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C? [A SAUKBERS-' 
 
 SSI MEDICAL HAND-ATLASES. 
 
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 The series of books included under this title are authorized translations 
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ATLAS AND EPITOME 
 
 OF 
 
 HUMAN HISTOLOGY 
 
 AND 
 
 MICROSCOPIC ANATOMY 
 
 DOCTOR JOHANNES |OBOTTA 
 
 Of the University of Wurzburg, Bavaria 
 
 EDITED, WITH EXTENSIVE ADDITIONS, BY 
 
 G. CARL HUBER, M.D. 
 
 Junior Professor of Anatomy and Director of the Histologic Laboratory at the 
 University of Michigan 
 
 2lutborf3e5 ^Translation from tbe ©etman 
 
 With 171 Illustrations on 80 Lithographic Tlates, %ttf >. 
 
 68 Text Illustrations ,<■ ' y . "4=-, 
 
 LIBRARY. 
 
 PHILADELPHIA AND LONDON 
 
 W. B. SAUNDERS & COMPANY 
 !903 
 
 T 
 
Copyright, 1903, by W. B. SAUNDERS & COMPANY. 
 
 Registered at Stationers' Hall, London, England. 
 
 551 
 
 ELEOTHOTYPED BY PRESS OF 
 
 WESTCOTT Bl THOMSON, PHILADA. W. B. SAUNDERS &. COMPANY- 
 
This American Edition is gratefully and respectfully dedicated by 
 the Editor to 
 
 Doctor Hermann Kiefer 
 
 a long time Regent of the University of Michigan, in recognition 
 of his services to Medical Education. 
 
EDITOR'S PREFACE. 
 
 Considering the fact that there are already a number 
 of excellent and widely known text-books and atlases of 
 histology, it may seem like a hazardous venture to enter 
 upon the field with something new. Sobotta has, how- 
 ever, in his " Atlas und Grundriss der Histologie und 
 mikroskopischen Anatomie des Menschen," succeeded in 
 combining an abundance of well-chosen and most accurate 
 illustrations with a concise text in such a manner as to 
 make it both atlas and text-book. 
 
 The illustrations comprise eighty lithographic plates, 
 which have been reproduced with the aid of over thirty 
 colors, and sixty-eight figures reproduced with the aid of 
 photomechanical methods. The publishers have spared 
 no expense in the reproduction of plates and figures ; they 
 have been printed with the greatest care and exactness, 
 and portray most faithfully the microscopic preparations 
 reproduced. The original drawings which formed the basis 
 of nearly all the illustrations of this volume were made after 
 the following method, suggested by Sobotta : The prepa- 
 rations were photographed under the same magnification as 
 that under which they were drawn. The photographs were 
 then used as a basis for the drawings, in that outline draw- 
 ings, even to the finest details, were traced on tracing-paper; 
 these outline drawings were then transferred to drawing- 
 paper. This method assures exactness of magnification ; 
 by means of it distortion is avoided, and during the prep- 
 aration of the drawing the photograph serves as a control 
 picture. As the details of a drawing, especially of a gen- 
 
6 EDITOR'S PREFACE. 
 
 eral view under low magnification, are nearly always filled 
 in under a lens of higher power, there is always a danger 
 that the cell-nuclei are represented larger than the magnifi- 
 cation permits ; this is avoided by the above method. In 
 a few instances a number of photographs were combined 
 to make a single drawing. Some two hundred micro- 
 photographs were made for the figures represented in the 
 atlas. Nearly all the illustrations in the volume were 
 made under relatively low magnifications, such as are 
 used by the majority of students in the general micro- 
 scopic courses. Attention may especially be drawn to 
 numerous figures portraying, under very low magnifica- 
 tion, a general view of entire organs or parts of organs, thus 
 giving the student more accurate mental pictures of the 
 relations of the component structures than can be gained 
 by a study of figures giving small areas under higher 
 magnification. 
 
 The great majority of the illustrations were made from 
 sections prepared from human tissues, obtained from indi- 
 viduals who had been executed ; some few from tissues 
 taken from a body two and a half hours after death. 
 The tissues employed may therefore be regarded as fresh 
 and normal in every respect. Nearly all the microscopic 
 preparations reproduced were made by Sobotta ; a few- 
 were obtained from the anatomic collection at Wiirzburg ; 
 some few from private collections ; for these, appropriate 
 credit is given in the legends describing the respective 
 figures. Tissues from animals served the purpose when 
 it was desirable to illustrate a special structure or a char- 
 acteristic arrangement of tissue-elements, or in a few 
 instances when human tissues were not available. 
 
 The text is as brief and concise as possible.. Neither 
 references to literature nor disputed views could therefore 
 find place therein. It is limited to the generally recog- 
 nized facts of microscopic anatomy, and is written con- 
 nectedly and without special reference to the figures. In 
 assuming editorial responsibility for the text, the editor 
 
EDITOR'S PREFACE. 7 
 
 of this edition felt justified in bringing the views expressed 
 therein in conformity with his own observations. He has 
 thus annotated and altered very freely certain portions of 
 the sections on the adenoid tissues, blood and the blood- 
 forming organs, muscular tissues, special sense organs, 
 and peripheral nerve distributions, and has made other 
 minor changes as occasion permitted. Additions to the 
 text were now and then made. Certain sections were 
 rearranged without material alterations in contents, and in 
 many instances he has incorporated the foot-notes in the 
 text. 
 
 The illustrations, especially those on the lithographic 
 plates, receive especial explanation, the legends appearing 
 on the left side, while the plates are on the right. Plates 
 and text are therefore to a certain extent independent. 
 The reader may follow the text independently of the 
 plates, or interpret the latter by the help of the legends. 
 
 The translation from the German was executed by Dr. 
 Lydia M. DeWitt ; the editor is also under grateful obli- 
 gation to her for assistance in proof-reading. 
 
 G. Carl Hubek. 
 uxiveksity of michigan, 
 Ann Aebob, Michigan. 
 
CONTENTS. 
 
 THE HISTOLOGY OF CELLS AND TISSUES. page 
 
 I. The Cell 17 
 
 II. The Tissues of the Human Body 28 
 
 Epithelial Tissues 29 
 
 Supporting or Connective Tissues 40 
 
 Muscle Tissue 62 
 
 Nervous Tissues 70 
 
 THE MICROSCOPIC ANATOMY OF THE ORGANS. 
 
 I. The Skeletal System 81 
 
 Bone and Osseous Tissue 81 
 
 Bone Development 85 
 
 II. The Organs of the Muscular System 91 
 
 Muscles 91 
 
 Tendons 93 
 
 ill. The Organs of the Nervous System 95 
 
 1. The Central Nervous System 95 
 
 2. The Peripheral Nervous System 107 
 
 (a) The Peripheral Nerves ' 107 
 
 (b) The Peripheral Ganglia 108 
 
 (c) The Nerve-endings 109 
 
 IV. Blood and Lymph Vascular System 114 
 
 Heart 114 
 
 Blood-vessels 115 
 
 Lymphoid Tissue 120 
 
 Spleen 124 
 
 Thymus 126 
 
 V. The Digestive Organs 128 
 
 Oral Cavity 129 
 
 The Teeth 130 
 
 The Tongue 136 
 
 The Adenoid Structures of the Tongue and Pharynx . . 138 
 
 The Esophagus 141 
 
 The Stomach 143 
 
 The Small Intestine 145 
 
 The Large Intestine 149 
 
 The Lymphatic Structures of the Intestines 149 
 
 9 
 
10 CONTENTS. 
 
 PAGE 
 
 The Blood- and Lymph-vessels and Nerves of the Stomach 
 
 and Intestines ■ 151 
 
 The Salivary Glands 153 
 
 The Liver 161 
 
 VI. The Urinary Organs 166 
 
 The Kidneys 166 
 
 The Efferent Urinary Passages 173 
 
 VII. The Male Reproductive Organs 175 
 
 Testes 175 
 
 The Efferent Seminal Passages 1HO 
 
 VIII. The Female Reproductive Organs 1h~> 
 
 Ovary .... 185 
 
 Oviduct, Uterus, and Vagina 191 
 
 IX. The Respiratory Organs 196 
 
 The Nasal Cavity 196 
 
 Larynx, Trachea, and Bronchi 1!)7 
 
 The Bronchial Branches and Lungs 198 
 
 The Thyroid Gland 201 
 
 X. The Skin . . 201 
 
 Skin, Epidermis, and Cutis 201 
 
 The Epidermal Structures of the Skin 205 
 
 The Hair 205 
 
 The Nails 209 
 
 The Glands of the Skin 210 
 
 Mammary Glands 213 
 
 XI. The Special Sense Organs 214 
 
 The Organ of Vision 214 
 
 Tunica Externa Bulbi 215 
 
 Tunica Media Bulbi 217 
 
 Tunica. Interna Bulbi 221 
 
 Optic Nerve . 227 
 
 Vitreous Body and Zonula Ciliaris 228 
 
 Lens 22!) 
 
 Auxiliary Apparatus of the Eye . . . . 22!) 
 
 Eyelid 229 
 
 Lachrymal Gland 231 
 
 Organ of Hearing 232 
 
 External Ear 232 
 
 Inner Ear 233 
 
 Cochlea 234 
 
 Olfactory Organ 238 
 
 Organ of Taste 238 
 
 Index 241 
 
COLORED PLATES. 
 
 Plate 1. — Mitosis. 
 
 Figs. 1-10. — Ten Stages of Indirect Nuclear Division.. 
 Plate 2. — Epithelial Tissues. 
 
 Fig. 1. — Cell Boundaries. 
 
 Fig. 2. — Squamous Epithelium. 
 
 Fig. 3. — Cylindric Epithelium. 
 Plate 3. — Epithelial Tissues. 
 
 Fig. 1. — Transitional Epithelium. 
 
 Fig. 2.— Stratified Ciliated Epithelium. 
 
 Fig. 3. — Ciliated Epithelium of the Epididymis. 
 
 Fig. 4. — Pigment Epithelium. 
 Plate 4. — Connective Tissues. 
 
 Fig. 1. — Reticular Connective Tissue. 
 
 Fig. 2. —Interstitial Cells of Testis. 
 
 Fig. 3.— Mast-cells. 
 
 Fig. 4. — Connective-tissue Cells from Cornea. 
 Plate 5. — Blood and Bone-marrow. 
 
 Figs. 1-21. — Human Blood-corpuscles. 
 
 Figs. 22-31. — Elements of Bone-marrow. 
 Plate 6. — Muscular Tissues. 
 
 Fig. 1. — Pigmented Connective-tissue Cells. 
 
 Fig. 2. — Branched Striated Muscle-fibers. 
 
 Fig. 3. — Longitudinal .Section of Heart Muscle. 
 
 Fig. 4. — Transverse Section of Heart Muscle. 
 Plate 7. — Nerve-cells. 
 
 Fig. 1. — Isolated Multipolar Ganglion-cells. 
 
 Fig. 2. — The Same with Tigroid Substance Stained. 
 
 Fig. 3. — Spinal Ganglion-cells. 
 Plate 8. — Bone Development. Embryonal Finger in Longitudinal 
 
 Section. 
 Plate 9. — Bone Development. Embryonal Forearm in Cross-section. 
 Plate 10. — Bone Development. Embryonal Femur in Cross-section. 
 Plate 11. — Bone Development. 
 
 Fig. 1. — Embryonal Metacarpal Bone in Longitudinal Sec- 
 tion. 
 Figs. 2-6. — Bone Formation and Resorption in the Lower 
 Jaw of an Embryo. 
 Plate 12.— Muscle. 
 
 Fig. 1. — Transverse Section of the Omohyoideus. 
 Fig. 2. — A Neuromuscular Spindle from the Same Muscle. 
 11 
 
12 COLORED PLATES. 
 
 Plate 13. — Spinal Cord. Topographic Representation of the Cervical 
 
 Cord. (Carmin Stain.) 
 Plate 14. — Spinal Cord. Transverse Section of the Lumbar Cord. 
 
 (Weigert Stain.) 
 Plate 15. — Medulla Oblongata. Topographic Representation of the 
 Prolongation of the Cord in the Olivary Region. ( Weigert 
 Stain.) 
 Plate 16. — Cerebellum and Heart. 
 
 Fig. 1. — General View of the Structure of the Cerebellum. 
 (Carmin Stain.) 
 
 Fig. 2. — Papillary Muscle of Heart. 
 Plate 17. — Cerebellum, Sympathetic Ganglion. 
 
 Fig. 1. — Cerebellum in Weigert Stain. 
 
 Fig. 2. — Small Sympathetic Ganglion. 
 Plate 18. — Cerebral Cortex; Tactile Corpuscle. 
 
 Fig. 1. — Cerebral Cortex in Weigert Stain. 
 
 Fig. 2. — Taste-buds, Stained by the Intra-vitam Methylene- 
 blue Stain. 
 Plate 19. — Peripheral Nerves. 
 
 Fig. 1. — Peripheral Nerve, General View. 
 
 Fig. 2. — Portion of Fig. 1 under Higher Magnification. 
 Plate 20. — Peripheral Ganglia. 
 
 Fig. 1. — Sympathetic Ganglion in Weigert Stain. 
 
 Fig. 2. — Spinal Ganglion in Weigert Stain. 
 Plate 21. — Arteries. 
 
 Fig. 1. — Transverse Section of Aorta. 
 
 Fig. 2. — Transverse Section of Radial Artery. 
 Plate 22. — Blood-vessels. 
 
 Fig. 1 . — Transverse Section of a Vein Having Muscular Walls. 
 
 Fig. 2. — A Transverse Section of a Medium-sized, Fig. 3, of 
 a Small, and Fig. 4, of a Very Small Artery. 
 Plate 23. — Lymph-gland, Spleen. 
 
 Fig. 1. — General View of a Cervical Lymph-gland. 
 
 Fig. 2. — Rabbit's Spleen, Injected. 
 Plate 24.— Spleen. 
 
 Fig. 1. — General View of Human Spleen. 
 
 Fig. 2. — Spleen Nodule under Higher Magnification. 
 Plate 25.— Thymus. 
 
 Fig. 1. — General View of a Child's Thymus. 
 
 Fig. 2. — Hassal's Corpuscle from Thymus of an Adult. 
 Plate 26. — Lip. General View of Cross-section of Lip. 
 Plate 27. — Tooth Development. 
 
 Fig. 1. — First Stage of Tooth Development. 
 
 Fig. 2.— Third Stage. 
 Plate 28.— Tooth Development. 
 
 Fig. 1. — Second Stage. 
 
 Fig. 2. —Fourth Stage. 
 Plate 29.— Tongue. 
 
 Fig. 1. — Mucous Membrane of Tongue. 
 
 Fig. 2.— Papilla; of Tongue. 
 Plate 30.— Tonsils. General View of Palatal Tonsil. 
 
COLORED PLATES. 13 
 
 Plate 31.— Tongue. 
 
 Fig. 1. — Papilla Circumvallata. 
 
 Fig. 2. — Wandering of Lymphocytes through the Epi- 
 thelium of the Tonsil. 
 Plate 32. — Esophagus. General View of Esophagus. 
 Plate 33. — Esophagus, Stomach. 
 
 Fig. 1. — Esophagus. 
 
 Fig. 2. — General View of the Structure of the Wall of the 
 Stomach. 
 Plate 34.— Stomach. 
 
 Fig. 1. — General View of Mucous Membrane of Stomach. 
 
 Fig. 2. — Stomach Glands under Higher Magnification. 
 Plate 35. — Stomach, Duodenum. 
 
 Figs. 1 and 2. — Portions of Fundus Glands of Stomach. 
 
 Fig. 3. — General View of the Duodenum. 
 Plate 36. — Small Intestine. General View of Jejunum. 
 Plate 37. — Small Intestine. 
 
 Fig. 1. — Mucous Membrane and Villi. 
 
 Fig. 2. — Intestinal Glands. 
 Plate 38. — Large Intestine. 
 
 Fig. 1 . — General Vie w of Structure of Wall of Large Intestine. 
 
 Fig. 2. — Mucous Membrane of Rectum. 
 Plate 39. — Intestinal Epithelium, Goblet-cells. 
 
 Fig. 1. — Villi of Intestine. 
 
 Fig. 2. — Glands of Large Intestine. 
 Plate 40. — Transverse Section of Vermiform Appendix, Giving General 
 
 View. 
 Plate 41. — Nerve-plexus of Intestine. 
 
 Fig. 1. — Plexus Myentericus. 
 
 Fig. 2. — Plexus Submucosus. 
 Plate 42. — Salivary Glands. 
 
 Figs. 1 and 2. — Sublingual Gland. 
 Plate 43. — Salivary Glands. 
 
 Fig. 1. — Submaxillary. 
 
 Fig. 2.— Parotid. 
 Plate 44. — Pancreas. 
 
 Fig. 1. — General View. 
 
 Figs. 2 and 3. — Detail Figures of Pancreas. 
 Plate 45. — Liver. 
 
 Fig. 1. — General View of Liver. 
 
 Fig. 2. — Columns of Liver-cells. 
 Plate 46. — Liver. 
 
 Fig. 1. — Injected Liver of Rabbit. 
 
 Fig. 2. — Bile Capillaries of Rabbit's Liver. 
 Plate 47. — Liver. Doubly Injected Rabbit's Liver. (Bile Capillaries 
 
 Blue, Blood Capillaries Red. ) 
 Plate 48. — Kidney. General View of Structure of Kidney. 
 Plate 49. — Kidney. Cortical Substance of Kidney. 
 
 Fig. 1. — General View. 
 
 Fig. 2. — Glomerular Capsule and Uriniferous Tubule. 
 
 Fig. 3. — Brush Border. 
 
14 COLORED PLATES. 
 
 Plate 50.— Kidney. 
 
 Fig. 1 . — Medullary Substance. 
 
 Fig. 2. — Kidney Injected through Arteries. 
 Plate 51.— Kidney. 
 
 Fig. 1. — Injected Glomeruli. 
 
 Fig. 2. — Kidney of Guinea-pig, Injected through Veins. 
 Plate 52.— Ureter, Bladder. 
 
 Fig. 1.— Bladder. 
 
 Fig. 2. — Ureter. 
 Plate 53.— Testis. 
 
 Fig. 1. — General View of Testis, Epididymis, and Vas Def- 
 erens. 
 
 Fig. 2.— General View of Lobule of Testis. 
 Plate 54.— Testis. 
 
 Figs. 1-5. — Phases of Spermatogenesis. 
 Plate 55. — Epididymis. 
 
 Fig. 1. — Head of Epididymis (Ductus Efferentes). 
 
 Fig. 2. — Body of Epididymis (Ductus Epididymidis). 
 Plate 56. — Seminal Passages, Spermatic Cord. 
 
 Fig. 1. — Ductus Deferens. 
 
 Fig. 2. — Spermatic Cord. 
 Plate 57. — Urethra, Seminal Vesicle. 
 
 Fig. 1. — Pars Membranacea Urethrae. 
 
 Fig. 2. — Seminal Vesicle. 
 Plate 58.— Prostate. 
 
 Fig. 1. — Prostate. 
 
 Fig. 2. — Muscular Trabeculae of Frog's Bladder. 
 Plate 59.— Ovary. 
 
 Fig. 1. — Cortical Substance of Ovary. 
 
 Fig. 2. — Ovum and a Part of Discus Proligerus. 
 Plate 60.— Ovary, Oviduct. 
 
 Fig. 1. — Transverse Section of Oviduct. 
 
 Fig. 2. — Ovary of New-born Child. 
 Plate 61.— Uterus. 
 
 Fig. 1. — General View of Uterus. 
 
 Fig. 2. — Uterine Mucous Membrane. 
 Plate 62. — Suprarenals. 
 
 Fig. 1. — General View. 
 
 Fig. 2. — Under Higher Magnification. 
 Plate 63. —Nasal Mucous Membrane. 
 
 Fig. 1. — Olfactory Region. 
 
 Fig. 2. — Respiratory Region. 
 Plate 64. — Trachea. General View of Structure of Trachea. 
 Plate 65. — Lungs. Vascular Injection of Lung. 
 Plate 66.— Lung, Thyroid Gland. 
 
 Fig. 1.— Bronchus. 
 
 Fig. 2.— Thyroid Gland. 
 Plate 67.— Skin. 
 
 Fig. 1.— General View of Structure of Skin, 
 
 Fig. 2. — Injection Preparation of Skin. 
 
COLORED PLATES. 15 
 
 Plate (W.— Skin, Hair. 
 
 Fig. 1. — Papilla; of Epidermis and Corium. 
 
 Fig. 2.— Cells of Stratum Dentatum. 
 
 Fig. 3. — Longitudinal Section of Lower Portion of Eoot of 
 Hair. 
 Plate G9. — Hair. General View of Structure of Scalp, with Longi- 
 tudinal Section of Hairs. 
 Plate 70.— Hair. 
 
 Figs. 1 and 2. — Transverse Sections of Eoot of a Hair in the 
 Middle and Lower Portion. 
 Plate 71. — Hair, Sweat-glands. 
 
 Fig. 1. — Cross-section of Hair (General View). 
 
 Figs. 2-4. — Axillary Sweat-glands. 
 
 Fig. 5. — Sweat-glands of Scalp. 
 Plate 72. — Sebaceous Glands and Nails. 
 
 Fig. 1. — Sebaceous Gland. 
 
 Fig. 2. — Cross-section of Nail. 
 
 Fig. 3. — Longitudinal Section of Nail. 
 Plate 73. — Mammary Gland. 
 
 Fig. 1. — General View. 
 
 Fig. 2. — Detailed View of Human Mammary Gland: 
 
 Fig. 3. — Detailed View of the Mammary Gland of the Mouse. 
 Plate 74. — Eye. General View of the Eyeball (Horizontal Section). 
 Plate 75. — Eye. 
 
 Fig. 1. — Cornea. 
 
 Fig. 2. — Cross-section of the Three Tunics of the Eye. 
 Plate 76.— Eye. 
 
 Fig. 1. — Cornea, Iris, Corpus Ciliare. 
 
 Fig. 2. — Lens. 
 Plate 77.— Eye. 
 
 Fig. 1. — Cross-section of Eetina. 
 
 Fig. 2. — Fovea Centralis. 
 
 Fig. 3. — Ora Serrata. 
 Plate 78. — Eye, Lachrymal Gland. 
 
 Fig. 1. — Entrance of Optic Nerve. 
 
 Fig. 2. — Lachrymal Gland. 
 Plate 79. — Eyelid. General View of Eyelid. 
 Plate 80. — Organ of Hearing. 
 
 Fig. 1. — External Auditory Canal. 
 
 Fig. 2.— Cochlea. 
 
(A) THE HISTOLOGY OF CELLS AND 
 TISSUES. 
 
 I. THE CELL. 
 
 The cell is the ultimate unit of a living organism. 
 Every living organism originates from a cell. The pro- 
 tozoa consist of a single cell, while the metazoa are multi- 
 cellular. The cells of the metazoa are structurally and 
 functionally differentiated, cells having similar structure 
 and similar function being united into larger divisions 
 known as tissues. 
 
 Multicellular organisms, when fully developed, consist, 
 however, not only of cells, but also of cell-products. The 
 cells are therefore to be regarded as the primary elementary 
 constituents of more highly developed organisms, the sec- 
 ondary elementary constituents being the excretory or trans- 
 formation products of cells. In this latter category we 
 may place the fluids of the body, as well as the ground 
 substance, the cement substance, certain cuticular forma- 
 tions, granules, and especially fibers and fibrils. The 
 essential difference between the primary and secondary 
 elements of the body is that the primary elementary con- 
 stituents, the cells, are capable of independent proliferation, 
 while secondary elementary constituents have no such 
 power. Excretion or transformation products can take 
 their ori<rin only from the cellular elements. A new cell 
 may originate from a cell, but a new fiber cannot originate 
 from a fiber. 
 
 The form of the cell is manifold. The spherical form 
 may be regarded as fundamental, since it is the form pre- 
 sented by the ovum, the cell from which all other cells of 
 2 17 
 
18 ■ THE CELL. 
 
 the multicellular organism develop. The first embryonal " 
 cells which arise from the division of the impregnated 
 ovum generally present the spherical form. This funda- 
 mental form of' the cell, however, presents many variations, 
 according to the position and function of the differentiated 
 cells. 
 
 The size of the cell is subject to many variations analo- 
 gous to those of the form. The smallest cells measure 
 only 5 n or less, while the largest are visible macroscopic- 
 ally, as for instance the large ova of many animals. The 
 extreme size of such cells arises only through secondary . 
 deposition of food material in the cell-body. Most cells 
 are microscopic, only a few, as the large nerve-cells of 
 some animals, being visible with the unaided eye. 
 
 There are three essential or principal constituents of 
 the cell: (1) The cell-body or the protoplasm; (2) the 
 cell nucleus ; (3) the centroxome. In addition to these, the 
 cell may also contain other less important constituents. 
 Certain cells have no nucleus and, when fully differen- 
 tiated, no centrosome. Such cells, however, were origi- 
 nally nucleated (horny epithelial cells of the epidermis, 
 red blood-cells of mammalia, central fibers of the lens). 
 The non-nucleated condition represents, therefore, a state 
 of senility, occurring only in highly differentiated cells no 
 longer capable of division. (See pages 55 and 229.) 
 
 The cell protoplasm is an extremely complex albu- 
 minous substance and is the seat of the vitality of the 
 cell. Many of the vital phenomena are not discernible 
 even under a powerful microscope ; on the other hand, 
 life phenomena may manifest themselves in some form 
 of motion. 
 
 This movement of the protoplasm may display itself 
 under the form of the so-called ameboid motion, which 
 consists of slow changes of form of the protoplasm, 
 readily observed in the colorless blood-cells or leukoevtes 
 (see page 57), and may result in a locomotion of these 
 cells. By the extension of processes of the leukocytes, 
 
CELL PROTOPLASM. 19 
 
 so-called pseudopodia, these cells may not only move, but 
 also take up solid substances such as particles of dust, 
 bacteria, etc.; two processes surrounding the solid body 
 may flow together and thus inclose the foreign body in 
 the cell. 
 
 In other cells certain differentiated portions of the pro- 
 toplasm are endowed with motion, as the cilia of ciliated 
 cells and the flagella of the spermatozoa. In contradis- 
 tinction to the ameboid movement, the ciliary motion is 
 continuous and follows a certain law, in that the cilia move 
 always in a certain direction and create a continuous cil- 
 iary current. 1 
 
 The cell protoplasm presents a very complex structure, 
 concerning which, even at the present time, the views of 
 writers are widely at variance. According to the view 
 now most generally accepted, protoplasm presents a fibrillar 
 structure, the fibrils varying in size and arranged in the 
 form of a reticular network ; this is readily demonstrated 
 in many cells. These fibrils of the protoplasm constitute 
 the mitom, spongioplasm, or the fibrillar mass. Within this 
 thread-like structure, which is visible only with high or 
 with very high magnification, are scattered minute gran- 
 ules, observed more especially at the nodal points of the 
 network; these are known as microsomes. That portion 
 of the cell protoplasm not occupied by the fibrillar struc- 
 ture and the microsomes must be regarded as a fluid or 
 semi-fluid substance, the interfibrillar substance, or the 
 hyaloplasm. 2 
 
 In addition to these structures which occur throughout 
 the protoplasm, structures are often found which are to be 
 
 1 The so-called molecular motion, a dancing motion of fine granules 
 in fluids, is not an active motion. It occurs in the protoplasm of the 
 salivary corpuscles, dead, swollen leukocytes, and also in granules of 
 India ink suspended in a fluid, etc. 
 
 2 According to some observers, the protoplasm consists of granules, 
 which, if arranged in rows, may form threads. According to an idea 
 which is accepted by few and is scarcely worthy of belief, the proto- 
 plasm is composed of separate honeycomb-like spaces (foam theory). 
 
20 THE CELL. 
 
 regarded as inclosures or transformation products of the 
 protoplasm. Thus, in many cells, especially in gland- 
 cells at the time of secretion, are found larger or smaller 
 granules, so-called zymogen granules, which are looked 
 upon as products of metamorphosis of the protoplasm into 
 the special secretion of the gland (see page 35). Most 
 ganglion-cells contain in their protoplasm large granules 
 or flakes, which show affinity to basic dyes, which proba- 
 bly also have to do with the metamorphosis of the cells 
 and are known as tigroid granules (see page 73). Other 
 cells contain in their protoplasm a varying number of fat 
 droplets, which at times may fill the greater portion of the 
 cell, as in the cells of adipose tissue (see page 52). The 
 drops of sebum in the sebaceous glands of the skin show 
 a similar relation, since in their formation they lie in a pro- 
 toplasmic meshwork. The meshwork of the protoplasm 
 is, however, in this case secondary ; it develops only 
 through the formation of the secretion. 
 
 Other cell inclosures are the pigment granules; these are 
 smaller or larger granules, generally yellow, brown, or black 
 in color, and of irregular form. Now and then crystalloid 
 structures occur in the protoplasm of many cells, known 
 as crystalloids or protein crystals, and may result from the 
 crystallization of the albuminous substance. (See Plate 4, 
 Fig. 2.) Such structures have been observed in man hi 
 the epithelium of the lens and in the interstitial cells of the 
 testis. 
 
 The outermost layer of the cell protoplasm, in which 
 the mitom threads are generally coarser and more closely 
 woven, frequently becomes condensed to form a special 
 structure, known as the cell membrane; this can, in typical 
 cases, be separated from the cell. It is generally structure- 
 less. In some instances the peripheral, differentiated layer 
 of the protoplasm of the cell gradually changes to the ordi- 
 nary protoplasm. In these cases we speak of a ernsta. 
 
 The cell nucleus is a vesicular structure of very varia- 
 ble shape, lying in the interior of the cell. As a general 
 
CELL NUCLEUS. 21 
 
 rule, the form of the nucleus accommodates itself to the 
 form of the cell; thus very long, narrow cells have elon- 
 gated nuclei. The most varied forms of nuclei are, how- 
 ever, met with; they may be nearly or quite spherical, 
 many are ellipsoid, and in certain cases they are distinctly 
 lobulated or ring-shaped, or the nuclei are indented or com- 
 pressed on one or several sides, so that a polynuclear effect 
 may be produced. In certain cases two or more nuclei 
 may be found in a single cell (in many leukocytes, giant- 
 cells of the bone-marrow, occasionally in liver-cells, gang- 
 lion-cells, etc.). The nucleus is essentially the reproductive 
 organ of the cell. Non-nucleated cells (see page 18) are 
 therefore incapable of division. The cell nucleus contains 
 complex chemical constituents, which, according to their 
 reaction to staining reagents, are divisible into two classes, 
 known as the chromatic and the achromatic nuclear con- 
 stituents. The most important of these chemical constit- 
 uents of the nucleus is the chromatin, chemically nuclein, 1 
 which is regarded as that portion of the cell which trans- 
 mits the hereditary characteristics. It presents itself in 
 different forms according to the state of activity of the 
 nucleus (see page 22) ; usually, however, in the form of 
 strands or threads, which frequently anastomose and show 
 thickenings at the nodal points. The chromatin is sup- 
 ported by the achromatic substance, the limn, which, in 
 the form of very fine threads, forms a dense network in 
 the interior of the nucleus. In this network we find the 
 true nuclear corpuscles or nucleoli, which consist of a chro- 
 matic substance (chemically not nuclein, but paranuclein). 
 The nucleus is always, except during the process of nuclear 
 division, surrounded by a nuclear membrane, consisting of 
 an achromatic substance, amphipyrinin. The space within 
 
 1 The essential vital properties of the chromatin are not necessarily 
 united to the (chemical) nuclein, since nuclein is found in portions of 
 the body where there is no chromatin. The chemical and the anatomic 
 concepts of nuclein are not identical. 
 
22 TEE CELL. 
 
 the nuclear membrane in the meshes of the linin network 
 is filled with fluid, the nuclear sap. 
 
 The centrosome, the third constituent of the cell, 
 represents the dynamic center of the cell in the processes of 
 cell division. In the resting cell it appears as a single 
 or as two punctiform structures, which are probably gen- 
 erally less than 1 fi in diameter. Since the centrosome is 
 so small and so difficult to find, it has not yet been pos- 
 sible to demonstrate it in all the cells of the human body. 
 We need not, however, on this account doubt its existence. 
 In many animal cells (ova) centrosomes are often found of 
 considerably greater size. The centrosome often lies in a 
 small clear area of protoplasm, now and then showing fine 
 radiate lines. This structure often becomes prominent 
 only at the time of cell division. 
 
 PROLIFERATION OF CELLS. 
 
 Complex processes affecting more particularly the nucleus 
 manifest themselves during the proliferation of cells. The 
 division of the cell-body is without exceptiou preceded by 
 division of the nucleus; the former may eveu fail to take place 
 and the process then results in the formation of cells having 
 several or many nuclei. Structures which develop in this 
 way and have numerous nuclei in a common protoplasm 
 are known as syncitia x or plasmodia. Thus the trans- 
 versely striated muscle-fiber is a syncitium. In normal 
 human tissues probably all cells divide by what is known 
 as indirect cell division, l-ari/okinesis, or mitosis, in contra- 
 distinction to a less important type designated as direct or 
 amitotic cell division. 
 
 A number of phases or stages are usually distinguished 
 in the complicated process of mitosis. The first is the 
 
 1 Many authors use the term syncitium to denote a structure aris- 
 ing from the fusion of several cells, and Plasmodium to denote forms 
 arising from the division of the nucleus without any subsequent divi- 
 sion of the cell. 
 
PROLIFERATION OF CELLS. 23 
 
 so-called skein stage or prophase ; this is followed by the 
 second stage, that of the equatorial plate or monaster ^ 
 third, the stage of metakinesis ; fourth, the stage of the 
 daughter stars or diaster, the metaphase ; fifth, the phase 
 of the daughter skeins, the anaphase ; sixth, that of the 
 daughter nuclei, the telophase. 
 
 The structural changes manifested in the several phases 
 of mitosis are essentially as follows i 1 The nucleus of the 
 cell engaged in the preparatory stages of cell division 
 presents a peculiar rearrangement of its chromatin, which 
 begins to be grouped into distinct filaments. This arrange- 
 ment becomes more and more definite, until gradually 
 a certain number of distinct single threads are found. 
 These distinct chromatic threads are known as chromo- 
 somes. The number of chromosomes is constant in the 
 mitotically dividing cells of each species of animal. In 
 the higher animals the number twenty-four predominates, 
 while many lower animals have only four and some only 
 two. In certain cells these chromosomes are very short, 
 in some cases even granular in shape. It is not absolutely 
 certain whether this constancy of the number of chromo- 
 somes prevails in the cells of all human tissues, although 
 theoretically this ought to be the case. 
 
 The chromosomes usually appear in the form of loops ; 
 that is, each chromosome is bent at the middle at an 
 angle. The scattered chromosomes now form a close skein 
 (spirem), in which the loops are, as a rule, so arranged 
 that the closed portion of the loop points toward one point 
 of the periphery of the nucleus, the so-called pole field, 
 while the free ends of the loops point in the opposite 
 direction, the antipole field. At this stage the centro- 
 some, which remained at rest during the condition of labile 
 equilibrium of the cell, becomes active, assumes a position 
 in the pole field of the spirem, and appears to send deli- 
 cate rays in all directions. In the stage of the loose skein 
 
 1 The process is not quite the same in all mitoses. The variations 
 which occur are, however, unessential. 
 
24 THE CELL. 
 
 PLATE I.— MITOSIS. 
 
 Figs. 1-10.— Ten Stages of Indirect Nuclear Division (Mito= 
 sis) from the Oral Epithelium of the Larva of a Salamander. 
 
 X 500. 
 
 Technic : Chromic acid solution, 2 per cent. Hematoxylin and 
 eosin. 
 
 Fig. 1.— Cell with resting nucleus a short time before the begin- 
 ning of the mitosis. The nucleus shows distinct, irregularly con- 
 toured threads. 
 
 Fig. 2.— The nucleus of the cell is at the beginning of mitosis. 
 Distinct chromatin loops (chromosomes) are recognized. Stage of the 
 close skein. 
 
 Fig. 3.— The nuclear membrane has disappeared. In place of the 
 nucleus lies a loose skein of chromosomes (the pole field is at the left). 
 
 Fig. 4. — Mother star (monaster) viewed from above. 
 
 Fig. 5. — Mother star (monaster) viewed from the side. The chro- 
 mosomes, except two, are grouped around the equator of the achro- 
 matic spindle. 
 
 Fig. 6. — Mother star viewed from the side. The chromosomes 
 crowded closely around the equator of the spindle. 
 
 Fig. 7. — Stage of metakinesis. One-half of the longitudinally 
 divided chromosomes is drawn toward each pole of the spindle. 
 
 Fig. ft. — Beginning constriction of the cell-body. Stage of the 
 daughter star (diaster). 
 
 Fig. 9. — Completion of cell division. Transformation of the 
 daughter stars into skeins (dispirem). 
 
 Fig. 10. — Change of skeins into resting daughter nuclei (complete 
 daughter cells, telophase). 
 
 Reference letters: c, Centrosome; cli, chromosomes; p, polar rays; 
 ap, achromatic spindle ; x, scattered chromosomes. 
 
 the arrangement of the chromosomes is still move distinct. 
 These are now very regularly arranged and next undergo 
 a longitudinal cleavage of such a kind that each chromo- 
 some is divided longitudinally into two daughter chromo- 
 somes, which, however, for a variable time remain in 
 close apposition, and for this reason this longitudinal 
 division is not observed at this time unless the magnifica- 
 tion is sufficiently high. At the same time, the nuclear 
 membrane disappears and the nuclear fluid mingles with 
 the cell protoplasm; the cell has no longer a circumscribed 
 nucleus. The centrosome, in case the resting cell did not 
 contain two, now divides into two halves, which move 
 apart, and a small achromatic spivdle can now be reeoc- 
 
Tab. I 
 
 ¥ 
 
 
 .sp 
 
 r/l 
 
 
 dp- 
 
 
 LUA. AnsL E Reic/dwkl. Miindwn. 
 
PROLIFERATION OF CELLS. 25 
 
 nized between them ; this enlarges as the centrosomes con- 
 tinue to move apart. This is the anlage of the so-called 
 central spindle or the uniting filaments, a portion of the 
 achromatic spindle, which forms an essential portion of the 
 figure of mitotic cell division. There are further de- 
 veloped rays, which pass out from the centrosomes in 
 opposite directions toward the periphery of the cell ; these 
 are known as polar rays. The origin of this achro- 
 matic spindle is not as yet fully established. It would 
 seem probable, however, that the linin network of the 
 nucleus contributes to the formation of the structure. 
 
 While the spindle, the poles of which are formed by 
 the centrosomes, is still further increasing in size, the 
 chromosomes arrange themselves about the equator of the 
 spindle in nearly one plane, the equatorial plate. This 
 stage is designated as that of the mother star, or monaster. 
 The dividing cell is now easily distinguished from 
 the resting cell. In place of the nucleus a clear area 
 is found, in which may be observed the mother star, 
 or monaster, so named because, when viewed from one 
 pole, the chromosomes form a star-like figure. Besides the 
 fibers of the central spindle, another system of fibers 
 develops — that of the traction fibers or mantle filaments. 
 These are generally finer than those of the central spindle 
 and are present in greater numbers. They run from the 
 centrosomes to the chromosomes and attach themselves to 
 each of the latter in such a maimer that the fibers coming 
 from one centrosome insert themselves into the adjacent 
 half of the loop. In the mechanism of mitosis these fibers 
 are believed to play a part in the processes of metakinesis 
 which now follow ; they draw apart the halves of the 
 loops toward the opposite poles of the spindle. Meta- 
 kinesix begins when, in the equatorial plate, the longi- 
 tudinal cleavage of the chromosomes is very distinctly 
 seen ; the interspace between two daughter chromosomes 
 becomes gradually greater, a change in the whole mitotic 
 figure going hand in hand with this process. A double 
 
PROLIFERATION OF CELLS. 25 
 
 nized between them ; this enlarges as the centrosornes con- 
 tinue to move apart. This is the anlage of the so-called 
 central spindle or the uniting filaments, a portion of the 
 achromatic spindle, which forms an essential portion of the 
 figure of mitotic cell division. There are further de- 
 veloped rays, which pass out from the centrosornes in 
 opposite directions toward the periphery of the cell ; these 
 are known as polar rays. The origin of this achro- 
 matic spindle is not as yet fully established. It would 
 seem probable, however, that the linin network of the 
 nucleus contributes to the formation of the structure. 
 
 While the spindle, the poles of which are formed by 
 the centrosornes, is still further increasing in size, the 
 chromosomes arrange themselves about the equator of the 
 spindle in nearly one plane, the equatorial plate. This 
 stage is designated as that of the mother star, or monaster. 
 The dividing cell is now easily distinguished from 
 the resting cell. In place of the nucleus a clear area 
 is found, in which may be observed the mother star, 
 or monaster, so named because, when viewed from one 
 pole, the chromosomes form a star-like figure. Besides the 
 fibers of the central spindle, another system of fibers 
 develops — that of the traction fibers or mantle filaments. 
 These are generally finer than those of the central spindle 
 and are present in greater numbers. They run from the 
 centrosornes to the chromosomes and attach themselves to 
 each of the latter in such a manner that the fibers coming 
 from one centrosome insert themselves into the adjacent 
 half of the loop. In the mechanism of mitosis these fibers 
 are believed to play a part in the processes of metakinesis 
 which now follow ; they draw apart the halves of the 
 loops toward the opposite poles of the spindle. Ileta- 
 kinesix begins when, in the equatorial plate, the longi- 
 tudinal cleavage of the chromosomes is very distinctly 
 seen ; the interspace between two daughter chromosomes 
 becomes gradually greater, a change in the whole mitotic 
 figure going hand in hand with this process. A double 
 
26 THE CELL. 
 
 star or diaster develops, each daughter star moving grad- 
 ually nearer to its pole. At the same time a perceptible 
 elongation of the cell-body in the direction of the long axis 
 of the spindle takes place. 
 
 The two daughter stars are connected by achromatic 
 fibers, the so-called uniting fibers. These are probably the 
 remains of the central spindle and in the center of their 
 course often show thickenings called central spindle cor- 
 puscles, which mark the place of the future division of the 
 cell. Even in the diaster stage the remains of the traction 
 fibers still run from the chromosomes to the eentrosoraes, 
 but seem to become shorter and shorter the farther the 
 daughter stars are separated from each other. 
 
 When the daughter stars are farther separated, the divi- 
 sion of the cell-body begins by a gradual ring-shaped con- 
 striction of the cell near the middle (metaphase). "When 
 the constriction is nearly completed, a change of the daugh- 
 ter stars into skeins begins. Just as the mother star was 
 formed from the skein, so now a skein is formed from each 
 daughter star, and there is developed a mitotic figure 
 known as the dispirem. At the same time the remains of 
 the former spindle and the polar rays degenerate (ana- 
 phase). 
 
 After the division of the cell-body is completed, a 
 nuclear membrane is formed around each of the daughter 
 skeins, and the new nuclei — daughter nuclei — are formed. 
 The changes involved in this process, the alterations of 
 the chromatin, etc., are collected under the term telophase. 
 The division of the centrosome of each daughter cell may 
 now take place (see page 22). 
 
 When the indirect nuclear division is completed, each of 
 the daughter cells has received half of the cell-body of the 
 mother cell, half of the nucleus, — that is, half of each 
 chromosome, — and half of the centrosome, or one of the 
 two centrosomes now and then present in the resting cell. 
 Each daughter cell is therefore a counterpart of the mother 
 cell. 
 
PROLIFERATION OF CELLS. 27 
 
 Segmentation of the impregnated ovum also occurs after 
 the manner of mitotic division; in this case, however, half 
 of its chromosomes are supplied by the spermatozoon, the 
 male pronucleus, and half by the female pronucleus, the nu- 
 clear constituents of the matured ovum. It is not always 
 true that the resultant cells of a mitotic nuclear division are 
 of equal size. In the processes of maturation of the ovum, 
 an unequal division of the protoplasm takes place, since 
 the polar body, one of the division products, is very much 
 smaller than the other, the egg-cell. In the formation of 
 the second of the two polar bodies a reduction of the chro- 
 matin takes place, since tlie longitudinal cleavage is omitted 
 and the number of chromosomes is reduced one-half. 
 
 In many tissues of the human body, cell division takes 
 place continual/;/, as in the germ centers of the lymphoid 
 tissues (see page 121), in the tubular glands of the intes- 
 tines, and in the deeper layers of the epidermis. Other 
 cells of the human body, on the other hand, have a very 
 long life, so far as we know. Ganglion-cells, the majority 
 of gland-cells, many epithelial cells, probably exist during 
 the whole life and never show the phenomena of cell divi- 
 sion. In cold-blooded animals, in which it is possible to 
 make observations during the life of the animal, the time 
 of a mitosis has been established at six to eight hours ; in 
 the warm-blooded animals the process is probably com- 
 pleted in less than an hour. 
 
 The secondary elementary constituents of the hu- 
 man body may be present in the form of fluids, regarded as 
 the excretory products of the cells. The plasma of blood 
 and lymph, intercellular fluid, the synovial fluid and serous 
 fluids of bursas, joint cavities and body cavities may be men- 
 tioned under this head. If the excretory product of the 
 cell is semi-fluid or more or less solid we speak of ground 
 substance or cement substance, the latter when the intercel- 
 lular substance is found between the cells in small amount, 
 as in epithelial tissues, the former when the amount of 
 intercellular substance is predominant, as in cartilage, 
 
28 THE TISSUES. 
 
 bone, etc. Membranes and cuticular formations arise on the 
 surface of cells which are arranged in rows, such as epi- 
 thelia, through excretion from these and hardening of the 
 excreted membrane, so that each cell does not have a 
 crusta or membrane, but a common membrane develops, 
 which can be isolated. A typical example of such a mem- 
 branous formation is the lens capsule. Whether the mem- 
 brana propria of glands is to be regarded as an excretory 
 product of gland-cells is still open to discussion. Struc- 
 tureless membranes may arise from the fusion of cells, during 
 which process the nuclei of such cells may or may not 
 disappear. Membranes may also arise from the fusion of 
 fibers, the so-called fusion membranes. Elementary fibers 
 or fibrils are very widely distributed ; they arise for the 
 most part as direct transformation products of cells (accord- 
 ing to some investigators, from the homogeneous ground 
 substance). They occur as the fibrillar elements of the con- 
 nective tissue (the connective-tissue fibers), of the elastic 
 tissue (the elastic fibers). In the muscular tissues elemen- 
 tary fibrils occur as muscle fibrillar and in nerve-cells and 
 nerve-fibers as neurofibrils and as neuroglia fibers, the 
 supporting tissue of the central nervous system. 
 
 II. THE TISSUES OF THE HUMAN BODY. 
 
 The meaning of the term tissue cannot be defined with- 
 out qualification. In general we designate as tissues those 
 structures which are composed of equal or similar cells 
 arranged in a certain definite order and possessing a sim- 
 ilar function. By a strict interpretation of the histogen- 
 esis of tissues we are forced to recognize but two chief 
 types: (1) The epithelial tissues; (2) the connective 
 tissues (mesenchyme). Basing our subdivision on a func- 
 tional differentiation of these two chief types of tissues, 
 we may recognize two other divisions ; these are the mus- 
 cular and the nervous tissues ; the latter is of epithelial 
 
EPITHELIAL TISSUE. 29 
 
 origin, the former probably only partially so, the striated 
 muscle-fibers arising from epithelial cells, while the smooth 
 muscle-fibers are probably without exception of mesen- 
 chymal origin. 
 
 It is customary, therefore, to recognize in the fully 
 developed human body four types of tissues : (1) The 
 epithelial tissues ; (2) the supporting tissues or the con- 
 nective tissues ; (3) the muscular tissues ; (4) the nervous 
 tissues. 
 
 EPITHELIAL TISSUE. 
 
 Epithelial tissues consist of clearly defined, regularly 
 arranged cells, which clearly show their cellular nature 
 and which are separated by very small amounts of inter- 
 cellular substance. Aside from the occasional cuticular 
 formations, they give origin to no other secondary constit- 
 uents, and especially not to fibrous elements. 
 
 Epithelial tissue covers the whole surface of the body 
 and all mucous membranes and forms the essential por- 
 tion of all glands of the body. 
 
 According to the form of the elements, we distinguish 
 squamous, cubic, cylindric, pyramidal or prismatic, and 
 irregular epithelial cells ; epithelial cells which have cilia 
 are designated as ciliated epithelial cells, independently of 
 the form of the cells. Epithelial cells may be arranged 
 in a single layer or in several layers, so that we distinguish 
 simple and stratified epithelium. We also distinguish a 
 condition in which the main portion of the cells with the 
 nuclei lie in different planes, while fine processes or thin- 
 ner portions of the cells extend to the superficial surface 
 as well as to the base of the epithelium ; such epithelium 
 is known as pseudo-stratified, and it is often difficult to 
 determine whether we have stratified epithelium or one 
 presenting several rows of nuclei. 
 
 According to the form and arrangement of the epithelial 
 cells, we distinguish different types of epithelia. In the 
 human body the following types are recognized : 
 
30 the tissues. 
 
 Plate 2.— Epithelial Tissues. 
 
 Fig. 1. — Portion of the Great Omentum of a Rabbit, the 
 Cell Outlines Being Blackened by Silver. X 280. 
 
 The figure shows two layers of a simple pavement epithelium ( per- 
 itoneal mesothelium) . The cell boundaries are black, nuclei are stained 
 blue. 
 
 Technic : Silver impregnation. Hematoxylin. 
 
 Reference letters: k u Nuclei of superficial epithelial layer; k 2 , 
 nuclei of deeper epithelial layer. 
 
 Fig. 2. — Stratified Squamous Epithelium from the Human 
 Mouth. X 2H0. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows the typical structure of stratified squamous epi- 
 thelium, with indentations of the basal layer caused by low papillae 
 of the mucosa. Tbe deepest layer is cylindric, the most superficial 
 layers are of flattened cells. All the transitional forms are found 
 between them. In the deeper layers mitoses are seen ; leukocytes are 
 found scattered through the entire thickness of the epithelium. 
 
 Technic: Miiller's fluid, llematoxylin-eosin. 
 
 Reference letters : I, Leukocytes ; m, mitoses ■ p, papillae. 
 
 Fig. 3. — Cylindric Epithelium from the Human Intestinal 
 Tract. X 420. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows at the left three isolated cells from the intestinal 
 epithelium and at the right a number of the same kind of cells, which 
 are still attached. All the cells present on their superficial surface a 
 striated cuticular border. Leukocytes are found among the cells, and 
 some of them are acidophile. 
 
 Technic: Potassium bichromate and formalin. Hematoxylm-eosin. 
 
 Reference letters; 7, Leukocytes; l it eosinophile leukocytes. 
 
 1. Simple flattened or squamous epithelium, consisting of 
 a single layer of epithelial cells which are generally irregu- 
 larly polygonal. Occurs as the epithelium of the serous 
 cavities (mesothelium), of the alveoli of the lungs, of cer- 
 tain regions of the inner ear, and the intercalary portions 
 of many gland-ducts. 
 
 2. Simple cubic epithelium. Occurs as the epithelium 
 covering the choroid plexus of the brain, that of the lens 
 capsule, of the middle ear (frequently with cilia), of numer- 
 ous glands and excretory ducts of glands. 
 
 3. Simple columnar epithelium. Occurs as the epithe- 
 lium of the entire intestinal canal, of the gall-bladder, of 
 many gland-ducts. 
 
Tab. 2. 
 
 Firj.l- 
 
 •m 
 
 
 ^^ ® <33> t£ 
 ■ J* ® ® av ap 
 
 15 «s> 
 
 
 
 St 
 
 i$ 
 
 mu 
 
 
 
 t»*§ 
 
 
 %> 
 
 f 
 
 illil|ll^j# 
 
 Ficf.J. 
 
 M. 
 
 LUfi. An.iL F. RtiLCfihokl, Muuclien 
 
EPITHELIAL TISSUE. 31 
 
 J.. Simple ciliated epithelium. Occurs as the epithelium 
 of the uterus, of the oviduct, of the finer bronchial 
 branches of the lungs, of the accessory cavities of the nose, 
 of the middle ear, and the epithelium of the central canal 
 of the spinal cord. 
 
 5. Stratified pavement or squamous epithelium. This ter- 
 minology is inappropriate, as only a varying number of the 
 superficial layers consist of flattened cells, the cells of the 
 middle layers being polyhedral and those of the lowest 
 layers columnar. As a rule, the basal surface of this 
 variety of epithelium is not smooth, but indented by the 
 papillae of the connective-tissue layer which lies below. 
 Stratified squamous epithelium has a very wide distribu- 
 tion, occurring as the epithelium of the skin, the so-called 
 epidermis, in which the upper flattened layer is horny, the 
 epithelium of the mucous membrane of the mouth, phar- 
 ynx, vocal cords, esophagus, of portions of the conjunctiva 
 bnlbi, of the external auditory passage, of the vagina and 
 the female urethra, and the terminal portion of the male 
 urethra. The epithelium of the cornea consists of several 
 layers of cells, only a few of which are flattened, and rests 
 on connective tissue without papilla?. The epithelium of 
 the Graafian follicles of the ovary also simulates the strati- 
 fied squamous epithelium. 
 
 6. Stratified columnar epithelium has a limited distribu- 
 tion. It occurs in the larger excretory ducts of many 
 glands, especially the salivary glands, in the male urethra, 
 and on the conjunctiva palpebrarum. 
 
 7. Stratified ciliated epithelium. Its superficial cells are 
 prismatic and show cilia ; between their narrow ends are 
 found broad fusiform cells, and in the deeper portion near 
 the basal surface of the epithelium, rounded or pyramidal 
 cells. This epithelium has a wide distribution, lining the 
 entire respiratory tract — the nasal cavity, the upper por- 
 tion of the pharynx and the Eustach'an tube, the greater 
 part of the larynx, the trachea 'and all the larger bronchi ; 
 also the vas deferens and the ductus epididymidis ; the 
 
32 THE TISSUES. 
 
 latter has an especially tall columnar epithelium, with very 
 long, coarse cilia ; beneath and between the tall columnar 
 cells is a single layer of pyramidal cells. 
 
 8. Transitional epithelium. This is the epithelium of 
 the urinary passages and may be regarded as a modified 
 squamous epithelium, the uppermost layer of cells being 
 especially characteristic. The cells of this layer are large, 
 often polynuclear, flattened cubic, and have on their lower 
 surface several depressions for the cells of the next lower 
 layer. The upper portions of these cells of cubic or pris- 
 matic shape are somewhat rounded and fit into the depres- 
 sions in the under surface of the superficial cells. Then 
 follow one or two layers of irregularly rounded cells, and 
 below these, low columnar cells. This epithelium occurs 
 in the pelvis and calices of the kidney, in the ureter and 
 bladder. Transitional epithelium is capable of extreme 
 distention. In the bladder the form of the cells changes 
 considerably, so that in the empty condition the superficial 
 cells are cubic or almost columnar, while in the distended 
 condition they are nearly flat. 
 
 The epithelium of the tubules of the testes assumes an 
 especial arrangement, the form of which is very variable 
 and is dependent on the function. (See page 175.) 
 
 The Relations of the Epithelial Cells to Each 
 Other. — Between epithelial cells, united to form epi- 
 thelium, there is found a variable, though always small 
 amount of cement substance, which can be blackened under 
 special treatment with silver nitrate solutions. Frequently, 
 especially in pavement epithelium, there is observed an 
 interlocking of the intercellular bridges, serrated borders 
 of contiguous cells. (See Plate 2, Fig. 1.) In certain 
 epithelia, especially the middle layers of the stratified squam- 
 ous epithelium, contiguous cells are united by fine, bridge- 
 like, protoplasmic processes, so-called intereelluhir brhh/es. 
 These stand in relation with the fibrillar substance of the 
 cell. It is not yet established how widely distributed such 
 
EPITHELIAL TISSUE. 33 
 
 intercellular bridges are ; but it is doubtful whether they 
 are found between all epithelial cells. 
 
 Near the surface, especially of the columnar epithelium, 
 the cement substance becomes condensed, being thus differ- 
 entiated from the deeper semi-fluid cement. These firmer 
 bands of cement are called terminal ledges. The terminal 
 ledges form a perfect network, in the meshes of which the 
 tops of the epithelial cells fit. 
 
 The epithelial constituents of glandular tissue are known 
 as gland-cells. Their form differs in different glands, the 
 cubic form predominating. This type of epithelium will 
 be more fully considered in connection with the various 
 glands to be discussed. 
 
 Special Differentiation of Epithelial Cells. — Under 
 this heading we may consider primarily the motile appen- 
 dages of certain epithelial cells, the so-called cilia or fa- 
 gella. These consist of protoplasmic contractile fibers, 
 which are placed on the free surface of the cells consti- 
 tuting the ciliary border. Careful investigation of the 
 ciliated epithelium has shown that each cilium arises from 
 a small nodule situated at the upper end of the cell near 
 the free border. Cuticular borders are found in the form 
 of striated structures situated on the free surface of colum- 
 nar cells, especially of the intestine. This striated border 
 probably consists of small rod-like structures arranged in 
 a row. The epithelium of certain portions of the urinifer- 
 ous tubules presents a striated border, the so-called brush 
 jirocesses of the cells ; these are known to be made up of 
 short rods. It is probable that similar structures are also 
 to be found on the surface of the epithelial cells of the 
 olfactory mucous membrane. A striation of the basal por- 
 tion of the cells is seen in the cells of the excretory ducts 
 of many salivary glands and in certain epithelial cells of 
 the kidney. Epithelial cells may show a large number 
 of different kinds of cell-inclosures, as fat, pigment, crystal- 
 loids. Other peculiarities of epithelial cells depend upon 
 their secretory activity. Not only do the gland-cells func- 
 3 
 
34 the tissues. 
 
 Plate 3.— Epithelial Tissues. 
 
 Fig. 1.— Transitional Epithelium from the Human Ureter. 
 
 X 450. 
 
 The preparation was taken from an individual who had been exe- 
 cuted. 
 
 The figure shows the epithelium in the collapsed or slightly dis- 
 tended ureter. At the right is a polynuclear surface cell ; the upper- 
 most layer of the mucosa is seen under the epithelium. 
 
 Technic : Absolute alcohol. Hematoxylin-eosin. 
 
 Reference letters : 1, Surface cells ; 2, middle cellular layer ; 3, lower 
 layers of cells ; c, capillary vessels of the mucosa. 
 
 Fig. 2. —Stratified Ciliated Epithelium from the Regio Res= 
 piratoria of the Human Nasal Mucous Membrane. X 500. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows the usual picture of the stratified ciliated epithe- 
 lium with the high prismatic cells and the basal and replacement cells. 
 
 Technic : Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters : b, Basal cells ; c, columnar cells ; c , replacement 
 cells ; /, cilia. 
 
 Fig. ?,. — Ciliated Epithelium of the Ductus Epididymidis of 
 Man. X 420. 
 
 The preparation was taken from an executed individual. 
 
 The figure shows the peculiar two-layered epithelium of the ductus 
 epididymidis, with the long, whip-like cilia on the surface cells. 
 
 Technic : Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters : e, Cylindric cells ; r, round basal cells. 
 
 Fro. 4. — Pigment Epithelium of the Retina of the Cat. X 2K>. 
 
 The quite regular polygonal cells are almost filled with pigment 
 granules. The cell boundaries and the portion nearest to the nucleus 
 appear free from pigment. 
 
 Reference letter : k. Nucleus. 
 
 tionate as secreting or excreting cells, but also, to a 
 certain extent, all superficially placed epithelial cells ; 
 especially is this true of the epithelial cells of mucous 
 membranes. For this reason it is sometimes difficult to 
 determine whether we have before us a true simple gland 
 or a crypt or depression of the mucous membrane, since 
 the cells of the latter may also possess the power of 
 secreting. 
 
 The secretory activity of the epithelial cells is depend- 
 ent wholly on the protoplasm, the secretions being prod- 
 ucts of metamorphosis of the protoplasm. The process of 
 secretion is most easily recognized microscopically when it 
 

 ii 
 
 
 %i. 
 
 1 
 
 
 «|§«W' 
 
 ^.^. 
 
 © ® ® 
 
 ^J. 
 
 ®fe 
 
 sw 
 
 
 
 
 
 Fig. A. 
 
 Lith. Arist f. RzictdiolxL, Mundien . 
 
EPITHELIAL TMSL'K 35 
 
 concerns the formation of fat, as in the mammary glands, 
 or of the sebum of the sebaceous glands. In vacuoles of 
 the protoplasm the secretion is seen in droplets, 
 which are at first small, but gradually increase in size ; 
 either the enveloping border of protoplasm breaks down 
 and the secretion is set free, as in the mammary glands, 
 or, as in the sebaceous glands, the globules of secretion 
 which formed separately in the protoplasm become con- 
 fluent while the cell nucleus at the same time disappears 
 and the entire cell disintegrates. This disintegration of 
 the cells of the sebaceous glands represents the only 
 instance in the human body in which the cells break 
 down in the process of secretion. Goblet-cells now and 
 then break down after the evacuation of their contents ; 
 however, the process is not necessarily connected with the 
 secretion. The mucus-secreting cells, the so-called goblet- 
 cells, have a wide distribution, being especially prevalent 
 in the epithelium lining the respiratory passages and the 
 intestinal canal. They may be regarded as unicellular 
 glands. The secretion develops in the form of secretory 
 granules, appearing in the protoplasm in the free portion 
 of the cells and developed from the protoplasm. These 
 granules enlarge and become confluent. Probably each 
 cell of the intestinal epithelium may become a goblet-cell 
 in that the portion of the cell lying next to the surface of 
 the epithelium forms a mucous secretion from the proto- 
 plasm. The cell assumes the form of an open goblet just 
 before secretion, — that is, after the cell membrane has 
 ruptured, allowing the secretion to appear at the surface 
 of the cell. After evacuation of the secretion, the cell may 
 be restored to an ordinary epithelial cell. In other epi- 
 thelia, for instance in the epithelium of the stomach, the 
 formation of mucus seems to occur more simply, much as 
 in the gland-cells of mucous glands. In many other epi- 
 thelia, especially in many gland-cells, the secretory activity 
 is manifested by the occurrence of dainable granules in 
 the protoplasm, the so-called zymogen granules, which 
 
■Mi 
 
 THE TISSUES. 
 
 represent the preliminary stages of the formation of the 
 secretion. The gland-cells, the secretion of which is not 
 solid or semi-solid, as fat, sebum, mucus, but fluid, evac- 
 uate their secretions, not simply on the surface of the cells 
 into the lumen of the gland, but also by means of secretion 
 capillaries. These are fine, frequently anastomosing ducts, 
 having no walls of their own ; they may lie between 
 the cells, where the walls are formed of groove-like 
 depressions of the protoplasm of contiguous cells, known 
 as intercellular secretory capillaries, as for instance the 
 bile capillaries of the liver ; others extend into the proto- 
 
 Fig. 1. — Portion of the nracous membrane of the fundus of the 
 human stomach, treated by the Golgi method. X 420. The figure 
 shows very distinctly the intracellular secretion capillaries. /, Lumen 
 of the gland ; se, secretion capillaries of the parietal cells ; h, chief 
 cells ( single cells not visible ) . 
 
 plasm of cells, intracellular secretory capillaries, as in 
 certain cells in the glands of the fundus of the stomach. 
 
 Another special differentiation is seen in the eornification 
 of the cells of the superficial layers of the epidermis (see 
 page 202). Cornification is usually accompanied by loss 
 of the cell nucleus, but the cell is preserved. Cornifica- 
 tion is preceded by a granular condition of the cell proto- 
 plasm, the cells containing at this stage the so-called eleidin 
 or heratohyal'm granules (sec page 203). These granules 
 develop into the keratin of cornitied cells. 
 
 Epithelial tissue itself contains no blood-vessels, but be- 
 
E PITH EL I A L TISS UE. 
 
 37 
 
 tween the cells there are often found the terminal branches 
 of nerve-fibers. The epithelium is nourished from the 
 underlying layer of connective tissue. Capillaries, how- 
 ever, frequently come in direct contact with the epi- 
 thelial cells in certain glands where the original type of 
 epithelial arrangement is disturbed, as for instance in the 
 liver (see page 1G'2), where the blood capillaries lie directly 
 against the epithelial cells. 
 
 Forms of Glands. — Although glands are to be re- 
 garded as organs, yet it 
 seems advisable to discuss 
 here the forms of glands 1 
 
 which occur in the human 
 body. The glands are named 
 partly according to their 
 function (salivary glands, 
 sudoriferous glands, seba- 
 ceous glands) and partly 
 according to their position 
 (intestinal glands, thyroid). 
 
 The form of the secretory 
 acin i, or of the blind terminal 
 portions of the glandular sys- 
 tem, is the determining factor 
 in the classification of glands. 
 Taking this factor into con- 
 sideration we distinguish 
 two main classes of glands : 
 
 (1) Tubular, when the terminal portions have the shape 
 of tubes; (2) alveolar or acinous, when the terminal por- 
 tions are spherical or sac-like. There are certain transi- 
 tional forms between these two main types, since the 
 tubular terminal chambers of many glands may show sac- 
 like enlargements at their blind extremities and similar 
 enlargements at their sides ; these are known as tubulo- 
 alveolar glands. 
 
 By far the greatest number of the glands of the human 
 
 Fig. 2. — Portion of the human 
 pancreas treated by the Golgi 
 method. X 375. The figure 
 shows short, intercellular secre- 
 tory capillaries. I, Lumen of a 
 gland tubule ; sc, short secretion 
 capillary ; z, gland-cells (the 
 single cells are not visible). 
 
38 THE TISSUES. 
 
 body are tubular, or, more correctly stated, tubulo-alveolar. 
 In the simplest form, tubular glands occur as simple un- 
 branched tubules, as in the glands of the intestine (see 
 page 138); simple unbranched glands are, however, found 
 with the terminal portion coiled into a skein, as the sudorif- 
 erous or coil-glands of the skin. Other tubular glands 
 show a branching, especially toward their blind ends. The 
 glands of the fundus of the stomach and of the uterus 
 present this peculiarity to a slight degree, and the glands 
 of the pyloric region of the stomach to a greater degree. 
 
