intervention of at least one liver- ■cell. Livers in which the bile-capillaries have been injected by the natural method with indigo -carmine do not always demonstrate this. And here it may be remarked, that in artificial or forced injections of the bile-capillaries they are always distended beyond their natural diameters." 1 Hering : Ueber den Bau der Wirbelthierleber, and article on Liver in Strieker's Manual. 2 Compare Figs. 84 and 85. after Hering. Even in Fig. 84 the bile-capillaries are larger than they ought to be. In an article on the liver by Dr. W. G Davis, in the Amer. Jour. Med. Sci., Vol. LXXVIII., the distention of the capillaries is excessive. THE LIVER AND BILIARY APPARATUS. 195 By conjoined natural injection of the bile-capillaries and artificial injection of the portal system with carmine-glycerine by the methods above detailed, very gratifying results are ob- tained. Care must be taken, however, not to use too much force during the process of in- jection, and only such por- tions of the liver should be chosen for sections as show, by their red color, a perfect filling of the portal branches. While the elimination of the indigo-carmine is taking place within the liver of the living animal, the bile-capilla- ries probably contain the salt in a soluble form. The addi- tion of absolute alcohol at once precipitates this color- ing reagent in the form of exceedingly fine stellate crys- tals, or as finely granular mat- ter, which may in some meas- ure account for the angular character of the biliary capil- laries, as seen in such specimens. Gentle curves, such as are represented in Fig. 85, never appear. The constringing action of the alcohol on the liver-cells has unquestionably some effect, and therefore modifies the normal appearance. Natural injections further show the great preponderance of the biliary- over the blood-capillaries. In the liver of a dog, for instance, each liver-cell seems suspended within two or three (rarely four) bile-capillaries, and where the latter are Pio. 86. — Liver of a three-months1 child, hard- ened in chromic acid. The capillaries are filled with red blood-corpuscles (indicated by colorless rings) and a few leucocytes. The cross section of a bile-capillary is shown within the boundary line of any two con- tiguous cells. A similar cross section is shown in the canal formed by three adjoining liver-cells. One need only compare Fig. 3 in Davis's article with Fig. 84 of Hering's, which, by the way, is a good illustration. The first to describe the intralobular network of bile-capillaries were Andrejevic (Ueber der feineren Bau der Leber. Wiener Sitzungsbericht, 1801) and MacGillavry (Zur Anat. d. Leber. Wiener Sitzungsbericht, 1864). Chronszewski was the first to inject the bile-capillaries by natural injection (Virchow's Archiv, Bd. 86). MacGillavry Chronszewski, Budge, and others, described the bile-capillariea as possessing true walls. 196 MANUAL OF HISTOLOGY. < .. * ,->. i> joined together the calibre of the capillary is markedly in- creased. Sections made parallel to the external surface of the liver, immediately under the capsule, generally cut the centra] vein transversely, and such sec- tions show that the bile-capillaries possess a somewhat radial course (Fig. 87;. Human livers can rarely be obtained in a fresh state, and examinations of their bile-capil- laries are therefore attended with difficulty. Do the bile-capillaries possess walls of their own f — This ques- tion must be answered in the affirmative. In specimens where the bile-capillaries have been in- jected by the natural method, cross sections of such capillaries will demonstrate, with high pow- ers, that there is a dot of blue indigo-carmine surrounded by a distinct circle which is perfectly transparent and in marked contrast to the somewhat yellowish color of the adjoining liver-cells. (See Fig. 88.) It is more difficult to see this in sections which cut the capillaries in their longitudinal diam- eters, but where two or more capil- laries unite this halo is again seen. That this appearance is due to the pres- ence of a true wall seems clear, but all doubts will be dispelled by watching the diffusion which takes place in such a section on the addition of a few drops of water under the cover glass. The indigo-carmine becomes dissolved in the wrater, forming a deep blue liquid Fig. S7.— Capillary bile-ducts of a rabbit, distended by artificial injoction : 1, a portion of a lobule ; a, central vein ; b, b. interlobular veins ; c, c. bile-ducts ; rf, d, blood-capillaries ; e, e, bile-capillaries. which stains the surrounding cells and Fig. 88. — Liver of the dog. Nat- ural injection of bile - capillaries. showing double contour of the capil- laries, which are only partly filled with injection. Cross sections of 1 iric s showadotof iadigo- carmine surrounded by a distinct halo. The woodcut does not show this satisfactorily. In the specimen the lines corresponding to the walls of the capillaries are of the utmost delicacy. Magnified 450 diam. vessels of a uniform color. While watching a bile-capillary during the progress of this action it appears to stand out more prominently than before, and its walls become more distinct. In a few moments the cells will have become swollen by the imbibition of water, and the picture gradually THE LIVER AXD BILIARY APPARATUS. 197 fades, until at length it would be difficult to even locate the original seat of the capillary. I have verified this over and i again. The capillary walls seem to be structureless ; at -: with a power of 1,-AuO diameters I have been unable to ray structure. The membrana propria of the inter- lobular bile-ducts is continued on to the capillaries within the lobule. Herlni'. Henle, and others do not believe that the bile-capillaries possess ■walls of their own, but suppose them to be contained -within the boundary surface of the liver-cells, the latter taking the place of the epithelium of the interlobular bile-ducts. Henle further quotes Scbweigger-Seidel (in the Archie fur path. AnaL and PJa/s., XXYLT., 505. 1863), -who injected the bile-capillaries -with faintly colored gelatine, and showed that by warming the sbde the gela- tine dissolved 'without leaving any residue whatever. From what has been said of artificial injections, and recognizing the extreme delicacy of the bile-cap- illaries, it is not surprising that this result was obtained after injecting a warm . m of gelatine into the capillaries. The walls of these capillaries are homogeneous and exceedingly dehcate, so that they are destroyed by a mod- legree of heat. Very soon after death they undergo a sort of liquefac- tion, and -what was before a vessel with true walls is now an open channel, through which an artificial fluid can be made to force its way. At first the elimination of the indigo-carmine takes place in the bile-capillaries on the external border of the lobule, and somewhat later the capillaries about the central vein be- come filled. Neither the protoplasm of the liver-cells nor their nuclei ever become stained with the blue solution during the process of elimination ; such coloring would be the result of -mortem diffusion. But the cylindrical epithelium of the lored blue, and indubitably these glands excrete the i Limine, as do the c ills of the convoluted tubules of the kidney. WTiether they secrete any substance during life, or what that substance may be, has not yet been determined. Theile, Kolliker, and Kiernan suppose that these glands secrete a mucous • ;nce which becomes mixed with the bile. Henle regards these glands and excavations as reservoirs which are occasionally filled with bile. From what has be*-n it would appear that the cylindrical epithelium of the glands eliminate the indigo-carmine, and hence we may suppose that -ecrete some fluid or substance during life. gall-bladder^— The walls of the gall-bladder are about 198 MANUAL OF HISTOLOGY. 2 mm. thick, and are composed of three coats : ' an internal, mucous and muscular ; a middle, of connective tissue ; and an external, the serous. The internal coat, 0.4 to 0.5 mm. thick, is composed of alternating layers of connective tissue and smooth muscle fibres, the most internal being a layer of connective tissue which contains a tine meshed capillary net- work. The connective tissue is dense and the muscle fibres are arranged in the form of interlacing bands. The internal sur- face is lined by a layer of cylindrical cells bearing a thickened, striated edge, and the surface is traversed by a network of small intersecting ridges, forming, as it were, a sort of lattice- work. The middle coat, 0.5 to 1 mm. thick, is formed of con- nective tissue, the meshes of which are wider on the internal than at the external surface. This coat contains the larger vessels and nerves. The external, or serous coat is thin, and consists of a layer of dense connective tissue and peritoneum. A few mucous glands s are found scattered here and there in the walls of the gall-bladder. Sections from this organ, hard- ened in alcohol, may be stained with the carmine or picro-car- mine solution and mounted in glycerine or balsam. The cystic and common ducts resemble in structure the hepatic duct. The inner surface of the former is thrown into crescentic ridges, and in the region of the neck of the gall- bladder the connective tissue of the internal coat shows a circular arrangement. The ducts contain no muscle fibres. The lympli-vessels. — These may be divided into a series of superficial and deep channels. The former are situated in the capsule of the "liver and form a capillary reticulum with small meshes, the larger branches of which accompany the arteries in pairs and communicate with each other by trans- verse anastomoses. They are found in Glisson's capsule, and they also form a network somewhat larger meshed than the preceding. They accompany the hepatic artery and portal vein and their branches into the interior of the liver, and form anastomoses with the superficial lymph-vessels. The lymph- canals may easily be injected with colored material (carmine- glycerine) by filling a large hypodermic syringe with the liquid and injecting one of the larger lymph- vessels in the liilus of 1 Henle : Eingeweidelehre. 2Luschka: Virchow's Archiv, 1857, and Zeitschr. f. rat. Med., 1858. BIBLIOGRAPHY. 199 the liver. The syringe may be refilled three or four times without removing the canula, and the injection must be made in the direction of the normal lymph-current. In this way the colored liquid will flow backward into the smaller vessels. During the injection of the larger branches their proximal ends should be secured by clamps or ligatures. The nerves of the liver enter the organ at the hilus and fol- low the course of the vessels. They are composed mostly of non-medullated elements, a few medullated fibres being found in the larger branches. They cannot be traced into the lobules. BIBLIOGRAPHY. Kiernan. Anat. and Phys. of the Liver. Philos. Trans. 1833. Lambron. Archiv. gen. 1841. Krukenberg. Miiller's Archiv. 1843. Weber, E. H. Miiller's Archiv. 1843. Program, col. fasc, II. Lips., 1851. Theile. Wagner's Handworterb. Bd. II. 1844. Retzius. Miiller's Archiv. 1849. Wedl. Sitzungsber. d. Wiener Akad. 1850. Rainey. Quart. Jour. Microsc. Sc. Vol. 1. 1853. Gerlach. Gewebelehre. 1854 Beale. Philos. Trans. 1855. Anat. of the Liver. 1856. Archives of Med. Vols. I. and II. Virchow. Virchow's Archiv. Bd. XI. 1857. Luschka. Henle u. Pfeuffer's Zeitsch. Bd. IV. 1858. Budge. Reichert u. Du Bois-Reymond's Archiv. 1859. His. Zeitschft. f. wiss. Zoologie. Bd. X. 1860. Wagner, E. Archiv d. Heilkunde. 1860. Oester. Zeitschrft. f. prak. Heilkunde, 1861. Ebertii. Zeitschrft. f. wiss. Zoologie. 1860. Med. Centralbl. 1866. Virchow's Archiv. 1867. Schultze's Archiv f. mik. Anat. Bd. III. Andrejevic. Sitzungsber. d. Wiener Akad. 1861. Riess. Reichert u. Du Bois-Reymond's Archiv. 1863. Sciiweigger-Seidel. Reichert u. Du Bois-Reymond's Archiv. 1863. MacGillavry. Sitzungsber. der Wiener Akad. 1864. IBMIN0BR. Zeitschft. f. wiss. Zoologie. Bd. XVI. 1866. CimoNs/.KWSKi. Virchow's Archiv. Bd. XXXV. 1866. IIering. Sitzungsber. d. Wiener Akad. 1866. Strieker's Handbuch. Bd. I. 1871. KOLLIKBB. Handbuch d. Gewebelehre. 1867. Von BiEftlADECiu. Sitzungsber. d. Wiener Akad. 1867. HEmENiiAiN. Studien aus d. phys. Instituts z. Breslau. Heft IV. 1868. KisaELEW. Med. Centralbl. 1869. 200 .MANUAL OF HISTOLOGY. Pfluger. Pfliiger's Archiv. Bd. II. 18G9. u. IV. 1871. ESNLE. Ein^evveidelehre. 1873. Leqiios. Jour, de l'anat. et de la phys. 1874. COHNHEIM U. LlTTETT. Virchow's Archiv. Bd. LXVI. 187G. EWALD u. Kikiine. Verhand. Naturhist. raed. Vereius zu Heidelberg. 1 Bd. 5 Hft. 1876. Kolatscuewsky. Schultze's Archiv. Bd. XIII. 187G. Turner. Journ. of Anat. and Phys. Vol. XI. 1877. Wendt. Med. Centralblatt. No. 15. 1878. Davis. Amer. Jour. Med. So. Vol. LXXVIII. 1879. FiUTSCir. Archiv. fur Anat. und Phys. Phys. Abtheil. 1879. Klein and Smith. Atlas of Histolojy. Part X. 1879—1881. CHAPTER XIV. THE KIDNEY. Br ABRAHAM MAYER, M.D., Curator of the Manhattan Eye and Ear Hospital, New York City. General plan of structure. — The glandular substance of the kidney is divided into two parts, an external or convex por- tion, called the cortical substance, or cortex, and an internal or concave portion, the medullary substance, or medulla. This division can be readily seen by cutting a kidney into two equal parts in the line of its long diameter. An intermediate zone, which separates the cortical from the medullary sub- stance, is called the boundary layer of the kidney. The whole organ is enveloped in a fibrous membrane, the capsule. The medullary substance contains the pyramids of the kid- ney, and is therefore also called the pyramidal portion. The apex of each pyramid, the papilla, projects into a special arm of the renal pelvis, viz., a calyx; the base or expanded por- tion is directed toward the cortical substance, and sends pro- longations into the latter. An examination of the cortical substance shows it to be composed of two distinct varieties of tissue, running parallel to one another toward the free surface. One has a fibrous ap- pearance, and is composed of cylindrical cords. It is a con- tinuation of the pyramids. These pyramidal prolongations ' (Henle) are also called medullary rays (Fig. 89). The other portion, situated between the prolongations, is a granular-look- ing material, called the cortical substance proper, or labyrinth of I/udwig* The latter contains numerous small bodies, which are of a distinctly red color when there is a large 1 Lud wig und Zawarykin : Zeitschrft. fiir rat. Med., 18G3. They are also called the prolongations of Ferrein. 5 Ludwig : Strieker's Manual, p. 401. 202 MANUAL OF HISTOLOGY. amount of blood in the kidney ; they are the Malpighian bodies, or glomeruli (Fig. 89, E). The boundary layer ' is characterized by numerous blood- vessels, some of which unite to form an arcade (Fig. 89, C), which is parallel to the convex surface of the kidne}', and from which branches are given off to the cortical substance proper. The renal artery, before it enters the hilum of the kidney, divides into branches, which pierce the medulla between the pyramids and ascend toward the cortical substance until they reach the boundary layer. Here they divide obliquely or at right angles to give off smaller branches, which have the direction and arched ppearance above referred to (Fig. 89, C). These arched vessels then send off the branches already men- tioned, which traversing the centres of the cortical substance proper, at right angles to the parent stem (Fig. 89, D), extend almost to the capsule of the kidney. On their way they in turn give off smaller twigs, each of which bears a glomerulus upon its extremity (Fig. 89, E). In this way there is an alternate arrangement of pyramidal prolongation and cortical substance proper (Fig. 90). Though he pyramidal prolongations almost reach the capsule of the kidney, they never quite touch it, being sep- arated by the interposition of some cortical substance proper (Fig. 89). Specimens for study should be made from a fresh kidney, in which the renal artery has been injected with carmine-gela- tine, the whole organ having been subsequently immersed in alcohol of 50 per cent, strength. When in that fluid it is to be divided into four or more parts, allowed to remain therein for Fig. 89. — Human kidney. Vertical section through cortical and medullary substances : A, branch of renal artery ; B, vein, immediately beneath former, but hardly visible in the figure ; C, arched arterial branches in the boundary layer; D, artery of the cortical substance proper ; E, Malpighian bodies or glomeruli : F, medullary rays or pyramidal prolonga- tions ; G, vessels of the medulla, the vasa recta, x 10. 'Henle: Grenzschicht, Eingeweidelehre . THE KIDNEY. 203 twenty-four hours, afterward transferred to stronger alcohol, then to absolute alcohol, and finally mounted in dammar or balsam. Vertical sections show the arrangement represented in Figs. 89 and 90 ; transverse sections, the appearance of Fig. 92. The substance of the kidney is composed of secreting and collecting tubules, vessels, and a stroma, which fills the inter- Fig. 90.— Human kidney. Vertical section through cortical portion : A, pyramidal prolongation ; B, cortical substance proper ; C, artery ; D, glomerulus, x 64. spaces between the tubules, and is more abundant in the med- ullary than in the cortical substance. In human adults this connective material is found in small quantity and is a sort of colloid substance. In the lower animals it is more abundant, and assumes the character of real connective tissue. In young infants there is said to be a greater proportionate amount of this tissue than in subsequent life. Tlte renal tubules. — The tubules are found both in the corti- 204 MANUAL OF HISTOLOGY. cal and medullary substances ; they are of different diameters and pursue either a straight or tortuous course. Some have a basement membrane {membrana or tunica propria), on which the epithelium rests ; others appear to have none. The tu- bules are clothed with epithelium of different varieties. Speci- mens should be made from a kidney that has lain for twenty- four hours in a 5 per cent, solution of chromic acid. A small — j Pig. 91.— Schematic representation of the kidney: A, medulla; B, boundary layer ; C, cortical por- tion; a, renal artery ; b, renal vein: c, artery penetrating cortex; T), capsule enclosing glomerulus: E, capillaries ; F, convoluted tubules of first order ; G, looped tubule, descending branch ; H, looped tubule, ascending branch ; I, convoluted tubule of second order ; J, collecting tubule ; K, vasa recta. piece of the gland is to be placed on a slide, and a drop of glycer- ine added ; the tubules may be isolated by teasing with needles. In Fig. 91 there is a schematic representation of the vascular distribution and course of the tubules in one of the pyramids. Each tubule takes its origin in an expansion that surrounds the glomerulus, and is called Bowman's or Mailer's capsule.1 1 Midler, in 1830, described the capsules, but regarded them as vesicles which had no connection whatever with the uriniferous tubules. Bowman, in Philosoph. Trans- act., 1843. THE KIDNEY. 205 It is round or elliptical in shape, and has a diameter of about 0.2 mm. Where the capsule empties its contents into the tubule, there is a slight constriction known as the neck ; it is veiy distinct in some of the lower animals. The canal then en- larges and begins to pursue a tortuous course in the cortical substance ; it is now called a convoluted tube ' (Fig. 91, F). It next undergoes sudden diminution in size and passes straight through the medulla until, at a variable point, it bends upon itself, forming a loop ; then, ascending, it increases in calibre, and in the cortical substance becomes convoluted for the second time. Those canals that are nearest the glomeruli are called convo- luted tubules of the first order, the others convoluted tubules of the second order. Between these two are the looped tubules of Henle, just described, each being divided into a descending and ascending branch (Fig. 91, Gr and H). The convoluted tubules of the second order terminate by emptying into tubules of greater diameter, called collecting tubules* which descend through the cortical and medullary substances, and, receiving other collecting tubules on the way, finally empty into the pelvis of the kidney (Fig. 91, J). At the base of each pyramid there are a vast number of col- lecting tubules, but as they successively empty into larger collecting tubes, the area they occupy is thereby diminished ; at the apex of the papillae, where they ultimately discharge the urine into the pelvis of the kidneys, there are only about twenty in number. This gradual coalescence of the tubes gives to the pyramids a conical shape, but the breadth of the base is also partly due to the presence of the looped tubules which pass down into the pyramids for a varying depth. The larger collecting tubules may be readily injected with Beale's blue fluid 3 or carmine-gelatine, either directly or from the ureters ; it will be found, however, that the injection will seldom extend beyond the looped tubules, owing to the small diameter of the descending branches. 1 Tubnlus contortus. i Straight tubules of Bellini. 3 Glycerine, pure, 2 oz. ; tr. perchloride iron, 10 drops ; ferrocyan. potassium, 3 grains ; strong hydrochl. acid, 3 drops; water, 1 oz. Mix the tincture of iron with one ounce of the glycerine ; and the f errocyanide of potassium, first dissolved in a little water, with the other ounce ; mix gradually, and shake during admixture ; add the iron to the ferrocyanide ; laBtly, add the water and hydrochloric acid. Beale : Microscope, p. b7. 206 MANUAL OF HISTOLOGY. Bowman's capsule is composed of a structureless basement- membrane surrounding each glomerulus. Upon the inner sur- face of these capsules is a continuous layer of flat, epithelioid cells,1 which are continued over the glomerulus itself.2 Occa- sionally an epithelioid cell may be seen between the vessels of the coil composing the glomerulus. Each capsule is pierced by two vessels, called, respectively, afferent and efferent. The former enters the capsule and forms Fia. 92. — Human kidney. Transverse section of cortical portion, showing the alternating arrangement of pyramidal ray and cortical substance proper : A, A, pyramidal rays ; B, convoluted tubule ; C, glom- erulus ; D, D, arterial vessels, x 55. the glomerulus, while the latter makes its exit close to the en- trance of the former. The layer of epithelium above described passes over from the inner surface of the capsule on to the glomerulus about the points of entrance and exit just men- tioned. On the opposite side, the capsule becomes continuous with a convoluted tubule. To obtain specimens, the renal artery of a fresh kidney should be injected with blue gelatine and then placed in alcohol. Vertical and transverse sections of the cor- tical substance may then be made. They should be stained in carmine and examined in glycerine, or the artery may be in- jected with absolute alcohol and the sections stained as above. The epithelium of the tubules.— The basement-membranes of the convoluted tubules of the first order are in direct con- tinuation with the basement-membranes of the capsules. Their diameter averages 0.04 mm. The epithelium of these canals is 1 Schweigger-Seidel : Die Nieren. Halle, 1865. Henle : Eingeweidelehre, p. 329. Heidenhain : Zur anat. d. Nieren, in Schultze's Archiv, Bd. X., Hft. I. Mayer : His- tology of the Kidney. Dis. Inaug., 1876. Also Bowman, Johnson, Frerichs, etc. 8 Gerlach, Heidenhain. THE KIDNEY. 2or peculiar, and was first correctly described by Heidenhain. According to this writer, the greater part of the cell-protoplasm assumes the form of small, cylindrical bodies, the so-called rods of Heidenhain, giving the epithelium a stri- ated appearance (Fig. 93). To exhibit these appearances, the cortical sub- stance of a dog's or rabbit's kidney should be cut into small pieces and immersed for twenty- four hours or more in a 5 per cent, solution of the neutral chromate of ammonia. After this time has elapsed, a small piece of the gland is to be placed on a slide and a drop of glycerine added ; the specimen may then be teased and ex- amined. Portions of the convoluted tubules will be found floating about in the glycerine, and should be closely scrutinized. By this mode of preparation, individual epithelioid corpuscles can- not be recognized ; on the contrary, they seem to merge with one another. The tubule may be regarded as made up of rods transversely dis- posed, with nuclei embedded in a pulpy mass that appears to fill its lumen, the whole envel- oped by the membrana propria. The rods sur- round the nuclei, and are not all of the same length. They appear to be hollow, as shown by their sometimes containing fatty granules. Here and there in the specimen a separate corpuscle will present itself to the eye; in such instances the rods can readily be made out (Fig. 94, A). In the kidney of the rat these bodies may be isolated with little diffi- culty (Fig. 94, B). At one end the rods rest against the membrana propria, to which they are attached by a colloid material ; their other extremity is lost in the protoplasm of the cap- sule, which latter lies internal to them and appears to have the character of a pulpy mass containing nuclei. In the dog, the nucleus of each cell is about midway between the lumen and the membrana propria. It is surrounded by rods (Fig. 94, A). In the rat this is not the case (Fig. 94, B). Assuming that the rods begin at the membrana propria, they are directed Fig. 93.— Convo- luted tubule from the kidney of a dog. Neutral chromate of ammonia prepara- tion. The tubule normally appears darker than is rep- resented in the fig- ure, x 4S0. A- Fio. 04.— iHolated cells from the convoluted tu- bnlei exhibiting rod-like epithelium : A, kidney of dog; II, kidney of rat. x 450. 208 MANUAL OF HISTOLOGY. toward the centre of the lumen of the tubule, and the distance between any two adjoining rods at the periphery is necessarily greater than at the centre. For the same reason, also, the rods are more distinctly defined in the former situation ; the micro- meter .screw will have to be used in tracing them inward. Transverse sections of the cortical substance may be made by freezing small pieces which have been immersed in a solu- tion of the neutral chromate of ammonia. Such sections should be examined in glycerine, or, better, in a saturated solution of the chloride of potassium in glycerine.1 The radial direction of the rods is beautifully seen in such specimens (Fig. 95, C), Fig. 95. — Kidney of dog. Transverse section through the medullary portion, about midway between the apex and boundary layer. Neutral chromate of ammonia preparation : A, blood-vessel ; B. looped tubule, descending portion; C, looped tubule, ascending portion; D, collecting tubule; E, connective tissue, y. 30U. and the individual cells are more clearly denned. Another method of exhibiting these rod epithelia is to inject the artery or vein of a fresh, bloodless kidney with a cold saturated solu- tion of the chloride of potassium, then, after placing the whole organ in alcohol, divide it in small pieces under that fluid. After a day or two sections may be made ; they then should be immersed for a short time in absolute alcohol and clarified by oil of turpentine. Such specimens show the epithelium to perfection and may be preserved for a considerable time. Per- manent specimens can be made by substituting resinous turpen- 1 The glycerine should be heated in a porcelain evaporating-dish, the chloride of potassium added, and the whole mixture stirred for several minutes with a glass rod. The glycerine is ready for use after cooling. TIIE KIDNEY. 209 tine1 for the common oil. The renal artery or vein may also be injected with absolute alcohol, and sections prepared as above. But the epithelium suffers in this way, for the alcohol causes the rods to shrink, and the colloid substance between the rods coagulates. Still, the striated appearance is seen near the membrana propria. Another fact which seems to have es- caped Heidenhain is that alcohol so injected causes the nuclei of the cells to recede toward the membrana propria by its action on the rods. The action of water on the rods is peculiar. A fresh kidney must be used and a portion of the cortical substance placed on a slide, together with a drop of water ; it is then to be teased with needles and immediately examined. At first the rods are not distinctly brought into view, but they soon appear with their contours sharply delineated. This appearance, however, does not last very long, for the epithelium soon imbibes water, swells, and then forms an indistinct mass. In the neck of the convoluted tubules of the frog, coluber, etc., the epithelium is ciliated. In the frog the cilia have great length, but the convoluted tubules do not have the rod epithe- lium. In the dog, cat, rabbit, etc., the rod epithelium begins at the neck of the tubule and is continued as far as the loops. The convoluted tubules of the first order, after ramifying in the cortical substance, become continuous with the looped tubules of Henle, as already described.3 The change takes place in the vicinity of the boundary layer. The looped tubules. — The looped tubules traverse the medulla for a greater or lesser distance. A few almost reach the apices of the pyramids ; others extend but a short distance below the boundary layer, while a third class occupies an inter- mediate position. Good specimens are obtained by macerating vertical sections of the medulla in a solution of caustic potassa (i to 1 per cent.). The potassa destroys the epithelium, the stroma, and the blood-corpuscles, but leaves the basement- 1 Resinous turpentine is prepared as follows : some common oil of turpentine is poured upon a deep plate, so as to form a thin layer, and a piece of fine muslin is snugly fastened over it to keep out the dust. The liquid is now exposed to the ac- tion of the air. In a few days, if the weather Vie warm, or a week or more, if the weather be cold, the turpentine will have become thick, yellow, and resinous, and is now no longer transparent. Resinous turpentine, prepared in this way, forms one of the host preserving agents. Its use will be spoken of further on. s Heple: Eingeweidel., 2te Aufl., p. 316. 210 MANUAL OF HISTOLOGY. membrane perfectly intact. A fresh kidney is necessary, and one slightly infiltrated with fat makes the best specimens. Another method is to embed the kidney of a dog or rabbit in powdered chlorate of potassa, adding enough dilute nitric or hydrochloric acid to cover the crystals. After some hours the connective tissue in the gland will have been destroyed. Portions of the medulla should then be placed upon a slide with a drop of glycerine and teased slightly. A great many of the loops are broken in this way, to be sure, but still some will be seen. By this method the epithelium of the narrow branch is not destroyed. The epithelium of the looped tiibules. — The descending branch of the loop is small in diameter (0.02 mm.) and pos- sesses a peculiar distinctive epithelium. The corpuscles are Hat, have prominent nuclei/ and rest against the membrana propria. The disproportionate size of the nuclei causes the corpuscle to project into the lumen. But these prominences do not obstruct the passage, for each one corresponds to the space between two on FIG. 96.— Kidney of dog. Descending portion of tile Opposite Side of tile til" Henle's looped tubule. -i bule, so that there is no bar to the urine, but the passage is made more or less spiral (Fig. 96). The corpuscles are of a light color. Specimens should be made from a gland that has been macerated in a 5 per cent, solution of the neutral chromate of ammonia; they should be examined in glycerine. The length of the narrow portion of the loop is variable in man, the pig, and horse. The second portion of the looped tubule is wider and its epithelium peculiar. In man both the loop and ascending branch are wide, usually ; especially is this the case with loops high up in the medulla ; in the rabbit it is the ascending branch only that has this property. Generall}' speaking, the length of the broader branch of the loop exceeds that of the narrow portion. The diameter of the broad portion averages 0.04 mm. The epithelium has the same character as that in 'the convoluted tubules ; it is striated and possesses rods.1 It is not precisely similar, however. The width of the individual cells is not so great as in the former, and hence the lumen in 1 Heidenhain : loc. cit. Henle : loc. cit. , p. 317. THE KIDNEY. 211 this portion of the loop is greater than in the convoluted tu- bules. Specimens prepared with the neutral chromate of am- monia, as before detailed, give good results. Vertical sections may be made from a kidney macerated in the ammonia solu- tion and afterward treated with alcohol ; or, better, from frozen specimens. The broader extremity of the looped tubule ascends through the medulla into the cortical substance and becomes continu- ous with a convoluted tubule of the second order (Fig. 91, i). These tubules, the intercalated portions,1 greatly resemble con- voluted tubules of the first order, as already mentioned. Spe- cimens should be prepared in the same way as those of the latter. The convoluted tubules of the second order, after rami- fying in the cortical substance, terminate by emptying into the collecting tubules (Fig. 91, J). The collecting tubules and their epitJielium. — The collecting tubules3 possess cylindrical epithelia, the bases of which are irregular and present point-like prolongations 3 (Fig. 97), which interdigitate with one another. The nuclei in the smaller collecting tubules are large and ver}^ prominent, but the protoplasm which sur- rounds them is not very abundant. The base- ment membrane is comparatively thick and exhibits a double contour. The smaller col- lecting tubules are situated in the cortical sub- stance, a little distance below the capsule. ' " Fig. 97.— Kidney of Their diameter ranges between 0.04 and 0.06 d°s- isolated ceii* of ° two collecting tubules, mm. The small tubules unite to form larger showing ii^niar base ° and point-Uke prolonga- ones, and these again to form tubules of still a°™ j :."< fr0™ 's,m.allef ~ collecting tubule; o, larger diameter. The irregular appearance at £y£onexn45oboundary the bases of the epithelia is the same in the larger trunks as in the smaller branches ; in the former, how- ever, the cells are larger, and the protoplasm more voluminous than in the latter. The nuclei have about the same size in each (Fig. 98). The basement-membrane diminishes in impor- tance in an inverse ratio with the size of the collecting tubules. In the smaller ones it is prominent and possesses a double con- 1 Schweigger-Seidel : Schaltstiicke ; Roth : Verbindungscaniile (connecting tu- bules). • Open tubules of Henle. Zur Anat. der Niere. Oottingen, 18G2. 3 Ileidenhain : loc. cit. 212 MANUAL OF HISTOLOGY. tour; in those of intermediate size it is thin, and has but a single contour ; the largest tubes possess no basement- mem- brane whatever. In the latter the great cylindrical cells are held together by the prolongations above mentioned and a colloid substance. The diameter of the largest tubules at the apices of the pyramids is 0.2 to 0.3 mm., after the first division 0.1 to 0.2 mm., the smallest being about 0.06 mm. The height of the epithelium in the largest tubules is between 0.02 and 0.04 mm. ; in those at the boundary layer about 0.015 mm. Good specimens are obtained by im- mersing a fresh gland in dilute muriatic or nitric acid for a variable period (six to twenty- four hours), and examining in dilute gly- cerine. The collecting tubules1 should be injected from the ureter with blue or red gel- atine, and the whole organ immersed in alco- hol, until ready for cutting. Sections made parallel to the collecting tubules produce splendid specimens. The connection between the collecting and convoluted tubules of the human kidney cannot be shown by injection, for the colored fluid thrown in from the ure- ter rarely reaches the convoluted tubules of the first order. In the lower animals — fishes, frogs, etc. — however, if the ureter be injected under constant pressure the entire length of the urin- iferous tubules may be filled with the carmine, or, better, Berlin blue2 fluid. Fig. 98. —Kidney of dog. Small collecting tu- bule above the boundary layer, x 450. 1 In the pig Henle finds that two large collecting tubules begin at the apex of each pyramid, then run along the outer borders of the cortical substance proper, high up into the cortex, and there unite by forming a loop. Henle states that the convoluted tubules empty into these, or their divisions by intercalated portions, which he calls communicating tubules ( Vcrbindungscanitichen). Eingeweidel. , p. :J24. 9 This has been done by Frey with fishes and amphibia; by Hiifner with birds, fishes, etc. ; by Gross with fishes and tritons, and by Hyrtl with some sorts of fishes. According to Seraphina Schachowa (Unters. ueber die Niere. Diss. Bern, 1876) the convoluted tubule of the first order is connected to Henle' s loop by a spiral tubule, while the ascending portion of the loop exhibits an expanded part immediately above the loop, and a spiral part, which latter becomes continuous with the ascending limb of the loop. Between the ascending part of the loop and the intercalated portion Scbachowa describes a new tubule, which she calls the "irregular tubule." The spiral tubule is lined with an epithelium which has a striated appearance in THE KIDNEY. 213 TJie Mood-vessels of the kidney.— The renal artery and vein, before entering the hilum, divide and subdivide within the sinus of the kidney. Small branches, which are given off at the hilum, also supply the fibrous capsule of the gland. Veins accompany the arteries as far as the arches already referred to. But here a difference is to be noted. The arteries never anas- tomose, but form the straight vessels of the cortical substance proper, which again send off twigs to form the glomeruli. Pig. 9!). — Kidney of pig. Injection of artery and vein. Vertical section at boundary layer: A, artery ; B, vein : C, glomerulus ; D, capillaries of the cortical portion ; E, vasa recta formed from capillaries D. x 96. At the arches, however, the veins anastomose, and a branch accompanies the straight artery of the cortical substance proper (Fig. 99, B). The glomerulus is formed from the arterial twig above referred to (Fig. 89, D). This enters the capsule directly opposite to the point where the latter becomes continuous with a convoluted tubule, and divides into two or more its first portion. The expanded part of the ascending loop is lined with cells having very thick prominent rods, and whose lumen is exceedingly small. The irregular tubule has an angular, irregular outline, is of very varying diameter, in some portions two, three, or four times as broad as in other portions, a condition due to its peculiar lining epithelia, which are angular and present numerous pro- cesses ; the rods arc exceedingly thick and prominent. As yet I have been unable to confirm Schachowa's researches. 214 MANUAL OF HISTOLOGY. branches which subdivide again and again (Fig. 100) to form loops or coils ; these latter unite again and form a vessel equal in size to the one which entered the capsule. The first is called, as already described, the affer- ent ; the second, the efferent vessel, and the glomerulus is formed by the division and reunion of the branches of these two vessels ; the whole form- ing a rounded tuft within the capsule. The vessels of which a glomerulus is composed have the same diameter as fig. loo.-Giomeruius from kidney small capillaries ; their coats are struc- of pig. Ludwig. n -. .-._.. ,, . . , tureless and provided with elliptical nuclei. The efferent vessels are not veins ; on leaving the cap- sules they break up into capillaries, which anastomose freely with each other and surround the tubules of the cortex, form- ing, in this way, a network with circular meshes (Fig. 99, D). At the boundary layer the capillaries unite to form vessels which are two to three times larger than the original capillaries. These vessels take a straight course through the medulla to- ward the apices forming the so-called vasa recta ' (Figs. 99, E, and 89, G). The vessels immediately below the boundary layer are arranged in bundles at the side of the pyramidal prolonga- tions, and run parallel with them in that part of the medulla (Fig. 89). They give off branches in the medulla, and near the apices of the pyramids again form a capillary network which surrounds the collecting tubules. The returning vessels (veins) have about the same course, anastomose freely with each other, and empty into the venous arches at the boundary layer. Other veins are formed by the union of capillaries immediately underneath the capsule ; these have a stellate form,3 the centre of each star indicating the commencement of a vein. Such veins, passing downward through the cortex and receiving branches on the way, empty finally into the venous arches above referred to. The venous arches also give rise to vessels of larger calibre, which run parallel to and accompany the ar- teries of the medulla, and at last unite to form the renal vein. Injections of the kidney. —The kidney may be injected with gelatine either through the artery or vein. It is best accom- Donders : Physiol. , L s Vence Stellatce, Verheyen. THE KIDNEY. 215 plished by the artery, under constant pressure (mercury). Beale's blue injecting fluid ' answers very well ; the writer's car- mine-glycerine fluid3 also ads exceedingly well, but it is very difficult to obtain a good double injection of artery and vein. I have found the most successful method to be the following : Take a fresh bloodless kidney (dog, pig) and inject the vein under constant pressure with the blue gelatine mass.3 Next place the kidney in iced water for a few minutes to harden the gelatine, and then attach to the artery a very small constant- pressure injecting apparatus, the receptacle for the injecting fluid containing the writer' s carmine fluid. After regulating the amount of pressure, the whole apparatus, with the kidney, is placed within the receiver of an air-pump and the air slowly exhausted. In this way the arteries become filled with fluid. Allow the gland to harden in alcohol and mount the sections in balsam or dammar. Kidneys in which the vein and artery have been injected may have the collecting tubules filled from the ureter with yellow injecting fluid, thus making a trijxle injection. Sections of kidney hardened in alcohol may be stained with borax- carmine, and afterward bleached in a di- lute hydrochloric acid (1 to 10) solution, or a concentrated one of oxalic acid. When the vessels of a kidney have been injected with blue gelatine, staining with carmine gives good results. Thiersch's yellow injecting fluid is made as follows : Prepare a solution of bichromate of potassa, one part of the salt to eleven parts of water, and a solu- tion of nitrate of lead of the same strength. One part of the potassa solution is placed in a small basin and mixed with four parts of a concentrated solution of gelatine. Two parts of the lead solution are placed in another basin and mixed with four parts of jelly. These are to be slowly and thoroughly mixed together at a temperature of 75° to 90°, and then heated in a water-bath at a temperature of 212' for half an hour or more. Filter carefully through flannel (Beale : Microscope, p. 90). The kidney stroma. — In the cortical substance the stroma is reduced to a colloid material which binds the tubules to- gether. In the lower part of the medulla, in the fresh state, 1 See page 205. ' Carmine, 5 grammes; glycerine (anhydrous), 50 grammes; add caustic potassa until the carmine is dissolved, and neutralize with pure, concentrated muriatic acid. 'Jelatine should be first immersed in water until it becomes softened and then gently heated until dissolved. Add soluble Berlin blue, or Beale's blue fluid, until a good color is obtained. Inject while hot. 216 MANUAL OF HISTOLOGY. the stroma is a colorless, transparent substance, which, after immersion for a variable time in a solution of eliminate of po- tassa or ammonia, resolves itself into a thin fibrous reticulum, containing at regular intervals round or elliptical nuclei;' these, according to Schweigger-Seidel, belong to stellate or spindle-shaped corpuscles, which may be isolated by macera- tion in hydrochloric acid. The nuclei are only seen in the lower portion of the medulla ; the fibrous appearance of the stroma is retained some distance beyond this point. The nerves follow the course of the arteries of the kidney and seem to supply only those vessels. The lymphatics at the hilum are derived from the interior of the organ, and from a network of small lymph-branches situated between the bundles of fibres of the capsule. The latter communicate with lymph-canals in the interior of the organ.2 The capsule of the kidney is a fibrous tissue, containing some few elastic filaments. It is divisible into two layers, an outer and an inner one. The former, about 0.1 to 0.2 mm. in thickness is continuous with the connective tissue which sur- rounds the blood-vessels at the hilum ; the latter, about 0.025 mm. in thickness, terminates at the points where the papillae enter the calices. Immediately underneath the inner layer, is a large meshed reticulum of smooth muscle-fibres,3 some of which traverse the substance of the gland for a short distance. The calyx, at its junction with the papilla, is covered with epithelium, which is continued on to the apex of the papilla ; it contains, in addition, muscle-fibres disposed at right angles to one another, and connective tissue. Natural injection of the tubules of the Mdney by the sulphindir/ate of soda* — The first to inject the kidney in this way was Chronsczewski ; b but his experiments were not very successful, at least so far as the kidney was concerned. Those of Heidenhain 6 which have been confirmed by the writer,7 give 1 Henle : loc. cit. 2 Ludwig, in Strieker's Manual. 3 Eberth : Med. Centralbl., No. 15, 1872. 4 Commonly known in the laboratory and in commerce as indigo-carmine. 5 Chronsczewski, in Virchow's Archiv, Bd. XXXI., p. 187; also Bd. XXXV., p. 158. 6 Max Schultze's Archiv, Bd. X., p. 1, and Pfliiger's Archiv, Bd. IX., p. 1. 7 Mayer ; Histol. of Kidney. Prize dissert., 1876. THE KIDNEY. 217 the most satisfactory results. To insure this desirable end, it is necessary that the sulphindigate of soda be pure. O. Maschke, of Breslau, the apothecary who manufactures the pure sulphin- digate of soda for Prof. Heidenhain, writes to that author as follows : " The indigo- sulphate of soda was prepared from the phoenicin-sulphate of soda. If the latter compound be heated for half to one hour, at a temperature of 60° to 70 D C, with five or six times its volume of sulphuric acid of a specific gravity of 1,840, it resolves itself completely into indigo- disulphate of soda and indigo-monosulphate of soda (indigunterschwefelsaures Natron). I have chosen this mode of preparing the salt because the indigo-gelatine and indigo- brown can easily be separated from the phoenicin-sulphate of soda, without marked loss, and in this way I obtain a sufficiently pure substance for future use. An easier method of preparing the salt is the formula given by Crum and Berzelius. One part of best indigo in powder is gradually added to seven or eight parts of pure sulphuric acid, specific gravity 1,840, in a large vessel, and the two thoroughly mixed. After the liquid has ceased to froth, the vessel is covered with an animal membrane and put aside for three days, during which interval it is to be frequently shaken. To this solution thirty to forty volumes of water are added, and the whole carefully filtered. To the resulting clear solution as many parts by weight of crystallized carbonate of soda as there were of sulphuric acid, are added. Owing to the effervescence which now takes i^lace, the vessel in which the mixture is prepared must be of large size. For this reason it is better to substitute the acetate of soda, or chloride of sodium, or simply sulphate of soda, for the formation and precipitation of the indigo-disulphate of soda takes place with any soda salt which does not decompose the indigo -disulphuric acid. The mixture is now filtered, and the precipitate dried over a water-bath. It is then pulverized and treated re- peatedly wTith absolute alcohol, which dissolves any indigo-monosulphate of soda, acetate of soda, or indigo-red, which may have remained." In this way the indigo-carmine is obtained in a pure state. The crystals are copper-colored, but the salt is blue in the pulverized state. The indigo-carmine of commerce is an impure article and cannot be used for natural injection. For injection, a cold saturated solution of the sulphindigate of soda is used ; the salt may be dissolved in boiling distilled water, and the solution allowed to cool. A dog or rabbit answers for the purpose of injecting. The animal is properly fastened to a board, and the external or internal jugular vein dissected up and exposed. In either of these vessels a canula with stop-cock, previously filled with the indigo-carmine solution, is inserted. The injection into the jugular may be made downward or upward — the latter is preferable. A syr- inge, graduated in cubic centimetres and containing the sol- ution of indigo-carmine, is now attached to the canula, the stop-cock opened and a small quantity of the solution injected 2 IS MANUAL OF HISTOLOGY. into the vein. Not more than 5 c.c. should be injected at one time. If the animal be a white rabbit, the result of the firsl injection shows itself in a few seconds, for the animal soon becomes quite blue. After five or ten minutes another 5 c.c. of the solution may be injected, and so on until 20 to £0 c.c. of indigo-carmine solution have been employed, the amount varying according to the size of the animal. The excretion of blue urine takes place soon after the first injection of indigo-carmine. As soon as a sufficient quantity has been excreted the animal is killed in the following manner : The abdomen is opened and the descending aorta looked for ; when found, the canula of a syringe, filled with absolute alcohol, is attached. The jugular vein is now cut across, and while the animal bleeds to death absolute alcohol is injected up the aorta or into the renal arteries. A safer and better way is to inject the renal artery at once with absolute alcohol ; in either case the renal veins should be cut across. The kidney is at once removed, placed in absolute alcohol, and then divided into several pieces, to insure a rapid action of the spirit. While the indigo-carmine is being injected into the jugular vein, the animal should be wrapped up in flannel or cotton- batting so as to be kept warm. No air should be allowed to enter the vein, or the animal may die before the experiment is concluded. Injection of absolute alcohol through the renal artery should be accomplished before the animal has bled to death, or, at least, immediately afterward. When the kidney has been thoroughly hardened, vertical and transverse sections are to be made through the cortical and medullary substances, and examined in glycerine saturated in chloride of potassium ; or, better still, in resinous turpentine. If the injection of absolute alcohol be delayed, either through lack of skill in the experimenter, or any mishap, the indigo salt within the kidney becomes diffused over the entire organ by absorption of water from the contained ves- sels, and the whole kidney becomes of a uniform blue color. Such glands must be laid aside, for sections made therefrom, even after immersion in abso- lute alcohol, are worthless, and will only confuse the microscopist. The abso- lute alcohol of the shops is not always absolute, as is well known. It has a great affinity for water, and, in handling, rapidly absorbs moisture from the air. To make it absolute, I heat sulphate of copper (pure) at a low red-heat. This drives out the water of crystallization, and changes the color from blue to white. Of this I mix a large spoonful or more, while still hot, with a pint of the so-called absolute alcohol, and tightly cork the vessel, which is then to be THE KIDNEY. 219 shaken occasionally, but not used for a week or more. The affinity that water lias for anhydrous sulphate of copper is greater than that of the alcohol, and the latter readily gives it up. As soon as the anhydrous sulphate regains its water of crystallization it assumes a blue color again. Everywhere in the sections it will be seen that the glomeruli or their capsules are entirely free from color, while all the tubules possessing the rod-epithelium have a more or less blue color, according to the quantity of indigo-carmine excreted. The lumina of the convoluted and other tubules are generally filled with the crystallized indigo-salt. In examining sections, it soon becomes evident that the convoluted tubules and that part of Henle's loop which possesses the rod-epithelium, alone excrete the indigo-salt, while the other tubules merely contain it in their lumen, the salt having been washed down, as it were, from above by the water filtered through the capillaries of the glomeruli. Instead of using the sulphindigate of soda, Heidenhain, in his second series of experiments, substituted a solution of uric acid in caustic soda. The renal artery was injected with alcohol containing acetic acid. The result showed that urate of soda, like the indigo-salt, was excreted only by the tubules pos- sessing the rod-epithelium. The capsules were entirely free. The addition of acetic acid to the alcohol caused the uric acid to be precipitated in the shape of rhomboid crystals within the tubules. In this condition Heidenhain found them. The hypothesis set down by Bowman, years ago, that the tubules of the kidney excrete the solid constituents of the urine merely, while the glome- ruli serve as a filter for the fluid portion, is therefore correct. If the quantity of indigo solution injected into the jugular be small, and the animal killed soon after, the kidney being treated as above detailed, the microscopic sections exhibit the following appearance: glomerulus and capsule are not acted upon ; the narrower branch of the loop and the collect- ing tubules are free from any crystallized salt, and their epi- thelium clear. In the convoluted tubules and the broad part of the loop, the following phenomena may also be observed : their lumina are entirely free from any deposit of indigo-car- mine, though here and there the rod-epithelium is not stained. In the greater number it is colored of a light blue color. In some the rods and nuclei are uniformly stained ; in others the rods alone show the blue color, while the nuclei are not stained. This constitutes the first stage of the excretion of indigo-car- 220 MANUAL OF HISTOLOGY. mine through the kidneys. If a larger quantity of indigo solution be injected, and the animal dealt with as above, the second stage of the excretion is seen. Here, again, the glome- ruli, the capsules, and the collecting-tubules are free from color, the rod-epithelium stained blue, and their nuclei dark blue (Fig. 101, F). In a few of the convoluted tubules and the ascending broad branches of the loop, crystals of indigo-salt Pig. 101. — Kidney of dog. Natural injection of secreting portion, artificial injection of artery, vein, and capillaries. Transverse section through cortical substance : A, afferent vessel, filled with injected material; B, efferent vessel, also filled with injection; E, glomerulus, injected and ljing within its cap- sule : epithelium of latter distinctly seen : D, capillaries surrounding the convoluted tubules, and dis- tended with the injection ; at this point four capillaries are seen to unite and form a vein: C. convo- luted tubule, filled with crystals of indigo-carmine; F, convoluted tubule, in which the nuclei have a dark color. The striations of Heidenhain are beautifully shown in the convoluted tubules, x 200. fill the lumina. So, also, in some of the descending narrow branches of the loop. In the third stage the rods are color- less, while their nuclei are still blue. Masses of the indigo salt fill the lumina of the convoluted, looped, and collecting tubules ; the glomeruli and their capsules are colorless. In the last stage, the salt is contained in the lumina of the col- lecting tubules only, all the rest of the gland being free from it, and consequently colorless. From the above it will be THE KIDNEY. 221 seen that the rod-epithelium alone excretes the indigo-salt, and it may be presumed, therefore, that the function of the glome- ruli is to act as a niter for the fluid portion of the urine. Thus the salt is washed from the convoluted into the collecting tubules, and thence into the pelvis of the kidney. The action of absolute alcohol on a solution of sulphindigate of soda is to precipitate that salt. It is this action within the kidney which fixes the dye, as above set forth. Beautiful specimens may also be obtained by various modi- fications of the above process. The following formulae and results are given by Heiclenhain : 1. Eabbit or dog; section of spinal cord, injection of only 5 c.c. of the in- digo solution, the animal being killed after ten minutes. Result : pyramidal portion and boundary layer free from indigo-blue. In the cortical substance, some of the convoluted tubules are filled with the crystalline salt ; in the greater number the epithelium is colored of a uniform blue, the nuclei possess- ing the same tint ; the lumen is usually free. 2. Same conditions as above, excepting that 20 or 25 c.c. of the solution is injected. Medulla free from indigo blue. In the cortex a great many of the tubules are filled with the pigment, while the epithelium is stained blue, the nuclei of a deep blue color. 