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FORH NO. 609; 12.23,32: 76.500

MANUAL

OF

HUMAN MICROSCOPICAL ANATOMY.

MANUAL

OF

HUMAN MICROSCOPICAL ANATOMY.

BY

A. KOLLIKER,

PROFESSOR OF ANATOMY AND PHISIOLGGT IN WUKEEURO.

TRANSLATED BY /

5Tif -

GEORGE BUSK, F.R.S., and THOMAS HUXLEY, F.R.S.

EDITED, WITH NOTES AND ADDITIONS,

BY

J. DA COSTA, M.D.

> '1 ■'
• , i

ILLUSTRATEIO'B? I'HR:iE H.TNDiaED ^JSJ} TjaiSTEEif^I ENGRAVINGS ON WOOD,

PHILADELPHIA:
LIPPINCOTT, GRAMBO & CO.,

1854.

1-^

/

< «■ *'■ •■ »■

EDITOR'S PREFACE.

The absence from our medical literature of a systematic treatise on
Microscopical Anatomy, in its connection with Physiology and Pathology,
induced the Editor nearly a year since, to undertake a translation of
Prof. Kolliker's Manual of Human Microscopical Anatomy. Whilst his
translation was in progress, he learned that the Sydenham Society in-
tended to publish an English edition of the work, and that, indeed, the
first volume of this was ready to be issued. As the time and labor requi-
site for an original translation, would have prolonged the publication of
this work far beyond that of the Sydenham Society, the Editor did not
judge it expedient, to delay the appearance of an American edition longer
than was necessary. He resolved, therefore, to adopt the translation
published by the Sydenham Society, and merely to append such notes
as he intended to have added to his own edition.

The work itself does not need any lengthy comment ; the distinguished
name of the author being a sufficient guarantee of its excellence. It
was published in the latter months of 1852, under the title of " Hand-
buch der Gewebelehre" (Manual of Human Histology), and was designed
by the author to serve as a text-book for students and practitioners
of medicine, by giving a condensed view of the elementary parts of the
Human Organism. By appending a full account of the method to be
employed in the investigation of the separate tissues and organs, as
well as the sources from which further information might be derived,
the author has, at the same time, rendered his work a valuable guide for
independent research.

The Translators have faithfully rendered the text of the original.
They have also added several sentences from Professor Kolliker's larger
work on Microscopical Anatomy, and, in the shape of Notes and an
Appendix, many original observations of their own.

XIV EDITOES PREFACE.

In the preparation of an American edition, the Editor has endeavored
to note all the more recent contributions to Histology. Following
the example of the Translators, he has also incorporated into the text
many paragraphs from the author's larger work, and he hopes, that the
volume, as it now stands, may be considered as a fair exponent of the
actual state of the science. A recent kind communication from the
author, enables the Editor to state, that he, at least, has not changed
his views on any material points. All slight deviations from the opinions
expressed by Prof. Kolliker in the original edition of this work, as well
as his later researches, the Editor has been careful to notice. In making
these additions he has endeavored not to lose si^ht of the original in-
tention of the author, which he ventures to believe he has furthered
by the addition of short pathological notes, wherever the nature of the
text seemed to call for them. For convenience of reference, an index
has also been added, which was wanting in the German, as well as in
the English edition.

By a comparison with the original, the Editor has further been able
to correct many errors with regard to the measurements. The signs
('" for a line, " for an inch) in which these latter were expressed by
the author, had been retained by the Translators. As they are not at
all employed in this country, it was thought more advisable to substi-
tute for them, in every instance, the words they denote.

The wood-cuts are those used in the original German edition, the
publishers having spared neither trouble nor expense to render the
present volume as complete as possible.

The Editor's additions are enclosed in brackets, and mostly marked
with his initials.

Philadelphia, July, 1854.

AUTIIOE^S PUEEACE.

Medicine has reached a point, at ■which Microscopical Anatomy
appears to constitute its foundation, quite as much as the Anatomy of
the Organs and Systems ; and when a profound study of Physiology
and Pathological Anatomy is impossible, without an accurate acquaint-
ance, also, with the most minute structural conditions. It seems, there-
fore, to be the task of the cultivators of this branch of science, to com-
municate the results of their researches, not only to their fellow inqui-
rers, and to those who have, in other ways, gone more deeply into
medical science, but to all who are devoted to the study of Man in
general, and especially to render them easily available by students and
practitioners. The attainment of this object is sought, in the present
work, by giving a view, as condensed as possible, of the relations of the
elementary parts of the body, and of the more intimate structure of the
organs. In the execution of this plan, with the exception of some im-
portant, but still doubtful questions, all polemical disquisition is avoided,
and the History of the Science also left altogether in the background ;
whilst as constant reference as could in any way be admitted, has been
made to Physiology and Pathological Anatomy, as well as to Compara-
tive Histology.

For further information, the Author refers to more detailed Anato-
mical works, and particularly to his "Microscopical Anatomy," in
which the data for all that is here only briefly expressed, will be found.

WcRZBUKG, August Ist, 1852.

CONTENTS.

INTRODUCTION.

SECT.

1. Historical Introduction, ....

2. Present position of the Science,

3. Aids to the Study (Literature, Microscope, Preparations),

PAGE.

33
34
36

GENERAL HISTOLOGY.

I.— OF THE ELEMENTARY PARTS,

4. Simple and compound elementary parts, ,

5. Plastic fluid, fundamental substance, .

pp.

39, 40.

39

40

A. SIMPLE ELEMENTARY PARTS, pp. 41-70.

1. Elementary Granules, — vesicles, nuclei —

6

2. Of the Cells:—

7. Composition, .....

8. Form, chemical relations, nucleus, nucleolus,

9. Cell-formation, .....

10. Free cell-formation, ....

11. Endogenous cell-formation, ....

12. Multiplication of cells by division,

13. Theory of cell-formation, ....

14. Vital phenomena of cells, growth,

15. Processes in the interior of the cells — Absorption,

16. Excretive processes, ....

17. Contractility of the cells, ....

18. Metamorphoses of the cells, kinds of cells.

B. HIGHER ELEMENTARY PARTS, pp. 70-72

19.

41

43

44
48
48
49
54
56
59
61
67
68
69

70

IL— OF THE TISSUES, ORGANS, AND SYSTEMS, pp. 72-119.

20. Enumeration of them,

21. Epidermic tissue,

72
74

xvm

CONTENTS.

SECT.

22. Carlilaginons tissue,

23. Elastic tissue,

24. Connective tissue,

25. Osseous tissue,

26. Tissue of the smooth muscles,

27. Tissue of the striped muscles,

28. Nerve-tissue,

29. Tissue of the true glands,

30. Tissue of the blood-vascular glands,

PAGE

78

81

89

99

102

106

109

113

116

SPECIAL HISTOLOGY.

OF THE EXTERNAL INTEGUMENT, pp. 119-222.
I.— OF THE SKIN IN THE MORE RESTRICTED SENSE, pp. 119-159.

A. CUTIS DERMA, pp. 119-139.

31. Parts of the common integument, .

32. Subcutaneous cellular tissue,

33. Parts of the cori«m, tactile papillse, .

34. Connective tissue, elastic fibres, and muscles of the corium,

35. Fat-cells, .....

36. Vessels of the Skin, ....

37. Nerves, .....

38. Development of the Cutis,

39. Phy.siological remarks,

B. CUTICLE OR EPIDERMIS, pp. 139-159.

40. Parts of the Epidermis, .....

41. JVIucous layer, .....

42. Horny layer, ......

43. Colour of the Epidermis, ....

44. Thickness of the Epidermis, ....

45. Physical and Chemical relations, .

46. Growth and regeneration, ....

47. Development, .....

119
119
120
123
125
127
129
134
135

139
140
142
143
145
146
150
154

II.— OF THE NAILS, pp. 159-171.

48. Parts of the Nail,

49. Structure of the Nail,

50. Relation of the Nail to the epidermis,

51. Growth of the Nails,

52. Development of the Nails,

159
161
164
165
169

III._OF THE HAIRS, pp. 171-199.

OF THE UAIRS IN THE MOKE RESTRICTED SENSE.

53. Parts of the Hair, ....••

171

CONTENTS.

XIX

SECT.

54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.

Disposition and size of the Hairs, ....

External peculiarities, and Chemical connposition of the Hairs,

Strncture of the Hairs, cortical substance,

iSIeduilary substance, .....

Cuticular covering, ......

Hair-follicles, ......

Hair-follicle in the more restricted sense,

Root-sheaths, ......

Development of the Hair, .....

Shedding of the Hair, .....

Physiological remarks, .....

PAGE

171

172
173
177

180
182
182
184
186
191
193

IY._OF THE CUTANEOUS GLANDS, pp. 199, 222.

A. OF THE SUDORIPAROUS GLANDS, pp. 199-209.

65. Disposition, ........

66. Structure, ........

67. ]\Iore intimate structure of the glandular coil, . . . ,

68. Secretion of the sudoriparous glands, ....

69. Sweat-Ducts, ........

70. Development of the sudoriparous glands, ....

B. OF THE CEEUMINOUS GLANDS, pp. 209-212.

71. Structure, ........

72. Secretion and development, .....

199
199
200
202
204
205

209

210

C. OF THE SEBACEOUS GLANDS, pp. 212-222.

73. Structure, form, and disposition, ....

74. More intimate structure, ......

75. Development, .......

OF THE MUSCULAR SYSTEM, pp. 222-266.

76. Definition of it, .....

77. Structure of the muscular fibres,

78. The mode in which they are associated,

79. Connection with other parts,

80. Structure of the tendons, ....

81. Connection of the tendons with other parts,

82. Accessory organs of the muscles and tendons,

83. Ve.ssels of the muscles and accessory organs, .

84. Nerves of the muscles, ....

85. Chemical and physical relations of the muscles,

86. Development of the muscles and tendons, .

87. Physiological remarks, ....

OF THE OSSEOUS SYSTEM, pp. 266-345.

88. Definition, form, occurrence, .....

89. Intimate structure of the osseous tissue,

212
216

218

222
223
229
231
232
235
238
243
245
250
253
259

266
267

XX

CONTENTS.

SECT.

90. Matrix of bone, ......

91. LacunoD and canaliculi, .....

92. Periosteum, ......

93. Marrow, .......

94. Articulations of the bones : (A.) Synarthrosis,

95. (7?.) Movable articulation, Diarthrosis,

96. Articular capsules, ......

97. Physical and chemical properties of the bones and their accessory

98. Vessels of the bones, &c., .....

99. Nerves of the osseous system, .....

100. Development of the bones. . '. . .

101. Primordial cartilaginous skeleton, ....

102. Metamorphoses of the primordial cartilaginous skeleton,

103. Changes in the ossifying cartilage, ....

104. Ossification of the cartilage, ....

105. Elementary processes in the layers formed from the periosteum

106. Bones, not primarily cartilaginous,

107. Growth of the secondary cranial bones,

108. Vital phenomena in the mature bones,

OF THE NERVOUS SYSTEM, pp. 345-436

109. Definition, division, ......

organs,

PAGE

270
275
281
282
284
291
295
299
301
303
306
306
310
314
316
324
330
330
336

345

ELEMENTS OF THE NEKVOUS SYSTEM, pp. 345-359.

110. Nerve-lubes or fibres,

111. Nerve-cells,

345
356

CENTRAL NEEVOTJS SYSTEM, pp. 859-404.

112. Spinal cord, .....

113. Conjectural course of the fibres in the spinal cord,

114. Medulla oblongata and Pons Varolii,

115. Cerebellum, . . . . . . '

117. Ganglia of the cerebrum, ....

117. Hemispheres of the cerebrum,

118. Membranes and vessels of the central nervous system,

359
369
372
379
382
385
392

PERIPHERAL NERVOUS SYSTEM, pp. 404-430.

119. Spinal nerves, .....

120. Structure of the spinal ganglia,

121. Further course of the spinal nerves,

122. Cerebral nerves, .....

123. Ganglionic nerves, ....

124. Main trunk of the ganglionic nerves,

125. Peripheral distribution of the ganglionic nerves,

126. Development of the elements of the nervous system,

127. Functions of the nervous system,

404

,

. 405

411

,

. 416

418

,

. 418

423

,

. 426

431

CONTENTS. XXI

OF THE DIGESTIVE ORGANS, pp. 430-568.
OF THE INTESTINAL CANAL, pp. 43G-528.

SECT. PAGE

128. General structure, ........ 436

OF THE ORAL CAVITY, pp. 436-499.

A. OF THE MUCOUS MEMBRANE OF THE ORAL CAVITY, pp. 436-441.

129. Mucous membrane and submucous tissue, .... 436

130. Epithelium of the cavity of the mouth, .... 438

B. OF THE TONGUE, pp. 441-455.

131. Muscular structure of the tongue, ...... 441

132. Mucous membrane of the tongue. ..... 446

C. OF THE GLANDS OF THE ORAL CAVITF, pp. 455-467.

1. Mucous Glands: —

133. Different kinds of glands, ....... 455

134. Their more intimate structure, ... . 456

2. Follicular Glands:—

135. Simple follicles and Tonsils,

3. Salivary Glands: —

136. .....

D. OF THE TEETH, pp

137. Constituent parts, .

138. Dentine {substantia cbwnea),

139. Enamel i^substaiitia vitrea),

140. Cement {substantia ostcoidea), .

141. Soft parts of the teeth,

142. Development of the teeth,

143. Physiological conditions of the teeth.

467-499.

459
463

467
468
476
480
483
484
494

OF THE ORGANS OF DEGLUTITION, pp. 499-502.

1. THE PHARYNX.

144. . . . . . . . . . . 499

* "1. THE (ESOPHAGUS.

145. ..... . . . . .501

OF THE ALIMENTARY CANAL, pp. 502-528.

146. General conformation, . . . . . . 502

147. Peritoneum, . . . . . . . . 502

148. Muscular coat of the alimentary canal, .... 503

149. Mucous membrane of the stomach, ■ . . . . . 505

XXll CONTENTS.

SECT. PAGE

150. Gaslric glands, ....... 506

151. Other particulars of the mucous membrane, . . . . 509

152. Mucous membrane of the small iute.stine, .... 511

153. Villi of the small intestine, ...... 511

154. Glands of the small intestine, ...... 518

155. Closed follicles of the small intestine, ..... 520

156. Mucous Membrane of the large intestine, .... 524

157. Development of the intestinal canal, ..... 526

OF THE LIVER, pp. 528-549.

158. General structure, ........ 528

159. More intimate structure, ...... 528

160. Hepatic cells and cell networks, ...... 532

161. Excretory ducts of the liver, ...... 537

162. Vessels and nerves of the liver, ...... 541

163. Development of the liver, ...... 546

OF THE PANCREAS, pp. 549-551.

164. .......... 549

OF THE SPLEEN, pp. 551-5G8.

165. General structure, ........ 551

166. Coats and trabecular structure of the spleen, .... 551

167. Malpighian structure of the spleen, ..... 552

168. Red substance of the spleen, ..... 556

169. Vessels and nerves of the spleen, . . . . . . 562

170. Physiological remarks, ....... 567

OF THE RESPIRATORY ORGANS, pp. 508-595.

171. Enumeration of the respiratory organs, .... 568

OF THE LUNGS, pp. 568-585.

172. General structure, ........ 568

173. Larynx, .... .... 569

174. Trachea, ......... 572

175. Lungs, ......... 574

176. Air-vessels and cells, ....... 575

177. Minute structure of the bronchia:, ..... 578

178. Vessels and nerves of the lungs, ...... 580

179. Development of the lungs, ...... 583

OF THE THYROID GLAND, pp. 585-589.

180. General structure of the thyroid gland, .... 585

181. Minute structure, ....... 586

OF THE THYMUS, pp. 589-595.

182. General structure of the ^/i.3/mMS, ...... 589

183. Minute structure, ....... 591

184. Development of the thymus, ...... 593

CONTENTS. XXm

OF THE URINARY ORGANS, pp. 505-613.

SECT. PAGE

185. Enumeration of the urinary organs, ..... 595

186. A'tV/HCT/s— general structure of, . . . . . . 595

187. Composition of the renal substance, ..... 596

188. Ttibiili uiiiiifcri, ....... 598

189. Vessels and nerves of the kidneys, ..... 602

190. Urinary passages, ....... 607

191. riiysioiogical remarks, ....... 608

OF THE SUPRARENAL GLANDS, pp. 613-618.

192. General description of the suprarenal glands, .... 613

193. IMinute structure, ....... 613

194. Vessels and nerves, . . . . . . .615

195. Physiological remarks, ...... 616

OF THE SEXUAL ORGANS, pp. 618-667.

A. MALE SEXUAL ORGANS, pp. G18-G40.

196. Enumeration of the male sexual organs, .... 618

197. Testes, ......... 618

198. Tubuli seminiferi, ....... 621

199. Membranes, vessels and nerves of the to^es, .... 626

200. Vasa deferentia, vesiculce seminales, and accessory glands, . . 627

201. Organ of copulation, . . . . . ' . .630

202. Physiological remarks, . . . . . . ' 634

B. FEMALE SEXUAL ORGANS, pp. 640-6G0.

203. Enumeration of the female sexual organs, .... 640

204. Ovary, ixirovarium, ....... 640

205. Detachment and re-formation of the ova, ..... 643

206. Uterus and oviducts, ....... 646

207. Changes in the uterus at the menstrual period and in pregnancy, . 649

208. Vagina and external genitals, ...... 654

209. Physiological remarks, ....... 656

C. OF TUE LACTEAL GLANDS, 660-667. ^

210. Their structure, ....... 660

211. Physiological remarks, ....... 663

OF THE VASCULAR SYSTEM, pp. 667-715.

212. Its elements, ........ 667

I.— OF THE HEART, pp. 667-674.

213.. . . . . . . . . . 667

IL— OF THE BLOODVESSELS, pp. 674-693.

214. General structure of the bloodvessels, ..... 674

215. Arteries, ........ 678

216. Veins, ......... 684

217. Capillaries, ........ 689

XXIV CONTENTS.

III.— OF THE LYMPHATIC SYSTEM, pp. 693-699.

SECT. PAGE

218. Lymphatic vessels, ....... 693

219. Lymphatic glands, ....... 695

IV.— OP THE BLOOD AND LYMPH, pp. 699-725.

220. Different kinds of fluids included in those terms, and their mode of

occurrence, ........ 699

221. General structure of the morphological elements, . . . 700

222. Of the blood, ........ 70.3

223. Physiological remarks, . . . . . . 715

OF THE HIGHER ORGANS OF SENSE, pp. 725-785.

I.— OF THE ORGAN OF VISION, pp. 725-767.

224. Its parts, ......... 725

A. OF THE EYEBALL, pp. 725-757.

225. Fibrous tunic of the eye, ...... 725

226. Vascular tunic, ........ 733

227. Nervous tunic, . ... . . . , 739

228. The lens, ......... 750

229. The vitreous humor, . . . . . . . 753

B. ACCESSORY ORGAKS, pp. 757-760.

230. Eyelids, conjunctiva, lachrymal apparatus, .... 757

231. Physiological remarks, ...... 760

II.— OF THE ORGAN OF HEARING, pp. 767-778.

232. . . ... . . . . .767

233. External and middle ear, . . . . . ' . 767

234. The vestibule and semicircular canals, ..... 769

235. Cochlea, ........ 770

IIL— OF THE OLFACTORY ORGAN, pp. 778-785.

236. Its parts, ......... 778

APPENDIX.

1. Corpuscula tacUs and Pacinian bodies, ..... 785

2. Malpighian bodies of the spleen, . ... . . 786

3. Corpora hitea, ........ 787

4. Development of the teeth, ....... 789

LIST OF ILLUSTRATIONS.

FIG.

1. Nerve-cells of the Thalamus Opticus of Man, ....

2. Contents of a Malpighian Corpuscle of the Ox, . . .

3. Cells from the Cephalic Cartilage of a Tadpole,

4. Nuclei from the Ovum of an Ascaris dentata, ....

5. Ova of Ascarus nigrovenosa, ......

6. Cartilage-cells from Articular Cartilage of the Condyle of the Femur of Man,

7. Cells from the Medullary Cavities of the Flat Bones of the Skull in Man,

8. Dividing Blood-corpuscles of the Chick, ....

9. Dentine Cells, from the Dog, ......

10. Cartilage Cells of Man, .......

11. Bone-cells from a Rachitic Bone, ......

12. Plates of the Horny Layer of the Epidermis in Man, .

13. Epidermis of a two months' Human Embryo, ..."

14. Epithelial Cells of the Bloodvessels, .....

15. Epithelium of the Intestinal Villi of the Piabbit, ....

16. Ciliated cells from the finer Bronchia}, . . . . •

17. A simple Papilla with manifold Vessels and Epithelium from the Gums of a Child

18. Ciliated Epithelium from the Trachea of Man,

19. Portion of the Chorda Dorsalis of an Embryo Sheep,

20. Cartilage Cells from the White Layer of the Cricoid Cartilage,

21. Portion of a Human Epiglottis, ......

22. Elastic Network from the Tunica Media of the Pulmonary Artery of a Horse

23. Bundles of Connective Tissue from the Arachnoid of Man,

24. Network of Fine Elastic Fibres from the Peritoneum of a Child,

25. Elastic Membrane from the Tunica Media of the Carotid of a Horse,

26. Formative Cells of Elastic Fibres, from the Tendo-Achillis,

27. Stellate Formative Cells of the Nucleus Fibres of Tendo-Achillis of a new

born Infant, ........

28. Lax Connective Tissue with Fat-cells, from Man, ....

29. Formative Cells of the Connective Tissue from the Skin of a Sheep's Embryo,

30. Formative Cells of the Areolated Connective Tissue from the Allantois of £

Sheep's Embryo, .......

31. Perpendicular section of a Parietal Bone, .....

32. Developing Bone-cells from a Rachitic Bone, ....

33. jSIuscular Fibre-cell from the Small Intestine of Man,

34. Muscular Fibre-cell from the Investment of the Spleen of a Dog,

35. Muscular Fibres from Man, ......

3G. Primitive Fibrils from a Primitive Bundle of the Axolotl,

PAGE

44

48
50
50
51
53
53
54
55
60
(30
75
76
76
76
76
77
77
80
80
81
81
82
82
82

83

89
90

90
99
100
103
103
106
106

XXVI

LIST OF ILLUSTRATIONS.

FIG.

37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
63.
54.

56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.

72.
73.
74.
75.
76.
77.
78.
79.
80.

81.
82.
83.
84.

85.

86.
87.

Tubular Nerve-fibres of Man, ......

Nerve-cell of the Pike, .......

Nerve-cells from the floor of the Fourth Ventricle iu Man,

Network of Hepatic Cells, ......

Two of the Smallest Lobes of the Lung from a new-born Child,
Gastric Gland from the Pylorus of the Dog, ....

Glandular Vesicles from the Thyroid Gland of a Child,

Malpighian Coi'puscle from the Spleen of the Ox,

Perpendicular section of the Skin of the Ball of the Thumb,

Compound Papilhv of the Surface of the Hand,

Horizontal Section of the Skin of the Heel, ....

Two Papilla; of the Surface of the Hand, ....

Elastic Fibres from the Fascia Lata of Man, ....

Normal Fat-cells from the Breast, .....

Fat-cells with Crystals of Margarin, .....

Vessels of the Fat- cells ; after Todd and Bowman,

Vessels of the Papilla; of the Cutis; after Berres, ....

Two Papilla; from the extremities of the Fingers, with Axile-corpuscles,

A. Surface of the Palm from within, .....

B. Perpendicular section of the Skin of the Negro,
Horny Epidermic Plates of Man, . .....

Horny Plates boiled with Caustic Potassa, ....

Transverse section through the Body and Bed of the Nail,

Capillaries of the Bed of the Nail ; after Berres,

Longitudinal section through the Matrix of the Nail,

Transverse section through the Body of the Nail,

Nail Plates boiled with Caustic Soda, .....

Hair and Hair-sacs of middling size, .....

Plates of the Cortical Substance of a Hair, ....

White Hair after treatment with Caustic Soda,

Cells from the Cortex of the Pioot of the Hair, ....

Cells from deepest part of Hair Bulb, .....

Root of a dark Hair acted upon by Caustic Soda, ....

Medullary Cells of Hair, ......

Surface of the Shaft of a White Hair, .....

Portion of the transverse fibrous layer and structureless membrane of a Human

Hair-sac, ........

Elements of the inner Root-sheath, .....

Rudiment of the Hair from the Brow of a Human Embrj^o,

Rudiment of the Hair from the Eyebrow, .....

Rudimental Hair from the Eyebrow, .....

Eyelashes of a Child, .......

Eyelashes with the Root-sheaths from a Child,

A Sudoriparous Coil and its Vessels, .....

Sweat-ducts, ........

Perpendicular section through the Epidermis and outer surface of the

Corium, . . . .

Rudiment of a Sudoriparous Gland of a Human Embryo, .
Rudiment of a Sudoriparous Gland from a seven months' Fcetus,
Perpendicular section through the Skin of the External Auditory Meatus,
Sebaceous Glands from the Nose, .....

A Gland from the Nose, with Hair-sac opening into it, .

Two Sebaceous Glands, .......

A Glandular Vesicle of a common Sebaceous Gland,

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201

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213
213
215
216

LIST OF ILLUSTRATIONS.

XXVU

Fir,.

88.

an.

90.
91.
92.
93.
9-1.
95.
9G.
97.
98.
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100.

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IIG.

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132.

133.

134.

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136.

137.

138.

139.

140.

The development of the' Sebaceous Glands in a six months' Foetus,
Primitive Fibrils from a primitive fasciculus of the Axolotl,
Transvei'se sections of Muscular Fibre,
Human Muscular Fibre treated with Acetic Acid,

A Primitive Fasciculus, separating transversely into discs; after Bowm
Primitive Fibres from a transversely striated Muscle of a Bug, .
Transverse section of Rectus Capitis Anticus Major of Man, .
Transverse section of a Tendon of a Calf, ....

Tendon of the Tibialis Posticus, ....

A Primitive Fasciculus from Intercostal JMuscle of Man, .
Disposition of Muscular Fibres at their insertion into the Tendon
Insertion of the Tendo-Achillis into the Calcaneum,
Cartilage-cells from the Vaginal Ligaments surrounding the Tendons of
Popliti\3us, .......

Capillary Vessels in AFuscle, ......

Expansion of the Nerves in the Omo-hyoid muscle of Man,
Divisions of the Primitive Nerve-fibres in Muscle,
Divisions of Nerve-fibres in Thoracic ^luscle of the Frog,
Primitive Fasciculi of a Human Embryo, ....

Primitive Fibres of a Human Embryo, ....

From the Tendo-Achillis of a New-born Child,

Primitive Fibres from the Alar Muscles of the Dung-fly, .

Primitive Fascicuhv of a Frog's Muscle in different degrees of Extension

Transverse section of Human Femur, ....

Haversian Canals from Superficial Layer of Human Femur, .

Transverse section of Human Metacarpal Bone,

Transverse section of Shaft of Humerus, ....

Perpendicular section of Parietal Bone, ....

Transverse section of Shaft of Humerus, ....

Section parallel with Surface of Human Femur, .

Lacunce and Canaliculi of Parietal Bone, ....

Surface of a Tibia of Calf, .....

Bony Spicule from Apophysis, .....

Fat-cells from Marrow of Human Femur,

Transverse section of Ligamentum Nuchaj of Ox,

Cells from Gelatinous Nucleus of the Lig. Intervertebralia,

Cartilaginous border of Human Symphysis, ....

Human Cartilage Cells, ......

Perpendicular section of Articular Cartilage of Human Metacarpal Bone
Diagram of Transverse Section of Phalangeal Articulation,
Synovial Membrane of Phalangeal Articulation,
Falciform Ligament of Knee, ....

Cartilage Cells from Humerus of Embryo of Sheep,
Perpendicular section of Ossifying border of Shaft of Femur,
Femur of a Child, .....

Femur of a Rachitic Child,

Transverse section of Metatarsus of Calf,

Diagram of Growth of Cylindrical Bone, .

Parietal Bone of Foetus,

Parietal Bone of new-born Child, .

Nerve Fibres of Man, ....

Human Nerve-tubes,

Nerve Fibres, .....

Nerve-cells from Acoustic Nerve, .

an,

the

PACK

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XXVUl

LIST OF ILLUSTRATIONS.

FIG.

141.

142.

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IGO.

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189.

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191.

192.

193.

194.

Transverse section of Spinal cord, ....

Cells from Gray Central Nucleus of Cord,

Nerve-cells from Anterior Cornua of Cord in Man,

Vertical section of Spinal Cord, .....

Five transverse sections of Human Spinal Cord,

Transverse section through Human Medulla Oblongata, .

Nerve-cells of the Substantia Ferruginea,

Large Cells of Cortical Substance of Human Cerebellum,

Internal portions of Gray Layer of Human Cerebral Convolutions,

Finest Nerve-tubes of Superficial White Substance of Human Cerebrum

Ependyma in Man, ....

Vessels of Cerebral Substance of Sheep, .

Brain-sand from Pineal Gland,

Lumbar Ganglion of Young Dog,

Ganglion Globules from Gasserian Ganglion of Cat,

Cells from Sheath of Nerve-cells of Spinal Ganglia in Man,

Coccygeal Nerve, with an adherent Nerve-cell,

Nerve-cell of the Pike, ....

A Pacinian Body in Man,

Transverse section of Ischiatic Nerve,

Ganglion of Sympathetic Nerve of Rabbit,

From the Sympathetic in Man,

Nerve-cells from the Cardiac Ganglion of the Frog,

Nerve-cells from Spinal Ganglion of Human Embryo, . .

Nerve-fibres from Ischiatic Nerve of Human Embryo,

Nerve from the Tail of a Tadpole, ....

Simple Papilla, with Vessels and Epithelium,

Epithelial cells in Oral Cavity of Man, ....

Longitudinal section of Human Tongue,

Transverse section of Human Tongue, ....

Portion of longitudinal section of Human Tongue,
Branched Primitive Muscular Bundle from Tongue of Frog,
Two Papillaj Filiformes of Man; after Todd and Bowman,
Papilla Fungiformis ; after Todd and Bowman,
Papilla Circumvallata of Man, ....

Epithelial Cells covered with Granular Matrix of Fungus,

Papilla Filiformis invested by a Fungus,

Racemose Mucous Glands from the Floor of the Oral Cavity,

Diagram of two Ducts of a Lobe of a Mucous Gland, .

Two Glandular Vesicles of a racemose Mucous Gland of Man,

Follicular Gland from the root of the Tongue in Man,

Vesicles of a few follicles from a Human Tonsil,

Human Molar Tooth, ......

Transverse section of Dentinal Canals, ....

Dentinal Tubules, ......

Transverse section through the Dentinal Canal of a Human Tooth,
Perpendicular sectioa of the Apex of an Incisor Tooth,
Dentine with Dentinal Globular and Interglobular Spaces,
Surface of Enamel from the Calf, ....

Enamel Prisms from Man, ......

Dentine and Enamel from Man, ....

Dentine and Cement from Fang of Incisor Tooth, .
Cement and Dentine of the Root of an old Tooth,
Lower Jaw of a Human Foetus,

I'AOE

361

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478

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479

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482

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LIST OF ILLUSTRATIONS.

XXIX

FIG.

195. Diagram of the Development of a Milk-tooth ; after Goodsir,

196. Tooth-sac of Incisor of a Fa?tus, ....

197. Surface of Dentinal Pulp of an Infant, .

198. Transverse section of Human (Esophagus,

199. Muscular-tibre Cells from (Esophageal Mucous Membrane,

200. Stomach of Man, ......

201. Muscular-fibre Cells from Small Intestine,

202. Bloodvessels of Smooth Muscles of Intestine,

203. Perpendicular section through Tunics of Pig's Stomach,

204. Mucous Gastric Gland of a Dog, . ■ .

205. Vessels of Large Intestine of a Dog,

206. Section through the Walls of a Calf's Ileum,

207. Intestinal Villus of a Young Kitten,

208. Vessels of Villi of the Mouse; after Gerlach,

209. Villi without Epithelium and with a Lacteal,

210. Intestinal Villi of the Cat, .

211. Allli with the Epithelium, from the Eabbit,

212. Lieberkiihnian Glands of the Pig, .

213. Peyer's Patch, in Man,

214. Portion of a Peyer's Patch of an Old Man,

215. Horizontal section from the middle of Peyer's Follicle of the Eabbit,
210. Solitary Follicle from the Small Intestine ; after Bcihm, .

217. Solitary Follicle from the Colon of a Child,

218. Segment of a Pig's Liver, ....

219. Portal Vessel of the Pig ; after Kiernan,

220. Hepatic Cells of Man, ....

221. Hepatic Cell-network, ....

222. Hepatic Cell-network and its capillaries, .

223. Hepatic Veins of the Rabbit, .

224. Arterial Network upon surface of a Child's Liver,

225. Vessels of the Pancreas of a Rabbit,

226. Section through the middle of the Spleen of an Ox,

227. Fibres from the Pulp of Human Spleen,

228. Artery covered with Malpighian Corpuscles from Spleen of Dog,

229. Malpighian Corpuscles from Spleen of an Ox, .

230. Contents of a Malpighian Corpuscle,

231. Blood-corpuscle-holding Cells and their Metamorphoses,

232. Artery from the Spleen of a Pig, ....

233. Ciliated Epithelium from the Human Trachea,

234. Vertical Section through Anterior Wall of Human Trachea,

235. Lymphatics in the Tracheal Mucous Membrane of Man,

236. Pulmonary Lobules from a Child, ....

237. External Surface of the Lung of a Cow,

238. Human Air-cell, ......

239. Capillary plexus of Human Air-cell,

240. Gland-vesicles from the Thyroid Gland of a Child,

241. Gland-vesicles of Thyroid filled with Colored Matter,

242. Portion of Thymus of a Calf, ....

243. Half of Human Thymus, ....

244. Section of an injected Lobule of Thymus of a Child,

245. Vertical section of an injected Rabbit's Kidney,

246. Tubuli Uriniferi of Man, .....

247. A Malpighian Corpuscle, ....

248. From the Human Kidney; after Bowman,

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XXX

LIST OP ILLUSTRATIONS.

FIG.

249.
250.
251.
252.
253.
254.
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256.
257.
258.
259.
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261.
262.
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292.
293.
294.
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296.
297.
298.
299.
300.
801.
302.

Malpighian Corpuscle from Kidney of a Horse,

Transverse section through Cortical Tubules, .

Epithelium of Pelvis of Human Kidney,

Vertical section through Suprarenal Capsule in jMan,

From the Suprarenal Capsule of Man,

Section of Suprarenal Body of the Calf,

Section through Testis and its Tunics in Man,

Diagram of the Course of a Spermatic Tubule,

Human Testis and Epididymis ; after Arnold,

Portion of a Spermatic Tube in Man, .

Human Spermatic Filaments,

Development of the Spermatic Filaments in a Rabbit,

Glands of a Littre, .....

Arteries from Corpora Cavernosa Penis,

Section through the Ovary of a Woman,

Graafian Follicle of the Sow, ....

Human Ovulum, .....

Two Corpora Lutea, .....

IVIuscular Elements from the Uterus in Pregnancy,

Muscular Fibre-cell from a Gravid Uterus,

Uterine Gland, .....

Muscular Fibre-cell of the Uterus,

Graafian Follicles from Ovary of a Newly-born Child,

Lobules of the Lacteal Gland of a Puerperal Female,

Development of Lacteal Gland,

Elementary Forms in Milk, ....

Anastomosing Primitive Fasciculus from the Human Heart,

Diagram showing the course of the Muscular Fibres of the Heart

Elastic ^lembrane from the Tunica Media of the Popliteal Arterj

Muscular Fibre-cells from the Human Arteries,

Artery and Vein from Mesentery of a Child,

Artery and Vein treated with Acetic Acid,

Transverse section of Art. Prof. Femoris of Man, .

Transverse section of Aorta, ....

Muscular Fibre-cell from innermost layer of Axillary Artery,

Transverse section of the Sapliena Vein,

Muscular Fibre-cell from Renal Vein of Man,

Longitudinal section of Inferior Vena Cava,

Finest Vessels on the arterial side of the Capillaries,

Capillary Lymphatic from the tail of a Tadpole,

Transverse section of Human Thoracic Duct,

Elements of the Chyle, ....

Human Blood-globules, .....

Colorless Blood-globules, ....

Blood-cells of the Frog and of the Pigeon,

Capillaries from the Tail of a Tadpole,

Blood-corpuscles of a Foetal Lamb,

Transverse section of Eye, ....

Capillaries and Lymphatics of Cornea of a Kitten,

Nerves of the Cornea of a Rabbit,

Cells from the Stroma of the Choroid,

Cells of the Pigmentum Nigrum of Man,

Vessels of the Choroid and Iris of a Child ; after Arnold,

Vertical Transverse section of Human Retina,

in

Man,

PAGE

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. 682
683
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731
732
734
735
737
739

LIST OF ILLUSTRATIONS.

XXXI

m.

303. Element-; of Human Retina, .....

304. Bacillar Layer of Retina, ......

305. Nerve-cells from Retina of the Ox, ....

306. Fibres of the Lens, from the Ox, . . . . .

307. Human lens ; after Arnold, .....

308. Transverse section of a Semicircular Canal, ....

309. Vertical section of the Lamina Spiralis ; after Corti,

310. Vestibular surface of the Lamina Spiralis Membranacca,

311. Bipolar Ganglion-globule from Lamina Spiralis of a Pig; after Corti,

312. From Nasal Mucous Membrane of the Sheep,

313. From the Olfactory Nerve of Man, ....

■P.KOE

740
742
743
751
753
769
771
771
774
780
782

INTEODUCTIOK

§ 1. The doctrine of the elementary structure of Plants and Animals,
belongs to the last two centuries, originating with Marcellus Malpighi
(1628-94), and Anton van Leeuwenhoek (1632-1723), at the period
when the assistance of magnifying glasses, powerful, though of very
simple form, was first offered to observers. The ultimate constituents
in respect of form, of organisms, were unknown to antiquity and to the
middle ages, for although Aristotle and Galen speak of the homogeneous
and heterogeneous parts of the body (partes similares et dissimilares),
and Fallopius (1523-62) defined still more exactly the idea of " Tissues,"
and even attempted to classify them (' Tractatus quinque de partibus
similaribus,' opera, torn. ii. Francof. 1600), yet the minuter structures
"were completely hidden from these investigators. Brilliant as were the
first efi"orts of the young science under the guidance of these men and after-
wards of a Ruysch, Swammerdam, and others, yet they were not adequate
to acquire a safe footing for it, since, on the one hand, the philosophers
were far too little masters of microscopic investigation to strive at once,
with a clear insight, towards the true goal; while, on the other, the deve-
lopment of other branches of study, as of the grosser Anatomy, of Physio-
logy, of Embryology, and of Comparative Anatomy, claimed too large a
share of their attention. It thus happened that, with the exception
of a few to some extent important works (Fontana, Muys, Lieberkiihn,
Hewson, Prochaska), Histology made no considerable progress during-
the whole of the 18th century, and acquired no importance greater than
that due to a disjointed collection of isolated observations. It was in
the year 1801 that it first acquired a rank co-equal with that of its
sister anatomical sciences by the genius of a man to whom indeed, Histo-
logy owes no great discoveries, but who understood, as no one before
him had done, so to arrange existing materials and so to connect
them with Physiology and Medicine, that for the future its independence
was assured. In fact, Bichat's ' Anatomic Gendrale' (Paris, 1801),
was the first attempt to treat Histology scientifically, and on this ac-
count merely, it constitutes an epoch ; but besides this, its importance

3

34 INTRODUCTION.

■was still greater, Inasmuch as the tissues were not merely clearly defined
and fully and logically treated of, but full account was taken of their
physiological functions and morbid alterations. To this great internal
progress, the present century has added an ever-increasing perfection
of the external aids of the microscope, and a steadily increasing zeal in
the investigation of nature, so that it is not to be wondered at, that in
its five decades, it has left far behind all that was done in the century
and a half of its earlier existence. In the last thirty years particularly,
discoveries have so trodden upon one another's heels, that it must be
considered truly fortunate that a bond of connection has arisen, and
that Microscopical Anatomy has thus escaped the danger of becoming,
as in earlier days, lost in minutipe. In the year 1838, in fact, the
demonstration by Dr. Th. Schwann, of the originally perfectly identical
cellular composition of all animal organisms, and of the origin of their
higher structures from these elements, afforded the appropriate concep-
tion which united all previous observations, and afforded a clue for
further investigations. If Bichat founded histology more theoretically
by constructing a system and carrying it out logically, Schwann has,
by his investigations, afforded a basis of fact, and has thus won the
second laurels in this field. What has been done in this science since
Schwann, has been indeed of great importance to physiology and medi-
cine, and in part of great value in a purely scientific point of view,
inasmuch as a great deal which Schwann only indicated, or shortly
adverted to, as the genesis of the cell, the import of the nucleus, the
development of the higher tissues, their chemical relations, &c., has re-
ceived a further development; but all this has not amounted to a step
so greatly in advance as to constitute a new epoch. If, without pre-
tensions to prescience, it be permitted to speak of the future, this
condition of Histology will last as long as no essential advance is made
towards penetrating more deeply into organic structure, and becoming
acquainted with those elements, of which that which we at present hold
to be simple, is composed. If it be possible that the molecules which
constitute cell-membranes, muscular fibrils, axile fibre of nerves, &c.,
should be discovered, and the laws of their apposition, and of the altera-
tions which they undergo in the course of the origin, the growth, and
the activity of the present so-called elementary parts, should be made
out, then a new era will commence for Histology, and the discoverer
of the law of cell genesis, or of a molecular theory/, will be as much or
more celebrated than the originator of the doctrine of the composition
of all animal tissues out of cells.

§ 2. In characterizing the present position of Histology and of its
objects, Ave must by no means forget that, properly speaking, it con-
siders only one of the three aspects which the elementary parts present

I INTRODUCTION. 35

to observation, namely, their form. Microscopical anatomy is concerned
■with the understanding of the microscopic forms, and with the laws of
their structure and development, not with any general doctrine of the
elementary parts. Composition and function are only involved, so far
as they relate to the origin of forms and to their variety. Whatever
else respecting the activity of the perfect elements and their chemical
relations is to be found in Histology, is there either on practical grounds
in order to give some useful application of the morphological conditions,
or to complete them ; or from its intimate alliance with the subject, it is
added only because physiology proper does not afford a due place for
the functions of the elementary parts.

If Histology is to attain the rank of a science, its first need is to
have as broad and certain an objective basis as possible. To this end
the minuter structural characters of animal organisms are to be examined
on all sides, and not only in fully formed structures, but in all the
earlier periods from their first development. When the morphological
elements have been perfectly made out, the next object is to discover
the laws according to which they arise, wherein one must not fail to
have regard also to their relations of composition and function. In dis-
covering these laws, here as in the experimental sciences generally,
continual observation separates more and more, among the collective
mass of scattered facts and observations, the occasional from the con-
stant, the accidental from the essential, till at last a series of more and
more general expressions of the facts arises, — from which, in the end,
mathematical expressions or formulae proceed, and thus the laws are
enunciated.

If we inquire how far Histology has satisfied these requirements,
and what are its prospects in the immediate future, the answer must be
a modest one. Not only does it not possess a single law, but the
materials at hand from which such should be deduced, are as yet re-
latively so scanty, that not even any considerable number of general
propositions appear well founded. Not to speak of a complete know-
ledge of the minuter structure of animals in general, we are not ac-
quainted with the structure of a single creature throughout, not even
of man, although he has been so frequently the object of investigation,
— and therefore it has hitherto been impossible to bring the science
essentially any nearer its goal. It would, however, be unjust to over-
look and depreciate what we do possess ; and it may at any rate be said
that we have acquired a rich store of facts and a few more trustworthy
general propositions. To indicate only the more important of the for-
mer, it may be mentioned, that we have a very sufficient acquaintance
with the perfect elementary parts cf the higher animals, and that we
also understand their development, with the exception of the elastic
tissue, and of the elements of the teeth and bones. The mode in which

36 I N T 11 0 D U C T T 0 N.

these are united into organs has been less examined, yet on this head
also, much has been added of late, especially in man, whose individual
organs with the exception of the nervous system, the higher organs of
sense, and a few glands (the liver, blood-vascular glands), have been
almost exhaustively investigated. If the like progress continue to be
made, the structure of the human body will in a few years be so clearly
made out, that, except perhaps in the nervous system, nothing more of
importance will remain to be done with our present modes of investiga-
tion. With comparative Histology it is otherwise ; hardly commenced,
not years but decades will be needed to carry out the necessary investi-
gations. Whoever will do good work in this field must, by monographs of
typical forms embracing their whole structure from the earliest periods
of development,* obtain a general vieAv of all the divisions of the ani-
mal kingdom, and then, by the methods above described, strive to
develop their laws.

As regards the general propositions of Histology, the science has
made no important progress since Schwann, however much has been
attained by the confirmation of the broad outlines of his doctrines.
The position that all the higher animals at one time consist wholly of
cells and develop from these their higher elementary parts, stands firm,
though it must not be understood as if cells, or their derivatives, were
the sole possible or existing elements of animals. In the same way,
Schwann's conception of the genesis of cells, though considerably
modified and extended, has not been essentially changed, since the cell
nucleus still remains as the principal factor of cell-development and of
cell-multiplication. Least advance has been made in the laws which
regulate the origin of cells and of the higher elements, and our acquain-
tance with the elementary processes which take place during the for-
mation of organs must be regarded as very slight. Yet the right track
in clearing up these points has been entered upon ; and a logical inves-
tigation of tlie chemical relations of the elementary parts and of their
molecular forces, after the manner of Donders, Ludwig, and others, com-
bined with a more profound microscopical examination of them, such
as has already taken place with regard to the muscles and nerves, —
further, a histological treatment of embryology, such as has been at-
tempted by Reichert, Vogt, and myself, will assuredly raise the veil, and
bring us, step by step, nearer to the desired though perhaps never to
be reached, end.

§ 3. The aids in studying Histology may here be best shortly ad-
verted to. With respect to the literature of the subject, the more impor-

* [See a very praisewoitliy monograph of this kind by Leydig, Beitrage ziir Mikrosko-
pischen Anaromie und Entwickekings-gescliichte der Rochen u. Haie, 1S52. (Microscopic
Anatomy and Development of the Rays and Sharks.) — Trs.]

INTRODUCTION. 37

tant monographic works arc cited under their appropriate section, and
here only those hirgc independent works will be noticed, in which further
instruction is to be found. It is right to head the list with Schwann's
* Mikroskopische Untersuchungen liber die Uebereinstimmung in der
Struktur und dem Wachsthum der Thiere und Pflanzen' (Berlin, 1839),*
abstracted in Froriep's 'Neue Notizen' (1838), as the most fitting intro-
duction to Histology. Beside this, we may name X. Bichat, 'Anatomie
Gdndrale,' Tom. iv. (Paris, 1801) ; E. 11. Weber, 'Ilandbuchder Ana-
tomie des ]Menschen von Hildebrandt,^Bd. 1, 'Algemeine Anatomie'
(Braunschweig, 1830), a work distinguished in its day, and even now
indispensably necessary, as a store of old literature [or Ed. 4 (Stuttgart,
1833)]; Brun's 'Lehrbuchder Allgemeinen Anatomie des Menschen'
(Braunschweig, 1841), very clear, concise, and good ; Henle, ' Allgemeine
Anatomie' (Leipzig, 1841), containing a classical account of Histo-
logy in the year 1840, many original statements, and physiological,
pathological, and historical remarks ; G. Valentin, article ' Gewebe,'
in R. Wagner's ' Handworterbuch d. Physiologic,' Bd. i. (1842); R. B.
Todd and W. Bowman, ' The Physiological Anatomy and Physiology of
Man,' Parts i. ii. (London 1845-47), mostly based upon original observa-
tions, very comprehensive and good [also Parts iii. iv. (1847-52)] ;
Bendz, ' Haandbogi den almindelige Anatomie' (Kiobenhavn, 1846-47),
with industriously collected historical data ; A. Kcilliker, ' Mikrosko-
pische Anatomie oder Gewebelehre des Menschen, Band II. Specielle
Gewebelehre, 1, Hiilfte. u. 2 ; Halfte. 1 Abtheilung' (Leipzig, 1850-52),
containing an exposition, as complete as possible, of the minute struc-
ture of the organs and systems of man. With these are to be compared
the yearly Reports of Henle, in Cannstatt's ' Jahresbericht,' and those
of Reichert, in Mliller's ' Archiv,' in the latter of which, more objective
views and an earlier appearance would be desirable.

Useful figures are found in all the works above cited, with the excep-
tion of those of Bichat, Weber, and Bruns; furthermore, the figures of
injections in Berres' 'Anatomie der Mikroskopischen Gebilde des raen-
schlichen Korpers,' Heft 1-12 (Wien, 1836-42), are for the most
part excellent, as are the representations of tissues in R. Wagner's
' Icones Physiologic^,' second edition, by A. Ecker. Those of Langen-
beck, ' Mikroskopisch-anatomische Abbildungen.' Lief. 1-4 (Gottingen,
1846-51) ; of A. H. Hassall, ' The Microscopic Anatomy of the Human
Body' (London, 1846-49) ; and Mandl, 'Anatomie Microscopique' (Paris
1838-48), are middling ; while on the other hand, those given by
Quekett, ' Catalogue of the Histological Series in the Museum of the
Royal College of Surgeons of England' (London, 1850), are admirable.

As regards Microscopes, I may express my opinion that of the more
easily accessible, those of Plossl, Oberhiiuser, and Schick, take the first

* Translated for tlie Sydenham Society, 1817.

33 INTRODUCTION.

rank. In Italy, Amici ; in England, Ross, Powell, and others, produce
instruments quite equal to the above, but out of the question for Ger-
many; among small, cheap, but not particularly useful instruments for
students and physicians, for 115 to 150 francs, George Oberhauser
(Rue Dauphine, 19, Paris), furnishes the best. The much-famed instru-
ments of Nachet are good, but inferior to those of Oberhauser ;- on the
other hand, the small ones of Schick for 40 thalers [80 dollars], and those
of PliJssl for 70 to 100 Fl. [30 to 45 dollars], would be very serviceable
if these artists were as productive as Oberhauser.* For the use of the mi-
croscope I refer to J. Vogel, "Anleitung zura Gebrauche des Mikroskops"
(Leipzig, 1841); H. von Mohl, "Mikrographie" (Tubingen, 1846); Hart-
ing, " Het Mikroskoop deszelfs gebruik, geschiedenis en tegenwoordige
toestand" (Utrecht, 1848-50), 3 Theile; Purkinje, article "Mikroskop,"
in Wagner's " Handworterbuch der Physiologic," Bd. 2, 1844; in which
works, as well as in that of Quekett, " A Practical Treatise on the Use
of the Microscope" (London, 1848, translated, by Hartmann, Weimar,
1850, [also Ed. 2, London, 1852)]; and Robin, " Du Microscope et des
Injections dans leurs applications a TAnatomie et a la Pathologie"
(Paris, 1848), the preparation of microscopical objects is in part very
elaborately treated of.

A collection of microscopical preparations is indispensably necessary
for a more exact study of Histology, especially sections of bones and
teeth and injections. Every one may with a little trouble, form a mode-
rate collection for himself, hints towards which he will find in the para-
graphs standing at the end of each section of the special part, as
well as in the works just cited. Microscopical preparations may also
be exchanged with or purchased of Hyrtl, in Vienna ; Dr. Oschatz, in
Berlin ; Topping, Smith, and Beck, Hett and others, in London ; and
also in Paris. The largest private and public collections of microscopi-
cal preparations exist in Vienna, with Hyrtl (injections) ; in Utrecht,
■with Harting and Schroder van der Kolk (injections, sections, muscles,
nerves) ; in London, in the College of Surgeons (animal and vegetable
tissues of all kinds); with Tomes (sections of bones and teeth) ; and
■with Carpenter (hard tissues of the lower animals).

* [The opinion expressed in the above lines with regard to microscopes seems entirely
too national. For clearness of definition of the object glasses and neatness of the stand, the
instruments furnished by Ross, and Powell, and Lcaland, are not only " quite equal," but
far superior to those of PlOssl, Oberhauser, or Scliiek, the only objection to them being their
high price. Of the cheaper microscopes, those most used at present in this country and in
England are the small instruments of Nachet (Rue Serpente, Paris), the glasses of which
are superior to those of PlOssl and Schick, whilst the great convenience of the present stand,
modelled according to the English style, renders them preferable to those of Oberhauser.
In this country microscopes have been made by Mr. Spencer, of New York, the lenses
of which are not inferior to the best glasses either of Ross, or of Powell and Lealand, but
which are as yet too expensive to be introduced into general use. — DaC]

THE

GENERAL ANATOMY OF THE TISSUES.

I. OF THE ELEMENTARY PARTS.

§ 4. If the solid and fluid constituents of the human body be examined
with the aid of strong magnifying powers, it appears at once that the
smallest parts which they exhibit to the naked eye, as granules, fibres,
tubes, membranes, &c., are not the ultimate elements in respect of form,
but on the contrary, that all, in conjunction with a universally distri-
buted, fluid, semi-fluid, or even solid, homogeneous, uniting substance,
contain minute particles which differ in different organs but in the
same organs have always a similar appearance. There are various
kinds of these so-called elementary parts, simple and compound. The
simplest are quite homogeneous, without any trace of their being com-
posed of heterogeneous portions and are nearly allied to the inorganic
forms, the crystalline granules and crystals, which also occur in the
animal organism. Others already show that they have suffered a diffe-
rentiation into an investment and determinate, though homogeneous
contents : in others again, the contents present differences. The most
important among all these forms, which may be comprehended under
the general title of ''^simple elementary parts,'' are the cells, which not
only form the starting-point of every animal and vegetable organism, but
also, either as cells or after having undergone manifold metamorphoses,
make Up the body of the perfect animal, and in the simplest animal
and vegetable formations (unicellular animals and plants), even enjoy
an independent existence. Compared with cells, all other simple ele-
mentary parts have quite a subordinate importance, so far as their direct
participation in the formation of the tissues and organs is concerned ;
while, from their being almost all contained in the interior of cells and
from their being concerned in many and most important ways in the
vital processes of these cells, their importance in other respects is very
great.

The simple elementary parts, which at first wholly comprise the com-
mencing animal (or plant), often unite in the course of development in

40 GENERAL ANATOMY OF THETISSUES.

such a manner that they lose their independence and cease to exist as
isolated elements. In this manner compound forms arise, each of which
answers genetically to a whole series of simple ones, and which may
most fittingly be called the " idgher elementary parts." Such a coa-
lescence has been observed with certainty only in cells, and from these
most of the tubular and fibrous elements of the body are produced.

§ 5. Formative and Nutritive Fluid — Interstitial substance or matrix.
— While in plants the elementary parts in by far the majority of cases,
unite directly with one another, in animals there is a very wide differ-
ence ; a peculiar interstitial substance which combines them, and is ulti-
mately derived from the blood, is always in a lower or more distant rela-
tion therewith. If this take a direct share in the formation of the elemen-
tary parts it is called "formative fluid," Cytohlastema (Schleiden), from
xoVo;, a vesicle, and ^Xk^tt^ixx^ germ substance ; if it be present for their
maintenance, it is called '■^nutritive fluid;'' if it have nothing to do
with either the one or the other of these functions, it is called the "ma-
trix" or connecting substance. The cytohlastema is usually quite fluid,
as in the blood, in the chyle, in many glandular secretions, in the con-
tents of the glandular follicles, and in many embryonic organs ; more
rarely, viscid and like mucus, as in the gelatinous cellular tissue of
embryos [vide infra), still more rarely solid, as the blastema from which
the villi of the chorion arise and grow. The ^'■nutritive fluid'' takes
the place of the formative fluid in all perfect organs ; and except when
it is contained in special canals and cavities, as in bones, teeth, and
perhaps in some cellular organs, is present in so small a quantity, that
it cannot be directly observed. A matrix, lastly, is found in cartilages
and bones as a solid, homogeneous, granular, or even fibrous substance
connecting the cellular elements and for the most part arising from the
blood, independently of them.

The occurrence of a solid blastema, growing independently, in the
villi of the chorion and of a solid matrix deposited directly out of the
blood demonstrates that all parts of the body are not, as Schwann was
disposed to believe, without exception developed from cells or in depen-
dence upon cells. A few more recent authors, as Reichert, Donders,
and Virchow, also consider that the connective tissue, excepting its elas-
tic element, is to be reckoned among those tissues which are not at all,
■or not wholly, derived from cells ; but, as we shall see below, incorrectly.
On the other hand, it is certain that in pathological formations such
masses very frequently occur, fibrinous exudations becoming changed in
great measure, without previous organization, i. e. cell formation into
permanent tissues.*

[* The Enamel and the Dentine of the teetli, ami the so-called Cuticle of the hair (see §§
0 1 Hair and Teeth, and ' Quarterly Journal of Microscopical Science' for April, 1853), must

ELEMENTARY GRANULES. 41

A. SIMPLE ELEMENTARY PARTS.

1. ELEMENTARY GRANULES, ELEMENTARY VESICLES, NUCLEI.

§ G. In almost all animal fluids, ■whether contained in canals, or enclosed
in cells, as well as in many more solid tissues, there are found and often
in immense quantities, roundish corpuscles of very small, hardly mea-
urable dimensions. Henle has called them "elementary granules,"
and has expressed the opinion that they are vesicular. This, however,
is not always true, since it is demonstrable that many of these corpus-
cles possess no investment. Such is the case with the fatty particles
which occur in many cells and glandular secretions, with the granules of
the black pigment of the eye and of other colored cells, the granular
precipitates of biliary coloring matter, of different salts in the kidneys,
and in the urine ; lastly, the protein granules (albuminous granules)
which are found free in certain portions of the gray substance of the
central nervous system and of the retina. Among the pathological but
very common formations, we must enumerate here amorphous deposits,
the colloid granules in the thyroid and elsewhere, and the corpuscula
amijlacca of the central nervous system, although these sometimes attain
a very considerable size. All these granules want the properties ob-
served in the higher elementary parts, such as endogenous growth, mul-
tiplication, assimilation, and excretion, and so far incline towards the
purely inorganic forms — crystals ; which are also found, though less
commonly, in the organism, as for example in the spleen, in the lungs
(black columns), in the ear, in the cells of the preputial glands of the
rat, in the blood-corpuscles of the dog and of fishes, in the fat-cells of
man, and in the cells of the chorion of the embryo of sheep.

Elementary vesicles also occur very frequently, and are for the most
part allied, physiologically, with the elementary granules, since, once
formed they do not increase, and neither multiply by division nor by
endogenous development. The milk-globules may with tolerable cer-
tainty be arranged among these ; at first included within the cells of
the nascent milk, they are subsequently found free, in enormous numbers,
in the perfect secretion, and, as Henle first stated, consist of the fatty
matter of the milk, with an investment of casein. The immeasurably
small molecules of the chyle and of the blood, are also, according to
II. MUller's investigation, fat globules with a protein envelop, and
similar vesicles may be found in most other fluids containing fat and
albumen in abundance. In fact, since the discovery of Ascherson
(MUller's ' Archiv,' 1840, p. 49), that whenever fluid fat and fluid albu-
men are shaken together, the fat globules which are formed always

certainly be regarded as structures which are not derived directly from the metamorphosis of
cells. We are inclined also to believe, that the opinion of Reichert, Donders, and Virchow,
as to the nature of the connective tissue deserves much more attention than Professor Kolli-
ker seems disposed to bestow on it. See §§ on Connective and Elastic Tissues. — Trs.]

42 GENERAL ANATOJIY OF THE TISSUES.

become surrounded by an albuminous coat, it is more than probable that
whenever, in the body, fat and albumen in the fluid condition come into
contact, similar vesicles are produced.

A peculiar class of elementary vesicles is formed by the elements
which occur in the yelk of certain animals. We are best acquainted
with them in the yelk of the hen's egg,* in whose proper yelk-substance
and yelk-cavity the globules which have been so long known are all vesi-
cular, but have not the nature of cells. The membranes of these yelk-
vesicles are excessively delicate and consist of a protein compound; the
contents are fluid albumen, and, in the globules of the yelk-cavity, there
is usually a large parietal fat globule, while in the others there are many
smaller and larger ones. The development of these vesicles proceeds,-
in all probability, from the fat globules as in other elementary vesicles,
from which, however, they are distinguished by the fact that they dis-
tinctly possess the power of growth, during which their contents undergo
metamorphosis, since in many the number of fat globules increases with
age. Similar vesicles exist, also, in the yelk of fishes, Crustacea, and
spiders, and here, as in birds, they have only a temporary importance,
since they are not directly applied to the formation of the embryo, but
only serve to nourish it.

Lastl}^ free nuclei occur in many localities, either temporarily, where
cells are formed immediately round nuclei, as in the chyle, the blood-
vascular glands, the Peyerian patches; or permanently, as proper ele-
ments of the tissue, in the wall of the thymus vesicles, in the rust-colored
layer of the cerebellum, and in the granular layer of the retina. f

Von Wittich ('De Hyraenogonia albuminis,' Regimontanii. 1850),
has lately given some information upon the formation of the so-called
Ascliersonian vesicles. According to Wittich, whenever oil and albumen
come in contact, a portion of the oil is saponified by uniting with the
alkali of the layer of albumen in contact with it, and this layer being
thus rendered insoluble by the deprivation of its alkali becomes precipi-
tated and thus forms the Aschersonian so-called haptogen membrane.
According to this explanation the process would be purely chemical and
not physical, and still less vital. In opposition to this view, how-
ever, Harting ('Ned. Lane' Sept. 1851), observed, not long' ago, the
formation of pseudo-cells by the agitation of albumen with mercury, in
which case the albumen must be solidified, in the same way as by the mere
shaking with water or otherwise (Melsens, in 'Bull, de I'Acad. de Bel-
gique,' 1850. Harting, &c.). Again, if by the bringing together of

* [It is, however, by no means certain that the yelk-corpnscles of the hen's egg are elemen-
tary grannies. According to Dr. H. Meckel (Die Bikhing der fur partielle Furchungbestiinm-
ten Eier der Vogel, &c., Siebold and Kolliker's ' Zeitschrift,' 1852,) iliey are altered celLs. —
Trs.]

■f [The blood corpuscles of man and the mammalia shouUl be added to this list. See
Wliarton Jones, 'Phil. Transactions,' 1S4G. — Trs.]

CELLS.

43

albumen and chloroform, scrum-casein and fat, choiidrin and chloro-
form,— albuminous, casein, and chondrin membranes are formed, as
Panum observed (see in part, ' Archiv f. Path. Anatomic,' iv. "2), it can
hardly be permissible to assume any chemical action.

II. OP THE CELLS.

7. The cells, celhdcv, called also elementary cells, or nucleated cells,
are perfectly closed vesicles of 0-005 0-01 of a Paris line,* in mean

* [The measurements employed by Prof. Kolliker are, according to the old Frencdi
standard, of inches and lines. In the original work a line is expressed by "', an inch by ".
As these signs are not used in this country, I have, In every instance, substituted the
words for the signs. Most Engli?h and American authors express the size of objects in
fractions of an inch, but rarely in lines. The English inch and line differ but little from
the Paris inch and line. The old Paris inch (") was divided into 12 lines ('") ; one line
being equal to ts'jths, or rather more than the 11th of an English inch : hence the diflerence
between a Paris line and an English line is very slight; jj^th of an English line being
equal to ^^jd of a Paris line: an English inch is thus exactly 11-2G Paris lir.es. All the
Fiench and many of the continental mi('rosco[)ists employ the recent French measure-
ments: the centimetre and millimetre. The proportion they bear to the English and French
inch is as follows: one millimetre ^'"'"j is equal to U-U39.37, or about j-^jth of an English
inch, or to ^V^' o' ^ Paris line. The subjoined table of the main measurements, noted
throughout the work in lines, reduced to fractions of an English inch, and parts of millime-
tres, will aid the student in forming a comparative estimate of the size of objects, as
measured by observers in different countries: —

TABLE OF MEASURKMEMTS.

01 of

a Paris line.

j| jth of

an Eng

ish inch.

0 22 millimetres.

001

i.

££

ttVj

ti

«

0-022 "

0-01

((

<i

^HS

ti

it

0-09 «

0-001

i(

(1

TT2^(J

it

it

00022 "

0-003

(C

«

TvAff

it

ti

0-0068 "

0-004

((

l<

^s'tj

it

ti

0009 "

0-005

(C

((

WjiS

ti

ti

0011 «

0-008

ii

le

ttVb^

<t

:i

0-018 «

0010

it

u

To 5

c<

it

0-036 "

0-028

It

It

4 (Iff

it

a

0 063 "

0035

a

((

sh

ti

it

0079 «

0 072

it

it

I
TTfiJ

it

a

0-17 ««

0-0001

it

it

TlAlTir

u

it

0-0002 "

00004

a

ti

58TJ?

ti

it

0 0009 "

00008

i(

«

TTiTB'S'

it

a

00018 "

0-0012

it

ti

55T5-

it

(C

00027 "

0-0016

ti

it

fij'jff

ti

it

0-0036 "

00025

■i

it

iTifflT

it

it

0-0056 «

00033

ti

it

3455

If

ti

0-0074 "

00045

it

it

2:^ff(r

(t

it

00100 "

0-0055

it

(C

Jff??

it

II

0-012 "

0 OCOOl

(£

((

JTshoU

it

<c

000002 "

oooooa

it

I(

TJSflijiy

it

it

00002 '•

DaC]

44

GENERAL ANATOMY OP THE TISSUES.

Fig. 1.

diameter, in which we may distinguish a special investment, the cell mem-
brane and contents. The latter are
always composed of a fluid, containing
formed particles of various kinds, and a
peculiar rounded body, the cell-nucleus,
which again contains in its interior a
fluid and a still smaller corpuscle, the
nucleolus. These cells, which must be
considered to be endowed with peculiar
vital powers, and to be capable of ab-
sorption and assimilation, of growth
and of multiplication, not only at the earliest period entirely compose
the body of the higher and that of most of the lower animals, but almost
wholly generate the higher elementary parts of the fully developed body.
In fact, even in adult animals, we find in very many places that the ele-
ments are simply in the condition of cells, and that as such they take a
more or less marked share in the performance of the organic functions.

It is not yet quite decided what part cells play in the composition of
the simplest animals. Siebold and I have expressed the opinion that
the Protozoa, like the simplest plants, are unicellular organisms, but
it is granted that no demonstration of this has been given in many,
especially the Rhizopods. In all creatures above the Protozoa, it would
seem to be certain that their body proceeds from a mass of cells, although
in the fully formed animals, as for example the Hydra, according to
Ecker,* this is not always clearly demonstrable.

§ 8. A more exact consideration of the relations of cells give us the
following results. Their fundamental form is globular or lenticular ; it
is such in all cells during their earliest state, and is permanent in those
which occur in the fluids (blood-corpuscles, &c.). Less common forms
are : 1. Polygonal (pavement epithelium). 2. Conical or pyramidal
(ciliated epithelium). 3. Cylindrical (cylinder epithelium). 4. Spindle-
shaped (contractile fibre-cells). 5. Squamous (epidermic scales). 6. Stel-
late (nerve-cells). The size of cells descends upon the one hand, as in
many young cells, blood-cells, &c., as low as 0-002-0-003 of a line,
and upon the other attains, as in the cysts of the semen and the nerve-

FiG. 1. — Nerve-cells of the Thalamus opticus of man, — three of them having their processes
torn off. Magnified 350 diam.

* [The tissite of the Hydra presents no essential features of dilference from that of the higher
animals, and closely resembles the most superficial layer of the dermis in the latter. In its
outer part the so-called nuclei are almost wholly converted into thread-cells; but they may
be very readily demonstrated in their ordinary condition in the deeper portions. The resem-
blance of the gelatinous tissue of the disk of the Medusae to Professor Kolliker's " reticulative
connective tissue'" is still more striking. — Trs.]

CELLS. 45.

cells, that of 0-02-0-0-4 of a line. The largest animal cells are the
yelk-cclls or ova, especially those of birds and amphibia, and a few of
those animals which consist of single cells, these, in certain Gregarinre,
attaining O'T of a line.

The membrane of the cells is generally very delicate, smooth, hardly
separable, and marked by a single contour, rarely of any considerable
density or measurable thickness ; with our present optical instruments
it exhibits no structure of any kind. In the interior of the cells there
are invariably found, at a certain time, one or many nuclei, besides
fluid and granules of various proportions and of different natures. Cells
which contain only fluid are rare (fat-cells, blood-cells, cells of the chorda
dorsalis), and it is colorless or reddish ; in general they contain, in
addition, corpuscles in greater or less number (elementary granules,
elementary vesicles, perhaps crystals), and in fact, as a rule, young cells
possess few, while older ones contain many, which are very often more
densely grouped round the nucleus, or occupy only a single spot (colored
nerve-cells).

The cliemical composition of the cells is as yet very obscure. The
contents in most cells present certain generally disseminated substances,
which occur dissolved in the nutritive fluid or cytoblastema, as water,
albumen, fat, extractive matter, salts ; a nitrogenous substance, which
is precipitated by water and by dilute acids, thus resembling mucus, is
very extensively distributed, and considerably impedes the microscopical
analysis of the cells and tissues, inasmuch as it causes them to be ob-
scure and granular, instead of clear and transparent. Many cells con-
tain yet other compounds, as those of the liver, of the kidneys, of the
blood, (fcc. The cell-memhranc consists of a nitrogenous substance,
which is unquestionably a protein compound in 3^oung cells, as we may
conclude from its solubility in acetic acid (partly even in the cold) and
in dilute caustic alkalies. Subsequently the membrane in many cells,
yet by no means in all (e. g. not in the blood-corpuscles, in the deepest
cells of the epidermis and epithelium, nor in the cells of the glandular
follicles), becomes less soluble, and here and there more or less approxi-
mates the substance of the elastic tissue.

The cell-nucleus is a globular or lenticular, clear, or yellowish body,
which in the mean measures 0'002-0-004 of a line, and rarely, as in
the ganglion-globules and ova, attains a diameter of 0*01-0-04 of a
line. All nuclei are vesicles, as Schwann supposed and as I have
recognized to be their original and universal structure in embryos
and adult animals. The membrane is very delicate in the smaller
ones, appearing as a simple, fine, dark line ; in the larger it is more
marked, even of measurable thickness and limited by a double contour,
as in the nuclei of the ganglion-globules, of ova and of many embryos.
The contents of the nuclear vesicle consist, excepting the nucleolus,

46 GENERAL ANATOMY OF THE TISSUES.

almost invariably of a pellucid or slightly yellowish — never more darkly
tinged — fluid, in which water and acetic acid precipitate the same dark
granules, as in the cells, for which reason, the nuclei never preserve their
natural homogeneous clear appearance, when examined according to the
ordinary methods. More rarely the nuclei have formed contents, as
the spermatic filament in the semen ; in ova peculiar granules, the so-
called germinal spots ; also in the fat of Piseicola (Leydig). In respect
of their chemical composition, only this much can be said of the nuclei,
that their membranes are nitrogenous, and in general but little different
from the substance forming the younger cell-membranes; they are, how-
ever, dissolved more slowly in alkalies, and are but slightly attacked by
dilute acetic and mineral acids. In the latter circumstance they ap-
proximate the elastic tissue, from which, however, they are most essen-
tially distinguished by their easy solubility in alkalies.

The nuclei are found, so far as I have observed, in all cells of embryos
without exception, and in those of adults, so long as the cells are still
young. In general only a single nucleus exists in each cell, except
when it is multiplying ; in the latter case, however, two or more nuclei
arise, according to the number of the developing cells. In certain cells
we meet with more numerous nuclei ; thus, in those of the semen, 4,
10, 20, and more; also in the substantia grisea centralis of the spinal
cord, of the supra-renal capsules, of the pituitary body, in the hepatic
cells of embryos, in the foetal medullary cells of bone, and elsewhere.
That nuclei also occur free, and take part in the formation of certain
tissues, has already been stated.

The nucleoli are round, sharply defined, generally dark, fat-like gra-
nules, which, on the average, measure 0-001-0-0015 of a line, are often
almost immeasurably small, and in embryos, in the germinal vesicles of
ova as the germinal spots, and in the ganglion-globules, attain the size
of 0-003-0-01 of a line. In all probability they are always vesicular,
as may be surmised from their sharply circumscribed form, their simi-
larity to elementary vesicles, and also from the circumstance that in
certain cells, especially in ova and ganglion-globules, a larger or smaller
cavity filled with fluid frequently becomes developed in them. The
chemical composition of the nucleoli is unknown : their external
appearance, their similarity to the elementary vesicles, their disap-
pearance in caustic alkalies, and their insolubility in acetic acid,
would lead us to suppose them to be fat ; the membranes may, as in
the elementary vesicles, be a protein compound. Nucleoli are found
in the great majority of nuclei, so long as these are still young, and
in many during their whole existence ; but nuclei also exist, in which
nucleoli cannot be recognized with certainty, or at least become ob-
vious only at a later period; and therefore, at present, the nucleolus
cannot be so unconditionally recognized to be an essential constituent

CELLS. 47

of the cell, as the nucleus. Generally, a nucleus contains only one
nucleolus, frequently there are two, rarely three, and, in solitary cases,
four or five may be present, which are then either eccentric or lie free
in the nucleus.

A short time since, Bonders, in a very remarkable work [vide infra),
expressed the opinion that all cell-membranes consist of one and the
same, or at least of very nearly allied substances, which agree in their
characters with the elastic tissue. For my own part I believe that all
animal cell-membranes consist originally of the same substance — of a
protein compound, in fact ; that, however, in consequence of its subse-
quent metamorphoses, it may acquire differences of composition and
of reaction. Many membranes in this manner become more resistant
with time and, as Donders justly states, approach elastic tissue ; others
change into collagenous tissue, as those of the formative cells of the
connective tissue,* and of the cartilage cells during ossification ; others
into syntoniti, as in the smooth muscles ; into the so-called horn, and
so on. If we assume the primitive cell-membrane to be a protein com-
pound, and from the reaction of young cells and of embryonic paren-
chyma it can hardl}^ be otherwise, we obtain a correspondence with the
vegetable cell, since in this case the primordial utricle, consisting of a
protein compound, can be considered as the analogue of the animal cell-
membrane, whilst the cellulose membrane appears as a secondary pro-
duct, as an excretion. Such may be the true condition also in those
animal structures of the Tunicata which are formed of cellulose, in which
case my assertion that here the cell-membranes are composed of woody
fibre, and that of Schacht (MUllcr's "Archiv," 1851), that they
are nitrogenous, would coincide. If future investigation justify this
comparison of the animal cell with the primordial utricle of plants, the
further question would arise in animals, whether perhaps all the so-called
metamorphoses of the cell-membrane are not to be laid to the account
of deposits which are throtvn doivn upon the outer side of it, similarly
to the cellulose in plants, so that, perhaps, together with the original
protein membrane, other secondary collagenous or elastic membranes,
&c., might be distinguished, and even the most considerable thicken-
ings of the animal cell be produced, in a manner analogous to that
which occurs in the ligneous tissues of plants on the outer side of the
protein membrane; so that, for example, within ossified cartilage-cells
the original cell-membrane might perhaps still exist.

In all normal cells of the higher animals, the nuclei can be readily
shown by the vesicles, and most beautifully so in embryos ; only in those
cells which arise directly around nuclei, are the nuclei at first more

* [The term "connective tissue'' (Bindegewebe) lias been used liy tlie translators to de-
signate the tissue more generally known as '• white fibrous tissue. " — DaC]

48 GENERAL ANATOMY OP TIIE TISSUES.

homogeneous, and subsequently exhibit a distinct membrane. In
jjathological formations, this character of the nucleus, which may be
called an undeveloped form, is very frequent, and the nucleus-like
structures in the Protozoa are also for the most part homogeneous
bodies.

§ 9. Development of Cells. — With regard to the development of cells,
we have to distinguish between their free origin and their production
by the intermediation of other cells. In the former case the cells are
developed, independently of others, in a plastic fluid, the cytoblastema
of Schleiden, containing chiefly fat, protein, and salts in solution ; in
the other, or in cell-multiplication, the existent cells either produce the
so-called daughter or secondary cells within themselves, or multiply by
division ; eyidogenous cell formation and fissiparous cellformatioyi. Both
kinds of cell-formation agree in this, that the cell nuclei play a very
important part, and appear to be the proper centres of development of
the young cells.

§ 10. Free cell-development is, in man and the higher animals, far
less common than has been hitherto assumed, and under this category
we can enumerate, so far as is at present known, only the development
of the chyle and lymph corpuscles, of the cells of certain glandular
secretions (spermatic cells, ova), and gland-like organs (closed follicles
of the intestine, lymph glands, splenic corpuscles and pulp, thymus) ;
lastly, of the cellular elements in the pregnant uterus, in the corpus
Fig. 2. liiteum, in the medulla of foetal bones, and in the soft

„''-%. ..« ossifying blastemata. The separate steps of the process
'^^^^ ^ in this mode of cell-development have as yet been traced
^^^m /mJ principally in the first-named cells, but much is yet want-
ci.3.9^ W^ ing to complete our knowledge of it. This much is cer-
tain, that the origin of the cells is always preceded by the development
of cell-nuclei, while it is doubtful, on the other hand, how these are
formed. In the chyle and in the spleen we see as the first indication of
cell-formation rounded homogeneous-looking corpuscles of 0*001--002
of a line, which, increasing somewhat in size, soon clearly appear
to be vesicles, and often, upon the addition of water, exhibit in their
interior, together with small granules, a large granule, like a nucleolus.
Whether this last, as is certainly the case in the dependent mode of
cell-development, arises before the nucleus and is the condition of the
development of the latter, or whether it is formed subsequently therein;
how, again, the nuclei themselves are developed, whether as originally
homogeneous corpuscles, which subsequently exhibit a difi"erentiation

Fig. 2. — Contents of a Malpigliian corpuscle of the ox: a, small j b, larger cells; c, free
nuclei ; magnified 350 diameters.

CELLS. 49

into inner and outer parts, — envelop, and contents, or whether they
are not, from the first, vesicular, cannot at present be decided.

The nuclei being once formed, the cell-membranes are developed
around them, though not always in the same way. In the first place
they may be applied directly around the nucleus, so that the nascent
cell is but little larger than its nucleus ; or, in the second place, the
latter may become surrounded by a greater or smaller quantity of solidi-
fying cytoblastema, and it is only around this enveloping mass, which
I have called an investing globule, that a membrane forms. This last
occurrence in the free cell-formation has hitherto been observed only
in the ovum, in which the germinal vesicle, i. e. the nucleus of the egg-
cell, being first formed, surrounds itself with some yelk before the vitel-
lary membrane appears. On the other hand, cell-development directly
round the nucleus takes place in all the other localities which have been
mentioned above, and is demonstrated by the occurrence, among free
nuclei and large cells, of very small cells, which closely invest the nu-
cleus or are but little separated from it. It may, hoAvever, be remarked,
that perhaps in these cases also, the cell-membranes at their origin
are separated from the nuclei by a very small quantity of cytoblastema,
so small as to be incapable of detection.

Free cell-formation is exceedingly frequent in pathological produc-
tions, and the cells in pus and in exudations of all kinds arise in this
manner ; in fact, all pathological cell-formation properly comes under
this head. Usually the cell-membranes here arise directly round the
nucleus, less commonly as it would seem round investing globules.
With regard to physiological processes, as has been already shown, free
cell-development has been much too readily taken for granted; and
especially as regards the epithelial and horny tissues, as well as in many
glandular secretions, it has been assumed without any sufficient grounds.
Botany knows no free cell-development.*

§ 11. The development of cells within other cells, or their endoge-
nous origin, is of very frequent occurrence, and easy to be observed
in embryos. The commonest form of this cell genesis is, that a so-called
parent cell produces tivo secondary cells, which /rom the first wholly fill

* [There cannot Ije said to be any evidence of the occurrence of free cell-development in
animals, so long as in any case cited it is not shown that the first-formed particles which
make their appearance cannot have derived their oriirin from jire-existing formed particles,
either by the detachment or fission of the latter. Not only does this condition remain unful-
filled for all the instances cited, but it has not been attempted, and would seem to be im-
possible. In patliological exudations, lor instance, who shall determine that the first struc-
tural elements wldch appear, granules, free •• nuclei," exudation corpuscles, &c., are not
directly derived cither from the blood, or from the tissue into which the exudation has taken
place 1 — Trs.]

4

50

GENERAL ANATOMY OF THE TISSUES.

it. The first thing to be observed in this case, in the parent cell, is a

metamorphosis of its nucleus, which grows, ac-
quires two nucleoli, becomes elongated, and
divides into two. When this has once taken
•'^ place, the nuclei become somewhat divaricated
and then a wall of separation arises between
the cells, which divides tha parent cell into
two perfectly distinct spaces, each of which con-
tains a single nucleus and one half of the con-
tents. The mode in which the multiplication
of the nucleus takes place, has not yet been
made out with exactness. This much, however,
is certain, that where clear observation is pos-
sible, it is always the nucleoli which first divide into two and then diverge
a little. In the nuclei, which have at the same time slightly elongated,
there then usually appears, making 'the first trace of their division, a
median partition, which in favorable cases may be recognized as com-
posed of two secondary nuclei applied to one another by their flat sides
and completely filling the parent nucleus. Very frequently we see, in
the course of this process of multiplication of the nuclei, no-
thing more than, first an elongated nucleus, with a partition and
two nucleoli, and then two hemispherical nuclei applied by their
plane faces to one another, without its being possible to demon-
strate with certainty any endogenous development of nuclei ;
so much the less, as it is not to be doubted that, together with the latter
process, a multiplication of nuclei hy division takes place, in which an
elongated parent nucleus, with two nucleoli, breaks up into two by the
formation of a constriction which gradually deepens in the middle.

The further destiny of the parent cells, with a partition and two
nuclei, is not always the same. As a rule, it appears that in each, two
perfect secondary cells afterwards become evident, which may serve as
a demonstration that the partition is double from the very first. At
other times, distinct secondary cells are not recognizable, which however
does not imply that there exists a mode of cell-development by the mere
formation of partitions, but only that in such cases the secondary cells
do not become distinctly separated from the parent cells. Whether the
one process or the other take place, it rarely stops at one performance,
but is generally repeated a certain, often very considerable number of
times ; in fact, as long as the organism grows. The parent cells either
remain, or they cease earlier or later to be histologically distinct struc-

Fig. 4.

Fig. 3. — From the cephalic cartilage of an advanced tadpole. Parent cells, with 1 and
2 nuclei, or 2-4 secondary cells, and some interstitial substance ; magnified 350 diameters.

FiQ. 4. — An elongated nucleus, and one containing two secondary nuclei, from the ovum
of an Ascaris dentata; magnified 350 diameters.

CELLS.

51

tures, and coalesce with the substance which unites the cells as a matrix.
The occurrence of this ondogenous cell-development, which may be
called cell-development around the collective contents, and which agrees
in all essential points with free cell-development around investing masses,
has been made out with certainty in the young cartilage of all animals,
and probably occurs in embryonic organs in general, in which, from the
moment when they consist of actual cells, the total growth essentially
depends upon a self -multiplication of the cells without free-cell develop-
ment. Since, however, it is as yet undecided, whether perhaps cell-de-
velopment by division, to which attention has been very lately drawn,
does not play a part in the one case or in the other, our judgment, so
far as regards the latter, must as yet be suspended, until more particu-
lar investigations have been undertaken ; and the same holds good for
many organs of the adult, as the horny tissues and certain glandular
secretions. Only, when secondary cells are observed in parent cells, as
especially in the pituitary body and in the supra-renal capsules, there
can of course be no doubt as to the existence of endogenous cell-develop-
ment.

Besides these most usual forms of cell-development, there exist yet a
few others.

1. In the ova of most animals a peculiar process, the so-called
cleavage of the yelk, occurs at the earliest period of development,
which is to be regarded as the introduction to the formation of the first
cells of the embryo; and since the ovum has the nature of a simple cell,
it is a case of endogenous cell-development. This cleavage takes place
as follows. After the original nucleus of the egg-cell, the germinal
vesicle, has disappeared with the occurrence of fecundation, the granules
of the yelk no longer form a com-
pact mass as before, but become
dispersed and fill the whole egg-

cell. Then, as the earliest sign
of commencing development, there
arises in the midst of the yelk,
around a new nucleolus, a new
nucleus, the primary nucleus of the embryo, which operates as a centre
of attraction upon the yelk and unites it again into a globular mass, the
first '•'■cleavage mass" (Furchungs-kugel). In the further course of de-
velopment two new nuclei are formed by endogenous development from
the first nucleus, and these, as soon as they have become freed by the
solution of the parent nucleus, separate from one another for a short
distance, act as new centres upon the yelk, and thus break up the first

Fig. 5. — Tlie ova oi^scaris vigovenosa, — 1 from the second, 2 from the third, and 3 from
the fifth stage of division, with 2, 4, and IG division-masses: a, chorion; b, cleavage masse?.
In 1 the nucleus of the lower mass contains two nucleoli, in 2 the lowest contains two nuclei.

52 GENERAL ANATOMY OF THE TISSUES.

cleavage mass into two. In this way the multiplication of nuclei and
of cleavage masses proceeds, — the former always taking the lead, until
a very great number of small globules are produced which fill the whole
cavity of the yelk-cell ; it is only in exceptional cases that the cleavage-
masses break up after the development of three or four nuclei within
them ; so that then, instead of two, three or four cleavage-masses imme-
diately proceed from one. This process is called total cleavage, because
here the whole yelk is disposed around the newly-developed nuclei :
partial cleavage is essentially similar, differing only in the circumstance
that it is not the whole yelk, but a greater or lesser portion, according
to the animal, which invests the nascent nuclei.

When the process has attained a certain stage, the cleavage-masses
all together, or in successive layers, surround themselves with membranes,
and become actual cells, whence we are justified in considering this to
be a process of endogenous cell-development. In fact, it is nothing else
than an introduction to cell-development in the egg-cell, and differs
from the ordinary phenomena of that class only in this, that firstly, the
nucleus of the parent cell or the germinal vesicle, in most cases (Miiller
saw a division of it occur in the Molluscs which are developed within
Synapta digitata*) has nothing to do with it ; secondly, that the parent
cell itself persists ; and thirdly, that the investing globules developed by
the successive multiplication of nuclei become cells only in the latest
generations. This view is the more justifiable, as the cells which have
arisen in consequence of the metamorphosis of the last cleavage-masses
long continue to multiply by endogenous development ; and the whole
process of division may be regarded as a kind of endogenous cell-deve-
lopment, in which, on account of the rapidity with which the nuclei mul-
tiply, no formation of cell-membrane takes place in the early genera-
tions of "cleavage-masses."

2. Closely allied, in some respects, to the cleavage process, are those
forms of endogenous cell-development, in which, a greater or smaller
number of secondary cells are developed within persistent parent cells,
as we see here and there in the cartilages, in the supra-renal capsules,
and in the pituitary body. In this case there either arise in the ordinary
manner, in a cell, two secondary cells, which wholly or partially fill it,
and from these by continued multiplication, other generations, which
sometimes lie quite free, and sometimes are wholly or partially included
in the parent cells of the second generation ; or a more free development
of a secondary cell within a parent cell occurs, from which cell-develop-
ment then takes place in one mode or in the other.

In connection with the process of endogenous cell-development, we may
very properly speak of the formation of a great number of nuclei within
cells, a process which is frequently the precursor of cell-development,

* [Dr. Nelson (Phil. Trans., 1852, p. 580), has observed the same thing in Jlscaris mystax.
— Trs.]

CELLS.

53

but which may also continue alone. Even in the common endogenous
cell-development (and also
in the cleavage process) we
not unfrequently observe
three and four nuclei in a
parent cell, so that then,
instead of two secondary
cells, many arise at once,
e. g. in the hepatic cells of
embryos. In certain ani-
mals [CucuUamis, Ascaris
dentata, Distoma, Cestoi-
dea), instead of cleavage
masses, nuclei alone are
developed in the first stages
of development, and it is
only later, when by succes- i
sive endogenous multiplica-
tion these have increased to
a great bulk, that they be-
come surrounded by cell
membranes. Something
similar appears to take
place in the cells of the
germ in the Crustacea, in which 10-20 nuclei are often found (Rathke,
' De Anim. Crustac. gen.,' Regim. fis. 7

1844.) On the other hand, the nu-
merous nuclei in the spermatic cells
of most animals are, in general, in
no way connected with cell-develop-
ment, since the spermatic filaments
are developed in them ; and the like
holds good of those cells of the lower
animals, whose multitudinous nuclei
are changed into thread-cells. The
import of the number of nuclei in
certain nerve-cells, and in the large
cells of the bone-medulla, which Robin and I have observed, is doubt-
ful ; in the latter, I think it is not improbable that the multiplication

Fig. G. — Cartilage cells from a fibroii?, velvety, articular cartilage of the condyle of the
femur of man, magnified 350 diameters; all lying in a fibrous matrix, and readily isolated:
a, simple cells, with or without a thickened wall, with 1 or 2 nuclei; b, secondary cells, or
cells of the first generation, with 1 or 2 nuclei; 1, 2-5 or more, in parent cells; b, c, cells
of the second generation, 1-3 in number, in cells of the first ; d, freed groups of secondary cells.

Fig. 7. — a. Peculiar granulated cells with many nuclei from the youngest medullary cavi-
ties of the flat bones of the skull in man. Magnified 350 diameters.

«r'

54 GENERAL ANATOMY OF THE TISSUES.

of the nuclei is preliminary to their breaking up into smaller cells. In
all these cases, it may be easily demonstrated that the nuclei multiply
spontaneously, but it is generally doubtful whether this happens by
division or by endogenous development.

Cell-development round a mass of blastema containing a nucleus in
its interior, which may take place either freely or in an endogenous
manner (cell-development round portions of contents), had long ago
been seen by Von Siebold in the ova of Bistoma globiporum, and by
Bergmann in the cleavage-masses of Rana, but no further importance
was attached to it. Vogt and Niigeli were the first who regarded this
cell-development as a deviation from the theory of Schleiden and
Schwann, whereupon, supported by observations upon embryos, I (in
1844, " Entwick. d. Cephalopoden") placed this as a second kind of
cell-development under the name of " cell-development round investing
masses," beside that which takes place immediately round nuclei, and
pointed out its very extensive occurrence, especially in embryos, where
at first it is the sole mode. Later observations upon normal and patho-
logical products have supported this view, and at the present time the
formation of a cell-membrane immediately around the nucleus requires
demonstration, rather than the opposite method. Endogenous cell-
development occurs in many pathological products, — most frequently in
cancer, yet the steps of the process have not yet been exactly made out.
In plants this mode of multiplication of cells is the most extensive, and
it occurs commonly as "cell-development around portions of contents,"
more rarely (in the embryo sac) by free development within parent cells.*

§ 12. ^ multiplication of cells hy division certainly takes place in
the red blood-corpuscles of the embryos of Birds and Mammalia, and

in the first colorless blood-corpuscles of the
^'^^ Tadpole (Remak). It takes place also, in all

^ probability, in the colorless blood-corpuscles of
embryos, and in the chyle-corpuscles of adult
Mammalia under certain circumstances. In all
^ ^§ ^^ these cases, we see, in elongating cells, the pro-

duction of two nuclei from the originally simple

Fig. S. — Dividing blood corpuscles of the chick; magnified 350 diam.

* [The endogenous development of secondary " nuclei'' seems to us to be extremely doubt-
ful, even upon the evidence adduced, and u'e have been imable to observe anything indi-
cating that regularity of occurrence and importance of function attril)uted to the nucleolus by
Professor Kolliker. In cartilage, in the tooth-pulp, in the homogeneous layers of the cutis,
and in other localities, in which unaltered " nuclei'' occur, the presence and number of the
granules which might be called nucleoli is in the highest degree variable and uncertain.
The same irregularity as to the presence of nucleoli occurs in the plant [vide Von Mohl, 1. c,
and Schacht, " Die Pflanzenzelle," p. 30).

Upon this subject consult the valuable memoir of Remak (Ueber extra-cellulare Enste-
hung Thierischen Zellen,"' &c., Miill. Archiv, 1S52), which by no means deserves the epi-
thet of" no longer available ;'' in fact, Remak's views seem to be essentially correct. — Tks.]

CELLS.

55

Fig. 9.

nucleus, apparently by division ; the cells then suffer constriction in
the middle, and contract more and more around the nuclei, as they recede
from each other, and at last separate into two cells, each of which con-
tains a nucleus. In the chick we see blood-corpuscles in all conceiva-
ble stages of separation, so that at length they are connected only by
a delicate thread, and there can be no doubt whatever as to the actual
occurrence of this process.

Whether division ever take place in other cells than these is not yet
determined. If it be allowable to explain, by this process of division,
the occurrence of constricted cells with
two nuclei, we may suppose it to take
place in the nerve-cells, which, in young
mammalia, are not unfrequently more
or less divided or even united merely
by a narrow isthmus, and also in the
ciliated epithelium cells, which, al-
though rarely, present two or three
enlargements lying one behind the
other, each with a nucleus. A peculiar
kind of cell-development, which is very
closely related to division, occurs in
the formative cells of the ivory, which
as they go on growing, multiply their
nuclei and become constricted from
time to time, so that whilst the portion
next the ivory ossifies, the other serves in a manner as a reserve for the
subsequent formation of fresh ossifying tissue.

Schwann knew nothing of the occurrence of cell-division. The first
"who observed it in the blood-corpuscles of embryos was Remak ("Med.
Verein." 1841, No. 27; Schmidt, " JahrbUcher," 1841, p. 145; Can-
statt, " Jahresb.," 1841), yet he subsequently retracted his opinion
(" Diagn. und Pathol. Untersuchungen," p. 100), and only now, since I
have confirmed it and declared it to be true (Wiegm. " Archiv,"
Jabrg. 13, Bd. 1, p. 19), has he again advocated it (" Entwick. d. Wir-
belthiere,' I.) It is extremely probable that this mode of cell-development
occurs very extensively, and it may perhaps turn out that in many em-
bryos and adult tissues, in which a self-multiplication of the cell is cer-
tain, and yet in which no parent cells with secondary cells can be demon-
strated, cell-development by division may occur instead of endogenous
cell-development. It is certain that the. transverse and longitudinal
division of the Protozoa is to be placed here, since these animals have

Fig. 9. — Dentine cells from the dog ; magnified 300 diam.

56 GENERAL ANATOMY OF THE TISSUES.

the structure of simple cells, and the nucleus-like body they contain
takes a share in the process of cell division, like that of the cell-nucleus
in common cells. In pathological formations cell division has not yet
been observed. In the vegetable kingdom it is rare, and has been seen
only in the lower organisms ; unless, indeed, we are to reckon here the
constriction of the primordial utricle observed by Von Mohl in the course
of endogenous cell-development.*

§ 18. Theory of Q ell-development. — Among the few hypotheses which
have, up to the present time, been proposed in explanation of the develop-
ment of cells, that of Schwann, who compares it with the formation of crys-
tals, is certainly the most attractive. Without overlooking the differences
between a crystal and a cell, which chiefly consist in the former being
solid and homogeneous, in its growing by apposition, and in its being
bounded by plane surfaces and angles, Schwann endeavors to explain
cell-development as a crystallization of organic matter, and to deduce
from the permeability of the latter the differences in the phenomena
presented by the two. In a fluid containing organic matters dissolved

* [There can, we think, be little doubt that Von Mohl is quite correct in the view he takes
of the multiplication of cells in plants by division, and therefore we are by no means inclined
to agree with Professor Kolliker, as to the rarity of this form of cell-multiplication in die
vegetable kingdom, nor, consequently, in what he says at the conclusion of the preceding
note. All botanists of any note (Nageli, Von Mohl, Hoffmeister, Alex. Braun, Schacht, Hen-
frey) maintain at the present time, that the process of cell-division so far from being "rare,"'
is that which occurs in by far the great majority of cases in plants. " That the formation
of cells, in all organs of plants (except the cells originating in the embryo sac), depends
upon the division of older cells, is an opinion, whicli could not for a long time past be op-
posed by any carefid observer, unless he were misled by preconceived notions.' (Von
Mohl, "Anatomy and Physiology of the Vegetable Cell,'' 1851, Henfrey's translation). Nor
can we agree with Professor Kolliker's estimate of the relative frequency of occurrence and
importance of endogenous cell-development and cell-division in the animal world. In young
cartilage, which is cited by our author as a locality in which endogenous cell-development
takes place, we must afllrm, on tlie contrary, that the process is as much one of cell-division
as it is in any plant. At this perioil the so-called " nuclei" of the cartilage completely fill
their cavities (c. g. nasal cartilage of four months' foetus), and may be seen in all stages of
division. The walls of the cavities grow in, pari passu, and eventually form a partition
between the two nuclei, or rather primordial utricles, which have been thus developed from
one.

Remak, who, in a very valuable paper (Ueber die Entstehung der Bindegewebes und
Knorpels, Mull. Archiv, 1852), has advocated this view, so far as cartilage and connective-
tisue are concerned, does not appear to have seen the necessity of extending it to the other
tissues. As Reichert, however, long since pointed out (see note, § on Connective Tissue)
whatever determines the nature of the cartilage corpuscle, and of its matrix, determines that
of all the other tissues whose anatomical continuity with cartilage can be traced directly or
indirectly. Thus a direct anatomical continuity may be shown to exist between the matrix
of cartilage, the apparent fibrilhe of cennective tissue, the librilkeof muscle, the homogeneous
matrix of the cutis and of its papilke, and the so-called walls of the epithelial cells; while
a perfect identity in size, structure, and relation, may be traced between the corpuscles of
cartilage, the "nuclei" of connective tissue, those of muscle, of the papillae and of the epithe-
lial cells. — Tes.]

CELLS. 57

in considerable proportions, a granule, the nucleolus, is precipitated.
Once formed, this attracts nutriment from the cytoblastema, and thus
becomes the nucleus, which Schwann considers to be solid. This still
goes on attracting to itself a substance, which, becoming more and more
condensed, at last forms a membrane ; which, allowing the passage of
fluid cytoblastema through its pores, becomes detached from the nucleus,
and we have a cell. In this exposition, we must admire not only the
skilful, acute working out of the fundamental idea which the original
treatise manifests, but also the assumption of a molecular attraction in
cell-development, analogous to that which occurs in the formation of
crystals, for the existence of which there is, in fact, decisive evidence
(only in part, however, known to Schwann), such as the action of the
nuclei in the cleavage process, in cell-division, in cell-development, round
portions of contents, in the cyclosis, and in the formation of granular
precipitates in cells.* On the other hand, it is evidently going too far
to call cell-development simply a crystallization of permeable organic
substances, since in this case important differences are overlooked, and
non-essentials are made unduly prominent. For it must not be forgot-
ten that organic permeable substances also crystallize ; that, in fact, if
Reichert have observed correctly (MUller's " Archiv," 1849), and I see
no reason for doubt, histogenetic substances capable of forming tissues, as
albumen for instance, assume a crystalline form. Hence the molecular
attraction concerned in the formation of cells is so far peculiar, that — 1, it
never produces geometrical solids, but even in the nucleus and nucleolus
determines the globular form ; 2, that it aggregates, not homogeneous but
chemically different substances, as those which constitute the nucleus
and the cell-membrane ; 3, lastly, that without exception, in the develop-
ment of the cell-membrane it limits itself, and does not, like the crystal-
lizing force, repeatedly apply layer upon layer. Of these differences,
the two latter might perhaps be set aside, if with regard to the second
point, it were assumed that the nuclei at first consist of the same sub-
stance as the cell-membranes, or are almost identical with them in
chemical composition ; or if we referred to the fact that in crystalliza-
tion also, different substances may unite into one crystal, or that a
substance, b, may crystallize round a substance, a.

In order to diminish the force of the third fact adduced (this objec-
tion, indeed, does not hold with regard to endogenous development, and
therefore in almost all plants, since it is impossible here that the cells
should produce any more layers around themselves), it might be urged
that the permeability of the organic membranes, the exchange of con-
stituents which take place between the juices of the cell and the cyto-
blastema, and the application of the molecules attracted from the cyto-
blastema to the growth of the membrane, and to precipitates within the

* [See note, p. 52. — Tks.]

58 GENERAL ANATOMY OF THE TISSUES.

interior, are perhaps the reasons why the cells develop no new circum-
ferential layers. It is not necessary to carry out this last possibility
any further, nor to bring forward the difficulties which are opposed to
this view also, — among which not the smallest is, that the organic deve-
lopment of vesicles does not stop at the formation of nuclei, but is only
finished with the completion of the cell membrane ; since in any case
the facts brought forward ard more than enough to demonstrate the
insufficiency of Schwann's hypothesis. I do not see, however, any-
thing better or more positive to substitute in its place, and I therefore
think it will be most expedient simply to group together the ascertained
facts into a few general propositions, which may, perhaps, be done as
follows. •

1. The nucleus of the cell arises in the first place, as a precipitate in
an organizable fluid, and afterwards becomes consolidated in such a
manner, that a special investment and contents with a nucleolus appear.
Its development may in this case be compared to that of inorganic pre-
cipitates, yet the constantly globular figure, and the size of nuclei
which are just formed, indicate some essential though not yet recognized
condition peculiar to them. Secondly, cell-nuclei are produced endo-
genously in nuclei, or by their division under the influence of a nucleo-
lus, which also divides. Here is one condition which is never presented
by crystals, — the division from an internal cause ; while the other, the
influence of the nucleoli upon the nucleus, can hardly be comprehended
in any but a physical way, as a molecular attraction proceeding from
the nucleoli, of an indefinable nature, which at last draws the entire
half of the parent nucleus within its influence.

2. In the development of cells by division, the cell-nucleus plays
exactly the same part which was previously ascribed to the nucleolus,
and the occurrence of the formation of cells in this manner demonstrates
that chemical conditions are not necessarily concerned therein.

3. In cell development around portions of contents, and in the
cleavage process, the nuclei also operate as simple centres of attraction
(einfach attrahirend) upon a certain mass of blastema, and then follows
the formation of a membrane upon the surface of this mass, which is
most simply understood as a condensation of the blastema.

4. In cell-development directly around the nucleus, the investment with
blastema is wanting, and the nucleus develops the membrane imme-
diately around itself. This process admits of both a physical and a chemi-
cal explanation. In the first place, we may with Schwann assume
that the nucleus attracts molecules, which, when they have reached a
certain amount, condense into a membrane, and, by growing, become
detached from the nucleus. Or secondly, it is conceivable, that the nucleus
in some manner initiates chemical processes, which terminate with the
formation of a membrane around it. In this way a coagulable sub-

CELLS. 59

stance might be produced within and excreted from it ; or, like rennet
upon casein, it might act upon the protein combinations in the cjto-
blastema, in such a manner that they should coagulate where in contact
with it ; or lastly, by the extraction of the alkali it might render an
albuminous substance insoluble, as is the case in the development of
Ascherson's vesicles. Which of these various possibilities really obtains,
must at present remain undetermined, yet, for my own part, I should
prefer the first view, in order to retain one and the same condition, a
physical one, for all the different modes of cell-development.

I do not think it necessary to enter at greater length, in the present
place, into this very obscure subject, and I will therefore only once
more express my opinion, that I hold the physical processes of cell-
development, which may pass under the general name of molecular at-
traction, to be something quite different from those which attend crystal-
lization. Although in both, solids arise out of fluids, and grow by the -;
further agglomeration of molecules, yet in cell-development different
substances are as a rule superimposed, plane geometrical solids are never
formed, and the process is always limited in the same way, after the
formation of the cell-membrane. Since organic and even histogenetic
substances are crystallizable, the reason of cell-development is not to be
found in permeability nor in any of the other properties of organic com-
pounds, which in fact, even if the substances did not crystallize, would
not suffice to explain all the peculiarities of cells in question, nor their
power of self-division and multiplication ; but in those peculiar, as yet
unknown combinations of the powers of nature which are concerned in
organic development. To discover these is the further and difficult
task of Histology, w^hich to this end must be wholly directed to the so-
called molecular forces of organic forms, especially to those electrical
phenomena which must indubitably occur in the cells as well as in their
derivative structures, the nerve-tubes and muscular fibres.*

§ 14. Vital Phenomena of the Perfect Cells. Gfroivth. — The cells,
when once completed, perform a considerable number of functions, which
relate as well to the form of the whole cell and of its contents, as to their
chemical composition, and are called growth and change of substance.

• [The essential distinction between living organized matter (tlie cell) and mere inorganic
formed matter (the crystal) api)ears to us to be here overlooked. If some inorganic substance
should be discovered crystallizing in the form of nucleated cells, it would not the more ap-
proximate to an animal or vegetable cell ; for the essential character of the latter, which
is its passage through a definite succession of slates and not its form merehj, would still be absent.
It is this characteristic peculiarity of organized living beings, which has been exhibited
widi so much force by Alex. Braun, in the plant, under the somewhat fanciful title of ' Ver-
jungung' (rejuvenescence), but which equally obtains in the animal. The crystal tends to
attain a permanent condition, the cell towards its own disappearance, either by death or
division. The crystal tend.s towards an equilibrium with the forces around it, the cell
incessantly disturbs that equilibrium, — life and change being one. — Trs.]

60

GENERAL ANATOMY OF THE TISSUES.

Fig. 10,

Fisr.ll.

'/ v/

ifo '/^

#

As to growth, it occurs perhaps in all cells, though not in all to the
same extent. It is clearly manifested in all those cells which are
formed directly round a nucleus, since in this case the membranes which
at first closely invest the nucleus, in time become more and more sepa-
rated, whilst the cells which arise around portions of contents or invest-
ing masses, and are from the first provided with contents, often
increase in size but very slightly. Growth is either in surface or in
thickness. The former appears very usually to be general, when cells
increase without altering their form, e. g. the ova, many nerve-cells,
&c. ; frequently however it is partial, as in all cells which depart from
the primitive globular form, in such a manner that the cell-membranes
cnly add new substance and extend at two or more points. Growth in
thickness also occurs, to a certain
extent, in all cells, since all cell-
membranes become someA\hat
thicker with age ; and it produces
in some localities a very consider-
able thickening of the membrane,
occasionally with evident lamina-
tion (as in the cartilage cells), and
even gives rise to certain structures (Fig. 11), which have the greatest
similarity to the sclerogenous cells of plants (bone-cells).

The nuclei and nucleoli also take part, to a certain extent, in the
growth of the cells. In the former, a general growth is easily demon-
strable in all growing cells ; in many, as in those of the smooth muscles,
of the epithelium of the vessels, of the formative cells of elastic tissue,
and others, there is also a partial growth, in consequence of which they
often assume the form of long slender rods. The nucleoli also not un-
frequently grow with their cells (nerve-cells, ova) ; but except when
dividing they never assume any but the globular form.

SchAvann has given an explanation of the growth, as well of the cell
as of the nucleus. He considers that the molecules of the cell-mem-
brane exert an attractive influence upon the fluid which surrounds them,
and deposits its newly-formed particles among themselves ; if the depo-
sition take place between molecules already present in the substance of
the membrane, the cell becomes distended ; if it take place only in the
direction of the radius of the cell, the membrane becomes thickened.

■B/,%:

'I c

Fig. 10. — Cartilage cells of man. Two cells witli thickened walls, from the cartilage of
the great cornu of the hyoid bone, containing a clear drop of fat beside their nucleus. Mag-
nified 350 diameters.

Fig. 11. — Six developing bone-cells from a rickety bone as yet sharply defined from the
interstitial substance: — «, simple bone-cells; 6, a compound one, answering to a parent cell
with two secondary cells; c, similar ones with three cells. Magnified 350 diameters.

* [This increased thickness of the cell-wall with age is well seen in all epithelial tissues
normal as well as pathological. — DaC]

CELLS. 61

The nucleus grows less than the cell, because as soon as the latter is
formed it no lonjrer comes into direct contact with the concentrated
cytoblastema. General growth takes place when the molecules of the
membranes all attract equally; partial growth, when this happens only
or especially at particular spots, where the apposition of new matter
takes place to a greater extent. With reference to the mode of forma-
tion of precipitates and of crystals, this theory appears to me to ex-
plain very well the phenomena of general growth, supposing that we
ascribe to the cell-membrane the faculty of readily taking up molecules
and applying them to its increase. Such, however, must be the case,
for the relations of the nuclei, which even when free, never grow very
considerably, and particularly never in one direction,'^ show that the
power of growth is not simply innate in every organic membrane, mani-
festing itself when sufficient formative material is offered, but requires
peculiar conditions which are realized only in the cell-membrane. To
account for partial growth, Schwann's view must be somewhat extended ;
for only those modes of growth in which the cells, during their increase
in certain directions, lose nothing of their original dimensions in others,
can be interpreted in Schwann's way, but not those in which the cells
become narrower as they elongate ; here we must assume that whilst
new substance is deposited in the one direction, in the other an absorption
takes place, for we can in nowise consider the process to be a mechani-
cal one. For the rest, it may be remarked, that partial growth may
depend upon the occurrence of assimilation, in particular cells, only in
certain directions, as in the thickened vegetable cells with pore-canals,
which is possibly connected with a one-sided direction of the currents in
the cell-contents.

§ 15. Processes in the Interior of the Cells. — In order to obtain a clear
conception of the processes which go on in the interior of cells, it would
before all things be necessary to have a more exact acquaintance with
the chemical composition of the cell-contents than we at present possess.
Only two kinds of cells, the ovum and the blood-globule, have been in-
vestigated with care [see Remarks) ; but these have such peculiar rela-
tions that they can hardly be regarded as types of cells in general.
However, we may from these analyses draw certain inferences with
regard to other cells, and bearing in mind what micro-chemical investi-
gation teaches us, it may be permissible to regard the cell-contents in
general, as a moderately concentrated solution of protein with alkaline
and earthy salts, and dissolved or suspended fatty particles. From
these common characters, presented without doubt by all cells, at least
in their young condition, many cells differ very widely, insomuch as
either some of these constituents greatly predominate or altogether new

* [Tins is surely incorrect. Tlie " nuclei" in the hair-pulp, in the tooth pulp, in connec-
tive tissue, in organic muscle, grow in one direction to a very considerable extent. — Tes].

62 GENERAL ANATOMY OF THE TISSUES.

substances occur. Thus, there exist cells with much protein, as the
nerve-cells ; and with much fat, as the fat-cells, the cells of the seba-
ceous follicles, of the milk-glands, &c. ; — then such as contain hsematin,
pigment, biliary, and urinary constituents, mucus (epithelium-cells), milk,
sugar, &c. &c.

The phenomena manifested by these, so variously constituted cell-
contents, during life, may be best enumerated as — absorption, assimila-
tion, and excretion. These depend principally upon chemical and
physical conditions, and are to a great extent capable of microscopic
investigation, since very frequently the changes of form in the cell and
the changes of its contents go hand in hand. Absorption is manifested
in all cells, but to far the greatest extent in those which at first have
little or no contents save the nucleus. In these, the primary cause of
the absorption is not to be sought in endosmose, but, as Schwann has
indicated, in this — that while the membranes grow by the attraction of
material from the surrounding fluid, by virtue of their porosity they
allow substances to penetrate into the interior. This filling, however,
does not take place by the cells admitting every kind of matter indis-
criminately, but they exhibit peculiar relations to the cytoblastema,
varying with the period and with the locality ; so that they take up one
constituent and reject another ; and the like occurs with the absorptive
powers of those cells which possess contents from their earliest exis-
tence.

That this is actually the case, is demonstrated, for instance, by the
fact, that in embryos, notwithstanding the identity of the formative
material in all cells, i. e. the plasma of the blood, some take up more of
one substance, some more of another ; and it is still more clearly evi-
denced by the fact, that the cell-contents of probably all cells are
chemically different from the cytoblastema out of which they are formed
and by which they are nourished, as has been clearly shown lately, in
the ova and blood-corpuscles, which for example contain far more po-
tassa than the blood. The reason of this phenomenon may be generally
stated to be, that the cell-membranes do not act as mere filters, but
allow one substance or another to permeate them, according to their
chemical composition, the constitution of the fluid which imbues them,
their condition of aggregation, and their thickness.

Endosmose must also be taken into account as a condition in the ab-
sorptive actions of cells, though hitherto it has been too freely appealed
to, and cells have been too often considered as vesicles provided with
merely indifferent porous membranes. That endosmose operates is not
to be denied, when it is observed how the addition of concentrated or
diluted solutions, causes cells to dilate or to collapse, yet it is not easy
to determine what influence such conditions have during life, nor what
results are produced by the combined operation of the cell-membranes

CELLS. 63

and their contents. From a few facts in vegetable physiology (growth
of plants in arsenical and cupreous solutions, without the admission of
these substances), it might be believed that the membranes exercised
the more important influence in determining absorption.

It is an important question whether the substances received by the
cells and composing them become modified by their vital processes.
Schwann has answered it in the afl5rmative, and has denominated meta-
bolic processes of cells, all those chemical metamorphoses Avhich go on in
them and in their separate parts ; and justly so, for the occurrence of
such chemical changes is not only very probable a priori, since in plants
all such metamorphoses (and these of the most various kinds) take place
in the cells, but may very easily be demonstrated by observation. These
changes affect, firstly, the cell-membrane, and secondly, the cell-contents.
As regards the former, this much is certain, that the membranes of most
cells not only become denser and more solid with age, but also that
they take on a diff'erent chemical constitution, though it is impossible in
particular cases to say on what the change depends. In the horny tissues,
the membranes of the young cells are easily soluble in alkalies and acids,
whilst subsequently they sometimes offer extreme resistance to their
action : the same takes place in a few of the higher elementary parts,
as the nervous tubules, the animal muscles, and the capillaries, in which
the sarcolemma, the sheath of the nerve fibre, the capillary membranes,
which are metamorphosed cell-membranes, react in a very different
manner from the original formative cells. In the cartilage cells also,
the membrane becomes more resistanfwith age, and in the course of
ossification not only thickens, but is for the most part changed into col-
lagenous tissue, which is subsequently impregnated with calcareous salts.
These examples, which might be multiplied, may suffice to demonstrate
the occurrence of a metamorphosis of the cell-membranes ; further inves-
tigations will be needed to show upon what it depends, whether, as it
would seem, the original animal cell-membrane actually alters in compo-
sition in course of time, or whether the change in the reaction depends
upon the addition of foreign substances, on the incrustation of the mem-
branes with salts, and so forth, such as botanists are inclined to assume
for the vegetable cell-membranes, or whether it depends upon secondary
deposits on the exterior of the original membranes.

The changes of the cell-contents are of two kinds, formative and re-
solvent. Both processes are easily followed in the embryos of different
animals, in which, in the first place, the primary formative cells, which
at the beginning are distended with the elements of the yelk, especially
with oil, acquire by degrees more fluid and homogeneous contents, the
yelk granules dissolving, sometimes from the cell-membrane towards the
nucleus, sometimes from within outwards ; and secondly, in cells thus
formed, the most various new formations take place, among which that

64 GENERAL ANATOMY OF THE TISSUES.

of hgcmatin, of difierent kinds of pigment, and of fat, are the most
obvious. But metamorphoses of the cell-contents are very common in
adult animals also, and are at the same time very important, since in
many places, on account of the great number of cells which are affected
in the same way at the same time, unexpectedly great results are pro-
duced, as one of the most important of which we may name the biliary
secretion, which is brought about, so to say, only by the activity of the
many millions of cells which form the liver. A pretty series of changes
may also be traced in the fat-cells, which, according to the deficiency or
superfluity of nutritive fluid, in the one case lose their proper contents,
and may even become cells containing mere serum, in others are filled
to bursting with drops of oil ; again, in the cells of the fat-secreting
glands, which at first contain but little fat, and finally become crammed
with it ; and also in the lymph-corpuscles, which develop the coloring
matter of the blood within themselves, and thus become blood-corpus-
cles.* The formation of mucus, again, must probably be assigned to
the epithelial cells of the mucous glands and mucous membranes ; that
of the so-called pepsin to the cells of the gastric glands ; and that of
semen to the spermatic cells. A multiplicity of confirmatory evidence
is afforded by comparative anatomy, and I will here only advert to the
development of the concretions of uric acid in the renal cells of the mol-
lusca, that of sepia in the cells of the ink bag of the Cephalopod, of
crystals and concretions of different kinds in the cells of the invertebrata,
and of certain pigments in those of the mollusca. Pathological anatomy
affords us the pigment formations, the metamorphoses of cells containing
blood-corpuscles, and the fatty deposits in cells of all kinds.

Manifold morphological phenomena go hand in hand with these
changes, such as the thickenings of the cell-membrane, which have been
already adverted to, with laminated depositions upon their inner surface,
and even with the formation of pore-canals ; as the precipitation in the
cell-contents of granules of different sorts, as of pigment, albumen,
casein (in the yelk, perhaps in the hepatic cells) ; and as the formation
of fat drops, of elementary vesicles, of concretions, crystals, and nuclei.
Even movements resembling the cyclosis of plants appear to occur in
the cells of the lower animals (seen by me in the cells of the arms of a
minute Medusa, a new u3^gmopsis from the Mediterranean, and of Poly-
clinum stellatum), and in Protozoa (currents in Loxodes bursaria, con-
tracted vesicles in different genera) ; while on the other hand, the Brownian
molecular movements, i. e. a more or less active tremulous motion
of granules without further change of place, which may be observed in
many cells under the microscope, most beautifully in the pigment cells
of the eye, are also, perhaps, hardly to be reckoned among vital pheno-
mena.

* [In the oviparous vertebrata — Tks.]

CELLS. 65

The nuclei also occasionally, though upon the uholc rarely, take part
in the changes of the cells. The commonest of these appearances is
their becoming clear, as a consequence of the liquefaction of the at first
more viscid contents, upon which circumstance it depends that in 3'oung
cells they are homogeneous, while in the larger they evidently appear to
be vesicles. A formation of granules in the nuclei is very rare (see
above) ; concretions, coloring matters, and crystals, are also not found
here in animals ; on the other hand, the development of the urticating
threads in certain animals and that of the spermatozoa, takes place in
nuclei.

In endeavoring to explain the metabolic processes of cells, we must
in all cases especially regard the cell-nucleus ; for just as it excites the
development of the cell, so is it the centre of the currents of the contents,
and of the deposits and solutions ; but it is not to be regarded as tire
sole agent, for, firstly, it does not appear why the cell-contents should
not, like the cytoblastema, become changed of themselves ; and, secondly,
the changes of the cell-membrane are, at all events, more independent,
and probably also have a certain influence upon the cell-contents, as
the depositions which take place upon it, and the solution of the solid
contents which often occurs in its neighborhood, demonstrate. To
assume with Schwann a special metabolic force is incorrect, for, in the
first place, the causes of the metabolic phenomena are certainly very
various ; and, secondly, there is every reason to reduce them to known
molecular forces. Thus, for instance, even the action of the nucleus*
may not unfittingly be compared with the so-called catalytic, or contact
action, inasmuch as it is hardly at all altered during the changes of the
cells, and consists of a nitrogenous substance, which like pepsin (which
is also nothing but cell-contents), very readily produces a chemical altera-
tion in other substances. The relation of the cell-membrane to absorp-
tion also, may even now be referred to the general laws of imbibition
and difi"usion.

I here give two analyses as examples of the chemical composition of
the cell-contents. The yelk of the hen's egg contains: water, 48*55;
casein, 13-93; albumen, mixed with casein, 0-892; albumen, 2-841;
membranes of the yelk vesicles, 0-459 ; fats, 81"146 (30-46 according
to Gobley), consisting of olein and margarin; 21*304; cholesterine,
0*438 ; lecithin (containing phosphoric acid), 8*426 ; and cerebrin ; salts,
1*523; a hundred parts of the ash yielded, potass, 8-60-8-93 ; chloride
of sodium, 9*12 ; phosphatic salts, 06*7-67-8 ; lime, 12-21 ; magnesia,
2-07; oxide of iron, 1-45; silica, 0-055. The blood-corpuscles contain:

* [This "adton of nucleus" is a wholly hypothetical though a very general assumption
It is important to bear in mind, on the contrary, that there is every reason to believe that
the molecular and chemical changes of the cell-membrane and the nucleus are independent
of one another. — Tks.]

5

66 GENERAL ANATOMY OF THE TISSUES.

water, 68-88 ; hsematin, 1-67 ; globulin and membranes, 28-22 ; fat, 0'23 ;
extractive matters, 0-26; mineral substances (Avithout iron), 0-81; of
which chlorine, 0-16 ; sulphuric acid, 0*006 ; phosphoric acid, 0-4 ;
potassium, 0*33; sodium, 0-10; oxygen, 0*06; phosphate of lime, 0-01 ;
phosphate of magnesia, 0-007. To these must also be added, free oxygen
and carbonic acid, which likewise occur in the yelk.

We have here instances of cells containing much protein, and espe-
cially fat, and may consider them to be fair examples of this kind of cell.
The comparison of the contents of these cells with the plasma of the
blood, out of which those of the one kind are formed, while the others
live in it, is very interesting. In the blood-globules there is a consider-
able preponderance of solid constituents, since the blood-plasma only
contains about 10 per cent, of solids, which is evidence that there are
cells whose contents do not attain an equilibrium with the cytoblastema
by which they are supported. With regard to particular substances,
the blood-corpuscles contain more fat ; hajmatin, which is not found in
the plasma; more potassa and phosphoric acid; less chlorine, extractive
matters, soda, and earths. The yelk of the hen's egg contains also con-
siderably more solid constituents than the blood, which however is here
less surprising than in the blood-corpuscles which swim in the blood-
plasma. It is interesting, that the relative proportions of the different
substances are quite different in this case from the other. We have,
namely, an exceedingly large quantity of fat, more protein and salts ;
and among the latter, again, more potassa, and also more earthy salts.

Even these facts indicate a considerable independence of action in
the cells ; but those which have been lately made known by Ludwig,
tend still more forcibly in the same direction ; for the influence of the
nerves upon the salivary glands discovered by this observer must, I
believe, be so interpreted, that it is not only the meynhrance 2Jroprix
of the vesicles of the salivary glands, which are so altered in their mole-
cular relations by the nervous influence that they directly exercise an
energetic attraction upon the blood-plasma which surrounds them, but
the epithelial cells which line them also. If this really be the case, we
have an insight into an altogether new condition regulating the absorp-
tive powers of cells, and at the same time cell-life is brought into such
connection with the activity of the nervous system, that it no longer
appears out of reason to speak of the positive functions of the latter.
Such relations are in nowise opposed to analogy, since in the contrac-
tile elements we have already a connection between nervous activity
and the modification of cell-contents, which perhaps upon farther inves-
tigation may come under the same general category as the foregoing.
In any case, these considerations lead anew to an exact investigation of
the molecular forces of cells, especially of those electrical phenomena
which will certainly be found in them.

CELLS. 67

Very recently Bonders (Ncderlandsch. Lancet.) has justly brought
forward a character which until now had received no attention, viz., the
elasticity of the cell-membranes and the pressure consequently exercised
upon the cell-contents. It is an ascertained fact that the cell-membranes
are elastic ; and it thence naturally follows that, according to the greater
or less amount of the contents of the cells, so will these suffer a greater
or less pressure. This, however, reacts again upon the absorptive and
excretive processes, so that under a more considerable pressure the
latter, under a less, the former prevails, and in certain circumstances
it may conduce to the maintaining of a regular interchange of sub-
stances, Donders believes, that the greater density of the cell-contents
may be derived from their always being under greater pressure than
the cytoblastema.

§ 16. Excretive processes. — The vegetative functions of animal cells
are not limited to mere absorption and metamorphosis, but substances
are excreted as a result of their operation. This may take place in two
ways.

1. The cells give out unaltered, the substances ivhich they have re-
ceived from without. — This occurs in the epithelium cells of those glands
which, like the kidneys, lachrymal glands, lungs, &c., simply permit of
the discharge of substances from the blood, also in those cells which
line the serous membranes, and probably many others.

2. The cells excrete substances which they have prepared tvithin them-
selves.— Thus the blood-cells give up their hcematin in dilute blood-
plasma ; the fat-cells their fat in emaciated persons ; the hepatic cells,
bile ; those of the gastric glands, gastric juice ; those of the mucous
glands and membranes, mucus.

The occurrence of these excretions, of which, in fact, there are assu-
redly very many with which we are still unacquainted, may in some^
cases be explained by exosmose ; in others, however, as in the secretions
of the glands, this cannot take place. Here the exit of the contents is
a consequence of the pressure to which they are exposed, which pres-
sure is to be referred upon the one hand to the force of the blood, on
the other to an attractive force exercised by the cells themselves in ab-
sorbing the substances, and to the elasticity of the cell-membranes.

The excreted matters in general no longer continue in the organism,
but are completely removed as in the glands ; in a few localities they
remain, taking a solid form, as extra-cellular substance, outside the cells,
and form the genuine membrance proprice of the glands {e. g. of the renal
canals), the proper envelop of the chorda dorsalis, and probably also the
so-called vitreous membranes (capsule of the lens, membrana Demoursii).
An intercellular substance is rare in animals, for the matrix of the
cartilages and bones, which for the most part is not excreted by the

68 GENERAL ANATOMY OF THE TISSUES.

cells, but is deposited from the blood-plasma or is even formed out of
cells, does not come under this head. It may be said to be present in
a smaller quantity and more fluid, however, not only in the cellular
tissues, but also in the higher structures, among which there everywhere
exists a small quantity of connecting substance. Intercellular spaces
developed by the excretions of cells between one another, have not
been demonstrated with certainty in animals, yet it is probable that
most glandular cavities and those of the heart and of the great vessels
are of this nature, since they appear to rise by the excretion of fluid in
the interior of originally compact masses of cells.

My view, that the genuine, membrance prop^nce and the vitreous
membranes are formed as excretions, is founded particularly upon the
examination of the chorda dorsalis and of the renal canals, in which it
may be readily shown that the structureless membranes are secondary
formations, arise in intimate union with the cells of this part, and from
the very first appear perfectly homogeneous. The supposition of many
authors, especially of Reichert, that these membranes belong to the
homogeneous connective tissue, is readily refuted by chemical examina-
tion, since they yield no gelatine, but consist of a substance which most
closely approximates to the sarcolemma and elastic tissue (comp. Men-
sonides in 'Nederl. Lancet.' d. iv. GOi, and Bonders, ibid. August, 1851,
p. 73). To what extent homogeneous membranes formed by excretions
from cells, occur among animals is not yet determined, but the homoge-
neous chitin-investments of the intestine, and of the external surface in
the Articulata, appear to be of this nature.

§ 17. Contractility of the Cells. — Among the vital phenomena of cells
must be enumerated those contractions which are manifested by cell-
membranes and also by cell-contents. Contractile cell-membranes are
possessed by many if not all Protozoa ; and among subordinate cells, by
the yelk-cells of the Pladarise, the heart-cells of many embryos {Alytes,
Sepia, Limax), the cells of the tail of embryo Botrylli. The cilia also,
as processes of the cell-membrane, may be mentioned here. Contractile
cell-contents are found in the fibre-cells of the smooth muscles, in the
stellate cells of the skin of the embryo of Limax, and in the animal
muscular fibres ; which last, as they consist of a number of united cells,
may be here enumerated. Here also I place the contractile phenomena
exhibited by the contents of the Protozoa (contractile vesicles) and by
the Rhizopoda.*

* [To this list of contractile cells must be added tlie colorless corpuscle of the blood of
man, the Frog, and the Skate, and probably that of other Vertebrata (Wharton Jones, /. c),
the cells which lie in the meshes of the areolar tissue of the disc of the Medusce {Cyaticpa)
and the young epithelium cells (mucus-corpuscles) of the mucous membranes, in which
most distinct protean movements, like those of the colorless corpuscle, may be observed.

' CELLS. 69

Donders has recently promulgated the view that it is only the cell-
contents which are contractile, not the cell-membranes. xVlthough it
must be granted, that it is difficult, in the cases in question, to decide
what part of the cell contracts, yet it seems very hazardous to endeavor
to refer the movements of the cilia in plants and animals, in free and
combined cells, to indemonstrable contents in these cilia communicating
with the cell. In the cells of the Planarije and in the Protozoa, any
one who has actually seen the movements will hardly refer them to
anything but the cell-membranes. In the transversely striated muscular
fibres on the other hand, it is evidently the fibrillaa or the contents
which are contractile, and the sarcolemma, as an elastic yielding body,
only moves with them : the same appears to hold good with the muscular
fibre-cells, in which a special membrane cannot bo demonstrated.

§ 18. Metamorphoses of Cells — Kinds of Cells. — The destination of
the cells which are found at an early period in the organism is very
various. A very considerable portion of them remain but for a short
time in their primitive condition, and subsequently coalesce with others
to form the higher elementary parts. Another portion, while they enter
into no such combinations, change more or less their previous nature ;
as the horny plates of the epidermis and nails. Many cells, lastly,
never become metamorphosed at all, but remain as cells, until sooner
or later, often not before the decay of the organism, they disappear
accidentally or typically, as the epithelia, glandular parenchymata, &c.

The permanent cells may be most conveniently arranged under the
following heads : —

1. True cells, which have in no essential respect altered their cellular
nature. These occur in the epidermis [stratum Malpigldi) and the
epithelia; in the blood, chyle, lymph; in the glandular secretions, in
the fatty tissue, in the gray nervous substance, the red bone-medulla ; in
the glands (liver, spleen, suprarenal capsules, closed glandular follicles),
and the cartilages. According to their form, these cells may be divided
into round, discoid, cylindrical, conical with cilia, and stellate; accord-
ing to their contents, they may be distinguished as containing fat, protein
or serum, hsematin, bilin, pepsin, mucus, or pigment ; and as to their
modes of occurrence, some are either isolated in fluids or in solid tis-
sues, others are united into a simple cellular parenchyma, while others
are conjoined by an intercellular substance of one kind or another.

It is certainly the membrane which contracts in these cases, for it pushes out processes
which are only subsequently filled by the granular contents.

In the lower plants (Alga) the occurrence of contractile processes in the shape of cilia is
universal, and the contractility of the cell substance in the zoospores of Volvox is evinced
by the occurrence of a rhythmically contracting space in them. [See Busk on Volvox globator,
'' Quarterly Journ. of Micr. Sc," No. 2, 1853.)— Tks.]

70 GENERAL ANATOMY OF THE TISSUES.

2. 3Ieta7norpIiosed cells, which have more or less altered their original
structure. To these belong : —

a. The lior7iy scales : flattened, polygonal, or fusiform : their membrane
being fused into one mass with the contents. In the epidermis, the
laminated pavement epithelium, the hairs and nails.

b. The contractile fih-e cells: fusiform, slightly flattened, considerably
elongated cells, whose membrane, together with its soft solid contents is
changed into a contractile substance. In the smooth muscles,

c. The tubules of the lens : very much elongated cells, with viscid,
albuminous contents.

d. Thejyrisjus of the enamel: greatly elongated, prismatic, and strongly
calcified cells.

e. The bone cells : thickened cells with pore canals which have coa-
lesced with the homogeneous matrix of the bones and anastomose by
means of excavations in it.

/. The transversely striated muscular cells : large polygonal cells,
whose contents have become metamorphosed into a transversely striated
tissue, such as is found in the transversely striated muscular fibre. In
the endocardium of ruminants.

B. HIGHER ELEMENTARY PARTS.

§ 19. The higher elementary parts correspond, genetically, to a whole
series of the simple ones, and it is the cells only, so far as we know,
which possess the faculty of producing them. The manner in which this
takes place varies. Either the cells while they coalesce retain their cellu-
lar nature, and to a certain extent their independence, in which case we
have, according as they are fusiform or stellate cells, cell-fibres or cell-
reticulations; or the cells in uniting totally surrender their indepen-
dence, in which case they form, if they are arranged in lines, elongated
elementary parts ; or are united by many offsets, — networks ; or are
fused together upon all sides, — membranes. The two former of these
again, according to the kind of modification undergone by the contents
of the united cells, appear either a.s fibres, bundles o? fibrillar and tubes,
or as fibre-networks and tubular plexuses. Since all these elementary
parts will be spoken of at length afterwards, among the tissues, we may
here simply enumerate them as follows. They are : —

a. The cell-fibres and cell-networks. — To these belong a part of the
nuclear fibres of authors, the cartilage cells of certain Plagiostome
fishes (see Leydig, "Beitrage zur mikr. Anat. u. Entwickel. d. Rochen
u. Haie.," Leipzig, 1852), the pigment cells of the lamina fusca, pia
mater, and of Batrachian larvae, the networks of the nerve cells in the
brain of the Torpedo (R. Wagner), the fatty substance of the Lepidoptera
(H. Meyer, " Zeitschrift fiir wiss. Zool.," Bd. i. st. 178).

CELLS. 71

I). The elastic fibres, fibrous networks, and fibres.

c. The fibres of connective [areolar] tissue, the nctivorks of connective
tissue (reticulated connective tissue), and the membranes composed of
connective tissue (homogeneous connective tissue).

d. The transversely striated muscular fibres and muscular fibre net-
ivorks.

e. The nerve-fibres and nerve-fibre networks.

f. The capillary plexuses of the blood-vessels and lymphatics.

g. The trachese and tracheal plexuses of the invertebrata.

All these higher elementary parts possess essentially the same proper-
ties as cells, especially growth in length and thickness, absorption,
metamorphoses, and excretion, an^ to some extent contractility ; to-
gether with other functions which may perhaps also be demonstrated in
cells. Their growth is manifested by the fact, that all, without excep-
tion, are much shorter and narrower immediately after their formation
than subsequently ; their absorptive powers, by the dependence of their
functions upon the circulation, by the phenomena of resorption in the
lymphatics and blood-vascular capillaries, and by the above-mentioned
growth, which can only take place by the reception of substances into
their interior. A metamorphic and an excretive power must be assumed
to exist in them ; it is testified by the well-known peculiar products of
decomposition of the muscles, and also by the continual transmission
of blood-plasma through the walls of the capillaries. The muscular
fibrils possess contractility, and the processes in the nerve-fibres, though
very peculiar, and at present not to be defined more nearly, may
nevertheless in some respects be compared to the functions of the nerve-
cells.

With regard to the trachese, which are placed here only for complete-
ness' sake, I long since found that their terminations are formed by the
coalescence of stellate cells into tubes, in which the original cell-contents
either remain or become developed into a spiral fibre ; and I published
a concise notice of the fact in the year 1849 (" Zeitschrift fiir wiss.
Zool.," Bd. i. p. 215, Anmerkung), a view which has since been con-
firmed by H. Meyer (Ibid. Bd. i.), and more recently by Leydig (Ibid.
Bd. lii. Heft 4.)

Literature of the Elementary Parts. — In addition to Schwann's work
quoted above, may be named: Kolliker, "die Lehre von der thierischen
Zelle," in Schleiden u. Niigeli's " Zeitschrift fiir wiss. Botanik.," Heft
ii. 1845; Remak, " U eber extracellulare Entstehung thierischen Zellen
und die Vermehrung derselben durch Theilung u. Uber Entstehung des
Bindegewebes u. d. Knorpel," in Mailer's " Archiv," 1852, i. (Xo longer
available. Bcmak assumes quite confidently, what I only indicated, that
animal cells have a primordial utricle, without giving any demonstration of

72 GENERAL ANATOMY OF THE TISSUES.

the fact; he ascribes the multiplication of cells by division to be widely
extended through embryonic tissues ; finds (what others will not
easily succeed in doing) two membranes in the later cleavage-masses,
and wrongly, denies altogether the occurrence of free cell-development) ;
also the treatise of Donders, cited below under the head of elastic tissue ;
and the embryological monographs of Reichert, Bischoff, Vogt, Remak,
and myself. Inasmuch also, as the doctrine of the vegetable cell is impor-
tant for zoologists, I call attention to Schleiden's first treatise (" Ab-
handlung liber die Bildung d. Pflanzenzelle," Mull. "Arch.," 1837); to
his " Elements of Botany ;" to Nageli's Essay " Ueber die Pflanzenzelle,"
in the "Zeitschrift flir wissenschaftlich. Botanik," Heft ii. ; and to
Mohl's monograph upon this subject, in Wagner's " Handworterbuch"
(" Mohl on the Vegetable Cell," translated by A. Henfrey, London,
1852). [To these should be added the important monographs of
Schleiden, " Beitriige zur Phytogenesis," in Muller's Archiv, p. 137;
of Rosenthal, " De formatione granulosa in nervis aliisque partibus
organismi animalis," Vratislavire, 1837 ; of Kramer "Bemerkungen liber
das Zellenleben in der Entwickelung des Froscheies" in Mliller's Archiv,
1848, and the more recent works of Dr. Schacht, on the " Vegetable
Cell" (Die "Pflanzenzelle") Berlin, 1852 ; and of Alex. Brown on
"Rejuvenescence" (Verjllngung), Leipzig, 1851. — DaC]

III. OF THE TISSUES, ORGANS, AND SYSTEMS.

§ 20. The elementary parts of both the simpler and the higher kinds,
are not dispersed irregularly in the body, but are united according to
determinate laws, into the so-called tissues and organs. Under the
first denomination comes every constant arrangement of the elementary
parts always recurring in similar modes in the same parts ; under that
of an organ, on the other hand, a certain sum of elementary parts of a
definite form and function. When several or many organs of a similar
or diff"erent kind are united into a higher unity, this is called a system..

The tissues are of diff"erent kinds, according as structural elements of
one kind only occur in them, or as various elements and even organs
take part in their formation. We can thence distinguish simple and
complex tissues, which, however, cannot be sharply separated from one
another, and which may be most fittingly arranged in the following
series : —

{a.) Simple tissues.

1. Epidermic tissue.

2. Cartilaginous tissue.

3. Elastic tissue.

4. Connective tissue.*

* [Fibrous tissue, see note, p. 47. — Ed.]

TISSUES. 73

{b.) Complex tissues.

5. Osseous tissue.

6. Smooth muscular tissue.

7. Transversely striated muscular tissue.

8. Nervous tissue.

9. The tissue of the blood-vascular crlands.
10. The tissue of the true glands.

The organs may be divided like the tissues, into simple and complex.

To the simple belong: —

[a.) Ilorny tissue, as the epidermis, the epithelia, hairs, nails, and
the lens, which consist solely and wholly of epithelial cells of one kind
or another.

(5.) The true cartilages and the elastic cartilages, which in their inte-
rior, with few exceptions, consist only of cartilaginous tissue, though
externally they possess a vascular and nervous coat, the perichondrium.

(c.) The elastic ligaments, consisting of elastic fibres, with some con-
nective tissue, and containing only at the surface a few vessels and
nerves.

{d.) The tendons, ligaments, true fibrous membranes, and fihro-carti-
lages, containing a preponderance of connective tissue, intermixed with
fine elastic fibres, and sometimes cartilage cells in small quantities, and
almost entirely devoid of vessels and nerves.

Complex organs are : —

(e.) The smooth muscles and muscular membranes ; and —

(/.) The transversely striated muscles and muscular membranes, both
of which, besides their contractile elements, are abundantly intermingled
with connective tissue, nerves, and blood-vessels.

(g.) The nerves, ganglia, and higher central organs of the nervous
system, contain besides gray and white nervous substance, many blood-
vessels, and special fibrous investments.

{h.) The vessels are composed of connective and elastic tissue, muscles
and epithelium in various proportions, and are provided with vessels and
nerves, only in their outermost layers.

{i.) The bones and teeth, which, together with their characteristic tis-
sues, have peculiar soft structures, containing many vessels and nerves,
and the former medulla also.

{k.) The blood-vascular glands, composed of a peculiar glandular ele-
ment, in the form of closed follicles of difi'erent kinds, and many blood-
vessels ; with nerves also, and with abundant but generally non-con-
tractile fibrous tissue.

{I.) The true glands ; glandular follicles, vesicles or tubes with many
vessels, nerves, and investing fibrous tissue.

[in.) The vascular membranes, as the skin, the mucous, serous, and
proper vascular membranes, which in a matrix composed of connective

74 GENERAL ANATOMY OF THE TISSUES.

and elastic tissue, generally contain very numerous blood-vessels and
lymphatics, in part also simple glands and nerves, and are invested by
special epithelial layers.

{n.) The separate organs of the tractus intestinaUs, as the tongue,
the oral cavity, the pharynx, the oesophagus, the stomach, and so forth,
into the constitution of which, mucous, muscular, and serous membranes,
grouped in various ways, enter.

(o.) The higher organs of sense, into which almost all the tissues and
many more simple organs enter.

Lastly, the organs enter into the formation of peculiar systems, of
which we may distinguish the following : —

1. The external cutaneous syste7n, consisting of the corium, the epi-
dermis, the horny tissues, and the larger (lacteal gland) and smaller
glands of the skin.

2. TJic osseous system, consisting of the bones, cartilages, ligaments,
and articular capsules.

3. TJte muscular system, consisting of the muscles of the trunk and
of the extremities, the tendons, fascioe, tendinous ligaments, and hursce
mucosce.

4. The nervous system, composed of the larger and smaller central
organs, the nerves and the higher organs of sense.

5. Tlie vascular system, consisting of the heart, the blood and lymph-
vessels, and the lymphatic glands.

6. The intestinal system, composed of the intestinal canal, the organs
of respiration, with the thymus and thyroid, the salivary glands, the
liver, and the spleen.

7. The urinal and sexual systems.

As the separate organs and systems are particularly considered in the
special part of this work, it is not necessary to speak at greater length
of them here, and it is only requisite to define the tissues somewhat
more closely — taking occasion at the same time to refer to some gene-
ralities concerninfj the organs.

§21. Epidermic Tissue. — The morphological character of the epi-
dermis is, that it is wholly constituted by independent cells intimately
united together without any visible matrix, which are generally nucleated
and in part are true vesicles, while in part they are metamorphosed into
solid scales. In its chemical characters this tissue is but little known,
though this much has been made out, that its cells contain chiefly an
albuminous substance, in part also mucous ; and at first all possess easily
soluble protein membranes, which however, subsequently, become par-
tially changed into a substance which more or less resists acids and
alkalies, — the so-called horn. The physiological import of the epidermic
tissue is to serve as a defensive covering to those parts of the organism

TISSUES, ORGANS, AND SYSTEMS. 75

which abound in vessels and nerves, and by the activity of its elements
to take part in secretion and absorption. All epidermic tissues are non-
vascular, and support themselves from a plasma which is yielded by the
deeper-seated vessels. They are very easily regenerated when their
superficial portions are removed, and in this case they grow chiefly by
the development of new elements in the deeper layers ; even when wholly
lost they are readily reproduced.

The epidermic tissue takes the following forms : —

1. Corneous tissue. — This always consists of compact masses of cells,
which are soft in the neighborhood of their vascular basis, but at a
greater distance become more or less solid and hard (corneous), and fre-
quently lose their originally vesicular constitution and nucleus, and
become the so-called horny scales. The following organs are formed by
this tissue : —

a. The Epidermis ; which invests the exterior of the body, and is
continuous at the great apertures of the inter- Fi"-.i2.

nal cavities with the epithelium. It consists of
two tolerably distinct layers; the mucous layer ^,
{rcte mucosu7n), with soft, rounded polygonal , 'q]
cells, which, under certain circumstances, con- K^
tain coloring matter. This layer applies itself
accurately to all the inequalities of the corium
(which nourishes the epidermis), and externally
passes into the polygonal scales of the horny
layer.

b. The Nails. — These may be regarded as a modification of the epi-
dermis, whose horny layer has attained a still greater density ; and,
with its rete mucosum, lies upon a special depressed surface of the cutis,
— the bed of the nail ; and is partly sunk in a peculiar cleft, — the fold
of the nail.

e. The Eairs. — Filiform epidermic* structures, seated upon a vas-
cular papilla, in a peculiar sac, the hair sac, which is a process of the
corium, and is lined by a continuation of the epidermis. The structural
elements in the region of the papilla are soft and vesicular ; the more
distant are metamorphosed into three kinds of cells — plates, flat fibres,
and more or less rounded irregular cells.

2. Epithelium. — Soft nucleated cells, nowhere densely corneous ;
rounded, polygonal, fusiform, cylindrical or conical in shape ; sometimes
possessing cilia, sometimes not, and occurring in one or many layers.
Hence we have the following forms : —

Fig. 1-2. — Platesof the horny layer in man, magnified 350 diameters. 1, without addition,
viewed from the surface, one, with a nucleus : 2, from the side.

* [It is to lie questioned if the hairs are truly epidermic structures, vide infra, § Hair. — Trs.]

76

GENERAL ANATOMY OF THE TISSUES.

a. Epithelium in a single stratum.

(].) With rounded, polygonal (?e??s (pavement-epithelium in a single
layer).

This exists as an investment of the true serous membranes, of most
synovial membranes, of the cerebral ventricles {ependyma) of the mem-
brane of Demours, of the back of the iris, and of the inner surface of the
choroid (pigment layer), of the capsule of the lens and of the retina, of the
internal ear, of the endocardium, of the veins, of many glandular vesicles
and canals (racemose glands, kidneys, sudoriparous and ceruminous
glands, lungs), and of the ductus interlohulares of the liver.

Fie. 13.

Fig. 14.

M i

(2.) With f}isiform., superficially-united cells (fusiform epithelium).

Epithelium of the arteries, and of many veins.

(3.) With cylindrical cells (cylinder-epithelium).

In the intestine from the cardia to the anus, in Lieberklihn's glands,
in the excretory ducts of the gastric glands, as well as of all the other
glands which open into the intestine ; also of the lacteal and lachrymal
glands ; in the male urethra, the vas deferens, the vesicular seminales, the
excretory ducts of the prostate, of Cowper's, Bartholini's, and the ute-

rine glands

Fig. 15.

Fisr. 16.

(4.) With cylindrical or conical ciliated cells (simple, ciliated cylinder-
epithelium).

Epithelium of the finest bronchioe, of the nasal cavities, of the inner
surface of the memhrana tympani, of the Eustachian tube, of the uterus.

Fig. 13. — Epidermis of a two months' human embryo, still soft like epithelium; mag-
nified 350 diam.

Fig. 14. — Epithelial cells of the vessels, the longer ones from the arteries, the shorter
from the veins.

Fig? 15. — Ejiithelium of the intestinal villi of the rabbit; magnified 300 diam.

Fig. 1G. — Ciliated cells from the finer bronchice; magnified 359 diam.

TISSUES, ORGANS, AND SYSTEMS.

77

from the middle of the cervix, up the Fallopian tubes, as far as the outer
surface of the fmlmce.

(5.) With rounded ciliated cells (simple ciliated pavement-epithelium).

Epithelium of the cerebral cavities of embryos.

h. UpitJielium in many layers : —

(1.) With cylindrical or rounded cells belozv, rounded, polygonal, more
or less flattened cells above (laminated pavement-epithelium).

Epithelium of the oral cavity, of the lower half of the pharynx, of
the oesophagus, of the lachrymal canals, of the conjunctiva, of the tym-
panic cavity, of the vagina and female urethra, of the urinary bladder,
of the ureters and pelves of the kidneys, and of certain synovial mem-
branes.

(2.) With rounded cells beloiv, more elongated ones in the middle, and
ciliated conical ones above (laminated ciliary epithelium).

Epithelium of the larynx, trachea, and larger bronchire ; of the nasal

ii

cavity, with the exception of the regie
olfactoria ; of the lachrymal sac and
duct; of the upper half of the pharynx.
Among the epidermic tissues, we
may also enumerate the crystalline lens and the enamel.* The former
consists of long tubular cells filled with albumen, which, as the study of
development teaches, are formed by the metamorphosis of a part of the
epidermis. The latter contains prismatic, densely-ossified long fibres,
■which, in all probability, are also nothing more than excessively elon-
gated epithelial cells of the enamel organ of the embryonic tooth sac.

The epidermic tissue is found through almost the -whole animal king-
dom, and as regards its elements, it exhibits no very considerable devia-

FiG. 17. — A simple papilla with manifold vessels and epithelium, from the gums of a
child ; magnified 250 diam.

Fig. 18. — Ciliated epithelium from the trachea of a man; magnified 300 diam.; a. outer-
most part of the elastic longitudinal fibres ; 6, homogeneous outermost layer of the mucous
membranes; c, deepest round cells ; rf, median long cells; c, outermost ciliated cells.

* [I'ide infra, note § on the Teeth.]

78 GENERAL ANATOMY OF THE TISSUES.

tions in animals. One of its kinds, the liorny tissue, appears to occur
more generally, and to some extent in peculiar forms. To it belong (a),
among structures which appertain to the skin : claws, hoofs, horns, spines,
plates, and discs, bristles, feathers, and penis-spines, (i), among appen-
dages of the mucous membranes : the horny sheaths of the beaks of
birds, of Chelonia, of the Siren and Ornitliorhynchus ; the horny teeth
of the cyclostome fishes ; of the Ornitliorhynchus, of the gill rays of
fishes, and of Batrachian larvae; the whalebone, the spines and plates
of the tongue of Birds, Mammalia, and some Amphibia; the spines of
the oesophagus of Chelonia; the jaws of Cephalopoda and other inver-
tebrata ; the gastric teeth of many mollusks ; the horny plates of the
bird's stomach. In all these structures, but often only by the aid of
caustic alkalies, horny plates of one kind or another, as in the corneous
structures of man, are discoverable. On the other hand, the hard tis-
sues of the Articulata differ not only morphologically, but also chemically
from them, consisting as they do of a peculiar substance, chitin, and
exhibiting no cellular structure.

[The epidermic tissue is a frequent constituent of pathological for-
mations. It is met with in skin and mucous membrane, forming epi-
dermic hypertrophies, as corns and warts ; also in the so-called epidermic
or epithelial tumors, and as a covering on the surfaces of adhesions.
The variety of the epidermic tissue generally observed in these forma-
tions is the pavement-epithelium, with cells slightly modified by mutual
pressure, but not differing otherwise from normal pavement-epithelium.
Cylindrical and ciliated epithelium occur but rarely as abnormal pro-
ducts. Chemically, the epithelium of pathological tissues presents the
same reactions as that of normal tissues. — DaC]

Literature. — Purkinje et Valentin, " De phoenomeno generali et fuii-
damentali motus vibratorii continui," Vratisl. 1835 (Discovery of ciliary
movement in the higher animals); Henle, "Symbols ad anatom. vill.
int.," Berol. 1837 ; " On the distribution of the epithelium in the human
body," Berlin, 1838 ; and upon the development of mucus and pus, and
their relation to the epidermis (first exact description of the different
epidermic cells) ; Valentin, art. Ciliary Motion, in Wagner's " Hand-
Avorterbuch ;" Jiische, "De telis epithelialibus in specie et de iis vasorum
in genere," Dorp. 1847. [Pathologically, the epidermic tissue'is con-
sidered by Mayer ; " These sur les tumours epidermiques," Paris, 1846 ;
by Bennett, " On Cancerous and Cancroid Growths," Edinb., 1849 ;
by Lebert, in his Monograph, " Du Cancer et du Cancroide de la Peau,"
Paris, 1851 ; by Virchow, Wurzb. Verhandl., 1850, and in the recent
works of Paget, "Surgical Pathology," London, 1853, and of Wedl,
" Grundzuge der Pathologischen Histologie," Wien, 1854. — DaC]

§ 22. Cartilage. — Cartilage consists of a solid, but elastic, bluish, milk-
white or yellowish substance, which presents two morphological condi-

TISSUES, ORGANS, AND SYSTExMS. 79

tions ; appearing, firstly, as a simple 'parencltyma composed of cells ; and
secondly, as a cellular tissue, with an intermediate substance or matrix
between the elements. The cartilage-cells present little peculiarity in re-
spect of form ; they are generally round or elongated, frequently flat-
tened or fusiform, very rarely stellate (in Cuttle-fishes and Sharks,
and in enchondroma). Their membrane is ordinarily thick, frequently
invested by concentric laminre ; the contents are clear and more fluid,
with a single nucleus, and, though not constantly, with one or many fat
globules. The interstitial substance is either homogeneous or finely
granulated or fibrous, even with clear separable fibres. The chemical
characters of cartilage are in some respects but little known. It" is
ascertained, however, that the cells and the intermediate substance are
composed of diff'erent substances. The membranes of the cartilage cells,
in fact, are not dissolved by boiling, and offer a lengthened resistance to
alkalies and acids, peculiarities which distinguish them from the sub-
stances which yield gelatine, but approximate them to elastic tissue.
The contents of the cells coagulate in water and dilute acids, and are
readily dissolved by alkalies. The interstitial substance is, in most c^x-
tWag^es, chondrin, and only in the reticulated cartilages is it a substance
closely allied to that of the elastic tissue. Consequently the cartilages,
which consist only of cartilage cells, yield no gelatine upon boiling, and
its occurrence is no essential character of cartilage. Physiologically,
the solidity and elasticity of the cartilages are particularly to be noted,
as by these properties it is fitted for its various uses. In growing carti-
lages the change of material is very energetic; they constantly contain,
in certain localities, numerous bloodvessels in peculiar canals ; and, as I
have demonstrated in the nasal cartilage of the calf, even nerves. Their
growth takes place, firstly, by endogenous multiplication of cells, traces
of which are always clearly to be observed in perfect cartilages ; and
secondly, by the deposition between the cells, which originally exist
alone in all cartilages, of an interstitial substance from the blood-plasma,
which, according to Schwann, at first yields no chondrin even in the
true cartilages, and subsequently gradually increases in quantity. In
perfect cartilages the nutrition is by no means energetic ; and it has,
apart from the vessels of the perichondrium which invests many carti-
lages, and those of the neighboring bone, no particular agent, except in
the cartilages (septum of the nose) of a few mammalia, and in the pla-
giostome fishes, in some of which last, according to Leydig, even in old
individuals, vascular canals exist [Raja), in others anastomosing, fusi-
form, or stellate corpuscles (Sharks). With age, the intermediate sub-
stance of certain true cartilages readily becomes fibrous, and very similar
in its chemical characters to that of the reticulated cartilage, which de-
monstrates that these two kinds of cartilage are not widely separated ;
the true cartilages also not uncommonly ossify, vessels, cartilage, and

80

GENEUAL ANATOMY OF THE TISSUES.

medulla being formed in them at the same time. Cartilage possesses no
power of regeneration, nor do wounds in cartilage unite by cartilage ;
on the other hand, an adventitious development of cartilage is not un-
common.

The different cartilages are : —

a. Cartilage without interstitial substance, or parenchymatous carti-
lage. To this belong the chorda dorsalis of the embryo and of many
adult fish ; many foetal cartilages ; the cartilages of the gill laminse of
fishes in part ; and those of the external ear of many mammalia.

h. Cartilage with interstitial substance.

1. With a more homogeneous, chondro-yielding substance : true carti-
lage, hyaline cartilage : it is found in the larger cartilages of the respi-
ratory organs, those of the articulations, of the ribs, and of the nose ;
also in all symphyses and synchondroses immediately in contact with
the bones ; in the talus ossis cuboidci, and in the so-called ossifying carti-
lages of the foetus.

2. With a fibrous interstitial substance, yielding no chondrin, or but
very little: reticulated cartilage, yellow cartilage, fibro-cartilage in

Fig. 19.

Tisr. 20.

part ; epiglottis, cartilagines Santoriniance, Wrisbergiance, cartilage
of the ear and of the Eustachian tube ; ligamenta intervertebralia in
part.

In the Invertebrata many tissues of a similar consistence to cartilage
are found, but true cartilage has hitherto been discovered only in the
Cuttle-fishes.

[Cartilage is frequently observed in situations where it does not
occur normally. This pathological cartilage resembles morphologically
and chemically, the ordinary cartilage, and more especially the variety
with an interstitial substance. — DaC]

Fig. 19. — Portion of the chorda dorsalis of an embryo sheep, G lines long: a, sheath ; 6,
cells, with clear vascular spaces.

Fig 20. — Cartilage cells from the white layer of the cricoid cartilage: from man — magni-
fied 350 diameters.

TISSUES, ORGANS, AND SYSTEMS.

81

Literature. — Meckauer, "De penitiori cartilaginum structura Diss.,"
Vratisl. 183G; J. Mliller, in "Poggcndorf's Annalen," 183G, p. 293;
Rathke, in Froriep's "Notizen," 1847, p. 306; A. Bergmann, "De car-
tilaginibus Disq. niicr.," MitaviiB, 1850. [Leidy, "On the structure of
articular cartilage," American Journal of Med. Sci. April, 1849.]

§ 28. Elastic Tissue.* — The elements of elastic tissue are cylindrical
or band-like fibres, with dark contours, which vary in their diameter
from immeasurable fineness up to a thickness of 0-003, and even 0-005
of a line (in animals even to as much as 0-008 of a line), and when they
are present in quantity, exhibit a yellowish color. These so-called
elastic fibres are, when perfectly formed, quite solid, but may subse-
quently acquire little cavities in particular spots ; and these, in one
animal, the Giraffe (Quekett, "Histological Catalogue," i.), are so regu-
lar, that the fibres present a pretty transversely striated appear-
ance. The margins of the elastic fibres are in general quite rectilinear,
but in some rare cases appear to be notched and even, as Virchow saw
them, in newly-developed tissues, beset with a great number of shorter
and longer pointed processes. Hitherto the elastic fibres have been
separated from the nucleus-fibres : since, however, the latter are dis-

Fig. 21.

i^-^.

tinguished from the former in nothing but their diameter ; furthermore,
as all elastic fibres are originally as fine as nucleus-fibres ; and since,
finally, the latter are not formed of nuclei alone, it will be better wholly
to suppress the name of nucleus-fibres, and to divide the elastic fibres simply
mio finer and coarser. The elastic fibres are found either isolated as
longer or shorter fibres, which may be straight or wind spirally round
other parts (bundles of connective tissue, nerves), and in this case they
are commonly of the finer kind ; or by the anastomosis of fibres of dif-
ferent sizes, a so-called /firows elastic network is formed, which is some-

FiG. 21. — Portion of a human epiglottis; magnified S'lO diameters.

Fig. 22. — Elastic network from the tunica media of the pulmonary artery of a horse,
with lacunce in the fibre ; magnified 350 diameters.

* [Yellow fibrous tissues — DtiC]

82

GENERAL ANATOMY OF THE TI8SUES.

times expanded in a membranous form, and sometimes penetrates other
tissues to various depths. A modification of this fibrous elastic network
is formed by the elastic membranes, in which the fibres are so closely
interwoven, that a connected membrane arises, which in the most extreme
cases no longer exhibits any indication of its previous nature, and ap-
pears as a perfectly homogeneous membrane with smaller gaps (the
fenestrated membrane of Henle).

Fig. 23. Fig. 24.

Fig. 25

t

,1 !■

■\

Hi

/i:^

Chemically, elastic tissue presents very decided reactions, but the
composition of its substance is not yet exactly known. In cold concen-
trated acetic acid, the elastic fibres, except that they swell a little, are
not afiected ;* if boiled for a whole day, however, they are gradually dis-

FiG. 23. — Two secondary bundles of connective tissue from the arachnoid of man with
coiled and straight (intestinal) fine elastic fibres, and acetic acid added ; magnified 350
diameters.

Fig. 24. — Network of fine elastic fibre from the peritoneum of a child; magnified 350
diameters.

Fig. 25. — Elastic membrane from the tunica media of the carotid of the horse; magni-
fied 350 diameters.

* [The difficulty with which acetic acid acts on elastic (yellow fibrous) tissue, presents an
important means of distinction between it and the connective (white fibrous) tissue, the
fibres of which are readily rendered transparent by its action. In tissues in which the
elastic fibres are mixed up, or concealed by the fibres of connective tissue, acetic acid

TISSUES, ORGANS, AND SYSTEMS.

83

Fiff. 26.

Fi.-r. 27.

solved: nitric acid colors them yellow; IMillon's test* for protein tinges
them red; whilst sulphuric acidf and sugar have no action (red colora-
tion) upon them. In a moderately diluted solution of potassa, elastic
tissue remains, for a long time, unaltered in the cold, except that it
swells up and becomes somewhat paler. Heated for a day with it, it
becomes converted into a gelatinous mass. In water this tissue does
not alter, even after sixty hours' boiling, but changes by boiling for
thirty hours in Papin's digester into a brownish substance, smelling like
glue, but not gelatinizing, which is precipitated by tannic acid, tincture
of iodine, and corrosive sublimate, but not by the other tests for chondrin.
PhysiologieaUy, the prominent characteristic of this tissue is its elas-
ticity, in consequence of which it forms a most essential support to the
motor organs, and also plays an im-
portant part in other situations, e. g.
in the vocal ligaments. With respect
to its development, the supposition of
Schwann, that this tissue proceeds
from cells, receives increasing support
from modern investigations ; in fact,
in all those organs which subsequently
contain elastic tissue, there may be
discovered in embryos, peculiar fusi-
form or stellate, sharply-pointed cells,
which by their coalescence produce
long fibres or reticulations, in which
at first, those localities where the
bodies of the cells previously existed
may still be recognized as enlarge-
ments containing elongated nuclei in
their interior. In this condition the
fibres not unfrequently remain, and
they then form a modification of what
were formerly called nucleuB-fibres, or
every trace of their previous composi-

FiG. 26. — Formative cells of the elastic fibres, from the tendo-Achillis: a, of a four months'
embryo; 6, from a seven months' fcEtus, — a iew cells free, with one and two processes,
others united by twos and threes. — ^Magnified 350 diameters.

Fig. 27. — Stellate formative cellsof the nucleus-fibres out of the tendo-Achillis of a new-
born infant. — Magnified 350 diameters.

i

by rendering the latter transparent, permits us to investigate the former. In preparations
thus treated the subsequent addition of ammonia, by neutralizing the acid, causes the fibres
of the connective tissue to reappear, and those of the elastic tissue to recede. — DaC]

* [Millon's test (see Compt. Rend. t. 27, p. 42-44), is the most delicate test for protein
known. It consists in heating the suspected fluid or tissue from 60° to 100° in a soluUon
of one part of mercury, in two parts of nitric acid. If protein be present an intense red
color results, which does not disappear on prolonged boiling. — DaC]

t [The immediate elfect of sulphuric acid is to render the fibres more distinct. — DaC]

84 GENERAL ANATOJIY OF THE TISSUES.

tion disappears, so that quite homogeneous fibres or fibrous reticulations
are produced. These may then either remain through life as fine elastic
fibres and networks, or by increasing in thickness they may pass into
the coarser form of the tissue. The more homogeneous elastic mem-
branes are nothing but close elastic networks, whose fibres have so much
increased in diameter, that only narrow spaces remain between them.
The perfect elastic tissue appears to undergo very little change of sub-
stance— at least it is, so to speak, non-vascular, even when it occurs in
large masses ; on the other hand, in those forms which still present in-
dications of the original cells, a certain movement of the juices may
still take place. Elastic tissue is not known to be regenerated, but new
formations of it are not rare.

The elastic tissue is rarely found in large masses ; but it is very fre-
quently mixed with connective tissue, either in the form of isolated
fibres or of networks of various kinds. As true elastic organs we may
mention : —

a. The elastic ligaments, in which the tissue, with only a slight ad-
mixture of connective tissue and hardly any vessels and nerves, exists,
so to speak, in a pure form. As such we have the ligamenta suhflava of
the vertebrae, the ligamentum nucha', certain ligaments of the larynx,
the stylo-hyoid ligament, and the ligamentum suspensorium penis.

h. The elastic membranes, which appear in the form either of fibrous
networks or of fenestrated membranes, and are found in the walls of
the vessels, especially in those of the arteries, in the trachea and hron-
chice, and in i\iQ fascia superficialis.

In all the vertebrate classes the elastic tissue is found in the same
localities as in man, and in a few particular situations besides, as in the
ligaments of the cat's claw, in the alary membrane of mammals, in the
folds of the alary membrane and in the lung sacs of birds. In the In-
vertebrata this tissue appears to be rare, and it is not even certain that
the elastic ligaments which occur in them (as, for example, in bivalves),
agree anatomically and chemically with the elastic tissues of the higher
animals.

Of the different parts belonging to the elastic tissues, the so-called
nucleus-fibres of Gerber are almost alone those whose development has
been examined. With regard to these, Henle's view,* that they arise
by the coalescence of elongated nuclei, was almost universally received,
until lately Virchow and Donders nearly contemporaneously brought
forward another conception. Both these authors proceed from the in-
vestigation of the connective tissue, and show that what in it have been
held to be elongated, isolated, or more or less coalesced nuclei, are
nothing more than fusiform or stellate cells, with fine processes, which

* [See article " Kernfasern," MuUer's Arcliiv. 1838.— DaC.J

TISSUES, ORGANS, AND SYSTEMS. 85

closely surrounil a generally elongated nucleus, and are partly united
into fibres or networks. With regard to the development of these cells,
Virchow deduces from Schwann's observations, and Donders from his
own investigations, the result that the well-known fusiform cells in the
rudimentary areolar tissue of embryos are nothing more than the forma-
tive cells of the so-called nucleus-fibres ; to which, then, as a conse-
quence, it is added that the proper connective tissue does not proceed
from cells, but is nothing else than fibrillated cytoblastema. Hence
both these authors agree in placing connective tissue and cartilage side
by side and, in comparing the formative cells of the so-called nucleus-
fibres, which Virchow calls "connective-tissue corpuscles," (Binde-
gewebskorperchcn), with the cartilage-cells ; the interstitial substance
of the cartilage, with the fibrous part of the connective tissue. Virchow
goes still further, and compares even the bone substance to connective
tissue ; especially that which is developed by the ossification of what I
have called soft blastema, in which the bone cavities, he supposes, pro-
ceed from stellate anastomosing " connective-tissue corpuscles," a view
which seems chiefly to have led him to declare that the nucleus-fibres
are hollow, and form a great system of tubules and cavities through the
connective tissue, thus probably subserving nutrition. It could be
imagined that the nutritious fluid might thus be quickly conducted for
considerable distances, and uniformly distributed through the tissue, in
which case the nuclei must be considered to be the special regulative
portions of the apparatus, while the cells are simply conductors.

If we submit these diff'erent views to the test of observation, it results
that much is quite correct, but that some points are untenable. It is
true, that the so-called nucleus-fibres are developed from cells ; and the
fact is, indeed, noted in certain earlier statements and figures of Valen-
tin, Hassall, Quekett, and others. In the tissues of full-grown animals,
it is in many localities unquestionably impossible, in others very diffi-
cult, to attain to certainty upon these points, because here, even when
the nucleus-fibres still present indications of cells, the cell-membrane so
closely embraces the elongated and by no means vanished nucleus, that
it is often quite out of the question to decide whether we have a cell
with two or more slender processes, or a fusiform or stellate nucleus ;
on the other hand in young animals, in which also Virchow made his
first observations, and especially in embryos, it is easy to come to a
clear decision upon the matter. In man, I find the tendons, ligaments,
and the aponeurosis palmaris and plantaris, to be especially serviceable
objects ; but in all the places in which elastic tissue is mixed with con-
nective tissue, I was able to follow their development. The observation
is most successful in the foetus of three to four months. Here, in all
the more solid organs composed of connective tissue, — tendons, liga-
ments, fasciai, corium, — the proper connective-tissue fibrils are already

86 GENERAL ANATOMY OF THE TISSUES.

quite well developed, while of nuclear fibres, so to speak, there are no
traces. Instead of these, however, we find between the often very dis-
tinct bundles of connective tissue, a great number of fusiform cells of
0-01--015 of a line in length, which in their middle (of 0'002-0-003
of a line in breadth) enclose an elongated roundish clear nucleus with a
nucleolus, which completely fills them, and are prolonged at their ends
into fine dark threads. If we trace these cells, among which are always
scattered many round and elongated cells out of which they are formed,
and in older embryos a few stellate ones, with from 3 to 5 processes,
it is found that they gradually become longer and narrower, and from
the sixth month begin to coalesce with one another into elongated fibres
or networks ; up to a late period, however (even 7 to 8 months), these
formative cells of the elastic tissue may be easily isolated in abundance
from all forms of connective tissue, either singly or combined by twos
and threes. In the foetus at birth this can no longer be done ; but here
the complete nucleus-fibres, at least in the more solid forms of connec-
tive tissue, still clearly exhibit their composition out of fusiform and
stellate cells with nuclei ; which, as we have already seen, is occasion-
ally in some localities even the case in the adult.

What holds good of the nucleus-fibres may be asserted also of the
elastic fibres, which are not further treated of by Bonders and Virchow.
Valentin (Wagner's " Handw. d. Phys.," I. p. 668) found that the elastic
fibres of the ligamentum nuchce of the calf are considerably finer than
those of the ox, and I stated ("Zeitschrift fiirWiss. Zool.,"I. p. 77, Anm.)
that all the thick elastic fibres of the adult have at one time been com-
mon nucleus-fibres. In fact, we find in the new-born child not a single
true elastic fibre, since even those of the ligt. nuchce, of the Ugt. Jlava,
and of the aorta, when largest, do not measure more than 0*0008-*001
of a line. This circumstance alone, might, if we take into account the
close resemblance of the elastic and so-called nucleus-fibres in other
respects, be considered as a demonstration that the former are also
developed out of cells, but we have in addition direct evidence that
this is their mode of development

In the aorta, in the ligt. nuchce, and in the fascia superjicialis abdo-
minis of human embryos of the fourth and fifth months, we find the
same short fusiform cells as in the common connective tissue ; and
their coalescence into originally finer fibres, though perhaps not quite
so readily demonstrable as in the former localities, may yet be made
out with certainty, so that the agreement in their genesis of the finer
with the coarser elastic fibres, may be considered to be established.

Not, however, to the same extent, as with regard to the genesis of
the finer elastic fibres, can I agree with the authors mentioned in other
points. In the first place, concerning the physiological import of the
so-called nucleus-fibres, I grant to Virchow, that even in the adult.

TISSUES, ORGANS, AND SYSTEMS. 87

in some places, they appear to retain more their original character of
a system of canals ; yet I can by no means allow, that these nucleus-
fibres are to be regarded as a system of tubules subserving nutrition.
In my opinion, all fine elastic fibres, which no longer present any trace of
the original cell, i. e. those of the areolar connective tissue of i\iQ corium,
fascise, of the perimysium, of the periosteum, of the dura mater, of the
serous membranes, of the walls of the vessels, and of mucous membranes,
are solid fibres, and only of service to the organism so far as they are
elastic.

A relation to nutrition can only be supposed of those elastic elements
of the tendons, ligaments, and of the cornea, which present condi-
tions more nearly embryonic ; but even with respect to these it does not
appear so evident that it can be decidedly afiirmed. In the tendons
and ligaments, for instance, it is plain that a part only of the elastic
elements are not quite fully developed, so that possibly cavities may still
exist in them ; while the rest, much more considerable, are as com-
pletely developed as elsewhere, and offer no trace of a cavity. If,
now, it were assumed that the former have a determinate relation to
the conduction of the nutritive fluid, it would yet remain unexplained
w'hy, in certain regions, these organs were more favored than in others.
If it be further considered, that in the tendons and ligaments, as in the
connective tissue in general, vegetative molecular changes and nutri-
tion are assuredly at their lowest stage, — furthermore, that the arrange-
ment of the nucleus-fibres (their more longitudinal course, the want of
anastomosis of the nucleus-fibres of the different secondary bundles in
tendons) appears very little fitted to conduct nutritious fluids from the
surfaces of these organs, where only the vessels are found, into their
interior, — ^there will appear no great necessity for entering further into
this hypothesis. For the cornea alone, where the elastic tissue remains
in a quite embryonic stage, should I be inclined to adopt Virchow's
hypothesis ; and, as respects the other tissues, I can only grant that,
when the elastic elements are in such an imperfectly developed condi-
tion that they still contain canals for greater or less distances, they
may have a share in the distribution of the nutritive fluid which natu-
rally interpenetrates these organs, and, therefore, in their nutrition, but
that this must rather be regarded as a secondary function, and will not
justify their approximation to the fine canals of the teeth and bones,
which exist specially for the purpose of nutrition.

Such a function might much rather be ascribed to the undeveloped
nucleus-fibres and their formative cells in the immature (pathological
or normal) connective tissue ; for here, at least, the anatomical and
physiological relations of the tissue are not opposed to such an assump-
tion; it would amount to little more, however, than what may be asserted
of every undeveloped fibrous tissue.

88 GENERAL ANATOMY OF THE TISSUES.

A second and much more important point in whicli I differ from
Bonders and Virchow is the general mode of looking at the connective
tissue. Both these writers hold that it is not composed of cells, but is
developed by the fibrillation of a homogeneous cytoblastema ; and they
believe that all the fusiform embryonic cells, which since Schwann's
time have been regarded as its formative cells, belong not to it, but to
the elastic tissue. I can by no means admit such a view, and it seems
to me to be comprehensible, only when we recollect that these authors
arrived at it more upon theoretical grounds, than by direct observation.
With Virchow, a passage in Schwann appears to have been conclusive,
where he describes the embryonic connective tissue as a gelatinous homo-
geneous mass, which dissolves upon boiling, and contains cells distri-
buted through it which are not affected by the boiling. Virchow does
not hesitate to extend this to all connective tissue, and to assume that
the substance soluble in water answers to the subsequently fibrous con-
nective tissue, while the insoluble cells are the formative cells of the so-
called nucleus-fibres. Here, however, he has omitted to notice that
Schwann speaks only of a determinate form of tissue, the lax.0Y areolated^
and describes in a totally different manner the formation of the more
solid connective tissue, e. g. of a tendon. In this case we find, in direct
contrast to the former, no trace of cytoblastema, which can in no way
be directly observed, the tendon consisting throughout of fibre-cells,
either isolated or united into bundles of connective tissue.

To observe this, however, the examination must be made at a very
early period, since, as Schwann has justly remarked, the elements of
the fibrous tissue are very early developed ; a circumstance from ne-
glecting to observe which, it seems that Bonders has been led to adopt
the same view as Virchow. For my own part I have found Schwann's
statements confirmed in all essential points, with the single exception
that he was unacquainted with the formative cells of the elastic fibres,
and confounds them with those of the connective tissue. My observa-
tions upon these points are to be found in the following section. Hence
I cannot admit that cartilage and connective tissue are nearly allied,
inasmuch as the fundamental substances of both, even if chemically
agreeing, yet, genetically, are very different.

Literature. — A. Eulenberg, "de tela elastica," 1836; Virchow, "die
Identitiit von Knochen, Knorpel und Bindegewebskorperchen, sowie
ueber Schleimgewebe," in the " Verhandlungen der Phys. Med. Gesell-
schaft in Wiirzburg," Bd. II. 1851, p. 150; and " Weitere Beitrage
z. Kenntniss d. Structur der Gewebe der Bindesubstanz." Ebend. II.
p. 314; Donde.rs in the "Nederlansch Lancet.," 1851, July and August;
and in the " Zeitschrift fiir wissen. ZooL," Bd. III. p. 348; Kolliker,
" Ueber die Entwicklung der sogenannten Kernfasern, der elastichen
Fasern und des Bindegewebes;" in "Verb. d. Phys. Med. Ges. in
WUrzburg," Bd. III. H. 1.

TISSUES, ORGANS, AND SYSTEMS.

89

§ 24. Connective Tissue [fibrous and areolar tissue]. — The elemen-
tary parts Avhich are found in connective tissue may be divided into the
essential, never-failing components, and those Avhich are met with only
in certain localities. To the former
belongs the fasciculated as well as the
more homogeneous connective tissue ; to
the latter, elastic fibres in their diflerent
forms and conditions of development,
fat cells, cartilage cells, and pigment
cells of different kinds. Besides these,
connective tissue contains also no in-
considerable quantity of a gelatinous
intermediate substance. The bundles
of the connective tissue are, among
the essential elements, those which
occur most frequently ; each of them
consists of a certain number of very
fine fibrils, the connective fibrils, which
are distinguished from their nearest
allies, the finest elastic fibres and mus-
cular fibrils, by their smaller diameter
(0-0003-0-0005 of a line), their pale
color, their homogeneous appearance,
and the complete absence of striation.
They are united by means of a small
quantity of a clear connecting sub-
stance, and thus form the bundles in
question, which in many respects re-
semble those of the transversely striated muscles, but differ from them
in the absence of any special investm.ent comparable to the sarcolemma,
and in their smaller mean diameter (0-004-0-005 of a line.) They are
either long, slightly wavy cords, of uniform thickness throughout, which
are not directly connected together, but arranged in different ways near
and above one another, forming great lamellne and bundles ; or they
coalesce like the elastic networks into meshes, and thus form what I
have called the reticulative connective tissue. In rare cases the bundles
appear not to be composed of fibrils, but are more homogeneous, as in
the neurilemma, where they are known as Remak's fibres. Besides this
form of connective tissue, there exists a second, rarer kind, in which
neither bundles nor fibrils can be clearly distinguished, but only a mem-
branous or more or less solid, finely granulated, or slightly striated, even
perfectly homogeneous, clear tissue; homogeneous (or Reichert's) connec-
tive tissue. The other elements which occur in connective tissue pre-

FiG. 28. — Lax connective tissue with fat-cells from man; magnified 350 diam.

90

GENERAL ANATOMY OF THE TISSUES.

Fig. 30.

sent nothing remarkable, and will be more particularly treated of in their
proper places in the special part.

The chemical relations of connective tissues are well known : proper
connective substance when boiled yields common gelatine, and contains
besides a fluid, whose nature, on account of its generally minute quantity,
cannot be investigated. Only where it exists in considerable proportion,
as in the gelatinous connective tissue of embryos, can the presence of
much albumen and mucus be easily demonstrated in it. The chemical
qualities of the other constituents of the connective tissue will be spoken
of in their place.

Connective tissue is of utility to the organism according to its compo-
sition,— sometimes as a solid unyielding substance ; sometimes as a soft
support for vessels, nerves, and glands ; sometimes, finally, as a yielding
tissue, filling up spaces, and facilitating changes of position. Where
elastic elements are present in it in great quantities, its nature alters;
and a great abundance of fat or cartilage cells gives it an unusual soft-
ness or resistance. The connective tissue is invariably developed from
cells, and, in fact, from fusiform or stellate vesicles, which become
united into long fibres or networks, and often break up into fibrils before
their union. The mode in which this takes place is not yet quite made

out, but it is most proba-

Fiff. 29. ' ^

ble that the cells, as they
elongate, change with
their membrane and con-
tents, into a homogeneous
softish mass, which sub-
sequently breaks up into
a bundle of fine fibrils
and some intermediate
substance. The develop-
ment of the homogeneous
connective tissue has as
yet been little investiga-
ted, but it would seem,
like the other, to proceed
from a fusion of rounded
or elongated cells, which
are perhaps united by an intermediate substance, in which the meta-
morphic process has only gone so far as the development of a homoge-
neous mass, but has not attained the stage of fibrillation. The bundles

Fia. 29. — Formative cells of the connective tissues from the skin of the trunk in a sheep's
embryo, 7 lines long: a, cell without any indication of fibrils; b, with commencing; c, with
distinct fibrils. — Magnified 350 diameters.

Fig. 30. — Three formative cells of the areolated connective tissue from the allantois of a
sheep's embryo, 7 lines long. — Magnified 350 diameters.

TISSUES, ORGANS, AND SYSTEMS. 91

of the connective tissue, when once formed, grow in length and thick-
ness like the elastic fibres, until they have attained the size which they
possess in the adult ; however, there arise subsequently, in many places,
additional elements, which arc combined with the original ones. The
perfect connective tissue, when unmixed, is almost non-vascular, and with
regard to nutrition, it is certainly very low in the scale, whence it
undergoes hardly any morbid changes. Tlie vascular connective tissue
is an exception to this rule, but the changes in this case depend not
upon any peculiarity in the connective tissue itself, but are determined
by the vessels, fat-cells, &c., contained in it. The bundles of fibrils of
the connective tissue and the elastic fibres stand at the bottom of the
series of the higher elementary parts, and thence most readily adapt
themselves to the regeneration of lost substance, or to the increase of
parts which already exist.

The union of the different elements of the connective tissue is effected
in many ways, but the following forms are most worthy of distinction : —

1. Solid con7iective tissue (formed connective tissue, Henle). In this
the elements are intimately united, and in such a manner, that simple
organs of well-marked form proceed from them. To this belong: —

a. The tendons and ligaments, with parallel bundles, united by loose
connective tissue into larger cords, between which a relatively very
small number only of fine elastic fibres, and fibrous networks, pene-
trate.

b. The fibro-cartilages have the same structure as the tendons and
ligaments, but with numerous scattered cartilage cells, and without finer
elastic fibres. They exist either as special organs, such as the cartila-
gines inter art iculares and the cotyloid ligaments, or in particular parts
of other organs composed of connective tissue, especially in the tendons,
the tendinous sheaths, and the ligaments.

c. The fibrous membranes are distinguished from a, only by the fre-
quent interweaving of the bundles, and generally by the more considera-
ble number of the elastic fibres. Here may be enumerated : —

1. The muscular fascice, which have more the structure of tendons.

2. The periosteal membranes and the perichondrial membranes, con-
taining sometimes a great number of elastic elements.

3. The ivhite dense tunics of many soft organs, as the dura mater, the
neurilemma, the sclerotic and cornea, the fibrous coat of the spleen and
kidneys, the tunica albuginea of the ovaries and testes, penis, and
clitoris. In the last-mentioned parts, and in the spleen, these coats,
which consist of a solid connective tissue and numerous fine elastic fibres,
are continued into the interior, Avhere, mixed to some extent with smooth
muscles, they constitute a more or less complete framework, which
appears in the form of partitions, or of a stroma, or of a trabecular net-
work. In the cornea we find a modification, inasmuch as the connective

92 GENERAL ANATOMY OF THE TISSUES.

tissue is ti'ansparent, contains fine elastic tissue in a more embryonic
state, and when boiled in water yields chondrin and not gelatine.

d. The serous membranes consist of a connective tissue, rich in fine
elastic fibres, whose bundles anastomose, or are interwoven in different
modes ; and sometimes also, especially at the surface of these membranes,
appear more homogeneous. The serous membranes, which never possess
glands, and upon the whole but few vessels and nerves, line the cavities
which contain the viscera, and present an inner surface, which is smooth
and shining from the presence of an epithelial investment. They do not
necessarily form closed sacs, as was formerly believed, but may have
apertures in certain localities (abdominal apertures of the Fallopian
tubes), or may be wholly wanting, as upon the articular cartilages ; or
the areolar foundation may be absent, as in the so-called external lamina
of the araelinoidea cerebri. To these membranes belong I., the true
serous membranes, as the arachnoidea, the pleura, the pericardium, the
peritoneum, and the tunica vaginalis propria, which all, normally,
secrete only a minute quantity of serous fluid ; and 2, the synovial mem-
branes or capsules of the joints, bursce mucosae, and the tendinous
sheaths, which afford a viscid yellow, secretion, — the synovia — contain-
ing albumen and mucus.

e. The corium consists of a dense network of bundles of connective
tissue, which at the surface, and in the papillne, gives place to an indis-
tinctly fibrillated, in part even more homogeneous tissue, and contains a
great quantity of finer and coarser elastic networks, as well as very
numerous vessels and nerves.

The corium supports the papillse upon its outer surface, and is here
covered by the epidermis, in connection with which it forms the external
skin ; from the deeper parts it is separated by a soft tissue, generally
very rich in fat, the subcutaneous connective tissue, adipose membrane,
or panniculus adiposus.

f. The mucous membranes essentially consist of a very vascular basis
of connective tissue, well supplied with nerves, — the proper mucous
membrane — of an epithelial layer covering it, and of a submucous
areolar tissue, which in the intestine is also called the tunica nervea.
The former is of the same structure as the corium, only softer, and not
unfrequently poor in elastic tissue. The mucous membranes are distin-
guished from the serous, in general by their greater vascularity, their
more considerable thickness, their numerous glands, and the mucous
secretion, which may be especially ascribed to their soft epithelium ;
though there are mucous membranes which are as delicate and glandless
as serous membranes ; and, on the other hand, the synovial capsules may
approximate the mucous membranes in their vascularity and the nature
of their secretion. The mucous membranes and the external skin are
analogous in all their principal components, whence the transitions

TISSUES, ORGANS, AND SYSTEMS. 93

between the two, such as exist upon the lips, eyelids, and elsewhere,
are not surprising. To the mucous membranes belong the innermost
coat of the tractus intcstinalis ; the lining of the nasal passages, and of
their secondary cavities ; the Eustachian tube, the tympanum and mas-
toid cells, and the conjunctiva. Among the glands, all the larger, pre-
sent in their excretory ducts, a distinct mucous membrane, as the lungs
from the glottis to the finest broncliKS ; the liver in the larger gall-ducts
and in the gall-bladder ; the pancreas in the ductus pancreaticus ; the
urinary and sexual organs ; in the urethra, bladder, ureters, pelvis of
the kidneys, vagina, uterus, and oviducts ; and in the ducts and follicles
of the mammary gland ; in the seminal vesicles, and in the vas deferens.
In all these glands the coats of the mucous membrane pass immediately
into the walls of the glandular tubes and vesicles, which might thus be
regarded as composed of a more delicate mucous membrane. The same
might be said of the smaller glands, as those of the intestine, which are
directly connected with the larger mucous expansions, only in that case
the smaller glands of the skin must be regarded as attenuated processes
of it. Inasmuch as both physiology and development support this view,
it would seem to be at any rate justifiable; yet every one is free, not-
withstanding, to look more to the differences which certainly do exist
between the parts in question, and to consider them as distinct struc-
tures.

g. The membranes of the veins, lymphatics, the adventitious coat of
the arteries, and the endocardium, consist of a loose connective tissue
not altogether dissimilar to that of the fibrous membranes, and of finer
or coarser elastic fibrous networks, with which in the veins smooth
muscles are also partly mixed.

h. The so-called vascular memhraiies (tutiicce vasculosce), to which
belong the pia mater, with the plexus cltoroidei, the choroid coat and the
iris, all contain very numerous vessels, which, however, appear to have less
reference to the membranes themselves than to the nutrition of other
organs. Supporting these vessels we have either a common connective
tissue, in which there are no elastic fibres (iris, p>ia mater), with paral-
lel, matted, and anastomosing bundles, or a homogeneous connective
tissue {jilexus choroidei, choroidca), to which, as in the choroid, peculiar
elements, namely, anastomosing cells, generally filled with more or less
pigment, may be added.

i. The homogeneous connective tissue. — In many organs we find mem-
branes whose chemical nature agrees with that of connective tissue, but
which neither contain distinct bundles nor fibres, and appear to be more
homogeneous. Such is the homogeneous tissue which often invests the
bundles of the arachnoid singly, or in a number together ; the coats of
the Malpighian corpuscles of the spleen, and of the glandular follicles
of the intestine (tonsils, lingual-follicles, the solitary and Peyerian

94 GENERAL ANATOMY OF THE TISSUES.

glands), certain of the so-called memhrance. "prop'icB of the glands ap-
pear to come under this head also ; yet, since some of them do not
belong here, and consist of a very different substance from connective
tissue, as, for example, that of the kidneys, and since we have no thorough
investigation of these structures, for the present nothing decided can be
said upon the subject.

h. Loose or areolated connective tissue^ (" amorphous connective tissue"
of Henle), consists of a soft meshwork of reticulated, or variously inter-
woven bundles of connective tissue, which in larger or smaller quantity
constitute a filling up and uniting mass between the organs and their
parts, and appear under two forms : —

1. As adipose tissue, when numerous fat-cells are contained in the
meshes of an areolated tissue which is usually very poor in elastic fibres.

2. As common lax connective tissue, when the latter are few or want-
ing. The adipose tissue occurs principally in the skin forming the
panniculus adiposus ; in the larger cylindrical bones, as yellow bone-
medulla ; in the orbit ; around the kidneys ; in the mesentery and the
omentum ; around the spinal marrow ; in the nerves and vessels, and
in muscles. The areolated connective tissue is widely distributed be-
tween the separate organs and the viscera of the neck, thorax, abdomen,
and pelvis, and everywhere along the course of the vessels and nerves,
and in the interior of the muscles, nerves, and glands.

The connective tissue is found in all the four classes of the vertebrata
in about the same condition as in man ; while, on the other hand, in the
invertebrata it is very rare, and when present is more homogeneous,
or consists of isolated cells and intermediate substance, rarely more
fibrous, as in Cephalopoda, in the mantle of bivalves, in the peduncle
of the LinguliTS, and of the Cirripeds. Fat-cells also do not occur
among the lower animals to the same extent as among the higher. The
firm connective tissue is here replaced by a chitinous substance, or by
one consisting of cellulose, and by calcareous or horny tissues.

Opinions are still divided as to the structure and development of the
connective tissue. Whilst the majority ascribe a distinctly fibrous struc-
ture to it, and suppose it to consist of bundles, and these again of fibrils,
Reichert considers this tissue to be more homogeneous, and regards the
fibrillation partly as artificial, partly as the expression of a folding, a
view to which Bidder and Virchow are also inclined. For my own
part, I find a certain amount of truth in Reichert's conception, inso-
much as it is not to be denied that there also exists a non-fibrillated,
more homogeneous connective tissue, which had previously been little
investigated ; but I am nevertheless of opinion, that, as applied to the

* [Tliis second variety, " loose or areolated connective tissue," is generally described as
areolar tissue, or under the faulty name of cellular tissue. — DaC]

TISSUES, ORGANS, AS D SYSTEMS. 95

great mass of the organs composed of connective tissue, it is incorrect.
The possibility of maixing out fibrils in delicate membranes, even Avith-
out preparation, the ease in whicli these may be isolated in tendons and
ligaments, and lastly, the circumstance that the fibrils may be demon-
strated upon transverse sections of the tendons, and of the more solid
connective tissue in general, are for me sufficient reasons for retaining
the old view.

With respect to the development of the connective tissue, I distinguish
two types which correspond with its two principal forms, the solid and
the areolated. The former is developed out of masses of cells without
any demonstrable matrix, by the elongation of the cells, their breaking
up into fibrils, and their coalescence. This is most obvious in the ten-
dons and ligaments, which, as observations upon Batrachian larv5« and
upon mammalian embryos show, at first consist entirely of common,
rounded, formative cells, which about the same time as the transversely
striated muscles are formed (in mammalia in the second month), become
fusiform. The further development demonstrates (what had escaped
Schwann) that only one portion of these fusiform cells, and in fact cells
which are remarkable for their size and paler contours, become bundles
of connective tissue, while the others, which Schwann in part depicts
rightly (Tab. III. fig. 11 ; the smallest cell, fig. 6, from connective
tissue, the cell b, and the lowest cell upon the right side), remain for a
time as fusiform elements, and only subsequently become fused into
elastic fibres. There arises, at last, out of the cells alone, with no dis-
tinguishable matrix, a compact tissue composed of two chemically quite
distinct fibres. The areolated connective tissue differs from the former
in the circumstance that, if not from the beginning yet from the time
at which the cells become elongated, an abundant gelatinous interme-
diate substance is developed between them, which does not yield gela-
tine, and never becomes converted into it, but contains albumen and a
substance similar to mucus ; Schwann, indeed, found a substance re-
sembling pt/in, in this tissue. Although all embryologists know that
the areolated connective tissue is at first of a gelatinous consistence,
as for example, under the skin, in the neck, in the omentum, behind the
peritoneum, in the orbit, and in the bones, no one has yet drawn atten-
tion to the general occurrence of that intermediate substance which
was observed by Schwann in a single locality. I originally became ac-
quainted with this tissue between the chorion and amnion, and at first
paid more attention to its reticulated anastomosing cells. Subsequently
when I examined it more closely in the enamel organ of the embryonic
tooth sac, I paid attention to the peculiar intermediate substance, and
at the same time Virchow described this tissue from the umbilical cord,
where the gelatinous tissue of Wharton entirely consists of it. Virchow
believed that it ought to be distinguished from connective tissue, and

96 GENERAL ANATOMY OF THE TISSUES.

proposed the denomination of mucous tissue {tissu muqueux) for it. I
considered it from the first to be connective tissue, and I now feel the
more inclined to remain of this opinion, because I find that every de-
scription of the areolated connective tissue of embryos originally com-
mences under this form, and therefore the circumstance that the tissue
in the umbilical cord never arrives at perfection, cannot determine its
nature.

The mode in which the gelatiniform connective tissue is developed is
this : one portion of the cells contained in the gelatinous basis changes
into connective tissue by becoming fusiform, and breaking up into common
or reticulated anastomosing connective tissue, which, however, as Schwann
has already stated, at first yields no gelatine. In this manner a closer or
denser network arises, in the interspaces of which the intermediate sub-
stance or matrix, and a remainder of the previous formative cells, are
contained. In the further course of development, new cells proceed
from the matrix, which hereby diminishes by degrees in quantity, and
at the same time the original network consolidates, fresh cells being
added to it, a part of which also become elastic fibres and vessels. If
subsequently the areolated connective tissue includes no adipose cells,
the gelatinous tissue ends by completely disappearing, and nothing re-
mains but a loose fibrous tissue, containing at most somewhat less fluid,
and loose cells in its meshes ; if, on the other hand, it becomes con-
verted into an adipose tissue, the spaces remain, and a great part of the
cells which have arisen at the expense of the gelatinous substance, sub-
sequently pass, by the development of fat in their interior, into fat-
cells.

In the gelatinous tissue of Wharton, between the chorion and amnion,
and in part of the enamel organ, the areolated connective tissue remains
more in its foetal condition of a gelatinous tissue, yet there exists no
natural line of demarcation from ordinary connective tissue, so much
the less, since in the gelatinous substance of Wharton, in older embryos
even fibrils are quite evident, and in the enamel organ the passage of a
part of the gelatinous tissue into common connective tissue is demon-
strable.

So much for the two types of development of the connective tissue.
We have yet to state how the bundles become chemically and morpho-
logically what they are. In the first place, I may observe that the for-
mative cells of the connective tissue are not originally distinguishable
from the other formative cells of the embryo, do not dissolve by boiling
in water, and therefore contain no gelatine. Even when the cells have
evidently become fusiform, and have already coalesced into bundles and
networks, they still, as Schwann has already stated, yield no gelatine.
Therefore, in this case, the change of the cells into a collagenous sub-
stance, goes on as slowly as in the matrix of the cartilages, which,

TISSUES, ORGANS, AND SYSTEMS. 97

according to Schwann, also, at first, yields no gelatine, and therefore it
is no objection to the above view of the nature of Wharton's gelatinous
tissue, that it 3nclds no gelatine on boiling, as Scherer has found. How
the collagenous matter is formed out of cells, whether the contents only,
or the membrane also, takes part therein, it is very difficult to say ; in
any case, from what we know of the contents of embryonic cells, it can
hardly be any but a protein substance which yields the gelatine, and,
from what takes place in the ossification of the cartilage cells, it seems
very probable that the cell-membranes and contents together become
metamorphosed into a collagenous substance.

The morphological change which the formative cells of the connective
tissue undergo, in the course of their passage into bundles of fibrils, is
very probably this, that after their membranes and contents are fused
into a homogeneous semi-solid mass, they then secondarily break up into
fibrils ; the latter process taking place in the same manner as we see it
occur in the contents of the animal muscular fibres. Herewith, as a
rule, the nuclei of the cells eventually disappear, or if they remain, as
we see occasionally in connective tissue, still they never become changed
into the so-called nucleus fibres.

Though in physiological connective tissue, development from cells
must be most decidedly affirmed, it does not therefore follow that a sub-
stance which chemically and morphologically closely resembles con-
nective tissue, may not arise in a different manner. We know, in fact,
that the collagenous basis of cartilage, when it breaks up into fibres,
becomes deceptively similar to connective tissue, and furthermore, that
fibrous exudations may become changed into a fibrous substance which
is scarcely, perhaps not at all, to be distinguished from genuine con-
nective tissue. There also exists, however, a j^cithologicaltrue connective
tissue in cicatrices of all kinds, and perliajJS elseivhere, loliich is deve-
loped from cells ; and for my own part, therefore, I am opposed to the
classino; together of all connective tissues. We must in our classifica-
tions not only distinguish similarity or identity in structure and chemi-
cal composition, but embrace all the conditions, and especially the
genesis; and thence we must distinguish both the collagenous fibrous
cartilage and the collagenous organized fibrine, from true connective
tissue, — just as we separate the true elastic fibre, from the chemically
and morphologically, very similar fibres of the reticulated cartilages and
from certain forms of metamorphosed fibrine. On the other hand, the
connective tissue which has not been developed from cells, may justly
and properly be arranged with cartilage.*

* [Tlie arguments brought forward by Professor Kolliker in support of liis views with
regard to the nature and mode of development of connective tissue, appear to us not to
preponderate against those of Reichert, Virchow, and Remak, and to be opposed to

7

98 GENERAL ANATOMY OF THE TISSUES.

Literature. — C. B. Reichert, " Vergleichende Beobachtungen iiber
das Bindegewebe und die verwandten Gebilde," Dorpat, 1845; Luschka,

our own observations, whicli agree in all essential points with those of the last-named
authors.

There are two questions in dispute. The first, the structure of the connective tissue; the
second, the homology of its various constituents with those of other tissues, and of cells in
general.

With respect to the first question, it is admitted on all hands that ordinary connective
tissue (e. g. of the tendons) is composed of two elements : a, a network of elastic tissue,
which is not acted upon by cold acetic acid ; b, a substance which is swollen up by acetic
acid, and has a more or less fibrillated appearance, contained in the meshes of the elastic
tissue. Now it has been demonstrated by Virchow, and the fact is admitted by both Kol-
liker (supra) and Reichert (Zur Streitfrage iiber die Gebilde der Binde-substanz, tiber die
Spiralfaser, &c., Mtiller's " Archiv," 1852), that the elastic fibres are originally cells, and
therefore that they are homologous with the cartilage-cell, i. e. the cartilage-cavity with its
\va]l plus the cartilage-corpuscle or nucleus. That this is the case is very evident upon ex-
amining in a yoimg animal (e. g. kitten) the insertion of the tendo-Achillis into the cartila-
ginous extremity of the os raids. It is here easy enough to see that the oval or rounded cells
of the true cartilage pass in the most gradual manner into the elongated elastic fibres of the
true tendon. The cells retain their cavities for a considerable time, but eventually the nuclei
and the thin layer of substance which immediately forms the wall of the cavity, become
fused into one mass, and altered in chemical composition. A like alteration afiects the
matrix in various irregular directions, so that the delicate elastic connecting fibres are formed,
and constitute a network through the whole tendon. These connecting fibres are often
branched, and even appear fibrillated at the ends, especially if torn out from their connection
vi^ith one another, and in this condition they exactly resemble the bodies figured by Professor
Kolliker as the " fusiform formative cells"' (Fig. 29.) That they have nothing to do with the
development of the "fibrillated" collagenous substance is, however, obvious, from this very
simple circumstance, — that the latter lies between them, and in jmrt replaces the rest of the
matrix of the cartilage, into which it can be directly traced. It will not be said in this case,
that the "fibrillated" tissue of the tendo-Achillis is only "deceptively similar" to true con-
nective tissue — and yet the transition of true cartilage into true connective tissue, is not less
certainly demonstrable in the intervertebral cartilages, &c.

As Reichert, then, long since indicated, in illustrating his " law of continuity" (a law whose
full importance, it may be observed, has yet to be developed), and as he and Virchow have
since demonstrated, the elastic element of fully-formed connective tissue represents the car-
tilage-cells, while the collagenous element represents the matrix of the cartilage, and is not
developed from distinct cells.

With regard to the structure of the latter element, Reichert, in his last communication,
after considering Koiliker"s arguments, denies the truth of his statement, that the ends of the
fibrils may be seen in transverse sections of the tendons (§ Tendon, infra,) and retains his
opinion that it is not truly fibrillated in the uninjured state, but that it is simply plaited.
Some remarkable observations upon the behavior of the "connective fibril bundles" with
acids and alkalies, to which Reichert first drew attention in 1S4G, and which have been
since extended by Dr. Paulsen (Bericht., Miiller's " Archiv," 1849), are, as the former points
out, of the greatest importance in determining the nature of this tissue, and remind one
somewhat of the equally puzzling structure of the starch-corpuscle. Dr. Paulsen states, that
if a piece of tendon be kept for twenty-four hours in a solution of caustic potash often per
cent, strength, it changes into a viscid hyaline mass, so transparent that it can hardly be dis-
tinguished from the surrounding fluid. This substance can be torn with equal ease in any
direction, and no fibrous structure can in any way be detected in it. Under the microscope
the mass is quite transparent, and shows no trace of the well-known striation. However,
the connective tissue is at this time by no means dissolved, nor is its texture destroyed. If
the potass be removed by acetic acid, and this, if it be in excess, by washing, the original

TISSUES, ORGANS, AND SYSTEMS. 99

"Die Structur der serosen Iliiute." Besides ■which, consult the works
of Virchow, Donders, Rcmak, and myself, cited above.

§ 25. Osseous Tissue. — Morphologically, the osseous tissue consists
essentially of a matrix, and, Fig. 31.

scattered through it, of a
multitude of microscopic
cavities, the bone corpuscles^ ^^^ ' ' ' " ' ' '-■ '■ -^ • ■■Mp;^ 'f^p-^

or lacuiiK, of 0-006-0-014 -— ^' ^^^^-^^^^

of a line in leno-th, 0-003- ., -^- -v '

O'OOO of a line in breadth, 5^
and0-002-0-004of aline in . ii^^> ;

thickness. The former, of i

a white color, is sometimes more homogeneous, sometimes finely granular,

Fio. 31. — A portion of a peipendictilar section of a parietal bone ; magnified 350 diameters :
a, lacunae with pale only partially visible canaliculi, filled as in the natural condition with
fluid; b, granulated matrix. The striated parts indicate the boundaries of the lamellae.

texture returns. The author justly remarks, that if the connective tissue consisted of separate
fibrils the impossibility of isolating them in the distended condition would be quite inex-
plicable. It is however intelligible, that in consequence of such an alteration in the con-
nective tissue its cleavability may be diminished or destroyed, which does away with the
necessity of supposing a fibrous structure. On the other hand, if a piece of tendon be
hardened by a strong solution of caustic potash, or by nitric or hydrochloric acids, no fibres
can be demonstrated in it (Bericht., pp. 40, 41). It is easy enough to verify the truth of these
statements, by treating a piece of tenduious tissue with acetic acid, when, as is well known,
the fibrillated appearance disappears; then keeping in view one of the distended and trans-
parent "bundles," slowly add a solution of caustic ammonia, the transparent mass will be
seen gradually to shrink, and eventually to resume what appears to be a most distinctly
fibrous appearance.

The gelatinous or rather gelatinifnrm areulated connective tissue of Professor Kdlliker is simply
ordinary connective tissue, in which the collagenous element is not yet or but little formed.
Its development may be readily traced to the most superficial layer of the skin and mucous
membranes, or in the tooth-pulp, or the so called actinenchyma of the enamel organ in the
calf, &c. The epiglottis of the kitten is particularly to be recommended, as this tissue can
be observed passing on the one side into the homogeneous layer of the corium next to the
epithelium, and on the other into the so-called fibro-cartilage of the epiglottis.

In all these cases, the mode of development of the areolated connective tissue is essen-
tially similar to that observed by Remak (Ueber die Entstehung des Bindegewebes, &c.,
JIull. •' Archiv," 1852, I.) in the frog. The layer of the tissue next the epidermis or epi-
thelium, is composed of a nearly homogeneous substance (matrix.) in which lie corpuscles
(so-called nuclei), the whole in fact corresponding exactly with embryonic cartilage. In-
ternal to this, vacuolar cavities have been formed in the matrix between the corpuscles, the
substance of the matrix appearing as bands or fibres between these vacuolce. The latter
enlarging, the substance of the matrix is more and more broken up into bands, in which
dilatations remain where the "nuclei' are situated, so that the bands often resemble fusiform
or stellate cells. A structure of this kind which imdergoes no further chemical or morpho-
logical alteration, constitutes the gela'.iniforni conneclive tissue; and it is unquestionable, that
its subsequent conversion into perfect areolated connective tissue is efiected, as Professor
Kolliker states, by the direct passage of these fusiform bodies into the pseudo-fibrillated

100 GENERAL ANATOMY OF THE TISSUES.

very frequently lamellated, and hard and brittle from its being inti-
matel}' combined with calcareous salts ; the lacimce are for the most part
lenticular, and are united by very numerous fine processes, the canali-
culi ; by which some of them also open upon the outer surface of the
bones and into the larger and smaller medullary and vascular spaces in
the interior. The lacunce and canalicuU contain a clear substance which
may be regarded as the nutritive fluid of the bones, and besides, a cell-
nucleus appears in many cases, perhaps constantly, to be enclosed within
the lacunge. Besides these two most essential elements, which exist in
all bones, numerous vessels and nerves occur in most, as well as, fre-
quently, a peculiar substance, the medulla, which supports them, and
consists either of common fatty tissue, or of a loose, scanty, connective
tissue, with few fat-cells and many peculiar, so-called medulla-cells.
These soft parts fill up the larger cavities in the interior of the bones
and in the spongy substance ; but are to be found also, at least partially,
in narrow canals which penetrate the compact substance, the vascular or
Haversian canals, Avhich open in all directions upon the outer and inner
surfaces of the bones.

The matrix of the osseous tissue is composed of an intimate combina-
tion of an organic substance, which perfectly agrees with that of the
connective tissue, and of inorganic compounds, among which the phos-
phate and carbonate of lime are the principal constituents. The fluid
contained in the cavities and canals is not thoroughly understood, but it
probably presents a preponderance of albumen, fat, and salts, like the
serum. The bones, from their solidity and inflexibility, serve as sup-
j.ig_ 32. ports to the softer organs or for their more

secure enclosure ; and also perform special func-
tions ; as, for example, the auditory ossicles and
the parts of the labyrinth which conduct the
sonorous vibrations. The development of the
bones takes place in two modes : firstly, by the
metamorphosis of genuine cartilage, and secondly,
by that of a soft blastema composed of indiff"erent

Fig. 32. — Six develoiung bone-cells from a rickety bone, as yet sharply defined from the
interstitial substance: a, simple bone-cells; b, compound ones running to a parent cell, with
two secondary cells; c, such arising from three cells. — Magnified 350 diameters.

bundles of the collagenous substance. But it is their outer portion only, that therefore
which corresponds with the matrix of cartilage, which becomes thus changed — the elastic
element being developed as before, not from separate cells, but by the chemical metamor-
phosis of the matrix immediately around the cavity which contains the -'nucleus," and in
various other directions.

That the pseudo-fibrillated portion of the connective tissue corresponds with the matrix
of the cartilages is then, we think, certain. Whether with Remak we are to regard both
these as cell-walls, or with Reichert as intercellular substances, must be discussed hereafter.
(See General Appendix.) — Trs.]

TISSUES, ORGANS, AND SYSTEMS. 101

cells and of a fibrous substance similar to connective tissue. In both
cases it is the cells — in the one the cartilage cells, in the other, cells
Avithout any defined character — which form the lacunce and canaliculi
by the thickening of their walls, with a contemporaneous development
of pore canals, which subsequently grow into the matrix and unite with
one another; whilst the matrix of the cartilage and the fibrous sub-
stance harden into the matrix of the bone by the deposition of calca-
reous salts, which likewise infiltrate the thickened cell-walls. The
nutrition of the bones is very energetic, and is efiected by the vessels of
the investing periosteum, and, if they be present, by those of the
medulla and the Haversian canals also. The bones have a great capa-
city of regeneration, and readily unite ; in fact, very great losses of
substance are repaired, or even whole bones, if the periosteum be left :
adventitious development of bone is also very common.

The osseous tissue is found, firstly, in the bones of the skeleton, to
which also the auditory ossicles and the hyoid bone belong ; secondly,
in the bones of the muscular system, as the sesamoid bones and the
ossifications of tendons ; thirdly, in the subsfantia osteoidea, or tooth
cement. Many cartilages ossify with tolerable regularity as they grow
older ; as the costal-cartilages, and those of the larynx.

Dentine may be regarded as a modification of osseous substance,
which, instead of solitary lacunce, presents long canals, — the dental
canals ; besides which, it exhibits some chemical modifications. The
development of the dentine leads to the conclusion that it is an osseous
structure, whose cells, in the course of their ossification and thickening,
become united into tubes, and have very little or no intermediate sub-
stance ; a view which gains additional support from the numerous transi-
tional forms, to be observed in animals, between typical dentine and
osseous tissue.

In the Vertebrata, bone is found more extensively distributed than in
man. It exists in the skin (Armadillo, Tortoises, Lizards, Fishes), in
the heart (the cardiac bone of the Ruminants and Pachydermata), in
the muscular system (diaphragmatic bone of the Camel, Lama, and
Porcupine, ossified tendons of birds), in the eye (sclerotic ring of Birds,
Chelonians, and Saurians, bony scales of the sclerotic of many Fishes),
in the external portion of the nose (proboscis of the Pig and Mole, os
prcenasale of the Sloth), in the tongue {os entoglossum of Fishes and
Birds), in the respiratory organs (laryngeal, tracheal, and bronchial
bones of many Birds), in the sexual organs [penis-hone of Mammalia),
in the osseous system [ossa sterno-costalia of birds and some mammals).
In the Invertebrata true bones are never found, baing, in them, replaced
by the so-called calcareous skeletons, which principally consist of car-

102 GENERAL ANATOMY OF THE TISSUES.

bonate of lime, and arise in different structures as incrustations of homo-
geneous tissues and of cellular parenchymata, as solidifying excretions of
calcareous matter, or as deposits of calcareous concretions. The teeth
are limited to the three well-known classes of vertebrata. In the
Plf^iostomata, structures precisely similar to the teeth occur as cuta-
neous spines.

Literature. — Deutsch, " De penitiori ossium structura Observationes,"
Diss. Vrat.j 1834 ; Miescher, " De inflammatione ossium eorumque ana-
tome generali." Accedunt observat. auct. J. Mliller, Berol., 1836 ;
Schwann, article " Knochengewebe," in " Berl. encyclop. Worterbuch
der med. Wiss.," Bd. xx. p. 102; Tomes, article Osseous Tissue, in
"Cyclop, of Anatomy," vol. iii.*

§ 26. Structure of the Smooth Muscles. — The smooth muscles consist
essentially of microscopic, usually fusiform, more rarely shorter and
broader fibres, to which I have given the name of "contractile or mus-
cular fibre-cells." Each of these elements, in the mean from 0-02-
0*04 of a line long, 0'002-0-003 of a line broad, is an elongated cell,
wherein, however, no difference between contents and membrane can be
distinguished ; but which consists of an apparently homogeneous, often
finely granulated or slightly striated, soft substance, in which without
exception in the middle of the fibre a generally columnar elongated
nucleus exists. These fibre-cells are united by means of a substance
which cannot be directly demonstrated, into flattened or rounded cords,
the bundles of the smooth muscles ; which are then united, by delicate
investments of connective tissue with fine elastic fibres (a kind of -peri-
mysium)., into more considerable masses, in which numerous vessels and
a relatively small number of nerves are distributed. Chemically, the
principal constituent of smooth muscle is a nitrogenous substance similar
to fibrin, the so-called muscular fibrin or syntonin (Lehmann), which,
from the observations that have hitherto been made, is distinguished
from blood fibrin only in this, that it is not dissolved by solution of
nitre, nor by carbonate of potass, but very easily by dilute hydrochloric
acid.

* [While perfectly agreeing with Professor KoUiker's general view of the relations between
dentine and hone^ namely, that the canals in the former represent the cavities and canaliculi
which exist in the latter structure, we do not think that liis statement of the mode in which
the process of calcification of the dentine takes place is correct. So far as we have seen,
the dentine is never developed by the immediate ossification of cells, nor do the latter take
any direct share in its formation. [See Quarterly Journal of Micros. Sc, April, 1852.) It
may be said that dentine is bone, in which, in consequence of the early disappearance of the
" nuclei" from the ossifying blastema, the lacuna are not formed, the dentinal tubes present-
ing only the canalicidi. — Trs.]

TISSUES, ORGANS, AND SYSTEMS. 103

The pliysiological importance of the smootli muscles lies in their con-
tractile power; in consequence of which they afford
considerable assistance to the functions of the diff'er- ^"'s-^^- ^'''^■'^^■

ent viscera. The development of their elements takes
place simply by the elongation of rounded cells, the
membranes and contents uniting into a homogeneous
soft substance. The nutrition of the smooth muscles
Avould seem to go on very actively, according to the
later investigations upon the fluid wliich bathes them,
•which, according to Lehmann, has most generally a
distinctly acid reaction, and together with lactic,
acetic, and butyric acid, contains ereatin and inosit ;
and the same conclusion may be deduced from the fre- |
quent occurrence of physiological (in the uterus) and ^|
pathological hypertrophies and atrophies of them.
Whether smooth muscles are regenerated, or whether
loss of their substance is replaced by a similar tissue,
is unknown ; on the other hand, new formations of
them appear to occur in uterine tumors.

The smooth muscular fibres never form large iso- §i
lated muscles in the human body ; as, for example,
is the case in the genito-rectal muscles of mammalia, 1
but exist either scattered in the connective tissue, or
in the form of muscular membranes. In both cases
the bundles are either parallel or interwoven into net-
works. Their distribution is as follows : —

1. In the Intestinal canal the smooth muscle
forms : first, the tunica musculosa from the lower
half of the oesophagus, where sraoth bundles are still
mingled with transversely striated fibres, as far as
the sphincter ani internus : secondly, the muscular layers of the mucous
membrane, from the oesophagus to the anus: and thirdly, scattered mus-
cular bunjdles in the villi.

2. In the Respiratory organs, a layer of smooth muscles appears in
the posterior wall of the trachea, and accompanies the hro7ichice, even
to their finest ramifications, as a complete circularly fibrous membrane.

3. In the Salivary glands, this tissue is found solely in Wharton's
duct ; and here only scantily, and forming an incomplete coat.

4. The Liver has a perfect muscular layer in the gall-bladder, and
scattered smooth muscles also in the ductus choledochus.

5. The Spleen has this kind of muscle in many animals in its outer

Fig. 33. — INIuscular fibre-cell from the small intestine of man.

Fig. 34. — Muscular fibre-cell from the fibrous investment of the spleen of the dog ; magni-
fied 35U diam.

104 GENERAL ANATOMY OF THE TISSUES.

coat, and in the traheculce, mixed with connective tissue and elastic
fibres.

6. In the Urinary organs the smooth muscles are found in the
calices and pelves of the kidneys, form a complete muscular layer in
the ureters and urinary bladder, but are only sparingly to be found in
the urethra.*

7. The Female sexual organs possess smooth muscles in the oviducts,
the uterus, where during pregnancy their elements become excessively
developed, and attain a length of ^ of a line, the vagina, the corpora
cavernosa, and in the broad ligaments of the uterus in different places.

8. In the 3Iale sexual organs they are found in the dartos, between
the t. vaginalis communis and propria, in the vas deferens, vesiculse
seminales, the prostate, around Cowper's glands, and in the corpora
cavernosa penis.

9. In the Vascular system smooth muscles exist in the tunica media
of all, especially of the smaller arteries ; also in that of most veins,
and of the lymphatics, with the exception of the finest ; furthermore,
in the lymphatic glands (Heyfelder) ; and lastly in the tunica adventitia
of many veins. The elements, in vessels of middle dimensions, are
everywhere fusiform fibre-cells ; in the large arteries, on the other
hand, shorter plates, which often resemble certain forms of pavement
epithelium ; and in the smallest arteries they are more elongated, or
even round cells, forms which must be considered as less developed.

10. In the Eye, smooth muscles form the sphincter and dilator pu-
pilloi and the tensor clioroidece.

11. In the ^kin, lastly, this tissue appears besides in the dartos,
in the form of minute muscles upon the hair sacs, in the areola, and
in the nipple, and in many of the sudoriparous and sebaceous follicles. f

The elements of the smooth muscles were formerly universally re-
garded as elongated bands containing many nuclei, which were sup-
posed to be developed by the coalescence of numerous mutually applied
cells. In 1847 I showed that this is not the case ; that, on ^the other
hand, the elements of these muscles are only modified simple cells ; and
at the same time I demonstrated, that these contractile fibre-cells occur
wherever contractile connective tissue had previously been assumed to

* [Mr. Hancock (On tlie Anatomy and Physiology of tlie Jlale Urethra, London, 1852),
wlio had made out the existence of the organic muscular layer in the urethra indepen-
dently, attributes to it much more anatomical and physiological importance. (See below,
§ Urinary Organs.) — Trs.]

t [These muscles have also been seen by Mr. Lister (Quart. Journal of Microscop.
Science, vol. i. p. 203), in the scalp. Mr. Lister found the muscles in this situation smaller
(ir^jth of an inch) than those measured by Kolliker. They possessed extremely distinct
nuclei, but instead of uniting in flat bundles were often circular, sometimes elliptical or
polygonal. — DaC]

TISSUES, ORGANS, AND SYSTEMS. 105

exist, and also, that they are to be found in many localities in uhich
their presence had not been suspected. These views, notwithstanding
contradiction at first from certain quarters, are now universally con-
firmed ; a result to which lleichert, by the discovery of a reagent, which
readily enables even those who are less practised, easily to isolate the con-
tractile fibre-cells, viz. : nitric and hydrochloric acids of 20 per cent.
(MUller, "Archiv," 1849, and Paulsen, " Obs. Microchem.," 1849) ;
and Lehmann, by his chemical investigations upon this tissue, have
contributed their share. Contractile fibre-cells occur in all four classes
of the Vertebrata, but appear to be wholly wanting in the Invertebrata,
since the smooth fibres of these creatures, which have been thought to
be such, are allied genetically to the transversely striated muscles of the
higher animals.

Their occurrence in the Vertebrata is in some respects peculiar,
and I will here mention the following localities in which they are found :
In the skin of Birds, as the muscles of the quill-feathers — in this case
with tendons of elastic tissue; in that of the Orang-outang, in the hair-
sacs, as in man; in the iris of the Amphibia; in the campanula Hal-
leri of the osseous Fishes (Leydig); in the swimming bladder of Fishes;
in the lungs of the Frog (in Triton they are here wanting) ; in the me-
sentery of the Plagiostomata, or Psanimosaurus and Leposternon (Ley-
dig u. Brlicke) ; in the genito-rectal muscle of Mammals. In the giz-
zard of birds these muscles are of a bright red color, and are united
with a tendinous membrane.

Literature. — Kblliker, "Ueber den Bau und die Verbreitung der
glatten Muskeln.," in the "Mittheilungen der Naturf. Gesellschaft in
Zurich," 1847, p. 18, and " Zeitschrift fiir wiss. Zool.," Bd. I. 1849;
C. R. Walther, " NonnuUa de musculis liBvibus.," Diss. Lips. 1851.*
[Jos. Lister, " Observations on the Contractile Tissue of the Iris,"
Quart. Journ. Mic. Sc, vol. I. p. 8, PI. i., and " Observations on the
Muscular Tissue of the Skin," Quart. Journ. Mic. Sc. vol. I. p. 263. —
DaC]

* [Reichert (Bericlit, 1849, Muller, " Archiv.,") states that, according to Paulsen, the action
of a solution of caustic potass of 50 per cent, causes the smooth muscles to become wavy,
and thus to assume a transversely striated appearance under the microscope. Macerated
in such a solution for three days, they break up into small globules; striated muscle behaves
in a similar manner, and the globules correspond in size to the interval between two strite.

Eyiandt (Obs. Microscop. de musculis organicis in hominis cute obviis. Diss, inaug., Dorp.
1850, c. Tab. lithog.), denies the existence oC free smooth muscles in \he papilla and areola
mamma', in the scrotum, in the skin of the penis or of the prepuce, and in the pcrinaum. Nor does
he find them in the outer layers of the hair-sacs (apart from the arrectores pili), in the glan-
dules sudoriferee of the axilla, of the anus, Sec, nor in the glandidce ceruminosa. The smooth
muscles observed in the papilla and areola mamma, in the skin of the penis, and the peri-
Daeum, he considers to belong to a greatly developed vascular layer. (See, however, the
remarks of Prof. Kolliker upon Eylandt's statements, at the end of § 34.) — Trs.]

106

GENERAL ANATOMY OF THE TISSUES.

§27. Transversely Striated 3Iuscular Tissue. — The elements of this tis-
sue consist essentially of the so-called muscular fibres or primitive muscu-
lar bundles, each of which, 0-004-0-03 of a line thick, consists of fine
fibrils surrounded by a special homogeneous, delicate, elastic investment,
the sarcolemma : the fibrils are generally enlarged at regular intervals,
so that they appear to consist of a series of many portions, and give a

transversely striated as-
^'s-35. Fig. 36. pgg^ j-Q |.j^g muscular

fibres, or they appear
more even, and then the
primitive bundles pre-
sent a longitudinal stria-
tion. Besides these
fibrils, the muscular
-i fibres contain nothing
but a small quantity of
viscid substance uniting
them, and a certain num-
ber of rounded or elon-
gated cell-nuclei, which
generally lie against
the inner surface of the
sarcolemma. The associ-
ation of the muscular
fibres into muscles and
muscular membranes occurs in such a manner that they either apply
themselves parallel to one another, or are united into true networks of
transversely striated muscles. They then receive an investment of more
delicate or firmer connective tissue, the so-called perimysium, with which
finer elastic fibres and also fat-cells are frequently mingled ; and are,
besides, surrounded by numerous blood-vessels and nerves.

In chemical characters the principal substance of the transversely
striated muscular fibres agrees perfectly with the syntonin referred to in
the previous section. The sarcolemma is very resistant to acids and
alkalies, whilst the nuclei present the common characters of those organs.
A fluid with an acid reaction may be expressed from the muscles, in
which Liebig and Scherer have discovered an interesting series of non-
nitrogenous and nitrogenous products of the decomposition of the mus-
cular tissue.

The transversely striated muscles are in a high degree contractile, and

Fig. 35. — Two muscular fibres of man ; magnified 350 diam. In one the bundle of fibrils,
b, is torn, and the sarcolemma, a, is to be seen as a mere empty tube.

Fig. 36. — Primitive fibrils from a primitive bundle of the Axolotl {Siredon pisciformis) •
a, a small bundle of them ; b, an isolated fibril, magnified GOO diam.

TISSUES, ORGANS, AND SYSTEMS. 107

are the chief instruments of the animal motions. Their elements are
developed by the coalescence of round or stellate cells, Avhose contents
change into a homogeneous, semi-fluid substance, and then break up
into fibrils. Once formed, the muscular fibres grow by the elongation
and thickening of their elements, and in their complete condition they
enjoy a very energetic nutrition, -which is especially manifested by the
multiform products of their decomposition, as well as by the circum-
stance that their powers are exhausted in a short time when the circula-
tion is suspended. Wounds of the muscles never heal by transversely
striated muscular substance ; but an adventitious formation of this tissue
appears to occur sometimes, though rarely.

Transversely striated muscular tissue is found in the following parts:

1. In the muscles of the trunk and extremities ; of the globe of the
eye^ and all those of the ear.

2. In the muscles of many organs ; as the larynx, j^harynx, tongue,
and oesophagus (upper half), the end of the rectum [sphincter cxternus,
levator ani), the genital organs {hulbo-ischio-cavernosus, urethralis trans-
versus, transversi perincei, cremaster, muscular fibres of the round liga-
ments of the uterus, in part).

3. In certain parts of the vascular system, e. g. in the heart and in
the walls of the great veins which open into it.

The muscular fibres of animals are not all composed of bundles of
transversely striated fibrils, but present a series of other forms, which
may best be grouped in the following manner : —

1. Muscular tubes, with homogeneous, semi-solid, not transversely stri-
ated contents (most Mollusks, Worms, and Radiata).

2. Muscular tubes with a membrane, a semi-fluid, homogeneous, cor-
tical layer in contact with it, and a fluid or granular, frequently trans-
versely striated or nucleated central substance. (Muscles of Petromy-
zon in part, certain muscles [of the lateral line and of the spiracles] of
the plagiostome and osseous Fishes. Muscles of the Hirudinidce, Lum-
hricidce, of Paludina in part, and of Carinaria.)

3. Similar muscular tubes with a transversely striated cortical layer
without distinct fibrils. (Many muscular fibrils of the Hirundifiidce, and
of the muscles of Fishes enumerated under 2.)

4. Muscular fibres without any internal cavity, with a sarcolemma
and transversely striated contents, which do not break up into fibrils,
but frequently into discs (Bowman), Salpce, some Radiata, many Arti-
culata.

5. Similar muscular fibres, which readily break up into fibrils. (Most
Vertebrata, certain muscles of Insects.)

6. Simple isolated cells, whose contents are changed into a trans-
versely striated substance, which either fills the whole cell or forms only
a thin layer upon its membrane. Here my observations lead me to place

108 GENEKAL ANATOMY OF THE TISSUES.

the peculiar cartilaginous striae, which Purkinje (Mikr. neurol. Beobach-
tungen, in Mull. "Arch.," 1845) found in the endocardium of Ruminants.
They consist of large polygonal cells with beautiful nuclei, which in-
ternally, but as it seems only upon their wall, contain a transversely
striated substance, which is not distinguishable from that in the muscular
fibres.

All these forms are readily comprehended, if the genesis of the true
transversely striated muscular fibres in the higher vertebrata be properly
understood (see the special part, Muscles) ; and I cannot agree with the
supposition of Stannius (Gott. Nachr., 1851, p. 17), that the transversely
striated muscular fibrils are developed according to many essentially
different types. Even the gap wliich lias hitherto separated the smooth
from the transversely striated muscles becomes less, when we remember
that the so-called transversely striated muscular fibrils may also have
homogeneous non-striated contents, and also that even when transversely
striated they may appear as isolated cells."^

Muscular fibres of the same description as the transversely striated
muscles, and in part actually striated, are very widely distributed. In
the Vertebrata such muscles are found in the oesophagus of some Mam-
malia and of the plagiostome fishes, in the intestine of Tiyica chrysitis,
in the stomach of Cohitis fossilis, around the poison gland of Snakes,
and in the contractile organ of the pharynx of the Carp ; in the skin of
Mammalia, Birds, Snakes, and tailless Batrachians (so called cutaneous
muscles), in the tactile hairs of mammals, in the lymph hearts of many Birds
and Amphibia ; in the auriculo-ventricular valve of the right side in Birds,
and the Oriiithorhynchus ; upon the vena cava inferior of the Seal,
close above the diaphragm : in the interior of the eye of Birds ; and round
Cowper's and the anal glands of mammals. In the Invertebrata, as we
have mentioned, all the muscles belong to this category^ whether they
be transversely striated or not ; and they are found, therefore, in the
heart, the intestine, the gejiitalia, and often clearly striated.

The anastomosis of the primitive bundles of the muscles, with which
Leeuwenhoek was already acquaintedf and which I rediscovered in the
heart of the frog, has now been seen in many places, and appears to be
constant in the hearts of the lymph and blood-vascular systems of all
animals, and in the muscles of the Invertebrata, especially those of the
vegetative and generative organs. (Hessling, Leydig.) Simple arbores-

* [The muscles of the Medusae consist of flat, fusiform bands, whose ends are interlaced
like those of smooth muscle, but which present the most distinct transverse strice. — Trs.]

f [It has been pointed out to us by Professor Sharpey, that Leeuwenhoek was not
acquainted with the anastomosis of the primary bundles of the cardiac muscles, but has
described and figured only that of the secondary bundles, which is indeed obvious upon
reference to Leeuwenhoek's Plate (" Experimenta et Contemplationes," Op. Om. Lugd.Bat.
torn. i. p. 409, 1722) ; the ascription in the text is therefore an error. For other remarks upon
the muscular tissue, vide infra, § Muscle. — Trs.]

TISSUES, ORGANS, AND SYSTEMS. 109

cent branchings of muscular fibres, which Corti and I noticed in the
tongue of the frog, are on tlie other hand rare, and have been seen else-
where only in Artemia salina and in the oral and anal disc of Piscicola
(Ley dig).*

Literature. — W. Bowman, article Muscle and Muscular Motion, in
Todd's " CyclopDsdia of Anatomy," and " On the Minute Structure of
Voluntary Muscle," in " Phil. Trans.," 1840 II. 1841, I. ; J. Hoist, " De
Structurii Musculorum in genere et annulatorum Musculis in Specie,"
Dorp. 1846; M. Barry, "Neue Unters. iiber die schraubenformige Be-
schaifcnheit der Elementarfasern d. Muskeln, nebst Beobachtungen liber
die musculos. Natur d. Flimraerharchen" (Miill. "Arch.," 1850, p. 529).

§ 28. Nervous tissue. — The essential elements of this tissue are of
two kinds, the nerve-fibres and nerve-cells {ganglion-globules). The pri-
mitive fibres or tubules of the nerves have either a distinct medulla or
they have none. The former consist of three parts : of a structureless
delicate membrane, the sheath of the primitive tubules ; of a central,
soft, but elastic fibre, the central or axis band {axis cylinder, Purkinje ;
'primitive band of Remak) ; and of a viscid white layer placed between
them, the medullary sheath. In the tubules without medulla, which in
man occur only in certain peripheral expansions (retina, olfactory organ,
cornea. Pacinian corpuscles), the structureless coat contains nothing but
a homogeneous or finely-granulai-, clear substance, which appears to be
identical with the central band of the other tubules, and at any rate
may be considered analogous to it, so that the medullary layer may be
supposed to be absent in these. The primitive nerve-tubules of both
kinds, especially of the former, occur of very different dimensions, and
may thence be divided into fine ones of 0-0005-0-002 of a line, those of
a medium size of 0-002-0-004, and thick ones of 0-004-0-01 of a line.
Their course is either isolated, so that one tubule runs from the centre to
the periphery; or they divide, especially in their terminal expansions,
into a greater or smaller number of branches; or, lastly, they form
actual anastomoses and networks. Besides this, many nerve-tubules are
connected with nerve-cells, so that they either arise from them or are
interrupted in their course by interposed nerve-cells. These nerve-cells,
or as they are called in the ganglia, ganglion-cells, ov ganglion-globules,
are endowed with the common attributes of cells. Their membrane
presents no peculiarity, except that, frequently, it is very delicate, and
even, as in the great central masses, eventually perhaps wholly disap-
pears. The contents are finely-granulated, semi-solid, often contain

* [Such branched muscular fibres may be found beautifully marked in the upper lip of the
Rat, and in tlie tongue oiMan and Animals. See article " Tongue," by Dr. Hyde Salter, in
Todd's "Clycopaidia."— Tks.]

110

GENERAL ANATOMY OF THE TISSUES.

pigment, and without exception enclose a distinct vesicular nucleus with
a large nucleolus. In size, the nerve-cells vary from 0'003-0-04 of a
line, and as regards their form, they may be distinguished principally

Fig. 37.

Fig. oS

a..J,

into round, fusiform, and stellate. The
two latter kinds are produced by the
prolongation of many nerve-cells into
two, three, to eight and more, pro-
cesses, which in some cases, after a short course, pass into medullated
nerve-fibres, in others, present a more marked independence, since,
preserving a complete resemblance to non-medullated nerves, they
often run for a considerable distance, and branch out in manifold ways.
In what manner finally these processes end, whether free or in con-
nection with nerve-tubules or by anastomosis with similar processes, is
not yet made out ; though, upon the whole, it would seem to be not im-
probable that all three possibilities may occur in different localities.

Nerve-fibres and nerve-cells are combined into two substances, which in
extreme cases present very wide differences, the gray and the white sub-
stances. The former constitutes the so-called white medulla or medullary
substance of the spinal cord and brain, and the nerves ; it consists essen-
tially of nerve tubules, united into bundles or interwoven into plexuses,
with bloodvessels ; added to which, in the peripheral nerves, we have

Fig. 37. Tubular nerve-fibres of man. Four of them fine, two of tliem being varicose,

one of a medium thickness with a simple contour, and four thick ones; two having double
contours, and two with granular contents. — Magnified 350 diameters.

Fig. 3S. — Nerve-cell of the Pike (so-called bipolar), passing at its two ends into dark-bor-
dered nervous tubules, treated with arsenious acid: «, membrane of the cell; fc, nerve-
sheaths- c medulla of the nerve; d, axis-fibres connected with the contents of the nerve-
cell; e, retracted from the membrane. — Magnified 300 diameters.

TISSUES, ORGANS, AND SYSTEMS.

Ill

special investments of connective tissue, the so-called neurilernma. The
grot/ substaiwe contains a great preponderance of nerve-cells, besides
Avhich, in certain localities, there is a finely-granular matrix and free
nuclei; but it is rarely found quite unmixed, being usually mingled more

Fig. 30.

or less with nerve-fibres. This is more especially the case in most gan-
glia, in the gray substance of the spinal cord, and in the so-called gan-
glia of the cerebrum ; -while, on the other hand, in the gray cortex of
the cerebrum and cerebellum, it is found in some localities almost with-
out nervous fibres. This substance possesses vessels even in much
greater abundance than the white; and in the peripheral ganglia there
are also different forms of connective tissue, which serve to invest their
separate parts.

The chemical composition of the nervous substance has hitherto, by
no means, been sufficiently investigated. In the white substance, the
central bands of the nerve-tubules consist of a protein compound very
similar to the fibrin of the muscles ; the medullary sheath, chiefly of fats
of different kinds, and the membrane, of a substance similar to the sar-
colemma. The gray substance contains a preponderance of albuminous
matter, besides a considerable quantity of fat.

The physiological importance of the nervous tissue consists, in the
first place, in its subserving movement and sensation ; secondly, in its

Fig. 30. — Nerve-cells of the substantia ferntginca from the floor of the fourth ventricle in
man ; magnified 350 diameters.

112 GENERAL ANATOMY OF THE TISSUES.

exerting a certain influence upon the vegetative functions ; and thirdly,
in its serving as a substratum to the psychical activities ; in all which
capacities, according to what we know at present, the gray substance
performs the more important part, the white acting rather as a con-
necting conductor between _ it and the organs. The nerve-cells are
developed from the common formative cells of the embryo, whilst
the nervous tubules proceed from the coalescence of the membrane
and contents of many such cells, of a rounded, fusiform, or stellate
shape; with this, in the medullary tubules a peculiar modification of the
contents occurs, in consequence of which it is divided into a central
solid filament and a softer investment. The nutrition in the nervous
tissue must be very active, especially in the gray substance, as the great
quantity of blood which flows into it clearly shows, but the products of
its decomposition are wholly unknown. The white nervous substance is
regenerated pretty readily in the peripheral nerves, and as it would
seem, in the spinal cord also. The adventitious formation of nervous
tubules has been observed in pathological, new formations, and according
to Virchow's observations, It would even appear that an abnormal de-
velopment of gray substance may occur.

The organs composed of nervous substance are : the peripheral nerve-
bords, nerve-membranes and nerve-tubules, the ganglia, the spinal cord,
and the brain.

Medullated nerve-fibres are found only in the Vertebrata, and even
in that class not In every division, as for example. In Petromyzon (Stan-
nius). Fibres without medulla always occur together with the former,
and in general in the same localities as In man ; but in other situations
also, as in the skin of the Mammalia, in the electric organs of Fishes,
and in the sympathetic nerve of the Plagiostomata (Leydig). Where
nerves are found in the Invertebrata, they contain only pale fibres with-
out medulla, whose structure often completely resembles that of the
embryonic fibres of higher animals, especially as regards the occurrence
of great nucleated enlargements in the terminal expansions, which re-
mains of the original formative cells, have, recently, less properly been
considered to be ganglion-globules.

Literature. — G. Valentin, " On the course and termination of the
nerves," in the "Nov. Act. Natur. Curios.," vol. xvili. t. I. ; R. Remak,
" Observations anatomlcaj et microscop. de syst. nerv. struct.," Berol.,
1838; A. Hannover, "Recherches microscopiques sur le systeme ner-
veux," Copenhague, 1844 ; R. Wagner, " Neue Unters. liber den Bau und
die Endigungen der Nerven und die Structur der Ganglion," Leipzig,
1847; and "Neurologlsche Untersuchungen," in Gottingen "Anzelge,"
1850 ; Bidder and Reichert, " Zur Lehre vom Verhiiltniss der Gangllen-
korperzuden Nervenfasern," Leipzig, 1847; Ch. Robin, in "I'lnstltut.,"

TISSUES, ORGANS, AND SYSTEMS.

113

1846, Nos. G87-699, and 1848, No. 733 ; Kcilliker, " Neurologische
Bemcrkungcn," in " Zcitsch. fur Aviss. Zool.," i. p. 185.

§29. True Glandular Tissue. — The most essential constituents of the
true glands arc the secreting elements., which appear as aggregations of
cells, as closed glandular vesicles, and as open glandular vesicles and
glandular tubes, containing as their most important constituent the so-
called gland-cells. These cells are for the most part polygonal or cylin-
drical, and perfectly resemble certain epithelial cells, but upon the other
hand, they are frequently distinguished and characterized by peculiar
contents. The union of these cells into the secreting parts of the glands
is efiected either directly or with the co-operation of homogeneous mem-
branes, the so-called memhrance propria;, and of connective tissue. In
this manner the secreting glandular elements, different in nature accord-
ing to the different glands, are formed ; and becoming invested with
vessels, nerves, and connective tissue, with which elastic fibres, fat-
cells, and even muscles, are mingled, they are combined into the larger
and smaller divisions of the glands. The principal forms of the secret-
ing glandular elements in man are the following : —

1. Solid networks of cells without investing membrane. In the liver
(Fig. 40).

2, Closed vesicles with a fibrous membrane and epithelium. Graafian
vesicles, mucous follicles (so-called ovula Nabotld), in the cervix uteri.

FiR. 40.

Fix. 41.

3. Rounded or elongated glandular vesicles, ivith a meynbrana propria
and an epithelium. In the racemose glands (Fig. 41).

Fig. 40. — Network of hepatic cells, b ; and finest ductus inlerlobulares, a ; of man after
nature; the union of both diagrammatic; c, vascular spaces. — Magnified 350 diameters.

Fig. 41. — Two of the smallest lobes of the lung, a a ; with air-cells, b b ; and the finest
bronchial ramifications, cc; upon which also air-cells are seated. From a new-born chiUl ;
semi-diagrammatic figure. — Magnified 25 diameters.

S

114

GENERAL ANATOMY OF THE TISSUES.

4. Glandular tubes, ivitli a memhrana propria, or a fibrous membrane
and an epithelium. Tubular glands (Fig. 42).

To these elements are also added (except in those glands enumerated
under 2, which become emptied of their contents bj the occasional
bursting of their follicles, and the simplest tubular glands) special excre-
tory ducts, which, after manifold ramifications either pass directly into
the glandular vesicles and glandular tubes, or, as in the liver, are simply
applied to the secreting networks of cells. These ducts are at first
similar in their structure to the secreting parts, but they always possess
epithelial cells, which have not the specific contents of the proper gland
cells, and mostly also exhibit a different form. The wider excretory
ducts consist of a fibrous investment and of an epithelium, and often
also, possess a muscular layer, and in their ultimate divisions, a fibrous,
a muscular, and a mucous layer very frequently exist as special struc-
tures.

Chemically, the glands are, as yet, little known. The glandular
cells, the most important structures, are allied in this respect also to the
epithelial structures, only that frequently, they contain in their interior
peculiar substances, — as fat, the constituents of the bile, of the urine, of
the gastric juice, mucus, &c., and thence assume a specific character.

The true glands either separate certain constituents
from the blood, or by means of it, elaborate peculiar
substances of structural elements, and according: as
they do the one or the other, is the import of their
separate parts different. In the former glands the
cells play a more subordinate part, and are at most
of importance, so far merely, as they impede the
passage of this or that constituent of the blood, and
allow only certain of them to pass (kidneys, lachrymal
glands, small sudoriparous glands, lungs) ; whilst in
others, the cells take a very important share in the
formation of the glandular fluid, by producing within
them the specific secretion, which then either drains
out of them (liver, mucous glands, gastric glands, pro-
state, Cowper's glands, salivary glands, pancreas), or be-
comes free by the gradual dissolution and breaking up of
the cells themselves (lacteal glands, fat glands, testis,
larger sudoriparous and ceruminous glands). In the for-
mer case, as in the Graafian follicles, a peculiar cell-
development may take place in the secretion which is
formed, whilst in the latter, new elements continually arise in place of
those gland-cells which are removed as they attain their full develop-

FiG. 42. — Gastric gland from the pylorus of the do<f, with cylinder-epithelium : a, larger
glandular cavity ; 6, tubular ajipendages of it.

Fig. 42.

^%

■'^

TISSUES, ORGANS, AND SYSTEMS. 11

r

ment, in consequence of which the character of these cells as a coating
of the glandular canals is frequently lost, and they appear simply as
a part of the secretion (testis, lacteal gland during lactation). All the
glands here mentioned, Avith the exception of the sexual, are developed
from the internal and external epithelial structures of the body, con-
joined Avith the vascular membranes which support these epithelia.
Some of them originate as involutions of these membranes, and retain
the cavities throughout the course of their development (lungs, small
intestinal glands), others are at first hollow, but afterwards increase by
the addition of solid out-growths (liver) ; others, again, are solid from
the very first, continue to grow in this condition, and only secondarily
come to possess cavities (cutaneous glands, racemose glands). The
nutrition of the glands goes on with great energy, and they belong to
the most vascular organs of the body. Except in the uterine glands
no regeneration of the glandular substance takes place, but hypertrophy
occurs in them, and even the accidental formation of minute glands.

The true glands of the human body may, according to the form of
their ultimate elements, above described, be divided as follows : —

1. Glands witli closed glandular vesicles, which dehisce periodically.
Ovary, follicles of the uterus.

2. Crlands whose 'parenchyma consists of cells united into a netioorh.
Liver.

3. Racemose glands, in which rounded and elongated glandular
vesicles are seated upon the ultimate ends of the excretory ducts.

a. Simple, w'ith one or few glandular lobules. Mucous glands, seba-
ceous glands, Meibomian glands.

h. Composite, with many glandular lobules. Lachrymal glands, sali-
vary glands, pancreas, prostate, Cowper's and Bartholini's glands, lac-
teal glands, lungs.

4. Tubular glands, whose secreting elements have the form of
canals.

a. Simple, consisting of only one or a few c^cal tubes. Tubular
glands of the stomach and intestine, uterine glands, sudoriparous and
ceruminous glands.

h. Composite, with many branched glandular canals, which may also
be united into a network. Testis, kidney.

The forms of the glands of animals, notwithstanding their variety,
may, with few exceptions, be brought under one of the four categories
here established. The following are worthy of particular notice : 1.
The glandular cells, with peculiar excretory ducts, to be found in some
Articulata, which either, singly, form glands, or are united together
in numbers by a memhrana propria. 2. The occurrence of a structure-
less, chitinous memhrana intima in many glands of the Articulata. 3.

116 GENERAL ANATOMY OF THE TISSUES.

The formation of certain secretions {^TJric acid and hilin in Mollusks,
hilin in Crustacea] within special spontaneously enlarging " secreting
vesicles," (Nageli, H. Meckel), which may be compared to the yelk
vesicles (§ 6). 4. The colossal size (up to 0*1 of a line) of many glan-
dular cells of Insects, and the peculiar ramifications of their nuclei.

Literature. — J. Muller, " De Glandularum secernentium structura,
penitiori," Lips. 1830; H. Meckel, " Micrographie einiger Driisenappa-
rate niederer Thiere," in Miill. "Arch.," 1846 ; Fr. Leydig's " Verglei-
chend-anatomische Abhandlungen," in "Zeitschrift fiir wiss. Zool."

§ 30. Tissue of tlte Blood-vascular Cflands. — Under this denomination
are most appropriately comprised, a series of organs, which agree in this,
that in a peculiar glandular structure, they elaborate from the blood or
other juices certain substances which arc not excreted by special, per-
manent, or periodically-formed excretory ducts, but simply by infiltra-
tion from the tissue, and are afterwards applied in one way or another
to the general purposes of the organism.

It may be, that this wide definition includes organs, which it will be
necessary to separate in future ; but with our present slight knowledge
of these structures, it is the only one which is possible without entering
more fully into the subject.

The essential glandular tissue of the organs in question appears under
the following forms : —

1. As a parenchyma of larger and smaller cells, imbedded in a stroma
of connective tissue. Supra-renal bodies, anterior lobes of the hypo-
physis cerebri. Some of the cells here attain the great size of 0*04 of
a line; and then contain, together with a granular substance, many
nuclei, and perhaps secondary cells.

2. As closed follicles, each of which consists of a memhrana propria
with an epithelium upon its inner side, and has clear contents: thyroidea.
The follicles, which are not enlarged cells, are surrounded by a large
quantity of connective tissue, and are united by it into smaller and
larger lobules.

3. As closed follicles, with a membrane of connective tissue, and con-
tents consisting of nuclei, cells and some fluid. Among these I enume-
rate—

a. The solitary follicles of the stomach and intestine ; and
h. The aggregated follicles of the small intestine, or Peyer's patches
(in animals those of the stomach and large intestine also), both of which
contain numerous bloodvessels in the interior of the follicles.

c. The follicular glands in the root of the tongue, the tonsils, and
the pharyngeal follicles, which in the walls of their sacs, contain many

TISSUES, ORGANS, AND SYSTEMS.

117

closed follicles like those above mentioned, but, so far as v;e as yet
know, without vessels in their interior.

Fis. 43.

Fipr. 44.

,/

d. Tlie lymphatic glands, which appear to consist of follicles like
those of the Peyerian patches.

4. As a cellulai' parenchyma, which contains numerous closed follicles
like those just described : Spleen.

5. As racemose, aggregated, glandular vesicles opening into a common
closed canal or broad space, whose thick walls are formed of a delicate
investment of connective tissue, and of a soft substance consisting of
many nuclei and of vessels : Thymus.

We know little of the chemical nature of these organs, which are all
more or less richly supplied Avith bloodvessels. Those enumerated
under 1, 2, 3, and 5, contain much protein and fat in their tissue, as
also do the follicles of those included under the fourth form, while the
remaining parenchyma of the spleen possesses peculiar corpuscles, not
yet completely investigated, which seem to indicate an energetic, retro-
gressive metamorphosis. We know little of the physiological functions
of these glands ; and here it need merely be remarked, that in the
spleen, the thyroid, the thymus, the supra-renal capsules, and the pitui-
tary body, it can only be the blood which yields material to them, and
only the blood- and lymph-vessels which again receive the substances
given off externally or internally (thymus) by them. In the follicular
glands of the mouth and pharynx, the secretions are poured into the
wider cavities of the glands, and ultimately into those organs, Avhilst in

Fig. 43. — A few of the glandular vesicles from the thyroid gland of a child: a, connective
tissue between them; 6, membrane of the glandular vesicles; c, their epithelium — Magni-
fied 250 diameters.

Fig. 44. — A Malpighian corpuscle from the spleen of the ox : a, wall of the corpuscle ; b,
contents ; c, wall of the artery upon which it is seated ; (/, sheath of the latter. — Magnified
150 diameters.

118 GENERAL ANATOMY OF THE TISSUES.

the intestinal follicles, it is doubtful whether they excrete substances
into the intestine, or receive them from thence to give them up again to
the vessels. In the lymphatic glands, the ducts supply the glandular
follicles with matters which they take up again when further elaborated.

The development of the blood-vascular glands is still very obscure ;
although this much appears certain, that most of them are developed
without the participation of the intestinal epithelium, either from the
fibrous wall of the intestine or from the same blastema as that which
produces the sexual glands. The thymus and thyroid alone are to be
regarded, according to Remak, as diverticula of the intestinal canal.

The nutrition of most of these glandular structures is very energetic,
as the abundance of the blood they contain and their frequent morbid
alterations show: the hypophysis cerebri and the supra-renal capsules
alone, in this respect, occupy a lower grade.

Literature. — A. Ecker, art. "Blood-vascular Glands," in "Wagner's
Handw. d. Phys.," Bd. IV. 1849. [H. Gray, " On the Development of
the Ductless Glands in the Chick," Philosoph. Trans., 1852. — Trs.]

SrECIAL HISTOLOGY.

OF THE EXTERNAL INTEGUMENT.

I.— OF THE SKIN IN THE STRICTER SENSE.

Fis. 45.

L-h.

a

--/

/...

.^-' c

A. CUTIS.

§ 31. The external slciyi, Integumentum commune (Fig. 45), consists
essentially of an internal
layer formed principally
of connective tissue, and
rich in vessels and
nerves, the true skin,
cutis, derma (Fig. 45,
c, d) ; and of an external
layer composed of cells
only, the epidermis (Fig.
45, a, h) ; and it contains
in addition many pecu-
liar, glandular and horny
organs.

The cutis may be
again subdivided into
two layers, the subcu-
taneous cellular tissue,
tela cellulosa subcutanea
(Fig. 45, d) ; and the
proper corium (Fig. 45,
c) ; the latter of which, from its rich nervous and vascular supply, forms
the most important part of the skin.

§ 32. The suhcutaneous cellular tissue is a tolerably firm membrane,
constituted chiefly of connective tissue, which in by far the most parts

Fig. 45. — Perpendicular section through the whole skin of the ball of the thumb, trans-
versely through three ridges of the cutis: a, horny layer of the epidermis; 6, its mucous
layer; e, corium : d, pan7iiadus adiposus (upper part) ; e, papillffi of the cutis;/, fat masses; g,
sudoriparous glands; h, their canals; i, sweat-pores. — Magnified 20 diameters.

V

120 SPECIAL HISTOLOGY.

of the body encloses within its meshes a considerable quantity of fat-cells
(Fig. 45,/), thus forming the pajinieul as adiposus ; in some situations,
however, as for example in the scrotum, thepew^s, and the nyinpJice, &c.,
it contains but little or even no fat. The innermost layer of the subcu-
taneous cellular tissue, which upon the trunk and thighs forms a tolera-
bly firm fatless texture, the fascia superficialis, rests upon different
organs, as muscular fascice, j^'^'^'iosteum, and pericliondrium, muscles,
and the deeper accumulations of fat, and is more or less closely united
with them. The union is looser upon the trunk, the two distal divisions
of the limbs, the back of the hand and foot, the neck, and especially on
the eyelids ; the penis, scrotum, and on the extensor side of the articu-
lations, where the subcutaneous mucous bursa;, as they are called, are
frequently situated, as, for instance, in the knee, elbow, and phalangeal
joints. A more close connection sometimes exists — as where tendinous
fibres or processes (aponeurosis palmaris and plantaris, tinea alba), or
muscles (palmaris brevis, levator labii superioris alceque 7iasi, levator
labii superioris, &c.), are inserted into the skin ; sometimes, — as where
the innermost layers of the subcutaneous cellular tissue are blended, as
it were, by means of short, strong, filaments of connective tissue with
the subjacent m\x?,c\e,fascice, tendons, &c., particularly, therefore, on the
head, especially on the alee nasi and lips, the forehead and temples, the
ear, mouth, and occiput; on i\\e glans penis, hexiQn.i\\ the nails, &c. In
general, where the fat forms a thick layer, the skin is less movable than
when from any cause it is less abundant or entirely absent.

