IBID

arinitu iHcbiral (Collcqr

v

A MANUAL

HISTOLOGY

EDITED AND PEEPAKED BY

THOMAS E. SATTERTHWAITE, M.D.,

OF NEW YORK

President of the New York Pathological Society, Pathologist to the St. Luke's and
Presbyterian Hospitals, etc.

IN ASSOCIATION WITH

DRS. THOMAS DWIGHT, J. COLLINS WARREN, WILLIAM P. WHITNEY, CLARENCE J.
BLAKE, and C. H. WILLIAMS, of Boston; DR. J. HENRY C. SIMES, of Philadel-
phia; DR. BENJAMIN F. WESTBROOK, of Brooklyn; and DRS. EDMUND C.
WENDT, ABRAHAM MAYER, R. W. AMIDON, A. R. ROBINSON, W. R.
BIRDSALL, D. BRYSON DELAVAN, C. L. DANA, andW. H.
PORTER, of New York City

WITH ONE HUNDRED AND NINETY-EIGHT ILLUSTRATIONS

NEW YORK
WILLIAM WOOD & COMPANY

1881

COPTBIOHT BT

WILLIAM WOOD & COMPANY
1881

TROWS

PRINTING AND BOOKBINDING COMPANY

201-313 Knit latA Street

NEW YORK

PREFACE.

FOR some years past there has been a general demand
among the members of our profession for a manual of Histol-
ogy, summarizing, in concise and plain language, our present
knowledge in this fundamental branch of medicine. It is true
many books have been written -on the subject, but their great
brevity, on the one hand, or an unnecessary diffuseness on the
other, have prevented them from meeting with acceptance at
the hands of physicians and students. In the one class belong
the little handbooks of Rutherford and Schaefer, which have
done much to simplify and therefore popularize histology, but
they were intended for beginners, and especially students doing
class-work under the laboratory system now so much in vogue.
But both physician and student" need something of wider scope,
and they have been compelled to turn to Klein & Smith,
Strieker, or Frey, though no one of these excellent works is
thoroughly adapted to their wants.

Apart from the expense of the two former, they all are
deficient in matters relating to human histology.

The practical experience of a teacher made it evident also
that the volume to fill such an obvious gap should take the
form of a text-book. And the present time seemed opportune
for its appearance, since we have latterly made much positive

jv PREFACE.

advance in historical studies, while histologists themselves
:llv now more of one mind in microscopical matters. That such
a book should appear under American auspices seemed further
to be eminently proper, as we have in various parts of the coun-
try a goodly number of medical men who are either engaged
in" teaching histology or in studying some special branch of it.
The advantages of utilizing their accumulated experiences
I therefore apparent by the editor, and he gladly applied
to them for assistance when it was found that one individual
could not prepare the volume within a reasonable time or
in a manner that would be satisfactory. It is hoped that
the names of the collaborators furnish a sufficient guarantee
that proper representatives of American histology have been
selected. In some respects the. object sought for has not been
wholly attained, as, for example, in the effort to separate
purely human histology from the comparative. But this is
impossible at the present time, mainly because our knowl-
edge is still too limited. It is a matter of regret, also, that the
original illustrations have been so few in comparison with the
total number, but the great expense attending their production
would not warrant any one in attempting much in this direc-
tion. Through the kind co-operation, however, of Messrs. Wil-
liam Wood & Co., the editor has been able to utilize many
excellent cuts that were in their possession.

As a further means of relieving the tedium associated witli
a work that is so largely descriptive, the various authors havo
aimed to intersperse here and there throughout the text mat-
ters of physiological or pathological import. Still, intelligent
practitioners do not have to be reminded that rational thera-
pfutics has found a substantial support in the revelations of
pathological anatomy, which, in turn, rests upon histology,

PREFACE. V

so that tlie relation between microscopic anatomy and the sci-
entific practice of medicine is readily appreciated.

Emanating as the volume does from American sources, the
editor finds it a fitting place to give proper space to American
contributions, and the reader may therefore find due notice of
the physiological desquamation of bloodvessels, considerations
on the nature of nerve-termini, matters relating to the intimate
structure of the striped muscular fibre and nerves, with the
results of studies on the structure and development of certain
connective substances, and novelties in microscopic apparatus
and methods. A special chapter is also given to the thick
cutis vera, now for the first time described as a distinctive
portion of the skin. In it will be found detailed the discovery
of the fat-columns, which are .calculated to explain certain
pathological changes that have been imperfectly understood.

The first chapters of the book are devoted to the mechanism
of the microscope, and to certain formal methods of work with
which the beginner should be familiar. Of the illustrations,
sixty-five were prepared for the volume, while forty have never,
it is believed, appeared in book-form. The remainder are
mostly from the manuals of Strieker and Frey.

A limited number of bibliographical references have been in-
serted where it was thought they were desirable in guiding
the reader to the literature of the subject. For the prepara-
tion of these tables and much valuable assistance, the editor
here desires to express his thanks to Dr. E. C. "Wendt, of this
city.

It was thought best to omit the subject of optical principles
which figure so conspicuously in some of our histological
manuals. Those who wish information on these matters are
referred to any of the standard text-books on physics, where

yi PREFACE.

subject is treated at greater length than was permissible in
the present instance.

For a similar reason, and also because it would prove a
needless expense, the price-lists of instrument-makers have
been omitted. Full particulars relating to the various sorts of
microscopes and their accessories can be obtained from any
of the leading opticians, who from time to time issue lists con-
taining ample illustrations of the most recent improvements
in all that pertains to practical working of the instrument.

In conclusion, the editor finds himself compelled to reiter-
ate the well- worn statement, that circumstances over which he
lias had no control have united to delay the press- work of
the volume, and at the end have made its final revision rather
hasty. A kind indulgence is therefore asked for any error
that may, through oversight, have escaped his notice.

T. E. S.

TABLE OF CONTENTS.

PART I.

CHAPTEK I.

BY THOMAS E. SATTERTHWAITE, M.D.

MATERIALS REQUISITE FOR HISTOLOGICAL WORK. — How TO USE THE MICRO-
SCOPE.— TESTING THE MICROSCOPE. — ITS USES. Page 1

Appliances for microscopic work, 1. Chemical reagents, 3. Illumina-
tion, 4. Stage diaphragms, 5. The mirrors, 5. Direct and oblique light, 5.
Arrangement of the object, 6. Kind of lens to use, 6. How to keep the
instrument clean, 7. Magnifying power of a lens, 7. How to estimate the
size of an object, 8. Testing a lens, 8. How to illuminate the object, 9.
Testing the eye-piece, 10. Testing high lenses, 10. Measuring the angle of
a lens, 10.

CHAPTER II.

BY THOMAS K SATTERTHWAITE, M.D.

METHODS FOR PREPARING MICROSCOPIC OBJECTS Page 12

General directions, 12. To prepare fresh objects for rapid examination,
13. Ordinary methods of preparing tissues, 13. Miiller's fluid, 14. Potas-
sium bichromate solution, 14. Ammonia bichromate solution, 14. Alcohol
and acetic acid mixtures, 14, 15. Molybdate of ammonia, 15. Solution of
osmic and chromic acids, 15. Alcohol and acetic acid, and muriatic acid
solution, 15. Method of hardening the brain, 15. How to embed speci-
mens, 15. Embedding in glycerine and tragacanth, 16. The hand section-
cutter, 10. Freezing section-cutters, 17. Hailes' microtome, 19. The
Vincent microtome, 21. Staining fluids, ammonia carmine, 21. Borax car-
mine, 22. Double staining, 22. Haematoxylon solutions, 23, 24. Solutions
for multiple staining, 24, 25. Preparation of the cornea, 25. Triple stain-

i TABLE OF CONTENTS.

Ing, 36. Doable, triple and quadruple staining, 26. Bismark brown, 26.
Solution of alum carmine, 27. Naphthaline yellow for bone, 27. Methyl
green and induline, 27. Purpurine, 28. French archil, 28. Alizarine, 28.
Metallic solutions, staining with osmic and oxalic acids, 28. Chloride of
gold and lemon jnice, 28. Nitrate of silver, 29. Chloride of gold, 29.
Osmic acid, 29. Methyl green for waxy change, 29. Wickersheimer'a
liquid, 29. Methods of injecting the blood-vessels, 30.

CHAPTER III.

BY THOMAS E. SATTERTHWAITE, M.D.

THE BLOOD Page, 34

Bed corpuscles, 34. Comparative measurements in men, and animals, 36.
Number of, 37. Corpuscles in an indifferent fluid, 38. Brownian and
amoeboid movements, 39. Heating slide, 40. Action of dilute salt solution,
40. Action of distilled water- -irrigation, 41. Action of carbonic acid gas,
42. Action of acids, 43. Action of alkalies, 44. Action of electricity, 44.
Exhibition of the circulation, 45. Internal structure of red corpuscles, 46.
Development, 47. White corpuscles, 48. Counting corpuscles, 48. Blood
crystals, 53. Haemoglobin, 53. Hajmochromometer, 54. Bibliography, 54.

CHAPTER IV.

BY THOMAS E. SATTERTHWAITE, M.D.

EPITHELIUM \ page 5G

Ordinary flattened or squamous epithelium, 57. Ciliated epithelium, 58.
Effect of reagents, 59. Columnar or cylindrical epithelium, 60. Other va-
rieties, 61. Structure of epithelial corpuscles, 61. Bibliography, 61.

CHAPTER Y.

BY THOMAS E. SATTERTHWAITE, M.D.

Tire CONNECTIVE SUBSTANCE GROUP. -Mucous OR GELATINOUS TISSUE. -
ISSUE. -NKI-KOGMA.— FAT TISSUE.— FIBROUS TISSUE PROP-

BB. — CORNEAL TISSUE.— IXTKKMUSCULAR TISSUE.— TENDON TISSUE —

ELASTIC TISSUE ; Page Q2

Connective substances in general, 62. Mucous or gelatinous tissue, 63.

slopment of fibrous tissue, 64, 65. Fibrous tissue, 66. Adenoid tissue

euroglia, 70. Tendon tissue, 72. Fat tissue, 73. Intermuscular

lorneal tissue, 75. Elastic tissue, 77. Pavement endothe-

1mm, 80. Bibliography, 81.

TABLE OF CONTENTS. IX

CHAPTER VI.

BY THOMAS E. SATTERTHWAITE, M.D.

THE CONNECTIVE-SUBSTANCE GKOUP (Continued). — CARTILAGE Page 83

Hyaline cartilage, 82. Parenchymatous cartilage, 83. Division of the
corpuscle, 84. Calcifications, 84. Methods of studying hyaline cartilage,
84. Yellow elastic cartilage, 85. Fibrous cartilage, 86. Structure of cor-
puscle, 87. Bibliography, 88.

CHAPTER VII.

BY THOMAS E. SATTERTHWAITE, M.D.

THE CONNECTIVE-SUBSTANCE GROUP ( Continued). — BONE Page 89

Compact tissue, 89. Ossein, 89. Bone-corpuscles, 90. Haversian sys-
tem, 90. Preparation of dry bone, 92. Preparations of decalcified bone, 92.
Sharpey's fibres, 94. Cancellous tissue, 94. Marrow, 95. Periosteum, 95.
Development of bone, 96 ; through cartilage, 97 ; from membrane, de-
velopment and absorption, 99. Howship's lacunae, 100. Formation of cal-
lus, 100. Bibliography, 101.

CHAPTER VIII.

BT THOMAS E. SATTERTHWAITE, M.D.

THE TEETH Page 102

The enamel, 102. Dentine or ivory, 103. Dentinal globules, 104. Cement, .
105. Pulp, 105. Development of teeth, 105. Primary enamel organ, 107.
Development of enamel, 108. Bibliography, 108.

CHAPTER IX.

BY THOMAS E. SATTERTHWAITE, M.D.

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM Page 109

Nerve-fibres, 109. Myelinic fibres, 109. Staining in picro-carmine, 111.
Staining with silver, 112. Staining with osmic acid, 113. Semi-desicca-
tion, 113. Transverse sections of myelinic nerves, 114. Preparation by
ammonia bichromate, 115. Modern conceptions of myeliuic nerves, 116.
Fibres of Remak, preparations in osmic acid and picro-carmine, 118. Prep-
arations of Remak's fibres in h&matoxylon, 118. Ganglionic bodies, 119.
Ganglia of the cranial and spinal nerves, 120. Gasserian ganglion, 120.
Ganglionic bodies of the spinal cord, 120. Brain, 121. Sympathetic, 121.
Meissner's plexus, 122. Auerbach's plexus, 123. Termination of nerves,
123. Tactile corpuscles, 124. Pacinian bodies, 124. Nerve-terminations
in muscle, 125 ; in epithelium, 120. Connective tissue of nerves, 126.
Bibliography, 127

TABLE OF CONTENTS.

PART II.

CHAPTER X.

BY THOMAS D WIGHT, M.D.

..Page 128

MCSCTLAR FIBRE

Involuntary muscular fibre, 128. Voluntary muscular fibre, 130. Physi-
ological attributes, 134. Nuclei and muscle corpuscles, 136. Conclusions,
137. Peculiarities of voluntary muscles, 138. Termination of muscle in
tendon, 139. Muscular fibre of the heart, 140. Bibliography, 140.

CHAPTER XL

BY EDMUND C. WENDT, M.D.

THE BLOOD-VESSELS Page \&

Capillary blood-vessels, 142. Vascular endothelium, 143. Capillaries
proper, 144. Genesis, reproduction, and regeneration of capillaries, 150.
Arteries, 151. Veins, 155. Peculiar vascular structures, 158. Blood-vas-
cular glands, vascular plexuses, 158. Intercarotid gland, 160.' Corpora
cavernosa, 160. Vasa vasorum, lymphatics, and nerves, 161. Bibliography,
162.

CHAPTER XII.

BY W. R. BIRDSALL, M.D.

Tire LYMPHATIC SYSTEM Page 163

Modern views of, relative to connective tissue, 163. General histology,
164. Lymphatics of the mesentery, 165. Klein's studies on the omentum,
166. Perilymphangeal nodules, 167. Development of fat-tissue, 168. Lym-
phatic radicles, 168. Artificial injection of lymphatics, 169. Endothelium
and stomata, 169. False stomata, 170, 171. Intimate structure of lym-
phatic vessels, 172. Variations in shape, 173. Topographical peculiarities,
174. Thoracic duct, 174. Subarachnoid and subdural spaces, 175. Lym-
phaticn of tendons, 175. Lymphatic glands, 175. Nerves of lymphatic
nodes, 179. Injection of a lymphatic gland, 179. Method of studying, 179.
Kanvier's method, 180. Other methods of injecting glands, 180. Bibli-
ography, 182.

TABLE OF CONTENTS. xl

CHAPTER XIII.

BY A. MAYER, M.D.

THE LIVER AND BILIARY APPARATUS Page 183

Hepatic lobules, 183. Blood-vessels, 186. Connective tissue, 188. Liver-
cells, 189. Larger biie-ducts, 191. Glands of the ducts, 191. Capillary
bile-ducts, 192. Do the bile-capillaries possess walls ? 196. Gall-bladder,
197. Lymph-vessels of the liver, 198. Nerves, 199. Bibliography, 199.

CHAPTER XIV.

BY A. MAYER, M.D.
THE KIDNEY Page 201

General structure, 201. Renal tubules, 203. Their epithelium, 206. The
loops, 209. Their epithelium, 210. Intercalated portions, 211. Collecting
tubules, 211. Their epithelium, 211. Blood-vessels of the kidney, 213. In-
jecting the kidney, 214. Kidney stroma. 215. Nerves, lymphatics, capsule,
calyx, 216. Natural injection by the sulphindigate of soda, 216. Bibliog-
raphy, 222.

CHAPTER XY.

BY J. HENRY C. SIMES, M.D.

MALE EXTERNAL AND INTERNAL ORGANS OP GENERATION, WITH THEIR
GLANDULAR APPENDAGES Page 223

Penis, 223. Urethra, 225. Cowper's glands, 227. Prostate, 227. Testi-
cles, 229. Tunica vaginalis, 230. Hydatid of Morgagni, 231. Vas defe-
rens, 232. Seminal vesicles, 235. Bibliography, 238.

CHAPTER XVI.

BY J. HENRY C. SIMES, M.D.

FEMALE EXTERNAL AND INTERNAL ORGANS OP GENERATION, WITH THEIR
GLANDULAR APPENDAGES. — PLACENTA Page 240

Labia majora, 240. Labia minora, 240. Clitoris, 240. Vestibule, 241.
Glands of Bartholine, 241. Hymen, 241. Vagina, 241. Urethra, 242.
Uterus, 243 ; Mucous membrane of, 243. Ovula Nabothi, 244. Fallopian
tubes, 246. Ovary, 246. Graafian follicles, 248. Parovarium, 350. Pla-
centa, 251. Bibliography, 251.

TABLE OF CONTENTS.

CHAPTER XYII.

BY BENJAMIN F.' WESTBROOK, M.D.

TIIK RESPIRATORY TRACT Pase 253

Larynx, '.53. Ligaments of, 253. Cartilages, 254. Epiglottis, 255.
Mucous membrane, 2.55. Trachea and primary bronchi, 257. Smaller bron-
chi and lungs, 259. Pleura, 2G5. Lymphatics of, 267. Pleural append-
ages, 267. Bibliography, 267.

CHAPTER 'XYIII.

BY A. R. ROBINSON, M.D.

THE SKIN P<*9* 269

General plan of arrangement, 269. Structure, 270. Different layers,
271. Epidermis, 271. Rete Malpighii, 271. Granular layer, 274. Stratum
lucidum, 274. Corneous layer, 274 Subcutaneous connective-tissue layer,
275. Pacinian corpuscles, corium, 277. Blood-vessels, 279. Nerves, 279.
Tactile corpuscles, 280. Sweat-glands, 282. Muscles, 287. The hair, 288.
Nails, 293. Bibliography, 295.

CHAPTER XIX.

BY R, W. AMIDON, M.D.

TIIE CENTRAL NERVOUS SYSTEM .Page 296

Spinal dura mater, 296. Spinal arachnoid, 297. Spinal pia mater, 297.
General histology of the spinal cord, 298. Nerve -elements of the cord, 299.
Special studies in different portions of the cord, 301. Medulla oblongata,
807. Olivary body, 310. Cerebellum, 317. Cerebral ganglia, 319. Cere-
bral ventricles, 319, Cerebral cortex, 321. Structure of cortex, 323. Bib-
liography, 325.

CHAPTER XX.

BY C. H. WILLIAMS, M.D.

THE EYE page 328

Eyelids, 828. Eyelashes, 328. Tarsus, 829. Meibomian glands, 329.
Conjunctiva, 380. Cornea, 331. Sclera, 337. Vitreous layer, 339. Ciliary
body, 340. Retina, 343. Lens, 350. Lachrymal gland, 351 . Bibliography,
852.

CHAPTER XXL

BY W. F. WHITNEY, M.D., AND CLARENCE J. BLAKE, M.D.

AR Pagem

External ear. 353. Middle ear, 355. Eustachian tube, 355. Internal
ear, 357. Membranous labyrinth, 358. Cochlea, 362. Bibliography, 367.

TABLE OF CONTENTS.

PART III.

CHAPTER XXII.

BY D. BRYSON DELAVAN, M.D.

TIIE NASAL FOSSAE, PHARYNX, AND TONSILS Page 368

Vestibulum nasi, 868. Respiratory region, 368. Olfactory region, 370.
Olfactory nerves, 372. Bowman's glands, 372. Pharynx, 373. Tonsils,
373. Bibliography, 375.

CHAPTER XXIII.

BY D. BRYSON DELAVAN, M.D.

THE MOUTH AND TONGUE Page 377

Tunica propria, 377. Blood-vessels, 379. Lymphatics, 379. The tongue,
380. Papillae, 380. Taste-goblets, 381. Bibliography, 384.

CHAPTER XXIY.

BY EDMUND 0. WENDT, M.D.

THE ALIMENTABY CANAL Page 386

(Esophagus, 386. Stomach, 388. Small intestine, 394. Large intestine,
400. Rectum, 401. Bibliography, 402.

CHAPTER XXV.

BY C. L. DANA, M.D.

THE SPLEEN, PANCKEAS, THYMUS, THYROID, AND PINEAL GLANDS, AND
PITUITARY BODY Page 403

The spleen — coats, 403, 404. Malpighian corpuscles, 404. Pulp, 406.
Blood-vessels, 407. Lymphatics, 409. Nerves, 409. Development, 409.
Pancreas— excretory duct, 411. Blood-vessels, 411. Lymphatics, 411.
Nerves, 411. Development, 411. Thymus gland, 412. Capsule, 412. Fol-
licles, 412. Central canal, 414. Blood-vessels, lymphatics, development, 414.
Thyroid body, 415. Blood-vessels, 416. Lymphatics, 416. Nerves, 416.
Pineal gland, 417. Pituitary body, 417. Bibliography, 418.

TABLE OF CONTENTS.

CHAPTER XXVI.

BY J. COLLINS WARREN, M.D.

THE THICK CUTIS VERA Page 420

Fat-columns, 421. Blood-vessels, 423. Lymphatics, 424.

CHAPTER XXVII.

BY EDMUND C. WENDT, M.D.

URINARY EXCRETORY PASSAGES.— SUPRARENAL CAPSULES Page 428

Renal pelvis, 428. Ureters, 429. Bladder, 430. Suprarenal capsules,
431. Bibliography, 437.

CHAPTER XXVIII.

BY W. H. PORTER, M.D., AND E. C. WENDT, M.D.

MAMMARY GLAND Page 439

General considerations, 439. Nipple, 440. Galactophorous ducts, 441.
Milk reservoirs, 441. Areola mammae, 442. Arteries, 442. Lymphatics,
443. Nerves, 443. Structure of expanded gland, 444. Of involuted gland,
446. Rauber'a views, 450. Corpuscles of Donne, 450. Milk, 451. Devel-
opment, 452. Flan of histological study, 455. Bibliography, 456.

MANUAL OF HISTOLOGY

AND

HISTOLOGICAL METHODS.

CHAPTER I.

MATERIALS REQUISITE FOR HISTOLOGICAL WORK— HOW TO USE
THE MICROSCOPE— TESTING THE MICROSCOPE— ITS USES.

VERY little apparatus and few reagents are essential for gen-
eral histological work. Such as are really needed may be so
arranged as to fit in a box or bag, that can be carried in the
hand. First of all, the student should be provided with a

Fio. 2.

Fio. a— Curved Iris Scissors.

pair of small forceps, with either curved or straight points
(Figs. 1, 2), according to individual fancy; a pair of delicate
curved iris scissors (Fig. 3) ; a few pipettes; a glass rod or

2 MANUAL OF HISTOLOGY.

two ; a spoon (Fig. 4) for lifting sections of tissues from the
fluids in which they have been immersed ; a pair of needles
(Fig. 6) in handles for teasing or tearing tissues ; (the handles
used for crochet needles, or the pin-slides sold by jewelers,
may be fitted with ordinary milliner's needles, which are long,
delicate, and flexible, and therefore well adapted for • this

Fio. 4.

Fio. 5.— Microscopic Needle-holder.

work) a sable or camel's hair brush for removing cellular
elements, so as to bring particular parts into prominence ; bibu-
lous paper ; a sharp knife (Fig. 6) for cutting thin sections ; l

1 For this purpose the razors made by Le Coultre, in Geneva, have been highly
recommended, but good knives may be obtained of almost any cutler ; indeed, most
of the makers of surgical instruments furnish them ; they are usually flat on one
side and slightly concave on the other.

MATERIALS REQUISITE FOR HISTOLOGICAL WORK.

five or six shallow porcelain dishes, ounce gallipots, with flat
bottoms, in which to soak the tissues when they have been cut ;
glass slides for mounting specimens (the ordinary size is 3 x 1
inch) ; thin glass or mica covers (squares or circles) for cover-
ing the specimens (three-quarters of an inch is a good diameter).

Mica covers are much cheaper than glass, and are suitable for rapid work
and when it is not desirable to make permanent preparations.

FIG. 8.— Beer's Cataract Knife.

In addition, a small Beer's cataract knife (Fig. 8) will be
found useful for puncturing vessels and hollow organs to obtain
samples of their fluid contents. All of these articles may easily
be contained in the drawer of a box 10 x 12 inches in size ; ' the
upper portion will hold the necessary reagents. These latter
should comprise a small amount of a three-fourths per cent,
aqueous solution of sodium chloride, about an equal amount
of distilled water, dilute acetic acid, glycerine, and iodized se-
rum;* a fluid ounce of each will be all that is necessary, and
for convenience of use they may be put in corked bottles pro-
vided with capped pipettes passing through the corks. The
vials and perforated corks may be obtained of almost any
apothecary. The cap being of rubber, very small quantities
of the fluid can be withdrawn from the bottle and pressed out
as desired, either upon the slide or otherwise.

Other reagents required are oil of cloves in a two-ounce
stoppered bottle ; dammar varnish or Canada balsam, each in
a capped bottle (Fig. 7), containing a glass rod ; a solution of
logwood, and another of borax carmine,* in ordinary glass
stoppered two-ounce bottles, and a small vial of asphalt or
some similar cement. It will be useful, in addition, to have a
small bottle (4 oz.) of absolute alcohol, another (8 oz.) of com-
mercial alcohol, some Muller's fluid3 (8 oz.), and a solution of
the bichromate of potassium (gr. xv. — 3 j.).

1 T. H. McAllister, optician, No. 49 Nassau Street, New York City, has made one
for me which answers the purpose satisfactorily. Miller Bros., No. 69 Nassau Street
and 1213 Broadway, New York City, also make and furnish cases for the same
purpose.

8 Formula in the chapter on General Methods.

3 Ibid.

4 MANUAL OF HISTOLOGY.

No good liistological work can be done without a note-book
to record the results of observation. All such memoranda will
be very useful for subsequent reference. A Jieating slide, a
gas chamber and a slide arranged for conducting electric cur-
rents may also be desirable. They will be described in the
chapter on the Blood.

The following substances that cannot be contained in a box,
and are necessary in some forms of microscopic work, may be
mentioned: osmic acid (1 percent.), nitric acid (C. P.), distilled
water, olive oil, caustic soda or potash, chloride of gold (£ per
cent, sol.).'

It is also very convenient to have at hand a short wooden
rule which is divided into inches and tenths of an inch. The
stage micrometer is also equally necessary. Other accessory
materials will be described in their proper places.

HOW TO USE THE MICROSCOPE.1

Illumination. — When the instrument is ready for use it
should be placed upon a firm and rather low table, near a
window, which does not receive the direct rays of the sun. If
daylight is not to be obtained, a small kerosene hand-lamp will
answer sufficiently well for illuminating purposes. The flame
should be on a level with the reflecting mirror of the micro-
scope, and quite near it. Sometimes a condenser is interposed,
but this is rarely necessary, and, indeed, it may be said that it
never comes into use in histological work.

A thin sheet of blue glass may sometimes be found to assist
the eye when artificial illumination is used, as the light is made
white. Some microscope makers furnish with their instru-
ments a set of blue glasses varying in color from very light to
dark blue. They are rarely needed, as the eye soon becomes
accustomed to continuous work for long sittings, even when
strong light is employed. Those who work much with the
microscope keep both eyes open, and- use first one and then

1 Formula in the chapter on General Methods.

1 It is presumed that students engaging in histological work are more or less
familiar with the mechanism of the microscope. For this reason the subject of
optical principles and the description of the different parts of a microscope are omitted
here. Those who may wish special information on these points are referred to Ap-
pendix A.

the other. Some find it a great assistance to direct the un-
engaged eye upon a dark object, such as a blackened card,
which they fasten to the tube of the instrument near its top.

As it is desirable that the lamp should only illuminate the
reflector, a great many ingenious contrivances have been made
to cut off the superfluous light. For this purpose some micros-
copists interpose a piece of thin board, or a thick card, having
a circular opening between the lamp and the reflector.

Stage diaphragms. — When the pencil of light has been
reflected from the mirror upon the opening in the stage, it is
plain that a larger or smaller amount of light will pass, accord-
ing to the size of the opening. The appliances that regulate
this matter are called stage diaphragms — sometimes they are
simply cylindrical tubes with capped upper extremities, each
tube being provided with caps of varying aperture. The tubes
are pushed into the stage from beneath. When polished they
undoubtedly aid in converging the light upon the aperture.
Other diaphragms are simply round holes in a circular revolving
plate which is set into the stage.

The diameters of the apertures vary from that of a pin's
point to about three-fourths of an inch or even more.

The revolving diaphragms have now come into general use,
because they work simply and efficiently. Mr. Wale has de-
vised one that is extremely ingenious. It has the advantage
of a cylindrical diaphragm, in so far as it converges the pencil
of light upon the diaphragmatic opening, while the size of the
opening is regulated by the action of a single thumb-screw.'
It acts as the iris does in enlarging or diminishing the pupil,
from which its name, the iris diaphragm.

The mirrors. — Of these there should be two, one plane when
a diffuse light is needed ; the other concave for a concentrated
beam. The latter is frequently used, the former seldom.

Direct and oblique light. — Thus far the descriptions have
applied to direct light, and it is the only kind much used in
histological work. In testing a lens, however, as with a diatom,
it is often necessary to use oblique light in order to resolve a
line or series of lines. In such cases the aperture in the stage
should be made as large as possible, and the mirror, concave or
plane, is to be carried well up under the stage, to the left or

1 See Appendix A.

0 MANUAL OF HISTOLOGY.

n-hr, so that the pencil of light may be thrown across the
object. By this means, little inequalities of the surface which
would be invisible under direct light are clearly demonstrated.
The poorer lenses, however, are those which necessitate oblique
light. When reference is made to the definition of the lens,
direct light is intended.

Arrangement of the object.— When the object is to be ex-
amined, it should be placed upon the glass slide, which is usu-
ally one by three inches in superficial measurement, and as
tli in as is compatible with the usages to which it is put in
ordinary microscopic work. The glass should be white in color,
and free from any imperfections that can be detected by the eye.
Usually a drop or two of water, a drop of glycerine, or a drop
of water and glycerine in equal parts, is placed upon the slide.

The object is then immersed in the liquid. It takes some
little time for the fluid to permeate the specimen, so that it is
ready for study. When pure glycerine is used fully ten minutes
will generally elapse before the specimen is transparent. A
covering glass is then cautiously let fall upon the liquid, care
being taken that no bubble of air enters. The cover is then
pressed down. In such cases, when the object is studied with
high powers, the cover will often slowly rise and separate itself
from the slide, so that the forceps or the finger may be neces-
sary to press it back. This inconvenience is obviated by paint-
ing a little Canada balsam or cement around the 'edge of the
cover so as to hold it down.

The kind of a, lens to be used. — For the first examination a
low objective should be used, with a medium, not short, eye-
piece. The tube should then be carried down until the object
comes within the focus. Low powers should always be used
at first, because they give a good idea of the object in its gen-
eral features.

Then the tube may be withdrawn, and a higher power sub-
stituted, and so on, until the specimen has been studied in all
its details. A convenient accessory is now made by most of
the instrument makers; it is a "nose-piece" — a brass attach-
ment which is screwed into the end of the tube, and carries two
or more lenses.1

1 The double angular nose-piece made by Schrauer, 46 Nassau Street, costs $6,
the triple, $20 ; all of the microscope makers are now prepared to furnish them.

TESTING THE MICROSCOPE ITS USES. 7

The first named is usually fitted with a f and a \ inch lens ;
in addition to these a TV immersion may be used for the triple
nose-piece.

How to Tceep the instrument clean. — After using the instru-
ment it should always be wiped dry, as it is damp from the
moisture of the breath and hands. The lenses should be re-
turned to their cases, and, if necessary, the surfaces are to be
rubbed off with a bit of soft chamois skin or fine linen. Water
will remove almost all the dirt from the anterior lens, but occa-
sionally it may be necessary to use alcohol. In such cases but
very little is requisite, as it may penetrate behind the anterior
lens and dissolve the Canada balsam that cements the different
portions together.

It is well for the student to familiarize himself at first with
certain common objects that are apt to be met with in all
forms of microscopic work, such as the little foreign substances
that go to make up the dust of rooms ; these include minute
bits of wood, cotton and linen fibres, particles of wool, hairs of
various animals, feathers, etc.

The imperfections in the glass should also be noted, and
especially the curious red figures sometimes resembling butter-
fly wings, caused by an accumulation in the flaws of the glass
of a red substance — the red oxide of iron— used by manufac-
turers in polishing glass. These red figures are often wonder-
fully alike, and have given rise to singular errors among micro-
scopical workers.

TESTING THE MICROSCOPE— ITS USES.

Magnifying power of a lens. — To determine the actual
magnifying power of a lens in combination with the particular
eye-piece that happens to be in use, the ordinary method is as
follows :

The glass stage micrometer, which is ruled off into tenths,
hundredths, and thousandths of an inch, is placed upon the
stage and focussed. This having been done, the wooden rule,
which we have already alluded to and which is divided into
inches and tenths of an inch, is laid alongside of the micro-
meter-slide.

One eye, looking outside of the tube, reads off the number

S MANUAL OF HISTOLOGY.

of divisions of the wooden rule corresponding to a single divi-
sion of the micrometer slide as seen with the other eye directed
through the tube of the microscope.

By this method of double vision, as it were, a comparison is
instituted between the two rules, and the ratio that one bears
to the other may be estimated.

Suppose, for example, thatT<rVo of an inch on the scale of the
stage micrometer is equal to W of an inch on the wooden rule.
The ratio of T^W to & will represent the magnifying power
of that particular combination. Reducing these fractions to
a common denominator they stand to one another as 1 to 200.
The object has therefore been magnified two hundred times.

With a short eye-piece the power is greater and it increases
in proportion as the tube is drawn out. It is customary how
ever to assume a certain length of the draw-tube as the stand-
ard : this is twenty-five centimetres or about eight inches.

How to estimate the size of an object. — To estimate the size
of an object is a much easier task. Place the stage micrometer
upon the stage of the microscope and then slip the micrometer
eye-piece into the draw-tube. The micrometer eye-piece is
simply an ordinary ocular with a glass cover fitted into the
diaphragm. The micrometer consists of a series of parallel
lines ruled across it at regular distances apart. By focussing
the lines on the stage micrometer one may readily count the
actual fractions of an inch corresponding to a single division
in the micrometer eye-piece.

Thus, for example, if we find that a single division of the
micrometer eye-piece corresponds to T5Vir of an inch, and that
a lymphoid corpuscle covers half a division, its diameter is
necessarily -g-^ of an inch.

Testing a lens. — A lens should be free from certain defects,
as we have already stated. First of all it should have no
spherical aberration ; the objects seen upon the edge of the
field should be sharply defined, and all objects having parallel
sides should appear as such. In other words, they should not
be distorted.

Secondly, they should have no color or, at least, as little
as possible. This defect, however, has never been entirely
overcome ; some glasses are over-corrected and then the pre-
vailing color is blue ; others are under-corrected and then the
prevailing color is red.

TESTING THE MICROSCOPE — ITS USES. 0

It is a matter of some indifference which color prevails.
These defects are best seen by observing a bubble of air in a
fluid specimen. The prevailing color is seen at the periphery
of the bubble.

Thirdly, all objects in the field should appear with equal
distinctness, whether at the periphery or in the centre. If a
fine powder, such as lycopodium be strewn over the field, the
granules should be seen as distinctly at the edges as at the
centre ; an ordinary thin section of any microscopic object will
also exhibit this defect, if it exist.

Fourthly, the glasses should have good penetration. This
enables the observer to see the general aspect of bodies better,
though it may not make him see objects quite as sharply ; the
former depending upon a large angle of aperture, and the latter
(definition) upon a small one.

To be able to have at the same time both great resolving
and great defining power is the highest desideratum, and it has
been the merit of our American makers to increase the angle
of aperture and still maintain a high defining power.

For ordinary histological purposes, a lens that will show
the oscillatory movement in the mucous or salivary corpuscles
is sufficiently high for practical purposes. This is accomplished
by the ordinary student's one-fifth of Grunow, for example.
If, however, we are studying the delicate intercellular sub-
stance of the brain and connective-tissue corpuscles, bacteria,
etc., a somewhat higher power is needed.

For such studies it is desirable to have an immersion lens, such as the No. 10
or 12 Hartnack or Prazmowski, or a ^ or -fa of other good makers, such as
Wale, Tolles, etc.

In using these high powers it is necessary to place a single drop of water
on the anterior lens and depress the tube until the drop touches the circle
or cover. The drop of water utilizes light that would otherwise be lost, mag-
nifies slightly, and corrects, so that the image is made brighter and more
distinct.

The new oil immersion of Zeiss is highly recommended by Woodward of
Washington. In using such a lens, a drop of oil is substituted for water. We
are hardly yet prepared to decide whether oil is preferable on the whole to
water.

How to illuminate the microscope. — In doing ordinary
microscopic work it is best to use day-light, such as is reflected
from a clear sky. It is not well to use direct sun-light, but to

10 MANUAL OF HISTOLOGY.

receive illumination from a point opposite to the sun. North
light is very excellent.

If artificial light is to be used, an ordinary kerosene burner
will answer sufficiently well, even better than gas. Some of
the highest lenses require artificial light.

Testing the eye-piece. — Eye-pieces are usually free from
serious defects, but if we are desirous of testing one, the fol-
lowing method may be followed :

Select a combination of lens and eye-piece that gives a per-
fectly flat field. Then remove the eye-piece and substitute the
one that is to be tested. If now the image is no longer flat,
the eye-piece has aberration of form and should be rejected.

Testing Jiigh lenses. — In combinations that magnify about
five hundred times, a good test is ihepleurosigma angulatum,
one of the diatoms. A lens that will demonstrate three sets of
lines by direct light has a proper amount of defining power,
and with the other qualifications already mentioned, is suit-
able for the finer sorts of microscopical work. This task is
easily accomplished by either the No. 10 immersion of Hart-
nack or Prazmowski, the ^ of Wale, and also by lenses of other
good makers.

To test the magnifying power of lenses even more accurately,
Nobert's test plates may be used. They consist of bands of
fine lines from nineteen to thirty in number.

It has usually been thought that the eighth or ninth of
their series is a good test ; the nineteenth band,1 however, has
been defined by a ten immersion Hartnack, and probably by a
goodly number of American lenses. (See Appendix.)

Measuring the angle of a lens. — Take an instrument of
which the pillar is hinged, and which also revolves on its ver-
tical axis.

Measure off on the table, in front of the instrument, a semi-
circle with the pillar as a fixed point. Divide the semicircle
into the proper number of degrees, viz., 180.

Place opposite the instrument, and without the circle, a
candle or lamp. Then interpose between the two a screen hav-
ing an aperture to admit a small beam of light. Revolve the
tube on its axis until the light can no longer be seen ; then

1 According to Carpenter, the nineteenth band contains 113,595.13580 spaces to
the inch.

TESTING THE MICROSCOPE ITS USES. 11

count off the number of degrees which the instrument has
passed over. Suppose, that, in a given case, the number be
seventy ; then revolve the instrument in the opposite direction
and count as before. The number of degrees will of course be
the same.

Add the two figures together, and the total number of de-
grees (viz., 140) will represent the angle of aperture.

CHAPTER II.

General directions.— Microscopic work should be done at a
rather low table, not more than thirty inches high, and resting
squarely upon the floor, so that it cannot be jarred by move-
ments in the room. In most laboratories small and short mi-
croscopes are preferred ; they are now made by nearly every
optician. The total height, when the stand is vertical, need
not be more than eleven or twelve inches. For various reasons,
which soon become apparent to those who do much histological
work, it is seldom necessary to provide the stand with a hinge-
joint, which allows the tube to be inclined toward the observer.
A vertical and rigid stand is steadier, less expensive, and, ex-
cept in very rare instances, all that is required in medical work.

When the microscopist is about to commence his examina-
tion, he should select the various materials that* are likely to
be needed, and place them near him on the table, so as to be
within easy reach of his hand. Special tables for microscopic
work may be provided with rows of drawers upon either side
of the worker. In them should be kept all the microscopic
accessories that he expects to use, such as glass slides and
covers, wooden boxes for specimens, labels, a note-book for
rough sketches and annotations, a bit of chamois skin for
cleaning the lenses and other adjuvants which are found useful.
By so doing, these materials are kept free from dust, and stand
ready for use at any time. A small vessel holding clean water
to wash the covers and slides, a receptacle of some kind for
the waste, and a clean, fine, and soft towel should not be for-
gotten, as they are always useful for every kind of microscopic
work.

The instrument is best kept under a bell-glass on the table.
If, however, it has to be taken about from place to place, it

METHODS FOR PREPARING MICROSCOPIC OBJECTS. 13

should be packed in its box, and the accessories may also be
kept in a suitable chest, such as has been described, and which
is made by a number of opticians.

After the directions that have been given, it seems hardly
necessary to add that everything pertaining to the work should
be carefully cleansed after using, and put away in its proper
place, so as to be immediately available at any future time.
The expenditure of a little time in these details is more than
counterbalanced by the greater rapidity and effectiveness of
subsequent work.

How to pr&pare afresh microscopic object for rapid exam-
ination.— When practicable, every specimen should be studied
as early as possible after removal from the body, and this is
important even if it is to be hardened and prepared for per-
manent preservation.

Take a clean slide, which, of course, should be reasonably
thin ; place it before you upon a white ground (some micro-
scopists have a square plate of marble set into the table); mois-
ten the slide with a drop of some indifferent fluid, such as
iodized serum or, perhaps, a three-fourths per cent, aqueous
solution of common salt ; then place in the drop the fragment
to be examined. Small particles are more easily studied than
large ones. Usually the substance should be spread out a
little with needles.

In one or two minutes it is ready for examination. By this
method striped muscular tissue may easily be detected ; and it
also happens to be a good example because it is very frequently
brought to microscopists for examination. In certain forms of
dyspepsia, especially in women, it is common for ingested
meat to pass through the alimentary tract with very little
change. Prepared for the microscope in this simple way the
peculiar markings of striped muscle may be observed at once,
and even if the meat has been boiled.

If, however, the material to be examined is opaque, we add
to the drop of serum another of glycerine ; the latter alone re-
fracts the light too much, and is therefore undesirable. When,
however, it is combined with an equal amount of serum or the
salt solution, the fluid has a proper refractive power for most
histological purposes. The microscopist should now let fall
upon the drop a cover glass, and place the slide upon the stage
of the microscope. Nothing is required to keep the cover in

14 MANUAL OF HISTOLOGY.

place. Examine at first with a low power, and then with a
higher one, until the specimen has been studied in all its
details.

THE ORDINARY METHODS OF PREPARING TISSUES.

Mutter* s fluid. — It is customary to use Muller's fluid to
render tissues firm, so that they may be easily cut with the
knife, and made thin enough for microscopic studies. The for-
mula is (by weight) bichromate of potassium, 2 parts, sulphate
of soda, 1 part, distilled water, 100 parts. This fluid, which
is of a brown color and transparent, is admirably adapted for
hardening and preserving permanently nearly all the tissues of
the body ; though for the brain and cord it is unsatisfactory
without the subsequent use of other reagents. It is, however,
very cheap, and specimens may be preserved in it for years,
and still retain the characteristics which make them suitable
for microscopic study.

Potassium bichromate solution. — Some microscopists prefer
simply a solution of the bichromate of potassium (gr. xv. — § j.).
It is well, in this case, to put the specimens into a fresh solution
every day for several days. Subsequently they are to be hard-
ened in alcohol. The strength of the latter should at first be
eighty per cent., then ninety per cent., and finally may be
ninety-five per cent. The alcoholic process requires a few ad-
ditional days. Solutions containing chromic acid or the bi-
chromates are- objectionable if the specimen is to be used for
coarse demonstration, because the yellow or brown color of the
acids is diflicult to remove. Prolonged soaking in distilled
water will accomplish a great deal, but the final color is gener-
ally a clay brown. Of course this objection does not apply to
microscopic sections, and indeed it appears as if the chromic
acid and chromate solutions prepare them particularly well for
the process of staining in various colors.

Ammonia bichromate solution.— Gerlach has recommended
this reagent in one or two per cent, solutions for hardening the
brain and cord. It is to be used as the preceding (Prey).

Alcohol and acetic acid mixture (Lockhart Clarke). Two

objects were sought by their combination: one to coagulate
:il Luminous matters by the alcohol, the other to render them
transparent. The proportion was alcohol three parts and

THE ORDINARY METHODS OF PREPARING TISSUES. 15

acetic acid one part. It is said that by this method sections of
the cord may be made transparent in a few hours (Frey).

Alcohol and acetic acid mixture (Moleschott). — This ' ' strong
acetic acid mixture," of which the formula is strong acetic acid
(1.070 sp. gr.), 1 vol.; alcohol (.815 sp. gr.), 1 vol.; distilled
water, 2 vols., causes the connective- tissue substances to be-
come very transparent. Delicate textures do not tolerate it
well (Frey).

Molybdate of ammonia has been recommended by Krause
for hardening specimens. It has met with some favor.

Solution of osmic and chromic acids. — Flesch recommends
a union of these acids for hardening and decalcifying bone.
It is also useful for hardening other tissues. His formula is
as follows : osmic acid, 10 parts ; chromic acid, 25 ; aq. destill.,
100.

Alcolwl and acetic acid and muriatic acid solution. —
Beale gives the following formula: water, 1 oz. ; glycerine, 1
oz. ; spirit, 2 oz. ; acetic acid, 2 drachms ; hydrochloric acid,
£ drachm. This is said to harden well and be suited for epithe-
lial structures (Frey).

Method of hardening the brain. — Hamilton recommends
the following method : pieces of brain and cord cut into sec-
tions not more than an inch in length, or length and breadth,
are immersed in a fluid containing three parts of Miiller's fluid
and one of methyl alcohol, and put away for some three weeks
in a refrigerator. Then they are to be soaked in a solution of
the bichromate of ammonia (1-400) for a week ; another week
in a solution of 1-100 ; a third week in a solution of 1 to 50;
and finally kept in chloral hydrate (12 gr. to the ounce). Be-
fore cutting, they are to be washed twelve hours or more in
water ; they then are to stand forty-eight hours in a syrup
containing two parts of refined sugar to one of water. He then
cuts with Rutherford's microtome. Staining is done with
osmic acid and carmine.

For clarification he uses oil of cloves or turpentine.

How to embed specimens. — When a piece of tissue is so
small that it cannot be held in the hand, it is customary to
embed it in some substance of about the same consistence. A
combination of wax and oil answers the purpose very well ;
they should be mixed in about equal proportions in a porce-
lain dish, and then heated together until the wax is thoroughly

16 MANUAL OF HISTOLOGY.

melted. This having been done, a mould should be at hand to
receive both the embedding mixture and the piece of tissue.
Various moulds are in use. Some are made of tin-foil, and are
shaped like a common earthenware garden-pot.

A fine, long cambric needle should be passed through the tis-
sue, and then (the mould being placed in position) the point of the
needle is to be pushed through the bottom into the table beneath.

Then the mixture of the liquid wax and oil, which has been
heated to the point of melting and no more, should be poured
slowly into the mould, so as to slightly cover the specimen.
During the process of hardening, minute bubbles of air will be
liberated from the tissue ; they will escape more rapidly, and
the embedding material will harden more quickly arid thor-
oughly, if the microscopist blows gently and continuously on
the surface of the liquid. Just at the moment when the mass
is no longer liquid, the needle should be suddenly withdrawn.

As soon as it is hard throughout, the tin-foil mould may be
torn off by breaking the edge at any point with the finger.
The foil tears like paper.

When moulds are not at hand, an excellent substitute may
be made with ordinary writing paper. Some confectioners
make them of pressed paper.

Embedding in glycerine and tragacantli. — Mr. John Ste-
venson's plan is as follows : He takes two drachms of glyce-
rine and mixes them with one drachm and a half of powdered
gum tragacanth. The tissue to be cut is then placed in a small
pill-box, and the mixture poured in. The box is then laid
away in a cool place from eight to twelve hours, when sections
may be made with the knife. In case the specimen is to be
preserved for a longer time, the bottom of the box may be
taken off, and the side slit up. The specimen will now be
found embedded in a solid elastic cake, and may be slipped
into alcohol until required. When it is to be kept in spirits
less than twenty-eight hours, the mixture should be glycerine,
2 drachms ; powdered tragacanth, 1 drachm ; gum arabic, 15
grains. Tissues that have lain in spirit should be steeped in
cold water a few hours before embedding.

The hand section-cutter is used by some microscopists. It
is simply a cylinder which is designed to receive the object
and the material in which it is embedded. A plunger, which
is driven up from beneath by the revolution of a screw, pushes

THE ORDINARY METHODS OF PREPARING TISSUES. 17

up the specimen so that it may be sliced off by an ordinary
knife. For some purposes it is very useful.

Freezing section-cutters.— Of these there are many in use,
and they have certain advantages. In conjunction with Dr.
J. H. Hunt, of Brooklyn, I have devised a modification of the
ordinary instrument.1 (Fig. 9.)

Fio. 9. — Freezing section-cutter : B, metallic box : S, cylinder; a, well: c, c.
, A ; G, indicator ; D, milled head ; F. F, plugs ; E, K, tubes to fit in well ;
>x ; K, binding screw attaching box to table.

A, A
bo

', frame for holding knife
H, H, covers to metallic

It consists of the brass cylinder, S, made of rather large
size, and placed in the centre of a metallic box, B. The
length of the cylinder, with driver, D, is about five inches. The
diameter of the well, a, measures If inch. Fitted round and
about the cylinder is a plate of glass which from its smooth-
ness permits the knife to sweep it easily.

The knife, A, A, is large, measuring 13 inches in length, in-
cluding handle ; in breadth, If inch. It is fitted into a brass
frame, c, c, 7£ inches in length and 3| in breadth. Two strong
brass springs, and two sliding clamps, hold it in place. The
knife is slightly concave on both sides.

The well is so large that it will hold an ordinary kidney
after hardening, or at least so much of it that a transverse sec-

J Made by Miller Bros., 1213 Broadway, New York city.
2

18 MANUAL OF HISTOLOGY.

tion maybe made of the whole organ at one sweep of the knife.
The knife and. frame are modifications of those devised by Dr. E.
Curtis of this city, and the section-cutter and box are not dif-
ferent in any essential particulars from those in common use.

They are larger, however, and the indicator, G, enables the
observer to determine with accuracy the thickness of his sec-
tions. Thus, in my own instrument thirty-one turns of the
milled head drives the plug forward one inch.

Each revolution consequently drives the specimen forward
5Y inch. Now, the circumference of the milled head is marked
off into thirty divisions.

When the indicator marks that the plug has been driven
forward one division, the distance traversed will be 7^ inch.

It is easy, therefore, to determine the thickness of any sec-
tion with considerable accuracy.

When it is desirable to put the instrument in use, the
plug that is to be used is well oiled, as also the thread of the
driver, and the metallic box is filled with a mixture of ice and
snow.

It is necessary to be particular and oil the bearings
thoroughly, else they will bind and the instrument will be
clogged while the freezing process is going on. The usual
plan is to soak the tissue (as Dr. Pritchard suggests) in a
thick solution of gum, which cuts like cheese when frozen.
The soaking should continue for a number of hours, say until
the next day.

When the tissue is ready, a thick solution of the gum
should be poured into the well and the tissue held until it is
fixed by the ice. Some non-conductor is to be placed over
the well as soon as fixation has commenced, in order that ac-
cess of heat may be prevented.

If ice is used it should be ground up finely and then packed
tightly about the well; snow is better. The whole process
takes only ten or fifteen minutes. The freezing section-cutter
is of use when we are desirous of making a rapid examination
of fresh tissues.

It is obvious that they are seen under more natural circum-
stances than when they have passed through the bichromate
or chromic acid solutions, or alcohol, all of which cause more
or less change in such delicate substances.

It has been hoped that by the freezing method we should

THE ORDINARY J1ETHODS OF PREPARING TISSUES. 19

learn much that is new about the finer structures of the brain
and the character of the corpuscular elements of the body, but
as yet it has not reached our expectations.

Hailes 's microtome. — A very ingenious and excellent instru-
ment (Fig. 10) has been devised by Dr. William Hailes, Pro-
fessor of Histology and Pathological Anatomy at the Albany
Medical College. Objections to it will be mainly on the ground
of price.

Dr. Hailes uses it as a simple instrument or as a freez-
ing microtome, arranged either for ice and salt, ether-spray,
rhigoline, etc.

The employment of ice and salt (coarse) is preferred, be-
cause it costs but little and freezes the mass solidly and
quickly, and, if desired, 500 or 1,000 sections can be obtained
in a few moments, depending, of course, upon the rapidity
and skill of the operator.

The time of freezing is about seven minutes, except in
very warm weather, when it requires a few moments longer.

The instrument does not work quite so satisfactorily in very
warm weather, owing to the rapid melting at the surface of the
preparation.

It is absolutely necessary that the mass should be frozen
solid, or the sections cannot be cut smoothly.

An extra freezer may be employed, and while one specimen
is being cut the other is being frozen ; by exchanging cylinders
(they being interchangeable) no delay is necessary.

The art of cutting is readily acquired. Two hundred or
two hundred and ftfty sections have been made in a minute,
and of a uniform thickness of -^^ of an inch. It is not
necessary to remove the sections from the knife each time,
but twenty or thirty may be permitted to collect upon the
blade. They lie curled or folded up upon the knife, and when
placed in. water, straighten themselves out perfectly in the
course of a few hours. The knife employed is an ordinary
long knife from an amputating case.

Perfectly fresh tissues may be cut without any previous
preparation, using ordinary mucilage (acacia) to freeze in, but
most specimens require special preparation.

If preserved in Miiller's fluid, alcohol, etc., they require to
be washed thoroughly for several hours, and then, according
to the suggestion of Dr. David J. Hamilton, F.R.C.S., etc., of

20

MANUAL OF HISTOLOGY.

the University of Edinburgh, Scotland, the specimen is placed in
a strong syrup-(sugar, two ounces ; water, one ounce) for twenty-
four hours ; it is then removed to ordinary mucilage for forty-
eight hours, and finally is cut in the freezing microtome.

These sections may be kept indefinitely in a preservative

FIG. 10.

Fio. 11.

Fio. 10. — Poly-microtome (without freezing apparatus) : A, small well fitting on pyramidal bed-plate ;
B. pyramidal bed-plate containing different sizes; C, micrometer screw; D,- ratchet- wheel attached to
•crew ; E, lever actuating the micrometer screw by means of a pawl engaging in teeth of ratchet-wheel ;
F, arm carrying a dog, which prevents back motion of screw ; G, regulator for limiting the throw of
lever, and consequently governing the micrometer screw ; H, lever-nut for fixing regulator ; I, index, with
)>ointer and graduated scale, from 1/2400 inch to 1/200 inch ; K, knife for cutting sections ; L, knob to
turn micrometer screw direct when pawls are detached ; M, table clamp ; T, table of microtome, with
plan* top to facilitate cutting.

Fio. II. — (Very much reduced in size). A, B, tube containing specimen which is surrounded by freez-
ing mixture in tin receiver C, D ; E, F, revolving hopper with wings, W, W, for stirring the ice ; G, out-
let for melted ice.

fluid recommended by Dr. Hamilton:

<l"stil., aa. riv. ; acid, carbolic., gtt. iij.
addition of alcohol, 5 iJ-> is advisable.

B. Glycerin., aqme
Boil and filter. The

STAINING FLUIDS. 21

TJie Vincent microtome. — This instrument, which was de-
vised by Dr. Vincent, of New York city, is a flat piece of steel
(Fig. 12) 12 inches long by 2— 2£ inches wide, with a bevelled
cutting edge, 6 inches long. The handle is simply the rounded
and smoothed extremity of the knife.

It has been in use at the School of Histology connected with
the Columbia Veterinary College, and has proved to be a very
efficient knife.

The mode of action is very simple. The object having been
previously placed in any ordinary hand-cylinder and mounted

FIG. 12.

in wax, paraffine, or pith, the sections are made by a stroke of
the knife, which is pushed straight forward. As will be readily
seen, the larger the section the wider the knife must be.

The blade is made of the best plate steel, and is easily kept
in order.

STAINING FLUIDS.

Ammonia carmine. — This is one of the oldest and best
known solutions. Take one part, by weight, of the best car-
mine, which is known as " No. 40," dissolve it in 100 parts of
distilled water, and add one part of aqua ammonise. The pre-
vious dull color now gives place to a most brilliant and deep
red. It is necessary, however, that the carmine be either neu-
tral or very faintly alkaline, else the color will diffuse and the
tissues will not be differentiated. Expose the fluid, therefore,
for some weeks to the air, or evaporate over the water-bath
until the odor of ammonia is no longer perceptible.

The nuclei should be deeply and brightly stained, while the
intercellular substance is in no way affected. If, however,
diffusion has taken place, a great deal of it may be removed
by soaking the section in a saturated alcoholic solution of ox-
alic acid. When a brick-red color has in this way been ob-
tained, the object has been accomplished. Crystals of oxalic
acid are apt to be found in specimens that have been prepared

.,., MANUAL OF HISTOLOGY.

in this way. It is therefore desirable, after using the acid, to
wash thoroughly in alcohol or water.

'liurax carmine (Arnold's formula).-The following method
is given by Dr M. N. Miller as the one in use by students m
the historical laboratory of the New York University,
originated with Prof. J. W. S. Arnold. A saturated solution
,f borax is prepared in a wide-mouthed pint bottle. The borax
should be in some excess. - "No. 40" carmine is now added
to the solution under constant agitation, until after a whili
no longer dissolves, and an excess remains at the bottom of the
vial, mingled with the crystals of borax. After twenty-four
hours the supernatant fluid is decanted. To this clear portion
f. §ij. of alcohol are added, and f. 3 j. of caustic soda solution
(U. S. P.). The staining solution is now ready. Or, the alco-
hol may be omitted (Arnold), and the liquid evaporated to dry-
ness ; the red amorphous mass is then powdered. Of this,
15 grains are placed in an ounce of water, to which f . 3 j. of
alcohol is added.1

Sections, after staining, should be washed in alcohol to re-
move the superfluous coloring fluid, and then transferred to a
saturated solution of oxalic acid in alcohol to fix the color.
The oxalic acid is then washed out in alcohol ; finally the sec-
tions are cleared up in oil of cloves, and mounted in balsam or
dammar.

Double staining by borax carmine and indigo* carmine.—
Drs. W. T. Norris and E. O. Shakespeare, of Philadelphia,
have recommended a method which is a modification of Mer-
kel's. Two staining fluids are made, one red and the other
blue. The red one contains carmine, gr. 7£ ; borax, 3 ss. ; dis-
tilled water, § j. The blue contains indigo carmine, 3 ss. ; bo-
rax, 3ss.; and distilled water, §vij.

After thorough trituration the ingredients are mixed and
left in a vessel ; the supernatant fluid is then poured off. The
sections, if previously hardened in bichromate, picric acid, or
chromic acid, should be well washed ; they then are to be
placed for a few minutes in a mixture (equal parts) of the red
and blue fluids, then transferred, without washing, to a satura-
ted solution of oxalic acid and allowed to remain in it rather
less time than in the staining fluid. When sufficiently bleached

1 [This preparation of borax carmine is the best that I have ever used. — T. E. S.]

STAINING FLUIDS. 23

the sections should be washed in water until every trace of ox-
alic acid is removed. Sections thus prepared may be mounted
in balsam or dammar. Connective- tissue substances are blue,
while the nuclei are red. The osseous lamellae of bone are
blue, the cells in the lacunae red, while the marrow is apple-
green.

Picro-carmine (Miller's). — Add one part of a saturated so-
lution of picric acid to two parts of the i5-graih borax carmine
solution (Arnold's). The epithelium of the glands and the
muscles are stained yellow, while the nuclei of the cells and the
connective tissues acquire the carmine color. Sections should
remain in the picro-carmine solution for about twenty-four
hours. Next they are washed quickly in water, then in .alcohol,
after which they are transferred to the oil of cloves. (For Ran-
vier's method of making picro-carmine, see the chapter upon
the Histology of the Nervous System.)

HcEmatoxylin solution (Boehmer's). — Dissolve 20 grains of
haematoxylin in one-half an ounce of absolute alcohol ; then
dissolve 2 grains of alum in an ounce of water. Some drops of
the first solution are added to the second, which, after a short
time, becomes a beautiful violet. It improves after keeping for
a few days, and should always be filtered before using (Thin).

HcEmatoxylin solution (Kleinenburg's). — First make a satu-
rated solution of the chloride of lime in seventy per cent, alco-
hol, and add alum to saturation.

Then make a saturated solution of alum in seventy per
cent, alcohol. Add the first to the second in the proportion of
one to eight. To the mixture add a few drops of a saturated
solution of hsematoxylin in absolute alcohol (Thin).

H&matoxylin solution (Miller's method). — Take a pint bot-
tle, as in the former process, fill with water, and add about an
ounce of common extract of logwood in coarse powder. Allow
this to remain in a warm place for twenty -four hours, with
occasional stirring. After the expiration of this time add pow-
dered commercial alum until the liquid changes from the
muddy brown color given by the logwood to a brilliant purple.

The alum is to be added until no change is produced. An
excess of the salt will do no harm. Add about f. 3 j. of alcohol,
and after decanting or filtering it is ready for use. One
may omit the alcohol at this stage, and evaporate to dry ness
as in the borax-carmine process. The powder thus obtained is

24 MANUAL OF IHSTOLOGY.

added to water when required. Three grains to the ounce of
water will give a fluid that will stain alcohol-hardened tissue
in from ten to fifteen minutes. A solution containing ten
ir rains to the ounce will stain very quickly. If it is desired to
keep the solution, add f. § j- of alcohol for each ounce. Hsema-
toxylin stainings are soaked in water for a few minutes to
wash out the alum, then transferred to alcohol, clarified in the
clove oil, and finally mounted in balsam or dammar.

Klein's formula for hcematoxylin.—Mix in a mortar 5
grammes of the officinal extract of hsematoxylin, with 15
grammes of alum, and pulverize carefully. To this add grad-
ually 25 c.c. of distilled water, and filter. To the residue add
15 c.c. of distilled water and again mix in a mortar, and filter;
to this filtrate add 2 grammes of alcohol. Now mix the two
filtrates and keep in a glass-stoppered bottle. If the liquid
should at any time become muddy, filter again. Care must be
taken to prevent any acid from intermingling with the fluid.
Acids cause the hsematoxylin to turn red ; for this reason, sec-
tions which have been hardened in chromic acid should be
placed in a watch-glass and covered with distilled water, to
which add a drop or two of a 30 per cent, solution of caustic
potassa ; allow it to remain therein 10 to 15 minutes. To use
the hsematoxylin fluid, add a few drops to an ounce of distilled
water, so as to make a pale violet solution ; allow sections to
remain in this solution for 12 to 24 hours. Or, a- stronger so-
lution may be employed which will stain specimens in 10 to 30
minutes, and still give good results. Mount in- glycerine, ace-
tate of potassa, balsam, or better, resinous turpentine.

Eosine solution. — Eosine, first introduced by Fischer in
1875, is much used in staining fresh preparations. It is cus-
tomary to have a strong solution of one to ten or twenty on
hand. A few drops are then added to a watch-glassful of water
or alcohol. Fresh tissues are both stained and hardened. It
affects the body of the cells, together with the nuclei. It is apt
to diffuse, unless special care is taken, and long soaking, say
for twenty-four hours, is practised.

Double- staining with eosine and other aniline colors. —
Schiefferdecker first stains in an alcoholic solution of eosine
and then in a one per cent, watery solution of an aniline color
(dahlia, methyl violet, or aniline green). Care must be taken
not to extract the color when dehydrating the specimen in

STAINING FLUIDS. 25

alcohol according to the usual method ; very deep staining is
therefore desirable.

Green coloration of the nuclei. — To effect this, Tafani em-
ploys a fluid containing three or four parts of a saturated
watery solution of aniline blue to some six or seven parts of a
saturated watery solution of picric acid.

Eosine and hcematoxylinfor staining bone. — Busch recom-
mends eosine and hsematoxylin for double-staining the zone of
ossification in growing bone. The sections of decalcified bone
are first immersed a few days in a one-half per cent, chromic
acid solution, or in a one per cent, solution of the bichromate
of potassium, and then, after washing with water, in a watery
solution of eosine. In young bone, where ossification is pro-
gressing, the cartilage matrix is blue, while the nuclei of the
cartilage-cells adjoining the line of bone are red ; the contents
of the medullary spaces are also bright red, while in the bone
trabecles there is a combination of blue and red.

IHosme for permanent specimens. — Renaut has employed
eosine to differentiate all forms of protoplasm, whether bodies
or their processes. He either employs a watery solution alone,
or with the admixture of one-third its volume of alcohol.
The coloration is obtained after immersion of the sections from
one-half minute to one minute. They are then washed in
distilled water, and may be preserved in a neutral solution of
glycerine to which one per cent, of chloride of sodium has been
added to prevent the glycerine dissolving the eosine. These
preparations will then remain unchanged for months.

In examining the fixed corpuscles of the subcutaneous tis-
sue, the same author injects beneath the skin a solution of
eosine and water (1-500), and then removes a portion of the in-
filtrated tissue with the scissors. The fibrous fascicles are un-
affected, while the elastic fibres take the color deeply.

The fixed corpuscles appear as red granular plates, while
their nuclei take a very intense color. This reagent, therefore,
is well suited for the study of connective tissues. In special
instances the silver method may be used first, and then the
eosine.

Preparation of the cornea. — Klein has adopted the follow-
ing plan for exhibiting this most delicate tissue. He first burns
the centre of the cornea of a kitten with caustic potash, and
then, twenty-four hours later, brushes the surface with nitrate

•2(\ MANUAL OF HISTOLOGY.

of silver, and, half an hour afterward, immerses it in water
acidulated with acetic acid ; after a day or two it is found to
have a glutinous appearance. The lamellae are then easily
stripped off, and in the middle portions, the corneal corpuscles
assume a purplish-brown color while their nuclei are uncol-
ored. The outlines of the lymphatic channels are also sharply

Picro-hcematoxylin and eosine (triple-staining}. — Wendt
has described a method of double-staining by picric acid and
liMMiiatoxylin. Only the very thinnest sections, however, give
satisfactory results. A strong solution of hsematoxylin is first
employed. In this the sections are allowed to remain about
twelve hours. After washing them in water, they are placed
in a saturated solution of picric acid and carefully watched.
They may be removed from time to time, examined with a low
power, and, when properly stained, put in alcohol and mount-
ed in Canada balsam with as little delay as possible. To ob-
tain triple-staining, eosine may be conveniently combined with
this picro-hfematoxylin method. To insure good results some
amount of practice is necessary.

Double, triple, and quadruple staining. — Dr. Gibbes re-
commends for double-staining, immersion first in picro-carmine
and then in logwood, or which is better, immersion first in a
spirituous solution of rosine or aniline violet, and then in an
aqueous solution of aniline blue or iodine green. ' In obtaining
more than two colors there is considerable difficulty. To ac-
complish it he -uses first the chloride of gold or picro-carmine
and then the spirituous and aqueous solutions of the ani-
lines.

Staining with BismarJc brown. — Make a watery solution of
gr. ij. — §j., heat and filter; soak in the solution about three
minutes ; set the color with acetic acid (glacial) 4 per cent,
for half a minute. After dehydrating with alcohol mount in
dammar varnish. Weigert prepares the Bismark brown as
follows : he makes a concentrated aqueous solution by boil-
ing in water, filtering from time to time. He also uses a weak
alcoholic solution, and combines with other colors.

[To combine with eosine — put the sections in a strong aqueous solution of
Bismark brown ; remove after about two minutes, set in weak acetic acid (four
per cent.), then place in a weak alcoholic or aqueous solution of eosine, and
then again in the acetic acid solution.— T. E. S.]

STAINING FLUIDS. 27

Solution of alum-carmine. — Grenacher recommends this
fluid : Take a one to five per cent, solution of ordinary alum,
or ammonia alum ; boil with one-half to one per cent, powdered
carmine for twenty minutes. Filter, and add a little carbolic
acid to preserve.

NapWialine yellow for bone.— In sections of the femur
from a foetal pig, three and a half inches in length, the follow-
ing method was found to yield very excellent results :

After immersion for three days in Muller's fluid, sections
were made, and, after washing in water, immediately dipped in
an alcoholic solution of naphthaline yellow (gr. iv. — § j.) ; after
eight to ten minutes the sections were removed, and dipped in
a watery solution of acetic acid of three per cent. ; then they
were immersed for about ten minutes in the ordinary solution
of ammonia-carmine, rendered neutral by exposure to the
air.

The sections were again dipped in the acetic acid solution
in order to set the color, and then placed in alcohol of eighty
per cent., and subsequently in absolute alcohol.

The specimens thus stained showed a matrix of deep trans-
parent chrome yellow. The young bone-corpuscles and osteo-
blasts, on the other hand, together with the fibrous tissue,
assumed a brilliant rose color, thus affording an excellent con-
trast between forming and formed bone.

Staining witJi metliyl-green and induline. — Calberla has
introduced two new substances into use, viz., methyl-green and
induline. The one stains the nuclei of the cells of the sub-
cutaneous tissue, the nuclei of vessels and nerve-sheaths rose
color, while the cells of the corium and their nuclei are a
violet red ; the other colors the cells of the Malpighian layer
a greenish blue. Combinations of methyl green and eosine are
also recommended. Eosine (one part) and methyl green (sixty
parts) are to be dissolved in a thirty per cent, solution of warm
alcohol. The epithelial nuclei take a violet blue, the nuclei
of connective tissue a greenish blue, and the cell-body a red
color. Singular differentiations are made ; thus, while the
striated muscle is red, the nuclei are green. On the other
hand, smooth muscular tissue is green, and the intercellular
substance red. In the salivary glands the cells of the excretory
ducts are blue, while the so-called secretory cells are red. In-
duline dissolves in warm water and in dilute alcohol. Take a

28 MANUAL OF HISTOLOGY.

concentrated watery solution, dilute it with six times its
volume of .water, then immerse the preparations from 5 to 20
minutes, wash them out and clarify in oil of cloves or glycerine.
The peculiarity of this material is that it never affects the
nucleus, but only the cell-body. More frequently, however, it
is the intercellular substance that is colored blue.

Purpurine. — Ranvier has recommended this dye, which is
extracted from madder.- Alum (one part) is dissolved in dis-
tilled water (two hundred parts) ; the fluid is then heated to
the boiling point in a porcelain dish. Then a small quantity
of purpurine is dissolved in distilled water and added to it.
Sufficient purpurine should be added to leave a residue, by
which it is certain that the solution is saturated. While still
hot it is to be filtered into alcohol of one-fourth the total
volume. The fluid has an orange red color, and is more effi-
cient when fresh. Sections should be immersed from 24 to 48
hours.

French archil— Staining with extract. — Wedl uses this
substance, which, after the loss of the ammonia, is dissolved
in 20 c.c. absolute alcohol, 5 c.c. acetic acid of 1.070 sp. gr.,
and 40 c.c. of distilled water so as to make a saturated solu-
tion. Protoplasm and matrix, but not nuclei, are colored a
beautiful red.

Alizarine. — This aniline color is recommended by Than-
hoffer, but experience is limited with reference to it. It has a
golden yellow color, and is easily fixed by the tissues.

METALLIC SOLUTIONS.

Staining with osmic and oxalic acids. — Broesicke adopts
the following method :

Little pieces of fresh or freshly dried preparations are left
for an hour in a one per cent, solution of osmic acid ; then
they are carefully washed and soaked in a cold saturated solu-
tion of oxalic acid, and finally examined in water or gly-
cerine. ^ Elastic fibres are yellow, fat is black, .while the walls
of capillaries and many connective- tissue substances are
red.

Chloride of gold arid lemon juice. — Ranvier is in the
habit of demonstrating the corneal nerves by using lemon-

METALLIC SOLUTIONS. 20

juice in which the tissue is left five minutes. Then it is soaked
for 15 to 20 minutes in 3 c.c. of a one per cent, solution of the
gold chloride, and finally 25 to 30 minutes in distilled water
to which one or two drops of acetic acid has been added. After
two or three days' exposure to the sun, the fibres become dis-
tinct.

Nitrate of silver in solution (gr. j. — iv. — § j.) is much used.
The details of the method will be found in the Chapter on the
Lymphatics.

Chloride of gold has also been much used in studying
the so-called lymph-canalicular system of the cornea. The
method of employing it will be found in the section relating to
the cornea.

Osmic acid in solution is also very useful. Its effects are
given in the chapter on the General Histology of the Nervous
System.

Methyl-green for showing waxy change. — Curschmann, of
Hamburg, has recommended this reagent to effect the same
object as the violet de Paris of Cornil. A solution of about
five grains to the ounce is used. The specimens are bathed in
the fluid a few minutes or hours. They take the color quickly.
After staining they may be mounted in glycerine. The amy-
loid material assumes a brilliant rose color. The surrounding
tissue takes a dull green.

Wicker sheimer's preserving liquid.. — This material has
been extensively used of late, and there are several formulae
for it. Among the most recent modifications is that made by
the firm of Poetz & Flohr, of Berlin. For immersing speci-
mens the ingredients are : arsenious acid, 12 grains ; sodium
chloride, 60 grains; potassium sulphate, 150 grains; potassium
nitrate, 18 grains; potassium carbonate, 15 grains; water, 10
litres ; glycerine, 4 litres ; wood naphtha, £ litre. A modified
fluid is used for injecting the blood-vessels. This is suitable for
all fresh tissues, preserving them in their natural color and
consistence.

If the tissues are to be used subsequently for the micro-
scope, it is said that they should be washed thoroughly in
water, but it seems from recent experiments that the fluid un-
fits them for minute examination. It is also rather expensive,
and has an extremely pungent and unpleasant odor.

30 MANUAL OF HISTOLOGY.

METHODS OF INJECTING THE BLOOD-VESSELS.1

Good injections are hard to make, requiring skill, patience,
and practice. First of all, it is essential to have a perfectly
transparent injecting material. This is usually made up with
gelatine and colored by carmine or Prussian blue. When
carmine is used it is customary to dissolve it in ammonia, ni-
ter, and then add it to the solution of gelatine. In order to
obtain a neutral or faintly acid liquid, acetic acid is added,
drop by drop, until the alkalinity is overcome, but there must,
at the same time, be no precipitation of carmine, which is best
detected by the granules of carmine seen in the field of the
microscope. If alkaline, the color diffuses and the result is
a failure.

It is difficult to lay down any rule in reference to the amount
of acetic acid necessary ; the color of the liquid is the best
and only satisfactory test. The ammoniacal odor, if very
slight, cannot be detected, and therefore is useless as a test.
A slight excess of .acid, however, will do no harm.

The preparation of the blue injecting fluid is less difficult.

Usually Brucke's soluble Berlin blue is used; it can be
procured at most of the large drug stores, but if not obtaina-
ble, may be made as follows (Klein) :

" Take of potassic ferrocyanide 217 grammes, and dissolve in
one litre of water (solution A). Take one litre of a ten per cent,
solution of ferric chloride (solution B). Take four litres of a
saturated solution of sulphate of soda (solution C). Add to
A and B two litres of C. Then, with constant stirring, pour
the ferric chloride mixture into a vessel, collect the precipitate
upon a flannel strainer, returning any blue fluid which at first
escapes through the pores of the flannel ; allow the solutions
to drain oft*. Pour a little distilled water over the blue mass,
returning the first washing if colored, and renew the water
from day to day until it drips through permanently of a deep
blue color. This is a sign that the salts are washed away, and
all that is further necessary is to collect the pasty mass from
the strainer and allow it to dry."

Having obtained the soluble Berlin blue, it will be much

1 Prepared for the editor by Dr. W. H. Porter, Curator of the Presbyterian Hos-
pital, New York city.

METHODS OF INJECTING THE BLOOD-VESSELS. 31

simpler to inject both arteries and veins with the same solution.
If a small animal is to be employed (as the rabbit, for instance)
it will be found most convenient to inject through the aorta.
If, however, an organ from the human body is to be injected,
through the main vessels of that part. To commence with, the
kidney is probably the best, as it is small and of firm consis-
tence.

For injecting with the red gelatine liquid the following rules
will be found of service, and yield good results :

Take 40 grammes of Cox's best English gelatine, place it
in a jar, and add just water enough to cover it ; let it stand
for several hours, when it will imbibe the water, being hygro-
scopic ; it may then be dissolved over a water-bath.

Take of the carmine 22 grammes and dissolve in 40 c.c. of
aqua ammonite, then add 240 c.c. distilled water, and filter.
The preparation of the carmine solution had better be com-
menced the day before, as it takes about twenty-four hours to
filter. The gelatine and carmine solutions are raised, separately,
to the same temperature, when the gelatine solution is gradu-
ally added to the carmine solution, under constant stirring.
The injection fluid, which is now of a deep cherry-red color and
alkaline reaction, is precipitated with acetic acid until the deep
cherry color gives place to a bright red, and the ammoniacal
odor is exchanged for that of acetic acid. At this point a little
more acid may be added without doing harm. In case the
liquid should be found too concentrated, a little more water
may be added. For the blue mass the following method may
be adopted :

Take 66 grammes of gelatine, and prepare as in the former
case. Add 4 grammes of soluble Berlin blue in substance and
360 c.c. of water.

The blue will also be found slow in filtering. When both
are heated to the same temperature add the gelatine to the
blue solution, with constant stirring. When this has been
done, a solution of the iron salts may be added to intensify the
blue color, care being exercised not to add enough of the iron
to coagulate the gelatine. This liquid also may be diluted
if found so concentrated that it will not flow easily. The
liquids having been prepared, the organ carefully removed
from the body, thoroughly washed out and heated to a tem-
perature of 98° F., everything is ready for injection. The fill-

32 MANUAL OF HISTOLOGY.

ing of the vessels may be accomplished in one of two ways :
either by forcing in the fluid with a syringe or by the pressure
of a column of water. The syringe is the simplest, but requires
practice and skill in manipulation.

Having inserted the canula into the artery, the kidney may
be entirely filled with either the red or blue injecting liquid.
When the organ is seen to be swollen, tense, and well colored
the vessels must be tied off, and the kidney placed in a freez-
ing mixture until the gelatine has set. When this is accom-
plished, the organ should be cut into small pieces, and placed
first in a weak solution of alcohol (seventy per cent, or less),
and the strength of the alcohol gradually increased until the
specimen is sufficiently hard for cutting. The object of using
weak alcohol is to prevent too great shrinkage of the gelatine.
If two colors are used, it is impossible to tell beforehand how
much fluid will be necessary to fill the arterial arid venous sys-
tems, and not have the one encroach on the other. For an
ordinary kidney, about 250 c.c. of the injecting liquid should
be prepared to fill the arterial vessels, and nearly double to
fill the veins. The following rules must be observed in inject-
ing: keep the gelatine solutions and the organ as nearly as
possible at the same temperature. Immerse the organ in warm
water during the process. Avoid the entrance of air into the
canula when connecting the syringe. Inject slowly, and give
the fluid time to work its way into the minute capillary rami-
fications.

The above rules can be applied to any organ, with such
modifications as will suggest themselves to the operator.

BIBLIOGRAPHY.

KLEIN. Handbook of the Physiological Laboratory. Edited by Sanderson. Vol. I.

1873.

Bcscu. Arch. f. Mikroskop. Anat. XIV. 1877.

NORRIS and SHAKESPEARE. American Journal of the Medical Sciences, Oct. , 18T7.
EENAUT. Archives de physiol. 2me Serie, T. IV. 1877.
SCIIAEFER. Histology and the Microscope. Philadelphia, 1877.
TniN. Practical Histology. London, 1877.
WENDT. Ueber die Hardersche Dnise, etc. Strasaburg, 1877.
RANVIER. Trait6 technique d'histologie. Paris, 1877-8.
BROESICKK, J. Med. Centralblatt. 46. 1878.

BIBLIOGRAPHY. 33

CALBERLA. Morpholog. Jahrb. III. H. & S.'s Jahrb. I. 1878.

HAMILTON. Journal of Anatomy and Physiology. Vol. XII. 1878.

MILLER. New York Medical Record, Feb. 2, 1878, p. 97.

RANVIEB. Journ. de micrographie. H. & S.'s Jahrb. 1878.

SCHFEFFEBDECKEB. Arch. f. mikrosk. Anat. XIV. 1878.

TAFANI. Journal de micrographie. 1878.

WEDL. Virchow's Arcbiv, 74. 1878.

WEIGEBT. Arch. f. mikrosk. Anat. XV., p. 259. 1878.

FLESCH. Archiv f . mikrosk. Anat. XVI., p. 300. 1879.

GBENACHEB. Arch. f. mikrosk. Anat. XVI., p. 463. 1879.

KLEIN and E. NOBLE SMITH. Atlas of Histology. 1879-80.

COBSCHMANN. Archiv f. Path. Anat. LXXIX., III. 1880.

FBEY. The Microscope and Microscopical Technology. New York, 1880.

GIBBES. Lancet, March 20, 1880.

HAILES. An Improved Microtome. New York Medical Record, July 24, 1880.

THANHOFFEB, L. v. Das Mikroskop u. seine Anwendung. Stuttgart, 1880.

VINCENT. New York Medical Record, June 12, 1880.

WICKEBSHEIMEB. Arch. f. Pharm. New Remedies, May, 1880.

GIBBES. Practical Histology and Pathology. Philadelphia, 1881.

SEILEB. Compendium of Microscopical Technology. Philadelphia, 1881.

STOWELL. The Student's Manual of Histology. Detroit, 1881. •

HABBIS and POWEB. Manual for the Physiological Laboratory. New York, 1881.

3

CHAPTER III.

THE BLOOD.

Ix man and most vertebrates the blood consists of a clear
fluid, the liquor sanguinis or plasma, in which a large num-
ber of corpuscles are very evenly distributed. Of these there
are two prominent varieties, differing much in character — the
red and the colorless cr white. The former are greatly in ex-
cess, and give to the liquid its characteristic red appearance.

In relative proportion the two vary greatly within certain
limits. Usually there is but one of the white to 600 or 1,200 of
the red ; but these numerical relations are disturbed by vari-
ous diseases, and the white may equal the red, or even, in rare
cases, exceed them.

In fresh liquid blood the corpuscles are the only solid mat-
ters visible tinder the microscope ; nor is there any difference
in this respect with coagulated blood, when the quantity is
large. If, however, a little should be allowed to dry, fibrin
may be deposited under the form of delicate filaments, which
are superimposed on one another without definite order.

In one hundred volumes of blood there are said to be thirty-
six volumes of corpuscles and sixty- four of plasma. This ratio,
however, is altered somewhat by different conditions, such as
the age and health of the individual.

The red corpuscles in man and other mammals, with very
few exceptions, are bi-concave bodies, circular in outline. In
birds, amphibia, and almost all fishes they are also bi-concave
or hollowed out at the centre, but have an elliptical contour.
In the human species nuclei or central bodies appear at a very
early period of life, but subsequently are invisible, unless arti-
ficial means are used to display them. In birds, amphibia, and
fishes a rounded prominence is also seen at the centre, which is
particularly well marked when the corpuscle happens to be

THE BLOOD.

35

turned so that its edge meets the eye. This prominence cor-
responds to the ordinary nucleus of other elementary bodies or
cells. In this position the peculiar shape of the corpuscles,
with their constricted centres and rounded extremities, has
suggested a comparison between them and the little cakes
known as lady's-tingers. (See Fig. 13.)

It is obvious also that this varying thickness of the disk will
have some effect upon the microscopic image, for the whole
superficies cannot be in focus at one time, even when the cor-

FIG. 13. — Red corpuscles of
the frog. (Rollett.)

FIG. 14. — Hnman red bloort-corpn soles : a. globules
showing the double contour : ft. globules turned on
edge ; c, the same in rouleaux like coin. (Rollett.)

puscle is turned flatwise to the eye. There will be some differ-
ence between the level of the thickest and thinnest portions.
As a result, when one is dark the other is bright, when one is
well defined the other is blurred. This statement serves for an
explanation of the double contour that is sometimes observed
in human blood (see Fig. 14), though it has also been offered
in support of the theory that the semi-solid and elastic matter
of which the disk is mainly composed has an external envelope
or limiting membrane of different density. It is to be remem-
bered, however, that the property of double refraction which
explains the double contour, belongs to all transparent bodies
that have rounded edges, such as drops of water or oil, in
which cases there is plainty no enveloping or peripheral wall.
When the lens and eye-piece are suitably combined, as in the
best microscopes, the double marking is often difficult or im-
possible to discover. On the other hand a poor optical com-
bination will generally exhibit it to an unpleasant degree, and

36 MANUAL OF HISTOLOGY.

especially if great amplification is aimed at. Lenses of very
high power are also apt in any case to exhibit the same ap-
pearances.

Measurements of the red corpuscles in man and ani-
mals.— The average diameter of the human red globule is still
a matter of discussion. The faulty measurements of the older
writers have led to some misconception on these points, and the
matter has required new study. Welcker, who has long been
an authority on the Continent, gave .00774 mm. as the average
breadth in the human male, with a minimum of .0045 mm., the
latter from personal observation. A maximum of .010 mm.
has been given by Max Schultze, while Frey places the average
thickness at .0018 mm. Later investigations by Hayem show
that a diameter of .012 mm. or even .014 mm. may be reached,
while he has known it to fall as low as .0022 mm. Elsberg
gives the mean diameter of the red blood-corpuscle at .0075
mm., agreeing very nearly with Welcker. He has observed a
maximum of .01016 mm., and a minimum of .00422 mm.

Measurements of single corpuscles have no value in deter-
mining the particular animal from which the blood has been
obtained, and this is an object of prime importance in medico- .
legal cases. It is common, therefore, to make a hundred or
more single measurements, and then take the average of them.
And yet this figure may vary considerably in different individ-
uals, or even in the same one. In the blood of the puppy, for
instance (the size of the dog's corpuscle being very nearly
that of man's), a recent observer found that the average diame-
ter of fifty corpuscles varied only two-millionth of an inch
from a like average of fifty taken from his own blood. In
another instance, taking forty from a puppy, Jie found that
the average differed only seven-millionth of an inch from a
similar average of his own (Woodward).

Opposite is given a table of blood-corpuscle measurements
by Welcker and others.

By referring to it, the cat's and rabbit's corpuscles will be
found to have an average diameter which is not far distant
from man's and dog's, while the minimum and maximum
diameters of each show conclusively that a large number of
their corpuscles would be likely to equal man's, and there-
fore make it impossible to distinguish one from the other. To
obviate this source of error a very large number of corpuscles

THE BLOOD.

37

would have to be measured separately, as we have already
seen, and then an average taken of them all, before even a
guarded opinion could be given as to the source of the blood.
Still other difficulties, however, are apt to beset the microscop-
ist. The blood is usually dried and in small quantity. The
disks are then shrunken. If we endeavor to restore them to
their original shape, as by soaking in blood-serum, we are
never sure of having accomplished the object, or that we have
not overdone it. This statement will be better understood by
experiments that will be detailed at another point in this
chapter. Where blood-corpuscles are elliptical, as in birds,
there is much less opportunity for error.

Measurements of red Blood-corpuscles.

Maximum
diameter.

Minimum
diameter.

Average
diameter.

Dog ..

mm.
.0082

mm.
.0065

mm.
.0073

Cat

.0074

.0058

.0065

Rabbit

.0080

.0062

.0069

Sheep

.0056

.0038

.0050

Goat (old)

.0046

.0036

.0041

" (eight days old)

.0066

.0039

.0054

Moschus javanicus

.0030

.0022

.0025

Elephant

.0106

.0084

.0094

Pigeon (old)

.0160

.0132

.0147

" (fledsrlingr) .

.0140

.0116

.0126

Chicken

.0132

.0104

.0121

Duck

.0140

.0118

.0129

Vespertilion

.0066

.0054

.0061

Triton cristatus

.0327

.0259

.0293

Salamandra Cryptobranchus.

.0415

.0302

.0378

.0579

.0460

.0512

IJepidosiren annectens

.0440

.0360

.0410

Average
length.

Average
breadth.

mm.
.058

mm.
.034

.075

.047

The number of the red globules. — It has commonly been held
that the blood of an adult man contains 5,000,000 red corpus-
cles in each cubic millimetre. In anaemic conditions this num-
ber may be reduced below 3,000,000, while in fair physical

38 MANUAL OF HISTOLOGY.

l^ulth it has reached 6,000,000 and over. Under ordinary cir-
cunisianees 4,500,000 is thought to argue a fair bodily condi-
tion (Keyes).

Quite recently Hayem has given an instance where the number was reduced
to 800,000. This extraordinary state he has called aglobulie intense ; the name
(tr/lobxlie extreme was given to a condition observed on another occasion where
he counted only 450,000 corpuscles.

The Uood-globules in an indifferent fluid.— -In order to get
a proper conception of the various influences that act upon the
red corpuscles, so as to alter their form, size, and internal
appearance, it is essential to subject them to some of the more
common, such as water, acids, alkalies, electricity, etc. In
no other way can the student appreciate the extraordinary
changes which these bodies suffer, and indeed a knowledge of
such matters is quite necessary in studying the histology of
either normal or diseased tissues.

Unfortunately we are not always able to use human blood
for these demonstrations because the corpuscles are too small,
and consequently the alterations do not admit of easy observa-
tion. We naturally turn to an object that has larger corpuscles
and may be procured with little trouble or expense.

The frog is therefore selected, or, even better still, the newt,
which is especially well suited for this purpose. • At first the
blood may be examined in a menstruum similar to the liquor
sanguinis or plasma, and the frog's aqueous humor is usually
found satisfactory.

To a drop of this latter add an equal quantity of the blood,
mix them well with a glass rod, and adjust an ordinary
| inch circle. The aqueous humor exerts no special influ-
ence over the corpuscles, and is therefore called an indif-
ferent fluid. If it be impossible to obtain aqueous humor, an
excellent substitute may be found in the fresh fluid from a
hydrocele or ovarian cyst, or we may use serum to which iodine
has been added, which is then called iodized serum. To six
ounces of the fluid twenty grains of finely powdered iodine are
added. After prolonged agitation the iodine will be dissolved,
and the mixture thus prepared may be kept for a number of
months. Suspended in this liquid the blood is studied to
advantage with a lens of moderate power, such as an ordinary

THE BLOOD. 3«)

i inch. The contents of the disk will appear homogeneous,
which is a term that merely indicates an apparent absence of
structure. The nucleus and nucleolus should also be invisible.
The shape of the corpuscles is oval, and they are flattened and
have rounded edges, with hollowed centres, in which a promi-
nence is usually seen (Fig. 13). The protoplasm is the sub-
stance of which the disk is made ; it has a light yellow color,
and is dull or pellucid in appearance, much like semi-solid
jelly.

Brownian and amoeboid movements. — Using the same
method of preparation the white corpuscles or leucocytes are
seen to good advantage. They are much smaller than the red
disks (in the frog — the reverse of human blood), and there is
wide range in size, one histologist (Klein) having described as
many as thirty varieties. In the interior, little dark spots are
sometimes seen in constant vibration. By a skilled observer they
are readily detected, even with a good £ inch glass. When
such specks are numerous the bodies are said to be granular.
In the newt's blood this phenomenon is usually best seen.
The word granule has been applied in these cases from the
notion once prevalent that the little dots were molecules sus-
pended in a menstruum of some sort that filled the corpuscle.
This subject is now eliciting much study, but the movement,
whatever its significance may be, is called the Brownian move-
ment.

Klein, who states that the newt's leucocyte is traversed by an intracellular
network, believes that the movement just described is due to the motion of the
"disintegrated network " under the stimulus of imbibed water. Under this
explanation the oscillatory movement in the corpuscles of the human saliva
would indicate death rather than life. When fluid has been withdrawn by
evaporation the phenomenon ceases. According to other histologists this
vibratile motion is an indication of vital action.

The remarkable change in form which these corpuscles un-
dergo is a more positive indication of vital power in the leuco-
cyte. When the little body is placed under conditions which
imitate those of its natural state it commences to put forth
processes and then withdraw them, carrying on these move-
ments slowly, but with a certain degree of regularity. While
this is being accomplished the corpuscle is observed to move
about from place to place.

40

MANUAL OF HISTOLOGY.

Pio. 15.— Leucocytes: a, putting out pro-
sses ; ft, having withdrawn them. (Hollett.)

In Fig. 15 the leucocytes are seen. Those marked with the
letter a are engaged in amoeboid motion. The one marked b
i? in a state of contraction. . This phenomenon is called amoe-
boid movement, because it resem-
bles that of the amceba— the lit-
tle microscopic organism found
in stagnant water. In order to
permit these changes to continue
for some length of time, it is well
to paint a little oil or glycerine
around the edge of the circle.
Evaporation is thus prevented.

If the warm slide be used the
changes will follow with greater
rapidity. Both Brownian and
amo3boid movements are usually confined to a limited number
of the corpuscles, and the former often to only a small portion
of the interior.

The slide ' for heating consists of an ordinary glass slide
(Fig. 16) upon which is riveted a thin copper plate (b) perfor-
ated in the centre, so as to allow space for the drop of blood
which is to be examined. From the copper plate extends an
arm (c) over which is slipped a spiral copper wire (e), which is
heated by the flame of an alcohol lamp. By this means the
glass plate is kept warm and with it the drop of blood. In
order to secure a proper
amount of heat.and no
more, it is customary
to put a little bit of
cocoa butter upon the
corner of the slide. The
butter melts at the tem-
perature of the body,
and after this point has
been reached the lamp
should be carried along
the wire away from the slide until the precise distance is found
at which this particular degree of heat will be maintained.
Action of a dilute salt solution. — It is often difficult, and,

FIG. 16.— Slide for heating : a, slide; 6, copper plate ; c, arm
over which the spiral wire (<f ) is slipped

1 Made by T. H. McAllister, 49 Nassau Street, New York City.

THE BLOOD. 41

indeed, impossible, to obtain aqueous humor or even an animal
fluid such as has been described, and microscopists have accord-
ingly made use of a substitute that can be prepared at any time
and kept indefinitely. This is a solution of common salt in
distilled water (1 — 400). Add a drop of fresh frog's blood to a
drop of the salt solution, mix them well, and it will be seen
that the delicate protoplasm of the red blood-corpuscle, most
susceptible of change, is not altered in appearance, though the
body itself will change in form from the elliptical to the spher-
ical. This salt solution has been found, in practice, an excellent
substitute Jfor blood-serum, and is very generally used in ex-
amining fresh specimens, where it is important to avoid any
material change in the corpuscle.

Action of distilled water — Irrigation. — The effect of water
is also noteworthy, as it is a very important consideration in
both histological and pathological work, especially the latter.
Take a drop of frog's blood, add to it an equal quantity of
distilled water and apply a cover. The nucleus or central body
will now be readily seen, surrounded by a yellow border ; the
body of the corpuscle or peripheral part will at the same time
gradually become paler and larger. Now add distilled water
slowly, drop by drop, in the following way : Take a long strip
of tissue or filter paper about half the length of the slide and in
breadth equal to one-half the diameter of the cover. Apply
the water with an ordinary minim dropper, close to the edge of
the cover, on the side opposite to the paper strip. This latter
will now take up the excess of water and cause a stream to
pass through the specimen. This processes called irrigation.
Push the paper a short distance under the edge of the cover,
and the solid particles in the fluid will be carried to the edge
of the paper, where they will remain at rest and may be ob-
served at one's leisure.

This plan is often nseful in other sorts of microscopic work, as in looking
for renal casts, urinary crystals, etc. It may save much valuable time. I first
learned it from my friend, Dr. Edward Curtis, of this city.

Continued addition of water will cause the corpuscles to
swell and after a time burst, or, at any rate, become so expand-
ed that they can scarcely be seen. When water is applied
slowly to human blood, the corpuscles soon begin to lose their

MAXUAL OF HISTOLOGY.

disk-like form and assume a spheroidal, perhaps spherical con-
tour. The coloring matter then escapes, in most instances, and
they become quite transparent (see Fig. 17). Such corpuscles are
often seen in human urine where they appear as colorless rings.
In frog's or newt's blood the body of the disk first imbibes the

Fro. 17.— Human red blood-globules:
a, with haemoglobin ; 6, without it (Rol-

l3tt.)

FIG. 18. — Red corpuscles of the frog
that have imbibed water. (Rollett.)

water ; later, the nucleus, which then has a sharply defined
outline. Sometimes the material of which the body is largely
composed (haemoglobin) is gathered about the nucleus, sending
off radiating prolongations to the periphery, while the imbibed
fluid is stored in the intervening spaces (see Fig. 18).

Action of carbonic acid gas. — This experiment requires a
special apparatus. First of all it is essential to have a moist
chamber (Fig. 19).

Take a small, flat bit of wood about 1| inch wide, 3 inches
long, and f inch thick ; make a square opening in the centre,
sufficiently large to admit an ordinary £ inch cover-glass ; this
is to be pressed to the bottom and firmly fixed, thus making a

shallow well with a glass
bottom. Into this cham-
ber are admitted, through
side holes, glass tubes (one
on each side), so that air
or gases can be carried into the chamber. When in use, the
chamber is kept moist by a drop of water, which is put in
one corner of the well, while the specimen of blood to be ex-
amined is dropped upon a large glass cover, and the latter in-
verted over the mouth of the well. In determining the effect
of carbonic acid gas upon animal life, we have merely to con-
nect the gas-chamber just described with a jar in which carbonic

Fio. 19.— Moist chamber.

THE BLOOD. 43

acid gas is generated. Fig. 19 illustrates a gas or moist cham-
ber of the same general character, and devised by Dr. J. H.
Hunt, of Brooklyn. Take a large gallon flask, fill it partly
full of pulverized marble-dust, attach it by means of a rubber
tube through a perforated stopper to a Wolff's bottle, which
latter must be connected with the moist chamber. Now gener-
ate the carbonic acid gas in the flask by pouring muriatic acid
upon the marble-dust. When the gas is being evolved it will
be known by the ebullition of the water in the Wolff's bottle.
Now place the moist chamber upon the stage of the micro-
scope. Take a drop of newt's blood, dilute it with serum or an
indifferent fluid, and mount it upon a glass cover, which invert
over the well, first seeing that the edge of the cover is oiled, so
that it will remain in place. Now connect the tube of the moist
chamber with the tube of the gas-generator, and the carbonic
acid gas will enter and pass through the chamber. The rapidity
with which the current moves may be regulated by a spring
clip. As soon as the gas enters, the central body or nucleus
becomes distinctly visible, and is surrounded by a yellow halo ;
when, however, the gas is withdrawn and atmospheric air
is admitted, the nucleus and colored zone disappear. This
double experiment may be repeated a number of times. Finally
a point will be reached where all action will cease. This cen-
tral body, under such circumstances, has been called the zooid,
and the corpuscles proper the oiTcoid (Bruecke).

Action of acids upon tJie blood. — Acetic acid is commonly
used in observing the changes that are produced by an acid
solution.

Take the ordinary dilute watery solution of acetic acid
(1 per cent.) so much used in laboratories, add a drop of it to
an equal amount of frog's blood. The red globules instantly
exhibit nuclei. The colorless globules also cease their motion,
if any has existed, and they become granular and shrivelled.
The term granular is used merely in a relative sense and has no
special reference to granules whether present or not, but merely
to an appearance that has already been explained.

These phenomena are more marked if the solution is con-
centrated. The red bodies, also, in such case, are apt to crack
and split up. A good way of determining the proper strength
for the ordinary acetic acid solution is to pour a little into an
ordinary watch-glass, and then add chemically pure acetic

44 MANUAL OF HISTOLOGY.

acid drop by drop until the solution is faintly acid to the

taste.

Action of alkalies upon the blood.— Take a drop of the
newt's blood and mount it in a drop of serum or of salt solu-
tion. Then, affixing a strip of bibulous paper in the way that
has been described, add drop by drop a weak solution of aqua
ammonise. A similar strip of paper, somewhat larger in size,
upon the other side, will cause a current and carry the corpus-
cles to the side of the field where the paper strip is largest, and
there the corpuscles may be observed at rest, and the altera-
tions effected by the alkali duly noted. It will be seen that
after a little time the corpuscles, both red and colorless, will
swell up and finally, after a time, provided the alkali be in
sufficient amount, disappear or become so expanded as to be
invisible. Sometimes they will burst, leaving the field evenly
stained with a homogeneous glutinous-looking substance.

Action of electricity. — It seems to make little difference, so
far as the microscope is concerned, whether the continuous or
interrupted current is employed, as in either case the phe-
nomena observed are the same- in quality. Take bits of tin-
foil and attach them to an ordinary glass slide, in such a
way that they are just % inch distant from one another. The
pieces of foil should be triangular in shape and have their
pointed extremities turned to one another. The specimen
should be a drop of newt's blood diluted with an equal amount
of serum, both perfectly fresh. They should be intimately
mixed with a glass rod.

Depositing a drop of this solution upon a cover-glass, it
should be inverted and placed upon the slide in such a way
that it occupies an intermediate position between the bits of
tin-foil. The ordinary stage clips of the microscope are then
to be used in holding the slide firmly in position and to press
upon the tin-foil. The only remaining task is the attaching of
conducting wires from the electrical instrument, one to each
clip. The bits of tin-foil are easily fastened to the slide ; they
have merely to be hammered out flat, when they will adhere by
simple pressure. Sometimes it may be desirable to approxi-
mate the poles. In such cases it is necessary to use two fine
bits of platinum wire. They should be flattened, and shaped
like the letter S. Rest them upon the bits of tin-foil, opposite
to one another and at the required distance apart. The cover-

THE BLOOD. 45

glass should press on them. Some little mechanical dexterity
is required to get them in position, and they are apt, after using,
to become so charged that their action upon the corpuscles
commences before they are connected with the battery. The
phenomena at the negative pole are those of an acid ; at the
positive, those of an alkali. At a distance from the line of the
current, secondary changes occur of a less regular character.

Halting has devised an apparatus which is somewhat more
elaborate, but in principle the same.

Other changes in the red corpuscles.— It a drop of blood be
taken from the finger, by pricking with a needle (the triangu-
lar or glover's is the best), it will be seen
after a time that the exterior of the corpus-
cle is indented or crenated, as this change
is called. It is well shown in Fig. 20.

Examination of the circulation in the
web of a frog's foot. — Take a medium-sized
frog and curarize him by injecting beneath
the skin, with an ordinary hypodermic syr-
inge, two drops of a weak solution of curara
(1 — 2,000 in water) or a few minims of a 50 per cent, solution
of chloral hydrate (Schaefer). After a variable time the ani-
mal will be completely paralyzed, but the circulation will go
on as before.

There are many difficulties in the use of curara, depending on the variable
strength of the drug, the idiosyncrasies of the animal, and other causes that
we do not appear to understand. A solution which will produce a proper
amount of paralysis in a frog on one day will rapidly kill another frog the next
day. To ensure any reliability of action, it is well to have a specimen of
which the strength has been properly tested. Then, if time enough is at one's
disposal, a weak solution, such as the above, may be injected every hour until
the symptoms of the drug 'are apparent. If the subsequent recovery of the
animal is not of vital importance, the amount may be increased, for the circu-
lation will often be well shown, even if the animal does not eventually survive.

My friend, Dr. W. H. Welch, who is in charge of the Histological Labora-
tory at the Bellevue Medical College, employs a watery solution of curara.
He keeps on hand a \ per cent, solution of the drug ( 1 gramme to 200 c.c. of
distilled water), and then dilutes it as occasion may warrant to i per cent., or
even -fa per cent. (1 — 500 or 1 — 1,000). Of this diluted solution he injects four
or five drops into the dorsal lymph-sac of the frog. A still more dilute solu-
tion he is often in the habit of using, so that the frog does not come under the
influence of the drug for an hour or an hour and a half. After twenty-four to

46 MANUAL OF HISTOLOGY.

forty-eight hours the animals entirely recover, but if a stronger solution is
used, he finds the results are frequently fatal, though the animals may survive
long enough to 'permit a ready demonstration of the circulation, emigration of
leucocytes, etc.

Now envelop his body in a damp cloth and extend him upon
a cork plate about a quarter inch thick and large enough to
support the entire body. Make a small opening in the cork,
and over it place the web oi the frog's foot, fastening the latter
by ordinary pins.

The circulation may in this way be studied at one's leisure.
The red and white blood-corpuscles are seen in the arteries,
veins, and capillaries. While the red bodies pass rapidly
through the central portions of the vessels, the white creep
slowly along the walls, altering their shape as they meet with
any obstruction. Where, however, a small artery divides, it
will sometimes be seen that the corpuscles, especially the red,
are caught at the bifurcation ; parb bending to go down one
branch, and part down the other ; taking, in fact, the shape of
a saddle-bag. Such a phenomenon exhibits the elastic and
distensile properties of the corpuscle. Apply an irritant, such
as a weak solution of nitrate of silver, and after prolonged and
careful watching, the gradual exit of both white and red cor-
puscles may be seen. This procedure requires extreme pa-
tience and a co-operation of peculiarly fortunate conditions,
which are not likely to favor the beginner in microscopy.

Internal structure of the red corpuscles. — As yet the inti-
mate structure .of blood-corpuscles is a matter little understood,
though an abundance of theories are rife about it. Klein main-
tains that these corpuscles, in common with others in the body,
are traversed by an intracellular network. In the red cor-
puscles of the newt, especially, he says there is a network of
fibrils, with an interfibrillar hyaline ground substance, both
together forming the so-called stroma. The nucleus contains a
network of fibrils in connection with the network of the cor-
puscle proper ; the haemoglobin, a colored fluid, is contained in
the substance of the meshes of the network of the corpuscle
proper. Drs. Cutter, of Boston, and Heitzmann, of this city,
also state that there is an intracellular network. The former
regards it as due to the mycelium of a parasitic growth.

Dr. Elsberg, of this city, also states that he finds a reticu-
lar appearance after using a solution of the bichromate of

THE BLOOD. 47

potash (30 per cent, to 50 per cent, of a saturated solution in
water).

Real granules are often present in the corpuscles, as may be
proved by adding water in large quantity. They will then
become greatly distended, and bursting, the granules will be
scattered throughout the field.

If finely ground vermilion is sprinkled in the liquid, some
of the white corpuscles will take up the granules, perhaps with-
out losing their amoeboid character ; finally, they may eject
them after a longer or shorter sojourn.

According to Boettcher, the human red blood-corpuscle has a nucleus. He
exhibits it in the following way : Taking a saturated solution of corrosive subli-
mate in alcohol (96°), he diffuses about fifty volumes with one of blood. The
corpuscles are deprived of their haematin, but at the same time are preserved.
The mixture is frequently agitated, but in about twenty-four hours it is allowed
to subside, when the superincumbent fluid is poured off and alcohol added.
By further agitation for another twenty-four hours the corpuscles are thoroughly
washed, and then settle at the bottom of the vessel. Prof. Boettcher claims
in this way to have found three classes of red globules. The first are homo-
geneous and shiny throughout ; the second are clear externally, but granular
within ; the third variety exhibit a nucleus and nucleolus.

Development of the blood-corpuscles. — In early foetal life
all the corpuscles are colorless (Klein). According to Balfour
and Foster, both colored and colorless corpuscles, at least in
the chick, are developed from solid sprouts of protoplasm, de-
rived from the middle germinal layer. There seems good rea-
son, however, to believe that the leucocytes are formed in part,
at least, from the lymphatic glands, and Klein thinks that
they are thrown off from the "germinating buds" of serous
membranes. Later, the red ones make their appearance, and
for a time are nucleated. The investigations of Neumann and
Bizzozero, showing that the red corpuscles in the medulla of
bones are also nucleated, favors the theory that bone-marrow is
one of the theatres for such corpuscular metamorphosis.

According to Hayem the production of red corpuscles in the
blood is accomplished through the agency of hcematoblasts,
i.e., minute red corpuscles. In convalescence from acute fe-
vers, or after a considerable loss of blood, these smaller bodies
may be observed in the blood for a variable time, even some
weeks.

48 MANUAL OF HISTOLOGY.

According to Recklinghausen, the colorless corpuscles may be generated
from the red corpuscles, but it is probable that they may be formed in the tis-
sues at many points, and the connective substances through their intimate asso-
ciation with the lymphatics are capable of manufacturing them in almost any
quantity. Neither of the two varieties of corpuscles, the red or the white, have
a cell-wall or outer investing membrane that can be demonstrated, though it is
not unlikely that the outer layer of protoplasm has greater density than the
more internal portions.

White or colorless Hood-corpuscles. — The white blood-cor-
puscle is much larger, on an average, in the human species,
than the red. It is rounded in form, and is estimated as varying
between .0077 and .0120 mm. The average is .0091 mm. (Frey).
In contour they are apt to be more or less rough, and exhibit
processes. In some of these corpuscles the nucleus is distinct,
though when quite fresh a nucleus is rarely seen. If the eye
of the observer can watch the corpuscle when it is upon a
heated stage and under suitable conditions, its division may
be seen. The number contained in the system is variable, as
we shall see, depending upon a great number of conditions.

The personal observations of the author do not incline him
to regard the network which has attracted so much attention
of late years as satisfactorily shown to exist in living corpus-
cles, although there is no question but that it has been seen in
corpuscles after exposure to chemical reagents.

According to Dr. Richard Norris, there is, in mammals, a third corpuscular
element which is usually invisible and of the same size as the red ones. Some
doubt is thrown upon his alleged discovery, by the fact that the method he
employs is likely to produce artificial appearances, and therefore leads to the
supposition that the alleged bodies were merely red corpuscles decolorized.

Mode of counting the blood-corpuscles. — Thanks to the
instruments of Malassez, Hayem and Nachet, and Gowers, we
are in a position to count the red blood-corpuscles with a fair
degree of accuracy.

The methods are somewhat different, but are not difficult to
understand.

Schaefer describes his plans as follows : In order to separate
the corpuscles and prevent coagulation, the blood used is first
diluted to a definite extent — say a hundred times — with a 10
per cent, solution of sulphate of soda. The mixing can be per-
formed in a measuring-glass if the blood is in sufficient quan-

THE BLOOD. 49

tity, but if only a small drop is obtainable, such, for example,
as is got by pricking the finger, a mixer is better. This con-
sists of a capillary tube terminating in a bulb, the capacity of
the bulb between the marks 1 and 101 being exactly 100 times
that of the tube from its point to the mark 1. A small glass
ball is inclosed in the bulb, and serves, by its movements, to
facilitate the mixing. The capillary tube is allowed to fill with
blood as far as the mark 1 ; sulphate of soda solution is then
sucked up as far as the mark 101- As it passes in, it of course
pushes the blood before it into the bulb, and the two are there
thoroughly mixed by gentle agitation.

The next thing is to count the corpuscles in a known quan-
tity of the mixture. The most convenient plan is that of
Hay em and Nachet. A slide is used, having a glass ring £ mm.
in depth, cemented on to its upper surface. A drop of the
mixture, but not enough to fill the cell so formed, is placed in
the middle of the ring, and a perfectly flat cover-glass is so laid
on that the drop touches and adheres to it without reaching
the sides of the cell. The slide is placed on the microscope,
and as soon as the corpuscles have settled down to the bottom
of the drop, the number in a definite area is counted. If the
area chosen is % mm. square, this will give the number which
were contained in £ mm. cube of the mixture, and multiplying
this by the number of times the blood was diluted, the result
will be the number of corpuscles in | mm. cube of blood.
Schaefer thinks that it is more convenient to have the quad-
ratic markings upon the micrometer glass of the eye-piece than
upon the slide, which is a practical point. The quadratic
markings are shown in Fig. 22. To measure any square, it is
only necessary to take the stage micrometer, ruled in milli-
metres and decimals, and adjusting the draw tube, make the
side of one square correspond exactly to an interval of | mm.
on the stage micrometer. It will then be convenient to mark
the tube at this point, and then, in all subsequent work, if the
tube be kept at this line and a slide is used of the thickness of
the micrometer and the same lens and eye-piece, the side of a
square will always be £ mm. This method is the one in general
use.

Another less frequently employed is that of Malassez, which
is also described by Schaefer as follows : A little of the mixture
of blood and sulphate of soda is transferred to a very fine flat-
4

50

MANUAL OF HISTOLOGY.

tened capillary tube, the capacity of a given length of which has
been ascertained previously and marked on the slide to which
the tube is fixed. Thus, in his capillary tube a length of 400 mi-
cromillimetres represents the T?V.* Part of a cubic millimetre
of the mixture. The counting is performed with the aid of a
squared ocular micrometer, the microscope tube having been
previously so adjusted by the aid of a stage micrometer that
the side of the square shall have the value of one of the lengths
(400 n ' for example) marked on the slide. The result of the

SDi I

FIG. 21. — Hayem and Nachet's apparatus for blood -counting.

counting gives the number of corpuscles in a known quantity
(T«W c.mm.) of the mixture, and the number in a whole cubic
millimetre can therefore be readily determined.

Dr. Keyes uses a modification of the method of Hayem and
Nachet, making a dilution of 1 to 250, in order to render the
counting more easy. In Fig. 21 the pipette, A, is filled up to
the mark, 5 D ; it is then emptied into the glass vessel, F. The
pulp of the finger of the patient whose blood is to be tested
should be pierced with a triangular needle (glover's). Quick

1 A micromillimetre (/*) =

THE BLOOD.

51

but firm pressure down the finger will at once force out a drop
from the punctured spot. The blood must be drawn imme-
diately into the capillary pipette lest it coagulate. When the
pipette is full to the mark 2, its point should be rapidly wiped
clean of any blood adhering to the outside, and the contents at
once blown into the artificial serum in the cup, F. A little
suction back and forth clears the tube of any blood-corpuscles
which may have adhered to the glass within. Both tubes
should be carefully washed before being put away.

The mixture is now to be thoroughly agitated with the glass
rod, and before it has time to settle, a drop is placed in the
middle of the cell on the slide, D, care being taken that the
drop is not large enough to touch any part of the circumference
of the cell. The covering glass, E, should at once be placed
upon the cell. Should the drop be too large, so that when the
thin cover is adjusted it spreads out too much, the glass should
be cleansed and the attempt made anew. Finally, a small drop
of water or saliva is applied to the edge of the covering glass,
under which it circulates around the top of the cell, serving to
hold the cover in place and pre-
vent evaporation. The slide is
then put in position and when
the corpuscles have all settled
to the bottom of the fluid, the
counting should begin. The
following detailed plan is then
given by Dr. Keyes :

"It is better to count each
of the sixteen squares and write
down its number separately,
so that in counting the square
beneath it, should there be any
doubt about counting a given
corpuscle lying upon the line, a glance at the number recorded
for the square above may remove all doubt. Many corpuscles
will be found lying upon the outside lines bounding the large
square. I have adopted the rule of rejecting all those lying
upon the upper and right-hand outside lines (of the large
square) and counting all those lying on the lower and left-
hand outside lines.

After having thus obtained the nuiuber of red corpuscles

FIG. 22.— Blood corpuscles us seen with the
squared ocular micrometer. (Keyes.)

52 MANUAL OF HISTOLOGY.

-ituated within the large square, it becomes easy, by a simple
equation, to find the number in a cubic millimetre. A single
count, however, exposes to sources of error, and in order to
approach more nearly to exactness, I have uniformly counted
the number contained in the large square in five different por-
tions of the field (sometimes ten), and have taken a mean of the
whole number of counts as the standard.