3. Same conditions as in 2, excepting that the animal is killed one hour after injection. Nuclei of the rod-epithelium stained deep blue, rods clear ; convoluted and collecting tubules filled with crystals of pigment. Instead of using absolute alcohol for injecting the renal artery, the writer's carmine-glycerine fluid may be employed. After having injected the artery in this way, the kidney is placed in a vessel of absolute alcohol, and divided into small pieces while immersed in that fluid. The glycerine being anhy- drous, prevents the diffusion of the indigo-salt within the kid- ney, while the alcohol fixes the pigment. Sections should be made from the cortex and medulla, and mounted permanently in resinous turpentine. If the glycerine injection has been suc- cessful, all the glomeruli and capillaries will be filled with a transparent red mass (Fig. 101). If the indigo excretion has reached the third stage, the collecting tubules in the medulla will be filled with blue crystals of indigo-carmine, and the vasa recta with a red mass, the two arranged in alternate rows. Such specimens leave nothing to be desired in the way of demonstrating the structural relations just described. 222 MANUAL OF HISTOLOGY. BIBLIOGRAPHY. Ferrein. Mom. de l'acad., p. 502. Paris, 1753. MCller. De glandularum, etc. Leipz., 1830. And Unters. iib. d. Eingew. d. Fische. Berlin, 1845. Husciike. Lehre d. Eingeweide. Leipz., 1844. Gerlach. Muller's Archiv, p. 378, 1845, and p. 102, 1848. ViRCnow. Virchow's Archiv. Bd. XII., p. 310. 1857. Beer. Die Bindesubstanz d. Niere, etc. Berlin, 1859. Ludwig. Handb. d. Phys. Bd. II., p. 028. And Wiener med. Wochen. 1864. Roth. Diss. Bern, 1804. Chronsczewski. Virchow's Archiv. Bd. XXXI., p. 153. 1864. Sciiweigger-Seidel. Die Niere, etc. Halle, 1865. Stilllng. Ein Beitrag, etc., Diss. Marburg, 1865. Hufner. Vergl. Anat. u. Phys. d. Ham. Leipz., 1866. Lindgren. Z. f. rat. Med. 1868. Gross. Essai sur la structure microscopique des reins. Strassbourg, 1868. Isaacs. Jour, de la phys. Tome. L, p. 577. 1858. Ludwig. Strieker's Manual. 1871. Ebertii. Centralb. f. d. med. Wiss., p. 227. 1872. Henle. Eingevveidel., 2 Aufl. 1874. Frey. Mikroskop. 6 Aufl. 1877. And Handb. 4 Aufl. 1874. Heideniiain. Schultze's Archiv. Bd. X. 1874. And Pfhiger's Arch. Bd. IX. 1874. Schachowa. Unters. ab. d. Niere. Diss. Bern, 1876. Nussbaum. Beitr. z. Anat. und Phys. d. Niere Sitzungsber. d. Niederrh. u. Sw. Bonn, 1877. Runeberg. Nord. Med. Ark. XI., 2. No. 13. 1879. Hensciien. Akad. Afhandling in Upsula. Stockholm, 1879. Klein and Smith. Atlas of Histology. Part XI. 1880. CHAPTER XV. THE MALE EXTEENAL AND TNTEKNAL OEGANS OF GENEEATION, WITH THEIE GLANDULAR APPENDAGES. By Dr. J. HENRY C. SIMES, Lecturer on Histology, University of Pennsylvania. Penis. — The copulative organ of the male consists of erec- tile tissue, and is made up of three bodies, each enclosed in a fibrous membrane, the tunica albuginea. Two of these bodies are termed corpora cavernosa ; the third corpus spongiosum; through the latter the urethra passes. The tunica albuginea consists of connective tissue and elas- tic fibres, with some smooth muscular elements. From the in- ternal surface of this membrane arise numerous trabecule, or bands, composed of the same tissue as the membrane ; they divide and subdivide, forming a very intricate reticulum. The cavities thus formed freely communicate one with the other, and are lined with a single layer of flattened endothelial plates. This system of intercommunicating lacunae is in reality nothing but a true venous network. It is in direct communication with the veins of the organ. By the overfilling of these cavities with blood the erectile state is produced. Externally, the tunica albuginea is surrounded by loose subcutaneous tissue, in which numerous elastic fibres are pres- ent. Longitudinal bundles and a few oblique fibres of involun- tary muscle are also found in this areolar tissue. The skin cov- ering the penis is thin, and possesses numerous fine hairs, which have an increased length as the root of the organ is approached; they are connected with ordinary sebaceous glands which open into their follicles. Sudorific glands are also present in the skin of this organ. The internal leaf of the prepuce resembles closely a mucous membrane; papilla are numerous, but. there is an absence of hairs, and the seba- 224 MANUAL OF HISTOLOGY. ceous follicles (Tyson's glands) are sometimes difficult to find in the adult. In new-born children, however, these glands are abundant and well developed. The convoluted glands are here absent. The extremity of the penis terminates in a cone-shaped body, the glans penis, which has a cavernous structure very similar to that in the body of the organ, and differing only in the size of the meshes and the trabecular, the former being smaller and the latter more deli- cate. The external or mucous surface of the glans is covered with a laminated pavement epi- thelium, the cells of the upper layer being quite flat, those of the middle layer ribbed, while in the lowest layer they are colum- nar. There are numerous elastic fibres in the mucous membrane of the glans, and many single or branched papilhe are seen, some containing club-shaped nerve-terminations. The s}'stem of bloodvessels in connection with the penis con- sists of arteries, veins, capilla- ries, and cavernous spaces. The modes of communication between these several vascular structures are three : a direct passing of the blood from the larger arterial to the larger venous branches; a somewhat coarse venous reticu- lum communicating with a system of arterioles ; and, finally, a direct capillary anastomosis. The lymphatic system of the penis is represented by lymph- spaces, capillaries, and large trunks. The former, the spaces, are oblong in shape, and occur in the loose subcutaneous tissue surrounding the tunica albuginea ; they communicate with a capillary system, which is disposed in longitudinal meshes. The large lymph- trunks formed from these smaller vessels are Fig. 102.— Transverse section through the in- jected glans : a, epithelium of the urethra ; b, tunica mucosa ; c, corpus cavernosum urethra? ; rf, corpus cavernosum glandis : e, mucous mem- brane of the glans ; /, epithelium of the glans. Klein. THE MALE ORGANS OF GENERATION. 225 situated along the dorsum of the organ, and communicate with the lymph-glands in the pelvis and those of the groin. The nerves and their terminations in the penis are derived from the cerebro-spinal and sympathetic systems. In the loose tissue external to the tunica albuginea large medullated fibres are observed ; these give off smaller branches which enter the cavernous structure, and may be followed for some distance as medullated or non-medullated fibres. In this same tissue are found, at the root, shaft, and vicinity of the corona glandis, Pacinian corpuscles. They are oval in shape, and have their long diameter parallel to the long axis of the penis. These bodies have also been met with in the cavernous structure. The glans is especially rich in nervous elements, and here are found bodies known as the "genital nerve-corpuscles," situated in the tissue of the mucous membrane at the base of the papil- la3. These bodies are round in shape, vary in size from 0.1439 to 0.2001 mm. in diameter, and have characteristic constrictions upon their surface, giving them a mulberry-like appearance. The ordinary terminal bulbs of Krause are also met with in this location. The urethra of the male serves as the excretory canal for the urine and seminal fluid. An anatomical division is made into the prostatic, membranous, and spongy parts. The canal is lined with a mucous membrane, external to which there is a fibrous layer rich in elastic fibres, having a cavernous struc- ture ; external again to this is the muscular coat, composed of involuntary muscular fibres arranged in two layers, an internal, or longitudinal, and an external, or circular. There are also numerous fasciculi of oblique fibres, which serve to connect the two layers. The histological structure and arrangement of the three parts of the urethra are unlike, and must be separately studied, {a) In the prostatic portion the mucous membrane lies in longitudinal folds. A laminated epithelium covers the inferior wall, while the sides and superior wall are lined with a transitional variety. The prominence of this portion of the urethra, the colliculus seminalis, is composed of elastic tissue and smooth muscular cells, which form a cavernous structure. Throughout this spongy tissue, near the surface, are seen glands similar to those found in the prostate. Racemose glands (Littre'e glands), imperfectly developed, lined with cylindrical 15 226 MANUAL OF HISTOLOGY. epithelial cells in their acini, and at their orifices with lami- nated epithelium, are also present. The muscular tissue in this part of the urethra is intimately connected with that of fche prostate ; its fasciculi have generally a longitudinal direc- tion, and send off oblique bundles into the mucous mem- brane, (b) The membranous por- ^^fe^ / ^on °^ ^ie uretDra nas its niucous membrane covered by an epithe- lium similar to that met with in the prostatic portion. The glands of Littre are absent. Beneath the mucous membrane a long-meshed erectile tissue of a cavernous na- ture is found. Here the organic muscular layer is poorly devel- oped, and it is covered by trans- verse bundles of striped muscular fibres, the musculus urethralis. (c) Passing to the spongy portion, the mucous membrane is found thrown into longitudinal folds, which are in places connected by transverse ones, forming depressions, known as the lacunce Morgagnii. These are not glandular in their nature. The epithelium covering the mu- cous membrane in this portion is mostly cylindrical, but as it ap- proaches the meatus urinarius gradually assumes a pavement character. Glands of Littre are found throughout this part. The muscular elements are even less prominent here than in the membranous portion. Well-developed and numerous papilhe are seen projecting from the mucous membrane of the urethra into the epithelium. They possess a single capillary loop, or several loops are ob- served, especially in the fossa navicularis. These papilla? are absent or imperfectly developed at the points where a transitional epithelium is met with. Here the capillaries are arranged to con- stitute a reticulum beneath and parallel to the epithelial covering. The nerves of the urethra are found forming a network Fig. 103. — Transverse section through the spongy portion of the urethra corpus cavernosum urethra) : b, tunica mucosa ; c, muscular cords; d, vascular spaces of the corp. cavern. ; e, glands ; /, excretory duct of gland ; g, longitudinal muscles ; A, tunica albuginea. Klein. THE MALE ORGANS OF GENERATION. 227 around the muscular coat, similarly as elsewhere, in connection with smooth muscular fibres. Small nerve-fibres have been traced into the epithelial lining. Collections of ganglionic nerve-cells are found on the posterior surface of the membra- nous portion ; in the dense connective tissue at the posterior portion of the bulb ; and lastly, in the network of nerve-fibres around the vessels at the side of the bulb. The lymphatic system of the urethra is found in the mu- cous membrane, near the epithelium. It consists of a network of vessels with longitudinally arranged meshes ; they are con- nected with the lymphatic vessels of the bladder, and also open into the lymphatic canals of the glans penis. Cowpefs glands. — These organs, two in number, are situ- ated in the striated muscular tissue which surrounds the mem- branous portion of the urethra. They are lobulated, oval, and belong to the racemose group of glands. They are composed of acini and excretory ducts which unite to form a single duct for each gland, and discharge into the bulbous portion of the urethra. The acini constituting the several lobules are separated by connective tissue intermixed with smooth muscular fibres ; they possess a structureless membrana propria, and are lined with columnar cells, which are imbricated upon their outer thin portions. The ducts are lined with flattened columnar cells, and a layer of smooth muscular fibres is seen running along them. A capillary network surrounds the glandular structure. The prostate may be described as a glandular organ, pecu- liar in having its stroma composed of involuntary muscular elements. Externally it possesses a connective-tissue envelope which is united to bands of smooth muscular fibres that run in every direction, and constitute the cortical substance of the organ. From this cortex numerous bands or trabecuhe of a similar muscular nature proceed, forming an intricate network, and making up the greater part of the gland ; in the meshes of this reticulum is placed the glandular structure. Tin; thickness of the cortex, or the amount of glandular sub- stance, varies according to the position, whether behind or in front of the urethra, and it is found that the glandular struc- ture is comparatively more developed behind and in the lower portions than in front of the urethra. 228 MANUAL OF HISTOLOGT. The arrangement of the glandular elements is similar to that in the racemose glands, and consists of excretory ducts ter- minating in glandular vesicles or acini. The ducts which have their orifices in the urethra at its prostatic portion, and upon its inferior wall, are here lined with a transitional, or, when large, with a pavement epithelium, which gradually changes f w Mi$ I H V Ig88> mm fc |PP f Fro. 104. — Transverse section through the caput gallinaginis : a, epithelium of surface; b. vesicula pvostatica ; c, epithelium of the vesicula ; d, muscles ; e, ejaculatory duct : /, excretory duct of the pros- tatic glands ; g, upper wall of the urethra ; muscles running verticallj'. From a child. Klein. into a columnar variety as the ducts penetrate the organ. The basement-membrane is structureless, and is invested by a mus- cular layer. The acini are also lined by a columnar epithelium and possess a structureless membrana propria ; their shape is usually pyriform, and they have a diameter vaiying between 0.1254 and 0.23 mm. The epithelial cells of the acini frequently contain granules of brownish pigment. THE MALE ORGANS OF GENERATION. 229 Transversely striated muscular fibres are also met with in the prostate, both anterior and posterior to the urethra, ex- tending into the cortical substance, and between the glandular structure in the interior of the gland. The blood-vessels of the organ come from the large trunks surrounding it ; they pass into its structure and form a reticu- lated capillary system around the glandular substance. Medullated nerve-fibres are found surrounding the cortex in connection with groups of oval ganglionic centres. Paci- nian bodies are also ob- served in the cortex of the prostate, and in its interior are small medullated nerve- fibres which form a reticu- lum. A peculiar structure is found in the upper and pos- terior part of the prostate. It has the appearance of a duct, with walls resembling an artery, in so far as it consists of an internal longi- tudinal, a middle circular, and an external longitudi- nal coat. The middle coat is composed mostly of smooth mus- cular elements, while the external and internal coats are only partly made up of them. The interior of this structure is filled with a rich vascular network, pigment particles, and smooth muscular fibres. The nesicula prostatica, which forms a cul-de-sac in the middle of the prostate, beneath the middle lobe, opening by a duct at the summit of the colliculus seminalis, possesses a fibrous wall in which there are smooth muscular cells and is surrounded by a thin layer of cavernous tissue ; it is lined by a laminated epithelium, into which small conical papillae pro- ject ; small branched and tortuous glands are also found open- ing into its cavity. Fig. 105. — Transverse section through the central glandular substance of the prostate. From an adult. Klein. The testicles are glandular organs which secrete the sper- matic fluid, and are in the male organism the sexual represen- tatives of the ovaries in the female. 230 MANUAL OF HISTOLOGY. The glandular structure, together with the epididymis of the testicles, is enveloped by a dense librous membrane, the tunica albuginea. This is surrounded by a serous sac, the tunica vaginalis propria. Finally the testicle and spermatic cord are invested by the tunica vaginalis communis and the whole is contained in the scrotum. The tunica albuginea upon its external surface, or that covered by the tunica vaginalis propria, is smooth and shin- ing ; it consists of dense connective tissue with some elastic fibres ; upon the posterior border of the testicle it increases in thickness, and is here termed the corpus Higlimori, or medias- tinum testis, which passes into the gland. It also sends off from its whole internal surface numerous bands or trabecular the septula testis, which run toward the mediastinum, and divide the interior of the testicle into conical lobules, having their apices directed toward the corpus Highmori. These tra- becule contain smooth muscular fibres and blood-vessels. It is in these lobules or spaces that the secreting elements of the gland are situated. The serous sac, or tunica vaginalis, has its visceral layer, the tunica adnata, intimately united to the tunica albuginea over the testicle, but it is loosely attached to that over the epididy- mis. This membrane consists of connective tissue traversed by delicate elastic fibres, and lined on its surface with a layer of polyhedral cells, varying in size and containing oval nuclei with one or two nucleoli. Upon the upper portion of the tes- ticle and sharp edge of the epididymis, the tunica adnata is frequently found to possess tufted excrescences ; these pro- cesses are covered by several layers of flattened epithelial cells, or a single layer of round or cylindrical bodies. A capillary loop is seen extending into the tufts. The parietal layer of the tunica vaginalis propria consists of connective tissue, elastic fibres, and epithelium, as in the visceral layer. The tunica vaginalis communis, which covers the tunica vaginalis propria, is composed above of a loose, laminated con- nective tissue, but it becomes more dense below. Between this tunica and the tunica propria unstriped muscular fibres are found, while upon its external surface there are the strij>ed fibres of the cremaster muscle. Small non-vascular peduncu- lated excrescences are also found upon this surface. The mem- THE MALE ORGANS OF GENERATION. 231 brane is connected externally by connective tissue with the muscular layer of the scrotum, the dartos. The muscle of the scrotum, the dartos, consists of numerous smooth muscular fibres, arranged singly or forming a more or less continuous layer. The skin of the scrotum is peculiar in containing consider- able pigment, while there is an absence of fat in the subcu- taneous tissue. Hairs, large sebaceous follicles, and sweat- glands are also present in the skin of the scrotum. The hydatid of Morgagni is a structure found upon the anterior surface of the head of the epididymis, and is thought to be the remains of Miiller's duct. It is met with in two forms, either as a vesicle containing a clear fluid (with cells, and nuclei — ciliated epithelial cells are also at times present), and connected to the epididymis by a solid fibrous peduncle, or as a flattened structure possessing scarcely any stalk, which is simple or divided into lobules ; the latter form is most fre- quently seen. At times it is found to communicate with the canal of the epididymis. Between the head of the epididymis and the vas deferens, situated upon the posterior edge of the testicle, a small organ is seen, consisting of several whitish nodules. Each nodule is composed of a tube forming a number of convolutions and ter- minating in a club-shaped extremity. The tubes contain a clear fluid and are lined by a cylindrical epithelium, the cells of which are undergoing degeneration. Until ten years of age this organ is fully developed ; after this period it experiences degeneration. This structure is known as the organ of Gir- aldes, and represents the remains of the Wolffian bodies. The glandular or parenchymatous structure of the testicle consists of canals or seminiferous tubules about 0.1128 to 0.1421 mm. in diameter; they are. folded on themselves sev- eral times so as to constitute lobules, and are situated in the spaces formed by the trabecular of the tunica albuginea. The tubules not only are folded but divide and subdivide, anasto- mose, and terminate by loops. Toward the apices of the lob- ules the tubules gradually become more straight, fewer in number, and pass into the corpus Highmori, forming the rete testis. From the upper part of the rete emerge twelve to s<;vnteen larger tubules which pass through the tunica albu- ginea, after which they again become convoluted and form a 232 MANUAL OF HISTOLOGY. number of conical lobules, named the coni vasculosis which form the head of the epididymis. These tubules gradually unite to form a single canal, which is much convoluted, and develops an elongated body, the body and tail of the epididy- mis. The convolutions becoming less and less marked, the tube, increased in calibre, then leaves the testicle and ascends, at first somewhat spirally, but soon after in a perfectly straight course, constituting the vas deferens. Before this duct is formed, a short cajcal branch, named the vas aberrans, is at- tached to the tube. The seminiferous tubules either take their origin from blind extremities or anastomoses, the former being more frequently met with in children. Surrounding the tubules there is seen a framework of connective tissue, which proceeds from the septa. This intertubular connective tissue is distinctly lam- inated, and each lamella is formed of a fenestrated endothe- lial membrane, and a fenestrated connective-tissue membrane, which thus constitute numerous communicating spaces, that are the rootlets of the lymphatic system of the testis. The number of lamellae between the seminal tubes varies, and their relation to the tubes is very intimate, but depends upon the amount of fluid present in the interlamellar lymph-spaces. Groups of peculiar cells are found between the lamellae of the intertubular connective tissue. These cells have been observed by histologists, and by most are thought to be connective-tissue corpuscles. Klein, however, says they are epithelial in nature, and derived from the epithelial columns of the Wolffian body. In the meshes formed by this reticulated fibrous tissue are located the seminiferous tubules, the membrana propria of which is thought, on the one hand, to be structureless, or, on the other, to be composed of oval, flattened corpuscles, placed at regular intervals, which form an endothelial membrane. The tubules are found filled with corpuscles. Those at the periphery covering the membrana propria are round or polygonal in form, upon transverse section. In children, the cells of the tubules contain a finely granular and pale substance, but in adults they are filled with yellow pigment. Two typical forms of cor- puscle are observed, one with dark granular nuclei, the other with bright ones that have or have not nucleoli. The number of nuclei varies ; usually there are one or two ; but they may reach thirty or more. Many variousljT formed cells are seen, THE MALE ORGANS OF GENERATION. 233 which fact is held to indicate active proliferation. These bodies are termed seminal cells, and in the embryo are said to possess contractility and amoeboid movement. The seminiferous tubules upon entering the corpus High- mori lose their special external coat, which blends with the connective tissue of this region. Their epithelial lining con- sists of cylindrical cells with short cilia. After leaving the corpus Highmori and increasing in size, they have an additional coat of smooth muscular fibres, which, further down in the body of the epididymis, consists of two layers, an internal and an external or longitudinal coat. The epithelium lining the canal of the epididymis is composed of cells with long, oval nuclei, and provided with long tufts of cilia. Indeed, the lar- gest cilia found in the human body are upon the large cylindri- cal cells, which cover the upper part of the canal of the epi- didymis. Beneath this layer of ciliated bodies is a second of small, polyhedral ones with round nuclei. The vas deferens, which may be considered as analogous in many respects to the excretory duct of a glandular organ, is made up of an external or fibrous coat, a middle or mus- cular, and a mucous membrane, which is located most inter- nally. Covering this membrane are epithelial elements which differ in the various parts of the duct. At the beginning there is a single layer of cylindrical cells, between which, sometimes, there are spindle-shaped bodies ; the former possess delicate cilia. At about four centimetres from the epididymis the cilia are lost, but the character of the cells remains the same, ex- cept that a striated border can be seen in many. In children, a difference exists between the extra- and intra-abdominal por- tions of the duct. The former, or extra, is lined by a lami- nated epithelium, composed of a superficial layer of short cylindrical cells, beneath which are one or two layers of round or polyhedral cells. All these corpuscles have a relatively large nucleus. The intra-abdominal portion of the duct has a lining similar to that observed in the adult. The mucous coat is made up of connective tissue and elas- tic fibres, the former consisting of intersecting fasciculi, the latter of a close network. The membrane is thrown into two or three longitudinal folds or ruga?. Near the lower end of the vas deferens, in the ampulla, the longitudinal folds 234 MANUAL OF HISTOLOGY. are connected by transverse ones, and thus depressions are formed. The muscular coat consists of smooth muscular fibres ar- ranged in three layers: an inner, or longitudinal, which is feebly developed ; a middle, or circular, which is substantial in character, and an external or longitudinal. This coat is less developed in young children than in adults. In the external fibrous coat, or tunica adventitia of the vas deferens, are found bundles of smooth muscular fibres running longitudinally. They are derived from the cremaster interims, which muscle is well developed at the origin of the vas deferens, butgradually diminishes in sizeasit enters the abdominal cavity. The vas deferens possesses a dense plexus of medullated nerve-fibres, the spermatic plexus, situated in the tunica ad- ventitia. From this plexus several smaller trunks proceed which penetrate into the muscular and mucous coats. Scat- tered along these nerve-trunks are seen small ganglion-cells, which are round or oval. The blood-vessels of the testicle come from the internal spermatic artery and enter the gland partly at the corpus Ilighmori and partly upon its surface. They surround the seminiferous tubules as a capillary plexus of large meshes. The epididymis receives its blood from the deferential artery, and also to some extent from the vessels of the testicle. The vas deferens possesses a rich capillary network in its muscular coat and also in its mucous membrane beneath the epithelium. The nerves of the testicle come from the internal spermatic plexus ; their mode of termination has not as yet been satis- factorily explained. Letzerich, however, describes fine nerve- fibres in the testicles of mammals ; they penetrate the connec- tive tissue and membrana propria, terminating between this layer and the first row of cells in dark granular masses. The lymphatic system of the testicle consists of a series of lacunae, lined with endothelial cells, which surround the semi- niferous tubules; in the interstitial connective-tissue, these communicate with canals from which others are given off to the connective-tissue septa of the lobules. Beneath the tunica albuginea another network of lymphatic canals is also found, which penetrate the tunic, especially upon the dorsum of the organ, and finally, uniting with the lymphatics of the epididy- THE MALE OEGANS OF GENERATION". 235 mis and tunica vaginalis, form several large trunks, which fol- low the spermatic cord. Distinct networks of lymphatic ves- sels are found in the vascular and nervous layers of the sper- matic cord, and some are seen close to the muscular coat of the vas deferens. The seminal vesicles, designed as receptacles for the fluid secreted by the testicles, are, with some slight modifications, similar in structure to the vas deferens. They are composed of a mucous, muscular, and fibrous coat. The mucous mem- brane is covered with a superficial layer of cylindrical and a deep layer of polyhedral-epithelial cells, and is thrown into folds, longitudinal and transverse, forming depressions. The muscular coat consists of three layers, an internal or longi- tudinal, a middle or circular, and an external or longitudinal. The fibrous coat is abundantly supplied with networks of ves- sels and nerves. Here the ganglionic collections are highly developed, each corpuscle being quite large and containing a single nucleus, or even at times two. The ejaculatory ducts are, histologically, similar to the last described organs. As they approach the prostate their cylin- drical epithelium gradually changes into the transitional va- riety, and subsequently into the laminated pavement, as they approach their point of outlet in the urethra. Their mucous membrane is uneven from the longitudinal and transverse folds. After entering the prostate the muscular substance of the ducts undergoes cavernous transformation. When the testicle attains its full physiological develop- ment, which occurs in man at puberty, there is secreted by the organ a peculiar fluid, the semen or sperma. This fluid is whitish, slimy, and colorless, and has an alkaline or neutral re- action. Semen examined as discharged from the orifice of the urethra, incoitu, appears as a very different fluid, having re- ceived the secretions from the various accessory glands of the generative system. It is now more fluid, opaque, strongly al- kaline in reaction, and has acquired a peculiar odor. Placed under the microscope there is seen suspended in a hyaline fluid an infinite number of moving thread-like bodies called seminal filaments, spermatozoa, spermatozoids, seminal elements, etc. They are divided into a head, body or middle portion, and tail. 236 MANUAL OF HISTOLOGY. Fig. 100.— Seminal elements of man : a, undeveloped ; b, mature. St. George. They are as follows The shape of the head is pyriform, the broad part being con- nected with the body ; each has an average length of 0.0045 nun., and its breadth is about half as much. The middle por- tion or body is about 0.00G1 mm. long, while the tail measures about 0.0400 mm. Both the body and head of the seminal elements seem to be rigid, the terminal thread or tail having an active motion. From this description it will be seen that a com- parison of its structure with that of a ciliated epithelial cellis admissible, and indeed quite reasonable. The way in which spermatozoa are formed is still imperfectly known, and two different views claim our attention. a. The nucleus of the seminal cells moves to the periphery, then at the opposite side the proto- plasm of the cell is elongated into a caudal appendage ; the nucleus continuing to advance causes the protoplasm to be- come more and more elongated, and it is ultimately lengthened into a thread-like tail, while the nucleus, with its thin layer of protoplasm, constitutes the head. b. In this view the columnar or prismatic-shaped cells, the most external layer of cells ii 11- ing the seminal tubules, are thought to be the spermatozoa- producing elements. The inner remaining cells of the tu- bules experience no further development. During the active stage of the gland the spermatic cells become elongated, and extend into the centre of the tubule ; their free extremities become enlarged, and have a number of buds or club like pro- jections, eight to twelve, developed upon them. In each bud is formed a nucleus ; these nuclei eventually become the heads of spermatozoa, and the protoplasm is further developed into the body and tail. The cells from which the spermatozoa have their origin are named spermatoblasts. Klein, in his recent "Atlas of Histology," gives a very ex- tended description of the development of spermatozoa. Ac- cording to this writer there are several layers of epithelial cells lining the inside of the membrana propria of the seminal tubules. These layers he divides into an outer and inner. The outer, situated next to the membrana propria, embraces the germ-cells of Sertoli. The inner layer, those nearer the THE MALE ORGANS OF GENERATION. 237 lumen of the tubule, are the seminal cells of Sertoli. These latter are usually arranged in two or more layers, polyhedral in shape when placed closely together, but more spherical when next to the lumen of the tubule ; they are uniform in size and contain a single nucleus. The nucleus is spherical, possesses no limiting membrane, and contains a convolution of thick fibrils, or rods, in a transparent matrix. A more minute ex- amination of the nucleus shows that the fibrils are arranged in certain definite forms, which indicate changes preparatory to division, as has been pointed out by Strassburger, Hertwig, Flemming, and others. The various forms, taken by the nucleus before dividing, correspond to what is termed the "convolu- tion," the "basket," the "wreath," the "monaster," or the " dyaster." The entire process of the indirect division of the nucleus is termed by Flemming haryokinesis. Toward the lumen of the tube the above-described cells are seen with their nucleus either dividing or divided into two daughter-nuclei. From these daughter-nuclei are developed the daughter-cells, or spermatoblasts, and by an interesting series of changes the spermatozoa are formed. "The nucleus of the spermatoblasts at first retains its spher- ical shape, but is invested in a distinct membrane, the convo- lution of fibrils changes into a honey-combed reticulum, some- times with one or two nucleoli, and the nucleus is not placed in the centre but in the periphery of the cell." " Next the nucleus becomes uniform in its substance and transparent, all traces of a reticulum have disappeared. The cell-substance has collected at one end of the nucleus as an elliptical granular mass, and appears separated from it by a transparent, clear bag." " In the next stage the nucleus becomes flattened and dis- coid, so that when viewed from the surface it is broad and cir- cular, but appears narrow and staff-shaped when seen in profile. The cell-substance at this time is drawn out into a cylindrical or club-shaped granular body, separated from the nucleus by a shorter or longer clear tube, the former clear bag. At the front part of the nucleus is seen a short and tapering curved projection, and at its hind end — viz., that directed toward the clear tube and cell-substance — there is also to be found a short- pointed process extending into the clear tube just named." " In the next stage the nucleus becomes more flattened and 238 MANUAL OF HISTOLOGY. oblong. In the last stage the granular body lias become changed into a Long, thin, and homogeneous filament." " In what relation do, then, these different parts of the fully formed spermatozoon stand to the parts of the developing ele- ment— that is, the spermatoblasts A comparison shows al once that the head of the ripe spermatozoon is the changed nucleus of the spermatoblast ; that the filament, or tail, is de- rived from what has been mentioned above as the granular body of the original cell. The middle piece of Schweigger- Seidel is an outgrowth of the nucleus of the spermatoblast, that is, of the head, the spermatozoon, and the clear tube of the developing spermatozoon, described above as embracing the hind part of the nucleus and separating the latter from the granular body, is the sheath which, in some instances (triton and salamander), is observable on the middle piece of the fully formed spermatozoon.'' In short, the head of the spermatozoon is derived from the nucleus, while the tail has its origin from the body of the sper- matoblast. BIBLIOGRAPHY. Cooper, A. Obs. on the Struct, and Dis. of the Testis. London, 1830. Wa<;xer. Midler's Archiv. 1836. Panizza, B. Osservazioni anthropo-zoot.-fisiol. Pavia, 1836. Valentin. Ueb. d. Verl. d. Blutgef. im Penis d. Menschen. Midler's Arch. 1838. Kobelt. Die mannl. u. weibl. Wollustorgane. Freiburg, 1844. Koleiker. Gewebelehre und Verhandl. d. Vv'iirzb. med.-phys. Ges. 1851. Koiilratjscie Zur Anat. u. Phys. d. Beckenorgane. Leipzig, 1854. Sappey. L'urethre de 1'homme. 1854. Leydig, F. Zur Anat. d. mannl. Geschlechtsorg. in Zeitschr. f. wiss. Zool. Vol. II. And Histologic. 1857. Jar.tavay. Rech. anat. sur l'urethre de 1'homme. Paris, 1857. Merkee. Gottinger Nachrichten. No. 1, p. 7. 18G3. And Arch. f. mikr. Ann.t. Vol. I., p. 309. 1865. St. George, v. La Vaeette in Arch. f. mikr. Anat. Vol. I., p. 403. 18G5. And Strieker's Manual. Pettigrew, in Proc. Roy. Soc. Vol. XV., p. 244. 1866. ScrnvEioGER-SEiDEL, in Virch. Arch. Vol. XXXVII. , p. 225. 1866. Baebiana. Journal de l'anat. et de la phys., p. 218. 1868. Letzericii. in Virch. Arch. Vol. XLII., p. 570. 1^68. Stieda. T'ober den Bau des Menschen-Hoden, Arch. f. mikros. Anat. Vol. XIV., p. 17. 1877. BIBLIOGEAPHY. 239 Sertoli. Sulla struttura di canalicoli seminif. dei testicoli. Arch. p. le scien. med. Vol. II, p. 107. 1877. Menzel. TJeber Spermatozoen. Arch. f. klin. Chir. Vol. XXI., p. 518. 1877. Valentin, in Zeitschr. f. rat. Med. Vol. XVIII., p. 21. VoL XXI., p. S9. 1879. Langeu, in Wien. Sitz. Vol. XL VI, p. 120. 1879. Rotjget. Compt. rend. Vol. IV., p. 902. 1879. Frey, Heinrich. Histology and Histochemistry of Man. 1880. Klein. E., and Smith, E. Noble. Atlas of Histology. 1880. CHAPTER XVI. THE FEMALE EXTERNAL AND INTERNAL ORGANS OF GENERA TIOX, WITH THEIR GLANDULAR APPENDAGES— PLACENTA. Br Dr. J. HENRY C. SIMES, Lecturer on Histology, University of Penns3lvania. The external female genitals are the labia majora, labia minora, and clitoris. The labia majora are folds of skin, the subcutaneous tis- sue of which contains a large amount of adipose tissue. Their internal surface has the nature of a mucous membrane, while externally it is similar to the common integument. Here hairs, sebaceous glands, remarkable for their large size, and sweat- glands, are found. The papillae, vessels, nerves, and Pacinian corpuscles do not differ from those found elsewhere in the skin. The labia minora may be considered as folds of mucous membrane. They are covered by a laminated pavement-epi- thelium and the deepest layer contains pigment granules. Conical vascular papillae are seen beneath the epithelium. In the connective-tissue framework of the mucous membrane smooth muscular elements are found. Capillary networks are seen on the surface beneath the epithelium, and in the sub- stance of the membrane, from which arise small veins, consti- tuting a plexus, and giving this structure the character of an erectile tissue. Upon the external surface of the folds are found sebaceous glands without hairs. These glands are absent at birth. There is no adipose tissue in the labia minora. The clitoris is covered by a mucous membrane which is a continuation of that of the labia minora, and to which it is similar in structure, in so far as epithelium, mucous tissue, and papilla? are concerned. The mucous membrane covering the glans of the organ is found to have those peculiar nerve-termi- nations in its structure, the genital nerve-corpuscles, which THE FEMALE ORGANS OF GENERATION. 2-41 have been described as existing in the mucous membrane of the glans penis. Beneath the mucous membrane of the clitoris are found the corpora cavernosa and glans ; the latter is in connection with both bulbi testibuli, which correspond to the corpus spongio- sum urethra of the male. These structures consist of erectile or cavernous tissue, which, like that in the penis, is made up of a vascular network, mostly venous in character, and erectile in nature ; they are also surrounded by a fibrous tunic analogous to the tunica albuginea of the penis. The vestibule has its mucous membrane, which is a con- tinuation of the mucous membrane of the clitoris, thrown into a number of folds. Opening upon its surface are numerous ori- fices of racemose mucous glands. These glands are collected into groups around the orifice of the urethra and vagina. They consist of branched ducts, which at their deeper parts are de- veloped into a number of acini ; they are lined with a simple epithelium ; at their orifices they have the laminated pavement- epithelium of the mucous surface. These glands vary in diame- ter between 0.5 mm. to 2.5 mm. The vessels of the vestibule form a network near the mucous surface, and are connected to the capillary loops in the papilla?. Opening upon each side of the vaginal entrance is the orifice of the duct belonging to the gland of Bartholin*. These or- gans, two in number, are analogous to Cowper's glands in the male. They belong to the racemose group, and are composed of ducts and acini, which have an epithelium lining of cylin- drical cells. The hymen consists of a duplicature of the mucous mem- brane of the vagina. Its laminated epithelium is similar to that of the vestibule. The papillae are numerous, long, simple or multiple, and project from 0.2 to 0.3 mm. into the epithelial covering. The vascular and nervous supply is very abundant. The vagina consists of an external coat of connective tissue, a middle coat of muscular tissue, and an internal mucous coat. The mucous membrane is uneven, thrown into ridges and papil- lary elevations, which are especially well-marked in the neigh- borhood of the vaginal entrance. The epithelium lining the canal is a laminated pavement-epithelium, into which the vas- 16 242 MANUAL OF HISTOLOGY. cular papillae of the mucous membrane extend. In the latter coating are found numerous elastic fibres in the fasciculi of connective tissue ; bundles of smooth muscular cells are also present. Tubular glands, lined with ciliated columnar epithe- lium at their fundus, have been described as existing in the mucous membrane of the vagina by Preuschen. Hennig also speaks of similar glands being present in this membrane. The submucous tissue is very vascular and loose in texture. The muscular coat consists of an internal longitudinal and an ex- ternal circular layer of smooth muscular fibres, between which are many oblique connecting fasciculi. The external fibrous tissue is loose in texture, and has embedded in it the external venous plexus. The vascular system of the vagina is composed of arteries, veins, a venous plexus, and capillaries. The plexus is met with in the folds of the vagina. It is a cavernous structure possessing smooth muscular fibres, and has an arrangement of trabecular similar to that found in other erectile organs. The lymphatics and nerves of the mucous membrane of the vagina are abundant. The latter form networks in which there are found ganglion-cells, in groups or single ; as in the male genitals, these cells are of two sizes. The ultimate terminations of the nerve-fibres are as yet undetermined. The fluid secreted ,by this membrane has an acid reaction. The urethra possesses a mucous membrane covered by a transitional epithelium at its upper portion, the superficial layer of cells being short cylinders, which gradually become shorter, until the deepest layer is seen made up of rounded cells. The lower portion of the canal has a lining of laminated pave- ment-epithelium similar to that of the vestibule. The mucous membrane has numerous papilla extending into the epi- thelium. In this layer are seen at places many lymph-corpus- cles, sometimes amounting to an infiltration, when it may be considered as adenoid in nature. The submucous tissue is mostty composed of venous networks ; it is in fact a cavernous tissue. As in the male, there are present in the mucous mem- brane the glands of Littre, seen especially abundant near the meatus urlnarius. The muscular coat of the urethra consists of an internal longitudinal and an external circular layer of smooth muscular fibres ; in the external layer are also the THE FEMALE ORGANS OF GENERATION". 243 transversely striated muscular fibres of the urethral muscles. The external fibrous coat of the urethra consists of wavy con- nective-tissue fasciculi, which have a longitudinal and circular course. The uterus possesses an external covering of serous mem- brane, the peritoneum ; anteriorly it is more intimately con- nected with the organ than posteriorly, while at the sides the layers are separated, in order to permit the passage of blood- vessels, lymphatics, and nerves into the uterine substance. The tissue composing the greater part of the uterus is formed of smooth muscular fibres, the arrangement of which is very irregular, but three more or less distinct layers have been de- scribed. The external one, which is relatively thin, consists mostly of fibres running longitudinally, although many circu- lar fasciculi are seen. The middle layer exceeds the others in thickness, its fibres take a longitudinal, transverse, or oblique direction, while the internal layer is essentially circular, and forms the sphincters of the uterus. The contractile elements of these muscular layers are intimately united together by a cementing substance, forming fasciculi or bundles, which are again held together by connective tissue in which elastic fibres are found. The shape of the cells in the normal uterus is fusi- form, frequently very long, and in transverse section round or oval, with several angles. The nucleus is always single, rod- like or oblong in shape. The mucous membrane lining the uterus is closely connected to the muscular tissue. It has no connective-tissue framework of fibres, but its structure resembles the stroma of lymphoid organs, in which the framework is made up of spindle and fusiform cells. The surface of this membrane varies in differ- ent parts ; at the fundus and body it is smooth, except at the orifices of the Fallopian tubes, where there is a slight folding ; in the canal of the neck it is thrown into numerous branching folds, the pliccB palmatce. At the upper end of the isthmus of rh'i cervix a distinct border indicates the termination of the mucous membrane of the body. The epithelium covering this portion of the membrane is columnar in shape, and provided with short cilia. There are found in the mucous membrane of the fundus and body numerous tubular glands, which are either simple tubes or they divide about their middle, and ter- 244 MANUAL OF HISTOLOGY. minate in blind ends; frequently they have a spiral course, corkscrew-like ; but generally their direction is vertical to the plane of the membrane ; they open into the cavity of the uterus. The existence of a membrana propria in these glan- dule utriculares is denied by some, or if present it is only toward the orifice of the gland. In the pregnant organ, how- ever, an extremely delicate, structureless membrane, in which oval nuclei are found, is thought to represent such a structure. The cells lining these glands are prismatic in shape, their broad ends directed outward ; the slender extremities projecting into the lumen of the gland are provided with cilia. The mucous membrane lining the canal of the cervix is denser and thicker than that of the body. It possesses a con- nective-tissue investment which lies between it and the muscu- lar layer, and it also differs from the lining of the body in the presence of folds, which constitute the plicse palmatse. The epithelium covering this portion of the uterus is made up of cylindrical ciliated cells, in the upper two-thirds of the canal, but as the external os uteri is approached it gradually as- sumes the laminated pavement variety. Minute papillae, pro- vided with a capillary loop, are found in the lower half of the canal. The folds of membrane consist of a firm fibrous tissue, a few smooth muscular elements, and a scanty amount of elas- tic fibres. Here are also located the mucous follicles of the cervix, or, as some histologists consider them, depressions only of the mucous membrane ; they are lined with a cubical epi- thelium, and possess a structureless membrana propria, which is intimately connected to the connective tissue. From an occlusion of the orifices of these follicles there are developed small retention cysts containing mucoid fluid, usually round or oval, and measuring 0.3 to 0.5 mm. in length ; they are known as the ovula Nabothi. The fluid secreted by the mucous mem- brane of the uterus differs from that of the vaginal mucous membrane in having an alkaline reaction. The mucous membrane covering the intra-vaginal portion of the uterus is a continuation of the vaginal mucous mem- brane, consisting of a similar structure, and composed of a connective-tissue framework with papillse projecting into its covering of laminated pavement-epithelium. At times this por- tion is found to contain the ovula Nabothi. The uterus is a very vascular organ ; a capillary network is THE FEMALE ORGANS OF GENERATION. 245 found in the muscular coat and mucous membrane. In the latter such reticula are seen to surround the glands. The veins are very large, possess delicate walls, and are valveless. In the cervical portion, a more regular distribution of vessels is met with, and their walls are unusually thick. Numerous lymphatic vessels are found beneath the peri- toneal covering of the uterus, and arched passages are seen ending in loops or blind extremities under the mucous mem- brane of the cervix. Lymph clefts and vessels are also met with in the intermuscular connective-tissue. The nerves of the uterus are derived from the genital sper- matic ganglia. On the posterior wall of the neck a large ganglionic mass is met with, from which most of the nerves have their origin. Nervous filaments may be followed as far as the mucous membrane, and a few histologists have traced them into the papillae of the cervix, while in the muscular coat they are said to terminate in the nuclei of the muscular ele- ments. During the physiological function of menstruation and gestation the uterus experiences certain modifications. In the former there is an increase in the size of the organ, owing mostly to the great increase of blood in the vessels ; the glands of the mucous membrane are also increased in size. The discharge of blood during this period is due either to a rupture of the dis- tended capillaries, or a diapedesis, in which the walls remain uninjured. On microscopical examination of the menstrual fluid it is found to contain, besides the blood-elements, numer- ous uterine epithelial cells. The modifications of the uterus during gestation occur es- pecially in the muscular elements, which are greatly hyper- trophied, and there is also a new formation of them. The blood-vessels, lymphatics, and nerves also experience an in- crease in size, the latter by a thickening of their perineurium. The mucous membrane of the body of the uterus during gesta- tion is separated from the uterus, previously becoming thicker, softer, and more vascular, and constitutes the decidua. The cervical portion of the mucous membrane does not participate in this metamorphosis ; it retains its epithelium, and secretes a mucous plug, which fills the canal of the cervix during preg- nancy. Subsequent to delivery a new mucous membrane and glands are develojjed on the cavity of the uterus, and the hy- 24G MANUAL OF HISTOLOGY. pertrophied and newly formed muscular elements undergo retrograde development and fatty metamorphosis. The Fallopian tubes, or temporary ducts of the ovary, con- sist of an external covering furnished by the peritoneum, rich in connective tissue and blood-vessels ; a muscular coat made up of an outside layer of longitudinal, and an inside layer of circular involuntary muscular elements ; and, finally, an in- ternal mucous membrane. A division of the tube is made into two parts : that toward the uterus, into which it opens, the much narrower portion, is the isthmus, while the free half is the ampulla, which terminates in the fimbria. The mucous membrane, upon transverse section of the tube, in the narrow portion, is seen thrown into simple longitudinal folds, while in the ampulla the folds are much more complicated, and in a transverse section have a dendritic appearance. The epithelium covering the mucous membrane consists of ciliated columnar epithelial cells. The movements of the cilia occasion a current in the direction of the uterine opening. There is an absence of glands in the mucous membrane of the Fallopian tubes. The same histological elements are present in the fimbriae as in other portions of the tube, of which they are a direct contin- uation. The ovary for histological study may be divided into two parts, the cortex and medullary substance ; covering the cor- tex is a layer of columnar epithelial cells, named the ovarian or germ epithelium (Fig. 107). In a perpendicular section, the germ-epithelium is here and there seen to extend down into the substance of the organ and form tubes — the ovarial tubes. The cortical substance or parenchymal zone consists of several layers of dense connective tissue, in which are found ovarial tubes and ovarian foil ides. The most external follicles are im- perfectly developed, while those lying deeper are more highly developed and contain the ovum. Internal to the cortex is the medullary substance or vascular zone, in which are numerous blood-vessels, giving it the nature of a cavernous tissue. The stroma of the ovary consists of fibrillar connective tis- sue. In the vascular zone it is somewhat loose in texture, and contains a network of elastic tissue. There are also found in this zone fasciculi of smooth muscular fibres, which follow the THE FEMALE ORGANS OF GENERATION. 2-47 large and medium sized arteries, at times constituting a sheath for the vessels. In the stroma of the parenchymal zone the connective-tissue forms an outer layer of short, dense fibres «7\ I Fio. 107. — From the ovarium of a rather old bitch ; portion of a sagittal section, a, germ-epithelium ; 6, b, ovarial tubes ; c, c, younger follicles ; d, older follicle ; e, disoua proligerus, with egg ; /, epithelium of a MOOnd 'trg in the same follicle; fir, tunica fibrosa folliculi ; A. tunica propria folliculi; i, follicular epithelium fmi'mbnina granulosa); #, collapsed degenerated follicle; /, vessels: to, to, cell-tubes of the parovarium, both longitudinal and transverse sections; y. tubular sinking in of the germ-epitheliuro into the BUbotonoe of the ovary; z, commencement of the germ epithelium close to the lower border of the ovary. Waldeyer. which run in every direction, and an inner one abounding in cells, in which the follicles are seen. The blood-vessels enter the ovary at the hilum. The arteries hare a spiral, corkscrew-like course through the organ. At the hilum the veins form a convoluted mass, the bulb of the 248 MANUAL OF HISTOLOGY. ovary. A capillary reticulum surrounds the follicles, and is situated in their internal membrane. The stroma of the hilum contains numerous lymphatics, which have an arrangement similar to that of the veins. Sur- rounding the follicles in their external lamina is found a dense network of lymphatics. The nerves enter the ovary at the hilum with the arteries, and they have been followed into the stroma between the large follicles, but their ultimate terminations have not as yet been ascertained. The follicles of the ovary, or Graafian follicles, consist of a connective-tissue wall separable into two layers : an internal, which contains the small capillaries, and an external, contain- ing the large blood-vessels and lymphatics. The outer layer is made up of the same connective tissue as the stroma of the ovary, in which are numerous spindle-shaped cells. The inter- nal layer consists of connective tissue, in which are numerous and variously shaped cells, fusiform, stellate, and small round bodies, the latter possessing amoeboid movement ; there are also seen larger round or polygonal -shaped cells. This layer of corpuscles is the membrana granulosa. Within the follicle, and distending it, is an albuminous fluid holding a few bodies in suspension. Situated in the follicle, usually at that part most distant from the surface of the ovary— although this is not a rule without exception, since it is also found immediately below the most superficial part of the follicle— the ovum is found surrounded by a collection of cells of the granular mem- brane, known as the discus proligerus. Two kinds of cells form the discus proligerus, the follicular and egg epithelium ; the latter lie in immediate contact with the vitelline membrane, and are closely adherent to it. An examination of the mature ovum demonstrates it to measure 0.28 to 0.1379 mm. in diameter; it is spherical in shape, and is a typical cell, consisting of an investing mem- brane, the vitelline membrane, or zona pellucida, which is a dense, transparent, homogeneous substance, apparently pierced by numerous minute pores. This membrane is prob- ably developed from the cells of the discus proligerus, and from the layer described as the egg epithelium. The cell-contents, protoplasm, or vitellus is a granular mass composed of albu- minous and fatty particles, and a more or less distinct reticu- THE FEMALE ORGANS OP GENERATION". 