The external surface of the subcutaneous cellular tissue, is connected
by means of numerous filamentary processes of connective tissue, with
the cerium, and is not everywhere clearly distinct from it ; but a sepa-
ration between the subcutaneous cellular tissue and the cerium, may be
pretty readily eff'ected, especially when the former contains an abun-
dance of fat, with the exception of certain situations (head, cheeks, chin,
&c.), where the follicles of the larger and more closely set hairs pene-
trate deeply into the panniculus adiposus. The subcutaneous cellular
tissue of i\\Q pienis, scrotum {dartes), &c., passes into the cerium without
any distinct limitation.

The thickness of the subcutaneous cellular tissue varies very con-
siderably, as is well known, according to situation, age, sex, and the
individual. The fatless subcutaneous cellular tissue of the eyelids, and
of the upper and outer part of the ear, measures, according to Krause
^, on the penis ^, on the scrotum f of a line. The panniculus adiposus
is 1 line thick on the cranium, brow, nose, lobe of the ear, neck, dorsum
of the hand and foot, the knee and elbow ; in most other situations it is
2 to 6 lines, though in fat persons it may exceed 1 inch in thickness,
and in thin ones may sink below 1 line.

§ 33. The proper corium is a tough, slightly- elastic membrane, and is

OF THE SKIN.

121

composed principally of connective tissue, ayIucIi in tlic thicker parts
presents two, though not very Avell-dcfined layers, which may be desig-
nated the "reticular" and the " papillary" portions (^j*. reticularis and p.
papillaris). The former constitutes the inner layer of the coriuvi, and
consists of a white, reticulated membrane, frequently distinctly lami-
nated in its deeper portions, and containing in special, narrow or wide
scanty or numerous meshes, the hair follicles and cutaneous glands,
together with much fat. The papillary part of the corium is the reddish-
gray external superficial layer (Fig. 45), which in its dense, firm tissue,
contains the upper portion of the hair-follicles, and cutaneous glands,
and the terminal expansions of the vessels and nerves of the skin. Its
most important element consists in the cutaneous or tactile papillre,
papillce tactiis (Fig. 46) ; small, semi-transparent, flexible, but tolerably
solid elevations of the external surface of the eoriitm, which are ordi-
narily conical or clavate in form, but in certain places present numerous
points (compound papillce). With regard to their number and position,
the papilla; of the bed of the nail, of the palm of the hand, and of
the sole of the foot are very numerous (E. H. Weber enumerates
upon 1 square line of the vola manus, 81 compound or 150 to 200

Fi^'. 4G.

/..

/f

./^

A

/?,

! t-

Fig. 47.

i:i:iSS?miW

smaller puj^uUuj, and disposed with .^ _■,;:>;.- ;^;,,; ^

tolerable regularity in two principal v \ — ■ --^'r^vv -v 'r'

series, each of which has 2 to 5 papillre ; . ' ' :-

in the transverse direction, placed upon . V ^ •

linear elevations, ^^g to J of a line broad, ■'■-■■:j:,: ■-%%■■.:.

^y 20 to ^ of a line high, — the ridges of

the corium. The course of these ridges ,;, v

is visible, even externally in the epidermis, '^ ^

Fig. 4G. — Compound papillte of the surface of the hand, with two, three, and four
points : a, base of a papilla ; b 6, their separate processes ; c c, processes of papilla; whose base
is not visible. — Magnified GO diameters.

Fig. 47. — Horizontal section of the skin of the heel through the apices of the papilla- of one
entire and two half ridges. The serial arrangement of the papillfe corresponding with the
ridges of the cutis, is obvious, a. Horny layer of the epidermis between the ridges, which
from their undulating course are cut through in making a section through the points of the
jiapilhe. b, Stratum Malpighii of the epidermis, c, Papilke which are placed in more than
two rows; since, however, many of them are always seated upon a common base, there are,
so to say, only two rows of compound papilhc present, d, St7-atv?7i Malpighii between the
papilla- belonging to a common base, which, because it has a less thickness here, ajspears
somewhat clearer, c. Sweat canals. — Magnified GO diameters.

122

SPECIAL HISTOLOGY.

and therefore needs no further description. Elsewhere the papiUce are
more irreguhirly scattered, either very close together, as in the labia
minora, the clitoris, the jt>cnis, and the nipple, or somewhat more widely
apart, as upon the extremities, with the exception of the places named,
on the scrotum, the neck, chest, abdomen, and back.

The size of the j^'^P^ce varies considerably ; the shortest (5*5 to 4^,
of a line) occur in the face, especially upon the eyelids, brow, nose,
cheeks, and chin, where they are even wholly wanting, or are replaced by
a network of depressed ridges ; next upon the female breast (g^o to gg),
upon the scrotum, and at the base of the penis (g'g to 4'o of a line). In
most other situations their length is from A to 3^3 of a line. The
longest, [.2^j to 3^0 of a line) exist on the surface of the palm of the
hand, sole of the foot, and the nipple, where they are generally of the
compound kind ; further, the anterior and posterior extremities of the
bed of the nail (y^ to y'o), and the labia minora (50 to yo of a line).
The breadth of the base in most of the papillae about equals or is some-
what less than the length ; in a few, as in those of the scrotum, prepuce,
and root of the penis, it even exceeds the length by J or more, whence
these papilla3 exactly resemble warts, or even short ridges ; in the
longest papillf^, lastly, the breadth is ^ to J the length.

The thickness of the corium varies from \ to \\ of a line, and in most
places is about ^ to f of a line. It is the thinnest (| to |^ of a line) in
the meatus auditorhcs externus, in the eyelids, the red border of the lip,
the glans penis, and clitoridis; and thickest (| to 1 line) on the back,
chin, upper and lower lip, (the hairy part), the alee nasi, upon the ball
of the sole, the extremity of the great toe, the scapula, and the nates;
on the heel, 1 to li lines.

The principal chemical characters of the corium agree with those of

the connective tissues, of which it is
principally constituted. It putrefies
with difficulty, and not at all when
tanned ; it may be easily dried,
and then becomes yellowish, trans-
parent, and hard, but flexible and no
longer subject to putrefaction. In
boiling water, it at first shrinks,
eventually however dissolving, but
not with equal facility in all animals,
and in the young, more quickly than
^ in the old, into gelatine, colla ; and
^" the same chanjie is effected at the

Fiar. 48.

■fri V — "^^-^

lip-

■:^^^^i

Fig. 48. — Two papillte of the surface of the hand, from a slightly macerated skin; magni-
fied 350 diameters, a, Wavy, remarkably distinct fibrils of connective tissue; h, Transverse
elastic fibrils lying in the axis of a papilla and transverse nuclei, axile corpuscles, the corpus-
cula taclus of R. Wagner (see § 37) ; of nerves no trace is to be seen without reagents.

OF THE SKIN.

123

ordinary temperatures, ■when it is treated with dilute acids and
alkalies.

§ 34. Tlie corimn is principally composed of connective and elastic
tissue, containing in addition, smooth muscles, fat-cells, bloodvessels,
nerves, and lymphatics, in great abundance.

The connective tissue consists of the ordinary bundles, which are in
pare united into a network, as in the subcutaneous cellular tissue ; in part
into large secondary bundles, traheculce and lamince, which, in the jjcm-
7u'ciilus adiposiis, circumscribe larger and smaller spaces filled with fat ;
whilst in the fascia superficialis, and in the coriu7n, their connection is
very intimate, and they form, especially in the latter, a very dense tissue,
with indications of lamination. In the papUloi the fibrous structure is
not everywhere distinct, and instead of it there often exists a more
homogeneous tissue,* which frequently appears to be bounded by a

FiR. 49.

structureless membrane, which, however, does not admit of being actually
isolated.

The bursce mucosce suhcutanece are nothing but larger, simple, or par-
tially subdivided reticular spaces in the subcutaneous cellular tissue, in

Fig. 49. — J, Elastic fibres from the inner part of xhe fascia lata of man, closely interwoven,
and appearing like an elastic membrane; magnified 450 diameters. U, An elastic fibre
with a serrated edge, such as may also be seen occasionally in the cutis.

* [The most superficial layer of the cutis is invariably composed of a transparent matrix,
homogeneous or nearly so, in which nuclei are imbedded. The "indications of lamination''
are simply the commencement of the breaking up of this tissue into areolated connective
tissue, such as we have already described; see note, p. S.3. — Tks.]

124 SPECIAL HISTOLOGY.

the fascia superficialis {bursa olecranii)^ or between the laminge of the
fascia muscularis {bursa patellar). The internal walls, smooth but un-
even, are formed of common connective tissue, possess no epithelium,
and include a somewhat viscid, clear fluid.

The clastic tissue exists abundantly in almost all parts of the cutis ;
but, in general, far more sparingly than the connective tissue. More
rarely it occurs in the form of true elastic membranes, which may even
resemble the densest elastic networks of the arteries, as in the fascia
superficialis of the abdomen and thigh ; while more commonly it repre-
sents a loose reticulation of coarser or finer fibres, as in the corium.
The pctpilhe (but not all), and the pannicuhis acliposus, in which they
are sometimes wholly Avanting, contain only fine elastic (nucleus) fibre.

1. Smooth muscles, according to my observations, occur far more exten-
sively in the skin than has hitherto been supposed, and particularly in
the subcutaneous cellular tissue of the scrotum, or the tunica dartos,
which has thence received the name of " muscular membrane" (Fleisch-
haut), and of the penis, including the prepuce and the anterior part
of its body, where they run in the form of yellow bundles (whose ele-
ments are figured in § 26), measuring |- to J a line, partly contiguous
to the vessels and nerves, partly more isolated in the connective tissue ;
they are sometimes converted into a network, but are more usually dis-
posed parallel to the raphe of the scrotum and the longitudinal axis
of the penis, though, more particularly in the latter situation, they not
unfrequently form large transverse bundles.

2. In'the areola of the nipple, the smooth muscles, which are especially
well developed in the female, are disposed circularly in a delicate layer,
which becomes thicker internally towards the base of the nipple, and
are, for the most part, visible to the naked eye, on account of their
yellowish red color, and the thickness of their bundles (up to ^ of a line);
in the nipple itself they run in part circularly, in part perpendicularly,
and are united into a close network, through whose meshes the excretory
ducts of the lacteal glands pass.

3. Lastly, smooth muscles are also found in the superficial portions
of the corium, and in fact in all situations where hairs occur, in the
form of flat bundles, 0-1-0-16 of a line broad, which, singly or in pairs,
are invariably placed near the upper part of the hair-follicles and seba-
ceous glands.* They arise, probably, from the superficial part of the
coriuvi, and running obliquely from without inwards, towards the hair-
follicles, surround the sebaceous glands, and are inserted close behind
and near the base of those glands into the hair-follicles.

Quite recently Eylandt and Henle have added to our knowledge of
the smooth muscles of the skin. The existence of the little muscles of

* [Smooth muscular fibres have also been foimd in the scalp. See note p. 104. — DaC]

OF THE SKIN.

125

the hair-follicles, termed by Eylandt, ar^-ectores pill, has been confirmed
by both writers, only that they find them to be more delicate (Eylandt
0-02, Henle 0-04 of a line). Eylandt never noticed more than one
bundle passing to a hair-follicle, and Henle states that they subdivide
upwards into many bundles of 0-004 of a line, and may be traced im-
mediately under the epidermis as far as the papilltB. In the scrotum,
in the skin of i\\Q penis, the perina'um, the areola mamma', and in the
nipple, Eylandt could not find smooth muscles ; and he imagines that I
have confounded the circular muscles of the vessels with them, a sup-
position which I should not have allowed myself to entertain even
against a besrinner. Henle has seen the smooth muscles in all these
situations, which it is, in fact, very easy to do, though I think that he
goes to the other extreme in assuming the existence of smooth muscular
fasciculi in the hairless portions of the skin also, in the sudoriparous
glands, and in the vascular ramuscules (on their exterior), and, I believe,
that in these cases, he has been misled by fine nervous twigs, which, as
he himself states, may readily be confounded with smooth muscles, in
the boiled preparations which he employed.

Fig. 50.

Fig. 51.

§ 35. Fat-cells. — These cells are especially developed in the pannieu-
lus adiposus. In this situation the fat-cells do not form large conti-
nuous expansions, but occupy, in larger or smaller clusters, the variously
formed meshes of the connective tissue (Fig. 45/). Each of the yellow
clusters, or fat-lobules, which appear to the naked eye clearly defined,
has a special coating of connective tissue, in which the vessels intended
for the nutrition of the fat-cells are distributed, and consists either of
a simple aggregation of cells, or of a number, varying according to its
size, of smaller and smallest lobules, each of which again has its proper
delicate investment of connective tissue. According to Todd and Bow-
man, every cell even, has its own special covering and vessels ; but this

though true in many

cases, is certainly not so

in all. In the corium

the fat-cells are found

more in the deeper part 6-

round the hair-follicles

and sebaceous glands,

while they are wholly
wanting in the pars jJapillaris. In persons in tole-

FiG. 50. — Normal fat-cells from the breast; magnified 350 diameters: a, without reagents;
b, after being treated with ether, whereby the fat is exhausted, and the folded delicate
membrane remains.

Fig. 51. — Fat-cells with crystals of margarin ; magnified 350 diameters : a, cell with a
star of crystalline needles, as they maybe found not uncommonly in normal fat; b, ceil quite
filled with crystals, from the white fat-lobules of an emaciated subject.

126 SPECIAL HISTOLOGY.

rablygood condition, the fat-cells are always rounded or oval, 0-01-0-06of
a line in diameter, with a dark border, filled with fluid, pale yellow fat,
which forms a single drop — and with a parietal nucleus which is not
readily rendered visible (Fig. 50). In emaciated subjects, on the other
hand, hardly any cells of this kind are met with, but instead, more
or less abnormal forms : 1. Granular cells^ vi'iih numerous small fat-
drops, forming whitish-yellow clustered lobules ; 2. Fat-cells containing
seru7n, in yellow or reddish-brown minute lobular masses, which, to-
gether with the fat (which has become more or less diminished in quan-
tity, and usually appears as a single dark-colored globule), contain a
clear fluid and a distinct nucleus, and are considerably smaller than
the normal cells, 0-01-0-015 of a line; 3. Cells which contain no fat,
but onli/ serum, with a distinct nucleus, and having a delicate or
thickened membrane ; they occur in more gelatinous fatty tissue, or
mingled with the others ; they are also met with in oedema ; 4. Lastly,
Fat-cells containing crystals, either presenting 1 to 4 stars of acicular
crystals (margarin), together with a drop of fat, or being completely
filled with crystalline needles. The former occur among our normal
cells, the latter only in the white, more isolated, fat-lobules.

The nuclei in the fat-cells of the adult have not, as far as I am aware,
yet been observed, excepting by Bendz (Almind. "Anat." p. 122, tab.
I. fig. 4), who rarely, very rarely, noticed even two pale nuclei with
nucleoli. It is true that Mulder (p. 601), states that they are furnished
with one, rarely with two, nuclei, but Donders and Moleschott {ih., p.
602, et seq.), upon whom Mulder appears principally to rely, expressly
say that they did not detect the nuclei; nor does Donders (in the "Hol-
land. Beitr.," I. pp. 57, 61), say anything about nuclei. I invariably
find them when the fat has partially disappeared from the cell. In cells
completely filled, I first distinctly noticed them, in some cases in the
marrow, and in the fat-cells in the muscles ; but I do not hesitate in the
least to affirm their constant occurrence in all fat-cells, since no one can
suppose that they are not formed until after the disappearance of the
fatty contents. With respect to what Donders and Moleschott observe,
as to the existence of two membranes in the fat-cells, the outer of which
is said to be soluble in concentrated acetic acid, and in potass, and the
inner not; the former, as Donders himself elsewhere supposes, can be
regarded merely as connective tissue, which, in many instances, also
penetrates between the separate cells and connects them together, or, pro-
bably, is occasionally replaced by a homogeneous connective substance
(modified cytoblastema). The crystals in the fat-cells are considered by
Vogel to be margarin. As the forms of margarin and margaric acid
are very similar, the question can be decided only on chemical grounds,
and these appear to favor the latter.

OF THE SKIN. 127

The pathological conditions of the fat-cells, although as yet but little
investigated, corroborate my assertion of the constant occurrence of the
nucleus. Without relying upon Schwann's observation, that the fat-
cells of the subcutaneous cellular tissue of a rachitic child a year old, all
contained a nucleus, I would more particularly adduce the condition of
the fat-cells in cutaneous dropsy. In this affection, as long as the fat
in the imnmcuhis adiposus has not entirely disappeared, cells containing
serum, and but a small quantity of fat, are extremely abundant, and
exactly of the same form as those which arc found in emaciated subjects,
all with distinct nuclei ; and, besides these, there are num.erous cells con-
taining nothing but serum and also nucleated. In cases where the fat
may be said to have altogether disappeared, and the colorless subcuta-
neous cellular tissue is infiltrated throughout Avith water, I find the last-
mentioned cells in greatly preponderating quantity, and associated with
them, others of peculiar form. In the first place, fusiform or stellate
cells, with from three to five irregular, often tolerably long processes,
with a distinct nucleus, and mostly only scanty and minute, dark fat-
granules ; these, as the very numerous and various transitionary forms
indicate, being developed from diminished cells containing serum, and
from which the fat has been partially or wholly removed ; secondly,
roundish or elongated minute cells (0-003-0-006 of a line) closely filled
with dark granules, and without a visible nucleus, which, as is also
easy to be perceived, owe their origin to a diminution of the fat-cells
coincident with a change in their contents, and, on the other hand, are
metamorphosed into the cellules with little or no fat, and containing
serum, with which they are found associated. I may also mention that,
in the inflamed medulla in the articular ends of the bones, as, according
to Hasse, appears to be the case in rheumatism, I have seen the com-
mon fat cells transformed into round and even fusiform cells, contain-
ing serum and little fat, and occasionally furnished with nuclei. (From
KbUiker, "Mikrosk. Anat.," Vol. II. p. 18.)

§ 36. Vessels of the Skin. — In the subcutaneous cellular tissue the
arteries entering the skin give off many branches to the hair-follicles
(see below), the fat-lobules and the smooth muscles, which, for the most
part, form wide-meshed networks of fine capillaries ; more rarely, par-
ticularly in the fat-lobules, the network is closer. More externally they
supply the sudoriparous and sebaceous glands (see below), and also form
terminal expansions in the inner part of the coriuni [pars reticularis),
but not many : finally, they penetrate into the outermost part of the
papillary layer, and into" the papillce themselves, where they terminate
in a close network of capillaries with narrow meshes. This consists,
wherever there are papillce^ of two portions ; firstly, of a horizontal

128

SPECIAL HISTOLOGY.

plexus lying immediately under the surface covered by the epidermis,
and which is composed of larger vessels (of 0-01-0-005 of a line) with

Fis. 52.

wide, and of capillaries (of 0-003-0'005 of a line) with narrow meshes ; and

secondly, of very many separate
^'"- ^3- loops of the finest vessels (0-003

'Q^^^i^^^^^^W^i -0-004 of a line) which are given

^^#^!^?K*'S'>- -^il^^ii- ' off to the vapillce. With cer-

-^J

^'^SB^

either in the axis of the pcrpilla
or near the surface, almost as
far as its apex.

The larger trunks of the li/m-
pJiatic vessels are very easily recognizable in the subcutaneous cellular
tissue, and are very numerous. In the corium itself different anatomists,
Hasse, Lauth, Fohmann, &c., have demonstrated the lymphatics by in-
jecting them with quicksilver. All agree in this, that they form an ex-
cessively close network of fine vessels in its outermost part, — according
to Krause (1. c, p. Ill) of A-t,© of ^ line in diameter; the meshes of
which become wider internally, and finally open by single trunks into
the vessels of the subcutaneous cellular tissue. However, it is not by
any means known, whether the vessels composing these plexuses are
really the true commencement of the cutaneous lymphatics.

Fro. 52. — Vessels of the fat-cells. Ji. Vessels of a small fatlobule ; o, artery ; 6, vein.
B. Three fat-cells with their capillaries more magnified ; after Todd and Bowman. Magni-
fied 100 diameters.

Fig. 53. — Vessels oi x\\.e papilla of one entire and two half ridges of the cutis; after Berres.

OF THE SKI N.

129

Fig. 54.

§ 37. Nerves. — The skin, in those parts of it which border upon the
epidermis, particularly in some localities, is one of the structures most
richly provided with nerves in the human organism, whilst in its deeper
parts it is remarkable for their scantiness. In the panniculus adijjosus,
and in the fascia siqwrjiciah's, as yet, no nerves are known besides those,
which, giving off a succession of branches, traverse those parts to reach
the corium, or to supply the hair-glands, smooth muscles, and Pacinian
corpuscles, of which we shall speak further on. In the corium itself,
the trunks which enter through the meshes of the deeper layers ascend
by degrees, continually ramify-
ing, but without actually form-
ing, terminal expansions, to-
wards the pars papillaris. Here
they anastomose frequently, and
form rich terminal plexuses, in
which deeper and more superfi-
cial portions may be clearly dis-
tinguished, the former consist-
ing of fine branches still con-
taining many primitive tubules,
Avith wide meshes ; the second
of fibres single or united in pairs,
with narrow meshes. In this last or the fine terminal plexus, there also
occur (whether in all the fibres is as yet undecided) in man and in ani-
mals actual divisions of the jyrimitive tubules, so that they divide, gene-
rally at an acute angle, into two ; and from the plexus itself, the tubules
finally enter the base of the papillce in pairs, in order to run to their
extremities, and there unite in a loop.

The elements of the nerves of the skin exhibit no striking peculi-
arities ; the diameter of some, in the trunks in the subcutaneous cellular
tissue, is still as much as 0-005-0'006 of a line, and also in the deepest
part of the corium, whilst they become finer and finer outwards. In
the terminal plexus I find they vary according to the locality, from
0-003 to 0-OOlG, in the papillce. from 0-0008-0-002 of a line. In the
hand and foot the finest tubules vary between 0-0012-0'002 of a line;
in the glans penis, in the lips and nose, on the other hand, only from
0-0008-0-0012 of a line.

M/iM).

R. Wagner has recently published some statements ("Allg. Zeitung,"
Jan., Feb., 1852; "Getting. Nachricht," Feb., 1852), according to

FiO. 54. — Two papilla from the extremities of the fingers, without epithelium and with
axile corpuscles, a, and nerves, b. A. Simple papilla^ with four nerve-fibres and two termi-
nal loops, c. .S. Compound ;}a/jj7/a, with two vascular points with capillary loops, d; and
one nervous point with a terminal loop, e.

9

130 SPECIAL HISTOLOGY.

"which the relations of the nerves of the skin have hitherto been entirely
misconceived. From the investigations of G. Meissner and himself,
which were instituted upon the nerves of the palm of the hand, Wagner
divides the j^opiUce into nervous and vascular. The former are said to
contain a peculiar oval corpuscle in their axis, which consists of super-
imposed saccular or band-like laminae, resembling a fir-cone, and this
structure is regarded by Wagner, as a peculiar sensory apparatus, and
named by him "tactile corpuscle" [corpusculum factiis). Into these
the nerves — 1 to 3 fine dark-bordered tubules — are said to enter from
below, or from the side, and to terminate within them, either free, or
perhaps divided into many delicate branches. Wagner found these
corpuscles to be most abundant in the points of the fingers, and that
they were more and more rare towards the wrist. I have considered
it requisite to investigate these assertions, which are made with much
confidence, particularly as Wagner grounds upon them great expecta-
tions of the physiology of the sense of touch, and the following are the
results at which I have arrived.

Independently of the vessels and nerves, the papilloe consist, in the
main, of a sometimes more homogeneous, sometimes more distinctly
fibrillated collagenous substance, which there is no reason to distinguish
from connective tissue, and of fine elastic fibres in difi"erent stages of
development, as fusiform cells (corpuscles of the connective tissue, of
Virchow), cell networks, isolated fine elastic fibres and fibrous networks.
These elements are so distributed, that in most pajnUce a cortical layer
and an axile tract can be distinguished. In the former the fibrous
elements are disposed longitudinally, and the connective tissue is often
distinctly fibrillated, with the exception of the most superficial layer,
which forms a clear, homogeneous but not separable margin. In the
latter, on the other hand, the substance is more uniform and clear, and
in many places is separated from the outer layer by transverse elastic
fibres. When these latter, true elastic fibres, are not very closely dis-
posed, no one would be led to consider that there is anything peculiar
in this arrangement ; but undeveloped and very close together, as they
are in Wagner's corpuscle, it is otherwise. These are, in fact nothing
but the clear axis marked by transverse nuclei and nucleated fibres,
which I have already described ; and, if no reagents be added, they pre-
sent no other appearance than that which I have figured in my "Micro-
scopic Anatomy," Fig. 4, or in Fig. 48 of this work.

Dilute solution of soda, of which almost solely I have availed myself
in investigating the course of the nerves in the papilla?, often does not
render their contour at all more distinct, and I therefore paid no fur-
ther attention to their structure ; while, on the other hand, acetic acid,
which was also employed by Wagner and Meissner, brings out the axes
of the papillse generally, though not always, as oval, or cylindrical,

OF THE SKIN. 131

more sharply-defined bodies, to which the numerous transverse strias
give a certain vague similarity to a fir-cone (Fig. 54). In its more inti-
mate structure, such an " axilc corpuscle," as I call it, does not con-
sist of superimposed discs, as Wagner supposes, but of an internal mass
of homoircneous connective tissue, which is most distinct in transverse
sections, and when viewed from above ; and of an external generally
single layer of undeveloped elastic tissue, which, in the form of fusi-
form cells probably connected together and, more or less, drawn out
into fine fibres, with shorter or longer nuclei (these last were also seen
by Wagner), closely surrounds the internal substance in which here
and there similar corpuscles also appear to be contained. Moiyhologi-
cally, then, such a corpuscle is by no means peculiarly constructed, but
resembles the axis of certain other papilloe (e. g. of the sole of the foot),
which are surrounded by true elastic fibres, particularly their often less-
developed summits; it is very similar, again, to the bundles of connec-
tive tissue, with elastic fibres wound round them, such as are found in
the corium; indeed, the diff'erence consists principally in this, that the
axis-corpuscles contain more undeveloped elastic tissue ; a circumstance
easily comprehensible, since the papillce, as compared with the cutis
itself, consist altogether of a tissue which is in a more embryonic state.
With regard to their occurrence, axile corpuscles of the kind here de-
scribed occur only in certain papillse ; and, in fact, so far as my inves-
tigations hitherto extend, only in those of the jja^m and surface of the
hand, the red edges of the lijJS, and the tip of the tongue, not in those
of the toes, thorax, back, glans penis, nympthse, and only rarely in those
of the back of the hand and of the sole of the foot.* In the hand they

* [I have recently succeeoletl in detecting these tactile corpuscles in the toes. They cor-
respond exactly to the tactile corpuscles, as described by Wagner and Kolliker in other
parts, only they were far less numerous than on the pahn of the hand, or on the edges
of the lip. I first discovered them in the papillce of the toe of an infant, and have twice
since verified my observation. Their minute structure apparently consisted of superim-
posed discs, such as described by Wagner. They may be most conveniently studied in fine
transverse or perpendicular sections, which have been treated with acetic acid, or a dilute
solution of soda.

The nature of these so-called "tactile" or "axile" corpuscles is as yet a matter of dispute,
^lost recent observers seem to entertain regarding them the same views as Koiliker (see
Mr. DalzeU's, in the Edinburgh "Monthly Journal of Medical Science,"' March, 1853; also
Mr. Huxley, "Quart. Journal of Micr. Sc," Oct. 1853, and in Appendix to this work) ; yet
Wagner, (in bis reply to Kolliker, in " Muller's Archiv. 1852,") and more recently Meissner,
(" Beitrage Zur Anatomie und Physiologie der Haul," Leipsig,lS53) add additional observa-
tions in confirmation of the nature of these "corpuscula tactds" as fi[rst described by them.
Meissner has presented us with some very interesting researches on the relative frequency
of their occurrence in the papillte in different parts of the body. Thus he found on a sur-
face of 7 lines in length on the lips and apex of the tongue, only 4 or 5 ; on one square
line comprising 400 papillae of the last joint of the index finger, 108, but only 40 on the
second joint, 18 on the first. In the papillte at the root of the tongue, he was not able to
discover any of these bodies.

The tactile corpuscles are probably surrounded by a special membrane, since they can
be isolated. They have as yet only been observed in Man, and in the Ape. — DaC]

132 SPECIAL HISTOLOGY.

appear especially in the compoimd papillce, in particular cusps, one or
two together, which may project more or less, and are sometimes shorter,
frequently longer ; they occur more rarely in the simple jmjnllse, as
oval or cylindrical bodies, occupying ^ to |- the width of the summits of
the papillaj, and 4 to J, or as much as f the length. In the points of
the fingers, they occur in the proportion of 1 to every 2-4 jyapillce ;
in the first phalanx, on the other hand, in the length of 1 line, only
2-6 are to be found, and in the palm they are still more rare. Fre-
quently the axile corpuscles exhibit local constrictions, especially after
the addition of acetic acid, are even spirally contorted, so that they
often have a certain similarity to a bundle, of connective tissue treated in
the same way, or with a spiral sudoriparous duct. Upon the back of
the fingers and in the heel there appeared, in many individuals to be
no axile corpuscles in the papillae ; in a small number, however, they
were to be found even here, but scattered and small, in a few papillae.
In the lips, I saw in two individuals axile corpuscles similar to those
in the hand ; in one they were wanting. They existed only in that part
of the red margin of the lip, which is visible when the mouth is closed ;
they were very minute, and were placed partly in small projecting points
of the larger papillte, partly in depressions between two of their pro-
cesses. In the tongue^ in which, according to Wagner, something
similar to his corpuscles appears to exist, I met, in two cases, with no
axile corpuscles; whilst, in a third, I found them tolerably well deve-
loped in the papilla' fung if ormes of the point of the tongue (whether
they are to be found in the posterior ones I know not), whilst they were
wanting in the p. filiformes and p. circumvallatce. In the p>. fmigifor-
mes, one or many were situated in the point of the principal papilla,
without extending into its simple processes, and therefore lay, as it
were, at the bottom of a terminal pit, surrounded by the simple papillce.
With regard to the course of the nerves of the skin, Wagner confirms
the fact discovered by me, that even in man, the primitive tubules divide
in the terminal plexuses (which I have recently also observed in the
hand, the lips, and the tongue) ; and he further states that, in the
palm at least, only those papillge contain nerves which possess the axile
corpuscles, while they have no vessels. As regards the latter impor-
tant circumstance, all those who have occupied themselves more parti-
cularly with the investigation of the skin, must be aware that nerves
are not to be found in all the papillae ; but seeing the difficulty of dis-
covering the nerves in a dense organ like the skin, no one has thought
it requisite on this account to depart from the old notion that every
papilla contains a nerve, and is therefore a tactile process. Wagner
having observed the sharply-defined axile corpuscles of the hand, ap-
pears to have been surprised that they occurred only in certain papillge,
and that these had nerves ; and struck Avith this circumstance, adopted

OF THE SKIN. 133

the view referred to. As for myself, having again made long-continued
investigations into the skin of the palm of the hand, I find that those
points of the papilUc, or those independent papillif, which contain axile
corpuscles, do generally exhibit dark-bordered nerve-tubules very dis-
tinctly ; but from this I should, for the present at any rate, by no means be
led to conclude that the other papillae contain no nerves, but only vessels.

If it be considered that dark-bordered nerve-tubules, though indeed
rarely in proportion, are contained in vascular papillaj without axile
corpuscles, in the hand ; furthermore that in other places, as in the sole
of the foot and the lips, such papilloe are found ; and finally, that the
investigation of the cutaneous nerves is very difficult, it seems more
judicious to suspend one's judgment upon this question, especially as it
is possible, that pale, non-medullated, nerve-tubules, similar to those
which I discovered in the skin of the Mouse, exist in man also. How-
ever, I am by no means disinclined to agree with ^yagner this far,
that in the palm it is almost exclusively the ^papillie with axile corpuscles
which contain dark -bordered nerves, for to say the least, it is very re-
markable that in these papillie the nerves are so readily and satisfac-
torily displayed. As to the possible existence of non-medullated fibres
in the papilloe without axile corpuscles, it is certainly too soon to express
any definite opinion. "With regard to the vessels, it is incorrect, uncon-
ditionally to deny their existence in those papilla3 which contain nerves.
In the compound papillie it is unquestionably true, that the cusps with
axile corpuscles and nerves frequently contain no vessels ; at other times,
however, even these contain a capillary loop, and this is still more fre-
quently the case in the simple papillae with nerves. In the Jip, the
papillic containing nerves, whether they possess axile corpuscles or not
contain vessels for the most part, if not always, and there are rela-
tively very few papilla in which no nerves are visible. The tongue pos-
sesses vessels and nerves in all the larger papillse ; on the other hand,
I have as yet been unable to discover nerves in the simple papillae
buried in the epithelium. It is yet to be ascertained how the nerves are dis-
posed in other parts of the skin. It is surprising to me, that even in the
sole of the foot, dark-bordered nerve-tubules can so rarely be perceived
in the papillie, while in many situations they cannot be found at all.

Further investigations are required to determine to what extent dark-
bordered nerves are distributed in the papillae of the skin ; whether,
perhaps, non-medullated fibres occur instead of them ; or whether, in
certain situations, the nerves do not enter the papillae at all, but end in
the well-known superficial plexus at their base.

With respect to the dark-bordered nerves in the papillte of the hand,
"Wagner is wrong in asserting that the nervous loops which I have
figured are bloodvessels. He has only imperfectly seen the nerves of the
papillre in question, perhaps on account of his having preferred the use
of caustic soda, which more easily destroys them. Latterly, in making

134 SPECIAL HISTOLOGY.

very delicate investigations, I have used only acetic acid, and have
arrived at the following results: — Each point of a papillse, or each
papilla with an axile corpuscle, generally contains two, or as frequently
happens at the points of the fingers four, dark-bordered tubules, which,
surrounded by a neurilemma^ which has escaped previous observers,
pass upwards through the axis of the papilla to reach the base of the
axile corpuscle, as a fine, convoluted nervous twig of 0-006--012 of a line
in thickness. Here the nerve frequently becomes invisible, so that, as has
happened to Wagner, one may be led to believe that it enters the cor-
puscle, which is seated upon it, as upon a stalk, and there ends. How-
ever, if a number of fresh preparations be treated with acetic acid and
examined, the conviction is soon arrived at that this is merely apparent,
the nervous tubules in reality proceeding aloyig the outer surface of the
corpuscle, either as far as its point, or very nearly so. In the mean-
Avhile they either remain together or take an isolated course. In both
cases their neurilemma becomes excessively delicate, appearing finally
to vanish entirely, while the nerves themselves surround the axile cor-
puscle, passing round it either more directly, though in a slightly undu-
lating course, or forming one or several spiral coils (Fig. 54, B). As
regards the actual termination of the nervous tubules, I retain the opi-
nion I formerly expressed, inasmuch as, in at least six cases, I have
again most distinctly seen loops (Fig. 54). It is, however, always difficult
to observe them, and very frequently impossible, in spite of every exer-
tion; and therefore, as we are all liable to error, I will blame no one for
considering the termination of the nerves of the papillse to be unknown,
or for believing in the existence of free ends, which perhaps also exist,
and, at any rate, very frequently appear to exist. I only state what,
according to my best belief, I have seen ; and while I have no prejudice
in favor of loops, neither can I see anything alarming in their existence.
This much, however, is certain, that Wagner has not traced the nerves
in the papillae so far as they may be traced, and therefore, at present
at all events, can lay no claim to a decisive voice in the matter. How
the nerves in the papillae of the lips, tongue, and elsewhere, are disposed,
I have not yet ascertained with certainty ; but with regard to the first
of these, I believe I can also afiirra, that they do not terminate in the
axile corpuscles, but either merely pass by them or wind round them.
In the lips, in a single instance, I found well-marked nerve-coils in small
papill?e, or at the base of the large ones.

§ 38. Development of the Cutis. — The following may be taken as a

* [It is by no means easy to recognize this neurilemma. Indeed, even its existence is ques-
tioned by Meissner, who states that after the most careful observation, he has not been able to
detect a neurilemma in one single instance. The nerve itself he thinks does not terminate in
loops, as stipposed by Kolliker, but penetrates into the tactile corpuscles. The cross-striae
considered by Kolliker as elastic tissue, he justly describes as the termination of the dark-
bordered nerve-tubules, for the action of soda on them proves them to be such. — DaC]

OF THE SKIN. 135

general sketch of the development in the foetus, of the cutis in the
broadest sense of the term. It consists at first of cells, which though
not in man, yet in animals (the Frog, for instance) may be easily traced
back to the earliest formative cells of the embryo. A considerable pro-
portion of these cells are changed into connective tissue, becoming fusi-
form, coalescing, and eventually being converted into bundles of fibrils;
a process which appears to occur first in the fascia superjiciaUs, the sub-
cutaneous connective tissue, then in i\\Q pars reticularis o? the corium,
and finally in the papillary layer. Another portion of the cells are
converted into vessels and nerves, as can be seen even in man, and very
beautifully in the Batrachia (see my Memoir in the " Annales des
Sciences Naturelles," 1846) ; while a third, growing and developing fat
in its interior, becomes elastic fibres and fat-cells (vide supra, § 23).
The first foundations of all these parts having been laid, they continue to
increase in a manner which is not yet exactly made out. The cutis ob-
viously grows from within outwards (so that the papilloe arise and are
developed last of all), partly by the growth of its primitive elements,
partly at the expense of cells, which are perhaps mostly of new forma-
tion, and do not proceed from the original formative cells. The panni-
culus adiposus also increases, partly by the increase of the cells of which
it at first consists, partly by the subsequent development of others, as
well as of connective tissue and vessels. In this manner, the skin grows
for a long time after birth. In children below seven years of age, for
example, the cutis is, according to Krause, only half as thick as in the
adult, until at last, though at a time which is yet undetermined, the new
development of cells ceases, as at a later period, perhaps, does the ex-
tension of those elements, cells, fibres, &c., which are already formed.
The fat-cells of adults, in which the process of growth is especially ob-
vious, according to Harting, are in the orbit twice, in the palm three
times as large as in the new-born infant ; whence it results that they in-
crease in size in proportion to the parts of the body to which they belong.

In embryos of two months the skin is 0'006-0*01 of a line thick,
and wholly composed of cells. At the third month it is about 0'06 of
a line, and already presents tolerably distinct connective tissue. In the
fourth month the first lobules of fat appear, and the ridges of the hand
and sole of the foot. From the seventh month onwards the panniculus
adiposus is rapidly developed, and at birth it is relatively thicker than
in the adult.

§ 39. Physiological Remarks. — If we attempt to harmonise the ana-
tomical data here brought together, with the phenomena of sensation
exhibited by the skin, we meet with considerable difficulties. The more
intimate anatomy of the skin, as it is here detailed, fails to demonstrate
nerves in all the papillae, or even in the majority of them ; and yet ex-

136 SPECIAL HISTOLOGY.

periment teaches that though all points of the skin may not feel with
the same delicacy, they are all nevertheless sensitive. I hoped to be
able to submit Wagner's doctrine of the absence of nerves in many
papilljB to experimental proof, by examining the sensitiveness of various
parts of the body with the finest possible English sewing needle. At
first I really thought that I had found some places which were quite in-
sensible, whilst in others the slightest touch produced sensation ; but on
carrying the investigation further, it appeared that the very same place
was often sometimes sensible, sometimes not ; so that, finally, I came
to the conclusion that the very smallest portions 'of the skin are sensitive.
But since even in the palm of the hand the papill^B containing nerves
are widely dispersed, and in other places occur but rarely, or even not
at all, it only remains either to assume the existence of non-meduUated
nerve-fibres in all the papillte, or to have recourse to the nervous plexus
at the base of the papilloe. I should unhesitatingly prefer the latter
explanation, were it not : (1) that these plexuses are in many places so
very scanty, and (2) that the slightest touch of the epidermis produces
sensation ; for the present, therefore, I believe this must remain an open
question.

If we are not in a condition to understand how it is that every point
of the skin is sensitive, still less are we competent to explain the different
kinds of sensations. In this respect the following very general state-
ment may be made.

The excitement of the terminations of the nerves in the outermost
parts of the cutis and the papillae is either direct or indirect. The
former as it is produced, for example, when the cutis is laid bare, by
penetrating instruments and by fluids, is much more intense than that
which takes place through the mediation of the epidermis, one of the func-
tions of the latter being to act as a defence against too violent impressions,
and to blunt them according to its greater or less thickness. It can now
be partly explained on anatomical grounds, why the delicacy and viva-
city of the sense of touch are not everywhere equal, why they are less
upon the hairy scalp, the back, the two upper divisions of the extremities,
than on the face, on i\\Q genitalia, the hand and foot, the chest, and ab-
domen. In the first place, where the tactile sense is delicate, the epi-
dermis is in itself thin, as upon the eyelids and face, or has, at least a
thin horny layer, as upon the penis and clitoris, whilst upon the back
and extremities it is considerably thicker. Yet this circumstance is not
a sufficient explanation, for parts with a thicker epidermis, as the palm of
the hand and the sole of the foot are delicately sensitive, more so, in fact
than others with a thinner covering, as the back of the hand and foot.
Another condition must here obviously come into play, and it is, I think,
that the skin is not equally well provided ivith nerves in all its parts. Sim-
ple inspection teaches that the nerves upon the palm of the hand and

OF THE SKIN. 137

the sole of the foot nre more numerous than upon the back of the hand
and foot ; upon the <ilans penis and cUtoridis, the nipple, the face, they
are more abundant than upon the abdomen, back, and thigh, &c. &c. ;
and this is to some extent confirmed by my measurement of the sensi-
tive roots of the spinal nerves {vide "Mic. Anat.," p. 433). With the
number of the nerves, is connected that of the actually demonstrable
dark-contoured nerves in the papillae and the superficial nervous plexus,
for nowhere is this more considerable than in the points of the fingers,
the lips, the tip of the tongue, and the glans penis.

As to the local sensihility of the skin, it is the province of anatomy,
especially, to afford information, with regard to these two points : 1,
how it is that we do not distins-uish with the same clearness and exact-
ness, in all parts of the body, the point at which a single irritation
is applied : and 2, why two stimuli operating at the same time, under
certain circumstances, appear double, under others single (Weber's
experiment). I think that Weber's experiment cannot be explained by
the mode of distribution of the peripheral nerves, but depends very pro-
bably upon their central relations. It seems to me to be simplest to as-
sume, that every peripheral end of a nerve is capable, when irritated, of
producing a conscious sensation, but that, on account of the small num-
ber of nervous fibres (in X\iQ cerebrum) which unite these with the seat of
consciousness, if many contiguous, or even more distant, cutaneous nerves
are excited, only a single conscious sensation results. In this case, the
nerves of acutely sensitive parts must be connected with the seat of con-
sciousness by more numerous intermediate fibres than those of other locali-
ties, and at the ends of these fibres, also, we must suppose a sort of inter-
lacement to take place. Upon this hypothesis, the former of the two points
might be explained. A local irritation is, indeed, felt locally ; but, accord-
ing as the nerves implicated are united with the brain by more or fewer
conductors in the spinal cord, are we able to assign, more or less exactly,
the precise spot ; so that, in some cases the limits of error will not exceed
^1 line, while in others, they may extend to 1 or 1^ inch and more.

E. H. Weber has endeavored to demonstrate, in his last able Treatise
upon the sense of touch, that it is only the termination of the nerves in
the skin, not the fibres in the nervous trunks, which are the mediators
of the sensations of pressure, warmth, and cold ; and he has expressed
a supposition, that tactile organs as yet unknown may exist in the skin.
R. Wagner believes that he has, in fact, found these organs in his so-called
corpuscula tactus^ and he supposes that, composed as they are, accord-
ing to him, of superimposed membranes, in the interspaces of which a
very minute quantity of fluid is lodged, like elastic cushions, or a bladder
filled with water, they are specially fitted to receive impressions from the
epidermis at the extremity which is directed towards it, and to transmit
them to the ends of the nerves which lie in and upon them.

In my opinion, Weber's view of the greater sensibility of the termi-

138 SPECIAL HISTOLOGY.

nations of tlie nerves in the skin, can hardly be doubted ; but, on the
other hand, there is no obvious reason, a priori, Vfhj peculiar hitherto
unknown organs should exist to that end ; nor why the condition to
which I have already referred, the more isolated course of the fibres of
the nervous tubules in the papillte and terminal plexuses, their fineness,
superficial position, and the delicacy or absence of the neurilemma, may
not abundantly sufiice as an explanation. That Wagner's so-called cor-
puscula tactus, my axile corpuscles, are not tactile organs in the sense
intended by Weber, is easily demonstrable. Independently of the erro-
neousness of his views of their structure, and of the fact that the nerves
are not distributed in them, but only proceed along thera, outside, in
order, in many cases, to terminate even beyond thera — we find that all
the essential functions of the skin are also performed without such cor-
puscles. The feeling of warmth and cold, of orgasm, of tickling, of
pressure, of pricking, of burning, of pain, are found partly over the
whole surface of skin, partly in places where these corpuscles are cer-
tainly absent, which sufficiently shows that they have not in the remotest
degree the signification ascribed to them by Wagner. However, it is not
likely that they exist for nothing in those particular localities, in which
the sensibility to pressure is the greatest, and which we use especially
as tactile organs, as the ends of the fingers, the point of the tongue, and
the border of the lips ; and I consider them as parts, which in conse-
quence of their being composed principally of dense, imperfectly -formed
elastic tissue, confer a certain solidity upon the points of the papillse,
and serve as a firm support for the nerves, in consequence of which, a
pressure, which in other situations is not sufficient to affect the nerve,
here takes effect. They would, in fact, be organs, like the nails and
phalangeal bones, not essential and indispensable to the sense of touch,
but only conferring upon it a greater acuteness than elsewhere. If, in
this sense, they are to be called tactile corpuscles, I have nothing to say
against the terra, but then the phalanges and the nails, the " whiskers"
of animals, &c., equally deserve the name of tactile organs.

The contractility of the skin is exhibited in the wrinkling of the
scrotum and of the skin of the penis, the erection of the nipple, and the
occurrence of the so-called cutis anserina. It depends upon the smooth
muscles of the skin already described, which, as Froriep and subse-
quently Brown-Sequard and I have found, contract by electricity, inas-
much as by this means, even in the living subject, the cutis anserina,
the erection of the nipple, and, in recently-executed persons, a wrinkling
of the scrotum can be produced. In the erection of the nipple by gentle
mechanical irritation, the whole areola becomes dirainished by the con-
traction of its circular fibres, and thus protrudes the nipple whose mus-
cular fibres, in this case, seem to be relaxed. Cold causes the areola
and the nipple to contract, both becoming small and firm. The cutis
anserina, which consists in wholly local contractions of the portions of

OF THE SKIN.

139

the skin around tlie hair sacs by which their apertures arc protruded
conically, is exphiined simply by the existence of the muscles which I
discovered, and which pass obliquely from the superficial part of the
cutis down to the hair sacs, and Avhen they act, extrude the sacs, and
retract those portions of the skin whence they arise. The assumption
of a contractile connective tissue in the skin, as well as in other parts,
I must repudiate here, as I have already done (Mittheil. der Zliricher
Gesellschaft, 1847, p. 27), because the smooth muscles, which can be
microscopically demonstrated in the skin, and whose contraction by
galvanism may be experimentally shown, sufficiently account for all the
contractile phenomena which it exhibits.

B. EPIDERMIS.

§ 40. The corium is everywhere covered by a semitransparent mem-
brane formed wholly of cells, and containing neither vessels nor nerves,
— the epidennis^ which applies itself exactly to all the elevations and

Fiff. 55^.

depressions, and which accordingly upon its inner surface presents an
exact cast of the outer surface of the corium, the convexities and con-
cavities of course being reversed. Upon its outer surface, also, the
epidermis, to some extent, represents the form of the corium since the

Fig. 55 A. — Surface of the palm, from within : a, ridge answering to the groove between
the ridges of the cutis; b, a similar one corresponding with the cleft between the rows of
papillte; c, sweat ducts; rf, broader points of insertion of these into the epidermis; €, depres-
sions for the simple and compound papillie.

140

SPECIAL HISTOLOGY.

more marked elevations and depressions, such as the ridges of the palm
of the hand and of the sole of the foot, the folds at the joints, muscular
insertions, &c. are expressed in it, — the latter even more strongly ; on
the other hand, the papilla produce either no perceptible projection, or
hardly any.

The epidermis consists of two layers, chemically and morphologically
distinct, and which are separated by a tolerably sharp line of demarca-
tion, viz., the mucous layer and the horny layer.

§ 41. The mucous layer, stratum Malpigldi, rete or mucus llalpighii
[rete mucosum)^ of many authors, is that part of the epidermis which lies
immediately upon the coriwn, and almost everywhere appears undulated;
in many places it is distinguishable even to the naked eye by its color,
■which is whitish or variously tinged with brown, and it is further cha-
racterized by its small, soft, easily destroyed, peculiarly disposed cells.
Fig. 65 7?. The form of these cells and their dispo-

sition are not the same in all localities.
The innermost of them (Fig. 55 h), which,
without interspersed free nuclei or semi-
fluid substance, form a single layer resting
immediately upon the free surface of the
coriuvi, are elongated, and not unfre-
quently resemble the cells of cylinder-
epithelium ; they are placed perpendicu-
larly upon the corium ; their length is
about from 0-0033-0-006, their breadth
0-0025-0-003 of a line. Upon these im-
mediately follow in most places, elongated
or even round cells of 0-003-0-004 of a
line in many layers ; but in a few locali-
ties, as in the hand and foot, at the free
margin of the eyelids, in the mucous layer of the nails and hairs {vide
infra), there are interposed here and there, between the rounded and
elongated cells, one, two, or even three layers of similarly elongated and
perpendicularly disposed elements, so that the mucous layer, on account
of the numerous strata of perpendicular cells, has a striated appearance
in its deepest part, under a low power. This character is the more
striking, since the other elements of the mucous layer, the further they
are followed from the first, round cells outwards, become thinner in
another direction, i. e. become horizontally flattened (Fig. 55 c), and
finally in the uppermost layers are transformed into thick vesicles,
0-006-0-016 of a line broad, and 0-002-0-008 of a line thick. At the

Fig. 55 5. — Perpeiraicular section of tlie skin of the Negro (from the leg), aa, cutis-
papillffi ; 6, deepest intensely-colored layer of perpendicularly elongated cells of the stratum
mucosum; c, upper layer of the stratum mucosum: d, horny layer. — Magnified 250 diameters.

OF THE SKIN. 141

same time, from their mutual pressure, they acquire a polygonal form
■which may even be recognized in isolated cells.

All the cells of the mucous layer agree, in essential points, in their
structure, and arc nucleated vesicles distended with lluid. Their mem-
brane is pale, often difficult of demonstration in the smallest, frequently
quite distinct, always delicate, thicker in the larger ones, yet by no
means to be compared to that of the cells in the horny layer. The
contents are never quite fluid; but also, excepting in the colored epi-
dermis {vide infra), never normally contain larger particles, granules or
fat-drops for example ; but are finely granulated, with more or less
clearly-defined granules, Avhich invariably diminish in number in the
more external cells. The nucleus, lastly, is small in the smallest cells,
(0-0015-0-0025 of a line), in the large, of greater size (0-003-0-005 of
a line) ; globular or lenticular in the round and flattened cells; elongated
in the elongated cells. In the larger cells it appears obviously vesicular,
often with a nucleolus, and lies centrally in the midst of the contents ;
in the smaller it is apparently more homogeneous, without any visible
nucleolus, and so disposed that it is not unfrequently in contact with
one part or other of the cell-walls.

[Most authors admit the existence of a special membrane between
the cuticle and the corium. Krause (loc. cit. p. 112) describes on the
upper surface of the corium a perfectly transparent, textureless, semi-
fluid, tough mass of ^loth to 350th of a line in thickness, which he be-
lieves to be the cytoblastema of the epidermic cells, covered by a layer
of free nuclei and real cells. Ilenle (loc. cit. p. 1010) considers the
inferior layer of the cuticle as a continuous cytoblastema with inter-
spersed nuclei, and calls it the "intermediate skin." Such free nuclei
are admitted byBruns(loc. cit. p. 358), by Gunther (loc. cit. p. 257), by
Hyrtl (p. 379), by Hassall (loc. cit. p. 242), and others, whilst Reichert
(Mailer's Archiv, 1845), denies their occurrence, and also that of the
structureless membrane of Krause. Todd and Bowman (loc. cit. p. 413,
Fig. 84), regard the lower portion of the epidermis as consisting of fully-
developed cells (loc. cit. p. 404-411), and admit as the external border of
the corium a simple homogeneous and transparent membrane, " basement
membrane," which view Carpenter seems to share. My own observations
lead me to believe with Reichert, that the lowest layers of the epidermis
consist of fully-formed cells, as may be easily ascertained in most cases
by the addition of acetic acid, or diluted alkalies to fine vertical sections.
We are, therefore, not justified in drawing conclusions from those cases in
which the cells are not distinct, which, it is true, does not unfrequently
occur ; for even then the regularity of distance separating the nuclei, the
traces of cell-membranes observable as delicate strite between them, and
the distinct limitation of the Malpighian stratum, as it approaches the
corium, aiford certain evidences of the existence of fully-formed cells.
The homogeneous membrane of Krause, and the basement membrane of

142

SPECIAL HISTOLOGY.

Fig. 56.

the English authors, I believe to be identical. They are but the external
portion of the corium, which appears, especially around and between the
papillre, as a structureless and homogeneous membrane. A separation
from the corium of this narrow, and on its under surface, by no means
distinctly limited membrane, ought not to be attempted ; for although a
distinct membrane in the embryo, it cannot be obtained as a special layer
in the adult. (From Kolliker's Microsc. Anat. vol. ii. p. 47. — DaC.)]

§ 42. The liorny layer [stratum corneum), forms the external semi-
transparent part of the epidermis, which in white people is colorless,
and is composed almost wholly of uniform cells metamorphosed into
plates. The deepest plates are still very similar to the uppermost cells
of the stratum mucosum; but even in the second or third layer we find
the widely different ejnderjnic or hoimy jilates. They (Fig. 56, 1, 2, 3)

are, in fact, plates of moderate thickness, which
in the lower and middle parts of the horny layer
retain tolerably regular polygonal (4-5-6-sided)
and smooth surfaces ; in the upper layers, on
the other hand, they present more irregular
outlines, are variously crooked and curved, and
thence often appear to be wrinkled and folded.
These plates must be regarded as cells, com-
pletely flattened, and containing a very minute
quantity of viscid fluid ; and not, as might at
first be imagined, as homogeneous lamellae,
j composed throughout of the same substance ;
for by the addition of various reagents, espe-
cially of acetic acid and potassa, they swell up
and assume the form of vesicles (Fig. 57) ; at
the same time, a rudimentary nucleus becomes
obvious in a few, particularly in those from the
middle and inner layers, but by no means in
the majority of them, in the form of a flat,
homogeneous, rounded or elongated corpuscle,
0-003-0-004 of a line in length, and 0-002-
0-003 of a line in breadth, which, especially
when seen from the side, is easily recognized
by the dark contours which it then presents.
The size of the plates of the ordinary horny
layer varies from 0-008-0-016 of a line, and
in the outer layer it is commonly somewhat

Fig. 56. — Horny plates of man: 1, without addition, viewed from the surface one with a
nucleus; 2, from the side; 3, treated with water, granular and dark; 4, nucleated plate,
such as occur on the outer surface of the labia minora and on the glans penis. — Magnified
350 diameters.

OF THE SKIN. 143

greater than in the inner. Upon the bod}'- of the peti is the cells mea-
sure 0-008-0-012 of a line; upon the glacis, the largest are OOlG-0'02
of a line ; upon the outer side of the labia minora 0-012-0-02 ; on the
labia majora 0-01-0-016 of a line. These last, larger cells, all possess
distinct nuclei, and are almost identical with the epithelial plates, c. g.
of the cavity of the mouth and of the vagina (Fig. 56, 4).

Whilst the stratum Malpigliii, except in its upper layer, is but indis-
tinctly laminated, a clear lamination is obvious in the horny layer, inas-
much as its plates applied together horizontally, form strata in number
proportionate to the thickness of the horny layer (Fig. 55). It must
not be imagined that these strata are distinctly defined from one another ;
they are connected by their surfaces, and can only be detached and de-
monstrated adhering together in numbers, by dissection, which is much
facilitated by boiling or macerating the epidermis. The innermost, like
the stratum Alalpigliii^ taken together, exhibit a wavy course wher-
ever papillae exist, projecting outwards over the points of the papillae,
and following the depressions between them. This takes place in the
most striking manner where very much developed papilljs coexist with
a moderately thick rete 3Ialpighii, especially in the palm and in the sole
of the foot, in which (see the figure in the section on the sudoriparous
glands), the horny layer penetrates so deeply between the papillae, that
its deepest cells are on a level with half their height : where the papilla
are smaller, the horny layer sinks less deeply between them, or even lies
quite flat upon the stratum 3Ialpighii, as is the case where the papillae
are absent. From this cause the boundary-line between the horny layer
and the stratum mucosum in perpendicular sections, is sometimes straight,
sometimes wavy, with smaller or greater elevations and depressions.
The other parts of the horny layer take a more even course the further
they are from the mucous layer ; yet not merely in the hand and foot,
where, as is well known, the ridges of the corium are marked externally
upon the epidermis, but in many other localities, a slightly wavy course
of the uppermost layers may be perceived in perpendicular sections, and
slight elevations indicate externally the points beneath which the papillae
are seated. In the separate lamelloe the plates are sometimes irregular,
sometimes arranged circularly, as around the excretory ducts of the
glands and hair-follicles, and also round the papillae on the palm of the
hand and sole of the foot, as may be seen most readily at the apertures
of the sudoriparous glands.

§ 43. As regards the color of the epidermis, in the white races, as
has been said, the horny layer is colorless and transparent or slightly
yellowish, the mucous layer yellowish white or brownish. The color is
deepest in the areola and in the nipple, passing even into blackish-
brown, especially in women during pregnancy and after they have borne

144 SPECIAL HISTOLOGY.

children ; it is less intense in the labia majora, the scrotum, and the penis,
■where for the rest it varies greatly, being sometimes almost' entirely
absent, sometimes very distinct, and is least considerable in the axilla
and round the anus. Besides these situations, which in most individuals
are more or less tinged, in the dark-complexioned more than in the
fair, a lighter or more deeply colored, frequently very dark pigment is
deposited in various other localities in the sti-atum Malpighii; in preg-
nant women in the linea alba, and in the face (rhubarb-colored spots);
in persons who are exposed to the sun, in the face, especially the brow,
chin, and cheeks ; in the neck, the thorax, the back of the hands, the
forearm ; and in dark persons over almost the whole body. These
tints are not produced by special pigment cells, but are seated in the
common cells of the mucous layer, round whose nuclei a finely granular
or more homogeneous coloring matter or actual pigment granules are
deposited. When the skin is only slightly colored, it is mostly only the
neighborhood of the nuclei and in fact only of the lowermost layers of
cells which is implicated, so that in perpendicular sections the papillse
are seen to be surrounded by a yellowish fringe; darker shades are pro-
duced by the extension of the color to two, three, four, and more layers
of cells, and over the whole cell contents ; sometimes by a darker
coloration of the deepest layer of cells ; the two conditions commonly
coexisting. The horny layer also of the colored places of the skin,
has according to Krause, its cell walls slightly tinged; this appears,
however, only upon comparing them with those of uncolored parts of the
skin, and only in the more deeply-tinged parts. In the negro, and the
other colored human races, it is also only the epidermis which is colored,
whilst the corium completely resembles that of Europeans. The pig-
ment, however, is far darker and more abundant. In the Negro (Fig.
55), in whom, as regards the arrangement and size of the cells, the epi-
dermis is precisely like that of the European, it is the perpendicular
cells of the deepest part of the mucous layer which are darkest (dark
brown or blackish-brown), and they form a sharply marked fringe con-
trasted against the clear corium. To these succeed clearer but still
brown cells, which are accumulated particularly in the depressions be-
tween the papillre, but are also found on their points and lateral por-
tions in many layers ; finally at the boundary close to the horny layer
there follow brownish-yellow or yellow, often rather pale, more trans-
parent layers. All these cells are colored throughout, with the excep-
tion of their membranes, and especially the parts round the nuclei,
which, in the internal layers, are by far the darkest portions of the
cells.* The horny layer of the negro also inclines to yellow or brownish.

* [The pigment in these cells seems of two kinds: a less intense yellowish pigment, and
a dark granular pigment. The latter is irregularly dispersed throughout the contents of the
cell, and in some parts it is conglomerated into small masses. It is generally especially

OF THE SKIN. 145

In the yellowish skin of a Malay head in the anatomical collec-
tion at Wiirzburg, I find the same appearance as in a dark-colored
European scrotum. It follows, then, that the epidermis of the colored
races is, in no essential point, distinguishable from the colored regions
in the white man, and it even agrees in nearly all respects with that
of certain localities (the areola of the nipple, for instance).

Pathological coloration of the epidermis (freckles, mothers' marks,
&c.), according to Simon, Krause, Barensprung, and my own observa-
tions, is produced exactly as the more intensely colored spots in the
white man, and as the color of the negro's skin. Pigment deposits in
the corium and in the papillte, such as may be seen in cicatrices, after
chronic inflammation of the skin, and frequently as in ichthyosis and
many ncevi, associated with a colored epidermis, in which the pigment
is developed directly from the blood-corpuscles and their coloring mat-
ter, must be carefully distinguished from the foregoing.* Numerous
instances of partially or entirely white negroes and of black Europeans,
not as a consequence of change of climate, but as a congenital or sub-
sequently arising abnormal condition of the skin, have been noticed (see
Ilildebrandt. — AVeber, II. fig. 526 ; Flourens, Compt. rendus XVII.)
But, for the future, it. will have to be remembered, so far as the dark
coloration of Europeans is concerned, that it may also arise from a de-
position of the coloring matter of the bile.

§ 44. The thickness of the epidermis as a whole, varies exceedingly, de-
pending especially upon that of the horny layer. It measures : —

l-75th to l-50th of a line, upon the chin, the cheeks, and brow, in the
external auditory passages, and upon the eyelids:

1-oOth to l-25th of a line, upon the bridge of the nose, on the breast
and nipple of a female, on the back of the toes and fingers, upon the
neck and back, on the inner and outer side of the thigh, on the scro-
tum and the labia minora :

l-25th to l-16th of a line, on the edge of the eyelids, on the male chest
and nipple, the hairy scalp, the chin, penis, prepuce, and glans
penis:

1-1 6th to 1-lOth of a line, on the red external parts of the lips, on the
back of the hand:

1-1 0th to 1-7 th of a line, on the flexor side of the fingers and toes:

dense around the nucleus, which is itself but rarely recognizable, except by the aid of
reagents, and does not seem to contain any of these darker granules. — DaC.j

* [A colored epidermis may also be produced by a parasitic vegetable growth, as in the
disease called pityriasis versicolor, in which the yellowish color of the epidermis, is owing to
layers of filaments and spores deposited under the epidermic cells. — DaC]

10

14G SPECIAL HISTOLOGY.

1-3 to 1-2 of a line, on the palm : and —

3-4ths to l^d of a line, on the sole of the foot, in which two latter
localities the variations are greatest, independently of the circum-
stance, that in the furrows and at the joints the skin is thinner than
elsewhere.

With regard to the proportionate thickness of the horny and raucous
layers I find, in some localities, that the latter is constantly thicker
than the former ; i. c, in all parts of the face, in the hairy scalp, in the
penis, the glajis, the scrotum, the nipple, and the skin of the thorax
in man; in the labia majora and minora, on the back and neck. Here
the mucous layer is 3-6 times, or 2-3 times as thick as the horny layer,
according as its thickness is measured from the bases or from the points
of the papillce ; in a few of the localities mentioned, however, the stra-
tum Malpigldi is, in its thinnest parts, of the same thickness as the
epidermis, as in the glans. In the rest of the body both layers are
either equal in thickness, as in the external auditory passage, and here
and there upon the flexor side of the first two sections of the extremities,
or the horny layer is 2 to 5 times thicker than the mucous, and in the
thickest places even 10 to 12 times as thick.

The absolute thickness of the stratum 3Ialpigliii varies (at the base
of the papilloi) between 0*007 and 0-lG of a line ; where it is thicker
than the horny layer, it measures in the mean 0-04 of a line, where it
is thinner, 0-01-0-02 of a line. The horny layer by itself measures in
many places only 0*005 of a line, in others 1 line or more ; when its
thickness exceeds that of the stratum Malpighii, it is generally about
0*1-04 of a line, Avhen it is less, 0*01 of a line.

§ 45. Physical and Vital Properties. — The epidermis is but little
elastic, flexible in the living condition and not easily frangible, softer
in the deeper than in the superficial layers. The cells contain, neither
in their membranes nor between them, any demonstrable pores (apart
from the sudoriparous ducts and hair-sacs, which, in a manner, have
their outermost portions hollowed out in the epidermis), and form a
very solid, hardly a permeable substance. Many experiments, especially
those of Krause, show, that the horny layer of the epidermis permits
no fluids, except those which act chemically upon it, as the mineral acids
and the caustic alkalies, to pass through it, either by pores or by
imbibition, or by endosmose and exosmose, while it readily takes up
gaseous matters, or easily vaporizable substances (alcohol, ether, acetic
acid, ammonia, solutions of chloride of iron in ether, of acetate of lead in
alcohol), and gives them oft" (cutaneous evaporation). This conclusion
is not invalidated by the undeniable passage of water, liquid substances,
ointments, and even solid matter (sulphur, cinnabar), through the unin-

OF THE SKIN. 147

jured epidermis, since in these cases a mechanical intrusion of the sub-
stances, in and through the sudoriparous ducts and hair-sacs, or their
penetration into the sweat-ducts, and mingling with the sweat, explains
their absorption. The mucous layer, at any rate, is easily penetrated
by liquids, as is sufficiently shown by pathological anatomy (exudations
which penetrate the mucous and raise up the horny layer into a vesicle
the ready occurrence of absorption after the separation of the horny
and the superficial portion of the mucous layer, by the action of vesi-
cants).

In their chemical relations, it is indeed well known how the cells and
plates of the epidermis behave with regard to certain reagents, but
there exists, at present, no perfectly satisfactory total analysis of the
epidermis, with regard to its two layers which differ so widely ; and the
organic combinations, also, which occur in it, are not sufficiently known.

The so-called horn, which forms the membranes of the horny plates,
is insoluble in water, easily soluble in concentrated alkalies and con-
centrated sulphuric acid, whence the skin, if wetted with these sub-
stances, feels slippery and greasy ; there remains, however, a small residue
insoluble in alkalies ; concentrated acetic acid, also, dissolves it, first
rendering it gelatinous, by which it is distinguished from the protein
compound of the hair. It contains less sulphur than the hair and nails,
which is perhaps the reason why salts of lead, mercury, and bismuth,
color the hair but not the epidermis. Besides these, Mulder finds in
the horny layer a gelatinous matter, which is obtained by long boiling
in water, and which would appear to be of a collagenous nature. The
epidermis does not putrefy — it melts in the fire without bending or
swelling up, and burns with a clear flame.

The behavior of the epidermis towards reagents is particularly of
importance for the microscopist, on whose behoof I add the following
account.

After long maceration in water, the epidermis becomes detached in
portions, and under moderate pressure is resolved into a white powder,
consisting of the isolated horny plates, and the uppermost cell of the
rete Malpighii. Boiled in water, pieces of the horny layer break up
into their elements much more readily. Boiled in concentrated acetic
acid from 15 to 25 minutes, all the horny plates become perfectly isola-
ted, forming a cloudy, whitish deposit in the test tube ; they are ex-
ceedingly pale, so that they are often hardly visible under a full illu-
mination ; and are completely swollen up and changed into globular or
elongated, distended, but always more or less flattened vesicles of 0-02-
0-032 of a line in breadth, and 0-006-0-01 of a line in thickness, the nuclei
when they are present being also pale and hardly to be perceived. The

148

SPECIAL HISTOLOGY.

Fig. 57.

Malpighian layer becomes pale under the action of cold, concentrated
acetic acid, the cells and nuclei being rendered more distinct. The
cell-contents are partially dissolved: by longer action the contours of
the deepest layers of cells become invisible. The same thing occurs
after boiling for four minutes.

Caustic potass and soda act differently, according as the solutions used
are concentrated or diluted. In the latter case, immediately after the
addition of the reagent, the horny layer is rendered more clear, it swells
up and changes in a short time into a beautiful tissue of pellucid, glo-
bular vesicles, without nucleus or granules, and with sharp, moderately-
thick contours, 0-02-*032 of a line in breadth, and 0-016-0-02 of a line
in thickness. If concentrated, solutions of the caustic alkalies render
the plates at first smaller, so that they measure only 0-012-0-016 of a
line, and are at the same time more wrinkled and pale, but with defined,
dark contours ; in the course of an hour they swell up so as to appear
as cells, but it takes two or three hours to give them the aspect of the
plates which have been heated with dilute solutions. Boiled with these
fluids, even the dry horny layer swells up, in an instant, into the most
beautiful tissue of cells, Avithout either granules or nuclei (Fig. 57), and
at the same time the dissolving cell-contents mixed with the alkali, are

collected in the cells, into greater and
smaller granular masses ; after the
action of the heat for five hours, all the
cells disappear without leaving a trace,
and yellowish and pale fat-drops in no
great number, swim in the liquid. The
cells of the Malpighian layer are still
more acted upon by alkalies than those
of the horny stratum : they swell up
at once, and appear distinctly as deli-
cate vesicles; these then dissolve, all
but the uppermost two or three layers,
which require a longer time, like those of the horny stratum, though
less than the latter. The nuclei of all the cells withstand the operation
of this reagent even less than the cells ; whilst, when the latter are dis-
solved, a granular or striated substance remains behind, which is, pro-
bably, partly fat. Concentrated sulphuric acid, in five minutes, causes
the horny layer to swell up so much, that its elements, although still
remaining flattened and irregular, appear quite distinctly to be vesicles;
after half an hour they are somewhat more distended, and easily sepa-
rable from one another. By boiling with this acid the plates swell up

Fig. 57. — Horny plates boiled with caustic potassa and distended ; the contents partially
and wholly distended. — Magnified 350 diameters.

OF THE SKIN. 149

even in a minute, without exhibiting nuclei, and in two minutes they dis-
appear without leaving any trace. Boiling in dilute sulphuric acid ren-
ders the horny layer hard and transparent, and dissolves it wholly in 4—5
hours. The cells of the stratum dIalpigJni* are little altered by cold
sulphuric acid: on boiling, their contours and nuclei at first become more
distinct, but in about two minutes the whole is dissolved. Nitric acid colors
the epidermis yellow, softens and changes it into xantho-proteic acid.
The cells of the horny layers swell up somewhat, after a time, in the cold,
and become granular ; the stratum Malpighii is rendered granular and
indistinct, and sharply defined from the horny layer. Upon boiling, the
whole epidermis is entirely dissolved in half a minute. Hydrochloric
acid does not tinge the epidermis, and in the cold renders the cells of

* [I have recently investigated the reaction of the pigmental cells in the Malpighian
layer of the Negro, and with the following results. Macerated in water they remain
unchanged. Caustic polassa renders the outline of the cell more distinct, but produces no
eflect on the enclosed pigment. After acting for three or four hours it dissolves the cell,
and allows the dark pigment granules to escape. Boiled for ten minutes in a solution
of caustic potassa, the cells become larger and more distinct; in many, nuclei and dark
granules are visible ; and their color becomes clianged to a yellowisli brown. Prolonged
boiling dissolves the cells, but does not act on the granidar pigment ; caustic soda brings the
pigment cells distinctly into view and causes them to swell up. Continued action for one
or two hours, dissolves the cell and permits the unchanged black pigment to escape. Upon
boiling for about four minutes in caustic soda, rupture of the cell-wall vvitli escape of the
contents ensues.

Concentrated sulphuric acid has no etiect on the Malpighian layer. When first added the
cells are rendered more distinct ; after twenty-four hours no further etfect is observable.
Boiling in sulphuric acid produces no change on the cells; after a few minutes the whole
epidermis is dissolved. Nitric acid when first added had no decided action ; but after a few
hours it rendered the cells more indistinct, dissolving some, and staining the intermediate
tissue yellow. Soaked for twenty-four hours in nitric acid, the whole pigmentary layer
assumes a yellow color; the separate cells are scarcely recognizable. The rapidity with
which the whole epidermis when boiled in nitric acid is dissolved, makes it dilficult to
determine its eftect upon the Malpighian layer.

Hydrochloric arid does not act as powerfully as nitric acid. At first its addition produces
no etfect on the cells; in the course of a few hours, they become more indistinct, but are not
dissolved. The same result is obtained by allowing this acid to act for twenty-four hours.
The cells are then indistinct, but of a black color; boiled for two minutes they swell up,
enlarge, but are not rendered more distinct. More prolonged boiling (four or five minutes)
dissolves the whole epidermis. Acetic acid causes the pigment-cells to be more easily dis-
tinguished. In a preparation that had been placed for five weeks in concentrated acetic
acid, the cells were very distinct; but not otherwise altered. No effect was produced upon
the pigment.

The action of Nitrate of silver, as it stains the horny tissue, cannot be well ascertained. In
a preparation, that had been placed in a concentrated solution for twenty-four hours, the
pigment cells, as far as they could be studied, were of a more intense color, but not otherwise
altered. In alcohol and ether the epidermis is hardened and the pigment-cells of the
Malpighian layer are well and distinctly seen, but these reagents exert no action on them.
Boiled in ether the cells become distinct and of a lighter color. A solution of Iodine, colors
the whole epidermis immediately, and thus prevents the study of its special action upon
the pigmental cells of the Malpighian layer. — DaC]

150 SPECIAL HISTOLOGY.

the horny layer somewhat more distinct than nitric acid. After boil-
ing for a minute the horny layer becomes a beautiful cellular tissue,
exactly as after the addition of dilute solution of potass. In carbonate
of potass the epidermis is hardly changed at all. After seventeen
■weeks it is hardened and easily cut with a knife. Nitrate of silver
colors it violet or brownish-black, by the formation of oxide of silver,
of chloride of silver, and of black sulphuret of silver, in consequence
of the chloride of sodium and sulphur which it contains. Investigated
microscopically with the help of acetic acid, the tissue of the epider-
mis is seen to remain quite unchanged, and minute dark granules are
visible between its elements. Nitrate of mercury gives the epidermis a
reddish-brown hue, sulphurets of the alkalies render it brown and
black: many vegetable colors unite with it. In alcohol and ether it
is insoluble, with the exception of a small quantity of fat which it
contains.

From all this, it results, with regard to the elementary parts of the
epidermis, that they are cells, which, however, as the alkalies show, do
not everywhere present the same characters. In the stratum mucosum
they are actual vesicles and easily soluble — in the horny layer, scarcely
so ; and here, in fact, a distinction must be drawn between the resisting
cell-membrane and the cell-contents, which swell up and disappear more
readily; these, in the natural condition, form an apparently homogene-
ous simple plate, but the difference between them may be readily ex-
hibited by reagents. In what parts the small quantity of collagenous
substance, which has been noticed, has its seat, is not clear ; perhaps
it forms a portion of the contents, especially of the cells of the mucous
layer, or belongs, it may be, to an intermediate substance between the
cells, which, however, is not microscopically demonstrable. If the fat
of the epidermis is not merely accidental, arising from the cutaneous
secretions, it is most probably contained within the Malpighian cells.

Cruns, Todd and Bowman, Valentin and Brueh, recommend the use
of alkalies for the investigation of the epidermic tissues, but their full
importance was first shown by Donders (Mulder's " Phys. Chemie," p.
257, et seq., and " Hollandische Beitrage," I. u. 11). They are now
generally recognized as quite indispensable reagents for the investiga-
tion of the horny tissues ; but, as Paulsen (" Obs. Microchem.," &c.
Dorpat, 1848) and Ileichert (Miill. " Arch," 1847, Jahresbericht.) ad-
vise, it is well always to use only definite solutions. I may add, that a
great saving of time is effected by the heating of the tissues to be inves-
tigated in test tubes, with these and other reagents, as I have already
done in examining those tissues of animals which contain cellulose
("Annales d. Sc. Nat.," 1846).

§ 46. G-rowth and Regeneration. — The epidermis possesses no power
of continually active growth depending upon intrinsic causes and founded

OF THE SKIN. 151

upon the vital relations of its cells, or those which it has with the corium ;
it is essentially a stable tissue, which does not change in its elementary
parts, but, somewhat like a cartilage, has all its vital energies directed
to its unchanged self-maintenance as a whole (thickness of the whole
epidermis, proportion of the rete 31alj)ighu to the horny layer), and in
its separate parts. However, since a throwing-off of the external
layers, if not necessarily, yet accidentally, takes place almost con-
tinually over the whole body to a greater or less extent, the epidermis
is, so to speak, continually occupied in replacing what is lost, or in grow-
in'-^, and thus exhibits its vegetative life in a more remarkable manner.
AVhichever takes place, it is the corium and its vessels from which the
fluids required by the epidermis are derived. In every locality, we may
suppose, that a certain determinatequantity of plasma, corresponding with
the anatomical and physiological relations of the vessels of the corium
and the thickness of the epidermis, permeates the latter, and, when it
is not growing, simply fills its cells and plates (independently of that more
watery fluid which subserves the cutaneous evaporation), maintaining
their vital activity, and at the most causing temporary deposits of pig-
ment in the rete 3Ialpigliii. If, on the other hand, its outer layers be
removed, a certain amount of plasma becomes free and disposable, and
then regeneration takes place, which, if it proceed continuously, may
even be called growth. It is in this process that the vegetative life of
the epidermis-cells is most distinctly evidenced, particularly in the rete
Malpighii, where it is unquestionably most intense, exhibiting itself
especially in the multiplication and growth of the cells, and in their
chemical changes. In the horny stratum the phenomena are less strik-
inir, thouch it must not be considered to be inactive even in the uppermost
layer ; being by no means dead matter, as we evidently see, when under
certain conditions, especially under abnormal states of the corium —
the source of its nutrition — it sometimes becomes hypertrophied, some-
times completely dies away. We have not as yet, however, attained to
an exact insight into the vital manifestations of the epidermic cells, and
are therefore not in a condition to decide which of the phenomena pre-
sented by them are to be ascribed to their own activity, and which to
the nature of the plasma which nourishes them. The latter is certainly
of the greatest importance for the epidermis, and it is more than pro-
bable that most of its peculiarities, as, for instance, its typically difi'erent
thickness in different parts of the body, the difi'erent relations of the
stratum 3Ialpighii to the horny layer, and its pathological states, depend
upon qualitative and quantitative diff"erences in the plasma. Upon what
condition, furthermore, it depends, that in the Malpighian layer, the
changes of the cells are far more considerable than in the horny layer,
"whose elements all closely resemble one another, is as little obvious as

152 SPECIAL HISTOLOGY.

the cause of the somewhat defined line of demarcation between the two
layers, a condition which appears still more strikingly in the nails, and
would lead one to suppose that, at the first formation, and in the course
of the development of the epidermis and nails, a very considerable altera-
tion suddenly takes place at one point in their cells, thus determining
their separation into two layers.

In the deep fold of the skin which surrounds the glans penis and clito-
ridis, a continual desquamation and reproduction of the epidermic scales,
which are here soft and nucleated, takes place, in consequence of which
a peculiar secretion, the smegma preputii, is produced. Hitherto this
secretion has been erroneously, but almost universally, supposed to be a
sebaceous matter secreted by the preputial glands. The microscope
shows : 1, that in the female, Avhere the presence of smegma preputii
is constant, neither sebaceous nor any other glands exist upon the pre-
puce or glans clitoridis ; 2, that in the male, in whom such glands are
indeed found, they are commonly but insignificant in relation to the
quantity of smegma, and are often very few and scattered; 3, finally,
that the smegma, in both sexes, consists principally of cells of the same
form as those of the prepuce and glans peyiis and clitoridis; whence,
taking also into account the fact, that in the male it is generally dis-
tinctly composed of superimposed layers covering the whole prepuce con-
tinuously, whilst the sebaceous glands occur only isolated, it naturally
follows that the smegma is principally constituted of desquamated epi-
dermis. However, this does not exclude the preputial sebaceous matter
in the male from also taking a share in proportion to the number and
size of Tyson's glands, in the formation of what goes under the common
name of smegma. There would in this locality then, really be a con-
stant desquamation of the external, and a new development of the in-
ternal layers of the epidermis, but here there are special purposes in
view which elsewhere do not enter into consideration. The preputial
fold, in fact, is to be compared to a gland ; and as the secretions of these
are very often formed only by the continual casting off of the cells which
line them (e. g. sebaceous glands), so is that of the prepuce. We must
recollect that in many animals, e. g., the Weasel, the Beaver (E. H.
Weber), without essentially changing the character which it possesses
in man, the prepuce takes on a highly glandular nature, and that even
in man it yields a secretion which differs considerably from common epi-
dermis. According to Lehmann, the yellow, fatty, strongly-odorous
preputial smegma of man contains, when dried, in 100 parts : Ethereal
extract, 52-8 ; alcoholic extract, 7*4 ; aqueous extract, 6*1 ; earthy salts,
9*7 ; albuminous substances soluble in dilute acetic acid, 5-6; insoluble
residuum, 18'5. The ethereal extract contained saponifiable fat, choles-

OF THE SKIN. 153

k

terin, a non-saponifiable and uncrystallizable fat and bilin (Gallenstoff).

The smegma of the horse possessed nearly the same constituents ; and

among the salts, oxalate of lime; while in man, ammonio-phosphate of

magnesia occurred. The watery extract contained neither albumen nor

casein.

An extensive desquamation of the entire horny layer of the epidermis,
such as takes place in the embryo and in many animals, does not occur
in man except in certain morbid states. On the other hand, its power
of regeneration is exhibited in other modes than those which have been
mentioned. Excised portions of the epidermis, for instance, are very
readily replaced, and with tolerable rapidity, so long as the corium be
not injured ; and, in fact, not by the immediate deposition of epidermis
in the wound, but only by the growing up of the whole epidermis from
below. If the eorium be injured as well, an epidermis is, indeed, formed
upon the substance of the cicatrix, but without any of the previous ele-
vations and depressions of the internal and external surface, because
the new corium has neither papillae nor ridges. If the epidermis be
raised up into a vesicle by acrid substances, e. </., Tartar emetic, a slight
burn, &c., the wall of the vesicle, which consists of the horny layer and
some few layers of cells of the mucous layer, never again becomes adhe-
rent; but from the main substance of the mucous layer, which mostly
remains lying upon the papillre, a new horny layer is by degrees deve-
loped.

If we inquire more minutely into the mode of regeneration of the epi-
dermis, there can, in the first place, be no doubt that it takes place in
the Malpighian layer, inasmuch as losses of substance of the horny layer,
e. g. a piece cut out, are restored not by the formation of a new portion
in the gap, but by the growth outwards of a horny layer fi-om below
(the wound remaining wholly unchanged), which gradually raises the
bottom of the wound, and brings it to a level with the surrounding epi-
dermis, the latter, in consequence of the pressure that it suifers from the
growing portion, becoming everted and exfoliating. The reason of this
phenomenon is to be sought, simply in this, that the non-vascular epider-
mis draws the materials which it requires for its nutrition and regenera-
tion from the superficial vessels of the corium. It is more difficult to
ascertain from what portion of the Malpighian layer the regeneration
proceeds. If a layer of cytoblastema and of free nuclei existed upon
the surface of the corium, as many authors suppose, we might acquiesce
in the view, that the epidermis grows by free cell-development in those
innermost layers which rest immediately upon it ; but such a cytoblas-
tema, as we have seen, does not exist, the stratum MalpigJiii being in-
variably formed by perfect cells ; and thence nothing remains, but to
suppose an endogenous cell-development around portions of contents in

154 SPECIAL HISTOLOGY.

4

the deepest round cells, or a multiplication by division, for which
latter view the occasional occurrence of two nuclei in some of the softer
epidermic cells, seems to speak. It can be more easily made out, how,
in the course of the growth of the epidermis, the youngest epidermic
cells become changed into horny plates. The small and round vesicles
of the deeper layers of the stratum 3Ialpigldi become larger and flatter
the more they approach the surface, until at last they are completely
converted into flattened plates. In the meanwhile their nuclei at first
grow a little, and then, as a general rule, disappear wholly in the horny
layers ; whilst the cell-contents, which are granular in the mucous layer,
clearly distinct from the cell-membrane, and probably semi-fluid, become
more solid and homogeneous in the horny layer, and finally coalesce with
the cell-membranes. At the same time the latter are chemically altered,
becoming less and less soluble in caustic alkalies.

§ 47. Development of the Epidermis. — The first layers of the epi-
dermis are developed, in the Mammalia, by the metamorphosis of the
most superficial of the original formative cells which compose the young
embryo. When the rudiments of the stratum 3Ialpighii and horny layer
are once indicated, the former continues to increase in thickness, in con-
sequence of the multiplication of its elements, whilst the horny layer,
for the increase of its proper substance and to replace what it loses by
desquamation, recruits itself from it exactly as in the adult. How the
multiplication of the cells goes on in the rete Malpigliii has not been
directly observed ; but it is certainly not by free cell-development, since
in embryos of all ages the mucous layer consists wholly of cells, and free
nuclei are altogether absent. As regards the horizontal extension of the
epidermis, it appears, as Harting (" Rech. microm^tr," p. 47) justly ob-
serves, from the circumstance that the epidermic scales of the foetus and
of the adult differ very little in superficial size, that it can only in a
very slight degree be ascribed to the growth of its elements. In fact
the horny plates of the embryo of fifteen weeks already measure 0-009
-0-012, in the sixth month 0-01-0-012, in the seventh month 0-01-
0-014, in the new-born infant 0-012-0-016, in the adult 0-008-0-016
of a line. Since, however, keeping in mind the structure of the horny
layer, it cannot well be supposed that new scales are continually inter-
calated from below between its elements, and since a superficial multi-
plication of the cells of the rete, which also do not increase in size, must
certainly be granted, it seems impossible to admit any other conclusion
than that, in agreement with the great superficial growth of the cutis
and of the rete, and the small extensibility of the horny layers, a series
of desquamations of the latter take place, which, if this view be correct,
must likewise obtain after birth.

OF THE SKIN. 155

In an embryo of five weeks I found, in the place of the epidermis,
nothing but an external layer of polygonal cells of 0-012-0-02 of a line
in diameter, and an internal layer of small cells of 0-003-0-004 of a line ;
in embryos of fifteen weeks the epidermis is 0-01-0-012, of a line thick,
and composed as before, only that the deep layer of cells answering to
the stratum mucosum is often already double, and the external cells
measure only 0-009-0-012 of a line.

In the fifth month the epidermis in one instance measured on the heel
and ball of the hand 0-02-0-024 of a line, over the ridges of the cutis
0-036-0-04, in the furrows between them on the back 0-02-0-024 of a line,
of which thickness one-third may be regarded as belonging to the horny
layer and two-thirds to the rete Malpigliii. In a somewhat older embryo
it was, on the heel 0-06--064 of a line (raucous layer 0-05, horny layer
0-01-0-014), on the surface of the hand 0-05 of a line (mucous layer 0-04,
horny layer 0-01), on the back 0-02-0-024 of a line (mucous and horny
layers of equal thickness). The mucous layers consisted of many layers
of smaller cells, the lowest of which were already elongated, and stood
perpendicularly ; the horny layer, of at least two layers of polygonal
flattened cells, with round nuclei.

In the sixth month the epidermis upon the thorax measures 0-02-
0-022, on the palm of the hand 0-06, on the sole of the foot 0-07 of a
line, and everywhere it consists of many layers of cells. The outermost
one or two are composed of horny plates without nuclei 0-01-0-14 of a
line, perfectly similar to those of the external horny layer in adults ;
then follow 3-4 layers of polygonal cells, the largest 0-01-0-012 of a
line, with nuclei 0-004 of a line; finally a mucous layer, whose thickness
equals about one-half or two-fifths that of the whole epidermis, with at
least 3 or 4 layers of rounded cells of 0-003-0-004 of a line, the lowest
of which are somewhat elongated, and are seated perpendicularly upon
the cutis.

In the seventh month, I found in one embryo, that the epidermis
on the heel measured 0-12 of a line (mucous layer 0-072, horny layer
0-048), upon the back 0-07 of a line, (mucous layer 0-04 horny layer
0-03): in another it measured on the heel 0-12-0-14 of a line (mucous
layer 0-05-0-06, horny layer 0-07-0-08), on the knee 0-046-0-064 of
a line (mucous layer 0-016-0-024, horny layer 0-03-0-04). Both layers
of the epidermis are as sharply separated from one another as in adults,
and their elements similar to those of the perfect epidermis, especially
the lowest parts of the stratum Malpigldi and the plates of the horny
layer, which have no nuclei, and measure 0-01-0-014 of a line in the
uppermost layers.

In the new-born infant, apart from the thickness of the epidermis,
which in one case measured on the heel 0-1-0-11 of a line (mucous
layer 0-04-0-05, horny layer 0-06), nothing particular is to be observed,

156 SPECIAL HISTOLOGY.

except that by maceration, &c., it is much more easily separated from
the corium than in the adult. The non-nucleated horny plates measured
0-012--016, on the labia minora, where they possess nuclei 0-016-0'02
of a line.

During embryonic life a desquamation of the epidermis occurs, which
is perhaps repeated several times. Such is the fate, probably, of the
layer of polygonal cells which arises first of all, and which in the second
to the fourth months, becomes metamorphosed into an almost structure-
less membrane, and is then no longer to be found ; perhaps also of the
layer of epidermis, which covers the points of the hairs which have not
yet appeared externally [vide infra § Hairs); and in the second half of
the foetal period it may be easily demonstrated as an actively occurring
process. From the fifth month onwards, in fact, continually increasing
desquamation of the external epidermic cells takes place, and these
becoming in most parts mixed up with the sebaceous secretion of the
skin, form the so-called vernix easeosa or smegma emhryonum. This is
a whitish or yellowish, viscid, inodorous material, which, especially from
the sixth month onwards, covers the whole surface of the foetus with an
often considerably thick and even laminated substance, which is most
abundant upon the genitalia, on the flexor side of the joints (axilla,
knee, nates), on the sole, the palm, the back, the ear, and on the head
in large quantity, and when microscopically examined consists mainly
of epidermic cells, but also contains sebaceous cells and fat globules.
According to Davy ("Lend. Med. Gaz.," March, 1844) the vernix
easeosa contains in 100 parts, 5-75 elain, 3-13 margarin (8*88 fat) ; the
rest, 91-12 per cent., must be reckoned as epidermic scales, for since
the vernix easeosa contains no free fluid, the 77*87 per cent, water and
13-25 solid substance found by Davy must be laid to the account of
epidermic cells. This also holds good of Buek's analysis (" De Vernice
easeosa," Halis, 1844) who found in 100 parts, 10-15 fat, 5-40 epithe-
lium, and 84-45 water (so that there was 89-85 of epithelium) ; and also
in two other cases, in which the water was not exactly determined, he
found 14-80 and 9-31 per cent, of fat, and therefore 86-20 to 89-69 of
moist epithelium. According to Buck, the fat of the vernix easeosa
contains no cholesterin, as had been stated by Fromherz and Gugert,
but oleic acid, and either stearic or margaric acid, which are probably
not free, but combined with glycerine, — a circumstance which also
evidences its origin from the sebaceous glands, in which, normally, no
cholesterin is formed. Lehmann found (1. c.) in the dry vernix easeosa
of a nearly full-grown foetus, 47-5 per cent, of ethereal extract, 15-0 of
alcoholic extract, 3-3 of watery extract, 4-0 of acetic acid extract (earthy
phosphates and albuminous substances), epidermis and lanugo 23-7. In
the ethereal extract the reaction of bilin was absent and the fresh verwz'a;
contained a large quantity of water, Avhich in all probability had entered

OF THE SKIN. 157

its cells from the liquor amnik The smegyna generally appears about
the sixth month, varies greatly in quantity, and is, especially in newly-
born infants, sometimes very greatly developed (as much as 3i drachms,
Buck), sometimes wholly wanting; in which latter case it either becomes
mixed with the liquor amnii, which in fact often contains epidermic
cells as well as fat (Mark, in Heller's " Archiv," 1845, p. 218), or may
have been from the first, less developed. After birth the smegma is
thrown off in the course of from two to three days, and the permanent
epidermis appears, of whose further changes up to the adult state there
is little to be said. In a child four months old the epidermis measured: —

Epidermis in toto. Rett ilalp. Hnmy layer.

On the heel, . . 0-2C of a line. 0-12 of a line. 014 of a line.

On the back of the foot, 0 04S-0-0G of a line. 0 032-004 of a line. OOlG-0-02 of a line.

On the palm, . . O07-0-1 " 0-04-O07 " 003

On the back of the fingers, O-O.-JG-O-O? " 0-01-O05 " O-OlG-0-02 «

On comparing this with the adult, it is to be observed that the epidermis
of the young child is disproportionately thick, and that this thickness
depends especially upon the rete Malpiglui, whilst the horny layer
exhibits only a slight development. The pigment of the rete Malpigliii
arises, in the colored races, only after birth. P. Camper (" Kleinere
Schriften," 1782, Bd. I. p. 24) saw a negro child, which at its birth was
reddish, and hardly differed from that of a European, rapidly become
tinged black at the edges of the nails and round the nipple. On the
third day the genitalia became colored, and on the fifth and sixth the
blackness spread over the whole body. In Europeans also, at birth, the
pigment of the areola and of the other places which have been men-
tiotied, is not yet present: it is gradually developed in the course of the
first year, so that in children of two or three months old it is only indi-
cated.

In investigating the skin, perpendicular and horizontal sections of
fresh, dried, and boiled preparations are serviceable: they may be mois-
tened with an indiff'erent fluid or with various reagents, the most impor-
tant points in regard to whose effects have been noticed in the foregoing
paragraphs. The epidermis is separated from the corium by maceration,
by boiling, and where it is not thick, as on the genitalia, by acetic acid
and soda, easily and in large flakes, so that its lower surface and the
papillae of the corium become visible in the most beautiful manner, and
the latter may be examined singly or in groups. In the fresh skin their
position and number are quickly and easily to be recognized in horizon-
tal sections, passing through the papilli^ and the deep layers of the
epidermis. Its vessels are to be studied in thin parts of the skin [geni-
talia, lips), in the fresh condition, or in injected preparations with those
of the rest of the skin ; its nerves in perpendicular sections, in isolated

158 SPECIAL HISTOLOGY.

papilljB, or in thin portions of the skin (prepuce, glans, eyelids, conjunc-
tiva hulbi) after the addition of acetic acid and dilute solution of caustic
soda, or according to Gerber's and Krause's method. Gerber boils the
skin until it is transparent, lays it a few hours in oil of turpentine until
the nerves are ■white and glistening, and then examines them in fine
perpendicular sections made with the double knife. According to
Krause, the nerves are seen very well after treating the skin with nitric
acid, if the right amount of action is hit upon. The elastic tissue of the
skin comes out well under the action of acetic acid, soda, and potassa.
The smooth muscles may be readily isolated in the tunica dartos — with
more difficulty in the jyenis and in the areola, where it needs familiarity
wnth them, in order in all cases, to recognize them with the naked eye.
On the hair-sacs they are rendered visible microscopically, if a sac, with
the sebaceous glands which appertain to it, be isolated, especially after
the application of acetic acid, as small bundles near and in front of the
sebaceous glands, but best and very easily in perpendicular sections of
boiled skin (Henle). The examination of the fat-cells is especially in-
structive in thin persons, in whom their membranes and nuclei are
readily visible : in other cases their membranes are readily demonstrable
by the aid of ether, which extracts the fat ; but the nuclei are seen with
difficulty, though they may occasionally be discovered here and there
even in full cells. The epidermis must, for its Malpighian layer espe-
cially, be examined fresh, in fine perpendicular sections, to which acetic
acid and dilute solution of soda may be added ; the horny layer, par-
ticularly by the addition of alkalies, in perpendicular and horizontal
sections ; however, mere maceration in water separates its elements from
one another, and those who are practised can discover them in fresh
preparations, when viewed both laterally and from the surface.

Literature. — Gurlt, "Vergleichende Unters. liber die Haut des Men-
schen u. d. Haus-siiugethiere," &c., in Mull. " Archiv," 1835, p. 399
(good figures for the period) ; Raschkow, " Meletemata circa Mammal,
dentium evolutionem," Yratisl, 1835 (first more complete description
of the elements of the epidermis under Purkinje's guidance) ; Simon,
"Ueber die Structur der Warzen u. liber Pigmentbildung in der Haut,"
Mlill. "Arch.," 1840, p. 167 (pigment-cells in the rete of white persons) ;
Krause, article "Haut," in "Wagner's " Handworterbuch," II. 1844, p.
127 (a detailed and excellent treatise) ; Kolliker, " Zur Entwicklungs-
geschichte der iiussern Haut," in " Zeitschrift flir wiss. Zool.," Bd. II.
p. 67 ; "Histological Observations," ibid. II. p. 118; Eylandt, " De
musculis organicis in cute humana, obviis," Dorp. Liv., 1850. Besides
these refer particularly to the works of Simon (" Die Hautkrankheiten
durch anatomische Untersuchungen erliiutert," 2 Aufll., Berl., 1851);
Von Biirensprung (" Beitrilge zur Anat. u. Pathol, der menschlichen

OF THE NAILS.

159

Haut," 1848); and Kramer ("Ueber Condjlome u. Warzen," Getting.
1847). [Meissner, " Beitrage zur Anatoniie und Pliysiologie der Ilaut ;"
Leipzig, 1853.] Figures are given by R. Wagner, " Icon. pbys. ;" Ber-
res, tab. vi. vii. xxiv. (middling, witb tbe exception of what regards the
vessels); Arnold, " Icones org. sens.," tab. xi. (very pretty, but drawn
with too low magnifying powers) ; Hassall, tab. xxiv. xxvi. xxvii. (among
others, the skin of the negro also, and the areola of the wliite from
within, colored); and myself, "Mikr. Anatomie," Taf. i.

II. — OF TDE NAILS.

§ 48. The vails, tmgucs, are nothing but peciiUarJ^ metamorpliosed
parts of the epidermis, and like it they consist of two layers, — of a soft
mucous, and a horny layer, or tlie pro~per nail.

That part of the corium upon which the nail lies, or the bed of the
nail, corresponds exactly in form with it, is elongated, quadrangular,
arched in the middle, shelving off anteriorly and posteriorly, and espe-
cially on the sides. When the nail is removed by maceration in con-
nection with the epidermis, its anterior and middle parts are uncovered
whilst its lateral edges and its posterior segment, on the other hand,
are invested by a process of the cutis, the wall of the nail, which is
anteriorly depressed and rounded off, posteriorly more acute and longer,
and, taken together with the bed, forms a fold, the fold of the nail,
which receives the lateral edges and the posterior (2-3 lines) portion of
its root (Figs. 58, 60).

Tm. 58.

..-r

The bed of the nail presents upon its surface peculiar ridges, similar
to those of the palm and of the sole of the foot (Fig. 58 a). They
begin at the bottom of the fold of the nail, at the posterior border of
its bed, and, as Henle (p. 270) justly remarks, they run from the mid-
dle of it almost as from a pole. The middle ones pass directly for-
wards ; the lateral at first describe an arc, which is the more convex

Fig. 5S. — Transverse section through the body and bed of the nail, a, bed of the nail,
with its ridges (black) ; 6, corium of the lateral parts of the wall of the nail; c, straUmi Mai-
pighii of the nail with its ridges (white) ; c, horny layer on the wall of the nail ;/, horny layer
of the nail, or proper nail substance, with short notches upon its under surface.— Magnified
8 diameters.

160

SPECIAL HISTOLOGY.

the further out the ridges lie, and eventually are directed forwards like
the others. At a distance of 2| to 3| lines from their origin, thej all
at once become more prominent, and take on the form of true lamince
of 0-024 to 0-1 of aline in depth, which run directly almost to the anterior
edge of the bed of the nail, and then end suddenly, as if truncated.
The line of transition of the ridges into the lammce is convex anteriorly,
and divides the bed of the nail into two sections, differing both in their
extent and in their color : the posterior smaller one is nearly covered
by the wall of the nail and underlies its root, the anterior and reddish-
colored division underlying its body. The ridges and lamin?e of the bed
of the nail, the number of which varies between 50 and 90, are, at their
edges, beset with a series of short papilla of 0-008-0-016 of a line. In
addition, I can confirm Henld's statement that the bottom of the fold of
the nail exhibits a few transverse ridges with larger papillas directed
forwards ; further forwards where the lamina' cease, there are also long
isolated papillte. On the nail of the little toe, the papillae are frequently
rot seated upon ridges, but are more dispersed.

The wall of the nail has no ridges upon its lower surface, and rarely
a papilla here and there. These commence again upon its margin,
"where they are of some length, and are continued thence upon its upper
surface, which is in no respect distinguishable from the cutis of the back
of the fingers and toes.

The coriuni of the wall and of the bed of the nail
is dense, and for a considerable distance contains
but little fat; in the ridges and laminae with their
papillag, it is abundantly provided with fine elastic
fibres. The vessels are particularly numerous in
the anterior segment of the bed of the nail ; behind,
where the root of the nail lies, and in the wall they
are more scanty; their capillaries, 0"005-0'008 of
a line, form very distinct simple loops in the papilla?,
and single trunks often pass, even into many papillae.
The nerves have the same relations below as in the skin, but I have
hitherto been unable to detect their terminal loops or divisions in them.
In the nail itself we may distinguish, the root, the hody, and i\\e free
edge (Fig. 60). The soft root (Fig. 60 I) corresponds in its extent to the
posterior ridged segment of the bed of the nail, and is either wholly hidden
in the fold, or exposes a small semilunar surface, the lunula. The poste-
rior edge is attenuated, sliglitly bent upwards, and is the thinnest and most
flexible part of the nail. The hard body, which increases in thickness and
breadth from behind forwards [k), lies for the most part with its upper sur-
face uncovered; its somewhat sharp thin edges are hidden in the lateral

Fig. 59.

Fig. 59. — Capillaries of the bed of the nail, after Berres.

OF THE NAILS.

IGl

parts of the fold, and its under surface reposes upon the anterior seomient
of the bed of the nail : lastly, the free edge (m) is, in cut nails, directed

Fig. CO.

a ,.

Straight forwards, but if uncut, it curves downwards round the ball of
the finger and with the rest of the nail, attains to a length of as much
as two inches.

The lower surface of the hody and of the root answer in their form
exactly to the bed of the nail, and we therefore find lamina and ridges
upon them, as well as furrows, in the same order as on the latter, only
here the edges of the laminae are straight and not papillated, whilst the
furrows, instead of having an even bottom, as in the nail-bed, are pro-
vided with shallow pits for the reception of the papillae. By the mutual
interlocking of the elevations and depressions, the intimate union of
the nail with the corium is effected, which becomes still more close by
the application of the under surface of the wall of the nail upon its base
and edges.

The color of the nail, so long as it remains in its natural condition,
is whitish and transparent, at its free edges ; reddish in the body, with
the exception of a very narrow clear margin close behind the commence-
ment of the free edge ; in the lunula, whitish ; the color of the last two
portions arising principally from the corium and its blood-vessels which
shine through them. Separated from the corium and epidermis, the
nail is of a tolerably uniform Avhitish color, and transparent, though
somewhat whiter at the root than in the body.

§ 49. Structure of the Nail. — The nail consists in its deeper parts of
a soft, somewhat pale stratum mucosum, which is distinguished from the
hard external horny layer, or proper nail, still more sharply than in
the common epidermis. It covers the whole of the lower surface of the
root and body of the nail, frequently also a small part of the upper surface

Fig. go. — Longitudinal section through the middle of tlie nail and bed of the nail : a, bed
of the nail, and cutis of the back and points of the fingers; 6, mucous layer of the points of
the fingers ; c, of the nail ; d, of the bottom of the fold of the nail ; e, of the back of the finger ;
/, horny layer of the points of the fingers; g, beginning of them under the edge of the nail;
h, horny layer of the back of the fingers; i, ends of it upon the upper surface of the root of
the nail ; k, body; I, root ; m, free edge of the proper substance of the nail. — Magnified 8
diameters.

11

162

SPECIAL HISTOLOGY.

Fig. 61.

-^ (

a

of the root, and forms by itself the above-mentioned lamina on the under
surface of the nail. Its thickness at the posterior part of the root upon

the under side measures 0"12, on
the upper, 0'14 of a line ; close be-
hind the margin of the root, direct-
ly from behind forwards, 0*24-
0-26 of a line ; on the body of the
nail on the laminae, more poste-
riorly and at the edge 0-04-0'05
of a line ; in the middle, 0*06 even
/ ,-=;^"^- 3- - -i 0-08-0-96 and 0-12; between

. — _ _, ^ ^ these, 0-032-0-04 of a line.

r The Malpighian layer of the

nail, like that of the epidermis,
consists wholly of nucleated cells,
and agrees in all essential points
with it, except that the deep por-
tion contains many layers of elon-
gated (of 0-004-0-007 of a line)
perpendicular cells, in conse-
quence of which a striated appearance is produced, which has misled
Gunther, and probably Rainey also,* into supposing the existence of
peculiar glands under the nail. In the Negro, according to Bdclard
(Anat. Gen^rale, p. 309), the stratum Malpigliii of the nail is black ;
and according to Krause (1. c. p. 124), its cells would in this case appear
to contain dark-brown nuclei, as well as yellowish-brown ones, in dark
Europeans. According to Hassall (p. 252), the younger cells of the
nail {i. e., those of the stratum mucosum), generally contain pigment,
which I can confirm, at least in some cases.

The Jiorny layer of the nails, or its proper substance (Figs. 58/; 60
Tc, I, m. ; 61 c), is that hard brittle portion which forms its upper part
and its free edge. The under surface of this layer is quite smooth, pos-
teriorly at the root ; further forward it exhibits sharp ridges separated
by broad furrows, which are inserted into the furrows of the mucous
layer of the nail. These ridges of the proper nail substance appear in

Fig. G1. — Transverse section through the body of the nail; magnified 250 diameters.
A, cutis of the bed of the nail; B, mucous layer of the nail; C, horny layer of it, or proper
nail substance ; a, layers of the bed of the nail ; b, layers of the slrnhim Malpigkii of the
nail; c, ridges of the proper substance of the nail; d, deepest perpendicular cells of the
mucous layer of the nail; <?, upper fiat cells of it; /, nuclei of the proper .vubstance of the
nail.

* [With respect to Rainey's observations, Reichert, in his Report for 1849-50 (" Mali. Arch.,"'
1850-51) says, that the observation as to the follicles is quite correct, and that with Dr.
Ammons, who had studied the growth and regeneration of the nails for some years, he had
seen such capsules containing horny cells, with especial distinctness upon the bed of the
nail of the great toe. — Trs.]

OP THE NAILS.

163

transverse sections (Figs. 58, 61), as pointed processes of 0-01-0'02 of
a line in length, 'which, as a rule, are most strongly developed at the
edges of the nail, even to 0-04-0-06 of a line, and answer precisely in
their number to the laminie of the under side of the stratum Malpigldi.
The upper surface of the substance of the nail is smooth, taken as a
whole, yet sometimes even here, very distinct, parallel, longitudinal
streaks appear as the last, almost eflfiiced indications, of the inequalities
of its bed.

Usually, the thickness of this part of the nail continually increases
from the root to near the free edge, so that the body of the nail is, an-
teriorl}', at least three times thicker (from 0*3 to 0*4 of a line) than the
former; at the free edge again, it becomes somewhat less. In its trans-
verse diameter also, with the exception of the posterior edge of the root,
the substance of the nail is not everywhere equally thick ; it thins con-
siderably towards the lateral edges, so that at last the nails, where they
lie in the fold, measure not more than 0'06-0"12 of a line, and finally
terminate quite sharply.

With regard to the structure of the proper substance of the nail, it
can hardly be made out without the action of reagents. In perpen-
dicular sections we see, particularly in the body, nothing but horizontal,
fine, straight, or curved, closely-approximated lines, which one would be
inclined to consider as the optical expression of delicate, superimposed
lamellaj, and between these, a multitude of elongated, horizontal,
opaque or peculiar reddish-transparent striae, evidently nuclei. Only
upon the most posterior part of the root, and on the under surface, where
it meets the stratum 3Ialpighu, do more or less distinctly flattened cells
with nuclei appear disposed in layers. Horizontal sections show even
less than the perpendicular ones ; exhibiting a pale transparent sub-
stance, granular here and there, and
mostly without indication of any
structure whatsoever, occasionally
with very indistinct contours of plates
similar to those of the horny layer of
the epidermis. Very different are
the appearances presented after
treating the nail with alkalies and
certain acids.

If the substance of the nail be
boiled in dilute caustic soda, it be-
comes changed upon the first bub-
bling of the fluid into a beautiful
cellular tissue (Fig. 62, A, B), whose

Fig. 62.

Fig. 02. — Nail plates boiled with caustic soda
a, membranes of the distended elements of the nai
from the side. — Magnified 350 diameters.

^, from the side; B, from the snrface:
b, their nuclei, from the surface ; c.

161 SPECIAL HISTOLOGY.

polygonal elements all, without exception, the deep as well as the
superficial, possess nuclei of 0-0030-0"0046 of a line in length and
breadth, and 0'002 of a line in thickness, which, according as they
turn their surfaces or their edges to the observer, appear as rounded,
very pale, and finely-granulated discs, or as long, narrow, dark-con-
toured rods; it deserves further to be noted, that together with these,
large and very pale nuclei of 0*006-0-01 of a line, and more, occur in
considerable numbers, probably owing their existence to the excessive
action of the reagent which has swollen them up. Caustic soda and
potass also (which has a similar action upon the whole, though it acts
more upon the nuclei) demonstrate the important fact, that the cells of
the nail are flatter in the superficial than in the deeper layers. If, in
fact, a fine perpendicular section be moistened with cold, or better, with
hot solution of soda, we see the cellular structure of the nail appear
almost at the very instant it becomes moistened, without any obvious
enlargement of its elements ; and it is observable, at the same time, that
its deepest cells are at least as thick again as the most superficial.

If the soda solution acts longer, the section gradually swells up, in
the under cells first, on account of their greater softness, and only sub-
sequently in the flat and hard upper elements. By treating the nail
with cold sulphuric and nitric acids, and also by boiling with hydro-
chloric acid, its elements are isolated.

Taking these facts, together with what we see in the unaltered nail,
it results that its horny layer consists of closely united but not sharply
defined lamellee; each lamella being composed of one or many layers of
nucleated, polygonal, flat scales or plates, which, excepting their nuclei,
are very similar to those of the horny layer of the epidermis, and in
their deepest layers are thicker and somewhat less in circumference than
in the upper and uppermost layers. Those of 0-012-0'016 of a line,
may be regarded as of an average size, as may be seen upon the addition
of sulphuric acid, which otherwise exerts but little action, and at the
commencement of 'the operation of soda and potass.

§ 50. With respect to the relation of the 7iail to the epidermis, I must
especially refer to the perpendicular and transverse sections figured in
Figs. 58 and 60. They show, in the first place, that the epidermis ap-
plies itself upon the root, the posterior part of the body, and upon the
margins of the nail, and that it meets it under the free edge and on the
anterior parts of the lateral edges. This happens in such a manner,
that whilst the raucous layer of the epidermis passes continuously, and
without any line of demarcation, into that of the nail, the horny layer
is, properly speaking, never continued directly into the actual substance
of the nail, but partly applies itself with its lamellne parallel upon the
nail, partly abuts upon it at various oblique angles. At the root, the
horny layer passes more or less deeply into the fold of the nail, and at

OF THE NAILS. 165

the same time runs, in a thin layer which becomes very fine anteriorly,
upon the upper free part of the nail, as far as the end of the lunula or
the beginning of the body. Anteriorly and posteriorly, in which latter
region this layer not uncommonly reaches the posterior margin of the
root, its cells lie parallel to the upper surface of the nail ; while in the
middle, where it is thickest (Fig. 60 /), they are oblique or perpendicular
to it. At the free edge of the nail the relations of the parts are similar,
where the horny layer meeting the end of the under surface of the body
of the nail, partly with more horizontal, partly with oblique lamellae, is
perhaps also continued upon the commencement of the free edge. On
the lateral edges, again, the horny layer passes anteriorly, in horizontal
strata, under the nail ; more posteriorly it is arranged as upon the root,
or simply rests against the edge of the nail. The horny layer thus
forms a kind of sheath for the nail, which bears some resemblance to
the sheath of the hair, though it is much more imperfect. If we com-
pare the nail with the epidermis, we find, in the structure of its mucous
layer, not the slightest peculiarity of any importance, while the horny
layer is distinguished from that of the epidermis by its cells being
nucleated, harder, and chemically different ; by their flattening and in-
timate union. For the rest, the agreement of the two structures is so
close, that the proper nail may justly be considered, as it has long been,
a modified portion of the horny layer of the last joints of the fingers
and toes.

Accordino- to the chemical investio-ations of Scherer and Mulder, the
nails agree very closely with the epidermis ; and, according to Mulder,
they are distinguished from it, only by their somewhat greater propor-
tion of sulphur and carbon. In his last essay, he considers them to be
composed of protein -1- sulphamid (6-8 per cent, of the latter). This
agrees with the observed action of reagents, with which the plates of the
nail behave almost exactly like horny plates, only they are attacked
with more difficulty and possess nuclei. According to Lauth, the nails
contain more phosphate of lime than the epidermis, whence they derive
their hardness : this may be correct, although, as Mulders tates (" Phys.
Cheraie," p. 536), both yield about the same proportion of ash (1 per
cent.\

As regards the lamellar structure of the proper nail, it is to be re-
garded in the same light as that of the horny layer of the epidermis ; but
it is not so distinct, because the plates of the nail are more intimately
connected than the elements of the epidermis. Reagents, however,
render the lamellar structure very evident, and it is also clear in patho-
logically thickened and curved nails.

§ 51. Growth of the Nails. — The nails grow continually, as long as
they are cut; on the other hand, if uncut, their growth is limited. In

166 SPECIAL HISTOLOGY.

this case, as may be observed in those who are long confined to their
beds by sickness, and in the Eastern Asiatics, the nails become l|-2
inches long (in the Chinese, according to Hamilton, 2 inches), and to
curve round the points of the fingers and toes.

During the growth of the nail, the mucous layer does not change its
position at all, but its horny layer is constantly being thrust forward.
The formation of the latter goes on continually wherever it is in contact
with the stratum 3IaI]){ghu, in other words upon its whole under sur-
face, with the exception of the free anterior edge ; further, in many nails,
upon a very small portion of the upper surface of the root, finally, at
the posterior edge of the root itself. It is, however, the root portion
which grows fastest, whilst the body of the nail is more slowly developed,
which is demonstrated especially by the fact that it is not much thinner
at the boundary between the root and the body than it is anteriorly upon
the body itself, and that the transition of the cells of the stratum 3Ialpighii
into nail-cells is easily shown at the root, but with difficulty in the body.
By the constant addition of new cells at the edge of the root, the nail
grows forward ; by their addition to its under surface, it is thickened.
The longitudinal growth exceeds that in thickness, because the first
rounded cells, as they move from behind and below, forwards and up-
wards, become more and more flattened and elongated.

The mode in which the plates of the nail arise from the cells of the
mucous layer, is easily demonstrable at the root of the nail. Here, in
fact, the uppermost cells of the mucous layer are constructed very dif-
ferently from the deeper ones ; they are more or less flattened, and closely
resemble the cells of the epidermis, but they possess a nucleus, which,
however, is only to be discovered by adding caustic soda, and then with
diflSculty. If we follow these cells, which form a layer of 0'06-0'12 of
a line in thickness, toward the proper substance of the nail, we find
that they become more and more flattened, and at last pass without any
defined boundary into the latter, uniting together more closely, and
taking on a more transparent appearance.

In the body of the nail, the formation of nail substance is demonstrated
with more diflBculty, yet here, in opposition to Reichert, we must assume
that it does take place, because the nail almost invariably increases in
thickness even in the body, from behind forwards. However, there is
unquestionably, in this part, a sharper demarcation between the two
layers of the nail, than in the root ; but in fine sections it appears by
no means so sharp as in those which are commonly examined, and I find,
in fact, that the transition of the cells of the mucous layer into the plates
upon the body of the nail, is demonstrable with tolerable readiness, par-
ticularly on the addition of alkalies, where the ridges of the under sur-
face of the proper nail are well developed. Between the ridges also,
though no direct transition is recognizable, yet it may be observed that

OF THE NAILS. 1G7

the plates of the proper nail which border upon the mucous layer are
much less flattened than in the interior and on the surface, which also
indicates that they are developed upon the spot. In conclusion I must
add, in support of my view, that it is only in this way, that it becomes
explicable why the under surface of the proper nail substance upon the
root of the nail is almost smooth, while on the body of the nail it pre-
sents more or less prominent ridges. The origin or increase of these
ridges demonstrates clearly that nail-substance is also formed here.
Corresponding Avith these ridges and with the grooves between them, we
also find that the lowest layers of the nail plates, which are quite hori-
zontal upon the root, run with an undulating course upon the body (Fig.
61). The general result then is, that whilst the formation of the nail
goes on especially at its root, yet that plates are added to the body of
the nail from below, though more slowly and scantily, thus producing the
anterior thickening, or at least preventing the necessary thinning of the
nail anteriorly. It is to be remarked further, that the development of
nail-substance takes place in all parts of the middle line of the nail
more rapidly than in the lateral portions, which, anteriorly, are almost
as thin as in the root, though they possess longer processes below. But
even there, substance must be added to the body of the nail, because it
becomes broader anteriorly.

The plates of the substance of the nail once formed, alter in certain
respects, as they are pushed forwards and upwards by those which come
after them. In the first place, their nature becomes altered in a man-
ner which is little understood, the change consisting partly in the depo-
sition of more phosphate of lime, partly in a solidification (conversion
into horn) of their organic elements, particularly of the cell-mem-
branes, in consequence of which, from being soft, as at the root and
under surface of the nail, they become gradually harder and harder.
In the second place, like the horny cells of the epidermis, they are
very considerably flattened, and at the same time increase somewhat in
their longitudinal and transverse diameters; finally, they coalesce more
completely, so that they cannot be separately recognized, without the
action of reagents, in the upper and anterior parts of the nail, which
appear to be composed of nothing but a homogeneous substance which
tears in all directions ; whilst in the lower parts the separate nail-
plates are, at least, indicated, and are occasionally tolerably distinct.
On the other hand, the nuclei of the nail-plates do not disappear, and
in this lies a characteristic distinction between the horny layer of the
nail and that of the epidermis. They are to be seen in perpendicular sec-
tions, of fresh nails, and after treatment with caustic soda, and even in
the most superficial layers, though somewhat smaller and flatter than in
the deep layer. It follows then, that certain metamorphoses go on in
the proper substance of the nail, which as in the epidermis, are to be
ascribed to a peculiar growth and vital process in the nail-cells them-

1G8 SPECIAL HISTOLOGY.

selves. These seem to occur, however, almost solely in the lower and
posterior parts of the nail, for if, as Schwann states (Fig. 91), two points
be marked upon the posterior portion of the free surface of the nail,
one behind the other, by piercing it with a needle and coloring with
nitrate of silver, they in no wise alter their relative position in the course
of the two or three months, during which they are moving towards the
point of the nail.

As to the patJiological conditions of the nails, they are readily regene-
rated when they have been detached, in consequence of crushing, burn-
ing, freezing, cutaneous disorders (scarlet fever, &c.), injBammations,
exudations, suppurations, and effusions of blood in the bed of the nail;
in fact, as Pechlin (" Obs. Phys. Med.," p. 315) narrates, this regene-
ration may take place periodically ; in a boy, the nails, every autumn
became bluish-black and desquamated, together with the epidermis (the
horny layer ?), and were subsequently regenerated. In such a case, accord-
ing to Lauth (" M^m. sur divers points d'Anatomie," in the " Annales de
la Societe d'Histoire Naturelle de Strasbourg," t. i. ISSi), and Hyrtl
(" Anatomic," p. 882), the whole bed of the nail becomes covered by soft
horny plates, which harden by degrees, grow into a regular nail, and
eventually project with their free edges beyond the end of the finger.
When the last joint of the finger has been lost, rudimentary nails fre-
quently appear upon the back of the second and even of the first phalanx.
The older cases are quoted in Pauli ("De vulneribus sanandis," Got-
tingjie, 1825, p. 98), more recently Hyrtl (1. c.) saw such a nail 2 lines
long and 3 lines broad on the first phalanx of the thumb. As the for-
mation of nail-substance depends upon the vessels of the bed of the nail,
"we may, with Ilenle, assume that varying conditions of the latter
may frequently produce local thickening, thinning, or even detachment
of the nail, and that their deformities in cyanosis and phthisis depend
on these causes. The thickening and abnormal development of the
nails, however, arise very frequently, as I have observed, from a partial
obstruction of the capillaries of their bed. Thus in the lamellated nails
of old people, greatly thickened and curved downwards in front, I find
all the capillaries of the anterior segment of the bed of the nail closely
filled with fat granules of different sizes, and wholly impermeable to the
blood; in such a case the development of nail-substance can take place
only in small lamellre in the fold, which then, as may be readily under-
stood, are raised up by those which are growing behind into a continu-
ally more and more oblique position ; their posterior extremities forming,
on the surface of the nail, transverse streaks one behind another at
short intervals. After dividing the nervus ischiadicus, Steinrlick (" De
nervorum regeneratione," pp. 45-49) observed, in the Rabbit, that the
nails and hair fell off, which is a result of the influence of the nerves
upon the vessels. Finally, the shape of the bed of the nail also in-
fluences its formation. It is thus explained, how (see Henle, 1. c), after

OF THE NAILS. 169

inflammation and closure of the fold of the nail, the formation of new
nail at the posterior edge ceases, the nail no longer growing forwards,
but at all its edges exactly covering its bed.

§ 52. The development of the nail begins in the third month with the
formation of the bed and fold, which are marked off from the surround-
ing parts by the gradual growth of the skin into the wall of the nail.
At first the bed of the nail is lined by the same cells as those which form
the other parts of the epidermis (see § 47), only that even in the third
month the cells of the stratum Mcdpighii are distinguished by their
elongated and polygonal form (length 6-004, breadth 0-001-0-001(3 of
a line). In the fourth month there arises between the stratum Mal-
pigJiii and the horny layer of the bed of the nail, which latter is formed
by a simple laj^er of polygonal clearly nucleated cells, a simple lamina
of pale, flat, but also quadrangular and nucleated cells, 0*009 of a line
in diameter, which are closely united together, and must be regarded as
the first indication of the proper substance of the nail ; at the same time
also, the stratum 3IaJpiglni under these cells become thickened so that
it is certainly composed of, at least, two layers. The nail is therefore
at first ivJiolly included tvitliin the epidermis ; it is formed over tlie lohole
surface of the bed of the nail as a quadrangular plate, and arises between
the embryonic mucous layer and the horny layer, without doubt by a
metamorphosis of the cells of the mucous layer, as is probable, especially
from the minute size of the original cells of the nails. In the course of
its further development, the nail is thickened by the addition of new
cells from below (in the fifth month its thickness is about 0'024, in
the sixth 0*04 of a line, of which in the latter 0*025 must be reckoned
as proper nail-substance); it increases by the extension of its elements,
and by the addition of new ones at its edges ; but it remains, even to
the end of the fifth month, hidden under the horny layer of the epider-
mis, until finally it becomes free, and in the seventh month, even begins
to grow longitudinally, so that at this period, except in its greater
softness and its smaller dimensions, it presents no essential difference
from the perfect nail. With regard to the bed of the nail, its ridges
are already indicated at the end of the fourth month, and in the fifth
they are well-marked, 0-02-0-024 of a line deep, 0-004-0-005 of a
line broad, and 0-008-0-014 of a line distant; these measurements also
indicate the breadth of the laminse of the stratum Malpighii. At the
sixth month they are somcAvhat larger and further apart.

In the new-born infant, the whole nail is 0-3-0-34 of a line thick;
0-16 of a line being proper nail-substance, 0-14-0-18 of a line stratum
Malpigldi. Its elements are still almost identical with those at the sixth
month, and they appear with tolerable distinctness in the nail proper
without any reagents, as elongated polygonal nucleated plates 0 •002-0-28
of a line, as Schwann has already partly remarked. The free edge.

170 SPECIAL HISTOLOGY.

projecting far forwards, which is presented in all nails, is worthy of
remark. It is considerably thinner and narrower than the body, and is
separated from it by a semilunar line; it is rounded anteriorly, as much
as 2 lines long, and is plainly nothing but the nail of an earlier period
which has been thrust forward by the longitudinal growth of the nail in
the course of its development. In fact it nearly corresponds in size with
a nail of the sixth month.

Soon after birth the long free edge of the nail of the new-born infant
is cast off, at least once (according to Weber many times), in all pro-
bability in consequence of external mechanical violence, which it is
unable, owing to its delicacy, to resist. In the sixth and seventh months
after birth, I find that the nails which the child brought into the world,
are cojupletely replaced by new ones, and in the second and third years
the nail-plates are not distinguishable from those of the adult, whence
it follows that the nail increases in thickness, less in consequence of any
enlargement of its elements, than by the addition of new ones to its
edges and under-surface.

The investigation of the nail-cells and plates is best made in fine
sections of recent nails, with and without the addition of reagents,
especially caustic soda and sulphuric acid, concerning whose operation
the most important points have already been noted. To examine
the relations of the parts of the nail to one another, and to the epi-
dermis, the nails must be separated from the cutis by maceration, or by
boiling in water. It is then seen, that the nail is detached, with the
cuticle, from the finger ; and in transverse and longitudinal sections, its
mode of connection with the former is perceived. The bed of the nail
also, its laminoi and ridges, the fold and the lamince in the stratum
Malpighii of the nail, are easily seen, in this way. Since fine sections,
in such a nail, are not readily made, precisely in the most important
parts — the margins and roots, — it is necessary, for this purpose, to
employ fresh nails separated from the bone with the cutis, and dried.
These afford all the information required, portions of them swelling up
readily in water, and exhibiting the structure of the different layers,
with acetic acid and caustic soda, in the most distinct manner.

Literatwe. — A. Lauth, " Sur la disposition des ongles et des polls,"
Mem. de la Societe d'hist. nat. de Strasbourg, 1830-4 ; Gurlt, " Ueber
die hornigen Gebilde des Menschen u. der Haussaugethiere," Mlill.
"Arch.," 1836, p. 262; Reichert, in Mlill. "Arch.," 1811, Jahresbe-
richt; 0. Kohlrausch, "Recension von Henle's allgem. Anat.," in Get-
ting. "Anzeigen," 1843, p. 24; Rainey, "On the structure and forma-
tion of the nails of the fingers and toes," in "Trans, of Microsc. Society,"
March, 1849; Berthold, "Beobachtungen liber das quantitative Verhalt-
niss der Niigel- u. Haarbildung beim Menschen," in Mlill. "Arch.," 1850.

OF THE HAIRS.

171

Vvj. C3.

HI.— OF THE HAIRS.

§.53. In every hair we distinguish the free part or shaft, scapus, with
its tapering point, from the portion enclosed within tlic sac, the root,
radix. In straight hairs the former is generally straight and rounded;
in the wavy, undulated and somewhat flattened ; in the curly and woolly
hairs, it is twisted spirally and quite flat or
slightly ribbed. The root is always straight,
tolerably cylindrical, and softer and thicker
than the shaft, at least in its lower part;
in living hairs it ends in a still softer kuob-
like enlargement, 1-| to 3 times thicker
than the shaft, — the " bulb of the hair" [c),
which is placed, cap-like, upon a papillary
process of the sac, the "hair-papilla" (less
properly termed jjii//ja or blastema pili,
hair-germ), or in other words receives the
papilla in an excavation in its base.

§ 54. Disposition and Size of the Hairs.
— The hairs are distributed over almost the
whole surface of the body,* but exhibit very
considerable difierences in size and number,
according to their situation, to individual
peculiarity, age, sex, and race. As regards
the former, three varieties may be admitted,
besides many transitional forms: (1) long
soft hairs, of 1—3 feet and more in length,
0*02-0"05 of a line in thickness; (2) short
stiff thick hairs, of ^-^ of an inch in length,
and 0"03-0'07 of a line in thickness ; (3)
short, excessively-fine hairs, down {lanugo),
of 1-6 lines in length, and 0-006-0-01 of a line in thickness. The dis-
tribution of the first form is well known; to the second belong the hairs
at the entrance of the nostrils [vibrissce), in the external auditory
passage, the eyelashes [cilia), and eyebrows; to the third, finally, must
be referred the hairs on the face, trunk, and extremities, also those of

Fig. G3. — Hair ami hair sacs of middling size; magnified 50 diameters: a, hair shaft; b,
root of the hair; r, bulb of the hair; cl, ei)idermis of the hair; e, inner root-sheath; /, outer
root-sheafh ; g, structureless membrane of the hair sac ; h, transversely and longitudinal
fibrous layer thereof; i, papilla of the hair; k, excretory ducts of the sebaceous glands, with
epithelium aiid layers of fibres ; I, cutis at the aperture of the hair sac ; 711, stratum mucosum ;
n, horny layer of the epidermis, the latter somewhat retracted into the sac ; 0, end of the
inner root-sheath.

* [No hairs exist upon the upper eyelids, the lips, the palm of the hand, and sole of the
foot ; nor on the dorsum of the last joints of the fingers and toes, the inner surface of the
prepuce, and the glans penis. — Trs.]

. .-'i

,1..' ;

If

"I

172 SPECIAL HISTOLOGY.

the caruncula lachrymalis, and those (frequently absent) of the labia
minora (Henle).

The number of hairs upon a given extent of surface varies very n>uch,
depending especially upon age, sex, and the color of the hairs. Accord-
ing to Withof, on a surface of J of a square inch there were found 147
black, 162 brown, 182 fair hairs. In a moderately hairy man, he found
on ^ of a square inch, 293 upon the scalp, 39 on the chin, 34 on the
pubis, 23 on the fore arm, 19 upon the outer margin of the back of the
hand, 13 on the anterior surface of the leg. In men, closely set hairs
occur not unfrequently upon the chests, shoulders, and extremities.

The hairs are placed either singly, or in twos and threes, even four and
five together. The latter is the rule in the foetus, but the same disposi-
tion obtains also in adults, especially in the lanugo. As Osiander and
especially Eschricht, have shown, the direction of the hairs and hair-sacs
is rarely straight, but oblique, and in different degrees in different parts
of the body, as may be demonstrated with ease in the hairs of embryos,
and, though less obviously, in adults also. The regularity depends on this,
that the hairs being arranged in curved lines, which converge towards
either certain points or certain lines, or diverge from them in two or more
directions; there result a multitude of figures, which may with Eschricht
be denominated " streams," " whorls," and "crosses." Streams with
converging hairs are found, for example, in the median line of the back,
chest, and abdomen, in the line which answers to the ridge of the tibia,
&c. &c. ; streams with diverging hairs occur on the line between the
thorax and abdomen, on the one hand, and the back on the other, &c. ;
whorls and crosses Avith diverging hairs are found in the axilla, on the
scalp, at the internal angle of the eye ; with converging hairs, on the
elbow. For further details I must refer to Eschricht's figures and
descriptions, concerning which, however, it is to be remarked, that many
variations occur with regard to these points, and Eschricht's figures re-
present only some of them.

§ 55. External peculiarities and chemical composition of the Hairs. —
In embryos, the hairs are generally quite colorless and clear ; they very
slowly become colored, so that in youth they are, in general, paler than
in middle age. In the adult the downy hairs, which have remained in
a foetal condition as it were, are invariably the palest ; the longer ones
are always darker, and the darkest are those of the head, beard, and
puhis.

The hairs are very elastic ; according to Weber, they stretch without
breaking to nearly a third more than their length, and if they be
stretched only a fifth, they contract again so perfectly, that they remain
permanently only -j^i^th longer. They readily imbibe water, and as
readily give it out again ; they are therefore sometimes dry and brittle,
sometimes moist and soft, according as the skin or the atmosphere con-

OF THE U AIRS. 173

tains much or little moisture. They become longer or shorter, accord-
ing to the amount of moisture which they contain, whence their use in
Hygroraetry. In spite of their extensibility, their strength is consider-
able, and hairs of the head will bear at least 6 ounces without breaking.
Tlw chemical composition of the hairs is not yet sufficiently under-
stood, but they are chiefly composed of a nitrogenous substance, soluble
in alkalies with the evolution of ammonia, and insoluble in boiling acetic
acid. Scherer and Von Laer consider it to be a combination of protein
with sulphur, and the latter supposes, in addition, the existence of a
small quantity of a substance similar to gelatine, whilst Scherer regards
a second nitrogenous matter which he found, to be a product of decom-
position. Mulder considers the substance of the hairs to be a protein
compound combined with sulphamid, of which he finds 10 per cent.
Besides their nitrogenous constituents, the hairs, as even the earlier
investigations showed, contain a considerable quantity of dark or clear
fatty matter, which may be extracted by boiling in ether and alcohol.
From horn and epidermis, the substance of the hair is distinguished,
according to Mulder, especially by its insolubility in acetic acid and by
the same test, from albumen and fibrin. The hairs withstand putrefac-
tion better than any other part of the body, so that even mummy hairs
are found to be quite unchanged; in water they are not dissolved, except
in Papin's digester. Metallic oxides color the hair just as they do the
epidermis ; thus, for example, they are blackened by the salts of silver
and manganese, sulphurets of these metals being produced. Chlorine
bleaches them. The ash amounts to about 1-2 per cent., and contains
oxide of iron (more in dark hair) ; oxide of manganese ; silica (traces) ;
phosphate of magnesia and sulphate of alumina Avere found by Jahn in
white hairs; and according to Laugin, copper occurs in the greenish
hairs of those who work in copper and brass.

§ 56. With regard to their more intimate structure, two substances
may be distfnguished in all hairs v.-ithout exception, and in many there
are three: 1, the cortical substance, or better, fibrous substance, which
constitutes by far the most considerable portion of the hair and detei'-
mines its form ; 2, the cuticle, a delicate external investment of the
fibrous substance; 3, lastly, the central medullary substance, which is
often absent.

The cortical ov fibrous substance is longitudinally striated, very often
presents dark dots, is streaked or spotted and except in white hairs, in
which it is transparent, is more or less deeply colored ; the color is
sometimes distributed through the whole substance with tolerable regu-
larity, sometimes more concentrated in certain elongated, granular spots.
The more intimate structure of the cortex of the hair, and the significa-
tion of its spots and strife, cannot be properly understood without the
use of acids and alkalies (which afford important aid in the investigation

174

SPECIAL HISTOLOGY.

of the hairs in general) and other manipulations. If a hair be treated
with concentrated sulphuric acid at a warm temperature, its fibrous
substance is much more readily broken up than before, into fiat elon-
gated fibres of various breadths (commonly 0-002-0-005 of a line), which
are characterized particularly by their rigidity and brittleness, and by
their irregular, even notched, margins and ends : in pale hairs they are
clear, and in dark ones have a dark tinge. These so-called hair-fibres
Fig. 64. are not, however, the ultimate ele-

ments of the fibrous substance ; each
of them, in fact, consisting of an
aggregation of flat, moderately-long
fibre-cells or plates, which may be
found isolated among the fibres after
the thorough action of sulphuric acid.
These (Fig. 64), which may best be
named the 'plates of the fibrous sub-
stance, or the fibre-cells of the cortex^
are flat and generally fusiform, 0*024
-0-033 of a line long, 0-002-0-004,
or even 0-005 of a line broad, 0-0012
-0-0016 of a line thick, witli uneven
surfaces and irregular edges ; they
do not swell up into vesicles on the
addition of caustic alkalies, and they
very frequently exhibit a darker
streak in their interior, of which we
shall speak immediately ; under cer-
tain circumstances they also contain
granular pigment; for the rest they
are homogeneous, and present no
minuter elements, such as fibrillas or
the like. They appear* to be more
strongly united longitudinally, than
in the direction of their breadth,
whence it arises that the cortical sub-
stance easily breaks up into the long
fibres above mentioned. The fibres themselves (which I should not be
inclined to consider as compound elements of the cortical substance,
since their constituents are separable, and they themselves are far too
irregular), without constituting distinct lamelloe, like the plates of the
nail and of the epidermis, form a compact fibrous bundle, and in this

Fig. 64. — Plates or fibre-cells of the cortical substance of a hair treated with acetic acid ;
magnified 350 diameters : ^, isolated plates, 1, from the surface (3 single, 2 united) ; 2, from
the side. B, a lamella composed of many such plates.

OF THE UAIHS.

175

manner the cortical substance, which constitutes the principal bulk of
the hair, is produced.

The dark spots, dots, and streaks of the cortex, are very various in
their nature, and are principally : 1, (jranular jiigment ; 2, cavities
filled -with air or Jhiid; and 3, nuclei. The action of caustic potass and
soda, which soften and swell up the cortical substance without attack-
ing the spots (Fig. 67), shows that they are in great measure nothing
but aggregations of pigment granules, which are deposited in the plates
of the hair, are especially frequent in dark hairs, and vary very much
in respect to their size and form. Dark spots of a second kind are very
similar to the pigment deposits, but turn out on examination to be little
cavities filled tvith air. They are best studied in white hairs, where they
cannot possibly be confounded with pigment. Here we see dispersed
through the whole cortical substance round dots of 0-0004-'0008 of a
line, or longish streaks of 0'004 of a line in length, 0'0004-0'0008 of a
line in breadth, which, sometimes more scattered, sometimes more
numerous, and arranged in irregular lines, run parallel with the axis of
the hair. The dark contours and somewhat clear centre of these, attract
attention at once, and call to mind fat granules, which, in fact, for a
long time I held them to be ; but they are nothing but excessively minute
cavities filled with air, which- occur very frequently also in fair, bright-
brown, and bright-red hairs, often in very great numbers, while they
are wanting in very dark hairs, and
in the lower half of the root of all
hairs. Thirdly, there occur in the ^

cortex, other tolerably dark stria?

or lines, which in dark hairs are jj , ' Ml' Us3 1''' ilMil liii *^jI
commonly connected with the pig-
ment-spots in such a manner that |i
the striiB form the ends of the spots, |||
or pass through them axially ; in ||
white and pale hairs they appear not
unfrequently as prolongations of the |^
air cavities, but in both kinds of
hairs they often occur independently,
in various numbers and degrees of
distinctness. I hold these streaks,
wliich are commonly most distinct in
pale or bright-brown hairs without
any medulla, to be sometimes the ex-
pression of the composition of the hairs by the above described fibre-

FlO. 65. — J, a piece of a white hair after treatment with caustic soda; magnified 350
diameters: a, nucleated cells of the medulla without air; 6, cortical substance with a fine
fibrillation and prominent linear nuclei; c, epidermis with its plates projecting more than
usual ; jB, three isolated linear nuclei from the cortex.

Pi-
a"

65.

176 SPECIAL HISTOLOGY.

cells ; in other words, to be the boundary lines of the separate elements
of the cortex, and sometimes I consider them to be their nuclei. For,
even in the shaft of the hair, the cortical plates all contain fusiform
nuclei 0-01-0-016 of a line long, 0-0005-0-0012 of a line broad, which
may, in fact, be isolated by rubbing down white hairs which have been
boiled in caustic soda. Besides these, there appear in the cortical sub-
stance, and with especial distinctness in a whitish place immediately
above the bulb, certain fine strife, which are produced by inequalities in
the surface of the cortical plates, and which do not readily disappear,
even after the continued action of alkalies, but eventually give place to
a finely fibrous appearance ; they cannot be isolated, but are visible in
those portions of the cortex which have been separated by sulphuric
acid, and sometimes even are very distinct (Fig. 66).

The description of the cortex^ which has just been given, holds good
especially for the hair-shaft. In the root of the hair, so long as it is still
solid and brittle, we find essentially the same conditions ; and it is only
in its lower half, where it becomes gradually softer, at first finely fibrous
and then granular, that the structure of the cortex undergoes a progres-
sive change. Here, in fact, the above described plates are less rigid,
and take on more and more distinctly the form of elongated cells (Fig.
66) of 0-020-0-024 of a line in length, atid 0-009-0-011 of a line in
breadth, whose cylindrical, straight, or serpentine nuclei of 0-008-0-01
of a line, are very easily rendered visible by the action of acetic acid, and
may also be readily isolated. The soft and shortened plates then pass
into elongated, rounded cells, with short nuclei, the p.,

Fis. 66. O ' ' 1 • J

fibrous structure becoming more and more obliterated,
and these are finally continued without interruption into
the elements of the lowest and thickest part of the hair,
the bulb. They (Fig. 67) are nothing more than round
f jM cells of 0-003-0-006 of a line, which lie closely pressed

together ; and like the cells of the mucous layer of the epidermis
sometimes contain only colorless granules, sometimes are so
W full of dark pigment-granules, that they become true pigraent-
'■-^ cells. It must be added, that the chemical relations of the
cortex are altered in the lower half of the root, its elements becoming
more sensitive to the action of acetic acid, which does not affect the
plates of the shaft at all ; they swell up and dissolve in alkalies also,
much more quickly than those of the shaft.*

Fig. 06. — Two cells from the cortex of the root of the hair (the finely-striated part of it
immediately above the root), with distinct nuclei and a striated appearance; magnified
350 diameters.

Fig. 67. — Cells from the deepest part of the bulb of the hair; magnified 350 diameters:
a, from a colored bulb, with pigment-granules and somewhat hidden nucleus; 6, from a
white hair with a distinct nucleus and few granules.

*[Reicliert ("Bericht' for 1850, Mull. " Archiv," 1851) asserts that the cortical substance

OF THE HAIRS.

17T

The color of the cortical substance arises partly from spots of pio-ment,
to some extent from air cavities, and partly from a coloring matter dif-
fused through and combined with the substance of the cortical plates.
The first or the granular pigment, exhibits all shades from clear yellow,
through red and brown, to black; the diffused pigment is quite absent in
white hairs, and is scanty in clear, fair hairs ; it is most abundant in the
more opaque fair hairs, and in red as well as in dark hairs, in which it
may by itself give rise to an intense red or brown color. The color of
the cortex depends especially upon that of these two pigments, but
sometimes the one, sometimes the other predominates, and it is only in
the very light and in the very dark hairs that they are developed in about
equal proportions.

Fig. 68.

§ 57. The medullary substance is a streak or cord which extends in
the axis of the hair, from the
neighborhood of the bulb
nearly to the point (Figs. 65,
68). It is generally absent
in the lanugo and colored
hairs of the head, but is
usually present in the thick,
short hairs, and in the
stronger long ones, as well
as in the white hairs of the
head. If white hairs be
boiled with caustic soda until
they swell and coil up, we
can often, by the use of jii
simple pressure, demonstrate '
without further trouble, the
cellular structure of the
medullary cylinder, which is
then transparent for trans-

FiQ. 68. — A portion of tlie root of a dark hair slightly acted upon by caustic soda; a,
medulla, su\[ containing air, and with ceils, which appear pretty distinct; b, cortex with
pigment spots; r, inner layer of the epidermis; rf, outer layer of it ; e, inner layer of the inner
root-sheath (^Huxley's layer) ;/, outer fenestrated layer (Hetile's layer). Magnified 250 diameters.

of the hair is composed of superimposed laminae, and recommends, in order to demonstrate
the fact, that a hair should be treated with a solution of caustic potass of 10 per cent., and
then submitted to pressure. Under these circumstances, " beautiful lamella; appear. The
separate layers exhibit no trace of being composed of fusiform cells; they appear finely
striated, and in places, hyaline; sometimes elongated spots appear, of which it cannot be
determined with certainty whether they are nuclei or i)erforations in the membrane." In
some, there was no trace of these to be seen. Reichert considers the fibres of the cortex to
be artificial products, and was unable to convince himself of the existence of nuclei in this
part of the hair. — Tks.]

12

178 SPECIAL HISTOLOGY.

mitted light (Fig. 65 a). If a hair thus treated be carefully teased
out, it is easy to isolate the medullary cells, either in aggregate masses,
rig. 69. 01' even completely separate (Fig. 69). They are rectangular
^,^ or quadrangular, rarely rounded or fusiform of 0-007 — O'Ol
i'??!|'^, of a line in diameter, occasionally containing dark, fat-like
granules, and often when the alkali has not acted too strongly,
a rounded clear spot of 0-0016-0 -002 of a line, which is plainly
the rudiment of a nucleus, and which also seems to swell up somewhat
in soda.

In fresh hairs, the medulla in the shaft is silvery white or dark, an
appearance which, as many more favorable objects show, arises from
rounded- angular, granular corpuscles, black (opaque) or of a brilliant
white, according to the illumination, tolerably uniform in size, but varying
according to the hairs, from 0-0002-0-002 of a line and occupying the
medullary cells in great quantity (Fig. 68). These granules are not fat
or pigment, as has been hitherto universally supposed, but air-vesicles,
as may be readily demonstrated by boiling a white hair in ether or oil
of turpentine, in both of which cases the medulla becomes quite clear
and transparent. If such a hair, treated with water, be dried between
the fingers, it soon, often quite suddenly and visibly to the naked eye,
assumes its previous white color, and if immediately after drying, it be
placed under the microscope, without fluid, or with fluid at one end only,
nothinfr is easier than to see the re-entrance of the air and the conse-
quent darkening of the medulla. Not only in white hairs, but in dark
ones also, the medulla contains air in the fresh state, only in this case
it does not appear of a pure silvery white, but with a blonde, red or brown
tinge ; this does not arise from any special pigment, which is only found
occasionally in the medulla of dark hairs, but proceeds from its being
seen through the colored cortical substance. A more careful investi-
gation of the medullary cells shows, that while fresh they contain many
small cavities in a viscid substance ; in these lie the air vesicles, which
communicate to them the granular appearance above described. If we
observe the air which has been expelled refilling the medulla of a dried
hair, it seems as if all the cavities of one and the same cell communicated
with one another, at least the air frequently passes in continuous winding
streams from one cavity into the other ; indeed from the sudden manner
in which the air sometimes fills the medulla, it might almost be believed
that the cavities of contiguous cells were connected together. However
this may be in certain cases, it is conceivable, that even if the cavities
of the different cells are quite closed, and only separated from one
another by delicate partitions, the air still m-ay quickly fill the medulla
under the appearances we have noted. For the rest, the vacuities of

Fig. G9. — Ei.Kht medullary cells, with pale nuclei, and fatty granules, from a hair treated
with soda ; magnified .350 diameters.

OF THE HAIRS. 179

the medullary cells, whether they are quite closed or not, are of different
sizes, the aeriferous medulla appearing sometimes coarsely, sometimes
finely granular. I have also seen cases in which the medullary cells
obviously contained only a single large air-vesicle, and appeared almost
like small fat-cells. Very frequently single larger or smaller spots may be
observed in the medulla, Avhich contain no air, and are thence pale, and
this is constantly the case in the lowermost part of the medulla, close
above the bulb.

The medulla and the cortex are widely different if we compare the
extreme forms of their elements ; in the one case we have rigid homo-
geneous elongated plates, almost without contents, in the other rounded
vesicles filled with fluid or air. If, however, we take into account all
their conditions, we shall find that the limits are not so marked, and in
fact are often hardly distinguishable. On the one hand, for instance,
the medullary cells are not unfrequently of an elongated or short fusi-
form figure, whilst on the other the plates of the cortex present a con-
siderable cavity containing pigment. If such plates contain, instead of
pigment or the smaller air-vesicles, air in a larger cavity, as occurs
sometimes though not frequently, it is still more difiicult to distinguish
the two kinds of elements from one another, and the more so if, as in red
hairs, the medulla and cortex are in places, or for considerable distances,
not distinctly defined from one another, the superficial cells of the
medulla being scattered and passing quite gradually into the plates of
the cortex, which lie very close together and contain much air. It is
not intended to imply, by this, that the medulla and the cortex are
identical, but only that transitions exist, and that the differences which
occur are less marked than is commonly supposed.

The diameter of the medulla is generally, in proportion to that of the
hair itself, as 1 : 3-5 ; relatively and absolutely, it is thickest in short
thick hairs, thickest in the down and hairs of the head. In a transverse
section it presents a round or flattened figure, and the cells which com-
prise it are disposed in 1-5 or even more longitudinal series.

The medullary substance, the cells in which were first accurately de-
scribed by G. H. Meyer, varies most of all the constituents of the hair.
In the down of the hairs of the head, it has been stated, by some, that
it is wholly absent, which is to be corrected thus far, that it is certainly
generally absent in the former, and frequently in the latter, perhaps
more frequently, in certain individuals. In white hairs, even those of
the head, of a tolerable length and thickness, I have never failed to find
it always beautifully distinct. In rare cases the medullary tract is
double throughout (Bruns, figure in Hassall), more frequently di-vidcd in
places into two tracts, which soon unite again. In the lower part of
the root, the medulla, which is here clear, is often thicker, and exhibits

l&O SPECIAL HISTOLOGY.

the nuclei of its cells very distinctly, especially after the addition of
acetic acid. Steinlin and Eylandt assert of the medullary substance,
that it does not belong to the proper hair, but to its papilla, and origi-
nally represents a prolongation of this into the free part of the hair,
which then dries up. This is incorrect. The papilla or germ of the
hair is a part of the cutis, and has the same structure as the papilloi of
the latter, whilst the medulla of the hair is composed of isolated cells,
which by their resistance to alkalies, are in all respects allied to those
of the epidermis. On the other hand, in animals, as has long been
known, and as lately Brocker has especially shown, the papilla often
projects far, even to the point of the hairs, bristles or spines, subse-
quently drying up ; but in these instances, according to Brocker, it
never, even after the action of potass, exhibits a cellular texture, whilst
this is always obvious in the medullary substance, which is often present
at the same time. Such an elongation of the papillae may occasionally
be noticed even in man, to a certain extent ; thus Henle found it a few
times prolonged into a short point. But any prolongation of this kind
must be distinguished as decidedly from the cellular medullary substance,
as in animals.

§ 58. The cuticle of the Hair [cuticula), is a very thin, transparent
pellicle, which completely invests the hair, and is very closely united
with the cortical substance. In its normal position, and observed in an
unaltered hair, it is evidenced by hardly anything more than by nume-
rous dark, reticulated, irregular or even jagged lines, which surround
the hair at intervals 0 •002-0-006 of a line from one another, and occa-
sionally also by small serrations at its apparent edge (Fig. 70 A) ; if,
on the other hand, a hair be treated with alkalies, the cuticle is raised
in smaller or larger lamelliB from the fibrous substance, and is even
separated into its elements. These are quadrangular or rectangular
flat plates without nuclei, generally pale and transparent (Fig. 70 B),

which do not swell up into vesi-
4 Fig. -0. ^ ^|gg i^y ^i^g action of any re-

agent, and disposed in an im-
bricated manner, form a simple
membrane which completely
surrounds the cortex of the hair
in such a way, that the deeper
<C^_/N, l'""^ or lower cells cover the upper

^^^ ones. By sulphuric acid also

the structure of the epidermis is readily made out ; the hair is, as it were,

Fio. 70. — J, surface of the shaft of a white hair ; magnified 160 diameters. The curved
lines mark the free edges of the epidermic plates : B, epidermic plates from the surface,
isolated by the action of caustic soda ; magnified 350 diameters. One or both of tlieir longer
edges are bent round, and so appear dark.

OFTIIEHAIRS. 181

bristled at tlie edges with the erected phates and by scraping or rubbing,
the cuticle is less easily obtained in large lamellae, but is readily enough
reduced to its elementary parts.

On the shaft of the hair the cuticle consists only of a single layer of
plates 0-002-0-003 of a line thick, which measure 0-024-0-028 of a
line in the transverse direction of the hair ; 0-016-0-02 in that of its
length ; and are hardly more than 0-0005 of a line in thickness. The
same structure exists also in the upper part of the root of the hair;
of its lower part, on the other hand, so far as the inner root-sheath ex-
tends, two layers of the epidermis constantly occur. The outer (Fig.
(68 d is rendered especially obvious by the action of soda or potassa, and
with a little pressure frequently comes away from the hair with the inner
root-sheath, whilst the inner layer becoming undulated, remains lying
upon the cortical substance, and may be easily studied, as well in the
side view as upon its surface. In hairs that are torn out, this layer is
found only where they are covered by the inner root-sheath, otherwise
it remains behind in the hair-sac. Its elements also, are broad cells
without nuclei, covering one another like tiles, which do not swell up in
alkalies, and are soluble with great difficulty ; they are thicker than
those of the other layer, and measure only 0-002-0-004 of a line in the
direction of the length of the hair. The whole outer layer measures
0-0016-0 -002 of a line, whilst the inner layer upon the root has a thick-
ness of 0-0025-0-0035 of a line. Upon the bulb of the hair, the
two layers of cuticular plates pass with a tolerably defined margin
into soft nucleated cells, which are broad in the transverse direction of
the bulb, very short longitudinally, and somewhat longer in their third
diameter, which stands perpendicularly or obliquely to the longitudinal
axis of the hair. They are readily attacked by alkalies, or even by
acetic acid, possess without exception transverse and longish nuclei, and
finally pass, on the bulb, into the already described, round cells of which
it is formed.*

• [We cannot agree with Professor KoUiker that the cuticle of the hair passes into the
outer cells of the bulb. It may be worth devoting a little space to this matter, as the whole
question of the homology of the hair essentially turns upon it. So far from being able to
trace the two layers of the cuticle into the round cells of the bulb, we find that they cease
somewhat suddenly when the shaft begins to expand, while its substance is fibrous-looking
and contains only much elongated nuclei. Below this point, as Henle has correctly figured
in his '■ Allgemeine Anatomic," Pi. I. Fig. 14, the transverse striations of the cuticle are
absent ; and if the cuticular layer be viewed in section, it will be seen to be composed of a
more transparent substance, wliich gradually becomes thinner until it is hardly distin-
guishable as a distinct layer, and at the same time loses the oblique lamination, which it
has above, where it is continuous with the two layers of the cuticle proper. The careful
addition of caustic ammonia is particularly fitted to demonstrate the structure of this part.
In the first place, it raises up the outer layer of the cuticle from the inner, and shows that
the former, at any rate, is not continuous with any cells; and secondly, it dissolves and
forces out die .substance of the lower soft portion of the bulb, so that the lower part of the
cuticle may be obtained as a transparent, colorless, and^ independent sheath, even from

182 SPECIAL HISTOLOGY.

§ 59. The hair-sacs, folUculi pilorum^ are flask-like follicles 1-3
lines long, which embrace the roots of the hair tolerably closely, and, in
the lanugo, are lodged in the substance of the upper layers of the corium,
while in the stronger or long hairs, they generally project into its deeper
portion, and even extend for a greater or less distance into the subcu-
taneous cellular tissue. These follicles are simply to be regarded as invo-
lutions of the skin, with its two constituents, the corium and the epi-
dermis, and there may be distinguished, therefore, in each of them, an
external fibrous, vascular part, the proper hair-sac, and a non-vascular
cellular investment lining this, — the epidermis of the hair-sac ; or,
since it immediately surrounds the root of the hair, — the "root-sheath"
[vagina pili).

§ 60. The 2)roper hair-sac consists of two fibrous investments, an ex-
ternal and an internal, and of a structureless membrane ; it is on an
average 0-015-0*022 of a line thick, and contains in its lower part a
peculiar structure, the papilla of the hair.

The external fibrous 7nemhrane (Fig. 63 h), the thickest of the three
layers of the hair-sac, determines its external form, and by its innermost
layer is very closely connected with the corium. It consists of common
connective tissue with longitudinal fibres, without any intermixture of
elastic fibres, but with a considerable number of long fusiform nuclei ;
it contains a tolerably close plexus of capillaries, and exhibits also a
few nervous fibrils with occasional divisions.

The internal fibrous membrane (Fig. 71 a) is much more delicate than
the external ; bounded by smooth surfaces, and everywhere of equal
thickness, it extends from the bottom of the hair-sac as far only as the
entrance of the sebaceous glands. To all appearance, it contains neither
vessels nor nerves, and is composed solely of a simple layer of transverse
fibres, with a long narrow nuclei, which may be seen particularly well
in the empty hair-sacs of both coarse and fine hairs, with or without the

the very darkest hairs; lastly, under favorable circumstances, this reagent raises up a definite
basement membrane from the outer surface of the lowest part of the bulb, in immediate
contact with the rounded " nuclei"' of this part, and this basement membrane may be traced
upwards into direct continuity with the homogeneous portion of the cuticle above-described.
(In the " Edinburgh Mondily Journal of Medical Science,' for March, 1853, Mr. Dalzell
states that the papilla of the hair has a basement membrane. Is it this structure to which
he refers?) In all cases in which, in man or in animals, we have isolated the hair-bulb
from its sac, it seemed to have a definite limiting outer line down to the narrow neck by
which it passes into the hair-sac, though it was not often easy to obtain evidence that this
limiting line was the expression of a distinct basement membrane. However, the same
difficulty would occur with any dermic papilla ; and it seems to us that there is sufficient
evidence to show that the cuticle of the hair is not the product of any direct metamorphosis
of cells, but represents a modified basement membrane with a subjacent layer of peculiarly
altered blastema, corresponding precisely with the " Nasmyth's membrane"' and the enamel
of the teeth. Vide infra, § on Teeth. — Tbs.]

OF THE HAIRS.

183

I'ig. 71.

,a

nddition of acetic acitl. They resemble smooth muscular fibres, although
they cannot be completely isolated and actually recognized as true fusi-
form fibres with a single nucleus ; on which account, and especially as
no contractions of the hair-sacs have
in general been observed, I must for
the present refrain from positively
deciding upon their nature.

The third layer, lastly (Fig. 71 h\
is a transparent structureless mem-
brane, which, when the hairs are torn
out, invariably remains behind in the
hair-sac, and extends from its base,
though, as it would seem, without
covering the papilla, as far as the
inner root-sheath, and perhaps higher.
In the uninjured hair-sac it appears
only as a pale streak 0-001-0-0015,
rarely 0-002 of a line thick, between
the outer root-sheath and the trans-
versely fibrous layer of the hair-sac ;
by preparing an empty hair-sac, how-
ever, it can readily be obtained in ^^^^^^S^
large shreds, and then appears smooth ^^^^s=;s.i^_:^.^
externally ; internally it is covered
with very delicate, transverse, often anastomosing lines, which, like the
membrane itself, remain unchanged in acids and alkalies. Neither acids
nor alkalies bring out cells or nuclei in this membrane, and it therefore
probably belongs to the category of true structureless membranes.

The papilla of the hair (Fig. 63 i) also, less properly termed the hair-
germ, pidptapili, belongs to the sac, and corresponds with a papilla of
the cutis. It is generally seen but indistinctly, especially in dark hairs
with a colored bulb, either appearing, only as a clear, indistinctly defined
spot, or after the tearing out of the hair, remaining so covered by the
cells of the bulb that nothing can be made out of it. It is only in the
hair-sacs of white hairs, that its outlines can be more frequently distin-
guished without wholly isolating it, especially by the help of a little
pressure. Reagents, on the other hand, avail nothing, for they attack
the papilla to about the same extent as the bulb, with the sole exception
of a weak solution of caustic soda, in which it retains its outlines, for a

FlG.71. — A piece of the transverse fibrous layer, and of the structureless membrane
(vitreous membrane) of a human hair-sac, treated with acetic acid ; magnified 300 diame-
ters: a, transversely fibrous layer with elongated transverse nuclei; b, vitreous membrane
in apparent section; c, its edges, where the sheath which it forms is torn ; d, fine transverse
partly anastomosing lines (fibres) on their inner surface.

184 SPECIAL HISTOLOGY.

time at any rate, whilst the cells of the bulb are freed, and m:iy be
pressed out of the sac. The papilla is ovate or fungiform, l-4'o of a
line long, ti~2'(1 o^ ^ ^^^^ broad, and is connected with the layer of con-
nective tissue of the sac, by a pedicle ; it has sharp contours and a per-
fectly smooth surface, and in its structure completely agrees with the
papillae of the cutis, consisting of an indistinctly fibrous connective
tissue with scattered nuclei and fat granules, but not of cells. I have
taken every pains to discover vessels and nerves in the iso]st.ted jMjnllce,
but in vain ; even acetic acid and dilute solution of caustic soda, which
in general do such excellent service in these cases, have failed, and
Hassall and Gunther met with the same results. It must not hence
be concluded, that ihepapilla contains no vessels or nerves, for we know
that in other places, Avhere vessels do certainly exist, they often com-
pletely escape the eye ; as, for example, in the dermal j^aj^Hlce and in
the villi; and with respect to the nerves, in the papillae of the cutis.
In some animals the vessels may very readily be seen.

§ 61. The root sheath, or the epidermic investment of the hair-sac, is
continuous with the epidermis around the aperture of the follicle, and
may be divided into an external and an internal layer, which are dis-
tinctly defined from one another.

The external root-sheath is the continuation of the stratum Malpighii
of the epidermis, and lines the whole hair-sac, resting for its lower half
on the transparent membrane above described; higher up, when this
and the transverse fibres are absent, it lies directly upon the longitudi-
nally fibrous layer. Its structure corresponds exactly with that of the
stratum 3Ialpighii, even in the having the outermost cells, which in the
negro, according to Krause, are always brown, and in w^hites are so, at
least in the hairs of the labia majora, towards the upper part, arranged
perpendicularly. At the bottom of the hair-sac, the outer root-sheath,
its cells becoming gradually rounded, passes continuously, and without
any sharp line of demarcation, into the round cells of the hair-bulb which
cover the papilla. The outer root-sheath is generally about 3-5 times
as thick as the inner; but not unfrequently it becomes thinned towards
its upper part, and below invariably passes into a very thin lamella. In
the coarse hairs it measures in the middle of the root 0'018-0'03 of a
line, and presents 5-12 layers of cells.

The inner root-sheath (Fig. 68-e. g.) is a transparent membrane
which extends from almost the very bottom of the hair-sac, over more
than two-thirds of it, and then suddenly ceases. It is closely connected
externally with the outer root-sheath, internally with the cuticle of the
hair (its outer layer), so that normally there is no space between it and
the hair ; further it is distinguished by its great density and elasticity,
and it consists in all but its lowermost part, of two or even three layers

OF THE HAIRS.

185

of polygonal, elongated, transparent, and somewhat yellowish cells, all
of which have their longitudinal axes parallel to that of the hair (Fig. 68).
The outermost layer (Fig. 72, A), which alone was formerly known, the
inner root-sheath of Henle is formed of elongated cells without nuclei,
0-016-0-02 of a line in length, and 0-004-0-006 of a line in breadth,
which are intimately connected, and in the ordinary mode of investiga-
tion, after the addition of acetic acid, caustic soda, or potassa, which
swell up the hair, or after the hair has been teased out, present elon-
gated fissures between them, whence they appear like a fenestrated mem-
brane. In quite recent hairs, however, if all reagents and mechanical
injury have been avoided, we see hardly any trace of apertures in the
vpperhaU of the layer in question, and in the loiverhaU (from the finely
fibrous part of the cortex upwards), at most mere indications of them, in
the form of strife, clear or dark, according as they are in or out of focus,
and similar to those of the cortex of the shaft. We can hardly avoid
supposing, therefore, that the openings as they are commonly seen
(0-005-0-008 of a line in length, and 0-001-0-03 of a line in breadth),
are produced artificially by the teasing out of the membrane. Secondly,
cells also occur in the root-sheath, between which gaps are never visible.
These (Fig. 72, B), which form a simple or a double layer (Iluxleys

Fig. 72.

,--«

^■\A<Aij

\r:i u

layer), are constantly situated internal to the common, and as far as I
have seen, always single, fenestrated layer of cells ; they are shorter and

Fig. 72. — Elements of the inner root-sheath ; magnified 350 diameters. Jl, from tlie outer
layer, l,its isolated plates; 2, the same in connection, from the uppermost parts of rlie layer
in question, after treatment with caustic soda: a, apertures between ilie cells, b; B, cells of
the inner not-perforated layer, with elongated and slightly notched nuclei; C, nucleated cells
of the lowest part (single layer) of the inner sheath.

186 SPECIAL HISTOLOGY.

broader than the cells ■which have already been described (0-014 to
0-018 of a line long, 0-006 to 0-009 of a line broad), but are also poly-
gonal, and always possess, at least in the lower half of the root-sheath,
distinct elongated nuclei, often prolonged into points of 0-004-0-006 of
line. The diameter of the whole inner root-sheath is, upon the average,
0-006-0-015 of a line, whence it follows that its cells, of which there are
never more than three layers, are at least 0-002-0-005 of a line thick.
They are recognizable at once in their natural position, and by the teasing
out of the root-sheath, and are readily isolated by the use of soda and
potassa (Fig. 72), but without swelling up, a character which no less than
their great resistance to alkalies altogether, distinguishes their cells, in
common with the epidermic scales of the hairs, from all others.

At the bottom of the hair-sac, the inner root-sheath consists only of
a single layer of beautiful, large, polygonal, nucleated cells, without any
intermediate openings (Fig. 72, (7), which becoming at last soft, delicate,
and rounded, pass without defined limits into the outer layers of the
round cells of the hair-bulb. Superiorly, this membrane not unfrequently
becomes somewhat separated from the hair, and ends, not far from the
apertures of the sebaceous glands in a sharp, notched edge, formed by
its separate more or less projecting cells. Thence upwards, it is re-
placed by a layer of cells, in some cases at first nucleated, but at other
times not, which gradually approximates more and more, as it is traced
higher up, to the horny layer of the epidermis, into which it passes con-
tinuously ; it is not, however, any direct continuation of the inner root-
sheath.

§ 62. Development of tlie Hairs. — The first rudiments of the hairs are
flask-shaped, solid processes of the mucous lay er of the epidermis formed
hy its grotvth inwards, in which the internal and external cells subse-
quently become difi'erentiated in such a manner, that the former, a
gradual conversion into horn going on, are, in the axis of the rudiment,
metamorphosed, in the first place into a small delicate hair, and secondly,
around this into its internal sheath ; while the latter, undergoing less
alteration and remaining soft, constitute the outer root-sheath and the
soft cells of the hair-bulb. Hence the hairs and their sheaths arise at
once in their totality. The former, as minute hairs with root, shaft,
and point, and are therefore not developed point first, as the teeth are,
with their crown first, and still less as Simon has supposed, from their
root first. The elements of the youngest hairs are nothing but elongated
cells similar to those of the cortex of the later hairs, which are deve-
loped by the lengthening and chemical alteration of the innermost cells
of the rudiments of the hairs. Medullary cells are entirely wanting,
but the cuticle is clearly visible. The inner sheath is striated, presents
no openings, and consists of elongated cells, which have been developed

OF THE HAIRS. 187

from those lying between the hair and the outer sheath. The proper
hair-sac is formed, in its fibrous layers, essentially in loco, out of the
formative cells which surround the rudiment of the hair ; possibly, how-
ever, they may be considered as an involution of the cutis, produced by
the ingrowing process of the epidermis. Its structureless membrane,
which appears very early, is, not improbably, closely related to the ex-
ternal cells of the rudiment of the hair, answering to the outer hair-
sheath, and formed by an excretion from them like the membrance pro-
price of the glands; as to i\\Q papilla, it is hardly possible to consider it
as anything but an outgrowth of the fibrous layer of the hair-sac,
analogous to the papillae of the cutis in general ; though the circumstance
that it appears at a time when the hair-sac is hardly demonstrable as a
whole, and that it may always be pulled out together with the rudiments
of the hair and root-sheath, is apparently opposed to this view.

The first rudiments of the downy hairs and of their sheaths, are found
in the human embryo at the end of the third or at the beginning of the
fourth month, upon the forehead and eyebrows. They consist of papilli-
form masses of cells 0*02 of a line in diameter (Fig. 73) which are
visible, even to the naked eye, as minute whitish spots separated by
regular intervals. They are continuously connected with the rete 3Ial-
pigldi of the epidermis, and are nothing more than perfectly solid pro-
cesses of it, which penetrate obliquely Fig. 73.
into the cerium, and here lie in the
meshes of a delicate capillary network.
These cells are spherical, 0-003-0-004
of a line in diameter, and consist of a
clear granular substance and round
nuclei of 0-002-0-003 of a line.
Nothing was to be seen of any dermic "'^
investment of these rudiments ; in other words, the foundation of what
I have described as the proper hair-sac was not laid. In the fifteenth
week the processes were already larger (0-025-0-03 of a line long;,
0-013-0-02 of a line broad), flask-shaped, and surrounded by a thin
structureless investment, which was continued into a delicate membrane
lying between the cutis and the rete Malpighii, but united more closely
with the latter. Besides this investment, which is, probably, only the
structureless membrane which I have discovered in the perfect hair (see
§ CO), another external layer of cells occurs on the hair-sacs, which can

Fig. 73. — Rudiment of the hair from the brow of a human embryo, sixteen weeks old;
magnified 350 diameters: a, horny layer of the epidermis ; 6, its mucous layer; i, structure-
less membrane surrounding the rudiment of die hair and continued between the mucous
• layer and the corium ; fn, roundish, partly-elongated cells, which especially compose the
rudiment of the hair.

fii-

188 SPECIAL HISTOLOGY.

generally be separated only in shreds with it, from the cutis, rarely al-
together : this I regard as the first indication of the fibrous layers of
the hair-sacs. In the sixteenth and seventeenth weeks, the processes of
the mucous layer, which I will henceforward simply call " hair-rudi-
ments," increase in size up to •004-0-06 of a line in length, and 0-03-
0-04 of a line in breadth, and acquire thicker coverings, but as yet ex-
hibit no trace of a hair. In the eighteenth week these first appear in
the eyebrows, as hair-rudiments of 0'l-0-2 of a line, their central cells
becoming somewhat elongated, and arranging themselves with their lon-
gitudinal axes parallel to that of the rudiment, whilst the peripheral
cells are disposed with their now longer diameter transversely. A variety
of shade in the hitherto homogeneous hair-rudiment arises in this
manner, and a central substance, broad below, running above into a
sharp point, becomes marked oif from an outer portion, which is narrow
below and thick above. When the rudiment has attained a length of
0'22 of a line, this marking off is still more distinct, the rather longer
and especially broader, inner cone having a somewhat clearer appear-
ance (Fig. 74). Finally, in rudiments of hair of 0-28 of a line, the
inner cone is divided into two structures, a central portion somewhat
darker, and an external, perfectly transparent and glassy, — the hair
and the inner root-sheath, — whilst the peripheral cells which have re-
mained opaque, constitute unmistakably the outer root-sheath (Fig.
75 A). At the same time the papilla, which was even before (Fig. 74)
just traceable, becomes more distinct, and the proper hair-sac also more
recognizable, as the cells which lie external to its structureless membrane
begin to pass into fibres which may, even at this time, be known by their
decussation. The hair-sacs and hairs arise, in other places, exactly in
the same manner as in the eyebrows, except that their development takes
place somewhat later. In the fifteenth week, no rudiments of hairs are
visible, except on the forehead and eyebrows ; in the sixteenth and
seventeenth week they appear all over the head, back, chest, and ab-
domen ; and not till the twentieth week on the extremities. The hairs
themselves never make their appearance earlier than 3-5 weeks after
that of the rudiments ; in the nineteenth week, for example, the com-
mencement of hairs is nowhere to be seen, except on the forehead and
eyebrows ; and in the twenty-fourth week they are still absent upon the
hand and foot, and partly on the forearm and leg.

Once formed, the hairs and hair-sacs continue to grow. The former
sometimes penetrate the epidermis immediately (eyebrows, eyelashes,
Fig. 75), sometimes their points are insinuated between the horny layer
and the stratum Malpigliii, or among the elements of the horny layer
itself, and grow for a time covered by the epidermis (chest, abdomen,
back, extremities [?]), through which they eventually make their pas- »
sage. Involutions of the skin growing towards the hairs as they pass

OF THE HAIRS.

189

out, never exist, and the supposition that thej do, rests upon a wholly
subjective foundation.

Fig. 75.

Fig. 74.

The downy hairs, lanugo, the eruption of which is completed in the
23-25th week, are short fine hairs, whose peculiar arrangement has been
noted above. They measure on the bulb 0-01, on the shaft 0-006, at
the point 0-0012-0-002 of a line; are pale, or almost colorless, and
consist only of cortical substance and a cuticle. In man, the bulb is
usually colorless, and often rests upon a very distinct j^apiUa, arising
in the ordinary manner from the bottom of the hair-sac. It has the
same three layers as in the adult, and possesses a very well-developed
epidermic investment, consisting of an external root-sheath of 0'004-
0-012, and an inner sheath of 0-006-0-008 of a line, without openings.

After their eruption, the downy hairs grow slowly to a length of ^|-
of a line, and in fact to a greater length in the head than elsewhere.
Generally they remain to the end of foetal life, gradually acquiring a
darker color, becoming in many cases, as on the head, even blackish ;
another small portion falls off into the liquor aninii, is swallowed with

Fig. 74. — Rudiment of a hair from the eyebrow (0-22 of a Hne in length), its inner cells
forming a distinct cone, as yet without any hair, but with the papilla indicated : a, horny
layer of the epidermis; b, mucous layer; c, outer root-sheath of the subsequent sac; i, struc-
tureless membrane upon its outer side; h, papilla of the hair — Magnified 50 diameters.

Fig. 75. — ji, rudimental hair from the eyebrows, with just developed but not yet erupted
hair, of 0"28 of a line in length. The inner rootsheath projects beyond the point of the hair
somewhat at the upper part, and laterally at the neck of the sac; the first rudiments of the
sebaceous glands appear in the form of two papillary outgrowths from the outer root-sheath.
B, hair-sac from the same, with its hair just erupted ; the inner root-sheath projects through
the aperture of the hair-sac; the rudiments of sebaceous glands are as yet not developed;
a.b,c,h,i, have the same signification as in Fig. 74 : e, hair-bulb; /, liair-shaft; g, hair-point;
n, rudiments of the sebaceous glands.

190 SPECIAL HISTOLOGY.

this by the foetus, and may afterwards be found in the meconium. A
proper shedding of the hair does not take place at all in the foetus, so
far as I can see, infants being born ■with the lanugo ; as little does any
trace of a further formation of hair appear after its complete eruption.
The question whether the point of the hair is first formed, or whether
the latter is developed at once as a whole, is readily solved. Hairs
which are just formed, have a bulb Avith soft cells, a horny point and an
intermediate portion, in which the cells are converted into horn, and
are partly found passing into the cells of the root, whence there can be
no doubt that we have here a whole hair. That the horny part of this
hair subsequently forms the point of a larger hair, is of no importance;
and as little as the hairs of the head of a newly-born infant can be
called points of hairs, because they subsequently become the points of
larger hairs, can we so denominate these. Nor can it be said that the
first foetal hair subsequently becomes, in totality, the point of a larger
hair, since the hairs do not grow by the simple apposition of new ele-
ments, like the bones, but by the multiplication of their lowest soft cells,
some of which are always retained as a reserve for cells to be newly
developed, whilst the others are converted into horn ; whence also it
happens, that the cells even of a complete hair-bulb are to be regarded
as the successors of those of the foetal hair.*

* [From what has been said above (see note on the Cuticle) it is clear we do not share
Professor KoUiker's view that the hair is an epidermic production. Reichert's view, on the
other hand, that the hair results from the cornification of a dermic papilla or matrix, which
drying up and becoming filled with air, remains as the medullary portion, seems to us to be
nearer the truth. There can be no doubt of these two facts: 1, that no line of demarcation
can be traced between the papilla of the hair and its shaft; and 2, that in many animals
the papilla is vascular and nervous for a considerable distance into the shaft, and, therefore,
is certainly a dermic structure.

Whether Reichert's somewhat mechanical notion of the " drying up" of the matrix to form
the medulla is correct, is not of much importance, so long as we keep in view the unques-
tionable continuity of tissue and honiological identity, of the medulla and cortex with the
dermic papilla.

For us, in fact, the Hair is homologous in all its parts with the Tooth. The substance of
the shaft corresponds with the dentine, offering even rudimentary tubes in its aeriferous
cavities; the inner layer of the cuticle answers to the enamel, the outer to Nasmyth's mem-
brane ; and whoever will compare these structures will be struck by the similarity even in
their appearance. The sac answers to the dental capsule ; the outer root-sheath to the layer
of epithelium (enamel organ) next the capsule; the fenestrated membrane to the stellate
tissue ; and what Professor Kolliker calls " Huxley's layer," to the columnar epithelial layer
of the organon adamantince. The comparison may seem startling at first, but the examina-
tion of the development of the teeth of an osseous fish, for example, will suffice, we believe,
to afford full justification of it.

With respect to the not very important question, as to the nature of the first rudiment of
the hair-shaft, i. e. whether it is the point of a hair or a whole hair, we must confess that we
should be tempted to arrive at the ojiposite conclusion to our author. Inasmuch as the por-
tion of the hair which first appears becomes the point of the fully-grown hair, we should
say that the hairs are formed like the teeth, point first.

A hair, like a tooth, has a definite form to attain. As the latter has a peculiarly con-

OF THE II A I lis.

191

§ 63. Shedding of the Hair. — After birth, a toted shedding of the
hairs takes place in consequence of the development of new hairs zvithin
the hair-sacs of the lanugo, which gradually force out the old ones. This
sliedding of the hairs, which I discovered in the eyelashes of a child of
one year old, commences by an outgrowth of the soft round cells of the
bulb and of the neighboring outer root-sheath, from the bottoms of the
sacs of the lanugo, into long processes composed of cells, by which the

Fis?. 76.

Fis. 77.

i^Ki

■J I

hair is raised from its papilla, whilst at the same time it }
becomes converted into horn even in its lowermost por- S
tion. When these processes have attained a length of ^
0*25 of a line, a differentiation of their outer and inner
cells takes place, similar to that which has been already

Fig. 7G. — Tlie eyelashes of a child of one year old pulled out; magnified 20 diameters:
A, one with a process of the bulb or of the outer root-sheath, of 0'25 of a line, in which the
central cells are elongated (their pigment is not represented), and are clearly defined as a
cone from the external ones; B, eyelash in whose i^rocess, of 03 of a line, the inner cone is
metamorphosed into a hair and an inner root-sheath ; the old hair is pushed up, and like A
and Fig. 75, possesses no inner root-sheath : a, outer; b, inner root-sheath of the young hair;
c, pit for the papilla of the hair; rf, bulb; e, the shaft of the old hair; /, bulb; g, shaft; h,
point of the young hair; i, sebaceous glands; k, three sudoriparous canals, which in A open
into the upper part of the hair-sac; l, transition of the outer root-sheath into the rele mucosum
of the epidermis.

Fig. 77. — An eyelash with the root-sheaths from a child one year old, with an old and a
growing young hair, magnified 20 diameters: the young hair is wholly extruded, and now
two hairs appear at one aperture. A sudoriparous canal opens into the hair-sac. The
letters have the same signification as in Fig. 7(5.

structed and narrowed root when complete, so has the hair when it has attained its full
growth a peculiarly constructed bulb; and it is not a perfect hair until this peculiar bulb is
developed. Until it has attained this form it goes on growing; Init once having reached it,
it grows no more, but falls out and is replaced by a new hair (see following §). — Trs.J

192 SPECIAL niSTOLOGY.

described as occurring in those processes of the stratum Malpighii, in
■which the hairs of the lanugo are developed. The outer cells, in fact,
remaining round and colorless, as they were before, the inner ones begin
to develop pigment in their interior and to elongate, becoming distin-
guished at the same time from the former, as a conical substance with
its point directed upwards. At first (Fig. 76 A), this central substance
is quite soft, and like the layers of cells which surround it externally,
dissolves readily in solution of caustic soda ; subsequently, however,
when, together with the process which incloses it, it has elongated, its
elements harden, and separate into two portions, an enternal dark pig-
mented, and an external clear part, which are nothing else than a young
hair, together with its inner sheath (Fig. 76 B). The young hair,
whose point at first does not project beyond its inner root-sheath, now
grows gradually, forcing its point through the aperture of the old sac,
while at the same time its root-sheath elongates, and thrusts upwards
the bulb of the old hair, until at last it passes completely out, and makes
its appearance at the same opening with the old one, which is more
and more pushed up. When the development of the hair has gone
thus far, the last stage may be readily understood. The old hair, which
has for a long time ceased to grow, and to be connected with the bottom
of the sac, being thus extruded, falls out, while the young hair becomes
larger and stronger, and fills the gap left by the old one. The primary
cause of the dying away and casting off" of the old hair, I consider to
be the development of the processes of the hair-bulb and outer sheath
from the bottom of the sac, which has been described. As the sacs do
not elongate to a corresponding extent, they push upwards all those
parts which lie above them, and cause a continually increasing space to
exist between the papilla and the proper hair, or the point at which the
round cells of the bulb begin to elongate and undergo conversion into
horny matter.

The hair thus becomes in a manner detached from the source of its
nourishment ; it receives less and less blastema, at last ceasing to grow,
and becoming converted into horn in its lowest part. The cells of the
processes, on the other hand, which are connected with the papilla, are
incessantly supplied from it with new formative material, which for the
time they apply not to the formation of horny matter, but to their own
growth. In this manner the processes continue to grow, and mechani-
cally elevate the cornified root of the old hair with its sheaths, to the
aperture of the sebaceous glands, where to all appearance a partial so-
lution of the old sheaths takes place : this may be observed with cer-
tainty in the inner sheath, and must be assumed to occur in the outer.

All that has been said, holds good only with respect to the eyelashes.
The hairs of the head, and the other hairs of the body of the child (al-
most a year old) in question, never contained more than one hair, though

OF THE HAIRS. 193

their bnlbs presented processes without hairs like those which precede
the shedding of the ejchishes ; such processes, in fact, being of very
common occurrence in the hairs of chihh'cn within the first year. I be-
lieve I am not wrong, if from the presence of these processes I deduce
the universal occurrence of a shedding of the hairs, particularly as it is
certain that in many children within the first 2-6 months after birth,
the hairs of the head fall out and are replaced by new ones. How-
ever, further observation is necessary to determine what period is occu-
pied by this first shedding of the hair, in what hairs it occurs, and
whether perhaps the process is subsequently repeated.

If we compare the shedding of the hairs with their first develop-
ment, we find a great resemblance between the two processes. In both,
elongated projections, wholly formed of round soft cells, shoot like buds
from the stratum MaJpighii, in the one case of the skin itself, in the other
of the hair-sacs and hairs. In both, a separation of the inner from the outer
cells next takes place ; and while the latter are metamorphosed into the
outer root-sheath, the former become the inner root-sheath and the hair.
The latter arises, as is still more clear in the shedding of the hairs than in
their first development, like the nail, with all its parts at once, as a small
hair provided with point, shaft, and root, and which only subsequently
begins to grow, in consequence of which it enlarges in all its parts,
and finally reaches the surface. The difi'erences between the two modes
of development are very inconsiderable, and chiefly depend upon the
rudimentary hair-processes, in the one case proceeding from the hairs
themselves, but not in the other; and upon the circumstance that the
young hairs, although in both cases they lie at first in a closed space,
reach the surface more readily in the one case, than in the other.

In the periodical shedding of the hair of animals, the observations
of Heusinger and Kohlrausch, and lately those of Langer, Gegenbaur,
and Steinlin, show that the new hairs are also developed in the sacs of
the old ones ; although, according to the last author, with whom how-
ever Langer is not quite in accord, the process does not appear to be
exactly the same as in man.

§ 64. Pliysiological Observations. — The hairs have a definite length,
dependent upon locality and sex, but if they are cut they grow again,
and consequently exhibit the same conditions as the other horny textures.
The place from whence the growth of the hair proceeds is unquestionably
the bottom of the hair-sac. Here there arise around the papilla? with
the co-operation of a blastema formed out of its vessels or those of the
hair-sac, new elements, by the continual multiplication of the existing
cells, while those which are already present, somewhat higher up pass
uninterruptedly, the middle ones into medullary cells, the next into cor-

13

194 SPECIAL HISTOLOGY.

tical plates, the outermost into epidermic scales, and tlius the horny part
of the hair is continually forced from below upwards, and elongates.
In the latter no formation of elementary parts takes place, but at most
a certain metamorphosis of those which are already existent, which pro-
duces a gradual thinning of the root from the bulb upwards, until it
acquires the thickness of the shaft. Higher up still, these changes
of the elementary parts cease, whence cut hairs, for example, do not
produce new points. The root-sheaths and the outer layer of the epi-
dermis take no part in the growth of the cut hairs.

The complete hair, though non-vascular, is not a dead substance^ Al-
though the processes which go on in it are not at all understood, we
may suppose that fluids are diffused through it which subserve its nu-
trition and maintenance. These fluids are furnished from the vessels of
the papilla and sac of the hair, in all probability ascend (particularly
from the bulb) ; witliout any special canals through the cortex upwards,
and thus reach all parts of the hair. Having served for the nutrition
of the hair, they evaporate from its outer surface and are replaced by a
fresh supply. Perhaps the hairs also absorb fluids from without, though
of course only in the condition of vapor, like a hair used as a hygrometer ;
on the other hand I cannot believe that, as many authors would seem to
suppose, the secretion of the sebaceous glands passes from without into
the hairs, si^ice the perfectly closed cuticle is probably impervious
to it. In the same way it seems to be in nowise proved that the haii'S
are pervaded by a peculiar oleaginous fluid (Laer), which might proceed
from the medullary substance (Reichert), and which keeps it greasy,
for such a fluid has not been demonstrated, and the greasiness of the
hairs may be more simply explained by the externally adherent sebaceous
matter, which is readily visible. The existence of hair in the medullary
axis and in the cortex can only arise from a disproportion between the
supply of fluid from the hair-sac and the amount evaporated ; it is owing
as it were, to a drying-up of the hair, which, however, must not be sup-
posed to go so far that the hair contains no fluid in its aeriferous portion.
In any case, however, these portions are the most inactive, or relatively
dead parts of the hair ; the cortex, on the other hand, which is also
most readily altered by alkalies and acids, notwithstanding the apparent
hardness and density of its elements, is the most rich in juices, and is
that in which the nutritive process is most actively going on. Hence
it follows, that the hair lives, and is to a certain extent dependent upon
the collective organism, particularly on the skin, from whose vessels
[i. e. those of the hair-sac) it derives the materials necessary for its
maintenance. Therefore, as Henle well says, the condition of the hair
is a sort of index of that of the activity of the skin ; if they are soft and
shining, the skin is turgescent and transpires ; if they are dry, brittle,
and rough, then it may be concluded that the surface of the body is in
a collapsed condition.

OF THE HAIRS. 195

The falling out.of the hairs certainly depends, in many cases, — when,
for example, it takes place in the course of normal development, — on
nothing else than a want of the necessary nutritive material, which in
the instance already explained, in speaking of the shedding of the hairs,
depends on the detachment of the hair from its matrix by the abundant
production of cells at the bottom of the hair-sac. In age, perhaps, it
arises simply from the obliteration of the vessels of the hair-sacs.

The whitening of the hairs, which chiefly depends upon a decoloration
of the cortex, and less upon that of the almost colorless medulla, should
probably be here considered, for its normal occurrence in old age gives
it the significance of a retrogressive development.

The frequent occurrence of cases, in which the hair grows gray first
at its point or in the middle, and the Avell-established instances of its
rapidly becoming white, are interesting, and strongly testify to the
vitality of the hair ; but it has not yet been shown, what peculiar pro-
cesses in the elements of the hair produce the decoloration of its difi"erent
pigments.

As in youth hairs which are shed are replaced by others, so at a later
age something similar appears to occur. It is quite certain that during
the period of full health and activity, a continual replacem.ent of the
numerous hairs which fall out goes on ; furthermore that new hairs in
great numbers spring up at the time of puberty in certain localities, but
the manner in which this takes place is unknoAvn. Inasmuch as even in
adults we find hair-sacs with little processes downwards, whose proper
hair has an abrupt clavate end, as in the child ; since further, in this
case it not unfrequently happens that two hairs come out of one aper-
ture, and even exist together in one sac ; and, finally, since in hairs
which have fallen out spontaneously, we invariably find roots like those*
which exist in the extruded hairs of the first shedding, it may be
assumed that an actual shedding of the hairs occurs, even at a later
period, in such a manner that the old hair-sacs produce new hairs while
they throw oif the old ones. I do not, however, intend to aflSrm by
this, that an actual new formation of hairs does not occur after birth,
but only this much, that in adults they are certainly regenerated from
the already existing hair-sacs, especially if it be recollected that, accord-

• [Henle (" Allg. Anat.," p. 303) gives a very excellent description of this state of the
hair-bulb: " Instead of the soft cellular hair-bulb, we find an inconsiderable clavate enlarge-
ment, which is solid and fibrous, like the substance of the shaft, only more clear. From its
outer surface, short and irregular processes project downwards, which are probably the
notched lower edges of the outermost layers of the cortical substance ; they look like fibres
connecting the hair with the inner wall of the sac. This kind of root is found in hairs
which have fallen out spontaneously, and it is, therefore, probable that it belongs to a later
stage of development of the hair, or rather marks the conclusion of its development. When
the connection with the sac has ceased, which is the case in these clavate roots, the hair
grows no longer; probably it is no longer nourished, but falls out." — Trs.]

196 SPECIAL HISTOLOGY.

\

ing to Heusinger's observations, the -whiskers of dogs,* -when pulled out,
are produced from the same sacs in a few days, and also that during the
shedding of the hair in adult animals, according to Kohlrausch, the
young hairs are produced from the old sacs. Also, "^'hen the hairs
which have fallen out after a severe illness, are replaced, it is more
probable, since, according to E. H. Weber, the sacs of lost hairs remain
for a long time, that they arise in the old sacs, than that new ones are
developed.*

The multiplication of the cells of the bulb of the hair during its
growth takes place unquestionably, not by free cell-development, since
no trace of anything of the kind is to be seen in any bulb, but either
by endogenous cell-development round portions of contents, or by divi-
sion. I do not think that all those hairs which possess a sharply-defined
clavate bulb are on that account dead and ready to fall out. It is cer-
tainly thus in many cases ; but in others this condition indicates nothing
more than the normal termination of growth, whence of course, it does
not follow that the nutrition also has ceased. In proof of the occurrence
of a continual development of the hairs independently of the old hair-
sacs, the hairs which lie spirally cuided up under the epidermis and
subsequently break through it, upon the forearm, leg, &c., are frequently
cited. But I do not know that it would not be more correct to consider
this, with many pathologists, rather as an abnormal process. In the
first place this formation of the hairs by no means occurs in all per-
sons ; and secondly, where it does, there are found together with those
coiled-up hairs, which are apparently normally developed, others which
are evidently abnormal, in great quantities. These, often in consider-
able number (up to 9), with thick sheaths, lie in one sac and have
rounded points, with irregular bulbs. With respect to their relations,
it might for the present be Aviser, so long as an actual, normal new
development of hairs has not been demonstrated, not to assume it, and
to consider that, even at a later period, the development of new hairs
within the old sacs is the normal mode, especially since Dr. Langer has
actually observed it to take place in many instances in the very same
nif'nner as that which I hai'e described in children. The reason Avhy
the hairs grow continually, if they are cut, but not otherwise, is the
same as I have already adduced, to account for the same occurrence in the

* [Berthold (INTull " Areliiv, " 1S50) has coimrmnicatecl some curious statistics relative to
the growth of Hairs. The hairs of the head of a female of from 16 to 24 years of age, grow
at the rate of 7 lines a month. The growth of the hairs of the beard is quicker the oftener
they are cut; shaved every 12 hours they would attain a length of from 5^-12 inches per
annum; every 24 hours, from 5-7^ inches; every 36 hours, from 4—63 inches. They grow
faster by K during the day than during the night; and in IS days of summer, 0 026 more
than in IS days of winter. — Tes.]

OP TUE 11 AIRS. 197

nails. The vessels of the papilla excrete a certain quantity of nutritive
fluid, just so much as is sufficient to keep the whole hair continually
moist and in a state of vitality. If the hair be cut, more nutritive fluid
is supplied than the hair can use, and therefore it grows by the aid of
the superfluity until it has attained its typical length again, or if it be
continually cut, it as continually grows.

Dzondi, Ticffenbach ("Nonnullade regencratione ettransplantatione,"
Ilerbip, 1822) and Wiesemann (Do coalitu partiura. Lips. 1824) have
succeeded in transplanting the hairs with their sacs. Hairs are deve-
loped also in abnormal places, e. g. on mucous membranes^ in encysted
tumors, ovarian cysts, and in all these cases, even in the lungs (Mohr's
case), possess sacs, root-sheaths, and an otherwise normal structure.
No hairs are developed upon cicatrices of the skin. No satisfactory
reason can be given for the excessive growth of the hairs, nor for their
morbid universal falling out, together with their frequent reproduction
in the same way ; probably the principal causes are to be found in
increased or diminished exudations from the vessels of the papilla and
of the hair-sac, and more remotely in the state of the skin and the
organism in general. In other cases vegetable productions {fungi) in the
interior of the hair itself (in Herpes tonsurans, the " Teigne tondante,"
3Iahon\ according to Gruby [" Gaz. Med.," 1844, No. 14], and Malmsten,
(Mull. "Arch.," 1848, 1), or under the epidermis of the hair and around
it (in the Porrigo decalvans of Willan according to Gruby), are con-
cerned in the production of baldness, which then is limited {Alopecia
circumscripta). The process of becoming gray is also obscure, although
grief, excessive intellectual activity, and nervous influences are sometimes
evidently concerned in it. It is not until physiology and chemistry
have approached these latter processes, that we can hope for a scientific
pathology and treatment of the hair. Plica polonica, which, according
to Bidder (1. c), is a disease of the shaft of the hair, is said by Guens-
burg and Walther (Milller's " Archiv," 1844, p. 411, and 1845, p. 34),
to arise from o, fungus which is developed in the hairs (bulb, shaft), and
partly destroys them ; whilst Mlinter (ibid., 1845, p. 42) could find no
such fungus. This disease, as well as peculiar yellowish-white rings
upon the human hairs, consisting of epithelial cells without nuclei
(Svitzer, in " Fror. Notizen," 1848, No. 101), which appear to consist
of an altered secretion of the sebaceous glands, are less interesting
from a histological point of view, and therefore are but shortly adverted
to here.

For microscopic investigation, a white hair with its sac should be
chosen in the first instance, subsequently colored ones. Transverse
sections may be obtained, either by shaving twice at short intervals
(Henle) or by cutting hair on a ghiss (H. Meyer), or in a bundle be-
tween two cards (Bowman), or fixed in a cork (Ilartin) ; longitudinal

198 SPECIAL HISTOLOGY.

sections, by splicing a finer or splitting a coarser hair. The hair-sacs
may be examined, both isolated and with the hair ; their different layers
may be separated by preparations, and the nuclei of the external ones
may be demonstrated by acetic acid. Concerning the papillce, all that
is necessary has been said above; the whole upper part of the root-sheath
generally follows the hair when it is torn out, and in the macerated skin
it comes out very readily with the hair ; its cells may be made out with-
out addition, or by a little acetic acid or caustic soda. The inner root-
sheath is often to be found entire in torn out hairs, and may without
further preparation, or by stripping off the outer sheath, be readily re-
cognized in all its parts. Caustic soda and potassa acting for a short
time, make it still more distinct. The cuticle must particularly be exa-
mined with alkalies and sulphuric acid, like the hair itself. The most
important details upon this point have already been given, and more
may be found in Donders (1. c). I will only add that in this case also,
the application of a high temperature (see above, in the section on the
nails) saves much time. In investigating foetal hairs, in the very young
state it is sufficient to tear off the epidermis, attached to which the rudi-
ments of the hairs will be found. In older embryos, fine sections of the
skin must be made ; or the epidermis and the corium may be stripped
off together, in which case caustic soda is of assistance.

Literature. — Eble, " Die Lehre von den Haaren in der gesammten
organischen Natur.," 2 Bde., Wein, 1831; Eschricht, " Ueber die
Richtung der Haare am menschlichen Korper," in Miill. "Arch.," 1837,
p. 37 ; V. Laer, " De structura capill. hum. observationibus microscopicis
illustr.," "Dissert, inaug.," Traject. ad Rhenum, 1841, und "Annelin
der Chemie u, Pharmacie," Bd. 45, No. 147; G. Simon, " Zur Entwick-
lungsgeschchiteder Haare," Miill. "Arch.," 1841, p. 361 ; Krause, article
" Haut.," in AVagner's " Handworterbuch d. Phys." 1844, Bd. ii. p. 124 ;
Kohlrausch, " Ueber innere Wurzelscheide und Epithelium des Haares,"
Mull. "Arch.," 1846, p. 300; Jasche, " De telis epithelialibus in genere
et de lis vasorum in specie," Dorpat, 1847 ; Kiilliker, " Ueber den Bau
der Haarbalge und Haare," in the " Mitthiel d. ziirich., naturf.," Ges.,
1847, p. 177; Hessling, "Vom Haare und seinen Scheiden in Froriep
neue Notizen," 1848, No. 113; Langer, " Ueber den Ilaarwechsel, bei
Thieren und beim Menschen," in den " Denkschr. d. Wien," Akad.,
1850, Bd. i. The comparative anatomy of the hairs is treated of by
Heusinger in Meckel's "Arch," 1822, 1823, und "System der Histio-
logie;" Erdl, in "Abh.d. Miinch.," Akad., Bd. III. ii. ; Gegenbaur, in
" Verhund d. phys. med. Gesellschaft zu Wiirzburg," 1850; Steinlin, in
" Zeitschrift, fiir rationellen Medizin," Bd. IX. The allied horny tis-
sues are described in the "Dorpat. dissertations," by Brocker, " De
textura et formatione spinarum," 1849 ; Hehn, " De text, et form.
barbjB Balsenge," 1849 ; Schrenk, " De formatione pennje," 1849.

OF TUE GLANDS OF THE SKIN.

199

IV. OF THE GLANDS OF THE SKIN.

A. OF THE SUDORIPxVROUS GLANDS.

§ 65. The Sudoriparous Glands consist of a single delicate, more or
less convoluted tube, which secretes the sweat. Thcj are formed over
the whole surface of the skin, with the exception of the concave side of
the concha of the ear, of the external auditory meatus, the glans penis,
one lamella of the prepuce, and a few other localities ; and open upon
it by numerous fine apertures.

§ QQ. In every sudoriparous gland (Fig. 45, Fig. 78), we may distin-
guish, the glandular coil (Fig. 78 a. Fig. 75 g), or the proper glandj
from the excretory duct or

sudoriparous canal (Fig. 45 Fik-TS.

h, Fig. 78 b). The former is
a rounded or elongated corpus-
cle of a yellowish or transpa-
rent yellowish-red color, which
in general measures \-l of a
line ; but on the eyelids, the
integument of the penis, scro-
tum, nose, convex side of the
concha of the ear, on the
other hand, not more than

j()—j2 of ^ ^i^6 j whilst on

the areola of the nipple and

in its neighborhood, at the

root of the penis, and between

the scrotum and perinseum, it attains as much as J a line, and in the

hairy parts of the axilla reaches as much as |-1-1J line in thickness,

and 1—3 lines in breadth.

The sudoriparous glands, in most cases, are lodged in the meshes of
the pars reticidaris of the cerium, sometimes more superficially, some-
times deeper, surrounded by fat and loose connective tissue, together
with or among hair-sacs. They occur more rarely in the subcuta-
neous connective tissue, or at its boundaries, as for example in the
axilla, to some extent in the areola mammce, in the eyelids, penis, and
scrotum, the palm of the hand and sole of the foot. In the two last-
named localities, they are disposed in rows under the ridges of the cutis,

Fia. 78. — A sudoriparous coil and its vessels; magnified 35 diameters: a, glandular coil;
b, excretory duct or sweat duct; c, vessels of a glandular coil, according to Todd and Bow-
man.

C. -

200 SPECIAL HISTOLOGY.

and at tolerably equal distances apart ; in other places tliej are met
■with, usually in a regular manner, singly or in pairs, in each mesh of
the corium, although, according to Krauze, spaces of J-| a line exist,
•\vhcre they are totally absent, or occur in groups of three or four
close together. In the axilla, the glands form a connective layer under
the corium.

According to Krause, there occur on a square inch of the skin be-
tween 400 and 600 glands on the back of the trunk, the cheeks, and the two
superior segments of the lower extremities ; 924-1090 on the anterior
part of the trunk, on the neck, brow, the forearm, back of the hand
and foot ; 2685 on the sole of the foot ; and 2736 on the palm of
the hand. The total number of the sudoriparous glands, without reck-
oning those of the axilla, is estimated (somewhat too highly) by Krause
at 2,381,248, and their collective volume (with those of the axilla) at
39,653 cubic inches.

The vessels of the sudoriparous glands are particularly well seen in
those of the axilla (Fig. 78) ; in others, the vessels may also be seen
here and there (best in the penis, where, for example, glands of 0-36 of
a line are supplied by the most delicate ramifications of an artery of
0-06 of a line, in their interior) ; and in successful injections of the
skin, the glands appear as reddish corpuscles. iVerves have not hitherto
been found in them.

§ 67. Intimate Structure of the Glandular Coil. — The sudoriparous
glands, in general, consist of a single much convoluted canal (in one
case, according to Krause, |- of a line long), twined into a coil,
which retains pretty nearly the same diameter throughout its length,
and terminates, either upon the surface of the coil, or in its interior, in
a slightly enlarged blind extremity. In the large glands of the axilla
alone, the canal is usually divided, dichotomously, into branches, which
subdivide, and sometimes, though rarely, anastomose ; and after giving
off small csecal processes, each separate branch finally terminates in a
blind extremity. The glandular canals have either thin or thick walls
(Fig. 79). The former (Fig. 79 A) possess an external fibrous invest-
ment, consisting of indistinctly fibrous connective tissue, with scattered
elongated nuclei ; internally this is sharply limited, perhaps by a wiem-
hrana propria, and is covered by a single, double, or multiple layer of
polygonal cells of 0-005-0-007 of a line, which in their chemical rela-
tions, and otherwise, correspond perfectly with the deep cells of pave-
ment-epithelium, except that they almost invariably contain a few fatty
granules, and still more frequently a small quantity of yellowish or
brownish pigment-granules.

The thick-coated sudoriparous glandular canals (Fig. 79 B) possess,
besides the two layers just described, a middle layer of smooth muscles

OF THE GLANDS OF THE SKIN.

201

running longitudinally, whose elements are easily separable, as muscu-
lar fibre-cells of 0-015-0-04 of a line long, 0-002-0-005, or even 0008
of a line broad, occasionally with a few pigment-granules, and each con-
tainins a roundish elongated nucleus. Whenever the glandular tubes con-

rig. 79.

A

B

a

tain only fluid, the epithelium is a single very distinct layer of polygo-
nal cells of 0-006-0-015 of a line; in the opposite case it can be seen
only with difficulty or not at all. With respect to the occurrence of
these two forms of glandular canals, the thick muscular walls are found,
especially in the large glands of the axilla, whose cells all possess mus-
cular walls, and thence acquire a very peculiar striated appearance. I
have noticed a precisely similar structure only in the large glands of the
root of the penis and of the nipple, although it is true that there is
occasionally a muscular development, but slighter and only partial, in the
glands of the palm, whose wide canals are distinguished by the thickness
of their walls, and exhibit a muscular structure distinctly enough, though
thinner than elsewhere. The same description applies to certain glands
of the sci'otuni, and even of the back, of the labia majoi'a, of the mons
veneris^ and of the neighborhood of the anus; yet with this limitation,
that often only a small part of the glandular tube, perhaps merely its
crocal extremity, is provided with a muscular coat. The glands of the
leg, of the penis, of the thorax (the areola excepted), of the eyelids, and
the majority of those of the back and thigh, of the chest, and abdomen,
as well as of the two prominent segments of the upper extremity, are
delicate and without muscles.

The diameter of the glandular canals varies, in the smaller glands from
0-022-0-0-4 of a line, and is about 0-03 of a line on the average ; the

Fig. 79. — Sweauhicts ; magnified 350 diameters. .^, one with thin walls and a central cavity
without a muscular coat, from the hand : a, connective investment; b, epithelium; c, cavity.
P, a portion of a canal without a cavity, and with a delicate muscular layer, from the scro-
tum: a, connective tissue; 6, muscular layer; c, cells which fill the glandular canal with
yellow granules among their contents.

202 SPECIAL HISTOLOGY.

thickness of the walls, 0-002-0-003 ; of the epithelium, 0-006 ; of the
cavity, 0-004-0-01 of a line. Among the axillary glands some have
canals of 0-07-0-1, even 0-15 of a line, with walls 0-006 of a line in,
thickness, without the epithelium, and half of which is formed by the
muscular layer ; others and in fact the largest glands, possess canals of
0-03-0-06, with walls of 0-004 of a line ; in the areola and the genitalia
also, the dimensions of the larger glands vary, though within narrower
limits.

All the coils of the sudoriparous glands are penetrated by connec-
tive tissue, interspersed with fat-cells, which supports the vessels and
unites the separate convolutions of the tubes with one another ; some of
them have an external fibrous covering investing the whole coil (of com-
mon connective tissue with fusiform nuclei), which is particularly well
developed in those more isolated coils which are lodged in the subcuta-
neous cellular tissue (^penis, axilla, &c.)

§ 68. Secretion of the Sudoriparous Glands. — All the smaller sudori-
parous glands contain, as soon as any cavity is apparent in their canals,
which, however, is by no means always the case, nothing but a clear,
bright fluid, v*'ithout any formed contents. In the axillary glands, on
the other hand, the contents abound in formed particles, and appear
either as a grayish, transparent, semi-fluid substance, with innumerable
fine, pale granules, and often with solitary nuclei ; or as a whitish-yellow
tolerably viscid matter, with a varying quantity of larger, opaque,
colorless, or yellow granules, nuclei and cells, similar to the epithelial
cells above described. That these cell contents, which, as I have found,
contain much protein and fat, differ considerably from the common
siveat, which is fluid and presents no formed elements, and probably
rather approximate to the sebaceous secretion of the skin, is evident, on
which account we might be induced to remove the glands of the axilla
from the class of sudoriparous glands, and to regard their secretion as
of a peculiar kind. These glands, however, sometimes afford a secre-
tion containing but few granules, or even nothing but fluid ; and among
the larger axillary glands smaller ones occur, which, so far as regards
their contents, exhibit many transitions, on the one hand into the large,
and on the other into common small glands.* If we further consider

* [However true it may be that this secretion is sometimes fluid, and similar to that of
sudoriparous glands in other situations, this is the exception, and by no means the rule.
But it is not on account of their secretion, but mainly of their different structure, tliat these
glands have been separated from the common sudoriparous glands. They differ from them
by being united into groups, and by their yellowish color. In size, too, they vary. Many
are 5 or G times larger: some attain the size of 2 lines in diameter. The groups can be
readily seen with the unassisted eye, if the adipose tissue adhering to a flap of skin from the
axilla be removed. They then appear as small granulations of a reddish or rosy tint, and
are soft and pulpy. The excretory ducts are not spirally wound as in the ordinary sudori-
parous glands.

In the Negro these axillary glands as first pointed out by Prof Horner (American Journal

OF THE GLANDS OF THE SKIN. 203

that, occasionally, the sudoriparous glands in other situations, as, for
instance, in the areola of the nipple, contain a fluid abounding in granules,
it is clear that it is unadvisable to distinguish the large axillary glands
from the common kind, on account of the difference in their secretion ;
and the more so, indeed, because we by no means know whether the
latter, under certain circumstances, may not contain granules.

As respects the origin of the granular contents, they must be referred
to the cells which are developed in the glandular tubes. For we fre-
quently meet in these with cells containing the same granules, which
also occur free within the glandular canals ; and frequently may be said
to constitute their whole contents. It sometimes happens, also, that in
one and-the same gland the ends of the glandular tubes contain nothing
but cells, while the excretory duct exhibits hardly any trace of them,
presenting merely granules and scattered free nuclei ; and in this case
we can easily see that the cells, as they pass further upwards, become
broken up to a greater and greater extent, thus setting free their nuclei
and the granules in their interior. These cells plainly proceed from
the epithelial cells lining the canal of the sudoriparous coil ; for, in the
first place, the cells of the contents of the epithelium resemble one an-
other in all respects ; and secondly, where cellular or granular contents
are found in the glands themselves, the epithelium is for the most part
completely absent, so that the former rests immediately upon the muscu-
lar membrane. Now, since on the other hand, in those glands which
contain only a clear fluid, the epithelium is always easily seen, and
often presents many dark (even golden yellow) pigment granules in its
cells, it may perhaps be assumed, that the cells in the contents are
nothing but detached epithelium, and that the secretion mainly depends
upon a growth and continual casting ofl" of the epithelial cells.

The examination of the secretion of the sudoriparous glands is neither
chemically nor microscopically complete. As regards the former, the
fact that the axillary glands secrete fat and a nitrogenous substance
in large quantities, appear to me interesting, since from the obvious
similarity in structure between these and the other sudoriparous glands,
wc may perhaps draw some conclusions as to the secretion of the latter.
We already know that the ordinary perspiration contains nitrogenous
matters (extractive) ; and as Krause (1. c, p. 146) has clearly shown,
fat, also ; and it may be asked whether these substances do not perhaps
in certain situations (e. g. hand, foot) occur more abundantly, or under
certain conditions (local, adhesive, peculiarly odorous perspiration)
increase in quantity. The so-called sv/eat-corpuscles of Henle (1. c,
pp. 915 and 039), that is, structures similar to the mucus-corpuscles, I

of Med. Science, 184G), are much larger than in the White. To the secretion of these large
glands indeed, the peculiar smell of Negroes is attributed.

In the groin sudoriparous glands very similar in their structure to these axillary glands are
met with. — DaC]

204

SPECIAL HISTOLOGY.

Fig. 80.

have hitherto found neither in the sweat of man nor in the smaller
glands ; but I may remark that almost constantly, even in the smaller
sudoriparous glands, certain canals exist which present no cavity, but
are wholly filled with epithelial cells. These appeared to me always
to be near the blind end (Fig. 79, i?), whilst those which are nearer the
excretory duct, almost invariably exhibit a cavity 0'004-0*l of a line
in diameter. I consider it therefore to be not impossible, that in the
common sudoriparous glands, a cellular secretion is at times formed and
excreted in the same manner as in the axillary glands ; for from what
we see in the canals of the latter, it can hardly be doubted that granules,
nuclei, and perhaps also remains of cells, occur in the sweat of the
axilla. "Whether the sweat in different individuals and races of men
present notable difterences is unknown, for it is not ascertained that
the different odor of the cutaneous exhalation in the European and the
Negro, for instance, depends on the sweat or the material of the per-
spiration ; nor have its pathological relations been investigated, at all
events not microscopically.

§ 69. Sweat-Ducts. — The excretory ducts of the sudoriparous glands,
the sweat-ducts, or spiral canals (Figs. 45, 80), commence at the upper

end of the glandular coil as simple
canals, ascend with slight undulations
vertically through the corium, and then
penetrate between the papilla> (never
through their points), into the epider-
mis. Here they begin to twist, and
according to the thickness of the cuticle
they perform from 2—16 closer, or
more distant spiral turns, until even-
tually they terminate by small, round,
often funnel-shaped apertures, the so-
called sweat-2)ores on the free surface
of the epidermis.

The length of the sweat-ducts de-
pends on the situation of the glands
and the thickness of the skin. The
commencement of the duct is invaria-
bly narrower than the canal in the
coil itself, measuring 0-009-0-012 of
aline; it continues narrow up to its
entrance into the stratum Malpigltii

Fig. so. — Perpendicular section through the epidermis and outer surface of the corium of
the bulb of the thumb, transversely through two ridges, treated with acetic acid; n, horny
layer of the epidermis; b, mucous layer; c, cutis; d, simple pa])illa; c, compound papilla; /,
Cjiithelium of a sweat-duct passing into the mucous layer; g-, cavity of it in the cutis; /;, in
the horny layer ; i, sweat-pore. — Magnitied fjQ diameters.

..^

OF THE GLANDS OF TUE SKIN. 205

where it dilates to about double the size, i. e., to 0-024-0-28 of a line
(Fig. 80); retaining this breadth, it traverses the epidermis, and ter-
minates in an aperture of 5^-20 of a line. In the axillary glands, the
excretory duct measured in one case at the level of the sebaceous
glands O-OG-0-09 of a line, immediately under the epidermis 0-03, in the
epidermis itself 0-06 of a line. In the corium the sweat-ducts have
always a distinct cavity, an external investment of connective tissue,
with elongated nuclei (in the glands of the axilla, muscles also),
at all events, inferiorly, and an epithelium composed of at least
two layers of polygonal, nucleated cells without pigment granules.
"Where the ducts enter the epidermis, they lose their investm,ent of
connective tissue, which coalesces with the outermost layer of the corium,
and henceforward they are bounded by nothing but layers of cells,
which in the stratum 3Ialpighii are nucleated, but in the horny layer
are without nuclei. Chemically and morphologically they completely
resemble the epidermic cells, with the sole exception that they are dis-
posed more perpendicularly, paAicularly in the horny layer. The duct
has often a distinct cavity in the epidermis, at other times there is a
granular streak in the place of it, which is probably either a secretion
or a deposit from the secretion. The stveat-pores, whose disposition,
corresponding with that of the glands, is sometimes very regular, at
others more irregular, are distinguishable, even with the naked eye, in
the palm of the hand and sole of the foot. In other localities they are
visible only with the aid of the microscope ; occasionally the excretory
ducts of two glands unite into a single canal (Krause).

§ 70. Development of the Sudoriparous Glands. — The sudoriparous
glands first appear in the fifth month of embryonic life, and are originally
perfectli/ solid, slightlij flask-shaped, processes of the stratum 3Ialpighii of
the epidermis, and are very similar to the first rudiments of the hair-
sacs. In the earliest condition which I have observed, the processes
measured in the sole of the foot 0-03-0-09 of a line in length, and 0-01
of a line in breadth at the neck, at the bottom 0-018-0'02 of a line,
and even the very longest did not penetrate more than half through the
cutis, which was 0-25 of a line thick. They were entirely composed of
round cells, perfectly similar to those of the stratum Malpighii of the
epidermis ; besides which, each process had a delicate investment, which
was continuous with the boundary of the inner surface of the epidermis.
No trace of sweat-pores or ducts was visible. At the beginning of the
sixth month, the glands in the sole of the foot and palm of the hand
extend as far as the middle and inner fourth of the cutis, measure at
the clavate extremity 0-028-0-04 of a line, and 0-016-0-02 of a line in
the duct which arises from them, are already slightly serpentine, and
present a cavity, at all events partially in their narrow portion; they
do not, however, penetrate the cuticle, or in any way open on the

206

SPECIAL HISTOLOGY.

surface. It was not before the seventh month that I perceived, in the
same situations, the first indications of the sweat-pores and ducts in the

Fig. 81.

epidermis, though as yet very indistinct, and the latter forming only
half a spiral turn (Fig. 82, A) ; at the same time the part of the gland
which projected into the corium was more considerably developed,
reached as far as the innermost portion of that structure, and at its
csecal extremity was bent into a hook or even slightly convoluted, so as
to afford the first indication of a glandular coil of about 0*04 to 0-06 of
a line. The canal arising from it usually presented several marked
undulations, and measured in total thickness 0-015-0-022 of a line, with
a cavity of 0-003-0-00-i of a line, which frequently extended even to
the terminal coil: like the latter it was composed of the original though
thickened membrane continuous with the surface of the corium, and of
an epithelium consisting of many layers of pale, polygonal, or rounded
cells. The glands of the rest of the body about this period, appeared
to me to be similarly constituted. I can say nothing as to their
earlier condition, but even those of the axilla were in no wise distin-
guished from the rest. From this time the development goes on very
rapidly ; the end of the gland elongates more and more, and coils itself
up (Fig. 82 B), so that it assumes an appearance hardly different from
that which it presents in the adult. In the new-born infant, the glan-
dular coils in the heel measure 0*06-0"07 of a line (in a child of four
months O'06-O-l of a line on the heel, in the hand 0'12 of a line), present

Fig. 81. — Rudiment of a sudorij^arous gland of a human embryo at five months; magni-
fied 350 diameters: a, horny layer of the epidermis; 6, mucous layer; c, corium; d, rudimen-
tary glands, as yet without any cavity, and consisting of small round cells.

Fig. 82. — .4, rudiment of a sudoriparous gland from a seven months' fcetus ; magnified
50 diameters. The letters a, b, d, as in Fig. 81. The cavity e is present throughout, only it
does not extend quite so far as the end of the thicker part of the rudiment of the gland,
which becomes converted into the glandular coils. The continuation of the canals into the
epidermis and the sweat-pores,/, are present. B, a coil of a sudoriparous gland, from a
fcetus at the eighth month.

OF THE GLANDS OF THE SKIN. 207

much convoluted canals of 0-015-0-022 of a line, and traverse the epi-
dermis -with their already twisted ducts (in the corium of 0-008, in the
rde Malpighii of 0-022 of a lino).

It results from these facts that the sudoriparous glands are nothing
else than involutions of the skin, and do not begin as hollow structures,
but are at first a simple development of the stratum mucosum. By a
continual process of cell-multiplication, the original rudiments grow
deeper and deeper into the skin, acquire their peculiar spiral windings,
and divide into the glandular coil and the sweat-duct ; while at the same
time, either by liquefaction of their central part, which would thus, as
it were, represent a first secretion, or by the excretion of a fluid between
their cells, a cavity is produced. IIow the sweat-duct in the epidermis
and the pore are formed is doubtful ; probably by a formative process
in the epidermis itself. According to a few measurements which I have
instituted (" Mikroscop. Anat.," II. i. 171), a development of sudoripa-
rous glands appears to take place even after the fifth month, whilst
the whole number appears to exist at birth.

Little is known as to the 'pathological conditions of the sweat-glands.
Kohlrausch (Miiller's " Archiv," 1843, p. 3G6), has found them of con-
siderable size (J a line) in an ovarian cyst, together with hairs and
sebaceous follicles. In Elephantiasis graecorum, G. Simon and Brlicke
(Simon, " Hautkrank,," p. 268), noticed an increase in size of the sudo-
riparous glands, and Y. Barensprung observed the same thing in a kind
of wart (1. c, p. 81) ; the latter also found that these glands were atro-
phied in corns, and that the duct in the outer layers of the epidermis
had disappeared. The condition of the several glands in old age, in
cases where the secretion of sweat is altogether wanting, and in ab-
normal perspirations, is not known. In a remarkable case of Ichthyosis
congenita (very similar to that mentioned by Steinhausen, only more
marked) in a new-born infant, which was examined by Dr. H. Muller
and myself, the sudoriparous glands were present ; their excretory ducts,
so far as regards their course through the epidermis, which was thickened
to 2 lines, were partly disposed as usual, partly they were placed, as
in the sole of the foot, with their outer portions almost completely hori-
zontal, and ran in some places for as much as IJ line in this manner,
so that in superficial sections of the epidermis they appeared as parallel,
at first sight altogether abnormal canals, with a cavity of 0-0025-0-003
of a line. The contents of the ducts were very peculiar, consisting in-
variably of a multitude of white oil drops. I observed sudoriparous
glands also in the case described by Mohr, of a great cavity containing
hairs in the lung ("Berlin Med., Central-zeitung," 1839, No. 13), they
were about 0-21 of a line in diameter, and were contained in a panni-
culus adiposiis, with common fat-cells ; and it may be remarked that the

208 SPECIAL HISTOLOGY.

■wall of the cavltj besides the panniculus also presented a corium with
papillte, and an epidermis like the external integument.

3Iethod of Investigation. — To examine the position of the sudoriparous
glands and their excretory ducts, fine sections of fresh or slightly-dried
skin of the palm or sole should be prepared, and made transparent by
acetic acid or caustic soda. Gurlt used for this purpose skin hardened
and rendered transparent in a solution of carbonate of potassa [liquor
Jcali carbonici). Giraldes macerates the skin for twenty-four hours in
dilute nitric acid (1 part acid, 2 parts water), and for twenty-four hours
in water, — a process which, according to Krause, is very useful, as the
glands become yellow, and are readily distinguished. In macerated
pieces of the skin, the cellular lining of the sweat-ducts may be drawn
out of the corium, in the form of long tubes, with the epidermis ; in
delicate parts of the skin I have, not unfrequently, succeeded in doing
this after treatment with concentrated acetic acid. The investigation
of the glandular coils themselves is very easy in the axillary glands ; in
the others the skin must be prepared from within, and the glands sought
for partly upon the inner surface of the cuts, partly in its meshes, — a
method which readily succeeds, with a little attention, particularly in
the hand, foot, and nipple. The large glands of the ball of the foot of
the Dog, described by Gurlt, are particularly well-fitted for demonstra-
tion, and still more those of the prepuce and of the integuments of the
udder of the Horse, which lie quite loose in the subcutaneous tissue. If
it be desired to count the glands, their apertures may be sought for, or
a piece of skin of determinate size may be treated according to Giraldes'
method, and examined portion by portion (Krause). For the study of
the development of the glands, sections of the fresh and dried skin of
the heel and palm of embryos, may be made with the double knife or
razor. In embryos preserved in spirit, if the sections be fine, the glands
may also be very well seen, especially in the first moments of the action
of caustic soda.

Literature. — Breschet et Roussel de Vauzeme, "Recherches ana-
tomiques et physiologiques sur les appareils tegumentaires des animaux,"
in the " Annales des Sciences Nat.," 1834, pp. 167 and 321 (discovery
of the sudoriparous glands) ; Gurlt, " Vergleichende Untersuchungen
iiber die Haut des Menschen und der Haussauo-ethiere, besonders in
Bezug auf die Absonderungsorgane des Hauttalges und des Schweisses,"
in Muller's " Archiv," 1835, p. 399 (first good figures of the glands
themselves). [Robin, " Note sur une espece particuliere des glandes de la
peau de I'homme," in the "Annales des Sciences Nat.," 1845; Horner,
"On the Odoriferous Glands of the Negro," in American Journal of
Med. Sciences, 1846.] Besides these, compare especially the general
works of Todd and Bowman, Henle, Valentin, Hassall, and myself; the
above-cited treatises of Krause, myself, Simon, Von Barensprung, and
Wilson ; further the figures of Berres, tab. XXIV. ; R. Wagner, "Icon.

OF THE GLANDS OF THE SKIN. 209

Phys.," tab. XVL, fig. 9 ; F. Arnold, " Icon. Org. Sens.," tab. XL,
and my own " Mikr. Anat.," tab. I.

B. OF THE CERUMINOUS GLANDS.

§ 71. The ceruminous glands of the JEar are brownish simple glands,
in external appearance precisely similar to the sudoriparous glands, which
do not exist in the whole external auditory meatus, but only in its car-
tilaginous portion, where they are situated between the lining membrane
of the passage and the cartilage, or the fibrous substance which supplies
its place, in a tough subcutaneous tissue, containing little fat. They
form a connected yellowish-brown layer, visible enough to the naked
eye, which is thickest in the inner half of the cartilaginous meatus, and
becomes gradually thinner and more lax externally, extending, however,
quite as far as the cartihiginous meatus itself. Each ceruminous gland
consists of a glandular coil and an excretory duct. The former (Fig.
83 d), To~5~4 of ^ l'>^6 in size, is formed by the multitudinous convolu-
tions of a single canal of 0'03-0-06 on the average 0*04-0*05 of a line in
thickness, which occasionally, although not constantly, throws out little
diverticula, and terminates in a blind slightly enlarged end. From the
coil a short straight excretory duct, 0"0l7-0-024 of a line thick, passes
perpendicularly upwards, penetrates the corium and epidermis of the
auditory meatus, and usually opens independently in a circular pore of
0"04-4 of a line, or else into the upper part of a hair-sac.

The following is the intimate structure of the ceruminous glands.
The canals of the coil present a fibrous coat, and an epithelium, the
former being 0-004-0-005, the latter 0*004 of a line in thickness. The
fibrous covering presents exactly the same conditions as in the larger
sudoriparous glands, that is, it consists of an internal longitudinal layer of
smooth muscles, 0-0023-0-0026 of aline in diameter, and an external layer
of connective tissue, with scattered nuclei, and occasionally very fine trans-
verse nucleus-fibres. The epithelium rests immediately upon the mus-
cular layer, and consists of polygonal cells of 0-006-0"01 of a line in a
single layer, which contain a greater or smaller number of yellowish-
brown pigment-granules, of immeasui'able minuteness, insoluble in acids
and alkalies in the cold, or whitish fat-globules up to 0-001 of a line in
size, and which are so disposed that the whole lengths of a gland con-
tain generally only one and the same kind of granules ; whence it arises
that they appear either uniformly brownish or opaque (by reflected light
whitish). The contents of the glandular canals are sometimes a clear
fluid, sometimes a granular substance composed principally^ of cells ana-
logous to those of the epithelium, whence it would seem that the same
kind and mode of secretion occurs in them as in the sudoriparous glands.
The excretory ducts possess a coat of connective tissue, and an epi-
thelium consisting of several layers, and constituted of small nucleated

14

210

SPECIAL HISTOLOGY.

cells, without fat or pigment-granules. In their cavity, which is, hoAv-
ever, not always distinct, they sometimes contain a clear fluid, some-
times a small quantity of finely-granulated substance.

Fig. 83.

- /

^.. ..^

-^
...^'

§ 72. The Cerumen of the ear is commonly considered to be the
secretion of these glands, though this is only partially correct. If we
examine the yellow or broAvnish, soft or more solid, viscid substance
which is formed within the cartilaginous meatus, it is found to contain
various constituents : independently of a few hairs, occasionally an
Acarus foUiculorum, and epidermic cells in various numbers, there
occur, — 1. Very many cells completely filled with pale fatty matter of
0'009-0*02 of a line, usually of an oval, flattened, irregular shape ; in
•which, on the addition of water, or still better of caustic soda, the fat
is separated in isolated, round, or irregular dark drops. 2. Much free
fatty matter in the form of pale, small yellowish round drops, which, on the
addition of water, appear as dark spherical granules, from an immeasurable
minuteness up to 0'002 of a line and more; audit is only upon this addition
that they become quite distinct, but at the same time are decolorized.

Fig. 83. — Perpendicular section through the skin of the external auditory meatus;
a, corium ; h, siralum Malpighii ; c, horny layer of the epidermis; d, coil of the ceruminons
glands; e, their excretory ducts ; /, their apertures; g, hair-sacs ; A, sebaceous glands of the
meatus; i, masses of fat. — Magnified 20 diameters.

OF THE GLANDS OF THE SKIN. 211

3. Yellow or brownish granules, and masses of granules, free or rarely in
cells, few upon the whole. 4. Lastly, when the secretion is more fluid, also
a small quantity of a clear liquid. I consider that the first-named cells
belong to the sebaceous secretion of the external meatus ; but that the
remainder is the secretion of the ccruminous glands, which would, there-
fore, eliminate oily fluid with scattered brown granules. This being the
case, the analysis by Berzelius of the common ear-wax, a mixture of the
sebaceous and proper ceruminous secretion, must only be admitted with
caution. In my opinion, the brownish-yellow bitter substance, soluble
in alcohol and water, found by him, and the pale yellow strong-tasted
extractive matter, hardly soluble in water, and not at all in alcohol,
must be attributed to the ceruminous glands ; the remaining fat, the horny
matter, and probably also most of the albumen, to the sebaceous glands ;
wbilst the relations of the salts must, of course, be left undetermined.

The vessels of the ceruminous glands are disposed like those of the
sudoriparous ; in one case I noticed, in addition, a fine nervous fibre of
0-003 of a line in the midst of a gland. As to the development of these
glands I can only say, that in a foetus of five months they had the form
of straight, pale processes of the stratum Malpigliii of the epidermis of
the external auditory meatus, were entirely composed of nucleated cells,
and ended by a slightly enlarged termination somewhat twisted upon its
axis, in which the first indication of a glandular coil was presented. In
other words, these rudimentary glands exactly resembled the sudoripa-
rous glands at the same period ; and considering the great anatomical
resemblance between the two structures, I do not doubt for a moment
that the ceruminous glands, both in their first commencement and sub-
sequently, go through the same phases as the former.

According to all that I have seen of the ceruminous glands, I must
consider them to be mere modifications of the sudoriparous. In speak-
ing of these it has already been remarked, that their secretions are
certainly not everywhere identical, being in one locality more aqueous,
in another fatty and albuminous, with peculiar odorous ingredients.
Even although the cerumen may, to some extent, contain peculiar sub-
stances, e. </., the yellow bitter substance, which, however, according to
Lehmann, is not bilin, nevertheless, taking into account the other cor-
respondences (consider the almost constant and often very abundant
yellow granules in the sudoriparous glands, which are also insoluble iu
acids and alkalies), we may associate the ceruminous glands with the
sudoriparous, especially with the larger among the latter, which are
both anatomically and physiologically most closely allied to them ; in
fact, I am inclined, for my own part, to think, that the smallest pale
ceruminous glands at the commencement of the meatus are hardly dis-
tinguishable from common sudoriparous glands. Nothing is known of
the pathological conditions of the ceruminous glands — of the cerumen

212 SPECIAL HISTOLOGY.

itself we know that it is often quite solid, at other times fluid, puriform,
and pale colored. In the latter case, which is seen in congested condi-
tions of the external meatus, it contains far more fluid and free fat than
usual, and very beautiful cells containing fat.* With regard to the
mode of examining the ceruminous glands, I must refer to the sudori-
parous glands, with which they wholly agree in position, chemical rela-
tion to acids, alkalies, &c. &c.

Literature. — R. Wagner, " Icones Phys.," tab. xvi. fig. 11, A, B ;
Krause and Kohlrausch, in Muller's " Archiv," 1839, p. cxvi. ; Pappen-
heim, " Beitriige zur Kentniss der Structur des gesunden Ohres," in
Froriep's "Neue Notizen," 1838, No. 141, p. 131, and Specielle Gebe-
lehre d. Gehororgans (Breslau, 1840); Henle, "Allg. Anat." pp. 915,
916, 934, 941 ; Buschke "Eingeweidelehre," p. 819; Hassall, "Microsc.
Anatomy," &c., p. 427, pi. Ivii. ; Valentin, article " Gewebe," in Wagner's
"Handw. d. Phys.," i. p. 755.

C. OF THE SEBACEOUS GLANDS.

§ 73. The Sebaceous Cflands are small whitish glands, which exist in
almost every part of the skin, and which aff'ord the cutaneous sebaceous
or fatty secretion.

In form they vary very considerably ; the simplest (Fig, 84, A) are
short follicles of an elongated or pyriform shape ; in others — the simple
racemose glands — two, three, or even more follicles or vesicles are
united with a shorter or longer peduncle ; whilst in others, lastly (Figs.
84 B, 85), two, three, or more simple clusters of follicles communicate
with a common duct, constituting an elegant compound racemose gland.
Besides these three forms, which represent only the chief varieties, there
are a good many intermediate ones, which do not require any detailed
description.

The sebaceous glands occur principally in the hairy parts of the body,
opening, in common with the hair-sacs, upon the surface, whence they
have also been termed the glands of the hair-sacs.

In all the coarser hairs, the glands appear to be lateral appendages
of the hair-sacs, and open by narrow excretory ducts into them (Figs.

■* [There is an occasional ingredient in the so-called ccrmnen which is worthy of notice,
viz. a mucedinous fungus. Attention has been recently called to its occurrence by Dr.
Inman ('' Quarterly Journal of Micros. Science,"' January, 1S53), who states that a pellet of
ear-wax which he examined was composed of nothing but this fungus, with a minute por-
tion of epithelium. However, Professor Mayer, of Bonn, so long ago as 1844 ("Beobach-
timg Von Cysten mit Fadenpilzen aus dem aussern Gehorgange," &c., Muller's " Archiv,"
1844, p. 404), described at length the structure of certain sacs containing fungi, which were
extracted from the external auditory meatus of a girl eight years old, — in whom they appear
to have been at first accompanied by considerable deafness and irritation. The sacs were
as large as a pea, and open at one end; externally they were composed of layers of epithe-
lium scales, from which mucedinous threads, terminated by globular sporangia, projected into
the cavity of the sac. These sacs appear to have been repeatedly formed and discharged,
to a very considerable number. — Trs ]

OF THE GLANDS OF THE SKIN.

213

75, 76, 77, 83), whilst in the lanufjo the ducts and the hair-sacs are
often of about the same diameter (Fig. 84 B), and open into a common
canal, which may be regarded as a continuation of the one as much as
of the other ; or the ducts may even be the larger (Fig. 85), the hairs
bearing a subordinate relation to them, so that their sacs open into the
glands, and the hairs come out through the glandular opening itself. In
the hairless parts of the surface, sebaceous glands occur only in the
labia minora {vide § 54), and in the glatis peyiis and prepuce, whilst
they do not exist in the glans and prepuce of the clitoris. In general,
the glands are situated close to the hair-sacs in the superficial layer of
the coriiu7i, and are larger in the finer hairs than in the coarser; in

Fisr. 84. Fis- S5.

^Cl-

^■

r/

:<^y :

o -'S^/

m

particular cases, however, they present many
differences. With respect to the glands of the
larger hair-sacs, they are usually of the simple
racemose kind, having an average size of y^o~
y^g of a line, and are disposed around the sac to
the number of from 2 to 5. The smallest, of
0'1-0*16 of a line, occur in pairs, attached to

Fig. 84. — Sebaceous glands from the nose; magnified 50 diameters. j1, simple tubular
gland without any hair; B, compound gland, which has a common opening, with a hair-
sac : a, glandular epithehum, connected with b, the stratum Malpighii of the epidermis ■ c,
contents of the glands, sebaceous cells, and free fat; d, the separate racemes of the compound
gland ; c, liair-sacs (root-sheath), with the liair, /.

Fig. S5. — A large gland from the nose, with a little hair-sac opening into it; magnified
50 diameters. The letters a-f as in Fig. 84.

214 SPECIAL HISTOLOGY.

each hair of the scalp; they are somewhat larger, 0-16-0-24 of a line
in the hairs of the beard, and the longer hairs of the chest and axilla,
in which situations several glands are usually disposed around the hair
follicle; the largest of all exist on the mons veneris, the lahia majora,
and the scrotum, where, at all events in the last-mentioned locality, they
are found at the deepest boundary of the corium, and the glands, from
four to eight being connected together, represent beautiful rosettes ^-|-
—1 line broad. Attached to the sacs of the smaller coarse hairs, I find
smaller sebaceous glands of 0-06-0-24 of a line, mostly in pairs; and
also in the eyebrows, eyelids, and the hairs at the entrance of the nos-
trils. The lanuginous hairs have generally larger glands, or aggrega-
tions of glands of J-1 of a line ; these are best displayed in the nose,
the ear (concha, fossa scaphoidea), the joenis (anterior half), and the
areola mammoi, especially in the first of these situations, where the
glands often attain a colossal size, and altogether peculiar forms (Fig.
85) ; the glands generally have a diameter of \-^ of a line on the
caruncula lachrymaUs, the lips, brow, thorax, and abdomen ; they are
somewhat smaller, \-\ of a line, but almost always larger than in the
hairs of the scalp, in the eyelids, cheeks, neck, back, and extremities.
Of the glands which are not connected with hair-sacs, only a portion of
those of the lahia minora are of large size (0-14-0'5 of a line) and
rosette-shaped, with an aperture of 0"033 of a line ; the others are for the
most part simply tubular, and at most 0'12-0-16 of a line long, 0-04-
0'06 of a line broad. The glandular vesicles of the sebaceous glands
are either round, or pyriform and flask-shaped, or even elongated or
tubular. Their size varies exceedingly, from 0'06-0-16 of a line in
length, 0-02-0-1 of a line in breadth, and is in the mean 0*04 of a line in
the round ones ; 0*08 in length, and 0'03 of a line in breadth in the others.
The excretory ducts also have very different dimensions, sometimes long,
sometimes short, broad or narrow ; the principal excretory ducts measure
in the nose and lahia minora up to J of a line in length, yg-^ of a line
in breadth, and have an epithelium 0*015-0'03 of a line thick.

The sebaceous glands on the glans penis, and on the inner lamella of
the prepuce or "Tyson's glands," are very inconstant, occurring some-
times only in a very small number, sometimes in hundreds. They are
ordinary sebaceous glands, which are distinguished from those of other
regions by their not being connected with hair-sacs, and by their open-
ing independently on the surface of the skin. They may, generally, be
perceived by the naked eye as small whitish points, which do not project
above the skin ; and in sections of the skin treated with caustic soda or
acetic acid, their peculiarities may be readily studied with the micro-
scope. They appear to be sometimes tubular, at others, simply racemose ;
the former present a round or pyriform follicle of 0-048-0-12 of a line
in diameter, and a straight excretory duct of ^ of a line in length, and

OF THE GLANDS OF THE SKIN.

215

0-024-0-035 of a line in breadth ; the hitter have two to three, or at most
five, terminal vesicles, and measure 0-08-0*18 of aline altogether. The
apertures of both kinds of glands,
■which have a diameter of 0-02-0-06
of a line, are easily seen. "With re-
gard to the position of the glands,
I -would remark that I have never
failed in finding them, 10-50 and
more, in number, on the inner la-
mella of the prepuce, especially in
the neighborhood of the frceniilum,
and its anterior part ; while on the
glans itself and its neck, they are
sometimes totally absent, sometimes
they occur on its anterior surface,
and then generally in great numbers

(up to 100). On the prepuce, the glands are for the most part racemose,
in the j^enis more simple. Their contents exactly resemble those of the
sebaceous glands, viz. cells containing fat, of -which more will be said
below.

The sebaceous glands of the external sexual organs in the female, are
found, generally in great numbers, on the inner and outer surface of the
labia minora, and some of them are as large as those belonging to the
fine hairs on the labia majora, while some are smaller. I have never
found sebaceous glands in the glans and inner lamella of the p^ceputiiim
clitoridis, although Burkhardt speaks of such in the corona clitoridis,
but, in a few instances, I have met with them about the urethra and the
entrance of the vagina. Resembling the sebaceous glands in all essential
points, except their larger size, are the Meibomian glands in the eyelids,
of which a more particular description will be given when we treat of
the eye.

According to E. 11. ^Yeber (Froriep, "Notiz.," Marz, 1849), the
smegma prceputii of the Beaver, the " Castor" is not, in the main, a
glandular secretion, since only a small portion of the pouch in which it
is secreted is furnished with very simple, rounded, lenticular glandules,
the largest measuring g^l of a line. The secretion, in individuals of
both sexes, may rather be described as a laminated substance lining the
entire " castor pouch," and consisting merely of epidermic cells and
minute fatty globules. Lcydig (" Zeitsch. f. w. Zool.," Bd. II., pp. 22,
31, et seq.), finds no glands at all in the " castor-p£)uch ;" and according

Fig. so. — Two sebaceous glands; the larger, 1, from the inner lamella of the prepuce;
the smaller, 2, from tlie glans penis: a, glandular cpitlieliutn continued into the stratum
ilalpighii of the skin; b, c, contents of the gland, with scattered larger fat drops; g, horny
layer of the epidermis, projecting somewhat into the duct. — Magnified 50 diameters.

216

SPECIAL HISTOLOGY.

FiK.87.

to him, the same is the case in the prseputial sac of the Weasel, whilst
in the Rat and Mouse, the prepuce contains true sebaceous glands of a
complicated structure.

§ 74. The minute structure of the sebaceous glands may be described
as follows : — Each gland possesses an external delicate coat of connective
tissue, continued from the hair-sac, or, in the case of free glands, from
the co7-{um, and containing masses of cells, which exhibit different con-
ditions, according to the part of the gland. If we proceed from the
excretory duct of one of them (Fig. 88 B), we see, that not only the
fibrous coat of the hair-sac, but a portion of its inner root-sheath, also,
passes into the duct, and lines it with nucleated, rounded, or polygonal
cells, disposed in several (two to six) layers. This cellular layer is con-
tinued, becoming more and more delicate, into the remoter parts of the

gland, and ultimately pene-
trates into the proper glan-
dular vesicles, clothing them
with a single, rarely a double,
layer. Internally to these
<^^ / cells, which are distinguished
"^^f^ by a greater or smaller
number of fat granules from
the epithelial cells above
them, there immediately suc-
ceed, in the glandular vesicles
themselves, others (Fig. 87 B b) containing more fat ; and these finally pass
into the innermost cells of the glandular vesicles, which are invariably
larger (of 0"016-0-028 of a line) than the middle and outermost cells,
are rounded or elongated in their form, and so filled with colorless fat
that they might, not improperly, be termed sebaceous cells (Fig. 87 B).
The fat contained in them appears either still to retain the form of dis-
crete drops {bh), as in the outer cells, or, as is indeed more frequently
the case, under that of larger drops ; and in many cells there are but a
few of them, or even only a single one, which quite fills the cell [d) ; in
consequence of which these cells greatly resemble the fat-cells of the
panniculus adiposus. If these innermost cells, which rarely exhibit
any nucleus, are traced onward towards the excretory duct, nothing is

Fig. 87. — ^, a glandular vesicle of a common sebaceous gland ; magnified 250 diameters:
a, epithelium sharply defined, but without any investing memhrana propria^ and passing
continuously into the fat-cells, b (their contours are too indistinctly drawn), in the interior of
the glandular tube. — B, sebaceous cells from the glandular tube, and the cutaneous sebaceous
matter ; magnified 3-50 diameters : a, smaller nucleated cells, still more of an epithelial
character, and containing but little fat; 6, cells abounding in fat, without visible nucleus ;
c, cell in which the fat is beginning to flow into one mass; d, cell with one fat-drop ; e^f,
cells from which the fat has partially escaped.

OF THE GLANDS OF THE SKIN. 217

more easy to observe than that similar cells, applied uninterruptedly one
to the other, are continued into this also, i. e. into the canal lined by its
epithelium ; then, entering the hair-sac, they occupy the space between
the hair and the epidermis of the hair-sac, and are finally extruded.
These cells are the sole sources of the cutaneous sebaceous matter, a
substance which, -when fresh and at the common temperature, is semi-
fluid, but in the dead subject more consistent, like butter or soft cheese,
whitisii or whitish-yellow in color, sometimes viscid, at others friable.
Its cells, in the fresh secretion, adhere together more or less closely,
and are thence generally flattened and irregular in form ; their mem-
brane is not recognizable, and their contents are quite homogeneous,
and transparent, with a yellowish hue. If dilute alkalies, however, be
added, they swell up after a short time into beautiful round or elongated
vesicles, in which, in consequence of the penetration of the reagent, the
fat divides into separate drops of various sizes, and into irregular
masses ; at the same time the sebaceous matter becomes white, owing
to the numerous minute fatty particles which are produced, and larger
fat-drops are formed, probably in consequence of the solution of many
cells. Besides that in the cells, the sebaceous matter also contains /ree
fat, in larger or smaller quantity, and in some cases, perhaps, an exces-
sively minute amount of a clear fluid.

It appears, then, that the cutaneous sebaceous matter is a secretion,
consisting, so to speak, only of formed elements, either cells containing
fat alone, or cells together with drops of fat. These constituents are
formed in the vesicular ends of the glands, in consequence of a produc-
tion of cells, wdiich, as in the epidermic tissues in general, proceeds en-
tirely from the pre-existing cells, unaided by free cell-development, of
which there is in this case no indication. By endogenous development
round portions of contents, or by division, cells are continually produced
at the bottom of the glandular vesicles. These are at first pale, and
contain but few granules, like the epithelial cells from which they arise ;
but as they are forced towards the interior by cells developed after them,
they are very soon completely filled with moderately large, round, dark,
fat-granules. They thus proceed towards the excretory ducts ; and the
fat drops contained in them running more and more together, and the
membranes themselves becoming rather more resistant, they eventually
assume the form of the sebaceous cells above described. The free fatty
matter in the sebaceous secretion is formed, in certain cases, by the
solution of the cells whilst still in the interior of the glandular vesicles,
for, in fact, in many glands, free fat, in smaller or larger, often very
considerable drops (Fig. 86 B), is met with, even in the terminal
vesicles ; however, it is also, perhaps, produced in consequence of its
draining from closed cells, a supposition which is not a little strengthened
by the circumstance, that the fat-containing cells in the excreted seba-

218 SPECIAL HISTOLOGY.

ceous matter are seldom filled to distension, but appear for the most part
variously flattened, or even corrugated, and contain only a small quantity
of fat. Understood in this way, the formation of the cutaneous sebaceous
matter resembles in many respects that of the cuticle. The young, easily
soluble cells at the bottom of the glandular follicles may be compared
to the Malpighian cells of the ejiidermis, and the less soluble ones of
the secretion filled with fat, to the horny plates, which seems the more
appropriate, if we consider, 1, that the deep layer of the ejyidermis of
the hair-sac is continued into the ducts of the glands, and even the
outermost cells of the terminal vesicles; and 2, that the epidermis, in
some situations being constantly detached, form secretions (I refer to the
smegma prceputii of the penis and clitoris), substances which are, more-
over, to all appearance chemically allied to the sebaceous secretion ; for
the latter, it may be remarked, according to an analysis of the contents
of a distended gland by Esenbeck (Gmelin's " Handbuch der Chemie,"
Bd. ii.), contains principally, fat, 24*2 ; albumen and casein, 24*2 ; ex-
tractive matters, 24 ; and phosphate of lime, 20 per cent. ; substances
which are found, at all events in part, in the smegma.

Of nerves, I have seen no indication in the sebaceous glands, nor of
vessels distributed upon and between their lobules ; whilst numerous
minute vessels and even capillaries, undoubtedly exist around the larger
glands, most distinctly in the penis and scrotum, as well as in the
ear. I would, moreover, refer to the smooth muscles described above,
when speaking of the cutis, which are found in the neighborhood of the
sebaceous glands, and whose contraction is, perhaps, not inoperative
towards the emptying of their contents.

§ 75. Development of the Sebaceous Grlands. — The first formation of
the sebaceous glands takes place at the end of the fourth and in the
fifth month, and is intimately connected with that of the hair-sacs, since
they make their appearance simultaneously with the hairs, or shortly
after, as outgrowths of the hair-sacs ; whence they are not all formed
at once, but those of the eyebrows, forehead, &c., first, those of the ex-
tremities last. The mode of their development, more precisely described,
is as follows : AVhen the rudiments of the hair-sacs have attained a
considerable development, and the first indication of the hair is visible
in them (Fig. 75, A, B), there are perceptible, on their outer surface,
small, indistinctly-bounded papillary processes {u, v), which consist of a
cellular substance, solid throughout and continuous with the outer root-
sheath, and of a delicate investment, which is continuous with that of the
hair-sac. These processes of the external root-sheaths of the hair-sacs,
as they may properly be called, at first of 0-02-0 -03 of a line in length,
and 0-01-0'016 of a line in thickness, now begin to grow in proportion
to the hair-sacs, become globular, and finally, while they extend them-

OF THE GLANDS OF THE SKIN.

219

selves ami incline obliquely towards the bottom of the sac, pyriform
and flask-shaped. A formation of fat in the internal cells now com-
mences (Fig. 88, A), which, beginning at the bottom of the pyriform pro-
cesses, is continued, also, into their pedicles, and finally includes the
cells of the outer root-sheath, until at last the fat cells reach as far as
the canal of the hair-sac (Fig. 88, B). The gland and its contents are

Fig. 88.

A

c

.'Tt r. , •

ir

.1

-■X

»■

t

now complete, and it needs only that the cells at the bottom of the
gland, or the glandular vesicles, should multiply, to force the sebaceous
cells in the duct into the hair-sac, and fully to establish the secretion.
The sebaceous glands, therefore, like the sudoriparous, are, at first,
solid outgrowths of the Malpighian layer of the skin, for which an ex-
ternal opening is not developed till afterwards, and the first cutaneous
sebaceous matter is formed by a metamorphosis of the inner cells of the
rudiment of the gland, while the space which these cells occupied be-
comes the cavity of the gland, which, however, never appears empty,
but is continually filled by successive generations of cells.

The development of the glands, up to this point, proceeds pretty
quickly. It may be stated generally, that so long as the hairs have not
appeared externally, the rudiments of the glands are papillary, measure
scarcely more than 0-03 of a line, and for the most part contain cells
which are still quite pale ; after the hairs have made their appearance
externally, we find larger pyriform rudiments with a thicker end, of
0-024-0-05 of a line, the cells of which are partly still pale, partly

Fig. SS. — To elucidate tlie development of the sebaceous glands in a six-months' fcetus :
a, hair; b, inner root-sheatli, here more closely resembling the horny layer of the epidermis;
c, outer root-sheath ; rf, rudiments of the sebaceous glands. ^, flask-shaped rudiment of the
gland, with fat developed in the central cells; J5, larger rudiments; the development of fat
has taken place also in their neck, and fatty cells have been excreted into the hair-sac,
giving rise to the glandular cavity and the secretion. — Magnified about 250 diameters.

220 SPECIAL HISTOLOGY.

contain fat, and which now soon open into the hair-sac. In the fifth
month, therefore, the secretion has already begun in many places, and
in the sixth it is everywhere established. At the same time, however,
it is to be observed that, together with the original glands, which occur,
one or two together to each sac, in the sixth month, new rudiments are
produced, which generally lie deeper, and taking on the same course as
that which has been described, soon become secreting glands. The fatty
cells of the newly-formed glands invariably contain many fat-globules,
never a single large drop ; nuclei also occur in them, as in the pale cells
which surround them.