 Other tubular and tubulo-alveolar glands are much 
 branched, — that is, a larger number of greatly convoluted 
 tubules empty into a distinctly differentiated common duct, — 
 giving rise to a so-called system of ducts (see schemes 3, 5).* 
 This class comprises the duodenal glands and many small 
 glands of the oral cavity, of the pharynx, of the esoph- 
 agus, of the trachea, of the bronchi, of the nasal mucous 
 membrane, and of the urethra. Very many, and these 
 the largest of the tubular glands of the human body, are 
 compound glands and consist of many systems of ducts ; 
 into one large common duct several smaller ones open, 
 each of which again receives several tubular terminal 
 divisions of the gland. This category comprises all the 
 medium-sized and larger salivary and mucous glands, the 
 mammary gland, the lachrymal gland, the kidney, and 
 most of the glands of the genito-urinary apparatus, as 
 the prostate gland, bulbo-urethral and vestibular glands. 
 The testes, and especially the liver, represent compound 
 tubular glands, the tubules of which constantly anastomose. 
 On this account they are called reticular glands. 
 
 The alveolar glands are much less widely distributed 
 than the tubular glands. Alveolar glands which consist 
 of a single sac-like terminal chamber do not occur in 
 man, unless the ovary may be classed under this head. 
 On the other hand, branched alveolar glands consisting of 
 one system of ducts are frequently met with, as for in- 
 stance the sebaceous and Meibomian glands. In the 
 
EPITHELIAL TISSUE. 
 
 39 
 
 human body the one compound alveolar gland, consisting 
 of several systems of ducts, is the lung. 
 
 There are glands without excretory ducts, as the thy- 
 roid. These probably pour their secretion into the blood- 
 
 Fig. 3. — Diagrammatic representation of the forms of human 
 glands: 1, Straight, unbranched, simple tubular gland; 2, unbranched, 
 simple tubular gland, convoluted at the extremity ; 3, simple tubular 
 gland forked near the extremity; 4, simple tubular gland, showing 
 several branches ; 5, tubular gland, showing many branches (system 
 of ducts) ; 6, compound tubular gland ; 1', simple alveolar gland con- 
 sisting of one alveolus; 2', simple gland consisting of several alveoli ; 
 3' ', simple gland consisting of many alveoli ■ 4', compound alveolar 
 gland. 
 
 or lymph-vessels (so-called internal secretion). The ovary 
 empties its secretion, the ova, through the ruptured gland 
 follicles. The alveoli of glands consist, in addition to the 
 gland-cells, of a generally structureless membrane sur- 
 
40 THE TISSUES. 
 
 rounding the gland-cells, the so-called membrana propria, 
 which probably represents a membrane formed by the 
 fusion of connective-tissue cells (according to others, a 
 membrane formed by secretion of the epithelial cells). 
 Occasionally the membrana propria contains nuclei, a fact 
 which contraindicates a secretory origin. Other glands, 
 as the sudoriferous glands, have a layer of smooth muscle- 
 fibers between the glandular epithelium and the membrana 
 propria. 
 
 While the gland-cells represent the parenchyma of 
 glands, the interstitial tissue or stroma is formed of loose 
 connective tissue, which fills the interspaces between the 
 gland tubules, etc., and contains the blood-vessels and 
 nerves of the gland. 
 
 THE SUPPORTING OR CONNECTING TISSUES. 
 
 The entire group of connective tissues, forming an im- 
 portant part of the adult human body, has a common 
 histogenesis. 
 
 All forms of connective tissue develop from the mesen- 
 chyme, which is not present at the time when the blastoderm 
 consists of the three germ layers, the ectoderm, mesoderm, 
 and entoderm. It develops secondarily by cleavage (separa- 
 tion of single cells in certain regions) from the middle germ 
 layer or mesoderm, which then differentiates into an epi- 
 thelial portion, the mesothelium, and a connective-tissue 
 portion, the mesenchyme. The latter, at its first appear- 
 ance, consists of quite uniform branched cells, the embry- 
 onal connective-tissue cells. Later, however, manifold 
 differentiations occur, so that it becomes necessary to rec- 
 ognize a great number of subdivisions of the connective 
 tissues. In comparison with the epithelial tissues, con- 
 nective tissues are characterized by the fact that the secon- 
 dary elementary constituents, ground substance and fibers, 
 predominate, while the cells in the majority of connective 
 tissues are less prominent. 
 
CONNECTING TISSUE. 41 
 
 In the various types of connective tissues the following 
 elements may be recognized: (1) Cellular clement*, the con- 
 nective-tissue cells, or, as formerly designated, the connec- 
 tive-tissue corpuscles, with the aberrant forms of cells ; 
 (2) fibers or fibrillse ; these are divided into white fibrous 
 tissue-fibers, reticular fibers, and elastic fibers ; (3) ground 
 substance. 
 
 The cells of the different subdivisions of connective tis- 
 sues differ widely in shape and structure, although they all 
 develop from mesenchymal cells. The cells of gelatinous 
 connective tissues (see page 47) most nearly resemble the em- 
 bryonic type and are connected by distinct processes. The 
 cell-body of a connective-tissue cell is usually flattened and 
 presents several or many protoplasmic processes; stellate 
 forms are frequently met with, and now and then cells of 
 polygonal form. The processes of neighboring connective- 
 tissue cells frequently anastomose, as may be observed in 
 the large and typically shaped connective-tissue cells of the 
 cornea. In the majority of connective tissues the cells lie at 
 relatively great distances from each other and are separated 
 by large amounts of ground substance or fibrous tissue. 
 While most connective-tissue cells are relatively small and 
 flattened, certain varieties are characterized by their size 
 and their abundance of protoplasm; to this class belong the 
 so-called interstitial cells of the testis and ovary, the plasma- 
 cells and mast-cells of ordinary connective tissue, the last 
 of which show peculiar stainable granules (see page 59). 
 
 Marked variation from the general form of connective- 
 tissue cell is seen in cartilage (see page 48), in adenoid tis- 
 sue, and in adipose tissue. The cells of adenoid tissue 
 known as lymphocytes are of spherical form, with rela- 
 tively large, round nuclei. They stand in relation to cer- 
 tain cells of the blood, the so-called leukocytes (see under 
 Blood, page 57). The cells of adipose tissue consist, for 
 the most part, of large fat-drops, the nucleus and proto- 
 plasm of the cells being compressed and flat and crowded 
 to the periphery of the fat-drop. 
 
42 THE TISSUES. 
 
 PLATE 4— CONNECTIVE TISSUES. 
 
 Fig. 1.— Reticular Connective Tissue from a Human 
 Lymph=gland. X 280. 
 
 The preparation was taken from an individual who had been exe- 
 cuted. 
 
 The figure shows fine and coarser trabecules, which anastomose and 
 form a reticular framework. Bound or oval nuclei lie on the trabec- 
 ular 
 
 Technic : The preparation was made by shaking out the cells from 
 a section. Hematoxylin-eosin. 
 
 Reference letters : tr, A larger trabecula. 
 
 Fig. 2.— Interstitial Cells of Human Testis, with Crystal- 
 loids. X 500. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows eight of the large connective-tissue cells rich in 
 plasma, which are found together with the ordinary connective-tissue 
 cells as the interstitial tissue of the testis. Four of the cells con- 
 tain (one to three) crystalloids in longitudinal or cross-section. One 
 cell has two nuclei. 
 
 Technic : Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters : kr, Crystalloids ; x, transversely cut crystal- 
 loids. 
 
 Fig. 3— Mast=ceIIs from the Interstitial Connective Tissue 
 of the Dog's Prostate. X 500. 
 
 Besides the usual small cells, the figure shows four large connective- 
 tissue cells, the cell-body of which is filled with basophile granules. 
 The nucleus, on account of this fact , is not distinguishable. 
 
 Technic: Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters: m, Mast-cells; hdg, nuclei of ordinary connective- 
 tissue cells. 
 
 Fig. 4. — Connective=tissue Cells from the Cornea of the 
 Rabbit. X 500. 
 
 The figure shows the large connective-tissue cells of the cornea with 
 anastomosing processes. 
 
 Technic: Gold chlorid preparation. Formic acid. 
 
 The endothelial cells represent a special variety of con- 
 nective-tissue cells (see also page 115). These are flat- 
 tened cells, arranged like epithelium, and in many particu- 
 lars resemble simple squamous epithelium, from which 
 they differ genetically. Cement substance joins the cells, 
 which are often arranged with great regularity and which, 
 in a single layer, line the lumen of the blood- and lymph- 
 vessels and occasionally other cleft-like spaces of connec- 
 tive tissue, as for instance bursas, joint cavities, and 
 anterior chamber of the eye. 
 
Tab. 
 
 f- 
 
 v »^ 
 
 « 
 
 Fig.l. 
 
 «fc «■»«•» 
 
 ■ &i 
 
 ® 
 
 FT9 m 
 
 m.-iw ^ e--— , f "'9 
 
 © « < 
 9 g\ 
 
 Fig., 
 
 Fig., 
 
 Fig. 4-. 
 
 Lixh.. Anst F Retchtwld. Miinrhen . 
 
CONNECTING TISS ( 'E. 
 
 43 
 
 The cells of connective tissue may contain several kinds 
 of inclosures, as fat, pigment, crystalloids. 
 
 Three kinds of fibrous elements of connective tissue 
 are recognized. These differ morphologically as well as 
 chemically: (1) White fibrous connective-tissue fibers or 
 fibrillffi; (2) reticular fibers or fibrillse ; (3) elastic libers. 
 
 The lokite fibrous tissue fibrils are tine fibrous elements 
 less than 1 it in diameter, which yield gelatin on boiling 
 (collagenous connective tissue). They rarely occur singly, 
 but are very generally united into 
 finer or coarser bundles by an inter- 
 fibrillar cement substance. They 
 dissolve in caustic potash and be- 
 come swollen and transparent in 
 acetic acid, so that under the micro- 
 scope they are no longer discernible. 
 They digest very slowly in pan- 
 creatin. Reticular fibrils resemble 
 the fibrils of white fibrous connec- 
 tive tissue, but differ from them in 
 that they do not yield gelatin on 
 boiling. They are not digested in 
 pancreatin. 
 
 The clastic fibers vary very much 
 in thickness ; the finest are scarcely 
 larger than the connective-tissue 
 fibrils, while the largest are as large 
 as relatively large connective-tissue bundles, 
 easilv distinguished optically as well as chemically from 
 the connective-tissue fibers. They are strongly refractive 
 to light and resistant to alkalies and acids. Even the 
 largest elastic fibers cannot be broken up into fibrillse. 
 They are composed of a delicate outer sheath, which does 
 not stain in magenta, and an interior which stains deeply 
 with this stain. They yield no gelatin on boiling, but 
 they yield elastin. They are readily digested in pan- 
 creatin, less readily in pepsin. They occasionally form 
 
 Pig. 4.— Elastic 
 membrane from the 
 human arteria 1 lasilaris. 
 X 420. 
 
 Tl 
 
 icy are 
 
44 THE TISSUES. 
 
 fibrous networks, the meshes of which are so small that 
 elastic plates result, possessing only small openings, which 
 are called elastic membranes (Fig. 4). 
 
 The views of investigators pertaining to the develop- 
 ment of fibrous elements of connective tissue are still at 
 variance. Certain observers regard the fibrous elements 
 as products of excretion or fixation of the ground sub- 
 stance. 1 This view is supported by unsatisfactory evi- 
 dence. According to another theory, which is supported 
 by many observations, the fibrous structures of the connec- 
 tive tissues, including the elastic fibers, arise from the con- 
 nective-tissue cells themselves and in their protoplasm and 
 later become independent. 
 
 The ground substance of the various connective tis- 
 sues varies greatly ; it may be fluid or semi-fluid, as in the 
 blood and loose connective tissue, or it may have a solid 
 consistence, as in cartilage and bone (see under this tissue, 
 pages 48 and 81). Only rarely, as in many kinds of car- 
 tilage, do fibrous structures occur in the ground substance 
 (here they are chemically identical with the ground sub- 
 stance). As a general rule, the ground substance of the 
 various connective tissues is homogeneous. 
 
 According to the relation and morphologic character- 
 istics of the cells or of the intercellular substance, the fol- 
 lowing groups and varieties of connective tissue are dis- 
 tinguished : 
 
 Group A — Characterized by the Fibers: 
 
 1. Simple fibrillar connective tissue. 
 
 2. Elastic tissue. 
 
 Group B — Characterized by the Ground Substance : 
 
 1. Gelatinous connective tissue. 
 
 2. Cartilage. 
 
 3. Bone. 
 
 4. Dentine. 
 
 1 In the ground substance of hyaline cartilage, fibrous formations of 
 the ground substance occur, which are, however, chemically identical 
 with the ground substance itself and take their origin from it. 
 
CONNECTING TISSUE. 
 
 45 
 
 Group C — Characterized by the Cellular Elements: 
 
 1. Adipose tissue. 
 
 2. Pigmented connective tissue. 
 
 3. Reticular and adenoid connective tissue. 
 
 4. Blood and bone-marrow. 
 
 The simple fibrillar connective tissue may be further 
 subdivided into two classes, which are not very sharply 
 defined : (a) Loose connective tissue ; (b) formed connec- 
 
 b(U-:': 
 
 -> ef 
 
 "** 
 
 _:^j 
 
 Fig. 5. — Loose intermuscular connective tissue of man. X 140. 
 The figure shows the bundles of connective-tissue fibers, between 
 which are elastic fibers and a connective-tissue cell, hd, Connective- 
 tissue bundle ; ef, elastic fibers ; k, nucleus of connective-tissue cell. 
 
 five tissue. In structure the two forms are almost alike. 
 The differentiation rests on the manner in which the char- 
 acteristic elements of the connective tissue fibers or fibrils 
 are arranged. In loose connective tissue they are found 
 in bundles of different size, having a slightly wavy course. 
 Besides the bundles of connective-tissue fibers, loose con- 
 nective tissue always contains elastic fibers of varying 
 number and size, which can be easily distinguished from 
 
46 THE TISSUES. 
 
 the connective-tissue bundles by their different refraction 
 and by the different chemical reactions (see page 43). 
 
 Cells are found very sparingly in the ordinary loose 
 connective tissue of the human body, giving place almost 
 entirely to the fibrous elements. They are generally of 
 flattened form and lie on the connective-tissue bundles or 
 surround them like a ring. They almost always lie at con- 
 siderable distances from each other and constitute the so- 
 called fixed connective-tissue cells. Besides these, the fol- 
 lowing occur as cellular elements of loose connective tissue : 
 (1) Leukocytes (see page 57), which are found here as 
 in nearly all tissues of the human body, even in the 
 epithelium ; (2) plamm-celk and mud-cells, large connective- 
 tissue cells, which are rich in protoplasm (see page 
 41). Their number is very variable ; sometimes they are 
 found abundantly and again only singly or not at all. 
 
 Concerning the ground substance of loose connective 
 tissue we possess very little definite information ; it is 
 probably of a nearly fluid consistency. 
 
 The loose connective tissue is distributed over nearly 
 the entire body, but it is rarely found alone, being gen- 
 erally associated with adipose tissue, as intermuscular, sub- 
 cutaneous, submucous, and adventitious connective tissue. 
 The formed connective tissue is distinguished from the 
 loose especially by the fact that in the latter the connec- 
 tive-tissue bundles have no regular arrangement, while in 
 the former they are parallel or are arranged in a network. 
 The ground substance is present only in small amount ; 
 in tendon it is present mostly as cement substance. 
 Relatively few elastic fibers are present in tendon ; how- 
 ever, in the dense connective tissue of the cutis, elastic 
 fibers are abundant. The cells of formed connective 
 tissue are generally more abundant than in loose con- 
 nective tissue and are more regularly arranged, as is seen 
 especially in tendon. Between the formed and loose or 
 areolar connective tissue; there are many transition forms in 
 the human body. Areolar connective tissue also occurs 
 
CONNECTING TISSUE. 47 
 
 in the form of supporting tissue for the formed connective 
 tissues, as for instance in tendons (see page 93). 
 
 The dense or formed connective tissue is found with 
 parallel arrangement of its fibers in the tendons, fasciae, 
 and fibrous membranes, and in the cornea ; with reticular 
 arrangement of fibers and with more irregular course, fre- 
 quently passing over into other connective tissues without 
 any sharp boundary lines, in the peritoneum and great 
 omentum, in the cutis, and in the basal layer of mucous 
 membranes. 
 
 Elastic tissue, which is often not clearly separated 
 from fibrous connec- 
 tive tissue or passes 
 over into the latter 
 without distinct de- 
 marcation, is charac- 
 terized by the presence jjd<— 
 of numerous, generally 
 large, elastic fibers of 
 almost parallel ar- 
 rangement. Typical 
 elastic tissue is "found Fig. 6.— Portion of a cross-section 
 
 .i v of the ligamentum nuchse of the ox. 
 
 in the ligamentum nu- x 420 %^ Loose connective tissue; e , 
 
 chse, especially of large elastic fibers. 
 
 quadrupeds. In the 
 
 ligamentum nuchse are found large elastic fibers, which 
 
 frequently anastomose in a framework of loose connective 
 
 tissue. 
 
 Nearly pure elastic tissue is further found in the mucous 
 membranes of the respiratory tract, especially of the 
 larynx (membrana elastica), of the trachea, of the bronchi, 
 and of the lungs (alveolar wall) ; also in the vascular sys- 
 tem, in which elastic membranes occur in addition to the 
 elastic fibers (see page 43). 
 
 Gelatinous connective tissue, the first subdivision of 
 the connective tissues characterized by their ground sub- 
 stance, cannot be said to occur, as such, in the adult ; 
 
48 THE TISSUES. 
 
 Fig. 7. — Gelatinous connective tissue from a cross-section of the 
 umbilical cord of the new-born. X 280. F, Fibers ; Z, cells with 
 fine granules of fat in the protoplasm. 
 
 Fig. 8. — Portion of a cross-section of a human costal cartilage. 
 X 250. The figure shows the typical picture of a hyaline cartilage 
 with cartilage capsules, which contain two or more cells. In the 
 protoplasm, and also in the nuclei of the cells, fat droplets are found. 
 /, Fat droplets ; K, nuclei of cartilage cells ; kk, cartilage capsules ; 
 Z, cartilage cells. 
 
 however, several of the very loose connective tissues, with a 
 scarcity of fibers, possess a ground substance which is 
 gelatinous or semi-fluid, as for instance the tissue sur- 
 rounding the membranous semicircular canals, and such 
 connective tissues closely resemble gelatinous connective 
 tissue. In the new-born, typical gelatinous tissue is found 
 in the umbilical cord. The structure of this varies but 
 slightly from embryonal connective tissue, and of all the 
 varieties of connective tissue it is the one which most 
 closely resembles mesenchymal tissue. The ground sub- 
 stance is gelatinous, the tissue is rich in cells, the pro- 
 cesses of which distinctly anastomose. In mesenchymal 
 or embryonic connective tissue there are, when first devel- 
 oped, no fibers ; in gelatinous connective tissue they are 
 present in moderate number and, even when most fully 
 developed, form an inconspicuous portion of the tissue. 
 Very frequently gelatinous connective tissue occurs in 
 pathologic formations. 
 
 Cartilaginous tissue is readily distinguished from all 
 other kinds of connective tissue by its ground substance, 
 which, though elastic, is hard and, when uncalcified, can 
 be cut and yields chondrin on boiling. 1 Of the different 
 kinds of cartilage which occur in the animal kingdom, onlv 
 three are found in the human body : (1) Hyaline cartilage; 
 (2) elastic cartilage or reticular cartilage ; (3) connective- 
 tissue cartilage or white fibro-cartilage. 
 
 1 In a wider sense certain tissues are characterized as cartilage which 
 have a cartilaginous consistency, but which consist of pure connective 
 tissue (tarsal cartilage, etc.), or even the embryonal chorda dorsalis, 
 which genetically is quite a different structure. 
 

 
 I 
 
 \ 
 
 A 
 
 jfa.. 
 
 mi 
 
 z 
 
 Fig. 7. 
 
 /-' 
 
 r* - " 
 
 ~rZ 
 
 m^ -4 
 
 x '^ f° \ 
 
 .XSsfc 
 
 tc 
 
 : ,--- .... 
 
 Fig. 8. 
 
CONNECTING TISSUE. 49 
 
 Hyaline cartilage is opaque and bluish-white in color. 
 Its ground substance is homogeneous, transparent or trans- 
 lucent, and yields chondrin ; in the ground substance there 
 are found, especially as the age of the individual advances, 
 peculiar fibrillar structures, which, like the ground sub- 
 stance, yield chondrin on boiling. Calcification of the 
 ground substance occurs in many cartilages as age advances 
 and also during endochondral bone development. The 
 cartilage cells are found in spaces in the ground substance, 
 the cartilage spaces, occurring at variable distances from 
 each other. 
 
 In many hyaline cartilages each cartilage space is sur- 
 rounded by a narrow zone of ground substance which is 
 characterized by stronger refraction of the light ; this is 
 known as the capsule of the cartilage cell. In the cartilage 
 spaces are found the cartilage cells, which are round or 
 oval in shape and without processes. 1 They occur in 
 groups of one, two, or even occasionally more cells. 
 
 Young or embryonic cartilage is poor in ground sub- 
 stance and rich in cells. The cells divide mitotically and 
 a new capsule forms about each daughter cell, forming a 
 bridge of hyaline ground substance, so that each new cell 
 finally lies in a new space. In mature cartilage this does 
 not appear to happen in all cases ; for this reason, in most 
 hyaline cartilage, spaces are found which contain more than 
 one cell. It is very common to find two neighboring cells 
 which are flattened by contact; occasionally, especially in 
 costal cartilage, long cartilage spaces occur containing rows 
 of cartilage cells. We possess no evidence that cartilage 
 cells divide amitotically. Hyaline cartilage is very widely 
 distributed in the human body as the cartilages of the 
 joints, the costal cartilages, the nasal cartilage, certain of 
 the cartilages of the larynx, cartilage of the trachea and 
 of the larger bronchi. 
 
 Mastic cartilage is characterized by the presence of elastic 
 
 1 In lower animals there are varieties of cartilage in which the cells 
 are connected by processes. (See Nutrition of Cartilage.) 
 4 
 
50 THE TISSUES. 
 
 Fig. 9. — Portion of a cross-section of the elastic cartilage of the ex- 
 ternal ear of man. X 280. The figure shows the typical picture of 
 elastic cartilage, ef, Elastic fibers ; K, nuclei of cartilage cells ; kk, 
 capsules of cartilage cells. 
 
 Fig. 10.— Portion of a section of the intervertebral disc from man. 
 X 260. K, Nucleus of cartilage cell ; kk, cartilage capsules ; kk„ 
 cartilage capsules with calcification granules ; Z, cartilage cell. 
 
 fibers in the ground substance. In certain places the hyaline 
 cartilage passes over gradually and without any definite line 
 of demarcation into elastic cartilage. The latter, however, 
 also occurs independently. Elastic fibers, varying in size, 
 form dense networks, especially about the cartilage spaces. 
 Where the elastic cartilage occurs without transition into 
 hyaline cartilage, as in the cartilage of the pinna of the 
 ear and of the epiglottis, the network of elastic fibers is 
 dense and nearly fills the entire ground substance 
 throughout the cartilage. Where there is a gradual 
 transition from one kind of cartilage to the other, 
 as at the end of the vocal processes of the arytenoid 
 cartilages and generally in the cartilages of the smaller 
 bronchi, a few fine single elastic fibers are found in the 
 hyaline ground substance, which gradually become more 
 abundant and denser, and finally, forming networks, ac- 
 quire the same character as in pure elastic cartilage. 
 
 White Jibro-cartilage is characterized by the fact that 
 bundles of connective-tissue fibers are found in a very 
 small amount of ground substance, between which cartilage 
 cells lie in distinct cartilage spaces. The cartilaginous 
 nature of this form of cartilage is doubtful, especially as 
 it does not yield chondrin on boiling. The statements 
 regarding the occurrence of this form of cartilage, in places 
 where simple fibrous tissue seems to occur at times, are 
 very variable. In any case the occurrence of white fibro- 
 cartilage in man is limited to the fibro-cartilaginous inter- 
 vertebral discs and certain interarticular discs and liga- 
 ments. 
 
 Cartilage and dentine are probably the only kinds of 
 connective tissue which contain no blood- and lymph-ves- 
 
fStffii 
 
 8S-T& 
 
 
 
 >■«■ 
 
 «/ 
 
 Fig. 9. 
 
 H- X K 
 
 fcfci- 
 
 
 t: 
 
 R».;V * 
 
 «. - 
 
 Fig. 10. 
 
CONNECTING TISSUE. 51 
 
 sels and probably no nerves. Whether the hyaline ground 
 substance contains fine canals for carrying nutrition is 
 doubtful. In any case the nutrition of cartilage, which is 
 provided for from the firm connective-tissue capsule envel- 
 oping the cartilage, the perichondrium, seems imperfect, so 
 that the larger cartilages almost invariably, by the entrance 
 of blood-vessels from the perichondrium, begin to change 
 into bone tissue (large cartilages of the larynx). 
 
 The structure of bone and dentine will be discussed 
 when considering these tissues. We shall now consider the 
 third group of connective tissues, characterized by cellular 
 elements. 
 
 Adipose tissue in the fully developed condition consists 
 of collections of fat-cells. These are bound together by 
 bundles of loose areolar connective tissue to form fat- 
 lobules. 
 
 The fully developed fat-cell is spherical, has a distinct 
 cell membrane, and consists essentially of a large spherical 
 fat-drop, which crowds remains of protoplasm and nucleus 
 so that they represent only a narrow border within the 
 cell membrane. The flattened nucleus of the fat-cell 
 contains usually a refractive- globule, either a vacuole 
 or fat droplet. In the dead (cold) fat-cell, fatty acid crys- 
 tals often crystallize out in the form of needles. 
 
 Adipose tissue is very rich in blood-vessels, which, in 
 the form of capillaries, form a dense network between the 
 fat-cells. Adipose tissue is almost always found in com- 
 pany with loose connective tissue, so that sometimes one 
 and sometimes the other predominates. It occurs as sub- 
 cutaneous tissue mixed with loose connective tissue, and 
 also as interstitial tissue almost all over the body. 
 
 Adipose tissue may to a certain extent be formed from 
 ordinary connective tissue, since connective-tissue cells 
 form or take up small fat-drops, which become larger and 
 finally fill the whole cell in the typical way. Fat-cells 
 thus developed are not grouped into lobules of fat. On 
 the other hand, adipose tissue may become atrophic and 
 
52 
 
 THE TISSUES. 
 
 thus resemble fibrous connective tissue, in that the fat- 
 drops become smaller and finally entirely disappear. Such 
 atrophic adipose tissue is, however, not identical with 
 fibrous connective tissue. 
 
 Pigmented connective tissue (see Plate 6, Fig. 1) 
 is found very sparingly in the human body, while in the 
 
 lower animals it has 
 AT, a wide distribution, 
 
 and in certain forms 
 all the fibrous con- 
 nective tissue is pig- 
 mented. In man it 
 is constantly and 
 well developed only 
 in the choroid and 
 iris. The character- 
 istic feature of this 
 connective tissue is 
 that the relatively 
 abundant connec- 
 tive-tissue cells con- 
 tain fine differently 
 colored pigment 
 granules (yellow, 
 brown, or black), 
 which nearly fill the 
 body of the cell ; at 
 the same time the 
 tissue contains few 
 fibers. The presence 
 of pigment in con- 
 nective tissue is al- 
 ways associated with the protoplasm of the cells. Even 
 when pigment occurs in small amounts, in fibrous connective 
 tissue, as occasionally in the skin and in other places, it is 
 always carried by the cells. The pigmented connective 
 tissue in man is not sharply separated from ordinary con- 
 
 Fig. 11. — Adipose tissue from the orbital 
 cavity of man. / 280. The figure shows 
 fat-cells with fatty acid needles. The nuclei 
 contain vacuoles. &A", Nucleus of connec- 
 tive-tissue cell ; A,, nucleus of fat-cell 
 seen in surface view ; A",, nucleus of fat-cell 
 seen from the side ; M, membrane of fat- 
 cell ; X, crystals. 
 
CONNECTING TISSUE. 53 
 
 nective tissue. It is relatively rich in cells ; it generally 
 appears as areolar tissue, similar to the ordinary loose 
 connective tissue, but it is much poorer in fibers, which 
 rarely form large bundles. 
 
 Lymphoid or adenoid tissue is a form of connective 
 tissue which is very widely distributed in the human body. 
 It is found in a compact form in all lymph-glands, in the 
 thymus gland, spleen, and all the smaller lymphatic 
 structures of the digestive tract and of other mucous 
 membranes ; in the diffuse form it occurs in the red bone- 
 marrow and many mucous membranes, as for instance in 
 the uterus and the intestine. The lymphoid tissue may 
 be said to consist of two types of connective tissue, which 
 together form such organs as the lymph-glands, thymus, 
 and spleen ; one is a fine connective-tissue framework, 
 which is partly fibrous and partly cellular, the reticular 
 tissue, and the other a mass of round cells filling the in- 
 terstices of the reticulum. The elements of the latter 
 belong to the category of the lymphocytes and leukocytes or 
 colorless blood-cells (see page 57). They are round or 
 oval elements, with large round nuclei, and enter the cir- 
 culation as lymphocytes or mononuclear leukocytes. In 
 the bone-marrow (see page 61) and in the spleen other 
 forms of cells are found. In the lower vertebrates the 
 reticular connective tissue is formed of anastomosing stel- 
 late cells. In the higher vertebrates and especially in the 
 larger mammalia, the reticulum consists for the greater 
 part, and in certain regions perhaps even exclusively, of 
 finer and coarser branching and anastomosing connective- 
 tissue trabeculse, composed of reticular and white fibrous 
 tissue fibrils on which lie flattened cells. 
 
 With the exception of cartilage, dentine, and the connec- 
 tive tissue of the cornea, all forms of connective tissue 
 contain blood-vessels, though generally in small numbers. 
 The cornea contains nerves ; only cartilage, bone, and 
 dentine seem to be devoid of nerves. 
 
 Lymph-vessels, as such, are rarely found in connective 
 
54 
 
 THE TISSUES. 
 
 tissue, but the cell spaces and canaliculi are probably to 
 be regarded as the radicles of the lymph vascular system. 
 These are to be observed most distinctly in bone, lying 
 between the cells and the walls of the Haversian canals 
 and in the cornea, where they also occur as pericellular 
 spaces, between the cells and the ground substance. In 
 many kinds of connective tissue, the tissue fluid seems to 
 circulate in the ground substance, as in cartilage. 
 
 .-= i 
 
 Fig. 12.— Fresh blood without the addition of fluid. X 850. The 
 figure shows red and white blood-cells and blood platelets. e u Red 
 blood -cells seen on the flat surface; e.,, red blood-cells seen on edge 
 (rouleaux); e 3 , red blood-cells seen partly from the side; e it spherical 
 red blood-cells; /, leukocytes; p, blood platelets. 
 
 Blood. — Although in the adult body the blood, on account 
 of the lack of any regular arrangement of its elements, does 
 not appear as a typical tissue and is not so regarded by the 
 majority of authors, yet histogenetically it is scarcely to be 
 separated from the connective tissues, and we are therefore 
 
CONNECTING TISSUE. . 55 
 
 warranted in considering it a tissue with a fluid intercellu- 
 lar substance. 
 
 The blood is composed of a blood fluid, the blood 
 plasma, and of the formed elements, the blood-corpuscles 
 or blood-cells and the blood platelets. The blood plasma 
 is regarded as the intercellular substance, since it originates 
 embryologically as an intercellular substance. As the 
 blood plasma is homogeneous, it cannot be analyzed micro- 
 scopically. 
 
 Blood-corpuscles are divided into two main, sharply 
 defined groups — the colored blood-corpuscles, or erythro- 
 cytes, and the colorless or white corpuscles, the lympho- 
 cytes and leukocytes. The colored or red corpuscles 
 appear yellow under the microscope ; it is only in thicker 
 layers that they appear red. In the adult condition at 
 least they have no nuclei and are therefore non-nucleated 
 cells. The human red blood-cells measure on an average 
 7.5 p. in the long diameter and 1.6 /i in the short diameter. 
 In man one cubic millimeter contains on an average 
 5,000,000 red blood-cells. The views concerning the 
 structure of the red blood-cell are still somewhat at 
 variance, but it is very probable that it possesses a very 
 thin cell membrane ; within this is found a fine proto- 
 plasmic framework known as the stroma, the meshes of 
 which are filled with the coloring matter of the blood, the 
 hemoglobin. 
 
 Besides the disc-shaped cells, spherical red blood-cells 
 are occasionally found, and very rarely we may find in the 
 circulating blood nucleated immature red blood-corpuscles 
 (generally only after severe loss of blood). 
 
 The ordinary disc-shaped red blood-corpuscles of man 
 have a tendency, when they are present in the preparation 
 in large numbers and in a thick layer, to lie together and 
 form so-called rouleaux. They are very sensitive to 
 reagents and especially to evaporation, which produces a 
 concentration of the salt solution of the blood, so that 
 water is withdrawn from the blood-corpuscles. As a 
 
56 
 
 THE TISSUES. 
 
 result, the membrane shrinks and the so-called crenated 
 form of blood-corpuscles develops. Water, especially 
 distilled water, ether, chloroform, and many other reagents 
 remove the hemoglobin from the blood-cells, which are 
 
 Fig. 13. — Photographs of the Welcker blood-corpuscle models, 
 representing the corpuscles 1500 : 1. The figures after the name 
 give the size of the red hlood -corpuscles: 1, Proteus, 58 : 35 /i; - ; . frog, 
 22.3 : 15.7 fi;S, lizard, 15.79 : 9.9 p; 4, tench, 12.8 : 10.2/i;S, chaffinch, 
 12.4: 7.5//; 6, llama, 8 : 4//; 7, man, 7.2: 7.8,"; 8, dormouse, 6.2 fi; 
 9, goat, 5.4 u\ 10, muskox, 2.5 u. 
 
 then scarcely visible under the microscope, producing the 
 structures known as hlood shadows. 
 
 Only the blood-cells of mammalia are biconcave circu- 
 lar discs with rounded edges and non-nucleated. The 
 
CONNECTING TISSUE. 57 
 
 tylopods, camel, llama, and others, whose red blood-cor- 
 puscles are elliptic, but non-nucleated, are the only 
 exceptions to this rule. The red blood-cells of all other 
 vertebrates are nucleated biconvex discs of elliptic form, 
 the convexity being caused by the oval nucleus. 
 
 The amphibia have the largest blood-corpuscles, espe- 
 cially the tailed amphibia with persistent gills. The 
 smallest red blood-corpuscles are found in certain mamma- 
 lia (see Fig. 13). 
 
 It is forensically important to know the form a?nd size 
 of the blood-corpuscles. In size, the human blood-cor- 
 puscles stand nearest to those of many domestic animals. 
 It is therefore impossible, from the size of the corpuscles, 
 to reach a decision as to whether human blood or for in- 
 stance dog's blood is before us. 
 
 The hemoglobin from the blood-corpuscles crystallizes in 
 forms which are different in different animals (in man, in 
 rhombic prisms). It is possible to obtain hemoglobin crys- 
 tals only from fresh blood or from fresh clots, and even 
 this is often accomplished with difficulty. Occasionally, 
 but generally only pathologically, hematoidin crystals occur 
 in old blood exudates ; these represent a transformation 
 product of the hemoglobin. 
 
 Even from very old traces of the blood of every species 
 of animal whose blood-cells contain hemoglobin, crystals 
 of chlorid of hematin (hemin) can be obtained, which appear 
 in the form of long, needle-like, rhombic crystals of dark 
 brown color. 
 
 The discovery of hemin crystals shows only that blood 
 is before us and not that the blood is human. Frog's 
 blood and fish's blood, for instance, give the same hemin 
 crystals as human blood. 
 
 The colorless (white) blood-corpuscles form a large 
 group of cells of mesenchymal origin, which occur, not 
 only in the blood, but also in the lymph, as lymphocytes 
 form the chief constituent of adenoid connective tissue (see 
 page 53) ; they are also found scattered in almost every 
 
58 THE TISSUES. 
 
 variety of connective tissue and even occur between the 
 cells of epithelial tissues. The number of the white blood- 
 cells varies in circulating blood within certain limits, their 
 proportion to the erythrocytes being as 1 : 300 : 500. 
 
 Several varieties of white blood-cells are recognized, the 
 classification being based on the form, size, and structure 
 of the nucleus, on the relative amount and the structure 
 of the protoplasm, and on the origin. The following 
 varieties are distinguished : (1 ) Small and large lympho- 
 cytes ; (2) mononuclear leukocytes ; (3) transitional leuko- 
 cytes ; (4) polymorphonuclear leuko- 
 cytes and polynuclear leukocytes. 
 
 The lymphoaytcs vary in size from 
 5 [i to 7.5 p. and possess a relatively 
 large nucleus, which stains deeply and 
 is surrounded by a narrow zone of pro- 
 toplasm. They form about 20 per 
 cent, of the white blood-cells and are 
 developed in adenoid tissues. 
 S entelon 4 o7hemfn . The mononuclear leukocytes vary in 
 crystals from dried size from 7 /j. to 10 ji and possess a round 
 human blood. or ova ] nuc l euS) relatively smaller than 
 
 that of the lymphocytes and which, in 
 most dyes, is not colored very deeply. 
 They constitute 2 to 4 per cent, of the white blood-cells. 
 The mononuclear leukocytes very probably originate in the 
 spleen and bone-marrow and develop into the transitional 
 forms and these in turn into the polymorphonuclear forms. 
 The transitional leukocytes constitute from 2 to 4 per cent, 
 of the white blood-cells and possess a nucleus of more or 
 less pronounced horseshoe shape, of a size and structure 
 similar to that seen in the mononuclear varietv. The rjolv- 
 morphonuclear leukocytes form from 60 to 70 per cent, 
 of the white blood-cells and possess variously tabulated 
 nuclei, the several nuclear masses being united by delicate 
 threads of protoplasm. A polymorphonuclear leukocyte 
 develops into the polynuclear form when the delicate 
 
CONNECTING TISSUE. 59 
 
 bridges of nuclear substance uniting the several lobules 
 of the nucleus of the former break through. In the leuko- 
 cytes with polymorphous nuclei there is found in the 
 center of the lobular nuclear mass a centrosome which is 
 often difficult to demonstrate ; in the resting stage of the 
 cell, fine rays radiate from this. By means of special 
 staining methods, the presence of granules can be shown 
 in the protoplasm of the transitional, polymorphonuclear, 
 and polynuclear leukocytes of the blood and lymph and 
 of certain blood-forming organs ; in the latter, mononuclear 
 cells with round or oval nuclei, possessing granules in 
 their protoplasm, are found. These granules show specific 
 reaction toward certain anilin stains or combinations of 
 such stains, and according to their staining power they are 
 divided into the following sub-classes : (1) Those which 
 stain with the acid anilin dyes and especially with eosin 
 are known as oxyphile or eosinophile granules; (2) gran- 
 ules which show an affinity for basic stains are known as 
 basophile granules; (3) granules which stain in certain 
 combinations of acid and basic anilin stains, the so-called 
 neutral staining mixtures, are known as neutrophile gran- 
 ules ; (4) granules which stain in both basic and acid anilin 
 stains are designated amphophile granules. 
 
 The leukocytes with eosinophile granules form 1 to 4 
 per cent, of the circulating white blood-cells. The gran- 
 ules are coarse and can be recognized with moderately 
 high magnification even in unstained cells. They stain a 
 bright red in eosin and occur in normal blood in cells 
 with horseshoe-shaped or lobulated nuclei. In bone- 
 marrow they are also found in mononuclear cells with 
 round or oval nuclei. They are found in the connective 
 tissue of the intestine, and in certain pathologic states are 
 found in greatly increased numbers in connective tissue. 
 
 The basophile granules occur in two sizes : first, as 
 large granules very little smaller than the oxyphile ; these 
 are found in the so-called mast-cells (see page 41) and 
 rarely occur in the normal circulating blood, but are found 
 
60 THE TISSUES. 
 
 PLATE 5.— BLOOD. 
 
 Figs. 1-21. — BIood=corpuscIes from Human Blood. X 700. 
 
 The figure shows the different forms of erythrocytes, lymphocytes, 
 and leukocytes. 
 
 Technic: Dry preparation. Ether-alcohol. Hematoxylin-eosin. 
 In 1, 3, and 4, Ehrlieh's triacid solution. 
 
 Figs. 6-12. — Erythrocytes. 
 
 Fig. 9. — Nucleated red blood-corpuscles. 
 
 Figs. 1-5 and 13-21. — White blood-cells. 
 
 Fig. 1. — Small lymphocyte, having a small amount of protoplasm 
 and large nucleus. 
 
 Figs. 2 and 3. — Polynuclear leukocytes with neutrophile granula- 
 tion. 
 
 Figs. 4, 5, 14, 16, and 18. — Ordinary polynuclear leukocytes. 
 
 Figs. 15, 19, and 21. — Leukocytes of different sizes, having acid- 
 ophile (eosinophile) granulation. 
 
 Figs. 13 and 20. — Large lymphocytes. 
 
 Fig. 17. — Mononuclear leukocyte. 
 
 Figs. 22-31. — Elements of the Bone=marrow of a Mouse. 
 X 700. 
 
 The preparation was taken from the femur of a full-grown mouse. 
 
 The figure shows one of the large giant-cells of the bone-marrow, 
 ordinary and nucleated red blood-corpuscles, different kinds of marrow 
 cells including leukocytes, among them eosinophile cells and mitoti' 
 cally dividing cells. 
 
 Technic as above. 
 
 Fig. 22. — Polynuclear giant-cell. 
 
 Figs. 23-28. — Marrow-cells. 
 
 Fig. 23. — Marrow-cell with annular nucleus (goes through the 
 nuclear stage of 25 into that of 24 — that is, into the ordinary poly- 
 morphonuclear cell). 
 
 Figs. 25 and 26. — Acidophile cells. 
 
 Figs. 27 and 28. — Mitoses. 
 
 Fig. 29. — Ordinary erythrocyte. 
 
 Figs. 30 and 31. — Nucleated erythrocytes. 
 
 in certain pathologic conditions ; second, as very fine 
 granules which are visible only under high magnification ; 
 these are seen in the leukocytes of the circulating blood, 
 such cells forming a small percentage of the white blood- 
 cells. 
 
 The leukocytes with neutrophile granules form 65 to 
 68 per cent, of the polymorphonuclear forms found in the 
 circulating blood. Tiny are very fine granules, not read- 
 ily seen unless oil-immersion lenses are used. Neutro- 
 phile granules further occur in certain mononuclear cells 
 
Tab. S. 
 
 Ssfe 
 
 t^m. 
 
 . : 
 
 13 
 
 If 
 
 it I* 
 
 15 
 
 ill 
 
 /(? 
 
 
 « 
 
 // 
 
 
 
 
 .?/ 
 
 
 a? 
 
 
 JO 
 
 29 
 
 ( * 
 
 f\ ^* A 
 
CONNECTING TISSUE. 61 
 
 of the bone-marrow (myelocytes) ; in certain pathologic 
 conditions such cells are .seen in circulating blood. 
 
 Amphophile granules occur in the leukocytes of many 
 mammals, both in the circulating blood and in the bone- 
 marrow. 
 
 The blood platelets are colorless discs of round or oval 
 form, measuring 2 /i to 3 p., and are in proportion to the 
 red blood-cells as 1 : 25 or as 1 : 40. They are constant 
 constituents of the human blood. Their structure and 
 development have not yet been fully determined. Cer- 
 tain investigators regard them as nuclear fragments of 
 either the red blood-cells or of the leukocytes. Accord- 
 ing to more recent investigations, the blood platelets or 
 the thrombocytes, as they are known on account of their 
 relation to the coagulation of the blood, are small nucle- 
 ated cells, which are destroyed in the process of coagula- 
 tion. It has been shown that they possess ameboid 
 movement. 
 
 Red bone-marrow consists of a delicate reticulum of 
 fibrous and reticular connective tissue, in the meshes of 
 which are found numerous cellular elements. The cellu- 
 lar elements of the bone-marrow are : (1) Leukocytes and 
 lymphocytes, as found in circulating blood. (2) Myelocytes. 
 These are mononuclear cells, slightly larger than the leu- 
 kocytes, with round or oval nuclei, which stain faintly, 
 and a protoplasm containing neutrophile granules, now 
 and then vacuoles and pigment granules. These cells are 
 found in circulating blood in certain pathologic states. 
 (3) Numerous cells with eosinophile granules in the pro- 
 toplasm, the nuclei of which may be either round or oval, 
 horseshoe-shaped or polymorphous, are found. (4) We 
 further meet with cells with vacuolated or annular nuclei. 
 These cells probably develop into the leukocytes with 
 polymorphous nuclei. (5) Between the ordinary marrow- 
 cells are scattered rjiaut-cells, large, spherical cells, rich in 
 protoplasm, with several and often many nuclei. The 
 nuclei often lie in a group or mass, and occasionally in the 
 
62 THE TISSUES. 
 
 form of a crescent. The diameter of these cells often 
 reaches 100 /a (6) In addition to the fully developed red 
 blood-cells, we also find in the bone-marrow nucleated red 
 blood-cells still in the process of formation. The bone- 
 marrow is the seat of blood formation. In its tissue, new 
 red blood-cells are formed, the developmental stage of 
 which, here as well as in embryonal blood development, is 
 nucleated. They reach the veins of the bone-marrow 
 after they have lost their nuclei. There is as yet contro- 
 versy as to the manner in which the nucleus is lost. 
 Certain investigators believe that the nucleus is extruded, 
 while others state that it is absorbed or lost by chromat- 
 olysis. 
 
 MUSCLE TISSUE. 
 
 Both as to structure and function, muscidar tissue is 
 divided into two great subdivisions: (1) Transversely 
 striated or voluntary muscle (cardiac muscle is striated, 
 but involuntary); (2) non-striated, smooth, or involuntary. 
 
 Involuntary muscle consists of long, spindle-shaped 
 mononuclear cells, exhibiting the character of ordinary 
 cells. They vary in size, and especially in length, measur- 
 ing from 50 ji. to 150 p. in their long diameter and from 5 ji 
 to 8 fi in their thickest portions. Very large smooth 
 muscie-fibers are found in the musculature of the seminal 
 ducts, and still larger fibers in the musculature of the 
 pregnant uterus, where they may attain a length of 500 p.. 
 
 The typical smooth muscle-cell or fiber is fusiform. In 
 the middle of the thickest portion is found an elongated 
 nucleus, which has the form of a short rod with rounded 
 corners. The two ends of the smooth muscle-fiber are 
 sharply pointed. The protoplasm of the smooth muscle- 
 fiber stains quite intensely with acid anilin dyes, as eosin, 
 etc. ; as a result, smooth muscle can often be readilv dis- 
 tinguished from the surrounding connective tissue. In 
 the protoplasm of the larger cells a distinct longitudinal 
 striation may be observed, due to the presence of fibrils 
 
MUSCLE TISSUE. 63 
 
 which run parallel or nearly parallel to the long axis of 
 the cell ; these are more clearly made out in cross-sections 
 of the cells, in which they appear as minute granules. 
 
 The involuntary muscle-cells are inclosed within delicate 
 fenestrated connective-tissue membranes, so disposed that 
 two contiguous involuntary muscle-cells are separated by 
 a single membrane. The intercellular bridges described 
 by certain observers are due to faulty technic and are to 
 be regarded as artefacts. 
 
 Non-striated muscle-fibers may occur in relatively large, 
 compact masses, with regular arrangement of the cellular 
 elements, and then form the so-called involuntary muscula- 
 ture. The musculature of almost all the abdominal organs 
 is of this variety, as in the stomach, intestine, bladder, 
 uterus, etc. They also occur, however, scattered in small 
 
 Fig. 15. — Isolated involuntary muscle-cell from the intestine of a 
 frog, in the middle of which the nucleus is seen. X 320. 
 
 bundles and even in single fibers, as in the mucous mem- 
 brane of the stomach and in the villi of the intestine, 
 and in certain regions form typical networks, as in the 
 bladder. (See Plate 58, Fig. 2.) 
 
 Where involuntary muscle occurs in larger amounts, 
 bundles or fasciculi of the tissue are surrounded by con- 
 nective-tissue sheaths which penetrate between the single 
 groups of fibers. This connective tissue also carries the 
 abundant blood- and lymph-vessels. Blood capillaries are 
 found between the single muscle-fibers. Smooth muscu- 
 lature is supplied exclusively by the neuraxes of sympa- 
 thetic neurones. 
 
 Smooth musculature is very widely distributed in the 
 human body. It is found in the entire digestive canal 
 from the middle of the esophagus to the anus, in the gall- 
 
64 
 
 THE TISSUES. 
 
 bladder and the larger bile-duets, in the excretory ducts 
 of many glands, in the urinary passages, in the efferent 
 passages from the male and female reproductive organs, in 
 the blood and lymph vascular system, in the eye, in the 
 respiratory passages, and in the skin. 
 
 The elements "of transversely striated, voluntary- 
 muscle, in contrast to those of non-striated muscle, are not 
 simple cells, but cell syncitia or plasmodia. 
 
 Histogenctically, each striated muscle-cell or fiber arises 
 from a single cell (one of the cellular elements of the 
 myotomes of the primitive vertebrae). A proliferation of 
 
 Fig. 10. — Ends of three isolated striated muscle-fibers of the frog. 
 The figure at the left shows an intermuscular and at the right a ten- 
 dinous termination. X 100. 
 
 the nucleus takes place by mitotic division, without subse- 
 quent division of the protoplasm. At the same time a 
 very considerable elongation of the cell takes place with 
 development of contractile fibrillse. 
 
 The cross-striated muscular fibers are usually of long 
 cylindric shape, with rounded or beveled ends. They are 
 often of considerable length, measuring 12 cm. and more in 
 long parallel-fibered muscles. The thickness of the muscle- 
 fiber varies between about 10 (i and 100 //.. Each muscle- 
 fiber has two free ends; these may cither, as in short 
 muscles, run from tendon to tendon, or the fiber may begin 
 
MUSCLE TISSUE. 65 
 
 with the one free end in tendon and end free in muscle; 
 or, as is the ease in very long muscles, certain of the mus- 
 cle-fibers do not reach the tendon, but have two intermus- 
 cular ends. The tendon end* of the muscle-libers are gen- 
 erally rounded and characterized by collections of nuclei (see 
 Fig. K>). The intermuscular ends are beveled; the bev- 
 eled ends of adjoining muscle-fibers are said to be united 
 by cement substance. 
 
 Each striated muscle-fiber is surrounded by a dense 
 homogeneous membrane, the sarcolemma, which is easily 
 isolated; this represents the cell membrane of transversely 
 
 Fig. 17. — Longitudinal section of a small muscle-fiber from the 
 human eye muscle. \ 450. ai, Anisotropic substance; i, isotropic 
 substance: k. nuclei; s, sarcolemma. 
 
 striated muscle-fibers. Within the sarcolemma is contained 
 the muscle substance, in which are recognized the contrac- 
 tile ultimate fibrils, the interfibrillar substance, the sarco- 
 plasm, and the nuclei. 
 
 Functionally, the most important constituents are the 
 cross-striated contractile fibril/w, which give the character- 
 istic cross-striated appearance to the entire muscle-fiber. 
 Frequently also the fibrilla? give to the muscle-fiber a 
 distinct longitudinal striation, especially when the inter- 
 fibrilleir substance is relatively abundant, as in lower ani- 
 mals. 
 
 The fibrillae are fine fibrillar structures, arranged in the 
 5 
 
G6 
 
 THE TISSUES. 
 
 long axis of the fiber and taking up the entire length of 
 the fiber ; under the microscope they show alternate dark 
 and light segments. The segments which appear dark 
 consist of doubly refracting, anisotropic substance ; the 
 segments which appear light, of singly refracting, isotropic 
 substance. More careful investigation shows that in the 
 middle of the isotropic substance a fine anisotropic inter- 
 mediate disc is found, and similarly in the middle of each 
 
 Fig. 18. — Portion of a fresh, isolated, transversely striated muscle- 
 fiber of man. X 550. The figure shows the cross-striation ven T dis- 
 tinctly. We recognize in the middle of the anisotropic median disc the 
 isotropic median disc, and in the middle of the isotropic substance, the 
 anisotropic intermediate disc, ai, Anisotropic substance; >, isotropic 
 substance; msch, isotropic median disc; asch, anisotropic intermediate 
 disc. 
 
 anisotropic segment there occurs an isotropic median disc. 
 The fibrillse are firmly united by an interfibrillar sub- 
 stance, and can be recognized only after the use of 
 special methods. 
 
 The fibrillse are not evenly and regularly arranged 
 throughout the muscle-fiber, but are united into groups, 
 the so-called muscle columns. The several muscle columns 
 are separated by sarcoplasm, the remains of the original 
 
MUSCLE TISSUE. 
 
 67 
 
 cell protoplasm, not changed into fibrillar substance. The 
 relative amount of sarcoplasm varies in different muscle- 
 fibers, so that the boundaries of the muscle columns are 
 sometimes more and sometimes less distinct. Occasion- 
 ally, and especially in the vicinity of the nuclei, the sar- 
 coplasm contains granules, the so-called interstitial gran- 
 ules ; these are mostly fat and pigment granules. 
 
 k 
 
 Fig. 19.— Portion 
 of a cross-striated 
 muscle-fiber of the 
 larva of a salaman- 
 der ; this is breaking 
 up into fibrillae. X 
 700. 
 
 Fig. 20. — Cross-section of a human muscle- 
 fiber, rich in sarcoplasm. X 780. The figure 
 shows the arrangement of the muscle columns. 
 k, Nucleus of muscle-fiber; ms, muscle column; 
 s, sarcoplasm. 
 
 The disposition of the sarcoplasm and the arrange- 
 ment of the muscle columns are best recognized in the 
 cross-section of the muscle, in which we may recognize a 
 division into several irregularly outlined fields of different 
 sizes, known as Cohnheim's areas. 
 
 According to the amount of sarcoplasm, we distinguish 
 two kinds of muscle-fibers — so-called dark or red fibers, 
 
68 THE TISSUES. 
 
 rich in sarcoplasm, and light or white fibers, which are 
 poor in sarcoplasm. In general, the red fibers are found 
 in varying but small numbers scattered between the white 
 fibers. In certain animals, however, for instance in the 
 rabbit, certain muscles, as for example the semitendinosus, 
 consist entirely of the red variety of fibers, while other 
 muscles, as for example the semimembranosus, consist 
 entirely of the white variety of fibers. In many muscle- 
 fibers of the white variety the amount of sarcoplasm is 
 so small that it is difficult to distinguish between the sev- 
 eral muscle columns. 
 
 Besides the sarcoplasm found between the muscle col- 
 umns, collections of sarcoplasm are found around the 
 nuclei of the muscle-fiber. The nuclei of cross-striated 
 voluntary muscle-fibers are very numerous. Long fibers 
 have hundreds of nuclei. In the great majority of the 
 muscle-fibers all nuclei lie at the periphery, immediately 
 under the sarcolemma, in a small collection of sar- 
 coplasm. They have an elongated, elliptic form. 
 
 Branched, cross-striated muscle-fibers occur in certain 
 regions. The superficial musde-fibers of the tongue, 
 especially the ends of the fibers inserted into the mucous 
 membrane, show this peculiarity. The branches show the 
 same structure as the parent fiber. In the frog's tongue, 
 branched cross-striated muscle-fibers are very abundant 
 and complex. 
 
 Cross-striated muscle is very widely distributed ; it 
 comprises all skeletal muscles, the larger muscles of the 
 skin, the extrinsic eye muscles, the muscles of the middle 
 ear, portions of the musculature of the digestive tract 
 (tongue, pharynx, part of the esophagus), the larynx, the 
 muscles of the perineum, of the external genital organs, 
 and the sphincter muscles of the anus. 
 
 Heart mnwh occupies a special position, in that it differs 
 histogenetically and physiologically from voluntary, cross- 
 striated muscle, and structurally both from non-striated 
 muscle and from voluntary, cross-striated muscle. It is 
 
MUSCLE TISSUE. 69 
 
 cross-striated, but not subject to the will. In many 
 respects heart muscle resembles involuntary muscle more 
 closely ; it is, like involuntary muscle, developed from the 
 mesenchyme, and not, like striated, voluntary muscle, 
 from the myotomes. In many lower animals, as for in- 
 stance in the frog, heart-muscle fibers assume a distinct 
 median position between smooth and striated muscle, rather 
 more closely resembling the non-striated muscle. 
 
 Heart muscle, after fixation and hardening with the 
 majority of the reagents in ordinary use in the laboratories, 
 as also after treatment with macerating fluids, appears to 
 consist of irregularly shaped oblong cells, possessing 
 usually one, but occasionally two nuclei, situated in the 
 center of the cells. These cells appear to be cemented 
 end to end to form the heart-muscle fibers. The cells 
 show irregular but short side branches, which anastomose 
 with similar branches of neighboring cells. The heart- 
 muscle fibers show a distinct cross and longitudinal stri- 
 ation and possess relatively more sarcoplasm than do the 
 fibers of cross-striated, voluntary muscle tissue. The sar- 
 coplasm surrounds the axially placed nucleus and forms 
 distinct septa, which radiate from the nucleus to the 
 periphery. In this way the muscle fibrillar are arranged 
 in plates, which also radiate from the nucleus to the 
 periphery. Heart-muscle fibers possess no sarcolemma. 
 Very recent investigations, which seem very conclusive, 
 make it very doubtful whether the lines which have been 
 regarded as the boundary lines of cells are thus to be 
 interpreted, since it has been shown that they bound non- 
 nucleated areas of heart muscle, and further that the stri- 
 ated contractile fibers pass through such lines without 
 interruption, although they show slight alteration in struc- 
 ture and reaction toward staining reagents. According to 
 this view, heart muscle is regarded as a syncitial tissue, 
 the so-called boundary lines representing growth areas. 
 Only very careful embryologic investigation can throw 
 light on the histogenesis and histology of heart muscle. 
 
70 THE TISSUES. 
 
 PLATE 6.— MUSCULAR TISSUES. 
 
 Fig. 1. — Pigmented Connective=tissue Cells from the Human 
 Iris. X 420. 
 
 The preparation was taken from an executed individual. 
 
 The figure shows differently formed connective-tissue cells, the pro- 
 toplasm of which is filled with yellowish-brown and brown pigment 
 granules. 
 . Technic: Chromic acid solution (2 percent.). Hematoxylin-eosin. 
 
 Reference letter: k, Nucleus. 
 
 Fig. 2. — Branched Cross-striped Muscle=fibers from the 
 Human Tongue. X 220. 
 
 The preparation was taken from an executed individual. 
 
 The figure shows several longitudinally cut tongue muscle-fibers, 
 which fork at their insertion into the fascia linguae. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Eeference letters: r, Branchings; k, nuclei, some of which are seen 
 in surface view. 
 
 Fig. 3. — Portion of a Longitudinal Section through the 
 Human Heart Muscle. X 280. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows a number of heart-muscle fibers with their anas- 
 tomoses in longitudinal section; between them is seen the intermus- 
 cular connective tissue (perimysium ) . 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters for Figs. 3 and 4 : gr, Boundary lines ( these are 
 brought out too clearly in the printing); k, nucleus; pm, perimysium 
 internum; x, anastomoses. 
 
 Fig. 4— Portion of a Cross=section through Human Heart 
 Muscle. 
 
 The figure shows the variation in size of heart-muscle fibers, the 
 axially placed nuclei and the radialty arranged muscle columns. 
 
 Technic and lettering as in Fig. 3. 
 
 THE NERVOUS TISSUES. 
 
 Nervous tissue, like muscle tissue, is highly differenti- 
 ated, both as to the structure and the function of its ele- 
 ments. These are, for purposes of description, ordinarily 
 divided into three main groups : 
 
 1. Nerve-cells or ganglion-cells. 
 
 2. Nerve-fibers. 
 
 3. Nerve-supporting tissue or neuroglia. 
 
 It is more correct, however, to regard the nerve-cells 
 and the nerve-fibers as parts of the same element, since 
 both histogenetieally and structurally considered the 
 nerve-fibers are processes of the nerve-cells. The nerve- 
 
Tab. 6. 
 
 ;'«v 
 
 Fi B .l. 
 
 Tiff J. 
 
 Wirt Jl 
 
 
 Zitfl. An.it F, BeuMwld. Mtinchen 
 
NERVOUS TISSUES. 71 
 
 cells with their processes, as well as the supporting tissue, 
 the neuroglia, are of ectodermal origin ; indeed, they even 
 arise from similar ectodermal cells, although the support- 
 ing tissue, when fully developed, is in many respects sim- 
 ilar to connective tissue. The essential portions of the 
 nerve-fibers, the axis-cylinders or neuraxes, develop only 
 as processes of the nerve-cells, even when they attain 
 great length. In their course outside of the central ner- 
 vous system the neuraxes are surrounded by special sheaths, 
 which, with the neuraxes, constitute the nerve-fibers. In 
 this discussion we shall follow the above classification and 
 treat the nerve-fibers separately. The nerve-cells and the 
 axis-cylinder processes or neuraxes, the main constituents 
 of the nerve-fibers, accordingly form together the anatomic 
 units of the nervous system, the so-called neurones. A 
 neurone, therefore, consists of (1) the nerve-cell or 
 ganglion-cell with its protoplasmic branches, the dendrites 
 (see page 72) ; (2) the neuraxis with its collaterals ; (3) 
 the terminal branching of the neuraxis. 
 
 The " neurone concept " of the nervous system is now 
 very generally accepted. By it is meant that the nervous 
 tissues, like the other tissues of the body, are composed of 
 anatomic units (cells), which are morphologically, patho- 
 logically, and, to a certain extent, physiologically inde- 
 pendent of each other. The neurones come into relation 
 with each other only by contact. Recent observations 
 have thrown some doubt on the validity of this doctrine ; 
 in the strict sense it can no longer be supported, since 
 anastomoses of the terminal arborizations, and even of 
 ganglion-cells, have been shown beyond question. 
 
 Nerve-cells occur in the central nervous system, espe- 
 cially in its gray matter, in certain sense organs, as in the 
 retina and olfactory membrane, in the plexuses and ganglia 
 of the cerebro-spinal and sympathetic nervous systems. 
 
 The form of the ganglion-cells is very variable ; yet in 
 many regions there are found nerve-cells of fixed and 
 characteristic morphologic appearance, as in the brain 
 
72 THE TISSUES. 
 
 centers and especially in the cerebellum. Some charac- 
 teristic forms are limited exclusively to certain parts of 
 the nervous system. Besides the spherical cells of certain 
 of the peripheral ganglia, many kinds of polygonal cells 
 are found with many forms of processes. 
 
 The ganglion-cells in general are large cells rich in 
 protoplasm, being among the largest cells of the body. 
 Only a few varieties are small and have a small amount 
 of protoplasm. Ganglion-cells consist of protoplasm prob- 
 ably not bounded by a cell membrane and possess a very 
 characteristic nucleus. 
 
 The nucleus of ganglion-cells is relatively large and is 
 almost without exception spherical. It is poor in chroma- 
 tin and especially shows very few distinct chromatin 
 fibers, on account of which it has a clear, vesicular appear- 
 ance. Almost invariably it contains a large, distinct 
 nucleolus. 
 
 The protoplasm of ganglion-cells is unusually complex 
 and the investigations on this subject are not yet com- 
 plete. From it arise a varying number of processes. 
 Each ganglion-cell has at least one process, the axis- 
 cylinder process or neuraxis, which arises from the cell 
 either directly or by means of a so-called implantation 
 cone. After giving off some collateral branches, this gen- 
 erally becomes at once a nerve-fiber, which is usually 
 medullated. Occasionally, however, the neuraxis divides 
 at once after leaving the cell into its terminal arborization 
 without first becoming a part of a nerve-fiber. Nerve- 
 cells possessing a neuraxis of this type are known as 
 Golgi's cells or ganglion-cells of the second type. In addi- 
 tion to the neuraxes, which have few branches, most 
 ganglion-cells have a number of so-called dendrites; these, 
 and especially the larger ones, are direct continuations of 
 the protoplasm of the cell and show all the characteristics 
 of the protoplasm of ganglion-cells. The dendrites always 
 branch and generally form an extensive arborization which 
 can scarcely be followed to its end. We will mention 
 
NERVOUS TISSUES. 73 
 
 here only two functionally important constituents of the 
 ganglion-cell : First, its fibrils, called neurofibrils. These 
 form a network in the body of the ganglion-cell and 
 extend into the processes of the cell, and not simply into 
 the nerve processes, but also into the dendrites. They 
 form the conducting part of the nerve-fibers. In the 
 second place there are found in the cell-bodies of nearly 
 all ganglion-cells, especially in the bodies of the larger 
 ones, clusters of granules of different form, which stain 
 readily in certain basic dyes, and are known as j\7Ws 
 bodies or the tigroid substance. They are quite large 
 structures, irregularly polygonal and often elongated and 
 even spindle-shaped, and can be easily recognized under 
 moderate magnification. They occur in the different 
 ganglion-cells in varying number and size, and appear to 
 vary according to the functional activity of the cell and 
 to undergo changes in certain pathologic conditions. The 
 Nissl bodies are also found in the larger dendrites. It 
 should be stated that, according to the views of some 
 authors, the Nissl bodies are not found in the living 
 ganglion-cell, but arise only after death. As they can, 
 however, be recognized in fresh preparations of the cen- 
 tral nervous system, this is very improbable. 
 
 Larger ganglion-cells, especially the giant^cells of the 
 lower animals (as many fishes), which are recognized with 
 the unaided eye, contain peculiar canals in the protoplasm. 
 In the giant nerve-cells of many fishes true capillaries are 
 found; in others, the canals, which are much smaller and 
 narrower, appear to be intracellular lymph-canals or canal- 
 iculi. Among these are the so-called Holmgreen canals 
 and the reticular apparatus of Golgi. 
 