The computation is as follows : The glass cell on the slide
is | mm. deep. The eye-piece micrometer marks off £ mm.
square, therefore the count of red corpuscles (or white, as the
case may be) must indicate the number contained (in the dilu-
tion used) in £ mm. cube. But | mm. cube is ^ of a c.mm.,
therefore the number counted must be multiplied by 125 ; and
the blood was diluted by adding 250 parts of fluid to 1 of blood
(2 c.mm. to 500 c.mm.), therefore the product above obtained
must be again multiplied by 251 to get the number of corpus-
cles in a c.mm. of pure blood. Instead of multiplying twice, a
single multiplication by the product of 125 x 251, 31,375, will
give the same result."

This method should, theoretically, be absolutely accurate, but there are vari-
ous errors which will unavoidably creep in. First of all, the tubes should be
verified as to accuracy. This has been done for me at the Winchester Observa-
tory, of Yale College, by Leonard Waldo, Esq., the astronomer in charge. My
larger glass tube is slightly different in shape from the one here represented, and
is marked so that the line at \ indicates a capacity of 500 cubic millimetres
(0.5005 grammes of distilled water at 26.4° C.). The cubical contents of the
reservoir from the "point to the line i = 0.2425 + 0.008 = 2505 grammes =
250 c.mm., approximately. Accordingly, the marks i and \ indicate i and |
a cubic centimetre, within a. limit of error so small as to be practically insensi-
ble. The smaller glass tube, which is capillary, is marked 2, 2$, 4, and 5.
The level 5 indicates a capacity of 5 c.mm. The capacity between the pointed
extremity and 2 is 2 c.mm., less jfo c.mm. ; the space between 2 and 2| con-
tains .55 c.mm. ; the space between 2£ and 4 contains 1.45 c.mm. ; the space
between 4 and 5 contains exactly 1 c.mm. (Waldo). The determination of these
capacities was made by using distilled water, and comparing the weight, when
filled to the various levels, with the same tube after careful drying.

These estimates are given to show one of the errors which may be met
with, and that an instrument, before using, should be verified by some one who
has special means for determining capacities of this kind. My eye-piece mi-
crometer was made for me by Rogers, of Cambridge, and the entire field was
subdivided into squares, so that every portion of it may be counted without
moving the slide. My method has been practically the same as that of Dr.
K3yes, except that I prefer diluting with one thousand parts of the diluent,

THE H^EMOCHROMOMETER. 53

and use iodized serum in place of urine. The ordinary i per cent, solution
of common salt in water will also answer sufficiently well.

Recent investigations, such as those conducted by Drs. Cut-
ter and Bradford, of Boston, have established that there is
great variation in the number .of globules of an individual, de-
pending on various causes, such as the locality from which the
blood is drawn, the loss of fluids, as by diarrhoea, sweating,
increased urinary secretion, etc., and even the period of the
day, week, or year. These general conclusions have also been
sustained by Hayem, of Paris, in researches which are still
being prosecuted.

When one further considers that we have no definite stand-
ard of comparison ; that the instrument is apt to be imperfect ;
that there is a liability of errors to the amount of 10 per cent.;
that skill and practice are required in manipulation, it is by no
means difficult to see that the hsematometer is not calculated
at present to introduce much scientific precision into medicine,
unless the most extraordinary precautions are taken in every
case, and these all duly noted.

Blood crystals. — The pigment of the blood occurs usually
in an amorphous form, and is called haematine. The brownish
red needles found in extravasated blood are known as haema-
toidine.

Haemoglobin also occurs in most mammalian blood, and is
deposited under the form of rhombic plates. It is estimated
that about 125 grammes are present in the blood of a healthy
adult.

THE H^EMOCHROMOMETER.

According to Mantegazza and others, richness in haemoglo-
bin indicates a corresponding richness in red corpuscles, and
any special depth of color in the blood may be regarded as im-
plying a certain given number of red corpuscles to the cubic
millimetre. While this ratio appears to hold true in health, it
fails in disease. Thus, a condition which we recognize as ane-
mia may be almost wholly due to a loss of haemoglobin in the
corpuscle, or an actual loss of red corpuscles, together with a
diminished amount of haemoglobin in those that remain. In
the cachexia of cancer the number of the corpuscles may be
sustained, but their haemoglobin diminished. In diabetes mel-

54 MANUAL OF HISTOLOGY.

.

litus, on the other hand, there may be an excess of red cor-
puscles, while there is a diminution of their haemoglobin. In
ansemia, from hemorrhage, there is an actual loss both of cor-
puscles and of haemoglobin in those that remain.

To facilitate the estimation of haemoglobin, an instrument
has been devised by Malassez and Verick (Paris), called the
hcemochromometer,1 which is easily manipulated, and bids fail-
to establish some facts of -practical utility (see Archives de
Phys., 1877, p. 1).

It consists of a hand-screen, to which a movable prismatic
trough, containing a colored fluid, is attached, and a modified
Potain pipette. By means of this apparatus the richness of
the blood in haemoglobin, and the maximum quantity of oxy-
gen which it can absorb, may be determined. To use the ap-
paratus the pipette is first filled up to a certain point with the
blood to be examined, and then diluted with 100 parts of water.
The reservoir of the pipette is then filled with the diluted
blood. The screen has two holes ; behind one of these the
prismatic trough is made to slide up and down, the color of the
fluid contained in it of course varying in intensity, according
to the extent of the upward and downward motion.' Behind
the other opening the reservoir of the pipette is secured by
means of a little elastic ring. The screen is now held against
the light (preferably white light ; sunlight is to be especially
avoided), and the trough moved until the color of the blood
mixture is matched by its own color. Then the figure on the
scale attached to' one side of the trough is read off, and this
indicates, by reference to the table annexed to the apparatus,
the points to be determined. If the blood to be examined be
deeply colored, the aqueous blood-mixture is made in the pro-
portion of £ to 100 ; if it be but slightly colored, in the propor-
tion of 2 to 100.

BIBLIOGRAPHY.

WELCKER. Pragervierteljahreschr. XLIV., p. 60. 1854. Zeitschr. f. rat. Med.

3, XX., p. 280.

ScnoLTZE, MAX. Archiv f. mikrosk. Anat. I., p. 35. 1865.
HOI.LETT. Strieker's Manual of Histology. New York, 1872.
WOODWARD. Am. Jour, of the Med. Sci., Jan., 1875. N. Y. Med. Rec., Jan. 31, 1880.

1 To be obtained of J. F. Beynders & Co., New York city.

BIBLIOGRAPHY. 55

KELSCH. Arch, de Phys. Vol. II. 1875.

KEYES. Am. Jour, of the lied. Sci., Jan., 1876.

HEITZMANN. New York Med. Jour.. April, 1877.

MANTEGAZZA. Berl. Klin. Woch., April 1, 1878.

RANVIER, Traite technique d'histologie. Paris, 1877 et seq.

HAYEM. Archives de Phys. 2 Ser., T. VI., p. 201 et seq. 1879.

BIZZOZERO, G., and SALVIOLI, G. Centralb. f. d. Med. Wiss. 16, p. 273. 1879.

POUCHET. Gaz. Med. de Paris. 14, 16. 1879.

CUTLER, E. G., and BRADFORD, E. H. Journal of Phys. Vol. I. 1878—1879.

BOETTCHER. Archiv f. mikrosk. Anat. Bd. XIV. p. 73. 1877.

KLEIN and E. NOBLE SMITH. Atlas of Histology. 1879.

ELSBERG. Annals of the N. Y. Academy of Sciences. Vol. I. , Nos. 9 and 10. 1879.

(A very extensive bibliography.)

SATTERTHWAITE, T. E. Arch, of Comp. Med. N. Y. II. 1880.
BAXTER and WILLCOCK. Lancet, March 6, 13, 20, 1880.

CHAPTER IV.

EPITHELIUM.

THE skin, mucous surfaces of the body and various pas-
sages in connection with them, are evenly coated with bodies
of peculiar shape, which are united together to form a cover-
ing of one or more layers.

In some places, as upon the external portions of the epider-
mis, the corpuscles are more or less flattened. Elsewhere, as in
the ducts of secreting glands and in the trachea and fallopian
tubes, they are cylindrical, and the free extremities are often
surmounted by cilia— fine, hair- like processes, which have a
vibratile movement that propels solid matters, such as sputa
and ova, in some special direction. In other parts, again, as in
the collecting tubes of the kidney, near the apices of the pyra-
mids, a cuboidal variety is found. Intermediate or transitional
forms are also frequently met with in all parts of the body.

A characteristic of epithelium which is especially note-
worthy is that the same species is not found uniformly in the
same position. - Sometimes this mutation of type is governed
by the physical laws that regulate the growth and development
of the subject, or it may be a consequence of disease. An ex-
ample of the former peculiarity is to be noted in the larynx,
where the ciliated corpuscles of infancy part with their cilia
from advancing age, or indeed may become flattened.

As an example of pathological change it is not uncommon
to find villosities covered with the most beautifully marked
cylindrical epithelium, springing from the ordinary mucous
membrane, just where the superficial corpuscles happen to be
somewhat flattened in their normal state.

The use to which the part is put has also an important influ-
ence in governing the shape and other attributes of the corpus-
cles. Where they are exposed to the drying action of the air,
to harsh usage, and continued friction, as upon the hands and

EPITHELIUM. 57

feet, toey become flattened, dry, and horny ; in the interior of
the Cydy, on the other hand, where such conditions do not
exisf^they are succulent and pliable.

Ordinary flattened or squamous epithelium. — This is best
obtained by scraping the back of one' s tongue with a blunt
instrument. The scrapings should then be mounted in equal
parts of the common salt solution (i per cent.) and glycerine.
The epithelial bodies may in this way be readily studied. They
are separate or grouped together in collections of two or more.
In diameter they vary between -ffa-Q and -^ inch. The sur-
faces are all bevelled, and at the same time are uneven or
ridged ; consequently they overlap one another to a certain
degree, and the inequalities of one corpuscle fit into those of
another. The most superficial epithelium is the thinnest, and,
conversely, the deepest is apt to be the most nearly spheroidal.

Intermixed in the mucus will be seen the so-called mucous
or salivary corpuscles. They are not very numerous, but are de-
tected by the "molecular" or Brownian movement of their in-
terior. In size they closely resemble the white corpuscles of the
blood, but, as a rule, exhibit no amoeboid motion ; the white glob-
ules, on the other hand, rarely have any Brownian movement.

The surfaces of the epithelia are often so covered with bac-
teria that they are only recognized with some difficulty. These
little bodies are wonderfully uniform in size, and are disposed
in the most regular manner. .Looking straight down upon
them they appear to be minute spheres with a diameter aver-
aging between yyfonr and TTfonr inch- Closer inspection and
examination of the corpuscles at their free edges shows that
the bacteria are in reality rod-shaped, and that they adhere to
the corpuscles by their extremities, standing in such cases
vertical to the surface. A high power, such as the immersion
^, develops this point quite clearly.

Incidentally the mucin of the mucus may be seen to advan-
tage in the scrapings of the mouth or tongue. To a drop or two
add another drop of commercial alcohol and a drop of the or-
dinary hsematoxylin solution. The alcohol will coagulate the
mucin, which then takes the form of filaments and branching
networks ; the logwood will make them distinctly visible.

Epithelium from the skin may be studied in one of two
methods. Take a fresh specimen from the palmar surface of
the hand or plantar of the foot, freeze it in a section cutter,

58 MANUAL OF HISTOLOGY.

take off a thin slice with a knife, immerse for a few seconds in
a dilute solution of acetic acid (i per cent.), and then mq[nt in
glycerine and water ; or a similar portion of the skin nnfy be
steeped in a weak, sherry-colored, watery solution of the bichro-
mate of potassium (gr. ij.— iij.— f. | j.) for several days and then
hardened in alcohol, first of 80 per cent, then of 90 per cent.,
finally of 95 per cent, strength ; this latter process taking several
days, and ending when the specimen is thoroughly hard. Sec-
tions may then be made in the usual way. By the use of acetic
acid the nuclei will readily be seen in the lower strata of the epi-
dermis, while the outermost layers have none, or, at least, none
that can be demonstrated by the usual histological methods.

Three different strata can now be recognized : 1, the stra-
tum corneum, or corneous layer, in which the corpuscles are
flattened, and appear to have no nuclei ; 2, the rete mucosum,
or malpighian layer, immediately underlying the former, and
composed of cuboidal elements, armed with spines or prickles,
as they are often called ; lastly, 3, there is the pigmented layer,
which overlies the papillae. The bodies of the latter corpuscles
are infiltrated with particles of inelanine, which is the cause of
the dark color in the skin of the negro and swarthy races.

Maceration of the epidermis in liquor potassae is an excellent
method for exhibiting the individual elements ; after a few min-
utes they will swell up and detach themselves from one another.

It was thought, until quite recently, that these prickle cells interdigitate
with one another, but Banvier has claimed that they are continuous with those
of adjacent corpuscles (see chapter on the Skin). This point is difficult to set-
tle, as it requires a special method and lenses of high power. Kanvier injected
a one-fourth per cent, solution of osmic acid into the lower layers of the epider-
mis, using a hypodermic syringe, and driving the fluid right and left.

There is a form of flattened and pigmented epithelium that
may be seen by examining the external surface of the choroid,
the ciliary processes, and the posterior surface of the iris. In
the choroid these bodies look like a mosaic of polyhedral cells.
Such specimens may be permanently preserved by simply dry-
ing them, and then mounting in dammar or Canada balsam.

Ciliated epithelium. — The movement of living cilia is readily
seen. All that is necessary is to take the common frog (Rana
temporaria), draw out his tongue, and then observing the teat-
like projections at the posterior part, snip one off.

EPITHELIUM. 59

This little piece is then to be mounted in a one-fourth per
cent, salt solution, or serum, and examined. Along the free
edge of the mucous membrane the cilia will be seen engaged in
active vibratile motion. The appearance presented by a broad
expanse of moving cilia has been aptly described as resembling
a field of grain which is being swept by the wind, though the
motion is often much more rapid than this comparison would
imply. It will be seen that various substances, such as blood
globules, are propelled in a definite direction. When the frog's
mouth is open, all solid particles that are lodged upon the
mucous membrane are carried quietly but inevitably toward
the gullet, and down toward the stomach. The power of the
ciliary movement may be estimated, in a measure, by placing
some light but adhering body upon the anterior portion of the
roof of the mouth, and then inverting the animal. The sub-
stance immediately begins to ascend against gravity, and soon
is wedged in the gullet. The same force, though acting in an
opposite direction, expels mucus, pus, and indeed all solid
matters, from the cavities of the human lungs ; it also propels
the ova through the Fallopian tubes into the uterus. In ex-
cessive catarrh from mucous membranes the epithelial bodies
may themselves be expelled, so that they are not infrequently
found with their cilia attached, as in the nasal discharges. After
death cilia are hard to recognize ; they contract down to little
knobs on the surface of the cells, and can only be demonstrated
when the eye looks directly down upon them. Osmic acid is
useful to preserve them in their natural condition. Take a fresh
specimen and immerse it for twenty-four hours in a one-fourth
percent, osmic acid solution, arid for another twenty -four hours
in dilute alcohol ; then tease and mount in glycerine and water.
It will be observed that each cilium is a slim, straight rod, which
is apparently structureless ; they rest upon a band, which, with
a high power, may be seen to have vertical striations.

Effect of reagents.— By making use of the moist chamber
(Fig. 19, p. 42), and placing a drop of chloroform in the cor-
ner of the cell, it will be seen that the action of the cilia rap-
idly stops, while, if the chloroform be removed, it will again
resume its activity.

If carbonic acid gas is admitted, the action of the cilia will
at first be accelerated, but subsequently retarded, and eventu-
ally stopped (Kuehne).

60 MANUAL OF HISTOLOGY.

After shutting off the carbonic acid gas and admitting oxy-
gen, the action will again commence. When the ordinary
motion has ceased, the gradual application of heat will cause
it to return ; but if the temperature be raised continuously, a
point will soon be reached where the excessive heat will cause
the motion again to stop.

Columnar or cylindrical epithelium. — This is the epithe-
lium par excellence of the digestive tract, clothing the mucous
membrane from the cardiac orifice of the stomach to the anus.
It is also found at the orifices of the ducts of the large excretory
glands, such as the liver and pancreas, in the milk-passages of
the nipple, and in some parts of the generative system. These
cells are tall and narrow, standing vertical to the surface of the
mucous membrane. Sometimes they are broadest at their free
extremity, at other times about the middle, so that when viewed
from above they appear to be separated from one another. The
nuclei are rounded, and are either placed about the middle of
the cell or near the attached border. They admit of consider-
able variation, however, as to size and shape, some of those in
immediate contact being broad at one extremity, and some
broad at the others ; the free edge also may be uneven.

Scrape the surface of a frog's tongue or a rabbit's intestine
after washing ; the cells will be seen to advantage. Place
some of the scrapings in a drop of glycerine and water to
which another drop of dilute acetic aeid (i per cent.) has been
added, and mount. In this way the nuclei will be brought
clearly into view. The cells closely resemble in their shape
the columnar variety, except that they have no cilia. Among
them will almost always be found chalice or goblet cells. They
lie among the columnar corpuscles, and are usually shorter,
but broader, expanding in the centre, and terminating at their
attached extremities in a single or double process. The sur-
face is cupped. They contain one or more nuclei ; whether
they are a distinctive cell or not is as yet uncertain. Some
suppose them to be the ordinary columnar cell undergoing
mucoid degeneration ; others that they are not epithelial at
all. Frey regards them as artificial productions.1

1 The most rational explanation is that furnished by F. E. Schultze. The intra-
fibrillar substance U, according to this observer, converted into hygroscopic mucin,
which swells up. This constitutes a change in the cell which, from being columnar,
becomes goblet-shaped. The wall finally ruptures, and the mucin is poured out.

EPITHELIUM. 61

Other varieties of epithelium will be taken up in connection
with the different organs. As already stated, many transi-
tional varieties occur, even in direct association with the typi-
cal forms we have described. *

Structure of epithelial corpuscles. — According to the views
of Heitzmann, Klein, and others, the substance of the cor-
puscle is pervaded by a network, the minute fibres of which
may be seen under a lens of high power. The nucleus or cen-
tral body is also similarly provided. Within the meshes of
this network there is a hyaline substance, the abundance or
paucity of which determines the size of the meshes.

The "granules,1' which have often been described, are, ac-
cording to this view, the nodal points of the mesh work. It
is also stated that the epithelial cells sometimes have a fine
limiting membrane (Klein) ; but even in such instances it is
merely a condensation of the outer part of the corpuscle.
Within the nucleus there are also, according to the same ob-
servers, fibres, within the meshes of which are not infrequently
real granules (nucleoli). The epithelial corpuscles are at-
tached together, either by an interlacement of their processes,
as in the liver, or by a peculiar cement substance, as in pave-
ment epithelium, or by a continuity of their processes, as in the
rete mucosum.

Recent histological studies have narrowed the field formerly
occupied by the epithelial bodies, and, in accordance with
these views, the flattened corpuscles which cover serous mem-
branes, such as the pleura and peritoneum, will be arranged
under the connective-tissue series, rather than under the epi-
thelial. The reasons for this change will be given in a subse-
quent chapter.

BIBLIOGRAPHY.

SCHULTZE, M. Die Stachel- trad Riffzellen. Virchow's Arch., Vol. XXX., 1864,

p. 260.

SCHULTZE, P. B. Epithel. u. Drusenzellen. Arch. f. mikrosk. Anat. 1867.
RANVIER. Traite technique d'histologie. Paris, 1875.
DELAPIELD. Studies in Pathological Anat. New York, 1878 et aeq.
KI.EIN and E. NOBLE SMITH. Atlas of Histology. 1879-80.
HEITZMANN. New York Medical Record. July 31, 1880, p. 133.
FREY. The Microscope and Microscopical Technology. New York, 1880.

CHAPTER V.

THE CONNECTIVE SUBSTANCE GROUP.

MUCOUS OR GELATINOUS TISSUE ; ADENOID TISSUE ; NEUROG-
LIA ; FAT TISSUE ; FIBROUS TISSUE PROPER ; CORNEAL TIS-
SUE ; INTERMUSCULAR TISSUE ; TENDON TISSUE ; ELASTIC
TISSUE.

THE term connective substance was first proposed by Reich-
ert in 1845, and is now applied to a class of animal tissues whose
offices are very important in the economy. Prominent among
them is bone, which forms the solid framework of the body,
gives it strength, and supplies points of attachment for muscles
and tendons ; another group comprises the ligaments, which
assist in holding the bony parts, and also some organs, in their
proper relations ; others again, of a more delicate nature, fur-
nish support or protection for epithelial bodies, Wood -vessels,
and nerves. Just at the present time the histology of connec-
tive substances- has an important bearing on many points that
relate to inflammation, degeneration, and the development of
certain new growths, and it is therefore desirable to have a clear
conception of them. This object is best effected by studying
each variety separately, not only in its normal condition, but
under the changes it exhibits when acted on by the factors that
are concerned in the processes of disease.

It is a property of these substances that they supplant one
another at different times or under peculiar circumstances. As
an example, the hyaline cartilage of young life may change
into true bone in old age, while, on the other hand, there is
always a tendency for fully formed tissue, if inflamed, to re-
vert toward the embryonic type.

The connective substances may be subdivided as follows :
1, mucojis or gelatinous tissue ; 2, adenoid tissue ; 3, neurog-

THE CONNECTIVE SUBSTANCE GROUP.

63

lia ; 4, fat tissue ; 5, fibrous tissue proper ; 6, corneal tissue ;
7, iniejmuscular tissue ; 8, tendon tissue ; 9, elastic tissue ;
10, bone ; 11, cartilage ; 12, enamel ; and 13, dentine. The
word connective tissue\v&s first proposed by Johannes Mueller,
and is" sometimes used as synonymous with connective sub-
stance, but erroneously. The former is merely a variety of the
latter, and is usually intended to indicate one or other of the
flexible connective substances that form the interstitial material
of the body, and in that sense we shall use it for convenience
sake, but without implying any special histological character.

In precise histological descriptions it is always best to use
the special name of the variety intended, such as mucous tis-
sue, adenoid tissue, and the like, where the structure happens
to be known.

It is also well to state here that the term "cellular" tissue,
found in many of our anatomies, is apt to mislead the student.
The word "cellular" has no reference to cells, i.e., corpuscles,
but to the large cavities or spaces that exist in all loose connec-

Fio 23. — Gelatinous or mucous tissue. Human umbilical cord.

tive tissues, of which the subcutaneous is an example. These
spaces are easily seen by the naked eye, when inflated with air.

Mucous or gelatinous tis site.— This is the most simple
form that is met with. It is seen to great advantage in the
embryonic umbilical cord, which also contains several other
varieties of connective tissue.

The following method has been found best suited to demon-
strate it. Take a small piece of cord at about the third month
and immerse it a few weeks in Mueller's fluid ; make a thin sec-
tion through the very soft gelatinous part, then soak it a few
minutes in distilled water, to which subsequently a few drops

64

MANUAL OF HISTOLOGY.

of acetic acid are to be added so that the solution shall not con-
tain more than 1 per cent, of acid, and then mount in glyce-
rine. It will' then be seen that the softest portion contains
numbers of irregularly-shaped, thin plates, some provided with
an oval, flattened nucleus, others having none that are appa-
r.-nt (Fig. 23). Some of these flattened bodies anastomose by
these processes with those of other plates, others are quite free.
The substance lying between the cells, the intercellular sub-
stance, is quite homogeneous, or slightly granular, in the softest
portions, and has at first no defined fibrillation. In the neigh-
borhood of the former tissue, lines of fibrillation occur, while at
the same time these flattened bodies become smaller, although
they are still flattened (Fig. 24, 5). Mucous or gelatinous tissue,

Fro. 24.— Connective tissue In an advancing stage of development. Prom the umbilical cord.

as it is seen in the umbilical cord of an embryo, is properly an
embryonic or developmental form of connective tissue which is
never found in normal adult life. All the phases of develop-
ment may here be seen, from the most primitive, comprised in
Wharton's jelly, to the firm, fibrous fascicles that encircle the
vessels.

Properly speaking, the true mucous tissue is, as its name
implies, a viscid material, and, indeed, is much like half-set
glue, in which the corpuscles are scattered with little or even
no cohesion.

^ The intercellular substance differs from albumen in not con-
taining sulphur ; from chondrin and gelatin, in not being pre-
cipitated by boiling, tannin, or the bichloride of mercury.

THE CONNECTIVE SUBSTANCE GIIOUP. 65

At an early stage there are no marks of fibrillations in the
intercellular substance, but later fibrils are seen in the vicinity
of the corpuscles, and are some of the early signs that organi-
zation of the tissue is commencing.

The corpuscles at the same time become smaller, and about
the central body or nucleus we see a delicate expansion (Fig.
24 a), which is the envelope of the connective -tissue corpuscle—
a film of great tenuity. Klein believes that in these corpuscles
there are two portions, a granular or firmer part continuous
with the processes, and a delicate expansion that is hardly
visible. It is certain that the connective-tissue corpuscle is
frequently in connection with one or more of its fellows by a
mutual anastomosis of processes. The fibrillation appears to
be at first limited to certain areas about the cellular elements,
so that the long, flattened and pointed lamellae of fibrous tis-
sues on which the corpuscles are attached look like large cor-
puscles with correspondingly large nuclei. Using a camel' s-
hair brush and pencilling off the specimen under examination,
after soaking in a 10 per cent, watery solution of common salt,
the apparent nuclei with their delicate envelopes are partially
(Fig. 24 b) or wholly removed. We then see small strips of
more or less fibrillated tissue, having no central body that can
be recognized, even with the use of strong staining solutions.
These and similar observations tend to establish a conviction
that the fibrillated portion arises from the soft, gelatinous ma-
terial by a process of .fibrillation inaugurated by the presence
and under the formative action of the connective-tissue cor-
puscle. It is not impossible that the fibrin of the blood, which,
though fluid in the blood-current, is often known to be de-
posited in delicate filaments, may contribute largely, if not
wholly, to the formation of the fibrillae. As the tissue becomes
firmer, the little plates with their anastomosing branches form
a loose network which separates the fibrils into distinctive
bundles or fascicles, and encircles them more or less completely.

There is another view which is offered as an explanation of
the process by which connective tissue becomes organized. It
is this. The change is derived wholly from the corpuscles.
Some of them split up into fibrils, constituting the fibrous
part of the tissue ; the others remain, and are developed into
connective-tissue corpuscles. This view has the support of
excellent histologists.

5

f,6 MANUAL OF HISTOLOGY.

The white corpuscles of the blood are pre-eminently suited
for building tissue. When blood is organized, which occurs
not infrequently, the white corpuscles at once assume an im-
portant role, while the red are soon melted down into a homo-
geneous mass, that is usually absorbed. This change is ob-
served under various pathological conditions.

Fibrous tissue.— This substance, which is also known as
fibril] ated connective tissue, is the fully developed material
that has just been described. It occurs either in parallel

Fio. 25.— Reticular form of connective tissue. From the human umbilical cord.

bundles or fascicles, in interlacing lamellae, or as a fenestrated
material containing larger or smaller openings. A special va-
riety, the reticular, is seen to great advantage in the umbilical
cord of an infant at birth (Fig. 25).

If a cut be carried through the spongy portions of the cord,
it will be seen that the tissue is composed of bright, shining,
branching bundles, d, superimposed upon which are a num-
ber of oval, flattened plates, a, at intervals ; about them is

THE CONNECTIVE SUBSTANCE GROUP. 67

a delicate envelope, 5, which appears to be highly elastic, so
that it will stretch or relax, according as the networks are
compressed or dilated. By teasing with needles or immersion
for a few days in a 10 per cent, watery solution of common
salt, these corpuscles can often be separated from the bundles,
and then they will be seen to form a connected system. When
entirely isolated from one another, they often appear spindle-
shaped. That this is not their character may be shown by
passing a current of fluid through the specimen — a method
already described under the name of irrigation. It is accom-
plished in this way : having affixed small strips of filter-paper
to the edges of the cover on either side, and moistened one side
with fluid, the excess will be absorbed by the other slip, caus-
ing a current by which the corpuscles may be made to roll
over. We then learn that they are disks of an irregularly
flattened form, having longer or shorter processes (c, c, Fig.
25) — variations in form which seem to depend, in a great
measure, upon the tension to which they are exposed, and the
position they occupy in the tissue. This explanation will
serve to show why all measurements of such corpuscles are
merely approximative, and have but little value.

They are shrunken by immersion in alcohol, swollen by the
imbibition of water, are drawn out into long, flattened spindles
when the tissue is put on the stretch, or become rounded, per-
haps nearly spherical, during relaxation. They may assume
almost any form as the result of pressure.

The nucleus may be regarded as more of an exception to
this rule ; at any rate it seems that in fresh specimens, when
the substance has been swollen by immersion in water, it is
always oval and flattened.

The bundles upon which these bodies lie are somewhat
cylindrical in form, branched, and composed of separate fila-
ments, that can be separated by Mueller's fluid, or a 10 per
cent, waterj'' solution of common salt.

Two other forms of corpuscles may also be noticed : (1) the
kind observed by Waldeyer, and called plasma cells, and
thought by him to be corpuscles peculiarly prone to take up
fat to make fat tissue, bodies four or five times the size of
a lymphoid corpuscle, and rounded in form, containing a cen-
tral body ; and (2) the ordinary lymphoid corpuscles, seen at
times in all tissues.

08

MAXUAL OF HISTOLOGY.

The form of fibrous tissue that occurs in parallel lamellae is
well .shown in the mesentery of the frog, and in serous mem
branes generally. No great difficulty will be met with in pre-
paring this tissue, for it is only necessary to remove it from the
frog in the fresh state, acidulate it in a weak (1 per cent.)
watery solution of acetic acid, and mount it in glycerine.

It will be seen that these so-called spindle-cells are really
flattened plates, when viewed flat-wise, and generally irregu-
larly quadrilateral, though the form varies somewhat in each
instance.

It is not improbable that some which appear spindle-shaped,
and lie in the interfascicular spaces, have a double office, one
of which is to guard the nutrition of the tissue, and the other
to form a partial lining of a lymphatic channel. The researches

Fio. 26. — Connective tissue in the mesentery of the frog.

of Klein tend to establish this double relation, for they show
that these corpuscles lie in the walls of the lymphatic radicles,
which are themselves in direct communication with the perito-
neal cavity by breaks in the endothelial connective-tissue cor-
puscle coating and in actual apposition with the endothelial
elements of the serous membranes.

During the last few years there has been a tendency to regard the serous
membranes, especially such as have large openings and slight reticula, as
having no connective-tissue corpuscles, other than the endothelial, which form

THE CONNECTIVE SUBSTANCE GROUP. C9

a covering over them. In the larger trabecles, however, there are connec-
tive-tissue corpuscles, in addition to those just mentioned ; they are well
seen in profile, interposed between the bundles (Fig. 26).

Adenoid tissue (Fig. 27). — Adenoid tissue is the name given
to the delicate substance that forms the framework of the lym
phatic glands. It consists of fibres in networks which form an

FIG. 27.— Adenoid tisane from a human lymphatic glnnd.

intricate texture, that is filled with the rounded bodies com-
monly known as lymphoid cells. It is exceedingly difficult to
analyze these tissues, because it is not easy to demonstrate any-
thing that conveys to the eye our idea of a cell, i. e., excepting,
of course, the lymphoid corpuscle. The best mode of proced-
ure is the following : Take a lymphatic gland — such as the in-
guinal in the early stage of inflammation : harden at first, in
Mueller's fluid, and then in alcohol, and make sections through
it.

On viewing such a specimen under the microscope it will
exhibit a delicate meshwork, packed with lymphoid corpuscles
(Fig. 27, a). Now, if we take such a section and agitate it in a
test-tube with water for a considerable length of time, and then
place it upon a glass slide, pencilling it with a camel's-hair

70 MANUAL OF HISTOLOGY.

brush, most of the lymphoid cells will be removed, and the
delicate network, c, will be very thoroughly exposed.

It will be seen that, at certain parts of this meshwork, there
are flattened bodies, b, of small size, lying upon the larger
cords of the meshes. It has been held by Klein and other his-
tologists that the reticulum is made of branching corpuscles ;
but this statement must be modified. In some instances the
appearance of netted corpuscles is well seen in those portions
of the glands that are regarded as the lymph passages, where
the adenoid tissue forms the framework of the part. The net-
work seems to be comprised of delicate, silk-like cords, enclos-
ing vast numbers of lymphoid corpuscles, and exhibiting, at
the nodal points of the meshes, flattened corpuscles. These
delicate fibres, however, are often replaced by heavy trabecles,
c, such as are seen in the figure, and after continual inflamma-
tions the diameter of these latter may be found greater than
that of the spaces.

In these latter instances it is often difficult to find any cor-
puscular elements that may not be separated from the fibres ;
and, indeed, large areas of these fibrous networks may, by dil-
igent pencilling with a camel' s-hair brush, be swept clean of
corpuscles. But neither this rough method, nor agitation in a
test-tube, will always succeed in separating all the corpuscles
from the fibres, even after an immersion in common salt solu-
tion for many weeks. The sum of the whole matter is, that
adenoid tissue does not generally consist of a network of
branching corpuscles, as has been claimed, but rather of a net-
work of fibrous cords, on which the corpuscles are superim-
posed ; they may anastomose, but this point seems difficult to
demonstrate in most cases.

Possibly higher powers than those now in use. or some new
method may solve the question. Where the fibrous networks
have attained some thickness, there is no doubt that we find
the ordinary flattened connective-tissue plates lying on the
bundles and surrounded by a delicate envelope.

Neuroglia (Fig. 28).— But a short time since it was not
known positively whether the delicate, supporting substance of
the nervous system, especially of the brain, was granular or
fibrous. Even after Virchow insisted that this substance was
like the other tissues, known as connective, doubt was thrown
upon the matter, for the defining power of most objectives then

THE CONNECTIVE SUBSTANCE GEOUP.

71

used was insufficient to make out such delicate objects. At
the present time the actual existence of a network is hardly
called in question, for it may be demonstrated with really good
glasses, such as some of the immersion lenses (No. 10) of Hart-
nack's system, and, indeed, by other lenses made both at home
and abroad. As to the question of the corpuscular elements
there is more doubt, and it can hardly be said that their exact
form and shape have been definitely agreed upon by histolo-
gists. We find, it is true, that where there is a considerable
deposit of connective mate-
rial along the central canal of
the spinal cord, we have the
ordinary fibres and corpuscles
already described, and so, too,
near the surface of the con-
volutions. When, however,
we examine the supporting
substances of the white and
gray masses there is less cer-
tainty. The actual condition
may be tolerably well seen
by adopting the following
plan. Place any portion of
the brain or cord a few days
in a weak solution of bichro-
mate of potash (5 per cent.)
or Mueller's fluid, then immerse it in alcohol until hard ; make
thin sections and stain for twenty-four hours with the follow-
ing solution of hsematoxylin : hsematoxylini, gr. lij. ; aluminis,
1 j. ; aquae, 1 viij. ; mix arid strain.

Wash in distilled water and mount in glycerine, tease with
needles and examine with a high power ; there will then be
little difficulty in seeing that the delicate supporting substance
of both gray and white matter consists of fibres. They may
even be distinctly isolated, for the coloring matter darkens them
somewhat and they become hardened at the same time so as to
be somewhat stiff and unyielding. It will be seen that many
fibrils are disposed in parallel rows which perhaps can hardly
be called bundles, but rather thin laminae ; other similar fibrils
cross them at various angles, giving to the whole, with a
moderately high power, the appearance of a very delicato

FIG. 28. — Human brain showing neuroglia.

72

MANUAL OF HISTOLOGY.

UK '>h work, a. It does not appear as if the fibrilhe anastomose
with one another, though this point cannot now be definitely
settled. It must be stated that some of these fibrils are possi-
bly nerve-elements, and yet this is doubtful, because they do
not even seem to be connected with the nerve-fibres ' that are
distinctly shown by this method of preparation.

Granular appearances are always noted in the brain, which
is to be expected when cross-sections are made of the delicate
fibrillfe. Three kinds of corpuscles are met with in the brain
and medulla. The first are the variously shaped ganglionic
corpuscles or cells, Fig. 28, 5, b, b ; secondly, the ordinary
lymphoid cells, c, c, which are generally seen to have a pale
envelope about them ; lastly, smaller corpuscles, d. d, of irre-
gular shapes, and many of them undoubtedly flattened and
appearing to have branching processes. They may be found
in considerable numbers, and can be isolated so that there is no
doubt that they exist.

The fibrillje of the neuroglia do not differ substantially in
size from the fibrillje of fibrous tissues elsewhere.

Tendon-tissue (Fig. 29).— Tendon-tissue may be well studied

in the gastrocnemius of the
frog. It is prepared like
the preceding. If, how-
ever, it is desirable to show
the nuclei in adult tissue,
it is well to use nitrate of
silver. Cut a thin section
of a fresh tendon and ex-
pose it for a few minutes
in a \ per cent, solution
of nitrate of silver, until
the section is turbid or
milky, then place in the
sunlight, and in a few min-

Fio. 29.-Tend<m-tis8ue from the frog. .... .

utes the turbid color will

give place to dark brown or black, owing to the deposit of
silver, and the tissue may then be mounted in glycerine and
examined.

This method will show the corpuscular bodies to advantage.

1 To avoid confusion they are not represented in the drawing.

THE CONNECTIVE SUBSTANCE GROUP. 73

In some cases better results are obtained by the use of chloride
of gold. The method is as follows : Freeze a small portion of
a tendon, then make the thinnest possible section, acidulate it
slightly and immerse in a £ per cent, solution of chloride of
gold until a strong.yellow color has been obtained, then soak in
a i per cent, solution of dilute acetic acid and expose to the
sunlight until a purple or reddish color has been obtained.
This will take a variable time, and is not always successful, for
reasons which are not easy to understand.

At considerable distances from one another there will be
seen small dark bodies, which are the corpuscles already de-
scribed. It is difficult to determine whether or not these cor-
puscles are connected together. To isolate them, take a small
piece of young tendon- tissue, immerse three or four days in a
10 per cent, solution of common salt, and then tease. In this
way the cells may be liberated, and they will prove to be irre-
gularly flattened plates.

Sometimes they lie at the intersection of several bundles
and then have separate expansions for each bundle ; the plates
then lie at various angles with one another, and if one be seen
edgewise it looks as if the corpuscle proper were traversed by
a line.

Silver or gold, the latter especially, is generally necessary
to show the corpuscles in old tendons. The same method
shows the fibrillated tissue to advantage. The large tendon
bundles are often covered with endothelium (connective-tissue
corpuscles), which are continuous and form a complete invest-
ment.

For the smaller bundles the tendon- corpuscles do not by
any means form a connected sheath. In very young tendons
they are quite near to one another, though even at this time
they only form a partial investment for the bundles ; but as
the tendon grows older the corpuscles become smaller, with-
draw from one another, and sometimes almost disappear.

Tendon bundles, like other forms of connective tissue, are
often encased in a transparent, delicate membrane, not unlike
the sarcolemma of striped muscular tissue. It is well shown
by immersing the tendon in a dilute solution of acetic acid.

Fat tissue.— The ordinary fibrillated connective tissue often
becomes the deposit for oil, which fills the corpuscles, making
them swell out enormously. This is fat tissue. An excellent

74 MANUAL OF HISTOLOGY.

way of showing it consists in making a section through fat tis-
sue that has been hardened in alcohol or Mueller's fluid, or both.
The phenomena will, in this, way, be well shown. After im-
mersion in an acid solution, it will be seen that the fatty acids
crystallize in the centre of the sac.

The nature of the evidence that fat corpuscles are really the
altered corpuscles of the fibrous tissues is as follows: They
occupy the same position, being in rows, between the bundles,
just as the other corpuscles that we have mentioned ; a few oil
drops at first appear, then others, until finally they coalesce
into a single large drop, which fills the corpuscle ; if fat tissue
be pressed, and the oil escapes, the walls of the fat-corpuscles
collapse, and then the flattened nuclei may be observed on the
side of the cell-body.

Waldeyer believes that there is a peculiar corpuscle, three
to five times the size of the lymphoid, and roundish, which is
especially prone to take up fat, and be converted into a fat-
corpuscle.

This body, known as the plasma cell, is the second element
that forms the fat-cell. The change is said to occur only occa-
sionally, and under favorable conditions of alimentation
(Klein).

The same author states that there is also a third way in
which fat is formed : In many parts of serous membranes, espe-
cially in connection with the large vessels, there appear "no-
dules or cords, which are made up of multiplying connective-
tissue cells." The cells increase, the matrix is converted into a
network, lymph-corpuscles appear, the tissue is supplied with
arteries, veins, and capillaries, and resembles lymphatic tissue.
Sometimes these structures persist as they are ; in other cases
they are converted into fat -tissue.

Ranvier recommends the following plan of demonstrating
fat- tissue : He injects beneath the skin a weak solution of os-
mic acid (1-1000). The connective-tissue corpuscles may be
seen to be more or less filled with oil-globules.

The property of taking up oil is not peculiar to these cor-
puscles already described, but belongs, physiologically, to the
liver, to adult cartilage, the glandular elements of the female
breast during lactation, and the glandular epithelium of the
sebaceous glands.

Intermuscular tissue. — It has been claimed by some that

THE CONNECTIVE SUBSTANCE GROUP. 75

there is a form of spindle-cell in the intermuscular tissue of the
frog's thigh. This, however, is apparent rather than real. We
find broad plates, in which are oval, flattened bodies, placed at
certain distances apart (Fig. 31). These, seen in profile, appear
spindle-shaped. There is something peculiar about such
bodies, for they seem to bear a close relationship to the elastic
networks, «, so that, in some cases, it appears as if the flat-
tened central bodies were directly connected with the elastic
fibres, as stated by Boll.

In many instances these elastic fibres lie upon the plates, 6,
which themselves rest in a homogeneous, intermediate, and
apparently structureless substance.

This tissue is therefore similar, in some respects, to mucous
tissue.

Corneal tissue. — The cornea consists of thin, fibrous bands,
each one partly anastomosing with its adjacent neighbor.
Between them are well-marked corpuscles lying in clefts — the
corneal spaces.

The term corneal corpuscles, however, is even now applied
to the spaces by some of the best-known writers, and it seems
evident that there is doubt as to whether real corpuscles exist
or not. Recently the subject has been restudied by Waldeyer,
and the author has been able to verify his conclusions in a
great measure, both as to the character of the corpuscles and
the spaces in which they lie.

In general, these bodies appear, as stated by Waldeyer, to
be flat, having a considerable amount of protoplasmic material
about their nuclei (Fig. 30), though in the direction of the per-
iphery they gradually taper off into thin expansions, which are
nearly homogeneous, and extending from them are distinct
processes which in part unite with those of other corpuscles,
not materially differing in this respect from tendon-tissue and
the other varieties. In them is the same flattened, oval body,
which, when seen on the side, is rod-shaped, b, and is sur-
rounded by an irregular envelope that assumes almost any
shape. Thus the corpuscles are not always flat, though they
are usually so. Their shape depends upon many different
causes, such as the method of preparing the tissue, the amount
of laceration to which it is subjected, etc. The best method of
examining the cornea consists in preparing it by the gold me-
thod, already described.

MANUAL OF HISTOLOGY.

After the tissue has been properly stained, which is known
it has taken a mauve or violet tint, as already stated, the
specimen should be allowed to stand in the sun. Thin lamel-
la are then torn off with the forceps and mounted in dammar
varnish or Canada balsam.

After the specimen has been made thoroughly transparent
by soaking in oil of cloves, it will then be seen that there are
bodies within certain well-defined areas— the corneal spaces,

FIG. 80.— Corneal tissue. Prom the rabbit.

as they have been called by Recklinghausen and others. These
bodies are disposed at quite regular intervals throughout the
cornea, and are generally flat with rounded contours, though
often they have processes extending from them in various direc-
tions. In the accompanying drawing the spaces may be dis-
tinctly seen, as well as the variously shaped corneal corpuscles.
One, c, is crowded into the prolongation of a corneal space,
while another, 6, is connected by its processes with a neighbor-
ing corpuscle. One corneal space, a, is entirely empty. These
differing conditions are in a measure due, probably, to the

THE CONNECTIVE SUBSTANCE GROUP. 77

laceration of the tissue in preparing it, some of the bodies
having been torn out and others forced to the side of the cor-
neal space. There seems to be a very general agreement that
the intercellular substance may be separated into indepen-
dent fibrils ; but I have seen no decisive proof bearing on this
point.

Elastic tissue. — This differs from the other forms micro-
scopically and chemically, though it is often combined with
them in the body. It is also convenient to class it by itself
for other reasons, chief of which are, that its corpuscular ele-
ments have not yet been definitely shown in adult tissue.
Yirchow, some years ago, stated that this tissue, as well as
other connective substances, was composed of networks, the
substance of the fibres containing certain markings, and he in-
ferred that these latter might be the corpuscles of the tissue.
Elastic fibres were, however, according to him and others, noth-
ing but the ordinary fibrous tissue condensed. Each fibre was
hollow and capable of conveying the nutritive juices.

Henle, in his earlier writings, regarded the elastic fibres as
emanating from the nuclei, of which, in fact, he stated they
were prolongations. Subsequently, he seems to have believed
that the fibres originated in the basis substance.

Reichert could not trace the connection between the nuclei
and the elastic fibres, and, when the latter had formed, the
former had disappeared.

Boll, however, distinctly stated that the elastic fibres, each
one constituting an "elastic cord," arise from the plate-like
cells.

Ranvier examined tendon- tissue, as mentioned before, but
he was only able to find the elastic fibres after boiling the tis-
sue from eight to ten hours. It is proper, however, to add
here, that elastic fibres are very uncommon in tendon-tissue,
at least they have not often been observed.

The fibres of the elastic substance are pretty readily re-
cognized by the fact that they are not colored by carmine or
hsematoxylin, and do not swell with acetic acid ; they branch
dichotomously, these branches forming, with similar branches
of other elastic fibres, networks.

Elastic tissue prevails in the ligamentum nuchae of the ox,
in the serous membranes generally, and in the subcutaneous
connective tissue of the skin, as well as in the delicate inter-

78

MANUAL OF HISTOLOGY.

muscular substance already described. It will generally be
found that where this material occurs in bundles it is not be-
cause there are no meshes, but rather because they are com-
pressed latemlly, so as not to be apparent unless most carefully
teased apart. When such fibres are broken off, their extremi-
ties curl up ; further, the fibres are unaffected by being boiled
in solutions of strong acids and alkalies, such as 35 per cent.

' ^*-— ' ' ~~~

Pio. 31.— Elastic tissue networks. Prom the frog.

solutions of caustic potash, or nitric acid (standard prepara-
tions commonly used in laboratories), unless the action is pro-
longed for a considerable time. These networks are beautifully
shown by taking the mesentery of the frog when slightly con-
tracted after immersion in acetic acid. The fibrillated connec-
tive tissue will then swell up and become invisible, while the
elastic fibres are unaffected.

The ligamentum nuchae also affords an excellent oppor-
tunity for studying this tissue by itself. To render the work
more easy, the specimen may be allowed to soak a few days in
a 10 per cent, watery solution of common salt, so that it may
be the more easily teased. In the subcutaneous connective
tissue of the skin the elastic fibres are well shown by haerna-
toxylin preparations. Being unaffected by this staining solu-
tion they appear as bright, silk-like cords, which lie in close
apposition with the wavy bundles, and the branches arch over
the bundles, to anastomose with corresponding branches of
other bundles, so that in this way meshes are formed. Some
writers have spoken of little knobs at the nodal points of the
meshes, but these appearances have been illusory.

Recklinghausen seems to have believed with Virchow, that
the elastic fibres contain peculiar nuclei of their own, which in

THE CONNECTIVE SUBSTANCE GROUP. 79

adult tissue become extremely small, and are represented by
the dark markings seen in them. Thin, of London, has claimed
that they originate in branching corpuscles, which by their
coalescence form the network, and the remains of the nucleus
may be shown by hsematoxylin. These markings may, it is
true, be seen in the ligamentum nuchse of. the ox, but it is
doubtful whether they are nuclei or mere clefts in the tissue.
Examination by the author, with such high powers as Gund-
lach's No. 15 immersion, and Wale's ^u, have failed to clear
up the matter.

Good examples of human elastic tissue are found in the
sloughs of ulcers and in the sputa of phthisical patients.

In some portions of the body these networks are stouter,
as in the bronchi and trachea ; here they almost form a layer
by themselves ; some of the fibres are even said to have a
sheath.

There is a variety that has been called, by Henle, perforated
membrane . It is found in arteries and veins. The fibres are
broad and the meshes very small. There are also "continuous
elastic membranes." They are made up of fibrils, react chemi-
cally like elastic tissue, and have no meshes. Such is Bow-
man's elastic membrane in the human cornea, which is very
distinct in man, also Descemet's membrane— the posterior
elastic membrane of the cornea.

In various parts of the body, beneath the epithelium, there
are other elastic membranes which, will be noticed in their
proper places. The elastic membrane, made of endothelium,
and forming the basement membrane of gland-ducts, must not
be confounded with those first described.

The growth and development of connective tissue varies ac-
cording to the particular type. It is probable, however, that
all the corpuscles are first round, but soon become flattened
and have a delicate envelope (Fig. 32, &).

About this is a further lightly attached investment, which,
uniting with those of other similar bodies, is the commence-
ment of the intercellular substance. At first the plate-like
bodies lie in niches, as it were, in the intercellular substances,
and if one is brushed out it leaves a socket behind it (Fig. 32, c).
They are often arranged in rows, as in the drawing, which was
taken from a fibroma of the scalp. As the intercellular sub-
stance increases the corpuscles become smaller, while imme-

80

MANUAL OF HISTOLOGY.

diately under them thin laminae are formed, probably from
the effused fibrine— the commencement of fibrillation.

As the corpuscles become smaller their envelope shrinks,
and they recede from one another. Yet, in many cases, they
may retain connection with one another by means of their pro-
cesses. In advanced life these cor-
V puscles are generally more or less

mtfl *V flattened, but their form is also con-

5 ' /©; siderably modified by the age of the
^ !&2) tissues and various mechanical alter-
i » ations to which they are subjected,

according to the particular locality
in which they occur or the province
they have to fill.

By referring to Fig. 32 it will be
seen that the delicate protoplasm, 5,
has processes which come clearly in-
to view where the corpuscles are iso-
lated.

Pavement endotlielium (epUJieli-
um). — From the views that have been
advanced it is plain that we are pre-
pared to abandon the old idea that the
mesentery, peritoneum, the pleura,
endocardium, serous cavities, and ten-
Fl°- 32—Deveiopmentof fibrous tis- dinous sheaths are lined with epithe-

Rue. Fibroma of the scalp. ( *

Hum. It is becoming more and more

evident from studies in the lymphatics that they are lined with
connective-tissue corpuscles, which, on the one hand, are in
actual continuity with the interfascicular connective-tissue cor-
puscles, and, on the other, with the pavement corpuscles of
the serous cavities. It is but a step farther and in the same
direction to trace the endothelium of the endocardium out
through the arteries and veins into the capillaries and recog-
nize the connective-tissue corpuscle as the one cellular element
of all these tissues. The special methods by which these parts
are studied may be found described in the chapters more es-
pecially devoted to these topics. Nitrate of silver and chloride
of gold are still prominent among the reagents that demon-
strate them most distinctly.

Ehrlich has recently described peculiar connective-tissue

BIBLIOGRAPHY. 81

corpuscles, which he previously supposed to be identical with
Waldeyer's plasma cells, but which he is now inclined to re-
gard as a distinctive group of bodies. They are characterized
by a special power of intense coloration in specimens treated
with certain of the aniline dyes. Red and violet colors appear
to be best suited to reveal the presence of these bodies, called
by Ehrlich granular cells. Acetic acid produces a diffuse
staining of the nucleus in these aniline stained cells. At the
same time the conspicuous granules lose their color. The same
author also states that the granular cells commonly found in
such great abundance in inflammatory processes are not modi-
fied leucocytes, but are derived from the fixed connective-
tissue corpuscles.

According to Ravogli, the connective-tissue corpuscles of
the corium and subcutaneous tissue are branching cells, whose
processes unite to form anastomoses. With advancing age these
cells undergo structural alterations, and their processes begin
to form reticula of elastic tissue. Simultaneously with this
metamorphosis the cell-bodies are said to become flattened,
elongated, and united in longitudinal rows. At length the cells
as well as their processes are transformed into ordinary elastic
tissue.

BIBLIOGRAPHY.

SATTERTHWAITE, T. B. On the Structure and Development of Connective Sub-
stances (Prize Essay). New York Med. Jour., July, 1876, and Monthly Micro-
scop. Jour., October and November, 1876.

FLEMMING. Arch. f. Anat., etc. 1879. 401 — 454.

STRICKER. Allg. Wien. med. Ztg. 1879. XXIV., 547.

KOLLMANN. CentralbL f. d. med. Wiss. 1878. XVL, 881.

EHRLICH. Verhandl. d. Berliner phys GeselL Jan. 17, 1879; Arch. f. Anat. u.
Phys. Phys. Abtheil. pp. 166—169. 1879.

RAVOGLI. Wien. med. Jahrb. Heft 1, p. 49. 1879.
Also the more recent text-books of Klein and Banvier.

6

CHAPTER VI.

THE CONNECTIVE SUBSTANCE GEOUP— Continued.
CARTILAGE.

CARTILAGE is divided into three prominent varieties : 1,
hyaline ; 2, fibrous ; and 3, elastic or yellow. There is, in
addition, a form called ossifying, which will be described in
connection with the development of bone.

Hyaline cartilage is the tissue from which the bones of the
skeleton are first made ; it is also found in the articular and
costal cartilages, and in the cartilages of the larynx, trachea,
and bronchi ; possibly also in some of the nasal cartilages, and
in portions of the sternum. All of these tissues consist of a
solid material or matrix, in which are capsules which contain
the true cartilage corpuscles.

The character of the intercellular substance determines the
particular variety. Thus, hyaline cartilage appears, under the
microscope, to be structureless and homogeneous. Fibrous
cartilage, on the other hand, has distinct lines of fibrillation
extending through it. Elastic cartilage is permeated by net-
works of elastic fibrils.

Hyaline cartilage, though so-called because of its apparent
absence of structure, is now known to be less often structure-
less than has been supposed, for the researches of Tillmanns
have revealed distinct marks of fibrillation in some adult artic-
ular and costal cartilages. Soaking the tissue in a 10 per
cent, solution of common salt will dissolve out the cement sub-
stance and isolate fibrils, though the tissue has previously ap-
peared homogeneous. Staining with the picro-carminate of
ammonia (Ranvier's formula) will also demonstrate the fibrils.

Each capsule is probably invested by a delicate membrane,
which is thicker in some instances than in others. Extending

THE CONNECTIVE SUBSTANCE GROUP. 83

from this cavity are minute canals, which communicate with
those of other capsules in many instances, and thus, in all
probability, establish a system of serous channels which convey
the plasma tic fluid, i.e., the lymph.

Many years ago H. Mueller gave a description of minute passages radiating
out from the cartilage capsules. Since this time the matter has been studied
by numbers of observers, but opinions have been divided as to their existence.
More recently A. Budge has detailed a method by which he claims that a
complete lymphatic system can be demonstrated in hyaline cartilage. Em-
ploying a solution of Berlin blue, he injected the cartilage of an epiphysis from
which the articular lamella had been cut off. Having thus opened and exposed
the substance of the cartilage, he found it permeated with minute blue net-
works that were in communication with the cartilage capsules. A connection
with the lymphatics of the bone was also shown.

Nykamp, who prosecuted his investigations about the same time (1876-77),
verified the work of Budge, though his methods were different. He experi-
mented on rabbits, injecting one gramme of indigo carmine (in substance)
into the abdominal cavity. Blue granules appeared in certain spaces, which
had shown themselves to be hollow passages by a previous soaking in the neu-
tral chromate of ammonia. The cartilage commonly known as hyaline was
also, by this means, shown to be fibrillated.

Round about every cartilage capsule there is usually an
area of hyaline material. When ver}T thin sections of cartilage
are made, these areas sometimes become visible ; soaking in
acids is said also to bring them into prominence (Klein).

- The amount of intercellular substance in comparison with
the capsules varies ; as a rule, there is less of this substance
near the periphery of the cartilage. When the amount is so
very small that the tissue is almost cellular, it is called par-
cncliymatous cartilage; this condition is observed in all carti-
lages, at an early stage of development, and in some portions
of the adult forms. The cartilage corpuscles are rounded
bodies, sometimes oval and sometimes pyriform. In the nor-
mal condition they fill up the capsule, but after the application
of reagents that shrivel, such as alcohol, they are withdrawn
from the walls of the capsules, being only attached at a few
points (perhaps where their processes extend out through the
canaliouli).

The cell-corpuscles and nuclei are said, by some recent ob-
servers, to exhibit networks in their interior (Schleicher and
Flemming). They frequently contain, in addition, moving
bodies, which are often oil-globules of minute size.

84 MANUAL OF HISTOLOGY.

The cartilage capsules do not usually appear to have any
connection with one another when examined in an indifferent
fluid, though in the episternal cartilage of the frog, immedi-
ately beneath the perichondrium, a connection may occasion-
ally be seen.

Division of the cartilage corpuscle.— One of the prominent
features seen in cartilage is the division of the cartilage cor-
. puscle. First we notice the 'splitting of the nucleus ; then of
the corpuscle itself. When such a division has taken place
the corpuscles are called daughter-cells (Fig. 33). As a next
step each daughter-cell may divide and again subdivide, and

FIG. 33. — Fresh cartilage from the triton. (Rollett.)

thus we have developed in one capsule four or eight cor-
puscles. Sometimes it will be observed in the same specimen
that with each division of a corpuscle, hyaline matter from
without the capsule pushes in, and so from the original capsule
two are now formed.

Calcification of hyaline cartilage. — Hyaline cartilage in
old age is infiltrated by a deposit of the salts of lime, which,
when seen under the microscope, have a granular appearance.
The deposit occurs first round about the cartilage capsule
(Ranvier).

Nerves and blood-vessels are not supplied to hyaline car-
tilage proper, though blood-vessels which belong to adjacent
tissues sometimes dip into it or pass through it.

Methods of studying hyaline cartilage. — An excellent and
simple plan is to snip off the tip of the episternal cartilage

THE CONNECTIVE SUBSTANCE GROUP. 85

from the frog ; strip it of pericliondrium and mount in serum.
The shoulder-girdle of the triton (newt) may also be employed.
It will then be seen that there are numbers of granular cor-
puscles, with nuclei scattered irregularly throughout an ap-
parently homogeneous, i.e., structureless matrix. If now a
little water be added to the preparation, it will be seen that the
corpuscles are made to shrivel, and in so doing they expose
the wall of the cavity or capsule in which they lie. The cor-
puscles do not appear to have any uniform size or shape : some-
times they are single ; again they are double (daughter-cells) ;
occasionally they are united with the corpuscles in adjacent
capsules. The nucleus is apt to be round and full ; the corpus-
cles are apt to be filled with dark spherical bodies which are
usually fatty molecules, as may be shown by employing a di-
lute solution of osmic acid (I per cent.).

Using the silver method it will be seen that there exists, in the apparently
homogeneous matrix, numbers of corpuscles whose nature is not fully under-
stood. Incidentally it may be mentioned that the silver method often exhibits
curious markings in all tissues.

Sometimes these appearances are due to the silver itself, and some caution
is therefore necessary in deducing conclusions from the method.

The gold method l shows that there are concentric rings about the capsules,
but it is highly probable that this phenomenon is artificial.

Ranvier recommends, as a staining fluid, purpurine, the
formula of which is as follows : Take one gramme of powdered
alum and add to it two hundred grammes of distilled water,
which boil in a porcelain dish. To this solution add some pow-
dered purpurine diluted with water. If the boiling be now con-
tinued, a portion of the purpurine will dissolve. Filter while
warm, and receive the colored fluid in a flask which contains
60 c.c. of alcohol. This liquid has a rose-orange color. The
nuclei of the corpuscles will be colored red and have a double
contour ; the cell-body will be bright red.

Hyaline cartilage may be well exhibited in the respiratory
tract of young children, as in the cricoid cartilage of an infant
two or three years old.

Yellow elastic or reticular cartilage is a very distinctive
form. It consists of the hyaline variety permeated with elas-
tic networks. Examples of it may be obtained from the human

1 See chapter on General Methods.

86

MAXTJAL OF HISTOLOGY.

epiglottis, laryngeal cartilages, and the pinna of the ear (Fig.
The presence of elastic fibres is proved by their resistance
to boiling in acids and alkalies, and their failure to color with
carmine. Sections may be made with the knife and prepared
in almost any of the ways already mentioned.

The appearances already described are not^een in the early
development of elastic tissue, but are easily identified in adult

FIG. 34. — Section of the boiled and dried auricle of the human ear : a, retiform cartilage ; ft, connec-
tive tissue. (Rollett)

life. Even then the elastic fibrils may only be found in the in-
terior of the cartilage, while at the periphery the' matrix is
hyaline. Elastic cartilage is coated over with a delicate mem-
brane— the perichondrium.

Fibrous cartilage. — This variety is also known as fibril -
lated or fibro-cartilage. The matrix has probably no elastic
fibrils, but is interspersed with connective- tissue bundles. It
is found in the cartilages which make the lips of the joints, the
inter-articular cartilages, the cartilaginous deposits in tendons,
the cartilage of the symphysis pubis and of glenoid fossae, and
possibly in the intervertebral ligaments and sesamoid carti-
lages. There is often more or less hyaline material about them.
In many instances the line of distinction between cartilage and
fibrous tissue is difficult to make out. Where, however, dis-
tinct corpuscles can be demonstrated, the tissue may properly
be regarded as cartilage. These bodies are similar to those
seen in hyaline and reticular cartilage.

Division of the cartilage-corpuscle. — A problem that has

THE CONNECTIVE SUBSTANCE GROUP. 87

attracted the study of various histologists for a number of
years, since Leidy, in 1849, first directed attention to it, is the
mode in which cartilage-corpuscles divide. Various theories
have been afloat, each with its special supporters.

Dr. W. S. Bigelow, of this country, in 1878 reviewed the
subject carefully, pursuing his investigations on the* hyaline
cartilage of the triton, tree-toad, frog, various fishes, the guinea-
pig, total pig, and the human embryo in health and disease.
His inquiries were especially concerned with reference to the
statement of Buetschli, that in the divisions of the corpuscles,
the splitting of the nucleus and cell-body are simultaneous.
As the result of Dr. Bigelow' s work, he concludes that the old
theory is still tenable, viz., that at first there is a division of
the nucleus, and that subsequently a septum is found in the
cell-body. After division takes place the matrix of the carti-
lage penetrates between the corpuscles, and thus two cavities
are formed. This view has received confirmation from very
extended and elaborate researches by Schleicher, to which
Flemming has also expressed a provisional assent.

Structure of the cartilage-corpuscle. — According to Schlei-
cher the nuclei are provided with peculiar filaments and gran-
ules which u-ndergo amoeboid movements when they are in the
act of dividing. In the cell-body of young cartilage-corpuscles
he has seen no network, such as has been described by some
later writers (Heitzmann, Klein, etc.), though in the adult tissue
peculiar linear markings are evident. He thinks that the nu-
cleus is not permeated by a network, but is homogeneous.
Eeticulated appearances are apt, he thinks, to be the result of
using reagents that alter the natural quality of the tissues.
According to Flemming, the nucleus of the cartilage-corpus-
cles contains a network which gives the appearances described
as " coarsely granular."

In the drawings of this author the cell-bodies nowhere exhibit a network,
but, on the contrary, linear markings, which have often a concentric direction.
In many, the internal structure is represented as homogeneous. The conflict of
opinion now apparent in this matter, and the marked differences in the micro-
scopic drawings of the same object, make it apparent that these topics are still
to be regarded as subjudice.

Structure of the intercellular substance. — According to Spina there is an intra-
cellular substance in cartilage which is directly continuous with the intercel-
lular substance, which itself exhibits an extremely delicate network. This

88 MANUAL OF HISTOLOGY.

condition, which he regards as an early form of cartilage, undergoes changes,
in so far that the intercellular network is enlarged and narrowed so as to give
the appearance of fascicles or bundles of parallel fibres. The meshes are filled
with a finely granular substance which is thought to be partly formed at the
expense of the network. The method employed in demonstrating these ap-
pearances consisted in taking the articular extremities of frog's bones, im-
mersing them three to four days in alcohol, then cutting thin sections, and
finally, examining them in alcohol.

BIBLIOGRAPHY.

TILLMANNS. Archiv f. mikrosk. Anat. X. Bd. X. p. 401. 1874

BUDGE, A. Archiv f. mikrosk. Anat Bd. XIV., S. 65. 1877.

NYKAMP. Archiv f. mikrosk. Anat. Bd. XIV., S. 492. 1877.

HEITZMANN. Studien am Kuochen u. Enorpel. Wien. med. Jahrb. 1872. V. and

H.'B Bench t.
BIGELOW. W. S. Arch. f. mikrosk. Anat. XVI., 2. 1878.

SCHLEICHER. Ibid.

FLEMMING. Ibid.

KLEIN and E. NOBLE SMITH'S Atlas of Histology. 1879—1880.

RANVIER. Traite technique d'histologie. 1877.

BUETSCHLI. Zeitschr. f. wies. Zool. 29, p. 206.

SPINA, A. Sitzb. de k. Akad. der Wiss. Bd. LXXX., LXXXT. 1879, 1880.

CHAPTEK VII.

THE CONNECTIVE SUBSTANCE GROUP.— Continued.
BONE.

THERE are two principal varieties of bone known to anato-
mists, the compact and the cancellous or spongy. The former
is found in the shafts of all the long bones of the body and
along the outer surface of all the short and flat bones. The
latter occurs in the articular extremities of all long bones and
in the interior of all short and flat bones.

Compact tissue consists of an unyielding, almost inelastic,
massive framework, which is traversed by networks of blood-
vessels and -lymphatics, and perhaps by nerves. The dense
organic substance forming the groundwork of all bone — ossein
— is in reality nothing but a form of connective substance
almost precisely resembling ordinary fibrous tissue, but which
is evenly infiltrated with minute molecules of the carbonates
and phosphates of lime and some other inorganic salts. These
insoluble matters are so thoroughly intermixed with the fibrous
tissue that they give it great solidity, though at the same time
they restrict its flexibility, and therefore increase its suscepti-
bility to fracture.

Like other forms of the connective-tissue series, it contains
corpuscles that are disposed in a regular way between lamel-
lae, which here correspond to the fascicles of fibrous tissue. The
province of these corpuscles is doubtless the same as that of
other connective-tissue corpuscles, viz., to preside over the nu-
trition of the tissue in which they are found.

After decalcification by strong acids, such as the nitric or
muriatic, if the residue be boiled it will yield gelatin or chon-
drin.

These corpuscles that have just been described are not al-

00 MANUAL OF HISTOLOGY.

ways easily recognized, and, in fact, have often been ignored
by writers of anatomical text-books. They were not detected
for a long time, because the capsules in which they are em-
bedded received all the attention, and were even called bone-
corpuscles. But when it was discovered by Virchow that
these bodies had nuclei, and that they could be separated, to-
gether with their processes, from the bone, it was supposed
that the nutrition of the tissue was maintained through them,
acting in the capacity of hollow tubes. This view Virchow at
one time supported. Subsequently it was discovered that in-
jection fluids could be forced into the canaliculi and round
about the corpuscles, so that three facts became assured : (1)
the existence of capsules in the bony substance with radiating
and anastomosing passages, the lacunae and canaliculi ; (2) the
presence of nucleated and branched corpuscles in the lacunae ;
and of spaces (3) about the nucleated corpuscles and their
processes, suitable for the movement of fluids designed for the
nutrition of the part.

The structure of bone then became clear, and its similarity
with other connective substances well established. These bony
canaliculi extend to the wall of the Haversian canal, the great
channel conveying the blood-vessels and larger lymphatics.
Thus a lymph-canalicular system permeates the bone in close
connection with the blood-vessels, bathing every bone-cor-
puscle.

When a cross-section is made of any long bone, it will be
observed that most of the lamellae have a concentric arrange-
ment about each Haversian canal (Fig. 35, b). But it will also
be seen that there are other groups of lamellae whose arrange-
ment is slightly different. For example, at the periphery of
the bone their direction is parallel with the surface.

Such lamellae may be represented at a. They are known as
the intermediate or circumferential (Tomes and De Morgan).
Another group, only partly encircling each canal, is known as
the peripkeric or interstitial, c. The first mentioned, imme-
diately about the canal, are the concentric, b.

Schaefer believes with Sharpey that each lamella consists of fibres crossing
each other diagonally, and separated on either side by a homogeneons layer.
According to Von Ebner, the peculiar cross striations belong only to Canada
balsam preparations that are old. These markings are due to the peculiar
refractive power of the balsam which fills the canaliculi

THE CONNECTIVE SUBSTANCE GROUP.

91

The arrangement just described is found in all compact
bone where there is any considerable thickness, but when, as
in flat bones, the cortex is very thin, the lamellae often pursue
a straight and parallel course. Some of these lamellae or plates
exhibit transverse striations ; others are homogeneous.

In Fig. 35 may be seen the lacunae lying between the
lamellae. They appear
as dark spaces disposed
at quite regular intervals
and, having their long
axes parallel with the
course of the lamellae.
Laterally each corpuscle
gives off numbers of pro-
cesses, many of which
branch, while all, or near-
ly all, anastomose with
corresponding branch-
lets of other corpuscles-
A branchlet is also given
off from the end of each
corpuscle, and forms a
connection with the adjacent bodies lying in the same inter-
lamellar space and in the same plane.

The Haversian canals form a broad-meshed network through-
out the bone, establishing a communication between the central
marrow cavity and the external surface of the bone (Fig. 36).

The arrangement of parts comprised by each Haversian
canal, with its investing lamellae, and interposed lacunae and
their anastomosing caiialiculi constitutes an Haversian system.
Though found mainly in the compact tissue, they may also be
seen in the large trabeculae of the spongy substance. As seen
in Fig. 36, the Haversian canals form a network of which the
longitudinal tubes are the larger and longer. Besides convey-
ing blood-vessels and lymphatics they have a certain amount
of connective tissue which varies according to the locality, and
establishes a more or less complete connection between the con-
nective tissue of the marrow cavity and of the periosteum.

In young bone this is well seen ; in adult bone the direct
continuity can with difficulty be traced, as the vessels are apt
to fill the tubes pretty completely.

FIG. 35. — Transverse section of tinman femnr, deprived of
inorganic material by hydrochloric acid. (Rollett.)

92

MANUAL OF HISTOLOGY.

Preparation of dry bone. — In order to study the char-
acteristics which have just been described, any human long
bone may be taken. It should be stripped of its soft parts,
bleached, and well dried. Thin sections are then to be made
both in a longitudinal and transverse direction, with a watch-
spring saw.

Next, cleanse them well in water to which a little bicar-
bonate of soda has been added ; then place on a whetstone
and grind down by rubbing backward and forward with the

finger until they are suffi-
ciently thin ; or the sections
may be placed between two
plates of ground glass and
rubbed down.

Finally, when so thin that
type may be read through
them, mount either dry or
in Canada balsam or dam-
mar varnish. All the char-
acteristics already described
may then be seen.

Preparation of decalci-
fied bone. — Another method
consists in first removing the
earthy salts. If it is desira-
ble to accomplish the work
rapidly, cut the bone to be
prepared into the smallest
available pieces and immerse
from four to five days in a 10
per cent, watery solution of

Pro. 36. -Longitudinal section of human ulna, show- hydrochloric acid,
ing the Haversian canals forming meshes. (Eollett) mi

The completion of this

process may be determined by testing the bone with a fine cam-
bric needle. So long as it meets with resistance, the presence
of the bone-earths is certain ; on the other hand, if it enter
easily, the process of decalcification is over, and the piece ready
for cutting.

Now wash thoroughly in water, so as to remove the acid,
place in 80 per cent, alcohol, gradually increasing the strength
to 95 per cent. The specimen is then ready for use and may

THE CONNECTIVE SUBSTANCE GROUP.

93

be treated precisely as any other tissue of the body. If more
time is at the disposal of the student, chromic acid may be
used in a £ per cent, solution. This process is rather slow, re-
quiring several months. It may be materially hastened by the
use of nitric acid (2 per cent.). It has been found that after
immersion in chromic acid for a few days, the soft parts are
rendered insensible to the action of other strong acids, such as
nitric and hydrochloric, when used in the dilute form. These
chromic acid preparations are exceedingly beautiful objects

Fio. 37.— Bone lacunae with their process*. (Rollett.)

when seen with low powers. The matrix is of a deep grass
green. If a thin section is stained with borax-carmine (Arnold's
formula) the bone-corpuscles and connective tissue are stained
red, and the contrast of color brings out the finer elements
very distinctly.

Picro-carmine may also be used, and then the muscular tis-
sue, if any chance to adhere to the bone, is stained yellow ; or
eosine and hsematoxylin may be used instead of borax car-
mine, and thus very excellent examples of triple staining pro-
cured. Sometimes a saturated solution of picric acid is em-
ployed to decalcify, but the excess of acid, after taking out
the bone-earths should be thoroughly removed by soaking in

1)4 MANUAL OF HISTOLOGY.

water before immersion in any staining fluid. In preparing a
specimen for cutting with the knife it may conveniently be
held in the hand, or, if the microtome is used, the bone may
be embedded in the ordinary mixture of wax and oil, pith, or
liver, according to methods already described. Rutherford re-
commends glycerine jelly for this purpose.

Any of these plans of preparing decalcified bone will reveal
the presence of the bone-corpuscles within the lacunae. These
will be found to correspond quite closely in size and shape
with the cavities. They may also be shown to have a direct
continuity with the connective-tissue corpuscles of the perios-
teum. In growing bone this is more evident. A nucleus can
also sometimes be seen in the bone-corpuscle. In Fig. 36
the lacunae, with their canaliculi, are well shown.

Sharpens perforating fibres. — Attached to the outer sur-
face of compact tissue, and penetrating the bone at right an-
gles, are certain fibres which have been named after Sharpey,
their discoverer.

Take a flat bone of the skull that has been decalcified, seize
pieces with the forceps, tear them out from the surface, and
examine in water. In some of the fragments the bundles of
fibres will be seen ; in others the lamellae, perforated for the
fibres. If a portion of tendon adhere to the bone, and a sec-
tion be made through the two at their line of apparent junc-
tion, it will be seen that the tendon-fibres are continuous in
the bone with Sharpey' s fibres.

A very prevalent view is that they constitute the remains of
the periosteal processes, which we shall see are largely con-
cerned with the ultimate development of bone.

Cancellous tissue.— All of the elements of bone, that go to
make up a Haversian system, are found in the cancellous
tissue, so that, in this respect, it does not differ from the com-
part. The chief . peculiarity lies in the marrow cavities, or
channels, as they might appropriately be called, and they indi-
cate either, on the one hand, that the bone is passing through
a developmental stage ; or that it is being rarefied by a process
of retrograde metamorphosis ; or, finally, that it has reached a
stadium of repose in either of the first-named changes. These
points will be further particularized when the growth and de-
velopment of bone is explained, but the reader is now prepared

THE CONNECTIVE SUBSTANCE GEOUP. 95

for the rather remarkable proposition that compact bone is
formed out of spongy, and spongy out of compact.

These marrow channels are a series of branching and anasto-
mosing tubes, rich in corpuscular elements and vessels. In
young bone the latter are known as red marrow. When a
longitudinal section has been made through a tubular bone, it
will be seen that the channels are enclosed in an osseous net-
work, whose meshes differ much in shape. In the articular
extremities they are long and narrow ; at other points, more
nearly quadrilateral.

There is a second variety of marrow, known as yellow, which
is found in the central cavity of the long bones. The yellow
color is due to the presence of fat, though it also contains
peculiar, small, colorless corpuscles, not unlike the leucocytes
of the blood, and known as marrow-cells, together with the
ordinary branched and nucleated connective-tissue corpuscles,
also large multi-nucleated bodies that are usually granular and
sometimes striated, and blood-vessels. The large corpuscles
are the myeloplaxes of Robin (giant-cells).

The red marrow also contains marrow-cells, though but few
fat-cells. It is remarkable for being the seat of the peculiar
nucleated blood-corpuscles that have been described by Neu-
mann and Bizzozero. They are transitional between the white
and the red in size, and have a uniform yellowish green color
(Klein).

The authors above referred to found the nucleated corpuscles in the red
marrow of the ribs and bodies of the vertebrae ; they resembled blood-corpus-
cles that are found in the human embryo, and were regarded as evidence that
the bones have bloodmaking properties. Later researches (Orth and Litten)
have seemed to corroborate these views, and to have shown that in certain
morbid states of the blood, as in carcinoma, phthisis, and syphilis, an effort of
this kind is made for the relief of the constitutional infection. Experiments
upon dogs have also added further testimony and have shown that after extreme
artificial anrcmia there is a new formation of blood-globules, in which the
nucleated bodies play an active part, together with other elements, such as the
giant-corpuscles of Hayem, etc. These views, however, have met with opposi-
tion, and Rutherford (" Pract. Histology," p. 88) maintains that the nucleated
corpuscle is an indication of corpuscular disintegration rather than of new-
formation.

TJte periosteum is a layer of dense fibrous tissue closoly
covering the bone, and connected with it by a thinner layer of

96 MANUAL OF HISTOLOGY.

looser texture. The external portion may be composed of sin-
gle, double, or treble laminae of varying thickness. The inner
or osteogenetic portion is of. great interest and importance,
as it contains the osteoblasts, which are active agents in the
formation of a great part of all bones, as we shall presently
see.

Development of bone. — Views as to the method by which bone
is formed have undergone great changes within the past few
years, and it may be stated that most modern observers have
given in their adhesion to the theory that bone is not developed
by a calcification of cartilage, but by a long and complicated
series of changes inaugurated by the corpuscles of the marrow
cavities, on the one hand, and those of the periosteum, on the
other. These conclusions have been the result of very extended
researches conducted by a variety of methods and upon many
kinds of animals.

As the mode of growth in man and horned cattle is identical,
a good method of procedure is as follows. Take the hoof of a
yearling bullock, and, removing the bones, macerate them a
few days in a 10 per cent, watery solution of h37drochloric acid
and then in chromic acid (gr. ij. — §j.). In a few days they
will be decalcified sufficiently to allow of a thin section being
shaved off from the surface so as to include parts where ossifi-
cation has already commenced. The sections may then be
stained in a neutral solution of carmine and mounted. The
gradual stages between the advancing bone and the liquefying
cartilage can now- be studied. Following the changes from the
surface of the articulation toward the centre of the bone, there
is seen at first, beneath the fibrous layer, a stratum of hyaline
cartilage. The corpuscles are long, flattened, and lie parallel
with the surface. Passing to a greater depth they become
larger, and increase in number by gradual progression. As
these capsules enlarge and their contents multiply, they
begin to be arranged about the wall of the cavity, while
the matrix gradually wastes away. A little farther and
there is a deposit of calcific material in the intercapsular sub-
stance. Another step internally and the cartilage capsules
have in part coalesced, and now they are beginning to be filled
by the marrow tissue pushing up from the central parts of the
bone. When the connective tissues and vessels that constitute
this arborescent growth have entered the capsules, the corpus-

THE CONNECTIVE SUBSTANCE GROUP. 97

cles that line them are called osteoblasts. Whether or not they
are identical with the cartilage-corpuscles, or belong to the
budding marrow-processes, seems to be a matter of doubt.
Klein intimates that the cartilage-corpuscles disintegrate. Ran-
vier has seen no proof of it. It is probable that some of the
cartilage-corpuscles persist, certainly to a limited extent,
and preside over the remains of the calcified cartilage. The
bulk of the new bone is made up, however, of new material
which is deposited under the form of concentric lamellae about
the marrow cavities, most likely by a proliferation of the
osteoblasts.

These changes may all be observed to advantage in the
specimen just mentioned, and the successive gradations of the
process can be conveniently magnified, so as to be easily seen,
by making sections obliquely to the surface of the bone. With
a low power the specimens will have uncommon beauty, as the
corpuscles take the carmine well, while the interstitial tissue is
of a bright, transparent grass-green.

In a vertical section of a long bone, while the process is
essentially the same, there are some modifications in the suc-
cessive steps. Thus the spongy bone of the epiphysis en-
croaches on the cartilage, causing it to be absorbed in the man-
ner already described, but the intermediary cartilage, lying
between the e,piphysis and diaphysis, is seen to have its cor-
puscles arranged in long lines parallel with the axis of the
bone ("step-ladders"). The bone meshes of the encroaching
bone are also shaped in correspondence with the cartilage cap-
sules, that is, they are long and narrow.

Formation of bone through the medium of cartilage. — The
successive changes in this species of bone development have
been best described by Klein. According to him the hyaline
cartilage that is destined to prepare the way for bone is covered
with perichondrium, consisting like the periosteum of two
layers. This membrane does not at first contain mature fibrous
tissue, but merely the rudiments of it, under the form of spin-
dle-shaped corpuscles ; its internal layer, however, is early pro-
vided with spherical corpuscles, the future osteoblasts, and is
rich in vessels.

Subsequently this osteogenetic envelope puts out processes
(periosteal processes, Virchow) that penetrate into the carti-
lage-capsules, which, melting as the external growth makes its
7

98 MANUAL OF HISTOLOGY.

way inward, develop communications between the capsules, so
that in this way a cartilaginous network is formed that is filled
with the arborescent tissue. This change in the cartilage,
which is characterized by absorption and rarefaction, is called
chondro-porosis.

At a more advanced stage the cartilage around the oldest
channels has become transparent in places, while the walls are
irregular, because portions- of calcified trabeculse project into
them. These irregular spaces are called primary marrow
cavities. Now upon the walls may be seen, not the cartilage-
corpuscles, but the osteoblasts, which are proceeding to develop
concentric layers of osseous tissue.

When this process has been completed, the osseous tissue
will be found to have replaced the calcified cartilage, and true
bone has been formed. But this action may be no sooner
completed than absorption will again commence, and at first in
the last or most internal layer of the Haversian system. This
process is essential for the development of the central marrow
cavity. After an Haversian system has been removed, the
matrix will also disappear.

Now, while this cavity is filling up with marrow a gradual
development of bone is taking place from the periosteum,
which slowly encroaches upon the bone whose formation we
have just described.

This last stage results in the formation of 'adult bone.
When it has been completed all the first formed bone has
been absorbed before it. This periostea! or metaplastic bone
is at first spongy, as is all new bone ; in the fulfilment of its
task it next appears to form compact bone, and then part of
this latter is rarefied, as, for example, along the wall of the
central cavity. Thus, as we have already seen, compact bone
is formed from spongy, and spongy from compact. The peri-
pheric or interstitial lamellae are either the remains of calcified
and unabsorbed trabeculse, or perhaps the walls of other Haver-
sian systems forming sides of the bony network.

Formation of bone from membrane. — This second method
of bone-formation is seen in the bones of the skull and face.
The steps are precisely similar to those already described. The
inner layer of the periosteum, which is lined with osteoblasts,
produces both matrix and bone corpuscles by a process of bud-
ding. The change first begins at the points of ossification.

THE CONNECTIVE SUBSTANCE GROUP. 99

At first the bone is spongy, but later absorption takes place —
osteoporosis. Around some of the marrow-tubes concentric
lamellae are formed, and in this way a Haversian system de-
velops. The unabsorbed portions of the trabeculse are thought
to constitute the lamellae known as the intermediary. Com-
pact tissue is thus formed from spongy. This theory, which
has been placed in its present acceptable light by Klein, is very
simple and appears to accord with observation, and explains
all the phenomena. Yet those who have believed in the direct
transmutation of cartilage into bone are still in the field.
Kolliker maintains that both views are correct.

According to this last named author the differences between primary or
primordial and the tegumentary or secondary bones are, from a morphological
point of view, sharp and complete. The former are ossifications of the carti-
laginous skeleton.

The tegumentary are never cartilaginous at first ; the primordial bones, on
the other hand are, without exception, formed from cartilage. The method and
manner in which bony tissue is formed is the same in both bones. The pri-
mordial skeleton in the lower vertebrates ossifies only in part from the peri-
chondrium, in part perichondrally, and, in part, endochondrally.

According to Kassowitz, in the tuberosities and spines of the bones the
periosteal processes of the periosteum, which develop the bone, are primarily
cartilaginous, the fibrillated tissue being converted into hyaline cartilage,
which is at first calcified and then undergoes direct conversion into bone.

According to the experiments of Strawinsky a transplanted periosteum will
develop either bone or cartilage, when the conditions are favorable. The con-
ditions of nutrition determine which it shall be. When the supply is best,
cartilage is formed ; when poorest, bone.

The earliest evidences of ossification were seen by this observer between
the fourth and fifth days. The formation of vessels preceded that of bone.
Absorption commenced between the second week and the second month. The
new formation of periosteum is partly derived from the border of the wound
and partly from the Haversian canals, which contain a small amount of connec-
tive tissue.

Development of bone and absorption. — It has been seen
that these two processes go on hand in hand. As soon as the
periosteum has commenced to deposit new layers of bone on
the surface of the primary spongy bone, absorption takes place
along the marrow canal. First of all, as we have already said,
the innermost of the concentric lamellae yield. In this way
the Haversian canals are widened and become Haversian spaces,
as they were at first ; then the interstitial lamellae, and finally

100 MANUAL OF HISTOLOGY.

the spaces disappear, and in place of them there is a single
dilated central cavity.

Howship's lacunce are the pits or lacunae seen in bone
beneath the periosteum. They usually contain a multinuclear
corpuscle (giant-cell), which is in some way related to absorp-
tion, and, therefore, has received the name osteoclast (Kolli-
ker). It has been surmised (Klein) that they are the agents by
which an acid is formed that dissolves the lime-salts. Whether
they are developed out of the osteoblasts or not is a matter of
uncertainty.

All the steps, both in development and absorption of bone,
have been carefully studied and placed upon a most satisfac-
tory foundation (Lieberkiihn and Bermann). The absorption
of bone has also been actually proved by measurements of the
bones in children (Schwalbe). By comparing the bones of the
third and fourth years of life, it was found that the marrow
cavity had enlarged in the latter, while the compact bone had
diminished in thickness. The change commenced at the sixth
month. This physiological process is closely allied to the
pathological one exhibited in rachitis ; in the latter the de-
velopment of bone from the periosteum has the character of
foetal bone, but the formation of the lamellae is slow and
incomplete.

It has been claimed that the growth of bone takes place
by an expansion of the intercellular substance (Strelzoff), but
this is denied (Kolliker, Wegener, Schwalbe, and others).
The ossein appe'ars to increase somewhat, but it is at the ex-
pense of the bone- corpuscles, which are thereby diminished in
size.

Formation of callus. — The method is the same as in the de-
velopment from periosteum. A corpuscular blastema is devel-
oped from the periosteum and intermuscular tissue. This
presses in between the fibres and bundles of the loose con-
nective tissue, pressing them asunder, assuming considerable
volume. This new tissue is hyaline cartilage. In from three
to six weeks it ossifies, being in part directly transformed into
bone, in part mediately, i.e., through the agency of medullary
spaces and osteoblasts. Where the extremities of the bone are
widely separated there is a formation of bone in the medullary
spaces of the broken ends of the bones. The pre-existing bone-
corpuscles have no part in the new-formation. This compact

THE CONNECTIVE SUBSTANCE GROUP. 101

bone thus formed will be absorbed in a few months, in its
internal portions, by rarefying ostitis, so that the marrow cavi-
ties of the broken diaphysis will be in communication.

BIBLIOGRAPHY..

The student is referred, for further particulars, to Klein's Atlas of Histology, Ran-
vier's Traite technique d'histologie, Strieker's Manual of Histology, and also to the
following recent writers :

SCHAEFER. Pract Histology. 1872.

LIEBERKUHN and BERMANN. Ueber Resorption der Knochensubstanz. 1877.

AUFUECIIT. Ueber Riesenzellen in Elfenbeinstiften. Med. Centralblatt, No. 26.

Jahresb. d. Fortschritte der Anat. und Phys. 1878.
ARNOLD, J. Virchow's Archiv. Bd. 71, p. 17. 1877.
VON EBNER. Sitzungsbericht der Wiener Akad. IIL AbtheiL Bd. 75. Hofmann

und Schwalbe's Jahresb. 1878.

KASSOWITZ. Med. Centralblatt, No. 5. Hofmann und Schwalbe's Jahresb. 1878.
SCHWALBE. Sitzungsb. dermed. naturwiss. Gesellschaf t zu Jena. 1877. H. und S.'s

Jahresb. 1878.

STRAWINSKY. Ueber Knochenresorption. H. und S.'s Jahresbericht, p. 109, 1878.
LITTEN, M., and ORTH, J. Berliner klin. Woch. No. 51, p. 743. 18<7.
KOLLIKEB. Entwickelungsgeschichte. V. und S.'s Jahresb. 1878.

CHAPTER VIII.

THE TEETH.

FROM the standpoint of descriptive anatomy, every tooth is
composed of three parts : (1) the crown, that portion which
stands above the level of the mucous membrane of the gum ;
(2) the neck, a constricted part at the level of the gum ; and (3)
the root, which terminates in one or more fangs, and is firmly
embedded in the alveolar process of the jaw. Each fang also
is pierced from below by a canal, which extends up into the
crown, and is filled by a soft material rich in nerves and ves-
sels, called the pulp, which has the special province of sup-
plying nutriment to the dense tissue about it.

From a histological point of view, every tooth may be di-
vided into : 1, enamel ; 2, dentine, or ivory ; 3, cement, or true
bone. The enamel forms the covering for the crown, the cement
for the root ; but they meet at the neck, and there- the cement
slightly overlaps. The ivory or dentine lies intermediate be-
tween the outer coatings and the pulp.

The enamel. — This substance, which is the hardest met with
in the body, consists of a series of long polyhedral columns
grouped in bundles and disposed mostly at right angles to the
surface of the dentine which lies beneath it. Each column or
pillar is a hexagonal prism, having a diameter varying between
Tvfans and -^^ inch. When viewed in cross-section these col-
umns look like a tesselated pavement. They are not, however,
closely applied to one another, but have interspaces which are
said to be filled with a homogeneous substance or fluid.

All of the groups of columns do not stand vertical to the
dentine ; some are parallel to it, and thus are interwoven with
the vertical ones. This crossing of the fibres produces an
alternation of light and dark bands (Fig. 38, 1). But there are
other systems of markings. In the same figure are wavy

THE TEETH.

103

lines running parallel to the surface. These are the "brown,
parallel stripes of Retzius" They pursue a somewhat curved
course. No unity of opinion exists about their significance,
one (Hertz) attributing them to deposits of pigment, another
(Von Bibra) to the pres-
ence of the oxide of iron.
Still other striae are ob-
served, and are thought
to represent the zigzag
or spiral course of the
enamel prisms. It is
observed that when the
prisms are isolated, which
can be accomplished by
immersion in a dilute hy-
drochloric acid solution,
they have a somewhat
spiral form, and have
bulging sides and cross
markings, the signifi-
cance of which will be
alluded to at another
place.

Near the line of the
dentine there are spaces
between the prisms which
are continuous with the
cavities in the dentine.
These are called the in-
terglobular spaces of
Czermak. They also oc-
cur at irregular intervals

in the dentine. Flo 38.-Premolsr tooth of the cat, in tttu. Vertical

Tn iT-m-mcr enHipprQ section, magnified 15 diameters. 1, enamel with decnswitinjf
in yOUng SUUjeCIS and paraliei 8tri»; 2, dentine with Schreger's line*; 8, ce-

there is a delicate mem- -^ &SSS"1 °' "" ^^ * "
brane covering the sur-
face of the enamel. It is composed of laminated epithelial
scales, and corresponds to the corneous layer of the skin, of
which, indeed, it represents the vestiges.

The dentine or ivory (Fig. 38, 2) consists of a dense and
hard matrix impregnated with the salts of lime. It contains

104

MANUAL OF HISTOLOGY.

numerous passages having, like the enamel prisms, a direction
at right angles to the surface of the bone. These passages, the
dentinal canals, are united with one another laterally by
minute oblique branches, and form undoubtedly open channels
of communication between the pulp cavity and the spaces be-
tween the enamel prisms in the crown and the bone lacunae of

the cement in the fang. Each canal
is lined with a particularly delicate
and resistant membrane, the den-
tinal sheath of Neumann.

Upon the internal surface of the
dentine, or the external surface of
the pulp- tissue, is the layer of
odontoblasts (Schwann). These cor-
puscles, according to Waldeyer,
have long branching processes ex-
tending in three directions, inward
into the pulp-cavity, outward
through the dentinal channels,
forming the dentinal fibres of

i I' (111 INI [/ f, Tomes, and laterally so as to form

,1 ly \"^ \ connection with adjacent corpus-

y n 4 I, IV cles. On the outer surface of the

dentine the canals connect with
the interglobular spaces of Czer-
mak, and they in turn are con-
tinuous with interstices between

'( ill I H Ml 1\ \\ ^ie enamel prisms. The dentinal
/ Ff HI ill 1 1 1 r tubules never appear to be in di-
rect communication with the enam-
el spaces, but only mediately, as
has been described. These cavi-
ties are filled with protoplasmic
material. Those immediately adjoining the cement are small
in size, and form what is known as the granular layer of
Tomes or PurJcinje.

Dentinal globules (Fig. 39, 2) is the name given to certain
spheroidal masses that are regarded (Waldeyer) as calcified
remains of the corpuscles in the spaces. The contours of these
masses correspond in outline with those of the interglobular
spaces.

Pio. 39.— Canine tooth of man, present-
ing a portion of the transverse section of
the root : 1. cement with laree lacuna; and
parallel strife ; 2, inter<?lobular substance ;
«, dentinal tubules. Magnified 300 diame-
ters. (Waldeyer.)

THE TEETH. 105

Beneath the cement the intercommunication of interglobu-
lar spaces and bone-lacunse is well shown. The inter globular
substance is apt to be present in layers ; the lines which are
then called the incremental lines of Salter, are supposed to
show that there has been growth by successive stages. The
lines of Schreger (Fig. 38, 2) are also waving parallel lines ; they
are thought to be due to the curvature. of a series of adjacent
fibres. In some instances vascular channels have been found
in the dentine, which has acquired the name osteo or vaso-
dentine. In pathological conditions masses have also been
found containing bone-lacunse. They have been called odonto-
mata by Virchow.

The cement is true bone-tissue, containing lacunas and
canaliculi, and in them the bone-corpuscles with their pro-
cesses. The matrix is also subdivided into lamellae. The peri-
osteum of the gum dipping down into the bony socket from
the surface of the gum forms a coating over the cement. Oc-
casionally Haversian canals and blood-vessels are seen where
the cement is thick (Salter). Sharpey's fibres may also be seen,
according to Waldeyer.

The pulp is a substance that belongs to the connective-
tissue series. .Adjoining the dentine are two layers of corpus-
cles. The nearest are long cylindrical bodies whose oval nuclei
are distant from the dentine. Wedged in between them, and
forming a layer intermediate between them and the pulp, are
peculiar branched corpuscles of a spindle or pyramidal shape.
According to Klein, these latter send processes into the den-
tinal tubules, while, according to Waldeyer and Boll the odon-
toblasts send the fibres, and are also connected to one another
by lateral processes. The pulp tissue is very rich in non-
medullated nerves ; their prolongations penetrate between the
odontoblasts, but it is a matter of question whether they enter
the dentinal canals.

Capillaries are abundant and form close networks in the
pulp. The lymphatics are said to accompany the blood-vessels
and to be surrounded by endothelial sheaths.

Development of the teeth. — Waldeyer, whose views on the
teeth are the most complete and satisfactory extant, makes the
following succinct statement :

"The anatomical model of a tooth of a vertebrate animal
is a large papilla of the mouth or of the pharyngeal mucous

106

MANUAL OF HISTOLOGY.

membrane, which in consequence of chemical and histological
conversion of its constituents has acquired a remarkable degree
of hardness, and according to whether the connective-tissue
substance of the papilla participates in the hardening or not,
two large groups of teeth are distinguished — dentinal teeth and
horny teeth. The horny teeth are by far the most simple in

Fio. 40. — Vertical section of the Inferior maxilla of a hu-
man foetus,meuBuring 11 ctms. from the vertex to the coccyx.
Magnified 25 diameters. 1, dental groove; 2, remains of the
enamel germ ; 3, enamel organ presenting externally epitheli-
um, as also where it forms the enamel germ of the papillae of
the dental sacculus ; 4, secondary enamel germ : rudiment of
the permanent tooth ; 5, dental germ : 6, lower jaw ; 7,
Meeker B cartilage. (VValdeyer.)

Fio. 41. — 1, various forma of
odontoblasts, with the three kinds
of processes;, 2. three enamel
cells, with a few cells of the stra-
tum intermedium attached ; 3, an
enamel cell, with a small portion
of enamel ; 4, fragments of ena-
mel fibres from young and soft
enamel ; 5, old '.-namel fibres with
transverse rtrise and rounded ex-
tremities. (Wuldeyer.)

their structure. They appear as more or less developed papil-
lae covered with a thick horny investment. They are never
continuous with portions of the skeleton, but constitute the
transition to other horny formations, as hairs, stings, etc."

" In the dentinal teeth the connective-tissue matrix of the
papillsB plays a most important part in the hardening process,
which here proceeds in a manner precisely similar to the ossi-
fying process, except that no true bone is formed, but only an
allied substance, of much harder consistence, and differing
more or less in histological structure, termed dentine. The epi-
thelium of the tooth papillae either atrophies to a rudimentary

THE TEETIT.

107

horny investment — the cuticula (membrane of the enamel) — or
it becomes elongated in a remarkable manner into long, petri-
fied prisms, which collectively invest the dentine and are
known as the enamel."

Preparations for the development of the teeth take place at
a time when the epithelium of the mucous membrane of the
mouth is found growing downward, like a solid peg, with a
rounded extremity.

This has been called the primary enamel organ. As a next
step, the material which is to give form to the tooth pushes
upward as a papillary growth, and meeting
the epithelial peg, pushes in or invaginates
its rounded extremity. This is the tooth
papilla, and as it pushes upward the pri-
mary enamel organ becomes the secondary
enamel organ, or the enamel cap. We have
now two tissues which are embedded in the
soft embryonic substance, that happens at
this early period to be gelatinous. That
portion of it immediately surrounding the
papilla and cap is called the tootJi-sac.

The papilla, which becomes highly vas-
cular, is covered, on its outer surface, by
the odontoblasts, a layer of columnar epi-
thelial corpuscles, which elongating, are
transformed directly into the dentinal sub-
stance at their outer extremity.

According to Kolliker and others, they
excrete the dentine. The former view seems
to have the most weight of argument in its
favor, but it seems less likely that the odon-
toblasts both make the matrix and send
fibres into the tubulse. The view of Klein
already given seems to be preferable, and in conformity with
what we know of other connective substances.

The separation of the tooth-sac from the mucous membrane
is effected by the gelatinous tissue, which, gradually closing in
the neck of the sac, finally cuts it off. The epithelium of the
enamel cap is abundant and of various kinds; into it push a
number of papillary processes downward from the gelatinous
tissue. Later the enamel cap is changed into three membranes.

Fia. 42. — Longitudinal sec-
tion of a milk tooth from the
foetal sheep, carried through
the margin of the dentine
pulp and adjoining portion of
the enamel organ. Magni-
fied 200 diameters. 1, dental
sacculns; 2, external epithe-
lium and stratum interme-
dium here united to the in-
ternal epithelium or enamel
cells ; 3, after the disappear-
ance of the enamel pulp ; 4,
young layer of enamel de-
tached from the enamel cells ;

6, dentine; 6, odontoblaata;

7, part of the dentine pulp.
(Waldeyer.)

108 MANUAL OF HISTOLOGY.

The middle membrane is a peculiar cellular network, formed
by the transformation of the middle epithelium layer into a
network of cells, below which there is a deposit of a hyaline
material. The inner membrane is formed of cylindrical epithe-
lial bodies, which are called enamel-cells ; outside of them are
one or more layers of polygonal cells ; they form the stratum
intermedium of Hannover. The outer membrane is composed of
several layers. Finally, the middle membrane disappearing, the
outer and inner membranes are brought into close apposition.

Development of tlie enamel. — This is formed by the enamel-
cells (inner epithelium, Kolliker), presumably in the same
way as the dentine by the odontoblasts. There is a direct con-
version of the outer extremities of the enamel-bodies into en-
amel. Kolliker, Hertz, and Kollmann, however, regard the
enamel as an excretion from the enamel-cells. The former
view appears the more natural, especially as the enamel-prisms
are continuous with the enamel-cells, having the same form and
shape. The successive stages of growth, it is believed, give
rise to the transverse markings.

Whether or not, in the interstitial substance of the enamel,
there are corpuscular elements (Boedecker), is a matter that
will require further investigation. The outer membrane even-
tually gives rise to the cuticle covering the enamel.

The development of the cement takes place precisely as
bone is produced, viz., from the periosteum, or, which is the
same in this instance, from the fibrous tissue of the tooth-sac,
the periodontium.

BIBLIOGRAPHY.

The following systematic works and journal articles may be consulted :
RETZIUS. Miiller's Archives. 1837.
NASMYTH. Med.-Chir. Trans. Vol. 22. 1839.
KftLLiKER. Man. of Human Histology. 1853.
WENZKL. Arch. d. Heilkunde. 1868.
HKNLE. Anatomie. 1871.

STRICKER. Manual of Histology. Am. Ed. 1872.

TOMES. Manual of Dental Anatomy, Human and Comparative. Lond., 1876.
OWEN. Comparative Anat. and Phys. of Vertebrates. 1866.
BOEDECKER. Dental Cosmos. XXL, 409— 416. Phil., 1879.
HEITZMANN. Microscopic Anat. of Human Teeth. Med. Rec., N. Y 1879. XV.

187.
KLEIK . Atlas of Histology. 1879—80.

CHAPTER IX.

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM.

WE may gain a clear conception of the nervous system in
its general outlines by remembering that it consists essentially
of a series of delicate cords which, on the one hand, proceed
from the nucleated bodies of the gray matter, conveying voli-
tional impulses to the periphery of the organism ; or, on the
other hand, of sensitive peripheral extremities that take up the
impression of external objects and carry them back to the cen-
tral gray substance.

In either case both the conducting cords and the central
corpuscles of the gray matter possess no distinctive differences,
such as may.be appreciated by the microscope, while, on the
other hand, the peripheral termini appear under many different
forms, the peculiarity of ending being dependent in part upon
the type of tissue in which they are found, partly upon the
office they have to perform, and partly upon other causes that
a~re unknown to us. The nerve-centres are located in the brain,
spinal cord, and in the ganglia of the cerebro-spinal and sym-
pathetic system.

The methods of nerve-terminations that have been described
may be briefly enumerated here. They are by (1) peculiar
terminal bodies, (2) loops, (3) networks, (4) end bulbs, (5) proto-
plasmic bodies (cells), (6) free or pointed extremities.

1\'< rn-flhrrs. — Of fhrs» there are three kinds that have
distinctive differences : 1. The myelinic or medullated fibres.
2. Fibres of Remdk. 3. Ultimate fibrils. Intermediate forms,
such as have been described by various writers, under the names
of protoplasmic processes, primitive fasciculi or naked axis-
cylinders, varicose cylinders, etc., will be noticed in other con-
nections.

Myelinic fibres. — These are also known as the medullated.

HO MANUAL OF HISTOLOGY.

To the naked eye they appear white and glistening, and are
the main constituents of the peripheric nerves, though they

occur in less number in the sympathetic and also in the bruin
and cord. Each fibre is made up of three distinct parts : (a) a
central cylindrical cord, the axis-cylinder, about which is a (b)
coating of soft homogeneous fatty material, called myeline
(medulla, white substance of Schwann), forming for the axis-
cylinder a sort of tubular sheath, while exterior to both is a
delicate membrane or envelope (c), the sJieatJi of Schwann or
primitive sheath.1 These fibres run a parallel unbranching
course, except near their termini or origin, and are surrounded
by a connective-tissue coating of varying thickness. Their
diameter varies also according to their situation and the degree
of their tension or relaxation. In the nerve-trunks the average
diameter lies between ^ and ^ millimetre. In the brain they
are described as having sometimes a diameter of -^.millimetre,
but it is difficult to determine the presence of a medulla in such
small fibres.

To study the properties of a myelinic nerve, we may take a
portion of the sciatic from a frog that has just been killed.
Having removed it with care and placed it in a drop of water
on a slide, we should separate the fibres carefully with needles,
taking care not to tear them. Then adjusting a covering
glass, it will be seen that from the broken end of the nerve a
soft substance is exuding (Fig. 43, 6) ; in a few minutes it is
pushed off in the form of drops of irregular shapes (Fig. 43, c).
This material is the myeline or medulla. It will be seen to re-
fract the light strongly, and show concentric markings. It will
also be seen that each fibre has a double contour and is divided
at tolerably regular intervals by transverse divisions, which are
now known as Rangier1 s nodes. (See Fig. 47.) Midway be-
tween each node we may perhaps see an oval body surrounded
by a broad expansion of protoplasm. In a few fibres we may
even see that a fine thread-like process is projecting from the
broken ends of the nerve-fibre— the axis-cylinder (Fig. 43, d)—
while the whole fibre is enclosed by a delicate tightly investing
membrane, the sheath of Schwann. Possibly we may also see the

1 A most unfortunate source of confusion among histologists has arisen from the
use of the word neurilemma, which by some is spoken of as synonymous with
Schwann's sheath (Frey), and by others as the connective tissue which binds the
nerve-fibres together (Klein, Rutherford). We shall avoid the term altogether.

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. Ill

oblique or arrow markings (incisures of Schmidt) (Fig. 43, /),
which seem first to have been accurately described by Schmidt,
of New Orleans, later by Lantermann, of Cleveland, Shaw, and
others. The same appearances can be also obtained by the use
of iodized serum.

The double contour is not visible in all the myelinic nerves,
but is most marked where they show varicose swellings, a con-
dition that is due to a preponder-
ance of myeline at the enlarged
point. From this fact and anoth-
er, that the drops of myeline when
separated from the fibre show the
same double contour, it is argued
that the double marking in the
fibre is due to a refracting (double)
of the myeline, and has nothing to
do with the membranous sheath.
These varicosities just mentioned
are not to be confounded with the
bulgings of the ultimate fibrils, or
with the "necklace" appearances
seen in the course of the fibres of
Remak, both of which latter may
probably be regarded as artificial
productions, either from stretching
in the act of teasing or from the
imbibition of water. In the brain
of the calf they are frequently seen,
and they are said to be found in the
intracranial part of the olfactory,
optic, and acoustic nerves. The
fibres in which this change occurs
are usually quite small.

Staining in pier o-car mine. —

This reagent has been recommended by Ranvier. It is satis-
factorily prepared by Rutherford's process.1 Taking precau-
tions not to injure the nerve in removing it, mount in the solu-

1 He takes 100 c.c. of a saturated solution of picric acid. Next he prepares an
amtnoniacal solution of carmine by dissolving one gramme in a few c. c. of water,
with the aid of an excess of ammonia and heat. He then boils the picric acid solu-
tion on a sand-bath, and when boiling adds the carmine solution. The mixture is

Fia. 48.— a, Myelinic fibre In a state of
" coagulation ; " 6, myeline exuding from
the broken end of the fibre ; c, drops of mye-
line separated from the nerve-fibre ; </, nxm
cylinder ; f, nucleus of Henle's sheath ; /,
arrow markings.

112

MANUAL OF HISTOLOGY.

tion. The nuclei will then be stained a brick-red, while the
sheath of Schwann, and, in fact, the whole nerve, will be stained
yellow. It is said that, if the axis-cylinder projects, it will be
stained a bright red, though twenty-four hours may be required
to effect the staining. In my hands picro-carmine has not
proved so successful a coloring agent as some others.
(/ Staining with the nitrate of silver. — The sciatic or any
peripheral nerve may be employed. Expose it without re-
moval in a frog that has just been killed. Then dry up all
fluid from about it, and pour on a solution of the nitrate (1 to
1,000). In this way the nerve-fibres will be made rigid. They
are then to be removed with a pair of delicate scissors, and
placed in a flat vessel containing a little more of the solution.
After a few minutes the nerve will look turbid, and then it
should be cut out and washed in distilled water, and exposed
to the sunlight. In a variable time (ten to fifteen minutes) the
turbid appearance will give way to a brown coloration. Exam-
ining a single funicu-
lus or bundle in gly-
cerine, it wilt be seen
that it has an endothe-
lial coating of one or
more layers (Fig. 44).

If another funiculus
be separated with fine
needles,1 the same care
being taken to spread
the fibres apart and not
tease, and so lacerate
them, it will be seen
that each fibre con-
tains a series of Latin

crosses at certain pretty regular intervals. The transverse bar
of the cross corresponds to the "annular constriction" seen
in Ranvier's node, while the axis-cylinder forms the longitudi-
nal bar. Close observation with high powers will show that
this latter is marked by transverse lines of a dark brown or

then evaporated to dryness, the residue dissolved in 100 c.c. of water, and filtered.
If the solution is not clear, he adds more ammonia, evaporates, and then dissolves as
before.

1 Milliners' are the best

Fio. 44.— Funtculns or Nerve Bundle covered with Enrtothe-
linm (Epithelium). From the sciatic of the frog.— Hartnack.
object. 4, oc. 2.

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 113

black (Frommanrts lines). It appears probable, as Ranvier
explains, that, owing to the break in the myeline, at the " an-
nular constriction," the particles of silver gain an entrance to
the axis-cylinder at this the only unprotected spot. If the
action of the salt is long con-
tinued, the axis-cylinder is col-
ored for a somewhat longer
distance. The transverse bar
seems to be formed of two
conical segments set base to
base. The position of this bi-
conical segment usually cor-
responds in position with the
"annular constriction," but

if wrmlrl QT-»T\OQT- fVm <• tlia-tr mo-rr Fl°- 45-~ a' Ranvier"s disk ; ft, Frommann's lines ;
Id appear tnat tney may c, nucleus of interaimtilar segment.

be separated, for, when the

tissue of the nerve has been put upon the stretch, the biconical
segment may be drawn away from the annular constriction.
(See Fig. 45.)

Now, as Schwann's sheath is understood to end at the an-
nular constriction, where it is cemented to the next adjoining
segment just as epithelial cells are joined together, the biconi-
cal disk may belong to the axis-cylinder exclusively, and
merely constitute a dividing line between its segments. Ac-
cording to Engelmann, the axis-cylinder is divided up into
portions corresponding with the interannular segments.

According to Rawitz, Schwann's sheath does not end at the nodes, but is
continuous with the sheath of the adjacent interannular segment.

Staining of the nerve in osmic acid — semi-desiccation. —
Osmic acid is one of the most valuable reagents f or histological
work, and the method now to be described (a modification of
Ranvier' s ') succeeds well. Take the frog's sciatic, or any other
peripheral nerve, carefully remove a portion with the surround-
ing tissue, keep the whole extended with pins, upon a flat bit
of cork, and then dip it into a vessel containing a 1 per cent,
watery solution of osmic acid.2 The vessel is then to be exposed
to the light. The whole nerve will be more or less thoroughly

1 Lecjons sur 1'Histologie dn Systdme Nerveux, Paris, 1878.

' The solution should, of course, have been kept in a dark bottle away from the
light.

114

MANUAL OF HISTOLOGY.

stained in a few hours. The external portions, however, will
be stained in a few minutes, and they may be removed by care-
ful separation with fine needles. To mount, take a glass slide
and slip it under the nerve-fibres, while the needle is employed
to carry them up on to a dry part of the slide
where they can be placed side by side. Then
remove the excess of water with bibulous paper,
and let the fibres get so dry that they adhere
to the slide. Place about them a ring of tis-
sue-paper, so that when the cover is adjusted
it will not press upon the fibres. Fix the cover
at different points with paraflme, then put a
drop of glycerine upon one side, and a drop of
water upon the other. The union of water and
glycerine should be allowed to go on for
twenty-four hours in a damp place. The con-
strictions and arrow-markings are usually well
seen. The nuclei also are occasionally to be
found in a niche of the myeline. These bodies,
however, are better seen in specimens that have
been a short time (fifteen or twenty minutes)
in osmic acid, and then in picro-carmine a few
hours. It still is a question among histologists
whether the arrow-markings are artificial or
not ; each of the sections lying .between the
markings is called the cylindro-conical segment
(HoTilcylinder, Kuhnt). (See Fig. 43.)

Transverse sections of myelinic nerves. —
Certain points are best seen by making trans-
verse sections. Prepare the sciatic of a frog or
any of the human peripheral nerves by im-
mersing a few days in a sherry-colored solution
of bichromate of potash, or in Mueller's fluid,1
and then in 90 per cent, of alcohol, until the tis-
sue is hard enough to cut. Then it is to be
mounted in the microtome with wax and oil of
about its own consistence. Sections are to be made with the
razor; or it may be mounted in elder-pith in the following
way: bore out from the centre of the pith-cylinder a cylindri-

1 The well-known eye-fluid, of which the composition is : Bichromate of potash,
2 to 2$ grammes ; sulphate of soda, 1 gramme ; distilled water, 100 grammes.

Pio. 46. — Human
myelinic nerve : a, In-
terannular segment ; ft,
Kanvier's node ; 'c, nu-
cleus of the intcrnnnu-
lar segment sunonud-
ed by granular proto-
plasm; <t, Henle's
sheath with nucleus.

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 115

cal hole a little larger than the trunk of the nerve, then im-
merse the whole in water, and the pith will begin to swell. As
soon as it has firmly embraced the nerve, sections may be
made with the knife. Ammonia-carmine will stain the axis-
cylinder well, but the outline of the cut will appear irregular
rather than round. This appearance is doubtless artificial. In
my hands, borax-carmine ' has proved much better than the
ammonia-carmine, as it diffuses very little, and much of the
excess may be removed by dilute acetic acid (about J percent.),
in which the specimen should remain, from a few seconds to a
minute or two, until it has become bright to the eye. The fur-
ther steps in the process of making a permanent preparation
are the same as those for other specimens ; i.e., it may be
mounted in glycerine and water, or clarified by clove-oil and
mounted in dammar varnish or Canada balsam.

Preparation by tlie bichromate of ammonia. — Ranvier em-
ploys of this a 2 per cent, solution, allowing the specimen to
remain, with frequent changes of the
fluid, from two or three months to a
year. The sections are to be stained
in ammonia-carmine or picro-carmine,
and mounted in glycerine. It will
then be seen that immediately about
the axis-cylinder is a sheath. This is
called by Ranvier the sheath of Mauth-
ner, from the author who described it.
(See Fig. 46, 5.) Specimens prepared
in the ordinary way, by long immer- +£****•'• *' 8beathl
sion in Mueller's fluid alone, or sub-
sequently in the chromic acid solution (gr. ij. — § j.) and stained
with ammonia-carmine, occasionally show the same thing.