The further development of the sebaceous glands depends on the out-
growth of the external fatless cells of the originally simple tubular gland,
into solid processes, which by degrees become changed into glandular
vesicles, in the same way as the first rudiments. By repeated budding
of the primitive or secondary glandular vesicles, the larger clusters are
formed, and from them the most complicated forms which are met with.
The so-called glandular rosettes proceed, very often, from a single rudi-
ment, which, growing rapidly, surrounds the hair-sac on all sides ; at
other times, however, from two or more primary processes of the outer
root-sheath. In the seven months' foetus, most of the glands are simple
pedunculated follicles of 0-04-0-06 of a line in length, and 0-02-0-03 of
a line in breadth, which are appended, singly or in pairs, to the hair-
sacs ; in the ear alone, do four or five glands of the simplest kind sur-
round a sac, and form rosettes of not more than 0-06 of a line in dia-
meter ; in the nose, simple clusters of at most 0-1 of a line are presented.
In the new-born infant, instead of the simple follicles, simple racemose-
glands are found in all the above-mentioned situations, one, or more
rarely two, to a sac 0-l-0-r2 of a line in length, and only 0-01-0-06 of
a line in breadth ; on the chest, the glands are rosette-like, also on the
ear, temple, nose, nipple, labia majora, and scrotum^ where they mea-
sure 0-1, in the last four places even 0'4 of a line and more. From
these data, it results, that after birth an increase in size takes place in
most of the glands, and assuredly in the same manner as during the
foetal period, a view which is favored by the occasional occurrence of
pale, solid, glandular lobules, even in the adult ; certain glands arise
only after birth, viz. those of the labia minora.

Sebaceous glands also occur in abnormal localities ; thus Kohlrausch
(Mull. "Arch.," 1843, p. 365), observed them in an ovarian cyst, and
Von Biirensprung (1. c, p. 104) in a subcutaneous cystic tumor of the
brow; in both places they were connected with hair-sacs, whence it may,
perhaps, be concluded, that they are very frequently to be found in
cysts which contain hair. In fact I met with very beautiful sebaceous
glands, with a considerable amount of sebaceous matter, in the walls of

OF THE GLANDS OF THE SKIN. 221

the cyst containing hair, mentioned above, from the lung (Mohr's case);
Von Biirensprung has, he believes, though rarely, observed a new de-
velopment of sebaceous glands in cicatrices of some years' standing.
When the hairs fall out, the sebaceous glands seem to disappear, at
least I have repeatedly failed in finding them in bald places. Hyper-
trophy* of the sebaceous glands takes place, according to E. H.
"Weber (Meckel's "Archiv," 1827, p. 207), in cutaneous cancer; ac-
cording to Von Biirensprung in akrotJtT/mion, or moist warts (1. c,
p. 81), and in na'vus pilosus. The comedones also, among which I
place Lichen pilaris, at least as Simon defines it (1. c, p. 334),
are hair-sacs and sebaceous glands distended with sebaceous matter,
"which are especially frequent where the glands are distinguished by
their large size, as on the nose, the lips, the chin, the ear, the areola,
and the scrotum. They arise, either in consequence of the obstruc-
tion of the apertures of the hair-sacs by impurities, or of the formation
of a more viscid and consistent secretion ; and they contain, besides
one or many hairs, which may also be wanting, fatty cells, like those of
the normal cutaneous sebaceous matter, ejndermic cells proceeding from
the hair-sacs, free fat, often crystals of cholesterin and the Acarus
folliculorum. Milium consists of small white spots on the eyelids, the
root of the nose, the scrotum, and ear, which are formed, as Von Biiren-
sprung is certainly right in supposing, from the sebaceous glands also,
by their distension alone, without the hair-sacs ; in consequence of
■which, rounded prominences without any aperture are formed and raise
up the skin : their secretion, similar to that of the comedones, may still
frequently be pressed out through the hair-sacs. Finally, there can no
longer be any doubt that the sebaceous cysts which lie in the corium
itself {atheroma, steatoma, meliceris, and 7nolliiseum), must also be re-
garded as colossal hair-sacs with sebaceous glands. Further details may
be found in the works cited.

With respect to a little parasite, the Acarus folliculorum, which
resides in healthy and distended hair-sacs and sebaceous glands, I must
refer to G. Simon (1. c, p. 287). In the case of Icldhyosis congenita
above referred to. Dr. H. MUller and I found the excretory ducts of
the sebaceous glands in the epidermis everywhere dilated to 0-02-0*06
of a line, with saccular diverticula, often lying many together one
behind another, of 0 •04-0-12 of a line, and quite full of sebaceous
matter. Here and there a hair was found in one of these ducts, so
that it appeared at the same time to be a hair-sac.

In investigating the sebaceous glands, they should either be prepared
from within, by cutting them with the hair-sacs which belong to them
from the cutis, or perpendicular sections, not too fine, may be made.

* [These glands, when hypertrophicd, frequently lose their glandular structure, and are
changed into yellowish granular masses. — DaC]

222 SPECIAL HISTOLOGY.

The minuter structure may be best studied, at first in the glands of the
scrotum and penis, or labia minora, as these can be isolated without any
trouble ; to which end acetic acid, which renders the surrounding parts
transparent, is very serviceable. With the others, so far as form, posi-
tion, and size, are concerned, the use of alkalies, especially of caustic
soda, is most advisable, inasmuch as they clear all the other parts, while
they act but little on the glands on account of the quantity of fat they
contain. If it be desired to study, not so much the investments, as the
cells of the glands, obtaining at the same time a view of their whole
figure, there is no plan better than maceration ; the hairs with their
root-sheaths, and the cellular masses of the sebaceous glands, epithelium
and contents, may then be drawn out altogether. Where the epidermis
is thin (on the scrotum, labia 7najora, glans penis), the same end may
be attained in a short time by the dropping on it concentrated acetic
acid, and also by using caustic soda in the same manner, though with
greater destruction of the glandular cells. To study development, the
maceration of foetal skin, and the rendering it transparent by acetic
acid, are of great use. The fat-cells in the interior of the glands are
isolated with great ease by teasing out a large gland, and the secretion
may be examined without addition, and also with water and caustic soda.
Literature. — Compare the works cited above under the head of " Skin,"
by Gurlt, p. 409; Krause, p. 126; G. Simon, p. 9; Valentin, p. 758;
the "Essay on the Hairs," by Eschricht, which has been mentioned;
then the general works by Henle, p. 899 ; Todd and Bowman, p. 424,
fig. 92; riassall (pi. liv. should be liii.), p. 401; Bruns, p. 349; Gerber,
p. 75, figs. 40, 42, 43, 44, 45, 239; Arnold, part II., the figures of
Wagner, "Icon. Phys.," tab. xvi., fig. 11, c; Arnold, "Icon. Anatom.,"
Ease. II., tab. xi., fig. 10, and Berres, tab. xxiv., besides that G. Simon,
" Ueber die sogenannten Tyson'schen Driisen an der Eichel des miinn-
lichen Gliedes," in Mliller's "Archiv," 1844, p. 1.

OF THE MUSCULAR SYSTEM.

§ 76. To this system belong all the transversely striped muscles,
which, together with their accessory appendages, the tendons and
fasciae, serve for the movements of the skeleton, of the proper organs of
sense, and of the integuments. These muscles constitute a system
situated between the integuments and the bones, and between the bones
themselves, the individual parts of which are so associated and united by
common membranes, that they may conveniently be regarded as a whole.

§ 77. The proper elements of the muscles in question, visible even to

THE MUSCULAR SYSTEM.

223

Fi?. S9.

the naked eye, — the transversely striated (animal or voluntary) muscular
fibres, ov primitive fasciculi, — are distinguished, especially by their size
and the distinctness of their individual parts, from those of most of the
striped muscles occurring in other situations (heart, large venous trunks,
'pharynx, oesophagus, larynx, urethra). With respect to this latter
characteristic, it is to be remarked that the sheath of the primitive
fasciculus, or the sarcolemma,'^' in every fasciculus without exception,
especially on the addition of water, acetic acid, and alkalies, may at
once be recognized as a perfectly structureless, transparent, elastic,
smooth membrane, which in man, as in the mam-
malia, is distinguished by its delicacy from the same
tissue in the lower Vertebrata, and particularly in
the naked Amphibia. The muscular or primitive
fibrils may, though not without difficulty, be isolated,
especially in muscles that have undergone slight
maceration, or have been boiled, or immersed in
alcohol or chromic acid. In general they are vari-
cose, that is to say, present more or less distinct ^^^ffl \ .i
enlargements, at intervals of 0-0004-0-001 of a line ;
in consequence of which arrangement, and owing to "
the circumstance that the thicker and thinner spaces,
throughout the entire thickness of the fasciculus, are
placed regularly on the same level, the latter for the
most part appears to be marked with delicate trans-
verse hands. Occasionally, moreover, in addition, a
fine parallel striation is evident, or, more rarely,
where the enlargements on the fibrils are less appa-
rent or quite imperceptible, simply a longitudinal
striation. In adults, the fibrils do not enclose any central space or
canal (Jacquemin, Skey, Valentin), but, with the addition of a small
quantity of a connecting interstitial substance, constitute perfectly
compact fasciculi (Fig. 90). On the inner side of the sarcoleynma,

Fig. 89. — Primitive fibrils from a primitive fasciculus of the Axolotl (Siredon pisciformis) ;
magnified COO diameters: a, a small fascicular composed of them ; b, an isolated fibril.

* [It is greatly to be doubted whether the universality of the occurrence of this structure
should be so strongly affirmed. We liave been unable to detect it either in the muscular
bundles of the heart, or in the great majority of those of the tongue, or in any of the muscles
of a seven-months' foetus. In fact, the question of the existence of a sarcolemma as an
independent structure very much resembles that of the existence of " fibrils." The sarco-
lemma must be considered merely as the outer portion of the transparent, homogeneous
matrix, in which the " sarcous elements" are imbedded (vide infra); and the possibility of
raising it up by artificial means, or of observing its optical expression, as a distinct structure,
will depend upon the amount to which it is developed relatively to the various elements,
and the extent of chemical diirerentiaiion wliich has gone on it as compared with the rest
of the matrix. — Tns ]

224

SPECIAL HISTOLOGY.

numerous nuclei always exist, of a lenticular or fusiform shape, fre-
quently with 7iucleoU, and from 0-003-0-005 of a line long. These
nuclei are not placed with any regularity ; sometimes two or more at
the same level, or in rows, or alternately one behind the other. Fatty,
or yellowish pigment-granules, also, frequently occur around the nuclei
and between the fibrils, chiefly, however, in muscular fibres which are
not in a perfectly normal condition.

The form of the muscular fasciculi is rounded-polygonal. In thick-
ness they vary from 0-005-0'03 of a line, or more. In the trunk and
extremities they are invariably thicker (0-016-0-03 of a line) than on
the head, in which situation, especially in the facial muscles, they are

Fiff. 90.

Fis;. 91.

distinguished by the smallness of their fibres (0-005-0-016 of a line);
but, with respect to this, it is to be remarked that great differences not
unfrequently exist in one and the same muscle. From all that is known,
it would appear that there is no absolute difference in the size of the
muscular fibre in man and in woman, or between weak and robust indi-
viduals. On the other hand, it is not improbable that in one case one
extreme, and in a second the other, may prevail. The thickness of the
primitive fibrils, in man, amounts on the average to 0-0005 of a line;
their number, in one of the larger fasciculi, must reach several hundreds,
but is not accurately known. The distance between the transverse
stritB varies usually from 0-0004 to O'OOl of a line.

Various controversial opinions still prevail with respect to the consti-
tution of the muscular fibres. Several authors assert, or at all events
consider it probable, that the primitive fibrils are produced artificially.

Fig. 90. — Transverse section of some muscular fibres or primitive fasciculi from the
gastrocnemius of man ; magnified 300 diameters : a, sarcolemma and interstitial connective
tissue; b, transverse section of the muscular fibrils, with the interstitial substance.

Fig. 91. — Portion of a muscular fibre of man. treated with acetic acid, magnified 450
diameters: a, sarcolemma; b, a simple nucleus; c, double nucleus, surrounded with fatty-
molecules.

THE MUSCULAR SYSTEM.

225

Fisr. 92.

This is the opinion entertained by Remak, who thinks a pre-existing
division of the muscuhxr cylinder still problematical ; of BiUcke, who
appears to regard the contents of the muscle-tubes during life as fluid ;
of Du Bois-Reymond, and, above ail, of Bowman. According to the
latter, a division of the muscular fibres into " discs" (Fig. 92) is quite as
natural, although not so frequent, as that into fibrils,
and that they may be considered as columns composed
of such discs, quite as correctly as bundles of fibrils.
Were a muscular fibre completely divided in the direc-
tion of both the transverse and longitudinal striae,
rounded, angular, minute particles would be produced,
which may be termed primitive particles, or " sarcous
elements." In the fibre, these elementary particles are
connected in both directions, the same particles in the
one case constituting a "disc," and in the other a seg-
ment or joint of the fibrils. The division into discs,
upon which Bowman lays especial stress, would in my
opinion have been of importance had it occurred as fre-
quently as that into fibrils, and also, occasionally, in
recent muscle ; but it is not so, — for, in the first place,
nothing of the sort can ever be seen in recent muscles
of man and the higher animals ; and in the second place, even in mace-
rated or otherwise manipulated fasciculi, the breaking up into discs is
an extremely rare phenomenon ; whilst, on the other hand, the isolation
and exhibition of the fibrils may be obtained, in almost every instance,
by any one at all conversant with the subject. Moreover, in transverse
sections of perfectly fresh living muscles, as, for instance, of the thigh
of a Frog, made by means of the double-bladed knife, the transverse
section of the fibrils is just as evident and distinct as in dried muscles,
whilst, in precisely similar longitudijial sections, not a trace of the
"discs" can be detected. This fact at once sets aside all those views,
according to which the muscular fibres, during life, consist of a homo-
geneous, solid, or fluid substance, or of minute particles, connected in
tAvo directions. To Bowman's opinion, moreover, is opposed the fact
that his assumed "elementary particles," except in macerated muscles,
where such a thing readily occurs, can only with difficulty be obtained
in an isolated form, whilst, according to his view, such a disintegration,
in cases where these particles do not cohere firmly, either in a longitu-
dinal or transverse direction, would necessarily take place with equal

Fig. 92. — A, a primitive fasciculus, separating transversely into discs; magnified 350
diameters. It exhibits distinct transverse and fainter longitudinal striiF. The discs, of
which one more highly magnified is seen at B, are granular, ami consist of the primitive
particles (sarcous elements) of Bowman, or segments of the fibrils according to other
authors (after Bowman).

15

226

SPECIAL HISTOLOGY.

FiL'. 93.

facility in either ; and in the second place, that, in the thoracic muscles
of insects, the individual fibrils may be very distinctly and beautifully
seen (Fig. 93) in the muscles, when quite fresh. When we consider the
great similarity between the muscles of insects and of
the higher animals, in every essential particular, this
fact appears to me to be of a striking nature. I am,
therefore, from this and the other reasons assigned,
thoroughly convinced of the existence of fibrils during
life, and believe that, where they do not so readily
admit of being isolated, as in man and many animals,
they are connected by a homogeneous, tenacious (albu-
minous), interstitial substance, which is very evident in
a transverse section, and in fact so firmly, that, under
certain circumstances, transverse rupture of the fasciculi
may take place, that is to say, in the direction of the
thinner spaces of the fibrils ; as also occurs in other
fibres ; for instance, in the elastic tissue, smooth muscles,
and even in the corneous cells (internal root-sheath and
cortex of the hair). With all this, it must not be sup-
posed that fibrils exist in all muscular fibres of animals,
either themselves striped or corresponding to the striped fibres here
described. The study of development and of comparative anatomy
much rather teaches that the muscular fibre occurs in various conditions,
and, particularly, that it frequently exhibits more homogeneous contents,
with or without transverse striation, and without fibrils. This, however,
of course, affords no ground for the assumption of such a condition in
man and the mammalia also ; and although such muscular fibres, in
certain animals, readily break up into transverse segments (Leydig),
still, it is not thereby proved that in the higher animals a similar
division of the contents is to be regarded as natural, and that into
fibrils as artificially produced.

The diameter of the primitive fasciculi varies, not inconsiderably, in
different muscles, or in one and the same muscle. Henle (who is fol-
lowed by Gerlach), at an earlier period, assigned to them a diameter
of 0-005-0'006, and at most of 0-017 of a line; but more lately
(Stadelmann, " Sectiones transversse"), has declared that these measure-
ments are not universally correct. I will here give some particulars
upon which the measurements stated above, in the text, are founded.
In a female, the fasciculi of the sacro-lumhalis measured 0-016-0-028,
the majority 0"020-0-022 of a line; in the pectoralis major, 0"01-0*03,
most of them 0-02 of a line ; deltoid, O-OlG-0-026, the majority 0-02-
0-022 of a line; in the masseter, 0-006-0-02, the majority 0-01-0-018

Fig. 93. — Primitive fibres from a quite recent transversely-striated muscle of a Bug ;
magnified 350 diameters.

THE MUSCULAR SYSTEM. 227

of a line ; in the retraJiens auricula', 0-006-0-015, the greater part 0-008-
0-01 of a line. In a male, their diameter in the 'pectoralis amounted
to 0'018-0-28 of a line, the greater nutiiber measuring 0-02-0-022 of
a line ; in the deltoid, 0-012-0-02-i for the largest, and for the smaller
O-OlG-0-02 of a line ; in the obliquus abdominis ezternus, 0-16-0-024 and
0-016-0-02 of a line; in the orbicularis oris, 0-008-0-016 and 0-01-
0-012 of a line; in the frontalis, O-OOG-0-014 and 0-008-0-01 of a line.
In a second individual, the pectoralis major contained fibres of 0-0068-
0-024, most of them 0-018-0-02 of a line; the pyramidalis, some of
0-01-0-028, the majority 0-02 of a line.

With respect to the nature of the primitive fibrils, much still remains
to be cleared up. In general they must be regarded as solid ; and, in
fact, there is nothing to indicate the existence of a cavity in them. It
is fully ascertained that it is to them that the transverse striation of the
primitive fasciculus is due. It is still doubtful, however, whence the
appearance of transverse striation in the fibrils themselves arises ;
whether from their being spirally tu'isted (Arnold), from zigzag curva-
tures (Will), or from varicosities. All that I have seen leads me to
adopt the latter view, which is also that most generally entertained. I
do not deny that, in the examination of numerous fibrils, appearances
are occasionally met with, favorable to the other two views, and parti-
cularly to that of Will ; but it is much more usual to find simple nodular
enlargements. The large fibrils in the perennibranchiate Amphibia
[Siren, Proteus, Menopoma), (Fig. 89), are above all others adapted for
this investigation. In these animals, when they have been preserved
in spirit, the fibrils become isolated in considerable numbers, and may
be examined on all sides. It is the same with the muscles of the thorax
in Insects.

Quite lately Dr. Barry has propounded the view that each muscular
fibril is constituted of two spirally convoluted filaments running in the
same direction. I have seen nothing of the kind, and do not hesitate
to describe the whole of Dr. Barry's exposition as nothing but a myth,
and his figures as fantastical images.

As regards the notion adopted by Bowman, Dobie, and others, that
the fibrils are constituted of still more minute particles (sarcous ele-
ments), it may perhaps be stated, as the study of development shows, that
the fibrils do, in fact, at first appear to consist of separate particles.
But the question is whether in the adult such elementary particles con-
tinue to be evident, and this, at present, I am inclined to deny.

The nuclei of the muscular fibres, in man, are situated, as I agree
with Schwann in stating, only on the inner surface of the sarcolemma,
and not within the fibrils ; that they are not placed externally on the
fasciculi, as was formerly stated by Henle and Stadelmann, and more
lately by Gerlach, is readily perceived, when the muscles are treated

228 SPECIAL HISTOLOGY.

■with allcalies. Under these circumstances the partially-swollen nuclei
escape, together with the fibrils, in a state of solution, from the sheaths,
which remain behind, and before they are dissolved may be easily exa-
mined in an isolated state. In many muscles, even when there are no
granules between the fibrils, larger or smaller fatty molecules occur
around the nuclei.*

* [With regard to the vexed question of the iihimate structure of striped muscle, we ques-
tion if any real improvements have been made upon the description originally given by Mr.
Bowman (" Phil. Trans.," 1840), viz., that it consists of minute, dark, subangular particles,
the "sarcous elements," imbedded in a more transparent connecting substance or matrix;
that neither discs nor fibrils can be said to exist in the normal state, — the breaking up of the
muscular bundle into either of these elements, resulting simply from the manner in which
the lines of greatest cohesion are disposed, at the time when mechanical violence is applied
to it. The assertion in the text that the fresh muscle of man and the mammalia does not
break up into discs, is decidedly erroneous — as we have seen it occur repeatedly.

Nor can we grant the invisibility of the discs in longitudinal sections of muscle: what
may be the case in such sections made with the double knife, we do not know, — but in those
accidental longitudinal fractures of the muscular bundles of man, mammals, and insects,
which constantly occur, the edges of the discs are most distinct. Again, without making
any section at all, the discs may, especially in insects, be traced, by altering the focus of the
microscope, through the entire thickness of the bundles. The argument in the text, in fact,
proves too much; for if the fibrils are visible over the whole transverse section, their dark
parts (discs) alternating with the light ones, must be as visible in a section, made in any
longitudinal plane, as they are on the surface. However, that the appearance of discs shovdd
be absent in any longitudinal section of striped muscle is, to us, simply incomprehensible.

With regard to the thoracic muscles of insects, it is to be observed, in the first place, that
they do not represent ultimate fibrUs, but non-fibrillated primitive bundles. Dr. Auber, in a valu-
able paper in " Siebold and Kolliker's Zeitschrift" (H. 3 and 4, 1853), has already shown
that there is no defined line of demarcation to be drawn between these and the ordinary
muscles of insects, the two forms passing into one another by the peculiar flat bundles of
the Libellulidoe, though he still considers the thoracic muscles to represent ultimate fibrils.
His sole argument, however, is their resemblance to the ultimate fibrils of the higher animals,
which we think loses all force, when we consider a fact that he has overlooked, namely,
that the muscles of the legs, &c., present a very beautiful, though very delicate fibrillation —
the fibrils being not more than jjooo — ^iJooff''' °^ ^^ ^"'^'' "^ diameter; that is, not more
than from one-third to one-sixth the diameter of the thoracic muscles. Examined carefully
with a high power (GOO), with a good definition, the edges of the discs, which under a
iower power appeared very sharp and even, are seen to be distinctly granular, and to be
composed of minute, somewhat fusiform or rounded particles, not more than TTjjJ^nth of an
inch in diameter, distinct from one another, and imbedded in the general transparent matrix,
which is marked by fine longitudinal lines running between the rows of particles. Occa-
sionally, the broad, dark discs appear to be separated by a delicate line, and this line, if carefully
examined, is found to be composed of similar, but far more minute and paler particles. How-
ever, this appearance, though very common, is not to be met with in all the bundles. Acetic acid
swells the muscle up, and renders the sarcous elements still more distinct, though the whole
becomes very pale. If dilute ammonia be added to such a bundle, so as to neutralize the
acid, it resumes its original dimensions, and almost its original appearance, except that the
sarcous elements have often a wonderful sharpness of outline.

The thoracic fibres, treated with acetic acid, become exceedingly pale, and the distance
between the discs is much increased. The latter often assiuue a granular appearance, but
not so distinctly as in the former case; nor have we been able to detect any fibrillation of
the intermediate substance, nor any minute sarcous elements, in them. They share the
former character, however, no less than the latter, with multitudes of unquestionable mus-
cular bundles — so that taking into consideration the existence of fibrils very much minuter

TUE MUSCULAR SYSTEM. 229

§ 78. The muscular fibres in the trunk and extremities are, in general,
so associated, without the existence of any divisions, reticular connec-
tion, or termination in the interior of the muscles, as to constitute con-
tiguous prismatic bundles extending the entire length of the muscle.

than tlie tlioracic fibres in tlie muscles of insects, anil the grfdiial transition of the latter into
undoubted bundles, we do not liesitate to regard these thoracic fibres as homologous, not with
primitive fibrils, but with primitive bundles; and therefore to neglect any argument which
may be drawn from their existence, to that of primitive fibrils during life in the higher
animals.

The answer to the question, whether primitive fibrils exist during life or not, in fact, de-
pends very much upon the meaning of the words. If it be meant that the muscular bundle
is like a rope, the fibrils being the separate strands, united by " a homogeneous, tenacious
substance,' — we should say that nothing of the kind exists during Hfe. If, on the other
hand, it be meant only that the molecules of the muscle are so arranged as to break up more
readily and more frequently in the longitudinal direction than any other (just as a bar of
wrought iron would tear into longitudinal fibres rather than in any other way, though it
could by no means be said that it was composed of longitudinal fibres), why, there can be
no question that such is the fact. The behavior of a muscular fasciculus, under the alter-
nate action of acetic acid and ammonia, is as instructive with regard to this point, as that of
bundles of connective tissue.

The existence of varicosities of the fibrils must depend very much upon their state of ex-
tension. Normally, they do not exist, unless, perhaps, the fibril has been split off from the
very edge of a bundle, where the sarcoiis elements often project strongly. When very much
stretched again, since the sarcous elements are more solid and resisting than the matrix, they
will form knots, and the fibrils will appear more or less varicose. The great majority of in-
stances in which the fibrils appear varicose, however, depend on imperfect definition — and
the same may be said of supposed zigzag bendings; while the spiral fancies, on the other
hand, are more probably connected with an imperfect judgment. '

Recently, Drs. Sharpey (" Quain"s Elements") and Carpenter (" Manual of Physiology")
have advocated a view, the former, however, with some doubts (to which Professor Kolliker
does not refer), founded upon an examination of the preparations of muscular fibrils, made
by Mr. Lealand. They distinguish quadrilateral dark spaces in the fibrillse, each of which
is set, as it were, in a transparent frame of the same shape; these joined together constitute
the fibril, the lines of junction of the frames, or "cells" being indicated by a dark line. We
have repeatedly seen the appearances which are thus described; but so far as we have
been able to discover, they invariably arise from that peculiar interposition of rows of mi-
nute paler sarcous elements, between the ordinary broad dark ones, to which we have re-
ferred above in describing the muscles of insects.

Very often, the finer sarcous elements are completely wanting, as in the thoracic muscles
of Insects, in the muscles of the Frog, and in many of the bundles in Mammals; and in
these cases there is, of course, no evidence at all of the existence of any such -'cells."

In conclusion, we may state the view which we are led to take of the structure of striped
muscle, in a few words. In a homogeneous, transparent matrix, definite i^articles are im-
bedded— the sarcous elements, — which are arranged side by side, in even transverse rows.
In some'cases the sarcous elements are all of one size; in others, they are alternately larger
and smaller. The reason of this difference does not at present appear, but it is very pos-
sibly connected with the nutrition of the muscle. The matrix usually tends to break up
into longitudinal bands — the " fibrils," — which have the diameter either of a single sarcous
element, or of some multiple thereof; it likewise tends to break up in the transverse direc-
tion, giving way between the pairs of rows (discs) of sarcous elements ; but these cleavage
lines are no indication of the existence of discs or fibrils, as such in the unaltered muscle.
The sarcolcmma is simply the outer portion of the matrix, and its demonstrability as a sepa-
rate structure depends upon the extent to which it is developed, and the amount of chemical
change which it may have undergone relatively to the inner portion. — Tus.]

230

SPECIAL HISTOLOGY.

Fia-. 94.

These secondary muscular fasciculi, as thej are termed, are, each of
them, enclosed by a special envelop of connective tissue, and, several
together, united by stronger membranes into tertiary fasciculi, which,
lastly, in a greater or less number, unite and constitute the separate
bellies of the muscle, or muscles themselves. If the muscular fasciculi
are placed in the same plane, they constitute the membranous or fiat
muscles ; and when disposed in a thick bundle, the elongated or columnar
muscles. The muscles consequently are aggregations of numerous,

larger and smaller secondary
and tertiary fasciculi, the
sheaths or perimysium of
which constitute a connected
system, in which that por-
tion which surrounds the en-
tire muscle, as the perimy-
sium externum or muscular
sheath {vagina muscularis\
is to be distinguished from
the more internal elements
immediately surroundino; the
larger and smaller fasciculi and the muscular fibres — the perimysium
internum. The thickness of the secondary fasciculi varies from g to ^
a line ; that of the tertiary and still larger bundles, which are most
evident in muscles with coarse fibres [glutceus maximus, deltoideus), is
so various, and the division of the muscle in these more remote constitu-
ents is so arbitrary, that there is nothing specially to be said with re-
spect to them.

The muscular sheaths or envelops, perimysium, composed of con-
nective tissue, which are for the double purpose of conveying the vessels
and nerves of the muscles, and of connecting the muscular fibres and
supporting them when in action, vary in thickness according to the
greater or less size of the groups of fasciculi surrounded by them.
They are always, however, delicate, dull-Avhite, non-glistening tunics,
consisting of common connective tissue, and minute, isolated or anasto-
mosing elastic fibres, of at most 0-001 of a line in thickness, the latter
occurring in greater number, especially in the perimysium externum,
which may, consequently, very properly and conveniently, be regarded
as a semi-elastic membrane, and its function estimated in accordance
"with this structure. In all muscles, especially in those of a more lax
construction, a certain number of adipose cells of the usual kind (fre-

FiG. 94. — Transverse section from the rectus capitis anticus major of Man, magnified 350
diameters: a, external perimysium; b, perimysium internum; c, primitive fasciculus and
secondary muscular fasciculus.

THE MUSCULAR SYSTEM. 231

qnontly containing beautiful fat-crjstals) occur, and in fat persons they
are found quite in the interior.

[It was formerly supposed that the primitive muscular fasciculi ran
in a perfectly straight direction towards their insertions, without dividing
or anastomosing; but this is not correct. Recent investigations, made
partly alone, partly with the assistance of Dr. Corti, have demonstrated
the anastomosis of the fasciculi of striped muscles in the hearts probably
of all Mammalia. AYe observed anastomosing fasciculi in Man, in the
Rabbit, Dog, Cat, Calf, Frog, Heron, andLeydig has seen them in the Ruff.
In the Mammalia, and in Man, they are frequent, and extremely delicate,
and the anastomosis occurs by means of short transverse or oblique branches
extending between parallel fasciculi. In the larynx, oesophagus, pharynx,
and the tongue of the Rabbit, nothing similar to this was met with, but we
found in the tongue of the Frog, immediately under the mucous membrane
(which is readily removed in boiled preparations), the most delicate divi-
sions, although no anastomoses. Fasciculi of 0*03 of a line or more, could
be observed to form, by successively dividing at acute angles, large
bundles of fine branches (the finest, 0*0012 to 0-0016 of aline), which
were inserted into the mucous membrane of the tongue between its
glands. I have seen, also, in the lymph-heart of frogs, an anastomosis
of the striped muscles similar to that occurring in the heart, and Dr.
Leydig (Zeitschrift fur Wissenschaftliche Zoologie, Bd. I. Heft 2, 3),
has observed anastomoses in the muscles of Paludina virspara, which
genetically correspond to the striped muscles. In the muscles of the
trunk and extremities in Man and in the Mammalia, I have never been
able to discover even the trace of an anastomosis, although it occa-
sionally appeared to me, as if some fasciculi before or at their connec-
tion with tendons, divided within a short space two or three times. I
have certainly seen this division in the tails of batrachian-larvse, where
single fibres at their insertion into tendons separated into from three to
five conical branches. (From Kolliker's Micr. Anat., 1. 1, p. 210.) — DaC]

§ 79. Connection of the Muscles xoitli other parts. — The muscular
fibres are connected with the movable parts, the bones, cartilages, arti-
cular capsules, the skin, &c., partly in a direct manner, partly with the
intervention of fibrous elements, the tendons, /ascz'te, certain forms of
muscular ligaments and membranes {lig. interossece^ membrance, ohtura-
torice). Those muscles which are attached either wholl}'-, or at one or
the other end without the intervention of tendons, constitute on the
whole the smaller number. Where the muscular fibres arise directly
from bone [ohliqui, iliacus, psoas, glutaei, &c.) and cartilage (transversus
abdominis, diaphragm), or rest immediately upon those structures (ser-
rati, onoht/oideus, sterno-hi/oideus, aural muscles), they never extend

232 SPECIAL HISTOLOGY.

further than to the periosteum or perichondrium, terminating abruptly
on those membranes, with the fibres of which they are not, in any way,
continuous, nor do they come into immediate contact with the bone or
cartihage. Where the muscles extend to the skin, they either expand
immediately beneath, and without any connection with it, or radiate in
it, in the form of larger or smaller divergent fasciculi (facial muscles) ;
in which case they appear to be inserted, at all events occasionally, at
once into the filamentary processes of connective tissue.* But the pre-
cise mode of connection of these tissues has not yet been ascertained.

§ 80. The sinezvs, tendons, are brilliant, white or yellowish structures,
composed almost entirely of connective tissue. They are subdivided,
according to their figure, into the rounded, cord-like, true tendons, and
into membranous aponeuroses {centrum tendiyieum, galea, tendons of
the abdominal muscles, latissimus dorsi, cueullaris, &c.). The two
forms, either in their external configuration or internal constitution, do
not admit of definite distinction ; they consist of connective tissue,
which is characterized by the parallelism of its elementary fibres, its
consistence, and its 'poverty in elastic filaments. The elements of the
connective tissue, the fibrillar, may be readily perceived, in fresh tendon,
to be, as they are everywhere, extremely minute. In the cord like
tendons, they are slightly wavy in their course, all perfectly uniform ia
size, parallel to the long axis of the tendon, and in the recent state so
closely approximated, that the demonstration of the existence of jjriyjii-
tive fasciculi is not easy. Such fasciculi, however, do exist, having a
breadth of 0'006-0*008 of a line, and a rounded polygonal figure, as
may be seen, especially in transverse sections of dried tendons, particu-
larly on the addition of alkalies. But in the natural state they are so
firmly united that they cannot be isolated.

On the other hand, in true tendons, in the recent state, secondary
and tertiary fasciculi are very evident (Fig. 95). Delicate dissepiments,
in fact, of loose connective tissue, penetrate the substance of the tendon,

* [The insertion of muscles without the intermediation of tendons, directly into the con-
nective tissue of the skin and mucous membranes, is seen very beautifully in the tongue and
in the facial muscles of Mammals. The former case has been well-described by Dr. Salter
(Todd's " Cyclopaedia," article " Tongue') ; the latter may be examined with great ease in
the levator labii superioris of the Rat. Here the muscular bundles run in the subcutaneous
connective tissue, keeping a pretty even diameter until they nearly reach their insertions.
They then divide into many branches, each of which either tapers off to a conical extremity,
or divides into a number of delicate pointed processes. In either case, the ends of the mus-
cular fibre gradually or suddenly lose their striation, and pass directly into the irregular
nucleated bands of the connective tissue. No sarcolemma can be demonstrated in the
branched ends of the muscles, and the bands of the connective tissue are directly continuous
with the matrix of the muscle; the change, from the one to the other, being evidenced
merely by the appearance of the sarcous elements. Nothing can aftbrd a more complete
proof of the homology between the pseudo-fibrillated tissue of muscle and that of connective
tissue, tlian what we find here. — Trs.]

THE MUSCULAR SYSTEM.

233

The aponeuroses

and by their mutual connection form a continuous system of parallel
tubes, thus dividing the tendinous fibrils or primitive fasciculi into
numerous larger or smaller
groups. Secondary fasciculi,
mostly of a polygonal, or per-
haps rounded or elongated
figure, and having a diameter
of 0*03-0-0G of a line, may be
very readily distinguished ; and
tertiary fasciculi, "with poly-
gonal contours, of 0-1-0-05 of
a line, and more in diameter,
and bounded by rather stronger
dissepiments ; there are, also,
generally apparent, still larger r^
subdivisions, composed of nurae- /
reus tertiary fasciculi, and
which, being closely united in
very various numbers and
groups, by a common envelop
of lax connective tissue, constitute the tendon itself,
are constituted either in the same way as the true tendons, and consist
of several layers of parallel, secondary fasciculi, disposed contiguously
in the same plane, or more resemble the fibrous membranes, and present
primary and secondary fasciculi decussating in two or more directions
(abdominal muscles, diaphragm).

Fine elastic fibres (the so-termed nuclear fibres) occur in the secondary
fasciculi of all tendons, in various conditions of development : sometimes
as a series of slender fusiform cells connected by delicate processes ;
sometimes as fully-formed fibres of uniform thickness, or as isolated
fusiform cells. The arrangement of these elastic elements is uniform
throughout, and they run at regular distances, parallel to, and among
the fasciculi of connective tissue. Consequently, in the transverse
section of a tendon, the dark ends of the elastic fibres are apparent,
distributed, at constant distances of 0-007-0-008 of a line apart, over
the whole section. But, besides these stronger elastic filaments, mea-
suring from O-0005-O'OOl of a line, there exist in most, perhaps in all
tendons, extremely delicate fibrils of 0-0002-0-OOOi of a line, connecting
the former in various directions, so that in reality there is, in every ten-
don, an elastic network, penetrating and entwining the fasciculi of con-

FiG. 95. — Transverse section of a tendon of the calf, magnified 20 diameters: a, secondary
fasciculus; 6, tertiary ; c, nuclear fibres not quite in transverse section, but appearing as
little streaks in the former: d, interstitial connective tissue.

234

SPECIAL HISTOLOGY.

nective tissue. These fibrils may also be distinguished on a transverse

section, as minute dark points, or as lines
radiating from the coarser points exhibited
in the section (Fig. 96) ; and they are still
more evident in longitudinal sections, in
which, more especially, the whole of the
fibrous system just described comes very
readily into view. In such sections, also,
it is evident that, in every case in which
the formative cells of which the fibres are
constituted still retain a certain degi'ee of
independence, very distinct elongated nu-
clei exist in them. Besides these elastic
fibres, the tendons, in certain situations,
contain cartilage-cells [vid. infra), as well as common fat-cells, particu-
larly in the more lax tendons, as in the tendinous fibres of the in-
tercostal muscles, of the triangularis sterni, masseter, &c.

The transversely banded aspect of the tendons, to which their glisten-
ing appearance is due, depends simply upon the numerous curves of
their fibrils, which correspond with each other throughout the fasciculus ;
this appearance is destroyed when the tendon is forcibly stretched, and
merely indicates its innate elasticity, which comes into play in the
relaxed condition.

The primary tendinous fasciculi, according to Donders and Mole-
schott, are seen in transverse sections treated with potass. This reagent,
according to them, separates the secondary fasciculi into smaller ones,
each of which consists of from 5 to 10 primitive fasciculi. In moistened
transverse sections of dried tendon of man and the mammalia, I can
very distinctly recognize the primitive fasciculi, although they have
extremely delicate outlines. The appearance thus obtained affords an
indistinct image of that presented in a transverse section of muscle.
Even the very fibrils are, in this way, rendered distinct, a circumstance
which appears to me of the greatest importance. When a transverse,
not a longitudinal, section of tendon moistened with water or acetic acid
is examined, there will be observed in all the secondary fasciculi, or in
the primary when they can be distinguished, if not in all, yet in most
cases, an extremely regular and minute punctation, nearly like that of
the muscular fasciculi (Fig. 90), only not quite so distinct. The appa-
rent granules are pale, round, of the same diameter as the tendinous
fibrils which are obtained in other ways, and can be explained in no
other manner than as beinn; the transverse sections of such fibrils.

Fig. 96. — Tendon of the tibialis posticus (Man), magnified 60 diameters: a, secondary fas-
ciculi; b, thicker nuclear libres ; f, interstitial connective tissue.

THE MUSCULAR SYSTEM.

235

These facts, bettor than any other, contradict Reichert's view, according
to wliich the tendinous tissue is composed of a homogeneous substance.
( Vid. § 24, note.)

§ 81. Connections of the Tendons with other parts. — The tendons are
connected on the one side with the muscles, and on the other with the
various parts moved by the muscles. Even by the naked eye, it may
be seen that the former connection is effected in the one case in such
a way that the tendon and muscle are continued into each other recti-
linearly, and in the other so that the muscular fibres, with rounded
extremities, join the borders and surfaces of the tendons and aponeuroses
at an acute angle, as in the instance of the penniform muscles. The
microscopic conditions in these two cases are widely different. In the
former, the muscular fasciculi pass immediately into those of the tendon,
in such away that no sharply-defined limit exists between the two tissues,

g^:':^-:Vs

iyfe

ifefL.i'

and the entire fasciculus of muscular fibrils is con-
tinuous with a nearly equal-sized bundle of tendinous
fibrils (Fig. 97). Extraordinary as it may sound, I
must say — in order to describe the impression that
this sort of conjunction of muscle and tendon gives
me — that it is that of a continuous connection of the
muscular and tendinous fibrils. Where the muscular
fasciculi join the tendons and aponeuroses at an acute
angle, we find, in complete contrast with the condition
just described, an abrupt limit between the muscle
and tendon (Fig. 98). For, in this case, the fibres of
the muscle really end, for the most part, obliquely
truncated, with a slightly conical projecting terminal

Fig. 97. — A primitive fasciculus: a, from one of the internal intercostal muscles of Man,
continuous into a tendinous fasciculus, b, into which it passes without any defined limit. —
Magnified 350 diameters.

Fig. 98. — Disposition of the muscular fibres at their oblique insertion into the tendon of
the gastrocnemius (Man): a, a portion of the tendon cut longitudinally; 6, muscular fibres
■with slightly conical or truncated extremities, affixed in small depressions on the inner
aspect of the tendon, to the border of which the pcrimijsium intermun, c, is connected. — Mag-
nified 350 diameters.

236 SPECIAL HISTOLOGY.

surface, or, more rarely, perceptibly attenuated, though always rounded,
and are attached at a more or less acute angle to the surfaces of the
tendons and aponeuroses, and on the borders of the former. Notwith-
standing this, however, the connection between the two tissues is of the
most intimate kind. The extremities of the primitive fasciculi are in-
serted into minute pits in the surface of the tendon, whilst, at the same
time, the connective tissue between them, the perimt/siuni internum, is
continuous with that on the surface of the tendon. These relations are
best observed in muscles which have lain a long time in spirit, or been
boiled ; in which, also, the sacciform blind extremity of the sarcolemma
may occasionally be clearly seen. The last-described condition occurs
whenever muscular fibres and tendons meet obliquely, consequently in all
semipenniform and penniform muscles ; in those whose tendons of inser-
tion commence as membranous expansions [soleus, gastrocnemius, &c.),
and which arise from the surfaces of fasciae, bones, and cartilages.
Where, on the other hand, aponeuroses or tendons, with their elemen-
tary tissues, join muscles in a straight line, a real transition, for the
most part, takes place between the tendinous fasciculi and muscular
fibres, but not always, for, even in such apparently rectilinear transition
of muscles into tendons, there is frequently an oblique insertion of the
former, with free extremities, though at very acute angles ; in such
cases, for instance, as where tendons penetrate deeply into the substance
of a muscle, and there divide into separate fasciculi. From what I have
hitherto observed, there are many muscles in which all the fasciculi
connected with tendons begin or terminate free, and indeed scarcely
one in which tliis is not the case, with a greater or less number of fas-
ciculi ; whence it may be deduced, as a general rule, that the tendons
have for the most part a less diameter than the muscles.

Besides muscles, tendons are connected with bones, cartilages, fibrous
membranes {sclerotica, sheath of the optic nerve, tendinous fascia),
ligaments, and synovial membranes {suhcruralis, &c.). With the first-
named textures, the connection is either indirect, with the intervention
of the jyeriosteum and perichondrium, into the similarly constituted
elements of which the tendinous fibres, for the most part, are continuous,
or to the thickness of which they appear to add or direct. In the latter
case [tendo Acldllis, tendons of the quadriceps, j^ectoralis major, del-
toideus, latissimus dorsi, ilio-psoas, glutcei, &c.), the tendinous fasciculi
rest, at an acute or right angle, on the surface of the bones, and become
attached, without the intervention of the periosteum, which is wholly
wanting in these situations, to all the elevations and depressions of the
surface (Fig. 99). Close to the bones, the tendons frequently contain,
throughout a certain extent, delicate, isolated cartilage cells, which
are sometimes, however, contiguous and disposed in small rows. In
exceptional cases, I have also seen the tendinous fibrils, at their extre-

THE MUSCULAR SYSTEM.

OQ'

mities next the bone, entirely incnisted with calcareous salts, in the
form of granules (ossified). In fibrous membranes, the tendons cease

FiK. 99.

quite imperceptibly, and without any interruption of continuity {tensor
fascioe, biceps humeri).

In man, I must positively deny that the tendinous fasciculi are ever
connected merely with the sarcolemma (Reichert). Nor could I satisfy
myself that this is the case in the River-crab, in which the tendons, it
may be remarked, consist of chitine. Whilst other animals have afforded
indubitable evidence of the existence of the same conditions as in man,
the Frog, in particular, presents evidence of this fact ; in the tadpole
of which, owing to the sparing development of pigment in the tail, the
transition of the extremities of the muscular fibres, which are frequently
divided into three and five serrations, into the same number of minute
tendons, may be very distinctly seen. In the caudal muscles, also, of
the Cod, I noticed, very distinctly, the continuous connection of the
tendons and muscles ; in this case, owing to the shortness of the muscles,
many muscular fibres were even seen in their entire length, together
with the tendinous fasciculi at each end.*

Fig. 99. — Insertion of the tmdo Jlcldllis into the calcaneum of a Man sixty years old : A,
bone with lacunae, a; canalli and fat-cells, 6; J5, tendon with tendinous fibrils and cartilage
ceils, c. — Magnified 300 diameters.

* [There can be no do\ibt that both the modes of connection between muscles and their
tendons, described above, exist. Is it not possible that the gradual transition or the sliarp

238 SPECIAL HISTOLOGY.

§ 82. Accessory organs of the 3Iusdes and Tendons. — A. The mus-
cular envelops or fasciae are fibrous membranes surrounding single
muscles or entire groups of muscles, together with their tendons. They
differ in structure according to the degree in which they partake of the
character of tendons and ligaments, or of simj)le muscular sheaths ; in
the one case presenting that of tendons, and in the other of membranes
composed of connective tissue and elastic fibres. In the former case
they are white and glistening, and exhibit, in all respects, the structure
of tendons and aponeuroses ; in the latter they frequently contain a
larger quantity of fine elastic fibres in their connective tissue, and in
some places may even assume the structure and dull-yellow aspect of
the elastic membranes {vid. Fig. 49), and contain a close elastic network
of the strongest kind. The fascice are always of the tendinous character,
where for some mechanical purpose a tough unyielding structure is
requisite. They are of this kind, therefore : — 1. At their origin from
bones. 2. Where muscles arise from them, and they are of the nature
of aponeuroses. 3. Where tendons radiate into them, and they them-
selves act as terminal tendons. 4. Where thickened portions of them
supply the place of ligaments. On the other hand, they are more or
less elastic where they constitute a firm envelop to the muscles, but, at
the same time, one which does not impede their changes in form. This
is their character, especially in the middle of the limbs.

[The memhrance interossece (forearm, leg, foramen ovale), which are
not usually reckoned among the fasciae, are not apparently of the nature
of ligaments of the bones, but rather of intermuscular ligaments. The
plantar and palmar aponeuroses serve, in part, as tendons for the smaller
muscles of the hand and foot, but chiefly as ligaments for the retention
of the fl-exor tendons, in which respect they are analogous to the lig. cruci-
atum emyi dorsale, &c. In them, even in the adult, the entire course of
development of the nuclear fibres (minute elastic fibres), may be studied.
Between the fasciculi of connective tissue, straight series of 10 to 20 and
more, thickly placed, elliptical cells of 0-006 to 0-012 of aline, with round

line of demarcation between the muscle and its tendon may have some connection with the
age and completeness of the particular bundle examined? In the Frog, we have noticed
that, among neighboring bundles, some exhibit transitions between the proper muscular
tissue and the tendon, while others have the former very sharply defined ; and the exami-
nation of the insertion of the triceps extensor cubiti of a seven-months' fcEtus has afforded us
the most evident transitions from tendon into muscle, although the insertion of the bundles
is here very oblique. The best way of expressing the mode of connection of muscles with
their tendons, perhaps, woidd be to say that the matrix of the muscle and the matrix of the
connective tissue, into which it is inserted, whether in the form of tendon or otherwise, are
invariably continuous; the appearance of continuity or of discontinuity of the tv/o tissues)
arising solely from the sudden or gradual cessation of the deposit of the sarcous elements at
their point of junction.

The nature of the corpuscles which are to be found at the junction of tendons with bones
and cartilages — Professor KOlliker's "cartilage-corpuscles" — has been adverted to in the
note at p. 97. — Tks.]

THE MUSCULAR SYSTEM. 230

nuclei, and 2 to 6 minute opaque fat-granules, occasionally occur ; tlie
cells afterwards disappear, and the nuclei, which, on the addition of
acetic acid, appear a little yellowish, become more and more elongated,
and transformed into long, slender, straight, or slightly-curved fibres,
which are, finally, conjoined into long nuclear fibres; these fibres, how-
ever, upon the whole are rare. The elongated nuclei are not always
placed in a straight line, one behind the other, but frequently in an ob-
lique, and in various other directions. In this way are produced serpen-
tine nuclear fibres, which, even when fully formed, are still surrounded
with isolated fat-granules, and lie as it were in vacant spaces in the con-
nective tissue. In this case, consequently, the nuclear fibres are not
formed from the nuclei of the cells, from which the connective tissue is
formed, but from special cells of a temporary nature; which circum-
stance, were the fact of general application, would make it intelligible,
that nuclear fibres may both surround the secondary fasciculi of connec-
tive tissue, and also exist without any such tissue (membranous reticular
expansions of nuclear fibres, " Micr. Anat.," II. 1, p. 226)].

B. Ligaments of tlie tendons. — The tendons are retained in their posi-
tions by various ligaments. Independently of certain ligamentous por-
tions of the fasciffi, which, being attached to the bones, form tubular
processes around tendons, or otherwise confine them, there are the so-
called tendinous sheaths {Jig. vaginalia te7idinum), as for instance on the
flexor tendons of the fingers and toes, where they are formed of nume-
rous successive narrow bands, which in these situations serve to strengthen
the mucous sheaths. Other ligaments to be referred to this class, are
the lig. catyi pj-oprium, the trocldea, and the retinacula tendinum.

C. diucous biirsce and sheaths, — bursa' mucosa; et vaginoi synoviales. —
Where muscles or tendons, in their movements, rub upon hard parts
(bones, cartilages), or on other muscles, tendons, and ligaments, there
are found, between the parts in question, spaces filled with a slightly
viscid fluid, which, according to Virchow (WUrzb. "Verb." II. 281),
contain not mucus, but a material very similar to colloid matter, and
wdiich anatomists have been used to regard as lined with a special mem-
brane, a synovial m»mhra7ie. These spaces are said to constitute closed
sacs of a rounded or elongated form, which either simply invest the
opposed surfaces of bones and tendons, bones and muscles, &c., — bursce
mucosce ; or in the form of double, although connected tubes, cover at
the same time the surface of the tendons, and of the parts between
which the tendons play, — vagince synoviales. The truth of the matter
is this, that it is only the smallest- of these spaces which are lined with
a continuous membrane; most of them are in many situations without
such a lining. With respect to the mucous bursse, those appertaining to
the muscles {psoas, iliacus, deltoid, &c.), are, eminently, to be consi-
dered as continuous sacculi, whilst in those belonging to the tendons, a

240 SPECIAL HISTOLOGY.

membrane can only be detached in parts, and is found to be almost
■wholly wanting exactly at the points where the mutually gliding parts
are in contact. Precisely tlie same thing obtains in the synovial sheaths,
among which the common sheaths of the flexor tendons of the fingers
and toes, only in a certain measure, retain the form of a so-termed
serous sac, although, even in this case, many parts of the surface of the
tendons are without any such membranous lining. Whence it would
appear, that in this case, as in many others, the old doctrine of the ex-
istence of continuous serous sacs requires thorough emendation. In
most of the synovial sheaths, and in many mucous bursse, are found
occasionally, particularly in the retinacula, smaller or larger, reddish
fimbriated processes, exactly resembling those of the joints, and which,
in like manner, are nothing but vascular processes of the synovial mem-
brane.

D. Fihro-cartilages and sesamoid hones. — The tendons of some muscles
{tibialis posticus, peronceus longus), in those portions which run in the
tendinous sheaths, contain, imbedded in their substance, dense semi-carti-
laginous bodies, which are known under the name of sesamoid cartilages
[fibro-cartilagines sesamoidcoi), and when, as occasionally happens, they
become ossified, of sesamoid bones {ossa sesamoidea) ; the latter occur
normally, imbedded in the flexor tendons of the fingers and toes, pre-
senting one surface towards an articulation.

Respecting the more intimate structure of the last-mentioned parts,
the following is to be remarked. The sesamoid bones consist of common,
finely cancellated osseous substance, are on one side closely surrounded
by tendinous or ligamentous tissue, and on the other, which is invested
with a thin layer of cartilaginous substance, project into an articulation.
The ligaments of tendons, in correspondence with their function, possess
exactly the same firm structure as that of the tendinous portions of the
fascice and of the tendons themselves, and exhibit occasionally fine elas-
tic fibres in process of development, or the round formative cells of such
fibres disposed in rows. The retinacula tendinum have a more delicate
structure ; their function being rather to convey vessels to the tendons,
they consequently contain chiefly a more lax connective tissue, with fine
elastic fibres, and also fat-cells. The mucous bursre, which are invariably
thin-walled, consist, in as far as they possess a distinct membrane, of
fasciculi of connective tissue, crossing each other in the most various
directions, loosely connected, and in many places anastomosing, toge-
ther with some fine elastic fibres. The mucous sheaths, on the other
hand, in agreement with their double function, which in one respect is
that of a mucous bursa, and in another that of ligaments confining the
tendon or of tendinous sheaths, present in their thinner parts the struc-
ture of hursce mucosce, and in the thicker, an unmixed, dense connective
tissue, frequently with cells disposed in rows, which pass into elastic

THE MUSCULAR SYSTEM. 241

fibres. Both of these kinds of sacs are lined, on the inner surface, to-
gether with the parts contained in or otherwise bounding them, but onlj
in phices, with an epithelium, consisting for the most part of a simple layer
of nucleated polygonal cells 0-004-0-007 of a line in diameter. The parts
which are bare of epithelium, are: — many portions of the mucous sheaths,
and the tendons lying in them, and certain spots of the bursce mucosce
themselves, which are distinguishable by their dull lustre and yellowish
aspect, and which occur especially in those situations where the tendons
and parts surrounding them are exposed to a greater degree of pressure.
The common flexor sheath of the fingers is lined throughout with epi-
thelium ; and the same may be said of the mucous bursas, in which it is
only certain loop-like ligaments, which beyond the limits of the bursse
still surround the tendons, that do not present any cellular covering, as
is the case, occasionally, in the subscapularis poplitceus, &c.

All these bare places, which are uncovered by epithelium, invariably
exhibit, almost throughout, the nature o^ fibro-cartUages, the dense con-
nective tissue of which they are composed, and which for the most part
is furnished with but few elastic elements, containing a greater or less,
often a very considerable number of cartilage-cells (Fig. 99), amongst
which, the most frequent are rounded

. Fig. 100.

cells, with a dark contour, although by
no means with thick walls, measuring
0 •006-0-012 of a line, with a roundish
nucleus of 0"003 of a line, and clear fluid,
with or without some minute, opaque fatty granules. Besides these,
there are, moreover, elongated cells, with one or two nuclei ; round,
thin-walled cells, containing 1, 2-20 secondary cells, with thick walls,
and dark contours ; the mother-cells measuring as much as 0'02-0-03 of
a line ; and lastly, elongated cells, with concentric deposits, inclosing a
nucleus, or nucleated secondary cell. In the tendons, the simpler forms
of cells almost exclusively occur, and the cells, although frequently ex-
tremely numerous, are for the most part isolated, or, at most, disposed
in rows or groups of 2-6, which are contained in the connective tissue,
both superficially and more deeply. In most cases, the common con-
nective tissue alternates with one more resembling fibro-cartilage, so
that the tendon, on a transverse section, presents a speckled, white and
yellowish aspect ; or it maybe, that the outer surface only of the tendon
contains cartilage, the deeper portions retaining their usual condition.
Where the deposition of the cartilage cells is most abundant, the tendons
become thickened, or even studded, as it were, with distinct, fibro-carti-
laginous masses {peroneus longus, tib. posticus). In the raucous bursje
and the other parts above named, the cartilage cells are placed, not un-

FiG. 100. — Cartilage-cells from the vaginal ligaments surrounding tlie temions of the
/>op/i/£PMS, magnified 350 diameters: a, cell with one; 6, with two nuclei; c, cell with one;
d, with two secondary cells, both of which have rather thick contents.

16

212 SPECIAL HISTOLOGY.

frequently, in closer aggregation, or in longer rows of 5-10 cells or
more, in which rows the terminal cells are invariably the smallest, and
the middle ones the largest. On the cuboid bone, where the tendon of
the peroneus longus passes over it, there is a layer of true cartilage
-^— I a line thick.

The vascular processes of the tendinous sheaths and mucous bursse,
correspond with those of the articulations, only that they are for the
most part of smaller size.

The synovial sacs of the muscular system are not mere meshes of
connective tissue, like the subcutaneous mucous burs£e, since they have,
invariably, an epithelial lining in certain places ; they bear just as little
resemblance, however, to the proper serous sacs [2jleura,peritonceum, &c.),
because, with a few exceptions, their epithelium is never complete, and
also because the cellular coat of the serous membrane is almost uni-
versally wanting entirely in some spots. The synovial sacs of the mus-
cular system, on the other hand, and the synovial capsules, which also
never possess a complete epithelium, and frequently communicate with
mucous bursas {quadriceps femoris, pop)liteus, subscajndaris, &c.), belong
to one and the same category, and differ in some points from the serous
sacs ; with respect to which, however, it must not be forgotten that transi-
tionary forms between these two kinds of sacs exist.

No one seems to have remarked upon the occurrence of cartilage cells
in the various textures which go to the construction of the synovial sacs
of the muscular system (except in the fibro-cartilages of the tendons);
and the more so, because even Henle refers the fibro-cartilage of the
tendinous sheaths to his interarticular cartilages (bandscheiben). It is
quite true that the cartilage cells, while often occurring isolated in the
connective tissue, or more frequently only in certain spots aggregated
together, are not always readily seen ; they may, however, be recognized
in sufficiently thin sections, and very distinctly on the addition of acetic
acid. The cell-membranes are not in this case utterly destroyed, any
more than they are in the cartilage cells of the interarticular
ligaments, &c., and no doubt can be entertained as to their being
true cartilage cells, which, almost without exception, exist, not as a
tissue, but rather dispersed in the connective tissue. Those spots
in which they exist in great quantity may be described as fibro-car-
tilaginous places; but the distinction between these fibro-cartilages
and those of true fibres not of the nature of cellular tissue (epiglottis,
ossifying bones), must not be lost sight of. Genuine cartilage, as on
the cuboid bone, I have never as yet met with in any other tendinous
sheath; not even in the sulcus malleoli externi et interni ; in the sulcus
of the heel ; nor in the sheath of the peronceus on the longus calcaneum ;
in which situations, cartilage cells are, indeed, everywhere to be seen,
but only scattered in the connective tissue.

THE MUSCULAR SYSTEM.

243

"With respect to the rows of cells which are met with in ligaments of
the tendons, and in the tendinous sheaths, the nuclei of which, after the
disappearance of the cell, continue to grow and arrange themselves
together in the form of nuclear fibres, I cannot avoid remarking upon
their close resemblance to the more simple cartilage cells of the ten-
dinous sheaths and tendons, a resemblance so close, that I should almost
be inclined to indicate it as marking their identity, if it did not sound
altogether strange, to speak of a transition of the nuclei of cartilage cells
into nuclear fibres. If not as identical, still they may be regarded as
analogous formations ; and the rather so, because in almost every case
where cartilage cells occur in the connective tissue, rows of cells of this
kind, and their relation to elastic fibres may be shown to exist, as well
as in the interarticular cartilages, or ligamentous discs of Henle, as they
are termed, afterwards to be described. On the other hand, it is true,
similar rows of cells are to be found in the palmar fascia, tendons and
ligaments, although those structures possess no indubitable cartilage-cells.

§ 83. Vessels of the 3Iuscles and tlieir accessory Organs. A. Blood-
vessels.— The ramifications of the larger vessels present little that is
peculiar. The trunks reach the muscles in an oblique or transverse
direction and then subdivide, running
in the |>crm?/siMm internum, in an
arborescent manner, and at acute or
obtuse angles, so that every part of
the muscle is supplied by them. The
minutest arteries and veins usually ^^.-
run parallel with the muscular fibres,
between which they constitute a vas-
cular plexus, so characteristic that,
once seen, it can never be mistaken.
The interstices of the plexus are rec-
tangular, with the longer sides parallel
to the longitudinal axis of the muscle,
and it is of course composed of two ^.
sets of vessels, one longitudinal, which,
as is shown most conclusively in trans-
verse sections of injected muscle, lie
in the fissures between two muscular
fasciculi, or in the irregular spaces
left between several of them, and the
other transverse, which anastomosing
in various ways with the former, surround the muscular fibres.

Thus

Fig. 101. — Capillary vessels in muscle, magnified 350 diameters: a, artery; 6, vein;
c, capillary plexus.

24i SPECIAL HISTOLOGY.

each separate primitive fasciculus is lodged, to a certain extent, in a
plexus of capillaries, and being surrounded on all sides by them, is
very abundantly supplied with blood. The capillaries of muscle are
among the most minute in the human body, their diameter being often
less than that of the blood-corpuscles themselves. In one of Hyrtl's
preparations, they measure O-0025-O'OOo of a line ; in the 2y^GtoraUs
major, -when filled with blood, 0-002-0-003, and when empty 0-0016-
0-0020 of aline.

The tendons may be reckoned amongst those parts of the body which
are the most scantily supplied with blood-vessels. The smaller tendons,
in the interior, present no trace of vessels, whilst externally, in the more
lax connective tissue by which they are surrounded, there exists a wide-
meshed capillary plexus. In the larger tendons, a few vessels occur in
the superficial layers, and in the largest, by means of the microscope
and injection, a scanty vascular fietwork may also be rendered evident
in the deeper layers ; but even in this case the innermost portions of the
tendon are entirely without vessels. The tendon-ligaments present the
same conditions as the tendons, only, that in them even still fewer ves-
sels can be perceived. The thinner fascias, also, are altogether non-
vascular ; sparing ramifications, exclusive of those in the lax connective
tissue, amply supplied with blood-vessels, which covers their surface,
are found in the thicker fasciae, such as the fascia lata. The synovial
membranes of the muscular system, on the other hand, are very vascular,
and especially their processes ;* with respect to these synovial mem-
branes, however, since they agree in all respects with thesynovial capsules
of the osseous system, nothing further need be remarked in this place.

B. The muscles are very scantily supplied with lymphatics ; the
smaller muscles, in fact, such as the omohyoid, subcruraT, &c., have none
at all, either in their substance or on the surface ; and among the largest
muscles, it is only in some, that solitary lymphatics, measuring |- and J
of a line are seen accompanying the blood-vessels. The deep or mus-
cular blood-vessels in the extremities, it is truej are accompanied by
lymphatics, but these are few in number ; and from the latter two circum-
stances, it may be concluded, that even the larger muscles are but poorly
supplied with these vessels. If they had not actually been observed in
the fasciculi in certain cases, it might have been a question, whether
muscles in general did possess lymphatics at all ; the occurrence of
the deep lymphatic vessels proves nothing towards this, it being quite
possible that the contents of these vessels, scanty as they are, might be
derived from the skin [vola manus, planta pedis, &c.), from the joints,
or perhaps from the bones. It may also be concluded, that if a few

* [The vessels generally form loops, which communicate with each other by means of
delicate branches, and which can readily be traced to the extremity of each process. — DaC]

THE MUSCULAR SYSTEM. 245

lymphatics really exist in the larger muscles, they do not run among the
secondary fasciculi, but only in the more vascular jy'.rimyslum between
the larger and more lax subdivisions, and especially where the latter
contains adipose tissue, and is consequently soft, as, for instance, in the
glutceus, and in the superficial layers of the muscles.

Lymphatic vessels have never yet been noticed in tendons, fasciae,
and the synovial capsules of the muscular system. At the same time,
it cannot be said, at all events in the latter instance, that lymphatics
may not, as in other serous membranes, be contained in the sub-serous

connective tissue.

•

§ 84. Nerves of 3Iuscles. — The distribution of the muscular nerves,
■with respect even to their coarser relations, presents considerable pecu-
liarity, it being evident, in most muscles, that the nerves come in con-
tact with their fibres only at a few limited points, and are by no means
connected with them throughout their entire length. With respect to
the ultimate termination of the nerves, it may be stated that in all
muscles there exist anastomoses of the smaller branches, forming the so-
termed "plexuses." These anastomoses among the larger branches
are seen chiefly, if not altogether, where the entire ramification of the
nerves takes place within an extremely limited compass [vid. note) ;
elsewhere they rarely occur, or are wholly absent. Those between the
smaller and smallest branches {terminal plexuses, Valentin), on the
other hand, are very numerous everywhere, forming elongated roundish
meshes, which run for the most part parallel with the longitudinal
direction of the fasciculi. These terminal plexuses, composed, some-
times of smaller, sometimes of larger, meshes, and formed principally
by the ramules of one small branch, though not altogether isolated one
from the other, proceed to form what are termed by Valentin the ter-
minal loops; by which I understand nothing more than anastomoses of
the ultimate twigs, effected by means of one or a few primitive fibres
passing from one twig into another. It is consequently unimportant
whether they follow a straight course, or are curved in a looplike form
(Fig. 102). Whether, besides these loops, there are also free termina-
tions of the nerve-fibres, such as are known to exist in the lower animals,
and as I believed I once noticed in a Rabbit, is altogether doubtful;
whilst it is certain that, even in man, divisions of the nerve-fibres take
place, although they are rare, and detected with difficulty, and their
relation to the loops, it must be confessed, is still to be made out.

The trunks entering the muscles are composed principally of thick
nerve-fibres, about twelve of the finer ones occurring, on an average,
among 100 of the larger (Volkmann). They become smaller in the
interior of the muscle, so that the terminal plexus consists only of
extremely minute fibrils, measuring 000-1-0-0025 of a line in diameter.

246

SPECIAL HISTOLOGY.

In some cases, even, the gradual attenuation of the fibres may be
directly observed, proving that the diminution in size does not take
place, in this case at least, in consequence of division. Thus, in the

Fis:. 102.

Fiir. 103.

omohyoid, I have noticed several nerve-fibres of 0'004-0-0053 of a line,
derived from trunks measuring 0'05-0-07 of a line, become attenuated
(within a distance of 0-15-0-2 of a line), to a diameter of 0-002-0-0026
of a line, and, after a further course of 0-4-0*5 of a line, acquire that
of the smallest fibrils, or 0*001 of a line. Simultaneously with this
change in size, the nerve-fibres assumed in all respects the aspect of the
so-termed sympathetic nerves, and ultimately became pale, with a simple
contour line, and disposed to form varicosities ; at the same time that
they appeared to lose every vestige of a coat composed of connective
tissue, they still retained dark borders, and consequently Avere not non-
medullated fibres (or free axis-cylinders), such as are seen in other ter-
minations of nerves.

Nervi vasoruni (vascular nerves), accompanying the bundles of vessels,
occur in all muscles, and, according to the size of the latter, form
larger or smaller branches. They are composed only of the smallest
fibres, and always follow the course of the large vessels, which can still

Fig. 102. — Ultimate expansion of the nerves in the omohyoid muscle of Man, magnified
350 diameters, and treated with soda: a, interstices of the terminal plexus; b, terminal
loops ; c, muscular fibres.

Fig. 103. — Divisions of the primitive nerve-fibres in muscle, magnified 350 diameters :
»4, double division from the omohyoid muscle in Man; a, neurilemma ; Jj, division of a
nerve from a facial muscle of tlie Rabbit into three apparently pointed twigs.

THE MUSCULAR SYSTEM. 247

be recognized as arteries and veins. I have not seen how they termi-
nate ; and this much only I know — that they are never met with on the
capillaries, and very frequently, also, are not to be found on the smallest
arteries and veins. Occasionally, one or more fibrils from the terminal
plexus of the muscular nerves may be seen to join these vessels ; a cir-
cumstance quite in accordance with the demonstrable fact that the vas-
cular nerves in many parts, for instance in the extremities, are derived
from the spinal nerves. ,

The smaller tendons contain no nerves, and the larger, such as the
tendo AchiUis and the tendon of the quadriceps femoris^ only vascular
nerves. The fascke and sheaths of tendons are also Avithout nerves, as
well as the synovial capsules of the muscular system, so far as I am at
present aware.

In many of the small muscles, the extent of space included in the
distribution of the nerve is extremely limited, as for instance in the
superior belly of the omohyoid, in a portion of which, three inches long,
the space over which the nerves are distributed, does not exceed from
five to eight lines in length. The trunk of the nerve entering in the
middle of the transverse axis, divides into tAvo equal primary branches,
one passing towards the left, and the other towards the right, border of
the muscle, and each giving rise to numerous anastomosing branches of
all sizes, and thus supplying the entire thickness of the muscle from the
most superficial to the deepest layers. Whilst this distribution of the
nerve takes place at one point, — a distribution not unlike that in an
organ of sense, — the rest of the muscle presents the utmost poverty, or
even a complete deficiency, of nerves. In one case, which I examined
closely, I was unable, besides the few vascular nerves in these portions,
to detect more than three small nervous twigs of 0-021, 0-028, 0*042 of
a line, which, though derived from the main nerves, differed from the
other branches in their distribution. Two of them ran directly towards
the lower, and one towards the upper, end of the belly of the muscle,
giving off a few filaments composed of one or two primitive fibrils which
passed through the muscle, and terminated, a little before reaching the
intermediate and terminal tendons, in the most minute twicrs and single
nerve-fibrils. I found the same conditions of the nerves in the sub-
cruralis, and in one of the costo-cervical muscles (arising from the first
rib in the cervical fascia), as in the omohyoid ; in the sternohyoid,
sternothyroid, omohyoid (inferior belly), the same condition in some
parts was noticed, whilst, in others, one apparently different existed,
that.is to say, the branches of the nerves frequently did not all divide
at the same level, but were more widely spread. It was easily seen,
however, that the above-described mode of division essentially obtained,
also, in this case, — viz. : that the separate portions of the muscles are in

248 SPECIAL HISTOLOGY.

connection iintli the nervous plexuses, only at a point of limited extent.
The proof of the existence of similar conditions in other small muscles
■was more difficult, as in those of the orbit, where the nerves reach the
muscles at acute angles, follow a longer course in them, with their
primary branches, and form their ultimate ramifications at various,
more or less widely separated points ; yet even in this case it was
tolerably well made out. It is easy to understand that, in the larger
muscles, a microscopic examination, in toto, is impossible ; but it can be
shown in other ways, as by the preparation and examination of minute
flat fasciculi taken in their entire length, that conditions exist, at all
events in some of them, similar to those which appear to be evidenced
in the small muscles. It is thus seen, especially in muscles of lax
structure, that each fasciculus presents precisely the same conditions as
an entire smaller muscle. How the distribution of the nerves is effected
in muscles with long fasciculi {sartorius, latissimus dorsi, &c.), I have
not examined ; it is probable that in this case each primitive fasciculus
is joined by the nerves at several points, widely apart.

Valentin and Emmert, in the year 1836, simultaneously described the
terminations of the primitive nerve-fibres in the muscles, to be in the form
of loops, and the former maintained that the nerves of sensation termi-
nated in a similar way. But Physiology having more recently shown
that she does not well know what is to be done with these loops, and
Microscopic Anatomy having distinctly demonstrated the existence, in
many situations, of other modes of termination of the nerves (Pacinian
bodies, &c.), the loops have fallen into such discredit, that the question
now is, not as before, whether, besides the loops, there are other modes
of termination, but rather, whether loops really exist anywhere ? With
respect to the muscles especially, anatomists seem inclined to deny their
existence altogether, since divisions and terminations of nerve-fibres have
been discovered in them; but this conclusion, from what has been re-
marked above, would be incorrect. Henle also, in Canstatt's Jahresb.
f. 1847, p. 63, says, that in his opinion the loops had been too rashly
discarded; while on the other hand, Wagner, with reference to this ques-
tion, places the analogy with what is seen in the Frog, &;c., above direct
observation, and denies the existence of loops. With respect to divisions
of the nerves, Wagner ("Gott. Nach.," 1852, p. 27), finds them to be
tolerably frequent in the muscles of the Mouse. I would, moreover, re-
mark, that in one case, I think I noticed a minute ganglion with about
five, cells on a nervous twig in the omohyoid of man; the observation,
however, was not satisfactory, the muscle having been previously treated
with soda.

In the Invertebrata, many observers have long since described free
terminations of the nerve fibrils, and their insertion with expanded ends
into the muscular fibres, as Doyere in the Tardigrada, and Quatrefages

THE MUSCULAR SYSTEM. 249

in UoUdina, and some Rotifera ("Ann. d. Sc. N.," 184o, p. 300, and pi.
11, fig. 12). I myself, in a larva of Cliironomus (a dipterous insect),
noticed a single nerve-fibre, proceeding to the two muscular fasciculi of
the simple tarsus, bifurcate into two branches, which were implanted upon
the surface of the muscle, with somewhat expanded terminations. In
the Vertebrata, Miiller and Brlicke first described division of the nerves
in the orbital muscles of the Pike (J. Miiller, "Physiol.," 4th ed. vol. 1,
p. 524), and in Ampliioxiis, Quatrefages noticed conditions precisely like
those met with in the Invertebrata above mentioned. The observation
is easily confirmed, as respects the orbital muscles of the Pike, in which,
upon the teasing out of the fasciculus either of the fresh muscle as well
as after it had been treated with corrosive sublimate, and rendered trans-
parent by acetic acid, numerous divisions of the nerves are apparent.
They are nevertheless not nearly so frequent in this case, as in the Frog,
nor are the divisions more than bifid or trifid. Besides this, I was espe-
cially struck with the glaring contrast that was presented, to what is seen
in the Mammalia, in the enormous extent of space included in the dis-
tribution of the nerve-fibres; a distribution so extensive, that it is by no
means easy to find a single primitive fasciculus which has not a nerve-
fibre going to it; in many places even, the latter were seen in apposition
with a fasciculus throughout a great extent, and surrounding it with
loops, or with a variable number of spiral convolutions. A similar con-
dition was observed by R. Wagner in the orbital muscles of the Torpedo,
whilst in other muscles the nerves were very scantily supplied ("Gott.
Nach,," Oct., 1851). In the Amphibia, divisions and free terminations
of the nerves have been described by Wagner. The former are remark-
ably beautiful and numerous. They commence in nerve-fibres, measur-
ing 0-004-0-006 of a line, in the smaller trunks and branches, and are
several times repeated, with a gradual diminution of the fibres, until
extremely minute filaments measuring 0-001-0-0015 of a line are
formed. The divisions are for the most part di- or tri-chotomous, more
rarely multiple; in one instance, however, Wagner noticed eight ramus-
culi. The ultimate filaments are pale, and have a simple contour line.
They never penetrate into the muscular fasciculus, but, after running a
short distance, are either applied obliquely or transversely to it, or proceed
for some distance in close contiguity and parallel with it ; in either case,
becoming attenuated to a sharp point, and frequently as fine as a fibril
of connective tissue. All these conditions are best seen in the mylohyoi-
deus (Wagner), and above all, in a delicate cutaneous muscle of the
thorax, as was pointed out to me by Ecker, and in which the distribu-
tion of the nerves has recently been very accurately described by Reichert.
He observed in this case, as I had done in man, that only a small por-
tion of the muscle was well supplied with nerves, which were but spar-
ingly distributed to the other portions. The trunk of the nerve supply-

250

SPECIAL HISTOLOGY.

ing the 160-180 fasciculi of this muscle, contains, according to Reichert,
7-10 fibres, and ultimately, by continual division, forms 290-340

FifT. 104.

terminal filaments, so that there is more than one for each muscular
fasciculus.

§ 85. Chemical and Physical Relations of the 3Iuscles. — In 100
parts of fresh beef there are contained, according to Bibra, 72-56-
74-45 parts of water. The solid constituents (25-55-27'44) in a man
59 years old, were composed of a residue insoluble in boiling water,
alcohol, and ether, 16-83; soluble albumen and coloring matter, 1-75;
substance affording gelatine, 1-92; extractive matter and salts, 2-80;
fat, 4-24. The fat is derived chiefly from the blood, the fat-cells in the
muscles and their nerves, and in part perhaps from the muscular fibres
themselves, in which microscopic fat granules are, at all events occasion-
ally, evident. The gelatine is derived from the pei'imysium, in smaller
proportion also from the vessels and neurilemma; none, on the contrary,
is afforded by the sarcolemma, which is still apparent in muscles com-
pletely exhausted by boiling, whence (in opposition to Reichert) it is
evident that the sarcolemma should not be referred to connective tissue.
The inorganic salts and the albumen are principally afforded, probably
by the muscular fibre itself, as are also and above all the salts described
by Liebig and Scherer in the juice of muscles, of the lactic, acetic, bu-
tyric, and formic acids, the free lactic acid, the creatin and creatinin,

Fig. 104. — Divisions of nerve-fibres, in a small twig from the cutaneous thoracic muscle
of the Frog; magnified 350 diameters; a, bifurcation; b, threefold division.

THE MUSCULAR SYSTEM. 251

the siijrar of muscles or inosit, and tlic coloring matter, ^vllich substances,
even the last-named, are lodged partly in the fibrils themselves, partly
and chiefly, and this is the case especially with the albumen, in the in-
terstitial substance, by which the fibrils are connected together. The
16-83 parts of insoluble residue belong in part to the elastic tissue in
the vessels and pgr/wi^/smw, and to the smooth muscle in the vessels, but
principally to the muscular fibrils themselves, which, as we have before
seen (§ 27), consist of a substance allied to fibrin. The sarcoJemma is
less afi'ected by alkalies and acids than the fibrils, and approaches in its
nature more nearly to the memhrana propria of the glands, the walls of
the capillaries, and the membrane of many cells. The coloring matter
of the muscles (and the muscles themselves), like the blood, becomes
bright red in the air, or still more in oxygen gas, and is rendered dark
by sulphuretted hydrogen. It is extracted, and indeed readily, by water,
but not by salts, in which circumstance, that is to say, in an altera-
tion in the degree of concentration of the plasma with which the muscle
is imbued, is perhaps to be sought the principal reason for the readiness
with which the color of the muscles is altered in disease.

The muscles, although softer and more easily torn than the tendons,
possess, nevertheless, considerable tenacity, particularly during life, and
they have a certain degree of elasticity. During life, as has been cor-
rectly remarked by E. Weber, even when not under the influence of
the nerves, they are not for the most part in their natural form, but
stretched, or in a state of tension, and like harp-strings in the same
condition, exert an elastic force. This is satisfactorily shown when the
tendons of the extensor muscles in an animal's limb which is strongly
flexed, are cut through, the nerves having been previously divided,
whereupon the tendons are very considerably retracted (E. Weber).
This tension of the muscles varies very much, according to the position
of the limbs. It is very slight when the body is at rest with the limbs
semiflexed, still less or even wholly absent when a muscle falls into a
state of repose after it has acted powerfully upon the limb ; greater,
and manifested in the greatest degree, when the antagonists of a muscle
are acting with all their force. According to Weber, the living muscle,
when in a state of inactivity, may be compared with caoutchouc, seeing
that, like that substance, they possess a very great elastic extensibility ;
or, in other words, a slight but very jyerfect elasticity, as may be readily
perceived in the muscles even of dead animals, which may be alternately
stretched and allowed to retract. Owing to their elasticity, the muscles
offer scarcely any hindrance to the movements of the limbs, and in con-
sequence of its perfect nature, they recover their previous form and
length even after the greatest possible extension. This is exemplified
in the stretching of the abdominal muscles in pregnancy and in certain
pathological conditions. When the muscles are in a state of activity,

252 SPECIAL HISTOLOGY.

their elasticity alters in a very remarkable manner : 1. During the con-
traction they become more extensible or less elastic, on which account
they exert a much less force by their contraction than would otherwise
be the case, had their elasticity remained unchanged, and the same as
in the inactive condition. 2. The elasticity of the active muscle, in one
and the same muscle, is extremely variable ; it continues to diminish as
long as it is in action, whence arise the phenomena of fatigue and loss
of power in the muscles (E. Weber).

In the dead muscle, according to the same observer, the elasticity is
less i:)erfect; that is to say, the dead muscle, when stretched, does not
altogether resume its pristine form, and consequently is more readily
torn, although such a muscle as the gracilis may still be capable of sup-
porting a weight of eighty pounds without breaking. But at the same
time it is also less extensible, more rigid, less flexible, — or its elasticity
is greater. The phenomena of fatigue in the muscles are consequently
to be distinguished from those induced by death. In the former state,
the diminution of elasticity occurs during the influence of the nerves
and the contractions of the muscle itself, probably in consequence of
changed conditions in the molecular nutrition of the muscle, and is con-
sequently a vital phenomenon ; whilst in the latter case, innervation,
nutrition, and contraction have ceased, and the increase of elasticity,
which produces what is termed the rigor mortis, is a purely physical
phenomenon, and not to be confounded with the increased tension, which,
under the influence of life, takes place during the contraction of the
muscles, simultaneously with a diminution of the elasticity.

The tendons are very firm, and but slightly elastic; and contain,
according to Chevreuil, in 100 parts, only t)2"03 of water, considerably
less therefore than the muscles. They consist principally of a substance
affording gelatin, although they are transformed with more difficulty
than other parts into that principle.

In my opinion the muscles are sometimes in a state of tension, some-
times in their natural form, sometimes even compressed, and to all these
three conditions vital contraction may be superadded. If a muscle in
a state of extension contract, so as not to assume its natural form, it
will still be in a state of tension after the remission of the contraction,
and if divided will retract. On the other hand, if a muscle in its
natural form contract, it will, after the cessation of the nervous influence,
immediately become extended ; as, for instance, the contracted heart,
or an isolated muscle excited by galvanism. Consequently, when we
speak of the elasticity of muscles, their tension, not only when they
are extended, but also in the compressed condition, must be considered;
and this appears to me of some physiological importance, as in this Avay
the extension of contracted muscles (heart), and of muscles whose

THE MUSCULAR SYSTEM. 253

antagonists are paralyzed, becomes intelligible. With respect to the
cadaveric rigidity, the important facts have quite recently come to light,
that it may be arrested by the injection of blood (Bro\vn-S(iquard); and
also that it takes place even in the living animal, when the supply of
blood to a group of muscles is entirely cut off (Stannius). In the latter
case, the irritability of the nerves ceases at the same time, and on the
restoration of the circulation the normal conditions in both muscles and
nerves are also restored. By these facts, all hypotheses respecting the
occurrence of the cadaveric rigidity, except that of Weber, are contra-
dicted; even that of Brlicke, which asserts that it is caused by the
coagulation of the fibrin existing in the muscular fibre. But at the
same time the question also arises, as to what is the proximate cause of
the change in the elastic conditions of the muscles, whether it be due
to the death or cessation of activity of the nerves, or to the deficient
supply of blood to the muscles themselves ? Stannius decides in favor
of the former supposition, and is consequently driven to the conclusion,
that during life the motor nerves act upon the muscles, by reducing,
during the state of repose, their natural amount of elasticity, whilst in
the contraction of the muscle the influence of the nerves is momentarily
relaxed. Thus, according to Stannius, the rigidity connected with con-
traction, and vital contraction, would be identical, and nothing more
than the condition of the muscle when freed from all nervous influence,
and lasting until the nerve again puts the muscle into a state of rest,
or its substance is decomposed. I must own that in this view, which
moreover had already been proposed by Engel (" Zeitsch. der Wiener,"
Aerzte, 1841;'), I do not at present agree ; and in particular would
remark, that the circumstance of the contractions which occur during
life being much more considerable than those which attend the rigor
mortis, appears to be opposed to it.

§ 86. Development of the Muscles and Tendons. — The rudiments of
the muscles consist, originally, of the same formative cells as those of
which the rest of the body of the embryo is constituted ; and it is not
till afterwards that the muscles, tendons, &c., are gradually developed
by a histological differentiation. In man, the muscles are not evident
before the end of the second month ; at first, however, they cannot be
detected by the unaided eye ; they are soft, pale, gelatinous, and not
to be distinguished from their tendons. In the tenth and twelfth week
they are more distinct, especially in specimens preserved in alcohol ;
and at this time the tendons also may be distinguished as somewhat
clearer, but at the same time transparent streaks.

In the fourth month, both the muscles and tendons are still more
distinct, the former being, on the trunk, of a light reddish color, the
latter less transparent, and grayish, both retaining a soft consistence.

254

SPECIAL HISTOLOGY.

From this period, both textures acquire more and more of the configu-
ration which they afterwards retain, so that at the maturity of the
embryo, — excepting that the muscles are still softer and paler, and the
tendons more vascular and less white, — they no longer present any
difference worth notice.

With respect to their intimate conditions, the primitive fasciculi, in
the embryo, at the end of the second month, present the aspect of elon-
gated bands (Fig. 105) 0-001 of a line broad, Avith nodular enlargements
at different points, at which places are situated elongated nuclei ; the
bands exhibit either a homogeneous or finely granular aspect, and but
rarely an extremely faint indication of transverse striation. In their
further development, these primitive muscular fasciculi, which, as com-
parative histology teaches, originate in cells arranged in a linear series,
continue to increase in breadth and length, and their contents, the
original cell-contents, are developed into the muscular fibrils. In the
fourth month (Fig. 106) they measure for the most part 0*0028 — 0-005,
some even 0-006 of a line, whilst others do not exceed 0-0016, and
0-002 of a line. The larger ones are, still, always flattened, but of
uniform Avidth, and also considerably thicker than before, mostly with
evident longitudinal and transverse strioe, and even Avith fibrils, which
admit of being isolated. It is partially evident, even in a longitudinal

view, but still better in a trans-
verse section, that in many
cases, the fibrils do not occupy
the entire thickness of the pri-
mitive tube, but that they are
deposited around its j9erz)>/!er?/,
the interior being as yet filled
with a homogeneous substance
as at first, and Avhich now ap-
pears like a canal within the
fibrils. All the primitive tu-
bules possess a sarcolemma {b),
Avhich on the application of
acetic acid or soda, appears as
a very delicate membrane, Avhich
by the imbibition of water, may
occasionally be raised from the
fibrils. The tubes, moreover.

Fi?. 106.

Fig. 105. — Primitive fasciculi of an eight to nine weeks' human embryo; magnified 350
diameters: 1, two fibres witliout transverse striajj 2, fibres presenting the first indications
of transverse striation ; a, nuclei.

Fig. 106. — Primitive fibres of a four months' huinan embryo; magnified 350 diameters:
1, a fasciculus, with a clear, as yet, non-fibrillated substance in the interior: 2, fasciculus
without such contents, with an indication of transverse striation ; o, nuclei ; b, sarcolemma.

THE MUSCULAR SYSTEM. 255

as at first, present nuclei lying close upon the sarcolerama, and which
frequently cause rounded elevations on the surface of the tuhe, and may
be observed actively engaged in the process of multiplication. They
are all vesicular, roundish or elongated, with very distinct, simple or
double nucleoli measuring O-OOO-t-0-0008 of a line, and frequently with
two secondary cells in the interior. They are much more numerous
than previously, and most frequently disposed in pairs closely approxi-
mated ; but often, also, in groups of three or four or even six, either
contiguous or arranged serially. From this period to that of birth, no
further important change takes place in the muscular fasciculi, except
an increase in their size. In the new-born infant they measure 0-0056
-0*0063 of a line, are solid, rounded, polygonal, longitudinally or
transversely striated, according to circumstances, as in the adult, with
very readily isolated fibrils, and no longer any appearance of nuclei.

From what has been remarked, it is clear that the sarcolemma repre-
sents the sum of the membranes of the coalesced cells, and that the nuclei
of the youngest fasciculi are the original cell-nuclei, whose descendants
are represented in the nuclei of the older fibres, which have multiplied
by an endogenous process. The muscular fibrils are the altered contents
of the original tubes, become solid ; they appear, demonstrably in many
instances, to be formed on the inner surface of the sarcolemma, from
without to within, but in other cases probably in the whole of the tube
at once.

The growth of the entire muscle is chiefly to be referred to the in-
crease, both longitudinal and in thickness, of the primitive fasciculi ;
and the rudiments of all the future primitive fasciculi appear to be formed,
probably even as early as the original rudiments of the muscle itself —
in every case at the middle period of foetal life. In the embryo, at the
fourth or fifth month, they are perhaps five times as thick as in one at
two months ; in the new-born infant they measure for the most part
twice, occasionally even three and four times as much as in the fourth
and fifth month, and in the adult their size is perhaps five times greater
than in the new-born child. The number of fibrils must necessarily in-
crease in proportion to the size of the fasciculus, because, according to
Harting, they are but little thicker in the adult than in the foetus. The
pervmjsmm is developed, as I find in agreement with Valentin and
Schwann, after the type of the common connective tissue, from fusiform,
coalesced formative cells.

The elementary parts of the tendons are, in no case, formed earlier
than those of the muscles ; for, in embryos from the eighth to the ninth
week, I have never been able to detect a trace of them, although at this
time the muscular fibres are quite distinct. It is not till the third or
fourth month, when, moreover, they become distinctly visible to the
naked eye, that their elementary constituents can be made out, at this
time presenting the appearance of long parallel bands with elongated

256

SPECIAL HISTOLOGY.

nuclei, -which, as the observations of Schwann and myself (§ 2-4) on very
young animals show, are formed by the coalescence of fusiform cells.
As early as the fourth month they may be distinctly recognized as primi-
tive fasciculi, which are wavy, and present, at intervals, elongated nuclei
0-0035-0006 of a line long, and 0-0016 of a line broad, but are as yet
without distinct fibrils, and not more than 0*0012-0*0016 of a line wide.
Fig. 107. From this period up to the end of foetal life, the fasci-

culi gradually increase in width, so that in the new-
born infant they measure 0-002-00025 of a line; at
the same time their fibrils are developed, as are also
fine elastic filaments among the fasciculi, from special
fusiform formative cells (vide § 23). If these fasciculi
be compared with those of the adult, measuring 0-006
-0-008 of a line, it is obvious, that the fasciculi of the
tendons are continually acquiring an increase in thick-
ness from their first origin, so that their proportional
sizes in the four months' foetus, the new-born child, and
the adult, are about as 1 : 1, 8 : 6 ; and, also, that in
every case the growth of the tendons must in a great
measure be referred to the increased thickness and
elongation of their fasciculi. It would, moreover, appear, that subse-
quent to the primary rudiments of the tendons, new fasciculi continue
to be added during foetal life.

Some controversial opinions are still entertained Avith respect to the
development of the muscular fibres. Reichert and Hoist maintain that
each fibril is the product of a single cell, and regard it as the equivalent
of the smooth muscular fibre, or contractile fibre-cell. This view is er-
roneous, as is readily shown by the examination of the mammalian and
human embryo. Leydig's declaration, quite recently, in its favor
(Beitr. p. 78), is explained by his having confounded the peculiar secon-
dary muscular fasciculi in the plagiostomous fishes with the jjrimitive
fasciculi of the higher Vertebrata. In the Batrachia, according to
Lebert and Remak, in the development of the muscles, elongated simple
cells, with self-multiplying nuclei, are found, the contents of which cells
undergo a metamorphosis similar to that occurring in the elongated
muscular tubules formed of numerous cells, which, according to my ob-
servations, also exist in these animals. The contractile part of the mus-
cular fibre, whether it be transversely striped or not, and whether it
presents fibrils or not, is generally developed from without to within, in
the sarcolemma, forming a sort of tube which does not become solid till
afterwards ; less frequently it appears as a more solid cord on one side

Fig. ]07. — From the tendo ^rhillis of a new-born child, magnified 250 diameters^ and
treated with acetic acid, in order to show the fornuition of line elastic fibres.

THE MUSCULAR SYSTEM. 257

within the musculai' fibre. In the former case, the nuclei and the orifirinal
contents of the formative cells, which often contain a large quantity of
fatty matter, are situated in the interior of the embryonic muscular
tubule, or between it and the sarcolemma ; in the latter always close
upon the sarcolemma.

With respect to the pathological relations of these tissues, the follow-
ing remarks may be offered : The substance of the striated muscles is
not regenerated, and wounds of muscles heal simply with a tendinous
callus. A new formation of them has been noticed by Rokitansky
("Zeitsch. der Wiener," Aerzte, 1849, p. 331), in a case of tumor of
the testis in an individual 18 years old, and by Virchow ("Verb, der
Wurzb.," Ges., I.) in an ovarian tumor. In the latter case, which came
under ray own observation, there were elongated, fusiform, transversely
striated cells, each with a nucleus, similar to those described by Remak
in the Tadpole. The state of the elementary parts in hypertrophy of
the muscles is uncertain.* This condition, however, except in the tongue,
heart, and certain respiratory muscles (Bardeleben), does not perhaps
occur at all ; it is at all events extremely rare in the striped muscles.
(Romberg, "Nervenkr.," p. 291, asserts, that such a condition ensues
upon long-continued cramps, though it appears to me that this point is
not yet sufficiently established.) Equally uncertain, also, is the intimate
condition of the muscular elements in the increased development caused
by exercise, and whether this depend upon the growth of the pre-exist-
ing muscular fasciculi, or on the introduction of new ones — the latter of
which supposition may perhaps be affirmed without much chance of error,
in the case of the extreme degrees of pathological hypertrophy. Atrophy
of the muscles is very frequent, as in old age, paralysis, particularly of
the tongue, and in cases of lead-poisoning, and in the development of
cancer, fibrous tumors (consequent on inflammation), and of fat, &c.,
in the substance of the muscles. The processes, however, which are set
up in these cases, have as yet been but little investigated. In extreme
old age I find the fasciculi small, presenting occasionally a diameter of
not more than 0'004-0'008 of a line, easily broken up, mostly without
transverse stripes, and with the fibrils indistinct, whilst they frequently
contain yellowish or brown granules, as much as 0-001 of a line in size,
often in large quantity, and very many vesicular nuclei with nucleoli.

• [Wedl has observed longitudinal rows of yellow or brownish granules in hypertro-
phied as well as in atrophied muscle. These granules are not dissolved by acetic acid or
alkalies; and seem deposited around the nuclei of the sarcolemma. In hypertrophied
muscle, a peculiar gelatinous substance in the interstitial tissue is sometimes met with.
This causes the primitive fasciculi to adhere to each other, and generally results in a com-
plete softening and destruction of the sarcolemma, in the place of which we find a fine
granular mass.

The interstitial substance is sometimes found in an hypertrophied state. If this occur to
any extent it produces an atrophy of the muscular fibre. — DaC]

17

258 SPECIAL HISTOLOGY.

The nuclei often form continuous rows, or are accumulated on the inner
surface of the sarcolemma, exhibiting in a peculiar manner the same
distinct indications of an energetic multiplication by endogenous forma-
tion, as are presented in the embryo {vide this §, supra). In fatti/ de-
generation, the muscular fasciculi are, by degrees, replaced by connective
tissue and fat cells which are developed between them ; whilst, at the
same time, minute fatty molecules are developed in great number within
them, in place of the fibrils, which gradually disappear.

Paralyzed muscles were found by Reid (" On the relation between
Muscular Contractility and the Nervous System," "Edinburgh Monthly
Journal of Med.," 1841) to be thinner, softer, and paler; and Valentin
(" Phys.," 2 ed. 2 Th., p. 62) noticed in such cases that the transverse
stripes were indistinct, or had disappeared, and could no longer be pro-
duced by Avater, alcohol, &c. ; the longitudinal stripes existed, but did
not present their usual aspect, more resembling those of macerated
muscle. Subsequently the altered fasciculi disappeared in part, and
were to some extent replaced by fat. In a case of atrophy of the pec-
toralis major caused by cancer, I noticed conditions similar to those I
had observed in old age, viz. : destruction of the fibrils, the develop-
ment of brownish granules, and the presence of numerous nuclei, to-
gether with a clear fluid in the persistent sarcolemma ; and lastly a
diminution of the fasciculi, which did not measure more than 0*002-
0*004 of a line in width. I also believe, that I noticed in many fasci-
culi the development of larger, serially disposed cells, with very
large and distinct nuclei, exactly like the so-termed cancer-cells.
The condition of the muscles in emaciation is unknown. In an ema-
ciated Frog, which had fasted for eight months, Donders observed
that the fasciculi were more slender, which he attributed chiefly to the
removal of the interstitial substance between the fibrils. Paleness of
the muscles is very common in dropsy, chlorosis, paralysis, lead-poison-
ing, old age, &c. ; in which cases, probably the numerous brown or
yellow granules are formed from a portion of the coloring matter. .
This condition is generall}^ associated with softening, in which the fas-
ciculi no longer exhibit any distinct transverse striae or fibrils, and
readily break up into numerous particles, or even into a pultaceous
matter. In tetanus, in which rupture of a muscle frequently occurs,
Bowman ("Phil. Transact.," 1841, p. 69) observed on the fasciculi
numerous nodular enlargements, in which the transverse strise were very
closely approximated, and between them either actual rupture of the
fibrils, or at all events a considerable stretching and disorganization of
them, both of which states are clearly to be referred to a powerful and
irregular contraction. The muscles sometimes contain concretions,
particularly as the result of the cretification of pus, tubercles, and cys-
tecercMs- vesicles ; sometimes also true bones, such as are produced after
prolonged exercise in the deltoid and other muscles (Exercirknochen).

THE MUSCULAR SYSTEM.

259

Of parasites are to be noticed the not unfrequcnt Cystieercus celluloscc-
and Trichina spiralis; and, besides these, in the Eel a ncmatoid worm,
observed by Bowman (" Cyclop, of Anat." 11. p. 512) alive, in the al-
most empty sarcolemma. I met with something analogous to the latter,
some years ago, in the abdominal muscles of the Rat (as have V. Sie-
bold and Miescher also in the Mouse) ; that is to say white streaks 4-7
lines long, and 0-09-0-01 of a line wide, which, on microscopic exa-
mination, proved to be hollow primitive fasciculi, entirely filled with
elliptical, slightly curved corpuscles, 0'004-0-005 of a line long, by
0-0019 of a line wide, and manifestly ova. The portions of the fas-
ciculi thus transformed into pouches, had walls 0-009-0-01 of a line
thick, with transverse stripes, and were continuous at either end with
the perfectly normal fibre.

§ 87. Physiological Remarks. — The most remarkable peculiarity
of the muscles is their contractility. In each contraction, the primitive
fasciculi shorten themselves in a rectilinear direction, and at the same
time become thicker ; they do not, hoAvever, undergo any considerable
condensation. It is probable, that the contractions generally take
place simultaneously in every part of a fasciculus, although at the same
time it is not, of course, intended to be said that the contraction does
not commence at the points wdiere the terminations of the nerves occur,
and that this contraction does not precede, though by a space of time
immeasurably short, or at all events inappreciable by the eye, that of
the other portions of the fasciculus. Under certain conditions, how-
ever, successive, progressive, and partial contractions are
observed. If during the contraction of a muscle, its
longitudinal and transverse striae are noticed, it is diffi-
cult to show that where the former exist, they disappear
during the contraction, and give place to transverse
markings ; and that the latter, where they were already
present, become more distinct, and more closely approxi-
mated. Moreover, in the easily isolated fibrils of the
thoracic muscles of insects, it is easy to perceive that
they exhibit very variable conditions in different ani-
mals, and vary frequently in one and the same indivi-
dual. Sometimes they are almost without transverse
markings, and very pale ; sometimes darker, and with
distinct transverse lines; sometimes, again, very dis-
tinctly ringed ; and together with these varying condi-
tions, does the thickness of the fibrils and the distance
between the transverse striae, vary also ; so that the

Fig. 108. Primitive fibres from the alar muscles of the " Dung-Fly :" a, slender fibril,
with very distant delicate transverse stria; 6, thicker fibre, with closer, alternately stronger and
fainter stritp ; c, still thicker fibril, with the striae more closely approximated; rf, fibril with
lateral, alternate elevations (they have come out too dark). — Magnified 350 diameters.

Fig. lOS.

a

(/

.-

260 SPECIAL HISTOLOGY.

fibrils whicli exhibit the most distinct striation, are almost as thick again
as the others, and their transverse stria? are placed almost twice
as closely together. It may thence, perhaps, be allowable to con-
clude, that in the act of contraction the principal phenomenon con-'
sists in the shortening and thickening of the fibrils, and also, that
the changes in the fasciculus above noticed depend upon these changes
in the fibrils. The further question now arises: how is this shortening
of the fibrils effected ? and whence does the transverse striation arise ?
Is the latter connected with the vital conditions of the muscle, or is it
produced independently of these ? It is unnecessary to answer the latter
query in the affirmative, for dead muscles exhibit transverse stride, and
indeed, under the same conditions as the living. This is best shown in
muscles successively subjected to various degrees of tension ; and con-
sequently, all notion of a merely partial contraction of the fibril, which
arises on the first observation of these conditions, must be relinquished.
The transverse striation is manifestly merely a physical, not a vital
phenomenon. It arises, either because the fibrils are not homogeneous
throughout their whole length, but divided into numerous small seg-
ments, some of which are possessed of greater elasticity than the others;
or, in the opposite case, it may depend upon the circumstance, that the
fibrils are soft filaments, which, in shortening, become curved in a zig-
zag or wavy manner, or varicose. Which of these two views is the
correct one, cannot at present be determined ; and this much only can
be said, that in favor of the former supposition, the fact can be adduced,
that fibrils, after maceration, readily break up into minute particles
[sarcous elements, Bowman), and possibly consist of a series of such
elements connected by a heterogeneous interstitial substance ; whilst in
favor of the second, are the conditions presented in the fibrils of con-
nective tissue, which are undoubtedly homogeneous throughout, and yet
when made to contract by the application of acetic acid, exhibit extreme-
ly delicate transverse markings, in consequence of which, the fasciculi
composed of them frequently offer a deceptive resemblance to those of
striped muscle. It is difficult to say whether the sarcolemma partici-
pates actively in the shortening of the fibrils, although, especially from
the consideration of its chemical and physical properties, which ap-
proach those of elastic tissue, I am rather inclined to the opinion, that
its function, in the contraction of the fibre, is merely passive. The
same may with greater certainty be affirmed of the albuminous fluid
uniting the individual fibrils. Consequently, it is not the muscular
fasciculus, in toto, but only the fibrils, which are to be regarded as the
contractile elements ; a position which is not shaken by the circum-
stance, that other conditions occur in the smooth muscles, and in many
muscles in the Invertebrata (those that exhibit no fibrils).

This is not the place to dilate upon the causes to which the contrac-

THE MUSCULAR SYSTEM. 261

tions of the muscles are due, and by Avliich tlicy are necessarily produced,
and I Avill merely offer the following remarks. There can be no doubt
that the contractility of the muscular substance is a proper and inherent
attribute, and only called into manifest action to a certain extent through
the nerves; whilst it is equally certain, that there are no facts which
conclusively demonstrate, that the striped muscles contract indepen-
dently of a previous nervous influence. What the processes are which
take place in the fibrils during the contraction is wholly doubtful; but
it is to be hoped that the further investigation of the laws of the electric
currents in the muscles, prosecuted in the way so successfully pursued
by Du Bois Reymond (" Untersuchungen liber thier. Electricitat," Ber-
lin, 1848-49),* will throw some light upon this, as yet, obscure subject.
It would be more than bold to hazard an assertion with respect to the
nature and mode of action of the nerves upon the muscles, since we are
quite as much in the dark as to the processes which take place in the
nerves, as we are with regard to those occurring in the muscles them-
selves. From the anatomical facts, which prove, that in many animals
the motor nerve-fibres come in contact with each primitive muscular
fasciculus only at a few points, and never penetrate into its interior, it
is, however, rendered evident, that in the contraction of a muscle, the
nervous influence must act from a certain distance.

The muscles also possess sensibility, though of a rather peculiar kind,
because punctures, burns, and incisions into their substance, excite
scarcely any sensations worth naming, whilst every muscle, after long-
continued activity, as well as when affected with cramps or spasms, be-
comes painful and very sensitive to pressure. They are also endowed
■with an extremely delicate sense of feeling for their own state of con-
traction, so that they are capable of estimating very minute variations
in the force with which they act. The apparent contradiction between
these facts is easily accounted for, by the consideration that the muscu-
lar nerves contain but very few sensitive fibres, as is readily shown in
the nerves of the orbital muscles, &c. These fibres, to which probably
belong the few filaments above described, which are distributed over the
whole muscle, though too scanty to render a muscle sensible to local im-
pressions, nevertheless sufl^ice, when implicated in the contraction of the
entire muscular substance, to convey to the sensorium the degree of
pressure to which they are subjected, and, when the organs are over-
exerted, to induce pain, in consequence of the frequently-repeated irri-
tation which they have undergone, or of the compression they endure
from the rigidity of the muscle.

The mechanical relations of the muscles have been excellently treated
of in the article by E. Weber (1. c), from which the following conclusions
may be drawn. The extent of the shortening of the muscles amounts,

* Translated by Dr. Jones, London, 1S53.

262 SPECIAL HISTOLOGY.

in experiments upon animals, on the average to f ths, or in powerful
muscles even to |ths. The contractile force of a muscle does not de-
pend, cceteris imribus, upon its length, but solely on its transverse sec-
tional area; that is to say, on that of all its primitive fasciculi, so that
a longer and a shorter muscle exert the same force, when the sura of the
transverse sections of all the fasciculi is the same in both. According
to the observations of Schwann and Weber, the elasticity of the muscles
diminishes at each contraction, and consequently the molecular motions,
called into play in them under the nervous influence, must be connected
with a change in their substance of an altogether peculiar kind, which,
however, can certainly only be regarded as a secondary effect. The
degree of contraction differs according to the amount of antagonism
with which it meets ; if the latter be sufficiently powerful, no true move-
ment of the limb takes place, that is to say, the points of origin and
insertion of a flexor muscle (for instance) do not approximate ; never-
theless, the fibres themselves contract to a certain extent, in consequence
of which the whole muscle becomes tense. This tension must be care-
fully distinguished from that dependent upon the muscular elasticity,
which is generally much less considerable. What has been termed the
"tone" — tonus — of muscles, does not in most cases depend upon con-
traction, but is an elastic tension ; I therefore hold, that the posture of
the body and the occlusion of the transversely striated sphincters during
sleep, has nothing to do with a contraction of the muscles, although such
contraction is indubitably requisite to bring the body into this posture.
In my opinion, during sleep, all the muscles (of course, with the excep-
tion of the respiratory) are at rest, being held in a state of tension, and
of antagonism to their opponents merely by their elastic force, and are
consequently in the condition of a muscle Avhen supported, in a person
in the waking state. As for instance, a biceps, when the arm is bent,
may immediately lose its tension if the arm be supported, so in the same
way may all other voluntary muscles ; only it must not be forgotten,
that such a condition of muscular rest may ensue upon all conceivable
degrees of contraction. Even the orbicularis oris, when contracted, may
be at rest and lose its vital tension. The mouth, nevertheless, will re-
main closed, for this reason, that although the elastic force, as always
after a contraction, will not fail to exert a certain degree of extension
upon it, it is unable to open the mouth, owing to its limited amount and
inability to overcome the weight of the lips. I do not believe in any
muscular "tone," if under that term be understood a long-continued
involuntary contraction (though at first excited by the will) ; but am of
opinion, that what has been most generally described under this name,
is merely an elastic tension, which has been confounded Avith the con-
traction upon which it has ensued. From all we know, the nerves are
incapable of exciting a long persistent contraction in the striped muscles,

THE MUSCULAR SYSTEM. 263

but very capable of producing great effects, when the states of contrac-
tion and of rest are duly alternated, as for instance in walking, running,
&c., and in the heart and respiratory muscles.

The importance of this view of the nature of the muscular "tone,"
as regards the physiology of the nerves, is sufficiently obvious ; but in
pathology also, it may be employed, in explanation of the retraction of
divided muscles, and the shortening which takes place in muscles whose
antagonists are paralyzed. The former, as correctly pointed out by E.
"Weber, depends upon the elastic force, and takes place, as far as I know,
only in extended, tense muscles, but not in those which are in a state of
contraction, which, on the contrary, when cut across, immediately be-
come lengthened, as may be readily observed in the Frog. It is quite
true, that contractions also take place in divided muscles, in conse-
quence of nervous influence ; but these are never more than local, and
cease without the production of any important effect on the form of the
wound in the muscle.

The shortening which occurs in the antagonists of paralyzed muscles,
is not referable either to the elastic force of the non-paralyzed muscles,
which is much too slight to influence the position of a limb, or to their
persistent "tone," but depends simply upon the voluntary innervation
of the muscles, which are still in an active condition, and which, no
longer meeting with any opposition from their antagonists, draw the limb
in their own direction. The persistence of the oblique position which
now ensues, may be readily explained without our necessarily assuming
the existence of a permanent contraction, when it is considered that
muscles, the antagonists of which are paralyzed, never again become
elastically tense. In lead-palsy, for instance, when the first contraction
of the flexors, consequent upon the paralysis of the extensors, ceases,
the former, even under the most favorable circumstances, become ex-
tended only so far as to assume their natural form, a condition from
which necessarily results the semiflexed position of the part affected.
In accordance with this view, I regard the permanent condition of the
unaffected side of the face, in one-sided paralysis of the facial nerve, and
that of the upper eyelids in blepharoptosis, as produced, not by a per-
sistent contraction, but as indicative of a state of perfect rest in the
muscles, except when voluntary movements take place. The falling of
the upper eyelid is explained by the paralysis of the levator, and the
inability of the orbicularis, by its extension after a previous closure, to
raise the eyelid beyond a certain point. In the same way the distortion
of the face is produced, at first by the voluntary contraction consequent
on the paralysis, upon the cessation of which it is impossible that the
previous symmetry of the features should be restored, because the anta-
gonist muscles on the opposite side are paralyzed, and their slight elastic
force during life is insufficient, simply upon the cessation of the contrac-

264

SPECIAL HISTOLOGY.

Fig. 109.
^ J5

tion, to restore the pristine position of the lips, angle of the mouth, &c.
An actual distortion, therefore, dependent upon persistent muscular
contraction, can only take place in consequence of morbid conditions of
the central organs.

In the investigation of the muscles it is necessary that they should be
studied in the fresh state, and with the aid of various reagents. The
primitive fasciculi are most easily isolated in muscles which have been
boiled or immersed in spirit, in which also, the transverse striag are for
the most part very well displayed, as is also the case after treatment
■with corrosive sublimate or chromic acid. In the study of the transverse
strias, it is above all indispensable that the muscles should be viewed in
various degrees of extension and contraction (Fig. 109). The former

conditions, which are well worth observation, are
readily viewed, if long slender muscles, such as
the hyoglossi of the Frog, &c., are examined on a
wooden stage having a central opening filled in
with glass. It will then be seen, when no exten-
sion whatever is employed, that the transverse
strise are narrow (about 0'0004 of a line) and very
closely approximated, and that the fasciculus itself
is broad ; whilst, when it is extended to the utmost,
the stripes are 0*0008 of a line wide, and placed
at the same distance apart, and that the fasciculus is narrower. The
contractions must be observed either in fresh muscles still quivering, and
kept moist with serum, albumen, or vitreous humor ; or in the way pro-
posed by E. Weber, — and which consists in the galvanizing, by means
of the rotation apparatus, of the muscle to be examined, such, for in-
stance, as the abdominal muscles and slender muscles of the extremities
in the Frog, the diaphragm and cutaneous muscles of the smaller Mam-
malia, &c. For this purpose the muscle must be placed upon a piece of
looking-glass, from a small space in the middle of which the metallic
coating has been removed. One of the conducting wires is brought
through an opening in the stage, or else affixed to it so as to be im-
movably in contact with one of the portions of tinfoil. If the muscle
now be viewed under a magnifying power of 100 linear, whilst the second
conducting wire is brought in contact with the other portion of tinfoil,
the moment the circuit is completed, its fibres will be seen to contract in
a rectilinear direction, and at the same time to become thicker, whilst
the transverse strice are more closely approximated [vide Fig. 109, which
represents both a contracted and an extended muscle). The muscular
fibres remain in this condition so long as the galvanic influence is kept

Fig. 109. — A primitive fasciculus of a Frog's muscle in different degrees of extension :
A, the fasciculus, stretched and slender, with broad distant transverse strire ; B, the same not
extended, broader, and with narrower, closely approximated striae — Magnified 350 diameters^

THE MUSCULAR SYSTEM. 2G5

up, whilst when the circuit is broken they elongate themselves us rapidly
as they contracted, and present zigzag flexures, when the muscle is lying
free, but not when it is stretched by small weights attached to it by
threads. From this it is evident, that if zigzag flexures take place
during life, which is not yet known to occur, they can only arise when
muscles in the quiescent condition are not in a state of tension ; as, for
instance, in the case of a flexor muscle, which has come into a state of
rest after it has produced its full eff"ect upon the limb. The sarcolemma
is readily seen in the muscles of Amphibia and Fishes, especially in
specimens preserved in spirit, in which it frequently, but for the most
part in places, appears at a distance from the fibrils. In the higher
animals and in man, it is occasionally seen when the fasciculi are teased
out ; and also in macerated and boiled muscles, and on the addition of
acetic acid or alkalies. For this purpose I would especially recommend
caustic soda, which in many cases renders the contents of the muscular
tubules so fluid, that they escape in a continuous stream together with
the nuclei, when the sheaths come very clearly into view. In no case,
however, is the sarcolemma, in man, more beautifully exhibited than it is
in softened, atrophied muscles which have undergone fatty or other de-
generations ; and, in fact, the greater the degree of degeneration, the
more distinctly is this structure exhibited. The muscular fibrils, in fresh
muscles, are constantly visible only in a transverse section, and in the
thoracic muscles of insects, elsewhere it is true they are occasionally
seen, but more by chance than otherwise. They are easily isolated
artificially in preparations preserved in spirit, particularly in the peren-
nibranchiate Reptiles {Siredon, Proteus^ &c.), by treatment with chromic
acid (Hannover), by maceration for from 8 to 21 days, at a temperature
of 1-8° R. in water, to which, for the prevention of putrefaction, some
corrosive sublimate has been added (Schwann) ; maceration also in the
fluids of the mouth (Henle) allows of their being readily exhibited ;
whilst, according to Frerichs (Wagner, " Handworterb.," III. I. p. 814),
in the stomach, the fasciculi break up into Bowman's discs. The nuclei
of the fasciculi are best studied under the application of acetic acid ; by
soda {vide supra) they may be isolated, and by potassa be made to swell
considerably (Donders). On the subject of the eff'ect of various reagents
on the elementary tissues of muscle, the treatises of Donders (Holland.
"Beitriige") and Paulsen (" Observ. michrochem.," Dorpat, 1849) may
be consulted. The vessels of muscle are studied in fresh, thin muscles,
and in injected preparations; the nerves in the smallest human muscles,
in the muscles of the smaller Mammalia, in the cutaneous muscle on the
thorax of the Frog, with or without the addition of soda. The perimysium,
and the form and position of the muscular fibres, are very well shown
in transverse sections of half-dried muscles; and the same observation
holds good with respect to the elementary tissues of the tendons. The

266 SPECIAL HISTOLOGY.

insertions of the latter into the bones, and their cartilage-cells in those
situations are readily seen ; in the tendo Achillis, for instance, in vertical
sections of dried preparations; with respect to their relation to the
muscular fasciculi, vide supra, § 81, In order to examine the cartilage-
cells in tendons, thin horizontal sections are taken from the surface,
which are treated with acetic acid, or a very dilute solution of soda. For
the study of the development of muscle, the naked Amphibia must be
placed in the first rank, and the Mammalia only in the second.

Literature. — Besides the memoirs, cited in § 27, there are to be men-
tioned : G.Valentin, article " Muscles," in the " Encyclopaedic Dictionary
of the Medical Sciences," vol. xxiv. pp. 203-220, Berlin, 1840 ; H. R.
Ficinus, " De fibrse muscularis forma et structura Diss, inaug.," Lips.,
1836, 4, cum tab. ; F. Will, some remarks upon the origin of the trans-
verse stripes of muscles, in Mliller's "Archiv," 1843, p. 358 ; R. Remak,
on the " Development of the Primitive muscular Fasciculi," in Froriep's
"N. Notiz.," 1845, Nr. 768 ; Ed. Weber, art. "Muscular Motion," in
R. Wagner's "Manual of Physiology," vol. iii. 2d division, 1846 ; Kol-
liker, in "Ann. d. Sc. Nat.," 1846 ; Dobie, " Observations on the Minute
Structure and Mode of Contraction of Voluntary muscular Fibre," in
"Ann. Nat. Hist.," N. Ser. III. 1849 ; Lebert, " Recherches sur la For-
mation des Muscles dans les Animaux vertebras, in Ann. d. Sc. N.,"
1850, p. 205.

OF THE OSSEOUS SYSTEM.

§ 88. The Osseous System consists of a great number of hard organs,
the Bones, of a peculiar, uniform structure, which are united either
immediately or by means of other tissues, such as cartilage, ligaments,
or articular capsules, into a connected whole — the skeleton.

The osseous tissue, in man, presents two principal forms — the compact
and spongy. The perfect solidity of the former, however, is only appa-
rent, as, even to the naked eye, it is seen to be penetrated by narrow
channels which run in various directions, and by a still greater number
of similar but smaller canals, which are brought into view by the micro-
scope. These vascular or Haversian canals (medullary canals of authors),
may be said to be almost entirely absent in the spongy substance, in
which they are represented by wider, rounded, or elongated spaces,
visible to the unassisted eye, which are filled with marrow, in some
bones occupied by veins or nerves {cochlea), and termed the medullary
spaces or cells {cancelli, cellulce medullares). These spaces all anasto-
mose together, and are formed by the reticular arrangement of the small
quantity of osseous tissue, which is disposed in the form of fibres, lamim^,
and small rods. When the spaces are of a larger size, the substance is

THE OSSEOUS SYSTEM. 267

termed subst. ceUuJaris, and when smaller, suhst. reticidaris. The latter,
in some situations where the cavities are smaller, and the osseous parti-
tions stronger, approaches in character the compact substance, although
it does not actually become such ; and in others it passes without any
defined limit, into compact tissue. This does not, however, prove that
the two substances are identical, but as we learn from observation of
their development, depends simply upon the circumstance that the
spongy substance very frequently arises in a partial expansion of the
compact. The share taken by the two substances in the formation of
the different bones, and parts of bones, varies very considerably. It is
only in a few situations that the compact substance is met with by itself
without vascular canals — as in the lamina ipa-pyracea of the ethmoid
bone, some portions of the lachrymal and palate bones, &c. It occurs
more frequently, however, with vascular canals, and without spongy
substance as in many individuals in the thinnest portion of the scapula,
ilium, acetabulum, cranial bones {ala magna, parva of the sphenoid, the
orbital process of the frontal bone, &c.) Spongy substance with a thin
compact cortex, without vascular canals, exists in the auditory bones, on
the surfaces covered with cartilage of all bones, probably also in the
smaller spongy bones. In all other cases, and consequently in most
situations, the two substances are conjoined, but in such a way, that
sometimes the spongy substance predominates (spongy bones and parts
of bones), as in the vertebra', carpal and tarsal bones ; sometimes the
compact, as in the diaphyses of the long bones ; or the two are in equal
proportions, as in the fiat bones.

§ 89. Intimate Structure of the Osseous Tissue. — The osseous tissue
consists of a dense, for the most part indistinctly lamellar fundamental
substance or matrix, penetrated by vascular canals and numerous minute
microscopic spaces — the bone-cells, or lacuna' (bone-corpuscles of authors),
having very minute hollow processes, the bo7ie-canaliculi.

The vascular canals of the bones, or the Haversian canals {canalieuli
medullares), are minute tubules, having an average diameter of 0-01-
0-05 of a line, and in the extremes one varying from O-OO-l to 0-18 of a
line, and which, except in the thinner parts of the facial bones, as above
mentioned, exist universally in the compact substance, forming in it a
wide network similar to that of the capillaries. In the long bones, and
also in the ribs, clavicle, pubis, ischium, and lower jaw, they run chiefly
in a direction parallel to the long axis of the bone, and, as shown in
longitudinal sections, either parallel to the surface or perpendicular to
it, at distances varying from 0-06 to 0-14 of a line apart. They are
connected by transverse or oblique branches, which run in the direction
both of the radius and of the tangents of a transverse section of the
bone. Consequently, under a low magnifying power, in longitudinal

268

SPECIAL HISTOLOGY.

sections of one of those bones, either parallel to the surface or perpen-
dicular to it, closely approximated canals running parallel to each

Fi!?. 110.

J] ivV\<^

c--'

a'

/

i

! / \ity^ V

i

I

\,r\ \

f-

Y j'-'-'Sfctf

\'VrJ:^A\

Fi?. 111.

other, chiefly in a longitudinal direction, are seen, here and there ■with
connecting branches, and thus forming a network, consisting of elon-
gated, and most generally rectangular meshes (Fig. 111). And in a

transverse section — transverse sections
of the canals, placed at tolerably defi-
nite but small distances apart, are prin-
cipally apparent (Fig. 112) ; which,
more especially in younger bones, are
occasionally connected by a tangential
branch, and some anastomoses in the
direction of the radius. In transverse
sections of foetal and undeveloped bone
(in man even at the age of eighteen),'
scarcely any transverse canals occur,
but chiefly those running horizontally

Fig. 110. — Segment of a transverse section from the shaft of the /emrtr of an individual 18
years old : a, Haversian canals; 6, their openings internally; c, externally ; (i, osseous sub-
stance with lacunre. In this figure transverse sections of vascular canals and fundamental
lamelke are not shown. — Magnified 350 diameters.

Fig. 111. — Haversian canals from the superficial lamellss of the /wmr of an individual 18
years old, treated with hydrochloric acid: a, canals; 6, osseous substance with lacunae. —
Magnified GO diameters.

THE OSSEOUS SYSTEM. 269

in the direction of the tangents and radius (Fig. 110), so that the hones
appear to consist entirely of short thick lamell«j, each of which, upon
closer examination, is seen to belong to two canals, and exhibits a pale
central line, indicating the division between the two constituent portions
of which it is formed.

In the flat hones, the greater number of the canals do not run in the
direction of the thickness of the bone, but almost all, parallel Avith its
surface, and indeed in lines which may be conceived as radiating from
one point {tuber parietah, frontale, upper and anterior angle of the
scapula, articular portion of the ilium) in a penicillar or stellate manner
towards one or several sides ; or less frequently, as in the sternum, are
all parallel to each other. In the short bones, lastly, there is most
usually one predominant direction in which the canals run, as the ver-
tical in the vertebrae, — that of the long axis of the extremity in the
carpal and tarsal bones, &c. ; it must be remarked, however, that the
larger processes of these bones, as, for instance, the spinous processes
of the vertebra;, differ in this respect from the rest of the bone, and, like
those of other bOnes, such as the coracoid and styloid processes, exhibit
the same disposition of the canals as that which exists in one of the
shorter cylindrical bones. The lamellae, fibres, and bars of the spongy
substance, occasionally present a few vascular canals, but only when
they are of some thickness.

As the Haversian canals are vascular channels, they open in certain
situations : 1, externally, on the outer surface of the bone ; and, 2,
internally, on the w^alls of the medullary cavities and spaces. In both
situations, excessively fine and coarser pores may be everywhere per-
ceived, partly visible to the naked eye, and which are more numerous
in proportion to the thickness of the cortex of the bone. But the rela-
tion of the vascular canals in the compact substance to these canals
thus proceeding from within and without, only partially resembles that
between the branches and trunks of vessels, and only in the outermost
and innermost lamellae of the cortical substance. In the interior of the
cortical portion of a bone the canals are independent, and morphologi-
cally may be most aptly compared to a capillary network, which at its
borders is in connection at many points with larger canals. Where the
cortical substance rests upon the spongy substance, as in the interior of
the ends of the diaphyses, and in the lateral periphery of the apophyses,
the vascular canals, are continuous, sometimes abruptly, sometimes quite
gradually, expanding in an infundibuliform manner, and frequently
anastomosing, with smaller or larger medullary spaces, so that, very
often, no definite limit is perceptible between them. I have never yet
noticed cajcal terminations of the vascular canals ; it is, however, certain
that in many situations on the surface they must constitute, over exten-
sive spaces, closed networks, especially where very few or no vessels

270 SPECIAL HISTOLOGY.

enter the compact substance, as at the points of insertion of many
tendons and ligaments, and beneath several muscles (temporal).*

§ 90. The matrix of bone is lamellar, and the lamellae (Fig. 112) are
apparent in thin sections, but are still better shown in bones from which
the earthy matter has been removed, or which have been exposed to the
weather or calcined, in which cases the lamellse exfoliate, and, in the
cartilage of decalcified bones, may even be raised with the forceps. In
the middle portions of the cylindrical bones they constitute two systems :

one general, in which the lamelloe are parallel with the external and

internal surfaces of the bone, and 7iumerous special ones, around the
separate Haversian canals. These two systems are in some places in
immediate connection, but, in most, merely in apposition, and on that
account they may conveniently be regarded as of two kinds ; a view
with respect to them which is in some degree supported by the pheno-
mena presented in their development.

The lamellae of the Haversian canals (Fig. 112 c, 113 &) surround
those canals concentrically, in greater or less number. They consti-
tute, as it were, the walls of the canal, and are intimately united to each

* [A most valuable contribution to our knowledge of the structure and development of
Bone has lately been made by Messrs. Tomes and De Morgan, in their "Observations on
the Structure of Bone," read before the Royal Society in June, 1852, but not yet published.
We are enabled, however, by the kindness of those gentlemen in allowing us to inspect
many of their preparations, and in furnishing us with the proofs of their paper, to make
some very important additions and corrections to the text. We may add, that although we
do not always agree with Messrs. Tomes and De Morgan in the interpretation of the facts,
differences which we shall duly note, our own investigations have led us to believe that
their paper is by far the most accurate account of the process of ossification which has yet

appeared.

These writers have pointed out the important fact, that, besides the well-known Haver-
sian canals, other cavities exist in bone, which they denominate Haversian spaces. These
have irregular outlines similar to that of the surface of exfoliations, while the boundaries of
the Haversian canals are always more smooth and rounded. Again, in the latter, the
laminte are more or less conformable with the canal ; while the walls of the spaces are
formed by the imconformable edges and surfaces of the lamin;p of the adjacent Haversian
canals, which have, as it were, been eaten away to form the space. In fact, bone, so far
from being a permanent or stationary structure, is continually being deposited, and as con-
stantly re-absorbed. The Haversian spaces are the result of the absorption of previously-
existing osseous tissue ; but when this process has gone on to a certain extent, deposition
commences in the spaces, and they are converted into Haversian canals. The calibre of
these canals now becomes narrowed up to a certain point by the continual laminar deposi-
tion of ossific matter, which, after a while, is traversed by new absorptive tunnels, or
Haversian spaces, and is removed in its turn.

The spaces are very numerous and large in newly-formed bone situated near ossifying
cartilage ; while, in older bone, they are far less frequent and generally smaller. They are,
however' never absent ; being found even in old subjects. They may be observed in various
conditions in a series of sections. In one place the space will have attained a large size,
while, in another part of the same section, its commencement will be seen extending from
one side of an Haversian canal. One side of a space may be becoming the seat of a new
system, while the opposite is undergoing further enlargement. — Trs.]

THE OSSEOUS SYSTEM.

271

other, mucli in the same waj that the laminae of the walls of the 1
vessels are continuous with each other. The number of lamellix) belong-

arjjer

Fisr. 112.

Fig-. 113.

mg to a canal, and the collective thickness of the system formed bj
them varies not inconsiderably, and bears no constant relation to the
size of the canal, as is the case to some extent in the vessels ; small
canals, therefore, are not unfrequently surrounded by numerous lamellie,
and larger ones by but few.* In general, it may be said that the largest

Fio. 112.— Segment of a transverse section of a human metacarpal bone, treated with oil
Of turpentine : a, external surface of the bone, with the exterior fundamental lamelltc ; b,
internal surface towards the medullary cavity, with the inner lamells; c, Haversian canals
in transverse section with their lamellar systems; rf, interstitial lamella?; c, lacunce and
processes. — Magnified 90 diameters.

Fig. 113.— Portion of a transverse section of the shaft of the humerus, magnified 350 dia-
meters, treated with oil of turpentine: a. Haversian canals; 6. their lamellar systems, each
lamella presenting a more transparent and more opaque portion, with radiathig stria? in the
latter; c, darker lines, which probably indicate greater intermissions in the deposition of the
osseous substance; d, lacuna without visible rays. From a preparation by Dr. H. Mailer.

* [The "interstitial lamina?" are the remains of Haversian systems, the larger parts of
which have been removed by absorption to form new spaces. The irregular outline of the

272 SPECIAL HISTOLOGY.

canals have thin walls, those of a middle size thick ones, and the most
minute, again, walls of little thickness. The thinnest walls I have
commonly noticed measure 0-008-0'02, and the thickest, 0-08-0-1 of
a line. The thickness of the lamellfe varies between 0-002 and 0-005
of a line, being on the average 0-003 to 0-004 of a line ; in number
there are usually from eight to fifteen ; sometimes, however, no more
than four or five, and occasionally as many as from eighteen to twenty-
two.

The lamellae of the Haversian canals, together with their canals,
extend to the internal and external surfaces of the diapJi7/ses, where
they are connected with the general lamellte above mentioned, — the
fundamental lamellae (Fig. 111). The latter constitute an external and
an internal layer, and penetrate also into the substance of the diaph^sis,
where they are interposed between the separate lamellar systems and
the medullary canals. The two former layers, or the external and in-
ternal fundamental lamella', are parallel to the external and internal
surfaces of the bone, and vary in thickness apparently without any
definite rule, from 0-02 to O'o, or even 0-4 of a line. The latter, or
i7iterstitial fundamental lamellce, are seen most clearly where the super-
ficial fundamental laminse are developed, in partial connection and
parallel with which they extend from without inwards, and from within
outwards, some distance into the substance of the diapliyses, where they
are interposed, in masses varying in thickness from 0*02 to 0*12 of a
line, between the other lamellas (Fig. 112 d). In the interior of the
compact substance, on the other hand, in man, the Haversian systems
are so closely crowded that there can be no question as to the non-exis-
tence of lamellar groups between them, and it is evident that those
lamellae, which in a transverse section appear in man to be parallel
with the surface, almost all belong to horizontal canals; and it'is but
rarely that distinct interstitial masses are seen, as is usually the case in
other mammalia. The thickness of the separate laraellfB just described
is much the same as that of the lamellae of the Haversian canals, and
their number varies from 10 to 100.

We have hitherto considered only the diaphyses of the long bones.
In their apophyses, the thin cortical layer of compact substance natu-
rally presents only a few systems of Haversian canals, which, however,
are constituted as elsewhere. The exterior fundamental lamelhe are
few in number, and internally, owing to the existence there of the spongy
substance, they are wholly wanting. In the latter substance, the very
few Haversian canals present lamellar systems as usual, except that
they are thin, and the remainder, according to the condition of the
osseous network, consists of a lamellated and fibrous tissue, which in

outermost of the lamina of an Haversian canal (see Fig. 113) results from its being the first
dejiosition within the pre-formed irregular Haversian space. (Tomes and De Morgan, 1. c,
p. 5.)— Trs.]

Fi?. 114.

THE OSSEOUS SYSTEM. 273

general follows the contour of the medullary spaces and cells. The
flat and short bones present a similar arrangement internally, whilst the
cortical substance of these bones differs from that of the cylindrical,
only in the circumstance, that the fundamental lamellaj, in the flat bones,
form layers parallel with both surfaces of the bone. The thickness of
the fundamental lamelhxi in the cranial bones (parietal), is sometimes
the same in both aspects, and varies from 0-08 to 0*16 of a line, some-
times they are wanting in vascular situations, and in places, wholly so,
on the external aspect of the bone, in which case the Haversian lamellge
reach almost to the surface.

With respect to the intimate structure of the osseous lamellae, which
is best studied in transverse sections, dried, polished, and sufficiently
thin, there is usually evident, besides the bone-cells and canaliculi, in
the generally not very distinct lamellce, an extremely fine though very
distinct punctuated appearance, so that the whole osseous tissue appears
granular, and to be composed as it were of separate, densely crowded,
pale granules, measuring 0*0002 of a line (Fig. 114). If water or
weak syrup, or albumen, be applied to a slice of bone, it assumes a
condition probably similar
to that which it possesses
durino; life. The lamellce, ' ,"^— ^ ..a^-_:

for the most part (both in |c^ . ._ ■ . ' / :%■- ^

transverse and perpen- ll:..:,^-^., . ^ ' r jl -^

dicular sections), become
clearly visible, and their
granular aspect is quite dis-
tinct, although not so de- ,^
fined as before the bone was

thus treated. For in the first place, together with the granules, there is
exhibited a close, pale striation, referable to the canaliculi, which are filled
with fluid and wdiich, extending in various directions through the tissue,
renders its delineation more complex ; there are also apparent in each
lamella, as it were, two layers, one pale and more homogeneous, the
other darker and granular, which latter chiefly is striated. When this
condition is clearly displayed, an extremely delicate marking is produced,
resembling that seen in transverse sections of certain urinary calculi
(Fig. 113). When once seen in moistened sections, indications of this
arrangement will occasionally be observed in dried preparations. In
bone treated with hydrochloric acid, the granules and striae (dependent
on the canaliculi), in sections both transverse and pei'pendicular to the

Fig. 114. Portion of a perpendicular section of a parietal bone, magnified 300 diame-
ters : a, lacunse, with pale, only partially-visible prolongations, filled with fluid as in the
natural state : b, granular matrix. The striated places indicate the boundaries of the
lamellje.

18

- ..l

274 SPECIAL HISTOLOGY.

surface, ave less distinctly apparent, whilst the lamellar structure is very
manifest, and most generally two layers may be noticed in each lamella,
though by no means so clearly as shown in Fig. 113.* In sections
parallel to the surface, the bone, in many situations, appears almost
homogeneous throughout, presenting no trace of a granular structure,
whilst in others a structure of that kind is obscurely visible, together
with minute points (Deutsch), and besides these a longitudinal striation ;
which last gives the whole a fibrous aspect. From this circumstance,
many authors appear to have been led to describe the bone as composed
of fibres, but quite incorrectly, for although the study of their develop-
ment shows, that the ossifying parts are, to a certain extent, very dis-
tinctly fibrous, it is impossible to demonstrate anything of the sort in
perfect bone. On the other hand, there is no doubt that a coarsely
fibrous appearance exists, and especially in the bone-cartilage of the
compact substance, as has already been remarked by others, and which
is probably due to the fibrous fasciculi of the original blastema ; care
however should be taken not to look upon longitudinal sections of
lamellae as such fibres. f When bone is burnt and the fragments crushed,

* [According to Tomes and De Morgan, the lamince, when well developed, are always
constituted of two portions, — an outer, highly granular, often composed of a single line of
large granules, and an inner, which is singularly clear and transparent, and to all appear-
ance witliout graiuilation or any recognizable structure. This distinct separation into two
layers, however, does not always exist; and in a complete Haversian canal, the iimermost
lamina of all is frequently clear, glassy, and structureless.

The circumferential laminas are not so constantly present as is generally supposed, and
they rarely entirely surround the shaft of a long bone, still more rarely the flat bones. In
the fast-growing bones of young animals they are absent, while in adults they are usually
well developed in some jiarts ; so that their presence seems to indicate that the bone is
nearly stationary in its growth. In young, rapidly growing bone, the circumferential laminje
are replaced by a series which may be called the undidaling lamina. The surface of the
bone sends oft' processes, formetl of reduplicated lamince, which eventually arch over and
enclose those vessels of the periosteum which lie nearest them. The spaces thus formed
become the seat of Haversian systems. Young growing bone, therefore, may be distinguished
from that of adult animals, by its being composed of Haversian systems with intervening
unilnlating laminse. (Tomes and De Morgan, b. c, pp. 4-G.) — Tes.]

■)■ [Messrs. Tomes and De Morgan (1. c, pp. 13, 14) adduce very good reasons for believ-
ing that the fibrous appearance which may often be detected in the laraince of bone arises
from imperfect illumination and definition, and express their belief that bone substance "is
composed of granules or granular cells, imbedded in a more or less clear, homogeneous or
subgranular matrix." They go on to say, " Thus as regards the basement, homogeneous
tissue, it will be found that where lamination is highly developed, the laminee have a trans-
parent and structureless, and a more opaque and granular part, to which the former appears
to be the matrix. The peripheral lamina of the Haversian systems is generally clear and
free from granularity, and the internal lamina sometimes presents a similar structureless
appearance. The matter which fills up the Haversian systems in the full-grown antlers of
the CervidfE aflbrds another and a very striking example of transparent structureless osseous
tissue, which in this instance is the more distinct, from the absence of canaliculi in its sub-
stance. Then, again, we have another instance in the clear tissue which is sometimes found
between the superficial Haversian systems of ordinary bone. It has already been described
as a non-laminated element found on the surface of certain bones. In the instances already
cited, and no doubt in many others which may be fountl in the skeletons of the lower ver-

THE OSSEOUS SYSTEM. 275

it affords, according to Tomes, minute angular granules, from Uh to ^th
the diameter of the human blood corpuscle, and measuring, according
to Todd and Bo"\vraan, goouth-,:j0^5th of an inch, and which are also
rendered evident when bone is boiled in a Papins' digester. From these
particulars, and from the granular aspect of fresh bone, which has also
been noticed by Tomes and by Todd and Bowman, and moreover from
the pretty nearly equal size of the granules visible in it, with those
described by Tomes, and lastly, from the circumstance that bone treated
with hydrochloric acid, as well as when calcined, both present a perfectly
homogeneous substance without vacuities, it may be assumed that the
osseous tissue consists of an intimate mixture of inorganic and organic
compounds, in the form of closely connected minute granules.

§ 91. Bo7ie Cavities or Cells, and Canaliculi {lacunce et canalicuU
ossium). — In dried sections of bone, there are visible, scattered through-
out the entire osseous substance, in all the lamellie, microscopic melon-
seed-shaped corpuscles, with numerous, fine, ramified, and partially
anastomosing rays, whose opaque and white color (as viewed by direct
light) is due, not to the deposition of calcareous salts, as was formerly
supposed, and on which account they were termed " bone," or " calca-
reous corpuscles," but simply to their being filled with air. In fresh
bone, not yet deprived of its watery constituents, nothing can be seen
in these bone-cells or lacunse but clear contents with a nucleus, which
may best be described as the nutritive fluid of the bone, and conse-
quently the designation above given to these cavities is the most suitable.

The lacunrc are elliptical, flattened cavities, having an average length
of O'Ol of a line, O-OOit of a line wide, and 0*003 of a line thick, which
give off both from the borders, and particularly from the surfaces, a
great number of very fine canals, measuring 0-0005-0-0008 of a line in
diameter — the hone canaZ/cwZi above-mentioned (Figs. 115, 116, and 117)
The lacunae are equally numerous in both of the lamellar systems before.

tebrata, we have bone tissue •witbout obvious granularity, and without obvious structure ;
and although it forms but a small part of the general mass, yet from its constant presence
at all ages and in all subjects, it must be regarded as an integral and normal part of mam-
marial bone. The granular condition of bone tissue is tolerably obvious in all preparations,
though it is much more marked in some specimens than in others. The amount of the
component granules varies in dilTerent parts of the same specimen, and in specimens taken
from different parts of the skeleton. Thus, in one situation, we may see laminae with a
highly transparent part gradually merging into a transparent tissue, while in another the
laminte may be granular throughout. Again, in young bone developed in cartilage, the part
between the cells becomes highly granular, fragments of which may be found in certain
adult bones, as in the petrous portion of the temporal bone. Bone near the articular surface
frequently presents a well-marked granularity."

We may remark, in addition to this very just account of the minute structure of bone, that
of the lower vertebrata above referred to, the Skate offers one of the best examples of
structureless bone, in those polygonal plates which are developed (not on the surface, as is
commonly said, but) in the interior of the cartilaginous skeleton. — Tks.]

276

SPECIAL HISTOLOGY.

described, and are placed so close together, that, according to Harting
(1. c, p. 78), from 709 to 1120, or, on the average, 910 of them
occur within the space of a square millimeter. They lie for the
most part mthin the lamellae, but also between them, and are in-
variably placed with their broad sides parallel with the surfaces of
the lamelh"©. The cayialiculi proceeding from them are much branched,
and penetrate the osseous substance in all directions, their course
being irregular, and often actually curved. They proceed prin-
cipally, however, in the first place, from both surfaces of the lacunse
straight through the lamellae ; and secondly, parallel with the Ha-
versian canals, from the two poles of the lacunae. It is only in
certain limited spots that these canaliculi present coecal termina-

Fig. 115.

u

§

Fig. 116.
» i .C

■Ti-t

sir'' I

J'

%

^^■

/?/

4' i""-^"-'.'

mftHM

u*^;f/

*/,

m

-^■y

vx.

tions ; everywhere else some of them anastomose in the most various
ways with the canaliculi of the neighboring lacunae, whilst others

Fig. 115. — From a transverse section of tbe shaft of the humerus; magnified 300 diam.:
a, Haversian canals; h, lacunfe with their canals, in the Haversian lamellap; f, lacunse of
the interstitial lamelte; d, lacunas with unilateral canaliculi proceeding to the surface of
the Haversian system.

Fig. 116. — Section parallel with the surface from the shaft of a human /c??i?ir; magnified
100 diam. : a, vascular canals: 6, lacunDe seen from the side, belonging to the lamells; of
these canals ; c, lacunjE viewed on the flat side, in lamellrt which are cut horizontally.

THE OSSEOUS SYSTEM.

277

communicate with the vascular canals, the medullary cavities, and the
medullary spaces or cancelli of the spongy substance, or open on the
surface of the bone. The entire osseous substance, therefore, is petie-
trated by a connected system of cavities and canaliculi, by means of
which the nutritive juice secreted by the vessels is conveyed into its
densest tissue.

The lacunar and canaliculi do not exhibit precisely the same condi-
tions in every part of the bones. In the lamellar systems of the Ha-
versian canals, as seen in a transverse section, the elongated lacunoe,
by reason of their curvature, lie as it were concentric to the canal, and
their excessively numerous pores or canaliculi necessarily produce a
very close striation radiating from the vascular canal (Fig. 115).
The lacunne are sometimes extremely numerous, sometimes more
scanty ; in the former case they are, for the most part, arranged
in tolerably regular alternation, or one behind the other in the
direction of the radius of the lamellar system ; but they are also
frequently disposed very irregularly, either crowded together {vide
the lower part of Fig. 115), or separated by wider interspaces. In
horizontal and longitudinal sections of Haversian canals (Fig. 116),
when the section has passed through the middle of a canal, the
lacunas appear narrow and elongated, and disposed in rows one be-
hind the other, and in numerous layers parallel with the canal ; and
also furnished with numerous canaliculi, which proceed for the most part

A:

■J \y- '•' .

Y^iSii--^,

directly inwards and outwards (consequently transversely through the
lamcllaj), but partly in a direction parallel with the long axis of the

FiO. 117 — Lacunae viewed on the flat side, with the canahcidi, from the parietal bone;
magnified 40U diam.: the spots on the lacun;r or between them belong to canaliculi, which
are cut across, or are the openings of canaliculi into the lacunte ; aaa, groups of transverse
sections of canaliculi, each group belonging to a lacuna which has been destroyed in the
makinff of the section.

278 SPECIAL HISTOLOGY.

canal. If the section strike the surface of a system, the superficial
lacunae come into view, presenting very elegant forms, rounded or oval
(Figs. 115 cZj.and 117), surrounded in an irregular manner by a complete
tuft of canaliculi, which look directly towards the observer, and con-
sequently appear more or less shortened, and by a smaller number of
other canaliculi distributed on the surface of the lamellas. Occasion-
ally, even in the thinnest parts of a section, there occurs a tuft of canali-
culi, cut across transversely, and without the lacuna to which they
belong, whence these portions of bone exhibit a sievelike aspect. All
the canaliculi arising from the inner aspect of the innermost lacunae of
an Haversian system, proceed towards the canal, with which they, by
this means, communicate, as may be clearly seen in thin, perpendicular,
and transverse sections of bones filled with air, and in the walls of
medullary canals laid open longitudinally. From the borders and ex-
ternal aspect of the same lacunee other canaliculi are given off, which per-
haps occasionally terminate in blind extremities, but for the most part
communicate with those of the neighboring, and particularly of the outer
lacunre. The succeeding rows of lacunae are all mutually connected in a
similar way, and thus the network of canaliculi and lacunae extends to the
outermost lamellae of the system, where the lacunae either commuincate
with those of the contiguous systems or of the interstitial lamellae, or
terminate independently, in which latter case (Fig. 115 d) all the ca-
naliculi, or at least most, and the longest of them, proceed inwards, that
is to say, towards the vascular canal, from which they derive their
nutritive fluid.

In the interstitial osseous substance between the Haversian systems,
when it exists in small quantity, the few lacunce, frequently not more
than from 1 to 3 in number, are disposed more irregularly, and also
present a rounded form (Fig. 115 e); when the interstitial substance is
more abundant, and distinctly lamellar, the lacunar are also disposed
more regularly, with their sides parallel to those of the lamellae. The
canaliculi of these lacunae, in like manner, communicate with each
other, and with those of the neighboring sj'^stems. In the outer and
inner fundamental lamellae, lastly, the lacunae are all placed with their
surfaces parallel with those of the lamellae, and consequently looking,
for the most part, inwards and outwards, or towards the centre and
periphery of the bone. In transverse sections they precisely resemble
those of the Haversian systems, only that they are but little or not at
all curved, except in the smallest cylindrical bones. In longitudinal
sections, whether perpendicular or parallel to the surface, they present
the conditions above described, with this limitation, however, that a
larger number of lacunae, of course, are seen in the same space in the
latter case than in the former, and also that the sievelike aspect described
above is more frequently observed, giving the bone considerable resem-

THE OSSEOUS SYSTEM. 279

blance to certain sections of teeth (Fig. 117). The canaliculi of these
lainellsB communicate, in part as usual with each other, in part open on
the external and internal surfaces of the bone (Pig- 118). At the points
of insertion of tendons and ligaments

. Fi"-. 118.

into the bones, the canaliculi of the ^..^.i^t^.aMs^:^^^^.^,^'^^^^.^.-..^. . , ^ ,1,.-.,^-^

outermost lacuna) probably terminate i0-;^^ii^:^::-::y-:-lj-^^^^

in blind extremities ; a condition which i^^[^!i^i-}^^^!j::^i'^^i^'-^'^

obtains in every case, in those parts fe^i-V^^^ii^^i^/;;:" ^^•:-^^^^^

of bones which are covered with car- ^■';>>:V:':";v^''^"^

tihige (articular ends, ribs, surfaces of ^'/^//•-■y^^'irp'.'':''-''-^''::.:^-

the bodies of the vertebra?, (fee.) In V?"^-- ';.:V

the rods, fibres, and plates of the \.';i'. ;■■;.:: -'v^

spongy substance, the lacunar are dis- " '^ - •■-.

posed in every possible direction, but for the most part, with their long
axis parallel to that of the fibres, bars, &c., and with their flat surfaces
directed towards the cancelli. They anastomose also, in these situa-
tions, by means of their canaliculi ; and the most superficial lacuniTS
open freely into the cancelli.

The size and shape of the lacuna?, in man, upon the whole, vary but
little. By far the greater number are melon-seed-shaped or lenticul;^
some, more fusiform or spherical. In sections of bone well filled with
air, in which alone I have made my measurements, I find their average
length to be 0-01-0'014 of a line, frequently under and above that size,
or from 0*006 to 0-0 IG, rarely 0-02 or even 0-024 of a line (cranial
bones, lower jaw). The breadth, measured in horizontal sections, is
0-003-0'006 of a line; in transverse, it is usually somewhat greater, or
as much as 0*008, or even 0*01 of a line, because the limits between the
canaliculi and lacuna; cannot always be accurately defined. Their thick-
ness or depth, lastly, in the smallest lacuniB, is 0*003-0*001, and in the
larger 0-002-0-001 of a line. The diameter of the spherical lacunae is
0*000-0*008 of a line. The canaliculi are, on the average, 0*008-0*016
of a line long, seldom less or more, up to 0*02 and 0*024 of a line; in
diameter they measure 0*0004 of a line; at the finest extremities, 0*0005-
0-0008, on the average; 0*0008-0*001 of a line, at their origin from the
lacuna?. Their true distance apart, in horizontal sections, in which they
appear as holes, is 0*0008-0*002 of a line; in transverse sections, in
which they produce the radiating stria?, in consequence of their being
viewed in several planes, they appear to be somewhat closer together, or
at distances varying from 0*0008-0*0012 of a line. The circumference

Fio. 118. — Portion of the surface of the tibia of the calf, viewed on the externa! aspect,
magnified 350 diam. : the numerous points are the openings of the canalicuH ; the dark,
larger, indistinct spots indicate the lacunEe to which these canaliculi belong, appearing from
a greater depth.

280

SPECIAL HISTOLOGY.

of a lacunre, together with the radiating canaliculi belonging to it, forms
an imperfect sphere, having a diameter of from 0*02 to 0-034 of a line;
■with reference to which, however, it must not be forgotten, that individual
canaliculi transgress the usual length of the others, as I have, in fact,
measured anastomoses between two lacunae of the length of 0-04-0-0J:5
of a line.

The contents of the lacunce, according to the later investigations of
Bonders, Virchow, and myself, appear very closely to resemble those of
the cells of cartilage during life ; that is to say, they are clear, probably
viscid fluid, with a nucleus. If bone-cartilage be boiled in water or
caustic soda for 1 or 2 minutes, these nuclei often show themselves very
distinctly ; or opaque corpuscles make their appearance, which must be
regarded as the contracted cell-contents including the nucleus, and analo-
gous to the corpuscles in cartilage. A peculiar phenomenon is seen to
occur, when bone is macerated in hydrochloric acid, which was first
noticed by Virchow in a diseased, and afterwards in healthy bone, and

by myself in the eeme^itum of the horse's tooth,
— the lacunie become isolated, having longer or
shorter processes, and appear like independent
structures, or a sort of stellate cells. This
phenomenon seems to depend simply upon the

y^v/J' ^^^ \ circumstance, that the tissue immediately sur-
'^y^P^^^J^^ rounding the lacunae offers more resistance to

'^ X the action of the acid than it does elsewhere.

In the cementum of the horse's tooth, cells also
enclosing the lacuna?, and even Haversian ca-
nals, may be isolated, — the best proof, that everything which thus pre-
sents itself in an isolated form, is not necessarily a morphological unity.*

Fig. 119. — A bone spicule from an apophysis, with distinct lacunwand nuclei. Boiled in
water, and magnified 350 diameters.

* [It is of very great importance in histology to keep in mind the caution expressed in
the last paragraph of the text (see below, note § 101), which applies as well to optical as to
chemical distinctness.

Tomes and De Morgan assert that both the lacunce and canaliculi have parietes, which are
manifested by appearances similar to those observed in the dentinal tubes. They some-
times found the lacuna and canaliculi filled up to a great extent with solid matter, so as to
leave only a small space in the centre.

An important modification of the lacunce is described and figured by these authors (1. c, p.
8) in the circumferential laminre. Elongated tubes pass, in bundles or singly, more or less
obliquely from the surface towards the interior of the bone. When long, they are sometimes
bent once or twice at a sharp angle. They have parietes, and are connected laterally with
the canaliculi. They occur irregularly in the circumferential laminiP, and in these only.
[Similar .tubes exist in the cementum of tlie Teeth.]

We can confirm Messrs. Tomes and De Morgan's statement that the nuclei may be found
without (liiriculty in recent bone, and they may always be brought out with great distinctness
by the action of dilute hydrochloric or strong acetic acid. This is especially the case in

THE OSSEOUS SYSTEM. 281

§ 92. The Periosteum. — Among the soft tissues appertaining to
bone, the jjcriosteum is one of the most important. It is a more or less
transparent, sliglitly glistening or -whitish yellow, vascular, extensible
membrane, investing a great part of the surface of bones, and contribut-
ing most importantly to their nutrition, by the numerous vessels Avhich
it sends into their substance.

The periosteum is not, everywhere, constituted alike. Opaque, thick,
and for the most part with the glistening aspect of tendinous structures
where it is covered only by the skin, or is connected with fibrous parts,
such as ligaments, tendons, fascia>, and the dura mater cerebri, it is, on
the other hand, thin and transparent in situations where muscular fibres
arise directly from it without the intervention of tendon, and also on the
diaphi/ses, where the muscles nearly rest upon the bone, as on the ex-
ternal surface of the cranium [jyericranium), in the vertebral canal, and
in the orbit (periorbita). Where mucous membrane rests upon bone,
the periosteum is, in most cases, very intimately united to it by the sub-
mucous connective tissue, so that the two cannot be separated, and con-
stitute a single membrane, which, as in the palate, alveolar processes,
nares, kc, is of greater, or, as in the maxillary sinus, tympanum, ethmoid
cells, &c., of less thickness.

The connection of the periostewn with the bone itself is either more
lax, consisting in simple apposition, and by more delicate vessels which
penetrate the bone, or more intimate, taking place by means of larger
vessels and nerves, and by numerous tendinous filaments. The former
mode of connection is found especially where the periosteum is thin, and
the osseous substance more compact, as in the diaphjscs, on the inner
and outer surfaces, and in the sinuses of the cranium ; the latter, where
the periosteum is thicker, and the compact substance thinner, as, for
instance, in the apophyses, in the short bones, palate, and at the basis
of the cranium.

"With respect to the intimate structure of the periosteum, it will be

young bone. In old bone we have frequently been unable to discover them. Tomes and
De Morgan, however, state that the nuclei are visible in sections of a fossil bone (supposed
of a Pterodactyle) in their possession.

Another peculiar condition of the " lacunal cells," described by these authors, is their ossi-
fication. Tliey found the light and spongy bones of old people to yield, if broken, a white
powder, which was composed of large cells detached or united into masses. They are
spherical, and contain a dark granular nucleus, which is surrounded by a thick transparent
wall. Similar cells may be found adherent to the walls of the Haversian canals and can-
celli; and in this case their nuclei have assumed the form of lacuna, and the canaliculi of
adjacent lacuncR advance into them. Similar cells may be found in most preparations of
adult bone (1. c, p. 12).

We must confess that we doubt the as.^umption of a lacunal form by the '-nucleus" in
these^cases. We have repeatedly examined these bodies, but if the nucleus was visible at
all, we found it unchanged, and often adhering to one side of the lacuna. Again, it is ques-
tionable whether they may not rather be compared to the globules of dentine than to cells.
— Tks.]

282 ' SPECIAL HISTOLOGY.

found to present, almost universally, excepting where muscles arise
directly from it, two layers, which, although closely connected, differ,
more or less distinctly, in their structure. The outer layer is composed
chiefly of connective tissue, with occasional fat-cells, and is the principal
seat of the true periosteal vessels and nerves, whilst in the inner layer,
elastic fibres, commonly of the finer sort, constitute continuous, and often,
very thick networks — true elastic membranes — superimposed one upon
another, the connective tissue forming the less important element. Nerves
and vessels occur in this layer also, but they do little more than merely
pass through it, being destined for the bone itself.

The parts of the surface of bones unprovided with periosteum are :
1. The articular extremities covered with cartilage, and all other places
where the bone is covered with cartilage or fibro-cartilage. 2. Where
ligaments and tendons are attached to the borders and surfaces of bones
at a certain angle, as, for instance, at the insertions of the ligamenta
jiava, intervertebralia, iliosacra, interossea, teres ossis femoris, patellse
&c., of the tendons of the deltoid, coracobraehialis, popliteus, iliopsoas
triceps, surce, quadriceps femoris, glutcei, &c. In all these situations
the tendons, ligaments, and cartilages, are attached directly to the bone,
as has been already in part described, and not a trace of periosteum can
be detected.

§ 93. Marrotv of tJie Bones. — Almost all the larger cavities in the
bones are occupied by a soft, trasparent, yellowish or reddish, highly
vascular substance, the 3Iarroio (medulla ossiuyn). In the cylindrical
bones, this substance is found in the medullary canal, and in the cancelli
of the apophyses, whilst it is wanting in the compact substance, unless it
be in the larger canals; the same is the case in ihe fiat and short bones,
the cancelli of which are filled with marrow ; but the diploe of the flat
cranial bones, besides the marrow, also contains large veins, of which
more will be said afterwards. In accordance with what has been re-
marked, these venous spaces, the canales nutritii, Haversian canals, and
the above described nerve-canals and air-cavities of the bones, contain
no marrow.

The marrow appears in two forms, one yellow, the other red. The
former, as a semifluid substance, occurs principally in the long bones;
and according to Berzelius, consists, in the humerus of the Ox, of 96*0
fat, 1"0 connective tissue and vessels, and 3*0 fluid with extractive matter,
such as is found in muscle ; whilst the latter occurs in the apophyses,
flat and short bones, above all in the bodies of the vertebrae, the basis
cranii, the sternum, &c., and is distinguished not only by its reddish or
red colour and less consistence, but also by its chemical composition ;
for, according to Berzelius, this substance, in the diploe, contains 75*0

THE OSSEOUS SYSTEM. 283

water, 2-5-0 solid matters, such as albumen, fibrin, extractive matter,
and salts, similar to those of muscle, and merely traces of fat. With
respect to its structure, it presents, besides vessels and nerves, connective
tissue, fat-cells, free fat, a fluid, together with, lastly, peculiar minute
cells, marroiv-cells. Connective tissue and fat are universally present,
though in very various quantities. The former, on the surface of the
larger medullary masses of the diaphyses, is of rather firmer consistence,
but cannot properly be described as a medullary membrane [endosteum,
periosteum internum), because it does not admit of being separated as
a continuous structure. In the interior of the marrow in the spongy
bones, scarcely any connective tissue can be detected except in the larger
masses of it, whilst in the diaphyses, this tissue can be readily demon-
strated as a very lax and delicate, areolatcd structure, containing the fat
and supporting the vessels and nerves. Its elements correspond with
those of the lax connective tissue [vide § 24) ; although, as far as I have
seen, it does not contain any elastic filaments. Fat-cells of 0-016-0-032
of a line, not unfrequently Avith a distinct nucleus, occur in large quanti-
ties in the yellow, more dense marrow, quite as abundantly as in the
panniculus adiposus, but for the most part not aggregated into distinct
lobules. In the reddish marrow, when expressed, they are more rare ;
and in the red pulp of the bodies of the vertebrae and of the flat cranial
bones, they occur only in very minute, scanty accumulations, or alto-
gether isolated, to which circumstance, according to Berzelius, is owing
the small quantity of fat in the diploe. In dropsical marrow these cells
are frequently only half filled Avith fat, or with but one or
more globules, containing, besides, a large quantity of
serum ; and in hyperemia of the bones, they appear occa-
sionally to be diminished in size, and occasionally elongated
and fusiform. Free fat-glohules, and a clear or yellowish
fluid, are often met with in the softer kinds of marrow,
and frequently in considerable quantity. That the former
have not been set free from cells, in the preparation of the
specimen, may be satisfactorily shown, but it must remain uncertain
whether or not they are to be referred to cells that have ceased to exist.
Lastly, there occur, together with some fluid, in all the red, or even only
reddish marrow {tiever in the yellow), minute roundish, nucleated cells,
exactly like those of the young medulla {vid. infra, fig. 132). These me-
dulla-cells correspond in every particular with those, which Hasse and
I (" Zeitsch. f. ration. Medicin," Bd. V.) found in the hypersemiated red
marrow of the articular extremities of the cylindrical bones, but never-
theless normally exist in the vertehrce, the true cranial bones, in the
sternum, and in the ribs, whilst they are wanting in the long and short

Fig. 120. — Two fat-cells from the marrow of the human femur : a, nucleus; 6, cell-mem-
brane ; c, oil ; magnified 350 diameters.

284 SPECIAL HISTOLOGY.

bones of the extremities, and in the scapula and os innoniinatum, occur-
ring apparently in variable number in the bones of the face.*

§ 94. Connections of the Bones. — A. synarthrosis, connection Avithout
articulation.

1. By suture. In this mode of connection, the bones are united by
an extremely thin, membranous, whitish streak, to which authors have
incorrectly given the name of sutural cartilage. It is composed merely
of connective tissue, which, like that of the ligaments, extends, in short,
parallel fasciculi, from the border of one bone to that of the other, and
is characterized solely by the presence of numerous, short, unequal-sized,
usually elongated nuclei. This sutural ligament, as it may be termed,
is very evident as long as the cranial bones are still growing, at the same
time, that it is softer and differently constituted [vide infra). As the
growth of the cranium approaches its completion, this tissue gradually
disappears, becomes firmer, and, in old age, seems, in many places,
especially on the inner part of the sutures, and even before their com-
plete obliteration, to be entirely removed.

2. Connection hy ligament, syndesmosis, is effected by means o? fibrous
and elastic ligaments. The fibrous ligaments, constituting the majority
of the ligaments, are white and glistening, corresponding in their struc-
ture, partly with the aponeuroses and ligaments of the muscles, and
partly with the true tendons.

Elastic ligaments (Fig. 121), are, the ligamenta flava, between the
arches of the vertebrae, and the ligamentum nuchse, which, however, is
not nearly so well developed in man, as in some others of the Mammalia.
The ligamenta flava are yellowish, highly elastic, strong ligaments, the
elastic elements of which, in the form of roundish polygonal fibres, 0-0015
-0-004 of a line thick, united into a dense network, run parallel with the
long axis of the vertebral column, and give the longitudinal, fibrillar
aspect to the ligaments. Between these fibres, which are not collected
either into fasciculi or lamellce, but are continuously connected through-
out the entire thickness of each yellow ligament, there is interposed some
connective tissue, upon the whole in small quantity, but demonstrable in
every preparation, and occurring in the form of lax undulating fasciculi,

* [These nucleated medulla-cells exist in great number in the superior maxillary bone of
Man and of many of the Vertebrata. Several of them are sometimes enclosed in a common
cell-wall, forming a variety of cell, frequently seen in pathological formations, viz. the
parent-cell of the German authors, the plaque k noyaux multiples of Robin.

The occurrence of nucleated cells in the normal medulla of the bones of the face has been
mostly overlooked, and has hence given rise to many errors on the part of pathologists. In
the description of morbid changes of the bones of the face, especially in those of the superior
maxillary bone, representations are frequently given of small cancer-cells or nuclei, taken
from the interior of the bone, virhich are but the normal nucleated cells of the medulla.
Many tumors of the upper jaw have thus been pronounced cancerous, which were simply
non-malignant hypertrophies of the bone. — DaC]

THE OSSEOUS SYSTEM.

285

Tig. 121.

S^^

Avliicli are arranged parallel with the principal direction of the elastic

fibres. Accordino; to Todd and Bow-

man (p. 72), the stylo-hjoid, and

internal lateral ligament of the lower

jaw, arc, also, chiefly composed of

strong elastic fibres.

3. By cartilage, syncliondrosis.
This mode of connection is effected
either by cartilage alone, or asso-
ciated with fibro-cartilaginous and
fibrous tissue. The former condition
is observed in the adult, only between
the ribs and sternum, where, how-
ever, properly speaking, a true syn-
cJiondrosis exists only in the case of
the first rib, the rest, from the second
to the seventh, being connected with
the sternum at the anterior extre-
mity by articulation ; whilst the
false ribs are either free at the ex-
tremity, or are incurved one beneath
the other. In the symphysis pubis,
sacro-iliac synchondrosis, and the
junctions of the bodies of the verte-
Irce, the surfaces of the bones are
covered immediately by a layer of
true cartilage, which, in the two
former situations, is directly connected with the opposite layer, and in the
latter by means of a fibro-cartilaginous tissue, and is externally encircled
by fibro-cartilaginous, and fibrous, concentric layers. In the two former
of these instances, there is, not unfrequently, a cavity in the interior of
the connecting substance, so that the sacro-iliac sychondrosis, in particu-
lar, may also be regarded as a sort of articulation (Zaglas).

The intervertebral ligaments, or ligamentous discs, of the bodies of
the vertebrne, consist, 1, of exterior concentric layers of fibro-cartilage,
and whitish connective tissue ; 2, of a central, principally fibro-cartila-
ginous substance ; and 3, of two cartilaginous layers applied immedi-
ately upon the bones.

The concentric lamellce consist of alternate layers of connective tissue
and of fibro-cartilage, which latter, even in fresh transverse sections,

Fig. 121. — ^, a transverse section through a portion of the ligamentum nucha of the Ox,
magnified 350 diameters, and treated with soda : a, connective tissue, apparently homoge-
neous; b, transverse section of the elastic fibres (0-004-0 01 of a line in diameter). B, elastic
fibres; a, from a human lig. sidiflavum, together with some connective tissue, b, between
them, magnified 450 diameters.

286

SPECIAL HISTOLOGY.

may be recognized as dull yellow streaks, which become hard and trans-
parent in water. The fibro-cartilage, on microscopic examination, pre-
sents minute, elongated cartilage cells, disposed serially in a fibrous
tissue, differing from connective tissue in its greater rigidity, the absence
of distinct fibrils, its great resistance to alkalies and acetic acid, and the
total absence of elastic fibres.

The whitish layers of the outer laminse, although their fibrils are
rather more rigid than those of the common ligaments and tendons, are
less easily separated, and present but few fusiform cells, and frequently
no elastic fibres whatever among them, must nevertheless, at present, be
regarded as composed of connective tissue. These laminge are from J
to I of a line and more in thickness, and form entire circles or segments
of such, which, alternating with the somewhat thinner, and also fre-
quently incomplete, rings of fibro-cartilage, with which they are closely
connected, together with the latter constitute the larger half of the in-
tervertebral ligaments. The general direction of the fibres of both sets
of laminte is from above to below. They are, however, invariably
oblique, so that those of the different layers cross each other. Besides
•which, it must be remarked, that the individual layers themselves also
exhibit a more or less distinctly foliated structure, constituted in such a
manner that the fine lamellas, in the portions composed of connective
tissue, observe the same direction as the layers themselves, whilst in the
fibro-cartilaginous portions they are disposed more in the direction of
the radius of the ligamentous disc.

The softer central substance of the intervertebral ligaments, or the
gelatinous nucleus of authors, does not differ, essentially, from the por-
tions above described ; for, even in this situation, layers of connective
tissue occur, although they gradually diminish in proportion to the
fibro-cartilage, and are less distinctly defined. The nearer we approach
the centre, the less evident is any trace of an alternation of different

layers, and of a concentric ar-
rangement of them ; the whole
becomes transparent, soft, and,
finally, almost homogeneous. The
microscope shows the predomi-

Fifr. 122.

Z.

P

c

nance of fibro-cartilage, with

large cells (0-012-0-024 of a
line), frequently one within the
other (Fig. 122)-; the uniformly thickened walls of which, composed of

Fig. 122. — Cells from the gelatinous nucleus of the lig. intervertebralia : 1, large parent
cell, a, with a septum derived from two secondary cells of the first generation, and five
secondary cells, b, of the second generation; with concentrically thickened walls and
shrunken nuclei, c, in the small cell cavities: 2, parent cells, a, with two secondary cell.",
separated by a delicate septum, b, and which, with uniformly thickened walls, contain a
minute cavity and shrunken nucleus, c.

THE OSSEOUS SYSTEM. 287

concentric layers, often enclose merely a minute cavity, with a shrunken
nucleus; and besides these, smaller cells frequently in process of dissolu-
tion, isolated or aggregated together ; and, lastly, an indistinctly fibrous
or granular matrix, not unfrequently observed in a state of disintegra-
tion, and a considerable quantity of fluid contained in larger or smaller
areolar spaces in it. The more central portions of this fibrous substance
gradually pass into a thin, hard, yellowish lamella of true cartilage, with
thickened cells, not unfrequently beset with calcareous particles, which
adheres to the bone not unlike an articular cartilage, though less firmly.
More externally we find a cartilaginous substance, in the form of isola-
ted, minute, discoid plates or particles, which appear to be in more im-
mediate connection with the fibro-cartilaginous portions, and between
these a connective tissue, with scattered cartilage-cells, as in the inser-
tions of the tendons into the bones {vide § 81). The more exterior por-
tions of the surfaces of the bodies of the vertebrae, corresponding to these
parts of the discoid-ligaments, are, in contradistinction to the more in-
ternal portions, as it were porous, after the removal of the ligamentous
layer ; the medullary cavities or cancelli then being exposed. The
pores or cancelli are closed only by the cartilaginous substance of the
disc, whilst the fibrous tissue, with its vertical fibres, is firmly connected
with the interspaces between them.

Between the sacrum and coccyx, and the individual coccygeal verte-
brae, are interposed the so-called fahe intervertebral ligaments, consist-
ing of a more uniform fibrous substance, without any gelatinous nucleus.
The separate bones of the sacrum, at an early period, have true inter-
vertebral ligaments between them, which afterwards become ossified
from without to within, but in such a way, nevertheless, that even in the
adult, traces of the ligament may still be perceived in the centre. With
respect to the nature of the fibres of the intervertebral ligaments, Bon-
ders is inclined, especially from the consideration of their chemical re-
lations, to regard almost all of them, not as connective tissue, but as
analogous to the matrix of true cartilage, as is also H. Meyer (p. 300,
et seq., and p. 310). This opinion may be correct, as regards the cen-
tral, nuclear portion, and the fibro-cartilaginous laminse of the outer
portions, but hardly so with respect to the purely fibrous parts of the
latter. I believe, moreover, that it is not by chemistry, but by the
study of the development of these tissues, that the question will be
solved, because, although manifest, visible distinctions exist between the
fibrils of connective tissue developed from cells, and the fibrous inter-
cellular substance, viewed from a genetic point of view, chemistry pro-
bably is not in a condition to distinguish one from the other.* The in-

* [In onr note on the connective tissue, we have already expressed the views we enter-
tain of the homologies of tlie elements of cartilage and connective tissue ; and we need
merely add that we know of no locality in which the transition of the matrix of cartilage

288 SPECIAL HISTOLOGY.

tervertebral ligaments are liable to various forms of degeneration ; they
may become ossified, from their cartilaginous lamellte outwards, the
true fibrous substance probably at the same time disappearing ; and in
this way anchylosis of two vertebrae frequently takes place. They may
become atrophied, easily broken down, and disintegrated, either in the
nuclear portion, or elsewhere in circumscribed spots, into a dirty gru-
mous matter. And lastly, it would appear that although in the normal
state, they contain no vessels, vessels may, under certain morbid condi-
tions, be developed in them ; at all events, extravasations of blood are
not unfrequently met with, most generally close to the bones or in con-
nection with them.

In the si/mphysis pubis, the cartilaginous layer, which is thickest in
the centre and anteriorly, and connected with the bones by a very un-
even surface, consists, at the sides, where it is from J to 1 line thick,
of true cartilage, with a homogeneous, finely granular matrix and sim-
ple cells, measuring 0 •01-0-024 of a line. In the centre, the matrix is
softer and fibrous, and in this situation (more particularly, it would
appear, in the female sex), there occasionally exists an irregular narrow
cavity, with uneven walls, and containing a somewhat slimy fluid, origi-
nating evidently in a solution of the innermost cartilaginous layers, and
of which manifest traces may be perceived in the cartilaginous substance
immediately enclosing it. The outer layers of the symphysis, which, as
is well known, are most developed anteriorly and superiorly, do not
arise, with the exception of the outermost lamellse composed of pure
connective tissue, directly from the bones, but, properly speaking, unite
only the outer portions of the above-described cartilaginous layers, and
consist principally of a fibrous substance, to all appearance identical
with connective tissue, and occasionally containing cartilage cells.

The formation of the bone-corpuscles, as they are termed, may be
traced perhaps more clearly in the symphysis than anywhere else, except
in rachitic bone (Fig. 124). For at its osseous borders there are always
to be found, either half projecting from, or entirely lodged in, the carti-
lage, isolated, nucleated bone-corpuscles or cells, with homogeneous, and
(from calcareous salts) granular walls, measuring 0-012-0-016 of a line
with respect to which, from their development and from the considera-
tion of the contiguous cartilage-cells, all of which present more or less
thickened walls and rudiments of calcareous deposits, not the smallest
doubt can be entertained. Well-characterized, half and wholly ossified
parent cells of the same kind, with two secondary cells, and measuring
0*015-0-03 of a line, up to some including ten or twenty secondary cells

into the pseudo-fibrillated collagenous portion of connective tissue is more unmistakably
exhibited, than in the intervertebral cartilages of a young animal, e. g., a kitten. We have,
in that note, endeavored to sliow that the notion of the existence of any real difference in
the development of the fibrillated element in the different forms of connective tissue is un-
founded.— Trs.]

THE OSSEOUS SYSTEM.

289

and having a length of 0-05 of a line, may be distinctly noticed in almost
every preparation.

Fis. 123.

The sacro-iliac synchondrosis is effected by means of a flattened layer
of cartilage, |-1^- of a line in thickness, which is closely attached to the
articular surfaces of the corresponding bones, bet^Yeen which it is inter-
posed. The cartilage-cells close to the bone are flattened, with their
surfaces directed towards it, and present beautiful transitionary forms
into half and wholly isolated bone-cells, which exist on the border of the
bone. In the interior of this cartilaginous layer, according to Zaglas,
there is always a narrow cavity, which separates the cartilaginous layers
of the two bones completely, or almost com.pletely, from each other. It
contains a synovia-like fluid, and is bounded by smooth and even walls,
Avhich difi"er from the rest of the cartilaginous substance in their greater
hardness, as well as in their structure. The matrix of these cartila-
ginous layers, in the direction of the surface, is finely fibrous; the cells
are all of large size (as much as 0*035 of a line), with numerous secondary
cells and uncommonly thick walls, so that the cavities, even of the se-
condary cells, often appear extremely contracted ; but they do not exhi-
bit any distinct indication of pore-canals or calcareous deposit.

The costal cartilages are invested by a strong perichondrium, composed
of connective tissue and numerous elastic elements, which commences at
the sternal end in connection with the synovial membrane there existing,
and at the other is continuous with the periosteum of the ribs. The
cartilage, which is in connection with this membrane by a roughened
surface, is of considerable firmness although elastic, pale, yellow, or in
thin sections, exhibiting a transparent blue tint, internally almost always,

Fig. 123. — Cartilaginous border, towards the cartilage of the syiuphysis in Man; a, carti-
lage cells with thickened walls; 6, the same undergoing ossification; f, cells nearly ossified,
with homogeneous walls free in the matrix of the cartilage; d, similar cells with calcareous
granules; f, ossified cells at the border of the matrix of the bone containing calcareous gra-
nules, and half projecting from it. — Magnified .350 diameters.

19

290

SPECIAL HISTOLOGY.

Fig. 124.

in certain spots, of a yellowish-white color, with a silky lustre. Its
matrix in the latter situations presents a fibrous structure, and elsewhere
a finely granulated aspect. The outermost cells, to the depth of 0-06-
0-1 of a line, are elongated, flattened, parallel to the surface, most
usually small (sometimes not more than 0-006 of a line), but sometimes
larger, and filled with one or even many secondary cells, one placed be-
hind the other; more internally, without entirely losing their flattened
figure, they are larger (most of them 0-03-0-05 of a line), oval, and
round, and lie with their surfaces towards the ends of the cartilage, and
with their long axis for the most part in the direction of the radius of
the transverse section of the rib; in many cases, however, they are dis-
posed more irregularly. The largest of these cells (measuring as much
as 0-08 or, even O'l of a line), are found in the fibrous spots, and they, in
common with all the interior cells, contain secondary cells, in varying,
frequently in very considerable number (as many as 60 according to
Donders). The most remarkable characteristic of the elementary tissue

of the costal cartilage is the
large quantity of fat con-
tained in it. In the adult,
every cell, excepting the
most superficial, contains,
larger or smaller (from
0-0016-0-008 of a line),
sometimes spherical, some-
times more irregular fat-
drops, which frequently so
surround the nucleus as en-
tirely to conceal it from
view (Fig. 124 a, 5), whence
it has been assumed, though
not quite correctly, that the
The cartilage on the greater cornu of the
08 hjoides, and between the body and the greater cornu, and the incon-
stant cartilaginous appendage to the styloid process, differ in no respect
from costal cartilage, only that the cartilage cells in those instances do
not always contain large fat-globules.

The costal cartilages frequently become ossified in old age ; but this
ossification, as well as the fibrillation of the matrix, must not be re-
garded as a normal process, nor be placed in the same category with the
usual kind of ossification. The ossification is sometimes more limited,

Fig. 124. — Cartilage cells of Man, magnified 350 diameters: a, parent cell with three se-
condary cells containing oil, from a costal cartilage; b, two cells from the same situation in
which the globule of oil is surrounded by a pale border; c, two cells with thickened wails
from the cartilage of the greater cornu of the os hyoidcs, which together with the globule of
oil also contain a distinct nucleus.

fat is seated in the latter.

THE OSSEOUS SYSTEM. 291

sometimes more extensive. In the former case, it does not proceed
further than to the incrustation of the cartiLage-cells, and of the matrix
in which they are lodged, which has become fibrous ; in the latter, and
frequently, also, in the former, the ossification is preceded by the forma-
tion of hollow spaces in the cartilage, in which is deposited a cartilage-
marrow, containing vessels, which are connected, in part with those of
the perichondrium, in part with those of the ribs ; and the osseous sub-
stance is more that of normal bone, though almost always more opaque,
less homogeneous, and with imperfectly formed lacunoe, which frequently
contain a calcareous deposit. Under the name of cartilage-marroiv, are
understood the medulla-cells, fat-cells, bundles of connective tissue and
vessels which are presented instead of the detritus, afforded by the dis-
integration of cartilage, and which may be said to correspond in all re-
spects with those of developing foetal bone, and may be readily observed
in ossifying costal and laryngeal cartilages.

§ 95. B. Movable Articulation [Biartlirosis). — The articular extremi-
ties of the bones, or any other surfaces entering into the formation of a
joint, are invariably invested with a thin layer of cartilage, which in the
middle of the surfaces covered by it, is of tolerably uniform thickness,
gradually thinning as it extends outwardly, and finally terminating with
a very abrupt edge. This articular cartilage is closely applied to the
bone with a rough, hollowed or raised surface, but is not united to it by
any interposed substance ; and, on the opposite surface, it is in most joints
usually quite bare, and directed towards the cavity of the articulation.
Sometimes, however, it is invested with a special fibrous membrane, a
pericliondrium, which is an immediate prolongation of the periosteum,
and extends most generally only over a small portion of the cartilage,
gradually ceasing without any defined margin.* In some joints (shoulder,
hip) the more secure lodgment of the articular head of the bone is in-
sured by special cartilaginous lips. These are firm, yellowish-white,
fibrous rings, attached, at the border of the articular cartilage, by a
wider basis, immediately to the bone or partly to the cartilage. They
thin off to an acute edge, and for the most part free and uncovered by
the synovial membrane, or any epithelium, project into the articulation,
being exteriorly in relation with the periosteum and synovial capsule.

• [Reichert, who has paid particular attention to the question of the existence of an epi-
thelium upon the articular cartilages, says, that in the fcetal condition of Man and the domes-
tic Mammalia, an epithelium exists over the whole surface of the synovial capsules, and, on.
the articular cartilage, lies in immediate contact with its substance. It resembles the epi-
thelium of the vessels. In adults, on the other hand, he could discover an epithelium only
on those parts of the articular capsules which are not subject to friction ; and here it had the
same appearance as in the foital condition. It was wanting upon the articular cartilages and
their immediate neighborhood; but it was not uncommon to meet with fme desquamated
flakes of cartilage in the synovia, which fell readily into folds, and thus resembled a fibro-
cartilaginous tissue (Bericht, Muller"s " Archiv.," 1S49, p. IG.) — Trs.]

292

SPECIAL HISTOLOGY.

Fisr. 125.

c. '.;, «

*^"^-^H^;yi

As regards the intimate structure of the parts just described, the
articular cartilage, on completely formed bones (Fig. 125), and under

normal conditions, presents throughout, a
finely granular, in part almost homogeneous
matrix, in which are lodged delicate cartilage-
cells, which towards the surface of the carti-
lage are numerous and flattened, and lie
parallel to it; more deeply they are oval or
rounded, more rare, and disposed in various
directions ; and lastly, close to the bone
they are elongated, and placed vertically
with respect to the surface of the bone.
These cells all have distinct walls, easily dis-
tinguished from the matrix by the use of
acetic acid, clear, frequently granular con-
tents, containing, however, but little fat, and
a vesicular nucleus. They occur either
isolated or in groups, and present very fre-
quently two, four or even more secondary
cells, which in the flat cells are placed close
together, and in the elongated are disposed
in rows. On the condyle of the lower jaw,
as on the corresponding surface of the tem-
poral bone, until the bone is completely
formed, there is a thick layer of very dis-
tinctly marked cartilage-cells, covered, to-
wards the cavity of the articulation, by a
layer of connective tissue. This cartilaginous layer disappears by de-
grees, as the bone approaches its completion, and at last there remains
beneath the layer of connective tissue, now become both relatively and
absolutely thicker, merely an excessively thin and transparent lamina,
the elements of which, although morphologically not true bone-cells, nor
as yet ossified, still seem to resemble the latter more closely than cartilage-
cells.

The cartilaginous lips of the joints consist principally of connective
tissue, always containing, however, isolated cartilage-cells of a roundish
or elongated form, with a moderately thick membrane, distinct nucleus,
and occasionally fat-granules. I have not as yet noticed parent cells in

Fig. 125. — Articular cartilage of a human metacarpal bone, cut perpendicularly : a, most
superfici'i!, flattened cartilage cells; 5, middle round cells; c, innermost cells, disposed per-
pendicularly in small rows; rf, outermost layer of the bone with ossified fibrous matrix and
thick- walled cartilage cells, in this instance appearing dark from their containing air; e, true
bone-substance; /, ends of the cancelli of the apophyses; ^, one of the cancelli. — Magnified
90 diameters.

THE OSSEOUS SYSTEM. 293

this situation, "svhilst cells of the kind already described in the muscular
system (§ 82), arranged in series, are not unfrequently met with, and
might perhaps be regarded as cartilage-cells, although their nuclei exhibit
the most evident indications of a transition into nuclear fibres. The
articular cartilages, moreover, during their development, ■which ■vvill be
entered into more particularly afterwards, have no nerves or vessels, as
is the case also with the cartilaginous lips.*

The condition of the bone beneath the articular cartilages, requires
special notice. It consists, in almost all joints, in immediate contiguity
with the cartilage, of a layer of incompletchj formed bo)ie-substance,
and, more internally, of that tissue in its usual form (Fig. 125). The
layer in question, which is 0'04-0*16, or on the average 0-12 of a line
thick, is composed of a yellowish, mostly fibrous, hard, and truly ossified
matrix, containing, however, not a trace of Haversian canals or medul-
lary cavities, nor of any perfectly formed lacunoe ; instead of which it
presents roundish or elongated corpuscles, aggregated into little masses
or rows, the larger of which are 0-016-0-024 of a line in length, and
O-OOG-0-008 of a line in breadth, and the smaller 0-006-0-008 of a line
in length, and 0-004-0-005 of a line in breadth, which give thin sections
of the bone a perfectly opaque aspect, and consequently might be
regarded as bone-corpuscles (lacunae) filled with calcareous particles, as
which they have lately been considered by H. Meyer (1. c, p. 325, 326).
By the addition of spirit of turpentine, which, however, penetrates with
difficulty, this error is dissipated, and it is found, that as in the case of
the laeunce of dried bone, the opaque aspect is due only to the air con-
tained in them, and that the bodies in question are nothing more than
thick-walled cartilage-cells, retaining their contents (fat, nuclei), present-
ing occasionally indications of canaliculi, and perhaps also partly calci-
fied ; in other words, that they are undeveloped lacunre. The layer in
which these cells are lodged, and which, towards the cartilage, is bounded
by a straight line, occasionally dark from calcareous particles, and

* [Besides the elements above mentioned, we find according to Dr. Leidy (see Am. Jour, of
Med. So., April, 1849), numerous minute lacunar, as an occasional peculiarity in tlie structure
of articular cartilage. These lacunre are described by Dr. Leidy as existing in greatest abun-
dance in tlie deeper part of the cartilage ; but decreasing in number, as its free surface is ap-
proached. They are lenticular in outline, and measure from l-r200tb-l-3120th of an inch;
when well defined, they appear beneath tlie microscope more translucent than the cartilaginous
matrix in which they are situated. When viewed a little within the focus of the instrument,
they are of a deep black color, and oppose the transmission of all light. Another peculiarity de-
scribed by Dr. Leidy is the penetrature of the structure of the cartilage by fibres or columns
of bone. Tliese fibres are quite uniform in shape and structure, being compressed and
cylindrical ; in transverse sections tliey present an elliptical figure. They are not numerous,
and vary from a size not exceeding a cell-group of 5 cells to the size of four or five such
groups. They are concentrically laminated, and also present a radiated conformation, resetri-
bling somewhat the structure of an Haver^ian canal, but neither the canal nor the Purkin-
jean corpuscles are discernible in them. — DaC]

294 SPECIAL HISTOLOGY.

towards the true bone by a sinuous contour, in wliicli the limits, as it
were, of the individual lacunas are distinguishable, is not found either
exclusively in bones not yet fully formed, as Gerlach believes, nor only
at a more advanced age (from 30 upwards, and particularly in old men),
as H. Meyer states, but, at all events as far as my observation extends,
at all ages, from the complete development of the bone upwards, inva-
riably in every articulation, except that of the lower jaw and those on.
the OS hi/oides.*

The articular cartilage on the head of the femur, in a man 25 years
old, measured 1-1^ of a line in thickness ; on the condyles in the middle
1^, on the margin, |-1 line ; in the fovea j^cctelke, Ij-lf of a line ; in the
middle of the condyles of the tibia, 1 J of a line ; at the borders, |-|ths
of a line; in the middle of the patella, lj-l|ths of a line ; in the glenoid
cavity of the tibia, J-|ths of a line, on the body of the astragalus, on
the upper side, |ths, on the under, ^, on its head, |ths of a line ; at the
base of the first metatarsal bone, -§— |, on its head -Jd of a line, on
the inner cuneiform bone, in front, ^-^, behind, i-fths of a line. In
the foetus, about the middle period of uterine life, the vessels of the
synovial membrane, according to Tojnbee ("Phil. Transact.," 1841),
extend much further upon the articular cartilage ; of which fact, how-
ever, I have been unable to satisfy myself in the humerus of a five or
six month foetus, or in new-born infants. In pathological states endo-
genous cell-formation is met with in an unusual degree of perfection, and
more especially in all kinds of articular cartilages ; in which the parent
cells, frequently of very considerable size, Avith one or two generations
of secondary cells, and also containing fat, lie tolerably free in the fibrous
matrix, and admit of being readily isolated (vide also Ecker in Rosera
and Wunderlich's "Archiv," vol. II., 1843, p. 345). In the adult, the
articular cartilages are non-vascular, although the vessels of the syno-
vial membrane, at their border, often advance to some distance over them.
What Liston ("Med. Chir. Transact.," 1840, pp. 98-4) describes as
"vessels in the articular cartilage of several diseased joints, and as run-
ning straight in parallel lines from the injected membrane of the bone
into the cartilage, and as joining ^t their further extremities in that
tissue, thus forming long loops," were certainly nothing more than the
normal vessels of cartilage, which [vide infra) may be very beautifully
displayed even in individuals 18 years old. There cannot, therefore, be
any question of inflammation of the cartilages in the adult, though they
doubtless suffer in morbid conditions of the bones upon which they rest,
or in inflammation of the synovial membrane. They frequently assume
a fibrous structure, a change which is often attended with a simultaneous

* [This peculiarity of the bone beneath the articular cartilages was first pointed out by
Dr. Shavpey (Quain and Sharpey, 5th ed., p. clviii.), and is particularly described by Tomes
and De Morgan, 1. c, pp. 10, 11. — Tus ]

THE OSSEOUS SYSTEM.

295

increase in thickness, Cruveilhicv (" Diet, de M(^d. et Chir. prat." III.,
514) having noticed fibres of this kind as much as G lines in length, thus
far exceeding the normal thickness of articular cartilage. They some-
times wear away rapidly, or even disappear altogether (in suppuration
in the bone or in the articulation), so that the surface of the bone is left
exposed; they also undergo partial loses of substance; when they
exhibit ulcerous excavations, which may penetrate to the bone, or com-
mence on the osteal surface of the cartilage.

§ 96. The articular capsules [capsulce s. memhrance synoviales) are
not closed capsules, but short, wide tubular sacs, which are attached by
two open ends to the borders of the articular surfaces of the bones, and
thus connect them together. They are essentially more or less delicate,
transparent membranes, but are in many situations so closely and com-
pletely invested externally by fibrous layers — the fibrous capsules as they
are termed, — as on cursory inspection to present the aspect of tolerably
tough capsules. These fibrous coats are met with especially in situations
where the articulation is either wholly unprotected, or but thinly covered
by soft parts, or where a very firm connection is required (as in the hip-
joint); they are absent for the most part, or are undeveloped, where
muscles, tendons, and ligaments rest upon the articulation, or where, for
special purposes, the synovial membrane is exposed to more considerable
movements (as in the knee and elbow).

The relation of the articular capsules to the bones and articular car-
tilages, more precisely described, is as follows (Fig. 126) : — The articular
capsule is attached, either simply to the border of
the cartilaginous surface, extending thence directly
to the other bone [patella, ampliiartliroses) ; or it
may, in the first place, besides the border of the
cartilage, also invest a larger or smaller extent of
surface of the bone itself, and then pass to the
second bone, with which it is connected in the one
way or the other. In either of these cases the
synovial membrane does not adhere immediately to
the hard tissues subjacent to it, but is more or less
closely connected with the periosteum and peri-
chondrium, ultimately ceasing without any distinct
margin, not far from the border of the articular cartilage, with the
perichondrium of which it is inseparably united.

With respect to the intimate structure of these tissues, the synovial

Fig. 12G. — Diagram of a transverse section of a phalangeal articulation, partly after
Arnokl : a, bones ; 6, articular cartilage; c, periosteum continuous with the pcrkhnnd rkan of
tlie articular cartilage; d, synovial inembrane at the edge of the cartilage, connected at first
with the perichondrium ; c, its epithelium.

Fiff. 126.

296 SPECIAL HISTOLOGY.

membranes, distinct from the fibrous capsules, as tbej are termed,
which possess in all respects the structure of fibrous ligaments, consist :
— 1, of a layer of connective tissue, with not very numerous vessels and
nerves; and, 2, of an epitlielium. The latter is composed of from one
to four layers of large tessellated cells, measuring 0 005-0'008 of a
line, with roundish nuclei of 0-002-0-003 of a line. The former, in its
innermost part, is constituted of a layer of parallel fasciculi, "with indis-
tinct fibrils and elongated nuclei or fine elastic filaments ; more exter-
nally of decussating bundles, with a fine elastic network, occasionally
also of a network of bundles of connective tissue of very various thick-
ness, w'ith winding elastic fibres, exactly as in the arachnoid. Not
unfrequently, common fat-cells occur, dispersed here and there in the
meshes of the connective tissue, although upon the whole very rarely ;
and also a few scattered cartilage-cells, with tolerably thick, opaque
walls, and a distinct nucleus. The synovial membranes possess neither
glands nor papillae, whilst they present large adipose masses [pUcce adi-
posce) and vascular processes {plica; vasculosce, plicoi synoviales, liga-
menta mucosa, of authors). The former, at one time erroneously termed
"Haversian glands," are found principally in the hip- and knee-joints,
in the form of yellow or yellowish-red soft processes or folds, and con-
sist simply of large collections of fat-cells in vascular portions of the
synovial membrane. The latter are met with in almost every joint,
constituting, provided that the blood-vessels are filled, red, flattened
projections of the synovial membrane, with an indented and plicated
margin, and furnished with minute processes. These folds are usually
placed close to the junction of the synovial membrane with the carti-
lage, upon which they lie flat, thus forming, in many cases, a sort of
coronal around it ; in others they are more isolated, and placed in other
parts of the articulation. In their structure, they differ from the rest
of the synovial membrane principally in their great vascularity, con-
sisting as they do of little else than minute arteries and veins, and
delicate capillaries forming wavy loops at the edge of the processes, and
consequently they are very similar to the choroid plexuses in the ven-
tricles of the brain. Besides the vessels, they present a matrix of,
frequently, distinctly fibrous, connective tissue, the usual epitlielium of
the synovial membrane, occasionally solitary or numerous fat-cells, and,
more rarely, isolated cartilage-cells. At the edge, they are almost
invariably furnished with minute, foliated, conical, membranous pro-
cesses of the most extraordinary forms (often resembling the stems of a
cactus), which also frequently contain vessels, but are for the most part
constituted merely of an axis of indistinctly fibrous connective tissue,
with occasional cartilage-cells, and an epithelium, very thick in places.
The smaller ones frequently consist even of nothing but epitlielium,
or of little else than connective tissue.

THE OSSEOUS SYSTEM.

297

In many joints there ai-e firm, •whitish-yellow, fibrous plates, the
so-termed interarticular carti-
lages or ligaments, Avhich, either '°' ^~^'
projecting in pairs from the syno-
vial capsule, are interposed be-
tween the bones constituting the
articulation (knee), or form a
single diaphragm transversely
across the joint (articulations of
the jaw, clavicle, sternum, and
wrist). These processes consist
of a firm, fibrous tissue, the fibres
of which usually cross each other
in various directions, and are in
all respects closely allied to con-
nective tissue, but presenting less
distinct fibrils ; and, besides this,
of cartilao;e-cells and fine elastic
fibres.* The cartilage-cells, in the
most superficial layers, are more
solitary, in the deeper, disposed
more in roivs and smaller, ultimately being replaced by fine elastic fibres,
a certain number of which, at all events, appear to originate from cells
resembling the cartilage-cells. The interarticular ligaments, which,
from what has been said respecting them, must be enumerated among
the fibro-cartilages, are not covered by synovial membrane, though they
probably have an epithelial investment at the attached border, but only
for a small extent, — never over the entire surface. The articular liga-
ments, with the exception of the softer ligamentum teres, are composed
of the same firm connective tissue (in the costal ligaments containing
cartilage-cells), as that of which the tendons and the fibrous ligaments,
elsewhere, are constituted. The internal ligaments (lig. cruciate^), how-
ever, present softer connective tissue, containing vessels, and covered
with epithelium.

Fig. 127. — From the synovial membrane of a phalangeal articulation : ^, two non-vascular
appendages of the synovial processes, magnified 250 diameters: a, connective tissue in its
axis; 6, epithelium (in the peduncle of the larger process not distinctly cellular) continuous
with that on the free borders of the process; r, d, cartilage-cells; B, four cells from the
epithelium of the synovial membrane of the knee, one with two nuclei; magnified 350 dia-
meters.

* [Tliese interarticular fibro-cartilages lose in old persons their distinct filirous structure,
and assume a yellow or brownish color. Yet they never, according to \'ircliow (Arcliiv. f.
Path. Ariat.), become entirely homogeneous, since a careful examination will always permit
two directions of their fibres to be recognized, viz. : one parallel to the free edge, and the
other running vertically towards it. — DaC]

298

SPECIAL HISTOLOGY.

Fis. 128.

10

''i,:i

Within the synovial capsules is contained, in small quantity, a clear
yellowish fluid, which may be drawn out into threads, — the synovia,

— and which, in its chemical composition, ap-
pears very closely to resemble mucus, and
particularly in its containing mucin in solu-
, tion. Examined under the microscope, in its
normal condition, this secretion exhibits no-
thing worthy of much remark, consisting simply
of fluid which is rendered turbid bv acetic
acid, and very frequently contains epithelial
cells, w'hich have often undergone a fatty meta-
morphosis, nuclei of such cells, and fat globules ;
under conditions not quite normal, it may also
contain blood- and lymph-corpuscles, detached
1': i portions of the synovial processes of the arti-

j cular cartilage, and a structureless gelatinous

''';.tii;,ii ijiia'il' substance.

l£|fc'i

The normal, healthy synovia, which in the Ox, according to Frerichs
(Wagn. " Ilandb." III. 1), contains 94-8 water, 0'5 mucus and epithe-
lium, 0-07 fat, 3-5 albumen and extractive matter, and 0*9 salts, is a
secretion, not having essentially any formed elements in it, which
simply exudes from the vessels of the synovial membrane with the inter-
mediation of the epithelium ; andj-in fact, from all its vascular processes,
which are destined as it were for this special function, and always exist
at the border of a cartilage requiring a lubricating covering. The non-
vascular appendages of these processes give origin to the " loose carti-
lages," as they are termed ; they do this by their increasing in size and
solidity, and becoming detached from the vascular folds. These bodies
are also met with in mucous bursae and the sheaths of tendons, which
are also furnished with vascular folds [vid. sup. § 82) ; they consist of
connective tissue with elongated nuclei, coated with epithelium, and,
though not always, contain a variable number of scattered fat- and true
cartilage-cells ; and they are not developed externally to the synovial
membrane, but from an outgrowth of that membrane itself. Similar
solid bodies, moreover, may probably be produced in other ways ;
Bidder (" Zeitsch. f. rat. Medicln," vol. iii., p. 99, et seq.), at all events,
and Virchow ("Med. Zeitung," 1846, Nos. 2 and 3) have observed
similar bodies presenting no trace of organization. I am inclined, with
Virchow, who has actually demonstrated the presence of fibrin in them,
to regard them, in many cases, as fibrinous exudations, and in others as

Fig. 128. — From the falciform ligament of the knee : a, a filament of connective tissue
with oval cells disposed in a series, and resembling cartilage-cells; b, a similar filament
with more elongated cells and nuclei.

THE OSSEOUS SYSTEM. 299

solidified deposits from the synovia, Avliicli latter supposition is supported
b}' the frequent occurrence of curdy, more or less consistent, structure-
less masses, evidently inspissated synovia, in the tendinous sheaths of
the hand. Portions of bone, also, detached from outgrowths at the cir-
cumference of the articular ends of the bones, may find their way into
the interior of the articulation. The plicce adiposce have perhaps less
to do with the formation of the synovia than with the mechanism of the
joint, serving the purpose of filling up hollows.

§ 97. Physical and chemical loropertics of the Bones, and their acces-
sory Organs. — The bones are composed, besides a small quantity of
water (3-7u, according to Stark in the compact substance), and fat (2-3{j
Bibra), principally of a substance affording gelatine, and of inorganic
elements. The latter, in the adult, constitute two-thirds (68'82 Bibra)
of dry bone, and are nearly all left when the bone is calcined ; in which
case, if due care be taken, the bone completely retains its external
aspect, although it may be readily reduced to a white, opaque, friable,
heavy powder, the so-termed "bone earth." This consists chiefly of
57-59 y basic phosphate of lime (according to Ileintz, 3 atoms base, 1
atom acid), of carbonate of lime (7-8[5) and traces of fluate of lime,
phosphate of magnesia, silex (traces), and alkaline salts. A small part
of the salts of bone is also contained in the walls of the vessels and in
the lacunre, and this part is dissolved in water. The collagenous sub-
stance is the so-termed hone, forinative, or ossifying cartilage. It is
obtained when bone is treated at a low temperature with dilute hydro-
chloric, or nitric acid, in the form of a soft, flexible, elastic, light-yel-
lowish, cartilaginous, transparent substance, retaining accurately the
shape of the bone. This bone-cartilage constitutes about -^ of the dry
bone, putrefies when moist, and when dried, may be burnt away, leaving
a small quantity of ash. It is dissolved by boiling, and from its com-
bination with water is produced the gelatine, usually to the amount of
8 or 4 times its volume, and which may also be obtained directly by
long boiling of the bone in a Papin's digester.

With regard to the mode in which the principal constituent elements
of the osseous tissue are combined, it is certain that the bone earth does
not exist as a distinct deposit in any of the constituent parts of healthy,
fully formed bone, but rather, although in a solid form, only in a very
intimate union Avith the tissue. Since both the cartilage and the cal-
cined bone retain the figure of the bone, in all its particulars, indepen-
dently of each other, there can be no doubt, but that the most intimate
union of the two substances exists throughout the entire bone, which,
however, cannot be regarded as a chemical combination, principally for
the reason, that the proportional relations between the collagenous sub-
stance and the phosphate of lime are very variable ; and that, by simple

800 SPECIAL HISTOLOGY.

boiling under an increased pressure, the gelatine is separated from the
calcareous salts.

The pht/sieal properties of the bones correspond with their composi-
tion. Their hardness, density, and rigidity are due to the earthy,
whilst their elasticity and flexibility depend upon the organic constitu-
ents. In the normal bone of the adult, the two principal constituents
are united in such proportions, that the bones, together with consider-
able hardness and rigidity, have a certain degree of elasticity, though
slight, so that they possess a considerable resisting power, and are
broken, though not very readily, by the application of greater mechani-
cal force. At an earlier age, when the cartilage is in greater relative
proportion, the hardness of the bones is much less, their sustaining
power consequently less considerable, and they are more liable to be
bent ; whilst on the other hand, owing to their greater elasticity, they
are much less liable to be broken. This is the case in a much higher
degree in rachitis, in which morbid condition, the organic constituents
amount to from 70 to 80 per cent. A condition the reverse of this is
observed in old age, when the bones, though certainly harder, are more
brittle, and therefore more readily fractured, to which liability, however,
the rarefaction of the tissue which takes place in consequence of age,
partly contributes. The inflammability of bone depends upon its
organic basis, and its capability of resisting putrefaction to the inor-
ganic constituents. The latter being so intimately combined with the
animal tissues, serve as a protection to them, so that bones from ancient
burial-places, and those of fossil animals still retain the full proportion
of cartilasce.

The t7-ue cartilages, even in the foetus, contain, in their organic basis,
from 50 to 75 per cent, of water, 3 to 4 per cent, of salts (chiefly of
soda and carbonate of lime, and also some phosphate of lime and mag-
nesia). The organic basis has been hitherto supposed to consist entirely
oi chondrin, a substance allied to gelatin, soluble in boiling water and
gelatinising as it cools; but it was noticed by Bruns (p. 216), that the
matrix and the cells of cartilage were not equally soluble in water, and
Mulder and Donders have rendered it probable that the cliondrin, which
had hitherto been investigated, is not a simple substance, and that the
car|;ilages consist of several bodies of diff"erent natures, the matrix, and
the membranes of the parent cells, their contents, and the secondary
cells, of which the first is more soluble in water, potass, and sulphuric
acid, than the others.

The fibro-cartilages (cartilages containing connective tissue) have
been, as yet, but little investigated. J. Muller, in the interarticular
cartilages of the knee of the Sheep, found no chondrin ; whilst Donders,
on the other hand, met with it in the intervertebral ligaments (" Holl.
Beitr.," p. 264) ; he did not determine whether they also contained
gelatin. According to Virchow, the gelatinous, nuclear portion of these

THE OSSEOUS SYSTEM. 301

ligaments, in the new-boi*n cliild, consists of a substance very nearly
allied to that of "colloid" (Wurzb. " Verhandl," II. 283). The liga-
ments have the same chemical composition as the tendons.

§ 98. Vessels of the Bones and their accessory Organs. — A. Blood-
vessels. The periosteum, besides the numerous vessels passing to the
bone by which it is traversed, presents in its outer layer, composed of
connective tissue, a tolerably close network of minute capillaries (0-005
of a line). The blood-vessels of the hone itself are very numerous, as
may be seen in injected specimens, and also in recent bone full of blood.
In the long bones, the marrow and the spongy substance of the articular
ends are supplied by particular vessels, as is also the compact substance
of the shaft. The former, or vasa nutritia, enter the bone through large
special canals, one or two of which are found in the diaphijses, and
many in the apophyses. These vessels, with the exception of a few
twigs given off to the innermost Haversian canals of the compact sub-
stance, and which possess all the tunics proper to the vessels elsewhere
(even to the muscular), ramify in the marrow, where they form a true
capillary plexus — the vessels in which vary in size from 0-00-4 to 0'0052
of a line. The vessels of the compact substance arise, in great part,
from those of the periosteum, very soon lose the muscular coat, and
form, in the Haversian canals, which they either occupy by themselves,
or together with some medullary substance, a network of wide canals,
which from their structure, can only in the most trifling extent be re-
ferred to the capillary system, most of them possessing a layer of con-
nective tissue and an epithelium, and as it is only in the larger canals
that fine capillaries co-exist with the main vessel. The venous blood is
returned from all the long bones, in three ways : — 1, by a large vein
accompanying the nutritious artery, the ramifications of which it fol-
lows ; 2, by numerous large and small veins at the articular extremities ;
and, 3, lastly, by many small veins, which arise independently of each
other from the compact substance of the diaphyses, in which their roots,
as is correctly stated by Todd and Bowman, occupy the wider spaces
and sinuses, or pouch-like excavations, which are very evident even in
sections of bone.

■ All the vessels of bone, — the medullary vessels of the apopliyses and
of the diaphyses, as well as the vessels of the compact substance, —
communicate in a multiplicity of ways, so that the vascular system
throughout the entire bone constitutes a continuous whole, in which it
is possible for the blood from any one part to reach every other part ;
for it was observed by Bichat (" Anat. Gen(jral.," 1812, III. p. 37), in
an injected tibia, the nutritious artery of which was obliterated, that
the bifurcation of the vessel in the medullary canal was well injected,
and that the nutrition of the marrow was evidently unafl'ected.

802 SPECIAL HISTOLOGY.

In the short hones, the bloodvessels present pretty nearly the same
conditions as they do in the apophyses of the long bones ; the arteries
and veins of larger and smaller size entering and quitting the bone at
numerous points on the surface, and sometimes, as in the posterior
aspect of the bodies of the vertehrce, in very large trunks, — the vence
hasi-vertehrales of Breschet, furnishing a capillary plexus to the
medulla, and also penetrating into the few Haversian canals of these
bones.

In i\\Q flat hones, such as the scapula and os innominatum, there are
distinct nutritious foramina for the larger arteries and veins ; the com-
pact substance receiving finer vessels from the periosteum, and the
spongy substance being supplied by numerous and even large vessels,
as in the neighborhood of the articular cavities. In the flat cranial
hones, the arteries, for the most part, enter both the cortical and spongy
substance from without, on both surfaces, presenting the usual conditions,
whilst the venoi diploeticce, as they are termed, have only their extremi-
ties free in the medulla, as in other bones, their trunks, and larger and
smaller branches running independently and generally unassociated
with medullary substance in large, arborescent, special channels, the so-
termed "canals of Breschet," which open at determinate points with
large apertures [ernissaria Santorini), and communicate freely with the
veins of the dzira mater, with respect to which relations, however, works
on special anatomy must be consulted. The size and number of the
veins in the cranial bones, is, moreover, extremely variable, and they
are constantly becoming obliterated, particularly in old age, concomi-
tantly with the frequent diminution of the cliploe, on which account also
the venous canals and their openings {ernissaria) are of such variable
dimensions.

The articular and other cartilages of the osseous system, even the
fibro-cartilages, in the adult, normally contain no vessels at all, except
those of the perichondrium, which however in this respect is far inferior
to the pej'iosteum. But it may happen, that as in the costal cartilages
in the middle period of life and afterwards, vessels make their appear-
ance, in which case partial ossification frequently either precedes or
follows. Thefibroiis ligaineyits are poorly supplied with vessels, and par-
ticularly the elastic ligaments, and in this respect may be arranged with
the tendons, whilst the synovial membranes are characterized by the
considerable number of their bloodvessels. The above described synovial
folds are especially rich in this respect, as is also the synovial membrane
itself, which, everywhere beneath the epithelium, contains a pretty close
plexus of canals, from 0-004-0-01 of a line in diameter.

B. Lymphatics in hone, have been described by some older and more
recent authors (vid. Mikrosk. " Anat.," II. 1, 336), but their existence
is still not the less doubtful, and I have in vain endeavored to find such

THE OSSEOUS SYSTEM. 30

o

vessels. With respect to the other parts of the osseous system, the only-
question can be, as to whether the 2^<^^iosteiim and articular capsules
possess lymphatics. In the former, they have not yet been observed,
•whilst in the latter their existence has been asserted by several authors,
Cruveilhier, for example. It must be confessed, however, that it has
not been by any means proved that they arise in these structures, at all
events it appears to me to be very doubtful, whether the synovial mem-
branes themselves contain vessels of this kind, whilst it is perhaps certain
that lymphatics do exist in the loose connective tissue surrounding the
articular capsules, and between them and the periosteum of the apophy-
ses, particularly at the knee.

§ 99. Nerves of the Osseous System. — The 'periosteum is abundantly
supplied with nerves, the majority of which, however, do not belong
properly to it, but to the bone {yid. infra). With respect to the proper
periosteal nerves, it appears that their number, on the whole, is not
considerable, so that even in some places they may be entirely absent,
as in the neck of the femur, and beneath certain muscles [glutceus
minimus, peroncei, &c.) ; but there are perhaps but few bones in which
they do not exist in one part or another. These nerves lie in the same
layer as the vessels, sometimes along the larger branches, sometimes by
themselves, arising, at all events in part, from the larger nerves of the
bone itself, and are manifestly distributed over considerable spaces,
although their ramifications and anastomoses are scanty. In the larger
trunks of these nerves the primitive fibres measure, most generally 0-002
—0-004 of a line, though their size gradually lessens, partly owing to
actual divisions, which I have seen with the utmost distinctness in the
periosteiun of the fossce infra-spinata, and iliaca in man, and J. N.
Czermtik in that of the frontal bone in the Dog ; and in part by a
gradual attenuation, to a diameter of 0-0012-0-0016 of a line, many,
and perhaps all, terminating with free extremities. On the articular
ends of many bones, such as those of the elbow, knee, and knuckle-joints,
I have noticed the nerves to be more abundant than elsewhere, ramify-
ing and anastomosing in the vascular connective tissue covering the
2)eriostemT], and following princip-ally the course of the blood-vessels ;
but in these situations, divisions and terminations of the primitive fibres
did not come under my observation.

The nerves of the bone itself, which, with the exception perhaps of
the ossicula auditus and sesamoid bones, are universally present, do not
exhibit exactly the same conditions in all bones. In the larger ci/Iin-
drical bones, they penetrate, in company with the nutrient vessels, in
the form of one, or where two nutrient foramina exist, of two, pretty
considerable trunks (measuring as much as 0-16 of a line), visible to the
naked eye, directly into the medullary cavity, and are there distributed

804 SPECIAL HISTOLOGY.

into the medulla, following the course of the vessels, though not always
in apposition with them, towards the apophyses, and forming multifarious
ramifications, but, at least as far as I have seen, only few anastomoses.
In the second place, all these bones also present, in the ajjophyses^ nu-
merous finer nerves, accompanying the equally numerous blood-vessels
directly into the spongy substance, and ramifying in the medulla ; and
thirdly, extremely delicate filaments are sent even into the compact sub-
stance of the diaphyses, in company with the minute arteries by which
it is penetrated. There can be no doubt that these filaments are dis-
tributed in the compact substance, although I have never succeeded in
finding them within it. The smaller cylindrical bones of the hand and
foot present the same conditions Avith respect to their nerves as the
larger ones, except that in them, on account of the undeveloped con-
dition of the medullary cavities, the numerous nerves are not so regu-
larly divided into apophysal and diaphysal.

Of the short hones, I have found the vertebrae to be the most abun-
dantly supplied with nerves, and especially their bodies. The nerves
enter posteriorly in company with the arteries and veins [vence basi-ver-
tebrales), as well as anteriorly and on the sides, together with the vessels,
and are distributed in the marrow of the spongy substance. In the
astragalus also, calcaneum, os naviculare, cuboideum, and cuneiforme
internum, I have noticed, in the larger, several, and in the smaller, at
least one nervous filament.

In the scapula and os innominatum, the nerves are very numerous,
entering these bones chiefly at the points before indicated, with the
larger vessels, sometimes on the expanded portion, sometimes in the
neighborhood of the articular cavities. In the sternum also, and in
the flat cranial bones, the existence of nerves is demonstrated without
difficulty. In the latter, I have observed, even in the new-born infant,
in the occipital and parietal bones, nerves entering through the fora-
mina emissai'ia, which at this period also contain an artery ; and in the
adult, there are found in the parietal, frontal, and occipital bones,
although rarely, yet occasionally, microscopic filaments on the smaller
arteries, which enter the compact substance from without, and probably
penetrate as far as the diploe.

From these observations, together with those of Kobelt, Beck, Engel,
Luschka, &c., there can be no doubt that the bones are richly supplied
with nerves. With respect to the origin of these nerves, they have
already been traced by previous observers to the cerebral and spinal
nerves, as for instance the nerves of the diaphyses of the femur, tibia
and humerus, to the nn. cruralis, tibialis, ischiaticus, and p><i^forans
Casseri, as well as a nerve of the frontal bone to the n. supraorbitalis,
which observations, as far as they relate to the tibial nerve, have been
confirmed by my own, and by those of Luschka in the case of certain

THE OSSEOUS SYSTEM. 305

of the cranial bones, and of tlie vcrtehrce. Nevertheless, the sympa-
thetic participates in their formation, as Luschka, and before him,
Kobelt have observed with respect to the vertebral nerves. Microsco-
pical examination confirms this, inasmuch as the nerves of bone, in their
trunks and terminations, resemble in every respect the sensitive branches
of the spinal nerves, and contain, in the trunks, one-third of fibres,
measuring 0-005-0-OOG of a line; two-thirds measuring 0'002-0-004
of a line ; in the larger branches the majority of the fibres measure
0-002-0-003, but some as much as 0-006 of a line; and lastly, in the
finest ramifications, fibres of not more than 0'0012-0-00l6 of a line.
The periosteal nerves, also, which may frequently be seen to be con-
nected with the nerves of the bone, and may be traced to the nerves of
the extremity, are derived, probably in the greater proportion, from the
spinal nerves, although even in their case, perhaps, some participation
of the sympathetic cannot be denied.

How the nerves of bone terminate, I have not observed, and can only
remark, that from the nerves in the marrow, extremely delicate branches,
composed of neurilemma and one or two fibrils, are ultimately developed;
but as to what becomes of these I am ignorant. It is also, perhaps,
Avorthy of notice, that in two situations, before their entrance into the
bone, I have observed Pacinian bodies on the nerves ; viz. on the dia-
physal nerve of the tihia, two lines before its entrance into the foramen,
I noticed a single body, and two others on the largest nerve of the me-
tatarsal bone of the great toe, also just before it entered the bone.

I have never yet detected nerves in the ligaments, in Man (the liga-
mentum nucJue of the Ox contains some fine nervous twigs, accompany-
ing minute arteries ; the twigs measuring 0-004 of a line, with fine fibres
of O-012-O-OOlo of a line), but have no doubt that they, like the tendons,
inasmuch as that they contain vessels, are also furnished with a few
scattered nerves. On the other hand, the interosseous membrane of the
leg contains filaments derived from the interosseal nerve, which, formed
of from one to three fibrils, measuring 0-003-0-004 of a line, present
distinct ramifications and free terminations of the primitive fibrils. A
nerve of 0*03 of a line, which together with an artery entered the fibrous
external part of the symphysis pubis, may here be mentioned. With
regard to the cartilages, I have as yet noticed only in the cartilage-
canals in the septum narium of the Calf, together with vessels (arteries),
very distinct, fine nervous twigs, measuring O'006-O'Ol of a line, with
fibres of 0-0012-0-0016 of a line thick. In the articular capsules nume-
rous nerves exist, although they belong principally to the so-called fibrous
capsules, and to the loose connective tissue external to the synovial
membrane. In the knee I have seen nerves, even in the true synovial
membrane, although in general they are rare, and are most distinct in
the large vascular processes, which besides arteries, contain nerves of

20

306 SPECIAL HISTOLOGY.

0-007-0-008 of a line, with fine, also dividing filaments of 0-0008-0-002
of a line. I have also seen in the synovial membrane itself, close to the
condyles of the femur, tolerably numerous nerves composed of delicate
fibres.

§ 100. Development of the Bones. — In respect of their development,
the bones fall into two groups, viz., into those which are preformed in a
cartilaginous state (primary bones), and into those which from a small
beginning are developed in a soft blastema (secondary bones). The former,
while yet in the cartilaginous condition, present all their essential parts
(diaphyses and apophyses, body, arches, and processes, &c.), and as far
as their cartilaginous basis is concerned, originate like other cartilages,
and continue to grow more or less in the same manner. They afterwards
become ossified (in man, all of them) from within to without, transform-
ing a portion of the cartilage completely into bone, so that what was the
perichondrium becomes the periosteum, and afterwards attaining their
ultimate figure, partly by means of the remaining cartilage, which con-
tinuing to grow with them is successively ossified, and partly by means
of a soft, ossifying blastema, which is deposited layer upon layer on the
inner surface of the periosteum. In the second group, the bone is formed
from a very limited, soft, non-cartilaginous basis, and continues to grow
at the expense of that substance, which is continually developed anew,
first at the margins only, but afterwards also on the surfaces. When
these bones have attained a certain size, the blastema out of which they
have hitherto been developed may become, partially, cartilaginous, in
which case the cartilage stands in the same relation to the bone as it
does in the former instance. The greatest part of their formative sub-
stance, however, always remains in a soft condition, and from it, without
its ever becoming cartilaginous, the principal bulk of the bone is produced.

Frequently as the development of the osseous tissue has already been
discussed, still, in a general point of view, the mode in which the bones,
as organs, originate has hitherto been little considered, and I believe
that I was the first, in my " Zootomical Report," Leipzig, 1849, to es-
tablish the principal features of the process, and in my " Microscopical
Anatomy," II. 1, p. 344, et seq., to trace it in its more particular details.
H. Meyer (1. c.) agrees with me in most of the essential points, whilst
Robin advances many diflerent views, with which I do not accord, and
has to some extent entirely misunderstood my statements.

§ 101. The primary cartilaginous Skeleton of the human body, al-
though less complete than the subsequent osseous framework, is still
sufiiciently extensive. We find as portions of it : 1. A complete verte-
bral column, with as many cartilaginous, as there are afterwards osseous

THE OSSEOUS SYSTEM. 307

vertebrce, with cartilaginous processes, and with intervertebral ligaments.
2. Cartilaginous ribs, and a cartilaginous, entire sternum. 3. Wholly
cartilaginous extremities, with as many and similarly formed pieces as
there are afterwards bones, with the sole exception of the pelvic carti-
lages, which constitute a single mass. 4. And lastly, an incomplete
cartilaginous cranium. This i^rimordial cranium, as it is termed
("Mikrosk. Anat.," tab. iii. figs. 1-3), forms originally a continuous
cartilaginous substance, which corresponds, for the greater part, with
the occipital bone (except the upper half of the expanded portion), the
sphenoid (except the lamma externa of the pterygoid process), the mas-
toid and petrous portions of the temporal bone, the ethmoid, the inferior
turbinated bones, the ossicula auditus and the hyoid bone ; but it
also presents some cartilaginous portions, which never become ossified,
either remaining in the cartilaginous conditions during life, or afterwards
disappearing ; as for instance, Meckel's process, two cartilaginous la-
mcllaj below the nasal bones, a narrow cartilaginous band connectins: the
styloid process with the os hyoides, and two others, one of which extends
from the outer part of the ala parva laterally to the lamina cribrosa,
whilst the other stretches upAvards and forwards from the cartilaginous,
mastoid, and petrous portions of the temporal bone. Consequently, in
the cartilaginous cranium of man, the vault of the skull is totally want-
ing, and almost all the lateral portions, as well as nearly all of what
afterwards becomes the facial bones ; nevertheless, at all events in the
true cranium, the parts not formed of cartilage are closed by a fibrous
membrane, representing in fact the further development of the soft, pri-
mordial, cranial capsule, so that the cranium at this time, though only in
part cartilaginous, is yet fully as complete as at an earlier period, and
always corresponds to its original soft rudimental form. In other Mam-
malia, as for instance, in the Pig, the cranium is much more completely
cartilaginous ("Microskop. Anatomy," tab. iii. figs. 4, 5).

The complete development of the primordial cartilage, considered
histologically, has not yet been accurately traced in all its stages, either in
man or in mammalia. If we wish, therefore, to obtain anything like a
sufiicient idea of it, we must at present have recourse in a great measure
to the lower Vertebrata. If the cartilage of the spinal column and of
the head be examined in the batrachian larva, it is readily seen, that
they are invariably constituted, while still in the soft state, 'of the same
formative cells with vitelline corpuscles, as all the other organs. Before
the development of the external branchio3, these cartilage-cells present
the form of closely approximated spherical cells, 0-007 to 0-000 of a line
in size, with nuclei measuring 0-0045-0-006 of a line, and filled with the
well-known vitelline corpuscles ; afterwards, when the branchiae have
made their appearance, the granular contents of the cells begin to dis-
appear, from within to without, whilst the nuclei become more distinct,

308 SPECIAL HISTOLOGY.

lying in a clear fluid within them, and at the same time the cells slowly
increase in size. When the hranchire have disappeared, all the cartilage-
cells are already quite transparent, with distinct nuclei and walls, and
they now gradually increase to the size of 0-018-0-024 of a line, and
the nuclei to that of 0-005 and 0-007 of a line; the cells, from their
mutual pressure, become polygonal, and constitute one of the most
delicate cellular tissues possible. They now also begin to multiply by
endogenous cell-formation around portions of the contents (Niigeli), so
that in each cell two secondary cells are formed around the two nuclei
produced from the original nucleus, and entirely fill it; at the same time
they again increase, though very slowly, particularly in certain carti-
lages of the head, until they attain a size of 0-013-0-018 of a line, and
in some places of not more than 0-006-0-013 of a line; whilst between
them, a thick interstitial substance is formed out of the coalesced walls
of the different generations of cells. With respect to man and the
mammalia, it can only be stated as a supposition, that the cartilage-cells
originate in a modification of the primordial formative cells. This sup-
position is favored by the circumstance, that in a human embryo of
eight or nine weeks, the outer extremities of which were just developed,
they presented scarcely a trace of formed cartilage, the innermost cells
of the rudimentary extremities being hardly distinguishable from the
outer. They were 0-004-0-006 of a line, in size, spherical, with grayish
granular contents, and indistinct nuclei of 0*003 of a line, and formed a

tissue of some consistence, without any appre-
'°' " ■ ,ff ciable interstitial substance. The correspond-

ing cells in the embryo of a sheep 6-7 lines
in length were somewhat larger, although the
embryo was smaller than the human foetus
^''''^^i^^r'^^^tEM^^Z^^'' "^ ^^ove noticed. In this case (Fig. 129) they

^ measured for the most part, 0-006-0-01 of a
line, had distinct walls, nuclei, and clear,
aqueous, only slightly granular contents, and
were lodged in a scanty homogeneous interstitial substance, so that they
were only partially or not at all in contact with each other. The contents
of only a very few cells were still in the opaque condition, and these
were without any visible nucleus, others exhibited the commencement of
transparency from the metamorphosis of their contents. The further
development of the cartilage up to the end of foetal life, except in its
ossification, presents these characteristics, viz.: (1.) That the cells pre-
cisely like those in the batrachian larva, continually increase by endo-
genous cell-formation, whilst precisely as in the same instance, there is no

Fig. 129. — Cartilage-cells from the humerus of an embryo of the Sheep, G lines long:
a, cells with nucleus and clear contents (two cells retain remains of the earlier thick con-
tents) ; b, cells with consistent contents, without visible nucleus; c, intercellular substance.

THE OSSEOUS SYSTEM. 309

indication whatever afforded, of the production of cells independently of
those already in existence; and (2.) That the interstitial substance,
which in this case is manifestly formed, for the greater part, indepen-
dently of the cell membranes, is always increasing. With respect to
the cells, they are in the second costal cartilage of a four-month foetus,
according to Harting, 0-0036 of a line long, 0*0023 of a line wide, and
consequently their aggregate bulk pretty nearly corresponds with that
of the interstitial substance. In the embryo of the Pig, 3*5 lines long,
the space occupied by the nucleated, clear, thin-walled cells, is, accord-
ing to Schwann, thrice as great as that taken up by the interstitial sub-
stance. In a five-months' human embryo, I have myself noticed the
cartilage-cells, O'OOo-O-OOS of a line in diameter, with and without
secondary cells, some with, and some without distinct walls, and sepa-
rated from each other by a perfectly homogeneous substance, 0-002-
0-005 of a line thick. In the new-born child they measure, according
to Harting, 0-032-0028'"'" in length, and 0-0072'"'" in breadth, and are
three or four times as numerous as in the foetus at four months ; but on
the other hand, they occupy considerably less space, proportionally,
than the interstitial substance, the bulk constituted by which is more
than double that of the cells. After birth, in the non-ossifying carti-
lages, the interstitial substance and the cells increase in pretty nearly
an equal ratio, so that their relative proportions in the adult are about
the same as in the infant at birth. In the adult the cells are from 8 to
12 times larger than in the new-born child (Harting), but, according to
him, their number is diminished, so that they amount to not more than
half of what existed in the child, which is explained upon the supposition
of a coalescence of the cells. The numbers given by Harting do not
appear to me to afford sufficient ground for the establishment of his posi-
tion; and even should it be established, I cannot agree in the explana-
tion offered, not being aware of a single fact in favor of the notion of a
coalescence of cartilage cells.*

* [We have deferred to this place the remarks we have to make with regard to the struc-
ture of the cartilage, and its mode of growth; as a just conception upon this subject appears
to us to be essentially necessary to a comprehension of the mode of development of Bone, —
in fact, we might say, to clear notions upon the structure of the tissues generally; for as we
shall show more at length below, it was upon the structure of cartilage, and what he
supposed to be its similarity to that of vegetable tissue, that Schwann based the whole
nomenclature of his cell theory.

Now we may so far anticipate what we shall have to show hereafter, as to premise that
Schwann was misled upon two essential points, — the first being the supposition that the
histological elements of plants and animals are primarily independent, cells ; the second, the
notion that the " nucleus" of the animal, is homologous with the nucleus of the vegetable
tissue. It is, we believe, from the inextricable confusion produced by these fundamental
mistakes, which have been adopted by almost all Schwann's successors, that one-half of the
controversies with respect to the structureof cartilage and the process of ossification have
arisen. And yet to one who is free from them, nothing can be simpler.

We have already (note p. 5G) referred to the structure of fcEtal cartilage, but it may here

310 SPECIAL HISTOLOGY.

§ 102. 3Iefamorphoses of the lyrimordial cartilaginous Skeleton. — Of
the primordial cartilages, one portion undergoes further development
with the rest of the skeleton, constituting the permanent cartilages of

be described more at length. We found the cartilage of the septum nasi of a four-months'
human foetus to be composed of a homogeneous, soft matrix, without structure of any kind,
in ■which lay imbedded, rounded or irregular vesicular bodies, varying in diameter from
tA(T~?(5%5*'^ of an inch; the commonest size, however, being jj^L^-j-^j^th. These
" corpuscles'' frequently contained one or more granules, sometimes very small, sometimes
larger, and of a distinctly fatty nature; such fatty granules, also, were sometimes to be found
in the matrix around the corpuscles.

The cavities in which they lay, were, for the most part, just large enough to contain them,
and presented no walls or sharp lines of demarcation of any kind from the surrounding
substance.

When the corpuscles were as large as j ^'jjjjth of an inch, they occasionally contained a
round body of rather less than jg'onth, as a " nucleus."

The matrix was in some parts pale and indifferent ; but where the tissue had taken on
its definitely cartilaginous nature, the chondrinous substance into which it was converted re-
fracted the light much more strongly. In this part also, the cavities in which the corpuscles
lay, were often of considerably larger dimensions than the latter, and their walls exhibited a
sharp, dark line of definition from the surrounding substance, which was often brought out
much more strongly by the action of acetic acid. It appeared, in fact, that the conversion
into chondrin bad not quite reached the inner surface of the cavities, and hence they were
chemically and optically distinguished from the surrounding substance.

Now, of course, it matters very little what names are given to these parts, so long as they
are used only in one sense. Schwann considered the corpuscles to represent the "nuclei" of
plants, and therefore gave them that name. Henle, Reichert, KoUiker, and nearly all their
compatriots, Todd and Bowman, Leidy and Sharpey — follow him. As a consequence, they
consider the wall of the cavities to represent the cellulose "cell-wall" in plants; and there
has been much controversy as to how much of the matrix of the cartilage results from the
union of these "cell-walls," how much from the development of an intercellular substance;
a controversy which has extended itself to the determination of the homologies of the ele-
ments of every tissue. We must confess, it seems to us that the disputants have been
fighting for a shadow.

If, in fact, the youngest cartilage be composed of cells with distinct walls enclosing the cor-
puscles, of course these cells may be united by an intermediate, " intercellular" substance ;
and it will be an important question to determine in the further course of development
what arises from the walls and what from the substance which unites them. But if, on the
other hand, all this be pure hypothesis; if young cartilage be, as we have said, composed of
nothing but a continuous, homogeneous matrix, in which the corpuscles are imbedded, but
in which no other structure exists, what becomes of the controversy ?

We believe that not merely will the account we have given, be found to be correct, by
any one who will without prejudice examine into the subject, but it seems to result from the
observations, even of those who have interpreted the facts otherwise.

Schwann (" Mikros. Unters.," pp. 112, 113) describing the development of the cartilage of

Pelobates, says : " The new cells arise in the cytoblastema (matrix nobis) We see

at first mere cell-nuclei (corpuscles nobis), which are somewhat smaller than the nuclei of
the full-grown cells, a, b ; partly nuclei, which are closely surrounded by a cell, c, c ; in
short, all transitional forms, from mere cell-nuclei and nuclei surrounded by small cells, to
fully formed cells ; so that here, development takes place as in small cells, and the nucleus

is their actual cytoblast The cell-membrane becomes distinct only in the full-grown

state."

In the next page, Schwann speaks of the free-swimming nucleated corpuscles which he
obtained from the ossifying cartilage of a fretal pig, and which he considers to be identical
with the bodies already described in Pelobates. In reality, however, these bodies are not

THE OSSEOUS SYSTEM. 311

the nose, joints, si/mphi/ses, and synchondroses ; a second disappears
altogether in the course of development (certain cranial cartilages, vide

cells in the same sense, being merely the nuclei of Schwann and the nucleated form of the
corpuscles to which we have referred above.

Whatever Schwann's words may indicate, then, his observations tend to precisely the
same conclusion as our own.

Henle (" Allg. Anat.,"' pp. 803-SOS) follows Schwann, and equally fails to discriminate the
cells in Pelobatcs from the "cells"' in the fostal pig.

Reichert (in his admirable work, " Ueber das Bindegewebe," 184-5) recognizes the fact that
the cartilage-corpuscles are " nuclei" in Schwann's sense, and refers the appearance of a
distinct wall in the cavities, to an optical delusion. He asserts that young cartilage is com-
posed of distinct cells closely united together, without any measurable intercellular sub-
stance; as the cartilage grows, the latter increases, and eventually the cell-walls disappear.
The only evidence of the existence of these cells and intercellular substance offered by
Reichert, however, is the mode in which the tissue may be broken up ; a kind of evidence
whose value the purport of the rest of his book is to reduce (and most successfully) to
nothing.

In effect, therefore, Reichert's observations come to the result already stated, that the
fcetal cartilage is composed of a homogeneous matrix, in which the corpuscles are dis-
persed.

Robin (" Observations sur I'Osteogenie") takes nearly the same view of the structure of
cartilage as that we have indicated. " Cartilage is composed," he says, " of a homogeneous,
amorphous, dense, elastic, hyaline basis (si<6s/a«f«/onrfa»!e>i<a?c), in which cavities are hollowed
out, — cartilage-cavities. In each of these cavities we find one or many (sometimes 20 to 30)
cells, — cartilage-cells, whose parietes cannot be demonstrated to be distinct from their cavity.

These cells are more or less granular, and have a nucleolated nucleus In the fcetus,

up to the age of four or five months, more or less, the cartilage cavities do not enclose one or
more cells, but one or many masses of yellowish granulations, all of nearly the same size.
These masses are more or less distinctly defined at their edges, in general indistinctly, and
nearly reproduce the form of the cavity without ever filling it. They may be called carti-
lage-corpuscles. Authors have not generally remarked this fact. By degrees the cells which
replace these corpuscles are developed. These cells are formed all at once ; but the grades
of the process as regards the commencing cell or the pre-existing granulations are as yet but

little known Some authors wrongly call the cavities excavated in the fundamental

substance, cartilage-cells ; and to the true cartilage-cells and masses of yellowish granulations
or corpuscles, referred to above as existing in the fffital state alone, they give the name of
contents.'^

Remak (■' Ueber die Entstehung des Bindegewebes und des Knorpels," Miiller's " Archiv,"
1851-2) appears to have been the first, definitely to recognize the cartilage-corpuscles, as the
homologues of the primordial utricles of plants, — a great step, and one which appears to us
to lead to most important consequences. Like Schwann, however, led away by the gene-
rally assumed anatomical independence of the vegetable cells, Remak interprets the struc-
ture of cartilage in the same manner, and speaks of the secretion of the chondrinous wall
by the primordial utricles, as " parietal-substance" within the primary cell-membranes.
He adduces no evidence, however, that the facts are other than as we have stated them
to be.

Virchow (" Die Identitat von Knochen-, Knorpel-, und Bindegewebe-kOrperchen so wie
Qber Schleimgewebe," " Verhandlung d. Phys. Med. Gesellschaft," 1852) is an important wit-
ness in this matter. He says, " I have anew convinced myself that the so-called cartilage-
corpuscles are actual cells which lie in a cavity of the basis (Grundsiibstanz), or in a cell-
cavity presenting a double contour, and possess a membrane, granular contents, and a fre-
quently nucleolated nucleus. In the neighborhood of the line of ossification, in growing
cartilages, as well as in the young callus-cartilage of fractures, these cells are of very large
size, clear, and round ; in the neighborhood of the articular extremities, excessively small,

312 SPECIAL HISTOLOGY.

§ 101) ; the third and greatest part, ultimately becomes ossified, and
constitutes all the bones of the trunk and extremities, and a great part
of those of the cranium. All these bones are ossified, essentially in the

compressed, and dark. Under favorable circumstances, the cells, in simple cartilage, may
be isolated, and their peculiar relations with regard to acetic acid, which generally renders
them darker and collapsed, may be exhibited. Water also causes them to collapse, and
they thus occasionally form peculiar, jagged corpuscles, which one might be readily tempted
to confound with branched cells. The larger the original cell was, so much the more
branched does its collapsed mass appear." (p. 152.) "It might have been ex-
pected that in the course of ossification of the cartilage, these cells would be seen to pass

into the irregular, anastomosing bone-corpuscles; but nothing of the kind is visible

A point of difficult determination is, in general, the existence of actual cells in the small fiat
cavities of cartilage, e. g. towards the surface. Very frequently it would here seem as if the
membrane of the cell had coalesced with the intercellular substance, and only the contents
with the nucleus had remained behind. But on careful investigation especially under the
prolonged operation of acetic acid, frequently after maceration in hydrochloric acid, we
clearly see a complete cell with a nucleus and contents in the cavity" (p. 153).

Virchow gives no figures, but the above passages furnish so accurate an account of what
we have ourselves seen in young and in fully-formed cartilage, that we have thought we
could not do better than cite them. The jagged appearance of the corpuscles to which he
refers, is very common, and we have been led to suspect that it may arise from the same
cause as the very similar appearance often exhibited by the colorless corpuscles of the blood,
viz., a protean throwing out of processes.

When Virchow, however, describes the passage of these " cells'' into the branched or
stellate corpuscles of fibro-cartilage, and considers the latter to be metamorphosed cartilage-
corpuscles, he confounds together things which are essentially different. Careful examina-
tion of fojtal fibro-cartilage, e. g. the intervertebral fibro-cartilage of the Kitten, shows that
the stellate body is the ivall of the cartilage cavity, with processes which run out from it, the
original corpuscle remaining in the interior of the cavity, either unchanged or becoming
gradually lost, or fused into one mass with its walls.

The account of the structure of cartilage given by Tomes and De Morgan (1. c, pp. 15,
16) in all essential points agrees with that of Virchow. They call the corpuscles, granular
cartilage cells.

To recapitulate : — the /ac/s contained in other observations, as apart from the interpretation,
appear to agree perfectly with our own ; the result of which is, that in the fcEtal state, car-
tilage is composed of a homogeneous matrix, in which lie the corpuscles, in cavities which
they just fill; that their relation to the matrix is exactly that of the primordial utricles to
the cellulose wall in plants, and that like this they may or may not develop a nucleus ; that
with age they enlarge, but not so fast as the cavities, the walls of which become chemi-
cally altered into chondrin, a change which often takes place in such a manner as to give
rise to a lamination or to a difference in composition of the inner and outer portions. If the
cartilage be converted into fibro-cartilage, the outer part becomes changed into collagen,
while an alteration into a substance resembling elastic fibre, is effected in the inner portion,
and in the direction of certain lines radiating from it, just as we have seen the elastic ele-
ment to be developed in connective tissue (see § on Connective Tissue).

So much for the structure of cartilage: with regard to its development and multiplication
we must equally demur to the statements in the text. It is, indeed, very true, that no new
cartilage-cells arise independently of those which pre-exist: but in opposition to Professor
Kolliker we must agree with Leydig, Robin, Remak, and Tomes and De Morgan, that the
multiplication of the cartilage-cells invariably takes place by a process of division exactly
analogous to that which occurs in plants. So far as we have seen (and in ossifying carti-
lages, and in that of the Skate, it is easy to trace the process), the corpuscles first become con-
stricted, being found occasionally of an hour-glass shape; and eventually divide. The
matrix then grows in, so as to separate the two, and the process of fission is complete. — Tks.]

THE OSSEOUS SYSTEM. 313

same way. At one or more points {puncta ossijicatioms), in their inte-
rior, a deposition of calcareous matter commences, simultaneously ^Yith
a change in the cartilaginous elements; Avhich transformation proceeds
on some or on all sides, continually converting additional portions of the
cartilage into bone. Whilst this is going on, the cartilage, in most cases,
ceases to grow in one direction, and, consequently, is there soon entirely
converted into bone, whilst in others its growth continues, so that a new
cartilaginous, plastic material is furnished for the progressive increase
of the bone, which material, as in the epiphyses of the cylindrical bones,
is sometimes developed into distinct ossific centres or nuclei. When the
whole of the cartilage has been converted, and its perichondrium become
periosteum, the bone does not cease to enlarge, but a new and peculiar
mode of formation is now set up, in all these places, until its growth is
completed. This consists in the ossification, from that surface which is
in contact with the bone, of an organized, soft, plastic material, which
is deposited on the inner surface of the highly vascular pieriosteum, and
in proportion as this conversion into bone takes place on the one side,
fresh, fluid materials for it are afforded by the periosteum on the
other.

§ 103. Changes in the ossifying Cartilage. — The active vegetative
process in the cartilage-cells when ossification is going on, depends upon
this, — that the cells which were hitherto of small size, and contained but
few secondary cells, begin to grow, and successive generations of cells
to be produced in them, as may, also, be seen at the ossifying margins
of bones already existing, in which situation larger cells may be noticed
close to the bone, and others, which are smaller in proportion to their
distance from it. All the cells which are engaged in the incipient for-
mation of the bone, present clearer and, less frequently, granular con-
tents, a distinct, vesicular, round nucleus, with nucleolus and readily
distinguishable walls ; they are very quickly altered, however, on the
addition of water, acetic acid, alcohol, and by drying, &c., so that the
contents contract around the nucleus, and form a roundish, elongated,
irregular, even stellate, granular, opaque body [cartilage-corpuscle of
authors). Their size and mode of grouping vary, not inconsiderably,
according to age and situation. With respect to the former, they exhibit
during embryonic life a constant increase, whilst after birth they appear
to retain a uniform size ; and, as regards the latter, it may be stated as
a law, that where the ossification of the cartilage proceeds in one direc-
tion only, the cells, at the osseous border, are disposed in rows. This is
most distinctly seen, as has been long well known, in the extremities of
the diapltyses of the larger cylindrical bones, where the rows of cells are
very prettily arranged in parallel lines close together, and are of con-
siderable length ; it is also evident in the other long bones, as well as in

314

SPECIAL HISTOLOGY.

many others where the cartilage ossifies only on one side, as in the con-
necting surfaces of the vertehrce. Where, however, the ossific nuclei in
the centre of a cartilage enlarge on all sides, the cartilage-cells are con-
fusedly grouped in roundish, or oval, irregular little masses, as in the
short bones at their first formation, and in the einphyses. An accurate
comparison of the cells which are closer to the ossifying margin, with
those more remote from it, and of the groups formed by them, at once

Fig. 130.

Fi''. 131.

illiiilitti

.a

ol

shows that their particular disposition is directly related to their mode
of increase. Each individual group (or even two of them) corresponds,

Fig. 1 30. — Perpendicular section from the ossifying border of the shaft of the femur of a
child a fortnight old: a, cartilage, in which the cells the nearer they are to the ossifying
border are placed together in more extended longitudinal rows ; 6, ossifying border, the dark
streaks indicate the progressive ossification in the intercellular substance, the clearer lines
the cartilage-cells which ossify subsequently ; c, compact layer of bone near the ossifying
border; d, the substantia spongiosa formed in the osseous substance by resorption, with can-
celli, the contents of which are not shown. — Magnified 20 diameters.

Fig. 131. — Femur of a child a fortnight old, natural size: a, substantia compada of the
shaft ; b, medullary cavity ; c, substantia spongiosa of the shaft ; d, cartilaginous epiphysis with
vascular canals; e, osseous nucleus in the inferior epiphysis.

THE OSSEOUS SYSTEM. 315

in a certain measure, with a single primordial cell, and represents all the
descendants -wliicli in course of development have proceeded from it. In
the one case, all these newly-formed cells are disposed, one behind the
other, in a single or double linear series ; and in this way are produced,
by their further increase, the rows of cells above described, whilst in the
other they constitute a more globular mass. The primordial cells (first
parent-cells) during this procedure, sometimes disappear as distinct or-
ganisms, owing to the coalescence or fusion of their walls with the inter-
stitial substance, sometimes not ; and the same holds good with those of
the subsequent generations. The latter is usually the case in the rounded
masses of cells, owing to their smaller size, and around them a contour
line may for the most part be recognized, which is nothing more than
the distended wall of the first cell ; whilst in the rows of cells, the walls
of the original cells are not, usually, so merged in the intercellular sub-
stance as to escape recognition. The entire matrix, in which the just-
described, enlarged, and actively multiplying cells are enclosed, varies
very considerably in thickness in the dilTerent cartilages ; scanty around
the osseous nuclei in the epiphyses and short bones, it is ^ to J a line
thick in the diaphyses. It is universally characterized by its yellowish,
transparent color, and its streaky, apparently fibrous fundamental
structure, from the other cartilaginous parts, which are, as usual, bluish-
white, with a homogeneous or granular interstitial substance.

The vessels met with in the ossifying cartilages constitute a phenome-
non well worth attention ; from the middle of foetal life onwards, they
occur in many situations, preceding by a shorter or longer time the
appearance of the osseous nuclei, and accompanying their increase. I
have observed them in the articular cartilage of the epiphyses of the
long bones even in a person 18 years old. They entered the cartilage
in great number, perpendicularly from the bone, ramifying and terminat-
ing a little below its free surface. The cartilage-vessels invariably lie
in wide canals (measuring, even in a five months' foetus, 0-02-0'04 of
a line), excavated in the cartilage, and bounded by narrow, elongated
cartilage-cells, — the vascular canals of cartilage, or cartilage canals, —
which enter the cartilage from the perichondrium, and, when a vascular
ossific nucleus exists [diaphysis), also from the border of the ossifying
portion itself (though in less number, at all events at an earlier period),
penetrate it in straight lines, in various directions, giving ofi" a few
branches, and, to all appearance without any anastomoses, or other kind
of interconnection, end, for the most part, in blind, club-shaped dilata-
tions. These canals are produced by a resolution of the elements of the
cartilage, in the same way as the medullary cavities of the bone itself,
originally contain a plastic material composed of minute rounded cells
(cartilage-marrow), corresponding to the foetal cartilage-marrow, and
develop in a short time out of this material, true sanguiferous vessels,

316 SPECIAL HISTOLOGY.

and a wall composed of more or less developed connective tissue, and
subsequently also of elastic fibrils. As concerns the vessels themselves,
I have sometimes found, in a canal, only one large vessel (frequently
very distinctly arterial, with muscular walls), sometimes two such, some-
times capillaries in various numbers, but I am unable to explain how the
circulation is carried on in these vessels. There must either be anasto-
moses between the vessels of different canals, or if the latter be really
closed, arteries and veins both probably exist in one and the same canal.
The object of these vessels of cartilage appears to be one of a double cha-
racter; in the first place, to convey the materials requisite for its growth
and further development ; and secondly, to promote the ossification.
The former of these functions is very manifestly carried out in the thick
epiphysal cartilages, which grow to such a length before they become
ossified, and even afterwards continue to enlarge ; and the latter is pro-
bably effected principally in the short bones, which do not contain vessels
until just before the commencement of ossification. Notwithstanding
this, however, it is not intended to imply, that a cartilage cannot grow,
nor become ossified without vessels ; but although the latter condition
does in fact obtain in animals, and probably also in man, normally in
certain situations (on the appearance of the first points of ossification of
the embryo, those of the ossicula auditus, &c.), still, this does not prove
that the vessels when existing have no concern in the processes adverted
to ; and consequently it cannot be admitted, as lately supposed by H.
Meyer, that they are to be regarded in the light of accidental produc-
tions, and as standing in no necessary relation with the development of
the bone.

§ 104. — Ossification of the Cartilage. — The ossification of the matrix
generally precedes in some degree that of the cartilage-cells ; and,
under normal conditions, is primarily effected by a granular deposition
of calcareous salts (calcareous granules as they are termed). Where
the cells are disposed in rows, at the ossifying border, this deposition
of earthy matter always proceeds in the fibrous substance between the
rows of cells, forming processes, which, in a longitudinal section, assume
the appearance of pointed teeth, and surround the lowest portions of
the rows of cells like short tubes. The same disposition, essentially, is
also manifested in other situations, where the cartilage cells constitute
more rounded groups, only, that in this case the ossifying matrix sur-
rounds them more in a reticular manner. The calcareous granules or
particles, the first visible deposit of the earthy salts of bones, are of
a rounded angular figure, white by reflected, opaque by transmitted
light, easily dissolved with effervescence in acids, and differing in size
in different bones, from immeasurable minuteness up to 0*001, or even
1-002 of a line ; their size, however, does not appear to be regulated

THE OSSEOUS SYSTEM.

317

by period or situation, although there is no doubt tliat they are fre-
quently, in one place, of uniform minuteness, and in others uniformly
of coarser character, but rather by some change occurring in the supply
of plastic material to the ossifying border. If this earthy deposit be
traced in microscopical sections, from the margin of the ossification into
the interior of the young bone, it will be apparent, that it is to it, for
a certain distance, although with diminishing distinctness, that the
granular and opaque aspect of the margin itself is due ; the substance
gradually becomes more homogeneous, clearer, and more transparent,
ultimately acquiring the aspect of perfect bone. According to all
appearance, the primordial earthy granules or particles become gradu-
ally fused together, and thus impregnate the whole tissue of the matrix
of the cartilage, instead of, as

Fig. 132.

V:f

'II

■i^'i . i ml

before, separate portions, and
thenceforth disappear as iso-
lated, distinguishable pani-
cles.

With respect to the forma-
tion of the bone-cells, I believe,
that owing to the discovery
of an excellent subject fur
their observation, viz., rachitic
bone, I have put the matter,
as regards the most essential
particulars, in a clear point
of view. The bone-cells are
formed, — as Schwann thought
possible, and Henle supposed,
from analogy with the ligni-
fied vegetable cell with pores
or dotted canals, — from the
cartihige-cells, by the thick-
ening of their wall, with the
simultaneous formation of
canalicular vacuities in it,
and its ossification. In the ^

ossifying shaft of a rickety "TW^<yJH^^^M'!/^
bone (I'lg. 132) the morpho-
logy of this process may be most beautifully observed. If the rows of

Fig. 1.3'2,— From the ossifying border of the condyle of the /emwr of a rachitic child,
two years old, a, cartilage cells, simple and parent cells in series ; b, more homogeneous ;
c, striated matrix between them; d. cartilage-celLs at the commencement of their trans-
formation into bone-cells j e, the same further advanced, with very much thickened walls,
indication of canaliculi, commencing deposition of calcareous matter in the walls, whence
their darker color, though still with distinct nuclei; /, bone-cells still more developed and
more ossified, in an equally ossified, matrix. — Magnified 300 diameters.