 The main forms of nerve-cells are the following (given 
 more in detail in the chapter on the Central Nervous Sys- 
 tem, page 95): 
 
 1. Spherical ganglion-cells without dendrites and with one 
 neuraxis, so-called unipolar cells; after leaving the cell, 
 however, the neuraxis undergoes a T-shaped division, so 
 
74 the tissues. 
 
 Plate 7.— Nerve-cells. 
 
 Fig. 1.— Two Isolated Multipolar Ganglion=cells from the 
 Human Spinal Cord. X 160. 
 
 The figure shows two isolated ganglion-cells of the spinal cord, with 
 richly branching dendrites; the neuraxes (X) have been torn away. 
 
 Technic: Isolation in weak chromic acid solution. Curium. 
 
 Fig. 2. — Two Multipolar Ganglion-cells from the Lumbar 
 Enlargement of the Spinal Cord of a Child. X ^0. 
 
 The preparation was taken from a still-born child. 
 
 The figure shows the cell-body and the roots of the dendrites 
 of two ganglion-cells. The protoplasm of these contains numerous 
 intensely stained, irregular granules (tigroid substance). 
 
 Technic: Absolute alcohol. Methylene-blue according to Xissl. 
 
 Reference letters: D, Dendrite; A", nucleus; (, tigroid substance. 
 
 Figs. 3-5. — Three Cells from a Human Spinal Ganglion. 
 X -I:*. 
 
 The preparation was taken from one who had been executed. 
 The figure shows three spherical cells of different sizes, with their 
 nucleated capsules. One cell contains yellowish-brown pigment. 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 Reference letters: bH, connective-tissue capsule; p, pigment. 
 
 that the cells are really bipolar. This cell form is found 
 in the sensory cranial ganglia and the spinal ganglia. 
 
 2. Spherical or nearly spherical cells with one dendrite 
 and one new-axis arising from opposite ends of the cell, 
 so-called bipolar cells. They are found in the retina in 
 the inner granular or ganglion-cell layer and in the 
 ganglia of the acoustic nerve. 
 
 3. Spherical or nearly spherical cells with one neuraxis 
 and several short, fine dendrites which can be demonstrated 
 only by the help of special methods — multipolar cells. 
 They are found as the chief constituents of the sympa- 
 thetic ganglia. When stained after methods which do 
 not bring out the dendrites, these cells resemble the cells 
 of the spinal ganglia. 
 
 4. Large, irregularly shaped polygonal to short spindle- 
 shaped multipolar ganglion-ccllx, with one neura.vix and 
 several dendrites which pass in all directions from the 
 cell. To this class belong the multipolar cells of the 
 spinal cord, of the medulla oblongata, of the so-called 
 central gray nuclei and other portions of the brain. 
 

 
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 Fi ff .J 
 
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 Fig. 4-. 
 
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 Ay. J. 
 
 LUh.AristF. Reichhold, Miinclwii. 
 
NERVOUS TISSUES. 75 
 
 o. Multipolar ganglion-cells of regular form with one 
 neuraxis and with dendrites which arise from the cell- 
 body in a manner which is characteristic for the form of 
 the cell. The main representatives of this group are the 
 pyramidal cells of the cerebral cortex and the Purkinje 
 cells of the cerebellum. 
 
 6. Small multipolar cells with different forms of dendrites, 
 as certain cells of the granular and molecular layers of 
 the cerebellum, some cell forms of the cerebral cortex, 
 and others. 
 
 7. The multipolar Golgi cells, which have already been 
 mentioned and which are characterized by the peculiar 
 behavior of their neuraxes. 
 
 (b) Nerve-fibers. — The chief constituent of all nerve- 
 fibers is the neuraxis of the nerve-cell, which forms the 
 so-called axis-cylinder of the nerve-fiber. Each nerve- 
 fiber must therefore have an axis-cylinder. Some nerve- 
 fibers consist of naked axis-cylinders (fibers of the olfac- 
 tory nerve). The axis-cylinder has a distinctly fibrillar 
 structure (neurofibrils) and appears in the form of a 
 larger or smaller cylinder or band in the center of the 
 fiber, running uninterruptedly its whole length. The 
 neurofibrils are united by an interfibrillar substance, the 
 neuroplasm. This, the conducting portion of the fiber, 
 is surrounded by the medullary sheath and the sheath of 
 Schwann or the neurilemma. The origin of the former 
 is doubtful, but the latter is of mesenchymal origin. 
 
 Most of the cerebro-spinal fibers, and hence most of the 
 nerve-fibers of the body, possess both medullary sheath 
 and neurilemma outside of their course in the central 
 nervous system, but within this only a medullary sheath. 
 These nerve-fibers are called medullated and also, on ac- 
 count of their appearance in the fresh condition, dark-bor- 
 dered or doubly contoured fibers. They are of very varia- 
 ble size, varying between 1 jj. and 20 /i. In contrast to 
 these we have the non-medullated fibers, also known as pale 
 or Kemak's fibers, which consist only of axis-cylinder and 
 
76 
 
 THE TISSUES. 
 
 neurilemma; the latter is especially delicate in non-medul- 
 lated fibers. They occur especially in the sympathetic sys- 
 tem and to a less extent in the realm of the central nervous 
 system. The medullary sheath shows interruptions at reg- 
 
 Fig. 21. — Portion of a medul- 
 lated nerve-fiber from man. X 
 375. The figure shows a node 
 of Ranvier of the medullary 
 sheath. Lantermann's segments 
 may also he recognized, m, Med- 
 ullary sheath ; si/h, node of Kan- 
 vier. 
 
 a 
 
 Fig. 22. — Portion of a human 
 medullated nerve-fiber. Nucleus 
 and axis-cylinder stained with 
 carmin. X 375. a, Axis-cylin- 
 der ; /,-, nucleus ; m. medullary 
 sheath ; «, neurilemma. 
 
 ular intervals. These appear in the form of rings, the 
 so-called nodes of Ranvier, At the nodes the medullated 
 nerve-fiber consists only of axis-cylinder and neurilemma, 
 since the latter bends in to the axis-cylinder, which here 
 shows a bieonical enlargement. 
 
KEli VOL'S TISSUES. 77 
 
 Nodes of Ranvier are found at regular intervals, vary- 
 ing in different fibers, but in general the interval is greater 
 in large fibers than in small ones. The nodes are always 
 found at the point of division of a medullated nerve-fiber. 
 The portion of a fiber between two nodes is called an in- 
 ternodal segment. In large fibers the segments measure 
 about 1 mm., while in small fibers they are 0.1 mm. and 
 even less. 
 
 The medulla or myelin of the medullated nerve-fiber, the 
 constituent of the medullary sheath, is a substance which 
 refracts light strongly and is similar to fat; like the latter, 
 it is blackened by osmic acid. It is very sensitive to 
 reagents. With nearly every fixing method the medullary 
 sheath has a different appearance in microscopic prepara- 
 tions. Certain portions of the medullary sheath can be 
 differentially stained, after the use of special methods of 
 fixation. The Weigert stain for medullary sheaths is 
 based on this principle. 
 
 In the living nerve the medullary sheath is quite homo- 
 geneous, but readily changes and presents segments sepa- 
 rated from each other by clear fissures which are obliquely 
 placed. These segments are known as Schmidt-Lanter- 
 mann segments and are also visible in nerves after treat- 
 ment with osmic acid. Their significance is not known ; 
 it is quite probable that they are artefacts. On the 
 death of the nerve-fiber the myelin undergoes coagulation 
 changes, resulting in the formation of globules, esj)ecially 
 at the broken end of the fiber. 
 
 The sheath of Schwann (neurilemma) is a thin, structure- 
 less membrane of connective-tissue origin, which contains 
 a few long nuclei within a relatively large amount of 
 protoplasm. The nuclei are found on the inner surface of 
 the neurilemma and only one nucleus falls within each 
 internodal segment. The nuclei of the segments alternate 
 in their position. The non-medullated nerve-fibers, with 
 the exception of those of the olfactory nerves which do 
 not have special sheaths of Schwann, but bundles of which 
 
78 THE TISSUES. 
 
 Fig. 23. — Portion of a cross-section of the spinal cord of anew-born 
 child, treated by the Golgi method. X 120. The figure embraces 
 the region between the central canal and the base of the anterior 
 median fissure and shows the condition of the ependyma cells and 
 their processes, as well as two astrocytes. A, Astrocyte with long 
 processes; ep, ependyma, single cells, with processes blackened; fma, 
 base of the anterior median fissure. 
 
 Fig. 24. — Two short-rayed astrocytes from the gray substance of the 
 cerebral cortex of man. Golgi's silver method. X 250. The figure 
 shows two typical glia cells of the short-rayed type. Golgi method. 
 C, Capillary. 
 
 Fig. 25. — Two long-rayed astrocytes from a section through the 
 medulla oblongata of a new-born child. X HO. 
 
 retain special connective-tissue sheaths, consist only of the 
 axis-cylinder and the neurilemma, which is especially thin 
 and delicate. Their structure is, therefore, the same as 
 that of the medullated fibers, except that the medullary 
 sheath is lacking. (See Plate 17, Fig. 2.) 
 
 (c) The Neuroglia. — The neuroglia, the supporting 
 tissue of the nervous system, is found only in the central 
 nervous system and in the optic chiasm, optic nerves and 
 retina, and olfactory nerves. Owing to the fact that of 
 the several methods now at hand for staining neuroglia 
 differentially, no two give identical results, the views con- 
 cerning this tissue are still at variance. The investigation 
 of the neuroglia is further rendered more difficult by the 
 fact that it occurs in a pure form in only a few places, but 
 is generally associated with nerve-cells and nerve-fibers. 
 In tissue treated by the chrome-silver method of Golgi, all 
 neuroglia elements appear as cells with processes, the cells 
 and processes forming the framework of the central 
 nervous system. 
 
 In tissues treated after the complicated differential stain- 
 ing methods developed by Weigert, Mallorv, and Benda, 
 the neuroglia appears in the form of independent fibrils, 
 which are distinguished from the fibrils of fibrous connective 
 tissue by their chemical reaction, and which are either 
 entirely separated from the neuroglia cells, or pass through 
 the protoplasm of the latter. It is probable that originally 
 

 Fig. 25. 
 
 Fig. 24. 
 
NERVOUS TISSUES. 79 
 
 all neuroglia fibers are formed in and by the protoplasm 
 of neuroglia cells and later become independent of the cells. 
 Investigators who have made use of the chrome-silver 
 method of Golgi in their study of the neuroglia reach the 
 following conclusions: They distinguish two essentially 
 different cellular elements of the neuroglia: (1) The so- 
 called ependyma cells, cubic to cylindric epithelial cells 
 which line the cavities of the central nervous system ; (2) 
 stellate cells, the so-called spider cells or astrocytes. 
 
 Of all the elements of the central nervous system, the 
 ependyma cells are the least differentiated, retaining their 
 embryonal character longest. In preparations of the spi- 
 nal cord treated after the ordinary staining methods, these 
 elements appear as simple columnar cells, now and then 
 showing cilia. After the use of the Golgi method we rec- 
 ognize that each ependymal cell has a long process which 
 divides many times and in the embryonal condition extends 
 to the surface of the spinal cord. This character of the 
 ependyma cells is most distinct in the spinal cord, and the 
 processes of the cells extend to the base of the anterior 
 median fissure and to the posterior septum. 
 
 The spider cells or the astrocytes of the neuroglia are 
 characterized by numerous fine, either branched or un- 
 branched processes. The astrocytes are found, not like 
 the ependyma cells, limited to certain regions of the central 
 nervous system, but are very generally distributed through- 
 out the gray and white matter of the central nervous sys- 
 tem, the optic and portions of the olfactory nerves. They 
 originate partly from the ependyma cells which wander to- 
 ward the periphery, partly from other still undifferentia- 
 ted cells of the embryonal central nervous system, so- 
 called spongioblasts. All glia cells lie originally in what 
 is later the gray matter and reach the white matter only 
 secondarily. 
 
 The astrocytes are divided into the short-rayed or as- 
 trocytes with a few short branching processes, and long- 
 rayed astrocytes, which have many fine, long processes, 
 
80 THE TISSUES. 
 
 nearly or quite unbranched ; the two types of glia cells, 
 however, are not sharply separated from each other. The 
 former occur only in the gray substance, the latter in both 
 the gray and the white substance. In course and arrange- 
 ment their processes are fitted to their environment. Their 
 long processes often form dense networks. Many short- 
 rayed astrocytes appear related to the blood-vessels (capil- 
 laries) of the central nervous system, presenting an appear- 
 ance as though inserted into the wall of the vessels. 
 
 Investigators who have made use of special methods 
 for differentially staining the neuroglia have found that 
 what appear as processes of the ependyma cells and astro- 
 cytes are in reality sharply contoured fibers, which are 
 either wholly independent of the neuroglia cells or, if in 
 relation with the protoplasm of the cells, pass through it 
 without losing their identity and without suffering inter- 
 ruption. In such preparations it may be seen that the 
 neuroglia fibers pass over and under and along the sides 
 of the neuroglia cells, often following protoplasmic pro- 
 cesses of the cells, but are in no way continuous with the 
 protoplasm of the neuroglia cells. This view of the struc- 
 ture of neuroglia tissue is more in accord with the recent 
 investigations on this subject. 
 
OSSEOUS TISSUE. 81 
 
 (B) THE MICROSCOPIC ANATOMY OF 
 THE ORGANS. 
 
 I. THE SKELETAL SYSTEM. 
 
 Under the skeletal system we shall consider the bones, 
 the joints, and the ligaments. 
 
 During life the bones consist not only of osseous tissue, 
 but also of soft parts. The constituents of bone are as 
 follows : 
 
 1. Osseous tissue — (a) compact, (7>) spongy. 
 
 2. The osseous membrane or the periosteum. 
 
 3. The bone-marrow — (a) red, (b) yellow. 
 
 4. The articular cartilage. 
 
 5. Blood-vessels and nerves. 
 
 The osseous tissue forms the main mass of the entire 
 bone and shows a characteristic arrangement. It is classi- 
 fied under the connective tissues, and especially under that 
 group which is characterized by the structure and arrange- 
 ment of its ground substance. The ground substance of 
 bone is hard, as a result of the lime salts deposited in it 
 (calcium phosphate, calcium carbonate, and some calcium 
 fluorid). The lime salts are distributed in the ground sub- 
 stance in the form of molecules and are not recognizable 
 by optical means. It is thought that the lime salts are 
 deposited in the gelatin-yielding fibrils of the ground sub- 
 stance, as well as in the interfibrillar substance. Owing- 
 to this intimate relation of ground substance to the min- v 
 eral salts, a bone which has been macerated or even burned, 
 that is deprived of all its organic constituents, has the 
 same form that it would have had if it had been decalci- 
 fied or deprived of its calcium salts. In consequence of 
 this we can investigate the structure of bone in preparations 
 of decalcified and of macerated bone. 
 
 The cellular elements of osseous tissue, known as bone- 
 cells, or, according to the older designation, bone corpuscles, 
 6 
 
82 THE SKELETAL SYSTEM. 
 
 lie in spaces of the ground substance, the so-called bone- 
 spaces or tfieuiuv. The latter are most easily seen in thin 
 pieces of macerated bone. In such preparations the 
 lacunae are filled with air and, under the microscope, 
 appear black in transmitted light and white in reflected 
 light. The lacunae are elongated, flattened spaces, from 
 which fine canals proceed, the canaliculi. The canaliculi 
 of neighboring spaces anastomose with each other. The 
 bone-celh are found in the lacuna? and assume the shape of 
 the spaces in which they are found. They send processes 
 into the canaliculi into which they probably extend but a 
 short distance. It is, however, difficult to make a positive 
 statement concerning this point. In the earlier stages of 
 bone development there are undoubted anastomoses of 
 neighboring cells, but later probably not. 
 
 Compact as well as spongy bone consists of lamellce. 
 In the spongy bone these show no regular arrangement, 
 while in the compact bone there is a very typical arrange- 
 ment of the lamella?, dependent on the arrangement of the 
 blood-ixftsdx of the bone. The medium-sized and small 
 blood-vessels run in canals, known as the Haversian canal*. 
 The greater portion of com pact bone consists of lamella? 
 of ground substance arranged concentrically around these 
 canals ; the lamella? are known as the Haversian lamelke. 
 The lacuna? lie at the boundaries of two lamella?, so that 
 the long axis of the cell or lacuna coincides with that of 
 the Haversian canal, the canaliculi passing through the 
 substance of the lamella to the next row of lacuna?. The 
 innermost row of lacuna? is united by canaliculi with the 
 Haversian canal itself; the lacuna? are here very much 
 curved to correspond with the course of the lamella?, 
 especially when small Haversian canals are involved. 
 The lacuna? of neighboring lamella? usually alternate. 
 
 Besides the Haversian lamelhe, we distinguish two 
 other systems of lamelhe : (1) Those which run parallel 
 to the inner and outer surfaces of the bone, the so-called 
 ground lame/Ice or circumferential lamella? ; (2) those which 
 
OSSEOUS TISSUE. 
 
 83 
 
 run between the Haversian systems without relation to 
 them, but frequently parallel to the ground lamella?, the 
 interstitial lamella. In sections of decalcified bone or in 
 ground preparations of macerated bone, cut Haversian 
 lamellae are met with, which may be confused with the 
 interstitial lamellae. This very regular arrangement of 
 bone substance into lamellae with interlamellar cell-spaces 
 is not present in very thin layers of bone, as for instance 
 in the cementum of the tooth, where the cell-spaces have 
 an irregular arrangement. 
 
 X 
 
 ': A 
 
 ^^Bh 
 
 i 1 iF>* rt-iif*** 
 
 Fig. 26. — Portion of a cross-section of a metacarpal bone of man. 
 X 150. The figure shows three Haversian canals with the lamellae 
 belonging to them. The lacunae and canaliculi are easily recognized. 
 
 Occasionally some of the ground lamellae are lacking, 
 so that, for instance, the Haversian lamellae are joined 
 directly to the periosteum. The larger blood-vessels of 
 bone lie in canals which show no concentric lamellar 
 systems. These are called Volkmann's canals. They 
 gradually change into the Haversian canals surrounded by 
 lamellar systems, without any definite line of demarcation. 
 In the neighborhood of the periosteum the external cir- 
 cumferential lamellae show uncalcified connective-tissue 
 
84 THE SKELETAL SYSTEM. 
 
 Fig. 27. — Portion of a cross-section of a decalcified human raditis. 
 X 48. The figure shows the lamellar systems of compact bone, as 
 well as some trabecule of spongy bone, agl, External ground lam- 
 ellae ; igl, internal ground lamellae ; il, interstitial lamellae ; hi, Haver- 
 sian lamellae ; p, periosteum ; sp, trabecular of spongy bone. 
 
 fibers from the periosteum, which penetrate the lamellae 
 transversely or obliquely and are known as Sharpens 
 fibers. 
 
 The periosteum consists of fibrous connective tissue. It 
 is divided into an external fibrous layer which is rich in 
 blood-vessels, but contains few cells, and an inner cellular 
 layer containing few fibers and blood-vessels. The latter 
 layer often contains osteoblasts (see page 87). 
 
 The articular cartilages are usually of the hyaline variety 
 (see page 49). 
 
 The ligaments are fibrous structures consisting of dense 
 white fibrous connective tissue, with the exception of cer- 
 tain ligaments (nuchas, subflava), which are composed of 
 elastic fibers. The symphyses or sutures, on the other 
 hand, consist of very loose connective tissue. The labra 
 glenoidolia are not composed of hyaline cartilage, but con- 
 sist of very dense fibrous connective tissue, which often 
 shows the structure of white fibro-cartilage. The joint 
 cajisules and tendon sheaths consist of two layers — an 
 external fibrous layer of dense fibrous tissue, and an inner 
 synovial stratum, which is lined on its inner surface by 
 endothelial cells, though these are not always in a contin- 
 uous layer (see page 42). 
 
 The bone-marrow is divided into two classes — the red 
 and the yellow. In the adult, the yellow marrow pre- 
 dominates in the marrow canals and larger marrow spaces 
 of the long bones. It consists mostly of adipose tissue. 
 The red bone-marrow is found in the smaller marrow 
 spaces of spongy bone and is very rich in blood-vessels ; 
 the capillaries are partly devoid of endothelial walls. The 
 red bone-marrow consists of a delicate reticulum of white 
 fibrous and reticular connective tissue, in the meshes of 
 
-_-r^ ■-- 
 
 " " ' ' ', " — i"i|.. v 
 
 agU 
 
 KB* 
 
 M'. -J.'. 
 
BONE DEVELOPMENT. 85 
 
 which are found lymphocytes and leukocytes, myelocytes, 
 giant-cells, and the developmental forms of red blood-cells 
 (see page 62). 
 
 The blood-vessels of bone are distributed partly in the 
 periosteum ; others penetrate through the nutrient canal to 
 the bone-marrow. In the bone substance the larger ves- 
 sels lie in the Volkmann's canals, the smaller ones in the 
 Haversian canals. The lymph paths begin with the peri- 
 cellular spaces of the lacunae and canaliculi of bone and 
 continue as perivascular spaces following the blood-vessels. 
 
 The nerves of bone are found principally in the perios- 
 teum, where they terminate as free sensory endings or 
 Pacinian corpuscles. Vasomotor fibers accompany the 
 blood-vessels to the bone-marrow. The bone substance 
 itself is devoid of nerves. 
 
 BONE DEVELOPMENT. 
 
 The embryonal anlagen of the osseous skeleton are 
 partly of hyaline cartilage and partly of white fibrous 
 connective tissue. Accordingly we distinguish bone pre- 
 formed in cartilage or endochondral bone, and primary 
 and secondary connective-tissue bone, also known as intra- 
 membranous bone. 
 
 The process of bone development in the bones preformed 
 in cartilage is the more complicated, because in this, two 
 processes are taking place at the same time : first, that of 
 perichondral ossification, which originates from the peri- 
 chondrium of the cartilaginous anlagen of the skeleton; 
 and second, the endochondrcd ossification. The latter takes 
 place in the cartilaginous anlagen of the skeleton and is 
 accompanied by the breaking down of the cartilage. With 
 regard to the manner of bone formation the two processes 
 are essentially the same; nevertheless, the result of the 
 bone formation in endochondral ossification gives a dis- 
 tinctly different picture from that in perichondral ossifica- 
 tion, so that the osseous tissue arising from endochondral 
 
86 the skeletal system. 
 
 Plate 8.— Bone development. 
 
 Longitudinal Section of the Last Two Phalanges of a 
 Finger of a Five=month Human Embryo. X 15. 
 
 The figure shows the distinction between the processes of endo- 
 chondral and perichondral ossification. Bone tissue appears red, car- 
 tilage bright blue, calcified cartilage dark blue. The epiphyses are 
 still entirely cartilaginous. 
 
 Technic : Miiller's fluid with formalin. Hematoxylin-eosin. 
 
 Reference letters : eK, Endochondral bone with remains of calcified 
 cartilage matrix ; Kn, cartilage ; M, marrow space with marrow-cells 
 and blood-vessels ; pK, perichondral or intramembranous bone. 
 
 ossification is easily to be distinguished from that arising 
 by perichondral ossification. 
 
 The perichondral ossification begins somewhat earlier 
 than the endochondral ; in the middle of what is later the 
 diaphysis of a long bone, a layer of embryonic bone is 
 formed by the perichondrium, while at the same time and 
 in the same region the cartilage begins to calcify. 
 
 Calcium salts are deposited in the ground substance of 
 the cartilage, the cartilage spaces increase in size, and 
 finally there is a shrinking of the cartilage cells, which is 
 soon followed by the death of the cells. In the region of 
 the calcification of the cartilage, the further growth of car- 
 tilage ceases. In consequence of this, some time after the 
 beginning of ossification the cartilaginous portion of the 
 skeleton appears as if constricted in the region of the zone 
 of calcification. Cell divisions still take place after the 
 beginning of calcification, but no new cartilage spaces are 
 formed, so that several cells lie in one of the enlarged 
 cartilage spaces before they degenerate. 
 
 The formation of endochondral bone is initiated by the 
 penetration of a blood-vessel from the periosteum into the 
 calcified cartilage. The way through the calcified ground 
 substance of the cartilage is opened for the blood-vessel 
 by polynuclear giant-cells called osteoclasts, which have 
 the power of disintegrating calcified cartilaginous sub- 
 stance as well as bone (see page 91). The osteoclasts 
 break down the enlarged cartilage spaces, so that only 
 
Tab. 8. 
 
BONE DEVELOPMENT. 87 
 
 remains of the intervening walls, consisting of calcified 
 cartilage matrix, are left. The calcified cartilage matrix 
 stains a dark bluish-violet with hematoxylin, while the 
 uncalcified ground substance stains a light violet. In this 
 way anastomosing primary marroio spaces develop in the 
 bone anlage, which are at first small. These primary 
 marrow spaces are filled with cells derived from the inner 
 or osteogenetic layer of the embryonic periosteum (peri- 
 chondrium) and are known as osteoblasts. Certain of 
 these cells differentiate into the cells of what is later the 
 red bone-marrow. Between them numerous blood-vessels 
 are found. Around the remains of the calcified cartilage 
 matrix, which project freely into and bound the newly 
 formed marrow spaces, lie the osteoblasts, rich in proto- 
 plasm, oval or low cylindric in form ; these, especially 
 where they are arranged in rows, give the impression of 
 epithelium ; they are known as osteoblasts or bone-formers, 
 because they are the cells which deposit the osseous sub- 
 stance. Through the activity of the osteoblasts, osseous 
 matrix still free from cells is formed around the remains 
 of the cartilage matrix. This, therefore, always contains 
 within it, even when the formation of the bone is farther 
 advanced, calcified cartilage matrix in the form of ser- 
 rated lines and trabecular, which are easily distinguishable 
 in microscopic preparations by their color. When the 
 osteoblasts first deposit osseous substance, this is free from 
 cells. Gradually, however, osteoblasts are surrounded by 
 young osseous substance ; they then lose their bone- 
 forming function and become fixed bone-cells. Only the 
 spongy bone tissue is developed by endochondral bone 
 formation. 
 
 The process of perichondral ossification is very similar; 
 it has already begun when calcification occurs in the carti- 
 laginous portion. On the inner surface of the perichon- 
 drium at this time is found a tissue rich in cellular ele- 
 ments, known as the osteogenetic tissue. This contains, 
 on the side turned toward the bone anlage, a single layer 
 
08 the skeletal system. 
 
 Plate 9.— bone Development. 
 
 Cross=section through a Forearm Bone of a Six=month 
 Human Embryo. X 45. 
 
 Within the periosteal ring the figure shows bone formed by endo- 
 chondral and by perichondral ossification. On one side the latter is 
 markedly developed, while on the other side it is entirely absorbed, 
 so that here the endochondral bone reaches the periosteum. The endo- 
 chondral bone contains remnants of calcified cartilage matrix and is 
 separated from the perichondral bone by a blue boundary line of the 
 same substance. On the outer surface of the endochondral bone a 
 larger resorption surface is found with giant-cells in the lacuna?. The 
 perichondral bone shows on its outer surface an almost continuous 
 layer of osteoblasts. It already forms a compact mass with Haversian 
 canals. 
 
 Technie: Muller's fluid. Carmin-hematoxylin. 
 
 Reference letters: 617, Blood-vessels of bone-marrow; eK, endochon- 
 dral bone; gl, boundary line between endochondral and perichondral 
 bone; Hk, Haversian canals; Hk lt Haversian canals in process of forma- 
 tion; M, bone-marrow; ob, osteoblasts; p, periosteum; pK, perichon- 
 dral bone; Hz, giant-cells. 
 
 of very prominent osteoblasts, which deposit osseous sub- 
 stance on the calcified and constricted diaphyseal portion 
 of what is later endochondral bone. Thus, bone in this 
 region is apposed from without . In its earlier stages 
 perichondral bone is developed in a manner similar to 
 that of endochondral bone formation ; like the latter, peri- 
 chondral bone is at first free from cells ; as the process 
 proceeds, the osteoblasts are inclosed, other osteoblasts 
 continuing the further deposition of osseous tissue, even at 
 a time when the endochondral bone is still being formed. 
 
 Plate 10.— bone Development. 
 
 Cross=section of the Upper End of the Diaphysis of the 
 Femur of a Six=month Human Embryo. X 15. 
 
 The figure showsa large number of small trabecule of endochondral 
 bone, with the blue stellate figures of calcified cartilage matrix within 
 them. Between these are found numerous marrow spaces with marrow- 
 cells and blood-vessels. A thin, incomplete layer of perichondral bone 
 surrounds the endochondral bone, separated from it by a boundary line 
 of calcified cartilage matrix. 
 
 Technic: Muller's flnid. Carmin-hematoxylin. 
 
 Reference, letters: bg, Blood-vessels; ck, endochondral bone; gl, 
 boundary line between endochondral and perichondral bone; p, perios- 
 teum; p K, perichondral bone. 
 
Tab. 9. 
 
Tab. 10. 
 
BONE DEVELOPMENT. 89 
 
 The boundary line between the two kinds of bone can be 
 easily recognized by a fine line of calcified cartilaginous 
 matrix. The perichondral bone, of course, contains no 
 bits of cartilage matrix, as it is deposited outside of the 
 cartilaginous portion of the skeleton. 
 
 The apposition of new perichondral bone does not take 
 place by the simple deposition of osseous material on the 
 new bone which was formed earlier and the consequent 
 thickening of the original layers of bone ; but trabecular 
 of bone are developed, which become confluent and thus 
 inclose osteogenetic tissue. The cavities thus formed con- 
 tain blood-vessels and also on their inner surfaces layers 
 of osteoblasts, which constantly produce new osseous sub- 
 stance and thus diminish the size of the original cavity. 
 When the diminution in size has gone on until the cavity 
 is very little larger than the blood-vessel which it contains, 
 the osteoblastic activity ceases, the uninclosed osteoblasts 
 probably again becoming fixed connective-tissue cells, and 
 a Haversian canal is formed. In this way the perichon- 
 dral bone formed assumes gradually the structure of 
 ordinary compact bone. Perichondral ossification results 
 in the formation of compact bone. The greater portion 
 of the whole skeleton is therefore of fibrous tissue origin. 
 Up to the time of birth there is still a relatively large 
 amount of endochondral bone. During the first and 
 second years of life the greater portion of this is absorbed 
 and replaced by perichondral bone ; this is true of even 
 much of the spongy bone. As perichondral bone develops 
 from the outside, — that is, by apposition, — it does not 
 show a row of osteoblasts toward the marrow cavity. 
 
 The formation of intramembranous bone follows a simi- 
 lar course to that of perichondral bone. A layer of 
 osteoblasts is arranged around the calcifying bundles of 
 connective tissue ; numerous anastomosing trabeculse of 
 bone are thus formed, inclosing blood-vessels and forming 
 Haversian canals, quite as in perichondral ossification. 
 
 The process of ossification, as we have described it, is 
 
90 THE SKELETAL SYSTEM. 
 
 PLATE II— BONE DEVELOPMENT. 
 Fig. 1.— Portion of a Longitudinal Section of a Metacarpal 
 Bone of a Five=month Embryo. X 50 - 
 
 The figure represents the region of endochondral ossification of an 
 embryonal metacarpal bone and shows the changes which the cartilage 
 undergoes before its dissolution. Outside in the perichondrium is a 
 layer of perichondral bone. 
 
 Technio : Miiller's fluid with formalin. Hematoxylin-eosin. 
 
 Eeference letters : cK, Bone formed by endochondral ossification ; 
 Kn, cartilage ; Kn^ zone in which the cartilage cells are arranged in 
 rows ; A"« 2 , zone of enlarged cartilage cells and calcification of ground 
 substance ; KnB, remains of calcified cartilaginous matrix ; 31, marrow ; 
 pK, bone formed by perichondral ossification ; Ez, gianteells (osteo- 
 clasts). 
 
 Figs. 2-6.— Processes of Bone Formation and Bone Resorp= 
 tion in the Lower Jaw of a Seven=month Human Embryo. 
 X 420. 
 
 Technio: Miiller's fluid with formalin. Hematoxylin-eosin. 
 
 Fig. 2. — Young bone trabeculse just forming. Osteoblasts are 
 inclosed by bone substance and thus changed to bone-cells. 
 
 Fig. 3. — Giant-cells in the resting stage in the connective tissue. 
 
 Fig. 4. — Two active giant-cells in a small (almost resorbed) piece of 
 bone tissue. 
 
 Fig. 5. — Three giant-cells on the border of a large piece of bone. 
 One cell lies in a lacuna, the second is somewhat separated from the 
 bone, and the third is absorbing a projecting point of bone. 
 
 Fig. 6. — Giant-cell in a lacuna. The nuclei of the cells lie at the 
 side away from the resorption surface. 
 
 Eeference letters for Figs. 2-6: c, Capillary ; Kna, osseous tissue; 
 k nz, bone-cells; obi, osteoblasts; obl L , osteoblasts changing to bone-cells. 
 
 also characterized as the neoplastic type, in opposition to a 
 method of bone formation which occurs only in very few 
 places in the human body, in which there is a direct trans- 
 formation of the cartilage into bone, that is without prece- 
 dent degeneration of the cartilage, and which is known as 
 the metaplastic type. The only region where this method 
 of bone formation takes place to any extent is in the ossi- 
 fication of the articular processes of the lower jaw. It 
 would appear that here the cartilage cells change directly 
 into bone-cells. During the growth of bones, the absorp- 
 tion of osseous tissue goes on hand in hand with the 
 formation of new bone tissue ; in this way the marrow 
 canals and marrow spaces are enlarged. The absorption 
 
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MUSCLES. 91 
 
 of the bone already formed is brought about through the 
 agency of special cells, known as giant-cells or osteoclasts. 
 They are large, spherical, poly nuclear cells in the resting 
 stage, such as are found also in the bone-marrow. The 
 osteoclasts apply themselves to the bone to be absorbed 
 so that they fit the form of the surface ; thus they often 
 surround splinters of bone which are to be resorbed. 
 Some time after the application a pit is seen in the bone, 
 which often exactly corresponds to the form of the osteo- 
 clast ; these depressions are known as Howship's lacuna. 
 Where larger resorptions take place, the osteoclasts often 
 lie close together, and, forming pit after pit and dissolving 
 the bridges which separate them, may dissolve large sur- 
 faces of bone. Not simply during the entire time of 
 the growth of bone, but also in later life, areas are found 
 where bone is being resorbed. 
 
 II. THE ORGANS OF THE MUSCULAR SYSTEM. 
 
 The principal organs of the muscular system are the 
 muscles, tendons, and fasciae. 
 
 The muscles consist of a collection of transversely 
 striated muscular fibers, which are separated into sub- 
 divisions by strands of connective tissue. The external, 
 more markedly developed connective tissue is called the 
 perimysium externum. It sends strands of connective tis- 
 sue, known as perimysium internum, into the interior of 
 the muscle, which inclose irregular spaces and bound mus- 
 cle bundles of different sizes. The terminal processes of 
 the perimysium finally surround each single muscle-fiber 
 forming the endomysium. The perimysium is quite rich 
 in elastic fibers. At the nodal points of the perimysium 
 lie the larger blood-vessels and nerve-trunks of the muscle 
 and usually the large sensory nerve endings known as the 
 neuromuscular spindles. The latter are, however, not 
 found in all the muscles of the body ; they are lacking in 
 
92 tee muscular system. 
 
 Plate 12.— Muscle. 
 
 Fig. 1.— Portion of a Cross=section of the M. Omohyoideus 
 of Man. X 40. 
 
 The tissue was fixed two and one-half hours after death. 
 
 The figure shows the arrangement of the muscle bundles, of the 
 perimysium, of the blood-vessels, nerves, and of the neuromuscular 
 spindles (the curved line to the right is the free surface of the mus- 
 cle). 
 
 Technic: Zenker's fluid. Hematoxylin-eosin. 
 
 Reference letters: a, Artery; iff, blood-vessel (vein); msp, neuro- 
 muscular spindle; n, nerve; pine, perimysium externum ; pmi, perimy- 
 sium internum. 
 
 Fig. 2. — Cross=section of Neuromuscular Spindle from the 
 M. Omohyoideus of Man. 
 
 The figure gives the picture of a transversely cut neuromuscular 
 spindle with the neighboring transversely sectioned muscle-fibers. The 
 spindle, composed of a connective-tissue sheath, small muscle-fibers 
 and nerves, lies in the perimysium internum. Fine strands of the 
 latter penetrate between the single muscle-fibers surrounding the 
 spindle. 
 
 Technic, etc., as in the preceding figure. 
 
 Reference letters : bdg, Connective-tissue sheath of the spindle ; 
 M, muscle-fibers of the spindle with axial nuclei ; m, transversely 
 striated muscle-fiber in cross-section ; n, nerve-fiber ; pm, perimysium 
 of the single muscle-fibers. 
 
 the extrinsic eve muscles, in the intrinsic muscles of the 
 tongue, in the muscles of the face, and in certain other 
 smaller muscles. 
 
 The neuromuscular spindles are long fusiform structures, 
 which are generally arranged in the direction of the long 
 axis of the muscle and usually lie in the perimysium sep- 
 arated from the other muscle-fibers. The neuromuscular 
 spindle consists of a connective-tissue capsule, composed 
 of from four to eight concentric lamellae of fibrous con- 
 nective tissue, within which are found four to twenty 
 small muscle-fibers rich in sarcoplasm, known as the 
 intrafusal fibers. In them we may recognize a proximal 
 polar, an equatorial, and a distal polar region. In the 
 proximal and distal polar regions the intrafusal muscle- 
 fibers present the structure of striated muscle-fibers of the 
 red variety. In the equatorial region they are rich in 
 sarcoplasm and contain numerous nuclei, which are axially 
 
Tab. 12. 
 
 pm 
 
 msp 
 
 pmt 
 
 Fiff.l. 
 
 /,ith. Anst E Reichhold. Miirichcn . 
 
MUSCLES. 93 
 
 placed, the fibrillar structure appearing as a thin layer 
 about the periphery of the fibers. Surrounding the intra- 
 fusal fibers there is found a thin layer of connective tissue 
 known as the axial sheath, and between this and the cap- 
 sule there is found a large lymph-space, bridged by con- 
 nective-tissue trabeculse, to which the name of periaxial 
 space is given. The intrafusal muscle-fibers of the spin- 
 dle are not connected with other muscle-fibers, but begin 
 and end free in the sheath derived from the perimysium. 
 The neuromuscular spindles contain numerous nerves, 
 which show very characteristic endings (see page 113). 
 They are sensory organs, which subserve muscular sense. 
 
 The blood-vessels of muscle are very numerous. The 
 larger trunks run in the coarser strands and nodal points 
 of the perimysium. The branches pass into the muscle 
 bundles and each single muscle-fiber is surrounded by 
 small capillaries, which form long meshes around the 
 muscle-fiber. The nerves of muscle are numerous. They 
 are medullated and non-medullated; the former comprise 
 partly motor and partly sensory fibers. The motor fibers 
 end on the muscle-fibers themselves. Each muscle-fiber 
 contains at least one and generally several motor endings (see 
 page 109). The sensory fibers go in part to the neuro- 
 muscular spindles, the adventitia of blood-vessels, and the 
 connective tissue sheaths of muscles ; others pass to the 
 neurotendinous end-organs found in the tendons. The 
 non-medullated fibers end on the blood-vessels. 
 
 The tendons are connective-tissue organs, which are 
 composed of very regular parallel bundles of connective 
 tissue. The bundles, which are composed of formed con- 
 nective tissue poor in elastic fibers, are designated as ten- 
 don bundles (also called tendon bundles of the smallest 
 order, or primary tendon bundles, or tendon fasciculi). 
 Between the tendon bundles lie the stellate tendon cells, 
 connective-tissue cells, which, with their processes, sur- 
 round the tendon bundles, since they anastomose with the 
 processes of neighboring cells. In smaller mammalia 
 
94 
 
 THE MUSCULAR SYSTEM. 
 
 Fig. 28.— Cross-section of a human tendon. X 32. The prepara- 
 tion was taken from one who had been executed. The figure gives the 
 general structure of tendon. Reference letters for Figs. 28 and 29: 
 bdg, Strands of connective tissue; lnj, blood-vessels; Sb, larger tendon 
 bundles, bounded by strands of connective tissue; Sz, tendon cells. 
 
 (rat, mouse) the tendon cells possess a somewhat regular, 
 rectangular body with lamellar processes, the so-called 
 winged tendon cells. 
 
 Each tendon consists of a collection of tendon bundles, 
 which are held together by strands of areolar connective 
 tissue. The connective tissue which surrounds the whole 
 
 Fig. 29.— A portion of the section of tendon reproduced in Fig. 
 28, under higher magnification ( X (it). The figure shows the tendon 
 cells within the secondary tendon bundles. 
 
 tendon, and which is known as the external peritendineum, 
 sends processes into the interior of the tendon, forming 
 the internal peritendineum, which separates and surrounds 
 irregularly shaped groups of tendon bundles, forming the 
 so-called secondary tendon bundles, of which each larger ten- 
 don contains a number. 
 
Fig. 28. 
 
THE CENTRAL NERVOUS SYSTEM. 95 
 
 The tendons are very poor in blood-vessels, the larger 
 branches of which are found at the nodal points of the in- 
 ternal peritendineum. On the other hand, tendon has a 
 very rich supply of sensory nerves; certain of the sensory 
 nerve-fibers pass to the Yater-Pav'nuun corpuscles ; others 
 terminate in free sensory endings, while still others end in 
 the so-called neurotendinous spindles (see page 113) situ- 
 ated at the boundary line between muscle and tendon. 
 
 Fibrous membranes, aponeuroses, and fasciae have a 
 structure quite similar to that of tendons. 
 
 HI. ORGANS OF THE NERVOUS SYSTEM. 
 
 1. THE CENTRAL NERVOUS SYSTEM. 
 
 The space allotted to this section does not permit an 
 extended description of the structure of the entire central 
 nervous system, and especially not of the course of the 
 fibers contained therein. It is our purpose to describe 
 briefly the structure of the spinal cord, of the medulla 
 oblongata, of the cerebellar and cerebral cortex, so far as 
 the elements of the nervous system (see under nervous tis- 
 sues, page 70), by their combination, make up the struc- 
 ture of the parts to be considered. In regard to the rela- 
 tions of the course of the nerve-fibers, of the topography 
 of the several parts, etc., the text-books of anatomy, and 
 particularly the special texts on nervous anatomy, must 
 be consulted. The topography of the spinal cord and 
 medulla (olives) has been included in the legends accom- 
 panying Plates 13—15. 
 
 The gray matter of the spinal cord and of the medulla, 
 as well as of the entire brain, consists of neuroglia, gan- 
 glion-cells, and scattered medullated nerve-fibers ; the 
 white matter consists of medullated nerve-fibers devoid of 
 the sheath of Schwann, between which neuroglia is" found. 
 Processes of the pia mater of the spinal cord run into the 
 
96 the nervous system. 
 
 Plate 13.— Spinal Cord. 
 
 Cross=section of the Human Spinal Cord in the Region 
 of the Cervical Enlargement. X 8. 
 
 The preparation was taken from an adult and was fixed two and 
 one-hall hours after death. 
 
 Technic: Muller's fluid. Sodium carminate. 
 
 The figure gives a topographic picture of the spinal cord, the dis- 
 tribution of the gray and of the white matter, the distribution of the 
 columns and of the pia mater. 
 
 Reference letters: bg, Blood-vessels; ca, anterior horn of gray mat- 
 ter; ana, anterior commissure; x, region of the obliterated central' 
 canal; cp, posterior horns of gray matter; fa, funiculus anterior or 
 anterior column; /nm, anterior median fissure; fc, funiculus cuneatus 
 or the column of Burdach;/^, funiculus gracilis or the column of Goll; 
 fl, funiculus lateralis or lateral column; fr, formatio reticularis; pm, 
 pia mater; ra, anterior, ventral, or motor root-fibers; rp, posterior, 
 dorsal, or sensory root-fibers; sg, substantia gelatinosa of Rolando; 
 sp, posterior median septum. 
 
 white matter, partially dividing it into areas known as 
 columns. The nerve-fibers of the white substance run 
 within the columns, for the most part in the direction of 
 the long axis of the spinal cord; larger bundles running 
 transversely are found only in the ventral and dorsal root- 
 fibers. The structure of the white substance in its whole 
 breadth is very uniform. The neuroglia cells are scattered 
 here and there throughout the white matter, and the neurog- 
 lia fibers course between the nerve-fibers. A thicker layer 
 of glia fibers is found at the surface of the spinal cord 
 under the pia mater. 
 
 The gray matter of the spinal cord presents a more 
 complicated structure than the white matter. Its constit- 
 uents have in general the following relations: The gan- 
 glion-cells of the spinal cord are, without exception, multi- 
 polar cells, but of different sizes. The largest cells are 
 the motor cr/fs of the anterior horns, which are usually 
 arranged in several groups. The neuraxis of each cell 
 passes immediately into one of the nerve-fibers of the ante- 
 rior or ventral root. The cell-body is large, its branches, 
 especially at their origin from the cell-body, being large 
 and richly branched (see page 74). The other nerve-cells 
 
.by 
 
 jjin 
 
 J.ith,. Anst /:' ReidthpUl Muiiclien . 
 
TEE CENTRAL NERVOUS SYSTEM. 97 
 
 of the spinal cord are smaller and their dendrites are not 
 so well developed. As their neuraxes run into the col- 
 umns of the white matter, from which they may give off 
 at different levels collaterals which enter the gray matter, 
 these cells are called column cells. The neuraxes of cer- 
 tain of the column cells pass through the gray matter to 
 the opposite side of the cord; these are known as commis- 
 sural cells. The column and commissural cells lie scat- 
 tered through the gray matter, partly in groups, as for 
 instance the dorsal nucleus or column of Clarke, situated 
 at the base of the posterior horn and especially well devel- 
 oped in the lower dorsal and upper lumbar regions. Cer- 
 tain of the cells of the posterior horns have a neuraxis 
 which does not pass into a nerve-fiber, but breaks up 
 immediately into many branches ; these are the so-called 
 Golgi's cells (see page 75). 
 
 The nerve-fibers of the gray matter show a very compli- 
 cated arrangement. They are found in all parts of the 
 gray matter, partly singly, partly in small groups, and 
 only exceptionally in more compact bundles. They com- 
 prise the beginnings of the motor roots, which, soon after 
 their origin, receive medullary sheaths, further dorsal 
 root-fibers, which enter the gray substance through the 
 apices of the posterior horns and pass in this through the 
 substantia gelatinosa Rolandi and the region of the dorsal 
 nucleus to the anterior horn into the region of the large 
 motor ganglion-cells, forming the so-called reflex collateral 
 fibers ; others come in contact with the collaterals of column 
 cells. In the white commissure medullated fibers cross to 
 the opposite side of the spinal cord. 
 
 The neuroglia of the gray matter is found in the form 
 of ependymal cells lining the central canal or its remains, 
 in case the central canal is obliterated, and as neuroglia 
 cells and fibers, scattered throughout the gray matter. 
 Special collections of neuroglia cells and fibers are found 
 around the central canal, where they form a neurogliar 
 mass entirely free from nerve-cells and almost entirely 
 7 
 
98 the nervous system. 
 
 Plate 14.— Spinal Cord. 
 
 Cross=section of the Human Spinal Cord at the Level of 
 the Lumbar Enlargement (two-thirds of the section shown). 
 X15. 
 
 The tissue was fixed two and one-half hours after death. 
 
 The figure shows two-thirds of a transverse section of the spinal 
 cord with the surrounding pia mater. The medullated nerve-fibers 
 are dark blue, the nuclei red. We see the relation of the medullated 
 nerve-fibers to the gray substance and the white substance. 
 
 Technic : Miiller's fluid. "Weigert-Pal's method for staining the 
 medullary sheaths. Alum-carmin. 
 
 Reference letters : ena, Anterior white commissure ; Cc, remains of 
 the obliterated central canal ; fma, anterior median fissure ; gl, exter- 
 nal glia sheath ; Gz, ganglion-cells of the anterior horn ; nd, nucleus 
 dorsal is ; pm, pia mater ; Ra, anterior or ventral root-fibers ; Rp, pos- 
 terior or dorsal root-fibers ; sg, substantia gelatinosa of Rolando ; smp, 
 posterior median septum. 
 
 free from nerve-fibers. The substantia gelatinosa, on the 
 other hand, contains no excess of glia elements. 
 
 The blood-vexxek of the spinal cord enter the nerve sub- 
 stance from the pia mater ; the largest trunks are branches 
 of the anterior spinal artery, which penetrates the cord 
 from the base of the median fissure. The white matter is 
 very poor in blood-vessels, while the gray matter is very 
 vascular, being especially rich in capillaries. 
 
 The cerebellar cortex has a very characteristic struc- 
 ture different from that of all other parts of the brain. It 
 surrounds the white matter of the cerebellum, which con- 
 
 Plate 15.— medulla Oblongata. 
 
 Half of the Cross-section of the Human Medulla Obion, 
 gata in the Region of the Olives. X 6. 
 
 The preparation was taken from an adult. 
 
 The figure gives a picture of the structure of the medulla oblongata. 
 
 Technic : Miiller's fluid. Weigert-Pal's method for staining the 
 medullary sheaths. Alum-carmin. 
 
 Reference letters : fae, Fibrae arciformes externa; ; fco, fibrae cerebel- 
 lo-olivares ; frh, fossa rhomboidea ; fs, fasciculus solitarius ; %, nervus 
 hypoglossus ; nh y, nucleus nervi hypo.fflossi ; no, nucleus olivaris ; 
 nv, nucleus nervi vagi ; od, oliva dorsalis ; om, oliva medialis ; Pc, 
 pedunculus cerebelli ; Py, pyramid ; sra, substantia reticularis alba ; 
 srg, substantia reticularis grisea ; v, vagus nerve. 
 
Tah.H. 
 
 \ ,9m/? 
 
 'frn.a 
 
 pjn 
 
 Lilfi. Ansl E Keictihnlcl . Miiiirhen 
 
Tab. 15. 
 
 /Mi, Anst F. ReichJwhl, Uunchen . 
 
THE CENTRAL NERVOUS SYSTEM. 
 
 99 
 
 sists of medullated nerve-fibers and glia elements, and 
 v. hichj in the form of rays, forms the arbor vite. Structur- 
 ally considered, the gray matter of the cerebellar cortex 
 
 
 Fig. 30. — Portion of a transverse section of the human cerebellar 
 cortex stained by the Golgi method. X 100. The figure is combined 
 from two preparations: At the right, a cell of Purkinje; at the left, a 
 basket cell ( nerve process of the latter and bodies of the two Purkinje 
 cells are somewhat diagrammatic). C, Collaterals; D, dendrites; A", 
 granular layer; N, neuraxis. 
 
 consists of two layers, which are distinguishable macro- 
 scopically — the inner granular or rust-colored layer and 
 the outer molecular or gray layer, between which is found 
 a layer of ganglion-cells. 
 
100 the nervous system. 
 
 Plate 16— Cerebellum and Heart. 
 
 Fig. 1.— Portion of a Transverse Section of the Human 
 Cerebellum. X 20. 
 
 The figure gives a general picture of the structure of the cerebel- 
 lum. 
 
 Technic: Miiller's fluid. Sodium carminate. 
 
 Reference letters: bg, Blood-vessels of pia mater; Im, lamina medul- 
 laris, layer of medullated nerve-fibers; stc, stratum cinereum, or molec- 
 ular layer; stgr, stratum granulosum; stg, stratum of ganglion-cells. 
 
 Fig. 2. — Portion of a Transverse Section of a Papillary 
 Muscle of the Human Heart. 
 
 The preparation was taken from one who had been executed. 
 
 The figure gives a picture of the structure of the heart-wall. 
 X 125. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: bdg, Intermuscular connective tissue; en, endo- 
 thelium; end, endocardium; my, myocardium. 
 
 The cerebellar cortex, like the gray nuclei, is formed of 
 nerve-cells, nerve-fibers, and neuroglia. 
 
 The arrangement of the nerve-fibers of the cerebellar 
 cortex, the majority of which are medullated, is very sim- 
 ple. In the granular 
 zone the medullated 
 J 1 fibers course between 
 
 the small ganglion- 
 cells. At the border 
 of the molecular layer 
 ><* we find a somewhat 
 prominent layer of 
 horizontal fibers, 
 which, still medul- 
 Fig. 31.— Two small granular cells of lated, extend for some 
 
 the human cerebellar cortex, treated v . , • . .i „,„ 
 
 by Golgi's method. X 330. d, Den- (llst: " lce lnt ° the m0 " 
 
 drites; n, neuraxis. lecular layer, in the 
 
 outer zone of which 
 all the nerve-fibers lose their medullary sheaths. The 
 medullated fibers of the cerebellar cortex are partly the 
 collaterals of the neuraxes of Purkinje cells (see page 
 101), partly fibers from the brain, which enter through the 
 pedicle of the cerebellum and end in the cerebellum. 
 
Tab. 16. 
 
 Iig.1. 
 
 - ' - - ".■- \end 
 
 -»& 
 
 Eig.Z. 
 
THE CENTRAL NERVOUS SYSTEM. 101 
 
 The nerve-cells of the cerebellar cortex show the greatest 
 
 Fig. 32. — Portion of transverse section of the human cerebellar cor- 
 tex treated by the Golgi method. X 140. The figure shows the 
 small granular cells in the granular layer ; in the molecular layer are 
 shown small cortical cells and basket cells, gl, Glia cell of molecular 
 layer ; Kz, basket cell ; khz, small granular cell ; Rz, small cortical 
 cell ; stc, stratum cinereum or molecular layer ; stg, stratum granu- 
 losus. 
 
 possible variety in size and form. The cells of Purkinje 
 are the most characteristic and at the same time the largest. 
 
102 the nervous system. 
 
 plate 17.— Cerebellum, Sympathetic Ganglion. 
 
 Fig 1.— Part of a Transverse Section through a Portion of 
 the Cerebellum. X 30. 
 
 The figure shows the lamination of the cerebellum and the distribu- 
 tion of the medullated nerve-fibers. 
 
 Technio: Weigert's stain for medullary sheaths. 
 
 Reference letters: bg, Blood-vessels; Im, lamina medullaris; stc, 
 stratum cinereum ; stg, stratum gangliosum ; stgr, stratum granulosum. 
 
 Fig. 2.— Transverse Section through a Small Sympathetic 
 Ganglion. 
 
 The preparation was taken from an executed criminal. 
 
 The figure shows an entire small ganglion, surrounded by a con- 
 nective-tissue sheath, with nerves entering, from the neighborhood of 
 the seminal vesicle. The ganglion-cells, surrounded by nucleated cap- 
 sules, have two and even three nuclei. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Eeference letters: Bdg, Connective-tissue sheath ; Gz, ganglion-cells; 
 N, entering non-medullated nerve-fibers in longitudinal section; 
 N 1} non-medullated nerve-fibers in cross-section. 
 
 Their bodies lie in a single layer at the boundary of the 
 granular and molecular layers, although really in the latter, 
 constituting the layer of ganglion-cells. Their dendrites, 
 generally two in number, branch after the manner of a 
 wall-fruit tree, into very fine and closely crowded fibers, 
 which extend through the entire thickness of the molecular 
 layer, often reaching to the surface of the cortex. At the 
 surface of the convolutions the dendrites pass off from the 
 cell-body at an acute angle, but toward its base the angle 
 becomes gradually more obtuse, until at the root of the 
 convolution the dendrites pass out in almost opposite direc- 
 tions. The neuraxes of the cells of Purkinje pass through 
 the granular layer, where they give off recurrent collaterals, 
 and, as medullated nerve-fibers, pass into the medullary 
 substance, with the fibers of which they intermingle. 
 
 Besides the cells of Purkinje and their branches, the 
 molecular layer contains two other types of cells, between 
 which transition forms are said to occur. They are known 
 as basket cells and small vortical cells. Both are quite small 
 multipolar ganglion-cells. The basket cells have a long 
 neuraxis, which runs parallel to the boundary between the 
 
Tab. 17. 
 
 
 
 
 Bdg 
 
 \A as »Jl»oo-.'. \®»® » I.- ?. e ,*, w. ^ , /' 
 
 Ekf.Z. 
 
 
THE CENTRAL NERVOUS SYSTEM. 103 
 
 granular and molecular zones at the level at which the 
 dendrites of the cells of Purkinje are given off, and forms 
 with its end branches a basket-like network around the 
 bodies of these cells. The cortical cells found throughout 
 the molecular layer are small cells with short dendrites ; it is 
 thought that their neuraxes have no relation with the cell- 
 bodies of the cells of Purkinje. 
 
 The granular layer contains small ganglion-cells, which 
 have large nuclei and small cell-bodies, differing from those 
 of other ganglion-cells. They have very little similarity 
 to other nerve-cells, but resemble the cells of the inner gran- 
 ular layer of the retina. They are multipolar, with few 
 dendrites with peculiar claw-like endings. Their neur- 
 axes pass vertically up into the molecular layer, where 
 they undergo a T-shaped division and probably without 
 branching run parallel to the surface of the cerebellum, 
 passing through the dendrites of the cells of Purkinje. 
 Besides the ordinary small granular cells, there are also 
 large granular cells, which belong to the nerve-cells of 
 type II of Golgi (see page 72). Neither the neuraxes of 
 the small cells of the molecular layer nor those of the gran- 
 ular layer pass over into medullated nerve-fibers. In 
 Golgi preparations the neuroglia of the cerebellum presents 
 the following structure and distribution : Long-rayed as- 
 trocytes are found mainly in the White matter, short-rayed 
 cells in the granular zone, modified short-rayed cells in 
 the molecular layer, the cell-bodies being found in the re- 
 gion of the bodies of the cells of Purkinje and the pro- 
 cesses radiating out toward the surface of the cortex. 
 
 AVhile the cerebellar cortex shows throughout exactly 
 the same structure, the cerebral cortex has a somewhat dif- 
 ferent structure in the different regions ; its structure is 
 not so complicated as that of the cerebellum, and above 
 all no distinct layers, visible macroscopically, can be 
 recognized. 
 
 In general, the cerebral cortex is characterized by the 
 presence of one variety of nerve-cell, the pyramidal cell. 
 
THE CENTRAL NERVOUS SYSTEM. 103 
 
 granular and molecular zones at the level at which the 
 dendrites of the cells of Purkinje are given off, and forms 
 with its end branches a basket-like network around the 
 bodies of these cells. The cortical cells found throughout 
 the molecular layer are small cells with short dendrites ; it is 
 thought that their neuraxes have no relation with the cell- 
 bodies of the cells of Purkinje. 
 
 The granular layer contains small ganglion-cells, which 
 have large nuclei and small cell-bodies, differing from those 
 of other ganglion-cells. They have very little similarity 
 to other nerve-cells, but resemble the cells of the inner gran- 
 ular layer of the retina. They are multipolar, with few 
 dendrites with peculiar claw-like endings. Their neur- 
 axes pass vertically up into the molecular layer, where 
 they undergo a T-shaped division and probably without 
 branching run parallel to the surface of the cerebellum, 
 passing through the dendrites of the cells of Purkinje. 
 Besides the ordinary small granular cells, there are also 
 large granular cells, which belong to the nerve-cells of 
 type II of Golgi (see page 72). Neither the neuraxes of 
 the small cells of the molecular layer nor those of the gran- 
 ular layer pass over into medullated nerve-fibers. In 
 Golgi preparations the neuroglia of the cerebellum presents 
 the following structure and distribution : Long-rayed as- 
 trocytes are found mainly in the white matter, short-rayed 
 cells in the granular zone, modified short-rayed cells in 
 the molecular layer, the cell-bodies being found in the re- 
 gion of the bodies of the cells of Purkinje and the pro- 
 cesses radiating out toward the surface of the cortex. 
 
 While the cerebellar cortex shows throughout exactly 
 the same structure, the cerebral cortex has a somewhat dif- 
 ferent structure in the different regions ; its structure is 
 not so complicated as that of the cerebellum, and above 
 all no distinct layers, visible macroscopically, can be 
 recognized. 
 
 In general, the cerebral cortex is characterized by the 
 presence of one variety of nerve-cell, the pyramidal cell. 
 
104 
 
 THE NERVOUS SYSTEM. 
 
 The other ganglion-cells occurring in the cerebral cortex 
 may be regarded as modified pyramidal cells, so that the 
 cerebral cortex, in contrast to the cerebellar cortex, con- 
 tains but one essentially 
 characteristic variety of cell. 
 The following layers are 
 recognized in the cerebral 
 cortex : An outer molecular 
 layer containing numerous 
 neurogliar elements, the layer 
 of small pyramidal cells, the 
 layer of large pyramidal 
 cells, the layer of poly- 
 morphous cells ; then follows 
 the white matter, consisting 
 mainly of medullated nerve- 
 fibers. 
 
 The pyramidal cells have 
 three main dendrites, which 
 arise from the angles of the 
 pyramidal cell-bodies. The 
 cell-body stands with its 
 long axis vertical to the sur- 
 face of the convolutions. 
 The main dendrite, which 
 is at the same time the 
 longest, runs directly toward 
 the surface of the cortex. 
 The three dendrites branch 
 freely, but do not extend so 
 far as those of the cells of 
 Purkinje. The neuraxis of 
 the pyramidal cell arises 
 from its base, giving off 
 collaterals, and continues as 
 a medullated nerve-fiber into the white matter. The pyr- 
 amidal cells occur in typical form in the middle layer of the 
 
 Fig. 33.— A pyramidal cell of 
 the cerebral cortex of man. X 
 90. c, Collaterals ; d, dendrites ; 
 », neuraxis. 
 
THE CENTRAL NERVOUS SYSTEM. 105 
 
 cerebral cortex and the largest (up to 30 jx in size) in the 
 deeper portions of the middle layer. Certain very large 
 pyramidal cells, occurring in special regions of the cerebral 
 cortex, are known as giant pyramidal cells. It is customary 
 to speak of an outer layer of small pyramidal cells and a 
 deeper layer of large pyramidal cells, but the transition of 
 one layer into the other is gradual. In the outermost layer 
 of the cerebral cortex, which consists largely of the den- 
 drites of the pyramidal cells and neuroglia elements, 
 there are only smaller cells resembling nerve-cells, which 
 by some observers are also regarded as neuroglia cells. 
 In the deepest layer of the cortex, below the large pyr- 
 amidal cells, are found again some smaller cells, which 
 form a transition from pyramidal cells to irregular mul- 
 tipolar cells. The ascending dendrite is especially poorly 
 developed in them, or not developed at all. In addition 
 to the nerve-cells mentioned, we find in the cerebral cor- 
 tex ganglion-cells of type II (Golgi cells). 
 
 The nerve-fibers of the cerebral cortex radiate from the 
 medullary substance into the cortex. They are made up 
 of the neuraxes of the small and large pyramidal cells, 
 fibers of unknown origin which radiate into the cortex 
 and end there, and the tangential fibers of the cerebral cor- 
 tex. The latter run as very fine fibers, partly close under 
 the surface of the cerebral convolution in the external 
 molecular layer, partly at different levels parallel to the 
 surface, and in certain regions as a prominent layer half 
 way between the surface and the white substance, forming 
 the stripes of Vic d'Azyr or of Gennari. (See Plate 18.) 
 
 The neurogliar elements of the cerebral cortex present 
 no peculiarities ; in Golgi preparations the white sub- 
 stance contains especially long-rayed astrocytes, and the 
 gray substance contains short-rayed cells. 
 
 As in the spinal cord, the blood-vessels of the brain form 
 capillary networks principally in the gray substance. The 
 choroid ple.rn.ses of the brain ventricles contain many blood- 
 vessels, which are overlaid by cubical epithelial cells. 
 
106 THE NERVOUS SYSTEM. 
 
 Plate 18.— Cerebral Cortex ; Tactile Corpuscle. 
 Fig. 1— Portion of a Section of the Human Cerebral Cor- 
 tex Vertical to the Surface. X 20. 
 
 The figure shows the cross-section of the entire gray substance and 
 of the adjacent portion of the medullary substance. The medullated 
 nerve-fibers are stained. 
 
 Technic : Miiller's fluid. Weigert's stain for medullary sheaths. 
 
 Reference letters : alf, External tangential fibers ; intf, inner tan- 
 gential fibers ; M, medullary substance (white matter) ; B, cortex 
 (gray matter). 
 
 Fig. 2.— Longitudinal Section of a Papilla of the Corium 
 with Tactile Corpuscle. X 340. 
 
 Preparation from Prof. Kallius, Giittingen. 
 
 The figure shows a papilla of the corium, without the epidermis, 
 with a tactile corpuscle. The entering nerve with its extensions in 
 the corpuscle is stained blue. 
 
 Technic : Intra-vitam methylene-blue stain. Alum-carmin. 
 
 Reference letters : iif, Nerve-fiber. 
 
 The latter are the unchanged remains of the original epi- 
 thelium of the neural canal, since in these places it de- 
 velops neither into nerve substance nor into neuroglia. The 
 cells usually contain yellow pigment (see page 107). The 
 lymph-vessels of the central nervous system are mostly 
 perivascular and begin with pericellular spaces. Larger 
 lymph-vessels lie under the arachnoid and dura, con- 
 stituting the subarachnoid and subdural spaces. 
 
 The membranes of the central nervous system are of 
 connective tissue, the dura mater consisting of formed 
 connective tissue, the arachnoid and pia of looser con- 
 nective tissue, containing many blood-vessels. 
 
 The hypophysis is developed from two sources, the floor 
 of the thalamencephalon and the oral ectoderm. The 
 posterior or cerebral lobe is continuous with the infundib- 
 ulum, but contains very little or no nerve tissue; the ante- 
 rior, the larger lobe, developed from the oral ectoderm, is 
 
 Fig. 34. — Portion of a" vertical section of human cerebral cortex, 
 treated by the Golgi method. X 70. The figure shows the arrange- 
 ment of the different cells of the cerebral cortex . gP, Layer of large 
 pyramidal cells; kP, layer of small pyramidal cells; pZ, layer of 
 polymorphous cells. 
 
Tab. 18. 
 
 ■#«*'>^ '---"- ■ --■■-.. 
 