249 lum of fine fibrils. Within the vitellus is seen the nucleus or germinal vesicle (also presenting a delicate reticulum of fibrils), situated eccentrically, spherical in shape, measures 0.037 to 0.451 mm. in diameter, shining, transparent, and contains the nucleolus or germinal spot, which is a highly refractile body, finely granular, supposed to be non-vesicular, and measures 0.0046 to 0.0068 mm. in diameter. The mature Graafian follicle, which is seen on the surface Fig. 108. — A, primordial egg of the human being ; 8 months' foetus. B, primordial follicle of the rabbit. C, primordial follicle of a dove. D, a somewhat older follicle of the same animal ; commence- ment of the formation of the subordinate yolk. E, blind end of the ovary of an ascaris nigrovenosa ; germinal vesicles (some of which possess a germinal spot and Schri'm's "granule") in a diffuse mass of protoplasm. F, egg of the ascaris nigrovenosa from about the middle of the ovary ; Schron's granule ; commencement of the deposition of yolk-matter. G, egg from a follicle (2 mm. in diam.) of the rabbit : a. egg-epithelium ; 6, striated zone with radiating stria: ; c, germinal vesicle ; d, germinal spot ; e, yolk. Waldcycr. of the ovary, giving rise to a prominence, ruptures during the menstrual period and empties its contents, viz. : the ovum, fluid contents, and discus proligerus into the Fallopian tube. The cause of the rupture is an increase in the contents of the follicle, and a fatty metamorphosis of the cells of the wall of the follicle. As a result of this rupture of the Graafian vesi- cle, there is formed a yellow body, the corpus luteum, which 250 MANUAL OF HISTOLOGY. reaches its full development in a few weeks after the ruptur- ing of the follicle, or when impregnation has occurred after the lapse of two or three months. It consists of a central portion, at first red, becoming gray, and a peripheral portion, yellow in color, thrown into folds. These folds are made up of the in- ternal membrane and cells. The central portion in a fresh corpus luteum consists of a very vascular tissue, in which are seen numerous large cells, containing a red coloring substance and hsematoidin crystals. A retrograde metamorphosis occurs in the yellow body, supposed to be due to a want of nutrition caused by a wasting of the arteries, and there only remains a white cicatrix, the corpus albicans. The time required for the disappearance of a corpus luteum when impregnation has taken place— a true corpus luteum — is several months, lasting to the end of gestation ; but for the disappearance of a false corpus luteum, or when impregnation has not occurred, it only requires a few weeks. It is, however, to be remembered, that every Graafian follicle with its contents does not reach full de- velopment ; most of them experience fatty or colloid metamor- phosis. The ovaries have their origin from the Wolffian bodies. A thickening of the epithelial covering is early observed upon the side of these bodies ; at the same time and place a cellular projection growing from the connective tissue of the organ is noticed. From this increase of epithelium the Graafian folli- cles and ova are developed, later the ovarial epithelium ; from the connective tissue is built up the vascular system of the ovary. The Graafian follicles are developed from collections of cells, irregular in shape, or, as they are named, ova chains, consisting of small-sized peripheral cells, which later form the membrana granulosa, and the primordial ova ; these last are recognized by their large size, granular or reticulated protoplasm and central position. The ova chains are sometimes enclosed in a homogeneous membrana propria, forming a tubular structure, as in the cat ; this membrane, however, is not found in all ani- mals. These chains are developed by an ingrowth of the epi- thelial cells covering the surface of the ovary. The parovarmm, or remains of the Wolffian body, situated in the broad ligament, is made up of twelve to fifteen tubules, which possess a membrana propria, lined by a single layer of ciliated epithelium, and contain a transparent substance. THE FEMALE ORGANS OF GENERATION. 251 The placenta is divided into a uterine and foetal portion. The former consists of cells irregular in shape, containing one or several nuclei, and at times one or more nucleoli. These cells are separated by an intercellular substance, either hyaline, granular, or fibrous in nature. Fusiform cells, in which a rod- shaped nucleus is seen, are also found, and are thought to in- dicate the presence of smooth muscular elements. The tufts upon the surface of the uterine placenta, which divide and sub- divide, pass quite deeply into the foetal placenta, yet no direct transformation of them into the foetal tissue can be demon- strated ; they appear to terminate in fibrillated tissue, which contains none of the cellular elements of the uterine placenta. The blood-vessels of the uterine placenta are arteries and veins, with no intermediary capillary system ; they communi- cate by means of sinuous spaces, limited by placental tissue only. These spaces are said to possess a delicate limiting wall ; this statement, however, has not been confirmed. The foetal placenta is developed from the chorion, the villi or tufts of which growing into the uterine follicles are covered by a columnar epithelium. The blood-vessels in the villi do not lie directly in contact with the wall of the villus, but are separated from it by a perivascular space. Besides a direct communication of the arteries and veins, there is also a capil- lary system present in the villi. Connective tissue accompa- nies the vessels into the villi from the chorion. The variety of connective tissue here met with is the mucoid, consisting of round, spindle, and stellate-shaped cells, with a structureless intercellular substance. There is a direct transformation of this mucoid connective tissue into the connective tissue of the chorion. BIBLIOGRAPHY. BiscnoFF. Beitr. zur Lehre v. d. menschl. Eihiillen. 1834. Valentin, in Miiller's Arch., p. 520. 1838. GooDSEB. Anat. and Path. Researches. Edinburgh, 1845. KOBELT. Der Nebeneierstock des Weibes. Heidelberg, 1847. Steinun. Ueber d. Entw. d. Graaf. Foil. u. Eier d. Situgeth., Mittheil. d. Zii- richer naturf. Gesellsch. 1847. Robin. Arch, gonor. de mod. Vol. XVII., p. 258 and 405. 1848. And Vol. XVIII., p. 257. Also Gaz. med. No. 50. 1855. Rainey, in Phil. Trans., II. 1850. 252 MANUAL OF HISTOLOGY. Schroder VAN DER Kolk. Waarnemingen oves het Maaksel van de menschl. Placenta, etc. Amsterdam, 1851. Smith, Tyler-. Med. Chir. Trans. Vol. XXXV., 378. 1852. Remak. Unters. ueb. d. Entwick. d. Wirbelthiere. Berlin, 1855. Med. Centr. Zeit. No. 42. 1861. No. 3. 1802. Klebs, in Virch. Arch. Vol. XXVIII. 18G3. Pplugeii, E. Ueb. d. Eierstocke d. Siiugeth. u. d. Menschen. Leipzig, 1803. Spiegelberg. Virch. Arch. Vol. XXX, p. 4G6. 1864. KAMENBW. Unters. d. Blutgef. d. Mutterth. d. Placenta, Medicinsky Westnik. No. 13. 1864. Cornil, in Jour, de l'anat., p. 386. 1864. Unters. aus d. phys. Labor, zu Bonn, p. 173. Berlin, 1865. Polle. Die Nervenverbr. in d. weibl. Genital. Gottingen, 1865. His, in Arch. f. mikr. Anat. Vol. I., p. 151. 1805. St. George, v. La Valette, in Arch. f. mikr. Anat. Vol. II., p. 56. 1866. Perier. Anat. et phys. de l'ovaire. Paris, 1866. Stricker. Wien. Sitz. June, 1866. Langhans, in Virch. Arch. Vol. XXXVIII., p. 543. 1867. Fkankenhauser. Die Nerven. d. Gebiirmutter. Jena, 1867. Jassinski. Zur Lehre ueb. d. Struct, d. Placenta. Virch. Arch. 1867. Virchow. Bildg. d. Placenta, in Gesamm. Abhandlungen. 1853. Bidder. Ueb. Hist. d. Nachgeb., in Hoist's Beitr. z. Gyniicol. II. 1867. Ercolani. Giamb. delle gland, otricolare, etc. Bologna, 1868. Plikol, in Arch. f. mikr. Anat. Vol. V., p. 445. 1869. FriedlInder. Unters. ueb. d. Uterus. 1870. Hennig. Der Catarrh d. inn. weibl. Geschlechtsorg. 1870. Waldeyer. Eierstock. u. Ei. Leipzig, 1870. Lott and A. Rollet. Untersuchungen. II. Leipzig, 1871. Langhans. Unters. ueber d. menschl. Placenta. Arch. f. Anat. u. Phys. 1877. Leopold. Stud. ueb. d. Uterus-schleimhaut. Arch. f. Gyn. Vol. XI., p. 110 and 443. 1877. Also Vol. XII., p. 169. 1877. Hennig. Ueber Driisen der Vagina. Arch. f. Gyn. Vol. XII., p. 488. 1877. Foulis. The Development of the Ova, and the Structure of the Ovary, etc. Jour. of Anat. and Phys. Vol XIII., p. 353. 1878-79. Frey, Heinrich. Histology and Histochemistry of Man. 1880. Klein, E., and E. Noble Smith. Atlas of Histology. 1880. CHAPTER XVII. THE KESPIRATOEY TRACT. By BENJAMIN F. WESTBROOK, M.D., Lecturer on Anatomy and Pathological Anatomy at the Long Island College Hospital, Brooklyn, N. Y. The respiratory tract includes the nares and, perhaps, the pharynx, but as the latter is more commonly associated with the function of deglutition, and the former contain in their upper portions the organs of one of the special senses, they have been assigned to other portions of this work. This chap- ter is devoted exclusively to the consideration of those parts which are concerned in the respiratory process. As the pleura forms a part of the lung, and facilitates the movements of breathing, its structure may properly be described under this section. The air-tubes are in general made up of three layers : an outer of connective tissue and elastic fibres ; a middle, muscu- lar and cartilaginous ; and an inner of mucous membrane. Their structure is more complex in the upper, and simpler in the lower portions of the respiratory passages. Tfie larynx. — The muscles of the larynx are of the striped or voluntary variety. The ligaments and membranes are composed of yellow elas- tic fibres with some white fibrous tissue. Their structure can be easily demonstrated by the process of teasing or by employing the reagents ordinarily used for this class of tissues. The la- teral thyro-hyoid and the inferior thyro-arytenoid ligaments have the following peculiarities of structure : the lateral thyro- hyoid ligament usually encloses a small piece of hyaline carti- lage about the size and shape of a large grain of wheat. It is known as the cartilago triticea. In adult males it is usually calcified. It may be incorporated either with the cornu of the hyoid bone or with the superior cornu of the thyroid cartilage. 254 MANUAL OF HISTOLOGY. The inferior thyro-arytenoid ligaments, or true vocal cords, are made up almost entirely of yellow elastic fibres stretched across from the thyroid cartilage in front, to the vocal processes and adjacent anterior borders of the arytenoids behind. The elastic bundles originate, anteriorly, in a mass of connective tissue which occupies the angle of the thyroid. Posteriorly, many of the fibres are prolonged into the arytenoid cartilage, converting that part of it into reticular tissue. These liga- ments are continuous below with the lateral crico-thyroid mem- branes, and are described by some anatomists ' as their superior borders. The innermost fibres of the internal thyro-arytenoid mus- cle mingle with the outer fibres of this ligament, some ending in or taking their origin from them. The intimate relation be- tween the muscle and the ligament can be seen in a vertical sec- tion through the larynx. Of the laryngeal cartilages, the three larger are of the hyaline variety. Horizontal sections show a broad central area with two zones between it and either the outer or inner sur- face. The appearance of the zones or bands is thus described by Rheiner : 2 "1. A thin peripheral portion, appearing to the naked eye as a narrow, bluish, opalescent band, which con- sists of a transparent and longitudinally striated matrix with elongated cartilage-cells arranged parallel to the surface. 2. The intermediate layer, a narrow, whitish, opaque band, con- sisting of a dull yellowish ground-substance with numerous large mother-cells containing fatty daughter-cells. 3. The broad central layer, with a perfectly transparent homogeneous matrix and few cells. The intercellular substance increases, relatively to the contained cells, from without inward, and, in the interior, presents numerous large spaces in which no cells are found. In the thyroid and cricoid cartilages the outer peripheral zone is thicker and more easily distinguished than the inner." The following peculiarities are to be noted : the central por- tion of the thyroid, viz., that part which forms the anterior projection or angle, is distinguished by the great number and small size of its cells. It is penetrated by numerous fibres 1 Quain's Anatomy, eighth edition. Vol. II. , p. 284. 2 Quoted by Merkel in Anatomie u. Phys. des mensch. Stimm- u. Sprach-Organs. Leipzig, 1863, S. 166. THE RESPIRATORY TRACT. 255 from that mass of connective tissue from which the vocal cords take their origin. After prolonged maceration in some alka- line solution, this cartilage can be separated into three parts — two lateral and an anterior or median. The arytenoids are not composed exclusively of hyaline cartilage. The vocal process, as already mentioned, presents a yellow reticulated structure, the fibres of which are continuous with those of the true vocal cords. The apex has also a re- ticular structure when there is no joint between it and the cartilage of Santorini. The elastic tissue is then continuous with that which connects it with the corniculum. A hori- zontal section through the arytenoid at the level of the vocal process shows the reticular structure of the process, the hya- line character of the body of the cartilage, and the gradual transition from one to the other. The three cartilages already described are subject to calci- fication and partial ossification. This occurs more frequently and at an earlier age in the male than in the female. It also begins at a later date in those who have been castrated. It makes its first appearance at the points of muscular attach- ment. As the cartilages undergo calcification they increase in size, so that the calcified larynx of old age is larger than that of the young adult. The matrix also splits up into a fibrous texture, not affected by acetic acid. The cornicula laryngis or cartilages of Santorini and the cuneiform cartilages of Wrisberg, as well as the sesamoid cartilages (when they exist) are of the reticulated variety. The cartilago triticea is hyaline and prone to calcification. The epiglottis consists of reticular cartilage. On transverse section, however, the intercellular substance is seen to be a spongy elastic substance, granular on section ; at the periphery yellow fibres are present. The elastic cartilage should be ex- amined with a high power. The mucous membrane of the larynx varies in its structure in different situations. On the laryngeal surface of the epi- glottis it is thin. The epithelium in the upper half is in several layers. The deepest cells are somewhat columnar or pyramidal in form, while the superficial ones are flat. The lower half is covered by a stratified, columnar, ciliated epithelium. The epithelium rests upon a thin, apparently structureless basement-membrane. 256 MANUAL OF HISTOLOGY. The mucosa is made up of delicate connective-tissue fibres, en- closing in their meshes a series of lymph -spaces. Connective- tissue cells are also found here, and some elastic fibres. There are a few small papillae in the upper portion. The submucous layer is thin, contains many elastic fibres, and is continuous with the perichondrium. It contains the racemose mucous glands, whose ducts open upon the surface. Some of the larger glands are lodged in the depressions of the cartilage, and some are even situated on its anterior aspects, their ducts passing through to the posterior side. In the submucous tissue there are lymphatic follicles, some of which are arranged about the mucous glands and their ducts. The membrane covering the false vocal cords, arytenoid cartilages, and ary-epiglottic folds, as well as that lining the ventricles and inferior compartment of the larynx is thicker and more loosely attached to the subjacent parts. It is covered by stratified columnar, ciliated epithelium, except upon the edge of the false vocal cords and over the inner surfaces of the arytenoids, where it is of the pavement variety. The mucosa contains a large amount of tymphoid tissue, which holds in its meshes tymphoid cells. Closed lymph-follicles are also found in the submucous tissue of the false vocal cords and on the floor of the ventricle.1 That portion of the mucous membrane which covers the true vocal cords is thin, more closely attached, and has no mucous glands. In its anterior half it has numer- ous small papillaB (0.07 to 0.08 mm. in height, Coyne) project- ing at the edge and on the superior and inferior surfaces of the cord. They are composed of connective tissue, with many elas- tic fibres. Their vascular supply is slight. The membrane in this situation is covered by stratified pavement -epithelium, continuous posteriorly with that which covers the inner sur- faces of the arytenoids. Numerous racemose glands send their ducts obliquely upward and inward to discharge their secretion upon the upper and under surfaces of the vocal cords. In front of the corniculum laryngis, on either side, is a col- lection of racemose glands surrounding the cartilage of Wris- berg. Another collection is found between the arytenoids. The epithelium can be examined, either by scraping it from the surface, or in sections. The mucous glands are best seen 1 Coyne : Archiv. d. Phyaiologie, p. 92, 1874. THE RESPIRATORY TRACT. 257 in sections of the hardened larynx. They are lined by cubical glandular epithelium. The capillary blood-vessels of the laryn- geal mucous membrane are small with wide meshes, giving the membrane a paler appearance than that of the pharynx. The lymphatics are numerous in the mucous and sub- mucous layers. They may be injected with Berlin blue, by puncturing the submucous tissue. In the nervous filaments are ganglion cells. The mode of termination is not definitely known. But in the mucous membrane of the epiglottis end bulbs have been found. The methods of examination will be found elsewhere. The trachea and primary bronchi. — The rings of the trachea and bronchi are composed of hyaline cartilage. Longitudinal sections of these rings show that the cells lying near the peri- phery, underneath the perichondrium, are flattened, and ar- ranged with their long axes parallel to the surface. Internally they are oblong and perpendicular to the former. The ends of the incomplete rings are connected, posteriorly, by a layer of smooth muscular fibres, which are attached to the fibrous tissue of the perichondrium. The attachment is to the inner aspect of the ends of the cartilages, so as to throw the muscular layer forward of the most posterior projection of the rings. These muscular fibres also exist in the spaces between the rings, where they are attached, on either side, to the fibrous tissue of the tube. Outside of the transverse fibres are a few filaments which have a longitudinal direction. They are at- tached to the fibrous membrane. The fibrous membrane which encloses the cartilages and completes the framework of the tube is composed of connective tissue containing a considerable portion of elastic tissue, par- ticularly in its external portion. The outer layer of the fibrous membrane encloses both the cartilages and the muscle fibres. The inner layer is thin and lies between the rings and the glandular layer. The mucous membrane is covered by several layers of epi- thelial cells, the deeper bei ng more or less spherical or ovoid, whilst the superficial ones are columnar and ciliated. The columnar cells, losing their cilia, are continued into the ducts of the mucous glands. These glands are very numerous, and often of considerable size. They are racemose, the acini being 258 MANUAL OF HISTOLOGY. lined with cubical epithelium. Owing to the distention of some of the gland-cells by mucus or by the action of reagents, they assume a rounded form, and the nuclei are pressed against the attached ends of the cells. Such corpuscles are known as "goblet " cells. Some of the larger glands project posteriorly outside of the fibrous membrane, but the great majority of them are situated internally to that structure, and then form a dis- tinct layer, the "glandular layer." They are most abundant in the spaces between the cartilages. Their ducts pierce the .riTTTTTS^tv 13 Tt r Pig. 100. — Transverse section of bronchial twig, 6 mm. in diameter : a. outer fibrous layer ; ft, muscu- lar layer ; c, inner fibrous layer (mucosa) ; rf. epithelium. Magnified 3U diameters. F. E. Schulze. mucous membrane obliquely, so that the entire length of a duct is not usually found in a section of the tracheal wall. At short intervals, between the columnar cells of the surface, other cells are found, of a spindle shape, or somewhat stellate. These cells send processes upward to the surface and down- ward into the basilar membrane, where they become contin- uous with other branched cells. The prolongation which passes upward to the surface is usually single, though it may occasion- ally send off a delicate filamentary branch, which is lost in the cement substance between adjacent cells. The process, sometimes double, which passes downward connects with a tissue in the mucosa which resembles the lymph canalicular system of other parts. It is made up of a network of branched cells, or connective-tissue corpuscles, which line a series of spaces, that in turn communicate with the lymphatic capillaries of the mucous membrane. Sikorsky injected a watery solution of carminate of ammonia into the THE RESPIRATORY TRACT. 250 bronchial tubes of cats and dogs while the animals were liv- ing, and found, post-mortem, that the carmine had penetrated through the interepithelial cells above described into the lym- phatic vessels below. The interepithelial cells have a small nucleus which stains more deeply with hsematoxylon than do the nuclei of the ordi- nary epithelial cells. In vertical section they are more opaque than the epithelia, and, when seen on the surface of the mem- brane, appear as dark spots among the ciliated cells. The lymphatic capillaries join to form larger trunks which run along the sides of the bronchi communicating freely with each other and with those of the neighboring blood-vessels. They are called by Klein the peribronchial lymphatics. Beneath the mucosa, and between it and the mucous glands, are numerous bundles of yellow elastic tissue having a longi- tudinal direction. Some of the bands are quite thick, particu- larly in the posterior wall, and raise the mucous membrane in longitudinal folds. The mucous membrane of the trachea and bronchi has a rich network of capillaries. The racemose glands are also sup- plied with a vascular network which ramifies in the fibrous tis- sue by which they are surrounded. The natural injection of these vessels, which occurs in cases of bronchitis in the human subject, is often sufficient for their examination. The mode of termination of the nerves has not been ascer- tained. The trachea should be hardened in chromic acid or Miiller's fluid, followed by alcohol. The sections may be stained in hsematoxylon. In order to preserve the ciliated epithelium, it is well, as Professor Rutherford suggests, to cut the sections with the freezing microtome. The lymphatics can be injected by puncture. The smaller bronchi and lungs. — Beyond the primary bron- chi (or first division of the trachea) the muscular fibres encircle the tubes inside of the cartilaginous and fibrous layer ; indeed, the primar}'- divisions show the first sign of this new arrange- ment. The cartilages change from incomplete rings to irregu- larly shaped plates, which are found on all sides of the tubes, but their microscopic structure remains unaltered. The longi- tudinal elastic fibres are contained between the muscular and mucous coats. The tubes divide and subdivide generally in a 260 MANUAL OF HISTOLOGY. dichotomous manner, diminishing gradually in calibre, the combined area of the branches, however, always exceeding that of the trunk from which they spring. No change o'ccurs in their structure, except a gradual thinning of their walls, until they reach a diameter of about 1 mm., when the cartilages disappear and the attenuation is more marked. The circular muscular fibres continue to exist, as also the longitudinal elas- tic fibres, but the mucous glands disappear. After a still further division the tubes are diminished to a diameter of .20 to .30 mm., the muscular fibres become more sparse, and the epithelium is reduced to a single layer of low, somewhat cubi- cal cells, which are still ciliated. These are the lobular bronchi, each one going to a single pulmonary lobule. The lobular bronchi each give off ten to fifteen smaller tubes, known as the terminal bronchi or bronchioles. They are straight and cylin- drical, their walls are very thin and delicate, and their epithelial cells gradually lose their cilia and become flattened plates. Each bronchiole leads to a smaller division of the lob- ule, called an acinus or lobulette.1 The bronchioles divide into short canals, the alveolar passages, usually three Fig. 110. — A system of alveolar pas- o -i • mi • „n „ xUi sages with infumiibuii from an ape's for each acinus, lheir walls are thin lung: a, terminal bronchial twig ; b, &, tit t 11 ■ n _c intundibuia; c, c, alveolar passages, and bulge outward on all sides, iorm- Magnified 10 times. F. E. Schulze. . nl i • , . i • .■• ing, externally, little projections or elevations ; internally, shallow depressions or cavities which open into the calibre of the tube. They also give off secondary branches, called infundibula, which have groups of such little cavities attached to, and opening into them. The little cavities are the alveoli or air-cells of the lung. From this description it will be seen that each lobule has ten to fifteen acini or lobu- lettes, and that the lobulette is made up of alveoli or air-cells, which open into common spaces or infundibula, which in turn communicate with the alveolar passages. The alveoli, which are connected with the infundibula, are called terminal alve- oli ; those which open on the sides of the alveolar passage are called the parietal alveoli. The latter are called, by Dr. Wa- ters, the bronchial alveoli. The alveolar passages, infundibula, 1 Dr. Waters : The Anatomy of the Human Lung, London, 1860. THE RESPIRATORY TRACT. 261 and alveoli have a flat pavement epithelium resting on an ap- parently structureless basement-membrane. Outside of this are numerous elastic and muscular fibres, curving around the cavi- ties, and holding in their meshes the capillary blood-vessels. The muscular fibres are very numerous in the walls of the al- veolar passages and infundibula. The alveoli have a diameter of .1 to .4 mm., but their size varies greatly according to the degree of inflation of the lungs. Fig. 111.— Section through an infundibulum : a, entrance from the alveolar passage into the infundi- bulum ; &, nuclei of smooth muscular cells. Magnified 30 diameters. P. E. Schulze. The epithelium in the alveoli of the fetal lung is columnar in shape, so that a section of such a lung resembles a section of a glandular organ. But when the alveoli are distended at birth, the cells change their form. In transverse sections, either real or optical, of the alveolar walls, the epithelial plates pro- ject more or less into the cavity, according to the degree of dis- tention of the lung. This change of shape undoubtedly occurs during life with the alternating expansion and contraction of the thorax, and should be taken into account in considering the pathological changes of inflammation, collapse, etc. By injection of a weak solution of silver nitrate {\ per cent.) into the bronchi of a fresh lung, and its subsequent immersion in 262 MANUAL OF HISTOLOGY. alcohol, the lines between the epithelial plates can be demon- strated. The nuclei can be stained with carmine. Some of the cells are converted into hyaline plates. The alveolar epithelium of the human lung is not so readily demon- strated as that of animals, principally because too long a time usually elapses between death and the post-mortem dissection. In some traumatic cases an autopsy can be made early, and as Fig. 112. — Interior of an alveolus, between the alveolar epithelial cells. Lnng injected with a solution of nitrate of silver to show the lines F. E. Schulze. favorable opportunity had of examining these structures. They can be shown very well in fresh sections cut with Valentin's knife. The spaces between the alveoli and acini contain the elastic fibres mentioned above, together with a few oval connective- tissue nuclei and muscular elements. The lobules are held together by thin septa of connective tissue. The connective tissue is also found in the angles of division of the lobular bronchi and bronchioles. The muscle-cells may be identified by their elongated, fusiform nuclei. A further proof of their existence is found in certain cases of cirrhosis of the lung, in which many distinct muscular fibres are found in the new connective tissue.1 The branches of the pulmonary artery follow the course Buhl : Lungenentz. Tuberculosis, u. Schwindsucht, Miinchen. 1873, S. 358. THE RESPIRATORY TRACT. 263 of the bronchi as far as the lobules. The lobular brandies are terminal arteries — i.e., they do not anastomose with each other. They break up into very small branches, which encircle the alveoli and supply the . capillary plexuses of their walls. These capillaries are very small, and the network so line that, when injected, the open spaces are not as wide as the vessels themselves. This, however, will vary with the degree of dis- tention of the lung. Between two adjacent alveoli only one Pio. 113.— Section of human lung injected through the pulmonary artery : a, a, free alveolar margins ; 6, small arterial branch ; c. c, alveolar walla seen in transverse section. F. E. Schulze. capillary plexus is found, the branches of which are seen to pursue an undulating course, projecting, first, into the cavity on one side, then into that on the other. These unite again into veins which run irregularly through the lobules to unite upon the bronchi and follow their course to the root of the lung. The peculiarities of the pulmonary veins are, 1st, that their united calibre does not exceed (if it equals) that of the arteries ; 2d, that they have no valves. The bronchial vessels supply the coats of the bronchial tubes and the surrounding connective tissue and the pulmonary pleura. But the line of demarcation between the bronchial and pul- monary circulations is indistinct on the venous side, as injec- tions thrown into the bronchial arteries fill the pulmonary 2G4 MANUAL OF HISTOLOGY. veins and capillary plexuses and overflow into the pulmonary arteries.1 It appears from this that part of the blood from the bron- chial arteries does, or may, return through the pulmonary veins. In their course through the lung, the pulmonary arteries lie upon the upper and anterior aspect of the bronchial tubes, while the veins are found on their inferior surface. The bron- chial arteries follow the tubes and divide with them. The lymphatics of the alveolar septa are a series of lacunar spaces lined by branched connective- tissue corpuscles, whose nuclei have already been described as being visible in ordinary sections of the lung. In sections of a lung treated with silver nitrate the forms of the cells are distinguishable. According to Klein the pro- cesses of these cells pass upward between the epithelial plates of the alveoli so as to bring the cells into direct communica- tion with the cavity, just as we have .seen the interepithelial cells of the bronchial mucous membrane send certain processes upward between the columnar epithelia and others downward to the cells of the lymph lacunae. On examining the epithelium of an alveolus, small, round, dark spaces are seen between the cells ; these are said by Klein to be the projecting processes of the branched cells of the lymph lacunar system. The ends of these processes, both here and on the bronchial mucous mem- brane, are called pseudostomata, in contradistinction to the true stomata of the serous membranes. The small spaces, or lacunae, open into lymphatic radicles, which have a regular endothelial lining. These pass inward toward the root of the lung, upon the bronchi and the walls of the vessels. On the vascular walls they communicate freely with each other, and at times completely invest the vessel with a lymphatic sheath like that of the cerebral vessels. In this situation they are called perivascular lymphatics. The peri- vascular and peribronchial lymphatics communicate freely. At the surface of the lung there is a plexus immediately beneath the pleura (subpleural lymphatics) from which trunks of some size run to the root of the lung. They communicate with the perivascular system and witli the pleural cavity. The final termination of all these channels is in the bronchial glands. 1 Dr. Waters. THE RESPIRATORY TRACT. 265 Tlie nerves of the lungs are derived from the sympathetic and pneumogastric. Their mode of termination is not known. For the examination of the general structure of the lung it may be inflated and dried pretty rapidly in the sun or by a fire. For more careful examination it should be hardened in chromic acid, Muller' s fluid, or alcohol. The hardening fluid should be injected into the air- passages. In order to distend the vesicles it is well, before placing the lung in the hardening fluid, to inject the bronchi with simple gelatine. The vessels may also be injected with a colored mass. The lungs of the lower animals are used for these demonstrations, owing to the difficulty of obtaining normal human lungs in a perfectly fresh condition. The investigation of the lymphatics is attended with great difficulty. They may be demonstrated by the puncture method. Klein found that on injecting the blood-vessels, under high pressure, with Ber- lin blue or silver nitrate, some of the capillaries ruptured, and the fluid passed into the perivascular lymphatics. The pleura. — The pleura, like the other serous membranes, consists of a connective-tissue ground-substance covered by a single layer of polygonal endothelial cells. In the costal pleura the subserous connective tissue is more abundant, and its at- tachment to the thoracic wall is not so firm as is that of the pulmonary pleura to the lung. The structure of the pleura is most conveniently studied in the smaller mammals. It can also be demonstrated in young children. To demonstrate the endothelium of the surface, the thorax of a recently killed animal should be opened, care being taken not to rub or otherwise injure the pleura. The surfaces are to be washed by pouring distilled water over them, in order to remove the serum, and then a weak solution of silver nitrate (i — h Per cent.) allowed to flow over them. After a few mo- ments the surfaces are bathed with pure water. The diaphragm- atic or mediastinal portion is then excised with scissors, immersed in distilled water or glycerine, and exposed to the daylight until it takes a light reddish-brown color. It may now be floated on to a slide, carefully smoothed by traction at the edges, and mounted in glycerine. The portion excised should be large, so that it can be manipulated without touch- ing the part which is to be examined. For this reason it is well to take with it some of the surrounding structures, e.g., the 2GG MANUAL OF HISTOLOGY. entire diaphragm, with the mediastinal portion, together with the heart and pericardium. It will be seen that the endothelium is composed of a great number of polygonal plates whose edges are glued together by a substance which has been stained brown or black by the sil- ver. Nuclei are seen in many of them, or they can be shown by staining with carmine or hajmatoxylon. Small openings are to be seen in certain localities surrounded by cells of a more cubical form, with large, distinct nuclei. In other places small dark spots are seen between the cells. The openings are known as stomata, and communicate with lymphatic vessels running beneath the endothelium. The dark spots are pseudo- stomata, and are similar in their nature to the pseudo-stomata of the alveoli and bronchial mucous membrane ; i.e., they are the ends of processes of the branched cells of the ground-sub- stance reaching up between the endothelial plates. In order to demonstrate the ground- sub stance .or connective-tissue layer of the pleura, the fresh surface is carefully pencilled with a soft brush dipped in the fluid of the abdominal cavity, or in artificial serum. After washing with distilled water, the solu- tion of silver nitrate is poured over it, and it is treated as be- fore. On examination, the branched connective-tissue cells are seen communicating with each other by their processes. Blood-vessels and lymphatics are also seen, and in a favor- able place the endothelium of the latter is seen to be continuous with the branched cells. These cells line the cavities of the connective tissue, and belong to the lymph lacunar system. The lymphatic vessels accompany the blood-vessels, some- times ensheathing them. They are identified by the shape of their endothelial cells, which are wider and more polygonal in form than those of the veins. It will be seen from this descrip- tion that the serous membrane is a lymphatic structure. Its cavity communicates by means of the stomata with the lym- phatic vessels below, while, by means of the pseudo-stomata, it communicates with the lacunar spaces which are lined by the branched cells. To demonstrate the pulmonary pleura, the lungs should be excised, moderately distended with air (which is retained in them by ligature of the trachea), treated with silver nitrate, as already described, and then immersed in alcohol. After a few days sections are made parallel to the surface. THE RESPIRATORY TRACT. 267 If the lung be pencilled before it is treated with the silver solution the deeper structures can be examined. The sections should be mounted in glycerine with the external surface upward. The appearances here are similar to those already described. The capillary lymphatic-vessels communicate with the superficial pulmonary branches forming the subpleural lymphatics. The endothelial cells of the pulmonary pleura vary in shape according to the degree of distention of the lung. In the lung which has been inflated before hardening, the cells appear as flat plates, but in the atelectatic lung of a foetus, or the collapsed lung of an animal that has breathed, they are cubical or even columnar in shape. This difference is most marked in the guinea-pig, owing to the presence of a layer of muscular-fibres beneath the pleura of that animal. The tops of the cells which have this pyramidal shape are not flat as in true columnar epithelium, but rounded. This change of shape simply indicates that the cells accommodate themselves to changes of space. These changes, in a lesser degree, must be occurring constantly during life, with the movements of respi- ration. On the costal pleura, the stomata are only found in the intercostal spaces. Attached to the lower border of the lung are minute ap- pendages, the ^pleural appendages" forming a sort of fringe connected with the pleura. Some are visible to the naked eye, some microscopic. The larger are made up of connective tissue and blood-vessels, and, exceptionally, nervous fibres in the larger ones. They are covered by round cells, sometimes resembling epithelium. The smallest ones are structureless, and in general have no epithelial covering.1 BIBLIOGRAPHY. Coyne, P. Recherches sur l'anatomie normale de la muqueuse du Larynx. Ar- chives de Physiologie, p. 92. Paris, 1874. Stirling. Nervous Apparatus of the Lung. Brit. Med. Journal. Vol. II., p. 401. 1870. Cadiat. Des rapports entre le develop, du poumon et la structure. Jour, de l'anat. et de la Phys., No. 0, p. 591. 1877. And, Structure et devel. du poumon. Gaz. Med. de Paris, No. 17, p. 214. 1877. Luschka : Anatomie des Menschen, Bd. I., S. 293. 208 MANUAL OF HISTOLOGY. Gkanciier. Note sur leslyinphat. du poumon. Gaz. Med. de Paris, No. 9, p. 103. 1877. Aeby. Die Gestalt d. Bronchialbaumes u. die Homol. d. Lungenlappen beim Menschen. Med. Centralbl., No. 16, p. 290. 1878. Seiler, C. Researches on the Anatomy of the Vocal Cords. St. Louis Med. and Surg. Journal, p. 333. April 5, 1880. And, Minute Anatomy of the Larynx, Normal and Pathological. Archives of Laryngology. Vol. I., Nos. 1 and 2, and to be continued. 1880. CHAPTER XVIII. THE SKIN. Br A. R ROBINSON, M.D., Lecturer on Normal Histology in the Bellevue Hospital Medical College, New York. General plan of arrangement. — The integumentum commu- ne, or skin, forms the external covering of the body, which it mechanically protects, and at the same time is endowed with certain physiological functions. The surface of the skin in some parts of the body is smooth and soft ; in others it is more or less uneven and rough. This latter condition depends upon the presence of pores, hairs, furrows, and ridges. The pores correspond to the surface openings of the hair-follicles, sebaceous and sweat-glands. The hairs vary in amount of development according to their situation. In the so-called hairy regions they are largest ; other parts are provided only with a soft down (lanugo hairs). There are no hairs on the palms of the hands and soles of the feet, the dorsal surfaces of the terminal phalanges of the fingers and toes, the glans penis, and inner surface of the prepuce. The fur- rows are either long and deep, or short and superficial. The former are chiefly found in the flexures of the joints, and cor- respond to the folds in the derma produced by movements of the joint. The latter run between the papillary elevations, and, by crossing each other, divide the surface into a number of polygonal or lozenge-shaped fields. This division is well- marked on the backs of the hands. These superficial furrows are more developed on the extensor than on the flexor surfaces of the extremities, and in the lumbar region more than on the anterior surface of the abdomen. Their direction is dependent on the degree of the tension of the skin. The ridges correspond to the papillae, and are most developed on the palmar surfaces of the last digital phalanges. The color of the skin varies in 270 MANUAL OF HISTOLOGY. individuals according to race, and in the same individual ac- cording to the part of the body. The dark skin of some races depends upon the presence of pigment in the cells of the rete Malpighii. In the white race, dark pigment is usually pres- ent in greatest quantity in the areola? of the nipj)les and in the scrotum and labise. General structure. — The skin is composed of the follow^ ing parts : epidermis, corium, subcutaneous connective tissue, a ja Fig. 114.— Diagrammatic perpendicular section through the normal Rkin : a, epidermis ; b, rete Mal- pighii; c, papillary layer; d, corium; e, panniculus adiposus ; /, spirally bent end of excretory sweat- duct : g, straight portion of excretory duct of sweat-gland ; A, coil of sweat-duct ; i, hair-shaft ; k, root of hair; I, sebaceous gland. After Neumann. blood-vessels, nerves, lymphatics, sweat and sebaceous glands, hairs, and nails. A perpendicular section through the skin shows (Fig. 114) three well-marked layers ; the most superficial is called the epidermis proper, a, b ; the middle layer is the corium or cutis, d;&n& the deepest layer the subcutaneous connective tissue, e. The limit of the epidermis at its place of union with the corium is sharply defined, but the corium and subcutaneous connec- THE SKIN". 271 five tissue gradually merge into each other, the boundary be- tween them being only an artificial one. Commencing with the epidermis, we will describe in detail the minute structure of the different tissues and organs of the skin, omitting only the lymphatics. Description of the different layers. — The epidermis is generally subdivided into several layers, with specially distinc- tive names for each layer ; but though such a division has some practical value, histologically it is incorrect, as the cells of the lowest layer are transformed, at some period of their existence, in their movement toward the free surface, into the cells of the other layers. Examination with high powers also shows that the chan- ges in the molecular constitution or chemical condition of the cells of the 1nr^"^_V?ecel?s: -^alT lar layer ; c, stratum lucidum ; d, epidermis — changes which produce ^SS^^w^^171^ differences in their appearance — are quite gradual. Consequently, sharply defined layers are not found. For practical reasons, however, it is well to adopt the usual classification. In Fig. 115 these layers are shown. Another division is into Malpighian and corneous layers only, the former comprising the rete and the granular layer, and the latter the stratum lucidum and corneous layer. The Malpighian layer, as compared with the corneous layer, pre- sents a more or less dark, granular appearance, while the latter is homogeneous, and its cells have a lamellar arrangement. The rete Malpighii consists of nucleated corpuscles, rich in protoplasm, granular in appearance, and disposed more or less in parallel strata, the elements of the different layers differing somewhat from each other as regards their size and shape. The lowest layer consists of columnar-shaped cells arranged pali- sade-like, with their long axes more or less perpendicular to the surface of the corium. Where the papilla) are well developed, this perpendicular arrangement is not so marked. The base of some of these bodies terminates in a pointed extremity, which passes a short distance into the underlying corium. Each of them has an oval nucleus. The cell -body consists of a small quantity of slightly granular, shining protoplasm. The cor- puscles of this layer are not united to each other by bands, as 272 MANUAL OF HISTOLOGY. in the other layers. The next two or three strata consist of more or less potygonal-shaped bodies, each with a spherical nucleus. The cells of these layers are large, their contours sharply defined, and they contain more or less pigment. It is this substance deposited in the corpuscles that gives the charac- teristic color to the different races of mankind. Their cell-bod- ies are larger in proportion to the nucleus than in the first layer. In the succeeding layers the cells increase in size and are more granular in appearance, the cells and nuclei become flatter as they approach the granular layer, and, finally, lie with their long- axes parallel to the surface. The granular structure which in the lowest layer is most marked around the nucleus, gradu- ally extends toward the margin of the cells, as the surface is approached, so that finally a clear area is seen around the nucleus, whilst the remainder of the cell-body is markedly granular. At the same time the cell-body becomes firmer and the nucleus smaller. All the cells of the rete Malpighii, except those of the first row, are united to each other by filaments (Martin, Bizzozero, Heitzmann), the so-called pricldes of Max Schultze(Fig. 116). These uniting filaments or bands vary much as regards their size and length in different parts of the bod}^. They are most distinct wherever the Mal- pighian layer is well developed, but are thicker and longer in the lower rows of fig. lie.-" Prickie "ceiia cells than in the upper. At the stratum of the rote. x 1600. lucidum they cease to exist. Between neighboring corpuscles the length of these bands is in direct proportion to the distance between the borders of the cell- bodies. Hence, where three or four cells meet at one place, as in the centre of Fig. 116, the minute filaments are much longer than those uniting the bodies of closely adjoining cells. Examining these prickle-cells with the microscope, alternate dark and light bands are seen between the cell-borders. With a low power, these light bands appear to consist of spaces be- tween the connecting filaments, the dark lines being the con- necting filaments, but with a high power the latter can be recognized as spaces between the former. The light bands can be traced from the surface of one cell to the surface of another, whilst the dark lines are the spaces between these THE SKIN. 2 i 3 bands. These connecting cords sometimes divide and anas- tomose with each other, forming a sort of network between the cells. In this case, the dark spaces do not always extend from one cell-body to another, since they may corresrjond to the space between anastomosing filaments. These bands are therefore not the prickles of adjoining cells, which interlock with each other, but are true connecting filaments between cells of a common origin, and which have not yet become sepa- rated from each other. The connecting bands or fibres gradu- ally diminish in length and thickness from below upward, and finally cease to exist when the granular layer is reached. The spaces between the bands are filled with an inter- cellular albuminous substance, and they may be regarded as minute channels for the conveyance of nutriment to the cells of the epidermis. The above view of the "prickles" corre- sponds very closely with that held by Dr. Martin, and differs from that of later observers, who maintain that the dark lines are connecting bands, and the light lines the spaces between them. Owing to the close union of the Malpighian elements it is very difficult to isolate them. Perhaps the best way to accom- plish this result is by long immersion in iodized serum. Fig. 117 represents a cell isolated in this manner. Here ^Mh, the bands have been torn apart and the cell-surface is SMfe studded with thorn-like projections. Hardening in -^B?- chromic acid, with subsequent boiling in a moderately fig. lrr.-iso- , . - , J lated "prickle" strong solution of potash, causes a separation of the «di. mucous layer from the corium and a falling apart of the rete cells (Biesiadecki). The structure of the corpuscles, however, can be best studied when their normal relations with each other are preserved. Variations in the number of cellular lay- ers are of normal occurrence in the rete, although this portion of the skin shows the least variation as regards its thickness. The arrangement of the elements in these different strata is the same in all parts of the body, and appears to be independent of the thickness of this layer. As regards the direction of the long axes of the cells there is a gradual passing from the perpendicularly seated cells of the first layer to the horizontally lying cells of the uppermost io\v. The lower surface of the rete adapts itself to the upper surface of the corium, and between the papillae projects down- 274 MANUAL OF HISTOLOGY. Fig. IIS. — Horizontal section of skin through a papilla. The migrating cells are observed as dark bands between the epithelial cells and amongst the connective tissue of the papilla. Pagensteoher. ward and forms the interpapillary rete Malpigliii. Wandering lymphoid cells are frequently present in the rete. They are especially numerous in some pathological conditions. They (Fig. 118) are elongated spindle-shaped bodies lying between the rete cells, and sending out minute processes. They color deeply in carmine, have a small nucleus, and are most numerous in the lower part of the rete mucosum. The granular layer (Fig. 115, b) consists of one or two strata of flattened, granular- looking bodies, which, in perpendicular section appear spindle - shajDed, with their long diameter parallel to the free surface of the epidermis. In this stratum the cells are no longer connected with each other by bands, as in the pre- ceding layer. The nuclei of these corpuscles are very distinct, and flattened in the same direction as the cell-body. The latter has a very coarsely gran- ular appearance, which is most marked near the nucleus, and gradually diminishes in degree as the periphery of the cell is approached. The structure of these bodies is best shown with haematoxylon. The stratum lucidum, also called the stratum of OeM, is composed of at least three layers (Fig. 115, c). It presents a clear, homogeneous, or striated appearance. Within the flat- tened cells composing it, a staff-shaped nucleus is found. The cells of this layer are formed from those of the granular stra- tum. In their movement to the free surface the latter become less granular and the inter-granular substance grows more trans- parent and shining (Unna). This change from a granular to a homogeneous translucent appearance commences around the nucleus, whence it gradually extends to the periphery of the cell. The nucleus, also, usually becomes invisible. In vertical section the corneous layer appears (Fig. 115, d) to be composed of wavy fibres and horny, transparent cells of various sizes and shapes. This variation in bulk and form THE SKIN. 275 depends in great measure upon the thickness of the layer. The nearer we approach to the stratum lucidum, the more dis- tinct are the cells. If the layer is very thin the cells appear as elongated, fiat, or curved bodies, giving to this part of the epidermis a fibrous appearance. When the corneous stratum is thick these cells present various forms and sizes. The cor- puscles of the lower layers color slightly in carmine, are poly- gonal or spindle-shaped, and frequently contain a shrivelled nucleus. As the surface is approached they grow flatter and drier, are more bent upon themselves, and color less and less in carmine. The nucleus also becomes invisible. The most su- perficial layers are composed of elongated, flat, dried-up cells, the so-called epidermic scales. These bodies are best studied after they have been subjected to the action of liquor potassse, which causes them to swell up. The corpuscles of the stratum corneum are arranged in lay- ers as in the other parts of the epidermis, but the elements forming a layer are more closely united with each other than with those of the adjoining layers. Hence this stratum can be separated into lamellae, as occurs in some pathological states of the skin. It accompanies, for example, the formation of some vesicles, where the exuded liquid, prevented from pass- ing toward the surface, accumulates between the layers, and thus separates them from each other. The corneous layer participates in the elevations and de- pressions of the underlying layers. This causes the undulat- ing or wavy appearance of the lamellae, as observed in sections where the papillse are well developed. It varies greatly in thickness in different parts of the body, and reaches its great- est development on the palms of the hands and soles of the feet. Its thickness does not depend upon the rete Malpighii, as it sometimes forms a thin layer where the rete is thick, and vice versa. The subcutaneous connective-tissue layer of the skin con- sists principally of connective-tissue bundles, which, coming from the underlying fascia) of the muscles or from the peri- osteum, pass in an oblique direction to the corium. These fasciculi are generally cylindrical in form, and variable in size ; by their anastomoses or divisions they form larger or smaller networks, with correspondingly large or small interfascicular spaces. Generally large bundles anastomose with each other 276 MANUAL OF HISTOLOGY. in this layer, and hence a loose connective tissue is formed. Within this layer adipose tissue is found in greater or less quantity. The fat-cells are collected into masses or lobules, the number of cells which form a lobule varying greatly in num- ber. Each of these latter may be regarded as a fat-gland, as it is provided with an afferent artery, a capillary plexus between the corpuscles, and one or more efferent veins. Several lobules are sometimes united together in the form of an acinous-like gland, and are likewise seen to be surrounded by a general sheath of connective tissue. The individual fat-cells are round, flattened, polyhedral, or oval-shaped, the form depending upon the degree and direction of the pressure exerted upon them. Owing to the amount of fat-tissue so often found in this layer, it has been called the panniculus adiposus. Such fat-lobules are absent in the penis, scrotum, labise minorse, eyelids, and pinna. The corresponding spaces in these regions are tra- versed by fine connective- tissue bands or single fibrils. From this adipose tissue fat-columns pass upward in a somewhat oblique direction to the bases of the hair-follicles, especially to those of the fine hairs. Their long axes form a slight angle with the axes of the follicles, and they are nearly parallel to the erector pili muscles (Warren). In cases of starvation, in the so-called wasting diseases, and in all acute diseases at- tended with excessive loss of tissue, the fat-cells disappear to a greater or less extent. The skin, in such instances, becomes correspondingly flaccid and wrinkled. Adipose tissue gives to the skin its tension and fulness, and to the body its appear- ance of roundness or plumpness. Obesity consists in an exces- sive production of fat-cells. The interfascicular spaces differ in size in proportion to the amount of lymph present, and to the closeness of the anasto- moses between the bundles. In oedema the lymph-spaces are increased in size proportionately to the increased amount of liquid present. The interfascicular spaces all communicate with each other, as is shown by the rapidity with which a hypodermically injected liquid can be dispersed by manipu- lation. The connective-tissue cells of this layer and of the corium consist of branched cells (Ravogli) which surround the white fibrous bundles and send in processes between the fibres. Ac- cording to some observers, these cells are epithelioid in charac- the skin. 277 ter. The elastic-tissue fibres are developed' from the processes of the branched cells. Besides connective-tissue fibres and cells, lymphoid corpus- cles are present in this layer. They exist in greatest number near the blood-vessels and glands. In this situation they are of a roundish form, but in the parts distant from the blood- vessels they are more or less spindle-shaped, and are to bo regarded as wandering cells. The convoluted part of the sweat-glands and the lower part of the hair-follicles of deep-seated hairs lie in this layer. Blood-vessels, lymphatics, and nerves are present. The blood-vessels are large, and after giving off small branches to the hair- follicles, sweat-glands, and fat-lobules, pass upward to the corium. Pacinian corpuscles are found in connection with some of the nerves. For a description of these bodies the reader is re- ferred to the article on the nerves. The principal part of the corium consists of white fibrous and elastic tissue, the latter increasing in amount with advancing age. Here the white fibrous tissue forms a much denser, firmer structure than in the previous layer. It consists of deep oblique, and superficial horizontal bundles. The latter com- prise fine bundles of connective tissue which run parallel with the surface of the skin, and by their division and anastomoses form a very fine network with small interfascicular spaces. From this layer bundles pass upward into the papillae, and these form a second denser network. The deeper layer is formed by a continuation upward of the subcutaneous con- nective-tissue bundles. These pass upward in an oblique direc- tion, and as they reach the corium divide into fasciculi. Here they continue to divide and anastomose with each other and with fibres from the horizontally running bundles. The anas- tomoses are very close ; hence, the corium is formed of a dense network of connective tissue, except in those parts which are traversed by blood-vessels, lymphatic vessels, nerves, hair-folli- cles, and sebaceous and sweat glands. Immediately around the hair-follicles, sweat-ducts, and sebaceous glands the con- nective tissue is dense, and the fibres run parallel with the di- rection of the organs. Owing to the greater size of the connec- tive-tissue bundles in the lower part of the corium, and the consequent looseness of the network formed by their anasto- 278 MANUAL OF HISTOLOGY. moses, this part of the corium lias been called the pars reticu- laris corii, in contradistinction from the liner network formed in the upper part, to which the name pars papillaris lias been applied. But neither between these two parts nor between the subcutaneous layer and the corium is there any sharp dividing line, the transition being a gradual one. As already mentioned, the size of the interfascicular spaces depends upon the closeness of the anastomosis between the bundles and fibres. The direction of the bundles corresponds with that taken by the blood-vessels. The connective-tissue corpuscles of the corium resemble those found in the subcutaneous layer, and also bear the same relation to its connective-tissue bundles. From the upper portion of the corium fibres pass upward to make the papillse. The form of the papillae is very variable in different parts of the body. Where they are most developed, as on the inner surface of the terminal phalanges of the fingers and toes, they are conical in shape. In some other regions they form only slight elevations on the corium, giving a wave-like appearance to its upper surface. They consist of a close network of white, fibrous connective tissue combined, especially in the central part of the papilla, with a large number of elastic fibres. Those papillae which contain tactile corpuscles are called nerve-pa - pillffi. The corium is separated from the stratum mucosum by a thin, transparent basement-membrane, containing oval nuclei. Its under surface is not sharply defined, and from it prolonga- tions pass upward between the cylindrical cells of the rete, giving this surface a notched appearance similar to that ob- served on the inner margin of the internal sheath of the hair- follicle. Elastic fibres are present in large numbers in the corium, especially in its upper part, where they form a network around and between the white fibrous tissue-bundles. In the lower part of the corium they form a large network, which becomes finer as the surface is approached. The number of elastic fibres increases with advancing years. With this increase of elastic fibres there is a corresponding decrease of the white fibrous connective-tissue cells (Ravogli). Numerous wander- ing cells are met with in the corium, especially in the vicinity of the blood-vessels and glands. Hair-follicles, sebaceous THE SKIN. 279 glands, sweat-ducts, nerves, lymphatic vessels, and non-striated muscles are also present in this layer. For a fuller descrip- tion of the intimate structure of the connective-tissue bundles and cells, see the subject of connective tissues. Blood-vessels. — Only the corium and subcutaneous tissue are provided with blood-vessels. The arterial blood-vessels supplying the skin form two jDarallel horizontal layers, a su- perficial and a deep one. The deep layer lies in the subcuta- neous tissue, and consists of large vessels running parallel to the general surface. From this horizontally lying deep layer, branches are distributed to the sweat-glands and fat-follicles of this region. The principal branches, however, pass perpendicu- larly or obliquely upward through the corium to its upper part, and form immediately beneath the papillae (after free branch- ing and anastomosis) a superficial horizontal layer, the stratum subpapillare. From the vessels ascending through the corium branches are given off to the hair-follicles, sebaceous glands, and gen- eral tissue of the corium. From the stratum subpapillare small branches pass upward into fig. ii9.