Sometimes histologists find that embedding in gum succeeds
best in securing these transverse sections of nerves. The diffi-
culty of the task is one of considerable moment. The method
is as follows : Take a fresh nerve, harden it in osmic acid (1 per
cent., if it is desirable to expedite the process, or ^ per cent,
if it is not necessary to conclude the examination the same
day). Then, when the nerve is thoroughly blackened all through,

'The powder is prepared by Eimer & Amend, of this city (205 to 211 Third
Avenue), according to Arnold's formula. The strength required is gr. xv.— 5J-
distilled water.

116 MANUAL OF HISTOLOGY.

it is to be immersed in water for a few hours ; then in 90 per
cent, alcohol, and then in a weak solution of gum-arabic,
which fills the interstices between the bundles, and finally in
strong alcohol (95 per cent.), which hardens the gum sufficiently.
The sections, cut as thin as possible, should be placed on a
slide to remove the excess of alcohol, which may be done with
filter-paper. A drop of water is then to be added ; about
the cover put a few drops of carbolized water ; remove to a
damp place. At the end of twenty-four hours the gum will
have dissolved, and then the glycerine may be allowed to enter
slowly without displacing the elements (Ranvier).

In examining such cross-sections, the medullated nerves will
present various diameters, and the contour of the myelinic
sheath will vary in width and outline according as the cut
comes through the broadest part of the arrow-marking, or
through the thin overlapping parts. (See Fig. 43.) If the cut
chances to pass close to the annular constriction, no myeline
will of course be seen. For these reasons, the cross-sections of
such nerves, when stained with osmic acid, are very different.

Modern conceptions of myelinic nerves. — The specimens
that have been studied according to the methods given will not
have shown any termination of the nerves, or any division,
either into trunks of any considerable size or into the fibrils of
which they are said to be composed. They do, however, as we
have already said, dwdd&Jboth near their origin and near their
termination. It is presumed that each fibril of which the axis-
cylinder is composed passes directly through from its point of
origin of the nerve-centres, to its final point of distribution,
without branching. It is difficult, however, with the instru-
ments in ordinary use, to see any distinct marks of fibrillation
in cross-sections of the axis-cylinder, and it is in them that we
should expect to see them best. The ideas of Ranvier are well
worthy of consideration, as he has given more form and solid-
ity to our conception of the intimate structure of a myelinic
nerve-fibre than any previous writer. According to him, each
section of nerve between the annular constrictions represents
an ultimate morphological element. It is, in fact, a tubular
cell, whose proper external portion (the membrane of the cell,
according to common phraseology) is the sheath of .Schwann,
while the myeline or medulla fills the interior, just as in adi-
pose tissue a globule of oil fills out and distends an ordinary

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 117

connective-tissue corpuscle. Each of these bodies, which he
calls an interannular segment, begins and ends at the constric-
tion. It contains a single ovoid flattened nucleus, which fills
a niche in the myeline, and is surrounded by a broad, thin ex-
pansion of protoplasm (the body of the corpuscle). The axis-
cylinder has nothing to do with this body that we have de-
scribed, except that it pierces it. Instead of stopping short at
each constriction, it goes on indefinitely. As we have already
seen, the annular constriction and the biconical disk are not
always at the same point, which argues strongly for Ranvier's
views. The myelinic sheath probably protects the delicate
fibre from external injury, but whether it also insulates it, is
problematical. In the foetus all nerves are devoid of mveliae.

Fibres of Remak. — These are called by some the amyelinic
or non-medulla ted~ Jibres, by others the pale, gray, or gelati-
nous fibres. The term Remak's fibres has come into use re-
cently as the distinctive name for certain nerve-fibres abound-
ing in the sympathetic, as distinguished from others which
also contain no myeline, and are found in the cranial portions
oTlhe optic, auditory, and olfactory nerves. .Each fibre is
marked with oval nuclei at pretty short intervals, and has an
indistinct longitudinal striation, probably the evidence of fibrils
such as are believed to exist in the axis-cylinder. The nuclei
are imbedded in a homogeneous sheath. There being no breaks
in the continuity of the fibre, there can be no sheath of Schwann
in the sense that has been described. In diameter each fibre va-
ries between -fa and Tfjr millimetre. In 1838 Remak first called
attention to them, but his views were received with disfavor.
More recently, Max Schultze, Frey, Leydig, and Henle have
joined in representing them as long, cylindrical, continuous,
slightly striated, and dotted with nuclei.

The fibres of Remak are found in great abundance in all
the nerves of the organic system, but they also exist in all the
mixed nerves, varjring with the kind of nerve and the animal.
They are not found in special nerves. The pnetimogastric of the;
cat is well adapted for the study of them, as the myelinic fibres
are present in considerable quantity, and make the mechanical
separation of the bundle easy. Associated with them, fibres are
often seen, that are shown in Fig. 48, c. They are delicate,
run a wavy course, and sometimes exhibit curious varicosities
(a), (necklace appearance). The nuclei are placed at about the

118

MANUAL OF HISTOLOGY.

same distances apart as in the other form of fibre already men-
tioned.

Preparation in osmic acid and picro-carmine.— Remove
the pneumogastric in the following way, from a cat that has
just been killed : Having exposed the nerve, slip under it in
situ a long narrow strip of cork, to which, pin down the nerve
with some adjacent tissue, all of which may be removed at

once and placed in a solution
of osmic acid (1—1,000) for
twenty-four hours ; the nerve
may then be separated from
its attachments and placed
in the picro-carmine solution
for still another twenty -four
hours. The excess of the col-
oring agent may be removed
by dipping for a few seconds
in acetic-acid solution (£ per
cent.), and then the nerve
may be placed in alcohol,
afterwards in water, and fin-
ally mounted in glycerine.
It will be seen that the nerve-
fibres are stained a reddish
yellow, while the nuclei are
brick-red. The picric-acid
yellow is apt, however, to
diffuse. Careful separation
of the fibres may show that
they branch, as shown in Fig.
48, A, B ; and yet this char-
acteristic, which Ranvier in-
sists upon, is by no means
easy to see in most of the fibres, in fact it requires much care-
ful work before it is apparent. The myelinic nerves will be dis-
tinguished by their greater average size, their dusky, granular
medulla, broken at points, and by the axis-cylinder, which,
if it does not project, may be seen winding spirally along be-
neath its medullary coat. In them, too, as a rule, each in-
terannular segment contains but one nucleus.

Preparation of RemaJc's fibres in Ticematoxylin. — One of

</ 1 000 INCH

FlG. 48. — Fibres of Remak. A, Pneumogastric
of the cat — haematoxylin specimen : a, nerve nu-
clei ; b, appearances of branching ; c, connective-
ti.ssue sheath. II, Same. Picro-carmine specimen.
The branching in this case is more evident. C,
Same — haematoxylin specimen. The necklace ap-
pearance is xhown at a.

GENERAL HISTOLOGY- OF THE NERVOUS SYSTEM. 119

the most rapid and successful methods is by the use of hsema-
toxylin. The pneumogastric nerve of a cat is removed and
immediately placed in the hsematoxylin solution ; then, after
thorough staining, which may only take a few minutes, in
dilute acetic acid (£ per cent.), and finally mounted in gly-
cerine. In this way the nuclei will be stained a beautiful pur-
ple, while the fibres will be unaffected. The number of nuclei
and absence of medulla will serve to distinguish the fibres of
Remak from the medullated. It is difficult by any method of
preparation to see that there are any precise limits to the lon-
gitudinal lines in the fibres, i.e., that the striation is due to
little, short, narrow rods, lying side by side (Ranvier). The
nitrate of silver demonstrates no transverse markings and no
constrictions or crosses. There is but little likelihood in these
specimens to mistake the fibres for connective- tissue bundles.
In the first place, the nuclei, and what cell-bodies happen to
be about them, of the one, are small, flattened, ovoid bodies
occurring at pretty regular intervals, while the connective-tis-
sue corpuscles are usually larger, longer, and, though they
may appear oat- shaped, when the side is turned to the observer,
are broad plates with irregular edges when seen flatwise. In
the second place, the fibres run their course in long, narrow
bundles, as no connective tissue does.

Ganglionic bodies. — Of these there are three kinds : 1.
Those that are connected with the spinal and some cerebral
nerves. 2. Those found in the gray substance of the brain and
spinal cord. 3. Those in the ganglia of the sympathetic sys-
tem. These bodies are of such large size that they may often
be seen with the naked eye. In the human species they are
usually in close connection with the origin of the nerves, though
they also may be interspersed at points through the course of
the fibres or may be present near their points of distribution
(ganglia of Aueroach). Their immediate connection with the
nerve-fibre is made in the following ways : 1. A large process,
which does not at first appear to branch, passes off, and is
continuous with the axis-cylinder. 2. Fine branches are given
off from one or more corpuscles, and, uniting, contrive to form
a nerve-fibre (either a fibre of Remak or a myelinic fibre). 3.
These branches after combination may pass through a gangli-
onic corpuscle, which then is called bipolar (Gerlach, Wal-
deyer). In the sympathetic system we have the unbranched

120 MANUAL OP HISTOLOGY.

process and the superficial or spiral fibre, which corresponds to
the branched fibre of the ganglionic bodies of the brain and
spinal nerves.

Ganglia of the cranial and spinal nerves.— These organs,
which appear to the naked eye as nodular enlargements of the
nerves with which they are connected, consist of groups of
peculiar large corpuscles which are interspersed among the
nerve-fibres. In shape they are usually large and ovoid, or
pear-shaped. About and between them are bands of connective
tissue studded with nuclei, forming for each separate body a
kind of capsule ; the vascular supply to them is liberal. The
contents of these bodies are soft, elastic, and beset with gran-
ules. They have a large, globular, or ovoid nucleus or nucleo-
lus, and may appear to have no process, or to be unipolar or
bipolar, as in the lower animals.1

Examination of the Gasserian ganglion in the frog. —
Take a frog that has just been killed, or, better still, one that
has been some time in Mueller' s fluid ; trace the fifth nerve
into the skull. On it will be seen, just within the bone, a yel-
low enlargement. This is to be removed with forceps and
teased with needles. The ganglionic bodies usually appear to
have no processes (apolar), but they probably have one or more,
and the apparent absence of them is because they have been
torn off in teasing.

Examinatio7i of the ganglia of the spinal cord. — Take the
cord of a bullock, and prepare it while fresh, or after it has
been a greater or less time in Mueller' s fluid, or a weak so-
lution of the bichromate of potash (gr. xv. — § j.). Having cut
it into transverse segments, the gray substance may be easily
seen. Snip out with fine curved scissors small pieces from the
anterior horns in the lumbar regions where the corpuscles are
very numerous ; if the specimen be fresh, immerse in osmic
acid (1—1,000) for twenty -four hours. Then, by careful brush-
ing in water with the camel' s-hair brush, or by teasing, or agi-
tation in a test-tube with a little distilled water, some of the
ganglkmic corpuscles will be successfully removed. They will
be seen to vaTv^ much in size, and be multipolar, i.e., they will
exhibit a very lafge number of branches (Deiter 's protoplasmic
-^——— — ^^

1 According to Key and RetHj1^ they are probably all unipolar. Stud, in der
Anat. d. Nerven-Syst., 2 Halfte, vS*""! H.'s Jahresb., 1878.

GENERAL HISTOLOGY OP THE NERVOUS SYSTEM. 121

processes) which divide and subdivide, and, it is said, form a
network which unites with a similar one proceeding from the
ganglionic bodies of the posterior roots.

There is, in addition, a single straight process (naked axis-
cylinder), which, proceeding outward, soon receives a medul-
lary sheath. The nucleus is very large and circular, and usu-
ally displays a nucleolus. The contents of the body of the
corpuscles are more or less granular, and a mass of pigment in
granules is usually seen piled up in some one portion. The
corpuscles thus separated may be preserved in glycerine and
water, or, after staining in borax-carmine, in dammar varnish
or Canada balsam. In the posterior horns the corpuscles are
similar in character, but smaller. Gerlach claims that the
ganglionic bodies of the anterior horns are connected together
through networks formed of the branching processes given off
from each. Carriere, working under Prof. Kollman, of Mu-
nich, has examined the spinal cord of the calf in the fresh con-
dition, and has satisfied himself that the ganglionic corpuscles
are connected together by their fine processes, being thus in
agreement with Stilling, Wagner, Remak, and many others.—
Arch.f. mikroskop. Anat., xiv., 2, 1877.

Ganglionic- bodies in the human brain. — Thin sections
made through the cortex. of the human brain show that there
are conical ganglionic corpuscles of medium size, whose base
is directed toward the white substance, and apex toward the
superficies. From either end processes are given off, from the
broad end several, and from the apex a single one ; both subse-
quently branch. In the upper strata the corpuscles are small-
est. Disseminated throughout this substance are two other
forms of corpuscles, one star-shaped (spider-cells),1 and the
other the lymphoid corpuscles that belong to all tissues of the
body. Possibly the spider-cells, which have a variable number
of processes, are the cells of the neuroglia. Brush-cells * have
also been described. Perhaps they should also be regarded as
a variety of the spider-cells.

Ganglionic bodies of the sympathetic system. — They occur
either singly or in groups, interspersed among the nerve-fibres,
or in lines, or form enlargements in the nerve-plexuses, as

1 Described by Jastrowitz.

"Arch. 1 mikrosk. Anat, 1874, LXI., p. 93.

122 MANUAL OP HISTOLOGY.

in the digestive tract. Preparations of the cceliac ganglion of
the frog may be made according to the methods that have al-
ready been described. The aorta and bulbus arteriosus of the
frog are recommended by Klein, and the gold method is the best
to show them. It was in these corpuscles of the green tree-frog
that Beale noticed a spiral fibre. It was a delicate one, wind-
ing round the axis-cylinder, finally going off in an opposite
direction. He also thought, from an examination of the gan-
glia in the mammalia, that the same fibre existed in them. Sub-
sequently Julius Arnold corroborated his views, and even de-
scribed a network of fibres which was connected with the
nucleolus, and extended through the corpuscle, at its final
exit forming the spinal fibre. Recent observers, however, have
failed to confirm Arnold's opinion, and even the existence of a
spiral fibre is held to be in doubt.1 These corpuscles, which are
either globular or oblong, may appear to be apolar, unipolar,
bipolar (when two processes are given off in the opposite direc-
tions), or multipolar (when two are given off in the same direc-
tion, or several are given off in various directions).

Meissner1 s plexus. — This network, named after its dis-
coverer, is situated in the submucous tissue, and consists of
nerve-bundles of medium size, which have nodular enlarge-
ments studded with nuclei at certain points. An excellent
way of securing them is the following : Take a piece of cat's
intestine, three or four inches in length ; cleanse thoroughly
by passing through it a stream of water ; then ligate one ex-
tremity. Fill an ordinary two-ounce syringe with a solution of
the chloride of gold (i°). Slip the nozzle into the other end of
the intestine, and, tying it in, inject with such force as to dis-
tend the gut to its utmost extent without bursting. Then pass
another ligature round the gut beyond the nozzle, and draw it
tight. Remove the syringe, and place the specimen in an open
vessel containing the same solution, but allowing fully one-
half of it to be uncovered by the liquid. After twenty-four
hours the part thus exposed will have taken a mauve or violet
color. Then remove from the liquid, and open with scissors,
let it partly dry, and, seizing the mucous membrane with the
forceps, tear it off in pieces. The submucous tissue will then

1 Key and Retains did not find the spiral fibre in the human species, but in the
frog occasionally. Op. cit. Many other excellent observers agree with them.

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 123

be exposed, and small bits are to be torn out in a similar way.
They may be mounted in glycerine or dammar varnish. The
nerve-trunks can be readily seen ; they will contain, on an
average, from two to three fibres perhaps, and form a large-
ineshed plexus. The ganglionic enlargement may be found
where three or four bundles meet, or in the course of a single
bundle. The diameter of the enlargement is three to five times
the size of the bundle.

AuerbacTi1 s plexus, called after its discoverer, is seen by
taking the same specimen, and tearing out thin laminse from
the muscle, at the junction of their longitudinal and trans-
verse coats. The ganglionic bodies are nodular, and contain
numerous nuclei. It is said that they may be isolated by
immersion of the muscular tissue eight to ten days in a 10 per
cent, solution of common salt. Guinea-pigs furnish the best
specimens.1 There are both coarse and fine networks.

Termination of nerves. — There are various methods which
have been described, and these are : 1, by undivided or free
endings (tendons, conjunctiva) ; 2, by end bulbs (cornea) ; 3,
by terminal loops ; 4, in corpuscles (seminal canals — Letzerich) ;
5, by networks (peritoneum) ; or, finally, 6, in a special appa-
ratus (Pacinian pr Meissner's corpuscles). When nerves termi-
nate by networks, the meshes may be formed from the medul-
lated fibres, or those of Remak, and may consist of one or more
fine fibrils. They have been found in the skin, and are to be
seen in the submucous tissue of the intestines, in the cornea,
and elsewhere. Termination by bulbs has been closely investi-
gated by Krause. The bulbs are described as having a diam-
eter of ^ millimetre, and ovoid-shaped in man, with a thin
capsule of connective tissue. One or more fibres appear to
enter the bulb, and, penetrating some distance, end in a knob.
They have been found in the conjunctiva, in the mucous mem-
brane of the floor of the rnouth, lips, soft palate, and tongue,
and in the glans penis and clitoris. In the cavity of the mouth
they are placed in the papillae. The bodies Krause has 'ob-
served in the clitoris are somewhat peculiar ; they are variously
shaped, and have a mulberry-like surface.

These corpuscles, about which there has been so much dis-
cussion, and which some excellent observers (Waldeyer, Arnold)

1 Frey : Das Mikroskop. , Leipzig, 1877.

124 MANUAL OF HISTOLOGY.

hud failed to see, were investigated a few years ago by Long-
worth, of Cincinnati, and their existence established as a matter
of no doubt. He took the human eye, freshly removed with
the conjunctiva, and made the examination immediately. At-
taching the conjunctiva with threads, so that it preserved its
natural tension, he immersed it in a £ per cent, solution of os-
mic acid, or exposed it to the vapor of the same solution.
After twelve to twenty-four hours the membrane was deeply
stained, and the epithelium could usually be removed with
a brush or the finger-nail. Next, a thin piece of cornea was
removed and examined in water, or in 1 to 2 per cent, acetic-
acid solution. It was then mounted in glycerine. This method
was preferred to the gold chloride. In some conjunctive they
were found almost entirely absent ; in others, or in certain por-
tions, quite numerous. The entire interior was seen to be filled
with nucleated corpuscles. Waldeyer, in commenting on the
work of Dr. Longworth, agreed to it fully, and retracted his
former opinions. He places these bodies intermediate between
the tactile and Pacinian bodies.

The tactile corpuscles of the skin (called also Meissner's
or Wagner's corpuscles) are to be seen in the papillae, and
especially well in the tips of the fingers, and in the internal
genitals. They have a length of about -^ millimetre. Speci-
mens hardened and preserved in the ordinary way show them
well. They are oblong, rounded, and marke4 by transverse
wavy lines. A nerve-fibre may be seen running into their
centre.

The Pacinian bodies, discovered by Vater, in 1741, but first
carefully described by Pacini, of Pisa, are oval or pear-shaped
bodies, attached to the nerves like berries to a stem. They are
found in the subcutaneous tissues of the finger (Kolliker), in
the labia majora, prostate, corpora cavernosa, and in many
other places. They are seen to the best advantage, however,
in the mesentery of the cat, where they are so large as to be
easily visible to the naked eye.

Cut out a small piece of the mesentery, place it in a weak
solution of osmic acid (1—100), and after a few minutes, when
it has become brown, detach the capsule carefully with needles.
Mounting at once in glycerine, the whole interior of the Paci-
nian will be superbty shown, constituting one of the most beau-
tiful specimens in histology. The medullated nerve may be

GENERAL HISTOLOGY OF THE NERVOUS SYSTEM. 125

seen winding in at one end (Fig. 49), covered with a dense coat-
ing of connective tissue, and accompanied by a small artery.
After penetrating a variable distance, it leaves its medulla and
is continuous with a straight fibrillated band that is called the
core. It terminates in one or more granular expansions, appar-
ently. In two cases, how-
ever, I saw the nerve passing
through the body, giving off
its medulla on entering it, and
assuming it again on leaving.
This has been observed by
Klein, Pappenheim, and oth-
ers. Round about the core,
forming a series of pretty reg-
ularly oval markings, are con-
centric tunics. Toward the
periphery they are at a pret-
ty even distance apart. Be-
tween them, applied closely
to the tunics,1 are small ovoid
nuclei. The spaces between
the lamellae are probably
filled with a clear fluid. In
my experience these bodies
are not successfully pre-
served in glycerine, even after
hardening in osmic acid. The
chloride of gold may answer
better.

Nerve - terminations in
muscle are quite easily seen.
It is only necessary to take a

1.1 F'G. 49.— Pncinian body from the cat's mesentery.

bit of muscle from the thigh

of a frog just dead, and immerse it in dilute acetic acid, and
then in glycerine. When the tissue is thoroughly transpa-
rent, as it will be in a few minutes (ten or fifteen), there will
be little difficulty in finding a medullated nerve, and then in
tracing it into a muscle-fibre. Reaching the sarcolemma, it

1 According to Schaefer, the nuclei belong to epithelioid corpuscles which cover the
tunic on both sides. Practical Histology, p. 134; Quarterly Microscop. Journ.,

1875.

126 MANUAL OF HISTOLOGY.

penetrates it at a prominence (DoyerJs eminence). From tins
point it divides into fibrils, which form delicate networks, and
one or possibly two filaments will be seen to enter an irregular
body placed in the centre -of the fibre. This body is highly
nucleated, and may without much difficulty be distinguished
from the muscle nucleus, which lies either on the bundle or in
it. This body is called the motor ial plate. It is not certain,
however, that the ultimate fibrils actually end there, for in
some instances one is in connection with one side, and one with
the other. Varicosities are described in the primitive fibrils
when osmic acid or chloride of gold is used.

Gschleiden, of Breslau, one of the most recent writers on
this subject, has traced (in the leech) the ultimate fibrils to the
cement substance between the contractile muscle-corpuscles
(unstriped muscular tissue). He never saw them end in plates
or in networks. Ganglion-cells are closely attached to the
fibres near their termination, and they may be unipolar, bi-
polar, or even multipolar, the former being the most numer-
ous.

Termination of nerves in epithelial bodies has been de-
scribed by a good many observers. The demonstration of such
endings, however, is extremely difficult. The ultimate fibrils
are liable to be confounded with elastic tissue, possibly with
connective-tissue fibres. To be quite sure of their character
they should be traced into connection with nerve-trunks, on
the one hand, or ganglionic bodies on the other.

Connective tissue of nerves. — In our description we have
adhered to the 'idea that the sheath of Schwann is the one that
immediately incloses the medulla, without any intervening
substance. Ranvier has called the first sheath, exterior to
Schwann's, " the sheath of Herile" (Fig. 43, e.)

The term perineurium is often applied to the sheaths of the
funiculus or bundle. The connective tissue separating the
funiculi in a large trunk has been called the endoneurium,
while epineurium is the great sheath of the whole trunk.
Each bundle or funiculus, the smallest element that we see in
making a gross dissection of a nerve, is covered with one or
more layers of endothelium, forming a special sheath. These
funiculi do not run parallel without anastomosing, but two,
joining, form a third, which again divides.

There is much practical difficulty in the way of giving pre-

BIBLIOGRAPHY. 127

else limits to these sheaths, from the fact that they are apt to
be continuous with one another, while one or more may be
absent, according to the size or quality of the nerve.

BIBLIOGRAPHY.

COHNHEIM. Virchow's Archiv. Vol. XXXVIII. , p. 343. 1867.

CLEVELAND. Ueber d. feineren Bau d. Markhalt. Nervenfasern. Arch. f. mikrosk.
Anat., 1870. Vol. XIII., p. 1.

SCHULTZE, MAX. Strieker's Histology, p. 117. 1872.

SCHMIDT. On the Construction of the Dark or Double-bordered Nerve-fibre.
Month. Micros. Journ., May 1, 1874.

LONGWORTH. Arch. f. mikrosk. Anat Vol. IL 1875.

SCHAEFEB. Practical Histology. Quart. Mtcr. Journ., p. 134. 1875.

KRAUSE. Arch. f. mikrosk. Anat. Vol. XII. 1876.

SHAW. Some Peculiarities in the My clinic Peripheral Nerves, etc. Jour, of Nerv.
and Ment. Dis., Jan., 1876.

GSOTLEIDEN. Arch. f. mikrosk. Anat. VoL XIV. 1877.

RANVIER. Leoons sur Thistoire du systeme nerveux. 1878.

KEY and RETZIUS. Stud, in d. Anat. d. Nerv. -Syst. V. & H.'s Jahresb. 1878.

His, W. Arch. f. Anat. u. Phys., p. 455. 1879.

RAWITZ, B. Arch. f. Anat. u. Phys. 1879.

RUMPF. Zur Histol. d. Nervenfaser, etc. Unt. d. Phys. Inst. d. Univ. Heidelberg.
Vol. II.

SCHULTZE, H. Axencylinder u. Ganglienzelle. Arch. f. Anat. u. Phys. 1879.

KCHNE, W. Zur Histol. d. motor. Nervenendig. Unt. d. phys. Inst. d. Univ. Heidel-
berg. Vol. II.

HESSE, FR. Zur Kennt. d. peripher. Markhalt. Nervenfaser. Arch. f. Anat. u.
Phys. 1879.

KUHNE, W., and STEINER, J. Beobacht. ueber Markhaltige u. Marklose Nerven-
fasern. Unt. d. Phys. Inst. d. Univ. Heidelberg. Vol. III.

His, W. Ueber d. Anfange d. peripher. Nerven- System. Arch. f. Anat. u. Phys.,
p. 455. 1879.

WALDETER. Ueber die Endig. d. sensiblen Nerven. Arch, f . mikros. Anat. Vol.
XVII., pp. 367-382. 1880.

RANVIER. Le9ons d'anat. gen. App. nerveux term. , etc. Paris, 1880.

PART II.

CHAPTER X.

MUSCULAE FIBRE.

BY THOMAS DWIGHT, M.D.,
Instructor in Topographical Anatomy and in Histology at Harvard University.

THE physiological attribute of muscular tissue is contrac-
tility. This may or may not be under the control of the will.
The structure of voluntary muscular fibre is very different from
that of the involuntary.

This distinction, however, is not absolute. The muscular
fibre of the heart presents a structure intermediate between the
two typical forms. Striped fibres are found in some places, as,
for instance, in the upper part of the oesophagus, over which
most people have little or no control. There is also an un-
doubted difference in the manner of contraction among volun-
tary muscles. Whether this is associated with a difference of
structure is an interesting but very uncertain question that
will be alluded to later.

INVOLUNTARY MUSCULAR. FIBRE.

Unstriped muscular fibre is shown with great advantage in
the bladder of the frog. It should be stained with gold chlo-
ride, logwood, or carmine.1 After the specimen has lain two

1 If one's object is to study the muscular tissue only, gold has no advantages over
the other agents, and should not be used, because it is less certain. The writer has
obtained remarkably beautiful staininga of the bladder by using carmine, following
Beale's method.

INVOLUNTARY MUSCULAR FIBRE.

129

or three days in glycerine, the lining epithelium is easily
brushed off. The bladder of the frog is peculiarly favorable,
because it affords an opportunity of studying the fibres, both

Pio. 51.

Fio. 52.

Pio. 50.— Muscular fibres treated with serum. Fio. 51. — Muscular fibres from the muscular tissue
of the intestine, isolated by means of nitric acid. FIG. 52. — Muscular fibres from a pleuritic membrane.
J. Arnold.

separately and in bundles, in its walls and in the coats of the
minute arterioles which nourish it.

The plain fibre is composed simply of one or more elongated

9

130 MANUAL OF HISTOLOGY.

cells. (Fig. 50.) The nucleus is at about the middle. The cell
swells out around the nucleus, and quickly contracts again be-
yond it. A small cell, such as is found in the wall of a small
blood-vessel, is consequently spindle-shaped, but we find many
in the frog's bladder that run out into fine threads of indefinite
length. Sometimes one end of a cell divides into two fibres.
(See Figs. 51 and 52.)

The nucleus sometimes appears to be homogeneous, though
it usually contains one or more granules, sometimes considered
to be nucleoli. When using a high power the writer has some-
times found that the nucleus contained many granules, so ar-
ranged as to suggest very strongly a transverse striation. A
row of granules at each end of the nucleus is sometimes found.
Muscular fibres in the walls of small, transparent blood-vessels
are very instructive objects, because by changing the focus we
can observe them as they curve round the vessel, both in longi-
tudinal and in transverse section. At those places where a
transverse section of one end of the cell is in focus we see what
appears to be a granule merely. If another part near the nu-
cleus is brought into focus, it shows as a small circle, while if
the nucleus happens to be cut transversely, it gives the effect
of a dark spot inside a circle.

VOLUNTARY MUSCULAR FIBRE. •

lN"o tissue-is more easily recognized than striped muscular
'fibre, yet none is more difficult to understand.1

The fibres are cylinders or irregular prisms of varying length.
Their diameter in the human body varies, according to Frey,
from .0113 to .0563 mm. Each fibre is tightly inclosed in a struc-
tureless elastic membrane, called the sarcolemma. This sheath
is not very easily demonstrated ; but if fresh muscle be roughly
picked to pieces in water, shreds of it may be seen at the torn
ends of fibres, and sometimes it can be made out where the
muscular substance has been injured in the course of a fibre.

1 Any attempt at an account of the many views that have been and are held,
would make this article far too long. A few only will be mentioned, and these inci-
dentally. It is hoped that this defect, if it be one, will be compensated for by the
fulness of the bibliography.

VOLUNTARY MUSCULAR FIBRE.

131

The existence of a sarcolemma being admitted, it is clear
that it must be highly elastic so as to accommodate itself
to the changes both of length and breadth which the fibre
undergoes. The phenomena of contraction show, moreover,
that it must be attached at definite points to the muscular
substance.

Fresh muscular fibre of a vertebrate animal, when teased
out and examined under a moderately high power, presents a
series of alternate black and white cross stripes, which are
held to be characteristic of voluntary muscle. (Fig. 53.) This
appearance is beautifully distinct in some
fibres, and very vague in others. It may
vary greatly in different parts of the same
fibre ; the stripes may run perfectly straight
across the fibre ; they may present a uni-
form curve, or they may be interrupted at
intervals, some parts of the line being in
advance of others. (See Fig. 63. )

As a fibre taken from an animal im-
mediately after death naturally draws it-
self together (without, however, necessarily
presenting the phenomena of physiologi-
cal contraction), it is desirable to ascertain
whether this modifies the appearances. To
do this, fibres from a recently killed animal should be ex-
amined in a state of extension. A cut should be made in the
body of a muscle, a few fibres teased out and stretched on the
slide under the covering glass before their attached ends are
divided.

It will be seen that the light stripe is more affected by the
stretching than the dark one, though both are broader than in
the non-extended fibre ; but the most important effect is the
appearance, often seen with high powers, of a very narrow, in-
terrupted black line in the middle of the light band.

Beside this cross striation, the fibres of vertebrates show
more or less plainly minute longitudinal lines. It is to be no-
ticed that when the cross stripes are very distinct the longitu-
dinal ones are very faint, or even invisible, and that when the
latter are well marked the former are the reverse of it. Some
reagents tend to divide a fibre into disks, others into fibrillae.
Among the former are solutions of acetic acid in water (1 in

FIG. 53. — Striped muscular
fibre : a, black stripe ; 6, in-
termediate stripe; c, white
stripe ; n, nucleus. After
Ranvier.

132 MANUAL OF HISTOLOGY.

100 — 200), hydrochloric acid (1 in 50 — 200), and among the latter
a solution of chromic acid (1 in 200). It is very probable that
the amount of longitudinal striation varies in different muscles,
being related, perhaps, to physiological properties, or possibly
the result of mechanical causes. It is certain that both kinds
of striation may be found in great perfection in fibres treated
with almost any reagent that does not destroy them. Some-
times muscle is seen to be split into fibrillae, each of which
shows the transverse stripe, though the shreds are so fine that
each disk is represented by a dot merely.1 This may be de-
tected very well in the muscle of the lobster after it has been
picked to pieces in glycerine.

Returning to the transverse stripes in vertebrates, the striae
are very near together in the frog, and thus this useful animal
is not specially desirable. The muscle of the rabbit is much
better, and human muscle is, perhaps, better still. The muscle
of the human embryo in the last months of pregnancy is par-
ticularly good. A very high power will often show the narrow
black line in the midst of the white band. Sometimes one edge
of each black stripe will be very sharply marked against the
glaring white, while the other side will present a less marked
contrast. If the stage of the microscope admits of rotation," in-
structive effects can also be obtained. As the field turns round,
the brightness at the sharp border of the black stripe gradually
decreases, to return on the other side. Again, .this change may
not occur. Sometimes, when the upper edge of the fibre is pre-
cisely in focus, the black and white stripes may be made to ap-
parently exchange places, if the lens is slightly depressed. This
is probably to be accounted for as follows : First, we may for
the present assume that the black and white bands are caused
by disks of different nature. Take a series of such disks and
imagine them somewhat inclined to one side, like a roll of
coins on their edges leaning against a support. A vertical line,
representing the line of vision, that passes through a black disk
at the upper border of the roll will strike a light one at a
deeper level. A peculiar effect may be obtained by removing
the diaphragm and employing very oblique light. The black

1 The fact that muscle removed from the body can be reduced to nbrillse does not
prove that these are pre-existing elements.

' It is to be regretted that this movement is not more common.

VOLUNTARY MUSCULAR FIBRE.

133

band then is often replaced by two narrow black lines with a
light space between them. This is more frequently observed
when the rays strike the fibre longitudinally.

The fibres of invertebrates, though on the same plan as
those of higher animals, are better fitted for study, because the
elements are farther apart, and because the phenomena of con-
traction may, in some cases, at least, be observed under the
microscope.

The muscles from the thorax and legs of large flies are very
good. Merkel recommends that they be examined in fresh al-
bumen from the egg, in which they will continue to contract.
The fibre is crossed by narrow black stripes which, be it re-
membered once for all, correspond to the black stripes of ver-
tebrate muscle. On each side of these stripes there is a bright,
glittering border, which gradually shades off into a dull band,
midway between the two stripes. The substance between the
black stripes is all of one nature, the difference between its
middle and end portions being an
optical effect. The dull band corre-
sponds to the fine line which high
powers reveal in vertebrate muscle.
Its greater breadth is due to the
greater distance of the black stripes.

Fibres from the legs and wings
of the large water-beetles (Hydro-
philus and Dy tiscus) are admirable
objects. Schafer's valuable obser-
vations were made on those of the
legs. He found the black stripe to
consist of a double row of highly
refracting granules, which were the
ends of dumb-bells embedded in the
contractile substance. These struc-
tures are arranged side by side, the

adjacent ends of the dumb-bells forming the stripe, while the
handles constitute the slight longitudinal striations. (See Fig.
54.) The bright borders are due to the refraction of light from
the spherical heads of the dumb-bells. It is clear that they
must cause a greater amount of rays to pass through the sub-
stance directly beside them than go through the substance
midway between them, which latter appears dark in conse-

Pio. 54.— Muscle of large water-beetle
(Dytiscus) : a, dull band ; 6, bright space
around ; c, the highly refractive ends of
the dumb-bells ; </, the handles of the dumb-
bells ; 5, sorcolemma. After Schiifer.

134 MANUAL OF HISTOLOGY.

quence. Some years before Schafer's theory was advanced
Heppner had shown that the bright borders of the black stripe
must be due to the reflection of rays through them from the
surface of the stripe. The phenomena observed on rotating
the stage of the microscope are in accordance with this theory.
There are, no doubt, some apparent exceptions, but these lose
their weight when we consider how many elements there are
that complicate the problem. If, for instance, as is often the
case, the disks do not present their edges quite evenly to
the eye of the observer, but are somewhat inclined, like the
roll of coins above mentioned, the conditions are at once
changed. Again, light thrown up vertically through a small
diaphragm must produce different effects on the object from
light striking it very obliquely.

Some years ago the writer was fortunate enough to discover
an excellent object for the study of living muscular fibre in the
detached legs of the Gyrinus. This is a small beetle, known
in the country as the "lucky bug," which describes most ec-
centric figures on the surface of ponds. A leg should be cut
off close to the body, and examined in a drop of water under a
very thin covering glass. The shell is transparent, and as the
muscles are undisturbed, except in the segment cut in remov-
ing the leg, they are in a perfectly normal condition, lacking
only their vascular and nervous supply. They will frequently
contract for more than an hour, if the covering^ glass be lightly
tapped occasionally. The part of the leg known as the tibia,
which is easily recognized by a large Y-shaped air-tube, has
the thinnest shell, and is usually the best place for study,
though occasionally better views are obtained in the two parts
next above it, in which it is easier to find a single layer of fibres.
The leg is very apt to flex itself between the femur and tibia,
thus obscuring one of the best places. If necessary, this can
be prevented by putting a thin piece of paper against the inner
side of the leg. The anterior pair of legs, which project for-
ward, are made on another plan, and are less desirable. A
very high power is necessary, as, for instance, Hartnack's 10
immersion lens. Much practice also is needed to follow the
steps of contraction, and indeed this can be done only when it
has become very slow.

The fibre, when at rest and moderately stretched, appears
to be a cylinder with straight edges, and composed of a semi-

VOLUNTARY MUSCULAR FIBRE.

135

fluid, transparent ground-substance. This is crossed by the
black stripes with shining borders, such as have been described.
The black stripe usually appears
granular, and may be divided into
two parallel rows of granules. Some-
times the two borders are equally
bright ; sometimes one much out-
shines the other. Some fibres are
found which, not being subjected
to any tension, are much more
drawn together. The black bands
are, perhaps, only half so far apart
as in the case just described. They
are never divided into two, and
though some appear granular,
others are homogeneous. The edges
of the fibre are no longer straight,
but slightly scalloped, the centre
of each projection being midway
between the black stripes. (See
Fig. 55.)

When active contraction takes
place, the whole fibre is involved,
and presents nothing but a series
of transverse black and white bands
with scalloped edges. To study the
successive stages of contraction we
must wait until it is feeble and in-
volves but a small part of the fibre.
It runs like a wave from one end of
the fibre to the other, pauses a mo-
ment, and then runs back again,
and sometimes starts anew, but with
diminished force. It is hard to fol-
low the steps, for the elements are
changing their shape and position
at the same time ; the black stripes
become broader, less granular, and
each runs toward its neighbor in
the direction of the wave ; the gray
edge of the fibre bulges. As the

Pro. 56. — Semi-diagrammatic reprfr.
sentations of muscular fibres of (lyrinus.
Fibre supposed to be in situ and, showing
the different appearances which the black
stripe may present. The wave of contrac-
tion is travelling toward A. At C we
notice that a part of the fibre, after con-
traction, has been subjected to stretching
after the passage of the wave ; at B the
elements are in a state of active contrac-
tion. The longitudinal striation made
unavoidable in the woodcut, does not, aa a
rule, exist in the living fibre.

band disappears, and the
elements in front of the

136 MANUAL OF HISTOLOGY.

wave enter into the contracted condition, those behind as-
sume their normal state at first, but do not retain it, for they
are immediately subject to a severe stretching by the course
of the wave, and present 'new and very instructive appear-
ances. The fibre becomes much narrower, the black stripes
are resolved into two rows of granules some
distance apart. The whole substance of the
fibre is lighter than in the other conditions,
and though the bright borders of the stripes
are still there, they are much less glaring, and
present less contrast with the intermediate por-
tion.

In some of these fibres an indistinct longi-
tudinal striation is seen, but the writer is not
satisfied that it is in the substance of the fibre.
_ Transverse sections of muscle have been ap-

Fio. 58. — Trans- •

verse section of frozen peaied. to for elucidation of the structure of the

frogs muscle show- f

irvgcohnhetm's areas. gbre> Cohnheim showed B, network of whitish
lines surrounding small, dull-colored polygons
on cross-cuts of frozen muscle (Fig. 56). The muscles of the
crab are said to show this particularly well. Schafer found
in the muscles of the water-beetle the appearance of granules
on a clear ground. A similar appearance is seen in the fibres
of vertebrates. The writer has observed in the cross-section of
fibres from the tongue of the mocassin snake, granules which
presented, at least, the suggestion of bright points in their cen-
tre. In some fibres these were collected into groups, separated
by clear spaces.

Cohnheim's areas cannot be considered equivalent to fibril-
lae, but rather, as Kolliker claims, to bundles of them, sup-
posing always, we would add, that fibrillse exist at all. It is
pointed out in the account of the transverse striae that these
are often interrupted, and there is no doubt that this may be
due to the limits of the muscle-columns. Of course, we must
assume that there are many more columns than would be in-
ferred from these interruptions ; for if the transverse stripes of
two neighboring columns exactly correspond, no break will
appear.

Nuclei and muscle-corpuscles. — In mammalian muscle acetic
acid demonstrates a number of oval nuclei which may contain
one or more uucleoli. Their long axis runs in the same direc-

VOLUNTARY MUSCULAR FIBRE. 137

tion as that of the fibre. A small amount of granular matter
may be seen at their extremities. Cross cuts of fibres show
that, with possibly some exceptions, they lie directly beneath
the sarcolemma. In the frog, and in many invertebrates, as the
beetles, they lie in the substance of the fibre, and, especially
in the latter class of animals, are surrounded by a mass of
granular protoplasm. Weber denies that in the adult frog
they are surrounded by this mass.

Conclusions. — From what precedes, it seems demonstrated
that striped muscular fibre consists of a transparent, semifluid
ground-substance, which is the contractile element. At certain
intervals a double layer of minute granules or spherules is
placed, which practically forms a transverse disk. The refrac-
tion of the light causes the substance bordering this disk to
appear brighter than the intermediate portion, which is only
occasionally seen in mammalian muscle as an indistinct and
usually a broken line, because the black stripes are so near to-
gether that the bright borders of two neighboring ones coalesce.
In invertebrates, as beetles, for instance, they are so far apart
that the dim stripe is proportionally broad, but it necessarily
disappears when by contraction the black stripes are brought
nearer together. Variations in the direction of the light, or
any obliquity of the disks, will cause peculiar effects, well-
nigh defying analysis. The writer's views coincide, in the main,
with Schafer's, except that he cannot accept the "handles" of
the latter's dumb-bell-shaped structures. As the writer has
stated in another paper, muscles in the leg of the Gyrinus
which have been exhausted by electricity show the stripes very
indistinctly, and contain a number of stray granules. Klein
has pointed out that if fresh muscular fibre of the frog is
teased out in salt solution, when a break of the substance oc-
curs inside the sarcolemma, " inside this tube a greater or less
number of granules are observed in active molecular move-
ment." These observations appear to confirm the views given
above.

A good deal has been written about the effect of polarized
light on muscular fibre, and very different results have been
reached. Ranvier thinks it of no value in the discussion, be-
' cause the same substance may be either doubly or singly re-
fracting, according to the pressure to which it is subjected.
This is certainly a strong argument against its value, espe-

138 MANUAL OF HISTOLOGY.

cially in view of the discrepancy of the observations made

with it.

Each fibre is, moreover, divided longitudinally into a vary-
ing number of what are called muscle-columns, held together
probably by a delicate cement. Between these are lodged the
muscle-corpuscles in the lower forms of animals. In opposition
to most authorities, the writer is inclined to question the exist-
ence of fibrillse in the living muscle, at all events, as essential
parts of its structure. The granular appearance of cross sec-
tions is in accord with the views given above, and does not
necessarily imply the presence of fibrillse.

Peculiarities of voluntary muscles of different functions.
— Ranvier was the first to discover a physiological and struc-
tural difference in the red and white muscles of the rabbit' s
leg and in some other animals where both kinds exist. He
found that the semitendinosus of the rabbit, a red muscle, if
acted on by an induction current, gradually contracted till it
became tetanized, and remained so until the current was
stopped, when it gradually relaxed. White muscles, on the
other hand, when treated in the same way, contracted sud-
denly, and continued to give jerks corresponding to the inter-
ruptions of the current as long as it was continued. With its
cessation the muscle instantly returned to its original length.
From this he concludes that the white muscles are those of
sudden action, while the red ones serve to regulate power and
to maintain equilibrium. As to structure, he found out that
the white muscles had a very distinct transverse striation, and
a very faint longitudinal one, while in the red the longitudinal
lines were very marked, interrupting the cross ones at many
points, and giving the fibre a granular appearance. The nu-
clei were much more numerous in the red fibres, and, instead
of being flattened and situated just beneath the sarcolemma, as
in the white, were oval and projected into the fibre, some even
lying in its interior.

Ranvier showed later that the vascular supply of the red
muscles differed from the usual arrangement, which consists
simply in elongated meshes of capillaries in the main parallel
with the fibres. In red muscle, not only were the minute ves-
sels more numerous, but the longitudinal capillaries were more
varicose, the meshes nearly as broad as long, and the transverse
vessels, both of the capillaries and small veins, presented fusi-

VOLUNTARY MUSCULAR FIBRE.

130

form dilatations, the object being, as he points out, to keep the
muscle supplied with oxygen during its long-continued con-
traction, which must interrupt the circulation.

E. Meyer has since shown that Ranvier was over-hasty in
his generalization. What is true of the semitendinosus of the
rabbit is not necessarily true of other red muscles.

The writer is able to confirm this statement. As to the dif-
ference between the semitendinosus and white muscle, he is in-
clined to admit the greater number of nuclei of the former, but
the difference in the stripes did not seem to him conclusive.
The peculiarity, however, of the minute blood-vessels of the
semiteudinosus is very striking ; but in another red muscle of
the rabbit's thigh he did not find the same arrangement. The
richness of the capillary network varies greatly in different
muscles of the same animal. Future investigations will, per-
haps, show that modifications in the arrangement of the minute
blood-vessels correspond with the
function of the muscle.

The termination of muscle in ten-
don.— This occurs in several ways.
Sometimes the fibre divides again and
again, ending jn small bundles of
fibrillse which have lost all muscular
characteristics. Again, instead of
spreading out, a fibre may become
pointed, and the enveloping sarco-
lemma, reinforced with more or less
fibrous tissue, runs on as a delicate
tendon. Both these modes of end-
ing can be seen in the tongue.1 The
cases in which a fibre loses its stria-
tion, and is apparently continued as
a tendon of about the same size,
present greater difficulties. By sep-
arating the fibres of a frog killed

by immersion in hot water, Ranvier has succeeded in demon-
strating that the sarcolemma incloses the tendinous end of the
fibre. The whole subject, however, of the ending of the fibres
is not exhausted.

1 Thin sections of the hardened tongue of a small animal are to be recommended,
not only for the study of this point, but for that of striped muscle in general.

Fio. 57. — Anastomosing muscular
fibre of the heart, seen in a longitudinal
section. On the right, the limits of the
separate cells with their nuclei are ex-
hibited somewhat diagrammatically.
After Schweigger-Seidel. J. Arnold.

140 MANUAL OF HISTOLOGY.

TJie muscular fibre of the 7ieart.—This is transitional in
structure between the voluntary and the involuntary. The
fibres of the Ircart of the frog resemble chiefly the latter, being
made of elongated, narrow, nucleated cells, which differ from
it only in being transversely striped. In the mammalia the
fibres are broader and composed of nucleated cells placed end
to end. These cells frequently give off lateral processes which
support others, thus forming a network of fibres. The cells
have both a longitudinaland a transverse series of stripes,
but the latter are not so clear as in well-marked voluntary
muscle.

BIBLIOGRAPHY.

BOWMAN. On the Structure and Movements of Voluntary Muscle. Philosoph.

Transactions. 1840-41.

AMICI. Ueber die Muskelfaser. Virchow's Archiv. Bd. XVI. 1859.
WEISMANN. Ueber die Muskulatur des Herzens beim Menschen und in der Thier-

reihe. Reichert & Du Bois-Reymond's Archiv. 1861.
IBID. Ueber die Verbindung der Muskelfasern mit ibren Ansatzpunkten. Zeit-

schrift fur ration. Medicin. 3te Reihe. Bd. XII. 1861.
COHXIIEIM. Ueber den f eineren Bau der quergestreiften Muskelfaser. Virchow's

Archiv. Bd. XXXIV. 1865.

DWIGHT. The Structure and Action of Striated Muscular Fibre. Proceedings Bos-
ton Soc. Nat. Hist Vol. XVI. 1873.
SCHAEFER. On the Minute Structure of the Leg Muscles of the Water-Beetle.

Philos. Transact. 1873.
ENOELMANN. Mikroskopische Untersuchungen iiber die quergestreifte Muskelsub-

stanz. Pfliiger's Archiv. Bd. VII. 1873.
Ho M.IK KK. Handbuch der Gewebelehre. Leipzig, 1867.
HENBEN. Arbeiten aus dem Kieler physiologischen Institut. 1868.
HEPFNER. Ueber ein Eigenthumliches Verhalten der quergestreiften Muskelfaser.

Archiv fiir mikroscop. Anat. Bd. V. 1869.
DOENITZ. Beitrage ziir Kenntniss der quergestreiften Muskelfaser. Reichert & Du

Bois-Reymond's Archiv. 1871.

SCBWEIGER-SEIDEL. The Heart. Strieker's Histology. 1872.
MERKEL. Der quergestreifte MuskeL Archiv fiir mikro. Anatomie. Bd. VIII.

1872.
BHUKCKE, E. The Behavior of Muscular Fibres when examined by Polarized Light.

Strieker's Histology. 1872.
SACHS. Die quergestreifte Muskelfaser. Reichert & Du Bois-Reymond's Archiv.

1872.
WAGENKR. Ueber die quergestreifte Muskelfibrille. Archiv fiir mikro. Anat. Bd.

IX. 1873.

BIBLIOGRAPHY. 141

IBID. Ueber einige Erscheinungen an den Muskeln lebendiger Corethra plumicornis-
larven. Archiv. fur mikro. Anat. Bd. X. 1874.

KAUFMANN. Ueber Contraction der Muskelfaser. Reichert & Du Bois-Reymond's
Archiv. 1874.

THIN. On the Minute Anatomy of Muscle and Tendon. Edinburgh Medical Jour-
nal. Sept., 1874.

WEBER. Note sur les noyaux dee muscles strips chez la grenouille adulte. Archives
de physiologic. 1874.

RANVIER. De quelques fait relatifs a 1'histologie et.a la physiologic des muscles
stries. Archives de phyg. 1874.

IBID. Note sur les vaisseaux Banguins et la circulation dans les muscles rouges.
Archives de phys. 1874.

IBID. Traite technique d'histologie. Paris, 1875.

FBEDERICQ. Generation et structure du tissu musculaire. Bruxelles, 1875.

MEYEK. Ueber rothe und blase quergestreifte Muskeln. Reichert & Du Bois-
Reymond's Archiv. 1875.

FREDERICQ. Note sur la contraction dea muscles stries ohez 1'hydrophile. Bulletin
Acad. Roy. de Belgique. Tome XL. 1877.

RENATJT. Note sur les disques accessoires des disques minces dans les muscles
stries. Compt. rend. Tome LXXXV. No. 21. 1877.

BIEDERMANN. Zur Lehre vom Bau der quergestreif ten Muskelfaser. Wiener Acad.
Sitzungsbericht. Bd. LXXXV. No. 21. 1877.

SCHAEFER. Quain's Anatomy. Eighth edition. New York: Wm. Wood & Co.
1878.

NASSE. Zur microscopischen Untersuchung. des quergestreiften Muskels. Pfliiger's
Archiv. Bd. XVII. 1878.

FROBIEP. Ueber das. Sarcolemm und' die Muskelkerne. Archiv fiir Anatomic und
Entwickelungsgeschichte. 1878.

ENGELMANN. Nouvelles recherches sur les phenomenes microscopique de la con-
traction musculaire. Archives Neanderlaises des Sciences exactes et natu-
relles. 1878.

FLEMMING. Ueber Formen und Bedeutung der organischen Muskelzellen. Zeit-
schrift fiir wissenschaftliche Zoologie. XXX. Supplement. 1878.

UNGER. Untersnchungen iiber die quergestreiften Muskelfasern des lebenden Thiers.
Wiener medinische Jahrbiicher. 1879. (Largely pathological.)

NETYMAN. New Theory of Contraction of Striated Muscle, and Demonstration of
the Composition of the Broad Dark Bands. Journal of Anatomy and Physi-
ology. Vol. XIII. 1879.

CHITTENDEN. Histochemische Untersuchungen iiber das Sarcolemm und einige
verwandten Membranen. Untersuchungen aus der Physiol. Institut der Uni-
versitat Heidelberg. Bd. III. 1879.

KLEIN and SMITH. Atlas of Histology. Part V. 1879-80.

RANVIER. Legons d'anatomie generate sur le systeme musculaire. Paris, 1880.

CHAPTER XL

THE BLOOD-VESSELS.

BY EDMUND C. WENDT, M.D.,

Curator of St. Francis' Hospital, New York City, etc.

IN man, a closed circuit of branching tubes, which proceed
from a central organ, the heart, and, ramifying throughout the
body, return the blood to this central organ, constitutes the
blood- vascular system, as it has been named.

Of these vessels we recognize three different kinds : arteries,
capillaries, and veins. The arteries convey the blood to the
various capillary districts, whence it is again collected and car-
ried back to the heart by the veins.

The arteries, highly elastic throughout, are composed of
three superimposed layers or tunics. The veins, less elastic,
and consequently more flaccid and compressible^ likewise con-
sist of three coats or tunics. In both sets of vessels these
coats have received the names of intima for the inner, media
for the middle, and adventitia for the external layer. The
capillaries, intervening between the two, form minute branch-
ing tubules, which generally have but a single exceedingly
thin and permeable membrane as the sole constituent of their
walls.

Of course, all these vessels merge into one another, so that
a sharp line of demarcation can nowhere be drawn ; but in
their typical forms they present clearly defined structural dif-
ferences, necessitating a separate description of them. We
begin with the simplest and yet most important class :

The capillary blood-vessels. — They are composed, as we
have already said, of a single layer of cells, arranged in tubu-
lar form, and containing nuclei. These corpuscles are di-
rectly continuous, on the one hand, with the inner coat of

THE BLOOD-VESSELS. 143

the terminal arteries, and, on the other, with the intima of the
veins, hence also with the lining membrane of the heart. They
are called endothelia, and since they constitute the only struc-
tural elements which enter into the composition of all blood-
vessels, we will first consider them and their relations to these
vessels.

The vascular endothelium. — Histologists understand by
the term endothelium a thin layer of flattened cells lining the
free surface of various membranes, canals, sheaths, and cavi-
ties, all belonging to the serous type. Epithelium, on the
other hand, is found covering the skin and mucous surfaces.
All endothelia, in common with the blood, the blood-vessels,
and connective tissues, are derived from the mesoblast, or mid-
dle of the three fundamental layers of the embryo. The epi-
thelia, it will be remembered, originate in the two other layers,
called epiblast and hypoblast, respectively — the former being
the superior and the latter the inferior layer of the embryo.

In adult human subjects the vascular endothelia are made
up of thin, polygonal, sometimes irregularly pentagonal, flat-
tened cell-plates. Most of the elements are furnished with a
rounded or ovoid nucleus, of central or more or less peripheral
location (Fig. 58). Some have two nuclei. In general, the cells
are somewhat elongated in the longitudinal direction of the ves-
sel to which they belong. They also grow slightly narrower as
the calibre of the vessel decreases. Their borders are serrated
or scalloped, and dove-tailed into one another. An albuminoid
substance, ordinarily invisible, cements their- adjoining edges.
This substance has the peculiar property of effecting an ener-
getic reduction of silver nitrate. Hence, by proper manage-
ment, the outlines of each individual cell may be made visible
as a black zigzag surrounding a nucleus. Every cell represents
a plate-like expanse of modified protoplasm. Remnants of this
original substance may be seen to surround the nuclei of young
vessels, where they appear in the shape of varying quantities
of distinctly granular matter. Klein has described an intra-
cellular network, formed by plexuses of minute fibrils, and
associated with a second denser reticulum within the nucleus,
called the intranuclear network. Whatever interpretation we
choose to give these minute structures, the fact of their exist-
ence is indisputable. In man, however, their presence is not
as readily demonstrable as in animals.

144

MANUAL OF HISTOLOGY.

An isolated endothelial cell, when tilted up on its edge, pre-
sents the appearance of a straight or curved double contour,
with a central thickening corresponding to its nucleus. Viewed
en face, we observe the sinuous outline and the central or ec-
centric nucleus, with its surrounding granules of protoplasm.
The shape and contour of endothelial cells are subject to con-

a.

c •

Via. 58.— Endothelirfm of the carotid artery of man, after treatment with nitrate of silver: o, cells;
6, clearer, c, darker intermediate spaces ; d, intra-cellular circular and spotted markings. Eberth.

siderable variations in the different vascular districts. Such
differences also occur in the same district, with the varying de-
gree of expansion or contraction of the particular vessel under
observation.

TJie capillaries proper. — In point of wideness of distribu-
tion, this variety of blood-vessels greatly exceeds all others.
Indeed, the capillaries occupy a rank, in this respect, second
only to the connective-tissue group of histological struc-
tures. As regards importance to the economy, it will only be
necessary to advert to the vital processes of nutrition, secre-
tion, respiration, and excretion, to recall the quality and
extent of their physiological usefulness. Throughout the

THE BLOOD-VESSELS.

145

body ' capillary plexuses are interposed between arteries and
veins, which constitute a series of conveying and returning
tubes. Thereby the direct continuity of these blood-channels
is established.

It is in these intermediate territories, and in them only, that
the blood serves its true function of giving and taking. True
markets of exchange, then, these capillary districts, where the
system is supplied with new material, and in
return gets rid of useless or even deleterious
by-products of tissue-life. Hence, the para-
mount importance of these vessels in the
maintenance of life and health. Hence, also,
the direct practical utility of knowing their
minute anatoni}^ and physiological dignity.
Every practitioner of medicine will see the
important relation this branch of histology
holds to pathology, and therefore to thera-
peutics. At the same time we should not
forget that the role played b}r the capillaries
in the system is normally due to the inherent
mechanical and physical properties of a fine-
ly elastic animal membrane, rather than to
any specific action of their cellular constitu-
ents.

Robin, following Henle's example, dis-
tinguishes several varieties of these vessels. It
seems to me proper to limit the term capil-
laries to those minute tubules which are
entirely devoid of muscular elements. This
corresponds to the classification adopted by
Virchow, Kolliker, Eberth, Ranvier, Frey,
and others. It is the one therefore that has
generally been accepted, and is both simple
and logical.

The diameter of these tubules varies from
0.0045 to 0.0115 mm. Their structure is readily understood.
Examined in the living animal with a high power, we see mere-
ly a delicate, hyaline, double-contoured membrane, having an

1 Hoyer has shown that a direct communication of arterioles with venules occurs
normally in the tips of the fingers, the matrix of the nails, the tip of the nose, and
various other parts.
10

Pio. 59. — A rather Inrce
capillary from the hyaloid
of the frog, presenting a
membranous and nucleated
tunica adventitia. Eberth.

146

MANUAL OF HISTOLOGY.

average thickness of 1 to 2 micro-millimetres (0.001 — 0.002
mm.). This membrane forms a tubule, the parietes of which
are studded at intervals with rounded or oval nuclei, often
containing one or more bright nucleoli. When oval, these nu-
clei have their long axis parallel with the direction of the ves-
sel. Their average size is 0.0056 to 0.0074 mm. They possess
the property of eagerly imbibing most of the staining fluids
employed in histology, and of resisting the action of dilute
acids, alkalies, and other reagents. (See Fig. 59.)

Besides nuclei, the capillary wall contains at various points
peculiar granules, which indicate its protoplasmic nature. In
addition, Strieker and Eberth have described lateral processes
and pointed prolongations jutting out from the parietes of the

Fio. 60. — Capillaries of the lungs of the frog, with irregularly dentated cells : a, vascular meshes.
Eberth.

capillary tubes. In growing tissue these are readily demonstra-
ble, often forming thread-like connecting bridges between neigh-
boring vessels ; at a later period they are hollowed out into
true capillaries. The shorter sprouts are also protoplasmic
buds, capable of further development into similar vessels. (See
Fig. 61.) By employing weak solutions of silver nitrate, the
capillary-wall may be shown to consist of variously shaped
areas, each one corresponding to a nucleated cell. They are
the endothelia, and represent, as already stated, the sole essen-
tial constituents of all capillaries. Their form varies with the
calibre of the vessel, the smaller capillaries being composed of

THE BLOOD-VESSELS.

147

D,

corpuscles which are comparatively narrow, the larger vessels
having broader cells. In man they have an average length of
0.0756—0.0977 mm., and an average breadth of 0.01—0.05 mm.
The intercellular boundaries, brought out as dark lines by
means of the silver salt, frequently exhibit little nodular swell-
ings. (See Fig. 58.)

In addition to the ordinary endothelia, we find smaller
areas, generally without nuclei ; they have rounded or some-
what dentate contours,
and are interposed be-
tween the other cells.
Eberth believes that
some of these intercal-
ated areas, as Auerbach
has called them, proba-
bly correspond to por-
tions of strangulated vas-
cular cells. It is more
logical to regard them as
the remnants of an in-
complete endothelial des-
quamation, a process
which is of physiologi-
cal occurrence through-
out the blood-vessels.
These remaining bits are
finally destined to be-
come quite detached
from the vascular wall, and are then swept away by the rush
and flow of the blood-current. The detached portions of such
endothelia and their nuclei appear as free granules in the blood,
where they have puzzled many observers, and have been vari-
ously called microcytes, hcematoblasts, etc. From this descrip-
tion it is plain that Cohnheim's view, that these spaces are
openings or stomata, is not sustained. True, we find in serous
membranes of certain animals real openings, but these always
appear of rounded shape, and are, to say the least, not com-
monly observed in human blood-vessels. This statement of
the case does not militate against Cohnheim's well-known
views that the corpuscles emigrate through the vessels, for,
remembering the protoplasmic nature of the endothelial tubes,

FIG. 61. — A,A, stellate connective-tissue cells connected by
B,B, delicate protoplasmic threads to C,C, sprouts of endothe-
lial tubes ; D, protoplasm connecting two capillaries ; E, nu-
cleus imbedded in a primitive sprout of protoplasm, budding
from wall of capillary. Specimen prepared by silver nitrate.

148 MANUAL OF HISTOLOGY.

we can readily account for the phenomena in question. The
capillary-wall is elastic, extremely thin, and permeable. By
virtue of these qualities, it may allow the passage of a leu-
cocyte or colored globule through its substance without suf-
fering a permanent breach of continuity.

The writer's views on endothelial desquamation as a normal process of physi-
ological import may strike the reader as insufficiently substantiated by known
facts. But when we remember that similar processes have been actually ob-
served taking place under the microscope, all doubts as to the probability of
this endothelial desquamation should vanish. The author refers to the recent
observations of Altmann (Arch./, mikros. Anat., Vol. XVI., p. 111). This his-
tologist investigated the changes which take place in the serous epithelium
(i.e., endothelium) of the exposed frog's mesentery. Multiple swellings of the
endothelia were seen to occur ; then portions of these cells would become de-
tached. Such detached bits were found to resemble in their appearance ordi-
nary leucocytes. But, in spite of this apparent breaking up of the endo-
thelia into these nucleated corpuscles, they often retained their individuality
unaltered. The production of bodies resembling leucocytes from endothelia
has, therefore, been actually observed in connection with serous membranes,
and vascular desquamation is essentially the same process.

The capillary blood-vessels occupy the interstitial connec-
tive tissue of organs, without entering their parenchyma proper.
Cartilage, the teeth, the hairs and nails, the cornea, and cer-
tain structures of the nervous system and organs of special
sense are devoid of capillary supply.

Most of the larger tubes are invested by a 'delicate, exter-
nal, sheath-like structure, called the capillary adventitia or
vascular perUhelium. It is composed of a rather close net-
work of delicate connective- tissue librils. Prolongations of pe-
culiar stellate cells, which clasp the capillary-tube, may some-
times be seen to join these fibrils. (Fig. 62.) Such branching
cells are also encountered at some distance from the capillaries.
They show delicate processes, which may anastomose with the
offshoots of the adv.entitial corpuscles. In other places we
only find external plates of connective-tissue cells (Krause's ino-
blasts), which have become more or less fused with the capil-
lary-wall. In many instances the perithelium is inseparable
from the connective-tissue stroma surrounding the vessel.

In reference to the manner of anastomosis, the forms and
modes of ramification of different networks vary with the dif-
ferent tissues and organs of the body. Hence, a simple in-

THE BLOOD-VESSELS.

149

spection of capillary reticula will generally enable us to decide
the nature of the tissue or organ in question. From a physio-
logical point of view, we recognize a causal relation between
high capillary development and great functional activity.
Therefore, the abundance of capillaries will determine the
physiological importance of an organ.

The chief forms of ramification may be grouped as follows :
1. Loops (a), simple or compound; e.g., the skin and the hard

FIG. 62.— Capillaries from the hyaloid membrane of the frog : o,a, capillary-wall ; b,f>, nuclei of the

mme ; c,c. cells of the tunica aciventitia ; <i,rf, processes of these cells clasping the capillary-wall ; «, stel-
late cell anastomosing with the cells of the tunica adventitia. Eberth.

palate ; (b) reticulated (the intestinal villi). 2. Tufts (the kid-
ney). 3. Irregularly polygonal networks (the glands and the
mucous membranes). 4. Rounded reticula, with round or
polygonal meshes (adipose tissue). 5. Reticula with elongated
meshes (the muscles, bones, and tendons). There would be a
certain satisfaction in knowing that this or that vessel had a
precise breadth, and its coat a certain thickness. The precision
would be apparent, however, rather than real, because such

150

MANUAL OF HISTOLOGY.

measurements vary greatly at different times in the same ani-
mal, and even more so in different animals. It may be stated,
in general, that the calibre corresponds to the size of the largest
blood-globules. In man, therefore, we have an average diam-
eter of about 0.007 mm. The largest capillaries exist in the
mucous membrane of the stomach and colon, the periosteum
and bones, and the pituitary body. The smallest are found in
the skin, the small intestine, the lungs, the muscles, the gray
substance of the brain, and the retina (Valentin, Weber, and
Henle).

The genesis, reproduction, and regeneration of capillaries.
— There is still much uncertainty about the mode in which
blood-vessels are first formed in the embryo. My personal

Pio. 63. — Growth and development of capillaries by nucleated sprouts of protoplasm : A, poly-nucle-
ated large sprout with filiform process ; B,B. blood-globules; C, branched cell ; D, delicate protoplasmic
tendril linking C with E, a smaller mono- nucleated sprout of endothelial wall.

observations on this subject, while working recently under the
supervision of Kolliker, appear to confirm the view held by
Foster and Balfour. These authors' account .of the interesting
process may be summed up as follows : About the second day
of incubation in the chick, certain mesoblastic cells send out
solid processes, which, uniting, form a protoplasmic network
containing nuclei. A majority of the latter acquire a reddish
tint, and are ultimately transformed into colored blood-glob-
ules. Other nuclei, however, remain unaltered, and, receiving
an investment of protoplasm, form walls inclosing the reddened

THE BLOOD-VESSELS. 151

nuclei. The protoplasm of these central nuclei rapidly becomes
liquefied, thus forming the blood-plasma. And now we have a
system of communicating tubules, containing corpuscles float-
ing in a plasma, their walls consisting of nucleated cells.
Hence, the blood-vessels do not arise as intercellular spaces,
but are hollowed out to form channels in an originally solid
reticulum of protoplasm derived from mesoblastic cells.

This explanation of the way in which vessels are formed
aids us in understanding both how capillaries are reproduced
in the adult, and their regeneration under pathological condi-
tions. The capillary-wall itself, under the influence of favor-
ing circumstances, begins to bud, as it were ; the delicate proto-
plasmic sprouts send out more delicate filaments, which, uniting
with similar offshoots from neighboring vessels, establish a
connection between two capillaries. In due time these solid
structures undergo the familiar process of hollowing out, and
the newly formed vessel is complete. Frequently the proto-
plasmic threads communicate, forming a reticulum which Ran-
vier has called nasoformative network. This author also ob-
served that capillaries develop from special cells, termed
vasoformative cells. They resemble leucocytes, and form by
their prolongations a network of solid protoplasm. This is
originally quite independent of already existing capillaries.
Subsequently, however, a consolidation is effected, and the
blood then flows through these new channels in the usual
manner.

The author has been able to trace collections of emigrated
leucocytes through various stages of progressive development,
culminating in the formation of true capillaries. The experi-
mental investigations on this subject were carried out in Pro-
fessor v. Rindfleisch's laboratory, and have been fully described
by his former assistant, Dr. Ziegler, of Wurzburg.

The arteries. — If we follow the capillaries in a direction
toward the heart, we soon find the endothelial tube receiving
an investment of unstriped muscle-cells. These are wound
transversely or obliquely around the capillary, thus forming a
second tube, as it were, surrounding the first. External to the
muscular layer there appears some connective tissue, mingling
with which elastic elements may be observed. The direction
of these additional fibres is mainly longitudinal. They form
the third or external coat, called the adventilia, the second or

152

MANUAL OF HISTOLOGY.

middle being represented by the muscle- cells, and the first or
internal by the endothelial tube. The latter now receives the
name of intima. When the layers of its walls are arranged in
this simple manner the vessel is called an arteriole, and this
constitutes the type of all arteries.

Arterioles, however, commonly contain a few additional
fibres between the intima and the media, as the first indication
of what afterward becomes a special layer. This structure,
known as the internal elastic coat, attains considerable devel-
opment in the larger vessels. With the growth of an artery in
calibre its individual coats are reinforced by additional layers.
Hence the thickness of the entire wall increases at the same

Fio. 64. Fio. 65. Fia. 66.

Fio. 6-i. — Minute artery showing optical section of alternate groups of muscle-cells, and an external nu-
cleated membrane, representing the tunica a Ivcntitia.

Fio. (55.— A. intima ; B, delicate internal elastic coat ; E, media (as in Fig. 04) ;,D, adventitia. Artcriole,
from a child's mesentery.
, Fio. 66.— Elastic internal tunic of the basilar arteries.

time that its' structure is rendered more complex. But new
tissues never appear. Moreover, the increased thickness is not
uniformly proportionate to the enlarged calibre ; neither does it
take place by equal participation of the different tissues men-
tioned. In vessels of small and medium size there is a prepon-
derance of muscular over elastic elements. In the larger trunks
the reverse condition obtains. It is, therefore, proper to dis-
tinguish arteries of the muscular from those of an elastic type.
The latter class is represented by the principal distributing
trunks, all the remaining arteries belonging to the muscular
type. There exist, however, no abrupt lines of demarcation
between these main forms — the one merging gradually into the
other.

The interposition of the internal elastic coat between the

THE BLOOD-VESSELS.

153

intima and the media marks the transition of a minute into a

small artery. This new layer consists at lirst of delicate fibrils

of elastic tissue, or an apparently homogeneous membrane.

Vascular contraction throws it into folds, which appear as

longitudinal striae or a transverse series of continuous festoons.

As the vessel grows larger this coat gets thicker, becomes dis

tinctly fenestrated, and presents a reticulat-

ed appearance. It is now made up of inter-

lacing bundles of connective tissue and elas-

tic fibres, with spaces left between them.

The latter constitute the fenestrse of this

layer, which in the large vessels becomes a

double or triple lamellated membrane. Be-

tween it and the lining endothelium there

appears still another structure, which has re-

ceived various names from different authors.

Thus, Kolliker has called it the striated in-

ternal coat; Remak, the innermost longi-

tudinal fibrous coat ; and Eberth, the in-

ternal fibrous coat. We shall employ the

last term. The internal fibrous coat consists

at birth of a granular substance, which be-

comes distinctly fibrillated in the adult.

Embedded in this membrane lie numerous

branching corpuscles, containing large, con-

spicuous nuclei. Besides these cells, smaller,

so-called granulation-bodies are frequently

seen. So far from regarding them as of path-

ological origin (Eberth, in " Strieker's His-

tology"), I prefer to consider them as ma-

trix-cells for the regeneration of desquamated

i 4! i- \t f i •

endothelia. My reasons for so doing are », muscio nucleus ; c,

/• 1 1 T j. i i i i i f internal tunic ; rf, membrane

as lollows : In the blood-vessels of young formed of fusiform oeiu.
animals and newly born infants I have fre-
quently noticed thick, dark, and granular bodies immediately
below the endothelial lining. These subendothelial cell-plates
were smaller and more polyhedral than ordinary endothelia,
and invariably contained one or even two nuclei. They ap-
peared to resemble germinating endothelial cells, such as Klein
has described as occurring in serous membranes. They did
not, however, occur in single layers, as Klein has seen them,

PIO. 67.-smaii artery
unTd^ ve™t"tia! «?x.'nu'-

clei of the tunica ad ventitia;

154

MANUAL OF HISTOLOGY.

but in strata. They were observed in particular vessels of
young animals. It seems likely that these cells disappear or
shrivel with the growth of the individual, but their sudden reap-
pearance in pathological processes leads the author to believe
that at least some of them persist through life. Talma ( Vir-
chow's Arch., Vol. LXXVIL, pp. 242-269) observed similar
elements, but thinks they are derived from the ordinary en-
dothelia, instead of vice versa. He is also convinced that the
latter are merely modified leucocytes ; but this view has been
shown to be erroneous by Virchow (Archiv f. path. Anat,
Vol. LXXVIL, pp. 380-383). Endothelial desquamation is
probably, as already stated, a physiological process of constant

Fio. 68.— Transver-e section through small artery and vein : A, artery ; a. intima with bulging en-
dothelial cells, the vessel being drawn in a state of contraction ; 6, internal elastic coat, wavy for same
reason ; c, media ; a, adventitia. H, vein, same denominations.

occurrence, and in some respects analogous to the epithelial
shedding from the surface of the skin and mucous membranes.
The media musculosa, or middle coat, consists of superim-
posed layers of smooth muscle-elements disposed in groups.
Most of them lie transversely to the course of the vessel. The
intervals between neighboring groups are occupied by connec-
tive tissue and elastic fibres, arranged in networks. This inter-
stitial substance becomes augmented with the increasing calibre
of the artery. In the largest trunks it all but replaces the
muscle-cells. Here, however, the elastic fibres also reach their
maximum development, encroaching upon the connective-tissue
elements until the latter become quite inconspicuous. Besides
its principal transverse layer, the media also contains fusiform
muscle-cells, placed in an oblique or longitudinal direction.

THE BLOOD-VESSELS.

155

They are scattered irregularly throughout the middle coat.
Sometimes the intima and the adventitia also contain sparsely
distributed muscle-cells. The arterial muscular coat is dis-
tinctly separated from the intima by the interposition of the
internal elastic coat. Externally a sharp boundary is formed
either by the adventitia or by the external elastic coat. The
latter appears as a separate membrane in arteries of small and
medium size. There are, however, exceptions to this rule. The
external elastic coat consists of a close network of delicate

FIG. 69. — Longitudinal section of pulmonary artery. Mounted in glycerine and acetic acid after de-
siccation of the artery, a. Internal portion of intima ; 6, external portion of intima ; c, internal elastic
coat ; d, media, showing cross sections of muscle fibres and elastic tissue ; «, adventitia.

elastic fibrils, anastomosing with similar adventitial reticula.
The adventitia is composed of interlacing bundles of connec-
tive tissue, commingled with elastic lamellae of varying thick-
ness.

The veins.— From their origin in the capillaries to the point
where they enter the trunk proper, the veins preserve through-
out a uniform type of structure. But no sooner have they
penetrated into the visceral cavities of the body than we find
them undergoing considerable alterations, which may either
increase or diminish the complexity of their structure (Ran-
vier). The veins are far more numerous than the arteries.
They are also, as a rule, wider and more dilatable, and have
thinner coats. It is owing to the latter peculiarity that the

156

MANUAL OF HISTOLOGY.

color of the blood is seen through their semitranslucent walls.
Finally, they branch more frequently than the arteries. Three
main coats or tunics enter into the composition of most veins.

These resemble the corre-
sponding arterial struc-
tures, and have likewise
received the names of in-
Uma, for the internal endo-
thelial lining ; media, for
the middle muscular ; and
adventitia, for the external
connective-tissue coat.

Veins, however, differ
from arteries in the feebler
development of their mus-
cular coat, in the compara-
tive paucity of elastic ele-

Fio. 70. — Portion of innominate vein of dog, after in-
jection of R solution of silver nitrate. The endothelial
cells and their nuclei are visible. The media shines
through this layer.

ments, a greater laxity
of their intima, and the
presence in some of valves.
We may distinguish veins of smaller calibre, or venules,
from the vessels of medium and large size. The venules, like
the arterioles, in certain respects resemble the capillaries. As

Pio. 71. — Arteriole and vennle from child's mesentery, treatment by acetic acid and glycerine : A, ar-
tery ; a. nucleus of muscle-coll of media ; 6, same in transverse section (optical). B, vein ; c, nucleus of
connective tissue constituting media, which in these minute veins contains no muscle-cells ; «/, nucleated
connective tissue.

it may become important to differentiate the minuter forms
of vessels, we will here briefly indicate the main points of dis-
tinction between full-sized capillaries, small veins, and arte-

THE BLOOD-VESSELS.

157

rioles. In the latter, the endothelial cells are more nearly
fusiform, longer, and somewhat narrower than in the venules.
In the capillaries, their form and dimensions hold an interme-
diate position between the arterial and venous types. The
middle coat is entirely wanting in capillaries, and is much less
conspicuous in the small veins than in the arterioles. In fact,
under ordinary circumstances, the muscle-coat forms by far the
most characteristic distinguishing feature between these ves-
sels. Venules quite frequently have only a few sparsely scat-
tered muscle-cells, in place of the continuous muscular layer
which exists in minute
arteries. The former
also are either altoge-
ther deficient in the in-
ternal elastic coat, or the
presence of this struc-
ture is barely indicat-
ed by delicate elastic
fibres ; these latter usu-
ally have a longitudinal
direction. On the other
hand, arteries of corre-
sponding calibre are
mostly furnished with
a distinct elastic inner
coat. Finally, with re-
gard to the adventitia,
we find it more highly
developed proportionally in venous than in arterial vessels,
whereas capillaries commonly have only a few faint fibres to
denote the presence, in them also, of this coat.

The internal elastic coat of the larger and largest veins is
very feebly developed in comparison with that of the arteries.
Distinct fenestrated membranes are scarcely ever encountered.
Veins are likewise possessed of an internal fibrous layer, but
here again we observe that comparatively feeble development
of a coat which in the arteries is quite conspicuous.

Among the many special characteristics of the various
veins in different regions, we will only mention the following :
the jugular veins show well-marked elastic reticula, the meshes
of which contain sparse muscular elements. In the femoral,

FIG. 72. — Longitudinal section of popliteal vein : a, iiitimu ;
6, media ; c, adventitia.

158 MANUAL OF HISTOLOGY.

brachial, and subcutaneous branches there is a media of con-
siderable dimensions. The inferior vena cava has, in addition
to a transverse layer of muscle-cells, a longitudinal one of
greater thickness, and, besides these, contains muscle-cells,
which are scattered through its elastic coat. The veins of the
meninges of the encephalon and cord, the retina, the bones,
and the muscles, and the jugular, the subclavian, the innomi-
nate, and the thoracic portion of the vena cava are all entirely
devoid of a true muscular coat. The veins of the gravid ute-
rus have only longitudinal muscle-elements. In addition to an
outer longitudinal layer, the vena cava, the azygos, the renal,
the hepatic, the internal spermatic, and the axillary veins pos-
sess an inner circular layer. The iliac, the femoral, the popli-
teal, and several other veins contain a middle coat of transverse
muscle-cells, between internal and external longitudinal layers.

The valves of the veins consist of longitudinal bundles of
connective tissue commingled with scanty elastic fibrils, and
containing nucleated cells. The inner endothelial layer appears
to be a direct continuation of the intima of the vein. That
portion of the subendothelial tissue which does not face the
blood-current is less developed than the part turned toward it ;
the elastic fibres of the latter are also barely visible. The at-
tached valvular border frequently presents transversely dis-
posed muscle-elements. Eberth has denied their occurrence,
but they have been repeatedly observed by Banvier and other
competent histologists.

Peculiar vascular structures. — The following structures are
remarkable for the conspicuous and characteristic development
of their blood-vessels the vascular membranes, tunica vascu-
losce, such as the pia mater of the brain and spinal cord, and
the choroid coat of the eye. In these we find that the excessive
vascularity is intended to nourish, not the membranes them-
selves, but the organs which they invest.

Blood-vascular glands, vascular plexuses. — In man, two
bodies of peculiar structure represent this group. They are
the coccygeal gland of Luschka, and a rudimentary organ
called the intercarotid gland. Both consist essentially of con-
voluted blood-vessels and nerves, imbedded in a nucleated con-
nective-tissue stroma. The coccygeal gland is a small, rounded,
pinkish body, of rather firm consistence, and is connected by a
pedicle with the middle sacral artery. This pedicle contains

THE BLOOD-VESSELS.

159

blood-vessels and nerves. The arteries entering the gland-like
body become convoluted, and show numerous tubular, fusi-
form, or ampullar dilatations. Sometimes they have terminal
sacculi, closely resembling minute aneurisms, and giving the
organ its glandular appearance. Indeed, Luschka has called
them gland-tubules and vesicles. After death they are corn-

Pio. 73. — Section of a naturally Injected coccygeal gland : a, vessels ; b, collection of cells. Eberth.

monly found to be empty, but by proper management a good
natural injection with blood may be readily obtained. Both
capillaries and veins also present lateral varicosities, studding
them in great number. All these vessels have the usual endo-
thelial lining. External to this there appear aggregations of
rounded or polygonal cells. They are furnished with nuclei,
and receive an investment corresponding to the vascular ad-

160

MANUAL OF HISTOLOGY.

ventitia, but containing comparatively more nuclei than that
structure.

The intercarotid gland differs from the coccygeal in its
larger size, and because it -contains accumulations of ganglionic
nerve-cells. These are derived from the carotid plexus. Here
the vascular sacculi also more nearly resemble dilated capilla-
ries, whereas in the other body they approach the arterial type.
In all other respects the structure of these vascular plexuses
is identical. Some authors regard the spleen and the supra-
renal capsule as belonging to this group of blood-vascular
glands. The author sees no necessity for so considering them,

and the subject may
therefore be dis-
missed without fur-
ther comment.

Corpora caverno-
sa. — They consist in
great part of dilated
blood-vessels, chief-
ly of the venous
type. These inter-
communicate very
freely, and when

Pio. 74.— A, cellular vascular sheath, from the coccypeal plexus: failed With. DlOOd

O, connective tissue with scattered cells ind nuclei; 6, round and nnnao tV»o rkT-rrn-n tr\

polysronal cells lying immediately upon the capillary wall, c ; B, a CtlU UIgclIl LO

capillary from the coccypjal plexus, with a vascular sheath very rich . .-, ^pp n 1 ; „ r

in cells. References as in A. Eberth. clSSUme 1116 peculiar

condition known as

erection. The penis and the clitoris are supplied with caver-
nous bodies. The urethra of the female and the vestibule also
contain them. Interlacing bundles of muscle-fibres, together
with similar bands of connective tissue, form a framework for
the support of the vascular structures mentioned. The, latter
present the ordinary endothelial lining.

Several years ago Dr. H. J. Bigelow succeeded in demon-
strating the existence of cavernous tissue in the nasal fossae.
In a letter to the author, Dr. Bigelow states that his point
was " the demonstration of an abundant and true cavernous
structure and erectile tissue on and about the turbinated bones,
occupying the place of what had been previously supposed to
be only venous sinuses, the loops of Kohlrausch. The new re-
sult obtained was due to a different mode of preparation. Kohl-

BIBLIOGRAPHY. 161

rausch injected from the jugular vein ; I [Dr. Bigelow] inflated
the tissue locally, as if it were in the penis."

Vasa vasorum, lympJiatics, and nerves. — Nutrient ves-
sels are found in the walls of all the larger arteries and veins,
where they occupy the adventitia. Sometimes they are seen
to dip down into the outermost portions of the media. Lym-
pJiatics occur as clefts or spaces between the various tissues of
all arterial and venous trunks. Some vessels are ensheathed
by a lymphatic membrane, which is sometimes furnished with
a lining endothelium. Such structures are called perivascular,
or, better, circumvascular spaces. They may be found in
connection with the omental and the mesenteric vessels, also
the splenic and the hepatic arteries, as well as certain menin-
geal vessels of the brain and cord.

Nerve-fibres are seen to pass to many of the blood-vessels.
They enter the adventitia, and at its internal boundary sud-
denly appear to divide into numerous filaments, the ultimate
distribution of which has not hitherto been satisfactorily ascer-
tained. They seem to terminate in the muscle-cells of the
media. Beale considers the presence of ganglion-cells in the
vascular nerves as of constant occurrence. The author cannot
admit the truth of this general statement, having discovered
such cells in only exceptional instances. There is no discerni-
ble difference of structure between the vaso-constrictor and the
vaso-dilator nerve-fibres.

BIBLIOGRAPHY.

In addition to the well-known standard treatises by Bichat, Kolliker, Henle,
Sappey, Krause, Frey, Leydig, Teichmann, Strieker, Klein, Ranvier, Donders, Vier-
ordt, Luschka, Pouchet et Tourneux, the following may be consulted :
LUDWIG. De arteriarum tunicis. Lipsiae, 1739.
RAUSCHEL. De arteriarum et venarum structura. Vratisl. , 1836.
ROBIN. Sur la structure des arteres. Gompt. rend. 1847.
SCHULTZE. De art. struct. Gryph. , 1850.

REMAK. Hist. Bemerk. ueber d. Blutgefasswande. Miiller's Arch. , p. 96. 1850.
SEGOND. Syst. capillaire sanguin. Th£se. Paris, 1853.
REMAK. Entwickelung d. Wirbelthiere. Berlin, 1855.
REMAK. Klappend. Venen. Deut. Klinik. 1856.
HACKEL. Miiller'a Arch. 1857.
LUSCHKA. Virch. Arch. XVIII. , p. 106. 1860.
11

162 MANUAL OF HISTOLOGY.

HOYER. Arch. f. Anat., p. 244. 1865.

KLEBS. Virch. Arch. Vol. XXXII. , p. 172. 1865.

AEBY. Med. Cent. Zeit. No. XIV. 1865.

CHRZONSZCZEWBKY. Virch. Arch. VoL XXXV. 1865.

EBERTH. Virch. Arch. VoL XLIII., p. 136, and Centralblatt, p. 196. 1865.

AUKBBACH. Virch. Arch. Vol. XXXIII. 1865. Med. Cent. Zeit. No. X.

GIMBEKT. Structure et texture des art&res. These. Paris, 1865. Journ. de

1'anat. et de la phys. Robin, p. 536. 1865.
FASCE, LCIGI. Istologia della arterie. Palermo, 1865.
LANGHANS. Virchow's Arch. Vol. XXXVI., p. 197. 1866.
His. Die Haute und Hohlen d. Korper's. Basel, 1866.
LEGUOS. Journal de 1'auat. et de la phys. No. III., p. 275. 1868.
TOLUBEW. Beitr. z. Kennt. d. Baues u. d. Ent d. Capill. Arch. mikr. Anat., p.

49. 1869.

ZIEGLEK. Exp. Unt. ueber d. Herk. d. Tuberkelelemente. Wiirzburg, 1875.
ZIEGLEB. Unt. ueber pathol. Bind. u. Gefassneubildg. Wiirzburg, 1876.
KOLLIKER. Entwickelungsgeschichte. Leipzig, 1876.
DISSE. Arch. f. mikros. Anat. Vol. XVI. , p. 1. 1879.
ILLTMANN. Arch. f. mikros. Anat. VoL XVI., p. 111. 1879.

CHAPTER XII.

THE LYMPHATIC SYSTEM.
BY DR. W. B. BLRDSALL, NEW YORK CITT.

HISTOLOGICAL research has brought to light within recent
years no more important or interesting facts than those con-
nected with the lymphatic system ; interesting, in exhibiting
entirely new features in tissues which had previously been
carefully studied ; and important in their physiological, and,
particularly, in their pathological relations.

Assisted by experimental pathology, it is still in this direc-
tion that we are to look for advancement in pathological his-
tology, for there can be no doubt that heretofore too little
attention has been paid to the lymphatic system, both in its
histological details and in its topographical anatomy.

Present condition of the mews on the structure of the lym-
phatic system — Relations to the connective tissues. — Unfor-
tunately we have still a great variety of contradictory observa-
tions, and various interpretations of the same observations.
Through this maze of uncertainties it is not easy to lead the
student to a settled opinion, nor can all the phases of this many-
sided subject be presented. It shall be our aim, however, to
draw the outlines. If the student wishes to follow out the
controversies, he will be aided by the references which are
appended to this chapter.

It may be said that we have, to a great extent, returned to
the views of t"he "older anatomists and physiologists, and be-
lieve that the whole connective-tissue formation is a network of
channels ; that its interstices are, directly or indirectly, con-
nected with the lymphatic capillaries and larger vessels ; that,
in short, the lymphatic system is pre-eminently a connective-
tissue circulatory system, irregularly distributed, it is true, but

1C 4 MANUAL OF HISTOLOGY.

found in one form or another wherever this tissue exists, and
constituting in the serous membranes a great absorbent sys-
tem, with its special connections, the lacteals, the lymphatic
nodes or glands, and the' fat-tracts. The important patho-
logical processes, both acute and chronic, connected with these
membranes are due principally to the fact that they are parts
of this great lymphatic system.

Of course we must not lose sight of the connections of the
latter with the complimentary blood-vascular system ; the ten-
dency has been too much in the opposite direction, however,
and this more extensive, though less visible, system has been
too often neglected in favor of its more prominent companion,
in the consideration of processes of nutrition and of patho-
logical changes.

General histology of the lymphatic system — Previous
ideas. — In describing the lymphatic system, only its general
histology will be considered, the details of its special distribu-
tion and arrangement being classed with the description of the
different organs with which it is associated. Since the serous
membranes have come to be regarded as important parts of the
lymphatic system, being, in fact, great membranous expansions
of that system, they are naturally and easily considered in con-
nection with each other. It is not intended to treat of them
here in their special details, but merely to make a general his-
tological study of them as a class. It is convenient to begin
with them in taking up the study of the origin of the lymphatic
system.

With Virchow originated the theory that the starting-point
of the lymphatics is from hollow anastomosing cells, the con-
nective-tissue cells, whose prolongations communicate to form
continuous tubes. He termed them plasma cells. Kolliker
supported this doctrine, and a similar view was held by Ley-
dig. Henle held a different opinion, whilst Briicke and Ludwig
reverted to the ancient theory of Bichat, that the interstitial
spaces of the connective tissue are the true sources of the lym-
phatics. Recklinghausen, introducing nitrate of silver as a
reagent, showed that the lymphatic vessels are lined, and the
serous membranes covered, with flat cells, forming an endo-
thelial layer. He observed the passage of milk and fine gran-
ules, through openings in the central tendon of the diaphragm,
from the peritoneal to the pleural surface. He believed also

THE LYMPHATIC SYSTEM. 165

that lie had discovered a system of canaliculi in connective tis-
sue, which he termed sap or juice canaliculi (saf tkanalchen).
His views, as modified somewhat later, are, that the connective
tissue is traversed by serous canaliculi or plasmatic channels
which are directly continuous with the lymphatic vessels.
"Not mere fissures in the connective tissue, but interstices of
the fibrous fasciculi and lamellae of connective tissue, cemented
to one another by a tenacious, homogeneous, firm material, in
which the serous canaliculi are buried."

The lymphatics of the mesentery. — A portion of the mesen-
tery between the trabeculse, taken fresh from a cat and stained
with nitrate of silver, exhibits on both surfaces an endothelial
layer, the cells of which possess an irregular outline, marked
by the deposit of silver, either in a supposed intercellular sub-
stance or in crevices between the cells. Sometimes this outline
is polygonal, sometimes sinuous, crenated, or even sharply den-
tated. It may be an even, fine line, or it may possess irregu-
larities as if beaded. At the union of these lines, that is, where
two or more cells terminate, a round, irregularly triangular, or
spindle-shaped spot may be often observed, which is stained
like the intercellular line, or in a lighter or darker shade.
There are other spots of larger size, presenting the appearance
of openings ; we shall refer to them again. The surface of the
cells may be clear, or granular, sometimes it is quite dark, vary-
ing with the degree of staining and the condition of the tissue ;
a nucleus can usually be seen at a slightly deeper level. This
is plainly visible in unstained or slightly stained specimens, or
where special reagents have been used to make the nuclei promi-
nent, as haematoxylin or picro-carminate of ammonia. The
granular appearance spoken of is sometimes confined to a series
of cells which surround a stoma, or the black spots mentioned,
while the neighboring cells may be clear ; in other cases, sev-
eral corpuscles in the form of an irregular tract may present
this appearance.

Klein has observed cells which are club-shaped, undergoing a budding pro-
cess, i.e., giving off little bodies resembling lymphoid corpuscles. He has given
the term germinating endothelium to these cells. Other histologists have made
similar observations.

Underneath and around the nuclei a delicate, intricate, re-
ticulum of elastic fibres may be seen plainly in unstained speci-

166 MANUAL OF HISTOLOGY.

mens, and by careful focussing in silver preparations. Accord-
ing to Ranvier, they are connected near their point of union
by a very thin, elastic, fenestrated membrane. Below the layer
of elastic fibres is the connective tissue which forms the basis
of the membrane. It consists of fasciculi, which are straight,
or wavy, according to the degree of tension of the membrane,
or its fasciculi are held together by the elastic fibres, which
penetrate from the reticulum on each side. They usually pre-
sent a decidedly convoluted appearance in ordinary specimens,
and in consequence of the contiguous fasciculi not possessing
corresponding convolutions, clear interspaces are seen. Some-
times the fibres are very irregular in their arrangement. Ran-
vier claims that an interfascicular membrane can be demon-
strated here also. Ordinary flat, branching connective-tissue
cells are distributed through this tissue ; they lie upon and
between the fasciculi ; they are particularly numerous under
the endothelial layer. Lymphatic and blood-capillaries trav-
erse the interspaces and run upon the fasciculi. In the mesen-
tery and pleura they form a wide-meshed plexus ; in the peri-
cardium a close plexus.

To see the features of the deeper portions to advantage, we
must remove the superficial endothelial layer before staining
with silver.

'Klein's method of studying the omentum. — Klein has de-
scribed a very careful process for doing this, and as he claims
it must be followed in detail to obtain the results at which he
has arrived, we reproduce it : "To prepare the omentum, a rab-
bit is killed by bleeding ; the stomach is exposed ; after having
pushed the intestine to the right side, the free surface of the
omeutum is pencilled several times from the large curvature
toward the diaphragm, with a fine camel's-hair pencil moistened
with fluid of tliQ abdominal cavity. After that, a £ or % per
cent, solution of nitrate of silver is allowed to flow over the
omentum from a large capillary -tube until the membrane has
become slightly milky (one or two minutes are generally suffi-
cient) ; after that, the stomach, together with the omentum,
spleen, pancreas, and a portion of the duodenum is cut out and
transferred to a large capsule with distilled water ; after some
time the water is renewed and the omentum is separated under
water, together with the spleen and pancreas, from the stomach,
with scissors, and is transferred to common water. Those parts

THE LYMPHATIC SYSTEM. 1C7

of the omentum which are seen to contain small patches are cut

out and mounted A failure is more frequent than a

success. Either the surface has not been pencilled enough,
and then the endothelium of both surfaces is colored, and
consequently, hardly anything is to be seen of the cellular
elements of the ground-substance ; or the surface has been
pencilled too hard, and then the arrangement of the ground-
substance is altered, its bundles appear considerably stretched
and distinctly fibrillar."

When these patches referred to, found in the mesentery,
and particularly in the omentum, are examined, they are ob-
served, according to Klein, to consist of systems of somewhat
flattened, finely granular, nucleated, branched corpuscles con-
nected together ; the spaces which appear clear between them
forming the lacunae and canaliculi, corresponding to Reckling-
hausen's lymph canalicular system. The nuclei of these cells
are sharply defined, oval, and possess one or two nucleoli.
Lymphoid corpuscles are found in these spaces, and also
slightly larger corpuscles, which are supposed to be derived,
in part, at least, from the branched cells by a process of bud-
ding. Klein calls these patches lymphangeal patches or nod-
ules, and lymphangeal tracts. He divides them into two
classes.

The perilympTiangeal nodules or tracts which lie closely
connected with, but principally outside of, the lymphatic ves-
sels, are accumulations of more or less flat, branched cells,
which, by their growth and proximity to one another, make the
canaliculi shorter or close them entirely. The second class de-
velop within the lymphatic vessels, and are termed endolym-
phangeal nodules or tracts. They consist of those which
perfectly resemble adenoid or reticular tissue, and those which
are formed of a reticulum of branched cells, their spaces being
filled with liquid or a few lymphoid corpuscles. The last form
may have a rich blood-capillary plexus, and the branched cells
may possess buds, pedunculated and non-pedunculated, sup-
posed to represent different stages in the formation of a lym-
phoid corpuscle. These tracts and nodules are found most
frequently in the neighborhood of the Mood- vessels and trabe-
culse. In young animals they are much less numerous and
more isolated than in adults, where they have become fused
into extensive tracts in consequence of the growth and division

1C8 MANUAL OF HISTOLOGY.

of the branched cells. Ranvier has described similar struc-
tures under the name "taches laiteuses"

Development of fat-tissue. — Their relation to the develop-
ment of fat-cells is of extreme interest. If we accept the views
of Klein and Flemming, the branched cells are converted into
fat-cells, and the former observer has pointed out that, by fol-
lowing up a perilymphangeal tract into a vascularized fat- tract,
we may find all stages of conversion into fat-tissue. The fat-
tracts are found in the same location as the perilymphangeal
tracts, that is, along the larger blood-vessels, and the greater
the number of the former the less there are of the latter. The
conversion of branched cells into fat-cells varies in different
animals, and in different membranes of the same animal, and
under different conditions of nutrition. The formation of lym-
phoid corpuscles, supposed to go on from the branched cells,
must cease, necessarily, when they become converted into fat-
cells, and it is found that they are, in fact, present in less num-
bers when the latter process is going on. Let us consider the
relations of these branched cells to the lymphatics. The larger
blood-vessels are usually accompanied by a lymphatic on each
side, which gives off branches at irregular intervals, finally
breaking up into a capillary plexus, which may ensheath the
accompanying blood-vessels, or even enclose a blood-capillary
plexus. When the latter exists in a perilymphangeal nodule,
the lymphatic capillary may apparently communicate directly
with the lacunae and canaliculi, the endothelial cells compos-
ing the capillary being continuous with those which invest the
spaces, and covering externally, it may be, the blood-capillary
as well (Klein, Delatield).

Course and termination of the lymphatic radicles. — In
tracing the lymphatic capillaries we find that they run in every
direction, branching irregularly, and vary in calibre and num-
ber in different parts. It is very difficult to trace one of them
to a positive termination. The interstices of the connective-
tissue fasciculi in brushed silver preparations sometimes pre-
sent an irregular shape, as if they were enclosed by irregular
cells. This appears to me to be often due to the convolutions
of the fasciculi, made more irregular, perhaps, by a cement
substance, or an interfascicular substance, either fluid or semi-
fluid, which has been coagulated by the processes following
death, and by the action of our reagents. The irregular action

THE LYMPHATIC SYSTEM.

169

of silver, which produces so many doubtful pictures, may aid
in producing this appearance. The extreme mobility necessary
in some forms of connective tissue demands extreme flexibility
as a quality of its elements, thus facilitating great variation in
structural arrangement under different conditions.

Artificial injection of the lymphatics. — If we inject this
tissue, by puncture with a hypodermic syringe, we can fill the
lymphatic vessels and
also the interstices, so
that they are continu-
ous ; but the question
whether this is a natur-
al or an artificial trans-
ition is one about which
histologists still differ.
Theoretically, we may
consider that such com-
munications exist to
some extent, at least
when greatly increased
vascular tension takes
place. But, at the -same time, many, or even most of the in-
terstices may be closed spaces.

It is not a matter of great consequence, physiologically speak-
ing, since not only fluids but lymphoid corpuscles can penetrate
partitions which fail to resist so slight an injecting force as is
sufficient to unite these spaces and the lymphatic capillaries.1
The fact that injections can be made without forming a com-
munication (Frey) does not prove that the latter does not
exist ; it may be due to an imperfect injection. As we shall
see later, the wandering propensities of the lymphoid cor-
puscles would almost exclude the possibility of the connective-
tissue interstices remaining closed spaces everywhere.

EndotJielium and stomata. — We have already referred to

Fio. 75.— From mesentery of cat: silver-stained right por-
tion denuded of endothelinm. fchowinp, A. branched cells, with

B, intervening spaces ; left portion, endothelial layer preserved ;

C, pseurto-stomata ; D, nuclei ; E, elastic fibres.

1 Thorn a and Arnold have shown that injections into the veins, in a living animal,
of insoluble coloring matters (not distending the vessels, however), pass between the
endothelial cells and find their way into the clefts and channels of the deeper tissues.
The possibility of absorption taking place through the intercellular substance which,
after all, may only be a semifluid material filling a space which varies in size under
different conditions, throws light on many of the difficult problems of absorption,
secretion, and excretion, and numerous pathological processes.

170 MANUAL OF HISTOLOGY.

Recklinghausen's observation, that communication exists be-
tween the abdominal and pleural cavities by means of small
openings in the central tendon of the diaphragm. By injecting
some insoluble coloring matter, held by fluid in suspension,
into the abdominal cavity, he obtained a fine injection of the
lymphatics of the central tendon, and was able to detect the
substance on its pleural surface. The experiment may be re-
versed by injecting the pleural cavity. He was able to see the
actual passage of milk-globules into these openings by remov-
ing a portion of the fresh tendon upon a cork ring, its pleural
surface upward, placing a drop of milk upon it, and observing
with the microscope the nearly round openings, large enough
to admit at once two or three of the milk-globules which ran
toward these openings in little eddies, and disappeared below.
He stained this membrane with nitrate of silver, and found
that the openings corresponded to perforations between the
endothelial cells leading perpendicularly or , obliquely to the
lymphatics. Schweigger-Seidel and Doigiel observed similar
openings leading from the abdominal cavity, through the retro-
peritoneal membrane, into the cysternce lymphaticce magnet of
the frog. Dybkowsky showed that colored fluids placed in the
pleural cavity were absorbed by the lymphatics of the inter-
costal pleura. Schweigger-Seidel, Doigiel, and Ludwig con-
firmed the observations of Recklinghausen in connection with
the central tendon of the diaphragm, and it is' now generally
admitted that such openings exist, not always freely open,
however, but -sometimes with a valve-like cleft. It must not
be understood that the small bead-like spots and the dark
spots between the cells are true stomata. It is not definitely
known, in fact, what they really represent. Oedmannson first
described them, not only on the serous membranes, but also
on the endothelial layer of the chyle-vessels. They are very
numerous directly over the lymph-vessels of the central tendon
on its peritoneal surface (Dybkowsky).

Returner's mews on false stomata. — Ranvier has an in-
geneous theory explaining the formation of these objects,
which have been termed false stomata^ also of the true sto-
mata and the fenestra of the omen turn. He considers that the
lymphoid corpuscles, which are always to be found in serous
cavities, penetrate the membrane, making a depression or per-
foration, sometimes remaining, sometimes escaping again. In

THE LYMPHATIC SYSTEM. 171

the majority of cases the black spots are formed by the albu-
minous serum which these openings retain by capillary attrac-
tion, having been coagulated and stained by the nitrate of
silver, producing a plug. In other cases, a globular cell re-
sembling a lymphoid corpuscle occupies the stoma, surrounded
by a black margin due to the action of the silver. Other cells
have a greater resemblance to small endothelial cells than to
lymphoid corpuscles. The irregularity of their distribution in
different membranes, in different animals, and at different
ages, seems to favor the idea of such an accidental manner of
formation.

Klein on true and false stomata. — Klein divides the sto-
mata vera, or true stomata, into two classes : a, those which
form the mouth of a vertical lymphatic channel leading to a
superficial vessel (they have a
special endothelial lining) ; and
5, those formed by discontinuity
between the endothelium of the
surface leading into a simple
lymphatic sinus near the sur-
face, and lined only on the lower
surface with endothelium. Pseu-
do-stomata, or false stomata, may
be produced, according to this
observer, by the prolongations of
the sub- endothelial branched cells

VV/-K . -P-n^^ U-r, ™^-I^«4-;^, ,,4. FIG. 76.— Frond of fern (Osmnnda Clayto-

beCOmmg Iree by projection OUt- niana), under-surface *<*£• stomata.

ward between the endothelial

cells. In pathological conditions he has seen an extensive
cell-proliferation going on from one of these projecting pseudo-
stomata. Ranvier accounts for the origin of the fenestra
of the omentum in a similar manner, as for the stomata. It
is of interest to know that the openings do not exist before
birth, but increase in size and number as age advances.
Klein, on the other hand, considers that the openings in the
omentum are produced by a process of vacuolation. The
arrangement of the connective-tissue fasciculi around these
openings is not that of complete rings, but is such that each
opening is bordered by several fibres which take part in the
formation of other openings in consequence of the irregularity
in their arrangement. The endothelial cells may form a com-

172 MANUAL OF HISTOLOGY.

plete tube in some of the narrow trabeculse, in which a sin-
gle cell may complete the circumference. Klein states that
when these openings take place, the connective-tissue cells pre-
viously situated between the connective-tissue bundles, come
to lie on the lateral surface which is now free. This, he
thinks, establishes the fact that the latter may be converted
into true endothelial cells. Delafield, in considering the ques-
tion of the re-formation of the endothelium on serous mem-
branes, after hydrothorax, remarks that it would seem to be
reproduced from the old endothelium, or from migrating white

Fro. 77.— From silver-stained omentum of cat: A, fenestra; B, intercellular lines of upper surface ;
C, nuclei of same ; D, intercellular lines of lower surface ; B, nuclei of same ; F, nuclei in wall of opening ;
corresponding cell-forms, part of upper and part of lower surface.

blood-cells, or from sub-endothelial connective- tissue cells,
although he has not seen sufficient proof to establish any of
these theories.

TJie nerves of the peritoneum have been studied by Cyon.
They enter the mesentery with the blood-vessels as fasciculi of
medullated nerve-fibres, and, dividing laterally, lose their med-
ullary sheath and form a plexus, the fibres of which show
projecting nuclei at various points. The walls of the arteries
receive a rich supply of these fibres. A lymph-space, surround-
ing the fibres, can sometimes be demonstrated.

Intimate structure of lymphatic vessels. — A lymphatic ves-
sel may be considered as a serous membrane with only one free
surface, rolled in the form of a tube, its endothelial layer form-
ing the intima, resting upon an elastic reticulum, and an ad-
ventitia or external envelope of connective-tissue fasciculi, as
in the serous membranes. In the finest capillaries only the en-
dothelial layer is independent, although they lie surrounded

THE LYMPHATIC SYSTEM.

173

by elastic fibres and connective-tissue fasciculi. In the larger
trunks, smooth muscular elements form a middle layer. The
endothelial cells of the lymphatics have a more sinuous outline
than the spindle-shaped cells of the blood-capillaries ; they are
often irregularly dentated like the cranial sutures. The calibre
of the lymphatics is also much more irregular than that of
blood-vessels. As they increase in size, the tissues external to
the endothelium assume more and more the character of ves-

Fio. 78. — Central tendon of the rabbit, treated with solution of nitrate of silver, the most superficial
serous layer immediately adjoining the pericardium being shown : a, lymphatic capillaries ; 6, their ori-
gin ; c, serous canals with communications; d, serous canals equal in width to the origin of the lympha-
tic vessels ; e, blood-vessel with epithelial cells. Magnified 300 diameters. Recklinghausen.

sels with independent walls ; they finally resemble the veins
in the largest trunks, except that they possess more muscular
tissue than the latter.

The diameter of the lymphatic capillaries is very variable ;
they are generally larger than the blood-capillaries, ranging
from 0.013—0.045 mm. (Frey). Branches of 0.2256— .2609 mm.
may possess three layers (Kolliker). The vessels are richly
supplied with valves, which are formed from the intima.

Variations in shape. — Here let us consider an important
characteristic of the lymphatic system, viz., its irregularity.

174 MANUAL OF IIISTOLOGY.

In this respect it contrasts very decidedly with the blood-vas-
cular system. In the calibre of its vessels in different regions,
in different parts of the same organ, and even in different parts
of the same vessel, it is extremely irregular. A vessel of small
calibre may suddenly expand into a saccular shape, which
may have its diverticula or branches, or may form a cjiain of
lacunae. It is true that these dilatations are formed just in
front and behind the valves quite regularly, but they are also
found everywhere, being, in fact, a characteristic of these ves-
sels.

Topographical peculiarities. — Nor is a uniform direction to
be observed in the distribution of these vessels, for while they
usually accompany arteries, lying outside the accompanying
veins, they frequently take strange courses. A lymphatic may
suddenly leave its companions to strike across a comparatively
non-vascular field of tissue to share its fortunes with another
set of blood-vessels. Respecting the capillary lymphatics,
their place seems to be the middle ground between the blood-
capillaries, just where we would expect to find this drainage
system.1 They lie deeper in the skin and mucous membrane
than the blood-vessels (Recklinghausen). The dispute con-
cerning the question as to whether the smaller lymphatics
have a distinct wall or are simple spaces, probably has been
largely due to the variation in the structure of the lymphatics
in the same tissue or organ in different animals, %or in the same
animal at different ages.

The thoracic duct, which represents the other extreme in
the structure of lymphatic passages, has an endothelial layer
supported by a reticulum of elastic fibres, which mingles with
the next layer, consisting of smooth muscular elements run-
ning in every direction, the transverse elements predominating.
The adventitia of connective- tissue fasciculi and elastic fibres
completes its coats. The muscular layer in man is highly de-
veloped compared with quadrupeds (Ranvier).

1 On the external ear of a rat whose blood-vessels are injected with colored gela-
tine, and whose lymphatic vessels are rendered visible by silver, the larger centrifu-
gal lymph-vessels are seen, even with low powers, to be surrounded by a network of
blood-capillaries. The same has been demonstrated in the mesentery, the dia-
phragm, and the posterior extremities. — Ueber ein die Lymphgefasse nm-spinnendes
Netz von Blutcopillaren, von Alex. DogieL Arch. f. mikroskop.- Anat Bd. 17. 3.
Heft, S. 335-340.

THE LYMPHATIC SYSTEM. 175

TJie subarachnoid and subdural lymph-spaces and their
prolongations. — Axel Key and Retzius have shown that be-
sides the great subarachnoid and subdural lymph-spaces of
the brain and spinal cord, connecting with them are spaces en-
closing the nerve-fibres of the cord, and, what is still more
remarkable, extending outward on the peripheral nerves. The
nerves of special sense, the olfactory, the optic, and the audi-
tory, form no exception to this rule. Even the ganglia of the
sj^mpathetic system and their fibres have similar spaces, which
are in connection with the cord. Nor is this the end of the
intricate labyrinth. Each nerve-fibre has a space immediately
outside of the sheath of Schwann, between the latter and the
so-called fibrillary sheath, through which it communicates with
the perineural sheath-space, and through the latter with the
lymph -spaces of the central nervous system. That they are
true lymphatic spaces is shown by the fact that they are lined
by a layer of endothelial cells. Obersteiner demonstrated by
injections that the nerve-cells also possess pericellular spaces
connected with those of the corresponding fibres, a fact which
I can corroborate. Key and Retzius say that this whole lym-
phatic system is nowhere in direct communication with the
ordinary lymphatic system, and that they have never seen the
latter injected through the former, except when extravasation
occurred. Bogras was the first (1825) to inject the nerves. He
used quicksilver, and succeeded in injecting the peripheral
nerves up to the ganglia, and made injections from the dura
down to the ganglia. He failed with the olfactory, optic, and
acoustic. Cruveilhier, and later, Robin, confirmed the fact
that such injections are possible. Robin, in 1858, and after-
ward, His, in 1863, demonstrated the perivascular lymph-
spaces of the central nervous system.

Lymphatics of tendons. — Axel Key and Retzius, and also
Hertzog, have shown that the tendons possess spaces which
may be injected. From the spaces formed by the endotenium
and the peritenium, which communicate, connections exist
with the deep and superficial lymphatics of the tendon.

The development of the lymphatics is by a process of bud-
ding and vacuolation similar to that which takes place in the
blood-vessels.

Lymphatic glands. — We now pass to the consideration of
the lymphatic bodies called glands^ ganglia^ or nodes. Their

176 MANUAL OF HISTOLOGY.

distribution does not concern us here ; it is sufficient to say
that they are very variable in size and number in different
regions, being supplied to nearly all the lymphatic trunks,
with which they are connected by the so-called afferent and
efferent branches. The former usually consist of several small
branches ; the latter generally enter as single large trunks.

The shape of the lymph-nodes may be spherical, oval, ob-
long, or reniform. In the latter, which is by far the most fre-
quent form, the afferent vessels penetrate the capsule on the
convex surface, while the efferent branch escapes at the hilus.
In the other forms it is difficult to determine which are the
afferent and which the efferent vessels. A lymph-node con-
sists essentially of spheroidal and cylindrical masses of reticular
tissue, containing lymphoid corpuscles, richly supplied by a
blood-capillary system, and sustained in place by a framework
of connective tissue, with elastic and sometimes muscular ele-
ments, forming a network around the masses for the circula-
tion of lymph, and expanding externally to form a capsule.
The gland is usually divided by histologists into a cortical and
a medullary portion, the former being simply that part in which
the lymphoid masses assume a spheroidal form (the follicles),
this being the more peripheral portion of the node, or the part
farthest from the hilus, when that exists. The medullary sub-
division represents the remaining portion, and its lymphoid
material is in the form of cylindrical or cord-like prolongations
from the follicles. The capsule is composed of connective tis-
sue, the fibres of which run in different directions in its exter-
nal layers, possessing elastic fibres, flat cells, and a slight
amount of fat-tissue. The lymphatics of the capsule are found
mostly in its outer layers. The inner layers present a more
stratified appearance on account of the regularity of their
bundles and the interposed connective-tissue cells. An elastic
network and smooth muscular elements are found here, and
nlso in the septa, and are developed in some animals to a high
degree. It is from the inner layers of the capsule that the
septa are given off to form the framework of the node. These
consist primarily of trabeculse, which, passing between the fol-
licles, converge toward the medullary portion, where they inter-
lace with the lymphoid cords of the latter, and may again unite
at the hilus (stroma of His). They have a structure similar to
that found in the portion of the capsule from which they have

THE LYMPHATIC SYSTEM.