 &■■■: ■ . .-' - --- - - . ■ - -. ' 
 
 ;* " ■■._.. - .-.-- 1% . * - 
 
 ---,.. - . - • ----- , ■ - ; ■_•■_-■■ 
 
 •<///■ 
 
 «■//" 
 
 ft# ; 
 
 2 ^^ .ȣ 
 
 «o ap ^ *>*» ^ jC9k 'iiwSW w"o* , 
 
 Ficf.S. 
 
Fig. 34- 
 
THE PERIPHERAL NERVOUS SYSTEM. 
 
 107 
 
 made up of anastomosing trabecule or columns of cells, 
 of which are recognized two varieties, the chief and the 
 chromophile cells. 
 Now and then certain 
 of the trabecular pre- 
 sent a lumen and ap- 
 pear to have an inter- 
 nal secretion. A cap- 
 illary network is found 
 between the trabecular 
 of cells, accompanied 
 by a small amount of 
 fibrous connective tis- 
 
 Fig. 35. — Portion of choroid plexus 
 from the lateral ventricle of a human 
 brain, observed in the fresh condition. 
 X 250. e, Capillaries ; ep, epithelium. 
 
 The epiphysis or 
 pineal gland is devel- 
 oped from the roof of 
 the thalamencephalon. 
 In the higher verte- 
 brates it is a rudimentary structure. In it are found closed 
 alveoli, lined by a stratified epithelium, often containing 
 small concretions known as brain sand. It further con- 
 tains neuroglia tissue. 
 
 2. THE PERIPHERAL NERVOUS SYSTEM. 
 
 (a) The peripheral nerves. Every peripheral nerve 
 consists of a varying number of nerve bundles or nerve 
 funiculi ; these are cylindric cords consisting of groups of 
 medullated nerve-fibers. The nerve bundles vary greatly 
 in size, even in the same cross-section, and each one is sur- 
 rounded by a firm sheath pf connective tissue with elastic 
 fibers, the perineurium. From the perineurium processes 
 pass into the nerve bundle, known as endoneui-iwm ; these 
 form an irregular network and generally inclose irregularly 
 shaped secondary bundles. Each single nerve-fiber re- 
 ceives from the endoneurium a delicate sheath, the so-called 
 
108 THE NERVOUS SYSTEM. 
 
 PLATE 19— PERIPHERAL NERVES. 
 
 Fig. 1.— Transverse Section of a Human Peripheral Nerve. 
 
 X27. . 
 
 The preparation was taken from a man who had been executed. . 
 
 The figure gives a picture of a peripheral nerve with its connective- 
 tissue sheaths. 
 
 Technic : Miiller's fluid. Picric-acid acid-fuchsin according to Van 
 Gieson. 
 
 Reference letters : bg, Blood-vessels ; en, endoneurium ; epn, epi- 
 neurium ; pn, perineurium. 
 
 Fig. 2. — Portion of Fig. 1, under Higher Magnification. 
 X 280. 
 
 The figure shows cross-sections of fibers of very different sizes (axis 
 cylinder red and medullary substance yellow) within the endoneu- 
 rium. 
 
 Reference letters : o, Axis cylinder ; en, endoneurium ; ma, medul- 
 lary sheath. 
 
 Henle's fibrillar sheath. In the nerve bundle nearly all 
 the fibers run in the direction of the long axis of the nerve, 
 with the exception of places where branches are given off 
 or communications take place between the bundles. Each 
 larger nerve consists of a collection of nerve bundles, which 
 are held together by loose connective tissue, often contain- 
 ing fat-cells; this surrounds the entire nerve and is called 
 the epineurium. The sympathetic nerves have numerous 
 non-medullated nerve-fibers in addition to the varying 
 number of fine medullated fibers and a few large medul- 
 lated fibers. 
 
 (6) The peripheral ganglia ; cerebro-spinal and sympa- 
 thetic ganglia. These occur in all gradations of size — the 
 scattered ganglion-cells of the tongue, adrenal, etc., the 
 small ganglia of the intestine, and the large cornplexus of 
 the spinal and large sympathetic ganglia. 
 
 The spinal ganglia and the sensory cranial ganglia have 
 mainly the large, spherical, unipolar ganglion-cells (see 
 page 73). Each of these is surrounded by a nucleated 
 connective-tissue capsule or sheath, which is closely applied 
 to the cell-body (see Plate 7, Figs. 3-5). The dorsal sen- 
 sory spinal roots, in the course of which these cells are 
 interpolated, are made up of the two processes resulting 
 
Tab.19. 
 
 Iiff.1. 
 
 
 
 
 -%^. 
 
THE PERIPHERAL NERVOUS SYSTEM. 109 
 
 from the division of the single process of the cells ; one of 
 these two processes passes to the periphery and the other 
 toward the center. 
 
 The number of spinal ganglion-cells of the spinal gan- 
 glia is, however, much greater than that of the sensory root- 
 fibers which enter. There is in the spinal ganglia a second 
 form of cells, the neuraxes of which do not go into the 
 dorsal roots, but branch many times soon after their exit 
 from the ganglion-cells and end in extracapsular and intra- 
 capsular terminal branches which surround the cell-bodies 
 of the unipolar cells. Sympathetic nerve-fibers forming 
 plexuses are also found in the ganglia. 
 
 The sympathetic ganglia contain unipolar, bipolar, and 
 multipolar cells, their elements being ofteu polynuclear. 
 The cells of the sympathetic ganglia, like those of the 
 spinal ganglia, have a nucleated connective-tissue capsule. 
 The processes, dendrites as well as neuraxes, pierce this. 
 Most of the cells are motor ; their neuraxes pass into the 
 non-medullated nerve-fibers and innervate non-striped 
 muscle and heart muscle ; others are secretory, innervating 
 gland-cells. Another form of cell in the sympathetic 
 ganglia has very long dendrites, which run into the neigh- 
 boring ganglia ; the neuraxis, after proceeding for some 
 distance on its course, receives a thin medullary sheath. 
 These cells are thought to be sensory sympathetic cells. 
 The sympathetic ganglia contain also medullated cerebro- 
 spinal fibers, which terminate in intracapsular pericellular 
 baskets, and cerebro-spinal sensory fibers, which merely 
 pass through the ganglia. 
 
 (c) The nerve-endings. The nerve-endings may be 
 separated into motor and sensory nerve-endings. The for- 
 mer are found on the terminal branches of medullated 
 motor nerve-fibers of transversely striated muscle. On 
 reaching the muscle, medullated motor nerve-fibers rapidly 
 divide into a varying number of small medullated nerve- 
 fibers. Each one of these terminal medullated branches, 
 on reaching the muscle-fiber which it innervates, loses its 
 
110 THE NER VO US SYSTEM. 
 
 PLATE 20— PERIPHERAL GANGLIA. 
 
 Fig. 1. — Transverse Section of the Superior Cervical Gan= 
 glion of the Human Sympathetic Nervous System. X 26 - 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a picture of a sympathetic ganglion with numer- 
 ous typical sympathetic cells, and many darkly stained, but generally 
 very fine medullated nerve-fibers. (The numerous non-medullated 
 nerve-fibers are not visible on account of the low magnification. Com- 
 pare Fig. 2, Plate 17.) 
 
 Technic: Miiller's fluid, staining of medullary sheaths according to 
 the Weigert-Pal method. Alum-carmin. 
 
 Reference letters: <■/, Fibrous capsule; gz, ganglion-cells; ran, medul- 
 lated nerve-fibers. 
 
 Fig. 2.— Transverse Section through a Spinal Ganglion of 
 Man. X 12. 
 
 The preparation was made from tissue fixed two and one-half hours 
 after death. 
 
 The figure shows the two roots of the spinal cord surrounded by the 
 dura mater; the motor fibers are divided into two large bundles; those 
 of the sensory root are scattered through the ganglion. 
 
 Technic as in Fig. 1. 
 
 Reference letters: dm, Dura mater; F, fat tissue; frs, fibers from the 
 sensory roots; Gz, ganglion-cells; rm, motor root. 
 
 medullary sheath, while its neurilemma becomes contin- 
 uous with the sarcolemma of the muscle-fiber. The 
 neuraxis passes under the sarcolemma and ends after fur- 
 ther division in a mass of granular sarcoplasm known as 
 the sole plate or end-disc. In this sole plate are found 
 numerous nuclei, probably derived from the nuclei of the 
 muscle-fiber. Especially large motor end-plates and motor 
 endings are found in the reptilia. 
 
 The sensory nerve-endings are divided into two main 
 groups: (1) The simple endings or free sensory endings ; 
 (2) the special terminal apparatus or terminal corpuscles, 
 known as the encapsulated sensory nerve-endings. Between 
 
 Fig. 36. — Branching of a nerve in an abdominal muscle of a mouse, 
 prepared by gold impregnation. X 120. The figure shows the motor 
 end-plates on the muscle-fibers under low magnification, m, Muscle- 
 fiber; me, motor end-plates; »?, nerve. 
 
 Fig. 37. — Two motor end-plates from a muscle of a lizard. X 250. 
 The figure shows a smaller and a larger motor end-plate, prepared by 
 gold impregnation, n, Entering nerve-fibers; sch, end-plate, with the 
 terminal distribution of the nerve. 
 
Tab. 20. 
 
 Iig.1. 
 
 ■ 
 
 
 * -*■■"■■■ ■•;.••:•.•. ^,'M/ 
 
 : ::> 
 
 t-% 
 
 mm 
 
 :''• •''>; ■';", i* 
 
 < •■•t'i-v;-i!»«;-**f , j. ! *' 
 
 j;„i= •■ 
 
 Eiff.Z. 
 
 LWh. Ansi /•' Reichhold, Miiiuiwu . 
 
Fig. 36 
 
 I 
 
 ; mm 
 
 I? H 
 
 -sch 
 
 Fig- 37. 
 
THE PERIPHERAL NERVOUS SYSTEM. 
 
 Ill 
 
 the two are the sensory nerve-endings in the neuromuscu- 
 lar and neurotendinous nerve end-organs, which occupy 
 an intermediate position, in that they show free sensory 
 endings on muscle-fibers and tendon fasciculi, the whole 
 being surrounded by a thin connective-tissue capsule. 
 
 The/rt'e nerve-endings represent simple terminal branches 
 of the sensory nerves, which either end in a point or show 
 a terminal nodular enlargement ; these occur especially in 
 epithelia, but also in fibrous connective tissue. The occur- 
 rence of a terminal net- 
 
 work is doubtful. How 
 widely distributed the 
 
 Tz 
 
 simple free endings are 
 is at present somewhat 
 difficult to state. The 
 nerve-endings in the 
 ducts of all glands are 
 probably of this va- 
 riety. In many sense 
 organs also (organs of 
 hearing, taste, etc.) 
 the nerves spread out 
 in the form of some- 
 what modified, simple 
 endings. 
 
 The so-called tactile 
 cells of the skin form a 
 
 transition between the simple free endings in the epithelium 
 and the special terminal corpuscles or encapsulated endings 
 found without exception in the connective tissue. These 
 lie in the epidermis and consist of somewhat enlarged clear 
 epithelial cells to which a flat, saucer-like enlargement of 
 the nerve-fiber is applied, forming the so-called tactile 
 meniscus. 
 
 In true terminal corpuscles the free end of the nerve- 
 fiber may be found in a club-shaped mass of a granular 
 substance, in some instances nucleated, which by some 
 
 ■■•J/ 
 Tsch 
 
 Fig. 38. — Transverse section of two 
 Grandry's corpuscles from the tongue of 
 a duck. X 450. One of the corpuscles 
 shows two and. the other four tactile 
 cells. mn, Medullated nerve-fibers, 
 entering the corpuscle ; Tsch, tactile 
 discs; Tz, tactile cells. 
 
112 THE NER VO US SYSTEM. 
 
 Fig. 39. — Portion of a vertical section of a rabbit's cornea, treated 
 by the gold chlorid method. X 375. The figure shows the arrange- 
 ment of the nerves in and under the epithelium of the cornea, ep, 
 Epithelium ; /era, intra-epithelial nerves ; lea, lamina elastica anterior 
 (Bowman) ; n, larger nerve branches ; sen, subepithelial nerves ; sip, 
 stratum proprium cornese. 
 
 Fig. 40. — Vater-Pacinian corpuscle from the mesentery of the cat, 
 fixed in a platinum chlorid-osmic acid solution. X 45. The figure 
 gives a general view of the corpuscle and not a cross-section, a, Axis 
 cj'linder in the core; il; core ; tun, medullated nerve-fibers entering 
 the corpuscle. 
 
 Fig. 41. — Longitudinal section of a Herbst corpuscle from a duck's 
 tongue. X 380. h, Inner concentric sheaths ; k u nuclei of core ; k 2 , 
 nuclei of outer sheaths ; n, nerve-fiber (axis cylinder) in the corpuscle ; 
 mn, medullated nerve-fiber, penetrating the outer sheath. 
 
 observers is regarded as neuroplasm, and which is sur- 
 rounded by a connective-tissue sheath, as in the encapsul- 
 ated lamellar corpuscles or end-bulbs ; or the nerve-fibers 
 at their ends may show plate-like terminations, which 
 are found between peculiar epithelioid connective-tissue 
 cells (according to some authors epithelial cells), as in 
 Grandry's corpuscles. In man, only the former are found. 
 
 G run dry's corpuscles are especially frequent in the bill 
 and tongue of water birds. They consist of two or more 
 large, flattened, spherical or hemispherical protoplasmic 
 cells. Between the cells is found the terminal distribution 
 of a medullated nerve-fiber in the form of a disc, like ex- 
 pansions of the axis cylinders. The number of tactile 
 discs is therefore always less than the number of the cells. 
 Grandry's corpuscles possessing only two cells are found ; 
 corpuscles having four and even more cells are, however, 
 also met with. 
 
 The largest and best developed lamellar corpuscles of 
 the human body are the Vater-Pacinian corpuscles. They 
 are found principally in the subcutaneous fat tissue of the 
 vola manus, of the finger, and of the sole of the foot ; 
 also on and in tendons and fibrous sheaths of muscles, in 
 the periosteum, in the retroperitoneal region and mesen- 
 tery, and in the connective tissue surrounding lara;e arter- 
 ies and veins. They are especially large and numerous in 
 
A 
 
 
 ■ep 
 
 F'g- 39- 
 
THE PERIPHERAL NERVOUS SYSTEM. 113 
 
 the mesentery and mesorectum of the cat. They are 
 visible macroscopically, being two and even four milli- 
 meters in diameter. The medullated nerve-fiber enters 
 the corpuscles and becomes non-medullated at the boun- 
 dary of the inner and outer layers of the corpuscle. The 
 axis cylinder then runs within a club-shaped, granular, 
 protoplasmic mass, the so-called inner core, through the 
 axis of the corpuscle, to end in one or several knob-like 
 enlargements. In its course through the core the axis 
 cylinder gives off numerous short side branches. The 
 core, with the central axis cylinder, is surrounded by con- 
 centric connective-tissue sheaths or capsules, which are 
 rich in elastic fibers and have rows of nuclei between 
 them. In the neighborhood of the core the lamellae are 
 thin, but toward the periphery they are considerably 
 thicker. 
 
 The Herbst corpuscles of birds are very similar to the 
 Vater-Pacinian corpuscles ; they are, however, much 
 smaller and show at the outer surface of the core a single 
 or double row of nuclei, outside of which are seen several 
 slightly wavy, non-nucleated lamella? resembling elastic 
 tissue, and external to these a few not very well developed 
 connective-tissue sheaths with few nuclei. 
 
 The spherical end-bulbs of the conjunctiva, Meissner's 
 corpuscles, and the genital corpuscles and similar nerve- 
 endings form a distinct group, possessing a relatively thin 
 connective-tissue capsule surrounding a semi-fluid granu- 
 lar substance which we may designate as the core. One 
 or several medullated nerve-fibers enter each corpuscle, 
 and, after losing their medullary sheaths, undergo repeated 
 division, forming numerous varicose branches, which are 
 variously interwoven and intertwined. In Plate 18, Fig. 
 2, is shown a Meissner's corpuscle, seen in longitudinal 
 section. 
 
 The nerves of the neuromuscular and neurotendinous 
 spindles branch several times before reaching their respec- 
 tive spindles and, while still medullated, pass through the 
 8 
 
114 BLOOD AND LYMPH VASCULAR SYSTEM. 
 
 capsule and axial sheath. The medullary sheath is lost 
 within the axial sheath. In the former, the naked axis 
 cylinders end partly in rings or spirals and partly in 
 branched, flower-like endings, which surround the intra- 
 fusal muscle-fibers in the equatorial region of the spindle. 
 In the latter, the naked axis cylinders, after branching 
 several times, run along the intrafusal tendon fasciculi, 
 give off numerous side branches, which end in irregular 
 discs, which partly enclamp the tendon fasciculi. 
 
 IV. BLOOD AND LYMPH VASCULAR SYSTEM. 
 
 Under the blood and lymph vascular system we shall 
 consider the heart and blood-vessels, the lymph-vessels, 
 lymph-glands and smaller lymphatic structures, and the 
 spleen and thymus. 
 
 The heart is an enlarged and differentially developed 
 portion of the blood vascular system. In it are distin- 
 guished the following three layers: The inner, the endo- 
 cardium ; the middle, the myocardium ; and the external, 
 epicardium (see Plate 16, Fig. 2). 
 
 The endocardium consists of a layer of endothelial cells 
 (see page 42) beneath which is found a relatively thick layer 
 of fibro-elastic tissue, the elastic tissue being here and there 
 arranged in the form of elastic plates. Smooth muscle- 
 fibers are now and then found in the endocardium. The 
 myocardium consists of transversely striated heart muscle, 
 which occurs in several layers of complicated arrangement, 
 and in general takes its origin from the annuli fibrosi in 
 the region of the atrioventricular borders. 
 
 Perimysial sheaths of connective tissue envelop the fas- 
 ciculi of heart muscle, the finest strands of which sur- 
 round the single cross-striped fibers. This connective tis- 
 sue serves as the carrier of the nerves and blood-vessels of 
 the heart muscle, and in all essential points conducts itself 
 just as in ordinary cross-striped skeletal muscle (see Plate 
 6, Fig. 3). 
 
BLOOD-VESSELS. 115 
 
 The epieardium, the visceral layer of the serous pericar- 
 dium, consists of connective tissue, beneath which occurs 
 the subperi cardial adipose tissue. It is covered by a sin- 
 gle layer of flattened niesothelial cells. The heart receives 
 its nerve-supply from both the sympathetic and cerebro- 
 spinal nervous system. The sensory endings are found in 
 the epieardium and pericardium. The heart muscle re- 
 ceives its innervation from sympathetic neurones, the cell- 
 bodies of the majority of which are situated in ganglia 
 found in the heart ; others are in ganglia of the cervical 
 sympathetic. White rami, branches of the upper dorsal 
 nerves, end in these ganglia. 
 
 Like the interior of the heart, all the blood-vessels 
 are lined by a single layer of flattened endothelial cells. 
 The smallest vessels, the capillaries, consist of an endothe- 
 lial tube ; rarely, in the largest capillaries, some connec- 
 tive-tissue cells of the neighborhood are joined to the wall, 
 forming an adventitia capillaris. 
 
 In the capillaries of certain tissues, the cell boundaries 
 disappear, forming a syncitial endothelial tube, as for in- 
 stance in the glomerular capillaries of the human kidney. 
 The form of the endothelial cells is elongated, often very 
 long, especially so in many veins ; there are no essential 
 and characteristic differences in the structure and shape of 
 endothelial cells in the different portions of the vascular 
 system. The cell boundaries are best brought out by 
 treatment with silver nitrate, and consist of serrated lines. 
 Outside of the endothelial tube the arteries and veins pos- 
 sess a number of sheaths or membranes, which consist of 
 connective tissue, elastic tissue, and smooth muscle. These 
 three kinds of tissue are distributed in the vessel walls in 
 a manner varying not only in veins and arteries, but also 
 according to the size and caliber of the vessels concerned, 
 and in veins according to other considerations. 
 
 Although, according to more recent investigations, the 
 division of the vessel wall into three layers — namely, the 
 tunica intima, media, and adventitia — cannot be strictly 
 
116 BLOOD AND LYMPH VASCULAR SYSTEM. 
 
 maintained, and is even to a certain extent irrational, we 
 retain the old classification on account of convenience of 
 description. 
 
 In the structure of arteries we must distinguish large 
 arteries, as the aorta and its direct branches, median arter- 
 ies, from the brachial to the digital, and small arteries, 
 from branches of the digital to the precapillary arteries. 
 It is mainly in the media, the structure of which is depend- 
 ent on the caliber of the arteries, that the structural differ- 
 ences are manifested, since in the media of the larger ves- 
 sels the elastic elements predominate over the muscular, 
 while in that of the smaller arteries the elastic elements 
 are almost entirely wanting. 
 
 Fig 42. — Portion of small artery from the bladder of a frog, treated 
 with silver nitrate solution. V 375. The figure shows the endothe- 
 lial tube. Besides the nuclei, we see the cell boundaries, blackened 
 by the silver reaction. 
 
 The media of the smallest precapillary arteries consists 
 only of circularly arranged smooth muscle-fibers in from 
 one to three layers ; in arteries slightly larger, but still of 
 very small caliber, as for instance in branches of the digi- 
 tal arteries, fine elastic fibers are found in the media. The 
 larger the artery, the greater is the relative number of 
 elastic elements ; however, the number of elastic elements 
 does not in all arteries increase in proportion to the decrease 
 in the muscular tissue. The elastic elements of the media 
 of median arteries are quite uniformly distributed in the 
 form of finer and coarser fibers between the muscle-fibers 
 of the media, and like these are circularly arranged. In 
 
ARTERIES. 117 
 
 the larger of the median arteries, as the carotid, subcla- 
 vian, iliac, the elastic tissue begins to be more prominent in 
 the media, and at the same time elastic plates or fenestrated 
 membranes occur in place of the elastic fibers ; these also 
 are for the most part arranged circularly. In the aorta the 
 musculature becomes unimportant in contrast to the elastic 
 plates, which occur in many layers and make up almost 
 the entire thickness of the media. 
 
 The intima shows less marked changes in relation to the 
 caliber of the arteries. At the border of intima and media, 
 all arteries of every caliber present wavy, elastic plates, very 
 distinct and marked in the smallest arteries, the so-called 
 elastic intima. In the aorta the elastic intima is no longer 
 conspicuous, because the entire media, is filled with similar 
 elastic plates. In the smallest arteries this alone repre- 
 sents the intima, the endothelium resting directly upon it. 
 In the larger arteries, in the small and especially in the 
 medium-sized arteries, there is found a layer of suben- 
 dothelial connective tissue, consisting of fibrous and elastic 
 connective tissue and connective-tissue cells. 
 
 The tunica externa or adventitia of the arteries is formed 
 of loose connective tissue with elastic fibers and rarely also 
 smooth muscle. The smooth muscle cells are always lack- 
 ing in the large and small arteries, occurring occasionally 
 in some median arteries, but then only in the form of 
 sparsely distributed longitudinal bundles. In general the 
 adventitia of the arteries of the human being is free from 
 muscle. In certain mammals it is generally present; in 
 the aorta of cattle, for instance, it occurs as compact, longi- 
 tudinally arranged bundles. The adventitia is in general 
 thicker, the greater the caliber of the artery. The elastic 
 elements appear in the main in the form of longitudinal 
 fibers, which are few and fine in the smaller arteries, more 
 abundant and larger in the medium-sized arteries, in which 
 they occasionally form an elastica externa, and are espe- 
 cially well developed in the largest arteries, like the aorta 
 and its main branches. The adventitia of the latter and 
 
118 BLOOD AND LYMPH VASCULAR SYSTEM. 
 
 Plate 2i.— Arteries. 
 
 Fig. 1. — Part of a Cross-section of a Human Thoracic 
 Aorta. X 40. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows in the main the elastic elements of the aortic 
 wall. The musculature lying in the spaces between the elastic 
 plates of the media is not stained. 
 
 Teehnic : Miiller's fluid. Orcein. 
 
 Reference letters: J, Tunica intima; ilf, tunica media, with 
 many elastic plates; A, tunica externa adventitia, with vasa vasorum. 
 
 Fig. 2. — Part of a Cross-section of the Human Arteria 
 Radialis. X 170. 
 
 The preparation was taken from tissues fixed two and one-half 
 hours after death. 
 
 The figure shows the lamination of the artery wall. The elastic 
 layers are stained dark red with orcein; the cell nuclei, especially 
 those of the circular muscle of the media and those of the endothe- 
 lial cells, blue with hematoxylin. 
 
 Teehnic: Zenker's solution. Orcein-hematoxylin. 
 
 Reference letters: a, Small artery of the adventitia; A, tunica 
 adventitia; e!i, lamina elastica interna; J, tunica intima with the 
 endothelium ; 31, tunica media, forming toward the adventitia a kind 
 of elastica externa; rv, vasa vasorum. 
 
 of its main branches contains a well-developed network 
 of fiber strands of longitudinal course. 
 
 Only a few arteries, like the arteries of the brain, the 
 inner elastic elements of which are strongly and the outer 
 weakly developed, vary from this type. 
 
 The veins are much more difficult to classify than the 
 arteries, since the thickness and structure of their walls 
 depend, not alone on the caliber, but also on other factors, 
 such as the position of the vessels — for example the veins 
 found in the extremities, in the skin, in the abdomen, or 
 in the head. The veins of the abdomen and of the head 
 possess very little muscle, while the veins of the skin con- 
 tain a relatively large amount of muscle, so that their 
 walls are scarcely thinner than those of the arteries of the 
 same caliber — for instance the arteries which accompany 
 them. In other places the veins have much thinner walls 
 than the accompanying arteries. It may therefore be 
 seen that veins of the same caliber may show very differ- 
 ent structure and very different thickness of walls. 
 
m g .i. 
 
 
 
 T~^f 
 
 VW-- 
 
 Eiff.t 
 
 l.ith. Anst P. RtichJwId, Miinchen . 
 
VEINS. 119 
 
 In general the veins contain fewer elastic elements than 
 the arteries, and the media is relatively poor in muscle 
 even in veins which contain much muscle, while in other 
 veins it is scarcely demonstrable ; on the other hand, the 
 adventitia of the skin veins especially contains a consider- 
 able quantity of muscle. 
 
 The intima of the veins consists mostly of fibrous con- 
 nective tissue and contains only a few elastic fibers. It 
 also forms the valves of the veins. On the borders of the 
 media, or even within the intima, the elastic elements of 
 the intima collect into an elastica interna, which, however, 
 is not so well defined as in the arteries, nor has it the 
 wavy course, nor does it occur in all veins. 
 
 The media of veins, in so far as it may be differenti- 
 ated, contains the same elements as that of arteries, con- 
 sisting of circularly arranged muscle-fibers and elastic 
 fibers or networks ; but it also contains some connective 
 tissue, so that the muscle appears less compact. Only the 
 media of the muscular veins, however, is constructed in 
 this way ; in others, it is either very much reduced or 
 entirely lacking, as in the veins of the abdomen and head. 
 The adventitia of most veins contains longitudinal mv.sc/c 
 In muscular veins this lies in large, compact bundles 
 between networks of longitudinal elastic fibers. 
 
 The blood-vessels, at least the large and median arter- 
 ies and veins, but never the small ones and capillaries, 
 contain blood-vessels in their own walls, known as vasa 
 vasorum. These are to be found mostly in the adventitia, 
 but in the very large vessels, as the aorta, we find that 
 capillaries extend also into the external layers of the 
 media, while the externa contains the small nutrient 
 arteries and veins. 
 
 The nerve-fibers of the blood-vessels are in part non- 
 medullated sympathetic fibers for the muscle coats ; others 
 are medullated, .sensory fibers, which are in part distrib- 
 uted in the intima, the majority, however, terminating in 
 the externa. 
 
120 blood and lymph vascular system. 
 
 Plate 22.— Blood-vessels. 1 
 
 Fig. 1.— Cross-section of a Muscular Vein of the Pampini- 
 form Plexus. X 50. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a cross-section of a vein with longitudinal muscle 
 in the adventitia. The elastic tissue is stained dark violet. 
 
 Teehnic : Zenker's solution. Weigert's elastic tissue stain. Alum- 
 carmin. 
 
 Reference letters: A, Tunica externa or adventitia; J, tunica in- 
 tima ; M, tunica media with circular musculature ; //», longitudinal 
 muscle of the adventitia ; rv, vasa vasorum, among them a very small 
 artery of the caliber of that in Fig. 4. 
 
 Fig. 2. —Transverse Section of a Larger Branch of the Inter= 
 nal Spermatic Artery from the Spermatic Cord. X 80. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a typical picture of a small median artery. The 
 media contains smooth muscle and very few elastic fibers. 
 
 Teehnic as in Fig. 1. 
 
 Reference letters : A, Tunica adventitia ; ei, lamina elastica interna ; 
 en, endothelium ; J t intima ; M, media. 
 
 Fig. 3.— Transverse Section of a Small Branch of the Inter= 
 nal Spermatic Artery from the Spermatic Cord. X 220. 
 
 The figure shows the cross-section of a small artery. The intima is 
 reduced to the endothelium and the elastica interna ; the media con- 
 sists almost entirely of muscle ; there is a distinct elastica externa. 
 
 Teehnic as in Figs. 1 and 2. 
 
 Reference letters as in Figs. 1 and 2; ee, lamina elastica externa. 
 
 Fig. 4. — Cross-section of a Very Small Artery (PrecapiU 
 lary) from the Corium. 
 
 The figure shows the picture of a very small artery. The media- 
 consists of (inly two layers of muscle-fibers. 
 
 Teehnic and lettering as in Figs. 1-3. 
 
 The lymph-vcxxch are in all essentials like the blood- 
 vessels in structure, except that even the largest have only 
 very thin muscular walls. The lymph capillaries proba- 
 bly connect with spaces in the tissue in such a way that 
 the latter represent the radicles of the lymph-vessels, as 
 for instance the pericellular spaces. 
 
 Lymphoid tissue may be divided into two classes, 
 namely : (1) True lymph-glands, situated in the deeper 
 connective tissue; (2) lymph nodules or follicles, which 
 
 1 In the reproduction the red-stained muscle nuclei are represented 
 too large, especially in Fig. 1. 
 
Tub. 2 2. 
 
 "jmi* 
 
 
 Ml 
 
 jpp§ 
 
 mm 
 
 mm 
 
 jg?^-' 
 
 ^WlKi 
 
 •*Vii-i 
 
 .■^.'4 
 
 
 -*P-S' 
 
 
 Hfe 
 
 I P 
 
 .f a» 
 
 ^.z. 
 
 i»^.-„ 
 
 Eig.2. 
 
 
 Fig,?. 
 
 Fig. 4. 
 
LYMPHOID TISSUE. 121 
 
 are situated directly under or in the mucous membranes 
 and in intimate relation with their epithelial coverings. 
 
 The lymph-glands lie in the connective tissue and are 
 generally bean- or kidney-shaped bodies of different sizes. 
 The afferent lymph-vessels enter the gland through the 
 convex border, while the efferent vessels leave through 
 the hilum ; through the latter the nutrient blood-vessels 
 also enter. The lymph-glands are surrounded by a con- 
 nective-tissue capsule which occasionally contains smooth 
 muscle-fibers. It sends into the interior of the gland 
 processes, known as trabecular, which branch and anas- 
 tomose. In the anastomosing compartments formed by 
 these trabeculse there is found a reticular connective tis- 
 sue which is connected with the trabeculse (see page 43), 
 and which forms the stroma of the gland, while the par- 
 enchyma is represented by lymph-cells (see page 53). The 
 parenchyma is so arranged that we can distinguish in 
 lymph-glands a medullary and a cortical substance. 
 
 The cortical substance of lymph-glands, situated mainly 
 on the convex surface of the gland, contains between the 
 trabecular a number of spherical bodies, the lymph-nodes 
 or follicles, or the secondary nodes of lymph-glands. Their 
 number varies according to the size of the organ. Occa- 
 sionally neighboring follicles are connected. 
 
 The follicles of lymph-glands consist of lymph-cells 
 (see page 57), which are densely arranged at the periphery, 
 while in the center there is a clearer zone, the so-called 
 germ center. In the latter the lymph-cells are larger and 
 show distinct signs of proliferation by karyokinesis. 
 Around the germ center the lymph-cells are more densely 
 packed and are often arranged in quite regular concentric 
 rows; the reticulum of the node is extremely fine and 
 delicate. 
 
 Aside from the reticular connective tissue, the medul- 
 lary substance of lymph-glands is composed of irregularly 
 arranged anastomosing strands of lymph tissue, known as 
 the medullary cords of lymph-glands. These originate 
 
122 blood and lymph vascular system. 
 
 Plate 23.— lymph-gland, Spleen. 
 
 Fig. 1. — Transverse Section of a Human Cervical Lymph* 
 gland. X 18. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the general structure of a lymph-gland. 
 
 Technic: Sublimate. Hematoxylin-eosin. 
 
 Reference letters: Ig, Blood-vessels; cf, fibrous capsule; E, hilus; 
 Kz, germ center; nl, lymph-nodes; sc, cortical substance; sm, medul- 
 lary substance; tr, trabecules; via, afferent lymph- vessels; vie, efferent 
 lymph-vessels. 
 
 Fig. 2.— Portion of an Injected Spleen of a Rabbit. X 28. 
 
 The preparation was taken from the material of "the Institute for 
 Comparative Anatomy, Wiirzburg. 
 
 The arterial trunks of the lymph-nodes (Malpighian corpuscles) are 
 injected red, the veins and spleen sinuses blue. 
 
 Reference letters: a, Arteries of Malpighian corpuscle; Mkn, Mal- 
 pighian corpuscle; p, spleen pulp. 
 
 from the cortical substance, in which they are connected 
 wit!: the follicles, and pass through the entire medullary 
 substance. In these there are no germ centers. Between 
 the medullary cords are spaces, the so-called lymph sinuses, 
 which are enlarged lymph spaces interpolated in the lymph 
 current. The lymph sinuses are irregular and imperfectly 
 bounded spaces, traversed by quite large trabecular of retic- 
 ular tissue, so that they have no special wall. Similar 
 sinuses are found between the cortical follicles and the 
 trabecular and capsule. Lymph-vessels or capillaries do 
 not penetrate the cortical follicles. 
 
 The lymph-glands are rich in blood-vessels, the capil- 
 laries of winch are distributed in the medullary cords as 
 well as in the cortical follicles. 
 
 Medullated and non-medullated nerves reach the lymph- 
 glands; the former are no doubt sensory, although their 
 mode of ending has not been fully determined; the non- 
 medullated fibers are destined for the non-striated muscle 
 in the capsule and the vessels. 
 
 The lymph nodule* or follicles appear in two forms: (1) 
 As so-called solitary follicles (noduli lymphatici solitarii), 
 and (2) as agndnated follicles. The former are widely dis- 
 tributed in mucous membranes, while the latter occur in 
 
Tab.23. 
 
 
LYMPHOID TISSUE. 123 
 
 Payer's patches or the agminated glands and in the tonsils. 
 In structure they are in the main like the cortical follicles 
 of lymph-glands; they show no medullary cords nor lymph 
 sinuses and also no connective-tissue capsule; they often 
 contain, however, germ centers. The solitary follicles and 
 agminated glands are connected with lymph- vessels through 
 lymph spaces or imperfectly developed lymph sinuses sur- 
 rounding them and are in intimate relation with the super- 
 ficial epithelium (see page 139). These structures will be 
 considered more fully in the description of the digestive 
 tract. 
 
 It is very probable that the smallest of these structures 
 are not permanent, but continually form and disappear. 
 We see, therefore, all transition stages from diffuse lym- 
 phatic tissue (see page 53) and a distinctly circumscribed 
 collection of lymph-cells to the fully developed lymph- 
 node with germ center. 
 
 The Hemolymph Glands. — Certain lymph-glands, known 
 as hemolymph glands, are characterized by the presence 
 of blood sinuses and present structural peculiarities, 
 necessitating a separate description. Hemolymph glands 
 are numerous in the retroperitoneal region and are also 
 found in the prevertebral region of the thorax and neck. 
 As has been shown by Warthin, these glands may be 
 divided into two distinct types, to which he has given the 
 names of splenolymph and marrow-lymph glands, although 
 transitional forms between these two types are met with, 
 as also between lymph-glands and hemolymph glands. 
 The splenolymph glands resemble in structure the spleen. 
 They possess relatively thick fibro-elastic capsules contain- 
 ing now and then non-striated muscle tissue. Beneath 
 the capsule is found a well-developed blood sinus, which 
 now and then surrounds the gland tissue, and from which 
 anastomosing sinuses penetrate the gland and separate the 
 lymphoid tissue into irregularly shaped masses. The 
 lymphoid tissue resembles that found in lymph-glands. 
 The marrow-lymph glands are not so numerous as the 
 
124 BLOOD AND LYMPH VASCULAB SYSTEM. 
 
 PLATE 24.— SPLEEN. 
 
 Fig. 1— Portion of Section of Human Spleen. X 15. 
 
 The preparation was taken from one who had been executed. 
 
 The figure gives a general view of the structure of spleen. 
 
 Technic: Zenker's fluid. Hematoxylin-eosin. 
 
 Reference letters: a, Arteries in part with lymphoid sheaths; 
 cf, fibrous capsule; Kz, germ centers; Mk, Malpighian corpuscles ; 
 pi, spleen pulp; tr, trabecular; v, vein in trabecula. 
 
 Fig. 2. — Cross=section of Malpighian Corpuscle of Human 
 Spleen. X 100. 
 
 Technic and lettering as in Fig. 1. 
 
 splenolymph glands. They possess a thin fibrous capsule, 
 containing little clastic or muscle tissue. The blood 
 sinuses are not so well developed. In the lymphoid 
 tissue the eosinophilous and basophile cells are more 
 numerous than in the other type. Large cells similar to 
 those found in bone-marrow are now and then met with, 
 as well as cells containing fragments of erythrocytes. 
 
 The spleen is surrounded by a firm fibrous capsule, 
 consisting of fibro-elastic connective tissue and containing 
 a few non-striated muscle-fibers, and is covered by the 
 peritoneum. The capsule sends into the gland numerous 
 trabecular of similar structure, which branch and anasto- 
 mose to form the framework of the gland. The vessels 
 of the spleen, and especially the veins, are associated with 
 this framework. Professor F. P. Mall has recently shown 
 that the trabecular and vascular systems together outline 
 masses of spleen tissue, about 1 mm. in size, to which the 
 name of spleen lobule has been given. Each lobule is 
 bounded by three main trabecular, known as interlobular 
 trabecular, which are parts of the general trabecular sys- 
 tem of the spleen ; from each of these arise three intra- 
 lobular trabecular which by anastomosis form an intra- 
 lobular framework, dividing the lobule into about ten 
 smaller compartments. These compartments are occupied 
 by a cellular tissue known as spleen pulp, arranged in the 
 form of anastomosing columns or cords, known as pulp 
 cords and consisting of a fibrous reticulum, resulting from 
 
Tab. 24. 
 
 Mb 
 
 "i;i'V- fr 
 
 ^-- ■■<■■■'. ■■■'•'■■ '. 
 
 
 y '■■■ ' 
 
 1 L 
 
 Br*' 
 
 as 
 
 s v : ;; : 
 
 if'te 
 
 ;-C 
 
 '5/ 
 
 Fig.l. 
 
 h'z Eiq.Z. 
 
SPLEEN. 125 
 
 the further division of the trabecular system, in the 
 meshes of which are found the spleen cells. Between the 
 pulp cords there is found an anastomosing system of 
 venous spaces. A terminal branch of the splenic artery 
 enters at one end of the lobule and, passing up the center, 
 gives off branches to the spleen pulp in each of the com- 
 partments. In each compartment this arterial branch 
 divides repeatedly, the terminal branches coursing in the 
 pulp cords and giving oif numerous small branches, which 
 expand to form the ampullae of Thoma ; these are only 
 partly lined by endothelial cells, the wall of the remain- 
 ing portion being formed by the reticulum of the spleen 
 pulp. The ampulla? of Thoma are in communication with 
 the venous spaces between the pulp cords. These venous 
 spaces are the beginnings of the intralobular veins, which 
 in turn empty into the interlobular veins associated with 
 the interlobular trabecular. Throughout the spleen the 
 veins are found in the trabecular, through which they 
 leave the spleen at the hilum. The branches of the 
 splenic artery enter the spleen at the hilum and for a dis- 
 tance are found in the trabecular ; after leaving the tra- 
 becular the arterial branches divide repeatedly, forming a 
 large number of tuft-like arterioles. Soon after leaving 
 the trabecular, the adventitia of the arterial branches 
 assumes the character of lymphoid tissue, which is here 
 and there increased to form true lymph follicles with germ 
 centers. These are the spleen nodules or follicles, or the 
 Malpighian corpuscles, and in them the artery has gener- 
 allv an excentric position. Between the trabecular and 
 Malpighian corpuscles is observed the spleen pulp. The 
 larger vessels, especially the veins, are found in the tra- 
 becular. 
 
 In the meshes of the reticulum of the spleen pulp are 
 found red blood-cells with now and then nucleated forms, 
 the various kinds of lymphocytes and leukocytes, and 
 especially a relatively larger proportion of mononuclear 
 leukocytes ; large mononuclear cells containing red blood- 
 
126 BLOOD AND LYMPH VASCULAR SYSTEM. 
 
 PLATE 25.— THYMUS. 
 
 Fig. 1.— Portion of a Cross-section of the Thymus Gland 
 
 of a Fourteen = nionth-old Child. X 20. 
 
 The figure shows a general view of the thymus with its lobules and 
 connecting cords. 
 
 Technic: Miiller's fluid. Alum-carmin. 
 
 Reference letters : bg, Blood-vessels ; cB, Hassal's corpuscles ; llh, 
 thymus lobules ; mstr, medullary cords ; se, cortical substance ; sm, 
 medullary substance. 
 
 Fig. 2.— Hassal's Corpuscles from the Thymus of an Adult. 
 X 220. 
 
 The preparation was taken from a twenty-two-year-old man who 
 had been executed. 
 
 Within the still well-developed thymus tissue the figure shows 
 Hassal's corpuscles with the cells in part nucleated. 
 
 Technic : Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters : ek, Epithelial nuclei ; HK, Hassal's corpuscles ; 
 Ic, leukocytes ; It, lymphoid tissue. 
 
 corpuscles occur ; these cells are often pigmented, and in 
 carnivora are seen large polynuclear giant-cells, similar to 
 those found in the bone-marrow. 
 
 There are but few lymph-vessels in the spleen. Afferent 
 lymph-vessels are entirely lacking ; efferent lymph-vessels 
 occur, but pour their lymph into the splenic sinuses, which 
 are therefore filled with blood and lymph. 
 
 The spleen contains numerous non-rnedullated nerves, 
 which enter at the hilum in the form of small trunks and 
 are no doubt vascular nerves. A few medullated nerve- 
 fibers, probably sensory nerves, have also been traced into 
 the spleen. 
 
 The thymus is a lymphoid organ, which is at first epi- 
 thelial and represents a typical gland. In the course of 
 development lymph-cells take the place of the glandular 
 epithelium, which degenerates, with the exception of some 
 epithelial remains. In this way an organ develops, the 
 parenchyma of which is formed by lymphoid cells as in the 
 lymph-glands and spleen, the form of an epithelial gland 
 being, however, retained. 
 
 Connective-tissue trabecular separate a number of larger 
 lobes from each other, which are connected by solid cords 
 
Tab.2S. 
 
 
 
 
 
 FlCf.it. 
 
THYMUS. 127 
 
 of cells, the so-called medullary cords. The larger lobes 
 are more or less completely divided by connective-tissue 
 septa into smaller lobules, which in form resemble the 
 terminal divisions of alveolar glands. Each of these 
 lobules of the thymus consists of an outer cortical and an 
 inner medullary substance; generally several lobules are 
 connected by means of the medullary substance. The 
 cortical substance consists in the main of closely packed 
 lymphoid cells ; the medullary substance, of more loosely 
 arranged cells and peculiar clear bodies, which gen- 
 erally show a distinctly concentric lamination, with 
 nucleated cells in the interior ; these are known as 
 Hassal's corpuscles. They are regarded as the epithelial 
 remains of the original epithelial gland. Likewise, epi- 
 thelial nests may be occasionally found in the medullary 
 cords, which consist mostly of lymphoid cells. These 
 cords are the excretory ducts of the former glands, changed 
 to lymphoid tissue. 
 
 The thymus is the only lymphoid organ which lias no 
 follicles with germ centers. As, nevertheless, mitotic 
 divisions can be observed, it must be assumed that the 
 thymus, like the lymph-glands and the spleen, serves for 
 the new formation of lymphocytes and leukocytes. It is 
 also thought that, as in the red bone-marrow, red blood- 
 corpuscles are formed in the thymus. The thymus attains 
 its highest development in childhood ; later it is traversed 
 by much fat tissue, but is often still well preserved in the 
 adult. 
 
 The thymus receives many blood-vessels, which form 
 capillaries in the medullary, as well as in the cortical sub- 
 stance. Lymph-vessels are also found ; these form sinuses 
 in the cortex of the lobules. 
 
128 
 
 THE DIGESTIVE ORGANS. 
 
 V. THE DIGESTIVE ORGANS. 
 
 The organs of the digestive system comprise a tubular 
 structure, the digestive tract or intestinal canal, which 
 begins at the mouth and ends at the anus, and the glands 
 associated with it. 
 
 ..-ws 
 
 gls-- 
 
 ss 
 
 mm 
 
 rm 
 
 Fig. 43. — Diagram of digestive tract: ep, Epithelium; glm, glands 
 of mucous membrane; gls, glands of submucosa; gmy, ganglion of 
 myenteric plexus; gum, ganglion of submucous plexus; L, lumen; Im, 
 longitudinal muscle; mm, muscularis mucosae; rm, circular muscle; 
 s, serous coat; sm, submucosa; ss, subserosa; tp, mucosa. 
 
 The following layers or coats are recognized throughout 
 the entire extent of the inkdinal canal: (1) The mucous 
 membrane, tunica mucosa, consisting of (a) the epithelium, 
 (6) the tunica propria, which may contain straight or 
 
THE ORAL CAVITY. 129 
 
 branched tubular glands and the ducts of glands lying in 
 the submucosa, as well as solitary lymph-nodes, and (c) the 
 muscularis mucosae, consisting often of several layers of 
 non-striated muscle. These three constituents of the 
 mucous membrane are closely associated and take common 
 part in the formation of its folds. 
 
 2. Beneath the mucosa is found the submucosa, consisting 
 mainly of loose connective tissue. In it are found the 
 larger blood-vessels and nerve trunks for the mucous 
 membrane; in the duodenum it contains the secreting por- 
 tions of Brunner's glands, and in the greater portion of the 
 intestinal canal a portion of the solitary and aggregated 
 lymph nodules, and also adipose tissue. Owing to the 
 loose character of its tissue, the dislocation of the mucous 
 membrane, formation of folds, etc., are rendered possible. 
 
 3. External to the submucosa is the muscle layer (mus- 
 cularis), which is formed of non-striated muscle and often 
 of several layers, generally of an inner circular and an 
 outer longitudinal; between the two layers the muscular 
 nerves form a plexus with ganglia. 
 
 4. The muscle layers are covered by the serous layer, 
 which has on its surface a layer of mesothelial cells. Under 
 the serosa there is loose connective tissue, the subserosa. 
 
 THE ORAL CAVITY. 
 
 The mucous membrane of the oral cavity is lined 
 throughout with stratified squamous epithelium resting on 
 a papillated mucosa. In some portions of the mouth the 
 papillae are very high and project into the epithelium, 
 especially over the gums and at the red margin of the lips. 
 
 Since the mucous membrane of the mouth is not mov- 
 able on its underlying portions, as in the hard palate, the 
 submucosa- is often formed of a closely woven connective 
 tissue, which is firmly attached to the underlying tissue, 
 as for instance the periosteum of the palate. A muscularis 
 znucosce is lacking in the mucous membrane of the entire 
 9 
 
130 THE DIGESTIVE ORGANS. 
 
 PLATE 26.— LIP. 
 
 Sagittal Section through the Upper Lip of a Man. X 6. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the layers of the lip under low magnification; 
 skin, musculature, and mucous membrane, with the labial glands. 
 
 Technic: Miiller's solution. Hematoxylin -eosin. 
 
 Reference letters: a, Arteria labialis superior; gll, labial glands; 
 Lr, red portion of lip; moo, musculus orbicularis oris; p, hairs; lp, 
 tunica propria, mucous membrane of the lip. 
 
 mouth cavity. The submucosa contains tubulo-acinous 
 glands, the lip glands, palatal glands, etc. These will 
 receive consideration at another place. 
 
 THE TEETH. 
 
 The teeth are of ectodermal origin and may be regarded 
 as epidermal appendages ; they are not developed from the 
 entoderm as are the pharynx, glands and epithelium of 
 the intestinal canal, as the portion of the mouth cavity 
 developed from the oral pit in which the teeth are formed 
 docs not originally belong to the anlage of the intestines. 
 Certain of the lower vertebrates have teeth in the skin. 
 
 The teeth are exceedingly hard structures, differentiated 
 from epithelium and embryonic connective tissue. They 
 contain in the interior a narrow space open toward the 
 apex of the root of the tooth, the tooth pulp. Besides a 
 few delicate connective-tissue fibers, the latter contains 
 mainly the nerves and blood-vessels of the tooth and also 
 a single layer of cubical cells forming the lining of the 
 pulp cavity, which are arranged like epithelium .and are 
 
 Fig. 44. — Longitudinal section of a molar tooth of man. X 8. 
 The figure gives a general view of the structure of the tooth. The 
 pulp cavity is not cut its whole length in the two roots seen in the 
 section. We recognize the three main elements of the tooth — dentine, 
 enamel, and cementum — and their division into crown and root. On 
 account of the low magnification, the interglobular spaces appear only 
 as a dark zone on the surface of the dentine. C, Cementum; D, den- 
 tine; P, pulp cavity; S, enamel. 
 
Tab. 26. 
 
 moo 
 
 liih. Anst F. Reichhold., Mii/ichen.. 
 
Fig. 44- 
 
THE TEETH. 131 
 
 closely related to the osteoblasts of bone. They are here 
 characterized as odontoblasts. 
 
 The tooth proper consists of three substances, of which 
 one, the enamel, is of epithelial origin; the other two, the 
 dentine and cementum, are of connective-tissue origin ; the 
 dentine forms the main mass of the tooth. Enamel and 
 dentine are tissues which occur only in the tooth ; the 
 cementum, on the other hand, is bone tissue. In the three 
 macroscopically distinguishable portions of the tooth — the 
 crown, the neck, and the root — the three substances are 
 so disposed that the dentine occupies the interior of the 
 tooth in the crown as well as in the root, but nowhere 
 reaches the surface of the tooth, while the enamel covers 
 the dentine in the crown and ceases gradually toward the 
 neck, and the cementum forms a narrow layer, beginning 
 at the neck where the enamel terminates and increasing in 
 thickness toward the root. 
 
 Dentine (substantia eburnea) resembles osseous 1 tissue 
 in that it consists of a calcified ground substance with 
 calcified fibrillar, and of fine canals, the dentinal tubules, 
 which radiate from the pulp cavity. Dentine differs from 
 osseous tissue in that it contains no cells and no blood- 
 vessels. In the dentinal tubules are found the processes 
 of the odontoblasts, the dentinal fibers, which penetrate 
 them for a variable distance. The fibrils of connective 
 tissue in the calcified ground substance of the dentine are 
 arranged mainly in the direction of the long axis of the 
 tooth. The dentinal tubules or canals are fine canals, 4 p. 
 in width at their opening into the pulp cavity, which, near 
 the outer limits of the dentine, divide several times at an 
 acute angle, and finally, giving off very fine lateral 
 branches, lose themselves at the limits of the substance 
 in fine, blindly ending branches. 
 
 In the region of the crown of the tooth, not far from 
 the boundary line between dentine and enamel, there are 
 
 1 The osseous tissue of the teleosts is essentially a vascularized 
 dentine. 
 
132 THE DIGESTIVE ORGANS. 
 
 Fig. 45.— Cross-section of ahuman canine. X 25. The figure shows 
 under low power the relation of the dentinal tubules, of the granular 
 layer (small interglobular spaces) and of the eementum. In the cemen- 
 tum we recognize numerous bone spaces; the dentinal tubules branch 
 toward the granular layer. C, Cementum; D, dentine; K, granular 
 layer; P, root canal (pulp cavity). 
 
 Fig. 46. — Portion of the crown of a longitudinal section of a 
 human premolar. X 200. The figure shows the structure of a tooth 
 at the border of enamel and dentine. In the region of the dentine 
 two larger and two smaller interglobular spaces are shown. The 
 dentinal fibers branch and fork and with their processes pass beyond 
 the limits of the enamel. In the figure, the enamel prisms show 
 partly wavy curves and partly alternating stripes of darker and 
 brighter prisms (the parallel stripes of Eetzius). D, Dentine; Dk, 
 dentinal tubules ; Jg, interglobular spaces; S, enamel; Sp, enamel 
 prisms. 
 
 Fig. 47. — Portion of a longitudinal section of the root of a human 
 molar tooth. X 200. The figure shows the structure of the boundary 
 between dentine and cementum. In the cementum distinct bone 
 spaces with bone canaliculi are seen. The dentinal tubules here show 
 especially numerous divisions and lateral branches. The granular 
 layer shows small, irregular interglobular spaces. C, Cementum ; D, 
 dentine; Dk, dentinal tubules; K, granular layer (small interglobular 
 spaces) ; KH, bone spaces of the cementum. 
 
 found irregular spaces bounded by spherical surfaces (in 
 undecalcified tooth sections), which probably consist of 
 dentine which has remained uncalcified. These are very 
 variable and are designated as interglobular spaces. Similar 
 but much smaller spaces are found at the borders of the 
 dentine and cementum ; they are beyond the ends of the 
 dentinal tubules and form here a continuous limiting layer 
 between dentine and cementum known as Tomes' granular 
 layer. 
 
 The enamel consists of long six-sided prisms, the so- 
 called enamel prisms, 3-6 p in width, united by a small 
 amount of cement substance. The enamel prisms are not 
 straight, but present wavy borders, and run through the 
 entire thickness of the enamel. They appear structure- 
 less, though occasionally they show striation and may 
 be regarded as petrified epithelial cells. They contain 
 almost no organic substance (3-5 per cent.) and dissolve 
 entirely in mineral acids. 
 
' * 
 
 < *" 
 
 
 /,)'/'■ ': ■• ' V* } .J* Km- T - 
 
 m,*M ■ * 
 
 it *. 
 
 
 « *■ **!> * *■■■*■ &*» r^si' 
 
 F"&. 45- 
 
>Jg 
 
THE TEETH. 133 
 
 The surface of the enamel is covered by a structureless 
 membrane, the cuticula dentis. 
 
 The cementum presents the structure of osseous tissue, 
 usually, however, without showing the distinctive struc- 
 ture of compact bone — that is, without blood-vessels, 
 Haversian canals, and concentric lamella?. Only very 
 large teeth have lamellae in the cementum, as those of the 
 larger mammalia. Then we find also Haversian canals. 
 In man, lamellae only very rarely occur. Where the 
 cementum is thinnest, as in the neck, bone -corpuscles 
 may be wanting. 
 
 The blood-vessels and nerves of the tooth are found in 
 the pulp. The dentine is a tissue which is entirely free 
 from blood-vessels and nerves, and the cementum is 
 usually non-vascular. The enamel may be regarded as a 
 dead substance, which undergoes no metabolism and needs 
 no nourishment. 
 
 As has been previously stated (see page 130), the teeth 
 differentiate partly from the epithelium of the oral cavity 
 and partly from the connective tissue of the mucosa. The 
 process of tooth development is introduced by the epithe- 
 lium, which projects into the underlying connective tissue 
 in the form of a continuous ridge, the enamel ledge, parallel 
 to the margin of the jaw and not yet divided into tooth 
 anlagen. This appears at the end of the second month of 
 embryonal life. 
 
 Soon after the appearance of the enamel ledge there are 
 found in certain places, which correspond in position and 
 number to the deciduous teeth, collections of connective- 
 tissue cells under the epithelial ledge ; at the same time 
 opposite these, nodular enlargements of the enamel ledge 
 appear, the anlagen of the so-called enamel organs, while 
 the collections of connective tissue cells represent the an- 
 lagen of the dentinal papiUce. 
 
 With simultaneous enlargement of the enamel organ and 
 of the dentinal papilla by which the former more and more 
 surrounds the latter in the shape of a cap, there is a con- 
 
134 TBE, DIGESTIVE ORGANS. 
 
 PLATE 27.— TOOTH DEVELOPMENT. 
 
 Fig. 1. — Frontal Section through the Tongue and Lower 
 Jaw of a Three=month Human Embryo (First Stage of De= 
 velopment of Tooth), x 30. 
 
 The figure shows the cross-section of the tongue, of Meckel's carti- 
 lage, of the bone anlagen of the lower jaw, of the two dentinal ridges 
 of the lower jaw, with the tooth anlagen. 
 
 Technic : Picrin-sublimate. Carmin-hematoxylin-eosin. 
 
 Reference letters : SI, Meckel's cartilage ; m, anlage of lower jaw ; 
 pd, papilla of tooth; scho, enamel organ; Z, tongue. ■ 
 
 Fig. 3.— Portion of a Cross=section of the Tooth Anlage 
 of a Six-month Human Embryo (Third Stage of Tooth De= 
 velopment). X 150. 
 
 The figure shows the formation of dentine on the part of the odon- 
 toblasts and of enamel on the part of the enamel cells. The enamel 
 prisms are still separated by a relatively large amount of intercellular 
 substance. 
 
 Technic: Miiller's fluid-formalin. Hematoxylin-eosin. 
 
 Reference letters: as, External enamel cells ; D, dentine; ep, enamel 
 epithelium (inner enamel cells) ; od, odontoblasts; pd, papilla of tooth; 
 S, enamel; sj>, enamel pulp. 
 
 striction and separation of the several tooth anlagen from 
 the common enamel ledge, so that after a certain stage of 
 development the tooth anlagen are connected to the ledges 
 by a cord of epithelial cells. After the anlage of a de- 
 ciduous tooth, consisting of enamel organ and dentinal 
 papilla, is formed, this process is begun anew at the free 
 lower edge of the enamel ledge for the formation of the 
 anlage of the permanent tooth. 
 
 The epithelial enamel organ, surrounding in cap-like 
 fashion the connective-tissue dentinal papilla, consists of 
 a layer of cylindric cells with distinct cuticular border 
 resting on the connective-tissue papilla, the so-called 
 inner enamel cells, and an outer layer of flattened cells, the 
 outer enamel cells. Between these two layers is found a 
 tissue consisting of peculiarly modified stellate epithelial 
 cells with a relatively large amount of mucoid intercellular 
 substance, designated the enamel pulp. As the tooth de- 
 velops, the enamel pulp gradually disappears. 
 
 The connective-tissue dentinal papilla, on the other hand, 
 consists of mesenchymal tissue rich in cells, the upper layer 
 
n 
 
 f. 
 
 
 •••-'•'■,-7..T.^- j § , 
 
 r 
 
 •5S 
 
 
 C\j 
 
 
 
 
 
 # 
 
 ;# 
 
THE TEETH. 135 
 
 of which is formed of cells arranged like epithelium, the 
 odontoblasts. 
 
 The entire anlage of the tooth is surrounded by a con- 
 nective-tissue membrane, the so-called dentinal sac. 
 
 The dentine and enamel are developed as follows : The 
 odontoblasts excrete dentine on the surface turned toward 
 the enamel organ in a way similar to that in which the 
 osteoblasts produce bone. The formation of enamel now 
 begins by the excretion of enamel on the lower end, that 
 turned toward the dentinal papilla, of the cells constituting 
 the inner layer of enamel cells, which now show them- 
 selves as enameloblasts, since each separate cell forms a 
 gradually elongating prism of enamel, in its beginning 
 known as Tomes' process. The several prisms are sepa- 
 rated at first by large amounts of cement substance. Young 
 dentine and young enamel are thus contiguous. The 
 further development of the two main hard substances of 
 the tooth now goes on in such a way that the process 
 reaches its highest development at the apex of the den- 
 tinal papilla, so that the apex of the crown and the 
 crown itself are formed first. The enamel pulp is gradu- 
 ally resorbed and its place taken by the growing tooth. 
 The inner enamel cells with their cuticular borders form 
 the cuticula after the enamel formation is completed and 
 the cells are destroyed. The outer enamel cells suffer the 
 same fate. The tooth pulp is formed from the remains 
 of the connective tissue papilla. The cementum arises from 
 an ossification of the lower portion of the dentinal sac. 
 The development of the permanent teeth is similar to that 
 of the deciduous. 
 
 AA^hen the enamel and dentine formation has reached a 
 certain stage, the epithelial cord between the tooth anlage 
 and the enamel ledge disappears. Remains in the form 
 of cellular strands are often retained for some time and 
 form stratified epithelial bodies, the so-called glandulae 
 tartaricse. 
 
136 THE DIGESTIVE ORGANS. 
 
 PLATE 28.— TOOTH DEVELOPMENT. 
 
 Fig. 1. — Longitudinal Section of a Deciduous Tooth Anlage 
 of a Four=month Human Embryo (Second Stage of Develop= 
 ment of Tooth). X 40. 
 
 The figure shows a deciduous human tooth anlage before the begin- 
 ning of the formation of dentine and enamel. On the free edge of 
 the enamel ledge we see the anlage of the permanent tooth. 
 
 Technic: Picric acid sublimate. Hematoxylin-eosin. 
 
 Reference letters: as, External enamel cells; cl 2 , anlage of per- 
 manent tooth; ep, epithelium of mouth cavity; is, internal enamel 
 cells; Jc, anlage of bone of lower jaw; pd, dentinal papilla; sp, enamel 
 pulp; Zs, dentinal sac. 
 
 Fro. 2.— Longitudinal Section of the Anlage of the Decidu= 
 ous Tooth and of the Permanent Tooth of a New=born Child 
 (Fourth Stage of Development of Tooth). X 10. 
 
 The figure gives a general view of an older tooth anlage with well- 
 advanced dentine and enamel formation, besides the anlage of the 
 permanent tooth in the stage of Fig. 1. The latter is connected by 
 remains of the enamel ledge with the epithelium of the mouth cavity. 
 
 Technic: Miiller's fluid and formalin. Hematoxylin-eosin. 
 
 Eeference letters: D, Dentine ; D J , deciduous tooth anlage; D 11 , 
 anlage of permanent tooth ; ep, epithelium of mouth cavity ; gt, glan- 
 dula tartarica; K, bone of lower jaw; pd, papilla dentis; S, enamel 
 partly separated from the enamel epithelium at theleft; gp, enamel pulp. 
 
 THE TONQUE. 
 
 The tongue consists largely of striated muscle tissue 
 surrounded by a mucous membrane which is firmly 
 attached by means of an aponeurotic submucosa (fascia 
 linguae). We distinguish in the tongue an anterior papil- 
 lary and a posterior tonsillar portion. In the anterior 
 papillary portion there are found in man three forms of 
 papillae, — papillae filiformes, papillae fungiformes, and 
 papillae circumvallatse. It is a misnomer to desig- 
 nate the projections on the tongue as papilla: ; they 
 are villi, which may themselves bear papillae. l The fili- 
 
 1 By the term papilla is understood an arching of the connective 
 tissue, for instance of the corium of the skin into the epithelium, 
 without changing the superficial plane of the epithelium. Villi, on 
 the other hand, are structures of the mucous membrane, which project 
 above the surface and consist of connective tissue and epithelium. In 
 the skin there are normally no villi; when they arise (warts and con- 
 dylomata) , they are pathologic. 
 

 # 
 
 : <M 
 
 %%,_ 
 
 mm,. 
 
 
 "\ 
 
 
 
THE TONGUE. 137 
 
 form and fungiform papillae occur together on the entire 
 papillary portion of the tongue, while the circumvallate 
 papilla? are found in limited number near the tonsillar 
 region. 1 
 
 The papilhe filifonnes consist of a connective-tissue 
 fundament rich in elastic fibers and of a thread-like or 
 conical form. This is covered by a thick epithelium, the 
 superficial, flattened cells of which are arranged in many 
 layers and form slender, partly cornified projections. They 
 are the most numerous of the lingual papilla. Usually 
 they show three high secondary papilla? and on the surface 
 a varying number of processes of horny cells. 
 
 The papilhe fwngiformes have a broad connective-tissue 
 foundation, with several often quite broad and generally 
 not very high secondary papillae on the surface ; their 
 epithelial covering usually presents a relatively smooth 
 outer surface. Transition forms between the papillae fili- 
 formes and the papillae fungiformes are met with. 
 
 The papillae circumvallata? have the form of the fungi- 
 form papillae, except that they are larger and are sur- 
 rounded by an epithelial and connective-tissue wall, which 
 bears no papillae. Secondary papillae are found on the 
 upper and usually on the lateral surfaces. These are 
 generally relatively few. The connective-tissue founda- 
 tion of the papilla? circumvallata? contains many nerve- 
 fibers and also scattered ganglion-cells or groups of 
 ganglion-cells (see Plate 31, Fig. 1). Numerous taste 
 buds or gustatory organs are embedded in the epithelium 
 covering the lateral surface and the wall surrounding the 
 papillae circumvallata?. 
 
 1 The papillse foliatee, which are quite well developed at the side 
 of the tongue in many mammalia, are quite rudimentary in man; 
 they are structures consisting of a number of parallel folds of the 
 mucous membrane and contain numerous taste organs. 
 
138 THE DIGESTIVE ORGANS. 
 
 PLATE 29.— TONGUE. 
 
 Fig. 1. — Transverse Section through a Lingual Tonsil of 
 Man. X 30. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of a lingual tonsil. The epithelium 
 of the tonsillar crypt contains numerous leukocytes. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: Bh, Tonsillar crypt; d, excretory duct of gland; 
 ep, epithelium ; nf, lymph-nodes with germ center. 
 
 Fig. 2— Part of a Transverse Section of the Anterior Por= 
 tion of the Human Tongue, x 25. 
 
 The preparation was taken from fresh tissues, fixed two and one- 
 half hours after death. 
 