-Biooa-ves- .-, •■,-, i ,-, <• .-i t sels of the papillae : a, the papillae, where they become capillary ves- stratum subpapiuare ; &, sels, which proceed to the summit of the pap papilla. (See Fig. 119.) Before reaching this point, however, they frequently divide into two or more branches. Frequently, those papillse in which tactile corpuscles are seated have no blood-vessels. The veins are arranged on the same plan as the arteries : they form a superficial and a deep layer, and have their origin in the papillae. From the superficial layer larger vessels pass downward, receiving blood from the veins of the hair-follicles, sebaceous glands, and the general tissue of the corium, thus forming a deep subcutaneous layer or venous network. Nerves. — Medullated and non-medullated nerve-fibres are present in the skin. They are found in combination in the nerve- trunks of the subcutaneous tissue, the medullated fibres being most numerous in those regions of the skin where the Pacinian and tactile corpuscles are most abundant. In the subcuta- neous connective-tissue region, and in the lower part of the corium, some nerve-fibres leave the nerve-trunks and pass to t be glands, blood-vessels, and Pacinian corpuscles found in this legion. In the corium some of the fibres lose their medullary 280 KANUAE OF HISTOLOGY. sheath, and afterward continue their course as non-medullated iibres. The nerve-bundles pass upward in a more or less oblique direction from the subcutaneous connective tissue through the corium to the subpapillary network of blood-vessels, around which they form a plexus. From this subpapillary plexus medullated Iibres run upward and pass into the tactile cor- puscles. The non-medullated nerve-fibres form a reticulum around the blood-vessels of the pars reticularis corii and the capilla- ries of the papillae. They consist of thick or fine, smooth, varicose fibres with numerous nuclei. These fibres proceed from the network around the subpapillary blood-vessels up- ward toward the rete Malpighii, and either pass directly into the rete or run for a short distance parallel to its under sur- face, and then finally enter that layer. Within the epider- mis the fibres run between the cells and terminate in a manner not yet definitely known. Their mode of division and termina- tion within the epidermis is probably similar to that occurring in the cornea. Within the papillae the nerve-fibres frequently divide before entering the rete. The manner of distribution and termination of the non- medullated nerve-fibres can only be studied successfully in tis- sue stained with gold chloride. The tissue must be fresh, and a weak solution of the gold chloride used. When sufficiently stained the tissue is placed in distilled water slightly acidu- lated with acetic acid and exposed to the light. The Pacinian corpuscles are found in greatest abundance in the skin of the fingers, toes, palm of the hand, sole of the foot, but also occasionally in other regions of the skin. Their struc- ture is described in the article on the nervous system. Tactile corpuscles. — As already mentioned, some of the medullated nerve-fibres forming the plexus surrounding the subpapillary blood-vessels, pass upward and enter the so-called tactile corpuscles. These corpuscles are generally seated in the papillae, but occasionally they are found in the subpapillary region, i.e., the tipper part of the corium. The majority of the papillae containing such corpuscles have no blood-vessels. They are more or less oval in form, and can be easily recog- nized under the microscope by their dark contours and by the oblique lines produced by the transversely running connective- tissue fibres of the outer surface of the corpuscle. There may THE SEIN". 2S1 be two or more corpuscles within a single papilla (Thin), but each corpuscle invariably has a special nerve passing into it. Frequently, however, an appearance as if two corpuscles were present is produced by a single corpuscle having the shape of a figure 8. The medullated nerve-fibre, in passing to the corpuscle, pursues a more or less curved course, and usually enters it at or near its lower extremity. It may, however, en- ter at any part of the corpuscle, and sometimes winds around it for a considerable distance before entering. After entering the corpuscle the medullary sheath is lost, and its course now becomes difficult to pursue, except in the case of very small or young corpuscles. The intimate structure of these bodies and the arrangement of their formative elements are still mat- ters of discussion and uncertainty. The external portion of a corpuscle appears to be composed, in great part, of larger or smaller bundles of white, fibrous connective tissue anastomos- ing with each other and running transversely, or in a spiral direction, to the long diameter of the corpuscle. This part of the corpuscle differs, as regards irregularity of surface, with the size and the manner in which the fibrous fascicles divide and anastomose. The coarser the bundles and the anastomo- ses the more irregular will be its sur- face. Between the fibres are found oval or round bodies which color deep- ly in gold, and have been regarded as elastic elements (Thin). Other obser- vers consider them as connective tis- sue, or nerve-fibres. Some of these bodies undoubtedly represent the nerve-fibre in transverse or oblique section ; for the nerve pursues a more or less zigzag course within the corpuscle, and, consequently, a section of the body will probably show the nerve cut across in one or more places (Fig. 120, b). The arrangement of the elements forming the central part of the corpuscle is not yet thoroughly understood. These bodies have hitherto been usually regarded as end-organs — that is, it has been believed that the medullated nerve-fibre terminates within the corpuscle, hence the name, tactile corpuscle. Observers, however, have Pig. 120.— Tactile corpuscle, show- ing termination of nerve : a, corpuscle; 6, nerve, cut obliquely; c, apparent division of nerve-fibre ; e, similar ap- pearance as at c ; /, blood-vessel ; ff, rete cells ; h, nerve-fibre cut trans- versely. 282 MANUAL OF IIISTOLOGY. not agreed as to the mode of termination of the nerve, and some have maintained that it lias not been clearly proven that they really do terminate in the corpuscle. From specimens which I have recently obtained I am led to believe that the nerve does not terminate within the corpuscle, but passes on into the rete Malpighii. The best corpuscles for studying this point are small ones, as in these a section is more likely to include the entire upper extremity of the corpuscle at the same time that it is not too thick for examination with the microscope. Even in a small corpuscle, however, unless the nerve passes onward in a direct level with the corpuscle after leaving it, the nerve, in a vertical section, will be cut across, and it will, therefore, be impossible to follow it from the corpuscle into the rete. I believe the nerve frequently, perhaps generally, changes the direction of its course after leaving the corpuscle, and hence we often see a transverse section of the nerve at the upper extremity of the corpuscle. In Fig. 120 is seen the location of the termination of the nerve-fibre as observed in one of my specimens. In one place its course between the rete cells was very indistinct, though recognizable. The nerve passed obliquely upward be- tween the cells of the rete to the space between the second and third rows of cells, where it assumed a longitudinal di- rection. At the commencement of the curve the nerve ap- peared to have undergone division (c). After passing a short distance horizontally it ran almost perpendicularly downward, and near g was lost to view. At e it appeared to have again undergone division. According to the appearances here fig- ured the corpuscles are not the structures in which the nerve terminates, the latter passing from the corpuscle (as a non- medullated fibre) into the epidermis, where it divides and probably terminates in the same manner as the other nerves. This mode of termination cannot be regarded as strange, as we have already seen that some medullated nerve-fibres lose their medulla deeper in the corium, and afterward continue their course as non-medullated fibres. The tactile corpuscles are found in greatest number in the ends of the fingers. They are also present on other parts of the hand and on the foot, and sometimes in the lips and nipple. The sweat-glands. — The sweat-glands — glandular sudorif- THE SKIJST. 2S3 erce — are found in the skin of all parts of the body except that of the glans penis and margin of the lips. They are most nu- merous in the palms of the hands and the soles of the feet, -where they number, according to Krause, 2,685 to 2,736 to the square inch. A sweat-gland is composed of two parts, viz.: the gland proper, or secreting part, and an excretory duct. The gland proper lies in the subcutaneous tissue, and consists of the lower part of the sweat- gland rolled and coiled upon itself into a more or less globular form, the tube ter- minating in a cul-de-sac, the blind extrem- ity generally lying in the centre of the coil. The diameter of the secreting tube is greater than that of the excretory duct. The former is composed of secreting cells, unstriped muscular fibres, and a basement- membrane. The cells (glandular or secret- ing epithelial cells) are polygonal in shape and form only a single layer. They are strongly granular in appearance and have a very distinct nucleus. Their basal end is sometimes notched where they are in- serted into the basement-membrane. In normal conditions these bodies are never found in the sweat-fluid, but in inflamma- tion of the surrounding connective tissue they frequently become separated from the basement-membrane. Oil-globules are frequently seen in the cell- body, and are to be regarded as a normal constituent of the corpuscles. The basement-membrane is a thin, transparent structure, lying beneath the epithelial cells and composed of flat endo- thelial elements, as shown by the action of silver nitrate on the fresh tissue. In certain glands, especially those of the axilla, a layer of unstriped muscular fibres is found external to the basement- membrane. These fibres are present in only a small number of sweat-glands ; by their contraction they assist in the expul- sion of the secreted sweat. They are the smallest unstriped muscular fibres met with in the human body. — c Fig. 121. — Lower part of a sweat-gland : a. excretory duct ; 6, coil of secreting- tube ; c, se- creting-tube cut transversely; d, blood-vessels cut across. 28-4 MANUAL OF HISTOLOGY. The sweat-glands are surrounded by a somewhat loose fibrous connective tissue, from which fibres pass inward and form a closer network between the coils of the gland. Some of the fibres run parallel, and others transversely or obliquely, to the long diameter of the convoluted tube. A large nnmber of lymphoid cells are always present in this interglandular connective tissue. The sweat-glands are richly supplied with blood-vessels. The excretory duct passes upward from the gland proper in a more or less vertical direction through the different layers of the skin to its free surface, where it opens with a funnel- shaped orifice. In passing through the corium it pursues a straight or slightly wavy course, and enters the lowest part of the inter-papillary rete. The structure of this part of the excretory duct differs from that of the gland proper, in the shape of the cells, the absence of muscle-fibres, and the presence of a cuticula. This cuticula lines the inner surface of the epithelial coating and limits the lumen of the duct. As the rete Malpighii is entered there are generally two or more layers of cells lining the duct, the number increasing as the rete is approached. The transition from secreting cells to lining cells is gradual, so that the presence of a cuticula decides the nature of the tube. The basement- membrane corresponds in structure with that of the gland proper. The fibres of surrounding connective tissue run parallel with the duct. As the duct approaches the rete Malpighii its epithelial cells increase in number and form two or more layers, which are really only a continuation downward of the cells of the rete. When the duct enters the rete it loses its basement- membrane and is formed only of the cells of the mucous layer, which have become more or less flattened and spindle-shaped. The direction of the duct through the rete is sometimes straight and sometimes spiral. In passing through the stratum corneum the duct pursues a spiral direction on account of the horizontally flattened cells of this layer (see Fig. 114,/), and the number of spirals pres- ent depends upon its thickness. The largest number is found in the palms of the hands and soles of the feet, where it may amount to twenty or more, whilst on some parts of the body there is not even a single complete spiral. The wall of the THE SKLN". 285 duct is formed of the cells of the corneous layer, and the duct opens on the free surface at the summit of the ridges. The formation of the sweat-glands commences in the fifth month of foetal life by the pushing of epithelial cells from the rete mucosum into the cutis. In the seventh month the epi- thelial cells form a canal, and the lower end of the tube be- comes dilated and somewhat twisted. In the ninth month the tube is coiled upon itself to form the gland proper. According to Ranvier, who believes that the muscular fibres lie between the epithelial cells and the basement-membrane, the muscle- cells arise from the external cells of the gland proper by a process of simple differentiation. The lumen of the tube is formed not by a softening down of the central cells, but by the formation of the cuticula, which occurs first at the lowest part of the excretory duct (Ranvier). The sebaceous glands. — The sebaceous glands are seated in the corium and are in close connection with the hair-follicles. When the hairs are large the sebaceous glands appear as ap- pendages to the hair-follicles into which their ducts enter, and by which their contents are carried to the free surface. As regards the small downy, or lanugo hairs, they may be said to open into the ducts of the sebaceous glands, the ducts of the latter having in this case a much greater diameter than in the }:>revious instance. They also open directly on the free surface. The sebaceous glands are almost without exception acinous glands, the number of lobules forming a single gland, ranging from two to twenty, or more. The largest glands are seated in the nose, cheeks, scrotum, about the anus, and in the labia. Occasionally the secreting portion of a sebaceous gland con- sists of a single tubule, or sac, whose duct opens into a hair- follicle. Every sebaceous gland is composed of two parts, viz.: the secreting portion, or gland proper, and the duct. The gland proper is formed of a basement-membrane, or sac, externally, and secreting cells, or their products, internally. The basement- membrane is continuous with the transparent membrane de- scribed as lying directly beneath the rete Malpighii and above the corium, and has a similar structure. This basement-mem- brane pas-is from the sebaceous gland to the hair-follicle, where it forma tin- inner layer of the hair-sac. The membrane of the sebaceous gland is surrounded externally by bands of dense 286 MANUAL OF HISTOLOGY. connective tissue containing blood-vessels, nerves, and lym- phatics. The secreting part of the gland (Fig. 122, t) is composed of layers of cells very similar to the cells present in the epidermis, those of the outer part corresponding to the cells of the rete Malpighii. The first layer of cells, viz., those seated upon the basement-membrane, is composed of cylindrical, or cubical, cells, like those of the rete. They have a very distinct nucleus. Further inward the cells become larger, more or less polyhe- dral in form, and contain fat, which obscures or conceals the nucleus. If the fat is extracted the nucleus can be seen lying in the centre of the space previously occupied by the fat. The nearer the centre of the gland the greater the quantity of fat in the cells. The most external layer of cells contains but a small quantity. In the centre of the gland, free fat, fat-crys- tals, and remnants of epithelial cells are found. The duct of the sebaceous gland is similar in structure to that of the gland proper. Externally is the basement-mem- brane, lined inside by epidermis-like cells, containing more or less fat, and enclosing a central cavity through which the seba- ceous matter passes to reach the hair-follicle or the free surface. The contents of this canal are fat, fat-crystals, and remnants of epithelial cells. Internal to the polyhedral cells of the duct are the cells of the corneous layer of the epidermis, which di- minish in number in proportion to the distance from the free surface. In large hairs the duct of the sebaceous gland opens at an acute angle into the hair-follicle near its upper third, and the gland proper lies about on a level with the middle third of the hair-follicle. At the place of union of the hair-follicle with the sebaceous gland the cells of the latter become continuous with the cells of the external root-sheath of the hair. This latter root-sheath becomes continuous above with the cells of the rete Malpighii. The development of the sebaceous glands commences at the third month of foetal life, as a projection downward and out- ward of a part of the external root-sheath of the hair, at the place where the future opening of the duct will be situated. It consists, at first, entirely of epithelial cells, which by sub- sequent multiplication and further projection downward, form the sebaceous rocesses, which chiefly accompany the nerve-fibres. Three large prolongations of pia mater are of constant oc- currence, viz., the posterior median septum and a less complete septum on either side, dividing the posterior column into two ; the larger, anterior, or column of Burdach ; and the smaller, posterior, or column of Goll. The connective-tissue elements are best brought out by hsematoxylon. The blood-vessels of the cord are derived from its pia mater, follow its prolongations, and are most numerous in the gray matter, especially that of the anterior horns. In transverse sections there will be seen a clear space about all the blood- vessels. This is the perivascular space or lymph-channel, in which all the blood-vessels are contained. During life these sheaths probably serve a double purpose : an auxiliary nutri- ent function by lymph-circulation ; and a means of accommo- dating the ever-varying degrees of vascular distention. In some diseases they become enormously dilated. They are all connected with the space between the pia mater and the cord, and an injection forced into this space will follow the blood- vessels for long distances. These perivascular spaces are also said to be lined with endothelium. The vessels of the cord present no other peculiarities. Their structure is best brought out by the use of a dilute luematox- ylon solution, or by the slow carmine staining. The perivas- THE CENTRAL NERVOUS SYSTEM. 299 cular canals may be more clearly demonstrated by forcing a colored gelatine injection at any point under the spinal pia mater — care being taken, if the cord is cut, to secure the ends of the sections by ligatures. Nerve- elements of the cord. — The consideration of the ner- vous elements of the cord will now be taken up in a general way, and the peculiarities of different regions explained later. The wliite substance of the cord contains, besides the blood- vessels and neuroglia already mentioned, myelinic nerve-fibres of different sizes. These fibres pursue a vertical course, with the exception of those forming the root-radicles and commis- sures. On examination with a low power, the white substance, in a transverse section stained with carmine, seems to be a collec- tion of minute rings, each with a red dot in the centre. More highly magnified, the transverse section of a nerve-fibre appears as a delicate, rather irregular circle, on the circumference of which, in some cases, are seen nuclei resembling those of the sheath of Schwann, but which are really nuclei of the neurog- lia. Next comes a broad ring of colorless, transparent mate- rial, the medullary or myelinic- sheath, which very often ex- hibits concentric lamination. Lastly, usually in the centre, is seen the solid axis-cylinder. When these fibres pursue a more or less horizontal direc- tion they give the appearance of broad, clear bands traversed by longitudinal red fibres (axis-cylinders). The myelinic fibres average about 5 fil in diameter. Fibres, when isolated by teasing, present the varicose aspect of myelinic nerve-fibres, which lack the sheath of Schwann. To demonstrate this they are best treated when in the fresh state by osmic acid (see p. 114), the result being a black myelinic sheath and brownish axis-cylinder. The gray matter is composed of nerve-cells, medullated and non-medullated nerve-fibres, and an amorphous matrix. The most striking elements are the cells of the anterior horns. These, whether teased from specimens fresh or hardened in chromic acid, or whether examined in sections, always present the same general appearance. They are large, multipolar cells, having a slightly granular, protoplasmic body, a large, oval ft = micromillimetre = xoVu millimetre. 300 MANUAL OF HISTOLOGY. nucleus, and a round nucleolus. These cells are polyhedral in form, as is shown by the fact that sections made in all direc- tions give them the same pyramidal or polygonal outline. In nearly all the large cells there is in some part of the body an aggregation of granules, which are often distinctly pigmented, giving the appearance of a heap. Striations of the body have been frequently described and depicted (Schultze, Schmidt, etc.), and this appearance has been attributed by some to plications of a very delicate invest- ing membrane, by others to ex- pansions of the ultimate nervous nbrillse, of which the axis-cyl- inder was thought to be com- posed. The motor cells average about 40 fx,. in diameter. The cell -processes vary in number. Most of them are bifurcating. One, however, connected with nearly every cell, can be fol- lowed for a long distance with- out dividing, and when the cell is situated near the anterior rootlets this process joins them and acquires a m}7elinic sheath. This is called the axis-cylinder process. The branching pro- cesses are called the protoplasmic processes, and are supposed by some to freely anastomose with those of other cells. This anastomosis, if it exist at all, is very delicate, and difficult of demonstration. A certain number of the cells of the anterior horns, espe- cially those located in the lateral region of the cornua, present an elongated, fusiform aspect, and appear to have but two processes. The nerve-cells in the posterior horns are of an elongated oval or fusiform shape, their long diameter corre- sponding in direction with that of the posterior horn. They are very much smaller than the anterior cells, and less numerous. Their average diameter is about 15 ft. They are seldom seen to have processes. The myelinic nerve-fibres of the gray matter are seen prin- cipally in the anterior horns, and converging from the cell- groups to form the anterior root-radicles. Here and there fibres Fig. 126. — Diagram of a motor-cell from the anterior horn of a human cord in the cervical enlargement, x 300. THE CENTRAL NERVOUS SYSTEM. 301 appear in transverse section, which, singly or in bundles, pur- sue a longitudinal direction. Amyelinic fibres are found everywhere in the gray matter pursuing various courses. The gray commissure is composed almost completely of amyelinic fibres connecting the lateral gray masses. Besides the above-described elements the gray substance seems to have a structureless or slightly granular matrix, in which the other elements are embedded. In the study of the spinal gray matter osmic acid and carmine preparations are by far the most useful, although much is to be learned by the ex- amination of fresh specimens teased in serum. To study the cells, cut out a piece from the anterior horn of a fresh cord and tease in serum. A preliminary treatment with osmic acid or ammoniacal carmine is sometimes advantageous. The epithelium of the spinal cord lines the central canal. The most internal layer is of the cylindrical, ciliated variety. On account of the difficulty in obtaining fresh specimens the cilia are never seen in the human cord, though they undoubt- edly exist. The epithelial cells, as they do exist in the human cord, have a square base, taper to a slender thread toward the apex, which penetrates the layer of young, round epithe- lial cells, and is lost in the granular central gray matter. The cells of the second layer are round, granular, and thickly crowded. The subepithelial tissue, for some distance around the cen- tral canal, consists of embryonal cells in a granular matrix. The central canal1 has no constant shape, varies greatly in size, and is often choked with desquamated epithelium. Its position, as its name indicates, is in the middle of the gray commissure, on a line passing between the anterior fissure and posterior septum. The general features of the spinal cord hav- ing been pointed out, the peculiarities of different regions will now be shown. Special study of the different portions of the cord. — The cord will be studied from below upward. The mode of study will mainly be by sections made after Clarke's method. The cord, after slitting the dura mater with the scissors up the front and hack, is cut in segments 3 ctm. long, which adhere 1 Sometimes double. See Segnin : Am. Jour. Med. Sci., p. 427. 1872. 302 MANUAL OF HISTOLOGY. to the undivided dura mater. Thus prepared it is suspended in Miiller's fluid (see p. 15), or dilute chromic acid (see p. 14), until hardened. The segments are then embedded in a microtome (see p. 16), and horizontal, transverse sections made. These are washed in distilled water and stained with carmine or hsematoxylon (see p. 23). A few minutes' immer- sion in alcohol previous to this manipulation makes the tissues take the coloring more quickly. After staining and washing, dehydrate the sections with alcohol and absolute alcohol, make transparent with oil of cloves, and mount in Canada balsam or dammar varnish (see p. 23). Hidden in the cauda equina is found the filum terminate, which is the end of the cord. Sections near its end exhibit lit- tle of the structure of the cord. At a point where it is 1.5 mm. in diameter it presents the appearance of a peripheral nerve, except that it has an opening — the central canal — in its centre. Its transverse section shows a collection of large and small myelinic nerve-fibres pursuing a vertical direction. A little higher up, where the filum measures 2 mm. in diam- eter, there is little difference, except that the central canal is nearer the surface (anterior) and surrounded by a small amount of gray matter. Now and then there are seen small, oval nerve- cells in the region posterior and external to the central canal. A little higher still, where the filum is 3 mm. in transverse and 2 mm. in antero-posterior diameter, back of the central canal on each side, where the future posterior horn is to be, there is a small collection of spindle-shaped cells. Sections from a region a little above this present an entirety different picture. The gray substance is here much more devel- oped and occupies the larger part of the section. It is divided into a club-shaped anterior horn, containing a few large poly- hedral cells, and a posterior horn which is rounded and formed of peripherally directed nerve-fibres and oblong nerve-cells. From this point up sections gradually become more circular and develop more and more a resemblance to the structure of the cord, until, at a point where the sections are about 3.5 mm. in diameter, the anterior fissure and posterior septum become well marked. The anterior horns contain few cells, and the fibres emanating from them pursue a very oblique course down- ward through the anterior columns. From the lateral gray matter arise bundles of nerve-fibres THE CENTRAL NERVOUS SYSTEM. 303 Fig. 127.— Three sections of the filura terminate: a. its transformation into the coccy- geal nerve ; b, section higher up before the giving off of the last sacral filaments ; c, its commencement. which curve around the posterior horn,, and, meeting similar fibres from the posterior columns, together form the posterior nerve-root. These two bundles form an arciform structure sur- rounding the round extremity of the posterior horn. (See Fig. 127.) The gray commissure occupies one-third the diameter of the cord. The central canal is large, slit- ^ like, and antero-posterior in direction. To summarize then, there seems to be in the filum terminate, especially its lower por- tion, a preponderance of the posterior or sensory part of the cord. About two centimetres from the end of the cord nearly the same picture is pre- sented. The transverse section is circular and about 6 mm. in diameter. Many large nerve-cells appear at the outer side of the anterior cornua, mostly at their junc- tion with the posterior horns. Fibres from this cell-group, instead of running a direct course, curve backward and inward (see Fig. 127), then run forward and emerge from the anterior horns. Many oval cells appear in the posterior horns, which now reach the surface of the sec- tion, and the posterior roots begin to show their origin from the posterior columns and horns. In the lumbar enlargement trans- verse sections have a circular shape. (See Fig. 128.) The white substance here predominates, and has but one peculiarity, which will be noticed in greater or less prominence through- out the remainder of the cord. At the bottom of the anterior fissure is a broad band of white substance called the white commissure. This is formed of myelinic nerve-fibres, which pursue a course from the base of the anterior horn of one side, forward, across the median line and downward to join the anterior column of the opposite side at a lower level. (See Pig. 120.) The anterior horns in the lumbar region are large and square, as are also the cells contained in it. TJie gray Fig. 128. — Three diagrams show- ing the relations of gray and white matter in different regions of the cord: a. I timber enlargement; 6. mid-dorsal region ; c, cervical enlargement. 304 MANUAL OF ILTSTOLOGY. commissure is narrow, and the central canal lias its long diam- eter placed transversely to the cord. Transverse sections in the dorsal region are circular and 8 mm. in diameter. The white commissure is thin, otherwise the same structure as in the lumbar region is observed. The anterior horns are narrow and sparsely filled with rather small multipolar cells. No continuous tracts of nerve-fibres can be traced through the anterior columns, as their course is so oblique (downward) as to give almost a transverse section of the bun- dles. The posterior horns, just behind the gray commissure, are swollen out, and contain a number of large nerve-cells — some multipolar, some oval. They approach the type of the cells in the posterior horns. This collection of cells is called the column of Clarke. Transverse sections in the cervical enlargement measure about 14 mm. The antero-posterior diameter is about 11 mm. The white commissure in this region presents about the same characteristics as in the lumbar region. The anterior horns are fan-shaped ; the anterior roots curve forward, outward, and downward. The central canal is triangular. The posterior horns are slender, and contain a few small nerve-cells. The posterior roots are also more intimately connected with the posterior horns than lower down. In the upper cervical region the gray matter assumes more the shape of the dorsal gray matter. In the lateral region, at the junction of the anterior and posterior horns, longitudinal bun- dles of myelinic nerve-fibres begin to appear. These bundles curve over (see Fig. 129), and pass rather obliquely upward and outward through the lateral columns, emerging nearer the posterior than the anterior horns. They are joined by fibres curving back from the cells of the anterior horns, and also emanating from the central gray matter. In this structure is seen the first appearance of the spinal portion of the spinal accessory root-fibres. The longitudinal bundles mentioned Via. 1*29. — Diagram of transverse section of the cord in the upper cervical region, showing coarse connective-tissue reticulum in left half of diagram, commencing decussation of the lateral columns across the base of the anterior horn into the opposite anterior column, taking the place of the anterior commissure lower down, and the root of the spinal accessory, 11 : A. R. = anterior root; l'.Ii. = posterior root. In this figure and in others small crosses must be understood as nerve -cells. THE CENTRAL NERVOUS SYSTEM. 305 evidently come from cells of the anterior horns lower down. Some of the fibres, passing back from the anterior horns to join the root, are seen to arise directly from the motor cells. In taking leave of the cord, the introduction of a diagram1 showing its regional anatomy, looked at from a physiological standpoint, is deemed ad- vantageous. It will enable p the microscopist to properly record localized lesions. In studying the spinal cord by means of horizon- tal transverse sections, it is of the utmost importance, particularly in pathological cases, to know which is the right or left side, and whe- ther one is looking at the upper or under surface of a section. Of so much impor- tance is this knowledge, that some means must be employed to acquire it. One of the best means is a method devised by Dr. E. C. Seguin, and published in the translator's note appended to Schultze' s article on the spinal cord, in the American translation of Strieker's " Histology," p. 647. He there recommends, be- fore placing the segment of the cord in the microtome, that a slight longitudinal incision be made in the right lateral column. By this means all the sections have a nick in the right lateral column, and can easily be placed. This method, however, has many drawbacks. One is that it is a process easily forgotten during the manipulations. Another more serious drawback is the fact that, make the incision slight as you can, the resulting nick often causes extensive fissures and crumbling of the lateral column or whole section, especially in pathological or over- hardened specimens. The requirements by the new method are two: 1st, the sections must be nearly horizontal ; and 2d, they must be suf- FlG. 130. — Diagram of transverse section of the spinal cord : A. anterior median fissure ; P, posterior median septum ; 1, columns of Goll ; 2, columns of Burdach ; 3, direct cerebellar column : 4. crossed pyra- midal column ; 5. lat eral column ; (i, anterior funda- mental column ; 7, direct pyramidal column ; 8, pos- terior gray horns ; 9. anterior gray horns ; stippled part, gray matter : shaded part, assthesodic system ; unshaded part, kinesodic system. 1 Dr. E. C. Seguin : Lectures on Localization, in N. Y. Medical Record, April 27, 1878, p. '623. 20 306 MANUAL OF HISTOLOGY. ficiently well stained and transparent to demonstrate the con- stituent parts of myelinic nerve-fibres. The mode of determi- nation depends entirely on the fact that the anterior roots pursue an obliquely descending course through the anterior columns, and for this reason horizontal sections cut the ante- rior rootlets obliquely. (See Fig. 131.) What is the natural inference to draw from this fact \ It is this : let the reader look at the upper surface of a transverse section of the spinal cord and bring the anterior roots into the field ; that is, let him look down the anterior column. He readily perceives that the central ends of the anterior root- fibres are nearer his eye than the peripheral ends. He sees that while the central ends are at the focus, the peripheral ends are beyond the focus, and he needs to bring the eye nearer to define them. This nearing the focus also gives the fibre- bundle an apparent peripheral motion, while increasing the focal distance causes an apparent central motion. The application of this method to a chance section is easy. Suppose we examine the anterior columns of a section and find by focussing that the central ends of the anterior root-fibres are farther from the eye than the peripheral ends. We will immediately know we are looking up the cord or at the under surface of the section. Now, all it is necessary to do is to turn over the section, either in your mind or on the slide, and put the anterior horns forward. The section is then in position. In sections of the cord where the anterior roots do not show, the posterior roots may be used in a similar way, as they, too, pur- sue a slightly descending course. Their use is not so easy, as the fibres are short and pursue a slightly wavy course. In sections or fragments of sections, where neither of these struc- tures avail, a study of the course of the fibres in the anterior white commissure will lead to detection. These fibres pursue a course downward and across the median line, from the base of one anterior horn into the anterior column of the opposite side. Fig. 131. — Diagram of vertical section •of human cord through the anterior and posterior columns and the anterior horns. It is intended to demonstrate how a trans- verse, horizontal section. S, cuts the an- terior nerve-roots obliquely. (From Ar- chives of Medicine , August 1, 1879, p. 70.) THE MEDULLA OBLONGATA. 307 In sections of the upper cervical region the spinal accessory- roots may be made use of, remembering, however, that they pursue a course obliquely upward through the lateral columns. The application of these rules to the medulla will be pointed out later on. Note. — To demonstrate the obliquity of the anterior rootlets, find, by a trans- verse section, the exact direction of the anterior rootlets, and then make longi- tudinal sections through the anterior column and horn on this line. THE MEDULLA OBLONGATA. In the upper part of the cervical region changes take place in the arrangement of the elements of the cord transforming it into the medulla oblongata. The changes are as follows : be- fore the external signs of decussation ap- pear, it is seen that the fibres of the later- al columns change their vertical course and bend forward and inward. This fact is demonstrated by the oblique sections of bundles and fibres. A little higher these bundles and fibres can be traced across the gray matter be- hind the anterior horn into the opposite an- terior column, which is to become by this addition the anterior pyramid. The decussating fibres take the place of the ante- rior commissure lower down, and the fibres pass upward and forward across the median line. The fibres of the anterior columns do not decussate at all, but give way to and mingle witli the fibres from the lateral columns. The shape and structure of the anterior horns are about the same as lower down. The posterior horn expands suddenly at Fig. 132. — Diagram of the medulla, pons, etc., natural size, to Bhow the direction of sections for displaying the different nuclei and roots : 11', line of section to show the early decussation of the lateral columns and spinal accessory tract; 11, line of section to show the spinal accessory tract and decussation of the pyramids; 11 & 12, region of the spinal accessory and hypoglossal ; 10, pnen- mogastric ; 9, glosso-pharyugeal ; 8, acoustic ; (i & 7. abducens and facial ; 5, trigeminus ; 4, patheticus ; 3, motor oculi ; c. q., corpora quadrigemina ; c. c, crua cerebri. 308 MANUAL OF HISTOLOGY. its peripheral extremity into a bulbous termination (see Fig. 133), from which the posterior root emerges. The central gray matter between the two horns is traversed and intersected by the decussating fibres from the lateral columns. Numerous pro- longations from this gray matter spread out into the lateral columns, presenting a coarse reticulum, called the formatio Pig. 133. — Diagram of transverse section of human medulla below external decussation of pyramids, showing bulbous posterior horns: F R, formatio reticularis ; 11, spinal accessory root and decussation of the lateral columns. Fig. 134. — Diagram. Decussation of the pyra- mids, shows decussation of the lateral columns, the swelling of the posterior horns, the shrink- age of the anterior horns, the spinal accessory root 11, and a partial decussation of the posterior columns behind the central canal. reticularis. The gray commissure is very broad, the central canal having its long diameter directed antero-posteriorly. In sections at the decussation of the pyramids proper, i.e., where they are seen to decussate externally, a slightly different picture is presented. The lateral columns have nearly disap- peared, having now almost all entered into the decussation, which is here very broad (see Fig. 134), and presents a peculiar zigzag appearance from the interweaving of bundles of fibres from the opposite lateral columns. These fibres, after curving around the anterior columns for a short distance, seem to dis- appear by assuming a vertical direction. The club-shaped ex- tremities of the posterior horns remain, while the rest is pushed back into the posterior columns, and contains many large cells. The anterior horns are also displaced backward, pushed back by the anterior columns increased in size by the addition of the lateral columns. Hence, the anterior roots have a longer path through the anterior columns and approach the type of the hypoglossal nerve-roots seen a little higher up. (See Fig. 135.) The spinal accessory nerve curves out and back from the lateral gray matter where a group of cells is situated. THE MEDULLA OBLONGATA. 309 Let us next take up a section involving the lower end of the olivary body. We have the following view presented. The section is slightly cordiform. (See Fig. 135.) The decussa- ting fibres at the base of what remains of the anterior fissure, which has all along become shallower, now forms the com- mencement of the raphe, a structure which extends all through the rest of the medulla and pons, separating the two motor tracts. The union of the lateral and anterior columns now nearly complete, forms the anterior pyramids. The fibres here have a general vertical direction, except that a broad band which emerges from the decussation at the bottom of the anterior fissure, curves around the margin of the anterior pyramid, and then, sometimes in the sub- stance, sometimes at the surface of the medulla, almost completely sur- rounds it, the bundle becoming lon- gitudinal on the posterior surface. These bear the name of the arciform fibres. The rest of the white matter is so cut up as to render it hardly divisible into regions. The central canal, which is very long antero-posteriorly, has almost coalesced with the gradually deepening posterior furrow soon to become the fourth ventricle. The gray matter originally in the cord is now collected about the central canal. Anterior and external to the central canal there is a small group of multipolar cells. This is the remnant of the anterior horns, which have been continually crowded back by the accumulation of fibres in the anterior pyramids. These cells in every respect are similar to those in the anterior horns. Their processes give origin to fibres which course forward in two or three bundles through the white matter of the anterior pyramids, and emerge at about the junction of the anterior pyramids and the lateral white mass. A little farther back in the gray matter, behind the central canal, is a small group of nerve-cells the remains of the spinal accessory nucleus, from which a few fibres run in a straight course outward and slightly backward, through the lateral white matter. Additional collections of gray matter now begin Fig. 135. — One half of section at lower end of the olives : 11, upper spinal acces- sory root ; 12, lower hypoglossal roots. 310 MANUAL OF HISTOLOGY. to appear. In the posterior region is a large tract (see Fig. 135) containing scattered groups of many small cells evidently con- nected with the arciform fibres. This is probably a part of the lower origin of the pneumogastric. A little in front and external to this is a small group of larger nerve-cells which help to form the lower sensory origin of the fifth nerve. Still farther forward in the lateral region is a large collection of multipolar nerve-cells. Although this group is traversed in many directions by fibres, single and in bundles, still it seems to give rise to fibres which run back and upward, evidently to curve upon themselves and join the peripheral fibres of the spinal accessory root. (See Figs. 135 and 137.) Farther forward still there is a collection of small cells arranged in a wavy line (see Fig. 135), the commencement of the olivary nucleus. Through this the roots of the hypoglossus all pass. Some seem to be lost in it, others appear to arise from it, but this is probably due to the arrangement of roots often seen to curve into the nucleus and then out again. As this is the first appearance of the olivary body, it will be well here to describe it. THE OLIVARY BODY. The olivary nuclei are situated in the medulla, under the oval projections on its anterior surface called the olivary bodies. The nucleus consists of a strip of gray matter arranged in gen- eral like a piece of fluting folded on itself, so as to form almost an ellipse. From the concavities of the fold on either side pro- ceed bundles of fibres, the external ones joining the formatio reticularis, the internal ones passing into the raphe. Their connection with the hypoglossal roots is probably not im- portant. The intimate structure of the olivary fold is that of a dense gray matrix holding numerous small polyhedral cells having delicate protoplasmic processes. Let us now go a trifle higher (see Fig. 137), and observe that in sections the central canal, which has all along been elongat- ing and receding backward, now opens into the apex of the fourth ventricle. There is now, therefore, quite a deep notch in the posterior part of the section, covered with the same cylin- drical epithelium which lined the central canal. On each side, THE OLIVARY BODY. 311 and in front of the bottom of the fourth ventricle, lies a large group of multipolar cells, the hypoglossal nucleus^ from which bundles of fibres course forward through the olivary body, which is here much enlarged and more complex than in the last section. On the inner side of the hypoglossal roots in the olivary region is an elongated mass of gray matter con- taining small cells, called the parolwary nucleus. There is an oval group of fusiform cells at, behind, and external to the hypoglossal nucleus, from which indistinct and broken bands of fibres pass outward to emerge from the lateral re- gion of the medulla. This constitutes the upper spinal acces- sory nucleus and root. Behind this nucleus, forming the Fig. 136. — Diagram showing structure of one fold of the olivary nucleus : C, centripe- tal fibres; P, peripheral fibres, x 64. Fig. 137.— One-half transverse section of the human medulla at the point of fusion of the central canal and the posterior fissure to form the fourth ventricle : 11, spinal acces- sory root; 12, hypoglossal root; R, raphe. eminence on each side of the fourth ventricle, is a large mass of gray matter containing a great number of small nerve-cells, which also seems to be rather indistinctly connected with the spinal accessory root. External to this nucleus is a con- tinuation of the collection of large cells seen in the section lower down, the lower sensory nucleus of the fifth. In front of the spinal accessory root is seen a group of multipolar cells not so large as in preceding sections. The peripheral circular fibres in this region are confined to the anterior and external aspect of the medulla, and are still seen to be in connection with the raphe by the arcuate fibres which traverse obliquely the intervening nervous tissue. From this point to the middle of the olives, sections differ 312 MANUAL OF HISTOLOGY. Fig. 138. — One-half transverse section of the human medulla through the middle of the olives : 4, fourth ventricle; 10, pneumogastric root; 12, hypoglossal root. little, except that in this space the root-fibres of the spinal accessory seldom appear, although figured by most writers. The region formerly occupied by the spinal accessory nucleus contains a group of small cells which form part of the pneu- mogastric nucleus. The fibres between this nucleus and the point of exit of the pneumo- gastric root run so obliquely upward, that no direct connec- tion between them can be traced. It is in sections at the mid- dle of the olives that the pneu- mogastric begins to appear dis- tinctly. Most of its fibres seem to be connected with a small group of cells situated in the gray matter, at the junction of the funiculi graciles and the restiform body. The gray mat- ter of the restiform bodies is filled with small cells and con- tains many fibres having a peripheral direction posterior to the pneumogastric root — the beginning of the auditory nucleus and root. The olivary body here reaches its highest develop- ment and greatest dimensions. Behind the olivary body is a small group of cells, from which scattered fibres pass backward and inward toward the pneumogastric nucle- us. But most of them are lost by as- suming a longitudinal direction. This is probably the lower facial nucleus, to be described farther on. The arciform fibres are chiefly confined to the surface of the anterior pyramids and the olivary bod- ies. The fibres of the raphe pursue, in great part, an antero-posterior direction. Sections through the medulla at the upper part of the olivary bodies differ little from the former sections. But a small segment of the olivary bodies is present, and only a few of the hypoglossal roots remain. (See Fig. 139.) External to the remains of the hypoglossal nucleus is a nucleus of small cells Fio. 139.— One - h.ilf trans- verse section of the human me- dulla through the upper part of the olives bringing the glosso- pharyngeal tract (9.) and the lower part of the acoustic nucleus (80 into view. THE OLIVAKY BODY. 313 giving origin to a bundle of fibres, which pass out laterally just as does the pneumogastric lower down. This is the glosso- pharyngeal nerve and root. Farther still from the median line, in the floor of the fourth ventricle, is seen a group of small cells, the commencement of the acoustic nucleus. Scat- tered nerve-cells arising here pursue an obliquely forward and outward direction, making the lower margin of the auditory root. Transverse sections of the medulla just at the edge of the pons bring the acoustic region into view ; the upper olivary body is here visible. Behind this are scattered a few large cells, from which fibres pass backward to form higher the facial root. Fig. 140. — One-half transverse section of the human medulla just below the edge of the j>ons. Bhowing acoustic nucleus and roots which enclose the inferior cerebellar peduncle I. 0. P. : I. internal root ; E, external root ; «, up- per olivary nucleus; Lf, lower facial nucleus. 