818 SPECIAL HISTOLOGY.

cartilage-cells of the ossifying border, which in this case are of larger
size, be traced from without to within, it will soon be found, that at
the point where the deposition of calcareous salts (which takes place
for the most part without the formation of the calcareous granules)
commences, they exhibit, instead of a membrane indicated by a single,
tolerably strong line, a thicker coat, which on the inner side presents
delicate indentations. Even Avhen the thickness of this membrane
does not exceed 0-001 of a line (Fig. 132, d), it is obvious that the car-
tilage-cells are about to be transformed into bone-cells ; and this be-
comes still more evident, when, further on in the bone, the thickness
of the membranes in question, together with the simultaneous diminu-
tion of the cavity of the cell, is seen to be constantly increasing, the
indentations of the interior contour line to become more and more
marked, and, accompanying the progress of these changes, the walls to
become more and more dark from the addition of calcareous matter
(Fig. 132, e). The slow ossification of the matrix between the cells is
very favorable to the observation of these changes, allowing not only of
the accurate investigation of the first alterations in the cartilage-cells,
but also of their subsequent conditions, at a time when they must be
termed hone-cells and lacunce, being traced step by step. To this cir-
cumstance alone is also due the establishment of the interesting fact,
that cartilage-cells, enclosing secondary cells within them, are converted,
as a tvliole, into a single, compound bone-cell. Cells of this kind are
very frequently met with, having two cavities, which cells, according to
their degree of development, are sometimes wide and furnished with
short prolongations, and sometimes from their contracted cavity and
long canaliculi, resemble in all respects perfect bone-lacunre. Com-
pound cells, with 3, 4, and 5 cavities, each with the remains of the
original contents and nucleus, occur more rarely, though even such are
occasionally to be found in almost every preparation. The cartilage-
cells lying free, and. in close apposition, though in a non-ossified matrix,
having thus evidently become transformed into bone-cells with nuclei
and other contents, the ultimate changes now take place from which the
rickety bone-substance acquires pretty nearly the nature of the sound
tissue. These changes, in as far as they effect the bone-cells, chiefly
depend, in the first place, upon the commencement of ossification in
the matrix, but without any primary formation of calcareous particles ;
and secondly, upon the continually increasing deposition of earthy mat-
ter in it, and in the thickened cell-walls, owing to which, the new bone-
substance, to the naked eye, becomes more and more white, and under
the microscope appears more and more dark and transparent ; it now,
also, becomes more homogeneous, and the abrupt limits of the bone-cells
gradually less and less defined, till at last they appear, not as cellular
organisms lodged in the matrix, but to be confused with it, being recog-

THE OSSEOUS SYSTEM. 319

nizable only from their peculiar stellate cavities, — the so-termed hone-
corpuscles, or lacunce and canaliculi.

"With the kno\Yledgc thus obtained of the formation of the lacunse in
rachitic bone, the endeavor to arrive at an insight into the same process
in normal bone, is no longer attended with as much difficulty as before,
when the inquirer was involved in a maze of hypotheses of the most
various kinds, and all without any certain foundation. The investigation
of the conditions attending the development of bone, both in man and
other animals, must nevertheless still be regarded as troublesome, and
frequently little worth the pains bestowed upon it. It is, perhaps, cer-
tainly manifest {yid. " Mik. Anat.," tab. iii. fig. 6), that the bone-cells,
a little beyond the limit of ossification, become thickened, and, still
presenting the remains of their cavity and the nucleus, beset with cal-
careous particles ; and although such incrusted cells may even be isolated,
yet the mode in which the changes are eftected further on, is not, beyond
a short distance, I must affirm, to be seen with anything like the dis-
tinctness that it is in rachitic bone, because, more internally, the newly-
formed medulla with its vessels, and the calcareous particles, render
almost everything indistinct; and it is not till we get to the homogeneous
and more transparent osseous tissue beyond, that distinct, but almost
perfectly-formed lacunas come into view. Nevertheless, from all that
we see, there cannot be the least doubt, but that the processes are
essentially the same as in rachitis, only, that in the healthy bone the
ossification of the thickened walls of the cartilage cells, presents two
stages, instead of only one, as in the former case, inasmuch as they first
appear granular from the deposition of the calcareous particles, and
afterwards homogeneous. Moreover, even in perfectly normal bone, in
the adult, I have met with places (some of which, independently of me,
have also been lately described by H. Meyer (1. c.) ), such as the sym-
physis pubis, the synchondroses of the vertebrae, and those of the ilium,
sacrum, and the points of insertion into the bones of certain tendons
containing cartilage-cells. In all of these situations, at the line of
junction between the cartilage or tendon and the bone, cartilage-cells of
the most characteristic aspect may be seen, lying free in the cartilaginous
matrix, and presenting the most various degrees of transformation into
bone-cells ; some, in particular, having thickened walls, and a more or
less copious deposit of calcareous particles ; while others are almost
perfectly-formed bone-cells, with pores and a more homogeneous wall
(Fig. 123); so that I am able to afi'ord a certain support to the state-
ment given above with respect to the mode of origin of the bone-cells,
by the conditions presented in normal tissues also. In the last-named
situations I have, likewise, very distinctly and very frequently noticed,
half- or wholly-ossified parent-cells, containing from two to twelve
secondary cells.

820 SPECIAL HISTOLOGY.

There is another point in the development of the hone-cells still ob-
scure, or at least that has not been directly observed, viz., how their
pores or canaliculi become branched cavities, communicate with those of
other cells and acquire open orifices in certain situations. All that is
apparent in rachitic bone and elsewhere, is merely the circumstance,
that the thickening of the ossifying cartilage-cells does not proceed with
a straight but with an indented border, which is the case in fact from
the beginning up to their completion, and that the bone-cells have, at
first, more simple prolongations than afterwards. Observation teaches
nothing beyond this. Now, as there can be no doubt that the canaliculi
anastomose very freely, and also, that they frequently open on the outer
surface of the bone, or into the cavities in its interior, I do not for a
moment hesitate to express the opinion, that the canaliculi, arising as
simple branches from the lacunce, are continued or further developed by
absorption of the already formed bone-substance. How such an absorp-
tion takes place, cannot, it must be confessed, be explained ; but that
affords no ground of objection to the opinion, because we see a similar
process, though on a widely-different scale, take place in the formation
of the medullary cavities and cancelli {vid. infra). It would appear to
me, that currents of the nutritive fluid in the bone were chiefly concerned
in this further development of the canaliculi ; and the more so, because
the first rudiments of the canaliculi, like the pore-canals of lignifying
plant-cells, manifestly indicate nothing more than the points at which
the ossifying cartilage-cells continue to admit and emit fluid; on which
account, also, their direction is principally towards the internal and ex-
ternal surfaces of the bone, from which the nutritive plasma is derived.
It appears to me highly probable, that after the complete ossification of
the cartilaginous tissue, the nutritive fluid derived from the blood-vessels
of the periosteum and of the medullary cavities (1.) finds new ways for
itself towards the lacunce and their prolongations, which, as it may be
said, alone are still open to it, and in this way effects their opening on
the internal and external surfaces of the bone, and (2.) also burrows
passages from the cavities lying nearest to it, and thus ultimately pro-
duces a ramification of them, and brings about numerous communications
between the different cavities. In accordance with which, a secondary
formation of canaliculi must take place, not only in the region of the
thickened walls of the original cells, but also in the osseous matrix, and
this to a considerable extent, as is at once evident, when the distances
between the anastomosing cavities are compared with the diameter of
the original cartilage-cells.

The development of the medullary spaces {cancelli) and of the medulla,
is to a certain extent the last act in the transformation of cartilage into
bone. The medullary spaces do not arise in a coalescence of the cartilage-
cells, but from a solution of the more or less perfectly formed bone-sub-

THE OSSEOUS SYSTEM. 321

stance, exactly like the large medullary cavities of the cylindrical bones.
This is most distinctly and satisfactorily shown by the examination of
the diaphyses of a sound or rachitic bone, but especially in the latter.
At the limit of the ossification itself, the osseous tissue for a distance of
about J to J of a line, is quite compact, without a trace of larger cavi-
ties, and is composed in part of the ossified matrix, and in part of car-
tilage cells, more or less advanced in their transformation into bone-
cells ("Mik. Anat.," tab. iii.) ; beyond this part, however, cavities, at
first small, and more internally, larger, come into view, the whole rela-
tions of which show most convincingly that they do not originate in any
development of the existing elements. They have an extremely irre-
gular contour, are oval, or roundish and angular, and for the most part
broader than the cartilage-cells, appearing to be eaten out, as it were,
in the substance of the bone, and involving severally the compact tissue,
matrix, and bone-cells. When the borders and limitary surfaces of these
spaces are closely regarded, it is, in many instances, easy to notice bone-
cells more or less removed, half projecting from, or buried in the wall,
and between them projections of the ossified matrix, so that no doubt
can any longer be entertained with respect to the origin of the cavities.
It must b^ confessed that there is as little to be stated, in this case, as
in that of the origin of the analogous cartilage-canals, and the further
development of the canaUeuli of the bone-cells, with respect to the
mode in which this absorption takes place ; and the process is even still
more inexplicable, because, allowing that it really does take place, there
would then exist in the ossifying bone, at the same time and almost in
immediate contiguity, a formation of bone and a resolution of the tissue,
but very little less energetic. The above-described mode of formation
of the canceUi, nevertheless, is a morphological fact, and consequently,
the explanation of such a curious phenomenon becomes a problem to be
solved by chemistry and physiology. As in the diaphyses, so in the
ossification of all the other cartilages, medullary spaces are formed by
the resorption of the inner portions of that part which is half ossified.
But it must be stated, that these spaces do not present the same form,
direction, and size in every bone ; though with respect to this, it is un-
necessary to offer any special remarks, since the relations of this
primitive spongy substance are, in the main, the same as they are after-
wards. Still, it may be remarked, that in many bones, solitary spaces
are apparently developed immediately from cartilage-canals, seeing that
some at least of the latter, at the limit of ossification, communicate
directly with the spaces in the bone ; and, moreover, that not unfre-
quently, cartilaginous elements not yet wholly converted into bone-cells,
are drawn into the process of resolution.

The medullary cavities, however they arise, are filled with a soft,
reddish substance — foetal medulla. This substance at first consists of

21

322 SPECIAL HISTOLOGY.

nothing but a small quantity of fluid and many rounded cells, with one
or two nuclei and faintly-granular contents, of which I am unable to
say how they originate, but only this much, that they are altogether new
formations. In process of time these cells, which are in all respects
identical with those which occur, in the adult, in certain bones (ind.
supra), are developed in the usual way into connective tissue, blood-
vessels, fat-cells, and nerves. The formation of bloodvessels proceeds
with great rapidity, so that bones, very shortly after the development of
the medullary spaces, exhibit bloodvessels in them ; that of the fat and
nerves takes place more slowly, although the latter, at the period of
birth, of course with fewer filaments than subsequently, may be very
readily perceived in the large cylindrical bones, even more readily than
in the adult, because at this time the medulla may be more easily washed
away from them and the great vessels. The fat-cells at this period are
but few in number ; the medulla, in man at least, being colored entirely
red by the blood and the light reddish medulla-cells. After birth they
gradually multiply, till at last, the marrow, in consequence of their great
increase, and the disappearance of the medulla-cells, which are ulti-
mately all transformed into the elementary tissues of the permanent
medulla, acquires its subsequent color and consistence.

In many of the primarily cartilaginous bones of Birds and Amphibia,
the ossification of the cartilage commences, according to Rathke and
Reichert (1. c), on the outer aspect of the cartilage, so that at first a
cylinder of bone is formed with cartilage internally and at the extremi-
ties. The remainder of the internal cartilage then affords space to the
medulla, whilst the epiphyses are formed out of that of the extremities.

If the contents of the cartilage-cells, the "cartilage-corpuscles" of
authors, be really surrounded by a membrane, as Virchow supposes, it
may be assumed that a similar tunic, analogous to the primordial utricle
of the plant-cell [vid. sup. § 8), exists also around the contents of the
bone-cells, and that it takes an essential part, by its throwing out stel-
late processes, in the first formation of the canalicuU, their further elon-
gation and ultimate anastomoses. In this case, also, the stellate and
readily isolated cartilage-cells from an encliondroma described by Vir-
chow (WUrz. " Verb.," Bd. 1), around the internal portions of which the
contours of rounded cells were visible, would be intelligible, and even the
possibility of the isolation of stellate organisms from normal bone {vid.
sup.) be explicable. My exposition of the formation of the lacunce in
rachitic bone, is confirmed by Rokitansky and Virchow (AViirz. "Verb.,"
II.) ; whilst Robin declares that it is incorrect, giving a description of
their formation which is, to me, unintelligible. I recommend to his
notice rachitic bone, the cementum of the horse's tooth, and the symphy-
ses (§ 95), with which he is manifestly unacquainted, and hope that he

THli: OSSEOUS SYSTEM. 323

may then be inducetl no lon;2;cr to rc'rard Schwann's and my views as
antiquated.*

* [As we Imve already said, we must deny the existence of endogenous cell-development
in ossifyinj:, or any other cartilage. In fact, the process of mnltiplication of the corpusclee
(nuclei (?) of Kolliker, granular cartilage-cells of Tomes and De Morgan) is so clear, that
we are at a loss to comprehend how it can be mistaken. What is meant in the text by
" contents," as distinct from the corpuscles, we do not know. Messrs. Tomes and Morgan
describe the real changes which precede ossification, very exactly in a few words, thus :
" Cartilage previous to its conversion into bone undergoes a rapid growth, which takes place
principally in tlie direction of the long axis of the future bone. Each granular cell becomes
divided into two, by segmentation transverse to the lineof ossific advance. These are again
divided and the process repeated from time to time, until in the place of a single granular
cell we have a long line of cells extending from the unchanged cartilage to the point where
ossification has taken pJace'" (I. c, p. 16). "If attention be directed to the end of the line
furthest from the bone, the cells will be found small in size, granular, and with a percepti-
ble nucleus, but without an outer wall, distinguishable from the hyaline substance, which is
abundant between the contiguous lines, but small in quantity between the cells composing
the lines. But if the other end of the line be examined, very different conditions will be
observed. The granular cells will be seen to have become rounded in form, to have in-
creased to three times their original bulk, and to possess well-marked, circular nuclei. ..."
-p. 17.

So far, our own observations are in perfect accordance with those of Tomes and De Mor-
gan. They go on, however, to observe, " in addition to which, each granular cell will have
acquired a thick, pellucid, outer wall;" and with this last statement we can by no mean*
agree. Neither iti ]VIan, the Calf, the Rabbit, the Skate, nor in enchondroma. have we been
able to see anything of the regular development of such an envelop- in fact, in the great
majority of instances, we have convinced ourselves of the absence of anything of the kind —
there being nothing but a clear space between the corpuscle and the ossified wall of the
cavity in which it lies. Bodies corresponding with the lacunal cells — cartilage-corpuscles
that is, — invested by a thick coat of more or less granular, calcareous matter, may indeed
often be obtained free; but they arise, like the corresponding bodies in rickety bone, simply
from the deposition of calcareous matter in the cartilage-cavity before it has taken place
in the matrix, or from a want of union between the two deposits; and are therefore quite
accidental.

The lacuncE are developed, according to these authors, by the shooting out of the granular
cells into processes, and their direct conversion into the lacunce, the nucleus of the granule*-
cell remaining as the nucleus of the lacuna. On this point also, we must differ from thenr\,
and agree with Virchow (I. c, note, § 101) and Kolliker {supra, § 104), that the development
of the canaliculi is, by a process of resolution, quite independent of the corpuscles, which
simply diminish in size, and either remain as the so called " nuclei"' of the lacuna; or totally
disappear. We can especially recommend the Skate (2) as a subject in which to trace th«
process of formation of lacunae, as the bone is homogeneous and transparent, and in conse-
quence of being enclosed in a large mass of firm cartilage, may be cut with ease into very
thin sections. We have observed it with great clearness also in enchondroma.

There is one argument which seems to us conclusive on this point. Wherever the cana-
liculi can be seen at all, however young the tissue, they are i^erfectly clear and transparent.
If. however, they were formed by processes of the granular cells, they ought to be granular,
and more or less opaque.

Taking the same view of the structure of cartilage as Messrs. Tomes and De Morgan,
then, our view of the nature of the lacuna^, resulting from its ossification, agrees with that of
Professor Kolliker. Cartilage becomes bone by the deposit of calcareous salts in the matrix
and occasionally in its cavities. The lacuna- are spaces left round the corpuscles, from
which, by resorption, processes — the canaliculi, — are subsequently developed. If it be asked
how it is that the lacunte may frequently be demonstrated both optically and chemically as

324 ' SPECIAL HISTOLOGY.

§ 105. Elementary 2it"ocesses in the Layers formed from the Perios-
teum.— The periosteum of the priiuarilj cartilaginous bones, is propor-
tionally very thick and vascular, consisting, as early as at the fifth
month, of common connective tissue and fine elastic filaments, the latter
of which in process of time become stronger and stronger, occasionally
assuming the nature of elastic fibres. On the inner aspect of this fully
formed periosteum, there is now deposited an ossific blastema firmly ad-
herent to the bone (Fig. 133, B) ; so that when the periosteum is re-
moved, it generally remains upon it as a moderately thick, soft, whitish

yellow lamella, in which, microscopic ex-
amination shows the existence of a fibrous
tissue, with a not particularly distinct
fibrillar formation, something like imma-
ture connective tissue, and granular, oval,
or round nucleated cells, measuring 0-006
-0*01 of a line. When this lamella is
raised from the bone, it is found to be
very intimately connected with the most
superficial layers, and on its internal sur-
face a few little detached fragments of
bone, and scattered masses of reddish, soft medulla, from the most su-
perficial cancellar spaces, will be observed. The bone thus laid bare,
when the removal of the periosteal layer has been carefully conducted,
presents a rough, and as it were porous surface, with numerous medul-
lary spaces, and remains, superficially, in spots of greater or less extent,
quite soft, pale-yellow, and transparent, whilst more internally it becomes
firmer and whiter, ultimately acquiring the usual appearance of perfect
osseous tissue. When it is inquired, how the formation of bone, which
indubitably takes place in this situation, is effected, we refer to the blas-
tema just described, the cells of which, scattered in the fibrillated con-
nective tissue, have not the least resemblance to those of cartilage, but
appear exactly like the foetal medulla-cells, or formative cells of the

Fig. 133. — Transverse section from the surface of the shaft of the metatarsus of the Calf;
magnified 45 diam. : j1, periosteum : B, ossifying blastema ; C, young layer of bone, with
wide cavities, a, in which are lodged remains of the ossifying blastema, and reticular spi-
culse, b, which towards the blastema present a tolerably abrupt border; D, more developed
layer of bone, with Haversian canals, c, which are surrounded by their lamellae.

distinct bodies, we must call to mind the fact already referred to, that in cartilage, the wall
of the cavities have frequently undergone less change than, or a different change from, the
surrounding matrix; and therefore appear both optically and chemically distinct, though
they are by no means so, morphologically: and, therefore, that there is no difficulty in sup-
posing the same thing to occur in bone. The chemical diiierentiation of the wall of the
lacuna is, in fact, exactly comparable to that of the wall of the cavity which contains the
" nucleus" in connective tissue, and in fibro-cartilage ; and which gives rise to the formation
of the elastic element in those tissues. — Trs.]

THE OSSEOUS SYSTEM. 325

embryo. In fact, it is now, not difficult to show, that the outermost,
still soft bonc-lamellir; pass into the blastema in question, with their
separate spicuh^ and projections, and that (1.) the matrix of the bone
arises from its fibrous tissue, by the simple uniform deposition of cal-
careous salts, although usually, as it seems, without the previous ap-
pearance of calcareous granules ; and (2.) that the bone-cells are formed
out of the formative cells of the blastema. With resjiect to the latter,
however, the transformation cannot be followed step by step, as in
rachitic bones. This much, however, is always apparent, that the bone-
cells at first present larger cavities, less developed rays, and more dis-
tinct nuclei (the latter, as we know, remaining), and, as their occasion-
ally visible outlines prove, correspond entirely in size with the cells just
mentioned, so that I do not for a moment doubt, that they are formed
in this situation exactly as they are elsewhere. With respect to the
development of the ossifying blastema itself, it is at least clear, that it
is derived from the numerous vessels of the foetal and young periosteum ;
the origination of its fibres from fusiform cells, I have very frequently
observed in man and in animals, but with respect to the cells, can only
state that they occur of various sizes, and occasionally intermixed with
free nuclei.

The formation of bone in this blastema occurs wherever it is in con-
nection with the bone ; it does not, however, take place in connected but
in interrupted^ reticular lamellce. The roundish or elongated spaces
(Fig. 133, a), which, from the first, remain between the layers of osseous
tissue, and in the different layers communicate with each other, are no-
thing else than the rudiments of the Haversian or vascular canals of
the compact substance, and contain a soft, reddish medulla, which at
first is obviously nothing more than the unossified portion of the ossific
blastema, althoufrh it sometimes contains more formative cells than
connective tissue. The cells of these spaces are very soon transformed
into the usual, light-reddish medulla-cells, and partly into vessels which
communicate with those of the interior of the bone, and in part also
with those of the periosteum, with which, having once formed a junction,
they remain continuous during the entire growth of the bone in thick-
ness, so that the formation of the spaces in the bone is, at least after-
wards, preindicated by those, which, in accordance with what has been
said, proceed from the periosteum through the ossific blastema to the
bone. Besides medulla-cells and vessels as well as some connective
tissue, the bone-cavities of the periosteal layers also contain round,
elongated, or dentate, flattened, faintly granular cellular corpuscles of
0-01-0-02 of a line, or more in size, with from 3 to 12 or more vesicu-
lar nuclei and nucleoli, which are probably referable to the multiplica-
tion of the medulla-cells {vid. § 11). The periosteal layers, which,
agreeably to what has been stated, are from the first deposited in the

326 SPECIAL HISTOLOGY.

form of cribriform lamellos around the ossific-nuclei formed from carti-
lage, continue to be produced so long as the general growth of the bone
goes on, essentially in the same way, constituting the material by which
it increases in thickness ; but at the same time, more or less important
changes are set up in them ; the most considerable of which take place
in the large cylindrical bones. In these, we find, more distinctly indeed
after birth, that a large cavity is gradually formed in the interior, which
at first contains foetal medulla-cells, and afterwards perfectly formed
medulla. This medullary cavity is formed, in exact analogy with the
medullary spaces described in the preceding paragraphs, by the solution
of the osseous tissue of the shaft; at first, only of that which is formed
from the primitive cartilaginous rudiment, but soon, also of that deposi-
ted from the periosteum upon the former, its development proceeding in
a remarkable manner, as long as the general growth of the bone con-
tinues. Whence it comes to pass, that, as at the ends of the diaphyses,
so also on its surfaces, whilst new bone is continually deposited exte-
riorly, that which is already formed is as continually absorbed in the
interior; and in fact these two processes are so combined, that the bone,
during its development is, in a certain measure, several times regenera-
ted, and, for instance in the humerus of the adult, does not contain an
atom of the osseous tissue which existed at the time of birth, nor does
the bone at that period contain any of the tissue of which it was con-
stituted in the embryo at three months. These conditions will be
rendered most distinctly intelligible, and especially with respect to the
periosteal and cartilage layers, by means of a diagram (Fig, 134) which
I have for a long time employed in my lectures. If, in this figure, we
compare the primordial bone E E with the almost complete bone E"* E'',
it is apparent, that in the longitudinal growth of the diaphysis of the
latter on both sides, at the expense of the continually growing epiphy-
sal cartilage, an elongated cone of osseous substance, 1, 2, 1^ 2\ and 3,
4, 3', 4\ is produced, to which, ultimately, the epiphysal nuclei E'' E",
also originating in the cartilage, are joined, whilst, to increase its thick-
ness, the tubular layer P, PS^^P^ P^ which are constantly increasing in
length and, in the middle, in thickness, are applied to it. In a cylin-
drical bone of this kind consequently, the entire portion formed from
cartilage, presents a figure of a double cone with rounded bases ; and
that formed from the periosteal layers, 1, 2, 3, 4, P^, and V, 2', 3\ 4^,
P^, the form of an elongated tube thickest in the middle, and resem-
bling an elongated vertebra of a Fish, with conically hollowed, terminal
surfaces. The articular cartilage C, is the unossified portion of the
epiphysal cartilage, and the medulhiry cavity which is not shown in the
figure (it may be supposed to be indicated pretty nearly by the outlines
of the fourth bone E^ E^), is formed by the resorption of the entire

THE OSSEOUS SYSTEM.

327

i'isr. 134.

osseous substance derived from the cartilage and periosteum of the
younger bones ; — in this case the first three, E E, E' E\ and E^ E^

In the cylindrical bones, without a
medullary cavity, and in all other bones
containing nothing but spongy substance
in the interior, the absoprtion does not
proceed to nearly the same extent as it
does in the above described cases, that is
to say, only to the production of a looser
spongy substance in the interior, and,
consequently, we find, for instance in the
vertebrfB, more or less considerable re-
mains even of the earlier bone-substance.
In this situation also, the absorption al-
ways affects not merely the osseous nu-
cleus, formed from the cartilage, but like-
wise the periosteal layers, the latest of
which only remain more in their original
form, as the substantia compacta.

The Haversian canals do not originate,
as is sufficiently apparent from what has
been said, like the cancelli of the primary
bone-substance, from a solution of a pre-
existing tissue, but are nothing more than
open cavities, left from the commence-
ment., in the periosteal layers. They are
relatively, of a considerable size at an
early period {vid. also "Valentin. Entw,"
p. 262), measuring in the foetal humerus
at five months 0-016-0-024 of a line in
the femur at birth, accordincj to Hartingr

(p. 78), 0-10-0-024 of a line, just as in the most recently formed layers
also of a later period. Their contents have been already described. The
most important circumstance connected with them remaining to be no-
ticed, is the mode in which their lamellar systems originate. These
lamellae also are formed without the intervention of cartilage, and are
nothing more than deposits from the contents of the canals, which sub-

Fig. 131. Diagram of the growth of a cylindrical bone. B, primary riuliment, the dia-
physis ossified and the epiphyses cartilap;inous : A, the same bone in four stages of further
advance, E'PPE', F.^P'P'E^ P:»p2p2E3, E^F^pSE^ ; P P'P^ps, periosteal layers of these four
bones ; the space contained within 1, 2, 3, 4, and 1', 2', 3\ 4', indicates the portion which
in the largest bcnes is formed from cartilage ; E'E', cartilaginous epiphyses of the second
bone; E^E^, epiphyses of the third bone, in one of which is an osseous nucleus ; E^E'', E*
E*, epiphyses of the fourth and fifth bones, all with larger epiphysal nuclei : G, articular
cartilage ; /, K, interstitial cartilage between the ossified epiphyses and diaphyses.

328 SPECIAL HISTOLOGY.

stance, as has already been said, in respect of its fibres and cells,
entirely corresponds with the ossific blastema beneath the periosteum,
and, in a certain degree, is merely an originally unossified remainder of
it. These conditions are easily observed in young bones, in which, the
periosteal layers, before they have undergone any resolution, are
rendered more and more compact by these new, secondary lamellse; but
even at a later period a more or less ossified blastema (always without
calcareous granules) may very frequently be perceived on the walls of
the canals in question. Whilst the vascular canals are thus, on the one
side, undergoing contraction by the deposition of these secondary layers,
which, just as in the periosteum itself, appear laminated, — either be-
cause the ossific blastema itself is so constructed, or because the depo-
sition of bone takes place with periodical pauses, — they afterwards
widen, or at least some of them, by absorption, as for instance, the
canales tiutritii, the great vascular openings in the apophyses, kc. ; and
the compact substance, as has been already remarked, is also, in many
places partially, and in some even entirely, absorbed.

In what way the bone increases in thickness in the situations where
tendons and ligaments, tvitliout the intervention of periosteum, are
directly implanted into it — has not yet been made out. From the cir-
cumstance, that in the adult, in many of these situations, true cartilage-
cells occur among the tendinous fibres, and also, that their passage into
bone-cells may very clearly be observed, it might perhaps be concluded
that a similar process may take place at an earlier period also. In fact,
I have seen, even in young individuals, at the points of insertion of
many tendons and ligaments [tendo Aehillis, lig. calcaneo-cuboideum,
aponeurosis plantaris, ^-c.) into the bone, cartilage-cells, and their meta-
morphosis into bone-cells. Very frequently, also, tendons and ligaments
are attached to portions of the bone which remain long in the cartilagi-
nous condition, epiphyses, tuberositas calcanei, ^c, and the growth_ of
these parts, of course, is simply to be referred to the cartilage.

The formation of bone on the inner aspect of the periosteum is a fact
long well known, although it has, hitherto, generally been thought, that
in this situation also, it was preceded by a thin cartilaginous layer, until
the contrary was shown by Sharpey and myself. Since the discovery by
Duhamel ("Mdmoires de 1' Academic de Paris," 1742, p. 384, and 1743,
p. 138), that the bones of animals fed upon madder are colored red, a
great number of experiments have been made with that substance, espe-
cially by Flourens, in growing animals ; it being at first believed, that
it only colored those parts of the bones which were formed after its
administration. This method, however, has lost a good deal of its value
since it has been shown by Rutherford (in " Roberti Blake, Hiberni,
Dissert, inaugural, med. de dentium formatione et structura, in homiue

THE OSSEOUS SYSTEM. 329

ct in variis animalibus," Edinb. 1780), Gibson ("Memoirs of the Lite-
rjiry and Philosophical Society of Manchester," 2d series, vol. I. p. 14G),
Bibra (1. c), Brulle and Ilugueny (1. c), that when animals were fed
upon madder, the whole of the growing bones, as well as the bones of
adult animals, become colored, and especially so wherever they are in
more immediate connection with the bloodvessels; for even the medulla
is colored (Bibra). For which reason also, the innermost layers of the
Haversian canals, the periosteal surfaces, and the vascular, young bone-
substance, acquire a deeper color. There are, however, still some
points worth investigating in this way, particularly with relation to the
more recent statements of Brull^ and Hugueny, who, relying upon the
circumstance, that, as they assert, the decoloration of growing, colored
bones, is effected merely by the absorption of the colored portions,
believe they have found that the cylindrical bones also deposit osseous
substance from within, particularly in the apophyses; whilst on the outer
surface, absorption to the same extent takes place ; statements upon
which I will not, at present, give any decided opinion, although at the
same time I hold it as quite certain, that in many places an absorj)tion
does take place, on the exterior of the bone to a greater or less extent. It
is only by such an absorption that the enlargement of the foramen 7nag-
num from the sixth year upwards, at which time the portions of bone
surrounding it are united, can be explained. And the same may be said
with respect to the arches of the vertebrae, and numerous vascular and
nerve-openings [foramen ovale and rotundum of the sphenoid howe, fora-
mina inter transversaria, canalis carotieus, ^c. ^"C.). Consequently, the
law propounded by Serres (Meek. "Archiv," 1822, p. 455), that the
openings in bone enlarge by the growth of the individual pieces by which
they are bounded, is wholly incorrect, as applied to the openings and
canals in the middle of bones ; as had been already, to some extent, de-
clared by E. H. "Weber and Henle ; and even in other cases it holds
good only for the earliest periods.

The periosteal layers present a certain contrast to the osseous tissue
developed from cartilage. The former constitute principally the firm
cortex of the primarily cartilaginous bone, and are characterized by the
occurrence of Haversian canals and their lamellar systems, whilst the
latter produces the spongy substance, and contains no vascular canals.
It must not, however, be forgotten that even the periosteal layers all
have, at first, in a certain degree, a spongy structure, and in all these
bones, without exception, contribute, and frequently very essentially, to
the formation of the spongy substance; moreover, that in the cellular
substance, which originates from the cartilage, in the apophyses for in-
stance, secondary layers, similar to those of the Haversian canals, and
of the spongy substance which is formed out of the periosteal layers,
only not so much developed, appear to be formed. The morphological

330 SPECIAL HISTOLOGY.

and chemical relations of the matrix of these two forms of osseous
tissue have not as yet been determined. On the other hand the bone-
lacun?c of both kinds of tissue do not preseYit the least diflference.

§ 106. Bones not primarily cartilaginous occur, in Man, only in the
cranium. They originate outside the primordial cranium, between it
and the muscular system, and thus within the structure constituting the
vertebral system. They by no means exist as membranous and cartila-
ginous capsules on the first appearance of the cranium, their formation
not commencing till after that of the primordial cranium, from a secon-
dary hlasteyna, whence, in contradistinction to the other primary bones,
the formative material of which exists prior to the commencement of
ossification, they are termed secondam/ hones — or, also, because in most
places they are in contact with portions of the primordial cranium —
covering or overlaying hones (belegknochen). To this class belong, the
upper half of the expanded portion of the occipital bone, the parietal,
and frontal bones, the squamous portion and tympanic ring of the tem-
poral bone, the nasal, lachrymal, malar, and palate bones, the upper and
lower jaw, the vomer, and apparently, the internal lamella of the ptery-
goid process of the sphenoid, and the cornua sphenoidalia. The blastema
of these bones, which differs from that of the primary bones, in its being
successively developed in a membranous matrix, simultaneously with the
process of ossification, not existing previously in any considerable quan-
tity, presents essentially, exactly the same conditions as that of the
periosteal layers, and is also ossified in precisely the same way.

The notion that certain cranial bones, in man and the Mammalia, are
not developed from cartilage, is by no means new, although the morpho-
logy of the question was first established by Rathke, Reichert, Jacobson,
and myself; and its histology by Sharpey and myself. But with respect
to the latter subject, a controversy still exists as to the true nature of
the ossific blastema (as also, of that of the periosteal layers), — whether
it be a kind of connective tissue, as I believe, or a sort of cartilage, as
Reichert and A. Bidder assert, with respect to which more will be found
in my "Mikroskop. Anat." pp. 374, 375.

§ 107. The secondary cranial bones, all, in the first instance com-
mence in the form of a minute, elongated, or rounded, osseous nucleus,
consisting of a portion of fundamental substance or matrix, with a few
lacunae, and which is surrounded by a small quantity of soft blastema.
How this nucleus originates has not yet been observed, although from
the way in which its growth proceeds, it might be assumed with certainty,
that shortly previous to its first appearance, a minute lamella of the
soft blastema is formed in the situation of the future nucleus, which
lamella spreading from a single point, becomes ossified by the addition

THE OSSEOUS SYSTEM.

331

of earthy salts and the metamorphosis of its cells. The primary point
of ossification having thus appeared, for instance in the parietal bone,
its growth advances simultaneously with the horizontal extension of the
membraniform blastema, in such a way that a delicate lamina composed
of reticulated osseous spicules is shortly produced, from which, slender
rays stretch out into the still unossified blastema (Fig. 135). If this
formation be examined more closely, it will be observed, that the indi-
vidual bone-spicules originate in the membranous blastema, by the
ossification of its elements, and, that to a certain extent, the latter is
absorbed in the spaces occupied by the spicules, remains of it being left in
the interstices ; and moreover, that the formation of the osseous elements
proceeds exactly in the same way, that it does in the periosteal layers ; the

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rays of bone as they extend further into the soft blastema becoming
softer and paler, and containing less earthy matter, whilst their cells
become more and more like the soft formative cells, till, at last, the spi-
cules lose all distinct limitary outline, and are lost in the blastema. At
first, the growth of these bones proceeds in a superficial plane only, the
rays, as they extend and become connected by transverse branches con-
Fig. 135. Parietal bone of a fourteen-weeks' old fetus; magnified IS diameters.
Fig. 1.36. From the inner surface of the parietal bone of a new-born child ; magnified 300
diameters: a, bone with lacuna', still pale-colored and soft; b, border of the same; c, ossi-
fying blastema with its fibres and cells. B, three of these cells, magnified 350 diameters.

832 SPECIAL HISTOLOGY.

tinuing to add to the size of the original, reticuLated lamella, which,
however, shortly begins to increase in thickness by the deposition of
layers upon both sides of it ; the different portions, also, in proportion
to their age becoming more and more compact. The formation of the
thickening layers is to be referred to the periosteum, which is found on
the surfaces of the secondary bones, very soon after their formation has
begun, being developed either from their original blastema, or from the
contiguous tissues (perichondrium of the primordial cranium, muscular
and tendinous coverings), and proceeds exactly in the same way as in
the periosteal layers of the primary bones ; that is to say, on the inner
side of the periosteum, a soft blastema is deposited, which gradually
ossifies, from the bone outwards, without its ever being cartilaginous
(Fig. 136). In this way are now formed, chiefly on the outer, but also
on the inner surface of the primary osseous lamella, and proceeding
outwardly from it, successive, new laminae, in consequence of which
the rudimentary bone continually increases in thickness. All these new
lamellae, like the primary one, are at first perforated by reticular open-
ings, and the various sized, roundish or elongated interstices communi-
cate with those of the previously and subsequently formed layers, so
that the secondary osseous nuclei, like the periosteal layers, are from
the first, penetrated by a network of canals, which, as in those layers,
in part at least, soon present the appearance of Haversian canals. At
first, filled only with a soft blastema, the remains of the plastic material
of the various lamellge, these spaces, in consequence of the advance of
ossification in their interior, — which sometimes takes the form of bridges
stretching across them, sometimes of a deposit on their walls, — become
more and more contracted. Ultimately, some are entirely closed, whilst
others are converted into true vascular canals, the vessels being de-
veloped from their contents, which are composed during the time of
medulla-cells, and communicating with those of the periosteum. When
the bone has arrived at this stage, its subsequent changes are readily
followed. It continues to increase in breadth and thickness by the con-
stant addition of new blastema on its edges and surfaces, until it has
attained its typical form and size, and at the same time, by the solution
of its compact substance, additional spongy tissue (or even large cavities),
is formed in its interior, so that eventually, like bone developed from
cartilage and periosteal layers, it presents, externally, compact sub-
stance with Haversian canals ; and internally, medullary spaces (cancelli),
although with distinct secondary deposits.

The secondary cranial bones ossify, in part, earlier than the primary,
and mostly with only a single nucleus. The soft blastema out of
which they are formed, and which, so long as the bones continue to
grow, is to be found on their surfaces and edges, does not, like carti-

THE OSSEOUS SYSTEAI. 333

liige, grow independently 'U'ith them, but is developed by degrees, from
a plasma successively secreted from the vessels of the pc?-206'<e2<m, the
two lamelloe of which are conjoined at the margin of the ossifying
plate. The cells of this plasma, the metamorphosis of which, as in the
periosteal layers, cannot be followed in every particular, are elongated,
measuring in man, for the most part, O'006-O-Ol of a line, and pre-
senting granular contents with oval nuclei of 00028-0*00-18 of a line.
Such of these cells as are destined for the growth of the bone in thick-
ness, with the exception of those of the glenoid cavity of the temporal
bone, never present the slightest resemblance to cartilage-cells, and,
together with their matrix, invariably ossify without the appearance of
any calcareous particles ; those on the borders or extremities, on the
contrary, may, as it appears, subsequentli/, take on the nature of true
cartilage. The most striking example of this kind occurs in the con-
dyle of the inferior maxilla, where, even during foetal life, a thick car-
tilaginous layer is deposited, which so long as the growth of the bone
continues, precedes its longitudinal growth, exactly like an epiphysal
cartilaire. I have noticed the same thing in the articular fossa of the
temporal bone, where, however, the cartilage is less developed ; at the
angle of the inferior maxilla (in the Calf), and at the anterior extremi-
ties of each half of the same bone, which are connected by a semi-
fibrous, semi-cartilaginous substance, corresponding very nearly with
the symijliysis. This fact loses much of the singularity which at first
sight attaches to it, when we consider that all cartilage is at first soft,
and consists of common formative cells. It is, consequently, only ne-
cessary that the formative cells of the soft blastema of the secondary
bones, should, at a certain period, pass through the same changes as
those undergone by the formative cells of embryonic cartilage, in order
to effect the production of cartilage in the bones now in question.
Further investigation is required to show, vrhether cartilage of this
kind also occurs as a supplementary addition to other secondary bones,
and to what extent, in animals. Still, it may be noticed, that in
asserting as I have done, that all ossifications from a soft blastema
take place without the deposition of calcareous granules, this statement
is only in part correct, because it is quite true, in many cases, that this
sort of deposition does occur in them, though never at an early period,
and, generally speaking, hut rarely. The ossifying margin, moreover,
in these cases is never abrupt, as it is in ossifying cartilage.

The ultimate changes of the secondary bones have not yet been
closely investigated. Their mode of connection with each other, and
also with primary bones by suture and coalescence, is tolerably well
known. In the vault of the cranium, for instance, as the primary
ossific points first appear in the situation of the tuberosities of the
parietal and frontal bones, the bones are at first placed widely asunder,

334 SPECIAL HISTOLOGY.

and are connected merely by a fibrous membrane, the continuation of
the periosteal lamella of each, and which is united on the internal
aspect with the remains of the membranous cranium of the embryo,
and with the dura mater. The bones then continue to grow towards each
other, and at last constantly advancing in the above-described continua-
tion of the periosteum, come very nearly into contact at the frontal and
sagittal sutures; there remains, however, for a long time one large vacuity,
in particular, between them, — the anterior fontanelle, — but which closes
in the second year after birth ; whilst at the same time, the bones,
which, up to this period, adjoined each other with a straight line of
juncture, send out interdigitating tooth-like processes, till ultimately,
when their blastema is wholly consumed, they continue united only by
the remains of the periosteum (the sutural cartilage, as it is termed, or
better, the sutural ligament), but which also is capable of becoming
ossified sooner or later, and, indeed, invariably first on the inner aspect
of the suture, where the tooth-like processes are very little developed.
The changes of form in the entire bones during their development are
very remarkable, and have hardly been attended to. If a parietal
bone, for instance, of a foetus or new-born child, be compared with that
of an adult, it will be found that the former is much more curved, and
in no way at all represents a piece cut out of the middle of the latter.
The adult parietal bone consequently must have undergone a very
important alteration in the curvature of its surfaces, and this, as
mechanical conditions are out of the question, can only have been
effected by an unequal deposition of bone internally and externally, in
the middle and at the borders ; or by deposition on the one side and
absorption on the other. That unequal deposition does actually occur,
is seen, for example, in the juga cerehralia and impressiones digitatce,
the sulci meningei, &c. ; but it appears to me, that the whole matter
cannot be understood, unless we assume that heal absorptions also take
place in certain situations. How otherwise can be explained the in-
crease in breadth of the superior orbital ridge, the increase of distance
between the frontal eminences, even after the ossific union of the two
portions of the frontal bone, the change of form of the lower jaw (the
greater distance between the coronoid processes and the mental spine, the
alteration in its curvature, the partial removal and renewal of the alveola'),
&c.? We have already seen, that in the other bones, also, something
of the kind must be presumed to take place, and, consequently, cannot
hesitate to admit it in the present case, although the particulars of the
process be unknown. That this process occurs in the interior of the
secondary bones has been already mentioned. The formation of the
diploe, which becomes more evident in the tenth year, is to be referred
to it, as is also that of the frontal sinuses, and antrum Highmorianum,
which however does not take place till a later period.

THE OSSEOUS SYSTEM. 335

I would further rcmailc, that the secondary bones, so long as they are
in a growing state, are much more vascular than afterwards, even ex-
ceeding, in this respect, the periosteal layers of the other bones; on
which account their medulla, containing the multi-nuclear, enigmatical
bodies, already referred to, is of a redder color. The vessels enter these
bones at innumerable points on the surface, and, in the different bones,
run in vertical or horizontal canals. The latter is the case in the flatter
bones, in \Yhich the vascular channels run principally in the longitudinal
direction of the osseous rays proceeding from the primary point of ossi-
fication; and the former, in consequence of which the surface of the
bone frequently presents an extremely delicate, millepore-like aspect,
occurs in the thicker portions, A great many of these canals after-
wards become obliterated, or, at all events, very much contracted, whence
the surface of the bone is rendered smoother.

In conclusion to these remarks on the development of the bones, I
will add a few words regarding their conditions at different periods.
Valentin noticed the cartilaginous rudiments of the ribs in a human
embryo 6 lines long. That of the cranium is distinctly recognizable in
the sixth or seventh week, as well as those of the vertebral zone and that
of the extremities ; those of the extremities proper do not appear till later
(in the eighth or ninth week). Ossification commences as early as the
second month, first in the clavicles and lower jaw (fifth to seventh week),
then in the vertehrce, the humerus, femur, ribs, and the cartilaginous por-
tions of the lamina of the occipital bone. At the end of the second, and
beginning of the third month, ossification is apparent in the frontal bone,
scapidce, bones of the fore-arm and leg, and upper jaw ; in the third month,
in the rest of the cranial bones, with few exceptions, the metacarpal and
metatarsal bones, and phalanges ; in the fourth month, in the ilium and
ossieula auditus ; in the fourth or fifth month in the ethmoid, the turbi-
nated bones, the sternum, pubis, and ischium; in the sixth to the seventh
month, in the os calcis, and astragalus; in the eighth month, in the os
hyoides. At birth, the epiphyses of all the cylindrical bones are still
unossified, with the occasional exception of those at the lower extremity
of i\\Q femur and upper end of the tibia ; and besides these all the carpal
and the five smaller tarsal bones, the patella, sesamoid bones, and the
last segment of the coccyx. After birth, up to the fourth year, the
nuclei of these bones also make their appearance ; but, in the os pisiforme,
not till the twelfth year. The union of most of the epiphyses and pro-
cesses, with the diaphyscs takes place, in part at the time of puberty, in
part towards the end of the period of growth.*

* [Dr. Sharpey's discovery that certain bones of the skull are developed in the same man-
ner as those layers which are formed under the periosteum in the long bones, has been a
sort of apple of discord among histologists, and has produced a great variety of controversies
not only among them, but among comparative anatomists ; controversies wliose heat has

336 SPECIAL HISTOLOGY.

§ 108. The vital phenomena exhibited in the mature hones are not,
during the vigorous period of life, accompanied with any notable or active

been somewhat increased, as we think, by a want of perception among the combatants, of
the fact, that several totally distinct questions are involved. These questions seem to us to
be the following, and we shall endeavor to consider them in detail.

1. Whether the tissue from which "secondary" bone proceeds is cartilage, or not?

2. Whether it is morphologically homologous with cartilage, or not?

3. Whether ossification takes place in it in the same manner as in cartilage, or noti
And as the result of the answering these: — 4. Whether the ditlerences between the two

tissues are suflicient to constitute the basis of a classification of the bones or not'?

1. To answer this by saying with Meyer that every tissue which ossifies is cartilage, is
simply to beg the whole question. Cartilage we hold to be distinguished from inditierent
tissue, by the fact of its matrix containing chondrin. The substance which in the foetus con-
tains no chondrin, but will subsequently become a cartilage — though in common parlance it
is very convenient to call it " fcetal cartilage" — is no more cartilage than the cartilaginous
basis of a future bone, which might just as properly be called fcetal bone, is osseous tissue.
There can be no question then, we think, that Kolliker is in the right, as against Reichert,
Meyer, and others, when he says that secondary bone is not developed from cartilage, and
that, in this respect, it may be distinguished from primary bone.

2. Though this matrix of secondary bone, however, is assuredly not cartilage, it is another
matter whether it is, or is not, morphologically homologous with cartilage. To arrive at any
just conclusion on this head, it is necessary to understand the precise structure of this tissue,
which Messrs. Tomes and De Morgan have been the first to point out : ■' If attention be
directed to the part furthest removed from the bone, it will be seen that the membrane-like
mass is composed of oval cells with slight prolongations from the extremities, which are
frequently arranged in the form of bands of fibrous tissue. Dr. Sharpey has observed that
the membrane into which the bone extends is like fibrous tissue in an early stage of develop-
ment; and this observation is strictly true when confined to the part indicated, but the
analogy ceases [?] as we extend our examination towards the bone. Here, in the place
of cells with elongated processes, or cells arranged in fibre-like lines, we find cells aggre-
gated into a mass, and so closely packed as to leave little room for intermediate tissue. The
cells appear to have increased in size at the cost of the processes which existed at an early
stage of development and formed a bond of union between them. Everywhere about growling
bone, a careful examination will reveal cells attached to its surface, while the surface of the
bone itself will present a series of similar bodies ossified. To those we propose to give the
name o{ osteal cells, as distinguished from lacunal and other cells. In microscopic characters,
the osteal cells closely resemble the granular cells of temporary cartilage ; so closely, indeed,
that the latter, when detached from the cartilage, could not well be distinguished from them.
They are, for the most part, spherical or oval in form, and lie on the surface of the growing
bone in a crowded mass, held together by an intervening and apparently structureless
matrix. Here and there we find a cell which has accumulated about itself an outer invest-
ment of transparent tissue, and has, in fact, become developed into a lacunal cell destined
to become a lacuna" (1. c. p. 23).

The tissue, then, from which secondary bone immediately proceeds, is composed of a
homogeneous matrix, in which corpuscles, identical with the cartilage-corpuscles, are
imbedded: it is therefore identical, as Dr. Sharpey described it, with young connective
tissue; and as we have seen above (note, § 101), and as the authors state, with fcetal carti-
lage. Though not cartilage, therefore, it is homologous with it (as is, indeed, admitted by
Professor Koliiker) ; a fact which is still more strongly evidenced by the transition of carti-
lage into a similar tissue, at its edges (Tomes and De Morgan, 1. c. p. 24), which may readily
enough be observed, and which has been particularly shown by Reichert to occur between
the primary and secondary bones of the skull ("Zur Streitfrage tlber die Gebilde der Binde-
substanz, Ober die Spiralfaser und uber den Primordial-Schadel," Mailer's " Archiv," 1S53).

Now it seems to us that a tissue which is identical with the embryonic form of cartilage,

"^ THE OSSEOUS SYSTEM. 337

morphological changes. It is true that, during this period, some of the
processes above considered go on — such as the enlargement of the
sinuses in the cranial bones, of the points of insertion of muscles

whicli passes into adult cartilage, and diflers from cartilase only in tlie absence of chondrin
(in which respect ossified cartilage agrees with it), — is in a morphological jioint of view
homologous with cartilage.

3. With respect to the third question, — Sharpey and KoUiker are of opinion that the
deposit of calcareous matter and the formation of lacunte take place in the same manner as
in cartilage, i. e. that the calcareous salts are deposited evenly through the matrix, leaving
spaces round the corpuscles or " nuclei," from which the canaliculi are subsequently deve-
loped by resorption. Messrs. Tomes and De Morgan, on the other hand (see passage cited
above), maintain that secondary bone differs from primary, in so far as certain of the corpus-
cles— "osteal cells,'' — "arrange themselves side by side, and together whh the transparent
blastema in which they lie, become impregnated with ossific matter, and permanently fused
with the bone-tissue with which they lie in contact. By the linear arrangement of these
osteal cells, lamination is produced. In the case of new laminated bone, the cells are simply
ossified without arrangement. Lying amongst the osteal cells will be seen some which have
accumulated around them a quantity of tissue which forms a thick investment to them; they then
become granular, and take on in every respefct the characters of a lacunal cell. These are
found deposited at intervals along the line of ossification, and becoming blended with the
general mass, the granular cell remaining as a lacuna, and sending out processes in all direc-
tions" (" Abstract in Proceedings of Royal Society").

We must confess that all we have seen leads us to believe that the former of these
accounts is correct. We have never been able to find evidence of any of the corpuscles
becoming converted into "osteal cells," and we believe, for the following reasons, that this
process does not take place. In examining the growing Haversian canals in Man, and par-
ticularly in the Calf, we have very frequently found the innermost layer transparent, glassy,
and structureless — exhibiting nothing but the corpuscles ((/) lying in lacunas without canali-
culi. This layer would be as much as jjj'jjjth of an inch thick ; in the layer (c) immediately
external to it, however, the " osteal cells" were exceedingly well marked. The inner layer
looked like smooth ice, and the outer like ice which had cracked into innumerable tolerably
even portions — but these cracks were by no means produced by the canaliculi, which, as
yet, were hardly at all developed. Now it seems clear that if the " osteal cells" were pro-
duced by the calcification of certain of the corpuscles, they ought to be more obvious in the
young, inner layer, than in the outer ; whereas just the reverse occurs. The fact stated by
Messrs. Tomes and De Morgan, that lamination is less obvious in young than in old bone,
tends to exactly the same conclusion. Again, if the granular substance between the lacunae
were composed of calcified corpuscles — " osteal cells," the action of acids ought to bring thera
out as strongly as it does those of the lacunce; whereas neither in young bone nor in old can
anything of the kind be seen.

With respect to the lacunae, again, we have the same remarks to make as when speaking
of cartilage. We have never been able to find any trace of the development of the corpus-
cles (granular cells) into lacunte. As to the tissue which accumulates round them and forms
an investment, we have frequently observed the appearance described ; but this investment
was nothing but the clear, often homogeneous, calcareous matter, gradually encroaching on
tlie matrix and enclosing the corpuscles.

We consider, then, that the process of ossification in primary and secondary bone is iden-
tical; the deposition of the calcareous matter in granules or as a homogeneous infiltration,
being of no constancy or importance. In each case the deposit takes place in the matrix,
and leaves spaces (lacunae) round the corpuscles (nuclei, granular cells). Subsequently, the
canaliculi are developed in the matrix by a process of resorption ; while their walls and
those of the lacunae may or may not become chemically differentiated from it. At the same
time, the matrix may or may not break up into lamintB and "osteal cells" or granules. Its

22

338 SPECIAL HISTOLOGY.

and ligaments, and of the vascular channels ; but a more exten-
sive new formation of bone, ■whether periosteal or in the Haversian
systems, together with a simultaneous and more considerable absorption,
never occurs in them. It was formerly believed that the coloration of
the bones of adult animals by madder, proved that deposition of
bone substance continued to take place even in them, it being assumed
that newly forming osseous tissue only became colored ; but since it
has been shown, that bones already formed were likewise colored by
the same agent, and that colored bones in the adult did not lose their
color (Brulle and Hugueny), this view becomes untenable. Whether
in the perfect bone a change, if not of the elementary parts, but still of
the atoms, takes place, the same external figure remaining, is another
question, for the solution of which microscopy affords no facts. This
much is certain, that the organization of bone is such, that notwithstand-
ing the rigidity of their structure, they are in the most general and most
intimate relation with the nutritive plasma of the blood. In every situ-
ation where the osseous tissue is in connection with vessels, as on the
external surface, in the walls of the medullary cavities and cancelli, and
those of the Haversian canals, millions of closely crowded minute open-
ings exist. These convey the blood-plasma, by means of the canaliculi,
into the lacunar lying nearest to the surfaces mentioned, from which it is
then conducted by wider canaliculi to the more distant lacunae, as far as
the outermost layers of the Haversian lamellae, and those laminae of the
great lamellar system which are most remote from the vessels. When
the enormous number of the canaliculi and their multifarious anastomoses
are considered, it must be allowed that no tissue in the human body is
better provided for in respect of the distribution of the blood-plasma,
whilst in scarcely any other is the direct conveyance of the fluid to the
most minute particles more immediately necessary than in it. There
can be no doubt that the fluids, which this " plasmatic vascular system"
(Lessing) of the bones, obtains from the bloodvessels, probably some-
what modified by the influence of the nucleus which, as I have before
endeavored to show, is still retained in every lacunae, are most indis-
pensably requisite for the maintenance of the bone; for we see, that
when the supply of blood to a bone is impeded by the destruction of the

variability in this respect is neither more nor less remarkable than the greater or less fibril-
lation of the corresponding element of connective tissue, or than the inconstancy of the dis-
position of the cleavage lines of the same element in striped muscle.

As little is any line of demarcation to be drawn between primary and secondary bone
as regards the tissues from which they proceed. Inditferent tissue, in which calcareous
matter is deposited at once, is the basis of secondary bone ; an identical tissue — in which
to serve a temporary purpose chondrin is deposited, being subsequently withdrawn and
replaced by calcareous salts — is the basis of primary bone. And this paragraph may
serve as an answer to the fourth question. If it be correct, we cannot ima<iine that any
distinction of the bones into primary and secondary, upon the ground of their develop-
ment or non-development from cartilage, can be other than arbitrary. — Trs.]

THE OSSEOUS SYSTEM. 339

periosteum or of the medulla, by ligature of the vessels of the limb, or
by obliteration of the periosteal vessels by pressure from without
(aneurism, tumors), necrosis of the parts involved certainly ensues, and
can scarcely in any case be altogether obviated by the collateral circula-
tion which actually exists also in the bones (vid. sujjra). On the other
hand we are scarcely, at present, in a condition to say, how the circula-
tion of the plasma in the bones is carried on, though its movement to and
from vessels (perhaps from the arterial, through several lamellar systems
to the venous) must probably be assumed ; or what special changes in
the course of the nutrition of bone take place ; with the latter in par-
ticular we are unacquainted, because the chemical investigation of these
changes, and especially of the organic products of decomposition, is still
altogether imperfect.

That the osseous tissue is in a state of constant, and indeed very
energetic molecular change, is evidenced not only in its various morbid
conditions, but also by the alterations it undergoes in old age. These
alterations consist more especially in the disappearance of entire por-
tions of the bones, either externally or internally ; of the former, an
instance is afforded, in the entire removal of the alveolar processes of
the jaws, and the latter is seen in the greater porosity and fragility of
every kind of bone, such as the cylindrical bones and those of the
cranium, in the enlargement of the vascular openings (vertebrce, apo-
physes), and in the greater roughness of the surfaces of the bones.
'This senile atrophy of the bones may also be attended consecutively
with an internal addition of bone-substance, a sclerosis, as it is termed,
as in the flat bones of the cranium, in consequence of which, in direct
contrast to the phenomena elsewhere presented by senile bone, the diploe
disappears, its cancelli becoming filled up by new osseous tissue, whilst
the venous spaces and foramina emissaria are obliterated and the entire
bone rendered heavier.

With this abundant vascular supply, and certainly not sluggish mole-
cular change, it cannot be surprising that the bones should be so richly
furni:<hed with nerves, the principal function of which appears to me to
consist in the regulation of the conditions of the vascular system, by
their conveying to the central organ (spinal cord) through the sensitive
fibres intelligence of the state of the vessels, of the quantity of nutri-
tive fluid in the bone, and probably also of the modus of the molecular
change going on in themselves, and by means of the motor elements
their bringing a reflex influence from it, to the arteries and veins which
are manifestly furnished with contractile fibres. These unconscious and
involuntary alternations of influence of sensible and motor filaments,
are, as it appears to me, the most important phenomena of the innerva-
tion in bones, as well as in all other orfjans, the nerves of which are
not constantly in relation with the external world, and make it intelli-
gible, why it is, that no organ, containing nerves and vessels at all, .

o40 SPECIAL HISTOLOGY.

possesses nerves of only one kind. It is not, however, by this, intended
to imply that the nerves of bones do not convey conscious perceptions ;
it is possible that, through them, we obtain a certain degree of know-
ledge of the processes going on in the bones, of the degree of fulness
of the vascular system, the mechanical influences to Avhich they are
exposed from without in the movements caused by the action of the
muscles, the weight of the body, or of external objects, in lifting
weights, mastication, &c. ; but in any case this knowledge would be
very indeterminate, and the sensation excited not definitely localized,
being confused in the general feelings of fatigue, efibrt, or relaxation.
On the other hand, it is quite certain that the bones, in man, in many
diseases, and in consequence of mechanical injury, afford pain, which
latter fact has also been frequently noticed in animals, at all events,
upon irritation of the larger nervous trunks of the diaphyses. In man
the apophyses, in particular, and the vertebral and cranial bones, seem
readily to become painful, which is explained by the considerable number
of nerves immediately in the spongy substance. The compact substance,
on the other hand, might probably be regarded as scarcely obnoxious to
pain ; as, for instance, in resections, but not so perhaps the periosteum,
which less from its own nerves than as the vehicle of those of the bones
before they enter their destination, must naturally be affected in the
same way that they are. Whether the nerves of the bones through
which, perhaps, the conscious perceptions, but in any case the painful
impressions are conveyed, be identical with those through which the'
reflex actions, above referred to, are carried on, is not determined ; but,
looking at the origin of most of the bone-nerves from the cerebro-spinal
nerves, such an opinion might perhaps be maintained, it being premised
that the connections of the nerves with the brain are to be regarded as
less intimate than in the case, for instance, of the cutaneous nerves. I
would, in addition, call attention to the remarkable occurrence of nerves
in the cartilage of the septutn narium in the Calf, although I am unable
to say anything more with respect to their nature than with regard to
that of the nerves of bone.

On the subject of the numerous pathological changes which occur in
the bones, only some brief remarks can here be made. Fractures readily
unite, under but moderately favorable circumstances, by true bone-sub-
stance, which, in the cylindrical bones of animals is preceded by the
formation of a true cartilage, a fact of which I and others are satisfied ;
whilst, according to Paget, this rarely appears to be the case in man.
In the spongy bones, in fractures within the articular capsules, and
"under unfavorable circumstances, the fractured ends frequently unite
merely by a fibrous callus, a sort of articulation being formed between
them. After loss of substance the osseous tissue is readily regene-
rated; and it is the periosteum especially, which, in this case, as in

THE OSSEOUS SYSTEM. 341

the gro^vtll of a bone in thickness, plays the principal part in the resto-
ration ; of course by means of the exudation poured out from its vessels.
In animals, entire bones of the extremities, and ribs are regenerated,
pretty nearly in their original figure, not only when the periosteum has
been saved, of which many examples are exhibited in Heine's collec-
tion in WUrzburg, but even after entire excision with the periosteum, a
rudiment of the bone is reproduced (Heine). In man also, a good many
instances have been afforded of the reproduction of entire bones, such
as the lower jaw, the ribs, the scapula (Chopart) ; and the cases of
isolated, — in some instances large, portions of bone being so regene-
rated are very numerous. It is especially the diaphyses, which are
readily replaced, when they have been lost in one way or another, less
frequently the spongy bones and spongy parts of bones, and those of
the cranium ; in the latter, however, openings made by the trephine
are in many cases filled up, instead of fibrous membrane, with isolated
patches of bone, or even with an entire piece of bone ; in fact, trephined
portions of bone have united exactly in the same Avay as has been ob-
served to take place with portions of bone half cut oif (Pauli). Hyper-
tropJiT/ of bone assumes the most various forms, all of which may be
reduced under two principal types : 1, deposits on the surface, or ex-
ternal hyperostoses, which are formed chiefly from the pe^'iosfeum ; and
2, internal or scleroses, which consist in the filling up of the medullary
cavities and Haversian canals with new bone, and these two forms may
occur either separately or combined. The former takes place in inflam-
mations of the periosteum, either idiopathic or in connection with cancer,
arthritis, syphilis, &c., the latter not only consecutively in old age, but
also in rachitis, osteomalacia, and syphilis. With respect to the micro-
scopic conditions of these growths, Virchow deserves the credit of hav-
ing distinctly indicated ("Archiv, f. Pathol. Anat. I.," p. 135), that
the bony growths or osteophytes on the cranium are formed by a direct
ossification of connective tissue without any preliminary development
of cartilage, which is also undoubtedly the case in the filling up of the
losses of substance in the cranium, in regeneration proceeding from
the periosteum, and in most cases of sclerosis. The newly formed os-
seous substance is sometimes like the normal (many exostoses), some-
times more dense, with small vascular spaces and large irregular lacunae.
Atrophy of the bones is shown in their disappearance in totality in
consequence of chronic diseases, paralysis, anchylosis ; or in rarefaction
of the osseous tissue analogous to senile atrophy, in syphilis, lepra^
mercurial cachexy, paralysis, &c. Death of bone (necrosis) is observed
in cases where the periosteum has been destroyed ; in inflammations of
that membrane and of the bone, &c., for the most part attended with
an excessive growth of the remaining sound parts.* Peculiar morbid
conditions exist in osteomalacia and rachitis, but in neither of these

• [In necrosed bone, tlie bone-corpuscles are generally but little changed; the inter-cor-
puscular structure is granular and of a dark color. — DaC]

342 SPECIAL HISTOLOGY.

diseases have microscopical researches afforded anything worth men-
tion here, except what has been made known by H. Meyer and myself
(11. cc.) with respect to ossification in rachitis. In this case I have
found : 1, that in the disproportionately large epiphysal cartilages,
the layer of the ossifying cartilage-cells (those disposed in rows), mea-
sured, instead of |, 2 to 5 lines ; 2, that the ossifying border is toothed,
owing to the circumstance that the cartilage and bone interlace in
various ways; 3, and lastly, that in decidedly rachitic bones, the de-
position of calcareous granular particles is wanting, and the cartilage-
cells almost invariably, shortly before the matrix, and also without
any appearance of calcareous granules, are metamorphosed into bone-
cells, on which account the formation of the latter can, in no case, be
so well studied as in these bones [vid. supra). Accidental cartilage-
and bo7ie-formations are very frequent. The former tissue is met with,
notwithstanding that it is incapable of regeneration, and that wounds
of it heal only with a fibrous tissue, more rarely with bone (ribs), in
very many organs (bones, mammary glands, parotid, testicles, lungs,
and skin) forming what is termed encJwndroma ; moreover, as a new
covering on the osseous growths, at the border of the worn articular
ends of bones (Ecker). The latter is seen in ossifications of the per-
manent cartilages (ribs, larynx^ epiglottis, very rarely) of tendons
(exercir-knochen, for example), in the dura inater and arachnoid (Mies-
cher, Rokitansky), in the eye (Valentin), in the ovary, in fibrous
membranes (niembrana obturatoria), in enchondroma, in fibrous and
carcinomatous growths, and in the lungs (Mohr's cysts containing hair).
Even in these cases the osseous tissue does not essentially differ from the
normal, and it is formed, sometimes from a cartilaginous, sometimes,
and in fact mostly, from a soft blastema (Virchow, 1. c. p. 137).

In investigations relating to the structure of bone, good sections are,
above all things, requisite. With a fine saw, thin slices are made, which
are ground with water upon a smooth stone with the finger, or with a
second smaller stone, for some minutes (5-10), until they are rendered
uniformly transparent. The sections are then cleaned, and (the fat, if
they contain any, being removed by ether) may be employed, being
wetted with water, for the study of the Haversian canals and disposition
of the lacunse ; and with turpentine, for that of the various lamellar
systems. The lacunae and their prolongations, which, in sections, are
dark and very distinct, owing to their being filled with air, are com-
pletely filled by thin turpentine, so that the latter in great part, and
also the former, are very frequently rendered invisible ; the same thing
happens in water and thicker turpentine, though less rapidly, whence,
before these agents have produced their effect throughout, many of the
lacunse and canaliculi are beautifully shown. If it be desired to pre-
serve the lacunae and canaliculi permanently visible, it is best to polish
a thin section, by rubbing it between two glass plates. It may then be

THE OSSEOUS SYSTEM. 343

examined without the addition of fluid, and presents as perfect figures
as those represented in Figs. 115-117. The grinding of the bone with
oil is not to be recommended, because the lacuniB then become filled
with the oil, and even after thorough treatment with ether can seldom
be rendered distinct. Next to sections of bone, the investigation of the
bone-cartilage is the most worth while. This tissue is prepared by the
treating of bone in the cold, with diluted hydrochloric acid (1 part acid,
10-20 water), until the fluid, which is to be frequently changed, no
longer affords any precipitate with ammonia ; for which purpose, in
small fragments of bone, some hours, in entire bones several days, are
required. From the cartilage thus obtained, sections are now to be
made with a sharp knife in all directions, suitable chiefly for the study
of the Haversian canals and lamellae, which may even be raised from
the surface. The lacunie, also, are still visible ; their prolongations or
canaliculi appear as fine streaks, and their nuclei are seen without fur-
ther trouble, especially also after treatment with potassa, or in cartilage
which has been half dissolved by boiling in water. After long macera-
tion in hydrochloric acid, the lacunae even become isolated, as stellate
bodies with delicate walls, or, in the eementum of the horse's tooth, as
structures corresponding to the former cartilage-cells. After long
softening of bone-cartilage in water, the lamellar systems of the Haver-
sian canals become more or less completely separated, presenting the
appearance of short, coarse fibres among the larger lamellge (Gagliardi's
claviculi). If bone be exposed in a platinum capsule to a strong white
heat, the organic parts burn away, the bone becoming at first black,
and ultimately perfectly white ; and, if due care be taken, the earthy
constituents are left, completely retaining the original figure of the
bone. Preparations of this kind are proper for the study of the lami-
nated structure of the compact substance and of the lamellar systems
of the Haversian canals, which, in this case also, sometimes appear
isolated, as in macerated bone. For the microscopic examination of
the inorganic constituents of bone, sections are subjected to heat on
platinum foil, but they must be very thin, as they afterwards become
more opaque, and, on account of their fragility, except in minute frag-
ments, do not admit of being ground thinner (Bruns) ; or sections may
be boiled in caustic potassa. In either case, the lacunae are seen dis-
tinct, and empty^ with the beginnings of the canaliculi, in a finely
granular matrix. The natural condition of the lacunae is readily seen
in perfectly recent bone, in thin sections or laminae; as, for instance,
in many parts of the bones of the face. In recent bone, also, the
vessels may be studied, naturally injected, and with the microscope,
being thus, far fitter for the purpose than when injections, which often
fail, have been practised, and for the closer examination of which, more-
over, the bones must afterwards be macerated in hydrochloric acid, and
preserved in oil of turpentine. The nerves of the bones may be seen

344 SPECIAL HISTOLOGY.

by the naked eye, on the nutritious arteries of the larger cylindrical
bones, and readily, by the microscope, on the smaller vessels ; those of
the periosteum must be studied after the membrane has been rendered
transparent by caustic soda or acetic acid. The costal and articular
cartilages are the most suitable for the study of cartilage, the membranes
of the cartilage-cells being evident, sometimes without any addition,
sometimes after that of acetic acid or soda, which render the matrix
transparent. The development of bone may be investigated in a cylin-
drical bone, and in the parietal bone ; the formation of the lacunae, in
specie^ in rachitic bones, and in the osseous surfaces of the symphyses
and syncJiondroses.

Literature. — Besides the works cited in §§ 22 and 25, are to be
noticed, F. Bidder, " Zur Histogenese der Knochen" ("On the Histo-
genesis of Bone"), in MUller's " Arch." 1849, p. 292 ; E. v. Bibra,
" Chemische Untersuchungen Ub. die Knochen und Zahne des Menschen
und der Wirbelthiere" ("Chemical Researches on the Bones and Teeth
of Man and the Vertebrata") ; Schweinfurt, 1844; Votsch, "Die Hei-
lung der Knochenbriiche per primam intentionem" (" Union of Frac-
tures, &c."); Heidelberg, 1847; Kolliker, " Ueber Verknocherung bei
Rachitis, u. lib. den Bau der Synovialhaute" (" On Ossification in
Rachitis, and on the Structure of the Synovial Membranes"); "Mitth.
der Ziirich. nat. Gesellsch.," 1847, p. 98; Rokitansky, "Beitrage
zur Kenntniss des Verknocherungsprocesses" (" Contributions to a
knowledge of the process of Ossification"), in the " Zeitschrift der
Wiener Aerzte," 1848, p. 1 ; A. Krukenberg, " Zur Lehre vom
Rohrensysteme der Zahne und Knochen" (" On the Tubular Sys-
tem of the Teeth and Bones"), in MUller's " Archiv.," 1849, p. 403 ;
H. Meyer, " Der Knorpel u. seine Verknocherung" ("Cartilage and its
Ossification"), in Miill. "Archiv.," 1849, p. 292; Virchow, in " Ver-
handl. der Wiirzb. phys. med. Ges.," vol. i. No. 13; Robin, "Observa-
tions sur le developpement de la substance et du tissu des os," in " Mdm.
de la Society de Biologic," 1850, p. 179; Brulle and Hugu^ny, "Ex-
periences sur la ddveloppement des os dans les maramiferes et les
oiseaux, Ann. d. Sc. Nat.," 1845, Nov. p. 283 ; Flourens, in "Ann. d.
Sc. Nat.," 2 serie XIII. 103, ibid. XV. p. 202, ibid. 1845 ; Aout, p.
105, and Dec. p. 358 ; " Compt. rend.," T. XIX. p. 621 ; all his ob-
servations collected in " Th^orie exp^rimentale de la formation des os,"
Paris, 1847-8, avec 7 pi.; Beck, " Abh. Ub. ein. in Knochen verlau-
fende Nerven," Freiburg, 1846; Kolliker, "Ueber die Nerven der
Knocken" ("On the Nerves of Bone"), in Wurzb. "Verhandl.," 1. ;
Luschka, " Die Nerven in der harten Hirnhaut" (" The Nerves in the
Dura mater '), TUbingen, 1850: and " Die Nerven des Wirbelcanales
und der Wirbel" ("Nerves of the vertebral Canal and of the Verte-
brse"), TUb. 1850.

THE NERVOUS SYSTEM. 345

OF THE NERVOUS SYSTEM.

§ 109. The nervous si/stem, regarded in the more general anatomical
sense, constitutes a connected whole, consisting of two principal masses —
the spinal cord and brain, and of numerous cords — nerves — extending
from them to almost all the organs of the body. The two former — or
the central nervous system, the central organs, are to be regarded not
merely from an anatomical point of view, as affording origin to the
nerves, but, also, in o, physiological sense, as excitors of the movements,
and seat of the sensations, as well as of the mental or psychical actions,
and consequently as belonging to a higher or governing order of parts,
whilst to the latter must be ascribed more of a ministerial office — the
communication of the contractions and sensations. This mode of regard-
ing the two divisions of the nervous system, however, is only partially
correct, because, in the first place, in the central organs, as in the
nerves, very many subordinate parts exist ; and, secondly, because in
the peripheral nervous system, the so-termed ganglia, physiologically
and anatomically, represent central organs. The older division also of
the nervous system into animal and vegetative, after the observations of
recent times, can no longer be maintained ; and the latter, — the sym-
pathetic or ganglionic nervous system, can only be regarded as a por-
tion of the peripheral system, though undoubtedly peculiarly consti-
tuted.

ELEMENTS OF THE NERVOUS SYSTEM.

§ 110. The nerve-tubes or fibres (Figs. 137-139), also termed primi-
tive tubes, or primitive fibres of the nerves, are soft, fine, cylindrical
filaments having a diameter of 0-0005-0-01 of a line ; they constitute
the principal part of the nerves and of the white substance of the central
organs, although they are not wanting in the greater part of the gray
substance of the latter and in the ganglia. When examined in the re-
cent state and by transmitted light (Fig. 137) they appear as clear as
water, transparent, and with simple dark contours ; by reflected light —
glistening, opaline, like fat, in larger quantities together, Avhite, and for
the most part their appearance does not indicate that they are composed
of different constituent parts. But it is readily seen upon the applica-
tion of various methods, that they consist of three, entirely distinct,
component structures, viz. : of a delicate coat, and a viscid fluid, in the
centre of which is a soft but elastic fibre. The coat, or sheath of the
nerve-fibres (limitary membrane, Valentin) (Fig. 139, 1, 2, 3, 4, a) is
an excessively delicate, flexible, but elastic, perfectly structureless, and
transparent membrane, which, in quite unaltered nerve-fibres, except in
certain situations, is altogether invisible. But on the application of

346

SPECIAL HISTOLOGY.

suitable reagents, at least in the thicker fibres of the nerves and of the
central organs, it comes readily into view, corresponding in its chemical
characters, in all essential particulars, with the sarcolemraa of the mus-
cular fibres. In the finest fibres of the peripheral, as well as of the
central nervous system, the existence of this membrane has not yet been

Fis. 138.

demonstrated, and it must consequently for the present be left undecided
whether these fibres possess sheaths or not.

Within the structureless sheath, lies the nerve-medulla, or pulp,
("medullary sheath," Rosenthal and Purkinje, "white substance,"
Schwann), (Fig. 137, 3, h, Fig. 139, 3, 4, h) in the form of a cylin-
drical tube, closely and exactly surrounding the central fibre. In the
recent nerve-fibre this substance is perfectly homogeneous, fluid, but
viscid like a thick oil, and, according to the light by which it may be

Fig. 137. — Nerve-fibres, magnified 350 diameters. 1, from the Dog and Rabbit, in their
natural condition; o, fine; b, of medium thickness; c, coarse fibre from the peripheral
nerves: 2, from the Frog, with the addition of scrum ; a, drop of the contents expressed ; b,
axis-cylinder within the drop, continued into the tube : 3, from the spinal cord of Man, re-
cent, with serum added; a, sheath ; b, medullary sheath with double contour; f, axis-cylin-
der: 4, double-contoured fibre from the fourth ventricle in Man; the axis-cylinder, a, pro-
jecting and visible within the fibre : 5, two isolated axis-cylinders from the cord, one undu-
lated, the other of unequal thickness, with some medullary substance attached to it.

Fig. 138. — Nerve-tubes of Man, magnified 300 diameters: four fine, two of which are
varicose; one of medium size with simple contours; and four thick, two of which have
double contours, and two, gruraous contents.

THE NERVOUS SYSTEM. 347

viewed, transparent and clear, or Avhitisli and pearly, and it is obviously
to it that the peculiar glistening appearance of the nerves is due. The
nerve pulp is i-apidly and invariably altered by the application of cold
water, of most acids, and of many other reagents, the change consist-
ing principally in a coagulation of it, which takes place gradually from
without to within, sometimes involving the entire thickness, sometimes
only its outermost layer. In the latter case, are produced the well-
known nerve-fibres with double contour lines (Fig. 137, 2, 3, 4), or in
which the medullary sheath is, externally, coagulated to a greater or less
extent, rcn)aining fluid internally ; in the former case, with the contents
apparently wholly grumous and opaque (Fig. 138). The coagulated nerve-
medulla, in fact, seldom appears homogeneous, but most generally gru-
mous, granular, and as if composed of separate, irregular, larger and
smaller masses, and, upon the application of acetic acid, as if formed of
minute, separate, or reticularly united rods. The nerve-pulp is also
altered very readily by pressure. It sometimes escapes from the ends
of the tubes, or from hernial protrusions or ruptures of the sheath, form-
ing larger or smaller drops of every imaginable shape, regularly spherical,
clavate, fusiform, cylindrical, filamentary, or of the most bizarre figures,
which likewise coagulate either on the surface merely, or throughout,
and thence, like the nerves, appear with a double contour, or half or
wholly grumous. But, within the fibres also, its structural conditions
alter, for, instead of being continued through them as before, — as a
cylinder of uniform size, — it accumulates in places into larger masses.
In this way are produced the frequently described, varicose nerve-fibres
(Fig. 13(5), in which the medullary sheath presents sometimes, minute
moniliform enlargements, sometimes, various sized, irregularly distri-
buted nodosities, or even, in places, complete interruptions. All these
forms, in which the sheath frequently participates, but in which the cen-
tral fibre takes no part, arise artificially, and are developed most readily
in the finer fibres with more delicate sheaths, such as are found in the
central organs.

The central or axis-fibre of the nerve-tubes {^^ primitive band,'' Re-
mak, cylinder axis, Purkinje, Fig. 137, 2, 3, 4, 5 ; 139, 1), is a cylin-
drical or slightly flattened filament, which, in entire and unaltered nerve-
fibres, is as little recognizable as the sheath, being surrounded by the pulp,
and possessing the same refractive power, whilst it comes readily into
view when the fibre is torn or treated with various reagents ; and it may
thus be recognized as a constant structure, sometimes in the interior
of the fibre, and sometimes isolated. Under natural circumstances it
is pale, most generally homogeneous, more rarely, finely granular or
striated, bordered by straight or occasionally by irregular, pale contour
lines, and it is, generally, everywhere of uniform thickness: it is distin-
guished from the medullary sheath, especially by the circumstance, that

348

SPECIAL HISTOLOGY.

although soft and flexible, it is still, not fluid and viscous, but elastic
and solid, something like coagulated albumen, with which it also ap-
pears to agree in most of its chemical
characters. This axis-cylinder exists
in all nerve-fibres without exception,
even in the finest, and invariably pre-
sents the same characters, except
only, that it is sometimes thicker,
sometimes more slender, according
to the size of the fibre itself.

The nerve-fibres, in Avhich the
three structures above described can
be distinguished, and which we would
designate as the medidlated or dark-
bordered, constitute, it is true, the
greater proportion of those existing
in the body, but besides these there are still some forms requiring
more particular description. These are the nerve-fibres in which there
exists no trace of a medullary sheath ; whilst they have an outer sheath
and contents, sometimes identical with the axis-fibre of the other kind
of nerves, sometimes similar but more clear. These non-medullated
nerve-tubes occur, in the first place, as continuations to the other sort,
where the latter are in connection with nerve-cells ; and also as more
elongated, independent fibres, representing the so-termed processes of
the nerve-cells of authors ; and lastly, at the terminations of the dark-
bordered nerves. They may again be arranged in several subdivisions,
distinguished respectively by their having or not having nuclei, and
more or less transparent, more or less consistent contents. It must
also be added, that the dark-bordered fibres differ extremely — partly in
respect to the delicacy or firmness of their structure, and partly in their
diameter, which varies from 0*0005 to O'Ol of a line, or more, so that
they may be distinguished into fine and coarse, delicate or firm fibres ;
from which it is evident that the nerve-fibres, notwithstanding their
general tubular character, still differ pretty widely from each other in
various respects.

The tunic or sheath of the nerve-fibres, discovered by Schwann, in
most nerves is brought into view with some difficulty. It is only rarely,

Fig. 139. — Nerve-fibres, magnified 350 diameters. 1, from the Frog, boiled with alco-
hol and acetic acid ; a, sheath ; b, axis-cylinder ; c, crystals (fat ?) : 2, isolated sheath of a
Frog's nerve, boiled with soda : 3, from the floor of the fourth ventricle in Man, after treat-
ment with soda ; a, sheath ; 6, medulla flowing out in drops, the axis-cylinder is wanting
(having been drawn out in the preparation), and the pale streak is medulla : 4, from the
root of the n. abducens of Man, treated with soda ; a, sheath ; b, medulla, axis-cylinder not
visible.

THE NERVOUS SYSTEM. 349

as in the roots of certain cerebral nerves (those of the muscles of the
eye for instance), and of the spinal nerves that it appears distinct from
the contents ; its presence however is, with certainty, and readily de-
monstrated by the aid of chemical reagents. When the nerves are
boiled in absolute alcohol, soon after the removal of a considerable
part of the fatty matter of the pulp, the sheaths become tolerably dis-
tinct, as dark boundary lines ; and they are rendered remarkably and
beautifully so by a short boiling in acetic acid, during which, the
remaining contents of the nerve-sheaths, with the exception of the
central fibre, escape from them, whilst at the same time numerous (fat)
crystals (Fig. 139, 1) are formed. When boiled in alcohol and treated
in the cold with caustic soda, the nerve-fibres also exhibit the sheaths
very beautifully, as pale, frequently undulating contours of the color-
less, remaining contents ; and when such fibres are boiled for a moment
in caustic soda, numerous, elongated fragments of perfectly empty,
somewhat swollen nerve-sheaths, are detached, which, from their deli-
cacy, present a striking resemblance to the empty tubules of the mem-
Irana propria, of the tubuliuriniferi (Fig. 139, 2). The sheaths, how-
ever, are rendered most distinct by means of fuming nitric acid and the
subsequent addition of caustic potassa. In this case the fatty matter
of the medullary sheath escapes from the tubes in the form of color-
less drops, the axis cylinder is dissolved, and the yellow sheaths are
left empty, dilated and with swollen walls of 0-0004-0-0008 of a line
in thickness. In nerves treated with corrosive sublimate, according to
Czermaak(" Zeitsch. f. wissensch. Zoologie,"1850), the sheaths are, also,
often very prettily shown. It has not yet been determined whether the
finest nerve-fibres in the central organs, and in the peripheral nerves
(under O'OOl of a line) possess a structureless sheath. Analogy with
the coarser fibres is in favor of the existence of such sheaths, but on
the other hand there are some facts which would seem to indicate that
there are also, sheathless primitive nerve-fibres, both of the medullated
and of the non-medullated kinds. I have already (in my " Microscopical
Anatomy," II. 1, 396) remarked, that according to my observations in the
Tadpole, several dark-bordered fibres are developed in one and the
same structureless sheath formed by the coalescence of cell-membranes;
and that a similar thing (at least from R. Wagner's figures) occurs in
the electric organ of the Torpedo : in which cases special tunics can
scarcely be supposed to exist around each separate fibre. And, quite
recently, Stannius (" Gott. Nachr.," 1850) has found, in Petromyzon,
that the nerve-fibres of the central organs possess neither membra-
nous sheath nor pulp, and are, as it may be expressed, nothing more
than free axis-fibres. When to this, it is also added, that the impossi-
bility of demonstrating membranes, by no means certainly proves their
non-existence, still, the facts stated are worthy of all consideration,

350 ■ SPECIAL HISTOLOGY.

and we must, in this question, for the present, abstain from all conclu-
sions drawn from analogy.

[Of the chemical nature of the sheath of the nerve-fibres but
little is known. When boiled for about five minutes in concentra-
ted acetic acid, it is not dissolved, scarcely changed. It resists
boiling in caustic soda for a short time without altering, except that it
swells up a little ; longer boiling dissolves it. It remains unchanged in
water, alcohol or ether, even when boiled. Pettenkoffer's test for
bilin (sugar and sulphuric acid) which reddens protein and elein, but
according to Schulze, neither collagenous substances nor elastic tissue,
does not color the nerve-sheath. Yet its action cannot be ascertained
with the most desirable accuracy, since the nerve-medulla is simultane-
ously reddened. Sulphuric acid and potassa render the nerve-sheath
yellow (xantho-proteinic acid), producing the same effect as they do, ac-
cording to Paulsen, on elastic tissue. Hence it seems as if the nerve-
sheath agrees in composition with elastic tissue, except that it is evidently
less insoluble in alkalies. From Kolliker's Micr. Anat. II. 1. — DaC]

In order to see the medullary sheath or nerve-pulp in its normal con-
dition, a nerve of an animal just killed, without any addition, must be
quickly brought under the microscope ; in which case some isolated fibres
will always be seen quite unchanged, although, as the nerve dries, they
are very rapidly altered. Besides this method, I would also recommend
the examination of the nerves in the transparent parts of animals, either
alive or just killed (nictitating membrane, mucous membrane of the
Frog, tail of Tadpole, &c.), the observing of them on warmed pieces of
glass (Stark.), and after treatment with chromic acid, which frequently
preserves, particularly the cerebral fibres, quite uninjured. The nerve-
pulp or medulla is obviously a viscid, fluid, extensible, glutinous sub-
stance, to be compared in point of consistence with thick oil of turpen-
tine, and which under pressure assumes all possible figures, appearing
in the form of globules, filaments, and membranous masses, of very dif-
ferent aspects, with pale or dark borders, and opaque or clear. In
chemical composition it consists principally of fatty matter.

The central filament of the nerve-fibres, which was perhaps seen as
early as by Fontana, and Avith which we have become better acquainted
under the name of " primitive band" given to it by Remak, or " cylinder-
axis" as it haa been termed by Rosenthal and Purkinje, is indisputably
the most difficult of investigation, and the least known portion of the
nerves. There is no microscopist who has not frequently seen this axis-
fibre, but it may, without fear of contradiction, also be asserted, that
there is none, not even excepting Remak himself, its discoverer, who can
boast that he has studied and learned its relations in every particular.
For this reason, but few, as Hannover and J. Muller, are unconditionally

THE NERVOUS SYSTEM. 351

agreed with Remak and Purkinje in regarding the axis-e3'lindcr as a
constant element in recent nerve, whilst most observers have adopted the
views of Valentin ("Repert." 1838, p. 76, 1839, p. 79), and Henle
("Allg. Anat."), who regard it as not always present, but rather as a
secondary formation, which does not. exist during life, and as the un-
coagulated central portion of the contents of the nerve-fibre, which,
during life, are homogeneous. I have endeavored to the utmost of my
power to investigate the relations of this structure, and have arrived at
the following results :

1. The axis-cylinder is constantly present in every nerve-fibre^ hoth
central and peripheral, in fine and in coarse fibres, and after death is
appareyit before the nerves are treated ivitli any reagent whatsoever. In
the human nerves, in the brain and spinal cord, as they are commonly
obtained for examination, the axis-cylinder, when duly sought for, is
everywhere and with certainty to be recognized ; and in fact by far the
most easily in the central organs, where the absence of neurilemma and
the delicacy of the nerve-sheaths oppose but little hindrance to the
tearing asunder of the fibres. In these situations it may be seen in
nearly the finest fibres. It always presents the aspect of a pale filament,
which, together with a tolerable degree of consistence, is still very flexible
and at the same time highly elastic, as may be readily observed on com-
pression of small portions of the spinal cord (in which case very many
axis -cylinders are stretched and torn, retracting considerably, and
forming undulating curves). On the average it is about one-third as
wide as its nerve-fibre, and consequent!}^ varies a good deal in diameter,
is obviously quite solid, most generally homogeneous, but not unfre-
quently also, faintly striated or very finely granular. It most usually
follows a straight course, bordered by two parallel, pale contour lines,
occasionally, however, it is, in parts, thicker or more slender, though it
never presents varicosities like the nerve-fibres ; and it may, moreover,
be curved or even slightly undulating, and also perhaps with an irre-
gular, even jagged border.

2. When recent nerve-fibres of an animal just killed are treated with
proper reagents, the axis-fibre i7istantaneonsly appears. If a thin cuta-
neous nerve of the Frog, whilst under examination Avith a power mag-
nifying 100 times — be touched with a drop of glacial or concentrated
acetic acid, the nerve retracts and there appear instantaneously, at each
of the cut ends, large particles of the grumous nerve-pulp, and pale,
clear fibres ; and the same thing happens if the nerve have been pre-
viously teased out, and the fibres brought separately into view. The
clear fibres are evidently the axis-fibres, as they may readily be traced
into the projecting medullary sheaths and entire nerve-tubes, and in
other respects, also, present all the characters of those fibres, only that
they are much paler and broader (as much as O'OOl of a line, in the

352 SPECIAL HISTOLOGY.

peripheral thick fibres) and evidently swollen ; they frequently, also,
appear convoluted, or even spirally rolled, "which is owing, simply to the
shortening of the whole nerve caused by the acetic acid. The nerve-
pulp itself is rendered grumous by the same reagent ; the grumous
particles are sometimes granules,, sometimes very short rods, like fat-
crystals, which latter may be very often seen on the nerve-fibres, forming
stellate, acicular groups (margaric acid) ; alcohol and ether also render
the axis-cylinder very distinct, both, when recent nerves are treated
with those reagents in the cold, in which case their action must be rather
more prolonged, and when they are boiled in them. I can particularly
recommend the boiling in absolute alcohol, by which means excellent
preparations of the axis-fibres may be made, and in the shortest time.
Under this treatment the nerves become firmer, but still admit of being
readily torn into fibres, and always exhibit very numerous isolated central
fibres of considerable length, which, contrasted with those brought into
view by means of acetic acid, are, as it were, contracted (at most 0'002 of
a line wide), yellowish, firmer, and often convoluted or twisted. Ether
acts in the same manner. By both reagents the medullary sheaths are
rendered paler and grumous, the grumous particles frequently appearing,
as it were, to be united into a delicate network. When nerve-fibres are
boiled, first in ether and afterwards in alcohol, they become quite pale,
but the sheath and axis- cylinder perfectly distinct, the latter presenting
precisely the same appearance as after treatment with alcohol alone.
Consequently, it would seem, that the axis-fibres contain no trace of
fatty matter ; at all events, except that they shrink a little, they are
not altered by the action of ether and alcohol, and afterwards, also,
again enlarge, under acetic acid, into broad pale bands. Besides the
reagents above mentioned, the axis-fibres are particularly well displayed
by chromic acid (Hannover), corrosive sublimate (Purkinje, Czermak),
and gallic acid, but less readily in recent nerves, in which, it is true that
they become instantaneously manifest, although it is never, except by
accident, and rarely, that they can be isolated, than, especially after a
more prolonged immersion in those. The nerve-fibres under these cir-
cumstances appear contracted, the medullary sheath grumous, the axis-
cylinder more opaque and somewhat diminished, in chromic acid yellow-
ish, but in other respects exactly as above described. In the acoustic
nerve of the Sturgeon, Czermak, by means of corrosive sublimate, has
demonstrated in dividing nerve-fibres, the existence, also, of bifurcating
axis-cylinders. Iodine also or iodine combined with aqueous hydri-
odic acid (Lehmann) act very powerfully. In quite recent nerves it
instantaneously renders the medullary sheath wholly grumous, and not
only isolates numerous, somewhat shrunken axis-fibres, for a considerable
length, but renders them in many nerve-fibres very distinct in situ, and
usually appearing convoluted or serpentine. Hydrochloric, sulphuric,

THE NERVOUS SYSTEM. 353

and fuming nitric acids, in certain cases, also render the axis-cjlinders
apparent (Lehmann.)*

3. The axis-cylinder consists of a solid protein compound differirig
from common fibrin, and from the fibrin of the muscles. The chemical
nature of the axis-cylinder is difficult of investigation, because it cannot
be obtained in an isolated form in large quantity ; something, neverthe-
less, may be learned from microchemical reaction as has been shown by
Lehraann and myself. In concentrated acetic acid it swells up conside-
rably, but is dissolved with difficulty, and even after it has been boiled
continuously for several minutes, although pale, it always remains un-
changed. When boiled for a longer time in acetic acid it dissolves,
exactly like coagulated albumen, whilst the sheaths and some of the
contents remain undissolved. Alkalies (potassa, soda, ammonia), in the
cold, attack the axis-cylinder but slowly, though in soda it instantane-
ously becomes very pale and swells up to 0-004-0-005 or even 0-006
of a line. Longer immersion in soda dissolves it, and the same thing
takes place upon its being boiled, soon after the commencement of ebul-
lition in the fluid. In fuming nitric acid, it disappears in a short time
— less than half a minute, — exactly as is the case with coagulated albu-
men. Treated with nitric acid and potassa the axis-cylinder is rendered
yellow (xanthoproteinic acid) and may be seen spirally contracted, within
the nerve-fibres, which are also shortened, but not to the same extent.
On the other hand it is not colored by sugar and concentrated sulphuric
acid, which redden coagulated albumen, at most acquiring a yellowish or
pale-reddish hue. In water the axis-cylinder is unchanged, even when
boiled, in which case it is readily isolated and appears somewhat con-
tracted ; by ether and alcohol it is undissolved even by boiling, but
shrinks to some extent. The latter effect is produced also by corrosive
sublimate, chromic acid, iodine, and carbonate of potassa. Viewing all
these reactions together, it might perhaps be stated with certainty, that
the axis-cylinder is a coagulated protein compound which, however, dif-
fers from fibrin, inasmuch as it is insoluble in carbonate of potassa and
solution of nitre, and offers much greater resistance to acetic acid and
caustic alkalies. On the other hand, it agrees with the substance of
which the muscular fibres are composed, in its elasticity and insolubility
in carbonate of potassa, differing from it in its insolubility in dilute
hydrochloric acid, and difficult solubility in acetic acid.

These are the most important facts connected with the axis-cylinder.
The conclusion which may be drawn from them, appears to me, to be
simply this, that the axis-cylinder is not an artificial product, but that
it must be regarded as an essential constituent of the living nerves.

* [I have always obtained the best preparations by soaking a nerve for six or twelve days
in concentrated acetic acid. The axis-fibres can then be readily isolated; but are fragile
and devoid of their elasticity. — DaC.J

23

354 SPECIAL HISTOLOGY.

The only objection which can be urged against this opinion consists in
the circumstance, that the axis-fibre cannot be seen in living fresh
nerves, and that it cannot generally be distinguished, as a special
structure, in the interior of the nerve-tubes without the aid of reagents.
But it must be remarked that it can also he brought into view in nerves
that are still warm. Thus I find well-marked projecting axis-fibres at
the roots of the cerebral nerves in Frogs just killed, which I have
examined as quickly as possible, after the application of a solution of
sugar, particularly in those of the optic, trigeminal, and vagus, also in
the spinal nerves, for instance in the second. I see them under the
same conditions in the peripheral nerves of the Frog that have been
teased out, and, in these nerves, have on several occasions, even dis-
tinctly noticed the axis-fibres in the form of convoluted filaments, in
larger drops of the nerve-pulp expressed from the tubes (Fig. 137, 2).
The only fact, therefore, that can be adduced in opposition, is this, that
it is quite true that the axis-fibre cannot, with certainty, be perceived
in the iiiterior of the recent nerve-tubes themselves, except upon the
application of some reagent ; but this circumstance obviously proves
nothing at all, because neither can it be seen in the interior of tubes of
less recent nerve-substance, all of which, as innumerable examples of
isolated axis-fibres occurring in them, show, invariably contain such fibres.
The axis-cylinder, possessing the same refractive power as the still
fluid part of the medullary sheath, is necessarily indistinguishable from
it, but from this circumstance we cannot conclude that it is absent,
nor, equally, can such a conclusion be drawn from its invisibility in the
recent nerve-fibril. Taking all these circumstances together, I am
firmly convinced that a special, central structure exists even in recent
nerves, which is distinguished from the more external portion, — that is
from the medullary sheath, — not only by its chemical composition, as
appears to me to have been placed beyond all doubt, but also by its
consistence and elasticity, as well as by its possessing a determinate
form. The condition in which we obtain the axis-fibre in the human
nerves and central organs, by the addition of the serum of the blood,
albumen, or vitreous humor, appears to me to represent its natural
state ; on the other hand alcohol, ether, iodine, corrosive sublimate,
gallic, and chromic acid render it more consistent than it is normally ;
whilst acetic acid, dilute nitric acid, and alkalies exhibit it paler and
more swollen. The nerve-pulp forms a semi-fluid cortex around the
axis-fibre, and, though intimately connected, is not continuous with it.
By pressure, therefore, the pulp may very frequently be expressed, by
itself, from the ends of the tubes or from lateral rents of the sheath.
The drops of pulp thus formed, usually coagulate on the surface, re-
maining clear and transparent in the interior, like the central portion
of the nerve-tubes. Many authors have described these bodies as por-

THE NERVOUS SYSTEM. 355

tions of tlic "whole contents of the norvc-tube, and have reganU-d their
formation as a proof against the pre-existence of the axis-fibre, but
incorrectly. They belong to the medullary sheath only, which, in the
interior of all nerve fibres with only a double contour, is still for some
space perfectly clear and bright. An axis-fibre and a clear sjjace, in
fibres having a double contour, are therefore by no means identical, and
it is not at all surprising, nor opposed to the existence of an axis-cylin-
der, that a multitude of drops with a double contour and clear contents
should be obtained from such fibres. The medullary sheath may also
coagulate entirely, and then the axis-fibre remains evident, sometimes as
a transparent streak of uniform breadth throughout ; sometimes, when
the grumous particles are more numerous, it may be concealed by them,
so that the entire contents of the nerve appear to be coagulated. They
are so, however, only in appearance, the clear fibre always lying in the
interior ; and I have never yet seen it coagulated or grumous. Non-
medullated nerve-fibres occur in many situations. I enumerate among
them : 1, the pale fibres in the Pacinian bodies ; 2, the nucleated
pale fibres in the terminations of the olfactory nerves ; 3, the per-
fectly transparent, non-nucleated nerve-fibres in the cornea ; 4, the
pale, branched, and partially anastomosing terminations of the nerves
in the electrical organ of the Torpedo and Ray (R. Wagner, Ecker) ;
5, the similarly constituted terminations of the nerves in the skin of
the Mouse {yid. " Micr. Anat." § 11); G, the pale processes of the
nerve-cells in the central organs and ganglia, even though they may
not all pass into dark-bordered fibres. Of these fibres, those which
occur at the extremities of nerves were, even by the earliest observers
of them, unconditionally regarded as nerve-fibres ; and as respects the
processes of the nerve- cells, I described this to be their nature as early
as the year 1846 ; but these views could not be considered as fully es
tablished, until the relation of the fibres with the elements presenting
the dark borders was completely elucidated. But since it has been
ascertained by Schwann, Ecker, and myself, that the nerve-fibres of
the embryo are in precisely the same condition as the pale fibres now
in question, and since, I, Wagner, Robin, and Bidder and Reichert,
have shown that the pale processes of the nerve-cells pass into dark-
bordered fibres, it has become more possible to arrive at positive
conclusions on the subject. R. Wagner was the first to broach the
supposition, that the pale fibres in the Pacinian bodies, and in the elec-
tric organs, were nerve-sheaths, with axis-cylinders, and that the pro-
cesses which pass into nerve-fibres, were themselves bare axis-cylinders,
and, moreover, that the entire granular contents of a nerve-cell are
nothing but an axis-cylinder enlarged into a globular form ; and after
I had demonstrated the constant existence of the axis- cylinder in the
living nerve, and that it was a structure distinct from the medullary

356 SPECIAL HISTOLOGY.

sheath, I considered myself fully justified in asserting that the darh-
hordered nerve-fibres ^vere in direct connection on the one side through the
axis-cylinder^ with the pale processes of the nerve-cells and the contents
of those cells, and on the other, that they passed into the pale terminal
nerves in the situations above mentioned. But this, by itself as I believe,
affords no ground for the identification of the pale fibres in question, or
the contents of the nerve-cells, with the axis-cylinders. This could
only be established, if we knewwith certainty that the medullary sheath
of the dark-bordered nerve-fibres is superadded from without to the
contents of the pale embryonic fibres during the development of the
nerves, and is an entirely new formation between those contents and
the membranous sheath. This is not the case, however, it being on the
contrary more probable that the medullary sheath, which is also albu-
minous, is developed merely from a metamorphosis of the outermost
part of the embryonic nerve-contents, that is to say from the develop-
ment of fat in it, and that the axis-cylinder is the unaltered innermost
part of those contents. In this case all the structures, the nature of
which we are now discussing, would represent, not bare axis-cylinders,
but an entire embryonic nerve-tube, the contents of which were still
homogeneous, or had not undergone differentiation, and would also be
in continuous connection with all the parts of the dark-bordered fibres, —
a mode of explaining them to which, at all events at present, I am dis-
posed to give the preference. In addition I would remark, that the pale
nerve-fibres are also met with in different stages of development. The
nucleated fibres in the olfactory membrane remain altogether in the
stage of embryonic fibres, as also, to all appearance, do the pale rami-
fications in the electric organ, and the contents of both these kinds of
nerve-tubes would appear to have little agreement, in their consistence,
with an axis-fibre ; in the Pacinian bodies the contents of the pale fibres
in all respects, represent an axis-fibre, for it is probable that a sheath also
exists in this situation ; in the cornea, the contents of the transparent
terminal nerve-tubules are apparently more fluid ; and, lastly, with
respect to the processes of the nerve-cells, they consist, whether they
have a delicate sheath or not, of a substance often exactly resembling
an axis-cylinder, but which is also frequently of softer consistence, cor-
responding with the contents of the nerve-cell. The contents of the
pale, non-medullated nerve-tubes, therefore, although genetically com-
prehending more than an axis-fibre, still in all probability are capable
pretty nearly of assuming its nature.

§ 111, The nerve-cells (accessory corpuscles (Belegungskorper), nerve-
corpuscles, Valentin), (Fig. 140), are nucleated cells, occurring in great
numbers in the gray or colored substance of the central organs, in the
ganglia, and occasionally also in the trunks, and peripheral expansions
of the nerves {retina, cochlea, vestibule). The nerve-cells are covered

THE NERVOUS SYSTEM.

357

externally by a delicate, structureless membrane^ which in the cells of
the ganglia (ganglion-cells, -globules, -corpuscles), may be demonstrated
easily, but Avith great difficulty in those of the central organs ; the

Fi?. 140.

a...

application of reagents, however, will suffice to show, pretty distinctly,
that the membrane exists around the larger cells, even in these situa-
tions, whilst in the smallest, just as in the finest nerve-fibres, no mem-
brane has yet been observed, although one probably exists. The contents
of the nerve-cells are a soft, but tenacious, elastic substance, which be-
sides the nucleus consists of two elements ; firstly, of a clear, homoge-
neous, light-yellowish, or colorless matrix, upon which the physical
properties of the contents depend, and which is a protein-compound ;
and, secondly, of minute granules of different kinds. In the colorless nerve-
cells these present the form of uniform, roundish, for the most part,
minute and pale, more rarely, darker and larger corpuscles dispersed
throughout the entire contents of the cells, and imbedded in the tena-
cious matrix ; whilst in the colored cells, instead of these granules, more
or less yellowish, brown or blackish corpuscles occur. The latter are
most usually of a larger size, and are placed, closely aggregated, in a
mass near the nucleus ; in other instances, they nearly fill the entire
cell, giving it the aspect, in all respects, of a brown or blackish pigment-
cell. In the midst of these contents lies the nucleus, for the most part
as a very clear, spherical vesicle with distinct walls, perfectly transpa-

FiG. 140. — Nerve cells, from the acoustic nerve, magnified 350 diameters: 1, nerve-cells
with tiie origin of a fibre, from the anastomosis between the facia! and auditory nerves, in
the meatus audit, int. of the Ox ; a, membrane of the cell ; b, contents ; c, pigment ; d, nucleus ;
e, continuation of the sheath upon the nerve-fibre ;/, nerve-fibre : 2, two nerve-cells with
fibres, from the w. ampull. infer, of the Ox ; a, sheath with nuclei ; 6, membrane of the cell ;
c, nucleus ; d, the origin of a fibre with nucleated sheath : 3, isolated contents of a nerve-
cell, with nucleus and two nucleoli. For these drawings I am indebted to Dr. Corii.

858 ' SPECIAL HISTOLOGY.

rent contents, and one, or more rarely several, large opaque nucleoli,
which occasionally exhibit a cavity.

The size of the nerve-cells varies very much; like the fibres, they
occur as large, small, and middle-sized. The extreme dimensions of the
cells are 0-002-0-003, and 0-05-0-OG of a line. The nuclei, which for
the most part are in proportion to the cells, measure from 0"0015-0'008
of a line; the nucleoli 0-0005-0-003 of a line. The nerve-cells, more-
over;'are distinguished according as they are: 1, thin ox thick-walled,
of which the former are found almost wholly in the spinal cord and
brain ; and 2, as they are independent cells, or are furnished ivitlt pale
processes, of which they may have one, two, or several (uni-, hi-, multi-
polar cells), and which are frequently ramified, and the former, in many
situations, continuous with dark-bordered nerve-fibres, and even having
the nature of non-medullated nerve-fibres. Besides the nerve-cells,
there also exist in the gray-substance of the higher central organs, as
constant constituents, a finely granular pale substance, which has the
greatest resemblance to the contents of the cells, and besides this, in
places, large accumulations of free cell-nuclei. Similar elements are
contained in the retina, and according to Wagner and Robin in the
ganglia of the Plagiostomata.

The nerve-cells are simple cells, as which they were understood even
by Schwann; this is clearly and manifestly shown by their form, their
chemical composition, and their development. When Bidder, more
lately (1. c), relying upon the fact that the nerve-cells in many situa-
tions are in connection at each end with dark-bordered nerve-fibres, pro-
pounds the opinion -that they are membraneless masses, imbedded in
dilatations of the nerve-tubes, he has overlooked those cells from which
no fibres are given off, which possess exactly the same membrane as
those with processes ; and has not considered that there also exist nerve-
cells with a single, and others with numerous processes, as applied to
which, his view would be altogether unnatural; and lastly, that the
development of these bodies indicates that the nerve-cell is formed m
toto, whether it possess processes or not, from a simple cell. It has not
yet been determined whether the nerve-cells of the large central organs
have membranes or not ; Stannius was unable to detect them in the
Lamprey, and R. Wagner says the same of the nerve-corpuscles of the
electric lobes of the Ray. I think I have seen a membrane in the large,
many-rayed corpuscles in the spinal-cord and cerebellum of man, and
occasionally, also, in others, but I freely acknowledge that no membrane
can be detected in all the smaller cells, nor in the processes of the cen-
tral cells in general. This does not, however, appear sufficient to justify
the denial of the existence of membranes in these instances, and I
believe, that in this case, as in that of the finest nerve-tubes, we must

THE NERVOUS SYSTEM. 359

for the present abstain from any definite opinion. The processes of the
nerve-cells, in the brain and spinal cord, which were first noticed by
Purkinje, will be more minutely described when we come to speak of
the central organs, and the question will there be discussed as to their
relation to the central fibres. In the ganglia, there are no cells with
branched processes, instead of which we find only those with one, two,
rarely three or four, pale appendages, which are continuous with dark-
bordered tubes. The nerve-cells consist, for the most part, of a coagu-
lated, although soft protein-compound, which appears to correspond very
closely with that of the axis-fibres. It has not been ascertained whether
the membranes and nuclei differ essentially from it. The fatty matter,
which has also been found in small quantity in the gray substance, con-
stitutes in every case the opaque granules in the cells, and appears to
exist in other conditions also, in their contents. When isolated nerve-
cells are compressed, they become much flattened, resuming their pris-
tine form when the pressure is removed. Their processes also are very
elastic, and like the axis-fibres may be considerably extended, and after-
wards again retract themselves.

As our knowledge of the chemical composition of the gray and white
substance still leaves much to be desired, I content myself with the fol-
lowing statements. Lassaigne, in the brain of a lunatic, found —

Gray substance. White substance.

Water 852 73 0

Albuminous matter ...... 7-5 99

Colorless fat ....... 10 13-9

Red fat 3'7 09

Osmazome, lactates ...... 1'4 i'O

Phosphates 1-2 1-3

According to Fremy (Comptes rendus, tom. ix. p. 703, "Ann. d.
Chem. und Pharm. 1841," vol. xl. p. 69), the brain (both substances
together) contains —

Water 80

Albumen .......... 7

Fatty matter ......... 5

Osmazome and salts ........ 8

100

Which almost exactly agrees with Vauquelin's analysis, who more-
over estimates the osmazome at 1*12, and the salts at 6-65; whilst it
differs from that of Denis, who found much more fatty matter (12-40
in a man 20 years old, 13-3 in one aged 78), and less water (78 and 76[}).

CENTEAL NERVOUS SYSTEM.

§ 112. Spinal Cord. — The nervous elements are so disposed in the
spinal cord, that its external, white substance is constituted almost ex-

360 SPECIAL HISTOLOGY.

clusively of nerve-fibres, whilst the gray nuclear portion with its pro-
longations, the cornua, or horns, is formed, in almost equal proportions,
of nerve- fibres and cells.

The white substance of the spinal cord may, for the purpose of de-
scription, be most conveniently, and in accordance with usage, divided
into two halves, and each of these into three columns. The anterior
columns [funiculi anteriores), are, towards the interior, almost com-
pletely separated from each other by the anterior fissure [fissura ante-
rior), which extends the whole length of the cord, and into which a
vascular process of the jwia mater penetrates. At the bottom of the
fissure, however, the columns are united by the anterior or white com-
missure [com. alba) ; externally, they extend as far as the points of exit
of the anterior roots of the nerves, or to the sulcus lateralis anterior,
but are here inseparably connected with the lateral columns {funiculi
laterales), which again, at the points of exit of the posterior roots, where
the sulcus lateralis 2)osterior is situate, are continuous, without any line
of demarcation, with the posterior columns. The latter {funiculi pos-
teriores) appear indeed as if they were in contact in the posterior mesial
line, because the posterior longitudinal fissure described by many anato-
mists, does not exist in man, except in the lumbar enlargement of the
cord, and in the superior cervical region ; but they are nevertheless
separated, to such a degree, throughout the whole length of the cord
by very numerous vessels, which in the posterior mesial line penetrate
as far as the gray nuclear portion, that the columns in most places are
not even in contact, and even where they are, they are merely in juxta-
position, and never by any means continuous into each other. Thus
the white substance of the cord represents two halves, united only by
the anterior white commissure, and each of which is divided more arti-
ficially into three columns, which occupy the depressions left between
the projecting processes of the gray substance.

The grai/ substance presents a central portion, more of a riband-like
form, and four laminae projecting laterally from it, so that its transverse
section forms a cross. The central portion or the grat/ commissure, in
the adult, does not, normally, contain any canal, such as exists in the
foetus, and consists of a central, cylindrical, or flattened tract, consti-
tuted principally of nerve-cells, of a yellowish color — the gray nucleus
{subst. grisea. centralis), and of nerve-fibres running transversely, con-
tinued beyond the nucleus, before and behind it — the gray or posterior
commissures. Of the lamina, in a transverse section also termed horns,
the anterior are thicker, and shorter, of a uniform gray color, composed
of larger and smaller nerve-cells, and of delicate nerve-fibres of me-
dium fineness ; the posterior, longer and thinner, are constituted at
their roots like the former, only most usually of smaller cells ; but at
the free edge are invested with a more transparent layer, containing

THE NERVOUS SYSTEM.

361

Fig. 141.

a preponderance of smaller nerve-cells — the substantia gelatinosa of
Rolando. Of the roots of the spinal nerves, the anterior penetrate be-
tween the anterior and lateral columns, di-
rectly to the anterior horns, and the poste-
rior are lost between the lateral and pos-
terior columns, passing through the substan-
tia gelatinosa into the posterior laminte or
horns.

With respect to the intimate structure of
the spinal cord, we have to distinguish in the
white substance : — 1, horizontal ; and 2, lon-
gitudinal fibres. The latter, in all situations,
except in the anterior commissure, are in
great part altogether unmixed with horizon-
tal fibres, and everywhere, both superficially

and deeply, run parallel with each other, but they are never in-
terlaced, nor do they ever constitute smaller fasciculi. The number
diminishes from above downwards, because, as will be afterwards
shown, they successively pass inwards towards the gray substance,
presenting the general characters of the central nerve-fibres ; that
is to say, the delicacy of sheath, disposition to the formation of vari-
cosities, and to the breaking up into separate fragments, which are
constituted either of all the elementary parts of the nerve-tubes, or
consist of nothing more than an axis-fibre, or of the medullary sheath.
Their diameter amounts to 0-0012-0-0048, on the average 0-002-0-003
of a line, and, in one and the same fibre is, evidently, always nearly
the same, since, in the white substance, neither divisions nor any other
kind of alteration in diameter of the fibres are found to exist. The
transverse fibres occur : — 1, in those portions of the lateral and pos-
terior columns which adjoin the horns of the gray substance, and the
description of which will be given afterwards with that of the gray
substance ; 2, in the white commissure ; and, 3, at the points of
entrance of the roots of the nerves. The ivJiite, or anterior commissure

Fig. 141. — Transverse section through the spinal cord in the superior kinibar region, mag-
nified about 30 diameters, half diagrammatic : a, anterior column ; b, lateral columns, motor
portion; c, lateral columns, sensitive portion; c/, posterior columns; e, anterior longitudinal
fissure; /, posterior longitudinal fissure ; g, motor roots ; h, their internal fasciculus; i, their
external fasciculus ; k, decussation of the anterior columns in the anterior commissure ; I,
gray fibres of the lateral columns passing into the anterior gray commissure; wi, gray cen-
tral nucleus, here internally w^ith two groups of somewhat darker cells ; n, posterior gray
commissure, with a vessel cut across; o, fibres of the posterior column passing into the gray
commissure ; p, fibres of the sensitive roots going off to the lateral columns; q, similar fibres
entering the posterior column ; r, longitudinal fasciculi of fibres passing into the sensitive
roots; s, substantia gelatinosa, whh traversing bundles of the sensitive roots, w ; t, sensitive
radical fibres running horizontally forwards to the gray commissure ; u, large cells of the
anterior cornua (the puncta), inner group ; v, the same, outer group.

3G2 SPECIAL HISTOLOGY.

(Fig. 141, Jc), is not a commissure in the common sense of the word.
It is formed by those nerve-fibres of the anterior columns, which are, in
succession, the most deeply placed, and which bending obliquely inwards,
cross in front of the gray commissure ; the fibres coming from the right
anterior column, passing, in a radiating manner and horizontally, to the
left anterior horn of the gray substance, and those from the left anterior
column passing in like manner to the 7-ufJit anterior horn. The anterior
commissure, therefore, represents a decussation, or crossing of the
anterior colwnns, and would be better designated as such. It varies
both in thickness and breadth ; it is thickest in the region of the two
enlargements, and is least so in the middle of the dorsal portion of the
cord. Its breadth is regulated pretty nearly by that of the cord, and
of the bottom of the anterior fissure ; being greatest in the cervical
enlargement, and from this point decreasing pretty uniformly in both
directions. The decussating fibres measure 0-0012-0-003 of a line,
and, as they diverge in the anterior horns, evidently in some degree
decrease in diameter.

The roots of the spinal nerves (Fig. 141, g, w), without any communi-
cation with the longitudinal fibres, are continued, in larger fasciculi, from
the sulcus lateralis anterior and posterior, either horizontally or slightly
ascending between those fibres, in order, all of them, to enter the ante-
rior and posterior gray lamina, where we shall again meet them. Their
nerve-fibres (in the posterior roots, about |ds measuring 0'004-0*008,
and §d 0*0012-0*003 of a line, in the anterior about fths measuring
from 0-006-0-011, and ith 0-0025-0 -003 of a line) present, as soon
as they have entered the cord, all the characters of the central fibres,
the largest, at their commencement, measuring about 0"004-0"006 of
a line, in the sensitive, up to 0*008 of a line, in the motor roots.
They continue, however, distinctly and constantly decreasing in size,
until ultimately, the former, when they enter the gray substance, have
a diameter scarcely more than 0*0012-0-0028 of a line, and the latter
in like manner one of not more than O'OOl, or in some of 0*006 of a line.

In the gra?/ substance, the nerve-cells and fibres deserve special
consideration. The former present very various forms, all, however,
corresponding in one respect, that they are invariably furnished with
processes or prolongations, and, for the most part, with many such,
which repeatedly branching, ultimately terminate in extremely fine,
pale fibrils, like the finest axis-fibres. I distinguish : — 1. The cells of
the central gray substance. These (Fig. 142) are 0*004-0*008 of a
line, in size, always pale and finely granuUir, with multiple nuclei and
branching pale processes, constituting as it would seem the principal
bulk of the central gray substance ; but in which, dark, true nerve-
fibres also occur although of nearly the finest kind, which can scarcely
be recognized as such, and are indeed very few in number, and quite

THE NERVOUS SYSTEM.

3G3

FiiT. 142.

isolated; besides these, there are a good many extremely fine, pale
fibrils, like the processes of the cells, only more extended, and running
in a transverse and longitudinal direction, of which nothing more can
be said, as to whether they are nerve-tubes,
or are to be referred to the processes of
the cells. The gray central substance,
taken altogether, is thickest in the lumbar
enlargement, and on a transverse section is
of a pyriform, scutate, or cordate figure ;
next to this stands the cervical enlarge-
ment; and lastly, the superior cervical and
dorsal portions, in which latter parts its
transverse section presents an ellipse, in
the cervical region, with the longer dia-
meter much developed. It occasionally y^^l
exhibits, especially in the lumbar region,
indications of its being constituted of two
halves, inasmuch as the middle appears
somewdiat clearer, and the lateral portions,
owing to the accumulation of fatty gra-
nules in the cells, more opaque. 2. With
the above-described cells, those of the suh-
stantia gelatinosa^ pretty nearly agree, only that they are of a faint,
yellowish color, and have 1-3 processes and simple nuclei. Besides
these cells, the substantia gelatinosa also contains the fasciculi of fibres
of the posterior roots which pass through it, and numerous other true
nerve-fibres [vid. infra). 3. Much-developed, well-marked nerve-cells
are seated especially at the apex of the anterior horn, forming an inter-
nal and an external group (Fig. 112, m, v), but occurring also in the other
portions of the anterior, as well as, though in less number, in the poste-
rior horns, whilst they are never met with in the suhst. gelatinosa, nor
in the gray commissure. All these cells (Fig. 143) are 0"03-0*06 of a
line, in size, with nuclei measuring 0'005-0-008 of a line, are fusiform
or polygonal, frequently containing brown, pigmentary matter, and fur-
nished with from 2 to 9, or even more branched processes, which at
their origin are often 0-004-0-005 of a line thick. These processes
may be traced to a length of 0-1-0-24 of a line, and ultimately termi-
nate in fine fibrils, all of which, scarcely more than O'OOOi of a line thick,
are contained within the gray substance. Besides these large and, for
the most part, many-rayed cells, there are also found in the gray sub-
stance though more widely scattered among its nerve-fibres, very numer-
ous, smaller cells, which constitute a complete series between the large cells

Fig. 142. — Cells from the gray central nucleus of the cord in Man, magnified 350 diam.
* [The gray matter of the posterior horn. — DaC]

364

SPECIAL HISTOLOGY.

and those of the substantia c/elatinosa, and consequently require no fur-
ther description.

The nerve-fibres of the gray substance are excessively numerous, so
much so as to constitute in any case the half of its bulk, if not more, and
exhibit the same conditions as those of the medullary substance, except
that, on the average, they are not more than half as thick, or even less
(not more than 0-0008 of a line) ; fibres, however, also occur of the same

size as those in the white substance and in the entering roots of the
nerves, especially in the anterior horns, though more widely scattered,
and principally towards the anterior roots. The investigation of the
course of these nerve-fibres in the gray substance is one of the most
difficult tasks in microscopy. If we observe, above all, the roots of the
peripheral nerves (Figs. 141, 144), it is apparent : — 1. that the motor
filaments in them, after they have entered the sulcus lateralis anterior^
and the contiguous portions of the anterior and lateral columns, and
penetrated horizontally between the longitudinal fibres of the white sub-
stance, are continued further in the gray substance of the anterior
horns, principally in two directions. The fibres of one bundle, and
indeed of that which enters the most internally (Fig. 141, h), proceed
directly backwards and a little inwards, without forming any plexus, or

Fig. 143. — Large nevve-cells with processes from the anterior cornua of the spinal cord
in Man ; magnified 350 diameters.

THE NERVOUS SYSTEM. 365

subdividing to any considerable extent into subordinate fasciculi, to the
innermost portions of the anterior horns, skirting the anterior columns.
In this course they pass through tlic inner group of the many-rayed,
large nerve-cells, in perfectly compact bundles, however, and having no
connection whatever with the processes of the cells, as may be readily
perceived under a strong magnifying power, when the individual nerve-
fibres may be traced quite beyond these cells. Now, if these bundles
derived from the anterior roots are traced further it will be perceived,
in favorable sections, that they extend to the lateral parts of the anterior
commissure, continuing to run in the anterior horns, and, that ultimately,
forming more or less Avell-marked curves, they are continuous with its
fibres, and in fact are disposed in such a way, that the root-fibres of the
right side pass into the left anterior column, and those of the left side
into the right. Consequently there is established in the white commis-
sure a connection of the longitudinal fibres of the anterior columns and
of a part of the motor roots, together with a total decussation.

A large number of the fibres of the motor roots take no part in the
above-described decussation, and are wholly unconnected with the
anterior fasciculi, — these are the root-fibres which enter the anterior
horns the most externally. Forming, for the most part, smaller fasci-
culi, or even as separate fibres, and therefore, less easily observable,
they run in part directly backwards, and in part arch outwards, but
ultimately bend towards the anterior half of the lateral column, where
they pass between the outer groups of the large, many-rayed cells of
the anterior horns, and then enter the lateral column in a horizontal
direction. These transverse fibres now penetrate to various depths
(nearly half, or even more) into the lateral column, then curve uptvards,
and after running thus a short distance, appear as longitudinal fibres.
Consequently, to express the same thing in other words, a second por-
tion of the motor roots arises from the anterior half of the lateral column
of the same side, and quits the spinal cord ivithout previously undergo-
ing any decussation.

It is, moreover, worthy of remark, that most of the fibres, perhaps
all, which join the motor roots from the anterior and lateral columns,
undergo considerable changes in their diameter. Those of the anterior
column measure; as has been observed before, at their commencement,
on the average, 0-002-0-004: of a line, in the anterior commissure
scarcely more than 0-003, and in the gray substance hardly more than
0'002 of a line ; and the same is the case also with those of the lateral
columns ; which, however, even while still in the interior of the column,
where their direction is horizontal, measure scarcely more than 0-002
of a line. This diminution in size, however, is again succeeded by an
increase in thickness, which takes place, in part, within the gray sub-
stance, in part at the point where the radical bundles quit it, the amount

366 SPECIAL HISTOLOGY.

of which increase has been already stated in numbers ; so that, proceed-
ing from the peripheral nerves, we find them gradually diminishing in
Pi„ j4^ size from their entrance into the cord

ale- i/ e y until they reach the gray substance,

l^i-j ^, u.„ .i_-.-H*m. and again enlarging from the point

^ yf , - \ where they join the longitudinal ele-

^ \ ments of the white substance, but not

#i to such an extent as ever to attain

L,, ^ nearly their pristine diameter. Of

^/. M|f " divisions in the fibres of the anterior

/ ' ^v roots in the anterior horns, I have seen

\'\ / as little indication, as elsewhere in the

^ -i~4£i '^ ^ spinal cord.

ft _ The liobterior roots of the nerves, as

-^ gi ^ has been already noticed, penetrate,

4^^; ^ ^m\ «^n»^^ like the anterior, also horizontally, or

*" "' in a slightly ascending direction, from

the sulcus lateralis posterior, through the longitudinal fibres of the white
substance as far as the posterior horns. Here they divide into separate,
slenderer, or thicker fasciculi (from 0-01-0-02 of a line), (Figs. 141, s,
144, b), and continue, each bundle by itself, in a straight course, and
without any direct connection with nerve-cells, quite through the sub-
stantia gelatinosa into the substantia grisea. In this course they follow
two directions. One portion of them bends upwards, in a uniform curve,
or nearly at a right angle, proceeds in the most posterior part of the
substantia grisea, close in front of the substantia gelatinosa in a longi-
tudinal direction, and gradually joins chiefly the posterior column, but
in part also the posterior portions of the lateral column, being continued
further, as its longitudinal fibres (Figs. 141, r, 144, g). A second por-
tion of the sensitive roots (Figs. 141, t, 144), penetrates, always in a
fascicular form, between the above-mentioned longitudinal bundles fur-
ther forwards, losing itself in the posterior and in the lateral columns,
and also entering the gray commissures. In horizontal sections, the
former fibres are frequently very distinct, particularly those going off
to the posterior columns (Fig. 141, p, q). I have seen them most dis-
tinctly in the inferior extremity of the spinal cord, below the lumbar
enlargement, where they ran towards the conus medullaris, close up to

Fig. 144. — Vertical section through the cord, midway between the gray eornua and the
point of entrance of the roots of the nerves, magnified about 25 diameters : a, posterior
column with the sensitive roots, A, traversing it; b, substantia gelatinosa ; c, prolongations of
the posterior roots, which bend round in front of the substantia gelatinosa and run longitudi-
nally, in order there to join more particularly the posterior column; rf, basis of the posterior
eornua, with the ends of the horizontal portion of the sensitive roots apparent (owing to
their being cut across); e, anterior c-ornua with the large nerve-cells (the spots), and the also
horizontal and divided continuations of the motor roots ;/, anterior column traversed by the
motor roots, i.

THE NERVOUS SYSTEM. 367

the gi'ay contra! nucleus, and did not bend backwards until they reached
the posterior columns ; they were also Avell displayed in the lumbar en-
largement, between the substantia gelatinosa and the posterior commis-
sure. The horizontal radical fibres, also, which proceed to the lateral
columns, are often exceedingly numerous, although much less so, appa-
rently, than those which enter the posterior columns. The connection
of the gray commissures with a portion of the sensitive radical fibres,
is, as regards the posterior fibres, not difficult to be seen, these fibres,
in part, at least, running backwards along the posterior columns, and
being continued directly into the fasciculi of the substantia gelatinosa.
In the anterior gray commissure, I have also noticed, though not a direct
connection with the sensitive roots, still, fibres which, running horizon-
tally in a direction towards the summits of the posterior horns, entered
those processes. The commissural fibres are, besides, connected not
only with the sensitive roots, but also, and indeed quite evidently, with
the posterior columns, and less distinctly with the lateral ; from the
anterior portions of which, adjoining the base of the posterior horns,
arched fasciculi pass into the commissures and become intermixed with
the other commissural fibres (Fig. 141, o and I). These fibres probably
pass over to the opposite side, into the commissures connected with the
posterior roots ; in which case, like the anterior halves of the cord, a
decussation of fibres also takes place in the posterior commissure. In
accordance with what has been remarked, the sensitive roots derive their
fibres principally from the posterior and lateral columns (the posterior
halves) on their own side, and probably also through the gray commis-
sures from the same columns on the other side.

The fibres of the sensitive roots also decrease in size as they traverse
the gray substance of the posterior horns. In the roots themselves
they still measure about 0*008 of a line ; in the substantia gelatinosa,
never more than O-OOl, in the substantia grisea, 0-001-0-003 of a
line; in the gray commissures, not more than 0*0008-0"0012, in
the posterior and lateral columns, again, 0-0012-0-004 of a line; in
connection with which, however, it should be remarked, that, in this
situation, the increase of size in the fibres which enter these columns
horizontally, is not perceptible at their commencement, as is shown more
particularly in vertical sections, made in the direction from within to
■without, through the posterior cornua. The variation in diameter may
even be directly observed, in many fibres in this situation ; as, for
instance, at the entrance of the roots into the gelatinous substance.

Besides these fibres, belonging to the motory and sensitive roots, there
exist, in the gray substance, a considerable number of nerve-fibres not
referable to the roots, and which until more is known about them may
be termed special spinal-medullary fibres.

The filum terminale contains, so far as it is hollow, as a continuation

3G8 SPECIAL HISTOLOGY.

of the gray substance of the cord, a gray, soft substance, consisting
chiefly of round, nucleated, pale cells, like nerve-cells, and measuring
0005-0'006 of a line. Besides these there occur, in its upper part
among the cells, true dark-bordered nerve-fibres, of various, and for. the
most part small diameter, and also numerous, fine, pale fibres, the nature
of which is not clear to me ; that is to say, whether they are processes
of cells or belong to the finest nerve-fibres. Remak (" Observ.," p. 18)
supposes, that in the Mammalia the true nerve-fibres of the filum all
go ofi" in lateral branches of it, the existence of which were detected by
him.

In the investigation of the course of the fibres in the spinal cord,
chromic acid, or instead of it, chromate of potassa, affords the principal
aid. It is not easy to hit upon the proper proportion of acid, and so to
harden the cord, previously stripped of its dura mater, and cut across
with a sharp knife at the points selected, that very thin transverse sections
may be taken from it. If the solution be too much diluted, the sub-
stance of the cord remains soft in the interior and spoils, if too concen-
trated it becomes fragile and friable, and larger sections of it cannot be
obtained. I have unfortunately neglected to estimate precisely the
proper percentage of acid or salt in the solution; and can only say this
much, that one of a wine-yellow color acted the best. Objects thus
properly hardened may be cut at pleasure with a razor, or other very
sharp instrument, if due care be taken, particularly in the avoiding of
any sawing motion ; and sections suitable even for the highest magnify-
ing powers may be procured and examined, either with or without
pressure or reagents, under various degrees of enlargement. The gray
substance is scarcely altered by the chromic acid, except that its ele-
ments are more easily separated, and I have in hardly any other way
seen its nerve-cells, together with their processes, and the nerve-fibres,
more beautifully displayed. If it be desired to examine the former, the
gray substance is broken up in water, which now no longer produces
any change ; or, what is best, in the solution of chromic acid itself; but
if the examination of the latter be wished, it is by far the best to employ
diluted caustic soda or potassa, which renders all the nerve-cells pale.
To those who may consider the application of these reagents as too
powerful for such delicate organs as the spinal cord, I would remark :
1, that, as stated by Hannover, chromic acid alters the nerve- fibres,
especially of the gray substance, so little, that most of them do not even
become varicose ; and 2d, that soda, added to a preparation made with
chromic acid, does not act upon the fibres for a long time, and only so
far as to render them more transparent and their medullary contents
fluid. I have never, under any circumstances, seen more beautiful
nerve-tubes of the gray substance, than in preparations made with

THE NERVOUS SYSTEM. 369

chromic acid, and I think that of all known means this is the best for
their study. In employing pressure, however, great care is requisite.
I make use of a compressor iiun by Nachet, which allows extremely thin
covering-glass to be employed, and consequently the highest magnifyino-
powers ; if I wish to apply more considerable pressure for the study of the
coarser conditions, the common apparatus suffices, with which, however,
with a shorter focal distance of the microscope, only lower powers can
be employed. I have had entire transverse sections of the spinal cord
before me, in which it might be said, that no part was disturbed from its
relative position, and yet, which admitted of the application of a mag-
nifying power of 350 diam. I would, moreover, remark, that the most
favorable place in the cord for the first investigation, is the lumbar
enlargement. In this situation the cord is not so thick, but that entire
sections of it may be obtained, besides which the white substance, which
is only an impediment, is thin, and the roots and commissures large and
more readily traced.

AVhether the nerve-fibres in the cord divide, has not yet been fully
ascertained, yet I think that I saw such an appearance, on one occa-
sion, in a dark-bordered fibre, and on another in an isolated axis-cylin-
der. In any case such divisions cannot be frequent, otherwise I must
have noticed them more often, having examined innumerable nerve-fibres
and axis-cylinders, expressly with reference to this point. Anastomoses
between the processes of branched nerve-fibres, which Schroder van der
Kolk thinks he has seen, I must, from my experience so far, doubt, but
I am not able to deny their possible occurrence.

§ 113. Probable course of the Fibres in the Cord. — We have found
that the motor and sensitive roots do not terminate at the point where
they are implanted into the gray substance of the cord, as at first sight
appears to be the case, but that the greater proportion of them are curved
upwards, accompanying the longitudinal fibres of the white substance.
The important question now arises, viz. : to ascertain what becomes of
these fibres, whether, after running a shorter or Jonger distance, they
terminate in the cord, or whether they all ascend to the brain. It is
well known, that until recently, most observers have been of the latter
opinion, which was founded less upon direct observation than on the
ground of probability, until Volkmann, in his deservedly celebrated
article, " Physiology of the Nerves," shook it to its foundations, carry-
ing the greater number of physiologists with him. I also was among
these, until I had myself investigated the conditions, for there could be
no doubt that Volkmann's theo-'y connected, in the most harmonious
way, the anatomical facts and the results of physiology as at that time
exhibited. When I now, notwithstanding this, abandon Volkmann's

theory of the termination of the spinal nerves in the cord, I am induced

24

370

SPECIAL HISTOLOGY.

Tig. 145.

to do so by weighty reasons, and much regretting that I am unable to
maintain a view, which appeared to throw so much light upon many diffi-
cult parts of the physiology of the nerves, and to be in accordance with
so many other anatomical conditions (ganglia, invertebrate animals).

Volkmann, in his hypothesis of the origination of the fibres in the
cord, relies upon the circumstance (1. c, p. 482, et seq.), that the spinal
cord is not of a pyramidal form with the base above, as must have been
the case had all the fibres of the roots of the nerves ascended towards
the cerebrum, but that it rather presents a local increase of the nervous
substance at the points of origin of large nerves, which enlargement is
not confined to the gray substance, but equally involves the white. That
this is the case Volkmann shows from four transverse sections of the
spinal cord of the Horse, and from a comparison of the diameter of the
cervical cord of Crotalus horridus, with that of all the nerve-roots of
the same animal, which was found to be eleven times greater than the
former. He also supports his view by the consideration : 1, that the
enlargements of the cord are always regulated by the size of the nerves
of the extremities, being sometimes wanting and sometimes enormously
developed ; 2, that the cord, at the points of exit of the largest nerves,
instead of becoming suddenly thinner, is in most cases
enlarged ; and 3, that the origin of the spinal acces-
sory nerve in this case loses all that is remarkable in it.
Now, if the spinal cord in man be examined with refe-
rence to the above points, it will present, in almost all
of them, exactly the contrary of what Volkmann noticed
in animals. In the first place, the ivTiite substance con-
stantly increases in tJiicTcness from helotv upwards, and
the enlargements of the cord depend upon an increase of
the gray substance more than anything else. That this is
the case, is evident at a glance, when sections, such as are
represented, after nature, in Fig. 145, are compared with
each other, and it also admits of being estimated in
numbers {vid. " Mikroskop. Anatomic," II. 1, p. 431).

This fact being established, it remains to determine

the proportion borne by the white substance in the

superior cervical region to the peripheral nerves. For

this purpose I instituted Volkmann's measurements in

man, and in a male and female 'cody estimated all the roots of the spinal

nerves on the left side; I determined, from the ascertained diameters,

Fig. 145. — Five transverse sections through ^ human spinal cord, hardened by chromic
acid, to show the relative proportions of the gray and white substances, — of the natural size :
Jt, from the conus medullaris, the diameter of the cord being 3| lines ; J5, from the lumbar
enlargement, transverse diameter 4| lines, antero-postenor 4| lines; C, from the dorsal part
of the cord, 4:1 and 3f lines ; D, from the cervical enlargement, G| and 4| lines ; E, from
the superior cervical portion, level with the second nerve, 6| and 4| lines.

THE NERVOUS SYSTEM. 37l

the transverse sectional surfaces of all the nerves in square lines, and
compared with them the transverse sectional area, taken with the utmost
possible nicety, of the white substance of the spinal cord, at the level
of the second cervical vertebra.

It is quite true that there was now evident a very considerable diflfe-
rence against the spinal cord ; but when the very great attenuation of the
nerve-fibres of the roots, at their entrance and in their further course in
the cord, was brought into account, which was not done by Volkmann,
the matter was entirely altered, and it became clear that the cord in the
male subject contained more than sufficient fibres to furnish the peripheral
ones, and in the female nearly sufficient, particularly when it is consi-
dered, moreover, that in the entire enumeration, the numbers were stated
rather in favor of the roots of the nevves,{vid. the calculation in " Mikro-
skop. Anatom.," 11. 1, § 116).

It appears, therefore, scarcely to admit of doubt, that the notion of a
termination of the peripheral nerves in the cord, has no support in mea-
surements such as those which, following Volkmann, I have adduced ;
and that the latter, even when all due allowance is made for the uncer-
tainty always incidental to such an inquiry, on the contrary indicate, at
all events the probability/, that the spinal nerves ascend to the cerebrum.
They give no further information, however, and it depends upon other
facts, whether such a central origin should be admitted or not, because
it is even conceivable, that the peripheral nerves may end in the cord,
and that the longitudinal fibres in the cord have a wholly different source.
Since it is scarcely probable that the tracing of the nerve-fibres through
the entire cord will be effected either at present or perhaps at any time,
it is necessary to look round for other facts, which may possibly afi"ord
conclusive evidence on the subject ; and such facts do exist. In the first
place, let us consider the course of the roots of the nerves in the cord,
such as it has been described above. We found, that after they had all
come, more or less, into contact with the gray substance, the greater
number of them cpuld be directly traced into connection with the longi-
tudinal fibres of the anterior, lateral, and posterior columns. From this
fact, together with my measurements, the passage of the greater part of
the peripheral nerve-fibres into the cerebrum, will appear to many to be
proved ; but, not to overlook anything, it may be further remarked, that
the radical fibres, running longitudinally in the substance of the cord,
may terminate in it, or after running in it may again enter the gray
substance higher up. The former supposition is now, it must be con-
fessed, but little probable, because in the first place, no one has yet
seen the terminations of nerve-fibres in the white substance ; and in the
second, because anything of the sort, for other reasons, would be very
surprising, nerve-fibres being nowhere known to commence in the white
substance ; and with respect to the latter, any re-entry of the roots of

372 SPECIAL HISTOLOGY.

the nerves into the substance could not escape notice. Since the junction
of the radical fibres ^vith the anterior, posterior, and lateral columns,
can be so well and so directly observed, the relation in question would
necessarily be evident also ; and yet in the course of my perfectly unpre-
judiced observations, I have never seen anything of the kind. Nothing,
therefore, remains but to assume, that the great majority of the periphe-
ral nerves really have a cerebral origin. Whether they all originate in
the brain (where, we shall afterwards see) or in part, though, from my
observations, but to a small extent, from the cord, cannot be determined,
any more than the question can be decided, whether the white substance
of the cord, besides the fibres derived from the peripheral nerves, also
contains others passing from the brain to the cord.

§ 114. The medulla oblongata and pons Varolii heloxig to the most
complex parts of the central nervous system, containing white and gray
substance, intermixed in very various modes. The lohite substance is, in
part, a continuation of that of the cord, in part distinct from it, and is
disposed in the following manner : the anterior columns of the spinal
cord diverge from each other at the commencement of the medulla oblon-
gata, allowing the decussating fibres of the corjwra pyramidalia to
appear. As they proceed, a smaller division joins the i^yramids, form-
ing their outer part, whilst the principal portion surrounding the olivary
bodies, internally and externally, whence they are also termed the oli-
vary columns, passes laterally, and then, divided into two bundles,
proceeds above the second transverse layer of fibres, through the pons.
One of these divisions constitutes the fillet {laqueus), which continued
above the crura cerebelli ad cerebrum, enters the posterior corpora quad-
rigemina, joining, within them, the corresponding division of the opposite
side. The second division, or bundle, lies externally and inferiorly to
the crura cerebelli, and enters the tegmentum of the cerebral peduncle.
Besides this, the olivary columns, corresponding to the anterior columns
of the cord, also, as it seems, give off fibres to the pejiunculis cerebelli.
The lateral columns of the spinal cord divide, on reaching the medulla
oblongata, into three bundles ; one of which, ascending in a tolerably
straight direction, is continuous with the fasciculus lateralis of the resti-
form body, and with it enters for the most part into the peduncle of the
cerebellum, and in small part into the tegmentum ; a second division
penetrates forwards between the divergent anterior columns, decussates
in two or three fasciculi with that of the other side {decussatio pyrami-
dw72), constituting the principal bulk of the pyramids ; a third division,
lastly, appears between the posterior columns at the bottom of the
rhomboid fossa, or fourth ventricle, as the eminentia teres. These latter
are continued, on the floor of the fourth ventricle and applied to each
other, into the tegmentum of the cerebral peduncles, whilst the pyra-

THE NERVOUS SYSTEM.

373

mids, passing between the first and second transverse layers of fibres of
the po7is, are continued into the base of the cerebral peduncles. The
posterior columns of the cord, lastly, chiefly constitute the fasciculi gra-
ciles and cuneati, the latter of which, in great part, enter the -pedunculi
cerehelli, whilst the remainder, ^n^ the fasciculi graciles, situated exter-
nally to the eminentice teretes, may be traced into the tegmentum of the
crura cerebri. All these fasciculi consist, besides the gray substance,
of parallel nerve-fibres of the same dimensions as those of the cord, that
is to say, from 0-001-0-004 of a line, seldom more.

Besides this white substance, the pons Varolii and medulla oblongata,
omitting the roots of the nerves, present a system of mostly horizontal

'SB

fibres. This system consists : 1, of the well-known transverse, arcuate
fibres, external to the corpora pyramidalia and olivaria ; 2, of straight

Fig. 146. — Transverse section through the medulla oblongata in Man. P, pyramids; 0,
olivary bodies ; ii'J, fascicukis lateralis; F.c, fasciculi cuneati; F.g,fasc. graciles ; i/, root of
hypoglossal nerve; F, root of n. vagus; F.a,fissura anterior; F .p, fisstir a posterior in the floor
of the fourth ventricle, or rhomboid fossa; i?, raphe: a, longitudinal fibres of the raphe ; b,
central gray layer with transverse fibres; c, expansion of these fibres in the olivary column
and body; rf, accessory olivary nucleus; e, hypoglossal nucleus ; f, decussaxion of the hypo-
glossal nerve ; g-, nucleus of the vagus; hhh, larger nerve-cells in the restiform bodies; i,
medullary mass in the interior of the olivary body, belonging to the internal transverse
fibres ; k, arcuate fibres external to the olivary body ; /, transverse fibres external to the
pyramids; m, n, o, gray nuclei in the pyramids and olivary columns. — Magnified 15
diameters.

374 SPECIAL HISTOLOGY.

fibres, which extend from before backwards, in the middle, through the
medulla oblorigata, contributing to the formation of the so-termed raphe
(Stilling) ; 3, and lastly, of very numerous fibres proceeding from this
raplie into the lateral halves of the medulla, following a more or less
curved direction. These latter, the interiial transverse fibres, commence
behind the pyramids, and the anterior of them as a large mass, very
minutely broken up by fine flattened fasciculi of the pyramidal and
olivary columns, penetrate from within into the corpus dentatum olivce,
the white substance of which is constituted by them ; they then expand
in a brush-like form, and are continued through the gray substance of
the corpus dentatum, ultimately turning backwards towards the fasciculus
cuneatus [corpus restiforme] and lateralis. In this course, the fibres
describe larger or smaller curves. The latter is the case with those
which come out from the posterior part of the olivary nucleus [^corpus
dentatuni\, and which go almost directly backwards and outwards
through the accessory olivary nucleus (Stilling), and the gray substance,
containing large cells, situated on its exterior; the former condition
obtains in the anterior fibres, which spread out in a radiating manner,
passing at first forwards between the pyramids and olivary nucleus, and
afterwards backwards in a sharp curve, superficially round the latter,
into the lateral fasciculi. A second division of the internal transverse
fibres goes behind the olivary nucleus with which it has no connection,
directly from the raphe, through the posterior part of the olivary
columns and the enmientice teretes, outwards and backwards, also into
the restiform body. All these fibres, and most of them obviously so,
are associated together, and appear to me to be continued from the
restiform bodies and the peduncles of the cerebellum, into the anterior
divisions of the medulla oblongata. With respect, however, to their
more intimate relations, concerning which Stilling's work and my
" Microscopical Anatomy" may be consulted, little is as yet known.

The gray substance, in the medulla oblongata, is collected into lai^ger
masses, chiefly in three situations, viz., in the olivary and restiform
bodies, and on the floor of the rhomboid fossa (fourth ventricle) : 1, the
gray substance of the olivary bodies forms, as is well known, a folded
lamella, constituting a capsule closed on all sides except the inner,
which, although it occupies the situation of the anterior horns of the
spinal cord, Avhich are continued nearly to its inferior border, still has
no direct connection with them ; appearing, also, to be otherwise isola-
ted from all other gray substance. AVithin it, besides the very numer-
ous nerve-fibres of the transverse fibre-system, which traverse it for the
most part in straight lines, there occur in great numbers smaller nerve-
cells, measuring 0-008-0-012 of a line in diameter, and of a rounded
form, with 3-5 branching processes, and containing in the interior yel-
lowish granules, to which the color of the olivary bodies is due. The

THE NERVOUS SYSTEM. 375

closest observation has failed to afford me any indication of a connection
between these cells and the fibres which run among them. On a level
with the two upper thirds of the olivary body, is placed, behind the
nucleus and wholly isolated from it, the body termed by Stilling the
accessory olivary nucleus, in the form of a flattened, yellowish band, of
exactly the same structure as the gray substance of the olivary body,
and also traversed by horizontal nerve-fibres, and in fact by fibres which
have for the most part already passed through the olivary body ; 2, in
the restiform bodies, the gray substance {corpus s. nucleus cinereus)
assumes the form of an ill-defined, elongated mass intermixed with very
numerous nerve-fibres, and which occupies mainly the fasciculus late-
ralis, but also extends into the fasciculi cuneatus and gracilis. This
structure may be described as a continuation of the posterior horns of
the spinal cord, even presenting, as Stilling correctly states, an indi-
cation of the substantia gelatinosa of those processes, of which it may
moreover be observed, that it is very remarkably developed in the upper-
most portions of the cord, as far as the commencement of the decussa-
tion of the pyramids, and has a position entirely lateral. The elements
of the gray substance of the restiform bodies are, besides, numerous
finer fibres, which appear to pass chiefly into the horizontal, internal
fibre-system, and many, rather pale, but in part brownish nerve-cells
with processes, pretty regularly disposed, and most of them of the same
size as those of the olivary bodies ; 3, the gray substance on i\\e floor of
the fourth ventricle, is the continuation of the gray nucleus of the spinal
cord, and forms a tolerably thick layer, extending from the calamus
scriptorius as far as the aqueductus Sylvii. It contains throughout,
numerous nerve-fibres, in part of very considerable diameter, up to
0-006, or even 0-008 of a line, in part of the finer and finest kinds, and
besides these, nothing but caudate nerve-cells of all dimensions from
0-006, up to 0-03 of a line, and more. The largest of these are con-
tained in the ala cinerea at the posterior extremity of the fourth ventri-
cle, and in the subst. ferruginea s. locus cinereus (Fig. 147), in which
latter situation, the cells also present well-marked pigmentary matter,
and very numerous, delicately branched processes. The small multi-
nuclear cells, which in the gray nucleus of the cord occur in the form of
a compact structure, are here entirely wanting, not being found beyond
the decussatio pyramidum. Besides these three masses of gray sub-
stance, which can in part be referred to that of the spinal cord, there
are found, in the medulla oblongata, some small collections of it, as in
the pyramids near the olivary bodies, and in the olivary columns, exter-
nal to the accessory nucleus, in all of which, as has been already stated
by Stilling, are also to be seen in part larger cells, all caudate (in the
latter situation measuring as much as 0-025 of a line), and finer nerve-
tubes. One part of the gray substance just described, that namely of

376

SPECIAL HISTOLOGY.

the anterior half of the fourth ventricle, belongs properly to the pons
Varolii. It also contains, in its interior, besides the just described

Fig. 147.

elements, above the transverse fibre-layer, both in the middle as well as
more laterally, many accumulations of gray substance, with larger and
smaller (as much as 0*02 of a line and more) nerve-cells, all caudate,
which are so irregularly imbedded among the longitudinal and transverse
fibres, as to require no detailed description, and are connected on the
one side with gray nuclei of the medulla oblongata, and on the other
with the substantia nigra of the crura cerebri.

The relations of the ten pairs of nerves which arise from the medulla
oblongata, the pons, and the crura, constitute a very difficult question.
But few inquirers have endeavored to solve it by other means than those
usually employed, that is to say, by the tracing of the fibres, with the
aid of the scalpel, which here goes no way at all. Among the excep-
tions are E, Weber (Art. " Muscular Motion," in Wagner's " Handw. d.
Phys." III. 2, pp. 20-22), who made his examination in preparations,
hardened by carbonate of potassa ; and Stilling, who pursued his by the
microscopical examination of sections, similarly hardened by means of
alcohol. My own results, obtained from preparations in chromic acid,
which had been for the most part made transparent by soda, agree in
almost every point with those of Stilling, which, at all events, among
all observations on the subject, have gone most deeply into the matter.

Fig. 147. — Nerve-cells of the substantia ferrvgima in the floor of the fourth ventricle or
rhomboid fossa, of Man ; magnified 350 diameters.

THE NEKVOUS SYSTEM. 377

The nerves in question arise, without exception, not from the columns \
or fibrous substance, out of which they proceed, but all penetrate more
or less deeply into the central parts, and all probably become connected,
some not till they have decussated like the trocldeares, with definite
parts of the gray substance, which Stilling not inappropriately terras
nerve nuclei [accessory nucleus, for instance). It is the floor of the
fourth ventricle, and of the aqueduct of Sylvius, which are more par-
ticularly concerned in this respect, since all the nerves above named, at
least in part, extend to them. The more minute consideration of these
relations maybe seen in Stilling's Work, and in " Mikroskop. Anatomie,"
11. 1, pp. 458-462.

Although a favorable judgment cannot be given upon Stilling and
Wallach's work on the spinal cord, I am still very far from disposed to
look down upon Stilling's anatomical writings in general, as would seem
to have been the fashion for some time past. I am much rather of
opinion, in which R. Wagner also coincides, that we have great reason
to thank this author for his works on the medulla oblongata and pons
Varolii ; for although there are some things in them which cannot be
maintained, and sufficient attention is not paid to the elementary con-
stituents, still it cannot be denied that they contain a mass of important
facts. I have tested, if not all, still the most important of Stilling's
statements, and have found them almost all fully confirmed, and am,
therefore, glad to take this opportunity of naming him, as the observer
to whom we are indebted for the first accurate investigation of the
course of the fibres in the central organs. I would also here, add : 1,
that in further investigations of this kind, chromic acid, or chromate
of potassa, is to be preferred to alcohol, particularly also when caustic
soda is cautiously employed for the tracing of the course of the nerve-
fibres in the gray substance thus rendered transparent ; and, 2, that in
conjunction with lower magnifying powers, the most powerful should be
employed, and the relations of the elementary constituents should also
be otherwise accurately investigated.

The question as to the origin of the nerves in the medulla oblongata, ~]
presents itself as one of the most difficult nature. Most anatomists
have hitherto been content to trace the roots of the nerves as far as one
or the other column ; but this is not sufficient. All the nerves enter at
least once, or even several times, into gray substance, in which, and no-
where else, are their origins to be sought for. Now, it must be con-
fessed, that through Stilling's great pains, the fruits of which I can, as
it may be said, fully confirm — all the ten pairs of nerves at present
under consideration have been traced in their roots, as far as perfectly
definite points of the gray substance ; but now comes for the first time
the further question : do they commence in these situations, or do they

378 SPECIAL HISTOLOGY.

proceed beyond them ? As true origins in the brain have never yet
been seen with certainty by any one, there remains nothing but physio-
logical analogies and reasons. As regards the former, we see in all the
spinal nerves, that they first penetrate transversely as far as the gray
substance, and then, only passing througli this, join the white columns,
and we may thence suppose that the cerebral nerves, which, in general,
so closely resemble them, are in the same condition, and the more so,
because these also at first penetrate transversely into the interior of the
medulla, and the gray substance, with which they come in contact,
corresponds with that of the cord. To this may be added also, that if
we make the ten last cerebral nerves terminate in the gray substance,
into which they may so readily be traced, the decussated influence of
the parts above, upon them, which appears to be established by patho-
logical phenomena, cannot be explained in the case of any one of them
except the trocldearis, which decussates before it reaches its gray sub-
stance. Now, in the accessorius and hypoglossus it is actually possible
to see that the fibres come out from the gray substance, reached by
them in the first instance, and afterwards decussate ; and the same
thing is also at least probable in the oculo-motorius ; so that I think it
may be, that all the nerves now in question undergo decussation, and
do not terminate in the so-termed nuclei of Stilling. Further investiga-
tion will have to show whether this [decussation] takes place in the
floor of the fourth ventricle, as would appear to be the case ; whether
all the fibres of these nerves take part in it ; and where the fibres pro-
ceed to after decussation. With respect to the latter, it may be sup-
posed from analogy with the spinal nerves, that the true origin of the
cerebral nerves is probably not in the medulla oblongata, but in the
corpora striata and optic thalanii. Of that portion of the jjortio viajor
n. trigemini, which is continued into the restiform body, this may espe-
cially be remarked, that it certainly does not originate in that part, but
winds round it to somewhere above, as is the case also with the n. acces-
sorius.

However, in stating, in accordance with what has been said, that I
do not consider it directly probable, that the sensitive and motor cere-
bral nerves originate in the medulla oblongata and pons, it is by no means
intended to imply that these parts may not, as central organs, exert
some influence upon them and the more deeply placed nerves. If the
medulla oblongata preside over the respiratory movements, if it and
the pons be the agents of multiplied reflex motions, this may be the
case, without its following that all the nerves called into action should
terminate in them, and simply for the reason that the gray substance,
so abundantly contained in them, influences the nerves which traverse
it, exactly as must be supposed to be the case in the spinal cord.

THE NERVOUS SYSTEM. 379

§ 115. The cercbeUum, with respect to the distribution of the ele-
mentary tissues, exhibits tolerably simple conditions, gray substance
occurring only on the surface of the convolutions, in the nucleus den-
tatus, and in the roof of the fourth ventricle ; all the remainder con-
sists of white substance. The latter is wholly constituted of parallel,
probably unbranched, dark-bordered nerve-fibres, possessing all the
characters of central fibres (softness, proneness to become varicose, easy
isolation of the axis-cylinder, &c.), are essentially alike in all situations,
as far as their condition can be observed, and present a diameter of
0'0012-0-004: of a line in the extremes, and of 0.002 of a line in the
mean. The grai/ substance occurs, in the first place, very scantily in
the roof of the fourth ventricle above the velum medullare mferius, in
the form of brown nerve-cells, measuring 0"02-0'03 of a line, scattered
in the white substance, and recognizable by a sharp eye without further
aid (the substantia ferruginea superior) ; and, secondly, in the nucleus
dentatus, the grayish-red lamella of which contains a considerable
number of yellowish pigment nerve-cells of a medium size (0-008—
0*016 of a line) with four or five processes, and which have no direct
connection with numerous nerve-fibres proceeding from the nucleus
dentatus into the medullary substance of the hemispheres, which pass
through among them.

The relations of the g rat/ substance on the surface of the convolutions
of the cerebellum are more complex [vide "Mikr. Anat.," PI. IV. fig. 4).
It consists everywhere, as is well known, of a layer, internally of a
rusty color, externally gray, which, except in the fissures, where the
internal layer is most usually thicker, presents pretty nearly the same,
but not everywhere an equal thickness.

The interna] ferruginous lager contains nerve-fibres and large masses
of free nuclei. The former arise, without exception, from the white
substance, and run, in general, parallel to each other, although on a
transverse section of any convolution slightly diverging in a penicillar
manner, directly into the ferrugineous layer. Within this layer they
also run from within to without as far as the gray layer, but are broken
up into numerous, for the most part, fine fasciculi, which are much inter-
laced, so that the whole ferrugineous layer is penetrated by a close but
delicate network of nerve-fibres, which recalls in appearance the ter-
minal plexuses in peripheral parts, as for instance, in the n. acusticus,
in the follicles of the vibrissce, &c. In the meshes formed by these
nerve-fibres lie a vast number of opaque, round corpuscles, measuring
0-002-0-004, in the mean 0-003 of a line, which are nothing else than
free nuclei, and which frequently also exhibit a distinct nucleolus, and
not unfrequently other granules.

In their passage through the ferrugineous layer, the nerve-fibres of
the white substance become gradually attenuated, most of them to a

880

SPECIAL HISTOLOGY.

diameter of 0-0012 of a line, and in this state enter the external gray
layer. This layer, although to outward appearance everywhere per-
fectly homogeneous, consists of two not well-defined laminjie, the inner
of which contains nerve-fibres and very well-marked, large nerve-cells,
■whilst the outer presents nothing but a finely-granular, pale, light-yel-
lowish substance, which is distributed generally throughout this gray
layer, and contains no nerve-cells. The gra7iular substance agrees
chemically, morphologically, and physically in all respects with the
already-described contents of the nerve-cell ; it is tenacious, elastic,
rendered more opaque by acetic acid, and more transparent in caustic
soda, in which it is, for the most part, dissolved, and exists in the purest
form in the outer half of the gray layer, that is to say, next to the pia
mater. The synall nerve-cells, speaking generally'', are very few in
number and indistinct. They occur scattered throughout the gray layer,
having a diameter of 0'004-0'008 of a line, more frequent towards the
ferrugineous layer than more externally, and when successfully prepared,
particularly by means of chromic acid, most of them exhibit delicate
processes, which, however, can never be traced to any distance, and are
frequently torn off close to the cells. Besides these cells, there also
occur here and there, but on the whole rarely, nuclei of 0-002-0-0048

Fig. 1-lS.

of a line, which, to all appearance, are free, as they are met with even
in the most carefully -made preparations. Entirely different from these
smaller elements, and very peculiar, are the large cells of the gray layer
(Fig. 148) discovered by Purkinje. These cells, measuring 0-016-0-03
of a line, and of a round pyriform or oval figure, with finely-granular,
colorless contents, occur only in the innermost portions of the gray,

Fig. 148. — Large cells of the gray layer of the cortical substance of the human cere-
bellum, magnified 350 diameters.

THE NERVOUS SYSTEM. 381

close to the ferrngineous layer, and tliej are, not unfrequently, at least
some of them, partly imbedded in its nuclei, in single or multiple layers,
and presenting 2-3, rarely 1-4, long and much branched processes,
directed particularly towards the outer surface of the convolutions, Avhich
are, almost without exception, at all events the strongest of them, given
off from the sides of the cells which look from the ferrngineous layer.
At their origin these processes are even 0-007, or as much as 0*008 of
a line thick, and extremely finely granular or very delicately striped.
As they proceed they become more homogeneous, and at the same time
divide into very numerous and extremely slender branches, so that at
last, from each process a large bundle of very fine filaments, having a
diameter, in the finest, of scarcely 0-0002 of a line, is produced, A
portion of these fibrils penetrate more horizontally into the gray layer,
although most of them stretch directly outwards, and appear to extend
nearly to the outer surface of the gray layer. That they extend very
far is certain, for in preparations made with chromic acid, I have iso-
lated some measuring 0-15-0-2 of a line, which were still not the finest ;
and in successful perpendicular sections through the cortical layers of
the convolutions, their principal branches appear as parallel, slightly
undulating fibres in close contiguity, extending through more than two-
thirds, or even three-fourths, of the gray layer, to which they give a
peculiar striated aspect. Whilst the principal prolongations of the pro-
cesses are, in this way, continued through the gray layer, they give off
their branches at acute or right angles, whence not unfrequently a
second striation is produced, crossing the one just described at a greater
or less angle.

In the innermost portion of the gray layer, among the large cells,
there moreover exists some nerve-jihres ', but which, owing to their deli-
cacy and the ease with which they are destroyed, it is very difiicult to
trace. Quitting the ferrugineous layer, and forming a continuous plexus,
they are distributed in the inner third of the gray lamina among the
large cells and their processes ; there mode of termination has escaped
my observation, the result of Avhich amounts only to this : 1, that they
become finer and paler, decreasing from their original thickness of
0-0012, ultimately to one of 0-OOOG and 0-0004 of a line, their dark
outlines also being replaced by a paler contour ; 2, that they certainly
do not form terminal loops, such as Valentin and Hyrtl, who have pro-
bably mistaken a fine plexus for such, think they have noticed ; but be-
coming isolated, and running in a more straight direction, and almost
as pale as the processes of the nerve-cells at the border of the inner
third of the gray lamina, are lost towards the middle of it.

The crura cerehelli are composed of nothing but parallel nerve-fibres,
•without any admixture of gray substance, corresponding with those of

382 SPECIAL HISTOLOGY.

the medullary substance of the cerebellum itself, as a continuation of
•which they are to be regarded.

' § 116. Ganglia of tlie Cerebrum. — The three pairs of cerebral gan-
glia, the corpora quadrigemina, optic tJialami, and corpora striata, all con-
sist of bulky collections of gray substance, and of nerve-fibres ; the former
of which are in part quite isolated [corp)us striatum), in part mutually con-
nected, and with more deeply lying portions of gray substance [thalami
optici, Corp. guadrigemina) ; the latter connect the ganglia, on the one
hand Avith the cerebellum and medulla oblongata, and on the other with
the hemispheres of the cerebrum.

The corpus striatum contains two large gray nuclei, the nucleus
caudatus anteriorly and superiorly, and the n. lenticularis posteriorly
and inferiorly, which are, however, connected in front, constituting a
single mass ; and besides these, the slender n. tceniceformis, with the
amygdalm external to the lenticular nucleus, and is in connection prin-
cipally with the basis of the cerebral peduncle or continuation of the
pyramid which expands in it, forming numerous white fasciculi. The
gray substance presents, as almost universally, nerve-cells and fine nerve-
fibres. The former, which measure from 0-006-0-018 of a line, are, in
part, colorless, and in part, contain pigment, as, especially, in the cau-
date nucleus and third segment of the lenticular nucleus ; they are fur-
nished with from two to five processes, and occur in greater numbers
according to the depth of color of the gray substance.

The nerve-fibres may be referred for the most part to those of the
basis of the crura cerebri. They present the form of dark-bordered
tubes from 0-0012-0-005, most of them from 0-002-0-004 of a line
in size, which, running parallel and close together in a straight direc-
tion, enter the first division of the lenticular nucleus, and the most
anterior, thickest portion of the caudate nucleus. When traced further
in the lenticular nucleus, it will be seen that they form larger and
smaller fasciculi, decreasing somewhat in size (most of them measuring
from 0-0012-0'003 of a line) and that, passing straight through the
more scanty gray substance of the first divisions of the lenticular
nucleus, they are all ultimately lost, spreading out in a penicillar form in
its outermost and largest division. That is to say, white fasciculi mea-
suring from 0-04-014 of a line, with fibres of 0-0012-0-002 of a line,
enter this division of the nucleus from the second ; and these fasciculi
in close contiguity, slightly diverging and subdividing into smaller bun-
dles, are continued further in a direction towards the outer border of
the lenticular nucleus, before reaching which they disappear to the
naked eye. If traced microscopically in preparations made with
chromic acid, it is apparent, that the fasciculi proceed nearly to the
outermost part of the lenticular nucleus, though gradually broken up

THE NERVOUS SYSTEM. 383

into smaller bundles and separate fibres, and most intricately interlaced
■with each other. That these fibres terminate here, and do not i^roceed
any further into the medullary substance of the hemispheres, may be
considered as made out, not the faintest indication of any further con-
tinuation being afforded, which, if it existed, could not escape being
seen : on the other hand it is doubtful how they terminate here. All
I have to state on the point is this : that the fibres of the nerve-fasciculi,
entering the third division of the lenticular nucleus, as may be directly
observed in a very great many instances, gradually become so much
attenuated, as ultimately to measure not more than 0-0008, 0*0006, or
even hardly 0*0004 of a line, and present an almost entirely pale aspect,
so that they can scarcely any longer be distinguished from the finer
processes of the nerve-cells ; with which in fact, unless everything is
deceptive, they most probably are actually connected. All the fibres,
also, which enter the caudate nucleus, present exactly the same condi-
tions ; some of these enter the nucleus directly from the basis of the
cerebral peduncle, others, which appear in its thinner portion, are
manifestly derived from the lenticular nucleus, the first two divisions of
which they traverse in the first instance ; in this case, also, there is no
transition of the fibres into the medullary substance of the hemispheres,
but a separation of the fasciculi into a plexus of the finest, almost non-
medullated fibres takes place, and probably a connection between them
and the cells.

Besides the above described, in any case very numerous, nerve-fibres
derived from the cerebral peduncles and terminating in the corpora
striata, the nuclei of those bodies contain a considerable number of
other fibres, whose origin it is, in part, difiicult, and, in part, impossi-
ble to assign. I think I can trace one set of these fibres to their
source. In the most external part of the large nucleus of the corpus
striatum, we find, on making various sections, a considerable number of
moderately strong fasciculi, though not visible to the naked eye, which
in their relative thickness and the diameter of their tubes (0-0012-0-002
of a line) differ from the fibres derived from the crus cerebri, which in
this situation are reduced to the most extreme attenuation and dispersed
in a plexiform manner. It is easily seen that all these fasciculi proceed
from the medullary substance of the hemispheres ; and, as it appears,
after they have run a certain distance parallel with the surface on the
border of the nucleus of the corpus striatum, that they enter it. Many
of these fibres are continued directly from the medullary substance
into the ganglia, and, in this way, decussate, at right angles, with the
former fibres. Assembled in fasciculi, these fibres penetrate more or
less deeply into the gray substance of the corpus striatum, and of the
third division of the lenticular nucleus ; and these terminate, as I think
I have observed, without any considerable expansion, the formation of

384 SPECIAL HISTOLOGY.

a plexus, or undergoing any farther decrease in size, their fibres form-
ing loops with closely approximated sides.

Although, speaking relatively, it is not difficult to make out the struc-
ture of the corpus striatum, at all events, in its principal features, it is
quite otherwise with the optic tludami and corpora quadrigemina, chiefly
because the nerve-fibres in these situations are not so much assembled
into fasciculi, but are more isolated and most intimately intermixed with
the gray substance, on which account they cannot be traced to any
great distance. The examination of the gray substance itself, however,
is perfectly easy even in these bodies, and its elements — the nerve-cells —
present nothing peculiar, except that, in the optic thalami, they are for
the most part more deeply colored, whilst those in the corpora quadrige-
mina are paler. With respect to the nerve-fibres, it is quite certain
that the superior portion of the crura cerebri, that is to say, the crura
cerehelli ad corpora quadrigemina, the continuations of the olivary
columns, portions of the corpora restiformia, and the eminentice teretes,
pass into the ganglia now under consideration, although I have not as
yet succeeded in eliciting anything determinate as to the course they
take. But I think it may be stated, that the fibrous masses above
named, in great part at least, are not continued into the medullary sub-
stance of the hemispheres, because, on the one hand, most of their fibres
decrease from the original diameter of 0'0012-0'004 of a line down to
the smallest, or less than O'OOl of a line ; and on the other, because no
such passage of the fibres can be perceived on that side of the optic
thalamus, which looks towards the medullary substance of the hemi-
spheres. The superficial white investment, however, of the ganglia in
question, must be excepted, which in any case may effect a relation
between them and the hemispheres, as its fibres, measuring 0-001-0'003
of a line, or even more, disposed in fasciculi, and crossing each other
horizontally in various directions, do not appear to terminate in it.
Neither is the relation of the optic thalami to the corpora quadrigemina,
and that of the foriiix to the latter, by any means clear, so that it is
pleasing, at all events, to find that another important question admits of
a more satisfactory solution. When the external portion of the optic
thalamus is examined, it will be found that it adjoins a considerable mass of
white substance, which at first sight appears to be a continuation of the
basis of the cerebral peduncles passing below and external to the optic
thalamus, between the lenticular and caudate nuclei of the corpus stria-
tum, to enter directly into the medullary substance of the hemispheres.
Closer observation renders it obvious, that this white substance, as has
been said before, in part enters the corpus striatum, particularly the
lenticular nucleus, and in part radiates from without inwards, from the
hemisphere into the optic thalamus. That is to say, very numerous
white fasciculi, visible even to the naked eye, coming from the hemi-

THE NERVOUS SYSTEM. 385

sphere tliroughout the entire height of the thalamus, enter the latter,
run towards the superior surface to the superior and internal border,
and the pulvinar, being ultimately lost exactly in the same way as are
the fibres continued from the cr^ts cerebri into the corpus striatum; that
is, these fasciculi, the elementary fibres of which originally measure
0'0012-0-0025 of a line, ultimately subdivide into extremely close plex-
uses composed of fibres of the most extreme fineness, 0"0004-0'0008 of
a line, the terminations of which cannot be traced.'

I will just notice the constitution of some structures connected with
the above-described ganglia. The substantia nigra of the crus cerebri
presents pigment-cells precisely similar to those of the substantia fer-
ruginea, except that they are for the most part rather smaller, and
have fewer processes, surrounded with nerve-fibres of the finest, and
also of the stronger kind. The commissura mollis contains smaller cells,
with 1, 2, 3, and more processes, and light-colored pigmentary contents;
and besides these, very many, plexiform, vertical, and horizontal, fine
fibres of 0-0012-0-OOlG of a line, with some still finer, less than 0-001,
and a few stronger measuring as much as 0'004 of a line. Tlh.Q pineal
gland exhibits pale, rounded cells, without any processes, and scattered
nerve-fibres of 0-001-0-002 of a line, and also, generally, a considerable
quantity of sabulous matter (brain-sand) {vid. § 118). Its peduncles,
their anterior prolongations, and the commissura posterior, contain fibres
measuring 0-001-0-003 of a line, and are composed in part also of the
finest fibres. The floor of the third ventricle presents, immediately
beneath and behind the anterior commissure, extremely large, and
smaller, colorless cells, with from one to four, occasionally very thick
processes. These are lodged in great number in a close plexus of fine
fibres of 0-0004-0-0012 of a line; and cells, in other respects exactly
similar, though not quite of the same size, also exist in the corpus mam-
millare, likewise intermixed Avith very numerous fibres of the finest sort;
there are other still smaller cells of 0-008-0-012 of a line, for the most
part with only two processes, in the tuber cinereum. The hypophysis
cerebri contains, in its anterior, reddish lobe, no nervous elements ; but
rather, according to Ecker (art. "Blood-vascular Glands," in Wagner,
" Handw. d. Physiol."), the elementary tissues of blood-vascular glands ;
that is to say, a vascular stroma of connective tissue, in the interstices
of which, lie vesicles (cells?) measuring 0-030-0'090'"'", containing
sometimes only nuclei, and a fine granular substance, sometimes distinct
cells, in older persons also colloid-like masses. The posterior, smaller
lobe consists of a fine granular substance, with nuclei and bloodvessels,
and also contains fine, varicose nerve-fibres, which, like the vessels,
descend from the infundibulum.

§ 117. Uemispheres of the Cerebrum. — The white substance of the

25

386 SPECIAL HISTOLOGY.

hemispheres of the brain consists entirely of nerve-fibres, of 0-00012-
0"003, on the average 0'002 of a h'ne in size, without any admixture
of gray substance. These fibres, of whose special course, we, as yet,
know extremely little, never form plexiform interlacements or fasci-
culi, but all run in parallel, and most generally, straight lines, and
undoubtedly proceed from the corpus callosum and ganglia of the cere-
brum as far as the superficial gray substance, whilst it must remain
undetermined whetlrer, in their course, they divide or not. But besides
these fibres, omitting also the commissura anterior, i\iQ fornix, and the
origin of the optic nerves, the hemispheres contain others crossing the
former at right angles. I have found these fibres, in the first place, on
the outer side of the corjnis striatum, in which situation they are to be
referred, in part, to the fibres which enter the corpus striatum from the
hemispheres and terminate in it ; perhaps, also, in part, to the expan-
sion of the corpus callosum in the inferior lobes ; and secondly, in the
most superficial layer of the white substance, near the gray cortical sub-
stance, where they occur in not inconsiderable numbers, and running, in
part, obliquely ; but of their origin nothing satisfactory could be ascer-
tained. Whether there are still other, and what traces of fibres, the
future must show.

The more intimate structure of the gray substance of the convolutions
is tolerably manifest {vid. "Mikroskop. Anatomic," PI. IV. fig. 2). It
is most conveniently divided into three layers, an external, ivhite ; a
middle, pure gray ; and an internal, yellowish red. The latter, in thick-
ness almost equal to the other two, usually presents, on its outermost
border, a clear, frequently white streak, and occasionally, more inter-
nally, a secoiid, thinner and less white layer, so that there are in fact
four or even six successive laminae ; 1, a yellowish-red layer (inner part) ;
2, the first v/hite streak ; 3, yellowish-red layer (outer part) ; 4, second
white streak ; 5, the gray layer ; 6, superficial white layer. The gray
substance contains, in its whole thickness, both nerve-cells and nerve-
fibres ; and besides these, much granular matrix-substance, exactly like
that of the cerebellum. The nerve-cells are not easily investigated,
except in preparations in chromic acid, and in all the three layers they
agree in this respect, that by far the greater number of them are fur-
nished with from one to six processes, which give off" numerous branches,
and ultimately form extremely fine, pale fibrils of about 0-000-4 of a line
in diameter, differing, however, in respect of size, number, &c. In the
superficial white layer the cells are few, small (0-004-0-008 of a line),
with one or two processes, and scattered in an abundant, finely granular
matrix. The middle or pure gray layer, most abounds in cells, which
in it, are closely aggregated also in a granular matrix. Their size
varies very considerably, some being very small (0-003-0-005 of a line),
frequently appearing as little more than nuclei, whilst there are many

THE NERVOUS SYSTEM.

387

others of larger dimensions, up to 0-OlG and 0*02 of a line (Fig. 149).
Their figure is pyriform or fusiform, tri- or multangular, also perhaps
more rounded, by far the greater number having from one to six pro-
cesses, usually three, four, or five ; and where this is not the case, they
may have been torn off in the preparation, since stumps of them may
be very readily noticed in the cells, which are altogether very delicate.
In the innermost yelloivish-red layer, lastly, the cells are again rather
more scanty, though still extremely abundant, otherwise presenting the
same characters as those in the gray substance, having sometimes pale,
sometimes pigmentary contents ; the latter in the inner layers more
particularly, and in old persons.

The nerve-fibres of the gray substance of the convolutions, arise, as it
is easy to demonstrate, from the medullary substance of the hemispheres,

Fiff. 149.

and penetrate, bundle after bundle, directly, and all parallel, into the
yellowish-red layer. Arrived here, many fibres separate from the rest,
and penetrate the yellowish-red layer in all directions, but more espe-
cially parallel to the surface, and consequently crossing the main fasci-
culi. "When these horizontal fibres are more closely aggregated, they
produce the above-described whiter or clearer streaks in this layer, the
outer of which streaks is situated exactly at the point, where the fasciculi
which enter the gray substance, are lost. In fact, as these proceed more
outwardly, they constantly decrease in size, owing to their giving off lateral

Fig. 140. — From the internal portion.s of the gray layer of the convokitions of the human
cerebrum, magnified 300 diameters. Nerve-cells: a, larger; b, smaller ; c, nerve-libres with
axis-cylinder.

388

SPECIAL HISTOLOGY.

Fiff. 150.

fibres, and to the attenuation and separation of their elements, until, when
they have reached the gray layer, they become lost to sight, although if
more closely traced they may still be perceived as intricately interlaced
fibrils of the utmost fineness, and with scarcely any appearance of dark
contours, only that there are a certain, though smaller number of fibres,
which, upon reaching the gray layer, do not lose their breadth and
dark contours, but are continued in a straight or oblique course through
it, extending horizontally to a further distance, in the outer white
layer. In this layer, consequently, we find a considerable number of
finer, and of the very finest fibres (Fig. 150), crossing each other in

various directions, and in
several superimposed layers,
which are obviously, as to
their origin, to be referred
to those arising from the
reddish-gray layer ; and
which probably also, as
Remak has assumed, are
derived, at the basis of the
cerebrum, from the anterior
extremity (knee) of the cor-
pus calloBuvi. How these
fibres are related to the cells
in the white layer is doubt-
ful, although this much is
certain, that many of them
return into the gray-red
substance from which they
arose, or in other words from loops, which were first described by
Valentin, and which I have very frequently and distinctly noticed in
chromic acid preparations treated with caustic soda. I have also
observed, in the gray-red substance, isolated loops with closely ap-
proximated sides, and. also with their convexity looking towards the
surface of the brain. The fasciculi of the gray-red substance contain
fibres which, at first, measure 0-0012-0-003 of a line, but almost all
of which ultimately decrease in size down to 0-001, and, in the gray
substance, acquire the diameter of the smallest nerve-tubes, 0*0004-
0-0008 of a line. The fibres given off from these fasciculi, within
the gray-red layer are, in part, of the same size as those in the
fasciculi, — which is the case particularly with those of the thicker white
streak, — in part finer. The fibres which proceed from these fasciculi
into the superficial white substance, are also, usually, of greater size, up

Fig. 150. — Finest nerve-tubes of the superficial white substance of the human cerebrum;
magnified 350 diameters.

THE NERVOUS SYSTEM. 389

to 0*003 of a line, many of which form loops ; there are, however, in
this laver together with these, some of the finest fibrils, measuring
0-0004 of a line. Notwithstanding all my endeavors, I have been unable
to discover any connection between the nerve-cells and fibres, in the
cortical portion of the cerebrum ; but the existence of such a connection
would appear to me to be nowhere so probable as here, where the nerve-
fibres, especially in the pure gray layer, assume so much the appearance
of processes of the cells, as almost to deceive the observer, and where, in
any case, they terminate. There are in this situation an immense
number of nerve-fibres, so fine and pale that they could scarcely be
regarded as such, were they not straighter than the processes, and did
they not, particularly when treated with soda, exhibit minute varicosi-
ties. If anywhere in the central organs, an origination of nerve-fibres
exists here, although it is quite intelligible that it should not yet have
been observed, when we consider the delicacies of the structures con-
cerned.

The corpus callosum presents, in the anterior portions of its body
above the septum pcllucidur)i, the fornix, and the corpora striata, dull
gray streaks, scattered in the white substance, in which the microscope
discovers no cells, but only clear vesicles of 0-003-0'004 of a line, with
nuclei, in the midst of numerous nerve-tubes, similar to what are met
with in certain fasciculi of fibres of the corpus striatum. Besides this,
Valentin (" Nervenl.," p. 244) occasionally noticed on the surface of the
corpus callosum, between the raphe and the strice ohtectoi, a delicate
gray investment with clear nerve-cells, which appears to be identical
w-ith \\\<i fasciola cinerea, which is continued into the fascia dentata of the
pes hippocampi major {yid. Arnold. "Bemerk," p. 87); otherwise the
corpus callosum is wholly composed of white medullary substance with
parallel nerve-fibres of exactly the same aspect and diameter as those
of the medullary substance of the hemispheres. The same may be said,
also, of the commissura anterior and fornix, which latter, however,
comes in contact with gray substance in very many ways, as in the optic
thalamus, from the tuberculum anterius of which its radix descendens
arises ; in the corpus mammillare (yid. sup. § IIG) ; at the commence-
ment of the radix ascendens ; in the floor of the third ventricle, to-
wards which some delicate fasciculi of the radix asceiidens are given off;
and at its point of junction with the septum pellueidum, which latter,
together with a common thick coat presenting much connective tissue
and corpuscula amylacea (yid. § 118), exhibits numerous plexuses of the
finest kind of nerve-fibres and nerve-cells, exactly as does the tuber
cinereum. The fibres of the fornix measure, in its white portions
0-0008-0-005, mostly 0-002-0-o63 of a line; in the optic thalamus (upper
part), and in the corpus mammillare, the fibres are only of the finest sort,
measuring 0-0004-0-001 of a line. The cornu ammonis, and the calcar

890 SPECIAL HISTOLOGY.

avis {pes luppocampi mmor), present nearly the same conditions as
those of" the cerebral convolutions ; in the gray substance of the former,
however, there is a peculiar sort of streak, containing chiefly round cells
"without processes, and closely aggregated.

Lastly, Ave have to consider the origin of the first two pairs of nerves.
The olfactory/ nerve contains, in the white portion of the tractus olfacto-
rius, fine nerve-fibres, of 0-0004, or at most 0*002 of a line, the finest,
pale-bordered, and apparently non-medullated ; and besides these, also
some gray substance, with fine granular structure, and cells of 0-007—
0-008 of a line. These cells, with some still smaller, down to a diameter
of 0-003 of a line, many with branched processes, constitute the
hulbus n. olfactorii, intermixed with numerous fine fibres, the relation of
which to the cells and to the true nerves of smell cannot be made out.
The op)tic nerve arises, with its tractus divided into two crura, from the
corpora geniculata, and the corpora quadrigemina and optic thalami ;
besides which, it is also in connection with the crura cerebri, the sub-
stantia perforata ayitica, the tuber cinereum, and the lamina teryiiinalis.
The precise origin of its fibres, dark-bordered tubes of 0*002 of a line,
is in Man unknown, but to draw conclusions from experiments in ani-
mals, it exists principally in the corpora quadrigemina, whilst we know
that they partially decussate in the chiasma (commissure). In this body,
however, there are, as stated by Arnold, Todd and Bowman, &c. : 1,
fibres which do not decussate, but are continued from the tractus into
the optic nerve of the same side ; and 2, commissural fibres, which may
indeed be divided into an anterior and posterior set, the latter constituting
a commissure between the two points of origin of the optic nerves, whilst
the anterior could only unite the two retinae. The existence of the
first-named fibres is certain, although they are much more scanty than
the decussating elements ; but that of the others also can hardly be
denied. Speaking physiologically, a commissure of the optic thalami
and corpora quadrigemina may perhaps be explained, but a commissure
also of the retince does not appear to be altogether impossible, because
■we know that the retina contains gray substance, and in it, nerve- cells
■with branched processes.

With respect to the origin of the nerve-fibres in the brain and higher
central organs, in general, it is several years since I first observed the
origin of dark-bordered fine fibres from the processes of the nerve-cells
iji the spinal cord of the Frog ("Zeitsch. f. wiss. Zooh," vol. I. p. 144,
tab. xi. Fig. 7). In man I have not as yet been so fortunate as to per-
ceive anything of the sort with certainty, though I do not myself doubt
that similar conditions obtain in this case also. In fact, R. Wagner and
Leuckart think they have seen, in man, the processes of the many-rayed
cells in the substantia ferruginca, passing into nerve-tubes (" Gott. An-

THE NERVOUS SYSTEM. 391

zeig.," ISoO, No. 43); as has Prof. Domrich, in the cortical substance
of the cerebellum, according to a communication to me by letter. R.
Wagner again (" Gott. Nachr.," Oct. 1851), has, recently, also found in
the electric lobes of the Ray, that from the many-rayed ganglion-globules
or nerve-cells, one or more, rarely two, unbranched processes are con-
tinued into dark-bordered fibres. He now explains this transition, in
the same way as before, saying that the processes were continued as
axis-cylinders into the dark-bordered tubes, in which Leydig, who has
observed the same transition in the cerehelluyn of the "Hammer-headed
Shark," agrees with him, as does Stannius, in the case of Petromyzon.
Nevertheless, it is still not quite evident to me, that any condition should
exist in this case, different from that which obtains in the ganglia, where
the processes of the nerve-cells are not simply axis-cylinders, but also
have a coat, which investing the medullary matter of the nerve, is con-
tinuous with the sheath of the dark-bordered tubes; although, seeing
that the presence of tunics on the nerve-corpuscles of the central organs,
and their processes, in general, is still a disputed point, I am prepared
to admit that the fact may be otherwise. These researches have opened
the way, and I -have no doubt, as I have already said in my jMicrosco-
pical Anatomy, that in time Ave shall succeed in demonstrating the origin
of dark-bordered tubes in many other situations in the central organs,
in man, and other animals. On the other hand, however, supported by
repeated investigation of the human brain, I must assert, that it is in
the highest degree probable that in many places it will be altogether
impossible to demonstrate the origin of fibres from nerve-cells, because
very many nerve-tubes, particularly those of the cortical substance of
the cerebellum and cerebrum, ultimately become so pale and slender, as
not to allow of their being distinguished from the processes of nerve-
cells. Whether the loops which distinctly exist in the convolutions of
the cerebrum, and which I have also seen in the corpora striata, are ter-
minations, or whether free prolongations of nerve-tubes exist, we know
not, and the less so because it cannot even be asserted that certain fibres
really so terminate. It may fairly be assumed that the fibres of the
corpus callosum and the commissural fibres in general, commence in the
one hemisphere in connection with cells and terminate in the other, and
that the fibres which proceed from the surface of the convolutions to the
optic thalami and corpora striata terminate in the latter, but to assert,
that it is so, is impossible, notwithstanding the visible loops, for it may
be that these latter are not terminations at all, and that the fibres in
question are all in the one place and the other in connection with nerve-
cells. That nerve-fibres should originate independently of any connec-
tion with cells would be contrary to all analogy, but in such an obscure
subject we must always be prepared for much that is new, and be careful
not wholly to reject any possibility, simply from a joriori considerations.

392 SPECIAL HISTOLOGY.

Several authors have noticed divisions of the nerve-tubes in the central
organs, such as, among the older ones, Ehrenberg, Volkmann, E. H.
Weber, and more lately also, Hessling ("Fror. N. Notiz.," Ap. 1849,
Jenaische, Ann. I. p. 283), E. Harless (ibid., p. 284), and SchafFner
(" Zeits. f. rat. Med.," IX.) in the brain of various vertebrate animals,
especially at the junction of the white and gray substance. I am not
inclined to doubt these statements, especially the latter, but I cannot
avoid the remark, that in the human brain, I have, hitherto, in vain
sought for divisions of this kind, and have had many hundreds of fibres
from the gray substance before me, under the most favorable circum-
stances, which presented no indications of the sort, whilst I have inva-
riably found such divisions in the spinal cord {vid. supra). The many-
rayed nerve-cells with branched processes are not as yet fully known in
all their relations. I have described their processes (as will be univer-
sally allowed, correctly), as a sort of pale, non-medullated nerve-tubes,
and have isolated them occasionally to the extent of | and J of a
line, without being able to notice anything more with regard to their
termination, than the fact of their ultimately assuming an extreme de-
gree of fineness. R. Wagner states, that those processes, which do not
pass into dark-bordered nerve-tubes, serve to connect the separate nerve-
cells together, but in so doing he manifestly says more than actual
observation warrants, as he has, hitherto, seen such a connection, only
in the electric lobes of the Ray. In the present state of neural Anatomy
there is nothing which should be more carefully avoided than the general
application of isolated observations, and I am therefore of opinion that
this question must as yet be regarded as an open one. It may indeed
be very consonant with physiological considerations, to explain the reflex
and alternating actions of separate sections of nerves by such connec-
tions between the cells, but it is precisely for that reason, that we should
be the more careful, and the more so because less obvious theories explain
the conditions just as well. I conclude, therefore, from the observations
hitherto made, only this much, that nerve-cells may anastomose, leaving
it to future inquiries to decide, whether they do so universally and with
all their processes, or whether in certain situations the latter do not
stretch out without any attachment, exerting a mutual influence and
affecting the nerve-fibres simply by juxtaposition, as appears to be the
case in the large nerve-cells of the cord and the roots of the spinal
nerves.

§ 118. Membranes and Vessels of the central Nervous System. —
A. Membranes. 1. Spinal cord. The dura mater s. meninx fibrosa is a
whitish yellow, occasionally glistening, firm, tolerably elastic membrane,
consisting of parallel and mostly longitudinal fasciculi of connective tis-
sue, and of a fine, elastic, fibrous network in almost equal proportions.

TUE NERVOUS SYSTEM. 393

The outer surface of the dura mater is, in front, where the membrane is
always at least as thin again as behind, pretty closely united to \\\q fas-
cia longitudinalis posterior of the spinal -column, free posteriorly and on
the sides, and separated from the arches of the vertehrce and their peri-
osteum by a space, occupied by a lax connective tissue with anastomosing
fasciculi scarcely more than 0004-0-005 of a line thick (reticular con-
nective tissue), containing a few elastic fibrils (convoluted and longitu-
dinal), and round, fusiform and stellate nucleated cells, similar to the
formative cells of the connective tissue, and besides these with larger or
smaller aggregations of frequently gelatiniform, transparent fat with
cells containing serous fluid. The vessels of this space are in part the
well-known plexus venosi, in part finer vessels, and also a network of the
finest capillaries in the lax connective tissue itself. The internal sur-
face of the dura mater would appear, from what is generally stated, to
be lined with an outer lamella of the arachnoid ; nothing, however, is
to be seen but an epithelium, composed of polygonal, flattened, nucleated
cells, on the innermost layer of the dura mater, and not a trace of any
special substratum. The ligamentum denticulatura has no epithelium,
and like the thickened processes of the /jw- mater, to which it is attached,
presents, in all respects, a structure similar to that of the dura mater.

The araclinoid membrane is constituted, not of an external and inter-
nal lamella, the former of which is united to the dura mater, the latter
free, but of a single layer corresponding to the internal lamella of authors.
It is an extremely delicate, transparent membrane, exactly correspond-
ing in extent and relations to the dura mater. Its outer surface, in the
posterior mesial line of the cervical portion, is connected with the dura
mater, above, by tolerably strong processes, lower down, by delicate
fibrils, elsewhere it is perfectly smooth and glistening, which appearance
depends upon an epithelium precisely like that of the dura mater, and
it is merely in apposition with that membrane, as the pulmonary pleura
is with the costal. The internal surface of the arachnoid is also smooth,
though without epithelium; it is separated from the spinal cord, and
Cauda equina by a large interspace, the subarachnoid space, affording,
however, numerous slender processes to the pia mater and the roots of
the nferves, which processes not only accompany the vessels and nerves,
but occur, especially in the posterior mesial line, arranged in a consecu-
tive series, and occasionally, particularly in the cervical region, form a
perforated or complete septum. As regards its intimate structure, the
arachnoid contains, chiefly, reticularly anastomosing bundles of con-
nective tissue of 0-001-0 -004 of a line, which are so united as to form
lamellre, some external with more slender, and some internal with
stronger fasciculi, and which are usually so surrounded by fine elastic
fibres, as to present a moniliform appearance when swollen by the appli-
cation of acetic acid (Fig. 23). In many fasciculi, these fibres are very

394 SPECIAL HISTOLOGY.

fine or wanting, others again, in addition, contain elastic fibres also in
the interior.

The vascular membrane , 2^'^'^ mater, very closely invests the spinal
cord and the gray substance of the filum terminale, penetrating on the
one hand into the anterior and posterior fissures, where it appears within
the spinal cord in the form of slender processes, and affording, on the
other, delicate sheaths to the roots of the nerves. It contains for the
most part common connective tissue with straight fibres, and, more rarely,
anastomosing bundles ; and besides these a good many nuclei often of a
lenticular form, with a few elastic fibrils. Here and there are met with
in the pia mater bright yellow or brown pigment-cells, of an irregular,
fusiform figure with fine prolonged ends and measuring 0-04-0*05 of a
line in length, which in the cervical region, owing to their greater num-
ber, give the membrane, not unfrequently, a brown or even blackish color.
2. Brain. — The membranes of the brain, though corresponding, in
general, with those of the spinal cord, yet present some differences. The
duj'a mater, in this situation, consisting of the true fibrous membrane of
that name and of the internal periosteum of the cranial bones, which, as
the immediate continuations of the corresponding membranes of the
spinal canal, become consolidated together at the level of the atlas, is,
in general, thicker and also whiter than in the spinal cord. Its external
or periosteal lamella, of a whitish-yellow color and rough, is attached
more or less firmly to the bones, supports the larger vasa meningea, and
is also otherwise more richly supplied with vessels than the internal
proper dura mater, with which, at an earlier period, it was more laxly
united, and from which, except where the sinuses are contained, it may
not unfrequently be separated even in the adult. The internal lamella
is less vascular, whiter, presenting in many places a glistening tendinous
aspect, and on its surface is quite smooth and for the most part even.
The processes of the dura mater, the greater and less falciform processes,
and the tentorium, appear as prolongations of this internal lamella ;
and between the two lamellae are situated, with few exceptions, the
venous canals or sinuses of the dura mater. Both lamellae contain con-
nective tissue of the same form as that in the tendons and ligaments,
with, for the most part, indistinct bundles, and parallel fibrils, which
either extend of a uniform size for considerable distances in it, or, espe-
cially as in the sinuses, form small, tendinous bands, crossing each other
in various directions, and containing among them a good many fine elastic
fibres. The internal surface of the dura mater is lined with a single
(according to Henle with more than one) layer of tessellated epithelial
cells, of 0-005-0-006 of a line in size, with rounded or elongated nuclei
measuring 0*002-0'004 of a line ; possessing no other covering which
might be described as a parietal lamella of the arachnoid {yid. Luschka,
Sercise Hiiute, p. 64).

THE NERVOUS SYSTEM. 395

The arachnoid memhrane of the brain differs from tliat of the spinal
cord, not so much in its structure as in its disposition. It is true, that
in this situation also, there is but one lamella demonstrable as a mem-
brane composed of connective tissue, which corresponds with the so-
termed visceral layer of the arachnoid of authors, and is also very closely
applied to the inner surface of the dura mater, but the arachnoid mem-
brane here is in much more intimate relation to the pia mater. That is
to say, instead of its being united with the latter, as in the cord, by scat-
tered fibres and lamella?, it is, in the brain, in many situations, as on all
the convolutions, and the projecting parts at the base of the brain,
adherent to and coalescent with it, and, elsewhere, where this is not the
case, united to it by numerous processes. For this reason, there exists,
in the brain, no continuous subarachnoid space, but numerous, larger
and smaller spaces, which only partially communicate. The larger of
these spaces between the cerebellum and medulla oblongata, and under
i\iQ pons Varolii, i\\e crura cerebri, the fossa Sylvii, &c., open directly
into the subarachnoid space of the spinal cord, whilst the smaller, corre-
sponding to the sulci, and over which the membrane composed of connec-
tive tissue is stretched, are perhaps partially in communication with each
other, but, at all events most of them, not with the larger spaces just
mentioned. The arachnoid, as has been correctly stated by Henle, is
nowhere in connection with the linint; membranes of the cerebral ven-
tricles. The structure of the membrane is the same as in the spinal
cord, except that the anastomosing fasciculi and spiral elastic fibres are
for the most part thicker, measuring as much as O'Ol or even 0*02 of a
line ; and the former frequently present, as it were, special and more
homogeneous sheaths of connective tissue, beneath which, fat- and pig-
ment-granules are often deposited. The outer surface is covered with
an epithelium in all respects like that of the dura mater.

The pia mater cerebri is more vascular but more delicate than that of
the spinal cord, and covers all the elevations and depressions on the
surface of the brain, if not very closely yet quite exactly, with the
single exception of the floor of the fourth ventricle, above which it is
stretched across from the calamus scriptorius, as far as the nodulus, the
free border of the vela medullaria inferiora and the flocculi, forming
the tela cliorioidea inferior, from which points it proceeds to invest the
under surface of the inferior vermiform j)'>'ocess and of the tonsillce.
The pia mater penetrates into the interior of the brain only at one
point, viz., at the transverse fissure of the cerebrum, where it passes
beneath the spleniiim corporis callosi, investing the vena magna Galeni,
as well as the pineal gland, forming the tela chorioidea superior, with
the plexus chorioideus ventriculi tertii ; and passing beneath \\\q fornix,
also constitutes the vascular plexuses of the lateral ventricles, which

396 SPECIAL HISTOLOGY.

are continuous witli the pia mater at the base of the brain, between the
cms cerebri and the inferior lobe. With respect to its intimate struc-
ture, the cerebral pia mater contains so many vessels, that in parts the
connective tissue which forms the matrix appears as a subordinate con-
stituent. It is rarely, as in the spinal cord, distinctly fibrous, for the
most part more homogeneous, approaching in character " Reichert's mem-
branes," or immature connective tissue, with a few nuclei and without
elastic fibres. Occasionally, however, the ina mater also contains
reticular connective tissue, as around the vena Galeni, the pineal gland,
the larger vessels, and also on the cerebellum. Fusiform pigment-cells
also occur here, as in the spinal cord, particularly on the medulla ob-
longata, and pons Varolii, but also, more anteriorly, at the base of the
brain as far as within the fissure of Sylvius, in which situation I have
noticed them even in the m. adventitia of smaller arteries.

Those portions of the pia mater which are in relation with the ven-
tricles, the telce chorioidece and plexus chorioidei, do not differ in their
structure from other portions of the membrane, except that, especially
in the plexus, they are composed almost wholly of vessels, and are fur-
nished with an epithelium at those points where they are not adherent
to the walls of the ventricles. This epithelium consists of a single
layer of roundish polygonal cells, O'008-O-Ol of a line in diameter, and
0-003-0-004 of a line in thickness, and usually containing together with
the rounded nucleus, yellowish granules, often in great numbers, and
one or two, dark, round oil-drops of 0-001-0-002 of a line in size. Ac-
cording to Henle, almost all these cells send out, from the angles towards
the layer of connective tissue of the plexus, short, slender, acuminate,
transparent, and colorless processes, like spines ; and according to
Valentin ("Physiol.," 2d ed., part 2, p. 22), in the Mammalia they also
support cilia. The epithelium is succeeded by a thin layer of apparently
homogeneous, connective tissue, beneath which is a very close inter-
lacement of larger and smaller vessels, between which no formed con-
nective tissue can be perceived, but only a clear, homogeneous, inter-
stitial substance.

All the portions of the ventricles which are not lined by the con-
tinuations of the pia mater, that is to say, the floor of the fourth
ventricle, the aqueductus Sylvii, the floor and the sides of the third
ventricle, the ventriculus septi lueidi, the roof of the lateral ventricles,
the anterior and the posterior cornua, and a considerable part of the
descending cornu, in the embryo also the cavity in the olfactory bulb,
and the canal in the spinal cord, have a special lining membrane, the
so-termed ependyma ventriculorum (Fig. 151). This is a simple tessel-
lated epithelium, which, according to Purkinje and Valentin (Miill.
" Arch.," 1836 ; Val. " Report.," 1836, p. 156), is said to exhibit ciliary

THE NERVOUS SYSTEM.

397

motion, a statement, however, which Virchow and I have not been able
to confirm in the case of an executed criminal.
It lies, normally, immediately upon the nerve-
substance, but there is so frequently developed ,<^^^^^ *
beneath it, especially in the fornix, the stria ^^^#
cornea, and the septum lucidum, a filamentous ^

layer, resembling connective tissue, 0-01-005 ^ @

of a line thick, that its occurrence at a certain ^

acre misht almost be described as constant, as ''"'^S
in fact it is by Virchow. The epithelium
sometimes presents, particularly as in the third ventricle, large cells of
0"008-0"012 of a line, with pigment-granules and masses, together with
nuclei, measuring 0"003 of a line; in other situations, as in the lateral
ventricles, the cells are not more than 0-005-0-007 of a line in size, but
almost as thick as wide, with roundish nuclei and a good many yellowish
granules, which are generally crowded in the interior.*

The vessels of the membranes just described present very various
conditions. In the first place, in the dura mater of the cord, if we ex-
cept those on the external surface and the numerous arteries and veins
of the cord by which it is perforated — the vessels are very few in num-
ber, and in this respect the membrane presents more of the conditions
of a muscular fascia or tendinous expansion. On the other hand, there
exist in this situation, between the dura mater and periosteum of the
vertebral canal, the well-known venous plexuses, as well as finer ramifi-
cations in the adipose tissue, which do not demand any further descrip-
tion. In the cranium, on the contrary, the entire dura mater is vascu-
lar, but especially in its external periosteal layer, which, partly for its
own supply, partly for that of the cranial bones, to which it gives off
numerous branches, supports the arterice rneningece, and also conveys
through its veins a portion of the blood returned from the bones.
Besides this, in the cerebral dura mater are lodged the venous sinuses^

FiO. 151. — Ependyma in man. ^, from the corpus striatum; 1, from the surface: 2, from
the side; a, epithelial cells; b, nerve-fibres lying beneath ; B, epithelium cells from the com-
tnissura mollis. — Magnified 350 diameters.

* [According to the recent researches of Virchow, the spinal ependyma differs some-
what from that lining the ventricles of the brain. It is more gelatinous and resistant,
and contains cells which are much larger than those of the cerebral epemlyma. It lies in
the middle of the gray matter, in the exact situation where the spinal cord exists in the
foetus, and forms a continuous filament, extending to the Jilum terminale.

The ependyma is prolonged without distinct boundaries, between the nervous elements.
Virchow has found a continuous layer of a similar substance in the interior of the higher
nerves of sense. He has quite recently also discovered in its deeper layers peculiar
granules, with the chemical reaction of cellulose. (Vide § 118, infra.) — DaC]

398 SPECIAL HISTOLOGY.

wliicli are simple excavations in it, for the conveyance of blood and
lined with an epithelium ; and most of which are obviously situated
between the periosteal lamella and the proper dura mater, thus, in their
position, corresponding with the plexus venosi spinales. The arachnoid
membrane, either of the spinal cord or of the brain, contains no proper
vessels [vid. Luschka, 1. c, p. 71), whilst the pia mater in both situa-
tions supports not only the very copious ramifications of the vessels of
the nervous substance itself, but is also supplied, with a tolerably rich,
proper capillary plexus of its own. In one portion of the pia mater,
viz., in the vascular plexuses, the vessels are distributed solely in the
membrane itself, the branches entering the nervous substance being of
subordinate importance. Lymphatics it is said have recently been in-
jected with air and quicksilver by Fohmann and Arnold, {vid. "Anat."
II. p. 618) both in the pia mater on the surface of the cerebrum and
cerebellum, as well as in the choroid plexus, but this observation appears
to me very much to demand confirmation.

The membranes of the central nervous system, also contain nerves, at
all events in part. In the dura mater of the cerebrum they run in the
periosteal lamella of the membrane, following pretty nearly the course
of the meningeal arteries, and are especially distinct on the a. meningea
media, which is accompained, not only by twigs of the nervi molles, but
also by a special nerve first noticed by Arnold {n. spinosus, Luschka),
which, according to Luschka, is derived from the third branch of the
n. trigeminus, the former of which are distributed with the vessels, and
the latter appears to be destined principally for the bones. Besides
these, Purkinje has noticed nerves on the anterior and posterior menin-
geal arteries, and Arnold long ago described the well-known n. tentorii
cerebelli, proceeding from the fifth pair, Avhich, as has been lately shown,
particularly by Pappenheim and Luschka (1. c), goes to the larger
sinuses of the dura mater. The elements of this white-looking nerve
and of the n. spinosus of Luschka, are those of the n. trigeminus, those
of the others, fine fibres, and in both situations they present divisions.
In the dura mater of the spinal cord, I, as well as Purkinje, have been
unable to detect any nerves ; they occur, however, as has been already
mentioned, in the periosteum of the vertebral canal, and on the arteries
going to the vertebrjB and cord, as well as in the sinuses and lax adipose
tissue of the canal (Luschka, 1. c).

In the aracJiJioid itself I have never noticed any nerves, but on the
vessels by which it is penetrated, and in the processes connecting it with
the pia mater, they may perhaps be seen, especially at the base of the
brain — to which nerves, those seen by Luschka (Serose Iliiute, p. 70),
notwithstanding the divisions observed in them, appear to me to belong.
Bochdalek (1. i. c.) has lately described nerves of the cerebral arachnoid,

THE NERVOUS SYSTEM. 399

derived from the n. accessoi'ius, the portio minor trigemini, and the facial
iiorve, but fails to show that they terminate in the membrane. When
tlie same author also finds extremely numerous nerves in the arachnoid
covering the cauda equina, he falls into the same error, as Rainey had
previously encountered in regarding connective tissue, disposed in the
more rare reticular form, as nerves. In the cauda equina, I am
acquainted with nerves only on the filum terminale, accompanying the
vessels, and nowhere else ; not even in the dura mater, into which Boch-
dalek equally supposes he has traced them.

The nerves discovered by Purkinje in the pia mater of the Ox, also
exist in man, in whom the pia mater of the cord, including the filum
terminale, is richly supplied with plexuses of fine nerves, measuring
0*0015-0'003 of a line, which throughout do little more than accom-
pany the vessels. At the base of the brain, many similar plexuses
occur on the arteries of the circle of ^Yillis, which, in twigs, at most
0-03 of a line in diameter, are distributed through the entire pia mater
of the brain, accompanying and always following the course of the
various vessels, with the exception of those of the cerebellum ; their
terminations, however, can nowhere be perceived. It is certain that
they do not accompany the arteries into the cerebral substance, and
that no nerves exist in the vascular plexuses ; whether there are any
or not on the vena Galeni, I have not yet inquired. The origin of these
nerves has been ascertained by Remak to be in the posterior roots, each
of which, as I have satisfied myself, in many situations, and as it appears
to me more frequently in the cervical portion of the cord, from the
fibres in closest contiguity to each other, sends out fine fibrils across the
subarachnoid space into the pia mater. As in this case, so also in the
cerebrum, besides the sympathetic nerves {plexus caroticus interims,
plexus vertebralis), the cerebral nerves may participate in the supplying
of the pia mater, since Bochdalek has noticed numerous fine twigs,
given off from the roots of many of the cerebral nerves, of the same
structure as the roots themselves, joining the nervous plexuses of the
arteries at the base of the brain and of the iiia mater of that region,
and of the cerebellum, as well as in the plexus chorioideus ventrie.
quart. (?). He also found that isolated fine filaments entered the pia
mater, directly from the medulla oblongata, the pons Varolii, and crura
cerebri, which were not previously conjoined with the neighboring ner-
vous trunks.

B. Vessels of tJie central nervous system. — With respect to the dis-
tribution and condition of the bloodvessels — the brain and spinal cord
agree almost entirely. After ramifying to a considerable extent in the
pia mater, the arteries enter the nervous substance, except in a few
situations {substantice perforata;, pons), as fine, though still distinct,

400

SPECIAL HISTOLOGY.

Fisr. 152.

arterial vessels, and ultimately subdivide, by continuous ramification, for

the most part at acute angles into a
rather wide network of very fine capil-
laries, from which again the venous
radicles arise, joining so as to form the
well-known trunks, both on the surface
and in the interior (Fig. 152). The
gray substance is invariably much
more richly supplied with vessels than
the white, the plexus formed by them
being closer, and the capillary vessels
themselves of less calibre, to which its
color is in some respect due. Accord-
ing to E. H. Weber, the interstices of
the capillaries in the medullary sub-
stance, measure 0-0142 of a line in
width and 0-025 of a line in length ;
in an injected preparation by Gerlach
of the sheep's brain, the breadth of the
interstices in the gray substance was
three or four times less than in the white.
In the spinal cord, the disposition of the entering trunks is sometimes very
regularly in series. Two series of vessels of this kind exist in the bottom
of the anterior fissure, which, from the processes of the j^za mater, pene-
trate the gray substance on the right and left; whilst a third series corre-
sponds to the posterior fissure, and others not unfrequently also to the
roots and the processes of the Ugamentum denticulum. All these vessels
enter the gray substance without undergoing any direct or considerable
decrease in size, and there find their ultimate distribution. In the brain
very delicate parallel vessels are met with in the gray substance of the
cerebellum, less distinctly in the cerebrum and other parts. The structure
of the vessels is, in general, the same as elsewhere. The arteries, upon
their entrance into the nervous substance, possess three coats — the
tunica adventitia, though resistant, is a thin and apparently quite homo-
geneous membrane ; the t. media is purely muscular; and the t. intima
formed of nothing but a very delicate elastic membrane, with openings,
and well-marked fusiform epithelial cells. One after another of these
coats is gradually lost, till before the capillaries are reached, we find
nothing but the t. adventitia, and scattered, transversely placed, elon-
gated cells, with transverse nuclei and an epithelium ; with which class
of vessels are soon associated capillaries with a structureless membrane
and few or more nuclei, sometimes of great minuteness, the finest

Fig. 152. — 'Vessels of the cerebral substance of the Sheep, from one of Gerlach 's injec-
tions : a, of the gray ; 6, of the white substance.

THE NERVOUS SYSTEM.

401

measuring in the cord, 0'0022, in the brain 0-002 of a lino. Of the
veins, the largest, for the most part, do not present a trace of smooth
muscle, exhibiting nothing but connective tissue with nuclei, or fine
elastic filaments and epithelium ; in the smaller ones I have, occasion-
ally, though very rarely, observed contractile elements.

In the ventricles of the brain there exists, under normal conditions,
an extremely small quantity of clear serous fluid, which is manifestly
secreted by the arterial plexuses, and which, probably aided by the
ciliary movements, assists in the nutrition of the walls of the cavities.
A second fluid, the liquor cerehro-spinalis is contained in the suba-
rachnoid spaces above described, which according to Luschka, are lined
by an epithelium, and from the largest of which, extending from the
base of the brain to the termination of the canal of the dura mater
medullce, the fluid in question may be readily obtained. It is alkaline,
contains — of water 98'56 — albumen and extractive matter 0*55 — salts
0*84 per cent., principally chloride of sodium. Its principal function
appears to be to conduce to the more free motion of the central nervous
system, and to act as a regulator in varying degrees of fulness of the
vascular system.

A few pathological points may here be referred to. The ependyma
ventriculorum presents not only, as above mentioned, almost constantly
in places, a thin fibrous substratum, but is frequently, especially in
dropsy of the ventricles, and in old age, very much thickened by a
layer of that kind. In either case it invariably contains, as was first
mentioned by Purkinje, yellowish bodies, with con-
centric strire of a round or biscuit shape, and not
unlike starch granules. They are scarcely aff'ected
by acids, whilst in caustic alkali they become pale
and gradually dissolve. I find these corpuscula
amylacea (Fig. 153), almost always on the fornix,
the stria cornea^ and septum pellucidum, and also
else^Yhere in the walls of the ventricles, as well as
in the cortical substance of the brain, in the medul-
lary substance of the cord, and in the filum termi-
nale ; in the first-mentioned situations they frequently
occur in incredible quantity, close together, in the
newly formed connective tissue, or between the ner-
vous elements. That these bodies are a pathological ^
product is certain, but not so of what they consist, ^
or how they are formed, although everything indicates a nitrogenous

Fig. 153. — 1, " Brain-sand" from the pineal gland, in bundles of connective tissue: 2^
corpuscula amylacea from the ependyma of Man ; magnified 350 diameters.

26

Fig. 153.

402 SPECIAL HISTOLOGY.

substance, and a formation from successive deposits.* In the plexus
chorioidei, in the pineal gland, occasionally in the pia mater and

* [The recent investigations of these corpora amylacea by Virchow, (see Archiv. f. path.
Anat. Sept. 1853) have led him to the important discovery of their true nature, viz. : that
they are composed of a substance, resembling the celhilose in plants. The fact that in the
animal kingdom, starchy substances had only been found in a low class of the invertebrated
animals, induced Virchow to examine all starch-like bodies occurring in the higher classes
of the animal kingdom, and thus the exact composition of the corpora amylacea was ascer-
tained. As this discovery is of great importance, I shall quote the autlior's own words.

" In a histological point of view, it has often occurred to me, that the umbilical cord in
Man possessed a great similarity in its structure to the cellulose in the Ascidians. (See
Wvirzb. Verhandl. 1851, Vol. II. p. 161, note.) And I was the more confirmed in this idea
by Scliacht"s observations, so that ever since my researches have been more carefully directed
to this subject. But in most instances I searched in vain, as in the ova of amphibia and
fishes, the peculiar yelk-plates of which I described. (Zeitschrift fiir Wiss. Zoologie. 1852,
Vol. IV. p. 240.) I was more successful, however, recently, when I directed my attention
to the so-called " corpora amylacea " of the brain, of the exact nature of which, as compared
with the other starch-like bodies in man, I had not been able to form any very definite
conclusions. I soon found that on the application of iodine, they assumed a bluish tint, and
upon subsequently adding sulphuric acid, the exquisite violet color, which is known to be-
long to cellulose, and which appeared the more intense, as it formed a distinct contrast to
the surrounding yellow or brown nitrogenous substances.

" I have so frequently repeated these investigations, and with so many precautions, that I
consider the results as perfectly certain. For I have instituted comparative researches not
only in ditlerent liuman bodies, and in the most diflerent situations, but I have allowed the
reagents employed to act under all possible conditions."

The best manner, Virchow continues, to obtain this reaction is to allow an hydrated
solution of iodine to act on the bodies in question, and then to add a little diluted sulphu-
ric acid. Care should be taken not to add too much iodine at once, and to allow the
sulphuric acid to act very slowly. The most beautiful preparations were obtained by
adding a drop of sulphuric acid to the edge of the thin glass covering a preparation, and
allowing it then to remain undisturbed fjom twelve to twenty-four hours. Every precaution
having been taken against an accidental admixture of .-itarch or cellulose, the following results
were obtained : —

"The corpora amylacea are chemically different from the concentric spherical corpuscles
of which the brain-sand is composed, and with which tliey have liitherto been confounded.
The organic basis of these brain sand-granules, is evidently nitrogenous ; iodine and sul-
phuric acid color it an intense yellow. The same is true not only of the sandy matter in
the pineal gland, and the choroid plexuses, but also of that of the Pacchionian granulations
and of the dura mater, as well as of the dentated plates in the spinal arachnoid. In all
these parts, except in a few spots in the pineal gland, I have never obtained the characte-
ristic blue reaction. It would, therefore, be henceforth advisable to restrict the term ' cor-
pora amylacea' to these cellulose corpuscles.

" The cellulose granules seem to be connected with the presence of the ependyma sub-
stance in certain quantities, and might not improperly be considered as a part of it. But
how they are produced from it, it was impossible to recognize. They are usually minute,
scarcely corresponding in size to the nuclei of the ependyma. Can they originate from
these? The larger they are, the more distinctly laminated they appear. But they do not
exhibit anywhere a nitrogenous admixtin-e, distinguishable by its yellow color. Their
centre is generally of a darker blue, and hence, perhaps, denser than their border.

" The supposition, of these bodies being introduced from without, is the less probable
because a similar substance is nowhere else known. The cellulose in plants exhibits a
number of varieties, but this animal cellulose is distinguishable above all by its slight resis-
tance towards reagents; for concentrated acids and alkalies act on it more powerfully than
on vegetable cellulose."

TUE NERVOUS SYSTEM. 403

arachnoid (also in the cord), and although rarely, also in the walls
of the ventricles, there is furthermore met with, as a constant,
though pathological production, the gritty matter of the brain (brain-
sand). It consists of roundish, simple or mulberry-shaped, opaque,
mostly concentrically striated globules of 0-005-0-05 of a lino, and
together ^Yith them of angular bodies, of a stalactitic, clavate, or other
irregular figure, with an uneven, botryoidal, scaly surface ; and also in the
form of simple, cylindrical, rigid fibres, either branched or reticular, and
of fine particles. The brain-sand contains principally carbonate of lime,
but also phosphate of lime and magnesia, and an organic substance,
which after the salts have been removed, for the most part perfectly
retains the figure of the concretion, that is to say, of a concentrically
laminated pale body, or as clear fibres. It is quite certain that this
brain-sand, when it assumes the form of elongated, branched, reticular
bodies, is simply developed in the bundles of connective tissue (Fig.
153), as, not unfrequently, in the pineal gland and in the membranes
of the brain ; in other cases it appears to be an independent incrusta-
tion on fibrinous concretions. Whilst cells impregnated with calcareous
matter, which Remak (" Obs.," p. 26) supposed them to be, according
to Harless (Miill. "Arch.," 1845, p. 354), do not exist. Lastly, also,
may be mentioned the Paccldonian granulations of the jj/a mater, and
ossifications of the membranes. The former, which are situated prin-
cipally on both sides of the falx major, on the jiocculi, in the choroid
plexuses, &c., consist chiefly of a tough fibrous substance, not unlike
immature connective tissue, containing also undeveloped elastic tissue,
and corpuscula amylacea. The latter, which are true osseous plates,
occur sometimes on the inner surface of the cerebral dura mater, some-
times on the arachnoid, particularly of the cauda equina.

The cellulose corpuscles were found only in the substance of the ependyma of the
ventricles and its prolongations, including the transparent substance in the spinal marrow de-
scribed by Kelliker as the " substantia grisea centralis," but not in the cortical layer of the
brain, or in the interior of the cerebral substance. Neither was Virchow able to detect
them in the brain of a child, or, as Bernard's experiments might lead us to suppose, in the
brain of a Rabbit, and he is, therefore, inclined to attribute to them a pathological import.
Similar bodies have been found, by Rokitansky in the optic nerve, by Kolliker in the retina,
by Luschka in the ganglion of Gasser.

The exact chemical nature of these bodies has not, as yet, been satisfactorily ascertained.
They have not the pure reaction of vegetable cellulose, nor, as Bonders supposes them
to have, that of starch, and they might, perhaps, at present, be more properly called "amy-
loid'' corpuscles. If boiled in water they are dissolved.

This discovery of Virchow's is of great importance, not only with regard to the anatomy
of the corpora amylacea, but as establishing as an undoubted fact the existence of vegetable
matter as a part of the animal economy. Whether this be a pathological formation or
not, it is at present impossible to decide, the former is, however, highly probable, since
corpuscles with the same reaction have been found in certain abnormal conditions of the
spleen. (Vid. § 170, Spleen).— DaC]

404 SPECIAL HISTOLOGY.

PERIPHERAL NERVOUS SYSTEM.

§ 119. Spinal ner'ves. — The thirty-one pairs of nerves springing
from the spinal cord, arise, with few exceptions, by anterior and pos-
terior roots. Receiving a delicate tunic from the jfn'a mater, they con-
verge, and are continued across the subarachnoid space, to perforate,
independently of each other, the arachnoid and dura mater, from the
latter of which they obtain a firmer coat. Proceeding further, the pos-
terior root forms its ganglion, by the deposition around and among its
nerve-fibres, of ganglion-cells, which, to all appearance, give origin to
special nerve-tubes, the ganglionic fibres of the spinal-tierves, each for
the most part arising from a cell, and which have no further connection
•with the fibres of the posterior root passing through the ganglion, than
that, in their invariably peripheral course, they are in apposition, and
intermingled with the latter. The motor root never acquires ganglion-
cells, merely passing by the ganglion, in more or less close apposition
with it. Beyond the ganglion, the two roots are united in such a man-
ner that their elements are very intimately commingled, and a common
nervous trunk formed, containing in all its divisions sensitive and motor
elements. It is usually connected with the neighboring nerves above
and below it, in the formation of the well-known plexuses, afterwards
giving off its terminal branches to the muscles, integument, vessels of
the trunk and extremities, articular capsules, tendons, and bones. As in
the roots, so also in the branches of the common trunk, it is seen that
the motor twigs contain principally thick fibres, and those destined for
the integument and other organs above named, finer ones ; ultimately,
however, in the terminal ramifications, all the fibres are of uniform size.
The fibres of all the spinal nerves appear to run quite distinct from each
other, and to present no divisions in the trunks and branches, whilst, in
the terminal ramifications of them, divisions frequently occur, and, at
all events in certain animals (Mouse, batrachian larva), also reticular
anastomoses. They terminate either in loops, or in free prolongations,
the latter being the case, particularly, in the Pacinian bodies, which
are structures composed of numerous concentric capsules separated by
fluid, of an oval form, and measuring |-2 lines, found principally in
the hand and foot, and which usually contain the termination of a nerve-
fibre.

In the first and last pairs of spinal nerves occasionally only a single
root can be perceived, in the former case the motor, and in the latter
the sensitive. I have communicated the diameters of all the anterior
and posterior roots on the left side in a male and female body, in the
"Verb. d. Wiirzb. phys. med.," Gesellsch. 1850, Heft II. and the
transverse sectional areas deduced from these observations are given in

THE NERVOUS SYSTEM.

405

my "Microscopical Anatomy," § 116. The roots are furnished with a
delicate neurilemma, derived from the pia mater, and presenting a simi-
lar structure, which forms both an external sheath 0-002 of a line in
diameter, as well as internal septa to the individual fasciculi. The con-
tiguous roots frequently anastomose, and this is much more usually the
case with the sensitive roots ; in the cervical nerves in Man in parti-
cular, it is found to take place constantly in one or other of the nerves.

§ 120. The structure of the spinal ganglia, in the Mammalia, is a
difficult subject of investigation, but I think the following may be stated

with certainty respecting them.
The sensitive roots, so far as I
have hitherto been able to make
out, enter into no connection
with the nerve-cells in the gan-
glion, but forming one, or, in the
larger ganglia, several, or even
numerous fasciculi, which in the
latter case anastomose, simply
traverse it, to be reunited be-
low the ganglion into a single
trunk, which is then immediate-
ly blended with the motor root.
Most of the nerve-cells them-
selves appear to be in connec-
tion with the nerve-fibres, giv-
ing off either one or two, or
more rarelv, several. These
fibres, which I term ganglion-
jihres, proceed in a prepon-
derating majority perhaps all
of them peripherally, joining
and strengthening the perfora-
ting root-fibres ; so that each
is to be
of new

ganglion

as a source
fibres.*

regarded
nerve-

Fig. 154.

[f|la(rt,i,!l|i.L|ijw;H):!jri!j;i|jp|,y

i

y --

Fig. 154. — A lumbar ganglion of a young Dog, treated with soda, and magnified 45
diameters: S, sensitive roots; ilf, motor roots; R.a, anterior branch of the spinal nerve; R.j),
posterior branch; in both their composition from both roots is manifest ; G, ganglion, with
the cells and ganglion-fibres, which assist in the strengthening of the sensitive roots travers-
ing the ganglion.

* [The new " ganglion-fibres" join differently the nerve-fibres on which the ganglion is
seated, or by which it is perforated. In the large ganglia the new fibres penetrate in

406 SPECIAL HISTOLOGY.

The structure of the spinal ganglia (Fig. 154) is a difficult subject for
investigation, in Man. No complete results can be obtained from the
larger of them, but more may be made out in the smaller or smallest, as
in those of the fifth sacral nerve and n. coccygeus, which are to be sought
within the sac of the dura mater, also perhaps in the fourth sacral and
first cervical nerves. If a comparative examination be instituted, of the
spinal ganglia- of the smaller Mammalia (Rabbit, Puppy, Mole, Mouse,
Rat), and if not only the scalpel and needle be employed, but if the
entire ganglia be examined after the application of acetic acid, and above
all, of a dilute solution of soda, with the aid of the compressorium, a
satisfactory insight into their structure may be obtained. The fibres of
the roots of the nerves while passing through the ganglia present nothing
at all peculiar, that is to say, no change in size ; nor have I ever
observed any divisions of them, and I think it may be positively asserted,
that such an occurrence, if it take place at all, must be extremely rare,
as, notwithstanding that I have specially sought for it, and have been
able, in the lower Mammalia, to trace numerous nerve-fibres through the
entire ganglion, I have never noticed anything of the sort.

The principal constituents of the ganglia — the ganglion-globules or
-cells [nerve-cells] (Figs. 155 and 157), have a distinct outer coat,
are for the most part roundish, elongated, or pyriform, usually a
little flattened,and measure from 0-012 to 0-036, or even 0*04 of a
line; on the average 0-02-0 03 of a line. The contents are through-
out finely granular, and not unfrequently exhibit, in the vicinity of
the nucleus, an accumulation of yellow, or yellowish-brown, larger
pigment granules, which increases in age, and to which the gan-
glia are chiefly indebted for their yellow color. The nuclei measure

fasciculi between the perforating nerve-fibres ; in the smaller ganglia they either wind
around the nerve-fibres, or rim along the side of the nerve on which the ganglion is situated.
This depends mainly on the exact position of the ganglion. If it be placed in the middle of
the nerve, the former occurs, whilst if it be situated on one side of it, the latter is the more
frequent.

The new ganglion-fibres mostly proceed peripherally, but according to a recent observer,
Axmann (Beitrage zur Anatom. u. Phys. des Gangl. Syst., Berlin, 1853) this is not the case with
all of them. From many careful dissections he satisfied himself that whilst, as stated by
Kolliker and others, most of the new fibres, proceeding from every spinal ganglion, run in a
peripheral direction, and are distributed along with the cerebro-spinal nerve-fibres, to the
tissues subjected to will and sensation, some are connected through the rami communic antes
with the sympathetic system. He also found that a small number of the ganglion-fibres
penetrate through the roots of the cerebro-spinal nerves into the spinal column and brain,
where, he states, they have been frequently mistaken for attenuated cerebro-spinal nerve-
fibres. He adds, further, that he has been able to trace their connection with the spinal
ganglia in the Frog, Mouse, and Pike, and also in a human fcetus of six months. It is, how-
ever, difficult to understand how Axmann was able to determine that these fibres proceeded
from the ganglia to the spinal marrow, since they might be as readily supposed to have been
minute fibres proceeding from the ganglia of the spinal marrow towards the external
ganglia. — DaC]

THE NERVOUS SYSTEM.

407

These nerve-cells

Fisr. 155.

0-004-0-008, the nucleoli 0-0008-0-002 of a line.
are situated, in the first place, in larger
numbers on the surface of the ganglion, be-
tween the •neurilemuia and the perforating
radical fibres ; and secondly, at all events in
Man, in the interior, where they occupy the
interstices of the plexus formed by the nerve-
fibres. The individual cells are retained in
their situations by a special tissue, which
also separates them from the contiguous cells
and from the nerve-fibres. This tissue ap-
pears on isolated cells, as if it formed a spe-
cial coat to them, and is consecjuently termed
their external sheath, but in fact it repre-
sents a system of small septa, connected in a
complex manner, and pervading the entire
ganglion, receiving the separate cells in its meshes, and only more rarely
appearing as a definitely bounded coat on individual cells. This
structure is evidently to be referred to connective tissue ; it presents,
however, several forms, which have been, in part, already, properly dis-
tinguished by Valentin (Milll. "Arch." 1839, p, 143), viz. 1, in the form
of a sometimes homogeneous, sometimes more fibrous substance, with
scattered, flattened, roundish nuclei of 0-002-0*003 of a
line ; and, 2, in that of isolated elongated, triangular or
fusiform cells, measuring 0-003-0-005 of a line, with
nuclei as above,' and which sometimes may be supposed
to resemble epithelial cells, although, as is evident from
a comparison of their different forms, they rather cor-
respond with the developmental cells of connective, or of
elastic tissue (Fig. 156). Besides these two forms, the
former of which occurs everywhere, and the latter principally in the
larger ganglia, certain intermediate types are met with in Man, which
consist, as it were, of nucleated "fibres of Remak," as they are termed
(yid. infra), or, at all events, in the preparation, break up into such.

From by far the greatest number of the nerve-cells, in Man and the
Mammalia, are given off pale processes, 0-0015-0-0025 of a line, in all
respects corresponding to those of the central cells, but furnished with a
special sheath, and which, as I discovered in the year 1844 (" Selbst. u.

Fig. 155. — Ganglion-globules (nerve-cells) from the Gasserian ganglion of the Cat, mag-
nified 350 diam. : 1, cell with a short, pale process, showing the origin of a fibre, a;
sheath of the cell and nerve-tube, containing nuclei; b, cell-membrane of the nerve-cell;

2, cell with the origin of a fibre, without sheath; 6, cell-membrane of the nerve-cell;

3, nerve-cell, deprived, in the preparation of it, of its membrane and external sheath.

Fig. 1 5G. — Cells from the sheath of the nerve-cells of the spinal ganglia in Man, mag-
nified 350 diameters. .■

Fig. 156.

408

SPECIAL HISTOLOGY.

Fipr.157.

Abh. des Symp. Nerv.," Zurich, 1844, p. 22), are each of them con-
tinued into a dark-bordered nerve tube (Figs. 155, 157). The cells

observed by me had but one
process, the so-termed tmi-
polar-cells, and I at first
thought that such only ex-
isted in the spinal ganglia.
It now appears, however,
from more recent re-
searches, especially from
those of Stannius, that they
also contain cells with two
processes, one of which may again divide ; fresh and more extended in-
vestigations therefore are required to show how the matter really stands.
At present I think the following should be remarked : 1, in Man and
the Mammalia I have certainly established the fact of the existence of
unipolar-cells, and think it may also be asserted that they are very nu-
merous; 2, quite lately I have myself, although rarely, noticed cells
with two, pale processes, and I am willing to admit the possibility that
such cells frequently occur, as it is certain that many processes must be
torn off in the comparatively rude methods necessarily employed to
isolate the cells ; 3, when Stannius very recently noticed in a human
foetus, and in a foetal Calf, together with unipolar and apolar cells, in
the latter numerous bipolar cells, it should be inquired whether the lat-
ter were not cells which afterwards divide ? — because divisions of the
nerve-cells undoubtedly take place (vid. infra), — and in this way become
unipolar ; 4, whether the cells give off one or two fibres, one of the
latter does not go towards the centre and the other towards the peri-
phery, but both proceed in the latter direction ; at all events, in the
examination of all small ganglia, only such ganglion-fibres are visible.
Stannius, in bipolar cells of this kind from the Calf, also found the two
processes closely approximated ; 5, it is difficult to determine whether
cells without processes also occur in the spinal ganglia, seeing that the
processes are very readily detached, and that cells thus truncated may
very easily be regarded as apolar cells. In small ganglia in the Mam-
malia a fibre may be traced to each cell, whilst in the smallest spinal
ganglia in Man, and in the inconstant ganglia of the posterior roots
(vid. seq.), cells are not unfrequently met with, to which no fibre is at-
tached, and, consequently, I would, at present, merely state that, in any
case, fibres arise from the majority of the cells. In order to examine
these conditions, either the larger ganglia in Man are selected, which

Fig. 157. — Twigs of the coccygeal nerve within tlie dura mater, with an adherent, pedun-
culated nerve-cell in its nucleated sheath, from wliich the derivation of a fibre is very
distinctly seen ; magnified 350 diameters. From Man.

THE NERVOUS SYSTEM.

409

are torn into fibres as carefully as possible under a simple microscope,
until the fibres are traced to their origin, which may be done with a
little trouble in almost every ganglion, or the small ganglia of the fifth
sacral and coccygeal nerves are taken for the purpose. In these gan-
glia, in almost every individual, solitary and completely isolated, pedun-
culated, ganglion-globules are met with, close to or in the neighborhood
of the ganglia, each in its special sheath, which in this case appears to
be homogeneous (Fig. 157), and in many cases, the simple, dark nerve-
fibres lying in the peduncle of the globule, and frequently also its con-
nection with the cell, by means of a pale process, may be distinctly
perceived. In the ganglia aherrantia also of Ilyrtl, that is to say the
inconstant, larger or smaller collections of nerve-cells, which are found
in every subject upon the posterior roots of the
larger nerves, the simple origins of fibres may
occasionally be distinctly noticed. The dark-
colored fibres, arising from the nerve-cells,
simply constitute the continuation of the pale
processes of the cells, so that the membranes
and contents of each part pass continuously
into each other, and thus also the membrane
and the contents of the cells are connected with
the sheath of the nerve-tubes, the medullary
sheath, and the axis-cylinder. In older nerve-
cells, or by the operation of reagents (ar-
senious acid, chromic acid, iodine), the con-
tents of the cell become detached from the
membrane, and the axis-cylinder appears
as a direct continuation of the former (Fig.
158), as was first shown by Harting {vid.
also Stannius in " Gott. Anzeig.," 1850,
and Leydig, 1. c. Tab. 1, Fig. 9), which
is the best proof that the contents of the
nerve-cells cannot be understood as contained in a dilated nerve-tube.*

FiO. 158. — Nerve-cell of the Pike (bipolar, as they are termed), which is continued at each
end into dark-bordered nerve-tubes, treated with arsenious acid : a, sheatli of the nerve-cell;
6, sheath of nerve ; c, nerve-medulla ; rf, axis-cylinder continuous with the contents of the
nerve-cell ; e, which have shrunk away from the sheath. — Magnified 350 diameters.

• [The axis-cylinder is supposed by some observers not to be, as above stated, a continua-
tion of the contents of the cell, but rather of its nucleus. This continuation of the nucleus
into the.axis-cylinder is best seen in ganglia, which have been kept for some days in diluted
acetic acid. We are thus, according to Axmann (1. c.) not only able to see the connection of
the axis-cylinder with the nucleus, but also to isolate the nucleus with a portion of the axis-
cylinder attached to it. This continuation of the nucleus of the ganglion cell into the axis-
cylinder has been observed in all classes of animals. It was first described by Harless in
the ganglion corpuscles of the electric lobes of the Torpedo Galvani. — DaC]

410 SPECIAL HISTOLOGY.

The nerve-tubes or ganglion-fibres thus originating, which frequently
arch round or embrace the cells with several circular turns, are at first
fine, measuring 0-0015-0*0025 of a line, but (not continuing so as I
formerly supposed, when I was acquainted only with their origin), they
all very soon increase in size, as may be very readily observed in many
fibres, whilst still within the ganglion, up to 0-003 and 0*004, many even
to as much as 0-005 and 0-006 of a line; becoming, consequently, medium-
sized, and tliick nerve-fihres. The processes of the cells and the nerve-fibres
springing from them are also furnished with nucleated sheaths like
the cells themselves, the vaginal processes, as they are termed, which
they lose, however, at the point where they join the emergent trunk,
obtaining instead of it, as a coat, the common neurilemma of the
nerves.

The description I have above given of the conditions observable in
the spinal-ganglia in Man and the Mammalia, differs very considerably
from what was found by Bidder, Reichert, R. Wagner, and Robin, to be
the case in Fishes. The chief difference consists in this, that whilst in
the Mammalia, from all we know, the roots of the nerves have no direct
connection with the nerve-cells, and merely pass through the ganglion,
in Fishes, all the radical fibres are connected with the cells, so that each
fibre is interrupted by a bipolar cell, and independent ganglion-fibres are
wholly wanting. R. Wagner has thought, that what obtains in the Fish
might be applied, unconditionally, to all the Vertebrata, and asserts, that
the occurrence of bipolar cells in the course of the posterior radical
fibres is in accordance with Bell's doctrine, and a necessary contingent
in the mechanism of the sensitive fibres ; and moreover, that in this case
the highly important and long-sought distinction between sensitive and
motor primitive fibres, has been discovered. In opposition to this I have
expressed the opinion, that it is not a necessary postulate, that what is
found in the Fish should be applied to Man, and that the interruption of
a sensitive fibre by a nerve-cell does not distinguish it from a motor
fibre. Although Wagner has very recently characterized this opinion
of mine as unphysiological, he will not, at the same time, convince any
one that the spinal ganglia of the Mammalia are constructed as he thinks,
and I shall therefore wait to see whether further observations will con-
firm my observations or not. In order to complete them, I will more-
over mention, that direct measurement of the sensitive roots above and
below the ganglia, shows a not inconsiderable difference in favor of the
latter situation {yid. " Mikroskop. Anat.," II. p. 509), which as diffe-
rences in the thickness of the entering and emergent nerve-fibres, and
divisions of them within the ganglion do not exist, can only be referred
to the fibres which originate in the ganglion and proceed towards the
periphery, a view which is also confirmed by direct observation (Fig.

TUE NERVOUS SYSTEM. 411

154). With respect to the interesting observations on the structure of
the spinal ganglia of the lower animals, and particularly of Fishes, I
would refer especially to the works of 11. Wagner, Bidder, Robin, and
Stannius, cited below.

§ 121. Further course and termination of the Spinal Nerves. — Below
the spinal ganglion, the sensitive and motor roots unite to form a common
trunk, their fibres being intermixed in diverse ways, as may be very
distinctly perceived in small animals. All the subsequent branches,
both of the anterior and posterior main divisions, as well as their fur-
ther continuations, are consequently of a mixed nature, formed of por-
tions derived from both roots ; a condition which they retain up to their
ultimate distribution. Here, however, an alteration takes place, the
motor fibres going off in by far the larger proportion into the muscular
branches, and the sensitive chiefly to the cutaneous. Where the gan-
glion-fibres which arise in the spinal ganglia are distributed, cannot be
ascertained anatomically.* When their physiological relations, how-
ever, are considered, it would appear as by far the most probable sup-
position, that they do not, as at first sight one would be inclined to
suppose, join the sympathetic in the rami communicantes, but, that ac-
companying the spinal nerves, they are continued chiefly into the vascular
branches, and consequently are distributed in the integuments, muscles,
bones, joints, tendons, and vnQxnhxdiXiQa {periosteum, pia mater, &c.), but
also, perhaps, to the glands and involuntary muscles of the skin. The
nerve-fibres in the main trunks of the spinal nerves present the same
diameter as in the roots, that is to say, there are finer and thicker
tubes, and a certain number of intermediate forms ; but, as they pro-
ceed, the fibres separate, the thicker going more to the muscular
branches, and the thinner into the cutaneous nerves. According; to the
statements of Bidder and Volkmann, the proportion of the fine to the
thick fibres is, in man, as 1. 1 : 1, in the muscular nerves as 0. 1-0-33 : 1 ;
statements which I can but confirm, adding to them, that the nerves of
the bones contain, in the trunks, one-third of thick and two-thirds of
fine, whilst those of the articulations, tendons, and membranes, exhibit
a great preponderance of fine fibres. In my opinion, most of the fine
fibres contained in the branches of the spinal nerves must be regarded
as derived from the spinal cord, and as being, in their function, quite of
equal importance with the thick fibres, and at present, the only thing
that remains unascertained, is whether they all ascend to the brain, or
perhaps in part arise in the spinal cord; upon which point reference
may be made to § 112.

The spinal nerves are composed in general of parallel tubes, for the

* [Vid. note, § 120.— DaC]

412 SPECIAL HISTOLOGY.

most part undulating, upon which circumstance their transversely banded
aspect depends ; they exhibit, however, in their course, very frequent
anastomoses, in which way the various larger and smaWer plexuses with
decussating fibres are formed. The formation of these plexuses is due
to an interchange of entire fasciculi or fibres, never to a connection be-
tween the individual primitive fibres, and in a microscopical point of
view affords no point worthy of remark.

Divisions of the nerve-fibres do not occur, according to our present
experience, in the trunks and larger branches of the spinal nerves of the
Mammalia [in Fishes, Stannius noticed numerous divisions in the trunks
of the m.otor and mixed nerves ("Archivflir phys.," Heilk. 1850, p.
77)], nor do they exhibit any considerable change in their diameter ;
but in the ultimate ramifications, on the other hand, it is certain that
such divisions do take place, even in Man, accompanied by a very con-
siderable diminution in the size of the fibres ;* with respect to which con-
ditions, and the terminations in the skin, muscles, bones, and membranes
in general, reference may be made to the detailed descriptions given in
the proper places.

One kind, only, of termination of the spinal nerves, is still to be
noticed here, — that in the Pacinian bodies. The small bodies, so named
by Henle and myself (" Ueber die Pacin. Korperchen des Menschen und
der Thiere," Zurich, 1844), were first accurately described by the Italian,
Pacini ("Nuovi organi scoperti nel corpo umano," Pistoja, 1840), espe-
cially in the nerves of the palm of the hand and sole of the foot, and,
in fact, as Langer of Vienna afterwards showed, had been previously
noticed by A. Vater (J.G. Lehmann, " De consensu partium corp. hum.,"
Vitembergge, 1741), although their nature had not been recognized.
These organs are of an elliptical or pyriforra shape, of a whitish trans-
parent color, with whiter streaks internally, and measure |-2 lines in
size ; in Man, they are constantly found on the cutaneous nerves of the
palm of the hand and sole of the foot, in the subcutaneous connective
tissue itself, and most numerously in the fingers and toes, particularly
on the third phalanx, — according to Herbst ("Die Pacin. Korperchen
und ihre Bedeutung," Gutt., 1847), there are about 600 in the hand and
not quite so many in the foot; besides which, it must here also be
stated, that they are invariably found on the great sympathetic plexus,
in front of, and close to the abdominal aorta, behind the peritoneum,
particularly near the pancreas, frequently also in the mesentery, close
to the intestine ; and also occasionally on other nerves, such as the

* [The ultimate ramifications are supposed by Axmann (1. c), to be merely axis-cylinders
surrounded by the sheaths of the nerves, the granular contents of the nerve-tubes having
gradually disappeared. — DaC]

THE NERVOUS SYSTEM.

413

n. pudcndus communis^ on the glans pejiis (Fick) and bulb of the ure-
thra, on the intercostal nerves, sacral plexus,
cutaneous nerves of the upper- and fore- ^'?- ^^^•

arm, on the dorsum of the hand and foot,
and the cutaneous nerves of the neck.

The structure of the Pacinian bodies is,
upon the whole, simple (Fig. 159). Each of
them consists of very numerous (20-GO)
concentric layers of connective tissue, of
■which layers the external are separated by
wider, and the internal by narrower inter-
spaces, in which is contained a clear serous
moisture, which is collected in larger quan-
tity in an elongated central cavity, bounded
by the innermost lamella. Each body pre-
sents a rounded peduncle, formed from the
continuation of its lamellre, and connected
with a nervous twig, and in which a dark
nerve-fibre, 0-006-0-068 of a line (in the
Cat, 0-0044-0-0077 of a line) thick, runs to
the Pacinian body. This fibre enters the
central cavity from the penduncle, where it
becomes 0-006 of a line wide and 0-004
of a line thick, pale, non-medullated, almost
like an axis-cylinder, and terminates in the
upper part of the cavity, in a free, slightly
granular tubercle, the extremity being fre-
quently bifid or trifid. Further observa-
tions, and comparative anatomical details
with regard to these bodies, which are also

found in great number in many Mammalia, as well as in Birds, In the
skin, beak, and tongue (Herbst, Will), and with respect to which physio-
logy is still wholly in the dark, will be found in the works above quoted,
and also in Reichert (" Bindegewebe," p. 6-5), Herbst (" Gcitt. gel. Anz.,"
1848, Nos. 162, 163, 1850 ; " Nachr. v. d. Univ.," p. 204, 1851, p.
161), Will("Sitzungsber.d. Wiener Acad.," Feb., 1850), OsannC'Bericht
uber d. zoot. Anst. in Wiirzb.," 1849), Strahl (Muller's " Arch.," 1848,
p. 163), and Pappenheim (" Comptes rendus," xxiii. p. 68). [Todd and
Bowman, "Physiol. Anatomy," Part XL, p. 395, figs. 74, 75, 76; and
Bowman, art. "Pacinian Bodies," " Cyc. of Anat. and Phys."]

Fig. 159. — A Pacinian body in Man, magnified 350 diam. : a, its peduncle; 6, nerve-
fibre in it ; c, external ; d, internal layer of the sheath ; e, pale nerve-fibre in the cen-
tral cavity ; /, divisions and terminations of the same.

I

414 SPECIAL HISTOLOGY.

The spinal nerves, from their point of exit through the dura mater,
are enclosed by a firm sheath of connective tissue — the nerve-sheath, or
neurilemma — which also sends finer prolongations into the interior of
the nerves, and, as in the muscles, forms boundaries to larger or smaller
fasciculi, as well as extremely delicate septa between the individual
tubules (Fig. 160). In the ultimate ramifications, where isolated primi-
tive fibres, or some few of them, still often re-
tain an external coat, the neurilemma presents
the aspect of a homogeneous membrane, with
elongated nuclei of O'OOS of a line ; and it
presents this character also in the smaller
twigs of the cutaneous and muscular nerves,
"^ only that gradually the substance begins to

split, in a longitudinal direction, into fibres, the nuclei become longer
(0-005-0-008 of a line), frequently almost like those in smooth muscles,
and elastic fibres also make their appearance, which are not unfre-
quently entwined around whole fasciculi. The larger nerves, lastly
present common connective tissue, with distinct longitudinal fibrils, as
in fibrous membranes, intermixed with numerous reticulated elastic fila-
ments ; they still, however, exhibit, especially in the interior, immature
forms of connective tissue.

All the larger nerves contain vessels, although not in great number ;
they run principally in a longitudinal direction, and form a loose plexus
of minute capillaries of 0-002-0-004 of a line, with elongated inter-
stices, which invests the fasciculus, and, in fact, penetrates between its
elements ; never, however, surrounding individual primitive fibres, but
only entire divisions of them. The ganglia contain a delicate capillary
plexus, in the form of a network, so that each nerve-cell is surrounded
by special vessels. The Pacinian bodies also contain vessels, which
even penetrate as far as the central cavity (Todd and Bowman, II. p.
397, Fig. 75, and p. 399, Fig. 76 ; Herbst, Tab. IV. Figs. 1 and 2).

On the subject of the condition of the cutaneous nerves of animals, I
•would here add a few remarks. In the skin of the tail of batrachian
larvae [Rana, Biifo, Triton, Bomhinator, Alytes), I have described the
very delicate ramifications and plexuses of the embryonic pale nerve-
fibres ; and moreover, quite evident loops of the fully formed dark nerve-
tubes, and isolated divisions of the latter ("Ann. des S. Nat.," 1846,
p. 102, pi. 6, 7). In the full-grown Frog, according to Czermtik (Mlill.
"Archiv," 1819, p. 252), the nerves destined to the skin, form, on its
inner aspect, a wide network, already described by Burdach, from which

Fig. ICO. — Transverse section of the ischiatic nerve, magnified 15 diam. : a, general
sheath of the nerve; b, neurilemma of the tertiary fasciculi; c, secondary nervous fasciculi,
in part with special sheaths. From the Calf

THE NERVOUS SYSTEM. 415

again numerous fasciculi arc given off, penetrate the derma perpendicu-
larly, and, having reached the superficial glandular layer of the skin,
form a superficial nervous-plexus between the glands. "With respect to
the true termination of the nerve-fibres, Czerraiik arrived at no definite
results, but made the interesting discovery that thick and thin nerve-
fibres of the deeper plexus divide dichotomously very frequently and
repeatedly, and thus spread themselves over larger surfaces; of Avhich
divisions I have most fully satisfied myself from preparations furnished
by Czermtik. Similar conditions were found by Leydig (" Zeitsch. f.
wissen. ZooL," III.) in the skin of Fishes; where also exist superficial
and deeper plexuses, with numerous divisions of finer and thicker tubes,
all of which on the surface ultimately become quite fine, pale, and finally
invisible. In the Invertebrata, as appears from Leydig's researches in
Argulus, and especially in Carinaria, conditions are met with perfectly
analogous to those described by me in the nerves of the Tadpole ; and I
cannot agree with Leydig, when he describes the nucleated enlarge-
ments as nerve-cells. On the other hand, the conditions observed in
Arteviia and Corcthra are perhaps, peculiar, because in these instances
larger branches of the cutaneous nerves are, at their extremities, in con-
nection with numerous roundish vesicles, which might have the function
of nerve-cells (" Zeitsch. f. wiss. Zool.," vol. I. iii.).

In the integuments of the Mammalia and of Man, except in the Paci-
nian bodies, until a short time since, no one had seen anything of divi-
sions in the nerve-tubes ; all observers rather agreeing that terminal
loops existed there, especially in the papillse. But it now appears, from
the researches of myself, J. N. Czermak, and C. Gegenbaur, that pro-
bably loops and divisions, and occasionally even free terminations, all
exist in that situation. That in Man, terminal loops occur in the
papillae, and divisions in the terminal plexuses, I have already men-
tioned ; the latter are especially well shown in the conjunctiva scleroticce,
where free terminations also appear to exist, and where peculiar convo-
lutions of nerves (nerven-knauel), similar to those formerly described by
Gerber* [vide " Micr. Anat.," II. i. p. 31, Fig. 13 A, 3), present them-
selves. Czermdk, moreover, observed divisions of the cutaneous nerves
in the Mouse, and I myself a transition of the dark-bordered nerves into
pale anastomosing filaments, of O-OOl-O'OOOo of a line, exactly resem-
bling the embryonic fibres in the Tadpole (" Micr. Anat.," II. i. p. 24) ;
lastly, Gegenbaur has noticed numerous divisions in the expansion of the
nerves of the tactile hairs in the Mammalia. Further experience will
have to show in what relative proportions the loops, divisions, and free
terminations, stand with respect to each other, and whether in the diffe-
rent Mammalia, notwithstanding any apparent difference, some corre-
spondence obtains or not.

* ["General Anatomy," translated by G. Gulliver, p. 263, pi. 19, Figs. 99, 100.— Trs.]

416 SPECIAL HISTOLOGY.

§ 122. Cerebral Nerves. — The sensitive and motor nerves arising in
the brain, correspond in most particulars so closely with the spinal
nerves, that a short description of them will suffice ; and with respect
to the higher nerves of sense, they Avill be afterwards described, more
fully, in connection with the organs to which they belong.