177

their origin. These septa are not complete partitions, but consti-
tute an open framework, which, in consequence of its radiating
arrangement, produces wider spaces in the cortical than in the
medullary portion. To this the follicles correspond by being
broadest at their peripheral portions. It must not be under-
stood that the lymphoid masses, either follicular or cylindri-
cal, are closely embraced by the septa ; they, are separated from
the latter, and from the sheath as well, by spaces, the " invest-
ing spaces of the follicular portion" (Frey), or sinuses of the

FIG. 79. — Section of the medullary Riibstnnce of a lymphatic gland from the ox : a, follicular cord ; ft,
trabeculae ; c, path pursued by the lymph ; d, blood-vessels. Magnified 300 diameters. Recklinghausen.

cortical substance (Ranvier), and the lymph-passages (Frey)
or cavernous plexus (Ranvier) of the medullary portion. These
spaces are maintained by a network of fine fibres (Center-fibres
of Frey) derived from the septa, being given off at nearly right
angles to the latter. The bundles of fibres composing them
divide and reunite, forming meshes, and extend to the follicles
and cords. In reality, they do not end here, but are continued
to form the reticular tissue of these bodies by dividing into a
still finer network, which differs in the different portions only

178 MANUAL OF HISTOLOGY.

by slight variations in the size of the meshes and the fineness of
the fibres, the meshes being longer and narrower in the peri-
pheral portions of the follicles and in the cords than in the
central part of the former. This sort of tissue has received
different names : cytogenous tissue (Kolliker), adenoid tissue
(His), reticular tissue (Frey, Ranvier). It is, as the latter name
implies, a network, the fibres of which run in ev.ery direction,
being applied to one another in the same manner as the fibres
of the omentum. already described. The nuclei, which are
more oval and larger than the lymphoid corpuscles, appear at
the junction of fibres, simply rest upon them, and can be re-
moved by brushing. They are endothelial cells, and in silver-
stained preparations an endothelial layer can be seen to cover
the septa, the reticulum of the lymph-passages, and the folli-
cles in the same manner that the fine bundles of the omentum
are covered ; that is, the spaces between the bundles are no-
where covered, but each bundle is wrapped by these cells.
This can only be seen after the lymphoid corpuscles that occupy
the meshes have been removed by brushing. The endothelial
layer is continuous with that of the afferent and efferent lym-
phatic vessels, which communicate with the lymph-spaces of
the node, as shown by injections.

According to Klein, the clinical nature of reticular tissue
does not correspond to connective tissue proper or to elastic
tissue. Filling the meshes of the follicular and cylindrical
portions of the lymphoid masses are the lymphoid corpuscles,
two or more in each mesh. Lymphoid corpuscles are also
found in the investing or lymph-spaces, but they are easily
brushed out, while a much longer brushing is required to de-
tach them from the other portions. The corpuscles are some-
what larger than the colorless blood-corpuscles, though vari-
able in size. They possess a single prominent nucleus, which
is readily stained by most coloring matters. The amount of
protoplasm they possess is small. When examined in a moist
chamber at a temperature of 36° to 37° C., some of them ex-
hibit amoeboid movements, the small ones having the least
protoplasm around their nuclei being most active (Ranvier).
Klein states that corpuscles are to be found which are larger
than the others, having more protoplasm, and often two nuclei.
He considers them in a more advanced stage of development
than the others.

THE LYMPHATIC SYSTEM. 179

The arteries and veins of the lymphatic nodes have their
chief entrance at the hilus, with the efferent lymphatic vessels.
The main trunks divide to pass into the septa. Still finer
divisions pass into the reticular tissue, forming a rich capillary
network in the follicles and cylinders, most marked at the sur-
face of these bodies. In the cylinders a single axial arterial
branch, surrounded by a peripheral capillary system, may fur-
nish the supply. Another source of blood-supply may be from
the capsule ; small branches, both arterial and venous, which
ramify in its layers, send finer branches inward, encircling the
follicles and traversing the septa and reticulum of the lymph-
spaces. The capillaries possess, besides their proper wall, a
sheath derived from the reticulum.

Nerves of the lymphatic nodes. — Little is known on this
point. Nerve-fibres enter with the blood-vessels in some of
the larger glands of man (Kolliker), and non-medullated nerve-
fibres have been seen in the lymphatic nodes of the ox. Con-
cerning the lymphatics, they exist, as we have seen, in the
outer layers of the capsule, and do not differ from those in
other regions, forming a network in the capsule. They are
continuous externally, with the afferent lymphatics, and inter-
nally with the lymph-spaces already described.

The numerous lymphoid organs are all constructed upon a
plan similar to that of the nodes, in that they all represent
modifications in the arrangement of reticular tissue and its
vascular supply.

Injection of a lymphatic gland. — We may obtain an injec-
tion of the lymph-passages in the node by puncturing the
capsule with an ordinary hypodermic syringe (a method for
which we are indebted to Hyrtl), and injecting a mixture of
Prussian blue and gelatine (soluble blue, 25, solid gelatine, 1).
It is best to inject one of a series of connected nodes, in place,
exposing them by dissection in a freshly killed animal. One
gland is then injected from the other through the afferent and
efferent vessels (Ranvier). They are excised and hardened in
Miiller's fluid or alcohol ; sections are then made with a micro-
tome, after which they may be washed in water, stained for a
few minutes in picro-carminate of ammonia (1 per cent.), again
washed, and then mounted in glycerine or Canada balsam.

Method of studying the gland substance. — For the purpose
of demonstrating the reticulum of the lymph-spaces and the

180 MANUAL OF HISTOLOGY.

lymphoid masses, the node must be hardened in alcohol, bi-
chromate of potassa, or (Ranvier's method) placed for twenty-
four hours in a concentrated solution of picric acid ; sections
are then to be made, after which they are gently brushed and
agitated in water with a camel' s-hair brush to disengage the
lymphoid corpuscles (we are indebted to His for the method of
brushing). After staining, preferably with hematoxylin, which
exhibits, in a beautiful manner, the lymphoid corpuscles and
the darker nuclei of the endothelial layer, they may be
mounted in the usual manner.

Returner's plan. — The plan particularly recommended by
Ranvier is as follows : the node remains for twenty-four hours
in a mixture of alcohol (36° Cartier), one part, water, two
parts ; then for twenty-four hours in a syrupy solution of gum-
arabic, and is afterward hardened in alcohol sufficiently for
section cutting in a microtome. Floating them in a shallow,
flat dish, in water two or three centimetres deep, the gum is
dissolved, and the brush used in a very delicate manner ; the
sections may then be stained and mounted, as described above.
The degree of hardness, and the force and duration of the brush-
ing process, will determine the result, which practice only will
make perfect. The lymphoid corpuscles in the lymph-passages,
that is to say, in the parts which fill with the blue injection
fluid, as previously described, are first removed, and additional
brushing, when the proper degree of hardening has been at-
tained, will enable one to remove these bodies from the folli-
cles and cords, and also to remove the endothelial cells which
rest upon the fibres of the reticulum and septa.

Other methods of injecting glands. — A node removed imme-
diately after death and injected by puncture with a 1 per cent,
solution of hyperosmic acid, then placed in water for one or
two hours, and afterward hardened in alcohol, cut in sections,
colored by picrocarminate of ammonia, and mounted, gives
good results.

The best method for showing the endothelial layer is by
interstitial injection (puncture) with a solution of nitrate of
silver, 1—300 ; harden afterward by freezing, and make sec-
tions.

Before closing this chapter, let us take a retrospective view
of our subject. In doing so, it is almost impossible to avoid
associating the connective- tissue cell with other forms which

TUB LYMPHATIC SYSTEM. 181

seem to be its antecedents, modifications, or derivatives, viz.,
the extensive system of branched corpuscles in the matrix of
the serous membranes, whose growth and proliferation form
large tracts when they possess a sufficient blood-supply, and
between which the lymph circulates, affording a channel of
escape for the dischaiged bits of protoplasm, their offspring ;
the throwing off of similar bits of protoplasm by the surface
endothelium of the serous membranes ; the probable transfor-
mation of the branched cells into fat-cells, and the conversion of a
branched connective- tissue cell into an endothelial cell, when it
reaches a free surface. Again, the fact that similar endothelial
cells line the blood and lymph channels, and also cover thereti-
culum of the lymphatic nodes and follicles, and that in the
latter forms, when we have also a rich capillary blood-supply —
that is, a supply of oxygen — the accumulation and probable
elaboration, if not proliferation, of lymphoid corpuscles goes on
in a more extensive manner than in the lyinphangeal tracts ;
taken together, all point to the idea that they are different
forms of protoplasm which have been converted, or are con-
vertible, one into the other under proper conditions of tempera-
ture, food-supply, and excitability, the definite limitations of
which are but imperfectly known.

In the germinating tracts, superficial and deep, of the serous
membranes, in the lymphatic nodes and follicles of the ali-
mentary canal, and also in the lymphoid organs (spleen, ton-
sils, etc.), we have active forms, reproduction by budding, and
division. The formation of the lymphoid corpuscles, which
may be considered as so many amoebae sporting in a nutritious
fluid, and engorging themselves with that which is brought to
them by the agency of the absorbents and lymph-channels,
under conditions favorable to great activity, free to penetrate
most of the tissues, and, perhaps, become fixed forms. These
processes of activity, when confined to the limits of the organs
mentioned, are conducive to life and growth, but occurring in
the allied forms that have become fixed, as the corneal branched
cells, the connective-tissue cells, or the endothelial cells, to any
considerable extent, inaugurate the processes of disease and
death. Thus these comparatively indefinite and undifferen-
tiated forms of protoplasm may be said to be keys to life and
death.

182 MANUAL OF HISTOLOGY.

BIBLIOGRAPHY.

Authors referred to in the text :
BICHAT. Anat. gen. Second edition. 1812.
IBID. Traite" des membranes. 1816.
RKMAK. Muller's Archiv. 1850.

BRUCKE. Ueber die Chylusgefasse, etc. Sitzb. der Wiener Akad. 1853.
LETDIO. Lehrbuch d. Histologie, etc. 1857.
VIRCHOW. Cellular Pathology. 1860.
OEDMANNSON. Virchow's Archiv. Bd. 26. 1863.
CHRZONSZCZEWSKY. Virchow's Archiv. Bd. 31. 1864.
His. Archiv f. mikrosk. Anat. Bd. I. 1865.

SCHWEIGQER-SEIDEL and DOIGIEL. Arbeit, a. d. phys. Lab. z. Leipzig. 1866.
KOLLIKER. Handbuch der Gewebelehre. 1867.
CYON. Arbeit, a. d. Phys. Anstalt. in Leipsig. 1868.
ROBIN. Diet Ency. Sc. Med. 1870.

RECKLINGHAUSEN. The Lymphatic System. Strieker's Histology. 1872.
KLEIN. The Lymphatic System. 1873.
DYBKOWSKY. Arbeit, a. d. Phys. Anstalt. in Leipsig.
ARNOLD, J. Archiv f. path. Anat. Bd. 58, p. 203. 1873.
THIN. Proc. Royal Soc. Vol. 22. 1874.

THOMA. Centralbl. f. d. med. Wiss. 1875. Archiv f. path. Anat. Bd. 64. 1875.
KEY, AXEL, and RETZIUS. Archiv f. mikrosk. Anat. Bd. IX. 1875. (Abstract of

large work on the nervous system. )
HERTZOG. Zeitschr. f. Anat. und Entwick. 1875.
RANVIER. Traite technique d'histologie. 1877 et seq.
DELAFIELD. Path. Studies. New York, 1878—80.
FREY. The Microscope, etc. New York, 1880.

Among the more recent authors that have written on this subject are :
HOGGAN. Proc. Royal Soc. 1876—77. (Two articles. )
LEWIS. Proc. Roy. Society. 1877.

ROBIN and CADIAT. Journ. de 1'anat. et de la phys. 1876. No. 6.
BUDGR. Arch. f. mikrosk. Anat. Bd. X. 1876.
RIEDEL. Archiv f. mikrosk. Anat. Bd. XI. 1877.
WITTICH. Mittheil. a. d. k. phys. Lab. 1878.
MIERZYEWSKI. Jour, de 1'anat. et de la phys. Paris, 1879.
RENAUT. Comptes rendus A cad. des Sci. Paris, 1879.
WEBER-LIEL. Arch. f. path. Anat. Bd. LXXVII. 1879.
FISCHER. Arch. f. mikr. Anat. XVII. 1879-80.
SITNA. Wien. med. Presse. XXI. 1879.

CHAPTER XIII.

THE LIVER AND BILIARY APPARATUS.

BY DR. ABRAHAM MAYER,

Curator of the Manhattan Eye and Ear Hospital, New York City.

THE liver is enclosed in a connective-tissue capsule, the
peritoneum, which also gives off secondary folds, or duplica-
tures, called ligaments, by which the organ is held in proper
connection with the adjacent parts. The thickness of the cap-
sule is about 0.03 mm., and its free surface is covered with the
flattened corpuscles that belong to 'serous membranes gener-
ally. This connective-tissue covering is furthermore composed
of thin laminae, which contain a large number of elastic fibres.
At the transverse fissure, where it is continued into the inte-
rior of the organ, the same character is maintained. Here it
encircles vessels, ducts, and nerves, forming the so-called
Glisson's capsule, which, indeed, with its minute ramifications,
traverses the whole interior of the gland. The liver contains,
in addition to the glandular substance, blood-vessels, lympha-
tics, nerves, and gland-ducts, the whole held together by the
framework of connective tissue just mentioned, which in the
human species is but imperfectly developed.

The hepatic lobules. — The glandular parenchyma consists
of the so-called hepatic lobules, which in the human liver are
not completely separated from one another, for the reason
just named. In some of the lower animals, however, this sepa-
ration is more perfect. In the hog's liver, for example, the
septa are so well developed that the lobules are plainly recog-
nizable by the naked eye.

To isolate the human lobules is a matter of some difficulty ;
but it can be accomplished by macerating the organ in water
from twelve to twenty -four hours.

These lobules are also known as the hepatic acini, or in-

184

MANUAL OF HISTOLOGY.

sula of the liver. Their form is irregularly polyhedral, and
they usually measure about 4x1 mm. At their bases they
are attached to short twigs of the hepatic vein, which have a
thickness of from 0.08—0.06 mm., and traverse the lobules in
the axes of their long diameters. As the hepatic vein ascends
through the lobule, it gives off innumerable capillary branches,
almost at right angles to its course. The latter pursue their
way to the periphery of the lobule, and hence have a radial
direction. These capillaries further subdivide within the lob-
ules, and are united to each other by transverse branches,
forming a network with small meshes. At the periphery the

capillaries join the rami-
fications of the portal
vein. The latter divides
within the liver into nu-
merous branches, which
again subdivide at the
surfaces of the lobules.
Their ultimate ramifica-
tions form the boundary
lines between adjoining
hepatic lobules, and it
is for this reason that
they have been called
interlobitlar veins.1 For
a similar reason the
branches of the hepatic vein, which traverse the centres of
the lobules, have been called intralobular l or central veins *
(Fig. 80).

The interlobular veins are contained within interlobular or
intermediate (Hering) canals ; these are easily demonstrable in
the hog's liver. In this animal the adjoining edges of three
or four hepatic lobules combine to form a canal which con-
tains the interlobular vessels. The latter are surrounded by
connective tissue, which is continuous with that of the septa
between the lobules. In the human liver there is a similar
arrangement, but in it the septa of connective tissue do not
completely separate the lobules, and, excepting at the inter-

Fia. 80.— Injected liver of rabbit, showing branches to
portal vein, capillaries, and the hepatic veins in the centres of
two lobules. Frey.

'Kiernan: Philosoph. Trans., 1833.

* Venae Centrales, Krugenberg, Muller's Archiv, 1843.

THE LIVER AND BILIARY APPARATUS.

185

lobular canals, the parenchyma of contiguous lobules appears
to coalesce.

Nevertheless, the substance of the human liver can be di-
vided into distinct lobules, and the terminal branches of the
portal veins may be regarded as their natural boundaries (Figs.
80 and 87). Starting with the portal veins, therefore, the course
of the blood is as follows : portal veins, interlobular veins, cap-
illaries, intralobular veins, hepatic veins, and inferior vena
cava.

Sublobular veins, according to Kiernan, are such branches of the hepatic
vein as are placed under the bases of several lobules, and collect the blood
from their central veins.

The liver may be injected either through the portal or he-
patic veins, or through both. Good specimens may be ob-
tained by injecting the fresh liver of a dog or rabbit with
carmine - gelatine through
the portal vein, then inject-
ing fluid Berlin blue into the
hepatic vein, and afterward
hardening the organ in alco-
hol. The central vein and
adjacent capillaries will thus
be filled with a blue mass,
while the interlobular and
portal veins, with the per-
ipheral capillaries, will con-
tain the transparent red
mass.

The color of the cut sur-
face of the liver in its natu-
ral condition is of a uniform reddish brown tint, and its lobular
structure is not readily made out. Usually, however, we find
two shades or gradations in color ; one, corresponding to the
central veins of the lobules, is of a dark red ; the other, corre-
sponding to the periphery of the lobules, is a lighter and yel-
lowish red.

Occasionally these conditions are found to be reversed,
and the difference of color is due to the fact that after death
the central and other hepatic veins are filled with blood, while
the portal and its branches are empty ; and also because

FIG. 81. — TranRVPrce Fection of a human lobule,
showing opening for central vein. Ecker.

186 MANUAL OF HISTOLOGY.

the deposit of bile-pigment takes place at the centres of the
lobules about the intralobular veins ; whereas a fatty infiltra-
tion, such as may occur in normal livers, takes place at the
periphery. Not uncommonly the yellowish red color at the
boundary of the lobules exists under the form of delicate
markings, which are nothing more than the empty interlobular
branches of the portal vein.

Kiernan occasionally observed in young subjects that the portal vein was
distended with blood, while the hepatic vein was empty. In such cases the
periphery of the lobules was of a darker color than their centres.

TJie blood-vessels of the liver. — These have been partly de-
scribed above. The hepatic artery, and duct, and portal vein
enter the liver at the transverse fissure, enclosed within Glis-
son's capsule, and continuously subdivide as they push their
way through the parenchyma. The subdivisions of the portal
vein never anastomose, but are distributed around the surfaces
of the lobules, forming their boundaries. At the periphery
they break up into capillaries which enter the lobules. These
are about 0.02 mm. in diameter, and form a network, the
meshes of which are scarcely wider than capillaries. Within the
lobule the capillaries unite to form the central vein, and these
then empty into branches of the hepatic vein. The subdivi-
sions of the hepatic vein are also devoid of anastomoses, but
after traversing the posterior portion of the .liver in canals
(which they embrace closely), unite to form the hepatic vein.
A peculiarity of this latter vein is the fact that its larger
branches give off successively small lateral twigs, which enter
the bases of the neighboring lobules, so that after dividing
such a branch lengthwise it would seem to be pierced by small
circular openings, which are the orifices of the lateral branches.

Not unfrequently a central (hepatic) vein will divide into
two branches within a lobule, in which case the latter seems
to possess two apices, which become joined together as we ap-
proach its base. The connection between the portal and hepatic
veins takes place only through their capillaries.

The hepatic artery is comparatively small. It enters the
liver together with the duct and portal vein, and at once breaks
up into branches, which, anastomosing with each other, form a
large-meshed network. The arterial branches are distributed
to the vessels mentioned, which they enclose, and also to the

THE LIVER AND BILIAKY APPARATUS. 187

connective tissue which surrounds the latter. The hepatic arte-
ry also gives off nutrient branches which supply its own walls,
and small twigs, which, piercing the substance of the liver be-
tween the lobules, supply the branches of the hepatic vein.
The ultimate branches of the artery are contained within the
interlobular canals, and break up into capillaries at the peri-
phery of the lobules, which they traverse for a short distance
to form a distinct network. There is no communication between
the intralobular capillaries of the hepatic artery and those of
the portal vein. The former seem destined to supply the ad-
jacent vessels, and probably the small amount of iutralobular
connective tissue to be spoken of hereafter.

It has been thought by some (Chroaszewski, Bindfleisch, and others) that the
capillaries of the hepatic artery end midway between the interlobular and cen-
tral veins, within the lobule. Beale and Kiernan have noticed that an arterial
branch here and there enters a lobule ; while Theile, Davis, and others describe
a capillary network about the periphery of the lobules.

Finally, branches of 0.05 to 0.1 mm. in diameter are dis-
tributed to the capsule of the liver, where they break up into
capillaries, radiating in all directions and anastomosing with
each other to form "a large-meshed network, which communi-
cates with the capillaries of the phrenic, mammary, and supra-
renal arteries. This plexus empties into small twigs, the so-
called inner roots of the portal vein.

The capillaries of the liver may be injected either through
the hepatic or portal vein, or both, as before stated. For in-
jecting the hepatic artery the author prefers his cold solution
of carmine-glycerine.1 The gland to be injected must be as
fresh as possible. If, for example, a dog be selected for this
purpose, the abdomen should be opened and the animal allowed
to bleed to death by section of the vena cava. Now introduce
into the hepatic artery the canula of a syringe tilled with the
carmine-glycerine, secure it in place and inject. Harden the
organ in alcohol, cut sections, and mount in balsam. The liver
will not be uniformly injected, and only those portions can be
utilized in which the injected mass seems to be widely diffused.

If, in addition to the artery, the hepatic vein be injected
with a blue colored mass, beautiful results may be obtained.
Sections in which the lobules are cut transversely show the

1 See chapter on the Kidney.

188

MANUAL OF HISTOLOGY.

central veins occupying the position of the axes of the lobules
and the capillaries, pursuing a radial course and anastomosing
with each other by transverse communications.

Since the capillaries successively divide from the centre
toward the periphery, it follows that they are much less numer-
ous at the former than at the latter point. A section through
the long axis of an acinus will show that the central vein is
divided lengthwise, and that the capillaries are given off from
it almost at right angles to its course.

Nearer the summit of the lobule, however, the central vein
is seen to break up into diverging capillaries. If the section
has been made to one side of the central vein, but yet parallel
with its axis, many capillaries will be cut across, more or less
transversely, and will then appear as small, circular, or oval
rings.

The connective tissue of the liver. — Glisson's capsule is
formed of longitudinal bundles of connective tissue which are

loosely interwoven. It serves
to bind together the hepatic
artery, portal vein, and hepatic
duct, and also fills out the
small spaces left between the
ramifications of these vessels
(Fig. 82). Sections from a liver
hardened in chromic acid or
alcohol, and immersed in a di-
lute solution of caustic potassa,
or simply pencilled, show the
connective tissue well. About
the hepatic vein it is thin and
dense, and firmly united to the glandular structure, so that
when cut transversely these vessels appear to gape. In the
camel the connective tissue is greatly developed,1 even more so
than in the hog. The interlobular septa are very dense and
fibrillated ; in the interior of the lobule the connective tissue
has a lamellar structure.

According to Ewald and Kuehne, minute bundles of fibrous tissue extend
beyond this interlobular connective tissue, and piercing the lobules eventually
surround the central veins.

FIG. 82. —Connective- tissue of a child's liver,
after hardening in alcohol and pencilling : «, a,
capillary vecxels containing a few blood-globules ;
6, 6, connective-tissne fibrils ; c, c, liver cells not
removed by pencilling.

1 Turner, Wm., Journal of Anat and Phys., Vol. XI., p. 2.

THE LIVER AND BILIARY APPARATUS. 189

TJie liter-cells. — The liver-cells are found lying within the
meshes of the capillary network of the lobules. If we bear in
mind the shape of the intralobular capillary reticulum, the
arrangement of the hepatic cells will be readily understood.
The meshes of the capillary network have about the same
diameter as the capillaries themselves. Hence it follows that
the cells which occupy these meshes must also have the appear-
ance of a reticulum. But inasmuch as the vascular meshes
contain two or three liver-cells, it is evident that two neighbor-
ing capillaries must be separated from each other by at least
one liver-cell. Hence, in sections where the capillaries are cut
transversely, their circular openings will be surrounded by a
ring of liver-cells, or a circle of capillaries will enclose a mass
of glandular substance. In sections which cut the central
vein transversely the radiating capillaries will enclose radiat-
ing rows of liver-cells. (See Fig. 81.) These are either joined
to one another by the intervention of other liver-cells, or
they are separated from one another by transverse capillary
branches.

On the other hand, in sections where the central vein is cut
lengthwise, the (nearly) parallel intralobular capillaries will ap-
pear separated from one another by correspond-
ing rows of liver-cells. The glandular substance
of the liver would then be composed of small,
solid columns or rows of cells united to each
other by other cells, thus forming one connected
mass, and containing within its meshes the cap-
illary network. In the fresh state the liver-cells
appear as spherical or egg-shaped bodies, usu-
ally presenting facets. They are somewhat flat-
tened by being pressed against one another (Fig.
83). Corpuscles possessing processes are some- „ Fl°- ss.- Human

1 liver-cells : rt, with sin-

timeS fOUnd. •?'<» nucleus; 6, with

_. . . double nucleus. Prey.

The hepatic cells are about 0.013—0.02 mm.
in diameter, and possess one or two nuclei,1 which are gener-
ally spherical, although they occasionally appear to be flat-
tened ; the diameter is 0.006—0.007 mm. The liver-cells do
not possess any membrana propria, but a hardened boundary
layer seems to exist in its place. It is probable also that the

1 Occasionally three or five nuclei, especially in young subjects (Beale).

100 MANUAL OF HISTOLOGY.

cells are bonnd together by a colloid substance, although this
is a point which has not yet been definitely settled.

Sections of a dog's liver, immersed for a short time in dilute osmic acid, will
occasionally exhibit a brown or black tracing between adjoining cells. Pres-
sure on the cover glass will part them and leave the darkened material free in
the field of vision. I have satisfied myself that this tracing is not of a nerve,
biliary duct, or connective-tissue fibril ; it is either a portion of the boundary-
layer of a liver-cell, or, as I suppose, a colloid substance between two cells.
This appearance, however, is not constant.

The protoplasm is of a dark brownish or greenish color. It
is viscid, and contains numerous granules of small size, in ad-
dition to smaller or larger fat-droplets.1 In livers hardened by
chromic acid or alcohol, the shrinkage of the cells causes them
to appear polyhedral, and they also seem much darker than in
the fresh state. If the portal or hepatic vein has been injected,
the cells will show distinct indentations produced by the dis-
tended capillaries.

When liver-cells are treated with diluted acetic acid, their
protoplasm becomes pale, while their nuclei are rendered more
conspicuous. In a dilute solution of caustic potassa the cells
swell up, become rounded, and are finally dissolved. With
water they also swell up, become paler and more rounded, and
at length disintegrate. In the fresh state, by the addition of
an indifferent fluid (i per cent, solution of chloride of sodium,
or iodized serum), the liver-cells are said to show protoplasmic
movements. The granular substance of the liver-cells has
been shown (by Schiff, in frogs, and by Nasse, in certain mam-
malia) to consist of an animal amylum, which is converted into
sugar through the agency of a peculiar ferment.

The fat-droplets may be either small in number and size or
quite numerous and large. Not infrequently they coalesce to
form larger fat-globules. In the so-called fatty infiltration they
are very large, and compose the greater part of the cells. The
nuclei are granular, and where two or more of them occupy
the same cell, they may apparently be united to each other.

1 According to Kupffer and Klein the substance of the cells is composed of a
honeycombed network, i.e., an intracellular reticulum. Klein says the nucleus is lim-
ited by a thin membrane, and includes an intranuclear network, containing occa-
sionally one or two nucleoli. The intranuclear network is in continuity with the
ictracellular one, and the network of contiguous cells are in connection with one
another (Klein and Smith : Atlas of Histology).

THE LIVER AND BILIARY APPARATUS. 191

Division of a nucleus, as described by Kolliker, I have never been able to
confirm. When two nuclei are placed in contact, there may be an appear-
ance of division, but the actual process is not easy to see.

Thin liver sections may be stained either in carmine fluid or
hsematoxylon, and preserved in glycerine or balsam.

The larger bile-ducts. — If, for the sake of convenience, we
imagine that the hepatic duct enters the liver to be distributed
to its substance, we may describe it as giving off two primary
branches at the transverse fissure, one passing to the right
lobe, the other to the left. As these branches continue their
course, following the subdivisions of the hepatic artery and
portal vein, they also undergo successive divisions, and at
length enter the interlobular canals. In this position their
diameter varies between 0.02 and 0.03 mm.

The primary branches do not, however, pass unchanged
into the liver tissue. They ramify even before entering the
gland, but such vessels are distributed only to the under
surface (Henle). Other biliary ducts, given off in the trans-
verse fissure, form a network on the upper surface, as may be
demonstrated by injecting the hepatic duct with carmine-gly-
cerine. The branches of these networks then enter the liver-
tissue and ramify throughout it, following the subdivisions of
the hepatic artery and portal vein.

As the divisions of the hepatic duct diminish in size, the
thickness of their walls undergoes proportionate diminution.
The trunk of the hepatic duct comprises an internal layer
measuring 0.15 mm. in thickness, and an external layer of 0.2
— 0.3 mm. Both of these coats are composed, according to
Henle, of interlacing connective-tissue bundles, in which elas-
tic fibres are freely intermixed. These ducts have an internal
lining of cylindrical epithelium, which is 0.05 mm. in height.
Even where the branches measure only 0.2 mm. in diameter
they have cylindrical epithelium surrounded by a single layer
of connective tissue longitudinally disposed, in which there
are also muscle-corpuscles, distinguished by their long, rod-
shaped nuclei (Heidenhain). The most minute biliary pas-
sages consist of a structureless membrana propria, which is
lined with flattened cylindrical epithelia.

Glands of the ducts. — In the trunk of the hepatic duct and
its subdivisions, down to those branches of which the diameter
is not less than 0.5 mm., the mucous membrane is provided

192 MANUAL OF HISTOLOGY.

with numerous irregular excavations, measuring 0.15 — 0.3 mm.
in their long diameter. In this trunk there occur also a great
number of pores or orifices, which, on examination, prove to
be the mouths of the passages leading from simple and com-
pound gland -like bodies, the so-called glands of the bile-ducts.
The simple glands consist merely of single vesicles, or alveoli,
with afferent passages, all of which are imbedded in the mu-
cous membrane ; or of two or more vesicles with a single pas-
sage. The compound glands are formed by the union of two
or more simple ones, which have a common passage. The}^ are
quite large, and their expanded portions lie on the outer sur-
face of the hepatic duct. When filled by injection with gela-
tine they are visible to the naked eye. The passages pierce
the walls of the duct at an acute angle, pursuing a course
within its walls, nearly parallel to the duct itself ; the opening
into the mucous membrane is therefore quite a distance from
the gland-vesicles. According to Henle, these compound glands
are not found in the larger branches of the hepatic duct, but
they occur frequently in the network of bile-ducts situated
in the transverse fissure. Allusion has already been made to
them. The vesicles measure 0.04 mm. in diameter, and, like the
excavations in the larger branches of the duct, are lined with a
cylindrical epithelium, in no way differing from that of the
duct itself ; the afferent passages also possess the same kind
of epithelium.

Structures allied to these excavations and glands occur in
small number, in the bile-ducts ' which are found in the liga-
mentum triangulare and on the diaphragm, where they appear-
as villous prominences on the duct- walls.

According to Theile, Weber, and others, these bile-ducts represent the last
vestiges of an atrophied liver substance, the existence of which dates back to
infancy, or perhaps to fetal life.

The excavations in the larger branches are either simple
diverticula of the internal walls, or the openings of lateral bile-
ducts ; the punctate pores are the orifices of the outlet pas-
sages of duct-glands.

Capillary bile-ducts.— When the larger bile -ducts, by con-

1 Vasa aberrantia of E. H. Weber.

THE LIVER ATTD BILIARY APPARATUS. 193

tinuous subdivision, have at length reached the interlobular
canals, in conjunction with the branches of the portal vein and
hepatic artery, they send capillary branches within the sub-
stance of the lobule, and thus form an intralobular network.
These capillary ducts are of extreme delicacy, measuring only
from 0.001 to 0.0012 mm.

In order to demonstrate them fully they should be filled by
natural injection. The substance to be employed for this pur-
pose is a solution of pure indigo-carmine. The animal serving
for injection (rabbit or dog) should be secured in the manner
described in the chapter on the Kidney, where all the neces-
sary manipulations are fully detailed. The best results are
obtained by injecting a cold, saturated solution of indigo-
carmine into the external jugular vein, directing the stream
toward the periphery (brain) ; 5 or 10 ctgms. are to be injected
at intervals of thirty to forty minutes, and the injection con-
tinued until from 25 to 50 ctgms. have been used, the amount
varying according to the size of the animal. It takes a longer
time for the elimination of indigo-carmine through the capillary
bile-ducts than for the same process by way of the renal tubules,
and a larger amount of solution will therefore have to be em-
ployed. As soon as large quantities of the indigo solution have
been injected into the jugular vein, the animal becomes uncon-
scious and there is a decrease of temperature ; hence, it should
be covered over with layers of cotton-batting. After a variable
time (three to twelve hours) the animal is killed in the follow-
ing manner : The abdomen is opened and the canula of a large
syringe filled with absolute alcohol secured in the lumen of the
portal vein ; the inferior vena cava is then cut across above the
entrance of the hepatic vein, and the piston of the syringe
pushed home. The liver, which before was of a uniform blue
color, now presents a marbled appearance, not unlike that of
malachite.

Or, the portal vein may be injected with the writer's carmine-
glycerine, the vena cava having been divided as above. In
either case the liver is to be removed at once and placed in a
vessel containing absolute alcohol, and while immersed in that
fluid cut into small fragments. Sections may then be made in
a few hours.

The arrangement of the bile-capillaries differs in different
animals. In the rabbit, for instance, they lie between the ad-

194

MANUAL OF HISTOLOGY.

joining surfaces of two contiguous cells, and rarely in the
canals formed by the edges of three or more cells (Hering '). So
that while the blood-capillaries occupy the canals previously
described, the bile-capillaries form an independent network be-
tween the boundary surfaces of the liver-cells (Figs. 84 and 85). '
In cross sections they may be seen, appearing as small, circular

FIQ. 85.

Flos. 84 and 85.— Injected liver of rabbit. The narrow, reticulated bile-capillaries are shaded with
longitudinal, the broader blood-capillaries with transverse lines. Within the boundary line or septum of
two contiguous cells the cross-section of a bile-capillary is seen as a dark spot or point. The liver celU
contain one or two nuclei. In Fig. 84, the bile-capillaries are slightly distended by the artificial injec-
tion ; in Fig. 85, markedly so: Hering.

openings between the cells, while in longitudinal sections they
present a linear arrangement (Figs. 85 and 86). In the dog
this arrangement is the same, only here the bile-capillaries
occur more frequently in the canals formed by the edges of the
lower cells.

x

According to Hering, both in rabbits' and dogs' livers the blood-capillaries
are separated from the bile-capillaries by the intervention of at least one liver-
cell. Livers in which the bile-capillaries have been injected by the natural
method with indigo-carmine do not always demonstrate this. And here it may
be remarked, that in artificial or forced injections of the bile-capillaries they
are always distended beyond their natural diameters.*

1 Hering : Ueber den Ban der Wirbelthierleber, and article on Liver in Strieker's
Manual.

* Compare Figs. 84 and 85, after Hering. Even in Fig. 84 the bile-capillaries are
larger than they ougbt to be. In an article on the liver by Dr. W. G- Davis, in the
Amer. Jour. Med. Sci., Vol. LXXVIII., the distention of the capillaries is excessive.

THE LIVER AND BILIARY APPARATUS.

195

By conjoined natural injection of the bile-capillaries and
artificial injection of the portal system with carmine-glycerine
by the methods above detailed, very gratifying results are ob-
tained. Care must be taken,
however, not to use too much
force during the process of in-
jection, and only such por-
tions of the liver should be
chosen for sections as show,
by their red color, a perfect
filling of the portal branches.

While the elimination of
the indigo-carmine is taking
place within the liver of the
living animal, the bile-capilla-
ries probably contain the salt
in a soluble form. The addi-
tion of absolute alcohol at
once precipitates this color-
ing reagent in the form of
exceedingly fine stellate crys-
tals, or as finely granular mat-
ter, which may in some meas-
ure account for the angular
character of the biliary capil-
laries, as seen in such specimens. Gentle curves, such as are
represented in Fig. 85, never appear. The constringing action
of the alcohol on the liver-cells has unquestionably some effect,
and therefore modifies the normal appearance.

Natural injections further show the great preponderance of
the biliary- over the blood-capillaries. In the liver of a dog,
for instance, each liver-cell seems suspended within two or
three (rarely four) bile-capillaries, and where the latter are

Flo. 86. — Liver of a three-months1 child, hard-
ened in chromic acid. The capillaries are filled with
red blood-corpuscles (Indicated by colorless rings) and
a few leucocytes. The cross section of a bile-capillary
is shown within the boundary line of any two con-
tiguous cells. A similar cross section is shown in
the canal formed by three adjoining liver-cells.

One need only compare Fig. 3 in Davis's article with Fig. 84 of Bering's, which, by
the way, is a good illustration.

The first to describe the intralobular network of bile-capillaries were Andrejevic
(Ueber der feineren Ban der Leber. Wiener Sitzungsbericht. 1861) and MacQillavry
(Zur Aiiat. d. Leber. Wiener Sitzungsbericht, 1864). Chronszewski was the first to
inject the bile-capillaries by natural injection (Virchow's Archiv, Bd. 35). MacGillavry
Chronszewski, Budge, and others, described the bile-capillaries as possessing true
walls.

196

MANUAL OF HISTOLOGY.

V

joined together the calibre of the capillary is markedly in-
rivax-tl. Sections made parallel to the external surface of the
liver, immediately under the capsule, generally cut the central

vein transversely, and such sec-
(/ /,.?-3*\ tions show that the bile-capillaries

/tldHHJI possess a somewhat radial course

(Fig. 87). Human livers can rarely
be obtained in a fresh state, and
examinations of their bile-capil-
laries are therefore attended with
difficulty.

Do the bile-capillaries possess
walls of tJieir own f — This ques-
tion must be answered in the
affirmative. In specimens where
the bile-capillaries have been in-
jected by the natural method,
cross sections of such capillaries
will demonstrate, with high pow-
ers, that there is a dot of blue indigo-carmine surrounded by
a distinct circle which is perfectly transparent and in marked
contrast to the somewhat yellowish color of the adjoining
liver-cells. (See Fig. 88.) It is more difficult to see this in
sections which cut the capillaries in their longitudinal diam-
eters, but where two or more capil-
laries unite this halo is again seen.
That this appearance is due to the pres-
ence of a true wall seems clear, but all
doubts will be dispelled by watching
the diffusion which takes place in such
a section on the addition of a few drops
of water under the cover glass. The
indigo-carmine becomes dissolved in
the water, forming a deep blue liquid
which stains the surrounding cells and
vessels of a uniform color. While
watching a bile-capillary during the
progress of this action it appears to
stand out more prominently than before, and its walls become
more distinct. In a few moments the cells will have become
swollen by the imbibition of water, and the picture gradually

FIG. 87.— Capillary bile-ducts of a rabbit,
distended by artificial injection : 1, a portion
of a lobule ; 0, central vein ; 6, 6, interlobnlar
veins ; c, c, bile-ducts ; d, d, blood-capillaries ;
e, e, bile capillaries.

Fro. 88.— Liver of the dog. Nat-
ural injection of bile - capillaries,
showing double contour of the capil-
laries, which are only partly filled
with injection. Cross sections of
the capillaries show a dot of indigo-
carmine surrounded by a distinct
halo. The woodcut does not show
this satisfactorily. In the specimen
the lines corresponding to the walls
of the capillaries are of the utmost
delicacy. Magnified 450 diam.

THE LIVER AND BILIARY APPARATUS. 197

fades, until at length it would be difficult to even locate the
original seat of the capillary. I have verified this over and
over again. The capillary walls seem to be structureless ; at
least with a power of 1,400 diameters I have been unable to
detect any structure. The membrana propria of the inter-
lobular bile-ducts is continued on to the capillaries within the
lobule.

Hering, Henle, and others do not believe that the bile-capillaries possess
walls of their own, but suppose them to be contained within the boundary
surface of the liver-cells, the latter taking the place of the epithelium of the
inteiiobular bile-ducts. Henle further quotes Schweigger-Seidel (in the Archiv
far path. Anal, und Phys., XXYTI., 505, 1863), who injected the bile-capillaries
with faintly colored gelatine, and showed that by warming the slide the gela-
tine dissolved without leaving any residue whatever. From what has been
said of artificial injections, and recognizing the extreme delicacy of the bile-cap-
illaries, it is not surprising that this result was obtained after injecting a warm
solution of gelatine into the capillaries. The walls of these capillaries are
homogeneous and exceedingly delicate, so that they are destroyed by a mod-
erate degree of heat. Very soon after death they undergo a sort of liquefac-
tion, and what was before a vessel with true walls is now an open channel,
through which an artificial fluid can be made to force its way.

At first the elimination of the indigo-carmine takes place
in the bile-capillaries on the external border of the lobule,
and somewhat later the capillaries about the central vein be-
come filled. Neither the protoplasm of the liver-cells nor their
nuclei ever become stained with the blue solution during the
process of elimination ; such coloring would be the result of
post-mortem diffusion. But the cylindrical epithelium of the
glands is colored blue, and indubitably these glands excrete
the indigo-carmine, as do the cells of the convoluted tubules of
the kidney. Whether they secrete any substance during life,
or what that substance may be, has not yet been determined.

Theile, Kolliker, and Kiernan suppose that these glands secrete a mucous
substance which becomes mixed with the bile. Henle regards these glands
and excavations as reservoirs which are occasionally filled with bile. From
what has been said above it would appear that the cylindrical epithelium of
the glands eliminates the indigo-carmine, and hence we may suppose that
they secrete some fluid or substance during life.

TJie gall-bladder. — The walls of the gall-bladder are about

198 MANUAL OF HISTOLOGY.

2 mm. thick, and are composed of three coats : ' an internal,
mucous and muscular ; a middle, of connective tissue ; and
an external, the serous. .The internal coat, 0.4 to 0.5 mm.
thick, is composed of alternating layers of connective tissue
and smooth muscle fibres, the most internal being a layer of
connective tissue which contains a fine meshed capillary net-
work. The connective tissue is dense and the muscle fibres are
arranged in the form of interlacing bands. The internal sur-
face is lined by a layer of cylindrical cells bearing a thickened,
striated edge, and the surface is traversed by a network of
small intersecting ridges, forming, as it were, a sort of lattice-
work. The middle coat, 0.5 to 1 mm. thick, is formed of con-
nective tissue, the meshes of which are wider on the internal
than at the external surface. This coat contains the larger
vessels and nerves. The external, or serous coat is thin, and
consists of a layer of dense connective tissue and peritoneum.
A few mucous glands* are found scattered here and there in
the walls of the gall-bladder. Sections from this organ, hard-
ened in alcohol, may be stained with the carmine or picro-car-
mine solution and mounted in glycerine or balsam.

The cystic and common ducts resemble in structure the
hepatic duct. The inner surface of the former is thrown into
crescentic ridges, and in the region of the neck of the gall-
bladder the connective tissue of the internal coat shows a
circular arrangement. The ducts contain no muscle fibres.

The lymph-vessels. — These may be divided into a series
of superficial -and deep channels. The former are situated in
the capsule of the liver and form a capillary reticulum with
small meshes, the larger branches of which accompany the
arteries in pairs and communicate with each other by trans-
verse anastomoses. They are found in Glisson's capsule, and
they also form a network somewhat larger meshed than the
preceding. They accompany the hepatic artery and portal
vein and their branches into the interior of the liver, and form
anastomoses with the superficial lymph- vessels. The lymph-
canals may easily be injected with colored material (carmine-
glycerine) by filling a large hypodermic syringe with the liquid
and injecting one of the larger lymph-vessels in the hilus of

1 Henle : Eingeweidelehre.

'Luschka: Virchow's Archiv, 1857, and Zeitechr. f. rat. Med., 1858.

BIBLIOGRAPHY. 199

the liver. The syringe may be refilled three or four times
without removing the canula, and the injection must be made
in the direction of the normal lymph-current. In this way
the colored liquid will flow backward into the smaller vessels.
During the injection of the larger branches their proximal ends
should be secured by clamps or ligatures.

The nerves of the liver enter the organ at the hilus and fol-
low the course of the vessels. They are composed mostly of
non-medullated elements, a few medullated fibres being found
in the larger branches. They cannot be traced into the lobules.

BIBLIOGRAPHY.

KIERNAN. Anat. and Phys. of the Liver. Philos. Trans. 1833.

LAMBRON. Archiv. gen. 1841.

KRUKENBERG. Miiller's Archiv. 1843.

WEBER, E. H. Mailer's Archiv. 1843. Program. coL fasc., II. Lips., 1851.

TIIEILE. Wagner's Handworterb. Bd. II. 1844.

RETZIUS. Miiller's Archiv. 1849.

WEDL. Sitzungsber. d. Wiener Akad. 1850.

RAINEY. Quart. Jour. Microsc. Sc. Vol. I. 1853.

GERLACH. Gewebelehre. 1854.

BEALE. Philos. Trans. 1855. Anat of the Liver. 1856. Archives of Med. Vols.

I. and II.

VIRCHOW. Virchow's Archiv. Bd. XI. 1857.
LUSCHKA. Henle u. Pfeuffer's Zeitsch. Bd. IV. 1858.
BUDGE. Reichert u. Du Bois Reymond's Archiv. 1859.
His. Zeitschft. f. wiss. Zoologie. Bd. X. 1860.
WAGNER, E. Archiv d. Heilkunde. 1860. Oester. Zeitschrft f. prak. Heilkunde,

1861.
EBERTH. Zeitschrft. f. wiss. Zoologie. 1860. Med. Centralbl. 1866. Virchow's

Archiv. 1867. Schultze's Archiv f. mik. Anat Bd. IIL
ANDREJEVIC. Sitzungsber. d. Wiener Akad. 1861.
RIKSS. Reichert u. Du Bois-Reymond's Archiv. 1863.
SCHWEIGGER-SEIDEL. Reichert u. Du Bois-Reymond's Archiv. 1863.
MACGILLAVRT. Sitzungsber. der Wiener Akad. 1864.
IRMINGER. Zeitschft. f. wiss. Zoologie. Bd. XVI. 1866.
CIIRONSZEWSKI. Virchow's Archiv. Bd. XXXV. 1866.
HERING. Sitzungsber. d. Wiener Akad. 1866. Strieker's Handbuch. Bd. I.

1871.

KOLLIKER. Handbuch d. Gewebelehre. 1867.
VON BIESIADECKI. Sitzungsber. d. Wiener Akad. 1867.
HEIDENHAIN. Studien aus d. phys. Institute z. Brealau. Heft IV. 1868.
KISSELEW. Med. Centralbl. 1869.

200 MANUAL OF HISTOLOGY.

PFL.CGEK. Pfliiger's Archiv. Bd. II. 1869. n. IV. 1871.
HENCE. Eingeweidelehre. 1873.
' LEOROS. Jour, de 1'anat. et de la phys. 1874.
COHNHEIM a. LITTEN. Virchow's Archiv. Bd. LXVI. 1876.
EWALD u. KUEHNB. Verhand. Naturhist. med. Vereins zu Heidelberg. 1 Bd. 5

Hft. 1876.

KOLATSCHEWSKY. Schultze's Archiv. Bd. XIII. 1876.
TURNER. Journ. of Anat. and Phys. Vol. XI. 1877.
WENDT. Med. Centralblatt No. 15. 1878.
DAVIS. Amer. Jour. Med. So. Vol. LXXVIII. 1879.
FRITSCH. Archiv. fur Anat. und Phys. Phys. Abtheil. 1879.
KLEIN and SMITH. Atlas of Histolojy. Part X. 1879—1881.

CHAPTER XIV.

THE KIDNEY.

Br ABRAHAM MAYER, M.D.,

Curator of the Manhattan Eye and Ear Hospital, New York City.

General plan of structure. — The glandular substance of the
kidney is divided into two parts, an external or convex por-
tion, called the cortical substance, or cortex, and an internal
or concave portion, the medullary substance, or medulla.
This division can be readily seen by cutting a kidney into two
equal parts in the line of its long diameter. An intermediate
zone, which separates the cortical from the medullary sub-
stance, is called the boundary layer of the kidney. The whole
organ is enveloped in a fibrous membrane, the capsule.

The medullary substance contains the pyramids of the kid-
ney, and is therefore also called the pyramidal portion. The
apex of each pyramid, the papilla, projects into a special arm
of the renal pelvis, viz., a calyx; the base or expanded por-
tion is directed toward the cortical substance, and sends pro-
longations into the latter.

An examination of the cortical substance shows it to be
composed of two distinct varieties of tissue, running parallel
to one another toward the free surface. One has a fibrous ap-
pearance, and is composed of cylindrical cords. It is a con-
tinuation of the pyramids. These pyramidal prolongations '
(Henle) are also called medullary rays (Fig. 89). The other
portion, situated between the prolongations, is a granular-look-
ing material, called the cortical substance proper, or labyrinth
of Ludwig.* The latter contains numerous small bodies,
which are of a distinctly red color when there is a large

1 Ludwig und Zawarykin : Zeitschrft f iir rat. Med,, 1863. They are also called
the prolongations of Ferrein.

2 Ludwig : Strieker's Manual, p. 461.

202

MANUAL OF HISTOLOGY.

amount of blood in the kidney ; they are the Malpighian
bodies, or glomeruli (Fig. 89, E).

The boundary layer ' is characterized by numerous blood-
vessels, some of which unite to form an arcade (Fig. 89, C),
which is parallel to the convex surface of the kidney, and from
which branches are given off to the cortical substance proper.

The renal artery, before it enters the
hilum of the kidney, divides into
branches, which pierce the medulla
between the pyramids and ascend
toward the cortical substance until
they reach the boundary layer. Here
they divide obliquely or at right
angles to give off smaller branches,
which have the direction and arched
ppearance above referred to (Fig.
89, C). These arched vessels then
send off the branches already men-
tioned, which traversing the centres
of the cortical substance proper, afc
right angles to the parent stem (Fig.
89, D), extend almost to the capsule
of the kidney. On their way they in
turn give off smaller twigs, each of
which bears a glomerulus upon its
extremity (Fig. 89, E). In this way
there is an alternate arrangement of
pyramidal prolongation and cortical
substance proper (Fig. 90). Though
he pyramidal prolongations almost
reach the capsule of the kidney,
they never quite touch it, being sep-
arated by the interposition of some cortical substance proper
(Fig. 89).

Specimens for study should be made from a fresh kidney,
in which the renal artery has been injected with carmine-gela-
tine, the whole organ having been subsequently immersed in
alcohol of 50 per cent, strength. When in that fluid it is to be
divided into four or more parts, allowed to remain therein for

Fio. 89. — Human kidney. Vertical
section through cortical and medullary
substances : A. branch of renal artery ;
B, vein, immediately beneath former, but
hardly visible in the figure; C, arched
arterial branches in the boundary layer ;

D, artery of the cortical substance proper ;

E, Malpighian bodies or glomeruli : F,
medullary rays or pyramidal prolonga-
tions ; O, vessels of the medulla, the vasa
recta, x 10.

'Henle: Grenzschicht, Eingeweidelehre.

THE KIDNEY.

203

twenty-four hours, afterward transferred to stronger alcohol,
then to absolute alcohol, and finally mounted in dammar or
balsam. Vertical sections show the arrangement represented
in Figs. 89 and 90 ; transverse sections, the appearance of
Fig. 92.

The substance of the kidney is composed of secreting and
collecting tubules, vessels, and a stroma, which fills the inter-

Fro. 90.— Human kidney. Vertical section through cortical portion : A, pyramidal prolongation ; B,
cortical substance proper ; C, artery ; D, glomerulus. x 64.

spaces between the tubules, and is more abundant in the med-
ullary than in the cortical substance. In human adults this
connective material is found in small quantity and is a sort of
colloid substance. In the lower animals it is more abundant,
and assumes the character of real connective tissue. In young
infants there is said to be a greater proportionate amount of
this tissue than in subsequent life.

The renal tubules. — The tubules are found both in the corti-

204

MANUAL OF HISTOLOGY.

cal and medullary substances ; they are of different diameters
and pursue either a straight or tortuous course. Some have a
basement membrane (membrana or tunica propria), on which
the epithelium rests ; others appear to have none. The tu-
bules are clothed with epithelium of different varieties. Speci-
mens should be made from a kidney that has lain for twenty-
four hours in a 5 per cent, solution of chromic acid. A small

FIG. 91. — Schematic representation of the kidney : A, medulla ; B, boundary layer ; 0, cortical por-
tion ; a, renal artery ; b, renal vein ; c, artery penetrating cortex ; D, capsule enclosing glomerulns ; E,
capillaries ; F, convoluted tubules of first order ; O, looped tubule, descending branch ; H, looped tubule,
ascending branch ; I, convoluted tubule of second order ; J, collecting tubule ; K, vasa recta.

piece of the gland is to be placed on a slide, and a drop of glycer-
ine added ; the tubules may be isolated by teasing with needles.
In Fig. 91 there is a schematic representation of the vascular
distribution and course of the tubules in one of the pyramids.
Each tubule takes its origin in an expansion that surrounds
the glomerulus, and is called Bowman 's or Muller's capsule.1

1 Miiller, in 1830, described the capsules, but regarded them as vesicles which had
no connection whatever with the uriniferoua tubules. Bowman, in Philosoph. Trans-
act., 1842.

THE KIDISTET. 205

It is round or elliptical in shape, and has a diameter of about
0.2 mm. Where the capsule empties its contents into the
tubule, there is a slight constriction known as the neck ; it is
very distinct in some of the lower animals. The canal then en-
larges and begins to pursue a tortuous course in the cortical
substance ; it is now called a convoluted tube ' (Fig. 91, F). It
next undergoes sudden diminution in size and passes straight
through the medulla iintil, at a variable point, it bends upon
itself, forming a loop ; then, ascending, it increases in calibre, and
in the cortical substance becomes convoluted for the second time.
Those canals that are nearest the glomeruli are called convo-
luted tubules of the first order, the others convoluted tubules
of the second order. Between these two are the looped tubules
of ffenle, just described, each being divided into a descending
and ascending branch (Fig. 91, G and H). The convoluted
tubules of the second order terminate by emptying into tubules
of greater diameter, called collecting tubules,* which descend
through the cortical and medullary substances, and, receiving
other collecting tubules on the way, finally empty into the
pelvis of the kidney (Fig. 91, J).

At the base of each pyramid there are a vast number of col-
lecting tubules, but as they successively empty into larger
collecting tubes, the area they occupy is thereby diminished ;
at the apex of the papillae, where they ultimately discharge
the urine into the pelvis of the kidneys, there are only about
twenty in number. This gradual coalescence of the tubes gives
to the pyramids a conical shape, but the breadth of the base is
also partly due to the presence of the looped tubules which
pass down into the pyramids for a varying depth.

The larger collecting tubules may be readily injected with
Beale's blue fluid ' or carmine-gelatine, either directly or from
the ureters ; it will be found, however, that the injection will
seldom extend beyond the looped tubules, owing to the small
diameter of the descending branches.

1 Tubulus contortus. * Straight tubules of Bellini.

8 Glycerine, pure, 2 oz. ; tr. perchloride iron, 10 drops ; ferrocyan. potassium, 8
grains ; strong hydrochl. acid, 3 drops ; water, 1 oz. Mix the tincture of iron with
one ounce of the glycerine ; and the ferrocyanide of potassium, first dissolved in a little
water, with the other ounce ; mix gradually, and shake during admixture ; add the
iron to the ferrocyanide ; lastly, add the water and hydrochloric acid. Beale :
Microscope, p. 87.

206

MANUAL OF HISTOLOGY.

Bowman's capsule is composed of a structureless basement-
membrane surrounding each glomerulus. Upon the inner sur-
face of these capsules is a .continuous layer of flat, epithelioid
cells,1 which are continued over the glomerulus itself.3 Occa-
sionally an epithelioid cell may be seen between the vessels of
the coil composing the glomerulus.

Each capsule is pierced by two vessels, called, respectively,
afferent and efferent. The former enters the capsule and forms

-c

Pio. 92.— Human kidney. Transverse section of cortical portion, showing the alternating arrangement
of pyramidal ray and cortical substance proper : A, A, pyramidal rays ; B, convoluted tubule ; C, glom-
ernlus ; D, D, arterial vessels, x 65.

the glomerulus, while the latter makes its exit close to the en-
trance of the former. The layer of epithelium above described
passes over from the inner surface of the capsule on to the
glomerulus about the points of entrance and exit just men-
tioned. On the opposite side, the capsule becomes continuous
with a convoluted tubule. To obtain specimens, the renal artery
of a fresh kidney should be injected with blue gelatine and then
placed in alcohol. Vertical and transverse sections of the cor-
tical substance may then be made. They should be stained in
carmine and examined in glycerine, or the artery may be in-
jected with absolute alcohol and the sections stained as above.
The epithelium of the tubules. — The basement-membranes
of the convoluted tubules of the first order are in direct con-
tinuation with the basement-membranes of the capsules. Their
diameter averages 0.04 mm. The epithelium of these canals is

1 Schwelgger-Seidel : Die Nieren. Halle, 1865. Henle : Eingeweidelehre, p. 329.
Heidenhain : Zur anat d. Nieren, in Schultze's Archiv, Bd. X., Hft. I. Mayer : His-
tology of the Kidney, Dis. Inaug., 1876. Also Bowman, Johnson, Frerichs, etc.

* Gerlach, Heidenhain.

THE KIDNEY.

207

peculiar, and was first correctly described by Heidenhain.
According to this writer, the greater part of the cell-protoplasm
assumes the form of small, cylindrical bodies, the so-called
rods of Heiderihain, giving the epithelium a stri-
ated appearance (Fig. 93).

To exhibit these appearances, the cortical sub-
stance of a dog's or rabbit's kidney should be
cut into small pieces and immersed for twenty-
four hours or more in a 5 per cent, solution of
the neutral chromate of ammonia. After this
time has elapsed, a small piece of the gland is to
be placed on a slide and a drop of glycerine
added ; the specimen may then be teased and ex-
amined. Portions of the convoluted tubules will
be found floating about in the glycerine, and
should be closely scrutinized. By this mode of
preparation, individual epithelioid corpuscles can-
not be recognized ; on the contrary, they seem
to merge with one another. The tubule may be
regarded as made up of rods transversely dis-
posed, with nuclei embedded in a pulpy mass
that appears to fill its lumen, the whole envel-
oped by the membrana propria. The rods sur-
round the nuclei; and are not all of the same length. They
appear to be hollow, as shown by their sometimes containing
fatty granules. Here and there in the specimen a separate
corpuscle will present itself to the eye; in
such instances the rods can readily be made
out (Fig. 94, A). In the kidney of the rat
these bodies may be isolated with little diffi-
culty (Fig. 94, B). At one end the rods rest
against the membrana propria, to which they
are attached by a colloid material ; their other
extremity is lost in the protoplasm of the cap-
sule, which latter lies internal to them and
appears to have the character of a pulpy mass
containing nuclei. In the dog, the nucleus of
each cell is about midway between the lumen
and the membrana propria. It is surrounded by rods (Fig.
94, A). In the rat this is not the case (Fig. 94, B). Assuming
that the rods begin at the membrana propria, they are directed

FIG. 93. — Convo-
luted tubule from
the kidney of a dog.
Neutral chromate of
ammonia prepara-
tion. The tubule
normally appears
darker than is rep-
resented in the fig-
ure, x 480.

A-

Pio. 94.— Isolated cells
from the convoluted tu-
bules exhibiting rod-like
epithelium : A, kidney of
dog; B. kidney of rat.
x450.

208 MANUAL OF HISTOLOGY.

toward the centre of the lumen of the tubule, and the distance
between any .two adjoining rods at the periphery is necessarily
greater than at the centre. .For the same reason, also, the rods
are more distinctly defined in the former situation ; the micro-
meter screw will have to be used in tracing them inward.

Transverse sections of the cortical substance may be made
by freezing small pieces which have been immersed in a solu-
tion of the neutral chromate of ammonia. Such sections should
be examined in glycerine, or, better, in a saturated solution of
the chloride of potassium in glycerine.1 The radial direction
of the rods is beautifully seen in such specimens (Fig. 95, C),

FIG. 95. — Kidney of dog. Transverse section through the medullary portion, about midway between
the apex and boundary layer. Neutral chromate of ammonia preparation : A, blood-vessel ; B. looped
tubule, descending portion ; C, looped tubule, ascending portion ; D, collecting tubule ; B, connective
tiwue. x 300.

and the individual cells are more clearly defined. Another
method of exhibiting these rod epithelia is to inject the artery
or vein of a fresh, bloodless kidney with a cold saturated solu-
tion of the chloride of potassium, then, after placing the whole
organ in alcohol, divide it in small pieces under that fluid.
After a day or two sections may be made ; they then should be
immersed for a short time in absolute alcohol and clarified by
oil of turpentine. Such specimens show the epithelium to
perfection and may be preserved for a considerable time. Per-
manent specimens can be made by substituting resinous turpen-

1 The glycerine should be heated in a porcelain evaporating-dish, the chloride of
potassium added, and the whole mixture stirred for several minutes with a glass rod.
The glycerine is ready for use after cooling.

THE KIDNEY. 209

tine1 for the common oil. The renal artery or vein may also
be injected with absolute alcohol, and sections prepared as
above. But the epithelium suffers in this way, for the alcohol
causes the rods to shrink, and the colloid substance between
the rods coagulates. Still, the striated appearance is seen near
the membrana propria. Another fact which seems to have es-
caped Heidenhain is that alcohol so injected causes the nuclei
of the cells to recede toward the membrana propria by its
action on the rods.

The action of water on the rods is peculiar. A fresh kidney
must be used and a portion of the cortical substance placed on
a slide, together with a drop of water ; it is then to be teased
with needles and immediately examined. At first the rods are
not distinctly brought into view, but they soon appear with
their contours sharply delineated. This appearance, however,
does not last very long, for the epithelium soon imbibes water,
swells, and then forms an indistinct mass.

In the neck of the convoluted tubules of the frog, coluber,
etc., the epithelium is ciliated. In the frog the cilia have great
length, but the convoluted tubules do not have the rod epithe-
lium. In the dog, cat,-rabbit, etc., the rod epithelium begins
at the neck of the tubule and is continued as far as the loops.

The convoluted tubules of the first order, after ramifying
in the cortical substance, become continuous with the looped
tubules of Henle, as already described." The change takes
place in the vicinity of the boundary layer.

The looped tubules. — The looped tubules traverse the
medulla for a greater or lesser distance. A few almost reach
the apices of the pyramids ; others extend but a short distance
below the boundary layer, while a third class occupies an inter-
mediate position. Good specimens are obtained by macerating
vertical sections of the medulla in a solution of caustic potassa
(i to 1 per cent.). The potassa destroys the epithelium, the
stroma, and the blood-corpuscles, but leaves the basement-

1 Resinous turpentine is prepared as follows : some common oil of turpentine is
poured upon a deep plate, so as to form a thin layer, and a piece of fine muslin is
snugly fastened over it to keep out the dust. The liquid is now exposed to the ac-
tion of the air. In a few days, if the weather be warm, or a week or more, if the
weather be cold, the turpentine will have become thick, yellow, and resinous, and is
now no longer transparent. Resinous turpentine, prepared in this way, forms one of
the best preserving agents. Its use will be spoken of further on.

8 Henle: Eingeweidel., 2te Aufl., p. 316.

210 MANUAL OF HISTOLOGY.

membrane perfectly intact. A fresh kidney is necessary, and
one slightly infiltrated with fat makes the best specimens.
Another method is to embed the kidney of a dog or rabbit
in powdered chlorate of potassa, adding enough dilute nitric
or hydrochloric acid to cover the crystals. After some hours
the connective tissue in the gland will have been destroyed.
Portions of the medulla should then be placed upon a slide
with a drop of glycerine, and teased slightly. A great many
of the loops are broken in this way, to be sure, but still some
will be seen. By this method the epithelium of the narrow
branch is not destroyed.

TJie epithelium of the looped tufiules. — The descending
branch of the loop is small in diameter (0.02 mm.) and pos-
sesses a peculiar distinctive epithelium. The corpuscles are
flat, have prominent nuclei, and rest against the membrana
propria. The disproportionate size of the nuclei causes the
corpuscle to project into the lumen. But these prominences

do not obstruct the passage,
for each one corresponds to
the space between two on

Fro. 96.— Kidney of dog. Descending portion of the Opposite side of the tU-
Henle'e looped tubule. r .

bule, so that there is no bar

to the urine, but the passage is made more or less spiral (Fig.
96). The corpuscles are of a light color. Specimens should
be made from a gland that has been macerated in a 5 per cent,
solution of the neutral chromate of ammonia; they should
be examined-in glycerine. The length of the narrow portion
of the loop is variable in man, the pig, and horse.

The second portion of the looped tubule is wider and its
epithelium peculiar. In man both the loop and ascending
branch are wide, usually ; especially is this the case with loops
high up in the medulla ; in the rabbit it is the ascending
branch only that has this property. Generally speaking, the
length of the broader branch of the loop exceeds that of the
narrow portion. The diameter of the broad portion averages
0.04mm. The epithelium has the same character as that in
'the convoluted tubules ; it is striated and possesses rods.1 It
is not precisely similar, however. The width of the individual
cells is not so great as in the former, and hence the lumen in

1 Heidenhain : loc. cit. Henle : loc. cit. , p. 317.

THE KIDNEY. 211

this portion of the loop is greater than in the convoluted tu-
bules. Specimens prepared with the neutral chromate of am-
monia, as before detailed, give good results. Vertical sections
may be made from a kidney macerated in the ammonia solu-
tion and afterward treated with alcohol ; or, better, from frozen
specimens.

The broader extremity of the looped tubule ascends through
the medulla into the cortical substance and becomes continu-
ous with a convoluted tubule of the second order (Fig. 91, i).
These tubules, the intercalated portions,1 greatly resemble con-
voluted tubules of the first order, as already mentioned. Spe-
cimens should be prepared in the same way as those of the
latter. The convoluted tubules of the second order, after rami-
fying in the cortical substance, terminate by emptying into the
collecting tubules (Fig. 91, J).

The collecting tubules and their epithelium. — The collecting
tubules a possess cylindrical epithelia, the bases of which are
irregular and present point-like prolongations 3 (Fig. 97), which
interdigitate with one another. The nuclei in
the smaller collecting tubules are large and
very prominent, but the protoplasm which sur-
rounds them is not very abundant. The base-
ment membrane is comparatively thick and
exhibits a double contour. The smaller col-
lecting tubules are situated in the cortical sub-
stance, a little distance below the capsule.

_., . ' Pio. 97.— Kidney of

llieir diameter ranges between 0.04 and 0.06 A°K- isolated ceiu Or

Y two collecting tubule-*,

mm. Ihe small tubules unite to form larger snowing irregular base

and point-like prolonga-

ones, and these again to form tubules of still tkms: a, from smallest

° collecting tnbnle; ft,

larger diameter. The irregular appearance at [a°™onexn|^ boand*ry
the bases of the epithelia is the same in the
larger trunks as in the smaller branches ; in the former, how-
ever, the cells are larger, and the protoplasm more voluminous
than in the latter. The nuclei have about the same size in
each (Fig. 98). The basement-membrane diminishes in impor-
tance in an inverse ratio with the size of the collecting tubules.
In the smaller ones it is prominent and possesses a double con-

1 Schweigger-Seidel : Schaltstiicke ; Roth : Verbindungscanale (connecting tu-
bules).

* Open tubules of Henle. Zur Anat. der Niere. Gottingen, 1862.
9 Heidenhain : loo. cit.

212

MANUAL OF HISTOLOGY.

tour; in those of intermediate size it is thin, and has but a
single contour ; the largest tubes possess no basement-mem-
brane whatever. In the latter the great cylindrical cells are
held together by the prolongations above mentioned and a
colloid substance. The diameter of the largest tubules at the
apices of the pyramids is 0.2 to 0.3 mm., after the first division
0.1 to 0.2 mm., the smallest being about 0.06
mm. The height of the epithelium in the
largest tubules is between 0.02 and 0.04 mm. ;
in those at the boundary layer about 0.015
mm. Good specimens are obtained by im-
mersing a fresh gland in dilute muriatic or
nitric acid for a variable period (six to twenty-
four hours), and examining in dilute gly-
cerine. The collecting tubules' should be
injected from the ureter with blue or red gel-
atine, and the whole organ immersed in alco-
hol, until ready for cutting. Sections made
parallel to the collecting tubules produce
splendid specimens. The connection between
the collecting and convoluted tubules of the
human kidney cannot be shown by injection,
for the colored fluid thrown in from the ure-
ter rarely reaches the convoluted tubules of the first order. In
the lower animals — fishes, frogs, etc. — however, if the ureter be
injected under constant pressure the entire length of the urin-
iferous tubules may be filled with the carmine, or, better, Berlin
blue2 fluid.

Fio. 98. — Kidney of
dog. Small collecting tu-
bule above the boundary
layer, x 450.

1 In the pig Henle finds that two large collecting tubules begin at the apex of
each pyramid, then run along the outer borders of the cortical substance proper,
high up into the cortex, and there unite by forming a loop. Henle states that
the convoluted tubules empty into these, or their divisions by intercalated portions,
which he calls communicating tubules ( Verbindunffscanalchen). Eingeweidel. , p. £24.

* This has been done by Frey with fishes and amphibia; by Hiifner with birds,
fishes, etc. ; by Gross with fishes and tritons, and by Hyrtl with some sorts of fishes.
According to Seraphina Schachowa (Unters. ueber die Niere. Diss. Bern. 18?(i) the
convoluted tubule of the first order is connected to Henle's loop by a spiral tubule,
while the ascending portion of the loop exhibits an expanded part immediately above
the loop, and a spiral part, which latter becomes continuous with the ascending limb
of the loop. Between the ascending part of the loop and the intercalated portion
Scbachowa describes a new tubule, which she calls the "irregular tubule."

The spiral tubule is lined with an epithelium which has a striated appearance in

THE KIDNEY.

213

The blood-vessels of the kidney. — The renal artery and vein,
•before entering the hilum, divide and subdivide within the
sinus of the kidney. Small branches, which are given off at
the hilum, also supply the fibrous capsule of the gland. Veins
accompany the arteries as far as the arches already referred to.
But here a difference is to be noted. The arteries never anas-
tomose, but form the straight vessels of the cortical substance
proper, which again send off twigs to form the glomeruli.

Pio. 99. — Kidney of pig. Injection of artery and vein. Vertical section at bonndary layer : A,
artery ; B, vein : C, gloaierulus ; D, capillaries of the cortical portion ; E, vasa recta formed from
capillaries D. x 96.

At the arches, however, the veins anastomose, and a branch
accompanies the straight artery of the cortical substance proper
(Fig. 99, B). The glomerulus is formed from the arterial twig
above referred to (Fig. 89, D). This enters the capsule directly
opposite to the point where the latter becomes continuous
with a convoluted tubule, and divides into two or more

its first portion. The expanded part of the ascending loop is lined with cells having
very thick prominent rods, and whose lumen is exceedingly small.

The irreg-'itar tubule has an angular, irregular outline, is of very varying diameter,
in some portions two, three, or four times as broad as in other portions, a condition
due to its peculiar lining epithelia, which are angular and present numerous pro-
cesses ; the rods are exceedingly thick and prominent.

As yet I have been unable to confirm Schachowa's researches.

214 MANUAL OF HISTOLOGY.

branches which subdivide again and again (Fig. 100) to form
loops or coils'; these latter unite again and form a vessel equal
in size to the one which entered the capsule. The first is

called, as already described, the affer-
ent ; the second, the efferent vessel,
and the glomerulus is formed by the
division and reunion of the branches
of these two vessels ; the whole form-
ing a rounded tuft within the capsule.
The vessels of which a glomerulus is
composed have the same diameter as
. loo.-Giomeruius from kidney small capillaries ; their coats are struc-
tureless and provided with elliptical

nuclei. The efferent vessels are not veins ; on leaving the cap-
sules they break up into capillaries, which anastomose freely
with each other and surround the tubules of the cortex, form-
ing, in this way, a network with circular meshes (Fig. 99, D).

At the boundary layer the capillaries unite to form vessels
which are two to three times larger than the original capillaries.
These vessels take a straight course through the medulla to-
ward the apices forming the so-called vasa recta l (Figs. 99, E,
and 89, G). The vessels immediately below the boundary layer
are arranged in bundles at the side of the pyramidal prolonga-
tions, and run parallel with them in that part of the medulla
(Fig. 89). They give off branches in the medulla, and near the
apices of the pyramids again form a capillary network which
surrounds the collecting tubules. The returning vessels (veins)
have about the same course, anastomose freely with each other,
and empty into the venous arches at the boundary layer.
Other veins are formed by the union of capillaries immediately
underneath the capsule ; these have a stellate form,* the centre
of each star indicating the commencement of a vein. Such
veins, passing downward through the cortex and receiving
branches on the way, empty finally into the venous arches
above referred to. The venous arches also give rise to vessels
of larger calibre, which run parallel to and accompany the ar-
teries of the medulla, and at last unite to form the renal vein.

Injections of the kidney. —The kidney may be injected with
gelatine either through the artery or vein. It is best accom-

1 Dondera : Physiol., L * Vena SteUatce, Verheyen.

THE KIDNEY. 215

plished by the artery, under constant pressure (mercury).
Beale's blue injecting fluid ' answers very well ; the writer's car-
mine-glycerine fluid* also acts exceedingly well, but it is very
difficult to obtain a good double injection of artery and vein.
I have found the most successful method to be the following :
Take a fresh bloodless kidney (dog, pig) and inject the vein
under constant pressure with the blue gelatine mass.8 Next
place the kidney in iced water for a few minutes to harden the
gelatine, and then attach to the artery a very small constant-
pressure injecting .apparatus, the receptacle for the injecting
fluid containing the writer' s carmine fluid. After regulating the
amount of pressure, the whole apparatus, with the kidney, is
placed within the receiver of an air-pump and the air slowly
exhausted. In this way the arteries become filled with fluid.
Allow the gland to harden in alcohol and mount the sections
in balsam or dammar. Kidneys in which the vein and artery
have been injected may have the collecting tubules filled from
the ureter with yellow injecting fluid, thus making a triple
injection. Sections of kidney hardened in alcohol may be
stained with borax- carmine, and afterward bleached in a di-
lute hydrochloric acid (1 to 10) solution, or a concentrated one
of oxalic acid. When the vessels of a kidney have been injected
with blue gelatine, staining with carmine gives good results.

Thierscli's yellow injecting fluid is made as follows : Prepare a solution of
bichromate of potassa, one part of the salt to eleven parts of water, and a solu-
tion of nitrate of lead of the same strength. One part of the potassa solution
is placed in a small basin and mixed with four parts of a concentrated solution
of gelatine. Two parts of the lead solution are placed in another basin and
mixed with four parts of jelly. These are to be slowly and thoroughly mixed
together at a temperature of 75° to 90°, and then heated in a water-bath at a
temperature of 212° for half an hour or more. Filter carefully through flannel
(Beale : Microscope, p. 90).

The Mdney stroma.—In the cortical substance the stroma
is reduced to a colloid material which binds the tubules to-
gether. In the lower part of the medulla, in the fresh state,

1 See page 205.

'•'Carmine, 5 grammes; glycerine (anhydrous), 50 grammes; add caustic potassa
until the carmino is dissolved, and neutralize with pure, concentrated muriatic acid.

* Gelatine should be first immersed in water until it becomes softened and then
gently heated until dissolved. Add soluble Berlin blue, or Beale's blue thud, until a
good color is obtained. Inject while hot.

216 MANUAL OF HISTOLOGY.

the stroma is a colorless, transparent substance, which, after
immersion for a variable time in a solution of chromate of po-
tassa or ammonia, resolves itself into a thin fibrous reticulum,
containing at regular intervals round or elliptical nuclei;1
these, according to Schweigger-Seidel, belong to stellate or
spindle-shaped corpuscles, which may be isolated by macera-
tion in hydrochloric acid. The nuclei are only seen in the
lower portion of the medulla ; the fibrous appearance of the
stroma is retained some distance beyond this point.

The nerves follow the course of the arteries of the kidney
and seem to supply only those vessels.

The lymphatics at the hilum are derived from the interior
of the organ, and from a network of small lymph-branches
situated between the bundles of fibres of the capsule. The
latter communicate with lymph-canals in the interior of the
organ.*

The capsule of the kidney is a fibrous tissue, containing
some few elastic filaments. It is divisible into two layers, an
outer and an inner one. The former, about 0.1 to 0.2 mm. in
thickness is continuous with the connective tissue which sur-
rounds the blood-vessels at the hilum ; the latter, about 0.025
mm. in thickness, terminates at the points where the papillae
enter the calices. Immediately underneath the inner layer, is
a large meshed reticulum of smooth muscle-fibres,3 some of
which traverse the substance of the gland for a short distance.

The calyx, at its junction with the papilla, is covered with
epithelium, which is continued on to the apex of the papilla ;
it contains, in addition, muscle-fibres disposed at right angles
to one another, and connective tissue.

Natural injection of the tubules of the Tcidney by the
sulphindifjate of soda.* — The first to inject the kidney in this
way was Chronsczewski ; 6 but his experiments were not very
successful, at least so far as the kidney was concerned. Those
of Heidenhain ' which have been confirmed by the writer,7 give

1 Henle : loc. cit. 8 Ludwig, in Strieker's Manual.

* Eberth : Med. Centralbl., No. 15, 1872.

4 Commonly known in the laboratory and in commerce as indigo-carmine.

5 Chronsczewski, in Virchow's Archiv, Bd. XXXI., p. 187; also Bd. XXXV., p.
158.

« Max Schultze's Archiv, Bd. X., p. 1, and Pfluger's Archiv, Bd. IX., p. 1.
1 Mayer : Histol. of Kidney. Prize dissert. , 1876.

THE KIDNEY. 217

the most satisfactory results. To insure this desirable end, it
is necessary that the sulphindigate of soda be pure.

O. Maschke, of Breslau, the apothecary who manufactures the pure sulphin-
digate of soda for Prof. Heidenhain, writes to that author as follows : " The
indigo- sulphate of soda was prepared from the phcenicin-sulphate of soda. If
the latter compound be heated for half to one hour, at a temperature of 60° to
70° C., with five or six times its volume of sulphuric acid of a specific gravity
of 1,840, it resolves itself completely into indigo- disulphate of soda and
indigo-monosulphate of soda (indigunterschwefelsaures Natron). I have
chosen this mode of preparing the salt because the indigo-gelatine and indigo-
brown can easily be separated from the phoenicin-sulphate of soda, without
marked loss, and in this way I obtain a sufficiently pure substance for future
use. An easier method of preparing the salt is the formula given by Crum
and Berzelius. One part of best indigo in powder is gradually added to seven
or eight parts of pure sulphuric acid, specific gravity 1,840, in a large vessel,
and the two thoroughly mixed. After the liquid has ceased to froth, the
vessel is covered with an animal membrane and put aside for three days, during
which interval it is to be frequently shaken. To this solution thirty to forty
volumes of water are added, and the whole carefully filtered. To the resulting
clear solution as many parts by weight of crystallized carbonate of soda as
there were of sulphuric acid, are added. Owing to the effervescence which
now takes place, the vessel in which the mixture is prepared must be of large
size. For this reason it is better to substitute the acetate of soda, or chloride
of sodium, or simply sulphate of soda, for the formation and precipitation of
the indigo-disulphate of soda takes place with any soda salt which does not
decompose the indigo -disulphuric acid. The mixture is now filtered, and the
precipitate dried over a water-bath. It is then pulverized and treated re-
peatedly with absolute alcohol, which dissolves any indigo-monosulphate of
soda, acetate of soda, or indigo-red, which may have remained." In this way
the indigo-carmine is obtained in a pure state. The crystals are copper-colored,
but the salt is blue in the pulverized state. The indigo-carmine of commerce
is an impure article and cannot be used for natural injection.

For injection, a cold saturated solution of the sulphindigate
of soda is used ; the salt may be dissolved in boiling distilled
water, and the solution allowed to cool. A dog or rabbit
answers for the purpose of injecting. The animal is properly
fastened to a board, and the external or internal jugular vein
dissected up and exposed. In either of these vessels a canula
with stop-cock, previously filled with the indigo- carmine
solution, is inserted. The injection into the jugular may be
made downward or upward — the latter is preferable. A syr-
inge, graduated in cubic centimetres and containing the sol-
ution of indigo-carmine, is now attached to the canula, the
stop-cock opened and a small quantity of the solution injected

218 MANUAL OF HISTOLOGY.

into the vein. Not more than 5 c.c. should be injected at one
time. If the animal be a white rabbit, the result of the first
injection shows itself in a 'few seconds, for the animal soon
becomes quite blue. After five or ten minutes another 5 c.c.
of the solution may be injected, and so on until 20 to 50 c.c. of
indigo-carmine solution have been employed, the amount
varying according to the size of the animal.

The excretion of blue 'urine takes place soon after the first
injection of indigo-carmine. As soon as a sufficient quantity
has been excreted the animal is killed in the following manner :
The abdomen is opened and the descending aorta looked for ;
when found, the canula of a syringe, filled with absolute alcohol,
is attached. The jugular vein is now cut across, and while
the animal bleeds to death absolute alcohol is injected up the
aorta or into the renal arteries. A safer and better way is to
inject the renal artery at once with absolute alcohol ; in either
case the renal veins should be cut across. The kidney is at
once removed, placed in absolute alcohol, and then divided
into several pieces, to insure a rapid action of the spirit.
While the indigo -carmine is being injected into the jugular
vein, the animal should be wrapped up in flannel or cotton-
batting so as to be kept warm. No air should be allowed to
enter the vein, or the animal may die before the experiment is
concluded. Injection of absolute alcohol through the renal
artery should be accomplished before the animal has bled to
death, or, at least, immediately afterward. When the kidney
has been thoroughly hardened, vertical and transverse sections
are to be made through the cortical and medullary substances,
and examined in glycerine saturated in chloride of potassium ;
or, better still, in resinous turpentine.

If the injection of absolute alcohol be delayed, either through lack of skill in
the experimenter, or any mishap, the indigo salt within the kidney becomes
diffused over the entire organ by absorption of water from the contained ves-
sels, and the whole kidney becomes of a uniform blue color. Such glands
must be laid aside, for sections made therefrom, even after immersion in abso-
lute alcohol, are worthless, and will only confuse the microscopist. The abso-
lute alcohol of the shops is not always absolute, as is well known. It has a
great affinity for water, and, in handling, rapidly absorbs moisture from the air.
To make it absolute, I heat sulphate of copper (pure) at a low red-heat. This
drives out the water of crystallization, and changes the color from blue to
white. Of this I mix a large spoonful or more, while still hot, with a pint of
the so-called absolute alcohol, and tightly cork the vessel, which is then to be

THE KIDNEY. 219

shaken occasionally, but not used for a week or more. The affinity that water
has for anhydrous sulphate of copper is greater than that of the alcohol, and
the latter readily gives it up. As soon as the anhydrous sulphate regains its
water of crystallization it assumes a blue color again.

Everywhere in the sections it will be seen that the glomeruli
or their capsules are entirely free from color, while all the
tubules possessing the rod-epithelium have a more or less blue
color, according to the quantity of indigo-carmine excreted.
The lumina of the convoluted and other tubules are generally
filled with the crystallized indigo-salt. In examining sections,
it soon becomes evident that the convoluted tubules and that
part of Henle's loop which possesses the rod-epithelium, alone
excrete the indigo-salt, while the other tubules merely contain
it in their lumen, the salt having been washed down, as it were,
from above by the water filtered through the capillaries of the
glomeruli.

Instead of using the sulphindigate of soda, Heidenhain, in his second series
of experiments, substituted a solution of uric acid in caustic soda. The renal
artery was injected with alcohol containing acetic acid. The result showed
that urate of soda, like the indigo-salt, was excreted only by the tubules pos-
sessing the rod-epithelium. The capsules were entirely free. The addition of
acetic acid to the alcohol caused the uric acid to be precipitated in the shape
of rhomboid crystals within the tubules. In this condition Heidenhain found
them. The hypothesis set down by Bowman, years ago, that the tubules of
the kidney excrete the solid constituents of the urine merely, while the glome-
ruli serve as a filter for the fluid portion, is therefore correct.

If the quantity of indigo solution injected into the jugular
be small, and the animal killed soon after, the kidney being
treated as above detailed, the microscopic sections exhibit
the following appearance : glomerulus and capsule are not
acted upon ; the narrower branch of the loop and the collect-
ing tubules are free from any crystallized salt, and their epi-
thelium clear. In the convoluted tubules and the broad part
of the loop, the following phenomena may also be observed :
their lumina are entirely free from any deposit of indigo-car-
mine, though here and there the rod-epithelium is not stained.
In the greater number it is colored of a light blue color. In some
the rods and nuclei are uniformly stained ; in others the rods
alone show the blue color, while the nuclei are not stained.
This constitutes the first stage of the excretion of indigo-car-

220

MANUAL OF HISTOLOGY.

mine through the kidneys. If a larger quantity of indigo
solution be injected, and the animal dealt with as above, the
second stage of the excretion is seen. Here, again, the glome-
ruli, the capsules, and the collecting-tubules are free from
color, the rod-epithelium stained blue, and their nuclei dark
blue (Fig. 101, F). In a few of the convoluted tubules and the
ascending broad branches of the loop, crystals of indigo-salt

PIG. 101. — Kidney of dog. Natural injection of secreting portion, artificial injection of artery, vein,
and capillaries. Transverse section through cortical substance : A, afferent vessel, filled with injected
material ; B, efferent vessel, also filled with injection ; B, glomernlus, injected and lying within its cap-
sule: epithelium of latter distinctly seen : D, capillaries surrounding the convoluted tubules, and dis-
tended with the injection ; at this point four capillaries are seen to unite and form a vein ; C, convo-
luted tubule, filled with crystals of indigo-carmine ; F, convoluted tubule, in which the nuclei have a
dark color. The striations of Heidenhain are beautifully shown in the convoluted tubules, x 200.

fill the lumina. So, also, in some of the descending narrow
branches of the loop. In the third stage the rods are color-
less, while their nuclei are still blue. Masses of the indigo-
salt fill the lumina of the convoluted, looped, and collecting
tubules ; the glomeruli and their capsules are colorless. In
the last stage, the salt is contained in the lumina of the col-
lecting tubules only, all the rest of the gland being free from
it, and consequently colorless. From the above it will be

THE KIDNEY. 221

seen that the rod-epithelium alone excretes the indigo-salt, and
it may be presumed, therefore, that the function of the glome-
ruli is to act as a filter for the fluid portion of the urine. Thus
the salt is washed from the convoluted into the collecting
tubules, and thence into the pelvis of the kidney. The action
of absolute alcohol on a solution of sulphindigate of soda is to
precipitate that salt. It is this action within the kidney which
fixes the dye, as above set forth.

Beautiful specimens may also be obtained by various modi-
fications of the above process.

The following formulae and results are given by Heidenhain :

1. Babbit or dog ; section of spinal cord, injection of only 5 c.c. of the in-
digo solution, the animal being killed after ten minutes. Result : pyramidal
portion and boundary layer free from indigo-blue. In the cortical substance,
some of the convoluted tubules are filled with the crystalline salt ; in the
greater number the epithelium is colored of a uniform blue, the nuclei possess-
ing the same tint ; the lumen is usually free.

2. Same conditions as above, excepting that 20 or 25 c.c. of the solution
is injected. Medulla free from indigo blue. In the cortex a great many of the
tubules are filled with the pigment, while the epithelium is stained blue, the
nuclei of a deep blue color.

3. Same conditions as in 2, excepting that the animal is killed one hour
after injection. Nuclei of the rod-epithelium stained deep blue, rods clear ;
convoluted and collecting tubules filled with crystals of pigment.

Instead of using absolute alcohol for injecting the renal
artery, the writer's carmine-glycerine fluid may be employed.
After having injected the artery in this way, the kidney is
placed in a vessel of absolute alcohol, and divided into small
pieces while immersed in that fluid. The glycerine being anhy-
drous, prevents the diffusion of the indigo-salt within the kid-
ney, while the alcohol fixes the pigment. Sections should be
made from the cortex and medulla, and mounted permanently
in resinous turpentine. If the glycerine injection has been suc-
cessful, all the glomeruli and capillaries will be filled with a
transparent red mass (Fig. 101). If the indigo excretion has
reached the third stage, the collecting tubules in the medulla
will be filled with blue crystals of indigo-carmine, and the vasa
recta with a red mass, the two arranged in alternate rows.
Such specimens leave nothing to be desired in the way of
demonstrating the structural relations just described.

222 MANUAL OF HISTOLOGY.

BIBLIOGRAPHY.

FERREIK. Mem. de 1'acad., p. 503. Paris, 1753.

MOLLER. De glandularum, etc. Leipz., 1830. And Unters. ub. d. Eingew. d.

Fische. Berlin, 1845.

HCBCHKE. Lehre d. Eingeweide. Leipz., 1844.
GERLACH. Mullet's Archiv, p. 378, 1845, and p. 102, 1848.
VIRCHOW. Virchow's Archiv. Bd. XII., p. 310. 1857.
BEER. Die Bindesubstanz d. Niere, etc. Berlin, 1859.

Luowia. Handb. d. Phys. Bd. IL, p. 628. And Wiener med. Wochen. 1864.
BOTH. Diss. Bern, 1864.

CHRONSCZEWSKI. Virchow's Archiv. Bd. XXXI., p. 153. 1864.
SCHWEIGGER-SEIDEL. Die Niere, etc. Halle, 1865.
STILLING. Ein Beitrag, etc. , Diss. Marburg, 1865.
H0FNER. Vergl. Anat. u. Phys. d. Harn. Leipz., 1866.
LINDGREN. Z. f. rat. Med. 1868.

GROSS. Essai sur la structure microscopique des reins. Strassbourg, 1868.
ISAACS. Jour, de la phys. Tome. I., p. 577. 1858.
LUDWIG. Strieker's Manual. 1871.
EBERTH. Centralb. f. d. med. Wiss., p. 227. 1872.
HENLE. Eingeweidel., 2 Aufl. 1874.

FREY. Mikroskop. 6 Aufl. 1877. And Handb. 4 Aufl. 1874.
HKIDENHAIN. Schultze's Archiv. Bd. X. 1874. And Pfluger's Arch. Bd. IX.

1874.

SCHACHOWA. Unters. ub. d. Niere. Diss. Bern, 1876.
NPSSBAUM. Beitr. z. Anat. und Phys. d. Niere Sitzungsber. d. Niederrh. u. Sw.

Bonn, 1877.

RUNEBERG. Nord. Med. Ark. XI., 2. No. 13. 1879.
HENSCHEN. Akad. Afhandling in Upsula. Stockholm, 1879. .
KLEIN and SMITH. Atlas of Histology. Part XI. 1880.

CHAPTER XV.

THE MALE EXTEKNAL AND INTERNAL ORGANS OF GENERATION,
WITH THEIR GLANDULAR APPENDAGES.

BY DR. J. HENRY C. SIMES,
Lecturer on Histology, University of Pennsylvania.

Penis. — The copulative organ of the male consists of erec-
tile tissue, and is made up of three bodies, each enclosed in a
fibrous membrane, the tunica albuginea. Two of these bodies
are termed corpora cavernosa; the third corpus spongiosum ;
through the latter the urethra passes.

The tunica albuginea consists of connective tissue and elas-
tic fibres, with some smooth muscular elements. From the in-
ternal surface of this membrane arise numerous trabeculae, or
bands, composed of the same tissue as the membrane ; they
divide and subdivide, forming a very intricate reticulum. The
cavities thus formed freely communicate one with the other,
and are lined with a single layer of flattened endothelial plates.
This system of intercommunicating lacunae is in reality nothing
but a true venous network. It is in direct communication with
the veins of the organ. By the overfilling of these cavities with
blood the erectile state is produced.

Externally, the tunica albuginea is surrounded by loose
subcutaneous tissue, in which numerous elastic fibres are pres-
ent. Longitudinal bundles and a few oblique fibres of involun-
tary muscle are also found in this areolar tissue. The skin cov-
ering the penis is thin, and possesses numerous fine hairs,
which have an increased length as the root of the organ is
approached ; they are connected with ordinary sebaceous
glands which open into their follicles. Sudorific glands are
also present in the skin of this organ. The internal leaf of
the prepuce resembles closely a mucous membrane; papillae
are numerous, but there is an absence of hairs, and the seba-

224

MANUAL OF HISTOLOGY.

ceous follicles (Tyson's glands) are sometimes difficult to find
in the adult. • In new^born children, however, these glands are
abundant and well developed. The convoluted glands are here
absent.

The extremity of the penis terminates in a cone-shaped
body, the glans penis, which has a cavernous structure very
similar to that in the body of the organ, and differing only

in the size of the meshes and
the trabeculse, the former being
smaller and the latter more deli-
cate. The external or mucous
surface of the glans is covered
with a laminated pavement epi-
thelium, the cells of the upper
layer being quite flat, those of

the middle layer ribbed, while in
^ . . , i ,

the lowest l&yer they are colum-
nar. There are numerous elastic
fibres in the mucous membrane
of the glans, and many single
or branched papillae are seen,
some containing club - shaped
nerve-termi nations.

The system of blood-vessels
in connection with the penis con-
sists of arteries, veins, capilla-
ries, and cavernous spaces. The

. _^ modes of communication between

^s^£^S*£^ir these several vascular structures
FIO. m-Transverse section throng the in- are three : a direct passing of the

jected g)an» : a, epithelium of the urethra ; 6, , , , „ ,, .,

blood from the larger arterial to
the larger venous branches; a
somewhat coarse venous reticu-
lum communicating with a system of arterioles ; and, finally,
a direct capillary anastomosis.

The lymphatic system of the penis is represented by lymph-
spaces, capillaries, and large trunks. The former, the spaces,
are oblong in shape, and occur in the loose subcutaneous tissue
surrounding the tunica albuginea ; they communicate with a
capillary system, which is disposed in longitudinal meshes.
The large lymph-trunks formed from these smaller vessels are

tunica muco*a ; c, corpus cavernosnm urethras ;
rf, corpus cavemosum plandis ; e, mucous mem-
brane of the glans ; /, epithelium of the glans.
Klein.

THE MALE ORGANS OF GENERATION. 225

situated along the dorsum of the organ, and communicate with
the lymph-glands in the pelvis and those of the groin.

The nerves and their terminations in the penis are derived
from the cerebro-spinal and sympathetic systems. In the loose
tissue external to the tunica albuginea large medullated fibres
are observed ; these give off smaller branches which enter the
cavernous structure, and may be followed for some distance as
medullated or non-medullated fibres. In this same tissue are
found, at the root, shaft, and vicinity of the corona glandis,
Pacinian corpuscles. They are oval in shape, and have their
long diameter parallel to the long axis of the penis. These
bodies have also been met with in the cavernous structure.
The glans is especially rich in nervous elements, and here are
found bodies known as the "genital nerve-corpuscles," situated
in the tissue of the mucous membrane at the base of the papil-
Ise. These bodies are round in shape, vary in size from 0.1439
to 0.2001 mm. in diameter, and have characteristic constrictions
upon their surface, giving them a mulberry-like appearance.
The ordinary terminal bulbs of Krause are also met with in
this location.

The urethra of the male serves as the excretory canal for
the urine and seminal fluid. An anatomical division is made
into the prostatic, membranous, and spongy parts. The canal
is lined with a mucous membrane, external to which there is a
fibrous layer rich in elastic fibres, having a cavernous struc-
ture ; external again to this is the muscular coat, composed of
involuntary muscular fibres arranged in two layers, an internal,
or longitudinal, and an external, or circular. There are also
numerous fasciculi of oblique fibres, which serve to connect the
two layers.

The histological structure and arrangement of the three
parts of the urethra are unlike, and must be separately
studied, (a) In the prostatic portion the mucous membrane
lies in longitudinal folds. A laminated epithelium covers the
inferior wall, while the sides and superior wall are lined with
a transitional variety. The prominence of this portion of the
urethra, the colliculus seminalis, is composed of elastic tissue
and smooth muscular cells, which form a cavernous structure.
Throughout this spongy tissue, near the surface, are seen
glands similar to those found in the prostate. Racemose glands
(Littre's glands), imperfectly developed, lined with cylindrical

15

226

MANUAL OF HISTOLOGY.

epithelial cells in their acini, and at their orifices with lami^
nated epithelium, are also present. The muscular tissue in
this part of the urethra is intimately connected with that of
the prostate ; its fasciculi have generally a longitudinal direc-
tion, and send off oblique bundles into the mucous mem-
brane. (5) The membranous por-
tion of the urethra has its mucous
membrane covered by an epithe-
lium similar to that met with in
the prostatic portion. The glands
of Littre are absent. Beneath the
mucous membrane a long-meshed
erectile tissue of a cavernous na-
ture is found. Here the organic
muscular layer is poorly devel-
oped, and it is covered by trans-
verse bundles of striped muscular
fibres, the musculusurethr alis. (c)
Passing to the spongy portion, the
mucous membrane is found thrown
into longitudinal folds, which are
in places connected by transverse
ones, forming depressions, known
as the lacunae Morgagnii. These
are not glandular in 'their nature.
The epithelium covering the mu-
cous membrane in this portion is
mostly cylindrical, but as it ap-
proaches the meatus urinarms
gradually assumes a pavement

character. Glands of Littre are found throughout this part.
The muscular elements are even less prominent here than in
the membranous portion.

Well-developed and numerous papillae are seen projecting
from the mucous membrane of the urethra into the epithelium.
They possess a single capillary loop, or several loops are ob-
served, especially in the fossa navicularis. These papillae are
absent or imperfectly developed at the points where a transitional
epithelium is met with. Here the capillaries are arranged to con-
stitute a reticulum beneath and parallel to the epithelial covering.
The nerves of the urethra are found forming a network

Flo. 103.— Transverse section through
the spongy portion of the urethra (corpus
cavernosum urethra) : 6, tunica mucosa ; c,
muscular cords; d, vascular spaces of the
corp. cavern. ; «, glands ; /, excretory duct
of gland ; g, longitudinal muscles ; A, tunica
albuginea. Klein.

THE MALE ORGANS OF GENERATION. 227

around the muscular coat, similarly as elsewhere, in connection
with smooth muscular fibres. Small nerve-fibres have been
traced into the epithelial lining. Collections of ganglionic
nerve-cells are found on the posterior surface of the membra-
nous portion ; in the dense connective tissue at the posterior
portion of the bulb ; and lastly, in the network of nerve-fibres
around the vessels at the side of the bulb.

The lymphatic system of the urethra is found in the mu-
cous membrane, near the epithelium. It consists of a network
of vessels with longitudinally arranged meshes ; they are con-
nected with the lymphatic vessels of the bladder, and also open
into the lymphatic canals of the glans penis.

Cowper's glands. — These organs, two in number, are situ-
ated in the striated muscular tissue which surrounds the mem-
branous portion of the urethra. They are lobulated, oval, and
belong to the racemose group of glands. They are composed
of acini and excretory ducts which unite to form a single duct
for each gland, and discharge into the bulbous portion of the
urethra. The acini constituting the several lobules are separated
by connective tissue intermixed with smooth muscular fibres ;
they possess a structureless membrana propria, and are lined
with columnar cells, which are imbricated upon their outer thin
portions. The ducts are lined with flattened columnar cells,
and a layer of smooth muscular fibres is seen running along
them. A capillary network surrounds the glandular structure.

The prostate may be described as a glandular organ, pecu-
liar in having its stroma composed of involuntary muscular
elements. Externally it possesses a connective-tissue envelope
which is united to bands of smooth muscular fibres that run
in every direction, and constitute the cortical substance of
the organ. From this cortex numerous bands or trabeculze
of a similar muscular nature proceed, forming an intricate
network, and making up the greater part of the gland ; in the
meshes of this reticulum is placed the glandular structure.
The thickness of the cortex, or the amount of glandular sub-
stance, varies according to the position, whether behind or in
front of the urethra, and it is found that the glandular struc-
ture is comparatively more developed behind and in the lower
portions than in front of the urethra.

228

MANUAL OF HISTOLOGY.

The arrangement of the glandular elements is similar to
that in the racemose glands, and consists of excretory ducts ter-
minating in glandular vesicles or acini. The ducts which have
their orifices in the urethra at its prostatic portion, and upon
its inferior wall, are here lined with a transitional, or, when
large, with a pavement epithelium, which gradually changes

, vesicula
the pros-

into a columnar variety as the ducts penetrate the organ. The
basement-membrane is structureless, and is invested by a mus-
cular layer. The acini are also lined by a columnar epithelium
and possess a structureless membrana propria ; their shape is
usually pyriform, and they have a diameter varying between
0.1254 and 0.23 mm. The epithelial cells of the acini frequently
contain granules of brownish pigment.

THE MALE ORGANS OF GENERATION.

229

Transversely striated muscular fibres are also met with in
the prostate, both anterior and posterior to the urethra, ex-
tending into the cortical substance, and between the glandular
structure in the interior of the gland.

The blood-vessels of the organ come from the large trunks
surrounding it ; they pass into its structure and form a reticu-
lated capillary system around the glandular substance.

Medullated nerve-fibres are found surrounding the cortex
in connection with groups of oval gariglionic centres. Paci-
nian bodies are also ob-
served in the cortex of the
prostate, and in its interior
are small medullated nerve-
fibres which form a reticu-
lum.

A peculiar structure is
found in the upper and pos-
terior part of the prostate.
It has the appearance of a
duct, with walls resembling
an artery, in so far as it
consists of an internal longi-
tudinal, a middle circular,
and an external longitudi-
nal coat. The middle coat is composed mostly of smooth mus-
cular elements, while the external and internal coats are only
partly made up of them. The interior of this structure is filled
with a rich vascular network, pigment particles, and smooth
muscular fibres.

The vesicula prostatica, which forms a cul-de-sac in the
middle of the prostate, beneath the middle lobe, opening by a
duct at the summit of the colliculus semmalis, possesses a
fibrous wall in which there are smooth muscular cells and is
surrounded by a thin layer of cavernous tissue ; it is lined by
a laminated epithelium, into which small conical papillae pro-
ject ; small branched and tortuous glands are also found open-
ing into its cavity.

The testicles are glandular organs which secrete the sper-
matic fluid, and are in the male organism the sexual represen-
tatives of the ovaries in the female.

FIG. 105. — Transverse section through the central
glandular substance of the prostate. From an adult.
Klein.

230 MANUAL OF HISTOLOGY.

The glandular structure, together with the epididymis of the
testicles, is enveloped by a dense tibrous membrane, the tunica
albuginea. This is surrounded by a serous sac, the tunica
vaginalis propria. Finally the testicle and spermatic cord are
invested by the tunica vaginalis communis and the whole is
contained in the scrotum.

The tunica albuginea upon its external surface, or that
covered by the tunica vaginalis propria, is smooth and shin-
ing ; it consists of dense connective tissue with some elastic
fibres ; upon the posterior border of the testicle it increases in
thickness, and is here termed the corpus JfigTimori, or medias-
tinum test is, which passes into the gland. It also sends off
from its whole internal surface numerous bands or trabeculse,
the septula testis, which run toward the mediastinum, and
divide the interior of the testicle into conical lobules, having
their apices directed toward the corpus Highmori. These tra-
beculse contain smooth muscular fibres and blood-vessels. It
is in these lobules or spaces that the secreting elements of the
gland are situated.

The serous sac, or tunica vaginalis, has its visceral layer, the
tunica adnata, intimately united to the tunica albuginea over
the testicle, but it is loosely attached to that over the epididy-
mis. This membrane consists of connective tissue traversed
by delicate elastic fibres, and lined on its surface wjth a layer
of polyhedral cells, varying in size and containing oval nuclei
with one or two nucleoli. Upon the upper portion of the tes-
ticle and sharp edge of the epididymis, the tunica adnata is
frequently found to possess tufted excrescences ; these pro-
cesses are covered by several layers of flattened epithelial cells,
or a single layer of round or cylindrical -bodies. A capillary
loop is seen extending into the tufts.

The parietal layer of the tunica vaginalis propria consists
of connective tissue, elastic fibres, and epithelium, as in the
visceral layer.

The tunica vaginalis communis, which covers the tunica
vaginalis propria, is composed above of a loose, laminated con-
nective tissue, but it becomes more dense below. Between
this tunica and the tunica propria unstriped muscular fibres
are found, while upon its external surface there are the striped
fibres of the cremaster muscle. Small non-vascular peduncu-
lated excrescences are also found upon this surface. The mem-

THE MALE ORGANS OF GENERATION. 231

brane is connected externally by connective tissue with the
muscular layer of the scrotum, the dartos.

The muscle of the scrotum, the dartos, consists of numerous
smooth muscular fibres, arranged singly or forming a more or
less continuous layer.

The skin of the scrotum is peculiar in containing consider-
able pigment, while there is an absence of fat in the subcu-
taneous tissue. Hairs, large sebaceous follicles, and sweat-
glands are also present in the skin of the scrotum.

The Tiydatid of Morgagni is a structure found upon the
anterior surface of the head of the epididymis, and is thought
to be the remains of Miiller' s duct. It is met with in two
forms, either as a vesicle containing a clear fluid (with cells,
and nuclei — ciliated epithelial cells are also at times present),
and connected to the epididymis by a solid fibrous peduncle, or
as a flattened structure possessing scarcely any stalk, which
is simple or divided into lobules ; the latter form is most fre-
quently seen. At times it is found to communicate with the
canal of the epididymis.

Between the head of the epididymis and the vas deferens,
situated upon the posterior edge of the testicle, a small organ
is seen, consisting of several whitish nodules. Each nodule is
composed of a tube forming a number of convolutions and ter-
minating in a club-shaped extremity. The tubes contain a
clear fluid and are lined by a cylindrical epithelium, the cells
of which are undergoing degeneration. Until ten years of age
this organ is fully developed ; after this period it experiences
degeneration. This structure is known as the organ of Gir-
aldes, and represents the remains of the Wolflian bodies.

The glandular or parenchymatous structure of the testicle
consists of canals or seminiferous tubules about 0.1128 to
0.1421 mm. in diameter ; they are folded on themselves sev-
eral times so as to constitute lobules, and are situated in the
spaces formed by the trabeculse of the tunica albuginea. The
tubules not only are folded but divide and subdivide, anasto-
mose, and terminate by loops. Toward the apices of the lob-
ules the tubules gradually become more straight, fewer in
number, and pass into the corpus Highmori, forming the
rete test is. From the upper part of the rete emerge twelve to
seventeen larger tubules which pass through the tunica albu-
ginea, after which they again become convoluted and form a

232 MANUAL OF HISTOLOGY.

number of conical lobules, named the coni vasculosi, which
form the head of the epididymis. These tubules gradually
unite to form a single canal, which is much convoluted, and
develops an elongated body, the body and tail of the epididy-
mis. The convolutions becoming less and less marked, the
tube, increased in calibre, then leaves the testicle and ascends,
at first somewhat spirally, but soon after in a perfectly straight
course, constituting the vas deferens. Before this duct is
formed, a short csecal branch, named the vas dberrans, is at-
tached to the tube.

The seminiferous tubules either take their origin from blind
extremities or anastomoses, the former being more frequently
met with in children. Surrounding the tubules there is seen
a framework of connective tissue, which proceeds from the
septa. This intertubular connective tissue is distinctly lam-
inated, and each lamella is formed of a fenestrated endothe-
lial membrane, and a fenestrated connective- tissue membrane,
which thus constitute numerous communicating spaces, that
are the rootlets of the lymphatic system of the testis. The
number of lamellae between the seminal tubes varies, and their
relation to the tubes is very intimate, but depends upon the
amount of fluid present in the interlamellar lymph-spaces.
Groups of peculiar cells are found between the lamellae of the
intertubular connective tissue. These cells have be.en observed
by histologists, and by most are thought to be connective-tissue
corpuscles. Klein, however, says they are epithelial in nature,
and derived from the epithelial columns of the Wolffian body.

In the meshes formed by this reticulated fibrous tissue are
located the seminiferous tubules, the membrana propria of
which is thought, on the one hand, to be structureless, or, on
the other, to be composed of oval, flattened corpuscles, placed
at regular intervals, which form an endothelial membrane. The
tubules are found filled with corpuscles. Those at the periphery
covering the membrana propria are round or polygonal in form,
upon transverse section. In children, the cells of the tubules
contain a finely granular and pale substance, but in adults
they are filled with yellow pigment. Two typical forms of cor-
puscle are observed, one with dark granular nuclei, the other
with bright ones that have or have not nucleoli. The number
of nuclei varies ; usually there are one or two ; but they may
reach thirty or more. Many variously formed cells are seen,

THE MALE ORGANS OF GENERATION. 233

which fact is held to indicate active proliferation. These bodies
are termed seminal cells, and in the embryo are said to possess
contractility and amoaboid movement.

The seminiferous tubules upon entering the corpus High-
mori lose their special external coat, which blends with the
connective tissue of this region. Their epithelial lining con-
sists of cylindrical cells with short cilia. After* leaving tho
corpus Highmori and increasing in size, they have an additional
coat of smooth muscular fibres, which, further down in the
body of the epididymis, consists of two layers, an internal and
an external or longitudinal coat. The epithelium lining the
canal of the epididymis is composed of cells with long, oval
nuclei, and provided with long tufts of cilia. Indeed, the lar-
gest cilia found in the human body are upon the large cylindri-
cal cells, which cover the upper part of the canal of the epi-
didymis. Beneath this layer of ciliated bodies is a second of
small, polyhedral ones Vvith round nuclei.

The vas deferens, which may be considered as analogous
in many respects to the excretory duct of a glandular organ,
is made up of an external or fibrous coat, a middle or mus-
cular, and a mucous membrane, which is located most inter-
nally. Covering this membrane are epithelial .elements which
differ in the various parts of the duct. At the beginning there
is a single layer of cylindrical cells, between which, sometimes,
there are spindle-shaped bodies ; the former possess delicate
cilia. At about four centimetres from the epididymis the cilia
are lost, but the character of the cells remains the same, ex-
cept that a striated border can be seen in many. In children,
a difference exists between the extra- and intra-abdominal por-
tions of the duct. The former, or extra, is lined by a lami-
nated epithelium, composed of a superficial layer of short
cylindrical cells, beneath which are one or two layers of round
or polyhedral cells.. All these corpuscles have a relatively
large nucleus. The intra-abdominal portion of the duct has a
lining similar to that observed in the adult.

The mucous coat is made up of connective tissue and elas-
tic fibres, the former consisting of intersecting fasciculi, the
latter of a close network. The membrane is thrown into
two or three longitudinal folds or rugae. Near the lower end
of the vas deferens, in the ampulla, the longitudinal folds

234 MANUAL OF HISTOLOGY.

are connected by transverse ones, and thus depressions are
formed.

The muscular coat consists of smooth muscular fibres ar-
ranged in three layers : an inner, or longitudinal, which is
feebly developed ; a middle, or circular, which is substantial in
character, and an external or longitudinal. This coat is less
developed in young children than in adults.

In the external fibrous coat, or tunica adventitia of the vas
deferens, are found bundles of smooth muscular fibres running
longitudinally. They are derived from the cremaster interims,
which muscle is well developed at the origin of the vas deferens,
but gradually diminishes in size as it enters the abdominal cavity.

The vas deferens possesses a dense plexus of medullated
nerve-fibres,- the spermatic plexus, situated in the tunica ad-
ventitia. From this plexus several smaller trunks proceed
which penetrate into the muscular and mucous coats. Scat-
tered along these nerve-trunks are seen small ganglion-cells,
which are round or oval.

The blood-vessels of the testicle come from the internal
spermatic artery and enter the gland partly at the corpus
Ilighmori and partly upon its surface. They surround the
seminiferous tubules as a capillary plexus of large meshes.
The epididymis receives its blood from the deferential artery,
and also to some extent from the vessels of the testicle. The
tas deferens possesses a rich capillary network in its muscular
coat and also in its mucous membrane beneath the epithelium.

The nerves of the testicle come from the internal spermatic
plexus ; their mode of termination has not as yet been satis-
factorily explained. Letzerich, however, describes fine nerve-
fibres in the testicles of mammals ; they penetrate the connec-
tive tissue and membrana propria, terminating between this
layer and the first row of cells in dark granular masses.

The lymphatic system of the testicle consists of a series of
lacuna, lined with endothelial cells, which surround the semi-
niferous tubules; in the interstitial connective-tissue, these
communicate with canals from which others are given off to
the connective-tissue septa of the lobules. Beneath the tunica
albuginea another network of lymphatic canals is also found,
which penetrate the tunic, especially upon the dorsum of the
organ, and finally, uniting with the lymphatics of the epididy-

THE MALE ORGANS OF GENERATION. 235

mis and tunica vaginalis, form several large trunks, wliich fol-
low the spermatic cord. Distinct networks of lymphatic ves-
sels are found in the vascular and nervous layers of the sper-
matic cord, and some are seen close to the muscular coat of the
vas deferens.

The seminal vesicles, designed as receptacles for the fluid
secreted by the testicles, are, with some slight modifications,
similar in structure to the vas deferens. They are composed
of a mucous, muscular, and fibrous coat. The mucous mem-
brane is covered with a superficial layer of cylindrical and a
deep layer of polyhedral-epithelial cells, and is thrown into
folds, longitudinal and transverse, forming depressions. The
muscular coat consists of three layers, an internal or longi-
tudinal, a middle or circular, and an external or longitudinal.
The fibrous coat is abundantly supplied with networks of ves-
sels and nerves. Here the ganglionic collections are highly
developed, each corpuscle being quite large and containing a
single nucleus, or even at times two.

The ejaculatory ducts are, histologically, similar to the last
described organs. As they approach the prostate their cylin-
drical epithelium gradually changes into the transitional va-
riety j and subsequently into the laminated pavement, as they
approach their point of outlet in the urethra. Their mucous
membrane is uneven from the longitudinal and transverse
folds. After entering the prostate the muscular substance of
the ducts undergoes cavernous transformation.

When the testicle attains its full physiological develop-
ment, which occurs in man at puberty, there is secreted by the
organ a peculiar fluid, the semen or sperma. This fluid is
whitish, slimy, and colorless, and has an alkaline or neutral re-
action. Semen examined as discharged from the orifice of the
urethra, in coitu, appears as a very different fluid, having re-
ceived the secretions from the various accessory glands of the
generative system. It is now more fluid, opaque, strongly al-
kaline in reaction, and has acquired a peculiar odor. Placed
under the microscope there is seen suspended in a hyaline fluid
an infinite number of moving thread-like bodies called seminal
filaments, spermatozoa, spermatozoids, seminal elements, etc.
They are divided into a head, body or middle portion, and tail.

236

MANUAL OF II1STOLOGY.

Fio. 106. — Seminal elements of
man : a, undeveloped ; 6, mature.
St. George.

They are as follows

The shape of the head is pyriform, the broad part being con-
nected with the body ; each has an average length of 0.0045
mm., and its breadth is about half as much. The middle por-
tion or body is about 0.0061 mm. long, while the tail measures

about 0.0406 mm. Both the body and
head of the seminal elements seem to
be rigid, the terminal thread or tail
having an active motion. From this
description it will be seen that a com-
parison of its structure with that of a
cilia ted epithelial cell is admissible, and
indeed quite reasonable.