3 diams. Pig. 141. — Diagram of a transverse section just above the edge of the pons, having the obliquity given it in Fig. 132, 6 & 7 : f>, abducens root ; 7, facial root. For other explanations, see text. Occupying the floor of the fourth ventricle is a large mass of gray matter, from which the acoustic arises. This gray matter contains many small round and some multipolar cells. The nerve has two roots, one internal, the other external. (See Fig. 140.) The former arises from fibres emerging from the raphe Dear the fourth ventricle and from the gray matter just external to it, and pursues a course downward and forward through the lateral white matter. This root, at its point of emergence, is joined by fibres from the posterior root curving 'around the surface of the medulla, like, if not identical with, the arciform fibres. The external root has also one origin from the gray matter near the median line, and curving outward on 314 MANUAL OF HISTOLOGY. the floor of the fourth ventricle (forming the linece transversa) it receives additions from the lateral gray mass, and emerges from the medulla a little behind the internal root, which, how- ever, it soon joins. It is seen that the two roots embrace a column of white matter, which is the inferior peduncle of the cerebellum. (See Fig. 140.) In sections just above the edge of the pons, having the oblique direction given in Fig. 132, the region of the sixth and seventh nerves comes into view. The view presented here is different from that in the medulla below. In place of the narrow band of arciform fibres which covered the anterior re- gion of the medulla, nearly the anterior half of this section is composed of transverse, arciform fibres. Imbedded in this structure is a longitudinal bundle of white matter, the contin- uation of the anterior pyramid. The posterior half of the section contains the structures under consideration. From a group of multipolar cells at the floor of the fourth ventricle, some distance from the median line, several bands of fibres pass forward and slightly outward, in a somewhat sim- ilar way to the hypoglossal roots lower down. This is the nucleus and root of tlie abducens nerve. Internal to and behind the abducens nucleus, in almost all sections, is seen an oval bundle of what at first sight ap- pears to be longitudinal nerve- fibres. Closer examination, how- ever, shows the fibres to be not straight but looped, and in suc- cessful sections the following ap- pearances are presented. Behind the anterior pyramids and out- side of the abducens root is seen a group of multipolar cells oc- Fig. 142. — Diagram of course of fibres In D . ■* x . the "genu "of the root of the facial nerve: n, cUPVinff tile Same location aS tile fibres coming from the nucleus ; g, the " genu,'* * * ° or coil where the fibres change their direction m'OUP Called tile lower facial HU- R, the root proper of the facial nerve. ° L cleus, lower down. Arising from this, and pursuing a course backward and inward, are numer- ous fibres ; these reach the oval bundle before mentioned, enter it, curl upon themselves (see Fig. 142), and emerge at about their point of entrance. The fibres mentioned as appearing longitudinal undoubtedly come from the lower facial nucleus, and curl upon themselves like the rest. THE OLIVAKY BODY. 315 Some fibres (commissural) join the root from the raphe, and others seem to arise from the abducens nucleus, though this is denied by many authors. The fibres which seem to arise from the abducens nucleus are probably fibres from the anterior nucleus of the facial, which do not traverse the coil ("genu," as it is called), but enter the root directly. The facial root thus formed goes directly outward at first toward the external angle of the fourth ventricle, then turns sharply forward to emerge at the junction of the pons and medulla external to the sixth root. Many authors, first of whom was Clarke, describe an inferior nucleus of the facial nerve, supposing it to innervate the lips and mouth, basing their assertions as much on the seat of lesion in labio-glosso- pharyngeal paralysis as on anatomical evidence. There can be but little doubt as to its existence, and probably it corre- sponds to the group of cells seen in Figs. 137 and 138. Sections of the pons above this point soon begin to show traces of the fifth nerve. (See Fig. 143.) The picture we get in transverse sections at the emergence of the fifth root is, in front, two large bundles of longitudinal nerve-fibres sur- rounded by the arciform fibres and separated by the raphe ; behind, the gray matter of the fourth ventricle, which here is pentagonal in shape and is covered in by the base of the , *"* -43'- Dia=ram showing origin and course •> of the trigeminus nerve. cerebellum, the inferior vermi- form process. Emerging from the gray matter in front of the external corner of the ventricle, and also joined by fibres from above and below, is a large bundle of fibres which pursue a diagonal course outward and forward, to emerge from the side of the pons. This is the sensory root of the fifth nerve. Inter- nal to this root, just after its formation, is seen in successful sections a large group of multipolar cells sending off fibres, the motor root, which join the sensory root and emerge with it. A collection of large, oval, pigmented cells here underlie the exte- rior part of the fourth ventricle and form the locus cceruleus. It seems to have an indistinct connection with the trigeminal 316 MANUAL OF HISTOLOGY. Fig. 144. — Diagram showing ori- gin of the third and fourth nerves from the gray matter about the aque- duct of Sylvius: c. c, eras cerebri; 3, third nerve ; 4, fourth nerve. sensory root, and Meynert makes it one of its points of origin. The sensory root is reinforced by fibres from a group of large oval cells external to the fourth ventricle and by the so- called descending branch (Meynert), which is seen in trans- verse section in the same location com- ing from regions still higher up. Some fibres also come from the raphe and arcuate fibres, and others from the low- er sensory origin of the fifth, which occupies a lateral position in all the sections up from the spinal accessory region of the medulla. Higher in the pons, where the ante- rior motor tracts or pyramids, before mentioned, begin to separate into the crura cerebri, the fourth nerves are seen. They are supposed to arise from a nucleus at the floor of the fourth ven- tricle lower down, curve around the outer wall of the ventricle, decussate in the median line in the valve of Vieussens, and pass from the pons behind the tubercula quadrigemina. From this point they curve forward around the crura, on the outer side of which they appear at the base of the brain. At about this point and a little higher are seen bundles of fibres emerging from the gray matter containing small cells, in front of the fourth ventricle, diverging and pursuing an arcuate course through the crura, to converge again and emerge from the inner side of each crus. (See Fig. 144.) This consti- tutes the nucleus of origin, the course and point of emergence of the third nerve — a view hard to get unless just the right obliquity is given to the section. Imbedded in the crus, in the region through which the third nerve passes, is a collection of pigmented cells forming the locus niger. Higher the crura separate and enter their respective hemispheres. Their further course is better shown by a trans- verse vertical section of the hemispheres at the large part of the thalamus opticus. (See Fig. 145.) Here we see a great part of the substance of the crus flat- tened in form passing upward, between the optic thalamus and a gray mass called the nucleus lenticularis, forming what is THE CEREBELLUM. 317 denominated the internal capsule. The posterior third of the internal capsule is distributed to the posterior part of the hemisphere, and when destroyed produces loss of sensibility on the opposite side of the body. The anterior two-thirds of the internal capsule is distributed to the middle or motor re- gion of the hemisphere, and its destruction causes a paralysis Fig. 145.— Modified from Charcot's diagram to show position, relation, and distribution of the inter- senting the'radia'tion of the' internal capsule vertically to the motor region of the cortex.— From "Lec- tures on Localization," by Dr. E. C. Seguin : New York Medical Record, p. 142, August ii, 18(8. of the opposite side of the body. The fibres expanding from the internal capsule, joined by those emanating from the gan- glia at the base and the corpus callosum, form a fan-shaped expansion of white fibres called the corona radiata. THE CEREBELLUM. The white centre of the cerebellum, formed from the ex- pansion of the peduncular tracts, incloses a collection of gray substance, the corpus dentatum, This body, visible in all sections, bears some resemblance to the olivary body in the medulla, on account of its irregular, dentated outline. Its greater consistence causes it to stand out in a section from the surrounding tissue. In intimate structure this body consists 318 MANUAL OF HISTOLOGY. of a collection of small fusiform and polyhedral cells with minute processes, imbedded in a basis-substance much more dense than the surrounding white matter. The body is made to appear striated in a peripheral direction by bundles of fibres and blood-vessels pursuing a parallel course. The surface of the cerebellum, deeply gashed by sulci and their subdivisions, presents, on section, its well-known com- pound, arborescent appearance. This arrangement of the gray matter causes the greatest possible surface to come in con- tact with the blood-current furnished by the pia mater, and hence secures the greatest nutrition of the elements of the cortex. The gray matter of the cortex is easily divisible into an external or granular layer, a middle or cellular layer, and an internal or nuclear layer. The latter consists of a vast number of small granular cells about the size of white blood- corpuscles, which take staining fluids with great avidity. The middle stratum is a clear space in which there is a single layer of large corpuscles, called the cells of PurJcinje, 10 to 40 ft. in diameter. They are scattered at some distance from each other, and present pe- culiarities pos- sessed by no other cells in the body. The cells are of large size, vary- ing in form from «V« fusiform to flask- accord- I ■■» \ . >, . » Fro. 146.— Diagram of the cerebellar cortex, showing the large cells of shaped, Purkinje. £ ' mg to the plane of the section. Their central side is round, and in most cases has no processes. Often the usual rounded contour of the cell- body is broken by an angle, seemingly the remains of a broken process. Here and there a large non-branching axis-cylinder process is seen emerging from the base of a cell and pursuing a course parallel to the cortex. That these basal processes exist in all cases, and ultimately acquire a myelinic sheath, there is no doubt. (See Fig. 146.) From the peripheral side large arborescent processes spring, THE CEREBRAL GANGLIA. 319 which pursue quite a direct course through the external or granular layer and disappear when near the periphery. The primary processes, one or two in number, have a tendency to spring from the cell-body at an obtuse angle, and give off at almost right angles to themselves the straight peripheral pro- cesses already mentioned. The nuclei of these cells are oval and coarsely granular ; the nucleolus is round and small. TJie cortex proper consists of a granular matrix vertically striated by the cell-processes and parallel blood-vessels. There is also a moderate sprinkling of small round cells and nuclei similar to those in the third layer. The cortex is very vascular. THE CEREBRAL GANGLIA. As examples of these structures the optic thalami and cor- pora striata may be taken. They are collections of gray matter through which part of the fibres, emanating from the crura to help form the corona radiata, pass. In the corpus striatum these fibres pass through in bundles visible to the naked eye, which gives to this body its striated appearance. These bundles radiate toward the periphery of the body, thus leaving ever increasing spaces between them. These spaces at the base of the body, at the point of entrance of the bundles from the crura, are narrow, filled with nerve- fibres running in horizontal, vertical, and diagonal directions, seemingly commissural in nature, and multipolar cells few in number, large, and resembling somewhat cells of the anterior horns of the spinal cord, whose processes mingle with the fibres mentioned. Nearer the periphery of the organ, where the bun- dles of fibres are more widely separated, the intervening mass of fibres and cells abruptly changes to a finely granular gray ma- trix, holding in its substance numerous small blood-vessels and small nerve-cells, mostly round — some, however, triangular in shape, similar to those of the second layer of th'e cere- bral cortex. They have large nuclei and many delicate pro- cesses. The optic thalami consist of a mixture of gray matter and fibres, not, however, so regularly arranged as in the corpus striatum. The gray matter contains a few oval cells having many delicate processes. TJte cerebral ventricles. — Continuous with the central canal 320 MANUAL OF HISTOLOGY. Fio. 147. —Diagram illustrating the structure of the ependyma of the cere- bral ventricles. of the cord, and doubtless like it in function, the cerebral ven- tricles resemble it in their structure. They are lined through- out with a structure called the ependyma. This consists lirst of a finely granular layer covering all the nervous matter bounding the ventricles. Besides the minute granules, this layer contains a few small nuclei here and there, but no fibres. On its free surface rests a single layer of cylin- drical epithelium. The cells of this layer have square free cuds, while they are anchored by one or more delicate processes which emerge from the attached end and pierce the sub- jacent granular-matrix. These epi- thelia in the fresh state undoubtedly have cilia. This layer of epithelium is apt to be arranged in folds, giving a section of the ependyma a wavy appearance. The choroid plexus of the lateral ventricles has for its basis an artery which enters the descending horn of the lateral ven- tricle from the base of the brain. This artery gives oft0 along its course short arterial trunks which repeatedly subdivide, and each ultimate arteriole terminates in a convoluted capillary loop, resembling the Malpighian tuft of the kidney. Some of the twigs seem to end in a ca> cal extremity ; but it is doubtful whether they do, the preparations giving this appearance being prob- ably artificial. The peculiarity of the choroid plexus is that all the vessels composing it, large and small, are covered by a layer of potyhedral epithelial cells, each having one, sometimes two large nuclei. ■ This presents a beautiful example of the so-called tesselated epithelium, each cell being sepa- rated from its neighbor by a transparent intercellular sub- stance. This epithelial covering causes the tufts of the choroid plexus to resemble, in a degree, the villi of the chorion. The best plan in studying the choroid plexus is to use hsema- toxylon, or alcoholic specimens slightly teased. Fia. 148. — Diagram showing structure of the choroid plexus of the lateral ven- tricles. THE CEREBRAL GANGLIA. 321 The cerebral dura mater differs from the spinal in the fact that, its outer surface serving as periosteum, it lacks the layer of loose connective tissue present in the spinal dura mater. Its bulk consists of two layers of dense fibrous tissue running in opposite directions. The inner serous surface is coated with endothelium and lymphatics. The outer or periosteal surface is the most vascular. The cerebral differs from the spinal arach- noid only in being perhaps a little more closely attached to the pia mater. The pia mater of the brain is extremely vascu- lar, and shows more beautifully than the spinal membrane the system of perivascular spaces. The cerebral cortex. — The cerebral cortex is a thin sheet of gray matter spread on the outer surface of the hemispheres. The outer surface of the hemispheres is grooved by furrows (sulci) less deep in proportion to their size, and less regular than those of the cerebellum. The convolutions produced by these sulci, although seemingly very irregular, still have a cer- tain symmetry in different brains by which they can be classi- fied and named. A definite knowledge of these facts is neces- sary for an understanding of the current literature on the subject and of properly recording cases. The fetal hemisphere at an early date is smooth. Furrows soon begin to appear, the first and most important of which is the fissure of Sylvius, extending upward and backward, from about the anterior third of the base of the brain, and tliefis- sure of Rolando, running from near the posterior extremity of the fissure of Sylvius upward to the superior longitudinal fis- sure. One after another the other fissures appear, till in the adult brain they seem innumerable. Even here, however, there is a certain constant arrangement of fissures and convolutions on which a nomenclature may be based. The original fissures of Sylvius and Rolando remain. From the anterior inferior part of the frontal lobe three furrows run obliquely upward and backward toward the two fissures just named, dividing the frontal region into the three frontal con- volutions, while a convolution in frontof thefissureof Rolando receives the name of the ascending frontal or anterior central convolution. A similar convolution behind the fissure is called the ascending parietal or posterior central convolution. The parietal region is irregularly divided from above downward, as is also the temporo-sphenoidal and occipital region. The 21 322 MANUAL OF HISTOLOGY. base of the brain is also divided into a series of basal frontal, temporal and occipital convolutions. By far the most impor- tant region of the cortex, according to our present knowledge, is that along the fissures of Sylvius and Rolando, the so-called motor tract of the hemispheres. The exact physiological func- tions of the anterior frontal, the occipital, temporal, and basal Fig. 149. — Modified from Ferrier ; letters and figures the same : S, fissure of Sylvius; c, fissure of Ronaldo : po, parieto-occipital fissure ; A, ascending frontal gyrus ; B, ascending parietal gyrus ; F2, third frontal gyrus; P2', gyrus angularis ; circle I., seat of lesions which (on the left) cause aphasia; circle II., seat of lesions which convulse or paralyze the upper extremity cf the opposite side; dotted circle III., seat of lesions which probably convulse or paralyze the face on the opposite side ; dotted oval IV., seat of lesions which probably convulse or paralyze the lower extremity of the opposite side. These districts receive their blood-supply chiefly from the middle cerebral artery. — From Lectures on Localiza- tion by Dr. E. C. Seguin : N. Y. Medical Record, October 19, 1878, p. 301. regions of the hemispheres, is not known, inference, however, making them the seat of general and special sense, vaso-motor, psychic centres, etc., etc. The middle or fronto-parietal region, however, is the proven seat of motor centres for the face, limbs, and body, and the faculty of articulate language. The centre for speech occu- pies the region at the base of the third frontal convolution and the island of Reil on the left side, a similar location on the right side being occupied by a centre for articulatory movements. A little higher on the ascending frontal and parietal convolutions is an area having control over the move- ments of the tongue and face. Still higher is found a larger space, the centre for the arm of the opposite side. A larger space at the junction of the fissure of Rolando and the su- THE CEREBRAL GANGLIA. 323 i'l perior longitudinal fissure, including a tract on the inner aspect of the hemisphere, called the paracentral lobule, is the centre for movements of both extremities, especially the lower. On account of the anatomical variability of the convolutions in different brains, these centres must be allowed some lati- tude, and should not be made so small and exactly located as they are by some authors. Their location has been pretty definitely determined, however, by experimentation on animals, and lesions in man, such as trauma- tisms, neoplasms, abscesses, hemor- rhages, atrophy following amputa- tions, retarded development, etc. Possessing such important proper- ties we should naturally expect the cerebral cortex to be a very complex structure, and so it is. Minute structure of the cortex. — In order to get a satisfactory view of the elements of the cortex, great care has to be exercised in making sections. It is not enough to make a section exactly perpendicular to the cortex. The plane of the section must exactly coincide with the direction of the fibres of the corona radiata as they enter the convolution. This can be rather easily accomplished by paying close atten- tion to the arrangement of the white and gray matter in the piece from which the sections are to be made. Cuts with any obliquity will give erroneous impres- sions as to the exact shape and structure, especially of the cellular elements of the cortex. The cortex cerebri is generally divided into five layers, but it is easily divisible into three only. The outer layer, lying immediately under the pia mater, is more transparent than the rest, and is composed of a fine net- work of neuroglia containing many quite large openings, giving it a spongy appearance. It also contains a few large, round nuclei, and a small number of triangular nerve-cells. The second layer, thicker than the first, consists of a gray basis-substance, dense and granular, holding an immense num- ber of small, triangular and conical cells, their apex being di- '#!/ Pig. 150. — Diagram showing the elements and relation of parts in the cerebral cortex. (See text. ) 324 MANUAL OF HISTOLOGY. rected toward the periphery and often drawn out into a Blen- der axis-cylinder process, while from their baseseveral delicate processes are giv<-n off. These cells all have large nuclei and nucleoli. Here and there are seen larger conical cells, which will be described with tin- next layer. The characteristic fea- ture of the second layer, however, is the presence of a great number of small, round cells and free nuclei similar to those in the third layer of the cerebellar cortex. In the third layer the matrix is still more dense, and con- tains, besides a few small triangular cells, round cells, and free nuclei, a large number of large conical corpuscles, the so-called "giant cells" of the cortex, the distinguishing feature of this layer. When isolated from their surroundings these cells ap- pear like cones which taper gradually from a broad base to a very slender apex, which, when it attains the size of an a cylinder, can be traced for a long distance without showing a division. This undoubtedly terminates in a myelinic nerve- fibre. The base of the cell is not square, but crenated and notched by the giving off of numerous delicate basal processes which are lost in the granular matrix. The cells all have nuclei and nucleoli, most of which are round, but some of which seem also to have a triangular shape corresponding to the cell-body. The cells average 25 /x. in diameter. A great difference is made in the apparent shape of the cell by obliquity of the section. If the line of section is moderately oblique, it shortens the cells ; if still more oblique, it makes them very short and blunt ; while if the section is at right angles to their axis, all the cells appear round and of various sizes. In the deepest parts of this layer the giant-cells gradually disappear, and the gray matter of the cortex merges into the white matter. In the two inner layers of the cortex there are seen many fibres and bundles of fibres having a ver- tical direction, which, with the blood-vessels (the largest <>f which being perpendicular to the surface), give the cortex a somewhat striated appearance. We see, then, that the only difference between the second and third layers of the cortex is the greater number of small cells in the second and the greater number of large cells in the third, while the division of the third layer into three, as is accepted by most authors, seems purely arbitrary, there being a gradual gradation into the white substance. BIBLIOGRAPHY. 325 • Some writers ' lay much, stress on the difference of structure of the cortex in different regions of the hemisphere. It is true that, in the non-excitable or sensory regions, the cortex is thin- ner and perhaps less highly organized ; but here are met the same elements as form the cortex in the motor region (centre, for the arm, for instance). (See Fig. 150.) Even the giant-cells are found less numerously than in the motor regions. Another fact demands attention, that is, that the structure of the cortex is the same at the bottom of a fissure as on the surface of a convolution, and for this reason lesions of the sides and bottom of fissures should receive as much attention as those of the surface of the convolutions, implicating, as they do, equally im- portant structures. BIBLIOGRAPHY. Spinal Cord. Clarke, J. L. Researches into the Structure of the Spinal Cord. Philosoph. Transactions. 1850. Donders, F. C. Dissertatio anatomica inauguralia de cerebri et medulla; spinalis systemata vasorum capillari in statu sano et raorboso. 1853. Jacubowitscii, N. Mittheilungen uber die f einere Structur des Gehirns und Riicken- marks. Bieslau, 1857. jACUSowiTsrn, N. Further Researches into, etc. Breslau, 1858. Bidder, F., und Kupffer, C. Untersuchungen tiber die Textur des Riickenmarks, etc. Leipzig, 1859. Van Der KoLK, Sciiroeder. Minute Structure and Functions of the Spinal Cord and Medulla Oblongata, and on the Proximate Cause and Rational Treatment of Epilepsy. New Sydenham Society. London, 1859. BnLLENO, B. Neue Untersuchungen iieber den Bau des Riickenmarks. Cassel, 1859. Luts, J. Recherches sur le systeme nerveux curebro-spinal ; sa structure, ses fonc- tions et ses maladies. Paris, 18G5. His, W. Zum Lyraphsystein. Leipzig, 1805. Hik-' rriEi.D, Li:dovic. Traito et iconographie du systeme nerveux et des organea ', canal of Schlemm; c, c', membrane of Deacemet ; rf, process of the iris: J, iris; e, endothelium of the membrane of Descemet ; e\ e', e\ of the li^amentum pectinatum iridis ; e'\ e'\ e", of the iris ; /, meshwork of the space of Fontana ; m, musculus ciliaris. At the inner part of the sclera, close to its junction with the cornea and the ligament, is the canal of Schlemm («, v'), a ring- shaped passage, oval on section. It is lined with a single layer of endothelium, varies in size in different specimens, often ap- pearing as if divided into two parts, and, according to Wal- deyer, probably connects with the anterior chamber and also with the scleral veins. Through this passage and Montana's spaces the fluid of the anterior chamber is supposed to escape from the globe, and it is worthy of note that in glaucoma, with increased intra-ocular tension, we rind the iris attached to the periphery of the cor- THE EYE. 337 nea over a circular space which would entirely cover these probable channels of exit. Preparations of these parts can be made from eyes which have been placed in Miiller's fluid while quite fresh and al- lowed to remain in it three to four weeks, the fluid being re- newed from time to time. Hsematoxylon is well adapted for coloring them, and they may be preserved in glycerine. The sclera. — In the sclera we find the same minute struc- tures as in the cornea, i.e., bundles of fibres, cementing sub- stance, lymph-spaces, and fixed corpuscles. The fibres, how- ever, are not laminated, as in the cornea, but run in various directions, weaving a very dense tissue, so that the lymph- canals have a correspondingly tortuous course. Chemically there is a difference between the two, as the sclera is found to yield on boiling a true connective-tissue gelatine ; the cornea, on the other hand, a substance resem- bling chondrine. We find also in the sclera, near the foramen for the optic nerve, a few pigment-cells. The sclera is covered by the conjunctiva from the corneal border to the insertion of the recti muscles, and the fibres of the subconjunctival tissue pass directly into it. From the en- trance of the optic nerve to these muscular insertions, and even passing up between them, the scleral portions of Tenon's cap- sule form the covering, which consists of delicate filaments of connective tissue passing directly into the sclera itself. On the inner surface the sclera is covered with a large-celled endothe- lium lining the perichoroidal space. At the round opening for the entrance of the optic nerve, the outer fibres of the optic nerve sheath pass directly into the outer scleral layers ; the inner portions of the sheath partly mingle with the inner layers of the sclera, and partly, after the addition of some true scleral fibres, form the lamina cribrosa, a fine, sieve-like net- work of fibrous tissue, which stretches across the opening in the sclera on a level with its inner surface. This lamina can be easily shown in specimens where the delicate nerve-fibres which pass through its openings have been macerated out. The sclera is perforated in the equatorial region by the trunks of the vena? vorticosa? ; they are accompanied by the lymph-vessels which form the connection between the pericho- roidal and Tenon's lymph-spaces. The direction of the canal through which they pass is so oblique that it is supposed to be 22 338 MANUAL OF HISTOLOGY. easily contracted in diameter by any increase in intra-ocular pressure. The arteries of the sclera, with their thick adventitial coats, the peculiar sheaths of the veins and capillaries, as also the nerves, are best studied in hematoxylon preparations. A solu- tion of silver nitrate (a quarter to one per cent.) will expose the endothelial cells, while sections of the tissue may be made from specimens preserved in alcohol or Miiller's fluid. The tunica vasculosa, consisting of the choroid, ciliary body, and iris, forms one continuous mem- brane through which the principal blood-supply of the eye is carried. The choroid. — This tunic lines >c/ithe sclera from the entrance of the optic nerve to the junction of sclera and cornea, and is united to it at those points ; over the remaining portion there is a loose connection formed by scattered fibres and the numerous vessels and nerves which pass through the sclera to the cho- roid. The meshes of the open network between the laj^ers of the choroid and the sclera form lymph-sacs — the perichoroidal spaces — which connect with the sac enclosed in Tenon's capsule, and this in turn unites with the su- pra-vaginal space surrounding the sheath of the optic nerve. The choroid consists of several layers, with limits not distinctly marked. The lamina supraclwroidea (Fig. 154, sc) lies next the sclera, and consists of fine elastic and connective-tissue fibres, holding in their meshes pigmented and transparent cells: the first are stellate, often with projecting arms by which several are joined together ; the latter resemble lymph-cor- puscles. The layer of large vessels is traversed by branching arteries and veins ; between them are numerous pigmented corpuscles, a Fin. 154. — Scl ra, n ; choroid, ch ; ret- ina. ?■; perichoroidal space, p<.h; lamina ■supraehoroidea, sc ; lamina chorio-capilla- ris>, cc\ lamina vittca, »; layer of pigment- colls between choroid and retina, p. After Merkel. THE EYE. 339 while the whole is held together by the firm connective-tissue network which extends throughout the entire choroid. The lamina chorio-capillaris (cc) consists of a network of fine vessels interspersed with pigment, and extends over the whole inner portion of the choroid. The vitreous layer (v) is very closely connected with the lamina chorio-capillaris ; though it appears homogeneous, fibres may be detected in it after long maceration in a ten per cent, solution of common salt. Where this layer covers the cil- iary processes the surface is no longer smooth, but has fine, elevated ridges upon it ; here the membrane also is thicker, and is more easily affected by reagents. The dense lamina of hexagonal pigment-cells between the choroid and retina has sometimes been classed with the former, although it belongs more properly to the retina. The long and short posterior, and the anterior ciliary arte- ries, furnish the numerous blood-vessels which constitute the great mass of the choroid. The short posterior ciliary arteries, four to six in number, give off some twenty branches which penetrate the sclera, pursuing a straight course near where the optic nerve enters ; then, continuing their course in a tortuous manner, they divide into fine networks which supply the greater part of the lamina chorio-capillaris. About the entrance of the optic nerve they also form a network of fine vessels, and even send occasional branches to anastomose with vessels from the sheath and cen- tre of the optic nerve. The two long ciliary arteries penetrate the sclera in a very oblique course, a little anteriorly to those last mentioned, and in the horizontal meridian ; they pass forward in the outer lamina of the choroid without branching until they reach the ciliary muscle ; here they divide, and penetrating the muscle, form near the periphery of the iris a circle {circulus arteriosus iridis major) by uniting with the artery of the opposite side. The anterior ciliary arteries, eight to ten in number, arising from muscular branches of the ophthalmic artery, penetrate the sclera near the insertion of the recti tendons; they also unite with the circle just described, which forms the principal distributing point for the vessels of the iris and ciliary body. Prom this circle also are sent back a few small branches to unite with the choroidal capillaries, and there is formed the sole con- 340 MANUAL OF HISTOLOGY. nection between the short posterior or choroidal arteries pro- per and those which supply the circulus arteriosus. A small amount of t he blood which returns from the capillaries of the choroid, ciliary body and iris finds its exit from the eyeball through the veins accompanying the anterior and posterior ciliary arteries, but by far the larger part is collected by the large veins in the outer layers of the choroid (vena3 vorticosre), converging so as to form four or six great trunks, which perfo- rate the sclera obliquely in the equatorial region, and empty into the ophthalmic vein. The long and short ciliary nerves supply the tunica vascu- losawith fibres from the third and fifth pair and the sympa- thetic. The long nerves, two or three in number, are branches of the nasal division of the ophthalmic nerve ; the short, ten to fifteen in number, arise from the ciliary ganglion. These nerves penetrate the sclera near the optic nerve, and then, passing for- ward on the outer portion of the choroid, form, in the ciliary muscle, a fine plexus with ganglionic corpuscles at the nodal points of the meshes ; from this plexus fibres are distributed to the cornea and iris. At the junction of the anterior and middle thirds of the eyeball the choroid undergoes a change, the membrane be- comes thinner, the capillaries turn back toward the veins, only a few vessels continuing forward in a straight course. In this region the retina also undergoes a change and loses all its nervous elements, the connective tissue supporting fibres alone being continued forward under the name of the pars clli- aris retina. The very narrow zone between the points where these changes occur and the irregular line formed by the begin- ning of the ciliary processes is called the orbiculus ciliaris, and the line of origin of these processes the ora serrata. The ciliary body. — Crossing the orbiculus, the choroid is seen raised in radial folds, some seventy in number, which in- crease in size until they reach the thickness of a millimetre. This increase is caused by the development of smooth muscular fibres in addition to the usual constituents of the choroid. These fibres arise just behind the canal of Schlemm, from the sclera and cornea ; passing backward, they together form a ring, which on section appears as a right-angled triangle, with the base turned toward the anterior chamber, and the hy- pothenuse toward the vitreous (Fig. 155). THE EYE. 341 This triangle consists largely of the fibres of the ciliary mus- cle, which are divided into meridional fibres, or those which occupy the side next the sclera, and radial fibres, which pass Fig. 155. — Section through the ciliary region of a hypermetropic eye. Ivanof. from the point of origin to the hypothenuse ; the circular fibres of Muller's muscle lie next to the base of the triangle, and are concentrically arranged. In highly myopic eyes the meridional and radial fibres Fio. l.'O.— Sfction through the ciliary region of a myopic eye. Ivanof. are strongly developed (Fig. 156), while the circular fibres are icaroely seen, and the angle of the ciliary body at the point of origin is changed from a right to an acute angle. 342 MANUAL OF HISTOLOGY. In very hypermetropic eyes, on the contrary, tlie circular fibres are abundantly developed (Fig. 155), the meridional fibres are shorter, while the angle at the point of origin of the mus- cle becomes somewhat obtuse, so that by these changes one can determine, even in a microscopic section, what considerable refractive error the eyes have had. The meridional fibres are either prolonged some distance into the stroma of the choroid and end in a delicate fringe, or they terminate at the anterior and outer layers of this mem- brane in stellate knots with fine anastomosing branches. The radial fibres form a looser network than the last, but also have the same terminal interlacement of their fibres ; the circular fibres form fewer anastomoses, and only those bundles which lie next to the radial fibres are extensively connected with them. The nerves of the ciliary body are derived from the plexus formed in its stroma by the ciliary nerves ; the vessels are largely supplied from the circulus iridis major, lying in the an- terior part of the body. The iris arises from the anterior side of the ciliary body, and from the connective tissue surrounding the fibres of the ciliary muscle ; it is also attached to the cornea and sclera by the ligamentum pectinatum. (See Fig. 153). It consists of a loose connective-tissue stroma, which sup- ports a rich vascular network, a complete muscular structure, and the nerves. It is covered anteriorly by a continuation of the endothelium of the cornea, and posteriorly by a thick layer of pigment-cells continuous with those which line the ciliaiy body. The vessels arise from the circulus, have adventitial coats which are thick in proportion to their calibre, and pass radially to the margin of the pupil, where they form a network of fine capillaries, the circulus arteriosus iridis minor, ending final- ly in veins which return in the same general direction as the arteries, but lie beneath them, emptying finally into the venaB vorticosre. Near the margin of the pupil, and forming a ring about it 1 mm. in breadth by TV mm. in thickness, is the sphincter muscle of the iris. It is composed of unstriped muscular tissue, and is situated in the posterior portion of the iris. The dilator muscle, at its inner border, is in close connection with the sphincter, and its fibres run radially to the periphery THE EYE. 343 of the iris, where they are woven into a thick anastomosing circle. The nerves of the iris are derived from the ciliary plexus ; at the periphery they divide and scatter in various directions : the pale fibres to the posterior layers, forming a fine network about the dilator muscle; the fibres with a medullary sheath to the anterior portion ; another set supplies the sphincter muscle — these being, in the order of description, the branches possibly of the sympathetic, sensory, and of the third pair. The posterior surface of the iris, which, near the pupil, rests upon the anterior capsule of the lens, is covered with a thick layer of densely pigmented cells, the uvea, which can rarely be so separated as to determine their shape, and which appear to have no distinct limiting membrane behind them. This layer extends from the pupil, where it meets the endo- thelium of the anterior surface, back to the pigment of the ciliary body, with which it is continuous and from which it can be distinguished by having no connective tissue covering it. The pigmented cells, which are more or less thickly scat- tered through the stroma of the iris, determine the color of the anterior surface. Transverse sections through the sclera and choroid are best made from eyes hardened in Mailer' s fluid. An eye which has been injected with colored gelatine, introduced through the aorta after that vessel has been tied beyond the carotids, will show the fine meshes of the chorio-capillaris, when the pigment- layer covering the choroid has been brushed away under gly- cerine. Such injections are best made on albinotic rabbits. Good sections of the ciliary body can be made from eyes hardened in alcohol or M tiller's fluid, and the blood-vessels can be easily seen in injected specimens. The muscular tissue of tliis body and the iris may be examined in specimens treated with a 30 to 40 per cent, solution of potash. Carmine may then be used to color. The vessels of the iris, are best seen in the eyes of a young albino rabbit, injected with colored glycerine or Berlin blue. The retina lines the whole inner surface of the choroid as far as the ora serrata ; it is composed of nervous elements, connective tissue, and blood-vessels. The following division into well-marked layers from within outward has been generally adopted. (See Fig. 157). 344 MANUAL OF HISTOLOGY. k S. a, menibrana limitans interna. b, optic nerve fibre-layer. c, ganglion-cell layer. d, inner granular layer. e, inner nuclear layer. /, outer granular layer. g, outer nuclear layer. 7i, menibrana limitans externa. /, layer of rods and cones. Pigment layer. The fibres of the optic nerve generally lose their medullary sheath at the lamina cribrosa, and proceed thence as naked axis-cylinders through the opening in the choroid to the level of the retina, where they spread over its entire in- ner surface to form the nerve-fibre layer, which is thick in the vicinity of the nerve, but gradually decreases as it approaches the ora serrata, where it ends. At the macula lutea the fibres do not form a distinct layer, but, curving toward this spot from above and below, are lost in the layer of ganglion-cells, either entering them or passing on to the inner granular layer. The ganglion-cell layer consists of large branching cells in most places but one row deep, though near the macula there may be two or more layers. They are very transparent, have no visible cell-wall, and are provided with a varying number of pro- jecting arms ; when fresh they contain fine granular matter with a clear, large nuclei and nucleoli, and appear finely fibrillated. They receive an axis-cylinder on their inner side, and on the outer send out branches which ultimately divide into fine fibrillaB, and are lost at the inner granular layer in a tangled network. It is probable, however, that some of these fibres are connected with the cells of the inner nuclear layer. The inner granular layer partly surrounds the ganglion- f. Fig. 157. — Transverse sec- tion of the ret iua. After Ze- hender. THE EYE. 345 cells and forms a sort of spongy network between these and the inner nuclear layer ; its composition is still a matter of doubt, but it appears to be made up of a more or less homo- geneous substance, in which are numerous fine openings filled with some material of a peculiar refractive power. It does not belong to the nervous substance of the retina, and when placed in a 10 per cent, solution of common salt, dissolves, leaving the supporting connective-tissue fibres unaffected. The inner nuclear layer is made up of numerous oval cells with large nuclei ; they belong mostly to the nervous tissue, but scattered among them are also cells of the supporting con- nective-tissue framework. The nerve-cells resemble small bipolar ganglion-cells, hav- ing two fine processes, the inner of which probably connects with the ganglion-cell layer, or directly with the optic nerve fibres. Near the macula these cells are more numerous ; to- ward the ora serrata they gradually decrease in number. Next comes the outer granular layer, a thin stratum re- sembling the inner in appearance and composition ; here the fine fibres from the outer and inner nuclear layers become lost in a tangled mass. Between this layer and the membrana llmitans externa is the older layer of nuclei, made up of a number of oval cells, connected more or less closely with the inner ends of the rods and cones. The larger nerve-fibres, which pass through the outer gran- ular layer, are joined to the nuclei of the cones, which lie di- rectly within the membrana limitans and are connected to a prolongation of the base of the cones themselves. The smaller fibres pass to the nuclei of the rods, which form an irregular layer at varying distances from the limiting membrane, and from which fine tangled fibres pass to the base of the rods. These nuclei resemble those of the inner layer; they con- tain a small amount of granular matter with a nucleus and nu- cleoliis, and sometimes exhibit, as the result of post-mortem changes, peculiar transverse stripes. Directly beyond the membrana limitans externa, and rest- ing upon it, are the rods and cones, each composed of an outer and inner member. The rods are small, cylindrical bodies of high refractive power ; When fresh they appear homogeneous, but with the 346 MANUAL OF HISTOLOGY. beginning of decomposition, which occurs very quickly, the inner half appears us if filled with a finely granular substance, while the outer exhibits transverse striations, and finally breaks up into small disks, which can only be distinguished from those of the outer segment of the cones by their red color (visual purple of Kuhne), which soon fades on exposure to light. The inner segment of the cones is larger than that of the rods ; it tapers rapidly toward the outer part, where it is filled with a peculiar oval-shaped body ; the outer segment does not equal that of the rods in height, but divides into similar disks. The pigment-layer, in which the ends of the rods and cones are imbedded, consists of a single layer of hexagonal cells, more densely pigmented in the part next the retina, and by some observers said to be provided with fine processes, which are lodged between the rods and cones. This pigment is more dense at the macula and varies with the color of the person, being most abundant in negroes, wrhereas it is absent in albi- nos ; from this layer, according to Kuhne, the visual purple of the rods is reproduced. At the macula lutea, which is situated a little to the outer side of the entrance of the optic nerve, the ganglion-cell and inner nuclear layers have their greatest thickness. The fibres which pass from the outer granular to the outer nuclear layer are lengthened and run in a more horizontal direction toward the fovea, which forms a slight depression in the centre of the macula. Over this fovea the layers of nerve-fibres and ganglion-cells are absent, and the other laminae become so much thinned that the membrana limitans interna approaches nearly to the nuclear layer; the rods are also absent, and the cones be- come lengthened and slightly convergent. The membrana limitans interna lies between the retina and vitreous body ; it is a transparent homogeneous structure, and from its outer surface spring the connective-tissue fibres which form the supporting framework for the nervous part of the retina. These fibres arise in the form of thin fenestrated plates, connected together by numerous arms ; they soon contract, however, to smaller radiating bands, which surround the gan- glion-cells and pass on to the inner nuclear layer, where they THE EYE. 347 contain occasional nuclei. From this point they again ex- pand into broader sheets, which, after surrounding the outer nuclei, are united to form the membrana limitans externa. This membrane lies just at the base of the rods and cones, and it is provided with numerous holes, through which those struc- tures pass ; from its outer surface fibres extend up between the rods and cones to form supporting sheaths. The blood-vessels of the retina come from the arteria cen- tralis retinas, which usually divides into two or more branches at the entrance of the optic nerve ; these vessels lie in the layer of nerve-fibres, and, arching above and below the macula, give off numerous fine branches, from which capillaries penetrate as far as the inner nuclear layer. The larger retinal vessels are surrounded by lymph-spaces, which probably unite with those of the optic nerve. At the periphery the retina becomes much thinned, and at the ora serrata the nervous elements are discontinued, the con- nective tissue alone being prolonged over the ciliary body to its anterior angle, thus forming tliQpars ciliaris retinas. This membrane consists of long cylindrical cells of varying shapes ; they rest on the pigment and are covered by a thin stratum, which sends processes between them and seems to be a prolongation of the membrana limitans interna of the retina. It is very difficult to prepare good sections of the retina, but the following plan is recommended : enucleate with care the eye of a frog or some small animal, and immediately sus- pend it in a well-stoppered bottle containing a small bit of solid osmic acid : when sufficiently hard the posterior portion of the eye can be cut in pieces and sections made by imbed- ding or holding between pieces of liver. Another method is to place the eye unopened in Midler' s fluid for some two weeks, frequently changing the fluid ; af- terward harden in alcohol. Sections may then be made in the same manner as before. To obtain the separate constituents, place a fresh retina in a TV per cent, aqueous solution of osmic acid for fourteen days, then in glycerine for seventeen days; after this, place a small piece on a slide in glycerine, with the cover-glass so arranged that no pressure is made ii]>.), while the lower lip is called labium tympanieum (Fig. 163, Lt.)\ the space between the two lips has received the name of recessus interims. The crista spiralis is divided by a number of parallel furrows, which gives the surface a regular toothed appearance when seen from the vestibular surface. Hence, the portions between the furrows are called "auditory teeth." The under (vestibular) of the two lips is connected with the membrana basilaris (Fig. 163, Hn, Zp'\ which is com- posed of two layers of finely fibrillated connective tissue, and is covered on its tympanic surface by a layer of endothe- lium, and on the surface turned toward the ductus cochlearis by the organ of Corti and its supporting cells. The inner layer of this fine connective tissue is directly continued into the bases of the pillars of the organ of Corti next to be de- scribed. The organ of Corti, so named from its discoverer, is a com- plicated arrangement of cells in which the nerve terminates, and of other cells and their modifications, which apparently act as supports to these and as modifiers of the sound. The cells proper, in which the nerve terminates, have received the name of hair-cells, from the ciliated appendages which they carry (Fig. 163, a, a", a", «"), while the peculiar modified cells which are their chief support are called the pillars. The pillars (Fig. 163, ft, fa) are two slender, slightly shaped bodies, of a finely fibrillated structure, showing, however, in their early stages, the presence of nuclei. They stand upon the membrana basilaris, and are apparently to be directly fol- lowed into the fine layer of connective tissue beneath them. They are arranged in two rows, named inner and outer, ac- cording to their situation as regards the modiolus. The pillars are inclined toward each other, and the space between them is named the tunnel. The head of the outer is a little enlarged THE EAR. 3()5 and rounded, lying in a shallow depression in the head of the inner pillar, thus resembling a ball and socket-joint (Fig. 163, gia). The heads of the pillars, when seen from the surface, have Pio. 168. Section through the ductus cochlearia of a young dog: ,/f-r', IteiRsner'n membrane; /.o* and Lo ', vestibular and tympanic platen of the onseous lamina; gup, ganglion spiriiW- ; n, fine nerveB pawing through the babasmla perforata at J/n ; O, crista spiralis; Lo, Its vestibula or upper lip; rm. Ml. m'. the membrans) tcetoria (Corti's membrane; ; S*ni, recessus internus clothed with epithe- lium ; fl and/a, inner and outer pilar* of Oortl, a and n", a", a", inner and outer hair-cells, between the latter arc hor-n the M.ick -haped cell*, r. r. r ; Tn. nerve passing through the tunnel to reach one of the outer hair-cell* : I/z. Henson's prop will : 8p, Zp' zona pectifiata ; giU, inner and outer heads of the pillars of CortJ : ft//, plate called phalvox, which, when joined with its neighbor*, forms the lumina reti- cularis, in which the ends of the hair-cells an; supported; L>>p, ligainuutuin spirale ; Hv, stria vascu- laris. After Lavduwsky. 366 MANUAL OF HISTOLOGY. prolongations shaped a little like the bones of the lingers, and hence called phalanges (Fig. 163, Kp). These enclose spaces be- tween them, through which the ends of the hair-cells project. The network thus formed is called the lamina reticularis, and gives a very peculiar appearance when this portion of the organ is viewed from above. Corresponding to the pillars are rows of hair-cells termed inner and outer — a single row of the former (Fig. 163, a) and four rows of the latter (Fig. 1 63, a", a", a"). The shape of the cells of the inner row is cylindrical, having their base pro- longed into a fine thread expanding into a foot-stalk, which passes into the membrana basilaris. The top of the cell which passes through the opening in the lamina reticularis is pro- vided with fine cilia. The four rows of cells in connection with the outer pillar are of the same shape as those of the inner row, but, in addition, are joined at their lower part to peculiar cells shaped like a flask, large and rounded at the bottom, and tapering to a long and narrow neck. The tops of these cells reach to the lamina reticularis, but do not pass through it (Fig. 163, r, r, r, and b). Immediately adjoining the outer rows of hair-cells are several rows of cylindrical epithelial cells (Hen- son's prop-cells) (Fig. 163, Hz), which pass gradually into the short cubical epithelium forming the zona pectinata (Fig. 163, Zp to Zp') adjoining the epithelial lining of the ductus cochle- aris. The course of the nerve has already been followed to the ganglion spirale. From this point a number of fine trunks pass through a canal in the osseous portion of the lamina spi- ralis to the lower lip of the crista, which they leave as naked axis-cylinders by a number of small holes, called the habenula perforata (Fig. 163, Hn). After entering the ductus cochle- ars they divide into two chief bundles, one distributed to the inner hair-cells, and the other, passing between the bases of the inner pillars, crosses the tunnel and then again passes be- tween the outer pillars, and terminates finally in the outer hair-cells. Beyond the fact that they apply themselves directly to the surface of the hair-cells, their mode of ultimate ending is not known. From the upper edge of the crista spiralis, lying directly upon it and covering the whole of the organ of Corti, is the membrana tectoria (Corti' s membrane) (Fig. 163, Mt), a homo- BIBLIOGRAPHY. 367 geueous mass in which indistinct striations are to be seen. This is of the nature of a cuticular formation, and probably acts as a damper, preventing excessive vibrations of the organ of Corti. BIBLIOGRAPHY. Ruedlnger. The Eustachian Tube, etc. Strieker's Histology, New York. 1872. Trautmann. Der gelbe Fleck am Ende des Hammergriffes. Arch. f. Ohrenheilk. , Vol. XI., p. 99. 1876. Urbantschitsch. Zur Anat. d. Gehorknochelchen des Menchen. Arch. f. Ohren- heilk., VoL XL, p. 1. 1876. Politzkr. Ueber Anastoraosen d. Gefassbezirk d. Mittelohres u. d. Labyrinths. Arch. f. Ohrenh., Vol. XL, p. 237, 1877, and Wien. med. Woch., No. 30. 1876. Ueber-Liel. Die Membrana tympani secundaria. Monatsschr. f. Ohrenheilkunde, No. 4. 1876. L.wdowsky. Ueber d. akust. Endapparat d. Saugethiere. Arch. f. mikros. Anat., Vol. XIII. , p. 417. 1877. Kuhn. Untersuch. liber den hautigen Labyrinth der Knochenfische. Arch. f. mikr. Anat., Vol. XIV., p. 204. 1877. Moldenhauer. Beitr. zur. Anat. u. Entwickel. d. Menschl. Gehororganes. Arch. f. Ohrenheilkunde, Vol. XL, p. 225. 1877. Doran. Morphology of the Mammalian Ossicula Auditus. Trans. Linn. Soc. , London, Second series, Vol. I. 1877. Ueber-Liel. Der Aqueductua cochleae beim Menschen. Monatsschr. f. Ohrenheilk., Vol. XIII., No. 3, p. 33, 1878-79, and Virch. Arch., Vol. LXXVIL, p. 207, 1879; also Arch. f. Anat. u. Phys., Phys. Abtheilung, p. 188. 1878. Cisoff. Ueber d. Gehorlabyrinth d. Knorpelfische. Sitz. d. Naturf. Gesellsch. an d. K. Universit. zu Kasan. May, 1879. (Russian.) Pritciiard. The Organ of Corti in Mammals. The Lancet, 1876, p. 552, and Proc. Roy. Soc, Vol. XXIV., No. 168, p. 346, 1878 ; also The Termination of the Nerves in the Vestibule and Semicircular Canals of Mammals. Quart. Journ. Micros. Sc , New Series, No. 64, VoL XXI., p. 398 1879. Minot, C. S. Recent Investigations of the Histology of the Scala Media Cochleae. American Journal of Otology. April, 1881. PART III. CHAPTER XXII. THE NASAL FOSS^, PHARYNX, AND TONSILS. By D. BRYSON DELAVAN, M.D. Curator of the New York Hospital, New York City ; Member of the American Laryn- gological Association. The vestibulum nasi is that part of the nasal canal which is surrounded by the anterior cartilages of the nose. It is cov- ered by a continuation of the exterior skin, which gradually assumes the characteristics of a mucous membrane and pos- sesses several layers of pavement-epithelium, the uppermost of which is composed of horny cells. This epithelium extends backward to the anterior margin of the inferior turbinated bone and the commencement of the inferior nasal duct, where it becomes ciliated. The integument has also vascular papillae, with both simple and compound loops, and in the lower part of the nose long, stiff hairs (vibrissa?), as well as large sebaceous follicles. It is sparingly supplied with blood-vessels. The nerves are derived from the trigeminus, and consist of fila- ments, which probably end in terminal bulbs. The respiratory region. — The nasal fossae proper, with the exception of a limited part known as the olfactory region, may be regarded as a continuation of the respiratory tract. Each fossa communicates with four sinuses : the frontal, the sphe- noidal, the maxillary or antrum Highmorianum, and the pos- terior ethmoidal. The mucous membrane covering the respira- tory region and its accessory sinuses is called the Schneiderian or pituitary membrane. It is devoid of papilla?, and is covered with a cylindrical ciliated epithelium, like that of the trachea, THE NASAL FOSS.E, PHARYNX, AND TONSILS. 