 The figure shows transverse sections of filiform and fungiform 
 papillae. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: m, Musculature; p, secondary papillae; pfi, papil- 
 lae filiformes; pfu, papillae fungiformes; ip, mucous membrane; sm, 
 submucosa (fascia) linguae ; m, muscle. 
 
 THE ADENOID STRUCTURES OF THE TONGUE AND OF 
 THE PHARYNX. 
 
 The adenoid structures of this region belong to the 
 class of superficial lymph nodules (see page 122). They 
 are partly solitary follicles, as in the wall of the papillae 
 circurnvallatse, partly and most frequently agminated fol- 
 licles. The latter form on the tongue the so-called lingual 
 tonsils — folliculi linguales — and also the true tonsils. 
 
 The Ungual tonsils are flat, wart-like elevations, which 
 show in the middle a narrow but quite deep depression, 
 the tonsillar crypt. The walls of the crypts consist of lymph- 
 
 Plate 30.— Tonsils. 
 
 Transverse Section through the Pharyngeal Tonsil of 
 Man. X6J. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows in longitudinal section the pharyngeal tonsil with 
 its crypts, the lymphatic tissue, the connective-tissue septa, and the 
 surrounding palatal muscle. 
 
 Technic : Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: agp, Arcus glosso-palatinus; ep, epithelium; ft, 
 fossula tonsillaris ; M, transversely striated muscle ; nl, lymph 
 nodules; S, connective tissue septa; s*, remains of the tonsillar sinus. 
 
Tab.L'.'J. 
 
 *ss*9 
 
 ,*P*P? 
 
 Eig.l. 
 
 pfu^ 
 
 'A fV 
 
 ■M 
 
 
 \tf. *;'""* 
 
 H §!-■ 
 IK'", i 
 
 II; f 
 
 Eig.S. 
 
Tab. JO. 
 
 ■ ArLit V Rachfwhl. Miincken 
 
ADENOIDS OF TONGUE AND OF PHARYNX. 139 
 
 atic tissue with follicles and germ centers, which are sharply 
 limited from the surrounding connective tissue of the 
 mucosa of the tongue and from the musculature. The 
 crypt is covered by the stratified pavement epithelium of 
 the surface of the tongue ; the latter is, however, broken 
 through in many places by the leukocytes which are wan- 
 dering out. 
 
 The pharyngeal tonsils are of similar structure, contain- 
 ing, however, a much greater number of lymph-nodes. 
 Its lymphatic tissue is sharply separated from the closely 
 adjacent muscle and from the mucous glands of the palatal 
 arches. From the mucous membrane pass out many 
 irregularly formed crypts, often Avidened at the base and 
 provided with out-pouchings, the crypts or fossa? of the 
 tonsil. All these are surrounded by lymphatic tissue, with 
 secondary nodes and germ centers, and lined by stratified 
 pavement epithelium. Connective-tissue septa extend 
 from the underlying tissue of the tonsil into its lymphatic 
 tissue, so that each crypt or fossa has a wall consisting of 
 one layer of secondary nodules. The tonsil is thus divided 
 by the connective-tissue septa into a number of separate 
 compartments. 
 
 In the tonsils, as in all lymphatic tissues which are in 
 connection with the epithelium, we can observe the growth 
 and migration of the leukocytes through the epithelium. 
 This process appears more distinct where it is connected 
 with a stratified epithelium and where the leukocytes 
 wander through in large numbers ; this is the case 
 in the tonsils. In the tonsillar crypts, certain areas 
 of the stratified epithelium contain no leukocytes ; in some 
 regions the leukocytes are found singly between the 
 epithelial cells, while in others, groups of leukocytes 
 are found in the epithelium ; finally areas occur where 
 the leukocytes wander through in such numbers that the 
 epithelium is entirely filled by them and only a few groups 
 of epithelial cells are to be seen between large masses of 
 leukocytes. In this process the papillae of the mucous 
 
140 THE DIGESTIVE 0BQAN8. 
 
 PLATE 31— TONGUE. 
 
 Fig. 1. — Transverse Section through a Papilla Circumval= 
 lata of the Human Tongue. X 40. 
 
 The preparation was taken from tissue fixed two and one-half hours 
 after death. 
 
 The figure shows the structure of the circumvallate papilla, taste 
 buds, and the serous glands surrounding it. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: d, Excretory duct of gland; g, ganglion-cells; 
 glser, serous glands; Gkn, taste buds; m, transversely striated muscle- 
 fibers; n, nerve-fibers of the glossopharyngeal nerve; p, secondary 
 papillae; Bf, circular furrow around the circumvallate papilla; Bw, 
 circular wall of the papilla. 
 
 Fig. 2.— Transverse Section through a Portion of the 
 Mucous Membrane of a Tonsillar Crypt. X 220. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shows the wandering of the leukocytes of the mucous 
 membrane through the epithelium. At the left, a few leukocytes in 
 the epithelium; in the middle, there are several groups, and at the 
 right the epithelium is so filled with leukocytes that the epithelial 
 cells are found in the form of nests. The basement membrane of the 
 epithelium can no longer be distinguished at the right. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: dep, Desquamated epithelial cells in the tonsillar 
 crypt; ep, epithelium; epr, epithelial remains; I, leukocytes; ty, lymph- 
 oid tissue of the mucous membrane; x, leukocytes wandering into 
 the lumen. 
 
 membrane first disappear ; then, on account of the masses 
 of leukocytes contained in it, the epithelium increases in 
 thickness, and in places where the number of leukocytes 
 exceeds the number of epithelial cells, the sharp boundary 
 line between the epithelium and the lymphatic tissue of the 
 mucous membrane disappears. 
 
 The blood-vessels of the tongue are very abundant and 
 end partly in the musculature, partly in the mucous mem- 
 brane. The capillary networks of the latter are found 
 principally in the secondary papilla?, where, in tongues 
 which are not coated, — that is, when the superficial, partly 
 desquamated cells have been removed, — they shine through 
 from their exposed position, imparting the normal redness 
 to the tongue. The capillaries also form networks around 
 the glands and pass into the tonsillar tissue. 
 
 The lymj>li-rcssch of the tongue are most abundant in 
 
Tub.,'!/. 
 
 Gkn 
 
 C*"**' ■ 
 
 
 r *P ..... 
 
 
 ?-MM 
 
 "i gi'ser 
 
 
 "' " <OT 
 
 
 
 -3f*w- 
 
 
 /#' 
 
 69.: 
 
 ' : '^i%>.; . . R W 
 
 ■•IS' ■ 
 
 '■' <£■£'* " 
 
 /Yr/.i. 
 
 jf^: 4?. 
 
TEE ESOPHAGUS. 141 
 
 the tonsillar portion and form here a superficial network 
 which surrounds the lymph nodules. 
 
 The nerves of the tongue, especially the branch of the 
 glossopharyngeal going to the circumvallate papillae, show 
 small ganglia in their course. The tongue receives, be- 
 sides the motor nerves and the nerves ending in the taste 
 buds, branches of the lingual nerves which terminate in 
 repeatedly branched endings in the epithelium. 
 
 THE ESOPHAGUS. 
 
 The esophagus has throughout a stratified pavement 
 epithelium with papillae. The tunica propria of the 
 mucous membrane is composed of fibro-elastic connective 
 tissue and contains small lymph-nodes, which are occa- 
 sionally situated around the excretory ducts of the glands. 
 The muscularis mucosae is very well developed and consists 
 almost entirely of longitudinal bundles. The entire 
 mucous membrane, with the muscularis mucosas, shows 
 marked folds in the collapsed condition of the organ. 
 
 The mbmucosa of the esophagus is composed of very 
 loose connective tissue, which often contains fat ; in it are 
 found small mucous glands and the larger nerve bundles and 
 blood-vessels for the mucous membrane. The excretory 
 ducts of the glands pierce the muscularis mucosae and mucosa 
 in which they are often surrounded by lymph follicles 
 and open through the stratified pavement epithelium into 
 the lumen. Serous or mixed glands are occasionally 
 found. 
 
 Aside from the mucous glands, there also occur in the 
 esophagus quite constantly glands which have the char- 
 acter of the fundus glands of the stomach ; these are 
 found especially in the region just before the junction with 
 the stomach, and are therefore known as cardiac glands; 
 occasionally they occur, however, in other portions of the 
 esophagus and more frequently in the upper portion. 
 
 The muscle of the esophagus varies in different regions. 
 
14:2 THE DIGESTIVE ORGANS. 
 
 PLATE 32.— ESOPHAGUS. 
 
 Transverse Section of the Human Esophagus at the Level 
 of the Middle Third. X 10. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a general view of the structure of the esophagus. 
 The muscle is composed of a mixture of smooth and striped fibers. 
 
 Teehnic: Muller's fluid. Hemafcoxylin-eosin. 
 
 Reference letters: cp, Epithelium; gl, mucous glands of the sub- 
 mueosa; L, lumen; Lm, longitudinal muscle; mm, muscularis mucosae; 
 nl, lymph-node; Em, circular muscle; am, submucosa with faVcells, 
 blood-vessels, some longitudinal bundles of smooth muscle at the 
 limits of the circular muscle; fa, tunica ad ventitia; tp, tunica propria. 
 
 In the upper portion, about one-third, it is composed of 
 transversely striated elements; in the middle, of smooth 
 and striated; and in the lower third, entirely of the 
 non-striated variety. It shows a distinct inner circular 
 and outer longitudinal layer. The muscle is surrounded 
 on the outside by connective tissue, which forms an in- 
 distinctly bounded adventitia. 
 
 PLATE 33.— ESOPHAGUS, STOMACH. 
 
 Fig. l. — Portion of a Transverse Section of a Human 
 Esophagus, x in. 
 
 The preparation was taken from one who had been executed. 
 
 The figure shews all the layers of the wall of the esophagus. The 
 musculature consists of smooth and striped fibers mixed. In the 
 mucous membrane a solitary lymph-node is found and mucous glands 
 in the submucosa. 
 
 Teehnic: Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters: ep, Epithelium; gl, glands; glm, non-striated 
 longitudinal muscle; lm, longitudinal muscle (transversely striated!; 
 mm, muscularis mucosae; nl, solitary lymph-node; rm, circular muscle 
 (mixed); s»i, submucosa; tp, tunica propria. 
 
 Fig. 2. — Vertical Section of the Wall of the Stomach in 
 the Region of the Pylorus. X 20. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the layers of the wall of the 
 stomach. The mucous membrane contains long crypts and short 
 branched and twisted glands, as well as lymph-nodes. 
 
 Teehnic as in Fig. 1. 
 
 Reference letters: a, Artery of the submucosa; fg, gastric crypts; 
 M, muscularis; m, mucosa; mm, muscularis mucosae; nl, lymph-nodes; 
 sm, submucosa. 
 
Tab. 32. 
 
 
 
 LUh.Aruil !•' Keic/l/wld . Afimrhen. 
 
PS;*™ 
 
 •££ 
 
 *?•&&: 
 
 %#'*??!**?'■ 
 
 ■S&f <■'. . is 
 
 ■m : 
 
 ■■:?> 
 
 M Mi 
 
 ■. m 
 
 k 
 
 ■:■■ 
 
 \ \(i 
 
 </!'".$ 
 
 0g HP 1 
 
 Fiff.l. 
 
 Tab.. 33. 
 
 ep 
 
 'a 
 
 
 d 6 »4 
 
 
 *0 
 
 
 
 -rnrnm. 
 
 MSMZrA 
 
 .■-■■■ 
 
 Fiu.fi. 
 
 l.ilft.Anxt /•: Reitii twill. AffmrJun. 
 
THE STOMACH. 143 
 
 THE STOMACH. 
 
 The wall of the stomach shows in general the same 
 layers as that of the esophagus, with the addition that the 
 stomach is covered by peritoneum ; so that a serosa and 
 subserosa are added to the layers. 
 
 The epithelium of the surface of the stomach, which also 
 lines the crypts in which the glands terminate, is columnar ; 
 cells are covered with mucus on the side toward the free 
 surface and probably produce mucus like the goblet cells 
 (see page 35). 
 
 The tunica propria of the stomach is composed mainly 
 of tubular glands which open into the crypts ; only a rela- 
 tively small amount of interstitial tissue is foimd between 
 them. The shape and structure of the glands in the 
 region of the body of the stomach (cardiac portion, fundus, 
 and body) differ from those observed in the portion to- 
 ward the pylorus. We accordingly distinguish fundus 
 glands or glandu.be gastricce propria? and pyloric glands. 
 There is, however, no sharp boundary line between the 
 two regions, but a gradual transition of one type of gland 
 into the other. As the glands form the main portion of the 
 mucous membrane, they impress upon it their typical 
 character, so that we may speak of the fundus mucous 
 membrane and the pyloric membrane. 
 
 In the fundus region the gastric crypts are smaller and 
 shorter in proportion to the thickness of the mucous 
 membrane than in the pyloric region ; the glands of the 
 fundus region are much less branched and the tubules are 
 but little convoluted except at the base. Anastomosis 
 between neighboring glands has been observed. 
 
 The fundus glands contain two kinds of cells— chief 
 cells and parietal cells. The former may be regarded as 
 continuations of the surface epithelium ; they are relatively 
 small and of nearly cubical shape. The parietal cells are 
 large, round, or irregularly polygonal cells, have a dis- 
 tinctly granular protoplasm, and stain intensely with the 
 
144 THE DIGESTIVE ORGANS. 
 
 PLATE 34— STOMACH. 
 
 Fig. 1— Transverse Section through the Mucous Mem= 
 brane of the Fundus Region of the Stomach— General View. 
 
 X 45. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the mucosa of the stomach in 
 the fundus region. We recognize the relation of the gastric crypts, of 
 the glandulse gastricse propria;, and in these the distribution of the 
 parietal cells (stained yellowish-red). 
 
 Technic: Zenker's solution. Hematoxylin-orange. 
 
 Reference letters for Figs. 1-3: bg, Blood-vessels; bs, parietal cells; 
 cgl, neck of gland; fg, gastric crypt; fgl, fundus of gland; gig, body 
 of gland ; mm, muscularis mucosae ; nl, solitary lymph nodule. 
 
 Figs. 3 and 3. — Glands of Stomach under Somewhat Higher 
 Magnification, x 80. 
 
 Fig. 2 shows a distinct forking of a stomach gland ; Fig. 3 a gland 
 cut almost the entire length. Both preparations show the distribu- 
 tion of the parietal cells (reddish-yellow, bz) and chief cells (blue). 
 
 Technic and lettering as in Fig. 1. 
 
 acid anil in dyes. The parietal cells are found abundantly 
 between the chief cells, which they may equal in numbers 
 or even exceed in the so-called neck of the gland — that is, 
 the portion opening into the crypts ; in the body of the 
 gland they are scattered, and in the somewhat enlarged 
 and slightly convoluted gland fundus, but few are found. 
 The latter portion of the gland is therefore formed almost 
 entirely of chief cells. Between the chief cells, intercel- 
 lular and in the parietal cells, intracellular secretion capil- 
 laries are found (see page 36). 
 
 The pyloric glands open into relatively wide and deep 
 crypts. The glands are shorter than those of the fundus 
 region ; they are more branched and more convoluted, 
 especially at the base. They contain only one form 
 of cell, similar to the chief cells of the fundus glands. 
 Occasionally, however, scattered parietal cells are found in 
 this region. The portion of the mucous membrane of the 
 stomach not occupied by glands is filled by reticular con- 
 nective tissue rich in lymph-cells, into which single muscle- 
 fibers of the muscularis mucosae extend. 
 
 The lymph-cells form — more frequently in the pyloric 
 
Tab. j*. 
 
 j?<& 
 
 hg 
 
 
 nh 
 
 
 wmmsm 
 
 ' r '"safe™ ■""■\' ,/ "" ; ^/ 
 
 
 %.^. 
 
 ■ ■ :.r- • ,:■- 
 
 •;. ;;,.^»-" - 4, 
 
 
 
 '-• "• ,•.•'•:. j, 1 -'" .•»"•''" ?•:•'• '■■' '•*!• 
 ■;.'/'. .J., .:••■ ■*.-■••;, V'T'.'-v* ;:*•—■" "* 
 '-- •.-•.,;-.•. :''.Vr. ■:>»••" 
 
 
 ftf/J. 
 
 Z iift.. ^n.5/ 1 /•* ReiMwld . Mi'uifhen 
 
THE SMALL INTESTINE. 145 
 
 region — collections of solitary nodes, which are situated 
 chiefly in the deeper layer of the mucous membrane. 
 In the muscularis mucosae of the stomach, two layers can 
 be distinctly recognized — a circular and a longitudinal 
 layer. The submucosa is like that of the esophagus ; it 
 is composed of loose connective tissue, with many elastic 
 fibers and some adipose tissue. It also contains the blood- 
 vessels and nerves for the mucous membrane. The mus- 
 cular coat of the stomach consists of smooth muscle, 
 which, in the main, is arranged in two layers, an inner 
 circular and an outer longitudinal layer. To this, how- 
 ever, is added the radiation of the musculature of the 
 esophagus, which complicates the lamination of the mus- 
 cular coat of the stomach. 
 
 The serosa of the stomach is covered by a layer of 
 mesothelial cells. 
 
 THE SMALL INTESTINE. 
 
 In its whole course the small intestine shows in general 
 a very uniform structure and the same lamination as the 
 stomach. This is complicated only in the upper por- 
 tion of the intestine by the duodenal glands. The mucous 
 membrane of the small intestine is characterized by the 
 presence of villi (see page 136). The villi are high and 
 large, and at the same time somewhat flattened at their 
 beginning in the duodenum (occasionally they begin in the 
 stomach close to the pylorus), and extend to the valvula 
 colica. The villi of the ileum are much smaller and more 
 conical. They consist of slender processes of mucous 
 membrane, which are covered by epithelium. The epi- 
 thelium of the entire intestinal canal, from the pylorus to 
 the anus, is a simple columnar epithelium with striated 
 cuticular border (see page 33). The fornv- of the cells, 
 more especially at the apex of the villi, is generally pris- 
 matic. Goblet cells also occur in varying number (see page 
 35). Both forms of cells are found in the beginning of 
 10 
 
146 the digeht1ve organs. 
 
 Plate 3;.— Stomach, Duodenum. 
 
 Fig. 1.— Portion of a Tangential Section of the Mucous 
 Membrane of the Human Stomach (Fundus Region). X 300. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the transverse sections of five fundus glands and 
 the relation of the chief and parietal cells to the lumen. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters for Figs. 1 and 2: bz, Parietal cells ; hz, chief 
 cells; I, lumen; l u process of lumen between the parietal cells; tp, con- 
 nective-tissue cells of the tunica propria. 
 
 Fig. 2. — Portion of a Longitudinal Section of a Fundus 
 Gland. X 300. 
 
 Legend and lettering as in Fig. 1. 
 
 Fig. 3.— Portion of a Transverse Section of the Human Duo= 
 denum. X 40. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the relation of the duodenal glands (Branner), 
 of the villi, and the lamination of the intestine. 
 
 Technic: Potassium chromate and formalin. Hematoxylin-eosin. 
 
 Reference letters: gld, Duodenal glands (Brunner) ; gli, intestinal 
 glands (Lieberkiihn) ; gsm, ganglion of the submucous plexus ; M, 
 niuscularis (circular and longitudinal layers); mm, muscularis mu- 
 cosae; Mu, mucous membrane; SM, submucosa; ri, villi; x, places 
 where the duodenal glands have broken through the muscularis mu- 
 cosae. 
 
 the short tubular glands, the glands of Lieberkiihn, which 
 lie in the tunica propria of the small intestine. Under the 
 epithelium is a structureless basement membrane, which, 
 as it occasionally contains distinct nuclei, is probably of 
 connective-tissue origin. The epithelial cells in the lower 
 portion of Lieberkiihn's glands, the deepest cells forming 
 the real fundus of the gland, show a distinct granulation 
 of their protoplasm similar to that of gland-cells (see page 
 35), probably a preliminary stage of the secretion 
 (zymogen, so-called Paneth's cells). The adjoining cells 
 generally show mitotic division, more often seen in the 
 small intestine than in the large intestine. The nuclei of 
 the cells undergoing mitotic cell division always lie near 
 the lumen of the gland. The resulting cell proliferation 
 serves the purpose of regenerating the intestinal epi- 
 thelium, in that the cells are pushed from the depths of 
 the gland toward the surface of the villi. The cells thus 
 
Tab.35. 
 
 #'1 
 
 
 
 / 3 e^ 
 
 kK 
 
 © 
 
 
 gsm-- 
 
 t 
 
 ui-% 
 
 X \ % mm % 
 
 Fi.g.3. 
 
 gut 
 
 LWi. Anst E ReMiJiMd, Miinche 
 
THE SMALL INTESTINE. 147 
 
 pushed up serve to replace the goblet-cells which degen- 
 erate. It should, however, be remembered that the evac- 
 uation of the secretion of a goblet-cell does not necessitate 
 its degeneration ; on the contrary, it is more than probable 
 that there is no relation between the number of mitoses in 
 the intestinal glands and the number of goblet-cells ; 
 rather, when the number of the latter increases, the number 
 of the former decreases. In the ciliated epithelium of the 
 respiratory tract, the goblet-cells are often very abundant, 
 while mitoses are entirely lacking. 
 
 The tunica propria of the small intestine is a reticular 
 connective tissue and fills the interstices between the in- 
 testinal glands or glands of Lieberkuhn and forms the 
 greater portion of the villi. In the long axis of the latter 
 lies the axial villous space or the central chyle vessel, the 
 radicle of the lymph-vessels of the small intestine ; the 
 villi also contain blood capillaries and some non-striated 
 muscle-fibers, which extend from the muscularis mucosae 
 into the villus (see Plate 39). The portion of the tunica 
 propria lying between the intestinal glands as well as that 
 of the villi is rich in leukocytes. 
 
 The muscularis mucosae of the small intestine is well 
 developed and consists usually of two layers, an inner 
 circular and an outer longitudinal. 
 
 The submucosa of the small intestine consists of loose 
 connective tissue and in it are found blood-vessels and a 
 nerve plexus (see below). Fine vascular processes of the 
 submucosa project into the plicce circulares (Kerckring's 
 folds) formed of the entire mucous membrane, including 
 the muscularis mucosae. 
 
 The muscular coat of the small intestine is arranged in 
 two distinctly separated layers, an inner circular and an 
 outer longitudinal. The latter is covered by the serosa, 
 which has the same structure as that covering the stomach. 
 
 The upper end of the duodenum has a somewhat differ- 
 ent structure from that of the remaining portion of the 
 small intestine, by reason of the fact that the picture is 
 
148 the digestive organs. 
 
 Plate 36— Small intestine. 
 
 Portion of a Longitudinal Section through the Human 
 Jejunum. X 15. 
 
 The preparation was taken from a man -who had been executed. • 
 
 The figure shows the transverse section of the entire intestinal wall 
 with all its layers. Two valvulse conniventes (Kerckring's folds) are 
 seen in the section. The submucosa extends into these. 
 
 Technic: Absolute alcohol. Hematoxylin-eosin. 
 
 Reference letters: bg, Blood-vessels (veins of the submucosa); Irn, 
 longitudinal muscle; mm, muscularis mucosae; nls, solitary lymph 
 nodule; rin, circular muscle; sm, submucosa; sm^ submucosa of Kerck- 
 ring's folds; ri, villi. 
 
 here complicated by the duodenal glands in the submucosa. 
 In this portion of the duodenum, therefore, glands are found 
 in the submucosa as well as in the mucosa. The duodenal 
 glands, unlike those of the intestine, which are straight 
 tubules, are simple branched alveolo-tubular glands. The 
 cells of the terminal portion are similar to those of the 
 pyloric glands, on the one hand, and to the mucous cells 
 of the salivary glands, on the other hand. Their excre- 
 tory ducts penetrate the muscularis mucosae and mucosa 
 propria and open either into an intestinal gland or on the 
 
 plate 37.— Small intestine. 
 
 Fig. 1. — Portion of a Transverse Section of the Mucous 
 Membrane of the Human Small Intestine. X SO. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the longitudinal section of four villi, a number of 
 intestinal glands, the lymphoid mucous membrane, and the muscularis 
 mucosae. 
 
 Technic: Absolute alcohol. Hematoxylin-eosin. 
 
 Reference letters: ep, Epithelium; gli, intestinal glands (Lieber- 
 kiihn); m, smooth muscle-fibers of the villi; mm, muscularis mucosae; 
 tp, tunica propria. 
 
 Fig. 3.— Portion of a Section of the Mucous Membrane of 
 the Human Small Intestine (Duodenum), x 300. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the longitudinal section of two intestinal glands, 
 and the condition of the epithelium in these. 
 
 Technic: Potassium chromate-formalin. Hematoxylin-eosin. 
 
 Reference letters: 62, Goblet-cells; cl, eosinophile leukocytes; ep, 
 epithelium with cuticular border (edge of villi); Igli, lumen of intes- 
 tinal gland; mi, mitoses of epithelial cells of intestinal gland; Pz, cells 
 of Paneth with granulation. 
 
Tab.36. 
 
 Sm 
 Im rni /i 
 
 II .%' 
 
 |jfc- : 
 
 * -—7, '" W^ V * 
 
 1 •» 'lllilia 
 
 Ltth,.Anst.F. Relchhold.. ifiinctien. 
 
Tub. ,37. 
 
 1#^ 
 
 
 frr-1 'I'M 
 
 ''yi,ii'i'i« , i | '»,i ( ' l | ii J (-^ i "".^:'w^'^ x . 
 
 
 V- 
 
 
 Vj/nnjpVuil'Wi'j''''""'''."'" 1 '^ 
 
 9> --—:, 
 
 ttt0P*t!i 
 
 ' ,lA »'ft«;,MA/ 1 ,ll!»^.J™,;; ( ,,t"i'' ; ^<'* > ' A 
 
 g,wj(,, wA i„,„»A-.'''.::. , f.'^ 
 
 %i, 
 
 ^&« 
 
 /^SjQ 
 
 ■Hj 36° '-,43 S K« *« ^ *. 
 
 ^ 9^j m^ 
 
 ..^afSTj^!* «. 
 
 ^ 8 9T»9«"»9 9 9 *i«a>3a 8 » «V* 
 
 
 
 Mi* «'». 08»0 . (j0^.<§e 8tW»\ 
 
 <r-/// 
 
 
 %^. 
 
LYMPHATIC STRUCTURES OF THE INTESTINES. 149 
 
 free surface of the mucous membrane. In man, often con- 
 siderable portions of the duodenal glands (in the neighbor- 
 hood of the excretory ducts) lie within the muscularis 
 mucosae and therefore in the region of the mucous mem- 
 brane. 
 
 THE LARGE INTESTINE. 
 
 The wall of the large intestine differs in structure from 
 that of the small intestine in that the villi are lacking and 
 that the intestinal glands are longer, increasing in length 
 as we pass from the cecum toward the rectum. The glands 
 of the large intestines contain numerous goblet-cells toward 
 the base of the glands, especially in the central portion, 
 while the superficial epithelium and the mouths of the 
 glands have few goblet-cells ; this is in marked contrast 
 to the condition of the small intestine, where the majority 
 of the goblet-cells are found in the epithelium of the villi. 
 Except in the rectum, the longitudinal muscle of the large 
 intestine is arranged in three bundles or stripes, the taeniae 
 coli. 
 
 THE LYMPHATIC STRUCTURES OF THE INTESTINES. 
 
 The lymphatic structures of the intestinal canal appear 
 in the form of solitary follicles and agminated glands or 
 Peyer's patches. The latter are found only in the lower por- 
 tion of the ileum, the former occur in the entire intestinal 
 tract, large as well as small, being more frequent in the large 
 intestine and ileum than in the jejunum. In the small 
 intestine, as in the stomach, the solitary follicles are situ- 
 ated in the mucosa ; the villi are wanting over their pear- 
 shaped apices, which are in close relation to the epithelium. 
 In the large intestine the broader portion of the follicle is 
 in the submucosa — that is, it generally pushes the muscu- 
 laris mucosae markedly into the submucosa. The follicles 
 usually contain germ centers. 
 
 The Peyei's patches are elongated structures consisting 
 
150 THE DIGESTIVE ORGANS. 
 
 PLATE 38.— LARGE INTESTINE. 
 
 Fig. 1. — Transverse Section through the Entire Wall of 
 the Large Intestine (Descending Colon). X 30. 
 
 The preparation was taken from tissue fixed two and one-half hours 
 after death. 
 
 The figure shows the lamination of the wall of the large intestine. 
 
 Technio: Tellyesnicky's fluid. Hematoxylin-eosin. 
 
 Reference letters: ep, Epithelium; gli, intestinal glands; gray, gan- 
 glion of the myenteric plexus; lm, longitudinal muscular layer; mm, 
 muscularis mucosae; sm, submucosa; rm, circular muscular layer; tp, 
 tunica propria. 
 
 Fig. 2.— Portion of a Transverse Section of the Mucosa 
 of the Human Rectum. X 60. 
 
 The preparation was taken from a convict who had been executed. 
 
 The figure shows the mucous membrane of the rectum with the 
 glands of Lieberkiihn and a solitary follicle. The broader end of the 
 latter is apparently in the submucosa, but in reality it only pushes 
 the muscularis mucosae into the submucosa. 
 
 Technic: Zenker's fluid. Hematoxylin-eosin. 
 
 Reference letters: (7)?, Epithelium filled with leukocytes; gli, glan- 
 dular intestinales; l;z, germ centers; m, single muscle-fibers in the 
 mucous membrane; mm, muscularis mucosae; nl, solitary lymph-node; 
 X, section of intestinal glands. 
 
 of from ten to sixty adjacent solitary follicles connected 
 by their cortical zones. The follicles are spread out so 
 that they lie in a single layer and almost entirely in the 
 mucosa ; the apices, however, project as broad lymphoid 
 villi into the mucous membrane and into the intestinal 
 lumen. The villi are lacking over the Peyer's patches 
 (see Fig. 48). 
 
 In the vermiform process the arrangement is similar ; the 
 mucous membrane is rudimentary, consisting of only a 
 few glands, while the lymjjhatic tissue predominates in the 
 form of closely crowded solitary follicles with germ cen- 
 ters. The solitary follicles and lymphatic structures of 
 the intestine contain only blood capillaries — no lymph 
 capillaries at least in man. In the places where the 
 crowns of the solitary follicles or agminated follicles come 
 in contact with the columnar epithelium, this, like the 
 pavement epithelium of the tonsillar crypts and lingual 
 tonsils, is filled with leukocytes. Also, elsewhere, in 
 almost the entire intestinal canal, we occasionally find in 
 
Tab.38. 
 
 Fig.l. 
 
 \Im 
 
 ept 
 
 -— . — • ,j/i 
 
 
 v' - .':?:' 
 
 
 &<i^*'. ' :•': 
 
 ■.V...A: / . 1 '.«fiSSfS8 :•©%■; ■ /."Vf |.v| -:= ;'.; 
 
 pi:'.-. ■y: : .'.y_ , : y,/ ?jt*f; 1 , \ •} 
 
 mtmB 
 ■mmm 
 
 
 pi>^ //Z 
 
 :'"" 
 
 /br 
 
 Fi(/.,3. 
 
 Litfv. Anst.F. Reirfihold, Miinchm. 
 
SLOOD- AND LYMPH-VESSELS OF INTESTINES. 151 
 
 the columnar epithelium leukocytes arising from the 
 diffuse adenoid tissue of the mucous membrane (see Plate 
 2, Fig. 3). The leukocytes wander through the epi- 
 thelium of the vermiform appendix in great numbers, and 
 often fill its narrow lumen. 
 
 THE BLOOD= AND LYMPH-VESSELS AND NERVES OF 
 THE STOMACH AND INTESTINES. 
 
 The vessels and nerves are very similarly arranged in 
 the stomach and intestine. The arteries in the mesentery 
 which enter the intestine lie first in the subserous tissue 
 and give off branches to the muscularis, then form in the 
 submucosa a network from which branches arise which 
 supply the muscular coat and mucous membrane. Here 
 we find the capillary networks around the glands as well 
 as on the surface of the mucous membrane ; in the small 
 intestine, a small artery also goes to each villus, passing up 
 its center and breaking up into a capillary network, the 
 blood from which is collected into a small vein. The 
 capillaries of the villi lie immediately under the epi- 
 thelium. The venous radicles, especially of the stomach 
 and large intestine, are superficial. They arise from the 
 capillaries, which are relatively large, and form a super- 
 ficial network in the mucous membrane ; in the stomach 
 this is situated in the region of the necks of the glands, 
 therefore below the base of the crypts. 
 
 The lymph-vessels begin in the small intestine, as the 
 axial chyle vessels of the villi, while in the stomach and 
 large intestine they begin as lymph capillaries between 
 the glands ; especially large capillaries surround the 
 solitary lymph follicles, as well as the Peyer's patches. 
 In the submucosa and between the two muscle layers, the 
 lymph-vessels form networks. Large trunks run in the 
 subserous tissue to the mesentery. 
 
 The nerves of the stomach and intestine arise mainly 
 from the sympathetic, though certain medullated cerebro- 
 
152 the digestive organs. 
 
 plate 39.— Intestinal Epithelium, Goblet-cells. 
 
 Fig. 1.— Portion of a Longitudinal Section through the 
 Villi of the Human Small Intestine. X 325. 
 
 After a preparation of Professor Stohr, Wiirzburg. It was taken 
 from a man who had been executed. 
 
 The figure shows the structure of the intestinal villi, the diffuse 
 lymphoid tissue of the tunica propria, the axial chyle-vessel (only 
 part of which is met in the section), the columnar epithelium with 
 cuticular border zone and goblet-cells in different stages of secretion. 
 
 Technic: Flemming's solution. Hematoxylin, saffranin, picric 
 acid. 
 
 Reference letters: ach, Axial chyle-vessel of villus; bin, basal mem- 
 brane of epithelium; 6z,, goblet-cells, beginning of secretion in the 
 protoplasm; bz 2 , goblet-cells filled with secretion; bz 3 , goblet-cells 
 after the secretion is evacuated; c, cuticular border of epithelium; ep, 
 epithelium; M, evacuated mucus; tp, mucous membrane of villus. 
 
 Fig. 2. — Longitudinal Section of Two Glands of Human 
 Large Intestine. X 160. 
 
 After a preparation of Professor Stohr, Wiirzburg. This was taken 
 from a man who had been executed. 
 
 The figure shows especially the distribution of the goblet-cells, 
 which in the large intestine reach to the base of the glands. 
 
 Technic as in Fig. 1 . 
 
 spinal nerves terminate therein. The majority of the 
 nerve-fibers are non-medullated, and in the wall of the 
 stomach and intestine form two plexuses with small ganglia 
 at the nodal points. The larger plexus, the plexus myen- 
 fericus or Auerbach's plexus, is situated between the cir- 
 cular and longitudinal muscular layers and has larger 
 ganglia with multipolar nerve-cells and quite regularly 
 polygonal to rhombic meshes. The neuraxes of the 
 
 Fig. 48.— Part of a vertical section of the wall of the small intestine 
 of the cat. X '~0. The figure shows a cross-section of a Peyer's 
 patch, the broader portion of which, containing the germ center* lies 
 in the submucosa, while the apices of several nodes lie in the mucosa, 
 forming a broad lymphoid villus, hn, Lymphoid portion of the mu- 
 cous membrane; nl, lymph-nodes; M, muscularis; sm, submucosa; n, 
 intestinal villi. 
 
 Fig. 41). — Transverse section of an injected villus of an ape. X 
 500. The figure shows the cross-section of an intestinal villus, the 
 epithelium of which shows a very distinct striated cuticular border. 
 The blood-vessels are injected with Berlin blue, rich, Axial chvle- 
 vessel, compressed; cs, cuticular border; bz, goblet-cell; ep, epithelium- 
 I, leukocyte in epithelium. 
 
Tab. 3 .9. 
 
 &z , 
 
 •' »l 
 
 
 
 s* 
 
 5' • ' i-5 © • 
 
 
 
 
 - 
 
 ; l;c i 
 
 I 
 
 
 ,!..<'■ ; 
 
 M&M, &* « ; 
 
 - 
 
 
 
 P ; f ',■ 
 
 B ft e «\ ^ , o i *J 
 
 
 I J c %:^ „*«.«^8 *-,,*;.. 
 
 ^ o©' » © a & <S S« Of' ••" 
 
 'eflElf: 
 
 f . 
 
 
 «*> 
 
 ^.i. 
 
 °„ ~-^„t.fi.,«. »:», Kitfjuo*'^"***?* 
 
 
 
 Fiffi^. 
 
 
 /ttft. .4/wtf /:' Rpichhoid. Miinchen. 
 
A 
 
 ilii 
 
 
 ' ■ . o'.\- -■*■ 
 
 
 Vm 
 
 .■-!..-,;;.» /.?; 
 
 : : : 
 
 
 V WM^ 
 
 Fig. 48. 
 
 i>~ f m. 
 
 
 fflB5 
 
 I 
 ach 
 
 Fig. 49. 
 
THE SALIVARY GLANDS. 153 
 
 sympathetic neurones of the ganglia of this plexus supply 
 the musculature. 
 
 The plexus submucosus or Meissner's plexus is much 
 finer and less regular, its meshes being much smaller. 
 The neuraxes of the ganglia of this plexus innervate the 
 mucosa as well as the muscularis mucosae, and the plexus 
 therefore contains both motor and secretory fibers. Both 
 plexuses begin in the esophagus and extend to the rectum. 
 
 White rami fibers terminate in end-baskets surrounding 
 the cell-bodies of the sympathetic neurones situated in the 
 ganglia of both plexuses. The larger medullated fibers 
 are sensory cerebro-spinal fibers, the terminal branches of 
 which end in the epithelium and probably also in the walls 
 of the blood-vessels. 
 
 THE SALIVARY GLANDS. 
 
 Under this heading we shall consider the large salivary 
 glands, the small glands of the mouth, and the pancreas. 
 Certain of these glands secrete a serous secretion, rich in 
 albumin, known as albuminous or serous glands; others, a 
 mucous secretion, mucous glands ; and certain glands form 
 both serous and mucous secretion ; these are known as 
 mixed glands. The appearance of the gland-cells which 
 secrete the albuminous substance is essentially different 
 from that of those which secrete mucus, and the structure 
 of the mucus-secreting tubules — all these glands are tubular 
 or tubulo-alveolar — differs from that of the serous glands. 
 The tubules or alveoli of the serous glands are of small 
 caliber, have a very small lumen, often so small that it can 
 be seen only with difficulty. They are lined by a layer of 
 cubical, distinctly granular cells, the nuclei of which lie 
 about the middle of the cell. Between the serous cells, in- 
 tercellular secretion capillaries are found (see page 36). 
 
 The tubules or alveoli of the mucous glands are large, 
 their diameter being at least twice as great as that of the 
 serous tubules ; their lumen is large, their cells clear, 
 
154 the DIGESTIVE ORGANS. 
 
 PLATE 40.— VERMIFORM APPENDIX. 
 Transverse Section of the Human Vermiform Appendix. 
 
 X20. 
 
 The preparation was secured by means of an operation. 
 
 The figure shows the numerous solitary lymph follicles ot the 
 vermiform appendix and the few glands; in the lumen many leuko- 
 • cytes are seen; the musculature is very poorly developed. 
 
 Technic: Zenker's solution. Hematoxyliu-eosin. 
 
 Reference letters: e, Epithelium; F, adipose tissue of submncosa; 
 Z, lumen; M, musculature; al, lymphatic nodules. 
 
 with the nuclei pressed against the wall and often flattened. 
 When filled with secretion, these "cells are large, clear, 
 vesicular structures and stain readily with those dyes 
 which stain mucus. After the evacuation of their secre- 
 tion, they stain more deeply in the general stains and 
 appear darker in fresh preparations, but still differ from 
 the cells of the serous glands. Secretion capillaries are 
 lacking. 
 
 Tubules which contain only mucous cells are rare; 
 tubules containing only serous cells are found in serous 
 glands ; in certain glands — the majority of the so-called 
 mucuus glands — the tubules contain both mucous and 
 serous cells. 
 
 As has been stated, the salivary glands may be divided 
 into serous glands, pure mucous glands, and glands having 
 
 PLATE 41.— NERVE PLEXUS OF INTESTINE. 
 
 Fig. 1.— Surface Preparation of the Myenteric Plexus of 
 the Smail Intestine of the Guinea=pig. X 30. 
 
 The figure gives a general view of the distribution of the small 
 ganglia of the plexus, their connections and principal branches. 
 
 Technic: Dilute acetic acid. Gold chlorid, formic acid. 
 
 Reference letters: M, Musculature of intestine (one muscle laver 
 has been removed); G, ganglion, the darker spots are ganglion-cells. 
 
 Fig. 2— Portion of the Submucous Plexus of the Small 
 Intestine of the Rabbit. X *0. 
 
 Only the plexus is represented. 
 
 The figure shows the relation of the ganglia and the branches of 
 the plexus. 
 
 Technic as in Fig. 1. 
 
 Reference letter: g, Ganglia. 
 
Tab.40. 
 
 Lith. Anst F. Rtudrfwld. Miwrhp 
 

THE SALIVARY GLANDS. 155 
 
 both serous and mucous secretion, namely the mixed 
 glands. The latter are again divided into two subclasses: 
 glands with tubules which contain both serous and mucous 
 cells, and glands some of the tubules of which contain 
 only serous cells while others contain either only mucous 
 cells or both mucous and serous cells. The purely serous 
 glands are the parotid, the small glands in the region of 
 the circumvallate papillae of the tongue and the pancreas. 
 The purely mucous glands are the small glands at the root 
 of the tongue and in the region of the lingual and phar- 
 yngeal tonsils and the palatal glands. 1 
 
 Mixed glands of the first subdivision are the sublingual 
 glands and all other smaller glands of the mouth, as well 
 as the labial and buccal glands, glands of Nuhn, and 
 others. The submaxillary is the only mixed gland of the 
 second subdivision. 
 
 We will begin our more detailed consideration with the 
 four large salivary glands, the parotid, the submaxillary, 
 the sublingual, and the pancreas. They are all lobar, 
 compound tubular or tubulo-alveolar glands, and are com- 
 posed of many duct systems. The parotid has short 
 tubular, markedly convoluted terminal alveoli, which have 
 a very narrow lumen and only serous cells. The transi- 
 tion into the excretory duct system is made by long, very 
 narrow intermedia ry tubules, lined by much flattened cells. 
 Either singly or united, the intermediary ducts pass over 
 into the secretory or salivary ducts (see Fig. 50), which are 
 characterized by an epithelium of low columnar form, 
 distinctly striated on the basal side. The salivary ducts 
 then continue into larger portions of the duct system, 
 which show no basal striation of the cells and possess 
 two layers of epithelial cells as we approach the primary 
 branches of the main excretory ducts. Of these two layers 
 of cells, the cells of the lower layer are pyramidal and 
 of the upper, columnar. In the submaxillary gland, the 
 
 1 Purely mucous glands also occur in other portions of the digestive 
 tract, in the respiratory tract, genital organs, etc. 
 
156 the digestive organs. 
 
 Plate 42.— Salivary Glands. 
 
 Fig. 1.— Portion of Section of the Human Sublingual 
 Gland. X 40. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the boundaries of two lobes of the gland, with a 
 larger excretory duct and the adjacent gland tissue. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: bdg, Interlobular connective tissue with blood- 
 vessels; Dsj, larger excretory duct; Ds 2 , smaller portion of the duct 
 system (secretory tubes) ; mu, mucous alveoli as shown by reaction to 
 stain; v, veins. 1 
 
 Fig. 2.— Portion of a Transverse Section of the Human 
 Sublingual Gland. X 90. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a number of gland tubules, some cut longi- 
 tudinally, some transversely, and others tangentially. The distri- 
 bution of the serous and mucous cells of the tubules is to be seen. 
 ( In certain regions the section passes through only serous cells and 
 might therefore be confused with purely serous tubules. ) 
 
 Technic: Absolute alcohol. Hematoxylin. 
 
 Eeferenee letters: b, Interstitial connective tissue rich in lymph- 
 cells; km, demilune; sr, secretory tubule; tm, mixed-gland tubule in 
 longitudinal section. 
 
 majority of the tubules are like those of the parotid, con- 
 taining only serous cells. In addition to these there is a 
 small number of long, much convoluted, large mucous 
 tubules, which, however, especially at the blind ends, 
 contain small groups of serous cells; these are known as 
 the demilunes of Heidenhain or the crescents of Gianuzzi, 
 so called because the serous cells are often arranged on 
 the mucous cells in the shape of a ridge, and in cross- 
 section give the appearance of a demilune. Such a demi- 
 lune in the submaxillary is often formed by a single cell. 
 The duct system of the submaxillary is very similar to 
 that of the parotid ; only the intermediary duct is very 
 much shorter. The salivary ducts show areas with dis- 
 
 Reference letters for Figs. 50-53: a,, Large branch of the main ex- 
 cretory duet; f< 2 , smaller branches of the same; hm, demilune; s, inter- 
 mediary duct; sr, salivary ducts; tm, mixed tubules; fe, serous tubules; 
 t, tubules or alveoli/ (The serous cells are dark, the mucous clear.) 
 
 1 In one vein, the blood in printing has become spotted. 
 

 6d#m~ 
 
 ''■■■'■ J; :■-'.■■■ "nt r -. Ci....^K''- 
 
 — .V::. / /'/aft 
 
 . '"V--r-\.- ,-s ■ ■■■"'■;'"■ '<* ' '■>■ '■' 'f-'.' ,, 
 
 ."'X / •■•!.";.' 
 
 ^.i. 
 
 Tab.*2. 
 
 J-v'^'Zff- 
 
 ...>■■;- 
 
 ssfH 
 
 
 .-: & i "r:.v^>^,;;;-V;V^--:v:-"^.rp 
 
 sr . . 
 
 
 
 hm 
 
 Eiff., 
 
THE SALIVARY GLANDS. 
 
 157 
 
 Fig. 50. — Diagrammatic 
 representation of parotid 
 gland. 
 
 (For explanation ot lettering, see page 150. 
 
 Fig. 51. — Diagrammatic represen- 
 tation of submaxillary gland. 
 
158 THE DIGESTIVE ORGANS. 
 
 PLATE 43.— SALIVARY GLANDS. 
 
 Fig. 1.— Portion of the Cross=section of the Human Sub= 
 maxillary Gland. X 150. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the glands composed of two kinds of tubules — 
 purely serous and mixed. Moreover, intermediary ducts and salivary 
 ducts with striated epithelium are seen. 
 
 Technic: Absolute alcohol. Heniatoxylin-eosin. 
 
 Reference letters: Hm, Demilune; L, lumen of tubule; seh, inter- 
 mediary duct; .</■, salivary duct; tui, mixed tubules lined with mucous 
 cells and having serous cells in the demilunes; fe, serous tubules. 
 
 Fig. 2.— Small Area of a Relatively Thin Cross section of 
 the Human Parotid. X 280. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows cross-sections of a number of purely serous tubules 
 only one of which shows a distinct lumen. The relation of the inter- 
 mediary duct to the tubules and its transition to the salivary ducts 
 is shown. 
 
 Technic: Absolute alcohol. Hematoxylin-eosin. 
 
 Reference letters: I, Lumen of the tubule; sch, intermediary duct; 
 sr, salivary duct; t, tubules. 
 
 tinct basal striation ; the main excretory duct has two 
 layers of columnar epithelium, and outside of this, longi- 
 tudinal muscle. 
 
 The sublingual contains only mixed tubules. All the 
 tubules of the gland are therefore of similar structure and 
 similar to the mucous tubules of the submaxillary ; the 
 demilunes are, however, much larger, — that is, the serous 
 cells are much more abundant, — and often line the whole 
 extent of the lumen. It may therefore happen that cross- 
 sections of tubules of the sublingual are obtained, which 
 are composed only of serous cells and resemble very closely 
 the cross-sections of serous tubules. The duct system of 
 the sublingual differs from that of the parotid and sub- 
 maxillary in that the intermediary ducts are entirely lack- 
 ing. The tubules pass directly into salivary ducts, the 
 basal striation of whose cells is quite indistinct. 
 
 In the panerea* the secreting tubules are relatively short, 
 often thickened at the ends ; and are in the main similar to 
 those of the parotid, for they possess only serows cells. 
 The cells show, especially in the state of hunger, so-called 
 
Tab A3. 
 
 /m ffm 
 
 ■ •• . . , S „,:'••,•./■ . . • * . / - . .« .'- ••,•■■* ■ _< h r :,■ 
 
 • •. • . ••„ , - • , .« .•<■*:*• ".••?.-' • ". ' '."'■.:, •'**' 
 
 &K„V "*ff ? " ;.;.y ;.*„•/.'.«:; *'Si vl^ /#'** --V " ->'.. V' 
 
 J.,t? ". '>v ■ -•. ' v ,°" •.'.■*• '•■ --• ..••••"•-. - . .Us.?,- -,. 
 
 
 (• ...» r t Li-ii s B 
 
 •».>«>° 
 
 ; <. . tr l 
 
 
 i • 
 
 AV/; 
 
 
 .v,// 
 
 
 '\<5 
 
 
 
 
 
 e \ 
 
 • \ 
 8 / 
 
 
 A J 
 
 Eig.2. 
 
THE SALIVARY GLANDS. 
 
 159 
 
 Fig. 52. — Diagrammatic representa- 
 tion of the sublingual gland. 
 
 Fig. 53. — Diagrammatic 
 representation of the pan- 
 creas. 
 
 (For explanation of lettering, seepage 156.) 
 
 ( I f I t I I I I - I I I t - I I I . i , 
 
160 THE DIGESTIVE OROANS. 
 
 PLATE 44.— PANCREAS. 
 Fig. 1. — Portion of a Cross=section of the Human Pancreas. 
 
 xioo. 
 
 The preparation was taken from fresh human tissue, fixed two and 
 one-half hours after death. 
 
 The figure gives a general view of the structure of the gland. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: d, Branch of the pancreatic duct; sch, intermedi- 
 ary duct; is, cross-section of gland tubules. 
 
 Fig. 2.— Small Portion of Fig. 1 from the Human Pancreas. 
 X 420. 
 
 The figure shows the cross-section of the intermediary duct and of 
 some of the tubules connected with it. The relation of the centro- 
 acinar cells to the cells of the intermediary duct is shown. 
 
 Technic as in Fig. 1. 
 
 Reference letters: caz, Centro-acinar cells; drz, gland-cells; scht, in- 
 termediary duct. 
 
 Fig. 3.— Cross-section of Pancreatic Tubule. 
 
 ( From the same pancreas as Figs. 1 and 2. ) 
 
 The figure shows the zymogen granules of the inner portion of the 
 gland-cells. 
 
 Technic: Potassium chromate-formalin. Hematoxylin-eosin. 
 
 Reference letters: caz, Centro-acinar cells; Zg, zymogen granules. 
 
 zymogen granules on the side toward the lumen. It is 
 difficult to observe a lumen in the secreting tubules of the 
 pancreas, since this is generally filled with flattened cells 
 known as centro-acinar cells, which are regarded as a con- 
 tinuation of the flattened cells lining the long intermediary 
 duct of the pancreas into the lumen of the secreting tubules. 
 Salivary ducts are entirely lacking in the pancreas. The 
 intermediary ducts pass directly into the branches of the 
 main excretory duct, the pancreatic duct. The latter has 
 cubic to columnar, occasionally almost flat epithelium, 
 which is always in a single layer. Besides the tubular 
 system above described, the pancreas contains certain 
 structures known as the islands or areas of Langerhans. 
 The meaning of these structures is still obscure, although 
 it is generally believed that they form an internal secre- 
 tion. They are composed of trabecular and septa of epi- 
 thelial cells which neither form tubules nor connect with 
 the excretory ducts by means of intermediary ducts, but 
 are surrounded by dense capillary networks. 
 
Tab.**. 
 
 ,srA 
 
 lig.l. 
 
 i 
 
 
 ~-.~-.zff 
 
 Fiff.M. 
 
 aV« 
 
 © &mg? 
 
 
 «^fl 
 
 ® © "aft e 
 
 © @ 
 
 
 %<*. 
 
 ji Zitt. .4/u7 /? Reichhold. Miirichen . 
 
THE LIVER. 161 
 
 The smaller glands of the mouth usually consist of but 
 one duct system. The single excretory duct is lined by a 
 columnar epithelium, usually in many layers and occa- 
 sionally ciliated. Their tubules are sometimes mucous, 
 sometimes serous, and sometimes mixed (see page 153). 
 
 The salivary glands are rich in blood-vessels ; numer- 
 ous capillaries surround the tubules. In the interstitial 
 connective tissue are found the neuraxes of sympathetic 
 neurones, the branches of which probably penetrate the 
 membrana propria and end free between the cells of the 
 gland. The interstitial connective tissue of the sublingual 
 is rich in lymph-cells, collections of which occur, appearing 
 like solitary follicles, but having no germ centers. 
 
 THE LIVER. 
 
 The liver is a large compound tubular gland with anas- 
 tomosing tubules. This condition can, however, be recog- 
 nized only with difficulty in the fully developed human 
 gland, as the original character of the independent tubules 
 has been almost lost. There is also an intimate relation to 
 the vascular system which dominates the arrangement of 
 the former tubules. In this account of the structure of 
 the liver we will give first a purely descriptive considera- 
 tion of its structure, and in closing will attempt an eluci- 
 dation of the tubular character of the organ. 
 
 The liver is surrounded by a connective-tissue capsule, 
 known as the fibrous capsule or capsule of Glisson, which, 
 at the hilus of the liver, extends into the organ with the 
 blood-vessels. In many animals — for instance in the pig 
 — each liver lobule, the anatomic unit of the liver, is 
 surrounded by connective tissue from Glisson's capsule. 
 In man the connective tissue of the liver is not so well de- 
 veloped and only for a short distance does it form the 
 boundaries of adjacent lobules. The liver lobules are nearly 
 cylindric structures. They consist of anastomosing tra- 
 .becula? of liver-cells, which show a distinctly radial 
 11 
 
162 THE DIGESTIVE ORGANS. 
 
 PLATE 45.— LIVER. 
 
 Fig. 1. — Portion of a Transverse Section of the Human 
 Liver. X 35. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a number of liver lobules in cross-section, which 
 are relatively well separated from each other. 
 
 Teclmic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: cf, Interlobular connective tissue of Glisson's 
 capsule; db, bile-ducts; re, intralobular or central vein; rp, branches 
 of the portal vein, interlobular veins. 
 
 Fig. -2. —Portion of a Transverse Section of a Liver Lobule. 
 
 The figure shows the relation of the cords of liver-cells, their radial 
 arrangement, and their anastomoses. Some cells have two nuclei. 
 Teclmic, etc., as in Fig. 1. 
 Reference letters: c, Capillaries; /, fat droplets in liver-cells. 
 
 arrangement from the axis of the lobule. Each trabecula 
 consists of liver-cells arranged in close rows. The cells 
 are large (15—20 p), irregular, polyhedral, have no distinct 
 cell membrane, and are rich in protoplasm ; they have 
 relatively small nuclei (quite frequently there are two). 
 In the fresh condition the liver-cells are distinctly turbid 
 and granular (glycogen granules), and also contain fat in 
 smaller and larger droplets and bile pigment. Contiguous 
 liver-cells are in immediate contact and thus form cords 
 of wilt or trabeculse, consisting of one or two rows of cells 
 and anastomosing with neighboring cords without the in- 
 tervention of the membrana propria. 
 
 The arrangement of these cords of liver-cells is de- 
 pendent upon the arrangement of the blood-vessels, 
 which should therefore be considered first. The afferent 
 vessel of the liver is the portal vein. The hepatic artery 
 supplies only the walls of the bile-ducts, the interlobular 
 connective tissue, and the Glisson's capsule. Its capil- 
 laries pass directly into the branches of the portal vein. 
 Terminal branches of the portal vein run as vence inter- 
 lobulares in the connective tissue between the lobules. 
 Each lobule receives branches from several interlobular 
 veins. The interlobular veins run in company with the 
 small bile-ducts and with the arterial branches which 
 
TabAS. 
 
 np- 
 
 •<>*o;.l'' & 
 
 ■-.:;■ 
 
 ■ -: : : v '■'- 
 
 z\.^m? 
 
 30 
 
 
 
 i 
 
 © © * e> , „©&•„• --..-A 
 
 Zji't. ^osA /.' Reichhold, Munch en . 
 
THE LIVER. 
 
 163 
 
 vsl 
 
 Fig. 54. — Diagrammatic representation of liver lobule. The figure 
 shows a schematic longitudinal section ; at the. left the blood capillaries 
 and at the right the bile capillaries are represented, db, Bile-ducts; 
 vc, central or intralobular vein; vil, interlobular vein; vsl, sublobular 
 vein. 
 
164 the digestive organs. 
 
 plate 46.— Liver. 
 
 Fig. 1.— Portion of a Cross=section of the Liver of a 
 Rabbit, Which Has Been Completely Injected. X 45. 
 
 The figure shows a liver lobule in transverse section with injected 
 vessels, together with adjoining parts of neighboring lobules. It gives 
 a general view of the distribution of the blood-vessels in the liver 
 (bile-ducts in the interlobular connective tissue). 
 
 Technic: Injection with Berlin blue gelatin. Muller's fluid. 
 Borax-carmin. 
 
 Reference letters: c, Capillaries; db, bile-ducts; re, central or intra- 
 lobular vein ; ri, interlobular veins. 
 
 Fig. 2. — Portion of a Transverse Section of a Rabbit's 
 Liver Treated by the Golgi Method. X 300. 
 
 The figure shows the bile capillaries blackened by the Golgi 
 method. These show many short, fine, blind processes which extend 
 into the protoplasm of the liver-cells, short, intracellular secreting 
 capillaries. 
 
 Technic: Potassium chromate-formalin. Silver impregnation ac- 
 cording to Golgi method. Alum-carmin. 
 
 Reference letters: c, Blood capillaries; x ; ce U with many "secre- 
 tory capillaries." 
 
 supply the connective tissue and the walls of the bile- 
 ducts. 
 
 From the periphery of the lobule the interlobular veins 
 send toward the center of the lobule, through the network 
 of cords of liver-cells, numerous large capillaries which 
 frequently anastomose. In the axis of the lobule runs the 
 terminal branch or the radicle of the efferent venous sys- 
 tem of the liver, the hepatic vein. This is known as the 
 centra! or intralobular vein, so called from its position in 
 the liver lobule. It takes up the capillaries arising from 
 the interlobular veins. The central or intralobular vein 
 runs exactly in the axis of the lobule, beginning at its 
 apex by the confluence of capillaries (see diagram) as a 
 vein of the smallest caliber. During its course through 
 the lobule it takes up capillaries from all sides, so that it 
 increases in caliber and thus leaves the base of the lobule 
 to open into the sublobuhir vein, a larger branch of the 
 hepatic vein. 
 
 Each liver lobule is composed, therefore, of cords of 
 liver-cells and the capillaries lying between them. The 
 
Tab.4ff. 
 
 Tiff J . 
 
 Tig. , 
 
THE LIVER. 165 
 
 latter border directly on the liver-cells and usually run at 
 their edges. 
 
 In addition to the liver-cells and capillaries, there are 
 found in the liver lobule the following structures, which 
 are made visible only by special methods : A connective- 
 tissue framework within the liver lobule itself, which con- 
 sists of very fine fibers forming very delicate networks 
 around the capillaries, and known as " Gitterfasern," and 
 of star-shaped cells, the so-called stellate cells. The nuclei 
 of the latter lie between the liver-cells and are usually not 
 to be distinguished from the nuclei of the capillaries. 
 Reticular fibers, as well as stellate cells, appear only after 
 the use of special staining methods. 
 
 Another constituent of the liver which is usually difficult 
 to see is the bile capillaries, very fine ducts, lying between 
 the liver-cells, without special walls and opening into the 
 bile-ducts. The cubic epithelium of the latter represents 
 the direct continuation of the liver-cells, since, at the 
 periphery of the lobule, some cords of liver-cells have 
 lower and smaller cells which pass over gradually into the 
 epithelium of the bile-ducts (see diagram, Fig. 54). The 
 bile capillaries may be regarded as intercellular secretion 
 capillaries. They are formed by the two half grooves of 
 neighboring cell-surfaces. They represent a very narrow 
 and very fine network extending over the entire paren- 
 chyma of the liver, which has finer meshes than the blood 
 vascular system. In general the bile capillaries run over 
 the surface of the cells, while the blood capillaries run at 
 the corners. The bile capillaries, for the most part, form 
 anastomoses similar to those of the blood capillaries, but 
 they also j)ossess free intercellular and intracellular ends. 
 The latter are found as short processes projecting into the 
 cell protoplasm and terminating in nodular enlargements. 
 These may probably be re-formed and also disappear again. 
 The finer bile-ducts have a single layer of cubic epithelium ; 
 the larger ones, columnar epithelium with cuticular border. 
 The epithelium of the gall-bladder is similar. 
 
166 the urinary organs. 
 
 Plate 47.— liver. 
 
 Fig. 1.— Portion of a Transverse Section of the Injected 
 Liver of a Rabbit (Blood Capillaries Red, Bile Capillaries Blue). 
 
 X 280. 
 
 Material from the Institute for Comparative Anatomy, Wiirzburg. 
 
 The figure gives a general view of the two capillary networks and 
 their relation to the cords of liver-cells. 
 
 Fig. 2. — More Highly Magnified Area of the Same Prepara= 
 tion from the Rabbit's Liver as Fig. 1. X 500. 
 
 The figure shows blood capillaries, bile capillaries, and liver-cells 
 in their mutual relation. Many of the liver-cells contain two nuclei. 
 
 Reference letters: c, Blood capillaries; g, bile capillaries ; x> blind 
 ends of bile capillaries. 
 
 The nerves of the liver are mostly non-medullated, the 
 neuraxes of sympathetic neurones; they run with the 
 arteries, veins, and bile-ducts, and terminate in the wall 
 and epithelium of the bile-ducts, in the walls of the vessels, 
 and probably also on the liver-cells. 
 
 We may imagine that two neighboring cords of liver- 
 cells, with the bile capillaries lying between them, repre- 
 sent a former liver tubule without a membrana propria, 
 the greatly reduced lumen of which is the bile capillary 
 whose walls are formed by the two liver-cells. While the 
 wall of the tubule of the liver in man, at least in the 
 adult, is generally formed of but two cells, in many animals 
 and also in the human embryo more than two cells bound 
 the bile capillary, so that the liver tubule is quite similar 
 to that of an ordinary tubular gland. Each row of liver- 
 cells would at the same time belong to two or more tubules, 
 as usually a bile capillary runs on each surface of the liver- 
 cell. According to this conception each liver lobule con- 
 sists originally of a number of tubules arranged radially 
 to the axis of the lobule. 
 
 VI. THE URINARY ORGANS. 
 
 TheMchiey is a compound tubular gland, with the ureter 
 as its excretory duct. It is surrounded by a connective- 
 tissue capsule, the tunica albuginca. 
 
TabA7. 
 
 Fig. 1 . 
 
 Eig-,3. 
 
 lith. Anst F. liewhlwld, Alimehen . 
 
TEE KIDNEY. 167 
 
 The uriniferous tubules form the parenchyma of the kid- 
 ney. The secreting portion of these tubules lies in the 
 cortical substance, while those portions of the tubules which 
 form part of the excretory system are found mainly in the 
 medulla. The excretory ducts terminate at the apices of 
 the medullary pyramids. The beginning of each urinifer- 
 ous tubule is found in a spheric portion invaginated by a 
 plexus of arterioles and capillaries. The plexus of arterioles 
 and capillaries invaginating the beginning of each urinifer- 
 ous tubule is known as a glomerulus, and this with the 
 invaginated end of the tubule, known as Bowman's capsule, 
 constitutes a Malpighian corpuscle. Bowman's capsule is 
 a spheric, double-walled structure, invaginated by the 
 glomerulus, so that its two layers are almost in apposition. 
 The narrow interspace which remains is the beginning of 
 the lumen of the uriniferous tubule. Both layers of Bow- 
 man's capsule, especially the invaginated "visceral" por- 
 tion, have a very much flattened epithelium. The urinifer- 
 ous tubule itself is a much convoluted tubule of considerable 
 length and of characteristic structure in the various por- 
 tions. The first portion, adjacent to the Bowman's cap- 
 sule, is the tubulus contortus. Its lumen passes over directly 
 into that of the capsule, its cubic epithelium changing 
 quite abruptly into that of the capsular wall. The epithe- 
 lium of the tubuli contorti shows generally very indistinct 
 cell boundaries and a distinct striation of the basal portions 
 of the cells ; on the surface toward the lumen it pre- 
 sents a striated border resembling a cuticular formation 
 similar to the rod-like border of the intestinal epithelium. 
 This striated border is not always to be found and is said 
 to be influenced by the functional condition of the kidney. 
 The Malpighian corpuscles and the tubuli contorti always 
 lie in the cortex of the kidney. 
 
 Following the contorted or convoluted portion of the 
 uriniferous tubule is a segment which has the form of a 
 loop, formed by two parallel limbs, and extending deep 
 into the medullary substance ; the depth to which it ex- 
 
168 THE URINARY ORGANS. 
 
 Plate 48.— Kidney. 
 
 Portion of a Vertical Section of the Human Kidney. X 6. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the distribution of the cortical 
 and medullary substance of the kidney. The section extends from the 
 capsule into the papilla. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: a, Arteria arciformis; cr, Malpighian corpuscles; 
 pc, convoluted tubules of cortex; dp, papillary ducts; pr, medullary 
 rays of cortex; si; cortex; sm, medulla; if, tunica albuginea. 
 
 tends into the medullary substance depends upon the depth 
 in the cortex of the Malpighian corpuscle of the respective 
 tubule ; this loop structure of the uriniferous tubule is 
 known as Henk's loop. It consists of a thin, long de- 
 scending limb, which has quite flat epithelium and a rela- 
 tively large lumen, and a shorter, thicker ascending limb 
 with considerably higher epithelium of flattened cubic 
 shape resembling that of the convoluted tubules, but 
 somewhat lower and with indistinct cell boundaries. 
 