The way in which spermatozoa are
formed is still imperfectly known, and
two diiferent views claim our attention.
a. The nucleus of the seminal cells
moves to the periphery, then at the opposite side the proto-
plasm of the cell is elongated into a caudal appendage ; the
nucleus continuing to advance causes the protoplasm to be-
come more and more elongated, and it is ultimately lengthened
into a thread-like tail, while the nucleus, with its thin layer of
protoplasm, constitutes the head. b. In this view the columnar
or prismatic-shaped cells, the most external layer of cells fill-
ing the seminal tubules, are thought to be the spermatozoa-
producing elements. The inner remaining cells of the tu-
bules experience no further development. During the active
stage of the gland the spermatic cells become elongated, and
extend into the centre of the tubule ; their free extremities
become enlarged, and have a number of buds or club -like pro-
jections, eight to twelve, developed upon them. In each bud
is formed a nucleus ; these nuclei eventually become the
heads of spermatozoa, and the protoplasm is further developed
into the body and tail. The cells from which the spermatozoa
have their origin are named spermatoblasts.

Klein, in his recent "Atlas of Histology," gives a very ex-
tended description of the development of spermatozoa. Ac-
cording to this writer there are several layers of epithelial
cells lining the inside of the membrana propria of the seminal
tubules. These layers he divides into an outer and inner.
The outer, situated next to the membrana propria, embraces
the germ-cells of Sertoli. The inner layer, those nearer the

THE MALE ORGANS OF GENERATION. 237

lumen of the tubule, are the seminal cells of Sertoli. These
latter are usually arranged in two or more layers, polyhedral
in shape when placed closely together, but more spherical when
next to the lumen of the tubule ; they are uniform in size and
contain a single nucleus. The nucleus is spherical, possesses
no limiting membrane, and contains a convolution of thick
fibrils, or rods, in a transparent matrix. A more minute ex-
amination of the nucleus shows that the fibrils are arranged in
certain definite forms, which indicate changes preparatory to
division, as has been pointed out by Strassburger, Hertwig,
Flemming, and others. The various forms, taken by the nucleus
before dividing, correspond to what is termed the "convolu-
tion," the "basket," the "wreath," the "monaster," or the
" dyaster." The entire process of the indirect division of the
nucleus is termed by Flemming TcaryoJcinesis.

Toward the lumen of the tube the above-described cells are
seen with their nucleus either dividing or divided into two
daugliter -nuclei. From these daughter-nuclei are developed
the daughter-cells, or spermatoblasts, and by an interesting
series of changes the spermatozoa are formed.

"The nucleus of the spermatoblasts at first retains its spher-
ical shape, but is invested in a distinct membrane, the convo-
lution of fibrils changes into a honey-combed reticulum, some-
times with one or two nucleoli, and the nucleus is not placed
in the centre but in the periphery of the cell."

" Next the nucleus becomes uniform in its substance and
transparent, all traces of a reticulum have disappeared. The
cell-substance has collected at one end of the nucleus as an
elliptical granular mass, and appears separated from it by a
transparent, clear bag."

" In the next stage the nucleus becomes flattened and dis-
coid, so that when viewed from the surface it is broad and cir-
cular, but appears narrow and staff-shaped when seen in profile.
The cell-substance at this time is drawn out into a cylindrical
or club-shaped granular body, separated from the nucleus by
a shorter or longer clear tube, the former clear bag. At the
front part of the nucleus is seen a short and tapering curved
projection, and at its hind end — viz., that directed toward the
clear tube and cell-substance — there is also to be found a short-
pointed process extending into the clear tube just named."

" In the next stage the nucleus becomes more flattened and

238 MANUAL OF HISTOLOGY.

oblong. In the last stage the granular body has become
changed into a long, thin, and homogeneous filament."

" In what relation do, then, these different parts of the fully
formed spermatozoon stand to the parts of the developing ele-
ment— that is, the spermatoblast? A comparison shows at
once that the head of the ripe spermatozoon is the changed
nucleus of the spermatoblast ; that the filament, or tail, is de-
rived from what has been mentioned above as the granular
body of the original cell. The middle piece of Schweigger-
Seidel is an outgrowth of the nucleus of the spermatoblast,
that is, of the head, the spermatozoon, and the clear tube of
the developing spermatozoon, described above as embracing
the hind part of the nucleus and separating the latter from
the granular body, is the sheath which, in some instances
(triton and salamander), is observable on the middle piece of
the fully formed spermatozoon."

In short, the head of the spermatozoon is derived from the
nucleus, while the tail has its origin from the body of the sper-
matoblast.

BIBLIOGRAPHY.

COOPER, A. Obs. on the Struct, and Dis. of the Testis. London, 1830.

WAGNER. Miiller's Archiv. 1836.

PANIZZA, B. Oeservazioni anthropo-zoot. -fisiol. Pavia, 1836.

VALENTIN. Ueb. d. Verl. d. Blutgef. im Penis d. Menschen. Miiller's Arch. 1838.

KOBELT. Die miinnl. u. weibl. Wollustorgane. Freiburg, 1844.

KOLMKER. Gewebelehre und Verhandl. d. Wiirzb. med.-phys. Ges. 1851.

KOHLRAUSCH. Zur Anat. u. Phys. d. Beckenorgane. Leipzig, 1854.

SAPPET. L'urethre de Phomme. 1854.

LEYDIO, F. Zur Anat d. mannl. Geschlechtsorg. in Zeitschr. f. wiss. Zool. Vol. II.

And Histologie. 1857.

JARJAVAY. Rech. anat. sur 1'urethre de I'homme. Paris, 1857.
MERKEL. Gottinger Nachrichten. No. 1, p. 7. 1863. And Arch. f. mikr. Anat.

Vol. L, p. 309. 1865.
ST. GEORGE, v. LA V ALETTE in Arch. £. mikr. Anat Vol. I., p. 403. 1865. And

Strieker's Manual.

PETTIGREW, in Proo. Roy. Soc. Vol. XV., p. 244. 1866.
SCHWEIGGER-SEIDEL, in Virch. Arch. VoL XXXV1L, p. 225. 1866.
BALBIANA. Journal de 1'anat. et de la phys., p. 218. 1868.
LETZERICII. in Virch. Arch. Vol. XLII., p. 570. 1868.
STIEDA. Ueber den Bau des Menechen-Hoden, Arch. f. mikros. Anat Vol XIV.,

p. 17. 1877.

BIBLIOGRAPHY. 239

SERTOLT. Sulla struttura di canalicoli seminif. del testicoli. Arch. p. le scien.

med. VoL II., p. 107. 1877.

MENZIIL. Ueber Spermatozoon. Arch. f. klin. Chir. Vol. XXL, p. 518. 1877.
VALENTIN, in Zeitechr. f. rat. Med. Vol. XVIIL, p. 21. VoL XXL, p. 89. 1879.
LANDER, in Wien. Sitz. Vol. XLVL, p. 120. 1879.
ROUGET. Compt. rend. Vol. IV., p. 902. 1879.
FREY, HEINRICH. Histology and Histochemistry of Man. 1880.
KLEIN, E. , and SMITH, E. NOBLE. Atlas of Histology. 1 880.

CHAPTER XVI.

THE FEMALE EXTERNAL AND INTERNAL ORGANS OF GENERA
TION, WITH THEIR GLANDULAR APPENDAGES— PLACENTA.

BY DR. J. HENRY C. SIMES,
Lecturer on Histology, University of Pennsylvania.

THE external female genitals are the labia majora, labia
rainora, and clitoris.

The labia majora are folds of skin, the subcutaneous tis-
sue of which contains a large amount of adipose tissue. Their
internal surface has the nature of a mucous membrane, while
externally it is similar to the common integument. Here hairs,
sebaceous glands, remarkable for their large size, and sweat-
glands, are found. The papillae, vessels, nerves, and Pacinian
corpuscles do not differ from those found elsewhere in the skin.

The labia minora may be considered as folds of mucous
membrane. They are covered by a laminated pavement-epi-
thelium and the deepest layer contains pigment granules.
Conical vascular papillae are seen beneath the epithelium.
In the connective-tissue framework of the mucous membrane
smooth muscular elements are found. Capillary networks are
seen on the surface beneath the epithelium, and in the sub-
stance of the membrane, from which arise small veins, consti-
tuting a plexus, and giving this structure the character of an
erectile tissue. Upon the external surface of the folds are found
sebaceous glands without hairs. These glands are absent at
birth. There is no adipose tissue in the labia minora.

The clitoris is covered by a mucous membrane which is a
continuation of that of the labia minora, and to which it is
similar in structure, in so far as epithelium, mucous tissue, and
papillae are concerned. The mucous membrane covering the
glans of the organ is found to have those peculiar nerve-termi-
nations in its structure, the genital nerve-corpuscles, which

THE FEMALE ORGANS OF GENERATION. 241

have been described as existing in the mucous membrane of
the glans penis.

Beneath the mucous membrane of the clitoris are found the
corpora cavernosa and glans ; the latter is in connection with
both bulbi vestibuli, which correspond to the corpus spongio-
sum urethrse of the male. These structures consist of erectile
or cavernous tissue, which, like that in the penis, is made up of
a vascular network, mostly venous in character, and erectile in
nature ; they are also surrounded by a fibrous tunic analogous
to the tunica albuginea of the penis.

The vestibule has its mucous membrane, which is a con-
tinuation of the mucous membrane of the clitoris, thrown into
a number of folds. Opening upon its surface are numerous ori-
fices of racemose mucous glands. These glands are collected
into groups around the orifice of the urethra and vagina. They
consist of branched ducts, which at their deeper parts are de-
veloped into a number of acini ; they are lined with a simple
epithelium ; at their orifices they have the laminated pavement-
epithelium of the mucous surface. These glands vary in diame-
ter between 0.5 mm. to 2.5 mm. The vessels of the vestibule
form a network near the mucous surface, and are connected to
the capillary loops in the papillae.

Opening upon each side of the vaginal entrance is the orifice
of the duct belonging to the gland of Bartholine. These or-
gans, two in number, are analogous to Cowper's glands in the
male. They belong to the racemose group, and are composed
of ducts and acini, which have an epithelium lining of cylin-
drical cells.

The hymen consists of a duplicature of the mucous mem-
brane of the vagina. Its laminated epithelium is similar to
that of the vestibule. The papillae are numerous, long, simple
or multiple, and project from 0.2 to 0.3 mm. into the epithelial
covering. The vascular and nervous supply is very abundant.

The vagina consists of an external coat of connective tissue,
a middle coat of muscular tissue, and an internal mucous coat.
The mucous membrane is uneven, thrown into ridges and papil-
lary elevations, which are especially well-marked in the neigh-
borhood of the vaginal entrance. The epithelium lining the
canal is a laminated pavement-epithelium, into which the vas-

16

242 MANUAL OF HISTOLOGY.

cular papillae of the mucous membrane extend. In the latter
coating are found numerous elastic fibres in the fasciculi of
connective tissue ; bundles of smooth muscular cells are also
present. Tubular glands, lined with ciliated columnar epithe-
lium at their fundus, have been described as existing in the
mucous membrane of the vagina by Preuschen. Hennig also
speaks of similar glands being present in this membrane. The
submucous tissue is very vascular and loose in texture. The
muscular coat consists of an internal longitudinal and an ex-
ternal circular layer of smooth muscular fibres, between which
are many oblique connecting fasciculi. The external fibrous
tissue is loose in texture, and has embedded in it the external
venous plexus.

The vascular system of the vagina is composed of arteries,
veins, a venous plexus, and capillaries. The plexus is met
with in the folds of the vagina. It is a cavernous structure
possessing smooth muscular fibres, and has an arrangement of
trabeculfe similar to that found in other erectile organs.

The lymphatics and nerves of the mucous membrane of the
vagina are abundant. The latter form networks in which there
are found ganglion-cells, in groups or single ; as in the male
genitals, these cells are of two sizes. The ultimate terminations
of the nerve-fibres are as yet undetermined. The fluid secreted
by this membrane has an acid reaction.

The urethra possesses a mucous membrane covered by a
transitional epithelium at its upper portion, the superficial
layer of cells being short cylinders, which gradually become
shorter, until the deepest layer is seen made up of rounded cells.
The lower portion of the canal has a lining of laminated pave-
ment-epithelium similar to that of the vestibule. The mucous
membrane has numerous papillae extending into the epi-
thelium. In this layer are seen at places many lymph-corpus-
cles, sometimes amounting to an infiltration, when it may be
considered as adenoid in nature. The submucous tissue is
mostly composed of venous networks ; it is in fact a cavernous
tissue. As in the male, there are present in the mucous mem-
brane the glands of Littre, seen especially abundant near the
meatus urinarius. The muscular coat of the urethra consists
of an internal longitudinal and an external circular layer of
smooth muscular fibres ; in the external layer are also the

THE FEMALE ORGANS OF GENERATION. 243

transversely striated muscular fibres of the urethral muscles.
The external fibrous coat of the urethra consists of wavy con-
nective-tissue fasciculi, which have a longitudinal and circular
course.

The uterus possesses an external covering of serous mem-
brane, the peritoneum ; anteriorly it is more intimately con-
nected with the organ than posteriorly, while at the sides the
layers are separated, in order to permit the passage of blood-
vessels, lymphatics, and nerves into the uterine substance.
The tissue composing the greater part of the uterus is formed
of smooth muscular fibres, the arrangement of which is very
irregular, but three more or less distinct layers have been de-
scribed. The external one, which is relatively thin, consists
mostly of fibres running longitudinally, although many circu-
lar fasciculi are seen. The middle layer exceeds the others in
thickness, its fibres take a longitudinal, transverse, or oblique
direction, while the internal layer is essentially circular, and
forms the sphincters of the uterus. The contractile elements
of these muscular layers are intimately united together by a
cementing substance, forming fasciculi or bundles, which are
again held together by connective tissue in which elastic fibres
are found. The shape of the cells in the normal uterus is fusi-
form, frequently very long, and in transverse section round or
oval, with several angles. The nucleus is always single, rod-
like or oblong in shape.

The mucous membrane lining the uterus is closely connected
to the muscular tissue. It has no connective-tissue framework
of fibres, but its structure resembles the stroma of lymphoid
organs, in which the framework is made up of spindle and
fusiform cells. The surface of this membrane varies in differ-
ent parts ; at the fundus and body it is smooth, except at the
orifices of the Fallopian tubes, where there is a slight folding ;
in the canal of the neck it is thrown into numerous branching
folds, the plica palmatce. At the upper end of the isthmus of
the cervix a distinct border indicates the termination of the
mucous membrane of the body. The epithelium covering this
portion of the membrane is columnar in shape, and provided
with short cilia. There are found in the mucous membrane
of the fundus and body numerous tubular glands, which are
either simple tubes or they divide about their middle, and ter-

244 MANUAL OF HISTOLOGY.

rainate in blind ends; frequently they have a spiral course,
corkscrew-like ; but generally their direction is vertical to the
plane of the membrane; they open into the cavity of the
uterus. The existence of a membrana propria in these glan-
dules utriculares is denied by some, or if present it is only
toward the orifice of the gland. In the pregnant organ, how-
ever, an extremely delicate, structureless membrane, in which
oval nuclei are found, is thought to represent such a structure.
The cells lining these glands are prismatic in shape, their broad
ends directed outward ; the slender extremities projecting into
the lumen of the gland are provided with cilia.

The mucous membrane lining the canal of the cervix is
denser and thicker than that of the body. It possesses a con-
nective-tissue investment which lies between it and the muscu-
lar layer, and it also differs from the lining of the body in the
presence of folds, which constitute the plicae palmatse. The
epithelium covering this portion of the uterus is made up of
cylindrical ciliated cells, in the upper two-thirds of the canal,
but as the external os uteri is approached it gradually as-
sumes the laminated pavement variety. Minute papillae, pro-
vided with a capillary loop, are found in the lower half of the
canal. The folds of membrane consist of a firm fibrous tissue,
a few smooth muscular elements, and a scanty amount of elas-
tic fibres. Here are also located the mucous follicles of the
cervix, or, as some histologists consider them, depressions only
of the mucous membrane; they are lined with a cubical epi-
thelium, and possess a structureless membrana propria, which
is intimately connected to the connective tissue. From an
occlusion of the orifices of these follicles there are developed
small retention cysts containing mucoid fluid, usually round or
oval, and measuring 0.3 to 0.5 mm. in length ; they are known
as the ovula Nabotlii. The fluid secreted by the mucous mem-
brane of the uterus differs from that of the vaginal mucous
membrane in having an alkaline reaction.

The mucous membrane covering the intra-vaginal portion
of the uterus is a continuation of the vaginal mucous mem-
brane, consisting of a similar structure, and composed of a
connective-tissue framework with papillae projecting into its
covering of laminated pavement-epithelium. At times this por-
tion is found to contain the ovula Nabothi.

The uterus is a very vascular organ ; a capillary network is

THE FEMALE ORGANS OF GENERATION. 245

found in the muscular coat and mucous membrane. In the
latter such reticula are seen to surround the glands. The veins
are very large, possess delicate walls, and are valveless. In the
cervical portion, a more regular distribution of vessels is met
with, and their walls are unusually thick.

Numerous lymphatic vessels are found beneath the peri-
toneal covering of the uterus, and arched passages are seen
ending in loops or blind extremities under the mucous mem-
brane of the cervix. Lymph clefts and vessels are also met
with in the intermuscular connective- tissue.

The nerves of the uterus are derived from the genital sper-
matic ganglia. On the posterior wall of the neck a large
ganglionic mass is met with, from which most of the nerves
have their origin. Nervous filaments may be followed as far
as the mucous membrane, and a few histologists have traced
them into the papillae of the cervix, while in the muscular coat
they are said to terminate in the nuclei of the muscular ele-
ments.

During the physiological function of menstruation and
gestation the uterus experiences certain modifications. In the
former there is an increase in the size of the organ, owing mostly
to the great increase of blood in the vessels ; the glands of the
mucous membrane are also increased in size. The discharge of
blood during this period is due either to a rupture of the dis-
tended capillaries, or a diapedesis, in which the walls remain
uninjured. On microscopical examination of the menstrual
fluid it is found to contain, besides the blood-elements, numer-
ous uterine epithelial cells.

The modifications of the uterus during gestation occur es-
pecially in the muscular elements, which are greatly hyper-
trophied, and there is also a new formation of them. The
blood-vessels, lymphatics, and nerves also experience an in-
crease in size, the latter by a thickening of their perineurium.
The mucous membrane of the body of the uterus during gesta-
tion is separated from the uterus, previously becoming thicker,
softer, and more vascular, and constitutes the decidua. The
cervical portion of the mucous membrane does not participate
in this metamorphosis ; it retains its epithelium, and secretes a
mucous plug, which fills the canal of the cervix during preg-
nancy. Subsequent to delivery a new mucous membrane and
glands are developed on the cavity of the uterus, and the hy-

240 MANUAL OF HISTOLOGY.

pertropliied and newly formed muscular elements undergo
retrograde development and fatty metamorphosis.

The Fallopian tubes, or temporary ducts of the ovary, con-
sist of an external covering furnished by the peritoneum, rich
in connective tissue and blood-vessels ; a muscular coat made
up of an outside layer of longitudinal, and an inside layer of
circular involuntary muscular elements ; and, finally, an in-
ternal mucous membrane. A division of the tube is made into
two parts : that toward the uterus, into which it opens, the
much narrower portion, is the isthmus, while the free half is
the ampulla, which terminates in the fimbrice. The mucous
membrane, upon transverse section of the tube, in the narrow
portion, is seen thrown into simple longitudinal folds, while in
the ampulla the folds are much more complicated, and in a
transverse section have a dendritic appearance. The epithelium
covering the mucous membrane consists of ciliated columnar
epithelial cells. The movements of the cilia occasion a current
in the direction of the uterine opening. There is an absence of
glands in the mucous membrane of the Fallopian tubes. The
same histological elements are present in the fimbrise as in
other portions of the tube, of which they are a direct contin-
uation.

The ovary for histological study may be divided into two
parts, the cortex and medullary substance ; covering the cor-
tex is a layer of columnar epithelial cells, named the ovarian
or germ epithelium (Fig. 107). In a perpendicular section, the
germ-epithelium is here and there seen to extend down into
the substance of the organ and form tubes — the ovarial tubes.
The cortical substance or parenchymal zone consists of several
layers of dense connective tissue, in which are found ovarial
tubes and ovarian follicles. The most external follicles are im-
perfectly developed, while those lying deeper are more highly
developed and contain the ovum. Internal to the cortex is the
medullary substance or vascular zone, in which are numerous
blood-vessels, giving it the nature of a cavernous tissue.

The stroma of the ovary consists of fibrillar connective tis-
sue. In the vascular zone it is somewhat loose in texture, and
contains a network of elastic tissue. There are also found in
this zone fasciculi of smooth muscular fibres, which follow the

THE FEMALE ORGANS OF GENERATION.

247

large and medium sized arteries, at times constituting a slieatli
for the vessels. In the stroma of the parenchymal zone the
connective-tissue forms an outer layer of short, dense fibres

FIG. 107. — From the ovarinm of a rather old bitch ; portion of a sagittal section, a, germ-epithelinm ;
6, 6, ovarial tubes ; c, c, younger follicles ; d, older follicle ; «, discus prollgerus, with egg ; /, epithelium
of o second egg in the same follicle ; g, tunica flbrosa folliculi ; A, tunica propria follicnli ; t, folliculur
epithelium (mombrnna granulosa) ; k, collapse d. degenerated follicle ; /, vessels : m, TO, cell-tubes of the
parovarium, both longitudinal and transverse sections ; y. tubular sinking in of the germ-epithelium into
the substance of the ovary; », commencement of the germ- epithelium cloae to the lower border of the
ovary. Walileyer.

which run in every direction, and an inner one abounding in
cells, in which the follicles are seen.

The blood-vessels enter the ovary at the hilum. The arteries
have a spiral, corkscrew-like course through the organ. At
the hilum the veins form a convoluted mass, the bulb of the

248 MANUAL OF HISTOLOGY.

ovary. A capillary reticulum surrounds the follicles, and is
situated in their internal membrane.

The stroma of the hilum contains numerous lymphatics,
which have an arrangement similar to that of the veins. Sur-
rounding the follicles in their external lamina is found a dense
network of lymphatics.

The nerves enter the ovary at the hilum with the arteries,
and they have been followed into the stroma between the large
follicles, but their ultimate terminations have not as yet been
ascertained.

The follicles of the ovary, or Graafian follicles, consist of a
connective-tissue wall separable into two layers : an internal,
which contains the small capillaries, and an external, contain-
ing the large blood-vessels and lymphatics. The outer layer is
made up of the same connective tissue as the stroma of the
ovary, in which are numerous spindle-shaped cells. The inter-
nal layer consists of connective tissue, in which are numerous
and variously shaped cells, fusiform, stellate, and small round
bodies, the latter possessing amo3boid movement ; there are
also seen larger round or polygonal-shaped cells. This layer of
corpuscles is the metnbrana granulosa. Within the follicle,
and distending it, is an albuminous fluid holding a few bodies
in suspension. Situated in the follicle, usually at that part
most distant from the surface of the ovary — although this is
not a rule without exception, since it is also found immediately
below the most superficial part of the follicle — the ovum is
found surrounded by a collection of cells of the granular mem-
brane, known as the discus proligerus. Two kinds of cells
form the discus proligerus, the follicular and egg epithelium ;
the latter lie in immediate contact with the vitelline membrane,
and are closely adherent to it.

An examination of the mature ovum demonstrates it to
measure 0.28 to 0.1379 mm. in diameter; it is spherical in
shape, and is a typical cell, consisting of an investing mem-
brane, the vitelline membrane, or zona pellucida, which is
a dense> transparent, homogeneous substance, apparently
pierced by numerous minute pores. This membrane is prob-
ably developed from the cells of the discus proligerus, and from
the layer described as the egg epithelium. The cell-contents,
protoplasm, or vitellus is a granular mass composed of albu-
minous and fatty particles, and a more or less distinct reticu-

THE FEMALE ORGANS OF GENERATION.

249

lum of fine fibrils. Within the vitellus is seen the nucleus or
germinal vesicle (also presenting a delicate reticulum of fibrils),
situated eccentrically, spherical in shape, measures 0.037 to
0.451 mm. in diameter, shining, transparent, and contains the
nucleolus or germinal spot, which is a highly refractile body,
finely granular, supposed to be non- vesicular, and measures
0.0046 to 0.0068 mm. in diameter.

The mature Graafian follicle, which is seen on the surface

Fio. 108. — A, primordial egg of the human being: 8 month*' fostus. B, primordial follicle of the
rabbit. C, primordial follicle of a dove. D, a somewhat older follicle of the same animal ; commence-
ment of the formation of the subordinate yolk. E. blind end of the ovary of an nscaris nigrovenosa ;
germinal vesicles (some of which possess a germinal spot and Schriin's "granule") in a diffuse mass of
protoplasm. F, egg of the ascaris nigrovenosa from about the middle of the ovary ; Schron's grannie ;
commencement of the deposition of yolk-matter. (?, egg from a follicle (2 mm. in diam.) of the rabbit :
a. egg-epithelium ; 6, striated zone with radiating striae ; c, germinal vesicle ; d, germinal spot ; «, yolk.
Waldeycr.

of the ovary, giving rise to a prominence, ruptures during the
menstrual period and empties its contents, viz. : the ovum,
fluid contents, and discus proligerus into the Fallopian tube.
The cause of the rupture is an increase in the contents of the
follicle, and a fatty metamorphosis of the cells of the wall of
the follicle. As a result of this rupture of the Graafian vesi-
cle, there is formed a yellow body, the corpus lideum, which

250 MANUAL OF HISTOLOGY.

reaches its full development in a few weeks after the ruptur-
ing of the follicle, or when impregnation has occurred after the
lapse of two or three months. It consists of a central portion,
at iirst red, becoming gray, and a peripheral portion, yellow in
color, thrown into folds. These folds are made up of the in-
ternal membrane and cells. The central portion in a fresh
corpus luteum consists of a very vascular tissue, in which are
seen numerous large cells, containing a red coloring substance
and hsematoidin crystals. A retrograde metamorphosis occurs
in the yellow body, supposed to be due to a want of nutrition
caused by a wasting of the arteries, and there only remains a
white cicatrix, the corpus albicans. The time required for
the disappearance of a corpus luteum when impregnation has
taken place— a true corpus luteum — is several months, lasting
to the end of gestation ; but for the disappearance of a false
corpus luteum, or when impregnation has not occurred, it only
requires a few weeks. It is, however, to be remembered, that
every Graafian follicle with its contents does not reach full de-
velopment ; most of them experience fatty or colloid metamor-
phosis.

The ovaries have their origin from the Wolffian bodies. A
thickening of the epithelial covering is early observed upon
the side of these bodies ; at the same time and place a cellular
projection growing from the connective tissue of the. organ is
noticed. From this increase of -epithelium the Graafian folli-
cles and ova are developed, later the ovarial epithelium ; from
the connective tissue is built up the vascular system of the ovary.

The Graafian follicles are developed from collections of cells,
irregular in shape, or, as they are named, ova chains, consisting
of small-sized peripheral cells, which later form the membrana
granulosa, and the primordial ova ; these last are recognized
by their large size, granular or reticulated protoplasm and
central position. The ova chains are sometimes enclosed in a
homogeneous membrana propria, forming a tubular structure,
as in the cat ; this membrane, however, is not found in all ani-
mals. These chains are developed by an ingrowth of the epi-
thelial cells covering the surface of the ovary.

The parovarium, or remains of the Wolffian body, situated
in the broad ligament, is made up of twelve to fifteen tubules,
which possess a membrana propria, lined by a single layer of
ciliated epithelium, and contain a transparent substance.

THE FEMALE ORGANS OF GENERATION. 251

The placenta is divided into a uterine and total portion.
The former consists of cells irregular in shape, containing one
or several nuclei, and at times one or more nucleoli. These
cells are separated by an intercellular substance, either hyaline,
granular, or fibrous in nature. Fusiform cells, in which a rod-
shaped nucleus is seen, are also found, and are thought to in-
dicate the presence of smooth muscular elements. The tufts
upon the surface of the uterine placenta, which divide and sub-
divide, pass quite deeply into the foetal placenta, yet no direct
transformation of them into the foetal tissue can be demon-
strated ; they appear to terminate in fibrillated tissue, which
contains none of the cellular elements of the uterine placenta.

The blood-vessels of the uterine placenta are arteries and
veins, with no intermediary capillary system ; they communi-
cate by means of sinuous spaces, limited by placental tissue
only. These spaces are said to possess a delicate limiting wall ;
this statement, however, has not been confirmed.

The foetal placenta is developed from the chorion, the villi
or tufts of which growing into the uterine follicles are covered
by a columnar epithelium. The blood-vessels in the villi do
not lie directly in contact with the wall of the villus, but are
separated from it by a perivascular space. Besides a direct
communication of the arteries and veins, there is also a capil-
lary system present in the villi. Connective tissue accompa-
nies the vessels into the villi from the chorion. The variety of
connective tissue here met with is the mucoid, consisting of
round, spindle, and stellate-shaped cells, with a structureless
intercellular substance. There is a direct transformation of
this mucoid connective tissue into the connective tissue of the
chorion.

BIBLIOGRAPHY.

BISCHOPP. Beitr. zur Lehre v. d. menschl. Eihiillen. 1834.

VALENTIN, in Mailer's Arch., p. 526. 1838.

GOODSIR. Anat. and Path. Researches. Edinburgh, 1845.

KOBELT. Der Nebeneierstock des Weibes. Heidelberg, 1847.

STEINLIN. Ueber d. Entw. d. Graaf. Foil. u. Eier d. Saugeth., Mittheil. d. Zu-

richer naturf. Gesellsch. 1847.
ROBIN. Arch, gener. de med. Vol. XVII., p. 258 and 405. 1848. And Vol.

XVIII., p. 257. Also Gaz. m&L No. 50. 1855.
RAINEY, in Phil. Trans., II. 1850.

252 MANUAL OF HISTOLOGY.

SCIIR&DKR VAN DER KOLK. Waaraemingen oves het Maaksel van de menschl.

Placenta, etc. Amsterdam, 1851.

SMITH, TYLER-. Med. Chir. Trans. Vol. .XXXV., 378. 1852.
REMAK. Unters. ueb. d. Entwick. d. Wirbelthiere. Berlin, 1855. Med. Centr.

Zeit. No. 42. 1861. No. 3. 1862.
KLEBS, in Virch. Arch. Vol. XXVIII. 1863.

PFLOOEII, E. Ueb. d. Eierstocke d. Saugeth. u. d. Menschen. Leipzig, 1863.
SPIEGELBERG. Virch. Arch. .VoL XXX., p. 466. 1864.
KAMENEW. Unters. d. Blutgef. d. Mutterth. d. Placenta, Medicinsky Westnik.

No. 13. 1864.
CORNIL, in Jour, de 1'anat., p. 386. 1864. Unters. aua d. phys. Labor, zu Bonn,

p. 173. Berlin, 1865.

POLLS. Die Nervenverbr. in d. weibl. Genital. Gottingen, 1865.
His, in Arch. f. mikr. Anat. Vol. I., p. 151. 1865.

ST. GEORGE, v. LA VALETTE, in Arch. f. mikr. Anat. Vol. II., p. 56. 1866.
PEKIER. Anat. et phys. de 1'ovaire. Paris, 1866.
STRICKER. Wien. Sitz. June, 1866.
LANGHANS, in Virch. Arch. Vol. XXXVIII., p. 543. 1867.
FRANKENHAUSER. Die Nerven. d. Gebarmutter. Jena, 1867.
JASSINSKL Zur Lehre ueb. d. Struct, d. Placenta. Virch. Arch. 1867.
VIRCHOW. Bildg. d. Placenta, in Gesamm. Abhandlungen. 1853.
BIDDER. Ueb. Hist. d. Nachgeb., in Hoist's Beitr. z. Gynacol. IL 1867.
ERCOLANI. Giamb. delle gland, otricolare, etc. Bologna, 1868.
PLIKOL, in Arch. f. mikr. Anat. Vol. V., p. 445. 1869.
FRIEDLANDER. Unters. ueb. d. Uterus. 1870.
HENNIG. Der Catarrh d. inn. weibl. Geschlechtsorg. 1870.
WALDEYEU. Eieratock. u. Ei. Leipzig, 1870.
LOTT and A. ROLLET. Untersuchungen. II. Leipzig, 1871.
LANGHANS. Unters. ueber d. menschl. Placenta. Arch. f. Anat. u. Phys. 1877.
LEOPOLD. Stud. ueb. d. Uterus-schleimhaut. Arch. f. Gyn. Vol. XI.«, p. 110 and

443. 1877. Also Vol. XII., p. 169. 1877.

HENNIG. Ueber Driisen der Vagina. Arch. f. Gyn. VoL XII., p. 488.- 1877.
FOULIS. The Development of the Ova, and the Structure of the Ovary, etc. Jour.

of Anat. and Phys. Vol XIII., p. 353. 1878-79.
FREY, HEINRICH. Histology and Histochemistry of Man. 1880,
KLEIN, E., and E. NOBLE SMITH. Atlas of Histology. 1880.

CHAPTER XVII.

THE KESPIKATOBY TEACT.

BY BENJAMIN F. WESTBROOK, MID.,

Lecturer on Anatomy and Pathological Anatomy at the Long Island College Hospital,

Brooklyn, N. Y.

THE respiratory tract includes the nares and, perhaps, the
pharynx, but as the latter is more commonly associated with
the function of deglutition, and the former contain in their
upper portions the organs of one of the special senses, they
have been assigned to other portions of this work. This chap-
ter is devoted exclusively to the consideration of those parts
which are concerned in the respiratory process. As the pleura
forms a part of the lung, and facilitates the movements of
breathing, its structure may properly be described under this
section.

The air-tubes are in general made up of three layers : an
outer of connective tissue and elastic fibres ; a middle, muscu-
lar and cartilaginous; and an inner of mucous membrane.
Their structure is more complex in the upper, and simpler in
the lower portions of the respiratory passages.

The larynx. — The muscles of the larynx are of the striped
or voluntary variety.

The ligaments and membranes are composed of yellow elas-
tic fibres with some white fibrous tissue. Their structure can be
easily demonstrated by the process of teasing or by employing
the reagents ordinarily used for this class of tissues. The la-
teral thyro-hyoid and the inferior thyro-arytenoid ligaments
have the following peculiarities of structure : the lateral thyro-
hyoid ligament usually encloses a small piece of hyalinecarti-.
lage about the size and shape of a large grain of wheat. It
is known as the cartilago triticea. In adult males it is usually
calcified. It may be incorporated either with the cornu of the
hyoid bone or with the superior cornu of the thyroid cartilage.

254 MANUAL OF HISTOLOGY.

The inferior thyro-arytenoid ligaments, or true weal cords,
are made up almost entirely of yellow elastic fibres stretched
across from the thyroid cartilage in front, to the vocal processes
and adjacent anterior borders of the arytenoids behind. The
elastic bundles originate, anteriorly, in a mass of connective
tissue which occupies the angle of the thyroid. Posteriorly,
many of the fibres are prolonged into the arytenoid cartilage,
converting that part of it into reticular tissue. These liga-
ments are continuous below with the lateral crico- thyroid mem-
branes, and are described by some anatomists * as their superior
borders.

The innermost fibres of the internal thyro-arytenoid mus-
cle mingle with the outer fibres of this ligament, some ending
in or taking their origin from them. The intimate relation be-
tween the muscle and the ligament can be seen in a vertical sec-
tion through the larynx.

Of the laryngeal cartilages, the three larger are of the
hyaline variety. Horizontal sections show a broad central area
with two zones between it and either the outer or inner sur-
face. The appearance of the zones or bands is thus described
by Rheiner : * "1. A thin peripheral portion, appearing to the
naked eye as a narrow, bluish, opalescent band, which con-
sists of a transparent and longitudinally striated matrix with
elongated cartilage-cells arranged parallel to the surface. 2.
The intermediate layer, a narrow, whitish, opaque band, con-
sisting of a dull yellowish ground-substance with numerous
large mother-cells containing fatty daughter-cells. 3. The
broad central layer, with a perfectly transparent homogeneous
matrix and few cells. The intercellular substance increases,
relatively to the contained cells, from without inward, and, in
the interior, presents numerous large spaces in which no cells
are found. In the thyroid and cricoid cartilages the outer
peripheral zone is thicker and more easily distinguished than
the inner."

The following peculiarities are to be noted : the central por-
tion of the thyroid, viz., that part which forms the anterior
projection or angle, is distinguished by the great number and
small size of its cells. It ia penetrated by numerous fibres

' Qaain's Anatomy, eighth edition, Vol. II.. p. 284.

* Quoted by Merkel in Anatomie u. Phys. des mensch. Stimm- u. Sprach-Organs.
Leipzig, 1863, S. 166.

THE RESPIRATORY TRACT. 255

from that mass of connective tissue from which the vocal cords
take their origin. After prolonged maceration in some alka-
line solution, this cartilage can be separated into three parts —
two lateral and an anterior or median.

The arytenoids are not composed exclusively of hyaline
cartilage. The vocal process, as already mentioned, presents a
yellow reticulated structure, the fibres of which are continuous
with those of the true vocal cords. The apex has also a re-
ticular structure when there is no joint between it and the
cartilage of Santorini. The elastic tissue is then continuous
with that which connects it with the corniculum. A hori-
zontal section through the arytenoid at the level of the vocal
process shows the reticular structure of the process, the hya-
line character of the body of the cartilage, and the gradual
transition from one to the other.

The three cartilages already described are subject to calci-
fication and partial ossification. This occurs more frequently
and at an earlier age in the male than in the female. It also
begins at a later date in those who have been castrated. It
makes its first appearance at the points of muscular attach-
ment. As the cartilages undergo calcification they increase in
size, so that the calcified larynx of old age is larger than that
of the young adult. The matrix also splits up into a fibrous
texture, not aifected by acetic acid.

The cornicula laryngis or cartilages of Santorini and the
cuneiform cartilages of Wrisberg, as well as the sesamoid
cartilages (when they exist) are of the reticulated variety.
The cartilago triticea is hyaline and prone to calcification.

The epiglottis consists of reticular cartilage. On transverse
section, however, the intercellular substance is seen to be a
spongy elastic substance, granular on section ; at the periphery
yellow fibres are present. The elastic cartilage should be ex-
amined with a high power.

The mucous membrane of the larynx varies in its structure
in different situations. On the laryngeal surface of the epi-
glottis it is thin.

The epithelium in the upper half is in several layers. The
deepest cells are somewhat columnar or pyramidal in form,
while the superficial ones are flat. The lower half is covered by
a stratified, columnar, ciliated epithelium. The epithelium rests
upon a thin, apparently structureless basement-membrane.

256 MANUAL OF HISTOLOGY.

The mucosa is made up of delicate connective-tissue fibres, en-
closing in their meshes a series of lymph -spaces. Connective-
tissue cells are also found here, and some elastic fibres. There
are a few small papillae in the upper portion. The submucous
layer is thin, contains many elastic fibres, and is continuous
with the perichondrium. It contains the racemose mucous
glands, whose ducts open upon the surface. Some of the larger
glands are lodged in the depressions of the cartilage, and some
are even situated on its anterior aspects, their ducts passing
through to the posterior side.

In the submucous tissue there are lymphatic follicles, some
of which are arranged about the mucous glands and their ducts.

The membrane covering the false vocal cords, arytenoid
cartilages, and ary-epiglottic folds, as well as that lining the
ventricles and inferior compartment of the larynx is thicker
and more loosely attached to the subjacent parts. It is covered
by stratified columnar, ciliated epithelium, except upon the
edge of the false vocal cords and over the inner surfaces of the
arytenoids, where it is of the pavement variety. The mucosa
contains a large amount of lymphoid tissue, which holds in its
meshes lymphoid cells. Closed lymph-follicles are also found
in the submucous tissue of the false vocal cords and on the
floor of the ventricle.1 That portion of the mucous membrane
which covers the true vocal cords is thin, more closely attached,
and has no mucous glands. In its anterior half it ha's numer-
ous small papillae (0.07 to 0.08 mm. in height, Coyne) project-
ing at the edge and 'on the superior and inferior surfaces of the
cord. They are composed of connective tissue, with many elas-
tic fibres. Their vascular supply is slight. The membrane in
this situation is covered by stratified pavement -epithelium,
continuous posteriorly with that which covers the inner sur-
faces of the arytenoids. Numerous racemose glands send their
ducts obliquely upward and inward to discharge their secretion
upon the upper and under surfaces of the vocal cords.

In front of the corniculum laryngis, on either side, is a col-
lection of racemose glands surrounding the cartilage of Wris-
berg. Another collection is found between the arytenoids.

The epithelium can be examined, either by scraping it from
the surface, or in sections. The mucous glands are best seen

1 Coyne : Archiv. d. Physiologie, p. 92, 1874.

THE RESPIRATORY TRACT. 257

in sections of the hardened larynx. They are lined by cubical
glandular epithelium. The capillary blood-vessels of the laryn-
geal mucous membrane are small with wide meshes, giving the
membrane a paler appearance than that of the pharynx.

The lymphatics are numerous in the mucous and sub-
mucous layers. They may be injected with Berlin blue, by
puncturing the submucous tissue.

In the nervous filaments are ganglion cells. The mode of
termination is not definitely known. But in the mucous
membrane of the epiglottis end bulbs have been found. The
methods of examination will be found elsewhere.

The trachea and primary bronchi. — The rings of the trachea
and bronchi are composed of hyaline cartilage. Longitudinal
sections of these rings show that the cells lying near the peri-
phery, underneath the perichondrium, are flattened, and ar-
ranged with their long axes parallel to the surface. Internally
they are oblong and perpendicular to the former.

The ends of the incomplete rings are connected, posteriorly,
by a layer of smooth muscular fibres, which are attached to
the fibrous tissue of the perichondrium. The attachment is
to the inner aspect of the ends of the cartilages, so as to throw
the muscular layer forward of the most posterior projection of
the rings.

These muscular fibres also exist in the spaces between the
rings, where they are attached, on either side, to the fibrous
tissue of the tube. Outside of the transverse fibres are a few
filaments which have a longitudinal direction. They are at-
tached to the fibrous membrane.

The fibrous membrane which encloses the cartilages and
completes the framework of the tube is composed of connective
tissue containing a considerable portion of elastic tissue, par-
ticularly in its external portion. The outer lajrer of the fibrous
membrane encloses both the cartilages and the muscle fibres.
The inner layer is thin and lies between the rings and the
glandular layer.

The mucous membrane is covered by several layers of epi-
thelial cells, the deeper being more or less spherical or ovoid,
whilst the superficial ones are columnar and ciliated. The
columnar cells, losing their cilia, are continued into the ducts
of the mucous glands. These glands are very numerous, and
often of considerable size. They are racemose, the acini being

258

MANUAL OF IIISTOLOGY.

lined with cubical epithelium. Owing to the distention of some
of the gland-cells by mucus or by the action of reagents, they
assume a rounded form, and the nuclei are pressed against the
attached ends of the cells. Such corpuscles are known as
4 'goblet " cells. Some of the larger glands project posteriorly
outside of the fibrous membrane, but the great majority of them
are situated internally to that structure, and then form a dis-
tinct layer, the "glandular layer." They are most abundant
in the spaces between the cartilages. Their ducts pierce the

deb

Pio. 109. — Transverse section of bronchial twig, 6 mm. in diameter : a. outer fibrous layer ; ft, muscu-
lar layer ; c, inner fibrous layer (inucosa) ; rf. epithelium. Magnified 30 diameters. F. E. Schulze.

mucous membrane obliquely, so that the entire length of a
duct is not usually found in a section of the tracheal wall.
At short intervals, between the columnar cells of the surface,
other cells are found, of a spindle shape, or somewhat stellate.
These cells send processes upward to the surface and down-
ward into the basilar membrane, where they become contin-
uous with other branched cells. The prolongation which passes
upward to the surface is usually single, though it may occasion-
ally send off a delicate filamentary branch, which is lost in
the cement substance between adjacent cells.

The process, sometimes double, which passes downward
connects with a tissue in the mucosa which resembles the
lymph canalicular system of other parts. It is made up of
a network of branched cells, or connective-tissue corpuscles,
which line a series of spaces, that in turn communicate with
the lymphatic capillaries of the mucous membrane. Sikorsky
injected a watery solution of carminate of ammonia into the

THE RESPIRATORY TRACT. 259

bronchial tubes of cats and dogs while the animals were liv-
ing, and found, post-mortem, that the carmine had penetrated
through the interepithelial cells above described into the lym-
phatic vessels below.

The interepithelial cells have a small nucleus which stains
more deeply with hsematoxylon than do the nuclei of the ordi-
nary epithelial cells. In vertical section they are more opaque
than the epithelia, and, when seen on the surface of the mem-
brane, appear as dark spots among the ciliated cells.

The lymphatic capillaries join to form larger trunks which
run along the sides of the bronchi communicating freely with
each other and with those of the neighboring blood-vessels.
They are called by Klein the peribroncMal lymphatics.

Beneath the mucosa, and between it and the mucous glands,
are numerous bundles of yellow elastic tissue having a longi-
tudinal direction. Some of the bands are quite thick, particu-
larly in the posterior wall, and raise the mucous membrane in
longitudirial folds.

The mucous membrane of the trachea and bronchi has a
rich network of capillaries. The racemose glands are also sup-
plied with a vascular network which ramifies in the fibrous tis-
sue by which they are surrounded. The natural injection of
these vessels, which occurs in cases of bronchitis in the human
subject, is often sufficient for their examination.

The mode of termination of the nerves has not been ascer-
tained.

The trachea should be hardened in chromic acid or Muller's
fluid, followed by alcohol. The sections may be stained in
hsematoxylon. In order to preserve the ciliated epithelium, it
is well, as Professor Rutherford suggests, to cut the sections
with the freezing microtome. The lymphatics can be injected
by puncture.

The smaller bronchi and lungs.— 'Beyond, the primary bron-
chi (or first division of the trachea) the muscular fibres encircle
the tubes inside of the cartilaginous and fibrous layer ; indeed,
the primar}?- divisions show the first sign of this new arrange-
ment. The cartilages change from incomplete rings to irregu-
larly shaped plates, which are found on all sides of the tubes,
but their microscopic structure remains unaltered. The longi-
tudinal elastic fibres are contained between the muscular and
mucous coats. The tubes divide and subdivide generally in a

260 MANUAL OF HISTOLOGY.

dichotomous manner, diminishing gradually in calibre, the
combined area of the branches, however, always exceeding that
of the trunk from which they' spring. No change occurs in
their structure, except a gradual thinning of their walls, until
they reach a diameter of about 1 mm., when the cartilages
disappear and the attenuation is more marked. The circular
muscular fibres continue to exist, as also the longitudinal elas-
tic fibres, but the mucous glands disappear. After a still
further division the tubes are diminished to a diameter of .20
to .30 mm., the muscular fibres become more sparse, and the
epithelium is reduced to a single layer of low, somewhat cubi-
cal cells, which are still ciliated. These are the lobular bronchi,
each one going to a single pulmonary lobule. The lobular
bronchi each give off ten to fifteen smaller tubes, known as the
terminal bronchi or bronchioles. They are straight and cylin-
drical, their walls are very thin and
delicate, and their epithelial cells
gradually lose their cilia and become
flattened plates. Each bronchiole
leads to a smaller division of the lob-
ule, called an acinus or lobulette.1 The
bronchioles divide into short canals,
the alveolar passages, usually three

Fio. 110. — A system of alveolar pas- • -i • mu • 11 j.u*

ges with infuridibuii from an ape's for each acinus. Their walls are thin

Inng : a, terminal bronchial twig ; 6. 6, 111 -i 1 1 '• i _e

intnndibuia; c, c, alveolar passages, and bulge outward on all sides, torm-

Magnifled 10 times. F. E. Schulze. . ,, , . . . , ..

ing, externally, little projections or

elevations ; internally, shallow depressions or cavities which
open into the calibre of the tube. They also give off secondary
branches, called infundibula, which have groups of such little
cavities attached to, and opening into them. The little cavities
are the alveoli or air-cells of the lung. From this description
it will be seen that each lobule has ten to fifteen acini or lobu-
lettes, and that the lobulette is made up of alveoli or air-cells,
which open into common spaces or infundibula, which in turn
communicate with the alveolar passages. The alveoli, which
are connected with the infundibula, are called terminal alve-
oli ; those which open on the sides of the alveolar passage are
called the parietal alveoli. The latter are called, by Dr. Wa-
ters, the broncJiial alveoli. The alveolar passages, infundibula,

1 Dr. Waters : The Anatomy of the Human Lung, London, I860.

THE RESPIRATORY TRACT.

2C1

and alveoli have a flat pavement epithelium resting on an ap-
parently structureless basement-membrane. Outside of this are
numerous elastic and muscular fibres, curving around the cavi-
ties, and holding in their meshes the capillary blood-vessels.
The muscular fibres are very numerous in the walls of the al-
veolar passages and infundibula. The alveoli have a diameter
of .1 to .4 mm., but their size varies greatly according to the
degree of inflation of the lungs.

FIG. III.— Section through an infundibultim : a, entrance from the alveolar passage into the infundi-
bulntn ; o, nuclei of smooth muscular cells. Magnified 30 diameters. F. B. Schulze.

The epithelium in the alveoli of the fetal lung is columnar
in shape, so that a section of such a lung resembles a section
of a glandular organ. But when the alveoli are distended at
birth, the cells change their form. In transverse sections, either
real or optical, of the alveolar walls, the epithelial plates pro-
ject more or less into the cavity, according to the degree of dis-
tention of the lung: This change of shape undoubtedly occurs
during life with the alternating expansion and contraction of
the thorax, and should be taken into account in considering
the pathological changes of inflammation, collapse, etc. By
injection of a weak solution of silver nitrate (£ per cent.) into
the bronchi of a fresh lung, and its subsequent immersion in

262

MANUAL OF HISTOLOGY.

alcohol, the lines between the epithelial plates can be demon-
strated. The nuclei can be s.tained with carmine.

Some of the cells are converted into hyaline plates. The
alveolar epithelium of the human lung is not so readily demon-
strated as that of animals, principally because too long a time
usually elapses between death and the post-mortem dissection.
In some traumatic cases an autopsy can be made early, and as

Pio. 112.— Interior of an alveolus. LunR injected with a solution of nitrate of silVer to show the lines
between the alveolar epithelial cells. F. E. Schnlze.

favorable opportunity had of examining these structures. They
can be shown very well in fresh sections cut with Valentin's
knife.

The spaces between the alveoli and acini contain the elastic
fibres mentioned above, together with a few oval connective-
tissue nuclei and muscular elements. The lobules are held
together by thin septa of connective tissue. The connective
tissue is also found in the angles of division of the lobular
bronchi and bronchioles.

The muscle-cells may be identified by their elongated,
fusiform nuclei. A further proof of their 'existence is found
in certain cases of cirrhosis of the lung, in which many distinct
muscular fibres are found in the new connective tissue.1

The branches of the pulmonary artery follow the course

1 Buhl : Lungenentz. Tuberculosis, u. Schwindsucht, Miinchen. 1873, S. 358.

THE RESPIRATORY TRACT. 263

of the bronchi as far as the lobules. The lobular branches
are terminal arteries — i.e., they do not anastomose with each
other. They break up into very small branches, which encircle
the alveoli and supply the capillary plexuses of their walls.
These capillaries are very small, and the network so fine that,
when injected, the open spaces are not as wide as the vessels
themselves. This, however, will vary with the degree of dis-
tention of the lung. Between two adjacent alveoli only one

Pro. 113.— Section of human lung injected through the pulmonary artery : a, a, free alveolar margins ;
6, small arterial branch ; c, c, alveolar walls seen in transverse section. F. E. Schulze.

capillary plexus is found, the branches of which are seen to
pursue an undulating course, projecting, first, into the cavity
on one side, then into that an the other. These unite again
into veins which run irregularly through the lobules to unite
upon the bronchi and follow their course to the root of the
lung. The peculiarities of the pulmonary veins are, 1st, that
their united calibre does not exceed (if it equals) that of the
arteries ; 2d, that they have no valves. The bronchial vessels
supply the coats of the bronchial tubes and the surrounding
connective tissue and the pulmonary pleura.

But the line of demarcation between the bronchial and pul-
monary circulations is indistinct on the venous side, as injec-
tions thrown into the bronchial arteries fill the pulmonary

2G4 MANUAL OF HISTOLOGY.

veins and capillary plexuses and overflow into the pulmonary
arteries.1

It appears from this that part of the blood from the bron-
chial arteries does, or may, return through the pulmonary veins.
In their course through the lung, the pulmonary arteries lie
upon the upper and anterior aspect of the bronchial tubes,
while the veins are found on their inferior surface. The bron-
chial arteries follow the tubes and divide with them.

The lymphatics of the alveolar septa are a series of lacunar
spaces lined by branched connective- tissue corpuscles, whose
nuclei have already been described as being visible in ordinary
sections of the lung.

In sections of a lung treated with silver nitrate the forms
of the cells are distinguishable. According to Klein the pro-
cesses of these cells pass upward between the epithelial plates
of the alveoli so as to bring the cells into direct communica-
tion with the cavity, just as we have seen the interepithelial
cells of the bronchial mucous membrane send certain processes
upward between the columnar epithelia and others downward
to the cells of the lymph lacunae. On examining the epithelium
of an alveolus, small, round, dark spaces are seen between the
cells ; these are said by Klein to be the projecting processes of
the branched cells of the lymph lacunar system. The ends of
these processes, both here and on the bronchial mtjcous mem-
brane, are called pseudostomata, in contradistinction to the
true stomata of the serous membranes.

The small spaces, or lacunae, open into lymphatic radicles,
which have a regular endothelial lining. These pass inward
toward the root of the lung, upon t^e bronchi and the walls
of the vessels. On the vascular walls they communicate freely
with each other, and at times completely invest the vessel with
a lymphatic sheath like that of the cerebral vessels. In this
situation they are called perivascular lymphatics. The peri-
vascular and peribronchial lymphatics communicate freely. At
the surface of the lung there is a plexus immediately beneath
the pleura (subpleural lymphatics) from which trunks of some
size run to the root of the lung. They communicate with the
perivascular system and with the pleural cavity. The final
termination of all these channels is in the bronchial glands.

1 Dr. Waters.

THE RESPIRATORY TRACT. 265

The nerves of the lungs are derived from the sympathetic
and pneumogastric. Their mode of termination is not known.

For the examination of the general structure of the lung it
may be inflated and dried pretty rapidly in the sun or by a
fire. For more careful examination it should be hardened in
chromic acid, Miiller's fluid, or alcohol. The hardening fluid
should be injected into the air- passages.

In order to distend the vesicles it is well, before placing the
lung in the hardening fluid, to inject the bronchi with simple
gelatine. The vessels may also be injected with a colored
mass. The lungs of the lower animals are used for these
demonstrations, owing- to the difficulty of obtaining normal
human lungs in a perfectly fresh condition. The investigation
of the lymphatics is attended with great difficulty. They may
be demonstrated by the puncture method. Klein found that
on injecting the blood-vessels, under high pressure, with Ber-
lin blue or silver nitrate, some of the capillaries ruptured, and
the fluid passed into the perivascular lymphatics.

The pleura. — The pleura, like the other serous membranes,
consists of a connective-tissue ground-substance covered by a
single layer of polygonal endothelial cells. In the costal pleura
the subserous connective tissue is more abundant, and its at-
tachment to the thoracic wall is not so firm as is that of the
pulmonary pleura to the lung. The structure of the pleura is
most conveniently studied in the smaller mammals. It can
also be demonstrated in young children.

To demonstrate the endothelium of the surface, the thorax
of a recently killed animal should be opened, care being taken
not to rub or otherwise injure the pleura. The surfaces are to
be washed by pouring distilled water over them, in order to
remove the serum, and then a weak solution of silver nitrate
(i — \ Per cent.) allowed to flow over them. After a few mo-
ments the surfaces are bathed with pure water. The diaphragm-
atic or mediastinal portion is then excised with scissors,
immersed in distilled water or glycerine, and exposed to the
daylight until it takes a light reddish-brown color. It may
now be floated on to a slide, carefully smoothed by traction at
the edges, and mounted in glycerine. The portion excised
should be large, so that it can be manipulated without touch-
ing the part which is to be examined. For this reason it is well
to take with it some of the surrounding structures, e.g., the

266 MANUAL OF HISTOLOGY.

entire diaphragm, with the mediastinal portion, together with
the heart and pericardium.

It will be seen that the endothelium is composed of a great
number of polygonal plates whose edges are glued together by
a substance which has been stained brown or black by the sil-
ver. Nuclei are seen in many of them, or they can be shown
by staining with carmine or hsematoxylon. Small openings
are to be seen in certain localities surrounded by cells of a
more cubical form, with large, distinct nuclei. In other places
small dark spots are seen between the cells. The openings are
known as stomata, and communicate with lymphatic vessels
running beneath the endothelium. The dark spots &re pseudo-
stomata, and are similar in their nature to the pseudo-stomata
of the alveoli and bronchial mucous membrane; i.e., they are
the ends of processes of the branched cells of the ground-sub-
stance reaching up between the endothelial plates. In order
to demonstrate the ground-substance or connective-tissue layer
of the pleura, the fresh surface is carefulty pencilled with a
soft brush dipped in the fluid of the abdominal cavity, or in
artificial serum. After washing with distilled water, the solu-
tion of silver nitrate is poured over it, and it is treated as be-
fore. On examination, the branched connective-tissue cells
are seen communicating with each other by their processes.

Blood-vessels and lymphatics are also seen, and in a favor-
able place the endothelium of the latter is seen to be continuous
with the branched cells. These cells line the cavities of the
connective tissue, and belong to the lymph lacunar system.

The lymphatic vessels accompany the blood-vessels, some-
times ensheathing them. They are identified by the shape of
their endothelial cells, which are wider and more polygonal in
form than those of the veins. It will be seen from this descrip-
tion that the serous membrane is a lymphatic structure. Its
cavity communicates by means of the stomata with the lym-
phatic vessels below, while, by means of the pseudo-stomata,
it communicates with the lacunar spaces which are lined by
the branched cells. To demonstrate the pulmonary pleura,
the lungs should be excised, moderately distended with air
(which is retained in them by ligature of the trachea), treated
with silver nitrate, as already described, and then immersed in
alcohol. After a few days sections are made parallel to the
surface.

THE RESPIRATORY TRACT. 267

If the lung be pencilled before it is treated with the silver
solution the deeper structures can be examined. The sections
should be mounted in glycerine with the external surface
upward. The appearances here are similar to those already
described. The capillary lymphatic-vessels communicate with
the superficial pulmonary branches forming the subpleural
lymphatics.

The endothelial cells of the pulmonary pleura vary in
shape according to the degree of distention of the lung. In
the lung which has been inflated before hardening, the cells
appear as flat plates, but in the atelectatic lung of a fetus, or
the collapsed lung of an animal that has breathed, they are
cubical or even columnar in shape. This difference is most
marked in the guinea-pig, owing to the presence of a layer of
muscular-fibres beneath the pleura of that animal. The tops
of the cells which have this pyramidal shape are not flat as in
true columnar epithelium, but rounded. This change of shape
simply indicates that the cells accommodate themselves to
changes of space. These changes, in a lesser degree, must be
occurring constantly during life, with the movements of respi-
ration. On the costal pleura, the stomata are only found in
the intercostal spaces.

Attached to the lower border of the lung are minute ap-
pendages, the "pleural appendages" forming a sort of fringe
connected with the pleura. Some are visible to the naked
eye, some microscopic. The larger are made up of connective
tissue and blood-vessels, and, exceptionally, nervous fibres in
the larger ones. They are covered by round cells, sometimes
resembling epithelium. The smallest ones are structureless,
and in general have no epithelial covering.1

BIBLIOGRAPHY.

COYNE, P. Recherches sur 1' anatomic normale de la nraqueuse du Larynx. Ar-
chives de Physiologic, p. 92. Paris, 1874.

STIRLING. Nervous Apparatus of the Lung. Brit. Med. Journal. Vol. II., p. 401.
1876.

CADIAT. Des rapports entre le develop, du poumon et la structure. Jour, de
1'anat. et de la Phys., No. 6, p. 591. 1877. And, Structure et de>el. du
poumon. Gaz. Med. de Paris, No. 17, p. 214. 1877.

1 Luschka : Anatomic des Menschen, Bd. I., S. 293.

268 MANUAL OF HISTOLOGY.

GRANCIIEIC. Note BUT leslymphat. du poumon. Gaz. Med. de Paris, No. 9, p. 103.

1877.
AEBY. Die Gestalt d. Bronchialbaumes u. die Ilomol. d. Lungenlappen beiin

Menschen. Med. CentralbL, No. 16, p. 290. 1878.
SEILER, C. Researches on the Anatomy of the Vocal Cords. St. Louis Med. and

Surg. Journal, p. 333. April 5, 1880. And, Minute Anatomy of the Larynx

Normal and Pathological. Archives of Laryngology. Vol. I., Nos. 1 and 2

and to be continued. 1880.

CHAPTER XVIII.

THE SKIN.

Br A. R ROBINSON, M.D.,

Lecturer on Normal Histology in the Bellevue Hospital Medical College, New York.

General plan of arrangement. — The integumentum commu-
ne, or skin, forms the external covering of the body, which
it mechanically protects, and at the same time is endowed
with certain physiological functions. The surface of the skin
in some parts of the body is smooth and soft ; in others it
is more or less uneven and rough. This latter condition
depends upon the presence of pores, hairs, furrows, and
ridges. The pores correspond to the surface openings of the
hair-follicles, sebaceous and sweat-glands. The hairs vary
in amount of development according to their situation. In
the so-called hairy regions they are largest ; other parts are
provided only with a soft down (lanugo hairs). There are
no hairs on the palms of the hands and soles of the feet, the
dorsal surfaces of the terminal phalanges of the fingers and toes,
the glans penis, and inner surface of the prepuce. The fur-
rows are either long and deep, or short and superficial. The
former are chiefly found in the flexures of the joints, and cor-
respond to the folds in the derma produced by movements of
the joint. The latter run between the papillary elevations,
and, by crossing each other, divide the surface into a number
of polygonal or lozenge-shaped fields. This division is well-
marked on the backs of the hands. These superficial furrows
are more developed on the extensor than on the flexor surfaces
of the extremities, and in the lumbar region more than on the
anterior surface of the abdomen. Their direction is dependent
on the degree of the tension of the skin. The ridges correspond
to the papillse, and are most developed on the palmar surfaces
of the last digital phalanges. The color of the skin varies in

270

MANUAL OF HISTOLOGY.

individuals according to race, and in the same individual ac-
cording to the part of the body. The dark skin of some races
depends upon the presence of 'pigment in the cells of the rete
Malpighii. In the white race, dark pigment is usually pres-
ent in greatest quantity in the areolse of the nipples and in
the scrotum and labise.

General structure. — The skin is composed of the follow^
ing parts : epidermis, corium, subcutaneous connective tissue,

Pio. 114.— Diagrammatic perpendicular section through the normal skin : a, epidermis ; b, rete Mal-
pighil; c, papillary layer; d, corinm; e, panniculns adiposus; /, spirally bent end of excretory sweat-
dnct : 0, straight portion of excretory duct of sweat-gland ; A, coil of sweat-duct ; i, hair-shaft ; *, root
of hair ; 1, sebaceous gland. After Neumann.

blood-vessels, nerves, lymphatics, sweat and sebaceous glands,
hairs, and nails.

A perpendicular section through the skin shows (Fig. 114)
three well-marked layers ; the most superficial is called the
epidermis proper, a, b ; the middle layer is the corium or cutis,
d ; and the deepest layer the subcutaneous connective tissue, e.
The limit of the epidermis at its place of union with the corium
is sharply denned, but the corium and subcutaneous connec-

THE SKIN. 271

tive tissue gradually merge into each other, the boundary be-
tween them being only an artificial one.

Commencing with the epidermis, we will describe in detail
the minute structure of the different tissues and organs of the
skin, omitting only the lymphatics.

Description of the different layers. — The epidermis is
generally subdivided into several layers, with specially distinc-
tive names for each layer ; but though such a division has
some practical value, histologically it
is incorrect, as the cells of the lowest
layer are transformed, at some period
of their existence, in their movement
toward the free surface, into the cells
of the other layers. Examination with
high powers also shows that the chan-
ges in the molecular constitution or
chemical condition of the cells of the
epidermis — changes which produce
differences in their appearance — are

quite gradual. Consequently, sharply defined layers are not
found. For practical reasons, however, it is well to adopt the
usual classification. In Pig. 115 these layers are shown.

Another division is into Malpighian and corneous layers
only, the former comprising the rete and the granular layer,
and the latter the stratum lucidum and corneous layer. The
Malpighian layer, as compared with the corneous layer, pre-
sents a more or less dark, granular appearance, while the latter
is homogeneous, and its cells have a lamellar arrangement.

The rete MalpigTiii consists of nucleated corpuscles, rich in
protoplasm, granular in appearance, and disposed more or less
in parallel strata, the elements of the different layers differing
somewhat from each other as regards their size and shape. The
lowest layer consists of columnar-shaped cells arranged pali-
sade-like, with their long axes more or less perpendicular to the
surface of the corium. Where the papillae are well developed,
this perpendicular arrangement is not so marked. The base of
some of these bodies terminates in a pointed extremity, which
passes a short distance into the underlying corium. Each of
them has an oval nucleus. The cell-body consists of a small
quantity of slightly granular, shining protoplasm. The cor-
puscles of this layer are not united to each other by bands, as

272 MANUAL OF HISTOLOGY.

in the other layers. The next two or three strata consist of
more or less polygonal-shaped bodies, each with a spherical
nucleus. The cells of these' layers are large, their contours
sharpl}' defined, and they contain more or less pigment. It is
this substance deposited in the corpuscles that gives the charac-
teristic color to the different races of mankind. Their cell-bod-
ies are larger in proportion to the nucleus than in the first layer.
In the succeeding layers the cells increase in size and are more
granular in appearance, the cells and nuclei become flatter as
they approach the granular layer, and, finally, lie with their long
axes parallel to the surface. The granular structure which in
the lowest layer is most marked around the nucleus, gradu-
ally extends toward the margin of the cells, as the surface is
approached, so that finally a clear area is seen around the
nucleus, whilst the remainder of the cell-body is markedly
granular. At the same time the cell-body becomes firmer and
the nucleus smaller.

All the cells of the rete Malpighii, except those of the first
row, are united to each other by filaments (Martin, Bizzozero,
Heitzmann), the so-called prickles of Max
Schultze (Fig. 116). These uniting filaments
or bands vary much as regards their size
and length in different parts of the body.
They are most distinct wherever the Mal-
pighian layer is well developed, but are
thicker and longer in the lower rows of
Fia lie.-" prickie "ceiis cells than in the upper. At the stratum
lucidum they cease to exist. Between
neighboring corpuscles the length of these bands is in direct
proportion to the distance between the borders of the cell-
bodies. Hence, where three or four cells meet at one place,
as in the centre of Fig. 116, the minute filaments are much
longer than those uniting the bodies of closely adjoining cells.
Examining these prickle-cells with the microscope, alternate
dark and light bands are seen between the cell-borders. With
a low power, these light bands appear to consist of spaces be-
tween the connecting filaments, the dark lines being the con-
necting filaments, but with a high power the latter can be
recognized as spaces between the former. The light bands
can be traced from the surface of one cell to the surface of
another, whilst the dark lines are the spaces between these

THE SKIN. 273

bands. These connecting cords sometimes divide and anas-
tomose with each other, forming a sort of network between the
cells. In this case, the dark spaces do not always extend
from one cell-body to another, since they may correspond to
the space between anastomosing filaments. These bands are
therefore not the prickles of adjoining cells, which interlock
with each other, but are true connecting filaments between
cells of a common origin, and which have not yet become sepa-
rated from each other. The connecting bands or fibres gradu-
ally diminish in length and thickness from below upward, and
finally cease to exist when the granular layer is reached.

The spaces between the bands are filled with an inter-
cellular albuminous substance, and they may be regarded as
minute channels for the conveyance of nutriment to the cells
of the epidermis. The above view of the "prickles" corre-
sponds very closely with that held by Dr. Martin, and differs
from that of later observers, who maintain that the dark lines
are connecting bands, and the light lines the spaces between
them.

Owing to the close union of the Malpighian elements it is
very difficult to isolate them. Perhaps the best way to accom-
plish this result is by long immersion in iodized serum. Fig.
117 represents a cell isolated in this manner. Here
the bands have been torn apart and the cell-surface is
studded with thorn-like projections. Hardening in
chromic acid, with subseq uent boiling in a moderately FIO. m.-i*>-

, ,. . * lated "prickle"

strong solution of potash, causes a separation of the <*»•
mucous layer from the corium and a falling apart of the rete
cells (Biesiadecki). The structure of the corpuscles, however,
can be best studied when their normal relations with each
other are preserved. Variations in the number of cellular lay-
ers are of normal occurrence in the rete, although this portion
of the skin shows the least variation as regards its thickness.
The arrangement of the elements in these different strata is the
same in all parts of the body, and appears to be independent
of the thickness of this layer.

As regards the direction of the long axes of the cells there
is a gradual passing from the perpendicularly seated cells of
the first layer to the horizontally lying cells of the uppermost
row. The lower surface of the rete adapts itself to the upper
surface of the corium, and between the papillae projects down-

274

MANUAL OF HISTOLOGY.

FIG. 11&— Horizontal section of skin through a
papilla. The migrating cells are observed as dark
bands between the epithelial cells and amongst the
connective tissue of the papilla. Pagensteoher.

ward and forms the interpapillary rete Malpigliii. Wandering
lymphoid cells' are frequently present in the rete. They are
especially numerous in some pathological conditions. They
(Fig. 118) are elongated spindle-shaped bodies lying between
the rete cells, and sending out minute processes. They color

deeply in carmine, have a
small nucleus, and are most
numerous in the lower part
of the rete mucosum.

The granular layer (Fig.
115, 6) consists of one or two
strata of flattened, granular-
looking bodies, which, in
perpendicular section appear
spindle - shaped, with their
long diameter parallel to the
free surface of the epidermis.
In this stratum the cells are
no longer connected with each
other by bands, as in the pre-
ceding layer. The nuclei of
these corpuscles are very distinct, and flattened in the same
direction as the cell-body. The latter has a very coarsely gran-
ular appearance, which is most marked near the nucleus, and
gradually diminishes in degree as the periphery of the cell is
approached. The structure of these bodies is best shown with
hsematoxylon.

The stratum lucidum, also called the stratum of OeM, is
composed of at least three layers (Fig. 115, c). It presents a
clear, homogeneous, or striated appearance. Within the flat-
tened cells composing it, a staff-shaped nucleus is found. The
cells of this layer are formed from those of the granular stra-
tum. In their movement to the free surface the latter become
less granular and the inter-granular substance grows more trans-
parent and shining (Unna). This change from a granular to a
homogeneous translucent appearance commences around the
nucleus, whence it gradually extends to the periphery of the
cell. The nucleus, also, usually becomes invisible.

In vertical section the corneous layer appears (Fig. 115, d)
to be composed of wavy fibres and horny, transparent cells
of various sizes and shapes. This variation in bulk and form

THE SKIN. 275

depends in great measure upon the thickness of the layer.
The nearer we approach to the stratum lucidum, the more dis-
tinct are the cells. If the layer is very thin the cells appear
as elongated, flat, or curved bodies, giving to this part of the
epidermis a fibrous appearance. When the corneous stratum
is thick these cells present various forms and sizes. The cor-
puscles of the lower layers color slightly in carmine, are poly-
gonal or spindle-shaped, and frequently contain a shrivelled
nucleus. As the surface is approached they grow flatter and
drier, are more bent upon themselves, and color less and less in
carmine. The nucleus also becomes invisible. The most su-
. perficial layers are composed of elongated, flat, dried-up cells,
the so-called epidermic scales. These bodies are best studied
after they have been subjected to the action of liquor potassse,
which causes them to swell up.

The corpuscles of the stratum corneum are arranged in lay-
ers as in the other parts of the epidermis, but the elements
forming a layer are more closely united with each other than
with those of the adjoining layers. Hence this stratum can be
separated into lamellae, as occurs in some pathological states
of the skin. It accompanies, for example, the formation of
some vesicles, where the exuded liquid, prevented from pass-
ing toward the surface, accumulates between the layers, and
thus separates them from each other.

The corneous layer participates in the elevations and de-
pressions of the underlying layers. This causes the undulat-
ing or wavy appearance of the lamellge, as observed in sections
where the papillae are well developed. It varies greatly in
thickness in different parts of the body, and reaches its great-
est development on the palms of the hands and soles of the feet.
Its thickness does not depend upon the rete Malpighii, as it
sometimes forms a thin layer where the rete is thick, and vice
versa.

The subcutaneous connective-tissue layer of the skin con-
sists principally of connective-tissue bundles, which, coming
from the underlying fasciae of the muscles or from the peri-
osteum, pass in an oblique direction to the corium. These
fasciculi are generally cylindrical in form, and variable in size ;
by their anastomoses or divisions they form larger or smaller
networks, with correspondingly large or small interfascicular
spaces. Generally large bundles anastomose with each other

276 MANUAL OF HISTOLOGY.

in this layer, and hence a loose connective tissue is formed.
Within this layer adipose tissue is found in greater or less
quantity. The fat-cells are collected into masses or lobules, the
number of cells which form a lobule varying greatly in num-
ber. Each of these latter may be regarded as a fat-gland, as it
is provided with an afferent artery, a capillary plexus between
the corpuscles, and one or more efferent veins. Several lobules
are sometimes united together in the form of an acinous-like
gland, and are likewise seen to be surrounded by a general
sheath of connective tissue. The individual fat-cells are round,
flattened, polyhedral, or oval-shaped, the form depending upon
the degree and direction of the pressure exerted upon them.
Owing to the amount of fat-tissue so often found in this layer,
it has been called the panniculus adiposus. Such fat-lobules
are absent in the penis, scrotum, labise minorse, eyelids, and
pinna. The corresponding spaces in these regions are tra-
versed by fine connective- tissue bands or single fibrils. From
this adipose tissue fat-columns pass upward in a somewhat
oblique direction to the bases of the hair-follicles, especial!}7"
to those of the fine hairs. Their long axes form a slight angle
with the axes of the follicles, and they are nearly parallel to
the erector pili muscles (Warren). In cases of starvation, in
the so-called wasting diseases, and in all acute diseases at-
tended with excessive loss of tissue, the fat-cells ^disappear to
a greater or less extent. The skin, in such instances, becomes
correspondingly flaccid and wrinkled. Adipose tissue gives to
the skin its tension and fulness, and to the body its appear-
ance of roundness or plumpness. Obesity consists in an exces-
sive production of fat-cells.

The interfascicular spaces differ in size in proportion to the
amount of lymph present, and to the closeness of the anasto-
moses between the bundles. In oedema the lymph-spaces are
increased in size proportionately to the increased amount of
liquid present. The interfascicular spaces all communicate
with each other, as is shown by the rapidity with which a
hypodermically injected liquid can be dispersed by manipu-
lation.

The connective-tissue cells of this layer and of the corium
consist of branched cells (Ravogli) which surround the white
fibrous bundles and send in processes between the fibres. Ac-
cording to some observers, these cells are epithelioid in charac-

THE SKIN. 277

ter. The elastic-tissue fibres are developed from the processes
of the branched cells.

Besides connective- tissue fibres and cells, lymphoid corpus-
cles are present in this layer. They exist in greatest number
near the blood-vessels and glands. In this situation they are
of a roundish form, but in the parts distant from the blood-
vessels they are more or less spindle-shaped, and are to be
regarded as wandering cells.

The convoluted part of the sweat-glands and the lower part
of the hair-follicles of deep-seated hairs lie in this layer.

Blood-vessels, lymphatics, and nerves are present. The
blood-vessels are large, 'and after giving off small branches to
the hair-follicles, sweat-glands, and fat-lobules, pass upward
to the corium.

Pacinian corpuscles are found in connection with some of
the nerves. For a description of these bodies the reader is re-
ferred to the article on the nerves.

The principal part of the corium consists of white fibrous and
elastic tissue, the latter increasing in amount with advancing
age. Here the white fibrous tissue forms a much denser, firmer
structure than in the previous layer. It consists of deep
oblique, and superficial horizontal bundles. The latter com-
prise fine bundles of connective tissue which run parallel with
the surface of the skin, and by their division and anastomoses
form a very fine network with small interfascicular spaces.
From this layer bundles pass upward into the papillae, and
these form a second denser network. The deeper layer is
formed by a continuation upward of the subcutaneous con-
nective-tissue bundles. These pass upward in an oblique direc-
tion, and as they reach the corium divide into fasciculi. Here
they continue to divide and anastomose with each other and
with fibres from the horizontally running bundles. The anas-
tomoses are very close ; hence, the corium is formed of a dense
network of connective tissue, except in those parts which are
traversed by blood-vessels, lymphatic vessels, nerves, hair-folli-
cles, and sebaceous and sweat glands. Immediately around
the hair-follicles, sweat-ducts, and sebaceous glands the con-
nective tissue is dense, and the fibres run parallel with the di-
rection of the organs. Owing to the greater size of the connec-
tive-tissue bundles in the lower part of the corium, and the
consequent looseness of the network formed by their anasto-

278 MANUAL OF HISTOLOGY.

moses, tliis part of the coriura has been called the pars retlcu-
laris cor ii, in contradistinction from the finer network formed
in the upper part, to which the name pars papillaris has been
applied. But neither between these two parts nor between the
subcutaneous layer and the corium is there any sharp dividing
line, the transition being a gradual one.

As already mentioned, the size of the interfascicular spaces
depends upon the closeness of the anastomosis between the
bundles and fibres. The direction of the bundles corresponds
with that taken by the blood-vessels.

The connective-tissue corpuscles of the corium resemble
those found in the subcutaneous layer, and also bear the same
relation to its connective-tissue bundles. From the upper
portion of the corium fibres pass upward to make the papillae.
The form of the papilla is very variable in different parts of
the body. Where they are most developed, as on the inner
surface of the terminal phalanges of the fingers and toes, they
are conical in shape. In some other regions they form only
slight elevations on the corium, giving a wave-like appearance
to its upper surface. They consist of a close network of white,
fibrous connective tissue combined, especially in the central
part of the papilla, with a large number of elastic fibres. Those
papillae which contain tactile corpuscles are called nerve-pa-
pillae.

The corium is separated from the stratum mucosum by a
thin, transparent basement-membrane, containing oval nuclei.
Its under surface is not sharply defined, and from it prolonga-
tions pass upward between the cylindrical cells of the rete,
giving this surface a notched appearance similar to that ob-
served on the inner margin of the internal sheath of the hair-
follicle.

Elastic fibres are present in large numbers in the corium,
especially in its upper part, where they form a network around
and between the white fibrous tissue-bundles. In the lower
part of the corium they form a large network, which becomes
finer as the surface is approached. The number of elastic
fibres increases with advancing years. With this increase of
clastic fibres there is a corresponding decrease of the white
fibrous connective-tissue cells (Ravogli). Numerous wander-
ing cells are met with in the corium, especially in the vicinity
of the blood-vessels and glands. Hair-follicles, sebaceous

THE SKIN. 279

glands, sweat-ducts, nerves, lymphatic vessels, and non-striated
muscles are also present in this layer. For a fuller descrip-
tion of the intimate structure of the connective-tissue bundles
and cells, see the subject of connective tissues.

Blood-vessels. — Only the corium and subcutaneous tissue
are provided with blood-vessels. The arterial Hood-vessels
supplying the skin form two parallel horizontal layers, a su-
perficial and a deep one. The deep layer lies in the subcuta-
neous tissue, and consists of large vessels running parallel to
the general surface. From this horizontally lying deep layer,
branches are distributed to the sweat-glands and fat-follicles of
this region. The principal branches, however, pass perpendicu-
larly or obliquely upward through the corium to its upper part,
and form immediately beneath the papillae (after free branch-
ing and anastomosis) a superficial horizontal layer, the stratum
subpapillare. From the vessels ascending
through the corium branches are given off to
the hair-follicles, sebaceous glands, and gen-
eral tissue of the corium. From the stratum
subpapillare small branches pass upward into "PIG. ii9.-Biood-ve«-
the papillae, where they become capillary ves- Stratum ^ubpSpulare'; l\
sels, which proceed to the summit of the
papilla. (See Fig. 119.) Before reaching this point, however,
they frequently divide into two or more branches. Frequently,
those papillae in which tactile corpuscles are seated have no
blood-vessels.

The veins are arranged on the same plan as the arteries :
they form a superficial and a deep layer, and have their origin
in the papillae. From the superficial layer larger vessels pass
downward, receiving blood from the veins of the hair-follicles,
sebaceous glands, and the general tissue of the corium, thus
forming a deep subcutaneous layer or venous network.

JVerves. — Medullated and non-medullated nerve-fibres are
present in the skin. They are found in combination in the nerve-
trunks of the subcutaneous tissue, the medullated fibres being
most numerous in those regions of the skin where the Pacinian
and tactile corpuscles are most abundant. In the subcuta-
neous connective-tissue region, and in the lower part of the
corium, some nerve-fibres leave the nerve-trunks and pass to
the glands, blood-vessels, and Pacinian corpuscles found in this
region. In the corium some of the fibres lose their medullary

MANUAL OF HISTOLOGY.

sheath, and afterward continue their course as non- medulla ted
fibres. The nerve-bundles pass upward in a more or less oblique
direction from the subcutaneous connective tissue through the
corium to the subpapillary network of blood-vessels, around
which they form a plexus. From this subpapillary plexus
medullated fibres run upward and pass into the tactile cor-
puscles.

The non-medullated nerve-fibres form a reticulum around
the blood-vessels of the pars reticularis corii and the capilla-
ries of the papillae. They consist of thick or fine, smooth,
varicose fibres with numerous nuclei. These fibres proceed
from the network around the subpapillary blood-vessels up-
ward toward the rete Malpighii, and either pass directly into
the rete or run for a short distance parallel to its under sur-
face, and then finally enter that layer. Within the epider-
mis the fibres run between the cells and terminate in a manner
not yet definitely known. Their mode of division and termina-
tion within the epidermis is probably similar to that occurring
in the cornea. Within the papillae the nerve-fibres frequently
divide before entering the rete.

The manner of distribution and termination of the non-
medullated nerve-fibres can only be studied successfully in tis-
sue stained with gold chloride. The tissue must be fresh, and
a weak solution of the gold chloride used. When sufficiently
stained the tissue is placed in distilled water slightly acidu-
lated with acetic acid and exposed to the light.

The Pacinian corpuscles are found in greatest abundance in
the skin of the fingers, toes, palm of the hand, sole of the foot,
but also occasionally in other regions of the skin. Their struc-
ture is described in the article on the nervous system.

Tactile corpuscles. — As already mentioned, some of the
medullated nerve-fibres forming the plexus surrounding the
subpapillary blood-vessels, pass upward and enter the so-called
tactile corpuscles. These corpuscles are generally seated in the
papillae, but occasionally they are found in the subpapillary
region, i.e., the upper part of the corium. The majority of
the papillae containing such corpuscles have no blood-vessels.
They are more or less oval in form, and can be easily recog-
nized under the microscope by their dark contours and by the
oblique lines produced by the transversely running connective-
tissue fibres of the outer surface of the corpuscle. There may

THE SKIN.

281

be two or more corpuscles within a single papilla (Thin), but
each corpuscle invariably has a special nerve passing into it.
Frequently, however, an appearance as if two corpuscles were
present is produced by a single corpuscle having the shape
of a figure 8. The medullated nerve-fibre, in passing to the
corpuscle, pursues a more or less curved course, and usually
enters it at or near its lower extremity. It may, however, en-
ter at any part of the corpuscle, and sometimes winds around
it for a considerable distance before entering. After entering
the corpuscle the medullary sheath is lost, and its course now
becomes difficult to pursue, except in the case of very small
or young corpuscles. The intimate structure of these bodies
and the arrangement of their formative elements are still mat-
ters of discussion and uncertainty. The external portion of a
corpuscle appears to be composed, in great part, of larger or
smaller bundles of white, fibrous connective tissue anastomos-
ing with each other and running transversely, or in a spiral
direction, to the long diameter of the corpuscle. This part
of the corpuscle differs, as regards
irregularity of surface, with the size
and the manner in which the fibrous
fascicles divide and anastomose. The
coarser the bundles and the anastomo-
ses the more irregular will be its sur-
face. Between the fibres are found
oval or round bodies which color deep-
ly in gold, and have been regarded as
elastic elements (Thin). Other obser-
vers consider them as connective tis-
sue, or nerve-fibres. Some of these
bodies undoubtedly represent the
nerve-fibre in transverse or oblique
section ; for the nerve pursues a more
or less zigzag course within the corpuscle, and, consequently,
a section of the body will probably show the nerve cut across
in one or more places (Fig. 120, Z>). The arrangement of the
elements forming the central part of the corpuscle is not yet
thoroughly understood. These bodies have hitherto been
usually regarded as end-organs — that is, it has been believed
that the medullated nerve-fibre terminates within the corpuscle,
hence the name, tactile corpuscle. Observers, however, have

f...

FIG. 120.— Tactile corpuscle, show-
ing termination of nerve : a, corpuscle;
6, nerve, cut obliquely; c, apparent
division of nerve-fibre ; e, similar ap-
pearance as at c ; /, blood-vessel ; g,
rete cells; h, nerve-fibre cut trans-
versely.

282 MANUAL OF HISTOLOGY.

not agreed as to the mode of termination of the nerve, and
some have maintained that it has not been clearly proven that
they really do terminate in the corpuscle. From specimens
which I have recently obtained I am led to believe that the
nerve does not terminate within the corpuscle, but passes on
into the rete Malpighii.

The best corpuscles for studying this point are small ones,
as in these a section is more likely to include the entire upper
extremity of the corpuscle at the same time that it is not too
thick for examination with the microscope. Even in a small
corpuscle, however, unless the nerve passes onward in a direct
level with the corpuscle after leaving it, the nerve, in a vertical
section, will be cut across, and it will, therefore, be impossible
to follow it from the corpuscle into the rete. I believe the
nerve frequently, perhaps generally, changes the direction of
its course after leaving the corpuscle, and hence we often see
a transverse section of the nerve at the upper extremity of the
corpuscle. In Fig. 120 is seen the location of the termination
of the nerve-fibre as observed in one of my specimens. In
one place its course between the rete cells was very indistinct,
though recognizable. The nerve passed obliquely upward be-
tween the cells of the rete to the space between the second
and third rows of cells, where it assumed a longitudinal di-
rection. At the commencement of the curve tjie nerve ap-
peared to have undergone division (c). After passing a short
distance horizontally it ran almost perpendicularly downward,
and near g was lost to view. At e it appeared to have again
undergone division. According to the appearances here fig-
ured the corpuscles are not the structures in which the nerve
terminates, the latter passing from the corpuscle (as a non-
medullated fibre) into the epidermis, where it divides and
probably terminates in the same manner as the other nerves.
This mode of termination cannot be regarded as strange, as we
have already seen that some medullated nerve-fibres lose their
medulla deeper in the corium, and afterward continue their
course as non-medullated fibres.

The tactile corpuscles are found in greatest number in
the ends of the fingers. They are also present on other parts
of the hand and on the foot, and sometimes in the lips and
nipple.

The sweat-glands.— The sweat-glands— glandulce sudorif-

THE SKIX.

erce — are found in the skin of all parts of the body except that
of the glans penis and margin of the lips. They are most nu-
merous in the palms of the hands and the soles of the feet,
where they number, according to Krause, 2,685 to 2,736 to the
square inch.

A sweat-gland is composed of two parts, viz.: the gland
proper, or secreting part, and an excretory duct. The gland
proper lies in the subcutaneous tissue,
and consists of the lower part of the sweat-
gland rolled and coiled upon itself into a
more or less globular form, the tube ter-
minating in a cul-de-sac, the blind extrem-
ity generally lying in the centre of the coil.
The diameter of the secreting tube is
greater than that of the excretory duct.
The former is composed of secreting cells,
unstriped muscular fibres, and a basement-
membrane. The cells (glandular or secret-
ing epithelial cells) are polygonal in shape
and form only a single layer. They are
strongly granular in appearance and have
a very distinct nucleus. Their basal end
is sometimes notched where they are in-
serted into the basement-membrane. In
normal conditions these bodies are never
found in the sweat-fluid, but in inflamma-
tion of the surrounding connective tissue
they frequently become separated from
the basement-membrane. Oil-globules are frequently seen in
the cell- body, and are to be regarded as a normal constituent
of the corpuscles.

The basement-membrane is a thin, transparent structure,
lying beneath the epithelial cells and composed of flat endo-
thelial elements, as shown by the action of silver nitrate on
the fresh tissue.

In certain glands, especially those of the axilla, a layer of
unstriped muscular fibres is found external to the basement-
membrane. These fibres are present in only a small number
of sweat-glands ; by their contraction they assist in the expul-
sion- of the secreted sweat. They are the smallest unstriped
muscular fibres met with in the human body.

Flo, 121. — Lower part of a
sweat-gland : a, excretory duct ;
6, coil of secreting-tube ; c, se-
creting-tnbe cut transversely;
</, blood-vessels cut across.

28-i MANUAL OF HISTOLOGY.

The sweat-glands are surrounded by a somewhat loose
fibrous connective tissue, from which fibres pass inward and
form a closer network between the coils of the gland. Some
of the fibres run parallel, and others transversely or obliquely,
to the long diameter of the convoluted tube. A large number
of lymphoid cells are always present in this interglandular
connective tissue. The sweat-glands are richly supplied with
blood-vessels.

The excretory duct passes upward from the gland proper
in a more or less vertical direction through the different layers
of the skin to its free surface, where it opens with a funnel-
shaped orifice. In passing through the corium it pursues a
straight or slightly wavy course, and enters the lowest part
of the inter-papillary rete. The structure of this part of
the excretory duct differs from that of the gland proper, in
the shape of the cells, the absence of muscle-fibres, and the
presence of a cuticula. This cuticula lines the inner surface
of the epithelial coating and limits the lumen of the duct.
As the rete Malpighii is entered there are generally two or
more layers of cells lining the duct, the number increasing
as the rete is approached. The transition from secreting cells
to lining cells is gradual, so that the presence of a cuticula
decides the nature of the tube. The basement -membrane
corresponds in structure with that of the gland proper. The
fibres of surrounding connective tissue run parallel with the
duct.

As the duct approaches the rete Malpighii its epithelial
cells increase in number and form two or more layers, which
are really only a continuation downward of the cells of the
rete. When the duct enters the rete it loses its basement-
membrane and is formed only of the cells of the mucous layer,
which have become more or less flattened and spindle-shaped.
The direction of the duct through the rete is sometimes straight
and sometimes spiral.

In passing through the stratum corneum the duct pursues
a spiral direction on account of the horizontally flattened cells
of this layer (see Fig. 114, /), and the number of spirals pres-
ent depends upon its thickness. The largest number is found
in the palms of the hands and soles of the feet, where it may
amount to twenty or more, whilst on some parts of the body
there is not even a single complete spiral. The wall of the

THE SKIN. 285

duct is formed of the cells of the corneous layer, and the duct
opens on the free surface at the summit of the ridges.

The formation of the sweat-glands commences in the fifth
month of total life by the pushing of epithelial cells from the
rete mucosum into the cutis. In the seventh month the epi-
thelial cells form a canal, and the lower end of the tube be-
comes dilated and somewhat twisted. In the ninth month the
tube is coiled upon itself to form the gland proper. According
to Ranvier, who believes that the muscular fibres lie between
the epithelial cells and the basement-membrane, the muscle-
cells arise from the external cells of the gland proper by a
process of simple differentiation. The lumen of the tube is
formed not by a softening down of the central cells, but by the
formation of the cuticula, which occurs first at the lowest part
of the excretory duct (Ranvier).

The sebaceous glands. — The sebaceous glands are seated in
the corium and are in close connection with the hair-follicles.
When the hairs are large the sebaceous glands appear as ap-
pendages to the hair-follicles into which their ducts enter, and
by which their contents are carried to the free surface. As
regards the small downy, or lanugo hairs, they may be said to
open into the ducts of the sebaceous glands, the ducts of the
latter having in this case a much greater diameter than in the
previous instance. They also open directly on the free surface.

The sebaceous glands are almost without exception acinous
glands, the number of lobules forming a single gland, ranging
from two to twenty, or more. The largest glands are seated in
the nose, cheeks, scrotum, about the anus, and in the labia.
Occasionally the secreting portion of a sebaceous gland con-
sists of a single tubule, or sac, whose duct opens into a hair-
follicle.

Every sebaceous gland is composed of two parts, viz.: the
secreting portion, or gland proper, and the duct. The gland
proper is formed of a basement-membrane, or sac, externally,
and secreting cells, or their products, internally. The basement-
membrane is continuous with the transparent membrane de-
scribed as lying directly beneath the rete Malpighii and above
the corium, and has a similar structure. This basement-mem-
brane passes from the sebaceous gland to the hair-follicle, where
it forms the inner layer of the hair-sac. The membrane of the
sebaceous gland is surrounded externally by bands of dense

286 MANUAL OF HISTOLOGY.

connective tissue containing blood-vessels, nerves, and lym-
phatics.

The secreting part of the gland (Fig. 122, f) is composed of
layers of cells very similar to the cells present in the epidermis,
those of the outer part corresponding to the cells of the rete
Malpighii. The first layer of cells, viz., those seated upon the
basement-membrane, is composed of cylindrical, or cubical,
cells, like those of the rete. They have a very distinct nucleus.
Further inward the cells become larger, more or less polyhe-
dral in form, and contain fat, which obscures or conceals the
nucleus. If the fat is extracted the nucleus can be seen lying
in the centre of the space previously occupied by the fat. The
nearer the centre of the gland the greater the quantity of fat
in the cells. The most external layer of cells contains but a
small quantity. In the centre of the gland, free fat, fat-crys-
tals, and remnants of epithelial cells are found.

The duct of the sebaceous gland is similar in structure to
that of the gland proper. Externally is the basement-mem-
brane, lined inside by epidermis-like cells, containing more or
less fat, and enclosing a central cavity through which the seba-
ceous matter passes to reach the hair-follicle or the free surface.
The contents of this canal are fat, fat-crystals, and remnants
of epithelial cells. Internal to the polyhedral cells of the duct
are the cells of the corneous layer of the epidermis, which di-
minish in number in proportion to the distance from the free
surface.

In large hairs the duct of the sebaceous gland opens at an
acute angle into the hair-follicle near its upper third, and the
gland proper lies about on a level with the middle third of the
hair- follicle.

At the place of union of the hair-follicle with the sebaceous
gland the cells of the latter become continuous with the cells
of the external root-sheath of the hair. This latter root-sheath
becomes continuous above with the cells of the rete Malpighii.

The development of the sebaceous glands commences at the
third month of fratal life, as a projection downward and out-
ward of a part of the external root-sheath of the hair, at the
place where the future opening of the duct will be situated.
It consists, at first, entirely of epithelial cells, which by sub-
sequent multiplication and further projection downward, form
the sebaceous gland.

THE SKIN. 287

Muscles. — Striated and non-striated muscles are present in
the skin. The former are found both in the smooth and in the
bearded parts of the face, and also in the nose. They arise from
the deeply seated muscles, and passing vertically, or more or
less obliquely, upward between the hair-follicles and the glands
of the skin, terminate in the corium.

The non-striated muscles are very numerous, and run either
in a parallel or in an oblique direction to the general surface
of the skin. Those lying parallel with the general surface run
either in a straight or circular direction. When they run in a
straight direction and anastomose with each other they form
a network, as in the scrotum, prepuce, and perineum. The
straight running muscles are found, especially in the scalp and
in the axilla, both above and below the sweat-glands. Where
the muscles have a circular course, as in the areola of the nip-
ple, a continuous ring muscle is formed.

The majority of the muscles running in an oblique direc-
tion have a special relation to the hair-follicles. The muscle
arises from the internal sheath of the hair-follicle and passing
obliquely upward, skirting the lower surface of the sebaceous
gland, terminates in the upper part of the corium (Fig. 122, ri).
Occasionally two muscles, situated on opposite sides, arise
from a single hair-follicle sheath. A muscle in its course up-
ward frequently divides into two or more bundles, these sec-
ondary bundles afterward pursuing different directions from
each other, and sometimes uniting with fibres from other mus-
cles, form a network in the corium. Sometimes an entire
muscle, or a secondary bundle, passes upward into a papilla
of the cutis and is inserted into the dense fibrous connective tis-
sue directly beneath the rete Malpighii. Occasionally several
secondary bundles run nearly parallel with each other and ter-
minate either separately in the corium, or conjointly, after
uniting.

The skin is provided with other muscles which have no spe-
cial relation to the hair- follicles, but pass more or less verti-
cally upward from the subcutaneous tissue to be inserted in
the corium.

The number of muscles present in the skin varies in differ-
ent regions of the body. They are most numerous in the scro-
1 um. The order of frequency in the different parts of the body
is as follows : Scrotum, penis, anterior part of perinseum, scalp,

288

MANUAL OF HISTOLOGY.

forearm, thigh, arm, shoulder, forehead, abdominal wall, ax-
illa, fore-leg, face, volar and dorsal surfaces of the hands and

feet (Neumann). They are less
developed on the flexor than on
the extensor surfaces.

The size of the individual mus-
cles varies according to the person
and the region of the body. It is
impossible, therefore, to recognize
with certainty a slight hypertro-
phy or atrophy of these structures.
For information as to their
blood, lymph, and nerve supply
see the article on unstriped muscle.
The hair. — The parts to be
studied in connection with the hair
proper are the hair-follicle and
the hair-papilla. Th e hair proper
is a cylindrical structure seated
within the hair-follicle and upon
the hair-papilla. Its base lies
embedded either in the subcuta-
neous connective tissue or in the
corium. The portion of the hair
proper within the follicle is called
the root of the hair, and the re-
mainder the shaft of the hair.
The true hair-follicle includes all
that part of the hair-sac below
the place where the sebaceous
duct enters the hair-follicle. It
is of very variable size and con-
sists of a blind extremity and a
funnel-shaped orifice (a). The
follicle is narrowed just below
this funnel-shaped orifice and
forms the so-called neck of the
hair-follicle (b). This is the nar-
rowest part of the follicle, and
is the place where the duct of the sebaceous gland enters.
From the neck downward the hair-follicle increases in size, be-

Pio. 122.— Hair from beard: a, canal of
exit ; 6, neck of hair-follicle ; c. lower part of
hair-follicle : d. external sheath of hair-folli-
cle ; «, internal sheath of hair-follicle : /. ex-
ternal root-t-heath of hair; g, internal root-
Bheath of hair ; A, cortical substance ; t, me-
dulla of hair ; I, root of hair ; m, fat-cells ; n,
arector pili ; o, papilla of skin ; p, papilla of
hair ; i, rete mucosum : t, sebaceous gland ;
ep, stratum cornenm, which is continued into
the follicle. UicRiadcckl.

THE SKIN". 289

ing largest at its lower end, where it rests upon the papilla.
Below the neck we have the follicle and the root of the hair.

The follicle consists, anatomically, of three layers : the ex-
ternal, middle, and internal hair-follicle sheaths.

The external sTieath of the follicle (d) consists of connective-
tissue fibres, which extend from the upper corium and running
parallel to the long axis of the hair-follicle surround the base
of the latter and send some fibres into the papilla. The fibres
forming the inner portion of this sheath are arranged much
more closely than the fibres forming the external part. In this
latter situation there is no sharp dividing line between the
sheath and the surrounding loose connective tissue, the one
merging gradually into the other. Within this sheath run the
special blood-vessels and nerves of the hair-follicle.

The middle slieatli of the follicle consists of a few transverse-
ly running connective-tissue fibres, between which lie oval nuclei
imbedded in a granular substance. These latter, probably,
represent organic muscle-cells. This sheath begins at the neck
of the follicle and, surrounding its lower part, passes also within
the papilla. In this tissue is a close network of blood-capil-
laries. Nerves have not as yet been observed, though they
probably exist.

The internal sJieatJi of the follicle is composed of a trans-
parent, homogeneous-looking structure — the basement-mem-
brane, which is not altered by the action of acids or alkalies.
It is merely a continuation of the transparent membrane found
between the rete mucosum and the corium, which it resembles
in its structure. It contains neither blood-vessels nor nerves.
The external surface is smooth, but the internal surface has a
notched appearance, caused by prolongations inward between
the cells of the external root-sheath of the hair.

The hair-papilla is formed from the stroma of the hair-fol-
licle sheaths, especially from that of the middle sheath. It
consists of connective-tissue fibres, between which are found
numerous round cells. The internal follicle sheath separates
it from the root of the hair. Within the papilla are found
one or more arteries and veins besides non-medullated nerve-
fibres. The papilla has a narrow neck, a thicker body, and
a conical apex. It is, on an average, twice as long as it is
broad. The breadth is in direct proportion to the length of
the hair.

290 MANUAL OF HISTOLOGY.

The hair-follicles and hairs stand obliquely to the surface
of the skin. • Their direction varies in different regions of the
body, and depends upon the structure of the connective tissue
of the corium and the degree of its tension. The contents of
the hair-follicles are the external and internal root-sheaths and
the hair proper.

The external root-sheath (f) adjoins the inner follicle sheath
and consists of rete cells continued into the hair-follicle from
the general rete mucosum layer of the skin. This sheath does
not extend as far as the lowest part of the follicle, generally
ending about on a level with the apex of the hair-papilla,
though it is sometimes continued as far as the base of the
latter. All the different kinds of cells present in the epi-
dermis are also found in this sheath as far down as the neck
of the follicle. Beyond this point the cells of the rete Mal-
pighii only enter into its formation. The number of rows of
cells forming it is subject to great variation. It diminishes
as the base Of the follicle is approached, so that finally the
sheath is formed of a single row of cells. At the neck of
the follicle the sheath is usually narrower than directly above
or below this point, owing to the pressure to which the cells
are here subjected. Their form is very similar to that of
the corresponding cells of the rete mucosum. Those of the
deepest row are cylindrical, and those of the second row
polyhedral. In the other rows the cells are flatter, with the
exception of the most internal row, where all these bodies
are large and round. This last row is not subject to the same
changes as the others, and has been considered to be a distinct,
independent row of cells (Unna). The nuclei of all the cells
color strongly in carmine, hsematoxylon, etc. Nerve-fibres have
been described as running between the cells of this sheath
(Langerhans).

The internal root-sheath (g) lies in direct contact with the
external root-sheath. It is usually described as consisting of
two layers, an external one, also called the slieatJi of Henle,
and an internal one, or sheath of Huxley. Strictly speak-
ing, this division into two sheaths is incorrect, as it has been
shown (Unna) that the two sheaths supposed to be distinct
,have a common origin from the cylindrical epithelial cells sur-
'rounding the neck of the hair-papilla at its lowest part. These
cells color very deeply in carmine. They surround the root of

THE SKIN. 291

the hair like a sheath. In the thick hairs of the beard the
sheath consists of three rows of cells — the external row, after-
ward forming Henle's sheath, and the two inner rows of cells,
the sheath of Huxley. In finer hairs there are only two layers of
such cells. These corpuscles are originally similar in structure,
having a very granular appearance and an indistinct nucleus.
The sheath is thinnest where the hair-papilla is broadest.
The cells of the external layer (Henle's) become paler and lose
their nuclei earlier than those of the inner layer, so that on a
level with the upper part of the papilla there is a marked dif-
ference in the appearance of the two layers of cells. Formerly
it was supposed (Biesiadecki) that Henle's sheath commenced
at this point and was a product of the external root-sheath,
corresponding in this respect with the corneous layer of the
epidermis. The cells of Huxley's layer afterward become
transparent also and lose their nuclei, and can then no longer
be distinguished from the cells of Henle's layer. The internal
root-sheath is now formed of transparent, non-nucleated, spin-
dle-shaped, or flattened bodies which surround the hair-cuti-
cula as far as the neck of the hair-follicle.

Within the internal root-sheath lies the hair proper, which
consists of a knobbed extremity, the root of the hair, and a
cylindrical portion, the shaft. Between the hair proper and
Huxley's layer lies the hair-cuticula. This latter consists of
two rows of cells — an external one, closely united with Hux-
ley's layer, and an internal one, united to the hair-shaft. They
both arise from the cylindrical cells seated directly upon the
upper part of the neck of the papilla to the inside of the cells
producing the internal root-sheath. The cells of the inner
cuticula (the hair-cuticula) are at first round, then cuboid in
form, and finally, long and prismatic. Above the papilla they
are more elongated, and commence to overlap the cells above
them. With the flattening out of the cells they assume the
form of rhomboid or ovoid plates, so that above the free sur-
face of the skin one cell partly covers the bodies of four or five
others. At first they lie perpendicularly to the long axis of the
hair, but afterward they are parallel with it. Above the papilla
they form spiral rows around the hair shaft, so that in any sec-
tion of this part the cells appear of a long cylindrical or spin-
dle-shape. The external or root-sheath cuticula consists at
first of round cells which afterward flatten and lie in the same

292

MANUAL OF HISTOLOGY.

direction as the flat cells of the previous cuticula. Before the
internal root-sheath is pierced by the growing hair both cuti-
culffi are composed of similar cells.

The root of the hair consists of cells closely resembling
those of the rete mucosum. The corpuscles seated directly
upon the basement-membrane of the papilla are cylindrical in
form, and the more superficial ones polyhedral. Near the hair-
shaft they are spindle-shaped and firmer. The lower cells of
the central part of the root of the hair are round, have a large
nucleus, and a small amount of cell-body. Afterward the cell-
body increases in size. They bear a close resemblance to em-
bryonic corpuscles and color deeply in carmine. In the upper
part of the root of the hair the cells of the external part of the
bulb become oblong, spindle-formed, and, finally, are lengthened

out like fibres, in which condition they
form the fibrous part of the hair-shaft.
The pigment in the root of the hair is
sharply limited externally by the cells
of the hair-cuticula.

The shaft of the hair consists of a
central part or medulla, and a fibrous
portion covered by the hair-cuticula.
The medulla consists of potyhedral
cells containing fat and pigment gran-
ules. Toward the free end of the hair
it becomes smaller, and finally ends
near the point. The fibrous portion
forms the principal part of the hair-
shaft, and consists of flattened, fusi-
form cells, containing numerous spin-
dle-shaped granules.

From the foregoing description of
the hair and its follicle it is clear that
in transverse sections it will present
different appearances, according to the

situation in which the section is made. A description of trans-
Terse sections in different regions of the hair is here unneces-
sary. We reproduce, however, above, a figure from Biesiadecki,
which will sufficiently explain this matter (Fig. 123).

A hair increases in length by the formation of new elements
in its root, and they, by their subsequent elongation and move-

PlO. 123. — Transverse section of
the hair beneath the neck of the hair-
follicle : a, external sheath of the hair-
follicle ; 6, transversely cut blood-ves-
sels ; c. Inner sheath of hair-follicle ;
< basement-membrane of hair-follicle;
«, cxtenwl root^sheath :/, cells of Ren-
te's layer ; g, cells of Huxley's layer ;
A, cuticnla ; I, hair-shaft.

THE SKIN. 293

ment upward, push the sliaf t of the hair and its cuticula before
them. The structure of an adult hair can be best studied in
the stiff, gray hairs of the beard. For the study of the origin
of the root-sheaths young hairs should be chosen. There are
still many points in regard to the structure of the skin and its
appendages which appear to be rather doubtful, owing to our
insufficient knowledge. The first development of the hair-fol-
licle takes place at the end of the third or beginning of the
fourth month, and it originates as a projection downward of
the cells of the rete mucosum. It is seen as a finger-shaped
collection of rete cells surrounded by the connective tissue of
the corium. The papilla is formed later. By the numerical
increase of round cells the follicle is enlarged, and the external
cells are pushed sideward, thus forming the external root-
sheath. The origin of the other parts of the hair has been
already described. The first hairs are always of the lanugo
kind — that is, they are fine hairs, with a very short hair-folli-
cle. In certain regions the hairs always remain fine ; in other
parts they give place to thicker ones. In the latter case a pro-
longation downward of the external root-sheath takes place.
This forms the hair-papilla. The papilla of the first hair atro-
phies, the hair falls out, and its place is occupied by a thick
hair. The permanent hair grows to a certain length, which
varies in different persons and in different parts of the body.
If a hair has reached its proper term of existence it falls out
and is replaced by a new hair, which grows from the old
papilla. A hair ceases to be produced when no new cells are
formed in the hair-root. The last-formed cells become con-
verted into the hair proper, and form a conical or knobbed ex-
tremity to the lower end of the hair-shaft.

The nails. — The nail is merely a modification of the epi-
dermis, and differs from the stratum corneum only in being
harder and firmer. It is a longish, four-sided, hard, elastic,
transparent, dense, flat body, situated in a fold of the skin on
the dorsal surface of the terminal phalanges of the fingers and
toes. It is slightly curved in its long diameter, the convex sur-
face being above and the concave below. Its posterior and two
lateral sides are connected with the other structures of the skin ;
the anterior side is free. The fold of skin in which the pos-
terior and two lateral surfaces are imbedded increases in depth
from before back ward, and at the posterior margin is continued

294

MANUAL OF HISTOLOGY.

forward for a short distance on the surface of the nail. This
fold of skin is called the nail fold, and the tissue upon which
the nail is seated is termed the bed of the nail. That part of
the nail imbedded in the flesh posteriorly is the root of the nail,
and the remainder its body. The flesh underlying the root—
the corium — is called the matrix, and that underlying the body
of the nail the bed of the nail proper. The matrix and bed of
the nail proper are separated by a more or less convex line, gen-
erally easily seen through the nail and known as the lunula.
The bed of the nail is composed of corium and rete Malpighii
tissue. There is no fat in its subcutaneous tissue. The rete
here dips down between the papillae of the corium as in other
parts of the skin. The papillae in the matrix project forward,
and are shorter and closer together than in the bed of the nail

FIG. 124. — Transverse section of the nail through the bed of the nail proper : a, nail : 6, loose cor-
neous layer beneath it : c, mucous layer : d, transversely divided nail ridces: e. nail-fold without papillae ;
/. the horny layer of the nail-fold which has pushed forward on the nail ; <j, papillae of the skin of the
finger.

proper. In this latter structure the papillae also project for-
ward (Fig. 124, d] and increase in length as the free margin of
the nail is approached. The rete Malpighii covers the papillae
of the nail, forming cones, which till the space between the
papillae. In the bed of the nail proper the transition from rete
cells to horny cells is very rapid, whilst in the matrix it is
gradual. Consequently, this portion of the nail is softer than
the other. It is from the matrix that the nail is formed, and
from the corneous cells of the body of the nail that the nail is
made thicker. The soft cells are directed forward and become
more horny as they advance. The under surface of the nail-
fold covering the posterior part of the nail is provided with
epidermis, which is continued forward a short distance on the
upper surface of the nail.

THE SKIN. 295

The tissue of the nail is nourished by blood from the bed of
the nail and from the nail-fold. Nails grow more rapidly in
children than in adults, and more rapidly in summer than in
winter. The rapidity of growth varies according to the person
and the particular nail. The rate of growth in individual nails
can be learned by observing the rate of progress toward the free
margin of the white spots seen on nails.

The nail begins to form in the third month of intra-uterine
life as a fold covered with a layer of embryonic epidermic cells.
In the fourth month a layer of new cells, which afterward be-
come the horny cells of ihe nail, appear between the rete Mal-
pighii and the embryonic epidermic corpuscles. At the fifth
month the epidermic covering disappears and the nail lies ex-
posed. Between the sixth and eighth months the nails are
somewhat firm, but do not quite extend to the ends of the
fingers. At the eighth month the nails are well developed and
extend to the extremities of the fingers.

For the microscopical study of the horny part of the nail,
sulphuric acid, or caustic soda, or potash must be employed to
soften the corpuscles. For the other structures of the nail no
special procedure is necessary.

BIBLIOGRAPHY.

WAGNER. Mullet's Archiv. 1852.

MEISSNER. Beitrage z. Anat. u. Phys. d. Haut. Leipzig, 1853.

OEIIL, E. Annali univ. di med. 1857.

KKAUSE. Die term. Korp. d. einf. Sens. Nerven. Hannover, 1860.

SCIIROEN. Contrib. alia anat. fi&iolog. e patholog. della cute umana. Torino, 1865.

AUFFHAMEII. Wurzburger Verhandlungen. Band I. 1809.

THOMSA. Arch. f. Dermat. 1873.

LOTT. Ueber den feineren ban u. die phys. Regeneration des Epithels. Leipzig,

1874.

THIN. Journal of Anat. and Phys. Vol. VIII. 1874.
REYNOLD. Ueber die Knaiteldrusen des Menschen. Virchow's Archiv. Bd. LXI.

1874.

UNNA, P. Archiv f. mikrosk. Anat XII. 1876.
FISCHER, E. Ibid.

RAVOGM. Med. Jahr. Wien. H. I. 1879.,
RANVIER. La France medicale. January, 1880.

CHAPTER XIX.

THE CENTRAL NERVOUS SYSTEM.
BY R W. AMIDON, M.D., NEW YOBK CITT.

THE spinal dura mater is a serous membrane. Its structure
from without inward is : first, loose connective tissue ; then dense
fibrous tissue ; lastly, a layer of lymph-vessels and endothe-
lium. If one tears, with forceps, a shred from the outer surface
of the dura mater, fresh or hardened, stains with luematoxylon,
teases, and examines in glycerine, there is seen a loose network
of connective- tissue bundles containing free and fixed connec-
tive-tissue cells, blood-vessels, minute nerves, and some fat-
cells. This layer is continuous with the loose adipose tissue
which normally surrounds the dura mater. The denser tissue
next in order may be treated in the same way, and perhaps a
few spindle-shaped connective-tissue cells and elastic fibres
may be isolated.

On transverse section, however (a very difficult thing to
make, by the way), the bulk of the membrane is seen to be a
dense mass, 0.5 — 1.0 mm. thick, composed of longitudinal and
horizontal connective-tissue bundles, interspersed here and
there with elastic fibres. In this layer blood-vessels and nerves
are very scanty and small.

Next, immerse a piece of dura mater, as fresh as possible,
in a one per cent, solution of nitrate of silver. Leave it for sev-
eral hours, and then expose it for a few minutes to the sunlight.
When a brown tint is developed on the inner surface, remove
it, wash it in distilled water, and strip off the internal surface
with forceps.

The shreds of tissue thus obtained show beautifully the
structure common to all serous membranes : first, a delicate en-
dothelial layer (see Fig. 125), consisting of flat, unequal, irreg-
ularly shaped cells, most of which are furnished with large,

THE CENTRAL NERVOUS SYSTEM.