The motor cerebral nerves, the third, fourth, sixth, seventh, and
twelfth pairs, with respect both to their roots and to their course and
distribution, present exactly the same conditions as the motor roots and
muscular branches of the spinal nerves, with the sole exception, that by
all these nerves, from their anastomosing with sensitive nerves, some
sensitive fibres are conveyed to the muscles. It deserves remark : 1,
that according to Rosenthal and Purkinje, nerve-cells exist in the trunk
of the oculo-motorius in the Ox, which, however. Bidder (p. 32) was
unable to find ; 2, that the facial nerve, in its gangliform enlargement,
presents a number of larger nerve-cells, through which, however, accord-
ing to Reraak, only part of the fibres pass (Miill. " Archiv." 1841);
3, that according to Volkmann (in Bidder's " Ganglien-kcirper," p. 68),
the small root of the hypoglossal nerve in the Calf, which is furnished
with a ganglion, produces motor effects. What is the significance of
this occurrence of nerve-cells in motor nerves has not been ascertained.
Probably simple fibres having a peripheral destination arise from them,
exactly as in the spinal ganglia. In any case it shows that ganglia are
not necessarily placed only on sensitive nerves. The fifth, ninth, and
tenth pairs, resemble the spinal nerves, inasmuch as that they all con-
tain motor and sensitive elements. In the trigeminus the small root
exhibits a preponderance of thick fibres; the larger, numerous fine
fibres. The Gasserian ganglion, as well as the smaller ganglionic body
seated upon it, contains many larger and smaller nerve-cells of O'OOS-
0-030 of a line, with nucleated sheaths, and presents the same conditions,
according to my observations, in small Mammalia and in Man, as a spi-
nal ganglion, that is to say, it is simply traversed by the fibres of the
greater root, and, from unipolar cells, gives origin to numerous nerve-
fibres of medium size, which go to join the emergent branches. Bipolar
cells also occur, but, as it appears, in less quantity, and anything that
can be said about apolar cells is as applicable here as in the case of the
spinal ganglia. The ultimate distribution of the n. trigeminus is for the
most part similar to that of the cutaneous nerves, and, in particular, the
existence of divisions of the nerve-tubes may be distinctly demonstrated
in the mucous membranes, as in the conjunctiva at the edge of the cor-
nea, in the ciliary ligament, in the tooth-pulp, and in the papillae of the
tongue. Terminal loops and free terminations appear to exist in the
papillffi of the mucous membrane of the mouth and tongue, and in the
conjunctiva, whilst in the cornea, the extremities of the nerves are quite

THE NERVOUS SYSTEM. 417

trnnsparent and pale, and constitute a wide-mesbed plexus without any
divisions. "With respect to the ganglia, which are placed on the n.
trigeminus [ganglion ciliarc, otieum, sphenopalatinum, linguale, supra-
maxiUai'c), I find their structure more to resemble that of the sympa-
thetic ganglia, only that they contain a considerable number of larger
nerve-cells. The glossopJiar^ngeus, although endowed with. motor pro-
perties, still, according to Volkmann (Miill. " Arch.," 1840, p. 488),
has no fibres which do not pass through one or other of its ganglia. In
its roots, which contain numerous fine fibres, there are, according to
Bidder (1. c. p. 30), in the Mammalia, not unfrequently, isolated nerve-
cells, often placed free upon it, in which, as in similar cells, on the roots
of the n. vagus, the giving off of two middle-sized fibres, it is said, may
occasionally be readily perceived. The gaugVia. o^ the glossophargngeus
present the same conditions as the spinal ganglia, that is to say, the
radical fibres simply traverse them, and, within the ganglion, fibres arise
from cells, which are for the most part unipolar ; its ultimate ramifica-
tion in the tympanic cavity and in the tongue, contains small ganglia,
and otherwise corresponds with that of the w. trigeminus {p. major). In
Man, all the roots of the n. vagus enter the jugular ganglion, whilst in
some of the Mammalia — Dog, Cat, Rabbit, according to Remak (in Fro-
riep's "Not.," 1837, No. 54), in the Dog and Sheep, according to Volk-
mann (Miiller's "Arch.," 1840, p. 491), but not in the Calf, in which
nerve-cells occur in the apparently motor root, it has also a primary
fasciculus, which has no connection with the ganglion. In the ganglion
jugulare and in the intumeseentia ganglioformis of the facial nerve, I
have not been able to find anything different from the spinal ganglia,
only, that the nerve-cells measure occasionally no more than 0*009 of a
line, although it is true that there are also a great many as large as 0*03
of a line. The ultimate distribution of the nerve exhibits, as Bidder
and Volkmann correctly state, a constant kind of separation of thicker
and more slender fibres, so that the branches to the oesophagus, heart,
and stomach, are composed almost entirely of fine fibres, whilst in those
going to the lungs, and in the laryyigeus superior, the fine are to the
thick fibres as 2 to 1 ; and in the laryngeus inferior and the rami plia-
ryngei, as 1 to 6-10. All these fine fibres are very far from being
derived from the sympathetic, as they occur in preponderating quantity
even in the roots of the vagus, and are also numerous in the laryngeus
superior. Many of them, moreover, may be nothing more than attenu-
ated or originally finer ganglion-fibres, as they are termed, arising in the
ganglia of the vagus itself, and which likewise I should not refer to the
sympathetic. With respect to the terminations of the vagus, reference
must be made below to the proper places. The n. accessorius Willisii,
although perhaps also in part sensitive, has no nerve-cells, and in its

27

418 SPECIAL HISTOLOGY.

distribution and termination, so far as is known, presents nothing
peculiar.

Terminal loops within the trunks of nerves had been already noticed
by Gerber, and have lately been described by Valentin in the vagus
(pectoral portion) of the Mouse and Shrew-mouse, but without their
expressing any opinion with respect to their signification. Still more
mysterious are the nervous filaments seen by Remak and Bochdalek,
coming out from, and again re-entering the brain.

§ 123. Ganglionic Nerves. — Under this name, perhaps, is most
suitably designated the n. sym'pathicus, as it is termed, — the sympa-
thetic or vegetative nervous system, — as it presupposes no physiological
hypothesis, but simply expresses the fact, which, anatomically, is most
apparent to the eye. The ganglionic nerves are neither a wholly inde-
pendent part of the nervous system (Reil, Bichat), nor a mere section of
the cerebro-spinal nerves ; but on the one hand, from the very numerous
fine nerve-fibres originating in their ganglia — ganglio7i-fibres of the sym-
pathetic,— form an independent system ; whilst on the other, they are
also connected with the spinal cord and brain, owing to their receiving a
smaller number of fibres of the other nerves. Upon comparing the
ganglionic nerves with the cerebro-spinal, we find, that the former, as
they are constituted from a double source, in a certain respect undoubt-
edly resemble the latter, which are also formed from ganglionic fibres of
the spinal ganglia, and from others proceeding from the cord ; but they
difi"er, particularly in this respect, that they possess a much greater
number of independent elements, of ganglia and ganglionic fibres, and
enter into much more numerous anastomoses with each other. Conse-
quently, although we appear to be justified from an anatomical point of
view, in considering the ganglionic nerves by themselves, still they must
not be regarded as something altogether peculiar, seeing that, essentially,
every nerve exhibits the same principal elements, and some cerebral
nerves, vagus, glossopharyngeus, possess even numerous peripheral
ganglia ; and moreover, because comparative Anatomy shows that they
are produced from the spinal nerves, and Physiology the absence of
peculiar functions in them.

§ 124. The principal trunk of the ganglionic nerves [nervus sympa-
thicus). The n. sympathicus in man appears as a whitish, or white
nerve, the dark-bordered fibres of which usually run parallel with each
other, without divisions or anastomoses, some measuring 0-0025-0-006
of a line or even more, and others not more than 0-0012-0-0025 of a

THE NERVOUS SYSTEM.

419

line. Tliese finer and coarser fibres are partially intermixed, partly

Fig. 161.

Fig. 162.

_--_fZ

disposed more in a fascicular manner, the

latter being the case near the ganglia of

the main trunk and in that part itself.

The structure of the ganglia is, in the

main, similar to that of the spinal ganglia.

Each of them consists : 1, of perforating

nerve-fibres, proceeding from one part of

^^^ , ■:? the trunk to the other; 2, of a certain

1^. '■*^-~-^^' . number of finer tubules originating in the

I ganglion ; and 3, of numerous nerve-cells;

^l|,;|iri'vl besides these the rami commwiicantes

also enter the ganglia, and a certain num-
ber of peripheral branches are given off" from it. The nerve-cells in the
sympathetic (Fig. 162 E), present, in all essential particulars, precisely
the same conditions as those in the spinal ganglia, only that they are,
on an average, smaller, measuring 0-006-0-018, 0-008-0-01 of a line
in the mean, with less and paler pigment, or even colorless and usually
pretty uniformly rounded. As respects the origin of the nerve-fibres of
the main trunk, it is, in the first place, evident, that they are in great
part derived from the rami communicantes -which arise immediately
below the spinal ganglia from the trunks of the spinal nerves ; that they
are in general formed like the sensitive roots of those nerves (that is,
contain a preponderance of finer fibres), and, whether simple or com-
pound, that they are manifestly connected with both roots. From all
that has hitherto been made out, the fibres of these connecting branches
are derived chiefly from the spinal cord and from the spinal ganglia,

Fig. 161. — Sixth thoracic ganglion, on the left side, of the sympathetic nerve of the Rabbit,
viewed from behind, treated with soda, and magnified 40 diam. : T. 2, trunk of the sympa-
thetic; R. c. R. c, rami communicantes, each dividing into two branches; Spl.,n. splancknictia ;
S, twigs of the ganglion with two stronger fibres and finer filaments, probably going to
vessels; G, nerve-cells, and ganglion-fibres joining the main trunk.

Fig. 1G2. — From the sympathetic in Man, magnified 350 diam. : J, a portion of a graynerve
treated with acetic acid ; a, fine nerve-tubes : b, nuclei of the fibres of Remak. B, Three
nerve-cells, one with a pale process.

420 SPECIAL HISTOLOGY.

and are consequently roots of the symfathetic ; in a smaller proportion,
however, they might be derived from the sympathetic, and joining them-
selves to the spinal 'nerves are further distributed peripherally together
"with them. Having entered the main trunk of the sympathetic, the
rami commumcantes, so far as they are derived from the spinal nerves,
almost invariably run, dividing into two or several branches upwards
and downwards in it, towards its cephalic and pelvic extremities, being
in apposition with the longitudinal fibres of the trunk. In the Rabbit,
the fibres of a given ramus eommunicans may very frequently be traced
as far as the nearest ganglion and beyond it, in separate peripheral
branches, but, in general, the course of the individual fasciculi very
soon escapes the eye. It may nevertheless be asserted with great cer-
tainty, that they all gradually go off in the peripheral branches of the
main trunk, for in the first place all these branches frequently contain,
in considerable quantity, the same dark -bordered thicker fibres, as those
which are contained in the rami communicant es, and secondly their ter-
mination or origin is never observed in the main trunk itself; which
circumstance is also the principal reason why the rami communicantes
can be regarded not as branches of the sympathetic, but only as its
roots.

Besides the fine and coarser fibres of the rami communicantes^ the
main trunk of the sympathetic contains other fibres in very great
numbers, which are dark-bordered, but pale, finest nerve-tubes measur-
ing 0-0012-0-002 of a line, with respect to which I unhesitatingly assert,
that they originate in it, and are in no way continuations of the rami
communicantes, as has been quite recently supposed, since the discovery
of the bipolar ganglion-cells in Fishes. In the Mammalia it is, in fact,
extremely easy to prove, by the examination of entire sympathetic
ganglia under the careful application of dilute soda and compression,
that the great majority of the fibres of the rami communicantes have
not the slightest connection with the ganglion-cells, but much rather
that they simply pass through the ganglia, and ultimately go off in the
peripheral branches. Now, as, besides these fibres in the main trunk,
numerous other fibres of the finest kind exist, which can in no way be
assigned to the rami communicantes, it is clear, that they must be struc-
tures of entirely new formation. This conclusion appears to be the
more legitimate, when it is added, that it is not, as I first and many
since have shown, by any means so difficult to demonstrate simple
origins of fibres in the sympathetic ganglia of the Mammalia and
Amphibia, and that, in the ganglia a considerable portion of fine fibres
assume the aspect of so-called convoluted fibres, that is to say, of fibres
"winding about in various directions through the mass of cells. From
what I have seen in the Mammalia and man, the sympathetic ganglia
correspond so far with those of the spinal nerves, that they contain a

THE NERVOUS SYSTEM. 421

prepontlerance of unipolar, rarely of bipolar cells, differing, however, in
this respect, that apolar cells certainly exist in them in more consider-
able quantity, and the ganglion fibres arising in them are invariably of
the finest kind, occurring in the peripheral nerves, and probably in most
cases, quit the ganglia in various directions. As for a topographical
tracing of the various fibres in the main trunk of the sympathetic, with
reference to their origin from particular rami communicantes and
ganglia, and their continuation into particular peripheral branches, —
if more be required than what has already been stated — it is not by any
means at present to be thought of, but must be reserved for future in-
vestigation.

It has been asserted, that the smaller cells in the ganglia of the
sympathetic are different from the larger cells in the spinal ganglia, for
instance ; and also that they are connected only with fine nerve-tubes
(Robin), but this is not correct, as is apparent in part from the observa-
tions of Wagner and Stannius ; for we find: 1, in the ganglia of the
cerebral and spinal nerves of the Mammalia and of man, all intermediate
sizes between larger and smaller nerve-cells, and also, occasionally,
though rarely, larger cells, measuring as much as 0"03 of a line in the
sympathetic ganglia ; and we may also be convinced, 2, that the diame-
ter of the nerve-fibres originating in the first-named ganglia, is not at
all regulated by that of the cells, all their ganglion-fibres being pretty
nearly of the same size, and which is confirmed also by the bipolar cells
of Fishes, where the one fibre arising from the cell is often considerably
thicker than the other ; in Petromyzon, according to Stannius, even
six times. Should it be at all supposed that the small cells are peculiar
to the sympathetic nerve alone, I must, as above, with respect to the
nerve-fibres, remark, that not to mention the ganglia of the roots of the
cerebral and spinal nerves, small nerve-cells also occur in situations
■where there can be no question about the sympathetic, as in the spinal
cord and brain, and, — if instances of the same kind in the peripheral
nerves be desired — in the retina and cocJdea. At all events, this much is
certain, that the ganglia of the ganglionic system of nerves constantly
present smaller nerve-cells, and that the fibres arising from them are
of the fine kind only.

Bidder and Volkmann have shown, in the Frog, that the greater part
of the fibres of the rami communicantes are distributed peripherally,
with the spinal nerves, and that only a small portion of them, which
moreover are derived from the spinal ganglia, should be regarded as
roots of the sympathetic. But I think I have noticed in the Rabbit
and in Man, that the rami communicantes have chiefly a central des-
tination. Still, in man, fibres also occur very frequently — according to
Luschka always, — which must be regarded as branches of the sympa-

422 SPECIAL HISTOLOGY.

thetic going to the peripheral distribution of the spinal nerves, from
which again twigs are given off to nerves of the vertebrae ; with respect
to which conditions the more detailed observations given in my " Mikr.
Anat.," II. p. 525, and particularly those of Luschka (" Nerven des
Wirbelcanals," p. 10 et seq.) may be consulted. With regard to the
question, whence the fibres are derived which join the main trunk of
the sympathetic from the spinal nerves, it is certain that that portion of
the rami communicantes, Avhich arises from the motor root, and which,
according to Luschka, is always a white filament, takes its origin from
the cord (or brain) itself, but as regards the other, proceeding from the
sensitive root, it may be formed, in part or wholly, from fibres origi-
nating in the ganglion. The latter, however, appears to be improbable,
for two reasons : 1, because in that case, the existence of conscious
sensations from parts supplied by the sympathetic would scarcely be
conceivable ; and 2, because the fibres originating in the spinal ganglia
are of medium size, whilst, in the rami communicantes, upon the whole,
only a few of that kind occur, and these, moreover, must be referred to
the motor root.

We may here offer a few remarks upon the Jlne fibres of the gan-
glionic nerves. It has been long known, that the sympathetic contains
a larger proportion of finer nerve-fibres than the cerebro-spinal nerves,
but it was not till 1842 that Bidder and Volkmann labored to show,
that these fibres are not only smaller, but also, in other respects, ana-
tomically different ; on which account in contradistinction to the thick
fibres of the cerebro-spinal nerves, they termed them sym'pathetic nerve-
fibres. In opposition to this, Valentin (" Rep.," 1843, p. 103) and I
(" Sympath.," p. 10 et seq.) have endeavored to prove, that the fine
fibres in the sympathetic do not constitute a special class, and in this I
think we were tolerably successful. The principal reasons are as fol-
lows : 1. Fine and thick nerve-fibres do not differ intrinsically in any
essential respect except in size, and present the most numerous interme-
diate dimensions. 2. Fine nerve-fibres having exactly the same charac-
ters as those of the so-termed sympathetic exist in many other situations,
as for instance, — in Man and the Mammalia, — in the posterior roots of
the spinal nerves and of the sensitive cerebral nerves, in which situations,
as I have already shown, there can be no question whatever as to a
derivation of the fibres from the sympathetic, and where we have pre-
sented to us, nothing but fine cerebro-spinal fibres; similar fibres are
contained by thousands in the spinal cord and brain, as well as in the
two higher nerves of sense. 3. All thick nerve-fibres decrease in size
in their ultimate ramifications, owing to divisions, or direct diminution,
so that ultimately they acquire the diameter and nature of the fine,
and finest kinds of fibres. 4. All thick nerve-fibres in the course of
their development are, at one time, exactly in the condition of the so-

THE NERVOUS SYSTEM. 423

termed sympathetic fibres. From these facts it would appear certainly
evident, that it is impossible to regard the fine fibres of the sympathetic
as altogether of a special nature, and peculiar to it alone, and that it
will not do, in the anatomical point of view, to classify the fibres accord-
ing to their size, very many in fact, in their course, assuming all possi-
ble degrees of thickness. Allowing that the great number of very fine
pale fibres in the sympathetic is a prominent anatomical fact, as is also
indeed the case in the higher nerves of sense and in the gray substance,
still, speaking physiologically, I am by no means of opinion that the
fineness of the fibres in the sympathetic indicates anything of a special
nature in them, and which does not exist elsewhere, but perhaps, that
where this condition does exist both in them and in other situations, it
is connected with a distinct kind of function.

§ 125. Peripheral distributmi of the ganglionic Nerves. — From the
main trunk of the sympathetic arise the branches proceeding to the
periphery, which without exception, receive finer and thick fibres from
it, but besides these, in part at least, contain other special elements, to
which is due their varied aspect. Some of them, for instance, are
white, as is the main trunk in most situations, such are the n. splanch-
nici ; others grayish white, as the nervi intestinales, the nerves of the
unimpregnated uterus (Remak, " Darmnerven System," p. 30); others
again gray, and at the same time less firm to the feel, as the w. caroti-
cus, internifs, the nn. carotid externi s. violles, the nn. cardiaci, the
vascular branches in general, the branches connecting the large ganglia
and plexuses in the abdomen, those which enter the glands, and the
pelvic plexuses. The peculiar condition of the latter nerves depends,
in part, upon the paler color of the fine fibres of the sympathetic itself,
but in great measure upon the presence of the fibres, named after their
discoverer, the fibres of Remak ("gelatinous fibres " of Henle), which
were at first regarded as a kind of nerve-tubes, and of which, even now,
some cannot be convinced that they are only a sort of connective tissue.
They are sometimes more readily isolated, sometimes more united into
a compact substance resembling homogeneous connective tissue. In the
former case they present the aspect of flat, pale fibres, 0-0015-0-0025
of a line broad, and 0-0006 of a line thick, of an indistinctly striated,
granular, or more homogeneous substance ; and which, under the action
of dilute organic acids, exhibit precisely the same conditions as connec-
tive tissue, and from point to point are furnished with, mostly elongated,
or fusiform nuclei, 0-003-0-007 of a line long, 0-002-0-003 of a line
broad. These fibres, again, are found in almost all the gray portions
of the ganglionic nerves — I cannot find them in many parts of the
pelvic plexuses in Man, where they are replaced by a non-nucleated
abundant connective tissue, though they are said by Remak to abound

424 SPECIAL HISTOLOGY.

in the nerves of the impregnated uterus (" Darmnervensjst.," p. 30)
in very great quantity, so that they amount to from three to ten times
the number of the dark-bordered true nerve-fibres. Thev constitute
the main part of the proper basis of these trunks, and the dark-bor-
dered tubes extend through them, sometimes more isolated, sometimes
assembled in larger or smaller fasciculi ; more rarely, and only in the
neighborhood of the ganglia themselves, do they appear to form sheaths
to individual tubes of the finest kind. Besides these " fibres of Remak,"
the peripheral ramifications of the sympathetic are, above all, distin-
guished by a great number of ganglia. These bodies, of a larger or less
size, some even microscopic, are placed on the branches or terminations,
and, indeed, the microscopic ganglia, so far as is hitherto known, on the
nervi carotid, in the pharyngeal plexus, in the heart, at the root of the
lungs and in the lungs, on the suprarenal capsules, in the lymphatic
glands, in the kidneys of Man occasionally, on the posterior wall of the
bladder, in the muscular substance of the neck of the uterus in the
Sow, in the plexus cavernosi, and with respect to their distribution, will
be further adverted to when we come to speak of the viscera. I will
here remark in general^ concerning them that with respect to the size
and figure of the nerve-cells, and the origination of fine fibres, they
present precisely the same conditions as the ganglia of the main trunk.
As regards the last point, it may be especially noticed, that in one situa-
tion the origin of nerve-fibres from unipolar cells, and the rarity of the
double origin of fibres, is particularly well displayed, viz. in the septum
of the heart in the Frog (Fig. 163), where R. Wagner has also described
their occurrence. These gano-lia, therefore, are also
sources of nerve-fibres, and the emergent branches
always contain more than the roots, on the supposition
that the fibres come out only in one direction, which
perhaps in most places may be the case. In the same
situation also, it is most readily and satisfactorily
seen that many of the cells are apolar and without
any processes (Fig. 163); as is also most plainly shown
in the cardiac ganglia and small ganglia, on the wall
of the urinary bladder in Bomhinator, in which ganglia, as well as in
the similar ganglia in the Frog, the conditions described are as manifest
as possible.

How the fibres arising from these various localities, from the rami
communicantes, the ganglia of the main trunk, and the peripheral gan-
glia, are disposed in their ultimate distribution, is as yet very doubtful.
Many peripheral branches anastomose with other, nerves, and thus escape
all further research, as the nn. carotid extcrni and internus, the latter
of which, containing scarcely anything but fine fibres and numerous

Fig. 163. — Nerve-cells from the cardiac ganglia of the Frog, magnified 350 diam.: one
with the origin of a nerve-tube.

THE NERVOUS SYSTEM. 425

"fibres of Rcmak," I do not look upon in the common sense as a root,
but as a branch, arising from the superior cervical ganglion, and pro-
bably the other cervical ganglia ; as well as the rami communicantcSj
seeing that individual fibres of them, actually join peripherally the
spinal nerves; and the rami cardiaci, pulmonales, &c. Other branches
in the parenchyma of the organs become so fine, that it is impossible to
trace them. What has been as yet established respecting their ultimate
course, is as follows : 1. Divisions occur in the branches and terminal
ramifications of the sympathetic, as in the nerves of the spleen, the
Pacinian bodies in the mesentery, in the nerves accompanying the
mesenteric vessels in the Frog, in those which exist temporarily in the
uterus of the Rodentia, of the lungs and stomach of the Frog and
Rabbit, of the dura mater on the meningeal arteries, in branches of the
sympathetic of the Sturgeon, in the cardiac nerves of the Amphibia,
and in those of the urinary bladder in the Rabbit and Mouse. 2. There
are free terminations of the nerves, as in the Pacinian bodies and on the
mesenteric vessels in the Frog. 3. The thicker fibres of the sympathetic
ultimateJy so decrease in size as to becoine of the fine kind; as may be
readily seen in the rami intestinales, lineales, and hepatici, which, indeed,
even in the interior of the organs in question, contain some coarser
nerve-fibres, but ultimately lose them. The actual terminations, how-
ever, in the organs themselves, in the heart, lungs, stomach, intestine,
kidneys, spleen, liver, uterus, &c., are as yet quite unknown ; although
from the impossibility of finding any dark-bordered fibres in the ultimate
ramifications of these nerves, it may be supposed that they terminate,
almost everywhere, in non-medullated, embryonic fibres. In fact, I
have, at all events hitherto, in vain endeavored to find a trace of them.
Schaffner says, that in the heart of Bombinator he has seen the passage
of the dark-bordered fibres into pale, anastomosing fibrils of the finest
kind, whilst Pappenheim (1. c.) describes loops in the nerves of the
kidney.

As regards the nature of the "fibres of Remak," most recent ob-
servers incline to the opinion first advanced by Valentin (" Report.,"
1838, p. 72; Muller's " Archiv," 1839, p. 107), that they are not nerve-
fibres at all, but to be referred to the connective tissue of the nerves ;
whilst Remak still thinks himself obliged to adhere to his previous
opinion, that they are, or may be, in part at least, nerve-fibres (" Darm.
nervensyst.," p. 30). As for myself, I freely acknowledge the force of
the reasons adduced by the latter observer, which are based chiefly upon
the similarity of the fibres in question to the pale embryonic nerve-
fibres, inasmuch as that even in the adult, nucleated nerve-fibres are met
with in the olfactory nerve ; but I am compelled, nevertheless, as before,
fully to concur with Valentin, as do also Bidder and Volkmann, and

426 SPECIAL HISTOLOGY. '

many others. My reasons are the following : 1. The " fibres of Remak,"
as may be easily shown, arise from the sheath of the nerve-cells of the
sympathetic ganglia, and are continued in the nervous trunks, surround-
ing the nerve-fibres arising from the ganglia. Now as it is certain that
these sheaths are a sort of connective tissue, as is apparent also from
the spinal ganglia, where they occur in precisely a similar way, only
more scantily and without their being continued into the nerves, it fol-
lows that the "fibres of Remak" can scarcely be anything else. 2. The
finest twigs of the spinal nerves also exhibit nucleated fibres, in all re-
spects like those of Remak, as for instance, those going to the skin, &c, ;
with respect to which, as they are wanting in the trunks of the nerves,
there can be no question at all of their not being nerve-fibres. 3. The
quantity of the "fibres of Remak" always diminishes towards the finest
ramifications, which could not be the case were they nerves. It is not,
indeed, altogether correct, as stated by Valentin, that they are not to be
found in the finer intestinal nerves, for there can be no doubt that they
do exist there, though much more rarely than in the trunks of the nerves,
and are only to be brought into view by compression. According to
Remak (Mull. "Arch.," 1844, p. 464), they also exist in the cardiac
nerves of the Mammalia ; although as far as I can perceive, only in the
immediate neighborhood of the ganglia. Relying upon these reasons,
I continue in the firm persuasion that the nucleated fibres in the sympa-
thetic nerve of adult Mammalia are a form of the neurilemma; but I will
not omit to remark, that I consider it quite impossible to determine, in
undeveloped nerves, what is neurilemma and what young nerve-fibres.
Thus in the Rabbit, 2-6 months old, in the n. caroticus internus, not a
single developed nerve-fibre is to be met with, and apparently nothing
but " fibres of Remak," although it is quite certain that together with
them, there must also exist the rudiments of numerous dark-bordered
fibres. In the nerves of the spleen, in the Calf, in like manner, nume-
rous nucleated fibres are met with, though in the terminations {vide
" Cyclopedia of Anatomy," III. p. 795, figs. 539 and 540), which, pro-
bably, afterwards become nerve-fibres. In young animals, consequently ,
tve must not look for a decision of the question; Avhilst in older ones, it is
quite otherwise. In them, a nucleated fibre can only he regarded as
a nerve when it can he traced into a dark-hordered fibre, or to a true
process of a nerve-cell ; and this, as we have seen, is not the case in
those of the sympathetic system. It may, however, be remarked, that
"fibres of Remak" also occur in the ganglia of the main sympathetic
trunk, but that they do not, for the most part, extend to any distance
beyond them, so that usually but few are contained in the trunk of the
nerve itself.

§ 126. Development of the elements of the Nervous System. — The

THE NERVOUS SYSTEM.

427

ncrve-cclls, wherever they may occur, arc nothing else than transforma-
tions of the so-called embryonic-cells; some of which simply enlarge,
whilst others throw out a varying number of processes, and are, at all
events in part, connected with nerve-fibres.

Many nerve-cells also appear, at a subsequent period, to increase by
division ; at all events, I do not know how otherwise to explain the fre-
quent occurrence of two nuclei in the nerve-cells of young animals,
especially in the ganglia ; and the cells connected by communicating
filaments, which have been noticed by various observers.

Fig. 164.

The peripheral nerve-jihres all originate on the spot, but their subse-
quent development proceeds in such a way that the central extremities
always precede the peripheral. With the exception of the extremi-
ties of the nerves, they are developed from fusiform nucleated cells,
which are nothing else than modifications of the primordial formative
cells of the embryo, and are conjoined into pale, flattened, elongated,
nucleated tubules or fibres 0-001-0-003 of a line, broad. Now, at first
the nerves consist only of fibres of this kind, and of the rudiment of
the neurilemma, being gray or dull white, like the sympathetic filaments ;
subsequently, in the human embryo at the fourth or fifth month, they
always assume a whiter color, and the proper white or medullary sub-
stance continues to be more and more developed in them. Of the three
possible modes of development of this substance propounded by Schwann,
one only, in the present state of things, can come into question, that
namely, as to whether the medullary sheath is a structure deposited
between the membrane and the contents of the embryonic nucleated
fibres; in which case the contents of the latter would become the axis-
fibre. But besides this, the medullary sheath may originate in what did

Fig. IGt. — Nerve-cell from a spinal ganglion of a sixteen weeks' human embryo: a, nucleus
in the pale process of the cell ; 2, self developing nerve-tubes from the brain of a two-months'
human embryo; 3, cells frotn the gray cerebral substance of the same embryo.

Fig. 165. — 1, two nerve-fibres from the ischiatic nerve of a sixteen- weeks' embryo; 2,
nerve-tubes from a newly-littered Rabbit; a, their sheath ; 6, nucleus; c, medullary sheath;
3, nerve-fibre from the tail of the Tadpole ; a, b, c, as before ; at d, the fibre retains its
embryonic character; the dark-bordered fibre shows a division.

428

SPECIAL HISTOLOGY.

Fiff. 166.

not occur to Schwann, viz., a chemical metamorphosis of the external
portion of the contents of the embryonic fibres ; and the axis-fibre may
be only the remainder of those contents which has not undergone a fatty
metamorphosis. It is difiicult to determine which of these two views is
correct. Direct observation shows only this much, that the contents of
the pale embryonic fibres invariably, by degrees, obtain dark contours,
and ultimately present the aspect of a true dark-bordered fibre, whilst
it teaches nothing Avith respect to the proper origin of the white sub-
stance. Since, however, it can be proved, that the fibres, whilst they
undergo this change, do not alter in size, the supposition I have expressed
would still appear the more correct.

The development of the terminations of the nerves, which appears

in some respects to present condi-
tions different from those exhibited
in the trunks, may, as I have
shown (" Annal. d. sc. nat.,"
1846, p. 102, tab. 6, 7), be readily
traced in the tails of the larvae of
the naked Amphibia (Fig. 165, 3;
Fig. 166). We there find, as is
mentioned by Schwann (p. 177),
the primary rudiments of the
nerves to be pale branched fibres,
measuring 0-001-0-002 of a line,
which here and there anastomose,
all finally terminating in free
fibrils of the finest kind, measur-
ing 0-0002-0-0004ofaline. There
is no difficulty in showing that
these fibres arise from the coa-
lescence of fusiform or stellate
cells, for, in the first place, such
cells may be seen, in part, still in
close apposition with, but inde-
pendent of them; in part more or
less connected by means of their
processes ; and, secondly, cell-nu-
clei occur at the divisions of the
fibres, which are there somewhat
dilated ; and, at all events, in
young larvae, with them are asso-

FiG. 1C)6. — Nerves from the tail of a Tadpole, magnified 350 diameters: 1, embryonic
nerve-fibres, in which more than one dark-bordered tube has become developed ; 2, similar
fibres containing but one lube, whicli in one fibre ceases at b ; 3, embryonic pale fibres j
4, fusiform cells connected together, and with a complete nerve-fibre.

THE NERVOUS SYSTEM. 429

ciated the well-known angular vitelline corpuscles, witli which at first,
all the cells of the embryo are filled. At first the number of pale
embryonic nerves is very small, and limited to a few short trunks closely
applied to the muscular structures in the tail ; but they are gradually
developed, in the direction from the centre towards the periphery, fur-
ther into the transparent portion of the tail, new cells being continually
added in connection with the existing trunks, whilst the latter them-
selves, almost in the same manner as the capillaries of these larvae,
unite directly by delicate offsets. When these fine ramifications — with
respect to the nervous nature of which no doubt can be entertained, as
it is evident that the larvae in which they exist already possess very
acute sensibility — are once formed, the followinsr further changes then
take place. Whilst the fibres gradually enlarge to twice or four times
their orginal diameter, there are by degrees developed in them, and in
fact from the trunk towards the branches, dark-bordered, fine primitive
fibres, which in no case owe their origin to newly added medullary
sheaths, but are certainly formed solely from a metamorphosis of a part
of the contents of the pale fibres. In connection with this, however,
the following conditions, which have not yet been observed in the higher
animals, are to be remarked: 1, where a pale embryonic fibre bifurcates,
there occasionally, though not always, also takes place a division of the
dark-bordered tube developed within it ; 2, the dark-bordered tubes
scarcely ever completely fill the pale fibres in which they are formed,
but a space, frequently of the same diameter as that of the tubes, is
most usually left between them and the membranes of the embryonic
fibres, in which space occasionally the nuclei of the primordial formative
cells may be perceived ; 3, in the trunks and main branches of the
embryonic fibres, several (2-4) dark-bordered tubules are undoubtedly
developed within one and the same embryonic fibre ; a very remarkable
condition, which shows that there are even dark-bordered fibres which do
not possess a structureless sheath {yid. note to § 110), and resembling
what exists in the muscular fasciculus, in which, in like manner, within a
single tubule, numerous finer elements are produced. As the tail of
the Tadpole is afterwards thrown off, it is to be regretted that its in-
teresting nerves cannot be traced to the same state of completion, as
can be done in those of other situations. It is obvious, however, in the
oldest Tadpoles, that the nerves are somewhat thicker than they are
originally, and that they extend towards the periphery sometimes in
loops, sometimes with free ends, but in such a way that the primary-
pale fibres continue to exist, and proceeding from the dark-bordered
fibres, constitute a very fine terminal nervous plexus, with anastomoses
and free ends.

I should not have delayed so long on the subject of the nerves in the

430 SPECIAL HISTOLOGY.

Tadpole, did not similar conditions most probably also obtain in many
other terminations of nerves. This is certain as regards those of the
electric organ of the Ray, which, even when developed, agree in many
respects with those of the more advanced Tadpole, and as Ecker has
lately shown (" Zeitsch. fur wissensch. Zoologie," 1849, p. 38), are de-
veloped in precisely the same manner. The nerves, also, in the skin of
the Mouse {vid. note to § 121), evidently belong to the same category ;
and consequently it may hereafter be shown, that wherever peripheral
divisions of nerves occur, their development proceeds essentially as it is
here described.

With respect to the development of the nerve-filres in the central
organs, we possess but few researches. Of the fibres in the ganglia, I
can only observe, that they are developed subsequently to those of the
nerves, and probably from smaller fusiform cells, which may be noticed
in association with the nerve-cells. On one occasion, in a spinal gan-
glion of a four months' human embryo, I noticed a cell of this kind in
connection with the process of a nerve-cell (Fig. 164). The formation of
the fibres in the cord and brain is extremely difficult of investigation,
and is best studied with the aid of chromic acid. In the human embryo,
I find, as early as the end of the second month, the commencement of
the formation of the tubules in question, the white substance being dis-
tinctly finely striated, and manifestly containing, in places, very delicate
fusiform cells, which are sometimes independent or isolated, sometimes
connected, two or three, or several together (Fig. 164). All these cells
are at first pale, investing the nucleus, which measures 0*002-0*003 of a
line quite closely, and having processes almost as fine as the fibrils of
connective tissue. In the fourth month, when the two kinds of sub-
stance are quite distinct, nuclei are still occasionally to be seen in the
now wider fibres, but in some they have disappeared, although the fibres
are without dark contours ; which are not developed before the middle
period of foetal life (in the foetal Calf, when more than 12 inches long,
according to Valentin), and, indeed, first in the spinal cord.

As regards the subsequent changes in the nerve-fibres, it has already
been remarked, that they occasionally increase very considerably in
thickness. According to Harting (1. c, p. 75), the fibres of the median
nerve which have not yet acquired dark contours, measure in a four
months' human embryo, on the average 3*4'"'", in a new-born child
10"4™'", in the adult 166"'™. The increased thickness of the nerves
themselves appears, according to Harting, from the fourth month
onwards, to depend solely upon the enlargement of the already existing
elements, the foetus and new-born child already possessing the same
number of primitive-fibres as the adult.

It remains to be observed, that extremely hxf patJiological changes of

THE NERVOUS SYSTEM. 431

the nervous elements are known. In the nerve-cells of the brain, the
deposition of pigmentary matter becomes excessive, particularly in old
age ; and fatty deposition also takes place (Virchow, " Archiv," I. 1).
Valentin thinks that ho has observed a regeneration of nerve-cells in the
superior cervical ganglion of the Rabbit. Nerve-fibres are readily de-
stroyed, as in consequence of extravasation of blood, tumors, softening,
fibroid growths, &c., in which cases the medullary substance breaks up
into larger or smaller, coagulated or fluid masses, of very various con-
figuration, whilst the axis-fibres seem to disappea,r. In atropliied nerves,
the fibres are observed to be thinner, easily broken up, and, instead of
the medullary matter, are frequently, in parts, entirely occupied by
minute fatty molecules, as was seen on one occasion by Virchow, in a
human optic nerve, and by myself in the nerves of a Frog. Nerves
that have been cut across, readily unite ; portions of peripheral nerves
from 8-12 lines even are restored by true nervous tissue (Bidder, 1. c,
p. 65; Valentin " c?e funct. nei'v.," p. 159, § 323; and '■'• Phys.^'" 2
Aufl. I. 2, 716). Should the union of a divided nerve not take place,
the peripheral end undergoes a gradual change in a particular way,
■with a simultaneous extinction of the nervous activity. The nerve-
fibres generally become yellowish, soft, lacerable, and lose their trans-
versely banded and glistening aspect. They no longer present any
trace of a double contour, their medullary substance is wholly coagu-
lated, and their breadth frequently very various (Stannius in Mlill.
"Arch.," 1847, p. 452). Whether the axis-fibres undergo change, we
are, unfortunately, not informed. According to Brown-Sequard, incised
"wounds, even of the spinal cord, in the Rabbit, united. Hypertropldes
of the nerve-substance itself are unknown, although probably such a
condition occurs in the neurilemma. Virchow noticed a new formation
of fine nerves in pleuritic and peritoneal adhesions, and, according to
the same observer, it would appear that gray nerve-substance may be
formed on the walls of the cerebral ventricles.

§ 127. With respect to the functions of the nervous system, the follow-
ing remarks, which are immediately pertinent to the anatomical facts, may
sufiice. As regards the two elementary portions of the nervous system,
anatomical investigation shows, that all its divisions, -which preside over
the higher functions, contain gray substance in greater or less quantity,
as in the sympathetic, the ganglia of the spinal and cerebral nerves,
and in the spinal cord and brain ; whilst the nerves which act only as a
conducting apparatus, contain nothing but nerve-fibres. This being
admitted to be the attribute of the gray substance, it may further be
inquired whether it presents differences in its structure, as it does in its
functions. With respect to this I would remark as follows : the largest
nerve-cells are met with in situations from which motory effects proceed,

432 SPECIAL HISTOLOGY.

as in the anterior horns of the spinal cord, amongst the fibres of the
anterior roots, in the medulla oblongata, at the points of origin of the
motor cerebral nerves, in the cortical substance of the cerebellum, the
23ons Va7'olii and crura cerebri; whilst the smallest cells are found in the
sensitive regions, as in the posterior horns of the spinal cord, the corpora
restiformia, and quadrigemina. There does not, however, appear to be
any constant relation between the size of the cells and the existence of
sensitive or motor functions, for, in the ganglia of the cerebro-spinal
nerves and of the sympathetic, and in the optic thalami, both sorts of
fibres arise, in one place, from small, and in another from large cells.
It seems, therefore, as in the case of the nerve-fibres, that there are large
and small motor cells, as well as sensitive cells of various dimensions, a
fact which is confirmed by comparative anatomy, as the large bipolar
cells in Fishes are manifestly sensitive. No essential difference can be
pointed out between sensitive and motor cells, whether the latter be of
uniform or of difi'erent size, and in particular the variations existing
between such cells are not greater than those between the motor cells in
different localities. Even the cells in the cortical substance of the brain,
to which physiologists assign the mental manifestations, with our present
means of research, exhibit no perceptible peculiarities. The nerve-cells,
however, may be divided into those which are in direct connection with
nerve-fibres, and those which are not thus connected, but independent.
The former, of course, are to be especially regarded as sensitive and
motor ; with respect to the latter, anatomy to some extent affords no
information, inasmuch as, that they present no processes, as in the sym-
pathetic ganglia, and in some situations in the brain ; as regards those
furnished with processes, particularly the many-rayed cells, which in
many situations undoubtedly are not prolonged into nerve-fibres, it
might be considered certain that they, — both larger and smaller, by
means of their processes which fulfil the functions of nerves, and whether
the latter anastomose or not, — bring different regions of the central
organs into mutual connection, and participate in the reflex phenomena,
the sympathies, and other modes of association of the functions. Cells
of this kind exist in the spinal cord and brain everywhere in very large
quantity, but not in the ganglia, although it is not, from this, intended
to imply that no reflex actions are performed in those bodies.

Respecting the nerve-fibres, anatomy is not in a condition to point out
any difference in them, between the sensitive and motor nerves ; a cir-
cumstance, however, which, physiologically, can afford no reason to
ascribe identical functions to them. As regards the various sizes of the
nerve-fibres, the numerous changes in diameter, undergone in their
course by all the cerebro-spinal nerves, very obviously indicate that
these proportions have no relation to the functions of the fibres in gene-
ral. Nevertheless, I do not look upon these relations of size as alto-

THE NERVOUS SYSTEM. 433

gotlicr of little consequence, and in particular does the attenuation of the
fibres, where they extend through gray substance [vid. sup., § 112),
appear to me to be important, as also their diminution at their origins
and terminations. It is, however, difficult to perceive the physiological
import of these facts. Were it the case, that in the nerve-fibres the axis-
cylinder alone was the conducting, and the medullary-sheath, an insu-
lating substance, and could it be proved that the medullary sheaths were
wanting in the attenuated portions, the peculiar activity of the nerve-
fibres in these situations (the transverse conduction in the spinal cord,
the acuteness of sensibility at the terminations, &c.) would be satisfac-
torily explained. It is well known that such a notion has already been
entertained by various writers, and its conception has usually proceeded
upon the idea that a close alliance or identity exists between electricity
and the nervous force, and the medullary sheath abounding in fatty
matter, has from this point of view been regarded as an insulator. But
(1) it is anything but demonstrated, that the nerves possess no other
active force but electricity ; and (2) there is nothing to indicate an
absence of the medullary sheath, and a free condition of the axis-fibres
in many peripheral extremities of the nerves (skin, muscles), and in
those portions of the central organs (spinal cord) in which a transverse
conduction is evident. The question always remains, whether the medul-
lary sheath, although not altogether, yet at all events partially, may not
insulate more or less, according to its thickness. Since, however, this
membrane is wanting not only in many terminations of nerves, where an
insulated conducting faculty might not be required, but also in other
situations, as in the Invertebrata and the nerves of Petromyzon gene-
rally, as well as in the processes of the nerve-cells which certainly act as
nerves, in the central organs of the higher animals, and in the finest
nerve-fibres in those situations (brain), the notion that such is its effect
in the dark-borderved nerves loses all ground of support. It would
seem to me, that the medullary sheath represents nothing more than a
protective soft envelope for the tender central fibre. This mode of expla-
nation also, renders it intelligible, why it is, that in dark-bordered
nerves, where the medullary sheath is thin or wanting, and the central
fibre is in a more free condition, the nerve-fibres are more readily excited
and able to communicate their conditions ; and as regards the pale nerve-
fibres, in this case they would essentially have the same functions as the
others, and the absence of the medullary sheath in them could either be
explained on the supposition, that they are less readily excitable, as in
the invertebrate animals, and the Cijclostomata, or because they occur
in situations where a protective tunic to the nerve-fibres is no longer
required, as in the retina, in the nasal mucous membrane, in the gray-
substance, and in the electric organs, or even where its refractive power
upon light would be prejudicial to a certain object, as in the cornea. A

28

434 SPECIAL HISTOLOGY.

similar mechanical function appears to me to be performed by tlie fine
granular substance, which in the higher central organs is found in so
many situations supporting the most delicate nerve-fibres, cells, and
processes.

With respect to the methods to be employed in investiyations of the
nervous system, the principal have been noticed in the preceding sec-
tions. I will, here, once more advert to the importance of preparations
made with chromic acid in the investigation of the course of the fibres,
and in the examination of the central nerve-cells ; and direct attention
to the dilute solution of caustic soda for the detecting of nerve-fibres in
non-transparent tissues, — without which two means very many points
would remain in the dark. In this way also the extreme proneness to
become changed, of the gray and white substances, and particularly the
ready disruption of the processes of the nerve-cells, and the varicosity,
coagulation, and destruction of the nerve-fibres, are at once removed or
avoided. The brain and spinal cord, as well as the elements of the
ganglia, are best studied in the human subject, but the course of the
fibres in them, and, above all, the terminations of the nerves, are best
investigated in the smaller Mammalia, and only in the second place in
Man. In the searching for the minute ganglia in the heart, Ludwig
recommends the treatment with phosphoric acid and the solution of iodine
in hydriodic acid, the latter so diluted that it has only a tinge of brown.
For the development of the nerves, the human and mammalian embryo
are quite suitable ; but the batrachian larvse, and if opportunity ofi'er,
the electric organs of the embryo Ray, in which the conditions are by
far the most clearly displayed, should not be overlooked.

Literature of the Nervous System. — C. G. Ehrenberg, " Beobachtung
einer bisher unbekannten Structur des Seelenorgans des Menschen"
(Observation of a hitherto unknown structure in the Human Brain),
Berlin, 1836; G. Valentin, in Mlill. "Archiv," 1839, p. 139, 1840, p.
218, in Valentin's " Repertorium," 1838, p. 77, 1840, p. 79, 1841, p.
96, 1843, p. 96, and: " Hirn- und Nervenlehre" (Treatise on the Brain
and Nerves), Leipzic, 1841 ; J. E. Purkinje, in the "Bericht liber die
Versammlung deutscher Naturforscher," in Prague, for the year 1837,
Prague, 1838, p. 177, and in Mlill. " Archiv," 1845, p. 281 ; R. Remak,
in Mull. "Archiv," 1841, p. 506, 1844, p. 461, " Ueb. ein selbstandiges
Darmnervensystem" (On an independent system of intestinal nerves),
Berlin, 1847; J. F. Rosenthal, '•'' De formatione granulosa in nervis
aliisque ijartihus organismi anijnalis," VratisL, 1839 ; A. W. Volk-
mann, in Mull. "Archiv," 1838, p. 274, and 1840, p. 510; Artie.
"Nervenphysiologie," in Wagner's " Handw. der Phys.," II.; F. H.
Bidder and A. W. Volkmann, " Die Selbstandigkeit des sympathischen
Nervensy stems durch anatomische Untersuchungen nachgewiesen" (The

THE NERVOUS SYSTEAI. 435

independence of tlie sympathetic Nervous System, proved by anatomical
Researches), Leipzic, 1842; Stilling and Wallach, " Untersuchungen
liber die Textur des Riickenmarks" (Researches on the Texture of the
Spinal Cord), Leipzig, 1842; Stilling, "Ueber die Medulla oblongata,''
Erlancren, 1843; "Researches on the Structure and Functions of the
Brain. I. On the Structure of the ijons Varolii" Jena, 1846 ; A.
Kijlliker, " Die Selbstandigkeit u. Abhiingigkeit des sympathischen Ner-
vensystems, durch anatomiscbe Untersuchungen bewiesen" (The inde-
pendence and dependence of the Sympathetic Nervous System, shown
by anatomical researches), Zurich, 1844 ; P. Savi, "Etudes anatomiques
sur le systeme nerveux de la Torpille," Paris, 1843. As an appendix
to Matteucci, "Traite des phdnomdues dlectro-physiques des animaux,"
Paris, 1844 ; R. Wagner, " Ueber d. innern Bau der electrischen Organe
im Zitterrochen" (On the intimate Structure of the Electric Organ in
the Ray), Gottingen, 1847. With a plate; "Sympathetic Nerve,"
"Structure of Ganglia," and "Terminations of Nerves," in Wagner's
" Handw. d. Physiol.," part III. p. 360 ; " Sympathetic Ganglia of the
Heart," ibid., p. 452; "Neurological Researches," in Getting. "Nach-
richt v. d. Univcrsit., &c.," Feb. 1851, No. 14; H. Stannius, "Das
peripherische Nervensystem der Fische" (Peripheral Nervous System of
Fish), Rostock, 1849. Moreover, in the " Archiv dlir phys.," Heilk.
1850, and in Gott. " Nachricht, &c.," 1850, Nos. 6-16, 1851, No. 17 ;
J. N. Czermak, " Ueber die Hautnerven der Frosche" (On the Cuta-
neous Nerves of the Frog), Mlill. "Archiv," 1849, p. 252; " Veraste-
lung der Primitivfasern des iV! aeusticus" (Ramifications of the primitive
Fibres of the Acoustic Nerve), in "Zeitscb. f. wissen. Zoologie," II.
1850, p. 105. [To these should be added: Robin, "Memoires sur la
Structure des Ganglions," in the Journal de I'lnstitut, 1847, N. 687,
and 1848, N. 733, also in the Comptes Rendus, xxiv. p. 1019 ; Axmann,
Beitrage zur Microscopischen Anatomie des Ganglien Nervensystems
des Menschen und der Wirbelthiere, Berlin, 1853 ; Virchow, Uebereine
im Gehirn und RUckenmark des Menschen aufgefundene substanz mit
der chemischen reaction der cellulose. (On a substance found in the
brain and spinal marrow of Man, presenting the chemical reaction of
cellulose), in " Archiv" f. Path. Anat. vi. I, 1853. — Ed.] Besides
these, should be consulted the general works of Schwann, Henle, Valen-
tin, Todd and Bowman, Bruns, and myself, which also give figures ; the
Reports of Ilenle and Reichert ; and the memoirs cited under the
descriptions of the nerves of the different organs, and in the various
sections.

436 SPECIAL HISTOLOGY.

OF THE DIGESTIVE ORGANS.

I.— OF THE INTESTINAL CANAL.

§ 128. The intestinal canal is composed fundamentally of the so-
called membranes of the intestine. The innermost of these, the mucous
membrane^ membrana mucosa, corresponds in its structure with the skin,
and like it possesses, (1) a non-vascular investment composed of cells —
the epithelium ; (2) the m.ucous membrane, more strictly speaking, com-
posed of connecting and elastic tissues ; containing vessels, nerves,
smooth muscular fibres, and different forms of minute glands, and often
presenting peculiar processes {papillce, villi); and (3) an external layer
of loose connective tissue, the submucous cellular tissue. The second
intestinal tunic, the muscular membrane, tunica muscularis, is provided,
for a certain distance at the commencement and at the termination of
the intestine, with striated fibres, but in the remainder of its extent the
muscles are everyAvhere of the smooth kind, and form in general two
distinct layers ; an external, with longitudinal, and an internal, with
transverse fibres ; more rarely there are three separate layers. The
third membrane, the serous, tunica serosa, exists only upon those por-
tions of the intestine which occupy the cavities of the abdomen and
pelvis ; it is a delicate, transparent membrane, poor in nerves and ves-
sels, and provided with an epithelium ; it invests the intestinal canal, and
connects it with the walls of the abdominal cavity and with the other
viscera.

OF THE ORAL CAVITY.

A. OF THE MUCOUS MEMBRANE OF THE ORAL CAVITY.

§ 129. The commencement of the intestine maybe said to have only
one tunic, the mucous membrane, which is applied more or less closely
to the bones and muscles bounding the oral cavity ; and is distin-
guished by its not inconsiderable thickness, by its red color, arising from
the abundance of its vessels, and by its numerous nerves and papillce.

The proper mucous membra^ie, although it is continuous with, and
gradually passes into, the cutis upon the lips, is more transparent and
softer than the corium ; however, it possesses considerable firmness and
is still more extensible. Like the thinnest portions of the cutis, it con-
sists of a single layer, 0-1-0-2 of a line in thickness, and presents a
great number of papillce, like those of the skin, upon its outer surface;
they are in general simple but occasionally bifurcated (when hypertro-
phied they may possess even more processes), are conical or filiform,

THE ORAL CAVITY. 437

0-10-0'18 of a line in length, 0-02-0-04 of a line in breadth (extremes,
0-024-0-28 of a line in length, 0-004-0-05 of a line in breadth), and
stand, Avithout any very regular distribution, so close together, that their
bases are almost in contact and are rarely more than their own breadth
apart.

Besides these papilla^ the mucous membrane presents upon its free
surface the orifice of the naso-palatine duct, and a great number of
glandular apertures, a few of which are situated at the extremities of
large papillary elevations.

The subtnncous cellular tissue of the mouth varies in its structure.
On the floor of the oral cavity, on the anterior surface of the epiglottis,
and especially upon the frcena of the lips, of the tongue, and of the
epiglottis, it is thin and yielding ; and therefore, in these localities, the
mucous membrane is very movable upon the subjacent parts. Where
glands occur in the submucous tissue, it is more solid, as in the lips and
cheeks ; at the root of the tongue, and on the soft palate, it may be
said to be firmly fixed, and here, especially in the last-named localities,
we find large masses of fat in it. The submucous tissue is very dense,
firm and of a whitish color, upon the alveolar processes ; where, united
into one mass with the proper mucous membrane and the periosteum, it
forms the gums ; upon the hard palate, to which the mucous membrane
is attached by an immovable thick fibrous layer, which in some parts
contains glands ; and finally upon the tongue, where the papillae are situ-
ated. In the latter case, there is a very close union between the mucous
membrane and the muscular tissue, the processes of many muscular
fibres extending into it and terminating especially in a white, very solid,
and dense, tendinous layer, which is in immediate contiguity with the
upper longitudinal muscular fibres, and has been described as i\\e fascia
linguce (Zaglas).

With respect to the minute structure of the mucous membrane of the
mouth, connective tissue is the predominant constituent of the submu-
cous cellular tissue, while throughout the proper mucous membrane, very
numerous elastic elements are everywhere found. In both localities, the
former usually presents itself in bundles of 0-002-0-005 of a line in
breadth, not united into a network, but while they cross one another in
the most various directions, presenting a certain indistinct lamination.
The felted mass of connective fibrils becomes densest towards the epi-
thelium, and finally passes into a more structureless layer, which in my
opinion is here, as little as in the corium, to be considered a special mem-
brane.* In the intei'ior of the papill(X also, with the exception of those
of the tongue, a fibrous structure is usually very indistinct, the whole
more resembling a homogeneous substance, slightly granular. The

* [This structureless layer is the " basement membrane" of Todd and Bowman, who
describe it as a separate membrane. — DaC]

438

SPECIAL HISTOLOGY.

Fi?.167.

elastic element in the subcutaneous cellular tissue has generall}^ the form
of scattered, interstitial, and occasionally, though more rarely, of spi-
rally convoluted, fine fibres ; here and there, as in i\\Q frenulum epiglot-
tidis, they are not only more abundant, but thicker. The latter is inva-
riably the case in the proper mucous membrane, which, even close to the
epithelium, contains in the midst of its connective tissue, very close and
intimately connected networks of elastic fibrils, or (and this is the
general rule) of moderately thick elastic fibres of 0-001-0-0015 of a line.
Spirally convoluted elastic fibres exist here also, though rarely. In
addition, the mucous membrane contains common fat-cells, sometimes in
groups, sometimes more isolated, and especially in the submucous layer.
The vessels of the mucous membrane are very numerous, and present
essentially the same arrangement as in the skin. The smaller papilloe

contain only a single capillary loop,
whilst in the larger, either simple or
branched, a network of capillaries
may be observed (Fig. 167) ; this is
especially the case in the gums, the
palate, the glandular region of the
root of the tongue, the lips, and the
lower surface of the tongue. The
investigation of the nerves presents
many difficulties. If caustic alkalies
be added, a wide network of the finer
and finest branches is rendered dis-
tinct in the outermost layers of the
mucous membrane, in which also,
divisions of the nervous fibrils may
be observed in some localities, par-
ticularly upon the anterior surface of the epiglottis ; on the other hand,
it is often impossible to detect so much as a trace of nerves in the
papilloe. Sometimes, however, even in these, especially in the larger,
one or two, often twisted, nerve-fibrils of 0-02 of a line in diameter,
diminishing to 0-0012 of a line, may be detected, without its being
possible to make out their ultimate destination ; upon the lip the papillce
possess axile-corpuscles similar to, but smaller than, those of the hand,
though not in all individuals. I found here, also, the nerve-coils
described by Gerber (see § 37). Of the origin and relation, in the
t. mucosa itself, of the abundant lymphatic vessels of the oral mucous
membrane, nothing is known.

§ 130. The epithelium of the cavity of the mouth (Fig. 167), is a
^o-GsWedi pavement epithelium, consisting of many superimposed layers

Fig. 167. — A simple papilla with manifold vessels and epithelium, from the gum of a
jhild ; magnified 250 diameters.

THE ORAL CAVITY.

439

of roundish, polygonal, more or less flattened cells. Taken altogether,
this epithelium is a transparent, whitish, pellicle, 0-1-0-2 of a line thick
on the average, very flexible, but possessing little elasticity or firmness ;
it may be detached in considerable flakes by macerating and scraping
the mucous membrane, and also by the use of acetic acid. Its elements
are, throughout, nucleated cells, whose arrangement and structure,
strongly recall those of the epidermis ; they are not, as in the latter
case, distinguishable into two sharply defined lamince, but constitute one
connected layer, more resembling the mucous layer, but representing the
horny layer also. The cells are thus disposed, from within outwards ;
immediately upon the free surface of the mucous membrane, and upon
the papillce, rest many layers of small vesicles of 0-004-0*005 of a line
(Fig. 167), the deepest of which are, almost without exception, elongated
and larger (0-006-0-009 of a line), and disposed perpendicularly. To
these succeed many layers of roundish, angular, flattened cells, which
gradually increase in size, become flatter from within outwards, and
assume a more and more distinctly polygonal form (Fig. 168, b).

Fig. 168.

On the outer surface, finally, we meet, gradually proceeding from the
deeper cells, with a few layers of the so-called epithelial plates (Fig,
168, a), that is, large (0-02-0-036 of a line) bodies with rounded cor-
ners, in which the flattening has gone so far that they no longer de-
serve the title of vesicles.

All these cells possess a delicate membrane, easily demonstrable by
alkalies and acetic acid ; clear contents, present in greater or smaller
quantity, according to the amount of flattening, with frequently a few
fatty granules, and invariably a nucleus. In the smallest cells the
nuclei measure from 0-002-0-003 of a line, they are elongated or round,
and usually without any distinct nucleolus ; in the polygonal cells there
are invariably one or two beautiful, clearly vesicular, usually spherical
nuclei, of 0-004-0-005 of a line, with clear contents, and 1-2 nucleoli;

Fig. 168. — Epithelial cells in the oral cavity of Man: a. large; b, middle-sized; c, the
same with two nuclei ; magnified 350 diameters.

440 SPECIAL HISTOLOGY.

finally, in the plates, the nuclei have begun to retrograde, are smaller,
0-004-0-006 of a line long, 0-002-0-0015 of a line broad, generally flat-
tened and more homogeneous, without any distinct cavity or nucleolus^ or
containing instead several granules. With respect to its chemical rela-
tions, the pavement-epithelium of the mouth agrees, so far as we know,
in all essential points with the mucous layer of the epidermis, and
with the deepest layer of the horny lamina, particularly in the circum-
stance, that even the plates readily swell up in alkalies ; the reader
may therefore be referred to § 45.

The most essential -pliysiological characters of the epithelium of the
oral cavity are, the continual change to which it is subjected, and its
relations as regards absorption and secretion. With respect to the for-
mer, it may be said that the epithelium undergoes a continual desqua-
mation, which, however, does not here, any more than in the epidermis,
appear to be the effect of special vital energies in the mucous membrane,
or in the epithelial cells, but rather to result from the manifold mecha-
nical disturbances to which the surface of the oral mucous membrane is
subjected during mastication and speaking. On the one hand, these
disturbances give rise to a constant detachment of the uppermost plates ;
and on the other, an uninterrupted regeneration of the lost parts takes
place, a process which I am disposed to interpret in this case exactly as
I have done in § 46, for the epidermis, and in § 64, for the hairs. As
regards the exact mode of that growth of the oral epithelium, which,
from what has been said, must perhaps, always be going on in one part
or another, we invariably find, upon the surface of the epithelium,
during and after very copious desquamation, large, completely flattened
cells (which, of course, possess no power of multiplication), never
younger and smaller structures, and, therefore, the reparation of any
loss cannot take place by the formation of new cells at the surface of
the epithelium ; on the contrary, everything indicates that the renewal
occurs in the layers of smallest cells, for although no new development
of cells can here be directly observed, yet the analogy with other epi-
dermic structures, and the frequent occurrence of two nuclei in the cells
of these layers, nay, even of constricted cells [Bowman, compare § 46),
are striking facts in favor of the multiplication of the cells which al-
ready exist (by division) and against their actual new formation.

The epithelium of the oral cavity, although thick, is yet readily pei--
meable, differing widely in this respect from the epidermis, which pre-
sents similar relations, only in the stratum Malpighii. Fluids of the
most different description permeate it from without, and once in contact
with the mucous membrane, may either be absorbed by its vessels, or
perceived by its nerves. Other conditions remaining the same, the
activity of the sensitive and absorbent powers will depend upon the

TUE TONGUE. 441

thinness of the epithelial layer, particularly of the plates, which must
always be least permeable, and upon the abundance and superficiality
of the vessels and nerves ; and these considerations readily explain why
the lips, in which the papilhv are very nnnierous, and nearly reach the
surface of the epidermis, possess a more delicate sensibility than the
gums ; and why the point of the tongue, whose papillce even project
with a thinner covering, is still more sensitive (compare, also, on the
import of the axile Corpuscles, § 39). The epithelium is permeable
outwards, as well as inwards, and permits of the passage of plasma
from the vessels of the mucous membrane into the cavity of the mouth.
In this manner, like the epidermis in relation to the cutaneous perspira-
tion, it participates in the formation of the mucous fluid, which is
yielded, not only by the glands which open into the oral cavity, but
also by the whole surface of the mucous membrane.

B. OF THE TONGUE.

§ 131. The Tongue is a mass of muscles attached to a particular
bone, the os hi/oides, and covered by the mucous membrane of the cavity
of the mouth ; its muscular elements, 0"009-0-028 of a line in breadth,
are distinguished from those of the external transversely striated mus-
cles, only by being interwoven in the most complex manner, so that in
the interior of the tongue the lingual muscles cannot be separately
demonstrated as such, but only as secondary bundles and fibres.

The framework of the tongue may be said to be formed by the two
genio-glossi, the musculus transversus Imguce, and the fihro-cartilage of
the tongue. The latter, which is also called the lingual cartilage (Fig.
170, e), is a dense, whitish-yellow, fibrous lamella, placed perpendicu-
larly in the middle of the tongue, between the two genio-glo8si. extending
through the whole length of the organ, and is not very appropriately
named, inasmuch as it is composed of common tendinous or ligamentous
tissue. It commences, low down, upon the body of the hyoid bone, in
connection with a broad fibrous lamella, memhrana hgpoglossa (Bh^ndin)^
which stretches from the hyoid bone to the root of the tongue, and
covers the extremity of the genio-glossiis, very soon attains the level of
the musculus transversus, and, upon the anterior third of the tongue,
gradually diminishes, as far as its point, where it terminates very low
down. Superiorly, the septum Unguce, as this fibrous mass, 0-12 of a
line thick, might well be termed, ascends to within l|-2 lines distance
from the dorsum of the tongue ; inferiorly, it extends to where the
genio-glossi, become lost in the fleshy mass of the tongue, and termi-
nates here, not with a defined border, but by passing into the perimy-
sium, between the two genio-glossi. On each side of this sep)tum, the
genio-glossi spread out, fan-like, into the tongue (Fig. 169, g, 170, g,
171,/), so that they occupy the middle of the organ from its point to

442

SPECIAL HISTOLOGY.

its root, forming a long, moderately broad, fleshy mass, which, however,
is anything but compact. The genio-glossi, in fact, when they have
entered the tongue, exchange a few bundles here and there, along the
lower edge of the septum, and then break up on each side into a great
number of lamellce, which lie one behind the other, separated by small
interspaces, in which are the transverse muscular fibres of the tongue ;
the lamellce are, for the most part, perpendicular, but some curve for-
wards and backwards, towards the dorsum of the tongue.

The fibres of the genio-glossus, thus separated into distinct lamellce,
which have, on the average, a thickness of 0-06-0'14 of a line, extend
as far as the septuvi, and then gradually take a new arrangement, so as
to be directed from behind forwards. For whilst, previously, the genio-
glossi were broken up into transverse lamelloe, by the bands of the

transversus, they are now separated longitudinally by the interposition
of the bundles of the superior longitudinal muscle of the tongue, between
their fibres. These perpendicular longitudinal lamellce are very distinct
in the two anterior thirds of the tongue, less so in the vicinity of the
fapilloe circmnvallatce, where, especially in the middle of the tongue,
the genio-glossus passes, in more isolated bundles to the mucous mem-
brane ; in the root of the tongue, finally, they cannot be demonstrated
at all. The genio-glossus ends upon the upper surface of the tongue,
in such a manner, that its primitive bundles, immediately beneath the
mucous membrane, are continuous, in groups, with little tendinous
streaks of connective tissue, which then partly become lost in the

Fig. 109. — Longitudinal section of the human tongue, natural size; the outlines after
Arnold Icon. org. (sens.) : g.h, gcnio-hyoidcus ; h, hyoid bone ; g, genio-glossKS ; g\ glosso-epi-
glotticus ; tr, transversus lingu<E ; l.s,longitudinalis superior; e, epiglottis ; m, maxilla inferior;
d, incisor tooth ; o, orbicularis oris ; l.m, levator menti ; /. glandulcE labialis ; foUiculi linguales ;
gl, glandula linguales cum ductibus.

THE TONGUE.

443

/..

Fig. 170.

/'^

deeper, very firm layer of the mucous membrane, to be described pre-
sently, and partly run as far as the bases of the pajnllce. At the root
of the tongue, the gcnio-glossus does not reach so far as the mucous
membrane, which may here be easily dissected away, with its mucous
sacs, from the more deeply situated racemose glands, but ends upon and
between the latter, uniting with them, or with a dense fibrous tissue
between them, by means of tendinous strict.

The transverse muscle or the transverse fibres of the tongue [trans-
versus linguce sive fibrce transversales, Fig. 169, tr., 170, tr., 171, g),
consists of very numerous lamellce belonging to each half of the tongue,
which penetrate with great
regularity between the
transverse lamellce of the
genio-glossus, and are to
be found in all sections of
the organ. 1^ ach. lamella
is 0'l-0-16 of a line thick,
and in the middle of the
tongue fths of a line deep ;
it is usually perpendicu-
lar and its muscular fibres
extend from the septum
linguce to the lateral bor-
der of the tongue. They arise, so to say, directly from the whole surface
of the septum, by the intermediation of a small quantity of a transverse
tendinous tissue, distinct from its longitudinal fibres, and pass, united
into small flat bundles, at first, directly outwards. In their further
course, they curve upwards, and finally, the uppermost shortest fibres
reach the sides of the dorsum of the tongue, the inferior longer ones,
its proper lateral margin, where they also become attached to the
mucous membrane by means of short bands of connective tissue. The
other lingual muscles form, in a manner, the sheath of the organ and,
in their course, partly follow the above, partly take their own special
direction.

The hyo-glossus [haseo- and cerato-glossus of authors), has, at the
sides of the tongue, nearly the same relations as the genio-gJossus, in
the middle. Its coarser bundles, in fact, break up when they have

Fig. 170. — Transverse section of the human tongue, a little in front of tlie papillcB circumval-
latce : g, genio-glossus ; Li, longitudinatis inferior (Hngualis) with the arteria ranina ; tr, trans-
versus, visible in its whole extent on the left side, on the right only at the edge and between
the divaricating bundles of xhe getiioglossus ; g, termination of the genio-glossus upon the
mucous membrane; h, termination of the hyoglossus ; l.s, longitudinalis superior, with flat
bundles interposed between the perpendicular fibres ; d, glands of the margin of the tongue ;
st.gl, stylo-fflossus.

444 SPECIAL HISTOLOGY.

reached the lower surface of the margin of the tongue, into a great
number of thin transverse lamelke, 'which, more or less curved, pene-
trate superiorly between the lamellce of the transverse muscle and in
their further course, present exactly the same relations as those of the
genio-glossus, to which they are applied externally, except, that as their
fibres ascend towards the dorsum of the tongue, they take a slightly
oblique direction inwards. Upon the dorsum of the tongue, the Jiyo-
gJossus lies between the genio-glossus and the upper edge of the trans-
versus; it presents, like the former, longitudinal plates, with perpendi-
cular fibres, between which the upper longitudinal fibres lie, and it
finally, also, terminates in the mucous membrane. The expansion of
the liyo-glossus is most distinct and strongest, in the middle of the
tongue, where the chief mass of the baseo-glossus lies ; it is only behind
that it becomes more indistinct, the lamellce of the cerato-glossus being
here very delicate, and lying more horizontally ; however, they still pene-
trate between those of the transversus and terminate upon the dorsum
of the tongue.

The stglo-glossus (Fig. 170, st. gl.), in general, divides into two
bundles, which have totally different relations ; the posterior, smaller
one, passes between the cerato-glossus and baseo-glossus, and between
the fasciculi of the latter, directly inwards, penetrating, in a few
bundles, between the lamellce of the lingualis and genio-glossus.^ as far
as the septum linguce, where it becomes attached, in common with the
somewhat superior fibres of the transverse muscle. The principal mass
of the stylo-glossus passes inwards and downwards at the margin of the
tongue, unites in front of the liyo-glossus yfiihtlie lingualis inferior', and
terminates in the mucous membrane of the lower surface of the apex of
the tongue and of the point itself; the anterior bundles of the two
muscles becoming united in an arch.

The lingualis of authors, which I shall call lingualis or Ion gitucUn alts
inferior (Fig. 170, /. i), is a tolerably strong, longitudinal bundle of
muscular fibres placed upon the lower surface of the tongue, between
the genio-glossus and hgo-glossus, but whose commencement and termi-
nation are not readily discoverable. The posterior portion of the lin-
gualis inferior appears at first to become lost in numerous superimposed
flat bundles between the transverse fibres of the genio-glossus [glosso-
'pharyngeus), of the stylo-glossus, and of the transversus, at the root of
the tongue ; more carefully traced, however, it is found that these, like
the posterior portions of the genio-glossus, break up into many lamellce,
which ascend, slightly curved, between the transverse fibres, as far as
the outer portions of the glandular layer of the root of the tongue ; and
finally, like the plates of the genio-glossus, which lie internal to them,
end in it. Anteriorly the lingualis inferior unites with the larger
bundles of the stylo-glossus ; ending at the point of the tongue with

THE TONaUE.

445

them, and also, applying itself anteriorly to the Jti/o-glossus, it sends
many delicate lamelke between the transverse muscles as far as the
dorsum of the tongue, presenting, in fact, at the border of the anterior
third of the tongue, the same relations as the hyo-glossus further back-
wards.

Finally, there exist in man yet another longitudinal^, or Ungualis
superior, and isolated perpendicular fibres. The Ion gitudinalis superior
(Figs. 169, 170, l.s, 171, e), constitutes a longitudi-
nally fibrous layer placed between the uppermost fibres
of the transversns and the mucous membrane, which
occupies the whole breadth and length of the tongue
and proceeds from the chondro-glossus (overlooked by
most anatomists), which arises from the smaller cornu
of the hyoid bone as a moderately large bundle, sepa-
rated from the haseo- and cerato-glossus by the lingual
artery and the glosso-pharyngeal nerve. It passes
forwards, under the deep glandular layer of the root
of the tongue, and in part through the midst of the
termination of the genio-glossiis and Ungualis inferior ;
occupies, a little in front of the papillce circiimvallatce,
almost the entire half of the tongue, and thence passes
forwards in the form of narrow bundles, united here
and there at acute angles, immediately under the mu-
cous membrane, between the ends of the genio-glossi
and Jigo-glossi, as far as the point of the tongue, here to
become lost in the integument on its upper surface.
Since these longitudinal fibres become thicker anteriorly, it is probable
that independent, superior longitudinal fibres, arising from the mucous
membrane of the dorsum of the tongue, and ending upon it, become
associated with them. I ^nd perpendicular fibres, \\hich do notarise
from without, only in the apex of the tongue, where delicate bundles of
them are stretched between the upper and lower layers of mucous
membrane.

The lamelliTe of the most anterior part of the transversns pass be-
tween the inner portions of these bundles, whilst between their extre-
mities the longitudinalis superior and inferior and stylo-glossus pene-
trate with tolerable regularity, so that transverse sections exhibit an
alternation of perpendicular and longitudinal fibres, such as that which
appeal's in the dorsal part of the tongue in Fig. 170.

It remains to be added, that the palato-glossus muscle becomes in
part lost, together with the cerato-glossus, in the mucous membrane of

Fig. 171 — Portion of a longitudinal section through the side of the human tongue: a,
papilhi futigiformis ; b, papilla filiforvns ; c, mucous membrane ; rf, fibrous layer below it ;
e, longitudinalis superior ; /, ge/iio-glossus ; g, ira/isi'crsus, cut across.

446

SPECIAL HISTOLOGY.

the lateral borders of the tongue, and in part seems to unite -with the
larger bundles of the stjjlo-glossus.

If, after thus describing the separate muscles of the tongue, both ex-
ternal and internal, we consider the general structure of the organ, it
appears that its proper substance presents essentially only three sets of
muscular fibres, which may be denominated perpendicular, transverse,
and longitudinal. The perpendicular fibres arise from the genio-glossi
in the middle ; from the lingualis and hjo^glossus laterally ; at the
apex, also, from the perpendicularis ; and they form from the point to
the root, a great number of transverse lamellxe, occupying nearly the
entire breadth of the halves of the tongue, whose fibres pass in general
from the lower surface to the upper. The transverse fibres, derived
from the transversus and in part from the stylo-glossus, are inserted in
so many, usually somewhat thicker, lamellce, between the above named,
commencing at the sejjtum and ending at the lateral edges and partly
upon the surface; the longitudinal fibres, lastly, belong to the lingualis
superior {chondro-glossus), the lingualis inferior and stylo-glossus, cover
the upper surface, the margin, and in part the lower surface, and lie for
Fis- 172. the most part immediately beneath the mucous

membrane. The various layers of muscles of the
tongue are invariably separated from one another
by a thin perimysium, and where larger vessels
and nerves run, by thicker masses of connective
tissue ; besides which, there are in many localities,
larger or smaller aggregations of common fat-
cells, which especially abound between the genio-
^M glossi at the septum, at the root of the tongue,
'"" and under the mucous membrane.

In the tongue of the Frog very beautiful in-
stances of division of the transversely striated
fibres occur (Fig. 172), of which I have not been
able to find any certain trace in man. Occasion-
ally, however, it has seemed to me that the fibres
of the genio-glossus exhibited divisions shortly
before their passage into tendinous bands.

§ 132. On the dorsum of the tongue, from the foramen ccecum as far
as its point, the mucous membrane differs from that of the rest of the
oral cavity, in being very closely united with the subjacent muscular
tissue, and in possessing a great number of processes, the well-known
lingual or gustatory papilla;. The 6-12 papillce circumvallatce consist,

Fig. 172. — A branched primitive muscular bundle, of 0-018 of a line, from the tongue of
the Frog ; magnified 350 diameters.

THE TONGUE. 447

■when they are ■well developed, of a central round papilla, flattened
at the end, having a diameter of ^-1 line, and J-| or even f of a
line high ; and of a lower uniform wall ^-|- of a line broad, which
closely surrounds the papilla, particularly at its base. These pajnllce,
however, vary much in number, size, and position, and occasionally pass
into the fungiform kind ; which is especially true of the posterior ones
lying in the foramen cceeum, or Morgagyiii. The papillae anterior to
the circumvallatce, are arranged in more or less regular rows, which in
general run parallel to the latter, and pass, upon the border of the
tongue, into laminated, sometimes not even notched folds, which can no
longer be considered as i^apillce. The pajnllce fungiformes or clavatce
are 0*3-0*8 of a line in length, 0'2-0'5 of a line in breadth ; they have
smooth surfaces and, during life, are readily recognised by their red
color ; they abound particularly upon the anterior half of the tongue,
scattered over its surface at tolerably regular intervals of ^1 line and
more ; and at the point, indeed, they are often so thickly crowded as to
be in contact ; they are not absent, however, upon the posterior half, as
far back as ihe papillce eircumvallatce. The 'papillce filiformes or conicce
are ^^h lines in length, and 0-1-0-2 of a line in breadth, and rendered
very obvious by their number and whitish color ; they occupy, in close
contact with one another, the intervals between the fungiform kind, and
invariably appear most densely crowded and best developed, with brush-
like ends, in the concave side of the V of the circumvallate popiYte, and
in the middle line of the centre of the tongue. Towards the edges and
the point, the j^ajt^iYZce themselves, as well as their processes, become
shorter, and to some extent more scanty, so that they gradually pass
into the lamince to which we have referred, and also in many respects
approximate the fungiform papillce ; from which, in fact, so far as the
structure of their surface is concerned, they become hardly distinguish-
able.

Besides iYiQ^Q papillce which project freely, there may also be observed
over the whole gustatory region of the tongue, smaller ones completely
buried in the epithelium, which are perfectly similar to those of the non-
gustatory parts of the organ.

With respect to the minuter structure of the mucous membrane of the
tongue, that part of it which presents no projecting papillce, differs in
no respect from the mucous membrane of the oral cavity, and possesses,
in fact, a laminated pavement epithelium of 0*045 of a line in thickness at
the root of the tongue, of O'06-O-l of a line on the lower surface of its
apex, Avith simple small imbcdded^;a^;i7/a3of0-024-0-05 of aline in length,
0"004-0-02 of a line in breadth, which are not absent even upon the ante-
rior surface of the epiglottis, and between it and the papillce circumvallatce.
In the proper gustatory region of the tongue the submucous tissue is
•wholly absent, the mucous membrane being united with the muscular

448

SPECIAL HISTOLOGY.

substance by means of a dense biyer of connective tissue (see above
§ 131) ; it has itself a dense and solid appearance, though in conse-
quence of the presence of a considerable quantity of elastic tissue, of
common fat cells of 0-016-0*024 of a line, and of its abundant vascular
supply, it is tolerably elastic.

The papillce filiformes or conicce (Fig. 173), are conical processes of
mucous membrane beset either at their extremities only, or over their
whole surface, with a certain number (5-20) of smaller secondary
papillce of 0-1-0-14 of a line in length. The whole is invested with a

Fig. 173.

Fis. 174.

thick epithelial coat drawn out at its extremity into a number of long,
thin (0-01-0-02 of a line), fine and often subdivided, processes (Fig. 173,/),

Fig. 173. — Two papilla; filiformes oimB.n, one with its epithelium magnified 35 diameters.
After Todd and Bowman: p, \\\e papilla themselves; «, v, arterial and venous vessels of
papilla, together with the capillary loops, which, however, ought to enter the secondary
papilla.

Fig. 174. — ji, papilla fungiformis, with its secondary or simple papijln?,/), on one side still
covered with epithelium, e ; magnified 35 diameters. B, the same, with only the outlines
of the epithelium, e, and the vessels; a, artery; v, vein; d, capillary loops of the simple
papilla;; e, capillaries in the simple papilla' of the mucous membrane at the base of the p.
fungiformis ; magnified 18 diameters. After Todd and Bowman.

THE TONGUE. 449

whicli give the papilla the aspect of a fine brush, and may attain a
length of as much as 0-5-0-6-0-7 of a line, with a breadth of 0-02-0-028
of a line at their base. The superficial layers of this epithelium resemble
the epidermic plates in their long resistance to the action of acids and
alkalies, and consist, especially the epithelial processes, only of solid
horny scales of 0-022 to 0*028 of a line, which frequently form a more
solid axis, and of an external cortex composed of overlapping plates, so
that the Avhole mass may, with some justice, be compared to a hair.

The primary 'papilla of the ^?. fiUformes contains distinct connective
tissue, and a very considerable number of elastic fibrils, which as 10-20
wavy threads of 0-0004-0'0008 of a line, penetrate even to the points of
the simple papillae, and give to the whole cone and its processes a cer-
tain solidity and firmness which are not possessed by the simple papillae of
the mucous membrane. A minute artery ramifies in each filiform papilla,
in such a manner, that every simple papilla contains a capillary loop of
0-004-0 -005 of a line, from whose reunion a small vein arises. It is dif-
ficult to discover the nerves, on account of the abundant elastic tissue ;
and in many papilla they may be sought in vain. In the majority, how-
ever, at least at the base of the papillie, they are quite distinct, in the
form of one or two delicate trunks, with 5-10, dark-edged primitive
fibrils of 0'002-0"003 of a line, which gradually become finer as they
run towards the point. I have been unable to make out with certainty
how the nerves terminate, yet everything appeared to indicate the exist-
ence of loops, not, however, in the simple papilloe, but at their base. In
animals these loops are more distinct, as for example, in the calf, where
every filiform papilla receives 10-12 primitive fibrils, of 0-002-0"003 of
a line, which diminish to O'OOl of a line, and do not enter the simple
papillae.

The papillce fungiformes consist of a clavate primary papilla, whose
entire surface is beset with closely placed, conical, secondary papillae,
0*1-0 -12 of a line in length, and invested with a simple epithelium,
such as is met with elsewhere in the oral cavity, without filiform pro-
cesses, or any very Jiorny cells, and which, measured from their points,
has a thickness of 0*04-0*05 of a line. The primary papilla contains
far less elastic tissue than the pap illce fiUformes, and it is almost wholly
■wanting in the secondary papillos ; on the other hand, a network of
bundles of connective tissue of 0*002-0*003 of a line in breadth, is
very distinct. The vessels present the same arrangement as in the p.
fiUformes, only that they are much more numerous ; and as regards the
nerves, one or two larger trunks of 0*04-0*08 of a line, enter into
every fungiform papilla, together with many minute filaments, which,
spreading out in the form of a brush, and repeatedly anastomosing (see

Zeitschrift fur Wiss. Zool., B. IV. Tab. IV.), finally diverge in all direc-

29

450

SPECIAL HISTOLOGY.

Fis. 175.

tions towards the secondary papillre, and their axile corpuscles (see

§37).

The nerves, which in the trunks measured 0 •002-0-004, on the
average 0-003 of a line, diminish in size during their course, so that at
the base of the papilla?, their diameter is not more than 0-001-0-0015
of a line, and they also exhibit distinct divisions ; I have not yet
observed their terminations with certainty, but have thought that in
some cases I could detect loops, in others, free ends, without, however,
pledging myself either to the one or the other.

In the 2^apill(x circiimvallatce the central papilla, which may be re-
garded as a depressed papilla fungiformis, is closely covered upon its

plane terminal surface with
simple conical elevations, and
is invested externally by an
epithelium of uniform thick-
ness, without any special
processes and prolongations.
The wall is a simple elevation
of the mucous membrane,
possessing a smooth epithelial investment, beneath which its upper bor-
der is produced into many rows of simple conical secondary papillae.
The elastic tissue is usually absent in the papillae, otherwise, they have
the same structure as the fungiform kind, only they are still more abun-
dantly provided with nerves. Every proper papilla circumvallata con-
tains in its lowest portions several nervous trunks o( 0-05-0 '08 of a line
in diameter, which as they ascend, subdivide into a very elegant plexus,
from which the nerves of the secondary papillaj radiate upon all sides.
In other respects, they resemble the p. fungiformes, except that the
nerve-tubules, even in the trunks, have not a greater average diameter
than 0-002, and the largest not more than 0-003 of a line, while at the
base of the secondary papillae it is not more than 0-001-0-0015 of a line.
The walls of these papillas also contain many nerves, whose ultimate
disposition appears to be exactly the same as in the papilla themselves.

The lingual papillae present many varieties, the following of which are
the most important: 1. The jyapillce fiUformes are all elongated, and
provided with very considerable epithelial processes. The appearance
of what is commonly called a gastric furred tongue, depends principally
upon the growth of the epithelial processes of the papillce fiUformes,
which, all directed backwards and in close apposition, form apparently
a peculiar white coating. If the processes become longer, so that the

Fig. 175. — Papilla nrcxtmvallata of Man in section: ./?, proper papilla; B, wall; «, epithe-
lium ; c. secondary papilla : bb, nerves' of the papilla and of the wall. — Magnified about 10
diameters.

THE TONGUE.

451

papiUce filiformes measure li-2 lines, we have the lingua hirsuta or
t'27/osrt, which is not uncommon in various disorders; and at length forms
may be produced, in which the tongue looks as if it were covered with
hairs, 4-6 lines long. 2. The papUlx jiUformes possess very small
epithelial processes, or none at all, and are hardly distinguishable from
the smaller ji). fungiformes. 3. The papillce filiformes do not exist as
special elevations, but are imbedded in a general epithelial investment of
the dorsum of the tongue. Tongues may be observed, particularly in
old people, which, without being furred, in some spots or over a large
extent, present no papillte at all, but have either a perfectly smooth
surface, or exhibit only a few linear elevations, corresponding with the
rows of papillae which would, otherwise, exist there. In these places we
find the epithelium more developed, and beneath it small papillse, more
of the ordinary form. Tongues which, with better developed papillse
present a smooth surface, are again different from these ; here the smooth
or cracked surface is produced by the papillae being glued together by
superabundant epithelium, mucus, blood, pus-corpuscles, and mucedi-
nous or yeast-like fungi. 4. The epithelial p)rocesses of the filiform
papillce are covered tvith mucedinous fungi. Every microscopist is
doubtless acquainted with brownish, elongated bodies (0'12-0"24 of a
line in length, 0'04-0-08 of a line in breadth), consisting of a dark axis

Fi". 176.

and a finely granular cortex, from the coating of the tongue. The
centre of these bodies only is composed of cornified epithelial cells,

Fig. 176. — A mass of epithelial cells covered with the granular matrix of the fungus, b,
from which a luxuriant growth of mucedinous filaments, c, proceeds j magniiied 350 dia-
meters. From Man.

452

SPECIAL HISTOLOGY.

Fig. 177.

which become isolated and swell up by the action of caustic potassa and

soda, especially with heat, and are derived
from the epithelial processes of the papilloe
jiliformes ; the granular cortex again, is
nothino; but the matrix of a mucedinous
fungus of only 0-0006 of a line in diameter,
which, agreeing completely with the well-
known filaments upon the teeth, is often
rooted in immense quantities in it. In the
dead subject we readily recognise the epi-
thelial cells, covered with fungi, either with
or without projecting mucedinous filaments,
even in situ (Fig. 177) ; and in living per-
sons, they may be procured in any quan-
In twenty or thirty healthy young people,
I have hardly once failed to find the granular covering upon the epithe-
lial processes, even in a perfectly clean, red tongue.

The more fur there is, the more abundant is the matrix, land the
mucedinous filaments are also apparent, though they are rarely (three
or four times in thirty cases) found so clear and distinct as in Fig. 176,
and in general are not met with in more than a third of those persons
yfhose papillce Jiliformes are not altogether in a normal condition.*

tity by scraping the tongue.

Fig. 177. — A papilla filifor?nis, whose, here, short epithelial processes are invested by the
matrix of the fungus, from which also single filaments are growing out.

*[ This vegetable is probably the one to which Robin (Hist, natur. des Vegetaux Para-
sites), has given the name of oidium albicans. He has most frequently met with it in
a variety of aphtha, the " muquet " of the French. In this disease the irregular white
patches on the mucous membrane of the tongue, which were formerly supposed to be the
result of a diphtheritic inflammation, are found to consist of a vegetable growth. Robin (loc.
cit.) describes this vegetable as formed by distinct tubular filaments, which sometimes enclose
granules, and which always originate from spores. The spores are spherical and have well-
marked contours and a brilliant centre. They generally enclose numerous fine molecules,
sometimes one or two larger movable granules. Robin has observed this vegetable growth
whenever the mucus of the oral cavity was changed in its character. He agrees, there-
fore, with Kolliker in considering it neither as a constant symptom of any disease, nor as a
disease in itself

In some recent investigations upon the " fur " of the tongue, I have satisfied myself
of the almost constant presence of these fungi, especially of the granular matrix. In acute
diseases (as in erysipelas and peritonitis), in which the tongue was much coated, the
mucedinous filaments were also always found well developed. They were firmly adhe-
rent to isolated epithelial cells, by which they were sometimes concealed, but were easily
rendered apparent by the aid of a solution of carbonate of soda. In one case of typhoid
fever I discovered large distinct spores. Prof Clark, of New York, has observed these
vegetable growths in cases of extreme debility, especially in infants exhausted by diar-
rha-a and dysentery.

The main constituents, however, of the fur of the tongue are layers of epithelial
cells in ditferent stages of development. If the tongue be much coated, the cells on the

TUB TONGUE. 453

The phjsiological results of the anatomical data which have been
communicated, may be thus summed up : the papillce jiliformes are
neither gustatory nor delicate tactile organs, since their thick, and what
is more to the point, greatly cornified epithelium, is very little fitted to
allow of the passage of fluids capable of being tasted, or of other in-
fluences, to the scattered nerves, which only attain to the base of the
simple papilhv!. With Todd and Bowman, I consider that t\\Q j). jili-
formes have a similar ofl^ce to the lingual spines of animals, which are
nothing but modified filiform papillae, and I therefore ascribe to them
a certain importance for the conveyance and retention of the morsels of
food, and I consider that their epithelium serves, at the same time, as a
protecting investment for the tongue. The two other kinds of papillae
subserve the sense of taste and are, besides, the seat of ordinary sensa-
tion (for mechanical irritation, temperatures, &c.), for which functions
they are excellently fitted by their thin, soft epithelium, the softness
of the tissue of their papillae, and by the superficial position (in the
secondary papillie), and the great number of their nerves. The sensi-
bility of the tongue is most delicate where the papillce fungiformes are
most closely set, i. e., at the apex, which, on that account, and also per-
haps by reason of the solid axile corpuscles in many of the papilke, is
especially fitted for a tactile organ ; at the root of the tongue it is more
obtuse, and is accompanied by peculiar sensations ; the sense of taste is
much more acute at the root of the tongue than in the other regions,
the point not excepted. The reason of this lies neither in the epithelium,
nor in the fundamental structure of the papillae, which are essentially
similar in both i]\Q papillce circumvallatce a,nd fungiformes, but is, very
possibly, to be sought for in the nerves. In the p. circumvallatce, the
nervous fibres are always finer, and not only absolutely, but also rela-
tively, considerably more numerous than in iha fungiformes, so that they
possess more papillas and nervous terminations in the same space. The
fineness of the nerves especially, together with the smaller quantity of
medullary sheath and the more superficial position of the axis-fibre,
which indeed is the case in all the nerves of the higher senses, may
perhaps explain why tastable substances act here not only more power-
fully, but when they are no longer perceptible by more dense elements

surface are generally very granular, and from being contracted and in close apposition, they
bear a certain resemblance to fibrous tissue. The use of reagents, however, especially of
alkalies, will always render their cellular nature apparent.

The dark color of the fur, sometimes seen, may be owing to large accumulations of the
fungi between the cells, or else to the presence of pigment granules. The latter, if
abundant, may cause the tongue to appear as if covered with a thin layer of ink. A
case is reported by Dr. Eulenberg (Archiv f. phis. Hellk. 1S53), in which the whole tongue
was covered by a perfectly black fur, which, when examined microscopically, consisted of
distinct, angular pigment corpuscles lying between the epithelial cells. — DaC].

454 SPECIAL HISTOLOGY.

of the nerves. If this peculiarity be insufficient to account for the
differences in the sense of taste possessed by the two kinds of papiHie,
they can only be referred to the central organs, or ascribed to specific
actions in the nervous fibres themselves, which, however, is only making
a public confession of the hiatus in our knowledge.

Remak* discovered microscopic ganglia upon the expansion of the

*[Remak, " Ueber die Ganglien der Znnge bei Sangethieren und beim Menschen." The
author finds ganglia upon the branches of the glosso-pharyngeal and of the gustatory nerves,
and not upon those of the ninth nerve ; small ganglia were sometimes observed near branches
of the latter, but were never actually connected with them, and probably belonged to neigh-
boring branches of the gustatory. Remak compares these ganglia with those observed by
himself in the heart, contractile wall of the bronchise, posterior wall of the tirinary bladder,
and muscular wall of the uterus, and with the ganglia of the cavernous plexus described by
Muller; and his reasons against their connection with the nerves of sense appear to us
sufficiently important to be given in his own words.

" The terminal branches of both nerves (glosso-pharyngeal and gustatory nerves) form a
very dense plexus before entering the papillae. Neither in this plexus, ncr within the pa-
pillae themselves, could ganglion-globules ever be detected. It must be remembered, further,
that the ganglia upon the thicker branches of the glosso-pharyngeal and gustatory are always
hemiganglia^ that is, they do not occupy the whole thickness of the nerve — a bundle of tu-
bules, which takes no share in the formation of the ganglia, passing over them. Those
ganglia which lie in the neighborhood of the papilke have the same structure. Far more
numerous are the hologanglia,i. e. those in which all the nervous fibres become lost between
the ganglion globules (probably pass into them), but these are found only in the finest lateral
branchlets. They are almost always multipolar, i. e. they are connected with more than
two nervous trunks, and these are very widely diflerent from the nerves which constitute
the papillary plexus. While the latter present very delicate sheaths, and consist of evident
dark-edged fibres, the processes of the hohganglia are closely surrounded and enveloped by
very dense sheaths, and contain, particularly in the lingual branch of the fifth, both in man
and in the sheep and calf, a very large quantity of the well-known nucleated fibres, so that
it is at times difilcult to find a single dark edged fibre in one of these nerves. In other cases,
the processes of the ganglia are delicate nerves (of ^ijf of a line), which possess a solid
sheath, and a single dark-edged nervous fibre enclosed by it. The fine lateral branches of the
hemiganglia upon the thicker branches of the nerves present the same appearances. No
fibres can ever be traced from a ganglion to t!ie papillce. Another circumstance which
speaks against the relation of the ganglia to those fibres of the gustatory nerve which are
distributed to the mucous membrane is, that I could never, in spite of every exertion, find
ganglia upon the terminal branches of the gustatory nerve of the apex of the tongue of the
sheep. I believe that a certain value may be attributed to this negative result, as I never
failed to find ganglia upon the other branches of the gustatory nerve, up to within about an
inch of the apex of the tongue."

Remak gives, further, the following reasons for believing that the ganglia are related to
the mucous glands. •' 1. The lingual ganglia always occur in the neighborhood of the
mucous glands, or of their excretory duets. 2. That the smaller number of mucous glands
in the anterior region of the tongue (in the sheep or calf), corresponds with the smaller
numberof ganglia upon the branches of the gustatory nerve. 3. That little ganglia exist
upon the branches of the gustatory nerve distributed to the maxillary glands, and to the
ductus Whartonianus, whilst in man there is the well-known maxillary ganglion. 4. That
in the point of the tongue of the sheep, in which he could find no ganglia on the branches
of the fifth, there are no mucous glands. 5. That in the walls of the i:>harynx and larynx,
upon which he also fotmd small ganglia on the branches of tlie glosso-pharyngeal and supe-
rior laryngeal nerves (Med. Zeit., 1840, No. 2), the mucous glands are very numerous. G.

GLANDS OF THE ORAL CAVITY. 455

glosso-pJiar?/7if/eal nerve in the tongue, and these have been recently sub-
jected by myself (Micr. Anat. II, 2, p. 32), and by Ilcmak (Mlill. Arch.,
1852) to a more exact investigation. Rcmak found such ganglia also
upon the branches of the gustatory division of the fifth nerve in the
Sheep and Calf, as far as close to the apex of the tongue, though they
were smaller and more scanty than those upon the glosso-pharyngeus ;
whilst on the other hand, in man, they were wanting upon the thicker
branches of the gustatory division of the fifth, and were to be found
only as very minute ganglia upon the more delicate internal branches.
Remak endeavors to demonstrate some relation between these ganglia
and the lingual glands, and draws a functional parallel between them
and the ganglion litiguale, a view plausible enough, and against which
I only have to remark, 1. That ganglia exist not only upon the branches
distributed to the mucous membrane, but also upon those passing to the
papillae, and in regions of the tongue (the point) where no glands are
found ; and, 2. That the glandular region of the root of the tongue,
also, possesses gustatory sensibility. Upon these grounds, I think it is
impossible, for the present, wholly to deny a relation of the ganglia in
question, to the sensations.

C. OF THE GLANDS OF THE ORAL CAVITY.
I. — MUCOUS GLANDS.

§ 133. The mucous glands of the oral cavity are yellowish or whitish
racemose glands, usually of a rounded form, and tuberculated surface of
|~2 lines in diameter, which in general lie immediately external to the
mucous membrane and yield a mucous secretion.

According to the localities in which they are found, the mucous glands
present somewhat different relations and receive different names.

1. The labial glands, J— 1| lines in diameter, lie between the muscular
layer and the raucous membrane, are very numerous, and form an almost-
continuous glandular ring round the oral aperture, which commences at
3 lines distance from the red edge of the lips, and possesses a breadth of
about J a line.

2. The buccal glands, lying further outwards, covered by the bucci-
nator muscle, are tolerably numerous but smaller ; a few large glands
appear at the aperture of Stenon's duct upon the buccinator muscle, and
still further backwards in the neighborhood of the last molar tooth
{molar glands).

3. The palatine glands. — Those of the hard palate are small and

Tlmt in the sheep and calf he lias observed little ganglia upon the surface of the ductus
Whartonianus, which are connected with a plexus of delicate nerves investing the duct." —
Tes.]

456 SPECIAL HISTOLOGY.

hardly pass beyond its middle anteriorly, while on the other hand, those
of the soft palate form a considerable layer of glands upon its under
side, which anteriorly measures as much as 3-4 lines, diminishing, how-
ever, somewhat towards the free edge and the uvula. On the posterior
surface of the soft palate, also, glands exist, but they are much smaller,
and do not always form a connected layer.

4. The lingual glands, among which I distinguish : —

a. The mucous glands of the root of the tongue. — These form a stra-
tum, in parts very thick, of glands |^-2 lines in diameter, beneath the
simple mucous sacs of the root of the tongue, to which we shall have to
refer hereafter, and the pajnllce circumvallatce ; it presents, especially
beneath the former, a thickness of as much as 4 lines, and extends almost
continuously from one tonsil to the other. In front of the foramen
ccecum these glands are smaller and more scattered, but a few occur
more or less deep in the muscular substance in front of the most anterior
pajjillce circumvallatce ; they are never found, however, further forwards
than the middle of the tongue.

The excretory ducts of the glands, which are interwoven with the
extremities of the genio-glossus and partly united with them, are as much
as 6 lines long in the posterior glands, and open, as E. H. Weber first
showed, by a funnel-shaped expansion into the simple mucous sacs of
the root ; in the neighborhood of the papillce circumvallatce, on the other
hand, they open independently between the lingual papillse, and into the
clefts which surround the circumvallate papillae, a few also on the walls
of the foramen ccecum.

b. The marginal glands of the root of the tongue. — At the borders of
the root of the tongue we find, at the level of the jjapillce circumvallatce
many perpendicular laminated folds, to which reference has already been
made, and between them fine apertures, which belong to a special small
group of glands lying in the midst of the expansion of the hgo-glossus
and transversus. In animals, these glands, as well as the folds'(Mayer's
organ), are often very greatly developed. (See Brlihl, 1. c.)

c. The glands of the jJoint of the tongue. — On the lower surface of the
apex of the tongue, but still in the substance of the lingualis inferior
and stylo-glossus, there lie, right and left, two elongated broad glandular
masses 6-10 lines long, 2-3 lines thick, 3-4 lines broad, where 5 or
6 excretory ducts open upon peculiar lobed folds of mucous membrane
close to the frenulum linguce ; these glands were long ago accurately
described by Blandin, and have been recently rescued from oblivion by
Nuhn.

§ 134. Intimate structure of the mucous glands. — All these glands
agree in the essential characters of their intimate organization and inva-
riably consist of a certain number of glandular lobes with a branched

GLANDS OF THE ORAL CAVITY.

457

excretory duct. The lobes, of ^vhich in the simplest glands (Fig. 178),
only a few (4-8) exist, are in their
circumference generally elonga-
ted, pyriform, or rounded, not rare-
ly flattened, 0-5-0-72 of a line
long, 0-2-0-48 of a line broad, and
are each seated upon a branch 0*03-
0*05 of a line thick, of the excre-
tory duct, which measures 0-12-
0*3, or even 0-5 of a line (in the
glands of the root of the tongue), f
They consist of a number of coiled
canals, presenting numerous simple
or compound, vesicular diverticula \ ■ : ; \

(Fig. 179), and appear to be the \ ""'^h^'' '; < \

immediate continuations of the ex-
cretory ducts of the lobes, which,
as soon as they have entered the
latter, usually without diminishing

in diameter, breakup successively into a certain number of them. What
have been called the glandular vesicles or acini, are nothing more than

^X:^

the dilatations and terminations of these canals, or ultimate branches of
the excretory ducts. Examined superficially, and under low magnifying
powers, they all appear uniformly rounded or pyriform; the exact ana-
lysis of a whole lobe, or still better of a dissected and injected gland,
shows, however, that their form is very various, rounded, pyriform, or
elongated. It is impossible to describe at length all the forms which
they assume ; I will therefore only remark, that the ends of the glandu-
lar lobes frequently repeat, on a small scale, the figure and structure of
the seminal vesicles, and refer to the subjoined diagrammatic figure.

Fig. 178. — Racemose mucous gland from tlie floor of the oral cavity : a, investment of
connective tissue ; 6, excretory duct ; c, glandular vesicles ; d, ducts of the lobes ; from Man. —
Magnified 50 diameters.

Fig. 179. — Diagram of two ducts of a lobe of a mucous gland: a, excretory duct of the
lobe; 6, secondary branch; c, the glandular vesicles upon it in situ; d, the same separated
and the duct unfolded.

458 SPECIAL HISTOLOGY.

All the finest glandular ducts and vesicles, whose diameter varies from
0*02 to 0"08 of a line, consist of a peculiar, structureless coat, the mem-
hrana projjria^ of 0'0008-0-0012 of a line in thickness, and of an epi-
thelium (Fig. 180), which, in fresh preparations, appears as a continuous

investment of the glandular extremities, but is
^'«-^^°- very readily detached, and then fills the glan-

dular vesicles as a granular mass. The epithelial
cells constitute a simple layer upon the rtiimhrana
•r jiroiyria^ have 3-6 sides, are often somewhat
elongated, 0-005-0-006 of a line broad, 0-003-
O'OOJ: of a line thick, and invariably contain, be-
sides a rounded or elongated nucleus of 0-002-0-003 of a line, often
presenting a distinct nucleolus, a certain number of larger or smaller
granules, which sometimes simply resemble white fat, sometimes are
colored yellowish and brownish, and contribute to the hue of the glands
themselves.

The elements of the glandular lobes which have been just described,
though they are all applied very closely together, so, indeed, as not un-
commonly to be flattened against one another, yet always present a
small quantity of interposed connective tissue, by which the vessels of
the lobes are supported. Besides this, the separate lobes and the entire
glands are invested by dense coats of a connective tissue, with elastic
fibres, which may, in addition, contain fat-cells. In small glands, such
as Fig. 178, the only distinguishable subdivisions are the lobes, glan-
dular vesicles, and cajca, which have been described ; in the larger, on
the other hand, as in the glands of the lips and palate, the smallest
lobes are surrounded in groups by somewhat stronger sheaths of con-
nective tissue, so that a certain number of secondary lobes are formed,
each of which corresponds with a simple gland and also has the same
size, i. g., about \-\\ lines.

The excretory ducts of the lobes have a coat of connective tissue,
with networks of fine elastic fibres, and a simple layer of cylindrical
cells 0-008-0-01 of a line thick. In the principal excretory ducts, the
wall, which is very rich in elastic fibres, measures, even in the smallest
glands, 0-02, in the larger as much as 0-03 and O-Ol of a line, the epi-
thelium 0-01-0'012 of 'a line. Of muscular fibres I saw no trace what-
soever, either in the glands themselves or in their excretory ducts ; on
the other hand, they possess many minute vessels, which penetrate with
the excretory duct or otherwise between the lobes, and form, in the in-
terior, a Avide network of capillaries of 0-003 of a line, which encircle
the separate ceeca and vesicles, so that each of them is in contact with

Fig. 180. — Two glandular vesicles of a racemose rrmcous gland of Man, magnified 300
diameters; a, inembrana propria ; 6, epithelium, as it appears in the apparent section of a
vesicle; c, the same seen upon its surface.

GLANDS OF THE ORAL CAVITY. 459

at least 3-4 capillaries. Nerves exist abundantly upon the excretory
ducts and, occasionally, moderately fine tubules are found in the glands
themselves.

The secretion of the racemose glands is a clear, yellowish mucus, with
only accidentally intermingled granules, nuclei, and remains of cells,
which coagulates in acetic acid and is insoluble in an excess of it, re-
maining as a viscid mass, striated, or deceptively similar to a fibrous
tissue. It fills the excretory ducts and the other cavities of the gland
to their ultimate extremities, being readily rendered obvious in them by
acetic acid. I have never found the so-called mucous corpuscles, as'they
exist in the fluids of the mouth, in a mucous gland, and I believe that,
normally, the secretion of mucus goeson without the production of cells.

II. — FOLLICULAR GLANDS.

§135. The follicular glands of the cavity of the mouth are: firstly,
simple follicles at the root of the tongue and, secondly, compound follicles
at the sides of the isthmus fauciuni, — the tonsils. These organs agree so
perfectly in structure, that the tonsils may be regarded as an aggrega-
tion of simple follicular glands, while, on the other hand, they are so
widely different from the mucous glands that they can on no account be
classified with them.

The simple follicular glands of the root of the tongue (Fig. 169, /),
form an almost continuous layer from the papillce vallatw as far as the
ejn'glottis and from one tonsil to the other, lying immediately under the
mucous membrane, and above the mucous glands. Their position is so
superficial, that the separate glands are visible from without, like little
elevations upon the mucous membrane, and allow their number and
arrangement to be recognized. "When dissected out, we see that each
follicle is a lenticular or globular mass of ^-2 lines in diameter, invested
upon its outer surface by the mucous membrane, which is here very thin,
lying loosely in the submucous tissue and receiving upon its under sur-
face the excretory duct of a more deeply disposed mucous gland. In
the midst of the free surface a punctiform aperture, often tolerably wide
i-J a line, is easily perceived by the naked eye ; it leads into a funnel-
shaped cavity, which is remarkable on the one hand for its narrowness,
in relation to the size of the sac, and on the other, for its thick walls,
and is usually filled with a grayish mucous material.

Each follicle (Fig. 181) is a thick-coated capsule, externally surrounded
by a fibrous investment connected with the deep layers of the mucous
membrane ; internally, it is lined by a process of the mucous membrane
of the oral cavity, Avith its papilloe and epithelium, and contains between
the two, imbedded in a delicate, fibrous, vascular matrix, a certain
number of large, completely closed capsules, or follicles (Fig. 181, g),
which are about i'o-| of a line in diameter, round or elongated in form

460

SPECIAL HISTOLOGY.

Fiff. ISl.

"^^'^'J4-UA,'JXiJJ,

l<..jif '^ _^

present a whitish color, and closely resemble the capsules of Peyer's
patches, the solitary glands, the vesicles of the spleen and of the

lymphatic glands. They con-
sist of a tolerably solid coat,
about 0-002--003 of a line
thick, composed of more ho-
mogeneous connective tissue,
without elastic fibres, and
of grayish white contents,
which, when the follicle is
pricked, exude in the form of
a drop, which becomes diffused
through water, and consists of a fluid with formed particles. The former,
alkaline in its reaction, is present in excessively small quantity, so that
it appears to be merely the connecting medium of the latter, which
consist of cells of 0-003-0-005 and free nuclei of 0'002-0-0025 of a
line without any determinate character. Acetic acid renders the cells
granular, and thence communicates a whitish tinge to the contents ; but
it precipitates no mucus, the fluid differing decidedly in this respect from
the ordinary mucous secretion and agreeing with that of the splenic cor-
puscles. The position of the follicles is usually such, that they form a
connected, almost simple layer, between the external coat and the epi-
thelium of the follicular glands, yet there are localities, at least in ani-
mals, where two follicles are found behind one another, or at greater
intervals.

The vessels of the follicular glands are very numerous, and may often
be traced naturally injected, in man. Small arteries enter from without,
passing through the fibrous coat to the interior, ramify between the folli-
cles, as they ascend, in an elegant arborescent manner, and terminate
in the papilla and on the follicles. The vessels of the former present
the same relations as those of the other simple papillie, and are either
simple or complex loops ; around the follicles they form an exceedingly
elegant and abundant network, whose finest vessels, 0'004-0"006 of a
line in diameter, take a wavy course, forming a moderately close net-
work immediately upon the membrane of the follicle. The efferent
veins converge from these two localities, and are wide and numerous.
Lymphatic vessels also, according to E. H. Weber (Meckel's Archiv,
1827, p. 282), appear to proceed from these glands, and I have myself
noticed nerves upon them.

The tonsils are, according to my investigations, nothing but an aggre-

FiG. 181. — Follicular gland from the root of the tongue in Man: a, epithelium lining it; b,
papillae; c. external surface of the follicular gland, with the coat of connective tissue; e,
cavity of the gland ; /, epithelium; g, follicle in the thick wall of the gland. Magnified 30
diameters.

GLANDS OF THE ORAL CAVITY. 461

gation of a certain number (10 to 20) of compound follicular glands,
which, intimately united and held together by a common investment, form
a large hemispherical organ ; the apertures of the follicles frequently
unite, so as ultimately to form only a small number. Each section of
the tonsil, much as it may vary in the form of its cavity and its external
appearance, has exactly the same structure. Proceeding from the oral
cavity, we observe that its epithelium enters into the separate cavities of
the tonsil and, becoming somewhat thinner, completely lines all the
secondary cavities. Beneath it we find a grayish, soft, very vascular
membrane ^— J of a line thick ; and still more externally, a dense, rela-
tively thick fibrous covering, which, when two lobes or sections of the
tonsils are in contact, belongs to them in common, and is in contact at
their outer extremities with the common coat of the organ. The soft
thick layer between the epithelium and the fibrous investment has the
same composition as the corresponding layer of the follicular glands of
the root of the tongue. Here also we meet with conical or filiform, even
slightly branched papillaj, of 0-06-0-08 of a line in length, 0-01-0-03
of a line in breadth, directed towards the epithelium ; internally to these,
round, completely closed follicles one close to the other, of the same size
and possessing the same contents as those previously described ; and
finally, a soft fibrous tissue connecting them, and containincr numerous
vessels. The vessels are still more numerous than in the follicles of the
tongue, though their ramifications -are essentially similar, except that
the papillae frequently contain multi-
ple loops, and the networks around Fig.i82.
the capsules are still closer (Fig. 182).
The fibrous investment, lastly, con-
sists of connective tissue, with elastic
fibres and receives certain muscular
fibres from the superior constrictor of
the pharynx. Nerves may be detected
on the external surface of the tonsil, Iw^^^^v --.
and in the papillie, but, as in the case '^l^^kj^^f^'lult
of the follicular glands of the root of

the tongue, I have failed to observe ^^ ' -35^^-

them in the proper membrane of the follicles.

Corresponding with their structural similarity is the resemblance in
the secretion of the tonsils and that of the lingual follicles, though the
former is not easily obtained pure on account of the tonsils also receiv-
ing the ducts of mucous glands. It is a grayish-white mucous substance,
which, however, so far as I have been able to observe, contains no mucus,
but is composed either of cast-off epithelial plates alone, or of a mixture

Fia. 182. — Vessels of a few follicles from a human tonsil, seen from the cavity of a sac,
and magnified 60 diameters.

462 SPECIAL HISTOLOGY.

of these with cells and nuclei, perfectly identical with those contained
in the parietal follicles of the tonsillar cavities. How these cells are
formed and whence they arise, I know not. It would seem probable
that they proceed from follicles which have burst, a process which may
really occur in man, though from what is observed in animals we can
hardly assume their dehiscence to be a normal process.*

In man it is quite impossible, in a vast number of cases, to find the
follicles which we have described in the walls of the tonsils, a circum-
stance which appears to me to be explained by the frequent morbid
changes to which these organs are subject. In fact, in the course of
inflammations of the tonsils and their sequelce, the contents of the folli-
cles appear to alter, the follicles themselves becoming distended, and
finally bursting. The closed sacs, filled with purulent or caseous masses,
which are described in diseased tonsils, when they do not exceed a certain
size, may be nothing else than such follicles ; and by their bursting they
may yield those masses of secretion which are accumulated in the larger
cavities. It thus happens, that the normal structure is frequently no longer
recognizable in the walls of the tonsils, and that we find, at most, recently
opened follicles, or more usually nothing but a granular mass interpene-
trated by fibres and vessels, with remains of papill?e and of epithelium.

On the other hand, however, the frequent pathological degenerations
have this advantage, that if we hapj5en to hit upon the right period, all
the follicles may be seen enlarged, but still closed and beautifully
injected, so that it is quite impossible to overlook them. An instance
of such a hyperasraic tonsil, with distended, lingual follicular glands,
the follicles attaining a size of 0'36-0-48 of a line, was what first led
me to a conception of the true structure of these parts, which has been
only verified by subsequent investigations. The difficulties attending
the investigation in man disappear in many animals, and I can especially
recommend the tonsils of the Pig and Sheep, the lingual follicular glands
of the Ox and the tonsil-like organs at the entrance of the larynx in
the Pig, Sheep, and Ox, in which the structure may be always readily
made out, both in fresh organs and in those which have been hardened
in strong alcohol.

With respect to the secretion of the tonsils in man, it is certainly ab-
normal in many cases, in the dead subjects which are accessible for
investigation ; for instance, when the cavities contain considerable quau-

* [In the Mikroskopische Anatomic, B. II. H. 11., p. 46, Professor Kolliker adds a few
points to the account here given of the structure of the tonsils. In man, racemose glands
are not unfrequently met with external to the tonsils, and probably open in them ; and in
the Calf, a considerable number of such glands may be found between the lobes of the
organ. In opposition to Frerichs (Wagn. Handw. III., p. 745), Kolliker states that he lias
"not yet" found solitary glands like those of the intestine in the mucous membrane of the
mouth. — Tbs.]

GLANDS OF THE ORAL CAVITY. 4G3

titles of a grayish, yellowish, or greenish, sometimes softer, sometimes
more consistent mucus, if it may be so called, the constituents of these
contents being larger and smaller cells, with a single nucleus, some of
which have undergone a very obvious fatty metamorphosis, while others
have cavities and thickened membranes ; further, epithelium (not ciliated
cylinders, as Valentin states, having probably confounded with such, the
deepest, here very much elongated, cells of the pavement epithelium),
occasionally abundant cholesterin crystals and mucedinous fungi. The
secretion is more normal if it consist only of epithelium, of small cells
without fat and of free nuclei, the two latter elements being perfectly
similar to those in the follicles; such great masses of them, however,
are often found, that we must suppose they have been developed in
excess.

In any case I am disposed to consider such cells and nuclei as the
proper secretion of the tonsils, inasmuch as, in animals, as for example,
the Sheep, we find similar contents, though their amount is often small.
It is difficult to decide whether they are afforded by the follicles or not ;
certain it is, that they are identical with the contents of the latter, and
that in man the follicles burst, but the former might be accidental, and
the latter only a morbid process.

In fact, however frequently the tonsils of animals are examined, no
ruptured follicles are ever met with ; they are always entirely closed,
and the epithelium extends them, so that one is led to the belief that the
secretion is developed independently, out of a substance excreted into
the cavity of the organ. That this is possible and actually takes place,
indeed, elsewhere {e. g. suppuration upon mucous membranes which are
still covered by their epithelium), is not to be denied ; and the sole
difficulty about such a hypothesis is, that in this case the import of the
tonsillar and lingual follicular glands (for which, also, all that has been
said, holds good), becomes highly problematical. If they do not occa-
sionally burst, their function, as regards secretion, can only be to elabo-
rate in their interior a fluid, which when it subsequently enters the
cavity of the gland, is especially fitted to form its proper secretion.
For the rest, the similarity of the follicles in question, especially with
those of the solitary and Peyerian glands, and also with those of the
spleen* and lymphatic glands, would indicate another series of possi-
bilities, into which, however, I will not enter, because in all the organs
in question the anatomical facts and the physiological relations have
hitherto been by no means completely determined.

III. — SALIVARY GLANDS.

§ 136. The salivary glands, i. e. the parotid, the submaxillary, the
sublingual, and i^mni's glands, agree so closely in their structure with

* [For some additional facts in favor of these resemblances, see notes § Spleen. — Tes.]

464 SPECIAL HISTOLOGY.

the racemose mucous glands, that it wouhl be quite superfluous to enter
into any detailed description of them. They are compound racemose
glands, and they might be regarded as aggregations of numerous mucous
glandules. In fact, the primary and secondary lobulations which are
observed in these glands correspond, the latter to the entire mucous
gland, the former to its lobes. The secondary lobulations then become
united into still larger groups, and a certain number of these constitute
the whole gland. The excretory ducts correspond with the number of
the lobulations of the gland ; they are more or less branched, and ia
their final relations resemble those of the mucous glands.

The more intimate structure of the salivary glands presents nothing
remarkable. The glandular vesicles have about the same diameter —
0'016-0-024-0-03 of a line, in all three descriptions of glands ; they are
as variously formed as in the mucous glands, and proceed in a similar
manner from the excretory ducts. Their membrana propria frequently
presents a double contour, and is, internally, always clothed with a
pavement epithelium, whose cells of 0-005-0'008 of a line have a single
nucleus, and may be obtained in beautiful series by coarsely crushing
the gland ; they are distinguished by their greater proportion of fatty
granules and pigment granules from those of most mucous glands,
whence the glandular vesicles themselves present a somewhat dark
appearance. Here, also, acetic acid makes the contents of the cells
turbid, the addition of an excess even not restoring their clearness, and
it is not therefore advisable to make use of it in our examinations; a
very dilute solution of caustic soda, which allows the epithelial cells to
be seen iyi situ, is more to be recommended.

The excretory ducts of the salivary glands possess a single layer of
cylinder epithelium, whose cells measure 0*016 of a line in length. The
remaining portion of the wall, which is very thick in Stenons duct, but
much thinner in the others, has a dense, solid structure, and consists of
connective tissue, with a very close network of fine, and moderately
thick, elastic fibres. It is only in Wharton s duct that we find, exter-
nal to the epithelium, and to a double layer of elastic membranes whose
elements are disposed transversely and longitudinally, a thin stratum of
smooth muscles, which, however, can only be demonstrated and isolated
with very great difficulty. They are disposed longitudinally, have short
nuclei of 0-004-0-006 of a line, at most 0-008 of a line, and are covered
externally by a layer of connective tissue with elastic fibres.

The vessels of the salivary glands are very numerous, and present the
ordinary structure. The capillaries have a diameter of 0-003-0-004 of
a line, and form broad netwoi'ks in which the glandular vesicles are im-
bedded, so that each vesicle receives its blood from several directions.
A considerable number of vessels are distributed also to the excretory
ducts. Lymphatics are found in the salivary glands, but their internal

GLANDS OF THE ORAL CAVITY. 465

relations are unknown. Nerves proceed from the 2^^^xus caroticus ex-
ternum, with the vessels, into the interior of the glands; in addition, the
ganglion Unguale [ling uaJ is and chorda t?/mpani) supplies the two smaller
pair of glands, and the facial nerve, probably with the anterior auricular,
the parotid. I may remark, with regard to the distribution of these
numerous nerves, that here also it is impossible to find any in the smallest
lobules of the glands, while on the other hand they are readily discovered
upon the larger vessels and the excretory ducts. In animals I found
particularly rich nervous networks upon Rivints duets, the tubules
having a diameter of 0*001-0"002 of a lino.

The secretion of the salivary glands normally contains no formed ele-
ments, but may accidentally present cylindrical cells from the excretory
ducts, or scattered, half-disorganized cells from the glandular vesicles.
Its physical and chemical properties, in the different salivary glands,
appear to differ in some respects. The parotid saliva is clear and fluid,
and, like the glandular vesicles themselves, contains no mucus. Ber-
nard and Jacubowitsch found the secretion of the sub-maxillary gland in
the dog to be viscid, and capable of being drawn out into threads ; ac-
cording to Bernard also, a watery extract of the gland itself contains
mucus.

In man, the ductus Whartonianus, if laid open, is usually found to
contain a small quantity of a kind of mucous fluid, which, however, con-
sists chiefly of cylinder epithelium and broken-up epithelial cells of the
glandular vesicles themselves, containing only a very small amount of a
substance which coagulates in acetic acid, and is, perhaps, mucus. The
glandular vesicles, on the other hand, if crushed, usually yield a con-
siderable quantity of mucus, which coagulates into threads by the action
of acetic acid. The vesicles of the proper sublingual gland contain
still more mucus, and the ductus Bartliolinianus also commonly presents
distinct evidence of it. With respect to Rivinis ducts, they are filled,
in man and animals, with the same yellowish, viscid, amorphous fluid,
coagulating into threads by the action of acetic acid, which is met with
in the ducts of the small mucous glands, while the glandular vesicles
themselves also contain abundant mucus. From all that has been said,
it would seem that jR/ymz's glands, as I will call them, must be excluded
from the class of salivary glands, and, as regards the three larger glands,
their secretion does not appear to be identical, but sometimes to contain
mucus (submaxillary and particularly the sublingual), sometimes to want
it (parotid).

"We may take this opportunity of making some observations w^ith
respect to the salivary, or mucous corpuscles, of authors ; rounded cells
of 0-005 of a line, with one or many nuclei, which are always to be met

30

466 SPECIAL HISTOLOGY.

with in the fluid of the mouth, and are usually supposed to be derived
from the mucous or salivary glands, yet wrongly, since the examination
of both these kinds of glands, and of their ducts, teaches us that they
excrete no formed elements. In my opinion the mucous corpuscles are
nothing but products of the mucous membrane of the oral cavity — not
normal, although they are almost constant, but a kind of exudation- or
pus-corpuscles, with which they have, as is well known, the closest pos-
sible resemblance in structure. Many authors considejr them to be
abortive epithelial cells of the oral cavity ; but in that case the epithe-
lium of the localities in which they are found must Avant the outermost
layer of large, flattened scales, which is hij no means the case. In my
own person, at any rate, I find mucous corpuscles on the gums, the lips,
cheeks, and tongue, in localities in which the epithelium is ivholly un-
injured ; and by scraping with a knife I can often obtain entire
lamellffi of epithelial plates, covered with mucous corpuscles. I do not
mean to affirm by this, that in little sores, arising from whatever cause,
upon the gum, for instance, where the epithelium is wholly or partly
wanting, or when it is lost more extensively, in consequence of disease,
that mucous- or exudation-corpuscles may not be developed, as upon
other sore surfaces, and then might be regarded as abortive epithelium-
cells, but only, that this does not take place in the oral cavity under
ordinary circumstances. I consider, therefore, that the so-called mucus,
or salivary corpuscles, are exudation-corpuscles, and consequently totally
distinct from epithelial cells ; and I regard their formation to be analo-
gous to that of the pus-corpuscles in catarrh, which also very often takes
place upon unbroken epithelial surfaces. It is thus readily explained
how it is that they are almost entirely absent in many individuals, while
in others who are subject to irritation of the mucous membrane of the
mouth they are very abundant, and that they have been observed in
saliva, obtained from a fistulous aperture (Sebastian, in "Van Setten,
Diss, de Saliva." 1837, p. 12).

The best mode of examining the oral mucous membrane is by making
perpendicular sections of portions, either fresh, or dried, or hardened
in absolute alcohol, in which the papillae and epithelium are very dis-
tinct, and become still more so by the use of very dilute caustic soda ;
by the aid of which also the deepest perpendicular epithelial cells are
rendered readily visible. The papillae may be studied in macerated
portions, or if it be only required to ascertain their position and form,
in perpendicular or horizontal sections, treated with concentrated caustic
potassa, on which the epithelium is dissolved. Tlie lingual papillae may
be treated in the same manner; the epithelium upon which, especially
on the filiformes, moreover, is often entirely absent. The nerves of all
these parts are best seen under the use of dilute caustic soda; acetic

THE TEETH. 467

acid is also frequently of service. The muscular substance of the tongue
must be examined by minute dissection, a method which may be car-
ried very far, especially in tongues which are half macerated from hav-
ing long lain in spirit. Recent tongues are also of use, but are by no
means so good, and it is usually necessary to boil them until they are
quite soft ; and to procure sections for the microscope the tongue may
be dried or hardened by boiling, or by strong alcohol. In all three
methods caustic soda is of great service in clearing up the tissue,
although it undoubtedly attacks the muscular fibres a little. Perpen-
dicuhar ami longitudinal sections in various directions are to be recom-
mended, especially in the glandular region. With respect to the glands,
the most important points have been already stated.

Literature. — W. Bowman, Art. " Mucous Membrane," in Todd's
" Cyclopaedia of Anatomy," April, 1842; E. H. Weber, " Ueber die
Schloimbalo-e und zusammengesetzten Driisen der Zunge und liber den
Bau der Parotis," in Meckel's "Archiv," 1827, pp. 276-280; A. Se-
bastian, " Recherches anatomiques, physiologiques et pathologiques sur
les glandes labiales," Groningue, 1842; Nuhn, "Ueber eine bis jetzt
nicht naher beschriebene Drlise im Innern der Zungenspitze," Mann-
heim, 1845; N. Ward, Art. "Salivary Glands," in Todd's " Cyc. of
Anat.," Sept. 1848, part xxxiii. p. 421 ; C. Rahn, "Einiges iiber die
Speichelsecretion," Zurich, 1850; C. Ludwig, " Neue Versuche liber
die Beihlilfe der Nerven zur Speichelsecretion," in "Mitth. der ZUrch.
nat. Ges.," 1850, Nos. 53 and 54, and " Zeitschr. f. rat. Med.," 1851 ;
C. J. Baur, "Ueber den Bau der Zunge," in Meckel's "Archiv,"
1822, p. 350 ; P. N. Gerdy, " De la Structure de la Langue," in " Re-
cherches d'Anatornie, de Physiologic, et de Pathologic," Paris, 1823 ;
P. F. Blandin, "Sur la structure de la Langue," in the "Archiv.
g^ndr. de Medecine," 1823; J. Zaglas on the "Muscular Structure of
the Tongue of Man and certain Mammalia," in the " Annals of Anatomy
and Physiology," ed. by J. Goodsir, 1850, I. p. 1; H. Hyde Salter,
Art. "Tongue," in Todd's " Cycl. of Anat.," iv. June an<l September,
1850 ; C. B. Briihl, " Ueber den Bau der Zunge der Haussaugethiere,"
in " Kleine Beitrage zur Anatomic d. Haussaugethiere," Wien, 1850,
pp. 1-6; Sappey, " Ueber die Lymphgefasse der Zunge," in " Comptes
rendus," 1847, p. 26; and " Froriep's Notizen," 1848, vi. p. 88.
Besides these, compare the anatomical works of E. H. Weber, Valentin
(ini Handw. d. Phys.), Todd and Bowman, Henle, Arnold, Huschke,
Krause, and myself* the figures of Berres, Arnold, and Langenbeck.

D. OF THE TEETH.

§ 137. The teeth are hard organs inserted into the alveolar processes
of the jaws, which although to some extent identical in structure with

468

SPECIAL HISTOLOGY.

bone, and in other respects clearly allied to it, must, from their develop-
ment, be regarded as modifications of the mucous membrane.

In every tooth we must distinguish the tooth proj^er, and the soft
strvetures; the former consists of a free part, the croivn, and of an im-
bedded portion, the simple or multiple fangs, whose special forms are
treated of in anatomical works ; they contain internally a small cavity,
the pulp cavity/, which extends through each fang as an elongated canal
opening at its point by a simple, or more rarely double (Havers, Rascli-
kow) fine aperture.

Among the soft parts we may enumerate first, the gum, gingiva, a
dense mass formed by the union of the mucous membrane and of the
periosteum of the jaw, which surrounds the lower half of the crown or
the 7iecJc of the tooth. Secondly, the periosteum of the alveolus, which

Fi-r. 183.

/.

unites the tooth very closely with
the alveolus. Finally, the pulj?, a
soft, vascular and nervous mass,
which occupies the cavity of the
tooth, and is connected with the
pteriosteum of the alveolus, through
the aperture in the fang.

The proper tooth (Fig. 183) con-
sists of three distinct structures.
1. The dentine, which constitutes its principal mass, and determines its
general form. 2. The enamel, which forms a tolerably thick invest-
ment to the crown ; and 3. The cement, which covers the fang exter-
nally.

§ 138. The dentine or ivory (Fig. 183, d), is yellowish-white and
translucent or transparent, in thin sections of a recent tooth ; when dry
it has a silky or satiny aspect, in consequence of the reception of air
into a special system of canals. It is considerably harder and more

Fig. 183. — Molar tooth (Iniinan) ; magnified about 5 diameters: 1, longitudinal ; 2, trans-
verse section: a, enamel ; i, pulp cavity; c, cement; (/, dentine, with its canals.

TUE TEETH.

469

brittle than eitlier tlie cement or bone, but, on the other hand, vieUls in
these qualities to the enamel. With the exception of a very small spot
in the root, the dentine forms the sole boundary of the pulp cavity, and
in an uninjured tooth it is never exposed, inasmuch as it is covered,
even upon the neck of the tooth, by a thin layer of enamel, and when
this ceases, by cement.

The dentine consists of a matrix and of a multitude of canals which
traverse it, the dentinal tubules or canals. In the recent tooth, the for-
mer is, even in the finest sections^ quite homogeneous, without the
slightest trace of cells, fibres, or other elements. After the extraction
of the calcareous salts from the dentine, it exhibits, however, a great
tendency to tear up into coarse fibr^, parallel to the dentinal canals;
from these, finer fibres of 0-00i2-0-00o of a line may be detached, their
irregular form, however, shows them to be artificial products, and in
fact they owe their existence simply to the circumstance, that the denti-
nal canals run close together and parallel to one another throuo-h the
dentine. The matrix exists in all parts of the dentine, but not every-
where to the same amount. In general there is less of it in the crown
than in the root, and in the neighborhood of the pulp cavity than in that
of the enamel and cement.

The dentinal canals (Figs. 184, 187) are microscopic tubules of 0-0006-
0-001 of a line (in the root some reach 0-002 of a line), which commence
by open mouths upon the wall of
the pulp cavity, and traverse the
■whole thickness of the dentine to
the cement and enamel. Each
canal has a special wall, rather less
in thickness than its diameter,
■which can only be observed in trans-
verse sections (and then not al-
■ways), as a narrow, yellowish ring surrounding the cavity; in longi-
tudinal sections, on the other hand, it is almost entirely invisible.
During life the canals contain a clear fluid and they cannot therefore
readily be detected in recent preparations ; it is different in dry sections,
when they become filled with air, and appear separately as black lines
by transmitted light, and by reflected, as silvery threads. On account
of the immense numbers of the dentinal canals, so great in some situa-
tions that their walls are almost in contact, dry sections appear milk-
white, and if not very thin, are quite unfit for microscopic investigation,
unless the air has been previously expelled from the canals by any clear
and not viscid fluid.

Fig:. 1S4.

Fig. 1 84. — Transverse section of dentinal canals as they are comnaonly seen, magnified
450 diameters : a, canals very clo;e together ; b, more dispersed.

470

SPECIAL HISTOLOGY.

The dentinal canals present certain constant peculiarities in their
course which may be best gathered from Figs. 185 and 187; it is not
straight but tvavT/, and in addition, thej present numerous rayniji-

Fig. 1S5. Fi-. 1S6.

catioris and anastomoses. Each canal
describes, in general, two or three large
curvatures, and a very great number (as
many as 200 in 1 line, according to
E,etzius) of small curvatures, which are
sometimes more or less strongly marked
and occasionally have even the appear-
ance of actual zigzags, or spiral wind-
ings. The ramifications of the canals
(Figs. 185 and 186), appear in the first
place as divisions, and then as true rami-
fications ; the former are very frequently
to be met with close to the origin of the
tubules from the pulp cavity, and are
almost always bifurcations, of such a kind
that one canal divides at an acute angle
into two of almost the original diameter.
These divisions may be repeated 2-5
times altogether, and even still oftener,
so that at last, 4-8-16, and even more
canals, proceed from a single one. The
canals, already somewhat narrowed after
division, then run close together and tole-
rably parallel, towards the surface of the
dentine, and excepting in the root, branch

Fig. 1S5. — Dentinal tubules I'lom the root, magnified 3'iO diameters: a, internal surface of
the dentine, with scattered canals; /;, their divisions; c, terminations with loops; rf, granu-
lar layer, consisting of small dentinal globules at the boundary of the dentine; e, bone
lacuncE, one anastomosing with dentinal canals. From Man.

Fig. 18G. — Transverse section through the dentinal canals of the root, a, in order to ex-
hibit their excessively numerous anastomoses ; magnified 350 diameters. From Man.

THE TEETH. 471

again only in its outer half or third ; the ramifications appearing, in the
root, as tine twigs given off from the principal canal, while in the crown,
they more resemble dichotomous divisions. In the latter case, they are for
the most part rare, in the former, it is otherwise ; the branches, which
are usually close together and given off at right or acute angles from
the trunk canal, having sometimes the appearance of a feather, some-
times that of a brush, the latter being most common when the twigs are
large and undergo further branchings. According to their more or less
frequent ramification, are the e7ids of the dentinal canals more or less
fine ; frequently appearing merely as excessively fine, pale lines, like
fibrils of connective tissue, and finally disappear. When they are dis-
tinct, they either become lost upon the surface of the dentine in a gra-
nular layer, which we shall have to consider presently, or they enter the
innermost portions of the enamel and cement, or finally they are con-
nected in pairs by loops in the dentine (terminal loops of the dentinal
canals). The branches of the principal canals are, almost always, very
fine and usually simple, though sometimes ramified ; they serve, as may
be best seen in the root, where they are excessively numerous, to con-
nect neighboring or even distant canals ; such anastomoses having either
the form of simple, transverse canals or of loops. The ultimate branches
present the same relations as the forked or simple terminations of the
principal canals, and end either free or by loops, in the dentine, or are
continued beyond it.

The chemical composition of dried dentine is, according to Von
Bibra : —

Molar of a

Molar of a

Incisor of tl

Woman of 25.

Man.

same Man

Phosphate of lime, with

some fluoride

of calcium,

. 6754

66-72

Carbonate of lime.

7-97

3-36

Phosphate of magnesia,

2-49

1-08

Salts, ....

1-00

0-83

Cartilage,

. 20-42

27-61

Fat

0 58

D-40

10000

10000

Organic substance,

. 21-00

2801

28-70

Inorganic substance.

. 7900

71-99

71-30

In fresh teeth, Pepys found 28 p. c. cartilage, 62 inorganic matter,
10 water and loss; and according to Tomes, teeth, after the pulp is
removed, lose in drying |-,V of their weight. The organic basis of
the teeth, which may readily be obtained by treating them with hydro-
chloric acid, is identical in all respects with that of the bones, and is
readily changed into gelatin by boiling. This so-called cartilage of

472 SPECIAL niSTOLOGY.

the tooth retains the exact form of the dentine and its external struc-
ture also ; the tubules, however, are seen with difficulty. If it be
macerated in acids or alkalies until quite soft, the matrix undergoes
incipient solution, hut the dentinal tubules, with their loalls, offer greater
resistance, and may he readily and abundantly isolated (see " Mikr.
Anat." ii. 2, p. 61, fig. 189). By still longer maceration, all is dis-
solved. If teeth be heated to redness, or treated with caustic alkalies,
the inorganic portions likewise retain the form of the tooth. It follows,
then, that the same intimate mixture of inorganic and organic parts
occurs in the teeth, as in the bones, with which they so closely agree
in their chemical composition.

The apparent tvalls of the dentinal tubuli, which are commonly visible
in transverse sections (Fig. 184), are not the actual walls of the canals,
but rings, which result from our invariably viewing a certain length of
the canals in the always more or less thick sections, their undulated
course giving the walls a greater apparent thickness than they really
possess. If in any transverse section the apertures of the canals be
exactly brought into focus, we perceive, instead of the dark ring, only
a very narrow yellowish border, which is what I consider to be the
actual wall. That such is the case, appears from the examination of
transverse and oblique sections of canals filled with fluid, in which short,
yellow tubules and small rings of almost the same diameter as that of
the cavities of the canals, may be clearly recognized.

The dentine occasionally presents indications of lamination in the
form of arched lines running more or less parallel and at different dis-
tances, often quite close together (Fig. 187) ; which in transverse sec-
tions appear as rings, and are especially distinct in the crown. These,
the contour lines of Owen,* are not the same with the glistening,
indistinctly defined striiB observed by Schreger, which run exactly

* [This is not exactly correct. The term " contour lines," as used by Professor Owen
("Report of British Association" for 1S3S, p. 135, and " Odontography," pp. 4G0, 4G4, G41),
includes both descriptions of markings mentioned in the text, but is more especially em-
ployed for Schreger"s. The ordinary contour lines, in fact, are stated by Professor Owen to
proceed from " a short bend" of the tubuli " parallel with the outer contour of the crown ;"
from these, the Professor distinjruishes the " strong contour lines," in the ivory of the ele-
phant's tusk, as being produced by " strata of extremely minute opaque cellules." It should
be observed, however, that Retzius had long before drawn attention to these peculiar strice.
In his admirable memoir, published in JNIuller's Archiv, for 1837, he says, p. 507, "In the
incisor teeth of the horse, also, many less transparent striae running parallel with the cavitas
pulpcE may be seen, like the annual rings in the trunk of a tree. They proceeded in this
case, however, not merely from certain parallel flexures of the tubes, but especially from
similar calcareous cells, which had accumulated in one zone for the greatest part of the length
of the tooth. Tab. xxii. Fig. 3." See also his explanation of the zones in the P^lejihant's
tooth, at pp. 510-11. — Trs.]

THE TEETH.

473

Fiff. 187.

parallel to the pulp cavit}'', and arise from the primary curvatures of the
dentinal canals, and which are the ex-
pression of the laminar mode of de-
posit of the dentine. In animals they
are at times singularly beautiful, espe-
cially in the Cetacea and Pachyder-
mata (Zeuglodon, Dugong, Elephant),
and also in the Walrus. Here, as well
as in fossil teeth, we very frequently
observe a breaking up of the dentine
into lamelliC (Owen), indications of
which may be found also in fresh human
teeth and in the dental cartilaare.

Upon the crown, the dentinal canals
not unfrequently pass for some distance
into the enamel, and expand here and
there, into larger cavities (Fig. 191),
which should perhaps rather be regarded
as pathological. Similar not quite nor-
mal formations are the interglohular
spaces in the dentine itself (Fig. 188).
Czermdk has conferred this name upon
certain very irregular cavities, bounded
by globular processes of the dentine,,

■which are, it may be said, never entirely absent in the teeth. In the crown
they are found most frequently in the neighborhood of the enamel, and

Fi-. 188.

[ll]wM^

often form a thin curved layer, extending along its whole inner surface,

Fig. 187. — Perpendicular section of the apex of an incisor tooth (human), magnified 7
diameters : a, pulp cavity; b, dentine ; c, arched contour lines, with interglobular spaces; rf,
cement; e, enamel, the various directions of the fibres being indicated ; ff, lines of color of
the enamel.

Fig. ISS. — A morsel of dentine with dentinal globules and interglobular spaces filled
with air between them ; magnified 300 diameters.

474 SPECIAL HISTOLOGY.

■\vhich, upon close examination, is seen to be composed of a multitude
of thin layers, receiving the ends of the contour lines (Fig. 187). They
also occur, however, more internally, but always in longitudinal sections,
in lines which correspond with the contour lines. The spaces are some-
times very wide, intersecting or interrupting in their course many den-
tinal canals ; sometimes they are very small, so that only a few canals
are touched by them. In the former case, their limits are formed by
distinct globular projections of 0-002-0-012 of a line, and more, which
are pierced by dentinal canals, and have precisely the same aspect as
the dentine, of which they are obviously nothing but portions; whilst
in the latter, such dentinal globules, as I will term them, are not always
distinct. Tliis is especially true of the smallest spaces, which, on
account of their notched form, and their communications with dentinal
canals, might be taken for osseous lacunce, and indeed have been so
regarded ; yet, at least in the crown, it is almost always easy to recog-
nize their identity with the larger spaces. Greater difficulty is met
with upon the fang, where small interglobular spaces and globules form
a zone (the gi'miular layer of Tomes), which often appears like a layer
of small osseous lacuniTe or of simple granules. I have but rarely
observed actual lacunar in normal dentine ; they were, when present,
invariably situated at the boundary of the cement (Fig. 185) ; on the
other hand, interglobular spaces and dentinal globules are to be met
•with in the interior of the dentine of the root, and with especial dis-
tinctness on the walls of the pulp cavity, in which latter locality the
globules often give rise to irregularities visible to the naked eye, or
even to a botryoidal appearance. The interglobular spaces Avhose pre-
sence is normal in developing teeth, contain during life, not fluid, as
might at first sight be expected, but a soft substance resembling tooth
cartilage and possessing a canaliculated structure, like the dentine itself.
It is remarkable that this substance offers a greater resistance to long
maceration in hydrochloric acid than the matrix of the actually ossified
tooth, and therefore, like the dentinal canals, it may be completely
isolated. In sections, this interglobular substance usually dries up in
such a manner that a cavity is produced, into which air penetrates ; it
is properly only in reference to these, that interglobular spaces can be
spoken of. Many teeth, indeed, exhibit no interglobular substance,
but they occasionally present the outlines of dentinal globules, in the
form of delicate arched lines.

Dentine containing Haversian canals, the so-called " vaso-c?ew^me"
of Owen, which exists in many animals, is rarely found in man, and I
am only acquainted Avith one case, observed by Tomes (1. c. p. 225), in
which the vascular canals were numerous ; on the other hand, in the
dentine with irregular tubuli, which is formed in obliteration of the pulp
cavity, we occasionally meet with scattered Haversian canals and

THE TEETH. 475

rounded cavities, like osseous lacuna;, constituting the so-called osteo-
dentinc of Owen.*

* [Considerable discrepancies will be met with if we compare the various statements of
authors who have described the ultimate structure of the dentine.

1. According to Rctzius, the dentine contains cells^ but these cells, in his view, are cavities
analos.'ous tn bone lacima, in which the dentinal canals terminate.

2. Mr. Nasmyth took a totally ditTerent view from this. The matrix, or, as he calls it,
" interfibrous substance of the dentine," is, he says, composed entirely of cells; but these
cells are solid bodies, lie between, and form the boundaries of the canals. His "cells" and
those of Retzius had exactly as much, or as little relation to one another, as the "osteal cells"
of Tomes and De Morgan (to which we have referred in the note to § 107, p. 335), have
to osseous lacuna;.

3. Professor Owen likewise affirms, that the dentine is made up of "cells" — his " dentinal
cells," — which, however, can hardly be identical with Czermak's "dentine globules,"' as
stated in the text. We find it, in fact, somewhat difficult to understand what these "dentinal
cells" are, inasmuch as we are unable to reconcile the various definitions of their nature
which may be found in the " Odontography." In the first i)lace, at p. 462, it is stated, in a
note, that "the true dentinal or calcigerous cells include many tubes and intertubular spaces,
and it is much more exact to say, that those cells contain a tubular structure, than that the
interstitial space is cellular." In perfect accordance with this, we find, on referring to plate
123, fig. 1, which represents a section of human dentine, that the "dentinal cells" which
are marked d'd', are traversed by from seven to eleven dentinal tubules.

But at p. 4G3, the passage in which reference is made to this figure, runs thus: " the den-
tinal cells of the human tooth are subcircular, about jjj'nj'h of an inch in diameter. They
seem most numerous from being most conspicuous near the periphery of the dentine, as
originally described by me in the dentine of the Crocodile."

And in the Introduction, p. xlvi. we find: "The diameter of the dentinal or calcified pri-
mary cells of the pulp, is usually one-fourth or one-half larger tlian that of the blood-discs
manifest in them."

Now, how is it possible, that a body jj'yiyth of an inch in diameter, can have passing
through it seven tubules, each of which is jjjojfs'^' of an inch in diameter? To say nothing
of the circumstance, that these tubules are at the very least yjojij'^^ '-'^ ^" '""^'^ apart.
Halve the actual diameters of the tubules and arrange them close together, and they will
barely squeeze into jjj'og''^ °^ ^'^ inch. We conclude, therefore, as the definitions and the
figures of these dentinal cells are at variance, that we are not justified in making any defi.-
nite statement about them.

4. Mr. Tomes asserts in his lectures, that the "intertiib\)lar tissue is itself made up of
minute granules closely united," which pass into those of his "granular layer;"' an opinion
which seems to us to be most nearly in accordance with fact. We may observe, that the
dentine globules and interglobular spaces of Czermdk, had been previously very carefully
figured and described by Mr. Tomes, in his lectures, p. 45.

5. The views of Czermak are stated in the text. Mr. James A. Salter (On certain Ap-
pearances occurring in the Dentine, dej)endent on its mode of Calcification. " Quarterly
Journ. of Mic. Science," vol I., p. 252, 1853), has confirmed Czermak's results, and has
added some very interesting observations of his own. He considers that the contour lines,
which he prefers to call "contour-markings," may arise from various causes, not only from
those pointed out by Czermdk — curving* and local enlargements of the canals and inter-
lobular spaces, but also from a difference in density without alteration of structure; and he
States as a general law, that the curves of the contour markings are in proportion to the
primary curves of the dentinal tubes at any particular spot, and cross them at right angles.
No markings are more divergent than the outline of the tooth, and passing from within out-
ward, they abut in succession upon the external surface of the dentine, under the enamel
and crusta petrosa, in the form of granular patches. The outer extremities of these patches

476 SPECIAL HISTOLOGY.

§ 139. The Enamel, substantia vitrea, forms a continuous layer
investing the crown of the tooth ; it is thickest upon the masticating sur-
face, and gradually diminishes towards the roots until at last it termi-
nates by a sharply-defined or sometimes slightly-notched border, ceasing
sooner upon the contiguous surfaces of the crowns, than upon their inner
and outer sides. The external surface of the enamel appears smooth,
but is always marked by delicate, close, transverse ridges, among which
more marked circular elevations may occur.* A delicate membrane,
discovered by Nasmyth, and which I will denominate the cuticle of the
enaynel [Nasmytli s membrane, TRS.],t entirely covers, but is so closely

look like white rings on the surfoce of the tooth. They are composed of coarse globular
dentine, and gradually thin out internally into mere streaks. When a tooth is macerated in
acid, it may be brolcen uji into cones (triangles in section), as Dr. Sharpey first indicated,
formed by the normal dentine between the contour markings. In transverse sections, the
cones become, of course, rings. Finally, Mr. Salter points out that the enamel is almost al-
ways imperfect opposite die "patches" at the outer ends of the contour lines. — Trs.]

* [Czermak (1. c. pp. 4, 5) states that the fine regular annular ridges and furrows upon the
surface of the enamel, characterize the permanent teeth, and are not present upon the enamel
of the milk set. The ridges are closest at the margin of tlie crown, and most distant towards
its centre, where they finally disappear. In the space of a line, there were, at the margin
of the enamel, 84-72 ridges; more internally, 3G-30 ; and where they began to be indistinct
only 18-12.— Trs.]

t [We have ventured to substitute the name " Nasmyth's membrane," for that of the "cuti-
cle of the enamel," used by Professor Kolliker, inasmuch as the latter term gives a false idea
of the relations of this important structure, which is much more than a mere "cuticle of the
enamel," and is in fact, as one of us has already shown (Huxley, On the Development of
the Teeth, " Quarterly Journal of Mic. Science," vol. I. p. 149, 1853), the calcified membrana
preformativa of the whole pulp.

This structure was first described, in its true relation to the dental tissues, by Mr. Nasmyth,
in a memoir read before the Medical and Cliirurgical Society, in January, 1839, and which,
illustrated with very good figures, was published in the twenty-second volume of the So-
ciety's Transactions (p. 310-328). Mr. Nasmyth states, that his attention had been drawn to
fragments of a membrane which he found floating in the acid in which teeth had been
macerated; "after a minute and careful examination, however, I was able to demonstrate
with the greatest certainty, that they were derived from the external surface of the enamel,
and that they were continuous with the structure covering the fang, which latter is itself
continued into the chamber of the tooth. I afterwards succeeded in tracing this covering on
the whole surface of the enamel and fang of the tooth in one continuous envelop ; and
eventually, I was enabled to remove it from the crown of the tooth in the form of a distinct
coat or capsule ; this covering, which I proved to exist externally to the enamel, I have
termed 'the persistent dental capsule,' " p. 312.

" In all cases where this covering has been removed by means of acid, it has, of course,
the appearance of a simple membrane, in consequence of the earthy deposits having been
dissolved, and of there being only present the animal tissue. The structure and appearance
of the covering detached in this nranner from tlie enamel, are the same in every respect as
those observed in the capsule of the unextruded tooth ; consisting, like it, of two layers, fibrous
externally, and having on its internal surface the peculiar reticulated appearance common
to both, and shown at Plate V. Fig. 6," p. 313.

"On examining carefully fine sections of .-several teeth under the microscope, I perceived
here also, that the structure in question was continuous with the crusta pelrosa of the fang of
the tooth," p. 313.

THE TEETH. 477

united Avith, the enamel, that it can be demonstrated only by the use of
hydrochloric acid. According to Berzelius and llctzius,* a similar mem-
brane exists between the internal usually irregular surface of the enamel,
and the dentine, but I have been unable to find it. The enamel is bluish,
transparent in thin sections and much more brittle and harder than the
other dental structures, so that it is hardly touched by the knife, and
yields sparks with steel (Nasmyth). Chemically, it may be regarded as
osseous substance, containing the smallest possible proportion of organic
matter ; but whether the latter belong to the class of collagenous sub-
stances or not is uncertain. According to Von Bibra, the enamel
contains: —

From a Molar

of

a '

From a Molar of

Womau 25 years

of

age.

an adult Man.

Phosphate of lime, with some fluoride of cal-

cium, ..... . . .

S1-C3

89-82

Carbonate of lime, . . . . .

888

4-37

Phosphate of Magnesia, . . . .

2-55

1-34

Salts,

0-97

0 88

Cartilage, . ......

5-97

3-39

Fat,

a trace

0-20

100-00 10000

Organic matters, ...... 597 3-59

Inorsanic matters, ...... 94 03 9G-51

The enamel, as its fibrous structure indicates, consists entirely of the
so-called prisms or fibres of the enamel (Fig. 189) ; long, solid prisms

Mr. Nasmyth does not distinguish quite clearly in the text, between the proper capsular
membrane on the fang and the crusta petrosa itself, though his figures (PI. 5, Figs, 4, 5) exhibit
the two structures as sufficiently distinct, and he hesitates, at p. 316, to decide what relation
the outer layer of pale yellowish or brown substance in the cement of the teeth of the Elk,
Ox, Bradypus, &c., may have to the '• persistent capsule."'

We have not retained Mr. Nasmyth"s own term for his discovery, because, as one of U3
has endeavored to show (Huxley, 1. c.) while he accurately described its relations to the
other dental tissues, he mistook its true nature. (See Appendix, § 8, on the Development of
the Teeth.) But, on the other hand, as no one lias, before or since, distinctly described his
"persistent capsule," we have thought it desirable that his name should be associated with
the structure.^TRS.]

-* [Berzelius and Retzius obviously sawNasmytlfs membrane (Retzius, in IMiill. Archiv,
1837, pp. 53, 54). The latter says, that on macerating a large piece of enamel from the fossil
tooth of a horse (dug out of a peat-moss) in dilute acid, he found after the enamel was dis-
solved, a membrane swimming in the fluid, "I examined it immediately under a conside-
rable magnifying power; it appeared to be pierced by a multitude of closely arranged little
holes, but exhibited no trace of fibres." But he states expressly, that this membrane was
"internal to the enamel fibres, as Berzelius clearly points out," and therefore failed to recog-
nize its true relations with the enamel. — Tr.s.]

478

SPECIAL HISTOLOGY.

Fig. 189.

Fijr. 190.

of 0-0015-0*0022 of a line in breadth, irregular in shape, but commonly
hexagonal or pentagonal, which usually occupy the
whole thickness of the enamel, resting with one ex-
tremity upon the dentine, and with the other upon
Nasmyth's membrane. In adult teeth, these elements
may be very readily detected in transverse and longi-
tudinal sections, but can hardly be isolated for any
great length; it is otherwise in young or developing
teeth, where the enamel is much softer and may be
cut with a knife. In such isolated prisms, whose broken ends may by
accident appear pointed, whence they have been called " enamel
needles," the surfaces and edges may be very well seen. We may also
very frequently observe upon them, particularly after the addition of
dilute hvdrochloric acid, more or less distinct transverse striae 0-0014-
0-002 of a line apart, which arise from slight varicosities, and give the
fibres a certain resemblance to muscular bundles, or rather colossal mus-
cular fibrils. They certainly do not
indicate a cellular composition. If
the action of the hydrochloric acid
be allowed to go on, the fibres soon
become quite pale, the transverse
striation disappears, and nothing re-
mains but a delicate framework cor-
responding with the previously solid
fibres, and which often presents cer-
tain appearances of tubes. In the
end this also becomes almost com-
pletely destroyed by the action of
the acid, so that in teeth which have
been thus macerated hardly any-
thing remains of the enamel, which
does not, like the dentine, retain its form.

The prisms of the enamel are uJiited very intricately without any in-
termediate substance. I have not been able to convince myself that
canals constantly exist between the prisms,* but it is certain that cavi-

Fio. 189. — Surface of the enamel, with the ends of the enamel prisms, magnified 350
diameters. From the Calf.

Fig. 190. — Enamel prisms isolated, after the slight action of hydrochloric acid; magni-
fied 350 diameters. From Man.

* [With respect to this point, opinions differ ; Todd and Bowman consider that canals
normally exist between the enamel prisms. Tomes finds canals in the enamel prisms of
young animals, and sometimes in a part or the whole length of them in old teeth. Kolliker
(Mikr. Anat. 77) has not yet observed any such cases. Czermak (I.e. p. 13) believes that,
in a few cases, he has observed " very numerous delicate enamel tubules arranged in close
series." — Trs.]

THE TEETH.

479

ties of various kinds mny be not nufrequcntly found in the enamel. Such,
for instance, are — 1. The continuations of the dentinal canals into the
enamel, to which reference has been made above, with the elongated
cavities at the border of the dentine which arise from their expansion
(Fig. 191, c); and 2. The cleft like gaps in the middle and external
portions of the enamel (Fig. 191), which are not in communication with
the preceding, are never entirely absent in any enamel, and often occur
in very gteat numbers, as narrower or wider spaces which, however,
never contain air.

The general course of the prisms of the enamel resembles that of the
dentinal canals of the crown of the tooth, but extensive flexures are
only to be met with towards the masticating surface. Most of the
prisms extend through the whole thickness of the
enamel, but this is not the case with all. They
also decussate in a peculiar manner ; thus, in
some transverse sections, we observe annular
layers of prisms, 0-08-0-12 of a line thick,
extending from the dentine to the surface of the
enamel, and corresponding Avith fine circular lines
upon its exterior ; in each layer, all the prisms
take a similar direction, which is different from
that of the prisms of the contiguous layers, so
that perpendicular sections of such enamel, espe-
cially when moistened with hydrochloric acid,
have a very singular striated appearance, arising
from the dark transverse, and clear longitudinal
sections of the prisms being alternately presented
to the eye.

A similar decussation of the prisms occurs
constantly at the masticating surface, and here
the layers of enamel take a generally annular
arrangement, so that they describe circles, in the
molars, and ellipses in the incisor teeth ; however,
towards the centre of the masticating surface,
irregularities occur which we are not yet in a condition to explain.
Care must be taken not to confound the colorless strice which indicate
these peculiar arrangements of the enamel fibres, with certain hroivnish
lines or colored streaks which cross the prisms in various directions, and
in perpendicular sections appear like oblique ascending lines or arches
(Fig. 187) ; in transverse sections, like circles in the external layers of

Fig. 191. — Dentine and enamel, magnified 350 diameters; Man : a, cnticle of the enamel
(Nasmytli's membrane) ; b, enamel prisms with transverse markings and interposed clefts ;
c, larger cavities in the enamel ; d, dentine.

480 SPECIAL HISTOLOGY.

enamel, rarely extending through its "whole thickness. These I regard
as the expression of the lamellated development of the enamel.

Nasmytlis membrane is a calcified, structureless membrane, 0-0004—
0"0008 of a line thick, distinguished by the great resistance it oifers to
chemical reagents, and its consequent appropriateness as a defence for
the crown of the tooth. It is not altered by maceration in water, and
is not dissolved by boiling in water, concentrated acetic acid, hydro-
chloric acid, sulphuric acid, and nitric acid ; the latter only fenders it
yellow. In caustic alkalies it remains unchanged. Boiled with caustic
potassa and soda, it becomes white and somewhat disintegrated, but still
forms a connected mass ; the potassa is rendered slightly turbid by the
addition of hydrochloric acid, but clears with an excess. The membrane
burns with an ammoniacal odor, and yields a calcareous spongy coal.

§ 140. The Cement, substantia ostoidea, cementum (Fig. 185), is a
cortical layer of true osseous tissue, which covers the fangs, and in the
many-fanged teeth, ^not uncommonly unites them all together. It com-
mences where the enamel ceases, as a very thin layer, either simply
abutting upon, or slightly overlapping it, increases in thickness lower
down, and finally attains its maximum at the ends of the fangs, and on
the alveolar surface of the molar teeth between the fangs. Its internal
surface is, in man, very intimately united with the dentine, but without
any connecting substance, so that frequently, at least under high powers,
the limit of the two structures is not altogether sharply defined. The
external surface is very closely surrounded by the periosteum of the
alveolar cavity, but is not so firmly united with the gum ; after the
removal of these soft parts it is usually irregular, and is frequently
marked with annular striations. The cement is the least hard of the
three dental tissues, and is, chemically, almost identical with bone.
Von Bibra found : —

In Man. In the Ox.

Organic matters, 29 42 32-24

Inorganic matters, ...... 70 58 67-7G

100-00 10000

The latter, thus composed : —

Pliosphate of lime and fluoride of calcium, ..... 58-73

Carbonate of lime, .......... 722

Pliosphate of magnesia, 0-99

Salts, 0 8-2

Cartilage, 31-31

Fat, 0-93

100-00

The earthy salts are readily extracted from the cement by acids, a

THE TEETH.

481

white cartilage remaining, which may easily be separated from the den-
tine, and usually, when boiled, yields gelatin.

Like bone, the cement consists of matrix and of lacuncp, but rarely
contains Haversian canals and vessels. Besides these, peculiar canals
aiuiloirous to those of the dentine are found, and other more abnormal

cavities

The matrix is sometimes granular, sometimes transversely striated,
sometimes amorphous, and frequently laminated like bone. The lacunce

Fisr. 192.

resemble in all essential characters those of the bones, so that any de-
tailed description may be dispensed with. They are distinguished only
by the great variety which they present in number, form, and size (0-005-
0*02, even to 0'03 of a line), and the unusual number and length (as much
as 0"03 of a line), of their canalieuli. The majority are oval, and lie
parallel to the axis of the tooth, others are rounded and pyriform. Those
are most remarkable which have a very elongated form, together with a
narrow, canal-like cavity (Fig. 185), inasmuch as their resemblance to
the dentinal canals is unmistakable. The canalieuli often resemble
feathers and brushes, and unless the lacunce are altogether isolated,
connect them with one another, and anastomose with the ends of the
dentinal canals. In the thinnest part of the cement, towards the crown,
the lacunce are invariably absent ; they are first met with, as a rule,
about the middle of the fang, but are here scattered and solitary ; towards
the extremity their number gradually increases, and they not unfre-
quently take on a very regular arrangement, as in the external layer of
the long bones, lying in series in the layers of the cement, and sending
most of their canalieuli inwards and outwards, so as to give rise to an
even, fine, transverse striation of the cement. The thicker layers of

Fig. 1D2. — Dentine and cement from tbe middle of the fang of an incisor tooth: a, dentinal
canals; b, interglohular spaces, having the appearance of osseous lacuna; c, smaller inter-
globular spaces; d, commencement of the cement, with many canals close together; e, its
lameUa ; f. lacunce; g, canals; from Man. Magnified 350 diameters.

31

482

SPECIAL HISTOLOGY.

cement which occur in old teeth, present immense quantities of lacunre,

but these are to a great extent irregular, and have mostly the elongated

Fi-. 193. form. Many lacunoe are bordered, singly

or in groups, by a very distinct, clear,
yellowish, slightly undulated margin,
which partially or entirely surrounds
them ; it has perhaps some relation to
the cells from which the cavities are
developed.

Haversian canals do not occur in
young teeth, where the cement has only
its normal thickness ; but they are very
common in old teeth, especially molars,
and in hyperostoses one, three, or more
enter the cement from without, branch
out two or three times, and then termi-
nate in blind extremities. Their diameter
is too small (0-005-0-01 of a line), to
contain medulla as well as bloodvessels, and they are commonly like
those of the bones, surrounded by a few connective lamellee.

Besides these vacuities, the cement occasionally presents peculiar
sinuous cavities, which are certainly pathological products (see " Mikr.
Anat." II. 2, p. 82, Fig. 202); and frequently canals, like dentinal
canals (Fig- 1^'2), which are sometimes closely set, at others more iso-
lated, occasionally ramified, and very frequently connected with the
ends of the dentinal canals, and with the canaliculi of the osseous
lacuna'.

In the cement of the SoUpcclia, the osseous lacuna? with their canali-
culi, of the innermost layers, are frequently enclosed within actual cells,
as Gerber first pointed out. If such cement be macerated in hydro-
chloric acid, these cells maybe readily isolated, and present the following
characters, which are not unimportant in their bearing upon the nature
of the lacunoe. 1. The lacuniie frequently occur in twos and threes in a
single cell, exactly as I have seen in rickety bones. 2. The substance
which immediately surrounds the cavities and their processes, is not so
readily soluble in hydrochloric acid as the other parts of the thickened
cell. In fact, while the cells appear generally pale, a dark notched body,
which often contains a very distinct cavity, is very obvious in their
interior ; and as we see by comparing it with these lacunfe of the cement,
the contours of whose cells are no longer visible, is nothing else than
the innermost portion of the thickened wall of the original cell. In the

Fig. 19-3. — Cement and dentine of the root of an old tooth: a, pulp cavity: b, dentine; c,
cement, with lacnncc; f, Haversian canals. From Man.

THETEETH. 48

o

last-mentioned lacunrc, in fact, it is easy to demonstrate, by the aid of
acetic acid, a special wall, ■whicli is at first thick, but subsequently
becomes thinner ; and occasionally sucli lacunar, with walls which give
off a few processes externally, may be isolated. These lacunoc are fre-
quently empty, but in other cases they contain a substance which at
first also resists hydrochloric acid, wherein, howevei', I could discover no ■
nucleus.*

§ 141. The so/i{^;a?*^s of the teeth are: the ])e7'io8feu77i of tJie alveolus, the
dental puljj, and the gum. The periostemn of the alveolus is very inti-
mately connected with the fangs of the tooth, and has the same structure
as any other periosteum, except that it is softer, contains no elastic ele-
ment, and possesses an abundant nervous network, containing many thick
fibres.

The dental pulp — the remains of the foetal dental papilla — arises from
the periosteum at the bottom of the alveolus, enters the fangs, and, as a
continuous, soft, reddish, very vascular and nervous substance, fills their
canals and the pulp cavity in such a manner as to be everywhere in close
adherence to the inner surface of the dentine. The pulp consists of an
indistinctly fibrous connective tissue, totally destitute of the elastic ele-
ment, but containing many dispersed, round and elongated nuclei ; and
except that it occasionally contains narrow bundles, almost like imper-
fect foetal connective tissue. A fluid may be expressed from it which,
like mucus, is coagulated by acetic acid and is not dissolved in an excess ;
and, similarly, the entire pulp is rendered whitish by acetic acid, never
becoming transparent like perfect connective tissue. This substance
constitutes the principal mass of the pulp, so far as the vessels and
nerves extend ; but upon its surface we find, immediately beneath a deli-
cate structureless membrane, a layer of 0'02-0"04 of a line thick, com-
posed of many series of cells, 0*012 of a line long, 0-002-0-003 of a line
broad, cylindrical or pointed at one end, with long narrow nucko-
lated nuclei of 0-005 of a line, arranged perpendicularly to the
surface of the pulp like a cylinder epithelium. More internally these
regular series are no longer recognizable, but the cells, without losing
their close radial arrangement, are more intermixed, and pass, finally,

* [The structure of the cement on the fang of the still uncut molar of the calf, is very
peculiar and instructive. It is here a white, friable substance, about Jj of an inch thick,
bounded externally by a delicate Nasmyth's membrane. Its outer three-fourths are com-
posed of straight parallel fibres, resembling those of the enamel, but -^^ of an inch long. The
inner fourth consists of similar fibres inextricably interlaced, cemented into a mass by a cal-
careous deposit, and containing here and there, spaces or lacuna-, yg'^jy of an inch in length,
as it were left among the fibres. This structure appears to become obliterated with age, as
the cement on the fang of the molar immediately in front of this, which had cut the gum,
had the ordinary appearance. (Huxley, 1. c.) — Ti^s.]

484 SPECIAL HISTOLOGY.

by shorter and rounder cells, without any sharp lines of demarcation,
into the vascular tissue of the pulp. These cells corespond with the
formative cells of the dentine, to be described presently, and they afford
the materials for the deposits of dentine upon the walls of the pulp
cavity, which takes place even in the adult.

The vessels 0? the pulp are excessively numerous, whence its red color.
3-10 small arteries enter each pulp of a simple tooth, and ultimately
form, as well in its interior as upon its surface, a loose plexus of capil-
laries, 0-004-0-006 of a line in diameter, which also exhibits here and
there upon the surface distinct loops from which the veins arise. The
pulp appears to contain no li/mj^haties, but its nerves^ are extremely
abundant. Arising from the well-known nervi dentales, there passes
into every fang a large trunk of 0-03-0-04, and besides, as many as six
or more, fine branches of 0-01-0-02 of a line, which contain fibres of
0-0016-0-003 of a line. They ascend at first without any considerable
anastomoses and only giving off a few filaments ; but in the thicker part
of the pulp they form a rich plexus, with elongated meshes and divisions
of the nerve tubules, and so gradually break up into fine primitive
fibres of 0-001-0-0016 of a line. I am inclined to think their final
termination is in loops, but I grant that so long as the primitive fibrils
in those loops which unquestionably do occur, have not been traced from
trunk to trunk, which no one has yet done, the subject is open to doubt.

The gum, gingiva, that portion of the oral mucous membrane which
unites the alveolar margins of the jaw and the necks of the teeth, is a
pale red vascular tissue, which is tolerably soft, but feels firm on ac-
count of the subjacent hard parts : it, attains, where it lies upon the
teeth, a thickness of J-IA- lines, and possesses papilltB of a considerable
size (of 0-15-0-3 of a line; in old people they even reach 0*7 of a line
in length, and like the papiUce filiformes are covered with secondary
papillfie), and a pavement epithelium, which, between the papilh-e, has a
thickness of 0-23-0-4 of a line. I could find no glands upon the gum,
but care must be taken not to confound with them certain rounded de-
pressions of the epithelium of 0-8-0-15 of a line in diameter, with
more cornified cells, which occur not unfrequently upon its upper por-
tions.

§ 142. Development of the Teeth. — The development of the twenty
milk teeth commences in the sixth week of foetal life, by the formation
of a groove in the upper and lower margin of the jaws, in which,
up till the tenth week, twenty dental papilla gradually make their ap-

* [The nerves of the alveolar periosteum and of the pulp, are particularly described by
Czermdk (I. c. pp. 27, 28).— Tns.]

THE TEETH.

485

pearance. Partitions are now developed, so that each papilhi soon lies

in a special cavitj. In the course

of the fourth month, these cavities

gradually contract, the papilhx; at

the same time assuming the forms

of the future teeth, and finally they

close up completely ; this takes place,

however, in such a manner that a

little cavity is developed ahove each

" tooth-sac," and thus " reserve

sacs," in which the pulp begins to

be developed in the course of the

fifth month, are formed for the

twenty anterior permanent teeth.

J

Fig. 195.

These ^^ reserve sacs" at first lie above the milk sacs, but by degrees
they retreat backwards, and are received into hollows of the bony alveoli
as they are formed round the milk teeth (Fig. 195, [/, h). Those of the
incisors and canines eventually become completely separated from the

Fig. 194. — Lower jaw of a human foetus, nine weeks old, magnified 0 diameters: a,
the tongue thrown bacl; ; b, riglit half of the lip depressed; i', left half of the lip fiit oft";
c, outer alveolar wall; d, inner alveolar wall; e, papilla of the first molar; /, papilla of the
canine; g, of the second ; /(, of the first incisor; i, folds where the ditrltts Riuiitiaui subse-
quently open.

Fig. 195. — Diagram of the development of a milk-tooth, and of its corresponding perma-
nent tooth, after Goodsir : a, dental furrow ; b, tl\e same, with hs, papilla; c, the same begin-
ning to close, with the rudiment of the reserve cavity ; d, the same, still more closed ; <?, tooth,
sac completed, with a " reserve cavity ;"/, the reserve cavity moving backwards; g, the same
become quite posterior, with a pulp; A, the alveoli of both sacs are forming, the milk-tooth
has emerged ; i, the permanent tooth forming, its deeper seated sac has a giibernacidum.

486 SPECIAL HISTOLOGY.

alveoli of tlic corresponding milk teeth, but those of the premolars* open
into the bottom of the alveoli of the deciduous molars.

The sacs of all these teeth are produced at their apices into a solid
cord, which extends either to the gum, or, as in the two premolars, to
the periosteum in the bottom of the alveoli of the two deciduous molars
(Fig. 195, i), and has been erroneously described as a guhernaculum, or
guiding cord for the teeth in their eruption.

The sac of the anterior of the three permanent molars, arises, together
with its papilla, in the sixteenth or seventeenth week, quite indepen-
dently, from the posterior extremity of the primitive dental groove, and
closes in such a manner that a reserve sac remains between it and the
mucous membrane (Mikr. Anat. Fig. 206). It is not till the seventh or
eighth month after birth that the latter elongates behind the first sac,
arches into the margin of the jaw, produces a papilla from its base, and
becomes constricted off into the sac of the second molar. The remainder
of the cavity falls into a line with the other sacs, and forms that of the
wisdom tooth.

The formation of milk teeth begins at about the fifth month of foetal
life, and at the seventh, ossification has commenced in all of them. The
first step is the formation of a little scale of dentine upon the apex of
the pulp ; in the molar teeth there are at first several of these scales,
corresponding with the several elevations of the pulp, but they soon coa-
lesce. Immediately after the appearance of this dentinal scale, a thin
layer of enamel is deposited from the so-called enamel organ upon the
roof of the sac, and whicli coalescing with the dentine, forms the first
rudiment of the crown of the teeth. The scale of dentine extends over
the pulp and becomes thicker, so that it soon rests like a cap upon the
pulp, and finally forms a sort of capsule for it, which, as ossification
proceeds and the pulp diminishes, closely and completely embraces it;
the deposition of enamel goes on simultaneously, so that it soon proceeds
from the entire surface of the enamel organ, and becomes more and more

* [Instead of the loose phraseology " small " and " large "' molars, &c., we have adopted
the philosophiinil nomenclature of the teeth, introduced by Professor Owen (see his Article
on the Teeth, in Todd's Cyclopedia), and thus explained by him : " Those teeth which are
implanted in the premaxillary bones, and in the corresponding part of the lower jaw, are
called ' incisors,' whatever be their shape or size ; the tooth in the maxillary bone, which is
situated at or near to the suture with the premaxillary, is the ' canine,' as is also that tooth
in the lower jaw, whicli in opposing it, passes in front of its crown when the mouth is closed.
The other teeth of the first set, are the 'deciduous molars;' the teeth which displaces them
vertically, are the ' premolars :' the more posterior teedi which are not displaced by vertical
successors, are the molars properly so called."

It results from this, that the so-called bicuspid and "first molar " of the permanent set in
man (Professor Kolliker's ",small molars") are the premolars; being, in fact, the third and
fourth of the typical dentition ; the first and second premolars and the third incisor of the
typicardentition, not being developed in man. The nomenclature of the teeth, from being
merely technical and arbitrary, has thus, by Professor Owen's recourse to development
become scientific. — Tiis.]

THE TEETH. 487

considerable. In this manner, the whole enamel is eventually deposited
around the dentinal layer of tlic crown, while the enamel organ and the
pulp gradually diminish, until the former is represented only by a deli-
cate membrane ; and the latter presents similar relations to that of the
perfect tooth. As yet there exists no trace of either fang or cement ;
they are not formed till the crown is nearly complete, and the tooth is
about to emerge. About this time the pulp undergoes a considerable
longitudinal growth, while the enamel organ becomes atrophied ; and
upoa the newly formed portion only dentine, that of the fang, is de-
veloped. The tooth, thus forced upwards, begins to press against the
upper wall of its sac, and the firm gum which is closely united with it;
in which an independent process of absorption also takes place, and the
tooth finally makes its appearance. The gum now contracts around it,
and the rest of the dental sac becomes closely applied to the fang, and
constitutes the alveolar periosteum.

The milk-tooth attains completeness : 1, by the addition of the
remainder of the fang, and the constant elevation of the crown to its
normal length ; and 2, by a deposition which takes place from the sac,
now united with the alveolar periosteum, which commenced even before
eruption, and by which the cement is applied around the fang, while at
the same time the tooth is thickened by internal deposition, the pulp
diminishing to a corresponding extent. In teeth with several fangs, the
pulp, which is at first simple, divides as it elongates, near its point of
attachment, a separate fang being developed around each portion. The
eruption of the milk teeth takes place in the following order : central
incisors of the lower jaw in the oth — 8th month ; central incisors of the
upper jaw a few weeks later ; lateral incisors in the 7th — Oth month,
those of the lower jaw first ; anterior molars in the 12th — IJith month,
those of the lower jaAV first; canine in the 16th — 20th month; second
molars between the 20th and 30th months.

The permanent teeth are developed in precisely the same Avay as the
milk-teeth. Their ossification begins, somewhat antecedent to birth,
in the first molar, extends, in the first, second, and third years, to tlio
incisors, canines, and premolars, and finally reaches the second molar ;
so that in the 6th — 7th year there are 48 teeth co-existing in the tAvo
jaws, i. e., twenty milk teeth, and all the permanent set with the excep-
tion of the wisdom teeth (third molar). When the shedding of the
teeth takes place, the bony partitions which separate the alveoli of the
permanent from those of the milk teeth are absorbed, and at the same
time the fangs of the latter gradually disappear from below in a manner
which is not yet understood. The permanent teeth, whose fangs in the
meanwhile have elongated, thus become placed immediately under the
loosened crowns of the milk teeth, which finally, as the others protrude,
fall out and make way for them. The permanent teeth emerge in the

488

SPECIAL HISTOLOGY.

following order : first molar in the seventh year, inner incisor in the
eighth year, lateral incisor in the ninth year, first premolar in the tenth
year, second premolar in the eleventh year, canine in the twelfth year,
second molar in the thirteenth year, third molar (wisdom tooth), between
the seventeenth and nineteenth years.

The gum in the foetus, and especially in newly born infants before
the eruption of the milk teeth, is whitish and very firm, almost cartila-
ginous, whence perhaps it has also been called gum-cartilage, although
it has not the slightest resemblance to cartilage in structure, but consists
of the ordinary elements of mucous membrane, but with a considerable
admixture of a more tendinous tissue. The bodies of the size of millet-
seed, contained in it, described by Serres, the so-called glandulce

Fig. 196.

tartaricce, which are supposed to secrete the " tartar " of the teeth, are
aggregations of epithelium, and are probably pathological* (see Mikr.
Anat. II. 2, p. 92).

The dental sacs consist of connective tissue, in which vessels and nerves
are distributed ; from their base proceeds the dental pulj), which, in

Fig. 196. — -./^j tontli-sac of the second incisor of an eight-months' foslus, from the broad
surface, magnified 7 diameters: a, dental sac: b, enamel pulp; c, enamel membrane; d,
enamel ; e, dentine ; _/, dentinal cells ; g, limits of the cap of the dentine; h, dental pulp ; i,
free edge of the enamel organ. B, first incisor of the same embryo from the narrow surface :
letters as before; a, dentinal cap in ioto ; k, nerves and vessels of the pulp.

* [They have a diameter of from 0'24-0'3G of a line, and are composed throughout of
nvimerous concentric layers of ordinary epithelial plates, or of softer scales, with cholesterine
crystals and granules. Besides these, microscopic bodies of 0-02-0-12 of a line, soft, and
with only indications of lamination, are found in the gum (KoUiker, 1. c). The true nature
of these glands was pointed out by Purkinje and Raschkow. — Trs.]

THE TEETH.

489

Fiff. 197.

form, resembles the tooth to which it belongs, and consists of an internal
portion rich in vessels, and eventually in nerves also, and of a non-
vascular external portion. The latter is bounded by a delicate structure-
less membrane, the memhrana 'prceformativa (Raschkow), which has no
further relation to the development of the tooth. Beneath this, lie
cells of 0-016-0-02-i of. a line in length, and 0-002-0-0045 of a line in
breadth, Avith very beautiful, vesicular nuclei, and distinct, single or
multiple nucleoli ; they are arranged close together over the whole
surface of the pulp (Fig. 197), like an epithelium, though not so sharply
defined internally as it would be, but
gradually passing, at least apparently,
by smaller cells, into the parenchyma.
In vascular pulps (Fig. 107), an addi-
tional boundary line may be traced, inas-
much as the capillary loops in which the
vessels terminate, do not penetrate be-
tween the cylindrical cells, but end close
to one another upon their inner surface;
so that, considering that the dentine is
produced by the cells in question, we
might be justified in terming them the
dentinal membrane^ or memhrana eboris.
The internal portions of the pulp consist
throughout of an originally granular or homogeneous, afterwards more
fibrous matrix, containing many rounded or elongated nuclei, which
must be regarded as a sort of connective tissue. Vessels are developed
in great numbers in the pulp at the period when ossification commences ;
the most numerous perpendicular loops of capillaries of about 0-006 of
a line existing in contiguity with the ossifying surface. The iierves
accompany the vessels, but are developed later ; their number is very
considerable and their distribution resembles that in the pulp of the
perfect tooth.

The enamel organ [organ adamantince), is applied to the pulp like a
cap by its internal, concave surface, and is connected externally with
the dental sac, in such a manner, however, that at the base of the pulp
it presents a very small free edge. Its structure is very peculiar. The
principal mass consists of anastomosing stellate cells (Fig. 196, b), ov-
reticulated connective tissue, containing in its meshes a great quantity
of fluid, rich in albumen and mucus. This gelatinous connective tissue
is most abundant immediately before the commencement of ossification,
and in its earliest stages. Thus, in the fifth and sixth months it mea-
sures j%-l of a line ; in the new-born infant, on the other hand, only

Fig. 107. — Surface of tlie dentinal pulp of a newly-born infant: a, dentinal cells: 6, their
appendages; c, vascular part of the pulp ; magnified 300 diameters.

490 SPECIAL HISTOLOGY.

0*16-0'2 of a line. At this period it contains vessels in its outer third
and its network is metamorphosed into true connective tissue (Mikr.
Anat. ii. Fig. 211). On the inner side of the spongy tissue of the
enamel organ, lies the so-called enamel memhrane^ 7nemhrana adaman-
tince (Raschkow), a true cylinder epithelium, of which it need only be
said that its cells measure 0'012 of a line in length, and 0-002 of a line
in breadth, are finely granular and delicate, and possess nuclei fre-
quently situated at the ends of the cells.

The development of the dental tissues has, hitherto, always been re-
garded as a very difficult subject. The simplest relations are presented
in the enamel, where there can be no doubt whatever that the enamel-
cells become, by their complete ossification, the enamel-fibres. As soon
as only a small portion of the cells has become ossified (without the
previous deposit of calcareous matter in a granular form), a little scale
of enamel is recognizable upon the somewhat larger cap of dentine,
Avhich has also just been produced. The deposition of calcareous mat-
ter in the cells constantly advances outwards, until at last they are en-
tirely converted into enamel fibres, and extends at the same time to
other cells, so that the layer of enamel increases in width. During this
process, the enamel membrane does not disappear in the locality in
which ossification commenced, but retains, there and elsewhere, the
same thickness, so long as the deposition of enamel continues : its ossi-
fying part, therefore, must be replaced by the incessant development of
new substance, which takes place apparently, not by the apposition of
new cells, but by the continual growth of the old ones. The enamel
organ has assuredly some very important relation to the development
of the enamel ; probably serving by the abundance of albumen and of
mucus in its meshes, as a storehouse, out of which the enamel membrane,
distant as it is from bloodvessels, is enabled to draw the materials for
its increase. In fact, the spongy tissue is seen to decrease more and
more during the development of the enamel, and finally, when the
enamel is complete, to disappear.

In the development of the dentine, as in that of the enamel, it is not
the whole pulp which shares in the process, but only its most external,
epithelium-like layer of cells, wdiich appears to maintain a constant
thickness by the elongation of the original cells, accompanied by a con-
tinual multiplication of their nuclei (Mikr. Anat. ii. 2, p. 103 et seq.)
I by no means intend to assert that one and the same cell suffices for the
whole duration of the development of the dentine, although this is not
at all inconceivable; indeed, I consider it possible that the dental cells
are from time to time replaced by others, which are formed upon their
inner surface ; but what I deny is, that the whole pulp is simply changed
progressively, from without inwards, into dentinal cells and ossified, and
I am of opinion that, like the spongy tissue of the enamel organ, the

THE TEETH. 491

only import of the pulp in the development of the dentine is to sup-
port the vessels which are necessary to enable the dentinal cells to grow
at all.

The diminution of the pulp, therefore, is very readily intelligible
without supposing it to be ossified from without inwards ; it takes place,
like the diminution of the contents of the wide Haversian canals of
foetal bones when the lamella are deposited upon their walls, by a
gradual resorption of its tissue, which, as in the latter case, is soft and
full of juices; and it is by no means necessary to suppose any extensive
retrogressive metamorphosis of its vessels.

"With regard to i\\Q formation of the dentine from the dentinal cells,
it is certain that no other tissue than these cells contributes anything to
its development and that they, like those of the enamel membrane, be-
come dentine by the gradual reception of calcai-eous salts. The dentinal
tubules are either the remains of the cavities of the dentinal cells, whose
walls, in the course of ossification, thicken and harden into them, but
do not quite close, or they are developed from the elongated and coalesced
nuclei of the dentinal cells whose cavity persists ; or finally, they are
the result of a process of resorption in the primarily homogeneous den-
tinal tissue, analogous to the formation of the Haversian canals, or of
those in the cement. Of these three hypotheses, the second would, at
first sight, appear the most probable, if we consider that the dentinal
tubules may be isolated, with distinct walls, that the dentinal cells are
abundantly provided with nuclei, and that certain filiform prolongations
of the dentinal cells which I have noticed (Figs. 9 and 197, and Mikr.
Anat., II., 2, p. 105), might be regarded as elongated nuclei ; but there
is one very remarkable fact, tliat no trace of anij elongation of the nuclei
can he discovered hy the most careful investigation. The third hypo-
thesis is indeed conceivable, but in opposition to it, we find that pores
and canals exist even in the youngest and softest dentine, when the de-
velopment of the tooth is at all advanced, and therefore, that they can
hardly be regarded as secondary formations. In favor of the first sup-
position, on the other hand, it may be said, that it would, if true, indi-
cate a close agreement between dentine and osseous tissue, structures
which are in every case nearly allied, inasmuch as the dentinal tubules
would be homologous with long and narrow, simple or possibly coalesced,
osseous lacunce. Certain objections may bo urged, which are not, per-
haps, so important as they at first appear. These are, in the first place,
that the dentinal canals have special walls and may be isolated as tubes,
which might be regarded as demonstrative evidence that they are deve-
loped out of peculiar vesicular structures, either nuclei or cells; and
secondly, that upon this supposition, the filamentous appendages to the
dentinal cells are not so readily interpreted. But as regards the former,
we have recently learnt that the osseous lacunce and canaliculi may also

492 SPECIAL HISTOLOGY.

be isolated, with special walls wliich are not those of the original cells,
and the same is true of the Haversian canals, whence it would be con-
ceivable that the walls of the dentinal canals also, although originally
and genetically not special structures, might eventually become so.
Since, again, the processes of the dentinal cells may be nothing else
than the still soft part of the cells in which ossification is commencing,
this first hypothesis may be regarded as having a certain claim to con-
sideration, the more so as the osseous lacunar in the teeth frequently as-
sume forms resembling those of the dentinal canals, often communicate
with them, and, at least in animals, are interposed among them.

To sum up, it may be said, that in any case, the matrix of the dentine
proceeds from the cylindrical cells investing the pulp of the tooth, which
undergo a greater or less elongation, coalesce and ossify. The dentinal
canals either arise from the nuclei of these cells, or are, and this at
present appears to me to be more probable, the remains of the cavities
of the cells, whose boundaries have undergone a greater consolidation,
and therefore correspond with osseous lacunce. The divisions of the
canals are explained, if we conceive, either that the dentinal cells divide
longitudinally from time to time, as I believe I have actually observed,
or that a cell coalesces Avith two of its predecessors. As to the more
delicate ramifications, we can only suppose that they are formed by a
secondary process of resorption in already formed dentine, like that
which must be assumed to occur in the osseous lacuna', to account for
the anastomoses of their canalicuU, and their communication with
Haversian canals ; at least, I see no possibility, whatever view we take,
of explaining their formation in any other way, without coming into
opposition with well-ascertained facts. No such process as the thicken-
ing and ossification of dentinal cells accompanied by the formation of
pore-canals can be observed, so that the fine lateral branches appear to
be entirely of secondary origin.

In the course of the ossification of the dentine, at least in man, we
find that the deposition of calcareous salts in the recently-formed,
structurally characterized, though only slightly hardened dentine, takes
place in such a manner that the whole appears to consist of isolated
globules. These globules, which are visible not only at later periods,
but in the earliest cap of dentine, and are best seen at the edge of the
root of a large tooth viewed externally, eventually disappear if develop-
ment proceed normally, calcareous matter being deposited between
them, so that the dentine becomes quite homogeneous and clear; in the
opposite case, they persist in greater or less number, and the spaces
between them, which are nothing but the interglobular spaces above
described, contain unossified dentine.

According to my observations, the development of the cement takes
place from that portion of the dental sac which lies between the pulp

THE TEETH. 493

and the enamel organ, and commences, even before the eruption of the
teeth, contemporaneously with the formation of their fangs. About
this time the dental sac elongates inferiorly, applies itself to the grow-
ing fang, yields, from its abundant vascular network, a soft blastema,
in which nucleated cells are developed, and then ossification takes place.
The cement, therefore, is not formed by the ossification of the sac itself.
I met with the first traces of it in newly-born infants, in the form of
isolated, elongated, or rounded scales, which were firmly attached to
the dentine of the, as yet, very short fang, and looked exactly like the
developing osseous substance in the cranial bones ; the smallest exhi-
bited distinct osseous lacuna', and a faint yellow tinge, but were quite
soft and transparent, passing at their edges into a clear cellular blas-
tema ; in the larger ones, the margins were similar, but the centre was
darker and firmer, and in this way every stage of transition to actual
bone was presented, without any granular deposit of calcareous matter.
With the elongation of the fang, new osseous scales of this kind were
formed and gradually coalesced from above downwards into a single
layer, to which continual additions were made from without, until the
whole thickness of the cement was produced.

I am unacquainted with the manner in which the Nasmyth's mem-
brane is produced. No structureless layer exists upon the enamel
organ, by the ossification of which it might be supposed to be formed,
and therefore I should be inclined to regard it as a calcified, amorphous
exudation secreted from the enamel organ immediately after the ossifi-
cation of the last enamel cells, which glues together and protects the
ends of the prisms of the enamel.

If we now, in conclusion, take a general view of the different struc-
tures in the teeth and their mutual relations, we perceive that althougli
they agree in certain respects, yet they cannot be brought under one
class. Dentine and cement are much more closely allied to one ano-
ther, than to enamel, and should it prove to be correct that the den-
tinal canals are formed by the coalescence of the cavities of thickened,
elongated cells, the dentine will correspond Avith an osseous tissue,
whose matrix is constituted only by the thickened walls of the original
cells, and whose lacunce are all directly connected. Cement, or bone
and dentine, often have a very close external resemblance to one another,
particularly, on the one hand, when the latter is traversed by numerous
Haversian canals, and, as Retzius believes he has observed, contains
osseous lacunar ; and, on the other hand, when, in bone, the lacuna? are
either greatly elongated, with numerous canaliculi, vascular canals also
existing; or when with few lacunce, i\\Q canalicuU are numerous and
parallel, like dentinal canals. This much is certain, that the two sub-
stances never become exactly alike, and it is probable that their develop-
ment is always to a certain extent different.

494 SPECIAL HISTOLOGY.

The enamel may be best compared with a dentine whose cells are
ossified throughout, and which, therefore presents no canals, like that
in the outermost layers of fishes' teeth; at least the two substances
agree in this, that they are entirely composed of elongated cells without
any connecting matrix. When canals occur in the enamel, it acquires a
very great similarity to dentine ; but these canals probably have a to-
tally different import to those in the dentine, viz. — that of cavities
which proceed from absorption. With the cement, the enamel has, in
genera], no analogy, though there is a kind of homogeneous cement with
an indistinct transverse striation which, at least externally, looks some-
what like enamel, but has hardly, like the latter, arisen from elongated
cells. If Ave consider the nature of the parts from which the various
substances are developed, the dentine, formed from the vascular part of
the raucous membrane of the mouth, is a true product of the homologue
of the derma {schleimhaut-production)^i\\e enamel ViVi epithelial structure,
and the cement an investing substance, afforded by the mucous membrane.

§ 143. The substance of the perfect tooth, though hard, is by no
means incapable of molecular change, as its various diseases best show.
The functions of the lacunce and their canaliculi in the bones are here
performed by the dentinal canals with their ramifications, the laciaue and
canaliculi in the cement, and the fissures between the prisms of the
enamel. All these' cavities, during life, contain a fluid, derived on the
one side, from the vessel of the pulp, on the other, from those of the
alveolar periosteum, and permit of changes in the substance, though
they maybe slow. Nothing definite, however, is known about the latter,
but from the circumstance that perfect dentine is not colored when an
:f.nimal is fed with madder (Hunter, Flourens, and others : compare Henle,
|). 878), it may be concluded, that they are far less active than in the
iones, and perhaps take place in such a manner that the calcareous
matters are not at all or only very slowly renewed. The dentine is un-
•doubtedly best provided with fluid supplies, from its being penetrated by
•very numerous and frequently anastomosing canals. We can as little
;Suppose any regular circulation in it as in the bones ; but it may be
.assumed that a certain movement takes place, proportionate to the
Amount of the exudative and absorptive processes in the pulp, of the
waste in the tooth itself, and of the supply afforded to the enamel and
cement and probably given off from the latter tissues externally. Though
the enamel is not impermeable, it permits of the passage of fluids with
■difiiculty, as is best shown by the circumstance that the nerves of the
■dental pulp are not affected by acids, so long as the coating of enamel
is entire, but readily enough, when, as in the incisors, the dentine is ex-
posed. The enamel, again, is the hardest dental tissue, possesses scarcely
.any organic matrix and no constant systems of canals. Nasmyth's

THE TEETH. 495

mcrabrano, which is attacked with so much difficulty by chemical
reagents, is, very probably, still more impenetrable than the enamel
itself, and hence these two substances serve admirably to protect the
teeth. The sensibility of the teeth arises from the nerves of their pulp ;
they are affected by contact, heat, cold, and chemical agents. Slight
mechanical influence can only act by the vibrations which they may
communicate to the substance of the tooth and thence to the pulp ; it
is therefore the more remarkable that the teeth have a certain sense of
locality, so that it is possible to distinguish whether they are touched
internally or externally, above or below, on the right or on the left side.
The sensibility of the teeth is indeed tolerably delicate, especially on
the masticating surface, where the smallest foreign bodies, as hairs,
grains of sand, &c., are perceived when these surfaces are rubbed
against one another ; and as regards its acuteness, it is, in disease at
least, excessive, which is sufficiently explained by the considerable num-
ber of nerves in the pulp and the readiness with which they may be
compressed within their hard receptacle.

With age the teeth become denser ; the pulp cavity is filled with a
kind of irregular dentine and may be totally obliterated, which is, per-
haps, the normal cause of their falling out. In certain cases observed
by Tomes, the fangs in old age were quite transparent, like horn.

The following remarks may be made upon the patlwlogy of the teeth.
Permanent teeth which have fallen out are sometimes replaced by a third
dentition ; but it must not be forgotten that the milk teeth occasionally
remain beyond their time, and care must be taken not to confound a
second tooth, late in its eruption, with a third. Teeth which have been
extracted may be replaced (in fifteen months a canine tooth which had
been extracted from the upper jaw was perfectly firm again). An abnor-
mal development of the teeth takes place particularly in the ovarium,
but also elsewhere. Fractures of the teeth may be reunited when they
occur within the alveoli, by imperfect dentine or cement. Regeneration
of the Avorn down parts takes place only in animals (Rodents, e.g.) in
which the teeth constantly grow. Hypertropliy of the cement (the
so-called exostosis), deposits of dentine in the walls of the pulp cavity
and ossification of the pulp itself, are exceedingly common, and result
from chronic inflammation o? the periosteum and pulp.* A partial dis-

• [Weill in his recent work (Grundzuge der path. Histol.) has added some very inte-
resting observations to our knowledge of the structural changes occurring in the different
parts of teeth. In hypertrophy oi^ die cement he observed die canaliculi dilated, so as to
form Haversian canals, and agrees with Kolliker (vid. § 140 supra) as to the frequency of the
hypertrophy of the entire cement in old teeth. In partial hypertrophies of the cement he
detected numerous dentinal globules, bounded by irregular fissures, and on their external
border many bone-corpuscles. These latter were separated from each odier by a yellowish
intercorpuscular substance, and in many instances by peculiar sinuous cavities, which traversed
the lamellceof the osseous substance.

496 SPECIAL HISTOLOGY.

appearance of the fang is not uncommon. Necrosis of the teeth takes
place when the periosteum has been stripped off, or the pulp has died.
The teeth become rough and dark, even black, and finally fall out. The
nature and causes of dental caries are doubtful. It attacks living: and
false teeth (Tomes), and always begins on the exterior, from Nasmyth's
membrane (Ficinus), whence the fluids of the mouth have been supposed
to have considerable influence upon it; it does not follow, however, that
one living tooth may not be more disposed to it than another, being ren-
dered less capable of resistance either by its chemical composition, or by
the mode of its nutrition. Caries, however, is assuredly not a simple
solution of the salts by the oral fluids, but a solution accompanied by a
putrefactive decomposition of the organic elements of the tooth, which
becomes covered with infusoria and fungi ; in fact, according to Ficinus's
observations, the latter growths would appear to play the more impor-
tant part, inasmuch as the decay of the teeth usually commences in those
localities in which undisturbed opportunity is given to these organisms
to develop, as in the cracks and pits of the enamel, in the depressions
of the molar teeth, in the clefts between the teeth, but not where the
dentine is otherwise exposed, as on the masticating surface, in filed
places, &c. The usual coui-se of caries is, that the discolored spots of the
cuticle of the enamel, covered with living and growing organisms (infu-
sorial animalcules, similar to a Vibrio, which Ficiyius calls Denticola,
mucedinous fungi (Erdl, Klenke, Tomes), similar to those which are
found upon the tongue, and which Ficinus wrongly refers to the Denti-
colce) first lose their calcareous salts, and then break up into angular,
cellular pieces, as if they had been treated with hydrochloric acid. The
decay then penetrates through the enamel to the dentine, always first
softening it, so that it yields not more than 10 per cent, of ash (Ficinus),
and then decomposing it. The dentine is more aff"ected by this process
than the enamel, its canal first becoming filled with the fluids proceeding
from its decomposition, which may reach the pulp and give rise to pain,
unless, as Tomes found, the dentinal canals in the neighboring healthy

The deposits of dentine in the walls of the pulp-cavity, the " osteo-dentine" of Owen, he
regards as mainly originating from the dentinal globules, which to him are protein-bodies.
This osteo-dentine partakes in some instances more of the nature of bone, than of dentine,
but consists generally of a central substance and of tubnles radiating from it; it frequently
appears to be formed of concentric layers. The central substance Wedl describes as con-
sisting either of hyaline dentinal globules, of a grayish, amorphous mass, or of distinct
bone-corpuscles of varying shapes, separated by spaces resembling Haversian canals. The
newly-formed tubules run from this central mass towards the dentine of the tooth, with the
canals of which they communicate. Sometimes they are intersected in their course by
the presence of many dentinal globules, or by irregular lacuna;. In all instances of these
formations, that he has examined, the dentinal globules existed in great abundance. The
dark color of the globules, wherever met with, Wedl is disposed to attribute to their retro-
gressive metamorphosis, whilst he regards the dark color of the interglobular spaces as
dependent on a deposit of brown pigment in their interior. — DaC]

THE TEETH. 497

portions become obliterated bj deposits, or the pulp is protected by new
masses of dentine developed in the cavity* (Ficinus, Tomes). Eventually
a brownish deposit takes place in the tubules and then the intermediate
substance becomes completely broken up. In this manner the process
of decomposition extends further and further, until at last the crown
collapses, the root also becoming dissolved and finally falling out.

In jaundice, the teeth not uncommonly assume a yellow color, which
is occasionally almost as intense as in the skin, and in asphyxiated per-
sons they are said frequently to be red ; both facts being explicable only
by the supposition that the coloring matter of the bile and of the blood
transudes into the dentinal tubuli. In rachitis the teeth remain unaf-
fected. In the mucus upon the teeth, an abundant growth of the muce-
dinous fungi which have been mentioned, is always to be met with in a
finely granular matrix, surrounding mucus- or epithelium-corpuscles ;
besides w"hich we find the infusoria of carious teeth and the earthy
deposits of the oral fluids. If this mucus accumulates, it hardens and
forms the tartar of the teeth, which consists, according to Berzelius, of
earthy phosphates 79-0, mucus 12*5, ptyalin 1"0, organic matter, soluble
in hydrochloric acid, 7"0.

The best mode of examination of the teeth is by making fine sections
and preparations softened in hydrochloric acid. To obtain good speci-
mens of the former it is necessary to employ only young and fresh teeth,
as the enamel otherwise readily breaks off. A longitudinal or trans-
verse slice should be first taken off with a fine saw, and may then be
rubbed down, first upon a coarser and then upon a finer stone, as thin
as possible ; the section should then be cleaned and polished between
two glass plates, until its surface is as smooth and shining as it can be
made, and finally washed with ether in order to remove any impurities
it may have contracted. When well polished and dried, all the dentinal
canals and lacutue will be filled with air, and the section may be pre-
served without further addition under a glass plate, cemented by some
thick and quickly solidifying varnish. Such polished sections are pre-
ferable to any others, which, on account of their irregular surface, re-
quire to be covered with different fluids, as Canada balsam, oil of tur-
pentine, &c., in order to be examined by high magnifying powers. It
almost always happens, in fact, that some portion of these fluids enters
the dentinal tubules, which then become quite clear and indistinct and
invisible in their finer ramifications. A very viscid varnish alone is of
any service. In preparing these sections of the teeth, the slices may

* ["It is worthy of mention, also, that in the teeth of the liare, the sow, and the stag,
especially in the molars, stony masses are constantly found. They are semi-transparent, for
the most part oval and rounded bodies, situated in the axis of the dental pulp, towards its
apex, in irregular rows, never extending the whole length of the dental pulp, but only to a
greater or less distance from the coronal extremity." Raschkow, Meletemata, &c., cited and
translated in Nasmyth's " Researches'' (1839), p. 139. — Trs.]

32

498 SPECIAL HISTOLOGY.

also first be aflSxed to pieces of glass with Canada balsam, and then be
rubbed down with a file and polished, on one side first, and then bj
warming the balsam and turning the section round, upon the other.
When such a section has been washed with ether and dried, it is as
good as one prepared with water only. Two sections made perpendicu-
larly to one another through the middle of the crown and fang of a
tooth, from before backwards, and from right to left, are sufiicient to
exhibit the most important features of the teeth ; but sections ought
also to be prepared, showing the surface of the pulp cavity and that of
the enamel ; and also dijBferent oblique and transverse sections through
the commencement of the dentinal canals of the fangs, to exhibit the
anastomoses of their branches. The dental cai^tilage is easily demon-
strable by maceration in hydrochloric acid, a process which requires a
longer or shorter time according to the concentration of the acid and
its more or less frequent renewal, taking 3-4 days in strong acid and in
dilute, from 5-8. If it be desired to soften the tooth so much that the
tubules may be isolated, it must be left for about eight days in con-
centrated hydrochloric acid; in thin sections of dental cartilage 12-24
hours' treatment with sulphuric and hydrochloric acid, and a few hours
with dilute solutions of caustic potassa and soda, are sufficient for this
purpose. It is very instructive also to macerate thin sections of teeth
in acid and to examine them upon glass plates at intervals, until they
entirely break up. The enamel prisms are readily isolated in develop-
ing enamel ; the transverse lines are seen best when the object is mois-
tened with hydrochloric acid, and the transverse sections of the prisms
are seen exceedingly well in longitudinal sections, in some layers. The
early development may be studied in embryos of two, three or four
months with the simple microscope and in transverse sections of parts
hardened in spirit ; the structure of the dental sac, and the development
of the dental tissues in foetuses of four, five, and six months, and in
new-born infants, both in fresh subjects and, if it be desired to recognise
the relations of the enamel organ, in spirit-preparations also, in which
its structure is very well retained. The pulp of mature teeth is obtained
by breaking them in a vice, and their nerves are best seen on the addi-
tion of dilute solution of caustic soda.

Literature of the Teeth. — L. Frankel, " De penitiori dentium human-
orum structura, observationes," Vratislav, 1835 ; and Retzius, " Be-
merkungen liber den innernBau der Ziilinen," in Mlill. " Arch.," 1837;
J. Tomes, "A Course of Lectures on Dental Physiology and Surgery,"
London, 1848; R. Owen, "Odontography," London, 1840-45, 1 vol.,
with atlas of 150 plates; and article "Teeth," in "Cyclopaedia of
Anatomy," IV. p. 864 ; Krukenberg, " Zur Lehre vom Rohrensysteme
der Zahne und Knochen," in Mlill. " Archiv," 1849, p. 403 ; J. Czer-
mak, " Beitrage zur mikroskopischen Anatomic der menschlichen Zahne,

THE PHARYNX. 499

in Zeitschr. fiir. wiss. Zool." 1850, bd. II. p. 295; Arnold, in " der
Salzbiirger med. Zeitung," 1831, p. 236 ; Rascbkow, " Meletematacirca
dentinin mamraaliuni evolutioncm," Vratisl. 1835; Goodsir, in " Ediub.
Med. and Surg. Journal," 1838, No. XXXI. 1; and Froricp's " Neue
Kotizen," Nos. 199, 200, 202, 203; Marcuson, "Ueber die Entwick-
lung der Zabne der Siiugetbiere," aus dem " Bulletin Phys. Math." VIII.,
No 20, Petersburgb, 1850. On Dental Caries consult Erdl. in " Allg.
Zeitung flir Chirurgie von Rohatzscb," 1843, No. 19 ; Ficinus, in
"Journal flir Chirurgie von Walthcr and Ammon," 1846, p. 1 ; Klenke,
"Die Yerderbniss der Ziihne," Leipsig, 1850. The Comparative
Anatomy of the teeth is treated of microscopically in the works of Owen
and Retzius above cited ; also by Erdl, in the " Abhandlungen der
Math. Phys. Klasse, der Konigl. Bayer. Akad." bd. III. Abth. 2 ;
Tomes, in the "Phil. Trans." 1849-50 (Marsupialia and Rodentia) ;
Agassiz, in the "Poissons fossiles ;" Henle and J. Mliller, " Syst.
Beschreibung der Plagiostomen," 1838.

[To these should be added: Blake, "Essay," &c., 1801; Hunter,
"Treatise on the Natural History and Diseases of the Human Teeth,"
edited by Thomas Bell ("Works by Palmer, 1835, vol. ii.) ; Tomes, "On
the Structure of the Teeth, the Vascularity of those Organs, and their
relation to Bone," Proceedings of the Royal Society, June, 1838 ; Owen,
" On the Structure of the Teeth, and the resemblance of Ivory to Bone,"
British Association Reports, 1838; Nasmyth, " Medico-Chirurgical
Transactions," 1839 ; "Proceedings of the British Association," 1839;
" Researches on the Development, Structure, and Diseases of the Teeth,"
1849 ; Huxley, " On the Development of the Teeth," " Quarterly
Journal of Micr. Science," 1853; Salter, "On certain appearances
occurring in Dentine," ibid. 1853. — Trs.]

OF THE ORGANS OF DEGLUTITION.
I. THE PHARYNX.

§ 144. The alimentary canal assumes a greater independence in the
pharynx, acquiring a special investment of transversely striated muscles,
the constrictores and levatores, which, however, do not entirely surround
it and arise for the most part from bones. The thickness of the walls
of the pharynx is about 2 lines on an average, depending principally
upon this muscular layer, external to which there is a tense fibrous mem-
brane, composed of connective tissue and elastic fibres, while internally
it is separated by a layer of submucous connective tissue from the
mucous membrane. The latter is paler than that of the oral cavity and
its structure in the upper half of the pharynx differs considerably from
that in the lower half. In the latter locality, that is, below the pha-
ryngo-palatine arches, or in the region through which the food passes,
it possesses a tessellated epithelium similar in structure and thickness to

500 SPECIAL HISTOLOGY.

that of the oral cavity ; above them, on the other hand, that is, on the
posterior surface of the soft palate from its free edge, upon the upper
surface of the uvula, in the region of the choance and Eustachian tubes,
and upon the vault of the pharynx, there is a ciliated epithelium like
that in the nasal cavity and larynx, to the description of which, below,
the reader may be referred. In this upper or respiratory section, the
mucous membrane is also redder, thicker, and more glandular than in
the lower division, otherwise, however, its structure is pretty much the
same, with the exception that it presents no papillffi, which, however, in
some parts of the lower division are very little developed and rare, and
would even appear to be entirely wanting. Compared with that of the
oral cavity I find the mucous membrane of the pharynx to possess much
more and much stronger elastic tissue, which, in the deeper layers, forms
connected, very dense, elastic membranes.

The pharynx contains two sorts oi glands ; 1, racemose mucous glands
{vide supra, § 13-i), and, 2, follicular glands. The former ^—1 line in
diameter, have distinct apertures and abound more particularly in the
upper portions of the pharynx, where they form a perfectly continuous
layer on the posterior wall, in the neighborhood of the pharyngeal open-
ing of the Eustachian tubes, and upon the posterior surface of the velum,
diminishing in number lower down. Follicular glands, simple as well as
compound, analogous to the tonsils, are met with in the vault of the
pharynx, where the mucous membrane is closely attached to the base of
the skull. Here a glandular mass, stretching from one Eustachian open-
ing to the other, and from one to four lines thick, may constantly be met .
with ; it is, upon the whole, smaller, but otherwise its structure resem-
l)les, in all essential respects, that of the tonsils (§ 135). Besides this
mass, whose largest sacculations are situated in the middle of the roof
of the pharynx, and in the recesses behind the Eustachian apertures,
^and which, in aged persons, frequently present enlarged cavities, filled
Tvith puriform masses, there occur round the apertures of the tubes,
and upon them, towards the clwana^, on the posterior surface of the
velum palati, and on the lateral walls of the pharynx, as far as the
level of the epiglottis, more or less numerous, smaller and larger fol-
licles, whose size is too great for apertures of the mucous glands, and
which have in all probability the same structure as the simple follicles
of the root of the tongue, and receive the excretory ducts of the mucous
glands.

The mucous membrane of the pharynx is rich in bloodvessels and
■lymphatics. The former constitute superficially a network with elon-
gated meshes, sending short loops into the rudimentary papilloe. The
nerves are very numerous, form superficial and deep plexuses, the former
with fine fibres of 0'001--0015 of a line, which occasionally divide, and
"whose ultimate terminations escape the eye.

THE (ESOPHAGUS.

501

II. THE (ESOPHAGUS.

§ 145. The wall of the oesophagus, 1|-1:^ lines thick, consists, exter-
nally, of a fibrous membrane composed of connective tissue, with exceed-
ingly beautiful elastic fibres. To this succeeds a muscular membrane
|-1 line thick, composed of an external, longitudinally fibrous layer,
having a thickness of 0*5 of a line, and of an internal, circularly fibrous
layer of 0-24-0*3 of a line, which are in close apposition. From the
pharynx, where the longitudinal fibres arise in two bundles from the
constrictor infimus, united with a third from the cricoid cartilage, they
extend as far as the stomach, with whose muscles they are partly con-
tinuous. In the upper third of the oeso^yJiagus, as far as its entrance into
the thorax, transversely striated muscles alone are found, arranged in
bundles of 0'04-0-24 of a line, which sometimes distinctly anastomose.
Further downwards smooth muscles of the same structure as those in
the intestine {infra) make their appearance, in the first place in the cir-
cular layer, and subsequently, among the longitudinal fibres ; the pro-

Fis. 198.

Fig. 199.

portion of these gradually increases,
until at last, in the lower fourth,
smooth muscle altogether predomi-
nates. Isolated, transversely-stri-
ated muscles, however, are, accord-
ing to Ficinus, to be met with as far
as the cardia. Most internally we
find, separated from the muscular
coat by a white, soft layer of sub-
mucous connective tissue {tunica nervea of the ancients), the pale-red
mucous membrane, which below takes on a whitish tint. Its total thick-

FlG. 198. — Transverse section from the middle of the oesophagus (Man), magnified 1-2
diameters: a, fibrous investment; 6, longitudinal muscles ; f, transverse muscles; d, tunica
nervea; e, longitudinal muscles of the mucous membrane; /papilla;; g:, epithelium ; A, aper-
ture of a mucous gland ; i, mass of fat.

Fio. 199. — Muscular-fibre cells from the cesophageal mucous membrane of the Pig, after
being treated with nitric acid of 20 per cent.; inagnified 15 diameters.

502 SPECIAL HISTOLOGY.

ness of 0-36-0'45 of a line is due, to the extent of about 0-1-0-12 of a line,
to its laminated, tessellated epithelium, Avhich presents the same structure
as in the oral cavity, with the exception, however, that the actual epithe-
lial plates constitute about a moiety of the whole, and, after a short mace-
ration, or, as frequently happens in the dead subject, spontaneously,
may be readily stripped off in large white sheets, either alone, or accom-
panied by adherent portions of the deeper layers. The proper mucous
membrane, measuring on the average 0*3 of a line, possesses numerous
conical papilhv of 0-04-0-05 of a line in length, and consists of ordinary
connective tissue, with fine elastic fibres, among which, however, as
Briicke and I have ascertained, a great quantity of longitudinal bundles
of smooth muscles, and in addition, more isolated groups of ordinary fat
cells and small racemose mucous glands, may be observed.

The oesophagus is moderately provided with lymphatics and blood-
vessels; the latter send loops into the papillce and form at their bases,
a not very wide network, like that in the pharynx. Nerves may also
be met with in considerable numbers in the mucous membrane, contain-
ing fine fibres of 0-0012-0-0015 of a line, but I have not yet succeeded
in tracing them into the papillce, nor in observing divisions, nor the
modes in which they terminate.

Literature. — C. Th. Tourtual, "Neue Untersuchungen iiber den Bau
des Menschlichen Schlund-und Kehlkopfes," Leipzig, 1846.

OF THE ALIMENTARY CANAL.

§ 146. Those parts Avhich constitute what may, more strictly speaking,
be called the alimentary canal, are the least fixed of all which compose
the alimentary tract and are almost invariably attached by special mem-
branous bands — the mesentcria — in the great cavity of the abdomen,
lined by the peritonaeum. With the exception of a small portion of the
rectum, the walls of the alimentary canal consist everywhere of three
tunics: sl serous — the peritonceum ; a muscular — consisting of two or
even three layers ; and a mucous membrane, the latter containing a
great number of glandular structures, which may be divided into three
groups, racemose mucous glands, tubular glands, and closed follicles.

§ 147. The peritoticEum is much thicker in its external or parietal,
than in its internal or visceral layer (in the former case 0-04-0-06, in
the latter 0-02-0-03 of a line), though its structure is essentially the
same in each locality. It consists principally of connective tissue with
distinct, variously interwoven bundles, and abundant reticulated elastic
fibres, which are coarser in the parietal lamina. A loose subserous con-
nective tissue, containing more or less fat, unites the peritonaeum with
the other organs, or, as in the mesenteric folds, connects its layers
together ; under the visceral lamina, however, it is very little developed
except in certain localities [colon, appendices epiploicoi), and in certain

THE ALIMENTARY CANAL.

503

folds of tlic pcntono'ian, it does not exist at all. The free surface of
both lamella} of the ■peritonanim is lined by a simple tessellated epithe-
lium, whose slightly flattened, polygonal, nucleated cells measure, on the
average, 0-01 of a line, they are so closely united and so constantly kept
moist, that the free serous surface appears perfectly smooth and shining.
The peritonceum is, in general, but scantily supplied with vessels ; they
are most abundant in the omenta^ in the visceral layer and in the sub-
serous tissue, in which last alone, lyinphaties have as yet been found.
The nerves are also but few, and are especially to be met with in the
omentum, the mesenterial and hepatic ligaments, where they accompany
the arteries.

§ 148. diuscidar tu7iic of the alimentary canal. — The whole alimen-
tary tract, from the stomach to the rectwn, possesses a special muscular
coat, which, however, does not everywhere present the same conditions.

In the stomach the muscular tunic varies in thickness; at the fundus
it is thin {^-^ of a line) ; in the middle, it has a thickness of about ^ a
line ; in the pyloric region, finally, about | or even I line. It consists
of three incomplete layers : 1,
most externally, longitudinal
fibres, especially at the cardia,
where they arise from the ex-
pansion of a part of the lon-
gitudinal fibres of the oesopha-
gus ; and also at the pylorus
and in the j^ar-s pylorica,
whence, tensely stretched, they
are continued upon the duo-
denum ; 2, circular muscles,
in the middle region, from the
fundus to the jyy lor us ; where
they are accumulated, consti-
tuting the so-called sphincter
of the 2^ylorus ; 3, most internally, oblique fibres, which, in connection
with the circular fibres, embrace the fundus as in a sling, and run ob-
liquely upon the anterior and posterior walls of the stomach, towards its
greater curvature, where they terminate upon the outer surface of the
mucous membrane or unite tojxether.

In the small intestine, the muscular coat is somewhat thicker in the
duodenum and the upper portions, than in the lower ; it has, in general,
a thickness of |— ^ of a line, and is composed only of longitudinal and
transverse fibres. The former are always less developed and do not

• Fig. 200. — Stomach of Man, reduced: a, CESophagus, with the longitudinal fibres ; tr,
transverse fibres (second layer), for the most part dissected off; t/, transverse fibres of the
fundus; o,fibr<B obliquce ; p, pylorus ; d, duodenum.

504 SPECIAL HISTOLOGY.

form a continuous layer, since they are very few or entirely absent along
the attachment of the mesentery ; they are usually most distinct upon
the free border, though even here they may be readily torn away with
the serous membrane, so as, at once, to leave the second layer exposed.
The latter is complete and continuous, consisting of circular bundles,
which not uncommonly anastomose at very acute angles.

In the large intestine, the longitudinal fibres are reduced to the three
ligamenta coll, muscular bands of 4-6, or even 8 lines broad, and ^-^
line thick, which commencing upon the ccecum are united upon the
sigmoid flexure, into a single longitudinally fibrous layer, which is con-
tinued upon the rectum. Beneath these bands there lies a continuous,
circularly fibrous layer, thinner than in the small intestines and more
especially developed in the duplicatures, which are known under the
name of the plicce sigmoidece.

Fig. 201. The rectum possesses a muscular layer of 1 line and more
thick, in which the more abundant longitudinal fibres lie ex-
ternal to the circular. The ultimate, somewhat thickened ex-
tremity of the circular fibres is the spJmicter ani internus, with
which the transversely striated sjjhincter externus and levator
ani are conjoined.

In their elementary structure, all the muscles of the proper
alimentary canal belong to the so-called smooth or non-striated
(vegetative, organic) muscles (see § 26). Their elements, the
fibre-cells, are fusiform, on the average 0-002-0-003 of a line
broad, and O-06-O'l of a line long, pale, flattened, and homo-
geneous, and provided with a nucleus 0-006-0-012 of a line
long, and 0-001-0-0028 of a line broad.

Many of the fibres present knot-like enlargements and fre-
quently zigzag flexures, which produce the transversely striated
appearance of the entire bundles of such muscles so frequently
met with in spirit preparations. The arrangement of the
fibre-cells in the different strata is simply this ; mutually applied
in their length and breadth and coherent, they are united into
thin muscular bands, which then, invested with a coating of
connective tissue and, frequently, also united into secondary
bundles, constitute the thinner or thicker muscular tunics of the
diff'erent regions ; which, again, are surrounded and separated
from the contiguous parts, by considerable layers of connective
tissue.

Bloodvessels are very abundant in the smooth muscles ; and
their capillaries, of 0-003-0-004 of a line, constitute a charac-
teristic* network with rectangular meshes.

Fig. 201. — Muscular fibre cell from tlie small intestine (human).

* [Hardly characteristic ; the vessels are arranged in precisely the same way in the fascial
• aponeuroses; e. g., the /asfia toa of the thigh. — Trs.]

THE STOMACH.

505

Nothing is known about the h/niphafics ; nor are the relations of the
nerves yet ascertained, except that Ecker has observed the division of

Fiff. 202.

fine nervous tubules in the muscular tunics of the stomach of the Frog
and Rabbit.

MUCOUS MEMBRANE OF THE STOMACH.

§ 149. The gastric mucous membrane is soft and loose in texture ;
and its color, during digestion, is reddish-gray or bright red, at other
times grayish. When the stomach is empty, the inner surface is thrown
into longitudinal folds, which disappear in its distended state. Further-
more, it presents, especially in the pyloric region, around the apertures
of the tubular or gastric glands, little reticulated folds or even isolated
villi^ {plicce villosce, Krause) of 0-024-0-048 or even 0-1 of a line,
( 3^0-2 5 Krause). Not unfrequently, also, the mucous membrane is
marked out especially upon the right side, by little shallow depressions,
into slightly raised polygonal areiB of |-2 lines, the so-called " etat
mamelonnd" of pathologists, which, however, is also exhibited by per-
fectly healthy stomachs. The mucous membrane is thinnest (^-J of a line),
at the cardia, in the middle it becomes thickened to J a line, and in the

Fig. 202. — Bloodvessels of the smootli muscles of the intestine, magnified 45 diameters.

* [These gastric villi have been recently accurately described and depicted by Dr. Neill,
(vid. Amer. Jonrn. of Med. Sc, Jan. 1S51.) By the aid of minute injections, Dr. Neill
found that the ridges between the orifices of the tubuli, formed of convoluted capillaries,
become larger and more elevated in the antrum pylori, and that as the pyloric orifice is
approached, distinct, conical villi make their appearance, which he thinks, have not been
previously described as constant by any of the writers on the subject. These villi are not
as large as those of the small intestines, but, otherwise, similar in appearance. They are
mainly composed of capillaries closely united by a basement membrane, and are covered
with a cylinder-epithelium. In the antrum pylori, alveoli of different shapes exist in the
interstices and at their bases. Whether they contain lacteals or not is doubtful.

The uses of these gastric villi have not as yet been ascertained. Dr. Neill (1. c.) suggests, that
they may be connected with the absorption of solutions of albuminous compounds. — DaC]

506

SPECIAL HISTOLOGY.

pyloric region to | or 1 "line, -which depends entirely upon the glandular
layer, since the epithelium and muscular layer everywhere possess the
same thickness. The submucous tissue is abundant and, as throughout
the whole intestine, contains occasional fat-cells.

§ 150, The gastric glands. — The gastric glands — the most important
part of the mucous membrane — are tubular glands which, set close

together, pass straight through the entire
^'^' -^^' thickness of the mucous membrane to its

muscular layer, and therefore vary, in the

different regions of the stomach, from I to

4J

or even 1 line, but are on the average J a
line in length. Each of them commences
as a cylindrical tube, of 0-03-0-04 of aline
in diameter, at the surface of the mucous
membrane, diminishes inferiorly to as little
as 0-014-0-02 of a line, and terminates by
a clavate or flask-shaped enlargement of
0-02-0-026-0-036 of a line. The lower
third of the glands is usually undulated or
even twisted into a corkscrew shape, espe-
cially at the pylorus ; occasionally it gives
off a shorter or longer csecal branch before
its termination. Every gastric gland is sur-
rounded by a delicate memhrana i^ropria and
possesses in its upper third, a cylindrical epithelium continuous with that
of the surface of the stomach ; for the inferior three-fourths of its extent,
on the other hand, it presents pale, finely granular, polygonal nucleated
cells of 0-006-0-01 of a line, which probably never constitute a distinct
epithelium, but appear completely to fill the tubes.*

Fig. 203. — Perpendicular section through the tunics of the Pig's stomach, from tlie pylorus,
magnified 30 diameters: a, glands; 6, muscular layer of the mucous membrane; c, submu-
cous tissue (Junica nerved), with divided vessels; rf, transverse layer of muscles; f, longitudi-
nal layer of muscles; /, serous membrane.

* [Professor Kolliker (" Verhandlungen der. Phys. Med. Gesellsch. zu WUrzb." vol. IV. 1,
p. 52), has recently had the opportunity, in a case of suicide by drow^ning, of examining
the human gastric mucous smembrane in a fresh and normal state. He directed par-
ticular attention to the glandular apparatus, and found that the gastric glands are not
as uniform in structure as above-described, but present three distinct types. 1. Simple
tubular glands with peptic cells,' (Labzellen). 2. Compound tubular glands with peptic
cells. 3. Compound tubular glands with cylinder epithelium. The first are the most
common ; they occur in the middle zone of the stomach, and are generally simple
tubular glands, some of which at their termination, give off short ca;cal branches. The
compound tubular glands with peptic cells occur in the narrow cardiac zone. They commence
by a tube of 0-04 to Q-OS""" long, 0 03 to 0 04'"'" broad, lined with cylinders. This divides
first into two or three, and then into four or seven equally long cylindrical tubules, which

» Vid. p. 508.

THE STOMACH.

507

In animals, the gastric glands are more complicated than in man,
frequently presenting dichotomous divisions and subdivisions of their

Fiff. 204.

Fig. 204. — .4, mucous gastric gland of a Dog, from the injlorus, with cylinder epithelium:
a, wide cavity of the gland; 6, its cttcal appendages. B, peptic gastric gland from the
middle of the stomach : a, common trunk of the glan<l ; 6, its chief branches ; c, terminal
caeca. INIagnified GO diameters. C, a portion of the cncca, magnified 3.50 diameters, and
viewed longitudinally. D, the same viewed in transverse section : a, membrana propria ; b,
large cells close to it ; c, small epithelium round the cavity.

are lined by rounded or oval cells (peptic-cells), and wliich run side by side to the base
of the mucous membrane. In these cells minute oil-globules are frequently observed. The
terminal tubules have a peculiar twisted appearance, which is dependent on nimierous
lateral dilatations. In this part of the stomach no racemose glands exist, although they are
found in the lower part of the (Esophagus.

Between both these forms of " peptic gastric glands," (Magensaftdriisen) Professor Kclli-
kcr observed, fasciculi of contractile fibre-cells, but he denies the existence of the spiral
fibre-cells investing the glands, as described by Ecker.

The compound tubular glands with cylinder-epithelium occur in the pyloric zone, and resem-
ble the last-described variety, with the exception, that the tubules are larger and devoid of
tlie rounded finely granulated peptic cells. Neither simple glands, nor racemose glands, as
stated by Ecker, are here observable.

These investigations of Professor Kolliker confirm the opinion of Donders, as to the exis-
tence of two varieties of glands in the human stomach, viz.: the proper gastric glands
(called by Kolliker from their secretion "peptic'' gastric glands) and the simple mucous
glands. These two distinct forms have been previously described in the stomach of Mam-
malia by Kolliker (Vid. § 150, infra and '■ Mikroscopische Anatomic" II. '2, p. 240), but in Man
their existence has hitherto not been satisfactorily ascertained. — DaC]

508 SPECIAL HISTOLOGY.

free ends; in many genera, they are of two very distinct kinds, the
mucous gastric glands, with a cylinder epithelium and the peptic gastric
glands (Magensaftdrlisen) with cells similar to those which exist in man.
A more detailed description of some forms will be found in my "Mikro-
skop. Anatomic" (II. 2, p. 140); and I here subjoin figures (p, 507) of
the two forms of the glands in the dog, merely to render my meaning
intelligible.

The secretion of the gastric glands has not been so completely exa-
mined in man, that we can say with certainty whether they all secrete
gastric juice or not. A few experiments which I instituted with regard
to this point, tend to show that here, as in animals, it is only particular
glands — those in fact of the middle of the stomach — which yield the
proper, active secretioii ; however, further observations must be made
on stomachs in the freshest and most normal state, to confirm this
result. In any case, the secretion of the glands is for the most part a
fluid, though in the mucus, a small quantity of which usually covers the
mucous membrane, we not only meet with half-destroyed cylinder
epithelium, but almost invariably, with a certain quantity of proper
glandular cells ; and it is impossible to say whether these are essential,
or only accidental constituents of the glandular secretion.

In many animals there are two secretions with different properties
corresponding with the two forms of gastric glands, a fact to which
Bischcflf and Wasmann first drew attention, and which I can confirm.
In the Dog, glands with cylinder epithelium exist in the pylorus ; those
with round cells in the remainder of the stomach ; there is the same
arrangement in Ruminants and in the Rabbit ; whilst in the Pig, it is
only the middle of the stomach and especially the great curvature,
which presents the latter glands. A series of experiments on artificial
digestion, which were carried out by Dr. Goll, of Zurich, and myself,
principally with the pig's stomach, afforded the distinct result, that, so
far as their solvent powers are concerned, the glands present very
different relations ; those with round cells act upon protein compounds
which have been coagulated by acids in a very short time, while those
with cylinder epithelium, either have no action at all or take a long time
to 2^^oduce a slight effect. Furthermore a well-marked acid reaction is
presented by that region of the stomach only in which the former glands
are situated. The active organic substance, p>epsin, is not contained in
the gastric mucus, which consisting of detached epithelium cylinders,
often form a thick- covering over the mucous membrane, but in the finely
granulated, rounded cells of the peptic gastric glands, to which there-
fore the term peptic cells (Labzellen, Frerichs)* may well be applied.
According to my observations, however, these peptic cells do not neces-
sarily become thrown off, nor take any direct share in digestion, but

* [Literally, "rennet-cells." — Tes.]

THE STOMACH. 509

frequently exert their action simply by pouring the juice Avhich they
prepare into the glands.

§ 151. We have seen, that beside the glands, only a very scanty tis-
sue enters into the mucous membrane. Around their extremities alone,
do we find a dense, continuous, reddish layer 0*022-0-04-4 of a line in
thickness (Brlicke), the muscular layer of the mucous membrane^ con-
sisting of bundles of common connective tissue and of smooth muscles,
interwoven, the latter of which cross one another principally in two
directions, and, in the Pig, even pass between the glands and into the
plicce villosa'. In man, we meet only with vessels, and an amorphous
connective tissue, without elastic fibrils, interposed between the gkands,
forming at the surface of the mucous membrane, a clear, perfectly
homogeneous stratum, the structureless memhrane of authors, which is
continuous with the membrance propria^ of the separate glandular
tubes, but cannot, like them, be isolated.

The whole internal surface of the stomach from the cardia (where
the tessellated epithelium of the oesophagus terminates by a sharp
notched edge), possesses a simple covering of cylindrical cells, about
0*01 of a line long on the average, which lie immediately upon the
outermost homogeneous portion of the mucous membrane, without any
interposed substance. During life, this cylinder epithelium — whose
other relations will be treated of below, in describing the small intes-
tine, Avhere a layer of exactly similar nature is to be met with — is
closely united with the mucous membrane, though not so intimately, but
that its elements are, at times, detached to a larger or smaller amount
by the mechanical violence to which it is necessarily occasionally sub-
jected in the stomach. After death this takes place so readily, that the
cells can bo seen in situ, in man, only under very favorable circum-
stances. Perhaps, also, detachment of the epithelium to a certain ex-
tent may take place normally, in one way or another, during digestion;
at least, in animals the quantity of loose epithelial cells is often very
great and they frequently almost entirely constitute the raucous coating
which covers the surface of the stomach.

Besides the tubular glands, the stomach also contains, though they
are inconstant and vary very much in number, closed follicles — the so-
called lenticular glands^ which are identical in structure with the soli-
tary follicles of the small intestine, and therefore need not be further
described in this place.*

• [" Although it may be that the lenticular glands of the stomach are always present in
children, they are certainly inconstant in adults, since in many cases no trace whatever can
be discovered of them. In other instances they are exceedingly numerous, covering the
whole surface of the stomach, but in this case, the invariably diseased state of the alimen-
tary tract, suggests the idea, that they stand in some connection with it. In many mammalia
no trace of such structure is to be found, while, according to BischolT (Mull. Arch. 1838),

510

SPECIAL HISTOLOGY.

Fi?. 205.

The bloodvessels of the gastric mucous membrane are very numerous,
and their distribution is quite characteristic (compare Fig. 205, repre-
senting the vessels of the large intestine, "whose
arrangement is almost the same). The arteries
begin to divide in the submucous connective tis-
sue, in such manner, that only their finer branches
reach the mucous membrane, in which, gradually
breaking up into capillaries, they ascend in great
numbers, perpendicularly, between the glands and
form a network of fine capillaries of 0'002-0*003
of a line, around the tubes, which extends as far
as to the apertures of the glands. Here this
network, which we may regard as continuous
through the whole stomach, passes into a super-
ficial reticulation of somewhat larger capillaries,
of 0-004:-0'008 of a line, whose meshes, in man,
are polygonal, 0'02-0*04 of a line in diameter,
and encircle the apertures of the glands ; it is
more complicated or more simple, according to the breadth of the in-
terspaces of the glands and the occurrence of elevations upon them, but
seems never to consist of simple vascular rings. From this network the
veins, which are relatively wide, arise by many radicles ; they then, fur-
ther apart from one another than the arteries, and receiving no more
blood, penetrate the glandular layer, and upon the outer surface of the
mucous membrane, enter, often at right angles, a wide venous network
with partly horizontal vessels, in the submucous tissue.

The lymphatics of the stomach form a superficial fine network and
a deen, coarse, one ; and can only be demonstrated by injection. The
numerous small branches which pass from the mucous membrane, their
aggregation into larger trunks, and final penetration of the muscular
tunic, are readily seen in large Mammalia, killed during digestion. The

Yio. 205. — Vessels of the large intestine of a Dog, the mucous membrane being cut
through perpendicularly ; a, artery ; b, capillary network of the surface, with glandular
apertures ; c, vein ; d, capillary network round the glandular tubules in the thickness of the
mucous membrane.

they occasionally exist in the dog, invariably in the pig, and so far as the latter animal is
concerned, I can, wi<:h Wasmann, confirm this statement. They are here, as Bischoff sup-
poses and as is evident from Wasmann's description, not isolated, but aggregated glands, true
minute Peyer's glands. The aggregations measure 1-2^ lines, are distributed especially upon
the cardia and small curvature, and are readily seen upon stripping oft" the muscular and sub-
mucous tissue. At first sight, they appear to lie entirely in the last-named layer, but if the
attempt be made to detach them, it is found that this cannot be done without tearing the
mucous membrane, to which they closely adhere. On the internal surface, small depres-
sions are seen where these patches occur, and the gastric glands are here either absent or
undeveloped." Kolliker, Mikr. Anat. II. 2, p. 151.— Trs.]

THE INTESTINES. • 511

nerves of the stomach, derived from the vagus and sympathetic, are
readily traced into the submucous tissue and they may also be observed
entering the muscular layer of the mucous membrane ; but it becomes
impossible to follow them further, principally because, in the interior of
the mucous membrane itself, they present no more dark-edged tubules,
but probably only the pale embryonic fibres.*

MUCOUS MEMBRANE OF THE S3IxVLL INTESTINE.

§ 152. The mucous membrane of the small intestine is thinner than
that of the stomach, but more complex in its structure, inasmuch as,
besides the tubular or LieberJcuhnian glands, it presents a great number
of permanent folds and villi ; also, imbedded in its substance, peculiar
closed follicles, the so-called solitary and Peyers glands and, in the sub-
mucous tissue of the duodenum, Brunners glands.

The mucous 7nemhrane consists of connective tissue, which is inter-
nally homogeneous or indistinctly fibrillated ; except where certain
glands exist, there is but little submucous tissue, so that it is pretty
closely connected with the muscular tunic. Upon the inner surface of
the mucous membrane, there rests a cylinder epithelium, to which further
reference will be made under the head of the villi ; whilst externally,
towards the submucous tissue, it is bounded by a lager of smooth muscles,
discovered by Brlicke, which measures, at most, 0-0177 of a line ; they
are disposed longitudinally and transversely, but in man their slight
development renders it often very difficult to discover them.

§ 153. The villi of the small intestine are small, whitish elevations of
the innermost portion of the mucous membrane, readily distinguishable
with the naked eye and Avhich, distributed upon and between the valvuke
conniventes [Kerkringian valves) through the whole extent of the small
intestine, from the pylorus to the sharp edge of the ileo-crecal valve
{valvula Bauhini), are set so close together as to give the mucous mem-
brane its well-known velvety appearance. They are most numerous
(50-90 upon a square line) in the duodenum and jejunum, less so in the
ileum (40-70 upon a square line). In the duodenum they are broader
and less elevated, resembling folds and laminoe 1-10-1-4 of a line in
height, 1-6-1-2 or even 3-4 of a line in breadth. In t\\e jejunum, they

* [ In his " Mikroskopische Anatomic," B. II. 2, pp. 149, 153, 104, Professor Kolliker shows
that the muscular layer of the mucous menjbrane of the stomach and intestine was discovered
by Middeldorpf (De Glandulis Brunnianis, Vratisl. 184G, c. tab.) but remained unnoticed
until it was rediscovered by Briicke and himself. In the small intestine there are, when
this muscular stratum is well developed, two layers, though they are not always complete ;
the external layer is composed of longitudinal, the internal of transverse fibres.

In the villi, the smooth muscular fibres have been found not only in many mammalia, but
also in birds. The contraction of the villi which they eflTect appears to have been noticed
by Lacauchie, Gruby and Delafond, so long ago as 1842. — Tus.]

512

SPECIAL HISTOLOGY.

appear for the most part to be conical and flattened ; frequently, they
are even foliated or cylindrical, clavate or filiform, the three latter forms

Fisr. 206.

Fi^. 207.

predominating in the Jejunum. The length of the villi is from 1-5-1-2
of a line ; the hreadth from 1-6-1-10, even 1-25 of a line ; the thickness
in the flattened forms 1-20 of a line.

The villi are composed of two portions, a deeper, belonging to the
mucous membrane and an epithelial, superficial coat. The contour of
the former or villus proper, is similar to that of the entire villus; it is
simply a solid process of the mucous membrane, containing bloodvessels,
lymphatics and smooth muscles, whose matrix, through which a variable
number of roundish nuclei are scattered, in general exhibits no morpho-
logical character more decided than that of the mucous membrane itself,
yet must most undoubtedly be regarded as a metamorposed connective
tissue, without any intermixture of elastic tissue. The bloodvessels of the

Fig. 20G. — Section through the walls of the lowest portion of a Calf's ileum, magnified CO
diameters: a, villi ; b, Lieberkiihn's glands; c, muscular layer of the mucous membrane; d,
follicles of a Pcyer's patch; c, remainder of the submucous tissue iinder them; /, circular
muscles; g, longitudinal muscles.

Fig. 207. — Intestinal villus of a young Kitten without its epithelium, to which acetic acid
has been added ; «, boundary of the villus; b, subjacent nuclei; c, nuclei of the smooth mus-
cles; d, round nuclei in the centre of the villus.

THE INTESTINES.

513

Fiff. 208.

Fio:. 209.

villi (Fig. 208) are so numerous, that -when ^Yell injectcti, those whose epi-
thelium has been detached become colored throughout ; and, in living
animals, or those which have
just been killed, each villuSy if
viewed from above, appears as
a red dot surrounded by a
clear ring. In man, every
villus contains a close network
of capillaries of 0-003-0-005
of a line, with rounded or elon-
gated nuclei, which lies imme-
diately beneath the homoge-
neous external layer of the
matrix'^ and is supplied by one,
two, or three small arteries of

0-01-0-016 of a line. The blood is usually carried back directly into the
larger trunks of the submucous tissue, by a vein of 0*022 of a line,
which does not arise, as in animals, by the
arching round of the artery, but proceeds
from the gradual confluence of the finest capil-
laries.

The relations of the lacfeals in the villi
of man, have not hitherto been perfectly
made out; for although the majority of
investigators are inclined, like the older ob-
servers, to suppose that they commence by
one or two crecal branches, yet recently, more
and more voices appear to be raised for the
view that they originate in a plexiform man-
ner. As to my own opinion, I can affirm no-
thing with respect to the human subject, since I
have never succeeded in meeting with i'z7/j dis-
tended with chyle, and in empty ones, I have
been unable to obtain any decisive evidence ;
on the other hand, in animals, I feel certain
that in many cases only a single lacteal, which
has a csecal and frequently enlarged end, and
whose diameter is much greater than that of
the capillaries, traverses the axis of the villus
(Fig. 209.)

Fig. 208. — Vessels of a few villi of the Mouse, after one of Gerlach's injections; magni-
45 diameters.

Fig. 209. — Two villi without epithelium and witli the lacteal in tlieir interior (from the
Calf), magnified 350 diameters, and treated with a dilute solution of caustic soda.

* [The " basement membrane"' of Todd and Bowman. — Ed.] <

33

■r

,^^

514

SPECIAL HISTOLOGY.

Fis. 210.

For mj OAvn part in fact, I believe that all the narrow cylindrical and
filiform villi will be found to present this condition, but that, on the
other hand, the number and mode of origin of the lacteals maj possibly be
different in the broad and foliaceous forms (see Mikr. Anat., ii. 2, p. 160).
In addition to these organs, the villi also contain, as Brlicke dis-
covered a short time ago, a thin layer
of lono-itudinal smooth muscles situ-
ated more centrally round the lacteals ;
these, however, are not always distinct
in man. They produce contractions of
the villi (Fig. 210), which are very
evident immediately after death, and
which, according to Brlicke, are also
■perceptible in the living animal. They
have, in all probability, an important
influence over the propulsion of the
chyle and of the venous blood in the
villi — always supposing that there is no
objection to the assumption that they
perform repeated contractions during life. Nothing is known of the
nerves in the villi.

The epithelium of the villi and of the rest of the surface of the
mucous membrane, although it is very intimately united with the deeper-
seated parts during life, only becoming detached accidentally or by dis-
ease, separates very readily in the dead subject, and can only be ob-
served in perfectly fresh portions of intestine. It consists everywhere
of a simple layer of cylindrical cells slightly narrowed below, of 0*01-
0-012 of a line in length, and 0-003-0-001 of a line in breadth, whose
contents are usually nothing but fine granules and an oval, clear, vesi^
cular nucleus, provided with one or two nucleoli. During life, these
cells, which agree in all their chemical characters with the deeper cells
of the oral epithelium, are so intimately united, that even after death
their contours, in a longitudinal view, are at first either not at all, or
only indistinctly distinguishable, though on the surface they have the
appearance of a beautiful mosaic. The cylinders only become quite
distinct when they are either spontaneously or artificially detached, a
process which usually takes place in such a manner that they hang
together in continuous portions, all the cells covering a villus sometimes
coming off together like the cahj'ptra of a moss. The addition of water
to these cells produces a separation of the cell contents from the broad
end, giving rise, in separate cells, to the appearance of a membrane
thickened upon one side and in series of cells or entire villi^ to that of

Fig. 210. — Two intestinal villi of the Cat, contracted, and magnified CO diameters.

THE INTESTINES.

515

a peculiar structureless coat, like the cuticle of plants ; by its longer
action, lio^vever, or by that of the intestinal fluids, the bursting of the

Fig. 211.

\ A

\ / t

/ f >, ^.

cells produces apertures in them, or they becotne distended into large
pyriform clear vesicles.

"We may here refer to the changes ivhich the epithelial cells and the
villi in general imdergo during digesiio7i. The most striking circum-
stance is the occurrence of fat in different parts of the villi, Avhich may
ahvays be observed during the formation of a fatty, milk'white chyle.
The succession of the morphological steps, at least as I have observed
them in animals, is as follows: The fat contained in the chyme at first
enters only isolated epithelial cells in different regions of the villi, so
that in each we soon observe a large ovate shining drop. The number
of these fat-cells rapidly increases, and then the villi acquire a very
peculiar appearance, often as if beset with pearls, from the irregular
alternation of cells filled with fat and consequently bright and shining,
with those which are empty and pale. In the end, all the cells become
filled with these drops and the epithelium appears quite dark by trans-
mitted, but whitish by reflected light, giving its aspect to the whole
villus. With the repletion of the entire epithelial covering of the villus

Fig. 211. — J, two villi, w'nh Xheir epithelium, fwm the Rabbit; magnified 73 diameters:
a, epithelium ; h, parenchyma of the villus. B, a detached sheet oi epithelium, magnified 300
diameters : a, membrane raised up by the action of water. C, single epitheUal cells, mag-
nified 3-jO diameters : a, with, b, without, a raised-up membrane ; c, a few cells from the
surface.

516 SPECIAL HISTOLOGY.

absorption commences, but up to tliis time nothing has entered the lac-
teals. This, however, soon takes place, and the first indication we ob-
serve, is the breaking up of the large drops of fat in the cells into many
tolerably minute fatty molecules. When this has occurred, these drops
penetrate by degrees, from all sides, into the parenchyma of the villus
itself, fill it more and more and, at last, enter the central lacteal, whose
whole length they eventually occupy. In the meanwhile, fresh fat has
been continually passing in from the intestinal canal, not in the form of
large drops, however, but henceforward, in small molecules or drops of
the same kind as those which were at first developed secondarily in the
cells. On the other hand, at a subsequent period, we not uncommonly
meet, in the interior of the villi, with large round drops, which appear
especially inclined to form considerable accumulations at their apex.
In man, I have not yet had the opportunity of tracing the process of
the absorption of fat, step by step, but we may here so frequently ob-
serve, on the one hand, cylindrical epithelial cells filled with fatty mole-
cules, and on the other, collections of larger and smaller drops of fat
in the parenchyma of the villi, especially at tlieir points and in their
axes, that I do not at all hesitate to suppose the process to be the same
as in animals, without, however, wishing to imply that all the steps are
identical. These observations demonstrate that fatty matters are ab-
sorbed as such and are not saponified ; on the other hand, it cannot at
present be certainly stated how it is possible that they penetrate the
membrane of the epithelial cells, the parenchyma of the villi, and the
walls of the lacteals. I should be most inclined to compare the whole
process to the imbibition of an emulsive fluid, such as milk, by a porous
body ; and I believe that the fatty molecules of the chyme are absorbed
simply in consequence of their being carried along with its fluid part.*

* [Professor Brucke, in a series of important papers on the " Lacteals and on the Absorp-
tion of Chyle" (Ueber die Chylusgefasse und die Resorption des Chylns), published in the
Transactions of the Vienna Academy for 1S54, has thrown much light on the difficult
question of the anatomy and physiology of the parts concerned in digestive absorption.

As the result of his observations on Man and on the Mammalia, Brucke states, that the
cylindrical epithelial cells covering the villi, are open at one extremity, and are not, as is
generally supposed, closed by a membrane, but merely by a thin layer of a mucilaginous
substance. This, he asserts, can be proved by observations on animals recently killed; for
if a portion of their intestinal mucous membrane be brought under the field of the micro-
scope, the formation of transparent vesicles, corresponding to each epithelial cell may be
easily seen. These vesicles form along the margin of the villus, and are the cell-contents
which have escaped from the open extremity of the cylindrical cell, enclosed by the muci-
laginous substance. They have hitherto been regarded as the cell-wall rendered prominent
by an expansion of the cell-contents [vid- supra, Fig 211, C a) • but that this view is in-
correct, is evident from the circumstance, that they lie perfectly isolated by the side of the
cells, widiout any change in the membrane of the latter being observable.

As another evidence of these epithelial cells not being closed cavities, Professor Brucke
adduces the fact, that even by the aid of the highest magnifying powers, no cell membrane
with pores can be distinguished. Yet the oil globules, which are always of a distinctly re-
cognizable size, are known to enter the cells, and it is diiricult to understand how they can
traverse a homogeneous membrane.

TUE INTESTINES. 517

While digestion is going on, we frequently find the whole parenchyma
of the villi densely filled with small nuclei, here and there surrounded

This difficulty is increased when we consider, tliat a trustworthy observer (Osierlein) has
detected soHd particles in tlie interior of the epithelial cells. By assuming, however, that
these latter are open at one extremity, and are isolated from the intestinal tube merely by a
thin layer of mucilaginous substance, which is easily traversed, Professor Brilcke thinks the
difficulty may be solved. The chyle, he states, passes from within the cell through an
opening in the opposite extremity into the villus. Within the villus, the molecules of chyle
lie in the lacteal and in the interstices of the delicate stroma, which connects the walls of
the villus with its muscular fibres and bloodvessels. The lacteal, Professor Brucke regards
not as a vessel, but as a mere cavity in the centre of the villus, without distinct walls. In
cylindrical villi he generally found one cavity, in broad villi, two, three, or even four dis-
tinct canals. Of the structureless, thin membrane, described by KoUiker as surrounding the
lactealsf he was not able to observe any traces. He also denies the commencement of the
lacteal by a distinct network, as stated by Hewson, Krause, and Hyrtl, and thinks that these
observers have mistaken capillaries for lacteals. The lacteal he regards, on the contrary,
as originating by irregular channels formed by the interstices in the tissues of the villus.

The commencement of the complete chyliferous vessels occurs in the deeper part of the
mucous membrane. In the submucous areolar tissue large vessels with distinct walls, and
furnished with valves and an epidielium, are observable. In the smaller ramifications
these cannot be detected; nor can a separate tunica propria of the walls be distinguished
from the areolar tissue which forms the adventitia. In the muscular layer the chyliferous
vessels have valves ; they are accompanied on each side by an artery and vein. In the
mucous and submucous tissue no such arrangement of the bloodvessels exists.

The chyle, Professor Brucke asserts, does- not enter the vessels merely from the villi, but
also from between them, and principally from between the glands of Lieberkuhn, where it
may be observed lying free in the interstices of the tissue. This commencement of the
chyliferous vessels by open extremities in the interstices of the stroma of tissues, he regards
as sufficient to account for the circumstance, that absorption may take place in parts of the
intestinal canal not possessed of villi, as in the large intestine. The lymphatics, as well as
the chyliferous vessels, he considers to commence by channels in the tissues, and thus
the curious fact noticed by him {vid. " Denkschriften der Wien Acad.," vol. ii. p. 21),
that a colored solution may penetrate through the capsules of the Peyerian glands and reach
the thoracic duct, is readily explained.

With regard to the anatomy of the chyliferous vessels after they leave the intestinal walls,
Brucke confirms the recent observations of Ludwig and Noll [vid. § 219, infra). The best
method to examine the commencements of the chyliferous vessels, is to allow the chyle
time to coagulate in the vessels, and then to render the walls of the intestine transparent.
This is most readily eflected by a solution of albumen in caustic potassa, to which enough
hydrochloric acid has been added to neutralize the alkali.

In the animals he examined, Professor Briieke found the arrangement of the chyliferous
vessels to be in the main similar to that in Man. In the Weasel there is no difference. In
the Rabbit the chyle is not contained in separate channels, but is situated, throughout the
whole thickness of the intestinal wall, in the interstices between the sheaths of the blood-
vessels. In this animal, therefore, the chyle is separated from the blood merely by the
thickness of the membranes of the bloodvessels, whilst in Man this is the case only in the
mucous layer of the intestine. In the Pig, the walls of the chyliferous vessels exhibit a
distinct layer of muscular fibres. In the Mouse, the deposits of chyle in the interstices be-
tween the glands of Lieberkahn are readily seen.

The contractions of the intestinal canal Brucke considers to be the principal means by
which the chyle is forced into the villi, these latter being kept erect and distended by the
pressure of the blood in their bloodvessels. As the chyle in the villi surrounds the blood-
vessels, a mutual interchange of some of the elements takes place ; the blood yields up fibrine
to the chyle, and the chyle a portion of its soluble parts to the blood.

When the villi are filled, the contraction of their muscular fibres presses the chyle into

518 SPECIAL HISTOLOGY.

by cell membranes, elements -whicli are perhaps never entirely absent
in a villus, but are at other times far fewer, and particularly are not to
be distinguished in its interior.*

§ 154. Crlands of the small intestine. — The small intestine contains
only two kinds of true glands ; viz., 1, tubular glands, which are dis-

the channels between the mucous and submucous membrane. If the villi be much dis-
tended, a portion of the chyle passes back again through the epithelial cells into the cavity
of the intestinal tube, and this is especially apt to occur when the chyle contains any par-
ticles too coarse to circulate. The chyle is propelled further by the muscular con-
tractions of the intestines into the vessels of the mesentery, whence it is pumped, as it
were, into the thoracic duct, by the alternating pressure on the intestinal walls during the
movements of resj^iration. This action is also aided to a slight extent by the contractions
of the muscular tissue of the chyliferous vessels.