 The ascending limb passes into the cortical substance 
 and continues as a short, slightly convoluted portion of the 
 tubule, the intermediary portion. It lies near the medul- 
 lary rays of the cortex and always lies deeper than the 
 convoluted tubule belonging to it. The epithelium of the 
 intermediary portion is formed of non-striated columnar 
 cells. 
 
 The intermediary portion is followed by the straight 
 uriniferous tubule, which is situated in the medullary rays 
 of the cortex of the kidney. The straight tubules or col- 
 lecting tubules form the beginnings of the excretory duct 
 system. Each collecting tubule takes up several urinifer- 
 ous tubules, and in the medullary rays, and especially in the 
 medulla, they unite at acute angles to form larger collect- 
 ing tubules ; and finally, with still greater increase of caliber, 
 they form the papillary duet opening on the area cribrosa of 
 the papilla. The collecting tubes have at first cubic epithe- 
 lium ; later it becomes columnar, and the papillary duct 
 has tall columnar epithelium. 
 
Tab.48. 
 
 r M':fi k ' : $ 
 
 4i\»i- *. r • • . V $ ■•• • i 
 
 -tr 
 
 W 
 
 mm: 
 
 
 LUh. Anst. /*' Reicflhold, Miiiiclwn . 
 
THE KIDNEY. 
 
 169 
 
 The entire uriniferous tube possesses a structureless 
 membrana propria, which, however, is not equally distinct 
 
 Fig. 55. — Diagrammatic representation of urinary tubule: egl, Cap- 
 sule of glomerulus; dp, papillary duet; A-,, narrow proximal limb of 
 Henle's loop; h 2 , wider distal limb of the loop; sr, collecting tube; tc, 
 contorted or convoluted tubule; sch, intermediary portion. 
 
 in all portions of the tube. Between the uriniferous 
 tubules there is found a small amount of interstitial con- 
 
170 the urinary organs. 
 
 Plate 49.— kidney. 
 
 Fig. 1. — Portion of a Vertical Section of the Cortical Sub- 
 stance of the Human Kidney. X 45. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the distribution of the straight and convoluted 
 tubules as well as of the Malpighian corpuscles. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: sc, Convoluted tubules; gl, glomeruli; sr, medul- 
 lary rays; //, tunica fibrosa or albuginea; ti, interstitial tissue with 
 blood-vessels. 
 
 Fig. 2. — Small Portion of the Cortical Substance of the 
 Human Kidney, Showing the Transition of a Convoluted 
 Tubule into the Bowman's Capsule. X 280. 
 
 The figure shows a glomerulus within its capsule. The flattened 
 epithelium of the latter passes immediately over into the cubic epithe- 
 lium of a convoluted tubule. In addition to this, we see transverse 
 sections of the convoluted tubules with striated epithelium, without 
 cell boundaries, and also sections of the intermediary tubules. 
 
 Technic, etc., as in Fig. 1. 
 
 Reference letters: cgl, Bowman's capsule; gl, glomerulus; Sch, inter- 
 mediary portion; tc, convoluted tubules; ti, interstitial connective 
 tissue; x> intermediary portion cut tangentially. 
 
 Fig. 3. — Epithelium of the Convoluted Tubules of the 
 Human Kidney, Showing Striated Border. X 500. 
 
 The figure shows a portion of the epithelium of the convoluted 
 tubule, which presents the striated border, but no basal striation. 
 
 Technic, etc., as in Fig. 1. 
 
 neeiive tissue, containing the blood-vessels and nerves of 
 the kidney. 
 
 The blood-resseh of the kidney are worthy of note. 
 The arteries enter the kidney substance at the base of the 
 pyramid, near the boundaries of the columns of Bertini. 
 Here the main trunks of the renal artery branch into the 
 arterue arciformes, arching at the boundaries of the cortical 
 and medullary substance. From the convex side of the 
 arch, which is turned toward the cortical substance, 
 branches arise, the so-called interlobular arteries, 1 which 
 ascend into the cortex, between the medullary rays toward 
 the surface of the kidney, and give off the vasa afferentia 
 for the glomeruli of the renal corpuscles. The glomeruli 
 
 1 So called because the portion of the urinary tubules belonging 
 to one papillary duct is regarded as a renal lobule. The renal lobules 
 are, however, not separated from each other. 
 
, «• * - 
 
 :-}&&; -i js ',4.,*-,. -'V'.;- -'•'-. ■■•; <>._.' ;-;■;<•'. ■...-.• L '- /.- 
 
 V*''k- V*:' ■":.> H ; ,' ■"■:■■' v^-;," ;**■■ 
 
 .1 -^\ 
 
 " ^ V: * ?A' ,: ? 'Svj /:■;;" < 
 
 ■fYtfJ". 
 
 
 
 Fig.JZ. 
 
 ©'•• % 
 
 'an ©" 
 <#> ' 
 
THE KIDNEY. 171 
 
 represent retia mirabilia, the efferent branches of the 
 glomeruli carrying arterial blood. The glomeruli of the 
 kidney are therefore inclosed in the arterial circle. The 
 afferent vessel, vas afferens, as well as the smaller efferent 
 vessel, the vas efferens, are arteries. The vascular wind- 
 ings of the glomerulus show the structure of capillaries, 
 possessing a syncitial endothelium, but they are larger 
 than ordinary capillaries. From the vasa efferentia of the 
 glomeruli arise true capillaries, which are distributed in 
 part to the convoluted tubules of the cortical substance and 
 in part extend as very small straight arteries, the so-called 
 arteriolar rectse, into the medullary substance. Cortical 
 branches also arise from the terminal branches of the in- 
 terlobular arteries. 
 
 From a number of capillaries and very small veins, the 
 veins of the cortex of the kidney collect quite suddenly in 
 the cortical substance just under the capsule to form the 
 venulce stellata:, which serve as points of origin for the 
 interlobular veins; these take up the capillary blood from 
 the deeper portions of the cortex. They accompany the 
 interlobular arteries and pass over into the venae, arciformes, 
 which, in position and other conditions, correspond to the 
 arterise arciformes. 
 
 While the cortex of the kidney is very rich in blood- 
 vessels, the reverse is the case in the medullary portion of 
 the kidney. As the large vessels of the kidney run at the 
 boundary of the cortex and medulla, no large blood-vessels 
 are contained in the medulla of the kidney. The arterial 
 and venous trunks of the medullary portion of the kidney 
 are characterized by a straight course parallel to the course 
 of the tubules and are known as the arteriolar and vena? 
 rectse. The capillaries form a long-meshed network. The 
 arteries of the medullary substance are in part direct 
 branches from the concavity of the arteria arciformis, 
 partly vasa efferentia of the deeper glomeruli, and partly 
 deep direct branches of the interlobular arteries. The 
 venulse rectse open directly into the vena? arciformes. 
 
172 THE URINARY ORGANS. 
 
 PLATE 50.— KIDNEY. 
 
 Fig. 1.— Transverse Section of the Medullary Substance 
 of the Human Kidney. X 150. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows sections of large collecting tubules with columnar 
 epithelium; smaller tubules with flattened cubic epithelium (descend- 
 ing limb of Henle's loop) and cross-sections of capillaries. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Eeference letters: e, Blood capillaries; Ha lt ascending limb of 
 Henle's loop; Hs 2 , descending limb of Henle's loop; tr, collecting 
 tubules. 
 
 Fig. 2.— Portion of a Transverse Section of a Human 
 Kidney Injected through the Arteries. X 15. 
 
 The figure shows the boundaries of cortical and medullary substance, 
 and the adjacent parts of both. It shows the principal relations of the 
 renal arteries. 
 
 Technic: Injection with Berlin blue gelatin. Miiller's fluid. 
 Borax-carmin. 
 
 Eeference letters: ai, Interlobular arteries; or, arteriolar recte; gl, 
 glomeruli ; va, vena arciformis. 
 
 Direct anastomoses between arteries and veins occur in the 
 kidney. 
 
 The lymph-vessels of the kidney run in company with the 
 arteries ; likewise, the sympathetic nerves form plexuses for 
 the blood-vessels and can be followed even to the glomeruli. 
 Sympathetic nerve-fibers terminate also on the epithelium 
 of the uriniferous tubules. 
 
 plate 51.— Kidney. 
 
 Fig. 1.— Two Injected Glomeruli of the Human Kidney. 
 
 X 120. 
 
 Reference letters: va, Vas afferens; ve, vas efferens. 
 
 Fig. 2.— Portion of a Cross=section through the Kidney of 
 a Quinea=pig, Injected through the Vein. X 15. 
 
 The figure shows the entire thickness of the cortical substance and 
 the greater portion of the medullary substance. Only the veins 
 and capillaries are injected, and not the arteries; hence not the glom- 
 eruli. 
 
 Technic: Injection with Berlin blue gelatin. Miiller's fluid. Borax- 
 carmin. 
 
 Reference letters: c„ Capillaries of the cortex; c 2 , capillaries of 
 the medullary substance; sc, cortical substance; sm, medulla; va, vena 
 arciformis; vr, venulse recta; vat. venulse stellate, partly passing into 
 the vena; interlobulares. 
 
Tab.SO. 
 
 Iig.1. 
 
 Fig.S. 
 

 Tab. 51. 
 
 Fig. 2. 
 
 v Ltth. Anst P. ' Reir/ihotd '.. Mundtjut,, 
 
THE EFFERENT URINARY PASSAGES. 173 
 
 THE EFFERENT URINARY PASSAGES. 
 
 The efferent urinary passages include the calices and 
 pelvis of the kidney, the ureter, the bladder, the female 
 urethra, and the beginning of the male urethra. These are 
 all lined with the same epithelium, the so-called transitional 
 epithelium (see page 32). 
 
 The mucous membrane of the ureter and its radicles, 
 which is much folded when empty, consists of a thin con- 
 nective-tissue membrane containing elastic fibers, which 
 passes without distinct boundaries into the submucosa. 
 There are no glands and no muscularis mucosae. The 
 mucous membrane contains numerous lymph-cells, which 
 occasionally form larger collections and are also met in 
 the epithelium. The muscidature of the ureter is charac- 
 terized by scattered bundles of muscle separated by con- 
 nective-tissue bundles. It is most fully developed in the 
 lower portion of the duct. It consists there of inner 
 longitudinal, middle circular, and outer longitudinal bun- 
 dles. The latter are almost entirely lacking in the upper 
 portion. The musculature is surrounded on the outside 
 by a connective-tissue adventitia. The blood capillaries of 
 the mucous membrane of the ureter are in direct contact 
 with the epithelium, so that in the folds they seem to lie 
 in the epithelium ; they lie, however, in small folds of 
 the mucosa practically composed of the capillaries. 
 
 The bladder is very similar in structure to the ureter. 
 The epithelium of the two is the same. The mucous 
 membrane of the bladder shows the same characteristics 
 as that of the ureter ; it not infrequently contains small 
 lymph-nodes. The submucosa, also, is not well separated 
 from the mucosa and contains adipose tissue occasionally. 
 The bladder, as well as the ureter, contains no glands. 
 
 The musculature of the bladder is much more developed 
 than that of the ureter, but it presents the same lamina- 
 tion, an inner and an outer longitudinal layer and a mid- 
 dle circular. The muscle layers, especially the inaex 
 
174 the urinary organs. 
 
 plate 52.— Ureter, Bladder. 
 Fig. 1.— Transverse Section of the Wall of the Human 
 Bladder. X 15. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the structure of the bladder. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: aim, External longitudinal layer of muscle; ep, 
 epithelium; ilm, inner longitudinal layer of muscle; rm, circular mus- 
 cle layer; sm, submucosa; ta, tunica adventitial tp, tunica propria. 
 
 Fig. 2.— Transverse Section through the Human Ureter. 
 
 X 25. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the structure of the ureter. 
 
 Technic: Absolute alcohol. Hematoxylin-eosin. 
 
 Reference letters: al, External longitudinal layer of muscle; ep, 
 epithelium; ilm, inner longitudinal layer of muscle; L, lumen; rm, 
 circular muscle layer; sm, submucosa ; ta, tunica adventitia; tp, tunica 
 propria. 
 
 longitudinal layer, show distinct reticular arrangement of 
 the fibers. The wall of the bladder of amphibia con- 
 tains perfect networks of smooth muscle-fibers (see Fig. 2, 
 Plate 58). The upper and posterior portions of the blad- 
 der have a serous covering of peritoneum. 
 
 There are said to be no lymph-vessels in the mucous 
 membrane of the bladder ; they occur in the musculature. 
 
 The outer portion of the female urethra is lined by 
 stratified pavement epithelium, while the inner is lined by 
 transitional epithelium. In the outermost portion of the 
 female urethra are found mucous glands. The mucous 
 membrane contains numerous veins, forming a dense 
 network. The female urethra is surrounded by a well- 
 developed muscle, which is arranged mostly in circular 
 layers. The inner layer of this muscle, in which the fibers 
 are arranged longitudinally, is permeated by the venous 
 plexus of the mucosa. 
 
 For the male urethra see the male reproductive organs. 
 
Tab. 5 2. 
 
 ..■■■■.■■ . i ' \u :mhA : ml 
 
 &•. 
 
 
 KttP 
 
 
 
 
 
 .<....%■;, •:. 
 
 jTOT.i 
 
 R..^ 
 
 Sta ^ 
 
 e'i 
 
 ,ta 
 
 t 
 
 «/ 
 
 ftf/.i'. 
 
 Um 
 
TESTIS. 175 
 
 VII. THE MALE REPRODUCTIVE ORGANS. 
 
 The testis is a compound tubular gland, with an anas- 
 tomosing duct system, which is surrounded by a firm con- 
 nective-tissue sheath, the tunica albuginea. On the pos- 
 terior surface of the testis a wedge-shaped connective-tissue 
 structure is found, known as the mediastinum testis or corpus 
 Highmori, from which pass vascular connective-tissue 
 trabecula?, the septula testis, to the tunica albuginea. 
 These bound the several pyramidal lobules of the testis, 
 the lobuli testis. The lobules contain the greatly con- 
 voluted tubuli seminiferi contort! , the true parenchyma of 
 the testis, between which strands of very loose connec- 
 tive tissue are found. In addition to the nerves and 
 blood-vessels, the interstitial connective tissue of the lobule 
 in man contains a varying number of large plasma cells 
 with relatively small nuclei, which contain fat droplets, 
 pigment, and crystalloids. In many animals these inter- 
 stitial cells, also called interstitial testicular cells, are very 
 well developed and scarcely less prominent than the 
 parenchyma, — for instance in the testis of the boar, — 
 which therefore appears brown in cross-section like the 
 liver. 
 
 The convoluted tubules of tlie testis begin in the lobule in 
 the neighborhood of the albuginea, partly in blind ends 
 and partly branched reticularly. Toward the boundary 
 of the mediastinum testis the tubules become less con- 
 voluted and finally straight, forming the tubuli recti ; these 
 continue into the rete testis situated in the mediastinum. 
 The latter represents the beginning of the excretory duct 
 system. 
 
 The walls of the convoluted tubules consist of several 
 nucleated layers, which have on their inner surface a strati- 
 fied epithelium varying in appearance and structure accord- 
 ing to the stage of spermatogenesis. For the same reason 
 the size of the normally relatively large lumen varies. 
 
176 THE MALE REPRODUCTIVE ORGANS. 
 
 PLATE 53.— TESTIS. 
 
 Fig. 1. — Transverse Section of the Testis, Epididymis, and 
 Vas Deferens of a Child. X 10. 
 
 The figure represents the general picture of the testis and its 
 adnexa. 
 
 Technic: Mliller's fluid. Hematoxylin-eosin. 
 
 Reference letters: bg, Blood-vessels (especially veins of the plexus 
 pampiniformis) ; dd, vas deferens; Ep, epididymis; I, lobules of testis; 
 m, mediastinum testis; rt, rete testis; s, septula testis; T, testis; ta, 
 tunica albuginea. 
 
 Fig. 2. — Portion of a Transverse Section of a Lobule of the 
 Human Testis. X 60. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the cross-seetion of the convoluted seminiferous 
 tubules and of the interstitial tissue of the testis. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Eeference letters: tc, Convoluted tubules; ti, interstitial tissue; Zz, 
 interstitial cells. 
 
 During spermatogenesis the epithelium of the convoluted 
 tubules is so arranged that the youngest generation of cells 
 is nearest to the lumen, the oldest toward the wall of the 
 canal. The secretion of the seminal tubules consists of 
 the spermatozoa or spermatosomes, peculiar motile cells, 
 consisting of three constituents — the body or head, the 
 middle piece, and the tail. 
 
 Under higher magnification, other structural peculiari- 
 ties belonging to the spermatosomes are observed in many 
 of the lower vertebrates, as well as in the higher animals 
 and man, notably a tail fiber and an undulating membrane. 
 The head consists of almost pure chromatin and is the 
 nucleus of the transformed cell. In the middle piece the 
 centrosome is represented and the tail fiber, which is char- 
 acterized by whip-like movements, is probably protoplas- 
 mic. In the fresh state the head appears dark, the 
 middle piece quite clear and transparent. 
 
 The mature spermatosomes of man are about 50 fi long; 
 the head is elliptic, about 4 p. long and 1\ p broad, with 
 the anterior end somewhat flattened, so that in lateral 
 view it appears pear-shaped. The middle piece is narrow, 
 short, cylindric, and the tail fiber is long. The spermaio- 
 
Tab.53. 
 
 3(1 «■««, c. 
 
 •4? 
 
 
 "SW 
 
 <&?®^&n 
 
 
 \ 
 
 
 ^S, 
 
 
 dd. 
 
 
 
 Fiif.l. 
 
 ■-.) .. 
 
 ^'^r 'i» ";-■ '''.9~*~-n 'y']^:^':.. ' ■■r'-'K:-, V .""0- ' '"-' 
 
 .•;■•:, v.:-„: ■•■■;!» 
 
 
TESTIS. 177 
 
 somes arise directly from one of the cells of the tubules of 
 the testis, the so-called spermatids, or sperm-cells. These 
 arise by mitotic division from the mother sperm-cells, or 
 spermatocytes. The spermatocytes arise from the primor- 
 dial cells, or the spermatogones. 
 
 Besides the three generations of cells whose end-pro- 
 ducts are the cellular secretion of the testis, the spermato- 
 somes, another variety of epithelial cell is found in the 
 epithelium of the tubuli contorti of the testis, which takes 
 no part in the process of spermatogenesis, but which serves 
 as a supporting element for the mature spermatosomes. 
 These cells are known as Sertoli's cells. Each cell has an 
 elongated nucleus, often pointed toward the lumen of the 
 tubule ; in comparison with the nuclei of the other epithe- 
 lial cells of the testis, it is noteworthy on account of the 
 small amount of chromatin. In the resting state the 
 nucleus is surrounded by a small amount of protoplasm. 
 In most mammalia the nuclei of the Sertoli cells lie adja- 
 cent to the wall of the tubule. In man, however, the 
 nuclei of the Sertoli cells lie nearer to the lumen of the 
 tubule, so that the pedicle of the spermatoblasts is very 
 short. 
 
 The transformation of the spermatids into spermatosomes 
 takes place in the following manner: The spermatids are 
 quite small round cells with spheric nuclei. The cells 
 assume an oval form, the nuclei being also elongated. 
 The latter become rich in chromatin and at the same time 
 smaller. The nucleus then recedes to the side of the cell 
 away from the lumen of the canal. A group of these 
 metamorphosed spermatids now enter into close relation 
 with a Sertoli cell, with the protoplasm of which their pro- 
 toplasm fuses. By this means a structure develops, which 
 is called a spermatoblast. Each spermatoblast consists of 
 the nucleus of the Sertoli cell, generally lying next to the 
 sheath of the tubule, of a protoplasmic pedicle, and of a 
 broad protoplasmic mass adjoining the lumen of the tubule 
 and consisting of the fused cell-bodies of the spermatids. 
 12 
 
178 THE MALE REPRODUCTIVE ORGANS. 
 
 PLATE 54.— TESTIS. 
 
 The figures of this plate represent portions of the convoluted tubules of 
 the human testis, during the process of spermatogenesis. 
 
 The material for the preparation was removed by an operation, 
 secured by Professor Benda, of Berlin, and was fixed in potassium 
 bichromate-nitric acid. Iron-hematoxylin-eosin. 
 
 Fig. 1— Portion of the Wall of the Tubule of the Testis, 
 Shortly After the Evacuation of a Generation of Spermat- 
 osomes. X 420. 
 
 The figure still shows some spermatosomes, which lie between the 
 innermost layers of spermatids and several layers of spermatogones; 
 between the latter and partly also between the spermatocytes are seen 
 the nuclei of the Sertoli cells; all cells are in the resting state. Out- 
 side is seen the membrane of the tubules, with flattened nuclei. 
 
 Fig. 2.— A Spermatoblast under Higher Magnification. 
 X 500. 
 
 Fig. 3. — Portion of a Seminal Tubule, in which the Trans- 
 formation of the Spermatids into Spermatosomes is Going 
 on. X -120. 
 
 The spermatids are elongated, their nuclei are small, rich in chro- 
 matin and excentric, but they have no connection with the Sertoli 
 cells. 
 
 Fig. 4. — Portion of a Seminal Tubule in the Stage of Sper= 
 matoblasts. X 420. 
 
 The maturing spermatosomes with the Sertoli cells form complexes 
 called spermatoblasts. Otherwise we find only spermatocytes and 
 spermatogones. 
 
 Fig. 5. — Portion of a Seminal Tubule in the Stage of Di- 
 vision of the Spermatocytes. X 420. 
 
 The spermatoblasts are present. The spermatocytes are seen partly 
 in mitotic division and partly already divided. 
 
 Reference letters for Figs. 1,3, 4, and 5: h, Connective-tissue sheath; 
 mi, mitoses in spermatocytes; spbl, spermatoblasts; spc, spermatocytes; 
 spg, spermatogones; spi, spermatids; sptz, spermatozoa; sZ, Sertoli's 
 cells. 
 
 As the elongated cell-bodies of the spermatids do not en- 
 tirely fuse with the spermatoblast, this structure presents 
 toward the lumen peculiar processes corresponding to the 
 elongated cell-bodies of the spermatids. In this proto- 
 plasm the nuclei of the spermatids undergo the entire 
 transformation into the heads of the spermatosomes, while 
 at the same time the centrosomes of the spermatids form 
 the middle piece of the spermatosomes. The contractile 
 tail filaments develop from the protoplasm of the sperma- 
 tids and probably also in part from that of the spermato- 
 
Tab. 54. 
 
 am «. <■ . ^ ' 3 * ®® 
 
 ^ <: « ® c *- * ® r, * c* * ® « ® 
 
 4{ 
 
 QSfe ' 
 
 
 i » 
 
 *«8> 
 
 fei ® f>cFi(j.l. 
 
 W 
 
 Eig.2. 
 
 @ * 
 
 spb? 
 
 y ».''■'...- -•s /? ^ 
 
 V2B 
 
 §fc #® 
 
 
 «L ® T i % 
 
 
 
 b ^~ 
 
 tty.4. 
 
 Fig.J. 
 
 , ; * v 
 
 
 «v-V/*' 
 
 ^'# <3-ij «® . 
 
 m 
 
 ■spec' 
 
 .ns *&? 
 
 <$& 
 
 m, 
 
 Fiff.S. 
 
 Lith. Anst E Reichlwld, Uiinxhen, 
 
TESTIS. 179 
 
 blasts. The greater portion of the protoplasm of the 
 spermatoblasts is not used in the formation of the spermat- 
 osomes, but breaks up in the lumen of the tubule after 
 these have entirely matured and been set free. 
 
 With the maturing of the spermatosomes and their 
 extrusion into the lumen of the tubules, their union 
 with the spermatoblasts ceases and the Sertoli cells re- 
 turn to the resting state, later to enter into connection 
 with new generations of spermatids and form spermato- 
 blasts. As the secretion of the testis consists of cells 
 arising from the transformation of the epithelial cells of 
 the convoluted tubules of the testis, the cells thus used 
 must be replaced by the division of the remaining cells. 
 This is done by the mother sperm-cells, which are again 
 regenerated by the spermatogones. 
 
 The spermatogones lie between the Sertoli cells and the 
 periphery of the tubule ; they are quite small round cells 
 with nuclei rich in chromatin. By division of a sper- 
 matogone there are formed two daughter cells, one of 
 which retains the position of the spermatogone near the 
 wall of the tubule and remains a spermatogone ; the other 
 daughter cell, which is situated toward the interior of the 
 tubule, becomes a mother sperm-cell or spermatocyte, and 
 increases considerably in size. 
 
 The spermatocytes are large round or polygonal cells, 
 with large nuclei, which show a distinct network of 
 chromatin fibers. They lie in one or two layers between 
 the spermatids and spermatogones. By means of two 
 mitotic divisions, which succeed each other with slight 
 intermission, they produce a generation of much smaller 
 cells, the above-described spermatids, which are in several 
 layers. It may therefore be seen that the convoluted 
 tubules of the testis have a different appearance, according 
 to the stage of spermatogenesis. It may be stated that in 
 many vertebrates, and especially in certain of the lower 
 vertebrates, the processes of spermatogenesis can be ob- 
 served much more distinctly than in man. 
 
180 the male reproductive organs. 
 
 Plate 5;.— Epididymis. 
 
 Fig. 1. — Portion of a Transverse Section of the Epididymis. 
 
 X80. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the cross-sections of the ductuli efierentes testis. 
 
 Teclmic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: bdg, Connective tissue; m, muscularis; x, crypts 
 of epithelium. 
 
 Fig. 2.— Portion of Transverse Section of the Epididymis. 
 X80. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the convoluted ductus epididymidis cut several 
 times. 
 
 Teclmic: Zenker's solution. Carmin-hematoxylin-eosin. 
 
 Reference letters: bdg, Connective tissue; c, capillaries; ep, epithe- 
 lium; L, lumen; Ic, leukocytes; m, muscularis; mp, membrana propria; 
 X, portions of the canal cut tangentially. 
 
 The tnbuli seminiferi contorti pass directly into the 
 tubuli recti and the rete testis. The tubuli recti are very- 
 small canals, lined by cubic or pavement cells in a single 
 layer. The tubuli recti unite to form a tubular network, 
 situated in the mediastinum testis and known as the rete 
 testis. The anastomosing tubules or spaces of the rete 
 testis are lined by a non-ciliated flattened or cubic epithe- 
 lium. From the tubular network arise from twelve to 
 fifteen tubules, the vasa efferentia, which pass to the globus 
 major of the epididymis. 
 
 The blood-vessels of the testis form dense capillary net- 
 works around the tubuli contorti. Numerous lymph- 
 canals are found especially under the tunica albuginea. 
 
 The nerves of the testis are non-medullated sympathetic 
 fibers, whose manner of ending has not yet been fully 
 determined, although they have been traced to the walls 
 of the tubuli contorti. 
 
 THE EFFERENT SEMINAL PASSAGES. 
 
 The tubules of the epididymis, comprising the vasa 
 effercntia and ductus epididymidis, the vas deferens, the semi- 
 nal vesicle, the prostate and urethra (see page 174), together 
 
Tab.SS. 
 
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THE EFFERENT SEMINAL PASSAGES. 181 
 
 with the smaller and larger glandular structures, belong 
 to the efferent seminal passages. The vasa efferentia are 
 large canals and are lined with two kinds of epithelial 
 cells ; the .cells of one variety are of relatively high col- 
 umnar shape ; of the other, low cubic. The cubic cells 
 lie between groups of the columnar cells, so as to form 
 intra-epithelial crypts. These crypts are regarded as 
 intra-epithelial glands. The columnar cells are usually, 
 though not always, ciliated, making the crypts appear still 
 deeper. The epithelium is surrounded by a single layer 
 of smooth muscle-cells and a thin layer of connective tissue. 
 The vasa efferentia unite to form the ductus epididymidis, 
 M'hich is much convoluted in the body of the epididymis 
 and is lined by a stratified ciliated epithelium, consisting 
 of two layers of cells (see page 31). 
 
 The layer of cells lying next to the lumen consists of 
 very high, narrow, cylindric cells, whose nuclei alternate 
 — that is, are at different levels. They bear long whip- 
 like cilia, each cell having but a small number. The cells 
 of the lower layer are spheric or somewhat flattened cells 
 (see Plate 3, Fig. 3). 
 
 Outside of the membrana propria there is found a rela- 
 tively thin layer of non-striated muscle-cells, which is 
 usually much more distinct in the lower portion of the 
 epididymis, and especially at the transition into the vas 
 deferens, than in the upper portion. 
 
 The vas deferens is a long canal with relatively nar- 
 row lumen, and especially well-developed muscular walls. 
 Its epithelium is similar to that of the ductus epididymidis, 
 consisting of a two-layered stratified ciliated epithelium. 
 It is seldom, however, that the ductus deferens is ciliated 
 throughout. Attention may here be drawn to the fact that 
 the epithelium of the seminal ducts, like much of the 
 epithelium of the seminal passages, undergoes manifold 
 variations. The mucosa, which can scarcely be separated 
 from the submucosa, contains no glands, but many elastic 
 fibers. The muscularis is very well developed and forms 
 
182 THE MALE REPRODUCTIVE ORGANS. 
 
 PLATE 56.— SEMINAL PASSAGES, SPERMATIC CORD. 
 
 Fig. 1.— Transverse Section of the Lower Portion of the 
 Vas Deferens of Man. X 25. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the lamination of the wall of the 
 seminal duct in the neighborhood of its opening into the prostate. 
 
 Technic: Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters: aim, External longitudinal layer of muscle; ep, 
 epithelium; g, blood-vessels; Urn, inner longitudinal layer of muscle; 
 L, lumen j, m, circular layer of muscle; ta, tunica ad ventitia. 
 
 Fig. 2. — Transverse Section of the Spermatic Cord of Man. 
 
 xio. 
 
 The preparation was taken from the spermatic cord of a man who 
 had been executed. 
 
 The figure shows the spermatic cord without its sheaths, also the 
 ductus deferens, the plexus venosus pampiniformis, arteries and 
 nerves. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: a, Arteries; del, transverse section of the seminal 
 duct, with highly developed external longitudinal muscular layer; F, 
 adipose tissue; m, nerves; v, muscular veins; x> valves of a vein. 
 
 nearly nine-tenths of the entire thickness of the wall. Its 
 lamination varies in the course of the duct. At first, in 
 the neighborhood of the epididymis, there is an inner 
 longitudinal, a middle circular, and an outer longitudinal 
 layer. In the terminal portion, a thin inner circular 
 layer is added and the other layers are often not so dis- 
 tinctly separated. The external connective-tissue sheath 
 of the ductus deferens contains many blood-vessels arid 
 also sympathetic nerves. In the region of the spermatic 
 cord we find, in addition to the ductus deferens, the veins 
 of the -pampiniform plexus ; these veins have a thick mus- 
 cle coat and contain valves. In the cord are also found 
 branches of the internal and external spermatic arteries 
 and the fibers of the cremaster muscle. 
 
 The ampulla of the ductus deferens, the seminal vesi- 
 cle, and the ejaculatory duct present essentially the same 
 structure. The non-ciliated columnar epithelium of the 
 seminal vesicles frequently contains pigment granules. 
 Besides the macroscopic folds of the muscular walls of the 
 seminal vesicles, the mucous membrane shows many micro- 
 
THE EFFERENT SEMINAL PASSAGES. 183 
 
 seopic folds, which form smaller and larger diverticula of 
 the mucous membrane. In addition to these, there are in 
 the poorly differentiated submucosa larger and more richly 
 branched diverticula and also branched tubular glands. 
 The musculature of the seminal vesicle is irregularly 
 arranged, but it contains mostly circular fibers. In the 
 neighborhood of the human seminal vesicles we often find 
 small sympathetic ganglia of the myospermatic plexus. 
 The secretion of the seminal vesicle is mucous. It usually 
 contains no spermatozoa. In many animals, especially 
 rodents (mouse, rat, guinea-pig), the secretion of the sem- 
 inal vesicle is ejaculated after the evacuation of the semen. 
 It consists of a mass which soon solidifies and closes the 
 vagina as a vaginal plug for about twenty-four hours. 
 These animals have very highly developed seminal vesicles. 
 
 The prostate is an organ composed of glandular tissue, 
 a relatively large amount of non-striated muscle, and a 
 relatively small amount of connective tissue ; it surrounds 
 the beginning of the urethra. The glandular part of the 
 prostate consists of a number of branched tubular or tubulo- 
 alveolar glands, opening into the urethra by separate 
 excretory ducts ; these have a relatively large lumen and 
 are lined by columnar or cubic epithelial cells. These 
 cells resemble the serous cells of the salivary glands more 
 than they do the mucous cells. Especially at advanced 
 age the enlarged lumina of the prostate gland contain strati- 
 fied concretions of a brownish color, the so-called prostatic 
 calculi. Between the separate glands and between the 
 alveoli of the glands, many smooth muscle-fibers are 
 found separated by a small amount of connective tissue. 
 
 The glandula bulbourethralis, or Cowper's gland, is 
 tubulo-alveolar, as its terminal compartments are partly 
 tubular and partly saccular. Like the smaller glands of 
 the urethra, it contains cells which resemble the mucous 
 cells of the salivary glands. Its excretory duct opens into 
 the membranous portion of the urethra. 
 
 The epithelium of the male urethra varies in the different 
 
184 THE MALE REPRODUCTIVE ORGANS. 
 
 PLATE 57.— URETHRA, SEMINAL VESICLE. 
 Fig. 1.— Transverse Section of the Pars Membranacea of 
 the Male Urethra. X 18. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the structure of the male urethra 
 under low magnification. 
 
 Technic: Miiller's fluid-formalin. Hematoxylin-eosin. 
 
 Reference letters: bg, Blood-vessels of mucous membrane (veins); 
 ep, epithelium; gl, urethral glands (Littre); they lie partly in the 
 submucosa (at the left) and partly in the museularis; hn, longitudinal 
 muscle; L, lumen; rm, circular muscle; tp, tunica propria or mucous 
 membrane. 
 
 Fig. 2. — Transverse Section of the Upper End of the Human 
 Seminal Vesicle. X 12. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure represents a slightly magnified general picture. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: bg, Blood-vessels in the adventitial connective 
 tissue; ep, epithelium; gl, gland-like crypts of the mucous membrane; 
 L, lumen; M, museularis; S, secretion retracted from the wall by 
 shrinking; tp, tunica propria or mucous membrane. 
 
 portions. The beginning — to the opening of the ejacula- 
 tory ducts — has still the transitional epithelium of the eifer- 
 ent urinary passages. The remaining portion of the male 
 urethra has generally stratified columnar epithelium, while 
 the terminal portion, the fossa navicularis, is lined by 
 stratified pavement epithelium, similar to the epithelium 
 of the glans penis. 
 
 PLATE 58.— PROSTATE. 
 Fig. 1. — Portion of a Transverse Section of the Prostate of 
 an Adult. X 45. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the prostatic gland tubules of very different size 
 and width, within a tissue which is very rich in smooth muscle-fibers 
 and relatively poor in connective tissue. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: ts, Gland tubules; m, musculature. 
 
 Fig. 2.— Portion of the Wall of a Distended Urinary 
 Bladder of a Frog. X 80. 
 
 The figure shows the reticular arrangement of the smooth muscle, 
 with connective-tissue cells lying between. The epithelium is absent. 
 
 Technic: Filling of the bladder with a solution of potassium chro- 
 mate. Penciling off the epithelium. Hematoxylin-eosin. 
 
 Reference letters: glm, Smooth muscle-tibers; bz, connective-tissue 
 cells. 
 
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OVARY. 185 
 
 The mucous membrane of the male urethra in the pars 
 membranacea and cavernosa is rich in elastic fibers and, 
 like the submucosa and the adjacent parts of the muscu- 
 laris, contains many wide veins, which form plexuses. 
 Mucous membrane and submucosa are quite intimately 
 connected, since there is no muscularis mucosae. The 
 submucosa contains branched tubulo-alveolar glands, small 
 mucous glands, known as the glands of Littre. 
 
 The musculature of the urethra consists of two not very 
 distinctly separated layers of non-striated muscle, a thinner 
 inner longitudinal layer and a thicker external circular 
 layer. In the prostatic and membranous portions, striated 
 muscle-fibers from the musculus transversus perinei pro- 
 fundus are added. 
 
 The penis consists essentially of the three cavernous 
 bodies: the two corpora cavernosa and the corpus spongi- 
 osum containing the urethra. The corpora cavernosa 
 have a strong connective-tissue sheath, the tunica albu- 
 ginea, and within this a meshwork of connective-tissue 
 septa, in which are found non-striated muscle-fibers. The 
 meshes are blood sinuses, into which, without changing into 
 capillaries, the arteries of the penis open. The tunica 
 albuginea of the corpus spongiosum is not so well devel- 
 oped as that of the corpora cavernosa. In the corpus 
 spongiosum, arteries open into the blood spaces of the 
 meshes by means of capillaries. Otherwise the structure 
 is the same as that of the corpora cavernosa of the penis. 
 The skin of the glans penis, as well as the mucous mem- 
 brane of the urethra, contains free nerve-endings and also 
 endings in the genital corpuscles. 
 
 VIII. THE FEMALE REPRODUCTIVE ORGANS. 
 
 The ovary is a gland having no direct excretory duct 
 (see page 39). In comparison with the ovaries of many 
 animals, the human ovary is very rich in connective tissue, 
 
186 THE FEMALE REPRODUCTIVE ORGANS. 
 
 PLATE 59.— OVARY. 
 
 Fig. 1. — Transverse Section through the Cortex of a 
 Human Ovary. X 50- 
 
 The preparation was taken from a fifteen-year-old girl (Professor 
 K. W. Zimmermann, of Bern). 
 
 The figure shows in the outer zone of the cortex numerous primor- 
 dial follicles and deeper in the tissues a larger Graafian follicle. 
 
 Eeference letters: A, Tunica albuginea; ep, follicular epithelium; 
 fp, primordial follicles; ov, ovulum in the discus proligerus; the, theca 
 externa folliculi; thi, theca interna folliculi with blood-vessels. 
 
 Fig. 2.— The Ovum, a Portion of the Discus Proligerus of 
 Fig. 1 under Higher Magnification. X 300. 
 
 The figure shows the ovum with i(g nucleus, the germinal vesicle, 
 surrounded by the zona pellucida, within the epithelial cells of the 
 discus proligerus, part of which show mitoses. 
 
 Eeference letters: Oo, Zona pellucida; Kf, germinal spot. 
 
 so that in comparison with the well-developed stroma of 
 the albuginea and of the cortex, the parenchyma formed 
 by the ovarian follicles is not prominent. The cortical 
 substance of the ovary is surrounded by a firm fibrous con- 
 nective-tissue albur/inea consisting of a felt-work of con- 
 nective-tissue bundles. In the cortex is found the paren- 
 chyma of the ovary. The medullary substance lies in the 
 neighborhood of the hilus ovarii and contains the blood- 
 vessels entering the organ, especially many veins. The 
 surface of the ovary is covered by peritoneum in such a 
 way that the connective tissue of the latter fuses with the 
 stroma of the ovary, while the peritoneal epithelium, in 
 the form of low columnar or cubic cells, covers the sur- 
 face of the organ. It is seen most distinctly in this form 
 in the ovary of the new-born and is known as germinal 
 epithelium, since from it the entire parenchyma of the 
 ovary is developed. The cortical substance of the ovary 
 contains numerous bundles of connective tissue which 
 connect with the albuginea. Between them lie the ovarian 
 follicles, so-called Graafian follicles, in various stages of 
 development, the youngest being nearest to the tunica 
 albuginea. The number of fully developed follicles is 
 always small. 
 
Tab. 59. 
 
 
 
 W* 
 
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OVARY. 187 
 
 The process of development of ova and ovarian follicles 
 may be recognized in the new-born and for some time 
 after birth. Some cells of the germinal epithelium of the 
 surface of the ovary increase in size by growth of the cell- 
 body, until they attain a relatively large size and spheric 
 form. Such cells are known as primordial ova or primary 
 eggs. Generally, several primordial ova are inclosed by 
 germinal epithelial cells, forming a plug-like growth of 
 the germinal epithelium, which penetrates the cortical sub- 
 stance and constitutes the egg-balls or egg-nests, so-called 
 Pfiiiger's tubes. Pfliiger's tubes, or the egg-nests, are not 
 hollow, but solid structures. Within the egg-nests each 
 primordial egg is surrounded by a single layer of flat to 
 cubic cells, the follicular cells, and a. primordial or primary 
 follicle is thus formed. The primordial follicles lie in 
 large numbers close under the albuginea in the outer layer 
 of the cortex. The further development goes on from 
 these to the mature Graafian follicles, the older and larger 
 follicles being pushed deeper into the cortical substance, 
 and thus nearer to the limits of the medullary substance. 
 
 The growth of the ovarian follicle proceeds in the fol- 
 lowing manner : There is first a proliferation of ike epi- 
 thelial cells of the follicle, the egg-cell being in this way 
 surrounded by several layers of cells. At the same time 
 a connective-tissue sheath from the ovarian stroma is 
 formed around the entire follicle, known as the theca fol- 
 liculi. As the ovum develops, it becomes surrounded by 
 a structureless or radially striated sheath, the zona pellu- 
 cida. The zona pellucida very probably arises from the 
 ovum itself and is to be regarded as a cell membrane. In 
 many animals — whether in man is doubtful — the outer 
 portion of it appears to be formed by the adjacent portions 
 of the follicular epithelium. 
 
 In the further growth of the ovarian follicle and with 
 further proliferation of the follicular epithelium there is 
 an excretion of fluid on the part of the follicular epithe- 
 lium, the liquor folliculi. This forms between the cells in 
 
188 TBE FEMALE REPRODUCTIVE ORGANS. 
 
 Fig. 56. — Graafian follicle of the ovary of the mouse in different 
 stages of- development. X 200. The figure shows the proliferation 
 of the epithelium and the formation of the liquor follieuli. e, Yolk 
 nucleus (centrosome); E, ovum; ef, follicular epithelium; Jc, nucleus 
 of ovum ; If, liquor follieuli ; thf, theca follieuli. 
 
 Fig. 57. — Portion of a cross-section through a fully developed cor- 
 pus luteum of a mouse. X 375. The figure shows the relation of the 
 hypertrophied epithelial cells to the blood capillaries and connective- 
 tissue cells, c, Capillaries; ep, epithelial cells of the corpus luteum; 
 Jcbdg, connective-tissue nuclei. 
 
 Fig. 58. — Small portion of a cross-section through an older corpus 
 luteum of a mouse. X 600. The epithelial cells contain fine fat 
 droplets, blackened by osmic acid. 
 
 one place or at the same time in several places of the fol- 
 licular epithelium, so that now the follicle assumes the 
 form of a vesicle. In this process the ovum is generally 
 crowded toward one wall by the collection of fluid. 
 
 The follicular epithelium generally consists of polygonal 
 cells ; only the outer cells bordering on the theca follieuli 
 and those next to the ovum, especially the cells lying next 
 to the zona pellucida, are columnar. The latter constitute 
 the corona radiata ; the mass of epithelial cells surround- 
 ing the ovum are called the discus proligerus. On the 
 rupture of the follicle these are evacuated with the ovum. 
 The theca follieuli of larger follicles has an outer fibrous 
 and an inner cellular layer, containing fat granules. The 
 ovary of many animals contains a large-celled interstitial 
 tissue, the cells of which resemble those of the inner layer 
 of the theca follieuli and may be mistaken for them. 
 
 While the ripening follicles push toward the inner 
 portion of the ovary as their development proceeds, the 
 follicles which have become markedly distended by the 
 collection of fluid again pass toward the surface, a part of 
 their wall touching the tunica albuginea and the surface of 
 the ovary, and thus occupy the entire thickness of the cor- 
 tical substance. "When the attenuated follicular wall rup- 
 tures, there is a laceration of the surface of the ovary, 
 which later heals by the formation of scar tissue. 
 
 After the rupture of the follicle its walls collapse. The 
 
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OVARY. 189 
 
 follicular epithelium which remains within the follicle 
 hypertrophies, the cells attaining many times their original 
 size. At the same time processes of connective tissue from 
 the theca folliculi containing blood-vessels penetrate be- 
 tween the epithelial cells. The structure which thus de- 
 velops is known as the corpus luteum, because its cells con- 
 tain a yellowish pigment known as lutein and are therefore 
 designated as lutein cells. Later the structure degenerates, 
 the epithelial cells (lutein cells) undergo fatty degeneration, 
 and the connective-tissue trabecular become atrophied, and 
 thus the corpus albicans is formed. On the rupture of the 
 follicle hemorrhages often take place on account of the 
 laceration of the blood-vessels. The remains of such hem- 
 orrhages are found in the form of hematoidin crystals. 
 The process of rupture of the follicle and formation of the 
 earlier stages of the corpus luteum has never been observed 
 in the human ovary. 
 
 The fully developed follicular ovum is a large, almost 
 perfectly spheric cell, which in the human ovary has a 
 diameter of about 250 [i. Its diameter, however, cannot 
 be ascertained with any degree of certainty, since mature 
 human ova — that is, after extrusion from a follicle — have 
 never been observed. 
 
 In mammalia its protoplasm contains, in varying, but 
 usually in small amount, fat-like constituents, known as 
 deutoplasm; this is found especially in the central portion 
 of the ovum. 
 
 The nucleus of the maturing ovum is spheric and gen- 
 erally contains a large nucleolus. The nucleus of the 
 ovum has long borne the name of the germinal vesicle, and 
 the nucleolus that of the germinal spot. The maturing ova 
 of mammalia, and also the human ova, contain, outside of 
 the nucleus, another small structure, the so-called yolk- 
 nucleus. It represents essentially the rudimentary centro- 
 some, which usually degenerates in the ovum before the com- 
 plete maturity of the cell is reached. In the maturation 
 of the ovum a short time before it is expelled from the 
 
190 the female reproductive organs. 
 
 Plate 60.— Ovary, Oviduct. 
 
 Fig. 1. — Transverse Section of the Uterine End of the 
 Human Oviduct. X 30. 
 
 The preparation was taken from a twenty-one-year-old woman. 
 
 The figure gives a general view of the structure of the oviduct in 
 close proximity to the uterus. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: A, Artery; L, lumen; m, circular layer of muscle; 
 tp, tunica propria; Im, longitudinal bundles of muscle; I", veins. 
 
 Fig. 2. — Portion of a Transverse Section of the Ovary of 
 a New=born Child. X 280. 
 
 The preparation was taken from a still-born child. 
 
 The figure shows very distinctly primordial ova in the germinal 
 epithelium, Pfluger's tubes, and groups and masses of primordial fol- 
 licles. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: e, Capillaries; ke, germinal epithelium; air, 
 stroma; fp, primary follicles; op, primordial ova. 
 
 ovary, the nucleus withdraws to the surface of the cell and 
 there passes through all the phenomena of mitosis (see 
 page 22). A spindle figure is formed and finally the cell 
 divides in such a way that the egg-protoplasm is divided 
 very unequally into a large egg-cell and a small cell, the 
 so-called first polar body. 
 
 Many of the primordial follicles formed in the ovary de- 
 generate ; and this takes place either in the earlier or later 
 stages of maturation or the ripe follicles fail to rupture and 
 degenerate. The former process is called atrophy and the 
 latter atresia of the follicles. In both cases, with certain 
 variations, the epithelium degenerates, and finally the egg- 
 cell also. The latter often shows peculiar degeneration 
 phenomena, which may be confused with an apparent 
 division. The zona pellucida is retained the longest. 
 
 The arteries of the ovary enter from the hilus of the 
 organ and form dense capillary plexuses in the theca of the 
 follicle, especially around the egg-nests. The vein* form a 
 plexus-like enlargement in the medullary substance. The 
 lymph-vessels have a similar arrangement. 
 
 The nerves of the ovary arise from the sympathetic, but 
 their manner of ending has not been fully determined. 
 
im 
 
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THE OVIDUCT, UTERUS, AND VAGINA. 191 
 
 THE OVIDUCT, UTERUS, AND VAQINA. 
 
 The oviduct lias a mucous membrane which is slightly 
 folded in the uterine portion, while in the ampullar portion 
 the folds are very high and branched. These are covered 
 by a simple columnar ciliated epithelium. The mucous 
 membrane is rich in lymph-cells, and, on account of the 
 want of a muscularis mucosae, it is poorly differentiated 
 from the submucosa. There are no glands in the oviduct, 
 but in the ampulla there are deep, branched crypts. The 
 musculature of the oviduct consists of a thick inner circular 
 layer of non-striated muscle and a thinner external longi- 
 tudinal layer. To these are added a serosa and a sub- 
 serosa. 
 
 The wall of the uterus has similar layers. We dis- 
 tinguish the mucous membrane, or endometrium, which, un- 
 like that of the oviduct, contains tubular glands (a sub- 
 mucosa is wanting), the muscidaris, and the serosa, which is 
 attached directly to the muscle without any subserosa. The 
 epithelium of the uterus is a simple ciliated columnar epithe- 
 lium. In the body of the uterus it is low columnar, as in the 
 oviduct, but in the cervix uteri the cells are considerably 
 higher. The mucous membrane of the entire uterus is 
 rich in lymph-cells and resembles a diffuse adenoid tissue 
 (compare page 53). Its entire thickness is filled with 
 simple tubular glands, which are either almost unbranched 
 tubules, much convoluted at their blind ends, or they 
 divide at acute angles and may anastomose with each other. 
 These are the uterine glands. They are lined with the 
 same kind of epithelium as lines the surface of the uterus. 
 The musculature of the uterus is bounded immediately by 
 the mucous membrane and is firmly united with it. It 
 consists practically of circular muscle. However, the 
 arrangement of its elements is by no means regular, as 
 very numerous oblique bundles are found beside and be- 
 tween the circular bundles. Moreover, the large blood- 
 vessels lying in this main muscle layer of the .uterus dis- 
 
192 the female reproductive organs. 
 
 Plate 6i.— Uterus. 
 
 Fig. 1. — Transverse Section of the Body of the Human 
 Uterus. X 3. 
 
 The figure gives a general view of the layers of the uterine wall. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Keference letters: g, Blood-vessels of the broad ligament and of the 
 uterine wall; I, lumen of the uterus; 11, broad ligament; Im, longi- 
 tudinal layer of muscle; to, circular layer of muscle; s, serosa; tp, 
 tunica propria, mucous membrane with the glands. 
 
 Fig. 2.— Transverse Section of the Mucous Membrane of 
 the Uterus. X 150. 
 
 The preparation was taken from a twenty-year-old nullipara. Fixed 
 eighteen hours after death. 
 
 The figure shows the lymphoid tissue in the mucous membrane, 
 with the large, convoluted, branched, and anastomosing glands. The 
 muscle layers follow directly upon the mucous membrane. 
 
 Reference letters: ep, Epithelium; gl, uterine glands; if, muscula- 
 ture ; x , uterine glands cut tangentially. 
 
 turb the arrangement to a certain extent. The external 
 longitudinal muscle layer, which is well developed in most 
 mammalia and- even in the ape, is in the human uterus re- 
 duced to a thin layer running in the anterior and posterior 
 surfaces of the organ. The cervical canal is lined by an 
 epithelium which resembles that found in the body of the 
 uterus, although the cells are more slender and much 
 higher. This ciliated epithelium usually extends to the 
 external os, although the stratified vaginal epithelium may 
 penetrate the canal for a distance. In addition to the 
 uterine glands, which are generally present in small num- 
 bers in this region, there are also found the cervical glands, 
 which are mucus-secreting glands. These glands often 
 contain mucus plugs, forming the so-called ovula Nabothi. 
 Here there are many individual differences. The longi- 
 tudinal layer of muscle is more strongly developed than in 
 the body of the uterus. 
 
 The blood-vessels of the uterus enter the uterus from 
 both sides with the peritoneum (ligamentum latum). The 
 vessels in the uterine wall send branches toward the main 
 
Im 
 
 
 • 
 
 ~lm 
 
 figf.1. 
 
 Fig.S. 
 
THE SUPRARENALS. 193 
 
 musculature. 1 From these the distribution proceeds to the 
 vessels supplying the musculature as well as those supply- 
 ing the mucous membrane. There are many lymph-ves- 
 sels in the uterus, in the mucous membrane, as well as in 
 the musculature. As in the intestine, the larger vessels 
 are found in the serosa. 
 
 The nerves of the uterus are for the most part the neu- 
 raxes of sympathetic neurones supplying the muscle. It 
 seems very probable that there are cerebro-spinal nerves, 
 the branches of which go to the mucous membrane and end 
 between the epithelial cells. 
 
 The vagina is lined by stratified pavement epithelium. 
 The mucous membrane presents papillse, contains no glands, 
 but sometimes has lymph-nodes. A submucosa is present, 
 but is not distinctly differentiated. The musculature con- 
 sists of smooth muscle-fibers, which form an inner circular 
 and an outer longitudinal layer. 
 
 The external female genital organs are in structure 
 partly like the vaginal mucous membrane and partly like 
 the skin. The region of the clitoris and the labia minora 
 contain many sebaceous glands. In the region of the 
 urethral opening mucous glands are found (glandulse vestib- 
 ulares minores). The glandula vestibularis major, or 
 gland of Bartholin, is quite similar in structure to the 
 glandula bulbo-urethralis of the male (see page 183). 
 
 THE SUPRARENALS. 
 
 Although the medullary substance of the adrenal ap- 
 pears to be intimately related to the sympathetic nervous 
 system, the entire organ, according to more recent investi- 
 gations, is probably to be considered histogenetically in the 
 urogenital apparatus. 
 
 1 The relation of the blood-vessels to the uterine musculature has 
 given rise to an entirely unwarranted classification of the uterine mus- 
 culature into a stratum vasculare, supravascujare, and infravasculare 
 pr submucosum. 
 13 
 
194 the female reproductive organs. 
 
 Plate 62.— Suprarenals. 
 
 Fig. 1. — Portion of a Transverse Section of the Human 
 Suprarenal. X 15. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general picture of the larger portion of the 
 adrenal. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters for Figs. 1 and 2: c, Capillaries of medullary sub- 
 stance; cf, capsula fibrosa; gz, ganglion-cells; », non-medullated nerve- 
 fibers; sc, cortical substance; sm, medullary substance; v, veins of 
 medullary substance; zf, zona fasciculate of the cortical substance; 
 zg, zona glomerulosa of the cortical substance ; zr, zona reticularis of 
 the cortical substance. 
 
 Fig. 2. — Transverse Section through the Cortex and Me= 
 dull?, of a Suprarenal of Man. X 80. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the subdivisions of the cortical substance, the 
 cords of cells, the nerves and blood-vessels of the medullary sub- 
 stance. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 The parenchyma of the adrenal consists of two distinctly 
 separated portions, the cortical and the medullary sub- 
 stance. In general the cortical substance forms the main 
 mass of the organ, the medullary substance being well 
 developed only in the central portions. The organ is sur- 
 rounded by a connective-tissue capsule, which sends pro- 
 cesses into the interior. 
 
 The cortical substance consists of radially arranged col- 
 umns of cells. From the capsule toward the medullary 
 substance we distinguish three zones : First, the zona 
 glomerulosa; in this the columns of cells appear as if 
 coiled up. Second, the zona fasciculata ; this represents 
 the greater portion of the cortical substance and shows 
 most distinctly the radial arrangement of the columns of 
 cells. Third, the zona reticularis, in which the columns 
 of cells become again irregular and anastomose in reticular 
 fashion. All the cells of the cortical substance are very 
 similar, of cubic or nearly spheric shape, and often con- 
 tain fat granules ; those of the deeper layers also usually 
 contain pigment granules. 
 
Tab.62. 
 
 i Mam* 
 
 v>-?>r 
 
 I 
 
 *. 
 
 
 1. 
 
 
 e^^sfe 
 
 ^iWSwia 
 
 
 
 if 
 
 
 %*'• ■'• . !: r'?.---*.. v .'-; /" .' , "*'---Y:.-' ■ '^.'-"' »,'-'..'"-.''<'*''"" , "/-'-".\f'.'v,;. ; v. '•. :':--- 
 
 
 ; ■."*'■■: '' ■'•' i', '■' ■:-" -'• •:i- ' '- ;;'- '-" t '.'.'■ ,~^-* <// 
 
 '™ " *. i ,w :. ' r'^ 
 
 
 *}?.*?. 
 
THE SUPRARENALS. 195 
 
 The medullary substance of the adrenals is not sub- 
 divided into zones, but presents throughout the same 
 structure. It consists of peculiar cells, which stain darkly 
 with chrome salts (also called chromaffin cells) and form 
 anastomosing chains. The cells are irregular polyhedral 
 to high columnar in form. The chains often border rela- 
 tively large vascular lumina or lymph clefts in such a way 
 that each generally oval cell of the medullary substance 
 in transverse section borders the vascular lumen with its 
 two narrow surfaces and the adjoining cells of the chain 
 with its two broader surfaces. 
 
 The connective-tissue framework of the adrenal consists 
 of a reticular connective tissue, the fibers of which run 
 parallel to the trabecule of cells in the cortex. The 
 adrenal is at the same time very rich in blood-vessels and 
 nerves and probably has intimate relations to both systems. 
 The blood-vessels form numerous capillaries in the cor- 
 tex as well as in the medulla of the adrenal. Those of 
 the cortex run in general parallel to the columns of cells 
 and between these, at least in the zona fasciculata and 
 reticularis, and in the outer cortical zone form small veins. 
 Besides capillaries, the medullary substance also contains 
 small arteries and especially many plexus-like veins, the 
 walls of which are rich in elastic fibers and often contain 
 thick adventitial bundles of smooth muscle-fibers. The 
 vessels of the medullary substance, especially its capil- 
 laries, lie in the spaces between the trabecular network 
 of medullary cells. The lyrnph-vessels of the adrenal are 
 likewise very abundant, especially in the medullary sub- 
 stance- 
 Numerous non-medullated nerve-trunks of the sympa- 
 thetic enter the adrenal. In their course within the adre- 
 nal they often show ganglion-celh in smaller or larger 
 groups and occasionally also circumscribed small ganglia. 
 The cortical substance is poorer in fibers and ganglion- 
 cells are not found here. The mode of ending of the 
 nerves has not been fully determined. 
 
196 TEE RESPIRATORY ORGANS. 
 
 PLATE 63— NASAL MUCOUS MEMBRANE. 
 
 Fig. 1.— Portion of a Transverse Section of the Olfactory 
 Region of Man. X 150. 
 
 The preparation was taken from a man who had been executed. 
 
 The section shows in cross-section a portion of the olfactory mucous 
 membrane from the superior turbinated bone. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Eeference letters: ep, Epithelium; 1, rod (hair) zone; 2, zone of 
 long nuclei; 3, zone of round nuclei; gl, olfactory glands; n, olfactory 
 nerve ; tp, tunica propria with blood-vessels. 
 
 Fig. 2. — Portion of a Transverse Section of the Lower 
 Half of the Nasal Wall, Respiratory Region. X 25. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the structure of the thick mucous membrane rich 
 in blood-vessels and glands and the adjacent portion of the bone. 
 
 Technic as in Fig. 1. 
 
 Eeference letters: Ac, Excretory duct of the gland; ep, epithelium; 
 gl, glands; K, hone; ip, tunica propria. 
 
 Occasionally accessory adrenals occur, most frequently in 
 the broad ligament of the uterus and in the neighborhood of 
 the epididymis. In this connection we should mention two 
 small structures of the human body, which are also rich in 
 blood-vessels and nerves — the carotid gland (glomus car- 
 oticum) and the coccygeal gland (glomus coccygeum). They 
 consist practically of capillary convolutions interspersed 
 with connective-tissue cells rich in protoplasm. According 
 to recent investigations, both types of glands are said to 
 take their origin from the vascular system. 
 
 IX. THE RESPIRATORY ORGANS. 
 
 THE NASAL CAVITY. 
 
 The mucous membrane of the nasal cavity is divided into 
 three portions, the vestibular, respiratory, and olfactory re- 
 gions. The vestibular region presents tlie structure of the 
 skin, with all its characteristics. 
 
 The respiratory region, the main portion of the nasal 
 mucous membrane, consists of a typical stratified ciliated 
 

 «*<&£ 
 
 Mff.l. 
 
 Eig.M. 
 
 Lith. Anst. /■■ ' ReicliJinUI . Miuicfu 
 
LARYNX, TRACBEA, AND BRONCHI. 197 
 
 columnar epithelium, which often contains goblet-cells, and 
 of a thick mucosa. The latter is connected to the periosteum 
 of the bone and the perichondrium of the cartilage without 
 the intervention of any submucosa. The mucous membrane 
 contains numerous simple branched tubular glands of mixed 
 character, containing both serous and mucous cells (see page 
 37). It is rich in blood-vessels, especially veins. The 
 accessory cavities of the nose present a relatively thin mu- 
 cous membrane, with few glands and a ciliated epithelium 
 in a single layer. 
 
 The mucous membrane of the olfactory region has a char- 
 acteristic epithelium, which is thicker than that of the res- 
 piratory region. Its upper layer especially consists of very 
 high columnar cells, showing no nuclei in the upper half. 
 The deeper layers are formed by spheric cells. Between 
 the high columnar epithelial cells are found the olfactory cells 
 (see page 238). The surface of the columnar cells shows a 
 border resembling a striated cuticular formation (cilia?). 
 The tunica propria of the olfactory region is not so thick as 
 in the respiratory region and contains a special kind of gl* 1 nvls, 
 simple tubular serous glands, which are but little branched 
 and are known as olfactory or Bowm&vi's glands. 
 
 The blood-vessels, especially the veins, are somewhat 
 less abundant than in th^ respiratory region. Numerous 
 bundles of non-medujffated olfactory nerves are found in 
 the mucosa under $ue olfactory epithelium. 
 
 LARYNX, TRACHEA, AND BRONCHI. 
 
 "With J^ e exception of the region of the vocal cords, the 
 free margin f the epiglottis, and a portion of the arytenoid 
 cartih^~ eS) -which are covered by stratified pavement epithelium, 
 th^i/mucous membrane of the larynx has stratified ciliated 
 e lKthelium like that of the respiratory region of the nasal 
 cavity and the upper portion of the pharynx. The tunica 
 P r 0bpria is unusually rich in elastic fibers, which form dense 
 
198 THE RESPIRATORY ORGANS. 
 
 PLATE 64.— TRACHEA. 
 Transverse Section of the Trachea of an Eight=year=oId 
 Boy. X 6J. 
 
 The figure gives a general picture of the structure of the trachea 
 and of the lamination of its walls. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters: ep, Epithelium ; gl, glands; Kn, cartilage; m, 
 muscularis; sin, submucosa; tp, tunica propria. 
 
 networks just under the epithelium, forming the membrana 
 elaslica. In other respects the mucous membrane of the 
 larynx has the same structure as that of the trachea. The 
 cartilages of the larynx are partly hyaline (thyroid, cricoid), 
 partly elastic (epiglottis), and partly mixed (arytenoid cartil- 
 ages) . 
 
 The trachea has a relatively thick mucous membrane, 
 which is rich in elastic fibers. The epithelium is stratified 
 ciliated columnar . Under the mucous membrane lies a 
 submucosa, which contains branched tubular glands of mixed 
 character, containing both mucous and serous cells. The 
 outer wall in the anterior three-fourths is formed of horse- 
 shoe-shaped hoops of hyaline cartilage ; in the posterior one- 
 fourth, by non-striated muscle. The glands are best devel- 
 oped in the posterior wall sad lie between or outside of the 
 muscle layer. 
 
 The large bronchi have the same^gtructure as the tra- 
 chea, except that they contain plates iu\gtead of hoops of 
 cartilage. 
 
 THE BRONCHIAL BRANCHES AND THE L\JNQS. 
 
 The large branches of the bronchi have the sam\struc- 
 ture as the trachea and the bronchi. The structure remains 
 essentially the same in the further branchings, with thVse 
 exceptions: The cartilages of the bronchi of medium; 
 size resemble elastic cartilage and no longer form half- 
 rings, but irregularly distributed plates. Cartilage plat, es 
 
Tab. 64. 
 
THE BRONCHIAL BRANCHES AND THE LUNGS. 199 
 
 are found in the bronchi until their caliber is 1 mm. The 
 non-striated muscle of the bronchi of medium size forms 
 a continuous layer of circularly arranged fibers ; this 
 layer becomes thinner as the caliber of the bronchi dimin- 
 ishes, but can still be followed beyond the limits of the 
 cartilage ; it lies within the cartilage plates. Besides this, 
 a change takes place in the epithelium of the bronchial 
 branches, so that the stratified ciliated epithelium is gradu- 
 ally reduced to a single layer (see Plate 66, Fig. 1). 
 
 The bronchi which have no cartilage, under 1 mm. in 
 caliber, are known as bronchioles. They still have a layer 
 of muscle and a single layer of cubic epithelium. 
 
 The bronchioles lead into the respiratory bronchioles and 
 these in turn into the terminal bronchioles or alveolar ducts, 
 the smallest terminal portions of the bronchial tree, which 
 serve partly for respiration. The terminal bronchioles are 
 characterized by the fact that their epithelium consists of 
 two kinds of cells: of small, round, nucleated cells, between 
 which large, flat, non-nucleated cells are found. The lat- 
 ter gradually appear in the shape of islands at the point of 
 transition from the bronchus into the respiratory portions 
 of the lung. Each terminal bronchus opens into three to 
 six nearly spheric spaces known as atria. Each atrium 
 opens into a number of irregular spaces known as air-sacs. 
 The air-sacs communicate with smaller spaces, the air-cells 
 or alveoli. Numerous alveoli are found on the wall of the 
 terminal bronchus. It contains a layer of non-striated 
 muscle. This layer of muscle does not extend beyond 
 the limits of the terminal bronchioles. The atria, air-sacs, 
 and alveoli are lined by flat, non-nucleated cells, among 
 which groups'of small, round, nucleated cells are found. 
 The alveolar wall is very thin, and, aside from the epithe- 
 lium, is formed by capillaries and a very small amount of 
 connective tissue and elastic fibers. The walls of neigh- 
 boring alveoli, especially their elastic tissue, fuse to form 
 alveolar sepia. By means of fine openings or pores in these 
 septa, neighboring alveoli communicate with each other. 
 