297

FIG. 125. — Diagram representing the internal surface of the
dura mater treated with nitrate of silver. Shows endothelium
with nuclei and intercellular masses of protoplasm and a lymph-
channel, L.c., lined by delicate endothelial cells, which termi-
nates at 8, an opening called a sterna about which is an aggre-
gation of nuclei, x 300.

round nuclei ; here and there are seen stomata marked by an ag-
gregation of nuclei, which are all located at the edge of the cells
surrounding a stoma ; secondly, irregularly disposed lymph-
spaces and vessels. The lymph-spaces appear as irregular,
transparent patches lying just under the endothelium, and
the lymph-vessels are
seen as varicose chan-
nels, which begin by
a blind extremity, an-
astomose freely, re-
ceive tributaries, and,
finally, empty by a
constricted orifice
called a stoma. Their
walls are in places
thin, but more often
thick and irregular
from the aggregation
of masses of protoplasm along the sides. The capillary lymph-
atic radicles are lined by a very delicate endothelial layer,
which can only be demonstrated in completely successful sil-
ver preparations. Some are seen to contain lymph-corpuscles,
others are found empty.

The spinal arachnoid is also a serous membrane, much more
delicate, however, than the dura mater. Its extreme thinness
allows it to be examined in the fresh state or stained by car-
mine or hsematoxylon. It is seen to be essentially a large-
meshed connective-tissue network, containing many elastic
fibres. Good silver preparations demonstrate an endothelial
coat and a lymph system similar to, but more delicate than
that of the dura mater. It is doubtful whether blood-vessels
exist in the arachnoid in its normal state.

The spinal pia mater consists of a small amount of connec-
tive tissue, holding together a vascular plexus. It is firmly
adherent to the cord, dips into all its fissures, and is intimately
connected and continuous with the connective-tissue frame-
work of the cord. The pia mater is best studied by means of
fresh specimens stained in haematoxylon, as this demonstrates
beautifully the different coats of the small vessels.

The spinal fluid should be clear, and contain only a few
lymph-corpuscles ; but it usually, when examined post-mor-

298 MANUAL OF HISTOLOGY.

tern, contains some blood-corpuscles and swollen epithelial
cells.

General histology of the spinal cord. — The spinal cord is
composed of connective tissue, blood-vessels, nerve-structures,
and epithelium.

The connective-tissue framework or neuroglia of the cord
is constructed as follows : At tolerably regular intervals the
pia mater at the periphery of the cord sends off prolonga-
tions which form septa, dividing the white substance into a
large number of prisms (base outward). From each of these
septa smaller branches spring, forming a delicate network, or
stroma, which encloses the nerve-fibres. Generally one, but
sometimes two or more fibres are contained in the same mesh.

At the points of junction of these ultimate fibres are seen,
here and there, small branching cells, the so-called spider- or
neuroglia-cells. This fibrous structure reaches to the central
gray matter and penetrates it by very delicate processes, which
chiefly accompany the nerve-fibres.

Three large prolongations of pia mater are of constant oc-
currence, viz., the posterior median septum and a less complete
septum on either side, dividing the posterior column into two ;
the larger, anterior, or column of BurdacJi ; and the smaller,
posterior, or column of Goll. The connective-tissue elements
are best brought out by hsematoxylon.

The blood-vessels of the cord are derived froni its pia mater,
follow its prolongations, and are most numerous in the gray
matter, especially that of the anterior horns. In transverse
sections there will be seen a clear space about all the blood-
vessels. This is the perivascular space or lymph-channel, in
which all the blood-vessels are contained. During life these
sheaths probably serve a double purpose : an auxiliary nutri-
ent function by lymph-circulation ; and a means of accommo-
dating the ever-varying degrees of vascular distention. In
some diseases they become enormously dilated. They are all
connected with the space between the pia mater and the cord,
and an injection forced into this space will follow the blood-
vessels for long distances. These perivascular spaces are also
said to be lined with endothelium.

The vessels of the cord present no other peculiarities. Their
structure is best brought out by the use of a dilute htematox-
ylon solution, or by the slow carmine staining. The perivas-

THE CENTRAL NERVOUS SYSTEM. 299

cular canals may be more clearly demonstrated by forcing a
colored gelatine injection at any point under the spinal pia
mater — care being taken, if the cord is cut, to secure the ends
of the sections by ligatures.

Nerve- elements of the cord. — The consideration of the ner-
vous elements of the cord will now be taken up in a general
way, and the peculiarities of different regions explained later.

The white substance of the cord contains, besides the blood-
vessels and neuroglia already mentioned, myelinic nerve-fibres
of different sizes. These fibres pursue a vertical course, with
the exception of those forming the root-radicles and commis-
sures.

On examination with a low power, the white substance, in a
transverse section stained with carmine, seems to be a collec-
tion of minute rings, each with a red dot in the centre. More
highly magnified, the transverse section of a nerve-fibre appears
as a delicate, rather irregular circle, on the circumference of
which, in some cases, are seen nuclei resembling those of the
sheath of Schwann, but which are really nuclei of the neurog-
lia. Next comes a broad ring of colorless, transparent mate-
rial, the medullary or myelinic- sheath, which very often ex-
hibits concentric lamination. Lastly, usually in the centre, is
seen the solid axis-cylinder.

When these fibres pursue a more or less horizontal direc-
tion they give the appearance of broad, clear bands traversed
by longitudinal red fibres (axis-cylinders). The myelinic fibres
average about 5 p1 in diameter. Fibres, when isolated by
teasing, present the varicose aspect of myelinic nerve-fibres,
which lack the sheath of Schwann. To demonstrate this they
are best treated when in the fresh state by osmic acid (see p.
114), the result being a black myelinic sheath and brownish
axis-cylinder.

The gray matter is composed of nerve-cells, medullated and
non-medullated nerve-fibres, and an amorphous matrix. The
most striking elements are the cells of the anterior horns.
These, whether teased from specimens fresh or hardened in
chromic acid, or whether examined in sections, always present
the same general appearance. They are large, multipolar cells,
having a slightly granular, protoplasmic body, a large, oval

ft = micromillimetre = Tihro millimetre.

300

MANUAL OF HISTOLOGY.

nucleus, and a round nucleolus. These cells are polyhedral in
form, as is shown by the fact that sections made in all direc-
tions give them the same pyramidal or polygonal outline. In
nearly all the large cells there is in some part of the body an
aggregation of granules, which are often distinctly pigmented,
giving the appearance of a heap.

Striations of the body have been frequently described and
depicted (Schultze, Schmidt, etc.), and this appearance has
been attributed by some to plications of a very delicate invest-
ing membrane, by others to ex-
pansions of the ultimate nervous
fibrillae, of which the axis-cyl-
inder was thought to be com-
posed. The motor cells average
about 40 p. in diameter. The
cell -processes vary in number.
Most of them are bifurcating.
One, however, connected with
nearly every cell, can be fol-
lowed for a long distance with-
out dividing, and when the cell
is situated near the anterior
rootlets this process joins them
and acquires a myelinic sheath.
This is called the axis-cylinder process. The branching pro-
cesses are called the protoplasmic processes, and are supposed
by some to freely anastomose with those of other cells. This
anastomosis, if it exist at all, is very delicate, and difficult of
demonstration.

A certain number of the cells of the anterior horns, espe-
cially those located in the lateral region of the cornua, present
an elongated, fusiform aspect, and appear to have but two
processes. The nerve-cells in the posterior horns are of an
elongated oval or fusiform shape, their long diameter corre-
sponding in direction with that of the posterior horn. They are
very much smaller than the anterior cells, and less numerous.
Their average diameter is about 15 /*. They are seldom seen
to have processes.

The myelinic nerve-fibres of the gray matter are seen prin-
cipally in the anterior horns, and converging from the cell-
groups to form the anterior root-radicles. Here and there fibres

Fio. 126. — Diagram of a motor-cell from the
anterior horn of a human cord in the cervical
enlargement, x £00.

THE CENTRAL NERVOUS SYSTEM. 301

appear in transverse section, which, singly or in bundles, pur-
sue a longitudinal direction.

Amyelinic fibres are found everywhere in the gray matter
pursuing various courses. The gray commissure is composed
almost completely of amyelinic fibres connecting the lateral
gray masses.

Besides the above-described elements the gray substance
seems to have a structureless or slightly granular matrix, in
which the other elements are embedded. In the study of the
spinal gray matter osmic acid and carmine preparations are by
far the most useful, although much is to be learned by the ex-
amination of fresh specimens teased in serum. To study the
cells, cut out a piece from the anterior horn of a fresh cord
and tease in serum. A preliminary treatment with osmic acid
or ammoniacal carmine is sometimes advantageous.

The epithelium of tlie spinal cord lines the central canal.
The most internal layer is of the cylindrical, ciliated variety.
On account of the difficulty in obtaining fresh specimens the
cilia are never seen in the human cord, though they undoubt-
edly exist. The epithelial cells, as they do exist in the human
cord, have a square base, taper to a slender thread toward
the apex, which penetrates the layer of young, round epithe-
lial cells, and is lost in the granular central gray matter. The
cells of the second layer are round, granular, and thickly
crowded.

The subepil7ielial tissue, for some distance around the cen-
tral canal, consists of embryonal cells in a granular matrix.

The central canal1 has no constant shape, varies greatly in
size, and is often choked with desquamated epithelium. Its
position, as its name indicates, is in the middle of the gray
commissure, on a line passing between the anterior fissure and
posterior septum. The general features of the spinal cord hav-
ing been pointed out, the peculiarities of different regions will
now be shown.

Special study of the different portions of tlie cord. — The
cord will be studied from below upward. The mode of study
will mainly be by sections made after Clarke's method. The
cord, after slitting the dura mater with the scissors up the
front and back, is cut in segments 3 ctm. long, which adhere

1 Sometimes double. See Seguin: Am. Jour. Med. Sci., p. 427. 1872.

302 MANUAL OF HISTOLOGY.

to the undivided dura mater. Thus prepared it is suspended
in Miiller's fluid (see p. 15), or dilute chromic acid (see p.
14), until hardened. The segments are then embedded in
a microtome (see p. 16), and horizontal, transverse sections
made. These are washed in distilled water and stained with
carmine or hsematoxylon (see p. 23). A few minutes' immer-
sion in alcohol previous to this manipulation makes the tissues
take the coloring more quickly. After staining and washing,
dehydrate the sections with alcohol and absolute alcohol, make
transparent with oil of cloves, and mount in Canada balsam or
dammar varnish (see p. 23).

Hidden in the cauda equina is found the filum terminale,
which is the end of the cord. Sections near its end exhibit lit-
tle of the structure of the cord. At a point where it is 1.5 mm.
in diameter it presents the appearance of a peripheral nerve,
except that it has an opening — the central canal — in its centre.
Its transverse section shows a collection of large and small
myelinic nerve-fibres pursuing a vertical direction.

A little higher up, where the filum measures 2 mm. in diam-
eter, there is little difference, except that the central canal is
nearer the surface (anterior) and surrounded by a small amount
of gray matter. Now and then there are seen small, oval nerve-
cells in the region posterior and external to the central canal.
A little higher still, where the filum is 3 mm. in transverse
and 2 mm. in antero-posterior diameter, back ' of the central
canal on each side, where the future posterior horn is to be,
there is a small collection of spindle-shaped cells.

Sections from a region a little above this present an entirely
different picture. The gray substance is here much more devel-
oped and occupies the larger part of the section. It is divided
into a club-shaped anterior horn, containing a few large poly-
hedral cells, and a posterior horn which is rounded and formed
of peripherally directed nerve-fibres and oblong nerve-cells.
From this point up sections gradually become more circular
and develop more and more a resemblance to the structure of
the cord, until, at a point where the sections are about 3.5 mm.
in diameter, the anterior fissure and posterior septum become
well marked. The anterior horns contain few cells, and the
fibres emanating from them pursue a very oblique course down-
ward through the anterior columns.

From the lateral gray matter arise bundles of nerve-fibres

THE CENTRAL NERVOUS SYSTEM.

303

FIG. 127.— Three sections
of the fllum terminals : «, its
transformation into the coccy-
geal nerve ; b, section higher
up before the giving off of the
last sacral filaments ; <;, its
commencement.

which curve around the posterior horn, and, meeting similar
fibres from the posterior columns, together form the posterior
nerve-root. These two bundles form an arciform structure sur-
rounding the round extremity of the posterior horn. (See Fig.
127.) The gray commissure occupies one-third the diameter of
the cord. The central canal is large, slit-
like, and antero-posterior in direction. To
summarize then, there seems to be in the
filum terminale, especially its lower por-
tion, a preponderance of the posterior or
sensory part of the cord.

About two centimetres from the end of
the cord nearly the same picture is pre-
sented. The transverse section is circular
and about 6 mm. in diameter. Many large
nerve-cells appear at the outer side of
the anterior cornua, mostly at their junc-
tion with the posterior horns. Fibres from
this cell-group, instead of running a direct course, curve
backward and inward (see Fig. 127), then run forward and
emerge from the anterior horns. Many oval cells appear in
the posterior horns, which now reach the surface of the sec-
tion, and the posterior roots begin to show their origin from

the posterior columns and horns.

In the lumbar enlargement trans-
verse sections have a circular shape.
(See Fig. 128.) The white substance
here predominates, and has but one
peculiarity, which will be noticed in
greater or less prominence through-
out the remainder of the cord. At
the bottom of the anterior fissure is a
broad band of white substance called
the white commissure. This is formed
of myelinic nerve-fibres, which pursue
a course from the base of the anterior
horn of one side, forward, across the
median line and downward to join the
anterior column of the opposite side at a lower level. (See
Fig. 129.) The anterior horns in the lumbar region are large
and square, as are also the cells contained in it. The gray

Pro. 128. — Three diagrams show-
ing the relations of gray and white
matter in different regions of the cord:
n. lumbar enlargement ; 6. mid-dorsal
region ; c, cervical enlargement.

304

MANUAL OF HISTOLOGY.

commissure is narrow, and the central canal has its long diam-
eter placed transversely to the cord.

Transverse sections in the dorsal region are circular and
8 mm. in diameter. The white commissure is thin, otherwise
the same structure as in the lumbar region is observed. The
anterior horns are narrow and sparsely filled with rather small
multipolar cells. No continuous tracts of nerve-fibres can be
traced through the anterior columns, as their course is so oblique
(downward) as to give almost a transverse section of the bun-
dles. The posterior horns, just behind the gray commissure,
are swollen out, and contain a number of large nerve-cells —
some multipolar, some oval. They approach the type of the
cells in the posterior horns. This collection of cells is called the
column of Clarke.

Transverse sections in the cervical enlargement measure
about 14 mm. The antero-posterior diameter is about 11 mm.
The white commissure in this region presents about the same
characteristics as in the lumbar region. The anterior horns are

fan-shaped ; the anterior roots
curve forward, outward, and
downward. The central canal is
triangular. The posterior horns
are slender, and contain a few
small nerve-cells. The posterior
roots are also more intimately
connected with the posterior

horns than lower down.

Pio. 129. — Diagram of transverse section of
the cord in the upper cervical region, showing
coarse connective-tissue reticulum in left half
of diagram, commencing decnssation of the
lateral columns across the base of the anterior
horn into the opposite anterior column, taking
the place of the anterior commissure lower
down, and the root of the spinal accessory, 11 :
A.R. = anterior root ; I'.R. = posterior root.
In thin figure and in others small crosses must
be understood as nerve-cells.

In tlie upper cervical region
the gray matter assumes more
the shape of the dorsal gray
matter. In the lateral region, at
the junction of the anterior and
posterior horns, longitudinal bun-
dles of myelinic nerve-fibres begin to appear. These bundles
curve over (see Fig. 129), and pass rather obliquely upward
and outward through the lateral columns, emerging nearer the
posterior than the anterior horns. They are joined by fibres
curving back from the cells of the anterior horns, and also
emanating from the central gray matter. In this structure is
seen the first appearance of the spinal portion of the spinal
accessory root-fibres. The longitudinal bundles mentioned

THE CENTRAL NERVOUS SYSTEM.

305

evidently come from cells of the anterior horns lower down.
Some of the fibres, passing back from the anterior horns to join
the root, are seen to arise directly from the motor cells.

In taking leave of the cord, the introduction of a diagram '
showing its regional anatomy, looked at from a physiological
standpoint, is deemed ad-
vantageous. It will enable p
the microscopist to properly
record localized lesions.

In studying the spinal
cord by means of horizon-
tal transverse sections, it is
of the utmost importance,
particularly in pathological
cases, to know which is the
right or left side, and whe-
ther one is looking at the
upper or under surface of a
section. Of so much impor-
tance is this knowledge,
that some means must be
employed to acquire it.

One of the best means is a method devised by Dr. E. C.
Seguin, and published in the translator's note appended to
Scjmltze's article on the spinal cord, in the American translation
of Strieker's " Histology," p. 647. He there recommends, be-
fore placing the segment of the cord in the microtome, that a
slight longitudinal incision be made in the right lateral column.
By this means all the sections have a nick in the right lateral
column, and can easily be placed. This method, however, has
many drawbacks. One is that it is a process easily forgotten
during the manipulations. Another more serious drawback is
the fact that, make the incision slight as you can, the resulting
nick often causes extensive fissures and crumbling of the lateral
column or whole section, especially in pathological or over-
hardened specimens.

The requirements by the new method are two : 1st, the
sections must be nearly horizontal ; and 2d, they must be suf-

FIG. 130. — Diagram of transverse section of the
spinal cord : A, anterior median fissure ; P, posterior
median septum ; 1, columns of Goll ; 2, columns of
Burdach ; 3, direct cerebellar column ; 4. crossed pyra-
midal column ; 5. lateral column ; (i, anterior funda-
mental column ; 7, direct pyramidal column ; 8, pos-
terior gray horns ; 9, anterior gray horns ; stippled
part, gray matter ; shaded part, sesthesodic system ;
unshaded part, kinesodic system.

1 Dr. E. C. Seguin : Lectures on Localization, in N. Y. Medical Record, April 27,
1878, p. 323.

20

306

MANUAL OF HISTOLOGY.

ficiently well stained and transparent to demonstrate the con-
stituent parts of myelinic nerve-fibres. The mode of determi-
nation depends entirely on the fact that the anterior roots
pursue an obliquely descending course through the anterior
columns, and for this reason horizontal sections cut the ante-
rior rootlets obliquely. (See Fig. 131.)

What is the natural inference to draw from this fact ? It is
this : let the reader look at the upper surface of a transverse
section of the spinal cord and bring the anterior roots into the
field ; that is, let him look down the anterior column. He
readily perceives that the central ends of the anterior root-
fibres are nearer his eye than the peripheral ends. He sees
that while the central ends are at the focus, the peripheral
ends are beyond the focus, and he needs to bring the eye nearer
to define them. This nearing the focus also gives the fibre-
bundle an apparent peripheral motion, while increasing the
focal distance causes an apparent central motion.

The application of this method to a chance section is easy.

Suppose we examine the anterior
columns of a section and find by
focussing that the central ends of
the anterior root-fibres are farther
from the eye than the peripheral
ends. We will immediately know
we are looking up 'the cord or^ at
the under surface of the section.
Now, all it is necessary to do is
to turn over the section, either in
your mind or on the slide, and put
the anterior horns forward. The
section is then in position.

In sections of the cord where
the anterior roots do not show, the
posterior roots may be used in a similar way, as they, too, pur-
sue a slightly descending course. Their use is not so easy, as
the fibres are short and pursue a slightly wavy course. In
sections or fragments of sections, where neither of these struc-
tures avail, a study of the course of the fibres in the anterior
white commissure will lead to detection. These fibres pursue
a course downward and across the median line, from the base of
one anterior horn into the anterior column of the opposite side.

Fio. 131. — Diagram of vertical section
of hnman cord through the anterior ami
posterior colnmns and the anterior horns.
It is intended to demonstrate how a trans-
verse, horizontal section. 8, cuts the an-
terior nerve-roots obliquely. (From Ar-
clUvet of Medicine, August], 1879, p. 70.)

THE MEDULLA OBLONGATA.

307

In sections of the upper cervical region the spinal accessory
roots may be made use of, remembering, however, that they
pursue a course obliquely upward through the lateral columns.

The application of these rules to the medulla will be pointed
out later on.

NOTE. — To demonstrate the obliquity of the anterior rootlets, find, by a trans-
verse section, the exact direction of the anterior rootlets, and then make longi-
tudinal sections through the anterior column and horn on this line.

THE MEDULLA OBLONGATA.

In the upper part of the cervical region changes take place
in the arrangement of the elements of the cord transforming it
into the medulla oblongata. The changes are as follows : be-
fore the external signs
of decussation ap-
pear, it is seen that
the fibres of the later-
al columns change
their vertical course //
and bend f orward and
inward. This fact is
demonstrated by the
oblique sections of
bundles and fibres. A
little higher these
bundles and fibres
can be traced across
the gray matter be-
hind the anterior horn
into the opposite an-
terior column, which is to become by this addition the anterior
pyramid. The decussating fibres take the place of the ante-
rior commissure lower down, and the fibres pass upward and
forward across the median line. The fibres of the anterior
columns do not decussate at all, but give way to and mingle
with the fibres from the lateral columns.

The shape and structure of the anterior horns are about the
same as lower down. The posterior horn expands suddenly at

Fro. 182. — Diagram of the medulla, perns, etc., natural size, to
show the direction of sections for displaying the different nuclei
and roots : 11', line of section to show the early decussation of thp
lateral columns and spinal accessory tract; 11. line of section to
show the spinal accessory tract and decuBsation of the pyramids ;
11 & 12, region of the spinal accessory and hypoglosqai ; 10, pnen-
mogastric ; 9, glosso-pharyngeal ; 8, acoustic ; 6 & 7. abdticens
and facial ; 5, trigeminns ; 4, patheticus ; 3, motor oculi ; c. g>.,
corpora quadngemina ; c. c., crus cerebri.

308

MANUAL OF HISTOLOGY.

its peripheral extremity into a bulbous termination (see Fig.
133), from which the posterior root emerges. The central gray
matter between the two horns is traversed and intersected by
the decussating fibres from the lateral columns. Numerous pro-
longations from this gray matter spread out into the lateral
columns, presenting a coarse reticulum, called iheformatio

FIG. 133.— Diagram of transverse section of
human medulla below external decussation of
pyramids, showing bulbous posterior horns:
F R, formatio reticulnriR ; 11, spinal accessory
root and decnssation of the lateral columns.

Flo. 134. — Diagram. Decnssation of the pyra-
mids, shows decussation of the lateral columns,
the swelling of the posterior horns, the shrink-
age of the anterior horns, the spinal accessory
root 11, and a partial decussation of the posterior
columns behind the central canal.

reticularis. The gray commissure is very broad, the central
canal having its long diameter directed antero-posteriorly.

In sections at the decussation of the pyramids proper, i.e.,
where they are seen to decussate externally, a slightly different
picture is presented. The lateral columns have nearly disap-
peared, having now almost all entered into the decussation,
which is here very broad (see Fig. 134), and presents a peculiar
zigzag appearance from the interweaving of bundles of fibres
from the opposite lateral columns. These fibres, after curving
around 'the anterior columns for a short distance, seem to dis-
appear by assuming a vertical direction. The club-shaped ex-
tremities of the posterior horns remain, while the rest is pushed
back into the posterior columns, and contains many large cells.

The anterior horns are also displaced backward, pushed
back by the anterior columns increased in size by the addition
of the lateral columns. Hence, the anterior roots have a longer
path through the anterior columns and approach the type of
the hypoglossal nerve-roots seen a little higher up. (See Fig.
135.) The spinal accessory nerve curves out and back from the
lateral gray matter where a group of cells is situated.

THE MEDULLA OBLONGATA.

309

Let us next take up a section involving the lower end of
the olivary body. We have the following view presented.
The section is slightly cordiform. (See Fig. 135.) The decussa-
ting fibres at the base of what remains of the anterior fissure,
which has all along become shallower, now forms the com-
mencement of the rapke, a structure which extends all through
the rest of the medulla and pons, separating the two motor
tracts. The union of the lateral and anterior columns now
nearly complete, forms the anterior
pyramids. The fibres here have a
general vertical direction, except
that a broad band which emerges
from the decussation at the bottom
of the anterior fissure, curves around
the margin of the anterior pyramid,
and then, sometimes in the sub-
stance, sometimes at the surface of
the medulla, almost completely sur-
rounds it, the bundle becoming lon-
gitudinal on the posterior surface.
These bear the name of the arciform
fibres. The rest of the white matter
is so cut up as to render it hardly
divisible into regions. The central canal, which is very long
antero-posteriorly, has almost coalesced with the gradually
deepening posterior furrow soon to become the fourth ventricle.

The gray matter originally in the cord is now collected
about the central canal. Anterior and external to the central
canal there is a small group of multipolar cells. This is the
remnant of the anterior horns, which have been continually
crowded back by the accumulation of fibres in the anterior
pyramids. These cells in every respect are similar to those in
the anterior horns. Their processes give origin to fibres which
course forward in two or three bundles through the white
matter of the anterior pyramids, and emerge at about the
junction of the anterior pyramids and the lateral white mass.

A little farther back in the gray matter, behind the central
canal, is a small group of nerve-cells the remains of the spinal
accessory nucleus, from which a few fibres run in a straight
course outward and slightly backward, through the lateral
white matter. Additional collections of gray matter now begin

FIG. 135. — One half of section at lower
end of the olives : 11, upper spinal acces-
sory root ; 12, lower hypoglossal roots.

310 MANUAL OF HISTOLOGY.

to appear. In the posterior region is a large tract (see Fig. 135)
containing- scattered groups of many small cells evidently con-
nected with the arciform fibres. This is probably a part of
the lower origin of the pneumogastric. A little in front and
external to this is a small group of larger nerve-cells which
help to form the lower sensory origin of the fifth nerve. Still
farther forward in the lateral region is a large collection of
multipolar nerve-cells. Although this group is traversed in
many directions by fibres, single and in bundles, still it seems
to give rise to fibres which run back and upward, evidently to
curve upon themselves and join the peripheral fibres of the
spinal accessory root. (See Figs. 135 and 137.)

Farther forward still there is a collection of small cells
arranged in a wavy line (see Fig. 135), the commencement of the
olivary nucleus. Through this the roots of the hypoglossus
all pass. Some seem to be lost in it, others appear to arise
from it, but this is probably due to the arrangement of roots
often seen to curve into the nucleus and then out again. As
this is the first appearance of the olivary body, it will be well
here to describe it.

THE OLIVARY BODY.

The olivary nuclei are situated in the medulla, under the
oval projections on its anterior surface called the olivary bodies.
The nucleus consists of a strip of gray matter arranged in gen-
eral like a piece of fluting folded on itself, so as to form almost
an ellipse. From the concavities of the fold on either side pro-
ceed bundles of fibres, the external ones joining the formatio
reticularis, the internal ones passing into the raphe. Their
connection with the hypoglossal roots is probably not 'im-
portant. The intimate structure of the olivary fold is that of a
dense gray matrix holding numerous small polyhedral cells
having delicate protoplasmic processes.

Let us now go a trifle higher (see Fig. 137), and observe that
in sections the central canal, which has all along been elongat-
ing and receding backward, now opens into the apex of the
fourth ventricle. There is now, therefore, quite a deep notch in
the posterior part of the section, covered with the same cylin-
drical epithelium which lined the central canal. On each side,

THE OLIVARY BODY.

311

and in front of the bottom of the fourth ventricle, lies a large
group of multipolar cells, the liypoglossal nucleus, from which
bundles of fibres course forward through the olivary body,
which is here much enlarged and more complex than in the
last section. On the inner side of the liypoglossal roots in
the olivary region is an elongated mass of gray matter con-
taining small cells, called the parolwary nucleus. There is
an oval group of fusiform cells at, behind, and external to
the hypoglossal nucleus, from which indistinct and broken
bands of fibres pass outward to emerge from the lateral re-
gion of the medulla. This constitutes the upper spinal acces-
sory nucleus and root. Behind this nucleus, forming the

FIG. 136. — Diajjram showing structure of
one fold of the olivary nucleus : C, centripe-
tal fibres; P, peripheral fibres, x 04.

FIG. 137. — One-half transverse section of
the human medulla at the point of fusion of
the central canal and the posterior fissure to
form the fourth ventricle : 11, spinal acces-
sory root ; 12, hypoglossal root ; B, raphe.

eminence on each side of the fourth ventricle, is a large mass
of gray matter containing a great number of small nerve-cells,
which also seems to be rather indistinctly connected with
the spinal accessory root. External to this nucleus is a con-
tinuation of the collection of large cells seen in the section
lower down, the lower sensory nucleus of the fifth. In front
of the spinal accessory root is seen a group of multipolar cells
not so large as in preceding sections. The peripheral circular
fibres in this region are confined to the anterior and external
aspect of the medulla, and are still seen to be in connection
witli the raphe by the arcuate fibres which traverse obliquely
the intervening nervous tissue.

From this point to the middle of the olives, sections differ

312

MANUAL OF HISTOLOGY.

FIG. 138. — One-half transverse section of the
human medulla through the middle of the olives :
4, fourth ventricle ; 10, pneumogastric root ; 12,
hypoglossal root.

little, except that in this space the root-fibres of the spinal
accessory seldom appear, although figured by most writers.
The region formerly occupied by the spinal accessory nucleus
contains a group of small cells which form part of the pneu-
mogastric nucleus. The fibres
between this nucleus and the
point of exit of the pneumo-
gastric root run so obliquely
upward, that no direct connec-
tion between them can be traced.
It is in sections at the mid-
dle of the olives that the pneu-
mogastric begins to appear dis-
tinctly. Most of its fibres seem
to be connected with a small
group of cells situated in the
gray matter, at the junction of
the funiculi graciles and the
restiform body. The gray mat-
ter of the restiform bodies is filled with small cells and con-
tains many fibres having a peripheral direction posterior to the
pneumogastric root — the beginning of the auditory nucleus
and root. The olivary body here reaches its highest develop-
ment and greatest dimensions.

Behind the olivary body is a small group' of cells, from
which scattered fibres pass backward and
inward toward the pneumogastric nucle-
us. But most of them are lost by as-
suming a longitudinal direction. This is
probably the lower facial nucleus, to be
described farther on. The arciform fibres
are chiefly confined to the surface of the
anterior pyramids and the olivary bod-
ies. The fibres of the raphe pursue, in
great part, an antero-posterior direction.
Sections through the medulla at the
upper part of the olivary bodies differ
little from the former sections. But a
small segment of the olivary bodies is present, and only a few
of the hypoglossal roots remain. (See Fig. 139.) External to the
remains of the hypoglossal nucleus is a nucleus of small cells

FlO. 189. — One • half trans-
verse section of the human me-
dulla through the upper part of
the olives bringing the glosso-
pharyngeal tract (9.) and the
lower part of the acoustic nucleus
(80 into view.

THE OLIVARY BODY.

313

giving origin to a bundle of fibres, which pass out laterally just
as does the pneumogastric lower down. This is the glosso-
pharyngeal nerve and root. Farther still from the median
line, in the floor of the fourth ventricle, is seen a group of
small cells, the commencement of the acoustic nucleus. Scat-
tered nerve-cells arising here pursue an obliquely forward and
outward direction, making the lower margin of the auditory
root.

Transverse sections of the medulla just at the edge of the
pons bring the acoustic region into view ; the upper olivary
body is here visible. Behind this are scattered a few large cells,
from which fibres pass backward to form higher the facial root.

Fio. 140.— One-half transverse section of
the human medulla just below the edge of tho
pons, showing acoustic nucleus and roots which
enclose the inferior cerebellar peduncle I. 0.
P. : I, internal root ; E, external root ; M, up-
per olivary nucleus ; Lf , lower facial nucleus.
3 diains.

FIG. 141. — Diagram of a transverse
•action just above the edge of the pona,
having the obliquity given it in Fig. 182,
6 & 7 : 6, abducens root ; 7, facial root.
For other explanations, see text.

Occupying the floor of the fourth ventricle is a large mass of
gray matter, from which the acoustic arises. This gray matter
contains many small round and some multipolar cells. The
nerve has two roots, one internal, the other external. (See
Fig. 140.) The former arises from fibres emerging from the
raphe near the fourth ventricle and from the gray matter just
external to it, and pursues a course downward and forward
through the lateral white matter. This root, at its point of
emergence, is joined by fibres from the posterior root curving
Jaround the surface of the medulla, like, if not identical with,
the arciform fibres. The external root has also one origin from
the gray matter near the median line, and curving outward on

314 MANUAL OF HISTOLOGY.

the floor of the fourth ventricle (forming the UnecB transfer see)
it receives additions from the lateral gray mass, and emerges
from the medulla a little behind the internal root, which, how-
ever, it soon joins.

It is seen that the two roots embrace a column of white
matter, which is the inferior peduncle oftJie cerebellum. (See
Fig. 140.) In sections just above the edge of the pons, having
the oblique direction given in Fig. 132, the region of the sixth
and seventh nerves comes into view. The view presented here
is different from that in the medulla below. In place of the
narrow band of arciform fibres which covered the anterior re-
gion of the medulla, nearly the anterior half of this section is
composed of transverse, arciform fibres. Imbedded in this
structure is a longitudinal bundle of white matter, the contin-
uation of the anterior pyramid. The posterior half of the
section contains the structures under consideration.

From a group of multipolar cells at the floor of the fourth
ventricle, some distance from the median line, several bands of
fibres pass forward and slightly outward, in a somewhat sim-
ilar way to the hypoglossal roots lower down. This is the
nucleus and root of the abducens nerve.

Internal to and behind the abducens nucleus, in almost
all sections, is seen an oval bundle of what at first sight ap-
pears to be longitudinal nerve-
fibres. Closer examination, how-
ever, shows the fibres to be not
straight but looped, and in suc-
cessful sections the following ap-
pearances are presented. Behind
the anterior pyramids and out-
side of the abducens root is seen

Fio. 142.-Diagr.n, of co*n* of fibres in a Sr°UP °f mnltipolar Cells OC-

KtaKS±SS£&9Si£i cupying the same location as the

or coil where the fibres change their direction rrrrmr* Pillar! flio Ir»-W7av fn fill Tin
B, the root proper of the facial nerve. 61OUP Called Ult LOW6J

cleus, lower down. Arising from

this, and pursuing a course backward and inward, are numer-
ous fibres ; these reach the oval bundle before mentioned, enter
it, curl upon themselves (see Fig. 142), and emerge at about
their point of entrance. The fibres mentioned as appearing
longitudinal undoubtedly come from the lower facial nucleus,
and curl upon themselves*like the rest.

THE OLIVAEY BODT. 315

Some fibres (commissural) join the root from the raphe, and
others seem to arise from the abducens nucleus, though this is
denied by many authors. The fibres which seem to arise from
the abducens nucleus are probably fibres from the anterior
nucleus of the facial, which do not traverse the coil ("genu,"
as it is called), but enter the root directly.

The facial root thus formed goes directly outward at first
toward the external angle of the fourth ventricle, then turns
sharply forward to emerge at the junction of the pons and
medulla external to the sixth root. Many authors, first of
whom was Clarke, describe an inferior nucleus of the facial
nerve, supposing it to innervate the lips and mouth, basing
their assertions as much on the seat of lesion in labio-glosso-
pharyngeal paralysis as on anatomical evidence. There can
be but little doubt as to its existence, and probably it corre-
sponds to the group of cells seen in Figs. 137 and 138.

Sections of the pons above this point soon begin to show
traces of the fifth nerve. (See
Fig. 143.) The picture we get
in transverse sections at the
emergence of the fifth root is,
in front, two large bundles of
longitudinal nerve-fibres sur-
rounded by the arciform fibres
and separated by the raphe ;
behind, the gray matter of the
fourth ventricle, which here is
pentagonal in shape and is
covered in by the base of the , IIG; i4s.-DiaKrwn showing origin and course

•f of the tngeminus nerve.

cerebellum, the inferior vermi-
form process. Emerging from the gray matter in front of the
external corner of the ventricle, and also joined by fibres from
above and below, is a large bundle of fibres which pursue a
diagonal course outward and forward, to emerge from the side
of the pons. This is the sensory root of the fifth nerve. Inter-
nal to this root, just after its formation, is seen in successful
sections a large group of multipolar cells sending off fibres, the
motor root, which join the sensory root and emerge with it. A
collection of large, oval, pigmented cells here underlie the exte-
rior part of the fourth ventricle and form the locus cceruleus.
It seems to have an indistinct connection with the trigeminal

316

MANUAL OF HISTOLOGY.

FIG. 144. — Diagram showing ori-
gin of the third and fourth nerves
from the gray matter about the aque-
duct of Sylvius: c. a, cms cerebri;
8, third nerve ; 4, fourth nerve.

sensory root, and Meynert makes it one of its points of
origin.

The sensory root is reinforced by fibres from a group of
large oval cells external to the fourth ventricle and by the so-
called descending branch (Meynert), which is seen in trans-
verse section in the same location com-
ing from regions still higher up. Some
fibres also come from the raphe and
arcuate fibres, and others from the low-
er sensory origin of the fifth, which
occupies a lateral position in all the
sections up from the spinal accessory
region of the medulla.

Higher in the pons, where the ante-
rior motor tracts or pyramids, before
mentioned, begin to separate into the
crura cerebri, the fourth nerves are
seen. They are supposed to arise from
a nucleus at the floor of the fourth ven-
tricle lower down, curve around the outer wall of the ventricle,
decussate in the median line in the valve of Vieussens, and
pass from the pons behind the tubercula quadrigemina. From
this point they curve forward around the crura, on the outer
side of which they appear at the base of the brain.

At about this point and a little higher are seen bundles of
fibres emerging from the gray matter containing small cells,
in front of the fourth ventricle, diverging and pursuing an
arcuate course through the crura, to converge again and emerge
from the inner side of each crus. (See Fig. 144.) This consti-
tutes the nucleus of origin, the course and point of emergence
of the third nerve — a view hard to get unless just the right
obliquity is given to the section.

Imbedded in the crus, in the region through which the third
nerve passes, is a collection of pigmented cells forming the locus
niger. Higher the crura separate and enter their respective
hemispheres. Their further course is better shown by a trans-
verse vertical section of the hemispheres at the large part of
the thalamus opticus. (See Fig. 145.)

Here we see a great part of the substance of the crus flat-
tened in form passing upward, between the optic thalamus and
a gray mass called the nucleus lenticularis, forming what is

THE CEREBELLUM.

317

denominated the internal capsule. The posterior third of the
internal capsule is distributed to the posterior part of the
hemisphere, and when destroyed produces loss of sensibility
on the opposite side of the body. The anterior two-thirds of
the internal capsule is distributed to the middle or motor re-
gion of the hemisphere, and its destruction causes a paralysis

EC NL

JC TO

Pro. 145. — Modified from Charcot's diagram to show position, relation, and distribution of the inter-
nal capsule ax seen in a vertical transverse section of the brain on a level with the greatest development
of TO, thalamns options ; 1C, location of the Internal capsule : NL, nucleus lenticularis : EC, external
capsule ; D, claustrum ; NC ; nucleus candatus ; MRC, motor regions of cortex cerebri ; 1, fibres repre-
senting the radiation of the internal capsule vertically to the motor region of the cortex. — From "Lec-
tures on Localization," by Dr. E. C. Seguin : New York Medical Record, p. 142, August 24, 1878.

of the opposite side of the body. The fibres expanding from
the internal capsule, joined by those emanating from the gan-
glia at the base and the corpus callosum, form a fan-shaped
expansion of white fibres called the corona radiata.

THE CEREBELLUM.

The white centre of the cerebellum, formed from the ex-
pansion of the peduncular tracts, incloses a collection of gray
substance, the corpus dentatum. This body, visible in all
sections, bears some resemblance to the olivary body in the
medulla, on account of its irregular, dentated outline. Its
greater consistence causes it to stand out in a section from the
surrounding tissue. In intimate structure this body consists

318

MANUAL OF HISTOLOGY.

of a collection of small fusiform and polyhedral cells with
minute processes, imbedded in a basis- substance much more
dense than the surrounding white matter. The body is made
to appear striated in a peripheral direction by bundles of
fibres and blood-vessels pursuing a parallel course.

The surface of the cerebellum, deeply gashed by sulci and
their subdivisions, presents, on section, its well-known com-
pound, arborescent appearance. This arrangement of the gray
matter causes the greatest possible surface to come in con-
tact with the blood-current furnished by the pia mater, and
hence secures the greatest nutrition of the elements of the
cortex. The gray matter of the cortex is easily divisible into
an external or granular layer, a middle or cellular layer, and
an internal or nuclear layer. The latter consists of a vast
number of small granular cells about the size of white blood-
corpuscles, which take staining fluids with great avidity. The
middle stratum is a clear space in which there is a single layer
of large corpuscles, called the cells of Purkinje, 10 to 40 /*. in

diameter. They
are scattered at
some distance
from each other,
and present pe-
culiarities pos-
sessed by no other
cells in the body.
The cells are of
large size, vary-
ing in form from,
fusiform to flask-

Purkin'e 4<$'~DiagrRm °f the cerebeUar cort6^ showing the large cells of shaped, aCCOrd-

ing to the plane of

the section. Their central side is round, and in most cases has
no processes. Often the usual rounded contour of the cell-
body is broken by an angle, seemingly the remains of a broken
process. Here and there a large non-branching axis-cylinder
process is seen emerging from the base of a cell and pursuing
a course parallel to the cortex. That these basal processes
exist in all cases, and ultimately acquire a myelinic sheath,
there is no doubt. (See Fig. 146.)

From the peripheral side large arborescent processes spring,

THE CEREBRAL GANGLIA. 319

which pursue quite a direct course through the external or
granular layer and disappear when near the periphery. The
primary processes, one or two in number, have a tendency to
spring from the cell-body at an obtuse angle, and give off at
almost right angles to themselves the straight peripheral pro-
cesses already mentioned. The nuclei of these cells are oval
and coarsely granular ; the nucleolus is round and small.

The cortex proper consists of a granular matrix vertically
striated by the cell-processes and parallel blood-vessels. There
is also a moderate sprinkling of small round cells and nuclei
similar to those in the third layer. The cortex is very vascular.

THE CEREBRAL GANGLIA.

As examples of these structures the optic thalami and cor-
pora striata may be taken. They are collections of gray matter
through which part of the fibres, emanating from the crura to
help form the corona radiata, pass.

In the corpus striatum these fibres pass through in bundles
visible to the naked eye, which gives to this body its striated
appearance. These bundles radiate toward the periphery of
the body, thus leaving ever increasing spaces between them.
These spaces at the base of the body, at the point of entrance
of the bundles from the crura, are narrow, filled with nerve-
fibres running in horizontal, vertical, and diagonal directions,
seemingly commissural in nature, and multipolar cells few in
number, large, and resembling somewhat cells of the anterior
horns of the spinal cord, whose processes mingle with the fibres
mentioned. Nearer the periphery of the organ, where the bun-
dles of fibres are more widely separated, the intervening mass of
fibres and cells abruptly changes to a finely granular gray ma-
trix, holding in its substance numerous small blood-vessels
and small nerve-cells, mostly round — some, however, triangular
in shape, similar to those of the second layer of the cere-
bral cortex. They have large nuclei and many delicate pro-
cesses.

The optic thalami consist of a mixture of gray matter and
fibres, not, however, so regularly arranged as in the corpus
striatum. The gray matter contains a few oval cells having
many delicate processes.

The cerebral ventricles. — Continuous with the central canal

320

MANUAL OF HISTOLOGY.

Fio. 147. — Diagram illustrating tba
structure of the ependyma of the cere-
bral ventricles.

of the cord, and doubtless like it in function, the cerebral ven-
tricles resemble it in their structure. They are lined through-
out with a structure called the ependyma. This consists first
of a finely granular layer covering all the nervous matter
bounding the ventricles. Besides the minute granules, this

layer contains a few small nuclei here
and there, but no fibres. On its free
surface rests a single layer of cylin-
drical epithelium. The cells of this
layer have square free ends, while
they are anchored by one or more
delicate processes which emerge from
the attached end and pierce the sub-
jacent granular-matrix. These epi-
thelia in the fresh state undoubtedly have cilia. This layer
of epithelium is apt to be arranged in folds, giving a section
of the ependyma a wavy appearance.

The chor old plexus of the lateral ventricles has for its basis
an artery which enters the descending horn of the lateral ven-
tricle from the base of the brain. This artery gives off along
its course short arterial trunks which repeatedly subdivide, and
each ultimate arteriole terminates in a convoluted capillary
loop, resembling the Malpighian tuft of the kidney. Some
of the twigs seem to end in a cse-
cal extremity ; but it is doubtful
whether they do, the preparations
giving this appearance being prob-
ably artificial. The peculiarity of
the choroid plexus is that all the
vessels composing it, large and
small, are covered by a layer of
polyhedral epithelial cells, each
having one, sometimes two large
nuclei. This presents a beautiful
example of the so-called tesselated
epithelium, each cell being sepa-
rated from its neighbor by a transparent intercellular sub-
stance. This epithelial covering causes the tufts of the choroid
plexus to resemble, in a degree, the villi of the chorion. The
best plan in studying the choroid plexus is to use hsema-
toxylon, or alcoholic specimens slightly teased.

Fio. 148. — Diagram showing structure
of the choroid plexus of the lateral ven-
tricles.

THE CEREBRAL GANGLIA. 321

The cerebral dura mater differs from the spinal in the fact
that, its outer surface serving as periosteum, it lacks the layer
of loose connective tissue present in the spinal dura mater.
Its bulk consists of two layers of dense fibrous tissue running
in opposite directions. The inner serous surface is coated with
endothelium and lymphatics. The outer or periosteal surface
is the most vascular. The cerebral differs from the spinal arach-
noid only in being perhaps a little more closely attached to
the pia mater. The pia mater of the brain is extremely vascu-
lar, and shows more beautifully than the spinal membrane the
system of perivascular spaces.

The cerebral cortex. — The cerebral cortex is a thin sheet of
gray matter spread on the outer surface of the hemispheres.
The outer surface of the hemispheres is grooved by furrows
(sulci) less deep in proportion to their size, and less regular
than those of the cerebellum. The convolutions produced by
these sulci, although seemingly very irregular, still have a cer-
tain symmetry in different brains by which they can be classi-
fied and named. A definite knowledge of these facts is neces-
sary for an understanding of the current literature on the
subject and of properly recording cases.

The fetal hemisphere at an early date is smooth. Furrows
soon begin to appear, the first and most important of which is
the fissure of Sylvius, extending upward and backward, from
about the anterior third of the base of the brain, and ihefis-
sure of Rolando, running from near the posterior extremity of
the fissure of Sylvius upward to the superior longitudinal fis-
sure. One after another the other fissures appear, till in the
adult brain they seem innumerable. Even here, however, there
is a certain constant arrangement of fissures and convolutions
on which a nomenclature may be based.

The original fissures of Sylvius and Rolando remain. From
the anterior inferior part of the frontal lobe three furrows run
obliquely upward and backward toward the two fissures just
named, dividing the frontal region into the three frontal con-
volutions, while a convolution in front of the fissure of Rolando
receives the name of the ascending frontal or anterior central
convolution. A similar convolution behind the fissure is called
the ascending parietal or posterior central convolution. The
parietal region- is irregularly divided from above downward,
as is also the temporo-sphenoidal and occipital region. The

21

322

MANUAL OF HISTOLOGY.

base of the brain is also divided into a series of basal frontal,
temporal and occipital convolutions. By far the most impor-
tant region of the cortex-, according to our present knowledge,
is that along the fissures of Sylvius and Rolando, the so-called
motor tract of the hemispheres. The exact physiological func-
tions of the anterior frontal, the occipital, temporal, and basal

Fio. 149.— Modified from Ferrier ; letters and figures the same : 8, fissure of Sylvius ; c, fissure of
Ronaldo ; po, parieto-occipital fissure ; A, ascending frontal gyrus ; B, ascending parietal gyrus ; F2,
third frontal gyrus; Pa', gyrus angularis ; circle I., seat of lesions which (on the left) cause aphasia;
circle II., seat of lesions which convulse or paralyze the upper extremity of the opposite Bide; dotted
circle III., seat of lesions which probably convulse or paralyze the face on the* opposite side; dotted oval
IV., seat of lesions which probably convulse or paralyze'the lower extremity of the opposite side. These
•districts receive their blood-supply chiefly from the middle cerebral artery. — From Lectures on Localiza-
tion by Dr. E. 0. Seguin : N. Y. Medical Record, October 19, 1878, p. 301.

regions of the hemispheres, is not known, inference, however,
making them the seat of general and special sense, vaso-motor,
psychic centres, etc., etc.

The middle or f ronto-parietal region, however, is the proven
seat of motor centres for the face, limbs, and body, and the
faculty of articulate language. The centre for speech occu-
pies the region at the base of the third frontal convolution
and the island of Reil on the left side, a similar location on
the right side being occupied by a centre for articulatory
movements. A little higher on the ascending frontal and
parietal convolutions is an area having control over the move-
ments of the tongue and face. Still higher is found a larger
space, the centre for the arm of the opposite side. A larger
space at the junction of the fissure of Rolando and the su-

THE CEREBRAL GANGLIA.

323

perior longitudinal fissure, including a tract 'on the inner
aspect of the hemisphere, called the paracentral lobule, is the
centre for movements of both extremities, especially the lower.
On account of the anatomical variability of the convolutions
in different brains, these centres must be allowed some lati-
tude, and should not be made so small and exactly located
as they are by some authors. Their location has been pretty
definitely determined, however, by experimentation on animals,
and lesions in man, such as trauma-
tisms, neoplasms, abscesses, hemor-
rhages, atrophy following amputa-
tions, retarded development, etc.

Possessing such important proper-
ties we should naturally expect the
cerebral cortex to be a very complex
structure, and so it is.

Minute structure of the cortex. —
In order to get a satisfactory view of
the elements of the cortex, great care
has to be exercised in making sections.
It is not enough to make a section
exactly perpendicular to the cortex.
The plane of the section must exactly
coincide with the direction of the fibres
of the corona radiata as they enter the
convolution. This can be rather easily
accomplished by paying close atten-
tion to the arrangement of the white
and gray matter in the piece from which the sections are to
be made. Cuts with any obliquity will give erroneous impres-
sions as to the exact shape and structure, especially of the
cellular elements of the cortex. The cortex cerebri is generally
divided into five layers, but it is easily divisible into three only.

The outer layer, lying immediately under the pia mater, is
more transparent than the rest, and is composed of a fine net-
work of neuroglia containing many quite large openings, giving
it a spongy appearance. It also contains a few large, round
nuclei, and a small number of triangular nerve-cells.

The second layer, thicker than the first, consists of a gray
basis-substance, dense and granular, holding an immense num-
ber of small, triangular and conical cells, their apex being di-

Pio. 150. — Diagram showing -the
elements and relation of parts in the
cerebral cortex. (See text.)

324 MANUAL OF HISTOLOGY.

rected toward the periphery and often drawn out into a slen-
der axis-cylinder process, while from their base several delicate
processes are given off. These cells all have large nuclei and
nucleoli. Here and there are seen larger conical cells, which
will be described with the next layer. The characteristic fea-
ture of the second layer, however, is the presence of a great
number of small, round cells and free nuclei similar to those in
the third layer of the cerebellar cortex.

In the third layer the matrix is still more dense, and con-
tains, besides a few small triangular cells, round cells, and free
nuclei, a large number of large conical corpuscles, the so-called
"giant cells" of the cortex, the distinguishing feature of this
layer. When isolated from their surroundings these cells ap-
pear like cones which taper gradually from a broad base to a
very slender apex, which, when it attains the size of an axis-
cylinder, can be traced for a long distance without showing a
division. This undoubtedly terminates in a myelinic nerve-
fibre. The base of the cell is not square, but crenated and
notched by the giving off of numerous delicate basal processes
which are lost in the granular matrix.

The cells all have nuclei and nucleoli, most of which are
round, but some of which seem also to have a triangular shape
corresponding to the cell-body. The cells average 25 p.. in
diameter. A great difference is made in the apparent shape of
the cell by obliquity of the section. If the line of section is
moderately oblique, it shortens the cells ; if still more oblique,
it makes them very short and blunt ; while if the section is at
right angles to their axis, all the cells appear round and of
various sizes. In the deepest parts of this layer the giant-cells
gradually disappear, and the gray matter of the cortex merges
into the white matter. In the two inner layers of the cortex
there are seen many fibres and bundles of fibres having a ver-
tical direction, which, with the blood-vessels (the largest of
which being perpendicular to the surface), give the cortex a
somewhat striated appearance.

We see, then, that the only difference between the second
and third layers of the cortex is the greater number of small
cells in the second and the greater number of large cells in the
third, while the division of the third layer into three, as is
accepted by most authors, seems purely arbitrary, there being
a gradual gradation into the white substance.

BIBLIOGRAPHY. 325

Some writers l lay much stress on the difference of structure
of the cortex in different regions of the hemisphere. It is true
that, in the non-excitable or sensory regions, the cortex is thin-
ner and perhaps less highly organized ; but here are met the
same elements as form the cortex in the motor region (centre,
for the arm, for instance). (See Fig. 150.) Even the giant-cells
are found less numerously than in the motor regions. Another
fact demands attention, that is, that the structure of the cortex
is the same at the bottom of a fissure as on the surface of a
convolution, and for this reason lesions of the sides and bottom
of fissures should receive as much attention as those of the
surface of the convolutions, implicating, as they do, equally im-
portant structures.

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JACUSOWITSCH, N. Further Researches into, etc. Breslau, 1858.
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LUTS, J. Recherches sur le systeme nerveux cerebro-spinal ; sa structure, ses fonc-

tions et ses maladies. Paris, 1865.
His, W. Zum Lymphsystem. Leipzig, 1865.
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JOLLY, F. Ueber die Ganglienzellen des Ruckenmarks. Miinchen, 1866.
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ERB, W. H. Diseases of the Spinal Cord and Medulla Oblongata (Anatomical Intro-
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Medical Record. 1878.

FORT, J. A. Lemons sur les centres nerveux. Paris, 1878.

HUGUENIN, G. Anatomie des centres nerveux. Traduit par Dr. Th. Keller.
Paris, 1879.

BRAIN.

BERLIN, RUDOLF. Beitrag zur Structurlehre des Grosshirnwindungen. Erlangen,

1858.

KUPKPER, GUST. De cornus ammonia textura. Dorpat, 1859.
CLARKE, J. L. Researches on the Intimate Structure of the Brain, Human and

Comparative. 1857 and 1867.
ARNDT, RUDOLF. Studien iiber die Architektonik der Grosshirnrinde des Men-

schen. Bonn, 1867-68.
JENSEN, JULIUS. Die Furchen und Windungen der menschlichen Grosshirn Hemis-

pharen. Berlin, 1870.
MEYNERT, T. The Brain of Mammals. Strieker's Histology. Am. edition. New

York, 1872.

HITZIQ, EDWARD. Untersuchungen fiber das Gehirn. Berlin, 1874.
CllARCOT, J. M. Lefons sur les localisations dans les maladies du cerveau, Paris,

1876.

BENEDIKT, MORIZ. Anatomische Studien an Verbrecher-Gehirnen. Wien, 1879.
BOYER, H. DE. Etudes topographiques sur les lesions corticales des hemispheres

c6rebranx. Paris, 1879.

FERRIER, DAVID. The Localization of Cerebral Disease. New York, 1879.
STRICKER und UNGER. Untersuchungen iiber den Bau der Grosshirnrinde. Wiener

Anzeiger, 1879.
BEVAN LEWIS and CLARKE, H. The Cortical Lamination of the Motor Area of

the Brain. Proceedings of the Royal Society, Vol. XXVII. 1879.

CEREBELLUM.

HESS, N. De cerebelli glornm textura. Dorpat, 1858.

SCHULTZE, F. E. Ueber den feineren Bau der Rinde des kleinen Gehimes. Ros-
tock, 1863.

CENTRAL NERVOUS SYSTEM.

DEITERS, OTTO. Untersuchungen iiber Gehirn und Riickenmark des Menschen und
der Saugethiere. Braunschweig, 1865.

BIBLIOGRAPHY. 327

DEECKE, THEODORE. Perivascular Spaces in the Nervous System. American Jour-
nal of Insanity. January, 1874.

WALDEYER. Beitrage zur Kenntniss dor Lymphbahnen dea Centralnervensyst.
Arch. f. raikr. Anat. 1879.

KESTEVEN, \V. H. The Structure and Functions of the Olivary Bodies. St. Bar-
tholomew's Hospital Reports. 1879.

SEE, MARC. Sur la communication des cavites ventriculaires de 1'ence'phale avec les
espaces sous-arachnoiidiens. Revue mensuelle. 1879.

BKOCA, P. Localisations cerebrates. Revue d'anthropoL 1879.

CHAPTER XX.

THE EYE.

BY C. H. WILLIAMS, M.D., BOSTON, MASS.

THE eyelids are very complicated structures. Their exter-
nal coating is formed of skin, which is modified for the special
purpose it has to serve in this situation. Beneath the skin is a
loose sheet of connective tissue ; still more internally is the lit-
tle orbicular is palpebrarum muscle ; behind this again is loose
connective tissue, which shades off gradually into the tarsus.
This latter is not formed of cartilage, as was formerly sup-
posed, but of dense fibrous tissue. The conjunctiva tarsi
lines the inner surface of the tarsus. The skin of the lids
exhibits the usual layers of horny, serrated, and cylindrical
epithelium. At the upper portions the papillae are sparsely
developed and short, but they gradually increase in size and
number as they approach the free edges. A peculiarity of this
skin are the pigment-cells, which are scattered throughout the
cutis. They 'are more abundant in brunettes than in blondes.

At the confronting margins of the lids are found the cilia
or eyelashes, which resemble the ordinary larger hairs in their
formation and mode of growth ; they are placed in two or
three rows, are well supplied with pigment, and have a definite
direction given to them by the deep follicles from which they
grow.

Ordinary sweat-glands are quite numerous, especially in the
upper portions of the lid ; at the lower border we occasionally
find them in a modified form, opening into sebaceous follicles
near or just behind the cilia ; they have a long and wide ori-
fice, and the tubules are filled with fine granular matter, con-
taining occasional roundish masses resembling particles of
albumen.

Beneath the cutis is a loose connective-tissue layer through

THE EYE. 329

which numerous blood-vessels and nerves pass ; behind this,
and covering the whole extent of the lid, are bundles of the
orbicularis palpebrarum ; some small fasciculi of this muscle
are also found at the lower and inner angle of the lid, enclosing
the openings of the Meibomian glands. These bundles, known
as the musculus ciliaris-Miolani, have fibres which are among
the smallest of the striped variety of muscular tissue.

Behind this layer is a thin sheet of loose connective tissue,
which merges without any sharp boundary line into the tar-
sus ; this latter body forms a leaf-shaped plate about twenty
millimetres in length by one millimetre in thickness, and is
composed of very dense connective-tissue fibres separated only
by minute lymph-spaces ; it has few blood-vessels or nerves,
and serves to give the requisite stiffness to the looser tissues of
the lid.

The Meibomian glands are imbedded in the tarsus. Their
excretory ducts, which are directed at right angles to the pal-
pebral margin, have their openings on the surface of the lid
near its posterior angle. They are lined with epithelium, which
at the external orifice is similar to that in the superficial parts
of the skin ; more internally it is serrated, while in the acini of
the gland it has a cuboidal shape. These glands have a straight
central tube, around which the acini are clustered, and into
which they discharge the sebum, a material composed of epi-
thelial cells that have undergone fatty degeneration. This
oleaginous substance serves to moisten the edges of the lid and
to prevent the overflow of tears.

Above the Meibomian glands, and in part imbedded in the
tarsus, are the acinous glands, which have their openings on
the surface of the conjunctiva fornicis. Above these glands
the smooth muscular fibres of the little palpebralis muscle of
Mutter are inserted, through a tendon, into the upper part of
the tarsus ; the fibres of this muscle are quite large and have
peculiar irregular cells with pigmented nuclei scattered
throughout them.

To prepare sections from the lids they should be pinned flat
on a piece of cork and then immersed in Miiller's fluid1 for
eight days. After being washed in water they are placed in
absolute alcohol until sufficiently hard ; or they may be hard-

1 See chapter on General Methods.

330 MANUAL OF HISTOLOGY.

ened by placing in the ordinary £ per cent, solution of chloride
of gold. This last method shows very clearly the nerves of
the lid and conjunctiva, which take a deep violet or mauve
color. For rapid work the lids may be hardened in a saturated
solution of picric acid. They may then be stained with picro-
carmine or hsematoxylon, and mounted in glycerine or balsam.
(See chapter on General Methods.)

The caruncula lacTirymalis is a small, rounded mass of
skin ; it is placed between the lids at their inner angle, and
contains hairs, vessels, and glands, such as are found else-
where in the cutis. Its office is to prevent the overflow of tears.

The conjunctiva. — Just behind the tarsus, and separated
from it by a thin layer of fibrillated connective tissue, is the
conjunctiva, which, after lining the inner surface of the lid,
passes backward as a loose connecting fold (fornix) to the
sclera, over which it is reflected forward as far as the margin
of the cornea. The conjunctiva consists of an external or
epithelial layer and a tunica propria or proper investing mem-
brane. There is also a subconjunctival layer.

The lower portion of the conjunctiva, where it takes its
origin from the margin of the lid, is quite smooth ; but near
the upper edge of the tarsus it becomes more or less infiltrated
with lymph- cells, and is thrown into numerous folds, which
have sometimes been mistaken for glands. The. epithelial ele-
ments of this part vary much in shape ; in general there are
two layers: a superficial one, composed of cylindrical bodies
which are a continuation of the superficial strata of the skin,
and a deeper one of small, round cells, representing the changed
cylindrical elements of the Malpighian layer or rete mucosum.

The tunica propria consists of fine connective- tissue fibres,
in which a few elastic fibrillse are interspersed. The subcon-
junctival layer resting immediately upon the tarsus is very
thin. That part of the conjunctiva forming the fornix has an
abundant subconjunctival tissue, which is composed of loose
elastic fibres and vessels ; the epithelial layers are also thicker
here, and small racemose glands, supposed to secrete mucus,
are also found there.

On the conjunctiva covering the bulb the epithelium con-
tains here and there the large mucus-cells corresponding to
the goblet-cells of the intestines. It gradually begins to change
its character and passes over into the variety which is seen in

THE EYE. 331

the cornea, and, in fact, is continuous with it. The tunica
propria has an abundant supply of blood-vessels, and is loosely
connected with the sclera by fibres, which become more numer-
ous and firm in the vicinity of the corneal margin.

The nerves of the conjunctiva may be seen by cutting small
pieces of fresh conjunctiva from a pig or calf and examining
them in aqueous humor, or in a 1 per cent, aqueous solution of
common salt — care being taken to support the cover-glass at
the sides, in order to avoid pressure. The nerve-fibres can then
be seen passing under the epithelium ; they can be distin-
guished with certainty by their annular constrictions (anneaux
constricteurs) ; after penetrating a short distance, however,
they lose their medullary sheath and form open networks
under the epithelium ; a few fibres find their way toward the
surface between the epithelial cells.

The gold method is of special use in exposing the finer
nerve-branches. The question of the manner in which the
nerves ultimately end is still a point in dispute.

The lymph-spaces of the conjunctiva are quite numerous,
especially near the corneal border ; here they are narrow, and
finally pass forward to unite with the lymph-spaces of the cor-
nea, from which they can be injected by means of a solution
of alkanet-root in turpentine.'

The normal conjunctiva does not have any true papillae, but
on the tarsal portion the surface often has small papilliform
projections covered with epithelium.

The cornea. — This tunic is covered with stratified epithe-
lium (a), comprising layers of flat, serrated, and cylindrical
cells. Directly beneath these is the anterior limiting or Bow-
man's membrane (b) ; this is a clear, homogeneous stratum,
which differs from the substantia propria of the cornea only in
containing no lymph-spaces or cells. It can be divided up
into the same tine fibres as the cornea itself, and its inner bor-
der has no distinct limit, the fibres passing directly into the
corneal tissue ; when this layer has been destroyed, as by a
perforating ulcer or wound, it is not regenerated.

The substantia propria of the cornea (5, c) is made up of
lamellae, like the leaves of a book ; these lamellae, which at
first appear homogeneous, can be separated into fine fibres, just

1 See chapter on General Methods.

332

MANUAL OF HISTOLOGY.

like other connective-tissue membranes, by dissolving out the
cementing substance in a 10 per cent, solution of common salt.
With the exception of thefibrce arcuatce, which curve for-
ward through several strata in the anterior portions of the
cornea, the fibres pursue the same direction as the layers ; but,
although most of the fibres run parallel to the surface of the
cornea, yet they may have a different direction in each layer,

f-tt

FIG. 151.— Meridional section through the cornea of the human adult, from an eye hardened in Mul-
er's fluid. The section was colored with carmine, and made transparent by the oil of cloves.

so that when viewed from above the fibres will appear to cross
one another. This explains the formation of the stellate fig-
ures which are sometimes observed after the injection of fatty
substances into the cornea, or by the infiltration of bacteria
between the fibrils.

In the intertibrillar material are found the lymph-canals
and spaces, which contain the fixed corneal corpuscles (Fig.
152). These spaces are stellate and broad when seen from above,
but thin and spindle-shaped on side view ; they have numer-
ous branches and branchlets given off from them at right
angles (lymphatic channels) (Fig. 162, A). The spaces and
branches usually lie in the plane of the lamellae, anastomose
freely with one another, and are filled with the corneal corpus-
cles and lymph (Fig. 162, B).

THE EYE.

333

In life these fixed bodies nearly fill the lymph-spaces and
conform to their size and shape ; they are flat corpuscles, usu-
ally nucleated, and have short, sharp-pointed processes, which
pass out into the minute lymph-canals. In the lymph-spaces
of the cornea are also found, even in normal conditions, a few
migratory cells, resembling white blood-corpuscles ; they are
very numerous when the cornea has been irritated, and can
be seen in a frog's cornea, which
has been kept five to fifteen
minutes in serum or aqueous
humor in a moist chamber, and
examined without pressure on
a warm slide.

Beneath the substantia pro-
pria of the cornea we find the
posterior limiting layer, or
Descemet's membrane (cT) (Fig.
151). This is transparent, ap-
parently homogeneous, rolls up
when cut, is intimately connect-
ed with the posterior fibres of
the cornea proper, and is lined
on its inner surface with endo-
thelium (e). It contains no cel-
lular bodies, but, like the anterior limiting layer, can be sepa-
rated into fibrillae, and appears to represent a concentration of
the corneal fibres rather than a separate structure.

The endothelium is a single layer of flat cells lining the
anterior chamber. Blood-vessels are found only in the normal
cornea at the periphery, where they form a fine network con-
necting with the conjunct! val and scleral vessels.

The 'nerves enter the cornea at the posterior part of the
periphery ; they soon lose their neurilemma and medullary
sheath, and pass forward obliquely, as small axis-cylinders,
toward the epithelial layer ; here they divide up into branch-
lets, often having a ganglionic enlargement at the point of divi-
sion. Under the epithelium these delicate fibres form a net-
work which sends some very minute filaments upward between
the epithelial cells. Their further course is unknown.

To separate the cornea into its constituent fibres, small pieces
should be soaked for twenty-four hours in a concentrated pi-

FIG. 152.— Lymph spaces and canals, A ; fixed
corneal cell, partly filling these spaces, B. After
Waldeyer.

334 MANUAL OF HISTOLOGY.

eric acid solution ; they can then be washed in water and easily
picked to pieces. In order to see the arrangement of the nbrillse
in the different layers, the cornea of a rabbit should be pricked
with a needle in several places ; then some highly infectious
fluid, as the exudation in puerperal peritonitis, is to be brushed
over the surface, and in a few days an infiltration will have
taken place throughout the interfibrillar substance. We shall
then see the lines of pus-cells crossing one another in different
directions, and sometimes collections of micrococci forming
stellate figures.

A very delicate preparation of the fixed corneal cells may
be made by removing a fresh cornea, and then immersing it
from three to six hours in aqueous humor, in a moist chamber.
In examining it take care, as before mentioned, to avoid any
pressure upon the cover-glass.

It is easier, however, to demonstrate the cells and lymph-
spaces by staining with silver or gold. To do this the nictitat-
ing membrane of a live frog should be cat off or held to one
side by an elevator ; the exposed cornea is then placed near the
mouth of a test-tube, in which some water has been raised
to the boiling point ; when the epithelium begins to appear
opaque it should be carefully wiped off with a fine cloth ; a
| per cent, aqueous solution of nitrate of silver is then applied ;
when the cornea has become thoroughly white tyy this method,
it is to be removed, washed in a weak solution of common salt,
placed in distilled water, and exposed to the light until it be-
comes brown. It should then be cut at the edges and mounted
in glycerine. In ten or fifteen minutes it. will be transparent
and ready for examination. Instead of removing the epithe-
lium by steam, a solution of silver nitrate (| per cent.) may be
used, the lids being held out of the way until the epithelium
appears whitish ; this outer layer is then removed, and the
same process repeated as before. The substantia propria as-
sumes a brown color, and the corpuscles appear as lighter spaces
in it. The nuclei may be exposed by hsematoxylon.

The best preparations, both for the lymph-spaces and the
nerves, are made with chloride of gold. A fresh cornea, pref-
erably one from a live pigeon, is removed immediately after
decapitation and immersed for five minutes in lemon -juice,
then washed in distilled water, placed for fifteen minutes in- a
1 per cent, solution of chloride of gold, again washed, and this

THE EYE. 335

time soaked for twenty-four hours (well protected from the
light) in a 2 per cent, solution of formic acid. After another
washing in distilled water the cornea should be cut in two and
placed in glycerine ; one portion can then be separated into
thin layers, by tearing with fine forceps or needles.

Examine in glycerine for the corneal corpuscles, nerves,
and lymph-spaces, which latter appear dark on a light blue
or red background ; or the piece may be imbedded in wax or
some such material, and sections made parallel to the surface
of the cornea. The remaining half of the specimen is to be
imbedded or held in liver or pith. Transverse sections may
then be made. These will exhibit on lucky sections the fine
plexuses of nerve-filaments under the epithelium, with occa-
sional fibres passing up between the individual corpuscles.
The different layers of the cornea will be well shown, also the
narrow corneal cells (as seen on side view), together with the
remains of the endothelial layer on the inner surface.

The peripheral portions of the cornea are particularly inter-
esting. We have here the transitions from cornea to conjunc-
tiva and sclera, the origin of the ciliary muscle, the ligament
of the iris, and the numerous vessels of the part.

The epithelium of the cornea (a) forms a gradual transition
into the epithelium of the conjunctiva, but the anterior limit-
ing membrane (Bowman's) becomes thinner as it approaches
the edge of the cornea, until finally it merges with the fibres
of the anterior corneal layers into the tunica propria of the
conjunctiva.

No sharp boundary line has been demonstrated between
the cornea and the sclera. Under the microscope the fibres
appear to have no distinct limit ; the lymph-spaces also of the
cornea are continued directly into the sclera, and the scleral
and corneal fixed corpuscles are much the same.

The posterior limiting membrane (DescemeV s) (c), like the
anterior, becomes gradually thinner and loses itself in a small
bundle of scleral fibres which surround the edge of the mem-
brane and form the anterior support to the ligamentum pec-
tinatum iridis.

The endothelium (Fig. 153 <?,) passes uninterruptedly over
this ligament (ef) and is reflected forward over the anterior sur-
face of the iris (e") to the edge of the pupil.

In the angle between the iris and cornea, forming buttresses,

336 MANUAL OF HISTOLOGY.

as it were, to hold the iris in position, is the ligament of the
iris (d), composed of loose connective tissue with an abundant
open mesh work, enclosing spaces (Fontantfs spaces), (/), which,
on the one hand, connect with the anterior chamber by small
openings lined with endothelium, and on the other with the
lymph^spaces of the cornea and sclera, as may be shown by
injecting a solution of aniline blue into the anterior chamber.

At the inner part of the .sclera, close to its junction with the
cornea and the ligament, is the canal of Schlemm (a, fl'), a ring-
shaped passage, oval on section. It is lined with a single layer
of endothelium, varies in size in different specimens, often ap-
pearing as if divided into two parts, and, according to Wal-
deyer, probably connects with the anterior chamber and also
with the scleral veins.

Through this passage and Montana's spaces the fluid of the
anterior chamber is supposed to escape from the globe, and it
is worthy of note that in glaucoma, with increased intra-ocular
tension, we find the iris attached to the periphery of the cor-

THE EYE. 337

nea over a circular space which would entirely cover these
probable channels of exit.

Preparations of these parts can be made from eyes which
have been placed in Muller's fluid while quite fresh and al-
lowed to remain in it three to four weeks, the fluid being re-
newed from time to time. Hsematoxylon is well adapted for
coloring them, and they may be preserved in glycerine.

The solera. — In the solera we find the same minute struc-
tures as in the cornea, i.e., bundles of fibres, cementing sub-
stance, lymph-spaces, and fixed corpuscles. The fibres, how-
ever, are not laminated, as in the cornea, but run in various
directions, weaving a very dense tissue, so that the lymph-
canals have a correspondingly tortuous course.

Chemically there is a difference between the two, as the
sclera is found to yield on boiling a true connective-tissue
gelatine ; the cornea, on the other hand, a substance resem-
bling chondrine. We find also in the sclera, near the foramen
for the optic nerve, a few pigment-cells.

The sclera is covered by the conjunctiva from the corneal
border to the insertion of the recti muscles, and the fibres of
the subconjunctival tissue pass directly into it. From the en-
trance of the optic nerve to these muscular insertions, and even
passing up between them, the scleral portions of Tenon's cap-
sule form the covering, which consists of delicate filaments of
connective tissue passing directly into the sclera itself. On the
inner surface the sclera is covered with a large-celled endothe-
lium lining the perichoroidal space. At the round opening
for the entrance of the optic nerve, the outer fibres of the optic
nerve sheath pass directly into the outer scleral layers ; the
inner portions of the sheath partly mingle with the inner
layers of the sclera, and partly, after the addition of some true
scleral fibres, form the lamina cribrosa, a fine, sieve-like net-
work of fibrous tissue, which stretches across the opening in
the sclera on a level with its inner surface. This lamina can
be easily shown in specimens where the delicate nerve-fibres
which pass through its openings have been macerated out.

The sclera is perforated in the equatorial region by the
trunks of the vena vorticosce ; they are accompanied by the
lymph-vessels which form the connection between the pericho-
roidal and Tenon's lymph-spaces. The direction of the canal
through which they pass is so oblique that it is supposed to be

22

338

MANUAL OF HISTOLOGY.

easily contracted in diameter by any increase in intra-ocular
pressure. •

The arteries of the sclera, with their thick adventitial coats,
the peculiar sheaths of the veins and capillaries, as also the
nerves, are best studied in hematoxylon preparations. A solu-
tion of silver nitrate (a quarter to one per cent.) will expose
the endothelial cells, while sections of the tissue may be
made from specimens preserved in alcohol or Miiller' s fluid.

The tunica vasculosa, consisting
of the choroid, ciliary body, and
iris, forms one continuous mem-
brane through which the principal
blood-supply of the eye is carried.
The choroid. — This tunic lines
>cAthe sclera from the entrance of the
optic nerve to the junction of sclera
and cornea, and is united to it at
those points ; over the remaining
portion there is a loose connection
formed by scattered fibres and the
numerous vessels and nerves which
pass through the sclera to the cho-
roid. The meshes of the open
network between the layers of
the choroid and the sclera form
lymph-sacs — the perichoroidal
spaces — which connect with the sac
enclosed in Tenon's capsule, and
this in turn unites with the su-
pra-vaginal space surrounding the
sheath of the optic nerve. The
choroid consists of several layers,
with limits not distinctly marked.
The lamina suprachoroidea (Fig. 154, sc) lies next the
sclera, and consists of fine elastic and connective-tissue fibres,
holding in their meshes pigmented and transparent cells:
the first are stellate, often with projecting arms by which
several are joined together ; the latter resemble lymph-cor-
puscles.

The layer of large vessels is traversed by branching arteries
and veins ; between them are numerous pigmented corpuscles,

Fio. 15-1 — Sclera, * ; choroid, cA ; ret-
ina, >•; perichoroidal space, /xA; lamina
Bnprachoroidea, »c ; lamina chorio-capilla-
ri», ex; ; lamina vitrea, c ; layer of pigment-
celU between cboroid and retina, p. After
Merkel.

THE EYE. 339

while the whole is held together by the firm connective- tissue
network which extends throughout the entire choroid.

The lamina clwrio-capillaris (cc) consists of a network of
line vessels interspersed with pigment, and extends over the
whole inner portion of the choroid.

The vitreous layer («) is very closely connected with the
lamina chorio-capillaris ; though it appears homogeneous,
fibres may be detected in it after long maceration in a ten per
cent, solution of common salt. Where this layer covers the cil-
ia^ processes the surface is no longer smooth, but has fine,
elevated ridges upon it ; here the membrane also is thicker,
and is more easily affected by reagents.

The dense lamina of hexagonal pigment-cells between the
choroid and retina has sometimes been classed with the former,
although it belongs more properly to the retina.

The long and short posterior, and the anterior ciliary arte-
ries, furnish the numerous blood-vessels which constitute the
great mass of the choroid.

The short posterior ciliary arteries, four to six in number,
give off some twenty branches which penetrate the sclera,
pursuing a straight course near where the optic nerve enters ;
then, continuing their course in a tortuous manner, they divide
into fine networks which supply the greater part of the lamina
chorio-capillaris. About the entrance of the optic nerve they
also form a network of fine vessels, and even send occasional
branches to anastomose with vessels from the sheath and cen-
tre of the optic nerve.

The two long ciliary arteries penetrate the sclera in a very
oblique course, a little anteriorly to those last mentioned, and
in the horizontal meridian ; they pass forward in the outer
lamina of the choroid without branching until they reach the
ciliary muscle ; here they divide, and penetrating the muscle,
form near the periphery of the iris a circle (circulus arteriosus
iridis major) by uniting with the artery of the opposite side.

The anterior ciliary arteries, eight to ten in number, arising
from muscular branches of the ophthalmic artery, penetrate
the sclera near the insertion of the recti tendons ; they also
unite with the circle just described, which forms the principal
distributing point for the vessels of the iris and ciliary body.
From this circle also are sent back a few small branches to unite
with the choroidal capillaries, and there is formed the sole con-

340 MANUAL OF HISTOLOGY.

nection between the short posterior or choroidal arteries pro-
per and those which supply the circulus arteriosus. A small
amount of the blood which returns from the capillaries of the
choroid, ciliary body and iris finds its exit from the eyeball
through the veins accompanying the anterior and posterior
ciliary arteries, but by far the larger part is collected by the
large veins in the outer layers of the choroid (venae vorticosse),
converging so as to form four or six great trunks, which perfo-
rate the sclera obliquely in the equatorial region, and empty
into the ophthalmic vein.

The long and short ciliary nerves supply the tunica vascu-
losa with fibres from the third and fifth pair and the sympa-
thetic. The long nerves, two or three in number, are branches
of the nasal division of the ophthalmic nerve ; the short, ten to
fifteen in number, arise from the ciliary ganglion. These nerves
penetrate the sclera near the optic nerve, and then, passing for-
ward on the outer portion of the choroid, form, in the ciliary
muscle, a fine plexus with ganglionic corpuscles at the nodal
points of the meshes ; from this plexus fibres are distributed
to the cornea and iris.

At the junction of the anterior and middle thirds of the
eyeball the choroid undergoes a change, the membrane be-
comes thinner, the capillaries turn back toward the veins, only
a few vessels continuing forward in a straight course.

In this region the retina also undergoes a change and loses
all its nervous elements, the connective tissue supporting fibres
alone being continued forward under the name of the pars cili-
aris retina. The very narrow zone between the points where
these changes occur and the irregular line formed by the begin-
ning of the ciliary processes is called the orliculus ciliaris,
and the line of origin of these processes the ora serrata.

The ciliary body.— Crossing the orbiculus, the choroid is
Been raised in radial folds, some seventy in number, which in-
crease in size until they reach the thickness of a millimetre.
This increase is caused by the development of smooth muscular
fibres in addition to the usual constituents of the choroid.

These fibres arise just behind the canal of Schlemm, from
the sclera and cornea ; passing backward, they together form

ring, which on section appears as a right-angled triangle,
with the base turned toward the anterior chamber, and the hy-
pothenuse toward the vitreous (Fig. 155).

THE EYE.

341

This triangle consists largely of the fibres of the ciliary mus-
cle, which are divided into meridional fibres, or those which
occupy the side next the sclera, and radial fibres, which pass

PIG. 155.— Section through the ciliary region of a hypermetroplc eye. Ivanot

from the point of origin to the hypothenuse ; the circular fibres
of Mailer's muscle lie next to the base of the triangle, and are
concentrically arranged.

In highly myopic eyes the meridional and radial fibres

Pro. 156.— Section through the ciliary region of a myopic eye. Ivanof .

are strongly developed (Fig. 156), while the circular fibres are
scarcely seen, and the angle of the ciliary body at the point of
origin is changed from a right to an acute angle.

342 MANUAL OF HISTOLOGY.

In very hypermetropic eyes, on the contrary, the circular
fibres are abundantly developed (Fig. 155), the meridional fibres
are shorter, while the angle at the point of origin of the mus-
cle becomes somewhat obtuse, so that by these changes one can
determine, even in a microscopic section, what considerable
refractive error the eyes have had.

The meridional fibres are either prolonged some distance
into the stroma of the ch'oroid and end in a delicate fringe, or
they terminate at the anterior and outer layers of this mem-
brane in stellate knots with fine anastomosing branches.

The radial fibres form a looser network than the last, but
also have the same terminal interlacement of their fibres ; the
circular fibres form fewer anastomoses, and only those bundles
which lie next to the radial fibres are extensively connected
with them.

The nerves of the ciliary body are derived from the plexus
formed in its stroma by the ciliary nerves ; the vessels are
largely supplied from the circulus iridis major, lying in the an-
terior part of the body.

The iris arises from the anterior side of the ciliary body,
and from the connective tissue surrounding the fibres of the
ciliary muscle ; it is also attached to the cornea and sclera by
the ligamentum pectinatum. (See Fig. 153).

It consists of a loose connective-tissue stroma, which sup-
ports a rich vascular network, a complete muscular structure,
and the nerves. It is covered anteriorly by a continuation of the
endothelium of the cornea, and posteriorly by a thick layer of
pigment-cells continuous with those which line the ciliary body.
The vessels arise from the circulus, have adventitial coats which
are thick in proportion to their calibre, and pass radially to
the margin of the pupil, where they form a network of fine
capillaries, the circulus arteriosus iridis minor, ending final-
ly in veins which return in the same general direction as the
arteries, but lie beneath them, emptying finally into the venae
vorticosae.

Near the margin of the pupil, and forming a ring about
it 1 mm. in breadth by -^ mm. in thickness, is the sphincter
muscle of the iris. It is composed of unstriped muscular tissue,
and is situated in the posterior portion of the iris.

The dilator muscle, at its inner border, is in close connection
with the sphincter, and its fibres run radially to the periphery

THE EYE. 343

of the iris, where they are woven into a thick anastomosing
circle.

The nerves of the iris are derived from the ciliary plexus ;
at the periphery they divide and scatter in various directions :
the pale fibres to the posterior layers, forming a fine network
about the dilator muscle; the fibres with a medullary sheath
to the anterior portion ; another set supplies the sphincter
muscle — these being, in the order of description, the branches
possibly of the sympathetic, sensory, and of the third pair.

The posterior surface of the iris, which, near the pupil, rests
upon the anterior capsule of the lens, is covered with a thick
layer of densely pigmented cells, the uvea, which can rarely be
so separated as to determine their shape, and which appear to
have no distinct limiting membrane behind them.

This layer extends from the pupil, where it meets the endo-
thelium of the anterior surface, back to the pigment of the
ciliary body, with which it is continuous and from which it can
be distinguished by having no connective tissue covering it.
The pigmented cells, which are more or less thickly scat-
tered through the stroma of the iris, determine the color of
the anterior surface.

Transverse sections through the sclera and choroid are best
made from eyes hardened in Muller's fluid. An eye which has
been injected with colored gelatine, introduced through the
aorta after that vessel has been tied beyond the carotids, will
show the fine meshes of the chorio-capillaris, when the pigment-
layer covering the choroid has been brushed away under gly-
cerine. Such injections are best made on albinotic rabbits.

Good sections of the ciliary body can be made from eyes
hardened in alcohol or Miiller's fluid, and the blood-vessels
can be easily seen in injected specimens. The muscular tissue
of this body and the iris may be examined in specimens treated
with a 30 to 40 per cent, solution of potash. Carmine may
then be used to color. The vessels of the iris are best seen in
the eyes of a young albino rabbit, injected with colored
glycerine or Berlin blue.

The retina, lines the whole inner surface of the choroid as
far as the ora serrata ; it is composed of nervous elements,
connective tissue, and blood-vessels.

The following division into well-marked layers from within
outward has been generally adopted. (See Fig. 157).

344

MANUAL OF HISTOLOGY.

a, membrana limitans interna.
&, optic nerve fibre-layer.

c, ganglion-cell layer.

d, inner granular layer.

e, inner nuclear layer.
/, outer granular layer.

<7, outer nuclear layer.
7i, membrana limitans' externa.
i, layer of rods and cones.
Pigment layer.

The fibres of the optic nerve generally lose their medullary
sheath at the lamina cribrosa, and proceed
thence as naked axis-cylinders through the
opening in the choroid to the level of the
retina, where the}7 spread over its entire in-
ner surface to form the nerve-fibre layer,
which is thick in the vicinity of the nerve,
but gradually decreases as it approaches
the ora serrata, where it ends.

At the macula lutea the fibres do not
form a distinct layer, but, curving toward
this spot from above and below, are lost
in the layer of ganglion-cells, either entering
them or passing on to the inner granular
layer.

The ganglion-cell layer consists of large
branching cells in most places but one row
deep, though near the macula there may
be two or more layers. They are very
u transparent, have no visible cell-wall, and
He. are provided with a varying number of pro-
jecting arms ; when fresh they contain fine
granular matter with a clear, large nuclei
and nucleoli, and appear finely fibrillated.

They receive an axis-cylinder on their
inner side, and on the outer send out
branches which ultimately divide into fine fibrillse, and are
lost at the inner granular layer in a tangled network. It is
probable, however, that some of these fibres are connected
with the cells of the inner nuclear layer.

The inner granular layer partly surrounds the ganglion-

FIG. 157. — Transverse nec-
tl«m of the retina. After Zc-
henilcr.

THE EYE. 345

cells and forms a sort of spongy network between these and
the inner nuclear layer ; its composition is still a matter of
doubt, but it appears to be made up of a more or less homo-
geneous substance, in which are numerous tine openings tilled
with some material of a peculiar refractive power. It does not
belong to the nervous substance of the retina, and when placed
in a 10 per cent, solution of common salt, dissolves, leaving the
supporting connective-tissue fibres unaffected.

The inner nuclear layer is made up of numerous oval cells
with large nuclei ; they belong mostly to the nervous tissue,
but scattered among them are also cells of the supporting con-
nective-tissue framework.

The nerve-cells resemble small bipolar ganglion-cells, hav-
ing two fine processes, the inner of which probably connects
with the ganglion-cell layer, or directly with the optic nerve
fibres. Near the macula these cells are more numerous ; to-
ward the ora serrata they gradually decrease in number.

Next comes the outer granular layer, a thin stratum re-
sembling the inner in appearance and composition ; here the
fine fibres from the outer and inner nuclear layers become lost
in a tangled mass.

Between this layer and the membrana limitans externa is
the outer layer of nuclei, made up of a number of oval cells,
connected more or less closely with the inner ends of the rods
and cones.

The larger nerve-fibres, which pass through the outer gran-
ular layer, are joined to the nuclei of the cones, which lie di-
rectly within the membrana limitans and are connected to a
prolongation of the base of the cones themselves. The smaller
fibres pass to the nuclei of the rods, which form an irregular
layer at varying distances from the limiting membrane, and
from which fine tangled fibres pass to the base of the rods.
These nuclei resemble those of the inner layer ; they con-
tain a small amount of granular matter with a nucleus and nu-
cleolus, and sometimes exhibit, as the result of post-mortem
changes, peculiar transverse stripes.

Directly beyond the membrana limitans externa, and rest-
ing upon it, are the rods and cones, each composed of an outer
' and inner member.

The rods are small, cylindrical bodies of high refractive
power ; when fresh they appear homogeneous, but with the

346 MANUAL OF HISTOLOGY.

beginning of decomposition, which occurs very quickly, the
inner half appears as if filled with a finely granular substance,
while the outer exhibits' transverse striations, and finally
bivaks up into small disks, which can only be distinguished
from those of the outer segment of the cones by their red color
(visual purple of Kuhne), which soon fades on exposure to
light.

The inner segment of the cones is larger than that of the
rods ; it tapers rapidly toward the outer part, where it is filled
with a peculiar oval-shaped body ; the outer segment does not
equal that of the rods in height, but divides into similar disks.

The pigment-layer, in which the ends of the rods and cones
are imbedded, consists of a single layer of hexagonal cells,
more densely pigmented in the part next the retina, and by
some observers said to be provided with fine processes, which
are lodged between the rods and cones. This pigment is more
dense at the macula and varies with the color of the person,
being most abundant in negroes, whereas it is absent in albi-
nos ; from this layer, according to Kiihne, the visual purple
of the rods is reproduced.

At the macula lutea, which is situated a little to the outer
side of the entrance of the optic nerve, the ganglion-cell and
inner nuclear layers have their greatest thickness. The fibres
which pass from the outer granular to the outer nuclear layer
are lengthened and run in a more horizontal direction toward
ihefovea, which forms a slight depression in the centre of the
macula.

Over this fovea the layers of nerve-fibres and ganglion-cells
are absent, and the other laminse become so much thinned
that the membrana limitans interna approaches nearly to the
nuclear layer; the rods are also absent, and the cones be-
come lengthened and slightly convergent.

The membrana limitans interna lies between the retina and
vitreous body ; it is a transparent homogeneous structure, and
from its outer surface spring the connective- tissue fibres which
form the supporting framework for the nervous part of the
retina.

These fibres arise in the form of thin fenestrated plates,
connected together by numerous arms ; they soon contract,
however, to smaller radiating bands, which surround the gan-
glion-cells and pass on to the inner nuclear layer, where they

THE EYE. 347

contain occasional nuclei. From this point they again ex-
pand into broader sheets, which, after surrounding the outer
nuclei, are united to form the membrana limitans externa.
This membrane lies just at the base of the rods and cones, and
it is provided with numerous holes, through which those struc-
tures pass ; from its outer surface fibres extend up between
the rods and cones to form supporting sheaths.

The blood-vessels of the retina come from the arteria cen-
tralis retince, which usually divides into two or more branches
at the entrance of the optic nerve ; these vessels lie in the layer
of nerve-fibres, and, arching above and below the macula, give
off numerous fine branches, from which capillaries penetrate
as far as the inner nuclear layer. The larger retinal vessels are
surrounded by lymph-spaces, which probably unite with those
of the optic nerve.

At the periphery the retina becomes much thinned, and at
the ora serrata the nervous elements are discontinued, the con-
nective tissue alone being prolonged over the ciliary body to
its anterior angle, thus forming the pars ciliaris retince.

This membrane consists of long cylindrical cells of varying
shapes ; they rest on the pigment and are covered by a thin
stratum, which sends processes between them and seems to be
a prolongation of the membrana limitans interna of the retina.

It is very difficult to prepare good sections of the retina,
but the following plan is recommended : enucleate with care
the eye of a frog or some small animal, and immediately sus-
pend it in a well-stoppered bottle containing a small bit of
solid osmic acid ; when sufficiently hard the posterior portion
of the eye can be cut in pieces and sections made by imbed-
ding or holding between pieces of liver.

Another method is to place the eye unopened in Miiller's
fluid for some two weeks, frequently changing the fluid ; af-
terward harden in alcohol. Sections may then be made in the
same manner as before.

To obtain the separate constituents, place a fresh retina in
a -jV per cent, aqueous solution of osmic acid for fourteen days,
then in glycerine for seventeen days ; after this, place a small
piece on a slide in glycerine, with the cover-glass so arranged
that no pressure is made upon the specimen ; now tap gently
on the centre of the glass until the motion of the fluid causes
the retina to fall apart.

348 MANUAL OF HISTOLOGY.

The optic nerve, after leaving the optic canal, passes through
the orbit surrounded by three coverings, continuations of the
cerebral membranes.

The dural coat, composed of dense connective tissue with a
few elastic fibres, forms the outer covering ; the fibres are at-
tached to the periosteum, where the nerve leaves the bony canal,
and where it enters the eyeball they are continued directly into
the outer layers of the sclera.

Within this covering, and separated from it by a very nar-
row space, are the delicate fibres of the arachnoidal coat,
and the lymph-space between the two is called the subdwral
space.

Within the arachnoidal coat, and separated from it by a
wide lymph-space, is the pial coat closely surrounding the
nerve-fibres, and sending processes of connective-tissue be-
tween their bundles. This membrane passes into the inner
layers of the sclera, and also sends numerous fibres to the la-
mina cribrosa. Its outer surface is covered with endothelium,
and between it and the arachnoid coat is the subaraclmoid
space, which reaches to the inner layers of the sclera, and is
continuous with the same space in the brain.

The optic nerve itself, closely surrounded by its vagina
fibrosa, passes forward through the orbit, receiving the central
artery and vein at about 15 to 20 mm. from the sclera. These
vessels pass to the centre of the nerve and lie in a connective-
tissue sheath until they emerge on the inner surface of the eye-
ball to branch over the retina.

On cross-sections of the nerve, bundles of connective tissue
are seen to pass inward from the pial sheath and form a cross-
network, through the openings of which the nerve-fibres pass.
On longitudinal sections the connective tissue appears in
irregular fenestrated sheaths ; this tissue can also be demon-
strated by macerating thick sections in a | per cent, solution
of chromic acid and then brushing out the nerve-elements.

These nerve-filaments themselves are extremely small, but
vary somewhat in size. They consist of an axis-cylinder sur-
rounded by its medullary sheath; they are grouped in large
bundles which pass through the meshes of the connective tis-
sue. The fibres appear to be held together by a kind of homo-
geneous albuminous substance— neuroglia, and have on their
surface occasional nucleated corpuscles, distinguished from

THE EYE. 349

those of the connective tissue by being larger and more irregu-
lar in shape.

Blood-vessels are found not only in the centre of the nerve,
but also scattered through various parts of the connective tis-
sues.

At the lamina cribrosa there is an anastomosis with the ves-
sels of the circle of Holler, which, coming from the short poste-
rior ciliary arteries, forms a vascular circle in the sclera, about
the entrance of the optic nerve.

Where the nerve-tibres pass through the sieve-like openings
of the lamina cribrosa they lose their medullary sheath, and
from that point pass on to the nerve-fibre layer of the retina
as transparent axis-cylinders ; but in rare cases the sheaths are
continued from the optic disk some little distance over the
retina, and are seen with the ophthalmoscope as very white
patches radiating out from the disk, or following the vessels
and gradually fading into the general color of the f undus by
a fine, fringe-like border.

The vitreous body is a transparent, jelly-like mass, of spher-
ical shape, with a depression at the anterior part, in which the
lens rests. Ifc is bounded behind and on the side by the retina,
in front by the lens with its attachments, and appears to have
no true hyaloid limiting-membrane of its own. It is very diffi-
cult to demonstrate any definite structure in this substance ;
toward the periphery it appears to be arranged somewhat in
concentric layers, but in the centre is more homogeneous.

From the optic disk to the lens there is a small canal about
1 mm. wide in front and spreading out behind ; it is lined
with very transparent cells, and filled with a substance <more
fluid than the rest of the vitreous ; it marks the position of the
arteria Jiyaloidea, which is usually obliterated at about the
seventh foetal month.

The vitreous body also contains numerous corpuscles, espe-
cially near the periphery ; these consist of round lymph-cells,
stellate cells, with one or more nuclei, and irregular arms, and
of branching cells which seem to have a transparent vesicle
filling up a part of their interior. The vitreous contains no
nerves, and after birth no blood-vessels ; it may be examined
fresh or hardened in a £ per cent, solution of chromic acid.
Sections may be colored blue with aniline, and preserved in
glycerine.

350

MANUAL OF HISTOLOGY.

The lens (Fig. 158) is a transparent, biconvex body, sur-
rounded by a structureless, elastic capsule, which is thicker in
front where it touches the iris, and thinner behind where it
rests in the fossa pateUaris of the vitreous.

The inner surface of the anterior capsule is covered with a
single layer of hexagonal epithelial cells, which become longer
near the equator of the lens, and gradually pass over into the
lens-fibre.

After birth these fibres consist of long, transparent tubes, on
section resembling flattened hexagons closely joined together

by their serrated edges; they are
arranged in concentric meridional
layers with their broad side out-
ward. They do not pass around
the entire circumference of the lens,
but arise on the anterior surface
from three lines, which, uniting at
the axis, make a figure like an in-
verted Y, with the arms set at an
angle of about 20° to each other ;
on the posterior surface this star
is reversed, the Y standing upright.
In adult life the rays are more
numerous, and the fluid contents
of the tubes become more solid and
of greater refractive power, espe-
cially toward the centre of the lens.
On a meridional section of the
lens one sees the concentric ar-
rangement of the lens-fibres, and near the equator a collection
of nuclei (the nuclear zone}. These nuclei belong to the lens-
fibres, each one of which originally had one, although in
adult life they are found more abundantly in the peripheral
region.

The fibres of the supporting ligament of the lens (the zonula
ciliaris) are attached to the anterior and posterior capsule near
the equator ; from here they converge to the apex of the ciliary
body, to which they are fastened.

The fibres form for the most part an anterior and posterior
layer, and have occasional nuclei, especially toward the ora
serrata ; between these layers is the canal of Petit, the result

Pio. 158. — Meridional section through
axis of the human lens.

THE EYE. 351

of post-mortem changes, which quickly destroy the delicate
fibres that ordinarily fill this space.

Specimens for study may be made in the following way :
harden an eye for fourteen days in Miiller's fluid ; then open,
remove the lens, and preserve in alcohol. Sections may be
made in any direction ; they should be colored with hema-
toxylou and mounted in glycerine.

To examine the epithelium under the anterior capsule, a
piece of capsule should be peeled off from a fresh lens and ex-
amined with, or without previous staining. Single lens-fibres
or groups of fibres may be obtained by macerating a portion
of lens in dilute sulphuric acid (i per cent.), or in a £ per
cent, solution of chromic acid, after which it can be easily
separated into its elementary parts.

The lachrymal gland is situated under the upper and outer
edge of the orbital wall, resting partly in a shallow fossa of the
frontal bone, to which it is attached by firm bands of connec-
tive tissue.

It is an acinous gland, divided into a larger upper portion
(glandula Galeni), some 20 mm. long, 10 wide, and 5 thick, and
a lower part of about half the size (glandula Monroi) ; they are
supplied with blood by a branch of the ophthalmic artery, and
with nerves from the fifth pair.

The connective tissue which envelops the gland also ramifies
through its substance, dividing it into numerous small alveoli,
in which are the true secreting cells of the gland, and from
which fine ducts pass out to coalesce, and finally discharge on
the free surface of the conjunctiva fornicis at its upper and
outer part.

The upper part of the gland is quite dense, but in the lower
portion the alveoli are less closely packed, and often near-
ly surrounded by the orbital fat. The alveoli are covered
by a fine membrane composed of flat cells with numerous
branches or processes, which spread in various directions and
serve to unite the cells of the investing membrane, and also the
different alveoli ; they form a shell which is surrounded on its
outer side by a distinct lymph-space, and on its inner surface
is lined by the secreting cells of the gland.

If these lymph-spaces have been injected with Berlin blue,
and especially if the blood-vessels are injected with some other
color, the arrangement of the lymph-spacea can be very well

352 MANUAL OF HISTOLOGY.

seen. The openings from the alveoli are at first lined with
fine, flat cells ; then, as the tube grows larger, they assume the
character of cylindrical epithelium.

BIBLIOGRAPHY.

GBAKFK u. SAEMTSCH. Handbuch der gesammten Augenheilkunde. Vol. I,

Leipzig, 1874.

J. ORTH. Cursua der normal en Htstologie. Berlin, 1878.
A. ALT. Lectures on the Human Eye. New York, 1880.

CHAPTER XXI.

THE EAE.
BY DBS. WILLIAM P. WHITNEY AND CLARENCE J. BLAKE, OP BOSTON.

FOLLOWING the natural order are to be considered, first, the
external ear with the meatus externus ; secondly, the middle
ear with the Eustachian tube; and thirdly, the internal ear
(membranous labyrinth and cochlea).

External ear. — This includes the auricle, the meatus exter-
nus, and the membrana tympani.

The auricle is formed by a cartilaginous plate, 1-2 mm. in
thickness. The line elastic fibres of this plate, which is of the
reticular variety of cartilage, can be traced into the perichon-
drium, and even into the subcutaneous tissue. Both perichon-
drium and subcutaneous tissue are rich in elastic fibres, the
latter varying greatly in amount in different parts of the ear,
being very sparingly developed on the concave surfaces, where
the skin is closely adherent to the perichondrium, and immov-
able in consequence, but more abundant on the convex sur-
faces, where the skin is movable ; it forms, together with the
fat enclosed in its meshes, the bulk of the lobule.

The cutis covering the auricle is a direct continuation of
that covering the face, and is well provided with downy hairs
and sebaceous glands. These latter reach their greatest devel-
opment in the depressions of the auricle, especially the concha.

The external meatus consists of a cartilaginous and an os-
seous portion. The former only differs in structure from the
auricle into which it passes, in the presence of the ceruminous
glands. These are tubular glands, having a coil at the bottom.
They consist of a membrana propria, on which is a layer of
cubical epithelium, and are the analogues of the sweat-glands.
In the osseous portion of the meatus the glands are sparingly
found, and the hairs are fewer and finer. Otherwise there is
33

354 MANUAL OF HISTOLOGY.

no difference between the two portions, except that the carti-
lage is replaced by bone.

The ear of a new-born -child can be easily removed with the
cartilaginous part of the meatus, and when hardened in Miil-
ler's fluid and afterward in alcohol, and imbedded in paraffine
or hardened liver, furnishes sections which, when colored with
hsematoxylon, show the different relations very clearly. The
osseous portion must first be decalcified by allowing the bone
to hang freely in a weak (i per cent.) solution of chromic
acid, often renewed, during several months. The specimens
are then to be well washed, hardened in alcohol, and prepared
as above.

At the inner end of the external meatus, and separating it
from the middle ear, is stretched the membrana tympani. The
tympanic ring, with the membrane attached to it, is to be care-
fully separated from the surrounding parts by means of bone-
scissors, and placed for five to fifteen minutes in a weak solu-
tion (two to five per cent.) of formic or acetic acid. It should
then be well washed in distilled water, and the external layer
of epithelium removed by a camel' s-hair brush, and finally
stained with hsemotoxylon and mounted in glycerine. In spe-
cimens thus prepared there are to be distinguished three lay-
ers, viz.: an external or cuticular layer, a middle or fibrous
layer (membrana propria), and an internal or mucous layer.

The cuticular layer is composed of simple pavement-epithe-
lium, without glands or hairs. It is thickest at the periphery,
and over the'handle of the hammer, and along its edge.

The fibrous layer (membrana propria) consists of two sets
of flattened, spindle-shaped fibres, with long, thin connective-
tissue corpuscles imbedded in them, and which have a close
analogy with the fibres of tendons. The outer series, lying
directly beneath the cutis, radiates from the handle of the
hammer toward the periphery, while the inner series circles
about the handle. At the periphery the two series interlace
with each other and with a few fibres coming from the cuticu-
lar and mucous layers to form the so-called tendinous ring, in
which are also to be found a few scattered cartilage-cells. This
ring is joined to the annulus tympanicus by a thin periosteum.
(The handle of the hammer is joined to the membrana tympani
by a cartilaginous formation which stands in close relation to
the membrana propria. This is a shallow groove of hyaline

THE EAR. 355

cartilage, in which the handle of the hammer lies, kept in place
by the mucous layer which passes over and is firmly adherent
to it ; the upper part of this furrow ends in a sort of cartilagi-
nous cap, into which the processus brevis fits.) Transverse
sections made after hardening the membrane in Miiller's fluid
and alcohol, and then imbedding, give the best idea of these
relations.

The inner or mucous layer is formed of flat epithelium, sup-
ported on a reticulated layer of connective tissue, and directly
continuous with the epithelial lining of the middle ear. The
arterial supply is furnished by a small arteriole, which follows
the handle of the malleolus, and gives off lateral capillaries
anastomosing with others coming from small branches which
enter at the periphery. The blood is collected into venous
trunks which pass out in a similar manner. Fine nerves are
said to be found in close connection with the vessels. They
apparently come from the sympathetic system.

The middle ear. — In order to obtain a clear idea of the rela-
tions and structure of the middle ear a fresh temporal bone,
with the soft parts still adherent, must be decalcified by soak-
ing for a long time in a £ per cent, solution of chromic acid,
which should be frequently changed ; it is then to be washed
in distilled water for twenty-four hours, and hardened in alco-
hol, when it will be ready for cutting.

A section from a specimen thus prepared shows that the
whole middle ear is lined by a layer of pavement-epithelium,
supported upon two layers of connective tissue, one serving as
a submucous layer and the other as a periosteum. This tis-
sue is thrown into ridges corresponding to the bony promi-
nences, in the hollows of which, the vessels and nerves lie. Ac-
cording to Kessel the submucous layer is provided with, oval
expansions, recalling the Pacinian bodies found in the mesen-
tery of the cat. The existence of muciparous glands in the
human tympanum has yet to be confirmed. A plexus of nerves
is described as distributed in the subepithelial tissue, in the
nodal points of which are found scattered ganglion-cells. The
lining of the tympanum passes directly into that of the mastoid
cells, and has there the same general arrangement.

The Eustachian tube. — In direct communication with the
tympanum stands the Eustachian tube, composed like the ex-
ternal ear of a cartilaginous and an osseous portion. The car-

356

MANUAL OF HISTOLOGY.

tilage, which gives the name to the anterior part of the tube
that stands in connection with the pharynx, is in the form of
a hook (Fig. 169, 2), with its short end directed downward and
inward. At the bend of the hook the opposing surfaces of car-
tilage cannot quite apply themselves to each other, and there
is thus left a little air-space between them, which Ruedinger
has termed the safety- tube (Fig. 159, 9). The cartilage is of the
hyaline variety, with small cells, which are much smaller and
more numerous at the periphery, thus forming a sort of peri-

Pro. 169. — Transverse section of Euntachlan tube and surrounding parts : 1, median cartilaginous plate ;
2, lateral cartilaginous hook : 3, musculus dilator tnbae ; 4, musculus levator veil palatini ; 6. fibre-carti-
lage basilaris : fl and 7, acinous glands ; 8, deposit of fat in the lateral wall : 9, safety-tube ; 10, accessory
fissure ; 11, fold of the mucous membrane ; 12, adjacent tissues. Ruedinger.

chondrium. The cartilage is joined to the osseous portion by
a narrow band of fibre-cartilage.

The musculus dilator tubse (Fig. 159, 3), which goes to form
the membranous (muscular) portion of the tube, is joined to
the short end of the hook along the whole length of the carti-
laginous portion. The muscle is of the striped variety, and is
inserted into the perichondrium by means of a very short, flat
tendon.

The entire tube is lined with a mucous membrane (Fig. 159,
11), continuous at one end with that of the pharynx, and at the

THE EAR. 357

other with that of the tympanum. This membrane consists of
several layers of cylindrical epithelial cells, the upper or inner
of which have their broa^ surfaces directed inward and carry
cilia. In the other layers the epithelia are wedge-shaped. The
epithelium rests upon a basement- membrane, beneath which is
a layer of connective tissue (Fig. 159, 5), in which lie the muci-
parous glands (Fig. 159, 6, 7), which are similar to those of
the pharynx and oesophagus, and lined with wedge-shaped
epithelium. These glands are absent in the safety-tube. A
plexus of nerves arising from the pharyngeal and tympanic
plexuses has been demonstrated, the final distribution of which
to the glands is probable.

Before leaving the middle ear a short mention of the os-
sicula and their mode of articulation is in place. The bones
are composed of an internal spongy and an external compact
portion. The former is very rich in blood-vessels. These
bones are covered in early life by the mucous membrane only,
but in later life there is also a thin periosteum to be seen.
Their articulation with each other is constructed similarly to
that of the larger joints ; i.e., their articular ends are sur-
rounded by a capsule in which is a synovial fluid. The method
of union of the foot- plate of the stapes with the fenestra ovale
is a little more complicated. The bottom and edges of the plate
are covered with a thin film of hyaline cartilage. The edges of
the window are also covered with cartilage, which is united to
that of the plate by means of a fine network of elastic tissue.
The base of the plate rests upon a firm connective-tissue layer,
a continuation of the periosteum lining the inside of the scala
tympani, and called the ligamentum baseos-stapedis.

The muscles connected with the ossicula belong to the
striped variety, and are connected to the bones by tendons,
which are covered by the mucous membrane wherever they
pass through the tympanum.

The internal ear. — The internal ear consists of two portions,
to which the auditory nerve is finally distributed, and which
are the essential parts concerned in the perception of sound.
These, are the membranous labyrinth and the cochlea.

In man and the higher vertebrates both of these parts are
enclosed within bony walls, a circumstance which makes their
histological study a matter of considerable difficulty. In fishes,
however, although the cochlea is represented merely by a small

358 MANUAL OF HISTOLOGY.

diverticulum (the lagena), the membranous labyrinth is fully
developed, and, as it is large and easy of access, has always
been a favorite object for demonstration. Its method of prep-
aration will be given here, while that for the cochlea will be
described farther on.

The membranous labyrinth. — Our knowledge of this part
has been chiefly derived from studies upon the pike (esox lu-
cius), perch (perca fluviatilis), or cod (gadus morrhua). The
head is divided longitudinally in the median line, and the brain
carefully removed by means of the handle of a scalpel, when
there is seen directly behind the eye a second cavity filled with
a grayish translucent mass, composed principally of fat and a
sort of mucous tissue. This can be removed with the aid of
fine forceps, and there is usually drawn out at the same time
more or less of the semicircular canals with their ampullae and
the remains of the utricle and saccule. With a little practice,
and by carefully freeing the canals from the short, bony chan-
nels by which they are held in place, the membranous laby-
rinth, with a portion of the acoustic nerve, can be removed
entire.

Within the utricle and saccule are found the otoliths, con-
cretions of lime. After the lime has been removed by means
of a weak acid, they show a coarse, fibrillated structure on
section. These serve as a ready means of distinguishing be-
tween the saccule and utricle, as the largest otolith (called
sagitta) and the smallest (asterix) occupy the saccule, the
former lying on the expansion of the acoustic nerve in the sac-
cule proper, while the latter lies on the expansion of the nerve
in that part of the saccule called the lagena, and which corre-
sponds to the cochlea of the higher animals. The medium-sized
stone (lapillus) lies upon the expansion of the nerve in the utri-
cle. The otoliths are embedded in a mucilaginous mass lying
directly upon the termination of the nerve. In the higher ani-
mals they are represented by cretaceous particles in the macula
acustica.

The labyrinth thus removed is to be placed, during twenty-
four hours, in a 1 per cent, solution of osmic acid, and then
carefully washed in distilled water. In order to obtain the
separate cells, the point where the nerve enters (known by its
darker color) is to be carefully teased with fine needles and
examined in glycerine. To obtain good sections, the por-

THE EAR. 359

tions of the canal where the nerve terminates, and the simi-
lar portion of the saccule and utricle, are to be placed for
twenty-four hours in a saturated solution of gum arable in
water, and then directly into strong alcohol for twenty-four
hours longer, when they will be ready for embedding. The
sections, made with a sharp razor, kept well wet with alcohol,
are to be deprived of their gum by passing a stream of distilled
water beneath the cover-glass, the water being replaced by a
solution composed of one part of a saturated solution of ace-
tate of potash and four parts each of glycerine and water.

The structure and arrangement of the semicircular canals,
except at the points of expansion of the nerve, is as follows :
In the osseous fishes the canals lie embedded in a mass of adi-
pose tissue, and are held in place by very short bony tubes ;
in the cartilaginous fishes (shark, skate) they lie in canals hol-
lowed out in the cartilage, while in man and the higher verte-
brates they are surrounded by bony walls.

In man the membranous part does not entirely fill up the
bony canals, but is adherent to the lining periosteum at one
point, and to the rest of the wall by bands of connective tissue
(called ligamentum labyrinthi canaliculorum et sacculorum), in
the interstices of which the perilymph circulates. In the fishes
the walls of the tubes and ampullae, as well as of the utricle
and saccule, are composed of what has been termed spindle-
cartilage. This consists of a homogeneous ground-substance,
like that of ordinary cartilage, in which lie embedded long,
spindle-shaped connective-tissue corpuscles, anastomosing with
each other in all directions, like the corpuscles of the cornea.
The whole is lined with a pavement-epithelium. In man the
structure is different. Here there are to be distinguished three
layers, viz., externally, a layer of connective tissue, composed
of fibrous tissue with numerous nuclei. This is connected at
one point with the periosteum, and passes into the ligamenta
labyrinthi canaliculorum at the other points of the circumfer-
ence ; secondly, of a hyaline layer, the tunica propria ; this is
raised into papilliform projections in certain parts of the tube.
The internal layer is composed of simple pavement-epithelium.

The distribution and termination of the nerve is as follows
in the fishes : The acoustic nerve divides into two branches,
the cochlear and vestibular, each of which gives off three fila-
ments. Those from the cochlear portion supply the saccule,

360

MANUAL OF HISTOLOGY.

lagena, and ampulla frontalis ; those from the vestibular
branch go to the utricle and the ampullae of the horizontal and
sagittal semicircular canals. The termination of the nerves in
the saccule and utricle is called macula acustica, and in the
ampullae, crista acustica.

The macula is a small, roundish spot, slightly projecting
above the surface. Thin sections through it show the presence
of three layers of cells. Directly upon the wall proper of the
canal lies a single row of small, round epithelial cells with
large nucleoli (Fig. 160, 1). Next come several rows of cells hav-

•cp. nerv.

cartilage.

Fio. 160.— Section through the ampulla frontalis of esox lucius: 1, basal cells ; 2, cells with thread-
like prolongations ; 3, cylindrical cells, with cilia. After Knhn.

ing a round or oblong (spindle-shaped) central portion, from
which are given off two filiform prolongations, the one passing
inward and standing in close connection with a fine plexus of
nerves lying in the layer of round cells mentioned above ; the
other also passing inward, but ending either as a free cilium
between the layer of cells next to be described, or being joined
to their inner extremity (Fig. 160, 2, and Fig. 161).

The inner layer consists of several rows of cylindrical epi-
thelial cells, having the end, which is directed inward, tapering
into a fine filament connected with those of the middle layer, as

c/t

THE EAR.

361

already described. The free surface of these cells is provided
with numerous hairs (Fig. 160, 3).

The arrangement of the cells in the crista acustica is essen-
tially the same as that of the ma- »
cula, with the exception that the
crista rests upon an infolding of
the wall called the septum nerveum
(Fig. 160, sep. nerv.), and has on
each side two half -moon -shaped
prominences of cylindrical epithe-
lium called the plana semilunata
(Fig. 160, pi. sem.), into which no
nerves have been traced. At the
point where the macula and plana
semilunata pass into the epithe-
lium lining the rest of the canal,
there is found an intermediate form
of cell, larger than the ordinary
epithelium, and separated one from
another by a fine web of connective
tissue. These have received the
name of protoplasmic cells, but as
yet their function has not been
discovered.