369 the ciliary current being invariably toward the choanse (poste- rior nares). It contains, also, goblet-cells. Under the epithe- lium is a true membrana mucosa, which forms at the same time a periosteum for the bones, and is composed almost en- tirely of connective tissue, scantily permeated, if at all, with elastic tissue-elements. The mucous membrane may be divided into two varieties : a thinner membrane, covering the internal surface of the turbinated bones and the accessory sinuses, and the thicker membrane of the nasal fossse proper. The thinner membrane contains many acinous glands. In the adjacent cavities they are less abundant, excepting upon the internal wall of the maxillary sinus. Here, and in the sphenoidal sinus, the glands consist of several cylindrical tubes with connecting single oblong acini. The epithelium of the latter is pyriform, while in the tubes it is cylindrical. The mucous membrane itself is pale in color, and scantily supplied with blood-vessels. Special nerve- terminations have been de- scribed in these sinuses. These are probably nothing more than terminations of fibres from the great sympathetic, having at their extremities ganglionic cellules. The thicker membrane covers the lower part of the nasal septum and the inferior and middle turbinated bones. It is lined with the same ciliated epithelium, and in the anterior two- thirds of the turbinated bones forms only a delicate, slightly corrugated covering for the subjacent parts. Poste- riorly, however, its surface is thrown into numerous thick folds, evidently designed to increase the extent of surface of the mucous membrane. The membrana mucosa forms a fibrous network, which passes between the glands and vessels and connects the mu- cous membrane with the periosteum. Its characteristics re- semble more nearly those of periosteum, so that it may properly be classed as a part of the latter. The glands of this region vary somewhat from the acinous type, and are composed of tortuous tubules, having many sinuses and oblong offshoots. They are lined on their inner surface with low cylindrical epi- thelium, and sometimes assume a circular, sometimes an oval or tubular shape in the microscopic section. The thickness of the pituitary mucous membrane is due not only to its mucous glands, but more particularly to the existence in it of true erec- tile tissue, as well as venous plexuses. (See p. 160). These are 24 370 MANUAL OF HISTOLOGY. most abundant at the posterior extremity of the inferior tur- binated bones. Some of these vessels are prolonged throughout the continuity of the bone on the lateral as well as the median side, to appear with greater frequency at the anterior extrem- ity, without, however, regaining the number or size which they possessed at their origin. Where they are less numerous the remaining space is almost entirely occupied by large mucous glands. In the bony framework of the inferior turbinated bone, large, bright interspaces are seen in the fine trabecular substance, which are filled with fibrous tissue containing pale lymphoid cells. In this fibrous tissue are usually found transverse sec- tions of delicate vessels, the walls of which are apparently composed of fibrous tissue. In order to reach the outer sur- face these vessels either perforate the bone or lie in recesses separated from the soft parts only by the j->eriosteum. In the middle three-fifths of the bone, where the osseous structure contains the largest cavities, we find in the vicinity of the ves- sels large, round, and polygonal, glistening cells, analogous to marrow-cells. A recent author believes most of the above- mentioned vessels to be lymphatics. The arteries of the infe- rior turbinated bone do not number more than three or four, and are derived from the posterior nasal artery. TJie olfactory region is situated in the uppermost portion of the nasal cavity. Its inferior limit in man has not yet been accurately determined. According to the generally received views of Schultze and Ecker, it is probably limited to the roof of the nasal fossas, the superior turbinated bone, and the cor- responding part of the septum. The mucous membrane of this region is of a dull, yellowish brown color, and is perceptibly thicker and softer than that of the respiratory region. This color proceeds from fine pigment-molecules, which are em- bedded partly in the bodies of the cylindrical epithelial cells, and partly in the cells of an especial gland-formation found here. Soon after death, however, it becomes unrecognizable. Under the microscope the olfactory region is seen to be bound- ed by a tolerably well-defined, serrated border, although isl- ands of ciliated epithelium, such as is found in the respira- tory region, are frequently found scattered about in different parts of it. The differences of structure in the olfactory mu- cous membrane depend upon the character of the epithelium, THE NASAL F0SS.E, PHARYNX, AND TONSILS. 371 the occurrence of peculiarly constructed glands — Bowman's glands — and upon the relations of the nerves. The fundamental layer of the mucous membrane is com- posed of a finely fibrillated connective tissue, rich in cells, the arrangement of which is determined by the numerously dis- tributed glands, nerves, and vessels which it contains. As in the other regions of the nasal cavity, the mucosa seems to pass, without a well-defined limit, into the periosteum. In many places aggregations of small pigmented nuclei are found, some in the shape of long strips tying near the nerve-branches, some in other situations, in rounded or irregular groups. The olfactory epithelium attains a considerable thickness. It consists of a single layer of very elongated cells, which Schultze has proved to be of two kinds, epithelial cells and olfactory cells. The olfactory cells are slender, delicate structures, in which may be distinguished a cell-body and two prolongations going in opposite directions — the one to the periphery, the other cen- trally. The bodies of the olfactory cells are not all located in the same plane of the epithelial stratum. The majority, how- ever, occupy its deeper portions. The cell-body appears spin- dle-shaped or pyriform. It is finely granulated, and has in its central and widest portion a spherical, light-colored, ill-de- fined nucleus. The peripheral prolongation is generally rod- shaped, but now and then presents slight sinuosities. It is sharply outlined and homogeneous, and its free extremity, in some animals (amphibia and birds), has a tuft of the most deli- cate hairs, which project above the surface of the epithelium. In man this is not the case. The opposite prolongation is ex- tremely delicate and perishable, and, by some methods of preparation, resembles the finest nerve-fibrils, sometimes cov- ered with varicosities, at others entirely smooth. It runs con- tinuously and undivided as far as the base of the epithelial stratum, where it appears to meet the final radiations of the olfactory nerve, partly intertwines with these radiations, and then escapee further investigation. The indifferent epithelial cells appear in the form of an elongated cylinder with a very fine, granulated cell-body and an ellipsoid nucleus. Near the latter the cell suddenly con- tract- into a slender, very pale, centrally directed prolongation, the inferior end of which becomes somewhat wide)' and 372 MANUAL OF HISTOLOGY. brandies into a number of delicate filaments, by means of which the cell is attached to the fundamental layer of connec- tive tissue. These widened extremities of the cells often con- tain a brownish, partly nuclear, partly diffused pigment. Viewed upon the plane surface, the number of olfactory cells is apparently larger than that of the cylindrical cells. Each one of the latter, however, is generally surrounded by six of the olfactory cells, which completely fill the intermediary spaces between the cylindrical bodies. Both varieties of cells are so accurately adjusted to each other that, especially in the wider portion of the epithelial cells, fine longitudinal furrows may be seen, into which the peripheral continuations of the olfactory cells have been received. The surface of the epithelium is covered by a delicate mem- brane, discovered by Yon Brunn, and called by him the mem- brana limitans olfactoria. He has compared it to the membrana limitans externa of the retina, and describes its free surface as being plane and even, while its lower surface covers completely the rounded terminations of the epithelial cells. The periph- eral prolongations of the olfactory cells pass through this membrane, and terminate with bare extremities at the level of its free plane. The olfactory nerves. — The brandies from the olfactory ganglia which emerge through the apertures of the lamina cri- brosa are composed entirely of non-medullated filaments, which resemble embryonic nerve-fibres. They next anastomose in the deeper layers of the mucous membrane, and form a dense plexiform meshwork, which sends fine branches toward the surface. In these branches the axis-cylinders are broken up into numerous, very fine, varicose fibrils, which ascend to the limit of the epithelial layer, where they are lost. Most au- thors agree with Schultze that there is a distinct connection between the nerve-fibrils and the olfactory cells. Exner be- lieves that the nerve-fibrils connect with the epithelial cells also. He argues, moreover, that intermediary forms, between the two varieties of epithelium, are found, which would prove that they are not different structures, but one and the same. Neither of these views has yet been established. Bowman'' s glands, peculiar to the olfactory mucous mem-, brane, are found in it in large numbers. They occupy almost the whole thickness of the mucous membrane, their bodies be- THE NASAL FOSSiE, PHARYNX, AND TONSILS. 373 ing located in the deeper layers of the connective tissue. In man their shape varies somewhat from that of simple tubules, as several glandular tubes ordinarily unite in a common excre- tory duct, so that, in some cases, the gland almost appears racemose. The glandular cells are partly round, partly irreg- ular in shape, and have many pale nuclei, together with a brownish-colored pigment. THE PHARYNX. The mucous membrane of the phaiynx is, in general, simi- lar to that of the mouth. It consists essentially of a stratified pavement-epithelium, a rather loosely woven submucosa, which contains aggregations of mucous glandules, and a tunica pro- pria composed of fibrillary connective tissue and furnished with papillae. The papillae are smaller than those found lower down in the oesophagus. The mucous glandules are most abundant in the superior part of the pharynx. The mucous membrane of the vault of the pharynx, and in the vicinity of the isthmus of the fauces, where it becomes continuous with the mucous membrane of the nasal cavity, to some extent assumes the characteristics of the latter. In this region the connective tissue is more or less thickly interspersed with lymphoid cells. It is provided, moreover, with ciliated cylindrical epithelium. In adults this epithelium extends some distance backward until it passes into the stratified pavement variety. In children, however, ciliated epithelium lines the whole naso-pharynx. In the upper and lateral parts of the pharynx are fonnd cer- tain aggregations of adenoid tissue, most abundantly in the vault of the pharynx, extending from one Eustachian tube to the other. This tissue is generalry quite diffuse, but is identi- cal in its structure with the lingual follicular glands and with the tonsils, and from this resemblance it has derived the name "pharyngeal tonsil." THE TONSILS. The tonsil consist s essentially of a reduplication, more or less extensive, of the oral mucous membrane, containing in its folds an abundance of the so-called adenoid tissue 374 MANUAL OF HISTOLOGY. Its gross structure varies in different animals. In some the organ is entirely absent. Its simplest form is found in the rab- bit, where it resembles a large lingual follicular gland. In man its usual shape is ovoid. Its average vertical diameter is 20 mm., and its transverse diameter 13 mm. Its surface is per- forated by a varying number of slit-like and circular depres- sions, the common orifices of the system of cavities which it contains. If the tonsil of the rabbit be considered a single follicular gland, we have in man a multiplication of this to the number of from eight to eighteen, the interval between each gland forming a "lacuna tonsillaris," crypt, or one of the sys- tem of cavities mentioned above. There are also in the interior of the tonsil single larger cavities, each of which includes sev- eral follicular folds and procures their common discharge at the periphery. The crypts generally are filled, more or less, with a yellowish substance composed of fat-molecules, detached pavement-epithelium, lymph-corpuscles, small molecular gran- ules, and cholesterin-crystals, which probably proceed from retained and decomposed epithelial matter, and perhaps now and then from the bursting of follicles whose cells have in- creased by proliferation and have undergone retrograde meta- morphosis and fatty degeneration. In its minute anatomy the tonsil is for the most part like other so-called adenoid glands. In common with the rest of the oral cavity, it is invested with a thick covering of pavement-epithelium, which rests upon a delicate endothelioid basement-membrane. Following this is a tolerably compact mucosa, formed of interlacing bands of fibrous connective tissue and containing many connective-tis- sue corpuscles. In the normal adult tonsil this structure is so delicate that sometimes it is hardly recognizable. From it bands of connective tissue extend centrally into the larger ton- sillary folds, and the whole forms essentially both an enclosure and a framework for the adenoid tissue or proper substance of the gland, as well as a nidus for its vessels. The minute struc- ture of the adenoid tissue of the tonsil does not differ from that of other follicular glands (those of the intestine, etc.), de- scribed elsewhere. Occasionally, in the tonsil the adenoid tis- sue extends so near the periphery as to penetrate the mucosa and encroach upon the epithelial layers. This is especially the case in the walls of the crypts, where the epithelium com- monly exists in a modified form, or is altogether wanting. The BIBLIOGRAPHY. 375 tonsil is supplied abundantly with racemose mucous glands, which are most numerous in the neighborhood of the hilus. Here, also, may be found small bundles of muscular fibres apparently independent. BIBLIOGRAPHY. Kolliker. Ueber das Geruchsorgan von Amphioxus. Muller's Archiv fur Anat. und Physiol. 1843. Kohlkatjsch. J. Muller's Archiv, pp. 8, 149. 1853. Ecker. In Berichte iiber die Verhandlungen zur Beforderung der Naturwiss. No. 12. Fribourg, 1855. Schulze, Max. Ueber die Endigungsweise der Geruchsnerven und die Epithelial- gebilde der Nasenschleimhaut. Monatsberichte der konigl. Acad, der Wis- sensch. Berlin, 1856. Ecker. Ueber die Geruchsschleimhaut des Menschen. Zeitschrift f . wiss. Zoologie. YIIL, p. 305. 1856. Ecker, A. Bericht iiber die Fortschritte, Anatomie und Physiologie f. d. Jahr 1856, p. 117. Von Henle und Meissner. Todd and Bowman. The Physiological Anatomy of Man. II. London, 1856. Seeberg. Disquisitiones Microscopicse de textura membranae pituitariae nasi. Diss. Inaug. Dorpati, 1856. K5lliker. Ausbreitung der Nerven in der Geruchsschleimhaut von Plagiostomen. Sitzber. der physik.-med. Gesellschaft, T. VIII. , pp. 31. Wiirtzburg, 1857. Ericiisen. De textura nervi olfactorii ejusque ramorum. Th. inaug. Dorpat, 1857. Hoyer. De tunicae mucosas narium structura. Berolini, 1857. Eckrardt. Ueber Endigungsweise der Geruchsnerven. Beitrag zur Anatomie und Physiologie. 4. Abhand., p. 97. 1858. Gastaldi. Nuovi Ricerche sopra la terminazione del nervo olfactorio, in memorie de l'Acad. reale della Scienza de Torino. XVII., p. 372. 1858. Fcnke, O. Lehrbuch der Physiologie. 2. Auflage. 1858. Kolliker. Handbuch der Gewebelehre. 3. Auflage, p. 680. 1859. Hoyer. Ueber die mikroskopischen Verhaltnisse der Nasenschleimhaut. In Muller's Archiv f. Anat. und Physiolog., 1861, p. 287 ; 1860, p. 6. Clarke, Lockhart. Ueber den Bau des Bulbus olfactorius und der Geruchs- schleimhaut. Zeitsch. f. wissens. Zoologie. XL 1862. Walter, G. Ueber den feineren Bau des Bulbus olfactorius. Virchow's Arch., T. XXII., p. 261. 1862. Hi.'.r.i:. Handbuch der systematischen Anatomie des Menschen. Bd. II. Braun- schweig, 1860. Zeknoff. Ueber das Geruchsorgan der Cephalopodon. Bull, de la Soc. imp. dea bc. nat de Moscow. 2e serie. XLII. 1869. Exner. Weitere Studien iiber die Structur der Riechschleimhaut bei Wirbelthie- ren. Sitzungsberichte der k. Akad. der Wissenschaften. Wien. Band LXV. 3. Abth. 1872. Et Bd. LIII. 1867-1869. 376 MANUAL OF HISTOLOGY. Heideniiain, A. Ueber die acinosen Driisen der Schleimhiiute, ins besondere der Nasenschleimhaut. Diss. Inaug. Breslau, 1870. Sciiulze, Max. Untersuchungen iiber den Bau der Nasenschleimhaut. InAbhand- lung. d. naturforscb. Gesellscbaft. VII. Halle, 1872. Babuciiin. Das Geruchsorgan. In Strieker's Ilandbucb. 1872. Mahtin. Studies from the Physiol. Lab. in the University of Cambridge. L 1873. Cisoff. Zur Kenntniss der Regio Olfactoria. Centralblatt. 1874. Bigelow, H. J. On tbe Anat. of the Turbinated Corpora Cavernosa. Boston, Med. and Surg. Journal. April, 25, 1875. Shofield, R. N. A. Taste-Goblets in tbe Epiglottis of the Dog and Cat. Journal of Anat. and Physiol. X. , p. 475. 187G. Honigsciimied. Ztschr. f. wiss. Zool. XXIX., S. 255. 1877. Davis, C. Die becherformigen Organe des Kehlkopfes. Arch. f. mikroskop. Anat., XIV., S. 158. 1877. Podwisotzky. Anatomische Untersuchungen iiber die Zungendriisen des Menschen und der Saugethiere. Inaugural Dissertation. Dorpat, 1878. LciWE. Beitrage zur Anatomie der Nase und Mundhohle. S. 20. Berlin, 1878. Zuckerkandl. Ueber die norm, med.-path. Anat. der Nasen- und angrenzenden Hohlen. All. Wien. med. Ztg., No. 51. 1879. Steinbrugge, H. The Histology of the Inferior Turbinated Bones and of the Tel- angiectatic Fibromata ArisiDg from These. Archives of Otology, New York, Oct., 1879. CHAPTER XXIII. THE MOUTH AND TONGUE. Bt d. bryson delavan, m.d. Curator of the New York Hospital, New York City ; Member of the American Laryn- gological Association. With the exception of a few remarkable modifications, the structure of the mucous membrane of the buccal cavity is the same throughout. The tunica propria consists of fibrillated connective tissue, made up of tolerably minute bundles of intertwining filaments. Between these appear many delicate, elastic fibres. Toward the epithelium this structure becomes less distinct, and an ex- ceedingly delicate, filamentous network is developed. The con- nective-tissue cells with their nuclei, on the other hand, become more marked. The surface of the tunica propria contains many slender papilla?, which penetrate more or less deeply into the epithelial covering. They have, also, the above-men- tioned filamentous structure, but contain few cellular elements. The transition of the tunica propria into submucous connec- tive tissue is, in general, hardly perceptible. The latter, how- ever, contains fewer elastic filaments and broader bundles of connective tissue. The epithelium lining the buccal cavity is, throughout, stratified pavement. The mucous membrane of the mouth varies in different regions as to the thickness of its different strata, the height of its papillae, and the condition of the submucous tissue. It is thickest and firmest in the gums and near the palate — particularly in the posterior section of the hard palate — and thinnest in its reduplications, e.g., the frce- num lingua), glosso-epiglottic fold, and the pillars of the fau- ces. Its firmness in the above places is due to the density of the submucosa, which forms, with the underlying periosteum, one compact mass of connective tissue. 378 MANUAL OF HISTOLOGY. Elsewhere the mucosa is looser, so that the mucous mem- brane is readily thrown into folds. It is thickest wherever it lias intervening layers of glands. In some places, especially in the lips and soft palate, the submucosa is crossed by bun- dles of striped muscular fibres, which are connected partly with the submucosa, and partly with the tunica propria. The papilla of the mucous membrane are most developed at the margin of the lip and its immediate vicinity, as well as on the gums, attaining here a height of 0.5 mm., and often termina- ting in a double point. In the reduplications of the mucous membrane (the fraenum linguae, etc.), and partly in the region of the hard palate, the papillae are very small, sometimes rudi- mentary. The thickness of the epithelial layer is proportion-* ate to the height of the papillae. Beginning at the vermilion border of the lips, and going backward, the epithelial cov- ering becomes progressively thicker, and is thickest at the posterior margin of the lip, decreasing rapidly on the pos- terior surface. Upon the cheeks and on the anterior surface of the hard jDalate the epithelium is of medium thickness ; it is thinnest on the floor of the mouth and on the above- mentioned reduplications. There are, however, deviations in these proportions, especially in the hard palate, where the papillae are in some cases absent. Moreover, the tunica pro- pria sometimes assumes an almost tendinous character. Cer- tain important aggregations of glands, the so-called mucous glandules, are found lodged in the submucous connective tis- sue of the mouth. These are the labial, buccal, palatal, and molar glandules. They are found as white, sharply defined knobs, visible to the naked eye upon the posterior surface of the lips, as well as upon the cheeks, palate, and bottom of the buccal cavity. In some cases they are aggregated into a few large clusters, while in others they are more scattered and smaller. The orifices of their ducts are best seen in the lining membrane by everting the lips or cheek. They belong to the acinous type, and have a short duct, generally somewhat curved, relatively wide, but somewhat contracted at the ori- fice. The greatest width of the tubes is at their place of seg- mentation. On the branches themselves are smaller ramifica- tions, which either terminate directly with globular or ellipsoid alveoli, or previously divide into one or more twigs. It often happens that a small group of acini, with a narrow common THE MOUTH AND TONGUE. 379 duct, situated near a larger duct, discharge into the latter near the surface of the mucous membrane, appearing like a small accessory glandule. The walls of the glandules consist of a structureless basement-membrane, upon the interior surface of which are superimposed cylindrical, clear, almost homogene- ous-looking cells, with oblong nuclei. As for the connection of the buccal mucous membrane with the underlying structures, different conditions obtain in differ- ent regions. Its connection with the hard palate and gums has been described above. Where it is superimposed upon a sharply defined muscle, e.g., over the floor of the mouth, and over the sublingual gland, it j^asses into the connective-tissue sheath of the part. The blood-vessels of the mucous membrane are arranged in two systems of superficially extended networks. The deeper one, located in the submucosa, is composed of the mutually anastomosing branches of the afferent and efferent vessels. From this network many smaller vessels penetrate into the tunica propria, which, by division into still smaller branches, and by frequent anastomoses with one another, form the more superficial and finer-meshed vascular net. In both nets the venous and arterial branches run tolerably parallel. From the superficial network very fine branches enter the papillae, where, according to their size, they form either capillary nets or sim- ple loops. The lympliatlcs form wide networks in the submucosa, and narrow nets in the tunica propria. Single small vessels cross those of the vascular nets. That lymphatics pene- trate the papillae is doubtful. The nerves of the buccal mu- cous membrane form in the submucosa more or less dense plexuses, in which many separations of the single nerve-fibrils may be noticed. Thence numerous filaments, partly isolated, partly arranged in small bundles, and always medullated, ramify, and radiate in wider ramifications toward the super- ficial layers of the mucous membrane. A certain number of nerve-fibrils approach the painllae, to implant themselves either at their bases or at the centre of their apices, some- linns even at their extremities, in the terminal bulbs of Kraust-. Such fibrils are most abundant in the lips and in the anterior surface of the velum palati, and in smaller quantity in the cheek and bottom of the mouth. Nerve-fibrils may some- 3S0 MANUAL OF HISTOLOGY. times be seen also with double contours, which wind, during their course, into a coil in the superficial layers of the mucous membrane. THE TONGUE. Although the mucous membrane of the tongue is, in the general details of its construction, similar to that of the rest of the buccal cavity, it nevertheless presents some striking pecu- liarities, mainly due to the configuration of its upper surface. This is covered by many closely aggregated prominences of the mucous membrane — the lingual papilla — which give it a roughened, fungoid appearance. Upon the under surface of the tongue the papilke are absent, but the mucous membrane here contains a large number of follicular glands. The lateral edges of the tongue are here and there covered with lingual pa- pillae, which are often arranged in rows, and toward the base of the tongue are replaced by the so-called fimbria lingua. Besides simple papillae, analogous to those of the skin, the lin- gual mucosa is studded with three distinct varieties of com- pound papillae — the filiform, the fungiform, and the circum- vallate. These are distinguished from the ordinary papilla3 of the mucous membrane, not only by their large size and their peculiar shapes, but also by their complicated structure, by the arrangement of their secondary papillae, and the conditions of their epithelial coverings. Between these three forms are several intermediary ones. The filiform papilla are found all over the dorsum of the tongue, anterior to the line of the cir- cumvallate papillae. Not only in different individuals, but also in the same tongue, there are marked variations in their form. At the tip and lateral edges of the tongue they are always smaller, and their filaments are wanting or merely ru- dimentary. Toward the centre of the tongue they gradually become larger and more abundant, and attain their highest development in the angle made by the circumvallate papillae. Their shape is that of a truncated cone, which has at its free extremity a central hollow or depression, around which is arranged, in a circular manner, a collection of thread-like pro- jections, or secondary papillae. Like the rest of the mucous membrane of the tongue, they are covered with stratified pave- ment-epithelium. In the secondary papillae of the larger fili- THE MOUTH AND TONGUE. 381 form papillae the epithelium is of the horny variety, and its arrangement is imbricated, the lower margin of each scale over- lapping the upper border of the scale next below it. In the axes of the filiform papillae large-sized arterial and venous capillaries extend. Each secondary papilla contains a vascu- lar loop. The papillae of smallest size contain a fine network of vessels, and in the posterior part of the tongue simple capil- lary loops. Neither the filiform papillae nor their secondary papillae contain nerve-fibrils. The latter are found, however, at the base of the papillae, where they end in rounded terminal bulbs. The fungiform papilla are larger than the filiform, and their epithelial covering is much thinner. They appear as rounded prominences, somewhat constricted at the base, and covered upon the sides and top with many cone-shaped second- ary papillae. The free surface of some fungiform papillae is smooth, the secondary papillae being farther apart. These are found most commonly at the lateral edges of the tongue, and are the so-called lenticular papillae. The distribution of the fungiform papillae is rather irregular, and it varies in different individuals. At the base of the tongue, and generally at its lateral portions, between the filiform papillae, they are some- times scarce and sometimes quite abundant. Toward the tip of the tongue they are smaller, while they are larger in the region of the circumvallate papillae. They are covered with several layers of pavement-epithelium, the deeper strata of which are formed by smaller polygonal prickle-cells. In this epithelial covering, upon the surface of the fungiform papillae, are constantly found peculiar bodies, called the "taste-goblets." The taste-goblets vary in size and shape in different ani- mals, and also in the same animal, according to the locality in which they are found. They usually resemble a short- necked flask, their longest diameter being the longitudinal. The lower part of the taste-goblet rests upon the submucosa ; the body, and more especially the part which corresponds to the neck of the flask, is surrounded by epithelial cells. Every taste-goblet has at the surface of the epithelium an opening called uporus, which word is frequently used not only to des- ignate the exterior opening, but also for the entire short canal in the epithelial layer. The diameter of the porus is from .0064 to .0198 mm. It is surrounded by two and sometimes by 3S2 MANUAL OF HISTOLOGY. three similarly formed cells. Sometimes the poms is formed by a single perforated ceil. The short canal in the epithelial cells is surrounded in like manner. In each taste-goblet two varieties of cells may be distinguished — the exterior or super- ficial cells, called roof- or supporting-cells, and the interior, or central cells, called taste- or rod-cells. The roof-cells, which may be considered as modified epithelial cells, surround the taste-goblets as petals envelop a bud. Their arrangement with relation to one another is imbricated. The cells themselves are long, narrow, spindle-shaped, and curved, and each one has a well-marked nucleus. The peripheral end of the cell is pointed, while the central extremity is sometimes ramified. The taste- or rod-cells are long, slender, and highly refractive. A nucleus of unusual size almost entirely fills their bodies, while their extremities pass into two distinct prolongations — the pe- ripheral or superior, and the central or inferior. The peripheral prolongation is moderately broad, and has a short, delicate extremity, which resembles a small rod or hair. Hence the name rod-cell. These rods are located inside the short canal, and rarely project above the porus. The inferior prolongation is divided into several rootlets. The connection of nerve-fila- ments with the taste-goblets has never yet been conclusively demonstrated, although all authorities agree as to the proba- bility of such connection. Many aggregations of ganglionic cells, of greater or less size, are found in the course of the nerve-bundles, near the circumvallate as well as near the fili- form papillae. In the fungiform papilla3 the nerves enter the axis of the papilla} as small trunks, composed of fibres with double contours. These divide into single nerve-filaments, some of which terminate in bulbs, which are located in the lat- eral surfaces of the fungiform papillae, under the secondary papillae. The fibrils which run into the axis pass into jmle ter- minal filaments, and disappear in a brush-like extremity in a granular mass composed of neurilemma— its nuclei, and nu- merous circular granules — the gustatory granules. These last consist of a globular nucleus, surrounded by a very small amount of cell-protoplasm. The resemblance of the above to the interior roof-cells of the acoustic terminal apparatus, and to the rods and cones of the retina, is striking. The conical or secondary papillae are of the same general construction as the fungiform throughout ; but they present THE MOUTH AND TONGUE. 383 the following differences of appearance : their epithelial cover- ing is thicker, and stratified somewhat after the manner of the filiform papillae, the taste-goblets are absent upon their sur- face, and the nerve-fibres, so far as they can be traced, termi- nate in bulbs. The circumvallate papilla?, about nine in number, are situ- ated at the back part of the tongue. They form an irregular row on each side and incline slightly from before backward toward the median line. At their point of junction is the fora- men caecum of Morgagni. Each circumvallate papilla consists of a broad, flat elevation of the mucous membrane, which is surrounded with a fossa. Its surface is covered with small secondary papillae, and the epithelium is like that of the fungiform papillae. Taste-goblets are found abundantly upon the lateral edges and toward the centre of the papillae. The blood-vessels are arranged as in the fungiform papillae, and each secondary papilla contains a vascular loop. The nerves are derived from the glossopharyngeal. They consist of single pale nerve-fibres, which form a network in the centre of the papillae and ascend toward its peripheral surface. The papillm foliatai, or fimbriae linguae, consist of several folds of the mucous membrane at the lateral edges of the tongue. Between them are scattered a few fungiform papil- lae, and they contain a considerable number of taste-goblets. Many excretory ducts of acinous glands empty at the bases of these folds. The sublingual mucous membrane includes that of the floor of the mouth. Both are of the same structure, and pass into each other by means of a reduplication, the fraenum linguae. The secreting glands of the root of the tongue are of two varieties— serous and mucous. The mucous glands are like those elswhere in the buccal cavity. Their ducts are some- times lined with ciliated epithelium. The glands themselves are not found in the neighborhood of the taste-goblets. The serous glands, on the other hand, are found most abundantly in those parts of the tongue which are most richly supplied with taste-goblets. Their ducts open into the grooves which are lined by the taste-goblets. The follicular glands, which form the collections of adenoid tissue found at the base and at the sides of the tongue, are not true glands, but rather elevations of the mucous membrane 384 MANUAL OF HISTOLOGY. caused by circumscribed collections of adenoid tissue found in the tunica propria. They resemble glands, in that they gener- ally possess a cavity of variable size which terminates at the surface of the follicle. The mass of adenoid tissue which com- poses the follicle is surrounded by fibres of connective tissue, which are sometimes so compactly woven as to form almost a capsule around it. Sometimes this capsule is wanting, but a gradual transition of the two neighboring forms of tissue is never seen. Above, the adenoid tissue extends as far as the epithelium, so that the papillae of the mucous membrane either disappear altogether or are only to be found occasionally, and then of small size. This adenoid tissue is in all its essentials similar to that found in the tonsils, the vault of the pharynx, and at scattered points in the adjacent tissues. The so-called mucous corpuscles of the saliva are probably lymph corpuscles which have escaped from the adenoid tissue just mentioned. BIBLIOGRAPHY. Albinus. Academicarum Annotationum. Lib. I. S. 58. (Quoted by J. Honig- schmied. ) Leidce, 1754. Bopp. Die Verrichtungen des fiinften Nervenpaares. Leipsig, 1832. Elsasser, in F. Majendie Lehrbuch der Pbysiologie, aus dem Franzosischen iiber- setzt mit Anmerkungen uad Zusatzen von D. C. L. Elsasser. 3 Aufl. I. Tu- bingen, 1834. Mayer, J. F. C. Neue Untersucbungen aus dem Gebiete der Anatomie und Pby- siologie. S. 25 und 26. Bonn, 1842. Bruhl. Ueber das Mayer' scbe Organ an der Zunge der Haus-Siiugethiere oder die seitliche Zungenrucken-Driise derselben. Vierteljabrscbrift fur wiss. Veter- inarkunde. I. S. 1C5. Wien, 1851. Kleine Beitrage zur Anatomie der Haus- Siiugetbiere. Wien, 1850. KoLLiKER, A. Microscopiscbe Anatomie. II. Specielle Gewebelehre. 2. Halfte. 1. Abtb. Leipzig, 1852. Schwalbe. Das Epitbel der Papilla? vallate. Vorlaufige Mittbeilung. Arch. f. microscop. Anat. III. S. 504. 1867. Derselbe Ueber die Gescbmacks- organe d. Saugetbiere und des Menscben. Arch. f. microscop. Anat. IV. S. 154. 1867. Und M. Schultze, Erklarung der Entdeckung der Schmeck- becher von G. Schwalbe betreffend. Arch, i . mikroskop. Anat. VIII. S. 660. 1872. Loven. Beitrage zur Kentniss vom Bau der Geschmackswarzchen der Zunge. Arcb. f. mikroskop. Anat. IV. S 96. 1867. Schwalbe. Zur Kentniss der Papillse fungiformea d. Saugetbiere. Central blatt f. d. med. Wiss. Nr. 28. S. 433. 1868. BIBLIOGRAPHY. 385 Von Wtss. Ueber ein neues Geschmacksorgan auf der Zunge des Kaninchens. Centralblatt f. d. med. Wiss. Nr. 35. S. 548. 1869. Derselbe, Die becher- formigen Organe der Zunge. M. Schultze. Arch, fur mikroskop. Anat. VI. S. 238. Kbatjse. Die Nervenendigung in der Zunge des Menschen. Gottinger Nacbricbten. S. 423. 1870. VERSON. Beitrage zur Kentniss des Keblkopfes und der Tracbea. Sitzgsbr. der wiener Acad. 1 Abth. LVII. S. 1093. 1868. Derselbe, Kehlkopf und Tracbea in Strickers Handbucb der Lebre von den Geweben. I. S. 456. Leipzig, 1871. Honigschmied, J. Beitrage zur mikroskop. Anatomie der Gescbmacksorgane. Ztschr. f. wissensch. Zool. XXIII. S. 414. Exner. Med. cbirurg. Rundschau, Juni Heft. S. 400. Wien, 1872. Ditlevsen. Unders Jgelse over Smaglogene paatungun hos patte dyrene og men- nesket. Kopenhagen, 1872. Referat in Hoffmann und Schwalbe Jahresb. I. Lib. S. 211. 1872. Honigschmied. Ein Beitrag tib. die Verbreitung der becherformigen Organe auf der Zunge der Siiugethiere. Centralbl. f. d. med. Wiss. No. 26. S. 401. 1872. Henle. Handbuch der system. Anatomie des Menschen. II. 2. Aufl. S. 873. 1873. Von Ebner, Ritter. Die acinosen Driisen der Zunge und ihre Beziehungen zu den Geschmacksorganen. Gratz, 1873. Sertoli, E. Osservazioni sulle terminazioni dei nervi del gusto. Gazetta Medico- Veterinaria. IV. 2. Separatabdruck. Deutsch in Molesch. Unters. XI. 4. Heft. S. 403. 1874. Hoffmann, A. Ueber die Verbreitung der Geschmacksorgane beim Menschen. Arch. f. pathol. Anat. LXII. S. 516. 1875. Watson, W. Spencer. Diseases of the Nose and its Accessory Cavities. London, 1875. Von Brunn. Untersuchungen iiber das Riechepithelium. Arch. f. mik. Anat. No. 11. 1875. Kratjse, W. Allgemeine und mikroskop. Anat. Hannover, 1876. Voltolini. Address delivered December 15, 1876, before the Silesian Association for National Culture. Kkause. Lehrbuch. Hannover, 1876. Kolliker. Ueber die Jacobson'schen Organe des Menschen. Festschrift zu Rineckers Jubilaum. Leipzig, 1877. PoNCnET et Tourneux. Precis d'histologie humaine. 1878. Lusciika. Das Epithelium der Riecbschleimhaut des Menschen. Centralbl f. die med Wissenschaft. Nr. 22. 1877. Wundt. Lehrbuch der Physiologic des Menschen. Stuttgart, 1878. 25 CHAPTER XXIV. THE ALIMENTARY CANAL. By EDMUND C. WENDT, M.D., Curator of the St. Francis' Hospital, etc., New York City. The human alimentary canal is a tube of great length, ex- tending: from the mouth to the anus. There are considerable variations of its calibre in the different regions of the body through which it passes. The two external openings of the digestive tract are continuous with the cutaneous surface of the body. Throughout its entire extent we find several super- imposed layers or membranes, which are from within outward : 1, a mucous membrane with its submucosa ; 2, the muscular coat ; and 3, a fibrous layer. In addition to these fundamental strata, we encounter certain special structures, which charac- terize the various parts of the canal. The buccal cavity and pharynx are elsewhere described ; we begin, therefore, with a consideration of THE (ESOPHAGUS. The walls of this section of the tract are directly continuous with those of the pharynx, and have an average thickness of from three to four millimetres. In the oesophagus, in addition to the four pharyngeal coats, a new layer appears between the epithelial stratum and the submucous tissue. This new struc- ture has received the name of muscularis mucosae. Hence, the different layers of the oesophagus are from within outward : 1. The mucous membrane. 2. The muscularis mucosae 3. A submucous layer. 4. The muscular coat. 5. A fibrous envelope. The mucous membrane presents comparatively long, coni- THE (ESOPHAGUS. 387 cal papillae of more or less dense connective tissue, containing looped blood-vessels, and lined throughout by stratified pave- ment-epithelium. These papillae attain a marked degree of development in the adult only. In infancy their future pres- ence is indicated by a wavy outline at the internal attached border of the epithelial stratum. This latter portion of the mu- cous membrane contributes 0.22 — 0.26 mm. toward the entire oesophageal thickness of about 4.0 millimetres. The muscularis mucosce con- sists chiefly of longitudinal, un- striped muscle-cells. They are disposed in bundles of differ- ent sizes, separated by varying amounts of connective tissue. Toward the inferior portion of the oesophagus these bundles approach each other, displacing the interposed tissue, and form- ing finally one continuous mus- cular layer. The thickness of this layer varies between 0.2 and 0.3 mm. The submucous layer is made up of fasciculated connective tissue and elastic fibres. It contains groups of fat-cells, and lodges the mucous glands. The latter closely resemble the glands found in the mouth. They consist of pyramidal or poly- gonal secreting-cells with conspicuous rounded nuclei, and ducts lined by cylindrical epithelia. The lower portion of the oesoph- agus contains smaller and more superficial acinous glands. In this region they are also found in greater abundance, and around the cardiac orifice they form almost a complete ring. The muscular coat has an inner circular and an outer longi- tudinal layer. In man it is formed of both varieties of muscle- cells, the striped and unstriped. The upper portion is composed of striped muscle only, whereas the lower half consists exclu- sively of the unstriped variety. Below the upper one-eighth of the oesophagus smooth muscle-cells first begin to be blended with the other variety ; they rapidly increase as we proceed Fig. 164.— Transverse section through the lower part of the oesophagus of the newly-born child : a, a, epithelium ; b, mucosa ; c, muscu- laris mucosa ; rf. submucous tissue: e, layer of circular muscular fibres : /, longitudinal muscu- lar layer ; y, external fibrous layer ; A, h, two of the ganglia of Auerbach. Klein. 388 MANUAL OF HISTOLOGY. downward, until at about the middle of its course the striped fibres entirely disappear, being replaced by continuous layers of unstriped muscle-cells. The fibrous envelope consists of connective tissue and elastic fibres, arranged so as to form a thin, peripheral, sheath-like membrane. Blood-vessels and lymphatics are found in less abundance in the oesophagus than in the mouth and pharynx. The for- mer are arranged in the shape of capillary networks in the mucosa. The papillary loops, already mentioned, take their origin from these reticula. The larger branches are found in the submucosa. The lymphatics occur as plexuses; one is situated superficially in the mucous membrane, and communi- cates by capillary vessels, with a second larger one, placed in the submucosa. The glands are said to have special lymphatics. Nerves. — An elaborate account of the mode of distribution of nerves in the oesophagus is given in Ranvier's " Lecons d'ana- tomie generale," 1880, p. 366 et seq. The following brief sum- mary gives the main points : Nervous filaments proceeding from the pneumogastricsfind their way to the striped muscles, where they terminate in the well-known eminences ordinarily found in that tissue. These terminal bodies are seen to be very numer- ous, a fact which corresponds to the importance and complex- ity of nervous action concerned in the process of deglutition. The terminal distribution in the unstriped muscle presents no striking peculiarity. Between the two layers of the muscle- coat we find an arrangement analogous to Auerbach's gangli- onic plexus, but the ganglia and their nerve-cells are larger and appear to be more numerous than in the intestine. The nerve- fibres proceeding from the vagus are medullated ; those from the ganglionic plexus belong of course to the non-medullated variety. THE STOMACH. The serous covering of this organ has the same general structure as all visceral peritoneum, being composed of a con- nective-tissue membrane lined by flat endothelial cells. The muscular coat of the stomach is divisible into three layers, composed of, 1, external longitudinal fibres ; 2, middle circular ; and 3, internal oblique fibres. All of these belong THE STOMACH. 389 exclusively to the unstriped ' variety of muscle-cells. A thickening of the inner circular layer constitutes the pyloric sphincter. The submucous layer is composed of loose connective tis- sue, and it is for this reason that the mucous membrane is so freely movable over the muscular coat. It is, moreover, owing to this peculiarity that, whenever and wherever muscular contraction takes place, the mucous mem- brane presents numerous folds, ridges, and eleva- tions. Thus, we may find in a perfectly healthy stom- ach appearances quite an- alogous to those described by pathologists as the so- called etat mamelonne of gastritis. The muscularis mucosce frequently presents two lay- ers of unstriped muscle- cells — an outer longitudinal and an inner circular one. In some regions we observe only one layer of longitu- dinal muscle-cells. The gastric mucous mem- brane is covered by a single layer of columnar epitheli- um, containing goblet-cells in greater or less abun- dance. These goblet-cells represent ordinary epithelia, which appear to be bulged out by mucoid contents. At the cardiac extremity of the stomach there is a sharp, serrated line of demarcation between the oesophageal and gastric epithelial lining. The surface-epithe- lium forms one continuous stratum, and is continued down into the ducts of the gastric glands. The latter occur in two distinct varieties, viz., peptic glands and pyloric glands. The peptic glands^ also called gastric glands, are cylindrical Fia. 165. — Transverse section through the fundus of the stomach in a child : a, a, cylindrical epithelium ; b, b, peptic tubes ; c, c, muscularis mucosas ; d, d, sub- mucous tissue ; e, circular muscular layer ; /, longi- tudinal muscular layer ; g, peritoneum ; A, A, ganglion of Auerbach. Klein. 390 MANUAL OF HISTOLOGY. tubules, nearly straight or slightly tortuous, with often a single rounded c*ecal extremity. However, the latter is sometimes double by dichotomous division, or we find many such blind terminal branches. Hence, we may speak of simple peptic glands and compound peptic glands. They are all placed ver- tically to the surface, and consist of a homo- geneous basement-mem- brane with a lining of secreting epithelia. (Fig. 166.) The basement- membrane contains flat- tened nuclei, and at its inner aspect it is fur- nished with flat, branch- ing adventitial cells. Each gland is divisible into a duct and gland proper. The latter, again, consists of a neck, body, and fundus. Usually, two, three, or even more of these glands, have a common duct. The length of the entire structure varies in the different gastric re- gions from 0.4 — 2.0 mm., in accordance with the thickness of the entire mucous membrane in the respective parts. The duct, amounting to about one-fourth of the whole length of the tube, is lined with one contin- uous layer of columnar epithelial cells, similar to the surface epithelium of the rest of the stomach. The neck, the thin- nest portion of the minute tube, has similar cells ; but they appear shorter, darker, and have a smaller ovoid nucleus. As regards its breadth, the body stands about midway between Fig. 1G6. — A, simple gastric gland : P, parietal ; and O, chief cells. B. compound gastric gland. Only the outline, denoting the membiana propria, is drawn. THE STOMACH. 391 the neck and the fundus, which latter is the thickest portion of the entire gland. In the neck we also find, in addition, to the cells already described, other corpuscles placed externally to the former. They are the parietal cells (Heidenhain), or delomorphous cells (Rollett), the former variety being termed chief cells (Heidenhain), or adelomorphous cells (Rollett), or simply peptic cells. The parietal cells occur as spheroidal, oval, or polygonal, rather opaque, sometimes very granular bodies, which lie beneath the basement-membrane, but com- monly outside the layer of ordinary chief cells. In the body of the gland- tube we again meet with these two forms of lin- ing-corpuscles. Here, however, the columnar or chief cells are longer than in the neck, and their bodies generally appear more transparent, while the nuclei, again spheroidal, are situ- ated nearer the external than the internal border. Klein de- scribes the substance of these cells as consisting of a delicate reticulum, with a small amount of a hyaline interstitial sub- stance in its meshes. The same author, also, invariably finds an intra-nuclear network. Others have been less fortunate in finding such appearances. The parietal cells of the body in all respects resemble those of the neck. As the fundus is ap- proached their number grows comparatively less. The pyloric glands, which some histologists insist on call- ing mucous glands, are lined throughout by a single layer of epithelium. This is composed of the ordinary columnar cells of the gastric surface. But the corpuscles here appear to be somewhat compressed, so that they seem less transparent than elsewhere. They are known to undergo certain changes dur- ing their passage from activity to rest. Examined in the latter condition, we find them more granular, and apparently smaller or shorter, than during and immediately after secre- tion. These glands have long ducts, each one serving for sev- eral secreting tubules. Their bodies are branched, and usually appear somewhat tortuous. When such glandules become somewhat more complex and grow larger (a change which nor- mally takes place in the duodenum), they are called Brunner's glands. Dr. Edinger has recently (Archiv f. milcr. Anat., Vol. XVII., p. 193) asserted that the gastric glands contain in reality only one kind of cellular element. He based his opinion on results obtained by treating the almost living mu- 302 MANUAL OF HISTOLOGY. cous membrane with osmic acid, after Nussbaum's method. By him the chief cells are said to develop into parietal cells, through an increass of their volume and a filling up with the gastric ferment. The considerations which led him to form this opinion are as follows : 1, the occurrence of bodies which represent transition-forms between chief cells and parietal cells ; 2, the analogy of this assumed metamorphosis of gas- tric corpuscles {i.e., the conversion of chief cells into parietal cells), with similar changes, known to occur in other glands during active secretion ; 3, the fact that many animals which secrete pepsin have only the parietal cells ; 4, the results of an examination of the mucous membrane of starving animals, which revealed only the chief-cell form of gastric corpuscles ; and 5, the apparent discrepancy in the descriptions of these bodies by competent histologists — some observers regarding the chief cells, others the parietal cells, as exclusively pepsin- ogenous. Still more recently, Stohr has {Verliandl. d. phys.-med. Gesel. in Wurzburg, 1881, p. 101) studied the histology of the gastric epithelium. His specimens were derived from the fresh stomach of a criminal immediately after execution of the latter. The man had taken no nourishment for some hours before his death. The principal conclusions of Stohr are : 1, the epithe- lia of the mucous glandules are not destroyed during the pro- cess of secretion, but, like those of the true gastric glands, con- tinue their existence ; 2, the parietal groups of cells represent those portions of the mucous corpuscles which have not un- dergone mucoid metamorphosis, being made up of unaltered protoplasm. From the above contradictory statements it appears that even to-day our intimate knowledge of the gastric mucous membrane, and especially its epithelia, is far from being in a satisfactory condition. It will have to be reserved for future investigations to dispel the uncertainty still existing with re- gard to some of the most interesting details of the physiologico- histological characteristics of the inner coat of the stomach. The blood-vessels of the stomach have an arrangement simi- lar to that of the oesophagus. In the mucous membrane, how- ever, we find abundant plexuses of capillary vessels surround- ing the gastric glands. These networks intercommunicate, and just beneath the surface-epithelium they become especially THE STOMACH. 393 close. From this point the veins take their origin. The ve- nous rootlets unite in a stellate manner to form larger branches, which descend almost vertically and empty into a venous retic- ulum situated between the glandular layer and the muscularis mucosae, and just above a similar arterial network. Lymphatics abound in the stomach. They appear to arise from superficial loops, which, anastomosing between the Fig. 167. — Lymphatics of the gastric mucous membrane of the human adult. Frey. glandular tubules, reach the fundal zone of these structures. There they form a network, and this is in communication with a plexus of larger vessels, situated in the submucous tissue. The distribution of the gastric nerves does not differ mate- rially from that of the small intestine, in the description of which this matter will receive more particular attention. Gan- glion-cells are frequently found both in the muscular layer and the submucosa ; in the latter we have a tolerably distinct plexus of nerve-filaments and ganglion-cells. Of the normal occurrence in the walls of the stomach, of true lymphoid follicles, the author has been unable to find convincing evidence. Nevertheless some writers assert that they are always to be found there. 394 MANUAL OF HISTOLOGY. THE SMALL INTESTINE. The serous coat presents no structural characteristics pecu- liar to itself, closely resembling the gastric peritoneum. It encloses a muscular coat and the mucous membrane, which are held together by connective tissue. The average thickness of these layers does not, in man, exceed 1.0 mm., of which three-fourths belong to the muscular, and one-fourth to the Fig. 108. — Longitudinal section of the small intestine of a rabbit : Z, Z, villi ; J, crypts; Pp, a Peyer'a patch ; K, cap of a follicle ; S, eabtnucosa ; m. m, muscularis mucosae ; R, circular muscular layer ; L, longitudinal muscular layer ; P, peritoneum. Verson. mucous coat. Of course, the contracted or relaxed condition of the intestinal tube at the time of measurement will appre- ciably influence these figures. But they represent the general ordinaiy average. The muscular coat has an external longitudinal and an in- ternal circular layer. Between the two we find Auerbach's THE SMALL INTESTINE. 395 plexus myentericus of flat nerve-fibres, which will be described farther on. The muscle-coat becomes gradually thinner as we pass from the duodenum to the ileo-csecal valve. In the for- mation of this thickened fold the longitudinal layer does not participate. The unstriped muscle-cells have an average length of 0.255 mm., and are about 0.005 mm. broad. They are arranged in bundles, surrounded by connective-tissue bands, with which elastic elements are abundantly interwoven. The mucous membrane is thrown into folds, and is studded with closely placed projections, called villi. The general di- rection of these folds, the valvulce connwentes Kerkririgii, is parallel to the transverse course of the circular muscle-layer. They run parallel to one another, or join at acute angles. The villi jut out into the lumen of the intestinal canal, as variously shaped projections, of an average length of 0.04 — 0.6 mm., and an average breadth of 0.00 — 0.12 mm. In general their form may be said to be conical or cylindrical ; but we always en- counter a great variety of shapes, in accordance with the varying states of contraction in the mus- cularis mucosae. Each villus con- sists of a large-meshed reticulum of connective tissue, infiltrated, as it were, with leucocytes, and con- taining flattened corpuscles, which resemble endothelial cells. One or several spaces, situated in the cen- tre of every villus, constitute the origin of the lacteal tubes. Ac- cording to Briicke, these chyle- ressels are covered by thin, but not continuous bundles of smooth muscle-fibres. Their walls show only a single layer of ordinary endothelial cells, witli clear oval nuclei. The free surface of the villi, like that of the stomach, is covered by a single layer of columnar epithelium. Each cell presents, in the recent state, a iim-lv striated hyaline band at its unattached border. This structure has, at different times, received various interpretations, and even now opinions Fig. 169. — Section of a villus from the intestine of a rabbit ; a, epithelium ; b% stroma; c, central cavity. Verson. 390 MANUAL OF HISTOLOGY. are much divided as to its true significance. Some histologists regard the strise as indicating so many minute pores for pur- poses of absorptive transmission ; others believe that the jux- taposition of numerous delicate rods explains the peculiar ap- pearance ; and Klein has lately asserted them to be merely prolongations of the fibrils of the cell-substance composing the epithelia. These stria? are always seen to run parallel to the long axis of the cells. Krause also described as of normal occurrence, a basal pro- cess extending at an obtuse angle from the attached surface of these bodies, and inserted into the delicately serrated border of the villi. Near its attached border each epithelium presents a bright ovoid nucleus, with one or more distinct nucleoli. Besides the ordinary corpuscles, we find interposed between them the so-called goblet-cells. These are derived from the former by mucoid infiltration of the cell-body, which is there- fore conspicuously bulged out. Lymph-corpuscles also occur between the epithelia. Immediately beneath this layer we find a delicate, homo- geneous basement-membrane, composed of flattened cells, re- sembling endothelia. The muscular is mucosa', or muscle of Briicke, is made up of a single or double layer of smooth muscle-cells. When double, an inner circular may be distinguished from an external longi- tudinal coat, both being always very attenuated. The submucous layer is formed of connective tissue, the supporting framework of which contains lymphatics, blood- vessels, nerves, and often groups of fat-cells. The glands of the small intestine are those of Brunner and the crypts of Lieberkuhn. In addition to these, however, there occur numerous lymphoid follicles, which, when found singly, are known as the solitary follicles, and, when grouped together, as agminated glands, or Peyef s patches. The solitary or closed follicles are real lymphoid glands, and, like these, con- sist of reticulated connective tissue, the meshes of which are replete with lymph-corpuscles. The jejunum, ileum, and colon all contain such follicles, but the agminated glands occur in the ileum, abounding especially at its lower part. Around each follicle we find a ring of villi and glands, which arrange- ment goes by the name of corona tubulorum (Miiller). The follicles receive an enveloping layer of nbro-connective tissue. THE SMALL INTESTINE. 