200 THE RESPIRATORY ORGANS. 
 
 Fig. 59. — Transverse section of a bronchiole of the human lung, 
 from the same preparation as Fig. 1, Plate 66. X 3*0. The figure 
 presents the transverse section of a small bronchial branch having 
 simple ciliated epithelium and no cartilaginous framework; in the 
 mucous membrane many elastic fibers are seen. 
 
 Fig. 60. — Portion of a thick cross-section of a human lung treated 
 with silver nitrate solution. X 160. The preparation was taken from 
 a man who had been executed. 
 
 In the preparation the cell boundaries of the epithelium are stained 
 black by the silver. The figure shows a respiratory bronchiole in its 
 branching from a smaller bronchial branch. The lower wall of the 
 bronchiole is seen, still lined by cubic epithelium. This is then grad- 
 ually broken up by islands of flattened cells. In the alveoli we see the 
 typical relation of the epithelium. A, Alveoli; brr, respiratory bron- 
 chiole; ep, cubic epithelium; ep u flattened epithelial cells; p, carbon 
 pigment. 
 
 The connective tissue which is present in very small 
 amount as interstitial tissue penetrates the lung along the 
 larger bronchial branches. Under the serous covering of 
 the lungs (pleura pulmonalis) it forms a thin layer and also 
 separates the several lobules of the lung — the lobuli pul- 
 monales — from each other. It often contains carbon pig- 
 ment which has been inspired M'ith the air. 
 
 The blood-vessels of the lung arise from the pulmonary 
 artery and the bronchial arteries. The latter supply the 
 walls of the bronchi, sending only relatively few branches 
 to the alveoli. The branches of the pulmonary artery 
 follow the course of the bronchi. They branch with these 
 and in the alveolar wall form a dense plexus of capil- 
 laries, which are especially large, so that the greatest part 
 of the surface of the alveolar wall and of its epithelium is 
 bounded by capillaries. The large, flat, non-nucleated 
 cells generally cover the capillaries ; the small round cells 
 lie in the spaces between the capillaries. From the capil- 
 laries arise the radicles of the pulmonary veins. 
 
 There are large numbers of h/mph-rcssels in the lungs. 
 They form two sets of vessels. The one is found in the 
 interlobular connective tissue and communicates with the 
 lymphatics of the pleura, where a rich plexus is found. 
 The deeper set accompanies the pulmonary artery j its 
 
4 
 
 
 
 Fip. 60. 
 
 epi ep 
 
THE THYROID GLAND. 201 
 
 vessels pass directly to the bronchial glands. Lymph- 
 glands are found at the hilus of the lung and nodules of 
 adenoid tissue along the larger bronchi and even on the 
 surface of the lung. 
 
 The nerves of the lung arise from the vagus and from 
 the sympathetic. Their mode of ending is not fully de- 
 termined. However, the final endings lie in the alveolar 
 walls, in the epithelium of the bronchi, and in the muscle 
 of the bronchi. Sympathetic ganglia are found in the 
 course of the nerves. 
 
 THE THYROID GLAND. 
 
 The thyroid gland may be considered here, although it 
 has only topographic relations with the respiratory system. 
 Originally it possesses an excretory duct system and is in 
 relation with the mouth by means of the ductus thyreo- 
 glossus. Later the duct is obliterated and the gland then 
 consists of the closed secreting compartments or alveoli. 
 The terminal compartments of the thyroid gland are short 
 branched tubules or alveoli. They are lined by a single 
 layer of columnar to cubic epithelium. The secretion of the 
 tubules or alveoli, called colloid, often fills their lumen com- 
 pletely and distends the walls to such an extent that the 
 epithelial cells lining them are flattened. The empty 
 tubules or alveoli therefore generally present the highest 
 epithelium. There is much evidence to show that the se- 
 cretion is taken up by the numerous lymph-vessels of the 
 gland. The thyroid contains numerous blood-vessels, which 
 form dense capillary networks around the tubules or alveoli, 
 likewise many lymph-vessels. Sympathetic nerve-fibers 
 terminate on the alveoli or tubules. 
 
 X. THE SKIN. 
 
 The skin is composed genetically of two main constitu- 
 ents : an ejnthelial tissue, the epidermis, and a connective 
 tissue, the cutis. Each of these consists of subdivisions. 
 
202 THE SKIN. 
 
 Plate 65.— Lungs. 
 
 Portion of a Transverse Section of a Human Lung, the 
 Blood-vessels of Which Have Been Injected with Blue Gela= 
 tin. X 100. 
 
 From material of the Wiirzburg Anatomical Institute. 
 
 The figure shows the cross-section of many alveoli, and in some 
 portions the surface of the alveolar wall is met. The latter is not 
 stained. 
 
 Eeference letters : a, Branch of pulmonary artery ; A, alveoli ; ca, 
 capillaries of alveolar wall seen from the surface ; s«, alveolar septa, 
 with the capillaries sectioned vertically; ti, interlobular interstitial 
 connective tissue; v, venous branch, the vena pulmonalis. 
 
 The epidermis is divided into four layers named from 
 without inward: (1) the stratum corneum; (2) the stratum 
 lucidum; (3) the stratum granulosum; (4) the stratum 
 germiuativum. 
 
 The stratum corneum consists of flat, horny, non-nucleated 
 cells, which in many places of the skin, for instance in 
 the palm of the hand, sole of the foot, are in many layers. 
 
 Plate 66.— Lung, Thyroid Gland. 
 
 Fig. 1.— Transverse Section of a Small Bronchial Branch 
 of the Human Lung, x 25. 
 
 The preparation was taken from a man who had been executed. 
 Prepared by Professor Braus, of Heidelberg. 
 
 The figure shows a small bronchus together with the • surrounding 
 lung tissue. The elastic fibers are stained dark violet. The muscula- 
 ture of the bronchial wall is so covered by the elastic fibers that it is 
 not visible uudei low magnification. 
 
 Technic: Zenker's solution. Weigert's elastic tissue stain. Alum- 
 carmin. 
 
 Reference letters: A, Alveoli; bg, blood-vessels; dgl, duct of bron- 
 chial gland; rp, epithelium; gl, mucous glands; n, transverse section 
 of a nerve; tp, tunica propria with elastic fibers; r, wall of a large 
 vein of the lung; Kn, cartilage. 
 
 Fig. 2— Portion of a Cross=section of the Thyroid Gland. 
 X 30. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the gland tubules of the thyroid gland, filled to 
 different degrees with the colloid substance. 
 
 Technic; Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters: bdg, Interstitial connective tissue; bg, blood- 
 vessels; C, colloid substance; is, gland alveoli. 
 
Tab.65. 
 
 Lith. Anst K Reichhoid. Munr.hm 
 
Fig.l. 
 
 bdt/ 
 
 
 
 ■O p^i ■ ■■ 
 
 *■■'-, /■■' V.'"*.V.\'""','-^ W ' ' -.--"--;' V. V. ; -■. . '■''■-"" "- \ '£ \'t"S7 ■'-".' X*i**i.'"^ 
 
 \ <■ i, \ ■ . , ■ ..■■■" 'f-,-.- -. . " r .*fc. ' -s'A 
 
 Fi(f£. 
 
 bff 
 
EPIDERMIS AND DERMIS. 203 
 
 The stratum lutidum can be differentiated distinctly only 
 when there is a strongly developed stratum corneum. It 
 consists of two, or at most three layers of flat, clear cells, 
 which are not yet completely cornified. It is not sharply 
 separated from the stratum corneum. The stratum granu- 
 losura also consists of two or three layers. It is especially 
 well developed in places in which the horny layer is well 
 developed. Its cells are flattened polygonal and contain 
 distinct, deeply staining granules known as keratohyalin 
 or eleidin granules 1 of irregular form and of different 
 size, which are to be regarded as the preliminary stages 
 of the horny substance, the keratin. The stratum germina- 
 tivum consists of many layers of cells, which are indented 
 by the papillae of the cutis, which lies below it. The cells 
 of the lowest layer, which lies next to the papilla, are 
 columnar, while the cells of the other layers are rounded 
 polygonal, except the upper ones which border upon the 
 stratum granulosum and, like the cells of this layer, are 
 flattened. The epithelial cells of the stratum germina- 
 tivum are connected by very distinct intercellular bridges 
 (see page 32), and on this account it is called the stratum 
 spinosum or dentatwm. The stratum germinativum fur- 
 nishes the cells for the regeneration of the external layers 
 of the stratum corneum, which are continually being 
 pushed off. The lowest layer of the stratum germina- 
 tivum, the layer of cylindric cells, shows constant mi- 
 toses. 
 
 The connective-tissue portion of the skin, the cutis, is 
 divided into two main layers, which are closely connected 
 and which pass over into each other without any distinct 
 line of demarcation. The corium borders on the epider- 
 mis and consists of formed, fibrous connective tissue, and 
 the tela subcutanea is characterized by the presence of 
 adipose tissue. 
 
 1 Keratohyalin and eleidin are used as synonymous terms by many 
 authors, while by others the term eleidin is given to the unformed 
 horny material of the stratum lucidum. 
 
204 THE SKIN. 
 
 Plate 67. —Skin. 
 
 Fig. 1.— Transverse Section of the Skin of the Vola Manns 
 of Man. X 15. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows a general picture of the structure and lamination 
 of the skin. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Eeference letters: a, Artery; C, corium; el, Vater-Pacinian corpuscle; 
 cp, epidermis; glsu, sudoriferous glands ; If, muscle-fibers of thepalmaris 
 brevis;p«, panniculus adiposus; stc, stratum corneum; slg, stratum 
 germinativum; Is, tela subcutanea. 
 
 Fig. 2. — Portion of a Transverse Section of the Injected 
 Skin of the Vola Manus. x 15. 
 
 The figure shows the principal relations of the blood-vessels of the 
 skin. 
 
 Technic: Injection with Berlin blue gelatin. Miiller's fluid. Borax- 
 carmin. 
 
 Eeference letters: C, Corium; gls, sudoriferous glands; p, papillae; 
 sire, stratum corneum of the epidermis; strg, stratum germinativum 
 of the epidermis; ts, tela subcutanea. 
 
 PLATE 68— SKIN, HAIR. 
 
 Fig. 1.— Portion of the Transverse Section of the Skin of 
 the Vola Manus of Man. x 170. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the structure of the different layers of the epi- 
 dermis and of the upper portion (stratum papillare) of the corium. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Eeference letters: bg, Blood-vessels of corium; C, corium; ds, ex- 
 cretory duct of a sweat-gland; ep, epidermis; n, nerve, entering a 
 tactile corpuscle; sic, stratum corneum of the epidermis; slg, stratum 
 germinativum; stgr, stratum granulosus; stl, stratum lucidum; tk, 
 tactile corpuscle. 
 
 Fig. 2— Single Cells of the Stratum Germinativum of the 
 Preparation in Fig. 1 . x 700. 
 
 The figure shows the intercellular bridges. 
 
 Fig. 3.— Lower Portion of a Longitudinal Section of the 
 Root of the Hair from the Human Scalp, x 100. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the relation of the different layers of the hair and 
 its root-sheaths in the region of the bulb of the hair. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Eeference letters: aw, External root-sheath; c, cuticle of hair; fp, 
 sheath of hair; gl, glassy membrane; iw, inner root-sheath; P, liair 
 papilla; sc, cortical substance of hair; scp, hair-shaft ; sm, medulla 
 of hair. 
 
lab. 6 7. 
 
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Tab. 68. 
 
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THE EPIDERMAL STRUCTURES OF THE SKIN. 205 
 
 The corium is again divided into the stratum papillare, 
 which bears the papillae, and the deeper stratum reticulare. 
 These two layers also have no sharp line of demarcation 
 between them. The corium is composed essentially of 
 dense connective tissue, the bundles of which cross and in- 
 terlace in all directions. The stratum reticulare, in which 
 the bundles are large and compactly interlaced, is poor in 
 cells, but rich in elastic fibers. The cells of the corium 
 are found between the bundles of connective tissue and 
 are consequently of flattened shape and have elongated 
 nuclei. The cutis also contains non-striated muscle, espe- 
 cially in the neighborhood of the hair, but occasionally 
 also independently of the hair, as in the tunica dartos of 
 the scrotum and in the region of the nipple. 
 
 The subcutaneous layer consists of strands of formed 
 connective tissue surrounding fat-lobules. 
 
 THE EPIDERMAL STRUCTURES OF THE SKIN. 
 
 Special structures originating from the epidermis are 
 contained in the three main layers of the skin. These 
 are hairs, nails, and glands. 
 
 The Hair. 
 
 The hairs are long, thread-like, horny structures, which 
 project beyond the surface of the skin. They are em- 
 bedded in an epithelial sheath of epidermal origin, which 
 is surrounded by a connective-tissue sheath from the 
 corium. The portion of the hair within the skin is known 
 as the root of the hair ; the free projecting portion, as the 
 hair-shaft. The hair-root ends in the hair-bulb. The 
 latter is invaginated by a vascular connective-tissue papilla 
 and lies, especially in the larger hairs, in the subcutaneous 
 layer, while the hair-root lies partly in this and partly in 
 the corium. The epidermal sheath of the hair-root is 
 designated as the root-sheath ; the connective-tissue sheath, 
 
206 THE SKIN. 
 
 Plate 69.— Hair. 
 
 Transverse Section of the Human Scalp. X 15- 
 
 The preparation was taken from a man who had been executed. 
 
 The figure is composed of parts of three sections. It shows a ro > 
 of hairs in longitudinal section, with sebaceous glands and Mm. ar- 
 rectores, club-hairs in different stages of degeneration, young hairs, 
 and new formation of hair. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Kef erence letters: Ap, Musculus arrector pili; c, corium; ep, epi- 
 dermis; fp, hair follicle; Gap, aponeurosis; gls, sudoriferous gland; 
 glsc, sebaceous glands; KH, club-hairs; pp, papilla of hair; Be, reti- 
 nacula cutis; Ep, root of hair; Sp, shaft of hair; ts, subcutaneous 
 layer; x> new formation of hair. 
 
 as the hair-sheath. The structure of the hair and its 
 sheaths can be best recognized in the larger hairs of the 
 body. 
 
 The hair-shaft consists of two main substances, the 
 cortical cells and the medullary cells. The latter may be 
 lacking. In the lower portion of the hair-root the cuti- 
 cula is added to these. The cortical cells form the main 
 mass of the hair. They are long, spindle-shaped cells, 
 somewhat longer in the upper than in the lower part of 
 the shaft of the hair-root, and contain a diffuse and gran- 
 ular pigment, which gives the color to the hair. They 
 possess elongated nuclei, which are often indistinct in the 
 free part of the hair-shaft, and somewhat shorter — that is, 
 more oval in the lower part of the hair-root. 
 
 The medulla of the hair, which is not always present, 
 forms the central portion of the hair-shaft, and is com- 
 posed of quite large, polygonal, unpigmented, nucleated 
 cells, arranged in two or three rows. 
 
 The cuticula of the hair is composed of flattened cells 
 arranged like tiles. These cells are nucleated in the 
 lower part of the root, then lose their nuclei, and finally 
 disappear in the upper part of the root. 
 
 The root-sheath of the hair consists of two parts, the so- 
 called inner and outer root-sheaths. The hair itself 
 corresponds to the stratum corneum of the epidermis ; the 
 inner root-sheath shows the structure of the stratum luci- 
 
> \ 
 
 Oaf —■ 
 
 % ' > 
 
 I 
 
THE EPIDERMAL STRUCTURES OF THE SKIN. 207 
 
 clum and granulosum ; the outer, that of the stratum ger- 
 minativum. The inner root-sheath consists of two to 
 three distinct layers : of the sheath cuticle, bordering upon 
 the hair cuticle, distinct only in the lower part of the root ; 
 of the inner Huxley's and the outer Henle's layers. The 
 sheath cuticle presents essentially the same structure as the 
 hair cuticle. Huxley's layer consists of cubic to low cylin- 
 dric cells in a single layer ; these in the lower portion of 
 the hair-root contain numerous keratohyalin granules. 
 Henle's sheath is composed of flattened cells, which are 
 nearly always non-nucleated. Only in the lowest portion 
 of the hair-root do the cells of Henle's layers contain 
 eleidin granules. In the upper portion of the hair-root 
 the inner root-sheath is comified. The outer root-sheath 
 shows the structure of the stratum germinativum of the 
 epidermis. It consists of a varying number of layers of 
 cells, fewer in the lower than in the upper portion of the 
 hair-root, the outer of which have a columnar form, the 
 middle polygonal, and the inner— that is, toward the inner 
 root-sheath — a flattened form. Where the hair passes 
 through the epidermis, the outer root-sheath joins with the 
 stratum germinativum of the epidermis without any sharp 
 line of demarcation. Like the cells of the stratum germi- 
 nativum, the cells of the outer root-sheath show mitoses. 
 The connective-tissue portion of the hair, the hair-sheath, 
 consists of a relatively thick, structureless, and non- 
 nucleated membrane, the so-called glassy membrane; ex- 
 ternal to this are two layers of connective-tissue fibers, an 
 inner circular and an outer longitudinal. Both, circular as 
 well as longitudinal, layers are free from elastic fibers. At 
 the base of the hair-bulb, at the neck of the papilla of the 
 hair, the elements of the root-sheath which here border on 
 the papilla do not present the lamination found in the other 
 portions of the hair follicle, as here the cells of all the layers 
 of the root-sheaths become nucleated and form a common 
 indifferent mass of cells bordering upon the lower portion 
 of the papilla. This mass of polygonal cells continues to 
 
208 THE SKIN. 
 
 PLATE 70.— HAIR. 
 
 Fig. 1.— Transverse Section through the Middle Portion 
 of a Hair=root of the Human Scalp. X 120. 
 
 The preparation was taken from a man who was executed. 
 
 The figure shows the hair, root-sheaths, and hair-bulb. The sec- 
 tion of the hair shows the medulla, which is stained red, and. the cor- 
 tical cells. 
 
 Technic : Miiller's fluid. Hematoxylin-eosin. 
 
 Reference letters for Figs. 1 and 2 : me, External root-sheaths; bg, 
 blood-vessels; c, cuticle of hair and of root-sheath; gl, glassy mem- 
 brane; hbl, longitudinal fibers of hair-sheath; hbr, circular fibers of 
 hair-sheath; «'u>, inner root-sheath; 1, Huxley's layer of the inner 
 root-sheath; S, Henle's layer of the inner root-sheath. 
 
 Fig. 2. — Transverse Section of the Lower Part of a Hair= 
 root from the Human Scalp. X 300. 
 
 The figure shows relatively thin external root-sheaths; the Hux- 
 ley's layer of the inner root-sheath contains numerous eleidin gran- 
 ules. Between it and the hair we see the cells of the cuticulse. The 
 hair itself has only cortical cells. 
 
 Technic and lettering the same as in Fig. 1. 
 
 the upper part of the papilla where the hair-shaft ap- 
 proaches the upper end of the papilla. Toward the sur- 
 face of the papilla the cells assume a columnar shape. 
 At the upper end of the papilla the indifferent cells of the 
 hair-bulb are mingled with intensely pigmented, peculiarly 
 branched cells. Mitotically dividing cells are uniformly 
 found in the cells of the hair-bulb and also in the outer 
 layers of the outer root-sheath. The shedding of hair is a 
 continuous process in man and does not occur periodically 
 as in the majority of mammals. In hairs to be shed the 
 pigmented portion of the hair-bulb cornifies. Such hairs 
 no longer have the power of growth and are gradually 
 pushed out of the root-sheath. Such degenerating hairs 
 are known as dub-hairs. They are met with in normal 
 scalps in all stages of degeneration. In this process 
 of degeneration the hair papilla remains and on the old 
 papilla a new hair is formed from the cells of the outer 
 root-sheath and from those of the indifferent matrix at 
 the base of the root. The hair may also be replaced in 
 the adult in the same way as the hair is formed in embry- 
 onic life — that is, by the ingrowth of a process from the 
 
Tab.70. 
 
 
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 SS* 
 
 -^ 
 
 >*T 
 
 Mr -' /l 
 
 '~te/~T., 
 
 
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 Fiq.Z. 
 
THE EPIDERMAL STRUCTURES OF THE SKIN. 209 
 
 epidermis ; from this the different parts of the hair are 
 differentiated, in a similar manner as in the embryo ; that 
 is, from the axis of the hair anlage is developed the hair- 
 shaft, and from the peripheral cells the root-sheaths. The 
 sebaceous glands develop as epithelial buds from the ecto- 
 dermal portion of the hair follicle, the hair-sheath from 
 the surrounding connective tissue. 
 
 In the corium non-striated muscle-fibers are constantly 
 found in connection with the larger hairs of the scalp ; 
 these are called arrectores pilorum; they arise from the 
 uppermost layers of the cutis, close under the papilla, 
 often by several roots, pass obliquely toward the hair- 
 shaft, into which they are inserted. At the point of in- 
 sertion there is a protuberance of the latter and with it 
 of the outer root-sheath. The arrector muscle usually 
 forms an acute angle with the hair ; the sebaceous gland 
 lies in this angle, so that the muscle also acts as an ex- 
 pressor sebi. 
 
 The Nails. 
 
 The nails are horny epidermal plates, the cells of which, 
 though still nucleated, are no longer capable of division. 
 The nail lies on the so-called nail-bed, from which it is 
 sharply separated ; the latter consists of the deeper layers 
 of the epidermis. The proximal portion of the nail ex- 
 tends into the nail-furrow and it is surrounded by the nail- 
 wall. Nail-wall and furrow are parts of the skin. The 
 horny layer of the nail-wall, which overlaps the nail, is 
 known as the eponychium. (See Plate 72.) 
 
 The nail-bed is the matrix for the growth of the nail, 
 the anterior part for the growth in thickness of the nail, 
 the posterior caring for the growth in length. The nail- 
 bed is formed from the stratum germinativum of the epi- 
 dermis ; a stratum granulosum is lacking here and thus 
 also the keratohyalin or eleidin granules, such as are found 
 in the cornification of the skin and hair; The corium has 
 no papilla? under the stratum germinativum of the nail, 
 14 
 
210 THE SKIN. 
 
 PLATE 71.— HAIR, SUDORIFEROUS GLANDS. 
 
 Fig. 1.— Portion of a Tangential Section of the Human 
 Scalp. X 20. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the grouping of the hairs, together with the 
 muscle and glands belonging to them. The section goes through the 
 upper portion of the hair-root. 
 
 Technic: Miiller's fluid. Hematoxylin-eosin. 
 
 Eeference letters: Ap, Arrectores pilorum; fp, hair-sheath; glse, 
 sebaceous gland ; glsu, sudoriferous gland ; x, empty hair-sheath. 
 
 Fig. 2.— Transverse Section of the Coil of a Sweat=gland 
 of the Axillary Space. X 50. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a picture of the large sudoriferous glands of the 
 axilla, lined with high epithelium. 
 
 Technic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters for Figs. 2-4: ep, Epithelial cells; L, lumen; 
 m, smooth muscle; mp, membrana propria; n, nuclei of smooth 
 muscle-fibers; S, drops of secretion; x, tubules cut tangentially. 
 
 Fig. 3. — Transverse Section of a Tubule of a Sweat-gland 
 of the Axilla, Lined with Very High Epithelium. X 160. 
 
 The figure shows a portion of the canal with very distinct mem- 
 brana propria. Between this and the epithelium we find smooth 
 muscle-fibers. 
 
 Fig. 4. — A Portion of a Tubule of a Sweat=gland of the 
 Axilla Cut Tangentially. X 160. 
 
 We see the subepithelial smooth muscle-fibers from the surface. 
 
 Fig. 5. — Sudoriferous Glands of the Human Scalp (from a 
 Thick Section). X 45. 
 
 Technic: Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters: cs, Gland-coil; ds. excretory duct; ps, place of 
 opening. 
 
 except a few under the posterior nail-furrow, but many 
 high longitudinal ridges rich in capillaries. 
 
 The Glands of the Skin. 
 
 The glands of the skin are divided into two classes — 
 sebaceous glands, or hair-sheath glands, and sweat-glands, 
 or sudoriferous glands. The sebaceous glands occur in 
 connection with the larger and smaller hairs ; they always 
 lie in the upper layer of the corium. In certain regions 
 of the body they are found independent of hairs, as for 
 instance in the labia minora. They represent glands hav- 
 
Tab. 71. 
 
 ..••••:'( # ^W 
 
 /Vy^. 
 
 ^ 
 
 
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 <*W«^ 
 
 :^: 
 
 
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 glsu 
 
 
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THE EPIDERMAL STRUCTURES OF THE SKIN. 211 
 
 ing few alveoli, the wide excretory ducts of which open 
 beside the hairs or around the smaller hairs. 
 
 The gland alveoli have no real lumen, but are quite filled 
 with the gland-cells. At the periphery of the alveolus 
 the latter are cubic and small, but they become larger and 
 larger toward the interior of the alveolus by the forma- 
 tion of drops of secretion in the protoplasm. With the 
 increase in the quantity of the secretion, the sebum, the 
 nucleus of the cell shrinks and degenerates. The elements 
 lying in the center of the alveolus consist of a collection 
 of drops of secretion arising from the cells, without nuclei. 
 The excretory duct of the sebaceous gland is lined by 
 stratified pavement epithelium like the epidermis and 
 passes immediately into this at the point of exit. 
 
 The sudoriferous glands of the skin are long tubular 
 glands much coiled at the blind end. The coil, at least 
 of the larger glands, lies in the tela subcutanea, the excre- 
 tory duct breaking through the corium and all the layers 
 of the epidermis. The coil of the larger sweat-glands, 
 especially the axillary glands, shows a high, often columnar 
 epithelium, followed by a layer of smooth muscle-fibers 
 and then a thick membrana propria. The coils of the 
 larger sweat-glands have a large lumen. The median and 
 smaller sweat-glands have coils of essentially the same 
 structure, except that they have a narrower lumen, lower 
 epithelium, and often a less distinct layer of smooth 
 muscle. The excretory duct of the sweat-gland is lined 
 with cubic epithelium and passes through the corium 
 nearly straight or a little winding. The cells of the duct 
 fuse with those of the stratum germinativum of the epi- 
 dermis. In the epidermis the duct of the sweat-glands 
 shows marked windings, which have a corkscrew arrange- 
 ment in the stratum corneum and there have no walls of 
 their own. They open into the porus sudoriferus. 
 
 The blood-vessels of the skin lie in the dermis ; the 
 larger branches in the tela subcutanea, the smaller branches 
 in the corium. They are characterized by rich anasto- 
 
212 THE SKIN. 
 
 Plate 72.— Sebaceous Glands, Nail. 
 
 Fig. 1. — Portion of a Cross=section through a Sebaceous 
 Gland of the Human Ala Nasi, x 280. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the cells of the sebaceous gland in the different 
 stages of secretion. 
 
 Technic: Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters : k, Unchanged cell nuclei ; kj , much shrunken 
 nuclei; Bz, border cells; Sz, cells filled with secretion. 
 
 Fig. 2. — Transverse Section of the Nail of a Two= year=old 
 Child, x 20. 
 
 The figure shows about two-thirds of the entire cross-section and 
 gives a general picture of the relation of nail-plate, of nail-furrow, 
 and of nail-wall. 
 
 Preparation from the collection of the Institute of Comparative 
 Anatomy of Wurzburg. 
 
 Reference letters for Figs. 2 and 3: bg, Blood-vessels of nail-bed; 
 e, cerium of nail-bed with the nail-furrows; epo, eponychium; glsu, 
 sudoriferous glands; N, nail-plate; Nb, stratum germinativum of 
 nail-bed; Nf, nail-furrow; Nu; nail-wall; P, papillse. 
 
 Fig. 3. — Posterior Portion of a Longitudinal Section of the 
 Nail of a New=born Child, x 25. 
 
 The figure shows the papillse of the nail matrix. 
 
 Technic : Muller's fluid. Hennitoxylin-eosin. 
 
 moses ; thick capillary networks surround the fat-lobules 
 of the tela subcutanea and the coils of the sweat-glands ; 
 moreover, capillary networks lie in the papillse of the 
 corium, where they approach close to the epidermis and 
 into the hair papillae. The outer layer, the longitudinal 
 layer of fibers of the hair-sheath, contains capillaries. The 
 veins form superficial networks in the deeper portions of 
 the corium. The lymph-vessels of the skin are found 
 abundantly in the region of the papillse and in the tela 
 subcutanea. 
 
 The nerves of the skin are almost exclusively sensory. 
 Motor nerves, the neuraxes of sympathetic neurones, pass 
 to the arrectores pilorum, as well as to the non-striated 
 muscle of the blood-vessels. The sensory nerves pene- 
 trate into the stratum germinativum of the epidermis, 
 terminating either as free sensory endings or in teloden- 
 dria with tactile discs. Other sensory nerves terminate in 
 the Meissner's corpuscles found in certain papillse of the 
 
Tab.72. 
 
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 [»'.-•"■ 9 
 
 > 
 
 ?» 
 
 J?z<- 
 
 « a" 
 
 % ... 
 
 jt- 
 
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 ® 
 
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 glsn 
 
 Fiff.3. 
 
 Lull. Anst F. RewtUwld, Mii/uAen . 
 
TEE EPIDERMAL STRUCTURES OF THE SKIN. 213 
 
 corium, or in the Pacinian corpuscles situated in the sub- 
 cutaneous layer. 
 
 The Mammary Gland. 
 
 The mammary gland is a large skin-gland of alveolar 
 character, or rather it is a collection of about fifteen 
 smaller glands, which represent modified sweat-glands. 
 Connective tissue surrounds the collection of glands and 
 makes them appear like one gland. Each single gland 
 corresponds to the lobe of the entire mammary gland and 
 represents a compound alveolar gland. The excretory duct 
 of the mammary gland presents an enlargement, the sinus 
 lactiferus, a short distance before it opens on the nipple. 
 The secreting alveoli are lined by cubic to columnar epi- 
 thelium, which, however, varies according to the stage of 
 secretion ; after evacuation of the secretion it is almost 
 flat. The secretion of the cells of the mammary gland 
 can be easily recognized, because, in addition to a fluid, 
 albuminous (casein) secretion, a solid substance (fat-drops) 
 is secreted. The fat-drops develop as small droplets in 
 the side of the cell turned toward the lumen, increase in 
 size, and finally are separated from it by a thin border of 
 protoplasm. This is fiually broken through and the fat- 
 drops reach the lumen. The empty cell then appears low, 
 often with flattened nucleus, as the fat-drop, as long as it 
 remains in the protoplasm of the cell, presses the nucleus 
 toward the wall. After the evacuation of the fat-drop 
 the cell again increases in height and may again secrete 
 milk (fat-drops). The alveoli of the mammary gland 
 are quite large and have a relatively large lumen. 
 
 The excretory duct is lined by cubic and in places by 
 a flattened epithelium. The blood-vessels form networks 
 around the gland alveoli. Lymph-vessels are abundant. 
 Their contents flow toward the glands of the axilla. 
 
 The mammary gland has a rich nerve-supply, consist- 
 ing mainly of the neuraxes of sympathetic neurones, 
 which end in terminal branches on the secretory cells. 
 
214 the special sense organs. 
 
 plate 73.— Mammary Glands. 
 
 F IG , 1. — Transverse Section of a Lobule of the Human 
 Mammary Gland at the Time of Lactation, x 50. 
 
 The material of this preparation was secured by operation. 
 
 The figure shows a part of a lobule of the mammary gland with a 
 larger excretory duct. Connective-tissue trabeculae separate the sev- 
 eral lobules. 
 
 Technic: Sublimate. Hematoxylin-eosin. 
 
 Reference letters : ds, Excretory duct; si, sinus lactiferus; ti, inter- 
 stitial, interlobular connective tissue; ts, secreting alveoli. 
 
 Fig. 2.— A Portion of the Above Section; Two Mammary 
 Gland Alveoli More Highly Magnified. X 420. 
 
 The figure shows two secreting alveoli. The glandular epithelium 
 is partly cylindric without drops of secretion; the drops of secretion 
 appear clear, because they consist of fat, which was removed by 
 treatment of the preparation; for the most part the cells contain 
 larger or smaller fat-drops, but partly (at x) the secretion has been 
 evacuated and the cell is flat. 
 
 Fig. 3. — Transverse Section through Three Alveoli of the 
 Mammary Gland of a Nursing Mouse. X 420. 
 
 The figure shows essentially the same as Fig. 2, only the drops of 
 secretion (fat) are blackened by osmic acid and are still visible after 
 the evacuation of the secretion into the lumen of the canal. 
 
 Technic : Flemming's solution. Safranin. 
 
 Reference letters: L, Lumen; s, drops of secretion before evacua- 
 tion; «!, drops of secretion after evacuation. 
 
 XL THE SPECIAL SENSE ORGANS. 
 
 THE ORGAN OF VISION. 
 
 Under the organ of vision we need to consider the eye- 
 ball, bulbus oculi, and its auxiliary apparatus, including 
 the eyelids and conjunctiva, the lachrymal apparatus, and 
 the motor apparatus of the eye — that is, muscles, tendons, 
 and fasciee. The eyeball represents a quite regularly 
 formed hollow sphere, the contents of which are for the 
 most part fluid or nearly fluid. At the anterior part of 
 the sphere is a segment of another sphere of smaller 
 radius. 
 
 The wall of the eyeball is formed by three tunics, the 
 sclera or tunica externa, the choroid or tunica media, also 
 
Tab.73. 
 
 
 
 ■^■■j^mm, as 
 
 Fig.l. 
 
 :■*&!&#$ R 
 
 tot •• - 
 
 9 ^ % 8S w 
 
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 mar • „- 
 
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 1?0 
 
 ^ *>$£>' 
 
 Eig.g. 
 
 litli. Ansl F. ReirfiJwUi, Miiiichm 
 
THE ORGAN OF VISION. 215 
 
 known as the uvea, and the retina or tunica interna. The 
 anterior segment is bounded by only one tunic, the tunica 
 externa or cornea. 
 
 The iris, which may be regarded as a septum contain- 
 ing an opening in its center and representing the forward 
 continuation of the choroid or middle tunic of the eye, 
 divides the cavity of the eyeball into a larger posterior 
 chamber and a smaller anterior chamber. The opening 
 of the iris, known as the pupil, incloses a biconvex body, 
 the lens, which is situated in the anterior portion of the 
 posterior chamber of the eye. The space behind the lens 
 is for the most part filled by the vitreous body, the super- 
 ficial layer of which thickens in the anterior part to form 
 the zonula ciliaris. 
 
 The space between the iris and cornea is known as the 
 anterior chamber of the eye. The optic nerve enters the 
 posterior surface of the bulb, nearer to the nasal than to 
 the temporal side. 
 
 The Sclera or Tunica Externa. 
 
 The anterior transparent portion of the external tunic, 
 the cornea, consists mainly of formed connective tissue, 
 the bundles of which are arranged very regularly in 
 lamellae. The epithelium of the cornea is on the surface 
 of this connective tissue. In descriptions of the cornea 
 we usually distinguish five layers, which are as follows, 
 named from the anterior portion posteriorly: (1) The epi- 
 thelium; (2) the anterior elastic membrane or Bowman's 
 membrane; (3) the substantia propria of the cornea; (4) 
 the posterior basal elastic membrane or Descemet's mem- 
 brane; (5) the endothelium of the anterior chamber. The 
 epithelium of the cornea passes over at the edge of the 
 cornea into the epithelium of the conjunctiva. Like this 
 it is a stratified pavement epithelium, but has no papillae 
 and only a few layers of the flattened cells. The . anterior 
 and posterior elastic membranes are non-nucleated, especially 
 differentiated lamellse of the substantia propria. The 
 
216 tee special sense organs. 
 
 Plate 74.— The Eye. 
 
 Horizontal Section through the Human Eyeball, x 4. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general picture of the entire bulb, with the 
 place of entrance of the optic nerve, and the fovea centralis, in which 
 regions the figure is slightly diagrammatic. 
 
 Technic : Chromic acid solution, 2 per cent. Hematoxylin-eosin. 
 
 Reference letters : C, Cornea; co, conjunctiva; coa, anterior cham- 
 ber of the eye, camera oculi anterior; cop, posterior chamber of the 
 eye, camera oculi posterior; fc, fovea centralis retinae; /, iris; imr, in- 
 sertion of the rectus muscle; L, lens; me, ciliary muscle in the ciliary 
 body; no, optic nerve; os, ora serrate; p, papilla of optic nerve; Sc, 
 sclera; Zc, zoDula ciliaris. 
 
 substantia propria of the cornea consists entirely of con- 
 nective tissue and has very distinct and very regularly ar- 
 ranged parallel lamellae, between which the corneal cor- 
 puscles are placed. The lamella? themselves consist of 
 firmly cemented bundles. 
 
 The corneal cells are large, well-developed connective- 
 tissue cells with lamellar processes. The cell-bodies are 
 flattened from before backward; the lamellar processes 
 pass between the lamellse and bundles of connective tissue, 
 branch and anastomose with the processes of neighboring 
 cells (see Plate 4, Fig. 4). The corneal endothelium con- 
 sists of very regular, flat polygonal connective-tissue cells, 
 which do not simply cover the posterior surface of the 
 cornea, but line the entire anterior chamber. 
 
 The larger posterior portion of the external tunic of 
 the eye, the sclera, shows essentially the same structure as 
 the substantia propria of the cornea, but there is a mani- 
 fold intertwining of the connective-tissue bundles. On 
 account of this the sclera is opaque and white. It also 
 contains fine elastic fibers which enter into the strands of 
 connective tissue, especially in the posterior portion of the 
 sclera. The cells of the sclera are less regularly arranged 
 and fewer in number than those of the cornea. The stratum 
 proprium of the cornea changes abruptly into the sclera at 
 the sclero-corneal junction. The sclera proper contains few 
 blood-vessels, while the cornea contains none. It is the 
 
Tab. 74. 
 
 imr 
 
THE ORGAN OF VISION. 217 
 
 only structure consisting of fibrous tissue which contains 
 no blood-vessels. In the region of the transition of the 
 cornea into the sclera and near the anterior chamber, a 
 circular vein is found running parallel to the edge of the 
 cornea, the venous sinus of the sclera or the canal of 
 Schlemm. 
 
 Lymph-vessels are also lacking in the external tunic of 
 the eye, as also in the entire bulbus. On the other hand, 
 very distinct pericellular lymph-spaces are found especially 
 in the cornea, which are connected with each other by 
 spaces corresponding to the processes of the cells. 
 
 The sclera contains few nerves. These are sensory and 
 terminate in endings resembling tendon corpuscles. The 
 cornea is very rich in nerves. These are also sensory, the 
 branches of which form plexuses in the substantia propria; 
 one situated near the anterior elastic membrane is especially 
 dense and is known as the subepithelial plexus. The ter- 
 minal branches of this plexus penetrate the corneal epi- 
 thelium, between the cells of which they terminate (see 
 Fig. 38). 
 
 The Tunica Media Bulbi (Uvea). 
 
 Between the sclera and the tunica media or choroid of 
 the eye, loose pigmented connective tissue is found, known 
 as the lamina suprachorioidea or lamina fusca. It contains 
 the larger nerves and blood-vessels for the choroid. 
 
 The middle tunic of the eye, uvea, is unusually vascu- 
 lar and contains in general all the essential blood-vessels 
 of the eye. In it are recognized three functionally and 
 structurally distinct regions — the choroid proper, the 
 ciliary body, and the iris. 
 
 The choroid consists of the following layers, enumerated 
 from without inward : (1) The lamina vasculosa or lamina 
 propria, the principal layer which contains the larger 
 vessels, both arteries and veins, between which there is 
 found a fibrous connective tissue, containing pigment 
 cells; the inner portion of this layer, for a thickness of 
 
218 THE SPECIAL SENSE ORGANS. 
 
 PLATE 75— THE EYE. 
 
 Fig. 1. — Portion of a Transverse Section of the Human 
 Cornea. X 90. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the lamination of the cornea. 
 
 Technic: Chromic acid solution, 2 per cent. Hematoxylin-eosin. 
 
 Reference letters: en, Endothelium; ep, epithelium; lea, anterior 
 elastic or Bowman's membrane; lep, posterior elastic or Descemet's 
 membrane; xp, stratum proprium. 
 
 Fig. 2. — Portion of a Transverse Section of the Three 
 Coats of the Eye of Man. X 80. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general picture of the structure of the three 
 tunics of the eye. 
 
 Technic : Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters: Ch, Choroid; die, chorio-capillaris; ES, episcle- 
 ral tissue; B, retina; Sk, sclera. 
 
 about 10 ft, consists mainly of elastic tissue, is free from 
 pigment, and is known as the boundary zone ; (2) a thin 
 layer, free from pigment and consisting mainly of large 
 capillary vessels, which serve for the nutrition of the outer 
 layers of the retina; this is known as the chorio-capiUary 
 layer or membrane; (3) a very thin, homogeneous mem- 
 brane, about 2 [i in thickness, the membrane of Bruch. 
 
 In the anterior half of the bulb the tunica media forms 
 two special structures, the ciliary body and the iris. The 
 former consists of two parts : the ciliary muscle, which lies 
 close to the adjacent sclera and is the muscle of accommo- 
 dation, and the processus ciliares, seventy to eighty meri- 
 dionally arranged, fold-like elevations, which project 
 toward the vitreous body. In the posterior portion they 
 are low and become gradually higher anteriorly toward 
 the edge of the lens. They are very rich in blood-vessels 
 and serve for the regulation of intra-oeular pressure. The 
 ciliary muscle consists of a mass of non-striated muscle 
 formed of outer meridional and inner radiatino- and cir- 
 cular bundles, passing over into each other without any 
 sharp line of demarcation. The meridional fibers are the 
 longest (tensor chorioidea-y, they originate from the inner 
 surface of the sclera in the region of the canal of 
 
Tab. 7. 5. 
 
 :;;v.y":":i:S.v«>>«/''<^^".i^<ri«"ftiVAw;>fe^^^^ , it 
 
 lig.l. 
 
 Jep 
 
 m^M •; ',', f ,;", -'iMf^rMlfi 
 
 ■■•■ 
 
 i «•: .'i 
 
 "' '^m^im 
 
 .1 ' ; j '■ 
 
 m 
 
 ' i 
 
 '■>,.- \ . f. i 'i '<;•• 1 1 i , i i hi 1 
 
 ■it > ... i ir i,' 
 
 t ' ..' ' ' i i ; 
 ,' ' i W 'I , 
 
 ' J.';'!' 1 !. 1 ,''V 
 
 if* 
 
 1 ' i ".' '/ 
 
 /My 
 
 i m - 1 
 
 ' • I I." I ■ '■!,' I 
 
 ' I' 1 1 1' ' ; II I 
 
 IS 
 
 >' ', r-i ' ',1'. -, , 
 
 ■ i r ' 
 
 TS 
 
 » 
 
 ' i>( .>, !:•(( 
 
 I ,' *\ 
 
 I " I 
 
 I ' I I ' > ' 
 
 ..' . I' 1 . ' I ' l , 
 
 
 If 
 
 If 
 
 13 
 
 If 
 
 i i Si 
 D [ml 
 
 «y 
 
 ■'■ ;!; ' ' ' < " ■ '' '.''M ^, 111 
 
 Fiff.Ji. 
 
THE ORGAN OF VISION. 219 
 
 Schlemra and extend backward over the origin of the 
 ciliary processes. 
 
 The iris is a thin membrane, in the center of which there 
 is found a circular opening, the pupil. It begins at the an- 
 terior edge of the ciliary body and extends to the edge of 
 the pupil, where it ends, generally slightly thickened. 
 We distinguish in the iris four layers: (1) The endothelium 
 of the anterior chamber, which covers the surface of the iris 
 bordering on the anterior chamber ; (2) the stratum pro- 
 prium iridis ; (3) the posterior elastic limiting membrane 
 or the membrane of Bruch ; (4) the pigment layer of the 
 iris; the latter, however, is the continuation of the tunica 
 interna. 
 
 The endothelium on the anterior surface of the iris is 
 similar to that on the posterior surface of the cornea. The 
 stratum proprium of the iris is divided into two parts 
 which pass over into each other without any sharp line of 
 demarcation — the anterior reticular membrane composed of 
 more densely woven connective tissue and the posterior 
 vascular and muscular layer. The latter consists of non- 
 striated muscle and numerous blood-vessels and connective 
 tissue whose cells contain much pigment in dark eyes and 
 a relatively small amount in blond eyes. The muscle of the 
 iris consists of the sphincter pupillce surrounding circularly 
 the edge of the pupil, and the dilatator pupillce consisting of 
 radiating bundles, lying close to the posterior basal mem- 
 brane. The two muscles are connected in the region of the 
 pupillary margin. The lamina basilaris corresponds in 
 appearance and structure to the similar lamella of the 
 choroid. For the pigment layer of the iris, see under the 
 retina. 
 
 The vessels of the choroid are essentially the short pos- 
 terior ciliary arteries, while the long posterior ciliary and 
 the anterior ciliary arteries provide for the nourishment of 
 the ciliary body and the iris. While the choroid vessels in 
 the lamina chorio-capillaris form a very narrow-meshed 
 capillary network, the vessels of the anterior part of the 
 
220 THE SPECIAL SENSE ORGANS. 
 
 PLATE 76— THE EYE. 
 Fig. 1.— Portion of a Horizontal Section of the Human Bulb 
 of the Eye ; Region of the Ciliary Body, x 15. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the transverse section of the entire iris, of the 
 ciliary body with the ciliary processes partly in surface view, the place 
 of junction of cornea and sclera, the conjunctiva bulbi, a portion of 
 the lens, and the fibers of the zonula. 
 
 Technic: Chromic acid, 2 per cent. Hematoxylin-eosin. 
 
 Reference letters: C, Cornea; Ch, choroid; Co, conjunctiva bulbi; 
 coa, anterior chamber of eye; cop, posterior chamber of eye; cl, cap- 
 sule of lens; Ir, iris; L, lens; le, lens epithelium; Me, ciliary muscle; 
 Pc, ciliary processes; Per, pars ciliaris retinae; Sc, sclera; Spp, sphinc- 
 ter muscle of pupil; sip, pigment layer of iris; scse, sinus venosus or 
 canal of Sehlemm; Z, zonula ciliaris. 
 
 Fig. 2. — Portion of a Horizontal Section of the Lens in the 
 Region of the Equator, x 220. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the epithelial fiber limits of the lens. The tran- 
 sition of the cubic lens epithelium of the anterior surface into the 
 elongated lens-fibers at the equator of tbe lens. 
 
 Technic as in Fig. 1. 
 
 Reference letters: cl, Capsule of lens; ep, lens epithelium; //, lens- 
 fibers. 
 
 uvea form at the base of the iris a vascular ring, the cir- 
 culus iridis major, from which the vessels of the ciliary 
 bodv and the radiating vessels (capillary vessels) of the iris 
 proceed, which surround the pupillary margin circularly, 
 forming the circulus iridis minor. The veins of the uvea 
 are, aside from the sinus venosus or canal of Sehlemm, 
 four large veins, lying in the region of the equator of the 
 bulbus, the vence vorticosce. The nerves of the choroid are 
 essentially vascular nerves, while those of the iris and cil- 
 iary body are muscular nerves from the sympathetic, the 
 sphincter of the pupil and the ciliary muscle receiving their 
 innervation through neuraxes of sympathetic neurones of 
 the ciliary ganglion, the dilator of the pupil through neu- 
 raxes of neurones of the superior cervical ganglion. Sen- 
 sory nerves terminate in free sensory endings in the 
 ciliary body and iris. 
 
Tab. 76. 
 
 jf- sip 
 
 ep 
 
 >*>*<%>. so, 
 
 ci 
 
 if 
 
 & ® a ^ 
 
 i 
 
 - 
 
 Eiff.S. 
 
THE ORGAN OF VISION. 221 
 
 Retina or Tunica Interna. 
 
 The tunica interna consists of two main layers, the pig- 
 ment epithelium and the true retina. They represent the 
 two adjacent layers of the secondary optic vesicle or optic 
 cup. 
 
 The pigment epithelium, the outer layer of the optic cup, 
 consists of very regular, hexagonal cells of flattened cubic 
 form, which consist of an outer half showing little pig- 
 ment and containing the nucleus, and an inner, markedly 
 pigmented half adjoining the retina (see Plate 3, Fig. 4). 
 
 The retina is divided into two main portions, the pars 
 optica or retina proper and the pars cceca. The latter is 
 divided again into the pars ciliaris and pars iridiea retina, 
 two portions which are not sharply separated. The pars 
 optica and the pars cseca are separated by a sharp line, 
 which has generally a slightly wavy course and is macro- 
 scopically visible, the ora serrata. The finer structure of 
 the retina is complicated and in some parts not fully in- 
 terpreted, so that the discussion is here limited to the most 
 important points and those which are well understood. 
 The structure of the retina proper (pars optica retinos) is 
 essentially as follows : It consists of three elements differ- 
 ing in structure and function : the supporting elements, the 
 nervous constituents, and the neuro-epithelial layer. The 
 supporting elements are intimately connected with the 
 other two constituents, and, like the elements of these, can 
 be distinguished in their whole extent only after the appli- 
 cation of special methods. On observation of the retina 
 by the usual methods of investigation, it appears to be 
 composed of a number of layers, which, reckoning from 
 within outward, are as follows: (1) Membrana limitans 
 interna ; (2) layer of optic nerve-fibers ; (3) layer of 
 ganglion-cells ; (4) inner reticular or plexiform layer ; 
 (5) inner granular layer ; (6) outer reticular or plexi- 
 form layer; (7) outer granular layer; (8) outer limit- 
 ing membrane ; (9) rods and cones. We retain here 
 the old classification of layers, which, in spite of its 
 
222 THE SPECIAL SENSE ORGANS. 
 
 incompleteness, cannot be dispensed with for the time 
 until a new and satisfactory nomenclature is at hand. 
 Of these layers, the limiting membranes belong to the sup- 
 porting elements, the layer of optic nerve-fibers, the layer 
 of ganglion-cells, the inner granular layer, and the inner 
 and part of the outer plexiform layers are to be counted 
 among the nervous constituents, while the outer granular 
 layer, with a portion of the- outer- plexiform layer and the 
 layer of rods and cones, represent the neuro-epithelium. 
 
 The supporting framework of the retina is formed of 
 the supporting fibers of Midler. These extend through the 
 entire thickness of the retina, beginning at the inner sur- 
 face of the retina with cone-shaped enlargements known 
 us foot-plates, which by their fusion form the internal lim- 
 iting membrane. They have nuclei which are situated in 
 the inner granular layer. It has been shown by means 
 of special methods that they give off lateral branches in 
 both plexiform layers, and in the granular layers show 
 impressions from the pressure of the elements of these 
 layers. The Midler's fibers form the external limiting 
 membrane, a membranous structure with openings for the 
 rods and cones and fine processes projecting between the 
 rods and cones called fiber baskets. Besides the Midler's 
 fibers, glia cells and fibers are found in the retina, but 
 only in the layer of optic nerve-fibers. 
 
 The layer of nerve-fibers is formed of the non-medullated 
 fibers of the optic nerve. They constitute in the main 
 the neuraxes of the nerve-cells of the ganglion-cell layer, 
 which contains large multipolar ganglion-cells. The den- 
 drites of these ganglion-cells spread out in the inner 
 plexiform or reticular layer. The inner plexiform layer 
 contains the terminal branchings of the dendrites of the 
 neurones of the ganglion-cell layer, as well as the neuraxes 
 of the neurones of the inner granular layer and dendrites 
 and neuraxes of other ganglion-cells. 
 
 The inner granular layer, or, as it may better be known, 
 the inner ganglion-cell layer, is composed of several dis- 
 
THE ORGAN OF VISION. 223 
 
 tinct kinds of elements : (1) The nuclei of the Miiller's 
 fibers ; (2) small bipolar ganglion-cells, the nuclei of 
 which represent the main mass of the " granules " of this 
 layer, the neuraxes of which penetrate into the inner 
 plexiform layer and there branch, while the dendritic pro- 
 cesses show the same relation to the outer plexiform layer ; 
 they are said to penetrate even to the cells of the outer 
 granular layer ; (3) two groups of cells, concerning the 
 relation of which the views are still contradictory. Cer- 
 tain of these cells bear the name of spongioblasts or 
 amakrine cells, also known as parareticular cells on account 
 of their situation at the borders of the inner plexiform or 
 reticular layer ; they are ganglion-cells of the second type 
 of Golgi's classification, with rich branching of their 
 neuraxes in the inner plexiform layer. Another type of 
 cells found in the inner granular layer is represented by 
 the horizontal cells ; they lie mostly at the borders of the 
 outer plexiform layer and send out a neuraxis which runs 
 horizontally. Together with the amakrine cells they are 
 said to form a reflex arc in the retina. The outer plexi- 
 form layer consists again of a dense network of cell pro- 
 cesses. The outer granular or nuclear layer contains two 
 kinds of cells : The main part is formed by the rod visual 
 cells ; the second form, the cone visual cells, lie with their 
 nuclei generally close to the outer limiting membrane. To 
 these cells belong also the rods and cones, which are prob- 
 ably to be regarded as cuticular formations of the cells. 
 The rod visual cell consists of the rod, lying outside of the 
 external limiting membrane, and the rod fiber, lying in- 
 ternal to that membrane. The rod fibers are long, slender 
 cells, which show an enlargement, the rod granule, at the 
 place of the nucleus. The inner central end of the fiber 
 is thickened at its ending in the plexiform layer. The 
 rod consists of a somewhat broader, rod-like, granular 
 inner segment and an exactly cylindric, somewhat nar- 
 rower homogeneous outer segment. The outer segment, 
 which is doubly refractive, may be separated by certain 
 
224 THE SPECIAL SENSE ORGANS. 
 
 reagents or by certain methods of staining into transverse 
 discs. The inner end of the inner segment shows a 
 delicate superficial striation. 
 
 ' Like the rod visual cells, the cone visual cells consist of 
 cones and cone fibers. In the cone fibers the nucleus lies 
 close to the external limiting membrane; the real fibers, 
 therefore, lie internal to the nucleus and extend through 
 the outer granular layer to the outer plexiform layer, 
 where each ends in a cone-shaped enlargement, the cone 
 foot. The cones, like the rods, have an inner and an outer 
 segment. The former are thick flask-shaped; the latter 
 are short, much shorter than the outer segments of the 
 rods, and have the form of a narrow cone. The structure 
 of the cones is otherwise essentially the same as that of 
 the rods. Not all cones have the same' form; at the 
 periphery of the retina, near the ora serrata, are very 
 short broad cones, while the region of the macula lutea has 
 long narrow cones, and the cones of the region of the 
 fovea centralis are so long and narrow that they assume 
 almost the form of rods and are known as foveal cones. 
 The number of rods is greater than that of the cones. 
 Generally four to five rods occur to each cone. Only in 
 the middle of the macula lutea and partly also in the 
 neighborhood of the ora serrata is the relative proportion 
 altered (see page 227). 
 
 The elements of the retina, aside from the amakrine and 
 horizontal cells, are so connected that the light impulse is 
 carried through the rod and cone fibers into the outer 
 plexiform layer. Here these are in contact with the per- 
 ipheral dendrites of the bipolar cells of the inner granules. 
 The bipolar cells of the inner granules again enter into 
 contact by means of their neuraxes with the dendrites of 
 the nerve-cells of the ganglion-cell layer, the neuraxes of 
 which form the optic fibers. Three portions of the retina 
 are especially distinguished on account of their structure : 
 the ora serrata, the fovea centralis, and the place of en- 
 trance of the optic nerve. 
 
THE OBQAN OF VISION. 
 
 225 
 
 Before reaching the ora serrata the retina becomes essen- 
 tially thinner. The optic fiber layer is entirely lacking; 
 only a few scattered ganglion-cells are found. Finally 
 
 Fig. 61. — Diagrammatic representation of the elements of the 
 retina and of its nervous relations (without consideration of the 
 amakrine and horizontal cells) ; to the left the supporting elements, to 
 the right the nervous elements and neuro-epithelium. fk, Fiber 
 baskets of Muller's fibers; k, nucleus of Miiller's fiber; rf, fiber cone 
 of Muller's fibers; stk, rod nucleus; zk, cone nucleus; 1, internal lim- 
 iting membrane; 2, layer of optic fibers; 3, ganglion-cell layer; 4, 
 inner plexiform layer; 5, inner granular layer; 6, outer plexiform 
 layer; 7, outer granular layer; 8, outer limiting membrane; 9, rods 
 and cones; 10, pigment epithelium. 
 
 the plexiform layers and the inner and outer granular lay- 
 ers become confluent and form the cubic epithelium of the 
 pars ciliaris retinae. Rods and especially broad, short 
 cones extend to near the edge of the ora serrata. Large 
 15 
 
'226 the special sense organs. 
 
 Plate 77.— Eye. 
 
 Fig. 1. — Portion of a Cross=section of the Retina of Man 
 in the Neighborhood of the Place of Entrance of the Optic 
 
 Nerve. X 180. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure represents the typical lamination of the retina. Nerve- 
 fiber, ganglion-cell, and inner granular layers are relatively well de- 
 veloped. 
 
 Techuic: Zenker's solution. Hematoxylin-eosin. 
 
 Reference letters for Figs. 1-3: 1, Internal limiting membrane; 2, 
 layer of optic nerve-fibers; 3, ganglion-cell layer; 4, inner plexiform 
 layer; 5, inner granular layer; 6, outer plexiform layer; 7, outer gran- 
 ular layer; 8, external limiting membrane; 9, rods and cones; 9*, 
 cones and foveal cones; 10, pigment epithelium; bg, blood-vessels of 
 the retina; eh, choroid; pa; pars ciliaris retinae; rf, Miiller's fibers; 
 r, vacuole. 
 
 Fig. 2. — Transverse Section through the Fovea Centralis 
 of the Human Retina. X 125. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows .the changes which the retinal layers undergo in 
 the region of the fovea centralis. 
 
 Teehnic: Sublimate. Hematoxylin-eosin. 
 
 Fig. :!.— Meridional Section through the Ora Serrata of 
 Man. /v 100. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the gradual confluence of all the retinal layers, 
 which often contain vacuoles, into the simple columnar cells of the 
 pars ciliaris retina?. 
 
 Teehnic: Chromic acid, 2 per cent. Hematoxylin-eosin. 
 
 hollow spaces are often found in varying number in the 
 retina at the ora serrata, thought to be due to edema. 
 
 The fovea centralis presents a number of peculiarities of 
 lamination, which continue partly into its nearest surround- 
 ings, but in the region of the macula lutea pass over into 
 the usual structure of the retina. 
 
 The ganglion-cell layer thickens considerably in the re- 
 gion of the fovea centralis and macula lutea, so that its 
 elements form from five to eight layers and the inner 
 granular layer is much broader. Henle's fiber layer, 
 cone and rod fibers, which here form a distinct layer be- 
 tween the outer granular and plexiform layers, is very 
 distinct. In. place of the rod and cone visual cells, cones 
 alone occur, which, toward the base or fundus of the fovea, 
 
Tab. 7 7. 
 
 J" ,> 
 
 / ^Sl jL ' __!' _ a <8 <*T « *L a « 9 ... 9 „ <S> 
 
 / 
 rf 
 
 j © # £» "a 
 
 F/yi. 
 
 
 ■•■'PPPI 
 
 F(c/.,2. 
 
 ^^fefi i: '"- :: -"^: 
 
 .•V.. '»..'•'' ."'•>*'':'>..■•."■'--* --. 
 
 C i Xi^& MVgfiijXrjL. .«.»'&££&■. .■•.., :■ : W 
 
 Fig.,3. 
 
 per 
 
 litk.Afist. E RpicMwUl. Miinehm . 
 
THE ORGAN OF VISION. 227 
 
 increase in length and diminish in caliber (compare page 
 224). Corresponding to this, the outer granular layer 
 consists only of cone visual cells, the nuclei of which do 
 not all lie in close relation to the external limiting mem- 
 brane, as in other parts of the retina. The fundus fovece 
 is characterized by the fact that nearly all the layers of the 
 retina are lacking except the foveal cones. All the others, 
 especially the inner layers, are here reduced to a minimum 
 and pushed aside and thus increase the slope of the de- 
 pression, the outer granular layer being reduced first. 
 
 At the point of entrance of the optic nerve, the optic 
 papilla, all the retinal layers are lacking except that of the 
 nerve-fibers. The pars cceca retina presents differences in 
 the regions of the pars iridica and pars ciliaris retina?, as 
 in the former the pigment epithelial layer and the retinal 
 layer are both pigmented, while in the latter the retinal 
 layer consists of cubic or low columnar unpigmented cells 
 in a single layer. 
 
 Only the pars optica retinae contains blood-vessels which 
 rise from the arteria centralis retinas and open into the 
 vena centralis. These blood-vessels nourish only the 
 inner layer of the retina and lie in the layer of nerve- 
 fibers, rarely in the layer of ganglion-cells. The fovea 
 centralis, as well as the neighborhood of the ora serrata, is 
 non-vascular. As has been stated, the outer layers of the 
 retina are supplied by the dense vascular network in the 
 chorio-capillary layer of the choroid, whose main function 
 this would seem to be. 
 
 The Optic Nerve. 
 
 The optic nerve has three sheaths, which correspond to 
 the dura mater, arachnoid, and pia mater of the central 
 nervous system. The fibers of the optic nerve, like those of 
 the central nervous system, are medullated, but are without 
 the sheath of Schwann. The pia mater sends numerous 
 septa into the interior of the nerve and thus forms small 
 bundles of optic nerve-fibers. Within the bundles the frame- 
 
228 the special sense organs. 
 
 plate 78.— Eye, lachrymal Gland. 
 
 Fig. 1. — Longitudinal Section of the Place of Entrance of 
 the Optic Nerve in the Human Eye. X 18. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the optic nerve with its sheaths and fiber-bun- 
 dles, the passage through the lamina cribrosa sclera; and the spreading 
 out of the fibers in the upper layer of the retina. In the axis the 
 vena centralis is met. Surrounding the papilla nervi optici we see the 
 cross-section of the coats of the eye. 
 
 Technic: Sublimate. Hematoxylin-eosin. 
 
 Eeference letters: Ch, Choroid; d, dural sheath of optic nerve; epn, 
 physiologic excavation of the papilla of the optic nerve; fno, bundles 
 of the optic nerve; Ic, lamina cribrosa of the sclera; no, optic nerve; 
 p, pia-arachnoidal sheath of the optic nerve; R, retina; 8c, sclera; vc, 
 vena centralis. 
 
 Fig. 2. — Portion of a Transverse Section of the Human 
 Lachrymal Gland. X 120. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure shows the loose arrangement of the lobules of the lach- 
 rymal gland, which are separated by connective tissue. In the gland 
 tissue secreting tubules and smaller excretory ducts are visible. 
 
 Technic: Sublimate. Hematoxylin-eosin. 
 
 Reference letters: bdg, Connective tissue rich in lymph-cells; ds t , 
 median excretory duct; ds?, small excretory duct; F, adipose tissue; 
 s, secretion; ts, tubule with branchings and dilations. 
 
 work is formed, not of endoneurium, as in the peripheral 
 nerves, but by neuroglia tissue. As in the central nervous 
 system, the optic nerve has a peripheral neurogliar mantle. 
 In the interior of the optic nerve are found the central 
 vein and artery of the retina. 
 
 The fibers of the optic nerve become non-medullated in 
 passing through the sclera. At the entrance of the optic 
 nerve the sclera is penetrated by small openings, this area 
 being known as the area cribrosa; the choroid is here en- 
 tirely lacking. The non-medullated fibers of the optic 
 nerve spread out on the retina, forming a flattened elevation 
 with a slight hollow in the center ; these are known as the 
 optic papilla, with the physiologic excavation in the center. 
 
 The Vitreous Body and the Zonula Ciliaris. 
 
 The vitreous body is rich in fluid and contains some few 
 connective-tissue fibers and leukocytes; connective-tissue 
 
Tab.78. 
 
 epn • 
 
 teV4- 
 
 Mg.l. 
 
 SS 
 
 ■ Sy~ f ^ -'■'''' : ' : ~ : ^ ■ ■:"' : ' '''" 
 
 p t 
 
 : ■y^)Q:.-9:-^ ?-M 
 
 4 ' '■-■■ o 
 
 
 fs<^:. 
 
 \„-bdff 
 
 F 
 
 Fiq.S. 
 
 Lith. Anst F Reidiiwlxl, Miinrhen . 
 
THE ORGAN OF VISION. 229 
 
 cells are said not to occur in the vitreous body. The 
 zonula ciliaris consists of structureless fibers, which arise 
 from the epithelial cells of the pars ciliaris retinse in the 
 valleys between the ciliary processes, and, covering the 
 ciliary processes, pass toward the lens. The zonula fibers 
 form several not sharply differentiated layers and cross 
 each other many times before reaching their attachment in 
 the region of the lens. 
 
 The Lens. 
 
 The lens is an epithelial structure which takes its origin 
 from the ectoderm. It consists of a homogeneous capsule, 
 the capsule of the lens, which is thinner behind than in 
 front, surrounds the entire lens, and bears on its inner 
 side, in the region of the anterior surface of the lens, a 
 simple cubic epithelium, the lens epithelium. At the 
 equator of the lens this changes gradually into fiber-like 
 cells which extend from the anterior surface of the poste- 
 rior capsule to the lens epithelium. The main mass of 
 the lens is formed of these lens-fibers (see Plate 76, Fig. 
 2). The lens-fibers are long, six-sided, often flattened 
 prisms, which generally have an oval nucleus; only the 
 so-called central fibers and transition fibers of the human 
 lens are non-nucleated. The main portion of the lens- 
 fibers are arranged in radial lamellae. The number of 
 these lamellse amounts to about 2000. Neither the vitre- 
 ous body nor the lens contains blood-vessels and nerves. 
 
 The Auxiliary Apparatus of the Eyeball. 
 
 The Eyelid. — The eyelids are folds of the skin, which 
 on the anterior surface present the usual structure of the 
 skin, while the posterior surface is covered by the conjunc- 
 tival mucous membrane. From before backward we dis- 
 tinguish in the eyelid the following layers: (1) The skin 
 with the lanugo hairs, sebaceous and sudoriferous glands; 
 (2) subcutaneous tissue; (3) the M. orbicularis palpebra- 
 rum ; (4) loose connective tissue with the main vessels of 
 
230 the special sense organs. 
 
 plate 79.— Eyelid. 
 