Covering the crista in the place
of an otolith is a gelatinous mass
in the form of a cup, having a stri-
ated appearance, and into which
the fine hairs of the internal sur-
face project. This is considered as
a cuticular formation, and is sup-
posed to act as a damper (Fig. 160,
cupula).

The nerve, after passing through
the wall at the point opposite the
crista or macula, loses all its
sheaths, and forms a fine plexus in
the outermost layer of cells, and

this plexus has been found to communicate with the inner
filaments of the middle layer of cells, the internal filaments of
which ended as free cilia or were joined to cells of the inner

Fio. 1B1.— Separate cells from the ma-
cula, Hhowing the connection of the cylin-
drical cells with the cells having thread-
like processed, and also the iiaraage of these
processes to the surface between the cells.
Kuhn.

362 MANUAL OF HISTOLOGY.

layer which were provided with cilia upon their free surface.
This can be best understood by a study of Figs. 160 and 161.
In man the arrangement,' as well as can be followed, is almost
identical with that of fishes.

TJie cocJdea. — There is no easy method of obtaining good
preparations of the cochlea, but that by which the best results
have been obtained is as follows : The portion of the temporal
bone containing the internal ear from a recently killed animal
(young cat, dog, or bat) is hardened for twenty-four hours in
•J to 1 per cent, solution of osmic acid in distilled water,
then placed in Muller's fluid for a week, and decalcified by a
0.01 per cent, solution of chloride of palladium. After decal-
cification it is to be washed in distilled water for a few minutes,
then soaked for twenty-four hours in a concentrated aqueous'
solution of pure gum arabic, and finally placed directly in
strong alcohol for twenty-four hours. After this hardening the
preparations are ready to be embedded in soap or hardened
liver, and cut. The razor is to be kept well wet with alcohol
while cutting. The sections are to be placed directly upon a
slide, and the gum removed by passing a stream of distilled
water under the covering-glass.

Small portions of the lamina spiralis can also be taken from
the fresh cochlea, after opening it carefully with the bone-for-
ceps, and placed in the vapor of osmic acid or in a £ to 1 per
cent, solution of the same for a few (twelve 'to twenty-four)
hours. The preparations thus treated may be teased in gly-
cerine, and the separate cells obtained.

The sections are to be made in a direction parallel with the
long axis of the cochlea, and if the central shaft (modiolus) is
cut through, the following picture will be presented : On each
side of the modiolus are seen sections of the canal of the coch-
lea, divided by a thin partition (the lamina spiralis, Fig. 162,
L sp) into an upper portion (the scala vestibuli, Fig. 162, SV)
and a lower (the scala tympani, Fig. 162, ST). The scala ves-
tibuli is further subdivided by means of a delicate membrane,
named after its discoverer the membrane of Reissner (Fig. 162,
ft /i)> which passes off at an angle from the middle of the
lamina spiralis and is inserted into the wall of the cochlea.
The portion of the canal thus cut off forms the ductus cochle-
aris (Fig. 162, e, et), and in it lies the peculiar body in which
the nerve terminates, and which is called the organ of Corti.

THE EAR.

363

The scala tympani is a blind canal, having at one extremity
the membrane which covers the fenestra rotunda, and at the
upper part terminating in. the cupula of the cochlea, where it

Lsp

PlO. 162.— Section of the cochlea of a human embryo at the fourth month, a. a, a, cartilaginoo*
incaoement of the cochlea; 6. fr, perichondrium ; c, mncuid tissue matrix of the modiolug; d, d, cartila-
ginous septa of the individual turns of the cochlea ; e — «4, sections of the ductus cochleariR ; /, /,. Reiss-
ner's membrane ; g, membrana tectoria. eomewlint lifted up from the subjacent parts ; A, rudiment of the
stria Tascularis ; <, rudiment of the subsequent organ of Corti ; L up, lamina spiralis ; Ol, Of,, ganglion
spirale with variono efferent and afferent bundles of nerves; ST, scala tympani; SV, scala vest.ibuli;
AT,, (SK,, STt, miiccid tissue where later the scala; of the last cochleal turn will be. i1-'. Waldeyer.

is said to enter into communication with the scala vestibuli
by a minute opening, the helicotrema.

The scala vestibuli stands in direct communication with the
perilymphatic space of the vestibular sacs, while the ductus
cochlearis is in communication with the saccule by means of
a slender canal (the canalis reuniens). The walls of the two
scalse are formed of a thin periosteum, on the surface of which

364 MANUAL OF HISTOLOGY.

there can be shown, by means of the silver method, a layer of
endothelium. This proves that the canals are of the nature of
serous cavities.

The lamina spiralis is composed of an osseous and a mem-
branous portion. The osseous portion reaches about one-half
the distance from the modiolus to the opposite wall, and on its
outer and vestibular portion is a mass of connective tissue
called crista spiralis (Fig. 163, Or.), the upper lip of which is
called labium vestibulare (Fig. 163, I/o.\ while the lower lip is
called labium tympanicum (Fig. 163, Lt.); the space between the
two lips has received the name of recessus internus. The crista
spiralis is divided by a number of parallel furrows, which gives
the surface a regular toothed appearance when seen from the
vestibular surface. Hence, the portions between the furrows
are called "auditory teeth."

The under (vestibular) of the two lips is connected with
the membrana basilaris (Fig. 163, Hn, Zp'\ which is com-
posed of two layers of finely fibrillated connective tissue,
'and is covered on its tympanic surface by a layer of endothe-
' Hum, and on the surface turned toward the ductus cochlearis
by the organ of Corti and its supporting cells. The inner
layer of this fine connective tissue is directly continued into
the bases of the pillars of the organ of Corti next to be de-
scribed.

The organ of Corti, so named from its discoverer, is a com-
plicated arrangement of cells in which the nerve terminates,
and of otner cells and their modifications, which apparently
act as supports to these and as modifiers of the sound. The
cells proper, in which the nerve terminates, have received the
name of hair-cells, from the ciliated appendages which they
carry (Fig. 163, a, a", a", a"\ while the peculiar modified cells
which are their chief support are called the pillars.

The pillars (Fig. 163, ft, fa) are two slender, slightly shaped
bodies, of a finely fibrillated structure, showing, however, in
their early stages, the presence of nuclei. They stand upon
the membrana basilaris, and are apparently to be directly fol-
lowed into the fine layer of connective tissue beneath them.
They are arranged in two rows, named inner and outer, ac-
cording to their situation as regards the modiolus. The pillars
are inclined toward each other, and the space between them is
named the tunnel. The head of the outer is a little enlarged

THE EAR,

and rounded, lying in a shallow depression in the head of the
inner pillar, thus resembling a ball and socket-joint (Fig. 163,
gia}. The heads of the pillars, when seen from the surface, have

Fio. 1(53. — Section through the dnctna cochlearis of a young dog : K-r', Reissner's membrane ; Los
and Los', vestibnlar and tympanic platen of the osseous lamina ; asp, ganglion spiritl*1 ; n, fine nervee
pawing through the habenula perforata at Jfn ; Cr, crista spiralia ; Lr, its vestibuln or upper lip ;
rm, Mt, m', the membrana tectoria (Corti's membrane); 8*tH, recessim internns clothed with epil he-
lium ; fl and /a, inner and outer pillarx of Corti , a and n", a", a", inner and outer liair-oells. between
the latter arc seen the fl.ink-Hhaped cells, r, r, r ; Tn. nerve passing through the tunnel to reach one of
the outer lmir-cell« : J/t. Hennon's prop-cells : ST>, Zt/ zona pectinata ; gta, inner and outer heads of the
pillars of Corti : A'/', plate called plialynx. which, when joined with its neighbors, forms the lamina n-ti-
cularis, in which the ends of the hair-oella are supported ; Li>p, ligamentum spirale ; <!>'t), stria voacu-
laris. AfUT Lax-dowsky.

366 MANUAL OF HISTOLOGY.

prolongations shaped a little like the bones of the fingers, and
hence called phalanges (Fig. 163, Kp). These enclose spaces be-
tween them, through which the ends of the hair-cells project.
The network thus formed is called the lamina reticularis, and
gives a very peculiar appearance when this portion of the organ
is viewed from above.

Corresponding to the pillars are rows of hair-cells termed
inner and outer — a single row of the former (Fig. 163, a) and
four rows of the latter (Fig. 163, a", a", a"). The shape of
the cells of the inner row is cylindrical, having their base pro-
longed into a fine thread expanding into a foot-stalk, which
passes into the membrana basilaris. The top of the cell which
passes through the opening in the lamina reticularis is pro-
vided with fine cilia. The four rows of cells in connection with
the outer pillar are of the same shape as those of the inner
row, but, in addition, are joined at their lower part to peculiar
cells shaped like a flask, large and rounded at the bottom, and
tapering to a long and narrow neck. The tops of these cells
reach to the lamina reticularis, but do not pass through it
(Fig. 163, r, r, r, and 5). Immediately adjoining the outer rows
of hair-cells are several rows of cylindrical epithelial cells (Hen-
son's prop-cells) (Fig. 163, ffz), which pass gradually into the
short cubical epithelium forming the zona pectinata (Fig. 163,
Zp to Zp') adjoining the epithelial lining of the ductus cochle-
aris.

The course of the nerve has already been followed to the
ganglion spirale. From this point a number of fine trunks
pass through a canal in the osseous portion of the lamina spi-
ralis to the lower lip of the crista, which they leave as naked
axis-cylinders by a number of small holes, called the habenula
perforata (Fig. 163, Hri). After entering the ductus cochle-
aris they divide into two chief bundles, one distributed to the
inner hair-cells, and the other, passing between the bases of
the inner pillars, crosses the tunnel and then again passes be-
tween the outer pillars, and terminates finally in the outer
hair-cells. Beyond the fact that they apply themselves directly
to the surface of the hair-cells, their mode of ultimate ending
is not known.

From the upper edge of the crista spiralis, lying directly
upon it and covering the whole of the organ of Corti, is the
membrana tectoria (Corti' s membrane) (Fig. 163, Mt), a homo-

BIBLIOGRAPHY. 367

geueous mass in which indistinct striations are to be seen.
This is of the nature of a cuticular formation, and probably
acts as a damper, preventing excessive vibrations of the organ
of Corti.

BIBLIOGRAPHY.

RUEDINGER. The Eustachian Tube, etc. Strieker's Histology, New York. 1872.
TRAUTMANN. Der gelbe Fleck am Eude des Hammergriffes. Arch. f. Ohrenheilk.,

Vol. XL, p. 99. 1876.

URBANTSCHITSCH. Zur Anat. d. Gehorknochelchen des Menchen. Arch. f. Ohren-
heilk., VoL XL, p. 1. 1876.
POM TZ Kit. Ueber Auastomosen d. Gefassbezirk d. Mittelohres u. d. Labyrinths.

Arch. f. Ohrenh., Vol. XL, p. 237, 1877, and Wien. med. Woch., No. 30. 1876.
UiiBEit-LiEL. Die Membrana tympani secundaria. Monatsschr. f. Ohreuheilkunde,

No. 4. 1876.
LAVDOWSKY. Ueber d. akust. Endapparat d. Saugethiere. Arch. f. mikros.

Anat, Vol. XIII. , p. 417. 1877.
KUIIN. Untersuch. iiber den hautigen Labyrinth der Knochenfische. Arch. f. mikr.

Anat., Vol. XIV., p. 284. 1877.
MOLDENHAUER. Beitr. zur. Anat. u. Entwickel. d. Menschl. Gehororganes.

Arch. f. Ohrenheilkunde, Vol. XL, p. 225. 1877.
DORAN. Morphology of the Mammalian Ossicula Auditus. Trans. Linn. Soc. ,

London, Second series, VoL I. 1877.
UEBER-LIEL. Der Aqueductus cochleae beim Menschen. Monatsschr. f. Ohrenheilk.,

VoL XIII., No. 3, p. 33, 1878-79, and Virch. Arch., Vol. LXXVII., p. 207,

1879; also Arch. f. Anat. u. Phys., Phys. Abtheilung, p. 188. 1878.
CISOFF. Ueber d. Gehorlabyrinth d. Knorpelfische. Sitz. d. Naturf. Gesellsch. an

d. K. Universit. zu Kasan. May, 1879. (Russian.)
PRITCHARD. The Organ of Corti in Mammals. The Lancet, 1876, p. 552, and

Proc. Roy. Soc., Vol. XXIV., No. 168, p. 346, 1878 ; also The Termination of

the Nerves in the Vestibule and Semicircular Canals of Mammals. Quart.

Journ. Micros. Sc., New Series, No. 64, VoL XXI., p. 398 1879.
MINOT, C. 8. Recent Investigations of the Histology of the Scala Media Cochleae.

American Journal of Otology. April, 1881.

PART III.

CHAPTEK XXII.

THE NASAL FOSSJE, PHARYNX, AND TONSILS.

BY D. BRYSON DELAVAN, M.D.

Curator of the New York Hospital, New York City ; Member of the American Laryn-

gological Association.

The vestibulum nasi is that part of the nasal canal which
is surrounded by the anterior cartilages of the nose. It is cov-
ered by a continuation of the exterior skin, which gradually
assumes the characteristics of a mucous membrane and pos-
sesses several layers of pavement-epithelium, the uppermost
of which is composed of horny cells. This epithelium extends
backward to the anterior margin of the inferior turbinated
bone and the commencement of the inferior nasal duct, where
it becomes ciliated. The integument has also vascular papillae,
with both simple and compound loops, and in the lower part
of the nose long, stiff hairs (vibrissae), as well as large sebaceous
follicles. It is sparingly supplied with blood-vessels. The
nerves are derived from the trigeminus, and consist of fila-
ments, which probably end in terminal bulbs.

The respiratory region. — The nasal fossae proper, with the
exception of a limited part known as the olfactory region, may
be regarded as a continuation of the respiratory tract. Each
fossa communicates with four sinuses : the frontal, the sphe-
noidal, the maxillary or antrum Highmorianum, and the pos-
terior ethmoidal. The mucous membrane covering the respira-
tory region and its accessory sinuses is called the Schneiderian
or pituitary membrane. It is devoid of papillae, and is covered
with a cylindrical ciliated epithelium, like that of the trachea,

THE NASAL FOSS.<E, PHARYNX, AND TONSILS. 369

the ciliary current Being invariably toward the choanse (poste-
rior nares). It contains, also, goblet-cells. Under the epithe-
lium is a true membrana mucosa, which forms at the same
time a periosteum for the bones, and is composed almost en-
tirely of connective tissue, scantily permeated, if at all, with
elastic tissue-elements. The mucous membrane may be divided
into two varieties : a thinner membrane, covering the internal
surface of the turbinated bones and the accessory sinuses, and
the thicker membrane of the nasal fossse proper.

The thinner membrane contains many acinous glands. In
the adjacent cavities they are less abundant, excepting upon
the internal wall of the maxillary sinus. Here, and in the
sphenoidal sinus, the glands consist of several cylindrical
tubes with connecting single oblong acini. The epithelium of
the latter is pyriform, while in the tubes it is C37lindrical. The
mucous membrane itself is pale in color, and scantily supplied
with blood-vessels. Special nerve-terminations have been de-
scribed in these sinuses. These are probably nothing more
than terminations of fibres from the great sympathetic, having
at their extremities ganglionic cellules.

The thicker membrane covers the lower part of the nasal
septum and the inferior and middle turbinated bones. It is
lined with the same ciliated epithelium, and in the anterior
two- thirds of the turbinated bones forms only a delicate,
slightly corrugated covering for the subjacent parts. Poste-
riorly, however, its surface is thrown into numerous thick
folds, evidently designed to increase the extent of surface of
the mucous membrane.

The membrana mucosa forms a fibrous network, which
passes between the glands and vessels and connects the mu-
cous membrane with the periosteum. Its characteristics re-
semble more nearly those of periosteum, so that it may properly
be classed as a part of the latter. The glands of this region
vary somewhat from the acinous type, and are composed of
tortuous tubules, having many sinuses and oblong offshoots.
They are lined on their inner surface with low cylindrical epi-
thelium, and sometimes assume a circular, sometimes an oval
or tubular shape in the microscopic section. The thickness of
the pituitary mucous membrane is due not only to its mucous
glands, but more particularly to the existence in it of true erec-
tile tissue, as well as venous plexuses. (See p. 160). These are
24

370 MANUAL OF HISTOLOGY.

most abundant at the posterior extremity of the inferior tur-
binated bones. Some of these vessels are prolonged throughout
the continuity of the bone on the lateral as well as the median
side, to appear with greater frequency at the anterior extrem-
ity, without, however, regaining the number or size which they
possessed at their origin. Where they are less numerous the
remaining space is almost entirely occupied by large mucous
glands.

In the bony framework of the inferior turbinated bone, large,
bright interspaces are seen in the fine trabecular substance,
which are filled with fibrous tissue containing pale lymphoid
cells. In this fibrous tissue are usually found transverse sec-
tions of delicate vessels, the walls of which are apparently
composed of fibrous tissue. In order to reach the outer sur-
face these vessels either perforate the bone or lie in recesses
separated from the soft parts only by the periosteum. In the
middle three-fifths of the bone, where the osseous structure
contains the largest cavities, we find in the vicinity of the ves-,
sels large, round, and polygonal, glistening cells, analogous to
marrow-cells. A recent author believes most of the above-
mentioned vessels to be lymphatics. The arteries of the infe-
rior turbinated bone do not number more than three or four,
and are derived from the posterior nasal artery.

TJie olfactory region is situated in the uppermost portion
of the nasal cavity. Its inferior limit in man has not yet been
accurately determined. According to the generally received
views of Schultze and Ecker, it is probably limited to the roof
of the nasal fossae, the superior turbinated bone, and the cor-
responding part of the septum. The mucous membrane of this
region is of a dull, yellowish brown color, and is perceptibly
thicker and softer than that of the respiratory region. This
color proceeds from fine pigment-molecules, which are em-
bedded partly in the bodies of the cylindrical epithelial cells,
and partly in the cells of an especial gland-formation found
here. Soon after death, however, it becomes unrecognizable.
Under the microscope the olfactory region is seen to be bound-
ed by a tolerably well-defined, serrated border, although isl-
ands of ciliated epithelium, such as is found in the respira-
tory region, are frequently found scattered about in different
parts of it. The differences of structure in the olfactory mu-
cous membrane depend upon the character of the epithelium,

THE NASAL FOSSAE, PHARYNX, AND TONSILS. 371

the occurrence of peculiarly constructed glands — Bowman's
glands — and upon the relations of the nerves.

The fundamental layer of the mucous membrane is com-
posed of a finely fibrillated connective tissue, rich in cells, the
arrangement of which is determined by the numerously dis-
tributed glands, nerves, and vessels which it contains. As. in
the other regions of the nasal cavity, the iriucosa seems to pass,
without a well-defined limit, into the periosteum. In many
places aggregations of small pigmented nuclei are found, some
in the shape of long strips lying near the nerve-branches, some
in other situations, in rounded or irregular groups.

The olfactory epithelium attains a considerable thickness.
It consists of a single layer of very elongated cells, which
Schultze has proved to be of two kinds, epithelial cells and
olfactory cells.

The olfactory cells are slender, delicate structures, in which
may be distinguished a cell-body and two prolongations going
in opposite directions — the one to the periphery, the other cen-
trally. The bodies of the olfactory cells are not all located in
the same plane of the epithelial stratum. The majority, how-
ever, occupy its deeper portions. The cell-body appears spin-
dle-shaped or pyriform. It is finely granulated, and has in its
central and widest portion a spherical, light-colored, ill-de-
fined nucleus. The peripheral prolongation is generally rod-
shaped, but now and then presents slight sinuosities. It is
sharply outlined and homogeneous, and its free extremity, in
some animals (amphibia and birds), has a tuft of the most deli-
cate hairs, which project above the surface of the epithelium.
In man this is not the case. The opposite prolongation is ex-
tremely delicate and perishable, and, by some methods of
preparation, resembles the finest nerve-fibrils, sometimes cov-
ered with varicosities, at others entirely smooth. It runs con-
tinuously and undivided as far as the base of the epithelial
stratum, where it appears to meet the final radiations of tin;
olfactory nerve, partly intertwines with these radiations, and
then escapes further investigation.

The indifferent epithelial cells appear in the form of an
elongated cylinder with a very fine, granulated cell-body and
an ellipsoid nucleus. Near the latter the cell suddenly con-
tracts into a slender, veiy pale, centrally directed prolongation,
the inferior end of which becomes somewhat wider, and

372 MANUAL OF HISTOLOGY.

branches into a number of delicate filaments, by means of
which the cell is attached to the fundamental layer of connec-
tive tissue. These widened extremities of the cells often con-
tain a brownish, partly nuclear, partly diffused pigment.
Viewed upon the plane surface, the number of olfactory cells
is apparently larger than that of the cylindrical cells. Each
one of the latter, however, is generally surrounded by six of
the olfactory cells, which completely fill the intermediary
spaces between the cylindrical bodies. Both varieties of cells
are so accurately adjusted to each other that, especially in the
wider portion of the epithelial cells, fine longitudinal furrows
may be seen, into which the peripheral continuations of the
olfactory cells have been received.

The surface of the epithelium is covered by a delicate mem-
brane, discovered by Von Brunn, and called by him the mem-
brana limitans olfactoria. He has compared it to themembrana
limitans externa of the retina, and describes its free surface as
being plane and even, while its lower surface covers completely
the rounded terminations of the epithelial cells. The periph-
eral prolongations of the olfactory cells pass through this
membrane, and terminate with bare extremities at the level of
its free plane.

The olfactory nerves. — The branches from the olfactory
ganglia which emerge through the apertures of ,the lamina cri-
brosa are composed entirely of non-medullated filaments, which
resemble embryonic nerve-fibres. They next anastomose in the
deeper layers of the mucous membrane, and form a dense
plexiform meshwork, which sends fine branches toward the
surface. In these branches the axis-cylinders are broken up
into numerous, very fine, varicose fibrils, which ascend to the
limit of the epithelial layer, where they are lost. Most au-
thors agree with Schultze that there is a distinct connection
between the nerve-fibrils and the olfactory cells. Exner be-
lieves that the nerve-fibrils connect with the epithelial cells
also. He argues, moreover, that intermediary forms, between
the two varieties of epithelium, are found, which would prove
that they are not different structures, but one and the same.
Neither of these views has yet been established.

Bowman' s glands, peculiar to the olfactory mucous mem-
brane, are found in it in large numbers. They occupy almost
the whole thickness of the mucous membrane, their bodies be-

THE NASAL FOSSAE, PHARYNX, AND TONSILS. 373

ing located in the deeper layers of the connective tissue. In
man their shape varies somewhat from that of simple tubules,
as several glandular tubes ordinarily unite in a common excre-
tory duct, so that, in some cases, the gland almost appears
racemose. The glandular cells are partly round, partly irreg-
ular in shape, and have many pale nuclei, together with a
brownish-colored pigment.

THE PHARYNX.

The mucous membrane of the pharynx is, in general, simi-
lar to that of the mouth. It consists essentially of a stratified
pavement-epithelium, a rather loosely woven submucosa, which
contains aggregations of mucous glandules, and a tunica pro-
pria composed of fibrillary connective tissue and furnished
with papillae. The papillae are smaller than those found lower
down in the oesophagus. The mucous glandules are most
abundant in the superior part of the pharynx. The mucous
membrane of the vault of the pharynx, and in the vicinity of
the isthmus of the fauces, where it becomes continuous with the
mucous membrane of the nasal cavity, to some extent assumes
the characteristics of the latter. In this region the connective
tissue is more or less thickly interspersed with lymphoid cells.
It is provided, moreover, with ciliated cylindrical epithelium.
In adults this epithelium extends some distance backward until
it passes into the stratified pavement variety. In children,
however, ciliated epithelium lines the whole naso-pharynx.
In the upper and lateral parts of the pharynx are found cer-
tain aggregations of adenoid tissue, most abundantly in the
vault of the pharynx, extending from one Eustachian tube to
the other. This tissue is generally quite diffuse, but is identi-
cal in its structure with the lingual follicular glands arid with
the tonsils, and from this resemblance it has derived the name
"pharyngeal tonsil."

THE TONSILS.

The tonsil consists essentially of a reduplication, more or
less extensive, of the oral mucous membrane, containing in its
folds an abundance of the so-called adenoid tissue.

374 MANUAL OF HISTOLOGY.

Its gross structure varies in different animals. In some the
organ is entirely absent. Its simplest form is found in the rab-
bit, where it resembles a large lingual f ollicular gland. In man
its usual shape is ovoid. Its average vertical diameter is 20
mm., and its transverse diameter 13 mm. Its surface is per-
forated by a varying number of slit-like and circular depres-
sions, the common orifices of the system of cavities which it
contains. If the tonsil of the rabbit be considered a single
follicular gland, we have in man a multiplication of this to the
number of from eight to eighteen, the interval between each
gland forming a "lacuna tonsillaris," crypt, or one of the sys-
tem of cavities mentioned above. There are also in the interior
of the tonsil single larger cavities, each of which includes sev-
eral follicular folds and procures their common discharge at
the periphery. The crypts generally are filled, more or less,
with a yellowish substance composed of fat-molecules, detached
pavement-epithelium, lymph-corpuscles, small molecular gran-
ules, and cholesterin-crystals, which probably proceed from
retained and decomposed epithelial matter, and perhaps now
and then from the bursting of follicles whose cells have in-
creased by proliferation and have undergone retrograde meta-
morphosis and fatty degeneration. In its minute anatomy the
tonsil is for the most part like other so-called adenoid glands.
In common with the rest of the oral cavity, it is invested with
a thick covering of pavement-epithelium, which rests upon a
delicate endothelioid basement-membrane. Following this is a
tolerably compact mucosa, formed of interlacing bands of
fibrous connective tissue and containing many connective-tis-
sue corpuscles. In the normal adult tonsil this structure is so
delicate that sometimes it is hardly recognizable. From it
bands of connective tissue extend centrally into the larger ton-
sillary folds, and the whole forms essentially both an enclosure
and a framework for the adenoid tissue or proper substance of
the gland, as well as a nidus for its vessels. The minute struc-
ture of the adenoid tissue of the tonsil does not differ from
that of other follicular glands (those of the intestine, etc.), de-
scribed elsewhere. Occasionally, in the tonsil the adenoid tis-
sue extends so near the periphery as to penetrate the mucosa
and encroach upon the epithelial layers. This is especially
the case in the walls of the crypts, where the epithelium com-
monly exists in a modified form, or is altogether wanting. The

BIBLIOGRAPHY. 375

tonsil is supplied abundantly with racemose mucous glands,
which are most numerous in the neighborhood of the hilus.
Here, also, may be found small bundles of muscular fibres
apparently independent. '

BIBLIOGRAPHY.

KOLLIKER. Ueber das Geruchsorgan von Amphioxus. Miiller's Archiv fur Anat.

und Physiol. 1843.

KOHLUAUSCH. J. Miiller's Archiv, pp. 8, 149. 1853.
ECKER. In Berichte iiber die Verhandlungen zur Beforderung der Naturwiss.

No. 12. Fribourg, 1855.
SCHULZE, MAX. Ueber die Endignngsweise der Geruchsnerven und die Epithelial-

gebilde der Nasenschleimhaut. Monatsberichte der konigl. Acad. der Wis-

sensch. Berlin, 1856.
ECKER. Ueber die Geruchsschleimhaut des Menschen. Zeitschrift f . wiss. Zoologie.

VIII., p. 305. 1856.
ECKER, A. Bericht iiber die Fortechritte, Anatomie und Physiologic f. d. Jahr

1856, p. 117. Von Henle und Meissner.

TODD and BOWMAN. The Physiological Anatomy of Man. II. London, 1856.
SEEBERG. Disquisitiones Microscopical de textura membranae pituitariiu nasi. Diss.

Inaug. Dorpati, 1856.
KOLLIKKU. Ausbreitung der Nerven in der Geruchsschleimhaut von Plagiostomen.

Sitzber. der physik.-med. Gesellschaft, T. VIII., pp. 31. Wiirtzburg, 1857.
ERICHSEN. De textura nervi olfactorii ejusque ramorum. Tb, inaug. Dorpat,

1857.

HOYER. De tunicaB mucosaa narium structura. Berolini, 1857.
ECKHARDT. Ueber Endigungsweise der Geruchsnerven. Beitrag zur Anatomie

und Physiologic. 4. Abhand., p. 97. 1858.
GASTALDI. Nuovi Ricerche sopra la terminazione del nervo olfactorio, in memorie

de 1'Acad. reale della Scienza de Torino. XVIL, p. 372. 1858.
FUNKE, O. Lehrbuch der Physiologic. 2. Auflage. 1858.
KSLLIKER. Handbuch der Gewebelehre. 3. Auflage, p. 680. 1859.
HOYER. Ueber die mikroskopischen Verhaltnisse der Nasenschleimhaut. In Miiller's

Archiv f. Anat. und Physiolog., 1861, p. 287 ; 1860, p. 6.

CLARKE, LOCKHART. Ueber den Bau des Bulbus olfactorius und der Geruchs-
schleimhaut. Zeitsch. f. wissens. Zoologie. XI. 1862.
WALTER, G. Ueber den f eineren Bau dea Bulbus olfactorius. Virchow's Arch. , T.

XXII., p. 261. 1862.

HENLE. Handbuch der systematischen Anatomie des Menschen. Bd. II. Braun-
schweig, 1866.
ZERNOFP. Ueber das Geruchsorgan der Cephalopodon, Bull, de la Soc. imp. des

sc. nat. de Moscow. 2e seVie. XLII. 1869.
EXNER. Weitere Studien iiber die Structur der Riechschleimhaut bei Wirbelthie-

ren. Sitzungsberichte der k. Akad. der Wissenschaften. Wien. Band LXV.

3. Abth. 1873. Et Bd. LIU. 1867-1869.

376

MANUAL OF HISTOLOGY.

HKIDENHAIN, A. Ueber die acinOsen Driisen der Schleimhaute, ins besondere der

Nasenachleimhaut. Diss. Inaug. Breslau, 1870.
SCHULZB, MAX.- Untersuchungen iiber den Bau der Nasenschleimhaut. InAbhand-

lung. d. naturforsch. Gesellschaft. VII. Halle, 1872.
BABUCIIIN. Das Geruchsorgan. In Strieker's Handbuch. 1872.
MARTIN. Studies from the Physiol. Lab. in the University of Cambridge. L 1873.
CISOFP. Zur Kenntniss der Regio Olfactoria. Centralblatt. 1874.
BIGELOW, H. J. On the Anat. of the Turbinated Corpora Cavernosa. Boston, Med.

and Surg. Journal. April, 25, 1875.
SHOPIELD, R. N. A. Taste-Goblete in the Epiglottis of the Dog and Cat. Journal

of Anat. and Physiol. X., p. 475. 1876.

HONIGSCHMIED. Ztschr. f. wiss. ZooL XXIX., S. 255. 1877.
DAVIS, C. Die becherf 6'nnigen Organe des Kehlkopf es. Arch. f. mikroskop. Anat. ,

XIV., S. 158. 1877.
PODWISOTZKY. Anatomische Untersuchungen iiber die Zungendriisen des Menschen

und der Saugethiere. Inaugural Dissertation. Dorpat, 1878.
LdWE. Beitrage zur Anatomic der Nase und Mundhohle. S. 20. Berlin, 1878.
ZUCKERKANDL. Ueber die norm, med.-path. Anat. der Nasen- und angrenzenden

Hohlen. AIL Wien. med. Ztg., No. 51. 1879.
STEINBRUQQE, H. The Histology of the Inferior Turbinated Bones and of the Tele-

angiectatio Fibromata Arising from These. Archives of Otology, New York,

Oct., 1879.

CHAPTER XXIII.

THE MOUTH AND TONGUE.

BY D. BRYSON DELAY AN, M.D.

Curator of the New York Hospital, New York City ; Member of the American Laryn-

gological Association.

WITH the exception of a few remarkable modifications, the
structure of the mucous membrane of the buccal cavity is the
same throughout.

The tunica propria consists of fibrillated connective tissue,
made up of tolerably minute bundles of intertwining filaments.
Between these appear many delicate, elastic fibres. Toward
the epithelium this structure becomes less distinct, and an ex-
ceedingly delicate, filamentous network is developed. The con-
nective-tissue cells with their nuclei, on the other hand, become
more marked. The surface of the tunica propria contains
many slender papillae, which penetrate more or less deeply
into the epithelial covering. They have, also, the above-men-
tioned filamentous structure, but contain few cellular elements.

The transition of the tunica propria into submucous connec-
tive tissue is, in general, hardly perceptible. The latter, how-
ever, contains fewer elastic filaments and broader bundles of
connective tissue. The epithelium lining the buccal cavity is,
throughout, stratified pavement. The mucous membrane of
the mouth varies in different regions as to the thickness of its
different strata, the height of its papillae, and the condition of
the submucous tissue. It is thickest and firmest in the gums
and near the palate — particularly in the posterior section of the
hard palate — and thinnest in its reduplications, e.g., the frce-
num linguae, glosso-epiglottic fold, and the pillars of the fau-
ces. Its firmness in the above places is due to the density of
the submucosa, which forms, with the underlying periosteum,
one compact mass of connective tissue.

378 MANUAL OF HISTOLOGY.

Elsewhere the mucosa is looser, so that the mucous mem-
brane is readily thrown into folds. It is thickest wherever it
has intervening layers of- glands. In some places, especially
in the lips and soft palate, the submucosa is crossed by bun-
dles of striped muscular fibres, which are connected partly
with the submucosa, and partly with' the tunica propria. The
papilla of the mucous membrane are most developed at the
margin of the lip and its immediate vicinity, as well as on the
gums, attaining here a height of 0.5 mm., and often termina-
ting in a double point. In the reduplications of the mucous
membrane (the frsenum linguae, etc.), and partly in the region
of the hard palate, the papillae are very small, sometimes rudi-
mentary. The thickness of the epithelial layer is proportion-
ate to the height of the papillse. Beginning at the vermilion
border of the lips, and going backward, the epithelial cov-
ering becomes progressively thicker, and is thickest at the
posterior margin of the lip, decreasing rapidly on the pos-
terior surface. Upon the cheeks and on the anterior surface
of the hard palate the epithelium is of medium thickness ;
it is thinnest on the floor of the mouth and on the above-
mentioned reduplications. There are, however, deviations in
these proportions, especially in the hard palate, where the
papillse are in some cases absent. Moreover, the tunica pro-
pria sometimes assumes an almost tendinous character. Cer-
tain important aggregations of glands, the so-called mucous
glandules, are found lodged in the submucous connective tis-
sue of the mouth. These are the labial, buccal, palatal, and
molar glandules. They are found as white, sharply defined
knobs, visible to the naked eye upon the posterior surface of
the lips, as well as upon the cheeks, palate, and bottom of the
buccal cavity. In some cases they are aggregated into a few
large clusters, while in others they are more scattered and
smaller. The orifices of their ducts are best seen in the lining
membrane by everting the lips or cheek. They belong to the
acinous type, and have a short duct, generally somewhat
curved, relatively wide, but somewhat contracted at the ori-
fice. The greatest width of the tubes is at their place of seg-
mentation. On the branches themselves are smaller ramifica-
tions, which either terminate directly with globular or ellipsoid
alveoli, or previously divide into one or more twigs. It often
happens that a small group of acini, with a narrow common

THE MOUTH AND TONGUE. 379

duct, situated near a larger duct, discharge into the latter near
the surface of the mucous membrane, appearing like a small
accessory glandule. The walls of the glandules consist of a
structureless basement-membrane, upon the interior surface of
which are superimposed cylindrical, clear, almost homogene-
ous-looking cells, with oblong nuclei.

As for the connection of the buccal mucous membrane with
the underlying structures, different conditions obtain in differ-
ent regions. Its connection with the hard palate and gums
has been described above. Where it is superimposed upon a
sharply defined muscle, e.g., over the floor of the mouth, and
over the sublingual gland, it passes into the connective- tissue
sheath of the part.

The blood-vessels of the mucous membrane are arranged in
two systems of superficially extended networks. The deeper
one, located in the submucosa, is composed of the mutually
anastomosing branches of the afferent and efferent vessels.
From this network many smaller vessels penetrate into the
tunica propria, which, by division into still smaller branches,
and by frequent anastomoses with one another, form the more
superficial and finer-meshed vascular net. In both nets the
venous and arterial branches run tolerably parallel. From the
superficial network very fine branches enter the papillae, where,
according to their size, they form either capillary nets or sim-
ple loops.

The lymphatics form wide networks in the submucosa,
and narrow nets in the tunica propria. Single small vessels
cross those of the vascular nets. That lymphatics pene-
trate the papillee is doubtful. The nerves of the buccal mu-
cous membrane form in the submucosa more or less dense
plexuses, in which many separations of the single nerve-fibrils
may be noticed. Thence numerous filaments, partly isolated,
partly arranged in small bundles, and always medullated,
ramify, and radiate in wider ramifications toward the super-
ficial layers of the mucous membrane. A certain number
of nerve-fibrils approach the papillae, to implant themselves
either at their bases or at the centre of their apices, some-
times even at their extremities, in the terminal bulbs of
Krause. Such fibrils are most abundant in the lips and in the
anterior surface of the velum palati, and in smaller quantity in
the cheek and bottom of the mouth. Nerve-fibrils may some-

380 MANUAL OF HISTOLOGY.

times be seen also with double contours, which wind, during
their course, into a coil in the superficial layers of the mucous
membrane.

THE TONGUE.

Although the mucous membrane of the tongue is, in the
general details of its construction, similar to that of the rest of
the buccal cavity, it nevertheless presents some striking pecu-
liarities, mainly due to the configuration of its upper surface.
This is covered by many closely aggregated prominences of
the mucous membrane — the lingual papilla — which give it a
roughened, fungoid appearance. Upon the under surface of
the tongue the papillae are absent, but the mucous membrane
here contains a large number of follicular glands. The lateral
edges of the tongue are here and there covered with lingual pa-
pillae, which are often arranged in rows, and toward the base
of the tongue are replaced by the so-called fimbricB linguce.
Besides simple papillae, analogous to those of the skin, the lin-
gual mucosa is studded with three distinct varieties of com-
pound papillae — the filiform, the fungifonn, and the circum-
vallate. These are distinguished from the ordinary papillae of
the mucous membrane, not only by their large size and their
peculiar shapes, but also by their complicated structure, by the
arrangement of their secondary papillae, and the conditions of
their epithelial coverings. Between these three forms are
several intermediary ones. The filiform papilla are found all
over the dorsum of the tongue, anterior to the line of the cir-
cumvallate papillae. Not only in different individuals, but
also in the same tongue, there are marked variations in their
form. At the tip and lateral edges of the tongue they are
always smaller, and their filaments are wanting or merely ru-
dimentary. Toward the centre of the tongue they gradually
become larger and more abundant, and attain their highest
development in the angle made by the circumvallate papillae.

Their shape is that of a truncated cone, which has at its
free extremity a central hollow or depression, around which is
arranged, in a circular manner, a collection of thread-like pro-
jections, or secondary papillae. Like the rest of the mucous
membrane of the tongue, they are covered with stratified pave-
ment-epithelium. In the secondary papillae of the larger fill-

THE MOUTH AND TONGUE. 381

form papillae the epithelium is of the horny variety, and its
arrangement is imbricated, the lower margin of each scale over-
lapping the upper border of the scale next below it. In the
axes of the filiform papillae large-sized arterial and venous
capillaries extend. Each secondary papilla contains a vascu-
lar loop. The papillae of smallest size contain a fine network
of vessels, and in the posterior part of the tongue simple capil-
lary loops. Neither the filiform papillae nor their secondary
papillae contain nerve-fibrils. The latter are found, however,
at the base of the papillae, where they end in rounded terminal
bulbs.

The fungiform papilla are larger than the filiform, and
their epithelial covering is much thinner. They appear as
rounded prominences, somewhat constricted at the base, and
covered upon the sides and top with many cone-shaped second-
ary papillae. The free surface of some fungiform papillae is
smooth, the secondary papillae being farther apart. These are
found most commonly at the lateral edges of the tongue, and
are the so-called lenticular papillae. The distribution of the
fungiform papillae is rather irregular, and it varies in different
individuals. At the base of the tongue, and generally at its
lateral portions, between the filiform papillae, they are some-
times scarce and sometimes quite abundant. Toward the tip
of the tongue they are smaller, while they are larger in the
region of the circumvallate papillae. They are covered with
several layers of pavement-epithelium, the deeper strata of
which are formed by smaller polygonal prickle-cells. In this
epithelial covering, upon the surface of the fungiform papillae,
are constantly found peculiar bodies, called the "taste-goblets."

The taste-goblets vary in size and shape in different ani-
mals, and also in the same animal, according to the locality
in which they are found. They usually resemble a short-
necked flask, their longest diameter being the longitudinal.
The lower part of the taste-goblet rests upon the submucosa ;
the body, and more especially the part which corresponds to
the neck of the flask, is surrounded by epithelial cells. Every
taste-goblet has at the surface of the epithelium an opening
called zporus, which word is frequently used not only to des-
ignate the exterior opening, but also for the entire short canal
in the epithelial layer. The diameter of the porus is from
.0064 to .0198 mm. It is surrounded by two and sometimes by

382 MANUAL OF HISTOLOGY.

three similarly formed cells. Sometimes the poms is formed
by a single- perforated cell. The short canal in the epithelial
cells is surrounded in like manner. In each taste-goblet two
varieties of cells may be distinguished — the exterior or super-
ficial cells, called roof- or supporting-cells, and the interior, or
central cells, called taste- or rod-cells. The roof -cells, which
may be considered as modified epithelial cells, surround the
taste-goblets as petals envelop a bud. Their arrangement with
relation to one another is imbricated. The cells themselves
are long, narrow, spindle-shaped, arid curved, and each one
has a well-marked nucleus. The peripheral end of the cell is
pointed, while the central extremity is sometimes ramified.
The taste- or rod-cells are long, slender, and highly refractive.
A nucleus of unusual size almost entirely fills their bodies, while
their extremities pass into two distinct prolongations — the pe-
ripheral or superior, and the central or inferior. The peripheral
prolongation is moderately broad, and has a short, delicate
extremity, which resembles a small rod or hair. Hence the
name rod-cell. These rods are located inside the short canal,
and rarely project above the porus. The inferior prolongation
is divided into several rootlets. The connection of nerve-fila-
ments with the taste-goblets has never yet been conclusively
demonstrated, although all authorities agree as to the proba-
bility of such connection. Many aggregations of ganglionic
cells, of greater or less size, are found in the course of the
nerve-bundles, near the circumvallate as well as near the fili-
form papillae. In the fungiform papillae the nerves enter the
axis of the papillae as small trunks, composed of fibres with
double contours. These divide into single nerve-filaments,
some of which terminate in bulbs, which are located in the lat-
eral surfaces of the fungiform papillae, under the secondary
papillae. The fibrils which run into the axis pass into pale ter-
minal filaments, and disappear in a brush-like extremity in a
granular mass composed of neurilemma— its nuclei, and nu-
merous circular granules — the gustatory granules. These last
consist of a globular nucleus, surrounded by a very small
amount of cell-protoplasm. The resemblance of the above to
the interior roof-cells of the acoustic terminal apparatus, and
to the rods and cones of the retina, is striking.

The conical or secondary papillae are of the same general
construction us the fungiform throughout ; but they present

THE MOUTH AND TONGUE. 383

the following differences of appearance : their epithelial cover-
ing is thicker, and stratified somewhat after the manner of the
filiform papillse, the taste-goblets are absent upon their sur-
face, and the nerve-fibres, so far as they can be traced, termi-
nate in bulbs.

The circumvallate papilla, about nine in number, are situ-
ated at the back part of the tongue. They form an irregular
row on each side and incline slightly from before backward
toward the median line. At their point of junction is t\\Q fora-
men ccecum of Morgagni. Each circumvallate papilla consists
of a broad, flat elevation of the mucous membrane, which is
surrounded with a fossa. Its surface is covered with small
secondary papillse, and the epithelium is like that of the
fungiform papillse. Taste-goblets are found abundantly upon
the lateral edges and toward the centre of the papillse. The
blood-vessels are arranged as in the fungiform papillse, and
each secondary papilla contains a vascular loop. The nerves
are derived from the glossopharyngeal. They consist of single
pale nerve-fibres, which form a network in the centre of the
papillae and ascend toward its peripheral surface.

The papilla foliatce, or fimbrise linguae, consist of several
folds of the mucous membrane at the lateral edges of the
tongue. Between them are scattered a few fungiform papil-
lse, and they contain a considerable number of taste-goblets.
Many excretory ducts of acinous glands empty at the bases of
these folds.

The sublingual mucous membrane includes that of the floor
of the mouth. Both are of the same structure, and pass into
each other by means of a reduplication, the frsenum linguse.

The secreting glands of the root of the tongue are of two
varieties — serous and mucous. The mucous glands are like
those elswhere in the buccal cavity. Their ducts are some-
times lined with ciliated epithelium. The glands themselves
are not found in the neighborhood of the taste-goblets. The
serous glands, on the other hand, are found most abundantly
in those parts of the tongue which are most richly supplied
with taste-goblets. Their ducts open into the grooves which
are lined by the taste-goblets.

The follicular glands, which form the collections of adenoid
tissue found at the base and at the sides of the tongue, are not
true glands, but rather elevations of the mucous membrane

384 MANUAL OF HISTOLOGY.

ciiused by circumscribed collections of adenoid tissue found in
the tunica propria. They resemble glands, in that they gener-
ally possess a cavity of variable size which terminates at the
surface of the follicle. The mass of adenoid tissue which com-
poses the follicle is surrounded by fibres of connective tissue,
which are sometimes so compactly woven as to form almost a
capsule around it. Sometimes this capsule is wanting, but a
gradual transition of the two neighboring forms of tissue is
never seen. Above, the adenoid tissue extends as far as the
epithelium, so that the papilla of the mucous membrane either
disappear altogether or are only to be found occasionally, and
then of small size. This adenoid tissue is in all its essentials
similar to that found in the tonsils, the vault of the pharynx,
and at scattered points in the adjacent tissues.

The so-called mucous corpuscles of the saliva are probably
lymph corpuscles which have escaped from the adenoid tissue
just mentioned.

BIBLIOGRAPHY.

ALBTOTJS. Academicarum Annotationum. Lib. I. S. 58. (Quoted by J. Honig-
schmied.) Leidce, 1754.

BOPP. Die Verrichtungen des fiinften Nervenpaares. Leipsig, 1832.

ELSABSER, in F. Majendie Lehrbuch der Physiologic, aus dem Franzosischen iiber-
setzt mit Anmerkungen und Zusatzen von D. C. L. Elsasser. 3 Aufl. I. Tu-
bingen, 1834.

MATER, J. F. C. Neue Untersuchungen aus dem Gebiete der Anatomie und Phy-
siologie. S. 25 und 26. Bonn, 1842.

BR0HL. Ueber das Mayer' sche Organ an der Zunge der Haus-Saugethiere oder die
seitliche Zungenrucken-Driise derselben. Vierteljahrschrift fur wiss. Veter-
inarkunde. I. S. 165. Wien, 1851. Kleine Beitrage zur Anatomie der Haus-
Saugethiere. Wien, 1850.

KiiLLiKER, A. Microscopische Anatomie. II. Specielle Gewebelehre. 2. Halfte.
1. Abth. Leipzig, 1852.

SCHWALBE. Das Epithel der Papillae vallatae. Vorlaufige Mittheilung. Arch. f.
microscop. Anat. III. S. 504. 1867. Derselbe ITeber die Geschmacks-
organe d. Saugethiere und des Menschen. Arch, f . microscop. Anat. IV. S.
154. 1867. Und M. Schultze, Erklarung der Entdeckung der Schmeck-
beoher von G. Schwalbe betreffend. Arch, i . mikroskop. Anat. VIII. S. 660.
1872.

LOVEN. Beitrage zur Eentniss vom Ban der Geschmackswarzchen der Zunge. Arch.
f. mikroskop. Anat. IV. S. 96. 1867.

SCHWALBE. Zur Kentniss der Papillae fungiformea d. Saugethiere. Centralblatt
f. d. med. Wisa. Nr. 28. S. 433. 1868.

BIBLIOGRAPHY. 385

VON WYSS. Ueber ein neues Geschmackaorgan auf der Zunge des Kaninchens.

Centralblatt f. d. med. Wiss. Nr. 35. S. 548. 1869. Derselbe, Die becher-

formigen Organe der Zunge. M. Schultze. Arch, fur mikroskop. Anat. VI.

S. 238.
KRAUSK. Die Nervenendigung in der Zunge des Menschen. Gottinger Nachrichten.

S. 423. 1870.
VERSON. Beitrage zur Kentniss des Kehlkopfes und der Trachea. Sitzgsbr. der

wiener Acad. 1 Abth. LVII. S. 1093. 1868. Derselbe, Kehlkopf und

Trachea in Strickers Handbuch der Lehre von den Geweben. I. S. 456.

Leipzig, 1871.
HiiNlGSCilMiED, J. Beitrage zur mikroskop. Auatomie der Geschmacksorgane.

Ztschr. f. wissensch. Zool. XXIII. S. 414.

EXNER. Med. chirurg. Rundschau, Juni Heft. S. 400. Wien, 1872.
DITLEVBEN. Undersjgelse over Smaglogene paatungun hos patte dyrene og men-

nesket. Kopenhagen, 1872. Referat in Hoffmann und Schwalbe Jahresb. I.

Lib. S. 211. 1872.
HONIGSCHMIED. Ein Beitrag ub. die Verbreitung der becherformigen Organe auf

der Zunge der Siiugethiere. Centralbl. f. d. med. Wiss. No. 26. S. 401.

1872.
HENLE. Handbuch der system. Anatomic des Menschen. II. 2. Aufl. S. 873.

1873.
VON EBNKR, RITTER. Die acinosen Driisen der Zunge und ihre Beziehungen zu den

Geschmacksorganen. Gratz, 1873.
SERTOLI, E. Osservazioni sulle terminazioni dei nervi del gusto. Gazetta Medico-

Veterinaria. IV. 2. Separatabdruck. Deutsch in Molesch. Unters. XI.

4. Heft. S. 403. 1874.
HOFFMANN, A. Ueber die Verbreitung der Geschmacksorgane beim Menschen.

Arch. f. pathol. Anat. LXII. S. 516. 1875.
WATSON, W. SPENCER. Diseases of the Nose and its Accessory Cavities. London,

1875.
VON BRUNN. Untersuchungen uber das Riechepithelium. Arch. f. mik. Anat.

No. 11. 1875.

KRAXTSE, W. Allgemeine und mikroskop. Anat. Hannover, 1876.
VOLTOLINI. Address delivered December 15, 1876, before the Silesian Association

for National Culture.
KRAUSE. Lehrbuch. Hannover, 1876.
KSiiLiKER. Ueber die Jacobson'schen Organe des Menschen. Festschrift zu Rineckers

Jubilaum. Leipzig, 1877.

PONCHET et TOURNEUX. Precis d'histologie humaine. 1878.
LUSCHKA. Das Epithelium der Riechschleimhaut des Menschen. Centralbl. f. die

med Wissenschaft. Nr. 22. 1877.

WUNDT. Lehrbuch der Physiologic des Menschen. Stuttgart, 1878.
25

CHAPTER XXIV.

THE ALIMENTABY CANAL.

BY EDMUND C. WENDT, M.D.,
Curator of the St. Francis' Hospital, etc., New York City.

THE human alimentary canal is a tube of great length, ex-
tending from the mouth to the anus. There are considerable
variations of its calibre in the different regions of the body
through which it passes. The two external openings of the
digestive tract are continuous with the cutaneous surface of
the body. Throughout its entire extent we find several super-
imposed layers or membranes, which are from within outward :
1, a mucous membrane with its submucosa ; 2, the muscular
coat ; and 3, a fibrous layer. In addition to these fundamental
strata, we encounter certain special structures, which charac-
terize the various parts of the canal. The buccal cavity and
pharynx are elsewhere described ; we begin, therefore, with a
consideration of

THE (ESOPHAGUS.

The walls of this section of the tract are directly continuous
with those of the pharynx, and have an average thickness of
from three to four millimetres. In the oesophagus, in addition
to the four pharyngeal coats, a new layer appears between the
epithelial stratum and the submucous tissue. This new struc-
ture has received the name of muscularis mucosae. Hence, the
different layers of the oesophagus are from within outward :

1. The mucous membrane.

2. The muscularis mucosse

3. A submucous layer.

4. The muscular coat.

5. A fibrous envelope.

The mucous membrane presents comparatively long, coni-

TfiE (ESOPHAGUS.

337

cal papillae of more or less dense connective tissue, containing
looped blood-vessels, and lined throughout by stratified pave-
ment-epithelium. These papillae attain a marked degree of
development in the adult only. In infancy their future pres-
ence is indicated by a wavy
outline at the internal attached
border of the epithelial stratum.
This latter portion qf the mu-
cous membrane contributes 0.22
— 0.26 mm. toward the entire
cesophageal thickness of about
4.0 millimetres.

The muscularis mucosce con-
sists chiefly of longitudinal, un-
striped muscle-cells. They are
disposed in bundles of differ-
ent sizes, separated by varying
amounts of connective tissue.
Toward the inferior portion of
the oesophagus these bundles
approach each other, displacing
the interposed tissue, and form-
ing finally one continuous mus-
cular layer. The thickness of this layer varies between 0.2
and 0.3 mm.

The submucous layer is made up of fasciculated connective
tissue and elastic fibres. It contains groups of fat-cells, and
lodges the mucous glands. The latter closely resemble the
glands found in the mouth. They consist of pyramidal or poly-
gonal secreting-cells with conspicuous rounded nuclei, and ducts
lined by cylindrical epithelia. The lower portion of the oesoph-
agus contains smaller and more superficial acinous glands.
In this region they are also found in greater abundance, and
around the cardiac orifice they form almost a complete ring.

The muscular coat has an inner circular and an outer longi-
tudinal layer. In man it is formed of both varieties of muscle-
cells, the striped and unstriped. The upper portion is composed
of striped muscle only, whereas the lower half consists exclu>-
sively of the unstriped variety. Below the upper one-eighth of
the oesophagus smooth muscle-cells first begin to be blended
with the other variety ; they rapidly increase as we proceed

FIG. 164. — Trnnsverse section through the
lower part of the resophagua of the newly-born
child : a, a, epithelium ; 6, mucosn ; c, rnnscil-
laris mucobse ; d, snbinncoiis tissue ; t. layer qf
circular muscular fibres ; /, longitudinal muscu-
lar layer ; (/, external fibrous layer ; A, A, two of
the ganglia of Anerbach. Klein.

388 MANUAL OF HISTOLOGY.

downward, until at about the middle of its course the striped
fibres entirely disappear, being replaced by continuous layers
of unstriped muscle-cells:

The fibrous envelope consists of connective tissue and elastic
fibres, arranged so as to form a thin, peripheral, sheath-like
membrane.

Blood-vessels and lymphatics are found in less abundance
in the oesophagus than -in the mouth and pharynx. The for-
mer are arranged in the shape of capillary networks in the
mucosa. The papillary loops, already mentioned, take their
origin from these reticula. The larger branches are found in
the submucosa. The lymphatics occur as plexuses; one is
situated superficially in the mucous membrane, and communi-
cates by capillary vessels, with a second larger one, placed in the
submucosa. The glands are said to have special lymphatics.

Nerves. — An elaborate account of the mode of distribution of
nerves in the oesophagus is given in Ranvier's " Lecons d'ana-
tomie generale," 1880, p. 366 et seq. The following brief sum-
mary gives the main points : Nervous filaments proceeding from
the pneumogastrics find their way to the striped muscles, where
they terminate in the well-known eminences ordinarily found in
that tissue. These terminal bodies are seen to be very numer-
ous, a fact which corresponds to the importance and complex-
ity of nervous action concerned in the process of deglutition.
The terminal distribution in the unstriped muscle presents no
striking peculiarity. Between the two layers of the muscle-
coat we find' an arrangement analogous to Auerbach's gangli-
onic plexus, but the ganglia and their nerve-cells are larger and
appear to be more numerous than in the intestine. The nerve-
fibres proceeding from the vagus are medullated ; those from
the ganglionic plexus belong of course to the non-medullated
variety.

THE STOMACH.

The serous covering of this organ has the same general
structure as all visceral peritoneum, being composed of a con-
nective-tissue membrane lined by flat endothelial cells.

The muscvlar coat of the stomach is divisible into three
layers, composed of, 1, external longitudinal fibres ; 2, middle
circular ; and 3, internal oblique fibres. All of these belong

THE STOMACH.

389

exclusively to the unstriped variety of muscle-cells. A
thickening of the inner circular layer constitutes the pyloric
sphincter.

The submucous layer is composed of loose connective tis-
sue, and it is for this reason that the mucous membrane is so
freely movable over the muscular coat. It is, moreover, owing
to this peculiarity that,
whenever and wherever
muscular contraction takes
place, the mucous mem-
brane presents numerous
folds, ridges, and eleva-
tions. Thus, we may find
in a perfectly healthy stom-
ach appearances quite an-
alogous to those described
by pathologists as the so-
called etat mamelonne of
gastritis.

The muscularis mucosce
frequently presents two lay-
ers of unstriped muscle-
cells — an outer longitudinal
and an inner circular one.
In some regions we observe
only one layer of longitu-
dinal muscle-cells.

The gastric mucous mem-
brane is covered by a single
layer of columnar epitheli-
um, containing goblet-cells
in greater or less abun-
dance. These goblet-cells
represent ordinary epithelia, which appear to be bulged out
by mucoid contents. At the cardiac extremity of the stomach
there is a sharp, serrated line of demarcation between the
O3sophageal and gastric epithelial lining. The surface-epithe-
lium forms one continuous stratum, and is continued down
into the ducts of the gastric glands. The latter occur in two
distinct varieties, viz., peptic glands and pyloric glands.

The peptic glands, also called gastric glands, are cylindrical

FIG. 165. — Transverse section through the fundne of
the stomach in a child : a, a, cylindrical epithelium ;
6, 6, peptic tubes ; c, c, muscularis mncosse ; d, d, cnb-
mncous tissue ; «, circular muscular layer: /, longi-
tudinal muscular layer ; g, peritoneum ; A, t>, ganglion
of Auerbach. Klein.

390

MANUAL OF HISTOLOGY.

tubules, nearly straight or slightly tortuous, with often a single
rounded caeca! extremity. However, the latter is sometimes
double by dichotomous division, or we find many such blind
terminal branches. Hence, we may speak of simple peptic
glands and compound peptic glands. They are all placed ver-
tically to the surface,
and consist of a homo-
geneous basement-mem-
brane with a lining of
secreting epithelia. (Fig.
166.) The basement-
membrane contains flat-
tened nuclei, and at its
inner aspect it is fur-
nished with flat, branch-
ing adventitial cells.
Each gland is divisible
into a duct and gland
proper. The latter,
again, consists of a neck,
body, and fundus.

Usually, two, three,
or even more of these
glands, have a common
duct. The length of the
entire structure varies in
the different gastric re-
gions from 0.4 — 2.0 mm.,
in accordance with the
thickness of the entire
mucous membrane in the
respective parts. The
duct, amounting to
about one-fourth of the
whole length of the tube,
is lined with one contin-
uous layer of columnar epithelial cells, similar to the surface
epithelium of the rest of the stomach. The neck, the thin-
nest portion of the minute tube, has similar cells ; but they
appear shorter, darker, and have a smaller ovoid nucleus. As
regards its breadth, the body stands about midway between

Flo. 166. — A, simple gastric gland : P, parietal ; and C,
chief cells. B, compound gantrta gland. Only the outline,
denoting the membrana propria, is drawn.

THE STOMACH. 391

the neck and the f undus, which latter is the thickest portion
of the entire gland. In the neck we also find, in addition to
the cells already described, other corpuscles placed externally
to the former. . They are the parietal cells (Heidenhain), or
delomorphous cells (Rollett), the former variety being termed
chief cells (Heidenhain), or adelomorphous cells (Rollett), or
simply peptic cells. The parietal cells occur as spheroidal,
oval, or polygonal, rather opaque, sometimes very granular
bodies, which lie beneath the basement-membrane, but com-
monly outside the layer of ordinary chief cells. In the body
of the gland-tube we again meet with these two forms of lin-
ing-corpuscles. Here, however, the columnar or chief cells are
longer than in the neck, and their bodies generally appear
more transparent, while the nuclei, again spheroidal, are situ-
ated nearer the external than the internal border. Klein de-
scribes the substance of these cells as consisting of a delicate
reticulum, with a small amount of a hyaline interstitial sub-
stance in its meshes. The same author, also, invariably finds
an intra-nuclear network. Others have been less fortunate in
finding such appearances. The parietal cells of the body in
all respects resemble those of the neck. As the fundus is ap-
proached their number grows comparatively less.

The pyloric glands, which some histologists insist on call-
ing mucous glands, are lined throughout by a single layer of
epithelium. This is composed of the ordinary columnar cells
of the gastric surface. But the corpuscles here appear to be
somewhat compressed, so that they seem less transparent than
elsewhere. They are known to undergo certain changes dur-
ing their passage from activity to rest. Examined in the
latter condition, we find them more granular, and apparently
smaller or shorter, than during and immediately after secre-
tion. These glands have long ducts, each one serving for sev-
eral secreting tubules. Their bodies are branched, and usually
appear somewhat tortuous. When such glandules become
somewhat more complex and grow larger (a change which nor-
mally takes place in the duodenum), they are called Brunner' s
glands.

Dr. Edinger has recently (Archiv f. mikr. Anat., Vol.
XVII., p. 193) asserted that the gastric glands contain in
reality only one kind of cellular element. He based his
opinion on results obtained by treating the almost living mu-

392 MANUAL OF HISTOLOGY.

cous membrane with osmic acid, after Nussbaum's method.
By him the chief cells are said to develop into parietal cells,
through an increase of their volume and a filling up with the
gastric ferment. The considerations which led him to form
this opinion are as follows : 1, the occurrence of bodies which
represent transition-forms between chief cells and parietal
cells ; 2, the analogy of this assumed metamorphosis of gas-
tric corpuscles (i.e., the conversion of chief cells into parietal
cells), with similar changes, known to occur in other glands
during active secretion ; 3, the fact that many animals which
secrete pepsin have only the parietal cells ; 4, the results of an
examination of the mucous membrane of starving animals,
which revealed only the chief -cell form of gastric corpuscles ;
and 5, the apparent discrepancy in the descriptions of these
bodies by competent histologists — some observers regarding
the chief cells, others the parietal cells, as exclusively pepsin-
ogenous.

Still more recently, Sto'hr has (VerTiandl. d. p7iys.-med.
Gesel. in Wurzburg, 1881, p. 101) studied the histology of the
gastric epithelium. His specimens were derived from the fresh
stomach of a criminal immediately after execution of the latter.
The man had taken no nourishment for some hours before his
death. The principal conclusions of Stohr are : 1, the epithe-
lia of the mucous glandules are not destroyed during the pro-
cess of secretion, but, like those of the true gastric glands, con-
tinue their existence ; 2, the parietal groups of cells represent
those portions of the mucous corpuscles which have not un-
dergone mucoid metamorphosis, being made up of unaltered
protoplasm.

From the above contradictory statements it appears that
even to-day our intimate knowledge of the gastric mucous
membrane, and especially its epithelia, is far from being in a
satisfactory condition. It will have to be reserved for future
investigations to dispel the uncertainty still existing with re-
gard to some of the most interesting details of the physiologico-
histological characteristics of the inner coat of the stomach.

The blood-vessels of the stomach have an arrangement simi-
lar to that of the oesophagus. In the mucous membrane, how-
ever, we find abundant plexuses of capillary vessels surround-
ing the gastric glands. These networks intercommunicate, and*
just beneath the surface-epithelium they become especially

THE STOMACH. 393

close. From this point the veins take their origin. The ve-
nous rootlets unite in a stellate manner to form larger branches,
which descend almost vertically and empty into a venous retic-
ulum situated between the glandular layer and the muscularis
mucosse, and just above a similar arterial network.

IsympTiatics abound in the stomach. They appear to
arise from superficial loops, which, anastomosing between the

FIG. 167. — Lymphatics of the gastric mucous membrane of the human adult. Frey.

glandular tubules, reach the fundal zone of these structures.
There they form a network, and this is in communication
with a plexus of larger vessels, situated in the submucous
tissue.

The distribution of the gastric nerves does not differ mate-
rially from that of the small intestine, in the description of
which this matter will receive more particular attention. Gan-
glion-cells are frequently found both in the muscular layer
and the submucosa ; in the latter we have a tolerably distinct
plexus of nerve-filaments and ganglion-cells.

Of the normal occurrence in the walls of the stomach, of
true lymphoid follicles, the author has been unable to find
convincing evidence. Nevertheless some writers assert that
they are always to be found there.

394

MANUAL OF HISTOLOGY.

THE SMALL INTESTINE.

The serous coat presents no structural characteristics pecu-
liar to itself, closely resembling the gastric peritoneum. It
encloses a muscular coat and the mucous membrane, which are
held together by connective tissue. The average thickness
of these3 layers does not, in man, exceed 1.0 mm., of which
three-fourths belong to the muscular, and one-fourth to the

Flo. 168.— Longitudinal section of the small intestine of a rabbit : Z, 55, villi : J, crypts; Pp, a Beyer's
patch ; K, cap of a follicle ; S, gubmucosa ; m. m, muscularis mueosse ; R, circular muscular layer ; L,
longitudinal muscular layer ; P, peritoneum. Verson.

mucous coat. Of course, the contracted or relaxed condition
of the intestinal tube at the time of measurement will appre-
ciably influence these figures. But they represent the general
ordinary average.

The muscular coat has an external longitudinal and an in-
ternal circular layer. Between the two we find Auerbach's

THE SMALL INTESTINE.

395

plexus myentericus of flat nerve-fibres, which will be described
farther on. The muscle-coat becomes gradually thinner as we
pass from the duodenum to the ileo-csecal valve. In the for-
mation of this thickened fold the longitudinal layer does not
participate.

The unstriped muscle-cells have an average length of 0.255
mm., and are about 0.005 mm. broad. They are arranged in
bundles, surrounded by connective-tissue bands, with which
elastic elements are abundantly interwoven.

The mucous membrane is thrown into folds, and is studded
with closely placed projections, called villi. The general di-
rection of these folds, the valvulce conniventes KerTtringii, is
parallel to the transverse course of the circular muscle-layer.
They run parallel to one another, or join at acute angles.

The mill jut out into the lumen of the intestinal canal, as
variously shaped projections, of an average length of 0.04 — 0.6
mm., and an average breadth of
0.06 — 0.12 mm. In general their
form may be said to be conical or
cylindrical ; but we always en-
counter a great variety of shapes,
in accordance with the varying
states of contraction in the mus-
cularis mucosae. Each villus con-
sists of a large-meshed reticulum
of connective tissue, infiltrated, as
it were, with leucocytes, and con-
taining flattened corpuscles, which
resemble endothelial cells. One or
several spaces, situated in the cen-
tre of every villus, constitute the
origin of the lacteal tubes. Ac-
cording to Briicke, these chyle-
vessels are covered by thin, but
not continuous bundles of smooth muscle-fibres. Their walls
show only a single layer of ordinary endothelial cells, with
clear oval nuclei. The free surface of the villi, like that of the
stomach, is covered by a single layer of columnar epithelium.
Each cell presents, in the recent state, a finety striated hyaline
band at its unattached border. This structure has, at different
times, received various interpretations, and even now opinions

Fio. 169. — Soction of a villus from the
intestine of a rabbit : a, epithelium ; 6,
Btrouia ; c, central cavity. Verson.

396 MANUAL OF HISTOLOGY.

are much divided as to its true significance. Some histologists
regard the striae as indicating so many minute pores for pur-
poses of absorptive transmission ; others believe that the jux-
taposition of numerous delicate rods explains the peculiar ap-
pearance; and Klein has lately asserted them to be merely
prolongations of the fibrils of the cell-substance composing
the epithelia. These striae are always seen to run parallel to
the long axis of the cells.

Krause also described as of normal occurrence, a basal pro-
cess extending at an obtuse angle from the attached surface of
these bodies, and inserted into the delicately serrated border
of the villi. Near its attached border each epithelium presents
a bright ovoid nucleus, with one or more distinct nncleoli.
Besides the ordinary corpuscles, we find interposed between
them the so-called goblet-cells. These are derived from the
former by mucoid infiltration of the cell-body, which is there-
fore conspicuously bulged out. Lymph-corpuscles also occur
between the epithelia.

Immediately beneath this layer we find a delicate, homo-
geneous basement-membrane, composed of flattened cells, re-
sembling endothelia.

The muscularis mucoscB, or muscle of Brucke, is made up of
a single or double layer of smooth muscle-cells. When double,
an inner circular may be distinguished from an external longi-
tudinal coat, both being always very attenuated*.

The submucous layer is formed of connective tissue, the
supporting framework of which contains lymphatics, blood-
vessels, nerves, and often groups of fat-cells.

The glands of tlie small intestine are those of Brunner and
the crypts of Lieberkiihn. In addition to these, however, there
occur numerous lymphoid follicles, which, when found singly,
are known as the solitary follicles, and, when grouped together,
as agminated glands, or Peyer's patches. The solitary or
closed follicles are real lymphoid glands, and, like these, con-
sist of reticulated connective tissue, the meshes of which are
replete with lymph-corpuscles. The jejunum, ileum, and colon
all contain sucli -follicles, but the agminated glands occur in
tli(> ileum, alxiuiKlinii; especially at its lower part. Around
each follicle we find a ring of villi and glands, which arrange-
ment goes by the name of corona tubulorum (Miiller). The
follicles receive an enveloping layer of nbro-connective tissue.

THE SMALL INTESTINE.

397

Brunner's glands lie in the submucosa, where they form
closely crowded tubules, separated by a small amount of con-
nective tissue. Smooth muscle-cells, starting from the muscu-
laris mucosse, are of ten seen to pass between them. These con-
voluted tubules resemble and correspond to the gastric glands,
but have here attained a much greater degree of development.

FIG. 170.— Vertical section throneh a human Peyer's patch, with Its lymphatics Injecfcd : a. Intestinal
villi with their lacteal ; 6. Lieberkiihnian glands; c, muscular layer of the mucous membrane: d, apex
of the follicle : e, middle zone of the follicle ; /, basis portion of the follicle ; g, continuation of the lacteals
of the intestinal villi into the mncons membrane proper: A, reticnlar expansion of the lymphatics in tho
middle zone : t, their coarse at the base of the follicle ; k, continuation into the lymphatics of the submn-
cous tissue ; /, follicular tissue in the latter. Frey.

They also appear to have been pushed down, as it were, from
the mucous into the submucous layer.

An individual gland consists of its long duct lined by col-
umnar epithelium, and the branched tubules, which frequently
have terminal clusters, resembling true acini. They are, how-
ever, only secondary or tertiary diverticula, so that Brunner's
glands really conform to the compound tubular type of secret-
ing structures (Renaut). Each ultimate diverticulum has an
external membrana propria composed of flattened endothelial
cells, and a lining of cylindrical, columnar, or prismatic secret-
ing epithelia, containing oval nuclei.

Histologists have described minute capillary channels pro-
ceeding from the central lumen of the gland, between the se- ,
creting-cells, ending just underneath the membrana propria.
The author believes these intercellular channels, as they have

398

MANUAL OF HISTOLOGY.

been called, to be the artificially altered cement-substance al-
ways present between such adjacent cells. Ikunner's glands
abound only in the duodenum, but a few may occasionally be
seen lower down the intestine. Their ducts, after traversing
the muscularis mucosse, ascend almost vertically between the
crypts, opening on the free surface of the mucous membrane.

Fig. 171.— Crypts and interfollicnlar connective tissue, from the intestine of the rabbit : K, crypt ;
a. n, epithelium ; <J, adenoid tissue, from which the cells have becfti removed by pencilling ; 'I', fibrous
tifume on the opposite side. Verson.

These crypts represent open spaces within the so-called
follicles of Lieberkukn, which are tubular glands placed verti-
cally in the intestinal mucous membrane, existing throughout
its entire extent.

They -form a continuous layer, except where the upward
projection of a lymph-follicle creates an interruption. These
glands open at the base of the villi, the epithelial covering of
the latter being continued down into the tubular depressions
which they constitute in the mucous membrane. The cells of
this stratum naturally appear broader at their attached than at

THE SMALL INTESTINE. 399

their free extremities. A continuation of the villous basement-
membrane forms the . membrana propria of the crypts of Lie-
berkuhn. External to this we find the surrounding connective
tissue, which is disposed in reticula, containing many leuco-
cytes in its meshes. Hence it is also known as adenoid tissue.

The blood-vessels enter and leave the intestine at the me-
senteric margin. The arteries, generally accompanied by one
or two veins, pierce the muscle-coat, giving off branches which
form networks in those layers, then enter the submucosa, where
they run parallel to the surface of the mucous membrane, and
finally send off vertical arterioles at the base of the villi. The
latter ascend on one side of the villus, and then suddenly
divide into a dense capillary network. This division takes
place near the middle, the capillaries then spreading out to the
apex and periphery. Here they become quite superficial, being
covered by the epithelial lining only. The venous rootlets of
the villus are generally two, or even three in number. About
the glands and follicles we encounter special networks with
variously shaped meshes.

Lymphatics are found in all the layers of the intestinal
canal. Those of the serous coat empty into the large mesen-
teric trunks. In an inward direction we also find a network of
lymph- capillaries between the two layers of the muscle-coat.
The submucous layer contains the perifollicular lymph-sinuses
situated at the base of these bodies, and a reticulum of larger
channels, many of which are found provided with valves. The
lymphatics of the mucous membrane are present in the shape
of capillary networks surrounding the intestinal glands.

In the villi we note, as already stated, one or more central
lacteals, communicating at the base of these structures with
the lymph-vascular networks situated around and between the
glands.

The nerves of the intestine are known as the vlexus of
AuerbacTi, and of Meissner. The former, situated between
the circular and longitudinal fibres of the musculbsa, is com-
posed of flattened nerve-branches, made up of numerous ulti-
mate fibrils. Small nodules, containing characteristic gan-
glion-cells, are also found, while little twigs are given off from
the plexus myentericus, to be distributed to the layers of the
musculosa.

•The plexus of Meissner is situated in the submucous tis-

400

MANUAL OF HISTOLOGY.

sue. Its component nerves are less flattened, but are likewise
provided with ganglia containing variously shaped ganglion-
cells. This plexus also gives origin to the secondary networks
of the muscularis mucosse, and is besides connected by certain
branches with Auerbach's plexus.

THE LARGE INTESTINE.

The histological structure of the colon, broadly speaking,
very nearly resembles that of the preceding section of the ali-
mentary canal. The lining epithelium of the mucous mem-
brane presents the same characteristic appearances as in the

Pio. 172.— Section of the large intestine of » rabbit: J, crypts of Lleberk'uhn : a, epithelium ; 6, mn-
ooe» ; m, muscularis mucosae ; », Eiibmuco.su : li, circular muscular layer ; Z, longitudinal muscular layer ;
p, peritoneum. Verson.

small intestine. The mucosa of the colon is, however, devoid
of villi ; but it shows numerous crescentic folds. The muscu-
laris mucosae will be found to answer to the description already
given of that layer in the small intestine.

The submucosa also shows the same morphological compo-
sition, but appears to be much richer in deposits of fat-cells.
Aggregations of lymph-follicles are not generally found, but
large, conspicuous solitary glands abound throughout.

The crypts of Lieberkuhn are identical with the glands of

THE RECTUM. 401

the same name found in the small intestine. As we approach
the rectum an increase in their length becomes apparent.

In the vermiform appendix we find the collection of solitary
lymph-follicles so closely placed that the space left between
adjoining glands does not equal in diameter that of these struc-
tures themselves.

The longitudinal layer of the muscle-coat is quite thin be-
tween the taenise coli, or flat longitudinal bands of the large
intestine. These bands themselves represent thickened layers
of the musculosa. It appears that the circular fibres are espe-
cially developed in the portions between the sacculi of the
csecum and colon.

The blood-vessels are arranged after the same plan as in the
small intestine. In the submucosa are contained large trunks,
running parallel to the surface. Capillaries arise from these,
and ascend almost vertically between the crypts of Lieberkiihn,
the capillary network surrounding those structures being only
moderately developed.

As regards the lymphatics, they have a distribution similar
in all essential respects to that found in the small intestine.

The nerves likewise imitate in their structure and arrange-
ment those encountered in the small intestine. Meissner's
plexus appears to be provided with comparatively large gan-
glia and relatively small component cells. The plexus of
Auerbach also attains conspicuous development in the large
intestine.

THE RECTUM.

The internal sphincter ani represents a thickening of the
circular layer of the muscle-coat. In its upper portion the
rectal mucous membrane is like the same structure of the large
intestine. Lower down we find the columnar epithelium grad-
ually replaced by stratified pavement-epithelium.

The follicles of Lieberkiihn are large and long. Finally,
the mucous membrane gradually passes into the ordinary in-
tegument surrounding the anal orifice.

The blood-vessels, lymphatics, and nerves resemble in their
distribution those of the colon, and are devoid of characteristic
peculiarities.

26

402 MANUAL OF HISTOLOGY.

BIBLIOGRAPHY.

BCETIM. De glandularum intest struct, penit. BeroL, 1835.

HENLE. Symbol, ad anat. vill. intest. Berol., 1837.

BISCHOFF. In Muller'a Archiv, p. 503, 1838.

WASH ANN. De digeatione nonnulla. Berol., 1839.

MIDDBLDORPF. De glandulis Brunnianis. Vratisl. , 1846.

BRETTAOER and STEINACH. Unt. iiber d. Cylinderepithel. Vienna, 1857.

LEYDIQ. Histologie. 1857.

AUBRBACH. Ueber einen Plexus myentericus. Breslau, 1862.

AUERBACH. Virch. Arch., VoL XXXIIL, p. 340. 1865.

LETZERICH. In Virchow's Archiv, Vol. XXXVII., p. 232. 1866.

EIMER. Zur Geschichte der Becherzellen. Berlin, 1868.

SCHWALBE. Arch. f. mikros. Anat, VoL VIII., p. 92. 1872.

HEIDENHAIN. Arch. f. mikros. Anat, Vol. VIII., p. 279. 1872.

GERLACH. Ber. d. sachs. Ges. der Wiss. Leipzig, February, 1873.

KRAUSE. Handb. d. menschl. Anat., Band I. 1876.

F. HOFFMANN. Die Follikel des Diinndarms beim Menschen. Munich, 1878.

SBRTOLI. Gontribuzioni all' aaatomia della mucosa gastrica. Arch, di med. veter.

Fasc. 3, p. 15. 1878.
RCDINGER. Beitr. z. Morphol. d. Gaumenseg. u. des Verdauungsapp. Stuttgart,

1879.
H SEWALL. Devel. and Regen. of the Gastric Gland, EpitheL, etc. Journal of

Phys., Vol. L, p. 321. 1879.
EDINGER. Zur Kenntniss d. Driisenzellen d. Magens. Arch. f. mikros. Anat., Vol.

XVII., p. 193. 1879.

RANVIER. Les muscles de Fcesophage. Journ. de micrographie, III., p. 9. 1879.
RENAUT, G. Note sur la structure des glandes a mucus du duodenum. Gaz. med.

de Paris, No. 41, 1879, and Progres med., No. 23, p. 439. 'l879.
RANVIER. Leqons d'anat. generate. Paris, 1880.
P. STOHR. Ueber -das Epithel. des menschl, Magens. Verhandl. der phys.-med.

Gesellschaft in Wurzburg, p. 101. 1881.

CHAPTER XXV.

THE SPLEEN, PANCEEAS, THYMUS, THYBOID AND PINEAL
GLANDS, AND PITUITARY BODY.

Br C. L. DANA, A.M., M.D.,

Professor of Physiology in the Woman's Medical College, New York City.

General structure. — This organ is composed of connective
tissue and muscular fibres, containing Malpighian corpuscles,
pulp-substance, blood-vessels, lymphatics, and nerves. An
outline of the general arrangement of these several elements
will make subsequent details clearer.

Within its peritoneal investment the spleen has, in the
first place, an elastic fibrous capsule ; this envelops the organ
and passes into its interior at the hilum. From the internal
surface of the capsule are given off fibrous bands and pro-
cesses — the trabeculse, which interlace and form a fine network.
In the meshes of this network is a soft, reddish substance — the
splenic pulp. The arteries, entering at the hilum, run along
the trabeculse and end in capillaries, which gradually break up
in the parenchyma. Attached to the walls of the arterioles
and bathed in the spleen-pulp are little bodies, called the
Malpighian corpuscles. The veins begin in the pulp, and,
gradually enlarging, pass out alongside the arteries. The
blood thus passes out of the capillaries, into the spleen -pulp,
and from thence is collected by the veins. It passes through
the blood-paths in the pulp much as the lymph passes through
lymph-paths in the lymphatic glands.

This unique structure is now to be considered in detail.

The peritoneal or serous coat of the spleen resembles the
peritoneum elsewhere. It is, in man especially, very firmly

404 MANUAL OF HISTOLOGY.

adherent to the fibrous coat beneath it, and closely invests the
organ. It is reflected off at the hiluin to form the gastro-
splenic omentum, and also at the upper border, where it in-
, vests the suspensory ligament.

The fibrous coat, or capsule of the spleen, is white in color,
and thicker than the serous coat. It is composed of fibrous
tissue, which is permeated very extensively by elastic fibres.
Mingled with them are a few smooth, muscular elements. At
the hilum this fibro-muscular coat surrounds the vessels and
nerves and passes into the substance of the spleen with them,
forming what is called the "capsule of Malpighi." It invests
the arteries and veins as far as their finer branches, and gives
off fibrous processes, which have a diameter of -fa mm. to
2 mm., and which help to make up the trabecular frame-
work of the spleen. This framework is formed by processes
sent off from the internal surface of the spleen's fibrous coat,
which join with the processes sent off from the capsule of
Malpighi, and interlace until a firm network is made. In this
structure lie embedded the spleen-pulp and the Malpighian
corpuscles. The fibrous sheath of the veins has a somewhat
peculiar arrangement. It becomes at once intimately adherent
to the venous walls, uniting them closely with the surrounding
parenchyma. As the veins grow smaller this fibrous coat splits
into bauds containing muscle-cells, which lie longitudinally
along the vessel-wall. These bands do not entirely surround
the vessel, however, but allow the thin endothelium and in-
tima to be seen between them. They finally leave the veins
to join the trabecular framework. The tissue composing this
framework is made up, like the capsule, of elastic and other
fibres, with a good many smooth muscle-fibres arranged longi-
tudinally along their course.

Malpighian corpuscles. — The Malpighian or spleen corpus-
cles are so intimately connected with the arteries that it will
be necessary first to trace in part the course of the latter. The
arteries of the spleen enter at the hilum, enclosed in a common
sheath with the veins and accompanied by the lymphatics.
They divide and subdivide very rapidly. When they have
reached a diameter of about two-tenths of a millimetre, the
veins leave them and take an independent course. At this
point of separation, or even sooner, the outer connective-tissue
coat of the artery begins to be transformed into the ordinary

THE SPLEEN.

405

adenoid tissue ; the fibrillae become more delicate and interlace
in a coarser mesh work ; in the interstices are lymph-cells and
at the nodal points are small nuclei. Klein describes large, flat-
tened endothelioid cells, " endothelioid plates," fixed upon the
reticulum. This lymphoid tissue surrounds the artery in a
loose coat of variable thickness. At certain points there is a
local hyperplasia of it ; it becomes massed into little ovoid or
spherical bodies, which are called Malpighian corpuscles.
These have a diameter of T27 to TV mm. They are attached
like buds to the artery, or, not rarely, the artery pierces them
centrally or eccentrically. When thus pierced the lymphoid
change in the arterial coats extends much deeper. The cor-
puscles resemble very closely the follicles in the solitary glands
of the intestine, as well
as those of the lymphatic
glands (Fig. 173). They
are composed of the same
retiform connective tis-
sue, in the meshes of
which are lymphoid cells,
with occasionally yellow
or brown pigment. This
retiform tissue becomes
denser near the external
part of the corpuscle,
but no distinct envelop-
ing membrane exists. In-
deed, the external sur-
face is generally connect-
ed by fibrillse with the
branching cells of the spleen-pulp surrounding it. Toward
the centre the retiform tissue is more open. The cells within
the meshes are lymph-cells of various sizes. They have an
average diameter of yf^ mm. The smaller ones have a single
nucleus, the larger may have several. An arterial twig enters
the corpuscle either from the attached artery or from the out-
side. It divides at once into capillaries, wnich, as a rule, have
no regular arrangement. They receive an adventitia of lymph-
oid tissue. Most of them soon lose this adventitia, their walls
become rich in nuclei, branching processes are given off, and
the structural character of the vessel is lost. They finally

Pio. 173. — Prom the spleen of the Tropldonotns Matrix :
a, follicle, with its capillary plexus ; 6, septum, with venous
plexus. Mailer.

406 MANUAL OF HISTOLOGY.

break up entirely, and their contents pass out at the periphery
of the corpuscles into the meshes of the pulp. It is to be
noted that the Malpighian -corpuscles are the only parts of the
spleen where capillaries exist to any extent. The arteries going
to the pulp for the most part break up at once.

The spleen-corpuscles differ from the lymph-follicles, par-
ticularly, in having fewer capillaries, no lymph-paths, and in
containing pigment in their meshes. The number of Malpig-
hian corpuscles in a spleen of ordinary size, as estimated by
Sappey, is about ten thousand ; but this applies to lower ani-
mals. In man they are smaller and less numerous. Pro-
tracted disease is thought to dimmish the number.

The spleen-pulp. — This is a soft, reddish brown substance,
looking, when squeezed out, like grumous blood. On expo-
sure to the air it acquires a redder hue. Under the microscope
it is found to present a honeycombed appearance, in the meshes
of which are numerous lymph-corpuscles, fragments of red
blood-corpuscles, so-called nuclei, and pigment-granules. Thus,
we have really only a modified form of adenoid tissue. Klein
considers that the network is made up of the large, flat endo-
thelioid cells above referred to. Processes branching from
these and uniting with each other form the meshes. I have
been unable to make out the structure as Klein describes it,
and his own observations and plates do not demonstrate it
satisfactorily. The branching endothelioid cells'are connected
with the breaking-up and the beginning of the blood-vessels,
but do not form the whole pulp reticulum.

The fibrillse of this retiform tissue are connected with the
external surface of the Malpighian corpuscles, with the lym-
phoid tissue that ensheaths the small arteries, with the fibrous
trabeculse of the spleen itself, and with the cell-nuclei of the
walls of the arterioles, capillaries, and venous radicles. From
these points they branch and interlace, enclosing the cellular
and other elements in their meshes. These branching fibrillse
are, as in other lymphoid tissue, of a pale, granular appearance.
The cells enclosed in the meshes are not crowded so closely
• together as are those in the Malpighian corpuscles (Fig. 174).
They are of different sizes ; the small ones are sometimes de-
scribed as free nuclei. The larger ones have one, two, or more
nuclei within them. These larger cells often contain red blood-
globules in various degrees of disintegration, a fact which gives

THE SPLEEN. 407

rise to the opinion that one of the" functions of the spleen is to
destroy them. The pigment-granules are found both without
and within the cells, and occasionally even stain the nodal
nuclei of the sustentacular tissue. The pigment is yellowish,
brown, or black, and there is enough of it to give a charac-
teristic dark color to the gross ap-
pearance of the spleen. In addition
to the pulp-elements mentioned, there
are, according to Fremke and Kolli-
ker, small, yellowish nucleated cells,
which are possibly young red blood-
globules.

The pulp-substance thus described
has arterioles and capillaries ending
and veins beginning in it. The blood
flows from the former, through the
spaces between the cells, into the lat- ve^us roote witiTi^compiete wans; a,

TT • • A. i.T venous branch. Frey.

ter. Here is every opportunity, there-
fore, for the blood to recruit itself with new white corpuscles,
and to enrich itself with albuminous and pigmentary matter
from disintegrated red globules. The analyses of the blood
in the splenic vein seem to show that it does do this.

Blood-ness els. — We have already described, to a certain
extent, the general arrangement of the blood-vessels, but some
further particulars remain to be noticed.

The splenic artery, the largest branch of the coeliac axis,
passes to the spleen in a course so tortuous as to shorten its
length in a straight line by one-third. It enters the gastro-
splenic omentum, divides generally into six branches, and
passes into the spleen at the hilum, where, in common with the
vein, it becomes surrounded by the capsule of Malpighii. The
branches then rapidly subdivide and decrease in size, but with-
out anastomosing. When about two-tenths of a millimetre in
diameter they leave the veins and receive their sheaths of lym-
phoid tissue and Malpighian bodies, as has been described.
They then end for the most part in capillaries, which pass to
the Malpighian bodies and there break up in the way above,
described. But there are other capillaries which pass into the
pulp-substance, where their walls gradually melt away, so to
speak, into the retiform tissue that surrounds them. If one
follows this change with a microscope, he will see the capil-

408

MANUAL OP HISTOLOGY.

lary tube becoming thinner and more freely studded with
nuclei ; from some of these nuclei processes are sent out which
connect with the fibrillaB of the pulp. At this stage injections
into the capillaries pass freely out into the surrounding tis-
sue. The exact point where the capillary wall merges into
the sustentacular tissue can hardly be determined.

The venous radicles begin in a somewhat similar way to
that in which the capillaries end (Fig. 174). The sustentacu-
lar fibrillae (endothelioid plates ?) appear to arrange themselves,
first of all, in a circular manner, occasionally interlacing at
right angles (Fig. 175). Lying within and upon the fibrillse

thus arranged are
oval cells with promi-
nent nuclei. These
nuclei are often con-
nected with the sus-
tentacular fibrillse
outside. These cells
are not adherent to
each other at first,
but, as the radicle be-
comes more perfect,
they unite to form a
complete wall ; the

FIG. 175.— From the pnlp of the human spleen, brushed preparation external layer of cir-
(combinntion): a, pulp strand with the delicate reticular framework ; _, , ,

transverse flection of the cavernous venous canal ; c, longitudinal sec- CUlar librill8B then
tion of such an one ; ti, capillary vessel in a pulp tube, dividing up at

« ; /, epithelium of the venous canal ; g, side view of the same ; A, its b 6 C O HI 6 S metamOr-
transverse section. 1'rey.

phosed into a tunica

intima ; finally, the thick oval cells are replaced by flat endo-
thelial cells, and the complete venule is formed.

Having shown how this vascular channel begins, we turn,
for convenience of description, to its other end. The splenic
vein enters the hilum, just as the artery does. As it subdi-
vides, however, it loses both tunica adventitia and tunica me-
dia. The internal tunic remains and becomes firmly united
with the fibrous trabeculae of the spleen, so that, on section,
the venous wall does not collapse, but appears like a part of
the parenchyma. After several subdivisions the veins begin
to anastomose, and they finally form a closely reticulated ar-
rangement of like-sized vessels having an average diameter
of T^f to Tf ff mm. These are called the cavernous veins. The

THE SPLEEN. 409

branches from them subdivide, pass into the pulp, and end in
the venous radicles we have described.

It is proper to state that some authors (Gray, Billroth,
Kolliker) believe that the capillaries connect directly with
these cavernous veins, pouring the blood into the lacunae which
they form. Others (Key, Stieda) believe that the sustenacular
tissue of the pulp is not composed of branching fibrillse, but
of collapsed capillaries, which connect the arteries with the
venous radicles. Such views cannot now be sustained.

The lymphatics of the spleen occur in two sets : one, the
trabecular, forms a close plexus in the external capsule and
sends deep branches along the trabeculse, to communicate with
the deep or perivascular set. This perivascular set arises from
the lymphoid sheaths of the arteries, and at first has no dis-
tinct channels. True lymphatics are soon formed, however,
which run along the arteries, generally one on each side. At
the hilum they unite with the trabecular set, and, passing along
the gastro-splenic omentum, enter the neighboring lymphatic
glands.

The nerves are derived from the solar plexus (right and left
semilunar ganglia and right pneumogastric). They enter the
hilum and follow the course of the arteries ; along their terminal
ramifications, according to Miiller, are oval ganglia, through
which a single fine capillary runs. On section of the nerves of
the spleen the organ dilates, and on electrical stimulation it
contracts.

Development. — The spleen is present in all vertebrates ex-
cept the septocardia and myxenoids (Miiller).

The organ is developed entirely from the mesoblast, and,
according to Peremeschko, is intimately related in its origin
with the pancreas, from which it is an offshoot. Its shape can
be recognized in the twelfth week. The capsule, trabecuhe, and
retiform connective tissue, are first formed ; then the cells and
Malpighian bodies appear, the latter at about the middle of
intra-uterine life.

Preparation of spleen for microscopical examination. —
The methods of preparing the spleen for examination are in
general like those for preparing lymphoid tissue anywhere.
The organ is very soft, and the object to be aimed at is to
harden it without interfering too much with its intimate struc-
ture. A good method is that of Klein. The spleen should be

410 MANUAL OF HISTOLOGY.

first washed out with £ per cent, solution of common salt until
the fluid from the vein is clear. Then inject TV per cent, solu-
tion of osmic acid or Mutter's fluid for twenty minutes. Then
place the spleen in Miiller's fluid for ten days, at the end of
this time small bits should be cut off and hardened in alcohol,
when it may be stained and mounted in the ordinary way.
The spleen of man is best prepared (E. Klein) by placing small
bits in a large excess of $ per cent, chromic acid for a week.
Then change it to a J per cent, solution, and in three days from
this to a i per cent, solution. Finally, bits are to be placed in
alcohol and hardened in the usual way.

I have obtained excellent sections, however, which answered
very well for demonstrations, by freezing the spleen of the
living cat with the ether-spray, making sections at once, and
staining them with Bismarck brown. In this way the retiform
tissue even may be seen.

THE PANCREAS.

The pancreas is a compound racemose gland. It is com-
posed of a central duct, which sends off branches that divide
and subdivide until they end after the usual manner of race-
mose glands, by opening into collections of little vesicles or
acini. This mode of structure divides the gland into small
lobules, between which runs areolar connective tissue. The
same tissue envelops the whole organ.

In each of the lobules will be found a number of acini
grouped around the terminal extremity of a duct. These
acini consist of a basement-membrane ; lining this and almost
filling the acinus are cubical epithelial cells. The basement-
membrane is composed of flat, stellate cells. Owing to their
branching, they do not form a completely homogeneous mem-
brane. The epithelial cells lining the acini are nucleated and
compressed closely together. Their internal portion, next the
lumen, is granular ; the external part is clear. This granular
part represents (Heidenhain) the mother-ferment, zymogen,
which is transformed subsequently into trypsin. It varies in
extent with the activity of the gland. During such activity
the cell is smaller and the granular part less. Between the
cells (Langerhaus, Saviotti) fine intercellular passages similar

THE PANCREAS.

411

to those in the liver-lobules have been described (Fig. 176).
These intercellular passages are claimed by some, however,
to be branching processes from the cells of the basement-mem-
brane. Others regard them as albuminous cement substances,
holding the secreting
corpuscles together.

Langerhaus describes
branching centro-acinal
cells connected on either
side with similar inter-
epithelial cells. (See Pit-
uitary Body.)

The excretory duct
of the pancreas is com-
posed of a basement-
membrane lined with
cells ; at the lower por-
tion small mucous
glands open into it. The
basement-membrane is
thickened with fibrous
tissue at first; but, as
the duct divides up into
smaller branches, this
disappears. The lining
cells are columnar in
shape near the mouth of the duct ; passing back, however,
they grow shorter and more flat. Finally, on reaching the
acini, they resemble endothelial cells, and, as such, line the
axial cavity of the acinus. Here they form the centro-acinal
cells referred to above.

The Hood-ness els of the pancreas are numerous, and form a
close capillary plexus around the basement-membrane of the
acini.

The lympJiatlcs probably arise from between the acini.
They pass out with the blood-vessels.

The nerves are supplied from the solar plexus ; through
this fibres come from the vagus. They end, according to Pflii-
ger, in a manner similar to that of the salivary glands ; fine
terminal filaments pass through the basement-membrane into
the lining cells of the acini. Section of the vagus stops the

Flo. 176. — Glandular canals of the rabbit's pancreas, after
Savlotti : a, Larger excretory duct ; 6, that of on acinus ; c,
fluest capillary ducts. Frey.

412 MANUAL OF HISTOLOGY.

secretion of the pancreas for a short time ; stimulation of its
central end does the same. On section of all the nerves going
to the gland, there is a paralytic flow of the pancreatic juice.

Development. — The pancreas appears very early in foetal
life, developing from a mass of mesoblastic tissue in the duo-
denal wall. It is probable that hypoblastic tissue from the
same region passes into it from the ducts.

THE THYMUS GLAND.

The thymus gland is an organ whose function is unknown ;
it may be classed, however, on account of its structure, with
the lymph-glands, its tissue being of the adenoid type. It is
loosely enclosed in a vascular connective-tissue capsule, which
sends septa and processes into the interior of the organ. These
divide it up into small lobules of the size of a pin's-head to
that of a pea. Within the lobules are the characteristic ele-
ments of the gland — the follicles — which are also known as the
acini, alveoli, or granules. Running spirally through each of
the two long lobes is a central band or canal, and, upon unrav-
elling the gland, the various lobules are seen to be arranged
about this.

The fibrous capsule is made up chiefly of white connective
tissue, mingled with which there are fine elastic fibres and stel-
late connective-tissue cells. At a few of the nodal points of the
larger reticulating fibres are found peculiar cavities, lined with
fusiform cells and containing a few lymph -corpuscles. They
are probably connected with the lymphatics, and the fibrous
capsule seems, as a whole, to be slightly touched with a
lymphoid metamorphosis. The extejinal surface of the cap-
sule is covered with a single layer of flat epithelial cells. Deep
in the capsule is a rich plexus of vessels, and scattered spar-
ingly through it are medullated nerve-fibres.

The follicles. — Enclosed in each of the lobules, and making
tip its substance, are from ten to fifteen, or even fifty (Frey),
small, spherical or polyhedral bodies. These are the follicles
of the gland. They are from -fa to ^ mm. in diameter, and
resemble very much the follicles in the lymphatic glands and
Peyer's patches, but present a more embryonal aspect. They
are held closely together by the surrounding tissue, which

THE TIIYMUS GLAND.

413

sends septa down between them for a short distance (Fig. 177).
On section each follicle is found to be composed of a cortical
and medullary portion. The medullary portion is often only
a cavity, and, as a rule, is found to connect, by a passage
through the cortex, with a general cavity in the centre of the
lobule. This latter cavity again connects with the spiral cen-
tral canal. The follicle is composed of reticular connective
tissue, in whose meshes are cells and the thymic juice. The
reticulum forms an adventitia for the blood-vessels. In the
cortical portion this reticular tissue is made up of small, nucle-
ated cells, with long, fine, branching processes. In the medul-
lary portion, when present, the reticular cells have large nuclei,
and their processes are
coarse and short. Within
the meshes of the structure
thus described are cells,
fat-globules, capillaries,
and a peculiar, transpar-
ent, acid, viscid, albumi-
nous fluid — the thymic
juice. The cells are : 1,
lymph-corpuscles, which
exist in the greatest abund-
ance ; 2, large, granular,
nucleated cells of various

5 many Of these have '»«• ITT.— Portion of the calfsthymun, after His: The

rings of the arterial branches (a) and venous branches (6)

PrOCeSSeS, and. they w1111 the capillary net-work (c) and the cavities of the
- J acini (d). Frey.

help to form, partly by a

process of vacuolation (Watney), the concentric corpuscles ;
3, giant cells ; 4, the concentric corpuscles of Hassall. These
last consist of one or more cells, around which are arranged
concentric layers of flat, epithelioid cells. This concentric en-
velope suggests the epithelial cylinders seen in carcinomatous
growths. One or two of these corpuscles may be enclosed in
another common envelope, thus forming a compound concen-
tric corpuscle. These corpuscles are strongly refractive, and
are readily stained with carmine. They lie near the arteries,
and have an intimate relation with them. According to Afan-
assien, indeed, they are developed from the endothelium of the
arterial wall. There is a vascular plexus about the follicles,
from which capillaries pass into the interior, forming a fine net-

414 MANUAL OF HISTOLOGY.

work. They generally pass in as far as the medullary portion
or central cavity, and form a ring about this.

The central canal, or band of the thymus, is lined with a
vascular membrane, and communicates with the central cavi-
ties of the lobules and follicles. Along its interior the bulg-
ings of attached vesicles, or groups of the same, may be seen.

Many authorities consider that the central cavities in the
follicles and lobules are produced artificially by the break-
ing down of the very delicate tissue. There is much proba-
bility that this is the case. More investigation, however, is
needed, and meanwhile the cavities and canals are described
as above, since it is extremely rare to find a human thymus in
which they do not appear to exist, no matter how careful the
preparation.

The blood-vessels. — The thymus is not a very vascular
gland. Its arteries are distributed in the capsule and along
the central band. From these parts they pass unaccompanied,
as a rule, by the veins, to the interlobular tissue, and are dis-
tributed to the follicles, as has been described.

The lymphatics accompany the blood-vessels along the
central band. From there it is stated (His) that they pass to
the interlobular tissue and are distributed around the follicles,
communicating by minute channels with the centre of the fol-
licle. This latter point, however, lacks confirmation.

Development. — The thymus gland is found in all vertebrates
except amphioxus (Huxley). It is developed, like the lym-
phatic glands, from the mesoblastic layer, and can be seen
early in foetal life. It appears first as a closed tube, which is
probably (Quain) a mass of embryonic cells enclosed in a mem-
branous capsule. Along this projections bud out which are
gradually transformed into lobules. By the twelfth week it
has become well developed.

The thymus is an organ of foetal and infant life only. It
grows rapidly until the second year, when it begins to undergo
a fatty degeneration and atrophy. By the seventh or eighth
year it is a small, fatty mass. This degeneration of the thy-
mus takes place in all the animals which have the gland.

THE THYKOID BODY.

415

THE THYROID BODY.

The thyroid body is a dark red, vascular organ, composed
of two lobes. It seems very possible that we may now legiti-
mately call it a secreting gland, whose product acts upon the
red blood-cells, and is carried away by the lymphatics.

The entire organ is enclosed in a thin, but firm, fibrous cap-
sule. This sends off processes to the interior, which interlace,
forming a sponge-like network. This network is thin, however,
and does not make up much of the substance of the gland. A
few elastic fibres run in it. Enclosed in the meshes of the frame-
work thus formed are the vesicles of the gland. These are
very numerous and make up the bulk of the organ. They are
minute, spherical, ovoid, or flattened bodies, whose diameter
is from yfg- mm. in the embryo to 2 mm. in the adult, and are
grouped into small lobules of various sizes. They consist of
a homogeneous connective-tissue basement-membrane, lining
which is a single layer of epithelial cells, the whole enclosing
a yellowish, transparent, viscid fluid. The
lining-cells, in adults, measure about yf-g-
mm. in height and y^ mm. in width. They
contain nuclei, and sometimes nucleoli.
They are loosely connected to the base-
ment-membrane, and, with extra-uterine
life, begin to break away into the interior
of the vesicle. Baber describes fine, longi-
tudinal striae passing from the base toward
the apex of the cell. These cells have a
tendency to undergo colloid degeneration.
The cell-body swells up, and bursting, the
contents spread out in the vesicle-cavity,
there to undergo or complete the metamor-
phosis (Fig. 178) mentioned. According
to Baber, however, the cells which undergo this degenera-
tion come from the connective tissue surrounding the vesicles.
They pass through the vesicle-wall into its cavity, and there
'gradually break up. This change goes on at the expense of
*the vesicle-wall and the intervesicular tissue, so that in time
the gland, without being much enlarged, may appear, on sec-
tion, almost like a single colloid mass.

Pio. 178.— Colloid metamor-
phosis : a, Gland vesicle of the
rabbit ; 6, commencing colloid
metamorphosis of the calf.
Frey.

416 MANUAL OF HISTOLOGY.

The normal fluid contents of the vesicle coagulates with
heat and alcohol, without losing its transparency. Floating in
it are granules, cells, and occasional translucent, curiously
shaped bodies called sympexions (Robin). The cells come
from the vesicle- wall and the intervesicular tissue. Many of
them have lost their nuclei. The "sympexions," if they uni-
formly occur, have not been shown to have any significance.

Baber has recently announced the very interesting fact that
large numbers of colored and colorless blood-corpuscles are to
be found in the vesicle-cavities of the thyroid of man and lower
vertebrates. The colored cells, which largely preponderate, are
in a state of partial disintegration. This explains the yellowish
color of the vesicle-contents, and the inference is drawn that the
thyroid has the function of destroying red blood-corpuscles.

The blood-vessels of the thyroid are quite numerous. They
ramify in the capsule along the trabeculse, and finally form a
rich plexus about the vesicles, but do not penetrate the inte-
rior. The walls of the veins are united firmly to the fibrous
reticulum of the gland, so that when a section of them is made
they do not collapse.

TJie lymphatics form large and numerous trunks, both on
the surface and in the interior of the organ. They originate
by coecal extremities lying in the tissue between the vesicles.
These unite to form trunks which surround the lobules, and
give off branches that pass to the capsule. TKere a thick, per-
ipheral network is formed, from which lymph-trunks pass to
the thoracic and right lymphatic ducts. They contain a viscid
substance like that in the vesicles themselves, and it seems
probable that they have something to do with carrying off this
fluid.

The nerves are from the middle and inferior cervical gan-
glia, but not (Frey) from the pneumogastric. They enter the
gland along the trabeculse and pass between the vesicles. Gan-
glion-cells, either single or in groups, are met with in their
course. The mode of termination is not known, more than
that they seem to dwindle away into fine, terminal fibres, that
are lost in the connective tissue.

THE PITUITARY BODY. 417

THE PINEAL GLAND.

The pineal gland, or conarium, is a small body, about the
size of a pea, resting upon the nates and covered by the back
part of the corpus callosum. It consists of a fibrous capsule
and framework, lying in which are vesicles, cells, blood-ves-
sels, and sabulous matter. There is generally a cavity near the
base of the gland.

The interior of the structure is divided into a cortical and
medullary portion. The former is composed of little vesicles,
resembling those of the pituitary body. The central portion
is filled with nerve-cells and sabulous matter, the latter lying
in the cavity at the base. The nerve-cells are of two kinds :
one, large, -fa mm. in diameter, and giving off long pro-
cesses ; the other, very small, ^ mm. in diameter, and giving
off processes, in the adult. Nerve-fibres run among these
cells, and connect them to the medullary substance of the
cerebral lobes and to the crura cerebri. They are considered,
by Meynert, to be ganglion-cells giving origin to fibres in the
crura cerebri.

The sabulous matter is composed of corpora amylacea and
of earthy salts combined with animal matter. The earthy
salts are : phosphate and carbonate of lime, phosphate of am-
monia, and magnesia (Stromeyer).

There is no doubt that the pineal gland contains consider-
able nervous tissue. It is not yet determined, however, whether
it should be considered a ganglionic centre or a structure of
similar character to the suprarenal capsules.

THE PITUITARY BODY.

The pituitary body (TiypopJiysis cerebri) is notable for the
peculiarity of its development and its uniform presence in all
vertebrates. It is a small, reddish gray, vascular mass, ovoid
in shape, and situated in the sella turcica. It is composed of
two lobes, anterior and posterior, the former being the larger.
In structure, the body, in its anterior lobe, has some resem-
blance to the suprarenal capsules, being composed of a con-
nective-tissue framework, in which lie blood-vessels and closed
vesicles. These latter consist of a homogeneous membrane en-

418 MANUAL OF HISTOLOGY.

closing nucleated and nucleolated cells, mostly epithelial in
character. These cells generally line the interior of the vesicle
and nearly fill its cavity,' so that on section the vesicle looks
somewhat like an acinus of the pancreas. In the centre there
is often a branched nucleated corpuscle connected with a simi-
lar cell on one or the other side (Klein). The cells vary much
in size. In the connective tissue around the vesicles are lym.
phatic spaces and blood-vessels.

The posterior lobe is smaller, darker, and more vascular
than the anterior. During foatal, and perhaps infant life, it
has a cavity in its interior lined with ciliated epithelium and
connected by the infundibulum with the third ventricle.

Development. — The pituitary body is formed by a diverticu-
lum from the future mouth (buccal epiblast), which projects
up to be transformed eventually into the anterior lobe ; and
another diverticulum from the wall of the vesicle of the third
ventricle, which projects down to form the posterior lobe
(Quain). Epiblastic and mesoblastic tissue are thus united in
the organ. The posterior lobe retains its nervous elements in
the lower animals, but in man contains little besides connective
tissue and blood-vessels.

BIBLIOGRAPHY.

THE SPLEEN.

MflLLER, WM. Ueber den feineren Bau der Milz Leipzig und Heidelberg, 1865.
PEREMESCHKO. Beitrage zur Anatomic der Milz, und Ueber die Entwicklung der

Milz. Sitzungsberichte der k. k. Akademie. Zu "Wien, 1867.
STRICKER, S. Manual of Histology. 1872.
QUAEN. Elements of Anatomy. New York, 1877.
BACELLI. Venous Circulation of the Spleen. Med. Times and Gaz., Vol. I., p. 532.

1878.

SAPPEY. Traite1 d'anatomie descriptive. 3me ed. rev. et amel. 1879.
EANVIER, L. Traite technique d'histo'ogie. 1879 et seq.
KLEIN, E. Quarterly Jour. Mic. Science. No. LX., p. 363. 1875. Also, Atlas of

Histology. Par. XIII. 1880.
FRET. Histology. 1880.

THE PANCREAS.

PFLCOER, E. P. W. Strieker's Manual of Histology. 1872.
BENAUT, J. Snr les organes lympho-glandulaires et le pancreas des vertebres.

Compt. rend. Acad. des Sciences. VoL LXXXIX.. p. 247. Paris, 1879.
FOSTER, M. Physiology. 1880.

BIBLIOGRAPHY. 419

THE THYMUS GLAND.
WATNEY, H. Note on the Minute Anatomy of the Thymus. Proc. Boy. Soc. , Vol.

XXVII., p. 369. London, 1878.
AF AN A ssi EN. Structure of Thymus. Archiv fur inikroskopische Anatomic, Band

XIV., Heft 134.

THE THYROID BODY.

BOECHAT, P. A. Thesis on the Structure of the Thyroid Gland. 1873.

BABEH, E. CRESWELL. Researches on the Minute Structure of the Thyroid Gland.

Philosophical Transactions Lond.Roy Soc., Vol. CLXVL, Pt. 2, p. 557. 1876.

Proc. Royal Soc., Vol. XXVII., p. 56. London, 1878.
ZEISS, OTTO. Mikroskopische Untersuchungen iiber den Bau der Schilddriise. Strass-

burg, 1877.
POENCARE, M. Contribution a 1'histoire da corps thyroi'de. Jour, de 1'anatomie,

p. 122. 1877.
KLEIN, E. Atlas of Histology. Par. XIIL 1880.

THE PITUITARY BODY.
Journal de mcdecine, de chirurgie et de pharmacologie de Bruxelles, Vol. LXIX. ,

p. 305. 1880.
KLEIN, E. Atlas of Histology. Par. XIIL 1880.

CHAPTER XXVI.

THE THICK CUTIS VEEA.
BT J. COLLINS WARREN, M.D.

THE portions of the skin usually selected for histological
purposes are those in which the papillae or hairs are best shown.
The glands are also carefully described ; but little attention,
however, has been given to the anatomy of the cutis vera as an
organ by itself, consequently those parts have not been ex-
amined where it is found in its most highly developed form.

The skin varies greatly in thickness ; on the inside of the
arms and thighs, and on the anterior aspect of the body gen-
erally, it is much thinner than behind. In the former case,
particularly in delicate women, it is exceedingly soft and plia-
ble, a thin fold being easily raised and rolled between the
thumb and finger. In the latter it is exceedingly thick in the
back and shoulders of hardy adults, appearing as a veritable
hide, being much thicker than the skin of many pachyderma-
tous animals. Here it measures 5.5 mm. and even more in
thickness; when tanned it resembles sole leather. This struc-
ture is composed of bundles of fibres interwoven in various di-
rections. On the surface of these bundles lie the flat connective-
tissue cells, disposed in rows and occupying the intervals, the
tissue being somewhat analagous to tendon. The cutis is, in
fact, a sort of tendon or aponeurosis ; from its under surface
it sends out fibrous prolongations of considerable size, and in
some animals these are actually attached to muscles.1 In man
we find them dipping down into the subcutaneous fat, in the
back forming a very dense and firm mesh-work. Fatty tumors

1 M. Renant : Anatomic generate de la peau ; Annales de Dermatologie eb de
Syphilographie ; Tome neuvieme, No. 0 ; Satterthwaite : New York Medical Journal,
July, 1875.

THE THICK CUTIS VEKA.

421

growing in this part of the panniculus adiposus are, for this
reason, extremely difficult to enucleate.

The papillae are but imperfectly formed, and are represented
by an undulating line. At short intervals are the follicles of
the lanugo hairs, which penetrate only the superficial layers of
the cutis, the sweep of whose fibres would be otherwise un-
broken were it not for the
existence of a structure,
hitherto undescribed,1 which
connects the bases of the
hair- follicle with those parts
in which we find the root of
the longer hairs imbedded
—the panniculus adiposus.
This consists of a nearly
vertical cleft, or slender col-
umnar-shaped space, ex-
tending from the last-named
structure in a somewhat ob-
lique direction through the
deeper and middle layers of
the cutis, and terminating

,-i , » ,1 » 11 . i " FIG. 179. — Section'of skin from beck of an ad tut,

at tile DaSe Ol tile lOlllCle showing colurana adiposaand lanupo hair. Magnified

, . -i ., mi,- about eight diameters: a, epidermis: 6, erector pili mns-

WniCtl reStS Upon It. IniS cle;rf,fatcolumn:«,8udoriparouKKland;/,cutisvera;0,

. . -. . -. . adipose tissue ; A, hair : *. c6ne fibreux ; p, lateral cleft.

space is occupied by adipose

tissue in its entire length ; hence, the term "fat-columns," or

"fat-canals,"8 would seem to be an appropriate name.

The length of this space (in very lean individuals the fat is
absent, and we then see a delicate mesh-work of connective tissue,
and the trunk of a blood-vessel) is about 4 mm. ; its width
rather exceeds that of the hair-follicle above. Its long axis is
placed at a slight angle to that of the follicle, which in most
cases is nearly perpendicular to the surface, and is nearly
parallel to that of the erector pili muscle (7;). At about the
middle of this axis are given off two horizontal prolongations,
usually partially filled with fat-tissue, appearing like a pair of

1 In the latest treatises of the skin, no such structure is described. See Die Haut-
krankheiten fur Aerzte und Studirende von Dr. Gustav Behrend. Berlin, 1879; Patho-
logie und Therapie der Hautkrankheiten von Dr. Moriz Kaposi. Wien, 1879.

s Note on the Anatomy and Pathology of the Skin, by J. C. Warren. Boston Hedi-
csl and Surgical Journal, April 19, 1877.