The results arrived at by Professor Brilcke, will, if corroborated by future research, tend
greatly to elucidate much that has hitherto been obscure in the physiology of the digestive
as well as of interstitial absorption. — DaC]

* [One of the most important contributions to our knowledge of the anatomy of the villi
and the general physiology of digestive absorption, which has appeared for a long time, is
Professor Briich's '-Beitrage zur Anatomic und Physiologie der Donndarm-Schleimhaut,"
in Siebold and KoUiker's " Zeitschrift," for April, 1S53. We subjoin the principal results
at which the Professor has arrived.

The epitlielium is not cast off during normal digestion and in freshly killed animals it is
somewhat difhcult to detach it from the mucous membrane. The cells of the epithelium
do not, as Weber stated, undergo any change of form during digestion andchylification, but
they become filled with fat, wliich gradually passes on into the villi, &c., so that in the
fasting state they are again free from any foreign contents.

The villi ordinarily contain two, but sometimes many, capillary trvmks, which ramify
principally at their apices, and superficially. Ramifications and anastomoses in the body of
the villi are less common. In dogs, many parallel vessels often run undivided for a con-
siderable distance, and have doubtless been confounded with a central lacteal.

In all the animals Briicli examined, and in man, he found that the villi had a striking
uniformity of structure. A single lacteal ran, without dividing, through the villus, and terminated
shortly befo7-e reaching its apex, in a cacal commonly enlarged fjirf (Liberkiihn's ampulla). The
lacteal had no wall, appearing to be a mere excavation in the villus. In cleft villi, the
lacteal was cleft, each end terminating in a caecum. In very rare cases, there were in
broad villi two lacteals, a shorter and a longer, terminating in distinct ampulla, side by side.
In tlie mucous membrane itself, the lacteals form a wide superficial network.

BrQcli accounts for the supposed lacteal network of the villi, by showing that the blood-
vessels are as capable of absorbing fat as the lacteals, and when filled, of course acquire the ap-
pearance of a lacteal network. In some cases he found the superficial capillary network of
a villus half red and half white, and it was frequently possible, when the fatty contents of
the capillary network were hidden by the preponderating blood, to render them obvious by
the action of water, which dissolved out the coloring matter and thus apparently converted
a capillary, into a lacteal network.

Professor Briich considers that the absorption of fit is a purely mechanical process, "just
as quicksilver is pressed through leather," and he doubts altogether that the lacteals have
any special absorbent fimction, or differ from ordinary lymphatics. However, we think
that the mechanical nature of the process is open to very great question, and we should
rather compare the manner in which fat enters a villus, to that in which the ingesta enter
nn .Sclinophrys ; one can as readily comprehend the existence of a selective power in the
former as in the latter case. That some such faculty exists would seem to be indicated by
the fact stated by Bruch, that the Liebcrkuhnian and Peyerian glands take no share in fatty
absorption ; though, on the ether hand, it must be remembered that Kolliker found the eggs
of Entozoa in the villi of rabbits (" Mikr. Anat.," B. II. 2, 173).— Trs.]

THE INTESTINES.

519

posed over the whole mucous membrane ; and 2, racemose glands, in
the submucous tissue of the duodenum.

The racemose glands, or as they are more commonly named, after
their discoverer, Brunners glands, form, at the commencement of the
duodenum, upon the outer side of the mucous membrane, a continuous
layer, which is best developed and thickest, close to the jyylorus, where
it constitutes a considerable glandular ring and extends about as far as
the aperture of the biliary ducts. If the two layers of the muscular
tissue be dissected off a stretched or distended duodenum, the glands
may readily be recognized as yellowish, flattened bodies of to-1| lines
(on the average \-\ a line,) with their angles rounded off, which, en-
closed within a little connective tissue, lie close to the mucous membrane
and send short excretory ducts into it. In their minute structure,
Brunner's glands, the terminal vesicles of which measure 0-03-0-06,
even 0-08 of a line, agree perfectly with the racemose glands of the oral
cavity and oesophagus. Their secretion is an alkaline mucus, in which
no formed elements are contained, having no digestive action upon
coagulated protein compounds and probably merely subservient to
mechanical ends.

The tubular, or Lieherkulinian glands [cryptce mucosa>), are distri-
buted over the whole small intestine, including the duodenum, as innu-
merable, straight, narrow creca, which occupy the entire thickness of
the mucous membrane and are frequently slightly enlarged at their ex-
tremities, though hardly ever dichotomously divided. The best idea of
their number is obtained by viewing the mucous membrane either from
above or in vertical section, under a low power. In the latter case, we
see the coeca standing close together, almost like palisades (Fig. 206) ;
in the former, we observe that the glands do not occupy the whole sur-
face, but only the interspaces between
the villi ; here, however, they exist in -
such numbers, as to leave no intervals
of any width, the mucous surface
between the villi appearing pierced
like a sieve. Even on Peyer's patches
and over the solitary follicles, these
glands are to be met with ; but in man,
they leave those portions of the mu-
cous membrane which lie immediately
over the centre of the follicles free,
and therefore are arranged like rings
around the follicles. The length of
the Licberkiihnian glands equals the
thickness of the mucous membrane and

Fig. Q12. — Licberkahnian glands of the Pig, magnified GO diameters : a, mcmhrana propria
and ei)ithelium ; 6, cavity.

Fis. 212.

520 SPECIAL HISTOLOGY.

varies from 1-4 of a line; their breadth is 0-028-0-036 of a line ; that
of their aperture, 0 •02-0-03 of a line. They are composed of a delicate
homogeneous membrane projyria and of a cylindrical epithelium, which,
even during chylification, never, like that of the intestine, contains fat ;
their cavity is filled, during life, by a clear, fluid secretion, the so-called
intestinal juice, which, however, becomes rapidly changed after death, or
on the addition of water, so that the glands appear to be filled with cells,
or with a granular mass.

The vessels of Brunner's glands have the same arrangement as those
of the salivary, whilst around Lieberklihn's ca'ca they follow exactly
the type of those of the stomach. A fine network of capillaries of
0"003 of a line, passes up round the ca^ca and, upon the surface of the
mucous membrane, enters an elegant polygonal reticulation of some-
what wider (0-01 of a line) vessels, which communicates on one side with
the vessels of the villi, on the other is directly continuous with veins,
which, after communicating with those of the villi, run directly out of
the mucous membrane. Hence, in this case also, the veins are con-
nected only with the superficial network round the glandular apertures
and with that in the villi, but not with that which surrounds the glands,
so that, as in the stomach, the vessels which supply the secretion im-
mediately succeed the arteries, and precede those to which the absor-
bent function is more especially assigned (comp. Frei, cited below).

Whence the small round cells, with a single nucleus, which are to be
met with in the intestinal mucus, proceed, is doubtful. I have not found
them in the glands and I can only refer them to the epithelium, .whence
I am inclined to suppose that these cells, which are usually few, arise
upon the surface of the mucous membrane, like the mucous corpuscles of
the oral cavity.

In various, particularly intestinal, disorders, in inflammations, typhus,
peritonitis, Bohm found a white viscid secretion in many Lieberklihnian
glands (Gland, int., p. 34), which, as subsequent observations of the
same author (Darmschleimhaut in der Cholera, p. 63) would indicate,
was merely an epithelium detached from the walls of the cavity, and
which had become aggregated into a compact plug. In cholera, accord-
ing to Bohm, this epithelium, as well as that of the whole intestine, is
thrown ofi".

§ 155. Closed follicles of the small intestines. — Vesicles of a peculiar
kind are found scattered, singly or in groups, over the walls of the small
intestine, of whose anatomical and physiological import we have, as yet,
attained no very clear idea and which may therefore, for the present, be
most fittingly described under a general denomination.

The most important of these are Peyers patches [glandiila' agminata^).
They are rounded, flattened organs, invariably situated along that sur-

THE INTESTINES.

521

Fig. 213.

face of the intestine ■\vliicli is opposite to the mesentery ; the}'' are most
distinct upon the inner surface, where they appear as rather depressed,
smooth spots, without any very sharp definition, but they are also recog-
nizable from the exterior, by the slight elevation to which they give rise;
by transmitted light they look like more opaque portions of the mem-
brane. These patches are usually most abundant in the ileum, but they
are not uncommonly to be met with in the lower part of the jejunum : —
occasionally they exist in its upper portion close to the duodenum and
even in the inferior horizontal portion of the duodenum itself. Ordi-
narily there are 20—30 of them ; when they are found higher up there
may be as many as 50-GO ; but they are
always most closely set in the lowest
portion of tlie ileum. The dimensions
of the separate patches are in general
the larger, the closer they are to the cce-
cum ; their length is usually 5-1 -J lines,
but may diminish to 3 and increase to
3-5 lines, or even 1 inch ; their breadth
varies from 3 to 5 or 9 lines. Where
the patches lie, the valvulce conniventes
are usually interrupted ; in the jejunurn,
however, these folds are also to be met
with ; upon the Peyer's patches and in the
ileum, row.s of closely set villi often take
their place.

More minutely examined, every J^eT/-
ers loatch is seen to be an aggregation
of closed follicles, o'i. 1-6-1-2-1 line in
diameter, either rounded or slightly co-
nical towards the intestinal cavity, which lie partly in the mucous mem-
brane itself, partly in the submucous tissue, and are, on the one side not
more than 0-02-0-03 of a line distant from the
mucous surface, while on the other, they are in
immediate contact with the muscular tunic, which
is here somewhat more closely united with the
mucous membrane. Vie^

the intestine, their most strikinji feature in Man 'WJ^VPA^h'TW^-^. J
is the presence of many

sions J-J-1 line apart, wnicn correspond wiiu '^^^\;
the separate follicles, and whose floor is, indeed.

Fig. 213. — A Peyer's patch (Man), magnified 4 dianneters: a, ordinary mucous surface,
with viUi; b, depressions upon tlie patches corresponding with the follicles; c, intermediate
substance, with small villi. .

Fig. 214. — Portion of a Peyer's patch of an old IMan, after Flouch : a, follicle, surrounded?
by the apertures of the Lieberktihnian glands; 6, villi; c, more isolated Lieberkiihniaa
follicles.

Fi?. 214.

522

SPECIAL HISTOLOGY.

rendered slightly convex by the latter, but which present no villi what-
soever. The remainder of the patch is occupied by common villi, or by
reticulated folds and by the apertures of the Lieberklihnian glands ; the
latter are disposed around the slight elevations produced by the follicles,
in circlets of 6-10 and more apertures, the coronce tuhulorum of authors.
^^c\i follicle of a patch possesses a perfectly closed, thick and tolera-
bly strong coat of indistinctly fibrillated connective tissue, with inter-
spersed nuclei ; within this are the contents, which are soft and grayish
(never milk-Avhite). They become slowly diffused through water and
consist of a little fluid, with innumerable nuclei and round cells of
0-004-0-008 of a line, which, when recent, appear quite homogeneous
and of a dull gray color, but are first cleared up and ultimately de-
stroyed by the action of water and of acetic acid, the nuclei at the same
time becoming granular and very distinct. Among these elements,
which here and there also contain fatty granules, and which, as the

FiR. 215.

comparison of their various forms shows, are constantly undergoing
progressive and retrogressive development, Frei and Ernst have demon-
strated the existence of numerous, but very fine bloodvessels of 0-0015
-0-004 of a line, which are connected with a rich vascular network
surrounding the follicle, and may be readily recognized in the contents
of the follicles of animals (Pig, e. g.), if they be quite fresh, and have
been extracted with care.

Little is known of the lymphatics of Peyer's patches. This much is
certain, however, that the number of lacteals wliich may he traced du-

FiG. 215. — Horizontal section from tlie middle of three Peyer's follicles of the Rabbit,
in order to show their internal vessels. After an injection by Frei.

THE INTESTINES. 523

ring digestion from the Peyerian 2^atches, is greater than that in other
jjarts of the intestine, although their villi ave fewer and less developed ;
on the other hand, we know nothing of the internal relations of these
vessels. They would seem to form networks around the separate folli-
cles, at least we see that they compass them externally ; but they do
not become inserted into, nor enter them, at any rate upon this surface,
as their milk-white color would render their detection easy. Although,
then, Briicke has recently affirmed the direct communication of the
follicles with lymphatics, I must, for these and other reasons (see Mikr.
Anat. II. 2, p. 188), at present doubt the fact.

The solitary follicles [glandulce solitaria') resemble the separate ele-
ments of Peyer's patches so closely in size, contents (I have also seen
the internal vessels in them), and general structure, ^.^ ^^^

that there is no reason for considering them as dis-

tinct, particularly since the number of the follicles i^ ''^^^w^^ ■ •
is subject to ail possible varieties; and since, in v/j^rS'^' '^S'-..--
animals at least, we find Peyer's patches with 2-3- '^fm^r.i'^ '^ "^^
5 follicles. In man, as all writers justly agree, ^^r-. .^^^'■
their number is exceedingly inconstant: sometimes '■\Wi''''Zt^'^r^''A
not one can be found, whilst in other cases, the whole - --^^'- - .^^—^
intestine, as far as the margins of the ileo-C£ecal valve, is thickly beset
with them, or lastly, they may occur in the ileum and jejunum, but in
no very great number. Their entire absence must probably be con-
sidered abnormal, since they are constant in newly-born children, being
more abundant in \)a.Q jejunum than in the ileum. The miliary vesicles,
however, which are often met with in immense quantities in the small
intestine and stomach, in catarrhal affections of the alimentary tract,
may very probably be entirely or partially pathological, since the occur-
rence of such follicles has been demonstrated in other organs also (in
the liver, according to Virchow). The solitary follicles have the same
sposition as the elements of the patches, only they occur also in the
mesenteric border and support villi upon their intestinal surface, which
is usually somewhat convex.

I consider it as quite certain, that the follicles of Peyer's patches
have no apertures, but I may here adduce the following facts. 1. In
animals examined while fresh, the capsules are invariably closed, as may
be very readily seen in the well-developed patches of the Pig, Sheep,
Cat, Dog, <S:c., which I particularly recommend for the examination of
these organs, because the patches in the human subject have so fre-
quently undergone alteration. 2. The appearance of an aperture may
proceed from the depression of the mucous membrane over the single
follicles, especially when the projecting portion of the wall of the folli-

FiG. 21G. — A solitary follicle, covered with villi, from the small intestine. After Biilim.

524 SPECIAL HISTOLOGY.

cles is not very tense. 3. In man, the closed follicles of the intestine
are subject to very many morbid changes ; they are frequently ruptured
and so altered, that in place of the patches nothing remains but a reti-
culated, indistinctly pitted surface. As Virchow was the first to show
(Med. Reform. 1848, No. 10, p. 64), they may also burst after death,
if they are allowed to stand in water or in a warm place ; whence, per-
haps, many of those apertures which are met with in the dead subject
should be regarded as the result of putrefactive change.

It is easy to understand, that little can be said concerning the phy-
siology of Peyer's follicles so long as their relations to the lymphatics
are not understood. They, and the follicles of the intestine in general,
appear to me to be closed glandular organs, analogous to the splenic
follicles, the tonsils, and the lymphatic glands, which contain peculiar
elements and^ vascular network. In these a constant development of
cells takes place and at the same time, substances are elaborated from
the plasma, supplied by the bloodvessels and perhaps also from matters
not of a fatty nature, absorbed from the intestine, a part of which, in
all probability, is at once taken up by the internal bloodvessels, while
the larger proportion is excreted and absorbed by the lymphatics. The
period of their greatest activity (when they become distended) coincides
with that of the intestinal absorption, either because they absorb from
the intestine or because they simply participate in the greater activity
of the intestine at this time ; and perhaps the more albuminous matters
which they yield may be connected with the development of cells in the
chyle. This hypothesis will hold good in its principal outlines, even if
in future the direct connection of the lymphatics with the follicles, or the
occurrence of lacteals ^Yithin them, should be demonstrated ; at any rate,
it will not be blamed for being too wide of the facts.

§ 156. 3iucous memhrmie of the large intestine. — The structure of
the mucous membrane in the large intestine agrees so closely in essen-
tials with that of the small intestine, that it may suffice here to draw
attention to a few points only.

The mucous membrane of the large intestine, if we except the rectu7n,
has no proper folds, for the transversely fibrous muscular layer also
enters into the ^:>ZiC(:f^ sigmoidecv. The villi also are absent, from the
edoje of the ileo-ctecal valve, into which the muscular tunic likewise
enters, onwards ; and the mucous surface, apart from some occasional,
hardly perceptible, small, wart-like elevations, is even and smooth. It
is difficult to detect the muscular layer of the mucous membrane in the
human colon, though it is unquestionably present ; it is more distinct in
the rectum. In animals I find it well developed. According to Brllcke,
in the colon (of animals ?) its longitudinally and transversely fibrous
layers, which also exist here, are only 0'013 of a line thick, the diminu-
tion having taken place at the expense of the external longitudinal

THE INTESTINES.

525

Fis:. 217

fibres, -which arc reduced to a threefohl or even only a twofold stratum ;
in the rectum, the hiycrs arc again of equal thickness, and, taken to-
gether, measure about 0*022, at the anus even 0-088 of a line and
more.

The glandular organs of the large intestine are Lieherk'dhn s glands
and solitary follicles ; the former, also termed glands of the large intcs-
tine, are distributed over its whole surface from the ileo-ctecal valve to
the anus and in the 2?rocessus vermicularis. They are closely set, and
have exactly the same structure as those of the small intestine, only, in
accordance with the greater thickness of the mucous membrane, they
are longer and broader {^l of a lino long, y.j-og of a line broad).
Here also I have found, in man and in animals, in the fresh state, no
formed contents besides a beautiful cylinder epithelium ; so that we have
no reason to suppose that the secretion is at all different from that in
the glands of the small intestine, especially as the mucous membrane
has, like that of the latter, an alkaline reaction, and, so far as my own
experiments go, is equally devoid of digestive action.

The solitary follicles are arranged close together in the processus ver-
micularis, are very frequent in the ca'cum and rectum, and are also
usually more abundant in the colon
than in the small intestine. They
are distinguished from those of the
latter locality by their larger size
(f-l-l|^ lines) and by the circum-
stance that upon each of the little
prominences of the mucous mem-
brane to which the follicles give rise,
there is a small pit-like, elongated
or rounded aperture, of 1-9-1-12 of
a line, which leads to a little depres-
sion of the mucous membrane above
the follicles. These pits, which are
totally absent in the normal follicles

of the small intestine, led Bohm formerly to regard the follicles as c?ecal
glands provided with apertures : this, however, is incorrect, for at the
bottom of this depression lies, as Brlicke has also remarked, a closed,
somewhat flattened follicle of exactly the same structure, even to the
internal vessels, as those of the small intestine.

The bloodvessels of the glands and follicles of the large intestine pre-
sent the same relations as in the small. Every Lieberkiihnian aperture
is encircled by a ring of vessels of 0-OOG-O-Ol of a line, which is some-

FiG. 217. — Solitary follicle from the colon of a Child, magnified 45 diameters: a. Lieber-
ktihn's glands ; i, muscular layer of the mucous membrane ; c, submucous tissue; rf, trans-
verse muscles ; e, serous membrane ; /", depression of the mucous membrane above the
follicle, a.

526 SPECIAL HISTOLOGY.

times single, sometimes, especially in the neighborhood of the solitary
follicles, multiple.

From these vessels "wider venous trunks arise and penetrate deeply
between the glands, which are themselves surrounded by a dense network
of fine capillaries derived immediately from the arteries (Fig. 205).
Nothing is known of either the lymphatics or the nerves in the mucous
membrane. The epithelium is precisely similar to that of the small
intestine, and, at the anus^ is separated by a pretty sharp line of demar-
cation, from the external epidermis.

§ 157. Development of the intestinal canal. The entire wall of the
intestine, various as its different structures may afterwards become, pro-
ceeds from two points of development: viz. in the first place from the
inferior lamina of the germinal membrane (mucous layer of Pander and
Eaer; raucous tunic, Reichert; glandular layer or intestinal glandular
layer, of Remak), which is not the foundation of the whole mucous mem-
brane, but only of the intestinal epithelium and of the intestinal glands ;
and 2, from the middle layer of the germinal membrane (vascular lamina,
Pander, memhrana intermedia, Reichert), which gives rise, in addition
to many other parts (muscles, bones, nerves, heart), to the vascular and
nervous fibrous coats of the intestine, as well as to the vessels, nerves,
and coats of the intestinal glands.

The inner layer or the epithelial tube consists from first to last of no-
thing but cells and becomes metamorphosed by their continual multipli-
cation, superficially and perpendicularly, which, according to Remak,
takes place by division, in the first place, into the future epithelia ; and in
the second, into the glands of the intestine. Of the latter, the Lieber-
kllhnian follicles are from the first, hollow diverticula of the epithelium,
whilst the salivary and Brunner's glands arise, like the sudoriparous
glands, as solid processes, which only subsequently acquire cavities and
become branched. The gastric glands and those of the large intestine
also certainly arise from the primitive epithelial tube — whether as diver-
ticula or as solid processes is not yet made out — and form at the com-
mencement a layer completely separated from the fibrous lamina of the
intestine ; whence, also, the epithelium in their neighborhood appears
much thicker than it subsequently is. At a later period, delicate vas-
cular processes grow from the fibrous layer between the glands, until at
length both layers, intimately united, constitute the proper mucous mem-
brane. Similar and more considerable processes of the fibrous layer
form the villi, whilst the muscular and serous tissues are developed from
its external portion.

The examination of the intestinal mucous membrane presents greater
difficulties than that of other parts. The epithelium is usually in a good

THE INTESTINES. 527

state of preservation only in quite fresh subjects, and generally breaks
up into its elements with extreme ease. The villi are best seen in thin
perpendicular sections, made with fine scissors, viewed with a low power,
and illuminated from above. During absorption, they are usually found
full of fat and nuclei, so that their separate portions are not perceived,
with the exception of the lacteals, which become distinct by the use of
acetic acid and still better by that of dilute caustic soda. At other
times, the muscles of the villi are easily recognized by their nuclei, on
the addition of acetic acid. Injections are required for the bloodvessels :
the best are made by injecting from both arteries and veins at the
same time, and should be preserved in fluid. The same holds good of
the other parts of the intestine, for which perpendicular sections are
especially instructive. For the glands, recent pieces of intestine are
particularly required, although it is often, as in the stomach, exceed-
ingly difficult to prepare them. Mucous membrane, hardened in alcohol,
pyroligneous acid, or chromic acid, or boiled in acetic acid of 80 per
cent, and dried, according to the method of Purkinje and Middeldorpf,
or saturated with gum and dried, thin transverse and longitudinal sec-
tions being made Avitli a sharp knife, according to Wasmann's method,
may be used, being first rendered clear by a little soda. The analysis
of the gastric mucous membrane into its elements, presents the greatest
difficulties, especially when it is as thick as in the Horse and Pig. In
the Dog, Cat, Rabbit, and in the Ruminants, the process is easier, since,
frequently, by merely scraping the mucous membrane with the back of
a knife, the epithelium of the glands may be drawn out in a connected
state and affords all the information required as to their form and lining.
Simple teasing out is also frequently sufficient to reduce the mucous
membrane of the animals in question into its elements.

Brunners glands offer no difficulties except in their excretory ducts,
which may, however, be clearly seen in perpendicular sections and in
animals, by teasing out the mucous membrane. The Lieberklihnian
glands, also, may generally be very readily isolated in their entire
length ; while the closed follicles should be carefully exposed from
without, isolated and opened ; or they may be studied in perpendicular
sections. The muscular tissue of the mucous membrane must be exposed
by removing the tunica nervea on its exterior and then separating it in
small segments from the glandular layer ; its elements maybe very well
seen by macerating it in nitric acid of 20 per cent.

Literature of the intestinal canal. — Th. L. W. Bischoff, " Ueber den
Bau der Magenschleimhaut," Mull. Arch. 1838, p. 503, with figures ;
AVasmann, " De digestione nonnulla," Berol., 1839, cum tab. ; L.
Bcihm, " De glandularum intestinalium structura penitiori," Berol.,
1835, 8 c. tab. ; and " Die kranke Darmschleimhaut in der Asiatischen
Cholera," BerL, 1838 ; J. Henle, " Symbolai ad anatomiam villorum

528 SPECIAL HISTOLOGY.

intestinalium impr. eorum epitlielii etvasorum lacteorum," c. tab. Berol.,
1837, 4to. ; J. Floucb, " Recberclies sur la membrane muqueuse intes-
tinale, in Mem. de la societc d'histoire natur. de Strasbourg," III. 3,
Strasb., 1845; A. Tb. Middeldorpf, " De glandulis Brunnianis,"
Vratisl. 1846, c. tab. ; E. H. Weber, in " MUlIer's Arcbiv," 1847, p.
400 ; and in " Bericbte der Koniglicben Sacbsiscben Gesellscbaft der
Wissenscbaften," Heft VII. 18 May, 1847, p. 245; Frericbs (and
Frei), Article, " Verdauung, in AVagner's Handw. d. Pbysiologie," Bd.
III. p. 738-755; R. 0. Ziegler, " Ueber die solltaren und Peyer'-
scben Follikcl," Wiirzburg, 1850, Diss. ; E. Brlicke, 1. " Ueber den
Bail und die pbysiologiscbe Bedeutung der Peyer'scben Drlisen, in
Denkscbriften der Wiener Akademie," bd. II. 1850, p. 21, witb 1 plate;
2. " Das Muskelsystem der Schleimbaut des Magens ;" and 3. " Ueber
ein in der Darmschleimbaut aufgefundenes Muskelsystem," in tbe " Be-
ricbten der Akademie," 1851 ; Kulliker, " Ueber das Vorkommen von
glatten Muskelfasern in Scbleimbauten," in " Zcitscbrift flir wiss.
Zoologie," III. 1851, p. 100, und Nachtrag dazu. Heft II. ; F. Ernst,
" Ueber die Anordnung der Blutgef iisse in den Darmbiiuten," Zuricb,
1851, Diss. c. tab.

[Brllcb, "Beitriige zur Anatomie und Pbysiologie des Dlinndarm-
Schleimbaut," Siebold and Kiilliker's " Zeitscbrift," 1853; also tbree
most important papers by Briicke, " Ueber die Aufsaugung des Cby-
lus," Sitzungsbericbte d. Wiener Akad. Dec. 1852 ; " Ueber den Urs-
prung und den Verlauf der Cb^dusgefasse," ibid. January, 1853, and
" Ueber die Chylusgefasse und die Fortbewegung des Cbylus," ibid.,
March, 1853, which have come into our hands too late for further re-
ference-=^' — Trs.]

OF THE LIVER.

§ 158. The liver, a large gland, is at once distinguished from those
•compound glands, such as the salivary, which have hitherto been de-
scribed, by the intimate connection of its larger subdivisions and by the
very peculiar structure of its secreting parenchyma, which elaborates
the bile. The component parts are, the secreting parenchyma, consist-
ing of the lobules or islets of the liver and of the networks of hepatic
•cells ; the hiliary passages which are formed in this, and the efferent
hiliary ducts ; very numerous bloodvessels ; a considerable number of
lymphatics and nerves ; and finally, a peritoneal investment.

§ 159. Secreting parenchyma, hepatic lobes and hepatic substance. —
If the surface or a section of the liver be regarded, it generally exhi-
bits a mottled appearance, which is usually of such a kind, that small,

* [See note, p. 51G.— DaC]

THE LIVER. 529

stellate, reddish or brown spots arc enclosed within a more yellowish-red
substance — medullary and cortical substance (Ferrcin). This variega-
tion proceeds from the usually unequal distribution of the blood in the
smallest trunks and in the capillaries, and in healthy persons it is re-
placed by a uniform reddish-brown color. The mottling of the surface
of the liver is frequently so regular as to have given rise to the suppo-
sition that it consists of lobes, especially as in an animal which is a fre-
quent subject of investigation, — the Pig, — they are very obvious ; but,
as E. II. Weber was the first to demonstrate, in 1842, in the human
liver nothing of the kind exists ; here, in fact, not only the secreting
elements, but the most important parts of the vascular system, i. e. the
capillary network between the portal and hepatic veins are intimately
connected together throughout the whole organ. Nevertheless, it Avould
be very erroneous to suppose that the secreting parenchyma of the
liver is everywhere homogeneous. Ultimate segments may be observed
in it, which have a certain independence, although they are in nowise
isolated. These hepatic lobules, as they may be called, if the term be
used in its most general signification, or hepatic islets, are thus pro-
duced : 1. The smallest branches of the afferent and efferent blood-
vessels, the vence inter- and intra-lobulares (Kiernan) are distributed at
pretty equal intervals through the whole liver, so that a portion of he-
patic substance of |^-|-1 line in diameter, is always found to give origin
in its interior, to a small twig of the hepatic vein receiving externally a
certain number of the minutest branches of the portal vein and of the
hepatic artery ; and, 2, The hepatic ducts do not commence irregularly
in the parenchyma, but are so disposed that they invariably arise at a
distance of ^-^ a line from the origins of the hepatic veins and take
the same course as the finest ramifications of the portal vein. In this
manner little masses, containing .only secreting parenchyma, capillaries
and the origins of hepatic veins, are marked out in the liver ; whilst in
their interspaces, together with parenchyma and capillaries, lie the ulti-
mate branches of the portal vein and hepatic artery and the origins of
the hepatic ducts, which, as they do not approach the masses from one,
but always from many sides, and are also supported and partially united
by connective tissue, form, if not complete, at all events partial zones
around them.

The livers of those animals which present lobes (Polar Bear, J. 31iillerj
Pig), are of the greatest value in comprehending the structure of the
organ, and I therefore here subjoin an account of the structure of the
Pig's liver. If we examine this organ in sections or otherwise, it is al-
ways seen to be divided into numerous small, rounded, polygonal, not
very regular arece of tolerably uniform size (1^-1 j lines), which consist of
the proper parenchyma of the liver and are bordered by whitish parti-

84

630

SPECIAL HISTOLOGY.

tions, readily visible to the naked eye. If a cut surface bo scraped
with the handle of a scalpel, angular masses of liver, equal in size to
these area?, are detached, the capsules which surrounded them remain-
ing behind as empty compartments, like a honeycomb. These become
still more distinct if a thin section of the liver is gently kneaded with
the fingers in water, and then washed and examined on a black ground,
in which case many compartments remain almost completely closed, and
still more resemble closed capsules. It must not be supposed, however,
that there are any complete special investments around each hepatic
lobule. On the other hand, the membranes by which they are formed,
always appertain to many lobules in common, so that the whole con-
stitutes a cellulated substance continuous throughout, whose partitions

Fi?. 218.

Fia-. 219.

(^■^

are all simple and cannot be divided into a number of lamellge. If we
trace out the capsules, or as they might better be termed, the partitions
of the lobes, we find that they are, for the most part, expansions of the
connective tissue, which accompanies the vena porta', cf'C, or of the so-
called capsule of Glisson, but are also connected with the serous in-
vestment of the liver and accompany the larger hepatic veins. Kiernan
was the first to take a just view of the relation of the lobules to the
hepatic vessels, when he said, that they are seated upon the branches
of the hepatic vein, like leaves upon their stalk. In fact we find, if a
small branch of the hepatic vein be slit up (Fig. 218, 6 h h) that it is

Fig. 21S. — Segment of a Pig's liver, with an hepatic vein laid open, somewhat magni-
fied : o, large vein, into which as yet no intralobular veins open; 6, its branches, with in-
tralobular veins, and the bases of the lobes shining through. After Kiernan.

Fig. 219.— Portal vessel of the Pig, cut open, with its accompanying branches of the he-
patic artery and duct. After Kiernan.

THE LIVER. 531

surrounded on all sides by the hepatic lobules and receives a single vein
from each, so that they actually appear to be attached to it by short
pedicles. Now since this takes place in exactly the same manner from
the veins of moderate size up to the intralobular veins, the hepatic
veins and lobules ma}'', not without reason, be compared to a tree whose
branches are so numerous and so closely beset with polygonal leaves
that the foliation, so to speak, constitutes one mass. Imagine now,
that another ramified system, composed of vessels, is introduced into
the expanded head of this tree, in such a manner that the larger vessels
lie in the clefts between its principal masses, the smaller and smallest
in those between the subordinate masses, ultimately penetrating into
the lobules themselves, so that every lobule is connected with many of
the finest twigs, receiving a coat from the connective tissue which ac-
companies them, and we shall have as distinct an idea as possible of the
relations of the vena jjortce. The hepatic duct and artery merely
accompany the vena portie, and, therefore, require no special notice.

In form, the lobes of the Pig's liver are angular, usually presenting
irregular four, five and six-sided figures in longitudinal and transverse
sections.

In the human liver, but very little connective tissue accompanies the
vena portce between the hepatic islets, and the latter can neither be said
to possess coats nor to be in any complete manner enclosed by the vessels.
In cirrhosis of the liver, on the other hand, an enormous increase takes
place in the amount of connective tissue contained in the parenchyma of
the liver, and the individual secreting segments may become prominent
or even form isolated lobules. The reddish-brown hepatic substance is
softer, because more macerated, and sinks in more than the rest, upon
the surface and in sections ; it may also be more easily scraped away and
sometimes readily falls out in fine segments. The cortical layer, which
forms a reticulation around the reddish-brown spots, presents narrower
places, fissurce interlobular es, Kiernan, and wider, spatia interlobular ia,
in which not uncommonly a bloody point may be seen, arising from a
portal vessel, but not so regularly as in the brown spots, where it arises
from the vena intralobular is and often appears stellate.

By the more complete filling up of the capillary network, it may hap-
pen, and, according to Theile, this is in fact the usual case in the majority
of human livers, that the fissurce interlobulares disappear, the brown
substance representing a network, and the yellow, occurring in isolated
spots. I find, as I have stated above, that perfectly fresh livers are, for
the most part, uniformly colored throughout. Kiernan describes, in
children, even a reversal of the coloring, which he considers to be
dependent upon congestion, more particularly of the vena portce, the
external portions of the hepatic lobes being thus more injected. Neither
Theile nor I have hitherto noticed this form.

532

SPECIAL HISTOLOGY.

Fisr. 220.

§ 160. Hepatic cells and cell-net works. — Every Jiepatic islet contains
two elements ; 1, a netivorh of capillaries, which, on the one hand, is
continuous with the finest portal branches, and on the other, unites into
the intralobular vein, one of the roots of the hepatic vein ; and 2, an
interlaced tissue of delicate columns, composed of nothing but cells, the
so-called hepatic cells, in close and immediate apposition. These two
networks are so interwoven that the interstices of the one are completely
filled by the solid portions of the other and leave no interspaces, at least
when the vessels contain blood or are injected. Not a trace of biliary
ducts is to be observed in this network : they are first met with at the
periphery of the hepatic islets, where also the finest portal branches
occur, without its having been possible, hitherto, to make out, directly,
their connection with the hepatic-cell-network, which is indubitably the
secreting portion of the liver.

The hepatic cells, which may be isolated with the greatest ease,* have
a diameter of 0-008-0-012 of a line on the average, 0-006-0-016 of a
line in extreme cases, and resemble tessellated epithelium-cells in form,
except that they are more irregular. Their membrane is delicate, and

perfectly closed, and their con-
tents, in perfectly normal livers,
such as are rarely met with in
man, but readily enough in ani-
mals, are a granular, yellowish,
semifluid substance, which, as
microscopic investigation shows,
probably contains the essential
element of the bile. In this lies a
round vesicular nucleolated nu-
cleus, of 0-003-0-004 of a line ;
and in many cells there are two.
Besides these, fat-drops and pigment granules are frequently to be met
with. The former (Fig. 220 e) occur in all the cells, when the liver has
undergone fatty degeneration, in such quantities that they become very
similar to certain forms of fat-cells ; and generally, as a few large or
many small drops, entirely fill the cell, so that the nucleus becomes invi-

FiG. 220. — Hepatic cells of Man, magnified 400 diameters: a, more normal cells ; b, with
pigment ; c, with fat.

* [This is true of the hepatic " cells'' of Man and many Mammalia, but not of all. In the
Rat, we could find no demarcation of the hepatic tissue into cells, the tissue resembling very
nearly that of tlie spleen. In Fishes, Dr. Handfield Jones has pointed out the existence of
all varietes in this respect, from free " nuclei," with oily and granular matter scattered through
a matrix, up to perfectly formed " cells." In the Pigeon, the same author finds no fully
formed cells, nor in the Duck; and he therefore draws the general conclusion, "that the
secreting process by no means requires the formation of perfect cells in order to eflect its
peculiar changes; these may certainly occur in blastematous matter, if the nucleus only be
present." " Philosoph. Transactions," 1849, p. 132.— Trs.]

THE LIVER.

533

sible. Every transition may be traced from these well-marked forms to
ordinary cells with a few minute drops or a single somewluit larger one;
and, in fact, these less fatty cells occur to a certain extent in almost
every body ordinarily subjected to examination, so that if their absence
in animals were not kept in mind, their occurrence, at least to a small
amount, might be regarded as normal. Tiie same may be said with
respect to the pigment molecules (Fig. 220 b). When these are very
abundant they are certainly pathological ; but when few, they can only
be regarded as a slight deviation from the normal state. They are small,
hardly exceeding 0-001 of a line, of a yellow, or brownish yellow color;
their chemical reactions are identical with those of the coloring matter of
the bile as it occurs in the intestinal canal, inasmuch as they are not
altered in color by nitric acid, nor dissolved by caustic alkalies.

The hepatic cells are so arranged in the islets as to form a network
by the simple apposition of their flat surfaces, without the assistance of
any foreign connecting intermediate substance or investing coat. The
simple or branched columns of hepatic cells, which are almost always
to be found among scraped off particles of the liver, and to which Henle
drew attention (AUg. Anat., p. 903), are nothing but fragments of the
hepatic cell-network, whose elements do not cohere very firmly. Taken
altogether, the network of every hepatic islet presents more rounded
meshes at the periphery, while in the centre they are constantly dis-
posed radially, whence, in a transverse section through the interlobular
vein, long ramified columns of hepatic cells are seen stretching from the
latter on all sides and
uniting by short lateral
anastomoses, so that the
intermediate meshes ap-
pear like narrow elonga-
ted clefts. The hepatic
cohcmns consist of 1-3,
more rarely of 4-5 rows
of cells, have a diameter
of 0-01-0-015 of a line
on the average, 0*006-
002 of a line in extreme
cases, and are generally
cylindrical or prismatic,
but not at all regularly
so; their surfaces are arched, plane, or, in some localities, depressed,
and have rounded or sharp angles. The meshes of the hepatic cell-
network correspond with the diameters of the capillaries and of the larger

Fio. 221. — Hepatic cell-network, 6, and finest ductus interlobulares, a, of Man, after nature,
the union of the two, diagrammatic ; magnified 350 diameters : c, vascular spaces.

Fi?. 221.

534 SPECIAL HISTOLOGY.

vessels which horder upon the hepatic islet, by which the j are perfectly
filled during life, and will be more thoroughly considered below.

If, as results from the above analysis, the secreting parenchyma of
the liver consists of a solid netivork of hepatic cells, one cannot but be
struck with its great difference from all the other glands of the body ;
and the important question arises, how, with this arrangement, the secre-
tion is conveyed from the interior of the cells, in which we suppose it to
be formed, and finally carried away. Anatomy here gives no sufiicient
reply ; for although the ramifications of the hepatic ducts have been
traced accompanying the vena portce as far as the hepatic islets, yet, as
respects the connection of their finest twigs with the hepatic network of
cells, no definite answer has been afforded ; and indeed, up to the pre-
sent time, no satisfactory account even of the structure of the former
has been given. Without entering further, in this place, into the dis-
tribution of the hepatic ducts, I will only observe, that in carefully
made microscopic preparations, we not unusually find fragments of the
finer and finest ducts, the ductus interlobular es of Kiernan, between the
hepatic islets, and readily obtain evidence that they are constructed
according to the ordinary type of excretory ducts. The minutest of
these canals, which I have met with, measured j^t, of a line in diameter,
possessed a cavity of 0-0033 of a line, and were composed of a simple
layer of common tessellated epithelium-cells, which were distinguished
from the hepatic cells by their small size (0-004-0-005 of a line), their
pale contents and the minuteness of their nuclei. I have frequently met
with such ducts as these ; they had no fibrous coat, perhaps because it
had been stripped off in preparing them ; but occasionally they seem to
possess a memhrana projjria, at least their external contours were
sharply defined. Larger canals, of O'O-i-0'05 of a line, always pos-
sessed a coat, and the epithelium was more cylindrical, though not com-
pletely so, inasmuch as the cells, with a breadth of 0-0048-0-0056 of a
line, measured only 0-006-0"0068 of a line in length. Often as I have
sought for a direct communication of the finest canals with the hepatic
networks, I have not yet directly observed it ; which is, indeed, by no
means surprising, if we consider the softness of the parts with which we
have to do ; but unfortunately the result is a hiatus in the minute
anatomy of the parts, which can hardly be made good by hypotheses.
As such, however, I would offer the supposition, that the finest ducts
impinge directly upon the columns of the network of hepatic cells, as
the diagram in Fig. 221 shows, so that their cavity is terminated by
hepatic cells : and, judging from the scantiness of the finest branches of
the hepatic duct, I believe that such communications exist, in no very
great numbers, at the circumference of the hepatic islets.

Whatever view we may take of the connection of the hepatic cell-net-
works with the efferent biliary canals, it is undeniable that any such

THE LIVER. 535

connection only takes place npo7i the surface of the hepatic islets and not
in tlicir interior, and that, therefore, the bile Avhich is formed here, must
he transmitted outwards from cell to cell. Such a process of transmis-
sion through closed cells, involves, as vegetable physiology teaches us,
no impossibilities; but it can hardly take place so rapidly as in those
localities uhere actual canals subserve this purpose. Since the bile, as
late investigations tend to show with increasing clearness, is not only
excreted from the blood, but absolutely formed in the liver, and is at the
same time by far the most complicated of all the secretions, it raay be
presumed that the peculiar arrangement of the secreting parenchyma
in the liver stands in relation with these peculiarities. In fact, the
plasma of the blood, in passing through many cells and being subjected
to the metabolic influence of each before it reaches the efferent duct,
must undergo very different changes from those which it suffers when
it is separated from the glandular canals only by a single layer of cells
and one or two structureless membranes. The resulting necessary
slowness of the secretion is compensated by the size of the organ and
the elaboration of the product.

If nitric acid be added to the hepatic cells, they assume a greenish-
yellow color, as was originally stated by Backer. Sugar and sulphuric
acid turn them red ; water produces an abundant precipitate of dark
granules in the cells, which are usually, readily and completely soluble
in acetic acid, so that they become more or less pale, often to a consi-
derable extent ; the same thing occurs if the acid be added directly.
If the liver be boiled, its parenchyma becomes hard and the cells ac-
quire a concentrated and wrinkled appearance. Dilute caustic alkalies
rapidly attack the hepatic cells in animals, and dissolve them ; in man
they resist somewhat longer, but from the very first swell up to about
twice their size, become very pale, and eventually also disappear.
Ether and alcohol render the cells smaller and granular, as do sulphuric
and nitric acids. The result of these and the above-mentioned facts is,
that the hepatic cells contain a considerable quantity of nitrogenous
substances, fat, coloring matter of the bile, and perhaps also its acids.
The nitrogenous compounds are of several kinds : albumen, which is met
"with in the watery extract of the liver, and a substance which is preci-
pitated by water, is readily soluble in acetic acid and resembles the
casein-like matter found in the serum of the blood (Pannum in Virchovv
and Reinhard's Archiv, b. IV. 1). The existence of the coloring matter
of the bile in the hepatic cells is not so much manifested by their re-
action Avith nitric acid, which is also exhibited by many other cells, as
by their general tint, and the frequent occurrence in them of prccipated
coloring matter of the bile. The existence of the fatty acids of the bile
in the hepatic cells is not directly demonstrable, since both albumen and
fat become red by the action of sulphuric acid and sugar (Schultze), but

636 SPECIAL HISTOLOGY.

is probable. Fat, however, certainly exists in them, even when it is not
microscopically demonstrable, as the collective analyses of the liver show.
Probably, also, the sugar which recent researches have demonstrated in
the liver will be found to exist in the parenchyma ; in the cells, there-
fore, and not in the blood only.

As the principal mass of the liver is formed by the hepatic cells, I
here add the results of one of the many analyses of the liver by Von
Bibra (" Chem. Fragmente liber die Leber und Galle," Braunschweig,
1849). He found, in 100 parts of the substance of the liver of a young
man who died suddenly —

Protein substance, insoluble in water, ..... 9'44

Albumen, 240

Collagenous substance, 3-37

Extractive matter, 607

Fat, 2-50

Water, 7617

100-00

One hundred parts of the water yielded 3*99 of ash,, containing espe-
cially phosphate of potassa, then phosphate of lime, some silica and iron,
and chloride of sodium. The protein substance, insoluble in water, pro-
ceeds from the nuclei and membranes of the hepatic cells and from the
contents to which we have referred. The albumen partly proceeds from
the blood, but certainly from the cells also. Von Bibra found neither
kreatin nor kreatinin in the extractive matters ; the coloring matter
which they contained did not present the same reaction as that of the
bile, whence A'^on Bibra draws the conclusion that this ingredient does
not exist as such in the cells. Finally, I may advert to the acid reac-
tion of the parenchyma of fresh liver, which I discovered (Art. "Spleen,"
in Todd's Cycloposdia), and which, in this case, is even more remarkable
than in the spleen. Von Bibra also found the watery extract of the
Ox's liver to have an acid reaction [l. c, p. 33), and has demonstrated
the existence of lactic acid in it.

There is no subject of minute anatomy upon which opinions are so
various, at the present time, as upon the structure of the secreting
parenchyma of the liver ; and yet, with the views which have been ex-
pressed in the preceding section, the only question that can arise is,
whether the finest biliary ducts are intercellular spaces, canalicular
spaces between the hepatic cells, as Henle and Gerlach consider, or
whether they consist of the columns of hepatic cells surrounded by
membrance p7'oprice. I have endeavored to show, in my " Mikr. Anat."
II. p. 221, that these notions are untenable, and that nothing remains
but to accept the view which has been offered, however paradoxical, as
the only one which at all corresponds with nature.*

»

[In animals the structure of the secreting parenchyma of the liver differs in many respects

THE LIVER. 537

§ 161. Excretory ducts of the liver. — The biliary duct and its branches
accompany the vena portce and hepatic arteiy, so that on one side of a
portal branch there is alwa^^s a much smaller biliary duct and artery,
which are included Avith it in a sheath of connective tissue, the so-called
capsule of Glisson. The hepatic ducts ramify, in Man, with the vena
porta; and may be dissected out for a long distance ; and with the mi-
croscope they may, in fresh and injected livers, be traced as far as the
lobules. Before reaching the latter, they either do not anastomose at
all or very sparingly ; the ductus interlobular es, however, as they have
been termed,. appear to be continuous with each other and thus to invest
the hepatic islets. From these ducts of 1-90-1-120 of a line branches
of 1-100-1-120 of a line proceed, in no very great numbers, to the
hepatic islets and become continuous with the hepatic network in the
mode above described. Perhaps the very fine biliary ducts, which I
have, as stated above, observed microscopically, with a diameter of 0*01
and a cavity of 00033 of a line, are identical with a part, at all events,

from tliat of Man. In the lowest forms of animal life, where no distinct digestive apparatus
exists no trace, accord-ing to Prof Leidy, of biliary structure is observable. When we rise
a little in the scale, as in the Polypi, certain cells forming part of the digestive cavity, pos-
sess the power of secreting a fluid analogous to bile. In many of the Annelida, we find
appended to the sides of the alimentary canals cjEca lined by small cells, which probably
secrete a biliary fluid. A similar substance is formed in the Myriapoda by the cells of the
long and delicate tubes, which empty into the intestine.

In insects the liver is formed of distinct, filiform, tortuous tubes, opening near the pyloric
extremity of the stoitiach by separate orifices into the sides of the alimentary canal. These
tubes consist of a transparent, amorphous, basement membrane, the inner surface of which
is covered by secreting cells. Thete cells arc generally round or oval, and contain molecular
matter, numerous fine oil-globules, a central granular nucleus and a transparent nucleolus.
The tubes are filled with fine granules and a great amount of oil; extremely minute respi-
ratory trachete are distributed to them.

In the Crustacea, as in the Cray-fish, the liver is formed of two large lobes, one on each
side of the intestine, united by an isthmus. Each lobe consists of conical caeca, composed
of a sac of basement membrane lined with numerous secreting cells, of a more or less
polygonal form. These cells have an average diameter of 02 of a line ; they increase in
size from the bottom of the caecum upwards, and obtain a gradual addition of oil-globules.
The central cavity of the caEx;a is filled with fat-globules and a finely granular mass.

In the Molluscs, as in the Snail and Slug, the liver is formed of several lobes, subdivided
into lobules, which are composed of numerous bulbiform circa of a polygonal shape. These
caca do xiot differ in structure from the caeca in the liver of the Crustacea. They are lined
with cells of an average diameter of 0'2 to 04 of a line, filled with oil-globules, and contain-
ing a granular nucleus with a hard transparent nucleolus. Around the caeca there is a net-
work of bloodvessels, to the parietes of which, Prof Leidy states, minute oil-globules and
nucleated fat-cells are frequently attached.

In the Verlebrata, the facts observed by Prof Leidy confirm the researches of Kiernan and
other recent observers. He considers, however, the biliary tubes to commence within the
lobules, and not merely, as stated by Koiliker, as a layer of cells, but as a network of distinct
tubules lined with a basement merrdjrane and an epithelium. Their diameter in different
animals is generally two and a half times the size of the secreting cells. (J^id. Leidy,
"Researches into the Comparative Structure of the Liver," in American Journal of Medical
Sciences, January 1&48.) — DaC]

538 SPECIAL HISTOLOGY.

of those "which have been injected as the origins of the hypothetical
lobular biliary ducts.

All the biliary ducts, down to those Trhich have a diameter of 0-1 of
a line, possess a thick fibrous membrane, composed of dense connective
tissue with many nuclei and elastic fibres, and a cylinder epithelium
0-01 of a line thick, which, in ducts under 0-04-0-05 of a line, becomes
gradually changed into a tessellated epithelium. The ductus communis
choledochus and the cystic duct are similarly constituted, only their walls
are thinner, and they may be readily separated into a fibrous and a mu-
cous layer, the latter of which contains also a few muscular Jibre-cells,
but on the whole so sparingly, that these ducts cannot be said to possess
any special muscular coat.

The gall-bladder has, between its ^Mritoneal covering and the abundant
subserous connective tissue, a delicate layer of muscles, whose fibre-cells,
0'03-0-04 of a line long, take more particularly a longitudinal and a
transverse direction and present only indistinct nuclei. The mucous
membrane is distinguished by many reticulated, more or less prominent
folds, which contain a capillary network, exactly like that of the folia-
ceous intestinal villi, and it is also provided with a cylinder epithelium,
whose cells are often, like the membranes of the gall-bladder, thoroughly
stained with bile ; their nuclei are not always distinct.

The walls of the biliary ducts contain a multitude of small, racemose,
yellowish mucous glands, the glands of the biliary ducts, whose vesicles
of 0"016-0-024 of a line, diifer in no essential respect from those of
other racemose glands. In the ductus hepaticus, choledochus, and in the
lower portion of the systicus, the glands in the fibrous tunic and parts
external to it, are very numerous, ^-1 line in diameter, opening singly
or many together by foramina of 0 •1-0-14 of a line, visible to the
naked eye, which give the mucous membrane of those canals a reticulated
appearance. At the commencement of the cystic duct the glands
are few, and in the gall-bladder itself, in which they are said to have
been met with, their occurrence is certainly not constant. On the other
hand, in the branches of the hepatic duct, down to id of aline in diame-
ter, such glands are again met with, many of them opening by a double
series of fine apertures which exist in these canals.

"We may refer here to certain peculiar ramifications of the biliary
duct, vasa aberrantia (E. H. Weber). They exist : 1, in the ligamentum
triangulare sinistrum, as 6-10 and more canals, 0"006-0-0027 of a line
in diameter, consisting of a fibrous membrane and small cells. Ferrein
and Kiernan traced them as far as the diaphragm, though for the most
part they only extend to the middle of the ligament, or not so far,
branching out, forming networks, or anastomosing in loops. According
to Theile, tolerably large biliary ducts frequently proceed as far as the

THE LIVER. 539

edge of the left lobe of the liver -without entering the triangular liga-
ment. 2. Anastomosinfi hiUarij ducts are also to be met with in the
membranous bridge ■which unites the Spigelian and right lobes behind the
inferior vena cava, also in the membranous band which frequently covers
the umbilical vein and at the edge of the cystic /ossa. 3, In the trans-
verse fissure of the liver, according to E. H. Weber, the right and left
branches of the ductus hepaticus and their smaller twigs give off nume-
rous fine ramuscules, which are distributed through the connective tissue
of the capsule of Glisson covering the fossa and form a network, which
unites the right and left hepatic ducts. Many small branches of
these ducts terminate by enlarged ends of 1-25-1-18 of a line, and
upon their walls a multitude of rounded elevations are met with, which,
like the walls of the smallest bro7ichice, appear to be formed by flattened
cells, which have coalesced with the canals and retain wide communi-
cations with their cavities. What AVeber thus describes as vasa aber-
rantia, were subsequently described by Theile as glands of the hiliary
ducts. He says, that the elongated glands are not merely curved in
various directions, but divide, the resulting branches reuniting with one
another, and with the surrounding glands, as may be observed in the
glands of the coarser and middle-sized biliary ducts — especially, also,
in the connective tissue of the transverse fissure, where the glandular
networks are connected with both branches of the biliary ducts. In
opposition to these views, Weber, in his latest work, adheres to his
former interpretation, and shows, against Theile, that mucous glands
and their ducts form networks and connect the ducts of other glands
nowhere else ; furthermore, that in the new-born infant, although
the network of the biliary ducts exist in the transverse fissure, those
branches which terminate in enlarged extremities are almost entirely
absent.

The relations of the finest ramifications of hepatic ducts, or of the
ductus interlohulares of Kiernan, have not yet been perfectly made out,
a subject which gave rise to many remarks in the previous section. I
will only add here, that some, as more especially Guillot, suppose, not
only that the ductus interlohulares anastomose, but also that their
branches are inter-connected in many 'ways, whilst others, as Theile,
describe their communications as scanty. For myself, though I have
observed anastomoses of the interlobular ducts, I have as yet met with
no communications between their branches, which, though they do not
enter the hepatic islets, may be called lobular branches. If they occur,
they are certainly few in number, for such branches may be isolated
for a considerable distance without any other trunks being seen either
to be given off from or to join them. Upon the whole, the interlobular
branches are anything but abundantly distributed, and, therefore, the
slowness of the biliary secretion is determined, not only by the pecu-

540 SPECIAL HISTOLOGY.

liar structure of the hepatic parenchyma, but also hj the small number
of the excreting canals.

The bile is normally quite fluid, being only accidentally mixed with
cylindrical epithelium-cells, derived from the coarser biliary ducts. I
have never met with hepatic cells in them, and the statements of those
who have afiirmed their existence have arisen, either from a mistake, or
from confounding with them the polygonal cells of the epithelium of
the ductus interlobular es. Constitutents which, though abnormal, are
very frequent, are — fat-drops, coloring matter of the bile in granules
or granular masses, which, as in the hepatic cells, so also in the bile
itself, are occasionally abundantly excreted ; more rarely there are
crystals of cholesterine, and especially the reddish needles of bilifiilvin,
lately observed by Virchow ("Mittheil d. Wiirzburg, Phys. Med. Ges."
I. p. 311).*

• [The view which Professor Kolliker takes of the mode of termination of the hepatic
ducts, can hardly be said to present any essential difference from tliat which Dr. Handheld
Jones has ably advocated in several successive papers in the " Philosophical Transactions"
(for 1846, 1849, and 1853), and which we here subjoin in his own words : —

" The liver, in all vertebrate animals, may be regarded as consisting of a secretory
parenchyma and of excretory ducts.

" The size of the excretory apparatus bears only a small proportion to that of the
secretory.

" These two portions of the liver are not continuous with one another, bnt are disposed
simply in a relation of juxtaposition.

" The action of the liver seems to consist in the transmission of bile, as it is formed, from
cell to cell, till it arrives in the neighborhood of the excretory ducts, by which it is absorbed.
This action is probably slow and very liable to be interfered with, contrasting remarkably
with that of the kidney, where a particular apparatus is added to insure completeness and
rapidity of action.

" The secretion of the hepatic cells is very liable to be retained within the gland, either in
the cells or in a free state.

"This circumstance, as well as its structural relations, seem to point out the liver as ap-
proximating to the class of ductless glands.

" For the same reason it is highly probable that a part of the secretion of the cells is
directly absorbed into the blood which traverses the lobules" (" Phil. Trans.," 1849, p. 132).

From an extensive series of researches in all classes of the Vertebrata, Dr. H. Jones comes
to the conclusion that the excretory system of the liver always terminates in closed tubes.
The ducts of the Sheep's liver, which in all essential particulars agrees with that of Man
and of the Pig, are thus described : —

" In the minutest branches (of the biliary ducts) which seem to be approaching their
termination, and which can sometimes be examined and isolated in the most satisfactory
manner, the epithelial particles are remarkably modified ; they can scarcely be said to exist
as separate individuals, but rather their nuclei, which are often large and distinct, are set
close together in a subgranular or homogeneous basis substance. In ducts where this con-
dition of epithelium exists, there is seldom any distinct trace of basement membrane ; the
margin, though sufficiently even, yet exhibiting the bulging outlines of the component nuclei;
still less is there any proper fibrous coat, though the ducts may be more or less involved in
the filamentary expansions of the capsule of Glisson. Ducts of this character have usually
a diameter of about jg'jgth of an inch; they can sometimes be followed for a considerable
distance without being seen to give off any branches, or to diminish much in calibre. Their
mode of termination is various — several have been distinctly seen to terminate by rounded

THE LIVER. 541

§ 102. Vessels and nerves of the liver. — The arrangement of the blood-
vessels in the liver distinguishes it from all other organs, inasmuch as,
besides an artery and an efferent vein, it possesses an additional,
afferent vein, the vena i^ortcc. While the latter is appropriated to the
supply of the secreting parenchyma, being directly continuous through
the capillary network with the hepatic vein, the artery is more espe-
cially distributed to the walls of the biliary ducts and of the portal vein,
to Glisson's capsule, and to the serous investment of the liver, taking
only a subordinate share in supplying the capillary network of the
hepatic islets. The ramifications of the portal vein, and of a few small
veins of the stomach and gall bladder (see Weber, Ann. Acad. 1845),
which enter the liver independently, take place for the most part dichoto-
mously ; but both larger and smaller branches, besides the main trunk,
into which they divide, give off a number of small vessels at right angles.
The latter, often after a very short course, at once enter the hepatic
islets contiguous to the largest vascular canals, while the larger portal
branches, ramifying continually, and becoming finer and finer, have,
according to their diameter, to take a longer or a shorter course through
the hepatic parenchyma in the canals lined by the capsule of Glisson,
before they enter the hepatic islets or lobules. Each of these receives,

and closed extremities, which have nearly the same diameter as the duct itself; others seem
to lose their tubular character, their nuclei becomes less closely set together, and the uniting
substance more faintly granular and indefinite; the duct, in short, gradually ceases, losing
all determinate structure. In some, of rather minute size, ^jj jj-jjj'ojj'h of an inch in dia-
meter, the exterior form remains distinct, but the canal is almost obliterated by the close ap-
proximation of the nuclei of the opposite walls. These structures now described, I believe
to be truly the terminal branches of the hepatic duct, from which they certainly originate.
They seem gradually to lay aside the several component tissues of the larger ducts, the
fibrous coat blending with the ramifications of Glisson's capsule, the basement membrane
imperceptibly ceasing, and the epithelium becoming resolved at last into its simple funda-
mental nuclei"' (1. c, p. 125).

It is important to remark, that in a Dog, Dr. H. Jones found biliary matter in the interlo-
bular fissures.

From the fact that in the contents of the hepatic ducts of Man and the Sheep, extracted by
means of a forceps and without injuring the organ, hepatic cells may be detected, Mr. Whar-
ton Jones ("Phil. Trans.," 1848) draws the conclusion that the hepatic cells are endogenous
cells, answering to the epithelium of odier glands — which was Henle's view. It is impossi-
ble to doubt a fact stated by so careful an observer; but, however these cells may have got
into the large biliary ducts, it is quite clear, from a comparison of diameters, that they can-
not enter the minutest ones — the total diameter of the latter being the same as that of the
cells, viz. yj'ggth of an inch.

We are strongly inclined to believe that the view taken by Dr. H. Jones is in the main
correct — that the liver is essentially of the same order as the " ductless" glands, and should
be placed in the same category as the Peyerian follicles, spleen, &c. In fact, startling as this
view may at first a[)pear, a very clear transition between the Peyerian follicles, &c., and the
liver, is afforded by the tonsils ; which, on the one hand, are identical with Peyer's follicles,
in so far as they are solid vascular networks, whose meshes are filled by a morphologically
indifferent tissue ; while, on the other hand, without differing from die liver in this respect
they resemble it in having these elements arranged around diverticula of the intestinal
mucous membrane. — Tes.]

542

SPECIAL HISTOLOGY.

from one or other set of vessels, at least 3, usually 4-5, smaller vessels of
1-120-1-60 of a line, which Kiernan calls vencv interlohulares. Such a
vein, however, is never distributed to only one hepatic islet, but always
to two, or even three. Their ultimate branches, the rami lobulares of
Kiernan, 10-20 in number, enter the neighboring hepatic islets, usually
at a right angle, and divide immediately into the capillary network,
without becoming, in man, directly united with one another. In fact,
the branches of the portal vein nowhere anastomose, but are connected
merely by the finest vascular network of the organ.

Fi? 222

Fijr. 223.

s.;*^--.--

^'^'^^y

V

jiiS^/ir^?£'.',

'■.'/

The capillar^/ netivork of the islets (Fig. 222) completely fills the
interspaces of the hepatic cell-network, so that the secreting parenchyma
consists actually of only two elements, the hepatic cells and the capilla-
ries. Exactly as the hepatic cell-network is continuous through the
entire liver, though being interrupted by the biliary ducts which pass off
and the vessels which enter, at regular intervals, it is divided into sepa-
rate, very minute areace — so the capillary network of the bloodvessels
passes from one hepatic islet to another, but is nevertheless discontinuous
in certain spots. The diameter of the capillaries is, in general, some-
what less than that of the hepatic cell-network, though relatively con-
siderable; in man it is, on the average, 0-004-0'0055, 0"002-0-01 pf a
line, in extreme instances ; the wide vessels being more especially found
in the neighborhood of the afferent and efferent veins, the narrowest in

Fia. 222. — Hepatic cell-network and its capillaries, magnified 350 diameters ; from the
Pig. Spaces are purposely left here and there between the cells and capillaries, which do
not exist in nature.

Fig. 223. — Segment of a very snccessfid injection of the hepatic veins of the Rabbit,
magnified 35 diameters. One vena intralobularis is visible in its entire course, but only the
radicles of the other. The capillaries of the lobtdes partly coalesce, and, in one place, two
venous radicles do so.

THE LIVER. 543

the interval between them. The meshes of the network correspond, of
course, in form, with the hepatic cell-network, and are thence more elon-
gated in the interior of the hepatic islets, more rounded externally,
■whilst their breadth corresponds with that of the columns of the hepatic
cells, being about O-OOG-0-02 of aline.

The hepatic veins essentially resemble the portal vein, in so far as
they possess no valves, branch out at acute angles and do not anasto-
mose ; their larger branches also receive numerous minute vessels, but
these lie isolated in special canals in the hepatic substance to which they
are firmly attached, whence they do not collapse when cut across, and,
at least in their finer ramifications, possess no external investment of
connective tissue, which is indeed but very rudimentary, even in the
largest trunks. The relations of the ultimate branches of the hepatic
vein, termed by Kiernan intra-lobular veins, and by Krukenberg, venoe
centrales lobulorum, are, however, totally different from those of the
portal ramuscules. These veins, which in Man are 0"012-0'03 of a line
in diameter, are best studied in some animal whose liver breaks up into
isolated lobules, as the Pig; after which Kiernan has given his some-
what diagrammatic figure. If we here open a small branch of the
hepatic vein, polygonal arere are descried through the walls of the ves-
sel— the outlines of those surfaces of the lobules which are turned towards
the vein (Fig. 218).

A minute vein which, in the centre of each of these surfaces, termed
by Kiernan "bases of the lobules," opens directly into the larger vessel
leads, if we trace it in the opposite direction, into the interior of a lobule,
where it arises from the capillary network ; but under no circumstances
is it continued into a second or third lobule. In this way only a single
vein, which may thence be called vena intralobularis, arises in each
lobule. The vessels into which these veins directly open are called by
Kiernan sublobidares, because they run along the basal surfaces of the
lobules. They are sometimes large, attaining as much as 1-2 lines in
the Pig, and then lie in canals which are surrounded by the basal sur-
faces of a certain number of lobules ; at other times they are smaller,
down to 1-30 of a line, in which case they only pass between the lobules.
The sublobular veins unite into larger veins, which continue to receive,
directly, but few or no other intralobular veins, and thence, are only
partly or not at all bounded by the basal surfaces of the lobules, but
only by their lateral or apical surfaces ("capsular surfaces," Kiernan).
Such veins, when they are smaller, still receive sublobular veins from
the groups of lobules which immediately surround them ; or, lastly, only
larirer veins, which have the same relations as themselves.

The intralobular veins are very simply arranged. Each of them
penetrates directly into the axis of an hepatic islet, or lobule, dividing
in the middle into two or three principal branches, which frequently

544 SPECIAL HISTOLOGY.

again subdivide. The capillaries open, not merely into the terminations
of these veins, but also into their trunks throughout their course ; in-
deed, according to Theile, the origins of the sublobular veins also re-
ceive capillaries. In all those hepatic lobules or islets whose apices are
turned either towards the surface of the liver, or to a laro-e vascular
trunk, the interlobular veins extend nearly to their extremities ; whilst
in others they stop more nearly in the middle, so that they are always
about half the diameter of the lobules distant from the nearest inter-
lobular veins of the vena iportce.

The hepatic artery^ for the most part, accompanies the portal vein and
the biliary canals, is enclosed with the latter in Glisson's capsule, and,
in its principal ramifications, presents precisely the same relations as
the portal vein. It is finally distributed upon the vessels and biliary
ducts, in Glisson's capsule, in the fibrous and serous coats of the liver,
and in the hepatic islets, whence its branches are denominated rami
vasculares, capsulares, and lobulares.

1. Rami vasculares. — As it divides, in company with the vena jjortce^
the hepatic artery gives off numerous small branches, almost at right
angles, which form a plexus in Glisson's capsule, from which some lobu-
lar branches for the parietes of the portal canal arise, on the side oppo-
site to the arterial trunks ; while many twigs proceed to the walls of the
portal vein, the larger branches of the artery itself, the hepatic veins,
Glisson's capsule and the biliary ducts. The distribution of the vessels
is particularly remarkable in the latter canals, so that, in a good injec-
tion, they appear almost as red as the arteries themselves.

A moderately close capillary network exists around all these parts,
even the glands of the biliary ducts, whence the' vence vasculares arise
and open, as Ferrein discovered and as all the moderns since Kiernan
have agreed, not into the hepatic vein, but into small portal twigs, as
these are leaving the larger branches in Glisson's capsule, and are there-
fore to be regarded as internal, or hejjatic radicles of the portal vein.
From this cause the portal vein may be partially injected from the
hepatic artery and conversely. Again, in injecting the hepatic artery
and the portal vein, the vascular network in question may be filled from
both sides ; while it is not possible directly to force injection from the
hepatic vein into them.

2. Rami capsulares. — -Independently of a few branches given off by
the artery, before its entrance into the liver, to the fossa ductus venosi,
to the ligamentum teres and suspensorium, all the arterial twigs of the
coats of the liver are the terminal prolongations of certain arteries which
penetrate the liver and appear in diff'erent parts of its surface between
the hepatic islets. At the points of exit, and even before reaching them,
these vessels, which have a diameter in the adult of 1-30-1-20 of a line,
in children as much as 1-5 of a line, break up into 3-5 radiated subordi-

THE LIVER.

545

natc branches, take for the most part a remarkable, corkscrew-like,
coiled course, repeatedly anastomosing, and thus spread over the whole
surface of the organ, as far as the great venous trunks [ve^ice hepatica',
vena portcc, cai'a inferior)^ i\ve fossce of the liver and its edges, as an
elegant arterial network. In the end, these arteries everywhere form
a capillary plexus Avith wide meshes, from whence, in many parts —
whether universally or not I do not know — veins arise, which run back

Fisr. 224.

parallel with the arteries, enter the liver and open into the portal
branches. Portal radicles, or vence adveJientes capsidares, must be de-
rived, therefore, from this region also. The arteries and veins of the

7 7 o

hepatic coats are in their terminal expansion connected, on the one
hand, with prolongations of the internal mammary, phrenic, cystic and
even the right suprarenal and renal vessels (Theile), and anastomose, on
the other side, in the hepatic /oss«, with those of Glisson's capsule, with
the vena cava and hepatic vein.

3. Hanii lohulares. — With every interlobular vein there runs a branch
of the 'hepatic artery, of at most ih of a line in diameter (Theile),
which, in the Pig, divides between the hepatic islets, in the capsules of
the lobules, into fine anastomosing twigs, and is directly connected with
the peripheral part of the capillary network of the hepatic islets or
lobules, formed, as stated above, by the portal vein. Arterial blood,
therefore, takes a part, although, perhaps, a minor one, in the prepara-
tion of the bile, and the hepatic artery is thus distinguished from the
bronchial arteries, whose blood is carried away by special veins.

The lymphatics of the liver are very numerous, and may be divided
into superficial networks, under the peritonemn ; and deep vessels,

Fig. 22 i. — Arterial network upon tlie convex surface of a childs liver. Natural size.

35

546 SPECIAL HISTOLOGY.

•which accompany the portal vein, and, in animals, at least, the hepatic
veins also. Both kinds of vessels are connected and proceed partly
through the dicqjh-agm into the thorax, partly to small lymphatic
glands in the 'porta hepatis, and to the intestinal plexus. The lympha-
tics of the gall-bladder are also exceedingly numerous.

The nerves of the liver are relatively very abundant. They arise
from the sympathetic, and, in a smaller proportion, from the vagus, and
are chiefly distributed with the hepatic artery, around which they form
closer and wider networks without ganglia. They always contain,
together with many fine tubules, and " Bemak's fibres," a few thick
fibres, and may be traced ; 1, to the gall-bladder and large biliary
ducts ; 2, in Glisso7is capsule as far as the interlobular arteries, where
their finest twigs, of 0-008-0-012 of a line, contain only nucleated
fibres ; 3, to the hepatic veins ; and lastly, 4, into the coats and liga-
ments of the organ.

§ 163. According to the latest observations, particularly of Bischoff
and Bemak, the development of the liver may thus be best understood.
The primary rudiment of the liver, which appears at a very early period
(about the 55-58 hour, in the Chick ; in Mammals, after the Wolffian
bodies and the allantois) consists of tAvo masses of cells, an external,
proceeding from the fibrous membrane of the intestine, and an internal,
epithelial, which at first form a simple, and afterwards a dichotomously
divided sac. S'olid processes, the hepatic cylinders of Reraak, are now
developed from the epithelial lamina, which, as in the intestine, consists
at first of round cells, probably in many layers, by the multiplication of
its cells, and extend into the outer lamina, branching out and anastoynos-
ing, whilst, at the same time, the cells of the outer lamina included in
the meshes of this network, multiply and become successively changed
into vessels, nerves, connective tissue, &c. The difficulty is to say how
this peculiar, reticulated parenchyma of cells and rudimentary vessels
becomes ultimately arranged as we know it to be. In the first place, as
regards the hepatic-cell-network and the islets or lobules of the complete
liver. They evidently proceed from the further growth of the original
hepatic-cell-network, to which by a continual new development of cells,
fresh processes are added, which unite into new networks, so that the
hepatic-cell-network of the adult liver is the direct progeny of the ori-
ginal reticulation. More detailed information concerning the separate
steps of the formation of the hepatic-cell-network, is at present wanting ;
yet from what is known it would appear to take place in somewhat dif-
ferent modes. Sometimes, in the subsequent stages, free cylindrical
processes of the hepatic-cell-network do not exist to any extent, but it
would appear to increase by the continual addition of new meshes at its
edges, perhaps also by the constant elongation of the existing columns
of hepatic cells and the development of fresh anastomoses between them ;

THE LIVER. 547

this is, if I have observed riglitlj, the case in man, ^Yherc even in the
seventh week I did not succeed in clearly distinguishing free hepatic
columns. At other times, free terminations of the hepatic columns arc
apparently developed for a considerable period, perhaps until the whole
organ has nearly arrived at perfection, their formation appearing to
precede by some time that of new anastomoses, as is the case in the
Chick and other Birds, and according to J. ]Miiller, in a few Mammals ;
in the latter of Avhich, according to Mliller's figures, the hepatic columns
are grouped in lobes. These free, superficial hepatic columns may perhaps
throw some light upon the meaning of Weber's and Krause's statements
respecting the biliary ducts with coecal ends upon the surface of the
liver. With regard to the biliary ducts, they are assuredly nothing but
secondary excavations of a part of the primarily solid hepatic columns
and of the larger internal tracts, which border upon the original epithe-
lial diverticulum and which all consist of many series of cells. The ex-
cavation commences in the common biliary duct, proceeds towards its
branches, and must be considered to take place exactly as in other glands,
i. c. either by solution of the inner cells of the rudimentary structures,
or by the excretion of a fluid between them and the consequent produc-
tion of a cavity. In this mode of regarding the matter, there is only
one point for consideration ; viz., that according to Remak, all the
hepatic columns, even the largest, form anastomoses, whilst, as is well
knoAvn, the biliary ducts ramify without anastomosing. The only solu-
tion of this difficulty, consists in assuming that the anastomoses of the
primary, largest hepatic columns do not continue in the course of the
further development, but that they are re-ahsorhed, a process which has
its analogue in many phenomena of foetal growth. In Man alone
might we find an exception, for it seems to me that the anastomoses of
the right and left hepatic duct, in the/ossa hepatis, described by E. H.
Weber, are perfectly well explained by Remak's observations, and are
simply the embryonic anastomoses of the rudiments of these canals^
which have attained to some, though no very great development. The*
mode of origin of the fibrous membranes of the biliary ducts becomes
readily comprehensible, if we reflect how the networks of hepatic columns
and the fibrous layers of the liver interdigitate ; so that layers of con-
nective tissue, &c., might be readily formed around the hepatic cylin-
ders from those elements of the fibrous layer which are nearest to them.
The further development of the vessels, nerves, &c., presents no difficul-
ties, taking place in the same way as in other organs. The gall-bladder
in the Chick, according to Remak, is a process, at first solid, of one
hepatic duct, which subsequently becomes hollow and rapidly increases
in size. I saw the folds of its mucous membrane, as early as in the
fifth month, in a human foetus.*

* [In liis last memoir (Philosopbioal Transactions, 1S53), Pr. Handfield Jones maintains
that, in Fishes, Amphibia, and Birds, the liver is developed independently of the intestine,

548 SPECIAL HISTOLOGY.

The investigation of the liver is best undertaken in the Pig, in which
animal the distinct demarcation of the lobules greatly facilitates the
comprehension of the relations of the secreting parenchyma, to the ves-
sels and hepatic ducts. The hepatic cells may be isolated with the
greatest ease in all animals, either singly, in series, or in reticulated
fragments ; but to comprehend rightly their collective arrangement no
better means exist than the making of fine sections in a fresh liver with
the double knife, for which, sections made off-hand with a razor, even
in a liver previously hardened in alcohol, pyroligneous acid, chromic
acid, &c., are by no means sufficient substitutes. We do not mean to
say that the hepatic-cell-network cannot be seen at all in this manner,
for it is visible even in opaque sections of liver by reflected light, but
merely that no complete view can thus be obtained. The finest hepatic
ducts are not readily found, though a careful search in nearly all sec-
tions which include many lobules, will almost certainly detect scattered
fragments of them, readily recognizable by their small polygonal cells,
at the edges of the lobules, and long examination may perhaps eventu-
ally discover such a fragment in connection with the hepatic-cell-net-
work, which, however, I have not yet succeeded in doing. The coarser
biliary ducts present no difficulties. Their glands are seen readily,
partly with the naked eye, partly by the use of dilute caustic soda.
Weber's anastomoses of the two hepatic ducts in the fossa transversa, are
visible in good injections. The vasa aherrantia, in the left triangular
ligament and in other localities, are readily perceived even without in-
jection, on the addition of acetic acid or of caustic soda. The nerves
and lymphatics of the liver are, except their finest portions, easily seen
in Man. The bloodvessels require good injections, for which purpose,
in the human subject, I especially recommend children's livers, in which
the distribution of the arteria hepatica in the serous coat, on the ves-
sels, &c., is beautifully distinct. The capillary network of the lobes
may readily be filled with fine injection, and a series of excellent pre-
parations of this kind, by various masters of the art, are everywhere
to be met with.

. Liter-atwe of the Liver. — F. Kiernan, " The iinatomy and Physio-
logy of the Liver," in " Phil. Trans.," 1833 ; E. H. Weber, " Annotat.
Anat. and Physiol.," Prol. VI. VII. and VIII. Lips. 1841 and 1842,
and "Programmata collecta Fasc," II. Lips., 1851; " Ueber den

and, that the first rucnment of the excretory apparatus is the gall bladder, whence ducts
extend on the one hand into the intestine, and on the otlier into the liver. He has not
traced the development of the liver in Mammalia.

Vogt, however (Embryogenie des Saiimons, p. 175), states that in Cwcgonus palea, the
liver is at first a rounded, solid mass of cells, in contact with a diverticulum of the intes-
tine— the future ductus choledochus ; and that, in the course of development, the diverticulum
grows into and ramifies in the mass— its ultimate branches terminating in cceca. The gall-
bladder is not formed till very late. — Trs.]

THE PANCREAS. 549

feineren Bander menscliliclien Leber," in " Mliller's Arcliiv," 1843^ p.
318; " Zustitze zu seinen Untersuchungon liber den Ban der Leber," in
"Bericbte d. K. Siichs. Ges. d. Wissensch. zu Leipzig," 1850, p. 151 ;
A. Krukenberg, " Untersucbungen liber den feineren Bau der mcnscb-
licben Leber," in " Mull. Arch.," 1843 ; Job. Miiller, in bis great
Work on tbe Glands, in bis " Pbjsiology," and " Mliller's Arcbiv,"
1843, p. 338; Tbeile, article "Leber," in R. Wagner's " Ilandw. der
Phys." II., p. 308, 1844; C. L. J. Backer, "Do Structure subtiliori
Ilepatis sani et morbosi. Diss. Inaug. Trajecti ad Rbenum," 1845 ;
Natalis Guillot, " Sur la Structure du Foie des Animaux vertebras," Ann.
d. Sc. Nat., 1848, p. 129; R. Retzius, " Ueber den Bau der Leber,"
in "Mull. Arch.," 1849, XL p. 141 ; C. Wedl, " Ueber die traubenfor-
migen Gallengangdrlisen," in " Sitzungsbericbt der Wiener Akad.,"
1850, Dec, p. 480, c. Tab. ; N. Weja, "Beitrage zur feineren Anato-
mic der Leber," in " MUll. Arch." 1851, p. 79; E. Von Bibra, "Che-
miscbe Fragmente liber die Leber und die Galle," Braunschweig, 1849.
The more minute comparative anatomy of the Liver is treated of by H.
Karsten, " Disq. microsc. et chem. hepatis et bilis Crustaceorum et
Molluscorum," in "Nova Acta Acad. Cur.," vol. XXI. 1, p. 295;
T. F. G. Schlemm, "Dehepate et bile crustaceorum et molluscorum
quorundara," Diss. Berol., 1844 ; Williams, in " Guy's Hosp. Rep." 184G ;
H. Meckel, " Mikrographie einigcr Drllsenapparate der niederen
Thiere," in "Mull. Arch.," 1849, p. 1 ; Fr. Will. " Ueber die Abson-
derung d. Galle," Erlangen, 1849 ; H. Jones, "Phil. Trans.," 1846,
1849; [J. Leidy, " Researches into the Comparative Structure of the
Liver," in Amer. Jour, of Med. Sciences, 1848 ; Wharton Jones,
'^Phil. Trans.," 1848; Handfield Jones, "Phil. Trans.," 1853.— DaC]

OF THE PANCREAS.

§ 164. The pancreas is a compound racemose gland, which so closely
resembles the salivary glands, that a short exposition of its peculiarities
will suffice. As in all such glands, larger, smaller, and smallest lobes,
may be very distinctly made out, the last being composed of microscopic
glandular vesicles, which are here characterized by their moderate size
0-02-0'04 of a line, and their usually rounded form. They possess a
memhrana propria and a tessellated epithelium, whose cells are very fre-
quently remarkable from tbe great number of fat-granules, so that the
glandular vesicles appear quite opaque and as if entirely filled with
secretion. The excretory ducts, which, as elsewhere, are connected
with the glandular vesicles, uniting into larger canals and, eventually,
into the duct of Wirsung, or pancreatic duct, are whitish and somewhat
thin walled. They are composed of connective tissue and of elastic
fibrils, and all possess an epithelium with small cylindrical cells, scarcely
exceedinoj 0'006-0-008 of a line in length, and 0-002 of a line in breadth.
In tbe walls of the pancreatic duct, and its larger branches, small

550

SPECIAL HISTOLOGY.

racemose glands of 0*06-0-08 of a line with vesicles of 0-016-0-02 of
a line, and a less fatty epithelium, are situated in considerable numbers ;
"whether they are mucous [/lands analogous to those of the biliary ducts,
or parts of the pancreas itself, I cannot say. The pancreas possesses
the ordinary investing tissue of the glands, with more or less abundant
fat-cells, in which the vessels and nerves of the gland are distributed.

Fis. 225.

The former present exactly the same relations as in the parotid, except
that the lymphatics appear to be more numerous ; the latter would seem
only to accompany the vessels and arise from the sympathetic, possess-
ing fine, and a few moderately thick tubules. The secretion of the pancreas
is normally perfectly fluid, only accidentally containing formed constitu-
ents, as detached epithelium of the glandular vesicles and of the ducts.

The development of the pancreas commences by the formation of a
divertioulu7n of the posterior wall of the duodenum and in its further
progress, exactly resembles the salivary glands, except that the rudiment
of the gland forms, from the first, a more compact mass and thence is
not so readily made out in detail.

The examination of the pancreas presents no difficulties, except that,
in Man, the fat in the epithelial cells of the glandular vesicles oiTers
some impediment and therefore the pancreas of Mammalia (Rabbit,
Mouse), which usually contains less fat, should be made use of. The
glandules in the ducts are best rendered visible by acetic acid.

\_Literature. — J. G. Wirsung, " Figura ductus cujusdam cum multi-
plicibus suis ramulis noviter in pancreate observati," Padov., 1643 ; J.

Fig. 225. Vessels of the pancreas of the Rabbit, magnified 45 diameters.

THE SPI^EEN.

551

Muller, "De glandul. sec. strnctura pcnitiori;" Wharton Jones in Philo-
sophical Transactions, 1848, II. p. 227 ; Verneuil, " Anatomic du Pan-
creas," in Oazette Medicale, 1851. — DaC]

OF THE SPLEEX.

§ 165. The spleeti, is a so-called blood-vascular gland, ^Yhich is in some
way concerned in the renewal of the blood, and probably with the secre-
tion of the bile also. It consists of ajib^'ous and serous coat and of a soft
2'xircnchjma, the latter being principally composed of reticularly inter-
woven solid bands, the splenic trabecula', enclosing a red substance, the
splenic pulp. In the latter we find, in addition, many peculiar white
corpuscles, the splenic or Malpighian corpuscles, while abundant vessels
and a certain number of nerves are distributed through its whole interior.

§ 166. Coats and Trabecular Tissue. — The peritoneal investment
covers the whole surface of the spleen, with the exception of the Jiilus,
where, forming a sheath around the vessels and nerves, it passes on to
the fundus of the stomach as the ligamentum g astro -lienale, and of the
upper extremity, from which it becomes detached, as the lig. phrenico-
lienale ; it adheres so closely to the fibrous coat in Man (though not in
Ruminants), that it can only be dissected from the organ in fragments.

The fibrous coat {tunica albuginea sen p)ropria) completely surrounds
the surface of the spleen, as a moderately thin and semi-transparent
but very strong membrane, and at the /uYus, passes into its interior, like
Glisson's capsule, accompanying the vessels in the form of peculiar
sheaths, the vagince vasorum. In man, it is composed of common connec-
tive tissue, with abundant networks of elastic fibres, whilst in some
animals, the Dog, Pig, Ass, Cat (not in the Rabbit, Horse, Ox, Hedge-
hog, Guicna-pig, and Bat), I find it to contain smooth muscles in consi-
derable numbers.*

The trabcculcc of the spleen are white, shining, flattened or cylindri-
cal fibres, having on an average, a diameter of yo-i" o^ ^ \n'iQ, which
are attached in great num-
bers to the inner surface of
the fibrous coat, and less
frequently to the outer sur-
face of the sheaths of the
vessels, and unite with simi-
lar trabcculcc in the interior,
into a network which extends
through the whole organ.
The interstices included in

Fig. 220. — Transverse section through the middle of an Ox-spleen, washed out, to show
the trabeculcE and their arrangement. Natural size.

* [The existence of these muscles in the ox"s spleen was first pointed out by Dr. Sharpey.
See Quain and Sharpey's Anatomy, p. lOSG (Vol. II., p. 498. Am. Ed.)— Tks.]

Fig. 220.

552

SPECIAL HISTOLOGY.

Fig. 227.

A

it all communicate, contain the red pulp of the spleen and the Malpig-
hian corpuscles, and although no one exactly resembles another, yet all
as regards form and size, present a certain similarity.

The older anatomists considered them to be regular cavities lined by a
membrane, like those of the corpora cavernosa penis, to which, indeed,
they are very similar in the arrangement of the limitary traheculce, but
there is nothing of this kind, as may be best demonstrated in sections
of the spleen, in which pulp has been removed by washing. Such a
preparation is best fitted for the study of the relations and connections
of the traheculcc ; and it is readily seen, that although very various in
size, they do not ramify after the fashion of vessels, but unite quite
irregularly. Where 4, 5, or more of these unequally thick traheculoi
unite, a flattened cylindrical enlargement, like a nervous ganglion,
usually exists ; these are more frequent towards the external surface of
the organ than in its internal portions and at tlie liilus, where the large
vessels already afford a sufficient support to the parenchyma and an
intimate union of the traheculce is less necessary.

The structure of the traheculce of the human spleen perfectly re-
sembles that of the fibrous coat ; they consist
of longitudinally fibrous connective tissue, with
intermingled fine elastic fibres. In animals,
on the other hand, smooth muscles exist, as I
showed in the year 1846, sometimes in all the
trabecular (Pig, Dog, Cat), sometimes (Ox),
only in the smaller ones, with respect to whose
distribution further particulars will be found
in my " Mikroskopische Anatomic," II. 2, p.
256. In the traheculce also, we find peculiar
spindle-shaped fibres, of 0-02-0-03 of a line
in length, and 0-002 of a line in breadth, with
undulated ends and .prominent enlargements,
in which rounded nuclei are situated. They
are to be met with in great numbers in the
splenic pulp of Man (Fig. 227 A), and I for-
merly, though as I now believe wrongly, took them to be 'smooth mus-
cles. What their nature is I cannot say, and I can only add that they
are also found coiled up in cell-like bodies* (Fig. 227 B).

§ 167. Malpigliian corpuscles, the splenic corpuscles, 3Ialpighian corjju-

FiG. 227. — Peculiar fibres from the pulp of the human spleen : ^, the same free; B, one
inclosed in a cell; magnified 350 diameters.

* [According to Mr. Wharton Jones (•' British and Foreign Med. Cliir. Review,"' Jan.,
1853), these cells, containing "peculiar fibres,"' are nothing but the ordinary nucleated fibres
of the pulp " circularly coiled, the coil being maintained by a tenacious inicrcelkilar substance
filling up the middle space." — Tks ]

I

THE SPLEEN.

553

Fig. 223.

scles or vesicles, are white roundish bodies, ^Yhich are imbedded in the red
substance of the spleen and are con-
nected ■with the smallest arteries.
They are constant only in quite
fresh and healthy subjects ; but
not at all, or rarely, in those who
die of disease, or after Ions; fastinu:.
It hence becomes comprehensible
that Von Ilessling found the cor-
puscles only IIG times in 960
examinations. In subjects whose
age was between the first and
second year, they were present in
every second individual ; from the
second to the tenth year, in every
third ; from the tenth to the four-
teenth, in every sixteenth ; and from
the fourteenth onwards, only in
every thirty-second. In the bodies

of those who die suddenly, as in consequence of accidents, suicide, or
judicial sentence (of the latter of whom I have examined three cases),
they are probably never absent ; and it is the same with the majority of
children. In these cases they are as numerous and as distinct as in
Mammalia. The size of the splenic corpuscles is liable to certain varia-
tions in Man and in animals, and has hitherto, for the most part, been
over-estimated, in consequence of their having been incompletely isolated.
Their diameter is from 1-10-1-3, on the average 1-G of a line ; and
very probably depends upon the varying condition of the chylopoietic
organs, so that the corpuscles are larger after food has been taken
than at other times ; though, in confirmation of Ecker's statement, I
can affirm that they are to be met with, beautifully developed, in fasting
animals also. We have no data of any kind with regard to this point
in Man.

The Blalpijiuan corpuscles, though imbedded in the red pulp and
hardly separable from it, are nevertheless always attached to a branch of
an artery, in such a manner that they either rest laterally immediately
upon a vessel, or are situated in its angle of division, or finally appear
stalked ; in which latter case, however, the stalk itself, again, is usually
a small artery. Their number is very considerable, arterial twigs of
0-02-0-04 of a line carrying 5-10 corpuscles, so that extracted with
them from the pulp, they present the figure of an elegent raceme (Fig.
2-J8). It appears to me that it Avould be rather under, than over

Fig. 228. — A portion of a small artery, with a branch covered vviih JSIalpighian corpus-
cles (Dog), magnified 10 diameters.

554

SPECIAL HISTOLOGY.

estimating tlie number of the Malpighian corpuscles to assume that every
1-1^ cubic line of the pulp contains a corpuscle.

With respect to its minute structure, every Malpighian corpuscle
possesses a special coat and contents, and is therefore a vesicle. The

membrane is colorless and transparent,
0-001-0-002 of a line thick, and every-
where exhibits a double contour, with
occasional intermediate concentric lines ;
it is intimately connected with the sheath
of the vessel, with which it also agrees
in structure, so far as it contains homo-
/ "^^^^^'C ., '■ ,^''' geneous connective tissue and elastic fibrils;

whilst, on the other hand, the smooth
muscles which are also present as longi-
tudinal fibres in these sheaths, are entirely
absent. In their interior, the Malpighian corpuscles contain no epithe-
lium, but are entirely filled by a viscid, grayish, continuous substance,
consisting of a small quantity of a clear, neutral fluid, coagulable by
heat, and therefore albuminous ; of many, rounded, larger and smaller
(from 0-003-0'006 of a line), pale cells, which usually possess a single
nucleus and become granulated by the action of water
and of a varying number of free nuclei. Besides these
cells, which frequently contain single fat-granules and

^l oft'er the most distinct evidence that in the Malpighian
^^ corpuscles a constant development of cells is going on, we
occasionally meet with blood corpuscles, either free or in
cells and, as I am inclined to believe from a single observation in the
spleen of a Cat, with fine bloodvessels, as in Peyer's follicles (see § 155).
The Malpighian corpuscles are completely closed, and are not con-
nected with the lymphatics, although this has been assserted by
different authors — among the moderns by Huschke, Gerlach, Polmann
and Schaffner. Anatomically, they are perfectly similar to the follicles
of Peyer's patches, and of the solitary glands, described above, and
very closely agree with those of the tonsils and lymphatics, whence
they may for the present be denominated gland-like follicles/''

Fig. 229. — A Malpighian corpuscle from the spleen of an Ox, magnified 150 diameters:
a, wall of the corpuscle; 6, contents; rf, sheath; and e, wall of the artery to which it is
attached.

Fig. 230. — Contents of a Malpighian corpuscle from the Ox : a, small ; b, large, cells; c,
free nuclei.

* [In a case of suicide, Prof Kolliker (Wiirzb. Verlmnd. IV. 1) has lately detected distinct
capillaries within the Malpighian corpuscles. Capillaries within the corpuscles he had
hitherto only seen in the spleen of a Cat; they have, however, from independent obser-
vations, already been described by Gerlach and Huxley as occurring in Man.

The Malpighian corpuscles undergo, in some diseases, a peculiar degeneration. Thus, in
the disease termed " waxy," or "colloid" spleen, they present the appearance of gelatinous

THE SPLEEN. 555

Malpigliian corpuscles have been discovered in all tlie Mammalia
wliich have hitherto been examined, and also occur in Birds. Anion"-
the scaly Amphibia they ^vere found by Joh. IMiillcr in one of the
Chclonia, and by myself in the Blindworm, -where the corpuscles were
surrounded by an exceedingly elegant network of capillaries. In
Frogs and Toads they are, according to Oesterlen, to be met with now
and then ; but I have not yet succeeded in finding any trace of them
in the naked Amphibia, nor in the fresh-water fishes. Leydig, how-
ever, has observed them in the Plagiostomata (Beitriig'c zur Anat.
der Rochen und Haic). Joh. Mliller's supposition that the Mal-
pighian corpuscles exist in all Vertebrata, is, therefore, not borne out,
a fact which is not without w^eight in considering their physiological
import. In a few Mammals the Malpighian corpuscles contain, though
not constantly, the same forms of retrograding blood corpuscles as
will be described to occur in the pulp, in the following section.*

granules, and are filled with a homogeneous mass, consisting of soft concentrically lami-
nated bodies. These bodies, which were formerly regarded as colloid, have recently been
found by Virchow (Archiv, f Patli. Anat. VI. 2) to be the result of a cellulose mdamorphosis,
for a watery solution of iodine, and the subsequent addition of sulphuric acid caused them to
assume the peculiar violet color which is known to belong to vegetable cellulose. — DaC]

* [The Malfiishian follicles of the spleen present three points of importance to the inves-
tigator. 1. Whether they have a capsule, and what is its nature? 2. The arrangement of
their vessels. 3. The structure of the substance which they contain.

1. The capsule and its nature. — We have been quite unable to convince ourselves of the
existence of any such capsule as that described by Professor Koliiker, in the Malpighian
follicles of Man, the Sheep, the Pig, the Cat (Kitten), or the Rat; in all of which we have
made very careful investigations with regard to this point. In Man, in the Pig, and in the
Cat, we are unable to distinguish any boimdary at all between the follicles and the sur-
rounding red pulp — the substance of the one appearing to pass into the other. At the line
of transition, however, the inditlerent tissue of the follicle underwent a partial metamor-
phosis and broke up, when teased out, into spindle-shaped bodies, containing ■' nuclei,"' or
short delicate fibres with " nuclei," exactly resembling, in Man, the structures described by
Professor Kolliker as peculiar fibres, and represented in Fig. 227.

In the Rat, this border zone of metamorphosed tissue was somewhat broader and firmer,
and when the follicle was compressed, appeared, particularly under a low power, like an
indistinctly fibrous coat, such as Professor Kolliker describes ; but when clo.<ely examined,
it was readily seen to be no distinct closed capsule, but to pass gradually, on the one hand.
into the pulp, and, on the other, into the contents of the follicle. The same is true of the
Malpighian follicles of the Sheep, where the appearance of a capsule, under a low power,
is often very distinct; and where imperfect elastic fibres may be met with in it.

In fact, our own observations are perfectly in agreement with those of Mr. Wharton
Jones (British and Foreign Med. Review, Jan., 1S33), and have led us completely to the
opinion of Remak (Ueber runde Blut-gerinnsel und iiber Pigment Kugelhaltige Zellen,
Mailer's "Archiv," 1S52), that the capsules of the follicles are by no means their essential
element, and that we must consider the spleen to be formed by two principal constituents ;
the first being the parenchyma, and the second a superadded fabric of bloodvessels, nerves,
lymphatics, elastic and contractile elements. The manner in which the latter are arranged
in and about the parenchyma is, in a manner, accidental and very variable. It may be, as
Remak says, either inter capillary, as in the pulp ; or vaginal, as in the sheaths of the arte-
ries ; or encysted, as at the angles of division of the arteries, in the IMalpighian follicles of
the Sheep.

To insist, therefore, upon the foUicnlar arrangement of the spleen, or indeed of any other

556 SPECIAL HISTOLOGY.

§ 1G8. The red substance of the spleeyi, the j^ulp, 07' parejichi/ma of
the spleen, is a soft reddish substance, -which fills up all the interspaces

of the vascular glands, as Sanders (On the Structure of the Spleen, " Annals of Anatomy
and Physiology," 1S50) and Kolliker do, seems to us to mistake accidental for essential
characters.

The results of comparative anatomical examination are strikingly in favor of tliis view
of the matter.

The Malpighian follicles of Birds and Amjiliibia have no capsules (Remak, Leydig). In
Bombinator igncus, according to Leydig, a white substance, the representative of the Mal-
pighian follicles,*lies in the middle of the spleen, surrounded by a red cortical pulp, into
which it directly passes.

On the other hand, Coluber natrii; a Reptile, presents the very opposite characters. Here
the red pulp is absent, and the sjileen has, as nearly as possible, the structure of an ordinary
lymphatic gland, consisting of a fibrous stroma, containing cavities full of indifferent tissue,
through which a capillary network, arising from the vessels'of the stroma, is distributed
(Leydig " Anatomisch-Histologische Untersuchnngen iiber Fische und Reptilien,'' 1S53).

In Fishes the same variation occurs. In Hexanchus there are thiclc-walled Slalpighian
corpuscles (Leydig). In other Plagiostomes and many osseous Fish there are no distinct
follicles, but tlie indifferent follicular tissue follows the sheaths of the arteries.

2. The arrangement of the vessels of the Malpighian follicles. — Johannes Miiller, v/ho gave
the first good account of the Malpighian follicles of vegetable feeders (AIuller"s " Archiv,"
1834), not only states that the follicles are, what all recent researches have shown them to
be — the representatives of portions of the sheaths of the arteries, but also that the arterial
twigs which supply them '-sometimes run beside the Malpighian bodies ■without giving
any branches to them, sometimes pass straight through the corpuscles''' (p. 8S). However, he
appears to be inclined to the opinion that the arterial twigs pass " not so inuch through the
middle of the corpuscles"' as in the thickness of their walls.

All subsequent writers have affirmed that the arterial twigs pass over the surface and
not through the substance of the Malpighian follicles, with the exception of Giinsburg and
of Dr. Sanders — who states, not in the paper Vv'c have cited, but in a subsequent communi-
cation to the Edinburgh Physiological Society (Jan. 31st, 1851), that by a peculiar method of
preparation, he had observed arterial twigs passing diametrically through the substance of
the follicles, " stains of blood also, often in linear arrangement, indicating capillaries, were
seen in the interior of the sacculi." With regard to the latter point, it will be observed that,
in the text, Professor Koiliker also records a single observation of minute bloodvessels in the
Malpighian follicles of the Cat.

In all the Mammalian spleens we have examined (Man, Sheep, Pig, Cat, Rat), we have
observed the passage of arteries through the iMalpighian follicles and the existence of a
capillary network in them, with the utmost ease; we are, indeed, at a loss to comprehend
how it is that I'revious observers have so generally overlooked facts so patent. The method
we have pursued has been merely to make a tolerably fine section, containing a Malpighian
follicle, with a sharp knife — to spread it out with needles, adding nolliing but a little weak
syrvp, and then, placing a thin glass plate over it, we have examined it with both the simple
and the compound microscope. The use of the former is especially to be recommended,
because by manipulating the covering plate, the whole follicle may be readily rolled about
under the eye, and the clearest evidence thus obtained that the arterioles pass through and
not over the surface of, the follicles. Acetic acid should not be used, as it renders the con-
tents of the follicle opaque; but the syrup is of great service, as it keeps the coloring matter
of the blood in the capillaries and renders them extremely obvious. The walls of the
capillaries are exceedingly delicate and often indistingui-shable as distinct structures. Both
the longitudinal inner coat and the transverse muscular coat of the arterioles are very well
developed in Man.

3. Structure of the " contents'^ of the Malpighian follicles. — We have been unable to find
either cavity or lliiid in the contents of the Malpighian follicles. So far as we have seen,
they are solid bodies — their outer portion or " wall"' being constituted as above described ;

THE SPLEEN. 557

between tlie larger trabcculre and the coarser vessels, and is so soft as
to be readil}' removed from a fragment of the organ. It consists of
three elements; viz., of the most delicate hloodvessels of the spleen, of
microscopic fibres and trabeciihv, and of peculiar cells of the parenchyma.
In ]\Ian and in Animals the occurrence of extravasated blood, in manifold
stages of metamorphosis, is so frequent, that it may be almost regarded
as a normal constituent. According to its amount and to the disten-
sion of the bloodvessels, the pulp appears sometimes of a brighter, some-
times of a darker blood-rod ; besides Avhich, however, it must bo noted
that the pulp has also its own proper red coloring matter.

The fibres of the pulp are of two kinds. Firstly, there are microscopic
traheeulce, answering completely to those visible with the naked eye and
possessing the same structure, except that in many Mamm.als they con-
tain more smooth muscles, or are even entirely composed of them. As
a general rule, their diameter varies between 0-005 and 0-01 of a line;
in quantity they differ in different animals and in different parts of the
spleen. In Man I find them to be more rare and broader than in other

while the inner is. to use the accurate phraseologyof Mr. Wharton Jones, composed, of '• nu-
cleated granular corpuscles and nucleated cells, similar to those of the red substance, coher-
ing together in a mass by means of a diffluent intercellular substance, and, interspersed
among these, a ^e\v somewhat larger nucleated cells" (1. c, p. 35).

Tlie iilea that the Malpighian corpuscles were hollow bodies originated with Malpighi
himself; but JMiillcr, in opposition to him and to Rudolphi, asserts very justly that in the
Pig, Sheep, and Ox, they are firm and resistant.

From all that has been said, it results very clearly that the only ditTerence between the
" pulp" and the " Malpighian follicles' of the spleen is one of degree, consisting in the greater
or less development of the vascular network and the greater or less amount of metamor-
phosis, which the elements of the parenchyma have undergone. It is, furthermore, suffi-
ciently obvious that the anatomical ditierences between a solitary Ibllicle of the intestine, a
Peyer's patch, a lymphatic gland, and a spleen, are also questions of degree. It is impos-
sible to distinguish, under the microscope, a minute lymphatic gland — such as may be met
with in the mesentery of the I\at, for example — from one of the follicles of the Peyer's
patches of the same animal. But as the intestinal follicles are aggregated to form the
Peyer's patches, so the lymphatic follicles are aggregated to form the large lymphatic glands ;
increase the vascularity of the struma of a lymphatic gland and we have a spleen.

On the other hand, we can state decidedly that the follicles of the tonsils, both in Man and
in the Sheep, are traversed abundantly by capillaries, so that they come under the same
category: differing, however, from the lymphatic glands and spleen, in that the follicles are
arranged, not in solid masses, but around diverticida of the intestinal mucous membrane,
which, in the tonsils (both in Man and in the Sheep), take the form of more or less irregu-
larly ramified (lucis. Starting, therefore, from the simple intestinal follicle, we have two
series of vascular glands — the one, the solid series, reaching its inmost comj^lexity in the
spleen (and jierhaps the supra-renal bodies and thymus) ; the other, the il ivcrdndar series.
Does the latter, however, reach its highest complication in the tonsils? or rather do not
these lead in the plainest way to the liver, which is, like them, essentially a solid mesh-
work of capillaries, filled by inditferent tissue and arranged around a complex diverticidum of
the intestine ? It appears to us that the structure of the tonsils aflbrds, in this way, an ana-
logical basis for the views of Dr. Handfield Jones; and tends greatly to support the doctrine,
that the liver is essentially one of the vascular glands. While adding ilie liver, however,
we should exclude the thyroid ; its structure being totally dili'erent from that of the rest of
the class. — Trs.]

558 SPECIAL HISTOLOGY.

Mammals, and perfectly identical in their structure Avith the larger tra-
heculce. Other fibres which occur in the pulp are plainly the termina-
tions of the vascular sheaths. They are very numerous, and usually
have the appearance of delicate, indistinct, fibrous membranes, without
any elastic element, which appear to connect the capillaries, and are,
perhaps, continuous with the finest trabecuhv.

The cells of the pulp, ov ixirenchyma-cells of the spleen, round cells
of 0-003-0*005 of a line, with single nuclei, are for the most part so
similar to those in the Malpighian corpuscles, that it is unnecessary to
enter upon a more minute description of them ; intermingled with them,
and, indeed, in larger quantities than in the Malpighian corpuscles, we
find/reg nuclei. Besides these, a few other elements may be met wuth :

1, pale round bodies, with a homogeneous aspect, somewhat larger
than the corpuscles of the blood, which appear either as free nuclei, or
as homogeneous nuclei, closely surrounded by a delicate investment ;

2, larger cells, up to 0-01 of a line in diameter — both of the completely
pale kind, with one or two nuclei, and also what I have called colorless
granule-cells — that is, cells with more or fewer colorless, dark fat-gra-
nules. Each of these elements exists in the splenic corpuscles also, but
never to so great an amount. The quantity of the different kinds of
parenchyma cells and of free nuclei in the pulp, is so considerable, that,
together with a small amount of a reddish-yellow fluid which unites
them, they constitute probably one-half of the bulk of the spleen. They
are not collected in large masses, but in small irregular aggregations of
different sizes, which occupy the interspaces between all the trabeculce
and vessels of every description, and surround the Malpighian corpus-
cles. The clearest conception of the arrangement is obtained, if we
consider that every segment of the red substance included within the
larger trabeculce has the same composition, on the small scale, as the
whole spleen has on the large. In fact, the microscopic trabeculce, the
terminations of the vascular sheaths and the finest vessels, present the
same relations as the large trabecule^ and vessels, while the small masses
of parenchyma cells correspond with the apparently homogeneous masses
of pulp, visible to the naked eye. There are no special investments
around the parenchyma-cells, but they lie everywhere in direct contact
v/ith the sheaths of the vessels, the trabeculce, and the sheaths of the
Malpighian corpuscles.

The red pulp of the spleen of Man and of Animals has a different
color at different times ; or rather the blood-corpuscles which it contains
and which, without the participation of any other element, give rise to
its color, present different conditions. In some animals, for instance,
its color is sometimes paler, more grayish-red, sometimes brown, or even
blackish-red. In the latter case, a quantity of changed blood-corpuscles
will be met with (to which we shall return subsequently) ; in the former,
on the other hand, it may be microscopically demonstrated that the red

THE SPLEEN. ' 559

f

color proceeds from uncliangcd blood-corpuscles, which may also be
readily expressed from the substance of the spleen and, on the addition
of water, in a short time lose all their coloring matter. In other ani-
mals the spleen, although it always has about the same, usually dark
color, yet contains in addition, sometimes only unchanged blood-cor-
puscles, sometimes multitudes of them in every stage of metamorphosis.
These are very striking, and in all animals consist essentially in this —
that, 1, the blood-corpuscles, becoming smaller and darker and, in the
lower Yertebrata, losing their elliptical form and taking a circular shape,
agglomerate together into rounded masses, which either persist in this
condition, or, combined with a certain amount of the plasma of the
blood, develop an envelope externally and a nucleus in their interior,
thus passing into round blood-corpuscle- lig. oo^^

holding cells, of 0-005-0-015 of a line,
containing 1-20 blood-corpuscles ; and
2, these masses and cells, their contained
blood-corpuscles gradually diminishing
in size and assuming a golden yellow,
brownish-red, or black color, either in
their entire state or after breaking up
into pigment granules, change into pig-
ment masses and pigmented granule cells ; and, finally, the latter, their
granules gradually becoming pale, pass into perfectly colorless cells. In
many cases the blood-corpuscles form no masses or cells, but pass through
the above-described stages of coloration and disintegration, like the others.*

Fig. 231. — Blood-corpuscle-holding cells and tlieir metamorphoses, from the spleen of the
Rabbit, magnified 350 diameters : a, two nucleated cells, with blood-corpuscles; h, similar
cells metamorphosed into brown pigment cells ; c, cells from which the color has disappeared
again ; rf, pigment granules which have arisen from metamorphosed free blood-corpuscles.

* [In his " Microscopical Anatomy,"' Prof. Kolliker states, that he has observed blood-
corpuscle-holding cells, and their breaking up into pigment granules, in the spleen of
almost all animals. In Mammalia the cells were generally seen with diiliculty. In the
Cat, Horse, Ass, and Bat, no distinct cells could be detected, although the pigment masses
and the pigmented granule-cells were easily observable. In Birds he met with cells con-
taining blood-corpuscles only in the Blackbird although in many {Falco albicilhis, Cundus
caiiortis) he was able to detect yellow pigmented granule-cells changing into black pigment.
In the naked Amphibia and in Fishes, he frequently found cells enclosing 5 to 20 blood-
corpuscles, in which the metamorphosis into pigment could easily be studied.

The " blood-corpuscle-holding cells"' and the supposed result of their metamorphoses —
pigment granules, are met with in great abundance in some of the diseases of the spleen.
Tlius in atropliy of tliis organ the trabecukc and the parenchymatous structure are filled
with masses of a dark molecular pigment. In the enlarged spleen of typhoid and inter-
mittent fever, Heschl detected many pigmented granule cells and dark pigment granules.
It is probable that cells enclosing blood-corpuscles exist, not only in the spleen, but wher-
ever many blood-corpuscles and large masses of pigment are observed. I have seen cells
resembling " blood-corpuscle-holding cells"' in melanosis of the eye, in congested lung.'!,
and as part of the peculiar dark granular matter, observed under the microscope, in the
black vomit of yellow fever. If in this last-named instance the cells were possessed of
distinct membranes or not, I was unable to determine. — DaC]

560 SPECIAL HISTOLOGY.

The changes undergone by the blood in the spleen, a subject which is
more fully treated of in my " Mikr. Anat.," IL, 2, pp. 268-270, and
which were observed and interpreted by Ecker, at the same time and in
the same manner as by myself, have lately become the subject of much
discussion. Gerlach, Schaflfner, and lately 0. Funke also {I. c), who
are completely at one with Ecker and myself as to the facts, differ alto-
gether in their interpretation of them ; and believe that, instead of their
being the result of a dissolution of the blood-corpuscles, they proceed
from a process of development of new corpuscles, and that therefore the
spleen — as, indeed, was Hewson's opinion — is a formative organ for
blood-corpuscles.

I have already, in another place (Zeitsch. fur wiss. Zool., p. 115),
confuted Gerlach's views, and I therefore consider it to be unnecessary to
enter, again, into this question, the less, as Ecker, after repeated, care-
ful investigations, quite agrees with me ; indeed no unprejudiced obser-
vation can tend to other conclusions than those at which we have arrived.
Remak has recently brought forward an entirely new view [1. i. c.)
From the known facts, that other pigment cells exist than those whose
coloring matter is derived from blood- corpuscles, and that effused blood
may form cell-like masses with blood-corpuscles, as Hasse and I have
more particularly shown — facts which he has strengthened by new cases
— Remak has allowed himself to be misled into asserting, not only that
no cells with enclosed blood-corpuscles exist at all, but also, that in the
spleen no blood-corpuscles are destroyed, i. e. change into pigment gra-
nules. This is so strong an assertion, that I see no necessity for my
contradicting it ; one might at last be required to demonstrate that there
are such things as cells and blooH-corpuscles. It will interest Remak
to learn that Virchow, as he tells me, has satisfied himself of the ex-
istence of the cells in question, though he explains their origin in ano-
ther mode, believing that the blood-corpuscles pass from without into
already existing cells — a supposition with which, at present, I cannot
exactly agree.

An important question arises, as to the im2:)ort of the changes in the
blood-corpuscles, whether they are 2^^^y biological or patliological'? On
the one hand, very weighty reasons present themselves for considering
the phenomena to be pormal, particularly their constant occurrence, as
it may be said, in so many living animals, especially in those living
under natural conditions, as Amphibia and Fishes ; secondly, the appa-
rent continuance of perfect health, notwithstanding the enormous quan-
tity of disintegrating blood-corpuscles ; thirdly, the occurrence of blood-
corpuscle-holding cells in bloodvessels which are not cut off from the
general circulation, as may be demonstrated in the Amphibia ; fourthly,
the absence of similar, constant changes in the blood, repeated at short
intervals, in other organs in the higher Vertebrata : and much more
might be added. To these facts, however, careful observation opposes

THE SPLEEN. 561

many others, wliich almost involuntarily load to the idea, that perhaps
all the changes of the blood-corpuscles in the spleen arc abnormal, a
view to which my observations in Fishes also tend. Here, 1, the meta-
morphoses of the blood-corpuscles in the spleen do not go on in the interior
of bloodvessels, but in extravasations which resemble pathological aneu-
7' ismata spuria (see "Mikr. Anat.," 11. 2; and Todd's "Cyclopaedia
of Anatomy and Physiology," Art. Spleen, fig.' 533; Ecker, "Icon.
Phys.," tab. vi. figs. 15, 16) ; 2, extravasations and metamorphoses of
their blood-corpuscles occur, not only in the spleen, but in other organs,
especially in the kidneys, where they are constant, and frequentl}"- also
in the liver and peritoneum.

If to these facts we also add, that in certain animals, e. g. the Cat,
the Sheep, &c., the changes of the blood-corpuscles in the spleen are
very rarely met with — furthermore, that their progress is not always
coincident with the stages of digestion — it becomes very difficult not to
believe that the phenomena are abnormal, especially if we consider that
similar phenomena certainly not physiological, such as the small eifusions
of blood into the lungs, bronchial glands and thyroid in Man, in the
lymphatic glands of the mesentery of the Pig and Rabbit, &c., are also,
on the one hand, almost as constant phenomena, and, on the other hand,
are accompanied by perfectly similar metamorphoses of the blood-corpus-
cles. However, in the latter cases, the quantit}' of the metamorphosed
blood-corpuscles is not to be compared to the immense number of those
which are constantly undergoing disintegration in the spleen ; and in
the second place, it is also possible that eifusion of blood may occur as
a physiological phenomenon, as into the Graafian follicles, and during
menstruation and the detachment of the placenta. And although all
animals do not present a microscopically demonstrable disintegration of
the blood-corpuscles in their spleen, yet it does not follow that the pro-
cess may not occur and that Avhen it can actually be demonstrated, it is
pathological. This much is at least certain, that congestions of blood
in the spleen occur in all animals, without exception; and it is almost
certain, that these congestions are, in Mammals, attended by extravasa-
tion. In these stagnations of blood, the blood-corpuscles may be disin-
tegrated, in some cases rapidly, in others slowly, which would constitute
an important difference for the observer ; it is also conceivable that they
and their consequences are physiological and have some great influence
upon life, since it is a fact, that in many animals they are constant, and
occur upon a very large scale.

For the present, therefore, so long as the pathological character of
the phenomena in question is not conclusively demonstrated, I must
maintain their physiological nature and regard the disintegration of
blood-corpuscles in the spleen as a normal occurrence.*

* [Willi respect to the "blood-corpuscle-holding cells," the reader will do well to consult

36

562 SPECIAL HISTOLOGY.

§ 169. Vessels and nerves. — As they enter the organ, the relatively
very large splenic artery and the still larger splenic vein, are accompa-
nied by those processes of the fibrous membrane, which have been
referred to as the vascular sheaths. In Man these processes form com-
plete investments around the vessels and nerves, somewhat after the
fashion of the capsule of Glisson, so that the arteries and nerves espe-
cially, can be readily isolated, while the veins, which on the side opposite
to the artery are more intimately connected with the sheath, are less
easily separable. At first the sheaths are as thick as the fibrous coat
itself and they retain this thickness so long as they surround the prin-
cipal branches of the vessels. The finer ramifications of the latter and
even those small branches which are given ofi" from the large ones, have
finer and finer sheaths, until at last, when the vessels are quite minute,
they become lost as thin membranes in the pulp. The thickness of any
sheath is always less than that of the wall of the artery to which it
belongs and greater than that of the vein, but after division the sheaths
become relatively stronger. It was remarked above, that a number of
the traheculce are inserted into the vascular sheaths and they therefore
take a share, together with the vessels which they inclose, in the forma-
tion of the dense network in the interior of the spleen. In Mammalia,
as in the Horse, Ass, Ox, Pig, Sheep, &c., the sheaths present difi"erent
relations, inasmuch as the smaller veins have none at all, and the larger
possess them only on the side on which the arteries and nerves lie. Only
the two principal venous trunks near the h.ilus have perfect sheaths,

Reinak"s very valuable and elaborate paper, "Ueber ninile Blutgerinnsel und iiber Pigment
kugel haltige Zellen," in MoUer's " Archiv," for 1852, and Mr. Wharton Jones's article on
the same subject in the "British and Foreign Med. Cliir. Review," for 1853, to which we
have already referred. Having carefully studied them, he will, we think, arrive very much
at our own conclusion, that as the question now stands, the very existence of "blood-cor-
puscle-holding cells'' must be consideretl as highly problematical.

Mr. Wharton Jones found the blood of the splenic vein to contain nucleated corpuscles
and fibres identical with those of the pulp, together with free nuclei similar to those of the
nucleated corpuscles; on tlie occurrence of which, he considers the statements as to the
abundance of colorless corpuscles in the blood of the splenic vein are founded. Some of
these elements were traced as far as the vena poiia, but in the hepatic veins they had mostly,
thougli not entirely, disappeared. He appears to be inclined to draw the conclusion that
some of the venous radicles of the spleen are connected with tlie pulp in the same way as
the hepatic ducts witli tlie parenchyma of the liver, and that the materials thus derived by
the blood from the spleen may concur in fitting it for the secretion of bile. Moleschott
(•'Ueber die Entwickelung der BlutkOrperchen,'' Milller's "Archiv," 1853), gives some
curious results obtained by extirpating the liver and spleen of Frogs. Normally, the car-
diac blood of Frogs contains about 8 red corpuscles to 1 colorless; after extirpation of the
liver, the proportion is 2-3 red corpuscles to 1 colorless. The blood of the spleen of Frogs
contains, normally, six times fewer red corpuscles in proportion to 1 white, than that of the
heart. After extirpation of the liver, there are 1-G colorless corpuscles to 1 red corpuscle
in the splenic blood. When the spleen alone has been extirpated, the proportion of red
corpuscles is slightly increased. Moleschott concludes that the liver favors the metamorphosis
of colorless into red corpuscles. However, we must confess that the results of the individual
experiments, from the average of which his conclusions are drawn, vary so widely as to
throw some doubt on the latter. — Trs ]

THE SPLEEN.

563

whilst the arteries, from the main trunks to the finest ramifications, all
possess them. The structure of the sheaths is precisely that of the
trabecuhv, but muscles are not always found in the former ^vhen they
are contained in the latter — e. g. in the Ox — \Yhile in the Pig they are
also very distinct in the sheaths.

The splenic artery, immediately it enters the organ, and all its prin-
cipal branches, divide and spread out into a great number of ramifica-
tions, the larger of which proceed towards the anterior margin of the
organ, the smaller towards the posterior, forming no anastomoses with
those of other principal branches. When they have diminished to the
diameter of 1-5-1-10 of a line, they separate from the veins, Avhich till
then had run in the same sheath with them, and become connected by

Fis. 232.

branches of 0-01-0-02 of a line, with the Malpighian corpuscles in the
manner Avhich has been described above ; perhaps, also, sending fine
branches into their interior (see § 167). Then, often closely applied to
the surface of the corpuscles, but, so far as I can observe, not passing
through them, as Joh. Miiller formerly supposed, they enter the red
pulp and immediately break up into elegant bundles of minute arteries,
the so-called penicilU (Fig. 232), which finally subdivide into true capil-
laries of 0-003-0-005 of a line, which throughout the pulp, round the
Malpighian corpuscles, as well as elsewhere, unite into a somewhat wider
network.

With respect to the veins, I must especially express myself against

Fig. 23'2. — An artery with its penicillatc ends, from tlie spleen of the Pig, magnified 25
diameters.

564 SPECIAL HISTOLOGY.

the existence of the venous tissues or spaces of ancient and modern
anatomists, in the human si^leen. The larger veins which still accom-
pany arteries, present no peculiarities, except in their width : all pos-
sess a membrane, which is, at least upon the side of the artery, easy of
demonstration, and, like the vascular sheath, gradually becomes thinner.
Apertures of more minute veins, the so-called stigmata BlalpigJiii, exist
only in inconsiderable numbers in the largest of these veins, Avhile in
the smaller, they are more frequent. From the point of divarication of
the arteries and veins, the relations of the latter become somewhat dif-
ferent. In the first place, they give off upon all sides a vast number of
small veins, usually at right angles, whence their walls appear in places
almost cribriform ; and secondly, their membranes become completely
coalescent with the sheaths of the vessels, so that ultimately the two
constitute only a single very delicate wall, which, however, may still be
easily detected in the very smallest vessels that can be isolated by dis-
section. I find dilatations of any kind in no part of these veins, only,
it is to be observed that they become narrowed more slowly than the
arteries. Their continuity with the capillaries takes place in exactly
the same manner as in all other organs and may be demonstrated with-
out difficulty, by injecting the veins of a well-preserved human spleen,
especially of a child. Neither does any trace of dilatations present
itself in this case.

The cajnUaries of the spleen have the ordinary structure, and a width
of 0-003-0-005 of a line; they are very numerous, and exist through-
out the pulp, where, round the Malpighian corpuscles, though not in
their coats, and elsewhere, they form a tolerably close network conti-
nuous through the whole spleen, only interrupted by the minutest trabe-
eulee and by the Malpighian corpuscles.

The human spleen possesses, relatively, very few lymijliatics. The
superficial set are distributed sparingly between the two coats, but can
hardly be recognized, except in the neighborhood of the Idlus and in
perfectly healthy spleens. The deep set may be discovered in the liilus,
whence also, few in number and small in diameter,, they accompany the
arteries, but cannot be traced by any means so far as these. In the
liilus both sets of lymphatics join, traverse a few small glands, which
exist in this locality, and finally unite into a trunk which opens into the
thoracic duct opposite the 11th or 12th dorsal vertebra. In diseased
spleens no trace of the superficial lymphatics can ordinarily be detected.
The nerves of the spleen, consisting of many fine and a few thick
tubules, with a moderate proportion of Remak's fibres, are derived from
the splenic plexus, formed by two or three trunks which surround the
splenic artery, and are continued on the arteries into the interior of the
organ, each dividing into one or two branches, anastomosing here and
there. In the Sheep and Ox, these splenic nerves are truly colossal, so

THE SPLEEN. 565

that, taken together, thoy equal the empty ami collapsed splenic artery,
this size, however, being attributable principally to the unusual quantity
of Reinak's fibres.

In animals, these nerves, which never possess ganglia, may be followed
into the spleen further than in Man; and, by the aid of the microscope,
I have frequently met with them even upon the arteries which support
the splenic corpuscles. As to their terminations, I can only state that
they pass into the pulp, and are still to be met with upon the arterial
pc7ucil(i. Here they ultimately become as delicate as the finest capilla-
ries, no longer possess dark-edged tubules, and, according to Ecker's
observations (1. c, p. 140, Fig. 10), probably end in free dichotomous
divisions. In the Calf, the nerves upon arteries of 1 line measure
0 •024-0-028, on the penicilU arteriarum 0-0048-0 -0056, in the midst
of the pulp 0-003-0-004 of a lino. In branches of 0-012-0-028 of
a line, I here still found a single dark-edged nerve-tubule, whilst all
the rest consisted of a striated nucleated tissue, which alone consti-
tuted the finer threads. It is improbable that this structure has here,
as in the trunks, the import of Remak's fibres; I should rather with
Ecker, consider it to be embryonic nervous tissue, such as we are
sufliciently acquainted with in other localities ; and I am inclined to
believe that the dark-edged tubules of the trunks finally pass into pale
fibres, as such compose entirely or almost entirely the ultimate twigs,
and then terminate by branching out. In the trunks of the splenic
nerves of the Calf, there are found, before their entrance into the spleen
and within it, numerous dichotomous divisions of the dark-edged, partly
coarser and partly finer primitive tubules, such as I have not hitherto
succeeded in detectins: in Man.

o

In regard to the structure of the veins, many of the Mammalia ap-
pear to resemble Man, while others, as the Horse, Ox, Sheep, Pig, pre-
sent very wide differences. In these animals a special venous membrane
and a vascular sheath are found only at the origins of the largest
venous trunks, while further in, they are visible only upon the side of
the arteries. In all the smaller veins, which run independently (with-
out arteries), no further trace of two coats is to be met with, in fact,
these veins appear to be mere excavations in the substance of the spleen,
especially as a number of anastomosing trabeculce with red pulp often
forming projecting knobs between them, are apparent upon their walls.
However, they always have a perfectly smooth and shining surface,
arising from spindle-shaped, tessellated epithelium-cells of 0-005-0-01 of
a line, which are only microscopically demonstrable. This epithelium cor-
responds perfectly with that of the larger veins, only that here it no
longer lies upon a special wall, but immediately upon the substance of
the spleen, i. e. upon the trabeculce and upon a delicate membranous

566 SPECIAL HISTOLOGY.

substance which bounds the pulp between them. Under these circum-
stances we may, with perfect justice, speak of venous sinuses ; the
more, if we consider that these, so to say, wall-less veins have a colos-
sal width, and are pierced by innumerable veins which open into them.
These smaller veins, again, may be traced for a considerable distance
with the scissors, but I have as yet never been able to succeed in demon-
strating in what manner they are continuous with the capillary network,
proceeding from the penicilli arteriarum, which here also is very dis-
tinct. I can hardly believe that it will ever be possible to make out this
continuity completely, for the finest veins, which are often bounded by
but a few traheculce, and indeed for the most part by the red pulp alone,
are such delicate canals, that the slightest mechanical force, as in in-
flating or injecting them, destroys them ; and even by the microscope
they are not discoverable. It may always be observed, however, that
they eventually become very minute, so small that it is impossible to
consider their origins as enlargements. For my own part, I believe,
that here also, the connection with the capillaries takes place quite in
the ordinary manner, with this distinction, however, that the veins in
arising from them possess only one membrane, an epithelium, and are
therefore perhaps connected in some other manner with their structureless
coat. Smaller series of more rounded epithelial cells, which are not
unfrecpently found on teasing out the pulp, probably belong to the
smallest veins.

In mammalia the lymphatics are stated by all authors to be extreme-
ly numerous, and this is perfectly true for the superficial vessels, which
in the Calf, for example, are exceedingly abundant and present nu-
merous anastomoses in the subserous cellular tissue. On the other hand,
I find that the deeper lymphatics are scanty. In the hilus of a calf's
spleen, for instance, I found but four lymphatic trunks with a collective
diameter of 0*17 of a line. The superficial and deep lymphatics would
appear to be, to a certain extent, connected ; inasmuch as a few scattered
lymphatics, which are probably connected with those which proceed from
the hilus, accompany the arteries which pass from the interior of the
spleen, to be distributed in its coats, and open into the superficial trunks.
The latter may readily, in the Ox, be traced for a certain distance into
the interior, so far that it can be seen that they not only at first, but
subsequently, always accompany the arteries. Their origin is unknown,
and I can only say, that in the Malpighian corpuscles and in the p)&ni-
cilli, as microscopic investigation shows, the arteries are no longer
accompanied by lymphatics. They probably, as in the liver, belong
only to the vascular sheaths. In structure, the splenic lymphatics
present no peculiarities, and they have valves.

The arteries in the human spleen are exceedingly muscular, which
sufficiently explains the dilatation and subsequent contraction of the

THE SPLEEN. 567

organ observed 5 or G hours after the ingestion of food, noticed bj
many observers. In animals, besides these contractile elements, tiic
muscles of the coats and trahccida' which I have discovered, may take
some part in this process, and their presence further accounts for the
circumstance that the spleens of Animals contract bj galvanism, uhile
that of man does not [vid. Mikr. Anat. 11. 2, p. 265).

§ 170. Physiological remarks. — The spleen is developed at the end
of the second month, in the ftictal mesogastrium, at the fundus of the
stomach, from a blastema which, derived from the middle layer of the
germ, independently of the stomach, the liver, or the pancreas, collects
in this situation. It is, at first, a whitish, often slightly lobed body
(0-72 of a line in length, 0-4 of a line in breadth, in the ninth to the
tenth week), which gradually becomes red and is very soon as rich in
blood and in vessels as in the adult. The roundish small cells, of which
the spleen is at first entirely constituted, become, in the third month,
partly developed into vessels and fibres, whilst another portion remains
as parenchyma cells. The Malpighian corpuscles are not formed till
subsequently, but may always be found at the end of the foetal period,
although considerably smaller than afterwards. I do not know how
they are formed, but I presume that they proceed from simple masses
of cells, whose external elements become metamorphosed into the coat
of connective tissue, whilst the internal ones, partly persisting in their
original condition, partly becoming metamorphosed into vessels, form the
contents.

This is not the place to discuss at length ihe functions of the spleen ;
I must refer to my " Mikroskopische Anatomie," II. 2, p. 282, and
content myself here with stating, that I consider the spleen to be an
organ into whose parenchyma constituents of the blood enter bodily and
at times in increased quantity, and, with the co-operation of cellular
elements, which are in a state of continual formation and solution, un-
dergo, more especially a retrogressive, but partly also a progressive
metamorphosis, in the end to be taken up again by the blood and
lymphatics, in order to be excreted from the body or further applied to
the purposes of the organism.

Up to a certain point the investigation of the spleen presents no dif-
ficulties ; the pulp, the trabecida', and the Malpighian corpuscles, are
at once obvious. The latter are most readily examined in the Pig and
Ox, where the coat and the contents may easily be isolated, and the
connection with the vessels is also apparent. To see blood-corpuscle-
holding cells, the addition of water must be avoided. The muscular
fibres are beautifully seen in the finer traheculce of the Ox, and in the
trabeculce of the Pig and Dog ; and here maceration in nitric acid, of

568 SPECIAL HISTOLOGY.

20 per cent., is of service. The arteries and capillaries are easily in-
jected; the veins Avith great difficulty; most readily in Man. The
nerves are found with ease on the arteries ; the lymphatics may be best
studied in the Ox.

Literature of tlie Spleeii. — M. Malpighi, " De liene," in " Exercit.
devise, struct,," Lond., 1669; J. Mliller, " Ueber die Structur der
eigenthliralichen Kcirperchen in der Milz einiger pflanzenfressenden
Thiere," jMiiller's "Archiv," 1834 (the first good anatomical work
since Malpighi) ; T. C II. Giesker, " Splenologie, I. anatomisch. phy-
siologische Untersuchungen uber die Milz," Zurich, 1835 (a very ela-
borate treatise) ; Schwager-Bardeleben, " Observationes micros, de gland,
ductu excretorio carentium structuru," Berol., 1841 ; Th. von Hessling,
"Untersuchungen liber die weissen Korperchen der menschlichen Milz,"
Regensburg, 1842; A. Kcilliker, "Ueber den Ban und die Verrich-
tungen der Milz," in Mittheil. " Der Zlirch. nat. Gesellschaft," 1847,
p. 120; "Ueber Blutkorperchen haltige Zellen," in "Zeitsch. fiir wiss.
Zool.," Bd. I. p. 261, and Bd. II. p. 115; art. "Spleen," in Todd's
"Cyclopaedia of Anatomy," June, 1849; A. Ecker, "Ueber die
Veranderungen, welche die Blutkorperchen in der Milz erleiden," in
"Zeitsch. fiir Rat. Medicin," VI. 1847, and art. " Blutgefassdriisen,"
in R. Wagner's "Handw. der Phys.," IV. 1, 1849; J. Landis, "Bei-
trage ^ur Lehre iiber die Verrichtungen der Milz," Ziirich, 1847 ; Ger-
lach, "Ueber die Blutkorperchen haltenden Zellen der Milz," in
" Zeitschrift fiir Rat. Medicin," VII. 1848; " Gewebelehre," p. 218 ;
R. Sanders, "On the Structure of the Spleen," in Goodsir's "Annals
of Anat.," I. 1850; 0. Funke, "Be sanguine venae lienalis," Lips.,
1851.

[Gray, " On the Development of the Ductless Glands in the Chick,"
"Phil. Trans.," 1852.— Trs.]

OF THE RESPIRATORY ORGANS.

§ 171. Under the head of respiratory organs are usually enumerated
only the larynx, trachea, and lungs ; but I consider it as most suitable
here to describe two organs connected genetically with those respiratory
organs of the embryo, which remain undeveloped, that is to say, the
branchial arches ; and which, physiologically, perhaps, belong to the
lungs — the thyroid gland and the thymus.

OF THE LUNGS.

§ 172. The structure of the lungs corresponds, in all respects, with
that of a compound racemose gland, presenting, in the lobes, lobules,
and air-cells, the proper glandular parenchyma ; whilst the bronchice,

THE LUNas. 5G9

traclica, and lartjnr, constitute the excretory apparatus. They differ
from common glands in this, that since in the lungs a double process —
an excretion and an absorption of maj;ters — is carried on, which affects
the Avhole mass of blood, the cavities are proportionately more capa-
cious, and also, on account of the special nature of their contents, of a
peculiarly compact, and, at the same time, elastic structure.

§ 173. The larynx is the most complex portion of what are termed the
air-passages, and consists, in the first place, of a firm framework, the
cartilages of the larynx, together with their ligaments; secondly, of nu-
merous small muscles attached to them ; and lastly, of a mucous mem-
brane, abounding in glands, with which they are lined.

The cartilages of the larynx are not all alike in their structure, some
being composed of common ca)'tilaginous tissue, others o^ fihro-cartilage,
whilst others, again, are constituted of the so-termed reticular or yelloio
cartilage. To the former belong the thyroid-, cricoid-, and arytenoid-
cartilages ; all of which present a more homogeneous, hyaline matrix,
with scattered cartilage cells imbedded in it (Fig. 20), and approach
nearest to the costal among the other true cartilages. Most externally
they contain flattened cells, to which succeeds a whitish layer, with nu-
merous large parent-cells and a more fibrous fundamental substance ;
and, lastly, in the interior, a larger proportion of matrix and minute
radiating cavities. The membranes of the cells are thickened, and, in
their interior, a large oil-drop is most usually found. Incrustations of
the cartilage-cells and of the matrix, with minute calcareous granules,
are very frequent in the laryngeal cartilages ; but besides these, true
ossifications occur, which are always attended with the formation of
larger cavities, filled with a well-marked, gelatiniform, vascular medulla.
The ejnglottis and the cartilages of Santorini and of Wrisherg, consist
of yelloiv or reticular cartilage {vide § 22, Fig. 21), presenting opaque,
very closely interlaced fibres, which, in animals [e. g. the Ox), are much
thicker than in Man, and clear cells, 0-01-0-02 of a line in size, in which
Henle, in one instance, noticed a concentric disposition of such a kind
that the remaining cavity of the cell resembled a simple bone-lacuna
with a few prolongations (Allg. Anat., Tab. V., Fig. 8). The cartilago
triticea consists of connective tissue wdth scattered cartilage-cells, and
is, consequently, common fibi-o-cartilage.

Of the ligaments of the larynx, the ligg. crico-thyreoideum medium
and tJtyreo-arytamoidea inferiora contain a preponderance of elastic tissue
and are of a yellow color : whilst others, such as the thyreo-arytcenoidea
superiora, hyo- and thyrco-einglottica, and the membr. hyo-thyrcoidea^
are characterized, at all events, by the great abundance of that element
which they present. The elastic fibres of the laryngeal ligaments are
of the finer sort, scarcely exceeding O'OOl of a line, and are united in

570 SPECIAL HISTOLOGY.

the usual manner into a very close elastic network ; which, however,
even where it is apparently most unmixed, contains some connective
tissue. The muscles of the larynx are all transversely striated with
fibres of O-OlG-0'024 of a line, and present the same structure as those
of the trunk. They arise from the cartilages, and are inserted into them,
and also into their elastic ligaments ; the latter being the case with the
tliyreo-arytcenoideus, which is for tlie most part lost on the concave side
of the vocal ligaments.

The mucous membrane of the larynx, the continuation of that of the
throat and mouth, is smooth, whitish red, and connected with the sub-
jacent parts by the ordinary, in some places abundant submucous con-
nective tissue. Except in the glottis, the mucous membrane, covered
only by a ciliated epithelium, and presenting no papillce, abounds in
finer elastic fibrous networks, particularly in its deeper portions ; whilst
the innermost layer, 0-03-0-04 of a line thick, consists principally of
connective tissue, and ceases in an inseparable, homogeneous border of
O'OO-l of a line. The ciliated epithelium, in the adult, commences at the
base of the epiglottis and, above the upper vocal ligaments, is composed
of several laminos {vide § 21), on the Avhole 0-024-0-04 of a line thick;
with the exception of the vocal ligaments, which, as was discovered by
H. Rheiner and I can confirm, have a squamose epithelium, it lines the
rest of the larynx throughout. The proper ciliated cylinders 0-015-
0*02 of a line long, and 0-0025-0-004 of a line broad in the mean, with
elongated round nuclei of 0-003-0-0045 of a line, and occasionally with
a few fat-granules, are mostly much acuminated, frequently even pro-
longed into slender filaments, which may attain such a length that the
entire cell may equal 0-024-0*027 of a line. The cilia are fine, trans-
parent, soft processes of the cell-membrane, 0-0016-0*0022 of a line
long, which arise from it with a rather broader basis, and terminate in
a pointed extremity. Most usually they are placed close together, over
the Avhole of the terminal surface of the cells, according to Valentin, on
the average, to the number of 10 to 22, which appears to be rather
under the mark ; more rarely they occur in smaller number, or even, as
it is said, singly upon a cell. But in this case, care must be taken not
to regard cohering cilia as single ones, as might happen, particularly in
the embryo. In their chemical relations the cells of the ciliated epithe-
lium correspond precisely with those of the cylinder-epithelium, and
especially, the separation of the cell membrane on the addition of w^ater,
may also be remarked in them. The cilia are of much more delicate
consistence than the cell membrane and are very readily detached upon
any maceration of the epithelium ; more or less altered by almost all
reagents, they are, by many, at once destroyed ; in chromic acid, how-
ever, they may be preserved pretty well. In man, the ciliary motion is
directed, in the trachea, from below upwards and may often be perceived

THE LUNGS.

571

fifty-two 01- even fifty-six and seventy-eight hours after death (Biermer,
Gossclin).* There is nothing to show the occurrence, normally, of a
desquamation of the ciliated epithelium of the larynx and air-passages.

Fi?. 233.

A

m

liiliis

Occasionally, it is true, isolated, ciliated cylinders are thrown off and
expelled with the mucus of the trachea, but of an extensive detachment
of the ciliated cells there is no indication. Even in diseases of the re-
spiratory passages, the detachment of the ciliated cells is by no means
so common a phenomenon as is believed by many, and the epithelium
may be frequently found uninjured under puriforra mucus, or even be-
neath croupose exudations. The mode in which the ciliated cylinders
that have been thrown off are replaced, is probably simply this : that
the deep cells multiply, perhaps by division [vide § 12), and succeed
them, the outermost again producing cilia.

The laryngeal mucous memhrayie contains a considerable number of

Fig. 233. — Ciliated epillielinm from the human trachea, magnified 350 diam. A, cpilhclium
tu situ: a, most external portion of the elastic longitudinal fibres; b, homogeneous, most ex-
ternal layer of the mucous membrane ; c, deepest, rounded cells ; d, middle, elongated cells ;
e, most superficial cells, supporting cilia. J3, isolated cells from the various layers.

[The motion of the cilia is destroyed by many chemical and mechanical agents, but
hitherto, notwithstanding the careful researches of Purkinje and Valentin (De phenomeno.
gen. et fundam. motus vibratorii continui, Vratisl. 1835, pp. 74-7G) none have been known
which possessed the power of re-exciting it. Virchow (Archiv f. path. Anat. VI. 1) has,
however, quite lately, whilst examining the epithelium of a human trachea, discovered
that by the application of a solution of potassa the ciliary motion may be recalled. Under
the action of the potassa, he states, isolated cilia begin at first to exhibit irregular, jerking
movements. The.'^e gradually acquire more regularity and force, until at last the rapid,
rhythmical, sweeping movement of a whole series of cells is restored. A solution of soda
acts in the same manner as one of potassa; a solution of ammonia produces, on the other
hand, at once a chemical decomposition. These experiments, Virchow thinks, prove con-
clusively, that the substance of the vibratile cilia approximates the contractile substance of
muscle (Syntoni)i of Lehmann). — DaC]

572 SPECIAL HISTOLOGY.

glandules, all of which belong to the category of minute racemose glands ;
and, like those of the oral cavity, pliarynx, &c., present rounded gland-
vesicles of 0-003-0-04 of a line with a tessellated epithelium, and excre-
tory ducts lined Avith a cylinder-epithelium. They are situated, in part
scattered as minute glandules of yVs o^ ^ ^'^i®? o" ^^® posterior surface
of the epiglottis, where they are frequently imbedded in depressions,
which may even perforate the cartilage, and in the cavity of the
larynx itself, where their arifices, such as might be produced by a
needle, are easily seen ; in part they occur at the entrance of the
larynx, in front of the arytenoid cartilages, forming a large aggre-
gate mass, a horizontal division of which envelops the cartilage of
Wrisberg, whilst a second dips down into the cavity of the larynx
[glandulce arytcenoidece laterales). Glandules are also placed upon
the arytcenoideus transversus and a considerable mass of them pre-
sents itself externally, in the ventricles of Morgagni, behind and
above the sacciform ligaments. The secretion of these glands, as of the
oral glands, is pure mucus, without any morphological elements.

The larynx is richly supplied with vessels and nerves. The former,
in the mucous membrane, present the same conditions as in the pharynx
and ultimately breaking up into capillaries, 0-003-0-004 of a line, form
a superficial plexus. The lymphatics arc numerous and are received by
the deep cervical glands. Of the nerves, we^learn from Bidder-Volck-
mann, that the more sensitive laryngeus superior contains a prepon-
derance of fine fibres, whilst the inferior, whose properties are more of
a motor nature, has more thick fibres. They terminate in the muscles,
the perichondrium and, especially, in the mucous membrane, in which
they are disposed as in the pharynx; the branches going to the epi-
glottis are also furnished with microscopic ganglia.

The glands of the larynx and of the air-passages are frequently
altered in catarrh, so that their vesicles measure as much as 0-08, or
even 0-15 of a line, and are filled with minute, rounded cells, which may
probably be compared with the mucous corpuscles formed on the sur-
faces of mucous membranes.

§ 174. The trachea and its branches are united to the contiguous
parts by a connective tissue abounding in well-defined elastic fibres ;
they are then surrounded by a tough, elastic, fibrous tissue, which
covers the cartilaginous rings, like a perichondrium, connects them
together, and, in a somewhat thinner layer, invests the posterior mem-
branous wall of the canal in question. To this layer succeed the carti-
lages, in front and on the sides, while posteriorly there is a layer of
smooth muscles. The former, ^-h a line thick, are constituted ex-
actly like the larger cartilages of the larynx, but exhibit no tendency
to become ossified. The muscles, on the contrary, from the trachea
onwards, cease to be of the striped kind and constitute, on the pos-

T n E LUNGS.

573

FiS. 234.

terior wall of the tube, only an incomplete layer, 0*3 of a line thick,
composed of transverse fibres ; on the outer aspect of which are isolated
longitudinal bundles, whose elements, 0-03 of a line long and 0-002-0-OOJ:
of a line wide, are united into small fasci-
culi, which arise by delicate minute tendons
of clastic tissue, in part from the inner sur-
face of the ends of the tracheal rings ; in
part, particularly the longitudinal bundles,
from the external fibrous membrane. ( Vid.
Mikr. Anat. 11. 2, Fig. 277.)

On the inner aspect of the cartilages
and muscles, which, to a certain extent, are
to be regarded as one layer, we find a stra-
tum about 0*12 of aline thick, of more com-
mon, close, connective tissue, and then the
true mucous memhrcine. This consists of
two layers ; an external composed of con-
nective tissue, 0*12 of a line in thickness ;
and an internal, yellow, of 0-09-0-1 of a
line, almost wholly elastic, the plcxiform
fibres of which, 0-0015 of a line in diame-
ter, run longitudinallu, and in places, espe-
cially on the posterior wall, often constitute
flattened fasciculi joined at acute angles.
The innermost portion of the elastic layer,
0-024-0-03 of aline thick, is, particularly
in the posterior wall, as in the larynx, fre-
quently composed more of connective tissue
with fine elastic fibrils ; it may also be raised
as a thin pellicle from the thicker elastic

layer, and internally always presents a more homogeneous layer, 0-005 of
a line thick. Upon this lies the ciliated epithelium, which is laminated
and differs in no respect from that of the larynx. Numerous glands
exist in the mucous membrane; these are : 1, smaller ones of 1-10-1-4 of
a line, found especially on the anterior wall, within the mucous mem-
brane and immediately exterior to the elastic layer ; and 2, larger, of
^-1 line, which occur more in the posterior wall, externally to the
muscles and the whole raucous membrane, or between the cartilages.
These glands differ from those of the larynx only inasmuch as the larger
of them alone have the usual tessellated epithelium in their vesicles ;

Fig. 234. — Vertical section through the anterior wall of the human trachea, magnified
45 diam.: a. fibrous coat; b. c, d, cartilage; b, external layer, with flattened cells; d, inter-
nal layer, with elongated elements; e, submucous connective tissue; /, portion 'of a mucous
gland ; g, elastic longitudinal fibrous layer ; h, epithelium, on which the cilia are not visible;
J, glandular orifice. •

574

SPECIAL HISTOLOGY.

•whilst the smaller, situated in the mucous membrane itself, and some
of which are in the strictest sense simple, or only bifurcated caecal folli-
cles, present in their oval gland-vesicles, 0-02-0'03 of a line in size,
a very narrow cavity and walls of 0-006-0 -01 of a line, a thickness
which may, perhaps, be referred altogether to the well-marked cylinder-
epithelium.

The bloodvessels of the trachea are very numerous, and, in the mucous
membrane, are especially characterized by the circumstance, that the

larger branches run chiefly
^^^- -'^- in a longitudinal direction,

whilst the superficial capillary
plexus, which is frequently
met with above the elastic
elements, close beneath the
homogeneous layer, more com-
monly forms rounded-angular
meshes. The trachea is abun-
dantly furnished with li/7n-
pJiatics ; and in one case I
found their commencement in
the mucous membrane, in the
form of wide-meshed plexuses
O-OOo-O-OOl of a line broad, of thin-walled vessels, from which, here
and there, isolated, ceecal processes were given off (Fig. 235). The
nei'ves also of the trachea are numerous, and present the same condi-
tions as those of the larynx.

§ 175. Lungs. — The lungs are two large, compound, racemose
glands, in which are to be distinguished: 1, a special serous coat —
the pleura; 2, the secreting parenchyma, consisting of the ramifica-
tions of the two bronchi, with their terminations, the air-cells, and
numerous vessels and yierves ; and 3, an interstitial tissue interposed
between these parts and uniting them into larger and smaller lobules.

The pleurce, in their structure, entirely correspond with the j^eri-
to7ieum, as in which, the parietal layer is the thicker, and consist of
connective tissue abounding in finer or coarser elastic elements, with a
tessellated epithelium, to which constituents, on the walls of the thorax,
as on the exterior of the pericardium, a more purely fibrous lamella is
superadded. Vessels are seen most abundantly in the pleura pulmonalis,
where, arising from the bronchial and pulmonary arteries, they ramify
in the subserous tissue ; whilst the parietal lamella is more scantily
supplied by the intercostal and mammary arteries. Luschka found nerves

Fig. 235. — Commencement of tlie lymphatics in the tracheal mucons membrane of Man,
magnified 350 diameters.

THE LUNGS.

575

Fis

■with finer and coarser fibres and traced tlicm, in tlic outer portions of
the membrane, to the phrenic and to the thoracic divisions of the sympa-
thetic. In Man, I have myself also seen, in the pZt'?ov( j^uhnonalis,
nerves, as much as 0-03G of a line in diameter, accompanying the
branches of the bronchial arteries, ■with middle-sized and thick fibres
and occasionally large scattered ganglion-glohil es, ■which ■were derived
from the plexus pulmonalis, and were probably afforded chiefly by the
vagus.

§ 176. Air-vessels and cells. — When the right and left bronchi have
reached the root of the lungs, they begin to branch, like the excretory
ducts of one of the larger glands, such as the liver, dividing for the
most part dichotomously and at acute angles, into smaller and smaller
branches ; but giving off, at the same time, from the sides of the laro'er
and middle-sized branches, numerous minute air-vessels, at a rirrht
angle, ■which like the terminations of the main ramifications, subdivide
in an arborescent manner. Thus is ultimately constituted an extremely
rich tree of air-vessels, whose finest ter-
minations, never anastomosing, extend
throu2:h the entire lunn; and arc to be
found in every part, on the surface as vfcU
as in the interior. With them, also, are
connected the ultimate elements of the air-
passages — the air-cells or pulmonarg vesi-
cles [vcsiculce s. cellulcc aerea! s. 3Ialpig-
Jiiance, alveoli pulmonum^ Rossignol), not,
as ■was formerly believed, by each finest
bronchial twig ierminating in a single
vesicle, but always by their communicating
with a whole group of air-cells. These
groups of vesicles correspond to the smallest
lobules of racemose glands, and conse-
quently there is no occasion whatever to designate them under any
other name, as was done b}^ Rossignol, who calls them infundibula,
although it must be allowed that their structure, in many respects, is
peculiar. For, whilst in other glands the vesicles, if not quite so isolated
from each other as has hitherto been supposed, still enjoy a certain
degree of independence, the pulmonary elements corresponding to
them, — the air-cells, — are, to a considerable extent, confluent with each
other, so that all the vesicles belonging to one lobule open, not into
ramifications of the finest bronchial twig going to it, but into a common
space, from which the air-vessel is afterwards developed. That this is

Fig. 230. — Two small pulmonary lobules, a a, with the air-cells, b b, and the finest bronchial
twigs, cc, upon which air-cells are also placed. From a new-born child : magnified 25
diameters. Half-diagrammatic.

576 SPECIAL HISTOLOGY.

the true condition of these parts is most readily shown when sections,
in various directions, of an inflated and dried lung are prepared, or a
preparation injected with a colored resinous material- is corroded by
hydrochloric acid. In preparations of this kind, vesicles either termi-
nal or otherwise pedunculated, or opening independently, are never met
with ; on the contrary, they always open in such a way, one into the
other, and coalesce to such an extent, as, in the aggregate, to form,
most usually, a pyriforra sacculus, with sinuous walls. These sacculi,
which are also identical with the finest lobules, or the infundihula of
Rossignol, must not, however, be regarded as sacs, furnished on their
walls with closely placed simple cells or alveoli, the latter, on the con-
trary, being always grouped in such a way that many of them do not
open directly in the larger space, but first into other alveoli, and through
them into the common cavitv. An idea of the whole relations of these
parts may be best arrived at if each pulmonary lobule be viewed as an
amphibian lung in miniature, or if it be conceived that the outer surface
of the dilated extremities of the bronchial tubes is thickly beset with
numerous racemose groups of vesicles, the constituents of which all
open into one another and into the common cavity. Understood in
this way the structure of the lungs, then, does not diifer in the least,
in any important respect, from that of the other racemose glands,
except that in the former, at all events in the adult, a partial confluence
of the gland-vesicles or air-cells of a lobule, appears to have taken
place, the dissepiments between them being here and there broken
through and reduced to isolated trahecidcc, as Adrian! correctl}'' observes.
The smallest air-vessels, 0-1-0-16 of a line in diameter, arising by
simple narrowing from the most minute lobules, are at first still beset
with simple air-cells, which may be termed parietal, and at first also,
have sinuous walls, a character, however, which is soon lost to be re-
placed by the usual smooth appearance which is afterwards retained.

The size of the air-cells varies very considerably even in a healthy
lung, amounting after death, and when they are wholly undistended
with air, to 1-6-1-10-1-18 of a line. But owing to its elasticity, every
air-cell may be dilated to twice or three times its natural size without
rupture, and is capable afterwards of returning to its pristine condition.
It will not be wrong to assume, that, in life, w^hen the lungs are filled
with the average quantity of air, the air-cells are at least one-third
larger than we find them after death ; and that, on the deepest possible
inspiration, the expansion reaches, perhaps to twice that dimension.
In empliysema, dilatations to this and even to a much more considerable
extent, are permanent, and ultimately lead to the rupture of the walls
of the alveoli belonging to a lobule, or even to the confluence of the
lobules themselves. The/or?^ of the alveoli, in a recent collapsed lung,
is most usually rounded or oval and, in one that has been inflated or

THE LUNGS.

577

injected, in consequence of their mutual pressure, rounded-angular ; the
air-cells of the surface of the lung are invariably polygonal and their
external sides are almost always nearly plane.

The lohulated strucUire of the lung is not nearly so distinct in the
human adult as in younger individuals and in animals. It is therefore
advisable, in the first instance, to seek for these conditions in the luntrs
of a child. In this case the separate lobules are still all distinctly
parted from each other by connective tissue and admit of being isolated,
so that the tolerably regular pyramidal form of the superficial, and the
more irregular one of the interior lobules can be satisfactorily perceived.
In the adult, also, these smallest lobules, in size -i-|-l line, still exist,
but are so intimately united, that, even on the surface of the lung, their
outlines are only 'perceived with difficulty and imperfectly ; and, in the

Fiff. 237.

interior of the organ, a more homogeneous structure, something like
that of the liver, is apparently presented. Secondary lobules, on the
other hand, of 5-J-I inch in size (lobules of authors) are, even in the
adult, most usually evident and the more so, because their boundaries
are indicated by streaks of pigmentary matter, which, in course of
time, is deposited in the continuous interlobular, connective tissue.
These lobules are ultimately united together by a more abundant inter-
stitial tissue, so as to form the large well-known lobes.

Thus the lung consists entirely of larger and smaller groups of air-
cells and smallest bronchial tubes, and accordingly the larger air-vessels
also fall into certain definite groups, each of which stands in relation
with only one of the former.

Fig. 237. — External surface of the lung of a Cow, with the air-cells injected with wax,
magnified 30 diameters; after Harting: a a, air-cells; 6 6, borders of the smallest lobules or
infundibula (Rossignol).

37

578 SPECIAL HISTOLOGY.

§ 177. The intimate structure of the bronchia' and air-cells is as fol-
lows. The bronchicv are in general constituted in the same way as the
air-tubes and their branches, although from the very commencement
some diiferences are presented, which become greater and greater in
their further course. It is most proper to distinguish in them two
membranes, a fibrous, still in part containing cartilages, and a mucous,
with a smooth muscular layer. The former, constituted of connective
tissue and elastic fibrils, is at first thick, as in the bronchi, but gradually
becomes thinner and thinner ; in broyichice less than ^ a line in dia-
meter, it is scarcely demonstrable with the scalpel ; and ultimately, in
their terminations, it coalesces with the mucous membrane, and the
more lax connective tissue uniting the bronchice with the parenchyma
of the lung. In this membrane are lodged the cartilages of the bron-
chice, Avhich, instead of being half-rings, are irregular angular plates,
distributed around the entire circumference of the tubes. These carti-
laginous plates, at first large and closely approximated, are soon more
widely separated at the points of origin of the branches, and become
smaller and smaller, until finally in tubes under J a line in diameter
they usually cease to exist (Gerlach would appear to have noticed some
even in tubes of -/oof a line in diameter). The structure of these carti-
lages, which are not unfrequently of a reddish hue, is at first exactly like
that of the tracheal rings, but in the smaller and smallest of them the
differences between the superficial and deeper cells disappear and the
tissue becomes homogeneous throughout, more like the interior of the
larger cartilages. In the largest bronchice the muscles present the form
of circular flattened fasciculi, which, except in old people, in whom
larger and smaller interstices occur between them, constitute a com-
pletely continuous layer, and as they are still seen in twigs of 1-10-1-12
of a line in diameter, probably exist even in the pulmonary lobules. The
mucous membrane is intimately united Avith the muscles, and at first is
of the same thickness as in the trachea, but this is gradually reduced, so
that tubes of less than J a line have only an extremely thin wall. This
everywhere consists, externally, of elastic, longitudinal fibres, the
bundles formed by which give the characteristic longitudinally striped
aspect to the inner surface of the broyichice, and also produce a less
distinct longitudinal plication of the mucous membrane ; secondly, of a
homogeneous layer 0-002-0-003 of a line thick ; and thirdly and lastly,
of a ciliated epithelium, which, in the larger bronchial tubes and down
to those of 1 line in diameter, is distinctly composed of several laminfe,
but is gradually reduced to a single layer of ciliated cells 0-006 of a
line in length. The bronchice are at first also furnished with racemose
glands, even in considerable number, which, however, are wanting in
tubes of 1-1^ lines.

THE LUNGS.

570

In the air-ceUs, I cannot admit the existence of more than two layers
— a fibrous membrane and an epithelium. The former is manifestly the
much attenuated mucous membrane and fibrous tunic of the brone?iia\
entirely deprived of the smootli muscles, and consisting of a homoge-
neous matrix of connective tissue, together Avith elastic fibres and
numerous vessels. The elastic fibres, 0-0005-0-002 of a line in size,
present the form chiefly of separate trabeculoe and fdaments, running
especially at the angles of the air-cells, "which have been flattened in
the distended condition, as well as around their openings ; they anasto-
mose with each other on every side and thus constitute a firm frame, on
■udiich the softer, vascular parts of the air-alveolre, composed of con-
nective tissue, are stretched. The structure of these elastic trabecular,
which, at the points where the air-cells abut upon each other, mutually
coalesce, so that the boundaries of the separate cells cannot for the
most part be recognized, is al-
most everywhere one of the
most close elastic networks
possible, the interstices of which
appear only as extremely nar-
row fissures, although occasion-
ally the fibres are more loosely
united, so that they are plainly
recognizable as elastic elements
of the usual kind. From the
trabecuhe also, but everywhere
sparingly, elastic fibres, in part
yery fine, proceed into the re-
mainder of the walls of the
air-cells, in which, by their
union, they constitute a wide
network. The connective tissue
of the air-cells, which appears
to be altogether homogeneous,
is quite a subordinate element

in their composition, compared with the elastic elements and vessels,
presenting itself, as it may be said, only in the walls of the alveolar,
between the elastic trabeculce, as a connective medium betw^een the
numerous capillaries.

The epithelium of the air-cells is of the common tessellated kind,
without cilia, and composed of polygonal, pale, granular cells, in mor-

FiG. 238. — Human air-cell, with the surrounding tissues, magnified 350 diameters : a,
epithelium ; 6, elastic trabeculce ; c, more delicate wall between the latter, with finer elastic
fibres.

580 SPECIAL HISTOLOGY.

bid states, containing fut, 0-005-0-007 of a line in diameter, and
O-OOo-O-OO-l of a line in thickness, resting immediately upon the
fibrous membrane of the air-cells. A regular detachment of this
epithelium is not to be supposed, any more than ^Yith that of the
trachea and bronchia', whilst it is indubitable, that by chance, or in
diseases of the air-passages, its isolated elements may become mixed
with the bronchial mucus. In Man, these cells are detached with
remarkable readiness, and then lie free in the air-cells and finest ramifi-
cations of the bronchia^, although in almost every lung, at all events in
some of the alveolae, they may still be seen in situ; and in animals
recently killed, the observation of their disposition presents no difficulty
whatever.

The interlobular connective tissue of the lungs, Avhich is contained
sparingly, even between the secondary lobules, and between the primary,
exists in inappreciably minute quantity, consists of common connective
tissue with fine elastic fibres, and contains, in the adult, a larger or
smaller quantity of blackish ingincnt, in the form of irregular, minute
granules, aggregations of granules, and also crystals, W'hich, it may be
said, are never enclosed in cells. The Avails of the alveoles themselves,
also, very frequently contain this pigment, which, when it is deposited
in smaller quantity and regularly, marks out very distinctly the con-
tours of the secondary lobules, and not unfrequently, also, to some
extent, those of the primary.

§ 178. Vessels and nerves of the lungs. — As regards their blood-
vessels, the lungs occupy a unique position, inasmuch as they possess
two complete vascular systems, for the most part distinct from each
other — that of the bronchial vessels, for the nutrition of certain por-
tions, and that of the pulmonary vessels, for the fulfilment of their
proper function. The branches of the pulmonary artery follow pretty
nearly the course of the bronchial tubes, which are most usually placed
below and behind them, with this diiference, that they divide dichoto-
mously with greater frequency, and consequently diminish more rapidly
in diameter. Ultimately, a twig goes to each secondary lobule, which
then subdivides into still finer ramuscules, in general corresponding in
number with the smallest lobules, and supplying the individual air-cells.
The course of these finest lobular arteries, as they may be termed, is
very easily traced in injected, inflated, and dried preparations ; and it
is apparent, that whilst traversing the uniting tissue between the
lobules {infundibula), they supply not one lobule alone, but always two
or even three of them with finer twigs. These penetrate from without,
upon and between the air-cells, divide repeatedly while running in the
larger elastic trabecules, anastomosing also occasionally, though not

THE LUNGS.

581

regularly, -n-ith each other, or with branches of other lobular arteries,
and, finally, terminate in the capillary j^Zexifs of the air-cells. This
plexus, Avliich is one of the

closest existing in Man, as Fig. 239.

estimated in moist prepara-
tions, presents rounded or
oval meshes 0-002-0-008 of
a line wide, and vessels of
0-003-0-005 of a line in
diameter. It lies in the wall
of the air-cells, at a distance
of about 0-001 of a line from
the epithelium, in the middle
of the fibrous tissue, and is
continuous, not only over all
the alveolce of one of the
smallest lobules, but, also, at
all events, in the adult, is

partially in connection with the plexuses of the contiguous lobules.
The pulmonary veins arise from the above-described capillary plexus,
with roots which lie more superficial than the arteries, and more exter-
nally on the smallest lobules, then run deeply between them, and unite
with other lobular veins into larger trunks, which proceed in part with
the arteries and bronchial tubes, in part more isolated by themselves,
through the pulmonary parenchyma.

The bronchial arteries are distributed, firstly, to the greater bronchice,
whose vessels present the same conditions as those of the trachea, then
to the pulmonary veins and arteries, the latter of which, in particular,
possess an extremely rich, vascular plexus, which may be traced as far
as branches of |- of a line, and less; lastly, to the pleura pulmonalis, the
branches destined for which are, some of them, given off even at the
Idlus and in the fissures between the main lobes, some also from the
vessels accompanying the bronchia, coming out between the secondary
lobules. Small vessels, moreover, Avhich are not derived from the
bronchial arteries, pass on the pulmonary ligaments to the 2')leura.

The lymphatics of the lungs are very numerous. The superficial
lymphatic vessels run in the subserous connective tissue and in the inter-
spaces between the larger and smaller lobules, forming a superficial,
finer, and a deep, coarser, angular network, which covers the entire sur-
face of the lungs, and on the one hand empties itself into special, super-
ficial trunks accompanying the bloodvessels of the pleura towards the
root of the lung, and, on the other, opens into the deeper vessels by
numerous trunks which penetrate between the lobules. These arise

Fig. 239. — Capillary plexus of Uje human air-cell, magnified GO diameters.

582 SPECIAL HISTOLOGY.

from the walls of the broncJnce and bloodvessels, particularly those of
the pulmonary arteries, running with those canals through the substance
of the lung, and through some minute lymphatic glands [glandulce
pidmonales), towards the root of the lung, in order, ultimately, to com-
municate with the larger bronchial glands.

The nerves of the lungs are derived from the vagus and sympathetic,
form the more ^czwij plexus pulmonalis anterior, and the richer pZea;.
p. posterior, and are distributed principally with the hroncldoi and the
pulmonary artery, occasionally, however, accompanying the pulmonary
veins and vasa hronchialia. In the interior of the lung they arc also
furnished with microscopic ganglia, and may be traced nearly to the
termination of the hroncldce.

It is very remarkable, that besides the air-cells, some other parts of
the lungs are also supplied by the vasa pulmonalia, such as the surface
of the lungs and the finer bronchia'. With respect to the former, even
in uninjected lungs, minute ramuscules of the pulmonary artery are
apparent in various situations on the surface of the lungs, ramifying
under the pleura. Reisseisen (p. 17) describes these vessels, and figures
them very beautifully (Table IV., V.) ; recently, Adrian! has traced
them in injected lungs and states that they penetrate into the interior,
much convoluted and freo^^uently anastomosing ; they are considerably
thicker, hov/ever, and form wider plexuses than those of the alveoli.
The blood from these plexuses is conveyed away, on the one hand, by
the superficial roots of the pulmonary veins, and, on the other, through
anastomoses with the ramifications of the vasa hronchialia in the pleura
pulmor^alis. That the pulmonar}'' artery also supplies the bronchia; to
some extent was stated by Arnold (Anat. II., p. 171); and to Adrian!
we are indebted for more precise information on this interesting subject.
According to them, the pulmonary artery and veins chiefly participate
in the formation of the capillary plexus on the surface of the bronchice,
which is characterized by the elongated form of its meshes, and is con-
stituted by vessels almost as fine as those of the air-cells (in Man, of
0-004-0-OOG of a line), whilst the bronchial vessels are specially destined
for the supply of the muscular and fibrous coats of those canals. It is
comprehensible, also, that in this situation the two vascular systems are,
to a certain extent, connected ; and consequently the older anatomists,
such as Hallcr, Summering, and Reisseisen, who speak of a connection
between the two vascular systems of the lungs, were quite right. Ac-
cording to Adriani and Rossignol, the bronchial arteries and veins may
be injected from the pulmonary veins, and inversely, the pulmonary
veins from the bronchial arteries; but the bronchial vessels cannot be
filled from the pulmonary arteries.

In accordance with these facts, a participation in the interchange of
gases may be ascribed also to the finest bronchia', but, on account of the

THE LUNGS. 583

already somewhat inci'cased thickness of the epitheJium in them, and the
rather -wider capillary plexus, to a less extent than in the air-cells.
Here, also, wc might recall to mind the dilatation of the bronchial arte-
ries and extension of their zone of distribution, in cases Avhere the circu-
lation through the pulmonary arteries is interrupted [vide Virchow, in
his " Archiv." III., 3, p. 456), in -which cases the bronchial arteries
frequently -wholly replace branches of the pulmonary artery, and become
respiratory vessels; conditions ^Yhich, from the occurrence of numerous
normal anastomoses between the two vascular systems, it is not difficult
to explain.

§ 179. Development of the limgs. — In the Mammalia, the lungs ap-
pear a little after the liver, in the form of two hollow protrusions of the
anterior wall of the phar?/nx, which are in close apposition, and soon
become furnished with 'a common peduncle — the rudiment of the larynx
and trachea — and in the composition of -v\'hich the epithelial tube and
the fibrous membrane of the intestine take an equal share.

In the further course of development, there springs from the extre-
mities of the original protrusions, a continually increasing number of
arborescent processes, which differ entirely from what may be observed
in most other glands. From their first formation they are always hollow,
and in the sixth month the air-cells are developed from their invariably
clavate, dilated extremities. During this growth of the glandular ele-
ments, the interior epithelium extends itself by spontaneous multiplica-
tion of its cylindrical cells (probably by division), whilst, at the same
time, the fibrous layer surrounding them also grows, and finally consti-
tutes the fibrous membrane of the hronchice and air-cells, together with
the vessels and nerves. In the second month, in the human embryo,
the large pulmonary lobes are already formed, and besides them, smaller
divisions also, 0*1G of a line in size, may be recognized, originating in
the dilated extremities of the hronchice, which, even at this time, are
considerably ramified. As development proceeds and the ramifications
of the hronchice are multiplied, these gland-granules, as I have termed
them, become more and more numerous, and ultimately, in the fifth
month, are aggregated so as to form smaller lobules, of 0-24-0'48 of a
line in size, each of -which, in all probability, is produced from a single
gland-granule, or bronchial termination of the second month. Each of
the gland-granules of these lobules, which correspond with the secondary
lobules of the future lung, by continued budding, finally constitutes a
primary lohule, which, -with air-cells of 0-025-0-3 of a line in size, first
becomes distinctly visible in the sixth month, althougli, up to the time
of birth, new alveoli are constantly superadded [vide "Mikr. Anat."
II. 2, p. 323). In the new-born child the secondary lobules measure
2-3-4 lines ; the alveoli, before they are filled with air, 0-03, and after

584 SPECIAL HISTOLOGY.

the first inspiration, 0-03-0-04-0-06 of a line ; the latter, at this time,
?.ppear to exist in the same number as in the adult, the further increase
of the lungs proceeding only from the expansion of all its parts.

[The '^tliological changes occurring in the tissue of the lung are
numerous. An atro'pliy of the parenchyma takes place in old age and
in emphysema. In the former, a thinning of the walls of the air-cells,
and a partial obliteration of the capillaries exists. In emphysema the
alveoli of the cells are enlarged, but the walls much attenuated; some-
times their rupture ensues and a communication between the sepa-
rate cells is established. Hypertrophy of the air-cells, with enlarge-
ment of the capillaries, is observed in the hypertrophy of the lung
which occurs from increased functional action. Obliteration of the air-
cells is mostly caused by exudation or deposit into the air-vesicles or
the interstitial tissue. In pneumonia this exudation occurs mainly
into the alveoli, sometimes, however, into the walls of the cell, the
interstitial, or even into the interlobular tissue (interlobular pneumonia).
The granular appearance of red hepatization is owing to a complete ex-
pansion of the air-cells by the plastic exudation. In gray hepatization
the walls of the cells and the interstitial tissue become softened, and
undergo a fatty metamorphosis.

Deposits of pigmeiit occur as a consequence of hepatization, or from
a simple congestion of the lung. The pigment is found in the inter-
stitial tissue, and sometimes exists in sufficient quantity to compress
the air-vesicles and produce their atrophy. It is formed either from
the coloring matter of the blood, or else by the blood corpuscles break-
ing up into distinct pigment-cells and granules (Virchow). Tubercle
is most generally deposited in the air-cells ; cancer more frequently in
the interstitial tissue.

Effusions of serum, or of blood, occur cither into the interstitial
tissue, or into the air-vesicles. In oedema the effused serum has its
seat in the air-cells, whilst in apoplexy of the lung, the blood is effused
in the interstitial tissue. K fatty degeneration of the epithelial cells is
observed in portions of lung, compressed by a pleuritic effusion, in ate-
lectasis (Reinhardt), and in splenization. Accidental formations (bone,
cartilage) and cysts have their seats generally in the interstitial tissue.
Destruction of the parenchyma of the lung is the result of inflammation,
gangrene, tubercle, or cancer. A microscopical examination of the de-
stroyed parts shows them to be infiltrated with fine fatty molecules; the
elastic elements of the air-cells are generally found well preserved. — DaC]

The investigation of the lungs presents no real difficulty, except in
one point ; that is, with respect to the relation of the pulmonary cells
to the terminations of the hronchice, but here the difficulties are very

THE THYROID GLAND. 585

considerable. In recent preparations it is obvious that the air-cells
communicate in many Avays, and in any case, that they are not merely
terminal on the extremities of the h'oncliia'. If it be desired to investi-
gate the Avhole subject, inflated and dried lungs (it is better in an
inflated lung to tie off an end and dry it by itself), or corroded prepara-
tions, or lungs injected "with uncolored substances (wax and resin) are
most suitable, and with such, a definite result will be obtained, after a
series of observations.

Before the injection of the hronehice is proceeded with, the air must
be exhausted in the air-pump, for which purpose, also, though less con-
veniently, a well-fitted syringe may be employed. The injection of the
bloodvessels is readily effected and the preparations should be kept
wet ; sometimes, when injected with opaque material, sometimes, follow-
ing the processes of Schroder and Ilarting, with transparent substances
(Prussian blue, &c.), dried preparations are to be preferred. The air-
cells and bronchice, the larynx and trachea, are readily examined. The
epithelium of the air-cells is obtained in large quantity in every section
through the luncr, as well as ciliated cells. If it be wished to study the
alveoli, the air must previously be carefully removed. These are best
displayed in Man, in whom, also, all the other parts, such as cartilage,
elastic elements, muscles, and glands, are easily obtainable.

Literature. — M. Malpighi, "De pulmonibus epistoloe II adBorellum."
Bonon. 1G61 ; F. D. Beisseisen, " Ueber den Bau der Lungen, eine
gekronte Preisschrift," Berlin, 1822; [Magendie, " Mdm sur la struc-
ture du poumon, in ' Journ. de Phys. exper. ;' " Rainey, " On the minute
structure of the lungs," Philosoph. Transact. 1845;] J. Moleschott, "De
Malpighianis pulmonum vesiculis," Ileidl. 1815, Diss, and, " Uebcr die
letzten Endigungen der feinsten Bronchien," in the Ilollandischen
Beitrtigen, I. p. 7 ; Bossignol, " Recherches sur la structure intime du
Poumon, Brux.," 184G ; A. Adrian!, " De subtiliori pulmonum struc-
tura." Trajecti ad Rhen. 1847, Diss.; Kostlin, " Zur normalem und
patholog. Anatomic der Lungen," in Gries. " Archiv," 1848, Heft. IV.
p. 282, and 1849, Heft II. p. 167 ; E. Schultz, " Disquisitiones de struc-
tura et textura canaliura aeriferorum," cum tab., DorpatiLiv. 1850.
Dissert.

OF THE THYEOID GLAND.

§ 180. The thi/roid gland, or body [glandula thyroidea), is a so-termed
"ductless gland," which in its external aspect much resembles the race-
mose glands, seeing that its round, closed gland-vesicles, ^\-.Ja of a line
in size, are surrounded by a fibrous stroma and subdivided into rounded
or elongated, often slightly polygonal lobules, \-^ of a line in size, —
the gland- granules of authors ; — and these again are associated into
larger, though not completely separated, lobes, out of which the main

586

SPECIAL HISTOLOGY.

divisions of the organ are then constituted; these have special, and
indeed thicker coats, with which, histly, a fibrous membrane investing
the whole organ is conjoined,

§ 181. With respect to its intimate structure, there is not much to
be said about the fibrous tissue or stroma of the thyroid gland, inasmuch
as it consists of common interlaced bundles of connective tissue, inter-
mixed with fine clastic fibres and also, on the surface, contains a certain
quantity of fat-cells. The gland vesicles themselves, in Man, present
such varied conditions of structure, that it is not easy to say what is
their normal state. According to what I have observed in Man and
also in animals, I must, with regard to this point, declare that, analo-
gous to the true gland vesicles, for instance, of the mucous glands, they
consist of a membrana propria, an epithelium, and fluid contents. The
membrane is quite homogeneous, transparent, and delicate, 0-0008 of a
line thick ; and, like all membranes of the sort, is rendered more distinct
by caustic alkalies, in which it swells up. On its inner surface lies a
single layer of epithelium, composed of polygonal, finely granular, trans-
parent cells of 0-004:-0-006 of a line, with simple nuclei ; whilst the
space surrounded by these cells is occupied with a clear, somewhat vis-
cous fluid, with a tinge of yellow
in its color, the behavior of which
towards alcohol and nitric acid
and when the gland is boiled,
clearly manifests the presence of
much albumen. This is the cha-
racter of the contents in the healthy
thyroid gland of Man, particularly
in children ; if the organ, how-
ever, is but very little altered,
conditions, in many respects dif-
ferent, are presented. Very fre-
quently, instead of a regular
epithelium, nothing is met with
but a fluid mixed with minute, clearer or darker granules and free
nuclei : althoue-h I am ifrnorant whether this condition of the contents
does not take place till after death, or whether it is to be regarded as
abnormal. For we so frequently observe, in the granular fluid, a greater
or less number of the same cells, Avhich at other times exist as epithe-
lium, often pale and as if half dissolved, that it is impossible to avoid
the conclusion, that in these cells we have an instance of that post-mor-
tem decomposition, so frequently observed in the human subject. On
the other hand, the pathological nature of the change in the thyroid

Fig. 240. — Some gland-vesicles from the thyroid gland of a Child, magnified 250 diam. :
a, connective tissue between them; h, membrane of the gland-vesicles; c, their cpithditim.

THE THYROID GLAND.

587

body and its vesicles, termed colloid, cannot bo <loubtcd, althougb this
morbid condition is so frequent, in certain minor degrees, that many
authors enumerate it under the physiological occurrences. In this de-
generation, there is deposited in the gland vesicles, ^vhich increase in
size at the same time, the
colloid substance, which also
occurs in other situations, in
the form of transparent, amor-
phous, light yellowish, soft,
solid, masses, by which they

are more or less filled. In the
lesser degrees of this change,
the vesicles are but little en-
larged, to as much as 0-05 of
a line in a transverse section,
presenting the appearance
of transparent yellowish-white
spots or granules, which have
been very aptly compared, by Eckcr, with boiled sago, and otherwise
retaining the usual structure. In a higher degree, the vesicles contain-
ing colloid are transformed into larger cysts, of -/0-2 of ^ Yi'aa, in which
the epithelium is rarely any longer distinct, but, together with the ab-
normal contents, rounded, pale cells, filled with colloid matter or gra-
nules, and nuclei, may occur ; these cysts compress the stroma and
ultimately, owing to a partial absorption of the walls, coalesce into still
larger sinuous cavities, the contents of which are afterwards frequently
altered in various ways, by extravasations and their metataorphoses.
In Mammalia and Birds, the thyroid body also occasionally contains
gland-vesicles slightly distended with colloid matter.

The bloodvessels of the thyroid gland are, as is well known, dispro-
portionately numerous, but in their coarser ramifications present nothing
worthy of remark. Each gland-vesicle is pi'ovided with some smaller
arteries, the subordinate branches of which are distributed and sub-
divided in the stroma between the vesicles, finallv constituting around

' t/ CD

each of them a delicate capillary plexus, with rounded-angular and
elonirated meshes of 0-008-0-016 of a line, and vessels of 0-00o-0-005
of a line, resembling that of the air-cells, except that the interstices are
wider. From this plexus the veiiis arise, which, in their further course,
only partially accompany the arteries, which they much exceed; in
number. Li/mj^hatics also occur in considerable number in the thyroid
gland; the relations of which, however, in the interior, are unknown.
The few nerves, lastly, are only vascular nerves, and are derived from
the cervical portions of the sympathetic.

Fig. 211. — Gland-vesicles of tlic tliyroul gland, filled witli colloid matter, magnified 00
diameters.

588 SPECIAL HISTOLOGY.

Ecker distinguishes the struma, which is by far the most frequent
degeneration of the thj^roid, into a vascular and a glandular. In the
latter, the above-described changes of the gland-vesicles take place,
"whilst in the vascular struma, which is not regarded by Rokitansky as
a special form, besides a hypersemiated condition, numerous aneurismal
dilatations of the smaller vessels, for the most part of those 0-030-0-040
of a line in size, which Ecker looks upon as arteries and larger capilla-
ries, are met with. From the bursting of these dilatations, apoplectic
cysts, of various sizes, subsequently ensue, wliich may exhibit phases of
the most various kinds, as the blood undergoes changes of one kind or
another ; fresh extravasations, and also exudations, are superadded, and
even normal tissue becomes involved in them. In vascular struma,
Ecker also very frequently met with a cretijication of the vessels, con-
sisting in the deposition of numerous scattered calcareous particles in
the walls of the smaller and smallest, dilated or normal vessels, so that
they appeared quite white ; and when the affection had advanced to the
highest stage, were obliterated and became concretions. In a certain
form of scrofula, Rokitansky describes an liypertrophy of the thyroid
gland, due to a multiplication of the normal glandular elements, taking
place by the production of new gland-vesicles, sometimes independent,
sometimes occurring in enlarged gland-vesicles, in growths inwards of
their walls.

According to Reraak, the thyroid body is developed by the constric-
tion of a portion of the anterior wall of the pliarynx, and the division
of this into two halves. In a human embryo, at the third month, I
found that the thyroid body was already composed of isolated vesicles
0"01G-0'05 of a line in size, consisting of a homogeneous envelop and
rounded-angular cells in the interior, and I think I perceived that this
follicle was multiplied by the formation of rounded buds and their sepa-
ration by constriction. If this really be the case, the entire develop-
ment, probably, of the thyroid gland would have to be regarded as a
continued growth and division of the glandular follicles, of which the
fission of the primary vesicular rudiment, observed by Remak, would be
merely the first phase. In this respect, also, a certain resemblance
with the thymus would be established, only that in the latter, both the
buds of the primary rudiment, as well as the later ones, are not de-
tached, but all remain in connection. The follicles of the thyroid
gland, therefore, would not be any kind of enlarged cells, and still less
metamorphosed nuclei (Rokitansky), but be equivalent to true gland-
follicles.

The investigation of the vesicles of the thyroid gland has mainly been
pursued in animals, especially in Birds, Amphibia, and in children;
and sections obtained by means of the double-bladed knife, or glands
that have been hardened, are most suitable for the purpose of studying

THE THYMUS. 589

the vesicles in detail, and in their mutual relations ; but the same object
may also be attained by minute dissection, and the teasing out of the
structure. Injections are very easily made and run very finely in
children ; they best exhibit the plexuses around the vesicles, in sections
taken from the surface.

Literature. — Schwagcr-Bardelcben, " Obs. micr. dc glandularum
ductu excret. carentium structura," Berol. 1841, Diss. ; Panagiotides
and K. Wagener, "Einige Beobachtungen liber die Schilddriise," in
Froriep's "N. Notiz." Bd. XL., p. 193; and Panagiotides, " De gland,
thyreoideai structura penitiori," Diss. Berol., 18-17; A. Ecker, "Vcr-
such einer Anatomic der primitiven Formen des Kropfes, &c.," in
"Henle and Pfeuffer's Zeitschrift," f. rat. Med. VI., Bd., p. 123, and
Article " Blood-vascular glands," in AYagner's " Handw. d. Physiol."
III. ; Rokitansk}^, in " Zeitsch. d. Wiener Aerzte," 1847, and " Zur
Anatomie des Kropfes," in " Denkschriften der kaiserl. Akad. zu
Wien," Bd. I., Wien, 1849.

OF THE THYMUS.

§ 182. The internal thoracic gland or tJiT/mus, also one of the so-
termed blood-vascular glands, is a bilobate, elongated, flattened organ,
broad inferiorly, invested and united to the surrounding parts by a lax
connective tissue. Larger lobules, measuring on the average 2-5 lines,
and of a rounded, oval, or pyriform shape, though for the most part
flattened figure, arc very distinctly apparent, even on superficial in-
spection ; these, although pretty closely approximated, are still united
merely by a yielding connective tissue, and may be separated without
difliculty. If these lobules be traced from without inwards, it is easily
perceived that they have no further mutual connection, although they
are invariably attached by a more slender portion, to a canal, which
traverses the interior of the gland, and is, in general, spirallj' convo-
luted, though not quite regularly so. When this canal, normally J-1^
lines in diameter, is opened, there are found on its inner surface a great
number of oval fissures or apertures, each of which leads to a lobule and
constitutes the outlet of a cavity contained in it. The resemblance of
this canal of the thymns a"nd of the closely approximated lobules open-
ing into it, to the excretory duct and the lobules of a true gland, is still
further heightened by the circumstance, that the lobules are composed
of smaller, also hollow subdivisions and the latter of rounded cor-
puscles, 1-5-1-3 of a line in size, like gland-vesicles, the gland- granules
[acini of authors), which may be recognized even on the exterior, and,
from their polygonal shape, give the surface of the lobules a delicate
mosaic aspect, not unlike that of the lungs. These gland-granules,
however, are not vesicles at all, such as the air-cells, which, among the

590

SPECIAL HISTOLOGY.

elements of the true glands, approach nearest to them in size, but solid
bodies, which, towards the cavity of the lobules or its accessory cavities,
are intimately coherent, whilst on the outer side they are separated

Fi-. 242

243.

^^^Mim^-

from each other. Each lobule may also be regarded as a thick-M^alled
vesicle, with protrusions, whose inner surface is even and continuous,
whilst the outer is subdivided into the above-mentioned gland-granules,
by more or less deep fissures.

In many cases, a condition different from that just described is met
with, inasmuch as, instead of a contracted canal, into which the cavities
of the gland-lobules open, each thymus contains a larger though con-
tracted cavity, i-1 inch wide, with which the gland-lobules communi-
cate by larger fissure-like openings. Many anatomists, and among the
more modern, particularly Sir A. Cooper, consider the existence of this
cavity as normal ; whilst others, at the head of whom is Simon, are dis-
posed to regard it as produced by the methods of investigation employed

Fig. 242. — Portion of the thymus of a Calf, unfolded : a, main canal ; b, glandular lobules ;
c, isolated gland-granules, seated upon tlie main canal. Natural size.

Fig. 243. — Half of the human thymus, with a large cavity in the inferior wide portion
and numerous orifices leading into the lobules.

THE THYMUS.

591

(injections, inflation). I believe that Simon is correct, when he asserts
that in such a (.lelicatc structure as the tJi?/mus, injection or inflation,
unless efl'ectcd with the greatest care, necessarily leads to error, and I am
also satisfied, that many of the observed " reservoirs" in the thi/mus
are only artificially produced ; but, nevertheless, I am of opinion, that
there really are thymus glands, containing, in "life, a central cavity
because I have seen such cavities extending through the entire thi/mus
or only through separate segments of it, and this in cases Avhere no pre-
paration of any kind or injection had been used. I look upon the oc-
currence of a narrow central canal, as the original and usual condition,
but believe, that in certain cases it may be expanded by a more abun-
dant formation of the secretion, and ultimately be converted into a large
cavity.

§ 183. Intimate structure of tlie thymus. — "When a lobule is stripped
of its investing coat, consisting of common connective tissue, with fine
elastic fibres of the finer sort and fre-
quently with scattered fat-cells, its ex- Pi^ 244
ternal surface, fissured in correspon-
dence with the separate gland-granules,

comes into view. Under stroncj mag-

nifjnng powers, there is now presented
a very thin (0-0005-0-001 of a line),
indistinctly fibrous, or almost homo-
geneous membrane, quite correctly de-
scribed by Simon, which is continuous
over an entire lobule or even the whole
gland, and must be placed in the same
category with the wall of the follicles
in Peyer's patches, the tonsils, &c.
Within this envelop, between it and
the cavity of the lobule, lies a grayish-
white, soft, easily lacerable substance,
^-J of a line thick, which, when ex-
amined microscopically, appears to consist of nothing but free nuclei
and minute cells, and on this account has, by agreement of all obser-
vers, hitherto been regarded as the secretion of the supposed gland-
vesicles. But this substance cannot be washed away, which would have
been the case had it lain loosely in the space enclosed by the delicate
membrane ; on the contrary, it exhibits a considerable degree of tough-
ness and resistance. AVhen examined more closely, it is, by degrees,

Fig. 244. — Transverse section tliroujih the summit of an injected lobule of the thymus in
a Child, magnified SOdiarn.: a, membrane of the lobule ; 6, membrane of the gland-granules;
c, cavity of the lobule from which the larger vessels branch out into the granules, on the
surface of which they terminate, occasionally forming loops.

592 SPECIAL HISTOLOGY.

apparent that other elements, to some extent of quite an unexpected
kind, enter into its composition ; as for instance, bloodvessels, and also
a smaller quantity of o, fibrous substance of the nature of connective tis-
sue, so that a structure not unlike that of the contents of the Peyerian
follicles is presented. «

Of the elements of the walls of the thymus-lobules, the vesicular,
together with a small quantity of a connecting fluid, constitute the main
bulk. Among these, free nuclei 0-002-0-005 of a line in size, of a
round slightly flattened shape, with homogeneous, clear contents, which
become troubled and granular in soda and acetic acid and with or with-
out a nucleolus, are always present in very great numbers. Secondly,
as I find, agreeing with Ecker but in opposition to Simon, cells also are
never wanting, though existing of very various sizes, from 0-004 to O'Ol
of a line, and, though varying in number as well, still much less nu-
merous than the nuclei. Their nuclei are for the most part simple and
distinct, and the contents pale or with scattered fat-granules, or, and
this Ecker says that he has noticed after the complete development of
the organ, they are without nuclei and entirely fxlled with fat. In the
midst of these elements run numerous bloodvessels of larger and smaller
size. The main trunks running on the outer aspect and close upon the
central cavity in the longitudinal direction of the organ, give off a large
number of branches to the central cavity, which, penetrating its walls,
reach its internal surface, and there ramify minutely in a delicate pelli-
cle, composed of connective tissue, with which it is lined, anastomosing
and also forming tolerably close capillary plexuses. From these arterial
plexuses, at every point where the lobules open, numerous vessels arise
and enter them, taking their course in the innermost portion of the
thick boundary wall, and then ramify towards the exterior-in the sepa-
rate gland-granules, so as to constitute a capillary plexus entirely filling
them, composed of vessels 0-003-0*005 of a line in diameter, and with
meshes of 0-01-0-02 of a line (Fig. 244). The distribution of these
vessels, in Man, is so limited to the interior of the gland-granules, that,
even when these have been most completely displayed, not a single vessel
is found on the outer aspect of their structureless investing membrane ;
on the contrary they are all seen terminating in loops close upon it.
Besides these bloodvessels a small quantity of connective tissue also ap-
pears to enter into the formation of the thick walls of the glandular
lobes ; at all events, in their innermost portions, where the larger
vessels are situated, we find, often with tolerable distinctness, a mem-
brane supporting them, analogous to that lining the central cavity. In
other cases, however, and especially in animals, an internal limitary
membrane of this kind cannot be demonstrated, and the cavities of the
lobules are bounded immediately by the granular substance connecting
the vessels, between which, only some delicate indications of fibres are

THE THYMUS. 593

apparent. In no case does there exist any epithcliura lining the cavi-
ties and consequently, the comparison of the innermost part of their wall
with a mucous membrane is untenable.

The common cavity or central canal of the thymus, presents the same
structure as the lobules, except that externally there is a thicker fibrous
layer, and internally a less thick granular stratum, with rather larger
vessels. In a fully developed thymus it, as well as all the secondary cavi-
ties, contains a grayish-white or milky, faintly acidj^itz't?, often in large
quantity, in which, together with a clear fluid abounding in albumen,
numerous nuclei, isolated cells and, under certain circumstances, also
concentrical corpuscles [vide infra) are contained. The lymphatics of
the thymus are numerous and nerves may be readily demonstrated upon
the arteries, although they cannot be traced as far as their terminations.

Besides the above-described normal elements, there occur, especially
at the period of involution of the organ, other peculiar spherical struc-
tures, which, with Ecker, I would terra the concentric corpuscles of the
thymus. They present very various forms, which, however, it seems to
me may conveniently be reduced to two ; viz. 1, simple, O'OOG-0'01 of
a line in size, with a thick concentrically striated membrane and agranu-
lar substance in the interior, sometimes appearing like a nucleus, some-
times as a cell; and 2, compound, as much as 0-01 or even 0-08 of a
line in size, and consisting of several simple corpuscles, surrounded by
a common laminated envelop. These bodies, which were first noticed
by Hassall and Virchow, and were further investigated by Ecker and
Bruch, it appears to me arise not from a direct metamorphosis of the
nuclei and cells in the wall of the glandular lobule, but from the succes-
sive deposition of an amorphous material around them ; and conse-
quently that they are analogous in their mode of formation to the cor-
puscula amylacea of the brain, the prostatic concretions, &;c. The lami-
nated portion consists of a substance certainly not of a fatty nature
which ofi"ers considerable resistance to alkalies, approaching the colloid
substance and the substance of the prostatic concretions and corpuscula
amylacea, being probably formed from a change in the albumen in the
glandular walls. The situation of these concentric corpuscles is ex-
ternal to the secretion of the thymus, and principally in the innermost
part of the glandular parietes, where the larger vessels occur.*

§ 184. Development of the Thymus. — According to Remak, the thymus
of the Chicken originates in the separation, by constriction, of the bor-
ders of the last two (third and fourth) branchial fissures, which arc lined

* [Wliatever may be the true nature of the Hassallian corpuscles, tlicy do not seem to be
an essential element of the thymus or its secretion, as they are not found in that body in
Fishes (Skate, Ray, Sturgeon, Zeus faber) ; although present in the Reptilia. Leydig, '• Anat.
histol. Untersuchung. Q. Fische iind Reptilien," pp. 21 and GG. — Tks.]

38

594 SPECIAL HISTOLOGY.

by the intestinal epithelium ; and at the period when the last three aortic
arches become detached from the walls of the loliarynx, these follow
them, and eventually lie as two elongated sacculi, on each side, between
them.

In the earliest state observed in Mammalia, e. g., in the foetal Calf, 1
line long, according to Bischoff the gland represents two delicate tracts
of blastema^ which descend from the larynx as far as the thorax and ap-
pear to be connected above with the thyroid body. Simon gives a simi-
lar description of the thymus in the foetal Calf and Swine, l-l^- inches
long, except that he makes no mention of any connection with the thy-
roid body, figuring the tract as a tube bounded by a delicate structure-
less membrane and filled with nuclei and a granular substance, which is
further developed by becoming thicker and longer, whilst at the same
time it pushes out, at fi.rst, simple and afterwards, more and more widely
ramifying buds. Thus in foetal calves, 2^-3 inches long, wart-like and
spherical, in part even shortly pedunculated offsets already existed,
"svhich subsequently increased in number, becoming produced, at first into
two and four and afterwards, successively, into still more globular bodies,
until ultimately the lobules were completed. In this way the primitive
tube would be converted into the central cavity of the tliymus and eacb
offset of it, in course of time, into nn entire lobule of the organ. In
the human subject, as early as in the seventh week, I have seen the
thymus lobate at the lower end and single above. In an embryo ten
•weeks old, the upper extremity was a delicate walled tube, 0-04-0'06 of
a line in diameter, filled with polygonal cells ; the lower portion, 0-16 of
a line thick, presented several rounded outgrowths, in part isolated, in
part grouped, to the number of from two to five together. The thicker,
inferior portion of the gland, was entirely covered with further developed
lobules 0-08-0-1 of a line in size, of which, again, more simple gland-
granules, each with a structureless membrane and contained cells, w^ere
visible. In the twelfth week I found the thymus not much larger, but
the horns broader, and, like the rest of the organ, covered with lobules
0-12-0-24 of a line in size. From this, although the first stages have
not yet been observed in Man, there can be no doubt that the mode of
development is the same as that observed by Simon in other Mammalia.

The later development of the thymus affords other interesting con-
ditions. In the embryo it continues to grow slowly from the third
month; in the sixth it extends as far as to the thyroid gland; and
from and after the seventh month begins to contain a whitish secretion.
After birth it is not stationary, as was formerly believed, but usually
continues to grow until the second year, and, indeed, at first very con-
siderably. After that period its growth ceases, though it still usually
remains for some time longer unchanged, until ultimately it becomes
atrophied, and finally disappears. The period at which these changes

THE URINARY ORGANS. 595

take place varies very mucli. Simon places the commencement of the
atrophy between the eighth to the twelfth years, a statement which,
from my own observations, and in accordance with those of Ecker, I
cannot consider as universally correct ; because, up to the twentieth
year, the thymus is frequently met with in a good state of nutrition,
distended with fluid, without any fatty metamorphosis, and presenting
the same structure as in children. It is still more difficult to assign the
time of its complete disappearance, for which no determinate age can
be indicated, although it is true that the thymus is usually not to be
found after the fortieth year. The disappearance takes place in con-
sequence of a gradual absorption, with a simultaneous development of
fat in the gland-granules, and of fat-cells in the interlobula'r connective
tissue. At the same time, also, the concentric corpuscles multiply
more and more, and ultimately, according to Ecker, even connective
tissue is developed in the lobules, the glandular structure being com-
pletely lost.

The investigation of the thymus is not easy. I recommend, in the
first place, boiled preparations, Avhich of themselves are very well
adapted for the investigation of the connection of the lobes wuth the
central canal, and the cavities in the lobules, and when hardened in
spirit are convenient for the making of fine sections. Besides this, the
hardening of recent preparations in alcohol, pyroligneous and chromic
acid, and the boiling of them in acetic acid, are advisable. The thy-
mus, also, of small Mammalia, which is membranous at the edges, is
well adapted to afford a general knowledge. But, moreover, and above
all, are injections of the human thymus indispensably requisite, without
which no satisfactory conclusions can be arrived at.

Literature. — S. C. Lucae, " Anat. Untersuchung. d. Thymus im
Menschen und in Thieren," Frankfurt am M. 1811 u. 12, 4to, und
"Anat. Bemerk. iiber die Divertikel am Darm. u. die Hcihlen des
Thymus," Nurnb. 1813, 4to ; F. C. Haugsted, " Thymi in hom. et per
ser. animal descrip.," Hafn., 1832, 8vo ; A. Cooper, "Anatomy of the
Thymus Gland," Lond., 1832, 4to ; J. Simon, "A Physiological Essay
on the Thymus Gland," Lond., 1845, 4to ; Ecker, Art. " Blutgefiiss-
driisen," in Wagner's " Handw. der Phys." III.

OF THE URINARY ORGANS.

§ 185. The urinary organs consist of the two kidneys— trua glands,
having a tubular structure, which secrete the urine — and of the secre-
tory urinary passages, the ureters, bladder, and urethra.

§ 186. In the kidneys, are to be distinguished the coa^sand the secre-

596 SPECIAL HISTOLOGY.

ting parenchyma. To the former belong the adipose capsule, as it is
termed [capsula s. tunica adiposa), constituted of lax connective tissue
abounding in fat cells, scarcely deserving the name of a special mem-
brane, and the fibrous turiic [tunica propria s. albuginea), aih'm but strong
coat, of a whitish color, composed of common connective tissue and
numerous fine elastic networks, which closely invests the kidney, and, at
the Iiilus, is in apposition with the pelvis of the gland and the vessels,
but does not penetrate into the interior of the organ.

The secreting parenchi/tnay which is abruptly defined from the fibrous
membrane, consists, as seen by the naked eye, of tAvo portions, the
7neduUa7-g andihe cortical substance, the former of which constitutes 8-15,
isolated, conical, masses converging towards the liilus, the pyramids of
Malp)ighi ; whilst the latter forms the entire cortical part of the organ,
and moreover, sends processes between the separate pyramids which
extend as far as the lulus, — the columnce Bertini, — and is apparently
continuous throughout the gland. Examined microscopically, however,
the cortical substance is found to be divided into as many segments as
there are pyramids, and the kidneys, therefore, may be regarded as made
up of a certain number of large, though closely connected lobes.

§ 187. Composition of the Renal Substance. — ^Both portions of the kid-
neys consist, essentially, of the uriniferous canals {tubuli urinifcri),
cylindrical tubules, measuring, on the average, 0-016-0-025 of a line.
They commence in each renal lobe or segment, in those portions of the
pyramids which are surrounded by the calices renales, or on the renal
papilloe, by, on the average, from 200 to 500 orifices, O'024-O-l of a line
wide, scattered over the surface of those processes ; they traverse the
pyramids in nearly a straight line and in close contiguity, whence they
are termed in that situation, tubuli recti (or Belliniani) (Fig. 245 h).
In this course, each of the straight canals divides repeatedly, most usually
under very acute angles and at first with a considerable diminution of
size, either into two (Fig. 245 Z), or more rarely into three or four, so that,
ultimately, a complete bundle of finer tubules is produced from them ; and
in this Avay the continued increase in breadth of the pyramids towards
the exterior is accounted for. At the same time, towards the base of
the pyramids, the connection of the ducts of Bellini is rendered less
close, by the interpolation between them, at regular distances, of large
vascular bundles [arteriolce and venulce rectce), and they become sepa-
rated on all sides from each other, so that, in perpendicular sec-
tions, the pyramids (the papillx of course excepted) in the entire
circumference appear to spread out into numerous small bundles or
pencils — the 'pyramids of Ferrcin of authors — but which, as sections
across them show, are only to be regarded as separate, sharply-defined
fasciculi. The tubuli uriniferi, even here, assume a slightly undulating

THE URINARY ORGANS.

697

Fig. 245.

course, but this becomes much more manifest in the cortical substance,
where they constitute the convoluted iiriniferous tubules [tuhuli contorti
s. corticalcs), Avhich at first sight, appear to be inextricably and irregu-
larly interwoven, each terminating, ulti-
mately, as Bowman discovered in the
year 1842, in a vesicular, dilated ex-
tremity, O'06-O-Ol of a line in dia-
meter, containing a vascular plexus of
a peculiar kind — the so-called Mal-
pighian body. Upon more minute ob-
servation, however, it is easy to perceive
the convoluted tiibuli are arranged in
columnar masses, -J-^ of a line wide,
extendino; throu2;h the entire thick-
ness of the cortical substance and in
close apposition, which, notwithstand-
ing their incomplete limitation from
each other, may nevertheless be desig-
nated fasciculi corticalcs, or lohuli re-
num (or the "pyramids of Ferrein" of
the older anatomists). In these co-
lumns (Fig, 245), the tuhuli uriniferi
are disposed, in miniature, in the same
way as in a renal lobe, so that in their
interior, more especially at the peri-
phery, convoluted canals may be dis-
tinajuished. When the arrangement of
these parts is accurately investigated,
it is seen that the ducts of Bellini, en-
tering a cortical lobule in a fascicular
manner, at first run in perfectly straight
lines (Fig. 245 6). Soon, however,
some, and further on, more and more,
of the canals are curved laterally (Fig.
245 wi), in order to reach, in a ser-

FiG. 245. — Vertical section through a portion of a pyramid and the cortical substance
belonging to it, of an injected Rabbit's kidney. The figure is half-diagrammatic ; magnified
30 diam. The vessels are rspresented on the left side, and on the right the course of the
tubuli uriniferi : a, artericB intcrlobulares, with the glomeruli 3fnljngluani, b, and their vasa effe-
rentia : c, vasa efferentia ; rf, cortical capillaries ; c. vasa efferentia of the outermost corpuscles,
proceeding to the superficial capillaries ; f,vasa efferentia of the innermost glomeruli^ continu-
ous with the artoto/<F rec/ff, gg g' ; /i, capillaries of the pyramids which are formed out of
the latter ; t, a venula recta, commencing at the papilla .- k, commencement of a straight
canal at the papilla : I, divisions of the same ; wi, convoluted tubules in the cortex, their whole
course not shown ; n, the same at the surface of the gland; o, their continuation in the
straight tubules of the cortex :p, their connection with the Malpighian capsules.

598 SPECIAL HISTOLOGY.

pentine course, the arterial twigs surrounding the cortical lobules ; until,
at last, the entire bundle of tubules is broken up, at some distance frona
the surface of the kidney (or of the centre of the columnce Bertini),
into convoluted canaliculi. The Malpighian bodies (Fig. 245 b), from
"which the tuhuli uriniferi arise, are found throughout the entire thick-
ness of the cortical substance, from the pyramids to within g'?) of a line
from the surface, as well as in the septa Bertini, down to the sinus of
the kidney and are disposed so regularly and in such numbers, around
the cortical lobules, that every transverse section through the cortex
always displays a red streak, caused by these corpuscles, between each
two lobules. Usually each of these streaks consists of a minute artery,
with from two to four, of Malpighian bodies supported by it, but not in
regular series, some of which stand more in relation with the one, and
others with the other cortical bundle. Each fasciculus of tuhuli urini-
feri, therefore, upon entering the cortical substance, is, from the first
entirely encompassed by the Malpighian bodies, and it is obvious that
some of the tuhuli quit it soon and others later, in order to reach their
appropriate Malpighian bodies. For the rest, each cortical tubule, after
its origin, is much convoluted, runs at first somewhat outwardly, and
then returns upon itself, to join the straight tubules of the cortical
fasciculus.

The number of the convoluted tuhuli uriniferi corresponds with that
of the Malpighian bodies and is consequently, in every instance, very
considerable. According to Huschke, 200 tubuli exist in etich fasciculus
corticalis, and 700 such fascic^di in a pyramid ; which calculation gives,
in fifteen pyramids, more than two millions of commencements of tuhuli
and Malpighian bodies. Since each papilla has about 500 or even more
orifices, it is possible that each cortical fascic^dus proceeds from a single
"duct of Bellini;" in any case, it is evident that in every straight
tubule the divisions are repeated at least ten times.*

§ 188. The tuhuli uriniferi, are everywhere composed of the same
elements; viz. of a memhrana pi'ojyria, and a tessellated epithelimn. The
former is a perfectly structureless, transparent, thin (0'0004-0*0008
of a line), but proportionately strong and elastic coat, which, particu-
larly in the straight tubules, may be very easily isolated for a considera-
ble extent, when it is very prone to fall into folds, which often present
the striated aspect of connective tissue. On the inner surface of this

* [It would scarcely be deduced, from what is said in the text, that the tubidi uriniferi, in
the cortical part of the kidney, anastomose very freely and frequently, although the fact of
their doing so has been long well known and often described. These anastomoses, how-
ever, and the general disposition of the tubules, are more particularly adverted to and well
depicted by Toynbee (■' Med. Chir. Transact.," 2d ser., vol. XL p. 308, pi. 7).— Trs.]

THE UllINARY ORGANS.

599

coat, which in its chemical characters is very closely allied to the sarco-
Icmma [vid. § 58), lies a single layer of polygonal, moderately thick
cells, surrounding the cavity of the tubuhis, which, from the readiness
Avith which they alter, have given rise to many erroneous representations
respecting the structure of the urinary ducts and their contents. For
instance, in the usual mode of examination in water, they expand,
owing to its absorption and become vesicularly distended, so that their
polygonal form and regular arrangement are lost ; the renal ducts,
within the structureless membrane, appearing to be entirely filled Avith

rounded larger cells and no longer to possess any cavity. The cells,
also, frequently burst, in which case the tuhidl contain nothing but a
fine granular substance, with 7i2tclei and clear albuminous drops escaped
from the cells. In kidneys not quite fresh, these changes proceed
spontaneously ; and, therefore, it is, above all things, necessary to exa-
mine the organ as soon as possible after death and to avoid all additions
capable of producing change. The contents of the epithelium cells
are, besides round nuclei of the usual kind, a most usually, very finely-
granular substance, which, on the addition of water, affords clear, light-
yellowish drops, probably of albumen, but is not otherwise changed ;

Fig. 246. — Two straight tuljuli uriniferi of Man, one with perfect epithelium, the other
half empty: a, membmna propria ; b, epithelium.

Fig. 247. — 1, a Majpighian corpuscle, ^, with the tubuhis urini/erus springing from it,
B, C ; Human; magnified 300 diam.; figure half-diagrammatic: a, membrane of the Mal-
pighian boily, continuous at b, with the mcmbrana propria of the convoluted tubule; c, epi-
thelium of tlieMalpighian body; rf, that of the tubule; f, dftaehed epithelium ;/, i'a« affercns ;
g, vas efftrens; h, glomerulus Malpighianus. 2, three ci)ithelial cells from the convoluted
tubule, magnified 350 diam.; one with oil drops.

600 SPECIAL HISTOLOGY.

under acetic acid the contents, together with the cell-membrane, are
rendered pale, and soon dissolve ; whilst the nuclei at the same time
soon become pale, and finally, on the application of caustic alkalies,
disappear in the same manner as the membrane. Besides these gra-
nules, which I do not hesitate to declare are a protein substance, and
the albumen in solution in the contents, the cells very commonly contain
some dark oil-drops, and more rarely one or another, exhibits granules
of yellow pigment.

The straight and convoluted canals, together with the general cha-
racters just described, present some differences. The former, although
originally of the considerable width of even 0-06-0-1 of a line, soon
diminish, in consequence of the divisions they undergo, to a diameter of
0-01-0-014-0-018 of a line, but in the " bundles of Ferrein," again
acquire the size of 0-02-0-24 of a line. With this diameter they enter
the cortical substance, but subsequently, in the proper convoluted
tubules, attain one of 0-033 of a line, though again somewhat constricted
close to their commencement. The membrana jiropria in the convoluted
tubules is more delicate (0-0003-0-0004 of a line) and isolated with
more difficulty, the epithelium, on the contrary, is usually thicker, with
cells measuring 0-008-0-012 of a line in width, and 0-004-0-005 of a
line in thickness; whilst in the straight tubules the cells are not more
than 0'004-0-006 of a line wide, and 0*004 of a line thick. Physiolo-
gically, it also seems to me worthy of remark, that the last cells have
clear, non-granular contents, whence, also, the medullary substance, in
the bloodless condition, appears whitish, whilst the cortical exhibits a
yellowish hue.

The Malpighian bodies present a very peculiar structure. They are
to be regarded as appendages of the convoluted tuhiili uriniferi, and
contain imbedded in their epithelium, and, as it may be said, entirely
filling their cavity, a compact, rounded vascular plexus — the glomerulus
I\Ialpighianus, the structure of which will be afterwards described. The
same membrana propria, which surrounds the tuhuli uriniferi, also
somewhat thickened (0-0005-0-0008 of a line) invests these bodies (Fig.
247 a); and the epithelium is likewise continued into the capsules thus
formed, only that its cells are smaller and less distinct, and invest the
vascular coil on the side directed towards the canal of the emergent
[tubulus uriniferus. This latter, generally somewhat constricted (Fig.
247, B), is inserted into the Malpighian capsule, most usually on the
opposite side to the afferent and efferent vessels ; but in accordance with
what has been said, its cavity penetrates into the capsule, only to an
inconsiderable extent ; inasmuch as the latter is almost entirely occupied
by the vessels and the epithelium surrounding them.*

* [With respect to the question of the cereal termination, or commencement, as it miglit
more properly be termed, of the tubuli tirinifcri in the Malpighian capsules, there is an

THE URINARY ORGANS. COl

The ciliary motion discovered by Bowman in the neck of the Mal-
pighian bodies of the Frog, and in the commencement of the tubuli
urinifcri, with the direction of the stream towards the ureter, is readily
confirmed, when the addition of water is avoided. It is absent, how-
ever, in Birds (Gerlach tliinks he has seen it on one occasion in the
Fowl) and other Mammalia, and was not noticed by mc in the cases of
two executed criminals, examined especially with respect to this point,
whilst it is found in Serpents, in the Salamander, Triton, Bomhinator,
Bufo, and is very well marked in Fishes, and also, according to
Reraak's and my own observations, in the Wolffian bodies, which have
the structure of kidneys, in the embryo of the Lizard ; in the last two
instances they are also met with in the uriniferous ducts at a greater
distance from the Malpighian bodies.

Of the very numerous 'pathological degenerations of the tuhuli urini-
feri, I will notice only the following : The memhrana i^ropria is fre-
quently thickened to 0-001, or even 0-002 of a line, when it often
presents, on the inner aspect, very delicate, closely approximated trans-
verse stricc. The epithelial cells, particularly in the cortical substance,
frequently contain oil-drops in considerable quantity, so as often to
present a deceptive resemblance to the cells of a fatty liver, and at the
same time they are usually enlarged to a diameter of 0-02 of a line.
Together with the oil, pigment granules (of the coloring matter of
urine ?) occur in them (also in the straight canals), whereas the concre-
tions of uric acid and calcareous s-alts, which are so frequently met
with in the canals of the tubules in the Vertebrata have not as vet
been demonstrated w^ith certainty in the cells themselves (in Fishes,
Simon, " Tlii/mus," p. 69, often found crystals in the renal cells).
Colloid-like, bright yellow masses are frequent in the epithelial cells,
which then most usually increase in size, dilate into slender cysts as

apparent discrepancy of opinion among anatomists. Bowman states tliat each tube com-
mences in a Malpighian capsule ; whilst Gerlach says that the capsules do not form the
extremities of the nriniferous tubes, but are merely diverticula, which communicate by a
small neck with the angle formed by the uriniferous tubes, winding through the cortical
part of the kidneys; or, as the same thing is described by Leydig (1. c, p. 32), with respect
to the kidney of the Sturgeon, two closely contiguous, uriniferous tubules, are connected with
the (Malpighian) capsule and continuous with it; in other words, the tubules join in a loop,
at the apex of which is a globose diverticulum, in which the glomerulus is lodged ; and
according to liim, the same arrangement obtains in the Reptilia. Now it seems that this
discrepancy admits of an easy explanation, for if wo suppose the constricted neck of the
diverticulum to be lengthened into a tube, we have at once the disposition described by
Bowman, viz. : a tube commencing in a dilatation containing the glomerulus and afterwards
anastomosing with another or with other tubules; and if the neck of the so-called diverti-
culum be very short, or, in other words, if the Malpighian capsule be sessile, we have the
arrangement described by Gerlach, &c. Mr. Toynbee's notion that the tubulus uriniferus
merely passes through the Malpighian capsule, forming a coil within it, appears to us to be
wholly inadmissible; but many of the appearances depicted in his very carefully-executed
figures (1. c.) would serve to support the opinion that the Malpighian body is more often
sessile than it would seem to be from Bowman's account. — Trs.]

602 SPECIAL HISTOLOGY.

much as 0*05-0'072 of a line long, and finally, by bursting, empty
themselves of the colloid substance, Avhence the latter is found free in
the uriniferous ducts, and also in the urine. A development of the
epithelial cells into other cysts, as is stated to take place by J. Simon,
and also by Gildemeester (Tijdschr. d. Nederl. Maatsch. 1850) has not
yet occurred to my observation, whilst I have noticed, as did Johnson,
very distinctly, in an atrophied kidney, a partition of the convoluted
tubules into closed cysts, to all appearance by a connective tissue
developed between and constricting them. These cysts had the same
structure as the tubules, and were either of the same diameter, or dis-
tended into vesicles, 0-1 of a line in width. The Malpighian bodies
also may expand into cysts, in which, together with a clear fluid, the
atrophied glomerulus is often visible on the wall. As abnormal con-
tents, the tuhuli uriniferi present : 1, hlood, most frequently in the
commencement of the convoluted tubules, especially the superficial,
often in such quantity as to produce bloody points as big as a pin's
head, and visible to the naked eye, which were formerly erroneously
regarded as distended Malpighian bodies ; 2, fihrine, in cylindrical
masses, corresponding to the cavity of the tubules ; 3, the above-
mentioned colloid-like substance ; 4, concretions in the ducts of Bellini,
consisting, in the adult, chiefly of carbonate and phosphate of lime
{^^ Kalkinfarct")', in new-born infants, of uric acid-salts {'■'■ Harnsiiu-
reinfarct," Virchow), which give the pyramids a brilliant gold-yellow
color, and, if not exclusively, still usually occur only in children who
have already respired (between the third and twentieth day after birth).
In the later stages of " Bright's disease," many tuhuli, which have lost
their epithelium in consequence of the exudations poured out in them,
become atrophied, and ultimately disappear altogether, whilst groups of
others are seen, filled with a fatty, broken-up exudation, and dilated
into minute nodosities (granulations, Christison).

§ 189. Vessels and Nerves. — The large renal artery divides, in the
pelvis of the kidney, into a certain number of branches, which, after sup-
plying the parts lying in the hilus, enter, above and below the renal
veins, the cortical substance interposed between the pyramids (the
columnce Bertini). From this point they are continued, repeatedly
dividing, close upon the boundary of the two renal substances, so that
around each pyramid a delicate ramification, but without any anasto-
moses, usually afforded only by two large arteries, is formed. From
this ramification, on the side looking towards the cortical substance,
there arise, with great regularity, and for the most part at right angles,
smaller arteries, which after a few or more repeated divisions give off
fine twigs, O'06-O'l of a line in diameter, which run outwardly in a
straight course between the cortical fasciculi or lobules, and are most

THE URINARY ORGANS.

603

fitly termed arterice interlobular es (Fig. 245 a). It is these twigs ■which
support the Malpighiau bodies, and, "with the exception of some branches
to the coats of the organ, they terminate excliisivdij in the format ion of
their vascular coils. In fact, each interlobuhxr artery gives off, in its
■whole length, on two, three, or four sides, a great number of fine twigs
possessing the structure of arteries and 0*008-0'02 of a line in diameter,

Fis. 248

V.

Fis. 249.

"VN-hich, after running a short distance, either directly or after dividing
once, penetrate the tunic of the Malpighian body, becoming the vasa
afferentia of its vascular coil. Each of these (Fig. 247, 248) consists
of a close convolution of fine vessels 0-004-0-008 of a line in diameter,
having the usual structure of capillaries (structureless coat and nuclei)
and possesses, besides the afferent artery, an efferent vessel, the vas
efferens. The mode in which these two vessels are connected is not
that which usually obtains in arteries and veins, but corresponds with

Fig. 248. — From the Human kidney, after Bowman: a, extremity of an interlobular
artery; b, afferent arteries; c, naked glomerulus ; rf, efferent vessel; e, glomeruli, surrounded
by the Malpighian capsules; /, tubtdi urinifcri springing from them. — ^Magnified 45
diameters.

Fig. 240. — Glomerulus from the innermost part of the cortex of the kidney of tlie Horse,
after Bowman: a, arler.iyiterlobtilaris ; af, vas affercns ; m vi, glomerulus; ef, vas efferens s.
arteriola recta ; 6, divisions of the same in the medullary substance. — Magnified 70 diameters.

604 SPECIAL HISTOLOGY.

the arrangement presented in the bipolar retia mirahilia, as they are
termed; the vas afferens, immediately after its entrance into the coil,
dividing into 5-8 branches and each of tliese into a bundle of capillaries,
which are much convoluted and interlaced, without anastomosing, and
ultimately, in the same way as that in which they were formed, reunite
into a single trunk. Usually the two main vessels enter and quit the
glomerulus near together, opposite the origin of the urinifero us duct,
and its finest vessels of 0-003-0.004 of a line, the peripheral loops as it
were, are invariably situated exactly at the commencement of the duct.
In Birds, Amphibia, and Fishes, each glomerulus consists of a single con-
voluted vessel.

The vasa efferentia, although composed of capillaries, are not veins,
but in their nature, and to some extent in their structure, minute arte-
ries, a character that they retain until, in their further course, they are
merged in the capillary plexus of the kidney. This plexus exists in the
cortical substance and in the pyramids, presenting somewhat different
characters in these two situations. In the former (Fig. 245, c^) the
vasa efferentia 0-004-0-008 of a line in size, after a short course, ter-
minate in a very rich plexus of capillaries 0-002-0-004-0-006 of a line
in diameter, the rounded-angular meshes of which, 0-005-0-015 of a
line wide, encompass the convoluted tuhuli on all sides and must be re-
garded as continuous throughout the whole cortical substance. The
efferent vessels of the glomeruli in nearest contiguit}'- to the Malpighian
pyramids alone present an exception to this condition, inasmuch as,
characterized by their more considerable size (0-01-0-016 of a line),
they are distributed not in the cortical substance, but in the pyramids,
and are distinguished by their long, straight course, and upon the whole,
scanty ramifications. These vessels (Fig. 245 g), which, with Arnold,
I would term arteriolce recat, penetrate around the entire circumference
of the pyramids, in a straight course, between the ducts of Bellini, and
descend, repeatedly dividing at acute angles, and gradually attenuated
to the diameter of 0-004-0-01 of a line, towards the pajnllce, in which, as
in the interior of the medullary substance (in the latter situation, either
by their extremities or by twigs given off at right angles), they are con-
tinuous with the capillaries in those regions, measuring from 0*002 to
0-004 of a line. These capillaries are very importantly distinguished
from those of the cortical substance by their less number and the elon-
gated figure of the meshes of the plexus which they form, although at
the boundary of the pyramids the two sets are continuous v/itli each
other. The renal veins commence in two situations, viz., at the sur-
face of the organ and at the apices of the papilla). In that situation,
minute venous radicles collect together from the outermost portions of
the capillary plexus of the cortical substance, which either regularly
surround each cortical lobule, and between them unite in a stellate

THE URINARY ORGANS. 605

manner {steUiilce Vcrheynii) into somc>Yliat larger roots, or, extending
over several or numerous lobules, collect into larger trunks. These two
sets of veins, forming the vena' interlobidan's, then penetrate more
deeply in company ^vith the arteries of the same name, between the
cortical fasciculi, where they arc enlarged by the accession of nume-
rous other venous radicles from the interior of the cortical substance,
and proceed to join the larger veins, either directly or united into some-
Avhat larger trunks, and for the most part at right angles. These lie,
together with the larger arteries, around the periphery of the pyramids,
ultimately opening into large veins without valves, as are all the renal
veins, and which lying singly close to the arteries, quit the kidney in
the same way. Previously to this, however, besides those of the columnce
Bertini, they receive the veins of the lyyramids, which commence in a
beautiful plexus surrounding the orifices of the tuhuli urinifcri on the
papillce, and ascend between the tuhuli recti, being strengthened by ad-
ditional radicles ; these united with the arteries of the pyramids, the
vasa efferentia of the innermost glomeruli or the arteriolce rectcc, into
larger vascular bundles, ]y'mg between the "pyramids of Ferrein,"
open into the arched, wider, venous ramification which encompasses the
pyramids.

The vessels of the membranes of the kidney, arise in part from the
art. renalis, before it enters the liilus, and from the suprarenal and
lumbar arteries, in part, also, they are branches of the arterice inter-
lobulares, which, after supplying the Malpighian bodies, send on fine
twigs to the fibrous coat, forming in it a wide-meshed capillary plexus,
which is also continuous with that of the capsula adijyosa.

The kidneys present, proportionally, but few lymphatics. They run,
in the interioi", along the larger vessels, and do not appear to extend
further than the vasa interlohularia. In the hilus, they unite into a
few small trunks, Avhich also receive lymphatic vessels from the pelvis
of the kidney and then open into the lumbar glands. Superficial
lymphatics, which have been described by the older anatomists (Nuck,
Cruikshank, Mascagni, &:c.), I have as yet not seen, except in the cap-
sula adiposa, but I am unwilling positively to deny their existence.

The renal nerves, from the cnsliac plexus of the sympathetic are tole-
rably numerous, form a plexus around the arteries, continue to present
a few ganglia in the hilus, and may be traced, in company with the
vessels, as far as the interlobular arteries. Where and how they ter-
minate is unknown.*

* [With respect to the termination of the nerves in the kidney, Mr. Toynbee (I.e., p. SOS)
makes the remarkable and very important observation, that "the filaments end by becoming
continuous with tlie parenchyma of tlie organ, precisely in the same way," he {^coes on to
say, " as he has observed those in the tail of a Tadpole to become directly continuous with
the radiating fibres of stellated corpuscles, and the filaments from the corpuscles to commu-
nicate with each other.'" — Tus ]

606

SPECIAL HISTOLOGY.

All these vessels and nerves are supported by a connective tissue,
which, at the same time, serves as a stroma for the secreting elements,
and is much more developed in the medullary substance than in the
cortical. At the surface of the gland, it is condensed into a membrane,
often very distinct, 0'01-0-02 of a line thick, which is but loosely con-
nected with the fibrous tunic, partly supports the superficial capillary
plexus, and is continuous with the internal stroma by numerous delicate
processes.

Fis-. 250.

l)\®li®

mm

In inflammations and exudations, the stroma is frequently so much
condensed as to be apparent on the most superficial inspection, or even,
more or less to compress the tuhuli uriniferi. The additional elements
consist chiefly of a fibrinous exudation, presenting various stages of
transition into connective tissue, partly also of such forms as are pecu-
liar to immature normal connective tissue, as fusiform cells, &;c. In the
case of the Malpighian bodies, these new formations present the form
of concentric, often very thick deposits, which constrict the afferent and
efferent vessels, thus inducing atrophy of the glomerulus, and very
essentially and prejudicially affecting the secretion of urine. In other
cases the increase of the stroma is only apparent, and depends upon the
atrophy of the secreting elements.

Fig. 250. — Transverse section through some straight cortical tubules, magnified 350
diameters ; from Man : a, transverse section of tuhuli uriniferi, the membrana propria only of
which remains ; /), similar tubules, with the cpithclimn still remaining; c, stroma of connec-
tive tissue, with elongated nuclei ; d, cavity in which a Malpighian corpuscle was con-
tained.

Fia. 251. — Epithelium of the pelvis of the Human kidney, magnified 350 diameters: ^,
isolated cells; B, the same in situ: a, small; b, large tessellated cells; c, the same with
nucleated corpuscles in the interior; t/, cylindrical and conical cells from the deeper layers;
c, transitional forms.

THE URINARY ORGANS. 607

§ 190. Excretory urinary passages. — The ■ureters, tlie pelvisy and
calices of the kidnej'', arc all composed of an external //6;-(nt.s membrane,
a smooth muscular layer, and a mucous membrane. The first, formed
of common connective tissue and elastic fibres, chiefly of the finer kind,
is continuous, at the point where the calices surround the papillce, with
the fibrous tunic of the kidney. The muscular layer in the ureters is
very distinct, with external, longitudinal, and internal transverse fibres,
to which, towards the bladder, internal longitudinal fibres also are
superadded. In the pelvis of the kidney the two muscular layers are
quite as thick as in the ureter, whilst in the calices they become thinner
and thinner, ceasing where the latter are inserted into the jjapilla.
The mucous membrane of all these parts is thin, tolerably vascular,
Avithout glands or papillce, and becoming very much thinner (0-005-0*01
of a line, without epithelium), is also continued upon the renal papillae,
being likewise connected with their interior stroma. Its epithelium,
0-02-0*04: of a line thick, is laminated and characterized by the variety
of form and size of its elements, of which the most deeply-seated cells
are rounded and small, those in the middle cylindrical or conical, 0*01—
0-02 of a line in length, and the superficial, rounded-polygonal scales
0-006-0"0J: of a line in size, or more flattened, and reaching a diameter
of 0"02 of a line. The frequent occurrence of two nuclei in these cells
is a striking fact, as well as of clear, darkish-colored round granules
0-001-0'002 of a line in size, which often almost assume the aspect of
nuclei.

The urinary bladder, besides its peritoneal investment, possesses the
same membrane as the ureters. The muscular coat presents, exter-
nally, the well-known longitudinal fibrous layer {detrusor urinai), with
parallel bundles, from which isolated fibres are continued upon the
urachus ; beneath these is a plexiform arrangement of oblique and
transverse, stronger and slender fasciculi, interwoven into a true plexus,
which do not completely cover the entire mucous membrane, and, at the
neck of the bladder, constitute a strong continuous circular fibrous layer
{sphincter vesica'). The corpus trigonum, in the fundus of the bladder,
is a thick layer of whitish-yellow fibres, lying immediately beneath the
mucous membrane, continuous with the longitudinal muscular fibres of
the ureters passing through the muscular coat of the bladder, and con-
tains chiefly longitudinal, but also some transverse fine elastic elements,
connective tissue, and smooth muscular fibres. The mucous membrane,
pale, smooth, and tolerably thick, except where the corpus trigonum is
situated, presents an abundant submucous layer, and consequently, when
the bladder contracts, is thrown into numerous folds. It presents no
villi, is tolerably rich in vessels, especially at the fundus and neck, less
so in nerves, which, however, especially in those two situations where
they are more abundant, may be recognized as dark-bordered, fine and

608 SPECIAL HISTOLOGY.

medium-sized fibres, and is covered with a laminated epithelium 0*03-
0-05 of a line thick, whose deeper elements are usually fusiform, conical
or cylindrical, the more superficial, rounded-polygonal, or flattened.
They exhibit the same want of uniformity in size as those of the pelvis
of the kidney, to which irregularity the numerous depressions of various
depths on the under surface of the uppermost cells, for the reception of
the ends of the deeper, elongated cells, much contribute; peculiar
stellate and dentate forms being thence produced. In the neck of the
bladder and towards i\\Q fundus, there occur mmwiQ glands, in the form
of simple pyriform follicles, or small aggregations of these (simple
racemose glands). These glands, 0-04-0-24 of a line in size, have
orifices of 0-02-0'05 of a line, a cylindrical epithelium, and contain a
clear nnicus. In pathological conditions, as Virchow informs me, they
are occasionally enlarged and filled with whitish mucous plugs.

The 7nale urethra will be described w'ith the sexual organs. That of
the female presents a reddish mucous membrane with numerous vessels,
especially in the form of much-developed venous plexuses in the sub-
mucous tissue (which Kobelt, without any reason, has described as a
corjyus spongiosum), and a squamous epithelium, the deeper-seated cells
of which are elongated, as in the bladder. There is an external mus-
cular tunic united with the mucous membrane, consisting of a thin
layer of longitudinal and transverse smooth muscles, intermixed with
much connective tissue and elastic fibres, and of the thick substance of
the musculus urethralis, the direction of the fibres in which is chiefly
transverse. A certain number of larger and smaller racemose mucous
glandules ("glands of Littre"), resembling in their structure those of
the bladder, except that they are usually somewhat larger and more
closely placed, pour their secretion into the urethra. Occasionally
these glands occur of larger size (as much as 2 lines), and prominent,
containing a colloid-like material in the distended vesicles.

§ 191. Pliysiological remarks. Development of the urinary organs.
— According to Remak, the kidneys in the Chicken are formed as two
protrusions of the intestine, in the constitution of which the epithelial
and the fibrous layers both take part, and, like the lungs, grow by the
ramification of their epithelial tube, and the augmentation in bulk of
the fibrous layer (Unters. z. Entw. d. Wirbelth. Tab. II., fig. 83-85).
In the Mammalia, the earliest stage of the development of the kidneys
has not yet been observed ; but what we do know from the labors of
Rathke, J. Mliller, Valentin, and Bischofi", with respect to its subse-
quent conditions, perfectly accords with the statements of Remak,
except that, in this case, the glandular canals appear to be developed
upon the type of the salivary glands,, and are not hollow from the com-
mencement. The rudimentary kidneys in the Mammalia, at first,

THE URINARY ORGANS. COO

present nothing but the pelvis and a certain number of chivntc hollow
protrusions continuous uith it — the calices. From each of the latter is
subsequent!}^ formed, by continued budding, a bundle of tuhuli nri)uferi,
each of which bundles ultimately constitutes a Malpighian pyramid and
the cortical substance appertaining to it ; whilst, at the same time, the
kidney expands into a corresponding number of lobes. The tuhuli
uriniferi are at first solid, composed solely of cells, and without any
membrana propria. In the course of development the latter arises,
probably from a plasma afforded by the cells, and the cavity of the
canal is formed, in consequence, it may be supposed, of the connection
of a fluid between the cells ; simultaneously with which the tubules
begin to grow rapidly in length, and to become convoluted. The Mal-
pighian bodies are originally nothing more than solid, clavate, thick-
ened extremities of the rudimentary tuhuli uriniferi. The interior
cells of these pyriform or rounded bodies, subsequently become capil-
laries, which are continuous at two points, with the vessels outside,
whilst the most exterior form the epithelium, which joins that of the
tuhulus uriniferus, and, like it, is invested with a memhrana projjria,
which is, of course, deficient where the afferent and efferent vessels
enter and emerge, at which point it may be said to be perforated. In
the newborn child, according to Harting, the renal canals are three
times more slender than in the adult, whence, as the kidney of the
latter is only twice the size of that of the child, it is obvious that, at
any rate after birth, no tubules are formed.

With respect to the physiological relations, I would merely offer the
following remarks. There can be no question that the peculiar vascular
conditions in the kidney, in accordance with which the blood circulates
in special coils projecting into the commencement of the tuhuli urini-
feri, before it passes into the proper capillary plexus of the organ, are
most intimately connected with the secretion of a large proportion of
water in the urine. The hindrance to the flow of the blood gives rise
to a considerable lateral pressure in the glomeruli, and a large quantity
of blood-plasma is forced through the thin opposing membrane (the walls
of the capillaries and the epithelium). Since all the elements of the
plasma are not found in the urine, and those that are, present in it
totally different proportions to those in which they exist in the blood, it
is obvious that the membrane in question does not act simply as a filter,
but also, for reasons at present unknown, retains certain substances
(protein-compounds, fat), whilst it allows others {urea, &c.) to pass
through with peculiar facility. In this Avay there is formed in the com-
mencements of the tuhuli uriniferi, probably a very diluted urine, which
afterwards, as it flows towards the pelvis of the kidney, reciprocally
acts and is acted upon by the blood circulating around the tuhuli urini-
feri, receiving additional substances from it (perhaps more urea), but

39

610 SPEC! A L H ISTOLOG Y.

also yielding up certain of its own constituents (water and salts), and
thus, at last, becomes true urine.

As regards the chemical composition of the kidney, we know very
little. Frerichs (1. c. p. 42) found, in a healthy kidney, 16-30-18S- solid
matter, 72-73-70 water. Of the former, the fat amounted to 0-63-0-l§,
although, according to Owen Rees, it may amount to 1-86; the greater
portion, however, is probably albumen, with regard to which, Ludwig
especially has shown, that it exists in large quantity in the kidney, a
fact that, from the micro-chemical characters of the epithelial cells of
the tuhuli uriniferi, cannot be wondered at.

In the higher animals, the secretion of the urine takes place without
any formation or dissolution of cells, and consequently the normal urine
just evacuated contains no morphological elements. It is only occa-
sionally that epithelial cells from the urinary passages, especially from
the bladder and urethra, occur in it ; but we almost always find mucus
from the same localities, forming clouds or a light sediment, occasionally
with mucous corpuscles; and last] j, spermatic flajnents after emissions.
In inflammations, hemorrhages, exudations, fatty kidney, we find pus
corjmsclcs, oil drops, blood globules, blood, and fibrinous coagula, moulded
in the tubuli uriniferi, in the form of cylindrical casts, and epithelium
from the tubuli, isolated or in continuous strings or tubes. Sedimentary
deposits of the salts of the urine are readily formed as the products of
decomposition. All normal urine without sediment, at a mean tempera-
ture, undergoes an acid fermentatioii, under the influence of the mucus
contained in it; and whilst fermentation and filamentary /im^rz are de-
veloped, forms, from the decomposition of the urinary coloring matter,
lactic or acetic acid, in consequence of which uric acid is set free from
its compounds and deposited, in the form o^ rhombic or prismatic crys-
tals, colored yellow or reddish by the coloring matter of the urine.
Sooner or later the acid disappears, and from the decomposition of the
urea, perhaps also of the coloring matter, the urine becomes ammoniacal
and alkaline, with large colorless pyramidal prisms, or needles grouped
in a stellate fashion and soluble in acetic acid, of the triple phosphate of
magnesia and ammonia, which, intermixed with numerous infusoria
{yibriones and monades) form a superficial pellicle, and with granules of
urate of ammonia, and also, it may be, of carbonate of lime, a white
sedimeiit. Under conditions not as yet known, and rarely, hexahedral
prisms of cystin appear in the urine ; more frequently, after the use of
drinks containing carbonic acid, and also in pregnant women, we find
the octohedrons of oxalate of lime insoluble in acetic acid. If the quan-
tity of uric acid be augmented, as after the inordinate use of nitrogenous
food with deficient exercise, in impaired digestion, fevers, &c. a more or
less abundant yellowish precipitate of urate of soda, in the form of

THE URINARY ORGANS. 611

isolated or aggregated granules, is formed as soon as the urine cools,
and becomes rcdissolved when it is again warmed. If, under these cir-
cumstances, the acid fermentation is set up, very considerable sediments
of colored crystals of uric acid (brickdust sediment) are often thrown
down. In injuries of the bladder, the urine frequently becomes alkales-
cent with great rapidity, when the above-mentioned crystals of triple
phosphate at once make their appearance; they are also very frequent
in pregnancy ; and when assuming the pellicular form above described,
were at one time regarded as a peculiar substance (Kiesteine).

The occurrence of albumen, fibrin, and fat, within the tuhuU urini-
feri, is, in my opinion, easily explained, upon the supposition, that in
such cases the circulation is obstructed, and an increased secretion of
the elements of the blood takes place in the Malpighian bodies and
tubuli uriniferi, in consequence of which the epithelium of those parts
which, as is well known, is found in these cases in considerable quantity
in the urine, is washed away, whence, of course, any further hindrance
to the continued passage of the above substances is removed. A per-
meation of fibrin through the epithelium is also conceivable, just as
much, for instance, as upon the mucous membrane of the respiratory
organs, although I do not believe that an increased pressure of such a
kind as to induce a transudation of fibrin could fail to affect the deli-
cate epithelium. When the epithelium is once removed, it becomes an
important question whether it is quickly restored ; and it appears to
me, that the frequent occurrence of small quantities of albuminous
matter in the urine often depends simply upon local deficiencies of the
epithelium caused in one way or another.

Investigation of the kidney. — The tubuli uriniferi are readily isolated
when the tissue of the organ is teased out ; the epithelium, memhrana
propria, and canal being distinctly recognizable if blood-serum, or a
solution of albumen be employed to moisten it. Together with entire
tubules, there will be found in every preparation numerous epithelial
cells, separate, or in groups, or even, as especially in the pyramids, in
the form of long continuous tubules. The latter often present a pecu-
liar aspect, for the most part collapsing, exhibiting somewhat flattened
cells, and resembling vessels. Equally frequent are longer or shorter
tubes of the memhrana p)ropria, which, when much plicated, cannot
always at once be recognized. In the examination of the pyramids,
the extremely numerous vessels must not be confounded with the
" ducts of Bellini," or the epithelial casts that have escaped from them.
The connection of the tubuli uriniferi with the Malpighian bodies is
easily discerned in the kidney of the Frog and of Fishes, upon careful
teasing out of the structure; but in Mammalia, also, it will rarely be

612 SPECIAL HISTOLOGY.

missed in fine, hardened sections, and especially in injected prepara-
tions. The glomeruli themselves may frequently be recognized when
naturally injected, and still better when artificially filled, which we may
very readily succeed in doing Avith any fine material thrown in by the
arteries. Similar injections, also, when successful, fill the whole capil-
lary plexus of the cortical substance and of the pyramids ; when this
portion of the circulatory apparatus, especially in perpendicular sec-
tions, may bo very satisfactorily made out. For the same purpose,
kidneys injected from the veins are employed, in which not only the
capillary plexus, but the glomeruli are filled ;* and for the study of the
va^a efferetitia, preparations not completely filled from the arteries are
suitable. The course of the tubuli uriniferi should be studied in fine
sections of kidneys hardened by immersion in alcohol, by boiling in
dilute nitric acid and drying (Wittich), or by chromic acid, and ren-
dered transparent by acetic acid ; or in sections, made with the double-
bladed knife, of recent, as well as of injected kidneys, in which the
most important conditions, even the divisions of the " ducts of Bellini,"
may be observed. Nevertheless, it is always expedient to inject the
tubuli uriniferi; and for this purpose, among the Mammalia, the
Horse appears to be best adapted. This filling may happen, in conse-
quence of accidental extravasation into the Malpighian capsules ; in
the injection of the arteries by this means, however, rarely more than
the convoluted tubuli are filled ; or it may be effected by injection from
the ureter with the aid of the air-pump (Huschke, Isis, 1826), or the
pelvis of the kidney being kept filled, if an endeavor be made by the
kneading of it with the hand, to force the material into the " ducts of
Bellini," and beyond them (Cayla). By means of a very fine canula,
the individual tubuli may also be injected directly from the papillce.

Literature. — M. Malpighi, "De Renibus, in Exercit. de vise, struct. ;"
Al. Schumlansky, "Diss, de structura renum," c. tab. Argentor. 1782,
4to ; W. Bowman, " On the structure and use of the Malpighian Bodies
of the Kidney," in "Phil. Trans.," 1842. I. p. 57; C. Ludwig, "Beit-
rage zur Lehre vom Mechanismus der Harnsecretion," Marburg, 1843 ;
and Art. " Niere," in Wagner's " Handw. d. Physiolog.," II. p. 628;
J. Gerlach, in " Muller's Archiv.," 1845 and 1848 ; Kolliker, in " Miill.
Archiv.," 1845; Remak, in "Froriep's N. Notiz.," No. 786, 1845, p.
308; F. Bidder, in " Mlill. Archiv.," 1845, and " Untersuch. uber die
Geschlechts- und Harnwerkzeuge der Amphibien," Dorpat, 1846; J.
Hyrtl, in " Zeits. d. Wien. Aerzte," 1846 ; [Jos. Toynbee, " On the In-
timate Structure of the Human Kidney," "Med. Chirur. Transact.," 2d
Ser. vol. II., p. 303, 1846;] C. v. Patruban, " Beitriige zur Anatomic

* [I have found that the Malpigliian corpuscles are filleil with much more difficulty, and
always imperfectly by injections thrown in by the veins. — DaC]

THE SUPRARENAL CxLANDS. 613

(lor menschlichen Niere," in " Prag. Viertelj." 1847, III. ; Gr. Johnson,
Art. '• lien," in " Cyclop, of Anat.," May, 1848 ; V. Carus, in " Zcitsch.
f. wiss. Zool.," XL, p. 61; v, Wittich, in " Arch, far path. Anat." III.,
1, 1849 ; V. Hessling, in " Froriep's N. Notiz.," 1840, p. 264, and " His-
tologische Beitrage zur Lehre von der Hnrnsecretion," Jena, 1851. Be-
sides which should be consulted the usual Manuals of Anatomy, espe-
cially those of Ilenle, Valentin, J. Muller, and myself; the "Memoirs
on Development," particularly of Valentin, Rathke, "Abhand zur
Entw." II., p. 97; J. Miiller, " De Gland, sec. structurd;" and lastly,
tlie "Annual Reports of Beichert," 1846 and 1849.

OF THE SUPRARENAL GLANDS.

§ 192. The suprarenal glands or capsules, glanclultv suprarenales, are
a pair of organs, in their structure approaching nearest to the blood-vas-
cular glands, but whose function is as yet altogether unknown. Each
consists of a moderately firm but thin coat composed of connective
tissue, which closely invests the entire organ and is connected by numer-
ous processes with the proper parenchyma, composed of a cortical and a
medullar!/ substance. The former, substantia corticalis, is more com-
pact, ^-^ a line thick, tearing readily in the direction of its thickness,
and, when torn, presenting a fibrous aspect. Its color is for the most part
whitish-yellow, or yellow, in the innermost third, however, usually pass-
ing into brownish yellow or brown, so that in a transverse section, two
layers may be distinguished, an external, bright-colored layer and an
internal, narrow, dark border. The medullar?/ substance is, normally,
of a brighter color than the cortical, being of a grayish-white with a
tinge of red, although when its numerous veins are full of blood, it may
assume a darker and more venous hue. Its consistence is softer than
that of the cortical substance, though not so much so as is usually be-
lieved, and with respect to its thickness, it is very inconsiderable (^-J
of a line) at the thin borders and at the upper and outer extremity of
the organ, whilst in the middle, and in the lower and inner half, it
amounts to as much as 1 or even 1-| lines. In the dead human subject,
the cortical substance very readily becomes detached from the medullary,
when the suprarenal gland presents a cavity, frequently occupying the
entire organ, and containing a dirty, pultaceous substance derived from
the half disintegrated brown layer of the cortex, mixed with blood, to-
gether with the less altered medullary substance; which, however, in
more rare instances, also becomes broken up.

§ 193. Intimate structure. — TJic cortical substance presents as a foun-
dation, a delicate meshwork of connective tissue, which, in connection
with the tunic and the thin, mutually connected lamina^ proceeding from

GU

SPECIAL HISTOLOGY,

it, pervades the entire layer, and forms the boundaries of very nume-
rous, closely-approximated compartments, O-OlG-0-02, or even 0-03 of
a line in diameter, which extend in a vertical direction from without to
within, through the entire thickness of the cortex. In these compart-
ments is lodged a granular substance, subdivided by delicate, oblique or
transverse dissepiments, into larger and smaller aggregations, which
Ecker describes as gland- follicUs, and as containing, within a structure-
less membrane, a granular material mixed with nuclei or even cells.
But in these '■'■cortical cijUnders" as I would term them, I have, in
most instances, noticed nothing but rounded-angular cells, 0-006-0-012
of a line in size, and believe that Ecker, from the more rare occurrence
of true follicles, has been induced to regard the compact aggregations

\\ ,-«■

Fi;;. 253.

of so-termed cells which occur in the interior of the cortex, and which
are 0-024- 0'048-0-OG of a line long, as special follicles. In fact, the
cortical cells, which, on the external and internal portions of the cortex,
are to be met with more isolated in the compartments, are in its inte-
rior, closely united into oval or cylindrical masses, in which the outlines
of the cells have frequently coalesced into a single, general contour-line.
I have never been able to detect any other membrane surrounding the
cells besides the connective tissue of the corresponding compartment,
and I have almost always succeeded, by pressure, or the addition of
alkalies, in isolating the cells, without bringing into view any special
sac. True follicles, I have hitherto seen only in the inner portions of
the cortex, in the form of round or oval vesicles 0 •02-0-3 of a line in
diameter, within which no cells like those of the cortical cylinders are
formed, but only a collection of oil-drops could be recognized, and which

Fig. 2.5"2. — Portion of n vertical section tliroujjh tlie cortex of tlie suprarenal body in Man:
o, septa of connective tissue: h, cortical cylinilcr, whose composition out of cells is more or
less distinctly manifest. — Mafcnified 300 diameters.

Fig. 253. — From tlie suprarenal liody of Man : a, five cells filled with pale contents, from
the summit of a cortical cylinder: b. piirment-cells from tlie innermost layer of the cortex:
c, fat-containing cells, frotn the yellow cortical layer; f/, a larger cyst filled with fat, from a
cortex of that kind (gland-follicle, Ecker); c, cells from the medullary snbstance, some with
processes. — Magnified 300 diameters.

THE SUPRARENAL GLANDS. 015

I have been inclined to regard as enlarged cells. The contents of the
cortical cells normally consist of fine granules of a nitrogenous sub-
stance; but to these are almost always added solitary fat-granules, which
in many cases (in the yellow cortical substance), exist in such quantity,
as entirely to fill the cells, Avhich then assume a deceptive resemblance
to those of a fatty liver. In the brown layer of the cortex, the cells are
entirely filled with brown pigment granules.

The medullary substance also has a stroma of connective tissue, which,
prolonged from the cortical lamellcX^, pervades the whole interior, for the
most part, in more delicate fasciculi, constituting a network with rather
narrow, rounded meshes. In this network lies a pale, fine-granular sub-
stance, in which, in Man, by careful manipulation, and in recent prepa-
rations, I have almost always noticed pale cells of 0-008-0-016 of a line,
which, in their fine-granular contents, occasionally presenting a few fat,
or pigment granules, their frequently very distinct nucleus with large
nucleoli, their angular form, and occasionally single or multiple, or even
branched processes, resemble the nerve-cells of the central organs,
although they cannot definitively be declared to be such.

§ 194. Vessels and nerves. — The bloodvessels of the suprarenal
glands are numerous, lie in the stroma of connective tissue, and form
two kinds of capillary plexuses ; one in the cortex with elongated
meshes, and one in the medullary substance with more rounded inter-
stices. The arteries arise as numerous (amounting to twenty) small ves-
sels from the neighboring larger trunks (phrenic, celiac, aortic, renal),
and either penetrate directly into the medullary substance or ramify in
the cortical. The latter, which are the more numerous, cover the outer
surface of the organ with their multiplied ramifications, and form a
wide capillary plexus even in the outer tunic. They then subdivide into
numerous fine twigs, and dip down into the dissepiment of the cortex,
in which, becoming more and more attenuated, they run straight to-
wards the medulla, being mutually connected in their course by pretty
numerous transverse anastomoses, so that the cortical cylinders are sur-
rounded by blood on all sides. The extremities of these vessels extend
to the interior of the medulla, where, in common with the arteries
which penetrate directly to the same point (of which, however, accord-
ing to Nagel, in the Sheep, some proceed from the medulla entirely to
the cortex) they form a rich capillary plexus of rather large vessels.
The veins arise chiefly from this latter plexus, and, within the medul-
lary substance, join the principal vein of the organ, — the v. suprarenalis
— which comes out on the anterior surface, at the so-termed hilus,
emptying itself, on the right side, into the vena cava and on the left,
into the renal vein. Besides these, a good many smaller veins arise
from the cortex, which either accompany the arteries in pairs, or pro-

616

SPECIAL HISTOLOGY.

Fis. 251.

ceed independently and open into the renal and phrenic veins, and into
the inferior vena cava. Of lymphatics, I have as yet noticed only a
few small trunks on the surface of the organ, but none in the interior
or corning out from it. The nerves of the suprarenal glands are, as
was correctly stated by Bergmann, extremely numerous, arising from
the semilunar ganglion and the renal plexus; according to Bergmann
also, to a small extent, from the vagus and phrenic nerves. In Man,
in the right suprarenal gland, I have counted thirty-three trunks, 8 of

1-5-1-10, 5 of 1-14-1-20, 7 of 1-25-1-33, and
13 of 1-45-1-50 of a line, and found that, with-
out exception, or at all events in a very prepon-
derating proportion, they were constituted of
dark-bordered, finer and medium-sized, or even
thick fibres ; were whitish or white and furnished
with isolated, larger or smaller ganglia. They
are especially apparent on the inferior half and
inner border of the organ, and appear to be all
destined for the medullary substance, in which, at
least in the Mammalia, an extremely rich jjlexus
of dark-bordered, finer fibres occurs, inclosed in
the trabeculce and connective tissue, their termi-
nations, however, being nowhere perceptible. In
man, the medullary substance is, in most in-
stances, so altered, that the nerves cannot be
traced farther than to their entrance into it, it be-
ing impossible to follow their farther distribution.

§ 195. Physiological remarks. — The suprarenal glands are developed
simultaneously with the kidneys and independently of them, from a
blastema derived from the middle germinal lamella (Remak), the first
appearance and growth of which is unknown, and are originally larger
than the kidneys. In the third month the two organs are of equal size ;
in the embryo at six months, the weight of the suprarenal capsule is, to
that of the kidney, as 2 to 5, in the mature embryo as 1 to 3, in the
child at birth as 1 to 8 (Meckel). In other Mammalia the suprarenal
glands are, from the first, smaller than the kidneys, and increase In the
same proportion with them. Little is known with respect to the histo-
logical development of the organ. I have, hitherto, investigated this
only in an embryo of three months, in which, like Ecker, I found the
cortex whitish, the medulla whitish-red, and both constituted of cells and
fibres. The cells measured 0-012-0*02 of a line, had well marked in part
colossal nuclei, with distinct nucleoli, and In the cortical part also fatty

Fig. 254. — Transverse section of the suprarenal body of the Calf, magnified aljout 15
diameters: treated witli soda: a, cortex; b, medulla; c, central vein surrounded with some
cortical subsiauce; d, three entering nerves; e, nerves, and their tlistribution in the interior.