 Vertical Section of the Upper Eyelid of Man. X 14. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the structure of the eyelid, show- 
 ing its different layers. Two cilia are met in the section, one of which 
 is in the process of falling out. A small accessory lachrymal gland is 
 seen on the conjunctival surface. 
 
 Technic: Muller's fluid. Hematoxylin-eosin. 
 
 Reference letters: at, Arterial arcus tarseus; C, cilia; dgl, excretory 
 duct of tarsal gland; glc, ciliary gland (Moll); glla, accessory lachry- 
 mal gland; git, Meibomian gland; McB, ciliary muscle of Riolani; 
 Mop, M. orbicularis palpebrarum; Mi, non-striated muscle-fibers of 
 the tarsal muscle and tendon of the levator palpebral superioris; nlc, 
 lymph-nodes of the conjunctiva palpebral; T, tarsus. 
 
 the lid j (5) the tarsus with the tarsal glands; (6) the 
 conjunctiva palpebrarum. 
 
 The skin of the lid presents no peculiarities. Between 
 the outer and inner edges of the lids it passes gradually 
 over into the conjunctiva. Here one or two layers of 
 relatively thick hairs are found, the cilia, which are char- 
 acterized by the fact that they are regularly and quite 
 frequently shed, and as a consequence club-hairs are often 
 found. In the region of the cilia are found the ciliary 
 glands or the glands of Moll, modified sudoriferous glands, 
 which differ from the ordinary sweat-glands in that they 
 branch and possess relatively large oval or spheric alveoli. 
 A portion of the palpebral muscle pushes between the cilia 
 and the inner edge of the lid and is designated as the 
 M. tarsalis, or the ciliary muscle of Riolani. This sur- 
 rounds the opening of the Meibomian glands to a varying 
 extent with bundles of transversely striated muscle. The 
 main mass of the palpebral muscle is separated from the 
 skin of the lids by loose subcutaneous connective tissue. 
 Between the muscle and the tarsus is loose connective 
 tissue often containing fat, which surrounds the larger 
 blood-vessels and nerve trunks of the lid. In the neigh- 
 borhood of the roots of the cilia the arterial arcus tarseus 
 is found. 
 
 The tarsus or lid cartilage is composed of dense formed 
 
% 
 
 \X:. 
 
 Tab, 7. 9. 
 
 
THE ORGAN OF VISION. 231 
 
 connective tissue. Its entire length is occupied by the 
 Meibomian glands, which correspond in their finer struc- 
 ture to the sebaceous glands of the hair-bulbs. They have 
 a long median duct, which is surrounded by the gland 
 alveoli. The large excretory duct, which has no alveoli, 
 is lined by stratified pavement epithelium and opens close 
 to the inner margin of the lid. The posterior surface of 
 the tarsus is covered by the conjunctiva palpebrarum, 
 which is attached to the tarsus. Its mucous membrane is 
 rich in lymph-cells, which form solitary follicles in the 
 region of the fornix conjunctivae. The mucous membrane 
 of the conjunctiva palpebrarum has no papillae; the epi- 
 thelium is stratified columnar, papillae occurring only in 
 the region of the fornix conjunctivae. At the upper end 
 of the tarsus is the insertion of the tendon of the 31. leva- 
 tor palpebral mingled with non-striated muscle-fibers. 
 Small accessory lachrymal glands, of the same structure as 
 the main glands, are often situated near the upper end of 
 the tarsus close under the conjunctiva. The conjunctiva 
 bulbi is covered by stratified pavement epithelium, under 
 which we find a papillated mucosa. The nerves of the 
 conjunctiva end partly in free endings and partly in 
 Krause's spheric end-bulbs. 
 
 The Lachrymal Glands. — The lachrymal gland is a 
 compound tubular gland, which is not sharply separated 
 from the surrounding tissue and is embedded in fat tissue. 
 Adipose tissue in variable amount is also found between 
 the lobules of the gland. (See Plate 78, Fig. 2.) The 
 cells of the secreting tubules, which are distinctly branched, 
 are cubic to columnar, and the lumen of the canals is gen- 
 erally quite narrow ; when the tubules are empty, the cells 
 are lower; but when they are filled with the secretion, 
 their surface on the side of the lumen appears clear. In 
 addition to these cells, much flatter cells occur, which are 
 easily distinguished from the columnar cells. Interme- 
 diary dads with low epithelium form the transition to the 
 excretory ducts, the smaller of which are lined by cubic 
 
232 the special sense organs. 
 
 plate 80.— Organ of hearing. 
 
 Fig. 1. — Portion of a Transverse Section of the External 
 Auditory Canal of Man. X 15. 
 
 The preparation was taken from a man who had been executed. 
 
 The figure gives a general view of the cartilaginous external audi- 
 tory canal. 
 
 Technic: MUller's fluid. Hematoxylin-eosin. 
 
 Reference letters: gh; Ceruminous glands; glse, sebaceous glands; 
 kn, cartilage. 
 
 Fig. 2. — Portion of a Cross=section of a Cochlea of a New= 
 born Child. X 50. 
 
 The preparation was taken from a still-born child. 
 
 The figure shows the cross-section of a duct of the osseous cochlea 
 and gives a general view of the ductus cochlearis. 
 
 Technic: Hermann's solution. Hematoxylin-eosin. 
 
 Reference letters: bg, Blood-vessels; dc, ductus cochlearis; gsp, 
 spiral ganglion ; Kn, bone; Up, limbus spiralis; Ispm, lamina spiralis 
 membranacea; Ispo, lamina spiralis ossea; mv, membrana vestibularis 
 or Reissner's membrane; n, nervus acusticus; set, scala tympani; vp, 
 vas prominens; scv, scala vestibuli. 
 
 epithelium, the larger by columnar epithelium showing 
 two layers of cells. Sympathetic nerve-fibers have been 
 traced to the cells of the secreting tubules. 
 
 THE ORGAN OP HEARING. 
 
 The organ of hearing consists of the external ear, the 
 middle ear, and the inner ear. The external ear is com- 
 posed of the pinna of the ear and the external auditory 
 canal. The tympanic membrane separates the external ear 
 from the middle ear. The external ear consists of a cartil- 
 aginous framework of elastic cartilage, which is covered 
 by skin. 
 
 The external auditory canal has a framework consisting 
 partly of elastic cartilage and partly of bone, to which is 
 intimately attached a thick mucous membrane. The latter 
 is really a continuation of the skin, and, like this, presents 
 stratified pavement epithelium with small hair follicles and 
 relatively large sebaceous glands and especially large 
 sudoriferous glands known as ceruminous glands. ' These 
 
Tab. 80. 
 
 fit re 
 
 
 / « WE 
 
 »*'-i^8 
 
 
 £323'/ - ■ £'■"'9 
 
 
 >,- : .'.\---,.-vr:. : .-,.... •..VV.v^V- 
 
 
 -fi^z. 
 
 i^:/ 
 
 lith.Art.st /■: Reu/tfw/d '. a/ureote 
 
TEE ORGAN OF HEARING. 233 
 
 have very large coils composed of branched tubules with 
 large lumen, high epithelium, and distinct non-striated 
 muscle-fibers, like the axillary glands (see page 211). 
 The excretory ducts are short in comparison with those of 
 other sudoriferous glands. The glandular epithelium con- 
 tains pigment granules and often fat granules. 
 
 The middle ear, the tympanic cavity, has a thin mucous 
 membrane, often with ciliated flattened epithelium, which 
 changes in the Eustachian tube to a stratified ciliated epi- 
 thelium. Glands are absent. The tympanic membrane 
 is a connective-tissue membrane, which is covered on the 
 tympanal side by the mucous membrane of the middle ear, 
 on the outer side by the mucous membrane of the external 
 auditory canal. 
 
 The Inner Ear (Labyrinth). 
 
 Sacculus, utriculus, and semicircular canals pre- 
 sent in general the same structure. 
 
 The membranous ducts are composed of a flattened epi- 
 thelium, a basal membrane, and a connective-tissue 
 sheath. Loose connective-tissue trabeculse unite the mem- 
 branous ducts to the bony wall. Between the connective- 
 tissue trabecular is found the perilymph. At the macuke 
 and crista acusticce the epithelium is thickened. In those 
 places where the endings of the vestibular nerve are dis- 
 tributed, a typical sensory epithelium is found, which 
 presents two kinds of cells: (1) The hair-cells, columnar 
 cells situated at the border, with ciliated margin ; the cilia 
 are known as auditory hairs; (2) the long fiber-cells occu- 
 pying the entire thickness of the epithelium, narrow and 
 broadened only at the lower basal ends. The fiber-cells 
 are probably supporting cells. On the auditory hairs are 
 crystals of calcium carbonate called otoliths. The fibers 
 of the N. vestibuli become non-medullated at the basal 
 surface of the epithelium, pass between the hair-cells, and 
 end on their lateral surfaces, at the same time branching 
 at their bases. 
 
234 THE SPECIAL SENSE ORGANS. 
 
 Fig. 62. — Transverse section of the osseous and membranous semi- 
 circular canal of a new-born child. X 55- The figure shows in the 
 upper portion, excentrically placed, the cross-section of the membran- 
 ous semicircular canal, which is connected with the osseous wall by 
 some few connective- tissue trabecule. b(fg, Connective-tissue trabec- 
 ular; bg, blood-vessels; ep, epithelium of the membranous duct; kn, 
 osseous wall; km; cartilaginous remains; p, periosteum. 
 
 Fig. 63. — Transverse section of the macula acustica of the cat. 
 X 120. The figure presents the thickening of the epithelium in the 
 region of the macula acustica and the entrance of the nerve, the fibers 
 of which are medullated until they reach the basal membrane, ep, 
 Columnar epithelium, forming the transition of the flattened epithe- 
 lium into the sensory epithelium; n, branch of nervus vestibuli; «/, 
 some medullated nerve-fibers approaching the epithelium. 
 
 The Cochlea. 
 
 The cochlea presents a far more complicated structure 
 than the semicircular canals. The membranous cochlea, 
 the ductus cochlearis, corresponds to the membranous semi- 
 circular canals ; the spaces of the scala tympani and scala 
 vestibuli represent the perilymphatic space. 
 
 The ductus cochlearis is a spirally twisted canal, tri- 
 angular in cross-section. The thin membrana vestibularis 
 or Reissner's membrane forms its boundary on the side 
 of the scala vestibuli j~~Its base consists of the lamina spi- 
 ralis membranacea and partly also of the lamina spiralis 
 ossea, which form the boundary on the side of the scala 
 tympani ; the lateral wall lies against the periosteum of 
 the outer wall of the bony cochlea. On the inner surface 
 of Reissner's membrane the epithelium of the cochlear duct 
 is flat ; on the lateral wall, cubic. The epithelium on the 
 membrana spiralis represents a highly differentiated and 
 specialized neuro-epithelium, the so-called organ of Corti. 
 Reissner's membrane is inserted on the surface of the 
 lamina spiralis ossea close to its free end, so that a part of 
 the osseous spiral lamina forms the tympanal boundary of 
 the cochlear duct. At the place of attachment of Reiss- 
 ner's membrane, the periosteum of the osseous spiral 
 membrane is thickened to form the limbus spiralis ; this 
 thickening projects freely into the cochlear duct and is 
 known as the labium vpstihulare. 
 
Tcnr^-. 
 
 Fig. 63. 
 
TEE ORGAN OF HEARING. 235 
 
 A similar periosteal thickening is found on the inner 
 surface of the outer cochlear wall, where the membranous 
 spiral lamina is attached ; this is known as the ligamen- 
 tum spirale. That portion of the ligamentum spirale 
 which forms the outer wall of the cochlear duct is rich in 
 blood-vessels and is designated as the stria vascularis ; in 
 it one very prominent vessel is found projecting into the 
 cochlear duct and the elevation is termed the vas promi- 
 nens. The membranous spiral lamina is a membrane 
 composed of fine connective-tissue fibers with oblong flat- 
 tened nuclei. It is attached to the free end of the osseous 
 spiral lamina at the labium tympanicum. The crypt of 
 the cochlear duct which lies between the labium vestibu- 
 lar and labium tympanicum is called the sulcus spiralis. 
 On the under surface of the membranous spiral lamina is 
 found a connective-tissue layer from the periosteum of the 
 scala tympani, the fibers and nuclei of which are vertical 
 to those of the membranous spiral lamina, the so-called 
 tympanal parietal layer. This generally contains a blood- 
 vessel, the vas spirale. The cubic to columnar epithelium 
 of the limhus spiralis changes at the labium vestibulare 
 into peculiar flat processes called auditory teeth. The 
 epithelial cells of this region form a thin cuticular struc- 
 ture of fibrous appearance, which is often slightly curved 
 at the end, extending from the labium vestibulare to the 
 cells of the organ of Corti. It is known as the membrana 
 tectoria. 
 
 The organ of Corti, which is formed from the epithe- 
 lium of the base of the cochlear duct, is situated on the 
 membranous spiral lamina. It is composed for the most 
 part of three special kinds of cells : the pillar cells, the 
 hair-cells, and the cells of Deiters. The pillar cells lie in 
 two spiral rows, an outer and an inner. They are to be 
 regarded as supporting cells of the organ of Corti. They 
 consist for the most part of a cornified substance and 
 stand with the base on the basilar membrane, while the 
 broadened heads are in contact with the pillars opposite ; 
 
236 THE SPECIAL SENSE ORGANS. 
 
 Fig. 64. — Longitudinal section of the cochlea of the cat. X 25. 
 The figure gives a general view of the cochlea. The section was cut 
 through the modiolus; in the modiolus of the cochlea we see the coch- 
 lear branch of the nervus acusticus and its branchings in the lamina 
 spiralis. The cochlear duct is met six times in the section, dc, Coch- 
 lear duct; gsp, spiral ganglion; Kn, osseous cochlear wall; Up, liga- 
 mentum spirale; msp, membrana spiralis; mv, membrana vestibularis; 
 N, nervus cochlearis; set, scala tympani; scv, scala vestibuli. 
 
 Fig. 65. — A portion of the section from Fig. 64 under higher mag- 
 nification. X 180. The figure shows the membranous spiral lamina, 
 with the organ of Corti upon it. ah, Outer hair-cells; apf, outer pil- 
 lars; Clz, cells of Claudius; Dz, cells of Deiters; essp, epithelium of 
 the sulcus spiralis; Hz, cells of Hensen; ih, inner hair-cells; ipf, in- 
 ner pillar cells; Iv, labium vestibulare; mb, membrana basilaris; mt, 
 membrana tectoria; n, branch of the cochlear nerve ; nf, non-medullated 
 nerve-fiber in the pillar tunnel; Nr, space of Nuel. 
 
 inner and outer pillars are articulated in such a way that 
 the inner pillar forms a concave articular surface for the 
 head of the outer pillar. In this way is formed a spiral 
 tunnel .filled with fluid, which is covered arch-like by the 
 pillar heads. The -nuclei of .the pillar cells lie within a 
 small amount of protoplasm in the side of the base of the 
 pillar which is nearest to the tunnel. The number of the 
 inner pillars is greater than that of the outer, as the 
 outer pillars are the broader. The hair-ceUs are divided 
 into inner and outer — that is, those that lie mesially and 
 laterally to the pillar tunnel. There is always only one row 
 of inner hair-cells and a somewhat varying number — gener- 
 ally three or four — of rows of outer hair-cells. They are 
 short, columnar, nucleated cells, having a sharp process at 
 the base, which does riot reach the basilar membrane. 
 On the surface they have fine stiff hairs. Between the 
 outer hair-cells and nearly filling the space between their 
 pointed basal processes are the cells of Deiters — long, nar- 
 row cells, which send a narrow process to the surface of 
 the auditory cells. Deiters' cells, like the pillar cells, are 
 supporting cells ; the upper end lying between the auditory 
 cells is slightly thickened into a head, known as the phalan- 
 geal process, so called because, when the organ of Corti is 
 viewed from the surface, the heads of the cells appear 
 
msp — 
 
 I V V i '5 
 
 ' V ipf ill ),/ «;,/• at,. ,j z f Iz 
 
 n essp 
 
 Pig- 65. 
 
 2iVi 
 
THE ORGAN OF BEARING. 237 
 
 arranged in rows in the spaces between the auditory cells. 
 Deiters' cells do not entirely fill the space between the 
 pillars and the first row of hair-cells, and the space 
 remaining is known as the space of Nuel, and is filled 
 with fluid. 
 
 The cubic epithelium of the sulcus spiralis is attached to 
 the inner hair-cells on the mesial side. The epithelium 
 of the so-called zona pectinata, a name given to that 
 portion of the membranous spiral lamina lying lateral to 
 and not covered by the organ of Corti, is at first columnar 
 and farther out cubic. Several rows of cells nearest to 
 the organ of Corti are known as the cells of Hensen, 
 while the remaining rows are the cells of Claudius. 
 
 The cochlear branch of the acoustic nerve runs in the 
 modiolus, the osseous cochlear axis, from which it 
 branches spirally in the base of the osseous spiral lamina 
 and forms the spiral ganglion. The cells of the ganglion 
 are bipolar. The neuraxes of the ganglion-cells form the 
 acoustic fibers and the dendrites pass to the organ of Corti, 
 the fibers running in the osseous spiral lamina to the 
 labium tympanicum ; they pass through small openings 
 and at the same time become non-medullated. Part of 
 these fibers run to the inner hair-cells, while part of them 
 cross the tunnel to the outer hair-cells. They probably 
 enter into union with the lower pointed ends of the cells, 
 but only into contact, not into cellular connection. 
 
 The labyrinth, vestibule as well as cochlea, receives 
 its blood-supply from a branch of the arteria auditiva 
 interna (Art. labyrinthi), which forms capillary networks 
 in the striae vasculares, in the ganglion spirale, in the 
 membrana spiralis, and the osseous walls of the scala 
 tympani and vestibuli. 
 
 The labyrinth has no special lymph-vessels, but only 
 the endolymphatic and perilymphatic lymph-spaces, which 
 are connected with the lymph-spaces of the membranes of 
 the brain. 
 
238 THE SPECIAL SENSE ORGANS. 
 
 Fig. 66. — Vertical section of the olfactory mucous membrane of a 
 man who had been executed. X 250. Preparations made by Prof. 
 K. W. Zimmermann, of Bern. The preparation was treated by the 
 Golgi method. The upper portion of the epithelium was unrecogniz- 
 able on account of the black precipitate. The connection of the olfac- 
 tory fibers with the olfactory cells can be recognized. E, Epithelium; 
 0, olfactory fibers; B, olfactory cells. 
 
 Fig. 67. — Vertical section of a taste-bud from the papilla foliata of 
 the rabbit. X 500. The figure shows the typical picture of a taste- 
 bud and its relation to the stratified pavement epithelium, stg, Gus- 
 tatory rods; dz, tegmental cells. 
 
 Fig. 68. — View of the taste-bud from the taste-pore. X 500. From 
 a section through the papilla foliata of the rabbit. The figure shows 
 very distinctly the crown of the taste-rods, ep, Stratified pavement 
 epithelium; dz, tegmental cells; gz, gustatory cells; pg, taste-pore; 
 stg, gustatory rods. 
 
 THE ORGAN OF SMELL. 
 
 The organ of smell is in the olfactory region of the 
 nasal cavity (see page 197). The olfactory cells are per- 
 ipheral ganglion-cells, for their centripetal processes pass 
 directly into a non-medullated olfactory fiber. They are 
 long narrow cells, which include the entire thickness of 
 the epithelium of the olfactory region and have in their 
 center an enlargement containing a nucleus. The end of 
 the cell which does not pass into a nerve-fiber extends to 
 the surface of the epithelium, which here forms a fine 
 cuticular formation, the membrana limitans olfactoria. 
 The ends of the olfactory cells present fine hairs. 
 
 THE ORGAN OF TASTE. 
 
 The organ of taste is found in man principally in the 
 form of taste-buds on the ci?-cumvallate papilke of the tongue 
 (see page 137), but also on other papillae. The papillct 
 foliata, of the rabbit contain numerous taste-buds. 
 
 The taste-buds are oval epithelial structures, pointed at the 
 upper end; they lie in the stratified pavement epithelium 
 in such a way that the broader base of the bud lies on the 
 
stg 
 
 CSS 
 
 <m 
 
 iH 
 
 Fig. 67. 
 
 Fig. 66. 
 
 PS stg 
 
 '(0/ 
 
 :<§> 
 
 
 
 -<3» 
 
 ''St- 
 
 ep 
 
 »/«:#* m 
 
 Fig. 68. 
 
THE ORGAN OF TASTE. 239 
 
 basal membrane, the point lying between the upper flat- 
 tened layers of cells, but always at the level of the surface. 
 At this point is found a funnel-shaped depression from the 
 surface, the taste-pore or canal, into which the point of the 
 taste-bud projects. The taste-buds themselves consist of 
 two kinds of cells, gustatory cells and tegmental cells. The 
 former are narrow, spindle-shaped cells, which occupy the 
 center of the bud. Their points extend to the taste-pore 
 and there bear a bright rod-shaped process, the gustatory rod. 
 A group of rod-bearing cells is inclosed by tegmental cells. 
 The latter are of different shapes, elongated, often crescent- 
 shaped, nucleated cells, which surround in several layers 
 the center of the bud which is formed by the gustatory 
 cells. The gustatory cells are epithelial cells, like the 
 auditory cells of the organ of Corti, and not ganglion-cells 
 like the olfactory cells. In consequence of this the nerve- 
 fibers of the ]ST. glosso-pharyngeus, which have become 
 non-medullated, enter into contact with the epithelial cells. 
 We distinguish intergemmal fibers, which end between the 
 taste-buds, and intragemmal fibers, which pass between the 
 tegmental cells to the gustatory cells and end free between 
 them. 
 
INDEX 
 
 Adenoid structures of tongue 
 and pharynx, 13S 
 
 tissue, 53 
 Adipose tissue, 51 
 Adrenals, 193 
 Alveolar glands, 37 
 Amakrine cells, 223 
 Arrectores pilorum, 209 
 Arteries, 116 
 
 Astrocytes of neuroglia, 79 
 Auditory teeth, 235 
 Axis-cvlinder of nerve-fibers, 
 
 75 
 
 Bile capillaries, 165 
 Bile-ducts, 165 
 Bladder, 173 
 Blood, 54 
 
 and lymph vascular system, 
 114 
 
 plasma, 55 
 
 platelets, 61 
 Blood-corpuscles, 55 
 
 red, 55 
 
 white, 57 
 Blood-vessels, 115 
 
 nerve-fibers of, 119 
 Bone, blood-vessels of, 82, 84 
 
 eanaliculi, 82 
 
 development, 85 
 
 endochondral, 85, 86 
 
 intramembranous, 89 
 
 nerves of, 85 
 
 perichondral, 85, 87 
 
 tissue, 81 
 Bone-cells, 81, 82 
 Bone-marrow, 84 
 
 giant-cells of, 86, 91 
 
 red, 61 
 
 16 241 
 
 Bowman's capsule, 167 
 
 glands, 197 
 Bronchi, 198 
 Bronchial branches, 198 
 Bronchioles, 199 
 Bruch's membrane, 218 
 
 Canaliculi, bone, 82 
 Capillaries, 115 
 
 bile, 165 
 
 secretion, 36 
 Capsule of Glisson, 161 
 Cartilage, connective-tissue, 50 
 
 elastic, 49 
 
 hyaline, 49 
 
 reticular, 49 
 
 white fibro-, 50 
 Cartilaginous tissue, 48 
 Cell, 17 
 
 amakrine, 223 
 
 bone-, 81, 82 
 
 centro-acinar, 160 
 
 chief, of stomach, 143 
 
 cone visual, 224 
 
 corneal, 216 
 
 Deiters', 236 
 
 enamel, inner, 134 
 outer, 134 
 
 endothelial, 42 
 
 ependyma, of neuroglia, 79 
 
 epithelial, cornification of, 36 
 relation of one to another 
 
 32 
 special differentiation of, 33 
 
 follicular, 187 
 
 form of, 17 
 
 ganglion-, 71. See also 
 Nerve-cells 
 
 giant-, 61 
 
242 
 
 INDEX. 
 
 ( 'ell, giant-, of bone-marrow, 86, 
 91 
 
 goblet, 35 
 
 Golgi's, 72 
 
 hair-, 236 
 
 lutein, 189 
 
 mast-, of loose connecting 
 tissue, 46 
 
 membrane, 20 
 
 nerve-, 71. See also Nerve- 
 cells 
 
 nucleus, 20 
 
 of connecting tissue, 41 
 
 of loose connecting tissue, 46 
 
 olfactory, 238 
 
 Paneth's, 146 
 
 parareticular, 223 
 
 parietal, 143 
 
 pillar, 235 
 
 plasma-, of loose connecting 
 tissue, 46 
 
 proliferation, 22 
 
 protoplasm, 18 
 foam theory of, 19 
 structure of, 19 
 
 Purkinje's, of cerebellar cor- 
 tex, 101 
 
 pyramidal, of cerebral cortex, 
 103 
 
 rod visual, 223 
 
 Sertoli's, 177 
 
 size of, 18 
 
 spider, of neuroglia, 79 
 
 stellate, of liver, 165 
 
 tendon, 93 
 Cementum, 131, 133 
 Central nervous system, 95. See 
 
 also Nervous system, central 
 Centro-acinar cells, 160 
 Centrosome, 22 
 Cerebellar cortex, 98 
 
 Purkinje's cells of, 101 
 Cerebral cortex, 103 
 
 pyramidal cell of, 101 
 Ceruminous glands, 232 
 Chief cells of stomach, 143 
 Chlorid of hematin, crystals of, 
 
 57 
 Choroid, 217 
 
 layers of, 217 
 
 Chromatin, 21 
 Chromosomes, 23 
 Cilia, 33 
 
 Ciliary body, 218 
 glands, 230 
 muscle, 218 
 processes, 218 
 Club-hairs, 208 
 Cochlea, 234 
 
 membranous, 234 
 Cochlear duct, 234 
 Colloid, 201 
 
 Concretions, prostatic, 183 
 Cone visual cells, 224 
 Conjunctiva bulbi, 231 
 
 palpebrarum, 231 
 Connecting tissue, 40 
 cartilage. 50 
 cells of, 41 
 elastic fibers of, 43 
 fibrous elements of, 43 
 formed, 45, 46 
 gelatinous, 47 
 ground substance of, 44 
 loose, 45 
 cells of, 46 
 leukocytes of, 4C 
 plasma-cells of, 46 
 lymph-vessels of, 53 
 pigmented, 52 
 reticular fibers of, 43 
 simple fibrillar, 45 
 white fibers of, 43 
 Corium, 203, 205 
 Cornea, 215 
 Corneal cells, 216 
 
 endothelium, 216 
 Cornification of epithelial cells, 
 
 36 
 Corpus luteum, 189 
 Corpuscles, blood-, 55 
 red, 55 
 white, 57 
 Grandry's, 112 
 Hassal's, 127 
 Herbst's, 113 
 Malpighian, 167 
 Vater-Pacinian, 112 
 Corti, organ of, 235 
 Cowper's gland, 183 
 
INDEX. 
 
 243 
 
 Ousta, 20 
 Crystalloids, 20 
 Crystals, hematoidin, 57 
 
 of chlorid of hematin, 57 
 Cuticula dentis, 133 
 
 of hair, 206 
 Cutis, 203 
 
 layers of, 203 
 
 Deitees' cells, 236 
 Dendrites, 72 
 Dentinal fibers, 131 
 
 papilla, 134 
 
 sac, 135 
 Dentine, 131 
 Deutoplasm, 189 
 Digestive organs, 128 
 Dilatator muscle of pupil, 219 
 Droplets, fat, 20 
 Ducts, system of, 38 
 Ductus cochlearis, 234 
 Duodenal glands, 148 
 Duodenum, 147 
 
 Ear, 232 
 
 Efferent seminal passages, 180 
 
 urinary passages, 173 
 Egg, tubes of Pfliiger, 187 
 Ejaculatory duct, 182 
 Elastic cartilage, 49 
 
 fibers of connecting tissue, 43 
 
 tissue, 47 
 Eleidin granules, 36 
 Enamel, 131, 132 
 
 cells, inner, 134 
 outer, 134 
 
 ledge, 133 
 
 organs, 133 
 
 pulp, 134 
 Endocardium, 114 
 Endochondral bone, 85, 86 
 Endomysium, 91 
 Endoneurium, 107 
 Endothelial cells, 42 
 Endothelium, corneal, 216 
 
 of iris, 219 
 Ependyma cells of neuroglia, 79 
 
 Epicardium, 115 
 
 Epidermal structures of skin, 
 
 205 
 Epidermis, 202 
 layers of, 202 
 Epineurium, 10 
 Epiphysis, 107 
 
 Epithelial cells, cornification of, 
 36 
 relation of, to each other, 
 
 32 
 special differentiation of, 
 33 
 tissue, 29 
 Epithelium, simple ciliated, 31 
 columnar, 30 
 cubic, 30 
 flattened, 30 
 squamous, 30, 31 
 stratified ciliated, 31 
 columnar, 31 
 pavement, 31 
 transitional, 32 
 Erythrocytes, 55 
 Esophagus, 141 
 Eye, 214 
 
 tunica externa of, 215 
 interna of, 221 
 media bulbi of, 217 
 Eyeball, auxiliary apparatus of, 
 
 229 
 Eyelids, 229 
 
 Fat droplets, 20 
 
 Female reproductive organs, 185 
 
 urethra, 174 
 Fiber, dentinal, 131 
 
 elastic, of connecting tissue, 
 43 
 
 Miiller's, of retina, 222 
 
 nerve-, 75. See also Nerve- 
 fibers 
 
 reticular, of connecting tis- 
 sue, 43 
 
 Sharpey's, 84 
 
 white, of connecting tissue, 43 
 Fibrillar connecting tissue, 
 
 simple, 45 
 Fibro-cartilage, white, 50 
 
244 
 
 INDEX. 
 
 Fibrous elements of connecting 
 
 tissue, 43 
 Flagella, 33 
 Foam theory of cell protoplasm, 
 
 19 
 Follicles, lymph, 121, 122 
 agminated, 122 
 solitary, 122 
 Follicular cells, 187 
 Formed connecting tissue, 45, 
 
 46 
 Fovea centralis of retina, 226 
 
 Ganglia, peripheral, 108 
 
 spinal, 108 
 
 sympathetic, 109 
 Ganglion-cells, 71. See also 
 
 Nerve-cells 
 Gelatinous connecting tissue, 47 
 Germinal epithelium of ovary, 
 
 186 
 Giant-cells, 61 
 
 of bone-marrow, 86, 91 
 Glands, alveolar, 37 
 
 Bowman's, 197 
 
 ceruminous, 232 
 
 ciliary, 230 
 
 Cowper's, 183 
 
 duodenal, 148 
 
 forms of, 37 
 
 hemolymph, 123 
 
 lachrymal, 231 
 
 lymph-, 121 
 
 mammary, 213 
 
 of Moll, 230 
 
 olfactory, 197 
 
 parotid, 155 
 
 pyloric, 144 
 
 salivary, 153 
 
 sebaceous, 210 
 
 sublingual, 158 
 
 submaxillary, 155 
 
 sweat-, 211 
 
 thyroid, 201 
 
 tubular, 37 
 
 unicellular, 35 
 Glandula bulbourethralis, 183 
 Glisson, capsule of, 161 
 Glomerulus, 167 
 
 Goblet-cells, 35 
 Golgi's cells, 72 
 Grandry's corpuscles, 112 
 Granules, eleidin, 36 
 
 keratohyalin, 36 
 
 pigment, 20 
 
 tigroid, 20 
 
 zymogen, 20, 35 
 Ground lamellae, 82 
 
 substance of connecting tis- 
 sue, 44 
 
 Hair, 205 
 Hair-cells, 236 
 Hair-shaft, 206 
 Hair-sheath, 207 
 Hassal's corpuscles, 127 
 Haversian canals, 82 
 
 lamella?, 82 
 Hearing, organ of, 232 
 Heart, 114 
 
 muscle, 68 
 Hematin, chlorid of, crystals of, 
 
 57 
 Hematoidin crystals, 57 
 Hemin, 57 
 Hemoglobin, 57 
 Hemolymph .glands, 123 
 Henle's fibrillar sheath, 108 
 
 layer, 207 
 
 loop, 168 
 Hepatic vein, 164 
 Herbst's corpuscles, 113 
 Howship's lacuna?, 91 
 Huxley's layer, 207 
 Hyaline cartilage,. 49 
 Hyaloplasm, 19 
 Hypophysis, 106 
 
 Interstitial lamella-, 83 
 Intestine, large, 149 
 
 small, 145 
 Intestines, blood-vessels of, 151 
 
 lymphatic structures of, 149 
 
 lymph-vessels of, 151 
 
 nerves of, 151 
 Intralobular vein, 164 
 Intramembranous bone, 89 
 
INDEX. 
 
 245 
 
 Involuntary muscle, 62 
 
 musculature, 63 
 Iris, 219 
 
 blood-vessels of, 219 
 
 endothelium of, 219 
 
 layers of, 219 
 
 muscle of, 219 
 
 stratum proprium of, 219 
 Islands of Langerhans, 160 
 
 Keratohyalin granules, 36 
 Kidney, 166 
 
 blood-vessels of, 170 
 
 Labyrinth, 233 
 Lachrymal glands, 231 
 Laeunte, bone, 82 
 
 Howship's, 91 
 Lamellse, bone, 82 
 
 ground, 82 
 
 Haversian, 82 
 
 interstitial, 83 
 Lamina choriocapillaris, 218 
 
 propria of choroid, 217 
 
 spiralis membranacea, 234, 
 235 
 ossea, 234 
 Langerhans, islands of, 160 
 Large intestine, 149 
 Larynx, 197 
 Lens, 229 
 Leukocytes, 57 
 
 of loose connecting tissue, 46 
 Ligaments, 84 
 Lingual tonsils, 138 
 Linin, 21 
 Liver, 161 
 
 lobules, 161 
 
 stellate cells of, 165 
 Loose connecting tissue, 45 
 cells of, 46 
 leukocytes of, 46 
 plasma-cells of, 46 
 Lungs and bronchial branches, 
 198 
 
 blood-vessels of, 200 
 
 lymph-vessels of, 200 
 
 nerves of, 201 
 
 Lutein cells, 189 
 
 Lymph follicles, 121, 122 
 agminated, 122 
 solitary, 122 
 vascular system, 114 
 
 Lymphatic structures of intes- 
 tines, 149 
 
 Lymph-glands, 121 
 
 Lymphocytes, 57, 58 
 
 Lymphoid tissue, 53, 120 
 
 Lymph-vessels, 120 
 
 Male reproductive organs, 175 
 
 urethra, 183 
 Malpighian corpuscle, 167 
 Mammary glands, 213 
 Marrow, bone-, 84 
 
 red, 61 
 Medulla of hair, 206 
 Medullated nerve-fibers, 75 
 
 myelin of, 77 
 Meissner's plexus, 153 
 Membrana propria, 40 
 
 vestibularis, 234 
 Membrane, cell, 20 
 
 nuclear, 21 
 Microscopic anatomy of the 
 
 organs of the body, 81 
 Microsomes, 19 
 Mitosis, 22 
 Moll, glands of, 230 
 Motor nerve-endings, 109 
 Miiller's fibers of retina, 222 
 Muscle, 91 
 
 ciliary, 218 
 
 heart, 68 
 
 involuntary, 62 
 
 transversely striated, 64 
 
 voluntary, 64 
 Muscular system, organs of, 91 
 
 tissue, 62 
 Musculature, involuntary, 63 
 Myelin of medullated nerve- 
 fibers, 77 
 Myelocytes, 61 
 Myocardium, 114 
 
 Nail-bed, 209 
 Nails, 209 
 
246 
 
 INDEX. 
 
 Nasal cavity, 196 
 Nerve, optic, 227 
 Nerve-cells, 71 
 
 form of, 71 
 
 neurofibrils of, 73 
 
 nucleus of, 72 
 
 protoplasm of, 72 
 
 tigroid substance of, 73 
 Nerve-endings, 109 
 
 motor, 109 
 
 sensory, 109, 110 
 
 encapsulated, 110, 111 
 free, 110, 111 
 Nerve-fibers, 75 
 
 axis-cylinder of, 75 
 
 medullated, 75 
 myelin of, 77 
 
 non-medullated, 75 
 Nervous system, central, 95 
 blood-vessels of, 105 
 lymph-vessels of, 106 
 membranes of, 106 
 organs of, 95 
 peripheral, 107 
 
 tissue, 70 
 Neuraxis, 72 
 Neurilemma, 77 
 Neurofibrils of nerve-cells, 73 
 Neuroglia, 78 
 
 ependyma cells of, 79 
 
 spider cells of, 79 
 Neuromuscular spindles, 92 
 Neurones, 71 
 Neuroplasm, 75 
 Neurotendinous spindles, 95 
 Nissl's bodies, 73 
 Nodes of Ranvier, 76 
 Non-medullated nerve-fibers, 75 
 Nuclear membrane, 21 
 
 sap, 22 
 Nucleoli, 21 
 Nucleus of nerve-cells, 72 
 
 Odontoblasts, 131, 
 Olfactory cells, 238 
 
 glands, 197 
 Optic nerve, 227 
 Oraserrata, 221, 225 
 Oral cavitv, 129 
 
 135 
 
 Organ of Corti, 235 
 Osseous tissue, 81 
 Osteoblasts, 87 
 Osteoclasts, 86, 91 
 Otoliths, 233 
 Ovary, 185 
 Oviduct, 191 
 
 Pancreas, 158 
 Paneth's cells, 146 
 Parareticular cells, 223 
 Parietal cells, 143 
 Parotid gland, 155 
 Penis, 185 
 
 Perichondral bone, 85, 87 
 Perimysium, 91 
 Perineurium, 107 
 Periosteum, 84 
 Peripheral ganglia, 108 
 
 nerves, 107 
 
 nervous system, 107 
 Peyer's patches, 149 
 Pfliiger, egg tubes of, 187 
 Pharyngeal tonsils, 139 
 Pharynx and tongue, adenoid 
 
 structures of, 138 
 Pigment granules, 20 
 Pigmented connective tissue, 
 
 52 
 Pillar cells, 235 
 Pineal gland, 107 
 Plasma, blood, 55 
 Plasma-cells of loose connecting 
 
 tissue, 46 
 Plasmodia, 22 
 Platelets, blood, 61 
 Portal vein, 162 
 Proliferation of cells, 22 
 Prostate, 183 
 Prostatic concretions, 183 
 Protoplasm, 18 
 
 cell theory of, 19 
 
 of nerve-cells, 72 
 
 structure of, 19 
 Purkinje's cells of cerebellar 
 
 cortex, 101 
 Pyloric glands, 144 
 Pyramidal cell of cerebral cortex, 
 
 103 
 
INDEX. 
 
 241 
 
 Ranvier, nodes of, 76 
 Red blood-corpuscles, 55 
 
 bone-marrow, 61 
 Reissner's membrane, 234 
 Reproductive organs, female, 
 185 
 male, 175 
 Respiratory organs, 196 
 Reticular cartilage, 49 
 
 fibers of connecting tissue, 43 
 Retina, 221 
 
 fovea centralis of, 226 
 
 layers of, 221 
 
 Muller's fibers of, 222 
 
 optic papilla of, 227 
 
 ora serrata of, 221, 225 
 Riolani, ciliary muscle of, 231 
 Rod visual cells, 223 
 Root-sheath of hair, 207 
 Rouleaux, 55 
 
 Sacculus, 233 
 Salivary ducts, 155 
 
 glands, 153 
 Sarcoplasm, 66 
 Schwann, sheath of, 77 
 Sclera, 215, 216 
 
 blood-vessels of, 216 
 
 nerves of, 217 
 Sebaceous glands, 210 
 Secretion capillaries, 36 
 Semicircular canals, 233 
 Seminal passages, efferent, 180 
 
 vesicle, 182 
 Sense organs, special, 214 
 Sensory nerve-endings, 109, 110 
 encapsulated, 110, 111 
 free, 110, 111 
 Sertoli's cells, 177 
 Sharpey's fibers, 84 
 Sheath of Schwann, 77 
 Simple epithelium, 30. See also 
 Epithelium 
 
 fibrillar connecting tissue, 45 
 Skeletal system, 81 
 Skin, 201 
 
 epidermal structures of, 205 
 
 glands of, 210 
 
 nerves of, 212 
 
 Small intestine, 145 
 Smell, organ of, 238 
 Special sense organs, 214 
 Spermatids, 177, 179 
 
 development of, into sperma- 
 tosomes, 177 
 Spermatoblast, 177 
 Spermatocytes, 177, 179 
 Spermatogones, 179 
 Spermatosomes, 176 
 
 development of, from sperma- 
 tids, 177 
 Sphincter muscle of pupil, 219 
 Spider cells of neuroglia, 79 
 Spinal cord, 95 
 
 ganglia, 108 
 Spleen, 124 
 Spongioblasts, 223 
 Squamous epithelium, 20, 31 
 Stellate cells of liver, 165 
 Stomach, 143 
 
 blood-vessels of, 151 
 
 lymph-vessels of, 151 
 
 nerves of, 151 
 Stratified ciliated epithelium, 31 
 
 columnar epithelium, 31 
 
 pavement epithelium, 31 
 Stratum corneum, 202 
 
 germinativum, 203 
 
 granulosum, 203 
 
 lucidum, 203 
 
 spinosum, 203 
 Sublingual gland, 158 
 Submaxillary gland, 155 
 Suprarenals, 193 
 Sweat-glands, 211 
 Sympathetic ganglia, 109 
 Syncitia, 22 
 System of ducts, 38 
 
 Tactile meniscus, 111 
 Taste, organ of, 238 
 Taste-buds, 238 
 Teeth, 130 
 
 auditory, 235 
 Tela subcutanea, 203 
 Tendon cells, 93 
 Tendons, 93 
 Testis, 175 
 
248 
 
 INDEX. 
 
 Testis, blood-vessels of, 180 
 
 nerves of, 180 
 Thymus, 126 
 Thyroid gland, 201 
 Tigroid granules, 20 
 
 substance, 73 
 Tissue, 28 
 adenoid, 53 
 adipose, 51 
 bone, 81 
 
 cartilaginous, 48 
 connective, 40 
 cells of, 41 
 elastic fibers of, 43 
 fibrous elements of, 43 
 ground substance of, 44 
 lymph-vessels of, 53 
 reticular fibers of, 43 
 simple fibrillar, 45 
 white fibers of, 43 
 elastic, 47 
 epithelial, 29 
 formed connecting, 45, 46 
 gelatinous connecting, 47 
 loose connecting, 45 
 cells of, 46 
 leukocytes of, 46 
 plasma-cells of, 46 
 lymphoid, 53 
 muscle, 62 
 nervous, 70 
 osseous, 81 
 
 pigmented connective, 52 
 Tomes' granular layer, 132 
 Tongue, 136 
 
 and pharynx, adenoid struc- 
 tures of, 138 
 blood-vessels of, 140 
 lymph-vessels of, 140 
 nerves of, 141 
 Tonsillar crypt, 138 
 Tonsils, lingual, 138 
 
 pharyngeal, 139 
 Tooth pulp, 130 
 TrabeculEe of lymph-glands, 121 
 
 Trachea, 198 
 
 Transitional epithelium, 32 
 
 Tubular glands, 37 
 
 Tunica externa of eye, 215 
 interna of eye, 221 
 media bulbi of eye, 217 
 
 Tympanic membrane, 233 
 
 Unicellular glands, 35 
 Ureter, 173 
 Urethra, female, 174 
 
 male, 183 
 Urinary organs, 166 
 
 passages, efferent, 173 
 Uriniferous tubules, 167 
 Uterus, 191 
 Utriculus, 233 
 
 Vagina, 193 
 
 Vas deferens, 181 
 
 Vascular system, lymph, 114 
 
 Vater-Pacinian corpuscles, 112 
 
 Veins, 118 
 
 hepatic, 164 
 
 intralobular, 164 
 
 portal, 162 
 Vision, organ of, 214 
 Visual cells, cone, 224 
 
 rod, 223 
 Vitreous body, 228 
 Volkmann's canals, 83 
 Voluntary muscle, 64 
 
 White blood-corpuscles, 57 
 fibers of connecting tissue, 43 
 fibro-cartilage, 50 
 
 Yolk-nucleus, 189 
 
 Zonula ciliaris, 228 
 Zymogen granules, 20, 35 
 
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 Atlas and Epitome of External Diseases of the Eye. 
 
 By Dr. O. Haab, of Ziirich. Edited, with additions, by G. E. 
 deSchweinitz, M. D., Professor of Ophthalmology, University 
 of Pennsylvania. With 76 colored illustrations on 40 litho- 
 graphic plates and 228 pages of text. Cloth, $3.00 net. 
 
 This new work of the distinguished Zurich ophthalmologist is destined 
 to become a valuable handbook in the library of every practising physician. 
 The conditions attending diseases of the external eye have probably never 
 been more clearly and comprehensively expounded than in the forelying 
 work, in which the pictorial most happily supplements the verbal description. 
 
 The Medical Record, New York 
 
 " The work is excellently suited to the student of ophthalmology and to the practising' 
 physician. It cannot fail to attain a well-deserved popularity." 
 
 They are convenient in size and uniformly bound 
 
12 SAUNDERS' MEDICAL HAND-ATLASES 
 
 Schaffer arid Edgar's 
 Labor arid Operative Obstetrics 
 
 Atlas and Epitome of Labor and Operative Obstetrics. 
 
 By Dr. 0, Schaffer, of Heidelberg. From the Fifth Revised 
 and Enlarged German Edition. Edited, with additions, by 
 J. Clifton Edgar, M. D., Professor of Obstetrics and Clinical 
 Midwifery, Cornell University Medical School. 14 lithographic 
 plates in colors; 139 other cuts; m pages of text. $2.00 net. 
 
 The book presents the act of parturition and the various obstetric opera- 
 tions in a series of easily understood illustrations. These are accompanied 
 by a text that treats the subject from a practical standpoint. 
 
 Dublin Journal of Medical Science, Dublin 
 
 " One fault Professor Schaffer's Atlases possess. Their name, and the extent and 
 number of the illustrations, are apt to lead one to suppose that they are merely ' atlases,' 
 whereas the truth really is they are also concise and modem epitomes of obstetrics." 
 
 Schaffer & Edgar's Obstetric 
 Diagnosis and Treatment 
 
 Atlas and Epitome of Obstetric Diagnosis and Treat- 
 ment. By Dr. O. Schaffer, of Heidelberg. From the Sec- 
 ond Revised German Edition. Edited, with additions, by J. 
 Clifton Edgar, M. D., Professor of Obstetrics and Clinical 
 Midwifery, Cornell University Medical School. 122 colored fig- 
 ures on 56 .plates; 38 other cuts; 315 pages of text. $3.00 net. 
 
 This book treats particularly of obstetric operations, and, besides the 
 wealth of beautiful lithographic illustrations, contains an extensive text of 
 great value. This text deals with the practical, clinical side of the subject. 
 
 New York Medical Journal 
 
 "The illustrations areadmirably executed, as they are in all of these atlases, and the 
 text can safely be commended, not only as elucidatory of the plates, but as expounding the 
 ■scientific midwifery of to-day." 
 
 These are the famous " Lehmann medicinische Handatlanten " 
 
SAUA'DEXS' MEDICAL HAND-ATLASES 13 
 
 Mracek and Stelwagon's 
 Skin 
 
 Atlas and Epitome of Diseases of the Skin. By Prof. 
 Dr. Franz Mracek, of Vienna. Edited, with additions, by 
 Henry W. Stelwagon, M. D., Clinical Professor of Derma- 
 tology, Jefferson Medical College, Philadelphia. With 63 colored 
 plates, 39 half-tone illustrations, and 200 pages of text. Cloth, 
 #3.50 net. 
 
 This volume, the outcome of years of scientific and artistic work, con- 
 tains, together with colored plates of unusual beauty, numerous illustrations 
 in black, and a text comprehending the entire field of dermatology. The 
 illustrations are all original and prepared from actual cases in Mracek' s clinic. 
 
 American Journal of the Medical Sciences 
 
 " The advantages which we see in this book and which recommend it to our minds are : 
 First, its handiness; secondly, the plates, which are excellent as regards drawing, color, 
 and the diagnostic points which they bring out. We most heartily recommend it." 
 
 Mracek and Bang's 
 Syphilis and Venereal Diseases 
 
 Atlas and Epitome of Syphilis and the Venereal Dis= 
 
 eases. By Prof. Dr. Franz Mracek, of Vienna. Edited, with 
 additions, by L. Bolton Bangs, M. D., Professor of Genito- 
 urinary Surgery, University and Bellevue Hospital Medical 
 College, New York. With 71 colored plates and 122 pages 
 of text. Cloth, $3.50 net. 
 
 According to the unanimous opinion of numerous authorities, to whom 
 the original illustrations of this book were presented, they surpass in beauty 
 anything of the kind that has been produced in this field, not only in Ger- 
 many, but throughout the literature of the world. 
 
 Robert L. Dickinson, M. D., 
 
 Art Editor of " The American Text-Book of Obstetrics" 
 
 " The book that appeals instantly to me for the strikingly successful, valuable, and 
 graphic character of its illustrations is the ' Atlas of Syphilis and the Venereal Diseases.' 
 I know of nothing in this country that can compare with it." 
 
 The lithographs, all made in Germany, are unrivalled 
 
I 4 SAUNDERS' MEDICAL HAND-ATLASES 
 
 Jakob and Fisher's 
 Nervous System & its Diseases 
 
 Atlas and Epitome of the Nervous System and its Dis- 
 eases. By Professor Dr. Chr. Jakob, of Erlangen. From 
 the Second Revised German Edition. Edited, with additions, 
 by Edward D. Fisher, M. D., Professor of Diseases of the Ner- 
 vous System, University and Bellevue Hospital Medical College, 
 New York. With 83 plates and copious text. Cloth, $3.50 net. 
 
 The matter is divided into Anatomy, Pathology, and Description of Dis- 
 eases of the Nervous System. The plates illustrate these divisions most 
 completely ; especially is this so in regard to pathology. The exact site and 
 character of the lesion are portrayed in such a way that they cannot fail to 
 impress themselves on the memory of the reader. 
 
 Philadelphia Medical Journal 
 
 " We know of no one work of anything like equal size which covers this important and 
 complicated field with the clearness and scientific fidelity of this hand-atlas." 
 
 Shaffer and Norris' 
 Gynecology 
 
 Atlas and Epitome of Gynecology. By Dr. O. Shaffer, 
 
 of Heidelberg. From the Second Revised and Enlarged German 
 
 Edition. Edited, with additions, by Richard C. Norris, A. M., 
 
 M. D., Gynecologist to Methodist-Episcopal and Philadelphia 
 
 Hospitals. With 207 colored figures on 90 plates, 65 text-cuts, 
 
 and 308 pages of text. Cloth, $3.50 net. 
 
 The value of this atlas will be found not only in the concise explanatory 
 text, but especially in the illustrations. The large number of colored plates, 
 reproducing the appearance of fresh specimens, will give the student a knowl- 
 edge of the changes induced by disease that cannot be obtained from mere 
 description. 
 
 Bulletin of Johns Hopkins Hospital, Baltimore 
 
 "The book contains much valuable material. Rarely have we seen such a valuable 
 collection of gynecological plates." 
 
 These books are next best to actual clinical work 
 
SAUNDERS' MEDICAL HAND-ATLASES 15 
 
 Hofmann and Peterson's 
 Leg'al Medicine 
 
 Atlas of Legal Medicine. By Dr. E. von Hofmann, of 
 Vienna. Edited by Frederick Peterson, M. D., Chief of 
 Clinic, Nervous Department, College of Physicians and Sur- 
 geons, New York. With 120 colored figures on 56 plates and 
 193 half-tone illustrations. Cloth, $3.50 net. 
 
 By reason of the wealth of illustrations and the fidelity of the colored 
 plates, the book supplements all the text-books on the subject. More- 
 over, it furnishes to every physician, student, and lawyer a veritable treasure- 
 house of information. 
 
 The Practitioner, London 
 
 " The illustrations appear to be the best that have ever been published in connection 
 ■with this department of medicine, and they cannot fail to be useful alike to the medical 
 jurist and to the student of forensic medicine." 
 
 Golebiewski and Bailey's 
 Accident Diseases 
 
 Atlas and Epitome of Diseases Caused by Accidents. 
 
 By Dr. Ed. Golebiewski, of Berlin. Edited, with additions, 
 by Pearce Bailey, M. D., Attending Physician to the Alms- 
 house and Incurable Hospitals, New York. With 71 colored 
 illustrations on 40 plates, 143 text-illustrations, and 549 pages 
 of text. Cloth, $4.00 net. 
 
 This work contains a full and scientific treatment of the subject of acci- 
 dent injury ; the functional disability caused thereby ; the medicolegal ques- 
 tions involved, and the amount of indemnity justified in given cases. 
 
 Medical Examiner and Practitioner 
 
 " It is a useful addition to life-insurance libraries, for lawyers, physicians, and for every 
 one who is brought in contact with the treatment or consideration of accidents or diseases 
 growing out of them, or legal complications flowing from them." 
 
 The " Atlas of Operative Surgery " has been adopted by U. S. Army 
 
16 SAUNDERS' MEDICAL HAND-ATLASES 
 
 Jakob and Eshner's 
 Internal Medicine & Diagnosis 
 
 Atlas and Epitome of Internal Medicine and Clinical 
 Diagnosis. By Dr. Chr. Jakob, of Erlangen. Edited, with 
 additions, by Augustus A. Eshner, M. D., Professor of Clin- 
 ical Medicine in the Philadelphia Polyclinic. With 182 colored 
 figures on 68 plates, 64 illustrations in black and white, and 
 259 pages of text. Cloth, $3.00 net. 
 
 In addition to an admirable atlas of clinical microscopy, this volume 
 describes the physical signs of all internal diseases in an instructive manner 
 by means of fifty colored schematic diagrams. As a means of instruction 
 its value is very great ; as a reference handbook it is admirable. 
 
 British Medical Journal 
 
 " Dr. Jakob's work deserves nothing but praise. The information is accurate and up 
 to present-day requirements." 
 
 Griinwald and Grayson's 
 Diseases of the Larynx 
 
 Atlas and Epitome of Diseases of the Larynx. By Dr. 
 
 L. Grunwald, of Munich. Edited, with additions, by Charles 
 P. Grayson, M. D., Physician-in-Charge, Throat and Nose 
 Department, Hospital of the University of Pennsylvania. With 
 107 colored figures on 44 plates, 25 text-illustrations, and 103 
 pages of text. Cloth, $2.50 net. 
 
 This atlas exemplifies a happy blending of the didactic and clinical, such 
 as is not to be found in any other volume upon this subject. The author 
 has given special attention to the clinical portion of the work, the sections 
 on diagnosis and treatment being particularly full. 
 
 The Medical Record, New York 
 
 " This is a goodwork of reference, being both practical and concise. ... It is a valu- 
 able addition to existing laryngeal text-books." 
 
 For " Special Offer " regarding these atlases see page I 
 
Atlas and Epitome of Internal Medicine and Clinical Diagnosis. By Dr. Chr. 
 Jakob, of Erlangen. Edited, with additions, by Augustus A. Eshneh, M. D., Profes- 
 sor of Clinical Medicine in the Philadelphia Polyclinic. With 179 colored figures on 68 
 plates and 259 pages of text. Cloth, #3.00 net. 
 
 " Dr. Jakob's work deserves nothing but praise. The information is accurate and up to 
 present-day requirements." — British Medical Journal. 
 
 Atlas of Legal Medicine. By Dr. E. von Hofmann, of Vienna. Edited, with addi- 
 tions, by Frederick Peterson, M. D., Chief of Clinic, Nervous Department, College 
 of Physicians and Surgeons, New York. With 120 colored figures on 56 plates and 193 
 half-tone illustrations. Cloth, $3.50 net. 
 
 " It is rare indeed that so large a series of illustrations are found which demonstrate so 
 well and so accurately the conditions which they are supposed to represent." — Boston 
 Medical and Surgical Journal. 
 
 Atlas and Epitome of Diseases of the Larynx. By Dr. L. Gkunwald, of Munich. 
 Edited, with additions, by Charles P. Grayson, M. D-, Physic ian-in-Charge, Throat 
 and Nose Department, Hospital of the University of Pennsylvania. With 107 colored 
 figures on 44 plates, 25 text-illustrations, and 103 pages of text. Cloth, #2.50 net. 
 
 " Excels everything we have hitherto seen in the way of coloured illustrations of diseases 
 of the larynx." — British Medical Journal. 
 
 Atlas and Epitome of Operative Surgery. By Dr. O. Zuckerkandl, of Vienna. 
 
 From the Second Revised and Enlarged German Edition. Edited, with additions, by 
 J. Chalmers DaCosta, M. D., Professor of the Principles of Surgery and of Clinical 
 Surgery, Jefferson Medical College, Philadelphia. Second Edition, Revised and Greatly 
 Enlarged. With 40 colored plates, 278 text-cuts, and 410 pages of text. Cloth, $3-5° net. 
 " It may be said that few, if any, books of this description are so comprehensive in their 
 scope." — Philadelphia Medical Journal. 
 
 Atlas and Epitome of Syphilis and the Venereal Diseases. By Prop. Dr. Franz 
 Mracek, of Vienna. Edited, with additions, by L. Bolton Bangs, M. D., Professor 
 of Genito-Urinary Surgery, University and Bellevue Hospital Medical College, New 
 York. With 71 colored pfates and 122 pages of text. Cloth, #3.50 net. 
 
 "A glance through the book is almost like actual attendance upon a famous clinic." — 
 Journal 0/ the American Medical Association. 
 
 Atlas and Epitome of External Diseases of the Eye. By Dr. O. Haab, of Zurich. 
 
 Edited, with additions, by G. E. de Schweinitz, M. D., Professor of Ophthalmology, 
 Jefferson Medical College, Philadelphia. With 76 colored illustrations on 40 plates and 
 228 pages of text. Cloth, $3.00 net. 
 
 " The work is excellently suited to the student of ophthalmology and to the practising 
 physician. The enviable status of the author and of the editor guarantees the excellence 
 of the work." — Medical Record, New York. 
 
 Atlas and Epitome of Skin Diseases. By Prof. Dr. Franz Mracek, of Vienna. 
 Edited, with additions by Henry W. Stblwagon, M. D., Clinical Professor of Derma- 
 tology, Jefferson Medical College, Philadelphia. With 63 colored plates, 39 half-tone 
 illustrations, and 200 pages of text. Cloth, #3.50 net. 
 
 " The illustrations are very well executed, and the coloring remarkably accurate ■ they 
 will serve as substitutes forclinical observation."— Medical Record, New York. 
 
 Atlas and Epitome of Special Pathologic Histology. By Dr. H. Durck, of Munich 
 Edited, with additions, by Ludvig Hektoen, M. D., Professor of Pathology Rush 
 Medical College, Chicago. In Two Parts. Part I.— Circulatory, Respiratory, and 
 Gastro-intestinal Tracts. Part II.— Liver, Urinary and Sexual Organs, Nervous Sys- 
 tem, Skin, Muscles, and Bones. With 243 colored figures on 122 plates, and 350 pages 
 of text " Per part : $3.00 net. 
 
 u Th %Yt°' k maintains the high standard of ta predecessors. The plates are most 
 beautifully reproduced and are accurate representations of the microscopic structure of 
 the various organs concerned and the changes produced by disease."— The Lancet, London. 
 
 Atlas and Epitome of Diseases Caused by Accidents. By Dr. Ed. Golebiewski of 
 Berlin. t translated and edited, with additions, by Pearce Bailey, M D. Attendine 
 Physician to the Almshouse and Incurable Hospitals, New York. With 71 colored fig? 
 ures on 40 plates; 143 text-illustrations; 549 pages of text. Cloth, $4.00 net. 
 
 " This volume appeals not only to the medical student and the practitioner, but to the 
 medico-legal specialist and accident insurance companies also.*'— New York Med. Jour. 
 
 Atlas and Epitome of Gynecology. By Dr. O. Schaeffer, of Heidelberg. From the 
 Second Revised and Enlarged German Edition. Edited, with additions, by Richard 
 C. Morris, A.M., M. D., Gynecologist to the Methodist Episcopal and Philadelphia 
 hospitals. With 207 colored illustrations on 90 plates, 65 text-illustrations, and 308 pages 
 ( ' ' #3-5o net. 
 
 ' The book contains much valuable material. . . . Rarely have we seen such a valuable 
 collection of gynecological plates."— Bulletin of Johns Hopkins Hospital. 
 
HAND-ATLASES 
 
 Atlas and Epitome of Labor ana Operative UDstetrics. By Dr. 0. Schaeffer, of 
 Heidelberg. From the Fifth Revised and Enlarged German Edition. Edited by J. 
 C. Edgar, M. D., Professor of Obstetrics and Clinical Midwifery, Cornell University 
 Medical School. With 14 lithographic plates in colors, 139 other illustrations. $2.00 net. 
 "A careful study of the plates and drawings is the next best thing to actual clinical 
 experience." — Buffalo Medical Journal. 
 
 Atlas and Epitome of Obstetrical Diagnosis and Treatment. By Dr. 0. Schaeffer, 
 of Heidelberg. From the Second Revised and Enlarged German Edition. Edited, 
 with additions, by J. C. Eugar, M. D., Professor of Obstetrics and Clinical Midwifery. 
 Cornell University Medical School, With 122 colored figures on 56 plates, 38 other illus- 
 trations, and 315 pages of text. Cloth, $3.00 net. 
 "The illustrations are admirably executed . . . and the text expounds the scientific 
 midwifery of to-day." — New York Medical Journal. 
 
 Atlas and Epitome of the Nervous System and Its Diseases. By Prof. Dk. Chr. 
 Jakob, of Erlangen. From the Second Revised and Enlarged German Edition. 
 Edited, with additions, by E. D. Fisher, M. D., Professor of Diseases of the Nervous 
 System, University and Bellevue Hospital Medical College, New York. 83 plates; 215 
 pages of text. #3-5° net. 
 
 " Represents with wonderful accuracy the macroscopic and microscopic anatomy'of 
 the nervous tissues as found in normal and pathologic conditions." — American Medicine. 
 
 Atlas and Epitome of Ophthalmoscopy and Ophthalmoscopic Diagnosis. By Dk. 
 
 O. Haab, of Zurich. From the Third Revised and Enlarged German Edition. Edited, 
 with additions, by G. E. de Schwejnitz, M. D., Professor oi "Ophthalmology, Jefferson 
 Medical College, Philadelphia. 152 colored figures; 82 pages «£ to«t. Gluth, #3.00 net. 
 *' Nowhere else can be found such a fine pictorial collection of changes and lesions of the 
 eye-fundus as this volume contains." — Journal of the American Medical Association. 
 
 Atlas of Bacteriology and Text-Book of Special Bacterlologic Diagnosis. By 
 Prof. Dr. K. B. Lehmann and Dk. R. O. Neumann, of Wurzburg. Front the Second 
 Revised and Enlarged German Edition. Edited, with additions, by G. H. Weaver, 
 M. D., Assistant Professor of Pathology and Bacteriology, Rush Medical College, 
 Chicago. Two volumes. Part I.— 632 colored figures on 6gplates. Part II. — 511 pages 
 of text, illustrated. Per volume : Cloth, $2.50 net. 
 
 " The illustrations . . . are works of art ; they are true in color and relationship and are 
 much superior to the usual photographic reproductions."— Buffalo Medical Journal. 
 
 Atlas and Epitome of Otology. By G. Bruhl, M. D., of Berlin, with the collaboration 
 of Prof. Dr. A. Politzer, of Vienna. Edited, with additions, by S. MacCiien Smith, 
 M. D., Clinical Professor of Otology, JefFerson Medical College, Philadelphia. 244 col- 
 ored figures on 39 lithographic plates, 99 text-illustrations, and 292 pages of text. Cloth, 
 $3.00 net. 
 
 A special feature is the very complete exposition of the minute anatomy of the ear. 
 The work contains everything of importance in the elementary study of the subject. 
 
 Atlas and Epitome of Abdominal Hernias. By Privatdocent Dk. Georc Sultan, 
 of Gottingen. Edited, with additions, by William B. Coley, Clinical Lecturer on Sur- 
 gery, Columbia University (College of Physicians and Surgeons), New York. With 119 
 illustrations, 36 of them in colors, and 277 pages of text. Cloth, $3.00 net. 
 The illustrations are not only very numerous, but they excel in character those of any 
 other work on' the subject. 
 
 Atlas and Epitome of Traumatic Fractures and Dislocations. By Prof. Dr. H. 
 Helferich, of Greifswald. Edited, with additions, by Joseph C. Bloodgood, Asso- 
 ciate in Surgery, Johns Hopkins University, Baltimore. With 216 colored figures on 64 
 lithographic plates, 190 text-cuts, and 353 pages of text. Cloth, $3.00 net. 
 Such a splendid collection of illustrations are possible only in a very large clinic, and 
 represent time, labor, and great care. 
 
 Atlas and Epitome of Diseases of Mouth, Throat, and Nose. By Dr. L. Grunwald, 
 of Munich. From the Second Revised and Enlarged German Edition. Edited, with 
 additions, by James E. Newcomb, M. D., Clinical Instructor in Laryngology, Cornell 
 University Medical School. With 42 colored figures, 39 text-cuts, and 225 pages of text. 
 In Press. 
 
 Atlas and Epitome of Normal Histology. By Privatdocent Dr. J. Sobotta, of 
 Wurzburg. Edited, with additions, by G. Carl Huber, M. D., Junior Professor of 
 Anatomy and Director of the Histological Laboratory, University of Michigan. With 
 80 colored figures and 68 text-cuts from the original of W. Freytag, and 275 pages of text. 
 
 Atlas and Epitome of Operative Gynecology. By Dr. Oskar Schaeffer, Privat- 
 docent at the University of Heidelberg. With 42 colored figures and 21 text-cuts from 
 the original of A. Schmitson, and 125 pages of text. 
 
 ADDITIONAL VOLUMES IN PREPARATION 
 
 Philada, W. B, SAUNDERS & CO. London