397 Bfunnefs glands lie in the submucosa, where they form closely crowded tubules, separated by a small amount of con- nective tissue. Smooth muscle-cells, starting from the muscu- laris mucosae, are often seen to pass between them. These con- voluted tubules resemble and correspond to the gastric glands, but have here attained a much greater degree of development. Fig. 170.— Vertical section throneh a human Peyer's patch, with its lymphatics injected : a, intestinal villi with their lactea's ; 6. Lieherkiihnian glands; c, muscular layer of the mucous membrane; rf, apex of the follicl» : e, middle zone of the follicle : /, basis portion of the follicle ; g», continuation of the lacteals of the intestinal villi into the mucous membrane proper; A, reticular expansion of the lymphatics in the middle zone : i, their course at the base of the follicle ; *, continuation into the lymphatics of the submu- cous tissue ; /, follicular tissue in the latter. Frey. They also appear to have been pushed down, as it were, from the mucous into the submucous layer. An individual gland consists of its long duct lined by col- umnar epithelium, and the branched tubules, which frequently have terminal clusters, resembling true acini. They are, how- ever, only secondary or tertiary diverticula, so that Brunner's glands really conform to the compound tubular type of secret- ing structures (Renaut). Each ultimate diverticulum has an external membrana propria composed of flattened endothelial cells, and a lining of cylindrical, columnar, or prismatic secret- ing epithelia, containing oval nuclei. Ilistologists have described minute capillary channels pro- ceeding from the central lumen of the gland, between the se- , creting-cells, ending just underneath the membrana propria. The author believes these intercellular channels, as they have 398 MAX UAL OF HISTOLOGY. been called, to be the artificially altered cement-substance al- ways present between such adjacent cells. Brunner's glands abound only in the duodenum, but a few may occasionally be seen lower down the intestine. Their ducts, after traversing the muscularis mucosa}, ascend almost vertically between the crypts, opening on the free surface of the mucous membrane. Fig. 171. — Crypts and interfollicular connective tissue, from the intestine of the rabbit: K, crypt; o, n, epithelium ; rf, adenoid tissue, from which the cells have been removed by pencilling ; T, fibrous tissue on the opposite side. Verson. These crypts represent open spaces within the so-called follicles of LieberJculin, which are tubular glands placed verti- cally in the intestinal mucous membrane, existing throughout its entire extent. They form a continuous layer, except where the upward projection of a lymph-follicle creates an interruption. These glands open at the base of the villi, the epithelial covering of the latter being continued down into the tubular depressions which they constitute in the mucous membrane. The cells of this stratum naturally appear broader at their attached than at THE SMALL INTESTINE. 399 their free extremities. A continuation of the villous basement- membrane forms the membrana propria of the crypts of Lie- berkiihn. External to this we find the surrounding connective tissue, which is disposed in reticula, containing many leuco- cytes in its meshes. Hence it is also known as adenoid tissue. The blood-vessels enter and leave the intestine at the me- senteric margin. The arteries, generally accompanied by one or two veins, pierce the muscle-coat, giving off branches which form networks in those layers, then enter the submucosa, where they run parallel to the surface of the mucous membrane, and finally send off vertical arterioles at the base of the villi. The latter ascend on one side of the villus, and then suddenly divide into a dense capillary network. This division takes place near the middle, the capillaries then spreading out to the apex and periphery. Here they become quite superficial, being covered by the epithelial lining only. The venous rootlets of the villus are generally two, or even three in number. About the glands and follicles we encounter special networks with variously shaped meshes. Lymphatics are found in all the layers of the intestinal canal. Those of the serous coat empty into the large mesen- teric trunks. In an inward direction we also find a network of lymph-capillaries between the two layers of the muscle-coat. The submucous layer contains the perifollicular lymph-sinuses situated at the base of these bodies, and a reticulum of larger channels, many of which are found provided with valves. The lymphatics of the mucous membrane are present in the shape of capillary networks surrounding the intestinal glands. In the villi we note, as already stated, one or more central lacteals, communicating at the base of these structures with the lymph-vascular networks situated around and between the glands. The nerves of the intestine are known as the plexus of AuerbacJt, and of Meissner. The former, situated between the circular and longitudinal fibres of the musculosa, is com- posed of flattened nerve-branches, made up of numerous ulti- mate fibrils. Small nodules, containing characteristic gan- glion-cells, are also found, while little twigs are given off from the plexus myentericus, to be distributed to the layers of the musculosa. The plexus of M< issuer is situated in the submucous tis- 400 MANUAL OF HISTOLOGY. sue. Its component nerves are less flattened, but are likewise provided with ganglia containing variously shaped ganglion- cells. This plexus also gives origin to the secondary networks of the muscularis mucosa), and is besides connected by certain branches with Auerbach's plexus. THE LARGE INTESTINE. The histological structure of the colon, broadly speaking, very nearly resembles that of the preceding section of the ali- mentary canal. The lining epithelium of the mucous mem- brane presents the same characteristic appearances as in the a \ w&illS Fio. 172. — Section of the Iarjre intestine of a rabbit: J, crypts of Lleberk'tlhn : a, epithelium ; 6, mu- cosa ; to, muscularis mucosa? ; s, submucosa : A', circular muscular layer ; L, longitudinal muscular layer ; p, peritoneum. Verson. small intestine. The mucosa of the colon is, however, devoid of villi ; but it shows numerous crescentic folds. The muscu- laris mucosae will be found to answer to the description already given of that layer in the small intestine. The submucosa also shows the same morphological compo- sition, but appears to be much richer in deposits of fat-cells. Aggregations of lymph-follicles are not generally found, but large, conspicuous solitary glands abound throughout. The crypts of Lieberkuhn are identical with the glands of THE RECTUM. 401 the same name found in the small intestine. As we approach the rectum an increase in their length becomes apparent. In the vermiform appendix we find the collection of solitary lymph-follicles so closely placed that the space left between adjoining glands does not equal in diameter that of these struc- tures themselves. The longitudinal layer of the muscle-coat is quite thin be- tween the taeniaB coli, or flat longitudinal bands of the large intestine. These bands themselves represent thickened layers of the musculosa. It appears that the circular fibres are espe- cially developed in the portions between the sacculi of the csecum and colon. The blood-vessels are arranged after the same plan as in the small intestine. In the submucosa are contained large trunks, running parallel to the surface. Capillaries arise from these, and ascend almost vertically between the crypts of Lieberkiihn, the capillary network surrounding those structures being only moderately developed. As regards the lymphatics, they have a distribution similar in all essential respects to that found in the small intestine. The nerves likewise imitate in their structure and arrange- ment those encountered in the small intestine. Meissner's plexus appears to be provided with comparatively large gan- glia and relatively small component cells. The plexus of Auerbach also attains conspicuous development in the large intestine. THE RECTUM. The internal sphincter ani represents a thickening of the circular layer of the muscle-coat. In its upper portion the rectal mucous membrane is like the same structure of the large intestine. Lower down we find the columnar epithelium grad- ually replaced by stratified pavement-epithelium. The follicles of Lieberkiihn are large and long. Finally, the mucous membrane gradually passes into the ordinary in- iment surrounding the anal orifice. The blood-vessels, lymphatics, and nerves resemble in their distribution those of the colon, and are devoid of characteristic peculiarities. 26 402 MANUAL OF HISTOLOGY. BIBLIOGRAPHY. Bcehm. De glandularum intest. struct, penit. Berol., 1835. Henle. Symbol, ad anat. vill. intest. Berol., 1837. Bischoff. In Miiller's Archiv, p. 503, 1838. Wasmann. De digestione nonnulla. Berol., 1839. MlDDELDOKPF. De glandulis Brunnianis. Vratisl., 1846. Brettauer and Steinach. Unt. iiber d. Cylinderepithel. Vienna, 1837. Leydig. Histologic 1857. Auerbach. Ueber einen Plexus myentericus. Breslau, 1862. Auerbach. Virch. Arch., Vol. XXXIII, p. 340. 1865. Letzericii. In Virchow's Archiv, Vol. XXXVII., p. 232. 1866. Eimer. Zur Geschichte der Becherzellen. Berlin, 1868. Schwalbe. Arch. f. mikxos. Anat., Vol. VIII., p. 92. 1872. Heidenhain. Arch. f. mikros. Anat., Vol. VIII., p. 279. 1872. Gerlach. Ber. d. sachs. Ges. der Wiss. Leipzig, February, 1873. Krause. Handb. d. menschl. Anat., Band I. 1876. F. Hoffmann. Die Follikel des Diinndarms beim Menschen. Munich, 1878. Sertoli. Contribuzioni all' anatomia della mucosa gastrica, Arch, di med. veter. Fasc. 3, p. 15. 1878. Rudinger. Beitr. z. Morphol. d. Gaumenseg. u. des Verdauungsapp. Stuttgart, 1879. H. Sewall. Devel. and Regen. of the Gastric Gland, Epithel. , etc. Journal of Phys., Vol. I., p. 321. 1879. Edinger. Zur Kenntniss d. Driisenzellen d. Magens. Arch, f . mikros. Anat. , Vol. XVII., p. 193. 1879. Ranvier. Les muscles de l'cesophage. Journ. de micrographie, III., p. 9. 1879. Renaut, G. Note sur la structure des glandes a, mucus du duodenum. Gaz. mud. de Paris, No. 41, 1879, and Progres med., No. 23, p. 439. 1879. Ranvier. Leqons d'anat. generale. Paris, 1880. P. Stoiir. Ueber das Epithel. des menschl. Magens. Verhandl. der phys. -med. Gesellschaft in Wurzburg, p. 101. 1881. CHAPTER XXV. THE SPLEEN, PANCKEAS, THYMUS, THYEOED AND PINEAL GLANDS, AND PITUITARY BODY. Br C. L. DANA, AM., M.D., Professor of Physiology in the Woman's Medical College, New York City. THE SPLEEN. General structure. — This organ is composed of connective tissue and muscular fibres, containing Malpighian corpuscles, pulp-substance, blood-vessels, lymphatics, and nerves. An outline of the general arrangement of these several elements will make subsequent details clearer. Within its peritoneal investment the spleen has, in the first place, an elastic fibrous capsule ; this envelops the organ and passes into its interior at the hilum. From the internal surface of the capsule are given off fibrous bands and pro- cesses— the trabecula3, which interlace and form a fine network. In the meshes of this network is a soft, reddish substance — the splenic pulp. The arteries, entering at the hilum, run along the trabecular and end in capillaries, which gradually break up in the parenchyma. Attached to the walls of the arterioles and bathed in the spleen-pulp are little bodies, called the Malpighian corpuscles. The veins begin in the pulp, and, gradually enlarging, pass out alongside the arteries. The blood thus passes out of the capillaries into the spleen-pulp, and from thence is collected by the veins. It passes through the blood-pal lis in the pulp much as the lymph passes through lymph-paths in the lymphatic glands. This unique structure is now to be considered in detail. Tim peritoneal or serous coat of the spleen resembles the peritoneum elsewhere. It is, in man especially, very firmly 404 MANUAL OF HISTOLOGY. adherent to the fibrous coat beneath it, and closely invests the organ. It is reflected off at the hilum to form the gastro- splenic omentum, and also at the upper border, where it in- vests the suspensory ligament. The fibrous coat, or capsule of the spleen, is white in color, and thicker than the serous coat. It is composed of fibrous tissue, which is permeated very extensively by elastic fibres. Mingled with them are a few smooth, muscular elements. At the hilum this fibro-muscular coat surrounds the vessels and nerves and passes into the substance of the spleen with them, forming what is called the "capsule of Malpighi." It invests the arteries and veins as far as their finer branches, and gives off fibrous processes, which have a diameter of T\ mm. to 2 mm., and which help to make up the trabecular frame- work of the spleen. This framework is formed by processes sent off from the internal surface of the spleen's fibrous coat, which join with the processes sent off from the capsule of Malpighi, and interlace until a firm network is made. In this structure lie embedded the spleen-pulp and the Malpighian corpuscles. The fibrous sheath of the veins has a somewhat peculiar arrangement. It becomes at once intimately adherent to the venous walls, uniting them closely with the surrounding parenchyma. As the veins grow smaller this fibrous coat splits into bands containing muscle-cells, which lie longitudinally along the vessel-wall. These bands do not entirely surround the vessel, however, but allow the thin endothelium and in- tima to be seen between them. They finally leave the veins to join the trabecular framework. The tissue composing this framework is made up, like the capsule, of elastic and other fibres, with a good many smooth muscle-fibres arranged longi- tudinally along their course. MalpigJdan corpuscles. — The Malpighian or spleen corpus- cles are so intimately connected with the arteries that it will be necessary first to trace in part the course of the latter. The arteries of the spleen enter at the hilum, enclosed in a common sheath with the veins and accompanied by the lymphatics. They divide and subdivide very rapidly. When they have reached a diameter of about two-tenths of a millimetre, the veins leave them and take an independent course. At this point of separation, or even sooner, the outer connective-tissue coat of the artery begins to be transformed into the ordinary THE SPLEEN. 405 adenoid tissue ; the fibrillse become more delicate and interlace in a coarser mesliwork ; in the interstices are lymph-cells and at the nodal points are small nuclei. Klein describes large, flat- tened endothelioid cells, " endothelioid plates," fixed upon the reticulum. This lymphoid tissue surrounds the artery in a loose coat of variable thickness. At certain points there is a local hyperplasia of it ; it becomes massed into little ovoid or spherical bodies, which are called Malpighian corpuscles. These have a diameter of T2¥ to T\ mm. They are attached like buds to the artery, or, not rarely, the artery pierces them centrally or eccentrically. When thus pierced the lymphoid change in the arterial coats extends much deeper. The cor- puscles resemble very closely the follicles in the solitary glands of the intestine, as well as those of the lymphatic glands (Fig. 173). They are composed of the same retiform connective tis- sue, in the meshes of which are lymphoid cells, with occasionally yellow or brown pigment. This retiform tissue becomes denser near the external part of the corpuscle, but no distinct envelop- ing membrane exists. In- deed, the external sur- face is generally connect- ed by fibril la3 with the branching cells of the spleen-pulp surrounding it. Toward the centre the retiform tissue is more open. The cells within the meshes are lymph-cells of various sizes. They have an average diameter of yfo- mm. The smaller ones have a single nucleus, the larger may have several. An arterial twig enters the corpuscle either from the attached artery or from the out- side It divides at once into capillaries, which, as a rule, have no regular arrangement. They receive an adventitia of lymph- oid tissue. Most of them soon lose this adventitia, their walls become rich in nuclei, branching processes are given off, and the structural character of the vessel is lost. They finally Fig. 173. — From the spleen of the Tropidonotus natrix : a, follicle, with its capillary plexus ; 6, septum, with venous plexus. Miiller. 406 MANUAL OF HISTOLOGY. break up entirely, and their contents pass out at the periphery of the corpuscles into the meshes of the pulp. It is to be noted that the Malpighian corpuscles are the only parts of the spleen where capillaries exist to any extent. The arteries going to the pulp for the most part break up at once. The spleen-corpuscles differ from the lymph-follicles, par- ticularly, in having fewer capillaries, no lymph-paths, and in containing pigment in their meshes. The number of Malpig- hian corpuscles in a spleen of ordinary size, as estimated by Sappey, is about ten thousand ; but this applies to lower ani- mals. In man they are smaller and less numerous. Pro- tracted disease is thought to diminish the number. The spleen-pulp. — This is a soft, reddish brown substance, looking, when squeezed out, like grumous blood. On expo- sure to the air it acquires a redder hue. Under the microscope it is found to present a honeycombed appearance, in the meshes of which are numerous lymph-corpuscles, fragments of red blood-corpuscles, so-called nuclei, and pigment-granules. Thus, we have really only a modified form of adenoid tissue. Klein considers that the network is made up of the large, flat endo- thelioid cells above referred to. Processes branching from these and uniting with each other form the meshes. I have been unable to make out the structure as Klein describes it, and his own observations and plates do not demonstrate it satisfactorily. The branching endothelioid cells are connected with the breaking-up and the beginning of the blood-vessels, but do not form the whole pulp reticulum. The fibril lse of this retiform tissue are connected with the external surface of the Malpighian corpuscles, with the lym- phoid tissue that ensheaths the small arteries, with the fibrous trabecule of the spleen itself, and with the cell-nuclei of the walls of the arterioles, capillaries, and venous radicles. From these points they branch and interlace, enclosing the cellular and other elements in their meshes. These branching fibril lae are, as in other lymphoid tissue, of a pale, granular appearance. The cells enclosed in the meshes are not crowded so closely together as are those in the Malpighian corpuscles (Fig. 174). They are of different sizes ; the small ones are sometimes de- scribed as free nuclei. The larger ones have one, two, or more nuclei within them. These larger cells often contain red blood- globules in various degrees of disintegration, a fact which gives THE SPLEEN. 407 rise to the opinion that one of the functions of the spleen is to destroy them. The pigment-granules are found both without and within the cells, and occasionally even stain the nodal nuclei of the sus tentacular tissue. The pigment is yellowish, brown, or black, and there is enough of it to give a charac- teristic dark color to the gross ap- pearance of the spleen. In addition to the pulp-elements mentioned, there are, according to F.remke and Kolli- ker, small, yellowish nucleated cells, which are possibly young red blood- globules. The pulp-substance thus described has arterioles and capillaries ending and veins beginning in it. The blood FlQ. m-From the sheep's 8Pieen flows from the former, through the SSK StSffi i,USSSSJK i ,-i n*i.iiii current: c, its continuation into the spaces between the cells, into the lat- venous roots with incomplete wans ; a, tt • . • i . i venous branch. Frey. ter. Here is every opportunity, there- fore, for the blood to recruit itself with new white corpuscles, and to enrich itself with albuminous and pigmentary matter from disintegrated red globules. The analyses of the blood in the splenic vein seem to show that it does do this. Blood-vessels. — We have already described, to a certain extent, the general arrangement of the blood-vessels, but some further particulars remain to be noticed. The splenic artery, the largest branch of the cceliac axis, passes to the spleen in a course so tortuous as to shorten its length in a straight line by one-third. It enters the gastro- splenic omentum, divides generally into six branches, and passes into the spleen at the hilum, where, in common with the vein, it becomes surrounded by the capsule of Malpigliii. The branches then rapidly subdivide and decrease in size, but with- out anastomosing. When about two-tenths of a millimetre in diameter they leave the veins and receive their sheaths of lym- phoid (issue and Malpighian bodies, as has been described. They then end for the most part in capillaries, which pass to the Malpighian bodies and there break up in the way above described. But there are other capillaries which pass into the pulp-substance, where their walls gradually melt away, so to speak, into the retiform tissue that surrounds them. If one follows this change with a microscope, he will see the capil- 408 MANUAL OF HISTOLOGY. lary tube becoming thinner and more freely studded with nuclei ; from some of these nuclei processes are sent out which connect with the fibrillar of the pulp. At this stag.' injections into the capillaries pass freely out into the surrounding tis- sue. The exact point where the capillary wall merges into the sustentacular tissue can hardly be determined. The venous radicles begin in a somewhat similar way to that in which the capillaries end (Fig. 174). The sustentacu- lar fibrillsB (endothelioid plates ?) appear to arrange themselves, first of all, in a circular manner, occasionally interlacing at right angles (Fig. 175). Lying within and upon the fibrillae thus arranged are oval cells with promi- nent nuclei. These nuclei are often con- nected with the sus- tentacular fibrillar outside. These cells are not adherent to each other at first, but, as the radicle be- comes more perfect, they unite to form a complete wall ; the external layer of cir- cular fibril] 3d then becomes metamor- phosed into a tunica intima ; finally, the thick oval cells are replaced by flat endo- thelial cells, and the complete venule is formed. Having shown how this vascular channel begins, we turn, for convenience of description, to its other end. The splenic vein enters the hilum, just as the artery does. As it subdi- vides, however, it loses both tunica adventitia and tunica me- dia. The internal tunic remains and becomes firmly united with, the fibrous trabecular of the spleen, so that, on section, the venous wall does not collapse, but appears like a part of the parenchyma. After several subdivisions the veins begin to anastomose, and they finally form a closely reticulated ar- rangement of like-sized vessels having an average diameter of Tfg- to T5(j- mm. These are called the cavernous veins. The Fig. 175. — From the pulp of the human spleen, brushed preparation {combination): a, pulp Btrand with the delicate reticular framework : transverse section of the cavernous venous canal ; c, longitudinal sec- tion of such an one ; '.„•. Btwrth. in front of the tipper end of either kidney. They are usually triangular or semilunar in shape, although round and oval forms are also met with. In structure they resemble the so- 432 MANUAL OF HISTOLOGY. m called blood-vascular glands, but their function is not known. They belong to the ductless variety of glands. Each suprarenal body consists of a capsule inclosing the paren- chyma, which shows a cortical and medullary substance. The cap- sule is formed of ordinary connec- tive tissue containing many deli- cate elastic fibrils. Externally it is surrounded by loose connective tissue, containing a greater or less proportion of adipose tissue, and internally it sends out trabecule, which traverse the entire organ, thus constituting and completing its frame-work. The cortical substance, as its name implies, occupies the exter- nal portion of the suprarenal body. It has an average thickness in man of 0.28 to 1.12 mm., is of a yellow- ish color, and may be divided into three layers or zones. The lim- its of demarcation between these layers are much less marked, however, than the corresponding boundary line between the corti- cal and medullary portions. In the human being the external layer of the cortex is distinctly separate from the middle one, but the latter shows no such sharp limit against the innermost layer. The cortex is a friable substance, and its broken surface presents a striated appearance. Owing to rapid post-mortem changes, the cortex in man is usually found to be separated from the medul- lary portion by a dirty brownish substance, containing modified blood and cortical corpuscles. MBfe Fig. 1S4. — Perpendicular section through the suprarenal capsule of man : 1, cortex ; 2, medulla ; a, capsule ; b, layer of outer cell- groups ; c, layer of cell-trabeculae (zona fasci- culata) ; d, layer of inner cell-groups ; e. med- ullary substance ; /, transverse section of a vein. Eberth. Fig. 185. —Single cells and cell-groups of the outermost cortical layer. Human suprarenal cap- sule. Eberth. SUPRARENAL CAPSULES. 433 The three layers of the cortex are an external one, or zona r/lomerulosa ; a middle one, or zona fasciculata / and an in- ternal one, or zona reticularis. The external layer consists of rounded or oval groups of cells, separated by delicate connective-tissue trabecular, which spring from the capsule. Similar cells are found throughout the entire cortex. They have been called the parenchymatous bodies or cells, although a better name is cortex corpuscles. In structure they resemble ordinary cells, consisting of poly- ==^^; -^ if- Fig. 1^6. — Horizontal section through the outermost cortical portions of the suprarenal capsule of the er, blind termination of a cylinder; 6, groove-shaped and cylindrical cortical trabecular; c, stroma. Ebcrih. hedral masses of protoplasm furnished with spherical nuclei and conspicuous nucleoli. Their protoplasm has a coarsely granular character, and, as a rule, contains more or less fat in greater or smaller droplets. The middle layer contains cortical corpuscles which are ar- ranged in almost parallel rows, and are so closely packed that this portion acquires a distinctly striated appearance. These cellular columns have received various names. By Ecker they were called gland tubules, Kolliker termed them cortical cylin- 23 434 MANUAL OF HISTOLOGY. ders, Eberth described them as cylindrical cell-trabeculse, or cortical trabecule, and Krause named them cellular pillars. These cellular rows, columns, or streaks, are by no means always cylindrical, for on cross-section they frequently present a semilunar, oval, or bean-shaped appearance. Their inner and outer terminations have a rounded shape, and near the former place they seem to anastomose with one another. At Tic. IS?.— Vertical section through the the cortical portion of the suprarenal capsule of the Horse, a, capsule ; 6, cell-trabeculae ; c, cell-groups. Eberth. the peripheral end they sometimes appear groove-shaped, or in horse-shoe form. Connective-tissue processes communicating with the cap- sule are found between the cell columns, but the latter are not completely isolated by them. These connective-tissue streaks also send off transverse or oblique fibres, so that occasionally the cells of the middle layer seem to be inclosed in basket-like meshes. In addition to fat-droplets, granules of pigment are SUPRARENAL CAPSULES. 435 found in the cells of the innermost portion of the middle layer. The external layer is made up of irregularly arranged cor- tical corpuscles. Nearly all the cells of this layer contain pigment granules. The connective-tissue here forms a reti- culum, with variously shaped meshes, which contain greater or smaller heaps of cells. The medullary substance has a whitish-gray appearance, and is of a more delicate consistency than the cortex. It consists ^"••"■?: ■*. ■'■ v, -• •' - - " §*?»£§ 'o-,-"-'> . ?Sn 'v "3«S3s r ;% t :7.v, -?\ s«tijaiL'*fi tW^ Fio. 188. — Vertical section through the medullary substance of the suprarenal capsule of the Cow. a, blood-vessels ; 6, trabecnte of medullary cells. Strieker. of a network of connective tissue, which contains in its meshes the medullary corpuscles. These are pale cells with spherical nuclei and large nucleoli. They may assume various shapes. In man they are generally of an irregularly stellate or polyg- onal form. Their protoplasm is finely granular, and they con- tain, as a rule, much less fat and pigment than the cortical corpuscles. Kolliker finds that they resemble the nerve-cells of the central nervous system, but he adds that they cannot be regarded as such nerve-elements. The medullary cells assume a yellow or brownish color when treated with chromate of potash or chromic acid. Since the cortex corpuscles are not thus colored, this peculiarity may serve to distinguish one cellular variety from the other. The connective-tissue framework of the medulla is called its 436 MANUAL OF HISTOLOGY. stroma, and its meshes in man have an oval or rounded form, so that, as a rule, the cell-groups have a similar shape. On the whole, we find a smaller proportion of connective tissue in the medulla than in the cortex. The blood-vessels of the suprarenal capsules occupy the stroma, and are found in great abundance. The arterial vessels arise from the aorta, the phrenic and renal arteries, and the cceliac axis. About twenty small branches pierce the capsule, and are distributed mainly to the cortex. The medullary sub- stance is very rich in venous plexuses. Capillary networks are found in both cortical and medullary portions. The veins uniting form one principal branch, which passes out at the hi- lus of the organ. The right suprarenal vein empties its blood into the vena cava inferior, the left one into the vena renalis sinistra. Lympliatics were seen by most observers only at the sur- face of the suprarenal capsules. Klein, however, has recently asserted that there exists between the cells "an anastomosing system of narrower and broader clefts, channels, and lacuna?, which belong to the lymphatic system." This applies to the zona fasciculata. In the other portions of the organ the same writer also finds lymph-spaces, and lymph-sinuses, occupying the regions "between the septa and trabecule of the frame- work on the one hand, and the cell -groups on the other." The nerves occur in comparatively greater abundance in these organs than in any other glandular structures of the hu- man body. Kolliker was able to count thirty-three branches in a single suprarenal capsule of a man. They are derived from the renal plexus, the pneumogastric and phrenic nerves, and semilunar ganglion. Very fine or medium-sized, dark-bor- dered fibres are commonly encountered, and t\\ey abound espe- cially in the medulla. Ganglion-cells are also frequently seen, and Virchow has traced them into the interior of the organ. In the cortical substances they are of rare occurrence. The terminal distribution of the nerves has not been hitherto ascertained, and it appears to be still a matter of doubt whether they ter- minate in the suprarenal body at all. Development. — In mammals the suprarenal capsule has an independent origin in a collection of tissue between the Wolff- ian bodies behind the mesentery and in front of the abdomi- nal aorta. (Kolliker.) The mesoderma at this point assumes BIBLIOGRAPHY. 437 a special structure. Certain of its cells form more or less cyl- indrical masses with a reticulated appearance. Between these cellular groups a network of blood-vessels is soon found, so that the whole structure is now not unlike embryonal hepatic tissue. In rabbits, Kolliker saw the first traces of these bodies about the twelfth or thirteenth day. On the sixteenth day they had already attained a length of 1.56 mm., and occupied a position along the vertebral column from the first to the fourth and part of the fifth lumbar vertebra. On cross sections of em- bryos sixteen days old, Kolliker found that the suprarenal cap- sules were distinctly separate at their upper borders, whereas their lower ends were joined together to form a single organ. The same writer also found a nervous ganglion at the coalesced central portions of somewhat older embryos. Behind the suprarenal capsules a second sympathetic ganglion was discovered. Remak and v. Brunn do not in all respects corroborate the statements of Kolliker. The latter was unable to ascertain any existing relationship between the nervous system and the suprarenal capsules. BIBLIOGRAPHY. Bergmanx. De glandulis suprarenalibus. Diss, inaug. Gottingen, 1839. Ecker. Der feinere Bau der Nebennieren beim Menschen und den vier Wirbelthier- klassen, 184G. Article " Blutgef iissdrusen " in Wagner's Handworterbuch der Physiologic Bd. IV. 1849. H. Fkey. Art. " Suprarenal Capsules" in Todd's Cyclopaedia of Anat. 1849. Remak. Untersuchungen ueber der Entwickelung d. Wirbeltbiere. Berlin, 1853- 1855. ViRcnow. Zur Chemie der Nebennieren. Virchow's Archiv, 1857. Leydig. Lehrbuch der Histologic, 1857. B. Werner. De capsulis supraren. Dorpat Dissertatio. 1857. Vrr,iT.\N-. Gaz. mod., p. 059. 1856; p. 84, 1857. Gaz. hebd., p. CG5, 1857. G. Harley. The Histology of the Suprarenal Capsules. Lancet, June 5th and 12th, 1858. Barkow. Anat. Unters. ueber die Harnblase. 1858. Palladino. Estratto del bulletino dell' ass d. natur e med. Anno I., No. 5. Napoli. BcRriuiARDT. Virchow's Arch., Vol. XVII., p. 94. 1859. G. Joesten. Archiv fur phyp. Heilkunde, S. 97. 18G4. A. MOBM. VIrobow't Archiv, Bd. XXIX., 8. 826. IIj.nle. Anatomic des Menschen. Bd. 2. 18GG. 438 MANUAL OF HISTOLOGY. Arnold, Jul. Ein Beitrag zu der feineren Structur und dem Chemismus der Ne- bennieren. Virchow's Archiv, Bd. 35, S. 64. 1866. Holm. Ueber die nervosen Elemente in den Nebennieren. Sitzungsberichte der Wiener Akademie. Ed. 53, 1. Abtheilung. I860. Grandry. Structure de la capsule surrenale. Journal de l'anatomie et de la physi- ologic 1867. Kolliker. Handbuch der Gewebelehre. 5. Aufl. 1867. Eberth. Strieker's Archiv. Kisselepp. Centralblatt, No. 22. 1868. Bouvin. Over der bouw en de beweging der Ureteres. Utrecht, 1869. Engelmann. Zur Phys. d. Ureters. Pfliiger's Arch., Vol. II, p. 243. 1869. Obersteiner, in Strieker's Manual. Unruh. Archiv f. Heilkunde, p. 289. 1872. v. Brunn. Archiv f. mikr. Anat., Vol. VIII., p. 618. 1872. Egli. Arch. f. mikros. Anat., Vol. IX., p. 653. 1873. Hamburger. Zur Histol. d. Nierenb. u. d. Harnleiter. Arch. f. mikr. Anat, Vol. XVII., p. 14. 1879. See also the text- books of Frey, Krause, Kolliker, and Henle. Braun. Ueber Bau u. Entw. der Nebennieren bei Reptilien. Zool. Anzeiger, Vol. II., No. 27, p. 238. 1879; und Arbeiten aus d. zool. -zootom. Institut in Wurzburg, Vol. V., p. 1. 1879. Kolliker. Entwickelungsgeschichte des Menschen. Leipzig, 1879. Klein, and S. Noble Smith. Atlas of Histology. 1880. CHAPTER XXVIII. THE MAMMARY GLAND. BrW. H. PORTER, M.D., and EDMUND C. WENDT, M.D., of New York City. General considerations. — By virtue of its intimate associa- tion with the function of reproduction, this organ occupies a distinctly peculiar position among the glands of the body. In the male it persists through life in the same rudimentary form which characterizes the mamma of both sexes at birth. Only in the female, and in her only at certain times, does this organ attain its complete histological maturity. It may be borne in mind, however, that in a few anomalous cases, male beings sup- plied with fully developed mammary glands have been ob- served. After conception, and as pregnancy advances, progressive evolution takes place within the mamma. This unfolding process at length culminates in exaggerated tissue-metamor- phosis, which in other organs we should scarcely hesitate to call pathological. In fact, Virchow and his followers all main- tain that the secretion of milk is the direct result of a fatty degeneration of mammary epithelium, and similar in all essential respects to the processes involved in the elaboration of the seba- ceous material from the cutaneous glands of that name. Bill- roth, indeed, calls the mammae cutaneous fat-glands (Hautfett- clrusen), and he does this in consideration of the mode of their development, and because they are placed immediately be- neath the integument. In spite of these statements, however, we must maintain that the mammae are radically different from ordinary sebaceous glands, and that the processes of secretion in the two sets of glands are quite distinct. The grounds on which we base this opinion will be amplified farther on. The secretory activity of the gland, consisting in the elaboration of milk, is, as a rule, called into play only during the period 440 MANUAL OF HISTOLOGY. of rapid growth and development already alluded to. In ex- ceptional instances, however, lacteal fluid may be secreted during the extra-puerperal period. The mamma) belong to the class of compound acinous or race- mose glands, and, like the other organs of this group, consist of a framework or stroma, and a proper secreting structure or parenchyma. As they appear to the naked eye, the bulk of the breasts is not their secreting parenchyma, but ordinary adipose tissue. This fills out the intervals between the lobes and lobules, and gives to the entire organ its smooth, round form. The different lobes have separate secretory ducts, which open upon the nipple. These ducts ramify throughout the substance of the gland tissue, and ultimately carry upon their terminal branches the clusters of secreting vesi- cles, called acini or alveoli. Accord- ing to Zocher and Hen nig, the true glandular substance has not a rounded shape, but shows a grouping into three principal divisions, one of which ex- tends far up in the direction of the axilla. It is separated from the axillary lymphatic glands only by a small amount of adipose tissue. This wrould explain the ease, readiness, and frequency with which these glands become implicated in ma- lignant disease of the mamma. Since the glands at birth differ very widely from the mamma? of adult women, and still more widely from those of pregnancy, it will be convenient to consider the histology of the organ under different aspects. This will be necessary, however, only with regard to the acini and the epithelia therein implanted, as these alone show such wide morphological divergencies in the dif- ferent phases of existence. The nipple (teat, mamilla, papilla mamma) is the one struc- ture belonging to the mamma which is least liable to modifica- tions of tissue due to age and sex. It generally assumes the shape of a pigmented conical or cylindrical projection, at the apex of which the galactophorous ducts have their terminal openings. It is composed principally of a rather loosely woven connective tissue, containing abundant corpuscles, and provided Fig. 189. — Terminal vesicles and stroma from the gland of a nursing woman. Langer. THE MAMMARY GLAND. 441 with elastic fibrils. This conjunctive tissue forms a supporting framework for the milk-ducts traversing the nipple. The latter show walls of rather dense fibrous tissue, with a large pro- portion of elastic elements, and are provided with a lining of one row of short cylindrical cells. As the external orifice is approached, these cells begin to take on the character of the ordinary epidermic corpuscles of the integument. Partsch has found in many animals that the secreting paren- chyma accompanied these ducts almost to their mamillary orifices. The occurrence of unstriped muscle in the nipple, accords with the fact of its erectile properties. But the exact mode of distribution of these elements is still a matter of controversy among histologists. From the researches of Winkler and Kolessnikow, recently confirmed by Partsch, it would appear that they occur not in the ducts themselves, but form an in- complete ring around and external to the same. In or around the smaller galactophorous ducts, muscle-cells cannot be unmis- takably recognized, though some authors have described their occurrence there. As regards the structure of these smaller galactoplwrous ducts {ductus lactiferi, milk-ducts) it is quite simple. Their membranous walls consist of a delicate and closely woven reticulum of connective tissue, with a large admixture of fine elastic fibres. Henle, Meckel, and Kolessnikow have described smooth muscle-cells in these canals, but, as already stated, Partsch and others have denied their existence. At any rate, on cross-sections the contracted condition of some of the larger ducts results in a stellate appearance of their lumina, whereas the smaller ducts always appear round or oval. The larger ducts traced into the gland tissue are found to be provided with saccular dilatations immediately beneath the nipple. These milk-reservoirs {sinus ductuum lactiferorum, sacculi lactiferi, or ampullw) may be 5 to 8 mm. broad, and thus become distinctly perceptible to the naked eye. Below these dilatations the ducts again grow narrower, and by numerous divisions and subdivisions form a system of ramifying tubes, which terminate in the secreting alveoli. The structure of the larger ducts does not materially differ from that of the smaller ones. Their walls are, of course, considerably thicker, and there is found in addition a greater proportion of elastic tis- 442 MANUAL OF HISTOLOGY. sue. All the different kinds of ducts show a lining composed of a single layer of short cylindrical cells, containing ellipsoid nuclei. The character of the lining cells is, however, gradually changed as the acini are approached, near which it merges into the alveolar epithelium by insensible gradations. Surrounding the nipple is a variously pigmented ring, called the areola mamnitf. Its surface is slightly corrugated, and this circumstance, taken in connection with its pigmentation, results in the production of the marked contrast it presents to the very white and soft integument covering the other portions of the female mamma. The areola is also provided with abun- dant unstriped muscle-fibres. Some of the latter surround the nipple in concentric rings, others pursue a radial course. The sudoriferous and sebaceous glands of the areola are conspic- uously developed, and lanugo hairs are also found. The fa- miliar changes which go on in the areola simultaneously with the development of pregnancy, are mainly due to increased blood-supply and additional pigmentation. The areola is also provided with small granules of secreting parenchyma. Some of these grains empty the products of their secretory activity by special recurrent ducts into the main excretory canals. But there are others which have special openings upon the free sur- face of the areola. Usually, little papillary eminences mark the presence of such orifices. These scattered bits of mam- mary parenchyma are known as the glandular aberrantes of Montgomery. Kolliker and others regard them as largely developed sebaceous glands. The arteries of the mamma are chiefly derived from the internal mammary artery and the long thoracic. The veins empty into the thoracic branches and cephalic vein. Both arterial and venous vessels proceed subcutaneously from the periphery to the nipple, whence branches are given off in a posterior direction. They. are not guided in their course by the distribution of the milk-ducts, but are distributed to the glandular parenchyma in such a way that each lobule has its own separate supply. Finally, under the areola the veins of the nipple form a circular anastomosing chain, known as the clrculus venosus of JIaller. Capillary vessels surround the acini, forming networks with rather close meshes. Of course, the varying states of expansion and contraction in the ultimate alveoli, which conditions correspond to phases of activity and THE MAMMARY GLAND. 443 rest, will materially affect the size and shape of the capillary- networks. They are, however, much less distinct and con- spicuous during the period of lactation than in the quiescent state of the gland. Rauber found in the glands of pregnant animals that the blood-vessels were not in immediate contact with the walls of the secreting vesicles, being separated from them by interposed lymph-channels. Coyne, Langhans, and Kolessnikow have also described these perialveolar lymph- spaces. Their presence is, indeed, readily demonstrated by injections with nitrate of silver solutions. In actively secreting glands these channels are sometimes packed with leucocytes, which also infiltrate the stroma of the organ. Lymphatics are plentiful in the mammary gland. We find them subcutaneously, as well as deep in the interior of the organ. Coyne, in 1874, described the perialveolar lymph- spaces, already mentioned, for the human mamma, and Koless- nikow, in 1870, perialveolar lymph- spaces for the mammary gland of the cow. Langhans succeeded in injecting a rich net- work of periacinal lymph-vessels, likewise lymph-channels around the excretory ducts and the lacteal sinuses. The lar- gest lymph-vessels are retro-glandular. They are without valves. The lymph-vessels of the nipple resemble those of the skin. There seems to be no free communication between the lacunal and interstitial spaces of connective tissue of the glands, and the proper lymph-channels. The principal lymph-vessels of the mamma, both deep and superficial branches, proceed to the glands of the axilla. But some of the mammary lymphatics also communicate, through intercostal branches, with the thoracic lymphatic glands. These are points worthy of remembrance in studying the mode of dissemination in mammary tumors. J\Terves abound less in the secreting structure of the mam- ma than in its integumentary apparatus. The majority are of spinal origin, although the sympathetic system is by no means excluded from representation. Branches from the fourth, fifth, and sixth intercostal nerves — the so-called rami glandit- A//V.S— accompany the milk-ducts, and ramify within the organ. Satisfactory evidence concerning the manner of their ultimate termination has, however, not been hitherto obtained. Most of the nerves in the interior of the organ belong to the vascular or vaso-motor variety, and many are seen to accompany the 444 MANUAL OF HISTOLOGY. blood-vessels. Eckliard lias given the most elaborate descrip- tion of the nerve-supply of the human mamma. Structure of fully expanded gland. — Immediately before, during, and after lactation, the mamma appears as a distinctly lobulated organ, having a pinkish or yellowish hue, and resem- bling in consistence the human pancreas or salivary gland. The different lobuli are made up of numerous ultimate acini, having, as a rule, a rounded, pyriform, or slightly poly- hedral shape. They are of nearly uni- form size, and are closely placed, being separated from one another by only sparing amounts of connective tissue, and the capillary vascular channels therein contained. Elastic fibres and smooth muscle-cells also occur, though not constantly, between the alveoli of the lobules. Lymphoid elements, as well as branched connective-tissue cor- puscles, are always encountered there in greater or less abundance. In addi- tion to these elements, large granular corpuscles containing nuclei are found. They are most numerous along the course of the blood-vessels, and appear to be identical with the so-called plasma cells of Waldeyer. Creighton, however, also describes similar cells in the interior of the alveoli, and believes that both are identical, maintain- ing that they are derived from the acinous epithelium. According to this author's description, such cells are " not infrequently seen in the tissue outside a lobule in rows three or four deep ; again, they are found in the interfascicular spaces among thelymphoid-cells," that have been already mentioned. These large, granular, and nucleated corpuscles are said to be filled with a bright yellow or golden pigment. Now, Creighton has pointed out that the periodical subsidence of the mammary function is accompanied by the formation of much corpuscular waste material. And the production of these remarkable yel- low cells, which finally leave the gland by way of the lymph- vessels, is, according to him, but a final phase of this process. The mammary epithelium which paves the acini has been variously described as consisting of flat polyhedral (Reinhard) ; ■Fig. 100. — Transverse section through the terminal vesicles of the planii in a nursing woman, showing interalveolar capillaries. Langer. THE MAMMAEY GLAND. 445 cubical, cylindrical (Kolessnikow) ; small polyhedral (Langer) ; and prismatic (Kehrer) cells. This discrepancy of opinion re- ceives its explanation from the fact that the epithelial cells Fig. 191. — Lobule of a mamma near the resting state. Numerous large pigmented cells within the acini and in the interlobular fibrillar tissue. Creighton. have a different appearance in the various conditions interven- ing between full activity and complete rest of the gland. Creighton has given a very satisfactory description of mam- mary epithelium. He states that in the fully expanded gland "the floor of an acinus in section is covered by a mosaic of polyhedric epithelial cells, usually to the number of fifteen or twenty, while in the larger elongated acini as many as thirty may be counted. The cells are usually pentagonal or hex- agonal, and the corners are sometimes rounded. In each cell there is a central round nucleus, which colors brightly with the staining fluid, and a broad fringe of protoplasm, which stains less deeply." The nucleus varies in its relative size, generally having a diameter equal to about one-third that of the entire cell. "In a profile view of an acinus, the epithelium appears as a circlet of oblong cells, in which the nucleus at the centre occu- pies almost the entire thickness of the cell. The mammary epithelial cell may therefore be described as a flattened poly- hedric body, with a thickness about one-half of its breadth. The substance of the nucleus is apparently homogeneous, with Fro. 192.— Fully expanded aci- nus, showing mosaic of polyhedral cells. Creighton. 446 MANUAL OF HISTOLOGY. a deeper line of staining round the margin ; a nucleolus is not always prominently seen." Structure of involuted mamma. — Having thus briefly indi- cated the main histological features of a fully evolved gland, we are now prepared to examine the mamma in a condition of advanced involution. By involution, in this sense, is meant the periodical return to inactivity, and not to final retrograde metamorphosis, which culminates in complete senile atrophy. The glandular lobules, then, in the involuted organ are again found to be composed of closely crowded alveoli. But all the lobules appear to have become smaller, and their acinous components are likewise shrunk- en. The basement-membrane of the latter does not appear to be materially altered, but its cellular contents are considerably changed. In place of the beautiful mosaic characteristic of the active gland, there now appears only an aggregation of nucleated corpuscles to the number of five or ten. Creighton describes them as "nothing else than a somewhat ir- regular heap of naked nuclei, with no fringe of protoplasm round them, and in size little, if at all, larger than the nucleus alone of the perfect epithelium." This description, how- ever, applies only to hardened specimens, for in fresh preparations the nuclei, as a rule, show a broader or narrower surrounding zone of protoplasm. As regards the diameter of the involuted acini, it is about one- fourth that of the actively secreting alveoli. Owing to the shrinkage in the glandular parenchyma, the blood-vessels and excretory ducts, as already stated, are more prominent in an involuted than in an active gland. It is not our purpose here to trace, step by step, the various processes by which a gland passes from the resting state to that condition of complete evolution which is alone compatible with active secretion. For the details of this interesting subject, the reader is referred to the work of Creighton. We may, how- ever, very briefly summarize this author's account of the trans- formations in question. The one essential circumstance char- acterizing the whole change is a process of vacuolation, which Creighton assumes to take place in the secreting cells. "The Fir.. 193. — Involnted mammary lobule, showing the nuclear contents of the alveoli. Creighton. THE MAMMARY GLAND. 44; most definite and unmistakable form of vacuolation is the sig- net-ring type." This process is, according to him, a true one of endogenous cell formation, resulting in this instance in the formation of milk. Moreover, large, granular, nucleated cells, filled with a bright yellow or golden pigment, "found both within the alveoli and in the interfibrillar spaces without them" ;f3ffiK^^w» Fig. 194. — Vacuolation of alveolar epithelium. From the udder of a ewe shortly after the end of lac- tation. The cells in situ are vacuolated cells, with the usual thin and, for the most part, uncolored hoop or ring of the vacuole, and the deeply stained peripheral mass. Creighton. characterize the last stage of involution, "and the pigment that belongs to them is to be found strewn over the lobules that have reached the resting state." Finally, Creighton as- serts that "the various forms of cells that characterize the various stages of involution must have resulted from a trans- formation de novo of the renewed epithelium, and not from successive changes upon the same cell." Each epithelial cell, therefore, that is used up in the formation of milk, has been at one time a perfect polyhedral corpuscle or fully equipped cell, and "has rapidly undergone the cycle of changes whereby its whole substance has been converted into milk," A distinguishing feature of one stage of evolution which 448 MANUAL OF HISTOLOGY. deserves to be mentioned, is " the presence in the cavities of the acini of a peculiar granular material, the coagulated con- dition oC a fluid." Partsch has also described the occurrence of this granular mass within the alveoli, and he states that the secreting epithelia, though of normal size, were furnished with shrunken nuclei, and showed numerous light spots, as if the cells were perforated and sieve-like. It would appear that this writer has ob- served the stage of vacuolation with- out, however, interpreting the same in Creighton's sense. Creighton also describes in certain glands the connective-tissue stroma as crowded with cellular elements, which he considers equally with the pigmented corpuscles as waste-cells of the secre- tion. Others (Winkler, Brunn, and par- ticularly Rauber) have assigned a far different significance to these bodies, as will appear farther on. Finally, Creigh- ton explains that the secretion of the mammary gland "may be said to be pro- duced by a transformation of the sub- stance of successive generations of epithelial cells, and in the state of full activity that transfor- mation of the substance is so complete, that it may be called a deliquescence." Although Creighton's investigations did not extend to the human mammary gland, there is ample ground for the belief that changes of evolution and involution similar to those which he has described in animals, constantly take place in the hu- man female as well. And even if we accept only some of his views on the inter-relations of physiological action and histo- logical appearance, the discrepancy still existing in the de- scriptions given by different authors will receive a more rational explanation than has hitherto been offered by writers on this subject. Certainly some of his assertions appear rather fanci- ful in their far-reaching novelty, nevertheless they deserve the attentive consideration which we have, at least, in part bestowed on them. From the results of our own examinations, we are unable Fig. 105. — Acini from a partly expanded gland, some of them filled with a granular material. From the mamma of a pregnant cat. Creighton. THE MAMMARY GLAND. 