THE SUPRARENAL GLANDS. 617

molecules. Of the nerves at that period I saw nothing. In a neAvly-horn
Rabbit, Ecker observed no appearance of follicles, whilst in a foetal Calf,
1 foot G inches long, he found them very distinct, but small (0-05-0-15'"'").
As regards the functions of the suprarenal glands, in the absence of
all physiological indications, and so long as the course of the nerves in
them is not much more accurately known, only very general observa-
tions can at present be offered. / consider the cortical and medullary
substances as physiologically distinct. The former may, provisionally,
be placed with the so-termed "blood-vascular glands," and a relation
to secretion assigned to it ; whilst the latter, on account of its extremely
abundant supply of nerves, must be regarded as an apparatus apper-
taining to the nervous system, in which the cellular elements and the
nervous plexus either exert the same reciprocal action as they do in the
gray nerve-substance, or stand in a relation as yet wholly unascertained,
towards each other. (For a more detailed account vid. Mikros. Anat.
II. 2, zw. Hiilfte.)*

* [The former and more recent researclies of Leydig (" Anatomisch-histologisclie Unters. fib.
Fische u. Reptilien," 1853) appear satisfactorily to show the identity of the suprarenal glands
of the xMammalia, with the yellow, vascular bodies seated, either on the kidney itself and
its etnulgent veins, or at a greater distance from those glands, on the veins near the epididy-
mis or ovaries, or upon the sympathetic nerve. Tiie study of these more simple forms has
also thrown very considerable light upon the structure and true imf)ort of the more compli-
cated organ in the Mammalia. In the Salamander, the ganglia of the sympathetic have a
very remarkable structure, and contain cellular elements of two very distinct kinds. Each
ganglion has a tunic of connective tissue which sends septa into the interior, v^'hich is thus
divided into distinct and occasionally, perfectly separate compartments. Tlie cells of both
kinds are enclosed -in these compartments, and are never intermixed in one and the same.
In some of the compartments, or as they might almost be termed, vesicles, the cells are
large, clear, and finely granular, with a vesicular nucleus and very transparent nucleolus.
From some of these cells, nerve-fibres are distinctly seen to proceed, and they would appear
to be of the bipolar kind of ganglion- or nerve-cells. The other kind of cells, contained in
perfectly distinct compartments, are much smaller and their contents of a peculiar dirty
yellow color, owing to which the perfectly transparent nucleus is rendered very distinct.

These two kinds of cells occur in very variable proportions in different ganglia. Now, if
the dirty yellow-colored ganglion-globules of one of these sympathetic ganglia be compared,
side by side, with the contents of one of the yellow bodies on the veins, or of the yellow
granular masses on the kidney, it will be at once apparent, that by a gradual transforma-
tion, they directly pass into the fatty, granular cells of the so-Xer n\e A suprarenes. And the
same transformation may lake place even in the sympathetic ganglia.

According to Leydig, the cor/ieaZ substance of the suprarenal capsules of the Mammalia
corresponds to the yellow, granular and striped suprarenal bodies of Fishes and Amphibia;
whilst the medullary substance of the Mammalian organ, which is abundantly supplied with
nerves and cells, very like the ganglion-globules, represents the other divisions of the sym-
pathetic ganglia: whence he concludes that Bcrgmann's view, according to which the
suprarenal capsules are closely related to the nervous system, is undoubtedly correct, and
that those organs bear the same relation to the ganglia of the sympathetic nerves, as the
pituitary body bears towards the brain. Besides this relation to the nervous system, how-
ever, they have an intimate one with the vascular; and are, therefore, always pervaded by a
very close capillary plexus. But in any case, he says, the suprarenal bodies must be re-
moved from the category of the so-termed blood-vascular glands, which would then include
only the thyroid and thymus, or should probably be abolished altogether, as an unmeaning
term. — Tks.]

618 SPECIAL HISTOLOGY.

In the investigation of the suprarenal glands, the larger Mammalia
ought, in the first place, to be chosen, and not till afterwards should
they be studied in Man. The cortical portion is readily examined when
its elements contain but little fat, and, above all, perpendicular sections
of fresh specimens, or of such as have been hardened in alcohol and in
chromic acid, which are afterwards to be rendered transparent by soda,
are to be recommended. The medullary substance, even in animals, is
very easily disintegrated, so that its elements are either not to be seen
at all in the normal state, or only partially, although they are occa-
sionally very beautifully displayed without any addition, as well as in
chromic-acid preparations. In animals, the nerves are very easily dis-
cerned in fine sections, after the addition of soda; and when their ex-
ternal visible points of entrance are exactly hit upon in the making of
the section, tlieir course through the cortical substance is readily brought
into view. For the vessels, injections should be employed, which are
best effected in the Sheep or sucking Pig, and which readily succeed
when made, as "well from the arteries as from the non-valvular veins.

Literature. — Nagel. "Diss, sistens ren. succent. mammal, descript.,"
Berol., 1838,>nd Miill. "Arch.," 1836; C. Bergmann, "Diss, de
glandulis suprarenal," c. tab. Glitt., 1839 ; A. Ecker, " Der feinere
Bau der Nebennieren beim Menschon," u. den 4 " Wirbelthierclassen,"
Braunschweig, 1846, und Art. "Blutgefassdriisen," in Wagner's
"Handw. d. ^Physiologic," Bd. IV. 1849; H. Frey, Art. "Suprarenal
Capsules," in Todd's " Cyclop, of Anat.," Oct., 1849.

[H. Gray, " On the development of the ductless Glands in the Chick,"
"Phil. Trans." 1852.— Trs.]

OF THE SEXUAL ORGANS.
A. MALE SEXUAL ORGANS.

§ 196. The male sexual organs consist, 1, of two glands for the se-
cretion of the semen, the testes, which, together with special tunics, the
tunicas vaginales, are contained in the scrotum ; 2, of their efferent
canals, the vasa deferentia and ejaculatory fZwc^s with their appendages,
the vesicular seminales ; 3, of the copulatory organs, the j^ewi's and its
muscles ; 4, and lastly, of special accessory glands, the prostate and
Cowpers glands.

§ 197. The testicles, testes, are a couple of true glands, containing
within a special tunic, the tunica albuginea, s. fibrosa, the secreting ele-
ments, in the form of complexly convoluted tubules, the spermatic tubes
or tuhuli seminiferi. The tunic is a white, dense and thick membrane,

THE SEXUAL ORGAN 5.

619

corresponding in structure, in all respects, with other fibrous membranes
(the dura mater especially), and everywhere surrounding the paren-
chyma of the testis as a closed capsule. Its external surface, except
where the epididymis is attached to the testis, is rendered smooth and.
glistening by a special covering, the tunica adnata, whilst the internal
is united with the substance of the gland by a thin layer of loose con-
nective tissue, and moreover, sends a considerable number of processes
into the interior; of which, the most important is the corpus Highmori

Fi-. 257

s. mediastinum testis, a vertical lamella of dense connective tissue ;f-l
inch long, and thick at its commencement, which extends from the pos-
terior border of the testis to a depth of 3-4 lines into the interior (Fig.

Fig. 255. — Transverse section tliroujrli tlie right testis and its tnnics, in Man : a, I. vaginalis
co))wmnis : b, t. vaginalis propria, outer lamella; c, cavity of the /. v. propria, which docs not
exist in life; d, inner lamella of the t. v. propria (adnata), coalescent with e, the /. albnginea;
f, continuation of the t. propria on the epididymis, g ; h, corpus Highnwrianum : i i i, branches
of the spermatic artefy ; k, vena spermalica interna ; I, vas deferens ; m, artery of the vas defe-
rens; n, lobuli testis; s, septula.

Fig. 25G. — Diafrram of the course of a spermatic tubule.

Fig. 257. — Human testis and epididyi7iis, afier Arnold: a, testis; 6, lobes; r, ductuli recti:
d, rete vascidosum ; e, vascula effcrentia ; f coni vasculosi; g, epididymis ; h.vas deferens; i, vag
aberrans ; »?i, branches of the spermatica hiterna of the testis and epididymis ; n, ramification oa
the testis; a, art. defcrentialis ; p, anastomosis with a branch of the spermatic.

620 SPECIAL HISTOLOGY.

255 h) ; but besides this, there are numerous lameHar processes {septula
testis) (Fig. 255 s) arising from the internal surface of the tunica alhu-
ginea, composed of more lax connective tissue, which, separating the
.divisions of the glandular structure from each other, and conveying the
vessels belonging to them, converge from a^ sides towards the corpus Higli-
mori^ and are attached by their acuminate terminations to its surfaces.
The glandular substance of the testis is not absolutely homogeneous,
but consists of a certain number (100-250) of pyriform lobules, lobuli
testis, which are not, however, everywhere wholly separated from each
other, and all converge with their points towards the corpus Highmo-
rianum, close to which they are shortest, whilst those between the
borders of the organ are the longest (Fig. 255 n, 257 h). Each of these
lobules is formed of from 1 to 3 seminal tubules or canaliculi, 1-8-1-15
of a line in diameter. These tubules, much convoluted, pretty frequently
dividing and also, perhaps, anastomosing, in their course, form a com-
pact substance and ultimately terminate at the thick end of the lobule,
at a greater or less distance from the surface, either in c?ecal ends or in
loops (Fig. 256 g). The spermatic canals of each particular lobule,
although joined to each other by some connective tissue and vessels, may
nevertheless, by careful dissection, be separated to a great extent, or
even wholly isolated. Their length, according to Lauth, is from 13 to
33 inches. At the pointed extremity of each lobule the spermatic canals
become straighter, when each by itself, or the two or three arising in
one lobule united into a simple canal, enter as the ductuli recti, 1-10 of
a line in diameter (Fig. 257 c), the base of the corpus Highnori, where
they form a very close plexus, 2-3 lines broad and IJ lines thick, and
extending the whole length of that body, — the rete testis (r. vasculosum
Ealleri) (Fig. 257 d). From the upper end of this plexus, the canals in
•which measure from 1-12 to 1-33 of a line (0'03-0-08 of a line), proceed
7-15 efferent canals, vasa efferentia testis s. Crraajiana, of i-^ of a line
(0'16-0*18 of a line) (Fig. 257 e), which, traversing the t. albughiea, are
continued into the epididgmis. Here they contract to 1-8 and 1-10 of
a line, are convoluted in exactly the same way as the spermatic canals
in the lobuli testis, but without presenting divisions or anastomoses, and
thus produce a certain number of conical bodies, the apices of which are
directed towards the testis, — the spermatic cones {coni vasculosi s. cor-
pora pgramidalia) (Fig. 251 f). These cones, united together by con-
nective tissue, constitute the head [globus major) of the epididymis, at
the upper and posterior border of which their canals gradually coalesce;
and thus is formed the simple thick duct of the epididymis, 0-16-0*2 of
a line in diameter (Fig. 257, g). This duct, convoluted in a well-known
manner, forms the body and tail [globus minor) of the epididymis,
usually giving off at its inferior extremity a csecal prolongation, vas
aberrans Halleri (Fig. 257, i) and is ultimately continuous with the

THE SEXUAL ORGANS.

621

spermatic tluct or vas deferens, which at first ^-J- of a line in diameter
and convoluted, soon increases to a size of -|-1 line, and becomes
straight (Fig. 257, h). The epididymU, moreover, has an extremely
delicate fibrous tunic (^ of a line) of a grayish-white color.

§ 198. Structure of the seminiferous tubes. — The seminal tubes of
the testis are, in proportion to their diameter, rather more firmly con-
structed than other glandular canals and consist of a fibrous membrane
and an epithelium. The former, from 0-0024-0-005, or in the mean
0-003-0-004 of a line thick, composed of an indistinctly fibrous C0D«ec-
tive tissue with longitudinal nuclei, without muscular fibres and rarely
presenting an indication of elastic fibrils, is tolerably firm and exten-
sible. A simple layer of roundish, polygonal
cells, of 0-005-0-008 of a line, occasionally
with an indication of a membrana propria as
a substratum, on the inner surface of this
fibrous membrane, completes the vascular ca-
nal, which thus obtains a wall, O-007-O'Ol of a
line in entire thickness. In younger subjects,
these cells are pale and finely granular, but
as age advances, a continually increasing num-
ber of fatty granules is collected in them,
"whence the seminiferous tubes sometimes ac-
quire a light yellowish, partially brownish ^
color, which is manifest very frequently in men even at the middle
period of life, and invariably in old age. The ductuli recti present the
same structure as the tubes ; whilst in the rete testis, no special fibrous
tunic can be distinguished, the canals in this portion of the gland ap-
pearing to be nothing more than cavities in the dense fibrous tissue of
the corpus Highmorianum., lined by an epithelium. In the coni vas-
culosi the fibrous coat again makes its appearance, and to it there is
now, also, added a layer of smooth muscles, which, in the form of trans-
verse and longitudinal fibres, are recognizable even in canals of ? to ^
of a line in diameter. The thicker portions of the canal of the epididy-
mis are constructed in the same way as the vasa deferentia [vid. infra),
with a cylindrical epithelium, Avhich, moreover, commences even in the
head of the epididymis.

The contents of the seminiferous tubes vary according to age. In
Boys and young Animals the slender tubuli contain nothing but minute,
clear cells, the most external of which might be regarded as epithelial
cells, although not always clearly distinguishable from the others. At
the age of puberty, together with the increased size of the tubuli semini-

FiG. 25S. — Portion of a spermatic tube in Man, magnified 350 diameters: a, fdjrous coat
with longitudinal nuclei; b, clear border, probably a. Jiiembrana propria ; c, epithelium.

622

SPECIAL HISTOLOGY.

feri, the elements contained in them also increase in circumference ;
and when the formation of semen has actually commenced, they appear
as clear, round cells and cysts of 0-005-0-03 of a line, which, according
to their size, enclose a .variable number of, from 1 to 10, or even 20,
clear nuclei of 0-0025-0-0035 of a line with nucleoli. At this time, in
many cases, an epithelium is not manifest, the seminal tubes rather
appearing to be occupied entirely and solely by the cells in question ;
at other times, and particularly in advanced years, an epithelium is
presented containing fat, or pigment-cells, and surrounding the other
elements. The latter, Avhether they occur in the one way or the other,
are the precursors of the semen, which, in the mature condition, entirely
consists of an extremely small quantity of a viscid fluid, and of innu-

Fig. 259.

Fis. 260.

merable minute, linear corpuscles having a peculiar movement, the
spermatic filaments or animalcules, fila spermatica, spermatozoa (also
spermatozoida). These spermatic filaments are perfectly homogeneous,
soft corpuscles, in which are distinguishable a thicker portion — the lody
or liead, — and a filamentary appendage, — the filament or tail. The
former is flattened and, viewed on the side, pyriform, with the acute
end in front ; on the surface oval, or even rounded anteriorly, and also,
though more towards the anterior part, slightly cupped ; so that it
sometimes appears clear in the middle, sometimes opaque. It is 0*0016—
0-0024 of a lino long, 0-008-0-0015 of a line wide, 0-0005-0-0008 of a
line thick, and according as it lies on the surface or edge, does it appear
clearer or more opaque, always presenting a peculiar fat-like, glistening

Fig. 259. — Spermatic filaments (human); 1, magnified 350 diameters; 2, magnified 800
diameters; «, viewed on the edge; b, on the flat surface.

Fig. 2G0. — Development of tlie spermatic filaments in the Rabbit: a, parent-cell (cyst)
with five nuclei: b, one with ten nuclei, each of which contains a convoluted spermatic fila-
ment ; c, an isolated nucleus with nucleoli ; c/, one with the spermatic filament ; e, a cyst with
a bundle of spermatic filaments; //. g g, immature spermatic filaments, with enlargements
in the filamentary portion ; A, a perfect spermatic filament, a, b. c. magnified 350 diameters ;
d — /(, magnified 500 diameters.

THE SEXUAL ORGANS. 623

aspect, and, particularly in a lateral view, dark borders. The pale
filamentary portion has an average length of 0*02 of a line, and at its
anterior end, ^vhere it joins the broader extremity of the body, with a
slight constriction, it is wider (0-000o-0-0005 of a line, and also flat-
tened, being gradually prolonged into an extremely fine point, scarcely
visible even under the highest magnifying powers. In vigorous men
the semen, throughout the vas deferens and in the globus minor of the
epididymis is composed of these corpuscles, occasionally intermixed
with isolated granules, nuclei, and cells, whilst in the upper part of the
epidid?/7nis and in the body of the testis other elements, such as the above-
described cells and cysts, preponderate more and more, and finally con-
stitute the entire secretion. These spermatic cells and cysts, as I term
them, have a definite relation to the spermatic filaments, for in each
nucleus, as was first shown by me, a spermatic filament is developed on
the inner wall, in the form of a spiral corpuscle with two or three turns.
How this really arises is unknown; very probably as a sort of deposit
from the contents of the nucleus, which at the same time become clear,
in the same way as the spiral filaments of 'the vegetable cell are formed ;
but it may at all events be asserted as a positive fact, that the testis
itself is the proper site of this development, so that, under normal condi-
tions, developed, spermatic filaments may always be found in the nuclei,
in the internal portions of the gland, and frequently in every seminiferous
tube without exception. But in the normal course of things the sper-
matic filaments in the testis itself do not become liberated at all, or in
very small proportion, and the tuhuli seminiferi, consequently, are by
no means the situation in which spermatic filaments are to be sought
for, although even here, on the addition of water, which causes the sub-
stance by which they are enclosed to burst, they will always be found.
They do not occur in the free state before reaching the rete testis and
eoni vasculosi. First, the nuclei burst, and the filaments remain in the
spermatic cells, in which, when numerous (10-20), they are very regu-
larly disposed in close apposition, with the heads and tails together, in
a curved bundle, or when in less number, confusedly aggregated. Ulti-
mately these cells and cysts also burst, the filaments are liberated, and,
forming a dense entangled crowd, entirely fill the epididymis, still in
part associated in bundles, which, however, also are soon broken up, in
part isolated. In the lower portion of the epididymis, the entire pro-
cess of development is usually concluded, though it happens, not unfre-
quently, that isolated transitional forms are conveyed still farther, and
are not completely developed before reaching the vas deferens.

The semen, regarded as a whole, as it is found in the vas deferens, is
a whitish, viscid, inodorous material, consisting almost entirely of sper-
matic filaments, and containing between those bodies an extremely
minute quantity of a connective fluid. The chemical composition of

624 SPECIAL HISTOLOGY.

this unmixed semen has not yet been investigated in Man ; but we
know through Frerichs, with regard to the semen of the Carp, that the
spermatic fluid contains no albumen, some little mucus, and, of salts,
chloride of sodium, and a small quantity of alkaline sulphates and
phosphates ; whilst the spermatozoa consist of a protein compound
(according to Frerichs, hinoxide o^ iJrotein), and contain besides 4-05ff of
a yellowish, butyraceous fat, and 5-21o' of phosphate of lime. The
semen, as ejaculated, is a mixture of pure semen, and of the secretions
of the vesiculce seminales, the prostate and Cowpers glands. It is, in
this condition, colorless, opalescent, with an alkaline reaction and pecu-
liar odor ; when emitted, it is viscid and glutinous, like albumen, but on
cooling becomes gelatinous, and after some time again thinner and
fluid. When examined microscopically it presents, besides the sperma-
tozoa, a moderate quantity of a clear fluid, which, on the addition of
water, presents irregular-sized whitish flocculi and fragments, and is
undoubtedly derived principally from the vesiculce seminales. This
gelatinizing substance, which Henle described as fihrin, and Lehmann
regards as an albuminate of soda, has been described by Vauquelin,
who analyzed human emitted semen, together with the substance of the
spermatic filaments, as spermatin, of which he found 60-, whilst besides
it there were present 90 0' water, 3° earthy phosphates, and lo soda.
When semen is dried, innumerable crystals of the triple phosphate of
magnesia and ammonia are formed among the undestroyed spermatozoa,
which generally, owing probably to the considerable quantity of car-
bonate of lime contained in them, are not easily destructible. They
may be demonstrated in seminal spots even after a long time, when
they are moistened ; resist putrefaction for a lengthened period in
water and animal fluids (Donne observed them even after three months
in putrid urine), and retain their form unchanged even after incinera-
tion (Valentin). Acetic acid has but little efi'ect upon the spermatic
filaments. Caustic potassa and soda render them pale, and dissolve
them, after from 15 to 30 minutes. Nitric acid (20[}) at first produces
scarcely any change, afterwards dissolving them. In sulphuric acid
their outline becomes extremely faint, and they swell up, but are not
entirely dissolved, as are, for instance, the epithelial cells of the seminal
tubes. They are not colored yellow by nitric acid and potassa, nor red
by sugar and sulphuric acid. Nitrate of potassa in a solution contain-
ing 6 per cent, does not dissolve them. In the pure semen the fila-
ments exhibit no movemeiits, or scarcely any, when it is too much con-
centrated. Their movements are first visible in the contents of the
vesiculce seminales, and in ejaculated semen, or when pure semen is
diluted. The movement of these bodies is effected solely by the alter-
nate flexure and extension, or serpentine motion of the filamentary
portion, in which way are produced such lively and various undulating.

THE SEXUAL ORGANS. 625

rotatory, quivering changes of place, during which the head or body
always precedes, that these elements of the semen were formerly
regarded as animals. The duration of the movements depends upon
various circumstances. In the dead body they are not unfrcquently
perceptible, even 12-24 hours after death (on one occasion Valentin
noticed faint motion at the end of even 84 hours), and in the female
genital organs in the Mammalia, they exhibit motion even after seven
or eight days. Water at first renders the motions more lively, but they
soon cease, and the filaments are not unfrcquently curved in a loop-
like form. Blood, milk, mucus, pus, syrup, and a diluted saline solu-
tion usually have no injurious efllect ; but it is otherwise with urine and
bile, the former particularly, when it is strongly acid or much diluted.
All chemical reagents, acids, metallic salts, caustic alkalies, &c., cause
the motion to cease, as do narcotics when they act chemically upon the
filaments, or are too much diluted.*

The formation of the spermatic filaments and of the semen, it is true,
usually ceases in old age, although they are not unfrequently found in
men of 60, 70, or even 80 years of age, and even accompanied — though
this, it must be confessed, is an unusual phenomenon — with the procrea-
tive faculty. After diseases, the spermatic filaments are as often found
to be present as absent ; and, with respect to the cause of their defi-
ciency, only this much can be stated, that it appears to depend princi-
pally upon impaired nutrition. f

* [Chloroform exerts the same influence upon the spermatozoa as it does upon all
motile tissues in animals and plants. The spermatozoa of the Frog, when exposed to the
dilute vapor of chloroform, gradually cease to move, regaining their motile property upon
exposure of the fluid to the air (at any rate many of them), and the filaments thus re-
vivified, appear to retain all their impregnating power. — Trs.]

■j" [The origin and development of the spermatic filaments have lately been accurately inves-
tigated by Dr. Burnett (vid. Mem. of Americ. Acad, of Arts and Sciences, v. i., 1853). From
an extensive series of researches in the vertebrate animals. Dr. Burnett concludes that the
morphological changes in the sperm-cell, preceding the formation of the spermatic filaments,
are identical in their character with the changes in the ovum, which are antecedent to the
formation of the new being. When the generative function begins to be developed,
the character of the epithelial cells, lining the tubules, is modified. The cells pass to
a higher degree in function, but do not undergo any change in structure, except a slight
increase in size. In this condition, they divide and subdivide, by a process similar to the
segmentation of the yelk, until they are entirely converted into a mulberry mass. A lique-
faction of the segmented contents into a minute granular blastema then ensues, and from
this the spermatic filaments are developed. In the Plagiostomes, Dr. Burnett was able
to observe the disappearance of the mulberry mass, and its replacement by a fasciculus
of spermatic filaments, although the exact metamorphosis by which the granular cellular
mass formed the bodies of the spermatozoids could not be detected. The spermatic filaments,
Dr. Burnett thinks, are not formed, as stated by Kolliker, by a deposit from the contents of
the sperm-cell or nucleus, but by an elongation of the cell or nucleus itself. The body of
the spermatozoid is developed from the cell, whilst the tail is probably subsequently formed
by an accumulation of minute granules.

The absence of these spermatic particles does not always, as above stated, depend upon
impaired nutrition. M. Gosselin (Archives Generales de Medicine, Sept., 1853) has noticed

40

626 SPECIAL HISTOLOGY.

§ 199. Membranes, vessels, and nerves of the testis. — The testes,
together with their fibrous tunic, and a portion of the ejndidi/mis, are
immediately invested by the tmiica vaginalis propria (Fig. 255, h, d, /),
a delicate serous membrane, which, at one time, was a part of the 'peri-
toneum, and corresponds with it in structure. Its epithelium, constituted
of a layer 0-005 of a line thick, of clear, polygonal cells, 0'005-0-008
of a line in size, with distinct nuclei, and occasionally with isolated, yel-
lowish pigment-granules rests on the testis, immediately upon the fibrous
membrane, or, at all events, in this situation, is inseparably united with
the fibrous coat constituting the tunica adnata testis, or the visceral
lamella of the t. v. propria; whilst, on the epididymis, the serous coat
may be distinctly separated, and, like its parietal portion, consists of
dense connective tissue containing elongated nuclei. The tunica vagi-
nalis communis, is a dense, tolerably thick membrane, consisting, on the
testis, of firm connective tissue, and higher up, of a more lax reticulated
tissue with elastic fibres ; it closely surrounds the tunica vaginalis propria,
and also invests the spermatic cord, and the lower end of the epididymis.
Between it, the tunica propria, and the epididymis, and firmly con-
nected with both tissues, is placed a layer of smooth muscles, usually
corresponding to the two lower thirds of the testis, — the internal mus-
cular tunic of the testis ; whilst on its outer side is inserted the cremaster,
composed of transversely striated fibres. The scrotum, lastly, is formed
by the external muscular tunic of the testis, which is more laxly con-
nected with the t. v. coynmunis, — the tunica dartos ; with respect to
which, vid. § 34 ; and by the external integument, which is characterized
by its thinness, the absence of fat, the color of its epidermis, and its,
mostly, large sebaceous and sweat-glands.

The bloodvessels of the testis and epididymis are derived from the
long and slender a. spermatica interna, which, running in the spermatic
cord, proceeds from its posterior aspect to the testis, and sometimes
entering at once the corpus Highmorianum, sometimes divided into nume-
rous branches, ramifies in the fibrous tunic of the testis, and on its inner
surface, proceeding towards the anterior border of the gland. The
coarser ramification in the parenchyma of the testis proceeds partly from
the corpus Highmorianum, partly from the points of origin of the septula
testis, from the tunica albuginea, into the septula, from which, again,
numerous more minute vessels penetrate into the interior of the lobules,
constituting a rather wide-meshed plexus of capillaries, 0'003-0'008 of
a line in diameter, around the tubuli seminiferi. In the epididymis

that in the semen of patients who had sulTered attacks of double epididymitis, the spermato-
zoids remained absent for months, even for years, after a complete restoration of the general
health. In some diseases, the spermatozoids themselves are changed. Thus, Lallemand
(Annales des Sciences Nat., torn. xv.. p. 30), states, that in patients broken down by seminal
losses, they appear imperfectly formed, the tails being rough, irregular, and indistinct. —
DaC]

THE SEXUAL ORGANS. 627

there is a similar though less abundant plexus, in the formation of ^vhich
the artery of the vas deferens also participates (Fig. 257), whilst the
scrotum and the t. vaginalis are richly supplied with vessels from the
aa. scrotales and spermatica externa. The veins accompany the arte-
ries, and ■with respect to the lymphatics, not only are those of the
scrotum and vaginal tunics extremely numerous, but, according to the
beautiful researches of Panizza (" Osservazioni," Tab. VIII.), confirmed
by Arnold, those of the testis are also very much developed. They pro-
ceed partly from the interior, partly from the surface of the testis and
epididymis, form beneath the tunica adnata beautiful plexuses, ulti-
mately connected by several trunks in the spermatic cord, and, together
with those of the vaginal tunics, communicate with the lumbar glands.

The few nerves of the testis are derived from the internal spermatic
plexus, and accompany the arteries to the gland. I have in vain endea-
vored to follow their course in the interior, where it but rarely happens
that dark-bordered nerves are seen, even accompanying the larger arte-
ries of the parenchyma.

§ 200. Vasa deferentia, vesicular seminales, accessory glands. — The
spermatic ducts, or vasa deferejitia, are cylindrical canals, having a mean
width of 1-lj lines, the walls being J-f of a line thick, and the cavity
|-|- of a line in diameter, and composed, most externally, of a thin
fibrous membrane, then of a strong, smooth-muscular layer, and most,
internally, of a mucous membrane. The muscular tunic, which is 0*38
-0*6 of a line thick, consists of an external, strong layer of longitudinal
fibres, a middle one, also strong, of transverse and oblique fibres, and
an internal thinner longitudinal layer, constituting not more than ^th of
the whole muscular tunic. The tissue is constituted of stiflf and pale
fibre-cells, as much as O'l of a line in length, and having an average
width of 0*004-0-006 of a line, intermixed with some connective tissue,
and a very few pale elastic fibrils. The mucous membrane, 0-12 of a line
thick, is white, longitudinally plicated, and in the last, broadest and
widest portions of the duct, presents numerous larger and smaller /ossce,
disposed in a reticular manner. Its external two-thirds are whiter, and
contain one of the closest felted tissues of elastic fibrils with which I am
acquainted ; whilst towards the interior is found a more transparent,
thinner layer, composed of an indistinctly fibrous connective tissue, with
nuclei, upon which rests a single layer of tessellated epithelium, consti-
tuted of cells 0-005-0'008 of a line in size, and which almost invariably
contain a certain number of brownish pigment-granules, from which the
internal surface of the mucous membrane acquires a yellowish hue. The
vessels of the vas deferens are very distinct in the external fibrous tunic,
but also penetrate into the muscular and mucous coats, constituting in
each, loose plexuses of capillaries 0'003-0-005 of a line in diameter.

628 SPECIAL HISTOLOGY.

According to Swan ("Nerves of the Human Body," PI. V., 82; VL,
81), the vas deferens within the pelvis is surrounded by numerous, but
fine nerves, which are in connection with those of the lateral and me-
dian, vesical and rectal nerves, as well as with those of the hypogastric
plexuses. I have myself also seen these nerves, which contain fine
fibres, and "fibres of Remak," but have been unable to trace them in
the interior.

The structure of the ejaculatory ducts and vesiculce seminales appears
to be the same as that of the vasa defej'entia ; the seminal vesicles, as is
•well known, being nothing more than appendages of the latter, furnished
with wart-like, saccular, or even branched processes. The ejaculatory
ducts, in their upper portions, present the same muscular structure as
the spermatic canal, only that their walls are more delicate. As they
approach the prostate, their membranes become still thinner, but never-
theless, even at the ultimate extremity, exhibit muscular fibres, mixed
with a considerable quantity of connective tissue and elastic fibrils. The
walls of the vesiculce seminales are much thinner than those of the vas
deferens, although they possess the same structure, except that the mani-
festly vascular mucous membrane is furnished throughout with reticular
fossce. Externally, the vesiculce seminales are invested with a membrane,
in part composed solely of connective tissue, in part, as on the posterior
surface, distinctly muscular, which is continued between the separate
convolutions of its canal, connecting them together ; and, at the inferior
end, passes from one vesicula seminalis to the other, in the form of a
broad muscular band. The contents of the vesiculce seminales are, nor-
mally, a clear, rather viscid fluid, which after death acquires a soft gela-
tinous consistence, though subsequently it becomes perfectly fluid ; it
contains a protein-compound very readily soluble in acetic acid and
which is obviously identical with that contained in the ejaculated semen.
With many other observers, I have so frequently seen spermatic fila-
ments in the vesiculce seminales, that I should describe their occurrence
there as normal, and assign a double function to the seminal vesicles ;
together with its principal one, of afi"ording a special secretion, that of
also performing the part of seminal receptacles. The nerves of the vesi-
culce seminales are derived from the sympathetic, and spinal cord, imme-
diately from the rich plexus seminalis, the filaments of which, in part,
penetrate the membranes of the vesicles, though they cannot be traced
further, in part proceed to the 'prostate, whose plexus — plex2is prostati-
cus — receives additions also from the vesical and inferior pelvic plexuses.

The prostate, according to my observations, is a very muscular organ,
so much so, that the glandular substance does not constitute more than
one third or a half of the whole mass. Proceeding from within to with-
out, there is presented in intimate connection with the thin mucous mem-
brane, the epithelium of which is always in two layers, though possess-

THE SEXUAL ORGANS. 629

ing a superficial lamella composed of cylindrical cells', a yellowish longi-
tudinally fibrous layer, which extends from the trigonum vesica?, to the
caput (jallinagmis, is, in fact, unconnected with the muscles of the blad-
der, and is composed, in equal proportions, of connective tissue with
elastic fibres, and of smooth muscles. To this succeeds a strong layer
of circular fibres of a similar structure, continuous with the sphincter
vesica; extending as far as the caput gallinaginis^ and which I term the
sphincter prostatcc. Beyond these difi"erent muscular layers, we come
at last to the proper glandular tissue of the prostate, which consequently
occupies, principally, the more external portions of the organ, although
it is true that isolated lobules encroach upon the circular fibres; its
numerous excretory ducts penetrate the longitudinal and transverse
fibres, and open on both sides of the caput gaUinaginis. The latter
consists of a grayish-red, tolerably dense substance, which may be very
readily split into fibres in the direction of the transverse diameter of
the organ, or more accurately described, radiates on all sides of the
upper surface of the organ, and is composed, in the first place, of vari-
ously-sized bundles of evidently smooth muscle, and secondly of the
glands of the prostate. The latter are 30-50 compound, racemose
glands, whose aggregate form is conical or pyriform, and which are dis-
tinguished from the usual kind of racemose glands by their more lax
structure, their evident composition of numerous, pedunculate, glandu-
lar vesicles, and the slight development of the extremely minute glan-
dular lobules, a condition which is partly connected with the abundant
fibrous tissue interposed between the glandular elements. The glandu-
lar vesicles are pyriform or roundish, O-Oo-O-l of a line in size, and
lined with polygonal or short, cylindrical epithelial cells, 0-004-0-005
of a line long, with brown pigment granules; whilst in the excretory
ducts, the same cylinders are met with as exist in the prostatic portion
of the urethra. The secretion of the prostate appears to be similar to
thut of the vesicular seminales ; at all events, according to Virchow, the
prostatic concretions, or stones, as they are termed — round, concentric
concretions, 0*03-0*l of a line, and more, in size, which are formed in
the glandular vesicles — consist of the same protein-compound, soluble
in acetic acid, w^hich is found in the vesiculce seminales. The prostate
possesses a fibrous coat, abounding in bundles of smooth muscles, and
closely investing the glandular tissue, and tolerably numerous vessels,
among which numerous capillaries surrounding the glandular elements,
and a rich venous plexus under the mucous membrane of the urethra,
are deserving of notice. The course of the nerves above described, in
the interior of the prostate, is unknown.

The uterus masculinus, or vesicula prostatica, situated in the caput
gaUinaginis, in the middle, between the ductus ejaculatorii, presents in
its whitish-yellow walls, lined with a cylinder-epithelium, principally

630 SPECIAL HISTOLOGY.

connective tissue and elastic fibrils, mih •which, in the neck of the blad-
der, a few, and, at its base, pretty numerous flat, smooth muscles are
intermixed.

The glands of Cotvper are compact, compound, racemose glands,
•whose ultimate vesicles, 0-02-0 -05 of a line in size, are lined -with a
tessellated epithelium., -whilst a cylindrical epithelium is found in the
excretory canals. The delicate membrane "with which the whole gland
is invested, as well as the fibrous stroma in its interior, is tolerably rich
in smooth muscles, which have lately been also found by me in the ex-
cretory canals, \ of a line wide, as a delicate longitudinal layer. The
secretion of these glands, which may be readily obtained from the ex-
cretory ducts, is common mucus.

§ 201. The organ of copulation, in Man, consists of the penis, an
organ which is composed of three erectile, highly vascular bodies — the
corpora spongiosa s. cavernosa ; it is attached to the pelvis, and traversed
by the urethra, invested by special fasciae and by the external integu-
ment, and furnished with three proper muscles.

The corpora cavernosa penis are two cylindrical bodies separated
posteriorly, united anteriorly, and parted only by a single incomplete
septum, in which are to be distinguished a special fibrous membrane
(tunica albuginea s. fibrosa), and the internal spongy tissue. The
former, which is a white, glistening, very strong membrane, ^ a line
in thickness, constitutes both the external tunic of the spongy bodies,
and also, in its anterior half — as a thin lamella, partially broken up into
separate fibres and laminoe — the septum between them ; it consists of
common fibrous tissue, like that of tendons and ligaments, with nume-
rous, well-developed, fine, elastic fibres. Within it lies the reddish
spongy substance, consisting of innumerable fibres, bars, and laminae,
united into a fine meshwork — the trabecular carp, cavernosorum ; and
with its minute, rounded-angular cavities, which anastomose on all sides,
and, in life, are filled with venous blood, the venous sinuses of the
spongy body, bears the most deceptive resemblance to a sponge. All
the trabecular, without exception, present precisely the same structure.
Externally they are covered by a simple layer of intimately connected
tessellated epithelium, the cells of which frequently do not admit of
being separated, — the epitheliiim of the venous spaces; to this succeeds
the proper fibrous tissue, which is composed on the one hand of almost
equal proportions of connective tissue and fine elastic fibres, and on the
other of smooth muscles, and in many, but by no means in all, the tra-
beculce, encloses larger or smaller arteries and nerves. The elements of
the trabecular muscles are not only at once distinctly recognizable from
their wholly characteristic nuclei, on the addition of acetic acid, but
may also be isolated in great numbers, and especially after treatment

THE SEXUAL ORGANS.

631

with nitric acid of 20;>, appearing as fibre-cells 0-02-0'03 of a line long,
0-002-0-0025 of a line broad.

The corpus cavcrnosiim urethrce {corpus spongiosum) is constructed
essentially in the same way as that of the penis, except that, 1, the
fibrous membrane, which in the bulb also forms the rudiment of a septum,
is much thinner, less white, and more abundantly supplied with elastic
elements ; 2, the intertrabecular spaces are smaller, being smallest in the
glans ; 3, and lastly, the traheculce are more delicate, and, beneath the
epithelium, richer in elastic fibrils ; having, however, in other respects,
the same structure as elsewhere.

This is the place also to speak of the male urethra, which at the
isthmus is an independent canal, whilst at its commencement and termi-
nation it consists merely of a canal of mucous membrane, supported by
the prostate and corpus cavernosum urethrce. The proper mucous mem-
brane, beneath a longitudinal layer of connective tissue abounding in
elastic fibres, presents not only, as already mentioned, in the prostatic
portion, but also in the membranous parts, although less developed,
smooth muscles mixed with the usual fibrous tissue, disposed longitudi-
nally and transversely ; to which again succeed the animal fibres of the
musculus 7irethralis. In the pars cavernosa, also, the submucous tissue
still presents, here and there, muscles of the same kind, and at a certain
depth longitudinal fibres are always found, with a greater or less inter-
mixture of such, which, however, cannot be referred to the corpus caver-
nosum, seeing that there are no venous spaces between them ; but which
rather form a continuous membrane, bounding the true corpora caver-
nosa,^ on the side towards the mucous membrane of the urethra. The
epithelium of the urethra is formed of pale cylinders, 0'012 of a line in
size ; beneath which, however, are found one, or perhaps two, layers of
round or oval cells. In the anterior
half of the fossa of Malpighi exist
papillw 0-03 of a line long, and a
tessellated epithelium, 0*04 of a line
thick. In the isthmus and pars caver-
nosa urethrce are found, in conside-
rable number, the so-termed " glands
of Littre," J-| a line in size, which,
speaking generally, rank with the
racemose glands, although distin-
guished from them by their tubular
form, and the frequently much con-
voluted course of the glandular vesi-

FiG. 261. — "Gland of Littre," from the /ossa Morgagni,in Man; magnified 500 diameters.

* [Mr. Hancock published, in 1851, an account of tlie distribution of tlie organic muscular
fibres of the urethra, essentially agreeing witli tlie above. He states that this internal mus-
cular coat of the corpus spongiosum, or, as Mr. Hancock prefers to call it, muscular coat of the

Fiff. 261.

632 SPECIAL HISTOLOGY.

cles, ^Yllicll are 0-04-0-08 of a line wide. More simple forms of glands
of this kind (Fig. 161) are occasionally met with intermixed with the
others ; and in the pars prostatica^ instead of them, we find minute
mucous follicles, similar to those which have been before described as
occurring in the cervix vesicce. The epitheliwn, both in the vesicles of
the "glands of Littre" and in the excretory ducts, 1-2 lines long,
which are directed forwards, penetrating the mucous membrane obliquely,
is cylindrical ; in the former situation, however, more or less approach-
ing the tessellated form (Fig. 261); the secretion is common mucus,
which in dilatations of the glandular follicles is, not unfrequently, col-
lected in some quantity. Some minute, inconstant fossse of the mucous
membrane have been termed laeunce Morgagni, in which I have been
unable to detect anything of a glandular nature. The fascia jjenis, a
tissue abounding in finer elastic fibres, surrounds the penis, from the
root to the glans, being, in the former situation, in connection with the
perineal fascia, and that of the inguinal region, and also contributes to
the formation of the susperisory ligament of the penis, a structure very
rich in true elastic tissue, which extends from the symphysis to the
dorsum p)enis. Externally it is continuous, without any line of demar-
cation, with the skin of the p)enis, which, up to the free border of the
prepuce, a simple duplicature of it, possesses the nature of the common
integument ; though certainly characterized by its delicacy, and the pre-
sence of a layer of smooth muscles in the abundant, fatless, subcutaneous
tissue, a continuation of the tunica dartos [vid. § 34), which extends as
far as into the prepuce. At the border of the prepuce the integument
of the penis assumes more of the nature of a mucous membrane, and is
no longer furnished with hairs and sudoriparous glands, although it has
well-developed papillce; it is still thinner than before, and on the glans
is intimately connected with the spongy body, and covered with a softer
cuticle (§ 42, Fig. 56, 4), always, however 0-035-0-056 of a line thick.
With respect to the sebaceous glands [gl. Tysonianai), which exist in
this situation, and the formation of the preputial smegma, consult §§
46, 74.

The arteries of the penis are derived from the p)udic, and are pecu-
liar only in the way in which they supply the corpora spongiosa. In
the corj}. cav. penis, except a few small twigs from the a. dorsalis, the

urethra, unites with the external coat, at the lips of the urethra, so as to form a sort of sphincter.
Mr. Hancock also discovered and described the abundant organic muscles surrounding the
vesicles and ducts of the prostate, which, though admitted in the text, were denied by Prof.
Kolliker, in his Essay upon the distribution of the organic muscles in Siebold and Kolliker,
Zeitschrift. Mr. Hancock further states that the muscular fibres of the membranous portion
of the urethra are continued over the inner and outer surfaces of the prostate, into the mus-
cular coat of the bladder, so that, according to his view, there is one continuous muscular
coat, from the bladder to the end of the penis, which twice separates into two layers; pos-
teriorly, to enclose the ])rostate, anteriorly, to envelop the spongy tissue of the corpus spon-
giosum.— See Hancock on the "Anatomy and Physiology of the Urethra," 1S52. — Tes.]

THE SEXUAL ORGANS.

633

a. profundce pmis alone run near the septum, surrounded by a sheath
of connective tissue continuous with the trabecular network, in fact
directly forwards, but giving off a small twig to the bulbs of the crura.
In this course they afford numerous, occasionally anastomosing branches
to the spongy substance, which, running in a convoluted manner (except
at the time of erection) in the axis of the trahecuhv, ramify in them, and
ultimately, without the formation of capillary plexuses open into the
venous spaces, by capillaries of 0-006-0-01 of a line in diameter. In
the posterior part of the penis there are numerous minute arterial
trunks, measuring 0'04-0-08 of a line in diameter, and for the most
part lying from 3-10 together, as was first observed by J. Mliller ; they
are contorted and convoluted in a peculiar, tendril-like manner {arterice
helicincr), and do not terminate in crecal ends, but, as I have ascertained,
give off from their clavate extremities minute vessels of 0-006-0-01 of a
line, which, like the other arterial prolongations, are continued further, and
terminate in the venous spaces. The arterial ramification is precisely

Fis:. 262.

similar, in the corpus cavernosum uretlirce, which is furnished with its
supply from art. bulbosce, bulbo-uretJirales, and dorsales, and in the bulb
there also exist art. helicince. The veins commence, as it may be said,
in the venous spaces which intercommunicate throughout ; and from
which, though not universally from the same situations, short efferent
canals, or ennssaria, receive the blood and convey it into the external
veins, furnished with special walls {vena dorsalis, v. v. profundas, and
bulbosce in particular). The lymphatics form very close and delicate
plexuses in the skin of the glans, the prepuce, and in the remainder of

Fig. 262. — Arteries from the corpora cavernosa penis of Man, injected ; magnified 30 diame-
ters. 1, one of the smaller arteries, with a lateral branch, dividing into two helicine arteries,
from the extremities of which two very small vessels proceed, and are continued into the
delicate traheculm ; 2, five helicine arteries placed on a short stem of a larger arterial divi-
sion ; from two of these, fine vessels are seen to be given off, the others appear to terminate
in cajcal ends : a, trabecular tissue, here presenting the form of sheaths to the arterial trunks
and helicine arteries; b. wall of the arteries.

634 SPECIAL HISTOLOGY.

the integument, and communicate with the superficial inguinal glands
through trunks accompanying the dorsal vessels. According to Mas-
cagni, Fohmann, and Panizza, there are also numerous lymphatics in the
glans surrounding the urethra, which run backwards on that canal, and
proceed to the pelvic glands.

The nerves of the Joe«.^'s are derived from the pudendal and the plexus
cavernosus of the si/mpatketic, the former of which are distributed
principally to the skin and the mucous membrane of the urethra, and,
in a small proportion only, to the corpora cavernosa, to which alone the
latter set of nerves is destined. The terminations of the former nerves
present the same conditions as those of the integuments ; numerous
divisions, in particular, and faint indications of axile corpuscles, occur in
the glans penis ; those of the latter nerves are not as yet known,
although, in the traheculce of the corpora cavernosa, nerves with fine
fibres, and "fibres of Remak," are readily demonstrated.

The smooth muscles of the corpora cavernosa are very distinctly
shown in i\\e penis of the Horse and Elephant, but are also not want-
ing in those of other Mammalia. The art. helicino', since Valentin and
Henle have declared them to be produced artificially, and to arise from
the inrolling of traheculce which have been cut across, or from the spon-
taneous retraction of certain arteries in stretched traheculce, have been
generally rejected,' but incorrectly. They do exist ; only I am satisfied
that the circumstance, noticed even by J. Muller, of the extremity of
one of these arteries, giving off an excessively delicate, almost capillary
vessel, occurs very frequently, and consequently, that the crecal termi-
nations are merely apparently such. That similar terminations do not
exist at all, cannot however, be definitively proved, and it is very pos-
sible that Mliller, in this respect also, may still be right. The art.
helicinw, therefore, are not simple vascular loops, as which they are
described by Arnold, although, in one instance, I have noticed such an
arrangement in place of them.

§ 202. Physiological remarks. — The development of the testes, com-
mencing in the second month, takes place, according to all that we
know, from a hlastema which appears independently on the inner side
of the Wolffian body ; and, at first, the form of the male sexual glands
entirely resembles that of the ovaries. At a subsequent period, when
the Wolffian body begins to waste, a portion of its fine canals, the
Malpighian corpuscles of which disappear, become connected with the
testes, and are formed into the epididymis, whilst at the same time the
excretory duct of the Wolffian body constitutes the vas deferens.* Then,

* [It is a curious fact connected with this alley;ed origin of tlie epididymis distinctly from
the rest of the gland, that, iu cystic disease of the testicle, eitlier of the innocent or tnalig-

THE SEXUAL ORGANS. 635

by .1 process not as yet accurately explained, the testes, with its perito-
neal investment, descends into the scrotmn under the agency of the
ffubernaculum, a process composed of transversely striated and smooth
muscles ; and by the growing together of the peritoneal protrusion
contained in the gubernaculum — the processus vaginalis peritoncei, —
with its own proper serous coat, acquires its tunica vaginalis propria.
The vesicula j^rostatica, the analogue of the uterus, and probably of
the vagina, is the remainder of the " Mullerian ducts," two canals,
descending on the external border of the Wolffian body, which, in the
female, form the oviduct and by the coalescence of their extremities,
the uterus and vagina; but in the male disappear, except the com-
mencement, which becomes the " hydatids of Morgagni," and the last
portion. The vesicular seininales are protrusions of the v. defercntia ;
and the prostate, Cotcper's, and the smaller glands, are most probably
formed, in analogy with other similar glands, from the epithelium of the
urethra. The penis is developed from the pelvic bones outwards, and
does not, till subsequently, include the urethra which is formed by the
closure of a groove on its inferior surface.

With respect to the histological development of these parts little is
known. The testes are constituted originally of a uniform cellular sub-
stance, which, however, soon begins to divide into transverse rows, form-
ing the rudiments of the seminal tubes. These are, at first, straight
C£ecal canals, extending from the outer border of the testis to the inte-
rior, which most probably originate as solid tracts of cells, and only
subsequently acquire a cavity and membrana propria. From the con-
tinued growth, especially in length, of these primary channels, and the
production of offsets from them, the later, convoluted and very long
seminal tubes arise ; it appearing, in fact, that an entire lobule of the
testis is formed from each of them. The tunica albuginea of the testis
and its internal prolongations arise from the primary blastema of the
gland, and make their appearance at the same time with the seminal
tubes.

With regard to the physiological relations of the male sexual organs,
in the adult, I would here notice the following points. The secretion of
semen, in animals, does not go on continuously, like that of the urine,
but is intermittent, taking place only at the time of rutting or heat. In
Man, the capability of producing semen, assuredly, always exists,
although it does not appear to follow from this, that semen is being con-
tinually formed, and that what is not emitted undergoes absorption ; and
consequently it seems justifiable to suppose that the seminal tubes secrete
semen only when the secretion has been partially evacuated externally,
either in consequence of sexual congress, or of seminal emissions, and

nant type, the affection is " the result of morbid changes in the ducts of the rete testis ; this
part of the gland being the sole seat of the disease." (Curling, " Med. Chir. Transact.,"
XXXVI. p. 456, 1S53).— Tbs.]

636 SPECIAL HISTOLOGY.

an excitement of the nervous system has caused an increased flow of
blood to the testis. There are no certain facts in favor of an absorption
of the semen when formed, which could only take place in the vasa de-
ferentia and vesicidce seminahs ; for what is observed in animals, after
the rutting season is over, has no reference to this point ; and the very
circumstance, that in the situations above-mentioned, no traces of disin-
tegration of the semen are ever found, appears to be very much opposed
to such a supposition. At the same time, however, it is perhaps unques-
tionable, that without seminal evacuations, a formation of semen may be
possible ; for it is sufficiently established, that a rich, heating diet, and
an unsatisfied sexual excitement, often produce a turgescence of these
organs, attended with painful sensations, and most probably with a for-
mation of semen. The subsequent removal of this fulness does not,
however, appear to me incontestably to prove any absorption, because a
difference in the quantity of blood in the testis, and the passing of the
semen into the v. deferentia are sufficient to account for the restoration
of the usual condition. The fluid constituting a seminal emission is not
pure semen, but in great part the secretion of the vesieulce seminales and
j)rostate, and afi"ords no criterion by which to estimate the energy of the
secretion of the testes. The formation of the seme7i itself certainly does
not proceed rapidly and copiously, as might be concluded from the rela-
tively small quantity of blood contained in the testes, and from its slow
motion in them, necessarily consequent upon the anatomical conditions;
and as is also evident from the fact, that after a few previous emissions,
even in the most vigorous organisms, a certain time is requisite for the
preparation of a fresh secretion. The secretions of the accessory glands
are perhaps simply intended for the dilution of the semen.

That the seminal filaments are not animalcules, but elementary parts
of the male organism, it is useless at the present time to attempt to de-
monstrate ; although it is still as much as ever unknown, and will not
easily soon be ascertained, what is efi'ected by their curious movements,
which are obviously intended to convey them to the ovum, from the ute-
rus, which they probably reach in fruitful congress. Nor, from the ex-
periments of Prevost, Dumas, Schwann, and Leuckart, and the later
researches of Newport (Phil. Trans. 1851, 1), can the least doubt be en-
tertained that they are the true impregnating agent, and for the purpose
of impregnation must necessarily come in contact with the ovum. The
circumstance that motile spermatic filaments alone possess the fertilizing
property, and, according to Newport, that the efi"ect upon the ovum takes
place immediately upon the contact, although a short duration of the
contact of the spermatic filament with the ovum is necessary to render it
efficient, also shows, as it appears to me, that they do not act by afford-
ing any material substance to the egg, but in consequence of their ex-
citing actions in it, as bodies in a state of peculiar activity. In my first

THE SEXUAL ORGANS. 637

work upon the spermatic fluid, in which I expressed this view, in order
to indicate a ground for discussion, I compared its influence upon the
ovum to that of a nerve-fibre upon a nerve-cell, or of a magnet upon
iron : and these comparisons, to which might be added the influence
which a part of an organism exerts upon a self-organizing exudation, or
an entire organism upon a part in a state of self-regeneration, still appear
to me the most suitable, if impregnation is in any way to be assimilated
with other processes ; but I have no objection to offer, should the chemi-
cal side of the question be advocated in preference, as by Bischoff, and
the functions of the semen be referred to the category of catalytic phe-
nomena.*

In the act of copulation, various motile phenomena are presented, of
which we need discuss only those conducive to ejaculation and erection.
In the former the vasa deferentia, provided as they are with a colossal
muscular apparatus, are chiefly operative ; these organs, as Virchow
and I found in an executed criminal, shorten and contract with remark-
able energy when excited by galvanism ; as also do the vesiculce semi-
nales, the highly muscular prostate, and, of course, the transversely
striated muscular tissue of the urethra and penis. Erection is caused,
as I have shown (" Wiirzb. Verb." Bd. II.), by a relaxation of the
muscular elements in the traheculce of the cavernous and spongy
bodies, and of the tunica media of the arteries of those parts ; in con-
sequence of which the tissue, like a sponge which has been compressed,
expands and becomes filled with blood. The rigidity ensues so soon as
the muscles are completely relaxed, and the sinuses filled to the utmost,
without there being any necessity that the return of the blood should
be impeded, and the circulation stopped. It ceases when the muscles
again contract, the venous spaces become narrowed, and the blood is
expressed from them. In the act of ejaculation, the ischio-cavernosi,

* [The later, most important researches of Dr. Neilson, respecting the impregnation of the
ovum in Ascaris myslax (" Phil. Transact.," 1852), and of Mr. Newport (op. cit.), with regard
to that of the Frog, in which he has been compelled to abandon his former opinion, that the
spermatozoa did not penetrate through the vitelline membrane, and has shown that, in that
case, as in the one so ably described by Dr. Neilson, those bodies penetrated into the sub-
stance of the vitellus in large numbers, where they underwent changes, and finally disap-
peared— render much of the above speculation on the subject of their influence in impreg-
nation futile. Whatever may be the nature of the influence conveyed to the viiellus by the
spermatic filaments, it must now perhaps be regarded as an established fact, that it cannot
be communicated except by an immediate contact between the motile filaments and the sub-
stance of the vitelhis, which thereupon undergoes segmentation, and the series of changes is
commenced, to terminate in the evolution of the embryo. Additional confirmation of the
same fact would be afforded by Dr. Kebers researches on the entrance of the spermatozoon
into the ovum of Unio ("De introitu Spermatozoorum,"' &c., 1852), could full reliance be
placed upon his results; but this, from some investigations of our own on the same subject
— both in Unio and in Pholas — we consider extremely doubtful. The appearances he de-
scribes, much more resemble those noticed by Von Wittich and Cams in the ovum of Spi-
ders.—Tbs ]

638 SPECIAL HISTOLOGY.

and the hulho-cavernosus muscles, which are formed of transversely
striated fibres, increase the rigidity of the anterior parts by the com-
pression of the root of the penis and dorsal veins ; but under no
circumstances can they, of themselves alone, contribute to the bringing
about of the erection. I am not aware that any more important func-
tion can be assigned to the helicine arteries ; this much being certain,
that the erection does not depend upon them, because they do not occur
in every part of the human penis, and are wanting in many animals.

The investigation of the male sexual organs presents, generally
speaking, no great difficulties. The tuhuli seminiferi are very readily
isolated, and when they are carefully unfolded some divisions are
always met with. In order to trace their entire course, they must be
injected according to the directions of Lauth or Cooper, which may be
found quoted in all Manuals of anatomy. Lauth places the testicle for
two or three hours in lukewarm water, then expresses the semen as
completely as possible from the epididymis, and immerses the gland
for 3-4 hours in a solution of carbonate of ammonia, or for 8-12 hours
in a saturated solution of carbonate of potassa, or a weak solution of
caustic potassa, which reagents partly dissolve the spermatic cells and
epithelia ; the testis is then again compressed, laid in alkaline water,
and injected with quicksilver, at first under a weak and afterwards
under a strong pressure, a process requiring from 1| to 2 hours. So
soon as the quicksilver has penetrated into the vas deferens, the column
must be lowered to 5 inches, for otherwise the tuhuli seminiferi, the
filling of which demands some hours more, burst. Cooper injected
from the vasa efferentia, into which he introduced a fine canula. For
microscopical investigation, Gerlach recommends a solution of gelatine,
with carmine or chromate of lead. The vas deferens is best studied in
transverse sections, after it has been hardened or dried, as are also the
prostatic glands ; whilst the muscles of the prostate and the corpora
cavernosa can be distinctly made out only in the recent state, or after
the application of nitric acid. The helicine arteries may be seen, even
in fresh preparations, close to the larger arterial trunks, but still better
after injection with fine materials.

Literature. — A. Cooper, " Obs. on the structure and diseases of the
testis," London, 1830, with twenty-four plates; E. A. Lauth, "Mem.
sur le testicule humain," in " Mem. de la sociiJt^ d'histoire naturelle de
Strasbourg," tom. I, 1833; C. Krause, "Verm. Beobachtungen"
(various observations), in MUU. "Arch." 1837, p. 20; E. H. Weber,
" De arteria spermatica deferente, de vesica prostatica et vesiculis semi-
nalibus," Progr., 1836, editum in Progr. collecta, II. 1851, p. 178;
" Zusatze zur Lehre vom Bau und den Verrichtungen der Geschlechtsor-
gane" (Contributions to the knowledge of the structure and functions of

THE SEXUAL ORGANS. 639

the sexual organs), Leipsic, 1846 ; C. J. Lampferhoff, " De vesicularum
seminalium natural et usu," Berol., 1835; Kijllikcr, " Ueber die glatten
Muskeln der Harn- und Geschlechtsorgane," in " Bcitriige zur Kcnntniss
der glatten Muskeln" (On the smooth muscles of the urinary and genital
Organs, in Contributions to the knowledge of the smooth muscles), in
"Zeitsch. f. wiss. Zoologie," I. ; Fr. Leydig, "Zur Anatomic der miinn-
lichcn Geschlechtsorgane und Analdrlisen der Siiugethierc" (On the
Anatomy of the male sexual Organs and anal glands of the Mammalia),
in " Zeits. f. wiss. Zoologie," II. ; A. v. Lceuwenhoek, " Arcana
Nature," p. 59; Prdvost and Dumas, "Ann. d. Sc. Nat.," III. 1824,
and "Mem. de la Soc. d'llist. Nat. de Geneve," tom. I. p. 180; R.
Wagner, "Die Genesis der Samenthierchen" (The genesis of the Sper-
matozoa), in Mlill. " Archiv," 1836, and " Fragmente zur Physiologic
der Zeugung" (Fragments on the physiology of Generation), Munich,
1836; A. Donnd, "Nouv. Expdr. sur les animalcules spermatiques,"
Paris, 1837, and "Cours de Microscopic," Paris, 18-li ; A. Kolliker,
" Beitriige zur Kcnntniss der Geschlechtsverhaltnisse und der Samen-
fiussigkeit wirbelloser Thiere" (Contributions to the knowledge of the
sexual relations and the seminal fluid of the Invertebrata), Berlin, 1841,
and " Die Bilduns; der Samenfiiden in Bliischen als allfremeines
Entwicklungsgesetz" (The formation of the spermatic filaments in cells,
as a general law of Development), in " Denkschr. d. schweiz. naturf.
Gesellsch,," Bd. VIII. 1846; Kramer, " Obs. microsc. et experimenta
de motu spermatozoorum," Gott.. 1842; Fr. Will, "Ueber die Secre-
tion des thierischen Samens" (On the secretion of the semen of animals),
Erlangen, 1849; R. Wagner and Leuckart, art. '■'■Semen," in Todd's
"Cycl. of Anat." Jan. 1849; Newport, "On the impregnation of the
ovum of the Amphibia," in "Phil. Trans." 1851, I.; B. Panizza,
" Osservazioni anthropo-zootomico-fisiologische," Pavia, 1836; J. Mliller,
" Entdeckung der bei der Erection wirksamen Arterien" (Discovery of
the Arteries which effect Erection), "Arch." 1835, p. 202 ; G.Valentin,
" Ueber den Verlauf der Blutgefiisse in dem Penis des Menschen" (On
the course of the bloodvessels in the human penis), Mlill. "Arch." 1838 ;
Kobelt, " Die Mannlichen und Weiblichen Wollustorgane" (The male
and female sexual organs), Freiburg, 1844 ; Herberg, " De erectione
penis," Lips. 1844; Kolliker, "Ueber das Anat. und Phys. Verhaltea
der Cavernosen Korper der Mannlichen Sexualorgane" (On the ana-
tomical and physiological relations of the corpora cavernosa of the male
sexual organs), in "Verhandl. der Wlirzb. Med. Phys." Ges. 1851.
[11. Hancock, " On the Anatomy and Physiology of the Male Urethra,
1852;" Fr. Leydig, " Zur Anat. d. miinnl, Geschlechtsorgane u. Anal-
drlisen der Saligethiere," in " Zcitschrift flir wiss. Zool." Bd. II. ; Waldo
J. Burnett, "Researches upon the origin, mode of development, and
nature of the Spermatic Particles among the four classes of Vertebrated

640 SPECIAL HISTOLOGY.

Animals, in Mem. of Americ. Acad, of Arts and Sciences," V. part 1,
1853; H. Luschka, " Die Append ienlargebilde des Hoden," in "Vir-
chow's Archiv," VI. 3, 1854.— DaC]

B. FEMALE SEXUAL ORGANS.

§ 203. The female sexual organs consist : 1, of two follicular glands,
in which the ova are formed — the ovaries — with the parovaria^ and the
two excretory ducts, Avhich, however, are not directly connected with
them, — the oviducts, or Fallopian tubes ; 2, of the uterus, for the re-
ception and nourishment of i\\Q foetus ; and 3, of the parts subservient
to the expulsion of the foetus, as well as to copulation — the vagina
and external genitals.

§ 204. Ovary, parovarium. — The ovaries, ovaria, are constituted of
special tunics, and of a stroma containing the ova, or the parenchyma.
The former consist of a peritoneal coat, which covers all but the inferior
border, and of a firm, Avhite, fibrous coat, the tunica alhuginea s. propria,
:^ of a line thick, which closely invests the whole parencliyma, and is
intimately connected with it without any abrupt line of demarcation ;
but does not send any processes into the interior, like the correspond-
ing coat of the testes, with which, otherwise, it precisely corresponds
in structure. The stroma is a grayish-red substance, of tolerably firm
consistence, composed of a nucleated, tough, fibrous,
though not distinctly fibrillar, connective tissue, in
which are lodged the ovisacs and the vessels of the
organ. From the inferior border of the ovary, where
the vessels enter, and ovisacs are never situated, the
stroma extends, in the form of a compact lamella, into
the interior of the ovary, from which it then radiates,
in larger and more slender bundles, towards both sur-
faces and the free border of the organ, so that, in a
transverse section, a penicillar arrangement is pre-
sented by them. The ovisacs or follicles, usually termed Grraafian vesicles,
folliculi ovarii s. Crrafiani, s. ovi-sacci, entirely closed, round follicles,
from J to 3 lines in mean size (Fig. 263 a, b), are imbedded in the more
peripheral portions of the stroma, so that, in a section, at all events, of
well-developed and normal ovaries, the parenchyma separates, as it
were, into a medullary and cortical substance, the latter of which only
as it may be said, contains the follicles. Ovaries in that condition,
also, should alone be made use of, for the obtaining of a correct notion

Fig. 263. — Transverse section through the ovary of a woman dead in the fifth month of
pregnancy : a, Graafian follicle of inferior, and b, of the superior surface, c, peritoneal
lamella of the lig. latum, continued upon the ovary, and coalescing with d, the t. albuginea ;
in the interior, two corpora albicantia (old corpora lulea) are visible ; c, stroma of the ovary.

THE SEXUAL ORGANS.. ^ 641

of tlic size, position, and number of the Graafian follicles. The latter
amounts to 30-50-100 in each ovary, and in many cases may reach
200 ; Avhilst in arrested or degenerated ovaries, such as are frequent
especially in old women, not more than 2 to 10, or even none at all,
are often met with.

Each follicle, in the fully formed condition, consists of a membrane
and contents. The former may be most aptly compared with a mucous
membrane and presents : 1, a highly vascular fibrous layer, tlieca folli-
culi V. Baer, s. tunica fihi'osa, of a proportionately not inconsiderable
thickness, which is united to the stroma of the ovary by a rather loose
connective tissue, and consequently can be readily stripped off in its
totality. Its external, somewhat firmer, reddish-white layer (Fig. 264
a), has been distinguished by v. Baer from the internal, thicker, softer,
and redder portion (Fig. 264 b) ; but at the same
time it should be remarked, that the inner layer
also may be again divided, and that both laminm
are composed of the same undeveloped, nucleated
connective tissue, intermixed with numerous,
mostly fusiform, formative cells. In young folli-
cles a delicate, structureless, membrana prop'ia,
bounds the fibrous coat on the inner aspect and
may, by the use of alkalies, even at a later
period, frequently be demonstrated as a distinct membrane. 2, an
epithelium [granular layer, membrana granulosa of authors), (Fig. 264
5, c). This membrane, 0-008-0*012 of a line or more, in thickness,
lines the entire follicle, and on the side looking towards the surface
of the ovary, where the ovum is situated, presents a wart-like thicken-
ing, projecting towards the interior and enveloping the ovum — the ger-
minal eminence, cumulus pi'oligerus, J of a line broad (Fig. 264 e).
Its roundish, polygonal cells, 0-003-0-004 of a line in size, with pro-
portionately large nuclei, and, frequently, some yellowish fatty granules
disposed in several layers, are extremely delicate, and after death soon
become indistinct, in consequence of which the whole epithelium pre-
sents the appearance of a fine granular membrane with numerous
nuclei. The interior of the follicles is occupied by a clear, light-yel-
lowish fluid — liquor folliculi — of the density of the serum of the blood,
containing, almost always, isolated granules, nuclei, and cells, which are
scarcely anything more than detached portions of the membrana granu-
losa, and do not originate in the fluid.

In the germinal eminence, close upon the fibrous membrane of the
follicle, and therefore in the most prominent part of it, is placed the

Fig. 2G4. — Graafian follicle of the Sow, magnified about 10 diameters: a, external ; b,
internal, layer of the fibrous membrane of the follicle: c, membrana granulosa; d, liquor
folliculi : e, germinal eminence, a projection of the membrana granulosa ; f, ovum with a zona
pellucida, vUellus, and germinal vesicle.

- 41

642 SPECIAL HISTOLOGY.

egg (ovulum), imbedded in the cells of which the eminence is composed,
and retained in its position by them. When the follicle bursts, or is
ruptured, the ovulum escapes, surrounded by the cells of the cumulus,
and the contiguous part of the epithelium, which encompass it, as a sort
of ring or disc {discus proligerus, germinal disc, v. Baer), enclosing it,
however, entirely, and by no means only attached to it in its greatest
breadth. The ovulum itself is a spherical vesicle, measuring when
mature 1-8-1-10 of a line, which, though in certain respects peculiar,
nevertheless possesses the nature and constitution of a simple cell. The
cell-membrane, or vitelline membrane, membrana vitellina, has the un-
usual thickness of 0'004-0-005 of a line, and, in microscopical figures,

surrounds the contents, or 7/elk {vitellus), as a
'^" ■ clear, transparent ring, whence it has received

the name of zona pellucida. It is structureless,
very elastic, and firm, so as to support a consi-
derable degree of extension without being torn ;
and in chemical characters corresponds, in every
particular, with the membrance proprice, § 16.
The light-yellow yelk, which in recent ovula com-
pletely fills the vitelline membrane, is composed of viscid fluid, having
numerous minute, pale granules dispersed in it, Avith which, in the
mature ova, some fatty granules are also associated, and, in the fully-
formed ovum, contains, excentrically, a well-marked vesicular nucleus,
0-02 of a line, with clear contents, and a homogeneous, round, parietal
nucleolus, 0-003 of a line in size, the germinal vesicle, vesictda germina-
tiva (the "vesicle of Purkinj^"), and the germinal spot, macula ger-
minativa (or " spot of Wagner") as they are here termed.

The parovarium (Nebeneierstock)- a rudiment of the Wolffian body of
the embryo, consists of a certain number of canals, 0-15-0-2 of a line
in diameter, diverging from the hilus ovarii into the " bat's wing,"
which in Man neither open into the ovarium nor are connected witl^
any other parts, and contain nothing but a little clear fluid. The tubes
are formed of a fibrous membrane, 0-020-0-024 of a line thick, and of a
single layer of pale, cylindrical, probably ciliated cells, and are of in-
terest only as the remains of an embryonic structure.

The arteries of the ovary, derived from the aa. spermatica and uterina,
and forming numerous minute trunks between the lajiiellse of the broad
ligaments, enter from the inferior border of the ovary, run in a serpen-
tine course in the internal portion of the stroma, and terminate partly
in the stroma itself and in the t. albuginea, but chiefly in the walls of
the Graafian follicles, where they form an exterior more coarse, and an

Fig. 265. — Human ovulum, from a follicle of the average size, magnified 250 diam. : a,
vitelline membrane (zona pellucida) ; b, external boimdary of the yelk, and also internal
boundary of the yelk-membrane ; c, germinal vesicle, with the germinal spot.

THE SEXUAL ORGANS. 643

inner finer plexus, which extends as far as the memhrana granulosa.
The veins arise in the same situation, are in Man, for the most part,
very beautifully displayed in the walls of the larger follicles, and ter-
minate in the uterine and internal spermatic veins. A few lymphatic
vessels come out from the Jiilus ovarii^ and proceed, in company with the
bloodvessels, to the lumbar, and pelvic glands. And with respect to
the nerves^ they arise from the spermatic plexus, enter as minute trunks
with fine fibres, and " fibres of Remak," together with the arteries,
into the ovary ; but as respects their ultimate condition, they have not
yet been investigated.

§ 205. Detachment and re-formation of the ova, — corjjora lutea.
From the commencement of puberty up to the period of involution, the
ovaries are the seat of a continual detachment of the ova hy dehiscence
of the Graafian vesicles, which, independently of sexual congress, takes
place in women and virgins, above all at the menstrual period, although
it may and does frequently occur at other times, under conditions not
yet accurately determined. In animals the same process is exhibited
at the time of "heat," although sexual congress appears to afford a
necessary impetus to its completion ; and in them the anatomical pro-
cesses may be more completely traced, whilst, in Man, the opportunity
for such observations is much more rarely afforded.

When the Graafian follicles approach the time of bursting, they gra-
dually enlarge to a circumference of 4 to 6 lines and more, and are
continually brought more and more near to the surface, until they
project beyond it, as wartlike or hemispherical elevations, covered only
by a thin pellicle of the much attenuated t. albuginea, with its peritoneal
lamella. At the same time their vessels are remarkably multiplied, and
by the continual exudation from them, the liquor folliculi is rendered
more and more abundant, whilst the fibrous coat of the follicle, at the
bottom and sides, but not where the oviduni is situated, becomes thick-
ened towards the interior ; the memhrana granulosa also swells a little,
and contains larger cells (up to 0-01 of a line.) When these processes
have advanced to a certain point, the thin, opposing coats can no longer
withstand the continued and ever-increasing pressure from the interior
of the follicle ; they give way at the most elevated, and most thinned
point, exactly where the ovulum is situated, and this body, surrounded
by the cells of the germinal eminence, if the oviduct has applied itself
exactly over the follicle, escapes into it. But the vital course of the
Graafian follicle is not hereupon concluded, for now a series of partly
new formations is presented in it, in consequence of which it at first
becomes a corpus luteum, as it is termed, and ultimately disappears
altogether.

These corpora lutea are displayed in the most complete state, when

644 SPECIAL HISTOLOGY.

conception and pregnancy ensue upon the detachment of the ovum, and,
when in perfection, appear as roundish or oval, firm hodies, mostly
rather larger than the former follicles, and are usually visible even on the
exterior as projections, exhibiting on the summit a stellate cicatrix,
arising from the rupture of the Graafian follicle. Exteriorly, these
bodies are bounded, towards the stroma of the ovary, by a thin whitish
fibrous membrane (Fig. 266, 2 /), succeeded by a yellowish vascular
lamella, which is much plicated, and consequently appears thicker (Fig.
266 c); and in the interior is a larger or smaller cavity filled, either with
coagulated blood (blood-clot), or with a somewhat gelatinous fluid tinged
with blood (Fig. 266 d e). With respect to the origin of these bodies,
it is easily perceptible, that their "nucleus" or contents consist of the
blood poured out upon the rupture of the follicle, frequently mixed with
some remains of the liquor folUcuU, and that the outer fibrous mem-
brane is the external layer of the original fibrous coat of the follicle ;
and as regards the yellow plicated cortical layer, this is referable for

the most part to the internal layer of the
^'^■"^*'' fibrous membrane of the original follicle,

which, even before the expulsion of the
ovum, becomes loosened in texture, and
afterwards rapidly expanded to the thick-
ness of ^-J a line and more. The remains
of the ejnthelium, or memhrana granulosa,
•'m^i^^r'^ which were not expelled with the ovum from

the follicle, also seem to contribute to this
thickening, though in a subordinate degree,
and by no means in the same proportion as
the layer in question; the increased thick-
ness of which is accompanied by the deve-
lopment of a vast number of smaller and
larger cells, which are, in part, transformed
into immature connective tissue and vessels, in part remain in the con-
dition of cells, characterized by their size, which reaches as much as
0'01-0*2 of a line, their well-marked, vesicular nuclei with nucleoli, and
a greater or less number of yellow oil-drops in the interior. The corpus
luteum, thus constituted, retains its original size for some time, up to
the second or third month of pregnancy ; because, whilst the contents
(whether these are a blood-clot, or a reddish gelatinous substance with
a small cavity in the interior) gradually diminish and lose their color,
the yellow cortical layer continues to increase in thickness, and, at the

Fig. 2GG. — Two corpora lutea, of the natural size, in a transverse section. 1, quite recent,
eight days after conception; 2, at the fifth month of pregnancy: a, t,albuginea; b, stroma
ovarii: c, thickened and pUcated fibrous membrane of the follicle (inner layer); d, blood-clot
within it; c, discolored blood-clot; /, fibrous coat bounding the corpus luteum.

THE SEXUAL ORGANS. 645

same time, its tissue to become more organized and more compact ; this
change taking place by the transformation, on the one side, of the in-
ternal substance into fibrous tissue, and on the other by the more
intimate fusion of the yellow cortex with it, and the more abundant
development of immature connective tissue in the former. In the fourth
and fifth months the atrophy of the corpus luteiim commences, and is
slowly continued to the end of pregnancy ; so that in persons dead in
childbed, it still measures 4 lines on the average, but afterwards more
rapidly, until ultimately, after some months, the metamorphosed Graa-
fian follicle has entirely disappeared, or become reduced to a diminutive,
variously colored corpuscle, which undoubtedly may still exist for a long
time, and, perhaps, is not removed altogether for some years. Such
arrested corpora lutea [corpora alhicantia and nigra, of authors) at first
retain a distinct limitation, a dentate nucleus, containing a minute
cavity of a grayish white, or red-brown, even black color depending upon
altered hematin, and a cortical substance presenting various tints of
yellow or yellowish-white, or even quite white, and often still distinctly
plicated, but subsequently they become mere amorphous spots, coales-
cent with the stroma of the ovary. Their elements are fibres, more of
an embryonic character, such as also form the ovarian stroma, together
with various pigmentary molecules and colored crystals (haimatoidin),
and a whitish-yellow fat, which latter at first occurs in the cortical sub-
stance still contained in larger, round, elongated, or fusiform cells, but
is ultimately liberated by their rupture, and at last subjected to a more
or less complete absorption.

In the corpora lutea, which are not formed at the time of a preg-
nancy, the same processes, in general, take place as in the others, but
with much greater rapidity ; so that these bodies have usually entirely
disappeared in the space of one or two months, or left only the merest
trace, whence they never possess the peculiar conformation of the
others, which have been termed the true corpora lutea.^'

The place of the numerous follicles which disappear from the ovaries
during the whole of the vigorous periods of life, is supplied by the
constant production, even in the adult, of new ovisacs, which are
developed into Graafian follicles. In animals, these new formations
which take place at the time of heat, and were first noticed by Barry,
Bischoff, and Steinlin, are very abundant, and very easily observed,

• [Besides the difference in size and the rapidity of their metamorphoses, the true corpora
lutea are distinguisliable from the corpora hitea formed ia the non-pregnant state by the
thickness of the wall, and by their different color. The convoluted wall of the true corpus
luteum is almost always twice as thick, whilst its color and that of the central coagulum,
is never of so decided a yellow, but has generally more of a dusky and indefinite hue ; a
difference which is probably owing to a less number of yellow oil-globules. (Vide Dalton's
Prize Essay, " On the Corpus Luteum of Menstruation and Pregnancy," Transactions of the
American Medical Association for 1851.) — DaC]

646 SPECIAL HISTOLOGY.

whilst in Man no opportunity has as yet been afforded of noticing
them, and it is only from the circumstance, that in this case also in
normal ovaries, follicles of the most various sizes are always met with,
that a continual formation of them may be concluded to take place.
In Man, it is also probable, that the times of conception and of men-
struation are those in which, especially, these productions take place,
which in animals, as respects their histology, originate in exactly the
same way, as will be afterwards described when we speak of the first
follicles of the embryo. [See Appendix, § corpora lutea. — Trs.]

§ 200. Oviducts and uterus. — Of the three coats of the oviduct, the
most external, which belongs to the jjeritoneiwi, presents nothing
worthy of remark. The middle, or smooth muscular coat, is of tolera-
ble thickness, especially in the internal half of the duct ; and consists
of external, longitudinal, and internal transverse fibres, the elements of
which, even at the time of pregnancy, can be isolated with some diffi-
culty, and are intermixed with much more undeveloped connective
tissue of the same form as in the stroma of the ovary. The innermost
coat is the mucous onemhrane, a thin, whitish-red, soft layer, which is
connected with the muscular tunic by a small quantity of submucous
connective tissue, presents no glands or villi, though it has a few lon-
gitudinal folds, and consists of undeveloped connective tissue, with
many fusiform formative cells. On its inner surface, from the uterus
to the free border of the fimhrice, lies a single layer of conical or
filiform, ciliated cells, of 0-006-0-01 of a line, whose distinct cilia
effect a current running from the ostium ahdominale to the ost. uteri-
num, which probably assists in the locomotion of the ovula, but not of
the spermatic fluid.

The uterus is constituted in the same way as the oviducts, except
that the muscular coat and mucous membrane are much stronger, and,
in some respects, differently constructed. In the pale red muscular
coat, three layers may, most conveniently, be distinguished, which,
however, cannot, as elsewhere (in the intestine for instance), be sharply
defined from each other. The external layer is composed of longitudi-
nal and transverse fibres, the former of which, forming a continuous,
thin stratum, intimately united to the serous coat, extend over the
fundus and the anterior and posterior surfaces, as far as the cervix,
whilst the stronger transverse fibres surround the organ, and are also,
to some extent, continued beyond the uterus, into the Ugg. rotunda,
ovarii, and lata, and upon the oviducts. The middle layer is the
strongest, presents transverse, longitudinal, and oblique, flat bundles,
which are interlaced in a complex manner, and contains larger vessels,
chiefly veins, whence, especially in the pregnant uterus, it presents a
spongy appearance. The innermost layer, lastly, is again thinner, and

THE SEXUAL ORGANS. 647

formed of a network of more slender, longitudinal, and of stronger,
transverse, and oblique fibres, which, at the openings of the oviducts,
frequently form very distinct rings. In the funduSy where the uterus
is thickest, the middle layer is strongest, and often appears to be com-
posed of several laminae ; whilst, at the thinner cervix, transverse fibres
especially, intermixed with isolated longitudinal ones, are met with.
In the neighborhood of the external os uteri, and in that part itself,
highly developed transverse fibres lie immediately beneath the mucous
membrane, and may be described as an ocelusor of it — spJtineter uteri.
As to the elements, all these layers consist of short (0- 02-0-03 of a
line) fusiform fibre-cells, with elongated oval nuclei, which, on account
of the great quantity of the nucleated embryonic connective tissue, of the
same constitution as in the stroma ovarii, by which the layers are per-
vaded, can only with difficulty bo isolated, and even with the aid of nitric '
acid, of 20S, are not brought into view so distinctly as elsewhere.

The mucous membrane of the uterus is of a white or Avhitish-red
color ; it is closely united with the muscular coat, from which it cannot
be raised ; in transverse sections, however, it is distinguishable from it
by its, mostly, brighter color, though rarely presenting any marked line
of demarcation. Except in its fundamental substance, consisting of the
connective tissue which exists everywhere in the female genital organs,
containing undeveloped nuclei and fibre-cells without elastic elements,
and the epithelium, which throughout appears as a ciliated epithelium
with pale cells, as much as 0*016 of a line in size, and delicate cilia
which vibrate from without to within, the mucous membrane is difi"er-
ently constituted in the body and fundus, and in the canal of the cervix.
In the former situations it is more delicate, redder, and thinner (from
|-1 line), smooth on the inner aspect, and without papilke, but occa-
sionally presenting a few large folds. In it are found very numerous
minute glands, the utricular glands of the uterus, or uterine glands
[glandulce utriculares s. uterince), which bear the closest resemblance
to the LieberkUhnian glands of the intestine ; they exhibit the form of
thickly placed follicles, either simple or bifurcated, and not unfrequently
spirally contorted at the end, and in length correspond with the thick-
ness of the mucous membrane, being 0-02-0'03 of a line broad. They
consist of a very delicate structureless membrane, and a uniform cylin-
der-epithelium, and open either singly or two or three together, with
orifices l-30th of a line wide. Normally, these glands contain no mor-
phological elements at all, but it is probable that their epithelium is
very easily detached, and may appear as a grayish-white secretion fill-
ing them.

In the cervix the mucous membrane is whiter, denser, and thicker
(1-1|- lines), particularly on the anterior and posterior walls, where the
well-known pliece palmatce are situated ; between which are found larger

648 SPECIAL HISTOLOGY.

and smaller, sinuous fossse lined with cylinder-epithelium, and as much
as 1 line and more in depth, and differing very essentially from common
mucous follicles, although, as the secreting organs of the viscid, crys-
talline mucus of the cervix uteri, they may be designated the mucous
follicles of the uterus. In this region also occur, in great abundance,
closed vesicles, -1-1-2 lines and more in size, filled Avith the same secre-
tion, and composed of a layer of connective tissue and short cylinder-
cells, the so-termed ovula Nabotlii, which, like the Graafian follicles,
might perhaps be regarded as closed glandular vesicles, bursting periodi-
cally, but which probably are nothing more than dilated and closed
mucous follicles, and in part also pathological new formations ; they
are likewise occasionally found in the mucous membrane of the body of
the uterus. The inferior third or half of the cervical canal contains
verrucose or filiform papillae, 0'l-0"3 of a line long, clothed with ciliated
cylinders, containing a single or several vascular loops, with very nu-
merous minute nuclei, and also, perhaps, pale oil-drops in their interior.
The distribution of the vessels in the unimpregnated uterus, does not
present much of a special nature. The larger arterial branches run in
the muscular substance, and ramify thence on both sides in the muscular
and mucous coats. The latter, as everywhere, has larger vessels in the
deeper, and finer in the superficial portion, and these, after they have
surrounded the glands with smaller capillaries, form an extremely rich
and delicate plexus of larger vessels (0-OOG-O-Ol of a line) on the sur-
face, from which arise the wide, thin-walled veins, unfurnished with
valves, which follow the course of the arteries towards the exterior.
The lymphatics, probably commencing in the mucous membrane, are
remarkably numerous, form coarser or finer networks under the peri-
toneal investment and proceed, in numerous, considerable trunks, ac-
companying the blood-vessels, in part to the pelvic glands, in part, with
the vasa spermatica, to the lumbar plexus. The nerves of the uterus,
containing numerous fine, and some thick nerve-fibres coming from the
hypogastric and pudendal plexuses, and united in a plexiform manner,
reach the uterus through the broad ligaments, and ramify, folloAving
principally the course of the vessels in the muscular substance, from
the fundus to the cervix, in which latter situation they are the most
abundant. They are white and, in the uterus, are not furnished with
any ganglia ; their condition in the mucous membrane, and their termi-
nations elsewhere, are unknown.

Of the ligaments of the uterus, the ligg. lata, anteriora, and p)oste-
riora, are duplicatures of the peritoneum, which contain, together with
the vessels and nerves passing to and from the uterus, a considerable
number of smooth muscular fibres continued into them from the uterus.
The same tissue also arising from the uterus, occurs more sparingly in
the ligg. ovarii, and in very considerable number in the ligg. rotunda^

THE SEXUAL ORGANS.

649

in the form of longitudinal bundles surrounded by connective tissue,
with ■which at the internal abdominal ring a good many transversely
striated muscular fibres, often extending nearly to the uterus, are
associated.

Jig. 267.

§ 207. Changes in the uteVus at the menstrual period and in preg-
nancy.— At the menstrual period, the whole uterus enlarges, and its
texture expands, ■which is perhaps to be attributed, chiefly, to the dis-
tension of the vessels, and the considerable infiltration of the entire
organ with blood-plasma ; at all events, beyond a greater facility in the
demonstration of its elements, I have been unable to perceive any fur-
ther alteration in the muscular coat. The mucous membrane, on the
other hand, in many cases really increases, being thickened to 1-2,
even 3, or, in its projecting folds, even to 5-6 lines ; it becomes softer
and presents, in its tissue, ■well-mai'ked, easily isolated, utricular glands,
1-3 lines long, and 0-036-0-04 of a line broad, and numerous immature,
round and fusiform cells. The bloodvessels of the mucous membrane,
■which chiefly afford the menstrual flux, are throughout the uterus, and
particularly in its body and fundus, extremely numerous and much dis-
tended, and this is especially the case
■with the superficial capillary plexus;
■whence also, the mucous membrane
presents a bright red color. With the
escape of the blood from the superfi-
cial, ruptured capillaries, the ejuthe-
lium of the mucous membrane is, in
great measure, thrown off, except that
of the cervix, and may always be found
in large quantity in the mucus mixed
with blood, which fills the cavity of the
icterus ; it is not, however, to be re-
garded as normal, if, after the men-
• strual period, or during it, the whole
uterine mucous membrane or portions
of it are detached. After the menstrual
period, the parts rapidly regain their
pristine condition, and the epithelium
is restored.

Changes of a totally different kind
are induced in the iiterus by preg-
nancy, among which, however, in a
microscopical point of view, the in-

FiG. 2G7. — Muscular elements from the ulcnis, in the fifth month of pregnancy ; a, formative
cells of the muscular fibres; b, younger; c, developed, fibre-cells. — Magnified 350 diameters.

/C^^<f

V'.

650

SPECIAL HISTOLOGY.

creased bulk of the organ only, is of interest. This enlargement, as
is well known, depends upon the great augmentation of
the circumference and of the cavity ; at first with in-
creased, and afterwards (usually from the fifth month
onwards) with a diminished thickness of the walls, and
an increase in bulk, amounting on the average to twenty-
four times the original size (J. F. Meckel, "Anat.," IV.
691). The mode in which this change is brought about
was, as regards the histological conditions, until a recent
period, it may be said, entirely unknown ; but, in the
main point, is now sufiiciently made out. The principal
changes occur in the muscular coat, to which the in-
creased volume of the utci'us is chiefly to be assigned,
and there are two processes which participate in
common in its production : in the first place, an en-
largement of the 2)7'e-cx{sting elements ; and secondly,
a new formation of them. The former is so conside-
rable, that the contractile fibre-cells,
instead of a length of 0-002-0-003
of a line, and width of 0-002 of a
line, as elsewhere, in the fifth month
present a length of 0-06-0-12, and
width of 0-0025-0-006, or even 0-01
of a line, and in the second half of
the sixth month, a length of 0*1-
0-25, a width of 0-004-0-006, and
a thickness of 0-002-0-0028 of a
line; consequently, their length is
increased from seven to eleven times,
and their width from twice to five
times. The new formation of mus-
cles may be observed in the first half
of pregnancy, especially in the in-
nermost layers of the muscular coat,
where newly originating cells, 0*01-
0-018 of a line in size, in all stages
of transition into fibre-cells of 0-02
-0-03 of a line, always occur in great
quantity ; but it takes place also in

Fig. 2G8. — a, muscular fibre-cell from a gra-
vid uterus, at the sixth month ; 6, its middle
portion, after treatment with acetic acid, and
exhibiting the appearance of a membrane ; c, nucleus of the fibre-cell. — Magnified 350
diameters.

Fig. 269.— a uterine gland from a woman in the first pregnancy, eight days after conception.

a I

THE SEXUAL ORGANS. 651

the outer layers. After the sixth month,. tliis orifrinatlon of muscles
seems to cease ; at least in the t\Yenty-sixth week, in the whole uterus I
have found nothing hut the above-mentioned colossal fibre-cells, and
no longer any trace of their earlier forms. Like the muscles, the
fibrous tissue which unites them also increases, and towards the end of
pregnancy, occasionally exhibits distinct fibrils. Whilst the muscular
coat grows in this way, the mucous membrane has also undergone mani-
fold changes. It is in it, especially, that the metamorphoses of the gravid
uterus commence, seeing that as early as the second week, it becomes
thickened to 2-3 lines, is softer, more lax, and redder, acquires more promi-
nent pliece, and is more distinctly defined from the muscular coat ; pecu-
liarities which, as time goes on, become more and more marked. Examined
microscopically, it is apparent, that not only are the vessels more dis-
tended, but also that an abundant new formation of connective tissue
has taken place in its parenehijma, and a considerable enlargement of
the utricular glands, which latter are, at this time, 2-3 lines long,
and 0-04-0-11, or, on the average, 0*08 of a line broad. As these
changes proceed, the greater part of the hypertrophied mucous mem-
brane is transformed into the well-known decidua vera, whilst another por-
tion, at the point of attachment of the ovu7n, is converted into the pla-
centa uterina, and by a growth from the border of this part, the reflexa
is produced around the ovum ; processes of which this is not the place
to speak farther. It can only be remarked that the utricular glands, in
the decidua vera, are gradually converted into wider follicles, the orifices
of which give rise to the appearance, as it were, of a cribriform perfora-
tion in that membrane and the border of the reflexa ; and moreover,
that the deciduce, from the second month OTiwards, though gradually
diminishing, it is true, in thickness, nevertheless, on account of the
enlargement of the internal surface of the uterus, are still far from
ceasing to increase in bulk ; and lastly, that their tissue at all times
consists of larger and smaller, round cells, Avith large, often compound
nuclei, in part of colossal fibre-cells with well-formed large nuclei, and,
particularly in the decidua vera, of vessels ; whilst in epithelium, except
in the first month, is no longer to be found upon the decidua;. The
mucous membrane of the cervix takes no part in the formation of the
deciduoi, and retains its epithelium (without cilia) during the whole time
of pregnancy. It also, however, swells, and its mucous follicles, espe-
cially, enlarge and secrete the well-known mucous plug which fills up
the entire canal of the cervix.

The serous coat also increases considerably in thickness, though not
to the same extent as the mucous membrane : whilst the thickening of
the uterine ligaments, particularly of the round ligaments, is very evi-
dent, and also depends upon changes in their smooth muscles similar to
those described in the muscles of the uterus, and probably also, upon an
increase of the transversely striated bundles. The growth of the

652

SPECIAL HISTOLOGY.

bloodvessels and lympliaticSy^ in length and calibre, is also very evident,
and is, in great part, to be referred to the enlargement and new forma-
tion of muscular elements, which, in the veins, are also demonstrable in
the t. adventitia and intima. With respect to the nerves, they also
become thickened, although it is doubtful whether new nerve-fibres are
really produced in them. On the other hand, it is certain that the pre-
existing elements increase in width and length, retain their dark bor-
ders for a greater distance, and may be traced further into the interior
than at other times.

The lessening of the uterus after parturition, and its restoration to a
condition, not, indeed, similar to the previous state, though closely ap-
proximated to it, does not take place in its various portions exactly in
the same way. In the muscular coat, an atrophy of the contractile
fibrous elements manifestly plays a principal part, since, as early as
three weeks after parturition, these fibres are again as
short (0*03 of a line) as in the virgin uterus, fat, at the
same time, being developed in their interior; but a
complete absorption of certain muscular fibres is also
probably superadded to this. A diiferent process takes
place in the mucous membrane, which, in the form of
the deciduce and placenta uterina, is completely thrown
off after parturition, and consequently has to be entirely
formed anew. The intimate nature of the processes
accompanying this unique kind of regeneration has not
yet been traced, though it is more than probable that
it is completed as early as within the first two or three
months after parturition. It is evident that, besides
this, the serous coat, the vessels and nerves of the
uterus, return to their former condition, but the precise
nature of this change in them has not yet been inves-
tigated.

It has been generally assumed, since Tiedemann,
that the nerves of the gravid uterus are thicker than in
the virgin state; but quite recently this has been alto-
gether disputed by Dr. Snow-Beck, and is only par-
tially admitted by Jobert de Lamballe (" Compt. rend.,"
1841, Mai), inasmuch as that he states that it is the in-
vesting connective tissue, but not the nerves themselves,
that is thickened. It is evident that very accurate mi-
ci-oscopic investigations are alone competent to decide
this question ; but such investigations are wanting. No

Fig. 270. — Muscular fibre-cell of the uterus, three weeks after parturition, four of them
treated with acetic acid, and pale: a, nuclei; g, fat-granules. — Magnified 350 diameters.

THE SEXUAL ORGANS. 653

conclusion, in the first place, can be drawn from Romaic's statement
(1. c), that the nerves, at the time of pregnancy, enlarge and acquire a
gray color, a change depending upon an increase of nucleated fibres,
because no grounds exist upon which it can be decided whether these
nucleated fibres are embryonic nerve-fibres, or a form of connective
tissue. On the other hand, we are indebted to Kilian for careful re-
searches in animals, which prove with certainty that the uterine nerves,
at the time of pregnancy, may be traced further into the substance of the
uterus, in the form of dark-bordered fibres ; whilst at an earlier period,
in part even before they enter the uterus, in part when they have scarcely
reached it, they possess the nature of embryonic non-medullated fibres.
For this reason, Kilian succeeded also in tracing the nerves in the gravid
uterus much further into the parenchyma than at other times. He perceived
no evidence of a formation of new nerve-fibres in the trunks, and regards
such an occurrence as improbable ; for otherwise a new formation of
ganglionic substance must also be assumed, which is unlikely. Some-
thing of the kind appears to me by no means impossible, because the
multiplication of the ganglion-cells and of the fibres would only take
place once — in the first pregnancy ; it is also conceivable that newly
formed nerve-fibres are added to the others simply as branches, and
consequently it will be more prudent to wait and see upon which side
Remak's statements, with respect to the human subject, incline. Upon
this, however, I would also remark, that a thickening of the nerves may
undoubtedly be produced by an increased size of the already existing
fibres and an augmentation of the neurilemma, and that the nerves, by
a multiplication of their ultimate divisions, are fully enabled to ramify
over larger spaces than at other times.

The increased size of the vessels, both of the arteries, and, above all,
of the veins, at the time of pregnancy, is very considerable ; owing to
which, at this period, the middle layer of the muscular substance, con-
taining the larger vessels, is much more distinct from the other two.
The alteration which takes place in the vessels of the mucous membrane,
at the point where the placenta is formed, cannot here be entered upon ;
and I will only remark that I agree w^ith those who believe that large
vascular trunks exist in the human uterine placenta, at the border and
on the convex surface, whilst in the interior there are only lacunce with-
out walls, between the ^;^7Z^ of the chorion [vide Kiwisch, " Geburtskunde,"
I. p. 151, et seq. ; C. Wild, "Zur Physiologic d. Placenta," Wurzb.,
1849 ; Virchow, " Archiv," III. p. 449 ; Schroder v. d. Kolk, in the
"Yerh. d. Nied. Instituts," 1851). In the rest of the decidua, the
capillaries are frequently excessively enlarged ; according to Virchow
(" Archiv. f. path. Anat.," III. p. 436), its superficial capillaries, in the
sixth week of pregnancy, reach the size of 0'027-0*045 of a line, and
become extremely thin-walled, as are, probably, also those in the part

654 SPECIAL HISTOLOGY.

where the placenta is situated, before their walls disappear and their
cavity is thrown into that of the lacunce. In the venous trunks of the
gravid uterus, besides the circular muscular layer, with much enlarged
fibre-cells, which exist, also in other situations, I have'found an external
and internal longitudinal muscular layer with similar colossal elements ;
so that here the increase of the walls may be directly demonstrated
("Zeitsch. f. wiss. Zool." I. 84).

§ 208. Vagina and external sexual parts. The walls of the vagina,
1 line thick, consist of an external fibrous coat, a middle muscular layer,
and a mucous membrane. The thin y^\\\iQ fibrous coat presents externally
a more lax, towards the interior a more dense connective tissue, with
numerous elastic fibres and venous plexuses, and passes, without any
line of demarcation, into the second, redder layer, which, together with
connective tissue and numerous veins, contains, particularly during
pregnancy, a good many, developed, smooth muscular fibres, which, with
their transverse and longitudinal bundles of fibre-cells, 0-04, 0-08 of a
line long, constitute a true muscular membrane. The mucous membrane
is of a pale red color, with numerous larger and smaller folds and eleva-
tions— the columnce rugosce ; it is composed of a dense connective tissue,
without glands, and containing elastic elements in extreme abundance,
to which its great firmness and extensibility are due. Its inner surface
presents numerous conical or filiform papilhie, from 0*06 to 0*08 of a line
in length, and 0-025 to 0-03 of a line in breadth, which are entirely
imbedded in a tessellated epithelium, 0"07-0-09 of a line thick, of the
same kind as that in the oesophagus, the uppermost scales of which,
having; a diameter of 0-01-0-015 of a line, contain nuclei of 0*003 of a
line. The hymen is a duplicature of the mucous membrane of the vagina,
and contains the same elements.

From the vayina the mucous membrane is also continued upon the
external genitals, invests the glans clitoridis and the vestibule, with the
orifice of the urethra; folds of it constituting the preputium clitoridis
and labia minora. On the labia majora, it is continuous uninterruptedly
with the external integument, which, on their inner side, and at the
commissura labioriwi, still bears a close resemblance to a mucous mem-
brane ; whilst on their border and outer surface, and on the mans veneris,
it resembles the cutis in all respects. The matrix of the mucous mem-
brane of the external genital organs, is a spongy, highly vascular, fatless
connective tissue, containing, however, a good many elastic fibres, and
which, in its condensed external layer, i-,^ of a line thick, correspond-
ing to the corium, is everywhere furnished with much-developed papillce,
in the labia minora 1-10-1-20, and on the clitoris 1-24-1-33 of a line
in length; and with a squamose epithelium of 0-04-0-12 of a line, the
most superficial cells of which are 0*01-0-02 of a line in size (Fig.

THE SEXUAL ORGANS. G55

56, 4). The labia majora, in the structure of their coverings, corres-
pond partly with the mucous membrane, in part approach the cutis, and
contain, in the interior, common adipose tissue.

The external genital organs are furnished with various smaller and
larger glands. Sebaceous glands, mostly of a rosette-form and consi-
derable size (^-1 line), occur in the labia majora, on the external and
internal aspects, in connection with larger and smaller hair-follicles;
moreover, in larger quantity in the labia minora, for the most part
without hairs and rather smaller (from y'^ to |- a line) ; occasionally,
also, around the orifice of the urethra, and laterally at the entrance of
the vagina. Common racemose mucous glands, ^-1^ lines in size, with
scarcely visible or tolerably wide openings, and having excretory ducts,
either short, or as much as 6 lines long, exist in very various number
around the orifice of the urethra, in the vestibule, and in the lateral
portions of the entrance of the vagina. Lastly, the two "glands of
Bartholin!," corresponding to Cowper's glands in the male, are situated
at the inferior extremity of the bulbi vestibuli ; they are common race-
mose mucous glands, 6 lines in size, with pyriform gland-vesicles lined
with a tessellated epithelium, 0"02-0"05 of a line in diameter, and lodged
in a compact nucleated connective tissue without muscular fibres. The
excretory ducts of these glands, 7-8 lines long, and | a line wide, have,
external to their mucous membrane, invested with a cylinder epithelium
0*01 of a line thick, a delicate longitudinal layer of smooth muscles, and
always contain a viscous, amorphous, clear, yellowish mucus.

The clitoris, with its two corpora cavernosa and glans attached to the
bulbi vestibuli, the divided corpus cavernosum urethrce of the female,
present, on a small scale, precisely the same conditions as the corre-
sponding parts and corpora cavernosa of the male ; and in them the
muscular elements are even more readily isolated than in man.

The bloodvessels of the vagina and of the external genital organs,
present, upon the whole, nothing much worthy of remark. In the
papillce of the various situations where they occur, we find, for the
most part, simple vascular loops ; it is only when the papillre are larger
or compound, such as abound around the orifice of the urethra, that
more complex loops occur. The corpora cavernosa have the same struc-
ture as in man ; and, according to Valentin, helicine arteries also ap-
pear to exist in the clitoris. The venous plexuses in the walls of the
vagina, above the bulbi vestibuli, are extremely rich ; but by no means,
as Kobelt assumes, represent true corpora cavernosa. The lymphatics
of the external genital organs, and of the vagitia, are numerous, and
communicate partly with the inguinal glands, partly with the pelvic
plexus. The nerves, lastly, are derived in part from the sympathetic,
in part from the pudendal plexus, and are extremely numerous, espe-
cially in the clitoris, but are also found without difliculty in the mucous

656

SPECIAL HISTOLOGY.

membrane of the vagina. In the latter situations they present divi-
sions, and their terminations have as yet been but little investigated. I
have never found nerves in papillai containing vessels, whilst, in the
clitoris, I have sometimes met with them in non-vascular, minute verru-
cosities, which also contained rudimentary axile corpuscles ; and I think
I have noticed here, as well as on the surface of the mucous membrane
itself, finer and coarser looplike terminations of nerves lying buried in
the bodies resembling axile corpuscles, which are also occasionally met
with in these situations. In the clitoris of the Sow, Dr. Nylander, of
Helsingfors, found Pacinian bodies, which I have also seen ; and looped
terminations of the nerves in the papillai.

§ 209. Physiological remarlcs. — In their development, the internal
female genital organs, as was noticed above in § 202, entirely correspond,
originally, with those of the male ; and it is not till after some time
that a difference in the histological development of the sexual glands is
manifested, consisting in this, that in the female, the Wolffian body,
except that it forms the parovarium, stands in no farther relation to the
genital apparatus, whilst the "ducts of Mliller" are formed into the
oviducts, uterus, and vagina. As regards the histological conditions,
the ovaries alone seem to present any great interest. These bodies are
composed at first of common formative cells, 0'005-0-009 of a line in

size, which afterwards pass, in part, into
fibres and vessels, in part persist as cells,
multiply spontaneously, probably by divi-
sion, and serve for the formation of the
Graafian follicles. These, according to
Barry, at first appear as spherical agglome-
rations, 0-01 of a line in size, of some few
cells, which contain, in the interior, a clear
vesicle — the germinal vesicle ; but, by the
formation of a delicate, structureless mem-
brane on the exterior, around the cells,
which then represent an epithelium, soon assume the nature of follicles.
Very young Graafian follicles of this kind [ovisacs, Barry) occur by
thousands in the ovaries of nearly mature embryos, and of new-born
children, in which the further development is very easily traced. Whilst
the follicle increases by the multiplication of the cells of its epithelium,
(the memhrana granulosa), and at the same time acquires an external
vascular, fibrous coat; a clear substance, in Man containing but few
granules, is collected in the interior, detaching the germinal vesicle,

Fig. 271. — Three Graafian follicles from the ovary of a newly-born female child, magni-
fied 350 diameters. 1, without; 2, with, acetic acid: a, structureless membrane of the
follicle ; 6, epithelium (memhrana granulosa) ; c, yelk ; d, germinal vesicle with spot ; «, nucleus
of the epithelial cells ; f, vitelline membrane, very delicate.

Fig. 271.

THE SEXUAL ORGANS. 657

0-0065-0-008 of a line in size, ^YitIl a germinal spot of 0-001-0-0015 of
a line, from the epithelium, to ^Yllich at first it was closely applied, and
forcino- it into the centre of the follicle. When this has attained the
size of 0*02 of a line, a membrane in close apposition with the memhrana
granulosa, and surrounding the germinal vesicle and the whole contents
of the follicle — the vitelline membrane — becomes evident ; which is re-
garded by all authors as a secondary formation, although it probably
exists, even in the very earliest rudiment of the follicle, as an extremely
delicate membrane, closely surrounding the germinal vesicle. At first
excessively delicate, and scarcely perceptible, the vitelline membrane,
when the follicle has increased in size and contains more fluid, becomes
more distinct, owing to its removal from the wall of the follicle, and
rapidly thickens. In follicles of 0-04-0-05 of a line, the ova are per-
fectly distinct and disproportionately large, with a delicate zona pellu-
cida, and still lying very close to the walls of the follicle. The further
development is apparent of itself; and I will only remark that, in the
new-born child, follicles visible to the naked eye will be more rarely
found ; whilst such make their appearance even before puberty, although
they undergo no considerable development before that period.

According to what has been said, the mode of origin of the Graafian
follicle ranks in every respect with that of the tubular glands. The for-
mer is an agglomeration of cells, at first, perhaps, without cavity or con-
tents, to which the structureless membrane is added, not by the coales-
cence of the outermost cells, but probably as an excretion from them,
and thus is formed the follicle, which therefore exactly corresponds with
a closed gland-vesicle, or a section of a tubular gland canal. How the
germinal vesicle, and the vitelline membrane arise, is doubtful ; the for-
mer is either a nucleus of new formation, originating in the minute cavity
of the follicle, about which a certain amount of vitellus is subsequently
collected, the cell, or vitelline membrane not being formed until after
this, from a sort of cell formation "around portions of contents;" or
the whole ovum, with the germinal vesicle, is nothing else than the cen-
tral cell of the primordial rudiment of the Graafian follicle, and conse-
quently co-existent with it. In any case it corresponds to a cell, and the
germinal vesicle is nothing but the cell-nucleus.

With respect to the ijhjsiological conditions of the mature, female
sexual organs, much has already been remarked in the preceding pages ;
and it will, therefore, here be sufiicient to say something about their
movements and secretions. In the ovaries, whose stroma frequently pre-
sents a deceptive appearance of muscularity, I have in vain sought for
muscles, with nitric acid of 20 g, although in recent preparations micro-
scopical appearances are occasionally obtained, which one is inclined to
explain as belonging to that tissue. That the oviducts are capable of

42

658 SPECIAL HISTOLOGY.

very active movements cannot be doubted, from the results of vivisec-
tions in animals, and microscopical researches in Man ; and in opposi-
tion to V. Kiwisch (" Geburtskunde," p. 96) I do not understand why
their application to the ovaries should not be brought about by move-
ments in them, together with a kind of erection dependent upon increased
fulness of the vessels, as has also been established by the experiments of
Gendrin and Raciborski (1. c. p. 412-417), in two women dead during
menstruation, and of Laahr ("De mutat. gen. mul. brevi post concept."
Halis, 1843) in the case of one who was killed shortly after coitus. As
regards the movements of the uterus, they are, at all events during par-
turition, very energetic, but take place even at other times. The mus-
cular tissue is so disposed, that at first a universal contraction of the
uterine cavity, but afterwards local, more or less extensive contractions,
also may be performed with great ease. Thus, in the act of parturition,
the cervix and the os uteri are at rest, whilst the fundus and body con-
tract, contractions of the former parts and of the vagina not ensuing
till subsequently. In convulsions, the whole uterus contracts closely
round the child ; in retention of the placenta, the contraction is entirely
local and confined to the fundus. It is probable that movements take
place at the time of menstruation and in the act of congress, but the
fact has not been ascertained. In the latter case, an opening of the os
uteri, and a dilatation of the canal of the cervix, are commonly supposed
to take place. If this is to be regarded as a spontaneous action of the
cervix, it Avould be justifiable, with Kiwisch (1. c. p. 103), to refuse assent
to the supposition, for the radiating fibres described by Kasper, which
alone could effect anything of the kind, do not exist ; the fact, neverthe-
less, is conceivable, if we assume a relaxation of the muscular element
in the cervix and os, together with a contraction, especially of the lon-
gitudinal fibres in the fundus and body. In comparing the uterus, as
respects the disposition of its muscular element and its movements, with
other organs, none affords so apt a comparison as the bladder, in which
the muscular tissue is arranged essentially in the same way, and a phy-
siological antagonism exists between the superior and inferior portions.
The sensibility of the uterus, and of the internal parts of the female
genital organs in general, is very slight; careful sounding of the uterine
cavity causes no sensation ; in like manner, contact with the vaginal por-
tion is, frequently, scarcely felt, whilst these parts give pain upon more
powerful pressure or traction, and when in a state of inflammation. The
sensibility of the vagina increases towards the inferior portion ; and as
regards the external organs, the clitoris is rendered especially susceptible
of sensation, by its abundant supply of nerves, as is also the entrance
to the vagina, particularly at the orifices of the glands of Bartholini or
Duverney.

The secretions of the female genital organs, except those of the ova-

THE SEXUAL ORGANS. 659

rium, are: 1, a ■whitish mucus in the uterus and vagina, which, in the
former situation, is derived chiefly from the uterine gUmds, and probably
differs in some respects from the other ; 2, a transparent viscous mucus
in the cervix uteri {vide supra) ; 3, the clear viscid secretion of the Bar-
tholinian glands, which is poured out in large quantity in copulation ;
and upon excitation, as was noticed by Huguier and Scanzoni, it even
frequently escapes in jets, which may be ascribed to the muscles of the
excretory ducts ; 4, the secretions of the minute subaceous and mucous
follicles of the external organs.

Investigation of the female organs. — The Graafian follicles should be
examined as fresh as possible, when the membrana granulosa and ova
will be seen in their natural relations. In ovisacs that have been longer
kept, the former floats about in flocculi in the liquor folliculi, and the
"germinal eminence" is also for the most part destroyed. In order to
make sure of obtaining the ovulum, the position of which is readily per-
ceived even in the still closed follicle, in certain animals, as in the Bitch,
for example, a large carefully extracted follicle is opened under water,
and the larger flocculi which escape are examined with a low magnifying
power ; it is also readily found when the contents of a follicle are care-
fully transferred to an .object-bearer. In rough sections, or when the
structure of the ovaries is teased out, ova are also always readily found,
although this is not exactly the mode of seeking for them to be recom-
mended. The muscular elements of the oviducts, uterus, vagina, &c.,
are investigated by means of careful dissection, as also in fine sections
of parts that have been hardened. Kasper especially recommends that
the uterus should be boiled for 10 minutes in water, and then placed for
24 hours in the most concentrated solution of carbonate of potassa, or
that it should be treated with pyroligneous acid, and the sections moist-
ened with dilute acetic acid; whilst Schwartz, according to Reichert,
dries the uterus hardened in alcohol, and renders the muscular fibres dis-
tinct by acting upon them for a short time with nitric acid of 20^. The
method, also, employed by Wittich (p. 486), should be used, according
to Gerlach. The contractile fibre-cells are nowhere more beautifully
displayed than in the gravid uterus. The uterine glands are best shown
at the menstrual period and in the first months after conception. The
ciliated epithelium is only to be seen in perfectly fresh subjects, and
best in the Fallopian tubes ; the non-ciliated cells, on the other hand,
are readily seen. The preparation of the external parts presents no
difficulty, and the directions already given are applicable to the glands,
nerves, ijapillce, and epithelium.

Literature. — C. E. v. Baer, " De ovi mammalium et hominis genesi,
epist.," Lips. 1827, and " Commentarius," in German, in Heusinger's
" Zeitsch.," II. ; Coste, " Recherches sur la gdndration des mammi-

660 SPECIAL HISTOLOGY.

feres," 1834; " Embryogenie comparde," Paris, 1837; "Etudes ovolo-
giques," in " Annal. Franc, et Etrang. d'Anat. et de Phjs.," II. 224,
1838; " Histoire gendrale et part, du developpement," Paris, 1847 ;
A. Bernhardt, " Symbolse ad ovi. mam. hist, ante prpegnat.," Vrat.,
1834, Diss. ; Pt. Wagner, " Ueber das Keimblaschen," in Miiller's
"Archiv," 1835, p. 373; " Prodromus hist, generationis," Lips,, 1836;
" Beitriige zur Zeiigung u. Entwicklung," in " Denkschrift der bayr.
Akad.," Bd. II. 1837, p. 511 ; M.Barry, " Researches in embryology,"
Series I. II. III. in " Philos. Trans.," 1838, 1840 ; Bischoflf, " Beweis
der von d. Begattung unabhangigen Reifung u. Losltisung d. Eier d.
Siiugethiere und des Menschen," Giessen, 1824; "Ann. d. Sc. Nat.,"
3, Ser. II. 1844, 304 ; Pouchet, " Theorie positive de I'ovuhTtion spon-
tanea," Paris, 1847 ; Z^vicky, " De corpor. luteorum origine," Turici,
1844; Kobelt, "Der Nebeneierstock des Weibes," Heidelberg, 1847:
W. Steinlin, " Ueber die Entwicklung der Graafschen Follikel und Eier
der Saugethiere," in " Mittheil der ZUrcher naturf. Gesellschaft," 1847,
p. 156 ; Fr. Tiedemann, " Tabulce nervorum uteri," Heidelb., 1822; G.
Kasper, " De structura fibrosa uteri non gravidi," Vratisl., 1840; E.
H. Weber, " Zusatze zur Lehre vom Ban der Geschlectsorgane," Leip-
zig, 1846 ; A. Kolliker, " Ueber die glatten Muskeln der weiblichen
Genitalien," in " Zeitschr. flir wissensch. Zool.," I.; Fr. Kilian, "Die
Structur des Uterus bei Thieren," I. II. Art. in " Zeitschr. f. ration.
Med.," Bd. VIIL IX. 1849 u. 1850 ; "Die Nerven des Uterus," ibid.,
1850, Bd. X. St. 41 ; R. Lee, " Memoirs on the ganglia and nerves of
the uterus," London, 1849 ; Th. Snow-Beck, " On the nerves of the
uterus," in "Philos. Trans.," II. 1846; Rainey, " On the structure
and use of the lig. rotundum uteri," in "Phil. Trans.," II. 1850; V.
Schwartz, " Observ. microsc. de decursu muscul. uteri et vaginse homi-
nis," Dorpat., 1850, Diss ; Robin, " Mdm. pour servir a I'hist. anat. et
pathol. de la membrane muqueuse uterine," in "Arch, gendr. de Med."
1848, torn. XVIL pp. 258 a 405, torn. XVIIL p. 257 ; Kobelt, " Die
mannlichen und weiblichen Wollustorgane," Freib., 1844 ; Tiedemann,
"Von den Duverney'schen Driisen des Weibes," Heidelberg, 1840 ; C.
Mandt, "Zur Anatomic der weiblichen Scheide," in " Zeitschr. flir rat.
Med.," VII. p. 1 ; Huguier, " Sur les appareils secrets des organes
gdnit. de la femme," in "Annal. d. Sc. Nat.," 1850, p. 239. [Dalton
" On the Corpus Luteum of Menstruation and Pregnancy," Philadelphia,
1851 ; BischofF, " Die Physiologic der Menstruation und Conception," in
"Zeitschr. fur. rat. Med." Bd. IV. 1. 1853.— DaC]

C. OF THE LACTEAL GLANDS.

§ 210. The lacteal glands {glandula lactiferm) are a pair of com-
pound racemose glands, which, in the male, are only rudimentary, but
in the female fully developed, and, after parturition, secrete the milk.

THE LACTEAL GLANDS.

661

"With respect to their structure, the lacteal glands, in all essential
particulars, completely correspond with the larger racemose glands, for
instance the parotid and the pancreas. Each gland consists of 15-24
or more, irregular, flattened lohes^ -| to 1 inch wide, with a rounded,
angular outline, which, although their cavities are quite distinct from
each other, cannot externally always be definitely separated. Each is
composed of a certain number of smaller and smallest lobules, and
these, lastly, of gland-vesicles. The latter are rounded, or pyriform,
0-05-0-07 in size, with a distinct constriction between them ; and the
smallest excretory ducts, as for instance, in the small mucous glands,
and as everywhere else, are formed of a structureless membrane and
tessellated epithelium, which, at the time of lactation, undergoes pecu-
liar metamorphoses. All these glandular elements are surrounded by
dense, white connective tissue, particularly abundant between the gland-
vesicles and smaller lobules, and

Fig. 272.

are united into a compact, large
glandulur mass, which is ultimate-
ly covered by a quantity of adi-
pose tissue, and in part by the
skin. The lacteal glands are,
properly speaking, not simple
glands, but like the lachrymal,
ajTorrecrations of these. From each
glandular lobe, by the coalescence
of the excretory ducts of the smal-
ler and larger lobules, there ulti-
mately proceeds a shorter or
longer duct, 1-2 lines in diameter,
the lacteal duct or canal {ductus
lactiferus s. galactophorus), which "^ W

running towards the nipple, dilates " ^'( ; ''

beneath the areola, into an elon-
gated sacculus, 2-1 lines wide, the lacteal sac or receptacle [sacculus s.
sinus lactiferus) ; afterwards contracting to 1 or i^ a line, it bends round
into the nipple, and ultimately opens, at its apex, in an independent
orifice, not more than 1-3-1-5 of a line in diameter, between the papillce
•which exist in that situation. All these excretory ducts, besides an
ejnthelium, which in the largest of them presents cylindrical cells,
0-006-0-01 of a line long, and in the finer ramifications, rounded poly-
gonal smaller cells, and a homogeneous layer beneath them, also possess
a white dense fibrous membrane, longitudinally plicated in the larger
canals, in which I have hitherto been unable to detect any indubitable

Fig. 272. — A few of the smallest lobules of the lacteal gland of a puerperal female, with
their ducts, magnified 70 diameters. After Langer.

y

662 SPECIAL HISTOLOGY.

muscular fibres, and nothing but a nucleated, longitudinally fibrous,
connective tissue \iiih. fine elastic fibres. Henle, however, more
recently, thinks that he has noticed longitudinal muscles in the lacteal
ducts, not those of the nipple, but more deeply within the gland.

The nipple {mamilla) and the areola, present numerous smooth mus-
cles, to which the contractility of those parts is owing {vid. § 34) ; a
delicate cuticle, the horny layer of which, in the female, is not more than
0-006 of a line thick, whilst the Malpighian layer has a thickness of 0-04
of a line and is colored in the deeper portion ; and compound ijapilloi
1-10-1-33 of a line long. On the breast itself, the ■papillce are small
(1-60—1-80 of a line) and simple, and the epidermis still finer (0-032—
0-04 of a line), although with a thicker horny layer of 0-02-0-024 of a
line. In the areola, especially at its borders, but not on the nipple
itself, there are large sudoriparous glands, often with peculiar contents,
and large sebaceous follicles with fine hairs, Avhich frequently form
\\ii\Q papilhc, visible on the exterior {yid. §§ 68 and 73). In the male,
I have seen sebaceous glands without hairs, also on the nipple.

The bloodvessels of the lacteal glands are numerous, and surround the
gland-vesicles with a rather close plexus of capillaries. The veins in
the areola constitute a circle, which is not always quite complete [circu-
liis venosus Halleri). The lymphatics are equally abundant in the skin
covering the gland, whilst in the gland itself they have not yet been
demonstrated. The nerves of the skin covering the mamma are derived
from the supraclavicular nerves, and the cutaneous branches of the
second, third, and fourth intercostals. In the interior of the gland, no
other nerves can be traced than a few fine twigs accompanying the
vessels, whose termination is unknown.

At the time of lactation the gland enlarges very considerably. Its
tissue is no longer uniform, whitish, and firm, but softer, granular, and
lobate, with a yellowish-red, glandular p)arenc]iyma, distinctly bounded
by the whitish, spongy interstitial tissue. The gland-vesicles and lacti-
ferous ducts are wider, filled with milk, and the vessels excessively
multiplied. In the external parts, the enlargement of the areola and.
of the nipple is especially worthy of remark ; the cause of which appears
to depend upon a growth of these parts, with all their elements, includ-
ing the muscular fibres and minute glands ; and not in a simple exten-
sion of the color over a larger surface. In the male, the lacteal gland
is quite rudimentary ^-2 inches broad, and 1-3 lines thick, not lobed,
and firm. The lacteal ducts have no sinuses, and are never so far de-
veloped as in the female, inasmuch as they either correspond in form
with those met with in the new-born child, or, in larger glands, are
more branched, and furnished with a certain number of terminal vesi-
cles, which, on account of their considerable size (they are three times
as large as the gland-vesicles in the female), are not to be regarded as

THE LACTEAL GLANDS.

663

true gland-vesicles. In rave, but well-established instances, the glands,
even in the male, have become so much developed as to be capable of
secreting milk.

§ 211. Physiological remarks. — The lacteal gland, in its develop-
ment, follows the same course as the other cutaneous glands, and is,
as I find ("Mittheil. d. ZUrcher nat. Gesells.," 1850, No. 41) in ac-
cordance with Langer (1. c), originally (in the fourth to the fifth
month) nothing but a solid papillary projection of the mucous layer of
the epidermis, which is invested by a layer of denser dermal tissue
(Fig. 273, ^). In the sixth to the seventh
month, it throw^s out a certain number of
buds, and in this way arise the first rudi-
ments of the subsequent lobes (Fig. 273, ^).
These are, at first, nothing but minute pyri-
form- or flask-shaped processes of the com-
mon rudiment of the gland, which do not
separate from each other until towards the
end of fostal life, at which time they open
externally ; whilst, at the same time, rounded
or elongated solid buds begin to appear at
their ends, which at this time are also solid.
At the period of birth, the gland measures
from li-4 lines, and already distinctly ex-
hibits a certain number (12-15) divisions, of

which the internal still approximate the rudimentary papilke, in fact
have either simple flask-like ends, or terminate in two or three sinuosi-
ties; whilst the others are in connection with a greater number. The ex-
cretory duct of each of these rudimentary lobules, which is either simple
or possesses two or three branches, is composed of a fibrous membrane
of immature, nucleated connective tissue, and an epithelium of small
cylindrical cells, and is manifestly hollow; whilst the dilated ends,
which cannot in this case, any more than in other glands in the process
of development, at this time be termed terminal vesicles, are still solid ;
being wholly composed, besides the fibrous tunic continued upon them
from the ducts, of minute nucleated cells. From this very simple form,
the latter one is thus developed : by the long-continued gemmation of
the primary and subsequently formed, clavate ends, and their simulta-
neous excavation, a much-branched duct, beset in its offsets with whole
groups of hollow gland-vesicles, is at last formed. These processes,

Fig. 273. — Development of the lacteal gland. 1, rudiment of the gland in a male embryo,
at five months ; a, horny layer ; 6, mucous layer of the epidermis ; c, process of the latter or
rudiment of the gland ; d, fibrous membrane around the same. 2, lacteal gland of a female
fcetus, at seven months, seen from above: a, central substance of the gland, witli larger (b)
and smaller (c) solid outgrowths, the rudiments of the large gland-lobes.

&^c

-.l"^

664 SPECIAL HISTOLOGY.

however, go on more slowly in the lacteal gland than in any other secre-
tory organs. According to Lunger, to whom we are indebted for care-
ful researches upon this subject, true terminal vesicles are never met
with in childhood, before menstruation is established, but, universally,
only undeveloped ducts with clavate ends. On the occurrence of puberty,
true gland-vesicles are formed, but at first only at the borders of the
gland, until, ultimately, in the first pregnancy, the entire gland is fully
developed. After the first lactation, it is true, the gland again dimi-
nishes in size, but all its constituent parts remain, and again enlarge in
the succeeding occasions of conception, without the addition of any new
parts. At the period of involution — probably also, if after a pregnancy,
too long a time has elapsed without the functions of the gland being
called into play — it undergoes a retrograde metamorphosis, until finally,
in old age, all the gland-vesicles have disappeared, and nothing but the
more or less persistent lactiferous ducts, with their epithelium in a state
of fatty degeneration, are to be found in the adipose cushion which sup-
plies the place of the glandular tissue.

The milJc, the secretion of the mammary glands, consists of a fluid,
the milk-plasma, and innumerable spherical, opaque corpuscles, with the
brilliant aspect of fat-drops, suspended in it. These corpuscles — the
milk-globules — vary in size, from immeasurable minuteness up to 0*001—
0-002 of a line and more, and most probably do not consist of the fatty
part of the milk alone, but have also a delicate investment of casein^

and it is to them that the whiteness of the
^'s-274. ^ j^^jlj. jg owing. With respect to the for-

mation of the milk, it is to be remarked
that, except at the periods of lactation and
pregnancy, the glands contain nothing but
a small quantity of a yellowish viscid
mucus, with a certain number of epithelial
cells, and are lined up to their extremities by an epithelium, Avhich in
that situation is tessellated, but externally is more cylindrical. With
conception, this state of things is altered. The cells of the gland-vesi-
cles begin to develop, at first a little, and subsequently more and more
fatty matter within them, and to enlarge, so as entirely to fill the tei'-
minal vesicles. To this is added, before the end of pregnancy, a new
formation of fat-containing cells in them, by which the older cells are
forced into the lactiferous ducts, which they gradually fill. Thus it
happens, that although a true secretion is not at that time set up, still
in the latter half of pregnancy a few drops of fluid may be expressed
from the gland, which, as is shown by its yellow color, is not milk, but
nevertheless contains a certain number of fat-globules from the more or

Fig. 274. — Elementary forms in milk, magnified 350 diameters : a, milk-globules; b, colos-
trum corpuscles; c, d, cells with fat-globules from the colostrum, one {d) with a nucleus.

THE LACTEAL GLANDS. 665

less disintegrated fatty cells, exactly resembling the subsequent milk-
globules, and also contains such cells either with or without a tunic —
the so-termed colostrum corpuscles. On the commencement of lactation
after parturition, the cell-formation in the gland-vesicles proceeds with
excessive energy, in consequence of which the secretion collected in the
lactiferous ducts and gland-vesicles is evacuated, as the colostrum or
immature milk, the true milk taking its place.

The latter, in the extremities of the gland, consists only of some
fluid and cells entirely filled with fat-globules, which sometimes occupy
the gland-vesicles alone, sometimes associated with pale epithelial cells,
which, however, always contain more or less fat, and originate either in
a free cell-formation or from epithelial cells, in a way analogous to that
in which the cutaneous sebaceous matter is formed {vide § 73), by their
continued multiplication. These cells, which I would designate milk-
cells, break up, so soon as they reach the lactiferous ducts into their
elements, the milk-globules ; the membrane, and for the most part also,
the nucleus, disappearing, without a vestige being left, so that the
milk, when secreted, usually presents no indication of its mode of
origin. At most, there occur in it a very few larger or smaller aggre-
gations of milk-globules, which, from their similarity to those met with
in the colostrum, may likewise be termed colostrum-corpuscles. The
secretion of the milk, therefore, depends essentially upon a formation
of fluid and fat-containing cells in the gland-vesicles, and consequently
falls into the category of those secretions into the composition of
which morphological elements enter ; above all to the fatty secretions,
such as the cutaneous sebaceous matter, in which cells of precisely
similar kind occur to those met with in the gland-vesicles of the lacteal
glands, and in the colostrum.

In the new-born child, the mammary gland very frequently contains
a small quantity of a fluid presenting the external and microscopical
characters of milk, the origin of which is probably related to the
formation of the glandular ducts.

"With respect to the colostrum-corpuscles and fat-globules of the
colostrum, Reinhardt was the first to prove, that the supposition
broached by Nasse and Ilenle, that these bodies are related to a forma-
tion of fat-containing cells in the mammary glands, and that the former
in their more usual form are nothing but membraneless cells, and the
latter oil-drops liberated from cells, is in every respect well founded,
although he is inclined to distinguish the formation of the colostrum
from the secretion of milk, and to regard the former as a pathological
process, as a fatty metamorphosis, by which the old epithelial cells of
the gland, previously to the formation of true milk, are evacuated
externally, and particularly because, in the true milk-formation, he

666 SPECIAL HISTOLOGY.

was unable to perceive any fat-containing cells. But since V. Bueren,
especially, has found such cells, and consequently the formation of the
milk and of the colostrum, seem to be morphologically quite identical,
such a separation of the two processes can no longer be defended ; and,
in cases of repeated parturition, the formation of colostrum can scarcely
be viewed in any other light than as the introduction to that of the
milk. On the other hand, I am quite of opinion, that the production
of the jfirst colostrum is connected with the excessive development of
the lacteal gland coincident with the first pregnancy ; and that it is
in part derived from the internal cells of the originally solid rudiments
which are removed, during the formation of the ultimate terminations
of the gland. I explain, in a similar way, the formation of milk in
the new-born child ; in which case, surely, no true secretion can be
thoucfht of.

Donne, the discoverer of the colostrum-corpuscles, states, that in
inflammations and tumefactions of the breast of nursing women, the
milk acquires the nature of colostrum ; which is, however, denied by
D'Outrepont and Munz (" Neue Zeitschrift f ur Geburtskunde," Bd.
10); in the same way, according to Lehmann (" Phys. Chemie," II.,
327, [transl. II., p. 334]) it would appear, that, in acute diseases
generally, and also in menstruation (Donnd, d'Outrepont), the milk
exhibits colostrum-corpuscles, which, when tliey exist in larger quan-
tity, are regarded by Donnd as indicative of bad milk. In hoof-mur-
rain" (" Klauenseuche"), Herberger and Donnd found the milk to
contain a good deal of colostrum. In sour milk the casein coagulates
into granules, and the milk-globules gradually run together into larger
drops. Blue and yellow milk, according to Fuchs (vide Scherer, art.
"Milk," in " Handw. d. Phys.," II., p. 470) contains colorless infuso-
ria, which he terms vibrio cyanogenus and xantJiogenus, which, Avhen
transferred to healthy milk, also color it ; a fact which, as regards blue
milk, is confirmed by Lehman (1. c, p. 335, Eng. transl.) ; according
to Bailleul (" Comptes rend.," t. 17, p. 1138), however, and Lehmann
[once only], a filamentary fungus is also found in that sort of milk.
Med milk has also been noticed by C. Nageli, and vegetable protococcus-
like growths found in it.

For the investigation of the mammary glands, those of pregnant or
nursing women, or of women who have borne children, should be pre-
ferably selected, because it is only in such that the gland-vesicles are
well developed. When the smallest lobules are teased out, their ele-
ments come readily into view; but if it be desired to examine into their
arrangement, fine sections of glands boiled in acetic acid and dried are
above all to be recommended, as well as injected preparations, which it
is not difficult to make from the lacteal sinuses. For the study of the
development of the gland, besides recent specimens, preparations made

THE HEART. 667

"with acetic acid arc necessary. The smooth muscles of the areola are
found by mere dissection, although not always very easily, as, except
during pregnancy, they are frequently very delicate.

Literature. — Rudolphi " Bcmcrk. liber den Bau der Brliste," in the
"Abh. der Berliner Akadcmie," 1831, p. 337; Astley Cooper, "The
Anatomy of the Breast," London, 1839, 4to ; C. Langer, " Ueber den
Bau und die Entwicklung der Milchdriisen, mit 3 Taf.," from the
" Denkschr. d. Wiener Akad.," Bd. III., Wien, 1851 ; A. Donnd, " Du
lait et en particulier du lait des nourrices," Paris, 1837; "Ueber die
mikroskopischen Korperchen im Colostrum.,'" Midler's "Arch.," 1839,
p. 182; " Cours de Microscopie," Paris, 1844; Fr. Simon, "Die
Frauenmilch, nach ihrem chemischen u. physiol. Verhalten dargestellt,"
Berlin, 1838 ; " Ueber die" Corps granuleux " von Donnd," in Miiller's
"Arch.," 1839, pp. 10 and 187 ; J. Henle, "Ueber die mikr. Bestaud-
theile der Milch," in Fror. "Notizen," 1839, No. 223; H. Nasse,
"Ueber die mikr. Bestandt. d. Milch," Muller's "Archiv," 1840, p.
259 ; Reinhardt, in "Arch. f. path. Anat.," Bd. I., pp. 52-04; Lam-
merts van Bueren, " Onderzoekingen over de Melkbolletjes," in the
"Nederl. Lancet," 2d ser., 4, Jaarg., p. 722, or " Observat. microscop.
de lacte," Traject. ad Rhenum, 1849, Diss. ; " De Ontwikkeling van
de Vormbestanddeelen der Melk," in the " Nederl. Lancet," 2d ser.,
5, Jaarg, p. 1 ; Fr. Will, "Ueber die Milchabsonderung," Erlangen,
1850, Programm. Besides which should be consulted the "General
Anatomy" of Henle, J. Muller's work on the Glands, and the Atlases
of Berres, Donne, and Mandl. [ Vid. also, " Observations on the
muscular tissue of the Skin," by Joseph Lister, M.B., "Quart. Journ.
Micros. Sc," vol. L, p. 262, 1853.— Trs.]

OF THE VASCULAR SYSTEM.

§ 212. The vascular system, consisting of the heart, with the blood
and lymphatic vessels, contains in its interior the Hood and the lymph
{chylus), with innumerable morphological particles. The lymphatic vas-
cular system presents special organs — the lymphatic glands.

1.— OF THE HEAPtT.

§ 213. The hea7't is a thick, hollow, muscular organ, divided into four
compartments, invested externally by a serous membrane — the pericar-
dium,— and lined internally by the endocardium, a continuation of the
walls of the great vessels, particularly of the tunica intima.

The pericardium does not differ in structure from other serous mem-
branes, as, for instance, the peritoneum. The outer lamella is consi-

668

SPECIAL HISTOLOGY.

derably the thicker; it is more fibrous towards the exterior, presenting,
towards the interior, numerous fine, elastic networks, which are imme-
diately covered with one or two layers of tessellated epithelium. Very
numerous elastic networks of the same kind are found also in the inner
thin lamella, which is, partly, very intimately united with the muscular
substance, and partly, especially in the sulci, separated from it by com-
mon adipose tissue, which, moreover, not unfrequently forms a subserous
fatty layer, extending almost over the entire heart. The vessels present
the same conditions as elsewhere ; and with respect to the nerves, twigs
from the phrenic and recurrent branch of the right vagus have been
demonstrated in the outer lamella of the pericardium (Luschka).

The muscular fibres of the heart are red and transversely striated,
but differ in many respects from those of the voluntary muscles. The
individual fibres themselves are, on the average, about -Jd more slender
(0-004-0-01 of a line), frequently more distinctly striated in the longi-
tudinal than in the transverse direction, and pretty readily divisible
into fibrils and minute particles (" sarcous elements," Bowman) ; their
sarcolemma is very delicate, or even wholly inappreciable ; and in the
fibres, there almost uniformly occur minute fatty granules, w^hich, with
the nucleus, are frequently disposed in a series in the axis of the fibre,
and, where the muscular tissue is degenerated, appear most usually to
be excessively multiplied, and also colored. Much more, however, than
by these characters, is the muscular tissue of the heart distinguished by
the intimate union of its elements, which, except on the internal surface
of the organ, not only never form manifestly distinct bundles, being
everywhere in close apposition with each other, and separated only by
a scanty connective tissue, but, as was discovered by Leeuwenhoek,*
and I also have found [vid. p. 108), are directly united
together in their elements. These anastomoses of the
muscular fibres, which are a universal attribute of the
cardiac muscular tissue, are effected in the human and
mammalian heart generally, chiefly, by short, oblique,
or transverse, usually small fasciculi, and are extremely
numerous, so that, in many places in the ventricles and
auricles (whether universally I know not), numerous in-
stances of them are presented in every minute portion.
Besides these, there also exist true divisions or fibres, by
which the thickness of separate portions of muscle may
be rendered more considerable than it was originally.

The course of the muscular fibres of the heart is extremely complex,
and a general outline only of it can here be given. The muscular struc-
tures of the ventricles and of the auricles are completely distinct from

Fig. 275. — Anastomosing primitive fasciculus from the human heart.

Fia-. 275

* [See note, p. 108,— Tes.]

THE HEART. 669

each other ; hoth, however, have as their chief point of oriofin the ostia
venosa of the ventricles, where tough, tendinous tracts — the so-called
annuli fihro-cartUaginei — are situated, two anterior, on the right and
left of the aortal opening, and one posterior, which runs backwards
also from the aorta to the border of the auriculo-ventricular septum,
where it splits into two slender crura. In the auricles are found :
1, fibres, which are common to both, in the form of transverse, flattened
bundles, which proceed chiefly anteriorly, but afterwards also superiorly
and posteriorly, from one auricle to the other, and are continued in
them as transverse fibres. 2, special fibres. These constitute, in the
first place, complete rings at the origins of the great veins, and at the
points of the appendices ; and, in the second place, a longitudinal layer
of some thickness beneath the endocardium, which springs from the
auriculo-ventricular openings, and is especially developed in the right
auricle [musculi pectinati). Besides these, there exist between the latter
muscles, and also in the auricles, numerous other small fasciculi, which,
on account of their irregularity, cannot be more particularly described.
The septum is to some extent common to both auricles. Its muscles
arise from the most anterior part of the upper border of the septum of
the ventricles, immediately behind the aorta, from the posterior fibro-
cartilage and arch to the right, around the fossa ovalis, in which only
slender fibres exist, in a superior and posterior direction, in order to
terminate, partly at the vena cava inferior, partly by forming a com-
plete ring ; whilst on the left, they surround the fossa ovalis in the
opposite direction.

The muscular structure of the ventricles is disposed so that on the
external and internal surfaces the fibres everywhere decussate; and in the
intermediate portion, every stage of transition from the one direction to
the other is presented. The muscular fibres arise at the ostia venosa
and at the arterial openings, in part immediately, and partly with the
intervention of short tendons, run more or less obliquely (and some
longitudinally or even transversely), and after they have surrounded a
portion of the ventricle in the longitudinal or transverse direction, curve
back again, and then terminate, some in the musculi papillares, and
cTiordce tendinea', whilst others are again inserted in the points of origin
above indicated, so that without being interrupted by tendons, they
describe large involved loops, or figure-of-8 turns of large size, and
running in very numerous and diverse directions.

The endocardium is a whitish membrane, investing all the elevations
and depressions of the internal surface of the heart, as well as the papil-
lary muscles and their tendons, and the valves. It is most developed in
the left auricle (as much as :^ of a line), and thinnest in the ventricles,
so that the muscular substance there presents its natural color. As
regards its structure, it consists of three layers ; an epithelium, an

670 SPECIAL HISTOLOGY.

elastic layer, upon which the varying thickness of the endocardium in
different situations depends, and a thin layer of connective tissue. The
first is a single, or, according to Luschka, perhaps a double layer of
polygonal, usually elongated, clear, flattened, nucleated cells, 0-007 to
0.012 of a line long, resting immediately upon the most superficial layer
of the elastic membrane, which may be said to consist of nothing but
very fine, longitudinal, elastic fibres. The remainder of this middle
layer is constituted of a matrix of common connective tissue with scat-
tered nuclei, through which the very abundant finer and coarser elastic
networks penetrate. This elastic element is so abundant, in fact, in the
auricles, and even mixed with true fenestrated membranes {vid. § 23) that
the endocardium of those cavities is rendered almost entirely a yellow,
elastic membrane, consisting of several lamina. Most externally, there
succeeds to this elastic layer, a stratum of connective tissue, of great
tenuity indeed, but which, nevertheless, both in the ventricles and in
the auricles, may easily be raised as an entire membrane. In the por-
tion bordering upon the elastic tissue this layer contains fine elastic
elements. It represents, in fact, a somewhat loose layer, like a sub-
serous connective tissue, uniting the muscles and the true endocardium.

The auriculo-ventricular valves are lamince springing from the fibrous
rings of the ostia venosa, in the thicker parts of which, a middle layer
of connective tissue with numerous elastic networks, and two lamellce of
the eiidocardium united with it, may be clearly distinguished. Towards
the free border, these three layers are conjoined so as to form a single
one, composed of connective tissue and fine elastic networks, over which
again the epithelium is continued. The semilunar valves present the
same conditions as the free border of the others, and with respect to the
cliordoe tendinea^ they are constituted of common tendinous tissue,
covered by a very thin layer of endocardium — consisting, indeed, merely
of epithelium and a fine elastic lamella.

The bloodvessels of the muscular substance of the heart are very
numerous, but differ in no respect from those of transversely striped
muscle (§ 77), except that the capillaries, owing to the slenderness of
the muscular fibre, often encompass several of them in common. The
endocardium is tolerably well supplied with vessels in its layer of con-
nective tissue, whilst they are more scanty in the proper endocardium..
In the auriculo-ventricular valves a few vessels are readily seen, not
only in animals but also in Man {vid. Luschka, 1. c, p. 182, Fig. 1),
some of which enter them from the papillary muscles, but chiefly from
the basis of the valves, and are also distributed in part, though sparingly,
in their proper endocardial investment. The semilunar valves possess
no vessels. Only a few lymphatics are found in the external lamella of
the 2:)e7'icardium, whilst they occur in greater abundance on the inner
lamella on the muscular substance, and may there be demonstrated

THE HEART. G71

readily enough, if the heart be placed for a few days in water, as Cruik-
shank correctly observes. Their trunks collect in the sulci, accompany-
ing the bloodvessels, and terminate in the glands, behind and below the
arch of the aorta, on the bifurcation of the trachea, to which the pulmo-
nary lymphatics also proceed. "Whether the substance of the heart and
the endocardium are also furnished with lymphatics, as is asserted by
some, is not yet determined. The nerves of the heart are numerous and
proceed principally from the cardiac plexus formed by the vagus and
sympathetic, beneath and behind the arch of the aorta. These nerves,
forming the more scanty 2^l^xus coronarius dexter, and the richer p. c.
sinister, accompany the vessels on the right and left ventricles and
auricles, run, in part with the vessels, in part crossing them in various
directions, toward the apex of the heart, and, whilst entering into nume-
rous anastomoses with each other, usually at acute angles, enter the
muscular substance at various points, some even in the coronary sulcus,
in order to terminate, partly in the muscular substance, and partly to
reach the laver of connective tissue of the endocardium. The cardiac
nerves, in Man, are gray, and, except the largest, contain only fine and
very pale fibres ; the latter, however, in the greater number, and inter-
mixed with not very numerous nucleated fibres. Although the nerves,
even in the endocardium, retain their dark borders and are tolerably
numerous, it has not hitherto been possible to discover their terminations
in that situation, any more than in the muscular substance. Ganglia
exist, not only in the cardiac plexus in various situations, but, as Remak
discovered, in the Calf, also in the muscular substance of the auricles
and ventricles, which is likewise true of man and other animals. These
ganglia are best known in the Frog, in which they are situated, espe-
cially in the septum, and at the junction of the auricles with the ven-
tricle, and contain apolar and unipolar cells (Ludwig, Bidder, R. Wagner,
myself). The minute fusiform enlargements on the external nervous
branches, especially noticed by Lee, are not ganglia, being merely thick-
enings of the neurilemma.

With respect to the particular direction of the muscular fibres of the
ventricles, the following remarks may be offered. On the external sur-
face of the ventricles there is a layer, J-1 line thick, which, on the left ven-
tricle, runs obliquely downwards from the pulmonary artery, the anterior
longitudinal sulcus and the left transverse sulcus, and in the middle of
the wall of the ventricle, descends very abruptly, almost vertically.
On the right ventricle, these fibres are oblique only on the conus arteri-
osus, whilst on the sides and posteriorly they are almost or quite trans-
verse. At the longitudinal sulci, the s.upcrficinl fibres are continued
from one ventricle upon the other, so that a small portion of those of the
left ventricle arise from the anterior side of the ostium venosum dextrum

672

SPECIAL HISTOLOGY.

and the greater part of those belonging to the right ventricle from the
posterior portion of the left ostium venosum. If the fibres of the left
ventricle are traced, it will be found, with the exception of those which
at the posterior longitudinal sulcus pass upon the right ventricle, that
they (Fig. 276 a, a' , a") run towards the apex of the heart, and there
form the well-known vortex, and then curve inwards, forming loops ; and
are continued as the innermost, for the most part longitudinal, fibres of
the cavity of the ventricle, and either ascend as high as the venous
openings, or terminate in the posterior papillary muscle. Upon removal
of this set of fibres, a thick layer comes into view, interposed between
its external and internal portions, the fasciculi in which, at first sight,
appear to surround the cavity of the ventricle in an oblique and trans-
verse direction, although they seem to arise, without exception, from the
ostia venosa, and again to terminate in the same situation, and to de-
scribe a figure-of-8 turn, still more distinctly than the external muscular
layer, as has been clearly shown by Ludwig. I find that the bundles of
this layer (Fig. 276 c, c' c" c'"), after their origin from the left border
Fi.j;. 270. of the ao7'ta and the anterior half of the ostium

venosum sinistrum, extend obliquely downwards,
and to the left (c), and then, before reaching the
apex of the heart, curve towards the posterior
wall of the ventricle (c'), whence they again as-
cend on the septum {c") and the anterior wall
{c'"), and are finally inserted in the whole extent
of the venous opening, and also in the upper bor-
der of the septum {c""). It is from these fibres
in the free wall of the ventricle that are derived
the deep layers which decussate with the superfi-
cial, and on the septum afford the fibres which, on the left side, run
obliquely from below and behind, upwards and forwards.

On the right ventricle, there are much fewer independent fibres than
on the left. Most of the superficial fasciculi are continued upon the
left ventricle ; both the anterior, which are continued over the anterior
longitudinal sulcus and lost in the vortex, and also many of those which,
at the posterior longitudinal sulcus, stretch from the left to the right
ventricle. These latter fibres, consequently, completely encircle the

Fig. 276. — Diagram of the left ventricle, with the septum, in order to show the course of
the muscular fibres, a a' a", svpcrftcialfibres : a, on the anterior wall ; a', the turning inwards
of them at the vortex ; a", their passage into the posterior papillary muscle, b, h', b", septal
fibres of the right side: b, their course, downwards and forwards ; 6', their passage into the
vortex and internal muscular layer of the left ventricle, as well as their termination in the
anterior papillary muscle,/)", c — c"", middle muscular layer: c, commencement at the right
side of the ostium venosum, and course on the anterior wall obliquely downwards and back-
wards ; c', curvature on the septutn, and course on it, c" ; c"', curvature on the anterior wall,
and deep course in it, to the end of the ostium venosum, c"".

THE HEART. 67

o

right ventricle, part of tlicm also entering tlic vortex, and part, in the
anterior longitudinal sulcus, joining the middle muscular layers of the
left ventricle. Independent, superficial fibres occur only : 1, at the
conus arteriosus, arising from the ostium venosum dextrum, between the
right auricle and the aorta, surrounding the conus arteriosus, and re-
turning thence, from the left, back to their point of origin ; 2, at the
apex of the right ventricle, where not unfrequently a distinct, second
vortex exists, in which case some of the superficial fibres arising from
the left ostium venosum also curve inwards in that vortex, as they do in
that of the left ventricle, and are continued into the superficial fibres of
the right ventricle, but, on account of their intricate interlacement,
cannot be traced further. Besides these, other deeper fibres cx\s>im the
right ventricle, which are disposed as follows: 1. From the upper bor-
der of the septum, and the left posterior side of the pulmonary opening,
flattened bundles commence and run in the septum, downwards and for-
wards, towards the apex of the heart and the anterior longitudinal sul-
cus, where they join the superficial fibres, and are continued with them
into the vortex, whence they may be traced as far as the anterior papil-
lary muscle of the left ventricle (Fig. 276 h, b', b"). 2. "With these fibres
arc associated others, running obliquely downwards and backwards,
from the right side of the pulmonary opening and the right portion of
the ostium venosum dextrum, beneath the superficial layer of fibres on
the free wall of the ventricle, as far as the posterior longitudinal sulcus,
■where they curve abruptly towards the septum, in which they accom-
pany the fibres described under (1), though more on the inferior half of
the septum, to the apex of the heart, and terminate in a similar way. 3.
With these fibres are also conjoined, to some extent, the elements of
the great papillary muscle of the right ventricle, Avhilst those of the two
smaller are continued into the fibres of the sep)tum described under (1).
Besides this, all these muscles furnish direct fibres, some of which de-
scend from the ostium venosuyji and return upon themselves, and some
proceed from the network of the trabcculce carnecc^w^^ cannot be traced
further.

It would appear therefore, that the auricles, as regards their muscular
structure, are almost distinct ; whilst in the ventricles, the entire super-
ficial, tolerably thick muscular layer is continuous all round and is dis-
posed as if the heart had only a single cavity. Properly speaking, the
left ventricle alone in this respect, is independent, in which there is not
only beneath the superficial layer a very thick muscular mass arising
and ending in it, to which, also, the greater part of the septum belongs,
but which also receives nearly all the deeper muscular layers arising on
the right side, in the free wall of the ventricle, and inserted into the
right portion of the septum. The heart, consequently, might be de-
scribed as composed of two muscular sacs ; the thinner of which is com-

43

674 SPECIAL HISTOLOGY.

mon to the wliolc ; the other and thicker belonghig only to the left di-
vision, and to some extent being interposed between the layers of the
former. To the latter would belong the entire septum, and the mid-
dle muscular substance of the left ventricle ; to the former, the superfi-
cial layers with their continuations in the innermost muscular strata,
and especially the whole of the free portion of the right ventricle.

2.— OF THE BLOODVESSELS.

§ 214. As regards their structure, the bloodvessels are divided into
arteries, capillaries, and veins ; but these three divisions are by no means
separated by definite limits, inasmuch as the capillaries are continuous
with the veins on the one hand, as imperceptibly as they commence from
the arteries on the other. At the same time it is true that both kinds
of larger vessels, although in their rudiments presenting a general con-
formity of structure, are still sharply and definitely distinguished in
many respects.

Concci'ning the tissues which enter into the composition of the vessels,
and the mode of their arrangement, the following general remarks may
be made. Whilst the true cajnllaries possess only a single perfectly
structureless coat, in the larger vessels, with few exceptions, the number
of tunics is increased to three, which may most suitably be described as
tunica intima, t. media, and t. externa s. adventitia. In these tunics
there are found, of the fibrous tissues of the body, in the first place, the
elastic and smooth muscular tissues, but the connective tissue, and even
the transversely striped muscular tissue are also represented in them ;
besides which, there exists epitltelia, peculiar homogeneous membranes,
vessels, and even nerves ; so that we have presented in them a com-
plexity of structure which renders a general description almost impossi-
ble and which can be made clear only by an accurate examination of each
particular element ; and the rather so, because the more extensively
distributed tissues assume very different forms. With respect to the
arrangement and subdivision of these tissues, they maybe said to exhibit
a very strong tendency to lamination and, in the different layers, to the
assumption of a constant direction in the course of their constituent
elements. The former of these dispositions, however, rarely extends to
the actual isolation of the individual layers ; and to the latter, though
more rarely, there are also exceptions. The tunica intima is the
thinnest of the membranes of the vessels, and always consists of a cel-
lular layer, the cpitlicliuin ; most usually also of an elastic membrane
in which a longitudinal direction of the fibres predominates ; to which
again may be superadded other layers of one kind or another, which
also almost invariably retain the longitudinal direction. The t. media
is for the most part a thick layer, and is especially the seat of the tra7is-

THE BLOODVESSELS.

675

verse elements ami of the musch'S, although in the veins it also contains
numerous longitudinal fibres, and in all the larger vessels presents, in
addition, elastic elements, and connective tissue in greater or less quan-
tity. The t. adventitia, lastly, again exhibits a preponderating longi-
tudinal fibrillation, is as thick as or thicker than the t. media, and con-
sists, for the most part, only of connective tissue and elastic net-
^vorks.

If the separate tissues of the vascular tunics are investigated some-
what more closely, it ^Yill be seen that the connective tissue appears
almost universally fully developed, with fine and coarse bundles and
distinct fibrils. It is only in the smallest arteries and veins that it is

Fi.^. 277,

replaced by a nucleated, indistinctly fibrous tissue, and ultimately
passes into a perfectly homogeneous, still occasionally nucleated, delicate
membrane. The elastic tissue nowhere presents such manifold forms as
it does in the vessels. From wide-meshed, lax networks of the finest,
middle-sized, and thickest fibres (Fig. 22, p. 81), up to the narrowest,
closest, membraniform interlacements of these fibres, all transitionary
forms are here met with ; and besides this, we may notice every degree of
transformation of the latter, or of the elastic reticulated membranes into
true elastic membranes, which either betray their derivation, in an elastic,
more or less indistinct, fibrous network pervading them, and distant
openings, or are transformed, either partially or entirely, into perfectly
homogeneous plates, exhibiting more or fewer openings (Fig. 25, p. 82).

Fig. 277. — Elastic membrane from the tunica media of tlie i^opliteal artery in Jlan, witVi
an indication of fibrous networks ; magnified 350 diameters.

Fig. 278. — Muscular fibre-cells from the human arteries, magnified 350 diameters. 1,
from the popliteal artery ; a, without, b, with acetic acid. 2, from a twig, ^ a line in
diameter, of the anterior tibial artery : a, nttdei of the cells.

676 SPECIAL HISTOLOGY.

In the smallest vessels, instead of the elastic elements, there occasionally
occur, especially in the t. advcntitia, fusiform cells, which can only be
regarded as undeveloped formative cells of elastic tissue. Transversely/
striped muscle is found only at the openings of the largest veins into
the heart ; -whilst, on the contrary, smooth muscles are extensively dis-
tributed, especially in vessels of a medium size, and also to some extent
in the larger vessels. The elements of these muscles, or the contractile
fibre-cells, in the majority of the vessels, present nothing peculiar,
except that their length never exceeds 0-04 of a line, and that they are
united, either directly, or with the intervention of connective tissue and
elastic fibrils, into flattened bundles and muscular membranes, more
rarely into reticulated muscular tissue. In the larger arteries, in place of
these elements, we find shorter plates resembling epithelium cells, always
with elongated nuclei; and in the smallest arteries and veins, slightly
elongated, or even roundish cells ; both which forms may be regarded
as being in a less developed condition.

A peculiar fibrous tissue is contained in the t. intima of the larger
vessels, which, since Henle, has generally been regarded as a meta-
morphosed epithelium. It consists of pale, usually striped, or it may
be, homogeneous lamellce^ Avith elongated (long-oval) nuclei disposed
parallel to the long axis of the vessel, and which may not unfrequently
be broken up into slender nucleated fusiform fibres, similar to certain
epithelial cells, or at all events, into fibres ; but at other times are more
homogeneous and without nuclei, or else appear to be transformed into
extremely delicate fibrous membranes, like the closest and finest elastic
networks. The similarity of these layers, which I shall term the
striped lamellce of the t. intima, or rather of the fibrous cells of which
they are fundamentally constituted, to the epitlielium of the vessels, is
nevertheless insufiicient to justify the supposition of their being derived
from the latter, since there are no facts to show that the true epithelial
cells and the striped lamellce stand in any genetic connection of such a
kind, as that the latter were at one time a true epitlielium and the
innermost layer in the vessel, being afterwards successively pushed
back, and their elements made to coalesce ; on the contrary, it seems
to be allowable to regard the epithelial cells and the formative cells of
thes^ layers as originally equivalent, and that in the course of develop-
ment, the one set are transformed in one direction, and the other in
another, and, in this way, ultimately become tissues of more or less
different kinds.

The epithelium of the vessels (Fig. 14, p. 76) presents two forms :
firstly, especially in the great veins, it appears under that of a tessel-
lated epithelium, with polygonal, mostly somewhat elongated cells ; and
secondly, as in most of the arteries, as a fusiform epithelium, with
acuminated, slender cells, 0-01-0-02 of a line long. Normally, it

THE BLOODVESSELS. 677

exists in all vessels, may almost always be pretty veadil}^ broken up
into its elements, and like other simple cpithclia, is not subject to any
constant detachment and restoration. With Remak, -we might describe
the epithelium as the cellular membrane of the vessels, since it differs
from other epithelia in this respect, that in the large vessels, it is often
continuous "with the striped lamella', "without any line of demarcation,
so that frequently it cannot be said "^vhere the one ceases and the others
commence ; but I should myself rather be inclined to retain the old
name, both because the innermost cellular layer of the vessels presents
in all respects the relations of a simple epithelium, and is, in many
situations (heart, smaller vessels) abruptly defined from the deeper
tissues. Even the circumstance particularly adduced by Remak, that
the vascular epithelium does not proceed from the embryonic epithelial
membrane, is not "with me decisive as to the propriety of separating it
from the other epithelia, inasmuch as the investments of the serous
sacs and synovial capsules, Avhich no one "will be disposed to separate
from the epithelia, are developed quite independently.

All the larger vessels do\Yn to those -^ a line in diameter and less,
possess nutritive vessels as they are termed (vasa vasorum s. nutrientia),
derived from minute contiguous arteries, and ramifying chiefly in the
t. adventitia, in ^vhich they constitute a rich capillary plexus "with
some"what rounded meshes, from which again the veins accompanying
the arteries arise, and which, in the case of the venous vasa vasorum,
pour their blood directly into the vein to which they belong. The t.
media of the larger arteries and veins, according to the concurrent
testimony of many authors, also contains vessels, although in very
small number, and only in the outer layers ; "whilst the internal layers
and the t. intima have always appeared to me to contain none at all ;
but even in these situations some observers would seem to have noticed
vessels (in the Ox, the vena cava inferior is richly provided with vessels
up to the t. intima). Nerves derived from the sympathetic and spinal
nerves may readily be seen going to many arteries, but frequently
appear merely to accompany them. Where they enter the coats of a
vessel they run only "within the t. adventitia, and in favorable instances,
in animals, divisions and free terminations of their fine fibres may be
perceived {vide "Mikros. Anat.," II., 1, p. 532-33). Many arteries are
■wholly without nerves, as those of the cerebral and spinal substance, of
the t. chorioidea, the placenta, as well as many arteries of muscles,
glands, and membranes, whence it is obvious, that nerves are not as
requisite for them as we have usually been inclined to believe. This
may be said more decisively "v\'ith respect to the veins, as it is only in
the larger ones that a few fine nerves can be demonstrated. Such have
been observed by Luschka in the sinuses of the dura mater, the veins of

678 SPECIAL HISTOLOGY.

the vertebral canal, the vence cavce, the jugular, iliac, and crural veins,
and in those of the liver by myself. They are derived both from the
sympathetic and the spinal nerves, and with regard to their termina-
tions have not yet been investigated. According to Luschka, they
would appear to extend to the innermost vascular tunic ; but this I have
not as yet been successful in observing.

§ 215. For more easy description, the arteries may be divided, ac-
cording as the middle tunic is purely muscular, or composed of muscu-
lar and clastic fibres intermixed, or else chiefly elastic, into small,
medium sized and large arteries ; and the more properly so, because,
concomitantly with the variations in the structure of the middle tunic,
the external and internal coats present a different conformation, at all
events, in many respects. A general characteristic of the arteries is
presented in the circumstance, that the middle tunic is very strong, and
consists of numerous, regularly disposed lamince, the elements of which
observe a transverse direction. In the largest arteries the t. media is
yellow, highly elastic, and of great thickness ; towards the periphery of
the body it gradually diminishes in thickness, and becomes redder and
more contractile, until, just before the capillaries are reached, it appears
quite thin and subsequently inapparent. The whitish t. intima is
always much thinner, and varies in thickness within narrower limits,
but this is also regulated by the size of the vessel ; whilst, on the con-
trary, the t. adventitia of the largest arteries is absolutely considerably
thinner than in those of a medium calibre, in which it often equals the
t. media in thickness, or may even exceed it. In a special exposition
of these points, it is best to begin with the smallest arteries as the
simplest in structure ; with these the others may be afterwards readily
compared.

Arteries under 4-5 or 1 line in diameter, with few exceptions, present,
until close to the capillaries, the following structure (Fig. 279). The t.
intima consists of only two lamince, an epithelium., and a peculiar, glis-
tening, less transparent membrane, wdiich I shall term the elastic inter-
nal tunic. The former contains well-marked, fusiform, pale cells with
long-oval nuclei, Avhich are readily separated in connection, in entire
fragments, or even in the form of perfect tubes ; but may also be iso-
lated, and then present no small resemblance, on the one hand, with the
fusiform cells of pathologists (also with the formative cells of the elastic
fibres and of connective tissue), and on the other with contractile fibre-
cells ; from the former, however, they are distinguished by the less atte-
nuation of their extremities and their paleness ; and from the latter by
their rigidity, by the nuclei never having the rod-like form, and by their
chemical reactions. The elastic tunic is, on the mean 0-001 of a line

THE BLOODVESSELS.

679

thick, and in the living subject is smooth!}^ stretched beneath the epithe-
lium, -whilst in empty arteries it almost always presents a greater or less
number of usually strong folds, and frequently also, numerous, fine trans-
verse ruga', which give it, although perfectly homogeneous, a peculiar lon-
gitudinallystriated aspect ; in addition, it appears almost always as a, fenes-
trated membrane, as it is termed, with various sized, distinctly marked reti-

Fig. 279.

culated fibres, and usually minute elongated openings; more rarely as a
true but very close network, of chiefly longitudinal elastic fibres, with nar-
row, elongated fissures, — and completely corresponds in aspect, in its
great elasticity, and its chemical reactions, with the elastic lamellce of the
t. media of the larger arteries. The middle tunic of the small arteries is
purely muscular, without the slightest admixture of connective tissue
and elastic elements, and is strono;er or weaker accordino; to the size of
the vessel (down to 0-03 of a line). In vessels of 1-10 of a line in dia-
meter, the fibre-cells, which are nnited into lamellce, may be pretty
readily isolated by dissection, and in still smaller ones by boiling and
maceration in nitric acid of 20 per cent., when they appear as delicate
fibrc-cells-0-02-0-03 of a line lonff, and 0-002-0-0025 of a line broad.
The t. adventitia consists of connective tissue and fine elastic fibres, and
is usually as thick as the t. media or even a little thicker.

Fig. 279. — An artery, o, 0-0G2, and vein, b, 0-0G7 of a line in diainoter; from the mesen-
tery of a child ; treated with acetic acid, and magnified 350 diameters: a, tunica adventitia,
with elongated nurlei ; 0, nuclei of the contractile fibre-cells of the t. media, viewed in part
on the flat surface, in part in apparent transverse section; y, nuclei of the epithelial cells; iT,
elastic longitudinal fibrous membrane.

680

SPECIAL HISTOLOGY.

t

Fig. 2S0.
S a-

ex

9 ^^

■=>-i ; '^

H-

&.^A

.Yv^'

iii-^

The above description of the structure liolds good of arteries down to
1-8 of a line in size, but nearer the capillaries the structure changes
more and more (Fig. 280). Even in arteries 1-10 of a line in diameter,
the t. adventitia contains no clastic tissue, being composed only of con-
nective tissue witli elongated nuohi, Avhich at first still retains its fibrous
character, but afterwards, though always nucleated, appears more homo-
geneous, and ultimately represents a thin, truly structureless membrane,
which, in vessels under 0*007 of a line disappears altogether. The annu-
lar fibrous coat in arteries less than 1-10 of a
line, down to those having a diameter of 1-25
of a line, still presents 2-3 layers of muscles
and a thickness of 0-005-0-008 of a line;
in smaller vessels it has but one layer, the
elements of Avhich at the same time become
shorter and shorter; and finally, in vessels
between 0'03-0'007 of a line, appear only in
the form of short, elongated or elliptical cells
of 0*015-0"006 of a line with shorter nuclei.
In vessels of 0-012 of a line in diameter,
these more embryonic forms of contractile
fibre-cells still constitute a connected lamina,
but after that, they are gradually separated
from each other (Fig. 280) and become wholly
lost. The t. intima, in vessels more than
0'028-0-03 of a line in size, has an elastic inner membrane, which, how-
ever, in its earliest form, is very delicate, and does not appear to attain
its full development in arteries less than 0'06-0"08 of a line in diameter.
On the other hand, the epithelium may be traced in vessels of not more
than 0*01 or even of 0*07 of a line ; and it may at the same time be
remarked, that its cells can no longer be isolated, and its presence only
be recognized from the closely placed elliptical nuclei.

Medium-sized arteries above 4-5 or 1 line, up to those of 2 and 3 lines
in diameter, at first, present no great alterations in the external and in-
ternal tunics, whilst the t. media is not only always increased in thick-
ness in proportion to the size of the vessel (from 0-05-0-12 of a line), but
is also changed in structure. For now, in addition to muscular layers, the
number of which constantly increases, but the elements of which are pre-
cisely the same as before, we observe fine elastic fibres, which, united into
wide-meshed networks, run, at first singly and with little regularity
among the muscular elements ; but in larger vessels of this category

Fig, 2S0. — An artery, a, of 0 01, and a vein, b, of 0015 of a line, from the mesentery of
a child, magnified 350 diameters, treated with acetic acid. The letters as in Fig. 279: «, t.
media of the vein, composed of nucleated connective tissue.

THE BLOODVESSELS.

G81

Fv'. 2S1.

arc accompanied by a certain amount of connective tissue, and here and
there exhibit a disposition to form
special layers alternating with the
muscular, though not presenting the
characters of a continuous network
throughout the t. media. Thus, al-
though the t. media is deprived of
its eminently contractile structure,
it must be allowed that tlie mus-
cular fibres here also still retain a considerable preponderance. The
t. intima in the medium-sized arteries has, not unfrequently, between
the elastic inner membrane and the epithelium, several other layers,
among which the above described striped lamellce are the most remark-
able. These lamella', composed of fine elastic networks, wider towards
the exterior, and lying in a homogeneous, granular or fibrillated con-
nective substance, constitute the middle lamina of the t. intima, the
elements of which also all run longitudinally, and are for that reason
readily distinguishable from the muscular layers of the t. media, to
which in some respects they bear a resemblance. The t. adventitia,
lastly, in almost all these arteries, exceeds the t. media in thickness, at-
taining 0-05-0-16of a line. Its elastic fibres at the same time become
stronger and stronger, and even in the vessels 1 line in diameter, a
considerable aggregation of them, where it adjoins the t. media, may be
perceived, the line of demarcation between the two tunics being in all
these arteries extremely well defined. This elastic membrane of the t.
adventitia is extremely well marked in the largest of the vessels belong-
ing to the class now under consideration, as in the external and internal
carotids, the crural, brachial, |?ro/^(n'^a/e7?^om, mesenteric, and creliac,
in which it measures from 0-013 to as much as 0-04 of a line, and more,
and is to some extent very distinctly laminated, the structure of the
lamellce very often closely approaching that of the true elastic mem-
branes. Besides this, the external layers of the t. adventitia also con-
tain elastic networks, only that the elements of the latter are some-
what finer and constitute minute lamella', but are conjoined with less
regularity. TJie largest of the medium-sized arteries cxhxh'xt an approach
to the largest arteries, inasmuch as, in their f. media certain portions
of the clastic networks constitute somewhat stronger elastic lamella;,
which, however, are continuous through the entire thickness of the
tunic, and also, more rarely, form true elastic membranes, by which
they are distinguished from the elastic plates of the annular fibrous

Fig. 281. — Transverse section of the art. profunda fcmoris of ^^an,magmCled 30 diameters:
a, t. intima, whh the elastic layer (the cpilhelium is not i^erceptible) ; b, t. media, v.' iihout
elastic la7tieUcB, hut whh fine elastic fibres; c,t. adventitia, wiih elastic networks and con-
nective tissue.

682

SPECIAL HISTOLOGY.

coat of the largest arteries, yet to be described. LameUce of the former
character are found in the inner layers of the t. media of the aa. cru-
ralis, mesenterica superior, cceliaca, iViaca externa hrachialis, and in
the external and internal carotids; whilst they occur in a remarkable
manner in the commencement of the tibialis antica and postica, and in
the popliteal artery throughout the entire middle tunic ; they are par-
ticularly well developed in the last-named vessel, which has also usually
somewhat thicker walls than the crural.

From the conditions of the t. media above stated, and in other re-
spects also, the transition from the medium-sized to the largest arteries
is rendered extremely gradual. With respect to the t. intima, its epi-
thelial cells in the latter are usually no longer so much elongated as in
the smaller vessels, though still retaining their fusiform figure and a
length of 0-006-0-01 of a line. The rest of this tissue does not neces-
sarily increase in amount with the size of the vessel, although it exhibits,
especially in the aorta, a great proneness to become thickened, so that
it is often difficult to determine its normal thickness. As regards its

Thr. 2S2.

structure, it consists chiefly of lamellce of a clear, sometimes homogeneous,
sometimes striated, or even distinctly fibrillated substance, presenting,
for the most part, the characters of connective tissue (Eulenberg ob-
tained some gelatin from the t. iyitima), and is pervaded by finer and
coarser longitudinal elastic networks. Usually these networks become
more and more close from within to without, and their elements stronger,
and on the side towards the t. media the inner membrane ceases, either
with an elastic close network or a true fenestrated more or less fibrous
membrane, obviously corresponding with the elastic inner membrane of
the small arteries. Immediately beneath the epithelium the elastic net-
works are either very fine, or are replaced by one or several clear layers

Fig. 2S2. — Transverse section of the aorta below the superior mesenteric artery. 1, t.
iniima ; 2, (. media ; 3, t. advenlitia : u, epithelium; b, striped lamella- ; c, elastic membrane
of the inlinia; (f, elastic lamellte of the t. media; e, its muscles and connective tissue;
J] elastic networks of the t. adccntitia. From Man. — Magnified 30 diameters, treated with
acetic acid.

THE BLOODVESSELS.

G83

FiL'. 283.

— the striped lamella^ — Avhicli, ^vllen niiclcatctl, often appear to consist
of coalesced epithelial cells; and when homogeneous and without nuclei,
to approach pale elastic membranes. In the annular fibrous layer, the
largest arteries present, as a new element, peculiar elastic membranes
or plates, which, except in the transverse disposition of their fibres, are
constituted in all essential respects in the same way as the elastic inner
membrane, particularly of the smaller arteries, and sometimes appear
as very thick networks of strong elastic fibres, sometimes as true fenes-
trated membranes with a less evident fibrous structure. These mem-
branes 0-001-0-0012'of a line thick, and the number of which may
amount to from 50 to 60, regularly alternate, at distances of 0-003-
0-008 of a line, with transverse layers of smooth muscle, which are per-
vaded by connective tissue and networks of medium-sized elastic fibres ;
nevertheless, they are not to be regarded merely as tubes inserted regu-
larly one within the other and having the interspaces occupied by muscles ;
for, in the first place, they are connected with each other and with
the finer elastic network pervading the muscular tissue, sometimes more
frequently, sometimes more sparingly ; and,
in the second place, they are not frequently
interrupted in spots, or replaced by com-
mon elastic networks. The plates are seen
most distinctly and most regularly disposed
in the abdominal aorta, the a. innominata,
the common carotid, and the smallest of
their immediate branches, although these
conditions vary considerably in different
individuals, so that in the want of very
extended researches no general statement with respect to them can be
propounded.

Another characteristic of the t. media is the slight development of its
muscular element. Contractile fibre-cells, it is true, may be found also
in the largest arteries throughout all the layers of the middle tunic ;
but, in the first place, compared with its other elements, the elastic
plates, the connective tissue, and the finer elastic networks, they con-
stitute only a very inconsiderable part of that membrane (J-J) ; and,
secondly, are so undeveloped in their elements, that it appears very
doubtful whether they possess any notable contractile power. For in
the aorta and the trunk of the pulmonary artery, the fibre-cells in the
inner layers of the t. media are often not longer than 0-01, and 0-004-
0-006 of a line broad, and quite flat, so that they are not unlike certain
epithelial cells; at the same time their figure is irregular, rectangular,
fusiform or clavate, though they still contain the well-known, rod-like

FiO. 2S3. — Muscular fibre-cells from the innermost layer of the axillary artery in 3Ian ;
magnified 350 diameters: a, without; h, with, acetic acid; a, nucleus of the fibres.

684: SPECIAL HISTOLOGY.

nuclei. In the outer layers the fibre-cells are more slender and more
elongated, up to 0-02 of a line, and at the same time more like the-SYoll-
marked muscular fibre-cells of other organs, though even there retaining
somewhat of a rigid and peculiar aspect. In the carotids, subclavian,
axillary and iliac arteries, the contractile elements have become more
developed, whence also the t. media of those arteries does not present
the pure yellow color of that of the largest vessels, but begins to assume
a reddish tinge. The t. advcntitia of the largest arteries is, relatively
and absolutely, thinner than in the smaller, amounting to 0'04-0'02 of a
line. Its structure, upon the whole, is the same as in other vessels,
although the elastic inner layer is less developed, and also very indis-
tinctly defined from the thick elastic elements of the t. media.

The t. intima of certain arteries also contains smootJi muscles, as I
have found in the axillary and popliteal arteries in Man, and as has
been lately demonstrated, particularly in the visceral arteries of the
Mammalia. In the largest arteries in Man this tunic is very frequently
thickened, in which condition a vast increase of the striped lamelljB in
particular takes place. In the t. wxdia of no artery is the muscular
element wholly wanting, and Henle erroneously adduces the arteries of
the retina in opposition to this, for it occurs in those arteries even in
branches of 0*03, and is not absent in any above 0*02 of a line. In
Animals the t. advcntitia of the large arteries contains muscles, but
not in Man.

§ 216. Veins. — The veins also admit of being divided into three
groups, small, medium-sized, and large, which, however, are not so
abruptly defined as is the case with the arteries. The veins, without
exception, have thinner walls than the urteries, which depends just as
much upon their containing a less considerable quantity of contractile,
as upon a more sparing development of the elastic elements ; Avhence
also the venous walls collapse more readily, and are less contractile.
The t. intima, in the larger veins is frequently not thicker than it is
in those of medium size ; it is less developed than in the arteries, but
in other respects, of the same structure. The t. media, which is never
yellow, but usually grayish-red, contains far more connective tissue,
fewer elastic fibres and muscles, and, what chiefly characterizes it,
always presents together with the transverse, longitudinal layers also.
It is in general thin, but absolutely stronger in the medium-sized veins
than in the larger, and in these also the muscular element is most
vigorously developed. The t. advcntitia, lastly, is usually the thickest
of the three coats, its relative and absolute thickness usually increasing
with the size of the vessels. In constitution it precisely resembles that

THE BLOODVESSELS.

685

of the arteries, except that in many veins, especially of the abdomen,
longitudinal muscles, occasionally very well developed, appear in it,
and give the entire venous wall a peculiar character.

The smallest veins (Fig. 280 6), may be said to consist solely of a
nucleated, indistinctly fibrous, or homogeneous connective tissue and an
epithelium. The elements of the latter are elliptical or round, with
oval or even rounded nuclei, whilst the former constitutes a proportion-
ately strong t. advcntitia, and besides that, a thinner layer, which sup-
plies the place of the t. media (Fig. 280 e), both having a longitudinal,
fibrous arrangement. Below the size of O'Ol of a line the veins gradu-
ally lose the external connective tissue and the epithelium, the t. media
appearing to pass into the structureless wall of the capillaries. A
muscular membrane, and in general, a layer of annular fibres are first
seen in veins more than 0-02 of a line in size, in the form, at first, of
widely separated, transversely oval cells, with short-oval, sometimes
even almost rounded, transverse nuclei. By degrees these cells become
more elongated, and more numerous, and ultimately, in vessels of 0-06-
0-08 of a line constitute a continuous layer (Fig. 279 /J), but which is
always less developed than the corresponding arterial tissue. This
continues to be the structure of veins up to the size of 0-1 of a line ;
when elastic networks, at first fine, begin gradually to make their ap-
pearance externally to the epithelium in the t.t. musculosa and advcn-
titia, whilst at the same time the muscular layers multiply, and even
admit connective tissue and fine elastic fibres among their elements.

Veins of the medium diameter of 1-3—1 lines, such as the cutaneous
veins, and deeper veins of the extremities up to the brachial and popli-
teal, the veins of the head and viscera, except the main trunks, are
characterized (particularly those of the lower extremity) by the not in-
considerable development of their annular fibrous membrane, which, as
in the arteries, is of a yellowish-red color, and striped transversely.
But even where thickest, it is far from equalling
that of the corresponding arterial vessels ; and
in thickness never exceeds 0-06 to 0-07 of a
line. It consists not only of transverse but also
of longitudinal layers, and in this respect like-
wise difl"ers from that of the arteries. The
transverse layers are composed of common, undu-
lating connective tissue, Avith fine, loosely ar-
ranged, or rather isolated elastic fibres (nucleated fibres, as they are

Fig. 284.

Fig. 284. — Transverse section of the vena saphcna magna, at the malldus, magnified 30
diameters: a, striped lamella and epithelium of the t. intima ; 6, its elastic membrane; c, longi-
tudinal, internal connective-tissue layer of the t. media, with elastic fibres; d, transverse
muscles, and e, longitudinal elastic networks, disposed in a laminated manner ;/, t. adventitia.

G86

SPECIAL HISTOLOGY.

Fi?. 2S5.

termed), and a large quantity of smooth onuscles, the fusiform elements

of which, 0-02-0-04 of a line long,
and 0-004-0-007 broad, present the
usual characters of contractile fibre-
cells, whilst the longitudinal laminc"e
consist of true, thick, and very thick,
reticulnted elastic fibres. With respect
to the mutual relations as lamince
of these tissues, it should be remark-
ed that in certain veins (popliteal,
2)7'ofunda femoris, saphena major' and
minor), the t. intima is succeeded by
a layer, formed solely of connective
tissue and finer elastic netwoi-ks, and
having a longitudinal fibrillation — the
longitudinal lamina of the t. media —
whilst in other veins the muscular ele-
ments extend also into the innermost
lamina. In this case, immediately
external to the t. intima, there is a
transverse layer of muscles, with con-
nective tissue and elastic fibrils, which three tissues, in these veins,
always accompany each other ; to this succeeds a regular alternation of
longitudinal, elastic, reticulated membranes, always in a single layer,
and transverse muscles with connective tissue, so that the t. media of
these veins presents a laminated aspect, somewhat resembling that of
the largest arteries. It should, however, be remarked, that the elastic,
reticulated membranes, although frequently very closely interwoven,
nevertheless never form homogeneous, elastic membranes ; moreover,
that they are occasionally interrupted, and, as longitudinal sections
manifestly show, are invariably continuous with one another through
the whole t. media. The number of these elastic lamellce fluctuates
between five and ten, and their interspaces vary in width from 0-00-4-
0-01 of a line. The t. intima of the medium-sized veins is 0'01-0-04 of
a line thick, and consists, where it is thinner, only of an epithelium with
shorter, though elongated cells, a striated, iiucleated lamella, and an
elastic longitudinal membrane, corresponding to the elastic inner mem-
brane of the arteries, but which scarcely ever appears as a truly homo-
geneous, fenestrated membrane, but most usually as an extremely close,
areolated network of finer and coarser elastic fibrils. Where the t.
intima is thicker, the striated lamellce are multiplied, and, above all, one
or even several additional networks of elastic, fine fibres make their ap-

FlG. 285. — Muscular fibre-cells from the renal vein of Man ; a, without ; b, with acetic
acid; a, nucleus of the latter. — Magnified 350 diameters.

THE BLOODVESSELS. 687

pearance on the inner aspect of the above-described elastic membrane,
which forms the limitary portion of the t. intlma. I have also seen
smooth muscles of the t. intima, in the veins of the gravid uterus, as
well as in the saphena major and popliteal vein ; and llcmak has con-
firmed their existence in the visceral veins of certain Mammalia. The
t. adventitia of these veins is almost invariably thicker than the t. media,
often twice as thick, rarely of equal strength. Usually it contains only
longitudinal, much interwoven, often very well-marked elastic networks
with thick fibres, and common connective tissue, but in the case of those
visceral veins, the trunks of which have longitudinal muscles in the t.
adventitia, similar muscular elements also extend for a certain distance
into the branches (vid. seq.)

The largest vehis are distinguished from those of the medium diameter
chiefly by the sparing development of the t. media, and especially of
its muscular elements ; a deficiency, however, it is true, often counter-
balanced by the presence of contractile elements in the t. adventitia.
The thickness of the t. intima is usually O'Ol of a line, when it presents
the same conditions as in the medium-sized veins. More rarely, as oc-
casionally in the vena cava inferior, in the trunks of the hepatic veins,
and in the vena innominata, it amounts to 0*02 and 0*03 of a line,
which increase of thickness is due to striped lamellce with niielei, and
fine, elastic, longitudinal networks, never to those composed of muscles.
The t. media, on the average, presents a thickness of 0-02-0-04 of a
line, but may occasionally, as at the commencement of the trunk of the
vena 2ior tee, in the uppermost part of the abdominal portion of the v.
cava inferior, and at the orifices of the hepatic veins, measure 0-05-0-12
or be tvholhj zvanting, as in the greater part of the v. cava inferior in
the liver, and in the further course of the largest hepatic veins. Its
structure, in all essential particulars, is the same as in the previous class
of vessels, except that the longitudinal elastic networks are intricately
connected together, and less distinctly, or not at all, laminated; the
transverse muscles, also, are scanty and indistinct, even where the t.
media possesses the considerable thickness above stated, and are more
abundantly intermixed with bundles of connective tissue. I have noticed
the muscles to be most developed in the splenic vein and v. "portce ; they
appeared to me to be wholly wanting in the abdominal portion of the
inferior vena cava below the liver, in certain spots, and also in the sub-
clavian vein, and in the terminal portions of the superior and inferior
vence cavce. The t. adventitia of the largest veins, is almost invariably
nearly twice as thick as the middle tunic, or even as much as five times
as thick, and exhibits, in its structure, the important difference, at least
in certain veins, as Reraak correctly states, that it contains a consider-
able quantity of longitudinal muscles. These are very distinct, as was
pointed out by Bernard (" Gaz. Med. de Paris," 1849, 17, 331), in the

688

SPECIAL HISTOLOGY.

hepatic portion of the inferior vena cava, Avhere their fasciculi, 0-01-
0-04 of a line thick, constitute a network pervading the inner half or
two inner thirds of the external membrane, which, where the t. media is
absent, rests immediately upon the t. intima, and may attain a thickness
of as much as 0-22 of a line. Besides this, I have found, as Remak has
also done, these contractile, longitudinal bundles (which never contain

A

HSiiiiiliW

mmimm

i ' V "v n.'"\'

connective tissue, though probably a certain number of elastic fibres),
still very well developed, in the trunks of the hepatic veins, in that of
the vena porta', and in the remaining portion of the inferior vena cava,
and have traced them as far as the splenic, superior mesenteric, exter-
nal iliac, and renal veins. Some were also to be found in the ve7ia
azygos, whilst they were altogether absent in the superior veins. These
muscles extended through the entire thickness of the t. adventitia, only
in the renal vein and vena porta', whilst in the other veins above enume-
rated, a greater or less portion of it, contained no muscular element,
and consisted as usual, of longitudinal connective tissue, and elastic
networks composed of strong fibres. The muscular layer of the t. ad-
ventitia therefore appears to be a special membrane of the vessels, and
occasion would be afforded to confound it with the undeveloped, or, as
has been stated, even absent t. media; an error, however, Avhich might
be readily avoided by tracing the conditions of the smaller veins. The
muscular layer of the t. adventitia, besides the contractile elements,
having a length of 0-02-0-04 of a line, which present the common cha-
racter, and numerous elastic longitudinal networks, invariably contains
.a certain amount of connective tissue, which, as it seems, is always
arranged transversely, so that the transverse elements, even in these
large veins, are compensated for though not exactly, by muscle. All
the large veins, which open into the heart, are furnished, for a short
distance, with an external annular layer of muscles similar to those of
the heart itself, and which also present anastomoses of the primitive

Fig. 280. — Longitudinal section of the inferior vena cava, in the liver, magnified 30
diameters: a, t. intima; b, t. media, without muscles, containing only connective tissue and
elastic fibres ; c, inner layer of the t. adventitia; a, its longitudinal muscles; /3, transverse
connective tissue of the same layer ; d, external portion of the t. adventitia, without muscles.

THE BLOODVESSELS. 689

fasciculi. According to Riiuschel, these muscles, in the region of the
superior vena cava, extend as far as to the subclavian vein, and may be
found also in the main branches of the pulmonary veins; and even, ac-
cording to Schrant, in the former case, more in the interior of the wall
of the vessels, and disposed longitudinally.

The veins in which the muscular element is excessivehj develojyed de-
mand special notice, and also those in which that element is wholly
luantiny. To the former class belong the veins of the gravid uterus, in
which besides the t. media, the ft. intima and adventitia also present
muscular layers, longitudinal in the two latter, the elements of which in
the 5th and 6th month exhibit the same colossal development as those
of the uterus itself. The muscular element is wanting : 1, in the veins
of the maternal portion of the placenta, in whose walls, externally to
the epithelium, large cells and fibres, which I regard as undeveloped
connective tissue, occur; 2, in most of the veins of the cerebral sub-
stance, and of the pia mater. These veins consist of a roundish epithe-
lium in a single layer, a thin longitudinal connective layer, with solitary
elongated nuclei, which supplies the place of the t. media, and in the
smaller vessels of a more homogeneous, and in the larger, of a fibrillated
and nucleated t. adventitia. It is but rarely that a faint indication of
muscles in the t. media is seen in the largest of these veins, as shown in
Fig. 279; 3, in the sinuses of the dura mater and the veins of Breschet
in the bones, which are furnished with a layer of connective tissue, occa-
sionally containing fine elastic fibres, external to a tessellated epithe-
lium, and which layer is continuous with that of the dura mater and of
the mieviiViX p)eriosteum. 4, in the venous sinuses of the corpora cavernosa
{vid. sup.), and of the spleen of certain Mammalia {yid. § 169). 5, in
the veins of the retina.

The valves of the veins consist chiefly of distinct connective tissue,
which, at their free border, runs transversely, containing numerous
elongated nuclei, and also isolated, undulating, usually fine, in part
strong, elastic fibres. Their surface is covered either with nothing but
an epithelium, with short cells, or in addition, there is beneath it, a very
fine clastic network, the prevailing direction of which is longitudinal.
The valves may, therefore, be regarded as continuations of the middle
and internal tunics, although muscular fibres, so far as I have seen, are
wanting in them (Wahlgren states that he has found such fibres in the
larger valves).

§ 217. Capillaries [vasa capillaria). — With the solitary exception of
the corpora cavernosa of the sexual organs, and of the uterine placenta,
the arteries and veins, in Man, are universally connected by the inter-
vention of a rich plexus of microscopically fine vessels, which, on account
of their slender dimensions, have been designated under the above name.

44

690 SPECIAL HISTOLOGY.

They are everywhere composed of a single, structureless membrane,
with ceW-nuclei, and are thus very essentially distinguished from the
larger vessels, although the transition from the one to the other is wholly
imperceptible ; so that at a certain point in the course of the vessels it
is quite impossible to detect the characters of either of the classes into
which Histology has been accustomed to divide them. Vessels of this
kind may be best described as venous and ar^terial transitionary vessels,
according as they lie on the one side or the other, and without any
farther alteration of the common classification, may be referred to the
capillaries.

The true capillaries, when more closely examined, exhibit the follow-
ing conditions: Their structureless membrane is perfectly clear and
transparent, sometimes delicate and presenting a simple contour, some-
times thicker (0-0008-0*001 of a line), and bordered by a double line. In
its microscopical reactions, it corresponds entirely with older cell mem-
branes and the sarcolcmma of the transversely striped muscles {yid. § 85),
and as regards its other properties, it is perfectly smooth on both
aspects, and notwithstanding its tenuity, tolerably resistant and elastic,
although very probably not contractile. It invariably presents a certain
number of elongated CQW-nuelei, 0'003-0'004 of a line in size, which are
disposed with wide interspaces, usually alternately on opposite sides of
the vessel, sometimes more approximated, or in close contiguity, though
rarely in actual contact ; and, when the capillary tunic is thin, are
situated on its inner side, when thicker, within its substance, in such a
way, however, as not unfrequently to cause projections of it on the outer
surface. The diameter of the capillaries, in Man, varies from 0*002 to
0*006 of a line; and, for the sake of description, they may be again
subdivided into finer, of 0-002-0-003 of a line, with few nuclei and
thinner walls; and coarser^ of 0-004-0-006 of a line, with a thicker
membrane and numerous nuclei ; although in so doing it is not intended
to draw any distinct limitation between them.

The capillaries, by their union, constitute the capillary plexuses,
retia capillaria, which have already been described in detail, in speak-
ing of the individual organs and tissues, and, consequently, here,
will be referred to only in brief and general terms'. The forms pre-
sented in these plexuses, which, notwithstanding considerable diver-
sities, are constant in the different organs, and according to their simi-
larity or diversity, more or less characteristic, depend to some ex-
tent upon the disposition of the elementary parts, and are also in
some degree dependent upon the energy of the functions. With
respect to the former, there are in many organs certain tissues, into
which vessels never penetrate, — as the transversely striped muscu-
lar fibres, the bundles of connective tissue, nerve-fibres, cells of all
kinds, gland-vesicles, and which, therefore, according to their form,

THE BLOODVESSELS.

G91

Fipr. 287

trace out dofinite courses for the capillaries, so tliat they sometimes
present elongated meshes, sometimes rounded, narroAver or wider reticu-
lations. The physiological energy is still more influential, and it is a
general rule, that the greater the activity of an organ, ■whether as
regards contractions or sensations, excretion or absorption, so much the
closer is the capillary network, and
so much the more abundant the
supply of blood. The capillary
plexuses are closest in the secernent
and absorbent organs, as in the
glands, above all in the lungs, liver,
and kidneys ; next in the integu-
ments and mucous membranes ; much
wider in the organs which receive
blood only for the purpose of their
own nutrition, as the muscles, nerves,
organs of sense, serous membranes,
tendons, and bones ; although among
these organs differences exist, as,
for instance, the muscles, and the
gray nerve-substance, are more abun-
dantly supplied than the other parts
above enumerated. The diameter
of the capillaries themselves is al-
most directly in an inverse rela-
tion, and they have the thinnest
walls and are smallest (0-002-0-003
of a line) in the nerves, muscles, retina^ and the Peyerian patches; in
the external integument and mucous membranes they attain the size of
0-003-0-005, in the glands and bones, lastly, one of 0-004-0-006 of
a line, and in the compact substance of the latter, although no
longer having, in all respects, the structure of capillaries, even the
diameter of O-008-O'Ol of a line. Physiology is not as yet in a con-
dition to explain these differences in all particulars, inasmuch as infor-
mation is wanting with respect to the laws of diffusion in the various
capillary membranes ; and also because the more minute conditions of
the sanguineous circulation, in the separate organs, are wholly un-
known.

The mode in which the capillaries pass into the larger vessels is diffi-
cult of investigation. On the arterial side it is found that the capil-

FlG. 287. — Finest vessels on the arterial side of the capillaries. 1, an artery of the

-smallest size ; 2, transitional vessel; 3, coarser capillary; 4, finer capillary : a, structureless

coat, with a few nuclei, representing the t. adventilia ; b, nuclei of the mirscular fibre-cells ;

c, nuclei within the minute artery, probably still belonging to an epithelium; d, nuclei of the

capillaries and transitional vessels. From the human brain ; magnified 300 diameters.

692 SPECIAL niSTOLOGY.

laries, as tliey become wider, present more closely placed nuclei, and
are then invested externally with a structureless t. adventitia, and soli-
tary muscle-cells, whence, when they have reached the diameter of
0-007 of a line, they already exhibit the aspect of the finest arteries
(Fig. 287, 1). Afterwards, the nuclei seem to be replaced by epithe-
liu7n cells, whilst the capillary membrane either ceases, or is continuous
with the elastic inner membrane. The venous transitionary vessels are
less characteristic for a greater length. The first thing that is super-
added, on this side, to the capillary membrane, is an external, homo-
geneous, nucleated layer, which may be regarded as a sort of connec-
tive tissue, and whilst the nuclei of the capillary vessels become more
closely approximated, gradually coalesces with their membranes. In
vessels of 0*01 of a line, the internal nuclei have become so numerous,
as clearly to represent the epithelium, and as at this time also, the
external layer has likewise received the addition of a nucleated lamina
— the t. adventitia — the now distinctly laminated vessel (Fig. 280) may
be termed a vein. It would consequentlj^ appear that the capillaries
are transformed into the larger vessels by the addition of layers on the
exterior and interior, whilst their proper membrane coalesces with these
layers, and is probably continuous with the fibrous layer of the t.
intima.

Besides the finest capillaries, which, however, always admit of the
passage of the very flexible blood-corpuscles, the older anatomists have
admitted the existence of still finer vessels — the so-termed vasa serosa
— which no longer allow of the passage of blood, but only of its plasma, —
a notion which has been abandoned by most modern authors. Hyrtl
alone thinks, that it is necessary to admit of the existence of vessels of
this kind in the cornea, because the vessels at its border escape the sight
without passing into veins, and are too small (in Man, when injected,
0-0009 of a line) to be capable of conveying blood-corpuscles. He thinks,
that still further on they are continued into vasa serosa, and probably
are connected with the, as yet undemonstrated, lymphatics. In oppo-
sition to this, Briicke and Gerlach remark, that the corneal vessels ter-
minate in true loops, and that it would thence appear that Hyrtl's state-
ments are based upon incomplete injections. I am able, however, to
state that something corresponding with the vasa serosa of authors does
actually exist in the cornea, having noticed that, in the Dog, fine and
the finest filaments are continued still further inwards, from the terminal
loops previous to the blood-corpuscles, which occur in that animal, as in
all others, at the margin of the cornea ; which filamentary prolongations
were connected in a reticular manner, and were usually slightly dilated
at the points of junction. Whether these filaments were holloAV, and
had any contents, and directly communicated with the canals of the true

THE LYMPHATICS.

693

capillaries, could not be determined, and I should not, therefore, at pre-
sent definitely declare them to be pervious parts of the vascular system ;
whilst I have not the least hesitation, nevertheless, in referring them to
that system, for although they may have no canal, they scarcely admit
of any other possible interpretation, than as being derived from the vas-
cular plexus, which covers almost the entire cornea in the child at birth,
and as being obliterated capillaries. Should these corneal elements not
turn out to be vasa serosa, I am acquainted, in the adult, with no situa-
tion in which such vessels exist, whilst vessels conveying plas7na are
everywhere present during the development of the capillaries, as a pre-
liminary phenomenon {vid. infra), and it is therefore intelligible that,
even at a subsequent period, scattered vessels of the kind should occa-
sionally be met with, as in the brain of the Calf, according to Henle ;
or may perhaps exist in great quantity, just as in the distribution of the
nerves, the terminations often retain the embryonic character.

3.— OF THE LYMPHATICS.

§ 218. The lymphatics, except in their contents, correspond so closely
with the veins, that a short exposition of their structure will suffice.

Fig. 288.
)

FlO. 2S8. — Capillary lymphatic from the tail of the Tadpole, magnified 350 diameters: a,
membrane; b, processes formed by it; c, remains of the contents of the cells forming these
vessels, in which nuclei are concealed ; e, Cfpcal terminations of the vessels ; /, one of these
terminations, still pretty distinctly recognizable as a formative cell ; g, isolated formative cells
about to join with the actual vessels.

694 SPECIAL HISTOLOGY.

The capillm'y lympJiatics, wliicli, in the three situations in -which they
have hitherto been seen with certainty — in the small intestine, the tail
of the Tadpole, and the mucous membrane of the trachea — commence
partly with free prolongations, in part in networks. I have, in a single
instance in the tracheal mucous membrane in Man, had an opportunity
of investigation, and they were found to consist of a delicate structure-
less wall, without distinct nuclei after the addition of soda, and having a
diameter of 0-003-0-005-0-01 of a line (Fig. 235). The same structure is
presented in the simple lacteals of the intestinal villi in Mammalia, ex-
cept that these measure 0-012-0-026 of a line, and have a somewhat
thicker wall. The lymphatics discovered by me in the tail of the Tad-
pole (Fig. 288), on the contrai-y, correspond entirely with the blood-capil-
laries, in the occurrence of nuclei on the inner side of the very delicate,
structureless membrane, whilst they differ from them in being furnished
with short, jagged processes with prolongations. The diameter of the
lymphatic capillaries in this situation is 0-002-0'015 of a line, and the
two main trunks of the tail, like those of the blood-vascular system itself,
have a perfect capillary structure.

In what way these capillary lymphatics are changed into the larger
lymphatic canals has not been seen by any one, or at all events has not
been investigated. The finest vessels, which have elsewhere come under
my observation, had a diameter of tq-1-\ of a line, and these, except
in the thickness of the individual layers, corresponded in all respects
with the larger vessels of 1-1-| lines. The latter, the medium- sized
lymphatics, present three tunics. The t. intima consists of an epithe-
lium, of elongated, although rather short cells, and of a single, rarely
double elastic reticulated ^nemhrane, longitudinally fibrillated, which,
as regards the thickness of its fibres, and the narrowness of the meshes,
exhibits manifold diversities ; but it never has thick fibres, nor does it
ever constitute a true elastic membrane (according to Weyrich, this
membrane is wanting in the lymphatics of the mesentery, whilst I have
always found it in those of the lumbar plexus, and in those of the ex-
tremities). This is succeeded by a stronger, t. media, composed of
transverse smooth muscles, with fine, also transverse elastic fibres ; and
lastlv, there is a t. udventitia, with longitudinal smooth-muscular fasci-
culi. The latter I have found, in the extremities, upon vessels of not
more than 1-lOth of a line, and I consider them a good distinctive cha-
racter between lymphatics and small veins [vid. " Mikrosk. Anat.," II.
p. 236).

The thoracic duct differs in some respects from the smaller lympha-
tics. The similarly constituted epithelium is succeeded by some striped
lamellce, and these by an elastic reticular membrane, longitudinally
fibrillated, although the entire t. intima scarcely measures 0*006-0 -01
of a line. The t. media, 0-025 of a line thick, commences with an

THE LYMPHATICS. 695

extremely thin layer of longitudinal connective tissue, with fine elastic
fibres, and consists, besides, of a transverse muscular layer, with
fine clastic fibres. The t. adventitia lastly, contains j,;^ ogg

longitudinal connective tissue, together with clastic
fibrils, and a few reticularly connected bundles of lon-
gitudinal muscles. The valves of this duct, and of
the lymphatics in general, correspond completely with
those of the veins.

The bloodvessels of the lymphatics present the same "
conditions in the thoracic duct as in the veins. No nerves have been
found in them.

>

§ 219. Lympliatic glands. — These glands [glandulce lympliatiecc) differ
very considerably from the rest of the blood-vascular glands Avith which
they are usually classed, and approach nearest to the Peyerian patches
of the intestine, although they do not vrholly correspond with them.
Every normal lymphatic gland, within a thin but tough sheath^ com-
posed of nucleated connective tissue and fine elastic fibrils, presents a
soft, whitish-red parenchyma, in which three elements, viz. a fibrous
tissue, a soft, pultaceous j^ulp, and bloodvessels, are manifest. The
fibrous tissue, formed partly of fibrous, and in part of more homoge-
neous connective tissue, Avith scattered fine elastic fibres, when the
gland is well developed, as is not always the case in Man, but almost
invariably in the Cat, Dog, Rabbit, Rat, &c., presents a large number
of thin (0*004-0-005 of a line and more) lamelloi arising from the
sheath, which are so regularly connected together as to constitute an
elegant areolated structure pervading the entire gland, all of whose
roundish spaces, ^-|- of a line wide, openly communicate, it is true,
with each other, but much less freely than is the case with the cells of
the corpora cavernosa, for instance. Now, since all these spaces are
occupied by the grayish-white pulp, the entire gland exhibits externally,
and, in some degree, also in a transverse section, a coarsely granular,
vesicular aspect, which was known even to the older anatomists, almost
like that of the Peyerian patches, since there may be distinguished in
it a great number of clear round bodies, like follicles, surrounded by
narrow, somewhat darker borders. But upon proceeding to isolate
these bodies we shall fail in the attempt, and the septa by which they
are parted will be found to be always common to several, something
like the walls of the alveoli in the adult lung. Consequently, notwith-
standing the similarity in outward appearance, and as we shall find, in
contents also, there is a very essential difference between the follicles of

Fig. 2S9. — Transverse section of tlie thoracic duct in Man, magnified 30 diameters :
a, epithelium, striped lameUce, and elastic inner membrane ; 6, longitudinal connecti%'e tissue
of the t. media; c, transverse muscles of the same tunic; d, t. advcnlilia, with c, the longitu-
dinal muscles.

696 SPECIAL HISTOLOGY.

the Peyerian patches, as well as of the spleen, and of the tonsils, and
the alveolar spaces iu the lymphatic glands, on -which account I shall
describe the latter as "aZreoZi."

The grayish-Tv-hite alkaline pulp which fills the spaces in question,
agrees in nearly all respects with that contained in the Peyerian folli-
cles, and consists of a certain proportion of fluid, and of very many
morphological elements. The latter are, in part free nuclei, of 0-002-
0-003 of a line, usually without distinct nucleoli, with homogeneous
contents, which are nevertheless rendered turbid by water ; in part
true, pale, uninuclear, round cells, most of which measure from 0-003-
0-004 of a line, with nuclei similar to those found in the free condition,
a certain number of larger size (0-005-0-007 of a line) with larger,
often distinctly vesicular nuclei and nucleoli, and occasionally a few fat
granules. These morphological elements also, to some extent, corre-
spond entirely with the cells of the lymph and chyle; a circumstance in
itself of no great significance, since no specific character can be as-
signed to either of them. The similarity of the contents of the alveoli of
the lymphatic glands, with those of the follicles of the Peyerian patches,
is still further increased by the circumstance, that they are also
penetrated by a fine vascular network, as I at least have observed, and
have already stated in another place ("Mikr. Anat.," II. 2, p. 192). For
the numerous bloodvessels of the lymphatic glands, which frequently
penetrate into the interior at a depressed hilu8-\\\.Q spot, are not dis-
tributed merely in the sep)ta of connective tissue, as has hitherto been
generally asserted, but, as I have seen in Man, also enter the pulp filling
the alveoli, where they run freely among the elements, and form a very
fine capillary plexus, bearing the closest resemblance to that of the
Peyerian follicles, except that in general it is rather wider, and fre-
quently also varicose.

The most difiicult part of the anatomy of these glands is the ascer-
taining of their connection with the lymphatic vessels. After the ma-
jority of the most recent authors had agreed in the assumption, that
the vasa inferentia and efferentia were connected by numerous anasto-
moses of convoluted and looped vessels, the proper parenchyma of the
glands being thus frequently left in the background or altogether for-
gotten, the number of those has latterly been much increased, who
advocate the view originally propounded by Malpighi, viz. that the lym-
phatic glands consist of an aggregation of anastomosing cells, into
which the vasa afferentia open, and from which the vasa efferentia pro-
ceed ; and, in particular, Ludwig and Noll have declared themselves
most decidedly in favor of this view. As for myself, it will be appa-
rent from the preceding account, that I am one of those who admit of
the existence of a special glandular element in the lymphatic glands,
and I consequently deny, in the most explicit terms, that they are com-

THE LYMPHATICS. 697

posed merely of a plexus of lymphatic vessels. As regards the relation
of the lymphatics to the glandular part or alveoli, together with their
contents, I formerly felt compelled to express myself in opposition to
the notion propounded by Ludwig and Noll, although without having
entered deeply into the subject, principally because, whilst it seemed to
me improbable, that the alveoli of the glands in question should contain
bloodvessels, and at the same time communicate with the lymphatics;
and, in the second place, because in cases where the vasa afferentia and
cffercntia were full of milk-white chyle, I was never able to perceive
similarly colored contents in the alveoli. These facts, indeed, still retain
all their weight with me ; but they are now more than outweighed by
further experience, so that it appears very doubtful whether they justify
the conclusions which I formerly thought might be deduced from them.
For I find, like Ludwig, in a considerable number of injections in the
human subject. Dog (cervical glands), and Ox (lumbar glands), that it
is impossible to fill lymphatic vessels in the interior of the glands, and
that the injection either colors only the ramifications of the vasa infe-
rentia upon the gland, or when it runs furj;her, as it may be more easily
made to do in animals than in Man, it enters the alveoli, which it fills
according to their position in the series, and escapes through the vasa
efferentia. Induced by the result of these experiments, I should now,
without being desirous of giving a definitive opinion, be inclined to side
with Ludwig, and to deny the existence of any direct connection between
the afferent and efferent lymphatics, or rather to view the alveoli of the
glands as a specially modified part of them.* In accordance Avith this
notion, the lymph would be poured out into the alveoli, and flow through
them in fine divided streams among the elements of Avhich their con-
tents are composed ; and, to this circumstance, it is probably owing that
it never has a milk-white color. In this process it is possible that some
of the cells of these contents, which so closely resemble the lymph-
corpuscles, may be detached and become disintegrated, whence the
chyle of the vasa efferentia abounds more in morphological elements,
than the fluid conveyed by the vasa efferentia. At the same time, I am
decidedly opposed to the view which would regard the morphological
contents of the alveoli as directly appertaining to the lymph, as lymph-
cells — which are there formed, and subsequently conveyed away from
the gland. I consider them rather as an independent, stationary,
glandular element, standing, indeed, in the closest relation with the
chyle, but not necessarily forming a part of it, or passing into the

• [In a paper since published, Prof. Kolliker states, that he is now entirely satisfied
of the correctness of the views of Ludwig and Noll. He considers, however, that
the lymphatics regain their coats in the medullary substance, where they form a niinuto
plexus, from which the vasa efferentia proceed {Vid. Kolliker, " Ueber den feineren Bau u.
die Functionen der Lymphdrusen,"' in " Verhand. d. Phys. Med. Ges.," in Wurzb. IV. 2, 1854.)
— DaC]

698 SPECIAL HISTOLOGY.

blood. If we ascribe to the alveoli of the lymphatic glands the function
of inducing a metamorphosis and changes in the lymphatic fluid flowing
through them, under the influence of the cells of its pulp, which are
manifestly in a continual process of development, of such a kind pro-
bably, that its elements are rendered more capable of development, or
new matters, such as fibrin, are mixed with it, the reason is at once
evident, why the lymphatic fluid should form more cells after its pas-
sage through the glands than previously. The well-known cases also
of "white blood," in which, together with an enormous increase in size
of the lymphatic glands, a vast multiplication of the colorless blood-
cells takes place (Virchow), may be explained in accordance with the
above view ; although, for the present, I am not disinclined to assume,
that although no constant and total passage of the pulp of the lym-
phatic glands into the lymph takes place, which from the anatomical
conditions is utterly impossible (considering the bloodvessels in the
alveoli), nevertheless a sort of commixture of it from the alveoli con-
tiguous to the vasa efferentia occurs, so that the lymphatic glands, after
all, at least to some extent, ajopear to afi'ord a site for the formation of
lymph-corpuscles.

The lymphatics of the lymphatic glands retain all their tunics up to
the gland. But as they ramify in an arborescent manner on the gland
and become smaller, they lose the muscular membrane, and enter the
alveoli, possessing only a layer of connective tissue with fine elastic
fibres, and an epithelium. The glands, at all events the larger ones,
always have some delicate nervous fikanents composed of fine fibres,
which enter in company with the bloodvessels, and are lost to sight in
the interior. The ganglia in the lymphatic glands, mentioned by
Schaff"ner (" Zeitsch. f. rat. Med.," VII. 177), I have not been able to
find, nor is that author's description of the kind to command much
confidence.

The above-described structure of the lymphatic glands does not apply
to all cases. In Man, and in other animals, there are small and smallest
glands, of 3-2-1, or even h a line, in which the interior does not dis-
tinctly exhibit the alveolar structure, appearing, on the contrary, to
be more continuous throughout, and homogeneous, notwithstanding a
good many traces of fibrous structure, which always exist in them. In
the larger glands also, especially in certain animals, a similar condition
of the contents is not unfrequently presented, which of course does not
materially afi'ect the above exposition of the structure of the lymphatic
glands, since, in such cases, we simply see a less developed condition
of the septa, -and a more intimate union of the individual parts of the
pulp.

0. Ileyfelder has lately described (1. c), in the lymphatic-glands of

THE BLOOD AND THE LYMPH. ■ G99

tlie Mouse, the Rat, and, to some extent, of the Rabbit, a complete
muscular layer. In the Bat also, the Dog, Sheep, Ox, Goose, and
Fowl, smooth muscles are said to occur sparingly, and to be fewest in
Man. Ilejfelder also says that they pass into the internal septa^ and
that in the Rabbit he has noticed contractions of the glands upon
electrical excitement, an experiment which has not yet succeeded
with me.

The lymphatic glands are subject to numerous degenerations. The
most frequent are extravasations of blood in the alveoli, and in conse-
quence of these effusions, depositions of pirjmenfary matter, which may
proceed to such an extent as to render the glands brownish-red, or even
black (bronchial glands) ; we also find thickenings of the sheath, and
of the internal septa ; fatty deposits in the bloodvessels ; hypertrophies,
with a uniform increase of all their parts ; tuberculosis and cancer."^

4.— OF THE BLOOD AXD THE LYMPH.

§ 220. Every part of the vascular system contains in its interior a special
liquid, consisting of a fluid and numerous morphological particles, and
which, according to its color, its occurrence in one or other division of
the system, and its other properties, is distinguishable on the one side
into ivhite and red blood, and lymph or chyle; and on the other, into
blood in the more strict sense of the term. Histology is concerned only
with the description of the morphological elements existing in these

* [Professor BrUcke, in a valuable communication read before tlie Vienna Academy,
March 31, 1S53 (" Ueber die Chylus-gefasse und die Fortbewegung der Chylus"), confirms
the account given by Ludwig and Noll of the structure of the lymphatic glands, and states
that the vasa inferentia break up into the porous, glandular tissue, out of which the vasa
efferentia arise anew. In the glands themselves, a distinction must be drawn between the
cortical substance, composed of round or ovate bodies, like the separate glandular bodies of
Pcyer's patches, and the medullary substance. The framework of the latter is formed by the
large bloodvessels, with their tunica; adventitia. One portion of their branches divides into
capillaries in the medullary substance, the rest enter the cortical substance. Tiie accom-
panying connective tissue becomes looser, the finer the branches. The fully developed
connective fibres disappear more and more, and in their place cytoblasts appear, with closely
investing cell-membranes, which nm out into two or tliree pointed, sometimes flat, usually
filiform processes, fitted together into a soft tissue, in which the cfipillaries of the medullary
substance lie. Round cells in different stages of development follow them, resembling the
lymph-corpuscles, and forming the immediate limit of the fine, irregular, frerjuently anasto-
mosing canals, which render the medullary substance as porous as a sponge. The whole
gland is enclosed in a membrane, which, as Heyfelder observed, is composed of connective
tissue and smooth fibre-cells, and sends sheaths in towards the medullary substance, whereby
imperfect compartments are formed, in which the glandular elements lie. The chyle of the
vasa inferentia traverses the glandular elements, enters the pores of the medullary substance,
and passes thence on the opposite side, between the glandular elements to the vasa inferentia.
" 1 have never,'' (says BrQcke) "observed the fat-drops of the chyle enter info the interior of
the glandular elements, which appear to be merely bathed with the fluid part of it. On the
other hand, the cells which are formed in the glandular elements pass as lymph-corpuscles
into the chyle." — Trs.]

700

SPECIAL HISTOLOGY.

fluids, among wliicli the blood- and lymph-corpuscles are by far the
most important, leaving the description of their other conditions to phy-
siology.

§ 221. The lymfli and the chjle^ like the blood, consist oi ^ lolasma^
which coagulates out of the vessels; and of ynoiyhological elements, in-
cluding elementary granules, nuclei, colorless cells, and red hlood-corpus-
cles, which, however, are not found in all parts of this vascular system,
nor everywhere in equal quantity. The elementary granules are im-
measurably minute granules, which, as has been shown by H. Mliller,
consist of fat and a protein-envelop, and are contained in vast numbers
in milky chyle, whose color is oiving to them alone, whilst, in the more
colorless lymph they are either wholly wanting, or are rare and scat-
tered. Free nuclei, 0-001-0'002 of a line in size, and of a more homo-
geneous aspect, becoming vesicular and granular on the addition of water,

I have hitherto noticed only in the commence-
ments of the lacteals in the mesentery, and in
the vasa efferentia of the mesenteric glands,
though even there scantily, and never in the
thoracic duct ; whilst the colorless cells, which
are identical in the chyle and in the lymph —
the chyle- or lymph-corpuscles of authors —
are found almost everywhere in the lymphatic
vascular system in considerable quantity.
These are rounded, pale cells, 0-0025-0-0055 of a line in diameter,
which, when examined in their native fluid, appear homogeneous or
finely granular, and contain a usually indistinctly transparent, homo-
geneous, slightly glistening, round nucleus; but on the addition of
water, the nucleus and contents are rendered turbid by a granular de-
posit, and on that of acetic acid, becomes transparent and pale, exhibit-
ing the strongly granulated contracted nuclei with extreme distinctness,
bursting at the same time, and allowing the contents to escape ; a change
that also frequently takes place, especially in the smaller cells, on the
addition of water, preceded by the appearance of clear albuminous drops.
Otherwise dilute solutions, when the lymph-cells are already spherical,
induce no very remarkable changes of form, whilst, in consequence of
the evaporation of the fluid, and by concentrated liquids, a considerable
contraction, and frequently also, a jagged outline, is caused in them
(Fig. 290 a).

In size, quantity, and shape, the lymph-corpuscles present diversities,
according to situation. In the commencement of the lacteals, which

Fig. 290. — Elements of the chyle: a, lymph-corpuscles become stellate by the escape of
their contents ; b, free nuclei ; c, one such, surrounded by a few granules ; d, e, minute lymph-
cells, some with a distinct nucleus ; /, g, larger cells, one with a visible nucleus; h, one such,
after the addition of a little water; i, with the addition of acetic acid.

THE BLOOD AND THE LYMPH. 701

are eminently adapted for such investigations, in tlio mesentery, and
before it reaches the lymphatic glands, the chyle contains but few, and
in the smallest mesenteric vessels -which allow of being examined, fre-
quently even no chyle-corpuscles at all. Where they do exist, which
is always the case in the larger trunks, they usually appear small
(0-002-0'003 of a line), closely investing the minute nucleus, and often
even, as it were, in process of formation by the apposition of granules.
As the chyle traverses the mesenteric glands, the cells become more
and more numerous and larger, so that in the lacteals at the root of
the mesentery (and also in the larger lymphatic trunks), together with
the small cells which are still present, we find numerous larger ones, up
to 0*0055 of a line in size. At the same time, at any rate in the Dog,
Cat, and Rabbit, a multiplication of the lymph-corpuscles by division
takes place more or less actively ; in this process the larger cells elon-
gate till they attain a length of 0-006-0-008 of a line, and when the
nucleus has divided, are separated into two by a median, circular con-
striction. This proceeding does not usually occur at all in the thoracic
duct, and consequently the larger cell-forms, of 0'004-0-0055 of a line
are here rare. In Animals, at all events, the majority of the cells in
this situation are larger than the blood-corpuscles, that is to say, they
are 0-0025-0-0035 of a line, whilst in Man, at least as observed by
Virchow and myself in an executed criminal, they were invariably
smaller (from 0*002 of a line on the average). The nuclei of these
lymph-corpuscles, which are imperceptible without the addition of acetic
acid, were for the most part single and round, occasionally, also, horse-
shoe shaped, or constricted in the middle, very rarely truly multiple.
In other Mammalia, cells having nuclei disintegrated by acetic acid, or
naturally constricted and multiple (3-5 fold) are very rare, omitting
those in process of division ; although occasionally such occur even in
considerable quantity.

lied hlood-corpuscles I have not as yet noticed in the human chyle,
when it has been carefully taken, and under normal conditions ; whilst
in animals these corpuscles almost always occur in the thoracic duct in
small quantity, and also frequently in the lymph of certain organs, as
of the spleen. As they do not exhibit the slightest trace of a develop-
ment within the lymphatics, I regard them as elements escaped from
the bloodvessels, and indeed, am of opinion, so long as direct connec-
tions between the two sets of vessels in the peripheral parts are not
shown to exist, that this passage is an accidental occurrence, from the
rupture of finer vessels, which, owing to the peculiar structure of cer-
tain organs, as the spleen and lymphatic glands, may be very readily
conceived ; and, indeed, as I have shown in the Tadpole, may be
directly observed. I would, however, remark, that I have not unfre-
quently met with brown, round granule cells, 0*004-0*005 of a line in

702 SPECIAL HISTOLOGY.

diameter, completely corresponding -with those mentioned as found in
the blood, and which are probably derived from the lymphatic glands.

From the above facts, it vt'ould seem not to admit of doubt that the
lymph-corpuscles are formed, like cells, by the development of mem-
branes around free nuclei, a process which is effected, in the first place,
in the commencements of the lymphatic vessels, but also, and chiefly,
in the vasa efferentia of the lymphatic glands. To this is superadded
the multiplication of cells by division, which does not always take place.
The total quantity of the corpuscles, contained in the lymph, compared .
with that of the blood-corpuscles, is very inconsiderable, not only in
the middle-sized and smaller trunks especially, of the lymphatics, but
even in the thoracic duct itself is very far from being in an equal pro-
portion; and even there all the elements of the fluid may readily be
perceived, without any dilution. More precise enumerations have not
yet been instituted, and it can only be added that considerable diversi-
ties exist, and that a milk-white chyle is not always also rich in cor-
puscles.*

* [Professor Kolliker appears not to be thoroughly acquainted with the very accurate and
extensive researches of Mr. Wliarton Jones, embodied in his memoir on " The Blood-cor-
puscle, considered in its different phases of development in the Animal Series," "Philoso-
phical Transactions," 184G; the publication of which will, we believe, be considered here-
after to constitute an epoch in our knowledge of the blood. It is shown in this Memoir that
" the lymph-corpuscle of the Vertebrata is identical with the corpuscle of their blood. In
the oviparous Vertebrata it occurs, like the corpuscle of their blood, in the two phases of
granule-cell and nucleated cell ; whilst in man and Mammifera it occurs like the corpuscle
of their blood in the three phases, of granule-cell, nucleated cell, and free celkcform nucleus.

" The only difference that exists between the corpuscle of the lymph and the corpuscle in
the blood is, as regards the oviparous Vertebrata, the little degree of coloration which the
colored stage of the nucleated cell as yet presents, and, as regards the Mammifera, the small
degree of coloration which the colored stage of the free cellitform nucleus has yet attained"
(p. 82).

JMr. Wharton Jones first pointed out in tliis jNIemoir the true nature of the process which
is described and figured in the text as the " bursting," &c., of the lymph-corpuscles. These
changes of form, in fact, are not in general produced by any such cause, but they arise from
the amaba-Uke motions of the corpuscles, observed by Mr. Jones in the Skate, Frog, and many
Invertebrata, and which maybe readily enough seen on a smaller scale in the colorless cor-
puscle of the human blood.

The subjoined description of the phenomena presented by the colorless corpuscle (granule-
cell, Jones) of the Skate will serve for all: —

" My attention was first attracted to the phenomenon, by observing a granule-cell with the
granules apparently escaping from it, as if burst (Fig. 3). But the cell soon appearing again
with all the granules collected together, I was led to watch, and soon perceived that the ap-
pearance of granules escaping as if from a burst cell, was owing to this: The transparent
and colorless cell-wall bulged out on one side, leaving the granules still agglomerated and
holding together, but this only for a short time ; for soon, single granules were seen to sepa-
rate and burst out from the rest, and to enter the hitherto empty compartment produced by
the bulging out of the cell-wall. ■ The regular manner in which this sometimes took place
was remarkable. I have actually seen the granules enter the compartment by one side,-
and circulate along the bulging cell-wall to the other side, until the whole compartment be-
came filled with granules. This having occurred, the bulging began to subside, but was
succeeded by the bulging of another part of the cell-wall, into which again a flow of gra-
nules took jilace, and so on all round the cell."

THE BLOOD AND THE LYMPH. 703

§ 222. Of tlie Blood. — The blood, so long as it is circulating in the
vessels, is a slightly glutinous fluid, in ^vhich only two elements, the
hlood-corpuscles, -globules, -cells {corpuscida s. (jlohuli s. cellulce sangui-
nis), the majority of which are of a red color while some are white, and
the colorless blood-plasma ijiquor s. p)lasma sanguinis), are to be distin-
guished ; when excluded from the circulation, it usually coagulates en-
tirely, by the solidification of the fibrin in solution in the ijlasma, and
afterwards by the contraction of the coagulated constituent, divides into
the " crassaraentum" and "serum." The former is of a deep red color
containing, together with the fibrin, almost all the colored, and most
of the colorless blood-corpuscles, with a portion of the still dissolved
parts of the plasma, whilst the remainder of the latter, together with
some of the colorless blood-corpuscles, constitutes the serum. In cer-
tain cases in Man, especially in disease, before the coagulation of the
blood has taken place, the colored corpuscles subside more or less deeply
below the surface of the fluid, when the crassamentum presents a super-
ficial colorless, or whitish stratum (inflammatory crust), consisting only
of the coagulated fibrin and colorless blood-cells, together with the fluid
with which they are imbued.

The colored or red blood-globules, or simply blood-globules, in which
alone the coloring matter of the blood resides, are minute non-nucleated
cells of a flattened, lenticular form, which are
contained in the blood in such vast quantity, that
unless it be diluted with serum, they do not
readily admit of exact investigation,* appearing
of themselves to constitute the blood. However
important it would be to know accurately the
proportion of the blood globules to the plasma,
their number and their volume, all researches hitherto have failed, owing
to the difiiculty of the subject ; and even the very recent statements of
Schmidt, according to which 47-54 parts of moist blood-globules exist
in 100 parts of human blood, can only be described as approximative.
One method only can be successful, consisting in the direct enumeration

Fig. 291. — Blood-globules of Man: a, viewed on the flat surface; 6, on the et^e; c, united
into rouleaux; d, rendered spherical by the addition of water; e, rendered colorless by the
same agent; /, blood-globules shrunken by the drying up of the fluid.

We have already pointed out the occurrence of similar amaha-like movements in the young
cells of mucous membranes detached during slight inflammation, and in the cells of the
gelatinous tissue of medusse; and we think that, very probably, it will eventually be found
to be a property of all young periplastic substance.

MM. Guerin-Meneville (1849-51), Davaine (1850), and Robin (1S53), appear also to have
observed these aniffia-like movements, without being acquainted with Mr. W. Jones's essay.
(See the " Histoire nat. des Vegetaux parasites," by M. Robin, p. 5G7). — Trs.]

* [We must caution the reader against being guided by this statement. Nothing is easier
than the examination of the blood as it is, — notliing more likely to mislead than the jpractice
of diluting it with any fluid whatsoever. — Trs.]

704 SPECIAL HISTOLOGY.

of the globules in accurately determined quantities of blood, and as pre-
cise a determination as possible of the volume of the individual corpus-
cles (Vierordt) ; but this method, if applied in such a way as to insure
correct results, demands so much time and trouble, that it cannot be
expected to obtain general application, and we must be contented with
an accurate investigation of the total quantity of blood-globules in a
single or in some few instances, an undertaking in which Vierordt is now
engaged.*

The red blood-globules, more minutely examined, present the follow-
ing characters : Their form is usually that of a biconcave or plane,
orbicular disk, with rounded borders, and consequently they present a
different aspect to the observer, according as the surfaces or borders are
turned towards him. In the former case they are pale yellow, orbicular
corpuscles, in which, according to the focussing of the microscope, the
slight central depression which almost always exists, is indicated, some-
times by a clear, sometimes by an opaque spot in the centre, the latter
appearance admitting of being confounded with a nucleus. Viewed on
the edge, on the other hand, they present the form of an elongated,
narrow ellipse, or of an ellipse constricted in the middle. The blood-
corpuscle is constituted of a very delicate, but nevertheless tolerably
firm, and at the same time, elastic, colorless cell-membrane, composed
of a protein substance closely allied io fibrin, and of colored viscid con-
tents formed of globulin and Jicematin, which in the adult present no
trace of morphological particles, of granules, or of a cell-nucleus; they

• [Vierordt's method, as lately published by him ("Schmidt's Jahrb.'' 4, 1S52) consists
in an actual enumeration of the blood-corpuscles, when mixed with fluids of a certain den-
sity. His mode of procedure is to take up a small quantity of blood by a capillary tube of
uniform size. The length of the blood-column in the tube is measured under a low mag-
nifying power, and multiplied by the diameter of the tube; and thus the total volume of the
blood-column is obtained. The blood is then allowed to run from the tube on to a glass slide,
is there spread out in narrow streaks, and intimately mixed with a solution of gum, or
albumen. The blood-streaks are successively brought under the divisions of an ocular
micrometer, and the number of corpuscles in each accurately counted. This process will
enable us to determine, with tolerable accuracy, the number of corpuscles in a certain quan-
tity of blood. It is, however, extremely laborious, since Vierordt himself states, that in
order to complete a single enumeration, nearly one \^-eek is required.

A mode of procedure by which the number of the blood-corpuscles may be more readily
ascertained, is the one proposed by Welcker (Archiv. des Vereins. fiir. Gem. Arb. B. 1, H, 2,
1853). This observer employs a stage micrometer, divided into a known number of paral-
lelograms. On this, the blood, mixed with a solution of albumen, is spread, and the corpus-
cles in each division counted, with the aid of an ocular micrometer. For practical purposes,
Welcker states that the number of the blood-corjiuscles maybe ascertained by a yet simpler
method. A measured quantity of blood is diluted with a certain quantity of fluid, the color
of the diluted blood is then compared with a color scale determined upon by previous ex-
periment, and by the degree of color, the number of the blood-corpuscles may be approxi-
mately estimated. By employing both these methods, Welcker was able to ascertain that
healthy blood (his own) contained about 4,000,000 corpuscles in a cubic millimetre, whilst
in a case of hysteria he found but 3,800,000, and in a patient in the last stage of consump-
tion, but 2,400,000 corpuscles.— DaC]

THE BLOOD AND THE LYMPH. 705

are consequently vesicles, whence the name " blood-cells" is to be pre-
ferred. The elasticity, softness, and flexibility of the membrane is so
considerable, that the corpuscles are rendered capable of passing through
vessels of less diameter than themselves, and when by pressure under
the microscope they have become elongated, flattened, or otherwise
altered in shape, of reassuming their original form. The blood-globules
are the better adapted for the former process, since their surface is per-
fectly smooth and slippery, so that they easily glide over the walls even
of the smallest capillaries, which present the same conditions.

The size of the blood-globules may diff'er in diff'erent individuals ; but
these diversities, owing to the minuteness of the bodies concerned, are
not altogether inconsiderable. As a general mean size, the most recent
inquiries of Ilarting (" Rech. micrometr.") from measurements of recent
blood-corpuscles, give a width of 0-0033 (1-300) and a thickness of
0-00062 of a line ; and of Schmidt, from the estimation of dried blood-
globules, a width of 0'0035 of a line, whilst, according to the former,
the mean Avidth in various individuals amounts to from 0-0028 to
0-0036, and according to Schmidt to 0-0032-0-0035 of a line, with
which numbers those given by other good observers essentially corre-
spond. The dift'erences in the same individual, found by Harting to exist
between the two extremes, amount, as regards the v»'idth, to O'OOIO-
0-0017, and for the thickness to 0-00009-0-0005 of a line; the ex-
tremes observed in general were 0-0020-0-0040 and 0-0005-0-0009
of a line ; and Schmidt states, that in 100 blood-corpuscles 95-98 are
of equal size. With respect to the size of the blood-globules in one and
the same individual, it may be stated in general, that it necessarily
diff'ers at diS"erent times, and especially that it necessarily increases or
diminishes according to the varying degrees of concentration of the
blood-plasma ; but on this subject we have scarcely any accurate re-
searches. Harting only says, that the biood-corpuscles of the same in-
dividual, measured after an interval of three years, presented the same
mean size, whilst in the same individual after a copious meal, somewhat
less average dimensions were exhibited (by about 0-00013 of a line), and
more considerable extremes. It has been remarked that determinate
data are wholly wanting as to the number of the blood-globules, and we
must await the results of Vierordt's researches. But, at all events, from
what has been ascertained with respect to the amount of solid constitu-
ents in the blood-globules, this much in general may be concluded, that
they are more numerous in the male than in the female sex ; moreover,
that after repeated venesection, during pregnancy and after prolonged
deprivation of food, they diminish in number; and in certain diseases,
as chlorosis and ayicemia, are also found to be much more scanty than
usual. At the same time, however, it is certain, that all the possible
variations are not as yet by any means exhausted, and it can scarely be

45

703 SPECIAL HISTOLOGY.

doubted, that in every individual the number of blood-cells is subject to
numerous, even daily changes, according to the conditions of supply and
waste, with Avhich we have still to be made accurately acquainted. The
volume of the blood-cells is estimated by Harting, regarding them as
short cylinders, as that of a cell of 0*0763 cubic millimeters; and the
iveAght, taking their specific gravity as equal to that of water, and ab-
stracting their central depression, at 1-13,114,000 milligramme. If, with
Schmidt, the blood is taken to contain 50 per cent, of corpuscles, and
the whole quantity of blood be estimated at 10 kilogrammes, we have a
total of 65 billions 570,000 millions. According to Schmidt, the spe-
cific gravity of the blood-corpuscles in men, is 1*0885-1'0889, and in
women 1*0880-1 '0886 — numbers wdiich must stand and fall with his
statements respecting the quantity of blood-corpuscles. Compared with
the other constituents of the blood, the corpuscles are heavier than the
serum and the ijJasma. In the former, and in defibrinated blood, they
form, upon standing, a red sediment, whilst in the plasma, owing to its
rapid coagulation, they do not usually subside below the level of the
fluid. This subsidence of the blood-cells, which, according to their own
density and that of the fluid in which they are suspended, may be slow
or rapid, is favored by their mutual cohesion, wdiich is observed especially
in inflammatory blood, in wdiich, from the rapid subsidence of the blood-
cells, part of the blood coagulates into a colorless mass ; but it also takes
place in perfectly healthy blood, and, in fact, constantly in little drops
obtained by trifling injuries of the skin, and frequently also in the blood
taken by venesection. The blood-globules in these instances apply
themselves to each other by their flat surfaces, and form, as it were,
columns or rouleaux, to the sides of which others may be again applied,
so that very complicated branched figures, and even networks are in this
way produced, covering the entire field of view (Fig. 291, c).

Besides the colored, the blood also contains a certain number of
colorless elements, of two kinds — elementary granules of a fatty nature,
and true cells. The former, which correspond entirely with those of the
chyle {vide § 221), occur in very varying number, sometimes very scantily
or not at all, sometimes in greater or even in vast numbers, so as to
give the serum a whitish or even milk-white color. From all that we
know, these must exist Avhen fat is introduced into the blood through
the chyle ; thus also in common alimentation, 3-6 hours and longer
after the taking of food, although in many cases they seem to disap-
pear in the course of the pulmonary circulation ; at all events Nasse
{vide Nasse, " Wagn. Handw. d. Phys.," I., p. 126) and others have
never found them in the systemic blood of healthy persons, a fact which
I can confirm as regards my own blood. In herbivorous Animals, on
the contrary, in the Goose, and in sucking Animals, the occurrence of
these molecules appears to be constant ; in pregnant women, also, and
after the free use of milk or alcoholic drinks, and also in famishing

THE BLOOD AND THE LYMPH. 707

persons (in consequence of an absorption of the fat of the bod}'), it
seems to be, at all events, very frequent. The colorless cells of the
^ohite /)Zooc?-corpuscles are derived from the chjlc ; and may, conse-
quently, be termed the chjh- or lympli-corpuscles of the blood. Some
of them are uninuclear, and correspond in all respects with the small
cellular elements of the chyle {vide § 221) ; some multinuclear, having
an avera"-e size of 0*005 of a line, in Avhich case
they so closely resemble pus-corpuscles, that it
is quite impossible to distinguish the one from
the other. The larger corpuscles are rarely as
granular as the smaller, usually tolerably homo-
geneous, often with clear contents, so that their
two or three, rounded, minute nuclei are at once
apparent.* Should this not be the case, acetic acid or water brings
the nuclei distinctly into view by rendering the contents clear, of which
occasionally a drop escapes from the ruptured cell ; at the same time,

Fia. 202. — Colorless blood-corpuscles, or lymph-corpuscles of the blood : a, b, smaller
cells, such as are found in the thoracic duct, viewed on the side (fl), and on the edge (ft) ;
c, c, the same with visible nudcus ; d. d, larger cells with tiuc/ci multiple ab origine ; e,e, c, the
same after having been acted upon by acetic acid, the nuclei disintegrated or becoming so.

■^ [With regard to the appearances presented by the "nucleus"' of the colorless corpus-
cle, ISh. Wharton Jones (1. c. p. 07 for the Frog, p. 72 for Man, the Horse, and the Ele-
phant) shows very clearly that the singleness or multiplicity of this body depends entirely
upon the strength of the acetic acid used to bring it out, and we can fully confirm his state-
ment so far as our own observations have gone. If the blood of Man, in fact, be diluted
first with water, and then only very dilute acetic acid be added, the '-nuclei" of the color-
less corpuscles will all, or almost all, be circular, with even edges. If, on the other hand,
strong acetic acid be added at once, every variety of form, from mere notching, to apparent
division into two, three, or four smaller ones, will be found. '' I am satisfied, however, that
this is, in both cases (granule-cell and nucleated cell) merely an apiiearance produced by
the shrivelling together of the walls of the single cellajform nucleus, in consequence of the
action of the acetic acid.

" It is proper to observe, that I have come to this conclusion, only after having particu-
larly tested the point by repeated, careful, prolonged, and varied observations. Nor is the
determination of the point of small moment, as on the apjiearance of a multiple nucleus,
which I have thus shown to be artificially produced, and on a similar, but I believe equally
artificially produced appearance of a multiple nucleus in the pus-corpuscle, a particular
view has been founded as to the first formation of the nucleus, and, indeed, as to cell-
development generally." (Wharton Jones, 1. c, pp. G7-S.)

It will be observed that in the text Professor Kolliker admhs that the multiple " nuclei'
may be still further broken up by the action of reagents.

The existence of any difference of .specific gravity between the colorless and the red
corpuscle? of the blood may be doubted; their relative positions in masses of blood, to
which reference is made above, being fully accounted for by the aggregation of the red
corpuscles into rolls.

With regard to the blood-corpuscles of the Invertebrata, Mr. Wharton Jones's Memoir,
above cited, should be consulted, as it contains the only complete account of them extant.
The statement in the text, that Amphioxus has no blood-corpuscles, is incorrect. It is, how-
ever, altogether exceptional airiong the Vertebrata, as its corpuscles are entirely of the
colorless kind. — Tns]

K

08 SPECIAL HISTOLOGY.

at all events under the former reagent, the nuclei not unfrequently are
farther disintegrated, and fall into irregular, jagged, and constricted
corpuscles, or are even resolved into a greater number, 4, 5, 6, and
more, of smaller granules, assuming, at the same time, a yellow color,
whilst the cell-membranes gradually disappear. The other reactions of
these colorless blood-corpuscles are those of the common indifferent
cells, and as regards their number, it is, compared with that of the
blood-corpuscles, very small, though not always the same, being depen-
dent upon the energy with which nutrition is going on, and therefore
more considerable when a large quantity of chyle has entered the
blood after a full meal. It is impossible to give any definite statement
as to their number, without perfectly accurate enumeration ; but this
much is certain, that the usual statement, that there is one colorless to
every ten colored blood-corpuscles, is quite incorrect. I find, with
Henle and Donders, that they are much less numerous than this, and am
of opinion, that when the latter, with Moleschott, reckons 5'1 colorless
to 2000 colored corpuscles, he is not far wrong. After meals, these
authors found the number of the latter augmented to 6*2, whilst in
fasting animals, as was also noticed by Heumann in Pigeons, they
diminished in number ; and after long fasting, at least in Frogs, they
saw them disappear altogether.* Their increase after venesections, not
only relatively but even absolutely, is a very remarkable circumstance ;
and this, as in the Horse, after very copious abstraction of blood (as
much as 50 lbs.) may proceed to such an extent, that the colored and.
colorless corpuscles appear to exist in equal numbers. The white cor-
puscles are lighter than the colored, and they are consequently more
numerous in the upper strata of the crassamentum. When the latter
presents a buffy coat, it always contains a great number of these cor-
puscles, and especially if their number has been augmented by previous
venesections, so as in such cases to constitute even half of the bufty
coat (Remak, Donders). Their less tendency to subside is, moreover,
increased by the circumstance, that although they have an uneven sur-

* [Moleschott has recently continued his researches on the relative number of the white
and the red corpuscles, and has arrived at some interesting results. In boys from 2^ to 12
years of age, he found as the mean in seven enumerations of the corpuscles, 4-5 colorless to
1000 colored; in adults from 21 to 49 years,-2'9 colorless to 1000 colored; in old men from
G2 to 78 years, 26 colorless to 1000 colored. In women from 14 to 38 years the average
was only 2'6 colorless to 1000 colored corpuscles, whilst in the blood of the same women
while menstruating, he counted 4 colorless to 1000 colored. An increase of the proportion
of the colorless corpuscles was also observed in pregnant women (3-6 colorless to 1000
colored), and in the blood of persons after meals which were rich in albuminous sub-
stances. After having partaken freely of the latter, he noticed in his own case 3-5 color-
less to 1000 colored corpuscles, whilst a few hours after a breakfast on non-albuminous
substances, he counted only 2'1 colorless to 1000 colored corpuscles. These observations
of Moleschott are important, and must be borne in mind in determining the number of the
colorless corpuscles in suspected cases of leucocythemia. — DaC]

THE BLOOD AND THE LYMPH. 709

face, and a disposition to cohere, they usually do not form any large
aggregations, and never constitute rouleaux.

Condition of the hlood-eorpusdes in various kinds of blood. — However
sensitive the blood-cells, out of the bodj', are towards various reagents,
they appear, within it, to be so constant, at all events as regards their
shape, that not only within the bounds of the physiological condition,
are no notable and uniform differences to be observed in them, in the
arterial and venous blood and the blood of the different ora;ans, but,
even in the most various diseases, no visible alterations are presented.
And yet it cannot be doubted that, as the color and chemical composi-
tion of the blood-cells vary, so also are their forms subject to certain
diversities and changes, according as the blood is more concentrated
or diluted, and abounds more or less with one saline constituent or ano-
ther, or with other substances ; but these changes of form are so incon-
siderable, that it cannot be wondered at, that we have not yet been in
a condition to recognize them with certainty. At all events, with
Henle, I must most expressly declare, that all these forms — the jagged
blood-corpuscle on the one side, and the diminutive, spherical, colored
or pale — are never met with in the circulatino; blood. Slight degrees
of flattening and distension may probably be noticed ; but in such re-
searches it should never be forgotten how quickly the blood-corpuscles
change their form, and care must be taken not to view a condition set
up out of the organism, as a natural one. The relations of the blood-
cells, as to their number, appear to vary more than their forms. As
respects the colored, they are more numerous in the venous than in the
arterial blood. In speaking of the venous blood, that of the hepatic
veins stands pre-eminent, containing, according to Lehmann, far more
blood-cells than that of the portal vein, and even exceeding in that
respect the somewhat rich blood of the jugular vein. The colorless
blood-cells, as I and Funke have found, exist in very great number in
the splenic blood, and indeed sometimes more in the form of uninuclear
cells, sometimes as multinuclear ; and also in the blood of the hepatic
veins, according to Lehmann, in which they are characterized by their
very various size {vid. § 223) ; I have noticed this, in many cases,
though by no means invariably, but am unable to regard it as an ex-
clusive character of the blood in the hepatic veins, because I have also
found the same multitude of colorless cells in perfectly healthy animals,
in the portal blood, as Lehmann has done in one case, as well as in the
blood of the pulmonary veins. Otherwise, however, the colorless cells
are more abundant in the venous, than in the arterial blood (Remak).
In the vena cava superior, and iliac vein of the Dog, Zimmerraann
noticed uninuclear cells, and, in the v. cava inferior, multinuclear ones.

Many experiments have already been made as to the influence of
various reagents on the blood-globules, although the results obtained

710 SPECIAL HISTOLOGY.

have in some measure been of very trifling importance ; and I, there-
fore, here adcJuce, chiefly from ray own researches on the subject of the
human blood-corpuscles, only what may serve to illustrate their anato-
mical and physiological relations. Water at first renders the blood-
globules spherical, and, owing to the diminution of the broad diameter,
consequent upon the increased thickness, smaller (from 0-002-0'0024
of a line), which may be best seen in corpuscles arranged in columns.
The size tlien usually remains without further change, and the coloring
matter and remainder of the contents slowly (sometimes suddenlj'", and
by fits and starts) escape, so that the fluid becomes dark-red, the cor-'
puscles at the same time losing their color, and acquiring the aspect of
colorless vesicles or rings, so faint, that it is often difiicult to perceive
them. But b}^ the addition of tincture of iodine, wdiich colors them
yellow, or of salts (common salt, nitre, &c.), of gallic or chromic acid,
which cause them to sbrink, and to present a more defined outline, they
may be readily brought into view ; and it is thus satisfactorily shown
that water, by no means dissolves, or destroys them. Some blood-
globules always withstand the influence of the water for a longer time,
and are still colored when all the rest have lost their coloring matter;
but it is not yet ascertained, whether these are to be regarded as of
younger formation, as is commonly supposed, or of older. The latter
notion seems to be favored by the circumstance that older cells usually
have firmer membranes than younger ones, and also that blood-corpus-
cles, left to their fate out of the circulation — for instance in extra-
vasated blood — always, in time, become more resistant; but it must be
allowed that, at present, no decisive opinion can be given either way.
Many other substances act in the same manner as water, only more
powerfully and even destructively, particularly acids and alkalies;
although not all with equal energy. Gallic and pyroligneous acids,
aqueous solutions of chlorine and iodine, sulphuric ether and chloro-
form, act very much in the same way as water. In the first three the
blood-globules remain as distinct, pale rings, whilst in sulphuric ether
they are instantaneously transformed into the most delicate and exces-
sivel}^ faint rings, ^-;^- the original size, and which it is very difficult to
perceive in the finely granular coagulum that is formed at the same
time, although they are rendered more distinct by the addition of salts
(nitre for instance). I have seen no evidence of an actual solution of
the cells. Chloroform acts in the same manner, only more slowly, and
the corpuscles first become considerably smaller, and of a glistening
yellow color. Acetic acir], of lOf,, at once renders the corpuscles ex-
tremely faint, so as to be scarcely perceptible, but they are by no means
dissolved, being visible, even at the end of several hours, in the form of
delicate rings. A solution, containing 20 per cent, of acid, acts more
energetically, and in glacial acetic acid, the cells are completely dis-
solved in the space of two hours, in the slimy brown blood. Concentrated

THE BLOOD AND THE LYMPH. 711

sulpJiuric acid renders the blood black-brown. The corpuscles become
pale, and although still retaining some color, are scarcely recognizable,
their contours running mutually together. On the addition of nitre or
7vater, which latter throws down a white precipitate, they again become
distinct as minute, duU-ycllow, round corpuscles. After some hours'
action of the acid all is dissolved. Concentrated hydrocldoric acid,
which colors the blood brown, and produces a white precipitate, con-
tracts most of the cells, which are gradually dissolved, and renders
many of them granular internally, also producing rents in some of them,
so that the contents escape, in the form of a pale streak, appearing like
a stalk to the corpuscle ; subsequently they become so faint in color as
to be scarcely perceptible, Avithout the aid of some saline solution.
After some hours many are dissolved, though a few offer a longer re-
sistance. Nitric acid, when concentrated, renders the blood olive-brown,
and the corpuscles greenish. The latter are corrugated, but are not
rendered smaller, and are partly enclosed in the coagulum, w'hicli is
formed at the same time, in part free, and lying above it. After several
hours there is still no indication of a solution going on, but this takes
place at the end of a day. Of the alkalies, potassa acts the most pow-
erfully. A solution containing 10 per cent, makes the blood black, and
at once dissolves all the blood-cells, first rendering them spherical and
smaller. The same thing takes place with a solution containing 20 per
cent, of the alkali, except that some of the cells remain for a time as
pale rings, whilst a concentrated solution of two parts potassa and one
part water does not attack the corpuscles, beyond making them very
small ; at the same time they remain spherical, or jagged and folded. The
whole blood is coagulated by this solution, and acquires, at first, a brick-
red, and afterwards, a bright brown color. On the subsequent addition
of water, the blood-corpuscles enlarge, as in no other reagent, to a size
of O'OOG of a line, remaining for the most part flat, and are then dis-
solved as in a dilute solution. Caustic soda, and caustic ammonia, in
solutions containing about 10 per cent., act like the corresponding
potassa-solution, only that the action is a little weaker, whilst concen-
trated caustic soda (1|- part to 1 part water) acts precisely like caustic
potassa. The same phenomenon of a diminution of the blood-cells, as
that caused by some of the reagents above noticed, is manifested also
in many other instances, and may be referred to the abstraction of ma-
terials, chiefly water, from the cells, as it is always concentrated solu-
tions which so act. In these cases, also, since the blood-globules reflect
the light from more numerous points, the color of the blood becomes
brighter, usually of a brick-red. Even the mere concentration of the
blood-plasma, by evaporation, causes the cells to shrink more or less, in
consequence of which they become either round, dark, brilliant globules,
0-001-0-002 of a line in size, or jagged, stellate bodies, or, lastly.

712 SPECIAL HISTOLOGY.

diversely bent and plicated discs. All concentrated solutions of metallic
and other salts, act in the same way, unless, like nitrate of silver, they
exert an immediately destructive influence. Donders and Moleschott
have carefully investigated the reactions, especially of such soluble
salts as exist in the blood, and have found that a concentrated solution
(1 part salt, 7 parts water) added to an equal volume of blood, dimi-
nishes all the cells, and reddens the blood. The cells are least affected
by the hydrochlorates of soda and potassa, much more by the phosphate
and carbonate of soda, and nitrate of potassa, most of all by the sul-
phates of soda and potassa. When diluted (1 part salt, 17 parts water),
all these salts color the blood a dark wine-red, and produce a distension
of the cells, rendering them pale, and completely dissolving them at the
end of four or five hours; in this regard the soda-compounds, except
common salt, which exerts no destructive action, prove more energetic
than those of potassa. I find changes similar to those caused by the
salts, to take place on the addition of alcohol, tincture of iodine., chromic
acid, and creasote, the first two of which merely render the blood-globules
smaller and corrugated, the latter also causing them to become granular
internally. In this respect the action of creasote is the most remark-
able, which transforms the blood-corpuscles partly into perfectly opaque,
even fat-like glistening granular and homogeneous granules and globules,
and partly into very beautiful clear vesicles, which may even be ren-
dered polygonal by their mutual pressure. Lastly, it is very important
to notice the influence of oxygen and of carbonic acid on the blood,
which by their reception into the interior of the cells, both in the body
(in the pulmonary and systemic capillaries) as well as externally to it,
as proved by experiment, produce sometimes a brighter, sometimes a
darker color in it. This takes place without any change of form in the
blood-corpuscles (J. MUller, and Todd and Bowman, in opposition to
Nasse and Harless), and the experiment may be alternately made several
times in succession with the same blood without any alteration of the
corpuscles (Magnus, Bischoff, Del'Espinasse, and Renemann, in opposi-
tion to Harless). Those gases also act upon the coloring matter of the
blood, when isolated, in the same way as upon the corpuscles (Magnus,
Marchand), and it is probable that the change of color is not connected
with any chemical change in the hcematin, but is a physical action of a
peculiar kind, analogous to similar changes of color in other fluids
caused by the absorption of gases.

Blood-corpuscles of other animals. — The non-nucleated blood-corpus-
cles of the Mammalia do not differ in form from those of Man, except
that in the Camel and Llama [Aiichenia Paco, A. Crlama, A. Vicugna)
they are oval, and 0-0038 of a line long ; they are mostly smaller than
in Man, as in the Dog, 0-0031, Babbit, Rat, 0-0028, Swine, 0-0027,
Horse and Ox, 0-0025, Cat, 0-0024, Sheep, 0-0022 of a line, the small-

THE BLOOD AND THE LYMPH. 713

lest (0-00094) in tlic Musk Deer ; seldom larger (0-005 of a line) as
in the Elephant. All the lower Vertebrata have, almost without
exception, oval, nucleated blood-corpuscles, of the shape' of a melon
seed. Those of Birds are from 0*004 to 0-008 of a line long, and con-
tain roundish nuclei ; those of the Amphibia measure between 0-008-
0-025 of a line in length, have round and oval nuclei, and are largest
in the naked Amphibia (Frog, 0-011-0-013 of a line long, 0-007-0-008
of a line broad; Proteus, 0-025 of a line long, 0-016 of a line broad,
Salamander, 0-02 of a line long); those of Fishes, lastly, are mostly
0-005-0-007 of a line long, except that in the Plagiostoraes they mea-
sure 0-01-0-015 of a line ; in the Lepidosiren they are 0-020 of a line
long, and 0-012 of a line broad. In BTyxine and Petromyzon they are
0*005 of a line in diameter, round and slightly biconcave. In Amphi-
oxus the blood-corpuscles are absent.* The blood-
corpuscles of the Invertebrata resemble the colorless
cells of the blood in the higher animals, and are almost
always uncolored.