422

MANUAL OF HISTOLOGY.

extended arms, or the remaining branches of a leafless trunk (p).
Near this point is suspended the coil of a sweat-gland (e), held
in place by a few delicate fibres which find their insertion at
the top of the canal or cleft. The duct of the gland runs to the
top of this space, whence it may be traced to the side of the
hair-follicle, whence it finds its way to the surface. (In dogs
the sweat-duct opens directly into the follicle, a short distance
from its mouth.) The fibres of the cutis appear, in vertical sec-
tions, to terminate abruptly at its edges. There does not ap-
pear to be any structure resembling a " limiting membrane."
At its base there is sometimes a slight widening of the cleft,
and on the side toward which its axis leans, the fibres of the
cutis collect to form a bundle which penetrates the subcutane-
ous fat (Cone fibreux de la
peau — #, Fig. 179). The upper
extremity is rounded off in
somewhat dome-shape.

The erector pili muscle, tak-
ing its origin from the papillary
layer of the cutis, is inserted
partly into the base of the fol-
licle, which its fibres embrace,
and partly into the apex of the
fat-canal ; in some sections the
fibres seem to penetrate this
space, but probably surround
it, although some of them may
be attached to those delicate
bands of fibrous tissue which traverse the column of fat-cells.
The muscle lies on the side corresponding with the inclination
of the hair externally, and appears almost continuous in its
direction with the fat-column beneath it.

The sebaceous gland lies between the muscle and the follicle
at the apex of the angle made by them ; a lobe is found also
on the opposite side.

The number of these columns corresponds to the number of
hairs, as they are not found elsewhere. In some sections of
kin, half an inch in length, as many as five may be counted ;
they are seen to best advantage in the thickest portions of the
skin, but may be found on the shoulders and arms, breast, ab-
domen, and lower extremities. At some points they appear

Fio. 180.— Section of Kkin from the shoulder of
an infant, magnified seventeen diameters : a, epi-
dermis ; 6, erector pili muscle ; c, sebaceous gland ;
<f, fat-column ; e, sudoriparous gland ; g, adipose
tisane ; A, hair.

THE THICK CUTIS VERA. 423

as slight indentations in the section ; at others as long canals.
They are well shown in the skin of an infant (Figure 180), and
in a foetus of nine months. In the pig, the lower border of the
cutis appears to the naked eye, when seen in section, like the
teeth of a saw. Under the microscope, the apex of each inden-
tation contains the bulb of a hair. In thick hides these inden-
tations become clefts or canals, and we find frequently a
sweat-gland situated at about the middle of each. The canals
are oblique, as are also the hair-follicles, and the axes of the
two are more nearly parallel than those in the human subject.

In thin skins the canals are either so short as hardly to pass
for such, or, if the hair is not of sufficient length to extend to
the bottom of the cutis, absent. A thick skin and the ex-
istence of downy hairs are, then, the conditions necessary for
the presence of this structure in its most marked forms. I have
not found them in the face, although in some individuals they
probably exist there, nor in the thinner skin already alluded to.
In the lip of the rat the long hairs are imbedded in a transpa-
rent, mucous-like connective tissue, and their roots are sur-
rounded by numerous bands of muscle. It is interesting to
note the fact, that under each root are to be found vertical rows
of fat-cells, arranged end on end like the beads of a rosary, but
there appears to be no cleft in the surrounding tissue to en-
close them. In order to obtain a preparation of skin which
shows these structures in their entire length, the section must
be made vertical to the surface, and in a direction which corre-
sponds with the inclination of the cleft of the hair above the
surface. This coincides with the fine folds or "grain" of the
skin. Sections made in any other direction give but a frag-
ment of the canal, which appears then nearly as an isolated
lobule of adipose tissue. Even with these precautions it is
difficult to obtain a good specimen, unless the razor is guided
by the eye and, as in embryonic skin, the canals are not large
enough to be seen, it is greatly a question of luck whether a
good section can be obtained.

TJie blood-vessels are well shown by an injection of Berlin
blue in the foetus near full term. In each canal, as -well as in
the intervals between them, the arterioles which nourish the
cutis ascend from the subcutaneous system of vessels, which
forms a fine net-work in the panniculus adiposus. Those m
the canals, on reaching the lateral clefts, bifurcate, giving a

424 MANUAL OF HISTOLOGY.

branch on either side, which anastomoses sparingly through
subdivisions with the adjacent arterioles in the middle layer of
the cutis, and give origin to the papillary and sub-papillary
network of capillaries, which here can be considered as one
and the same. At the point of bifurcation of the main vessel,
branches are given off which ascend farther in the canal and
form a delicate net- work surrounding the sudoriparous gland
("Wundernetz"). The anastomosis of the vessel about the
hair-follicle is particularly rich and fine, and unites intimately
with the superficial layer of capillaries. The hair-follicle, with
its subjacent fat-column, thus forms the centre of a rich system
of arterioles and capillaries, which extend from the panniculus
adiposus to the papillae.

The lymphatics. — The following experiments were made to
determine, the question of the presence of lymphatics in these
canals, and also to observe to what extent fiuids and particles,
pressed up from below, could be forced to the surface.

Skin was taken from the body of a lean adult, twenty-four hours after death.
A small amount of the loose areolar tissue was left adherent to its lower sur-
face. The skin being prepared by warming for a few minutes in water of
about 90° F., Berlin blue was injected, by means of a subcutaneous syringe,
into the loose areolar tissue, which was rapidly distended by the fluid. The
specimen was then thrown into strong alcohol. A similar fragment of skin
was stretched like a drum, over the end of a brass cylinder, to which it was
firmly attached by an open brass cap and screws. The cylinder being held
vertically, Berlin blue was poured upon the skin, the upper surface of which
looked downward. A rubber cork, perforated by a glass tube, was securely
fastened to the top of the cylinder, and the tube was connected with an appa-
ratus designed to exert any atmospheric pressure required. Pressure sufficient
to raise a column of mercury twenty-eight millimetres was continued for an
hour and a half, the skin being pressed out with great force in dome-shape
at the bottom of the cylinder, which was kept during this time in blood-warm
•water. The specimen was then placed in alcohol. It was observed that the
injection mass had gone, at one or two points, to the surface, and on making
vertical sections of the skin the next day, the cutis was found to be penetrated
by the mass in vertical blue lines, which united at various intervals by hori-
zontal branches, occasionally so numerous as to present an almost continuous
blue surface. The subcutaneous areolar tissue was almost uniformly colored
blue.

Opinions on the character and distribution of the lymphat-
ics of the skin seem to differ. For instance, Neumann de-
scribes them as vessels distributed through the skin in two

THE THICK CUT1S VERA. 425

horizontal layers — a superficial and a deep one — the vertical
connection between the two being found only at comparatively
rare intervals.1 Renaut regards the skin as a lymphatic sponge,
the minutest ramification being but the space between the bun-
dles of fibres ; the coarser differing from these in having an
endothelial lining (connective-tissue cells 1), there being in
neither case a true wall, which is found only in the lymphatic
vessels of the subcutaneous tissue.* Vertical sections taken
from the specimens of skin injected by puncture, showed a
similar, but not so complete an injection, as was effected by

Fio. 181. — Injected lymph-system magnified about eight diameters : o, epidermis; /, cuds vera; ff,
adipose tissue ; A, hair.

the present method. The latter seems to possess special ad-
vantage, as a larger lymph surface is exposed at one time.

Fig. 181 shows the route taken by the Berlin blue, which, as
will be seen, ascends in nearly vertical columns through the
fat-canals to the base of the hair-follicles, going round the
sides of the sweat-gland. When a slight amount only had
passed into the canal, a medium power of the microscope
showed the blue lying in and staining the tissue accom-
panying the ascending blood-vessel in the so-called "peri vas-
cular space." The lateral clefts were filled with the mass,

1 Zur Kenntniss der Lymphgefaase der Haut, von Isidor Neumann.
s Renuut. Op. cit.

42C MANUAL OF HISTOLOGY.

which extended far enough to communicate with that com-
ing from an adjacent column. From this point there is a
delicate and freely anastomosing network, marking out the
spaces between the bundles of fibres of the cutis. The lateral
anastomosis, lower down, is not so free, and in the uppermost
layers, owing probably to the compression of the bundles of
fibres, there is little blue to be seen. From the top of the canal
the injection surrounds the base of the hair-follicle, on one side
ascending vertically and giving off horizontal branches, and
on the other following the interval between the lower border of
the erector pili muscles and the fibres of the cutis. The main
route is through the canals, there being no penetration from
below elsewhere. A similar method of injection of these spaces
is seen in certain forms of disease. A subcutaneous, round-
celled sarcoma infiltrating the skin, gave a similar configura-
tion. Also that form of congenital nsevus which develops in
the panniculus adiposus, and in a few days after birth begins
to appear on the surface. Another instance is that variety
of purulent infiltration of the subcutaneous tissue, which is
most frequently seen under thick skin and known as carbun-
cle. The wandering cells find their way to the surface through
these canals, and thus give the characteristic, punched-out
appearance to the skin.

It is evident from these examples that a free communication
exists between the interspaces of the fibrous bundles of the
cutis, and the subcutaneous tissue, and that this is effected by
no closed system of vessels.

The special function of these canals is not so evident. In
addition to furnishing a route for the blood-vessels and lym-
phatics, there would seem to be some connection with the hair
and its apparatus. The constant relation which they bear to
this structure, and the erector pili muscle, would suggest an
arrangement designed to facilitate the action of the muscle,
according to Biesiadecki.1 This muscle, by its contraction,
raises the hair from the position which it occupies, nearly hori-
zontal to the surface, to a vertical one. Any movement of the
root of a lanugo hair would be well nigh impossible, imbedded
in the dense tissue of the cutis, were it not for a yielding
structure like that of the columns, an elongation of which

1 Strieker's Handbuch der Lehre von den Geweben des Menschen und der Thiere.

THE THICK CUTIS VERA. 427

would aid the contraction of the muscle. In specimens where
the muscle is found in a state of contraction, the hair-follicle
is bent like a bow, the root being drawn through the arc of a
circle. The presence of fat near the hair-bulb is made possible
by this structure, a condition which is constant with all hairs.
That the fat is not an incidental feature of their structure,
which might be considered merely a cleft for the transmission
of vessels, is rendered probable by the observation of rows of
fat-cells beneath each hair in the lip of the rat, where no special
channels exist, and, also, by the fact that such columns of fat
do not accompany the nutrient vessels of the skin, in those
parts where the hairs are not found. It seems, therefore,
probable, that this structure has some bearing upon the nu-
trition of the hair.

Sweat-glands are found not only in these canals, but else-
where in the thick cutis ; the coil of the gland is then usually
situated at a level a little below the middle of the cutis vera,
and not in the subcutaneous adipose tissue, as in thin skin.

CHAPTER XXVII.

URINARY EXCRETORY PASSAGES ; SUPRARENAL CAPSULES.

BY EDMUND C. WBNDT, M.D., NEW YORK CITY,
Curator of the St. Francis Hospital, etc.

THE renal pelvis, the calices, ureters, and bladder, all consist
essentially of three layers, which are an inner mucous mem-
brane, a middle muscular coat, and an external fibrous layer.

In the

RENAL PELVIS

we find the mucous membrane lined with stratified epithelium,
the cells of which are large and variously shaped. Three dif-
ferent forms are readily distinguished. The most superficial
layer consists of flat or polyhedral cells of various sizes, each
one containing a round or oval nucleus, or, as frequently hap-
pens, two nuclei. Peculiar dark granules, often of large size,
surround the nucleus, and are quite distinct from the finely
granular protoplasm of these cells. Then comes a layer of
conical or club-shaped bodies, each one again furnished with
a round or oval nucleus. Every cell also possesses a long
basal process, which appears to attach it to the subjacent
tissue. The bulbous portion of these corpuscles is turned
outward in the direction of the surface. Wedged in between
the processes just mentioned we find the third variety of
cellular elements. These are oval or rounded bodies contain-
ing ellipsoid nuclei. At the renal calices we find a sharp line
of demarcation between the cylindrical columnar epithelium
of the papillary ducts and the stratified pavement epithelium
of the pelvis. The epithelial layer has a thickness here of
0.045-0.09 mm.

The connective-tissue portion of the mucous membrane is
devoid of papillse, contains sparse elastic fibres, and is rich in

THE URETERS. 429

fixed corpuscles, the inoblasts of Krause. There is no true
basement-membrane. Below this stratum we find a submu-
cous layer, which is abundantly furnished with elastic tissue,
and contains a few simple acinous glands with ducts having a
lining of cylindrical epithelium.

The muscular coat is composed of bundles of smooth mus-
cle-cells forming an inner layer, with a peripheral direction of
its constituent anatomical elements, and an outer layer concen-
trically arranged. The "papillary sphincter" is but a thick-
ening of this latter layer.

The external fibrous layer forms a thin connective- tissue
membrane, not always clearly marked here, whereas in the ure-
ters and bladder it is found to be well developed.

The blood-vessels of the pelvis are derived from the renal
artery and vein, and form capillary networks characterized by
polygonal meshes. The lymphatics and nerves are found to
have the same distribution as in the ureters.

THE URETERS

have a structure which closely resembles that of the renal pel-
vis. The mucous membrane shows the same varieties of epithe-
lium ; its connective-tissue components are similarly arranged ;
and the external investing membrane is corriposed of the same
kind of tissue already described. But in addition to the two
muscular layers, which here attain a greater development, we
find a third muscle coat, so that we can now distinguish an in-
ternal and external longitudinal from a middle circular layer
of muscular elements.

Engelmann has described a close reticulum of blood capil-
laries lying immediately under the epithelial stratum, but its
existence is made doubtful by the negative statements of other
authors.

Glandular bodies are not found in the ureters. The peri-
pheral layer of fibrous connective- tissue possesses conspicuous
elastic bundles in the lower portion of the ureters.

The distribution of the blood-vessels is like that of the pel-
vis already described. The lymphatics are well developed here,
forming several networks in the different layers of the ducts.
Nerves are likewise readily distinguished, some of the nerve-

430

MANUAL OF HISTOLOGY.

fibres being also furnished with ganglion cells. Their mode of
termination in the muscular layer is not definitely known, but
may be assumed to resemble that of ordinary smooth muscu-
lar-tissue.

THE BLADDER

has the same type of structure as the ureters, but contains, in
addition, a serous covering in its upper portion. The different
coats of the bladder are, however, much thicker than the cor-
responding layers in the other urinary excretory passages.

The epithelial lining of the mucous membrane shows the
three varieties of its cellular elements in a clearly defined man-
ner.

The connective-tissue stratum presents no noteworthy pe-
culiarities, if we ex-
cept the comparative
abundance of simple
/ 1 -if7^ l!*/r-4O I acinous glands.

The bundles of
muscle -cells in the
muscular-coat inter-
lace, forming irregu-
lar, long-stretched
meshes. This irregu-
lar arrangement pre-
vents the distinct rec-
ognition of successive

Fio. 182.— Epithelium of the urinary bladder, o, a cell of the layei'S, eacll Wltll a
second layer ; 6, a cell of the first layer ; c, shows the first, second, i _ —-.^l ,T -rvroirn il i n rr r\ i
and third layers of the epithelium in connection. Obersteiner. •lcU&tJV prevailing C

rection. Nevertheless,

we find in the external portion of the muscle-coat some pre-
dominance of longitudinal bundles, together with an abundant
supply of elastic fibres. The anterior wall and vertex of the
bladder show this arrangement very conspicuously, in fact the
muscle-fibres have here received a separate name, that of detru-
sor urince. The vesical neck shows a tolerably distinct thicken-
ing of its circular muscle-fibres, which is known as the sphincter
vesiccR. It should always be borne in mind that the arrange-
ment of the muscular coat is apt to vary in different individuals,
the description here given will, however, be found to apply to
the majority of cases.

SUPRARENAL CAPSULES.

431

The blood-vessels form a capillary network in the mucous
membrane, which is situated about midway between the epi-
thelial stratum and the muscular coat. In other respects they
present no peculiarity worthy of note.

The lymphatics are less abundant in the bladder than in
the ureters. They, also, lack noteworthy peculiarities or
special features of interest.

Plexuses of nerve-fibres are found in the subserous connec-
tive-tissue, and also in the muscular coat. Microscopic ganglia
and groups of ganglion cells are also met with.

SUPRARENAL CAPSULES.

The suprarenal capsules (glandules suprarenales) are small
flattened bodies, two in number, situated somewhat above and

Pin. 183.— Cellular groups and trabcculte of the cortical substance, from the suprarenal capsule of the
Frog. Kberth.

in front of the upper end of either kidney. They are usually
triangular or semilunar in shape, although round and oval
forms are also met with. In structure they resemble the so-

432

MANUAL OF HISTOLOGY.

called blood-vascular glands, but their function is not known.

They belong, to the ductless variety of glands.

Each suprarenal body consists
of a capsule inclosing the paren-
chyma, which shows a cortical and
medullary substance. The cap-
sule is formed of ordinary connec-
tive tissue containing many deli-
cate elastic fibrils. Externally it
is surrounded by loose connective
tissue, containing a greater or less
proportion of adipose tissue, and
internally it sends out trabeculse,
which traverse the entire organ,
thus constituting and completing
its frame-work.

The cortical substance, as its
name implies, occupies the exter-
nal portion of the suprarenal body.
It has an average thickness in man
of 0.28 to 1.12 mm., is of a yellow-
ish color, and may be divided into
three layers or zones. The lim-
its of demarcation between these
layers are much 'less marked,
however, than the corresponding
boundary line between the corti-
cal and medullary portions. In
the human being the external layer
of the cortex is distinctly separate

from the middle one, but the latter shows no such sharp limit

against the innermost layer.

The cortex is a friable substance,

and its broken surface presents

a striated appearance. Owing to

rapid post-mortem changes, the

cortex in man is usually found

to be separated from the medul-
lary portion by a dirty brownish

substance, containing modified

blood and cortical corpuscles.

FIG. 184.— Perpendicular flection through
the suprarenal capsule of man : 1. cortex ; 2,
medulla; «. capsule: 6, layer of outer cell-
groups ; c, layer of cell-trabeculse (zona faaci-
culata); d, layer of inner cell-groups ; e, med-
ullary substance ; f, transverse section of a
vein. Eberth.

Fio. 185.— Single cells and cell-groups of the
outermost cortical layer. Human suprarenal cap-
sule. Eberth.

SUPRARENAL CAPSULES.

433

The three layers of the cortex are an external one,, or zona
glomerulosa ; a middle one, or zona fasciculata / and an in-
ternal one, or zona reticularis.

The external layer consists of rounded or oval groups of
cells, separated by delicate connective-tissue trabeculae, which
spring from the capsule. Similar cells are found throughout
the entire cortex. They have been called the parenchymatous
bodies or cells, although a better name is cortex corpuscles.
In structure they resemble ordinary cells, consisting of poly-

Fio. 186.— Horizontal section through the outermost cortical portions of the suprarenal capsule of the
Horse, a, blind termination of a cylinder ; t>, groove-shaped and cylindrical cortical trabeoulaa ; c, stroma.
Eberth.

hedral masses of protoplasm furnished with spherical nuclei
and conspicuous nucleoli. Their protoplasm has a coarsely
granular character, and, as a rule, contains more or less fat in
greater or smaller droplets.

The middle layer contains cortical corpuscles which are ar-
ranged in almost parallel rows, and are so closely packed that
this portion acquires a distinctly striated appearance. These
cellular columns have received various names. By Ecker they
were called gland tubules, Kolliker termed them cortical cylin-

28

434

ders, Eberth described them as cylindrical cell-trabeculge, or
cortical trabecuL-e, and Krause named them cellular pillars.
These cellular rows, columns, or streaks, are by no means
always cylindrical, for on cross-section they frequently present
a semilunar, oval, or bean-shaped appearance. Their inner
and outer terminations have a rounded shape, and near the
former place they seem to anastomose with one another. At

Tin. 1S7.— Vertical section through the the cortical portion of the suprarenal capsule of the Horse, a,
capsule ; 6, cell-trabeculoe ; c, cell-groups. Eberth.

the peripheral end they sometimes appear groove-shaped, or
in horse- shoe form.

Connective-tissue processes communicating with the cap-
sule are found between the cell columns, but the latter are not
completely isolated by them. These connective-tissue streaks
also send off transverse or oblique fibres, so that occasionally
the cells of the middle layer seem to be inclosed in basket-like
meshes. In addition to fat-droplets, granules of pigment are

SUPRARENAL CAPSULES.

435

found in the cells of the innermost portion of the middle
layer.

The external layer is made up of irregularly arranged cor-
tical corpuscles. Nearly all the cells of this layer contain
pigment granules. The connective-tissue here forms a reti-
culum, with variously shaped meshes, which contain greater
or smaller heaps of cells.

The medullary substance has a whitish-gray appearance, and
is of a more delicate consistency than the cortex. It consists

Fio. 188. — Vertical section throncrh the medullary subFtance of the suprarenal capsule of the Cow.
a, blood- vessels ; 6, trabecnlse of medullary cells. Strieker.

of a network of connective tissue, which contains in its meshes
the medullary corpuscles. These are pale cells with spherical
nuclei and large nucleoli. They may assume various shapes.
In man they are generally of an irregularly stellate or polyg-
onal form. Their protoplasm is finely granular, and they con-
tain, as a rule, much less fat and pigment than the cortical
corpuscles. Kolliker finds that they resemble the nerve-cells
of the central nervous system, but he adds that they cannot
be regarded as such nerve-elements. The medullary cells
assume a yellow or brownish color when treated with chromate
of potash or chromic acid. Since the cortex corpuscles are
not thus colored, this peculiar! ty may serve to distinguish one
cellular variety from the other.

The connective-tissue framework of the medulla is called its

430 MANUAL OF HISTOLOGY.

stroma, and its meshes in man have an oval or rounded form,
so that, as a rule, the cell-groups have a similar shape. On the
whole, we find a smaller proportion of connective tissue in the
medulla than in the cortex.

The blood-vessels of the suprarenal capsules occupy the
stroma, and are found in great abundance. The arterial vessels
arise from the aorta, the phrenic and renal arteries, and the
cffiliac axis. About twenty small branches pierce the capsule,
and are distributed mainly to the cortex. The medullary sub-
stance is very rich in venous plexuses. Capillary networks
are found in both cortical and medullary portions. The veins
uniting form one principal branch, which passes out at the hi-
lus of the organ. The right suprarenal vein empties its blood
into the vena cava inferior, the left one into the vena renalis
sinistra.

LympJiatics were seen by most observers only at the sur-
face of the suprarenal capsules. Klein, however, has recently
asserted that there exists between the cells "an anastomosing
system of narrower and broader clefts, channels, and lacunae,
which belong to the lymphatic system." This applies to the
zona fasciculata. In the other portions of the organ the same
writer also finds lymph-spaces, and lymph-sinuses, occupying
the regions "between the septa and trabeculse of the frame-
work on the one hand, and the cell -groups on the other."

The nerves occur in comparatively greater abundance in
these organs than in any other glandular structures of the hu-
man body. Kolliker was able to count thirty-three branches
in a single suprarenal capsule of a man. They are derived
from the renal plexus, the pneumogastric and phrenic nerves,
and semilunar ganglion. Very fine or medium-sized, dark-bor-
dered fibres are commonly encountered, and they abound espe-
cially in the medulla. Ganglion-cells are also frequently seen,
and Virchow has traced them into the interior of the organ. In
the cortical substances they are of rare occurrence. The terminal
distribution of the nerves has not been hitherto ascertained,
and it appears to be still a matter of doubt whether they ter-
minate in the suprarenal body at all.

Development. — In mammals the suprarenal capsule has an
independent origin in a collection of tissue between the Wolff-
ian bodies behind the mesentery and in front of the abdomi-
nal aorta. (Kolliker.) The mesoderma at this point assumes

BIBLIOGRAPHY. 437

a special structure. Certain of its cells form more or less cyl-
indrical masses with a reticulated appearance. Between these
cellular groups a network of blood-vessels is soon found, so
that the whole structure is now not unlike embryonal hepatic
tissue. In rabbits, Kolliker saw the first traces of these bodies
about the twelfth or thirteenth day. On the sixteenth day
they had already attained a length of 1.56 mm., and occupied
a position along the vertebral column from the first to the fourth
and part of the fifth lumbar vertebra. On cross sections of em-
bryos sixteen days old, Kolliker found that the suprarenal cap-
sules were distinctly separate at their upper borders, whereas
their lower ends were joined together to form a single organ.
The same writer also found a nervous ganglion at the coalesced
central portions of somewhat older embryos.

Behind the suprarenal capsules a second sympathetic
ganglion was discovered. Remak and v. Brunn do not in all
respects corroborate the statements of Kolliker. The latter
was unable to ascertain any existing relationship between the
nervous system and the suprarenal capsules.

BIBLIOGRAPHY.

BERGMANN. De glandnlis suprarenalibus. Diss. inaug. Gottingen, 1839.
ECKKU. Der feinere Bau der Nebennieren beim Menschen und den vier Wirbelthier-

klassen, 1846. Article u Blutgef assdriisen " in Wagner's Handworterbuch der

Physiologic, Bd. IV. 1849.

H. FRET. Art. " Suprarenal Capsules" in Todd's Cyclopa3dia of Anat. 1849.
REMAK. Untersuchungen ueber der Entwickelung d. Wirbelthiere. Berlin, 1853-

1855.

VIRCHOW. Zur Chemie der Nebennieren. Virchow's Archiv, 1857.
LEYDIG. Lebrbuch der Histologie, 1857.

B. WERNER. De capsulis supraren. Dorpat Dissertatio. 1857.
VULPIAN. Gaz. med., p. 659. 1856; p. 84, 1857. Gaz. hebd., p. 665, 1857.
G. HARLET. The Histology of the Suprarenal Capsules. Lancet, June 5th and

12th, 1858.

BARKOW. Anat "Outers, ueber die Harnblase. 1858.
PALLADINO. Estratto del bulletino dell' ass d. natur e med. Anno I., No. 5.

NapolL

BURCKHARDT. Virchow's Arch., Vol. XVII., p. 94. 1859.
G. JOESTEN. Archiv fur phye. Heilkunde, S. 97. 1864.
A. MOERS. Virchow's Archiv, Bd. XXIX. , S. 3:;G.
HENLE. Anatomic des Menschen. Bd. 2. 1866.

438

MANUAL OF HISTOLOGY.

ARNOLD, JUL, Bin Beitrag zu der feineren Structur und dem Chemiaraus der Ne-
bennieren. Virchow's Archiv, Bd. 35, S. 64. 1866.

HOLM. Ueber die nervosen Elemente in den Nebennieren. Sitzungsberichte der
Wiener Akademie. Ed. 53, 1. Abtheilung. 1866.

(JitAXDUY. Structure de la capsule surrenale. Journal de 1' anatomic et de la physi-
ologic. 1867.

KOLLIKER. Handbuch der Gewebelehre. 5. AufL 1867.

EBERTH. Strieker's Archiv.

KISSELEFF. Centralblatt, No. 22. 1868.

BOUVIN. Over der bouw en de beweging der Ureteres. Utrecht, 1869.

ENGELMANN. Zur Phys. d. Ureters. Pfliiger's Arch. , Vol. IL, p. 243. 1869.

OBERSTEINER, in Strieker's Manual

UNRDH. Archiv f. Heilkunde, p. 289. 1872.

v. BRUNN. Archiv f. mikr. Anat., Vol. VIII., p. 618. 1872.

EOLI. Arch. f. mikros. Anat., Vol. IX., p. 653. 1873.

HAMBURGER. Zur HistoL d. Nierenb. u. d. Harnleiter. Arch. f. mikr. Anat,
Vol. XVII, p. 14. 1879.

See also the text-books of Frey, Krause, Kolliker, and Henle.

BRAUN. Ueber Bau u. Entw. der Nebennieren bei Reptilien. Zool. Anzeiger, Vol.
IL, No. 27, p. 238. 1879; und Arbeiten aus d. zool. -zootom. lustitut in
Wiirzburg, Vol. V., p. 1. 1879.

KOLLIKER. Entwickelungsgeschichte des Menschen. Leipzig, 1879.

KLEIN, and S. NOBLE SMITH. Atlas of Histology. 1880.

CHAPTER XXVIII.

THE MAMMARY GLAND.
Br W. H. PORTER, M.D., and EDMUND C. WENDT, M.D., of New York City.

General considerations. — By virtue of its intimate associa-
tion with the function of reproduction, this organ occupies a
distinctly peculiar position among the glands of the body. In
the male it persists through life in the same rudimentary form
which characterizes the mamma of both sexes at birth. Only
in the female, and in her only at certain times, does this organ
attain its complete histological maturity. It may be borne in
mind, however, that in a few anomalous cases, male beings sup-
plied with fully developed mammary glands have been ob-
served.

After conception, and as pregnancy advances, progressive
evolution takes place within the mamma. This unfolding
process at length culminates in exaggerated tissue-metamor-
phosis, which in other organs we should scarcely hesitate to
call pathological. In fact, Virchow and his followers all main-
tain that the secretion of milk is the direct result of a fatty
degeneration of mammary epithelium, and similar in all essential
respects to the processes involved in the elaboration of the seba-
ceous material from the cutaneous glands of that name. Bill-
roth, indeed, calls the mammae cutaneous fat-glands (Hautfett-
drusen\ and he does this in consideration of the mode of their
development, and because they are placed immediately be-
neath the integument. In spite of these statements, however,
we must maintain that the mammae are radically different from
ordinary sebaceous glands, and that the processes of secretion
in the two sets of glands are quite distinct. The grounds on
which we base this opinion will be amplified farther on. The
secretory activity of the gland, consisting in the elaboration
of milk, is, as a rule, called into play only during the period

440 MANUAL OF HISTOLOGY.

of rapid growth and development already alluded to. In ex-
ceptional instances, however, lacteal fluid may be secreted
during the extra-puerperal, period.

The mammae belong to the class of compound acinous or race-
mose glands, and, like the other organs of this group, consist of
a framework or stroma, and a proper secreting structure or
parenchyma. As they appear to the naked eye, the bulk of
the breasts is not their secreting parenchyma, but ordinary
adipose tissue. This fills out the intervals between the lobes

and lobules, and gives to the entire
organ its smooth, round form. The
different lobes have separate secretory
ducts, which open upon the nipple.
These ducts ramify throughout the
substance of the gland tissue, and
ultimately carry upon their terminal
branches the clusters of secreting vesi-
cles, called acini or alveoli. Accord-
ing to Zocher and Hen nig, the true
glandular substance has not a rounded

FIG. 189. — Terminal vesicles and , -1,1 i

rtroma from the gland of a nursing shape, but ShOWS Si grOUpmg HltO three
woman. Langer. . ^ .',... ^ J ~ , . ,

principal divisions, one 01 which ex-
tends far up in the direction of the axilla. It is separated
from the axillary lymphatic glands only by a small amount of
adipose tissue. This would explain the ease, readiness, and
frequency with which these glands become implicated in ma-
lignant disease of the mamma.

Since the glands at birth differ very widely from the mammae
of adult women, and still more widely from those of pregnancy,
it will be convenient to consider the histology of the organ under
different aspects. This will be necessary, however, only with
regard to the acini and the epithelia therein implanted, as these
alone show such wide morphological divergencies in the dif-
ferent phases of existence.

The nipple (teat, mamilla, papilla mammce) is the one struc-
ture belonging to the mamma which is least liable to modifica-
tions of tissue due to age and sex. It generally assumes the
shape of a pigmented conical or cylindrical projection, at the
apex of which the galactophorous ducts have their terminal
openings. It is composed principally of a rather loosely woven
connective tissue, containing abundant corpuscles, and provided

THE MAMMARY GLAND. 441

i

with elastic fibrils. This conjunctive tissue forms a supporting
framework for the milk-ducts traversing the nipple. The latter
show walls of rather derive fibrous tissue, with a large pro-
portion of elastic elements, and are provided with a lining
of one row of short cylindrical cells. As the external orifice
is approached, these cells begin to take on the character
of the ordinary epidermic corpuscles of the integument.
Partsch has found in many animals that the secreting paren-
chyma accompanied these ducts almost to their mamillary
orifices.

The occurrence of unstriped muscle in the nipple, accords
with the fact of its erectile properties. But the exact mode of
distribution of these elements is still a matter of controversy
among histologists. From the researches of Winkler and
Kolessnikow, recently confirmed by Partsch, it would appear
that they occur not in the ducts themselves, but form an in-
complete ring around and external to the same. In or around
the smaller galactophorous ducts, muscle-cells cannot be unmis-
takably recognized, though some authors have described their
occurrence there.

As regards the structure of these smaller galactopliorous
ducts (ductm lactiferi, milk-ducts) it is quite simple. Their
membranous walls consist of a delicate and closely woven
reticulum of connective tissue, with a large admixture of fine
elastic fibres. Henle, Meckel, and Kolessnikow have described
smooth muscle-cells in these canals, but, as already stated,
Partsch and others have denied their existence. At any rate,
on cross-sections the contracted condition of some of the larger
ducts results in a stellate appearance of their lumina, whereas
the smaller ducts always appear round or oval.

The larger ducts traced into the gland tissue are found to
be provided with saccular dilatations immediately beneath the
nipple. These milk-reservoirs (sinus ductuum lactiferorum,
sacculi lactiferi, or ampullce) may be 5 to 8 mm. broad, and thus
become distinctly perceptible to the naked eye. Below these
dilatations the ducts again grow narrower, and by numerous
divisions and subdivisions form a system of ramifying tubes,
which terminate in the secreting alveoli. The structure of the
larger ducts does not materially differ from that of the smaller
ones. Their walls are, of course, considerably thicker, and
there is found in addition a greater proportion of elastic tis-

442 MANUAL OF HISTOLOGY.

sue. All the different kinds of ducts show a lining composed
of a single layer of short cylindrical cells, containing ellipsoid
nuclei. The character of the lining cells is, however, gradually
changed as the acini are approached, near which it merges into
the alveolar epithelium by insensible gradations.

Surrounding the nipple is a variously pigmented ring, called
the areola mammce. Its surface is slightly corrugated, and
this circumstance, taken in connection with its pigmentation,
results in the production of the marked contrast it presents to
the very white and soft integument covering the other portions
of the female mamma. The areola is also provided with abun-
dant unstriped muscle-fibres. Some of the latter surround the
nipple in concentric rings, others pursue a radial course. The
sudoriferous and sebaceous glands of the areola are conspic-
uously developed, and lanugo hairs are also found. The fa-
miliar changes which go on in the areola simultaneously with
the development of pregnancy, are mainly due to increased
blood-supply and additional pigmentation. The areola is also
provided with small granules of secreting parenchyma. Some
of these grains empty the products of their secretory activity
by special recurrent ducts into the main excretory canals. But
there are others which have special openings upon the free sur-
face of the areola. Usually, little papillary eminences mark
the presence of such orifices. These scattered bits of mam-
mary parenchyma are known as the glandules aberrantes of
Montgomery. Kolliker and others regard them as largely
developed seba'ceous glands.

The arteries of the mamma are chiefly derived from the
internal mammary artery and the long thoracic. The veins
empty into the thoracic branches and cephalic vein. Both
arterial and venous vessels proceed subcutaneously from the
periphery to the nipple, whence branches are given off in a
posterior direction. They are not guided in their course by
the distribution of the milk-ducts, but are distributed to the
glandular parenchyma in such a way that each lobule has its
own separate supply. Finally, under the areola the veins of
the nipple form a circular anastomosing chain, known as the
circulus venosus of Holler. Capillary vessels surround the
acini, forming networks with rather close meshes. Of course,
the varying states of expansion and contraction in the ultimate
alveoli, which conditions correspond to phases of activity and

THE MAMMARY GLAND. 443

rest, will materially affect tlie size and shape of the capillary
networks. They are, however, much less distinct and con-
spicuous during the period t>f lactation than in the quiescent
state of the gland. Rauber found in the glands of pregnant
animals that the blood-vessels were not in immediate contact
with the walls of the secreting vesicles, being separated from
them by interposed lymph-channels. Coyne, Langhans, and
Kolessnikow have also described these perialveolar lymph-
spaces. Their presence is, indeed, readily demonstrated by
injections with nitrate of silver solutions. In actively secreting
glands these channels are sometimes packed with leucocytes,
which also infiltrate the stroma of the organ.

Lymphatics are plentiful in the mammary gland. We find
them subcutaneously, as well as deep in the interior of the
organ. Coyne, in 1874, described the perialveolar lymph-
spaces, already mentioned, for the human mamma, and Koless-
nikow, in 1870, perialveolar lymph-spaces for the mammary
gland of the cow. Langhans succeeded in injecting a rich net-
work of periacinal lymph-vessels, likewise lymph-channels
around the excretory ducts and the lacteal sinuses. The lar-
gest lymph-vessels are retro-glandular. They are without
valves. The lymph-vessels of the nipple resemble those of
the skin. There seems to be no free communication between
the lacunal and interstitial spaces of connective tissue of the
glands, and the proper lymph-channels.

The principal lymph-vessels of the mamma, both deep and
superficial branches, proceed to the glands of the axilla. But
some of the mammary lymphatics also communicate, through
intercostal branches, with the thoracic lymphatic glands.
These are points worthy of remembrance in studying the mode
of dissemination in mammary tumors.

Nerves abound less in the secreting structure of the mam-
ma than in its integumentary apparatus. The majority are of
spinal origin, although the sympathetic system is by no means
excluded from representation. Branches from the fourth,
fifth, and sixth intercostal nerves — the so-called rami glandu-
lares — accompany the milk-ducts, and ramify within the organ.
Satisfactory evidence concerning the manner of their ultimate
termination has, however, not been hitherto obtained. Most
of the nerves in the interior of the organ belong to the vascular
or vaso-motor variety, and many are seen to accompany the

444

MANUAL OF HISTOLOGY.

blood-vessels. Eckhard has given the most elaborate descrip-
tion of the nerve-supply of the human mamma.

Structure of fully expanded gland. — Immediately before,
during, and after lactation, the mamma appears as a distinctly
lobulated organ, having a pinkish or yellowish hue, and resem-
bling in consistence the human pancreas or salivary gland.

The different lobuli are made up of numerous ultimate
acini, having, as a rule, a rounded, pyriform, or slightly poly-
hedral shape. They are of nearly uni-
form size, and are closely placed, being
separated from one another by only
sparing amounts of connective tissue,
and the capillary vascular channels
therein contained. Elastic fibres and
smooth muscle-cells also occur, though
not constantly, between the alveoli of
the lobules. Lymphoid elements, as
well as branched connective-tissue cor-
puscles, are always encountered there
in greater or less abundance. In addi-
tion to these elements, large granular
corpuscles containing nuclei are found.

Via. 190. — Transverse section
through the terminal vesicles of the
gland in a nursing woman, showing
interalveolar capillaries. Langer.

They are most numerous along the

course of the blood-vessels, and appear
to be identical with the so-called plasma cells of Waldeyer.
Creighton, however, also describes similar cells in the interior
of the alveoli,' and believes that both are identical, maintain-
ing that they are derived from the acinous epithelium.

According to this author's description, such cells are "not
infrequently seen in the tissue outside a lobule in rows three
or four deep ; again, they are found in the interfascicular spaces
among the lymphoid-cells," that have been already mentioned.
These large, granular, and nucleated corpuscles are said to be
filled with a bright yellow or golden pigment. Now, Creighton
has pointed out that the periodical subsidence of the mammary
function is accompanied by the formation of much corpuscular
waste material. And the production of these remarkable yel-
low cells, which finally leave the gland by way of the lymph-
vessels, is, according to him, but a final phase of this process.

The mammary epithelium which paves the acini has been
variously described as consisting of flat polyhedral (Reinhard) ;

THE MAMMARY GLAND.

445

cubical, cj'lindrical (Kolessnikow) ; small polyhedral (Langer) ;
and prismatic (Kehrer) cells. This discrepancy of opinion re-
ceives its explanation from, the fact that the epithelial cells

FIG. 191. — Lobule of a mamma near the resting state. Numerous large pigmented cells within the
acini and in the interlobular fibrillar tissue. Creighton.

have a different appearance in the various conditions interven-
ing between full activity and complete rest of the gland.

Creighton has given a very satisfactory description of mam-
mary epithelium. He states that in the fully expanded gland
" the floor of an acinus in section is covered by a mosaic of
polyhedric epithelial cells, usually to the number of fifteen
or twenty, while in 'the larger elongated
acini as many as thirty may be counted.
The cells are usually pentagonal or hex-
agonal, and the corners are sometimes
rounded. In each cell there is a central
round nucleus, which colors brightly
with the staining fluid, and a broad fringe
of protoplasm, which stains less deeply."
The nucleus varies in its relative size,
generally having a diameter equal to
about one-third that of the entire cell.
" In a profile view of an acinus, the epithelium appears as a
circlet of oblong cells, in which the nucleus at the centre occu-
pies almost the entire thickness of the cell. The mammary
epithelial cell may therefore be described as a flattened poly-
hedric body, with a thickness about one-half of its breadth.
The substance of the nucleus is apparently homogeneous, with

Fio. 192. — Fully expanded ad-
nus, showing mosaic of polyhedral
cells. Creighton.

44G

MANUAL OF HISTOLOGY.

a deeper line of staining round the margin ; a micleolus is not
always prominently seen."

Structure of involuted mamma. — Having thus briefly indi-
cated the main histological features of a fully evolved gland,
we are now prepared to examine the mamma in a condition of
advanced involution. By involution, in this sense, is meant
the periodical return to inactivity, and not to final retrograde
metamorphosis, which culminates in complete senile atrophy.
The glandular lobules, then, in the involuted organ are again
found to be composed of closely crowded alveoli. But all the
lobules appear to have become smaller, and
their acinous components are likewise shrunk-
en. The basement-membrane of the latter
does not appear to be materially altered, but
its cellular contents are considerably changed.
In place of the beautiful mosaic characteristic
of the active gland, there now appears only
an aggregation of nucleated corpuscles to the
number of five or ten. Creighton describes
them as "nothing else than a somewhat ir-
regular heap of naked nuclei, with no fringe
of protoplasm round them, and in size little,
if at all, larger than the nucleus alone of the
Perfect epithelium." This description, how-
ever> apples only to hardened 'specimens, for
in fresh preparations the nuclei, as a rule,
show a broader or narrower surrounding zone of protoplasm.
As regards the diameter of the involuted acini, it is about one-
fourth that of the actively secreting alveoli.

Owing to the shrinkage in the glandular parenchyma, the
blood-vessels and excretory ducts, as already stated, are more
prominent in an involuted than in an active gland.

It is not our purpose here to trace, step by step, the various
processes by which a gland passes from the resting state to
that condition of complete evolution which is alone compatible
with active secretion. For the details of this interesting subject,
the reader is referred to the work of Creighton. We may, how-
ever, very briefly summarize this author's account of the trans-
formations in question. The one essential circumstance char-
acterizing the whole change is a process of vacuolation, which
Creighton assumes to take place in the secreting cells. "The

of the

THE MAMMARY GLAND.

447

most definite and unmistakable form of vacuolation is the sig-
net-ring type." This process is, according to him, a true one
of endogenous cell 1'ormati.on, resulting in this instance in the
formation of milk. Moreover, large, granular, nucleated cells,
filled with a bright yellow or golden pigment, "found both
within the alveoli and in the interfibrillar spaces without them"

FIG. 194. — Vacnolation of alveolar epithelium. From the ndder of a ewe shortly after the end of lac-
tation. The cellR in situ are vacuolated cells, with the usual thin and, for the most part, uncolored hoop
or ring of the vacuole, and the deeply Plained peripheral mass. Creighton.

characterize the last stage of involution, "and the pigment
that belongs to them is to be found strewn over the lobules
that have reached the resting state." Finally, Creighton as-
serts that "the various forms of cells that characterize the
various stages of involution must have resulted from a trans-
formation de novo of the renewed epithelium, and not from
successive changes upon the same cell." Each epithelial cell,
therefore, that is used up in the formation of milk, has been at
one time a perfect polyhedral corpuscle or fully equipped cell,
and "has rapidly undergone the cycle of changes whereby
its whole substance has been converted into milk."

A distinguishing feature of one stage of evolution which

448

MANUAL OF HISTOLOGY.

deserves to be mentioned, is "the presence in the cavities of
the acini of -a peculiar granular material, the coagulated con-
dition of a fluid." Partsch has also described the occurrence
of this granular mass within the alveoli, and he states that the
secreting epithelia, though of normal size, were furnished with
shrunken nuclei, and showed numerous light spots, as if the

cells were perforated and sieve-like. It
would appear that this writer has ob-
served the stage of vacuolation with-
out, however, interpreting the same in
Creighton's sense.

Creighton also describes in certain
glands the connective-tissue stroma as
crowded with cellular elements, which
he considers equally with the pigmented
corpuscles as waste-cells of the secre-
tion. Others (Winkler, Brunn, and par-
ticularly Rauber) have assigned a far
different significance to these bodies, as
will appear farther on. Finally, Creigh-
ton explains that the secretion of the
mammary gland " may be said to be pro-
duced by a transformation of the sub-
stance of successive generations of

epithelial cells, and in the state of full activity that transfor-
mation of the substance is so complete, that it may be called a
deliquescence.""

Although Creighton's investigations did not extend to the
human mammary gland, there is ample ground for the belief
that changes of evolution and involution similar to those which
he has described in animals, constantly take place in the hu-
man female as well. And even if we accept only some of his
views on the inter-relations of physiological action and histo-
logical appearance, the discrepancy still existing in the de-
scriptions given by different authors will receive a more rational
explanation than has hitherto been offered by writers on this
subject. Certainly some of his assertions appear rather fanci-
ful in their far-reaching novelty, nevertheless they deserve the
attentive consideration which we have, at least, in part bestowed
on them.

From the results of our own examinations, we are unable

Pio. 195. — Acini from a partly
expanded gland, some of them
filled with a granular material.
From the mamma of a pregnant
cat. Creighton.

THE MAMMAKY GLAND. 449

to concede in all respects the correctness of Creighton's inter-
pretations. The evidences of epithelial destruction for purposes
of milk secretion, are not positive and convincing. In the Har-
derian gland, as well as in the mamma, we have observed the
extrusion of fat-droplets from cells replete with them without
destruction of the cell itself. Partsch agrees with us in assum-
ing that the cells may burst or otherwise discharge their con-
tents, and yet retain enough protoplasm to maintain their vital-
ity ; and also that the vital contractions of the protoplasm
may force out the oil-globules without destruction of the epi-
thelium. What Creighton has called vacuolation does not mean
death to the cells concerned in this action, for they retain their
nuclei and sufficient protoplasm to become re-established as
perfect epithelia. That this reformation of old epithelium
takes place, is proven by the fact that a new formation by
proliferation has never been observed, and by the additional
circumstance that the mammary acini never show more than
a single layer of lining-corpuscles, and, moreover, always show
this layer complete.

In this, as in many other respects, the mamma closely re-
sembles the Harderian gland, more particularly of the roden-
tia, as described by one of the writers in a monograph. The
basement-membrane of the acini in every particular also corre-
sponds in the two kinds of glands, being in both a homoge-
neous, apparently structureless membrane, with superimposed
branched adventitial cells, the so-called Stutzzellen of German
writers. A basket-shaped reticulum,-such as has been described
by Boll, Langer, Kolessnikow, Moullin, and others, is never
found to constitute this membrana propria, although artifi-
cially, appearances simulating a structure of this kind are
readily obtained, and have been interpreted by several histolo-
gists as natural occurrences.

In the cutaneous sebaceous glands the secreting vesicles are
filled with several superimposed layers of epithelia, and it is
this circumstance which leads to an entirely different mode
of secretion. For there it would indeed appear that the cells
undergoing fatty degeneration become detached from their
bases and find their way into the narrow lumen of the acinus.
The older or inner generation of cells thus vanishing is replaced
by new corpuscles formed by gradual proliferation from the
peripheral zone.

29

450 MANUAL OF HISTOLOGY.

Ranker's mews on the mamma and the lacteal secretion are
somewhat startling, but must occupy our attention here. From
a series of very carefully conducted examinations, principally
on the glands of guinea-pigs during and after pregnancy, he
feels justified in concluding that milk owes its orgin to the
entrance of countless leucocytes into the lumen of the gland-
vesicles. The emigrated lymphoid elements, he believes, pene-
trate the alveolar walls, passing through the single layer of
epithelial cells which line them. Arrived in the interior of an
ultimate acinus, the leucocytes undergo fatty metamorphosis,
and thus at length furnish the most essential and characteristic
ingredient of milk, viz., the milk-globules. Rauber, therefore,
discards the notion that the formed particles of the lacteal
secretion originate in the glandular epithelium, and represent
the elaborated products of its functional activity. He also
denies that previously formed milk globules, or colostrum cor-
puscles, ever pass through the alveolar walls. Thus the prim-
itive opinion advanced by Empedocles, describing milk as white
pus, is in a measure revived, and milk is held to be directly
derived from the white corpuscles of the blood.

Preparations of mammary glands taken from animals still
suckling their young, according to him, invariably show the
intraglandular lymph-vessels replete with leucocytes, the stro-
ma similarly infiltrated, identical corpuscles in ^greater or less
abundance within the vesicles, and transitional forms between
lymphoid-corpuscles and milk-globules. These claims, granted
to be facts, and considered in conjunction with the circum-
stance that epithelial proliferation is not seen, would certainly
go far to make Rauber' s theory seem a somewhat plausible
one. Nevertheless, we require corroborative evidence from
others, before his views can be accepted as anything more than
an ingenious hypothesis.

Rauber has also described the occurrence of a delicate stri-
ation within the epithelial cells of the alveoli. These striae are
said to be in all respects similar to those found in the secreting
elements of certain portions of the salivary glands and the
tubules of the kidneys.

As regards the corpuscles of Donne, or colostrum bodies,
most authors regard them as the products of desquamation of
the alveolar epithelium, the latter being in a condition of fatty
degeneration (Winkler, De Sinety, Buchholtz, and others).

THE MAMMARY GLAND. 451

Some liistologists, like Strieker, hold that oil-globules may be
expelled from the interior of fat-filled cells without disintegra-
tion of their protoplasmic bodies. It is an undoubtable fact
that colostrum corpuscles, when managed with proper precau-
tions, may be seen to yield droplets of fat under the micro-
scope, just as amoebae reject similar contained particles. Rau-
ber, however, maintains that these bodies represent leucocytes
in various stages of fatty metamorphosis, and he calls such
corpuscles, when found in the gland vesicles, galactoblasts.

In the gland of Harder, one of the writers has found the
spacious gland vesicles lined with very large epithelia ; and
these cells were in many animals entirely fat-filled. They se-
creted a greasy substance not unlike thick milk. Yet destruc-
tion of the cell-body did not occur, at least evidences of such
a process could not be obtained. Partsch has therefore antici-
pated the authors in their conclusion that the secretion of milk
is accomplished in much the same way in which the creamy pro-
ducts of the Harderian gland are formed, i.e., without total
destruction of epithelial cells. According to our view, then,
and it nearly coincides with the opinion of Strieker, Winkler,
and especially Partsch, the cells containing the fat-globules
may, indeed, burst and discharge their contents, but the nu-
cleus and sufficient protoplasm are retained to enable the epi-
thelium to recuperate, and in the course of time again and
again discharge its contents. Along with this mode of milk
secretion, a second process occurs. This consists of the gradual
extrusion of oil-droplets, the cell body remaining entirely in-
tact, since the mere vital contractions of the protoplasm suf-
fice to drive out one milk-globule after another.

When the activity of the gland is suddenly heightened in
the period immediately before childbirth, some few epithelial
cells are desquamated. These, appearing in the milk of most
women, are identical with the bodies known and described as
colostrum corpuscles.

Of other anatomical constituents of normal milk, we only
find the milk- or oil-globules. They are suspended in the fluid
emulsion which milk truly represents, in countless numbers.
They vary in size from 0.002 to 0.009 mm. A very delicate
fringe of protoplasm adheres to their periphery, and it is for
this reason that they may appear to become stained when sub-
mitted to the action of proper dyes.

452 MANUAL OF HISTOLOGY.

DEVELOPMENT OF THE GLAND.

Like the other cutaneous glands of the body, the mamma
is first formed by a proliferation inward of certain epidermal
cells. In other words, the breast results from a downward
extension of epiblastic corpuscles. The first unmistakable indi-
cation of the future gland is seen about the third or fourth month
of pregnancy. At that time it consists of a solid plug, or pro-

Fio. 196.— 1. Eudimentary form of gland Fm. 197.— Embryonal mamma: a, cen-

in human foetus: a, ft, epidermis : c, aggrega- tral mass, with b, aud c, variously shaped

tion of cells ; d, connective tissue layer. 2. From outgrowths. Frey.
a seven-months' foetus : a, central substance ;
b, larger, and c, smaller outgrowths. Frey.

cess, extending'downward from the rete-mucosum of the skin.
This has been called Drusenfeld, by Huss. From the internal
end of this solid process, sprouts, or offshoots, are developed,
and they represent the future separate glands constituting the
mature organ. These buds have a pyrif orm, or club-like shape,
and are surrounded by ordinary embryonal connective tissue.
The further growth of the gland takes place by a process of
continuous extension and subdivision, but indications of the
latter are not always found at birth. Ducts are already visible
in the new-born infant, but the aggregations of cells represent-
ing the future acini, remain without lumina for a much longer
period.

Th. Kolliker describes as a constant occurrence, especially
marked in the breasts of female infants, the dilatation of a
greater or smaller number of milk-ducts. Such ectatic-canals

DEVELOPMENT OF THE GLAND. 453

have their lumina filled with desquamated epithelial cells, and
a whitish, granular material. Formerly, these occurrences were
considered to be exceptional, and were regarded as having a
pathological significance. During the first year of extra-uterine
life, this characteristic process of progressive dilatation may
assume such large dimensions, that the mamma may come to
resemble cavernous tissue, the ectatic spaces of which are
paved with flattened epithelium. Within certain limits, Kolli-
ker regards this as a perfectly normal physiological event. But
he adds that an exaggerated process of this kind may result in
early mastitis. Such an occurrence, he thinks, may explain
the rudimentary development of the breasts observed in some
women of otherwise normal growth.

The post-embryonal growth of the mamma has been care-
fully studied by Langer, and his results and conclusions having
been confirmed by the investiga-
tions of Kolliker, Huss, and others,
must still be received as represent-
ing the true condition of things, in
spite of the novel and heterodox
views advanced by Creighton.

Up to the time of puberty, the
growth of the breast is very grad-
ual and quite insignificant, even in
females. Then, however, the ducts
begin to rapidly ramify in all di-
rections, and, by offshoots from va-
rious points, true acini are at length
developed. But they remain of .

* <i lar vesicles in a virgin. Langer.

small size until the stimulus of
pregnancy causes a further evolution. In the male, the exist-
ing ducts, as a rule, atrophy with advancing age. The evolu-
tion changes which the mamma undergoes during pregnancy,
have already been set forth, and there remain to be considered
only those final phases of metamorphosis which take place in
the climacteric period of life.

These are readily understood, consisting essentially of a
complete atrophy of all the secreting acini. Simultaneously
with these atrophic changes the epithelia of the galactophorous
ducts become flattened, and finally shrink, so as to form only
squamous plates, which line the ramifying processes of connec-

454: MANUAL OF HISTOLOGY.

tive tissue representing the former lactiferous canals. The
terminal portions of these larger duct- remnants are sometimes
connected with minute channels, the latter being the remnants
of collapsed smaller ducts. In some measure we find a com-
pensatory production of fat, which partly replaces the faded
acini. The breasts of old women, therefore, consist of fibrous
tissue, with a large proportion of elastic elements, fat-cells, and
the remnants of the ducts. It may be remarked that the latter
frequently show cystic dilatations, the cavities being filled with
a dirty, slimy fluid. The blood and lymph-vessels, but especi-
ally the latter, participate in the general atrophy of the tissues.

This succinct account concerning the histogenesis of the
mammary gland, does not, as already intimated, represent the
unchallenged opinion on its first development. For Creighton,
in the remarkable work already cited, radically opposes the
view that the mamma takes its origin from the epiblast. He
believes, on the contrary, that it starts from the mesoblast, or
connective-tissue layer of the embryo, and not the upper epi-
thelial layer or epiblast. According to him, moreover, and his
conclusions are based on developmental studies, chiefly of the
guinea-pig's gland, the process may be justly described as a
centripetal one, whereas the current view represents this gland-
develpoment as essentially centrifugal. We have already ex-
pressed our adherence to the current view, attributing this
growth to extension from a central point. Nevertheless, it
seems proper to briefly give the conclusions of Creighton, es-
pecially since they appear to be singularly corroborative of the
account given by Goodsir of this process, as early as 1842, an
account which has apparently remained almost unnoticed by
workers in this branch of scientific medicine.

Creighton then concludes his inquiry as follows :

"1. The mammary acini of the guinea-pig develop at many
separate points in a matrix- tissue. The embryo cells from
which they develop are of the same kind that give origin to
the surrounding fat-tissue. The process of development of the
mammary acini is, step-for-step, the same as that of the fat-
lobules."

" 2. The ducts of the mamma develop from the same matrix-
tissue, by direct aggregation of the embryonic-cells, along
predetermined lines. The ducts develop, in the individual
guinea-pig, before the acini, whereas, in the phylogenetic sue-

DEVELOPMENT OF THE GLAND. 455

cession, the ducts are a later acquisition. This reversal of the
order of acquisition of parts is in accordance with the prin-
ciple stated by Herbert Spencer, that 'under certain circum-
stances the direct mode of development tends to be substituted
for the indirect.' '

Hints regarding the Mstological study of the mamma. —
The evolution of the mammary structure progresses paripassu
with the development of its functional activity. It is the stim-
ulus of pregnancy which determines both. Nevertheless,
even during the period of its fullest physiological bloom, i.e.,
during lactation, variations in the degree of functional activity
normally take place. Moreover, the same gland may contain
lobules which are comparatively at rest, and others which are
at the full height of activity. This should always be borne in
mind in interpreting the results of histological inspection of
this organ, lest erroneous impressions be conveyed.

The alveolar epithelial cells will, therefore, not be found
alike in the different acini, nor yet even in the same vesicle.
We may find cuboidal cells, and cylindrical ones, and flattened
corpuscles, and in addition, various transitional forms between
these tj^pes.

The nucleus will appear round, or oval, and about 6-7 p in
diameter. Sometimes two nuclei may be found in one cell.
The radiating striation observed by Rauber in many cells, has
already received iriention. It is a noteworthy fact that the
cells themselves contain only a very small proportion of fatty
granules, whereas the intra-alveolar lumen is often replete
with the same.

In order, then, to study the histology of the gland at the
high-water-mark of its functional activity, animals should be
chosen which have either just given birth to their young,
or are about to do so. For the normal conditions of the
human mamma are rapidly transformed by post-mortem change,
if not previously altered in consequence of the disease which
caused the death of the individual. The organ may be exam-
ined fresh, or else hardened and then cut in sections to be
stained and mounted in the ordinary manner.

456 MANUAL OF HISTOLOGY.

BIBLIOGRAPHY.

RUDOLFI. Bemerkungen ueber den Bau der Briiste. Abhandl. der Berliner Akad.

1831.

DONNE, AL. Du lait, etc., en particulier de celui des nourrices. Paris, 1837.
COOPER. Anatomy of the Breast. 1839.

GCTERBOCK. Ueber die Donneschen Corps granuleux. Miiller's Archiv. 1839.
HENLE. Ueber die mikroskop. Bestandth. d. Milch. Froriep's Notizen. 1839.
FETZER. Ueber die weiblichen Briiste. Wiirzburg, 1840.
NASSE. Ueber die mikroskopischen Bestandtheile der Milch. Miiller's Archiv.

1840.

GOODSIR. Anatom, and Pathol. Observations. 1845.
REINHARDT. Ueber die Entetehung der Kornchenzellen. Virchow's Archiv. Vol. I.

1847.

WILL. Ueber die Milchabsonderung. Erlangen, 1850.
LANGER. Ueber den Bau und die Enfcwickelung der Milchdriise. Denkschr. d.

Wien. Akad. 1851. Also article on the Mammary Gland, in Strieker's His-
tology.

LUSCHKA. Zur Anatomic der Mannl. Brustdrusen. Miiller's Archiv. 1852.
ECKHARD. Beitr. zur Anat. u. Phys. 1. Band. 1. Heft Giessen, 1855.
VIRCHOW. Die Cellularpathologie, p. 305. 1859.
DUVAL. Du mamelon et de son aureole. Paris, 1861.
GRUBER. Ueber die Mannliche Brustdriise. Memoiren d. Petersburger Akad.

1866.
STRICKER. Ueber contractile Korper, etc. Sitzber. d. Akad. Wien. Vol. LIU.

1866.

ZOCHER. Beitr. zur Anat. u. Phys. d. weibl. Brust. Leipzig, 1869.
HENNIG. Beitrag. zur Morphologic der weibL Milchdriise. Arch. f. Gynakol. Vol.

II., p. 331. 1871.
Husa Beitrage zur -Entwickelung der Milchdriise beim Menschen, etc. Jenaische

Zeitschrift, VoL VII., 2. 1873.
LANGHANS. Die Lymphgefasse der Brustdrusen in ihren Beziehungen zum Krebse.

Arch, fur Gynakologie, Bd. VIII., S. 181. 1875. Also, Zur pathologischen

Hiatologie der weiblichen Brustdriise. Virchow's Archiv, p. 132. Bd. 58. 1873,
COYNE. Sur les lacunes lymphatiques de la glande mammaire. Soc. de Biologic.

21. Nov., 1874. Also, Sur les lacunes lymphatiques de la glande mammaire.

Gazette Hebdom., p. 775. 1874.

DE SINETY. Eecherches sur les globules du lait. Arch, de Phys. 1874.
VON BRUNN. Gottinger Nachrichten, No. 19. 1874.
LABBE and COYNE. Traite des tumeurs benignes du sein. 1876.
BUCHHOLTZ. Das Verhalten der Colostrumkorper, etc. Gottingen, 1877.
DE SINETY. Sur le develop, et 1'histol. comp. de la mamelle. Gaz. med. de Par's,

No. 6, p. 68. 1877.
KOLESSNIKOW. Die Histologie der Milchdruse der Kuh. Virchow's Archiv. Bd. 70,

p. 531. 1877.

SCHMID, H. Zur Lehre von der Milchsecretion. Wiirzburg, 1877.
WENDT. Ueber die Hardersche Druse der Saugethiere. Strassburg, 1877.
WINKLER. Bau der Milchdruse. Jahresber. d. Ges. f. Natur. u. Heilkunde. Dres-

BIBLIOGKAPHY. 457

den, 1874. Beitr. zur Histol u. Nervenverth. in d. Mamma. Archiv f. Gyna-
kol. Vol. XI. 1877.

K5LLIKER, TH. Beitrage zur Kermtniss der Brustdriise. Verb. d. phys.med.Gea.
zu Wiirzburg. 1879.

RAUBER. Ueber die Absonderung der Milch. Sitzber. d. naturf. Gesel. zu Leip-
zig, pp. 80-34. 1879. Also, Bemerkungen ueber den feineren Bau der Milch-
druse. Schmidt's Jahrb. 1879.

RAUBEH. Ueber den Ursprung der Milch. Leipzig, 1879.

BILLROTH. Die Krankheiten der Brustdriisen. Deutsche Chirurgie. Lieferung
41. 1880.

PARTSCH. Ueber den feineren Bau der Milchdriise. Breslau, 1880.

MOULLIN. The Membraua Propria of the Mammary Gland. Journ. of Anat. and
Phys. April, 1881.

See also the text-books of Sharpey and Quain, Frey, Kolliker, Kiause, and Sappey.

INDEX.

ACINI of expanded mamma, 444
of liver, 183
of lung, 260
of pancreas, 410
Adenoid tissue, 69

of lymph-glands, 178
Adventitia of capillaries, 148

of arteries, 151, 155
Afferent vessels of kidney, 206
Aghbulie intense, 38
Air-cells of lung, 260
Alcohol and acetic and muriatic acids, 15

and acetic acid mixture, 14, 15
ALIMENTARY CANAL, 386
general considerations, 386
LARGE INTESTINE, 400
blood-vessels of, 401
lymphatics of, 401
nerves of, 401
structure of, 400 '
(ESOPHAGUS, 383

blood-vessels of, 388
fibrous envelope of, 388
layers of, 386
lymphatics of, 388
mucous membrane of, 386
muscular coat of, 387
muscularis rnucosie of, 387
nerves of, 388
submucous layer of, 387
RECTUM, 401

sphincter ani of, 401
structure of, 401
SMALL INTESTINE, 394
blood-vessels of, 399
Brunner's glands of, 397
corona tubulorum of, 396
follicles of Lieberkiihn of, 398
glands of, 396
lymphatics of, 399

ALIMENTARY CANAL-
SMALL INTESTINE —

mucous membrane of, 895
muscular coat of, 394
muscularis mucosse of, 396
nerves of, 399

plexus of Auerbach, 399
plexus of Meissner, 399
Peyer's patches of, 396
serous coat of, 394
solitary follicles of, 396
submucous layer of, 396
valvulae conniventes of, 395
villi of, 395
STOMACH, 388

blood-vessels of, 392
compound peptic glands of, 390
etat mamdonne of, 389
lymphatics of, 393
mucous membrane of, 389
muscular coat of, 388
muscularis mucosre of, 389
nerves of, 393
peptic glands of, 389
pyloric glands of, 391
serous covering of, 388
submucous layer of, 389
VERMIFORM APPENDIX, 401

Alizarine, 28

Alum carmine, 27

Alveoli of lung, 260

Ammonia bichromate, 14

Amoeboid movement, 39, 40

Anastomosis of capillaries, 148

Angle of aperture, 11
of lenses, 10

Aperture, angle of, 11

Apparatus, general, for microscopical
work, 1, 2, 3, 4

Appendix vermiformis, 401

460

INDEX.

Arachnoid, spinal, 297

Archil, staining with French, 28

Arciform fibres of medulla oblongata,

394

Areola of mamma, 442
Arnold's borax carmine staining, 22
Arrangement of object, 6
Arteria centralis retinas, 347

hyaloidea, 349
Arteries, 152
Arteriolee, 152
Auerbach, intercalated areas of, 147

plexus of, 123, 399
Auricle of ear, 353
Axis-cylinder of nerve-fibres, 110

D ARTHOLINE, glands of, 241
-D Beale, spiral fibre of, 122
Bed of nail, 294
BIBLIOGRAPHY —

of alimentary canal, 402

of blood, 54

of blood-vessels, 1C1

of bone, 101

of brain, 326

of cartilage, 88

of central nervous system, 326

of cerebellum, 326

of connective substances, 81

of ear, 367

of epithelium, 61

of eye, 352

of female organs of generation, 251

of general methods, 32

of kidney, 222

of liver, 199

of lymphatic system, 182

of male organs of generation, 238

of mammary gland, 456

of mouth and tongue, 384

of muscle, 140

of nasal fossae, pharynx, and tonsils,
875

of nervous system, 127

of pancreas, 418

of pituitary body, 419

of respiratory tract, 267

of skin, 295

of spinal cord, 325

of spleen, 418

BIBLIOGRAPHY —
of teeth, 108
of thymus gland, 419
of thyroid body, 419
of urinary excretory passages and su-
prarenal capsules, 437
Bichromate of ammonia, 14

preparation of nerves with, 115
Bichromate of potassium, 14
Bigelow's studies on cartilage, 87
Bile-ducts, 191
Bismark brown, 26
Bladder, 430
BLOOD, 34

amoeboid movements of leucocytes

of, 39
Brownian movement in leucocytes of,

39
circulation of, examined during life,

45

curara for paralysis of frogs, 45
globules of, in different fluids, 38
granules of, 39
hasmatoblasts of, 47
heating slide for the study of, 40
liquor sanguinis, or plasma of, 34
red corpuscles of, 34

action of acids on, 43
of alkalies on, 44
of carbonic acid on, 42
of distilled water on, 41
of electricity on, 44
of salt solution on, 40
counting of, 48, 53
crenation of, 45
development of, 47
examination of, 47
haemochromometer for estimat-
ing richness, 53
haemoglobin of, 53
internal structure of, 46
Keyes's method of counting, 50
Malassez's method of counting,

50

measurement of, 36
number of, 37
stroma of, 46

third corpuscular element of, 48
white or colorless corpuscles of, 48
Blood-corpuscles, nucleated, 95
Blood-crystals, 53

INDEX.

461

BLOOD-VESSELS, 142

methods of injecting, 30

of bladder, 431

of choroid, 337

of cornea, 333

of iris, 343

of kidney, 213

of large intestine, 401

of liver, 186

of lung, 263

of lymph-glands, 179

of mamma, 442

of mouth, 379

of oesophagus, 388

of optic nerve, 349

of ovary, 247

of pancreas, 411

of penis, 224

of retina, 347

of skin, 279

of small intestine, 399

of spinal cord, 298

of spleen, 407

of stomach, 392

of suprarenals, 436

of testis, 234

of thymus, 414

of thyroid, 416

of uterus, 245

ARTERIES, 151

adventitia of, 151, 155
external elastic coat of, 155
internal elastic coat of, 152
internal fibrous coat of, 153
intima of, 152
media or musoulosa of, 154
muscular and elastic types of, 152

ARTERIOLES, 152

CAPILLARIES, anastomosis of, 148
endothelial desquamation, 147
endothelium, 143
genesis, reproduction, and regen-
eration of, 150
intercalated areas of, 147
intracellular network, 143
intranuclear network, 143
peri thel ium or adventitia of, 148
ramification of, 149
structure of, 146
varieties of, 145

COCCYOEAL GLAND OF LUSCHKA, 158

BLOOD-VESSELS—

CORPORA CAVERNOSA, 160

general remarks on, 142
INTERCAROTID GLAND, 160

lymphatics of, 161

nerves of, 161

perivascular spaces, 1 61

varieties of, 142

vasa vasorum, 161
VEINS, 155

distinction between veins, arte-
ries, and capillaries, 156

internal elastic coat of, 157

internal fibrous coat of, 157

points of difference from arte-
ries, 156

structure of, 156

valves of, 158

venules, 156

Boehmer's haematoxylon, 23
BONE, 89

cancellous tissue of, 94
chondro-porosis, 98
compact tissue of, 89
corpuscles of, 90
development of, 96, 99
formation of callus in, 100
formation of, from cartilage, 97

from membrane, 98
Haversian canals of, 91
Howship's lacunae of, 100
intermediary cartilage of, 97
lacunae of, 91
lamellae of, 90
marrow of, 95

cells of, 95

myeloplaxes, 95

primary cavities of, 98

red, 95

yellow, 95
metaplastic, 98

naphthaline yellow for staining, 27
osteoblasts, 96, 98
osteoclasts, 100
osteoporosis, 99
periosteal processes of, 94
periosteum of, 95
points of ossification, 98
preparation of, 92
Sharpey's fibres of, 94
varieties of, 89

462

INDEX.

Borax carmine, 22

Bowman's capsules of kidney, 204

glands of nose, 372

membrane, 79, 331
Brain, method of hardening, 15
Branched corpuscles of connective tissue,

67

Bronchioles, 260
Bronchi, primary, 257

smaller. 259

Brownian movement, 39
Brunner's glands, 397
Burdach, column of, 298

N of cartilage, 84
^ of cartilages of larynx, 255
Callus, formation of, 100
Calyx of kidney, 216
Canal, central, of spinal cord, 301

of Petit, 350

of Schlemm, 336
Canals, dentinal, 104

intermediate, of liver, 184

semicircular, 359
Capillaries, 142
Capillary bile-ducts, 192
Capsule, internal, of brain, 317

of kidney, 216

of liver, 183

of spleen, 404

of suprarenal bodies, 433

of Tenon, 337

of thymus, 412 '

of thyroid, 415
Capsules, suprarenal, 431
Carmine, alum, 27
CARTILAGE, 82

Bigelow's studies on, 87

capsules of, 82

corpuscles of, 82, 83
division of, 86
structure of, 87

daughter-cells, 84

fibrillation of, 83

fibrous, 86

hyaline, 82

calcification of, 84
methods of studying, 84

Intercellular substance of, 83, 87

intermediary, 97

parenchymatous, 83

CARTILAGE—

perichondrium of, 86

purpurine for staining, 85

reticular or yellow elastic, 85

varieties of, 82

Spina's views on, 87
Cartilages of bronchi, 257

of larynx, 254

Cartilago-triticea of larynx, 253
Caruncula lachrymalis, 330
Cavernous tissue, 160
Cells, giant, 95

of liver, 189
Cellular tissue, 63
Cement of teeth, 105
Central canal of spinal cord, 301
CENTRAL NERVOUS SYSTEM, 296

CEREBELLUM, 317

cells of Purkinje of, 318
corpus dentatum of, 317
cortex of, 319

cerebral ganglia, 319

cerebral ventricles, 319

CEREBRUM, 321
cortex of, 321
convolutions of, 321
fissure of Rolando, 321

of Sylvius, 321
island of Reil, 322
meninges of, 321
minute structure of, 323
cortex of, 323

motor tract of hemispheres, 322
paracentral lobule, 323

choroid plexus, 320

corona radiata, 317

corpus striatum, 319

ependyma, 320

internal capsule, 317

locus caeruleus, 315
niger, 316

medulla oblongata, 307
arciform fibres of, 309
central gray matter of, 308
decussating fibres of, 307
formatio-reticnlaris of, 308
raphe of, 307

nucleus lenticularis, 316

OLIVARY BODY, 310

glosso-pharyngeal, root of, 313
hypoglossal, nucleus of, 311

INDEX.

463

CENTRAL NERVOUS SYSTEM-
OLIVARY BODY —

nucleus and root of abducens

nerve, 314

parolivary nucleus of, 311
roots of fifth nerve, 315
upper spinal accessory, nucleus

of, 311

optic thalami, 319
pons, 315

spinal arachnoid, 297
spinal cord, 298

amyelinic fibres of, 301
blood-vessels of, 298
central canal of, 301
cervical enlargement of, 304
column of Burdach of, 298
column of Clarke of, 304
column of Goll of, 298
dorsal region of, 304
epithelium of, 301
filum terminale of, 302
general histology of, 298
gray commissure of, 304
gray matter of, 299
lumbar enlargement of, 303
methods of study of, 305
myelinic fibres of, 300
nerve-elements of, 299
neuroglia-cells of^ 298
root radicles of, 299
special study of different portions

of, 301

white commissure of, 303
white substance of, 299
spinal dura mater, 296
spinal fluid, 297
spinal pia mater, 297
Cerebellum, 317
Cerebral ganglia, 319
meninges, 321
ventricles, 319

Cervical enlargement of spinal cord, 304
Chalice cells, GO
Chamber, moist, 42
Chloride of gold, 28, 29
Chondro-porosis, 98
Choroid coat of eye, 338

plexus, 320
Cilia of eyelids, 328
Ciliary body, 340

Ciliated epithelium, 58
Circle of Haller, 349
Circulation of blood, 45
Circulua venosus of Haller, 442
Clarke, column of, 304
Clitoris, 240
Coats of arteries, 152
Coccygeal gland, 158
Cochlea, 362

Cohnheim's muscular areas, 1 36
Colostrum, 450
Columnar epithelium, 60
Column of Burdach, 298

of Clarke, 304

of Goll, 298

Columns, muscular, 138
Commissure, gray, of spinal cord, 304

white, of spinal cord, 303
Conjunctiva, 330

fornicis, 329

tarsi, 328
CONNECTIVE SUBSTANCES, 62

branched corpuscles of, 67

corpuscles of, 65

development of, 64, 65

fibrillated, 66

growth and development of, 79

intercellular substance of, 64

lymphoid corpuscles of, 67

of mesentery, 68

plasma-cells of, 67, 74

reticular form of, 66

of liver, 188

of nerves, 126

of skin, 275

Contraction, study of muscular, 135
Convoluted renal tubules, 205
Corium, 277
Cornea, 331

preparation of, 25
Corneal corpuscles, 75

tissue, 75

Corneous layer of skin, 274
Corniculum of larynx, 255
Corona radiata of brain, 317

tubulorum, 316
Corpora cavernosa, 160
Corpus albicans, 250

den tat urn cerebelli, 317

luteum, 249
Corpuscles, colostrum, 450

464

INDEX.

Corpuscles, corneal, 75

fixed, of cornea, 332

lymphoid, of lymph-glands, 178
of skin, 277

Malpighian, of spleen, 404

of bone, 90

of cartilage, 82, 83

of Donne, 450

of muscle, 136

tactile, 124

of skin, 280

of tendon-tissue, 73

yellow, of mamma, 444
Corpus striatum, 319
Cortex cerebri, 321
Cortex of cerebellum, 319

of kidney, 201

of suprarenal capsules, 432
Corti's membranes, 366

organ, 362, 364
Cowper's glands, 227
Creighton's views on the mamma, 445,

446, 454
Crista acnstica, 360

spiralis, 364
Crystalline lens, 350
Curara for producing paralysis, 45
Cuticula of teeth, 107
Cylindrical epithelium, 60
Cystic duct, 198
Czennak, iiiterglobular spaces of, 103

DARTOS, 231
Daughter-cells of cartilage, 84
Decidua, 245

Deiter's, protoplasmic processes of, 120
Dentine, 103, 106
Dentinal canals, 104

globules, 104

teeth, 106

Descemet's membrane, 79, 333
Detrusor urinae, 430
Development of blood-corpuscles, 47

of capillaries, 150

of bone, 96

of enamel, 108

of fat-tissue, 168

of hair, 293

of lymphatics. 175

of mamma, 452

of nail, 295

development of ovary, 250

of pancreas, 412

of sebaceous glands, 286

of spleen, 409

of suprarenals, 436

of sweat-glands, 282

of teeth, 105

of thymus, 414
diaphragms, 5
Dilator muscle of iris, 342
Direct light, 5

Division of cartilage corpuscle, 84, 186
Double staining with borax carmine and
indigo carmine, 22

with cosine and aniline colors, 24
Doyere's eminence, 126
Drusenfeld of mamma, 452
Duct, cystic, 198

of pancreas, 411

thoracic, 174
Ducts, ejaculatory, 235

galactophorons, 441
Ductus communis, 198
Dura mater, spinal, 296

E

AE, 353

Eustachian tube, S55

EXTERNAL ear, 353
auricle of, 353
meatus of, 353
mambrana tympani of, 354

INTERNAL ear, 357

"auditory teeth" of, 364

cochlea of , 362

Corti's membrana tectoria of,

366

crista acustica of, 360
crista spiralis of, 3(54
Henson's prop- cells of, 366
labium tympanicum of, 364
labium vestibnlare of, 364
lamina reticularis of, 366
lamina spiralis of, 362
macula acustica of, 360
membrana basilaris of, 364
membrane of Reissner, 362
membranous labyrinth of, 358
modiolus of, 362
organ of Corti, 362, 864
otoliths of, 358
recessus internus of, 364

INDEX.

405

EAR-
INTERNAL ear —
saccule of, 358
scala tympani of, 3(12
scala vestibuli of, 363
semicircular canals of, 309
utricle of, 356
zona pectinata of, 366

MIDDLE ear, 355
glands of, 355
structure of, 355
Ectasia of milk-ducts, 452
Efferent vessels of kidney, 206
Ejaculatory ducts, 235
Elastic fibres of skin, 277
Elastic tissue, 77

fibres of, 77

networks of, 78

of ligamentum nuchae, 79

perforated membrane of, 79
Electricity, action of, on blood, 44
Embedding specimens, 15, 16
Enamel, 102
Enamel organ, primary, 107

secondary, 107
Endoneurium, 126
Endothelium, 80

and stomata of lymphatics, 169

germinating, 165

vascular, 143
Eosine, 24, 25

and h;cmatoxylon, "25
Ependyma, 320
Epidermis, 271
Epididymis, 231
Epiglottis, 255
Epineurium, 126
Epithelium, 56

bacteria of, 57

ciliated, 58

columnar or cylindrical, 60

granules of, 61

networks of, 61

pigmented, 58

squamous or flattened, 57

structure of, 61
Epithelium of bladder, 430

of collecting tubules of kidney, 211

of involuted mamma, 446

of looped renal tubules, 210

of lung, 261
80

Epithelium of mamma, 444

of mouth, 377

olfactory, 371

of renal tubules, 206

of spinal cord, 301

of thyroid, 415
Erector pili muscles, 422
Etat mamelonne of stomach, 389
Eustachian tube, 355
Expanded mamma, structure of, 444
External ear, 353

External elastic coat of arteries, 155
EYE, 328

arteria hyaloidea of, 349

caruncula lachrymalis, 330

CILIARY body of, 340

in hypermetropic eye, 342
in myopic eye, 341

CHOROID, 338

blood-vessels of, 339
lamina chorio-capillaris of, 339
lamina suprachoroidea of, 33S
nerves of, 340
structure of, 338

CONJUNCTIVA, 330

lymph- spaces of, 331

CORNEA, 331

blood-vessels of, 333
Bowman's membrane of, 331
Descemet's membrane of, 338
nbrae arcuatae of, 332
fixed corpuscles of, 332
lamellae of, 331
nerves of, 333
preparation of, 334

EYELIDS, 328

conjunctiva fornicis, 329

conjunctiva tarsi, 328

cilia of, 328

Meibomian glands of, 329

muscle of Miiller, 329

orbicularis palpebrarum, 328

Riolani's muscle of, 329

tarsus of, 328

Fon tana's space of, 336

IRIS, 342

blood-vessels of, 343
dilator muscle of, 342
ligament of, 336
nerves of, 343
sphincter of, 342

4GO

INDEX.

EYE-
IRIS, uveaof, 343
LACHRYMAL gland, 351

glandula Galeni of, 351 .

glandula Monroi of, 351
LENS, 350

canal of Petit, 350

ligament of, 350

ligamentum pectinatum iridis, 335
OPTIC nerve, 348

blood-vessels of, 349

circle of Haller, 349

neuroglia of, 348

subdural space of, 348

vagina fibrosa of, 348
Orbicularis ciliaris, 340
Ora serrata, 340
RETINA, 343

arteria centralis of, 347

blood-vessels of, 347

ganglion-cell layer of, 344

inner granular layer of, 344

inner nuclear layer of, 345

layer of rods and cones of, 345

macula lutea of, 344, 346

membrana limitans externa of,
345

membrana limitans interna of,
346

outer granular layer of, 345

outer layer of, nuclei of, 345

pars ciliaris of, 347

pigment layer of, 346

preparation of, 347
Schlemm's canal, 336
SCLKRA, 337

lamina cribrosa of, 337

perichoroidal space of, 337

structure of, 337

Tenon's capsule of, 337

tunica vasculosa of, 338

venae vorticosae of, 337

vitreous body, 349

fossa patellaris of, 350

TULLOPIAN TUBES, 246

Fat-canals of cutis vera, 421
Fat-cells of skin, 276
Fat-columns of cutis vera, 421
Fat -tissue, 73

Fibrae arcuatae of cornea, 332
Fibres, muscular, 128
Fibrillation of cartilage, 83
Fibrous cartilage, 86

tissue, 66

Filum terminale of spinal cord, 302
Fimbriae of tongue, 380
Fissure of Rolando, 321

of Sylvius, 321
Fluid, spinal, 297
Follicles of Lieberkiihn, 398

of lymph-glands, 176

of thymus, 412
Fontana's spaces, 336
Foramen caecum of tongue, 383
Formation of bone, 97

of callus, 100
Formatio reticularis of medulla oblongata,

308

Fossae nasales, 368
Freezing section-cutter, 17
French archil, 28
Frog's bladder, muscle of, 129
Frommann's lines, 113

n ALACTOBLASTS, 451
^* Galactophorous ducts, 441
Gall-bladder, 197
Ganglia, cerebral, 319.
Ganglia of spinal cord, 120
Ganglionic bodies, 119, 121

corpuscles of brain, 72
Gas-chamber, 43
Gelatinous tissue, 63
Genital organs, female, 240

male, 223

Germinating eiidothelium, 165
Giant-cells, 95
Gibbes' double, triple, and quadruple

staining, 26
Giraldes, organ of, 231
Gland, coccygeal, 158

inter-carotid, 160

lachrymal, 351

pineal, 417

thymus, 412

thyroid, 415
Glands, Bowman's, of nose, 372

lymphatic, 176

Meibomian, 329

INDEX.

4G7

Glands of Bartholine, 241

'of bile-ducti, 191

of bronchi, 258

of Brunner, 897

of Cowper, 227

of larynx, 256

of .middle ear, 355

of small intestine, 366

of tongue, 383

peptic, 389

pylori c, 391

sebaceous, of skin, 285

sudoriparous, 282
Glans clitoridis, 241

penis, 224

Glandulae aberrantes mammae, 442
Glandula Galeni, 351

Monroi, 351

Glandules of mouth, 378
Glisson's capsule, 183
Glosso-pharyngeal root, 313
Goblet cells, 60
Gold, chloride of, 28
Goll, column of, 298
Graafian follicles, 248
Granular layer of skin, 274
Gray matter of spinal cord, 299
Green coloration of nuclei, 25
Growth, post-embryonal, of mamma, 453

TT^EMACHROMOMETER, 53
-*•-*- Haemoglobin, 53
Haematoblasts, 47
Haematometers, 50, 53
Haematoxylon, preparation of nerves in,
118

solution, 23, 24
Hailes's microtome, 19, 20
Hair, 288
Haller, circle of, 349

circulus venosus of, 442
Hamilton's preservative fluid, 20
Hand section -cutter, 16
Hardening of brain, 15
Haversian canals of bone, 91
Heart, muscular fibres of, 140
Heidenhain, rods of, 207
Henson's prop-cells, i>66
Hepatic artery, 186

cells, 189

Hints regarding study of mamma, 455

Horny teeth, 100

Howship's lacunae, 100

Hyaline cartilage, 82

Hydatid of Morgagni, 231

Hymen, 241

Hypermetropia, ciliary body in, 343

Hypoglossal nucleus, 311

TLLUMINATION, 4

-L Induline, 27

Infundibula of lung, 260

Injecting fluids, 30, 32

Injection of blood-vessels, 30, 31, 32

of cutis vera, 424

of kidney, 214

of liver, 185

of lymph-glands. 179

of lymphatics, 169
Instrument, care of, 7
Intercarotid gland, 160
Intercalated portions of renal tubules, 211
Intercellular substance of cartilage, 83

of connective tissue, 64
Intermuscular tissue, 74
Internal capsule of brain, 317
Internal elastic coat of arteries, 152

of veins, 157
Internal ear, 357
Internal fibrous coat of arteries, 153

of veins, 157
Intima of arteries. 152
Invertebrates, muscle of, 133
Involuntary muscle-fibre, 128
Involuted mamma, histology of, 440
Iodized serum, 38
Irrigation, method of, 41, 67
Iris, 342

diaphragm, 5
Island of Reil, 322
Ivory, 103

T7ARYOKINESIS, 237

-*•*• Keyes's method of counting blood -

globules, 51
KIDNEY, 201

afferent vessel of, capsule of, 206

blood-vessels of, 213

Bowman's capsules of, 204

calyx of, 216

408

INDEX.

KIDNEY—

capsule of, 21ft
collecting tubules of, 205
convoluted tubes of, 205
efferent vessel of capsules of, 206
epithelium of collecting tubules, 211
of looped tubules of, 210
of tubules of, 206
general plan of structure of, 201
boundary layer, 201
cortex, 201
medulla, 201
medullary rays, 201
injection of, 214
intercalated portions of tubules of,

211

looped tubules of, 209
lymphatics of, 216
membrana propria of tubules of, 203
method of preparing sections of, 208
natural injection of tubules of, 216,

220

nerves of, 216
rods of Heidenhain, 207
stroma of, 215
tubules of, 203
vasa recta of, 214
Kleinenburg's haematoxylon, 23
Klein's hasmatoxylon, 24
Klein's method of studying the omentum,

166
Kuhnt, Tiohlcylinder of, 114

T ABIA MAJORA, 240
-^ minora, 240
Labium tympanicnm, 364

vestibulare, 364
Labyrinth, 358
Lachrymal gland, 351
Lacunae, Howship's, 100
Lacunae of bone, 91
Lamellae of bone, 90
Lamina chorio-capillaris, 839
cribrosa of solera, 337
reticularis of ear, 366
spiral is, 362
suprachoroidea, 338
Large intestine, 400
Larynx, 253
Lens, 350

Lenses, high, testing of, 10
kinds of, 6

measuring angle of, 10
testing of, 8
Leucocytes, 39, 48
Lieberkiihn's follicles, 398
Ligament of iris, 336

of lens, 350

Ligaments of larynx, 253
I Ligamentum pectinatum iridis, 335
light, direct, 5

oblique, 5
aquor sanguinis, 34
JVER, 183
acini of, 183
bile-ducts, capillary, 192

Mayer's views on, 196, 197
natural injection of, 193
walls of, 196
bile -ducts, larger, 191
blood-vessels of, 186
capsule of, 183
cells of, 189
central veins of, 184
connective tissue of, 188
cystio duct, 198
ductus communis, 198
fat-droplets in cells of, 190
gall-bladder, 197
coats of, 198
glands of bile-ducts, 191
Glisson' s capsule of, 183
general plan of structure of, 183
hepatic artery, 186
hepatic lobules, 183
injection of, 185
interlobular septa of, 188
interlobular veins of, 184
intermediate canals of, 184
intralobular veins of, 184
lymph-vessels of, 198
nerves of, 199
sublobular veins of, 185
Lobule, paracentral, 323
Lobules of liver, 183
Lobulettes of lung, 260
Locus cseruleus, 315

niger, 316

Looped renal tubules, 207
Lumbar enlargement of spinal cord, 303
Lungs, 257

INDEX.

469

Lunula of nails, 294
Luschka's gland, 158
Lymphangeal nodules, 167

tracts, 167

Lymphatic glands, 176
Lymphatics of bladder, 431
of blood-vessels, 161
of kidney, 216
of large intestine, 401
of larynx, 257
of liver, 198
of lung, 264
of mamma, 443
of mouth, 379
of oesophagus, 388
of pancreas, 411
of small intestine, 399
of spleen, 409
of stomach, 393
of suprarenals, 436
of testis, 234
of thymus, 414
of thyroid, 416
LYMPHATIC SYSTEM, 163

artificial injection of lymphatics, 169
cysternas lymphaticae, 170
development of fat-tissue, 168
endolymphangeal tracts, 167
endothelium and stomata, 169
general histology of, J64
germinating endothelium of, 165
glands of, 175

adenoid or reticular tissue of,

178
afferent and efferent branches of,

176

follicles of, 176
injection of, 179

lymphoid corpuscles of, 178
medulla and cortex of, 176
methods of studying, 179
nerves of, 179

Ranvier's plan of injection of, 180
sinuses of, 177
stroma of, 176
vessels of, 179
Klein's method of studying omentum,

166
lymphangeal nodules or patches of,

167
lymphangeal tracts of, 167

LYMPHATIC SYSTEM—

lymphatic radicles, course and ter-
mination of, 108
lymphatics, 175

development of, 175
of mesentery, 165
of tendons, 175
lymphatic vessels, 172

intimate structure of, 172
topographical peculiarities of , 174
variations in shape of, 173
lymph-spaces, 175

eubarachnoid and subdural, 175
modern views on, 163
nerves of peritoneum, 172
perilymphangeal tracts, 167
plasma-cells, 164
plasmatic channels, 165
pseudo-stomata, 171
Ranvier's taches laiteuses, 168

views on false stomata, 170
relations to connective tissues, 163
retrospective view of, 181
sap-canaliculi of, 165
stomata of,' 165
stomata vera of, 171
thoracic duct, 174
Lymphoid cells of brain, 72
Lymphoid corpuscles of connective tirsue,
67

of lymph-glands, 178
of skin, 277

Lymph-spaces, subarachnoid, 175
Lymph-vessels of penis, 224

MACULA ACUSTICA, 360
lutea, 344, 346 '
Malassez's method of counting blood-cor-
puscles, 50
Malpighian corpuscles of spleen, 404

layer of skin, 271
Mammary epithelium, 444
MAMMARY GLAND, 439
areola of, 442
blood-vessels of, 442
circulus venosus of Haller of, 442
colostrum bodies, or corpuscles of

Donne, 450
development of, 452
Dnisenfeld, 452

470

INDEX.

MAMMARY GLAND—

ectasia of milk-ducts, 452
galactoblasts of. 451
galactophorous ducts of, 441
generjl considerations on, 439
glandular aberrantes of, 443
growth of, 4f>3

Creighton's views on, 454
Harderiau gland, similarity with, 449
lymphatics of, 443
membrana propria of, 449
milk-globules. 451
milk-reservoirs of, 441
nerves of, 443
nipple or mamilla of, 440
Partsch's views on milk-secretion, 451
Rauber's views on the mamma and

the lacteal secretion, 450
structure of fully expanded gland, 444
acini of, 444

Creighton's views on, 445
epithelium of, 444
plasma-cells of, 444
yellow cells of, 444
structure of involuted mamma, 446
Creighton's account of, 446
epithelium of, 446
vacuolation of epithelium of, 447
study of, 455
Stulzzellen of, 449
Wendt's views on secretion of milk,

449,451
Mammilla, 440
Marrow of bone, 95

Measurement of red blood-corpuscles, 35
Meatus auditorins externus, 353
urinarius of female, 242

of male, 226

Media or musculosa of arteries, 154
Medulla of suprarenal capsules, 435
oblongata, 307
of kidney, 201

Medullary rays of kidney, 201
Meibomian glands, 329
Meiwraer's plexus, 122, 399
Membrana basilaris of ear, 364
limitans olfactoria, 372
propria of mamma, 449
propria of renal tubules, 203
tectoria of ear, 366
tympani, 3o4

Membrane of Bowman, 79
of Corti, 366
of Descemet, 79
of Reissner, 362
Meninges of brain, 321
of spinal cord, 296
Metallic solutions, 28, 29
Metaplastic bone, 98
Methods for preparing objects, 12
of preparing tissues, 14
of studying hyaline cartilage, 84
of studying spinal cord, 305
Methyl-green, 29

and induline, 27
Micrometer, stage, 7
Microscope, how to use, 4

testing of, 7
Microtome, Hailes', 19, 20

Vincent's, 21
Middle ear, 355
Milk-ducts, 444
Milk-globules, 451
Milk reservoirs, 441
Miller's picro-carmine, 23
Mirrors, 5
Modiolus, 362
Moist chamber, 42, 43
Molybdate of ammonia, 15 '
Morgagni, hydatid of, 231
Motor tract of hemispheres, 322
MOUTH AND TONGUE, 377
MOXJTH, 377

blood-vessels of, 379
epithelium of, 377
glandules of, 378
lymphatics of, 379
nerves of, 379
submucous tissue of, 377
tunica propria of, 377
TONGUE, 380

circumvallate papillae of, 383
glands of, 383

filiform papillae of, 380
fimbriaB of, 380
foramen coecum of, 383
fungiform papillae of, 381
papillae foliatae of, 383
taste-goblets of, 381
Mucous membrane of larynx, 255
of oesophagus, 386
of small intestine, 395

INDEX.

471

Mucous membrane, of stomach, 389
Mucous tissue, 63
Muscle, 128

(Johnheim's areas of, 136

columns of, 138

conclusions regarding structure of, 137

fibres of, 128

of frog's bladder, 129

of fly, 133

of heart, 140

of human embryo, 132

of invertebrates, 133

of the "lucky bug" or gyrinus,

134
of water-beetles, 133

involuntary, 128

nuclei and corpuscles of, 136

peculiarities of, associated with differ-
ent functions, 138

polarized light for the study of, 137

red and white, of rabbit's leg, 138

sarcolemma. 130

striation of fresh, fibre, 131

study of contraction of, 135

termination of, in tendon, 139

transverse sections of, 136

vascular supply of, 138

voluntary fibre. 130

of Miiller, 329

of Riolani, 329

termination of nerves in, 125
Muscles of skin. 287
Muscular coat of oesophagus, 387

of small intestine, 394

of stomach, 388

fibres of heart, 140
Muscularis mucosae of oesophagus, 387

of small intestine, 396

of stomach, 389
Musculosa of arteries, 154
Mi-ller's fluid, 14

muscle, 329
Myelinic fibres of spinal cord, 301

nerve-fibres, 109, 116
Myeloplaxes, 95
Myopia, ciliary body in, 341

VfABOTH, ovula of, 244
•W Nail-fold, 294
Nails, 293
Naphthaline yellow, 27

NASAL FOSS^J, PHARYNX, and TON-
SILS, 368

NASAL FOSSAE, 368

Bowman's glands of, 372
indifferent cells of, 371
merabrana limitans, olfacloria of,

372

mucous membrane of, 368
olfactory cells of, 371
olfactory epithelium of, 371
olfactory nerves of, 372
olfactory region of, 370
thicker membrane of, 369
thinner membrane of, 369
respiratory region of, 368
vestibulum nasi, 368

PHARYNX, 373

mucous membrane of, 373
pharyngeal tonsil of, 373

TONSFLS, 373
Natural injection of liver, 193

of kidney, 216, 220
Nerve-elements of spinal cord, 299
Nerve-fibres, varieties of, 109
Nerves of bladder, 431

of blood-vessels, 161

of choroid, 340

of cornea, 333

of iris, 343

of kidney, 216

of large intestine, 401

of larynx, 257

of liver, 199

of lung, 265

of lymph-glands, 179

of mamma, 443

of mouth, 379

of oesophagus, 388

of ovary, 248

of pancreas, 411

of penis, 225

of peritoneum, 172

of skin, 279

of small intestine, 399

of spleen, 409

of stomach, 393

of suprarenals, 436

of thyroid. 416

of uterus, 245

olfactory, 372
Nerve -terminations, 109

472

INDEX.

NERVOUS SYSTEM, 109
Auerbach's plexus, 123
axis-cylinder, 110
connective tissue of nerves, 126
Deiter's protoplasmic processes, 120
Doyere's eminence, 126
endoneurium, 125
epineurium, 126
fibres of Remak, 117, 118

preparation of, in haematoxylon,

118

Frommann'a lines, 113
ganglia of cranial and spinal nerves,

120
ganglia of spinal cord, examination

of, 120

gang! ionic bodies, 119
of human brain, 121
of sympathetic system, 121
Gasserian ganglion, < xamination of,

in frog, 120

general histology of, 109
hoJilcylinder of Kuhnt, 114
incisions of Schmidt, 111
Meissner's plexus, 122
methods of nerve-termination, 109
moiorial plate, 126
myelinic fibres, 109

nerves, modern conceptions of,

116

myeline or medulla, 110
Pacinian bodies, 124
perineurium, 12?

preparation by bichromate of am-
monia, 115
preparation in osmic acid and picro-

carmine, 118
Ranvier's nodes, 110
sheath of Schwann, 110
spiral fibre of Beale, 122
staining of, in osmic acid, 113
stauiing of, in picro-carmine, 111
staining of. with silver nitrate,

112

tactile corpuscles, 124
termination of nerves, 123
in muscle, 125
in epithelial bodies, 126
varieties of nerve-fibres, 109
Nervous system, central, 296
Network of epithelial cells, 61

Neumann, dentinal sheath of, 104
Neuroglia, 70, 71

fibrillje of, 72

of optic nerve, 348

of spinal cord, 298
Nipple, 440
Nitrate of silver, 29

staining of nerves with, 112
Norris and Shakespeare's method of dou-
ble staining, 22
Nose, 368
Nose-piece, 5
Nuclei, green coloration of, 25

of muscle, 136
Nucleus and root of abducens, 314

lenticularis of brain, 316

of hypoglossus, 311

parolivary, 311

OBJECT, arrangement of, 6
size of. 8
Oblique light, 5
Odontoblasts, 104
Odontomata, 105
(Esophagus, 386
Olfactory epithelium, 371
nerves, 372
region, 370
Olivary body, 310
Optic nerve, 348
thalami, 319
Ora serrata, 340
Orbicularis ciliaris. 340
palpebrarum, 328
Organ of Corti, 362, 364

of Giraldes, 231

ORGANS OF GENERATION, FEMALE,
240
CLITORIS, 240

corpora cavernosa of, 241
genital nerve corpuscles of, 240
glans of, 241

GLANDS OP BAKTIIOLINE, 241
HYMEN, 241
FALLOPIAN TUBES, 246
ampulla of, 246
fimbrise of, 246
isthmus of, 246
LABIA MAJORA, 240
LABIA MINORA, 240

INDEX.

473

ORGANS OF GENERATION, FEMALE—
OVARY, 246

blood-vessels of, 247

corpus albicans of, 250

corpus luteum of, 249

development of, 250

Graafian follicles of, 248

nerves of, 248

stroma of, 246

tubes of, 246
PAROVARIUM, 250
PLACENTA, 251
URETHRA, 242

meatus urinarius of, 242
UTERUS —

changes of, during menstruation
and gestation, 245

decidua, 245

glands of, 244

mucous membrane of, 243

plicae palmatae of, 243

nerves of, 245

OB uteri, 244

ovula Nabothi, 244

vessels of, 245
VAGINA, 241

vascular system of, 242
VESTIBULE, 241

bulbi vestibuli, 241

ORGANS OF GENERATION, MALE, 223
COWPER'S GLANDS, 227
EPIDIDYMIS, 231

blood-vessels of, 234
EJACULATORY DUCTS, 235
HYDATID OP MORGAGNI, 231
karyokiuesis, 237
ORGAN OF GIRALD^S, 231
PENIS, 223

blood-vessels of, 224

genital nerve-corpuscles of, 225

glans penis, 224

lymph- vessels of, 224

nerves of, 225

tunica albuginea of, 223

Tyson's glands of, 224
PROSTATE GLAND, 227

acini of, 228

blood-vessels of, 229

epithelium of, 228

nerves of, 229

vesicula prostatica of, 229

ORGANS OF GENERATION, MALE—
SCROTUM, 231

dartos of, 231
semen or sperma, 235
seminal vesicles, 235
spermatoblasts, 236
SPERMATOZOA, 225

structure of, 236

development of, 236
TESTICLES, 229

blood-vessels of, 234

corpus Highmori of, 230

lymphatics of, 234

mediastinum of, 230

nerves of, 234

rete testis, 231

seminiferous tubules of, 231, 233

septula of, 230

tunica adnata of, 230

tunica albuginea of, 230

tunica vaginalis communis of, 230
URETHRA, 225

colliculus seminalis of, 225

lacunae Morgagnii of, 226

lymphatics of, 227

meatus urinarius of, 226

membranous portion of, 226

musculns urcthralis of, 220

nerves of, 226

papillae of, 226

prostatic portion of, 225

spongy portion of, 226

structure of, 225
vas aberrans, 232
VAS DEPERENS, 232, 233

ampulla of, 232

muscular coat of, 234

nerves of, 234
Organs of respiration, 253
Osmic acid, staining of nerves with, 1 1.5
Osmic acid and picro-carmine, preparation

of nerves in, 118
Osmic and chromic acids, 15
Osmic and oxalic acids, staining with, 23
Ossification, points of, 98
Osteoblasts, 96, 98
Osteoclasts, 100
Osteo- or vaso-dentine, 105
Osteoporosis, 9
Os uteri, 244
Otoliths, 358

474

INDEX.

Ovary, 246
Oviducts, 246
Ovula Nabothi, 244

PACINIAN BODIES, 134

•*• PANCREAS, 410

acini of, 420

blood-vessels of, 411

centro-acinal cells of, 411

development of, 412

excretory duct of, 411

lymphatics of, 411

nerves of, 411

trypsin, 410

zymogen, 410
Panniculus adiposus, 277
Papillae of cutis vera, 421
of hair, 289
of tongue, 380
Papillary sphincter, 429
Paracentral lobule, 323
Parenchymatous cartilage, 83
Parolivary nucleus, 311
Parovarium, 250

Partsch's views on secretion of milk, 451
Pavement endothelium, 80
Pelvis, renal, 428
Penis, 223
Peptic glands, 389
Perichondrium, 86
Perineurium, 126
Periodontium, 108 .
Periosteum, 95
Peritheliuin, 148
Perivascular spaces, 161
Petit, canal of, 350
Peyer's patches, 396
Pharyngeal tonsil, 373
Pharynx, 873
Pia mater, spinal, 297
Picro-carmine, 23

staining of nerve-fibres with, 111
Picro-haematoxylon and cosine, 26
Pigmented epithelium, 58
Pigment of retina, 346
Pineal gland, 417
Pituitary body, 417
Placenta, 251
Plasma, 34
cells, 164

Plasma of connective tissue, 67

of mamma, 444
Plasmatic channels, 165
Pleura, 265

Pleural appendages, 267 .

Plexus, choroid, 320

of Auerbach, 399

of Meissner, 399
Polarized light in the study of muscle,

137

Pons varolii, 315

Potassium bichromate solution, 14
Preparation of bone, 92

of cornea, 334

of fresh object, 13

of tissues, 13, 14

of mamma, 455

of microscopic objects, 12

of retina, 347

spleen, 409

Preserving fluid, Wickersheimer's, 29
Preservative fluid, Hamilton's, 20
Prickle cells, 58

of skin, 272

Prop-cells, Hen son' s, 366
Prostate gland, 227
Pseudostomata, 171

of pulmonary lymphatics, 264
Pulp of spleen, 406

of teeth, 102, 105

Purpurine for staining cartilage, 85
Pnrkinje, cells of, 318

granular layer of, 104
Purpurine, 28
Pyloric glands, 391

p ADICLES of lymphatics, 168
Av Ramification of capillaries, 149
Ranvier's nodes, 110

purpurine, 28

taches laiteuses, 168
Raphe of medulla oblongata, 309
Rauber's views on the mamma, 450
Rectum, 401

Red blood-corpuscles, 34
Reil, island of, 322
Reissner, membrane of, 362
Remak. fibres of, 117
Renal pelvis, 428

tubules, 203

INDEX.

475

RESPIRATORY TRACT, 253
LARYNX, 253

calcification of cartilages of, 255

cartilages of, 254

cartilago triticea of, 253

corniculum of, 255

epiglottis of, 255

glands of, 256

ligaments and membranes of, 253

lymphatics of, 257

mucous membrane of, 255

nerves of, 257

Santorini's cartilages of, 255

vocal cords of, 254

Wrisberg's cartilages of, 255
LUNGS, 259

acini or lobulettes of, 260

alveolar passages of, 260

alveoli or air-cells of, 260

blood-vessels of, 263

bronchioles of, 260

epithelium of alveoli of, 261

infundibula of, 260

lymphatics of, 264

nerves of, 265

plenral appendages, 267

pleura of, 265

pseudostomata of lymphatics of,
264

septa of, 262

smaller bronchi^ 259

subpleural' lymphatics, 267

terminal arteries of, 263
TRACHEA and PRIMARY BRONCHI, 257

cartilage rings of, 257

glands of, 258

mucous membrane of, 257
Rete Malpighii, 271

Reticular or yellow elastic cartilage, 85
Reticular form of connective-tissue, 66
Retina, 342

Retzius, stripes of, 103
Riolani's muscle, 329
Rolando, fissure of, 321
Root of hair, 288, 292
of nail, 294

a ACCULE of labyrinth, 358
^ Salter, incremental lines of, 105
Santorini's cartilage, 255
Sap-canaliculi, 165

Sarcolemma, 130
Sattertbwaite's section-cutter, 17
Scala tympani, 362

vestibuli, 362
Scales of epidermis, 275
Schlemm's canal, 336
Schmidt, incisures of, 111
Schreger, lines of, 105
Schwann, sheath of, 110
Solera, 337
Scrotum, 231
Sebaceous glands, 285
Section-cutters, 16, 17
Semen, 235

Semicircular canals, 359
Seminal vesicles, 235
Seminiferous tubules, 231
Septa of lung, 262
Shaft of hair, 288, 292
Sharpey's fibres of bone, 94
Sheath of Schwann, 110
Pheaths of hair, 289
Silver, nitrate of, 29
Sinuses of lymph-glands, 177
Size of object, 8
SKIN, 269

blood-vessels of, 279
CORIUM OP, 277

pars papillaris, 278
pars reticularis of, 278
corneous layer of, 274
elastic tissue fibres of, 277
epidermic scales, 275
EPIDERMIS, 271

general plan of arrangement of,

269

general structure of, 270
granular layer of, 274
HAIR, 288

development of, 293
papillae of, 289
root of, 288, 292
shaft of, 288. 292
sheaths of, 289
lymphoid corpuscles of, 277
muscles of, 287
NAILS, 293
bed of, 294
body of, 294
development of, 294
lunula of, 294

47G

INDEX.

HKDT-

NAILS —

nail and fold, 294

root of, 204
nerves of, 279
panniculus adiposus of, 276
rete Malpighii, 271

prickle cells of, 272
SEBACEOUS GLANDS OF, 285

development of, 280
stratum lucidum of, 274
stratum subpapillare of, 279
subcutaneous connective- tissue layer

of, 278
fat-cells of, 270

SWEAT-GLAND3 OF, 2S3

development of, 285
tactile corpuscles of, 280
Slide for heating. 40
Small intestine, 394
Sperma, 235
Spermatoblasta, 236
Spermatozoa, 235
Sphincter of iris, 343
ani, 401
papillary, 429
vesicse, 430
Spinal cord, 298

fluid, 397

Spina's views on cartilage, C7
SPLEEN, 403

blood-vessels of, 4C7
development of ,.409
fibrous coat or capsule of, 404
general structure of, 403
lymphatics of, 409
Malpighian corpuscles of, 404
nerves of, 409
preparation of, 409
pulp of, 406
serous coat of, 403
Squamous epithelium, 57
Stage diaphragms, 5

micrometer, 7

Stevenson, plan of imbedding, 10
Stomach, 383
Stomata of lymph-vessels, 165

vera, 171

Stratum intermedium of tooth, 108
lucidum of skin, 274
subpapillare of skin, 279

Striation of muscle, 131
Stroma of kidney, 215
Stutzzellen of mamma, 449
Subdural spaces of optic nerve, 348
Submucous layer of ossophagus, 387
of small intestine, 390
of stomach, 389
Subpleural lymphatics. 207
Sudoriferous glands, 2S2
SUPRARENAL CAPSULES, 431
blood-vessels of, 436
capsule of, 432

cortical substance of, 432
external layer of, 433
internal layer of, 435
middle layer of, 433
zona fasciculata of, 433
zona glomerulosa of , 433
zona reticularis of, 436
development of, 4o6
lymphatics of, 436
medullary substance of, 435
nerves of, 436
Sweat-glands, 282
Sylvian fissure, 321
Sympexions of thyroid, 415

rpACTILB CORPUSCLES, 124
-L Tarsus of eye, 328
Taste-globlets of tongue, 381
TEETH, 102

cement of, 105
dentinal canals of, 104
dentinal globules of, 104
dentinal fibres of tomes, 104
dentinal sheath of Neumann, 1 04
dentine or ivory, 103
development of, 105

cuticula, 107

dentinal teeth, 106

dentine, 106

horny teeth, 106

primary enamel organ, 107

secondary enamel organ. 107

stratum intermedium of, 108

tooth papilla, 107

tooth-sac, 107

development of enamel of, 108
enamel, 102
granular layer of Purkinje, 104

INDEX.

477

TEETH—

incremental lines of Salter, 105

interglobular spaces of Czermak^ 103

interglobular substance, 105

lines of Schreger, 105

parallel stripes of Retzius, 103

parts of, 102

periodontium of, 108

pulp of, 102, 105

odontoblasts, 104

odontomata, 105

osteo- or vaso-dentine, 105
Tendons, lymphatics of, 175
Tendon-tissue, 72
Tenon's capsule, 337
Termination of muscle in tendon, 139
Testicles, 229
Testing lenses, 8, 10

microscope, 7
Thalami optici, 319
THICK CUTIS VERA, 420

blood-vessels of, 423

erector pili muscles of, 422

fat-columns or fat-canals of, 421

fibrous prolongations of, 420

injection of, 424

lymphatics of, 424

papillae of, 421

Third corpuscular element of blood, 48
Thoracic duct, 174
THYMUS GLAND, 412 '

blood-vessels of, 414

capsule of, 412

cells of, 413

central canal of, 414

development of, 414

follicles of, 412

lymphatics of, 414

thymic juice of, 413
THYROID BODY, 415

blood-vessels of, 416

capsule of, 415

epithelium of, 415

lymphatics of, 416

nerves of, 416

sympexions of, 416

vesicles of, 415
Tissue, adenoid, 69

cellular, 63

connective, 63

corneal, 75

Tissue, elastic, 77

fat, 73

fibrous, 66

gelatinous, 63

intermuscular, 74

mucous, C3

tendon, 72

Tissue, compact, of bone, 89
Tomes, dentinal fibres of, 104
Tongue, 380
Tooth-sac, 107
Tonsil, pharyngeal, 373
Tonsils, 373
Trachea, 257
Triple staining, 26
Trypsin, 410
Tubules of kidney, 203
Tubules, seminiferous, 231
Tunica vauculosa of sclera, 338
Tympanum, 354
Types of arteries, 152
Tyson's glands, 224

TTRETERS, 429

U Urethra, female, 242
male, 225

URINARY EXCRETORY PASSAGES,
428
BLADDER, 430

blood-vessels of, 431
epithelium of, 430
connective tissue of, 430
detrusor urinas of, 430
lymphatics of, 431
muscular coat of, 430
nerves of, 431
sphincter vesicas, 430
RENAL PELVIS, 428
fibrous layer of, 429
mucous membrane of, 428
muscular coat of, 429
papillary sphincter of, 429
vessels and nerves of, 429
URETERS, 429

mucous membrane of, 429
muscular layers of, 429
vessels and nerves of, 429

Uterus, 243

Utricle of labyrinth, 358

Urea, 343

478

INDEX.

TTACUOLATION of mammary epithe-
V Hum, 447 .
Vagina, 241
Valves of veins, 158
Valvulae conniventes, 395
Vas aberrans, 232
Vasa recta of kidney, 214
Vas deferens, 232
Vasa vasorum, 161
Veins, 156

central, of liver, 184

interlobular, of liver, 1 84

intralobular, of liver, 184

sublobular, of liver, 185
Venae vorticosaj of sclera, 337
Ventricles of brain, 319
Venules, 156
Vermiform appendix, 401
Vertebrates, muscle of, 130
Vesical epithelium, 430
Vesicnlae seminales, 235
Vessels of muscle, 138
Vestibule of vagina, 241
Vestibulum nasi, 368
Villi of intestine, 395
Vincent's microtome, 21

Violet de Paris, 29
Vitreous body, 349
Vocal cords, 254
Voluntary muscle-fibre, 130

TIT ARM-SLIDE, 40

'' Waxy change, methyl-green for, 29
Wendt, method of triple staining, 2G

views on endothelial desquamaticu,
147

views on secretion of milk, 449, 451
White blood-globules, 39, 48
White substance of spinal cord, 299
Wickersheimer's preserving fluid, 29
Wrisberg's cartilage, 255

"YELLOW CELLS of mamma, 444.

ZONA FASCICTJLATA of suprarenals,
433

glomerulosa, 433
reticularis, 433
pectinata of ear, 366
Zymogen, 410

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