449 to concede in all respects the correctness of Creighton's inter- pretations. The evidences of epithelial destruction for purposes of milk secretion, are not positive and convincing. In the Har- derian gland, as well as in the mamma, we have observed the extrusion of fat-droplets from cells replete with them without destruction of the cell itself. Partsch agrees with us in assum- ing that the cells may burst or otherwise discharge their con- tents, and yet retain enough protoplasm to maintain their vital- ity ; and also that the vital contractions of the protoplasm may force out the oil-globules without destruction of the epi- thelium. What Creighton has called vacuolation does not mean death to the cells concerned in this action, for they retain their nuclei and sufficient protoplasm to become re-established as perfect epithelia. That this reformation of old epithelium takes place, is proven by the fact that a new formation by proliferation has never been observed, and by the additional circumstance that the mammary acini never show more than a single layer of lining-corpuscles, and, moreover, always show this layer complete. In this, as in many other respects, the mamma closely re- sembles the Harderian gland, more particularly of the roden- tia, as described by one of the writers in a monograph. The basement-membrane of the acini in every particular also corre- sponds in the two kinds of glands, being in both a homoge- neous, apparently structureless membrane, with superimposed branched adventitial cells, the so-called Stutzzellen of German writers. A basket-shaped reticulum, such as has been described by Boll, Langer, Kolessnikow, Moullin, and others, is never found to constitute this membrana propria, although artifi- cially, appearances simulating a structure of this kind are readily obtained, and have been interpreted by several histolo- gists as natural occurrences. In the cutaneous sebaceous glands the secreting vesicles are filh-d with several superimposed layers of epithelia, and it is this circumstance which leads to an entirely different mode of secretion. For there it would indeed appear that the cells undergoing fatty degeneration become detached from their bases and find their way into the narrow lumen of the acinus. The older or inner generation of cells thus vanishing is replaced by new corpuscles formed by gradual proliferation from the peripheral zone. 29 450 MANUAL OF HISTOLOGY. Hauberks views on the mamma and the lacteal secretion are somewhat startling, but must occupy our attention here. From a series of very carefully conducted examinations, principally on the glands of guinea-pigs during and after pregnancy, he feels justified in concluding that milk owes its orgin to the entrance of countless leucocytes into the lumen of the gland- vesicles. The emigrated lymphoid elements, he believes, pene- trate the alveolar walls, passing through the single layer of epithelial cells which line them. Arrived in the interior of an ultimate acinus, the leucocytes undergo fatty metamorphosis, and thus at length furnish the most essential and characteristic ingredient of milk, viz., the milk-globules. Rauber, therefore, discards the notion that the formed particles of the lacteal secretion originate in the glandular epithelium, and represent the elaborated products of its functional activity. He also denies that previously formed milk globules, or colostrum cor- puscles, ever pass through the alveolar walls. Thus the prim- itive opinion advanced by Empedocles, describing milk as white pus, is in a measure revived, and milk is held to be directly derived from the white corpuscles of the blood. Preparations of mammary glands taken from animals still suckling their young, according to him, invariably show the intraglandular lymph-vessels replete with leucocytes, the stro- ma similarly infiltrated, identical corpuscles in greater or less abundance within the vesicles, and transitional forms between lymphoid-corpuscles and milk-globules. These claims, granted to be facts, and considered in conjunction with the circum- stance that epithelial proliferation is not seen, would certainly go far to make Rauber' s theory seem a somewhat plausible one. Nevertheless, we require corroborative evidence from others, before his views can be accepted as anything more than an ingenious hypothesis. Rauber has also described the occurrence of a delicate stri- ation within the epithelial cells of the alveoli. These striae are said to be in all respects similar to those found in the secreting elements of certain portions of the salivary glands and the tubules of the kidneys. As regards the corpuscles of Donne, or colostrum bodies, most authors regard them as the products of desquamation of the alveolar epithelium, the latter being in a condition of fatty degeneration (Winkler, De Sinet}^, Buchholtz, and others). THE MAMMARY GLAND. 451 Some liistologists, like Strieker, hold that oil-globules may be expelled from the interior of fat-filled cells without disintegra- tion of their protoplasmic bodies. It is an undoubtable fact that colostrum corpuscles, when managed with proper precau- tions, may be seen to yield droplets of fat under the micro- scope, just as amoebae reject similar contained particles. Rau- ber, however, maintains that these bodies represent leucocytes in various stages of fatty metamorphosis, and he calls such corpuscles, when found in the gland vesicles, galactoblasts. In the gland of Harder, one of the writers has found the spacious gland vesicles lined with very large epithelia ; and these cells were in many animals entirely fat-filled. They se- creted a greasy substance not unlike thick milk. Yet destruc- tion of the cell-body did not occur, at least evidences of such a process could not be obtained. Partsch has therefore antici- pated the authors in their conclusion that the secretion of milk is accomplished in much the same way in which the creamy pro- ducts of the Harderian gland are formed, i.e., without total destruction of epithelial cells. According to our view, then, and it nearly coincides with the opinion of Strieker, Winkler, and especially Partsch, the cells containing the fat-globules may, indeed, burst and discharge their contents, but the nu- cleus and sufficient protoplasm are retained to enable the epi- thelium to recuperate, and in the course of time again and again discharge its contents. Along with this mode of milk secretion, a second process occurs. This consists of the gradual extrusion of oil-droplets, the cell body remaining entirely in- tact, since the mere vital contractions of the protoplasm suf- fice to drive out one milk-globule after another. When the activity of the gland is suddenly heightened in the period immediately before childbirth, some few epithelial cells are desquamated. These, appearing in the milk of most women, are identical with the bodies known and described as colostrum corpuscles. Of other anatomical constituents of normal milk, we only find the milk- or oil-globules. They are suspended in the fluid emulsion which milk truly represents, in countless numbers. They vary in size from 0.002 to 0.009 mm. A very delicate fringe of protoplasm adheres to their periphery, and it is for this reason that they may appear to become stained when sub- mitted to the action of proper dyes. 452 MANUAL OF HISTOLOGY. DEVELOPMENT OF THE GLAND. Like the other cutaneous glands of the body, the mamma is first formed by a proliferation inward of certain epidermal cells. In other words, the breast results from a downward extension of epiblastic corpuscles. The first unmistakable indi- cation of the future gland is seen about the third or fourth month of pregnancy. At that time it consists of a solid plug, or pro- Fig. 100.— 1. Rudimentary form of gland in human foetus: a, 6, epidermis : c, aggrega- tion of cells ; d, connective tissue layer. 2. From a seven-months' foetus : a, central substance ; b, larger, and C, smaller outgrowths. Frey. Fig. 197.— Embrj'onal mamma: a, cen- tral mass, with 6. and c, variously shaped outgrowths. Frey. cess, extending downward from the rete-mucosum of the skin. This has been called Driisenfeld, by Huss. From the internal end of this solid process, sprouts, or offshoots, are developed, and they represent the future separate glands constituting the mature organ. These buds have a pyriform, or club-like shape, and are surrounded by ordinary embryonal connective tissue. The further growth of the gland takes place by a process of continuous extension and subdivision, but indications of the latter are not always found at birth. Ducts are already visible in the new-born infant, but the aggregations of cells represent- ing the future acini, remain without lumina for a much longer period. Th. Kolliker describes as a constant occurrence, especially marked in the breasts of female infants, the dilatation of a greater or smaller number of milk-ducts. Such ectatic-canals DEVELOPMENT OF THE GLAND. 453 have their lamina filled with desquamated epithelial cells, and a whitish, granular material. Formerly, these occurrences were considered to be exceptional, and were regarded as having a pathological significance. During the first year of extra-uterine life, this characteristic process of progressive dilatation may assume such large dimensions, that the mamma may come to resemble cavernous tissue, the ectatic spaces of which are paved with flattened epithelium. Within certain limits, Kolli- ker regards this as a perfectly normal plrysiological event. But he adds that an exaggerated process of this kind may result in early mastitis. Such an occurrence, he thinks, may explain the rudimentary development of the breasts observed in some women of otherwise normal growth. The post-embryonal growth of the mamma has been care- fully studied by Langer, and his results and conclusions having been confirmed by the investiga- tions of Kolliker, Huss, and others, must still be received as represent- ing the true condition of things, in spite of the novel and heterodox views advanced by Creighton. Up to the time of jmberty, the growth of the breast is very grad- ual and quite insignificant, even in females. Then, however, the ducts begin to rapidly ramify in all di- rections, and, by offshoots from va- rious points, true acini are at length developed. But they remain of small size until the stimulus of pregnancy causes a further evolution. In the male, the exist- ing ducts, as a rule, atrophy with advancing age. The evolu- tion changes which the mamma undergoes during pregnancy, have already been set forth, and there remain to be considered only those final phases of metamorphosis which take place in the climacteric period of life. These are readily understood, consisting essentially of a complete atrophy of all tin: secreting acini. Simultaneously with t hese atrophic changes the epithelia of the galactpphorous ducts become flattened, and finally shrink, so as i<> form only squamous plates, which line tie; ramifying processes of connec- Fig. 198. — Transverse section of glandu- lar vesicles in a virgin. Langer. 454 MANUAL OF HISTOLOGY. tive tissue representing the former lactiferous canals. The terminal portions of these larger duct-remnants are sometimes connected with minute channels, the latter being the remnants of collapsed smaller ducts. In some measure we find a com- pensatory production of fat, which partly replaces the faded acini. The breasts of old women, therefore, consist of fibrous tissue, with a large proportion of elastic elements, fat-cells, and the remnants of the ducts. It may be remarked that the latter frequently show cystic dilatations, the cavities being filled with a dirty, slimy fluid. The blood and lymph-vessels, but especi- ally the latter, participate in the general atrophy of the tissues. This succinct account concerning the histogenesis of the mammary gland, does not, as already intimated, represent the unchallenged opinion on its first development. For Creighton, in the remarkable work already cited, radically opposes the view that the mamma takes its origin from the epiblast. He believes, on the contrary, that it starts from the mesoblast, or connective- tissue layer of the embryo, and not the upper epi- thelial layer or epiblast. According to him, moreover, and his conclusions are based on developmental studies, chiefly of the guinea-pig's gland, the process may be justly described as a centripetal one, whereas the current view represents this gland- develpoment as essentially centrifugal. We have already ex- pressed our adherence to the current view, attributing this growth to extension from a central point. Nevertheless, it seems proper to briefly give the conclusions of Creighton, es- pecially since they appear to be singularly corroborative of the account given by Goodsir of this process, as early as 1842, an account which has apparently remained almost unnoticed by workers in this branch of scientific medicine. Creighton then concludes his inquiry as follows : "1. The mammary acini of the guinea-pig develop at many separate points in a matrix-tissue. The embryo cells from which they develop are of the same kind that give origin to the surrounding fat-tissue. The process of development of the mammary acini is, step-for-step, the same as that of the fat- lob ales." " 2. The ducts of the mamma develop from the same matrix- tissue, by direct aggregation of the embryonic-cells, along predetermined lines. The ducts develop, in the individual guinea-pig, before the acini, whereas, in the phylogenetic sue- DEVELOPMENT OF THE GLAND. 455 cession, the ducts are a later acquisition. This reversal of the order of acquisition of parts is in accordance with the prin- ciple stated by Herbert Spencer, that 'under certain circum- stances the direct mode of development tends to be substituted for the indirect.' " Hints regarding the histological study of the mamma. — The evolution of the mammary structure progresses pari passu with the development of its functional activity. It is the stim- ulus of pregnancy which determines both. Nevertheless, even during the period of its fullest physiological bloom, i.e., during lactation, variations in the degree of functional activity normally take place. Moreover, the same gland may contain lobules which are comparatively at rest, and others which are at the full height of activity. This should always be borne in mind in interpreting the results of histological inspection of this organ, lest erroneous impressions be conveyed. The alveolar epithelial cells will, therefore, not be found alike in the different acini, nor yet even in the same vesicle. We may find cuboidal cells, and cylindrical ones, and flattened corpuscles, and in addition, various transitional forms between these t}'pes. The nucleus will appear round, or oval, and about 6-7 //. in diameter. Sometimes two nuclei may be found in one cell. The radiating striation observed by Rauber in many cells, has already received mention. It is a noteworthy fact that the cells themselves contain only a very small proportion of fatty granules, whereas the intra-alveolar lumen is often replete with the same. In order, then, to study the histology of the gland at the high-water-mark of its functional activity, animals should be chosen which have either just given birth to their young, or are about to do so. For the normal conditions of the human mamma are rapidly transformed by post-mortem change, if not previously altered in consequence of the disease which caused the death of the individual. The organ may be exam- ined fresh, or else hardened and then cut in sections to be stained and mounted in the ordinary manner. 456 MANUAL OF HISTOLOGY. BIBLIOGRAPHY. Rcdolpi. Bemerkungen ueber den Bau der Briiste. Abhandl. der Berliner Akad. 1831. Donne, Al. Du lait, etc., en particulier de celui des nourrices. Paris, 1837. Cooper. Anatomy of the Breast. 1889. GPterbock. Ueber die Douneschen Corps granuleux. Miiller's Arebiv. 1839. Henle. Ueber die mikroskop. Bestandth. d. Milch. Froriep's Notizen. 1839. Fetzeu. Ueber die weiblichen Briiste. Wurzburg, 1840. Nasse. Ueber die mikroskopischen Bestandtheile der Milch. Miiller's Archiv. 1840. Goodsir. Anatom. and Pathol. Observations. 1845. RiiiNiiARDT. Ueber die Entstehung der Kornchenzell en. Virchow's Archiv. Vol.1. 1847. Will. Ueber die Milchabsonderung. Erlangen, 1850. Langer. Ueber den Bau und die Entwickelung der Milchdriise. Denkschr. d. Wien. Akad. 1851. Also article on the Mammary Gland, in Strieker's His- tology. Luschka. Zur Anatomie der Mannl. Brustdriisen. Miiller's Archiv. 1852. Eckhard. Beitr. zur Anat. u. Phys. 1. Band. 1. Heft. Giessen, 1855. Viiu now. Die Cellularpathologie, p. 305. 1859. Duval. Du mamelon et de son aureole. Paris, 1861. Gruber. Ueber die Miinnliche Brustdriise. Memoiren d. Petersburger Akad. 1866. Stricker. Ueber contractile Korper, etc. Sitzber. d. Akad. "VVien. Vol. LIU. 1866. Zociier. Beitr. zur Anat. u. Phys. d. weibl. Brust. Leipzig, 1869. Hennig. Beitrag. zur Morphologie der weibl. Milchdriise. Arch. f. Gynakol. Vol. II., p. 331. 1871. Hess. Beitriige zur Entwickelung der Milchdriise beim Menschen, etc. Jenaische Zeitschrift, Vol. VII., 2. 1873. Langhans. Die Lymphgefiisse der Brustdriisen in ihren Beziehungen zum Krebse. Arch, fur Gynakologie, Bd. VIII., S. 181. 1875. Also, Zur pathologischen Histologic der weiblichen Brustdriise. Virchow's Archiv, p. 132. Bd. 58. 1873, Coyne. Sur les lacunes lymphatiques de la glande mammaire. Soc. de Biologic 21. Nov., 1874. Also, Sur les lacunes lymphatiques de la glande mammaire. Gazette Hebdom. , p. 775. 1874. De Sinety. Recherches sur les globules du lait. Arch, de Phys. 1874. Von Brunn. Gottinger Nachrichten, No. 19. 1874. Labbe and Coyne. Traite des tumeurs benignes du sein. 1876. Buciiiioltz. Das Verhalten der Colostrumkorper, etc. Gottingen, 1877. De Sinety. Sur le develop, et 1'histoL conip. de la mamelle. Gaz. med. de Paris, No. 6, p. 68. 1877. Kolessnikow. Die Histologie der Milchdriise der Kuh. Virchow's Archiv. Bd. 70, p. 531. 1877. Schmid, H. Zur Lehre von der Milchsecretion. Wurzburg, 1877. Wendt. Ueber die Hardersche Driise der Saugethiere. Strassburg. 1877. Winkler. Bau der Milchdriise. Jahresber. d. Ges. f. Natur. u. Heilkunde. Dres- BIBLIOGRAPHY. 457 den, 1874. Beitr. zur Histol u. Nervenverth. in d. Mamma. Archiv f. Gyna- kol. Vol. XI. 1877. KGlliker, Th. Beitrage zur Kermtniss der Brustdruse. Verh. d. phys.-ined. Ges. zu Wiirzburg. 1879. Rauber. Ueber die Absonderung der Milch. Sitzber. d. naturf . Gesel. zu Leip- zig, pp. 30-34. 1879. Also, Bemerkungen ueber den feineren Bau der Milch- driise. Schmidt's Jahrb. 1879. Rauber. Ueber den Ursprung der Milch. Leipzig, 1879. Billroth. Die Krankheiten der Brustdriisen. Deutsche Chirurgie. Lieferung 41. 1880. Partsch. Ueber den feineren Bau der Milchdriise. Breslau, 1880. Moullin. The Membrana Propria of the Mammary Gland. Journ. of Anat. and Phys. April, 1881. See also the text-books of Sharpey and Quain, Frey, Kolliker, Kiause, and Sappey. INDEX. ACINI of expanded mamma, 444 of liver, 183 of lung, 260 of pancreas, 410 Adenoid tissue, 69 of lymph -glands, 178 Adventitia of capillaries, 148 of arteries, 151, 155 Afferent vessels of kidney, 206 Aglobulie intense, 38 Air-cells of lung, 260 Alcohol and acetic and muriatic acids, 15 and acetic acid mixture, 14, 15 ALIMENTARY CANAL, 386 general considerations, 386 Large Intestine, 400 blood-vessels of, 401 lymphatics of, 401 nerves of, 401 structure of, 400 CEsopnAGus, 386 blood-vessels of, 388 fibrous envelope of, 388 layers of, 386 lymphatics of, 388 mucous membrane of, 386 muscular coat of, 387 muscularis mucosae of, 387 nerves of, 388 submucous layer of, 387 Rectcm, 401 sphincter ani of, 401 structure of, 401 Shall Ihtestihb, 394 blood-reMela of, 809 liruriner's glands of, ''Ml corona tubulorum of, 896 follicles of Lieberkiihn of, 398 glands of, 896 lymphatics of, 399 ALIMENTARY CANAL— Small Intestine — mucous membrane of, 395 muscular coat of, 394 muscularis mucosae of, 396 nerves of, 399 plexus of Auerbach, 399 plexus of Meissner, 399 Peyer's patches of, 396 serous coat of, 394 solitary follicles of, 396 submucous layer of, 396 valvuhe conniventes of, 395 villi of, 395 Stomach, 388 blood-vessels of, 392 compound peptic glands of, 390 etat mamelonne of, 389 lymphatics of, 393 mucous membrane of, 389 muscular coat of, 388 muscularis mucosa? of, 389 nerves of, 393 peptic glands of, 389 pyloric glands of, 391 serous covering of, 388 submucous layer of, 389 Vermiform Appendix, 401 Alizarine, 28 Alum carmine, 27 Alveoli of lung, 260 Ammonia bichromate, 14 Amoeboid movement, 39, 40 Anastomosis of capillaries, 148 Angle of aperture, 11 of lenses, 10 Aperture, angle of, 11 Apparatus, general, for microscopical work, 1, 2, 3, 4 Appendix vermiformis, 401 4G0 INDEX. Arachnoid, spinal, 297 Archil, staining with French, 28 Arciform fibres of medulla oblongata, 394 Areola of mamma, 442 Arnold's borax carmine staining, 22 Arrangement of object, 6 Arteria centralis retinas, 347 hyaloidea, 349 Arteries, 152 Arterioles, 152 Auerbach, intercalated areas of, 147 plexus of, 123, 399 Auricle of ear, 353 Axis-cylinder of nerve-fibres, 110 BARTHOLINE, glands of, 241 Beale, spiral fibre of, 122 Bed of nail, 294 Bibliography — of alimentary canal, 402 of blood, 54 of blood-vessels, 1G1 of bone, 101 of brain, 32G of cartilage, 88 of central nervous system, 326 of cerebellum, 326 of connective substances, 81 of ear, 367 of epithelium, 61 of eye, 352 of female organs of generation, 251 of general methods, 32 of kidney, 222 of liver, 199 of lymphatic system, 182 of male organs of generation, 238 of mammary gland, 456 of mouth and tongue, 384 of muscle, 140 of nasal fossse, pharynx, and tonsils, 375 of nervous system, 127 of pancreas, 418 of pituitary body, 419 of respiratory tract, 267 of skin, 295 of spinal cord, 325 of spleen, 418 BlBLIOGTUrilY— of teeth, 108 of thymus gland, 419 of thyroid body, 419 of urinary excretory passages and su- prarenal capsules, 437 Bichromate of ammonia, 14 preparation of nerves with, 115 Bichromate of potassium, 14 Bigelow's studies on cartilage, 87 Bile-ducts, 191 Bisi nark brown, 26 Bladder, 430 BLOOD, 34 amoeboid movements of leucocytes of, 39 Brownian movement in leucocytes of, 39 circulation of, examined during life, 45 curara for paralysis of frogs, 45 globules of, in different fluids, 38 granules of, 39 hamiatoblasts of, 47 heating slide for the study of, 40 liquor sanguinis, or plasma of, 34 red corpuscles of, 34 action of acids on, 43 of alkalies on, 44 of carbonic acid on, 42 of distilled water on, 41 of electricity on, 44 of salt solution on, 40 counting of, 48, 53 crenation of, 45 development of, 47 examination of, 47 haemochromometer for estimat- ing richness, 53 haemoglobin of, 53 internal structure of, 46 Keyes's method of counting, 50 Malassez's method of counting, 50 measurement of, 36 number of, 37 stroma of, 46 third corpuscular element of, 48 white or colorless corpuscles of, 48 Blood-corpuscles, nucleated, 95 Blood-crystals, 53 INDEX. 461 BLOOD-VESSELS, 142 methods of injecting, 30 of bladder, 431 of choroid, 337 of cornea, 333 of iris, 343 of kidney, 213 of large intestine, 401 of liver, 186 of lung. 2G3 of lymph-glands, 179 of mamma, 442 of mouth, 379 of oesophagus, 388 of optic nerve, 349 of ovary, 247 of pancreas. 411 of penis, 224 of retina, 347 of skin, 279 of small intestine, 399 of spinal cord, 298 of spleen, 407 of stomach, 392 of suprarenals, 436 of testis, 234 of thymus. 414 of thyroid, 416 of uterus, 245 ARTERIES, 151 adventitia of, 151, 155 external elastic coat of, 155 internal elastic coat of, 152 internal fibrous coat of, 153 intima of, 152 media or musculosa of, 154 muscular and elastic types of, 152 Arterioles, 152 Capillaries, anastomosis of, 148 endothelial desquamation, 147 endothelium, 143 genesis, reproduction, and regen- eration of, 150 intercalated areas of, 147 intracellular network, 143 intranuclear network, 143 perithelium or adventitia of, 148 ramification of, 149 structure of, 146 varieties of, 145 Coccygeal Gland of Luschka, 158 blood-vessels- Corpora Cavernosa, 160 general remarks on, 142 Intercarotid Gland, 100 lymphatics of, 161 nerves of, 161 perivascular spaces, 161 varieties of, 142 vasa vasorum, 161 Veins, 155 distinction between veins, arte- ries, and capillaries, 156 internal elastic coat of, 157 internal fibrous coat of, 157 points of difference from arte- ries, 156 structure of, 156 valves of, 158 venules, 156 Boehmer's haematoxylon, 23 BONE, 89 cancellous tissue of, 94 chondro-porosis, 98 compact tissue of, 89 corpuscles of, 90 development of, 96, 99 formation of callus in, 100 formation of, from cartilage, 97 from membrane, 98 Haversian canals of, 91 Howship's lacunae of, 100 intermediary cartilage of, 97 lacunae of, 91 lamellae of, 90 marrow of, 95 cells of, 95 myeloplaxes, 95 primary cavities of, 98 red, 95 yellow, 95 metaplastic, 98 naphthaline yellow for staining, 27 osteoblasts, 96, 98 osteoclasts, 100 osteoporosis, 99 periosteal processes of, 94 periosteum of, 90 points of ossification, 98 preparation of, 92 Sharpey's fibres of, 94 varieties of, 89 462 INDEX. Borax carmine, 22 Bowman's capsules of kidney, 204 glands of nose, 372 membrane, 79, 331 Brain, method of hardening, 15 Branched corpuscles of connective tissue, 67 Bronchioles, 2G0 Bronchi, primary, 257 smaller, 2.j9 Brownian movement, 39 Brunner's glands, 397 Burdach, column of, 298 CALCIFICATION of cartilage, 84 ^ of cartilages of larynx, 255 Callus, formation of, 100 Calyx of kidney, 216 Canal, central, of spinal cord, 301 of Petit, 350 of Schlemm, 336 Canals, dentinal, 104 intermediate, of liver, 184 semicircular, 359 Capillaries, 142 Capillary bile-ducts, 192 Capsule, internal, of brain, 317 of kidney, 216 of liver, 183 of spleen, 404 of suprarenal bodies, 432 of Tenon, 337 of thymus, 412 of thyroid, 415 Capsules, suprarenal, 431 Carmine, alum, 27 CARTILAGE, 82 Bigelow's studies on, 87 capsules of, 82 corpuscles of, 82, 83 division of, 86 structure of, 87 daughter- cells, 84 fibrillation of, 83 fibrous, 86 hyaline, 82 calcification of, 84 methods of studying, 84 intercellular substance of, 83, 87 intermediary, 97 parenchymatous, 83 CARTILAGE— perichondrium of, 86 purpurine for staining, 85 reticular or yellow elastic, 85 varieties of, 82 Spina's views on, 87 Cartilages of bronchi, 257 of larynx, 254 Cartilago-triticea of larynx, 253 Caruncula lachrymalis, 330 Cavernous tissue, 160 Cells, giant, 95 of liver, 189 Cellular tissue, 63 Cement of teeth, 105 Central canal of spinal cord, 301 CENTRAL NERVOUS SYSTEM, 296 Cerebellum, 317 cells of Purkinje of, 318 corpus dentatum of, 317 cortex of, 319 cerebral ganglia, 319 cerebral ventricles, 319 Cerebrum, 321 cortex of, 321 convolutions of, 321 fissure of Rolando, 321 of Sylvius, 321 island of Red, 322 meninges of, 321 minute structure of, 323 cortex of, 323 motor tract of hemispheres, 322 paracentral lobule, 323 choroid plexus, 320 corona radiata, 317 corpus striatum, 319 ependyma, 320 internal capsule, 317 locus casruleus, 315 niger, 316 medulla oblongata, 307 arciform fibres of, 309 central gray matter of, 308 decussating fibres of, 307 formatio-reticularis of, 308 raphe of, 307 nucleus lenticularis, 316 Olivary Body, 310 glossopharyngeal, root of, 313 hypoglossal, nucleus of, 311 INDEX. 463 CENTRAL NERVOUS SYSTEM— Olivary Body — nucleus and root of abducens nerve, 314 parolivary nucleus of, 311 roots of fifth nerve, 315 upper spinal accessory, nucleus of, 311 optic thalaini, 319 pons, 315 spinal arachnoid, 297 spinal cord, 298 amyelinic fibres of, 301 blood-vessels of, 298 central canal of, 301 cervical enlargement of, 304 column of Burdach of, 298 column of Clarke of, 301 column of Coll of, 298 dorsal region of, 304 epithelium of, 301 filum terminate of, 302 general histology of, 298 gray commissure of, 304 gray matter of, 299 lumbar enlargement of, 303 methods of study of, 305 myelinic fibres of, 300 nerve-elements of, 299 neuroglia-cells of, 298 root radicles of, 299 special study of different portions of, 301 white commissure of, 303 white substance of, 299 Bpinal dura mater, 290 spinal fluid, 297 spinal pia mater, 297 Cerebellum, 317 Cerebral ganglia, 319 meninges, 321 ventricles, 319 Cervical enlargement of spinal cord, 304 Chalice cells, 00 Chamber, moist, 42 Chloride of gold, 28, 29 Chondro-porosis, 98 Choroid coat of eye, 338 plexus, 320 Cilia of eyelids, 328 Ciliary body, 840 Ciliated epithelium, 58 Circle of Haller, 349 Circulation of blood, 45 Circulus venosus of Haller, 442 Clarke, column of, 304 Clitoris, 240 Coats of arteries, 152 Coccygeal gland, 158 Cochlea, 362 Cohnheim's muscular areas, 136 Colostrum, 450 Columnar epithelium, 60 Column of Burdach, 298 of Clarke, 304 of Goll, 298 Columns, muscular, 138 Commissure, gray, of spinal cord, 304 white, of spinal cord, 303 Conjunctiva, 330 fornicis, 329 tarsi, 328 CONNECTIVE SUBSTANCES, 62 branched corpuscles of, 67 corpuscles of, 65 development of, 64, 65 fibril] ated, 66 growth and development of, 79 intercellular substance of, 64 lymphoid corpuscles of, 67 of mesentery, 68 plasma-cells of, 67, 74 reticular form of, 66 of liver, 188 of nerves, 126 of skin, 275 Contraction, study of muscular, 135 Convoluted renal tubules, 205 Corium, 277 Cornea, 331 preparation of, 25 Corneal corpuscles, 75 tissue, 75 Corneous layer of skin, 274 Corniculum of larynx, 255 Corona radiata of brain, 317 tubulorum, 316 Corpora cavernosa, 160 Corpus albicans, 250 dentatum cerebelli, 317 luteum, 249 Corpuscles, colostrum, 450 464 INDEX. Corpuscles, corneal, 75 fixed, of cornea. 332 lymphoid, of lymph-glands, 178 of skin, 277 Malpighian, of spleen, 404 of bone, 90 of cartilage, 82, 83 of Donno, 450 of muscle, 136 tactile, 124 of skin, 280 of tendon-tissue, 73 yellow, of mamma, 444 Corpus striatum, 319 Cortex cerebri, 321 Cortex of cerebellum, 319 of kidney, 201 of suprarenal capsules, 432 Corti's membranes, 366 organ, 362, 364 Cowper's glands, 227 Creigh ton's views on the mamma, 445, 446, 454 Crista acustica, 360 spiralis, 364 Crystalline lens, 350 Curara for producing paralysis, 45 Cuticula of teeth, 107 Cylindrical epithelium, 60 Cystic duct, 198 Czermak, interglobular spaces of, 103 TiARTOS, 231 -*-' Daughter-cells of cartilage, 84 Decidua, 245 Deiter's, protoplasmic processes of, 120 Dentine, 103, 106 Dentinal canals, 104 globules, 104 teeth, 106 Descemet's membrane, 79, 333 Detrusor urinoe, 430 Development of blood-corpuscles, 47 of capillaries, 150 of bone, 96 of enamel, 108 of fat-tissue, 168 of hair, 293 of lymphatics. 175 of mamma, 452 of nail, 295 Development of ovary, 250 of pancreas, 4 1 2 of sebaceous glands, 286 of spleen, 409 of suprarenals, 436 of sweat-glands, 282 of teeth, 105 of thymus, 414 Diaphragms, 5 Dilator muscle of iris, 342 Direct light, 5 Division of cartilage corpuscle, 84, 186 Double staining with borax carmine and indigo carmine, 22 with eosine and aniline colors, 24 Doyere's eminence, 126 Dru&enfeld of mamma, 452 Duct, cystic, 198 of pancreas, 411 thoracic, 174 Ducts, ejaculatory, 235 galactophorous, 441 Ductus communis, 198 Dura mater, spinal, 296 I E AR, 353 Eustachian tube, C55 External ear, 353 auricle of. 353 meatus of, 353 membrana tympani of, 354 Internal ear, 357 "auditory teeth" of, 364 cochlea of, 362 Corti's membrana tectoria of, 366 crista acustica of, 360 crista spiralis of, 364 Henson's prop-cells of, 366 labium tympanicum of, 364 labium vestibulare of, 364 lamina reticularis of, 366 lamina spiralis of, 362 macula acustica of, 360 membrana basilaris of, 364 membrane of Reissner, 3G2 membranous labyrinth of, 358 modiolus of, 362 organ of Corti, 362, 364 otoliths of, S58 recessus internus of, 364 INDEX. 4G5 Ear- Internal ear— saccule of, 358 scala tympani of, 362 Bcala vestibuli of, 362 semicircular canals of, 359 utricle of, 358 zona pectinata of, 366 Middle ear, 355 glands of, 355 structure of, 355 Ectasia of milk-ducts. 452 Efferent vessels of kidney, 206 Ejaculatory ducts, 235 Elastic fibres of skin, 277 Elastic tissue, 77 fibres of, 77 networks of, 78 of ligamentum nuchae, 79 perforated membrane of, 79 Electricity, action of, on blood, 44 Embedding specimens, 15, 16 Enamel, 102 Enamel organ, primary, 107 secondary, 107 Eudoneurium, 126 Endothelium, 80 and stomata of lymphatics, 169 germinating, 165 vascular, 143 Eosine, 24, 25 and ha.-matoxylon, 25 Ependyma, 320 Epidermis, 271 Epididymis, 231 Epiglottis, 255 Epineurium, 126 Epithelium. •*",(; bacteria of, 57 ciliated, 68 columnar or cylindrical, 60 granules of, 61 networks of, 61 pigmented, 58 squamous or flattened, 57 structure of, 61 Epithelium of bladder, 430 of collecting tubules of kidney, 211 of involuted mamma, 446 of looped renal tubules, 210 of lung, 261 30 Epithelium of mamma, 444 of mouth, 377 olfactory, 371 of renal tubules, 206 of spinal cord, 301 of thyroid, 415 Erector pili muscles, 422 Etat mamelonne of stomach, 389 Eustachian tube, 355 Expanded mamma, structure of, 444 External ear, 353 External elastic coat of arteries, 155 EYE, 328 arteria hyaloidea of, 349 caruncula lachrymalis, 330 Ciliary body of, 340 in hypermetropic eye, 342 in myopic eye, 341 Choroid, 338 blood-vessels of, 339 lamina chorio-capillaris of, 339 lamina suprachoroidea of, 338 nerves of, 340 structure of, 338 Conjunctiva, 330 lymph-spaces of, 331 Cornea, 331 blood-vessels of, 333 Bowman's membrane of, 331 Descemet's membrane of, 333 fibras arcuatae of, 332 fixed corpuscles of, 332 lamella? of, 331 nerves of, 333 preparation of, 334 Eyelids, 328 conjunctiva fornicis, 329 conjunctiva tarsi, 328 cilia of, 328 Meibomian glands of, 329 muscle of Miiller, 329 orbicularis palpebrarum, 328 Riolani's muscle of, 329 tarsus of. 328 FontaDa's space of, 336 Iris, 342 blood-vessels of, 343 dilator muscle of, 342 ligament of, 336 nerves of, 343 Bphincter of, 342 4<;<; INDEX. EYE- Ihis, uvea of, 343 Lachrymal gland, 351 glandula Galeni of, 351 glandula Monroi of, 351 Lens, 350 canal of Petit, 350 ligament of, 350 ligamentum pectinatum iridis, 335 Optic nerve, 348 blood-vessels of, 349 circle of Haller, 349 neuroglia of, 348 subdural space of, 348 vagina fibrosa of, 348 Orbicularis ciliaris, 340 Ora serrata, 340 Retina, 343 arteria centralis of, 347 blood-vessels of, 347 ganglion-cell layer of, 344 inner granular layer of, 344 inner nuclear layer of, 345 layer of rods and cones of, 345 macula lutea of, 344, 346 membrana limitana externa of, 345 membrana limitans interna of, 346 outer granular layer of, 345 outer layer of, nuclei of, 345 pars ciliaris of, 347 pigment layer of, 346 preparation of, 347 Scblemm's canal, 336 Sclera, 337 lamina cribrosa of, 337 perichoroidal space of, 337 structure of, 337 Tenon's capsule of, 337 tunica vasculosa of, 338 venae vorticosas of, 337 vitreous body, 349 fossa patellaris of, 350 T^ALLOPIAN TUBES, 246 -*- Fat-canals of cutis vera, 421 Fat-cells of skin, 276 Fat-columns of cutis vera, 421 Fat-tissue, 73 Fibres arcuatcc of cornea, 332 Fibres, muscular, 128 Fibrillation of cartilage, 83 Fibrous cartilage, 86 tissue, 66 Filum terminale of spinal cord, 302 Fimbria? of tongue, 380 Fissure of Rolando, 321 of Sylvius, 321 Fluid, spinal, 297 Follicles of Lieberkuhn, 398 of lymph-glands, 176 of thymus, 412 Fontana's spaces, 336 Foramen caecum of tongue, 383 Formation of bone, 97 of callus, 100 Formatio reticularis of medulla oblongata, 308 Fossa? nasales, 368 Freezing section-cutter, 17 French archil, 28 Frog's bladder, muscle of, 129 Frommann's lines, 113 p ALACTOBLASTS, 451 ^ Galactophorous ducts, 441 Gall-bladder, 197 Ganglia, cerebral, 319 Ganglia of spinal cord, 120 Ganglionic bodies, 119, 121 corpuscles of brain, 72 Gas-chamber, 43 Gelatinous tissue, 63 Genital organs, female, 240 male, 223 Germinating endothelium, 165 Giant-cells, 95 Gibbes' double, triple, and quadruple staining, 26 Giraldes, organ of, 231 Gland, coccygeal, 158 inter-carotid, 160 lachrymal, 351 pineal, 417 thymus, 412 thyroid, 415 Glands, Bowman's, of nose, 372 lymphatic, 176 Meibomian, 329 INDEX. 407 Glands of Bartholine, 241 of bile-ducts 191 of bronchi, 258 of Brunner, 397 of Cowper, 227 of larynx, 256 of middle ear, 355 of small intestine, 366 of tongue, 383 peptic, 389 pyloric, 391 sebaceous, of skin, 285 sudoriparous, 282 Glans clitoridis, 241 penis, 224 Glandular aberrantes mammae, 442 Glandula Galeni, 351 Monroi, 351 Glandules of mouth, 378 Glisson's capsule, 183 Glosso-pharyngeal root, 313 Goblet cells, 60 Gold, chloride of, 28 Goll, column of, 298 Graafian follicles, 248 Granular layer of skin, 274 Gray matter of spiDal cord, 299 Green coloration of nuclei, 25 Growth, post-embryonal, of mamma, 453 TT^MACHROMOMETER, 53 -*--*- Haemoglobn, 53 Hsematoblasts, 47 Haematometers, 50, 53 Haematoxylon, preparation of nerves in, 118 solution. 25, 24 Hailes's microtome, 19, 20 Hair, 888 Haller, circle of, 349 circulus venosus of, 442 Hamilton's preservative fluid, 20 Hand section-cutter, 16 Hardening of brain, 15 Haversian canals of bone, 91 Heart, muscular fibres of, 140 Heidenbain, roda of. 207 Henson's prop-col N, 866 Hepatic artery, 186 cells, 189 Hints regarding study of mamma, 455 Horny teeth, 1U6 Howship's lacunae, 100 Hyaline cartilage, 82 Hydatid of Morgagni, 231 Hymen, 241 Hypermetropia, ciliary body in, 342 Hypoglossal nucleus, 311 TLLUMINATIOX, 4 J- Induline, 27 Infundibula of lung, 260 Injecting fluids, 30, 32 Injection of blood-vessels, 30, 31, 32 of cutis vera, 424 of kidney, 214 of liver, 185 of lymph-glands. 179 of lymphatics, 169 Instrument, care of, 7 Intercarotid g!and, 160 Intercalated portions of renal tubules. 211 Intercellular substance of cartilage, 83 of connective tissue, 64 Intermuscular tissue. 74 Internal capsule of brain, 317 Internal elastic coat of arteries, 152 of veins, 157 Internal ear, 357 Internal fibrous coat of arteries, 153 of veins, 157 Intima of arteries. 152 Invertebrates, muscle of, 133 Involuntary muscle-fibre, 128 Involuted mamma, histology of, 446 Iodized serum, 38 Irrigation, method of, 41, 67 Iris, 342 diaphragm, 5 Island of Reil, 322 Ivory, 103 T7 ARYOKINESIS, 237 -*-*• Keyes's method of counting blood - globules, 51 KIDNEY. 201 alb-rout vessel of, capsule of, 200 blood-vessels of, 213 Bowman's capsules of, 204 calyx of, 216 408 INDEX. KIDNEY— capsule of, 216 collecting tubules of, 205 convoluted tubes of, 2U5 efferent vessel of capsules of, 206 epithelium of collecting tubules, 211 of looped tubules of, 210 of tubules of, 206 general plan of structure of, 201 boundary layer, 201 cortex. 201 medulla, 201 medullary rays, 201 injection of, 214 intercalated portions of tubules of, 211 looped tubules of, 209 lymphatics of, 216 membrana propria of tubules of, 203 method of preparing sections of, 208 natural injection of tubules of, 216, 220 nerves of, 216 rods of Heidenhain, 207 stroma of, 215 tubules of, 203 vasa recta of, 214 Kleinenburg's haematoxylon, 23 Klein's hasmatoxylon, 24 Klein's method of studying the omentum, 166 Kuhnt, hoW cylinder of, 114 LABIA MAJOR A, 240 minora, 240 Labium tympanicum, 364 vestibulare, 364 Labyrinth, 358 Lachrymal gland, 351 Lacunae, Howship's, 100 Lacunas of bone, 91 Lamellae of bone, 90 Lamina chorio-capillaris, 339 cribrosa of sclera, 337 reticularis of ear, 366 spiralis, 362 suprachoroidea, 338 Large intestine, 400 Larynx, 253 LeDs, 350 Lenses, high, testing of, 10 kinds of, 6 measuring angle of, 10 testing of, 8 Leucocytes, 39, 48 Lieberkiihn's follicles, 398 Ligament of iris, 336 of lens. 350 Ligaments of larynx, 253 Ligamentum pectinatum iridis, 335 Light, direct, 5 oblique, 5 Liquor sanguinis, 34 LIVER, 183 acini of, 183 bile-ducts, capillary, 192 Mayer's views on, 196, 197 natural injection of, 193 walls of, 196 bile-ducts, larger, 191 blood-vessels of, 186 capsule of, 183 cells of, 189 central veins of, 184 connective tissue of, 188 cystic duct, 198 ductus communis, 198 fat-droplets in cells of, 190 gall-bladder, 197 coats of, 198 glands of bile-ducts, 191 Glisson' s capsule of, 183 general plan of structure of, 183 hepatic artery, 186 hepatic lobules, 183 injection of, 185 interlobular septa of, 188 interlobular veins of, 184 intermediate canals of, 184 intralobular veins of, 184 lymph-vessels of, 198 nerves of, 199 sublobular veins of, 185 Lobule, paracentral, 323 Lobules of liver, 183 Lobulettes of lung, 260 Locus caeruleus, 315 niger, 316 Looped renal tubules, 207 Lumbar enlargement of spinal cord, 303 Lungs, 257 INDEX. 469 Lunula of nails, 294 Luschka's gland, 158 Lymphangeal nodules, 167 tracts, 167 Lymphatic glands, 176 Lymphatics of bladder, 431 of blood-vessels, 161 of kidney, 216 of large intestine, 401 of larynx, 257 of liver, 198 of lung, 264 of mamma, 443 of mouth, 379 of oesophagus, 388 of pancreas, 411 of small intestine, 399 of spleen, 409 of stomach, 393 of suprarenals, 436 of testis, 234 of thymus, 414 of thyroid, 416 LYMPHATIC SYSTEM, 163 artificial injection of lymphatics, 169 cystemae lymphaticae, 170 development of fat-tissue, 168 endolymphangeal tracts, 167 endothelium and stomata, 169 general histology of, 164 germinating endothelium of, 165 glands of, 175 adenoid or reticular tissue of, 178 afferent and efferent branches of, 176 follicles of, 176 injection of, 179 lymphoid corpuscles of, 178 medulla and cortex of, 176 methods of studying, 179 nerves of, 179 Ranvier's plan of injection of, 180 sinuses of, 177 stroma of, 176 re*eli of, 179 Klein's method of studying omentum, 106 lymphangeal nodules or patches of, 167 lymphangeal tracts of, 167 LYMPHATIC SYSTEM— lymphatic radicles, course and ter- mination of, 168 lymphatics, 175 development of, 175 of mesentery, 165 of tendons, 175 lymphatic vessels, 172 intimate structure of, 172 topographical peculiarities of, 174 variations in shape of, 173 lymph-spaces, 175 subarachnoid and subdural, 175 modern views on, 163 nerves of peritoneum, 172 perilymphangeal tracts, 167 plasma-cells, 164 plasmatic channels, 165 pseudo-stomata, 171 Ranvier's taches laiteuses, 168 views on false stomata, 170 relations to connective tissues, 163 retrospective view of, 181 sap-canaliculi of, 165 stomata of, 165 stomata vera of, 171 thoracic duct, 174 Lymphoid cells of brain, 72 Lymphoid corpuscles cf connective tissue, 67 of lymph-glands, 178 of skin. 277 Lymph-spaces, subarachnoid, 175 Lymph-vessels of penis, 224 TVfACULA ACUSTICA, 360 111 lutea, 344, 346 Malassez's method of counting blood-cor- puscles, 50 Malpighian corpuscles of spleen, 404 layer of skin, 271 Mammary epithelium, 444 MAMMARY GLAND, 439 areola of, 442 blood-vessels of, 442 circulus venosus of Ilaller of, 442 colostrum bodies, or corpuscles of Donm':, 450 development of, 452 Driisenfeld, 452 470 INDEX. MAMMARY GLAND— ectasia of milk-ducts, 452 galactoblasts of, 451 galactophorous ducts of, 441 general considerations on, 439 glandule aberrantes of, 442 growth of, 453 Creighton's views on, 454 Harderian gland, similarity with, 449 lymphatics of, 44:! membrana propria of, 449 milk-globules, 451 milk-reservoirs of, 441 nerves of, 443 nipple or mamilla of, 440 Partsch's views on milk-secretion, 451 Rauber's views on the mamma and the lacteal secretion. 450 structure of fully expanded gland, 444 acini of, 444 Creighton's views on, 445 epithelium of, 444 plasma-cells of, 444 yellow cells of. 444 structure of involuted mamma, 446 Creighton's account of, 446 epithelium of, 446 vacuolation of epithelium of, 447 study of, 455 Stutszellen of, 449 Wendt's views on secretion of milk, 449, 451 Mammilla, 440 Marrow of bone, 95 Measurement of red blood-corpuscles, 35 Meatus audit >rius externus, 353 urinarius of female, 242 of male, 226 Media or musculosa of arteries, 154 Medulla of suprarenal capsules, 435 oblongata, 307 of kidney, 201 Medullary rays of kidney, 201 Meibomian glands, 329 Meissner's plexus, 122, 399 Membrana basilaris of ear, 364 limitans olfactoria, 372 propria of mamma, 449 propria of renal tubules, 203 tectoria of ear, 366 tympani, 354 Membrane of Bowman, 79 of Corti. 866 of Uescemet, 79 of Reissner, 362 Meninges of brain. 331 of spinal cord, ^!)(i Metallic solutions, 28, 29 Metaplastic bone, 98 Methods for preparing objects, 12 of preparing tissues, 14 of studying hyaline cartilage, 84 of studying spinal cord, 305 Methyl -green, 29 and induline, 27 Micrometer, stage, 7 Microscope, how to use, 4 testing of, 7 Microtome, Hailes', 19, 20 Vincent's, 21 Middle ear, 355 Milk-ducts, 444 Milk-globules, 451 Milk reservoirs, 441 Miller's picro-carmine, 23 Mirrors; 5 ; Modiolus, 362 Moist chamber, 42, 43 Molybdate of ammonia, 15 Morgagni, hydatid of, 231 Motor tract of hemispheres, 322 MOUTH AND TONGUE, 377 Mouth, 377 blood-vessels of, 379 epithelium of, 377 glandules of, 378 lymphatics of, 379 nerves of, 379 submucous tissue of, 377 tunica propria of, 377 Tongue, 380 circumvallate papilla; of, 383 glands of, 383 filiform papilla; of, 380 fimbria} of, 380 foramen coscum of, 383 fungiform papilla; of, 381 papillae foliatae of, 383 taste-goblets of, 381 Mucous membrane of larynx, 255 of oesophagus, 386 of small intestine, 395 INDEX. 471 Mucous membrane of stomach, 389 Mucous tissue, 63 Muscle, 128 Oohnheim's areas of, 136 columns of, 138 conclusions regarding structure of, 137 fibres of, 128 of frog's bladder, 129 of fly, 133 of heart, 140 of human embryo, 132 of invertebrates, 133 of the ' ' lucky bug " or gyrinus, 134 of water-beetles, 133 involuntary, 128 nuclei and corpuscles of, 136 peculiarities of, associated with differ- ent functions, 138 polarized light for the study of, 137 red and white, of rabbit's leg, 138 sarcolemma, 130 striation of fresh, fibre, 131 study of contraction of, 135 termination of, in tendon, 139 transverse sections of, 136 vascular supply of, 138 voluntary fibre. 130 of Miiller, 329 of Riolani, 329 termination of nerves in, 125 Muscles of skin, 287 Muscular coat of oesophagus, 387 of small intestine, 394 of stomach, 388 fibres of heart, 140 Muscularis mucosae of oesophagus, 387 of small intestine, 396 of stomach, 389 Musculosa of arteries, 154 Mi.ller's fluid, 14 muscle, 329 Myelinic fibres of spinal cord, 301 nerve-fibres, 109, 116 Myeloplaxes, 95 Myopia, ciliary body in, 341 VTABOTH, ovulaof, 244 1^ Nail-fold, 294 Nails. 2!K! Naphthaline yellow, 27 NASAL FOSS.E, PHARYNX, and TON- SILS, 368 Nasal Fossae, 368 Bowman's glands of, 372 indifferent cells of, 371 membrana limitans, olfactoria of, 372 mucous membrane of, 368 olfactory cells of, 371 olfactory epithelium of, 371 olfactory nerves of, 372 olfactory region of, 370 thicker membrane of, 369 thinner membrane of, 369 respiratory region of, 368 vestibulum nasi, 368 Pharynx, 373 mucous membrane of, 373 pharyngeal tonsil of, 373 Tonsils, 373 Natural injection of liver, 193 of kidney, 216, 220 Nerve-elements of spinal cord, 299 Nerve-fibres, varieties of, 109 Nerves of bladder, 4:J1 of blood-vessels, 161 of choroid, 340 of cornea, 333 of iris, 343 of kidney, 216 of large intestine, 401 of larynx, 257 of liver, 199 of lung, 265 of lymph- glands, 179 of mamma, 443 of mouth, 379 of oesophagus, 388 of ovary, 248 of pancreas, 411 of penis, 225 of peritoneum, 172 of skin, 279 of small intestine, 399 of spleen, 409 of stomach, 393 of suprarenals, 436 of thyroid, 416 of uterus, 245 olfactory, :;72 Nerve-terminations, 109 472 INDEX. NERVOUS SYSTEM, 109 Auerbach's plexus, 1:23 axis-cylinder, 110 connective tissue of nerves, 12G Deiter's protoplasmic processes, 120 Doyere's eminence, 120 endoneurium, 125 epineurium, 120 fibres of Remak, 117, 118 preparation of, in hasmatoxylon, 118 Fromrnann's lines, 113 ganglia of cranial and spinal nerves, 120 ganglia of spinal cord, examination of, 120 ganglionic bodies, 119 of human brain, 121 of sympathetic system, 121 Gasserian ganglion, examination of, in frog, 120 general histology of, 109 hohlcylinder of Kuhnt, 114 incisions of Schmidt, 111 Meissner's plexus, 122 methods of nerve-termination, 109 motorial plate, 126 myelinic fibres, 109 nerves, modern conceptions of, 116 myeline or medulla, 110 Pacinian bodies, 124 perineurium, 127 preparation by bichromate of am- monia, 115 preparation in osmic acid and picro- carmine, 118 Ranvier's nodes, 110 sheath of Schwann, 110 spiral fibre of Beale, 122 staining of, in osmic acid, 113 staining of, in picro-carmine, 111 staining of, with silver nitrate, 112 tactile corpuscles, 124 termination of nerves, 123 in muscle, 125 in epithelial bodies, 126 varieties of nerve-fibres, 109 Nervous sj-stem. central, 296 Network of epithelial cells, 61 Neumann, dentinal sheath of, 104 Neuroglia, 70, 71 fibrillar of, 72 of optic nerve, 348 of spinal cord, 298 Nipple, 440 Nitrate of silver, 29 staining of nerves with, 112 Norris and Shakespeare's method of dou- ble staining, 22 Nose, 368 Nose-piece, 5 Nuclei, green coloration of, 25 of muscle, 136 Nucleus and root of abducens, 314 lenticularis of brain, 316 of hypoglossus, 311 parolivary, 311 ABJECT, arrangement of, 6 ^ size of. 8 Oblique light, 5 Odontoblasts, 104 Odontomata, 105 CEsophagus, 386 Olfactory epithelium, 371 nerves, 372 region, 370 Olivary body, 310 Optic nerve, 348 thalami, 319 Ora serrata, 340 Orbicularis ciliaris, 340 palpebrarum, 328 Organ of Corti, 362, 364 of Giraldts, 231 ORGANS OF GENERATION, FEMALE, 240 Clitoris, 240 corpora cavernosa of, 241 genital nerve corpuscles of, 240 glans of. 241 Glands op Bartiioline, 241 Hymen, 241 Fallopian Tubes, 246 ampulla of, 246 fimbria? of, 246 isthmus of, 246 Labia majora, 240 Labia minora, 240 INDEX. 473 ORGANS OF GENERATION, FEMALE— Ovary, 246 blood-vessels of, 247 corpus albicans of, 250 corpus luteum of, 249 development of, 250 Graafian follicles of, 248 nerves of, 248 stroma of, 246 tubes of, 246 Parovarium, 250 Placenta, 251 Urethra, 242 meatus urinarius of, 242 Uterus — changes of, during menstruation and gestation, 245 decidua, 245 glands of, 24 i mucous membrane of, 243 plicae palmatae of, 243 nerves of, 245 os uteri, 244 ovula Nabothi, 244 vessels of, 245 Vagina, 241 vascular system of, 242 Vestibule, 24.1 bulbi vestibuli, 241 ORGANS OF GENERATION, MALE, 223 Cowpek's Glands, 227 Epididymis, 231 blood-vessels of, 234 Ejaculatory Ducts, 235 Hydatid of Morgagni, 231 karyokinesis, 237 Organ of Giraldes, 231 Penis, 223 blood-vessels of, 224 genital nerve-corpuscles of, 225 glans penis, 224 lymph -vessels of, 224 nerves of, 225 tunica albuginea of, 223 Tyson's glands of, 224 Prostatk Gland, 227 acini of, 228 bloodvessels of, 229 epithelium of, 228 norvfjs of, 229 vesicula prostatica of, 229 ORGANS OF GENERATION, MALE— Scrotum, 231 dartos of, 231 semen or sperma, 235 seminal vesicles, 235 spermatoblasts, 236 Spermatozoa, 225 structure of, 236 development of, 236 Testicles, 229 blood-vessels of, 234 corpus Highmori of, 230 lymphatics of, 234 mediastinum of, 230 nerves of, 234 rete testis, 231 seminiferous tubules of, 231, 233 septula of, 230 tunica adnata of, 230 tunica albuginea of, 230 tunica vaginalis communis of, 230 Urethra, 225 colliculus seminalis of, 225 lacunae Morgagnii of, 226 lymphatics of, 227 meatus urinarius of, 526 membranous portion of, 226 musculus urethralis of, 223 nerves of, 226 papillae of, 226 prostatic portion of, 225 spongy portion of, 226 structure of, 225 vas aberrans, 232 Vas deferens, 232, 233 ampulla of, 232 muscular coat of, 234 nerves of, 234 Organs of respiration, 253 Osmic acid, staining of nerves with, 1 13 Osmic acid and picro-carmine, preparation of nerves in, 118 Osmic and chromic acids, 15 Osmic and oxalic acids, staining with, 28 Ossification, points of, 98 Osteoblasts, 96, 98 Osteoclasts, 100 Osteo- or vaso-dentine, 105 Osteoporosis, 9 Os uteri, 244 Otoliths, 358 474 INDEX Ovary, 246 Oviducts, 24G Ovula Nabothi, 244 PACINIAN BODIES, 184 -*- Pancreas, 410 acini of, 420 blood-vessels of, 411 centro-acinal cells of, 411 development of, 412 excretory duct of, 411 lymphatics of, 411 nerves of, 411 trypsin, 410 zymogen, 410 Panniculus adiposus, 277 Papilla? of cutis vera, 421 of hair, 289 of tongue, 380 Papillary sphincter, 429 Paracentral lobule, 323 Parenchymatous cartilage, 83 Parolivary nucleus, 311 Parovarium, 250 Partsch's views on secretion of milk, 451 Pavement endothelium, 80 Pelvis, renal, 428 Penis, 223 Peptic glands, 389 Perichondrium, 86 Perineurium, 126 Periodontium, 108 Periosteum, 95 Perithelium, 148 Perivascular spaces, 161 Petit, canal of, 350 Peyer's patches, 396 Pharyngeal tonsil, 373 Pharynx, 873 Pia mater, spinal, 297 Picro-carmine, 23 staining of nerve-fibres with, 111 Picro-haematoxylon and eosine, 26 Pigmented epithelium, 58 Pigment of retina, 346 Pineal gland, 417 Pituitary body, 417 Placenta, 251 Plasma, 34 cells, 164 Plasma of connective taBSue, 67 of mamma, 11-1 Plasmatic channels, 1 66 Pleura, 265 Pleural appendages, 267 Plexus, choroid, 320 of Auerbach. 899 of Meissner, 399 Polarized light in the study of muscle, 137 Pons varolii, 315 Potassium bichromate solution, 14 Preparation of bone, 92 of cornea, 334 of fresh object, 13 of tissues, 13, 14 of mamma, 455 of microscopic objects, 12 of retina, 347 spleen, 409 Preserving fluid, Wickersheimer's, 29 Preservative fluid, Hamilton's, 20 Prickle cells, 58 of skin, 272 Prop-cells, Heneon's, 366 Prostate gland, 227 Pseudostomata, 171 of pulmonary lymphatics, 264 Pulp of spleen, 406 of teeth, 102, 105 Purpurine for staining cartilage, 85 Purkinje, cells of, 318 granular layer of, 104 Purpurine, 28 Pyloric glands, 391 RADICLES of lymphatics, 168 Ramification of capillaries, 149 Ranvier's nodes, 110 purpurine, 28 tacJiea laiteuses, 168 Raphe of medulla oblongata, 309 Rauber's views on the mamma, 450 Rectum, 401 Red blood-corpuscles, 34 Reil, island of, 322 Reissner, membrane of, 362 Remak, fibres of, 117 Renal pelvis, 428 tubules, 203 INDEX. 475 RESPIRATORY TRACT, 253 Larynx. 253 calcification of cartilages of, 255 cartilages of, 254 cartilago triticea of, 253 corniculum of, 255 epiglottis of, 255 glands of, 2oG ligaments aud membranes of, 253 lymphatics of, 257 mucous membrane of, 255 nerves of, 257 Santorini's cartilages of, 255 vocal cords of, 2.34 "Wrisberg's cartilages of, 255 Lungs, 2.j9 acini or lobulettes of, 2G0 alveolar passages of, 2G0 alveoli or air-cells of, 269 blood-vessels of, 2G:J bronchioles of, 260 epithelium of alveoli of, 261 infundibula of, 260 lymphatics of, 264 nerves of, 265 pleural appendages, 267 pleura of, 265 pseudostomata of lymphatics of, 264 septa of, 262 smaller bronchi, 259 subpleural lymphatics, 207 terminal arteries of, 263 Trachea and Primary Bronchi, 257 cartilage rings of, 257 glands of, 258 mucous membrane of, 257 Rete Malpighii. 271 Reticular or yellow elastic cartilage, 85 Reticular form of connective-tissue, 60 Retina, 842 Retains, stripes of, 108 Riolani's muscle, 329 Rolando, fissure of, 321 Root of hair, 288, 292 of nail, 294 QACOULB of labyrinth, 868 U Baiter, Incremental line* of , 105 Santorini's cartilage, 255 Sap-canaliculi, 165 Sarcolemma, 130 Satterthwaite's section -cutter, 17 Scala tympani, 362 vestibuli, 362 Scales of epidermis, 275 Schlemm's canal, 336 Schmidt, incisures of, 111 Schreger, lines of, 105 Schwann, sheath of, 110 Sclera, 337 Scrotum, 231 Sebaceous glands, 285 Section-cutters, 16, 17 Semen, 235 Semicircular canals, 359 Seminal vesicles, 235 Seminiferous tubules, 231 Septa of lung, 262 Shaft of hair, 288, 292 Sharpey's fibres of bone, 94 Sheath of Schwann, 110 Sheaths of hair, 289 Silver, nitrate of, 29 Sinuses of lymph-glands, 177 Size of object, 8 SKIN, 269 blood-vessels of, 279 Corium of, 277 pars papillaris, 278 pars reticularis of, 278 corneous layer of, 274 elastic tissue fibres of, 277 epidermic scales, 275 Epidermis, 271 general plan of arrangement of, 269 general structure of, 270 granular layer of, 274 Hair, 288 development of, 293 papillaj of, 289 root of, 288, 292 shaft of, 288. 292 ! hs of, 289 lymphoid corpuscles of, 277 muscles of, 287 Nails, 293 bed of, 294 body of, 294 development of, 294 lunula of, 294 476 INDEX. skin- Nails— nail and fold, 294 root of, 29-4 nerves of, 279 panniculus adiposus of, 276 rete Malpighii, 271 prickle cells of, 272 Sebaceous Glands ok, 285 development of, 2SG Btratum lucid u in of, 274 stratum subpapillare of, 279 subcutaneous connective-tissue ljyer of, 278 fat-cells of, 270 Sweat-Glands op, 2S2 development of, 285 tactile corpuscles of, 280 Slide for heating, 40 Small intestine, 394 Sperma, 235 Spermatoblasts, 230 Spermatozoa, 235 Sphincter of iris, 312 ani, 401 papillary, 429 vesicae, 430 Spinal cord, 298 fluid, 397 Spina's views on cartilage, C7 Spleen, 403 blood-vessels of, 4C7 development of, 409 fibrous coat or capsule of, 404 general structure of, 403 lymphatics of, 409 Malpighian corpuscles of, 404 nerves of, 409 preparation of, 409 pulp of, 406 serous coat of, 403 Squamous epithelium, 57 Stage diaphragms, 5 micrometer, 7 Stevenson, plan of imbedding, 10 Stomach, 388 Stomata of lymph-vessels, 165 vera, 171 Stratum intermedium of tooth, 108 lucidum of skin, 274 subpapillare of skin, 279 Striation of muscle, 131 Stroma of kidney, 215 Stutzzcllen of mamma, 449 Subdural spaces of optic nerve, 348 Submucous layer of oesophagus, 387 of small intestine, 896 of stomach, 389 Subpleural lymphatics. 267 Sudoriferous glands, 2^2 Supkakenal Capsules, 431 blood-vessels of, 4:50 capsule of, 432 cortical substance of, 432 external layer of, 433 internal layer of, 435 middle layer of, 433 zona fasciculata of, 433 zona glomerulosa of , 433 zona reticularis of, 430 development of, 436 lymphatics of, 430 medullary substance of, 435 nerves of, 430 Sweat-glands, 282 Sylvian fissure, 821 Sympexions of thyroid, 415 TACTILE CORPUSCLES, 124 Tarsus of eye, 328 Taste-globlets of tongue, 381 TEETH, 102 cement of, 105 dentinal canals of, 104 dentinal globules of, 1 04 dentinal fibres of tomes, 104 dentinal sheath of Neumann, 104 dentine or ivory, 103 development of, 105 cuticula, 107 dentinal teeth, 106 dentine, 106 horny teeth, 106 primary enamel organ, 107 secondary enamel organ, 107 stratum intermedium of, 108 tooth papilla, 107 tooth -sac, 107 development of enamel of, 108 enamel, 102 granular layer of Purkinje, 104 INDEX. 477 TEETH— incremental lines of Salter, 105 interglobular spaces of Czermak, 103 interglobular substance, 105 lines of Schreger, 105 parallel stripes of Retzius, 103 parts of, 102 periodontium of, 108 pulp of, 102, 105 odontoblasts, 104 odontomata, 105 osteo- or vaso-dentine, 105 Tendons, lymphatics of, 175 Tendon-tissue, 72 Tenon's capsule, 337 Termination of muscle in tendon, 139 Testicles, 229 Testing lenses, 8, 10 microscope, 7 Thalami optici, 319 THICK CUTIS VERA, 420 blood-vessels of, 423 erector pili muscles of, 422 fat-columns or fat-canals of, 421 fibrous prolongations of, 420 injection of, 424 lymphatics of, 424 papillae of, 421 Third corpuscular element of blood, 48 Thoracic duct, 174 THYMUS GLAND, 412 blood-vessels of, 414 capsule of, 412 cells of, 413 central canal of, 414 development of, 414 follicles of, 412 lymphatics of, 414 thymic juice of, 413 THYROID BODY, 415 blood-vessels of, 410 capsule of, 415 epithelium of, 415 lymphatics of, 410 nerves of, 410 •ympexiona of, 410 vesicles of, 415 Tissue, adenoid, 09 cellular, 68 ooimectiTe, ';•"> corneal, 75 Tissue, elastic, 77 fat, 73 fibrous, 60 gelatinous, 63 intermuscular, 74 mucous, G3 tendon, 72 Tissue, compact, of bone, 89 Tomes, dentinal fibres of, 104 Tongue, 380 Tooth-sac, 107 Tonsil, pharyngeal, 373 Tonsils, 373 Trachea, 257 Triple staining, 26 Trypsin, 410 Tubules of kidney, 203 Tubules, seminiferous, 231 Tunica vasculosa of sclera, 338 Tympanum, 354 Types of arteries, 152 Tyson's glands, 224 URETERS, 429 Urethra, female, 242 male, 225 URINARY EXCRETORY PASSAGES, 428 Bladder, 430 blood-vessels of, 431 epithelium of, 430 connective tissue of, 430 detrusor urinse of, 430 lymphatics of, 431 muscular coat of, 430 nerves of, 431 sphincter vesicae, 430 Renal Pelvis, 428 fibrous layer of, 429 mucous membrane of, 428 muscular coat of, 429 papillary sphincter of, 429 vessels and nerves of, 429 UBBTKBB, 429 mucous membrane of, 429 muscular layers of, 429 vessels and nerves of, 429 Uterus. 348 Utricle of labyriDth, 358 Urea, 848 478 INDEX. VACUOLATION of mammary epithe- lium, 447 Vagina, 241 Valves of veins, 158 Valvules conuiventes, 395 Vas aberrans, 232 Vasa recta of kidney, 214 Vas deferens, 232 Vasa vasorum, 161 Veins, 156 central, of liver, 184 interlobular, of liver, 1 84 intralobular, of liver, 184 sublobular, of liver, 185 Venae vorticosas of sclera, 337 Ventricles of brain, 3 19 Venules, 156 Vermiform appendix, 401 Vertebrates, muscle of, 130 Vesical epithelium, 430 Vesicular seminales, 235 Vessels of muscle, 138 Vestibule of vagina, 241 Vestibulum nasi, 368 Villi of intestine, 395 Vincent's microtome, 21 Violet de Paris, 29 Vitreous body, 349 Vocal cords, 254 Voluntary muscle-fibre, 130 WARM-SLIDE, 40 ' ' Waxy change, methyl-gieen for, 29 Wendt, method of triple staining, 2