The following should here be also noticed as extraor-
dinary constituents of the blood : 1, cells enclosing
hlood-corpuscles, noticed by Ecker and myself in the
blood of the spleen and hepatic vessels, and elsewhere also in the blood
{vid. Mikroskop. Anat., II. 3, p. 309, et seq.) 2, pigmented and color-
less granule-cells, observed by myself, Ecker, Meckel, Virchow, and
Funke, particularly in cases of intermittent fever and diseases of the
spleen (1. c.) 3, ^;flZe, fine-granular, roundish aggregations, in the blood
of the splenic vein (Funke). 4, peculiar concentric bodies, three to
four times larger than the white blood-cells, similar to those of the
thymus [vid. Henle, " Zeitsch. f. rat. Pathol.," Bd. VII. p. 44), found
by Hassall in fibrinous clots in the heart. 5, cells resembling pus-cor-
puscles, in tumors of the spleen and leuki^mia (Virchow) ; these bodies
are found in vast quantities, but, in their form, cannot in any way be
distinguished from the colorless blood-corpuscles. 6, caudate, p)ale or
pigmented cells (Virchow, "Arch.," II.) Besides these, should be no-
ticed, the morphological elements which are formed in the blood without
the body or in cases wliere the circulation has been obstructed — the
fibrinous coagula and crystals. The former are seen in coagulated
blood, usually in the form of fine, extremely closely interwoven fibrils,
disposed irregularly; occasionally as stronger, straiter fibres, having a
uniform width of 0-001-0-003 of a line ; not unfrequently also in the
shape of plates resembling epidermis scales (fibrinous flakes, Nasse). I
noticed crystals of a red color in normal blood in the year 1849

Fig. 293. — 1, blood cells of the Frog: a, viewed on the side ; b, on the edge ; r, rendered
colorless by water. 2, Blood-cells of the Pigeon : a, viewed on the side ; 6, on the edge.

• [Vid. Note, p. 707.— Trs.]

714 SPECIAL HISTOLOGY.

("Zeitscli. flir wissen. Zool.," I. p. 26G, Toikl's "Cyclop, of Anat."
Art. " Spleen," p. 792, and Mikros. Anat., II. p. 280), in the blood of
the Dog, of Fishes, and of a Pytlion ; sometimes ivitliin the blood-
globules, sometimes free in the blood, particularly of the liver and
spleen. Their occurrence in the former situation especially, appeared
to me to prove that they exist in the blood during life, and consist of
a substance allied to hematin and hematoidin (Virchow) ; but I also
showed that they were soluble in acetic and nitric acids, and in caustic
alkalies, and consequently that they are not identical with hematoidin.
Quite recently, Funke, without being acquainted with my observations,
has independently noticed these crystals in the blood of the Horse,
Dog, Man, and Fishes, and instituted very careful researches with re-
spect to them (" Z^g sanguine venss lienalis," Lips., 1851; also in
Henle's " Zeitsch. N. Folge," Bd. I. p. 172, and " Neue Beob. lib. d.
Krystalle d. Milzvenen- u. Fischblutes," ibid., II. p. 199), by which it
is rendered certain that these crystals arise out of the body. For more
particulars concerning them reference may be made to the works cited,*
and I will here only further notice that the crystals are most readily
formed, if a drop of blood covered with a piece of glass be allowed nearly
to dry, and a small quantity of water be added ; moreover, that the
crystals are formed not only in the blood of the splenic vein, as it at
first seemed, but in other kinds of blood also, in Man (I can obtain
crystals in my own venous blood) and other animals. They assume the
form of red or pale needles, columns, and plates, probably belonging to
the rhombic system (Funke), and also tetrahedral (in the Guinea Pig,
Lehmann, Funke), and are characterized by their little permanency,
since they perish in the air, are very soluble in water, and also in acetic
acid, alkalies, and nitric acid. Those found by me in the blood of the
Dog resisted the action of water, but I do not think that they were of
a different nature, and I should be inclined to refer this difference to
the greater resistance of the blood-globules themselves. Funke believes
that they consist of the albuminous contents of the blood-cells in com-
bination with hematin, relying, for support to this opinion, especially
upon their numbers, their occurrence in blood-cells, their formation, as
observed by him, from aggregations of blood-cells, and their absence
from the serum of the blood ; but I cannot regard this hypothesis as at

*[Also to Funke in "Schmidt's Jahrbttcher" No. IX. p. 1, and in his Atlas of Patholo-
gical Chemistry, Lei psic, 1S53; Robin and Verdcil " Traite de Cheniie Anatomiqne,"' torn.
III. p. 430; Kunde " Ueber Krystall-bilding in Bhite" in " Henleu. Pfeufer's Zeitschrift,'' II. p.
271, 1852, and in Memoires de la Soeiete de Biologie," IV. 1852; Parker '• Med. Times and
Gazette," 1852; Lehmann " Bericht d. Konigl. sach. Gesellschaft dec Wiss," Leipzig, 1853,
and in 2d Ed. of his " Physiologischc Chemie," Bd. II. p. 151 ; L. Teichmann, " Ueber die
Krystallization der organischen Bestandtheile des Bluts," in Zeitschrift fur. rat. Med. Bd.
III. H. 3. This last-named writer describes crystals procured from dried blood, differing
in form from the ordinary blood-crystals, and for which he proposes tlie name of " hiimin
crystals." — DaC]

TUE BLOOD AND THE LYIMPII. 715

present fully established, and it appears to me that further proof is re-
quired before Ave should admit the existence of crystals from the sub-
stances in question, and the more so, because colorless crystals are also
formed in the blood, quite independently of the blood-cells. Robin
and Verdeil, moreover, assert that they have also obtained crystals
from the serum of the blood ; and the quantity of the crystals is by no
means opposed to the notion that they arc derived from a salt of the
blood merely tinged with Jiconatin, since, in the case of fibrin -we see
that not much of a substance is required to occupy a large space.

§ 223. Physiological remarks. — Tlie development of the bloodvessels
takes place, essentially on the same type, in the heart, arteries, and
veins. The rudiments of all these vessels, and even of the heart, are
solid tracts of cells of greater or less thickness, -which, by the liquefac-
tion of their interior substance, and the metamorphosis of the central
cells into blood-globules, become cavities, which shortly coalesce, and
constitute a continuous passage for the blood. The heart and vessels
having remained for some time in this condition of cellular tubes, in
which state the former, moreover, exhibits contractions, the cells com-
posing the walls, with the exception of the innermost, begin to elongate
into fibres, and to represent the divers fibrous tissues and tunics. At
the same time the vessels become thicker and increase in circumference,
which at first is still to be referred to an increase in the number of the
cells, but subsequently, is brought about chiefly, or even solely, by the
growth of their elements in length and thickness. In the fifth month
of foetal life, all the larger and medium-sized vessels are formed, with
their tunics and tissues, and it is impossible to perceive any vestige of
formative cells. The tissues, however, appear to be still far from com-
pletion, the muscular fibres being short and delicate, and instead of the
strong elastic fibrous networks, we perceive only finer and the finest

* [Reicliert was the first to draw attention to tlie occurrence and nature of crystallized
albuminous matters colored with hcematin, in his " Beobaclitungen iiber eine eiweissartige,
Substanz in Krystallforni," ]Muller"s " Archiv," 1S49. These were tetrahedrons of as much
in some cases as 1-15 of a line long, and occurred upon the placenta and fcetal membranes
in a Guinea Pig. Their albuminous nature was confirmed by Schmidt and, Buchheim ; subse-
quently, " Bericht,'" IMuller's " Archiv," 1S52, Reichcrt states that he has again found the
crystals in the same locality, and that he has convinced himself, by further experiments,
that the dilierence observed between his crystals and those described by Kimde and Leh-
mann, arose entirely from the action of the spirit in which his first specimens had been
preserved. Reichcrt observed die development of crystals of the same kind, though
smaller, ia fresh blood taken from the heart of the Guinea Pig.

In connection with this subject. Dr. Ayres has recorded a very interesting observation
with regard to the occurrence of prismatic, more or less red crystals, in a band of olive-
green, almost black matter, having the appearance of coagulated blood at the margin of the
placenta of the Bitch (" Quarterly Journal of Mic. Science," vol. i. p. 299, with figures).
See also the papers of Dr. Parkes (" Med. Times and Gazette," 1852), and of Dr. Sieve-
king (" Brit, and For. Med. Chir. Rev.,'' 1853) on this subject.— Tbs.]

716 SPECIAL HISTOLOGY.

fibrils, and in the place of the elastic membranes themselves, only layers
of more or less coalescent, fusiform cells. The internal longitudinal
fibrous membrane alone, in many vessels, is at this time demonstrable
as a homogeneous elastic tunic immediately under the epithelium, but in
the smaller vessels this is wanting, and is replaced by a layer of elon-
gated cells, out of which it appears to be developed. It is thought that
similar cells are occasionally to be seen also in the adult, in whidi the
elastic inner membrane is likewise merged. The muscular fibres of the
heart arise, as in other situations, from the union of cells, but I have
not yet seen how their anastomoses are formed, whether from a branch-
ing of certain formative cells, or by the lateral apposition of small rows
of cells — probably in both ways.

The mode in which the development of the capillaries is effected, dif-
fers in toto from that observed in the larger vessels. The former, as
Schwann and I have shown, proceed from the coalescence of single cells.
At the primary origin of these vessels, tubules of some size are
formed, at first by the successive apposition in a straight line and the
coalescence of rounded-angular cells, and the subsequent absorption
of the septa and of the contents, but not of the nuclei, which remain
attached to the former cell-membrane, now become the capillary tunic.
Delicate pointed processes then project from the walls of these little
vessels, which rapidly elongate, and meeting similar pointed processes
of stellate cells dispersed in the surrounding tissue, coalesce with them.
At the same time, the other processes of these cells join, so that there
is soon produced a network of stellate cells, continuous with the already
formed capillarj^ tube or tubes. This net, however, is never spread, for
the prolongations, given off from already formed and pervious capil-
laries, and the neighboring cells connected with them are constantly and
rapidly transformed into fresh capillaries, by the continual increase in
size of the coalescing processes from their point of origin onwards, and
their becoming hollow. In this way are produced vessels which are at
first extremely fine, and admit only blood-plasma — true vasa plasmatica
s. serosa; but they rapidly enlarge, until at last the blood-globules are
transmitted through them, and the capillaries are perfected. Owing to
the circumstances, that while these processes of the stellate formative
cells thus enlarge, the bodies of the cells do not expand in a correspond-
ing manner, but appear as simple nodular points in the vessels, all ves-
tige of the original cellular network is gradually lost, and subsequently
the situation of the bodies of the cells can only be determined by the posi-
tion of the persistent nuclei. When finer tubules have once been formed
from the previous larger capillaries, the facilities for the passage of the
blood are continually undergoing augmentation, inasmuch as new stel-
late cells are constantly enlarging into vessels, whilst, at the same time,
fresh vascular material is as constantly furnished by the apposition of

THE BLOOD AND THE LYMPH.

717

new cells. New connections are also frequently formed between capil-
laries which are already pervious, partly by the direct meeting of pro-
longations from them, partly also by the mutual connection of formative
cells lodged in their interstices, whence, of course, the original net is
rendered closer. This mode of development, so far as I have seen, ob-
tains in all animals, without exception, in which capillaries exist, and
the various objections offered to the exposition given by Schwann and
myself, have chiefly arisen in the notion, that every network connecting
the arteries and veins in embryos, is a capillary plexus. This, however,
is by no means the case, and consequently the circumstance, that the
Avrongly termed capillaries of the germinal area arise after the type of
the larger vessels, is not an objection of the least weight in opposition
to us.

The capillaries of the lymphatic system, which may be readily traced
in the tail of batrachian larvce (Fig. fi-. 294.

228), exhibit, essentially, precisely
the same mode of development as
those of the blood-vascular svstem
(Fig. 294), except that anastomoses
are rare in them, and its course is
more limited to the mutual apposition
of fusiform cells, or of cells furnished
with three principal processes. Ob-
servations are wanting with respect
to the larger trunks of this system,
although it cannot be doubted, that
they follow exactly the same course
as the bloodvessels. Engel (1. c.) has
lately treated of the hjjnphatic glands,
and states, that they proceed from
lymphatic vessels which throw out
buds and are much convoluted.

The development of the hlood-cor-
imscles is pretty accurately known, in
the embryo, as concerns its principal
stages. The first blood-corpuscles, in
the Mammalia and other Yertebrata
in general, arc nucleated, colorless
cells, with granular contents ; they
are perfectly identical with the for-

Fio. 294.— Capillaries from tlie tail of a Tadpole : o, completed capillaries; b, ceW-muclei,
and remains of the contents of the original formative cells; f, cajcal process of a vessel;
d, stellate formative cell, connected by three prolongations, v.ith three processes of pervious
capillaries; e, blood-globules, still retaining some granular contents. — Magnified 350 dia-
meters.

718 SPECIAL HISTOLOGY.

mative cells of every part of the young embryo, and arise in the origi-
nally solid rudiments of the heart and great vessels, in some situations
very early, in others somewhat later, by the separation of the central
cells contained in the rudiments, in consequence of the development of
a fluid (the first blood-plasma) between them. The first perfect blood-
corpuscles arise from these colorless cells, which lose their granules,
and, except the nucleus^ become filled with hematin. These colorless,
nucleated, primary blood-cells are spherical, of a deeper color than the
blood-corpuscles of the adult, and larger (in a foetal Lamb, 3| lines
long, most of them were 0-005-0-0085, the minority 0-0025-()-0035
of a line ; in a human embryo, 4 lines long, according to Paget,
0'004-0-007 of a line), but in all other respects present the same condi-
tions, and, with their colorless formative cells, at first constitute the
sole elements of the blood. But many of them soon begin to multiply
by division ; to tins end they grow into elliptical, or even flattened
cells, 0*009 of a line long, 0-004-0-006 of a line broad, bearing a decep-
tive resemblance to the blood-corpuscles of the Amphibia; produce 2,
Pig. or,5. rarely 3 or 4, rounded nuclei, and afterwards

divide by one or several annular constrictions,
into 2, 3, or 4 new cells. AVhen the liver begins
to be formed, this multiplication of the blood-
cells in the entire mass of the blood ceases, and
in a short time (in the foetal Lamb, 11 lines
long) all trace even of their development out of
colorless formative cells is lost ; whilst at the
same time, as Reichert supposed and I have directly proved, a very
active formation of blood-cells is set up in the liver, a reason for which
ma}^ be found in the circumstance that, at this time, all the blood from
the umbilical vein, which supplies the embryo with new organizable
materials, first flows into the liver, instead of entering the general cir-
culation as before. In proportion to the extent in which this cell-
formation in the hepatic vessels is carried on, does the self-multiplication
of the blood-corpuscles become less and less considerable ; and instead
of it, a neiv formation of free colorless nucleated cells, having a mean
size of 0-003-0-004, and an extreme diameter of 0-0015-0-006 of a
line, is observed to take place in the blood and immediately around
nuclei, which also occur in the free condition ; and which cells after-
wards, still for the most part in the liver, are transformed, by the de-
velopment of coloring matter in their contents, into colored, nucleated
blood-cells, either immediately or after they have multiplied in a similar
way to that which the colored corpuscles had previously followed. This

Fig. 205. — Blood-corpuscles of a fanal Lamb, 3^ lines long: n, bi- and tri-nncleatcd, largo,
colored blood-globules, in various stages of division; 6, larger spherical, colored blood-cells,
one with a nucleus undergoing spontaneous division; c. a smaller one of the same kind. —
Magnified 300 diameters.

THE BLOOD AND THE LYMPH. 719

new formation of blood-corpuscles in the liver, with which the consider-
able size of, and the abundant supply of blood to, the embryonic liver,
is perfectly in accord, continues probably throughout the foetal life ; at
all events, I have found it in quite old embryos in jNIammalia, and also
in newly-born children, although it probably diminishes, pari passu, in
connection with the appearance of the ductus venosus (which, according
to Rathke, is a secondary formation) and its enlargement, because,
through it, a considerable portion of the blood from the umbilical vein
enters the circulation directly, and is diverted from the liver.

The further development of the nucleated, spherical blood-cells of
the embryo, M'hicli have originated in either way, takes place in this
manner : the cells gradually, and either directly, or after they have
multiplied in the mode above described, become more and more flat-
tened, and even present slight excavations, wdiilst their nuclei mani-
festly diminish, and on the application of acetic acid, exhibit a great
tendency to disintegration. Ultimately, the nuclei disappear alto-
gether, and the blood-cells become non-nucleated, like those of the
adult, of which they all soon assume the form, being at first somewhat
irregular. With respect to the period at which these non-nucleated
colored cells make their appearance, it must be remarked that in a
foetal Lamb, 3|^ lines long, I could perceive none of them, nor could
Paget in a human embryo, measuring 4 lines in the fourth week. In
foetal Lambs, 9 lines long, they were still very scanty, whilst in those
13 lines in length, they constituted by far the majority of the blood-
cells ; and in a human embryo, at three months, they formed, in the
hepatic blood \, and elsewhere about \-^ of the colored corpuscles. In
still older embryos, they preponderate greatly, so that in foetal Lambs
of 5-13 lines in length, the nucleated colored cells in the hepatic
blood constituted not more than \ or | of the blood-cells, and in the
rest of the blood, in the larger embryos, did not occur more abundantly
than the lymph-globules in the blood of the adult animal. At what
time, in the human embryo, the nucleated colored cells become more
rare and disappear, is not yet ascertained, although Paget saw them
still tolerably numerous in one instance in an embryo of five months.
The blood of the larger jMammalian embryos contains, not only in the
liver, but also elsewhere, besides the colored blood-globules, other color-
less cells in great number, and often as numerous as the colored, which
cells, there can perhaps be no doubt, are derived mainly from the liver,
in which, even in foetal Lambs 13 lines long, the colorless and slightly
colored, nucleated blood-cells constitute, perhaps, one-third of the
whole blood-corpuscles ; and in the latter periods of foetal life, are
probably also derived from the lymph. Whether these cells are meta-
morphosed into colored ones, is by no means determined, this much
only having been ascertained, that the transitionary forms between the

720 SPECIAL HISTOLOGY.

two, SO numerous in the hepatic blood, are ■wholly wanting in the rest
of that fluid.

The origination of the hlood-glohules after birth and in the adult,
notwithstanding the great pains specially devoted to this point, still
remains one of the most obscure parts in the history of the blood-cells ;
in my opinion, however, the notion which assumes that the red blood-
cells proceed from the smaller chyle-corpuscles, which lose their nuclei,
become flattened, and have hematin produced in them, is the one most
deserving of credit. These cells are about of the same size as the
blood-globules, or even rather smaller, have the same kind of membrane
as the latter, are flattened, and not unfrequently of a faint yellow
color, and consequently may, as we see in the colorless blood-cells of
the embryo, pass without any considerable change into colored cells.
Where and how this takes place, no one has seen ; and notwithstanding
all the trouble and care that I have devoted to the subject, I have
never noticed a nucleated colored blood-cell in the adult. The only
thing of the sort that I have met with, has been this, that in the pul-
monary veins, and occasionally also in other blood, the smaller lymph-
corpuscles were in many instances pretty distinctly colored, much more
so than in the thoracic duct, so that, except from their faintly granular
aspect, they were scarcely distinguishable from the true blood-cells
lying on their flat side ; and the more so, because they contained some-
what smaller nuclei than elsewhere ; but even this circumstance is
insuflicient to decide the question. The following points, however, may
be adduced as presenting very important analogies : 1, that in all the
lower Vertebrata, very distinctly, for instance, in the Amphibia, even in
adult animals, the origination of nucleated blodd-cells from the lymph-
corpuscles may be observed ; and, 2, that, in the human embryo, also,
the formation of the colored blood-globules from colorless cells, very
closely resembling the lymph-corpuscles, has been demonstrated by me
in the most decisive way. If to this it be added, that there is not the
slightest evidence of an independent, or other kind of origination of
blood-cells, it may perhaps be considered quite justifiable if I maintain
their origination from the lymph-corpuscles ; and, in order to explain the
reason why the transition itself has not yet been observed, if I broach
the supposition that it may take place too rapidly to be in any way
obvious with our means of observation.

Although in what has been said, I express myself in favor of the for-
mation of the red blood-cells from the elements of the lymph and of the
chyle, I would by no means assert that all the elements of those fluids
become blood-cells at every period of post-embryonic life. The micro-
scopical investigation of the blood would rather show, that they invari-
ably contain a certain number of larger pale cells with several nuclei,
or a single nucleus disintegrated by acetic acid, of which, although they
are certainly derived from the chyle, or are metamorphosed elements of

THE BLOOD AND THE LYMPH. 721

it, it is perhaps impossible to suppose that they ever become blooJ-cells.
This being established, it is a question ^vhether the change of the blood-
cells, their formation and their dissolution, is not perhaps mucli sloiver
than is commonly assumed, and whether they are not elementary parts
of a more stable nature than is supposed. I am unable to throw any
decided light upon this point, and will merely remark that in any case,
so long as the growth of the body goes on, and the quantity of blood is
augmented, an energetic formation of blood-cells must take place; in
opposition to which it is quite unascertained whether, in this period of
life, blood-cells are dissolved ; on which account, also, it cannot be
stated how many of the elements of the chyle undergo the metamor-
phosis into blood-corpuscles. In the adult, only this much should be
regarded as certain, that when from any cause the quantity of blood
has become diminished, it may be replaced together with the red blood-
cells; whilst it is altogether unascertained whether, under the usual
conditions, anything like an energetic solution and re-development
of those cells takes place. As their formation cannot be definitely ob-
served, nothing remains by which the question can be decided but
observations respecting the dissolution of the blood-globules; these ob-
servations, however, have by no means tended to demonstrate the occur-
rence of a constant change of the elements of the blood, taking place at
short intervals ; for although in the spleen of many animals a vast
quantity of blood-globules undergoing disintegration is met with, the
frequent and regular recurrence of a dissolution of those bodies in that
organ has not yet been proved. Taking everything into consideration,
I am therefore of opinion, that the question as to when, and to what
extent, blood-corpuscles perish and are again formed in the adult, can-
not be definitely decided from the facts at present in our possession,
although I am inclined to think that the elements of the blood are not
altogether such perishable structures as is commonly believed.

I have still to mention, that, quite recently, the view that the blood-
globules are formed independently in the blood, out of colorless cells, is
advocated by various authorities. Lehmann and Funke rely, the for-
mer on the large amount of colorless cells in the blood in the hepatic
veins, the latter on the similar condition of the blood in the splenic vein,
and they both consider it probable, that a new formation of red blood-
cells takes place within the bloodvessels of the liver and spleen. It
appears to me, that this question must be approached with very great
care, so long as the transition of the colorless cells into blood-corpus-
cles has not been directly observed, which in this case has by no means
been done. At present we are far too little acquainted with the vital
relations of the colorless cells in the blood to conclude, merely from
their existence, upon a formation of red blood-cells, and especially when
we remember the facts stated; since, as I have elsewhere shown ("Mikros.

46

722 SPECIAL niSTOLOGT.

Anat.," II. 2, p. 292), it is very possible that the colorless cells in ques-
tion, in the splenic and hepatic veins, are derived from the parenchyma
of the spleen, are only accidental constituents of the blood, and as their
frequently multiple nuclei seem to indicate, undergo no further develop-
ments, but are in a state of gradual removal.

The view propounded by Gerlach and others, that the cells contain-
ing blood-corpuscles, -which are met with frequently in the spleen and
occasionally in the blood, have a relation to the formation of blood-cells,
must decidedly be rejected, since the blood-corpuscles of all these cells
are in a state of dissolution.*

"■ [It is somewliat surprising that Professor Kcilliker should not have thought it necessary
to consider the doctrine advocated by Wharton Jones (1. c), the truth of which the latter
writer may, we think, be almost said to have demonstrated, viz. that the colored corpuscle
of the blood of Mammalia is the liomologue of tlie "nucleus" of the colorless corpuscle of
the same blood, and of the " nucleus"' of the corpuscle of the blood of oviparous Vertebrata
and of In vertebrata.

If we consider that it is admitted on all sides: i, that the colorless corpuscle of Mamma-
lian blood and the lymph-corpuscle are identical. 2, that these are identical with the color-
less and lymph-corpuscles of other Vertebrata. 3, that in the latter, the colored blood-corpuscle
proceeds from the colorless corpuscle : — only three hypotheses can well remain with regard
to the relation of the blood- and colorless corpuscles of Mammalia — viz.: that in the text;
that which supposes that they have an independent origin ; and that advocated by Wharton
Jones. The two former of these hypotheses are deficient in all positive basis, and the first
appears to us extremely improbable. On the other hand, the third tlieory appears to be in
harmony with all the known facts, and opposed to none. It is, shortly, that in Vertebrate
animals, the blood-corpuscle is found in three successive phases of development : that of
a cell with granular contents- — the granules being either fine or coarse ; that of a cell with-
out any contents except the " nucleus'' — the cell being either colorless or colored ; and,
finally, in that of a free cellffiform " nucleus,"' which is either colorless or colored. We
have thus three ^j/iases, each of which has two stages. The phases of granule-cell and nu-
cleated-cell are met with in all Vertebrata ; Amphioxus alone going no further than the
colorless stage of the second pliase. In the oviparous Vertebrata the blood-corpuscle pre-
sents the first two phases in both their stages. In the Mammalian cell, the phases exist in
all their stages ; but two of the latter, that of the colored nucleated cell and that of the
colorless free cellajform nucleus, occur but rarely and scantily. That the red corpuscle of
Mammals is the cellseform " nucleus" of the nucleated-cell stage, set free by the bursting of
this cell itself, and become filled and red by the secretion of globulin and coloring matter
into its interior, is strongly evidenced by the correspondence in size between the " nucleus"
and the red corpuscle, as the latter varies in different animals. In the Elephant the red
corpuscle is very largo, and in the Goat it is very small; the "nucleus" of the colorless cor-
puscle varies correspondingly. There is a similar correspondence in form ; and it is remark-
able that in the Paco, whose red corpuscles are, when fully formed, elliptical, while the
nuclei of the colorless corpuscles are for the most part circular, younger less-colored red
corpuscles are met with, which are circular and correspond in all respects with the "nuclei"
of the colorless corpuscles. In dealing with objections which might be raised from the
chemical and physical differences between the red corpuscles and the " nuclei,"' Wharton
Jones shows that these almost disappear if we select the youngest state of the red corpuscle
as one term of the comparison.

It is rare to meet with the transition stage between the phase of nucleated cell and that
of " free cellajform nucleus" in the blood of Man. We have, however, recently recorded
an observation of the kind in unaltered blood ("Quarterly Journal of Micr. Science," vol. i.
p. 145), where a well-marked red corpuscle was observed within what would otherwise
have been regarded as a colorless corpuscle, and occupying the place of its " nucleus;" and

THE BLOOD AND THE LYMPH. 723

The investigation of the heart, as regards the muscular fibres them-
selves, is easy, and their anastomoses "will be found without difficulty in
every carefully made preparation. But great difficulties attend the
tracing of the course of the fibres in that organ. Hearts that have
been macerated in weak spirit are best adapted to this purpose ; the
boiling in water, also, of the recent heart, or of hearts that have been
previously in salt for some weeks, has been long recommended, a method,
instead of which Purkinje and Palicki advise the boiling in a solution of
common salt, or still better of sulphide of lime ; whilst Ludwig, after
removing the pericardium, lays the heart in water, and repeats this
maceration each time after the removal of a layer of the muscular sub-
stance, using at the same time slight pressure. For the bloodvessels,
the tearing of them into lamellae with the forceps and scalpel, w^hich
alone was formerly employed, is not sufficient ; the examination of
transverse and longitudinal sections of the entire wall, being, in addition,
indispensably requisite. The best mode of proceeding is to dry portions
of the vessel stretched out upon paper, in which condition sections may
be made even of very small vessels, which are to be again moistened
■with water, and if it be wished to study the muscular structure, treated
with acetic or nitric acid of 20 per cent. (Weyrich), or else with caustic
soda, by which reagents the elastic tissue is also very beautifully dis-
played. For the speedy, isolated demonstration of the epithelium, the
elastic inner membrane, and the muscular tunic, the larger vessels at
the base of the brain have appeared to me to be the best adapted; the
elastic membranes of the t. inedia are readily isolated by maceration in
strong acetic acid. Its muscular fibres are always to be seen upon simple
teasing out ; or else readily, upon the addition of nitric acid. For the
study of the capillaries, the brain, the retina, the Tadpole and embryos
are above all to be recommended ; for their development, the Tadpole,
the allantois of embryos, and the vascular capsule of the lens. The
hlood should be examined, when it is possible, in the serum itself, after-
wards with the various reagents above noticed ; and regard must be
paid to the great tendency to change possessed by its elements. I inject
lymphatic glands with carmine and size, or with sealing-wax and resin
dissolved in alcohol; I also recommend sections of preparations hard-
ened in alcohol.

Literature. — J. C. Fr. Wolff, in the "Memoirs of the Petersburg
Academy," for the years 1780-92; J. Pteid, Art. "Heart," and B.
Searle, "Fibres of the Heart," in "Cyclop, of Anat.," II.; Par-

we may add that the same subject has recently afforded, in blood taken from the finger one
or two hours after breakfast, a very considerable proportion of such corpuscles with red
"nuclei," affording every transitional stage between the ordinary colorless corpuscle and
the free red celkeform nucleus. For these observations, however, water and very dilute
acetic acid were added to the blood. — Trs.]

724 SPECIAL HISTOLOGY.

chappe, " Du Coeur, cle sa structure et de ses rcouvements," Paris,
1844; C. Ludwig, " Bau der Herzventrikel," in '• Zeits. fur rat.
Med.," Bd. VII., p. 189, and " Ueber die Ilerznerven der Frosche,"
in Miiller's "Arcliiv," 1848, p. 139; Lusclika, "Das Endocardium
und die Endocarditis," in Vircliow's "Archiv," IV., p. 171; Remak,
"Ueber die Ganglien des Herzens," in Miiller's "Archiv," 1844, p.
463, and "Ueber den Bau des Herzens," ibid., 1850, p. 76; R. Lee,
" Memoir on the ganglia and nerves of the heart," London, 1851 [and
" On the Nerves which supply the Muscular Structure of the Heart,"
"Proceed. Roy. Soc," Nov. 17, 1853, vol. vi., No. 99, p. 337]; Bid-
der " Ueber die Nervencentra im Froschherzen," in Miiller's "Archiv,"
1852, p. 163; R. "Wagner, " Symp. Ganglien des Herzens," in
" Handw. d. Phys.," part XIIL, p. 360; F. Riiuschel, " De arteriar.
et venar. struct.," VratisL, 1836, Diss. ; Kolliker, " Ueber die Musku-
latur der Gefasse," in " Mitth. d. Zurch. naturf.," Ges., 1847, and
"Zeits. f. wiss. Zool.," I. ; " Sur le developpement des vaisseaux capil-
laires sanguins et lymphatiques," in "Ann d. Sc. Nat.," 1846 ; C.
Donders and II. Jansen, " Unters. liber die krankh. Veriinder. d.
Arterienwiinde," in "Archiv. f. phys.," Ileilk., VII., p. 361, also in
"Nederl. Lancet," I., p. 473; Jaesche, " De telis epithelialibus in
gener. et de iis vasorum in specie," Dorp., 1847; J. Engel, "Beitriige
zur Anatomic der Gefasse," in " Zeits. der Wiener," Aerzte, 1847, pp.
152, 315, 428, 1849, p. 121 ; R. Remak, " Histologische Bemerkungen
uber die Blutgefiisswande," in Mull. "Arch.," 1850; J. M. Schrant,
" Ontleedkundige Studien over de aderlijke bloedvaten," in " Tijdschr.
d. Maatsch. tot bevord. d. geneesk.," 1850, p. 2; M. Schultze, " De
arteriarurn structura,," Gryph., 1850; II. Weyrich, " De textura, et
structura vas lymphatic," Dorpat, 1851 ; Fr. Wahlgren, " Vensyste-
mets allmiinna Anatomi," Lund., 1851 ; F. Noll (and Ludwig), " Ueber
den Lymphstrom u. die Anatomic der Lymphdrlisen," in Plenle's
"Zeits.," IX., p. 52; Remak, "Ueber blutleere Gefasse im Sch\Yanze
d. Froschlarven," in Mull. "Arch.," 1850, pp. 79,183; J. Engel,
"Bau u. Entwicklung der Lymphdrlisen," in "Prag. Vierteljahrschrift,"
1850, p. Ill ; 0. Ileyfelder, " Ueber den Bau der Lymphdrlisen,"
Bresl., 1851 ; H. Nasse, Art. " Chylus, Lymphe, u. Blut," in Wag-
ner's " Handw. d. Physiol.," Bd. I. ; H. Mliller, "Beitrage z. Morpho-
logic des Chylus u. Eiters," in "Zeits. f. rat. Med.," 1845; R. Wag-
ner, "Beitrage z. vergl. Physiologie d. Blutes," Leipzig, 1833, and
"Nachtriige zur vergl. Physiol.," L, ibid., 1838; J. 0. Fahrner, "De
globulorum sanguinis origine," Turici, 1845 ; A. Kolliker, " Ueber die
Blutkorpcrchen eines menschl. Embryo und die Entwickl. d. Blutk. b.
Saugethieren," in " Zeitsch. f. rat. Med.," Bd. IV., 1846, p. 42 ; C.
Donders u. J. Moleschott, " Untersuch. li. d. Blutkorpcrchen," in the
"Holland. Beitragen," IIL, 360; Donders, in "Ned. Lancet," 1846;

THE EYE. 725

AYharton Jones, " The blood-corpuscle considered in its diff. phases of
development," in the " Phil. Trans.," 184G, IL, p. 82. Besides which
should be consulted the hand-books of E. 11. Weber and Henle, and
the recent embryological works of Vogt, Remak, Provost, Lebert, and
Courty. [The more recent publications on the vascular system are :
Von Ilessling " Ilistologische Mittheilungen," in Siebold and Kolli-
ker's Zeitschrift, v., p. 189 ; A. Kollikcr, " Ueber den feinern Bau
11. die Functionen der Lymphdrlisen," in " Verb d. pbys. med. Ges. in
Wurzb.," iv. 2, 1854; Rokitansky, "Ueber einige der wichtigsten
Krankhciten der Arterien," Wien, 1852; C. Wedl, "Ueber Blut. u.
Blutgefiiss Neubildung," in "Schmidt's JahrbUcher," No. 12, 1853; J.
Moleschott, " Ueber das Verhiiltniss der farblosen Blutzellen zu den
farbigen in verschiedenen Zustiindon des Menschen," in " Wiener
Mediz. Wochenbl." No. 8, 1854 ; T. Williams, " On the Blood proper
and the Chylaqueous Fluid of Invertebrate Animals," in "Phil.
Trans.," part ii., 1853, and " The Blood, its Chemistry, Physiology,
and Pathology," in British and Foreign Med. Chirurg. Review, Oct.
1853, and Jan. 1854.— DaC]

OF THE HIGHER ORGANS OF SENSE.

I. OF THE OPtGAN OF VISION.

§ 224. The visual organ consists of the eT/eball, or the proper sensi-
tive apparatus, and the accessor?/ parts, some for its protection, some for
its movement: viz. the eyelids, the ocular muscles, and the lachrymal
organs. The eyehall itself is a very complex organ, into the constitu-
tion of which nearly all the tissues of the body enter. It is composed
essentially of three tunics : ti fibrous — the sclerotica and cornea, a vas-
cular— the chorioidea and iris, and a 7iervous ; and of two internal
refractive media — the vitreous humor and the crystalline lens. .

A. OF THE EYEBALL.

§ 225. Fibrosis tunic of the Eye. — The external envelop of the eye-
ball is formed by a tough, fibrous membrane, composed chiefly of
connective tissue, which, to outward appearance, is divisible into a
smaller, anterior, transparent portion — the cornea; and a larger,
opaque, posterior part — the sclerotic ; but, as shown by its development
and more intimate structure, is to be regarded as a membrane continu-
ous throughout.

The sclerotica, also termed the tunica albuginca, is a white, very
tough and strong, fibrous membrane, which gradually diminishes in
thickness as it advances forwards from the posterior part of the eye,

726

SPECIAL HISTOLOGY.

where it is directly connected with the sheath of the optic nerve,
although it is again strengthened, in front, by the expanded tendons of
the recti muscles, -with which it is blended, afterwards becoming con-
tinuous with the cornea. When boiled, it affords common gelatin, and
it consists of true connective tissue, the fibrils of which are very dis-
tinctly manifest when the structure is teased out, or transverse sections

Fig. 296.

are treated with acetic acid. The bundles themselves are straighter, in
other respects as in the tendons, being intimately united and conjoined
into larger, thinner or thicker, flattened bands, which are disposed in

Fig. 20G. — Transverse section tlirough the tunics of tlie eye, in the region of the ciliary pro-
cesses, magnified \'2 diameters: Sf/., sclerotica: C, cornea ; Pr. cil., processus cUiaris ; C.a, an-
terior chamber; Cjj, posterior chamber; C. v. corpus vitreian ; C.P. cannlis Pctiti ; L,kns: I,
iris; a, conjunctiva cornccc, epithelium ; b, liomogeneous lamella beneath, continuous with the
conjunctiva sclerotica, x ; c, fibrous layer of the cornea; d, mcmbr. Dernoursii ; e, indication of
its epithelium ; /, termination of the mcinbrana Dernoursii, and its transition into peculiar
fibres, g, which are continued at i, upon the iris constituting the lig. pectinatum iriclis ; h,
canalis Schlemmii ; k, musculus ciliaris s. tensor chorioidew, springing from its inner wall, I; m,
pigment layer of the ciliary processes; n, the iris ; o, fibrous layer of the iris; p, indication
of its epithelium ; q, anterior wall of the capsule of the lens ; z, posterior wall ; s, indication
of the epithelium of the capsule ; t, zomda Zinnii, or anterior thickened portion of the hyaloid
membrane ; u, its free anterior lamina (proper zonula), inserted into the border of the lens :
V, its posterior lamina blended with the posterior wall of the lenticular capsule; ii', colorless
epithelium of the ciliary processes; iv', anterior termination of this ejoithelium. In part
after Bowman.

THE EYE. 727

the transverse and longitudinal directions, alternating pretty regularly
through the entire thickness of the tunic, and consequently in vertical
sections, producing a lamellated structure. Truly independent lamellce^
however, nowhere exist, the various longitudinal layers having numerous
points of connection, as have also the transverse lamince. However, on
the external, but more particularly on the internal surface of the sclerotic
the longitudinal fibres are collected into somewhat thicker plates, and
thus acquire a greater independence.

Numerous fine elastic elements pervade the connective tissue of the
sclerotic, of the same form as those in the tendons and ligaments (§ 80),
viz, : as a network of the finer or finest fibres, in which the sites of the
original formative cells are indicated by enlargements with nuclear rudi-
ments, so that the whole often very closely resembles anastomosing, fusi-
form, and stellate cells. During life, the elements of this network occa-
sionally appear still to possess cavities and fluid contents ; at any rate
in portions of a dried sclerotic, air is always to be seen in the bodies of
all the cells (these are the cretaceous corpuscles of Huschke), and con-
sequently, in this situation the opinion propounded by Virchow, that
channels of this kind are a sort of nutritive canals, would appear to be
completely justified, and the more so, because the vessels of this tunic
are at all events very scanty. They are derived chiefly from the ciliary
arteries and from those of the muscles of the eyeball, and constitute,
as I and Briicke have found, a tolerably wide-meshed network of capil-
laries of the last order. Bochdalek has recently described nerves (and
also Rahm, in the Rabbit) in the sclerotic, but with Arnold and Huschke,
I have hitherto been unable to satisfy myself that these are anything
more than branches, on its inner side, running to the ciliary ligament.

The cornea (Fig. 296 C) is perfectly transparent, still more compact
and tough than the sclerotic, and is composed of three special layers,
viz.: 4., of the conjunctival membrane {conjunctiva cornece) ; 2, of the
proper cornea; and 3, of the membrane -of Descemet ; the first and last
of which are formed of an epitJieliwJi and a subjacent structureless mem-
brane, and the middle one of a fibrous tissue of a peculiar kind.

The proper cornea, or the fibrous layer (Fig. 296 c), by far the most
important part of the whole tunic, consists of a fibrous substance closely
allied to connective tissue, but which, according to J. Mliller, affords
when boiled, not gelatin, but eliondrin. Its elements, pale bundles,
0-002-0 "OOi of a line in diameter, in which, at least when teased out,
finer fibrils are usually perceptible, sometimes more and sometimes less
distinctly, are united into flat bundles. These bundles, which have their
flat sides always parallel with the surface of the cornea, decussate in
various directions, and exhibit, if not complete lamella', yet a distinctly
laminated structure, owing to which the cornea is very readily torn and
penetrated in the direction of its surfaces, and with great difficulty in

728 SPECIAL HISTOLOGY.

that of its thickness. The correspondence of the corneal elements with
connective tissue is also shown by the following circumstances : 1, that
it is continuous at the border, by its elements, which in that situation
follow principally a radiating direction, directly and ivithout interruption
with the similarly disposed fibres of the sclerotic, so that there cannot
be the least question as to the non-existence of any natural demarcation
between the two tunics ; and 2, as Virchow was the first to show, that a
great number of anastomosing, fusiform and stellate, nucleated cells lie
among its bundles, just as they do in undeveloped elastic tissue (connec-
tive tissue-corpuscles of A^irchow), which also exist in the sclerotic,
though more branched. It can perhaps scarcely be doubted, that the
nutritive fluid, with which the cornea is constantly imbued in conside-
rable quantity, and which, in the large eyes of animals, may be directly
demonstrated by expression, is in great measure conveyed and distri-
buted in the interior, by the cells in question; a view which is only
strengthened by the knowledge that these cells, in morbid conditions of
the cornea, very frequently contain oil-drops, and occasionally, accord-
ing to Donders, even pigment, in their interior. The "corneal tubes"
injected by Bowman in the eye of the Ox and in that of Man must not
be confounded with this cellular network, and are probably to be ex-
plained as artificial dilatations of the minute interstices which normally
exist between the structural elements of the cornea, and which it is
thought may occasionally be perceived on microscopical examination.

The conjimctival memhrane of the cornea (Fig. 296 a, h) is composed
principally of a soft, laminated epithelium, 0-023-0-050 of a line thick,
in which the deeper layers of cells are elongated and placed vertically
upon the cornea, whilst the middle ones are more of a rounded form,
and as they approach the surface, pass into a layer, 0'008-0"01 of a line
thick, corresponding to the horny layer of the epidermis, composed of
plates 0-01-0-14 of a line in size, though still nucleated and soft. Many
of these latter cells, as I have shown ("Zeitsch. f. wiss. Botanik," II.,
p. 80), in consequence of their mutual pressure, present larger or smaller
pits, like certain cells in the urinary bladder, so as when viewed on the
side often to exhibit a stellate figure, which induced Valentin, who first
noticed this form, to regard them as cells with processes. Beneath the
epithelium, which, after death, is very soon rendered opaque by both
water and acetic acid, is a structureless lamella, first described by Bow-
man (anterior elastic lamella, of Bowman), 0-003-0'004 of a line thick,
which is especially evident in vertical sections and in folds of thin super-
ficial sections, upon the addition of alkalies, although it is by no means
so sharply defined from the true cornea as the membrane of Descemet,
nor does it seem to be of the same import as that membrane, but is per-
haps no more than the remainder of the vascular layer of the corneal
conjunctiva, which exists at an earlier period. Arched fibres, like rigid

THE EYE. 729

bundles of connective tissue or clastic fibres, are occasionally visible,
given off from it, and penetrating the cornea to a certain distance, ■vvliere

tbcv arc lost.

Tho 7ncinh7'ane of Descemct ov JDemows, also termed the membrane
of tlic aqueous humor (inemh. Descemeti, s. Demoursii s. humoris aquei)
(Fig. 296 (?), consists of an clastic membrane ratber laxly attached to
the corneal tissue — the proper membrane of Bescemet \_posterior elastic
lamina of the cornea, BoAvman], and of an epithelium on its inner sur-
face. The former is as clear as glass, brilliant, quite structureless,
easily laccrable, though tolerably firm, and so elastic, that -when it is
raised from the cornea by the scalpel and forceps, by boiling in water,
or by maceration in alkalies, under which treatment, as under reagents
in general, it does not lose its transparency, it always rolls up strongly
and towards the front. Towards the border of the cornea, the mem-
brane of Descemet, which is 0-006-0-008 of a line thick, and in chemi-
cal properties approaches the homogeneous membranes (§ 16), passes
into a peculiar system of fibres, first accurately'' described by Bowman.
This set of fibres commences at a short distance from the margin of the
cornea on the anterior surface of the membrane of Descemet (Fig. 296 g),
as an elongated network of fine fibrils, like the finer elastic fibrils, after-
wards gradually increasing in thickness, until at the very margin of the
cornea, the whole thickness of the membrane of Descemet is broken
up into a network of thicker fibres and trabecula', which turn over upon
the border of the iris (Fig. 296 i), and arc blended with its anterior
surface. Consequently, the membrane of Descemet does not cease, as
is usually stated, with a free border, but, on the contrary, is continued
(Fig. 296/) all round the anterior chamber, by numerous free processes
passing across it, upon the iris. The elements of this ligamentum
iridis pectinatum, as it is termed by Huek \_pillars of the iris, Bowman],
and which, according to Luschka, is much more distinct in the eyes of
certain animals (Dog, for instance) than in Man, were formerly
(" Zeitsch. f. wiss. ZooL," L, p. 54) referred by me to reticular connec-
tive tissue, at a time when I was acquainted with their form but not
with their reactions; now, however, I should rather be inclined to
describe them as an intermediate form between the connective and
elastic tissues. The bundles in question correspond with those of con-
nective tissue, in their width (0-004-0-012 of a line) and paleness, and
also in the circumstance that still finer fibrils are usually to be distin-
guished in them, whilst in their rigidity and chemical reactions they
approach the clastic tissue and the membrane of Descemet itself, of
which latter, though probably differing from it genetically, they are, in
the adult at any rate, an integral constituent.

The epithelium of the "membrane of Demours" (Fig. 296 e), which,
in Man, frequently does not retain the perfect condition, is a single
layer, 0-002-0-003 of a line thick, of well-formed, polygonal cells,

730 SPECIAL HISTOLOGY.

0-006-0-01 of a lino in size, "witli extremely fine and pale granular
contents, and round nuclei of 0-003-0-005 of a line. Towards the
border of the cornea the cells of which the epithelium is constituted
become smaller, and then ceases as a connected layer, whilst isolated
indications, usually of elongated, or even fusiform epithelial cells, are
continued, over the fibrous network of the lig. pectinatum, and sur-
rounding its elements, upon the border of the iris, where a perfect
epitlieliiim is again met with.*

The cornea in the adult is nearly altogether non-vascular, whilst, as
J. Muller and Henle first observed ("De memhr. pupill.," p. 44), in
the human embryo and foetal Lamb a rich capillary plexus exists in the
conjunctiva cornea;, but which does not appear to extend as far as the
centre. Towards the end of foetal life and after birth, this plexus dimi-
nishes in breadth, in animals to a less extent than in Man, so that in
the latter we find bloodvessels at the margin of the cornea, only in a
zone of |- or at most of 1 line in width. These vessels are for the most
part the fine and finest capillaries of 0-002-0 -004 of a line, forming one
or several rows of arches, and thus terminating ; they are lodged in the
substance of the conjunctiva, which here extends, in the form of a dis-
tinct layer, for a short distance upon the cornea, ceasing in its anterior
structureless lamella. In animals these superficial or conjunctival vessels
also exist, but are usually much better displayed, and extend further
towards the centre ; frequently over half the radius, or even beyond it.
Besides these, deeper capillaries derived from the sclerotic also occur in
the substance of the cornea, usually accompanying the nervous trunks,
in which they either form a single or a few very much elongated loops,
or extend a little beyond' them; they all terminate in loops, the finest
vessels constituting which, like the superficial capillaries, measure
scarcely more than 0*002 of a line. I have also noticed, in Man, these
peculiar corneal vessels accompanying the nervous trunks, although not
constantly and never so much developed.

Nothing certain is known of the lymphatics of the cornea (vid. also,
Arnold, "Anat." II. p. 988), though I have recently observed vessels
in the cornea of a young Cat (Fig. 297), which I can scarcely regard
as anything else than lymphatics. In this instance, at the margin of
the cornea, together with the very distinct capillary loops containing
blood-corpuscles, there were numerous wider vessels (of 0-01-0-02, or
even 0"03 of a line), which either extended singly into the cornea to the

* [This statement is directly opposed to Mr. Bowman's observations (op. c, p. 22), wlio
says, " that it would appear from wliat has been said concerning the conversion of the pos-
terior elastic lamina at its border into fibrous tissue, which in part passes through the
aqueous humor to the iris, that this epithelium must cease with the elastic lamina, since
there is no longer any stratum upon which it can rest." He has been unable " to discover
the smallest appearance of it upon the pillars of the iris, and conceives, therefore, that it is
limited to the cornea." And according to the same accurate observer, the front of the iris
has no true epithelial investment. — Tks.]

THE EYE.

731

same distance as the bloodvessels, and terminated in dilated clavate
ends, or in acuminate points, or two, three, or more together, formed
simple loops, from ■which in like manner other coecal processes were
given off. Notwithstanding their capacity these vessels presented a
delicate, structureless coat, with scattered, appressed nuclei, and con-
tained a clear fluid, in which frequently a few, and occasionally even a
good many clear spherical cells, exactly like lymph-corpuscles, were
visible. If I had found these vessels in other animals as well, I should
at once have declared them to be the commencements of the lymphatics
of the conjunctiva, but it appears to me, at present, more prudent to
regard this explanation perhaps as probable, but not as certain. For

Fiir. 297.

although, in this one instance of the Cat, the vessels in question were
very manifest in both cornece, so that I was able to point them out to
many of my colleagues, particularly to R. Virchow and II. Muller, I
have since been unable to perceive any decided indication of pale vessels
of the same kind, either in the adult Cat or in the newly born Kitten,
or in the Dog, Ox, Sheep, Pig, and Rabbit. But it is now well known
that the commencements of Ijanphatics, for once when they are distinct
(in the intestinal villi for instance), escape the sight perhaps twenty or
thirty times. Nevertheless, in this case there seems to be every reason
for caution. Should the vessels in question not be lymphatics, they
might be regarded as pathological excavations, or as transformations of
earlier embryonic corneal vessels ; but the manifest limitary membrane
of the canals is opposed to the former supposition, and the latter is
upset by the circumstance that they occurred in the same plane with
true vessels, and did not enter into the least anastomosis with them.

The nerves of the cornea discovered by Schlemm, are derived from
the nervuli ciliarcs, penetrate the sclerotic at its anterior border (in the

Fig. 297. — Capillaries and lymphatics (?) at the border of the cornea of a Kitten: a a,
trunks of the colorless vessels; b, ciccal clavate extremity of one of these vessels; c, pointed
prolongation ; d, loops ; e, blood-capillaries. — Magnified 250 diameters.

732

SPECIAL HISTOLOGY.

Fi"

29S.

Rabbit, according to Ralira, in the posterior half of the globe), and
thence enter the fibrous layer of the cornea. In Man, they are readily
found at the margin of that tunic, in the form of 24-36 finer and
thicker twigs, but scarcely exceeding 0*02 of a line in size. What

especially characterizes these nerves,
is not so much their mode of dis-
tribution, Avhich takes place with
numerous bifurcations and anasto-
moses, so as to produce a Avide ner-
vous plexus extending throughout
the cornea, as the circumstances that
they still contain dark-bordered
though fine (0-001-0-002 of a line),
primitive tubules, only at the mar-
gin of the cornea, in a zone not
always of uniform width, |-1 line
broad, and in their further course
present nothing but non-medullated
perfectly clear and transparent fibres, 0*0005-0-001 of a line at most in
diameter, so that they offer, at any rate, no more obstacle to the pas-
sage of the rays of light than the other corneal elements, as is evident
from the difficulty with which they are traced under the microscope.
The trunks of these nerves exhibit, though rarely, bifurcations of the
primitive tubules, but divisions of this kind are never presented in the
plexus formed by them, the conditions in which, however, on account of
their paleness, scarcely admit of being quite certainly traced. This
plexus is situated in the proper cornea, although nearer to its anterior
surface, and from the absence of any indication of free terminations to
the nerve-fibres, appears to consist altogether of anastomosing branches
of the finest sort, so that, though not in the form of loops, a mutual
connection of the nerve-tubes may be assumed to exist.

The bloodvessels of the conjunctiva cornece, in the healthy condition
of the organ, are very scanty, and the figures given by Roraer (Am-
mon's " Zeitsch." V. 21, Tab. I. Figs. 9, 11), and Arnold (" Icon. org.
sens," II. Fig. G), I regard as exceptional instances ; but, as is well
known, they may become so much developed, in inflammations, as
almost to cover the entire cornea. The proper corneal vessels also, in
such cases, appear to be developed more deeply in the interior. With
regard to the vam serosa of the cornea, vid. § 217. The statements
that have been made respecting the bloodvessels of the memhrana De-
moursii, in inflammation of the eye [vid. Henle, "De memb. pupill.," p.

Fig. 29S. — Coarser ramifications of the nerves of tlie cornea of the Rabbit. Where the
trunks are represented as dark, they contain dark-bordered primitive fibres.

THE EYE. 733

53), appear still to ilcmanJ confirmation ; and Arnold's " serous ves-
sels," in the normal condition of the membrane of Descemet ("Anat."
I. Tab. II. Fig. 5, II. p. 1015), are nothing more than the anastomo-
sing fibres of the ligamentum pectinatum of the ins. The cornea^
although vascular only at its margin, is nevertheless not unfavorably
circumstanced as regards its nutritive conditions. Wounds in it rapidly
unite, portions of the epithelium or even of the fibrous laj'er Avhen re-
moved, are restored, and ulcers are filled up from the bottom with new
corneal substance. Fatty deposits in its tissue, particularly in its cel-
lular elements (especially above and below, or even all round), produce
a yellow zone — the so-termed arcus senilis [gerontoxon]/^

§ 226. The vascular tunic {tunica vasculosa) or uvea. — The second
tunic of the eyeball is a highly vascular membrane, containing a great
amount of pigmentary matter, and divisible into a larger posterior por-
tion— the choroid, and a less extensive anterior segment — the iris.

The choroid is an easily lacerable membrane, 1-15-1-30 of a line
thick, extending from the entrance of the optic nerve, where it is per-
forated by a rounded opening, nearly to the anterior border of the
sclerotic, where it presents a thicker part — the corpus ciliare, and is
then continuous with the iris. Its external surface is attached not only
by larger vessels and nerves, but also otherwise, tolerably intimately, to
the sclerotic, so that in exposing the choroid a portion of the membrane
always remains more or less adherent to the sclerotic, in the form of a
brown tissue. This is the so-termed lamina fusca of authors, which
there is no ground for separating from the vascular tunic and regard-
ing as a distinct membrane, although in many instances scattered pig-
ment-cells, such as exist in it, are found to extend even into the con-
nective tissue of the sclerotic. The inner surface of the choroid is
smooth and, at the era serrata, very closely connected with the retina,
elsewhere more loosely ; whilst anteriorly to the ora serrata, and par-
ticularly in the processus ciliares, it is very intimately united with the
hyaloid m.embrane [zonula Zinnii), so that the two are never com-
pletely separable.

The choroid consists essentially of two portions, a vascular, external
thicker lager — the proper choroid, and an inner distinctly colored
lamina — the pigiyieiitum nigrum ; the former, however, may be again
subdivided into three, but by no means sharply defined layers, viz. : 1,
an external, brown, soft lamella, supporting the ciliary nerves and long
ciliary vessels, and, in front, containing the ciliary muscle — the outer
pigment-lager ; 2, the less deeply colored, proper vascular lager, with
the larger arteries and veins; and 3, a colorless, delicate, internal layer,

* [As shown by I\Ir. Edwin Canton in his " Observations on the Arcus senilis, or fatty-
degeneration of the Cornea." — " Lancet,' vol. i. 1850, p. 5G0. — Tes.]

734

SPECIAL HISTOLOGY.

Fig. 299.

containing an extremely abundant capillary plexus — the memhrana
cJioriocajjiUaris, which, however, does not extend further in front than
the ora serrata. The tissue of which the proper clioroid is constituted,
except the vessels and nerves, which indeed make up a considerable part
of it, and the ciliary muscle, is of a peculiar kind, and cannot conve-
niently be described under any particular head, but like the fibres of
the lig . pcctinatum of the iris, though in somewhat different respects, is
intermediate between the connective and elastic tissues. In the outer
portions of the tunic, this stroma is formed of fusiform or stellate, very
irregular, and extremely pale, or more or less brown nucleated cells,
0-008-0-02 of a line long, which anastomose frequently with each other
by shorter or longer, usually very delicate (0-0005 of a line), but rather
rigid processes, and from their great number represent a lax membra-
nous tissue. There would be nothing very pecu-
liar in this, and these cellular networks might
properly be classed with other similar anasto-
mosing pigment-cells, as for instance in the
batrachian larva (most characteristic in Alytes);
but in the inner layers of the choroid, and espe-
cially in the memhrana ehoriocapillaris, they
gradually pass into homogeneous, nucleated tis-
sue, at first containing a little pigment, but after-
wards none at all ; and which, although in ap-
pearance very similar to homogeneous connective
tissue, is distinguished from it by its resistance
to acids and alkalies, and approximates the elastic tissue, from which,
however, it likewise differs in its trifling elasticity and paleness; whence
it is better, at present, to regard it as sui generis.

The ciliary ligament of anatomists, or the musculus ciliaris s. tensor
chorioidece (Fig. 296 Jc), the really muscular nature of which was recog-
nized almost simultaneously by Brlicke and Bowman, is a tolerably
thick layer of radiating smooth muscular bundles, passing from the
most anterior border of the sclerotic upon the ciliary body, and ceasing
in its anterior half, opposite the part where the ciliary processes are
placed, internally. More precisely described, the ciliary muscle arises
where the sclerotic is grooved for the formation of the venous sinus of
Schlemm, and, in fact, from a special, dense, smooth tract (Fig. 296 Z),
which, forming the inner wall of the canal in question, coalesces with
the sclerotic, and also receives a portion of the fibrous network, into
which the memhrana DeJiioursii is prolonged, the fibres of which are
completely blended with the elements of the tract in question, and re-
semble the others in all respects except that they are much finer,

Fig. 299. — Cells from the stroma o^ \\\e choroid : a, pigment-cells; 6, uncolored fusiform
cells; c, anastomoses of the former. Human. — Magnified 300 diameters.

THE EYE. 735

anastomose more closely, and run in a circular direction. The ciliary
muscle terminates at the most adherent portion of the ciliary processes,
though not in those processes themselves, and- as regards the elements
of ■which it is composed, they are rather shorter (0-02 of aline) and
broader (O-OOS-O-OO-l of a line) than the common fibre-cells ; being at
the same time finely granular, soft, and so perishable, as, in jNIan, not
readily to admit of being isolated.

TXxQ pigmcntinn nigrum (Fig. 296 m) is a continuous, purely cellular
layer, completely investing the inner surface of the choroid and consist-
ing, as far as to the ova serrata, of a single layer of well-formed, almost
regularly hexahedral, contiguous cells, 0-006-0-008 of a line in diame-
ter, 0-004 of a line thick, disposed in an elegant mosaic manner, in
which the large quantity of brownish-black pigment usually prevents the
nucleus being apparent as more than a clear spot in the interior. On
the side towardsjhe retina, however, a narrow clear border is frequently
left free of color, showing that the cells must, at one time, have pos-
sessed contents or have had a thickened mem-
brane. From the oi-a serrata onwards, the ^^ Fi-. soo.
pigment-cells are disposed in several, at least ^^^
two, layers, become rounded, smaller, and ,^^^^^^
entirely filled with pigment, so that the nuclei %^^^^^.i^^^^^^
even are scarcely visible. All the pigment- ^P^^ ,»,
cells have extremely delicate walls, and are ^'h''.
very easily ruptured under pressure ; the pig-
ment is composed of minute, flattened, oval corpuscles, at most 0-0007
of a line long, and presenting, sometimes even while contained in the
cell, but still better when liberated, the phenomenon of molecular motion
in the most marked manner. The pigment of the clioroid is wanting in
the eyes of albinoes, as well as, at any rate partially, in the region of
the tapetum in animals ; but the cells, which would elsewhere contain it,
exist in both these instances, oidy perfectly colorless.

The iris differs from the choroid in containing true connective tissue,
the delicate, lax fasciculi of which, partly radiating, in part circular,
especially at the ciliary border, and much interlaced, constitute the prin-
cipal bulk of the stroma of this tunic, and, towards its surface, form a
more homogeneous layer. It contains a large number of elongated
nuclei, which, at any rate in part, are situated in fusiform cells, similar
to those of the cltoroid, only smaller; and also a few rigid, pale fibres,
which, as prolongations of the ligamentum iJectinatum of the iris, or of
the "membrane of Demours," are continued over a part of the anterior
surface; lastly, the smooth muscular fibres of the iris, presenting ex-
actly the same characters as those of the choroid [ciliary muscle]. In
Man, these fibres constitute a very distinct occlusor muscle of the piqnl

Fig. 300. — Cells of ihe pigmcntuni nigrum of Man: «, viewed on the surface ; b, on ilie
side ; c, pigment-granules.

73G SPECIAL HISTOLOGY.

{sphincter inipillce) in the form of a smooth ring, ^ of a line "wide, close
to the pujiillary margin of the iris, and somewhat nearer to the pos-
terior surface, which, in a blue iris, may be readily recognized after the
removal of the posterior pigment, with and without the application of
acetic acid, and may also be torn up into its elements, 0-02-0*03 of a
line long. Besides this larger muscular ring, I find, close to the annu-
lus iridis minor, another very narrow ring, nearer the anterior surface
of the iris, not more than 1-40 of a line in breadth. Brliche traces the
dilator pupilhe as far as the ligamentum pcctinatum and the border of
the vitreous lamella of the cornea, but I am unable to do so ; and it
rather appears to me to commence in the substance of the iris at the
ciliary margin. From what the difficulty of the investigation has
allowed me to see of this muscle, it consists of numerous slender fasci-
culi, which, far from constituting a continuous membrane, run inwards,
each separately between the vessels, and are inserted at the border of
the sphincter.'^

The iris differs from the cJwroid also, in possessing a cellular layer on
the anterior and posterior surfaces. The latter, the so-termed uvea of
authors, or the jngmentiim nigrum of the iris (Fig. 295 n) is a stratum,
0'0089 of a line thick, of minute, closely filled pigment-cells, like those
of the ciliary body, with which they are also uninterruptedly connected,
and which lines the whole of the posterior surface of the i?-is, extending
as far as the border of the pupil. When the iris is folded, the pig-
mentary stratum, or its free surface, appears to be bounded by a deli-
cate, but sharply defined line, which has been described by several
authors as a special membrane [membrana 'pigmenti, Krause, m.
limitans, Pacini [?], Brlicke, M. Jacobi, Arnold), and, in fact, in eyes
that have been kept for some time, and on the addition of alkalies, may
be raised in places from the pigment. But since, in such instances, the
pigmentary layer is always without any defined outline, and its granules
are exposed and dispersed, it appears to me that this membrane is
nothing more than the conjoined outer cell-walls of the pigment-cells,
which, as is known to be the case elsewhere (intestinal villi for instance)
are raised in their totality, and apparently as a special membrane. The
cellular layer of the anterior surface of the iris is a simple epithelium of
rounded and much flattened cells, which, when viewed in a fold of the
iris, are seen to constitute, not a continuous, clear border of uniform
breadth throughout, but on the contrary, only distinct, slight elevations.
This layer is better seen after the removal of the posterior pigment, in
a horizontal view, and also by scraping or shaving off the anterior sur-
face of the eV/s.f The color of the iris, in blue eyes, depends simply
upon the posterior pigment seen through its substance; whilst in

* [Compare Mr. Lister's " Observations on the contractile tissue of the Iris," " Quarterly
Journal of Micr. Science," vol. i. p. S, October, 1S52. — Tns.]
t [Hd. note, p. 730.— Trs.]

THE EYE.

737

Fipr. 301.

b^o^vnish-yello^v, brown, and black eyes, it is owing to a special iris-
2^i(/mcnt, wbich is very unequally tlistributeil, and thus produces the
peculiar markings of the anterior surface. This pigment is seated, in
the first place, in the stroma itself, and in fact, chiefly in its fusiform
cells, but also, as it appears to me, occurs free among the fibres and
vessels, and in the fibre-cells of the sphincter iJupilliV ; lastly, in the
anterior epithelial layer, it consists of larger and smaller cells, gold-
yellow or brownish irrcgular-sizcd granules, aggregations of granules and
streaks, never of the regular pigment-granules of the true ocular pigment.
The vessels of the tunica vasculosa are extremely numerous, and arc
variously disposed in its different parts. The choroid receives its blood
from the short posterior ciliary arteries, about twenty small vessels,
penetrating the sclerotic, in the posterior part of the eyeball, at a
greater or less distance from the optic nerve, and which, dividing in a
dichotomous manner in the middle or vascular layer of the choroid, run
anteriorly, and subdivide into three sets of branches : 1, external, which,
having attained a certain fineness by continued division, pass directly
into the vence vorticosa ; 2, internaJ, which pass into a capillary plexus
immediately beneath the pigment, in the so-termed mcmhrana chorioca-
pillaris, or Ruyschiana ; and 3, anterior, which are continued into the
ciliary body and iris. The above-mentioned capil-
lary plexus of the innermost layer of the choroid
— which in animals having a tapetum lies upon its
internal aspect, and may easily be demonstrated as
a special membrane, as may also occasionally be
done in Man— -is one of the most elegant and
closest that exists, inasmuch as its meshes, formed
by vessels of 0'004 of a line, do not measure more
than 0'002-0*005 of a line, the capillaries arising
from the larger vessels, as it were in a stelliform
manner. It extends, as has been already said, only
as far as the ora serrata, where it gives place to
somewhat coarser convolutions of vessels, O'OO-l of
a line in diameter, which, proceeding from the an-
terior branches of the short posterior ciliary arte-
ries, constitute the ciliary processes, and are so
closely approximated that, besides the vessels and
a homogeneous sheath supporting the processes, the
latter seem to contain no other tissue. From these
various points, and from the ciliary muscle, which

Fig. 301. — Vessels of tbe choroid and iris of a Child, after Arnold ; viewed from within;
magnified 10 diameters : a, capillary plexus of the posterior segment of the choroid, terminating
at the ora serrata, b ; c, arteries of the corona ciliaris, supplying the ciliary processes, (/, and
in part passing upon the iris, e ; f, capillary plexus on the inner surface of the pupillary
margin of the iris.

47

788 SPECIAL HISTOLOGY.

likewise obtains some twigs from the same arteries, the blood is returned
principally through the veacc vorticosce, which, lying upon the arteries,
constitute elegant vascular stars or vortices, two above and two below
(or it may be five or six); and also at the back of the eyeball, through
some minute vence ciliarcs posticce breves, all of which veins penetrate
the sclerotic in the same way as the arteries.

The iris receives its blood in the first place from the arteries of the
choroid, and secondly, from the long posterior and the anterior ciliary
arteries. The former, with their anterior branches, in part immediately
enter the iris, between the ciliary processes, and in part, after supplying
the ciliary processes, form small trunks at their border and anterior ex-
tremity, which are also continued upon the iris. The long ciliary
arteries; two in number, perforate the sclerotic on the right and left a
little anterior to the short ciliary vessels, run in the external pigment
layer of the choroid, as far as the tensor cJwrioidece, where, each
dividing into two branches and joining the ciliares a7iticcc, which to the
number of five or six penetrate the sclerotic in front, they constitute a
superficial irregular arterial circle in that muscle — the cireulus art.
iridis major. From this circle, together with small vessels passing
either from it, or from the vessels forming it to the tensor muscle, very
many convoluted branches, continued to the iris, are given off; which,
with the arteries already mentioned from the choroid, divide, partly
into a few true capillaries, a layer of which is found particularly at the
posterior surface of the pupillary margin, beneath the pigment (Arnold),
and partly run, continually dividing, as far as the pupillary margin,
wdiere, forming arched loops, they pass into fine, but still not capillary,
venous trunks, after they have constituted a second, usually irregular
cireulus arteriosus minor close to the annulus iridis minor. The veins
of the iris arise from the arteries and capillaries just mentioned, run,
except frequent transverse anastomosing branches, also in a radiating
manner, and open : 1, more from the posterior surface of the iris into
the vasa vorticosa ; 2, into the venoi ciliares joostica' longce ; and 3,
according to Arnold and Retzius, also into the "canal of Schlemm," a
narrow annular channel situated between the choroid and sclerotic
(Fig. 295 /i), from which the venulm ciliares anticce, passing through
the sclerotic, afterwards convey the blood outwardly.

The nerves of the tunica vaseulosa are also very numerous, but
destined solely for the ciliary muscle and the iris. They are the wer-
vuli ciliares, which perforate the sclerotic posteriorly, then run forwards
in the outer lamella of the choroid, partly in grooves in the sclerotic,
and, before entering the ciliary muscle, divide with repeated bifurca-
tions. Within the muscle they break up into a rich and close plexus,
numerous filaments from which proceed to the muscle and to the cornea,
while others constitute the proper nerves of the iris. The latter ac-

THE EYE.

739

company the vessels, dividing repeatedly, and ^vith frequent anasto-
moses, especially in the annuJus minor, to the pupilhiry margin, where
their mode of termination is at present unkno\Yn. The elements of all
these nerves are, in the trunks, of the medium and fine kinds, from
0-002-0-004, and in the iris of not more than 0-001-0-002 of a line.
I have never noticed ganglion-cells in them, nor in the ciliary muscle,
■where Bochdalek describes them as existing.

Some authors, and among them, recently, Bochdalek, believe that
they have seen scattered nerves in the choroid — a circumstance that I
am unable to confirm from my own observations. Quite recently,
Rainey (" Philos. Magaz.," Ma}^ 1851, p. 420) describes a transversely
striped choroideal muscle, occupying the posterior part of the choroid
and extending through its entire thickness in the form of variously de-
cussating layers, which he says may be most easily demonstrated in the
eye of the Sheep. I agree with Henle in thinking that these state-
ments rest upon deceptive grounds ; at all events, in the situation in
question, either in animals or in Man, I can discover nothing like mus-
cular fibres.

§ 227. Nervous membrane [retina). — The retina is the innermost of
the five tunics of the eyeball, and is in close apposition with the choroid,
though not coextensive with it, ending at the ora serrata in an undula-
ted margin [margo undulato-dentatus s. ora serrata retince), which is
very intimately connected, on the one side with the cJioroid, and on the
other with the hijaloid membrane. A continuation of the retina on the
ciliary portion of the hyaloid membrane, which is described by many
anatomists, does not exist.

The retina is a delicate mem-
brane ; when recent, almost per-
fectly transparent and clear, and
after death whitish and opaque.
It commences at the point of en-
trance of the optic nerve, with which
it is, in part, continuous. Its thick-
ness at first is 0-1 of a line, but
as it extends anteriorly it soon
diminishes to 0-06, until ultimately,
close to the anterior border of the

Fig. 502,

iliflllSflPiiff!^'---^

-A-

■ ^

Fig. 302. — Vertical transverse section of the retina of Man, from the posterior portion of
the membrane, magnified 250 diameters: a, hyaloid membrane with decumbent nuclei: b,
mcmbrana limit ans ; c, clear globules (epithelium?) ; d, expansion of the optic nerve; c, layer
of gray nerve-substance;/, internal granular layer; g, fine-granular layer, in which the
radiating fibres are more distinct than elsewhere; A, external granular layer; i, internal divi-
sion of the bacillar layer, with the "cones;" k, external division, with the prolongations of
the " cones" and the true " rods."

740

SPECIAL HISTOLOGY.

retina, it is not more than 0*04 of a line in thickness, and finally ter-
minates quite ahruptly. Notwithstanding this various thickness, the fol-
lo^Ying layers from Avithout to within may be evidently distinguished in
all parts of it; 1, the layer of rods and cones [bacillar layer]; 2, the
granular layer ; 3, the layer of gray nerve-substance ; 4, the expansion
of the optic nerve ; and 5, the limitary membrane. These layers, with
the exception of the innermost, which is of uniform thickness through-
out, in general become thinner towards the front, in correspondence with
the diminished thickness of the whole retina.

1. Tlie bacillar layer, stratum bacilloricm s. memh. Jacobi (Fig. 302
z, h), presents a very remarkable structure, being composed of innume-
rable rod-like and conical corpuscles, disposed with the utmost regularity
and reflecting the light very strongly. With the exception of H. Mul-
ler {yid. infra), this structure, in animals, has been understood quite
erroneously ; and even in Man it has been but very superficially known.
It consists of two elements — the rods, bacilli {k), and the cones, coni [i),
which together constitute a single layer, 0-036 of a line thick at the
bottom of the eye, more anteriorly 0*024, and quite in front not more
than 0-015 of a line in thickness. In general these bodies are so

arranged that the more nume-
rous rods have their largest end
directed outwards, whilst the
cones are disposed in the re-
verse direction, whence the lat-
ter, when imperfectly examined,
appear to constitute an inner,
distinct, thinner layer, lying
between the inner extremities
of the "rods."

In Man, the rods (Fig. 303,
1, /;;, 2) are cylindrical, slender,
elongated corpuscles, in wdiich
a larger external end, the pro-
pier rod, is to be distinguished
from a more slender internal
, portion, the prolongation or

Fig. 303. — Retinal elements of Man, magnified 350 diameters, l,"rods"' and radiating
fibres: /t, proper "rod ;" r, prolongation of its pointed inner extremity; /i, " granule'' (cell)
of the outer granular layer; /, enlarged extremity of the radiating fibres proceeding from
them to the surface of the optic layer; A/, "rod" seated on a " cone," i; r', fibre proceeding
from the latter, connected with the " granule,"/, of the inner granular layer, and the terminal
enlargement, I, on the inner surface of the retina; w, one of the fibrous bundles in which the
radiating fibres frequently terminate at their innermost extremity. 2, "rods"' torn off from
their fibres, in various states of curvature, &c. 3, fibres of the optic nerve : «, fc, straight,
coarser and finer fibres, with varicosities ; c, without varicosities. 4, two " cones," b, torn off
from their processes, (f, with somewhat altered " rods," a, at their outer ends ; f, nucleus of
the " cones."

THE EYE. 741

filamc7}t. The former portion of the rods, ■which alone almost has hitherto
been kno^Yn to anatomists, is a cylinder, 0-00T5-0-012-0-015 of a lino
long, 0-0008 of a line broad, and truncated at the outer end, whilst the
inner is produced into a short point, 0 •002-0-003 of a line in length,
■vshich is often separated from the rest of the "rod" by a faint transverse
line, and might even perhaps be assigned to the " filament." The latter
is an extremely delicate process, not more than 0-0002-0-000-3of a line in
thickness, of uniform width throughout, prolonged immediately from the
point of the "rod, "and, extending through the inner half of the bacillar
layer ; it is connected with the other elements of the retina in a manner
to be afterwards described. The filament is so delicate that it is usually
torn off near its origin on the slightest mechanical impression affecting the
bacillar layer; on which account also it has happened that observers hi-
therto have been acquainted only with the "proper rods," and, though they
had often seen the somewhat longer filaments attached to them, the latter
were regarded merely as artificial products. Since Hannover, also, the
points of these organs have been misplaced outwardly by all writers,
which is wholly incorrect. The substance of the " rods" is clear, homo-
geneous with a faint glistening fatty aspect, very soft and flexible, and
at the same time extremely fragile. Their delicacy is so great that they
underjio the most manifold chan^-es even in water, often even to their
being rendered unrecognizable, bending, as it were, into a hook of vari-
ous forms, curling and rolling up in all ways, or breaking up into two or
more pieces, and allowing clear drops to escape, which are often met
with on the external surface of the retina in vast quantity, derived partly
from the "rods," partly from the ruptured pigment-cells of the cJioroid.
One of the most usual changes consists in this, that the point, if it be
not detached, which is very frequently the case, becomes distended in a
varicose manner, and assumes a lancet-shape, or is even transformed
into a sphere, on which the "filament" of various lengths is placed, in
consequence of which, the obtuse end of the "rod" often presents a
hook-like curve or a slight enlargement. The "rods" are almost inva-
riably very much altered by reagents ; and, above all, the proper " rods,"
which, notwithstanding their greater bulk, yet offer less resistance than
the "filaments." Ether and alcohol cause them to contract and shrivel up,
often rendering them unrecognizable, but do not dissolve them. In acetic
acid of 10 per cent, they are immediately shortened very considerably,
swelling out in several places, and disintegrating into clear drops, which
at first offer some resistance, but afterwards disappear. Concentrated
acetic acid dissolves them in a short time, as do alkalies and mineral
acids ; whilst diluted chromic acid, although it causes them to shrink a
little, is the best preservative of them.

The '•'■cones'' (Fig. 303 ") are "rods" which instead of a filament are
furnished at their inner extremity with a conical or pyriform body, the

742 SPECIAL HISTOLOGY.

length of which equals half the thickness of the bacillar layer (from
0-007-0-015 of a line), and whose breadth is from 0-0025 to 0-0045
of a line. Each of these "cones" consists of an external, thicker and
longer, finely granular extremity, often more or less ventricose, which,
gradually diminishing in size, passes into a common "rod" without a
point, and of a shorter inner portion, somewhat constricted from the
other by a slight incurvation, in which an elongated or pyriform, more
opaque and brilliant body, 0-002-0-003 of a line in length, is enclosed.
On the internal aspect, these " cones," in which I can see nothing but a
cell with a nucleus, are, like the " rods," continued into the succeeding
layers of the retina, where we shall again have to consider them, by fine
filaments, 0-0004-0-0006 of a line in size, similar to those of the " rods."
The "rods" and "cones" are arranged vertically upon the retina,
like palisades, in close apposition, and consequently, one of their ends
is directed towards the choroid and the other towards the granular
layer. Close to the 7nacula lutea the "cones" form an almost continu-
ous stratum (Fig. 304 ^), so that the "rods" are placed only in single
series between them, but more anteriorly they are wider apart, the dis-
tance between them at first being about 0-002-0-003 of a line, and in the
anterior portions of the retina even 0-0004-0-005 of a line (Fig. 304 ^),
thus affording room for more "rods" in the interspaces. Viewed from

without, the bacillar layer, when its outermost sur-
face is brought into focus, exhibits rounded spaces,
placed at a greater or less depth, filled with a clear
substance, which also occupies elsewhere the inter-
stices between the elements of this layer. These
clear spaces, corresponding to the " cones," pre-
sent an internal, dark, smaller circle, the terminal
surface or apparent transverse section of the " rod"
which is seated upon the "cone," and are surrounded by the closely
crowded terminal surfaces of the " proper rods," disposed in a sort of
mosaic manner, their outlines being indicated by the single, double, or
multiple series of reticulations (Fig. 304).

2. The granular layer, stratum granulosum (Fig. 303 Ji, f), is com-
posed of opaque, granular corpuscles, reflecting the light tolerably
strongly, of a round or oval figure, and 0-002-0-004 of a line in size,
sometimes looking like free nuclei, sometimes like minute cells almost
entirely filled by large 7iuclei, although, according to my observations,
they should all be referred to the latter category. For I find, especially
in preparations made with chromic acid, that from both sides of every
granule very fine filaments, 0-0002-0-0003 of a line thick, are regularly

Fig. 304. — Bacillar layer from without. 1, at the "yellow spot" (only "cones") ; 2, at
the border of the same ; 3, from the middle of the retina: a, " cones," or vacuities corre-
sponding with them ; b, " rods " of the " cones," whose terminal surface is often placed rather
more deeply than that of the proper " rods," c. — Magnified 350 diameters.

THE EYE.

743

given off, which in many cases may be distinctly seen to proceed from
a pale border surrounding the granule, so that the whole is very like
a bipolar ganglion-cell in miniature. In Man, the granules, in the
greater part of the retina^ are disposed in two layers — an outer, thicker
of 0-013-0-OlG (A), and an inner, thinner (/), of 0-006-0-008 of a line
— which are parted from each other by a clear, fine-granular, and, to
some extent, vertically striated layer (r/), 0-006-0-008 of a line thick,
whilst, towards the ora serrata, the two constitute a single stratum
of not more than 0*015 of a line in thickness. The granules of the
inner layer are a trifle larger than those of the outer, and Avhen they
are oval, as is most usually the case, I find that they are placed with
the long axis in the direction of the thickness of the retina, so that their
processes, like those of the external layer, run directly outwards and
inwards.

3. The layer of cineritious cerebral substance (Fig. 302 e) is pretty
sharply defined on the side of the granular layer, and less so towards
that of the fibres of the optic nerve,
between the elements of which it pene-
trates more or less. It is composed of
a finely granular matrix, corresponding
exactly with that of the gray substance
on the surface of the cerebrum and cere-
helium, and of numerous nerve-cells scat-
tered in it. Of the latter, some, parti-
cularly in the outer half of this layer,
which is 0-008-0-012-0-02 of a line
thick, are small (0-003-0.006 of a line),
inconspicuous, and in fresh preparations
recognizable only by their beautiful vesi-
cular nuclei; whilst another portion,
forming an almost continuous laver on
the inner side, are of a larger size
(0-006-0-016 of a line). These cells

arc usually pyriform or rounded, or occasionally prolonged into 3-5
angles; and most of them, perhaps all, are furnished with pale pro-
cesses like those of the central nerve-cells — which were first noticed by
Bowman ("Lectures," &c., pp. 8-1 and 125), and afterwards also de-
scribed by Ilassall, Corti, and myself.* The processes occur either
single or in numbers varying from two to six and more ; are at first as
much as 0-002 of a line wide, but in their further course continually

Fig. 305. — Nerve-cells wiili processes from the rc/ina of the Ox, magnified 350 diameters.

* [Pacini appears to have been the fust to perceive the existence and true nature of
the caudate cells in this layer of tlic retina. ('■ Sulla tessitura int. dell. Retina,' 1844, p.
3-2.)— Trs.]

744 SPECIAL HISTOLOGY.

diminish in size, under repeated divisions, till they are reduced to fine
filaments of scarcely 0-0004 of a line in diameter, Avhich, in isolated
cells, terminate in torn ends. In every case in Avhich I have noticed
these nerve-cells distinctly in situ, their processes were given off towards
the exterior, and afterwards in their further course, without entering
the granular layer, appeared to he curved, in order to ramify in the
gray nervous layer itself. The nuclei of these nerve-cells, which behave
towards reagents like those of the cerebrum, measure 0-003-0-005 of a
line, and usually present a very distinct nucleolus.

4. On the inner aspect of the layer in question we find the expansion
of the optic nerve [d). This nerve, after quitting the cJiiasma (concern-
ing which vid. p. 390) and till it reaches the eye, presents the same
conditions as a common nerve ; its dark-bordered fibres, 0-0005 — 0-002
of a line in diameter, much disposed to become varicose, and between
which, according to Hassall, nerve-cells would also seem to occur, but
which I have not yet noticed, form polygonal bundles, 0-048-0-064 of a
line thick, surrounded by a nurilemma of the usual kind. When the
optic nerve reached the eye, its sheath is lost in the sclerotic, which
tunic is perforated for the entrance of the nerve by a funnel-shaped
opening, the narrower part being inward ; and the internal 7ieurilemma
also ceases on a level with the inner surface of the same tunic, where it
may be artificially displayed, as a cribriform lamella {lamina crihrosa of
authors), so that the fibres of the optic nerve enter the eye, each inde-
pendently, without their sheaths of connective tissue. Within the canal
of the sclerotic, and as far as the slight eminence, the colliculus nervi
optici, visible on the inner surface of the retina opposite its point of
entrance, the optic nerve retains its white color, and continues to pre-
sent dark-bordered tubules ; but, from that point onwards, its elements,
in Man and in many animals, become perfectly clear, yellowish or gray-
ish, and transparent, like the finest tubules in the central organs, mea-
suring on the average not more than 0-0006-0-0008 and a good many
only 0-0002-0-0004 of a line, whilst some, it is true, have a size of
0-004-0-0015 or even of 0-002 of a line. What chiefly distinguishes
these from other pale nerve-terminations, is the absence of nude} in
their course, a somewhat greater refractive power, and the frequent oc-
currence of varicosities, which two latter particulars would seem to in-
dicate, if not exactly a nerve-medulla as in the common nerves, still the
existence of partially semi-fluid and perhaps fatty contents, and assimi-
late the nerve-fibres of the retina to the most delicate elements of the
cerebrum. I .have not yet been able to demonstrate axis-fibres and
sheaths in the fibres of the retina, although I would not from that cir-
cumstance at present conclude that they do not exist.* At any rate

* [Here again, Professor KoP.iker is at variance with Mr. Bowman, who gives as one of
the peculiar characteristics of the fibres of the oj^tic nerve in the retina, that they have lost

THE EYE. 745

the retinal fibres are not composed solely of nerv'e-medulla, for, if tlicy
are treated never so thoroughly with ether, they always remain, smal-
ler indeed, but more distinct and more opaque than previously. Fibres
■which have been thus treated enlarge again in cold acetic acid, and dis-
solve in alkalies, and consequently consist, perhaps without doubt, chiefly
of a nitrogenous substance.

As respects the course of the nerve-fibres in the retina, this much is
certain, that they radiate on all sides from the collicidus nervi optici
and constitute a continuous membranous expansion, which extends as
far as the ora serraia retincr, and presents any considerable interrup-
tion only in the situation of the macula lutea. In this true nervous
membrane the fibres are associated into larger and smaller compressed
bundles, usually 0-01-0'012 of a line wide, which either mutually anas-
tomose at very acute angles, or run for considerable distances parallel
with each other. Notwithstanding all that has been stated by various
authors, it may be boldly asserted that the terminations of these nerves
are as yet wholly unknown ; and, as more Avill be said upon this subject
afterwards, I shall here merely remark that, in any case, they exist not
only in front, but in every part of the retina, because the layer of nerve-
fibres becomes visibly thicker from before to behind. I have estimated
its thickness, in Man, at the bottom of the eye at O'OoG, two lines
beyond the yellow spot at 0'006-0-008, and near the ora serrafa at
0-002 of a line.

5. The limitary menihrane, mcmhrana limitans'^ (b), is a delicate
membrane, 0*0005 of a line thick, intimately united with the rest of the
retina, which, when that structure is teazed out, and on the application
of reagents, is frequently detached in large shreds, and then appears
perfectly structureless. On its inner aspect, towards the hyaloid mem-
brane (a), when the retina is folded, flattened cell-nuclei are occasionally
perceptible, which certainly cannot be referred to an epithelium, and
scarcely to the vitreous body, as the latter is always readily separable
from the retina. It seems to be different with regard to a clear, light
yellowish border, 0-002-0-003 of a line wide, situated on the outer side
of the memhrana limitans, which, in folds of a perfectly fresh retina,
appears, as it were, to be completely blended with the limitary mem-
brane, but occasionally exhibits, more or less distinctly, the contours of
excessively clear and transparent spherical bodies [h), 0 •002-0-003 of a
line in size. At a longer interval after death, as well as on the addi-
tion of water, a large number of transparent globules, like drops of
albumen, are afforded by the clear border of the retina, which then dis-
appears altogether, except the memhrana limitans, frequently also,

" the tendency to fall into the varicose or beaded state ; in a word, that the fibres of the
nerve, in expanding into the retina, lose their white substance, but retain tlie axis- or cen-
tral fibre."' — Tes.]

* [So named by Pacini (1. c, p. 22). — Trs.]

74G SPECIAL HISTOLOGY.

tosetlier 'witli it. Todd and Bowman describe the clear bodies above
noticed as cells, and also figure a minute nuclear corpuscle in them;
and I will not directly contradict this notion, although I have not as
yet been in any way able to satisfy myself of the existence of nuclei and
true cells in this layer.

The condition of the retinal elements at the '"'' yellow spof is in many
respects peculiar. In the first place, any continuous layer of optic
fibres is there Avholly wanting, and the stratum of nerve-cells, which
are in close mutual apposition, lies immediately upon the membrana
limitans. Between these cells, however, nerve-fibres run equally from
the sides and the internal end of the spot into it, either isolated or in
very minute bundles, and terminate in a way that cannot be accurately
determined. In the centre of the macula lutea there is a thin unco-
lored spot in ivhicli the granular layer is loanting, from 0-08-0 •! of a line
in diameter, through which the pigment of the choroid is visible — the
so-termed foramen centrale. The plica centralis never exists during life ;
but this is not the case, probably, with the yellow color, which depends
upon diffused pigment pervading all the parts of the retina, except
the "rods." The latter, in this situation, assume the form of " cones"
exclusively, inasmuch as the "proper rods," as Henle (" Zeitsch. f. rat.
Path.," 1852, II. p, 307) correctly states, are wholly wanting in the
"yellow spot" and its immediate neighborhood. Instead of them, the
" cones" form a perfectly continuous layer, are more slender than else-
wdiere (not more than 0-002-0*0024 of a line in breadth), and support
at their outer end, here as elsewhere, not short points, as Henle states,
but the usual " rods," which in this situation are not more than 0-0006-
0-0007 of a line broad (Fig. 304).

After this description of the elements of the various retinal layers, it
will be as well to cast a glance upon their mutual connection. I have
ascertained, in the human eye, that the fibres proceeding from the
"rods" and "cones" inwards, and from the "granules," on both sides,
are connected, and simply constitute parts of a fibrous system of the
retina, as yet not recognized as a connected whole, except by II. Miil-
ler. This system, the greater number of whose elements are vertical,
penetrates the entire thickness of the tunic, and might be termed the
radiating fibre-system [radial fibres, H. Mliller), in contradistinction to
the horizontal, referable to the expansion of the optic nerve. Proceed-
ing from the bacillar layer, it is obvious, that the fine filaments arising
from the "rods" and " cones" are directly continuous with the similar
processes given off from the external side of the "granules," in such a
way that the filaments of the " rods" (Fig. 303 ^, rr) are connected with
the "granules" of the outer granular layer, and those of the " cones"
(Fig. 303 \ r) with the "granules" of the inner layer; in fact, each
"cone" or " rod" is in connection with a granule, the latter also per-

THE EYE. 747

haps ^Yith several. The filaments which run inwards from both kinds
of " granules," which may be pretty readily traced in vertical sections,
are continued in a straight line, or slightly curved, through the layer of
gray nerve-substance without any connection with its elements, and
enter the expansion of the optic nerve, where, as especially in the pos-
terior part of the eye, in which situation the layer of nerve-fibres is
thick, it is easy to perceive that they run in the narrow interstices be-
tween the nervous bundles, in a fascicular manner towards the memhrana
Umitans. I have taken much pains in the investigation of their re-
lations at the surface of the retina, and have arrived at the following
results. If the inner surface of the retina be examined under a strong
magnifying power, in its posterior half, where the fibrous bundles of the
optic nerve are still very distinct, a peculiar marking will be observed
between them, consisting of series of points, of minute stelliform
figures, or of little streaks, which often (also in animals, as the Ox for
instance) regularly converge towards each other from the bundles of
fibres like the rays of a feather. If these structures are traced in ver-
tical sections, it is easily seen that they are nothing but the extremities
of the radiating fibres dipping down between the nervous bundles, and
presenting a somewhat peculiar aspect. For, whilst in the deeper part
of the retina they are simple pale fibres, of at most 0-0008 of a line in
size, they are here so modified that some of them simply expand, and
terminate in a triangular pale corpuscle, O-0015-O-OOo of a line in
length and breadth (Fig. 303' I), from the internal angles of which, one
or two horizontal fibres are again given off; whilst the others, without
expanding, end in a complete bundle of 5-9 or more fine fibres (Fig.
303 ' n), which also turn to the sides and continue in the plane of the
nervous expansion. What further becomes of these latter, innermost
processes of the radiating fibre-system, I have not yet been fortunate
enough to observe, however zealously I have investigated the matter,
and regret that the decision of this very important point in the ana-
tomy of the retina must still be left in abeyance. The radiating fibres
either actually terminate in the filaments observed by me on the surface
of the expansion of the optic nerve, or they are continuous with the
true fibres of that nerve, or at any rate are in connection with them. In
a physiological point of view the latter supposition would, in any case,
be the most plausible ; and in support of it, it may be stated, that in
the true fibrous bundles of the retina, toijether with the varicose nerve-
tubules (Fig. 303^ a, h), there are fibres of another sort (Fig. 303^ c),
which, although of equal size, agree in all respects with the radiating
fibres in the absence of varicosities, and in their less straight or more
serpentine and irregular course. It may be that these fibres are the
direct continuations of the horizontal terminal processes of the radia-
ting fibres, which subsequently, in their further progress towards the

748 SPECIAL HISTOLOGY.

optic nerve, acquire more and more of the character of common nerve-
tubules, and follow a more direct course. However interesting this
notion may be, according to which the " rods" would be the termina-
tions of the optic fibres, the considerable difficulties attending it must
not be concealed ; among which not the least is the circumstance, that,
although the " rods" and " cones" are certainly fifty times more
numerous than the fibres of the optic nerve, yet the radiating fibres
arising from the former, on their passage into the optic fibres, subdivide,
and, as it must probably be assumed, are continuous with several of
them — a dlfiiculty, which might indeed be removed on the hypothesis,
that a single optic fibre receives or gives off numerous radiating fibres,
but is nevertheless of such a kind that I do not consider it advisable to
proceed any further upon a basis unsupported by facts.

In spite of the obscurity which, from what precedes, still hangs over
a very important point in the anatomy of the retina, phj^siology may
nevertheless even at present draw some useful conclusions from the facts
in our possession. In the first place, since the demonstration by H.
Mliller and myself of its connection with the radiating fibre-system and
the "granules," the bacillar layer appears in quite a different light from
that in which it was previously held, and it is now obviously impossible
to regard it, with Briicke, as a catoptric, reflecting apparatus. I look
upon the "rods" and " cones," which may also be said to correspond in
all chemical characters with the nerve-fibres of the retina, and the whola
of the radiating fibre-system of the retina, as true nervous elements ;
and venture at the same time to broach the bold supposition, founded
upon a less established basis, which has been already thrown out, that
the "rods" and "cones" are the true percipients of light, and that they
communicate their condition to the fibres of the optic nerve, by means
of the direct or indirect connection of their fibrous processes with the
former, through which again the impressions are conveyed to the seiiso-
rium. That the optic-fibres in the nervous expansion of the retina, do
not perceive light, appears to me to be proved by the circumstance : 1,
that the point of the retina, where those fibres alone, and no other ele-
ments of the retina, are found, viz. at the entrance of the optic nerve,
is not sensitive to light ; 2, that the optic fibres are superijjijjosed upon
each other in such numbers, in almost every part of the retina, and
above all in the neighborhood of the macula lutea, that it is impossible
they should perceive light, inasmuch as each luminous impression, owing
to the transparency of the fibres, must in any case always affect many
of them, and consequently would of necessity give rise to confused sen-
sations ; and 3, because the part of the retina in which there is no con-
tinuous layer of nerve-fibres on the inner surface, that is to say, the
"yellow spot," is the most sensitive to luminous impressions. Under
this notion, the import of the "rods," and their remarkable arrange-

THE EYE. 749

ment, would be intelligible, and the almost inexplicable correspondence
in the size of the images of the smallest distinguishable interspaces be-
tween two objects, with the diameter of the "rods" and "cones," be
placed in its true light. I consider it impossible to say anything with
respect to the import of the other elements of the retina, for although
the "granules" maybe compared to minute bipolar ganglion-corpuscles,
and their continuity with the radiating fibres is known, this affords as
little ground for discussion as to their function, as is given by the know-
ledge of the fact that the large nerve-cells of the inner layers have nu-
merous processes and probably free terminations.

The vessels of the retina are derived from the art. centralis retince,
which enters the eye enclosed in the optic nerve, and begins to ramify
from the centre of the collicidas ncrvi optici in 4 or 5 main branches.
Lodged at first only beneath the mevihrana limitans, these vessels pene-
trate through the layer of nerve-fibres into that of gray nerve-substance,
ramify in an elegant arborescent manner as far as the ora serrata, and
pass by their terminal prolongations on all sides into a rather wide-
meshed network of very fine capillaries (0-002-0-003 of a line), which is
lodged chiefly in the gray layer, but partly also in the expansion of the
optic nerve. In animals, the veins commence with a complete circle,
circidus venosus retince, at the ora serrata, accompany the arteries in
single trunks, and convei^ge to the vena centralis, which quits the eye
together with the artery. No large vessels exist in the "yellow spot,"
where there are only numerous capillaries. I have never yet met with
nerves on the retinal vessels, whilst on the outside of the larger vessels
I have occasionally noticed traces of an accompanying fibrous tissue, ap-
proaching nearest to the embryonic, reticular connective tissue.

The radiating fibre-system of the retina, though known in its separate
parts to older and more recent observers, had not been comprehended
in its connection, and we are very greatly indebted to H. Miiller for his
accurate investigations into this important structure in animals of every
class. I have repeated Mliller's observations in the human eye, which
was not investigated by him, and have been enabled to confirm in it all
that he has stated, and in some respects to carry the observations fur-
ther. The reason why the radiating fibre-system and the relation of
tlie " rods" to it has hitherto remained unknown, is because no one ex-
cept Bowman, so far as I am aware, has engaged in the indispensable
study of vertical sections of the retina, and moreover, because no one
had thought of applying chromic acid to that tunic, which has elsewhere
in the nervous tissues been of such important service, and although I
had particularly shown that the multipolar retinal cells were well pre-
served in it. If parts still fresh be taken for examination, in transverse
sections and chromic acid preparations, very satisfactory views of the

750 SPECIAL HISTOLOGY.

structures above described will be obtained, and it will excite surprise
that such numerous fibres pervading the entire retina should have been
hitherto overlooked. A wholly new investigation of the retina has com-
menced with what has been made known bj Muller and myself, but it
will still demand much time and pains before it can be conducted to any
certain results. Future inquirers should take up particularly the rela-
tions of the radiating and optic fibres in the eye, also the point whether
the latter subdivide in the retina, as is asserted by Hassall and Corti,
and lastly, whether the nerve-cells are directly connected with the
nerve-fibres (Corti) or not.*

§ 228. The crystalline lens is a perfectly transparent body, in rela-
tion by its posterior surface with the vitreous humor, and laterally with
the termination of the hyaloid membrane, the zonula Zinnii ; and in
which are to be distinguished the lens, properly so termed, and its
capsule.

The capsule of the lens consists of two elements — the ^jroper capsule
and the epithelium. The former is a perfectly structureless and trans-
parent, highly elastic membrane, enclosing the lens on all sides, as if
moulded to it, and parting it from the neighboring structures. If the
lens with its capsule be placed in water, the latter becomes considerably
distended by imbibition, whence it is apparent, that membranes of that
kind, notwithstanding their homogeneous structure, are yet very per-
meable, so that' the nutrition of the non-vascular lens is provided for
without difficulty, by means of materials penetrating from without. The
lenticular capsule, measuring in its anterior wall, 0'005-0-008 of a line,
and posteriorly to the attachment of the zonula Zimiii, where it is
abruptly thinned, not more than 0-002-0-003 of a line, may be readily
torn, punctured, or incised, whilst it oifers considerable resistance to a
blunt instrument. If an uninjured capsule be punctured, it contracts

* [Profs. Kolliker and Muller {vid. Comiites. rend. torn, xxxvii., Sept. 1S53) have since
Ijeen able by further researches, to confirm their views on the structure of the retina. They
state also, that they have succeeded in tracing in the human retina the direct connection of
the nerve-fibres with the nerve-cells — a fact first noticed by Corti in the Ruminants, and
to which they attach extreme physiological importance. The radial fibres proceeding
from the "rods," Kolliker observed frequently to unite into fasciculi, which was not the case
in those derived from the " cones." At the yellow spot, he found the nerve-cells to consti-
tute a thick layer, formed of from 9 to 12 rows of cells; but both he and Milller deny most
strongly the presence of nerve-fibres in this situation, although their existence has been
(juite lately again positively afilrmed by Hannover (Zeitschrift fiir wiss. Zool. B. V. H. 1,
1853).

The physiological conclusions which Kolliker and Miiller deduce from these more recent
anatomical observations are, in the main, the same as those above expressed. They seem,
however, less inclined to view the " rods" and " cones" as the only percipients of light, but
regard them more as conductors of the luminous impressions to the nerve-cells of the retina.
These they consider to form a true ganglion, capable of perceiving the light, the expansion
of the fibres of the optic nerve merely serving as a means of communication with the sen-
sorium. — DaC.j

THE EYE.

751

Vig. 306.

to such an extent, owing to its elasticity, that the lens not unfrequentlv
escapes spontaneously. In its micro-chemical reactions the capsule of
the lens behaves exactly like other transparent membranes, except that,
according to Strahl (" Archiv f. phys.," Ileilk., 1852) it would appear
to be dissolved by boiling in water. The epitheliiun of the capsule is
placed, not on the outer surface, as Br'iicke states, but on the inner,
towards the lens^ lining the anterior half of the capsule with a single
layer of beautifully clear, polygonal cells, of 0-006-0-01 of a lino, with
round nuclei. After death its elements are readily separated, expand
into transparent spherical vesicles, many of which burst, and together
Avith a few drops of aqueous humor which have penetrated into the in-
terior, constitute the so-termed aqua Morgagni, which during life, when
the epitltelium is accurately applied to the surface of the lens^ does not
exist at all.

The lens itself consists entirely of elongated, flat, hexahedral ele-
ments, 0-0025-0-005 of a line broad, and 0-009-0-0014 of a line
thick, of a perfectly transparent aspect, very flexible and soft, and
havino; a considerable degree of
toughness, which have usually
been described as the fibres of the
lens, although they are nothing
more than tliin-ivalled titles with \'
clear, viscous, albuminous con- \
tents, which, when the tubes are
torn, escape from them in the
form of large irregular drops, and
consequently might suitably be
described as the tubes of the hms.
As concerns the microscopic cha-
racters of these bodies, they are
distinguished by the circumstance
of their becoming opaque and
more distinct in all reagents by
which albumen is coagulated; con-
sequently, reagents of that kind,
particularly nitric acid, alcohol,
creasote, and chromic acid, are especially suitable for the investigation
of the leiis ; but in caustic alkalies they are quickly dissolved, and
they are also speedily attacked by acetic acid. The union of the tubes
which are more solid, slender, and opaque in the more compact inner
layers of the lens — the so-termed nucleus — than in the softer external
portions, is brought about simply by their apposition. They invariably

Fig. 300. — Fibres or tubes of the lens. 1, from the Ox, with slightly toothed borders; 2,
transverse section of the lenticular tubes of Man. — Magnified 350 diameters.

752 SPECIAL HISTOLOGY.

lie with their sides parallel to the surface of the lens, regularly inter-
digitating with each other bj their acute borders, so that, as is shown
in Fig. 306 ^, in the interior of the lens, each tube is surrounded by six
others, and their transverse section presents the aspect of a v«'all built
up of hexagonal bricks. As the edges and corresponding surfaces of
the tubes are usually somewhat uneven, or even toothed (in animals,
particularly Fishes, beautifully so) their lateral union is rendered more
intimate than it is between their border surfaces, and on this account
also the structure is more readily torn into lamellae in the direction of
the surfaces, than into vertical plates in that of its thickness. For the
same reason, also, a lamellar structure may be assigned to the lens, as
is commonly done, seeing that it is constituted of concentric laminge
like an onion, only it must not be forgotten that these laminae are not
regularly defined layers, and never consist of a single stratum of tubes,
and, moreover, what may prove of great physiological importance, that
the elements of the lens are, properly, still more regularly disposed in
the direction of its thickness, so that, throughout the lens, they cover
each other, and the latter might be regarded as consisting of very
numerous vertical segments, the thickness of which w^ould correspond
with the width of a single fibre. [Bowman, 1. c, p. 69.]

The coarse of the tubes of the lens in tlie separate lamellce is in
general such that both the superficial and the deeper, in the centre of
the lens, radiate towards the margins, and then curve round upon the
other surface, anterior or posterior, but in such a way that no fibre
extends through the entire semi-circumference of the lens, or reaches,
for instance, from the middle of the anterior surface to that of the
posterior. More precisely described, the tubes on the anterior and
posterior surfaces of the lens do not proceed exactly to the middle, but
terminate in a stelliform figure which exists in that situation. In the
foetus and in the new-born child, each of these stelliform figures of the
lens, which are readily seen by the naked eye, presents, three rays,
which usually meet, regularly, at angles of 120° ; in the anterior star,
two of the rays are directed, the one upwards and the other down-
wards ; the reverse being the case with the posterior "star," which,
therefore, as compared with the anterior, appears as it were turned
round in an arc of 60°. Now, the tubes arising from the middle of the
anterior "star" extend, on the posterior aspect, only as far as the
extremities of the three rays; and, on the other hand, those comraen-
cinrr from the posterior pole do not reach the middle of the anterior.
Similar conditions obtain in all the tubes situated between these two
points, so that none of them reach entirely round ; and all the tubes in
a layer are of equal length. Now precisely the same thing also exists
in the "nucleus" of the lens in the adult, whilst in the superficial
lamellce, and on the surface itself, we observe a more complex "star,"

THE EYE.

■with from nine to sixteen rays of various lengths, and rarely quite
uniform, among which, however, three principal rays may be distin-
guished. The course of the fibres is consequently rendered more com-
plex, and the rather so, because fibres attached to the sides of the rays
converge in an arched manner, so that the latter appear, as it were,
feathered, or form whirls {vortices lentis); but, notwithstanding this,
the course of the fibres remains essentially the same in all respects as
that above described, inasmuch as in this case also the anterior and
posterior "stars" do not correspond with each other, and no fibre

Fig. 307.

extends from the one pole to the other. In the " stars," the substance
of the lens is not formed of tubes as elsewhere, but is in part finely
granular, in part homogeneous; and, consequently, since the "stars"
involve all the layers, three or more, vertical, non-fibrous lamelloe
("central planes," Bowman) exist in each half of the letis. Moreover,
the tubes themselves in the neighborhood of the " stars" become less
distinct, are gradually fused together, and ultimately lost, without any
line of demarcation, in the substance ia question.

§ 229. The vitreous hody or humor, occupies the entire space between
the lens and the retina ; its relations being such that excepting at the
point of entrance of the optic nerve, where the connection is rather more
intimate, it is only in loose apposition with the retina, whilst it is very
closely united with the corona ciliaris and the leiis itself. The mem-
brane enclosing the vitreous body, or the hyaloid membrane, which
behind the ora serrata constitutes an extremely fine and delicate, per-
fectly transparent membrane scarcely perceptible under the microscope,
in front of that part becomes rather firmer (Fig. 296 t), and is continued
to the border of the lens as the j:>a7-s ciliaris hyaloidece s. zonula Zinnii
(" suspensory ligament of the lens," Bowman [and Retzius]), where it

Fig. 307. — Lens of the adult, after Arnold, to show the "star." 1, anterior aspect ; 2,
posterior.

48

754 SPECIAL HISTOLOGY.

becomes blended with the capsule of that bodj. In doing this it splits
into two lamella^ a posterior (y), which is blended with the capsule of
the lens a little behind its border, and cannot be traced further, so that
beyond that point the posterior wall of the lenticular capsule and the
vitreous body are directly in contact ; and an anterior {ii) connected
with the ciliary processes, — the zoiiula in the more restricted sense, —
Avhich is attached to the capsule of the lens a little in front of its margin.
Between the two lamellce and the border of the lens, there is left a space
surrounding the latter in an annular manner, and, in a transverse sec-
tion, of a triangular form — the canal of Petit ; — which, though con-
taining a little clear watery fluid, yet during life is very narrow, inas-
much as its anterior wall or the zonula Zinnii so long as it is continuous
with the ciliary processes, like them presents the aspect of a much pli-
cated membrane, and consequently is brought into close approximation
with the posterior wall, at as many points as there are ciliary processes.
These folds, however, are still visible where the zonula, quitting the
ciliary processes, is continued independently upon the border of the
lens, as a part of the posterior wall of the posterior chamber of the eye ;
and it is therefore attached to the capsule, not in a straight but in a
slightly undulating line.

With respect to the structure of the parts in question, much pains
have recently been bestowed upon the elucidation of that of the proper
vitreous body ; although it cannot be asserted that at present the truth
has been arrived at. Brilcke's view, according to which the vitreous
body, like an onion, consists of concentric lamella} parted by a gela-
tinous fluid, was contradicted by Bowman, who has shown, that the con-
centrated solution of acetate of lead used by Briicke for the exposition of
these lamellce, produces the appearance of lamination not only on the
superficial surface but also on that of any section whatever, but without
rendering true lamellie manifest. Hannover's opinion, according to
which, after treatment of the vitreous body with chromic a,cid, numerous
dissepiments are found in it, running from the surface towards the axis,
so that in a vertical section a number of " rays" are perceptible pro-
ceeding from the central point, and the whole resembles an orange laid
open, appears to have more in its favor, inasmuch as, at any rate, the
vitreous body of the new-born child, according to Bowman (Lectures, p.
100, and Fig. 5, p. 97), when treated with chromic acid, very distinctly
exhibits an areolated aspect of the kind described, but it should be re-
marked that from the same author's observations, the conditions are
widely different in the eye of the adult, for, in this instance, in chromic
acid preparations, a few concentric lamellce are found externally, to
which succeed very irregular radiating septa, and lastly an irregular
central cavity. If to this it be added that these lamellce formed by
chromic acid also cannot be demonstrated as true membranes, and that

THE EYE. 755

in the fresh vitreous body no trace of them is perceptible, the appear-
ances produced by this second reagent can likewise not to be considered
as proving much.

A more correct notion of the constitution of the vitreous body would
appear to be derivable from the study of its development. It has been
long known that the vitreous body in the foetus has vessels on its sur-
face and in the interior ; it might thence have been concluded that some
tissue for the support of these vessels must also exist — but no one has,
till recently, sought farther information with the aid of the microscope.
Bowman was the first (1. c, p. 100 and p. 97, Fig. 7) to remark, that
the vitreous body of the new-born child exhibited a very distinct and
peculiar fibrous structure, consisting in fact of a close network of fibres,
presenting at nodular enlargements [where the fibres join] "minute
nuclear granules resembling oil-particles, but not soluble in ether;"
the whole exhibiting " a peculiar fibrous texture not at all unlike that
of the enamel pulp" in the foetal tooth-sac, that is to say, to its gelati-
niform connective tissue. This agrees pretty nearly with what Virchow
has recently found. According to the latter author, the vitreous body
of a foetal Pig, -i lines long, consists of a homogeneous substance, con-
taining mucus, and faintly striated at distant spots, in which round
nucleated granular cells lie, scattered at regular distances apart. This
substance is surrounded by a delicate membrane, with very elegant vas-
cular networks and a fine fibrous areolated mesh-work containinG! nuclei
at the nodular intersections, and also enclosing in its meshes a gela-
tinous mucus with rounded cells. Consequently, and also because he
found mucus in the vitreous body in the adult, Virchow believes that
the tissue of the foetal corpus vitreum should be ranked with what he
terms "mucous tissue," corresponding with my gelatinous connective
tissue (§ 24) ; and that it might be assumed that, in the course of de-
velopment, the structure may so change that the cells disappear and the
intercellular substance alone remains. As regards my own views, I can
only partially agree with these authors. In the vitreous body of the
human foetus and of that of animals, I can perceive nothing but a homo-
geneous matrix containing mucus and numerous round or elongated
granular, nucleated cells, 0-004-0-01 of a line in size, dispersed in it at
pretty regular distances of 0-01-0-02, or even 0'03 of a line apart. It
is true I have also noticed stelliform anastomosing cells also, but only
on the outer side of the hyaloid membrane, and which when the vessels
once began to convey blood, could be easily shown to communicate with
them, and to be, in fact, capillaries in process of development. Of
membranes, such as Hannover describes, I have never seen any certain
indication "with the microscope ; and yet such membranes, did they
exist, would incontestably be as easily recognized, where they are
folded, as the excessively delicate hyaloid membrane itself. In the

756 SPECIAL HISTOLOGY.

vitreous body of the adult, of the previous conditions there was usually
nothing left but the homogeneous matrix^ the cells having disappeared;
I noticed the latter, however, in many instances, though rare and indis-
tinct, particularly in those parts of the organ bordering upon the lens
and the hyaloid membrane in general. From these observations I con-
clude that the vitreous body, at an early period probably presents a
sort of structure most nearly approximated to embryonic cellular tissue,
but that subsequently all trace of such a structure is normally lost, and
it consists merely of a more or less consistent mucus.

Zonula Zinnii. — At the ova serratcr, the hyaloid membrane comes
into intimate contact with the retina, and the latter again with the
clioroid, so that it is extremely difficult to display the relations of the
above-noticed zonula Zimiii. If this part be exposed from the outside,
some of the pigmentum nigrum of the ciliary processes is almost always
left adherent at certain spots and often over a considerable extent. If
the places where this is not the case are examined, it is evident that
the outermost lamina of the zonula is a grayish layer, extending exactly
so far as the lyrocessus ciliares are in connection with the zonula, and
ceasing anteriorly in a slightly toothed, irregular border. Under the
microscope there are always visible in this layer, even when the zone
appears quite clear, and particularly towards the front, a good many
rows of pale pigrnent-cells belonging to the clioroid, which are situated
principally in the folds in which the jn'ocessus ciliares were contained,
and give the entire zone a striped aspect. On the inner side of this
lies a single layer of clear, frequently very pale, polygonal, nucleated
cells, of 0*006-0*012 of a line in size, but which is never entire, being
always partially removed, together with the ciliary processes, on which
Henle and others have noticed it. This layer of cells does not belong
to the retina, as most authors assume, and still less to the hyaloid
membrane, but to the choroid, and is nothing more than a stratum of
cells not containing pigment, lying immediately upon the oorona ciliaris,
internally to the pigment (Fig. 296 w, w') ; it does not, however, in
any way appear to be a distinct epithelial layer, but only the uncolored
part of the pigmentary stratum, to which it would stand in the same
relation as the colorless epidermis-cells to the colored, in dark skins.
This colorless epithelium of the corona ciliaris, as I shall term these
cells, is most distinctly shown on the ciliaiy processes, as a clear border
sharply defined on the inner side, and often 0-006-0-008 of a line broad,
whose large, frequently shortly cylindrical cells, may usually be recog-
nized without any trouble, and are always rendered distinct by acetic
acid ; whence it is evident that the boundary is composed only of them,
and is not a special membrane. Posteriorly, this cellular stratum
reaches as far as the ova serrata, extending anteriorly to the termina-
tion of the ciliary processes (Fig. 296 iv'), and on either side it is con-

THE EYE. 757

tinuous, witliout any line of demarcation, ^Yith the pigmentary layer,
the clear cells being gradually replaced by cells containing pigment.

Excepting these cells, the zonula is a thin, transparent but tolerably
firm membrane, stretching from the ora serrata retincc as far as the
border of the lens, and appearing to be a continuation of the hyaloid
membrane. It consists of peculiar, pale fibres, already very Avell cha-
racterized by Ilcnle, resembling certain forms of reticular connective
tissue, except that they arc more rigid, usually present no distinct
fibrils, and are less swollen in acetic acid. They commence, very fine,
a little behind the ora serrata retince on the outer side of the hyaloid
membrane, although most intimately connected with it, in part like
fibrils of connective tissue, then run forwards, forming a layer at first
more lax, and becoming more and more dense, and increasing in thick-
ness (up to 0-004 or even 0-01 of a line and more), with numerous divi-
sions and anastomoses, and for the most part parallel with each other,
until they constitute, at the free portion of the zonula, a perfect, con-
tinuous layer — though still containing a few isolated bundles, and are
ultimately blended with the capsule of the lens. From the ora serrata
to the commencement of the "canal of Petit," no hyaloid membrane
besides the fibres of the zonula, can be any longer distinguished, whilst
at the canal itself, where the substance of the vitreous body is separated
from the fibrous layer, it is again furnished with a limitary membrane,
only thinner than before, which constitutes the posterior wall of the
" canal of Petit," and extends no farther than to the border of the lens,
where it ceases as a special membrane, the vitreous body being most
intimately united with the posterior lamina of the capsule of the lens.

M. Langenbeck, some years ago described, in the free portion of the
zonula Zinnii, what he believes to be a muscular ring, and terms the
musculus compressor lentis s. accommodatorius (" Klinisch. Beitrage zur
Ophthalmol.," 1849, p. (jQ), of which I have been unable to perceive any
indication. He has probably confounded the zonular fibres with such a
structure.

B. ACCESSORY ORGANS.

§ 230. The eyelids are supported by the so-termed tarsal cartilages
(tarsi), thin, semilunar, flexible, but tolerably elastic plates, attached
internally and externally by the fibrous, tarsal ligaments, — and belong-
ing, as far as their structure is concerned, to the solid, fascicular, con-
nective tissue, though occasionally containing a certain number of minute
cartilage cells. These plates, 0 •3-0-4 of a line thick, the fibres in which
chiefly run parallel with the borders, are covered externally by the orbi-
cularis palpebrarum and the integuments, and internally by the con-

758 SPECIAL HISTOLOGY.

junctiva. The sUn is here very thin (1-5-1-8 of a line), with scanty,
subcutaneous connective tissue containing no fat, a delicate cuticle,
0-055-0-058 of a line thick, and short papillce (of 0-060-0-066 of a line) ;
but it is furnished throughout with minute sudoriparous glands (of 1-10-
1-12 of a line) and almost invariably, with numerous minute hairs (fre-
quently, with contiguous sebaceous glands, but whether ahvays so pro-
vided I do not know). At the edges of the jjaljjehrce these hairs are more
considerably developed and constitute the eyelashes, which are also fur-
nished with sebaceous follicles. Agreeing in all respects, in structure
and secretion, with the sebaceous glands, the Meibomian glands, never-
theless, differ somewhat in form. They are imbedded in the tarsal car-
tilages, to the number of from twenty to forky, in the form of elongated,
white, delicate, parallel, racemose follicles, disposed in such a direction
that the long axes of the glands, cut those of the tarsal cartilages at a
right angle. Each of these glands which are visible at once upon
inverting the eyelid, and do not occupy the entire width of the tarsi^
consists of a straight excretory duct, 0-04-0 -05 of aline wide, which at its
orifice on the inner edge of the free palpebral border, is lined with com-
mon epidermis, including the horny and the mucous layers, and more
internally presents the usual structure observed in the sebaceous glands.
This canal, throughout its length, is beset with round or pyriform, shortly
pedunculated, gland-vesicles, 0-04-0-07-0-1 of a line in diameter, either
isolated or aggregated several together, in which, in a mode similar to that
already described in speaking of the sebaceous glands (§ 74), a constant
production of spherical, adipose cells, 0-005-0-01 of a line in size, takes
place ; the cells differing from the sebaceous cells, only in the circum-
stance that the oil-drops contained in them do not usually run together
into a single large drop, but remain separate. As these cells advance
towards the excretory duct they gradually break up into a whitish pul-
taceous substance composed of oil-drops, and form the so-termed lema
s. sebum 2)alpebrale. The orbicularis palpebrarum, constituted of trans-
versely striped, though rather slender and pale muscular fibres, lies im-
mediately beneath the skin, its stratum internum being separated from
the tarsi by a layer of lax, and to some extent adipose connective tissue,
so that it may be readily raised into a fold together with the integuments.
It is only towards the free margin that this muscle is more closely
attached to the tarsi, and there presents a bundle of fibres situated at
the very verge of the eyelid, which is parted from the rest of the muscle
by the follicles of the cilia — the so-termed ciliar muscle (musculus cili-
aris, Riolan).

The conjunctiva (a mucous membrane), commences at the free palpe-
bral margin, as an immediate continuation of the external integument,
lines the posterior surface of the eyelids, and is then reflected upon the
eyeball, investing the anterior part of the sclerotic and the entire cornea.

THE EYE. 759

The palpebral conjunctiva is a reddish membrane, 0-1 2-0-16 of a line
thick, very intimately connected with the posterior surface of the tarsi^
and consisting of a dense layer of connective tissue corresponding to
the cutis^ 0-08-0-11 of a line thick, and of a squamose epitlicUiim, 0-04
of a line in thickness, containing deeper cells of an elongated form, and
more superficially, polygonal, slightly flattened, nucleated, and (so far
as I have seen in Man) non-ciliated cells. Papillce also, similar to those
of the cutis, are met ■with in the palpebral conjunctiva, some of which
are smaller and more cylindrical, whilst others, particularly towards the
point of reflection of the membrane where it is generally thicker, are
larger (as much as 1-10 of a line long), more verrucose and fungiform.
At the line of reflection itself, Krause describes minute racemose mu-
cous glands, 1-5-1-26 of a line in size, but which do not always exist.
The conjunctiva scleroticce, is white, less dense and thinner than that of
the lids, tolerably rich in fine elastic fibres, and loosely and movably
attached to the sclerotic by an abundant submucous connective tissue,
containing more or fewer fat-cells. Papilloe are wholly wanting in this
portion, except at the line of reflection, as well as glands, whilst the epi-
thelium is well developed, as on the conjunctiva coj'necv, and beneath it
there is not unfrequently an outermost layer of the proper mucous mem-
brane, in the form of a very distinct structureless, narrow seam. At
the margin of the cornea, particularly in elderly persons, the conjunc-
tiva scleroticce forms a slight annular elevation J— 1 line broad, — the an-
nulus conjunctives, which encroaches a little upon the cornea at the lower,
and especially at the upper border. The corneal conjunctiva has been
already described, and it only remains to notice the 'plica semilunaris,
or the third palpebra at the inner canthus of the eye. This is a simple
duplicature of the sclerotic conjunctiva, which rises in front into a coni-
cal elevation — the caruncula lacltrymalis, — in which are seated about a
dozen fine hairs, surrounded by an equal number of rosette-like sebace-
ous follicles 1-5-1-4 of a line in size, encompassed by numerous fat-cells.
The lachrymal apparatus consists, in the first place, of the lachrymal
glands — a certain number of larger and smaller compound Kaeemose
glands, disposed in two groups — termed the superior and inferior lachry-
mal glands, and in the structure of the larger and smaller lobules, as
well as in the rounded gland-vesicles, 0-02-0-04 of a line in diameter,
precisely resembling the salivary and mucous glands (§§ 134, 135). The
excretory ducts of these glands, 6-12 in number, perforate the conjunc-
tiva in the fold between the outer part of the eyelid and the globe of
the eye ; they are excessively fine canaliculi, composed of connective
tissue, with a few nuclei and elastic fibrils, and of a cylindrical epithe-
lium. It is extremely difficult to display these canals in man, whilst in
animals (the Ox for instance) they are easy of demonstration. The pas-
sages by which the tears are conveyed away from the eye are con-

760 SPECIAL HISTOLOGY.

structed in the same simple manner as the excretory ducts of the lach-
rymal glands, consisting merely of a dense connective tissue mth nu-
merous networks of fine elastic fibres, particularly abundant in the
lachrymal canals, which appears to be a continuation of the mucous
membrane of the nose and of the conjunctiva, and of an ejntlielium
which, in the lachrymal canals, is of the squamous kind, and in the
lachrymal sac and nasal duct is furnished with vibratile cilia, as in the
cavity of the nares. The muscles of the globe of the eye and of the
eyelids, as well as the musculus JTorneri, are all composed of trans-
versely striped muscular fibres, and together with their tendons, pre-
sent no differences from those of the trunk and extremities. The fascia
hulbi oculi s. Tenoni is a true fibrous membrane, and the trocJilea is
formed principally of dense, connective tissue, in which only a few
cartilage cells can be seen.

The vessels of the organs described in this section present little
worthy of remark. Excepting those of the muscles and skin, they are
most abundant in the palpebral conjunctiva, in which they chiefly enter
the jJapili'-v, and in the next place in the lachrymal glands and the
caruncula lachrymalis. The sclerotic conjunctiva also contains numerous
vessels, and the Meibomian glands within the tarsi are also surrounded
by a few. Except in the skin of the eyelids, lymphatics have only been
demonstrated by Arnold in the conjuyictiva sclerotica;, where they form,
at the border of the cornea, a closer, and more externally a looser
plexus, passing outwards in several small trunks. The palpebrce and
conjunctiva are everywhere well supplied with nerves, but their rela-
tions have been minutely examined only in the conjunctiva. In this
membrane, in Man, I have found terminal plexuses as in the external
integument, with numerous divisions of fibres, 0-001-0-006 of a line
thick, extending up to the margin of the cornea, together with pretty
clear indications of loops and free terminations. Besides which, in one
instance, there were presented, towards the palpebral conjunctiva, pecu-
liar " nerve-coils," 0-02-0'028 of a line in size, into which a single
nerve-fibre usually entered, whilst 2-4 were given off from it [vid. " Mik.
Anat." II. 1, p. 31, Fig. 13, A, 3). The relations of the nerves of the
lachrymal apparatus are entirely unknown.

§ 231. Physiological remarks. — The eyeball is not developed from a
single point as a whole, but arises from the conjunction of formations,
proceeding on one side from the central nervous system, on another from
the skin, and, thirdly, from the parts lying between the two. In the
Chick, the 'primitive ocular vesicles arise before the commencement of
the second day, from the primitive cerebral vesicle or the anterior cere-
brum, in the form of two protrusions, at first sessile, but afterwards
having a hollow peduncle — the rudiment of the optic nerve. At the

THE EYE. 761

beginning of the third day, the formation of tlie Jens commences, from
the skin of the face covering these vesicles, by the thickening on the
inner aspect, and inversion of the epidermis, in consequence of which
the anterior wall of the primitive ocular vesicle is also inverted, and
becomes applied to the posterior wall, so that the cavity of the vesicle
is wholly obliterated. Now, at first, this secondare/ ocular vesicle
encompasses the lens, which in the mean time has been separated by
constriction from the epidermis, and comes into exact apposition with it
beneath, like a cup ; subsequently, however, the vitreous hod)/ is developed
between the two, in a special new cavity. How the latter is formed has
not yet been ascertained, although, as Schciler observes, it is most pro-
bable that it also grows in from the skin, — in fact, from the region
below and behind the lens, — and participates with the latter in the
inversion of the primitive ocular vesicle. According to E,emak, the
retina is formed from the inner, thicker wall of the inverted or second-
ary ocular vesicle, and from the outer and thinner, the clioroid, from
the anterior border of which the iris is not produced till afterwards.
The sclerotic and cornea are applied from without upon the eyeball
thus constituted, the former being to some extent a production of the
skin.

An interesting phenomenon is presented in the vessels existing in the
foetal eye, even in the transparent media. The vitreous body, on its
outer surface, between the hyaloid membrane and the retina, presents a
tolerably wide-meshed vascular plexus, which is supplied by branches
of the arteria centralis retince, given oflF from it at its entrance into the
eye, and anteriorly, at the border of the lens on the zoyiula Zinnii,
forms a vascular circle, the circulus arteriosus Mascagnii, from which
again vessels are given off to the memhrana capsulo-pupillaris, pre-
sently to be described. Besides this, a special arteria liyaloidea, also
derived from the central artery of the retina, runs in the so-termed
canalis hyaloideus, in a straight line through the vitreous body, to the
lens, and ramifies in the most elegant arborescent manner, at very acute
angles, in a membrane closely applied to the posterior wall of the len-
ticular capsule. This is nothing else than a portion of an external vas-
cular capsule, which at first very closely surrounds the lens, and in its
anterior wall is supplied by the continuations of the hyaloid artery,
coming round the border of the lens towards the front, with which
branches of the circulus arteriosus Mascagnii and of the anterior
border of the uvea are connected. Afterwards, when the lens retreats
from the cornea, with which it is, at first, in close apposition, and the
iris buds out from the border of the uvea, the anterior wall of the vas-
cular lenticular capsule is divided into two portions : one central and
anterior, which, arising from the border of the iris, and connected with
that membrane by vessels, closes the pupil — the memhrana pupillaris ;

762 SPECIAL HISTOLOGY.

and another, external and posterior, extending backwards from the
same points upon the border of the lejis — the memhrana capsulo-pupil-
aris. The latter becomes more and more distinct as the lens and
aqueous chambers are developed and the lens retreats, until at last it
represents a delicate membrane stretching across the posterior chamber.
The venous blood from all these parts is returned through the veins of
the iris, and from the outer surface of the vitreous body, also through
those of the retina, and perhaps through a vena hyaloidea, said to take
the same course as the artery, but of the existence of which many
authors doubt, and which I have never myself seen. With respect to
the genetic import of the vascular capsule, nothing has as yet been
ascertained. I find it to be composed of a homogeneous tissue, with a
few scattered cells, and regard it as a structure corresponding to the
cutis, which, in the formation of the lens, is detached from the skin,
together with a portion of the epidermis, and remains in the eye. The
vitreous body, then, may be understood as modified subcutaneous con-
nective tissue, — a supposition not at all incongruous with the observations
above adduced, and the more so, because, as I have shown (§ 24), all
the subcutaneous connective tissue of the foetus is at one time perfectly
gelatinous, and, like the enamel organ which also belongs to the same
tissue in specie, strikingly resembles the vitreous body in aspect and
consistence.

Concerning the histological development of the eyes, the following
only need be remarked. At an early period they consist in all their
parts of formative cells of uniform size, which, in process of time, are
metamorphosed into the various tissues. In the fibrous coat, in the
second and third month, the cells are developed, in the mode already
described (§ 24), into connective tissue, and at the same time the dis-
tinction is set up between the cornea and sclerotic, which are at first,
externally, exactly alike, and constitute only a single membrane. In
the uvea the cells are for the most part employed in the formation of
vessels ; another portion goes to the formation of the inner and outer
pigment-layers, pigment-granules being deposited in them at the com-
mencement of the third month, whilst another is transformed into
muscles, nerves, the epithelia and connective tissue of these membranes.
The development of the nerve-cells and of the so-termed " granules"
from embryonic cells, may be readily traced. I have observed the
same thing also with respect to the "cones;" and I think that, in the
Frog, it may be assumed with respect to the " rods" likewise, that they
are nothing but elongated cells ; whilst in the Mammalia, the formation
of the "rods," and of the nerve-fibres themselves, has not yet been
traced. The lens, lastly, is originally composed entirely of cells,
which, in course of time, are transformed into the tubes. The precise
nature of the processes attending these changes has not yet been

THE EYE. . 763

investlfrated, althoiiirh I ao;vee -with II. Mover in the conclusion, that
since the tubes, both in the foetus and child, present only a single
n2(ch'us, each of them is developed out of a single cell. These nuclei
taken as a whole, constitute a thin layer, extending from the borders of
the lens, through the middle of its anterior half, and slightly convex in
front (" nuclear zone," Meyer) ; the nuclei being smaller in the interior
portions, and as it were in progress of solution, whence it may cer-
tainly be concluded that the lens increases by the apposition of thin
layers from without. The formative cells of the tubes of the lens are
those which exist on the anterior half of the capsule and the starting
point of the formation of the lenticular elements, according to my
observation, is the entire anterior surface and the border of the organ-
Nuclei are visible in the tubes even in the lens of the adult, as was
known to Harting, though only at its margin.

With respect to the vessels of the foetal eye, Dr. Thiersch has quite
recently communicated to me a mass of interesting details, accomi>anied
by beautiful injections, to which I shall refer in the concluding part of
my "Microscopical Anatomy."

Investigation of the visual organ. — The fibrous tunic of the eye
should be examined in the recent condition, and in moistened sections
of dried preparations, which latter, especially of the cornea and at its
point of transition into the sclerotica, aiford very useful information.
If, after the removal of the vitreous body and lens, the iris and choroid
are dried, their connection with each other and with the fibrous tissue may
be studied. In order to view the nerves and vessels of the cornea, the
latter is removed by a circular section in the recent eye, together with
the margin of the sclerotic, the whole is divided into three or four seg-
ments, which, in order that they may lie the better, have little incisions
made into them around the edge, are moistened with the aqueous
humor, and covered with a thin plate. The nervous trunks, which are
here usually opaque, are then sought for at the border of the cornea, first
with a low power, and afterwards traced under a higher. The nerves
are beautifully displayed in the eye of the Rabbit, where I can perceive
their trunks with the naked eye, though they may usually be readily
found in other eyes also, but are always traced with difficulty towards
the centre. If the epithelium is cloudy, it must be removed by caustic
soda, which at first does not affect the nerves. The vessels under these
circumstances are usually full of blood, and consequently present no
difficulties. The corneal epithelium is visible on the surface in sections
of dried preparations, and is very well shown when the surface is
scraped. The "membrane of Demours" is very distinct in sections,
and frequently its epithelium also ; otherwise the latter is well seen on
the surface, and in detached shreds of the membrane. The passage of
this membrane into the ligamentum pectinatum of the iris, may be seen

764 SPECIAL HISTOLOGY.

in sections, and by careful dissection. In the latter case, the inner
wall of the "canal of Schlemm" should be carefully removed, together
with the iris and choroid, and an attempt made to raise from it portions
of the membrana Dernoursiana, which is not unfrequently successful.
The uvea ofters no difficulty. The pigment-cells of the stronia, with
their processes, and the inner pigment are readily seen ; the latter at
the margin of folds, and in carefully detached portions. For the inves-
tigation of the ciliary muscle, a fresh eye is requisite, as its elements
very soon become unrecognizable. The muscles of the iris should be
studied in a blue eye, and best in that of a child, after removal of the
posterior pigment ; and also in the eye of a white Rabbit, in which the
sphincter pupiUos may be readily seen without farther trouble on the
application of acetic acid. The same preparation should be employed
in order to examine the nerves of the iris, but a perfectly fresh eye and
a dilute solution of soda are indispensable. The retina should be
examined in the recent state, on the surface, in vertical sections, and at
the edges of folds, moistened with aqueous humor, and without any
covering glass ; and also with the aid of slight compression, and by the
teasing out of the tissue. Chromic acid preparations are very impor-
tant in the study of this structure. This reagent, it is true, affects the
"rods" to some extent, but preserves the other 'parts so much the
better, and without its aid Mliller and I should never have arrived at
the results above stated, although Hannover, on account of its influence
upon the "rods," erroneously considered it an unfit agent to employ.
The most advantageous mode of applying it, is to treat a fresh retina
at once Avith chromic acid, and to trace all the stages of its effect step
by step. If the solution be much diluted, the elements are very little
changed, and in particular may be easily isolated ; and if more con-
centrated, sections through the retina may be prepared, without which
no complete view of the structure of that tunic can be arrived at. I
apply it by extending a portion of the retina upon an object-bearer,
with a little chromic acid, in such a way that it should lie flat and not
float. Extremely fine slices may then be taken by a sharp convex
scalpel or razor from any sectional surface, by pressing downwards,
which, with a little pains, may be done easily enough. It is as well,
however, to guide the cutting scalpel by the handle of another held in
the other hand, until the edge of the former is brought immediately
over the border of the retina. When the nervous layers, which are
very well defined from each other, have been studied in sections of this
kind, which should be taken especially from the neighborhood of the
macula lutea, as well as from other situations in the transverse and
longitudinal directions, and which when useful necessarily exhibit only
a few layers of the elements, they may be carefully teased out or ren-
dered more transparent by soda, which last, however, is not generally
of much use, since it makes the elements pale. The hyaloid membrane

THE EYE. 765

is posteriorly always very readily detached from the retina, together
■with the vitreous body, and may be recognized in every eye, in sections
from the surface of that body, examined under the microscope, and, in
folds, occasionally by the naked eye. The zonula Zinnii, on the other
hand, in the recent eye, is always so covered by detached pigment and
the colorless epithelium of the ciliary processes, and at its posterior
border by the retina, that it cannot well be recognized in that situation,
and almost only in its free, most anterior portion. In such prepara-
tions, also, after the removal to the greatest possible extent of the
adherent parts by means of a hair pencil, pretty good views of it may
be obtained, particularly if, in addition to the viewing of the external
and internal surface of segments of the zonula detached from the
vitreous body, and of preparations made by the teasing out of the
structures, the borders of folds, especially of the inner surface, are
also examined, which, with some care, may be obtained to the whole
extent of the zonula, and of its points of connection with the retina.
The zonula, in connection with the hyaloid membrane, is very beauti-
fully and distinctly isolated from the retina and the cells of the ciliary
processes, in half-putrid eyes, and in macerated preparations of the
vitreous body ; and preparations of this kind are especially adapted to
show that the zonula is a part of the hyaloid membrane, as well as the
mode of origin and course of its fibres. For the study of the zonular
fibres I can also particularly recommend chromic acid preparations, in
which they become quite opaque and glistening, almost like elastic
fibres. The capsule of the lens and its epithelium present no difiicul-
ties. The tubes of the lens, when fresh, are very transparent, but in
dilute chromic acid they are rendered quite distinct. Sections of the
lens may be easily procured from preparations made in alcohol, or
chromic acid, or from dried and hardened preparations, which may be
rendered transparent again by means of acetic acid. The accessory
organs of the eyes require no particular remark, unless, with respect
to the Meibomian glands, it may be stated, that they are best seen in
tarsi which have been cleanly dissected and treated with acetic acid and
alkalies, and in longitudinal and transverse sections of similar prepara-
tions, dried.

Literature. — The "Eye" as a whole: Valentin, in his "Report.,"
1836 and 1837, and " Handw. d. Physiol.," I. p. 748 ; S. Pappenheim,
" Gewebelehre d. Auges," Berlin, 18-12 ; E. Brlicke, " Anat. Beschreib,
d. menschlichen Augapfels," Berlin, 1847; W. Bowman, "Lectures on
the parts concerned in the operations on the eye and on the structure of
the Retina and A''itreous Humor," London, 1849 ; A. Hannover, " Bidrag
til Ojets Anatomic, Physiologic og Pathologic," Copenhagen, 1850. Scle-
rotica: M. Erdl, "Disquisit. anat. de oculo," I. " De m. sclerotica,"

766 SPECIAL HISTOLOGY.

Monach., 1839 ; Bochdalek, " Ueber dieNervender Sclerotica^" in "Prag.
Viertelj.," 1849, IV., 119. Cornea: Kcilliker, "Ueber die Nerven
der Hornhaut," in "Mitth. d. naturf." Ges., in ZUrich, 1848, No. 19;
Rahn, " Ueber die Nerven der Hornhaut," in " Mitth. d. naturf.," Ges.,
in Zurich, 1850, No. 45 ; Luschka, " Die Nerven der durchsichtigen
Augenhaut," in " Zeitsch. f. rat. Med.," X., p. 20, and "Die Structur
der serosen Haute des Auges," in " Str. d. serosen Haute," Tubingen,
1851 ; Strube, "Der normale Bau der Cornea," Diss., Wurzburg, 1851.
Choroid and Iris : C. Krause, " Ueber die Pigmenthaut," in MUller's
"Arch.," 1837, p. 33 ; E. Briicke, "Ueber den 3Iusc. cramptonianus
u. d. Spannrauskel der Ghorioidea" in Miill. "Archiv.," 1846; Boch-
dalek, "Beitriige zur Anatomie des Auges," "Prag. Viertelj.," 1850,
I. Retina: G. Treviranus, "Ueber den Bau der Netzhaut," in his
"Beitragen," Bremen, 1835 and 1837; C. M. Gottsche, " Ueber d.
Nervenausbreitung d. Retina" in PfafF's " Mittheil. a. d. Geb. d. Med.,"
1846 [and " Ueber die Retina im Auge der Gratenfische," in Miill.
"Archiv," 1835, p. 457]; A. Michaelis, in Miiller's "Archiv," 1837,
p. 12, and "N. Acta," T. XIX., 1842; B. Langenbeck, " De retina
observat.," Gott., 1836 ; R. Reinak, " Zur mikrosk. Anatoraie der Re-
tina" in Miill. "Archiv," 1839; B. Lersch, " De retinae struct,
microsc," Berolini, 1840; A. Burow, "Ueber den Bau der macula
hitea" in Miill. "Archiv," 1840; F. Bidder, "Zur Anatomie der
Retina" in MUller's "Archiv," 1839 and 1841 ; R. Hannover, "Ueber
die Netzhaut," in MUller's "Archiv," 1840 and 1843, and "Reclierches
microsc. sur le syst. nerveux," Copenh,, 1844; E. Brixcke, " Ueber die
physiologische Bedeutung der stabformigen Korper," in MUller's
"Archiv," 1844, p. 444, and " Anat. Untersuchung Uber die sog. leuch-
tendcn Augen," ibid., 1845, p. 337 ; F. Pacini, ^' Sulla tessitura intima
della retina," in "Nuovi Annali delle scicnze naturali di Bologna,"
1845; H. MUUer, "Zur Histologic des Netzhaut," in "Zeitsch. fur
wissenschaft. Zool.," 1851, p. 234; Corti, " Beitrag zur xVnatomie der
Retina," in MUller's "Archiv," 1850, p. 274. [A. Kcilliker, "Zur
Anatomie und Physiologic der Retina," in " Verhandl, d. WUrzb.
phys. mod., Ges." Bd. III., p. 216; H. MUller, " Bemerkungen
liber den Bau n. die Funktion der Retina," ib., Bd. III., p. 336, and
Bd. IV., p. 96 ; also conjointly with Kcilliker, in " Verhandl. d.
WUrzb. phys. med. Ges.," p. 3, Bands. III. and IV., and in " Comptes
rendus de 1' Academic des Sciences," tom. XXXVII., No. 13,
Sept. 1853; A. Hannover, "Zur. Anatomie und Physiologie der Re-
tina," in "Zeitsch. f. Aviss. Zool.," Bd. X., p. 17, 1853.— Ed.]
Vitreous body: E. BrUcke, " Ueber den innern Bau des Glaskorpers,"
in Mull. "Archiv," 1843, p. 345, and 1845, p. 130; Hannover, " Ent-
deckung des Baues des Glaskorpers," in MUller's "Archiv," 1845, p.
467 ; W. Bowman (op. cit.), and in " Dublin Quarterly Journal," Aug.

THE EAR. 767

1845, p. 102; Vircliow, "Notiz liber den Glaskorpcr," in " Arcli. f.
path. Anatomic," IV., p. 468 [and V. 2, p. 298], and in " Verb. d.
WiJrzb. pbys. med.," Gesellsch., II., p. 317. Lens : W. Werneck,
" Mikr. Betracht. der Wasserbaut u. dcs Linsensysteras," in Amnion's
" Zeitscb.," Bd. IV. and V. ; R. Hannover, " Beobacbtungen iiber den
Ban der Linsc," in Mlill. "Arcbiv," 1845, p. 478; Ilarting, " His-
tolog. Anteekennigen," 1846, pp. 1-7, and " Rechercb. micromdtriques."
Development of the Eye : II. Scboler, " De oculi evolutione," Mitav.,
1849, Diss. ; Remak, in bis largo work, " Uebcr Entwicklungsge-
schicbte," 1850-51; Gray, "On the development of the retina and the
optic nerve," in "Phil. Trans.," I., 1850; Henle, "De raembr. pupil-
lari," Bonn., 1832; Reich, " De membr. pupillari," Berolini, 1833; J.
Muller, also Arnold, and Ilenle, on the "M. capsulo-pupill.," in Am-
mon's "Zeitscb.," II., p. 391, III., p. 37, IV., pp. 23 and 28. Besides
which, see Arnold, " Org. sensuum."

II.— OF THE ORGAN OF HEARING.

§ 232. The auditory organ consists of the proper sentient parts vf'ith.
the expansion of the acoustic nerve, which are contained in the osseous
substance of the labyrinth ; and of special accessory apparatus, the
external and middle ear, intended chiefly for the reception and conduc-
tion of the undulations of sound.

§ 233. External and middle ear. — The auricle [pinna) and the car-
tilaginous external auditory canal, are supported by the cartilage of the
ear {cartilago anris), \-\ line thick, and while retaining the thick
pericliondrium very flexible, but otherwise extremely brittle, and the
form of which is well known. This cartilage.^ in its more intimate struc-
ture, approaches the yellow or reticular cai'tilages, though it is distin-
guished by a considerable preponderance of cartilage-cells, O'Ol of a
line in diameter, •in the striated viatrix. It is covered by the external
integument, which, except in the lobule, contains no fat and on the con-
cave side of the auricle is closely adherent to the cartilage, where it is
characterized by a great abundance of glands. These are, in the first
place, common sebaceous follicles, which are most developed in the concha
and fossa scaphoidea, where they attain the diameter of ^-1 line ;
secondly, minute sudoriparous glands of 1-16 of a line on the convex
side of the pinna ; and, lastly, the ceruminous glands, already described
(§ 71, 72), in the cartilaginous, external auditory canal itself. In
the latter, the cutis measures 1-5-1-8 of a line in thickness, without the
epidermis, which is 1-75-1-50 of a line thick ; and presents, besides the
glandulce cerwninosce, hairs and sebaceous follicles in a dense subcu-
taneous tissue, whilst in the osseous part of the passage it is very thin,

768 SPECIAL HISTOLOGY.

contains no organs of any kind, and is blended very intimately with the
periosteum of the canal.

The middle eay\ in all its cavities, together with the ossicles, tendons,
and nerves contained in it, is lined with a delicate mucous membrane,
which, in the mastoid cells and on the ossicula audiMs, where it also
forms the inemh. ohturatoria stapedis, and on the memhrana tympani,
is still more delicate than in the accessory sinuses of the nose, being
thickest in the Eustachian tube. In the latter situation, its epithelium
is of the squamose, ciliated kind, 0-024 of a line thick, whilst in the
tympanic cavity it is changed into a thin, tessellated epitJieliiim, com-
posed of one or two layers, extending as far as the accessory cavities.
The memhraiia ti/mpani, which, according to Todd and Bowman, is
furnished with a ciliated ejntheliimi, consists of a middle fibrous plate,
which, at the sulcus tympanicus, in connection Avith the p)eriosteum of
the cavity of the tympcmu7n and of the osseous meatus and with the
€2itis lining the latter, commences in a dense tract of chiefly annular
fibres — the so-termed annulus cartilagineus, — and further inwards is
composed principally of slender radiating fasciculi converging towards
the centre, where the handle of the malleus is inserted into this mem-
brane, and in part reticulated, with undeveloped fine elastic fibres
(" connective tissue corpuscles," Virchow). Externally, this membrane
is covered by a delicate continuation of the epidermis of the external
meatus, and internally is lined by a fine investment of the mucous mem-
brane of the tympanum.

The ossicula auditus are composed principally of spongy osseous sub-
stance, with a thin compact cortex; and their articulations and liga-
ments resemble, in miniature, those of other similar organs in all re-
spe-cts, even down to the cartilaginous layer, consisting of scarcely more
than a single stratum. Their muscles, like those of the external ear,
are transversely striped. The Eustachian tube has in part, as a foun-
dation, cartilage which in structure approaches the true cartilages ;
usually, however, presenting a pale, fibrous matrix ; and containing, in
the cartilaginous portion, especially towards the aperture, numerous
racemose mucous glands, of precisely the same conformation as those
of the pharynx, in the mucous membrane of which organ that of the
Eustachian tube is imperceptibly lost. The external ear is supplied
with vessels and nerves, in the same manner as the external integuments.
In the middle ear, the mucous membrane, especially of the walls of the
tympanum, is highly vascular, as is also the Eustachian tube and the
memhrana tympani, in which latter the largest arteries and veins run
along the manubrium of the malleus in the middle coat, constituting
arterial and venous circles around the periphery of the membrane, and
also ramifying abundantly in the mucous membrane. The nerves are
derived principally from the ninth and fifth pairs, and upon the whole

THE EAR. 769

are scantily distributed in the mucous membrane and memhrana tympani.
With their terminations we are unacquainted, -whilst it is known that
the tympanic nerve contains numerous large ganglion-cells, either
isolated or aggregated into small ganglia.

§ 234. The inner surface of the vestibule and of the osseous semicir-
cular canals is lined by an extremely thin periosteum^ consisting of a
rigid, finely-fibrous connective tissue, without elastic fibres, but with nu-
merous nuclei and in many respects resembling the forms of fibre met
with in the inner wall of the "canal of Schlemm" in the eye. On the
surface of this p)eriosteum rests a tessellated epithelium in a single layer,
with delicate, polygonal, nucleated cells of 0-007-0-009 of a line, which,
as well as its certainly not very numerous vessels, stands in relation to
the perihjmp)ha s. aqua Cotunni, filling the osseous labyrinth. By the
conjunction of the periosteum of the labyrinth and the lining of the
tympanum, are produced the memhranoi tympani secundarice, which,
like the proper memhr. tympani, are composed of a middle fibrous layer
with vessels and scattered nervous filaments, and two epithelial layers.

The two sacculi and canals, contained in the interior of the vestibule
and of the osseous semicircular canals, all essentially present the same
structure. Their firm, transparent, and elastic
walls, which are tolerably thick in proportion to ^.^^s^^^ste^,^^

the minuteness of the parts (0-012-0-015 of a /^^^**''™''^^^^;-^
line in the canals, and 0'016 in the sacculi),
present, most externally, a membrane com-
posed of reticulated, fine fibres, approaching
very nearly to the outer colored layer of the

clwroid or the lamina fusea, like which it also occasionally contains irre-
gular brownish pigment-cells. This is succeeded, by a transparent,
glassy membrane, sharply defined, especially on the inner aspect, 0-004-
0*008 of a line thick, presenting in part a distinct, delicate, longitudinal
striation, and on the addition of acetic acid always exhibiting a multi-
tude of elongated nuclei, and which consequently cannot well be placed
in the same class with the memhrana; proprice, the capsule of the lens,
&c., although it very nearly approaches them in its chemical reactions.
The innermost layer, lastly, is a simple, readily disintegrated, tessellated
epithelium, 0'003 of a line, with sometimes larger, sometimes smaller
(0'004-0-008 of a line) polygonal cells, lining all the spaces in question,
and enclosing the so-termed endolymph. s. aquula vitrea auditiva, in
which, in Fishes, Barruel has ascertained the presence of mucus.

The vessels of the membranous labyrinth are tolerably numerous, and
are distributed in minute arteries and veins and abundant capillary net-

FlG. 308. — Transverse section of a semicircular canal, magnified 250 diameters: a, fibrous
membrane with nuclei; 6, homogeneous membrane; c, epithelium. From the Calf.

49

770 SPECIAL HISTOLOGY.

^YOl■ks, on the fibrous membrane and vitreous tunic of these parts, being
most abundant near the terminations of the nerves. Of these, we are
acquainted only with that of the acoustic nerve, which, with the nervus
vestibuli, supplies the three membranous canals and the elliptic sac-
culus, and, with a branch of the cochlear nerve, the round sacculus.
In the semicircular canals, the nerves are distributed only on the am-
2JuUce, and, indeed, enter each, as Steifensand has shown, in an inversion
or duplicature of the wall situated on the concave side of the canal,
which appears, viewed on the inside, as a transverse projection extend-
inir through about one-third of the circumference. Within these folds,
the nerves divide at first into two principal branches, which, diverging
towards both sides, penetrate into the vitreous membrane of the ampullce,
where each of them breaks up into a rich bundle of smaller, frequently
anastomosing ramuscules, which ultimately appear to terminate free, in
fine twigs, composed of from two to ten primitive fibres, 0-001-0-0015
of a line thick. In the saccuU, the distribution of the nerves is the
same, except that it occupies a larger space, and does not occur in a pro-
jection of the wall. In this situation, also, I think I have noticed free
prolongations of the attenuated nerves, although it may be very possible,
as Todd and Bowman point out, that they are continuous with very pale
fibres, in Avhich they ultimately terminate. In the situation of the ner-
vous expansion, we find, in each of the sacculi, a sharply defined spot,
as white as chalk, and readily seen by the naked eye, which is attached
to the inner wall of the sacculus by a perfectly clear membrane, 0-01 of
a line thick, and probably epithelial. These are the so-termed otoconia
of Breschet, or otolitJies, which are constituted of innumerable corpus-
cles, 0-0004-0-005 of a line long, and (in the largest) 0'001-0-002 of a
line broad, of a rounded or elongated form, or distinctly pointed at each
end, probably hexahedral prisms, suspended in a homogeneous substance.
They are composed of carbonate of lime, and are said to leave a resi-
duum of some organic matter ; but this I have not succeeded in observing.

§ 235. Cochlea. — The canal of the cocldea, filled by the fluid of the
labyrinth, is lined in both its scalm by a periosteum, here and there
presenting a small quantity of pigment, and which is constituted pre-
cisely like that of the vestibule, and also partially invests the lamina
spiralis ossea. An epithelium, 0*0005 of a line thick, with delicate,
flattened polygonal cells, 0 •007-0-009 of a line in size, covers this liga-
mentous membrane, and is also continued upon the lainina spiralis
memhranacea, where its nature is, to some extent, altered. The most
important part of the cochlea is the lamina spiralis, which, in its osseous
zone, contains narrow-meshed anastomosing canals for the reception of
the cochlear nerves, which canals, towards the free border of the lamina,
coalesce so as to form a fissure-like cavity and consequently, in this
situation, the osseous spiral lamina actually consists of two plates.

THE EAR.

71

§■•••

-^

C^..:

The membranous zone, liaving a constant widtli of 0-2 of a lino, is a2:ain
Fiir. G09. subdivided into a zona denticidata

and a zona 2Jectinata, the former
of which constitutes about the
inner two-thirds, and the latter
the outer third of the breadth of
the membranous lamina, and are
both characterized by a great
complexity of structure, the im-
portance of which was first, in
more recent times, pointed out
by Corti {I c.) {vid. Figs. 309,
310).

1. The zona denticulafa (d-v)
may be again subdivided into two
portions, an internal, the Iiaie-
nula interna s. sulcata (d-c/), and
an external, the habenula externa
s. denticulata (h-t). The former
is developed at d, as an immediate
continuation of the periosteum of
the lamina spiralis ossea, and, in
fact, only from that portion of it
which looks towards the scala
vestibuli, increasing in width and
thickness from the commence-
ment to the termination of the
cochlear canal. In the first and
second turns of the cocJdea, its
5; under surface supplies the place
of the 2)eriosteu7n upon the most
external portion of the osseous

8..

Fig. 309. — Vertical section of the lamina spiralis, at 6 lines from its commencement, mag-
nified about 225 diameters (Cat or Dog) ; the epithelial layer investing its upper and lower
surfaces is removed : a, periosteum of the osseous zone ; 6, the two lamelloe of the osseous
zone near its free border ; c, cf, c", termination of the auditory nerves ; d-iv, lamina spiralis
mcmbranacca ; d-w, zona denticulata; d-d'-f, habaiula sulcata; rf, place where the periosteum
is thickened ; e, granules in the groove of tlie habemda sulcata ; f-g, " teeth of the first series ;"
g-f-h, sulcus s. semicanalis spiralis ; /), its inferior wall : A;, epithelial cells at the entrance of
the sulcus spiralis; h-u/, habemda denticidata; h-m, apparent teeth ; «-.', " teeth of the second
series;"' /i-p, their posterior joint ; o, nucleated enlargement upon them; p-q and <;->•, articular
portions; r-t, anterior joint of the second row; s s s, three cylinder-cells, placed upon them;
/■r, membrane covering the Aatenw/a rfcn<i«/toa; i<, one of the epithelial cells underneath;
u/w, zona pectinata ; .r, periosteum, attaching the lamina spiralis (rmcsc. cochlears, Todd and
Bowman) ; y, vas spirale internum ; z, its inner coat. After Corti.

Fig. 310. — Vestibular surface of the lamina spiralis membranacea, magnified 225 diameters.
The letters are in part the same as in Fig. 309 : a a, cylindrical elevations of the habenula

772 SPECIAL HISTOLOGY.

zone, "vvliilst in the last half turn it is bounded only by the expansion of the
nerve, so that the liahenula sulcata, in the strict sense of the word, properly
constitutes, in this situation, only a part of the so-termed membranous
spiral lamina. On the upper surface of this layer, and on the outer border
of it, there is an uninterrupted series of clear, peculiarly glistening,
elongated, slightly clavate processes [g), the " teeth,'" as they are termed
"of the first series," which, in the first spiral turn of the cochlea, are
0-02 of a line long, 0-004-0-OOS of a line wide, and 0-003 of a line
thick, at their origin, whilst in the last turn they are not more than
0-015 of a line long and 0-003 of a line broad. They project, free,
into the scala vestihuli, and arch over the commencement of the hahenula
exteryia, so that between the two a tolerably deep sulcus, semicanalis
spiralis (Huschke), opening externally, is left. Towards the axis of
the cochlea the so termed "teeth" are directly continuous, with simi-
larly constituted, elongated ridges or costce (Fig. 309 a a), which are
occasionally conjoined in pairs, or divided into two, and still further
inwards break up into divisions, which become shorter and shorter and
smaller and smaller, being; at first elonsjated and afterwards rounded.
In the longitudinal and transverse grooves between these costa' and
tubercles and the teeth, there usually exists, in single series, rounded
or elongated, opaque glistening corpuscles (e), 0-0015-0-002-0-003 of
a line in size, which, on the addition of acetic acid, prove to be nuclei;
and by the same reagent, nucleiform strioi occasionally become distinct
in the pale and somewhat swollen " teeth " and costce, which parts,
consequently, as well as those presently to be described, I am inclined
to regard as belonging to the connective-tissue group.

The liahenula externa s. denticulata [h-t) arises under the base of the
"teeth" of the first series, directly from the just-described hahenula
sulcata, and constitutes at first the bottom of the spiral sulcus noticed
above. In most places its thickness does not amount to more than
0-001 of a line, which is also that of the rest of the membranous spiral
lamina, that is to say, of the zona pectinata, and its width increases
towards the cupola in proportion to the decreasing breadth of the hahe-
nula sulcata, so that it measures at first, not more than 0-05, and ulti-
mately, 0-1 of a line. With respect to its structure, it presents, on the
side of the scala vestihuli, a considerable number of elevations, whilst
towards the scala ti/Jiijjani it is perfectly smooth and even. These ele-
vations, proceeding from within to without, are as follow : — first, come
the so-termed "apparent teeth" ("dents apparents," Corti), a crowded

sulcata: /S, spot wliere a "tooth of the first series" originates; y, spaces between the "ap-
parent teeth;" J", anterior portion of a " tooth of the second series" thrown back; s, the same
in its natural position, without its epithelial cells; ^, the same with only tlie lowermost
epithelial cells; », the same with two of the lowermost cells; S-, streaks or slight elevations
of the zona jKclinata : k, periosteum, by which the lamina spiralis is attached, with spaces,
A, between the bundles. After Coiti.

THE EAR. 773

series of elongated projections, 0*08 of a line long, 0-002 of a line broad,
which, separated fiom each other by shallow grooves, are slightly raised
at the outer end, and then suddenly depressed. Externally to these
processes \vhich, in the first turn of the cochlea, are still situated on the
zona ossea, beneath the " teeth of the first series," and in that situation
present minute elongated holloAvs between their outer ends (Fig. 309, y),
but in the second and third turns are placed more externally than the
"teeth of the first series," being bounded on the under surface only by
the nerves, succeed in equal number the "teeth of the second series,"
(Corti) (n-t), very remarkable structures, of which the adjoining figure
will afford a better exposition than any description. Each of them
represents a little rod, somewhat compressed from above to below, and
lies free and mova4)le on the membranous spiral lamina, to which it is
affixed only by the inner extremity, as a continuation of which, there-
fore, these teeth must be regarded. Viewed more closely, each of them
presents three joints. The innermost (n-p), an attached joint, resem-
bles a cell of cylinder epithelimn, and contains in its somewhat dilated
internal extremity (o) a round nucleus, 0-005 of a line in size ; to this
succeed the middle joints {p, q, r) two equal, elongated, quadrangular
segments, 0-0044 of a line long, of the same homogeneous and glisten-
ing substance as that of which all these " teeth" in general are com-
posed (the coni artieulares of Corti), which are connected with each
other and with the internal and external joints, so as to allow the latter
a certain extent of motion up and down. The last joint, finally {r-t),
is at first attenuated, but towards the extremity again becomes wider
and bifurcate, and supports three nucleated segments attached to its
inner extremity, resembling pedunculated cells {s, s, s), one above the
other, the undermost being the longest, which may be termed " teeth
of the third series" (" cylinder epithelium-cells," Corti). The liahenula
denticiilata, as far as to the "teeth of the second series," is covered
by round or oval epithelium cells [h) which also occupy the spiral sulcus
below the " teeth of the first series," though lying free and separate in
immediate contiguity, and forming a continuous layer only on the ha-
oiuilus memhranaceus. Upon these cells and over the entire habenula
clenticulata, we then find a peculiar, thin, finely striated membrane {l-v),
which externally projects a little over the commencement of the zona
pectinata, though separated from it by some large epithelial cells {u),
and passing internally upon the habenula sulcata, where it is gradually
thinned and ultimately lost. This membrane, covered by the epithelium,
of the cochlear canal, can hardly be viewed as anything but a continua-
tion of the habenula sulcata, and may be most suitably compared with
the zona piectinata.

2. The zona pectinata (Todd and Bowman) [lu' -w), is the outer por-
tion of the membranous spiral lamina, smooth on both the upper and

774

SPECIAL HISTOLOGY.

Fig. 311.

under surfaces, and affixed at the outer side, on a projection of the
external wall of the cochlear canal. It is a perfectly homogeneous
lamella, hut, except at the herders, appears to he very closely rihhed,
and thence assumes a fibrous aspect. At its outer edge this lamina,
which seems to he opened out in a narrow horder, receives a peculiar'
fibrous substance {x) arising from the wall of the cochlea, which there
presents a minute osseous ridge (the lamina spiralis accessoria),
Huschke ; which Todd and Bowman describe as a cochlear muscle, but
in which I can perceive nothing but a form of nucleated connective
tissue, whence I shall term it the ligamentum spirale.

The nerves of the cochlea enter the cavities of the osseous zone from
the canal of the modiolus, and there form a close plexus of dark-
bordered fibres, 0-0015 of a line in diameter, throughout its whole
length, and which, as discovered by Corti, contains, at a very definite
spot not far from the border of the zone, an aggregation, at first, 0*1
of a line in width, of bipolar, oval, minute (0- 011-0-016 of a line long,
0 '0066-0-0097 of a line broad), and pale ganglion-cells, which it is very
probable intercept all the fibres of the cochlear nerves in their course.
The dark-bordered fibres proceeding from the external side of
these cells, are again disposed in anastomosing, and after-
wards in simply parallel, flattened bundles, which become
less and less close as they approach the hamulus, so that,
upon that process, the fibres may be perceived forming a sin-
gle layer, and even separated by interstices. The end of
these nerves, in all the parallel bundles and fibres, is always
in the same line, but in the first spiral turn will be found
nearer to the outer wall of the cochlea than it is higher up.
Besides this, there are terminations, also situated between
the two plates of the osseous zone, although exactly at its
border ; in the second turn, in an extent of 0*02-0-03 of a
line, and even outside it, on the under surface of the com-
mencement of the hahenula denticulata, consequently within
the scala tympani ; in the third half turn, lastly, they appear
in the form of a nervous border, 0-08-0-09 of a line broad,
also on the under surface of the hahenula sulcata. The
actual termination of the nerve-fibres which are reduced to
O'OOl of a line in diameter, appears to me, as well as to
Corti, to take place by their first becoming pale, and still finer, and
afterwards ceasing — and I must here express myself as decidedly
opposed to the notion of the existence of loops.*

Fig. 311. — Bipolar ganglion-globules from the zonula ossco of tlie lamina spiralis of the Pig,
magnified 350 diameters. After Corti.

• [More recent researches have induced Prof. Kcilliker to alter materially his views on
the termination of the cochlear nerve, and indeed of the structure of the cochlea itself. As
the result of careful investigations in the Ox, Cat, Pig, Rabbit, and in Man, he found that

THE EAK. 775

The vessels of the cocldea, though fine, are yet very numerous ; they
are distributer!, in the first place, to the parietal periosteum of the
cochlear canal, and secondly, to the lamina spiralis. In the former
situation, besides the capillary plexus, wnich is found throughout, they

the cochlear nervos do not terminate in the scala tympani, but tliat the fibres penetrate
through ojienings in the membranous himina spiralis into the scala vestibuli, where they
become attached to the " teeth of the second series." These latter as well as the peduncu-
lated cells they support, he now regards as a nervous apparatus constituting the true termi-
nations of the cochlear nerves, and, he adduces in proof of the correctness of this opinion
the following histological observations.

The membranous lamina spiralis, is not merely a continuation of the periosteum of the
vestibular surface of the osseous zone, but also of that of its tympanal surface. The first-
mentioned periosteal lamella forms the habcnula sulcata with its teeth and the commence-
ment of the habenula denticulata, and then unites externally to the " apparent teeth," and
the " teeth of the second series" with the other periosteal layer. This besides lining the
bone, extends bej'ond the edge of the osseous zone as a covering to the nerve-fibres, which
are thus, even after leaving the bone, enclosed between two layers of periosteum, and hence
do not, as stated by Corti, lie free in the scala tympani. Now in vertical sections of the
lamina spiralis, treated with chromic acid, the pale nerve-fibres may be traced running
towards the scala vestibuli, and perforating the habenula denticulata near the external
extremities of the " apparent teeth.' Exactly over the perforated portion of the habenula
denticulata (habcmda perforata) are seated the teeth of the second series, which may be
seen to be connected with the dark-bordered nerve-fibres, by means of delicate pale pro-
cesses.

The nervous nature of the " teeth of the second series" Kolliker states, becomes further
apparent by a micro-chemical analysis. Corti affirms them to be chemically similar to the
membranous lamina spiralis, but this Kolliker proves to be incorrect. He found them on
the contrary to correspond most closely to the dark-bordered nerve-fibres, and the processes
of the ganglion-cells. Caustic soda and potassa destroyed them almost immediately. The
addition of water produced in them two or three varicose enlargements, containing a fila-
ment precisely similar to an axis-cylinder. The nucleated swelling at their commencement
described by Corti, he regards as a bipolar ganglion globule, one process of which is con-
nected with the dark-bordered nerve-fibres, whilst the other supports three unipolar nerve-
cells (" three epithelial cells" of Corti).

Based upon these histological data, KOUiker advances some interesting and novel views
with regard to the physiology of the cochlea. The existence of tVie peculiar nervous appa-
ratus at the extremity of the cochlear nerves, renders it, he thinks, highly probable that this
is the only portion of the nerve which possesses the power of receiving sonorous undulations.
These undulations reach the cochlea through the fenestra ovalis, and are not communi-
cated, as most physiologists suppose, by the osseous lamina to the cochlear nerve, since the
latter lies free in the labyrinth and is unconnected with the osseous zone. The isolated po-
sition of the cochlear nerve, its movability and great softness, renders it, Kolliker further sur-
mises, specially applicable to receive the undulations transmitted by the lluitlof the labyrinth.
Regarding the special function of the cochlea, he is inclined to attribute to it a greater phy-
siological importance, than to any of the other parts of the labyrinth. The free position of
the expanded portion of the nerve, and the extent of surface over which its numerous
terminal fibres are spread, constitute it, he thinks, an organ of great delicacy of hearing,
enabling us to distinguish several sounds at once, and also to estimate accurately their
exact pitch. The ganglionic termination of the cochlear nerves, Kolliker concludes, esta-
blishes a surprising analogy between the auditory, and visual apparatus, since the sensory
nerves of both are possessed at their peripheral expansion of a ganglion, which receives the
impressions, the nerve-fibres merely serving to conduct them to the brain. [Vid. Kolliker,
"Ueber die Endigimgen des Nervus Cochlete und die Functions der Schnecke," Wurzburg,
1854.)— DaC]

776 SPECIAL UISTOLOGY.

constitute a peculiar vascular tract in the scala vestibuU, immediately
under the ligamentum sjnrale, — the st7'ia vascularis of Corti, and which
though continuous with the vessels of the periosteum, still lies ahove it,
imbedded, as it were, in the partially colored epitheliimi. In the zo7ia
spiralis, we find in the osseous portion, but also in the nervous expan-
sion itself, a rich capillary' plexus, continuous with a vas spirale running
on the under or vestibular surface of the zona memhranacea. throuich
the whole extent of the cochlea. This vessel, which is probably venous,
lies immediately under the hahenula denticulata, sometimes more
towards the interior, sometimes more externally, becoming, in the last
half turn of the cocJtlea, a capillary vessel of not more than 0*004 of
a line in diameter ; but towards the base, it gradually enlarges to
0-013 of a line, and is distinctly composed of two coats. In rare
instances, there are two capillary vasa spirala in the situation above
indicated, and on two occasions, in Man and in the Sheep, Corti
also noticed an external vas spirale, near the ligamentum spirale on
the zona pectinata, which, however, did not communicate with the
internal vessels, so that, speaking generally, the zona p)eetinata is
non-vascular.

Lastly, Ave have to consider the acoustic nerve. The fibres of its
trunk, in Man, measure 0-002-0-005 of a line, are very readily de-
stroyed, and have only a delicate neurilemma. Among these, in the
trunk itself and in the vestibular and cochlear nerves, there occur nu-
merous bipolar, apolar, and unipolar, pale and colored ganglion-cells,
measuring, in the Mammalia and in Man, 0-02-0"07 of a line, of which
the two latter forms are, as Stannius correctly observes, probably only
truncated bipolar cells, inasmuch as, particularly in Fishes, the acoustic
nerve contains cells of this kind only or nearly so. Similar cells, but
smaller, are also met with, as already mentioned, in the cochlea, as well
as in the nervous twigs in the vestibule (Pappenheim, Corti). Divisions
of the fibres of the auditory nerve Avere noticed by Czermdk in the
ultimate ramifications in the arnpullcs and sacculus of the Sturgeon, by
myself and Harless in the Frog, and by Leydig in the Chima^ra.

Of the developiment of the auditory organ, it need here merely be
mentioned, that according to Huschke's discovery, confirmed by Reiss-
ner and Remak, the membranous portions of the labyrinth are formed
from the external integument, simply by its inversion, and consequently
in their origin may be compared with the lens and vitreous body. To
this inversion, in which the cellular layers corresponding to the epider-
mis, principally, but not alone, as Remak believes, take part, the audi-
tory nerves are afterwards continued from the brain ; and from the
middle germinal layer are afi'orded the hard tissues and the rest of the
soft parts in order to complete the sentient organ. With respect to the

THE EAK. 777

histological development of tbe soft parts of the labyrinth, nothing of
consequence is known.

In the description of the cocJilea, I have altogether followed Corti,
having formerly satisfied myself of the correctness of his statements,
when that zealous and intelligent observer pursued his investigations in
Wurzburg ; and having also, recently, confirmed the greater part of
them by the examination of the human cochlea. At the same time the
parts of the hcibenula dcnticulata, which are so difiicult of investigation,
have always appeared to me to demand further consideration, and par-
ticularly with respect to the ascertaining of the kind and mode of the
movements of its processes, the relations of the epithelium, and of the
investing, structureless membrane. So long as these points are not as-
certained, all suppositions respecting the function of these delicate
structures are without any secure basis, and the physiology of the
cochlea, otherwise so difficult, is rendered only still more perplexed
[vid. Harless, 1. c). As regards the nature of the so-termed '' teeth,"
they are certainly, as Corti assumes, nothing more than developments
of the periosteum of the cochlear canal, and may, in my opinion,
although in chemical respects very similar to the vitreous membranes,
yet be regarded as belonging to the connective-tissue group. Whether
the three so-termed cylinder epithelium-cells (Corti) on the hahenida
denticidata are really epithelial, as Corti supposes, still demands inves-
tigation. These bodies, notwithstanding their great delicacy, appear
to me rather to be referable to the category of the other tissues of the
hahenida denticulata; and on that account I have termed them "teeth
of the third series."*

For the investigation of this organ, which, however, presents any
very considerable difficulties only in the labyrinth, perfectly fresh objects
are indispensable, and are best taken from animals just killed. For the
moistening of them, serum or syrup should be employed, when it is de-
sirable to view the parts in a perfectly normal condition. Successful
results will be obtained, especially if a certain amount of practice, in
the exposing and dissection of the delicate tissues with which we have
to do, be combined Avith great patience, seeing that it is often a matter
of chance whether any given relations are brought into view. In order
to see the nervous plexus of the osseous zone of the cochlea, the latter
must be deprived of its calcareous constituents by dilute muriatic acid;
whilst in the case of the ganglion-cells in that situation, the only means
of attaining our object consists in a careful breaking down of the osseous
zone in a neutral medium.

* {Vid. Note p. 775.— DaC]

778 SPECIAL HISTOLOGY.

) 5

Literature.— E. Husclike, in "Fror. Not.," 1832, No. 707; "Iris
1833, No. 18, 34 ; K. Steifensand, " Untersuchungen liber die Ampullen
des Geliororgans," in Mliller's " Arcliiv," 1835; S. Pappenheim, "Die
specielle Gewebelehre des Gehcirorgans," Breslau, 1840, and Froriep's
"Not.," 1838, Nos. 141, 194, and 195 ; G. Breschet, " Recherches sur
I'organe de I'ouie dans Thomme et les animaux vert(^br^s," 2d ed. Paris,
1840 ; E. Krieger, " De otolithis," Berol. 1840 ; Wharton Jones, " The
Organ of Hearing," in Todd's " Cjclopsedia," Vol. II. p. 529; J. Hyrtl,
"Ueber das innere Gehororgan des Menschen und der Siiugethiere,"
Prag., 1845 ; A. Corti, " Recherches sur I'organe de I'ouie des mam-
miferes," in Zeitsch., f. wiss. Zool. III., p. 109; Reissner, " De auris
interna) formatione," Dorpat, 1851; E. Harless, Art. " Horen," in
Wagner's "Handw. der Pliysiol." IV., p. 311, and " Munchn. GeL An-
zeiger," 1851, No. 31 and 37; Stannius, "Ueber die gangliose Natur
des Nervus acusticus," in Gcitt. Nachr., 1850, No. 16; lb., 1851, No.
17 ; [A. Kolliker, " Ueber die letzten Endigungen des Nervus CochleJB
und die Function der Schnecke," Wiirzburg, 1854. — DaC] Besides
which should be consulted the general works of Krause, Huschke, Ar-
nold, Todd and Bowman, Remak (Entwicklungsgeschichte), and the
'■'' Icones org. sensuum," of Arnold.

HI.— OF THE OLFACTORY ORGAN.

§ 236. The olfactory organ consists of the two nasal cavities, or fossce,
supported by bones and cartilages, and lined by a mucous membrane,
and of a certain number of accessory cavities, viz., the frontal, sphe-
noidal, and ethmoidal sitiuses and the antrum Highmori. Of all these
cavities, however, only the uppermost portions of the nasal fossiB, where
the olfactory nerve is distributed, are subservient to the sense of smell
itself, the others being either simple conducting canals, and participating
as well in the action of respiration, or at any rate having no direct rela-
tion to the olfactory sense.

The hard structures, just named, present nothing much worthy of
remark ; and of the bones it need merely be mentioned, that the thin-
nest parts of the ethmoid consist only of a fundamental substance and
bone-fibres, without any Haversian canals. The nasal cartilages are
true cartilages, and most nearly approach those of the larynx, except
that the contents of the cartilage-cells are usually very pale, and with-
out fat, the cell-walls little thickened, and the matrix finely granular.
Beneath the perichondrium there is, also in this situation, a layer of flat-
tened cells, which, on the septum attains a thickness of 0*024 of a line,
whilst in the interior the cells are more rounded, larger, and disposed in
rows, in the direction of the thickness of the septum.

With respect to the coverings of these parts, the integument of the
nose may be first noticed : it is characterized by a thin epidermis

THE NOSE. 779

0-024-0-032 of a line thick, a dense cutis of 1-4 with minute unde-
veloped impillce of 1-40-1-66 of a line, and fine hairs, as well as by a
close adipose tissue 1 line thick, intimately united with the cartilage,
containing large sebaceous follicles, extending into the latter, and minute
sudoriparous glands 1-10-1-12 of a line in diameter. This external
integument, with its sebaceous follicles, and with stronger hairs {vibrissce)
also extends a short distance into the nasal /osste, but not quite so far as
the point where the cartilaginous portion of the nose terminates, passing
imperceptibly into the mucous membrane of the olfactory organ, by
which all the remaining cavities are lined, though it does not everywhere
present the same conditions. As was discovered by Todd and Bowman,
and I can fully confirm, this mucous membrane is subdivided into a ciU-
atccl and a non-ciliated portion, the latter being limited to the uppermost
parts of the nasal fosscc, where the olfactory nerve is distributed, and
consequently should perhaps be termed the olfactory mucous membrane
in the stricter sense, whilst the other might retain the old name of
" Schneiderian membrane."

Upon first viewing the latter, it will be found that, although the epi-
thelium vibrates throughout, still that its structure is not everywhere
the same, and that we may conveniently distinguish in it the thicker
glandular mucous membrane of the proper nasal /ossfc from the thinner
membrane of the accessory sinuses, and of the interior of the spongy
bones. The epithelium^ in both situations, is squamose and ciliated, like
that of the larynx (Fig. 311^), measuring, in some places, 0-018-0-020
of a line in thickness, and in others as much as 0-042 of a line. In
Man it presents pale, fine-granular cells, of which the outermost ciliated
ones attain a length of 0*03 of a line, and in animals produce a current
running from before to behind. To this succeeds, a true m. mucosa,
wholly without elastic elements, or at all events very scantily supplied
with them, and composed chiefly of common connective tissue. In the
proper nasal fossce there are imbedded in this membrane very nume-
rous larger and smaller, racemose mucous glands of the usual kind,
with gland vesicles of 0*02-0-04 of a line, so that, in places, especially
at the borders of the septal cartilage, and on the inferior spongy bones,
it presents a thickness of 1-2 lines. The thickness of the mucous mem-
brane of these regions, however, does not depend upon the glands alone,
but also, especially at the border and posterior extremity of the inferior
spongy bone, upon abundant, almost cavernous venous plexuses in its
interior. In the accessory cavities, the glands are almost wholly want-
ing, and I have as yet only occasionally found them in the antrum High-
mori, where their excretory ducts and gland-vesicles are sometimes dilated
into cysts containing mucus, ^ a line in diameter. Except in these places,
the mucous membrane of the accessory cavities is extremely delicate
and inseparable, as a distinct membrane, from the periosteum lining them ;

'80

SPECIAL HISTOLOGY.

and the same may be said of it in the nasal fossoe themselves, particu-
larly in the glandular parts, notwithstanding the intimate connection of
the two. A remarkable appearance presented itself to me in the body
of a youth aged 15 (who, as I was informed by Virchow, also exhibited
ossifications in the lungs), consisting in the deposition — in the mucous
membrane, in all these accessory cavities, as well as in the similarly
constituted mucous membrane on the concave side of the spongy bones,
immediately beneath the epithelium — of calcareous salts, to such an ex-
tent, that its uppermost layer was transformed into a peculiar ossified
though still flexible membrane, in which there existed, in places, larger
and smaller, often very regularly disposed openings, but no evidence of
a special structure. Under this layer, which, where well developed, ap-
peared perfectly white, like a membrane filled wuth air-vesicles, as which
I at first regarded it, there always occurred a looser connective tissue
with vessels, of which latter, however, some were also incrusted ; and
in the deeper parts of the epithelial layer itself, there were scattered,
smaller, simple or aggregated concretions, like " brain-sand" in minia-
ture.

The proper olfactory mucous memhrmie of all the divisions of the
organ, occupies only the uppermost parts of the septum and of the

walls of the proper nasal /ossre, where
the superior spongy bones are situated,
to a distance of about |-1 inch down-
wards from the lamina crihrosa. It is
distinguishable, even by the naked
eye, from the contiguous ciliated mem-
brane, by its greater thickness and its
color, which is sometimes yellowish, as
in Man, the Sheep, and Calf; some-
times yellowish-brown or brown, as in
the Rabbit and Dog ; and, when ex-
amined microscopically, it is seen to
be bounded by a tolerably well-defined,
toothed or undulated border. The
differences of the structure depend
upon the condition of the epithelium,
the occurrence of numerous peculiarly
constructed glands, which I shall term
" Bowman's glands," and upon the relations of the nerves. The

Fis

312.

^^.■,.r-,^=;,,,.^,..-£.;^feri

laMiit'iiij

Fig. 312. — From the nasal mucous membrane of the Slieep ; magnified 150 diameters. 1,
from the regio olfactoria, transverse section of the mucous membrane : a, epitheUum without
cilia ; b, olfactory nerves, with a dividing, pale, nucleated fasciculus; c, one of "Bowman's
glands;" rf, its orifice. 2, ciliated epithelium of the Schneiderian membrane.

THE NOSE. 781

epithelium is not ciliated, of Avliich I have most fullj satisfied myself,
not indeed in Man, in whom I have never yet met with the epithelium
of the true olfactory region in a perfect condition, although the ciliated
epithelium occurred frequently enough still in a state of vibration, but
in the animals just named. It is also much tldclccr, so that in the
Sheep, in which the ciliated epithelium is 0-03 of a line, it measures
0-05, and in the Rabbit, the one is 0'04, and the other 0-07 of a line
thick. Notwithstanding this thickness, which is considerable for a
mucous membrane, it is remarkably delicate and soft, and is so much
affected by almost all reagents as to allow of its being studied only
with considerable trouble. According to my observations, it should be
described as a squamose c^Iinder-cpitheliuvi ; at all events, in opposi-
tion to Todd and Bowman, I always find as its outermost layer, one or
two strata of slender, vertical cells, 0-005-0-007 of a line long, whilst
it must be allowed that, more deeply, spherical elements, of 0-003-
0-004 of a line, alone appear to exist. All these cells have minute,
round nuclei, usually pale, finely granular contents of a brownish hue
in the deepest layer only in the Rabbit and Dog, and such delicate
membranes, that in water they instantly burst. Although the ciliated
cells of the nasal fossce are much more readily affected by water than
those of other situations, this is true to a much greater extent as
regards the cells of the olfactory region ; and the destructive effect of
the filling of the nasal cavities with water (E. H. Weber) and other
fluids is thus easily accounted for, as well as, on the other hand, is the
ready transition of volatile substances through the epithelium rendered
intelligible. For the moistening and protection of this epithelium
throughout the region in which it exists, it is furnished with a great
number of the " glands of Bowman," which is the more remarkable,
because the immediately contiguous, ciliated mucous membrane is but
scantily supplied with glands, or is wholly without them. These glands
are simple cylinders, either straight or slightly convoluted at the lower
end, and 0-08-0-1 of a line in length, or elongated pyriforra follicles,
situated principally between the larger branches of the olfactory nerves,
in crowded rows, in part, however, more isolated, as at the lower
boundaries of the olfactory region. They most nearly approach cer-
tain forms of the Licberkuhnian glands, and the sudoriparous glands of
the foetus. I have never yet noticed divisions of the follicles, although
it is very possible that I may have overlooked them, since these organs
are extremely delicate, and easily altered. Their canals, 0-014-0-025
of a line wide, are lined by a beautiful, simple epithelium, composed of
rounded polygonal cells, 0-006-0-008 of a line in size, containing more
or fewer yellowish or brownish pigment-granules, to which is due the
varying color of the olfactory mucous membrane. Their excretory

782

SPECIAL HISTOLOGY.

ducts are rather more contracted (0-008-0-012 of a line) than the
glandular canals, and ascend, always lined by rounded larger cells,
straight through the epithelium, in order to terminate on the surface
Avith rounded orifices, O'Ol of a line in diameter, surrounded by a few
large cells. The tissue beyond these glands is, as in other regions, soft
connective tissue, without elastic elements.

The mucous membrane, in the proper nasal cavities, is very richly
supplied with vessels, and less so in the accessory sinuses. The termi-
nal branches of these vessels form loose plexuses around the glands,
and in the trunks and branches of the olfactory nerves ; while on the
surface of the mucous membrane itself, they constitute a more close
network with numerous horizontal loops, at first sight leading to the
supposition of the presence of ^;a^)z7/ff, which, however, do not exist.
The branches, also, of the arteries and veins enter into numerous
anastomoses, and constitute (the latter especially) on the "inferior

Fis. 313.

spongy bones, the abundant spongiform plexus already noticed. Nothing
is known of the iT/mjyJiaties of the nasal mucous membrane. The
nerves are, in the first place, branches of the fifth pair (ethmoidal,
posterior nasal, and a branch of the greater anterior dental nerve), which
supply especially the ciliated region of the organ, presenting there the
same conditions as the nerves in other sentient mucous membranes (of
the i^harynx, for example), but also extend to the proper olfactory
region ; and, as I noticed in one instance in the Calf, send scattered
dark-bordered primitive fibres in the course of the branches of the
olfactory nerves. The olfactory nerve, in its tract and hulh, contains
dark-bordered fibres and nerve-cells, of which we have already spoken.

Fig. 313. — From the olfactory nerve of Man; magnified 350 diameters: A, nerve-tubes
from the traclus, in water; B, in syrup, appearing contracted ; C, nerve-cells, from the bulb;
Z>, nerve-fibres, from the brandies in the olfactory organ.

THE NOSE. 783

The nervi olfactoni, on the other hand, in Man and in other jMammalia,
even in the main trunks given off from the olfactory bulb, present no
•white meduHated fibres at all, but are wholly constituted of pale,
slightly granular flattened fibres, 0-002-0-003 of a line wide, with
elongated nuclei, which are closely adherent and retained in connection
by common sheaths of connective tissue, which arc somewhat thicker
and therefore whiter in the rami ad septum. With respect to the
origin of these fibres, which very closely resemble the embryonic nerve-
elements, whether they are derived from the olfactory hulb, or from the
cerehru7n itself, has by no means been as yet ascertained in Man, or in
other Mammalia, although, from the observations of Leydig in the
"Plagiostomata," ("Beitriige," p. 34, Tab. L, fig. 6), it is probable
that the former is the case. The termination of these nerves is yet
more doubtful. This much is readily seen, that the ner-vi olfactorii, in
their course in the mucous membrane of the olfactory region, are gra-
dually attenuated as they descend, in consequence of numerous divi-
sions at acute angles, and form a plexus which may also, in Mammalia,
be traced almost throughout the olfactory region ; but shortly before
reaching its border, these plexuses are always lost to sight, nor is any
other indication of terminal branches presented ; so that, as regards
the main fact, I remain quite in the dark. At present it appears to me
most probable that the terminal distribution takes place throughout the
non-ciliated region, and above all at its border ; at any rate I have
never yet been able to detect the filaments of the olfactory nerves in
the ciliated cpitlielium, although they can be traced down to twigs of
the size of 0*005-0'01 of a line. I have not seen the ganglion-globules
on the inner surface of the finer plexus mentioned by Valentin ("Ncr-
venlehre," p. 303), and the rather strange-looking " glands of Bow-
man," might have been mistaken for such bodies.

In the investigation of the olfactory 'organ, the chief difficulty arises
from the softness of the epithelium, and on this account a solution of
albumen, or laimor vitreus, only should be employed to moisten it.
Vertical sections in detached portions of the mucous membrane, are
best made with the scissors ; and the edges of folds not unfrequently
afford good sectional views. The mucous glands, are found in sections;
those of Bowman on teasing out the structure. Chromic acid cannot
be recommended for the olfactory nerves : teasing out the membrane is
the most suitable mode of proceeding ; as well as the compression of
fresh preparations or of preparations moistened with soda or acetic
acid ; lastly, the examination of mucous membrane macerated in water,
in which the nerves are preserved for a long time.

784 SPECIAL HISTOLOGY.

Literature. — Todd and Bowman (op. cit., II.) [Horn, "Uebcr die
Endschlingen des Geruclisnerven," Mlill. "Arcliiv," 1850. Dr. Horn
professes to have discovered looped terminations of the olfactory nerve
in the Frog (Trs.) ; 0. Kohlrausch, "Ueberdas Schwellgewebe an den
Muscheln der Nasenschleimhaut in ' Muller's Archiv,' " 1853 ; A. Kol-
liker, " Ueber den Ban der grauen Nervenfasern der Geruchsnerven in
'Verhand. d. phys. med. Ges.' zu Wurzburg," IV. 1, 1853.— DaC]

APPENDIX.

BY THE TRANSLATORS.

§ 1. The first section of the Appendix should, according to promise,
have been constituted of an exposition of the views which we have taken
with regard to the Cell-theory. Finding, however, that it would be
inexpedient to extend this already somewhat voluminous work by the
amount of space and number of illustrations which would be necessary for
a more complete discussion of the subject than has already appeared
in the pages of the "British and Foreign Medico-Chirurgical Review"
(October, 1853), we must refer the reader to the article in question.

We hope, however, in the course of a short time, to treat of the whole
subject at length in another place.

Corpuseiila tactus and Pacinian bodies. — In an essay on this sub-
ject, contained in the " Quarterly Journal of Microscopical Science,"
for October, 1853, we have endeavored to show that papillae which
contain ^^ corpuscula" may also possess a vascular loop, and that there
is, at any rate, no inverse relation between nerves and vessels in the
papillre, since in the Frog, the terminations of the nerves in the fungi-
form papillae of the tongue, first described by Dr. Waller ("Phil. Trans.,"
1848), take place in obviously vascular papillae. We regard the " cor-
pusculum" as no peculiar body, but simply as embryonic connective
tissue, differing from that of the rest of the papilla only in the regular
arrangement of its elastic element ; it is, in fact, the dilated termination
of the neurilemma of the nerve of the papilla.

With regard to the mode of termination of the nerves, while not
venturing to deny the existence of loops, we doubt it ; on the other
hand, repeated instances of the so-called free termination of dark-con-
toured nerve-tubules on the surface of the corpuscula are described and
figured (1. c, p. 3, Fig. 4). The termination is not really "free," inas-
much as the tubules become continuous, both here and in the Frog's
tongue, with the imperfect, reticulated, elastic fibrils of the papillae.

As respects the Pacinian bodies, we stated, at that time in opposition
to all authorities, that their central portion is solid and not hollow, and
that in Birds and in the human hand, the fluid supposed to exist be-

50

786 APPENDIX.

tween the concentric laminre was equally hypothetical. In structure,
the Pacinian body, in fact, is identical with the corimsculum tactus —
being a solid mass of connective tissue, -whose apparent lamination de-
pends on the regular disposition of its elastic elements. We stated
further, that the central nerve-tubule gradually terminates, passing into
the central solid axis of the Pacinian body. In reality, the Pacinian
bodies are also nothing more than thickened processes of the neurilemma
of the nerve to which they are attached, and differ from the tactile cor-
puscles only in the circumstance that in the latter the thickening takes
place on one side of the nerve-fibril, while in the Pacinian body it takes
place on both sides.

In the meanwhile, contemporaneous observations on this subject were
made by Leydig (" Ueber die Vater-Pacinischen Korperchen der
Taube") and by Kcilliker ("Einige Bemerkungen iiber die Pacinischen
Korperchen,") and were published in Siebold and Kolliker's " Zeit-
schrift," B. v., H. 1.

Leydig and Kolliker's results are, in the main, in accordance with
our own, especially as respects the solidity of the Pacinian body. The
"central cavity" is given up by both, but Ktilliker still maintains the
existence of a fluid between the outer layers, at least in the Cat. Ley-
dig regards the central solid axis of the Pacinian body in the Bird as
the expanded termination of the nerve itself.

Wagner had already drawn attention to the resemblance between the
corpuscula tactus and the Pacinian bodies ; Leydig further shows that
the latter form one series with the Savian bodies and the so-called muci-
parous canals of osseous and cartilaginous Fishes. We ventured, in the
paper in question, to add the "tactile hairs" or '■^ vibrissce" of Mam-
malia to this series of cutaneous organs, by showing that they are but a
further development of the muciparous canals — pointing out, at the same
time, that even the highest organs of sense, the Eye and the Ear, are
constructed upon the same principle.

§ 2. Malpighian bodies of the spleen. — Having recently carefully
investigated the structure of these organs, we have arrived at the fol-
lowing conclusions [vid. " Quarterly Journal of Micr. Science," Jan.
1854).

1. In the various animals examined (Man, Sheep, Pig, Rat, Kitten),
we find, as Dr. Sanders had already demonstrated in the Pig, that the
minute arterial twigs supplying the Malpighian bodies are not only dis-
tributed over, but enter and ramify in them, breaking up into their fine
penicillate branches as they pass out.

Furthermore, connecting these arterioles, there is a network of fine
capillaries, whose walls are hardly distinguishable, but which are readily
detected by using syrup, which retains the coloring matter in their con-
tained blood-corpuscles.

ATPENDIX. 787

The pulp of the Miilpigliian body stands, as Remak pointed out, in
the rehition oi' tioiica adventitia to the arterioles; it is composed of in-
different tissue, consisting of endoplasts imbedded in a homogeneous
periplast, and which may or may not become surrounded by cell-walls.

The Malpighian body has no wall, but passes insensibly, as Wharton
Jones had already shown, into the fusiform fibres of the red pulp.

We adduce evidence from Remak and Leydig that the Malpighian
bodies of other A^ertebrata present similar relations, and that the spleen,
lymphatics, Peyer's patches and the glandulce solitaricc, the supra-renal
capsules, thymus, and pituitary body, belong to the category of the so-
called "vascular" glands, all consisting essentially of masses of indif-
ferent tissue contained in a vascular plexus.

We proceed to show that the follicles of the tonsil are not closed,
but traversed by capillaries; and that it is a gland of the same class,
distinguished from a Peyer's patch only in the fact of its elements
being aggregated, not on a plane, but round a diverticulum of mucous
membrane.

Finally, we suggest that the liver itself is but a huge tonsil — a vascu-
lar gland, with what might be termed a false duct ; and we indicate the
agreement of this doctrine with the view taken by Dr. H. Jones with
regard to this organ, and we may add, with the recent beautiful re-
searches of Bernard.

%?>. Corporalutea. — Prof. Kolliker does not appear to be acquainted
■with the exact description of the structure of the corpora lutea, given
by Mr. Wharton Jones so long ago as 1843-4, in his " Report on the
Ova of Man and the Mammifera before and after Fecundation," " Brit,
and For. Med. Review," 1843, and in a paper entitled "Microscopical
Examination of an early Corpus Luteum," in the " London Med. Ga-
zette" for 1844. From the latter we extract the following passages,
premising that to the naked eye a section of this corpus luteum pre-
sented the appearance of a dark clot with a central membranous shred
from which processes radiated.

"The body in question (early corpus luteurn) is of a lenticular form,
about 6-10 inch in diameter, and about 4-10 inch thick, and projects on
the surface of the ovary by somewhat more than half its diameter. The
prominent part being covered merely by the indusium of the ovary,
the dark brown red color of the body shines through. Examined micro-
scopically the central membranous shred was found to present the fol-
lowing structure :

" 1. On its free surface a fine film of tessellated epithelium. 2. In-
vested by this epithelium Avas a stratum of finely interwoven transpa-
rent fibres, with dark contours, somewhat like elastic tissue. 3. Out-
side all was a layer identical in structure with the stroma of the ovary,

788 APPENDIX.

the same structure as that composing the principal thickness of the walls
of Graafian follicles.

"The membranous processes possessed a similar structure, and were
found to be continuous with the stroma of the ovary. That part of the
body next the substance of the ovary, had, by its pressure, so condensed
the stroma at the place, that the latter looked somewhat like an
external capsule sending processes inwards, which met and interwove
with those sent outward by the central membranous striae. But that
this appearance of external capsule was the result simply of the matting
of the stroma of the ovary by pressure, is shown by the circumstance
that it was absent at the peripheral part of the clot-like body, there
being there, as already said, merely the indusium.

" As to the microscopical characters of the clot-like matter itself,
this was found to consist of granulous corpuscles somewhat like so-
called compound inflammation globules closely aggregated, and red
blood-corpuscles interspersed amongst them. The latter had lost some
of their coloring matter, but the granulous corpuscles were tinged red,
as if they had imbibed it.

" The conclusion Avhich is to be drawn as to the nature of the body
from this investigation is, that it is a true corpus luteum in an early
stage ; that the central membranous shred is the wall of the Graafian
follicle, from which the ovum had escaped ; and that the clot-like mass
(which would by and by have acquired the characteristic yellow appear-
ance of the corpus luteum, traces of which could indeed in some deep
places be detected), together with the membranous processes extending
through it from the central shred to the stroma of the ovary, is the
stroma surrounding the Graafian follicle infiltrated with bloody-looking
matter."

With regard to the important question of the nature and reason of
the differences between true and false corpora lutea, Mr. Wharton Jones
observes :

"If in the human female, Graafian follicles burst periodically, inde-
pendently of coitus, why is there no corpus luteum left ? The explana-
tion which might be given of this is :

" By a slow, natural, and regular process, a Graafian follicle maturates,
points, bursts, and is evacuated like a small healthy abscess or pimple,
and like this the part quickly cicatrizes. A Graafian follicle, at the
time of coitus, not happening to be in this fully matured state, its
bursting is hastened by the process of congestion, exudation, and extra-
vasation above-described ; but when burst, the lymph and blood in an
altered state remain for a while in the form of a corpus luteum, which
may thus be compared to the hard base of an abscess evacuated prema-
turely. Though true corpora lutea, there is reason to believe, are
formed only after coitus, impregnation may take place without the for-

APPENDIX. 789

matlon of a corpus luteum. How is this ? The explanation which might
be oifercd of such rave cases is this : Coitus may have chanced to take
place at the very time when a Graafian follicle, having become mature,
had spontaneously given way and expelled the ovum. No congestion,
exudation, and extravasation, would in this case take place, but the part
would quickly close and cicatrize. 4. Lastly, what explanation can be
given of the origin of false corpora liitea ? To this it might be answered,
that from some circumstance or other, effusion of blood takes place into
the interior of a Graafian follicle, perhaps on the point of bursting
spontaneously. This blood coagulates and remains filling and distend-
ing the Graafian follicle, even although its walls may have subsequently
given way. But besides this effusion of blood, an exudation of lymph
takes place on the inner surface of the walls of the Graafian follicle, in
consequence of the irritation produced, which, becoming organized, pre-
sents the same yellow appearance as the substance of the true corpus
luteum formed outside the walls of the Graafian follicle.

" In conclusion, I would remark that, though physiologically one may
be permitted to speculate, as I have done, on the relation between the
occurrence of corpora lutea in the ovaries and preceding coitus, it would
be rash and unwarrantable in any one to pronounce positively from the
occurrence of a corpus luteum in the ovaries that coitus had taken place.
The discovery of an ovum in the uterus, in process of development,
could alone, in the present state of knowledge, warrant such an affirma-
tion in a court of law. But, on the other hand, the absence of a corpus
luteum could not warrant the affirmation that coitus had not taken place."

§ 4. Development of the Teeth. — In an Essay on this subject in the
" Quarterly Journal of Microscopical Science," for April, 1853, we have
taken a very different view from that advocated by Professor Kcllliker,
and which amounts to this, that all the tunics of the teeth are the result
of calcareous deposition from the pulp, the so-called " enamel organ"
taking no direct share whatever in the process. This view was based
upon observations made upon the teeth of all the principal orders of the
Yertebrata, i. £-., the Mackerel, the Skate, the Frog, the Calf, and Man;
and subsequent observations on these and on other animals, have only
confirmed our belief in the substantial truth of the matters of fact there
stated.

The keystone of the theory of dental development there enunciated
is the fact, that, in all the orders of the Vertebrata, a membrane homo-
logous with the so-called "persistent capsule," discovered, in 1839, by
Mr. Nasmy th, and which we have therefore denominated " Nasmyth's
membrane,'' can be demonstrated coverinor the enamel of the teeth and
extending over the dentine, to be continuous with the memhrana j^refor-
mativa and baseinent membrane of the sac, in an incompletely formed

790 APPENDIX.

tooth ; or -with tlie surface of the cement, in a fully developed one.
Nasmyth's membrane, in fact, is at first the membrana preformativa
more or less altered.

We hold this statement to be incontrovertible, nor less so the corre-
lated doctrine, that the enamel and cement, as well as the dentine, are
developed beneath Nasmyth's membrane, between it and the pulp ; that
the enamel is, consequently, during the whole course of its formation,
separated from the enamel-organ by Nasmyth's membrane ; and that,
therefore, the direct conversion of the long cylinders of the epithelium
into the fibres of the enamel, strongly as their mutual resemblance may
suggest the notion, is, to say the least, highly improbable.

Thirdly, we have met with no facts in opposition to what we have
stated with regard to the mode of development of dentine and the re-
lation of the latter to the pre-existing elements of the pulp, and we
believe that there is every reason to regard what we have there called
the " Deposition theory," as an established position. According to this
theory, the dentine is not the result of the conversion of the elements of
the pulp ; the cndoplasts of the latter never becoming engaged in the
calcareous deposit, as they are in bone ; but the young dentine is formed
by a deposit of transparent calcareous granules in a thin layer between
the pulp and the membrana jyreformativa. It must be understood, how-
ever, that the latter two structures are continuous, and that Avhen the den-
tine is said to be deposited between them it is not meant that any real
interval exists, but only that the outer portion of the periplast of the
pulp, of which the membrana preformativa constitutes a part, increases
and receives a calcareous deposit without any corresponding implication
of the endoplasts of the pulp.

The thinnest and youngest layer of the dentine appears to be struc-
tureless, which may, however, arise from the small quantity of calcareous
matter which it contains : subsequently, minute cavities, irregular in
form, and l-5000th of an inch apart, appear in it ; and these corre-
sponding with one another in successive layers of the dentine, become
the dentinal tubuli. The appearance of walls, &c., to these tubuli, we
consider to be the result of a subsequent differentiation in the dentine.

A careful study of the mode in which the dentine-like tegumentary
organs of many of the lower animals (Fishes, Articulata, MoUusca) are
formed, has afforded the fullest confirmation of this theory of the deve-
lopment of dentine, and we would recommend those who have any doubt
upon the subject to study the development of the spines of the Skate,
or that of the shell of the Crab or Lobster.

The mode of development of the enamel appears to us to be a very
difiicult subject, and requires to be most carefally studied. Taking
into consideration the facts that a distinction of a superficial and a deep
layer of calcified tissue is very general in the tegumentary organs —

APPENDIX. 791

that in a Molluscan sliell, for instance [e. g. Trigonia\ we may have a
superficial membranous hiyer corresponding with Nasmyth's membrane,
a deeper prismatic layer, whose prisms precisely resemble those of
enamel on a large scale, and an internal laminated tubular layer, corre-
sponding with dentine ; and knowing, further, that these varieties of
structure thus arranged are (whatever view we take of shell-structure)
nothing but the result of the diiferent modes in which calcified deposit
has successively taken place in the same organ, it is sufiiciently obvious
that there are abundant analogical grounds for considering the enamel
and the dentine as modifications of one and the same tissue.

Nof does the structure of the enamel in the Fish or the Batrachian
present any difficulty in the way of this view. It is, at most, indistinctly
fibrous and contains so large a quantity of calcareous matter in propor-
tion to the dentine, that the differences between the two may well be
supposed to arise — as we believe they do — from this circumstance
alone.

In the higher Vertebrata, however, when the enamel in its young
state consists of definite fibres composed of organic substance, which
are added to the surface of the tooth only after the formation of a sub-
jacent scale of dentine, it becomes more difficult to comprehend the
development of the former. There appears to be three possibilities.

1. What we call the primary scale of dentine is not, on the crown of
the tooth, dentine at all, but young enamel, becoming converted into
the latter structure, and not into the former, as development proceeds.
This appears, as first sight, a startling hypothesis enough ; but there
are, so far as we know, no means of disproving it. Young dentine can
only be known to be such by its relations ; in structure it is neither like
perfect dentine nor like perfect enamel ; but might readily be supposed
to be converted into either by variation in the quantity and mode of
deposition of its calcareous element. If this deposit be comparatively
small, leaving much of the organic basis, and not encroaching upon the
existing cavities, we have dentine ; increase the quantity of calcareous
salts, and break up the organic basis at the same time into fibres, and
enamel would be produced.

2. The enamel is the indirect product of the prismatic cells of the
enamel organ, whose inner extremities pass into successive layers of
membrane, which are applied upon and indistinguishably unite with the
membranaj^reformativa over the whole surface of the developing enamel.
The laminated membrane thus formed receives a calcareous deposit,
and breaks up into the prisms of the enamel.

This hypothesis likewise, at first sight, appears somewhat improbable,
but it may be strictly parallel with what occurs in the formation of
prismatic shell substance, where a laminated membranous substance is

792 APPENDIX.

produced from the cellular epidermis of the mantle, and subsequently
breaks up into the characteristic, large, transversely striated prisms.

3. The enamel is neither the result of the modification of the primary
"dentine," nor superimposed on this from the enamel organ, but a ter-
tium quid, the product of the growth and metamorphosis of that exces-
sively thin layer of organic matter which lies between the dentine and
the enamel.

In support of this view, also, a very close analogy may be found in
the mode of development of the shaft of the hair — a structure which
exhibits the closest correspondence with the teeth. The fibrous cortex
of the hair is, in fact, homologous with dentine ; it is a horny deiitine,
containing rudimentary canals. External to this substance we find two
layers ; the inner composed of parallel horny, structureless plates,
closely united and set obliquely on the shaft, in fact, a rudimentary
horny enamel ; the outer consisting of a tough areolated membrane,
outer layer of the cuticle, whose resemblance to Nasmyth's membrane
cannot be overlooked. Now, if we trace the development of these layers
in the long hairs of the head, we find that they pass on the bulb into a
structureless limitary membrane, beneath which lie the endoplasts of
the pulp ; this is, in fact, a memhrana preformativa of the hair pulp.
Passing from the base towards the apex of the hair, the deep endoplasts
become surrounded by the horny matter and the pigment-granules of
the cortex, while the superficial layer remains free from the latter, but
gradually becomes horny, and loses its endoplasts. Its outer portion
then becomes the areolated outer (Nasmyth's membrane) cuticular layer,
while its inner portion breaks up into the parallel plates of the inner
(enamel) cuticular layer. So far as we have been able to observe in
the long hair, however, the disappearance of the endoplasts takes place
before the areolation and lamination of the periplast which corresponded
to them, so that, as we have already stated (note, page 181), the
cuticle does here pass into an apparently structureless layer. This,
however, is not, as it seemed, a real discrepancy from Prof. Kolliker's
views, for in the short thick hairs, such as those of the nostril, the endo-
plasts persist longer, and we see that, as he states, the areolations of
the outer cuticle are the representatives of the cell-cavities of the outer
layer of the pulp ; while the laminoe of the inner layer are the result of
the lamination of the next layer of the pulp, whose endoplasts may be
seen gradually disappearing, whilst its periplast breaks up into plates.
Now in the long hairs we have a relation of the outer cuticle to the
cortex very similar to that of Nasmyth's membrane to the dentine before
the development of the enamel, and the conclusion is obvious, that as
the development of the inner layer of the cuticle takes place by the dif-
ferentiation of the intermediate substance between the cuticle and cortex,

APPENDIX. 793

SO thut of the enamel may take place in the same way in relation to
Nasmytli's membrane and the dentine.

These would appear to be the alternatives concerning the development
of the enamel. At present facts would seem to be wanting to deter-
mine definitely which should be accepted.

Finally comes the question of interpretation of the phenomena of de-
velopment of the dental tissues, and the determination of the homolo-
gies of the latter Avith the pre-existing elements of tlie mucous mem-
brane. Professor Kolliker's views are stated in the text. He consi-
ders the dentine and the cement to be the calcified cerium of the mucous
membrane, while the enamel is the calcified epithelium.

The view we have ourselves taken is that cement, dentine, and enamel,
are calcifications in the same constituent of the mucous membrane, and,
in fact, that they entirely belong to its corium or dermal element. Tak-
ing for granted that the membrana preformativa was a basement mem-
brane, and furthermore, the received doctrine that a basement mem-
brane marks the boundary between the dermal and epidermal elements
of integument or mucous membrane, it was, in fact, impossible to come
to any other conclusion. An extensive study of the integumentary
organs, however, has led us to reflect more closely upon this matter, and
to inquire what is a basement membrane, and what is the real distinc-
tion between the epidermic and the dermic elements of a membrane ?
We cannot here enter into the grounds for our conclusions (which will
be stated in full in a forthcoming article on the " Teguraentary Sys-
tem," in Todd's "Cyclopa3dia of Anatomy and Physiology"), but must
be content merely to state our conclusions that the existence of a base-
ment membrane, i. e., of a structureless membrane, internal or external
to it, proves nothing with regard to the dermic or epidermic nature of
an organ, but that we must be guided entirely by the direction of its
growth and metamorphosis. Every integument and every mucous
membrane may, in fact, be distinguished into three portions ; a central
plane of indifferent tissue, from which growth and metamorphosis take
place externally, to constitute the representative of epidermis or epithe-
lium, to which we propose to give the name of ecderon ; while internally,
growth and metamorphosis take place from the pentral plane, so as to
constitute the representative of the derm or "mucosa," which we have
termed the enderon.

Now the dental pulp is a process of the whole integument, and its
outer surface, although bounded by a " basement membrane," truly
represents the deepest layer of the ecderon of ordinary integument,
while its inner substance belongs to the enderon. Although, therefore,
the dentine is not a calcified cellular epidermis, it is a calcified ecderon,
and grows in the same manner as an ecderon would do. The cement

794 APPENDIX.

follows the dentine, and whatever the view we take of the development
of the enamel, it also belongs to the ecderon. Although, therefore, the
teeth are not, in the ordinary sense, epidermic structures, they are
homologous with the ecderon, and not with the true derma or enderon
of the mucous membrane.

INDEX.

Air-cells of lungs, stiuclure of, 575-575, 579.

Alimentary canal, muscular tunic of, 503; li-
terature of, 527. See Stomach, Intestine.

Arachnoid membrane, structure of, in spinal
cord, 39".); of brain, 395; vessels of, 398;
nerves ol, ib.

Areolar tissue, 9t; subcutaneous areolar
tissue, 119; fat cells in, 120, 125.

Arteries, structure of tunics of, (578-684 ; lite-
rature of, 724.

Articular capsules, 295.

Articular cartilage, structure of, 292, 293,
7tole ; condition of bone beneath, 293; vas-
cularity of, 291.

Aschers^on, vesicles of, 41.

A.xilecorpuscles, nature of, 130; terminations
of nerves in, 134.

Axillary glands, 202.

A.xmann, Dr., on ganglion-fibres, 406, 7iote;
on a.xis-cylinder, 409, note.

Ayres, Dr., on prismatic crystals in coagulated
blood of the Bitch, 715, note.

B.

Barry, Dr. .on structure of muscular fibre, 227.

Bernard, Al., on secretion of subin-i.\iilary,
465 ; on muscular fibres in inferior vena
cava, 687.

Berihold, Dr., on growth of hair. 196.

Berzelius, Frof , on medulla ot bone, 282.

Ijibra, Von, his analysis of muscle, 250; on
chemical composition of dentine, 471 ; of
enamel, 477; of the liver, 536.

Bichat. Prof, his influence on Histology, 33;
on vessels in bone, 301.

Bidder, Dr., on nerve-cells in the glosso-
pharyngeal nerve, 417.

Bile, constituents off 510.

Bischotf, Prof., on lenticular glands of sto-
mach, 509, note.

Bladder. See Urinary Bladder.

Blood, changes of, in spleen, 560; elements
of, 703 ; elementary granules of, 70(> ; ex-
traordinary constituents of, 713 : occurrence
of crystals iti, 714.

Blood-corpuscles, red, form and character of,
703, 704; nucleus of, 704, 722, 7iole ; me-
thod of enumerating, 701, note; size of,
705 ; diminution of number in disease, ih. ;
presence of, in chyle, 701 ; conditions of, in
various kinds of blood, 709; influence of
reagents upon, 710; forms in blood ot ani-
mals, 712, 722, 7iote ; development of, 717,
722.

Blood-corpuscles, colorless, form and origin
of, 707 ; relative number of, compared with

red, 708, 709; development of, into red,
718-723; literature of, 724.

Blood-corpuscle- holding cells, occurrence of
in spleen, 558-562; in congested lungs,
559, note; in black vomit, ih. ; import of,
560.

Blood-crystals, 714.

Blood-vascular glands, tissue of, 1 16-118.

Bloodvessels, varieties of, 674; tissues enter-
ing into their composition. 674-()78 ; de-
velopment of, 715; literature of, 724. See
Arteries, Veins, and Capillaries.

Bohm, Dr., on detachment of epithelium in
cholera. 520.

Bone, intimate structure of, 266-281 ; Haver-
sian canals of 2()7-27y ; lamcUas of, 270-
275 ; lacunfE and cells of, 275, 2'9 ; canaliculi
of, 276; contents of lacunas of, 280; peri-
osteum, 281; marrow of, 282; cells of
medulla of, 283, 284, note ; connections of,
284-291 ; physical and chemical properties
of, 299; vessels of, 301 ; lymphatics of 302 ;
nerves of, 303 ; development and formation
of, 306. 330; vital phenomena of, 336 ; pa-
thological changes of 340 ; investigation of,
342; literature of, 102, 344.

Bowman. Mr., on structure of muscular fibre,
225, 228, note; on rupture of muscular
fibrils in tetanus. 258 ; on ciliary motion in
Malpighian corpuscles, 601; on structure
of cornea, 728, 729; on nerve-cells of retina,
743 ; on constitution of vitreous humor,
754, 755 ; on glands in olfactory mucous
membrane, 780. See Todd and Bowman.

Brain, ganglia of, 382. See Cerebrum and
Cerebellum.

Brain-sand, 402, note, 403.

Bright's disease, tubuli uriniferi in, 602.

Bronchise, intimate structure of, 578; arteries
of, 581.

Briich, Prof, on the anatomy of the intestinal
villi, 518, 7iote.

Briicke, Prof., on cadaveric rigidity, 253; on
muscular fibre in villi, 514 ; on structure of
lacteals and absorption of chyle, 516, ?iote ;
on lymphatic glands, 699; on function of
bacillar layer of retina, 748; on structure of
vitreous body, 754.

Brulle and Hugueny, MM., experiments
upon bones of growing animals, 329, 338.

Brunner's glands, structure of, 519; vessels
of 520 ; method of examining, 527.

Burnett, Dr., on development of spermatic
filaments, 625, 7iotfi.

Bursae mucostE, structure of, 123, 239.

C.

Capillaries, structure of, 689-G93 ; develop-
ment of, 716.

796

INDEX.

Carpenter, Prof., on structure of muscular
fibrils, 229, note ; on basement membrane
in corium, 141.

Cartilage, its composition, 79; varieties of,
80; in pathological structure, 322; lite-
rature of, 81; costal cartilage, 290; of
articulations, 291 ; structure of, when loose
in joints, 298; chemical composition of,
300; nerves of, 305; development of, 307,
309, note; changes during ossification of,
313,316; vessels of, 315.

Cells, general anatomy of, 43-70; forms and
contents of, 44 ; size of, 44, 45 ; membranes
of, 45, 47; chemical composition of, 45;
nuclei of, 44, 45, 46 ; nucleoli of, 46 ; com-
parison wiih primordial utricle in plants,
47 ; development of, 48, 54 ; multiplication
by division, 54 ; vital phenomena of, 59, 60 ;
processes in the interior of, 61 ; changes
and chemical composition of contents, 165 ;
elasticity of cell-membranes, 67; excretive
processes,?/).; contraciility of, 68; meta-
morphoses of, 69, 70.

Cellular tissue. See Areolar tisszte.

Cement, chemical composiiion of, 480 ; struc-
ture of, 481 ; development of, 492.

Cerebellum, elementary tissues of, 379 ; gray
layer of, 380 ; composition of its crura, 381.

Cerebral nerves, structure of, 416.

Cerebro-spinal fluid, analysis of, 401.

Cerebrum, ganglia of, 382; structure of hypo-
physis, 385: corpora striata, 382; corpora
quadrigemina, 384 ; optic thalami, 384 ;
hemispheres of, 385 ; intimate structure of
cijnvoluiions, 3S() ; origin of nerve-iibres in,
390; membranes of, 392-399; cpendymaof
ventricles of, 397 ; vessels of, 400.

Ceruminous glands, structure ol', 209; secre-
tion of, 210-212; literature of, 212.

Choroid coat of eye, layers of, 733 ; pigmen-
tum nigrum, 735; vessels and nerves of,
737-739.

Chyle, elements of, 700.

Cilia, structure of, in cells lining laryn.x, 570.

Ciliary ligament, 734.

Ciliary motion, agents for re-e.\citing it. 571,
note; in neck of Malpighian border of
kidney, 601.

Clark, Prof., on vegetable growths on the
tongue, 452, ?iote.

Clitoris, 655.

Cochlea, parts of, 770-774; zona pectinata,
773; nerves of, 774-775, vessels of, 775;
physiology of, 775, note; investigation of,
777 ; literature of, 778.

Colostrum, 665, 666.

Conjunctiva, structure of palpebral, 759 ; of
corneal, 728; vessels ot, 732, 760.

Connective tissue, elements of, 89, 94 ; chemi-
cal reactions of, 90 ; development of, 90, 95,
97, note; forms of, 91-94 ; corpuscles of, 85.

Connective- tissue-corpuscles, 85.

Contractile tissue, dependent on muscular
fibre-cells, 104.

Colloid, occurrence of, in thyroid gland, 587;
in tubuli uriniferi of kidney, 601.

Cooper, Sir Astley, on cavity of thymus
gland, 590.

Copulation, motile phenomena in act of, 637.

Corium, structure of, 123 ; development of,
134.

Cornea, elements and structure of, 727-733;
vesselsandlymphaticsof,730; nervesof, 731.

Corpora lutea, formation of, 643 ; structure
ot, 645, 787.

Corpuscula amylacea, of nervous system, 41 ;
in ventricles ot the brain, 401, 402, tiote.

Corpus striatum, nerve-fibres of, 382.

Corii, Marquis, on connection of the nerve-
cells of the retina with the nerve-fibres,
750; on structure of cochlea, 772, 775, wo/e,
777.

Costal cartilage, structure of, 290.

Cowper, glatids of, 630, 635,

Cruveilhier, Prof., on pathological changes in
articular cartilage, 295 ; on lymphatics of
articular cartilage, 303.

Czermak, Prof., on structure of dentine, 475,
7iote.

D.

Dalton, Dr., on corpus luteum of menstruation
and pregnancy, 645, note.

Decidua;, 651, 653.

Deglutition, organs of,499-502. iS'ee Pharyn.x,
(Esophagus.

Demours, membrane of, 729.

Dentine, structure of, 469; canals of, 470;
chemical composition of, 471 ; formation of,
491.

Digestion, changes which the epithelial cells
and the villi undergo during, 515 ; organs
of, 43(j-568. .SVe Intestinal Canal, Liver,
atid Pancreas.

Donders, Prof., on development of connective
tissue, 85 ; on nature ol fibres of interver-
tebral ligaments, 287; on composition of
cartilage, 300.

Domie, M., on spermatozoa, 624; on colos-
trum in human milk, 666.

Ductless glands, tissue of, 116. See Spleen,
Thymus, Thyroid, and Supra-renal bodies.

Duhaniel, M., his experiments upon grow-
ing animals, 328.

Dura mater, structure of, 392, 394 ; vessels of,
397 ; nerves of, 398.

E.

Ear. structure of external canal, 767; ossicula
of, 768; memlirana tympaiii, 768; vesti-
bule and osseous semicircular canals, 71)9;
cochlea, 770-778; develoimient of, 776;
literature of, 778.

Ecker, Prof., on degeti^ralions of thyroid,
588; on structure and development of thy-
mus, 592, 595.

Elastic ligaments, 284.

Elastic Tissue, elements of, 81 ; chemical re-
actions of, 82; development of, 83 ; litera-
ture of, 88; presence of, in ligamentum
nuchaa, 284.

Elementary parts, simple, 39-70 ; higher, 70-
118 ; lite'rature of, 71.

Enamel, structure of, 476, 478; chemical
composition of, 477 ; Nasmyth's mem-
brane, 480; formation of, 489.

Endocardium, structure of, 669; nerves of,
671.

Ependyma, of ventricles, 396, 401 ; of spine,
397, note.

Epidermic Tissue, character of, 74 ; forms of,
75; prevalence of, in animal kingdom; in

INDEX.

f97

patholcgicnl formaiions, 78; litcraiure of,
78,

Epidermis, 13D-ir)8 ; Malpigliian layer, MO;
lioriiy layer, 142; color ot, 144; [iliysical
and vital proiierties ot, Mii : aciioii ot re-
agents on, 147, 148 ; on epidermis ot Negro,
'im, 7iole ; growth and regeneration, 151;
development of, 154.

Epididymis, (iCO, (!-J(j.

Epiglottis, structure of, 5G9 ; glandules of,
57-'.

Epitlielium, forms of, 7() ; of stomach, 50'J ;
of villi, 514 ; changes of, during digestion,
515, 511), note; ciliated, of larynx, 570; of
air-cells, 57i> ; of bronchiaj, 578 ; of uterus,
647 ; varieties of lining vessels, ()7(i ; of
membrane of Descemet, 729; of olfactory
organ, 779, 781.

Eulenberg, Dr., his case of black fur of the
tongue, 453.

Eye, tunics of, 725 ; sclerotic coat, 725 ; vas-
cular tunic, 733-739 ; retina, 739-750 ; lens,
750-753 ; vitreous humor, 753-777 ; acces-
sory organs of, 757-7tJ0 ; physiological re-
marks on, 7(J0 ; vessels ol foetus, 761 ;
histological development of, 762 ; inode of
investigating, 763; literature of, 765.

Eyelids, 757.

Fibro-cartilage,240 ; structure of interarticu-

lar, 297 ; chemical composition of, 300.
Fibrous tissues, 81, 89. See Connective and

Elastic Tissue.
Filum terminale, 367; corpuscula amylacea

in. 401.
Follicles, solitary, of small intestine, 523 ; of

large intestine, 525.
Fremy, >I.,on chemical composition of brain,

359.
Frerichs, Prof., on synovia, 298 ; on chemical

composition of kidney, 610; on semen of

the carp, 624.
Fuchs, Prof., on infusoria in milk, GGG.
Funke, Dr., on crystals in the blood, 714.

Gall-bladder, structure of, 538.

Ganglia, tibres of, 405; cells of, 109, 406;
upon glosso-pharyngeal nerve, 454.

Ganglion-globules. See Nerve-cells.

Ganglionic nerves, 418. See Sympathetic
nerve.

Gastric glands, structure of, 506, 507, note;
509, note; secretions of, 508.

Gelatiniform connective tissue, 96.

Genital organs, external, of male, 630; of
female, 655.

Gerber, Prof., his method of examining the
skin, 158.

Gerlach, Prof., on Malpighian bodies, 601,
note; on lormaiion of blood-globules, 722.

Glands, structure of, in oral cavity, 456 ; folli-
cular, 459; salivary, 4ti3; of stomach, 506 ;
of intestine, 51S-525; of larynx, 572; ot
trachea, 573; of Cowper, 630; of Littre,
631 ; of uterus, 647 ; of external genital
organs in female, 655 ; Meibomian, of eye-
lid, 758; "of Bowman," 781,

Ghniihdar tissue, varieties of, 113-115; lite-
rature ot, 1 1().

Glisson, capsule of, 532, 544, 546.

Gosselin, iVl., on composition of semen after
epididymitis, 625, itote.

Graafian vesicles, 640, 643, 645.

Granules, general consideration of, 41 ; tre-
mulous motion of, 64 ; formation of, in
nuclei, 64.

Gums, composition of, 484 ; in foetus, 488.

H.

Hair, disposition and size of, 171 ; chemical
composition of, 172 ; intimate structure of,
173-182; properties of, 182; papilla, 183;
root sheath of, 184; development of, 186;
shedding of, 191 ; physiological observa
tioiis on, 193 ; abiiornial conditions ot, 197 ;
method ot investigating, ih.; literature, 198.

Hancock, Mr., on organic muscular fibres of
the urethra, 631, note.

Hannover, Dr., on nerve-fibre in the yellow
spot ot the eye, '7f)0,7iote; on membranes in
foetal vitreous huinor, 755.

Hartiiig, Mr., his measurements of blood-cor-
puscles, 705.

Hassall, Mr., on corpuscles in Thymus, 593;
on peculiar concentric bodies in fibrinous
clots in the heart, 713.

Hasse, Prof., on medulla-cells in cylindrical
bones, 283.

Haversian canals, origin of, 318, 327.

Haversian glands, 296.

Heart, muscular structure of, 668, 671-674 ;
endocardium of, 669 ; bloodvessels of, 670 ;
valves of, ih.; nerves of, 671 ; development
ot, 715; mode of examining its structure,
723; literature of, 724.

Henle, Prof., on smooth muscles in skin, 121;
on hair-bulb, 195, 7iote; on cells of reticular
cartilage, 569; on composition of semen,
624; on absence of the "rods" in the yel-
low spot of the eye, 746.

Hepatic artery, branches of, 544-546.

Hepatic cells, 532-536.

Hepatic ducts, 537-539, 540,7iote; vasa aber-
rantia of, 538.

Heyfelder, Dr., on muscular layer in lympha-
tic ghmds, 698.

Horner, Prof., on axillary glands in Negro,
202, note.

Hyaloid membrane, 753, 755.

Hymen, tissues of, 654.

Hypophysis cerebri, structure of, 385.

Interlobular connective tissue of lungs, 580.

Interosseous membranes, structure of, 238.

Intervertebral ligaments, structure of, 286.

Intestinal canal, elementary composition of,
436; development ot, 526; literature of,
527. See Oral Cavity, Stomach, and In-
testine.

Intestine, small, mucous membrane of, 511 ;
villi of, 511-518 ; lacleals ot, 513, 516, note;
glands of, 518-520; closed follicles ot, 520-
524 ; mode of examination ot, 527 ; litera-
ture of, 527.

798

INDEX.

Intestine, large, mucous membrane of, 524 ;

glands oi', 5-2.) ; literature of, 5'27.
Iris, elements of, 735-738 ; cause of color of,

736 ; vessels and nerves of, 738, 739.

Jacob, membrane of, 782.

Jaundice, teeth in, 497.

Jobert de Lamballe, M., on nerves of gravid
uierus, 652.

Jones, Dr. Hanfield, his views on terinination
ol hepatic duct, 540, note; on the develop-
ment of the liver, 547, note.

Jones, Mr. Wharton, on iMalpighian follicles
ot spleen, 555, note; on blood of splenic
vein, 562, note; on the blood-corpuscles in
animals, 702, note; on nucleus of colorless
blood-corpuscles, 707, note; 722, note; on
corpora lutea, 787.

K.

Keber, Dr., on entrance of spermatozoon into
the ovum of Unio, 637, note.

Kidney, general composition of, 596; urinife-
rous tubules of, 597-i;02; Malpighian cor-
puscles, 598, 600; pathological degenera-
tions of, 601, 606, 611 ; vessels and nerves
of, 602, 606 ; stroma of, 60() ; calices and
pelvis, 607; chemical composition of, 610;
mode of investigation of, 611 ; literature,
612.

Kiernan, Mr. on structure of liver, 539, 543.

Kilian, Prof, on nerves of gravid uterus, 653.

Krause, Prof, on investigation of sudoriparous
glands, 208; on gastric villi, 505, jiote.

Lacteal glands, structure of, 661 ; enlarge-
ment of, during lactation, 662; physiological
remarks on, 663 ; secretion of. 664 ; me-
thod of examining, 666 ; literature of, 667.

Langenbeck. Prof, on muscular ring in zone
oi Zinn, 757.

Larynx, cartilages of, 569 ; ligaments of, ib. ;
mucous membrane of, 570 ; glands of, 572 ;
vessels and nerves of, ih.

Lassaigne, M., his analysis of brain, 359.

Lee, Dr., on ganglia in the heart, 671.

Leeuwenhoek, on anastomosis of primitive
fasciculi of muscle, 108, 668.

Lehmann, Prof, on fluid of vesicular semi-
nales, 624 ; on presence of colostrum-cor-
puscles in acute diseases, 666.

Leidy, Prof, on elements of articular car-
tilage, 293 ; on structure of liver, 537, note.

Lens, crystalline, elements of, 750-754 ; cap-
sule of. 750.

Leydig, Dr., on n^rve-fibrcs in the skin of
Fishes, 415; on Malpighian corpuscles in
Fishes and Reptiles, 555, 556, note; on
structure of supra-renal capsules of mam-
malia, 617, 7iote; on oriein of fibres of the
olfactory nerves in the Plagiostomata, 783.

LieberkLihnian glands, structure of, 519, 525 ;
viscid secretion of, 520.

Ligamenta flava, structure of, 284.

Ligaments, connecting bone, 284; between
vertebr;c, 285 ; nerves of 305.

Ligamentum nuchas, structure of, 281; nerves
of, 305.

Liston, Mr., on vessels of articular cartilage,
294.

Liver, component parts of, 528 ; arrangement
of, in animals, 529, 536, note ; in Man, 531 ;
secreting cells of, 532-536 ; capsule of, 532,
546; chemical analysis of, 536 ; excretory
ducts of, 537-540; secretion of 540; ar-
rangement of vessels in, 541-545; lym-
phatics in, 545 ; nerves of, 546; develop-
ment of, 546, 547; mode of investigating,
548 ; literature of, 548.

Loose cartilages, in joints, structure of, 298.

Ludwig, Prof., on albumen in healthy kid-
neys, 610; on muscular fibres of left
ventricle, 672.

Ltidwig and Nolla, MM., on structure of
lymphatic glands, 696, 699.

Lungs, intricate structure of, 574-581 ; vessels
and nerves of, 581-583; development of,
583 ; pathological changes in parenchyma,
584; mode of investigation, I'i.; literature
of, 585.

Luschka, Prof, on nerves of bone, 304; on
cellulose corpuscles in the ganglion of
Gasser, 403 ; on ligament of the iris in
animals, 729.

Lymph, elements of, 700; formation of cor-
puscles of, 702.

Lymphatics, structure of, 693.

Lymphatic glands, structure of, 695, 698;
connection of, wiih lymphatic vessels, 696;
degenerations of, 699

M.

Malpighi, Prof, on structure of lymphatic
glands, 696.

Malpighian corpuscles, of spleen, 552-556,
557, note, 786 ; of kidney, 597, 600.

Mammary Glands. .See Lacteal glands.

.Matrix, of tissues in general, 40 ; ot bone, 270.

Marrow. See Medulla.

Measurements, those generally employed, 43;
table of, ih.

Medulla, of borie, 282; of cartilage, 291;
composition of, in foetus, 322.

Medulla oblongata, structure of, 372 ; gray
substance of, 374 ; origin of nerves from,
376, 377.

Meibomian glands, 758.

Membrane of Descemet, 729, 734.

Microscopes, varieties of, 38.

Milk, constituents of, 664 ; varieties of, &66.

Mohl, Prof V^on, observations on cell-division
in plants, 56, note.

Moleschott, Dr., on development of blood-
corpuscles, 562, wo^e ; on relative number
of red and white corpuscles, 708.

Mouth. .S'ce Oral Cavity.

Mucous bursae, 239.

Mucous corpuscles, 465.

Mucous membranes, general structure of,
436; of mouth,*.; of tongue, 446; inti-
mate structure of glands of, 456 ; of
pharynx, 500; of intestine, 511, 524; of
larynx, 570; of bronchiaj, 578; olfactory,
780.

ALicous sheaths, 239.

INDEX.

799

Mu'ller, Dr. 11., on glands in ichtliyosis con-
genita. QSl ; on development of bone, SSHi ;
on radiating fibre-system in retina, 716,
7-t9, ?;")(), note.

IMiiller, Prof. J., on nerve-fibres in orbital
muscle of liie Pike, iV}; on inierarticular
cartilage, 300; on Malpighiaii corpuscles
of spleen, 555 ; on heiicine arteries, 633,
1)34 ; on composition of cornea. 7'27.

Mulder, Prof, on chemical examination of
the nails, 165 ; on organic basis of cartilage,

?m.

Muscle, striated, elements of, 223; constitu-
tion of fibres of, 225-230; nature of primi-
tive fibrils, 227; connection of, with other
parts, 231 ; vessels in, 243 ; lymphatics in,
245; nerves of, 245-250; chemical and
physical relations of, 250; development of,
253-257; pathological conditions of, 257—
25!.'; physiological remarks on, 25y-2()4 ;
method of investigating, 264-266; litera-
ture, 109, 266.

Muscular fibre. See Muscle.

Muscular fibre-cells. See Smooth muscular
fibres.

IVIuscular system, constituents of, 222, 266.

Muscular tissue, smooth, structure of, 102;
physiological importance of, 103; distribu-
tion of, 103; in contractile tissues, 104 ; in
vertebrala, 105; literature of, 106; action
of reagents on, 105; presence of, in walls of
oesophagus, 501 ; in intestine, 511 ; in villi,
514 ; in corpora cavernosa of penis, 630 ;
in coats of vessels, 676 ; in arteries, 683 ;
in veins, 686, 689,

Muscular tissue, striated, elements of, 106,
225; chemical composition of, 106; distri-
bution of, 107, 108 ; literature of, 108.

N.

Nails, layers of, 159; structure of, 161 ; ac-
tion of reagents on, 163; growth of, 166;
pathological conditions of, 168; develop-
ment of, 169; method of investigating, 170;
literature, 170.

Nasmyth, I\Ir., on structure of enamel, 476,
vote.

Neill, Dr., on gastric villi, 505, 7ioie.

Neilson, Dr., on impregnation of ovum in
Ascaris mysia.x, 637, 7iote.

Nerve-cells, structure of, 357-359; in me-
dulla oblongata, 376; in cerebellum, 380;
in ganglia, 406 ; pale processes of, 408 ; con-
nection of, with nerve-fibre, 409; in the
sympathetic, 421 ; development of, 427.

Nerve-fibre, structure of, 345-356; medulla
of, 346, 350; axis-cylinder of, 347, 351,
353-356 ; sheath of, 349, 350 ; in the skin
of animals, 414; terminations of, 415; by
loops, 415, 418; development of, in Tad-
pole, 428.

Nervous system, elements of, 345-359 ; di-
visions of, 345; central nervous system,
359; peripheral nervous system, 404; de-
velopment of elements of, 427-431 ; func-
tions of, 431: literature of, 112,434. See
Cerebrum, Spiiial Cord, Cerebellum, Me-
dulla oblongata. Nerve-fibre, Nerve-cells,
and Nervous Tissue.

Neruous tissue, elements of, 109, 345 ; varie-
ties of, 110; physiological importance of,

111; distribution of, 112; literature of, 112,
434; chemical composiiion of, 111, 359;
pathological changes of, 431 ; method to be
einploycd in investigations of, 434.

Newport, ]\Ir., on impregnation of ovum of
Frog, 636, 637, tiote.

Nipple, structure of, 662.

Nose. See Olfactory Organ.

Nuclei, occurring free, 42; multiplication of
by division, 50; origin and development of,
58 ; importance of, in cell development, ib. ;
occurrence of, in blood-corpuscles, 12-2,note.

Nucleus-fibres, 81, 84, 85.

0.

OEsophagus, structure of walls of, 501 ; litera-
ture of, 502.

ffisterlein, Prof, on epithelial cells of intes-
tine, 517, note.

Olfactory nerve, fibres of, 390, 783.

Olfactory organ, structure of. 778-783 ; mu-
cous membrane of, 780-783; mode of
investigating, 783 ; literature of^, 784.

Optic nerve, origin of fibres of, 390; course
of fibres in the eye, 744, 745.

Oral cavity, mucous membrane of, 436 ; mi-
nute structure of mucous membrane of,
437; vessels and lymphatics of, 438; epi-
thelium of, 439-441 ; mucous glands of,
455; their intimate structure, 456-459;
mode of examining its mucous membrane,
466 ; literature of, 467. See Teeth, Tongue.

Organs, classification of, 73, 74.

Osseous system, 266; nerves of, 303-306.
(5'ee Bone.)

Osseous i?ss2/e, elements of, 99, 267; distri-
bution of, in vertebrata, 101 ; literature of,
102, 344; forms of, 266. ^S'ee Bone.

Otolithes, composition of, 770.

Ovary, structure of, 640-642; mode of exa-
mining, 659 ; literature, ih.

Oviducts, 646.

Ovum, composition of, 642 ; detachment and
reformation of, 643.

Owen, Prof., on " contour lines" of dentine,
472 ; on dentine containing Haversian
canals, 474 ; on structure of dentine, 475,
note.

P.

Pacchionian granulations, 403.

Pacini, Prof., on termination of nerves in

corpuscles, 412.
Pacinian bodies, structure of, 413, 785.
Pancreas, structure of, 549 ; literature of, 550.
Panum, Dr., experiments on formation of

membranes, 43.
Parotid gland, 463.
Parovarium, 642.
Penis, structure of, 630, 634 ; arteries of, 633 ;

literature of, 639. i
Pericardium, 667.
Periosteum, structure of, 281 ; lymphatics of,

303 ; layers of bone formed on inner aspect

of, 324, 328; lining osseous semicircular

canals, 769.
Peritoneum, structure of, 502.
Peyer's glands, composition of, 521, 523 :

lymphatics of, 523, 524.

800

INDEX.

Pharynx, mucous membrane of, 500; glands
of, ih.

Pia niaier, of spinal cord, 394 ; of brain, 395 ;
bloodvessels and lymphatics of, 398 ; nerves
of, 399 ; Pacchionian granulations of, 403.

Pigment cells, 144; in skin of Negro, 144,
7iole.

Pineal gland, structure of, 385.

Placenta, 653.

Pleurae, structure of, 574.

Pons Varolii, 372, 376.

Prepuce, 632.

Primordial cartilaginous skeleton, 306; meta-
morphoses of, 310.

Prostate gland, structure of, 628-630; con-
cretions in, 629.

Purkinje, Prof, observations on endocar-
dium of Ruminants, 108; on nerves in the
pia mater of the Ox, 399.

Q.

Quekett, Prof , on elastic fibres in Giraffe, 81.

R.

Reichert, Dr., on crystalline form of histoge-
netic substances, 57 ; on fibrous tissue, 94 ;
on conical substance of hair, 176, note; on
epithelium upon articular cartilages, 291 ;
on cartilage corpuscles, 311, 7ioie; on crys-
tallized albuminous matter, 715.

Reid, Dr. John, observations on paralyzed
muscles, 258.

Reiney, Mr., on existence of a choroideal
muscle, 739.

Reinhardt, Dr., on colostrum, 665.

Remak, Prof., observations on cell-division,
55; on cartilage-corpuscles, 3l\, note; on
"fibres of Remak," 423, 426; on ganglia
upon glosso-pharyngeal nerve, 454 ; on de-
velopment of thyroid, 588 ; on development
of kidneys, 608.

Respiration, organs of, 568. See Larynx,
Trachea, and Lungs.

Retina, structure of layers of, 739-746 ; con-
dition of elements of, at yellow spot, 746 ;
connection of its various layers, 746-751 ;
physiological importance of the separate
layers, 748 ; especially of the radiating
fibre-system, 748, 749, 750, note; mode of
investigating, 764 ; literature, 766.

Retzius, Prof., on cells of dentine, 475, ?iote;
on Nasmyth's membrane, 477, note.

Robin, M., on structure of cartilage, 311, wo^e;
on formation of bone, 322; on vegetable
growth on the tongue, 452, 7iote; on crys-
tals obtained from blood-serum, 715.

Rokitansky, Prof, on new formation of mus-
cular fibre, 257 ; on hypertrophy of thyroid,
588.

S.

Saliva, 465.

Salivary glands, structure of, 464; secretion
of, 465.

Salter, Mr., on structure of dentine, 475, ww^e.

Schwann, Prof., importance of his researches
on Histology, 34 ; theory of cell develop-
ment, 56, 57 ; on development of connec-

tive tissue, 88, 95 ; on development of car-
tilage, 310; on nerves of vas deferens, 628.

Sclerotic coat of eye, structure of, 725-727.

Sebaceous glands, occurrence of, 212-215 ;
structure of, 216 ; development of, 218-
220 ; abnormal conditions of, 221 ; method
of investigating, 221 ; literature, 222.

Semen, spermaiozoids of, 622-624 ; chemical
composition of, 624 ; formation of, 635, 636.

Seminal tubes, 621.

Septum narium, nerves in, 305 ; structure of
cartilage of, 310, note.

Sesamoid bones, 240.

Sexual organs, male, 618; physiological re-
marks on, 634 ; literature of, 638. See
Testes, Penis, Prostate Gland.

Sexual organs, female, 640 ; physiological re-
marks on, 656 ; mode of investigating, 659 ;
literature of, ih.

Sharpey,Dr., on formation of certain bones of
the skull, 335, note.

Simon, Dr., on increase of sudoriparous glands
in elephantiasis, 207.

Simon, Mr., on struciure and development of
thymus gland, 590, 595.

Skin, layers of, 119-138; subcutaneous cel-
lular tissue, 120 ; corium, 121-125 ; fat cells,
125; vessels, 127 ; papillae, 121, 130; nerves
of, 129, 132 ; physiological remarks on, 135 ;
epiVZcrm/s, 139-158 ; literature, 158; method
of investigating, 157; glands of, 199-222.

Smooth muscular fibres, 102. See JSluscular
Tissue, smooth.

Spermatozoa, composition of, 622 ; move-
ments of, 624; action of reagents on, ih.;
formation of, 623,625 ; absence and changes
of, in disease, 625, note; as impregnating
agents, 636.

Spinal cord, division of, 360; intimate struc-
ture of white substance, 361 ; struciure of
gray substance, 362-3()5 ; posterior roots of
nerves in, 366 ; filum ter minale, 367 ; agents
for investigating the course of the fibres,
368; course of fibres in, 369; membranes
of, 392-399; vessel of, 400; structure of
ganglia of, 405.

Spinal nerves, origin of, 404 ; structure of
ganglia on, 405, 406, note; course and ter-
mination of, 411 ; termination of, in Paci-
nian bodies, 412 ; neurilemma of, 414 ; ves-
sels of, ih.

Spleen, coats and trabecular tissue of, 551 ;
Malpighian corpuscles, 552-556; pulp or
parenchyma, 556-559 ; changes undergone
by blood-corpuscles in, 559-562 ; vessels
and nerves of, 562-565; lymphatics of,
566; physiological remarks on, 567; inves-
tigation of, ih.; literature of, 563.

Stilling, Dr., on structure of spinal cord, 377.

Stomach, muscular tunic of, 503; mucous
membrane, 505; villi of, 505, note; glands
of, 50(i-509; epithelium, 509; bloodvessels
of, 510; lymphatics of, ih.; mode of ex-
amining, 527 ; literature, 527.

Sudoriparous glands, structure of, 200 ; secre-
tion of, 202 ; ducts of, 204 ; developiuent of,
205; pathological conditions of, 207; me-
thod of investigation of, 208 ; literature of,
ih.

Sublingual gland, 463.

Submaxillary gland, 4C3.

Supra renal capsules, intimate structure of,
613-615, 617, note; vessels and nerves of,

INDEX.

801

615 ; physiological remarks on, G16 ; inves-
tigation of, G18 ; literature of, il>.

Sympathetic nerve, fibres of, 118, '12Q; rami
comnuinicantes of, 41'.), 421 ; cells of gan-
glia of. 4t21, 4-24; peripheral distribution ot,
4J3 ; fibres of llemak, 4-23, 425 ; ultimate
course of branches of, 425.

Synapta digitata, development of cell iii, 52.

Symphysis pubis, cartilaginous layer of, 288;
formation of bone corpuscles in, ib.

Synovia, microscopical appearance of, 298;
chetnical coinposition of, 298.

Synovial membrane, 239; intimate structure

of, ^yc.

Sweat-glands. See Sudoriparous Glands.
Synovial sacs, 242 ; structure of, in muscular

system, 212; occurrence of cartilage cells

in, 242.

T.

Tactile corpuscles. .See A.xile Corpuscles.

Tarsal cartilages, 757.

Teeth, parts of, 468 ; dentine, 468; enamel,
476; cement, 480; pulp of, 483 ; develop-
ment of, 484-494, 789; pathology of, 495;
mode of e.xamining, 497; literature, 498.

Tendons, structure of, 232-235; ligaments of,
239; vessels of, 244; nerves of, 247; che-
mical composition, 252 ; development of,
255.

Testes, glandular substance of, 620 ; semini-
ferous tubes of, 621-624 ; secretion of, 624 ;
membranes, vessels, and nerves of, 626 ;
structure of vasa deferentia and ejaculatory
duct, 627, 628 ; development of, 634 ; me-
thod of examining, 638 ; literature of, ib.

Thoracic duct, 694.

Thyroid gland, structure of, 586 ; bloodves-
sels of, 587 ; developinent of, 588 ; patholo-
gical changes in, ib.; literature of, 5S9.

Thymus, structure of, 589-593; concentric
corpuscles of, 593; development of, 594;
investigation of, 595; literature of, ib.

Tissues, general anatomy of, 39-118 ; classi-
fication of, 72.

Todd and Bowman, Profs., on ligaments of
the lower jaw, 285 ; on vessels ot bone, 301 ;
on epithelium of menibrana tympani, 768 ;
on epithelium of olfactory mucous mem-
brane, 779, 780.

Tomes, .Mr., on composition of teeth, 471 ; on
enamel prisms. 478, 7iote.

Tomes and De Morgan. MM., on structure
and development of bone, 270, 7iote; 274,
7iote; 280, 7tole; 323, 7iote.

Tongue, muscles of, 441-446 ; division of
striated fibres in, 446 ; mucous membrane
of, 447; papilla; of, 447-451; mucedinous
fungi on, 451 ; fur of, in diseases, 451, 452,
7iote; physiology of papillae of, 453; nerves
of, 454 ; follicular glands of, 459; mode of
examining papillae, 466 ; literature. 467.

Tonsils, structure of, 461 ; vessels and nerves
of, ib.; secretion of, 462.

Toynbee, Mr., on termination of nerves in
kidney, 605, 7iote.

Trachea, tissues of, 572 ; glands of, 573 ; cili-
ated epithelium of, ib ; bloodvessels of, 574.

Trachea;, termination of, 71.

Tunica media, of arteries, 679, 682.

51

U.

Ureters, structure of, 607.

Urethra, female, structure of, 608.

Urethra, male, structure of, 631.

Urinary bladder, structure of, 607.

Urinary organs, enumeration of, 595; deve-
lopment of, 608 ; literature, 612. S'ee Kid-
neys. Ureters, Bladder, and Urethra.

Urine, secretion of, 610; sediments in, 610;
presence of albumen, fibrin, and fat in, 610,
611.

Uterus, structure of, 646-649 ; distribution of
vessels in, 648 ; ligaments of, ib.; changes
in, at menstrual period and in pregnancy,
649-654; nerves of, 652 ; mode of investi-
gating, 659; literature of, 660.

Vagina, 654.

Valentin, Prof., on termination of nerve-fibres
in muscle, 248; on development of bone,
335; on movements of spermatozoa, 625.

V'ascular system, 667-725 ; literature of, 723.
.See Heart, Bloodvessels, and Blood.

Vas deferens, 627.

Vasa vasorum, 677.

Vascular tunic of eye, 733. See Choroid and
Iris.

Vauquelin, M., his analysis of the brain, 359 ;
of human semen. 624.

Veins, structure of coals of, 684-689; valves
of, 689.

Ventricles of heart, fibres of, 672.

Vesicles, of Ascherson, 41; in milk, 41 ; in
the yelk-substance, 42.

Vesiculae seminales, structure of, 628.

Vierordi, Dr., on enumeration of blood-cor-
puscles, 704, 7io(e.

Villi, intestinal, 511 ; structure of, 512-514;
epithelium of, 514, 516, 7iole ; changes they
undergo during digestion, 515, 516, 7iole:
lacteals of, 513, 516, 7iotp.

Vitreous humor of eye, constitution of, 754-
757 ; investing membrane of, 754 ; develop-
ment of, 755.

Virchow, Prof., on connective-tissue cor-
puscles, 85; on gelatinous tissue of Whar-
ton,. 95; on mucous tissue, 96 ; on contents
of bursEe mucosae, 239; on interarticular
fibro-cartilage, 297, 7iote ; on cartilage-
corpuscles, 311, note; on microscopical
conditions of osseous growths, 341 ; on
spinal ependyma, 397, 7iot.e; on cellulose
nature of the corpora amylacea, 402, 7iote;
on colloid spleen, 554, 7iote; on agents for
restoring ciliary motion, 571, 7iote; on pro-
static concretions, 629; on cells resembling
pus-corpuscles in the blood, 713 ; on the
composition of the vitreous body in the
feet us, 755.

Volkmann, Prof, on origin of the fibres in
the spinal cord, 370 ; on structure of glosso-
pharyngeal nerve, 417.

W.

Wagner, Prof., on axile-corpuscles, 130; on

802

INDEX.

termination of nerves in muscle, 248, 249 ;
on ganglion-globules in the Ray, 391, 392 ;
on bipolar cells in Fishes, 410.

Weber, Prof., his experiments on touch, 137 ;
on smegma prreputii, 215 ; on elasticity of
muscles, 262 ; on branches of hepatic duct,
539.

Wedl, Dr., on hypertrophy of muscular fibre,
257, 7}ole; on structure of diseased teeth,
495, note.

Welcker, Dr., his method of counting blood-
corpuscles, 704, nofe.

Wrisberg, cartilage of, 569, 572.

X.

Xantliogenus, presence of, in milk, 666.

Yelk, cleavage of, 51.

Yellow fibrous tissue. See Elastic Tissue,

Zinn, zone of, 753, 754, 756,
Zona deniiculaia, 771.

THE END.

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MAR 6 1933